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Topic Review
Merchant Vessel
A merchant vessel, trading vessel or merchantman is a boat or ship that transports cargo or carries passengers for hire. This excludes pleasure craft that do not carry passengers for hire; warships are also excluded. They come in a myriad of sizes and shapes, from twenty-foot inflatable dive boats in Hawaii, to 5,000 passenger casino vessels on the Mississippi River, to tugboats plying New York Harbor, to 1,000 foot oil tankers and container ships at major ports, to a passenger carrying submarine in the U.S. Virgin Islands. Most countries of the world operate fleets of merchant ships. However, due to the high costs of operations, today these fleets are in many cases sailing under the flags of nations that specialize in providing manpower and services at favourable terms. Such flags are known as "flags of convenience". Currently, Liberia and Panama are particularly favoured. Ownership of the vessels can be by any country, however. The Greek-owned fleet is the largest in the world. Today, the Greek fleet accounts for some 16 per cent of the world’s tonnage; this makes it currently the largest single international merchant fleet in the world, albeit not the largest in history. During wars, merchant ships may be used as auxiliaries to the navies of their respective countries, and are called upon to deliver military personnel and materiel.
  • 2.8K
  • 25 Oct 2022
Topic Review
Hongdu L-15
The Hongdu L-15 Falcon (猎鹰) is a supersonic advanced training and light combat aircraft being developed by Nanchang-based Hongdu Aviation Industry Corporation (HAIC) to meet the Chinese People's Liberation Army Air Force (PLAAF) and People's Liberation Army Naval Air Force (PLANAF) lead-in fighter trainer (LIFT) requirements, as well as next-generation training and light combat needs for foreign customers.
  • 2.8K
  • 28 Nov 2022
Topic Review Peer Reviewed
Two-Lane Highways: Indispensable Rural Mobility
Two-lane highways refer to roadways consisting of two lanes in the cross section, one for each direction of travel. Occasionally, passing lanes may be added to one or two sides of the roadway extending the cross section to three or four lanes at those locations. In this entry, two-lane highways strictly refer to roads in rural areas meeting the previous definition and do not include urban and suburban streets.
  • 2.8K
  • 13 Apr 2022
Topic Review
LCD Projector
An LCD projector is a type of video projector for displaying video, images or computer data on a screen or other flat surface. It is a modern equivalent of the slide projector or overhead projector. To display images, LCD (liquid-crystal display) projectors typically send light from a metal-halide lamp through a prism or series of dichroic filters that separates light to three polysilicon panels – one each for the red, green and blue components of the video signal. As polarized light passes through the panels (combination of polarizer, LCD panel and analyzer), individual pixels can be opened to allow light to pass or closed to block the light. The combination of open and closed pixels can produce a wide range of colors and shades in the projected image. Metal-halide lamps are used because they output an ideal color temperature and a broad spectrum of color. These lamps also have the ability to produce an extremely large amount of light within a small area; current projectors average about 2,000 to 15,000 American National Standards Institute (ANSI) lumens. Other technologies, such as Digital Light Processing (DLP) and liquid crystal on silicon (LCOS) are also becoming more popular in modestly priced video projection.
  • 2.8K
  • 04 Nov 2022
Topic Review
Electromyography
Electromyography (EMG) is a bioelectrical signal to assess electrical activity produced by skeletal muscles. In the study of muscle fatigue, the electrophysiological measurement of muscles play a crucial role in collecting electrical signals from skeletal muscles. Since EMG signals usually contain a certain amount of noise, it is essential to obtain high quality data in the early stage. In addition, people prefer a painless and comfortable method when recording muscle contraction signals.  This review addresses the EMG data collection methods with good quality and less pain, their applications, and the examples of actual EMG data analysis.
  • 2.8K
  • 20 Feb 2021
Topic Review
Early Injection for Low Emissions
Low-emission and high-efficiency have always been the targets for Internal Combustion Engine development. For diesel engines, homogeneous charge (aka. HCCI) and premixed charge (aka. PCCI) combustion modes provide both low-emission and high-efficiency simultaneously. To achieve these advanced combustion modes, early injection is needed as a relatively longer air-fuel mixing time is guaranteed. Several key parameters, such as the injection timing, pressure, angle, directly determine the final combustion process and thus the emission and efficiency performance. The pros and cons of these key parameters are discussed in detail here to provide a good review of the early-injection strategy.
  • 2.8K
  • 28 Oct 2020
Topic Review
Waste Plastic Recycling and Technology
Plastic waste recycling refers to the waste management process that collects plastic waste materials and turns them into raw materials reused to produce other valuable products. Recycling is not only a method for disposing of plastic waste, but it is also an effective process to minimize the need for virgin plastics, which can help lessen global warming. According to the ASTM Standard D5033, plastic recycling can be categorized as primary, secondary, tertiary, and quaternary recycling. Based on the mechanism of the methods, plastic waste recycling can be classified as mechanical, chemical, and biological recycling. Chemical recycling, such as catalytic and thermal processes, can convert plastic waste into value-added chemicals/fuels. This process is a potential method to reduce plastic waste as a primary source of environmental issues.
  • 2.8K
  • 04 Aug 2022
Topic Review
Starlink (Satellite Constellation)
Starlink is a satellite constellation being constructed by American company SpaceX to provide satellite Internet access. The constellation will consist of thousands of mass-produced small satellites, working in combination with ground transceivers. SpaceX also plans to sell some of the satellites for military, scientific or exploratory purposes. (As of January 2020), SpaceX has deployed 182 satellites. They plan to deploy 60 more per Falcon 9 launch, with launches as often as every two weeks after late 2019. In total, nearly 12,000 satellites will be deployed by the mid-2020s, with a possible later extension to 42,000. The initial 12,000 satellites are planned to orbit in three orbital shells: first placing approximately 1,600 in a 550-kilometer-altitude (340 mi) shell, then approximately 2,800 Ku- and Ka-band spectrum satellites at 1,150 km (710 mi) and approximately 7,500 V-band satellites at 340 km (210 mi). Commercial operation could begin in 2020. Concerns have been raised about the long-term danger of space junk resulting from placing thousands of satellites in orbits above 1,000 kilometres (620 mi) and a possible impact on astronomy, although SpaceX is reportedly attempting to solve the issue. The total cost of the decade-long project to design, build and deploy the constellation was estimated by SpaceX in May 2018 to be about US$10 billion. Product development began in 2015, with the first two prototype test-flight satellites launched in February 2018. A second set of test satellites and the first large deployment of a piece of the constellation occurred on 24 May 2019 (UTC) when the first 60 operational satellites were launched. The SpaceX satellite development facility in Redmond, Washington, houses the Starlink research, development, manufacturing and on-orbit control operations.
  • 2.8K
  • 11 Nov 2022
Topic Review
List of ASTM International Standards (E)
This is a list of ASTM International standards for "Materials for Specific Applications".
  • 2.8K
  • 30 Sep 2022
Topic Review
Magnetic Fields in Food Processing
Magnetic fields (MF) are increasingly being applied in food processing to preserve food quality. They can be static (SMF), oscillating (OMF) or pulsed (PMF) depending on the type of equipment. The food characteristics can be influenced by several configurations of the applied magnetic field as its flux density, frequency, polarity, and exposure time. Several mechanisms have been proposed to explain the effects of magnetic fields on foods. Some of them propose interactions at the subatomic particle level that show quantum behavior, such as the radical pair and cyclotron resonance mechanisms. Other proposals are at the level of DNA, compounds, subcellular organelles, and cells.  The interactions between food and magnetic fields are addressed in a general way in this work, highlighting the applications and action model
  • 2.8K
  • 23 Jul 2020
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