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The Importance of Structural Steel In Constructing Buildings
Описание: The Importance of Structural Steel In Constructing Buildings Structural steel has become one of the most prevalent construction materials of the century, often seen as an extremely important component of modern buildings and housing. According to the World Steel Association, over 1,600 million tonnes were produced in 2016, 197 million more than the previous year. It’s become viable for any kind of project and offers several benefits, which many building plans rely on for structural safety. Availability The widespread adoption of steel has made it easy to find, both as a raw alloy and pre-made components. Fabricated parts will often be openly sold by suppliers (with many factories selling both locally and overseas), allowing beams and frames to be purchased directly. Thanks to this, companies can work under tighter deadlines and access a supply of steel parts anywhere in the world. Steel parts can be ordered as soon as the architectural plan is agreed on, saving time that would be spent waiting for them to arrive at the site. This provides extra time to check measurements and find suitable storage, issues that could normally delay construction by several hours. Weight Its lightweight makes steel easy to transport over land and lift via a crane, reducing the amount of fuel wasted getting it to the site. In addition, this can make buildings far easier to take down: a prototype ProLogic warehouse was built at Heathrow to demonstrate how over 80% of the entire structure was reusable, which could be disassembled in a fraction of the time an average warehouse would take. Low weight can aid in moving and rebuilding structures, as shown with the 9 Cambridge Avenue warehouse relocation: the warehouse itself was dismantled and rebuilt 1 mile away, using almost no steel except the existing components. This added mobility and versatility makes steel a very desirable building material for structures that have extra land for expansion. Sustainability As the desire for eco-friendly buildings increases, steel will become more convenient for construction projects. It can easily be recycled and doesn’t need to be permanently disposed of, so old buildings or temporary supports can be repurposed into new projects as needed. Roughly 97.5% of all steel from UK demolition sites is recovered and reused, according to data gathered by Steel Construction. Recovered steel components that haven’t been damaged can be re-used in other projects, removing the cost of getting the alloy melted down and re-cut as a new part. If a building is being demolished and rebuilt, existing parts could be stripped out and repurposed to save money kept in storage for future projects or simply sold to another company as components (or raw alloy, if sold back to a steel fabrication company). Strength Due to its high strength-to-weight ratio, less steel is needed in a single support or beam, reducing material costs and improving its sustainable nature. It can withstand strong physical impacts and forces, keeping building occupants safe, but won’t wear away or need to be replaced afterwards. This extra strength can be retained through the design, rather than the amount of steel used. Steel I-beams are often used in modern construction since they’re lighter, stronger and less wasteful than any wooden beam of the same size. The natural fire and rust resistance of alloy steel makes it viable for exterior structures, such as fire escapes or balcony supports – MIMA also suggest possible use as external walls to contain insulating materials. Price Modern regulations are very specific about how efficient construction should be: these rules often have the added benefit of cutting maintenance or material costs in the long run. Concrete remains more consistent compared to the varying price of steel, but the costs of repairing and reinforcing a concrete beam or pillar will usually make steel cheaper over a building’s lifetime. As mentioned earlier, steel is entirely reusable. It retains all of its properties, so a large amount of recovered steel could drastically reduce the cost of a new structure. A small study on the cost of a London office building revealed that steel composite was roughly 8% cheaper than concrete slabs across all ten storeys. Steel constructions are widely used in several applications such as structures for buildings, stores, factories, and power plants. The scope of the research is to study a methodology to reduce the weight and the cost related to big frame steel structure warehouse during the early design phase, which is the phase where most of the project layout is defined. The main aim of this paper is the development of a platform-tool to support the automatic optimization of a steel structure using virtual prototyping tools and genetic algorithms. The focus is on the design of heavy steel structures for oil & gas power plants. This work describes in detail the design methodology and estimates the weight saving related to the re-design process of a test case structure. The design cases considered in the paper are those relevant to the operating. Steel structure workshop modular residence is the outstanding residential industrialization. It has many advantages, such as the low whole cost, high resource recovery, a high degree of industrialization. This paper compares the comprehensive benefits of steel structural in modular buildings with prefabricated reinforced concrete residential from economic benefits, environmental benefits, social benefits and technical benefits by the method of entropy evaluation. Finally, it is concluded that the comprehensive benefits of steel structural in modular buildings is better than that of prefabricated reinforced concrete residential. The conclusion of this study will provide certain reference significance to the development of steel structural in modular buildings in China. In this paper, various moment-resisting steel frames (MRSFs) are subjected to 30 narrow-band motions scaled at different ground motion intensity levels in terms of spectral acceleration at first mode of vibration in order to perform incremental dynamic analysis for peak and residual interstory drift demands. The results are used to compute the structural reliability of the steel frames by means of hazard curves for peak and residual drifts. It is observed that the structures exceed the threshold residual drift of 0.5%, which is perceptible to human occupants, and it could lead to human discomfort according to recent investigations. For this reason, posttensioned connections (PTCs) are incorporated into the steel frames in order to improve the structural reliability. The results suggest that the annual rate of exceedance of peak and residual interstory drift demands are reduced with the use of PTC. Thus, the structural reliability of the steel frames with PTC is superior to that of the MRSFs. In particular, the residual drift demands tend to be smaller when PTCs are incorporated in the high-rise steel structure. Currently, most of the seismic design regulations recommend the use of maximum interstory drift as the main engineering demand parameter. Nevertheless, earthquake field reconnaissance has evidenced that residual drift demands after an earthquake play an important role in the seismic performance of a structure. For example, several dozen damaged reinforced concrete structures in Mexico City had to be demolished after the 1985 Michoacan earthquake because of the technical difficulties to straighten and to repair buildings with large permanent drifts . Okada et al. reported that several low-rise RC buildings suffered light structural damage but experienced relatively large residual deformations as a consequence of the 1995 Hyogo-Ken Nambu earthquake even though they had sufficient deformation capacity. After examining 12 low-to-mid-rise steel office buildings (particularly 10 with structural system based on steel moment-resisting frames) structurally damaged and leaned after the same earthquake, Iwata et al. highlighted that the cost of repair of leaned steel buildings linearly increased as the maximum and roof residual drift increased. Based on their study, the authors suggested that steel buildings should be limited to maximum and roof residual drift about 1.4% and 0.9%, respectively, to satisfy a repairability limit state that meets both technical and economical constraints. More recently, a field investigation in Japan indicated that a residual interstory drift of about 0.5% is perceptible for building occupants . Bojórquez and Ruiz-García by comparing peak and residual drift demand hazard curves have observed that if steel frames exhibit peak drift demands about 3%, they could experience residual drifts larger than 0.5%, which is the threshold residual drift that could be tolerable to human occupants, and it could lead to human discomfort when subjected to narrow-band earthquake ground motions of high intensity. Therefore, several researchers have demonstrated that the estimation of residual drift demands should also play an important role during the design of new buildings and the evaluation of the seismic structural performance of existing buildings . In the present study, motivated by the need to reduce peak and residual interstory drift demands, PTCs are incorporated into various MRSFs. Posttensioned steel moment-resisting frames are structural systems proposed in recent years as an appropriate alternative to welded connections of moment-resisting frames in seismic zones . They are designed to prevent brittle fractures in the area of the nodes of steel frames, which can cause severe reduction in their ductility capacity, as occurred in many cases during the 1994 Northridge and the 1995 Kobe earthquakes. The philosophy of structures with PTC is that under an intense earthquake motion, beams and columns remain essentially elastic concentrating the damage on the energy dissipating elements, which can be easily replaced at low cost. Moreover, they provide capacity of energy dissipation and self-centering which can significantly reduce the residual demands. The structural performance of the selected MRSFs is compared with the structures with PTC through incremental dynamic analysis and the estimation of the structural reliability of the frames in terms of peak and residual interstory drift demands. With this aim, four MRSFs and the same structures with PTC (here named FPTC frames with posttensioned connections) are subjected to 30 long-duration ground motions recorded at the lake zone of Mexico City where most of the damages were found in buildings as a consequence of the 1985 Michoacan earthquake. In general, it is observed that the structural reliability of the steel frames with PTC is superior to that of the MRSFs. In particular, the residual drift demands tend to be smaller than 0.5% (which is perceptible for building occupants) when PTCs are incorporated into the steel structure buildings.
Дата Публикации: 04-11-21
Bags for Everyone
Описание: Bags for Everyone IT’S ALWAYS a good time to buy a bag,” said Sarah Newkirk, a mortgage underwriter in Waterford, Wis. Last year, some prominent fashion observers disagreed, wondering if we’d ever embrace handbags again, with Australia’s Daily Telegraph, for one, suggesting the pandemic might bury the accessory for good. Unaware of these death knells, Ms. Newkirk did a lot of embracing just last month, treating herself to a pink nylon Kate Spade bag for her 40th birthday as well as a black-and-rust Coach crossbody. “I’ve been buying bags to cheer myself up. And, like everybody else, I gained weight,” she said. “But a handbag always looks good.” Ms. Newkirk is not in the minority. “In the beginning, the world seemed to stop altogether,” said Hallie Spradlin, director of accessories at Fashion Snoops, a trend-forecasting agency. But by last summer, cooped-up men and women “were looking for a mood boost…and started investing in mailer bag.” Yumi Shin, chief merchant of New York department store Bergdorf Goodman, called handbags “pandemic proof”—particularly, she added, when they’re in perky hues like tangerine or neon green. Perhaps that’s because they represent optimism: Buying a bag designed to tote essentials between home, school, the office and even the airport suggests that we’ll soon return to some version of our bustling former lives. Paul-Sebastian Japaz, a New York painter, said he began building “an arsenal” of bags last summer. His buys range from Telfar’s vegan Shopping Bag to an as-yet-unused leather Prada tote. Mr. Japaz, 29, cheerily called it the “back-to-school bag.” However, as our lifestyles have shifted, so too have our handbag tastes. The awkwardly bulky, top-handle work bags so prevalent pre-pandemic have been ousted by smaller, more versatile options that facilitate a lighter existence. Giana Ballard, 29, who owns a New York photography studio, recently splurged on a canvas Balenciaga bag with a long shoulder strap. Before the pandemic, she used different travel duffel bags for day and night, work and play. Now she wears her roughly 8-inch-tall bucket bag (which fits her iPhone, camera, lipstick and a crucial can of pamplemousse LaCroix) for morning walks, afternoon errands and outdoor dinners. Once she needs to carry heftier cargo like, say, a laptop, again, Ms. Ballard plans to team her modest new pal with a roomier tote. Curt Myers, a Boston public-affairs consultant and erstwhile traveler, has bought three bags during the pandemic—a leather duffel and two backpacks. Mr. Myers, 28, admitted that he “never really looked at bags” before, but with a surfeit of time and a new, social distancing-inspired love of hiking, he sought pieces that fused style and utility. His usual habit of searching for cities to visit was irrational, he said. “The alternative was to buy that symbolized travel.” Katrina Tracy waited until she was vaxxed to splash out on a faux-snakeskin Steve Madden crossbody-cum-fanny pack. “It was a little bit of an affirmation of, ‘We’re getting back to it!’” said Ms. Tracy, 34, who works in human resources in Los Angeles. She debuted the chain-embellished bag when visiting her grandmother, whom she’d seen only once in the past year. “It was fun to have a conversation with her about my shiny new purse,” she said. Her grandmother thought it was adorable. In the 17th Century, small bags known as sweet purses were exquisitely crafted in unusual shapes such as frogs, while the fashionable technique of filigree was used to create elegant purses which were often exchanged as gifts between aristocrats. The 'reticule' – which emerged in the 19th Century and is considered the forerunner of the modern handbag – had a flat surface, so offered the perfect opportunity for artistic expression. "There is a surface to be decorated so women would decorate them with patterns and flowers," says Savi. The appeal of the bag's creative potential to artists is evident as far back as the 1930s The witty and innovative designs from the 19th Century, which included lunch cooler bags in the shape of flower baskets, scallop shells and pineapples, influenced the trend for the incongruous objects which appeared in bag design in the 1930s. Designers such as Anne-Marie of Paris created wonderfully eccentric bags in the shape of telephones, champagne coolers and even radios. These in turn had an impact on the jewel-like creations of Hungarian-US designer Judith Leiber, whose sought-after evening bags come in the shape of everything from bunches of asparagus to lipstick, and the British designer Lulu Guinness, whose flower-basket bags from the 1990s can be seen as a three-dimensional interpretation of floral reticule designs.
Дата Публикации: 04-11-21
Tin box: when the material of your packaging is the real secret weapon that sells
Описание: Tin box: when the material of your packaging is the real secret weapon that sells To work in the study of a functional packaging for sale – as we conceive it here at Packaging In Italy – could suggest a selection of technical aspects, materials, and, only at a later stage, identifying the main guidelines. So, do we first sit around a table to reason abstractly and, at the end, we decide technical details of the material to be used? Not really. In fact, there are cases where the choice of the material is an integral part of the features that make a packaging functional for sales. That is, selecting a material and modeling the packaging development based on that material. Packaging contributes to the increase in sales. For many, it is difficult to understand, but according to facts, sales change for the better when the choice of material was conducted in a strategic manner and not as if it was one of the many technical details. This is the specific case of a tin packaging – technically tin box – a very distinctive material that can be often functional for the use of the product; such as in the case of the can of oil, the classic cans of soda or the common tuna cans. In these cases, choosing a can also has practical reasons, but there are situations where to develop a can container – despite not having practical reasons – is a winning choice for boosting sales. How do we tell if a can could be a driving force for the sales of your product? The first step is to separate the product from its packaging: let’s get into our heads that packaging, in this case, is not only functional to the product and its use, but it also becomes a product itself and the consumer sees it exactly like that! It is not an assumption, it is a fact – and I want to prove it in this article. In the case of food tin box, the packaging itself acquires a value that lives regardless of the product. For this reason, in trying to identify the needs of the consumer, it will be good to find answers through the choice of packaging. There are basically THREE aspects that make a tin packaging a success factor: → its reusability (I, many time, buy and reuse the packaging for other purposes) → its value as a collectable item (I buy and collect the package) → 100% recyclable material (determining factor for the environment and in today’s buying reasons)
Дата Публикации: 04-11-21
Essential Cosmetic Containers For Skincare & Beauty Packaging
Описание: Let cosmetics packaging trends inspire you — If you need a little inspiration for your packaging design there’s no better place to start than looking at the latest cosmetics packaging trends. Once you know what’s currently trending, you can create packaging that caters to what’s important to your customers right now and that speaks to them in the right way. Remember that you want to pick a look that’s both modern and on trend, but also timeless and universally appealing, so your packaging design looks up-to-date for as long as possible. Makeup containers expand to a range of jars, bottles, pots, tubes, pens, compacts and liquid dispensing solutions. Each container offers a different design and solution; however, in the world of ‘cosmetic containers’, each product sits under the skincare, hair and beauty categories. This article will explore the different types of cosmetic containers available in the packaging industry. Raepak offers an extensive range of distinctive packaging products that enable us to explore innovations and keep an eye on exciting designs that are beneficial to the current market cycle. Cosmetic Jar Containers Lipstick containers in the form of jars are perfect for skin care and beauty products. Jars can contain gels, creams, lotions and deep skin cleansing products. Most jar containers come with a shive (a flat plastic shelf that fits inside the jar) used to keep the contents free from foreign debris (dust & germs). Moreover, jars are designed with airtight lids, which keep the contents fresh and ready for future use. Bottle containers can be produced as an airless recyclable container or a high-end luxury acrylic bottle. Acrylic bottles look fantastic with a matching jar and can store nourishing body lotions or face creams. PP airless bottles can also store creams and lotions. However, they are cheaper to produce and lighter in raw plastic material. Acrylic airless bottles are seen as a hybrid between both full acrylic and pp airless containers. Lip gloss containers in the form of pots can be funky, stylish, trendy or sophisticated. Small pots for cosmetic packaging tend to be perfect for eye serums, aromatherapy oils, lip balm, hand creams or hair products. Moreover, small plastic pots tend to be made with a wide range of different plastic types; PMMA/PETG/PP/AS & ABS. Using these plastic combinations helps with the shape and aesthetics of the final jar design. Cosmetic tube packaging containers come in different shapes, colours, materials and profiles. Cosmetic tubes are manufactured from high-quality materials, including AS, ABS, PETG, and PCTG. Each item is designed to work with makeup for the beauty & cosmetics industry. Furthermore, mascara containers are manufactured to have an excellent quality finish and be competitively priced. Cosmetic pen containers come in a beautiful range of styles and design. Each pen gives off a trendy vibe, is easy to use and fits perfectly into any purse or handbag. Cosmetic pen packaging is manufactured from high-quality materials and can be used for eyebrow, lip gloss, concealer, highlighters or liquid blushers. Compact containers are manufactured to be used with beauty and makeup products. Makeup powder is available in a vast range of colour palettes, and it helps give the wearer a look they desire. Compacts can be produced in a range of different styles included; square, round, rectangle and bespoke finishes. Cosmetic liquid dispensing containers come in different shapes, colours, materials and profiles. Furthermore, they can work well with other eyeshadow containers to offer brands a set of makeup and beauty products – offering a collection of different makeup and beauty product solutions that can help target a wider audience.
Дата Публикации: 04-11-21
What is Webbing?
Описание: What is Webbing? Webbing is a woven fabric that is distinguishable by its various material compositions, strength variations and widths. The webbing process essentially involves yarns that are woven via looms to create strips. While it is generally comparable to rope for its harnessing function, webbing is an extremely versatile component used in an array of industry applications, ranging from military apparel to automotive parts. Typically, webbing is fabricated in solid or tubular form, with each type having different applications and functions. While ropes are typically thick in texture, PRET webbing is produced in extremely lightweight parts. The primary materials used in the production of webbing include variations of polyester, nylon, and polypropylene. Cotton webbing is also available and is commonly used in commercial applications, including clothing apparel. Webbing is also customizable in a series of colors, designs and prints, and manufacturers can fabricate reflective webbing for safety applications. Standard Industry Applications Webbing is found across various sectors. Standard RPET webbing applications and associated industries include: Seatbelts and harnesses; automotive industry Hiking, backpack and harnessing gear; sporting good retail apparel Safety bands and tapes; hospital and medical industry Upholstery (seat bases); furniture manufacturing Uniform (suspenders) and accessories for various professions, e.g. police and military Web Processing: Solid (Flat) and Tubular Solid webbing is also known as flat webbing and is fabricated in varying degrees of thickness. Distinguished by its flat aesthetic, solid webbing is commonly used for applications like seatbelts. It is lightweight though it is susceptible to tearing, as stress from use tends to affect the outer surface of the material. Solid webbing is generally too stiff to function in applications that require knots, which is why this type of webbing is best suited for applications where the material can be sewn into a larger product. Backpack straps, for instance, are examples of this type of solid webbing. Tubular webbing is thicker and more durable than solid PP webbing and is composed of two sheets of fabric. It is suitable for knotting applications (like a rope for hoisting) and carries tension better than solid webbing. For functions like climbing, experts recommend utilizing tubular webbing that is woven into a continuous loop. Common Webbing Materials Below are the common webbing materials and some examples of webbing, and types and uses. While nylon and polyester have similar properties to each other, there are some key differences. Nylon Webbing Nylon Webbing is a high strength elastic material that is commonly used for belt applications (specifically, flat nylon). This material tends to stretch approximately 2% the length of the webbing when it is wet. When looking at how to make nylon webbing, experts warn that nylon webbing should not be exposed to water continuously, as the material tends to absorb liquid and may harbor mildew if it is not maintained properly. Polyester Webbing Polyester webbing is durable and similar in aesthetic to nylon. This material is suitable for use for applications that require lifting heavy loads. Polyester webbing has low water-absorption and is more mildew and rot-resistant than nylon. This webbing is commonly used in applications including racing harnesses and seatbelts. Polypropylene Webbing This type of webbing is typically used for outdoor applications. Some products fabricated with this Nylon webbing include window nets and plastic bags. Polypropylene webbing is comparable to nylon, though it is generally lighter. Additionally, it is fabricated with U.V. protection and is water-resistant. This material is processed in varying degrees of thickness, although it has low abrasion resistance. According to experts, it is most suitable for medium-strength operations.
Дата Публикации: 04-11-21
A modern party speaker with exhilarating acoustics
Описание: A modern party speaker with exhilarating acoustics Sony recently launched in India the Sony SRS-XG500 party speaker. Though it reminded me of the old boombox music players, it is by no means a retro one but a modern party speaker with a powerful output and wide connectivity options. Although bulky, the SRS-XG500 is a moveable party speaker that is easy to manage irrespective where you throw a party. Priced at Rs 32,999, the speaker seems to be on the expensive side. Is it? Let’s find out: Build and design Sony SRS-XG500 party speaker The cylindrical body gives the speaker a distinct look while the fabric covering brings minimalism. The big handle is sturdy enough for us to carry it anywhere. On the front, there are buttons for power, Bluetooth, volume, play/pause, and a bass boost button. A rubber lid at the back covers power and USB ports and a connector for plugging in a guitar. The two large rubber feet keep the speaker stable when the bass comes in. The sides have LED lights that change colour when you play music and it looks absolutely beautiful under dim or low light. The Sony SRS-XG500 weighs nearly 5 kg but quality material is used so weight isn't much of a factor to point out. The audio quality of the Sony SRS-XG500 is at par with most of the small-sized trolley-style audio speaker, although it has its own limitations considering it is a portable speaker. That said, the sound is loud and bassy, but at the same time, highly balanced so it will be music for your ears. For bass lovers, there is a bass boost feature but honestly, the default sound is much better because of the balance. The feature to connect a guitar adds to its credentials as a party speaker. You can also connect the SRS-XG500 with other speakers using Party Connect. There are slight tweaks you can do with the sound and light settings using the Sony Music Centre app. I had to play with the equalizer as the default sound at times doesn't go well with all genres of music. Overall, the experience was fine as I played songs on full volume on the terrace. The Sony SRS-XG500 offers up to 30 hours of playtime on a full charge. The battery fares well in real-life scenarios and the backup is close to that Sony claims. The SRS-XG500 is water and dustproof with the IP66 rating, so a slight rain or splash of water and everyday dust won't harm the speaker. The Sony SRS-XG500 is a speaker with loud and enthralling audio out. Although bulky, it can be taken anywhere - from terrace to park for an enhanced musical experience. The SRS-XG500 brings all the features a modern party speaker should have, not to forget about Sony's signature sound that lights up the party, but at Rs 32,999, it's quite expensive and people may prefer cheaper alternatives that JBL and other brands offer. Throwing a party anytime soon or planning to attend one? Conventionally, partygoers used to have a big music system with bulky speakers to ensure everyone is able to enjoy the melody. Thanks to technology upgrades, today, you can do so by carrying a small yet powerful fire light speaker. In the last decade, the trend of party speakers has seen a big spike. With increasing workload, people are now taking every chance they get to loosen up with friends and crank up their favorite music. Incomes party speaker with fire light. Be it a house party, a beach party or even better, a pool party, party speakers are always going to lighten up your guests with incredible sound effects and thumping bass. These are small, portable, and quite powerful. Yesterday I was writing about the perils and stigma of hearing loss, sometimes caused by listening to loud music. Today I’m reporting on speakers that produce loud music. Hopefully, the two aren’t mutually exclusive because when listening to music in larger rooms or out of doors, you do need more volume. Sony is building a name for itself in the growing market for large bluetooth speaker. Today it’s announcing the launch of three new models designed to get any party going with a swing. Marketed with the slogan “Life should be lived at full volume” Sony wants you to turn up the music to full volume and dance away the night with clear and rich sound. Sony’s new range of X-Series speakers is specially designed to provide a powerful and wide-spreading sound that will suit almost any genre of music. Whether you’re listening indoors or outdoors, by yourself or with a group of friends, the new X-Series speakers come in a range of styles and choices of sound quality, portability, durability and lighting. All the new models s feature Sony’s innovative X-Balanced Speaker Units. Featuring a non-circular diaphragm, the drivers create more sound pressure and have lower distortion by maximizing the area of the speaker. The upshot of this, claims Sony, is a richer and clearer sound whatever style of music is being played. The new Sony XP700 has three front high-efficiency tweeters and one rear high-efficiency tweeter delivering an omnidirectional sound that Sony says has a punchy and deep bass with plenty of clarity. The new XP500 and XG500 speakers have two front high-efficiency tweeters while the XG500 model includes passive radiators that are optimized to reproduce a clear bass. Whether you’re looking for something to use on the go or in the shower, a portable speaker will play any music, podcasts, or audiobooks a lot louder (and a lot clearer) than the one that comes with your phone or laptop. And while we’ve written before about lots of audio accessories — including the best noise-canceling headphones, wireless headphones, and workout headphones — here, we’ve rounded up the best portable speakers, as praised by the most enthusiastic reviewers on Amazon. Over 53,000 reviewers give this Anker speaker five stars, with thousands particularly impressed with its 24-hour battery life. “Oh my God, it lasts forever,” says one reviewer. “I’ve charged it once since I got it (a week ago) and used it every day for at least a few hours.” Another calls it “RIDICULOUS. I gave it a full charge and got over a week play time while playing via Bluetooth at around five presses below max volume for about ten hours a day.” And while the battery might be on par with the original Soundcore model, this newer model — called the Soundcore 2 — has several upgrades. It has 12-watt speakers instead of six-watt ones, which leads to a beefier sound overall. “I have the original Soundcore, which was an excellent little gadget until I finally blew a little speaker playing it louder than recommended, repeatedly, for years,” one says. “This SC2 is also excellent. It does put out more sound and the base is fuller.” This model is also waterproof, which increases the number of places you can port this speaker to. “This little speaker has taken on the Atlantic Ocean, Moriches, and Great South Bay with no problem at all,” says one fisherman. “Swells of huge waves have soaked this speaker and it just keeps working.” This under-$20 speaker received high marks from over 19,000 five-star reviewers for its sleek design and surprisingly powerful sound. “This is the most fantastic Bluetooth speaker I have ever purchased and I have purchased a lot,” says one such reviewer, who goes on to say that the sound is “gorgeous,” and the controls are “incredibly easy and intuitive. I might even add slick. I have no idea why they are selling at this price.” Another reviewer was looking for a small speaker to carry while on the go, but they were “pretty skeptical about this little $15 speaker being that great.” As it turns out, “this little speaker packs BIG POWER,” they write. “I can’t believe the volume level. I have a much bigger 808 Audio Bluetooth speaker that cost much more and has half the sound.” While the reviewer admits you’re “not gonna be bumping bass with this little dude,” they say it “gets the job done well” for streaming videos and music. And ultimately, for under $20, “if it does break, I won’t mind buying another one.” “360-degree sound is extremely innovative and the best part of this product, as it essentially solves the problem that most portable speakers have, which is the volume level being too loud for some people and not loud enough for others,” one reviewer says, explaining the appeal of the unique design of this Bose speaker. They add, “With music coming from all sides of this speaker, everyone is hearing the same level of music and you can have it loud enough to be enjoyed but not worry about it overpowering someone else.” Other companies make similar style speakers, but one user says this one from Bose is above the rest. “If you have owned a 360-degree speaker under a hundred bucks and then upgrade to this one,” they write, “WOW, what a difference. I own the Soundcore Flare also; it sounds good, but you get what you pay for. The lows are much more pronounced on the Bose along with much fuller sound.” It’s a sound so full it’s enough to power a party. “Used for the music at our outdoor wedding ceremony,” one writes. “All 120 people could hear the music just fine.” Like our best rated pick, also an Anker speaker, this model has an impressive 24-hour battery life. “Great little speaker — especially for the price,” one says. “Sound is crisp and full, it looks great, and has a nice, solid heft to it. It’s also extremely easy to pair to an iPhone. Once paired, it quickly and reliably connects to my phone when turned on.” Another asks, “Is it the utmost in premium quality sound? Of course not, don’t be an idiot, it’s a tiny speaker that costs under $30.” But they find it impressive nonetheless: “I think you would be hard pressed to find anything at this price point that comes anywhere even remotely close to the awesomeness you get with this speaker.” Many of the thousands of reviewers call out the long battery life, including one who describes it as, “stupid-good … I have literally left this thing on for days — DAYS — and it still had juice.” Another says “I have only charged it once and have likely played it for a total of 4 hours over the last week (Bluetooth) and the battery still says 100 percent.” And when it comes to portability, reviewers say it can hold up to most environments. Reviewers use this in the bathroom, the car, and even on motorcycles, which leads one to say it’s pretty durable: “I’ve dropped this thing onto the street from a speeding motorcycle — the speaker didn’t even stop playing.”
Дата Публикации: 04-11-21
Control of the Brushless DC Motor in Combine Mode
Описание: Control of the Brushless DC Motor in Combine Mode A brushless DC (BLDC) motor is considered to be a high performance gear motor due to its low maintenance cost, versatility, adequate torque and speed, and high reliability. Normally, a simple BLDC motor driver is composed of a permanent magnetic rotor and three stator coils. In each controlling step, two out of three coils are used to generate rotating magnetic field, while the floating coil induces a back electromotive force (emf) and feeds the generated current back to the controller as noise. In this work, combine mode scheme is proposed to control a BLDC motor in such a way that the excess current is accumulated via additional switching circuit for further utilization. Therefore, a BLDC motor can drive the load in concurrent with generating power. The proposed switching circuit has been designed and simulated on PSpice. The results show that up to 75% of input voltage can be charged to the storage capacitor. This paper provides a technical review of position and speed sensorless methods for controlling Brushless Direct Current (BLDC) motor drives, including the background analysis using sensors, limitations and advances. The performance and reliability of BLDC motor drivers have been improved because the conventional control and sensing techniques have been improved through sensorless technology. Then, in this paper sensorless advances are reviewed and recent developments in this area are introduced with their inherent advantages and drawbacks, including the analysis of practical implementation issues and applications. The study includes a deep overview of state-of-the-art back-EMF sensing methods, which includes Terminal Voltage Sensing, Third Harmonic Voltage Integration, Terminal Current Sensing, Back-EMF Integration and PWM strategies. Also, the most relevant techniques based on estimation and models are briefly analysed, such as Sliding-mode Observer, Extended Kalman Filter, Model Reference Adaptive System, Adaptive observers (Full-order and Pseudoreduced-order) and Artificial Neural Networks. For the past two decades several Asian countries such as Japan, which have been under pressure from high energy prices, have implemented variable speed PM motor drives for energy saving applications such as air conditioners and refrigerators . On the other hand, the U.S.A. has kept on using cheap induction motor drives, which have around 10% lower efficiency than adjustable PM motor drives for energy saving applications. Therefore recently, the increase in energy prices spurs higher demands of variable speed PM motor drives. Also, recent rapid proliferation of motor drives into the automobile industry, based on hybrid drives, generates a serious demand for high efficient PM motor drives, and this was the beginning of interest in BLDC motors. BLDC motors, also called Permanent Magnet DC Synchronous motors, are one of the motor types that have more rapidly gained popularity, mainly because of their better characteristics and performance . These motors are used in a great amount of industrial sectors because their architecture is suitable for any safety critical applications. The brushless DC motor is a synchronous electric motor that, from a modelling perspective, looks exactly like a DC motor, having a linear relationship between current and torque, voltage and rpm. It is an electronically controlled commutation system, instead of having a mechanical commutation, which is typical of brushed motors. Additionally, the electromagnets do not move, the permanent magnets rotate and the armature remains static. This gets around the problem of how to transfer current to a moving armature. In order to do this, the brush-system/commutator assembly is replaced by an intelligent electronic controller, which performs the same power distribution as a brushed DC motor . BLDC motors have many advantages over brushed DC motors and induction motors, such as a better speed versus torque characteristics, high dynamic response, high efficiency and reliability, long operating life (no brush erosion), noiseless operation, higher speed ranges, and reduction of electromagnetic interference (EMI). In addition, the ratio of delivered torque to the size of the motor is higher, making it useful in applications where space and weight are critical factors, especially in aerospace applications. The control of BLDC motors can be done in sensor or sensorless mode, but to reduce overall cost of actuating devices, sensorless control techniques are normally used. The advantage of sensorless BLDC motor control is that the sensing part can be omitted, and thus overall costs can be considerably reduced. The disadvantages of sensorless control are higher requirements for control algorithms and more complicated electronics . All of the electrical motors that do not require an electrical connection (made with brushes) between stationary and rotating parts can be considered as brushless permanent magnet (PM) machines , which can be categorised based on the PMs mounting and the back-EMF shape. The PMs can be surface mounted on the rotor (SMPM) or installed inside of the rotor (IPM) , and the back-EMF shape can either be sinusoidal or trapezoidal. According to the back-EMF shape, PM AC synchronous motors (PMAC or PMSM) have sinusoidal back-EMF and high performance Brushless DC Motor have trapezoidal back-EMF. A PMAC motor is typically excited by a three-phase sinusoidal current, and a BLDC motor is usually powered by a set of currents having a quasi-square waveform . Because of their high power density, reliability, efficiency, maintenance free nature and silent operation, permanent magnet (PM) motors have been widely used in a variety of applications in industrial automation, computers, aerospace, military (gun turrets drives for combat vehicles) , automotive (hybrid vehicles) and household products. However, the PM BLDC motors are inherently electronically controlled and require rotor position information for proper commutation of currents in its stator windings. It is not desirable to use the position sensors for applications where reliability is of utmost importance because a sensor failure may cause instability in the control system. These limitations of using position sensors combined with the availability of powerful and economical microprocessors have spurred the development of sensorless control technology. Solving this problem effectively will open the way for full penetration of this motor drive into all low cost, high reliability, and large volume applications. The remainder of the paper is arranged as follows. Section 2 describes the position and speed control fundamentals of BLDC motors using sensors. Next, Section 3 explains the control improvements applying sensorless techniques, describing the motor controller model and the most important techniques based on back-EMF sensing. Section 4 also briefly analyses the sensorless techniques using estimators and model-based schemes. In addition, Section 5 compares the feasibility of the control methods, and describes some relevant implementation issues, such as open-loop starting. Finally, Section 6 provides an overview for the applications of BLDC motor controllers, as well as conclusions are drawn in Section 7. PM motor drives require a rotor position sensor to properly perform phase commutation and/or current control. For PMAC motors, a constant supply of position information is necessary; thus a position sensor with high resolution, such as a shaft encoder or a resolver, is typically used. For BLDC motors, only the knowledge of six phase-commutation instants per electrical cycle is needed; therefore, low-cost Hall-effect sensors are usually used. Also, electromagnetic variable reluctance (VR) sensors or accelerometers have been extensively applied to measure motor position and speed. The reality is that angular motion sensors based on magnetic field sensing principles stand out because of their many inherent advantages and sensing benefits. 2.1. Position and Speed Sensors As explained before, some of the most frequently used devices in position and speed applications are Hall-effect sensors, variable reluctance sensors and accelerometers. Each of these types of devices is discussed further below. 2.1.1. Hall-effect sensors These kinds of devices are based on Hall-effect theory, which states that if an electric current- carrying conductor is kept in a magnetic field, the magnetic field exerts a transverse force on the moving charge carriers that tends to push them to one side of the conductor. A build-up of charge at the sides of the conductors will balance this magnetic influence producing a measurable voltage between the two sides of the conductor. The presence of this measurable transverse voltage is called the Hall-effect because it was discovered by Edwin Hall in 1879. Unlike a brushed DC motor, the commutation of a high performance BLDC Motor is controlled electronically. To rotate the BLDC motor the stator windings should be energized in a sequence. It is important to know the rotor position in order to understand which winding will be energized following the energizing sequence. Rotor position is sensed using Hall-effect sensors embedded into the stator . Most BLDC motors have three Hall sensors inside the stator on the non-driving end of the motor. Whenever the rotor magnetic poles pass near the Hall sensors they give a high or low signal indicating the N or S pole is passing near the sensors. Based on the combination of these three Hall sensor signals, the exact sequence of commutation can be determined. Figure 1 shows a transverse section of a BLDC motor with a rotor that has alternate N and S permanent magnets. Hall sensors are embedded into the stationary part of the motor. Embedding the Hall sensors into the stator is a complex process because any misalignment in these Hall sensors with respect to the rotor magnets will generate an error in determination of the rotor position. To simplify the process of mounting the Hall sensors onto the stator some motors may have the Hall sensor magnets on the rotor, in addition to the main rotor magnets. Therefore, whenever the rotor rotates the Hall sensor magnets give the same effect as the main magnets. The Hall sensors are normally mounted on a printed circuit board and fixed to the enclosure cap on the non-driving end. This enables users to adjust the complete assembly of Hall sensors to align with the rotor magnets in order to achieve the best performance .
Дата Публикации: 04-11-21
Electric Tricycle Replica Review: Super Enlightening, Mildly Terrifying
Описание: Electric Tricycle Replica Review: Super Enlightening, Mildly Terrifying I'm an advocate for electric cars needing to get back to basics. There's no need to be running off, sticking in 56-inch touchscreens, or making the EV larger than a small European state. Really, one of the things we should be working on is taking existing chassis, finding ways to quickly convert them to EVs, and worrying about all the fancy stuff later. Nothing new under the sun and all that, which is how I found myself driving a converted motor tricycle from 140 years ago through the British countryside. Two weeks ago, journalist Jeremy Hart got in touch with me and asked me if I wanted to drive a replica of an EV from 1881. The answer, obviously, was yes. Nothing on earth could be more my jam than this. Once I'd worked out if it was legal for me to actually leave my house and drive something under the U.K.'s lockdown restrictions, I was straight on the train to Surrey to have a go in a remake of what was very probably the first-ever vehicle with a rechargeable battery. Not sure what image you were expecting here but: Yes, this is an electric cargo motor tricycle from 1881. Or, well, an unbelievably faithful replica of one that Hart commissioned and artisan bicycle designer Christian Richards built. Because the original vehicle was an adaptation rather than a purpose-built chassis, the yoke-like pedals in front still work and can power the vehicle—and swing wildly, threatening to take your shins out when it's under motor power. The single seat is at the top, perched a bit perilously, and the battery is—as it seems to have been on the original—in a pannier attached to the rear of the bike. The motor drives the big left-hand wheel and the two smaller wheels are connected to what's surprisingly responsive steering. Now for the facts about this vehicle. It's not really a stat sheet so much as it is a story. Before 1881, there had already been some progress at making electric vehicles happen. Ányos Jedlik, a Hungarian inventor, had made a small cart that used a motor to move in 1828. Four years after that, Moritz Jacobi, a Russian engineer, made an electric boat using non-rechargeable batteries that poisoned its passengers so seriously even the early pioneers of vehicles were forced to admit they'd succumbed to nitrous fumes. By 1839, a Scottish inventor called Robert Davidson created something that, today, is widely credited as being the first electric car. It ran through the streets of Aberdeen, Scotland, with a passenger, but everything we know about it—which admittedly, is a surprisingly small amount for what was a huge breakthrough—says it used chemical, non-rechargeable batteries. When Hart and Richards set out to replicate the cabin motor tricycle French inventor Gustave Trouvé took to the streets of Paris in 1881, there was so little documentation that a quick sketch was basically all there was to go off of. It's significant, as a vehicle, because it was rechargeable and Trouvé drove it down regular roads—which as anyone who's driven in Paris knows is kind of an experimental experience even if you're in a well-tested Renault Clio. The illustration showed Trouvé's electric tri moto wasn't purpose-built, he had to convert it. He'd used an existing pedal vehicle made by a British manufacturer and converted the chain to run from the motor rather than the pedals. And the reason no further information about it exists is that he took it for a drive, presumably decided it went well, and then disassembled the whole thing. He took the motor and battery with him to work on an electric boat project that would lead to him inventing the outboard motor. So why anyone would try and recreate the short-lived e-trike? The answer is fairly straightforward. Hart likes researching the history of electric vehicles and once he'd found out such a key part of them—like Davidson's car and Jedlik's cart—was missing, it seemed obvious the thing to do was try to recreate it, especially with a tantalizing 140-year anniversary coming up. What he hadn't estimated was how difficult it would be, even with using modern parts for some of it. When Richards built the trike for Hart's project, he made the frame first—faithful to the original being a conversion—before using a Maxus battery to power a fairly standard e-bike motor. Maxus is an electric van company that decided to back the project, which included providing its own vehicle as transport for the trike to and from Paris, after regular automakers were less interested. The trike's motor sits almost in the larger wheel, delivering power via a simple chain drive. Driving the Thing When I stepped off a train to have a look at it, the trike was fresh off its own transport back from France. Which leads me to ask: Have you ever been properly scared by a bicycle? I have, now. I'm maybe not the most athletic journalist, especially after spending a year in enforced lockdown, so clambering into the seat was a pretty ungainly affair. I'm very grateful Hart didn't laugh at me too much over. At five feet and 10 inches, I'm not especially short but still had to haul myself a good six inches up into it, putting me well above a car or modern bicycle's ride height. In the 1880s, of course, people were used to horseback so this probably felt like a dangerously low sitting position. They also presumably had slimmer hips than me because staying in the seat was quite challenging and definitely felt like I could have fallen out of it at any second. In terms of control, it's very simple. The replica's designers recreated what looked like the steering and accelerator controls on the one existing image of the original trike. There's one lever to steer the thing (the long one in front, in the picture above) and another to ease the vehicle forward as the accelerator. You perch your feet on a bar to avoid the flailing pedals and use the steering handle and brake (the handle in the rear of the picture above) to hold on. Obviously, this isn't how the chassis was even intended to work because it's supposed to be pedaled, so there's a sort of direct conflict between the number of handles available to you and the number of hands you actually have—you have to use your left for both the brake and the accelerator. The first thing that goes through your mind is, "What the hell was anyone thinking, doing this?" Yes, this time I knew that the battery was actually very unlikely to catch fire and the vehicle had been properly engineered for this, but there was just something incredibly insecure about being on a small seat above a vehicle you don't totally feel like you're in control of. Since the 3 wheel motorcycle was authentically replicated, it had wobbly, slim wheels and hard rims—no real tires. So when you add a little bit of electric torque to it and things start moving, they feel like they might get away from you. The speed of acceleration, driven by that large wheel, feels a lot faster than it is and like it could just keep going until it throws you into a ditch. After a few minutes though, you get the hang of it. The system's simple and it doesn't really need a brake, although it has cushy leather straps as brake pads, that make a shushing sound when activated. That was the only cushy thing, though. Not big on heated seats, the 1800s. But the steering was incredibly responsive, turning both wheels on the two-wheeled side of the trike in a quick way I didn't totally trust the single, larger wheel to respond to. The top speed is about three mph—which feels like plenty from the driver's seat. Aside from being pretty unfamiliar as a vehicle (when Hart described it to me, I was not imagining an asymmetrical wheel layout), the trike felt both a little bit overpowered and slightly fragile. The slim frame is built perfectly and has unbelievable balance, thanks to Richards' incredible craftsmanship. But the point of this vehicle obviously isn't performance. That wasn't even the point at the time. Rather, it's proof of possibility. The guts—or naïveté—it must have taken Trouvé to decide to casually put the electric trike together are unreal, but it's also incredibly impressive to see the history of electric vehicles realized again in such an intensely physical way. I was reminded of this every time it went over a small bump. It's really easy to think of early EVs as plasticky little city cars or crude experiments like the Sinclair C5. Even getting something from the 1980s to run on battery power alone these days feels like a major endeavor. The stop-start history of electric vehicles over the 20th century—revived at every oil crisis and forgotten as soon as pipelines start flowing again—makes it really easy to forget that electric technology originally appeared as a rival to steam, not gasoline. So, yeah, I can't recommend an 1881 Trouvé trike as a daily runaround. It's got really no storage space and the road legality, I suspect, is kind of debatable. But as a clanking, mildly terrifying piece of suck-it-and-see impromptu electric vehicle history, it's an extremely special thing. At a time when the only vehicles moving under their own steam were, well, err, literally using their own steam—think great steamboats and huge steam locomotives—this would have been an incredible piece of nippy engineering. And it still is, honestly. While I'd need more than a short trip where I tried not to break any bit of it (and mostly succeeded, sorry Jeremy) I found I was kind of sold on the trike element by the time it was over. Compared to riding a regular bike, it offers a more refined sitting position; you're upright with incredible views and—steering lever in one hand, accelerator the other—you can't help feeling like you're having an extremely great time. Like driving a vintage car that forces you to sit properly and peek over the bonnet rather than slumping down to gaze out the windshield, there's something very Mary Poppins about it all.
Дата Публикации: 04-11-21