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Topic Review
Atmospheric Turbulence
The foundation of any smart city requires an innovative and robust communication infrastructure. Many research communities envision free-space optical communication (FSO) as a promising backbone technology for the services and applications provided by such cities. However, the channel through which the FSO signal travels is the atmosphere. Therefore, the FSO performance is limited by the local weather conditions. The variation in meteorological variables leads to variations of the refractive index along the transmission path. These index inhomogeneities (i.e., atmospheric turbulence) can significantly degrade the performance of FSO systems.  The effect of atmospheric turbulence on FSO systems is a considerable challenge. Such turbulence can produce beam scintillation, spreading, and wandering, resulting in a significant reduction in BER performance and the inability to use the communication link.
  • 1.4K
  • 24 Apr 2022
Topic Review
City Car
A city car (also known as urban car or a mini) is a small car designed to be used primarily in urban areas and conurbations. The term is used along with other terms for small cars including subcompact in North America. The Euro NCAP calls all small cars superminis. The European Commission refers to A-segment (Utility/city class: entry level small passenger car). In Japan , the kei car is a specific type of small car. The term microcar is loosely used for very small cars, some of which overlap city car classification.
  • 1.4K
  • 01 Nov 2022
Topic Review
Gel Fuels Preparation
Gel fuels can become an alternative energy resource within the framework of the implementation of the program for developments in rocket and space technology. These propellants combine the advantages of solid and liquid rocket propellants, of which the main ones are related to safety aspects, energy efficiency and storage. The components range and gel fuels compositions are diverse, so the method of their preparation in each specific case can be quite different, especially when using thickeners of various origins.
  • 1.4K
  • 10 Jan 2023
Topic Review
Rigenera® Micrografts in Oral Regeneration
Biomaterials derive either from nature or synthesized in the laboratory using chemical approaches utilizing metallic components, polymers, ceramics, or composite materials. They are often used and adapted for medical applications. A biomaterial is also defined as autograft, allograft, or xenograft used as a transplant material. In the last decade also tissue engineering and stem cells were deeply studied trying to make better autologous biomaterials ready to be used in regenerative procedures. Micrografts are a new concept of biomaterial, they are enriched of progenitor cells that are a particular type of stem cell excellent in enhancing the regenerative potential. Moreover, another advantage is the easy handling and tissue availability.
  • 1.4K
  • 29 Oct 2020
Topic Review
Self-Discharge of Batteries
Self-discharge of batteries is a natural, but nevertheless quite unwelcome, phenome­non. Be­cause it is driven in its various forms by the same thermodynamic forces as the discharge dur­ing intended op­era­tion of the device it can only be slowed down by impeding the reaction kinet­ics of its vari­ous steps, i.e. their respective rates of reaction. This approach should be based on a deeper understanding of the various modes and mechanisms of self-discharge, which in turn de­pend on the battery chemistry, its mode of op­eration and environmental conditions. Typical exam­ples from representative battery chemis­tries are presented and observed effects are reviewed. As an outcome of a better understanding ap­proaches to reduce self-discharge are presented.
  • 1.4K
  • 22 Feb 2023
Topic Review
Dynamic Positioning
Dynamic positioning (DP) is a computer-controlled system to automatically maintain a vessel's position and heading by using its own propellers and thrusters. Position reference sensors, combined with wind sensors, motion sensors and gyrocompasses, provide information to the computer pertaining to the vessel's position and the magnitude and direction of environmental forces affecting its position. Examples of vessel types that employ DP include, but are not limited to, ships and semi-submersible mobile offshore drilling units (MODU), oceanographic research vessels, cable layer ships and cruise ships. The computer program contains a mathematical model of the vessel that includes information pertaining to the wind and current drag of the vessel and the location of the thrusters. This knowledge, combined with the sensor information, allows the computer to calculate the required steering angle and thruster output for each thruster. This allows operations at sea where mooring or anchoring is not feasible due to deep water, congestion on the sea bottom (pipelines, templates) or other problems. Dynamic positioning may either be absolute in that the position is locked to a fixed point over the bottom, or relative to a moving object like another ship or an underwater vehicle. One may also position the ship at a favorable angle towards wind, waves and current, called weathervaning. Dynamic positioning is used by much of the offshore oil industry, for example in the North Sea, Persian Gulf, Gulf of Mexico, West Africa, and off the coast of Brazil . There are currently more than 1800 DP ships.
  • 1.4K
  • 04 Nov 2022
Topic Review
Friction Spot Stir Welding
In the last decade, the friction stir welding of polymers has been increasingly investigated by the means of more and more sophisticated approaches. Since the early studies, which were aimed at proving the feasibility of the process for polymers and identifying suitable processing windows, great improvements have been achieved. This owes to the increasing care of academic researchers and industrial demands. These improvements have their roots in the promising results from pioneer studies; however, they are also the fruits of the adoption of more comprehensive approaches and the multidisciplinary analyses of results. The introduction of instrumented machines has enabled the online measurement of processing loads and temperature, and critical understanding of the principal aspects affecting the material flow and welds quality. Such improvements are also clearly demonstrated by the increase of the strength of recent joints (up to 99% of joining efficiency) as compared to those reached in early researches (almost 47%). This article provides a comprehensive review of the recent progresses on the process fundamentals, quality assessment and the influence of process parameters on the mechanical behavior. In addition, emphasis is given to new developments and future perspectives.
  • 1.4K
  • 28 Oct 2020
Topic Review
Meat Analogue
A meat analogue is a food industry term for a meat-like substance made from vegetarian ingredients. More common terms are plant-based meat, vegan meat, meat substitute, mock meat, meat alternative, imitation meat, or vegetarian meat, or, sometimes more pejoratively, fake meat or faux meat. Meat analogues typically approximate certain aesthetic qualities (such as texture, flavor, appearance) or chemical characteristics of specific types of meat. Many analogues are soy-based (e.g., tofu, tempeh) or gluten-based but now may also be made from pea protein. Other less common analogues include cottage cheese and mycoprotein. Because of their similarity to meats, they are frequently used in dishes and food practices similar to meat. The target market for meat analogues includes vegetarians, vegans, non-vegetarians seeking to reduce their meat consumption, and people following religious dietary laws in Hinduism, Judaism, Islam, Christian vegetarianism, and Buddhism. Increasingly, the global demand for sustainable diets in response to the outsized role animal products play in global warming and other environmental impacts has seen an increase in industries focused on finding substitutes similar to meat. However, the motivation for seeking out mock meats tends to vary depending on consumer group. The market for meat alternatives is highly dependent on "meat-reducers" — a consumer group who is primarily motivated by health consciousness and weight management. Consumers who identify as vegan, vegetarian or pescetarian are more likely to endorse concerns regarding animal welfare and/or environmentalism as primary motivators. Meat substitution has a long history. Tofu, a popular meat analogue made from soybeans, was known in China during the period of the Western Han dynasty (206 BCE – 9 CE). A document written by Tao Gu (903–970) describes how tofu was called "small mutton" and valued as an imitation meat. Meat analogues such as tofu and wheat gluten are associated with Buddhist cuisine in China and other parts of East Asia. In Medieval Europe, meat analogues were popular during the Christian observance of Lent, when the consumption of meat from warm-blooded animals is forbidden. In the 2010s, owing to concern over global warming, demand for meat from a growing middle class, and major investments by companies such as Beyond Meat and Impossible Foods, there was an increase in awareness and the market size for meat analogues in Western and Westernized markets.
  • 1.4K
  • 24 Oct 2022
Topic Review Peer Reviewed
Mechanics and Natural Philosophy in History
This entry presents a historical view of the meaning attributed to the terms mechanics and natural philosophy, from a hint to ancient Greece, the Middle Ages, and the Renaissance to a special focus on the 18th Century, which represents a turning point for the development of modern physics and science in general. Since we are not concerned with the summation of the histories of natural philosophy and mechanics, but only with their interrelations, this makes a detailed description of the two disciplines unnecessary.
  • 1.4K
  • 15 Sep 2022
Topic Review
Laser Welding Based on Digital Twins
The benefits of laser welding include higher production values, deeper penetration, higher welding speeds, adaptability, and higher power density. These characteristics make laser welding a superior process. Many industries are aware of the benefits of switching to lasers. Laser welding of aluminum alloys presents a daunting challenge, mainly because aluminum is a less reliable material for welding than other commercial metals such as steel, primarily because of its physical properties: high thermal conductivity, high reflectivity, and low viscosity.
  • 1.4K
  • 24 May 2022
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