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Topic Review
Rotor Dynamic Scattering
Rotor dynamic scattering refers to the phenomenon that a rotating rotor-like component continuously deflects incident radar waves in the observation field to generate dynamic echoes. This scattering feature has obvious dynamic characteristics and periodic characteristics. Factors such as observation angle, radar wave frequency, polarization mode, rotor disc angle and rotor carrier attitude angle are closely related. The emergence of dynamic scattering has transformed the rotor radar cross-section (RCS) problem from static solution to dynamic analysis. Studying rotor dynamic scattering has great engineering value for designing stealth rotors from the dynamic RCS level.
  • 1.5K
  • 30 Oct 2020
Topic Review
Classification of Architected Materials for Additive Manufacturing
One of the main advantages of Additive Manufacturing (AM) is the ability to produce topologically optimized parts with high geometric complexity. In this context, a plethora of architected materials was investigated and utilized in order to optimize the 3D design of existing parts, reducing their mass, topology-controlling their mechanical response, and adding remarkable physical properties, such as high porosity and high surface area to volume ratio.
  • 1.5K
  • 07 Sep 2022
Topic Review
SpaceX Dragon
Dragon, also known as Dragon 1 or Cargo Dragon, was a class of partially reusable cargo spacecraft developed by SpaceX, an American private space transportation company. Dragon was launched into orbit by the company's Falcon 9 launch vehicle to resupply the International Space Station (ISS). During its maiden flight in December 2010, Dragon became the first commercially built and operated spacecraft to be recovered successfully from orbit. On 25 May 2012, a cargo variant of Dragon became the first commercial spacecraft to successfully rendezvous with and attach to the ISS. SpaceX is contracted to deliver cargo to the ISS under NASA's Commercial Resupply Services program, and Dragon began regular cargo flights in October 2012. With the Dragon spacecraft and the Orbital ATK Cygnus, NASA seeks to increase its partnerships with domestic commercial aviation and aeronautics industry. On 3 June 2017, the C106 capsule, largely assembled from previously flown components from the CRS-4 mission in September 2014, was launched again for the first time on CRS-11, with the hull, structural elements, thrusters, harnesses, propellant tanks, plumbing and many of the avionics reused, while the heat shield, batteries and components exposed to sea water upon splashdown for recovery were replaced. SpaceX developed a second version called Dragon 2, which is capable of transporting humans. Flight testing was completed in 2019, after a delay caused by a test pad anomaly in April 2019, which resulted in the loss of a Dragon 2 capsule. The first flight of astronauts on Dragon 2 occurred on the Crew Dragon Demo-2 mission in May 2020. The last flight of the first version of the Dragon spacecraft (Dragon 1) launched 7 March 2020 (UTC); it was a cargo resupply mission (CRS-20) to International Space Station (ISS). This mission was the last mission of SpaceX of the first Commercial Resupply Services (CRS-1) program, and marked the retirement of the Dragon 1 fleet. Further SpaceX commercial resupply flights to ISS under the second Commercial Resupply Services (CRS-2) program use the cargo-carrying variant of the SpaceX Dragon 2 spacecraft.
  • 1.5K
  • 12 Oct 2022
Topic Review
Biomass Feedstocks Thermochemical Conversion Processes
An effective analytical technique for biomass characterisation is inevitable for biomass utilisation in energy production. To improve biomass processing, various thermal conversion methods such as torrefaction, pyrolysis, combustion, hydrothermal liquefaction, and gasification have been widely used to improve biomass processing. Thermogravimetric analysers (TG) and gas chromatography (GC) are among the most fundamental analytical techniques utilised in biomass thermal analysis. Thus, GC and TG, in combination with MS, FTIR, or two-dimensional analysis, were used to examine the key parameters of biomass feedstock and increase the productivity of energy crops. We can also determine the optimal ratio for combining two separate biomass or coals during co-pyrolysis and co-gasification to achieve the best synergetic relationship. 
  • 1.5K
  • 18 Sep 2021
Topic Review
First Assistant Engineer
A first assistant engineer (also called the second engineer in some countries) is a licensed member of the engineering department on a merchant vessel. This title is used for the person on a ship responsible for supervising the daily maintenance and operation of the engine department. They report directly to the chief engineer. On a merchant vessel, depending on term usage, "the First" or "the Second" is the marine engineer second in command of the engine department after the ship's chief engineer. Due to the supervisory role this engineer plays, in addition to being responsible for the refrigeration systems, main engines (steam/gas turbine, diesel), and any other equipment not assigned to the Second assistant engineer/third engineer or the Third assistant engineer/fourth engineer(s), he is typically the busiest engineer aboard the ship. If the engine room requires 24/7 attendance and other junior engineers can cover the three watch rotations, the first is usually a "day worker" from 0800-1700, with overtime hours varying according to ship/company. The first assistant/second engineer is usually in charge of preparing the engine room for arrival, departure, or standby and oversees major overhauls on critical equipment.
  • 1.5K
  • 03 Nov 2022
Topic Review
Safety and Barriers
The Architecture, Engineering, and Construction (AEC) industry is one of the most dangerous industries due to its unique nature. Safety is a critical issue in developed and developing countries.  Barriers that hinder the implementation of safety in projects and ways to improve safety performance was illustrated in this entry.
  • 1.5K
  • 20 Apr 2021
Topic Review
Biodiesel Production
Biodiesel produced through catalytic transesterification of triglycerides from edible and non-edible oils and alcohol is considered a clean and renewable alternative to traditional petro-diesel. Homogeneous alkaline catalysts have been widely used in this reaction due to their high activity. Optimization studies have been carried out to improve the biodiesel yields by modulation of the reaction conditions such as temperature, alcohol to oil ratio, catalysts concentration, time, and agitation speed. Several designs of experiments can be used to model to achieve this. 
  • 1.5K
  • 25 Feb 2021
Topic Review
Safe Mode (Spacecraft)
Safe mode is an operating mode of a modern unmanned spacecraft during which all non-essential systems are shut down and only essential functions such as thermal management, radio reception and attitude control are active. Safe mode is entered automatically upon the detection of a predefined operating condition or event that may indicate loss of control or damage to the spacecraft. Usually the trigger event is a system failure or detection of operating conditions considered dangerously out of the normal range. Cosmic rays penetrating spacecraft electrical systems can create false signals or commands and thus cause a trigger event. The central processor electronics are especially prone to such events. Another trigger is the lack of a received command within a given time window. Lack of received commands can be caused by hardware failures or mis-programming of the spacecraft, as in the case of the Viking 1 lander. The process of entering safe mode, sometimes referred to as safing, involves a number of immediate physical actions taken to prevent damage or complete loss. Power is removed from non-essential subsystems. Regaining attitude control, if lost, is the highest priority because it is necessary to maintain thermal balance and proper illumination of the solar panels. A tumbling or cartwheeling spacecraft can quickly roast, freeze or exhaust its battery power and be lost forever.
  • 1.5K
  • 02 Nov 2022
Topic Review
Shipunov 2A42
The Shipunov 2A42 is a Soviet/Russian 30 mm autocannon. It is built by the Tulamashzavod Joint Stock Company.
  • 1.5K
  • 11 Oct 2022
Topic Review
Green Bioprocessing of Algae-Derived Biopolymers
Algae-based biopolymers may be modified by adding additives, plasticizers, and compatibilizers to enhance the intermolecular force of contact between components, and boost material strength, flexibility, and durability. Moreover, biopolymers are widely used in cosmetics, medicines, and food packaging. Furthermore, algal biopolymer could be used as a food additive due to its high nutritional content.
  • 1.5K
  • 19 Jan 2023
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