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Topic Review
Snorkeling
Snorkeling (British and Commonwealth English spelling: snorkelling) is the practice of swimming on or through a body of water while equipped with a diving mask, a shaped breathing tube called a snorkel, and usually swimfins. In cooler waters, a wetsuit may also be worn. Use of this equipment allows the snorkeler to observe underwater attractions for extended periods with relatively little effort and to breathe while face-down at the surface. Snorkeling is a popular recreational activity, particularly at tropical resort locations. The primary appeal is the opportunity to observe underwater life in a natural setting without the complicated equipment and training required for scuba diving. It appeals to all ages because of how little effort there is, and without the exhaled bubbles of scuba-diving equipment. It is the basis of the two surface disciplines of the underwater sport of finswimming. Snorkeling is also used by scuba divers when on the surface, in underwater sports such as underwater hockey and underwater rugby, and as part of water-based searches conducted by search and rescue teams.
  • 742
  • 10 Oct 2022
Topic Review
Competitive Swimwear
Competitive swimwear refers to the swimsuit, clothing, equipment, and accessories used in the aquatic sports of swimming, diving, synchronized swimming, triathlon, and water polo. Some swimsuits are designed specifically for swimming competitions where they may be constructed of a special low resistance fabric that reduces skin drag. For some kinds of swimming and diving, special bodysuits called "diveskins" are worn. These suits are made from spandex and provide little thermal protection, but they do protect the skin from stings and abrasion. Most competitive swimmers also wear special swimsuits including partial bodysuits, racerback styles, jammers and racing briefs to assist their glide through the water thus gaining a speed advantage. Unlike regular swimsuits, which are designed mainly for the aesthetic appearances, swimsuits designed to be worn during competitions are manufactured to assist the athlete in swim competitions. They reduce friction and drag in the water, increasing the efficiency of the swimmer's forward motion. The tight fits allow for easy movement and are said to reduce muscle vibration, thus reducing drag. This also reduces the possibility that a high forwards dive will remove a divers swimwear. Starting around 2000, in an effort to improve the effectiveness of the swimsuits, engineers have taken to designing them to replicate the skin of sea-based animals, sharks in particular. In July 2009, FINA voted to ban non-textile (non-woven) swimsuits in competitive events from 2010. The new policy was implemented to combat the issues associated with performance enhancing swimsuits, hindering the ability to accurately measure the performance of swimmers. Subsequently, the new ruling states that men's swimsuits may maximally cover the area from the navel to the knee, and women's counterparts from the shoulder to the knee. Some swimmers use a specialized training suit called drag suits to artificially increase drag during practice. Drag suits are swimwear with an outer layer of looser fabric – often mesh or nylon – to increase resistance against the water and build up the swimmer's endurance. They come in a variety of styles, but most resemble a looser fitting square-cut or swim brief.
  • 962
  • 06 Oct 2022
Topic Review
Shark Barrier
A shark barrier (otherwise known as a "shark-proof enclosure" or "beach enclosure") is seabed-to-surface protective barrier that is placed around a beach to protect people from shark attacks. Often confused with shark nets, shark barriers form a fully enclosed swimming area that prevents sharks from entering (nets aim to reduce shark populations). Shark barrier design has evolved from rudimentary fencing materials to netted structures held in place with buoys and anchors. Recent designs have used plastics to increase strength, versatility and to reduce the environmental damage of bycatch.
  • 735
  • 27 Sep 2022
Topic Review
Photovoltaic Distributed Generators with an Energy Storage System
Disruptive events, such as the winter storm of 2021 that left 40 million people in the U.S. without power, have revealed the potential danger of societal dependence on centralized energy sources. Localized energy grids (called microgrids (MGs)) can help add energy reliability and independence by using distributed generators (DGs) with photovoltaic (PV) energy sources and energy storage systems (ESSs). Such MGs can independently energize critical energy demand nodes (DNs) when isolated from the primary grid with renewable energy. The optimal sizes and assignments of PVDG/ESS units to the DNs during outages are crucial to increasing energy reliability. 
  • 429
  • 27 Sep 2022
Topic Review
Fused Deposition Modeling of 3D Printed Part 
Fused deposition modeling (FDM) is the most economical additive manufacturing (AM) technology available for fabricating complex part geometries. Dimensional instabilities are challenges of FDM that depends on printing parameters. The selected printing parameters include layer height, number of perimeters, infill density, infill angle, print speed, nozzle temperature, bed temperature, and print orientation. Three-level definitive screening design (DSD) was used to plan experimental runs. 
  • 559
  • 26 Sep 2022
Topic Review
Mechanical Properties of WSF Sandwich Composite Plate
The woven spacer fabric (WSF) sandwich composite plate is mainly used in carriages, construction materials, shock absorbers, wind-turbine blades, etc., which require WSF sandwich composite plates with bending, compression, impact, shear, and peel performance. These properties are reviewed herein. More attention will be paid to mechanical research of WSF sandwich composite panels should use non-destructive testing technology.
  • 504
  • 20 Sep 2022
Topic Review
Processing Technology for WSF Sandwich Composite Plate
The dominant processing technology for the woven spacer fabric (WSF) sandwich composite plate includes preparing a composite of resin and filling of foam. This process begins with composite preparation, followed by filling, or filling first and then preparing the composite. The main difference is that the core layer in the first method is impregnated with resin, which can effectively improve the bearing capacity in the loading process, but the internal connection structure combined with the interface with foam is poor, which worsens the integrity of the plate, resulting in shear failure. The second preparation process can produce excellent integrity and good synergy between the filling material and the internal connection structure, but the carrying capacity is worse compared with that of the first preparation method. In the actual preparation process, fiber stiffness depends on the choice of the preparation method. For fiber with greater stiffness (such as carbon fiber, glass fiber, and basalt fiber), the method of first preparing the composite and then filling is generally adopted. In contrast, for fibers with high flexibility (such as polyester fiber, aramid, and polypropylene), the method of filling first and then preparing the composite is adopted.
  • 369
  • 16 Sep 2022
Topic Review
Digital Marketing Utilization Index in Digital Marketing Capability
The digital marketing utilization index (DMUI) measures an organization’s ability to utilize digital marketing to create value for the company through the utilization of the readiness of the innovation ecosystem, digital marketing technology, and digital transformation.
  • 1.9K
  • 06 Sep 2022
Topic Review
Be-Al Alloy
Be-Al alloy is a type of in situ metal matrix composite composed of a primary Be phase for strength and stiffness and a continuous Al matrix for ductility and toughness. Be-Al alloy  has the characteristics of low density (2.1-2.2 g/cm3), high elastic modulus (＞170 GPa) and specific stiffness (＞88 GPa/(g/cm3)) as a preferred material for lightweight aerospace products.
  • 879
  • 05 Sep 2022
Topic Review
Available Sampling Methods for Plastic Waste
Given the rapid development of plastics recycling in recent years, the need for guidelines for sampling and material characterization is steadily emerging. However, there still exists a considerable scarcity of methods that enable proper material data acquisition. It was found that neither the literature nor the standards provide a comprehensive practice that considers the distinctive characteristics of plastic waste and applies it to different situations along the value chain. Two variants of the proposed plan were evaluated based on the flake size distribution and the apparent density of four different pretreated polyolefin (PO) waste materials. Combining stratified random sampling with composite sampling yields a good sampling technique for rigid PO waste. Moreover, the analysis of a composite sample adequately conveys the true material properties of a sublot or lot.
  • 1.4K
  • 31 Aug 2022
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