llkktth100
- Создано: 26-11-21
- Последний вход: 26-11-21
Профиль пользователя
llkktth100 объявления
Amazing Ways to Use A Wooden Serving Tray
Описание: Amazing Ways to Use A Wooden Serving Tray Serving trays are handy items to have around the home, and a good-quality wooden serving tray ranks above all others. While a serving tray can serve many purposes, it is one of the most preferred home décor items for your personal as well as entertaining needs. Available in a variety of shapes and sizes, such as decorative round trays, wooden tray sets are a great investment as they make it easy to carry things around the home, serve food and drinks and use as a base for placing your décor items – a flower vase, terracotta figurines and even your green pots on a side table or a centre table. WONDERFUL WAYS TO USE A SERVING TRAY AT HOME No matter what you decide to do with a serving tray, one thing is for sure – serving platters are a great addition to your kitchen, dining space and even the bedroom. Think about breakfast in bed, and the first thing that comes to mind is a charming and decorate serving tray to hold your glass of fresh juice, a plate of sandwiches, and a bowl of corn flakes. On days when you are entertaining house guests in your garden, you can use decorative snacks serving tray to serve them tea/coffee and biscuits. Your guests will love your hospitality as well as compliment you on your exceptional taste in home décor. BEST-SELLING DECORATIVE WOODEN TRAYS ONLINE AT ARTYSTA GALLERY DINING TABLE SERVER A decorative wooden tray is an excellent purchase for placing condiments on your dining table. Take a look at our Handcrafted Decorative Wooden Tray with Kulhads that is great for serving tea/coffee. The beautiful Warli art adds to the tray’s appeal and celebrates India’s local art. Having evening tea in the living room with family and friends becomes even more special when you enjoy tasty snacks served in an eye-catching snacks tray. Our boat-shaped Sheesham wood handmade wooden tray with two ceramic bowls is a must-buy. Sometimes all you want to do is enjoy the pleasant weather, sipping tea and snacks from the comforts of your balcony or kitchen garden. Our Warli art Decorative Wooden tray set comes in handy here. Available in big and small sizes, the wooden trays with handles are just right for serving cups of tea/coffee, biscuits and tasty refreshments. Beautiful décor items can brighten up your home, especially when they are placed on cozy side tables. And to make the display even more attractive, you can use a lavish and lustrous antique oval-shaped wooden tray as a base. Artysta Gallery’s Teak and Pine wood oval tray with a gorgeous peacock design stands out for its shiny buffed polish and antique handles. You can even display your small indoor plants on it. Serving trays are undoubtedly one of the hardest working tableware you can have in your kitchen. But how often do we actually talk about them? Let alone think about investing in a nice collection. More often than not, we do not think much when it comes to the selection of serving trays to buy. Besides serving a myriad of purposes beyond transferring foods from one room to another, they also add to the décor and theme of your dining table. Whether you love to host tea parties and lunches or stay as a loner, a serving tray is of immense importance. There is no limit to things you can serve to your guests in a tray and there is no one size fits all when it comes to the serving tray to buy. While some serving trays are ideal for sharing a specific portion size of food, others allow you to carry your crockery and cutlery from kitchen to serving area. Types of serving trays to buy There is a wide variety of serving trays available in the market. When it is time to pick a serving tray to buy you can be flooded with a variety in terms of not just material, but also colour, sizes and designing of the tray. Keep in mind what you want to serve, in order to pick the right size and shape. You can visit Ellementry to buy the best ones for you. What to consider when buying a serving tray? It is, of course, important to give consideration to the size and material of the serving tray to buy but do not forget to make sure that the tray you pick is good to look at and offers a visual addition to your foods. You can take things up a notch and match the colour and style of your serving tray with that of the tableware you own. However, neutral trays like those made of wood are great to look at and can complement any table set up. Websites like Ellementry has a wide selection of wooden food tray to choose from in different shapes, colours and sizes. All these trays come in a collection of matching tableware to choose from to complete the look and are completely handcrafted. A nice well-sized tray can be kept at your beverage bar with drinks ready to be served. The guests can pick their favourite ones and help themselves while you get to have some free time to enjoy your own party. Having the drinks already placed in the tray can allow you to rotate them once in a while if required and lets you mingle up with the guests. Fruit platters For your next brunch, arrange freshly cut fruits on a wooden platter and be the talk of the town for your plating skills. Rather than placing the fruits in a bowl-like fruit salad, why not create a fruit platter and bring a little bit of style to your table? Assortment of cheese Cheese – who doesn’t love it, right? If you are not sure about things that you can serve to your guests in a tray, fret not. A collection of assorted cheese will never disappoint you. Just pick up some gouda, mozzarella and other favourites and place them on a wooden tray. Your guests will adore you! How about some breakfast in bed? Want to make your better half feel special? Planning to start a special occasion on a romantic note? What can be better than a scrumptious breakfast in bed? Just toss some eggs, pancakes and a cup of coffee on a beautiful tray like this shade of breakfast food wooden tray from Ellementry and thank us later! Keep a small bouquet of flowers along and you will not regret it! Tea There is no better way to use a tray other than serving your favourite tea. Whether you love a hot creamy masala chai, or you are more of a green tea person, a tray is essential for that perfect serving of tea. A big tray like this silver metal tray with handles from Ellementry can even accommodate some go-to snacks as well. Coffee Like to enjoy a cup of coffee with your partner. Well, you do need a nice tray to pep up your regular coffee drinking experience. A tray allows you to carry more than two coffee mugs along with some snacks at the same time besides adding a little more finesse to your experience. Snacks There is no limit to things that you can serve to your guests in a tray. Whether you are hosting a bunch of kids for a birthday party or your boss and his family are coming for drinks. You will, of course, need a couple of trays and platters to serve snacks or take them from the kitchen to the dining table. The final word Serving trays that are good to look at are no doubt versatile and a very useful accessory to have in your kitchen. While such trays come handy to serve food and drinks to your guests, they also make your tea and coffee drinking experience more delightful. Do not forget to complement your cups and trays! Besides using these trays for serving purposes, you can also invest in some beautiful pieces to add to your home décor. Keep it on your coffee table with a flower vase or a candle to add style to your living room décor. You can even place some trays on the dining table to keep your cutlery sorted or organise your cruet set and other mandates. What do you think of this article? Is there anything that we missed? What all things do you serve in a tray? We would love to have your feedback! Do let us know your views in comments below! Do not forget to check out our tray collection. Been a long while since you have added cool new things to your home collection? If the answer is yes, then it's time to change that and get shopping. Change is always good, and quirky new pieces can work instantly to elevate your experience as well as help you make an impression on your guests. So let's start with the basics, such as serving trays. With so many stunning options available - from striking woodwork to contemporary enamel detailing - you will find amazing ways to serve food and beverages, and even use these trays as decor pieces. Need proof? Take a look at these eight trendy serving trays from Amazon that you will love: 1. Printelligent Khirki Wooden Serving Tray In Block Style This gorgeous tray from Printelligent is sure to spark up your dining experience. The tray features a fun contemporary design with pretty printed blocks. It is made of fibre frame with acrylic inserts. This wooden tray from Paper Plane is designed to be large enough to conveniently serve a bunch of things. It can help you carry drinks, hold your favourite books and magazines or prop it on a shelf as a decorative piece. This multi-coloured wooden coffee tray from ExclusiveLane can be used for serving tea, coffee, breakfast and snacks for dining table and centre table. If you love colours, this is what you need to pick. This stylish and unique wooden tray can easily become a focal point of the living room. In addition to serving hot beverages and snacks, it is perfect for all occasions. Add a dash of warmth to your home with this adorable regal elephant round tray from Chumbak. Quaint, colourful and handy, it is perfect for kitty parties to breakfast in bed. A Nourishing Moment. Handcrafted trays help create meaningful experiences—like enjoying breakfast outside in the sunshine, gathering the things you need to care for someone you love, or holding your most treasured objects. Wood pieces like these need protection from water damage, so use coasters when carrying drinks—or display the trays on their own to enjoy their beauty. If you want to find wooden trays recommendation, then you’ve come to the right place. Because, in this article, I will show you the 7 best wooden trays recommendation that you need to check. Let’s get started! This elegant tray is curve-shaped, 16 x 12 x 2 (in), coated in dark brown with cutout grip handles. The decorative tray is very aesthetic for home decor. Why should you buy this tray? Because it is made from a 100% well-managed forest! The wooden tray with handles is an eco-friendly product to keep things clean and tidy! This wooden tray is uniquely made with many variations of sizes that you can choose based on your needs! It is handmade with materials that contain Baltic Birch Plywood, non-formaldehyde glue, varnished with non-toxic water-based dyes.
Дата Публикации: 26-11-21
Grow Lights for Indoor Plants and Indoor Gardening: An Overview
Описание: Grow Lights for Indoor Plants and Indoor Gardening: An Overview Warm vs cool? "Full-spectrum?" LED, CFL, or HID? Here's what you need to know about mars grow light for starting seeds, gardening inside, or houseplants. Indoor growing offers many advantages. The biggest benefits are the most obvious: garden pests can’t get at your plants, and you have total control over the weather. Yet unless you’re lucky enough to have a solarium or greenhouse attached to your home, providing sufficient light to your plants will likely be an obstacle (shade-tolerant houseplants excepted). South-facing windows may provide enough light for a tray or two of seedlings, but if you want to grow vegetables, or any other sun-loving plants, to maturity, you’re going to need LED grow light bar. The indoor lighting found in most homes does little to support photosynthesis. Traditional incandescent bulbs do not have the proper spectrum of light, or intensity, to supplant the sun. Household fluorescent bulbs can make effective grow lights, but only if they are placed in within a few inches of the foliage and left on for 16 hours per day – not ideal. When shopping for indoor led grow lights, you’ll notice they are labeled with numbers like 2700K or 4000K. This refers to their relative warmth or coolness on the color spectrum – the higher the number, the cooler the light. Foliage growth is generally best around 6500K, though many plants need a period of warmer light, around 3000K, in order to produce flowers, and thus fruit. In other words, if your goal is to simply produce seedlings, leafy green vegetables, or root crops, you only need higher spectrum bulbs. If you want to grow flowers, marijuana, or any fruiting plant (cucumbers, tomatoes, peppers, lemons, etc.), you’ll also require low spectrum bulbs. You can some types of bulbs are available in full-spectrum form, however, simplifying things. The standard fluorescent bulb, commonly denoted T12, makes a decent grow light for houseplants, starting seeds, supplementing the natural light of a window, and other situations where lighting needs are modest. They are fairly weak in light intensity, however, and must be placed within a few inches of the foliage to have much of an effect. , which are narrower in diameter than T12s (but still widely available wherever lightbulbs are sold), have a much higher light intensity, making them suitable as a sole light source for sun-loving plants. Compact fluorescent bulbs (CFLs) are an option for small spaces, or if you don’t like the look of long rectangular fluorescent light fixtures – CFLs will screw into an ordinary incandescent light fixture. Look for specialized full-spectrum fluorescent grow bulbs (like this , or , which fits into a standard socket) to provide the right balance of light for flowering plants. While they are considerably more expensive than fluorescent bulbs, LEDs use half the electricity and last five times longer, more than paying for themselves in the long run. The average LED bulb from the hardware store is not designed for plant growth, however – you need special , a relatively new technology that is increasingly available from horticultural suppliers. LED grow bulbs are capable of much greater light intensity than fluorescent bulbs and are available in full-spectrum form. An easy rule of thumb: Fluorescent bulbs are often used when growing just a handful of plants; LEDs are preferable for larger quantities since you can achieve higher light intensity per square foot. Another advantage of LEDs? They produce very little heat compared to other bulbs – an issue that can become problematic when you have a lot of lights in a small space. HID Grow Lights Before the advent of LED grow lights, were the main option for large indoor plantings. They are extremely powerful, but are expensive to purchase, consume electricity inefficiently, require special light fixtures, and give off a lot of heat. All that said, they are very effective and are still widely used. If you want to grow large plants like tomatoes or lemon bushes, HIDs are good bet because the light penetrates farther into the foliage than with other bulbs. There are two types of HID bulbs. High-pressure sodium (HPS) bulbs are best for flowering (low spectrum), while MH (metal halide) bulbs are required to support vegetative growth (high spectrum); the two types are often used in conjunction. Unfortunately, each type requires its own fixture. How to Install Weed Grow Lights Installation requirements vary drastically depending on the scope of your indoor garden and the type of bulb used. But here are a few basic steps to get you started. Figure out how many bulbs you need. Most edible plants require at least 30 watts per square foot, but fruiting species (like tomatoes) generally won’t produce abundant high-quality crops without 40 to 50 watts per square foot. Wattage is always indicated on the bulb package. Simply multiply the square footage of your growing area by the number of watts you plan to provide (between 30 and 50); then divide by the number of watts supplied by the bulbs you plan to use. Devise a light rack. You’ll need a way to support the bulbs over the plants at the proper height. And unless you’re growing something that will remain at more or less the same height throughout its lifespan, you’ll also need a way to raise the light rack as the plants grow. This is usually accomplished through some sort of pulley system or by hanging the light fixtures with metal chain – that way you can easily adjust the height by changing the link the light fixture is home from. are also available for purchase online. Add the necessary accoutrements. It is generally wise to plug your lights into a timer to ensure they get the proper amount of light, and that they get it at the same time each day. are available for indoor growing, though a standard also works. If your lights bring the temperature above 80 degrees or so in your growing area, install a ventilation system to prevent heat stress. Aficionados make use of reflectors and all sorts of other grow light accessories to achieve optimum results. How Long Should I Leave Grow Lights On? Plants grown indoors require more hours of light than those grown outdoors. 14 to 18 hours of light per day is recommended for most edible species when grown under artificial lighting. Don’t be tempted to leave the lights on 24-7, however – at least six hours of darkness each day is essential to plant health. As the plants grow, raise the light fixture accordingly to maintain the optimal distance, which varies depending on the type of bulb used and its wattage (the higher the wattage. As a self-confessed science geek I am fascinated by technology. Yet in the world of gardening this is often synonymous with the gimmicky (fibreglass meerkat solar light, anyone?) or the hugely complex and costly – think hydroponic growers that require a degree in electrical engineering to install. So it was with trepidation that I started experimenting with vegetable grow light last winter in my tiny flat. Nine months down the line I am a total convert, eulogising about them to all my gardening mates. They are something I feel could be a gamechanger to many modern gardeners, if we could only get over our preconceptions. This is why… Once upon a time grow lamps were massive, ungainly things – fluorescent tubes more than a metre long that required complex and hideous systems of stands, cables and reflectors. They were real power guzzlers, too, so not exactly great for the planet, or your wallet – which would already have taken a pretty eye-watering hit from the price of all the kit. They even kicked out quite a bit of heat, which apart from raising safety issues, could also damage the very plants you were trying to grow. However, recent breakthroughs in LED technology have created a new generation of effective, cool-running grow lights that cost a fraction of the old-school behemoths both to buy and to run, consuming (according to some manufacturers) 90% less energy. Crucially, they have shrunk down enough to be easily incorporated into average living room decor, some seamlessly integrated into planter-cum-lamp designs. Others are light and thin enough to be fixed pretty much invisibly into standard flat-pack shelves, turning existing pieces of furniture in my house into instant growing units. These LED lights are becoming increasingly widely available online and even at a certain Scandinavian home store. But why bother in the first place? Surely part of the pleasure of getting out in the garden is to escape the relentless march of technology into every aspect of our lives. Well, here’s what my little experiment has done for me: I was able to grow houseplants in parts of my dark, urban flat that I never could before. This is a huge bonus to an obsessive plant collector like me, and could make an even more dramatic difference to houseplant lovers in basement or north-facing flats where lack of light is a serious issue. Also, come spring seed sowing, I started off a good six weeks or so earlier and got zero etiolation on my baby plants. Stronger plants, much earlier, meant I got a bumper harvest of tomatoes and chillies weeks ahead of time. And all of this for the cost of a couple of desk lamps than run on minimal power. Brilliant! Tens of millions have placed their trust in the Guardian’s high-impact journalism since we started publishing 200 years ago, turning to us in moments of crisis, uncertainty, solidarity and hope. More than 1.5 million readers, from 180 countries, have recently taken the step to support us financially – keeping us open to all, and fiercely independent. With no shareholders or billionaire owner, we can set our own agenda and provide trustworthy journalism that’s free from commercial and political influence, offering a counterweight to the spread of misinformation. When it’s never mattered more, we can investigate and challenge without fear or favour. Unlike many others, Guardian journalism is available for everyone to read, regardless of what they can afford to pay. We do this because we believe in information equality. Greater numbers of people can keep track of global events, understand their impact on people and communities, and become inspired to take meaningful action. We aim to offer readers a comprehensive, international perspective on critical events shaping our world – from the Black Lives Matter movement, to the new American administration, Brexit, and the world's slow emergence from a global pandemic. We are committed to upholding our reputation for urgent, powerful reporting on the climate emergency, and made the decision to reject advertising from fossil fuel companies, divest from the oil and gas industries, and set a course to achieve net zero emissions by 2030. If there were ever a time to join us, it is now. Every contribution, however big or small, powers our journalism and sustains our future. Support the Guardian from as little as $1 – it only takes a minute. If you can, please consider supporting us with a regular amount each month. Thank you.
Дата Публикации: 26-11-21
Effects of Wearing Compression Stockings
Описание: Effects of Wearing Compression Stockings This systematic review investigated the effects of wearing below-knee compression stockings (CS) on exercise performance (or sports activity) and associated physiological and perceived indicators. We searched articles on PubMed using the following terms: “graduated compression stockings”; “compression stockings”; “graduated compression socks”; “compression socks” combined with “performance”, “athletes”, “exercise”, “exercise performance”, “fatigue”, “sports” and “recovery”, resulting in 1067 papers. After checking for inclusion criteria (e.g., original studies, healthy subjects, performance analysis), 21 studies were selected and analyzed. We conclude that wearing CS during exercise improved performance in a small number of studies. However, wearing CS could benefit muscle function indicators and perceived muscle soreness during the recovery period. Future research should investigate the chronic effect of CS on Sports Medicine and athletic performance. The prevention of deep venous thrombosis is one of the first evidence-based benefits of wearing compression sleeve, demonstrated by a clinical experiment in which CS improved the venous return by increasing femoral vein blood flow velocity in hospitalized patients.1 Over time, the interest from the basic medical area has expanded to other fields like Sports Medicine.2 Nowadays, recreational and professional athletes have used CS as a tool for improving performance or accelerate recovery from training or competitions, and also to reduce lower limb volume,3,4 relieve symptoms of muscle soreness, and fatigue.3–6 Such popularity is probably boosted by the possibility to obtain potential ergogenic benefits with a simple and low-cost aid. There are different types (e.g., shorts for thighs, full-leg) and application modes (e.g., using only after the exercise) for compression garments. However, using CS (bellow-knee) “only during” the exercise are probably more practical (than during recovery, after-exercise) for a significant number of sports/activities. For example, uniform issues would limit whole-body garments in some sports. Also, athletes living in tropical locations could be unmotivated to wear compression garments after training sessions once those garments usually promote higher skin temperatures.7,8 Additionally, there is limited evidence regarding the effects of wearing CS (only) during exercise/training/competition, which could be relevant for Sports Medicine professionals. Therefore, the purpose of this systematic review was to investigate the effect of wearing below-knee CS during exercise (or sports activity) on performance and associated physiological and perceptual indicators. A systematic literature search was performed by two independent reviewers in PubMed. The following terms: (i) “graduated soccer cotton basketball compression sock”; (ii) “compression stockings”; (iii) “graduated compression socks”; (iv) “compression socks” were combined with “performance”, “athletes”, “exercise”, “exercise performance”, “fatigue”, “sports” and “recovery” (Figure 1). The studies included in this review met the following inclusion criteria: 1) original studies; 2) comprised samples of adults (≥ 18 yr); 3) participants were healthy; 4) investigated the effects of wearing foot-to-knee (below knee) CS (during exercise) on exercise performance and physiological and perceptual indicators (e.g., muscle fatigue, muscle recovery, musle soreness); 5) trampoline sublimation weed white sock worn during the exercise/test/match; and 6) study protocol included exercise or effort tests and performance analysis. The literature search occurred between January 01, 1900, until June 30, 2019. We excluded the following type of articles: conference abstracts, case reports, short communications, systematic reviews, meta-analyses, theses, letters to the editor, and protocol papers. Also, we excluded studies involving unhealthy participants: e.g., patients with morbid conditions such as obesity, chronic venous insufficiency, diabetes, hypertension (but not limited to). Analysis The heterogeneity of the selected studies was considerable: e.g., exercise protocols, fitness level of the participants, variables measured. Thus, we have decided not to evaluate the studies chosen from a statistical point of view. Instead, we performed a qualitative analysis, conducted by two authors focusing on the effects reported by the authors and potential practical implications. All other authors read this qualitative analysis carefully, and edits have been incorporated. Figure 1 shows the search, selection, and inclusion process. The search displayed a total of 1067 papers, which were reduced to 370 after exclusion of duplicate publications. Then, we discarded 39 articles written in non-English languages.9 From the remaining 331 items, we excluded 261 by examining the title. Finally, from the remaining 70 articles, we selected 21 studies for this review according to our inclusion criteria (Figure 1). Table 1 presents a summary of the studies examining the effects of wearing below-knee CS during exercise on performance and associated indicators. Running was the most common type of exercise in the selected studies (76%, 16 out of the 21 studies), followed by soccer (two studies; 10%), triathlon, calf-rise exercise and cycle ergometer (one study each one; 5%). All studies were performed using a randomized experimental design, with the majority employing a crossover design strategy (13 studies, 62%) (Table 1). Only two studies found some beneficial effect of CS on performance, and a third study improved subsequent performance (Table 2). Two studies did not find performance effects of CS for the group mean, but the authors highlighted that CS promoted benefits for some individuals. The main effects of CS are presented with compressions between 20 and 30 mmHg. The range between the anti slip wool compression sock values is 12 to 28 mmHg, while the maximum values range from 15 to 33 mmHg. This systematic review aimed to investigate the effect of wearing below-knee CS during exercise on performance and associated indicators. The main finding is that wearing this kind of CS during exercise (or physical activity) improved performance in a minor part of the studies selected (i.e., 3 out of 21). However, a reasonable number of studies have shown evidence that wearing CS could benefit muscle function or fatigue indicators (e.g., CMJ, specific physical tests) and perceived muscle soreness just after the exercise protocol and/or hours after the exercise bout (e.g., during 1 h, 24 h recovery). CS and Performance Improvement One of the main reasons for wearing CS during exercise is probably the expectation of performance enhancement due to potential physiological effects.2 This includes better venous return which hasten metabolic removal from the exercising muscles31 and reduce cardiac load,26 improved proprioceptive feedback and better movement accuracy,32 reduced muscle oscillations, lower muscle damage, inflammation, and soreness.6,31 In the current review, only three studies found some CS-induced benefit on performance but did not present adirect mechanistic explanation. For example, astudy concluded that wearing CS (during two soccer matches, 72 hin-between) resulted in higher distances covered in high-intensity activities which are decisive for soccer. Also, CS promoted alower perceived muscle soreness in thesecond match.17 Although the authors did not measure any direct muscle damage marker, they suggested that CS probably protected the eccentric actions common in soccer matches,33 mechanically (i.e., smaller muscle oscillation).6 In this regard, the oscillating forces experienced by the muscle resulted in reduced muscle fatigue. Thus, the CS might offer a mechanical advantage reducing muscle oscillation and countering fatigue in high-intensity activities (e.g., intermittent acceleration, changing directions).34,35 Another study showed CS-induced ergogenic effects on performance. The authors found an improvement in running performance concomitantly with anaerobic and aerobic thresholds when participants wore CS.18 The benefits of CS-ergogenic effects on performance are attributed to enhanced biomechanical support of the muscles, leading to higher efficiency and lower metabolic costs at given workloads,18,36 reduction of muscular microtrauma,6 and enhanced the proprioception.32 During a 5 km running time-trial (Brophy-Williams et al15) the wearing CS did not affect immediate performance. However, CS generated a positive impact on subsequent 5 km running (i.e., less performance decrement from time-trial 1 to time-trial 2). Again, the underlying mechanism of such benefit is unclear but may be related to increased oxygen delivery, lower muscle oscillation, and better running mechanics.15 Despite the current results, the literature does not indicate robust evidence favoring the use of CS during exercise (i.e., only three studies found benefits on performance). Researchers should be careful in drawing conclusions. Considering that each specific study has (or had) a particular experimental design (e.g., exercise protocol, duration, intensity, variables measured, fitness level of the participants), it becomes difficult to generalize the results from the different studies. Thus, it is essential to consider the risk of bias and heterogeneity of the studies. As the same protocol does not conduct different studies, they will vary in the characteristics of the included population, interventions, diagnostic methods to access outcomes, etc. (clinical heterogeneity). Thus, these studies may be biased.37 Additionally, two studies did not find CS-induced effects on group mean performance, but the authors highlighted the individual improvements: 10 of 19 runners ran the 5 km time-trial approximately 10 s faster,25 and 10 of the 14 runners ran the 10 km time-trial10 approximately 20 s faster. Therefore, individual responses should be carefully evaluated in practical settings. CS, Muscle Function and Perceived Muscle Soreness Some studies in the current review have shown that CS can induce lower muscle fatigue after an exercise protocol with the same workload than a control condition.11,14,20,21 The lower after-exercise fatigue may suggest a preserved muscle function. Overall, such studies show the maintenance (based on baseline values) of muscle function by a smaller decrement of performance (or none) in specific muscular tests performed after the exercise protocol (e.g., running time-trial, soccer match). On the same reasoning, the lower perceived muscle soreness found in the current review is also a potential beneficial outcome from CS. The smaller muscle soreness may be particularly relevant for more prolonged periods with multiples exhausting physical activities performed with a short recovery period in-between.17 In one of the studies, competitive runners (VO2max ~69 mL.kg.min) completed four 10 km time-trial wearing control CS (0 mm Hg) and CS with different pressures in a randomized, counterbalanced order.11 The runners performed CMJ tests before and after running as a muscle function indicator. The results showed that CMJ height decreased after control running. However, CMJ performance was improved after running wearing CS (low and medium pressure), suggesting a better maintainance of muscle function. The authors speculated that improvements in proprioception to jump and reduced muscle oscillations due to CS probably collaborated with lower muscle fatigue.11 In other included study, highly trained runners participated in 3 simulated trail races (15.6 km, including uphill and downhill) in a randomized crossover trial.14 Authors measured indicators of muscle function (and also muscle perceived soreness) at baseline, 1, 24, and 48 h after-run. Muscle function decreased after the race, suggesting the appearance of fatigue, which was partially counteracted by CS. More specifically, a beneficial effect from wearing CS was found for isometric peak torque at 1 h and 24 h post-run and for CMJ throughout the 48 h recovery period. Perceived muscle soreness was also lower when runners wore CS during trail running compared with the control condition (1 h and 24 h post-run). Specific muscle contractions during trail running (e.g., eccentric on the downhill portion) might result in more extensive muscle oscillation and soreness. Thus, CS probably reduced the perceived muscle soreness due to the higher preservation of muscle function.14 Miyamoto et al20 showed that CS promoted a smaller extent of reduction (- 6.4 ± 8.5% for CS vs. ?16.5 ± 9.0% for control) of the evoked triplet torque, after a fatiguing protocol (15 sets X 10 repetitions) of calf-raise exercise. The authors suggested that mitigation of muscle fatigue observed in their study could be related to increased venous flow velocity and prevention of the lowering of the intramuscular pH.20 Positive CS-induced benefits on muscle fatigue was also described after a soccer match. Female players of both teams (50% each team, randomly wore CS or control socks) performed tests (agility T, standing heel-rise, and YoYo Intermittent Endurance II) 48 h before (baseline) and immediately after the game. CS resulted in less match-induced fatigue for agility T-test performance (maintenance for CS and decrement in control players) and heel-rise test (both groups had a decrement on the number of repetitions, but higher in control).21 In the current review, some researchers found a beneficial CS-effect on the perceived muscle soreness in lower extremities after the following exercises: high-intensity continuous 10 km road-running,10 15.6 km trail in mountainous terrain,14 in the second match of soccer (72 h between the first game),17 and 24 h post 5 km time-trial.25 Overall, those studies suggested a lower perception of muscle soreness due to less extensive muscle damage (lower muscle oscillation), and better proprioception. However, we cannot rule out a potential placebo effect, once it is hard to control such bias due to the nature of compressive CS versus control socks. CS, Other Potential Benefits, and Final Considerations Besides performance, muscle soreness, and muscle function indicators, 15 out of the 21 studies selected in this review presented other variables influenced by CS: lower blood lactate levels,13,22,23 and fibrinolytic activity,29 higher oxygen saturation,19 after the exercise protocol (recovery). Also, lower cardiac stress during exercise has been found.26 Mitigation of exercise-induced muscle damage is a possible effect according to authors that found benefit from wearing CS in this review. However, none of them measured blood markers of muscle damage (e.g., creatine kinase - CK, lactate dehydrogenase - LDH). Curiously, only three studies measured such markers after-exercise: a marathon race,12 a 15.6 km trail-running,14 and half-ironman triathlon competition,16 and found no effect from CS. The lack of measurements of muscle damage markers on several studies herein included may be due to the experimental design and the fact of “only” wearing the CS during the exercise (i.e., more focus on performance than recovery). Longer time-points of measurement after the activity (e.g., time-course of CK for at least 24 h after-exercise) could be necessary to detect a significant change in CK,38 for example. Finally, we highlight that in a real-world scenario, athletes probably will not use a promising ergogenic aid to improve performance (e.g., CS) only once, as the majority of studies included here. Athletes would perhaps try it in a couple of training session and one competition before to make a final decision. Also, in practical terms, athletes usually may combine different strategies to improve performance and later recovery, such as ischemic preconditioning,39,40 myofascial release, and cold water immersion.41 Currently, the effects of such strategies (isolated or combined) with CS are unknown. Therefore, the interpretation of our findings should have in mind “to see also the forest, not just the leaf”.
Дата Публикации: 26-11-21
A NONELASTIC RUBBER STRIP DRAIN
Описание: A NONELASTIC RUBBER STRIP DRAIN The use of doubled strips of rubber dam material for drains has become general in this clinic, especially for wounds that do not require irrigation. These have been found superior to tubing and the ordinary type of cigaret wicks because they are nonirritating to the wound and the capacity of the drain is increased as a result of the capillarity derived from the two opposed surfaces of the rubber dam material. On removal, these drains leave very little deformity in the tissue and they do not tend to plug the wound, as do wick or tube drains frequently. This type of material has the fault of stretching considerably and of sometimes breaking, a portion being left within the wound. To obviate this we have strengthened strips of rubber dam material by running a seam down the center with a sewing machine. This makes the rubber nonelastic and adds sufficiently to its tensile The proper assembly of underground precast concrete structures is often critical in the construction of underground structures. In particular, interfacial waterproofing between precast concrete segments is a key factor influencing use, safety, and life span. Current practice is to incorporate waterproofing rubber strips in the design. During the installation process, compressive stress is applied to the strip by post-tensioning to achieve performance. For this paper, lateral constraint compression tests were carried out on composite rubber seal strips that utilize putty. Special waterproofing and sealing test devices were designed to investigate corresponding relationships between water pressure and compressive stress (or strain). A relationship between water resistance pressure and compression stress and strain of the putty-based composite rubber strip was proposed based on the series tests and the control target of the minimum compression strain of the putty composite rubber strip was then suggested. Finally, full-scale waterproofing tests on tunnel joints were conducted. The experimental results provide a scientific reference for the engineering application and design of composite sealing rubber strips putty for underground post-tensioned precast concrete structures. Waterproofing is typically a key design goal for underground precast concrete structures (Ossai 2017). For modern tunnel structures, segments often require casting of high performance concrete with very low permeability (DAUB 2013). Therefore, the primary possible leakage point considered is the segmental joint (Yurkevich 1995; Lee and Ge 2001; Henn 2010; Wang et al. 2011; Wu et al. 2014; Fang et al. 2015; Soltani et al. 2018). For tunnel lining, one of the most significant factors impacting the overall behavior and structure response was the existence of the segmental joints for precast concrete units (Wood 1975; Koyama 2003). Due to the underground environment, repair after the leakage in the structure is very difficult. In general, design service life for underground structures ranges from 75 to 100 years. Structures within urban underground tunnel networks tend to deform due to the long-term dynamic load and impacts associated with surrounding buildings. Under working conditions, the largest deformation was frequently observed and entered into failure state at the joint (B?er et al. 2014; Huang et al. 2015; Hong et al. 2016). Therefore, waterproofing materials need to accommodate structural deformation. In present concrete construction, elastic rubber strips in sealing and waterproofing joints of assembling segments have been commonly used. For underground concrete structures, standard design for sealing joints uses Ethylene-Propylene-Diene Monomer (EPDM) polymer rubber strips arranged circumferentially on the end faces of the segment (Ding et al. 2017). Putty-based composite rubber strips have great viscosity and elasticity, which can compensate to a certain degree for the adverse effect of the interface defects at joints. To evaluate the waterproofing ability at joints, special attention is directed to the sealant behavior of the EPDM sealing strips. A time-dependent constitutive model is proposed to assess the long-term waterproof ability of EPDM rubber used in segmental joints (Shi et al. 2015). At present, there are few requirements for rubber strips in the design specifications, and there is limited understanding of the relationship between applied forces and waterproofing performance. In addition, precast concrete structures incorporate a groove at the joint interface for the rubber strip positioning (Hu et al. 2009). The type of groove at the joint interface can limit extruded profile epdm rubber seal strip lateral deformation, which can increase pressure on the strip and improve waterproofing ability. The various types of grooves offer different degrees of constraint. Therefore, mechanical properties of rubber strips along with groove design at precast concrete structure joints are key elements in waterproof design. The joint open width is also regarded as a key performance indicator, since it is the weakest part of the shield segmental lining (Liao et al. 2008; Zhang et al. 2015). As the weakest and vulnerable point in the segmental lining, joints have been investigated in experiments (Ding et al. 2013; Liu et al. 2015; Kiani et al. 2016), numerical analyses (Ding et al. 2004; Teachavorasinskun and Chub-uppakarn 2010) and case studies (Jun 2011; Basnet and Panthi 2018). Testing apparatus was designed to accurately monitor water leakage pressure of segmental joints under various combinations of opening and offsets (Ding et al. 2017). Molins and Arnau (2011) presented an in situ load test and 3D numerical simulation on a full-scale segmental lining for the Barcelona metro line. According to a case study in Shanghai, Huang et al. (2017) perceived that longitudinal joints of the metro tunnel have large open widths and lose waterproofing when disrupted by unexpected surcharges. In this paper, mechanical tests for compressive stress and strain of putty-based composite rubber strips along with waterproofing performance tests at the interface between putty-based composite rubber strips and concrete are conducted. These tests investigate influence of strip compressive force and the joint stretching value on waterproofing of sealing rubber strips. It attempts to establish a design model and proposed control target for mechanical and waterproofing properties of this new type of rubber strip. Waterproofing test of a full-scale tunnel joint is carried out. The research work of this paper provides a scientific reference for the engineering application and design of composite sealing rubber strips with putty for underground post-tensioned precast concrete structures. The putty-based composite silicone weather stripping extruded rubber strip was made up of Ethylene-Propylene-Diene Monomer polymer rubber (EPDM foam strip) and the external composite layer (putty paste) of high viscosity reactive polymer cement (butyl rubber). The primary reason for use of the composite was to take advantage of the external putty-based material’s properties of viscosity and superplasticity, which can heal mesoscopic cracks and defects on the surface of concrete structures to improve interface waterproof ability. Cross section dimensions and picture of the rubber strip are shown in Fig. 1. Figure 2 displays the lateral confinement loading test device, which is composed of two parts: convex shape of the upper part and concave shape of the lower part. The inner and outer diameter of the annular groove was 170 mm and 220 mm, respectively. The upper part has protrusion that squeezes the strip, and the annular groove is set at the lower part of the device with an annular rubber strip installed in it (see Fig. 2c). The length of the EPDM foam rubber in the elastic state has 640 mm, and the compression area is 15,315 mm2. Quasi-stress control was selected for the tests. Experimental results of the putty-based composite strip under lateral confinement for compressive stress and displacement are provided in Fig. 7. At the early stage of loading, the compressive stress of the composite strip gradually increased with the displacement. It was observed that the displacement dramatically increased and at the later stage of the loading when the load reached at 112.36 kN primarily maintained at 11 mm. At end of the test, the rubber strip was not crushed and the internal EPDM foam rubber after unloading almost recovered to its original shape. The maximum displacement of the putty-based composite rubber strip under lateral confinement was approximately 11 mm, which was brought on by the squeezing of the inner hole of the composite strip raising the internal pore of the EPDM rubber. The instantaneous elastic recovery during the unloading process was 85% of total deformation. The residual deformation of the composite rubber strip was gradually recovered to its original state with time. Eventually, the rubber strip was not damaged. The deformation recovery of the inner elastic material to its original shape can partly drive unrecoverable external putty material. In the loading process, the two end faces of the rubber sealing strip weatherstrip for window were partially extruded upon loading, since they were not restrained at the end face (see Fig. 8). When maximum deformation was reached, the upper and lower parts of the concrete were in contact with each other. There was an inflection point in the curves of the rubber strip in the two different grooves, as presented in Fig. 10. Before the point, the internal pore and middle hole of the sealing strip were not tightly compressed signifying that the compression strain increased gradually with compressive stress. Moreover, the relationship between compressive stress and compression strain for the two different sizes of groove were almost the same before the inflection point. At the inflection point, the central hole of sealing strip and the pore of foam rubber were completely compressed. The whole strip was so dense that the compressive force increased sharply with the compression strain. The compressive stresses of the sealing strip in the two different grooves at the inflection points were almost the same and their corresponding compression strain differed by roughly 20%. In the early stage of compression, the compression moduli of the Waterproof Rubber Seal Strip Gasket were almost the same under the two groove constraints. In the later stage of loading, the compression stress of 6 mm depth of groove was greater than that of 4 mm depth under the same compression strain, and the compressive strain of the 4 mm depth of groove was greater than that of the 6 mm depth of groove under the same stress. This was mainly attributed to the difference in the constraint degree of the groove to the strip at the later stage of loading. In the final stage, the two compression interfaces of the 6 mm depth specimens were close in contact with each other. The remaining space at the joint was rather small, and there was no compression space. However, there was still a large space between the two interfaces of the 4 mm deep specimens. This was mainly due to the sum of the strip deformation and groove depth limit. The bilinear outsourced line was taken as an approximate stress-deformation relation model as shown in Eq The tests started with two culverts gradually assembled in place. After initial post-tensioning, dial gauges were installed inside the culverts to measure joint space variations in the process of post-tensioning. Simultaneously, the strains on the post-tensioning steel bars were recorded. The water injection pump and water pressure gauges at the lower part of the water injection hole of the box culvert were installed. After the steel bars were set in the duct, the conductor was run through the perforated sheet. The sheet was tightly attached to the concrete surface and bolts fastened. Table 2 provides experimental results of the post-tensioning process. The upper and lower prestressed steel bars were tensioned at the same time, otherwise the friction resulted in the vertical location due to the friction at the bottom so that the two tendons were employed. Upon completion of a post-tensioning cycle, the gap change and steel strain were measured. The bolts were then fastened. The maximum tension force was 180 kN. During the post-tensioning process, strain of steel bars varied linearly, indicating that the post-tensioned steel bars were in the elastic state with strain close to the theoretical value. In order to investigate the waterproofing performance of the putty-based composite rubber, mechanical behavior tests using rubber strip and waterproofing performance tests of the interface between the strip and precast concrete were performed.
Дата Публикации: 26-11-21
Printed Circuit Boards
Описание: Printed Circuit Boards OrCAD PCB Editor is based on Allegro PCB Editor, so this book will be useful to new Allegro printed circuit boards Editor users as well. Allegro PCB Editor is a powerful, full-featured design tool. While OrCAD PCB Editor has inherited many of those features, including a common file format, it does not possess all of the capabilities available to the Allegro PCB tiers, such as Allegro High-Speed Option, Analog/RF Option, FPGA System Planner, Design Planning, and Miniaturization Option. Consequently most of the basic tools and features are described here, but only a few of the more-advanced tools are covered, as outlined later. PC board traces must be sized appropriately (both in width and thickness, or copper weight10) to carry the current that you need without excessive temperature rise. A rule of thumb is that a 10-mil-wide, 1-ounce PC board trace can carry in excess of 500 mA with a 20 °C temperature rise above ambient. PC board copper weight vs. trace thickness is shown in Table 15.5. An estimate of the current-carrying capability for 20 °C temperature rise of PC board traces is shown in Figure 15.12. The fusing current (Figure 15.13) for PC board traces is significantly higher. OK – So What’s a Printed Circuit Board? I’ve just mentioned a printed circuit board, but what exactly is a printed circuit board? Well, look inside any modern electronics appliance (television, computer, mobile phone, etc.) or even many electrical appliances (washing machine, iron, kettle, etc.) and you’ll see a printed circuit board – often known by the multilayer PCB. A printed circuit board is a thin baseboard (about 1.5 mm) of insulating material such as resin-bonded paper or fiberglass, with an even thinner layer of copper (about 0.2 mm) on one or both surfaces. (If copper is only on one surface it’s then known as single-sided printed circuit board; if copper is on both surfaces it’s known as double-sided printed circuit board.) The copper on the surface of a printed circuit board has been printed as a circuit (yes, OK, that’s why it’s called printed circuit board – geddit?), so that components on the printed circuit board can be soldered to the copper, and thus be connected to other components similarly soldered. Photo 12.1 shows a fairly modern printed circuit board to show you what they look like. The printed circuit board shown is quite a complex one, with hundreds of components – from a computer actually – but the printed circuit board in a washing machine, say, may only hold a handful of components. Photo 12.2 shows how the copper on a printed circuit board comprises a pattern of copper – sometimes called the copper track – rather than a solid layer. This pattern or track is the key to making connections between components. PCB design begins with an insulating base and adds metal tracks for electrical interconnect and the placement of suitable electronic components to define and create an electronic circuit that performs a required set of functions. The term printed isn’t exactly an accurate description of how the copper on the surface of a printed circuit board is formed. In fact, all printed circuit boards start life with a complete layer of copper on one or both sides of the insulating board. Then, unwanted copper is removed from the board, leaving the wanted copper pattern behind. Typically, this copper removal is usually – though not always – done by etching the copper away using strong chemicals. Figure 12.1 shows a cross-section of a simple printed circuit board. In it you can see the insulating board, the copper track, and the holes for component leads. Components fit to the printed circuit quite easily. Their leads are inserted through the board holes, and are then soldered to the copper track. Figure 12.2 shows how this works. In terms of the amateur enthusiast in electronics, simple (and relatively inexpensive) hand-tools are all that are required in this soldering process – we’ll look at these, and how to use them, later. Initially, a design specification (document) is written that identifies the required functionality of the thick copper PCB. From this, the designer creates the circuit design, which is entered into the PCB design tools. ? The design schematic is analyzed through simulation using a suitably defined test stimulus, and the operation of the design is verified. If the design does not meet the required specification, then either the design must be modified, or in extreme cases, the design specification must be changed. ? When the design schematic is complete, the PCB layout is created, taking into account layout directives (set by the particular design project) and the manufacturing process design rules. ? On successful completion of the layout, it undergoes analysis by (i) resimulating the schematic design to account for the track parasitic components (usually the parasitic capacitance is used), and (ii) using specially designed signal integrity tools to confirm that the circuit design on the PCB will function correctly. If not, the design layout, schematic, or specification will require modification. When all steps to layout have been completed, the design is ready for submission for manufacture. 1.2 EMC on the Printed Circuit Board Almost every printed circuit board (PCB) is different and completely application specific. Even within similar products the PCB can be different, for example open two PCs from different manufacturers, with the same processor, clock speed, keyboard interface, etc., the actual PCB layout will be different. This diversity means that every high tg PCB has a unique level of EMC performance, so what can possibly be done to ensure that this is within certain limits? It should not surprise circuit designers that the layout of the PCB can have a significant effect on the EMC performance of a system, usually more so than the actual choice of components. Consequently, PCB layout is one of the most critical areas of consideration for design to meet EMC regulations. The fact that there are so many different PCB designs in existence is a testimony to the low cost of producing a PCB, but relaying a complete PCB because of poor layout design causes significant increases in costs not present in the actual material price of the board. Relaying a PCB will create a delay in time to market, hence lost sales revenue. New PCB layouts or changes usually entail new solder masks, reprogramming component placement machines, rewriting the production instructions, etc., hence cost may not be present in the final product part cost, but in the development and production overhead. Although a significant factor in overall EMC performance, the recommendations for minimising the effect of PCB layout on EMC are general good PCB design practices. The cost of implementing these recommendations is solely in the time taken to ensure that these good design practices are implemented, vigilance and experience are the two main requirements, not necessarily new design software or extensive retraining. Printed circuit boards (PCBs) are by far the most common method of assembling modern electronic circuits. They comprise a sandwich of one or more insulating layers and one or more copper layers which contain the signal traces and the powers and grounds; the design of the layout of PCBs can be as demanding as the design of the electrical circuit. Most modern systems consist of multilayer boards of anywhere up to eight layers (or sometimes even more). Traditionally, components were mounted on the top layer in holes which extended through all layers. These are referred to as “through-hole” components. More recently, with the near universal adoption of surface mount components, you commonly find components mounted on both the top and the bottom layers. The design of the PCB can be as important as the circuit design to the overall performance of the final system. We shall discuss in this chapter the partitioning of the circuitry, the problem of interconnecting traces, parasitic components, grounding schemes, and decoupling. All of these are important in the success of a total design. PCB effects that are harmful to precision circuit performance include leakage resistances, IR voltage drops in trace foils, vias, and ground planes, the influence of stray capacitance, and dielectric absorption (DA). In addition, the tendency of PCBs to absorb atmospheric moisture (hygroscopicity) means that changes in humidity often cause the contributions of some parasitic effects to vary from day to day. In general, PCB effects can be divided into two broad categories—those that most noticeably affect the static or DC operation of the circuit, and those that most noticeably affect dynamic or AC circuit operation, especially at high frequencies. Another very broad area of high frequency PCB design is the topic of grounding. Grounding is a problem area in itself for all analog and mixed-signal designs, and it can be said that simply implementing a PCB-based circuit does not change the fact that proper techniques are required. Fortunately, certain principles of quality grounding, namely the use of ground planes, are intrinsic to the PCB environment. This factor is one of the more significant advantages to PCB-based analog designs, and appreciable discussion in this section is focused on this issue. Some other aspects of grounding that must be managed include the control of spurious ground and signal return voltages that can degrade performance. These voltages can be due to external signal coupling, common currents, or simply excessive IR drops in ground conductors. Proper conductor routing and sizing, as well as differential signal-handling and ground isolation techniques enable control of such parasitic voltages. One final area of grounding to be discussed is grounding appropriate for a mixed-signal, analog/digital environment. Indeed, the single issue of quality grounding can influence the entire layout philosophy of a high performance mixed-signal PCB design—as it well should. Function of OrCAD PCB Editor in the printed circuit board design process PCB Editor is used to design the PCB by generating a digital description of the board layers for photoplotters and CNC machines, which are used to manufacture the boards. Separate layers are used for routing copper traces on the top, bottom, and all inner layers; drill hole sizes and locations; soldermasks; silk screens; solder paste; part placement; and board dimensions. These layers are not all portrayed identically in PCB Editor. Some of the layers are shown from a positive perspective, meaning what you see with the software is what is placed onto the board, while other layers are shown from a negative perspective, meaning what you see with the software is what is removed from the board. The layers represented in the positive view are the board outline, routed copper, silk screens, solder paste, and assembly information. The layers represented in the negative view are drill holes and soldermasks. Copper plane layers are handled in a special way, as described next. Fig. 1.17 shows routed layers (top and bottom and an inner, for example) that PCB Editor shows in the positive perspective. The background is black and the traces and pads on each layer are a different color to make it easier to keep track of visually. The drill holes are not shown because, as mentioned already, the drilling process is a distinct step performed at a specific time during the manufacturing process. PCBs usually contain epoxy resin, fiberglass, copper, nickel, iron, aluminum and a certain amount of precious metals such as gold and silver; those materials and metals along with electronic parts are attached to the board by a solder containing lead and tin. The main material composition of PCBs was determined and is shown in Table 13.1. From the table, the composition of metals, ceramic and plastics could reach 40%, 30% and 30%, respectively. Further, the concentrations of precious metals in waste PCBs are richer than in natural ores, which makes their recycling important from both economic and environmental perspectives. Table 13.2 shows the average content and value ratio of different metals in PCBs. One can see that Au, Cu, Pd and Ag account for nearly all of the economic material value in waste PCBs. Therefore, PCB recycling focuses on recovering these metals above all else. For the technology and engineering of very complex boards, the United States, the United Kingdom, Germany and France still have a competitive advantage. There is every reason to believe that the advantage will soon be lost to Asia. Asia produces three-fourths of the world’s PCBs, with over 1000 manufacturers in China alone. The PCB industry, like the larger electronics industry, has always had a global component. Only in the past four years, however, has the US manufacturing base faced a serious decline. In 2003, the United States produced 15% of the world’s PCBs, trailing Japan, the largest producer at 29%, and China, the second largest at 17%. Taiwan was the fourth largest producer at 13%. Europe produced only 10%, and South Korea 8%. No American company is now among the top ten manufacturers of PCBs. China has overtaken Japan as the leader in PCB production and is forecast to produce $10.6 billion worth of PCBs, accounting for 25% of the world total (LaDou, 2006).
Дата Публикации: 26-11-21
Benefits of Playground Equipment
Описание: Benefits of Playground Equipment A playground is more than swings, slides and a means to entertain children. The type of play that happens on a playground represents one of the more important parts of a child’s development. Playgrounds are an essential element to the health and development of the mind and body. Playgrounds provide opportunities for children to practice a range of social, emotional, physical and mental skills. By understanding the benefits of adding stimulating and challenging outdoor playground equipment to your playground, you can increase the value of play. A well-designed playground entices children to play and teaches key developmental skills. Playground activities like swinging, climbing and sliding may appear to be "just fun" on the outside, but initiate important body systems to develop and function properly. The movements children perform on a playground build both gross and fine motor skills, along with core strength. Playground play also enhances the vestibular system — the sensory system that controls balance and coordination — and develops better body awareness. Self-led exploration on sensory play panels help children to further develop their senses. Our high-touch panels provide multiple ways to grow cognitive, tactile, sensory/motor, emotional/social and language skills, and invite children to play with each other and use their imaginations. Music Children can explore the power or rhythm, experience subtle shifts in tone, and discover the many ways individual sounds can be creatively combined through our collection of chimes, metallophones and drums. A playground provides the environment needed for children to engage in elements that develop key cognitive, social and physical skills. How children play, or their patterns of play, reinforce the importance of having a mixture of indoor playground equipment that encourages an assortment of play behaviors. In our whitepaper, Shaped by Play: How Play Types Impact Development, we discuss the findings of an observational study by the University of Minnesota Institute of Child Development that looked at how play spaces shape a child's development. The study suggests that different playground components facilitate different patterns of play and therefore reinforce different developmental skills. In the study, some components—like the overhead ladders and more complex rope climbers—seemed to attract older children and facilitate independent gross motor play. Sometimes children engaged in group games (e.g., tag) or simply talked to one another as they played (e.g., while swinging side-by-side). Other times, they participated in collaborative activities like pushing one another on the swings or working together to spin on the OmniSpin? Spinner. Play involving gross motor skills like custom climbers, rope climbers, overhead ladders, rock areas and slides occupied nearly half of kids' playground time. These are active play elements and in contrast to components that are designed to encourage sensory exploration (e.g., the Smart Play? Motion play structure) or that allow children to sit while someone else operates the equipment (e.g., the swings or We-saw?). When children engage in activities that build and develop gross motor skills they are building upper-body, lower-body and core strength, it can also increase heart rate and improve cardiovascular health, agility, balance, and hand-eye coordination. Additional Skills Supported by Play Patterns on a Playground Creativity is encouraged when children use child playground set as the basis for imaginative games. A child's imagination turns a climbing tower into a spaceship or boat. Their play morphs and adjusts to their skill level and they create an obstacle course or climb on the outside of a Netplex? playstructure instead of the inside to increase difficulty. Collaboration and cooperation can be encouraged by specific components that require children to work together. Slides or our ZipKrooz? zipline structures require turn-taking and communication. Our Global Motion? and seesaws also encourage collaboration because children can operate them as a team, some ride and some push. Sound and movement can even be utilized with Pulse? multisensory playground games to encourage collaboration in an interactive way. Problem-solving skills can be enhanced with various climbing elements. Children work to figure out how to physically navigate a piece of equipment, especially one that is new to them. Persistence can be encouraged when a child keeps trying and doesn't give up when experiencing a playground activity that is difficult such as crossing the monkey bars. Once a goal is achieved or a skill mastered, the child feels a huge sense of accomplishment and increased self-esteem from working hard to reach a goal. Playgrounds also offer the opportunity for children of different ages to learn from and help one another. Children will often copy or learn from older children or older children may help younger children—boosting them up while they were climbing, helping them on and off the equipment, encouraging them not to be scared, and offering to help them down from the top of a tall structure. These mixed-age social interactions are an important part of children's social experiences on the playground. The play patterns of children illustrate the importance of having a variety of school outdoor playground that encourages an assortment of play behaviors. Check out our many options of age-appropriate and challenging equipment or contact a Landscape Structures consultant . Most adults remember their school recess times with fondness. These opportunities to leave the constraints of the classroom behind and set out for another playground adventure are memories you cherish forever. However, today’s children are overwhelmed with an abundance of activities and fewer opportunities to enjoy outside play. Video games, TV, after-school activities and an increasing focus on academics have led to disappearing playgrounds and playtime. This reduction in free play can negatively impact the development of children. Playgrounds are essential safe spaces where children can be themselves and express their fun-loving nature while developing crucial cognitive, physical, social and emotional skills. In this post, we’ll explore why more and more child development experts are advocating for more playgrounds and the increasing importance of parks and playgrounds. Playgrounds are safe spaces where kids develop crucial physical, social, emotional and imaginative skills. In this article, we’ll take an in-depth look at how a child’s development benefits from playing on the playground. Learning Through Play You can’t have a playground without play. To put it simply, play is a spontaneous activity children engage in to have fun. Experts in a variety of fields including psychology, biology, health and education have conducted a multitude of studies on the concept of childhood play all proving the same critical fact — play is an essential aspect of learning. Play is fueled by a child’s curiosity. As a child grows, their play becomes more complex. Without being able to play, children’s ability to develop and learn is stunted. Just as eating and sleeping are essential to a child’s health, so too is play. Playgrounds are the perfect place for children to engage in free play. Structured play — including sports or organized activities — differs from free play. When kids are on the playground, different structures and spaces give them the freedom to choose how they want to play. They can explore their own natural tendencies, interact with a broader range of age groups and awaken their creative instincts. When you watch children on a playground, you’ll soon see that although they’re having fun, they’re definitely getting a workout. The CDC recommends children should have at least 60 minutes of moderate to vigorous physical activity every day — and the playground is the perfect place to get this done. Plus, when kids get into the habit of exercising and see it as an enjoyable experience, it encourages them to remain active as they get older. Playgrounds are a vital aspect of healthy development, providing a place for children to get a full-body workout, including exercises that strengthen their arms, legs, torso and so on. From the cardiovascular system to the circulatory system, each is nurtured and benefited through vigorous play. Children see a vast variety of physical benefits through preschool outdoor playground: Improved flexibility and balance Development of overall motor skills, dexterity and hand-eye coordination Opportunities to learn how to control their movement Improved instincts Promotion of healthy heart and lung function Stronger muscles Improved immune function Lowered risk of obesity and diabetes When children spend time on the playgrounds, they learn diverse skills and test their limits by trying out the various equipment. Slides, swings, climbers and more encourage kids to develop their agility, speed, strength, balance and coordination. Playgrounds are not generally a solitary activity. Whenever you visit a playground, other kids are bound to be there. When children meet other kids on the playground, it teaches them important lessons about social norms and how to interact with others, all of which will come in handy in adult relationships and their future workplace. Learned social skills include: The physical and social benefits of play are more obvious. However, there are also subtle emotional changes in your child’s wellbeing that may not be as recognizable, yet are still vitally important. Physical activity and unstructured playtime on a playground serve as a healthy way to help children deal with their emotions and reduce stress levels. Not only can play serve as a distraction from their problems, but happiness is a natural byproduct of outdoor activities. Children experience many other positive emotional impacts when they’re allowed the freedom to play on a playground. Playground play benefits children because it: Boosts self-confidence and self-esteem as they master challenging playground structures Allows them to retain a sense of control unavailable in many other parts of their lives Lowers tendencies to misbehave or bully, as kids’ attention is diverted with more positive activities Teaches them how to deal with challenges in a healthy way Kids do more than slide, swing and climb when on a playground. Just listen to the conversations, and you’ll realize a variety of other make-believe games are taking place. Imaginary play is a given whenever kids are on the playground. When children use their imagination and play make-believe, it teaches them social roles. Creativity also fosters a child’s ability to problem-solve and develop their personality. By using their imagination, kids can try out different ideas and identities. This helps them construct a strong sense of self, as they discover their likes, dislikes and beliefs. Although developing self-identity will continue throughout their young life, the foundation begins with these innocent make-believe activities on the playground. Makes Education More Fun When a child’s school has a playground, these short breaks allow kids freedom and fun, which, in turn, makes the educational experience more fun. In fact, researchers now understand the importance of playgrounds in schools and how they have an important impact on a child’s ability to learn and develop. Opportunities for play also have an effect on children’s attendance rate at the primary school level. When a child knows there will be opportunities to let loose, they often find it easier to listen and learn in the classroom environment.
Дата Публикации: 26-11-21
What are Membrane Switches?
Описание: What are Membrane Switches? Membrane switches are a type of human-machine interface characterized by being constructed from several layers of plastic films or other flexible materials. Conductive materials and graphic inks are printed or laminated onto the surface of these plastic films. They function by temporarily closing or opening an electric circuit. The compact and efficient construction of membrane switches makes them suitable for a vast array of applications such as household appliances and industrial equipment interfaces. Membrane switches have been around for about five decades. In the early 1970s, the first membrane keypads were introduced. They were made up of polycarbonate plastic films printed with copper or silver infused ink creating the electronic circuit. These were composed of two conductive layers with one spacer in between. The products were inexpensive but threatened by problems such as degradation and cracking of the polycarbonate film and missing tactile feedback. The next iteration solved the durability and quality-of-life issue by changing the plastic film into polyester and adding metal domes into the design. However, membrane switches have not been readily adopted since, during that time, the huge personal computer market was dominated by mechanical keyboards. Mechanical keyboards were preferred due to their more tactile feedback. Come the 1990s, thinner keyboard keys and membrane switches were used to make more compact and quieter keyboards. By that time, smaller electronic devices were the future of technology. The emergence of appliances and equipment with small electronic components further elevated the need for membrane switches. Today, the global membrane switch market has a market size of approximately $4.2 billion in 2015 and is expected to grow to $13 billion by 2025. Membrane switches are extensively used in industrial, medical, and consumer goods applications. Membrane switches are extensively used in a variety of applications may it be domestic, commercial, or industrial. There are other types and forms of user interfaces such as touchscreens, keyboards, switches, and selector knobs. Membrane switches are preferred because of their compact profile, simple construction, reliability, resistance to harmful elements, and low cost. These advantages are further elaborated below. Thin and compact profile: Each plastic layer of a OCA membrane switch can have a thickness of about 0.005 to 0.040 inches. They typically have three to six layers depending on the design. Even applying the conductive and graphic inks and installing other components such as the metallic domes and EMF screens, the final thickness still results in only a fraction of an inch. This makes them suitable for household appliances and equipment controllers with small form factors. Simple graphic interface construction: The preparation process for the graphic overlay is a straightforward process. The graphics design or artwork can be made from software such as AutoCAD, SolidWorks, and Adobe Illustrator. After creating the artwork, it is digitally printed onto the overlay. There is no need for additional machining processes such as embossing, engraving, or stamping. These additional processes are only done to improve aesthetics and tactile quality. However, digital printing is not the only method of creating graphic overlays. Screen printing is also used by many companies in the industry. Highly resistant against external elements: One popular advantage of membrane switches is their sealed construction. Sealing is achieved by pressure-sensitive adhesives or heat seals. Plastics such as polyesters and polycarbonates provide a sufficient barrier against moisture and chemicals, without reducing the visibility of the artwork. There are no cavities where hazardous liquids or gases can enter or accumulate. Membrane switches are the desired type of human-machine interface for devices with high protection ratings. Easy cleaning and maintenance: Since there are no cavities where water, dust, and contaminants can accumulate, membrane switches are easy to clean. The overlay can easily be wiped to remove any dirt. Their complete seal allows them to be subjected to equipment washdowns without any risk of damaging the control circuit. Moreover, because of very few moving parts, membrane switches require almost no maintenance. Sufficient tactile feedback: When compared to touch screen interfaces, membrane switches have an advantage because of their capability to provide tactile feedback. Tactile feedback is useful in applications where there is a risk of equipment malfunction or shutdown. This is possible when the wrong sequence of keys is pressed. Tactile feedback helps the operator know that the key is pressed. Shielding from environments with high electromagnetic interference: Unwanted electromagnetic frequencies and electrostatic discharges are potential threats to electronic devices. These can cause electronics to malfunction, especially controllers that use low power circuits. A layer of EMF shielding can be added to membrane switches by printing a grid or mesh using conductive ink. The EMF shield can be made without any discontinuity which defeats the purpose or lowers the efficiency of the shielding. Lower cost: Because of its small blueprint and readily available construction materials, membrane switches are more economical than touch screens or mechanical interfaces. They are made from lesser parts that can be easily assembled by basic processes such as applying pressure-sensitive adhesives or heat sealing. Its low cost makes it the desired interface for consumer goods or household appliances. Membrane switches are composed of several components in the form of layers that are assembled using pressure-sensitive adhesives or heat sealing films. Its main parts are an overlay containing the graphic elements; a circuit that includes the conductive tracks, metal domes, circuit tail, and terminals; and a spacer that maintains a break between the switch contacts. Overlay: Also known as top or graphic overlay, the overlay is the outermost layer of the elevator program control membrane switch. Since this layer is on the exposed side of the membrane switch, it is made from materials that have good flexibility, clarity, durability, chemical resistance, and barrier properties. There are two common materials used for making the overlay, Polyester: This is a plastic material commonly known as polyethylene terephthalate (PET). Polyester is known for its clarity, flexibility, and chemical resistance. Its flexibility allows it to be more durable than other materials, especially when used on switches with tactile feedback. To achieve good resistance to puncture and tearing, the film is made through a process called biaxial orientation. Polycarbonate: Polycarbonate is the desired film for industrial applications due to its inherent flame-retarding property and abrasion resistance even without additional surface treatments such as hard-coating. Polycarbonate is also more economical and easier to process than polyester. The film can be produced and processed quickly without worrying about shrinking and warping as experienced in working with polyester films. Other materials that can be used as overlays are acrylic, vinyl, and PVC. Graphics can be printed on the reverse side or front side. Reverse side or sub-surface printing is the more common method since it produces longer-lasting prints. The overlay plastic film protects the graphics from abrasion and chemical attack. Front side or top-surface printing, on the other hand, is done to create various features such as selective texture and windows. Domes: Domes are the components that provide tactile feedback. They can be made from metal or plastic. Metal Domes: Metal domes are made from stainless steel or copper alloys held in place by a dome retainer layer or a spacer layer. Aside from providing tactile feedback, metal domes also function as a part of the circuit. When pressed, the metal dome shorts the open contacts of the switch. Plastic or Poly Domes: Plastic domes are typically made from polyester because of their flexibility; hence "poly" domes. Poly domes have a layer of their own. In some designs, the poly dome layer can also become the overlay or graphics layer. The poly dome layer can be seen as a polyester film with domes or blister-like features. At the concave side of the dome is a printed conductive ink that completes the circuit when the button is pressed. Retainer Layer: The retainer layer with the primary function of holding the metal domes in place. This is commonly made from polyester film, similar to the poly dome layer. Spacer Layer: This layer is used to create a break in contact between the two conductors of the switch. This allows the switch to have its open position. In some designs of membrane switch with led, it can also act as a retainer to keep the metallic dome in place. The spacer layer has channels between the empty cavities or the sides of the keypad for venting air. This prevents air from being compressed in the cavity when the key is pressed. Circuit Layer: This layer is where the conductive paths of the switch are applied. These conductive paths can be produced through two main methods: screen printing and photochemical etching. Screen Printing: This method uses a stencil containing the pattern of the circuit. Silver conductive ink is flooded on the stencil which is placed above a substrate. The substrate used is typically a polyester film. This method is used for thinner and more flexible membrane keypads. Photochemical Etching: In contrast, this method uses a copper laminated substrate which is selectively patterned through photolithography and chemical etching. The result can be a printed circuit board (PCB) or a flexible printed circuit (FPC) that is thicker and more durable than screen-printed membrane keypads. Two-layer Circuit: In this design, the circuit layer is separated into two: the upper circuit and the lower circuit. Each circuit layer contains a conductive path that leads into or goes out of the switch. The two layers are separated by the spacer layer. When a switch is pressed, the upper circuit deflects and touches the lower circuit completing the circuit. Single-layer or Single-sided Circuit: As the name suggests, a single-layer switch has only one circuit layer. A break in the circuit is created by a discontinuity in the conductive path that is printed onto the substrate. The circuit is completed using a metallic dome or conductive ink printed on the reverse side of a plastic dome. When a key is pressed, the dome flattens against the circuit layer creating a single conductive path. Circuit Tail: The circuit tail is the part of the circuit that connects the membrane switch to the control unit of the machine. It is seen as a flat, flexible ribbon composed of several conductive tracks printed on a polyester strip. At the end of the circuit tail are standard connectors that match with the termination block of the control unit. Some common connector options are plain header, latching header, or solder tabs. The circuit tail can also be a ZIF (zero insertion force) style which basically differs on the force applied between the circuit tail and the control unit terminals. ZIF is used for more delicate circuits where the control unit terminals are weak and easy to damage. Mounting Adhesive: This is placed at the back of the hole filling membrane switch to facilitate assembly with the control unit. It is usually specified according to its bond strength, thickness, and operating temperature. The material used is an elastomeric compound which is usually composed of high strength or modified acrylic. Before selecting which membrane switch to use or supplier to order from, it is best to gain an understanding of its specifications and features. And like any other electronic or electrical device, it is important to fully determine the characteristics of the system where the interface will be installed. The electrical specifications of the membrane switch must be applicable to the system to prevent any electrical shorting or premature failure of the membrane switch or control unit. Moreover, there are other features that are worth noting such as coatings, backlighting, precision cutting, and so on.
Дата Публикации: 26-11-21
Study on two-stage mounting systems having distributed intermediate mass
Описание: Study on two-stage mounting systems having distributed intermediate mass The design logic and calculation method for determining mount stiffness and damping for a Powertrain Mounting System (PMS) based on reductions of vehicle vibration and noise contributed by mounts is proposed in this paper. Firstly, the design target for a PMS with regard to vibration and noise limitations of vehicle level contributed form mounts is described. Then a vehicle model with 13 Degree of Freedoms (DOFs) is proposed, which includes 6DOFs for the powertrain, 3 DOFs for the car body and 4DOFs for the four unsprung mass, and the dynamic equation for the model is derived. Some widely used models, such as the 6 DOFs model of the powertrain for the design calculation of a PMS, the 7 DOFs model (Body’s 3 DOFs; unsprung mass’s 4 DOFs) and the 9 DOFs model (powertrain’s 6 DOFs; Body’s 3 DOFs) for ride analysis of a vehicle, are the specific cases of the presented model of 13 DOF. Thirdly, the calculation method for obtaining the vibration of seat track and evaluation point and the noise at driver right ear is presented based on the mount forces and the vibration and noise transfer functions. An optimization process is proposed to get the mount stiffness and damping based on minimization of vehicle vibration and noise, and the optimized stiffness is validated by comparing the calculated vibration and noise and limitations. In the end of this paper, the natural frequencies and mode energies for the powertrain, the body and the unsprung mass are calculated using different models and the results are compared and analyzed. Nowadays, two-stage ballast mounting system having integral intermediate mass is widely applied and researched to attenuate vibration of marine machinery equipment, while two stage mounting system having distributed intermediate mass which has the feature of lightweight and installation dimension is rarely used and studied. The theoretical models of two types of mounting systems are set up and force transmissibility rate of the two mounting systems are deduced through four-pole parameters method. A scale experimental prototype is established to test the isolation efficiency of the two-stage mounting system having distributed intermediate mass. FEMs of the two systems are established to make a comparison ascertaining the difference between the two about vibration isolation efficiency at the different frequency. The result shows that two stage mounting system having distributed intermediate mass achieve better vibration isolation efficiency and take less space than two-stage mounting system having integral intermediate mass if with equivalent intermediate mass. Two-stage mounting system having distributed intermediate mass can meet the requirements of practical projects and provides a new way for engineer to refer to when meet with machinery equipment vibration problems. Keywords: two-stage mounting system, distributed intermediate mass, integral intermediate mass. 1. Introduction In many segments of industry the trend in the past few years has been towards more complex equipment and machines, which are lighter and more compact than their predecessors and which operate at greater speeds and power ratings. To the vibration engineer this trend has meant more problems associated with vibration isolation problems: i.e., more excitation available and more components likely to be affected adversely by them so that it has become increasingly important to provide vibration isolation systems that will retain their effectiveness . Machinery ground mounting system is one of the most significant vibration and noise attenuation technology of mechanical equipment . It has been extensively believed that the intermediate mass of two-stage double pole mounting system would be better to improve isolation efficiency than one-stage mounting system . At present, two-stage mounting system having frame structure intermediate mass like raft mounting system is widely used in the field of naval vessels which have been gaining widespread attention. In practical application, the intermediate mass usually takes amount of 20-30 % of the isolated mass , but in special cases where dimensions and weight are strictly limited, this way may not be suitable. Thus, the other Machinery mounting system that is two-stage mounting system having distributed intermediate mass which takes less space would play a more important role in the field of vibration noise controlling. The simplified theoretical and finite element model of the two kinds of two-stage mounting systems are analysed in the paper. The equation of two kinds of mounting systems’ isolation effectiveness expressed by transmissibility were deduced through four-pole parameter method. A comparison between the Single Pole Mounting System to ascertain the difference about vibration isolation efficiency at different specific frequency through FEM model analysis was made. A scale experimental platform was established to test the isolation efficiency of the two-stage mounting system having distributed intermediate mass. The research results based on the calculation and analysing on the two kinds of mounting systems can provide a reference for engineer when designing mounting system for machinery equipment. 2. Mounting system theoretical model 2.1. Basic theory of four-pole parameters method The behaviour of mounting systems is complicated and extremely hard to predict because of wave effects. To depict the behaviour of system’ dynamic performance is difficult so that to simplify practical mounting system is necessary . Four–pole parameters method is an essentially simple idea and for this reason is helpful in providing a point of view . All of the pertinent properties of a system can be expressed in terms of four pole parameters which characterize only the system for which they are determined; their value is not influenced by the preceding or subsequent mechanical systems. A linear mechanical system is shown schematically in Fig. 1. The system may be comprised one or more lumped or distributed elements, or be constructed from any combination of such elements. The input side of the system vibrates sinusoidally with a velocity in response to an applied force . In turn, the output side of the system exerts a force on the input side of some further system, sharing with it a common velocity . Thus the system shown is said to have input and output terminal pairs, a force and velocity at the input terminal pair giving rise to a force and velocity at the output terminal pair, the reaction of any subsequent mechanical system being accounted for. Forces are considered positive when directed to the right . Isolators made of hard elastic material were used in the upper mount whose natural frequency were about 8 Hz and stiffness is 1.5×10e6 N/m, damping factor 0.09. Air spring was used in the lower mount whose natural frequency was about 4 Hz, stiffness is 10e6 N/m and damping factor 0.05. Intermediate mass amounts about 20 % of the total mass of the upper body including a vibration generator to simulate vibration source and rack to hold it. The vibration generator generates vibration at a precise frequency. The isolation effectiveness expressed by acceleration tested by PULSE exploited by Brüel&Kj?r was shown in Table 1. All of the measurements summarized here were obtained after post-process using Pulse Reflex, driven by1/3 octave band filtered white noise, and by measuring 1/3 octave bands. Experimental results showed that satisfactory isolation effectiveness evaluated by vibration lever difference could be obtained by using distributed intermediate mass as frame structure intermediate mass does. To compare the isolation effectiveness of two-stage mounting system having integral intermediate mass with distributed intermediate mass. FEMs of the two types of mounting system was designed based on the scale experimental prototype having distributed intermediate mass was set up through ABAQUS as is shown in Fig. 10 and Fig. 11. Q235 whose density 7800 kg/m3, elasticity modulus 200 GPa, Poisson’s ratio 0.3 was used as the material of foundation, intermediate mass and rack to install a vibration generator. The upper and lower isolators were simulated by spring with three dimensional stiffness and both ends of the spring were six degrees of freedom coupling constrained to the foundation, upper rack and intermediate mass with its actual contract area respectively. Data of isolators’ three dimensional stiffness was obtained through practical testing so that can be used as input parameters. The foundation was six degrees of freedom coupling constrained to the ground. In this paper, four-pole parameter method and numerical calculation method were used to analyse the two types of two-stage mounting systems and a scale prototype was designed to test isolation effectiveness of two-stage mounting system having distributed intermediate mass. Results showed: 1) Two-stage of mounting system having distributed intermediate mass can satisfy the criterion of practical projects in isolation efficiency over 40 dB which provide a new way for designer to choose when making mounting plan. 2) When the carport mounting system having the same intermediate mass in quality, two-stage mounting system having distributed intermediate mass would obtain better isolation efficiency. The usual frame designs, however, incorporate extended structural members which exhibit modal behaviour at acoustic frequency; thus, such frames do not act as rigid masses at these frequencies and the advantages of a two-stage mounting system are lost. In many such installations it is likely that better high-frequency isolation, plus perhaps a saving in weight, may be obtained essentially by replacing the frame with distributed compact mass which will act as rigid mass at high frequency like the two-stage mounting system having distributed intermediate mass I discussed in the paper. Further research on how the vibration isolation effectiveness fluctuate with increasing intermediate compact mass and detailed physical explanation on why would distributed intermediate mass provide as well vibration isolation effectiveness as a frame structure intermediate masa work will be continued. The vibration isolation performance of the engine mounting system can be evaluated by the transmission force. The transmission force characteristics of engine mounting system are analyzed by simulation and test. The 6-DOF model of engine mounting system is established by ADAMS software. The results of modal parameters and transmission force of engine mounting system are obtained by simulation. The force sensor is made with resistance strain gauge. The sensor is calibrated by chassis dynamometer method. The transmission force of the engine mounting system is tested under the complete vehicle condition. The test results of transmission force and acceleration transmissibility are compared. It is proved that the transmission force is more suitable to evaluate the vibration isolation performance of the mounting system when the vehicle is running at medium and high speed. This article is to find optimized placement for an active solar farm mounting system suitable for a 6-DOF bar structure with two active paths. When a sinusoidal excitation force is applied to the structure, secondary force and phase of the two active supports can be calculated mathematically. When the position changes, the magnitude and phase of the secondary forces in each path will be analyzed using simulation. If the forces applied to the two active mounting system are relatively small and the phase does not change by 180 degrees, these specific positions of paths are considered as optimized positions of the active mounting system. Based on the simulation results, criteria for selecting the location are proposed, which will be very useful for proper selection of actuators for engine mount system. In automotive industries, engine vibration isolation has been always a difficult task and due to the trend of lighter weight and higher power of vehicles, it has become a more serious problem. In order to improve the NVH performance of mounting systems, active control methodologies have been applied and many research has focused on the position of the engine mount system to optimally reduce vibration. Genetic algorithms are utilized to find the optimized locations of piezoelectric actuators and sensors for active vibration control . For different engine installation positions, vibration characteristics of heavy commercial vehicles are studied. They demonstrate how to achieve the engine isolation by arranging the engine isolator in the longitudinal direction of the powertrain . Vibration reduction of a coupled path structure with a piezoelectric laminated actuator and a rubber bearing is studied and active path interactions are quantified based on the dynamic characteristics of the passive system . However, under the same excitation conditions, the vibration reduction could be changed as the position of the movable active engine mount changes. Thus, this research will focus on optimizing the location of active elements. In this study, the experimental setup shown in Fig. 1 is prepared and its numerical analysis would be presented. Upper and lower bars are representing the vehicle engine and the sub-frame, respectively. There are two paths made of a piezo-stack actuator and a rubber mount to provide active vibration isolation between the bars. At first, a parametric model is proposed for a given laboratory experiment structure and establish a motion equation. Then, numerical simulation will be performed and the results will be analyzed to determine the criteria for selecting the best location for the mounting system.
Дата Публикации: 26-11-21
Are magnetic eyelashes worth the hype?
Описание: Are magnetic eyelashes worth the hype? False lashes can leave you in a sticky situation ... literally! If you find yourself ripping out your own lashes or tugging at leftover goo two days later, then allow me to introduce you to the concept of magnetic lashes. What makes magnetic lashes so appealing is that they're reusable, they don't require messy glue and they're less likely to rip off your natural lashes. Basically, they seem like a cool, low-maintenance version of the original, glue-on version. While there are some luxe varieties on the market (around $70), Ardell just launched a drugstore version that's a lot more affordable (at $11). Instead of two magnets (like the first-generation versions), Ardell touts that these have anywhere from three to eight smaller, virtually invisible magnets embedded end to end so it will lay down seamlessly on the lashline and won’t bulge out in the middle. The company launched both full strips as well as accents, which are placed on the outer corners of the eyes. At TODAY Style, we had to give them all a try! The brand recommends applying a layer of mascara prior to application. This gives the lashes some grip and also helps natural lashes blend in. Lashes are marked as upper and lower in each package. I don't know exactly what would happen if you mixed them up (the thought gives me shivers), so let's assume we'll all delicately and mindfully place them back in their proper home after every use. It seemed simple enough: With the top strip, you line up the outside of the lash with the outer edge of your lashline. Next, you bring the bottom lashes to meet the top and when they are close enough — click — the magnets snap together and you're golden. I won't lie, there’s definitely a learning curve. That top lash will inevitably fall on the ground, the bottom one won't snap into place, but after a few attempts, I started to get the hang of positioning both. The most satisfying part is hearing it actually click into place. Success! If you do need to realign or start over, just grab the magnets at the base of your lashline and roll your thumb and index finger in opposite directions to unlock them. Then, gently slide them off your lashes. Things seemed to be going well until ... well, until I looked in the mirror. Yikes. They are a bit too bold for me! The lashes didn't blend well with my own and I could distinctly see the magnet on the underside of the lash. If I blinked slowly enough I could feel the cold magnet on my eyeball. It's a feeling that's tough to describe, but certainly not ideal. IF YOU CONSIDER a quick swipe of mascara sufficient lash enhancement, this news may confound you, but among a growing segment of America’s female population, false lashes are a daily staple. Touted by influencers like “Shahs of Sunset” star and Lilly Lashes founder Lilly Ghalichi, fake fringes are no longer fringe, with U.S. sales reaching nearly $270 million in 2018, up 31% from 2017, according to polling firm Nielsen. Fans of fake lashes value their exaggerated, eye-opening drama, but, with their messy, irritating glue, applying them has always been a pain. The even bigger news for lash lovers: Reusable magnetic fake lashes—which attach via a thin strip of magnets at the base instead of glue—have recently come on the scene. Intriguingly, I received a kit as a gift, but after one frustrating session trying to master the tweezer-like applicator, I understood why “how to apply magnetic lashes” was Google’s top trending beauty search in 2018. The struggle to get them on has spawned a subgenre of YouTube videos offering either clever hacks or brokenhearted reviews. These polarized (and polarizing) temporary lashes consist of a set of two lash strips studded with tiny magnets that adhere to each other, sandwiching the wearer’s own upper lashes. They’re typically made of synthetic or human hair, and for a luxe option Uptown Lashes sells a mink set ($30, uptownlashes.com). Some kits, such as the one from One Two Cosmetics, are sold with a tweezer-like applicator included ($69, onetwocosmetics.com). Ardell’s popular lashes are more of a deal starting at $14 a kit, with an applicator sold separately for $4 (ardellshop.com). Some women use tweezers or their fingers to apply the lashes. Though simple in concept, the process is difficult in practice due to the magnets’ minute size and the exacting placement required. New York-based makeup artist Mary Irwin said that a magnifying mirror could help, and recommends looking down into the mirror so you can see the underside of the lash. Then, dexterous users can “gently drop the top part of the magnetic lash above the natural lash,” which is the step that requires extensive practice. However, Ms. Irwin conceded that “for everyday wear, I don’t think they’re the most practical.” Having studied online tutorials carefully and still failed to apply my own set, I would have to agree. The boom of eyelash growth serums, lash extension and curling procedures, and lengthening mascaras should prove the point—the world is obsessed with the quest to longer, fuller eyelashes. But despite all this new beauty tech, applying false eyelashes is one tried-and-true trick that makeup artists and celebrities have been using for years. And the surge of magnetic eyelashes hitting the market proves this option isn't one to ignore. Once only adhered to your natural lash with adhesive glue, mink magnetic eyelashes secure to each other, and your lash line, with tiny magnets. The latest brand to launch this type of technology is celebrated falsies brand, Ardell. According to Jadene Munson, the Global Brand Ambassador, they "feature virtually invisible magnets placed along the lash line that lock together and secure the lash along your natural lash line." This brand's full strip lashes, specifically, feature four magnets for an impressive hold, while the accent lashes feature three magnets. Basically, you are sandwiching your natural eyelashes between two strips held together with magnetic force. It's relatively simple. Each product will differ slightly, so it's best to follow the instructions on the package. First, it's often recommended to trim the lash so it'll naturally fit along your natural lash line. Then, Munson recommends applying mascara to give your eyelashes more grip. For Ardell's strip eyelashes, the next step is to lay the Upper Magnetic Lash across the top of your lash line. Then, you place the Under Magnetic Lash from the tray and place it underneath your natural lash line. Thanks to the magnets, they will lock in place. Another popular brand is One Two Cosmetics, seen above. These magnetic lashes come in full strips or half lashes to accent the outer corners. This brand's magnetic lashes also come with an applicator that looks a little like tweezers, but you can apply them with your fingers, too. The same logic applies—the upper lash is magnetically attracted to the bottom—but you can watch this short video for a visual breakdown. To remove the Ardell lashes, Munson says to gently pull them apart by lifting the top lash up and pulling the bottom one down. You can also slide the top and bottom magnets away from each other "one by one." However, you should never pull them straight off, as this could harm your natural lashes. One Two recommends using your thumb and index finger to slide them apart. RELATED: The 10 Best Eyelash Growth Serums on the Market The Best Faux Mink Magnetic Eyelashes The two brands that are creating the most buzz are One Two ($59; hsn.com) and Ardell ($8; walmart.com), both of which are reusable. When deciding between the two, consider the price-tag, and also the material used. And if you have sensitivities or allergies, this is extremely important. Ardell's are made with 100 percent human hair, while One Two's are synthetic. We should note that while they're easier to use than traditional glue-on lashes, there is still a slight learning curve. Make sure to give yourself a few test-runs before applying them for an important event. As far as options go, both of these brands offer different styles to choose from, whether it's a bold and glamorous look you're attempting to recreate, or something more subtle and natural. In the world of eyelashes, there’s always a new product or two floating around that claims to be better at giving you the longer, fuller lashes you’ve wanted. We’ve been searching for ways to enhance our eyes for centuries. Nothing frames your eyes and makes them more noticeable than a great set of soft, voluminous lashes, and we would do practically anything to get them. One of the newer beauty trends to hit the eyelash scene are magnetic eyelash strips. We admit, our curiosity was piqued when we first heard of these. How can magnets help you get longer, fuller lashes? Is it safe? Affordable? You know we’re your eyelash info insiders, so we got the scoop on magnetic lashes so you don’t have to waste your time researching them for yourself. Serums, salon treatments, and miracle lash conditions may have all made a name for themselves in the realm of lash enhancement, but the tried-and-true method of eyelash lengthening and thickening has always been the use of falsies. This is the go-to method of eye enhancement for everyone from celebrities to the coworker sitting in the cubicle next to you. Eyelash strips are the industry standard for many reasons. They’re safe. Serums with certain formulas and salon extensions come with some pretty risky side effects. Skin and iris discoloration, natural eyelash loss, and eye infection are all safety concerns for these methods of enhancement. Eyelash strips are generally well tolerated by everyone and are safe to apply and remove on a daily basis. They’re affordable. Other methods of magnetic false eyelashes enhancement can be extremely expensive. A full set of professionally applied eyelash extensions alone can be upwards of $300, and that doesn’t factor in the cost for maintenance and upkeep. Serums are not much cheaper, considering that they often cost over $100 and usually last about thirty days. Once you stop using a serum, any lash lengthening effects disappear, so if you want to continue the effect a serum can potentially offer, you’ll need to continue using it. Eyelash strips cost a fraction of the price and are reusable twelve to fifteen times. Doe Lashes cost just under $13 per pair, which means you can have glamorous lashes all month for less than it costs you to go grab brunch with your friends. They’re instant. Other lash enhancement options may take time to provide results. Eyelash serums can take up to three to four weeks before taking effect, and that growth isn’t as noticeable or remarkable as a set of false lashes. Eyelash extensions can give you instant length and volume...after a few hours in the salon chair. Get comfortable in the chair, because you’ll be headed back to the salon for “fills” every few weeks. Eyelash strips can be easily applied and removed within minutes, without any in-between or continued maintenance required. They’re DIY. You can apply false eyelash strips at home without any prior experience and get professional looking, gorgeous results right in your own bathroom or bedroom, no tipping required. Since false eyelash strips are the industry standard for eyelash enhancement, it’s no surprise companies are continually trying to change or repackage the design. Magnetic lashes are different from strip lashes in how they attach to your lash line. Traditionally, eyelash strips attach just above your natural lash line with glue or a holding gel. Glue is the most traditional method of adhering false magnetic eyelash accessories to your lids, and a great quality glue can hold your lashes in place for hours on end. Depending on the brand, they can even endure things like sweat and water. Just like some companies sell eyeliner kits, you can also get lash kits for convenience. Magnetic lashes are held in place by complete magnetic contact. Think of it as using basically invisible magnets (or smaller magnets that are compact). You will have lashes with bottom magnets and an upper magnetic lash as well. To apply magnetic lashes, you will need to invest in not only specially made eyelash strips that have tiny magnets attached to the lash band, but also a specialty iron-oxide magnetic liner. Magnetic lashes are applied by first applying a thin strip of liquid iron-oxide eyeliner on top of your natural lash line, waiting for it to dry, and then clipping the magnetic lash strip to the eyeliner using an applicator tool. Some people like to put all their items on a small tray so they don't lose anything during the application process. To remove magnetic lashes, you’ll need to pull the magnetic lash bands off, and then remove the liner. Try using your index finger and thumb for a solid grip. Some companies suggest using olive oil to remove the eyeliner, while other manufacturers carry a specialized iron oxide eyeliner removing solution. It isn’t recommended you use regular eye makeup remover, as it may not be effective in removing the liner and can be damaging to the lash band if it is exposed to a remover containing oil.
Дата Публикации: 26-11-21
Structural behavior of precast concrete wall panels due to dynamic load: A review
Описание: Structural behavior of precast concrete wall panels due to dynamic load: A review The rapid population growth and urbanization have made a massive demand for the shelter and construction materials. Masonry walls are the major component in the housing sector and it has brittle characteristics and exhibit poor performance against the uncertain loads. Further, the structure requires heavier sections for carrying the dead weight of masonry walls. The present investigations are carried out to develop a simple, lightweight and cost effective technology for replacing the existing wall systems. The lightweight concrete is developed for the construction of cement wall panel. The EPS (Expanded Polystyrene) beads of 3 mm diameter size are mixed with concrete and developed a lightweight concrete with a density 9 kN/m3. The lightweight sandwich panel is cast with a lightweight concrete inner core and ferrocement outer skins. This lightweight wall panel is tested for in-plane compression loading. A nonlinear finite element analysis with damaged plasticity model is carried out with both material and geometrical nonlinearities. The experimental and analytical results were compared. The finite element study predicted the ultimate load carrying capacity of the sandwich panel with reasonable accuracy. The present study showed that the lightweight concrete is well suitable for the lightweight sandwich wall panels. Architectural precast concrete wall panels that act as loadbearing elements in a building are both a structurally efficient and economical means o f transferring floor and roof loads through the structure and into the foundation. In many cases, this integration can also simplify construction and reduce costs. This article presents the many benefit s that ca n be derived from using loadbearing architectural precast concrete walls in buildings. Discussed herein are the various shapes and sizes of wall pane ls, major design considerations, and when loadbearing or shear wall units should be the first design choice. The role o f connections, shear walls, and the use of precast concrete as forms for cast-in-place concrete is explained. In general, the design methods and techniques presented in this article apply to buildings in both seismic and non-seismic areas. The latter part of this article shows how these design principles can be applied in practice in a variety of buildings. These examples illustrate the use of window wall panels, spandrels, and solid or sandwich wall panels as the loadbearing wall members. When all the advantages of using architectural precast concrete as loadbearing walls are added up, it makes good sense to use this structural form in building applications. An experimental study has been carried out to determine the strength and behaviour of bamboo-reinforced concrete wood texture cement wall panel under one-way in-plane action. Three full-scale bamboo-reinforced concrete wall panels were tested to fail under a uniformly distributed load applied at an eccentricity of t/6. Slenderness ratio of all wall panels was kept constant as 25 with varying aspect ratio and thinness ratio. The influence of aspect ratio and thinness ratio on the ultimate strength and behaviour of wall panel was studied. The aspect ratio of wall panels considered includes 1, 1.204 and 1.515, and thinness ratio of wall panels includes 16.5, 20.75 and 25. Based on the study, an empirical equation for predicting the ultimate load of bamboo-reinforced concrete wall panel was proposed. The effect of the earthquake resulted in the destruction of infrastructure, especially residential buildings. The construction of decent housing with an adequate level of security is a demand. Generally, the most severe damage when an earthquake occurs is wall collapse of the houses. The precast panel wall is an alternative solution in answering the needs of post-earthquake housing development, because of the fast construction time and high calculation accuracy. The behavior of structural precast concrete split rock surface wall panels designed improperly instead of following the standard or regulations will likely encounter a poor performance during an earthquake compared to those designed in accordance with the standards. The purpose of the present study is to compile the findings from previous studies of precast concrete panel walls, especially their performances in handling earthquake load. It reveals that the stability, especially in ductility, affects the performance of precast concrete panel walls. In this study, the walls of precast concrete panels are made in half scale and given dynamic loads to simulate earthquake forces. This review is expected to provide guideline of similar subsequent research. It’s no wonder demand for precast is rising, especially considering the numerous benefits structural precast panels offer — from quick installation to fire resistance. 1. Thermal insulation All elements of a well-engineered structural precast panel work together to provide a high level of insulation. Manufacturers often use a combination of concrete and EPS foam that maximizes the foam in the concrete piece, increasing insulation capabilities. A building constructed of structural precast panels may reduce energy consumption by as much as 30%. 2. Sustainable materials Quite simply, a building made with structural precast panels will consume less energy, but an idea that should be at the heart of any sustainability conversation is product life. The use of concrete dates back to Roman times and its durability is still on display all across Europe. That raw, ancient building material has remained virtually unchanged for thousands of years. Many of the materials used in precast concrete are, as a rule, locally sourced, including the cement, the coarse and fine aggregates, and the steel. 3. Long-term viability and flexibility Structural precast allows for a very modular building envelope. As business requirements change and needs evolve, an existing precast building has the flexibility to be expanded and modified. With structural precast concrete panels, you can add or remove pedestrian doors and dock doors, incorporate daylighting options, and even remove 75% of a wall. And due to its modular design, total repurposing of a precast building is entirely possible; churches can become car dealerships, warehouses can become micro-breweries… the options are only limited by a property owner’s imagination. 4. Quick installation Speed is a critical hallmark of structural precast construction. “With precast panels, you can establish a larger completed footprint in a shorter amount of time,” says George Miks, director of engineering.“If you think of a masonry wall, what they send out to the site are a bunch of blocks that have to be assembled and constructed out in the field.” When structural precast panels arrive at a job site, the pieces are ready to install. If things go smoothly out in the field, an experienced crew can install 20 to 30, 12-foot panels in a day. 5. Load-bearing capabilities and wind resistance Structural precast concrete panels are comprised of high-strength concrete and prestressed steel strand. It’s relatively routine for precast concrete wall panels have a compressive strength of approximately 7,000 PSI. You can apply loads in excess of 100,000 pounds to the panels, Miks says. “When you build steel buildings, for instance, you have to put up perimeter beams and columns and then put steel skin against it. All of that steel has to support those enclosure panels,” Miks says. “With a structural precast wall system, you don’t need any of those perimeter beams and columns. You can just tip up the panel and have the roof steel members themselves attach to the precast. That also means you’ll be spending less on steel.” Precast also stands up to Mother Nature’s wrath, shrugging off tornadoes, flying projectiles and winds up to 250 miles per hour. 6. Fire and sound ratings Concrete is obviously an effective barrier for fire; it simply doesn’t burn well. Precast concrete thin cement rammed earth wall panels are capable of providing a two- to four-hour fire rating. Precast walls also stay intact even in hot chemical fires. Warehouses often use precast wall panels as dividers to protect goods on the other side of fire-prone areas. “The more delay you can create from one side to the other, the better chance of getting people out safely without incident and also the higher probability of protecting goods and services,” Miks says. Constructing a commercial structure is a huge undertaking and a significant investment. Whether you’re charged with the growth of a company, serving your community or building a legacy of your own, precast construction is a solid, responsible option said Miks. In this paper, an optimization-based design model of precast concrete cement rustic decoration wall panels for a building facade is presented. The key concept is an integrated model that can concurrently handle all of the related design and construction disciplines in the decision making process. The integrated model is decomposed hierarchically into several subproblems, thus a multilevel multiobjective optimization problem is obtained. Besides the multilevel aspect, the model presented can also handle knowledge-based requirements which are in general difficult to deal with by conventional hill-climbing optimization schemes. A solution procedure to solve this model is developed and applied to an example of PCWP for a four-story building facade.
Дата Публикации: 26-11-21