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HandWiki is the world's largest wiki-style encyclopedia dedicated to science, technology and computing. It allows you to create and edit articles as long as you have external citations and login account. In addition, this is a content management environment that can be used for collaborative editing of original scholarly content, such as books, manuals, monographs and tutorials.

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Biaxial Tensile Test
Biaxial tensile test is a tensile testing in which the sample is stretched in two distinct directions. This technique is used to obtain the mechanical characteristics of anisotropic materials, such as composite materials, textiles, and soft biological tissues. There are three main types of biaxial tensile testing: Bursting test, based on a circular specimen clamped along the edge and inflated by air or water under pressure until the specimen bursts; Cylinder test, based on a hollow cylinder subjected to internal pressure and axial pressure or tension; Plane biaxial test, which offers the best result because of the independent force introduction in the two main directions.
  • 2.1K
  • 28 Oct 2022
Topic Review
Ammonium Nitrate Disasters
When heated, ammonium nitrate decomposes non-explosively into gases including oxygen; however, it can be induced to decompose explosively by detonation. Large stockpiles of the material can be a major fire risk due to their supporting oxidation, and may also detonate, as happened in the Texas City disaster of 1947, which led to major changes in the regulations for storage and handling. There are two major classes of incidents resulting in explosions: In the first case, the explosion happens by the mechanism of shock to detonation transition. The initiation happens by an explosive charge going off in the mass, by the detonation of a shell thrown into the mass, or by detonation of an explosive mixture in contact with the mass. The examples are Kriewald, Morgan, Oppau, Tessenderlo, and Traskwood. In the second case, the explosion results from a fire that spreads into the ammonium nitrate (AN) itself (Texas City, Brest, Tianjin), or to a mixture of an ammonium nitrate with a combustible material during the fire. The fire must be confined at least to a degree for successful transition from a fire to an explosion (a phenomenon known as "deflagration to detonation transition", or DDT). Pure, compact AN is stable and very difficult to initiate. However, there are numerous cases when even impure AN did not explode in a fire. Ammonium nitrate decomposes in temperatures above 210 °C (410 °F). Pure AN is stable and will stop decomposing once the heat source is removed, but when catalysts are present, the reaction can become self-sustaining (known as self-sustaining decomposition, or SSD). This is a well-known hazard with some types of NPK fertilizers and is responsible for the loss of several cargo ships.
  • 2.1K
  • 28 Oct 2022
Topic Review
High-Dynamic-Range Imaging
In photography and videography, HDR or high-dynamic-range imaging is the set of techniques used to reproduce a greater range of luminosity than that which is possible with standard photographic techniques. Standard techniques allow differentiation only within a certain range of brightness. Outside this range, no features are visible because in the brighter areas everything appears pure white, and pure black in the darker areas. The ratio between the maximum and the minimum of the tonal value in an image is known as the dynamic range. HDR is useful for recording many real-world scenes containing very bright, direct sunlight to extreme shade, or very faint nebulae. High-dynamic-range (HDR) images are often created by capturing and then combining several different, narrower range, exposures of the same subject matter. The two primary types of HDR images are computer renderings and images resulting from merging multiple low-dynamic-range (LDR) or standard-dynamic-range (SDR) photographs. HDR images can also be acquired using special image sensors, such as an oversampled binary image sensor. Due to the limitations of printing and display contrast, the extended luminosity range of input HDR images has to be compressed to be made visible. The method of rendering an HDR image to a standard monitor or printing device is called tone mapping. This method reduces the overall contrast of an HDR image to facilitate display on devices or printouts with lower dynamic range, and can be applied to produce images with preserved local contrast (or exaggerated for artistic effect). "HDR" may refer to the overall process, to the HDR imaging process, or to HDR imaging represented on a low-dynamic-range display such as a screen or standard .jpg image.
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  • 28 Oct 2022
Topic Review
Uranium Sulfate
Uranium sulfate (U(SO4)2) is a water-soluble salt of uranium. It is a very toxic compound. Uranium sulfate minerals commonly are widespread around uranium bearing mine sites, where they usually form during the evaporation of acid sulfate-rich mine tailings which have been leached by oxygen-bearing waters. Uranium sulfate is a transitional compound in the production of Uranium hexafluoride. It was also used to fuel aqueous Homogeneous Reactors.
  • 1.3K
  • 28 Oct 2022
Topic Review
Early World Maps
The earliest known world maps date to classical antiquity, the oldest examples of the 6th to 5th centuries BCE still based on the flat Earth paradigm. World maps assuming a spherical Earth first appear in the Hellenistic period. The developments of Greek geography during this time, notably by Eratosthenes and Posidonius culminated in the Roman era, with Ptolemy's world map (2nd century CE), which would remain authoritative throughout the Middle Ages. Since Ptolemy, knowledge of the approximate size of the globe allowed cartographers to estimate the extent of their geographical knowledge, and to indicate parts of the globe known to exist but not yet explored as terra incognita. With the Age of Discovery, during the 15th to 18th centuries, world maps became increasingly accurate; exploration of Antarctica and the interior of Africa by western mapmakers was left to the 19th and early 20th century.
  • 37.1K
  • 28 Oct 2022
Topic Review
Causal Fermion System
The theory of causal fermion systems is an approach to describe fundamental physics. It provides a unification of the weak, the strong and the electromagnetic forces with gravity at the level of classical field theory. Moreover, it gives quantum mechanics as a limiting case and has revealed close connections to quantum field theory. Therefore, it is a candidate for a unified physical theory. Instead of introducing physical objects on a preexisting spacetime manifold, the general concept is to derive spacetime as well as all the objects therein as secondary objects from the structures of an underlying causal fermion system. This concept also makes it possible to generalize notions of differential geometry to the non-smooth setting. In particular, one can describe situations when spacetime no longer has a manifold structure on the microscopic scale (like a spacetime lattice or other discrete or continuous structures on the Planck scale). As a result, the theory of causal fermion systems is a proposal for quantum geometry and an approach to quantum gravity. Causal fermion systems were introduced by Felix Finster and collaborators.
  • 1.1K
  • 28 Oct 2022
Topic Review
Central African Lion
The Central African lion is a Panthera leo leo population in northern parts of Central and East Africa. This population has been fragmented into small and isolated groups since the 1950s. It is threatened by loss of habitat and prey base and trophy hunting. In 2005, a Lion Conservation Strategy was developed for West and Central Africa. Results of phylogeographic research indicate that the Central African lion clade forms a phylogenetic group with lion samples from West and North Africa, the Middle East and India . This group diverged from lions in southern parts of East and Southern Africa at least 50,000 years ago. Morphometric analysis of lion skulls corroborates the assessment of two major evolutionary lion clusters, one in Sub-Saharan Africa and the other in North Africa and Asia.
  • 4.3K
  • 31 Oct 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.
  • 60.4K
  • 28 Oct 2022
Topic Review
Dot-Com Bubble
The dot-com bubble (also known as the dot-com boom, the tech bubble, and the Internet bubble) was a historic economic bubble and period of excessive speculation that occurred roughly from 1995 to 2000, a period of extreme growth in the usage and adaptation of the Internet. The Nasdaq Composite stock market index, which included many Internet-based companies, peaked in value on March 10, 2000 before crashing. The burst of the bubble, known as the dot-com crash, lasted from March 11, 2000 to October 9, 2002. During the crash, many online shopping companies, such as Pets.com, Webvan, and Boo.com, as well as communication companies, such as Worldcom, NorthPoint Communications and Global Crossing failed and shut down. Others, such as Cisco, whose stock declined by 86%, and Qualcomm, lost a large portion of their market capitalization but survived, and some companies, such as eBay and Amazon.com, declined in value but recovered quickly.
  • 20.5K
  • 01 Nov 2022
Topic Review
Neurooncology
Neuro-oncology is the study of brain and spinal cord neoplasms, many of which are (at least eventually) very dangerous and life-threatening (astrocytoma, glioma, glioblastoma multiforme, ependymoma, pontine glioma, and brain stem tumors are among the many examples of these). Among the malignant brain cancers, gliomas of the brainstem and pons, glioblastoma multiforme, and high-grade (highly anaplastic) astrocytoma are among the worst. In these cases, untreated survival usually amounts to only a few months, and survival with current radiation and chemotherapy treatments may extend that time from around a year to a year and a half, possibly two or more, depending on the patient's condition, immune function, treatments used, and the specific type of malignant brain neoplasm. Surgery may in some cases be curative, but, as a general rule, malignant brain cancers tend to regenerate and emerge from remission easily, especially highly malignant cases. In such cases, the goal is to excise as much of the mass (tumor cells) and as much of the tumor margin as possible without endangering vital functions or other important cognitive abilities.
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