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Strain Rate Tensor
In continuum mechanics, the strain rate tensor is a physical quantity that describes the rate of change of the deformation of a material in the neighborhood of a certain point, at a certain moment of time. It can be defined as the derivative of the strain tensor with respect to time, or as the symmetric component of the gradient (derivative with respect to position) of the flow velocity. The strain rate tensor is a purely kinematic concept that describes the macroscopic motion of the material. Therefore, it does not depend on the nature of the material, or on the forces and stresses that may be acting on it; and it applies to any continuous medium, whether solid, liquid or gas. On the other hand, for any fluid except superfluids, any gradual change in its deformation (i.e. a non-zero strain rate tensor) gives rise to viscous forces in its interior, due to friction between adjacent fluid elements, that tend to oppose that change. At any point in the fluid, these stresses can be described by a viscous stress tensor that is, almost always, completely determined by the strain rate tensor and by certain intrinsic properties of the fluid at that point. Viscous stress also occur in solids, in addition to the elastic stress observed in static deformation; when it is too large to be ignored, the material is said to be viscoelastic.
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  • 02 Dec 2022
Topic Review
Power-Flow Study
In power engineering, the power-flow study, or load-flow study, is a numerical analysis of the flow of electric power in an interconnected system. A power-flow study usually uses simplified notations such as a one-line diagram and per-unit system, and focuses on various aspects of AC power parameters, such as voltages, voltage angles, real power and reactive power. It analyzes the power systems in normal steady-state operation. Power-flow or load-flow studies are important for planning future expansion of power systems as well as in determining the best operation of existing systems. The principal information obtained from the power-flow study is the magnitude and phase angle of the voltage at each bus, and the real and reactive power flowing in each line. Commercial power systems are usually too complex to allow for hand solution of the power flow. Special purpose network analyzers were built between 1929 and the early 1960s to provide laboratory-scale physical models of power systems. Large-scale digital computers replaced the analog methods with numerical solutions. In addition to a power-flow study, computer programs perform related calculations such as short-circuit fault analysis, stability studies (transient and steady-state), unit commitment and economic dispatch. In particular, some programs use linear programming to find the optimal power flow, the conditions which give the lowest cost per kilowatt hour delivered. A load flow study is especially valuable for a system with multiple load centers, such as a refinery complex. The power flow study is an analysis of the system’s capability to adequately supply the connected load. The total system losses, as well as individual line losses, also are tabulated. Transformer tap positions are selected to ensure the correct voltage at critical locations such as motor control centers. Performing a load flow study on an existing system provides insight and recommendations as to the system operation and optimization of control settings to obtain maximum capacity while minimizing the operating costs. The results of such an analysis are in terms of active power, reactive power, magnitude and phase angle. Furthermore, power-flow computations are crucial for optimal operations of groups of generating units. The Open Energy Modelling Initiative promotes open source load-flow models and other types of energy system models.
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  • 06 Dec 2022
Topic Review
Oblivious Ram
An Oblivious RAM (ORAM) simulator is a compiler that transforms algorithms in such a way that the resulting algorithms preserve the input-output behavior of the original algorithm but the distribution of memory access pattern of the transformed algorithm is independent of the memory access pattern of the original algorithm. The definition of ORAMs is motivated by the fact that an adversary can obtain nontrivial information about the execution of a program and the nature of the data that it is dealing with, just by observing the pattern in which various locations of memory are accessed during its execution. An adversary can get this information even if the data values are all encrypted. The definition suits equally well to the settings of protected programs running on unprotected shared memory as well as a client running a program on its system by accessing previously stored data on a remote server. The concept was formulated by Oded Goldreich in 1987.
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  • 02 Dec 2022
Topic Review
Overland Train
In the 1950s, LeTourneau Inc. developed several overland trains, essentially oversized semi-trailer trucks that could travel over almost any terrain. Their intention was to be able to handle logistics needs without being dependent on local road or rail systems, allowing them to operate in back-country areas. The US Army had three experimental units built, the largest reaching almost 600 feet (183 m) long, which holds the record for the longest off-road vehicle. Road trains are in use in certain roles today, but the US Army examples and a few derivatives appear to be the only off-road examples built.
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  • 02 Dec 2022
Biography
Thomas Henry Flewett
Thomas Henry Flewett, MD, FRCPath, FRCP (29 June 1922 – 12 December 2006) was a founder member (and subsequently Fellow) of the Royal College of Pathologists and was elected (by distinction) a Fellow of the Royal College of Physicians of London in 1978. He was chairman of the World Health Organisation (WHO) Steering Committee on Viral Diarrhoeal Diseases, 1990–3, and a member until 1996. His
  • 1.3K
  • 02 Dec 2022
Topic Review
Digital Journalism
Digital journalism also known as online journalism is a contemporary form of journalism where editorial content is distributed via the Internet as opposed to publishing via print or broadcast. What constitutes 'digital journalism' is debated by scholars. However the primary product of journalism, which is news and features on current affairs, is presented solely or in combination as text, audio, video, or some interactive forms like newsgames, and disseminated through digital media technology. Fewer barriers to entry, lowered distribution costs, and diverse computer networking technologies have led to the widespread practice of digital journalism. It has democratized the flow of information that was previously controlled by traditional media including newspapers, magazines, radio, and television. Some have asserted that a greater degree of creativity can be exercised with digital journalism when compared to traditional journalism and traditional media. The digital aspect may be central to the journalistic message and remains, to some extent, within the creative control of the writer, editor, and/or publisher.
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  • 02 Dec 2022
Topic Review
USS Aloha (SP-317)
USS Aloha (SP-317) was a United States Navy patrol vessel in commission from 1917 to 1919.
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  • 02 Dec 2022
Topic Review
Carbon Fixation
Carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide) is converted to organic compounds by living organisms. The compounds are then used to store energy and as structure for other biomolecules. Carbon is primarily fixed through photosynthesis, but some organisms use a process called chemosynthesis in the absence of sunlight. Organisms that grow by fixing carbon are called autotrophs, which include photoautotrophs (which use sunlight), and lithoautotrophs (which use inorganic oxidation). Heterotrophs are not themselves capable of carbon fixation but are able to grow by consuming the carbon fixed by autotrophs or other heterotrophs. "Fixed carbon", "reduced carbon", and "organic carbon" may all be used interchangeably to refer to various organic compounds.
  • 2.5K
  • 06 Dec 2022
Biography
Pandurang Shastri Athavale
Pandurang Shastri Athavale (19 October 1920 – 25 October 2003), also known as Dadaji, which literally translates as "elder brother" in Marathi, was an Indian activist, philosopher, spiritual leader, social revolutionary,[1] and religion reformist, who founded the Swadhyaya Parivar (Swadhyaya Family) in 1954.[2] Swadhyaya is a self-study process based on the Bhagavad Gita which has spread acros
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  • 02 Dec 2022
Topic Review
Depersonalization
Depersonalization can consist of a detachment within the self, regarding one's mind or body, or being a detached observer of oneself. Subjects feel they have changed and that the world has become vague, dreamlike, less real, lacking in significance or being outside reality while looking in. Chronic depersonalization refers to depersonalization/derealization disorder, which is classified by the DSM-5 as a dissociative disorder, based on the findings that depersonalization and derealization are prevalent in other dissociative disorders including dissociative identity disorder. Though degrees of depersonalization and derealization can happen to anyone who is subject to temporary anxiety or stress, chronic depersonalization is more related to individuals who have experienced a severe trauma or prolonged stress/anxiety. Depersonalization-derealization is the single most important symptom in the spectrum of dissociative disorders, including dissociative identity disorder and "dissociative disorder not otherwise specified" (DD-NOS). It is also a prominent symptom in some other non-dissociative disorders, such as anxiety disorders, clinical depression, bipolar disorder, schizophrenia, schizoid personality disorder, hypothyroidism or endocrine disorders, schizotypal personality disorder, borderline personality disorder, obsessive–compulsive disorder, migraines, and sleep deprivation; it can also be a symptom of some types of neurological seizure. In social psychology, and in particular self-categorization theory, the term depersonalization has a different meaning and refers to "the stereotypical perception of the self as an example of some defining social category".
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  • 02 Dec 2022
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