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Cistanches Herba: A Neuropharmacology Review
Описание: Cistanches Herba: A Neuropharmacology Review Cistanche extract products (family Orobanchaceae), commonly known as “desert ginseng” or Rou Cong Rong, is a global genus and commonly used for its neuroprotective, immunomodulatory, anti-oxidative, kidney impotence, laxative, anti-inflammatory, hepatoprotective, anti-bacterial, anti-viral, and anti-tumor effects in traditional herbal formulations in North Africa, Arabic, and Asian countries. The major bioactive compound present in this plant is phenylethanoid glycosides. In recent years, there has been great important in scientific investigation of the neuropharmacological effects of the bioactive compounds. The in vitro and in vivo studies suggests these compounds demonstrate neuropharmacological activities against a wide range of complex nervous system diseases which occurs through different mechanisms include improving immunity function and kidney aging, anti-lipid peroxidation, scavenging free radical, inducing the activation of caspase-3 and caspase-8. This review aims to summaries the various neuropharmacological effects and mechanisms of Cistanches Herba extracts and related compounds, including its efficacy as a cure for Alzheimer’s disease and Parkinson’s disease with reference to the published literature. Which provides guidance for further research on the clinical application of Cistanches Herba. Introduction Cistanches Herba, the dried stem of Cistanches species Cistanche deserticola Y.C.Ma (Figure 1) and Cistanche raw materials, is recorded in the Chinese Pharmacopeia (Committee, 2015). Other non-official species, such as C. sinensis Beck and C. salsa (C. A. Mey) Beck, are also used as Cistanches Herba in certain regions of China due to resource shortage. Cistanches Herba is one of the most valuable herbal drugs in traditional Chinese medicine, which supplements kidney functions, boosts the essence of blood, and moistens the large intestines to free stool (Medicine, 2005). Therefore, it is called “desert ginseng” in China because of the excellent medicinal functions and nourishing effects (Wang et al., 2012). Cistanches Herba, a global genus of holoparasitic desert plant, which is primarily endemic in North Africa, Arabic, and Asian countries (Nan et al., 2013). The primary producing areas of Cistanches Herba in China are Inner Mongolia and the provinces of Xinjiang, Gansu and Qinghai. Several chemical groups were isolated from Cistanches Herba, including PhGs (Figure 1), lignans, iridoids, and polysaccharides (Chen et al., 2013). Pharmacological studies demonstrated that Cistanches Herba exhibits neuroprotective, kidney impotence, laxative, anti-inflammatory, hepatoprotective, immunomodulatory, anti-oxidative, anti-bacterial, anti-viral, and anti-tumor effects (Hu and Feng, 2012). And our previous studies have distinguished Cistanches Herba from different geographic origins using a combination of DNA barcoding and UPLC-Q-TOF/MS technology. The Consumer Price Indexdatabase of China reports that 58 drugs from 12 different groups, including glycosides of Cistanche capsules and compound Cistanche Yizhicapsules, are authorized for the treatment of AD. Cistanches Herba wine and tea are produced in Alashan, Inner Mongolia, China, which might assist in Runchang catharsis and enhance the immune, endocrine regulation, and anti-aging systems of the body. Boschnalosides used as a therapeutic agent in Japan to treat sexual dysfunction and amnesia, and echinacoside is used in healthcare products in the United States to improve immunity (Cheng et al., 2005). Some researchers recently focused on the neuroprotective effects of Cistanche health products, but these effects have not been studied thoroughly (Table 1). This review presents and analyzes recent developments in the neuropharmacology of Cistanches Herba and provides a reference for the further study and clinical application of this medicinal plant. Cistanches Herba medicines have a long history of practical use, but scientists worldwide only began to disclose their chemical composition in the1980s. Figure 2 shows an analysis of the related literature. The cumulative histogram shows the number of studies increased over time, and the Chinese literature occupies the greatest proportion, which reveals the potential research value of Cistanches Herba. Figure 2A shows that the neuropharmacology related literature occupies the largest proportion of the nine areas of pharmacology, and this topic has become the most important area for research. Figure 2B exhibits the chemical research diversity of Cistanches Herba, with a substantial proportion of research on content determination. Further research may focus on neuropharmacology and component content. Cistanches Herba has a long history as a medicinal plant in China and Japan because of its wide spectrum of pharmacological activities. It is commonly called Rou Cong Rong in Chinese, and it was first listed medicinal use as a tonic agent in the Chinese Materia Medica Shen Nong’s Herbal Classic (Estern Han Dynasty) 2000 years ago, and later recorded in Yao Xing Lun in 1590. The Compendium of Materia Medica (Ben Cao Gang Mu, 1619) documented that Cistanches Herba invigorated the kidney to treat kidney deficiencies and geriatric constipation strengthened and nourished marrow and essence, protected semen, and moistened dryness to relax the bowels. These properties were also written in Ben Cao Hui Yan in 1619. A total of 200 medicinal books recorded the pharmacodynamics and use of Cistanches Herba in Chinese history. Cistanches Herba ranks first in Chinese traditional medicine to strengthen prescriptions, which ranks second in anti-aging prescriptions at the same time, behind Panax ginseng in past dynasties. Modern pharmacological investigations demonstrated that Cistanches Herba was used as a kidney-yang reinforcing Chinese medicinal tonic, but it is also exhibits anti-aging, improves memory, and enhances immunity effects (Table 1), which indicate that extracts or constituents from Cistanches Herba have a promising future for the treatment of diseases, particularly nervous system disorders. However, systematic data on the pharmacological activities of this agent is lacking. It is urgent and important to study the pharmacological effects and mechanisms of Cistanches Herba deeply in the future. Aging is an inevitable process of life. This process involves a series of degenerative changes in tissues and organ functions with advancing age. Studies on aging and anti-aging medicines have made significant progress in recent years. Therefore, anti-aging drugs are a current and prominent issue in gerontology. The aging process reflects a confluence of in vivo and in vitro factors. Aging is closely related to type 2 diabetes, atherosclerosis, and AD. Aging is also related to the decreased regeneration of cells, viscera deficiency, increased free radicals, body poisoning, and lack of rhythm when eating (Lopez-Otin et al., 2013). Aging is an inevitable process, but delaying this process is now possible. Several historical Chinese herbal pharmacopeias describe that Cistanche tubulosa supplements possesses anti-aging properties. PhGs and oligosaccharides are two types compounds isolated from Cistanches Herba that are the main active ingredients of this plant. In vivo studies established an aging mouse model caused by D-galactose. The mice were divided into normal control, model, Vitamin E and total glycoside groups, and all groups received different doses of various materials. The results suggested that the glycosides exhibited protective effects on the hippocampal ultrastructure, and glycosides may play a role in the delay of aging and the prevention and treatment of senile dementia via anti-oxidation (Wang X. et al., 2015). Xu et al. investigated the protective effect of Cistanches Herba alcohol extract on hepatic mitochondria and established an aging rat model caused by D-galactose. Rats were administered Cistanches Herba alcohol extract for 6 weeks. The results indicated that Ca2+-ATP enzyme activity was enhanced, and the MDA content in the hepatic mitochondria was reduced. These results further suggested that the Cistanches Herba alcohol extract effectively protected hepatic mitochondria in the D-galactose aging rat model (Xu et al., 2007). Xu and Liu (2008) examined the anti-aging effect of PhGs isolated from Cistanches Herba. The results confirmed that the PhGs improved learning and memory, exhibited antioxidant activity, and boosted the immune system. The results also demonstrated that the PhGs exhibited anti-aging effects via enhancement of anti-oxidation. The mechanism may be related to the free radical scavenging ability of PhGs. Polysaccharides of Cistanches Herba exhibit the same function as PhGs on anti-aging (Xu et al., 2008; Zhang et al., 2011). Zhang et al. (2014) also investigated a Cistanches Herba extraction 2014 and found that this extract extended life span. The results of studies on echinacoside and acteoside suggest that these components exhibit positive anti-aging effects (Zhang et al., 2008; Xie et al., 2009). Many studies of anti-aging involve Cistanches Herba, but these works are limited because the anti-aging mechanism is not known. There are three possible pathways to anti-aging, including improving immunity function and kidney aging, anti-lipid peroxidation. Immune theory of aging said that the decline of immune function is closely related to the aging organism. Thus, the immune function of the body can indirectly reflect the aging organism in a certain extent. The raised index of thymus and spleen, increased content of IFN-γin serum and decreased content of IL-6, increased capacity of peritoneal macrophage phagocytic and lymphocyte proliferation response always can improve the immunity aging, and then delay the organism aging. The expression of p53 from human fibroblastic cell down-regulated significantly in a dose dependent manner after treatment with echinacoside, and which may be correlated with the up-regulation of SIRT1. The PhGs can scavenge different ROS, including. O–2, H2O2 and ?OH, effectively and protect DNA damage through scavenging ?OH. In addition, the PhGs also can increase the content of RNS- NO, and then reduce the lipid peroxidation. Therefore, the real effective components of Cistanches Herba and what a role in anti-aging are important and appealing future research directions. Anti-oxidative and Anti-apoptotic Activity Cistanches Herba exhibits anti-oxidative, free radical-scavenging and anti-apoptotic activity via different mechanisms. Recent studies demonstrated the anti-oxidant activity of Cistanches Herba, particularly in the clearing of all types of free radicals in vivo and in vitro, improvement in the activity of anti-oxidant enzymes in the body, and inhibition of the formation of lipid peroxide, MDA, and brown fat (Wang et al., 2001; Wu and Fu, 2004; Luo et al., 2012; Song, 2013). Current studies demonstrated that cell apoptosis or programmed cell death is determined by heredity and is related to oxidation (Martin, 2011). Deng used the MTT assay to examine cell survival rate, agarose gel electrophoresis of DNA, and flow cytometry to detect cell apoptosis. The results suggested that the echinacoside extracted from Cistanches Herba exhibited protective effects on TNFα-induced SH-SY5Y cell apoptosis (Deng et al., 2005). Nerve cell protection exhibits a close connection with the reduction of active oxygen levels in cells, inhibition of caspasc-3 activity and maintenance of a high-energy state of mitochondrial membrane potential. Bao et al. (2010) investigated an extract of Cistanche tubulosa and discussed its anti-oxidant ability. These researchers conducted an in vitro study to compare the anti-oxidative properties of methanol and ethanol extracts. The results suggested that the two extracts exhibited high anti-oxidant ability, and 70% ethanol was the best extraction agent of C. tubulosa to ensure improved anti-oxidant activity (Bao et al., 2010). The PhGs from Cistanches Herba are considered the effective ingredients for anti-oxidative and anti-apoptotic activity in recent studies. The anti-oxidant mechanism is mainly related to the radical-scavenging activity. PhGs compounds, which are mostly provided with different amounts of phenolic hydroxyl, can be used as hydrogen donor to reductive radicals, and then reach to the purpose of radical scavenging. The herbal cistanches extract powder scavenge the free radicals mainly in two ways, including directly involving in the removal of free radicals or blocking their production and regulating the anti-oxidant enzymes related to the free radical metabolism in vivo, such as SOD, CAT and GPX (Ko and Leung, 2007). For another, the Glycosides of Cistanches Herba can prevent the apoptosis of cerebellar granule neurons by inhibiting the activities of caspase-3 and caspase-8. Therefore, the good oxidation resistance and anti-aging ability of Cistanches Herba may be applied to cosmetics. This application may be a new research direction in the future. Learning and Memory Enhancement Learning and memory are advanced functions of the brain, and these functions are important factors in determining intelligence. Learning and memory impairment is a common symptom in different types of encephalopathy, such as attention deficit and hyperactivity disorder in childhood, adolescent chorea, lobar atrophy disease, neurosis, senile cerebral arteriosclerosis, and dementia. Medicinal research demonstrated that the impairment of learning and memory is closely related to the impairment of synaptic transmission in the brain and the metabolism of neurotransmitters, other substances, and energy in the brain (Chen, 1993). Modern pharmacological studies determined that Cistanches Herba significantly improves learning and memory, and PhGs are the active chemical ingredients of this effect. Traditional Chinese medicine shows that learning and memory dysfunction exists in the Yang deficiency model of the spleen and kidney. Therefore, these two models are more suitable for the study of tonics in traditional Chinese medicine. Gao et al. (2005) examined the effects of Cistanches Herba glycosides on the learning and memory of kidney Yang deficiency mice. The results of this study demonstrated that the Yang deficiency symptoms of each dose group improved, and the number of animal deaths decreased significantly. However, the jumping latency of each dose group after hydrocortisone administration was significantly prolonged, and the number of errors during a 5-min period was reduced. Therefore, glycosides improved the learning and memory of kidney Yang deficiency mice induced by hydrocortisone and reduced the death rate of these animals (Gao et al., 2005). The current researchers established a scopolamine-induced learning and memory impairment mouse model to investigate the effects of the PhGs of Cistanches Herba. The results demonstrated that the PhGs of Cistanches Herba enhanced learning and memory (Li, 2011; Liu et al., 2011). Choi et al. (2011) also demonstrated that Cistanches Herba enhanced learning and memory via the induction of nerve growth factor. Vary factors related to cerebrovascular disease induce vascular dementia. This condition is an acquired intelligence-damaging syndrome of cognitive impairment, which is a primary type of senile dementia. Ischemic cerebrovascular disease occurs frequently in many cerebrovascular diseases induced by vascular dementia. Traditional medicine and modern pharmacology demonstrated that PhGs play an active role in neuroprotection (Feng et al., 2013; Liu et al., 2013; Zhu et al., 2013; Zhang, 2014). The reason why Cistanches Herba extract can improve learning and memory is partly due to neuronal cell differentiation, neurite outgrowth and presynaptic formation promoted. Cistanches Herba also improved cognitive behavior related to memory ability. Therefore, Cistanches Herba is a potential candidate for cognitive enhancement owing to its action as a nerve growth factor modulator. However, extensive research is necessary to discover the neuroprotective mechanism deeply. Further studies to determine the specific type of PhGs are expected to play a leading role in improving learning and addressing memory impairment.
Дата Публикации: 10-12-21
The Importance of Your Car’s Wheel Bearings
Описание: The Importance of Your Car’s Wheel Bearings A wheel bearing is a crucial part of the wheel assembly that connects the wheel and the axle. It is a set of steel balls (ball bearings) or tapers (tapered bearings), held together by a metal ring. It enables the wheel to rotate smoothly with a minimum of friction. Wheel bearings are safety critical components designed to sustain radial and axial loads caused by gravitation, acceleration, breaking & cornering forces, so they need to be replaced when they stop working properly. Faulty installation – inappropriate tools such as a hammer or an impact wrench can cause damage to the exterior and or interior of the wheel end bearing causing the wheel bearing to fail prematurely. Also, re-using the old accessories such as bolts, nuts, circlips, split pins, seals,… instead of replacing them with new ones can cause the wheel end bearing to operate under abnormal or unsafe conditions, increasing wheel end bearing wear and risk of a car accident. Impact damage or poor road quality – all impacts from driving through a pothole, driving over speed bumps or hitting the curbstone can damage a wheel bearing and reduce its lifespan. Poor quality wheel bearing – a wheel bearing is continuously under enormous pressure. Wheel bearings constructed of low-quality materials can have poor heat-treatment, resulting in premature wear and failure. Driving conditions – driving through deep water or mud can cause your wheel bearings to fail. Water, mud or other contaminants such as dust or road salt could get past the seals and enter the bearing, polluting the grease and wearing away the bearings. Car modifications – fitting bigger or wider rims, tires with lower thread walls, stiffer shock absorbers and suspension springs cause higher loads on the wheel bearing and can accelerate wear. Stick to rims, tires, shock absorbers and springs that are specified by the car manufacturer to minimize the impact on the longevity of the wheel bearings. It’s very rare for wheel bearings to fail immediately and completely after you notice the first symptom(s). Having said that, it is best to avoid driving with a worn wheel bearing for any length of time. As we’ve already seen, the wheel bearing is essential for connecting your wheel to your car, and any weakness in this connection could have severe consequences for your drive-axle and steering assembly – as well as for your safety. Replacing your wheel bearings Despite the fact that modern auto bearing are easier to install than previous generations, correct installation, the usage of appropriate tools and respecting the specified torque values are still essential for maximum performance, durability and safety. Therefore, we recommend having your wheel bearings fitted by a professional mechanic that has the skills and the tools to do the job. The content contained in this article is for entertainment and informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic. We encourage you to consult with a certified technician or mechanic if you have specific questions or concerns relating to any of the topics covered herein. Under no circumstances will we be liable for any loss or damage caused by your reliance on any content. The increasing preference for personal mobility in the post-COVID period will boost the growth of automobiles and components such as agriculture machinery bearing. Additionally, the Indian automotive bearings market is expected to benefit from the shift of production lines of the global automotive bearings manufacturers to the emerging economies. Nachi-Fujikoshi, a prominent manufacturer of automotive bearings, has announced its plan to move its production of general-purpose bearings from Japan and Taiwan to Thailand. The move is to reduce production costs for automotive bearings. The recent introduction of production-linked incentive (PLI) schemes for automotive components by the government of India will play a crucial role in attracting global players to set up manufacturing facilities in India. The growing demand for light-weight and durable bearings from the automotive industry is leading the prominent bearing manufacturers such as SKF India, Schaeffler India, and NRB Bearings to focus on adopting new raw materials, instead of traditional high-grade steel. For instance, SKF India is manufacturing automotive bearings with alloys that are 10%-12% lighter than traditional bearings made from high-grade steel. The vendors are increasing spending on R&D for the development of lightweight technology. In 2019, Schaeffler India spent 1.34% of revenue on R & D. Auto mechanics all over the country take advantage of the public’s limited knowledge about automotive mechanics and engineering. Many drivers assume that their mechanic knows more about the subject of what’s going on with their cars than they do, and feel they have no choice but to trust their “expert” opinions. This happens frequently with recommended part replacements—especially with wheel bearings. Wheel bearings play an integral role in your car’s overall functioning and performance. Wheel bearings can indeed become damaged or worn out over time, and under these circumstances it is critical to replace them if need be. However, this is one of the opportunities that automotive shops seize to upsell their product and services. If you’ve ever heard the phrase, “well, if you’ve replaced one you should replace the other” then you’ve likely overpaid for automotive services. In this article, we’ll talk about the importance of wheel bearings for your car. We’ll also discuss when industrial bearing should realistically be replaced and what you can do to keep your car in excellent condition moving forward. Wheel bearings are critical for your car’s performance. They reside inside a wheel to help the wheel rotate smoothly and competently by decreasing the amount of friction created by other various parts of the drivetrain system. When wheel bearings become damaged or require replacement, it can lead to devastating effects if not replaced properly. When wheel bearings are not replaced with the proper tools, equipment, and attention to detail, it can cause further, more significant damage to the part over time. Bearing assemblies are a simple mechanical design, but their function is essential to the smooth rotation of your wheels. When one wheel bearing goes bad, it can cause a concerning noise coming from your wheel, especially at higher speeds, and it can cause other gradual side effects to your alignment and wheel balance. When Wheel Bearings Need to Be Replaced Wheel bearings are made of tough, durable material, which means that they generally last a long time in cars. However, they can still require replacement under the right circumstances. If you have noticed any strange noises coming from your wheel as you’re driving, consider if any of the following could apply to your car: Accident Damage Although wheel bearings are sturdy parts alone, the impact from an accident can cause the auto wheel bearing to become damaged. After the rough impact of a car accident, especially if the accident was a side impact, it’s common to encounter broken seals in the bearing assembly, which leads to a contaminated bearing. When grease gets inside through a broken seal, it causes too much friction, which can chip the bearings and cause them to begin to malfunction. Improper Installation Wheel bearings need to be replaced under somewhat rare circumstances, including when they are replaced improperly to begin with. Whenever a wheel bearing or a bearing assembly is replaced, the wheels should be balanced and aligned in order to prevent further damage. This can save you a lot of money in the long run, all you need to do is find an honest mechanic! Engineering Defect Automotive engineering is not a perfect science; many vehicle parts come with defects and wear issues. Cars that are well designed generally have fewer defects, but some cars were simply manufactured with a propensity for wheel bearing issues somewhere throughout the course of the vehicle’s life. Usually automotive shops recommend that if one wheel bearing becomes damaged that the corresponding wheel’s bearing should also be replaced (i.e. front driver’s side and front passenger’s side). While this might make sense for the sake of symmetry, depending on the condition of the other wheel bearing it is usually not necessary to replace both for this reason alone. Here at Santa Barbara Autowerks we pride ourselves on honesty and integrity; we don’t offer services or replacements to our clients unless they’re necessary for their safety or will save them money and energy in the future. As one of the highest quality leading dealership alternatives in Santa Barbara, CA, we tailor our services to German-engineered vehicles, making us experts in German vehicle repair and maintenance. We are passionate about and highly experienced in working with cars like Audi, BMW, Mercedes, Porsche, MINI, and Volkswagen. If you think your German car’s wheel bearing might need to be replaced, please contact us for an honest, expert opinion without a hidden agenda.
Дата Публикации: 10-12-21
Industry Developments: Extrusion Profile Heat Sinks
Описание: Industry Developments: Extrusion Profile Heat Sinks Extruded metal heat sinks are among the lowest cost, widest used heat spreaders in electronics thermal management. Besides their affordability, extruded heat sinks are lightweight, readily cut to size and shape, and capable of high levels of cooling. Most extruded heat sinks are made from aluminum alloys, mainly from the 6000 alloy series, where aluminum dominates. Trace amounts of other elements are added, including magnesium and silicon. These alloys are easy to extrude and machine, are weldable, and can be hardened. Common alloys for extruded heat sinks are the 6063 metals. These can be extruded as complex shapes, with very smooth surfaces. 6061 aluminum is also used for extrusions. Its tensile strength (up to 240 MPa) is superior to 6063 alloys (up to 186 MPa). In addition to heat sinks, these aluminum alloys are popular for architectural applications such as window and door frames. The surfaces of these metals can be anodized to replace their naturally occurring surface layer of aluminum oxide. Anodizing provides more heat transfer, corrosion resistance and better adhesion for paint primers. It is an electrochemical process that increases surface emissivity, corrosion and wear resistance, and electrical isolation. The Extruding Process Aluminum alloys are popular for extruding as heat sinks because they provide both malleability and formability. They can be easily machined and are as little as one-third the density of steel. This results in extrusions that are both strong and stable, at a reduced cost relative to other materials. The aluminum extrusion process starts with designing and creating the die that will shape the heatsink extrusion. Once this has been done, a cylindrical billet of aluminum is heated up in a forge to high temperatures, generally between 800-925°F (427-496°C). Next, a lubricant is added to the aluminum to prevent it from sticking to any of the machinery. It is then placed on a loader and pressure is applied with a ram to push heated aluminum through the die. During this process, nitrogen is added in order to prevent oxidation. The extruded part will pass completely through the die and out the other side. It has now been elongated in the shape of the die opening. The finished extrusion is then cooled, and if necessary, a process of straightening and hardening creates the finished product. ging process before being ready for market. Finished heat sinks typically come with anodized surfaces, which can enhance their thermal performance. Alternatively, a chromate finish provides some corrosion protection, or can be used as a primer before a final paint or powder coating is applied. Shapes of Extruded Heat Sinks Extrusions tooling heat sink profiles range from simple flat back fin structures to complex geometries for optimized cooling. They can be used for natural (passive) or forced convection (active) with an added fan or blower. Extruded profiles can also include special geometries and groove patterns for use with clip or push pin attachment systems. 6063 aluminum alloy has a thermal conductivity of 201-218 W/(mK). Higher tensile strength 6061 aluminum’s thermal conductivity ranges from 151-202 W/(mK). Besides choosing the aluminum alloy, selecting an optimal extruded heat sink should factor in its overall dimensions and weight, the specified thermal resistance, and the extrusion shape (flat-back, flat-back with gap, hollow, double-sided, etc.). Extruded heat sinks can be designed with very thin, and thus more, fins than other sink types. They can be extruded with aspect ratios of around 8:1, which can greatly optimize heat sink performance. A heat sink’s aspect ratio is basically the comparison of its fin height to the distance between its fins. In typical heat sinks the aspect ratio is between 3:1 and 5:1. A high aspect extruded heat sink has taller fins with a smaller distance between them for a ratio that can be 8:1 to 16:1 or greater. Linear Cellular Alloys (LCAs) are metal honeycombs that are extruded using powder metal-oxide precursors and chemical reactions to obtain near fully dense metallic cell walls. Either ordered periodic or graded cell structures can be formed. In this work, the performance of heat sinks fabricated from stochastic cellular metals is compared to that of LCA heat sinks. Flash diffusivity experiments are performed to determine the in situ thermal properties of cell wall material. The pressure drop for unidirectional fluid flow in the honeycomb channels and the total heat transfer rate of LCA heat sinks are experimentally measured. These measurements are compared to values predicted from a finite difference code and commercial computational fluid dynamics (CFD) software. A three-dimensional finite element model of a multichip module (MCM) has been developed by using ANSYS? finite element simulation code. The model has been used for thermal characterization of the module. In addition, optimum dimensions of an external heat sink, which maintains the specified device’s junction temperature within desired operating temperature limits, are determined as functions of air flow rate and power density of surrounding semiconductor devices. Parametric studies have been performed to study the effects of heat sink height, width and length on junction-to-ambient thermal resistance of a high power application specific integrated circuit (ASIC) device found in the MCM assembly. A set of curves are generated to select either heat sink dimensions or air speed for a given design requirements. Influence of the power output of surrounding devices on the thermal performance of the high power ASIC device is also assessed. The predicted results indicate that the ASIC device’s junction temperature as well as junction-to-ambient resistance increase as the power of the surrounding packages increases. This effect diminishes if a sufficiently large heat sink is used to cool the package. There are different metals with different properties, some metals are used for luxury purposes such as diamond and gold, others are used for building purposes such as brass, nickel, steel, copper, and many more. Every piece of equipment, to work efficiently, requires a good building block. And while engineering important components it is extremely important to look at the qualities of the material that are going to be used and it is also important to keep a check on the factors that can affect the material, Aluminium in this case. Aluminum is considered the best option for engineering heat sinks because it is cost-friendly, lightweight and most importantly has great thermal conductivity. Which Metals Conduct Heat The Best? Copper and Aluminium among other metals have the highest thermal conductivity. Before using metal in any sort of application it is very important to check the thermal conductivity of that metal. The rate of thermal conductivity helps to decide which metal should be used for a specific purpose. Aluminum is a great conductor of heat, which makes it useful for constructing heat exchangers. On the other hand, steel is a very poor conductor of heat which makes it useful for high-temperature environments. This is why Aluminum is preferred to be used in constructing a heat sink. Thermal Conductivity Heat transfers in three ways; radiation, convection, and conduction. Thermal Conduction is a process where two objects of different temperatures come into contact with one another and when they meet fast-moving molecules from the warmer object transfer the energy to the slow-moving molecules in the cooler object. Aluminum heat sinks Aluminum is considered beneficial for electrical device managers. It is a great metal to be used in the construction of critical power cooling systems. Improvement in extrusion profile technology has made it possible to engineer heat sinks which call for a blend of greater strength and lighter weight. Aluminum in comparison with other metals such as copper has lower thermal conductivity but it is far too difficult to extrude them into the shape of a heat sink. Secondly, Aluminium is a lightweight metal, which is also another property that other metals do not possess. Heat Sinks Heat sinks are mainly used inside computers to cool down the CPU(Central Processing Unit), they are also used in lighting devices, LEDs, and power transistors. Heat sinks are designed in a way to have a large surface area to maximize the contact with the fluid medium, such as air or liquid coolant to absorb heat and direct it away from the device. Aluminum alloys are preferred to be used in constructing heat sinks. This is because Aluminium is lighter and cheaper than copper. How does a heat sink work? Computers heat up and if the heat is not removed from the device it can actually damage the entire system. To direct the heat away from the system it is necessary to install a heat exchanger. Heat sink directs the heat away from the computer, it does this by transferring the heat generated in the system to a fluid medium such as air or a liquid coolant, whereby it is directed away from the device. What is the purpose of a heat sink? The purpose of a CPU heatsink is basically the maintenance of the computer. Without a heat sink, the system can overheat and therefore can stop working efficiently. To ensure smooth working of the device it is important to install a heat sink to direct generated heat away from the system and prevent overheating. Why is a heat sink important? As stated above, a skived fin heatsink is vital for extending the life of a lighting device. It absorbs unnecessary heat and directs it away from the device. Heat sinks increase the efficiency of the device by removing the excess heat which is why it is an extremely important component. Without a heat sink, computers or other related devices can expire quicker. Heat sinks keep the system cool and provide a good working environment to the other components which heat up quite quickly. Factors Affecting Aluminum Heat Sink Quality Quality Requirements For Ingots The blend of alloys in an ingot must be strictly monitored and controlled, for purification purposes. To make sure that the structure and properties are not imbalanced it is important to make sure that the alloys are homogenized. The surface of the ingot must be smooth and there must not be any sand. The end of the ingot must be flat.
Дата Публикации: 10-12-21
Benefits Of Automatic Bagging Machines
Описание: Benefits Of Automatic Bagging Machines An Automatic Bagging Machine is a mechanism that automates the packaging process in production. The packaging machine automatically inserts the product in a bag or a pouch and seals it. By installing Automatic Bagging Machines in a company’s packaging operations, companies have several advantages on expenses and productivity. Businesses, large or small, are always looking for ways to maximize time and labour while reducing their production cost. Choosing the right type of Automatic Bagging Machines that suit business needs can help fulfill these objectives. There will be increased productivity, enhanced consistency, reduction in quality issues, and reduced workstations. Moreover, you will notice the improvement in packaging accuracy and the safety of both products and workers. You can install Automatic Bagging Machines in almost any production facility and use them to pack products such as cosmetics, pharmaceuticals, mechanic parts, food, and beverages. Benefits of Installing Automatic Bagging Machines There are numerous benefits associated with the installation of an Automatic Bagging System in production facilities. Here are some of the main advantages. Enhanced Efficiency Integrating Automatic Bagging Machines will help improve the efficiency of operations and your warehouse and reduce potential quality issues. Customisable Automatic Bagging Machines The Automatic Bagging Machines are customisable mainly to the production line requirement. With automated bagging, you can pack individual parts of a product. Automatic Bagging Machines are also suitable to be used with different packaging materials. Customize the colouring and size of the bags and preprinted styles. Product Safety In many instances, insufficient packaging may adversely affect the lifespan of goods. This is a common occurrence with products packaged through manual operations. An Automatic Bagging Machine will prevent mistakes. Automation will improve the quality of your Paper box packing machine and eliminate the chances of damage to goods or reduced shelf life. Improved Productivity Automatic Bagging Machines will reduce the chances of errors in the production line. Compared with manual labour, the productivity level will show improvement due to the speed and consistency associated with automatic bagging systems. Whether you use semi or fully Automated Bagging Machines, there will still be substantially more quantity produced than hand-packaging operations. The Automatic Bagging Machines involve loading a film roll or bagging on the system and pack one product after another quickly. Only when the bagging material runs out will it need someone to refill, saving time and money. Financial Benefits of Automatic Bagging Machines Cost savings and coming up with new solutions are always one of the top priorities of businesses. Automatic Bagging Machines can be a cost-effective investment in the long term. Not only will it improve production volumes but significantly reduce the workforce requirements. Reduce the cost of labour for sorting, processing, folding, and banding the products. For instance, if 20 employees currently working on your production lines handling the packaging and deploying an automatic bagging infrastructure will save you money by reducing the need to have 20 employees working on packaging and increasing production volume translating into increased revenue. Improved Sustainability One of the best ways is to reduce the need for transportation in your production process. Automatic Bagging Machines produce uniform packaging that allows more products to fit fewer trucks than hand-made inconsistent bagging. The packaging method helps you ship more items with a lower carbon footprint. Save cost on fuel budget while reducing greenhouse gas emissions. Saving on Material Costs Most companies have packaging requirements ranging from different bagging sizes. Instead of investing in purchasing and inventory various bags, Automatic Bagging Machines allow you to buy film rolls to make bags of different sizes. Moreover, using thinner gauge packaging film, there can be some additional savings on material cost. How to Evaluate Best Automatic Bagging Machines for Your Company Not only is it an effective method, but it also simplifies your packaging operations while saving money on many fronts. However, you must pay due diligence when looking for the right automatic bagging equipment for your company. Speak to the manufacturer about your specific needs and ways to improve the system’s efficiency. Moreover, you will always need employees to operate the machinery. Thus, make sure you pick something easy to use that requires minimal training. A packaging machine for penny carton box packing machine, such as bagels, bread, donuts, in pre-made plastic bags includes an endless chain carrying a plurality of regularly spaced bag grippers, the chain being entrained about sprocket wheels to define first and second flights. The bag grippers pick up a topmost bag from a stack while traversing the first flight and carry it to a bag filling station aligned with the second flight. An infeed conveyor has a plurality of transversely extending product trays containing the articles to be packaged which are transported with intermittent motion to the bag filling station in synchronism with the bag grippers. While the tray is stationary, movement of the bag gripper along the second flight draws the bag over the product-filled tray present at the bag filling station. A product pusher, synchronized with movement of the bag grippers and with the infeed conveyor, pushes the bagged products off the infeed conveyor onto a take-away conveyor. This invention relates generally to high-speed packaging equipment, and more particularly to a machine for bagging a stack of articles oriented in side-by-side relation into pre-made bags. II. Discussion of the Prior Art Certain articles or products are of a size and shape that may make it difficult to package on a high-speed basis. For example, bagels or donuts, because of their size and shape, make them somewhat difficult to mechanically manipulate so that they can be placed in polyethylene bags in a stacked relationship. This is referred to in the industry as "penny packing" because of the similarity to the way in which coins are loaded into paper coin wrappers. While loaves of sliced bread have been successfully wrapped by machines such as described in U.S. Pat. No. 3,868,807 and manufactured by Foremost Packaging Machine Company of Woodinville, Wash., efforts to mechanize the penny paper box packing machines, donuts, and the like, at high speeds have proven to be a challenge because of their more irregular shape. While the present invention has been devised to penny pack food items, like bagels and donuts, those skilled in the art will appreciate that the machine to be described hereinbelow can also be used for packaging other food items, e.g., bread, as well as non-food items, by merely making minor modifications to the shape and size of various machine parts. OBJECTS It is accordingly a principal object of the present invention to provide an improved apparatus and method for inserting products in stacked relation within pre-formed plastic or paper bags. Another object of the invention is to provide an improved packaging machine for placing articles, such as bagels, in plastic or paper bags on a continuous basis with very low machine down-time for cleaning, adjustment, maintenance and repair. Yet another object of the invention is to provide a high-speed packaging machine for face masks multiple pieces plastic bags packing machine in pre-made bags that is simple in construction and which can be manufactured at a relatively low cost. Still another object of the invention is to provide an improved packaging machine operating with a cycle time capable of producing bagged articles of a predetermined number of items per bag at a rate exceeding one per second. SUMMARY OF THE INVENTION The foregoing objects and advantages of the invention are achieved by constructing a packaging machine that includes a frame with an endless chain disposed about sprocket wheels mounted on the frame so that the chain defines first and second flights. The chain is adapted to be driven by an electric motor, and secured to the chain are a plurality of bag grippers that are designed to pick up a topmost bag from a stack of pre-formed bags as the gripper traverses one or the other of the first and second flights and then carries the bag to a bag filling station located in the other of the first and second flights. A product infeed conveyor transports trays of products to be packaged to the bag filling station where the products are temporarily held stationary and are oriented in a horizontally stacked relation. A bag carried by a bag gripper is drawn over a tray of products disposed in the bag filling station as the bag gripper moves in the other of the first and second flights. The packaging machine further includes a product take-away conveyor whose head end is positioned adjacent the bag filling station. A product pusher synchronized with the movement of the bag gripper and the product infeed conveyor is used to displace bag covered products from the bag filling station onto the product take-away conveyor. The desired synchronization is achieved by providing a rotatable indexing cam that is coupled to the electric motor driving the endless chain to which the bag grippers are affixed. The indexing cam has a cam profile thereon that cooperates with a cam follower that is operatively coupled to the infeed conveyor for controlling acceleration and deceleration thereof in a controlled fashion that reduces the effects of inertia on the products being carried. The product pusher is driven in a timed, reciprocating fashion through the bag filling station by means of a chain driven roller that periodically engages a shuttle mechanism to which the pusher is attached. Referring first to FIG. 1, there is indicated generally by numeral 10 the packaging machine comprising a preferred embodiment of the present invention. It is seen to include a structural frame, portions of which are identified by numeral 12. It may be fabricated out of steel tubes having a generally rectangular cross-section. The frame 12 is covered by sheet metal panels configured to shield the internal working mechanism of the packaging machine 12. Specifically, a top panel 14 is affixed to the frame 12 as are left and right end panels 16 and 18, respectively. A front panel 20 is partially broken away to better reveal certain internal working mechanism which will be described in greater detail hereinbelow. The partial perspective view of FIG. 3 is helpful in understanding the manner in which the bag grabber assemblies 28 are coupled to the parallel, spaced apart chains 30 and 32. Specifically, links of the two chains directly across from one another are replaced with specially shaped links 68 and 70 having an outwardly projecting stub with an aperture therethrough for receiving the cylindrical support arm member 26 therethrough. It can be appreciated that by virtue of this connection, the arm 26 at all times remains parallel to the shafts supporting the chain sprocket wheels throughout the entire orbital path defined by chains 30 and 32. Affixed to the end portion 72 of the support arm 26 is a cam follower mounting block 74 to which a pair of cam rollers 76 and 78 are journaled. The cam rollers cooperate with an elongated cam member 80 that is divided into an ascending ramp portion 82 (FIG. 3), a horizontal cam portion 84 (FIG. 2) and a descending ramp portion 86 (FIG. 2). The cooperation between the cam rollers 76 and 78 and the cam member 80 insures that the support arms 26 will remain aligned with the orbital slot 24 formed in the front cover member 22 to maintain the orientation of the bag grabbers; also the chains 30 and 32 would otherwise sag between their support points at the several sprocket wheels. With continued reference to FIG. 3, the mechanism used to assist the cam mounting block 74 in traversing the arcuate path about the sprocket wheels 46 and 56 will be described. Mounted to the frame proximate the pairs of end sprocket wheels 42, 54 and 46, 56 is a journal bearing 88 supporting a stub shaft 90 to which is affixed a lifter arm 92 and a chain sprocket wheel 94. A short, endless chain 93 is deployed over the sprocket wheel 94 and about a further sprocket wheel 96 affixed to and rotatable with the shaft 48. An identical assembly is associated with the end sprocket 42. The axle 98 on which the cam roller 76 is mounted extends laterally outward and affixed to the end thereof is a further roller 100. This roller 100 is adapted to be received in a arcuate groove 102 formed in the end of the lifter arm 92 and it also cooperates with a semicircular recess 104 formed in a guide plate 106 also mounted to the frame. When it is recognized that the bag grabbers 28 are spaced from one another by a predetermined distance equal to an integral number of revolutions of the end sprocket wheels 46 and 56, it can be appreciated how the arm 92 can be made to arrive at a precise time to engage the roller 100 so as to provide support to the cam follower mounting block 74 to maintain it in a horizontal disposition as it traverses the turn and again positions the elongated cam member 80 between the cam follower rollers 76 and 78. FIG. 4 is a detailed drawing of one of the bag grabbing mechanisms forming part of the packaging machine 10 of FIG. 1. The bag grabbers 28 each comprise first and second curved sheet metal jaws 102 and 104 that are suspended from the arm 26 that projects laterally outwardly through the slot 24 formed in the front panel 22 of the paper box gluing machine. The lowermost jaw 102 is welded or otherwise positively affixed to a shaft 106 which passes through first and second clamping rings 108 and 110. The clamping ring 110 is welded at 112 to a similar clamping ring 114 assembled onto the end of arm 26. This allows the entire assembly 28 to be adjusted in the lateral or horizontal direction by loosening the cap screws 116 and sliding the ring 114 along the shaft 26 to a desired position and then retightening the screw 116. Likewise, vertical adjustment of the bag grabber can be achieved by loosening the cap screw 118 on the clamping ring 110 and shifting the shaft 106 before retightening that cap screw. The clamping ring 108 has welded to it a bearing sleeve 120 and passing through the bearing sleeve is a cylindrical rod 122 to which the jaw 104 is attached. Secured to the other end of the rod 122 is a crank assembly including a hub 124 and a crank arm 126. Journaled to the end of the crank arm 126 opposite the hub 124 is a cam follower roller 128. A tension spring 130 is operatively coupled between the crank arm 126 and a pin 132 affixed to the shaft 106 to normally spread the jaws 102 and 104 apart from one another.
Дата Публикации: 10-12-21
Neutron and gamma radiation shielding properties
Описание: Neutron and gamma radiation shielding properties High performed new heavy concrete samples were designed and produced that absorption parameters were determined for gamma and neutron radiation by using Monte Carlo Simulation program GEANT4 code. In the sample production, many different materials were used such as; chromite (FeCr2O4), wolframite , hematite (Fe2O3), titanium oxide (TiO2), aluminum oxide (Al2O3), limonite (FeO (OH) nH2O), barite (BaSO4), materials. Furthermore, calcium aluminate cement (CAC) was utilized for high temperature resistant. In the current study, five different new heavy concrete samples were produced then physical and chemical strength of them tested. High-temperature-resistant tests were made at 1000°C and good resistance against high temperature was observed. Neutron equivalent dose measurements were made for by using 4.5 MeV energy 241Am-Be fast neutron source. Results compared with paraffin and conventional concrete. It was found that the new heavyweight concretes had the better absorption capacity than paraffin and conventional concrete. Gamma radiation absorption measurements also were carried out at the energies of 160, 276, 302, 356, and 383 keV by using 133Ba point radiation source. It has been suggested that the new produced concretes can be used for radiation safety in the nuclear applications. Radiation is often used in applications such as in energy production, in medicine diagnosis and treatment, in material research and investigation. In addition, it is also used in such areas as agriculture, archeology (in carbon determination), space exploration, military, geology, and many others (U.S. NRC, 2010). Radiation leaks may occur during these applications (Lamarsh, & Baratta, 2001); therefore, it must be properly shielded. In radiation shielding works, conventional materials such as concrete, steel, alloy, ceramic, glass, and polymers are widely used (Aygün et al., 2019; Kumar, Sayyed, Dong, & Xue, 2018; Sayyed, Akman, Kumar, & Ka?al, 2018). In these studies, concrete is among the most widely used materials (Li et al., 2017). Concrete is a composite material which glued in such a way that aggregate particles (sand, gravel, stone, and filler) with cement or a binder. Traditional concrete is not as effective in nuclear shielding material radiation, but it is a very common used building material. The traditional concrete lead bricks for radiation shielding characteristic may vary and is dependent on the chemical composition of the concrete. New types of concrete samples have been developed by different the aggregated used for preparing concrete, depending on the available natural and artificial materials (Mukhtar, Shamsad, Al-Dulaijan, Mohammed, & Akhtar, 2019; Chen, 1998). Heavy concrete is the most common material used in radiation shielding equipment. Heavy concrete is obtained by adding high-density aggregates into normal concrete. Normal-weight concrete density varied between 2200 and 2450 kg/m3 while heavy concrete’s density is ranging from about 2900 and 6000 kg/m3 (Nawy, 1997). Some natural minerals such as hematite, magnetite, limonite, serpentine, siderite and barite can be used as aggregates in heavy concrete production. In literature, numerous experimental and theoretical researches have been conducted to develop new heavy concrete. Different minerals like siderite, limonite were used to produce heavy concrete in order to provide gamma radiation shielding. It was reported that the gamma radiation absorption capacity of heavy concretes is high (Basyigit et al., 2011). Boron-containing multi-layered new heavy concretes were produced and radiation shielding properties were determined. It is reported that these concretes are very high in 14 MeV neutron absorption capacity (Sato, Maegawa, & Moshimatsu, 2011). In a different study, some metal oxides such as Al2O3, AS2O3, BaO, CaSO4, CdO, Cr2O3, CuO, Fe2O3, K2O, MgO, MnO, Na2O, NiO, P2O5, PbO4, SrO, TiO2 was used in the heavy concrete production, and it was stated that the use of these new heavy concretes in nuclear reactors is appropriate (Abdo, 2002; Erdem, Baykara, Do?ru, & Kulu?ztürk., 2010; Mortazavi, Mosleh-Shirazi, & Baradaran Ghahfarokhi et al., 2010). Seltborg et al.produced heavy concretes by using, such as calcium (Ca), strontium (Sr), barium (Ba), radium (Ra) magnesium (Mg) elements. They determined these heavy concretes can be used to shield gamma and neutron radiation in nuclear reactors (Seltborg et al., 2005). In the present study of tungsten oxide (WO3) gamma radiation mass attenuation coefficient in the concrete, the effect on the coefficient was investigated. Appropriate geometry found by using MCNPX and XCom simulation programs. It is found that shielding properties when nanoparticle WO3 doped in concrete more than microparticle WO3 (Tekin, Singh, & Manici, 2017). In another study, high-density concrete (ρ = 4.71 g/cm3) was made by using steel balls and in aggregate the debris of the demolished concrete buildings in the earthquake region in Fukushima. Good shield properties were determined this of heavy concrete and it is shown that can be used in storage radioactive waste (Sanjay, Yusuke, Kimura, Fujikura, & Araki, 2018). Heavy concrete was made using lead-zinc slag waste instead of sand which can be used gamma radiation shielding. Shielding and strength properties were investigated of this concrete and compared with conventional concrete. It is reported that lead–zinc slag waste concretes better radiation shielding and strength characteristic than conventional concretes (Mohamed, 2017). Medical cyclotron is a system designed for radiopharmaceutical production, which high-level radiation emit. Shielding wall thickness was calculated by using Monte Carlo simulation when cyclotron system used to operate that may occur radiation. Consequently, for shielding, radiation at 200-cm-thickness concrete wall need was determined (Jang, Kim, & Kim, 2017). Some mining wastes suitable for heavy concrete production. For instance, Gallala et al. have produced new heavy concrete by using barite-fluorspar mine waste (BFMW) aggregates and investigated their gamma radiation shielding, mechanical strength properties. The results clearly showed when ratio 25% BFMW added to concretes has better gamma radiation shielding and compressive strength properties than conventional concrete (Gallala et al., 2017). Tekin et al., using MCNPX code, demonstrated that high strength concrete containing nanoparticles of WO3 and Bi2O3 had enhanced shielding capacity for gamma radiation (Tekin, Sayyed, & Issa, 2018). Five different concrete types were made using magnetite aggregates and 0%, 2%, 4%, 6%, and 8% of titanium dioxide (TiO2) nanoparticles for nuclear power plant shielding material. Some of the protecting parameters such as MAC (mass attenuation coefficients) HVL (half-value layer), TVL (tenth value layer), and linear attenuation coefficients (LAC) were determined for 662, 1173, and 1332 ?keV energy of gamma ray used. It is reported, the significant effect on radiation shielding properties occurred within 8% of TiO2 nanoparticles (Iman et al., 2019). Some natural minerals can be using heavy concrete in production. Different concrete types which including natural perlite mineral and B4C have been experimentally investigated and gamma radiation shielding parameters have been determined (Agar et al., 2019) In this study, new concrete samples were designed and produced using Monte Carlo simulation program Geant4 code. The production of heavy concrete for radiation shield was made based on the concrete production process such as mixture proportion, ratio of water to cement, cement hydration. Furthermore, new concrete candidates with good radiation shielding ability at high temperature have been produced and it has been shown that raw materials such as chromite, wolframite can be used in production. In Monte Carlo simulation program, the Geant4 code is used to determine the interactions between radiation and materials. In addition, it can be used to predict nuclear events that may occur at the point of radiation and detector interaction. Geant4 software is the most developed, for analyses biological effects of radiation-induced and their modification nuclear shielding engineering. Also, Monte Carlo program Geant4 to simulate can be used to predict the transport, accumulation of incident particles through the walls of a nuclear power plant (Agostinelli et al., 2003). It is used in applications in nuclear physics, particle accelerator designing, space investigation, and medical physics. Detailed information can be found at www.Geant4.org. 2.2. Sample preparation New heavy concrete samples were produced by using different natural aggregates such as chrome ore (FeCr2O4), wolframite , hematite (Fe2O3), limonite (FeO (OH) nH2O), barite (BaSO4). Nickel oxide (NiO) was used to fill the pores that could form in the concrete. The chromium ore (FeCr2O4) mineral has a density of average 4.79 g/cm3 and it melts in temperature 1650–1660°C (Jay, Meegoda, Zhengbo, & Kamolpornwijit, 2007). The chrome ore sample was taken from the Kayseri city Yahyal? district chrome mine. This chrome ore contains such minerals 53.19% Cr2O3, 16.80% MgO, 11.15%Al2O3, 15.11%Fe, 2.72%SiO2, 0.007%S, and 0.005% P according to Eti (Chromium Ferrochrome Foundation). Wolframite is a mineral with a density of 7.1–7.5, average 7.3 g/cm3 and 11.70% MnO, 16.85% FeO, 71.46% WO3 including (Tolun., 1951). This ore was obtained from an Uluda? tungsten mine, which is located in the province of Bursa and is approximately 2200–2300 m high from the sea. According to the pioneering simulation work, both gamma and neutron radiation absorption cross-sectional values were determined higher in chromite and wolframite minerals. Furthermore, these minerals have both refractory properties and high mechanical strength and plenty of reserves. Therefore, these minerals were used in the production of heavy concrete. Hematite, titanium oxide, aluminum oxide, limonite, siderite, barite, materials are always used materials for the production of heavy concrete, but for that, the chromite and wolframite minerals are not very commonly used. The usage of natural chromite and wolframite minerals provided will be with this work in the nuclear industry. Chromium oxide (Cr2O3) was used to fill capillary cavities that may form in concretes. When concrete components were selected, the high macroscopic cross-sectional values were taken into account.
Дата Публикации: 10-12-21
Face masks hurting your ears? These easy solutions can help
Описание: Face masks hurting your ears? These easy solutions can help In this period of the Covid-19 pandemic, a protective mask has become a common object of use to contain virus transmission. The imminent need for masks has led many governments to produce them, including surgical masks with mask earloop or masks with side cuts at the ears. Among those on the market, surgical masks with elastic loops are the ones most chosen by parents for their children. These elastics cause constant compression on the skin and, consequently, on the cartilage of the auricle, leading to erythematous and painful lesions of the retroauricular skin when the masks are used for many hours a day. Pre-adolescent children have undeveloped auricular cartilage with less resistance to deformation; prolonged pressure from the elastic loops of the mask at the hollow or, even worse, at the anthelix level can influence the correct growth and angulation of the outer ear. In fact, unlike when using conservative methods for the treatment of protruding ears, this prolonged pressure can increase the cephaloauricular angle of the outer auricle. It is important for the authorities supplying the masks to be aware of this potential risk and for alternative solutions to be found while maintaining the possibility of legitimate prevention of the potential spread of the virus. We read with interest the article by Ors on prominent ear deformities and its recurrence rate. This article gives us the opportunity to better understand the effectiveness of nonsurgical options for the treatment of ear anomalies in young patients (5–14 years). The current COVID-19 pandemic has imposed the worldwide use of masks in addition to social distancing. The use of masks applies to everyone, even children, certainly if over the age of 5–6 years. The masks distributed to the population by government bodies are of various types, both as regards to their shape and the systems for fastening them to the head, but, basically, they are divided into 4 large categories: masks with elastic (ear loops), strips of fabric with lateral slits (side cuts at the ears), with tapes, single cervical band. Small children are rarely made to wear the masks with tapes, due to the difficulty in positioning and tying the tapes. The “single band” masks that wrap around the neck have the drawback of sliding downwards and, therefore, not keeping the nose covered; furthermore, if used during the summer season, they tend to produce a humid microenvironment that favours the development of dermatitis and eczema. Many adults (health care workers and others) complain about discomfort associated with round elastic earloop, due to the continuous pressure of the elastic behind the ear. Several methods have been proposed to overcome this problem: from the use of hairpins to hang the elastic bands from the forehead to the use of various types of bands that pass behind the back of the neck and to which the loops of the mask are attached. However, these methods used by adults are not used by children, resulting in constant pressure of the elastic on the skin of the posterior portion of the auricle. All bodies subject to the action of a force undergo deformation, which depends not only on the intensity of the force applied, but also on the nature of the body itself. In general, deformations can be of two types: elastic, which disappear when the force is no longer applied, and non-elastic, which remain even after applying the force. Cartilage has memory thanks to the presence of elastic fibres; although this allows it to return to its initial condition when deformed, if the stimulus persists, it can lead to permanent changes in its conformation. This principle has been used for many years for the conservative correction of protruding ears . Obviously, in order to use these non-surgical correction techniques (e.g. bands, patches, ear splint therapy) with benefit, the development of the various components of the ear must not be completed. This can happen if applied in children who are less than 8–10 years old, because after that age the cranial volume, with its appendages, almost completely reaches total growth . The literature reports important successes in the treatment of protruding ears with conservative methods, with a success rate that shows a decline from 91% in infants to 33% in 9-year-old children . The main advantage of this treatment is that it keeps the splint in position for a long time, so that it can exert constant pressure on the growing cartilage, changing it into the desired shape. The success of these conservative methods confirms that a constant pressure maintained for a long time on the cartilage of the ear of growing children can change the shape and increase the cephaloauricular angle of the outer auricle. Griffin et al. have demonstrated that the cartilage of the auricle has a homogeneous structure, although the concha has a greater resistance to deformation than the helix . This resistance is comparable to that of nasal cartilage (about 200 times lower than the resistance of Medpor prostheses used for ear reconstruction). The concha had a greater rate of loading than the antihelix when taking into consideration the anatomical structure of the cartilages. One reason for this difference may be that the concha is a curved structure, which can support compressive loads . Therefore, if a constant elastic force were applied at the level of the concha, it would be less harmful than if applied at the antihelix level. It is well known that the pressure of the mask elastic on the skin of the posterior concha of the auricle for a long time causes pain and erythema, due to the continuous rubbing of the elastic on the skin in the same position. This has led some users to apply silicone rear ear supports that decrease decubitus, but increase the distance of the auricle from the mastoid region. Others, on the other hand, prefer to change the position of the elastic by moving it more towards the antihelix than the mastoid region, thus applying an elastic force in an area where the cartilage has less resistance, with a consequent increase in the cephaloauricular angle of the outer auricle. Therefore, the use of surgical masks with flat elastic earloop in growing children for many hours a day not only leads to intolerance and decubitus of the retroauricular skin (as for adults), but can also influence the correct growth and angulation of the outer ear with the consequent increase in the incidence of protrusion of the outer auricle (Fig. 2a and b). One alternative to the surgical mask is the earmuffs mask (in which the ears are completely wrapped, held in place by mask elastic cord at the back of the ear) or the band mask with lateral slits at the ears: also these models, due to their conformation, tend to create a constant pressure on the antihelix, increasing the auriculocephalic angle (Fig. 2c). Many scientific societies of paediatrics and pedagogy have raised doubts about the risks that this situation of forced constriction by Covid-19 can cause on the normal psychophysical development of children; however, it has never been pointed out how the use of surgical masks with ear loops can be harmful to the correct development of the auricle by permanently modifying the cartilage of the concha in growing children. We are confident that highlighting this potential complication to those involved in the procurement of masks will stimulate the search for alternative solutions, while maintaining the possibility of legitimate prevention of the potential spread of the virus. Face masks are an essential part of protecting yourself and others from coronavirus, but that doesn't make them any easier to wear. Over the past few weeks, we've realized firsthand how masks can wreak all sorts of havoc on our skin. Now many of us are dealing with another unfortunate side effect: discomfort on our ears. Those loops that keep your mask in place can put a lot of pressure on your ears and aggravate your skin, but there are a few ways to prevent that. From skin care tips to face mask ear savers, these are the tricks experts swear by. The majority of us only wear a mask on Halloween as temporary props we can take off at any time. But now that we're wearing masks out in public on a regular basis, we're quickly realizing that they can be uncomfortable. "Moisture and friction can cause irritation, as prolonged mask use can irritate sensitive skin. Some masks are tied around the head, and some are fastened by loops that go over and around the ears, so the ears can (be) irritated as well," said Dr. David Lortscher, board-certified dermatologist and CEO of skin care brand Curology. Irritation can show up in many forms, including bruising, raw skin or increased acne and breakouts. When face mask straps rub against your ears, they create friction that can result in inflammation in the outer skin layer and blistering. "This can cause open wounds or scabbing of the skin, which increases your risk of developing an infection. Plus it makes it a challenge to apply a mask again over those areas," said Dr. Joshua Zeichner, board-certified dermatologist and director of cosmetic and clinical research at Mount Sinai Hospital's department of dermatology.
Дата Публикации: 10-12-21
Mystery of the wheelie suitcase: how gender stereotypes held back the history of invention
Описание: Mystery of the wheelie suitcase: how gender stereotypes held back the history of invention In 1970 an American ABS luggage executive unscrewed four castors from a wardrobe and fixed them to a suitcase. Then he put a strap on his contraption and trotted it gleefully around his house. This was how Bernard Sadow invented the world’s first rolling suitcase. It happened roughly 5,000 years after the invention of the wheel and barely one year after Nasa managed to put two men on the surface of the moon using the largest rocket ever built. We had driven an electric rover with wheels on a foreign heavenly body and even invented the hamster wheel. So why did it take us so long to put wheels on suitcases? This has become something of a classic mystery of innovation. Nobel prize-winning economist Robert Shiller discusses the matter in two different books, Narrative Economics and The New Financial Order. He sees it as an archetypal example of how innovation can be a very slow-footed thing: how the “blindingly obvious” can stare us expectantly in the face for an eternity. Nassim Nicholas Taleb is another world-renowned thinker who has pondered the mystery. Having lugged heavy suitcases through airports and railway stations for years, he was astonished by his own unquestioning acceptance of the status quo. Taleb sees the rolling suitcase as a parable of how we often tend to ignore the simplest solutions. As humans, we strive for the difficult, grandiose and complex. Technology – such as having wheels on suitcases – may appear obvious in hindsight, but that doesn’t mean it was obvious. Similarly, in management and innovation literature, the late invention of the rolling suitcase often appears as somewhat of a warning. A reminder of our limitations as innovators. But there is one factor that these thinkers have missed. I stumbled upon it when I was researching my book on women and innovation. I found a photo in a newspaper archive of a woman in a fur coat pulling a suitcase on wheels. It made me stop in my tracks because it was from 1952, 20 years before the official “invention” of the rolling suitcase. Fascinated, I kept looking. Soon, a completely different story about our limitations as innovators was rolling out. The modern suitcase was born at the end of the 19th century. When mass tourism first took off, Europe’s large railway stations were inundated with porters, who would help passengers with their bags. But, by the middle of the 20th century, the porters were dwindling in number, and passengers increasingly carried their own PP luggage. Advertisements for products applying the technology of the wheel to the suitcase can be found in British newspapers as early as the 1940s. These are not suitcases on wheels, exactly, but a gadget known as “the portable porter” – a wheeled device that can be strapped on to a suitcase. But it never really caught on. In 1967, a Leicestershire woman wrote a sharply worded letter to her local newspaper complaining that a bus conductor had forced her to buy an additional ticket for her rolling suitcase. The conductor argued that “anything on wheels should be classed as a pushchair”. She wondered what he would have done if she had boarded the bus wearing roller-skates. Would she be charged as a passenger or as a pram? The woman in the fur coat and the Leicestershire woman on the bus are the vital clues to this mystery. Suitcases with wheels existed decades before they were “invented” in 1972, but were considered niche products for women. And that a product for women could make life easier for men or completely disrupt the whole global ABS+PC luggage industry was not an idea the market was then ready to entertain. Resistance to the rolling suitcase had everything to do with gender. Sadow, the “official” inventor, described how difficult it was to get any US department store chains to sell it: “At this time, there was this macho feeling. Men used to carry on luggage for their wives. It was … the natural thing to do, I guess.” Two assumptions about gender were at work here. The first was that no man would ever roll a suitcase because it was simply “unmanly” to do so. The second was about the mobility of women. There was nothing preventing a woman from rolling a suitcase – she had no masculinity to prove. But women didn’t travel alone, the industry assumed. If a woman travelled, she would travel with a man who would then carry her bag for her. This is why the industry couldn’t see any commercial potential in the rolling suitcase. It took more than 15 years for the invention to go mainstream, even after Sadow had patented it. In the 1984 Hollywood film Romancing the Stone, a rolling suitcase is featured as something of a silly feminine thing. Kathleen Turner’s character insists on bringing her wheeled suitcase to the jungle, to the great annoyance of Michael Douglas, who is trying to save them from villains, while tracking down a legendary gigantic emerald. Then, in 1987, US pilot Robert Plath created the modern cabin bag. He turned Sadow’s suitcase on its side and made it smaller. In the 1980s, more women started to travel alone, without a man to carry their spinner luggage set. The wheeled suitcase carried with it a dream of greater mobility for women. Bit by bit, the rolling suitcase became a feature of the modern businessman’s arsenal. We forgot all about the intense and very gendered resistance the product had encountered. But we shouldn’t – because this story carries some important lessons about innovation that we need to hear today. We couldn’t see the genius of the wheeled suitcase because it didn’t align with our prevailing views on masculinity. In hindsight, we find this bizarre. How could the predominant view on masculinity turn out to be more stubborn than the market’s desire to make money? How could the crude idea that men must carry heavy things prevent us from seeing the potential in a product that would come to transform an entire global industry? But is it really that surprising? The world is full of people who would rather die than let go of certain notions of masculinity. Doctrines like “real men don’t eat vegetables”, “real men don’t get check-ups for minor things” and “real men don’t have sex with condoms” kill very real men every single day. Our society’s ideas on masculinity are some of our most unyielding ideas, and our culture often values the preservation of certain concepts of masculinity over life itself. In this context, such ideas are certainly powerful enough to hold back technological innovation. The rolling suitcase is far from the only example. When electric cars first emerged in the 1800s they came to be seen as “feminine” simply because they were slower and less dangerous. This held back the size of the electric car market, especially in the US, and contributed to us building a world for petrol-driven cars. When electric starters for petrol-driven cars were developed they were also considered to be something for the ladies. The assumption was that only women were demanding the type of safety measures that meant being able to start your car without having to crank it at risk of injury. Ideas about gender similarly delayed our efforts to meet the technological challenges of producing closed cars because it was seen as “unmanly” to have a roof on your car. Assumptions about masculinity play a similar role today in relation to innovation around sustainability. For example, we often think that consumption of meat and preferences for large cars – instead of travel by public transport – are essential features of masculinity. This holds innovation back and prevents us from imagining new ways of living powered by new technologies. Perhaps in the future we will laugh at our current struggle to get many men to adopt a more environmentally friendly lifestyle, in the same way that we shake our heads at how unthinkable it was for a man to wheel his suitcase 40 years ago. Ideas about gender also limit what we even count as technology. We talk about “the iron age” and “the bronze age”. We could also talk about “the ceramic age” and “the flax age”, since these technologies were just as important. But technologies associated with women are not considered to be inventions in the same way that those associated with men are. Gender answers the riddle of why it took 5,000 years for us to put wheels on suitcases. It’s perhaps easy to think that we wouldn’t make similar mistakes today. But many of the structural problems are still here. We still have male-dominated industries not interested in dealing with the fact that women influence 80% of all consumer decisions. Products are still being built and designed with only men in mind and we have a financial system that stubbornly refuses to see the potential of women’s ideas. Today, less than 1% of UK venture capital goes to all-female teams. Among the very few women who do get funded, a very large majority are white. Of course, venture capital isn’t everything – there are other ways to fund and scale innovation – but the fact that men, more or less, have a monopoly is certainly a symptom of an economy where women’s ideas are not heard. The many economists and thinkers who have thought about how we didn’t put wheels on suitcases until 1972 were right to note that this story is a symptom of a larger problem. It was just a slightly different problem than the one they imagined it to be. This article was amended on 8 July 2021. Bernard Sadow invented the rolling suitcase in 1970, not 1972, which was the year the invention was patented. Mother of Invention: How Good Ideas Get Ignored in an Economy Built for Men by Katrine Mar?al is published by William Collins (￡18.99). To support the Guardian order your copy at guardianbookshop.com. Delivery charges may apply. 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.
Дата Публикации: 10-12-21
CNC Milling vs. CNC Turning
Описание: CNC Milling vs. CNC Turning: All You Need to Know CNC machining is a rapid manufacturing process that turns digital 3D designs into plastic or metal parts by selectively cutting away material. Many companies require CNC machining service to make parts and prototypes, and many industries use the versatile technology. But CNC machining comes in various forms. Although all CNC machining technologies follow a similar workflow — software turns the digital design into machine instructions, which instruct the CNC machine to cut material — the hardware for cutting material can differ greatly between machines. This article discusses the main differences between two of those machines: CNC mills and CNC turning (or lathes centers). In the article we discuss the essential features of CNC milling parts and CNC turning while also presenting the main advantages of each technology and a selection of common parts that companies can manufacture using each process. CNC milling is one of the most common CNC machining service, and machinists can use it to make a wide variety of CNC machined parts. Prototype companies often use CNC mills to make one-off functional prototypes. CNC mills use computer instructions to move a rapidly rotating cutting tool along three or more axes. When the spinning cutting tool makes contact with the workpiece, it removes material in a controlled manner. The cutting tool makes a succession of passes against the surface of the workpiece until the workpiece resembles the desired part. Most CNC mills keep the workpiece stationary, holding it down on the machine bed with a vice. However, multi-axis CNC mills may rock or rotate the workpiece to create a greater number of cutting angles. This allows the machinist to create more complex parts without having to manually reorient the workpiece. Providers of rapid prototyping services use CNC machining because it is a one-stop, end-to-end process with short lead times. CNC turning is a form of CNC machining that machinists use to make rounded, cylindrical, and conical parts. Although it is less versatile than CNC milling, it is one of the most popular CNC machining services and rapid prototyping services. Machines that carry out CNC turning parts are called CNC lathes or CNC turning centers. They are different from CNC mills in that they rapidly rotate the workpiece in a chuck but do not rotate the cutting tool. The cutting tool, affixed to a turret, moves towards the spinning workpiece under computer instructions and removes material where necessary. A CNC lathe can cut the outside of the workpiece or bore through the inside to create tubular CNC machined parts. The turret of the machine may have multiple cutting tools that can be individually engaged as required. Advantages of CNC Milling CNC mills offer numerous advantages to manufacturers and prototype companies. Unlike lathes, mills are versatile machines capable of creating a range of different shapes. Furthermore, a variety of cutting tools can be used to serve different operations such as roughing and end-milling. Although they are manufacturing machines in their own right, mills are also useful for post-machining. For example, they can be used to add details to turned, molded, or 3D printed parts. CNC milling is also fast, repeatable, and inexpensive in low volumes — partly because it does not require tooling. It is therefore found among manufacturing services and rapid prototyping services. Advantages of CNC Turning The biggest advantage of CNC turning is its ability to create round profiles. It is much more difficult to achieve perfect roundness using other CNC machining parts services like CNC milling or CNC routing. CNC turning is also highly accurate, which makes it a valuable technology for boring holes of precise dimensions with set tolerances. CNC milling and CNC turning can be combined to reap the benefits of both processes. In most cases, CNC turning takes place first, allowing the machinist to mill further (asymmetrical) details on the part. As a rule of thumb, CNC turning is best for parts with round, cylindrical, or conical profiles, and aluminium CNC milling parts is best for everything else. If in doubt, a machining expert can guide you to the right CNC machining service for your unique project. That being said, CNC milling and CNC turning can be combined to good effect. If a part has a predominantly round shape but also requires asymmetrical cuts or features, CNC milling can follow CNC turning in sequence. And although it is less common, CNC turning can also follow CNC milling — if a boxy or irregular-shaped part requires a large hole bored through its center, for example. Finally, sometimes you don’t have to choose: CNC milling-turning centers integrate both technologies into a single production device. What is a CNC Milling Machine and how does it work? How do CNC milling machines compare to CNC Lathes? When do you need such a CNC machine tool? Focused on milling – the process of machining using rotating tools to gradually remove material from a workpiece – CNC milling machines are a mainstay for factories around the world. These machine tools make use of a variety of cutting tools along one or more axes to remove material from a workpiece through mechanical means. CNC milling machines are often used in a variety of manufacturing industries: from industries like aerospace, shipping, automobiles, and oil drilling / pumping and refining, to medical, FMC manufacturing, and precision engineering sectors. Also called CNC Machining Centers, the more advanced CNC milling machines can operate along multiple-axis. These may be fitted with automatic tool changers, advanced machine coolant systems, pallet changers, and advanced software to improve the efficiency and accuracy of machining processes. CNC Milling Machines are machine operated cutting tools that are programmed and managed by Computer Numerical Control (CNC) systems to accurately remove materials from a workpiece. The end result of the machining process is a specific part or product that is created using a Computer Aided Design (CAD) software. These machine tools are normally equipped with a main spindle and three-linear-axes to position or move the part to be machined. More advanced versions may have a 4th or 5th rotational axis to allow for more precise shapes of varying dimensions and sizes to be machined. CNC milling machines / machining centers normally employ a process of material cutting termed milling or machining – the milling process involves securing a piece of pre-shaped material (also known as the workpiece) to a fixture attached to a platform in the milling machine. A rapidly rotating tool (or a series of interchangeable tools) is then applied to the material to remove small chips of the material until the desired shape for the part is achieved. Depending on the material used for the part, as well as the complexity of the machined part, varying axes, cutting head speeds, and feed rates may be applied. Milling is normally used to machine parts that are not symmetrical from an axial perspective. These parts may have unique curvatures or surface contours, which may require a combination of drilling & tapping, grooves, slots, recesses, pockets and holes to work on them. They may also form parts of the tooling for other manufacturing processes – for example in the fabrication of 3D moulds. In the past, milling machines were manually operated. Operators had to use a combination of machines with different tools to machine a more complex part or product. Or they had to use various settings on one machine just to complete the job. With the advancement of technology such a CNC controls and Automatic Tool Changers (ATCs), greater efficiency, flexibility and speed can be achieved – even for more convoluted parts. The provision of digital readouts and measuring systems has also improved the accuracy of CNC machining processes. To cater to manufacturers that require the flexibility of “High Mix, Low Volume” (HMLV) or “small batch” production, CNC machining centers can be fitted with Pallet Changers or other automation solutions to form part of a Flexible Manufacturing Cell (FMC) or Flexible Manufacturing System (FMS). This allows such machines to cater to a wide variety of machining demands and needs. The general principle for a CNC milling machine or CNC machining center is that the part to be machined is clamped on top of the machine table. It could be clamped directly on the table itself, or held in place by a vice or fixture. The spindle (moving section) including the cutting tool is then either vertically or horizontally positioned. In that configuration, the tool can reach various X-Y-Z positions on the work piece and commence cutting and shaping actions. As it does so, the work piece or part may either be fixed, mounted, or moved/positioned by the table in a linear direction to the spindle with the cutting tool. This allows material to be removed according to the desired shape needed for the machined part. For a CNC milling machine (aka CNC machining center), the work piece is fixed or mounted in position using a vice or fixture while the cutting tool is manoeuvred on top of or around the piece. Material is then gradually removed using cutting tools or drills which rotate at high speed with varying feed rates along two or more axes. In the case of a CNC Lathe (aka CNC Turning Center), however, the work piece (usually cylindrical) is mounted on a rotating chuck or on the main spindle. It is then “turned” (hence the name turning Center) or rotated along a main axis while the cutting tool located in a rotational or positioning turret would move in a parallel direction to the piece. Material is then removed using stationery cutting tools. Thus, a CNC milling machine use a spinning tool with a stationery work piece, whereas a CNC Lathe would involve spinning the material to be worked on by a stationery cutting tool.
Дата Публикации: 10-12-21