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Topic Review
Green Monopropellants
Green propellants are usually defined as low-hazard, low-toxicity, environmentally friendly propellants that are considered safe during various phases of spacecraft development, launch, and operations. Such propellants provide safe handling and storability when compared to conventional toxic propellants such as hydrazine and its derivatives that require special handling protocols and adhering to strict safety measurements that, in addition to others, include using Self-Contained Atmospheric Protective Ensemble (SCAPE) suits. Due to their favorable characteristics, green propellants demonstrate higher commercial value by being able to cut costs related to transportation, storage, handling, and further reduces ground operations time. Recently, a more specified definition has been noted by Mayer et al. (2018) [3], based on the Acute Toxicity Classification (ATC) by the Global Harmonized System of classification and labeling of chemicals (GHS) [6], which denotes that propellants possessing ATC levels of three and safer are considered as green propellants. ATC levels are typically categorized on a 1:5 scale where level one denotes the most toxic class and level five is considered the least toxic class. Moreover, a controversial topic arises when referring to some modern green propellants, whether to address them by the term “monopropellants” or by more specific terms including (premixed propellants, fuel blends, or mixtures). Monopropellants are fundamentally defined as propellants consisting of chemical compounds (for example N2H4), which release energy through exothermic chemical decomposition. Since the evolution of liquid gun propellants based on HAN compound and other nitrate salts aqueous solutions, the term “monopropellants” was used to describe such premixed formulations. As widely used in literature and industry, some modern green propellants, for instance the Energetic Ionic Liquids (EILs), are undoubtedly classified and described as “monopropellants.” Basically, it can be interpreted from the previous that a "green monopropellant" may be defined as: "A low-hazard, low-toxicity, and safe-to handle propellant that is stored in a single tank and is able to decompose from its storage state by the help of a catalyst or other ignition method, such as thermal or electric ignition, can be considered a “green monopropellant” as long as it does not require another separately stored propellant for decomposition."
  • 8.4K
  • 28 Sep 2021
Topic Review
Addiction and Spending in Gacha Games
Gacha games are the most dominant games on the mobile market. These are free-to-play games with a lottery-like system, where the user pays with in-game currency to enter a draw in order to obtain the character or item they want. If a player does not obtain what he hoped for, there is the option of paying with his own money for more draws, and this is the main way to monetize the Gacha game.
  • 8.4K
  • 21 Jul 2023
Topic Review
Social Complexity
Social complexity refers to the intricate and interconnected nature of social systems, where various elements such as institutions, individuals, and cultural dynamics interact in non-linear and unpredictable ways. It involves the recognition that social phenomena often exhibit emergent properties that cannot be fully understood by analyzing individual components in isolation, emphasizing the need for interdisciplinary approaches to grasp the complexity of social structures and behaviors.
  • 8.4K
  • 26 Jan 2024
Topic Review
Grinder (Biohacking)
Grinders are people who apply the hacker ethic to improve their own bodies with do it yourself cybernetic devices or introducing Biochemicals into the body to enhance or change their bodies' functionality. Many grinders identify with the biopunk movement, open-source transhumanism, and techno-progressivism. The Grinder movement is strongly associated with the body modification movement and practices actual implantation of cybernetic devices in organic bodies as a method of working towards transhumanism, such as designing and installing do-it-yourself body-enhancements such as magnetic implants. Biohacking emerged in a growing trend of non-institutional science and technology development. According to Biohack.me, "Grinders are passionate individuals who believe the tools and knowledge of science belong to everyone. Grinders practice functional extreme body modification in an effort to improve the human condition. [Grinders] hack [them]selves with electronic hardware to extend and improve human capacities. Grinders believe in action, [thei]r bodies the experiment." "Biohacking" can also refer to managing one's own biology using a combination of medical, nutritional and electronic techniques. This may include the use of nootropics, non-toxic substances, and/or cybernetic devices for recording biometric data (as in the Quantified Self movement).
  • 8.4K
  • 21 Nov 2022
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
Red Supergiant Star
Red supergiants (RSGs) are stars with a supergiant luminosity class (Yerkes class I) of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Antares are the brightest and best known red supergiants (RSGs), indeed the only first magnitude red supergiant stars.
  • 8.4K
  • 18 Nov 2022
Topic Review
Seaport
Seaports are well known as the medium that has evolved into the central link between sea and land for complex marine activities. The growth in maritime logistics particularly necessitates a large volume of energy supply in order to maintain the operation of sea trade, resulting in an imbalance between generation and demand sides. Future projections for three major concerns show an increase in load demand, cost of operation, and environmental issues. The involvement of a variety of heavy loads such as all-electric ships, cranes, cold ironing, and buildings infrastructure renders it a complicated arrangement task in several aspects, which necessitates further research and leaves space for improvement.
  • 8.4K
  • 06 Dec 2021
Topic Review
Theories of International Trade
Economists have developed theories explaining World Trade, which are called” theories of international trade”. Theories of international trade explain what exactly happens in international trade, such as mercantilist theory. This theory was popular in the sixteenth and eighteenth centuries. During that time, a nation’s wealth consisted only of gold or other types of precious metals, so theorists suggested that nations begin to accumulate more and more gold and other types of metals. 
  • 8.4K
  • 08 Jul 2022
Topic Review
Derringer
A derringer is a small handgun that is neither a revolver nor a semi/fully automatic pistol. It is not to be confused with mini-revolvers or pocket pistols, although some later derringers were manufactured with the pepperbox configuration. The modern derringer is often multi-barreled, and is generally the smallest usable handgun of any given caliber and barrel length due to the lack of a moving action, which takes up more space behind the barrel. It is frequently used by women because it is easily concealable in a purse or a stocking. The original Philadelphia Deringer was a muzzleloading caplock single-shot pistol introduced in 1825 by Henry Deringer. In total, approximately 15,000 Deringer pistols were manufactured. All were single barrel pistols with back-action percussion locks, typically .41 caliber with rifled bores, and walnut stocks. Barrel length varied from 1.5 to 6 in (38 to 152 mm), and the hardware was commonly a copper-nickel alloy known as "German silver". The term "derringer" (/ˈdɛrɪndʒər/) became a genericized misspelling during the reporting of the Lincoln assassination, which was committed with a concealed Philadelphia Deringer. Many copies of the original Philadelphia Deringer pistol were made by other gunmakers worldwide, and the name remained often misspelled; this misspelling soon became an alternative generic term for any pocket pistol, along with the generic phrase "palm pistol'", which Deringer's competitors invented and used in their advertising. With the advent of metallic cartridges, pistols produced in the modern form are still commonly called "derringers".
  • 8.4K
  • 01 Nov 2022
Topic Review
Pollen Germination in Gymnosperms
Gymnosperms are amazing representatives of the flora. On the one hand, they are ancient plants with primitive characteristics of anatomical structure; on the other hand, they are perfectly adapted to their habitat and are the dominant species in many ecosystems due to their impressive size and longevity, with their reproductive system being of particular interest. It has progressive features, because in this group the reduced male gametophyte—pollen grain—first appeared, as well as the ability to form seeds. In addition, this group still represents a wide variety of reproductive patterns, strategies, and relationships. For example, the degree of gametophyte reduction varies, there are both zooidogamy and siphonogamy, and the reproductive process can both be relatively fast and last over several years.
  • 8.4K
  • 20 Jul 2021
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
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
The Sims 3 Stuff Packs
Stuff packs are minor expansion packs for The Sims 3 that add new items, clothing, and furniture to the game without implementing any significant changes to gameplay.
  • 8.4K
  • 11 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
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
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
Terminology of the British Isles
The terminology of the British Isles refers to the various words and phrases that are used to describe the different (and sometimes overlapping) geographical and political areas of the islands of Great Britain, Ireland, and the smaller islands which surround them. The terminology is often a source of confusion, partly owing to the similarity between some of the actual words used, but also because they are often used loosely. In addition, many of the words carry both geographical and political connotations which are affected by the history of the islands. The purpose of this article is to explain the meanings of and relationships among the terms in use; however many of these classifications are contentious and are the subject of disagreement (See the British Isles naming dispute).
  • 8.3K
  • 03 Nov 2022
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.
  • 8.3K
  • 30 Oct 2020
Topic Review
BMW 5 Series Gran Turismo
The BMW 5 Series Gran Turismo (also referred to as "5 Series GT") models are the 5-door fastback versions of the F10 5 Series model range and use the model code F07. The F07 uses the F10 platform and shares many components with the other 5 Series models. It was released in 2009. Engine choices were turbocharged straight-6 petrol, straight-6 diesel and V8 petrol. At launch, all models were rear-wheel drive ("sDrive"), with all-wheel drive ("xDrive") models being added in 2010. For the following G30 generation, the Gran Turismo models were moved to the 6 Series model range and renamed the G32 6 Series Gran Turismo.
  • 8.3K
  • 29 Sep 2022
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