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Topic Review
Green Monopropellants
Green propellants are usually defined as low-hazard, low-toxicity, environmentally friendly propellants that are considered safe during various phases of spacecraft development, launch, and operations. Such propellants provide safe handling and storability when compared to conventional toxic propellants such as hydrazine and its derivatives that require special handling protocols and adhering to strict safety measurements that, in addition to others, include using Self-Contained Atmospheric Protective Ensemble (SCAPE) suits. Due to their favorable characteristics, green propellants demonstrate higher commercial value by being able to cut costs related to transportation, storage, handling, and further reduces ground operations time. Recently, a more specified definition has been noted by Mayer et al. (2018) [3], based on the Acute Toxicity Classification (ATC) by the Global Harmonized System of classification and labeling of chemicals (GHS) [6], which denotes that propellants possessing ATC levels of three and safer are considered as green propellants. ATC levels are typically categorized on a 1:5 scale where level one denotes the most toxic class and level five is considered the least toxic class. Moreover, a controversial topic arises when referring to some modern green propellants, whether to address them by the term “monopropellants” or by more specific terms including (premixed propellants, fuel blends, or mixtures). Monopropellants are fundamentally defined as propellants consisting of chemical compounds (for example N2H4), which release energy through exothermic chemical decomposition. Since the evolution of liquid gun propellants based on HAN compound and other nitrate salts aqueous solutions, the term “monopropellants” was used to describe such premixed formulations. As widely used in literature and industry, some modern green propellants, for instance the Energetic Ionic Liquids (EILs), are undoubtedly classified and described as “monopropellants.” Basically, it can be interpreted from the previous that a "green monopropellant" may be defined as: "A low-hazard, low-toxicity, and safe-to handle propellant that is stored in a single tank and is able to decompose from its storage state by the help of a catalyst or other ignition method, such as thermal or electric ignition, can be considered a “green monopropellant” as long as it does not require another separately stored propellant for decomposition."
  • 4.6K
  • 28 Sep 2021
Topic Review
Turbocharged Direct Injection
Turbocharged direct injection or TDI is a design of turbodiesel engines featuring turbocharging and cylinder-direct fuel injection that was developed and produced by the Volkswagen Group (VW AG). These TDI engines are widely used in all mainstream Volkswagen Group marques of passenger cars and light commercial vehicles made by the company (particularly those sold in Europe). They are also used as marine engines in Volkswagen Marine and Volkswagen Industrial Motor applications. TDI engines installed in 2009 to 2015 model year Volkswagen Group cars sold through 18 September 2015 had an emissions defeat device, which activated emissions controls only during emissions testing. The emissions controls were suppressed otherwise, allowing the TDI engines to exceed legal limits on emissions. VW has admitted to using the illegal device in its TDI diesel cars. In many countries, TDI is a registered trademark of Volkswagen AG. The TDI designation has also been used on vehicles powered by Land Rover-designed diesel engines. These are unrelated to Volkswagen Group engines.
  • 4.5K
  • 08 Nov 2022
Topic Review
History and Basic Principle of E-Nose
Fermented foods and beverages have become a part of daily diets in several societies around the world. Emitted volatile organic compounds play an important role in the determination of the chemical composition and other information of fermented foods and beverages. Electronic nose (E-nose) technologies enable non-destructive measurement and fast analysis, have low operating costs and simplicity, and have been employed for this purpose.
  • 4.5K
  • 29 Jun 2022
Topic Review
E-reader
An e-reader, also called an e-book reader or e-book device, is a mobile electronic device that is designed primarily for the purpose of reading digital e-books and periodicals. Any device that can display text on a screen may act as an e-reader; however, specialized e-reader devices may optimize portability, readability, and battery life for this purpose. Their main advantage over printed books is portability. This is because an e-reader is capable of holding thousands of books while weighing less than one book, and the convenience provided due to add-on features.
  • 4.5K
  • 21 Oct 2022
Topic Review
Extended-Range Electric Vehicles
Extended-range electric vehicles (EREVs), commonly known as series hybrid electric vehicles (Series-HEV), have better autonomy than electric vehicles (EV) without range extenders (REs). EREVs can go from one city to another or make long journeys in general.
  • 4.4K
  • 03 Aug 2021
Topic Review
Bombardier Dash 8
The Bombardier Dash 8 or Q Series, previously known as the de Havilland Canada Dash 8 or DHC-8, is a series of twin-engined, medium-range, turboprop airliners. Introduced by de Havilland Canada (DHC) in 1984, they are now produced by Bombardier Aerospace. Over 1,000 Dash 8s of all models have been built. The Dash 8 was developed from the de Havilland Canada Dash 7, which featured extreme short take-off and landing (STOL) performance. With the Dash 8, DHC focused on improving cruise performance and lowering operational costs. The engine chosen was the Pratt & Whitney Canada PW100. The aircraft has been delivered in four series. The Series 100 has a maximum capacity of 39, the Series 200 has the same capacity but offers more powerful engines, the Series 300 is a stretched, 50-seat version, and the Series 400 is further stretched to 90 passengers. Models delivered after 1997 have cabin noise suppression and are designated with the prefix "Q". Production of the Series 100 ceased in 2005, followed by the 200 and 300 in 2009, leaving the Q400 as the only series still in production. Bombardier currently markets the aircraft as the Q Series, complementing the company's CRJ Series aircraft.
  • 4.4K
  • 21 Oct 2022
Topic Review
Hydrogen Storage Technologies
Storage is an essential topic when it comes to hydrogen integration in distribution networks and large-scale applications; the existence of a robust and reliable way of storing this energy vector is crucial to addressing the current potential demand for hydrogen in the energy market. Many forms of storage have been developed, which can mainly be divided into Physical-based and Material-based approaches. Physical storage includes compressed gas, liquid, and cryo-compressed hydrogen, and it is the most widely used storage type among these systems. 
  • 4.4K
  • 26 May 2022
Topic Review
Deep Eutectic Solvents (DES)
Deep eutectic solvent (DES) are a highly non-ideal mixture of two biodegradable components (HBA and HBD) associated with strong hydrogen bonding interactions. 
  • 4.4K
  • 08 Mar 2022
Topic Review
Gallium Nitride High-Electron-Mobility Transistor
In recent years, GaN-based devices have been widely used in a variety of application fields. GaN-based high-electron-mobility transistors (HEMTs) are superior to conventional silicon (Si) based devices in terms of switching frequency, power rating, thermal capability and efficiency, which are crucial factors to enhance the performances of advanced power converters. This paper addresses some fundamental issues concerning intrinsic features of GaN material and key technology in practical application of GaN-based power switching devices.
  • 4.4K
  • 30 Jul 2020
Topic Review
Copper Heap Leaching
Heap leaching is a firm extractive metallurgical technology facilitating the economical processing of different kinds of low-grade ores that are otherwise not exploited.
  • 4.4K
  • 13 Oct 2021
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