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Topic Review
Slow Sand Filtration for Raw Water Treatment
Filtration methods are traditional techniques of water purification used by mankind since ancient times. By filtering, water can be cleaned of sand, silt, turbidity, scale, and other suspended particles. Modern slow sand filters (SSFs) for water purification were first used in the 19th century in England. Therefore, they are often called English filters. The first slow filter was built by the English engineer James Simpson in 1829 in London to purify water from the river Thames.
  • 8.4K
  • 02 Jun 2023
Topic Review
Matthews Correlation Coefficient
The Matthews correlation coefficient (MCC) or phi coefficient is used in machine learning as a measure of the quality of binary (two-class) classifications, introduced by biochemist Brian W. Matthews in 1975. The MCC is defined identically to Pearson's phi coefficient, introduced by Karl Pearson, also known as the Yule phi coefficient from its introduction by Udny Yule in 1912. Despite these antecedents which predate Matthews's use by several decades, the term MCC is widely used in the field of bioinformatics and machine learning. The coefficient takes into account true and false positives and negatives and is generally regarded as a balanced measure which can be used even if the classes are of very different sizes. The MCC is in essence a correlation coefficient between the observed and predicted binary classifications; it returns a value between −1 and +1. A coefficient of +1 represents a perfect prediction, 0 no better than random prediction and −1 indicates total disagreement between prediction and observation. However, if MCC equals neither −1, 0, or +1, it is not a reliable indicator of how similar a predictor is to random guessing because MCC is dependent on the dataset. MCC is closely related to the chi-square statistic for a 2×2 contingency table where n is the total number of observations. While there is no perfect way of describing the confusion matrix of true and false positives and negatives by a single number, the Matthews correlation coefficient is generally regarded as being one of the best such measures. Other measures, such as the proportion of correct predictions (also termed accuracy), are not useful when the two classes are of very different sizes. For example, assigning every object to the larger set achieves a high proportion of correct predictions, but is not generally a useful classification. The MCC can be calculated directly from the confusion matrix using the formula: In this equation, TP is the number of true positives, TN the number of true negatives, FP the number of false positives and FN the number of false negatives. If any of the four sums in the denominator is zero, the denominator can be arbitrarily set to one; this results in a Matthews correlation coefficient of zero, which can be shown to be the correct limiting value. The MCC can be calculated with the formula: using the positive predictive value, the true positive rate, the true negative rate, the negative predictive value, the false discovery rate, the false negative rate, the false positive rate, and the false omission rate. The original formula as given by Matthews was: This is equal to the formula given above. As a correlation coefficient, the Matthews correlation coefficient is the geometric mean of the regression coefficients of the problem and its dual. The component regression coefficients of the Matthews correlation coefficient are Markedness (Δp) and Youden's J statistic (Informedness or Δp'). Markedness and Informedness correspond to different directions of information flow and generalize Youden's J statistic, the [math]\displaystyle{ \delta }[/math]p statistics and (as their geometric mean) the Matthews Correlation Coefficient to more than two classes. Some scientists claim the Matthews correlation coefficient to be the most informative single score to establish the quality of a binary classifier prediction in a confusion matrix context.
  • 8.4K
  • 18 Nov 2022
Topic Review
eCommerce and Small and Medium Enterprises
The rise of smaller businesses has been an essential trend since the 1990s, when they became engines for economic development. Now, Small and Medium Enterprises (SMEs) across the world are increasingly relying on eCommerce channels to create and capture value. The growth in eCommerce operations is being fueled by several global and technological developments. eCommerce allows SMEs to benefit from globalization by expanding their ability to access customers around the world and across customer demographics and categories. This emergence of a new range of markets has made strategic flexibility essential for SMEs, as such expansion requires a consistent rethinking and adapting to continually changing dynamics in a global environment.
  • 8.4K
  • 07 May 2022
Topic Review
Free Society
The term free society is used frequently by American libertarian theorists to denote a society in which their ideal political, legal and economic aims are in effect. In a theoretical free society, all individuals act voluntarily, having the freedom to obtain the power and resources to fulfill their own potential. Adlai Stevenson defined free societies as a society in which individuals find it "safe to be unpopular". Others, such as Chandran Kukathas, described a free society as dependent upon the "principle of freedom of association". Cindy Cohn has argued that the freedom to have a "private conversation" is "central to a free society". These interpretations can also be elaborated in terms of freedom of speech – if people have a right to express their views without fear of arrest, imprisonment, or physical harm. In a free society, individuals would organize in voluntary associations, including free market and communal societies. Individuals would gain more prosperity due to the lack of restrictions on trade and wealth creation.
  • 8.4K
  • 11 Oct 2022
Topic Review
Hauran
Hauran (Arabic: حوران / ALA-LC: Ḥawrān), also spelled Hawran, Houran and Horan, known to the Ancient Greeks and Romans as Auranitis, is a volcanic plateau, a geographic area and a people located in southwestern Syria and extending into the northwestern corner of Jordan, it’s known to be the birth place of the dabke dance which is the most popular dance in all of the Levant.
  • 8.4K
  • 10 Nov 2022
Topic Review
Triceratops
Triceratops (/traɪˈsɛrəˌtɒps/ trahy-ser-uh-tops; lit. three-horned face) is a genus of herbivorous chasmosaurine ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the Late Cretaceous period, about 68 million years ago in what is now North America. It is one of the last-known non-avian dinosaur genera, and became extinct in the Cretaceous–Paleogene extinction event 66 million years ago. The name Triceratops, which literally means 'three-horned face', is derived from the Greek words trí- (τρί-) meaning 'three', kéras (κέρας) meaning 'horn', and ṓps (ὤψ) meaning 'face'. Bearing a large bony frill, three horns on the skull, and a large four-legged body, exhibiting convergent evolution with rhinoceroses and bovines, Triceratops is one of the most recognizable of all dinosaurs and the most well-known ceratopsid. It was also one of the largest, up to 8–9 metres (26–30 ft) long and 5–9 metric tons (5.5–9.9 short tons) in body mass. It shared the landscape with and was most likely preyed upon by Tyrannosaurus, though it is less certain that two adults did battle in the fanciful manner often depicted in museum displays and popular images. The functions of the frills and three distinctive facial horns on its head have long inspired debate. Traditionally, these have been viewed as defensive weapons against predators. More recent interpretations find it probable that these features were primarily used in species identification, courtship, and dominance display, much like the antlers and horns of modern ungulates. Triceratops was traditionally placed within the "short-frilled" ceratopsids, but modern cladistic studies show it to be a member of the Chasmosaurinae which usually have long frills. Two species, T. horridus and T. prorsus, are considered valid today, from the seventeen species that have ever been named. Research published in 2010 concluded that the contemporaneous Torosaurus, a ceratopsid long regarded as a separate genus, represents Triceratops in its mature form. This view has been disputed; further data is needed to settle the debate. Triceratops has been documented by numerous remains collected since the genus was first described in 1889 by American paleontologist Othniel Charles Marsh. Specimens representing life stages from hatchling to adult have been found. As the archetypal ceratopsid, Triceratops is one of the most popular dinosaurs, and has been featured in film, postal stamps, and many other types of media.
  • 8.4K
  • 01 Nov 2022
Topic Review
Carbon Emission Efficiency
Carbon emission efficiency is an important concept in environmental science; it refers to the economic benefits generated by production activities that produce carbon emissions at the same time. The less carbon emissions generated per unit of economic output, the more carbon emission efficient it is.
  • 8.4K
  • 26 May 2022
Topic Review
Cultural Memory
Historic urban landscapes (HULs) are composed of layers of imbedded tangible and intangible features such as cultural memories. As the collective memories of city inhabitants, cultural memories can affect elements of social sustainability such as health, well-being, community identity, place perception and social engagement. This topic review points to the value of recalling cultural memory features in HULs, which can be used to achieve social sustainability.  In addition, it contributes to sustainable development through the contribution of cultural memory and its influence on the formation of place identity, sense of place, civic pride and quality of life in HULs. 
  • 8.4K
  • 27 Oct 2020
Topic Review
Land Suitability Assessment
Land suitability assessment is a method of land evaluation, which identifies the major limiting factors for planting a particular crop. Land suitability assessment includes qualitative and quantitative evaluation. In the qualitative land suitability evaluations, information about climate, hydrology, topography, vegetation, and soil properties is considered and in quantitative assessment, the results are more detailed and yield is estimated. At present study we prepared land suitability assessment map for rain-fed wheat and barley crops based on FAO "land suitability assessment framework" using parametric method and machine learning algorithms in Kurdistan Province, located in west of Iran. This is a unique study that compared two machine learning-based and traditional-based approaches for mapping current and potential future land suitability classes. Moreover, potential yield of rain-fed wheat and barley crop were computed by FAO model.
  • 8.4K
  • 30 Oct 2020
Topic Review
The Satanic Bible
The Satanic Bible is a collection of essays, observations, and rituals published by Anton LaVey in 1969. It is the central religious text of LaVeyan Satanism, and is considered the foundation of its philosophy and dogma. It has been described as the most important document to influence contemporary Satanism. Though The Satanic Bible is not considered to be sacred scripture in the way that the Christian Bible is to Christianity, LaVeyan Satanists regard it as an authoritative text as it is a contemporary text that has attained for them scriptural status. It extols the virtues of exploring one's own nature and instincts. Believers have been described as "atheistic Satanists" because they believe that God is not an external entity, but rather something that each person creates as a projection of their own personality—a benevolent and stabilizing force in their life. There have been thirty printings of The Satanic Bible, selling over a million copies. The Satanic Bible is composed of four books: The Book of Satan, The Book of Lucifer, The Book of Belial, and The Book of Leviathan. The Book of Satan challenges the Ten Commandments and the Golden Rule, and promotes Epicureanism. The Book of Lucifer holds most of the philosophy in The Satanic Bible, with twelve chapters discussing topics such as indulgence, love, hate, and sex. LaVey also uses the book to dispel rumors surrounding the religion. In The Book of Belial, LaVey details rituals and magic. He discusses the required mindset and focus for performing a ritual, and provides instructions for three rituals: those for sex, compassion, or destruction. The Book of Leviathan provides four invocations for Satan, lust, compassion, and destruction. It also lists the nineteen Enochian Keys (adapted from John Dee's Enochian keys), provided both in Enochian and in English translation. There have been both positive and negative reactions to The Satanic Bible. It has been described as "razor-sharp" and "influential". Criticism of The Satanic Bible stems both from qualms over LaVey's writing and disapproval of the content itself. LaVey has been criticized for plagiarizing sections, and accusations have been made that his philosophies are largely borrowed. Attempts have been made to ban the book in schools, public libraries, and prisons, though these attempts are somewhat rare.
  • 8.4K
  • 29 Nov 2022
Topic Review
Head-Up Display (Video Gaming)
In video gaming, the HUD (heads-up display) or status bar is the method by which information is visually relayed to the player as part of a game's user interface. It takes its name from the head-up displays used in modern aircraft. The HUD is frequently used to simultaneously display several pieces of information including the main character's health, items, and an indication of game progression (such as score or level).
  • 8.4K
  • 31 Oct 2022
Topic Review
Biochemistry of Hydrogen Peroxide
Hydrogen Peroxide (H2O2) is the nonionized 2-electron reduction product of unstable molecular oxygen (O2), which plays a central role in maintaining the redox cycle of living cells.
  • 8.3K
  • 10 Jan 2022
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.
  • 8.3K
  • 28 Oct 2022
Topic Review
List of Temples in Tamil Nadu
This is a list of temples in the Indian state of Tamil Nadu which is famed for Hindu temples, culture and tradition and commonly known as the Land of Temples. Tamil Nadu has more temples than any other states of India. Tamil Nadu is home to more than 40,000 Hindu, Buddhist, Jain, local deities, Ayyavazhi temples and is aptly called "the land of temples" by media. Many are at least 800 to 5000 years old and are found scattered all over the state. The rulers of various dynasties constructed these temples over centuries. Vimanas (storeys) and Gopuram (towering gateways to the temple complex) best characterize the temples of Tamil Nadu. As per Tamil Nadu Hindu Endowments Board, there are 38,615 temples. Most of the largest Hindu temples reside here. Studded with complex architecture, variety of sculptures, and rich inscriptions, the temples remain the very essence of the culture and heritage of Tamil land, with historical records dating back to at least 3,000 years. In Madurai, Meenakshi Amman Temple has high ‘Gopuram’ towers ornamented with colourful figures. On Pamban Island, Ramanathaswamy Temple is a famous pilgrimage site. The town of Kanyakumari, at India's southernmost tip, is the site of ritual sunrises. The state also abounds with temple tanks. The state has 2,359 temple tanks located in 1,586 temples. The government has identified 1,068 tanks for renovation. People from all over the world visits Temples of Tamil Nadu and it is the major Tourist attraction in India.
  • 8.3K
  • 07 Nov 2022
Biography
Victor Hugo
Victor Marie Hugo French: [viktɔʁ maʁi yɡo] 26 February 1802 – 22 May 1885) was a French poet, novelist, and dramatist of the Romantic movement. Hugo is considered to be one of the greatest and best-known French writers. Outside of France, his most famous works are the novels Les Misérables, 1862, and The Hunchback of Notre-Dame (French: Notre-Dame de Paris), 1831. In France, Hugo is kno
  • 8.3K
  • 30 Nov 2022
Topic Review
Bonded Marine Hoses for Floating Offshore Structures (FOS)
By characterisation, a marine hose is a unique type of flexible riser used in fluid transfer. By definition, a marine hose is simply a fluid transfer conduit utilised in transferring, discharging, loading, and transporting fluids from an oil well to the platform of a floating platform or a floating structure. The fluid transfer system for bonded marine hoses is dependent on floating offshore structures (FOS). Single Point Mooring (SPM) systems are component aspects of the techno-economic design and FOS operation.
  • 8.3K
  • 28 Mar 2022
Topic Review Peer Reviewed
OAM of Light: Origins and Applications
Orbital Angular Momentum (OAM) of light is generating growing interest within the scientific community. This entry reviews the origins and applications of OAM. It is the counterpart of linear momentum for systems in rotation. The general expression of OAM is discussed, followed by its implications in terms of phase distribution and donut-shaped intensity profiles. Applications described include the generation of optical torque, telecommunications enhancement, and the rotational Doppler effect, emphasizing the role and consequences of angular momentum. In particular, its use to manipulate systems or to detect rotations is described. Finally, further developments and technological barriers are considered.
  • 8.3K
  • 17 Sep 2025
Topic Review
Laser Absorption Spectroscopy
Laser absorption spectroscopy (LAS) is an absorption spectroscopic method that employs a laser as the light source and measures the chemical concentration based on detection of a variation of laser beam intensity after transmission along the optical path. 
  • 8.3K
  • 10 Sep 2020
Topic Review
Various Attachments for Implant Overdentures
This study presents an overview of the biomechanical and biomolecular aspects of various attachments for implant overdenture. We focused on the following topics: attachment systems, retention of various attachments, stress distribution with different attachments, the design and fabrication of attachments, digital techniques in overdenture attachments, and the effects of attachments in peri-implant health. We found that plastic resin is commonly used for ball and bar attachments, whereas nylon resin is commonly used in locator attachments. The locator system offers a valuable attachment option for implant-retained overdenture. Attachment retention reduces while lateral force increases with implant inclination in overdenture. The higher the retention of an overdenture attachment, the higher the transferred stresses. Additionally, clip loading produces more stress in implants and precision elements than bar-retained dentures. As such, we conclude that the ball and locator systems the best overdenture systems due to their superior tissue response, survival rate, and patient satisfaction.
  • 8.3K
  • 03 Nov 2021
Topic Review
Two-Dimensional Space
Two-dimensional space (also known as 2D space, 2-space, or bi-dimensional space) is a geometric setting in which two values (called parameters) are required to determine the position of an element (i.e., point). The set [math]\displaystyle{ \mathbb{R}^2 }[/math] of pairs of real numbers with appropriate structure often serves as the canonical example of a two-dimensional Euclidean space. For a generalization of the concept, see dimension. Two-dimensional space can be seen as a projection of the physical universe onto a plane. Usually, it is thought of as a Euclidean space and the two dimensions are called length and width.
  • 8.3K
  • 28 Nov 2022
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