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:
Most Viewed Latest Alphabetical (A-Z) Alphabetical (Z-A)
Filter:
All Topic Review Biography Peer Reviewed Entry Video Entry
Topic Review
Jet Engine Thrust
The familiar explanation for jet thrust is a "black box" description which only looks at what goes into the jet engine, air and fuel, and what comes out, exhaust gas and an unbalanced force. This force, called thrust, is the sum of the momentum difference between entry and exit and any unbalanced pressure force between entry and exit, as explained in "Thrust calculation". As an example, an early turbojet, the Bristol Olympus Mk. 101, had a momentum thrust of 9300 lb. and a pressure thrust of 1800 lb. giving a total of 11,100 lb. Looking inside the "black box" shows that the thrust results from all the unbalanced momentum and pressure forces created within the engine itself. These forces, some forwards and some rearwards, are across all the internal parts, both stationary and rotating, such as ducts, compressors, etc., which are in the primary gas flow which flows through the engine from front to rear. The algebraic sum of all these forces is delivered to the airframe for propulsion. "Flight" gives examples of these internal forces for two early jet engines, the Rolls-Royce Avon Ra.14 and the de Havilland Goblin
  • 12.4K
  • 23 Nov 2022
Topic Review
Hydrogen as an Alternative Fuel
Hydrogen is a very important fuel of our secure and clean energy future. Hydrogen will be the fuel of the future and gradually it will replace all current fossil fuels. Hydrogen can be used as a fuel for vehicles, to heat homes and offices, to produce electricity, and to fuel ships and aircraft. The present work provides an overview of hydrogen as an alternative fuel, which can be used in internal combustion engines and in fuel cells.
  • 12.4K
  • 27 Oct 2020
Topic Review
Fuel Economy in Aircraft
The fuel economy in aircraft is the measure of the transport energy efficiency of aircraft. Efficiency is increased with better aerodynamics and by reducing weight, and with improved engine BSFC and propulsive efficiency or TSFC. Endurance and range can be maximized with the optimum airspeed, and economy is better at optimum altitudes, usually higher. An airline efficiency depends on its fleet fuel burn, seating density, air cargo and passenger load factor, while operational procedures like maintenance and routing can save fuel. Average fuel burn of new aircraft fell 45% from 1968 to 2014, a compounded annual reduction 1.3% with a variable reduction rate. In 2018, CO₂ emissions totalled 747 million tonnes for passenger transport, for 8.5 trillion revenue passenger kilometres (RPK), giving an average of 88 gram CO₂ per RPK. A 88 gCO₂/km represents 28 g of fuel per km, or a 3.5 L/100 km (67 mpg‑US) fuel consumption. New technology can reduce engine fuel consumption, like higher pressure and bypass ratios, geared turbofans, open rotors, hybrid electric or fully electric propulsion; and airframe efficiency with retrofits, better materials and systems and advanced aerodynamics.
  • 12.4K
  • 01 Nov 2022
Topic Review
Value (Ethics)
In ethics, value denotes the degree of importance of some thing or action, with the aim of determining what actions are best to do or what way is best to live (normative ethics), or to describe the significance of different actions. Value systems are prospective and prescriptive beliefs; they affect ethical behavior of a person or are the basis of their intentional activities. Often primary values are strong and secondary values are suitable for changes. What makes an action valuable may in turn depend on the ethical values of the objects it increases, decreases or alters. An object with "ethic value" may be termed an "ethic or philosophic good" (noun sense). Values can be defined as broad preferences concerning appropriate courses of actions or outcomes. As such, values reflect a person's sense of right and wrong or what "ought" to be. "Equal rights for all", "Excellence deserves admiration", and "People should be treated with respect and dignity" are representatives of values. Values tend to influence attitudes and behavior and these types include ethical/moral values, doctrinal/ideological (religious, political) values, social values, and aesthetic values. It is debated whether some values that are not clearly physiologically determined, such as altruism, are intrinsic, and whether some, such as acquisitiveness, should be classified as vices or virtues.
  • 12.4K
  • 06 Oct 2022
Topic Review
Erikson's Stages of Psychosocial Development
Erikson's stages of psychosocial development, as articulated in the second half of the 20th century by Erik Erikson in collaboration with Joan Erikson, is a comprehensive psychoanalytic theory that identifies a series of eight stages that a healthy developing individual should pass through from infancy to late adulthood. According to Erikson’s theory the results from each stage, whether positive or negative, influences the results of succeeding stages. Erikson published a book called Childhood and Society around the 1950s that made his research well known on the eight stages of psychosocial development. Erikson was originally influenced by Sigmund Freud’s psychosexual stages of development. He began by working with Freud's theories specifically, but as he began to dive deeper into biopsychosocial development and how other environmental factors affect human development, he soon progressed past Freud’s theories and developed his own ideas. Erikson's stage theory characterizes an individual advancing through the eight life stages as a function of negotiating their biological and sociocultural forces. The two conflicting forces each have a psychosocial crisis which characterizes the eight stages. If an individual does indeed successfully reconcile these forces (favoring the first mentioned attribute in the crisis), they emerge from the stage with the corresponding virtue. For example, if an infant enters into the toddler stage (autonomy vs. shame and doubt) with more trust than mistrust, they carry the virtue of hope into the remaining life stages. The challenges of stages not successfully completed may be expected to return as problems in the future. However, mastery of a stage is not required to advance to the next stage. In one study, subjects showed significant development as a result of organized activities.
  • 12.4K
  • 20 Oct 2022
Biography
Thomas W. Campbell
Thomas Warren Campbell (December 9, 1944) is a physicist, lecturer, and author of the My Big T.O.E. (Theory of Everything) trilogy, a work that claims to unify general relativity, quantum mechanics, and metaphysics along with the origins of consciousness. The work is based on the simulation argument, which posits that reality is both virtual and subjective. Campbell agrees with other notable phi
  • 12.2K
  • 12 Dec 2022
Topic Review
Georgism
Georgism, also called in modern times geoism and known historically as the single tax movement, is an economic ideology holding that, although people should own the value they produce themselves, the economic rent derived from land – including from all natural resources, the commons, and urban locations – should belong equally to all members of society. Developed from the writings of American economist and social reformer Henry George, the Georgist paradigm seeks solutions to social and ecological problems, based on principles of land rights and public finance which attempt to integrate economic efficiency with social justice. Georgism is concerned with the distribution of economic rent caused by land ownership, natural monopolies, pollution and the control of commons, including title of ownership for natural resources and other contrived privileges (e.g. intellectual property). Any natural resource which is inherently limited in supply can generate economic rent, but the classical and most significant example of land monopoly involves the extraction of common ground rent from valuable urban locations. Georgists argue that taxing economic rent is efficient, fair and equitable. The main Georgist policy recommendation is a tax assessed on land value, arguing that revenues from a land value tax (LVT) can be used to reduce or eliminate existing taxes (such as on income, trade, or purchases) that are unfair and inefficient. Some Georgists also advocate for the return of surplus public revenue to the people by means of a basic income or citizen's dividend. The concept of gaining public revenues mainly from land and natural resource privileges was widely popularized by Henry George through his first book, Progress and Poverty (1879). The philosophical basis of Georgism dates back to several early thinkers such as John Locke, Baruch Spinoza and Thomas Paine. Economists since Adam Smith and David Ricardo have observed that a public levy on land value does not cause economic inefficiency, unlike other taxes. A land value tax also has progressive tax effects. Advocates of land value taxes argue that they would reduce economic inequality, increase economic efficiency, remove incentives to underutilize urban land and reduce property speculation. Georgist ideas were popular and influential during the late 19th and early 20th century. Political parties, institutions and communities were founded based on Georgist principles during that time. Early devotees of Henry George's economic philosophy were often termed Single Taxers for their political goal of raising public revenue mainly or only from a land value tax, although Georgists endorsed multiple forms of rent capture (e.g. seigniorage) as legitimate. The term Georgism was invented later, and some prefer the term geoism as more generic.
  • 12.2K
  • 08 Nov 2022
Topic Review
E-Government
E-government (short for electronic government) is the use of electronic communications devices, computers and the Internet to provide public services to citizens and other persons in a country or region. According to Jeong, 2007 the term consists of the digital interactions between a citizen and their government (C2G), between governments and other government agencies (G2G), between government and citizens (G2C), between government and employees (G2E), and between government and businesses/commerces (G2B). E-government delivery models can be broken down into the following categories: This interaction consists of citizens communicating with all levels of government (city, state/province, national, and international), facilitating citizen involvement in governance using information and communication technology (ICT) (such as computers and websites) and business process re-engineering (BPR). Brabham and Guth (2017) interviewed the third party designers of e-government tools in North America about the ideals of user interaction that they build into their technologies, which include progressive values, ubiquitous participation, geolocation, and education of the public. Other definitions are more away from technology as an object, to see them simply as facilitators or instruments and focus on specific changes in Public Administration issues, and in the internal transformation of a Government, is the case of the definition that established the specialist technologist Mauro D. Ríos in the paper "In search of a definition of Electronic Government", he says: "Digital Government is a new way of organization and management of public affairs, introducing positive transformational processes in management and the structure itself of the organization chart, adding value to the procedures and services provided, all through the introduction and continued appropriation of information and communication technologies as a facilitator of these transformations."
  • 12.2K
  • 08 Nov 2022
Topic Review
Wine Aroma and Flavor Compounds
Wine sensory experience includes flavor, aroma, color, and  even acoustic traits, which impact consumer acceptance. The quality of the wine can be negatively impacted by the presence of off-flavors and aromas. Flavor profiles of wines are the result of a vast number of variations in vineyard and winery production, including grape selection, winemaker’s knowledge and technique, and tools used to produce wines with a specific flavor. One of the most important “tools” for modulating flavor in wines is the choice of the yeasts. During alcoholic fermentation, the wine yeasts extract and metabolize compounds from the grape must by modifying grape-derived molecules, producing flavor-active compounds.
  • 12.2K
  • 29 Oct 2020
Topic Review
Mixer (Cooking)
A mixer is a kitchen device that uses a gear-driven mechanism to rotate a set of "beaters" in a bowl containing the food or liquids to be prepared by mixing them. Mixers help automate the repetitive tasks of stirring, whisking or beating. When the beaters are replaced by a dough hook, a mixer may also be used to knead.
  • 12.1K
  • 07 Nov 2022
Topic Review
Flavonoids—Classification and Natural Sources
       Flavonoids are small molecules, produced de novo by plants as secondary metabolites in response to diverse biotic and abiotic factors. These chemical compounds have a broad spectrum of established health-promoting effects. They are due to their antioxidative, anti-inflammatory, anti-mutagenic, and anti-carcinogenic properties coupled with their capacity to modulate key cellular enzyme functions. Flavonoids are widely distributed chemical compounds in the plant kingdom. Plants are therefore an inexhaustible source of flavonoids.
  • 12.1K
  • 02 Nov 2020
Topic Review
Parasocial Relationships
A parasocial relationship (PSR) is a one-sided relationship that media users form as a result of exposure to media personas. In 1956, the term parasocial relationship was coined by Donald Horton and R. Richard Wohl. They focused on the psychological attachment that was formed from viewing television personalities. Their work laid the foundation and popularized a wide range of research on parasocial phenomena. A parasocial interaction, an exposure that garners interest in a persona, becomes a parasocial relationship after repeated exposure to the media persona causes the media users to develop illusions of intimacy, friendship, and identification. Positive information learned about the media persona results in increased attraction and the relationship progresses. Parasocial relationships are enhanced due to trust and self-disclosure provided by the media persona. Media users are loyal and feel directly connected to the persona much like their close friends by observing and interpreting their appearance, gestures, voice, conversation, and conduct. Media personas have a significant amount of influence over media users, positive or negative, informing the way that they perceive certain topics or even their purchasing habits. Social media introduces additional opportunities for parasocial relationships to intensify because it provides more opportunities for intimate, reciprocal, and frequent interactions between the user and persona.
  • 12.1K
  • 24 Nov 2022
Topic Review
Flood Prediction Using ML Models
Floods are among the most destructive natural disasters, which are highly complex to model. The research on the advancement of flood prediction models contributed to risk reduction, policy suggestion, minimization of the loss of human life, and reduction of the property damage associated with floods. To mimic the complex mathematical expressions of physical processes of floods, during the past two decades, machine learning (ML) methods contributed highly in the advancement of prediction systems providing better performance and cost-effective solutions. Due to the vast benefits and potential of ML, its popularity dramatically increased among hydrologists.Researchers through introducing novel ML methods and hybridizing of the existing ones aim at discovering more accurate and efficient prediction models. The main contribution of this paper is to demonstrate the state of the art of ML models in flood prediction and to give insight into the most suitable models. In this paper, the literature where ML models were benchmarked through a qualitative analysis of robustness, accuracy, effectiveness, and speed are particularly investigated to provide an extensive overview on the various ML algorithms used in the field. The performance comparison of ML models presents an in-depth understanding of the different techniques within the framework of a comprehensive evaluation and discussion. As a result, this paper introduces the most promising prediction methods for both long-term and short-term floods. Furthermore, the major trends in improving the quality of flood prediction models are investigated. Among them, hybridization, data decomposition, algorithm ensemble, and model optimization are reported as the most effective strategies for the improvement of ML methods. This survey can be used as a guideline for hydrologists as well as climate scientists in choosing the proper ML method according to the prediction task.
  • 12.1K
  • 04 Jan 2023
Topic Review
Snakes and Ladders
Snakes and Ladders, known originally as Moksha Patam, is an ancient Indian board game for two or more players regarded today as a worldwide classic. It is played on a game board with numbered, gridded squares. A number of "ladders" and "snakes" are pictured on the board, each connecting two specific board squares. The object of the game is to navigate one's game piece, according to die rolls, from the start (bottom square) to the finish (top square), helped by climbing ladders but hindered by falling down snakes. The game is a simple race based on sheer luck, and it is popular with young children. The historic version had its roots in morality lessons, on which a player's progression up the board represented a life journey complicated by virtues (ladders) and vices (snakes). The game is also sold under other names such as Chutes and Ladders, Bible Ups and Downs, etc., some with a morality motif; a morality Chutes and Ladders was published by Milton Bradley starting from 1943.
  • 12.1K
  • 09 Oct 2022
Topic Review
Wiktionary
Wiktionary is a multilingual, web-based project to create a free content dictionary of all words in all languages. It is collaboratively edited via a wiki, and its name is a portmanteau of the words wiki and dictionary. It is available in 171 languages and in Simple English. Like its sister project Wikipedia, Wiktionary is run by the Wikimedia Foundation, and is written collaboratively by volunteers, dubbed "Wiktionarians". Its wiki software, MediaWiki, allows almost anyone with access to the website to create and edit entries. Because Wiktionary is not limited by print space considerations, most of Wiktionary's language editions provide definitions and translations of words from many languages, and some editions offer additional information typically found in thesauri and lexicons. The English Wiktionary includes a thesaurus (formerly known as Wikisaurus) of synonyms of various words. Wiktionary data are frequently used in various natural language processing tasks.
  • 12.0K
  • 08 Nov 2022
Topic Review
Vaginal Discharge
Vaginal discharge is a mixture of liquid, cells, and bacteria that lubricate and protect the vagina. This mixture is constantly produced by the cells of the vagina and cervix, and it exits the body through the vaginal opening. The composition, amount, and quality of discharge varies between individuals and can vary throughout the menstrual cycle and throughout the stages of sexual and reproductive development. Normal vaginal discharge may have a thin, watery consistency or a thick, sticky consistency, and it may be clear or white in color. Normal vaginal discharge may be large in volume but typically does not have a strong odor, nor is it typically associated with itching or pain. While most discharge is considered physiologic or represents normal functioning of the body, some changes in discharge can reflect infection or other pathological processes. Infections that may cause changes in vaginal discharge include vaginal yeast infections, bacterial vaginosis, and sexually transmitted infections. The characteristics of abnormal vaginal discharge vary depending on the cause, but common features include a change in color, a foul odor, and associated symptoms such as itching, burning, pelvic pain, or pain during sexual intercourse.
  • 12.0K
  • 14 Nov 2022
Topic Review
Kangiten
Kangi-ten (Japanese: 歓喜天, "God of Bliss") is a god (deva or ten) in Shingon and Tendai schools of Japanese Buddhism. He is generally considered the Japanese Buddhist form of the Hindu god of wisdom, Ganesha and is sometimes also identified with the bodhisattva Avalokiteshvara. He is also known as Kanki-ten, Shō-ten (聖天, "sacred god" or "noble god"), Daishō-ten ("great noble god"), Daishō Kangi-ten (大聖歓喜天), Tenson (天尊, "venerable god"), Kangi Jizai-ten (歓喜自在天), Shōden-sama, Vinayaka-ten, Binayaka-ten (毘那夜迦天), Ganapatei (誐那缽底) and Zōbi-ten (象鼻天). Kangiten has many aspects and names, associated with Vajrayana (Esoteric Buddhist, Tantric, mantrayana) schools, Shingon being one of them. Although Kangiten is depicted with an elephant's head like Ganesha as a single male deity, his most popular aspect is the Dual(-bodied) Kangiten or the Embracing Kangiten depicted as an elephant-headed male-female human couple standing in an embrace.
  • 11.9K
  • 18 Nov 2022
Topic Review
Amaterasu
Amaterasu (天照), Amaterasu-ōmikami (天照大神／天照大御神／天照皇大神), or Ōhirume-no-muchi-no-kami (大日孁貴神) is a deity of the Japanese myth cycle and also a major deity of the Shinto religion. She is seen as the goddess of the sun and the universe. The name Amaterasu is derived from Amateru and means "shining in heaven". The meaning of her whole name, Amaterasu-ōmikami, is "the great august kami (deity) who shines in the heaven".[N 1] According to the Kojiki and Nihon Shoki chronicles in Japanese mythology, the Emperors of Japan are considered to be direct descendants of Amaterasu.
  • 11.8K
  • 01 Nov 2022
Topic Review
Computational Chemistry Methods
The main objective of computational chemistry is to solve chemical problems by simulating chemical systems (molecular, biological, materials) in order to provide reliable, accurate and comprehensive information at an atomic level. To this end, there are two main methodological families: those based on quantum chemical methods and those based on molecular mechanics. The former are methods in which the electrons are explicitly accounted for, while in the latter their presence is hidden in the force field. 
  • 11.8K
  • 17 Jun 2021
Topic Review
Smart Clothing
Smart clothing can be defined as the intelligent system that senses and reacts to the changes and stimuli of the environment and the wearer’s conditions, such as electrical, thermal and magnetic ones. Smart clothing has various functions (e.g., protection, temperature regulation, monitoring, entertainment, expression of personality, etc.) and embodies many features (e.g., efficient, intelligent, computable, etc.), combining cutting-edge technologies in related fields such as electronic information, sensors and materials. Smart clothing has emerged to meet consumers’ personalized needs in healthcare, work, entertainment, etc., and has rapidly become a hotspot in the clothing industry and research field. However, as smart clothing gets popular, sustainability issues are becoming increasingly prominent during its development and circulation. 
  • 11.7K
  • 19 Apr 2022
  • Page
  • of
  • 2753
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Encyclopedia of Fungi
Encyclopedia of Digital Society, Industry 5.0 and Smart City
ScholarVision Creations
Feedback