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Topic Review
Pot-in-pot Refrigerator
A pot-in-pot refrigerator, clay pot cooler or zeer (Arabic: زير) is an evaporative cooling refrigeration device which does not use electricity. It uses a porous outer earthenware pot (lined with wet sand) containing an inner pot (which can be glazed to prevent penetration by the liquid) within which the food is placed. The evaporation of the outer liquid draws heat from the inner pot. The device can cool any substance, and requires only a flow of relatively dry air and a source of water.
  • 2.5K
  • 09 Oct 2022
Topic Review
Retrofitting and Strengthening of Structures
In civil engineering since antiquity, structural repair has been a very particular problem. Throughout history, human-constructed buildings have been destroyed due to time, natural disasters, and even building mistakes. In this respect, the field of engineering related to structural reconstruction and recovery seeks to identify methods and techniques to accomplish this important task. The pace of the degradation of concrete buildings throughout the world is frightening. It has now been verified that even if the structural design complies with all particular building code criteria such as concrete quality, cover, and so on, there is still an acceptable high risk of concrete degradation and reinforcing corrosion. Steel corrosion has been identified as the most severe cause of reinforced concrete degradation, capable of causing fractures, spalling the concrete cover, reducing the effective c/s area of the reinforcement, and ultimately leading to collapse. In order to repair and rehabilitate other buildings, this study sought to compile the main ideas, methods, and technologies used by these influential engineers. In fact, this report contains case studies on functional restoration. The document further addresses various types of building, such as pre-stressing, post-tensioning, deployment, and pre-stressing.
  • 2.5K
  • 24 Dec 2022
Topic Review
Puma (IFV)
The Puma is a Germany infantry fighting vehicle (IFV) (Schützenpanzer or short SPz) designed to replace the aging Marder IFVs currently in service with the German Army. Production of the first batch of 350 vehicles began in 2010 and is scheduled for completion by the second quarter of 2021. A second batch of 210 Pumas has received funding. Mass production began on 6 July 2009. The companies responsible for this project are Krauss-Maffei Wegmann and Rheinmetall Landsysteme, who created a joint venture in the form of Projekt System Management GmbH (PSM). The Puma is one of the world's best-protected IFVs, while still having a high power-to-weight ratio.
  • 2.5K
  • 28 Sep 2022
Topic Review
Current-Source Inverter
This entry addresses the topologies of the single-stage isolated matrix inverters with a grid-side switching stage based on the current source inverter (CSI). These inverters have been proposed for the uninterruptible power supplies, high and low-voltage/power photovoltaic systems, low-power fuel cell, different low- and high-voltage battery and/or electric vehicle chargers, audio amplifiers. The fully controlled switches on both terminals of these converters typically can provide the bidirectional power transfer capability, which is also addressed for most of the topologies. The other advantages include soft-switching of semiconductors and absence of the bulky DC-link capacitor. Average efficiency of today’s isolated matrix inverters is comparable with the two-stage power converters; however, due to absence of DC-link they can provide higher reliability and lower cost.
  • 2.5K
  • 28 Oct 2020
Topic Review
Multivariable Formulation of Surfactant-Oil-Water Systems
Surfactant-Oil-Water (SOW) systems are found in nature and synthetic products. They usually result in two immiscible phases, e.g., for two liquids, a water phase (often a brine), and an oily phase (which could be extremely complex as petroleum). Surfactant partitions between the two phases according to some physicochemical rules due to molecular interactions. There is a very particular formulation case in which SOW systems can form three immiscible phases, that is, two excess phases (water and oil) in equilibrium with a  so-called middle phase (because of an intermediate density that places it in the middle of a test tube). This middle phase is a so-called bicontinuous microemulsion which has no droplets dispersed in an external phase as a typical emulsion, but a complex single-phase structure similar to a disordered liquid crystal. When stirred, SOW systems can form multiple dispersed systems that can be described as macroemulsions or nanoemulsions depending on the drop size (O/W or W/O) or multiple emulsions (w/O/W or o/W/O) with droplets inside larger drops. Since the beginnings of the 20th century with Bancroft’s rule, the properties of these systems have been related to many thermodynamic variables, generally with one effect at a time. Nowadays, the generalized physicochemical concept of SOW systems with many formulation variables involved allows to make predictions in various application cases, even for very complex systems, as in enhanced oil recovery (EOR), crude oil dehydration, paints, foods, cosmetics and pharmaceutical formulations, that requires the control on 6-8 variables or even more. This is mainly because of the presence of mixtures of oils from linear alkanes to triglycerides or complex molecules perfumes, or a mixture of salts with cations from sodium to calcium or aluminum, and anions like chloride to phosphate. The complexity is even worse with mixtures of very different surface-active species, resulting in non-linear interactions.
  • 2.5K
  • 17 Aug 2021
Topic Review
List of SpaceX Starship Launches
Prototypes of the upper stage of the SpaceX Starship have been flown nine times.[lower-alpha 1] Designed and operated by private manufacturer SpaceX, the flown prototypes of Starship have been Starhopper, SN5, SN6, SN8, SN9, SN10, SN11, and SN15. Starship is planned to be a fully-reusable two-stage super heavy-lift launch vehicle and unusual for previous launch vehicle and spacecraft designs, the upper stage of Starship is intended to function both as a second stage to reach orbital velocity on launches from Earth, and also eventually be used in outer space as an on-orbit long-duration spacecraft. It is being designed to take people to Mars and beyond into the Solar System.
  • 2.5K
  • 20 Oct 2022
Topic Review
Smart Logistics in Industry 5.0
Given the importance of human centricity, resilience, and sustainability, the emerging concept of Industry 5.0 has pushed forward the research frontier of the technology-focused Industry 4.0 to a smart and harmonious socio-economic transition driven by both humans and technologies, where the role of the human in the technological transformation is predominantly focused on. The core elements of Industry 5.0 show that following the technology-centric transition of Industry 4.0, the societal, environmental, and human perspectives require more attention, which will yield significant impacts on logistics operations and management. For instance, the personalization of demands implies a personalized delivery system. Incorporating customers into the design requires highly intelligent CPS and system integration. Human–machine interaction triggers the interaction of various topics such as safety, human behavior, etc. Thus, there exist various challenges and approaches to addressing smart logistics issues in Industry 5.0. 
  • 2.5K
  • 21 Apr 2022
Topic Review
Centrifugal Fan
A centrifugal fan is a mechanical device for moving air or other gases in a direction at an angle to the incoming fluid. Centrifugal fans often contain a ducted housing to direct outgoing air in a specific direction or across a heat sink; such a fan is also called a blower, blower fan, biscuit blower, or squirrel-cage fan (because it looks like a hamster wheel). These fans increase the speed and volume of an air stream with the rotating impellers. Centrifugal fans use the kinetic energy of the impellers to increase the volume of the air stream, which in turn moves against the resistance caused by ducts, dampers and other components. Centrifugal fans displace air radially, changing the direction (typically by 90°) of the airflow. They are sturdy, quiet, reliable, and capable of operating over a wide range of conditions. Centrifugal fans are constant-displacement or constant-volume devices, meaning that, at a constant fan speed, a centrifugal fan moves a relatively constant volume of air rather than a constant mass. This means that the air velocity in a system is fixed even though the mass flow rate through the fan is not. Centrifugal fans are not positive-displacement devices and centrifugal fans have certain advantages and disadvantages when contrasted with positive-displacement blowers: centrifugal fans are more efficient, whereas positive-displacement blowers may have a lower capital cost. The centrifugal fan has a drum shape composed of a number of fan blades mounted around a hub. As shown in the animated figure, the hub turns on a driveshaft mounted in bearings in the fan housing. The gas enters from the side of the fan wheel, turns 90 degrees and accelerates due to centrifugal force as it flows over the fan blades and exits the fan housing.
  • 2.5K
  • 23 Oct 2022
Topic Review
Talkboy
Talkboy is a line of handheld voice recorder and sound novelty toys manufactured by Tiger Electronics (now owned by Hasbro) in the 1990s. The Talkboy was originally conceived as a cassette recorder and player prop for the 1992 film Home Alone 2: Lost in New York. At the request of director John Hughes and 20th Century Fox, Tiger designed and built the prop, and was given permission by the movie studio to sell a retail version of the toy. Two cassette recorders modeled after the film prop were released in 1992 and 1993, respectively. The original model did not have the variable-speed voice changer of the film version and sold only moderately during the 1992 holiday shopping season. In April 1993, Tiger released the Deluxe model, which added the voice-changing feature. Following the release of Home Alone 2 on home video in July with an insert advertising the Deluxe Talkboy, interest in the toy spiked. Retailers had severely underestimated demand, and as a result the Deluxe Talkboy was one of the most highly sought-after toys during the 1993 holiday shopping season, selling out of stores across the United States. A pink version of the cassette recorder called "Deluxe Talkgirl" was released in 1995. The success of the Talkboy cassette recorders spawned a product line of electronic toys. Tiger transitioned to digital recorders for subsequent devices, using solid-state storage and adding sound effects, beginning with "Talkboy/Talkgirl F/X+" pens in 1995, which sold more than a million units in 45 days.
  • 2.5K
  • 29 Nov 2022
Topic Review
E-Fuels
Power-to-X (PtX) are fuel production pathways in which electricity is converted into various gaseous or liquid fuels, such as e-hydrogen, e-methanol, e-methane, dimethyl ether (E-DME), e-ammonia, or e-diesel. These fuels are also named electrofuels (e-fuel) or power-to-liquid (PtL) and are mentioned in the Annexes of the RED II amendments as alternative options for the decarbonisation of the transport sector. Some of these molecules still contain carbon atoms, thus producing CO2 when used for energy production. The carbon source for the synthesis of e-fuels has to be carefully analysed to define them really carbon neutral.
  • 2.5K
  • 27 Feb 2023
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