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Topic Review
Can CFD Analysis Help PEM Fuel Cell Design and Operation?
Polymer electrolyte membrane (PEM) fuel cell system is an advanced power system for the future that is sustainable, clean and environmental friendly. PEM fuel cells are growing in importance as sources of sustainable energy and will doubtless form part of the changing program of energy resources in the future. PEM fuel cells are still undergoing intense development, and the combination of new and optimized materials, improved product development, novel architectures, more efficient transport processes, and design optimization and integration are expected to lead to major gains in performance, efficiency, reliability, manufacturability and cost-effectiveness. The difficult experimental environment of PEM fuel cell systems has stimulated efforts to develop models that could simulate and predict multi-dimensional coupled transport of reactants, heat and charged species using computational fluid dynamic (CFD) technology. The strength of the CFD numerical approach is in providing detailed insight into the various transport mechanisms and their interaction, and in the possibility of performing parameters sensitivity analyses. The results of CFD analyses are relevant in: conceptual studies of new designs, detailed product development, troubleshooting, and redesign. CFD analysis complements testing and experimentation, by reduces the total effort required in the experiment design and data acquisition. Relevant case studies and recent progress in CFD techniques used in PEM fuel cell development have been presented and analyzed. The CFD models are shown to be able to provide a computer-aided tool for design and optimize future PEM fuel cell with much higher power density, long cell life, and lower cost.
  • 7.2K
  • 26 Apr 2020
Topic Review
Early Germanic Law
Early Germanic law was the form of law followed by the early Germanic peoples. It was an important element of early Germanic culture. Several Latin law codes of the Germanic peoples written in the Early Middle Ages after the Fall of the Western Roman Empire (also known as leges barbarorum "laws of the barbarians") survive, dating to between the 5th and 9th centuries. They are influenced by Roman law, canon law, and earlier tribal customs. Central and West European Germanic law differed from North Germanic law. Germanic law was codified in writing under the influence of Roman law; previously it was held in the memory of designated individuals who acted as judges in confrontations and meted out justice according to customary rote, based on careful memorization of precedent. Among the Franks they were called rachimburgs. "Living libraries, they were law incarnate, unpredictable and terrifying." Power, whose origins were at once said to be magical, divine, and military, was, according to Michel Rouche, exercised jointly by the "throne-worthy" elected king and his free warrior companions. Oral law sufficed as long as the warband was not settled in one place. Germanic law made no provisions for the public welfare, the res publica of Romans. The language of all these continental codes was Latin; the only known codes drawn up in any Germanic language were the Anglo-Saxon laws, beginning with the Laws of Æthelberht (7th century). In the 13th century customary Saxon law was codified in the vernacular as the Sachsenspiegel. All these laws may be described in general as codes of governmental procedure and tariffs of compositions. They all present somewhat similar features with Salic law, the best-known example, but often differ from it in the date of compilation, the amounts of fines, the number and nature of the crimes, the number, rank, duties and titles of the officers, etc. In Germanic Europe in the Early Middle Ages, every man was tried according to the laws of his own ethnicity, whether Roman, Salian or Ripuarian Frank, Frisian, Burgundian, Visigoth, Bavarian etc. A number of separate codes were drawn up specifically to deal with cases between ethnic Romans. These codes differed from the normal ones that covered cases between Germanic peoples, or between Germanic people and Romans. The most notable of these are the Lex Romana Visigothorum or Breviary of Alaric (506), the Lex Romana Curiensis and the Lex Romana Burgundionum.
  • 7.2K
  • 02 Dec 2022
Topic Review
Mercedes-Benz W114
The Mercedes-Benz W114 and W115 models are a series of executive sedans and coupés introduced in 1968 by Mercedes-Benz, manufactured through model year 1976, and distinguished in the marketplace by names relating to their engine size. W114 models featured six-cylinder engines and were marketed as the 230, 250, and 280, while W115 models featured four-cylinder engines and were marketed as the 200, 220, 230, and 240. All were styled by Paul Bracq, featuring a three-box design. At the time Mercedes marketed sedans in two size classes, with the W114/W115 positioned below the Mercedes-Benz S-Class. Beginning in 1968, Mercedes marketed their model range as New Generation Models, giving their ID plates the designation '/8' (due to their 1968 Launch year). Because they were the only truly new cars of the so-called 'New Generation' and because of the '/8' or 'slash eight' designation, W114 and W115 models ultimately received the German nickname Strich Acht, loosely translated into the English stroke eight.
  • 7.2K
  • 04 Nov 2022
Topic Review
Zwitterionic Dental Biomaterials
Biofilms are formed on surfaces inside the oral cavity covered by the acquired pellicle and develop into a complex, dynamic, microbial environment. Oral biofilm is a causative factor of dental and periodontal diseases. Accordingly, novel materials that can resist biofilm formation have attracted significant attention. Zwitterionic polymers (ZPs) have unique features that resist protein adhesion and prevent biofilm formation while maintaining biocompatibility. Recent literature has reflected a rapid increase in the application of ZPs as coatings and additives with promising outcomes. 
  • 7.2K
  • 29 Dec 2020
Topic Review
MOFs and COFs
Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) are two innovative classes of porous coordination polymers. MOFs are three-dimensional materials made up of secondary building blocks comprised of metal ions/clusters and organic ligands whereas COFs are 2D or 3D highly porous organic solids made up by light elements (i.e., H, B, C, N, O). Both MOFs and COFs, being highly conjugated scaffolds, are very promising as photoactive materials for applications in photocatalysis and artificial photosynthesis because of their tunable electronic properties, high surface area, remarkable light and thermal stability, easy and relative low-cost synthesis, and structural versatility. 
  • 7.2K
  • 08 Dec 2020
Topic Review
Human Body Segments
The knowledge of human body proportions and segmental properties of limbs, head and trunk is of fundamental importance in biomechanical research. Given that many methods are employed, it is important to know which ones are currently available, which data on human body masses, lengths, center of mass (COM) location, weights and moment of inertia (MOI) are available and which methods are most suitable for specific research purposes. Graphical, optical, x-ray and derived techniques, MRI, laser, thermography, has been employed for in-vivo measurement, while direct measurements involve cadaveric studies with dissection and various methods of acquiring shape and size of body segments.
  • 7.2K
  • 20 Nov 2020
Topic Review
Developmental Psychology
Developmental psychology is the scientific study of how and why human beings change over the course of their life. Originally concerned with infants and children, the field has expanded to include adolescence, adult development, aging, and the entire lifespan. Developmental psychologists aim to explain how thinking, feeling, and behaviors change throughout life. This field examines change across three major dimensions: physical development, cognitive development, and social emotional development. Within these three dimensions are a broad range of topics including motor skills, executive functions, moral understanding, language acquisition, social change, personality, emotional development, self-concept, and identity formation. Developmental psychology examines the influences of nature and nurture on the process of human development, and processes of change in context across time. Many researchers are interested in the interactions among personal characteristics, the individual's behavior, and environmental factors, including the social context and the built environment. Ongoing debates in regards to developmental psychology include biological essentialism vs. neuroplasticity and stages of development vs. dynamic systems of development. Developmental psychology involves a range of fields, such as educational psychology, child psychopathology, forensic developmental psychology, child development, cognitive psychology, ecological psychology, and cultural psychology. Influential developmental psychologists from the 20th century include Urie Bronfenbrenner, Erik Erikson, Sigmund Freud, Jean Piaget, Barbara Rogoff, Esther Thelen, and Lev Vygotsky.
  • 7.2K
  • 30 Oct 2022
Topic Review
Tetrabutylammonium Bromide
During the last two decades, tetrabutylammonium bromide (TBAB) has gained significant attention as an efficient metal-free homogeneous phase-transfer catalyst. A catalytic amount of TBAB is sufficient to catalyze various alkylation, oxidation, reduction, and esterification processes. It is also employed as an efficient co-catalyst for numerous coupling reactions. It has also acted as an efficient zwitterionic solvent in many organic transformations under molten conditions.
  • 7.2K
  • 09 Feb 2021
Topic Review
Electromagnetic Aircraft Launch System
The Electromagnetic Aircraft Launch System (EMALS) is a type of aircraft launching system developed by General Atomics for the United States Navy. The system launches carrier-based aircraft by means of a catapult employing a linear induction motor rather than the conventional steam piston. EMALS was first installed on the United States Navy's Gerald R. Ford-class aircraft carrier, USS Gerald R. Ford. Its main advantage is that it accelerates aircraft more smoothly, putting less stress on their airframes. Compared to steam catapults, the EMALS also weighs less, is expected to cost less and require less maintenance, and can launch both heavier and lighter aircraft than a steam piston-driven system. It also reduces the carrier's requirement of fresh water, thus reducing the demand for energy-intensive desalination. China is reportedly developing a similar system which is expected to be used on China's Type 003 aircraft carriers.
  • 7.2K
  • 21 Nov 2022
Topic Review
Alaria alata
Alaria alata flukes are cosmopolitan parasites. In Europe, the definitive hosts are red foxes (Vulpes vulpes), wolves (Canis lupus), and raccoon dogs (Nyctereutes procyonoides), as well as animals that belong to the Felidae family. Intermediate hosts, such as snails and frogs, are the sources of infection for definitive hosts. The developmental stages of A. alata mesocercariae may occur in paratenic hosts, including many species of mammals, birds, and reptiles, as well as in wild boars (Sus scrofa), which are important from the zoonotic point of view. Alaria alata is a widespread trematode that is considered a potential cause of a human disease called alariosis, which is associated with the consumption of raw or undercooked meat of intermediate or paratenic hosts of this parasite.
  • 7.2K
  • 11 Aug 2021
Topic Review
VARTM Processed Composite Materials
Fiber-reinforced composite structures are used in different applications due to their excellent strength to weight ratio. Due to cost and tool handling issues in conventional manufacturing processes, like resin transfer molding (RTM) and autoclave, vacuum-assisted resin transfer molding (VARTM) is the best choice among industries. VARTM is highly productive and cheap. However, the VARTM process produces complex, lightweight, and bulky structures, suitable for mass and cost-effective production, but the presence of voids and fiber misalignment in the final processed composite influences its strength. Voids are the primary defects, and they cannot be eliminated completely, so a design without considering void defects will entail unreliability. Many conventional failure theories were used for composite design but did not consider the effect of voids defects, thus creating misleading failure characteristics.
  • 7.2K
  • 07 Apr 2021
Topic Review
Okra
Okra (Abelmoschus esculentus L.) is a popular vegetable crop with good nutritional significance, along with certain therapeutic values, which makes it a potential candidate in the use of a variety of nutraceuticals.
  • 7.2K
  • 16 Mar 2021
Topic Review
List of Peaks by Prominence
This is a list of mountain peaks ordered by their topographic prominence.
  • 7.2K
  • 18 Oct 2022
Topic Review
Hypertensive Nephropathy
Hypertension is one of the most common risk factors for developing chronic cardiovascular diseases, including hypertensive nephropathy. Within the glomerulus, hypertension causes damage and activation of mesangial cells (MCs), eliciting the production of large amounts of vasoactive and proinflammatory agents. Accordingly, the activation of AT1 receptors by the vasoactive molecule angiotensin II (AngII) contributes to the pathogenesis of renal damage, which is mediated mostly by the dysfunction of intracellular Ca2+ ([Ca2+]i) signaling. Similarly, inflammation entails complex processes, where [Ca2+]i also play crucial roles. Deregulation of this second messenger increases cell damage and promotes fibrosis, reduces renal blood flow, and impairs the glomerular filtration barrier. In vertebrates, [Ca2+]i signaling depends, in part, on the activity of two families of large-pore channels: hemichannels and pannexons. Interestingly, the opening of these channels depends on [Ca2+]i signaling. 
  • 7.2K
  • 23 Dec 2022
Biography
Mohamed Al-Fayed
Mohamed Al-Fayed (/ælfaɪˈɛd/; Egyptian Arabic: محمد أنور شاكر عبد السيد الفايد‎ [mahamad el fajed]; born 27 January 1929) is an Egyptian business magnate. Fayed's business interests include ownership of Hôtel Ritz Paris and formerly Harrods Department Store, Knightsbridge. Al-Fayed sold his ownership of Fulham F.C. to Shahid Khan in 2013.[1] In his personal life
  • 7.2K
  • 05 Dec 2022
Topic Review
West African Lion
The West African lion is a Panthera leo leo population in West Africa. It is listed as Critically Endangered on the IUCN Red List. This population is isolated and probably comprises fewer than 250 mature individuals. Already in 2004, the lion population in West and Central Africa was fragmented and estimated as comprising at most 1,800 individuals. The West African lion was formerly considered a distinct lion subspecies with the scientific name P. l. senegalensis. Results of phylogenetic research indicate that the West African lion population forms a distinct clade and is closely related to Central African, North African and Asian lion populations. The lion populations in North, West and Central Africa and Asia were therefore subsumed to P. l. leo in 2017.
  • 7.2K
  • 17 Oct 2022
Topic Review
Cup Lump Natural Rubber
Cup lump is obtained when fresh latex is extracted by tapping into a long cut made in a rubber tree and letting the drips pour into a plastic cup.
  • 7.2K
  • 05 May 2023
Topic Review
Sweatshop
A sweatshop or sweat factory is a crowded workplace with very poor, socially unacceptable or illegal working conditions. The work may be difficult, dangerous, climatically challenging or underpaid. Workers in sweatshops may work long hours with low pay, regardless of laws mandating overtime pay or a minimum wage; child labor laws may also be violated. The Fair Labor Association's "2006 Annual Public Report" inspected factories for FLA compliance in 18 countries including Bangladesh, El Salvador, Colombia, Guatemala, Malaysia, Thailand, Tunisia, Turkey, China, India, Vietnam, Honduras, Indonesia, Brazil, Mexico, and the US. The U.S. Department of Labor's "2015 Findings on the Worst Forms of Child Labor" found that "18 countries did not meet the International Labour Organization's recommendation for an adequate number of inspectors."
  • 7.2K
  • 31 Oct 2022
Topic Review
Networked Control System
An NCS consists of control loops joined through communication networks in which both the control signal and the feedback signal are exchanged between the system and the controller.
  • 7.1K
  • 01 Apr 2021
Topic Review
Glossary of Bird Terms
The following is a glossary of common English language terms used in the description of birds—warm-blooded vertebrates of the class Aves and the only living dinosaurs, characterized by feathers, the ability to fly in all but the approximately 60 extant species of flightless birds, toothless, beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart and a strong yet lightweight skeleton. Among other details such as size, proportions and shape, terms defining bird features developed and are used to describe features unique to the class—especially evolutionary adaptations that developed to aid flight. There are, for example, numerous terms describing the complex structural makeup of feathers (e.g., barbules, rachides and vanes); types of feathers (e.g., filoplume, pennaceous and plumulaceous feathers); and their growth and loss (e.g., colour morph, nuptial plumage and pterylosis). There are thousands of terms that are unique to the study of birds. This glossary makes no attempt to cover them all, concentrating on terms that might be found across descriptions of multiple bird species by bird enthusiasts and ornithologists. Though words that are not unique to birds are also covered, such as "back" or "belly", they are defined in relation to other unique features of external bird anatomy, sometimes called "topography". As a rule, this glossary does not contain individual entries on any of the approximately 9,700 recognized living individual bird species of the world.
  • 7.1K
  • 09 Nov 2022
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