Your browser does not fully support modern features. Please upgrade for a smoother experience.
Subject:
All Disciplines Arts & Humanities Biology & Life Sciences Business & Economics Chemistry & Materials Science Computer Science & Mathematics Engineering Environmental & Earth Sciences Medicine & Pharmacology Physical Sciences Public Health & Healthcare Social Sciences
Sort by:
Most Viewed Latest Alphabetical (A-Z) Alphabetical (Z-A)
Filter:
All Topic Review Biography Peer Reviewed Entry Video Entry
Topic Review
List of Most Successful U-boat Commanders
The list of most successful U-boat commanders contains the top-scoring German U-boat commanders in the two World Wars based on their total tonnage sunk. The tonnage figures (and sometimes the number of ships sunk) is still being debated among historians. This is often due to convoy battles at night when an attacking "wolfpack" fired torpedoes into the convoy and two (sometimes more) commanders claimed the same ship. Although post-war research has clarified most of those claims, some are still in question.
  • 8.5K
  • 04 Nov 2022
Topic Review
Biomass Gasification
Lignocellulosic gasification is a valid thermochemical approach for the conversion of organic solid matter into a gaseous mixture that is constituted of hydrogen, carbon monoxide, carbon dioxide and methane, named synthetic gas or syngas. Although about 55% of syngas is still produced from coal, biomass utilization, especially lignocellulose, is constantly growing. Indeed, gasification could be potentially applied to all different kinds of lignocellulosic biomass, unlike other conversion technologies. Moreover, in the last few decades, a wide range of applications of syngas have been intensively studied. Syngas can be directly used as a combustible substance in power plants for heat and power production (steam cycle, co-combustion, combustion in gas turbines or internal combustion engines, high temperature fuel cells), which represents the most common use of biomass-derived syngas. However, syngas also represents a platform that can be employed in a broad range of chemical and microbial processes, leading to gaseous and liquid fuels, as well as to chemicals. Chemical process research has mainly focused on transportation fuel production from syngas, such as Fischer–Tropsch liquid fuels, hydrogen, methanol, dimethyl ether (DME), mixed alcohols, and synthetic natural gas (SNG). Instead, the biochemical conversion route consists of syngas fermentation in which obligate anaerobic microorganisms convert syngas into organic acids, alcohols, and other chemicals. The most commonly used microorganisms are acetogens, which use the Wood–Ljungdahl metabolic pathway. Syngas fermentation is defined as an indirect fermentation process because biomass is not fed directly into the fermenter, but it is previously converted into syngas through gasification. 
  • 8.4K
  • 17 Dec 2020
Topic Review
Post-transition Metal
Post-transition metals are a set of metallic elements in the periodic table located between the transition metals to their left, and the metalloids to their right. Depending on where these adjacent groups are judged to begin and end, there are at least five competing proposals for which elements to include: the three most common contain six, ten and thirteen elements, respectively (see image). All proposals include gallium, indium, tin, thallium, lead, and bismuth. Physically, post-transition metals are soft (or brittle), have poor mechanical strength, and have melting points lower than those of the transition metals. Being close to the metal-nonmetal border, their crystalline structures tend to show covalent or directional bonding effects, having generally greater complexity or fewer nearest neighbours than other metallic elements. Chemically, they are characterised—to varying degrees—by covalent bonding tendencies, acid-base amphoterism and the formation of anionic species such as aluminates, stannates, and bismuthates (in the case of aluminium, tin, and bismuth, respectively). They can also form Zintl phases (half-metallic compounds formed between highly electropositive metals and moderately electronegative metals or metalloids). The name is universally used, but not officially sanctioned by any organization such as the IUPAC. The origin of the term is unclear: one early use was in 1940 in a chemistry text. Alternate names for this group are B-subgroup metals, other metals, and p-block metals; and at least thirteen other labels.
  • 8.4K
  • 21 Nov 2022
Topic Review
Phenomenology
Phenomenology (from Greek φαινόμενον, phainómenon "that which appears" and λόγος, lógos "study") is the philosophical study of the structures of experience and consciousness. As a philosophical movement it was founded in the early years of the 20th century by Edmund Husserl and was later expanded upon by a circle of his followers at the universities of Göttingen and Munich in Germany . It then spread to France , the United States , and elsewhere, often in contexts far removed from Husserl's early work. Phenomenology is not a unified movement; rather, the works of different authors share a 'family resemblance' but with many significant differences. Gabriella Farina states:Phenomenology, in Husserl's conception, is primarily concerned with the systematic reflection on and study of the structures of consciousness and the phenomena that appear in acts of consciousness. Phenomenology can be clearly differentiated from the Cartesian method of analysis which sees the world as objects, sets of objects, and objects acting and reacting upon one another. Husserl's conception of phenomenology has been criticized and developed not only by him but also by students and colleagues such as Edith Stein, Max Scheler, Roman Ingarden, and Dietrich von Hildebrand, by existentialists such as Nicolai Hartmann, Gabriel Marcel, Maurice Merleau-Ponty, and Jean-Paul Sartre, by hermeneutic philosophers such as Martin Heidegger, Hans-Georg Gadamer, and Paul Ricoeur, by later French philosophers such as Jean-Luc Marion, Michel Henry, Emmanuel Levinas, and Jacques Derrida, by sociologists such as Alfred Schütz and Eric Voegelin, and by Christian philosophers, such as Dallas Willard.
  • 8.4K
  • 28 Nov 2022
Topic Review
Fresh Fruit Supply Chain Optimization
The fresh fruit chain has been recognized as a very important and strategic part of the economic development of many countries. The planning framework for production and distribution is highly complex as a result. Mathematical models have been developed over the decades to deal with this complexity. This review focuses on the recent progress in mathematically based decision making to account for uncertainties in the fresh fruit supply chain
  • 8.4K
  • 27 Jul 2021
Topic Review
Compounds of Fluorine
Fluorine forms a great variety of chemical compounds, within which it always adopts an oxidation state of −1. With other atoms, fluorine forms either polar covalent bonds or ionic bonds. Most frequently, covalent bonds involving fluorine atoms are single bonds, although at least two examples of a higher order bond exist. Fluoride may act as a bridging ligand between two metals in some complex molecules. Molecules containing fluorine may also exhibit hydrogen bonding (a weaker bridging link to certain nonmetals). Fluorine's chemistry includes inorganic compounds formed with hydrogen, metals, nonmetals, and even noble gases; as well as a diverse set of organic compounds. For many elements (but not all) the highest known oxidation state can be achieved in a fluoride. For some elements this is achieved exclusively in a fluoride, for others exclusively in an oxide; and for still others (elements in certain groups) the highest oxidation states of oxides and fluorides are always equal.
  • 8.4K
  • 16 Nov 2022
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.
  • 8.4K
  • 08 Nov 2022
Topic Review
Extreme Weather Events of 535–536
The extreme weather events of 535–536 were the most severe and protracted short-term episodes of cooling in the Northern Hemisphere in the last 2,000 years. The event is thought to have been caused by an extensive atmospheric dust veil, possibly resulting from a large volcanic eruption conjectured to be either in Asia, the Americas, Europe, or other locations. Its effects were widespread, causing unseasonable weather, crop failures, and famines worldwide.
  • 8.4K
  • 23 Nov 2022
Topic Review
Design Considerations of Fixed and Floating Offshore Structures
Offshore structures exist in a variety of forms, and they are used for a variety of functions in varied sea depths. These structures are tailored for certain environments and sea depths and other design considerations. 
  • 8.4K
  • 29 Jul 2022
Topic Review
WikiLeaks
WikiLeaks (/ˈwɪkiliːks/) is an international non-profit organisation that publishes news leaks and classified media provided by anonymous sources. Its website, initiated in 2006 in Iceland by the organisation Sunshine Press, stated in 2015 that it had released online 10 million documents in its first 10 years. Julian Assange, an Australian Internet activist, is generally described as its founder and director. Since September 2018, Kristinn Hrafnsson has served as its editor-in-chief. WikiLeaks has variously described itself as an organization of journalists, political activists, mathematicians, and start-up company technologists, an intermediary between sources and journalists, an advocacy group for sources, and a public intelligence agency. The group has released a number of prominent document caches that exposed serious violations of human rights and civil liberties to the US and international public. Early releases included documentation of equipment expenditures and holdings in the Afghanistan war, a report about a corruption investigation in Kenya, and an operating procedures manual for the U.S. prison at Guantanamo Bay, Cuba. In April 2010, WikiLeaks released the Collateral Murder footage from the 12 July 2007 Baghdad airstrike in which Iraqi Reuters journalists were among several civilians killed. Other releases in 2010 included the Afghan War Diary and the "Iraq War Logs". The latter release allowed the mapping of 109,032 deaths in "significant" attacks by insurgents in Iraq that had been reported to Multi-National Force – Iraq, including about 15,000 that had not been previously published. In 2010, WikiLeaks also released classified diplomatic cables that had been sent to the US State Department. In April 2011, WikiLeaks began publishing 779 secret files relating to prisoners detained in the Guantanamo Bay detention camp. In 2012, WikiLeaks released the "Syria Files," over two million emails sent by Syrian politicians, corporations and government ministries. In 2015, WikiLeaks published Saudi Arabian diplomatic cables, documents detailing spying by the U.S. National Security Agency on successive French presidents, and the intellectual property chapter of the Trans-Pacific Partnership, a controversial international trade agreement which had been negotiated in secret. During the 2016 U.S. presidential election campaign, WikiLeaks released emails and other documents from the Democratic National Committee and from Hillary Clinton's campaign manager, John Podesta, showing that the party's national committee favoured Clinton over her rival Bernie Sanders in the primaries, leading to the resignation of DNC chairwoman Debbie Wasserman Schultz and an apology to Sanders from the DNC. These releases caused significant harm to the Clinton campaign, and have been attributed as a potential contributing factor to her loss in the general election against Donald Trump. The U.S. intelligence community expressed "high confidence" that the leaked emails had been hacked by Russia and supplied to WikiLeaks. WikiLeaks said that the source of the documents was not Russia or any other state. During the campaign, WikiLeaks promoted conspiracy theories about Hillary Clinton and the Democratic Party. In 2016, WikiLeaks released nearly 300,000 emails it described as coming from Turkey's ruling Justice and Development Party, later found to be taken from public mailing archives, and rereleased over 50,000 emails from the Turkish Minister of Energy and Natural Resources. In 2017, WikiLeaks published internal CIA documents describing tools used by the agency to hack devices including mobile phones and routers. In 2019, WikiLeaks published over 30,000 files as part of the Fishrot Files, exposing corruption at Samherji, a multinational fishing company based in Iceland. In October 2021, WikiLeaks' secure chat stopped working and in February 2022 their submission system and email server went offline. The organisation has been criticised for inadequately curating its content and violating the personal privacy of individuals. WikiLeaks has, for instance, revealed Social Security numbers, medical information, credit card numbers and details of suicide attempts.
  • 8.4K
  • 11 Oct 2022
Topic Review
Leucaena leucocephala as Protein Source
White leadtree or Leucaena (Leucaena leucocephala) (), also known as ipil-ipil, is native to Central America and has spread and/or naturalized all over the World at a latitude between 30° N and 30° S due to a shrub variety used as a shade tree for coffee, cocoa, hemp plantations, pepper, vanilla, and other essences.
  • 8.4K
  • 04 Aug 2021
Topic Review
Lewis's Trilemma
Lewis's trilemma is an apologetic argument traditionally used to argue for the divinity of Jesus by arguing that the only alternatives were that he was evil or deluded. One version was popularised by University of Oxford literary scholar and writer C. S. Lewis in a BBC radio talk and in his writings. It is sometimes described as the "Lunatic, Liar, or Lord", or "Mad, Bad, or God" argument. It takes the form of a trilemma — a choice among three options, each of which is in some way difficult to accept. This argument is very popular with Christian apologists, although some theologians and biblical scholars do not view Jesus as having claimed to be God. Some argue that he identified himself as a divine agent, with a unique relationship to Israel's God. Others see him as wanting to direct attention to the divine kingdom he proclaimed.
  • 8.4K
  • 10 Nov 2022
Topic Review
White–Juday Warp-Field Interferometer
The White–Juday warp-field interferometer is an experiment designed to detect a microscopic instance of a warping of spacetime. If such a warp is detected, it is hoped that more research into creating an Alcubierre warp bubble will be inspired. A research team led by Harold "Sonny" White in collaboration with Dr. Richard Juday at the NASA Johnson Space Center and Dakota State University are conducting experiments, but results so far have been inconclusive.
  • 8.4K
  • 24 Nov 2022
Topic Review
Responsive Architecture
Responsive architecture is a type of architecture, an artificial entity, that reacts to data and information collected by a variety of types of sensors. It is also defined as an interactive and collective platform where diverse computing or operating systems are executed, leading to architectural behaviors like changing forms or services.
  • 8.4K
  • 20 May 2021
Topic Review
International Trade Theory
International trade theory is a sub-field of economics which analyzes the patterns of international trade, its origins, and its welfare implications. International trade policy has been highly controversial since the 18th century. International trade theory and economics itself have developed as means to evaluate the effects of trade policies.
  • 8.4K
  • 14 Nov 2022
Topic Review
Mathematics of Sudoku
The class of Sudoku puzzles consists of a partially completed row-column grid of cells partitioned into N regions each of size N cells, to be filled in ("solved") using a prescribed set of N distinct symbols (typically the numbers {1, ..., N}), so that each row, column and region contains exactly one of each element of the set. The properties of Sudoku puzzles and their solutions can be investigated using mathematics and algorithms.
  • 8.4K
  • 12 Oct 2022
Topic Review
Cat Café
A cat café is a theme café whose attraction is cats who can be watched and played with. Patrons pay a cover fee, generally hourly, and thus cat cafés can be seen as a form of supervised indoor pet rental. "Cat café" has been officially recognized in the online edition of the Oxford Dictionary of English since August 2015.
  • 8.4K
  • 20 Oct 2022
Topic Review
Incineration Bottom Ash from Municipal Solid Waste
Incineration bottom ash (IBA) is the main residue from municipal solid waste (MSW) incineration and refers to the incombustible materials that remain in the furnace after combustion. IBA is a very heterogeneous material, comprising irregularly shaped particles and a wide particle size distribution. This material is a complex inorganic mixture generally composed of melt products, minerals, metallic compounds, ceramics, and glass [1]. The classification and the management practices of IBA differ worldwide and, particularly, among the EU Member States. However, different applications have been studied for this material.
  • 8.4K
  • 24 Dec 2021
Topic Review
Cluster Chemistry
In chemistry, a cluster is an ensemble of bound atoms or molecules that is intermediate in size between a molecule and a bulk solid. Clusters exist of diverse stoichiometries and nuclearities. For example, carbon and boron atoms form fullerene and borane clusters, respectively. Transition metals and main group elements form especially robust clusters. Clusters can also consist solely of a certain kind of molecules, such as water clusters. The phrase cluster was coined by F.A. Cotton in the early 1960s to refer to compounds containing metal–metal bonds. In another definition a cluster compound contains a group of two or more metal atoms where direct and substantial metal bonding is present. The prefixed terms "nuclear" and "metallic" are used and imply different meanings. For example, polynuclear refers to a cluster with more than one metal atom, regardless of the elemental identities. Heteronuclear refers to a cluster with at least two different metal elements. The main cluster types are "naked" clusters (without stabilizing ligands) and those with ligands. For transition metal clusters, typical stabilizing ligands include carbon monoxide, halides, isocyanides, alkenes, and hydrides. For main group elements, typical clusters are stabilized by hydride ligands. Transition metal clusters are frequently composed of refractory metal atoms. In general metal centers with extended d-orbitals form stable clusters because of favorable overlap of valence orbitals. Thus, metals with a low oxidation state for the later metals and mid-oxidation states for the early metals tend to form stable clusters. Polynuclear metal carbonyls are generally found in late transition metals with low formal oxidation states. The polyhedral skeletal electron pair theory or Wade's electron counting rules predict trends in the stability and structures of many metal clusters. Jemmis mno rules have provided additional insight into the relative stability of metal clusters.
  • 8.4K
  • 08 Nov 2022
Topic Review
Manufacturing Processes for Ceramic Matrix Composites
Materials such as ceramic matrix composites (CMCs) have been the focus of research and being tested in different conditions for several decades now. They are known as a subgroup of composite materials and ceramics. Ceramic composites were developed to control and address problems that occurred with other commonly used ceramics, such as silicon carbide, alumina, silicon nitride, aluminum nitride, and zirconia. Such ceramics fractured with ease, revealing scratches and cracks while mechanical and thermo-mechanical loads were applied to them. CMCs exhibit mechanical and thermal properties comparable with, and in some cases, even better than, the conventional superalloys used in aero-engines. However, their adoption relies on other variables as well, such as the cost of development, industrialization, manufacturing, and the availability of manufacturing technologies and systems.
  • 8.4K
  • 27 Apr 2023
  • Page
  • of
  • 2788
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Digital Society, Industry 5.0 and Smart City
Encyclopedia of Engineering
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Academic Video Service
Feedback