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Topic Review
Updated Principles of Sustainable Engineering
Sustainable engineering refers to the integration of social, environmental, and economic considerations into product, process, and energy system design methods. Additionally, sustainable engineering encourages the consideration of the complete product and process lifecycle during the design effort. 
  • 12.8K
  • 24 Jun 2022
Topic Review
M2 Browning
The M2 Machine Gun or Browning .50 Caliber Machine Gun is a heavy machine gun designed toward the end of World War I by John Browning. Its design is similar to Browning's earlier M1919 Browning machine gun, which was chambered for the .30-06 cartridge. The M2 uses the much larger and much more powerful .50 BMG cartridge, which was developed alongside and takes its name from the gun itself (BMG standing for Browning Machine Gun). It has been referred to as "Ma Deuce", in reference to its M2 nomenclature. The design has had many specific designations; the official designation for the current infantry type is Browning Machine Gun, Cal. .50, M2, HB, Flexible. It is effective against infantry, unarmored or lightly armored vehicles and boats, light fortifications and low-flying aircraft. The Browning .50 caliber machine gun has been used extensively as a vehicle weapon and for aircraft armament by the United States from the 1930s to the present. It was heavily used during World War II, the Korean War, the Vietnam War, the Falklands War, the Soviet–Afghan War, the Gulf War, the Iraq War and the War in Afghanistan in the 2000s and 2010s. It is the primary heavy machine gun of NATO countries, and has been used by many other countries as well. The M2 has been in use longer than any other firearm in U.S. inventory except the .45 ACP M1911 pistol, also designed by John Browning. The current M2HB is manufactured in the U.S. by General Dynamics and U.S. Ordnance for use by the U.S. government, and for allies via Foreign Military Sales, as well as foreign manufacturers such as FN Herstal.
  • 12.8K
  • 05 Dec 2022
Topic Review
HandWiki
HandWiki is an internet Wiki-style encyclopedia for professional researchers in various branches of science and computer science. As other Wiki type encyclopedias, HandWiki is designed for collaborative editing of articles. Unlike the traditional Wikipedia that uses the categories concept for all articles located in the main namespace, HandWiki uses dedicated namespaces for each topic. This allows creation of "Books" or "Manual" by grouping articles under the same namespace. According to the Handwiki designers, this can simplify organization of articles according to particular topic. HandWiki has the following topics included in the dedicated namespaces: Mathematics, Computers, Analysis, Physics, Astronomy, Biology, Chemistry, Unsolved. In addition to the categories preserved from Wikipedia, HandWiki has its own categories for original articles posted to HandWiki. One notable feature of HandWiki is that it allows to collaborate in real-time on many types of documents (lectures, books, technical documents, etc.) with multiple authors. The text can be protected from viewing, and can only be available for groups of people working on the same project. HandWiki can be used to convert such articles to LaTeX and to use BibTeX for referencing. These two features are a significant advantage for preparing research articles for publication. The HandWiki is designed using the MediaWiki software with additional extensions for inclusion of references to programming codes and BibTeX citations. Handwiki allows adding advertisements to the end of the articles. The advertising icons can be grouped according to the HandWiki topics.
  • 12.8K
  • 24 Apr 2026
Topic Review
Well-Defined
In mathematics, an expression is called well-defined or unambiguous if its definition assigns it a unique interpretation or value. Otherwise, the expression is said to be not well-defined, ill-defined or ambiguous. A function is well-defined if it gives the same result when the representation of the input is changed without changing the value of the input. For instance, if f takes real numbers as input, and if f(0.5) does not equal f(1/2) then f is not well-defined (and thus not a function). The term well-defined can also be used to indicate that a logical expression is unambiguous or uncontradictory. A function that is not well-defined is not the same as a function that is undefined. For example, if f(x) = 1/x, then the fact that f(0) is undefined does not mean that the f is not well-defined — but that 0 is simply not in the domain of f.
  • 12.8K
  • 01 Dec 2022
Topic Review
Great Soviet Encyclopedia
The Great Soviet Encyclopedia (GSE; Russian: Большая советская энциклопедия, БСЭ, Bolshaya sovetskaya entsiklopediya) is one of the largest Russian-language encyclopedias, published by the Soviet state from 1926 to 1990, and again since 2002 by Russia (under the name Bolshaya Rossiyskaya entsiklopediya or Great Russian Encyclopedia). The GSE claimed to be "the first Marxist-Leninist general-purpose encyclopedia".
  • 12.8K
  • 31 Oct 2022
Topic Review
Responses to Sneezing
In English-speaking countries, the common verbal response to another person's sneeze is "bless you", or, less commonly in the United States and Canada , "Gesundheit", the German word for health (and the response to sneezing in German-speaking countries). There are several proposed bless-you origins for use in the context of sneezing. In non-English-speaking cultures, words referencing good health or a long life are often used instead of "bless you," though some also use references to God. In some Asian cultures such as Korean and Japanese cultures, the practice of responding to another person's sneeze does not exist. In the Assyrian language, “Shemad Alaha”, “in God’s name”, is the response to a sneeze.
  • 12.8K
  • 01 Dec 2022
Topic Review
Philistinism
In the fields of philosophy and æsthetics, the derogatory term philistinism describes “the manners, habits, and character, or mode of thinking of a philistine”, manifested as an anti-intellectual social attitude that undervalues and despises art and beauty, intellect and spirituality. A philistine person is a man or woman of smugly narrow mind and of conventional morality whose materialistic views and tastes indicate a lack of and an indifference to cultural and æsthetic values. Since the 19th century, the contemporary denotation of philistinism, as the behaviour of "ignorant, ill-behaved persons lacking in culture or artistic appreciation, and only concerned with materialistic values" derives from Matthew Arnold's adaptation to English of the German word Philister, as applied by university students in their antagonistic relations with the townspeople of Jena, Germany, where, in 1689, a row resulted in several deaths. In the aftermath, the university cleric addressed the town-vs-gown matter with an admonishing sermon "The Philistines Be Upon Thee", drawn from the Book of Judges (Chapt. 16, 'Samson vs the Philistines'), of the Tanakh and of the Christian Old Testament. In Word Research and Word History, the philologist Friedrich Kluge said that the word philistine originally had a positive meaning that identified a tall and strong man, such as Goliath; later the meaning changed to identify the "guards of the city".
  • 12.8K
  • 22 Nov 2022
Topic Review
Microalgae Cell Disruption Methods
Microalgae are unicellular or simple multicellular photosynthetic microorganisms, which can normally be found in aquatic environments such as freshwater, seawater, or hypersaline lakes. These organisms can be eukaryotic or prokaryotic, the latter being the cyanobacteria, which are commonly referred to as microalgae.  The nature of the cell wall of a given microalgae species can vary, making it easier or harder to access its valuable contents. The rigidity of the cell wall can be provided, for example, by high levels of polysaccharides in the cell wall structure, such as glucose and mannose, present in Chlorella zofingiensis, or by complex sugars composition such as arabinose, galactose, rhamnose, mannose and xylose, as found in Tetraselmis suecia and T. striata. Algaenan or sporopollein is another extremely resistant biopolymer, a non-hydrolyzable biopolymer, composed of long ω-hydroxy fatty acids chains linked by several types of chemical bond, which confer its rigid properties, and that can be found in some species such as Chlorella spp., Nannochloropsis galditana and Scenedesmus spp. Arthorspira spp. cell wals contain peptidoglycan, being less rigid and, consequently, more susceptible to degradation. Thus, several methods can be applied to breakdown such molecules that, being part of the cell wall, present different level of rigidity and confer them protection against environment factors. The cell wall disruption methods include physical, chemical, enzymatic approaches. In this entry, it will be presented a brief description of these methods.
  • 12.7K
  • 29 Jan 2021
Topic Review
Space Shuttle Main Engine
The Aerojet Rocketdyne RS-25, otherwise known as the Space Shuttle main engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA's Space Shuttle and is planned to be used on its successor, the Space Launch System. Designed and manufactured in the United States by Rocketdyne (later known as Pratt & Whitney Rocketdyne and Aerojet Rocketdyne), the RS-25 burns cryogenic liquid hydrogen and liquid oxygen propellants, with each engine producing 1,859 kN (418,000 lbf) of thrust at liftoff. Although the RS-25 can trace its heritage back to the 1960s, concerted development of the engine began in the 1970s, with the first flight, STS-1, occurring on April 12, 1981. The RS-25 has undergone several upgrades over its operational history to improve the engine's reliability, safety, and maintenance load. Subsequently, the RS-25D is the most efficient liquid fuel rocket engine currently in use. The engine produces a specific impulse (Isp) of 452 seconds (4.43 km/s) in a vacuum, or 366 seconds (3.59 km/s) at sea level, has a mass of approximately 3.5 tonnes (7,700 pounds), and is capable of throttling between 67% and 109% of its rated power level in one-percent increments. The RS-25 operates at temperatures ranging from −253 °C (−423 °F) to 3300 °C (6000 °F). The Space Shuttle used a cluster of three RS-25 engines mounted in the stern structure of the orbiter, with fuel being drawn from the external tank. The engines were used for propulsion during the entirety of the spacecraft's ascent, with additional thrust being provided by two solid rocket boosters and the orbiter's two AJ-10 orbital maneuvering system engines. Following each flight, the RS-25 engines were removed from the orbiter, inspected, and refurbished before being reused on another mission.
  • 12.7K
  • 24 Oct 2022
Topic Review
Unmanned Systems
An Unmanned System (US) or Vehicle (UV) can be defined as an “electro-mechanical system, with no human operator aboard, that is able to exert its power to perform designed missions”
  • 12.7K
  • 17 Mar 2021
Topic Review
VANETs
A Vehicular Ad-hoc Network (VANET) comprises a group of moving or stationary vehicles connected by a wireless network. VANETs play a vital role in providing safety and comfort to drivers in vehicular environments. They provide smart traffic control and real-time information, event allocation.           
  • 12.7K
  • 16 Apr 2021
Topic Review
Pole Shift Hypothesis
The cataclysmic pole shift fringe theory suggests that there have been geologically rapid shifts in the relative positions of the modern-day geographic locations of the poles and the axis of rotation of the Earth, creating calamities such as floods and tectonic events. There is evidence of precession and changes in axial tilt, but this change is on much longer time-scales and does not involve relative motion of the spin axis with respect to the planet. However, in what is known as true polar wander, the solid Earth can rotate with respect to a fixed spin axis. Research shows that during the last 200 million years a total true polar wander of some 30° has occurred, but that no super-rapid shifts in the Earth's pole were found during this period. A characteristic rate of true polar wander is 1° or less per million years. Between approximately 790 and 810 million years ago, when the supercontinent Rodinia existed, two geologically rapid phases of true polar wander may have occurred. In each of these, the magnetic poles of the Earth shifted by approximately 55°.
  • 12.7K
  • 10 Oct 2022
Topic Review
Benazir Income Support Programme
The Benazir Income Support Programme (BISP) also Known as Ehsaas Programme Pakistan is a federal unconditional cash transfer poverty reduction program in Pakistan . Launched in July 2008, it is the largest single social safety net program in the country with nearly Rs. 90 billion ($900 million) distributed to 5.4 million beneficiaries in 2016. The Department for International Development of the United Kingdom is the largest foreign backer of the program, providing $244 million (or 27%) of the total funds in 2016 with the Pakistani Government providing the rest. As of 2016, the program distributes Rs.19,338 (or approx. $195) per annum distributed per month. The stipend is linked to the Consumer Price Index and is paid through a smart card. For now, Dr Sania Nishtar is Chairman of BISP in regime of PTI governance.
  • 12.7K
  • 21 Oct 2022
Topic Review
Force Field
In the context of chemistry and molecular modelling, a force field is a computational method that is used to estimate the forces between atoms within molecules and also between molecules. More precisely, the force field refers to the functional form and parameter sets used to calculate the potential energy of a system of atoms or coarse-grained particles in molecular mechanics, molecular dynamics, or Monte Carlo simulations. The parameters for a chosen energy function may be derived from experiments in physics and chemistry, calculations in quantum mechanics, or both. Force fields are interatomic potentials and utilize the same concept as force fields in classical physics, with the difference that the force field parameters in chemistry describe the energy landscape, from which the acting forces on every particle are derived as a gradient of the potential energy with respect to the particle coordinates. All-atom force fields provide parameters for every type of atom in a system, including hydrogen, while united-atom interatomic potentials treat the hydrogen and carbon atoms in methyl groups and methylene bridges as one interaction center. Coarse-grained potentials, which are often used in long-time simulations of macromolecules such as proteins, nucleic acids, and multi-component complexes, sacrifice chemical details for higher computing efficiency.
  • 12.7K
  • 10 Nov 2022
Topic Review
Alvin Plantinga's Free Will Defense
Alvin Plantinga's free will defense is a logical argument developed by American analytic philosopher Alvin Plantinga, the John A. O'Brien Professor of Philosophy Emeritus at the University of Notre Dame, and published in its final version in his 1977 book God, Freedom, and Evil. Plantinga's argument is a defense against the logical problem of evil as formulated by philosopher J. L. Mackie beginning in 1955. Mackie's formulation of the logical problem of evil argued that three attributes of God, omniscience, omnipotence, and omnibenevolence, in orthodox Christian theism are logically incompatible with the existence of evil. In 1982, Mackie conceded that Plantinga's defense successfully refuted his argument in The Miracle of Theism, though he did not claim that the problem of evil had been put to rest.
  • 12.7K
  • 18 Nov 2022
Topic Review
Biological Effects and Mechanisms of Electromagnetic Radiation
Modern humanity wades daily through various radiations, resulting in frequent exposure and causing potentially important biological effects. Among them, the brain is the organ most sensitive to electromagnetic radiation (EMR) exposure.
  • 12.7K
  • 31 Aug 2022
Topic Review
NASDAQ Composite
The NASDAQ Composite (ticker symbol ^IXIC) is a stock market index of the common stocks and similar securities (e.g. ADRs, tracking stocks, limited partnership interests) listed on the Nasdaq stock market. Along with the Dow Jones Industrial Average and S&P 500 it is one of the three most-followed indices in US stock markets. The composition of the NASDAQ Composite is heavily weighted towards information technology companies. The NASDAQ-100, whose components are a subset of the NASDAQ Composite's, accounts for over 90% of the NASDAQ Composite's movement, and there are many ETFs tracking its performance. The composite itself is calculated by taking the sum of the products of closing price and index share(capitalization-weighted) of all of the over 2500 securities in the index. The sum is then divided by a divisor which just serves to reduce the order of magnitude of the result.
  • 12.6K
  • 01 Dec 2022
Topic Review
Alternating Current Loss of Superconductors
Alternating current (AC) loss is generated due to the movement of magnetic vortices within the superconductor when experiencing time-varying currents or magnetic fields (or both). AC loss can be categorized into transport current loss and magnetization loss based on the AC source. Particularly, when a superconductor carries a direct current (DC) and is simultaneously exposed to an AC field, dynamic resistance occurs and leads to dynamic loss. Quantification and minimization of AC loss are crucial because the produced heat can not only present severe challenges to the cryogenic systems but also impair the reliability of superconducting devices, leaving a safety hazard. To quantify the AC loss of superconductors, analytical formulae, numerical models, and experimental measurements have been widely adopted. Concerning AC loss minimization techniques, the modification of superconductor structures (filamentation and twisting), flux diverters, as well as winding techniques have been widely exploited. This entry serves to clarify the characteristics and quantification methods of AC loss as well as its minimization techniques in superconductors. It is believed to help deepen the understanding of AC loss and deliver a helpful guideline for future research efforts.
  • 12.6K
  • 14 Sep 2021
Topic Review
Benzodiazepines
The Benzodiazepines (BDZs) are a group of components that receive their name because in their chemical structure have a benzene ring joined to other seven-members heterocyclic ring called Diazepine.
  • 12.6K
  • 13 Apr 2021
Topic Review
Henderson–Hasselbalch Equation
In chemistry, the Henderson–Hasselbalch equation describes the derivation of pH as a measure of acidity (using pKa, the negative log of the acid dissociation constant) in biological and chemical systems. The equation is also useful for estimating the pH of a buffer solution and finding the equilibrium pH in acid-base reactions (it is widely used to calculate the isoelectric point of proteins). The equation is given by: Here, [HA] is the molar concentration of the undissociated weak acid, [A⁻] is the molar concentration (molarity, M) of this acid's conjugate base and pKa is −log10 Ka where Ka is the acid dissociation constant, that is: In these equations, A⁻ denotes the ionic form of the relevant acid. Bracketed quantities such as [base] and [acid] denote the molar concentration of the quantity enclosed.
  • 12.6K
  • 14 Oct 2022
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