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Topic Review
Space Vector PWM Techniques
This entry elaborates the basic concept of space vector Pulse Width modulation technique for a three-phase voltage source inverter. Why space vector Pulse width modulation (PWM) is required and how it is implemented in the simulation model, is described in the entry.  A number of PWM scheme is used to obtain variable voltage and frequency supply from a power converter. The most widely used PWM schemes for three-phase voltage source inverter (VSI) are carrier-based sinusoidal PWM and space vector PWM (SVPWM). There is an increasing trend of using space vector PWM (SVPWM) because of their easier digital realization and better dc bus utilization. This entry focuses on step by step development of MATLAB/SIMULINK model of SVPWM. Firstly the model of a three-phase VSI is discussed based on space vector representation. Next simulation model of SVPWM is obtained using MATLAB/SIMULINK. Simulation results are also provided. 
  • 35.0K
  • 16 Jun 2022
Topic Review
Language Acquisition
Language acquisition is the process by which humans acquire the capacity to perceive and comprehend language (in other words, gain the ability to be aware of language and to understand it), as well as to produce and use words and sentences to communicate. Language acquisition involves structures, rules and representation. The capacity to successfully use language requires one to acquire a range of tools including phonology, morphology, syntax, semantics, and an extensive vocabulary. Language can be vocalized as in speech, or manual as in sign. Human language capacity is represented in the brain. Even though human language capacity is finite, one can say and understand an infinite number of sentences, which is based on a syntactic principle called recursion. Evidence suggests that every individual has three recursive mechanisms that allow sentences to go indeterminately. These three mechanisms are: relativization, complementation and coordination. There are two main guiding principles in first-language acquisition: speech perception always precedes speech production and the gradually evolving system by which a child learns a language is built up one step at a time, beginning with the distinction between individual phonemes. Linguists who are interested in child language acquisition for many years question how language is acquired, Lidz et al. states "The question of how these structures are acquired, then, is more properly understood as the question of how a learner takes the surface forms in the input and converts them into abstract linguistic rules and representations." Language acquisition usually refers to first-language acquisition, which studies infants' acquisition of their native language, whether that be spoken language or signed language as a result of prelingual deafness, though it can also refer to bilingual first language acquisition (BFLA), which refers to an infant's simultaneous acquisition of two native languages. This is distinguished from second-language acquisition, which deals with the acquisition (in both children and adults) of additional languages. In addition to speech, reading and writing a language with an entirely different script compounds the complexities of true foreign language literacy. Language acquisition is one of the quintessential human traits, because non-humans do not communicate by using language.
  • 34.5K
  • 18 Nov 2022
Topic Review
Harut and Marut
Harut and Marut (Arabic: هَارُوْت وَمَارُوْت) are two angels mentioned in Quran 2:102, who are said to have been located in Babylon. According to some narratives, those two angels were in the time of Idris. The Quran indicates that they were a trial for the people and through them the people were tested with sorcery. The story itself parallels a Jewish legend about the fallen angels Shemḥazaī, ʿUzza, and ʿAzaʾel. The names Hārūt and Mārūt appear to be etymologically related to those of Haurvatat and Ameretat, two Zoroastrian archangels. Haurvatat-Ameretat (Pahlavi hrwdʼd ʼmwrdʼd) appears in Sogdian language texts as hrwwt mrwwt. A relationship to Armenian hawrot mawrot has been suggested but is not confirmed. Muslim sources disagree, whether Harut and Marut can be considered fallen angels or not.
  • 33.9K
  • 15 Nov 2022
Topic Review
Psychological Manipulation
Psychological manipulation is a type of social influence that aims to change the behavior or perception of others through abusive, deceptive, or underhanded tactics. By advancing the interests of the manipulator, often at another's expense, such methods could be considered exploitative, abusive, devious, and deceptive. Social influence is not necessarily negative. For example, people such as friends, family and doctors, can try to persuade to change clearly unhelpful habits and behaviors. Social influence is generally perceived to be harmless when it respects the right of the influenced to accept or reject it, and is not unduly coercive. Depending on the context and motivations, social influence may constitute underhanded manipulation.
  • 32.3K
  • 28 Oct 2022
Topic Review
Neoliberalism (International Relations)
In the study of international relations, neoliberalism (or liberal institutionalism) is a school of thought which holds that international cooperation between states is feasible and sustainable, and that such cooperation can reduce conflict and competition. Neoliberalism is a revised version of liberalism. Alongside neorealism, neoliberalism is one of the two most influential contemporary approaches to international relations; the two perspectives have dominated international relations theory since the 1990s. Neoliberalism shares many assumptions as neorealism (namely, that the international system is anarchic, states are the main actors, and states rationally pursue their self-interest), but draws different conclusions from those assumptions. In contrast to neorealist scholarship which is skeptical of prospects for sustainable cooperation, neoliberalism argues that cooperation is feasible and sustainable. Neoliberals highlight the role of international institutions and regimes in facilitating cooperation between states. The main reason why international organizations facilitate cooperation is that they provide information, which reduces collective action problems among states in providing public goods and enforcing compliance. Robert Keohane's 1984 book After Hegemony used insights from the new institutional economics to argue that the international system could remain stable in the absence of a hegemon, thus rebutting hegemonic stability theory. Keohane showed that international cooperation could be sustained through repeated interactions, transparency, and monitoring.
  • 32.1K
  • 10 Nov 2022
Topic Review
Names of the Days of the Week
The names of the days of the week in many languages are derived from the names of the classical planets in Hellenistic astrology, which were in turn named after contemporary deities, a system introduced by the Roman Empire during Late Antiquity. In some other languages, the days are named after corresponding deities of the regional culture, either beginning with Sunday or with Monday. In the international standard ISO 8601, Monday is treated as the first day of the week.
  • 31.9K
  • 01 Nov 2022
Topic Review
Theories on Addiction of Smartphone and Internet
Excessive use of smartphones has been associated with a number of negative consequences for individuals. Some of these consequences relate to many symptoms of behavioral addiction. Addiction is defined as a pleasure-inducing behavior that through repeated exposure gradually leads to loss of control and further negative consequences.
  • 31.6K
  • 24 Jun 2022
Topic Review
Quetzalcoatl
Quetzalcoatl (/ˌkɛtsɑːlkoʊˈɑːtəl/; Spanish: [ket͡salˈkoatʊl] (listen); Template:Lang-nci-IPA, in honorific form: Quetzalcohuātzin, modern Nahuatl pronunciation (help·info)) is a deity in Mesoamerican culture and literature whose name comes from the Nahuatl language and means "feathered serpent" or "Quetzal-feathered Serpent". The earliest known documentation of the worship of a Feathered Serpent occurs in Teotihuacan in the first century BC or first century AD. That period lies within the Late Preclassic to Early Classic period (400 BC – 600 AD) of Mesoamerican chronology; veneration of the figure appears to have spread throughout Mesoamerica by the Late Classic period (600–900 AD). In the Postclassic period (900–1519 AD), the worship of the feathered-serpent deity centred in the primary Mexican religious center of Cholula. In this period the deity is known to have been named "Quetzalcoatl" by his Nahua followers. In the Maya area he was approximately equivalent to Kukulkan and Gukumatz, names that also roughly translate as "feathered serpent" in different Mayan languages. Quetzalcoatl, the Aztec god of wind, air, and learning, wears around his neck the "wind breastplate" ehecailacocozcatl, "the spirally voluted wind jewel" made of a conch shell. This talisman was a conch shell cut at the cross-section and was likely worn as a necklace by religious rulers, as such objects have been discovered in burials in archaeological sites throughout Mesoamerica, and potentially symbolized patterns witnessed in hurricanes, dust devils, seashells, and whirlpools, which were elemental forces that had significance in Aztec mythology. Codex drawings pictured both Quetzalcoatl and Xolotl wearing an ehecailacocozcatl around the neck. Additionally, at least one major cache of offerings includes knives and idols adorned with the symbols of more than one god, some of which were adorned with wind jewels. In the era following the 16th-century Spanish conquest of the Aztec Empire, a number of records conflated Quetzalcoatl with Ce Acatl Topiltzin, a ruler of the mythico-historic city of Tollan. Historians debate to what degree, or whether at all, these narratives about this legendary Toltec ruler describe historical events. Furthermore, early Spanish sources written by clerics tend to identify the god-ruler Quetzalcoatl of these narratives with either Hernán Cortés or Thomas the Apostle— identifications which have also become sources of a diversity of opinions about the nature of Quetzalcoatl. Among the Aztecs, whose beliefs are the best-documented in the historical sources, Quetzalcoatl was related to gods of the wind, of the planet Venus, of the dawn, of merchants and of arts, crafts and knowledge. He was also the patron god of the Aztec priesthood, of learning and knowledge. Quetzalcoatl was one of several important gods in the Aztec pantheon, along with the gods Tlaloc, Tezcatlipoca and Huitzilopochtli. Two other gods represented by the planet Venus are Quetzalcoatl's ally Tlaloc (the god of rain), and Quetzalcoatl's twin and psychopomp, Xolotl. Animals thought to represent Quetzalcoatl include resplendent quetzals, rattlesnakes (coatl meaning "serpent" in Nahuatl), crows, and macaws. In his form as Ehecatl he is the wind, and is represented by spider monkeys, ducks, and the wind itself. In his form as the morning star, Venus, he is also depicted as a harpy eagle. In Mazatec legends the astrologer deity Tlahuizcalpantecuhtli, who is also represented by Venus, bears a close relationship with Quetzalcoatl.
  • 30.1K
  • 11 Oct 2022
Topic Review
Now I Lay Me Down to Sleep
Now I lay me down to sleep is a classic children's bedtime prayer from the 18th century.
  • 29.3K
  • 14 Oct 2022
Topic Review
Information and Communication Technologies for Development
Information and communication technologies for development (ICT4D) refers to the application of information and communication technologies (ICT) toward social, economic, and political development, with a particular emphasis on helping poor and marginalized people and communities. It aims to help in international development by bridging the digital divide and providing equitable access to technologies. ICT4D is grounded in the notions of "development", "growth", "progress" and "globalization" and is often interpreted as the use of technology to deliver a greater good. Another similar term used in the literature is "digital development". ICT4D draws on theories and frameworks from many disciplines, including sociology, economics, development studies, library, information science, and communication studies.
  • 29.1K
  • 24 Oct 2022
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