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Topic Review
PSA XUD
The PSA XUD is a Diesel engine designed and built by PSA - Peugeot and Citroën. It is an Indirect injection (IDI) engine, that uses a version of the Ricardo Consulting Engineers Ricardo Comet V prechamber cylinder head design. The engine comes in 1.8 L (1,769 cc) N/A, 1.8 Turbo, 1.9 L (1,905 cc) N/A, Turbo, 2.1 12 valve N/A and Turbo and was the predecessor to the HDI range of engines. Early HDi Engines were a PSA design, later 16 valve engines were jointly developed with Ford.
  • 3.2K
  • 28 Oct 2022
Topic Review
Kerb Construction
Concrete kerbs can be prepared by precast and cast in situ methods. The precast concrete kerbs can be manufactured by conventional (using a vibrator), dry-pressed and wet-pressed methods and can be installed in almost all weather conditions. Possible rainfall, temperatures and sunlight hours are considered in casting in situ kerbs, and they are more labour-intensive compared to the precast variations. However, cast in situ kerb can better handle sudden changes of direction. There is no study found comparing different aspects of in situ casting and precast kerb. Both types of concrete kerb are suggested for construction by all authorities, such as the Austroads and AASHTO. The precast kerbs require manual placement and have been a major source of workplace injury in the United Kingdom. Past studies have suggested that the use of special lifting equipment (such as vacuum lifters, lifting clamps or stone magnets), reduction in kerb section length, reduction in kerb foundation depth, use of a lightweight or hollow concrete section or other lightweight materials, such as polymer, can reduce the likelihood of such workplace injuries and may also lead to quicker construction as well as better construction quality.
  • 3.2K
  • 28 Mar 2022
Topic Review
Groundwater Withdrawal-Induced Land Subsidence
Land subsidence is probably one of the most evident environmental effects of groundwater pumping. Globally, freshwater demand is the leading cause of this phenomenon. Land subsidence induced by aquifer system drainage can reach total values of up to 14.5 m. The spatial extension of this phenomenon is usually extensive and is often difficult to define clearly. Aquifer compaction contributes to many socio-economic effects and high infrastructure-related damage costs. Currently, many methods are used to analyze aquifer compaction. These include the fundamental relationship between groundwater head and groundwater flow direction, water pressure and aquifer matrix compressibility. Such solutions enable satisfactory modelling results. However, further research is needed to allow more efficient modelling of aquifer compaction. Recently, satellite radar interferometry (InSAR) has contributed to significant progress in monitoring and determining the spatio-temporal land subsidence distributions worldwide. Therefore, implementation of this approach can pave the way to the development of more efficient aquifer compaction models. This entry presents a comprehensive review of models used to predict land surface displacements caused by rock mass drainage, as well as (2) recent advances and (3) a summary of InSAR implementation over recent years to support the aquifer compaction modelling process. Therefore, the study presented would be of benefit to readers who are interested in the topic of interaction between the human population and the hydrogeological system in different regions. The research presented allows readers to better understand the factors, developments and effects of groundwater drainage and thus facilitate large - scale risk assessment and preventive planning.
  • 3.2K
  • 27 Oct 2020
Topic Review
CubeSat Missions and Their Antenna Designs
CubeSats are a class of miniaturized satellites that have become increasingly popular in academia and among hobbyists due to their short development time and low fabrication cost. Their compact size, lightweight characteristics, and ability to form a swarm enables them to communicate directly with one another to inspire new ideas on space exploration, space-based measurements, and implementation of the latest technology. CubeSat missions require specific antenna designs in order to achieve optimal performance and ensure mission success. Over the past, a plethora of antenna designs have been proposed and implemented on CubeSat missions. Several challenges arise when designing CubeSat antennas such as gain, polarization, frequency selection, pointing accuracy, coverage, and deployment mechanisms.
  • 3.2K
  • 18 Jul 2022
Topic Review
Panzer II Variants
The Panzerkampfwagen II (Pz.Kpfw.II) light tank, produced in Germany in the late 1930s and early 1940s had a wide array of variants, both as development of the light tank and for specialised tasks.
  • 3.2K
  • 02 Nov 2022
Topic Review
Solar Still
Solar stills are considered an essential component of solar energy utilization for converting sea, brackish, or wastewater to fresh water.
  • 3.2K
  • 30 Aug 2022
Topic Review
Starship (Spacecraft)
Starship is the fully reusable second stage and space vehicle of the SpaceX BFR "Super Heavy" rocket currently under development by SpaceX. It is a long-duration cargo- and passenger-carrying spacecraft that also serves as the BFR launch vehicle second stage and integrated payload section. Three 9-meter (30 ft)-diameter stainless steel Starship test articles are being built, and one had already begun integrated system testing by March 2019. The Starship test flight rocket—Starhopper—will be used for initial integrated testing of the Raptor rocket engine with a flight-capable propellant structure as well as for low-altitude, low-velocity flight testing of launches and landings. It began hotfire testing in April 2019. Two additional test articles, Starship orbital prototypes, are being built by competing teams in South Texas and along the space coast of Florida. They are planned to be used after mid-2019 for high-altitude, high-velocity testing. Integrated system testing of Starhopper, including the first flight test, began in April 2019. SpaceX is planning to launch commercial payloads using Starship no earlier than 2021.
  • 3.2K
  • 21 Oct 2022
Topic Review
Jagdtiger
The Jagdtiger ("Hunting Tiger"; officially designated Panzerjäger Tiger Ausf. B) is a German casemate-type heavy tank destroyer from World War II. It was built upon the slightly lengthened chassis of a Tiger II. Its ordnance inventory designation was Sd.Kfz. 186. The 71-tonne Jagdtiger was the heaviest armored fighting vehicle (AFV) used operationally by any participant nation of WWII and is the heaviest combat vehicle of any type to achieve series production during the conflict. The vehicle was armed with a 128 mm Pak 44 L/55 main gun which was capable of outranging and defeating any tank or AFV fielded by the Allied forces. It saw brief service in small numbers from late 1944 up until the end of the war on both the Western and Eastern Front. Although 150 were ordered, only around eighty were produced. Due to an excessive weight and a significantly underpowered drivetrain system, the Jagdtiger was continuously plagued with various mobility and mechanical problems. At present, three Jagdtigers survive in different museums around the world.
  • 3.2K
  • 17 Oct 2022
Topic Review
Methods for Recycling Heterogenous Catalysts
The rapid separation and efficient recycling of catalysts after a catalytic reaction are considered important requirements along with the high catalytic performances. In this view, although heterogeneous catalysis is generally less efficient if compared to the homogeneous type, it is generally preferred since it benefits from the easy recovery of the catalyst. Recycling of heterogeneous catalysts using traditional methods of separation such as extraction, filtration, vacuum distillation, or centrifugation is tedious and time-consuming. They are uneconomic processes and, hence, they cannot be carried out in the industrial scale.
  • 3.1K
  • 23 Jun 2021
Topic Review
History of Statistics
The history of statistics in the modern way is that it originates from the term statistics, found in 1749 in Germany. Although there have been changes to the interpretation of the word over time. The development of statistics is intimately connected on the one hand with the development of sovereign states, particularly European states following the peace of Westphalia (1648); and the other hand with the development of probability theory, which put statistics on a firm theoretical basis (see history of probability). In early times, the meaning was restricted to information about states, particularly demographics such as population. This was later extended to include all collections of information of all types, and later still it was extended to include the analysis and interpretation of such data. In modern terms, "statistics" means both sets of collected information, as in national accounts and temperature records, and analytical work which requires statistical inference. Statistical activities are often associated with models expressed using probabilities, hence the connection with probability theory. The large requirements of data processing have made statistics a key application of computing; see history of computing hardware. A number of statistical concepts have an important impact on a wide range of sciences. These include the design of experiments and approaches to statistical inference such as Bayesian inference, each of which can be considered to have their own sequence in the development of the ideas underlying modern statistics.
  • 3.1K
  • 19 Oct 2022
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