|
Core Concern
Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (manufacturing), used in casting and molding * Core (optical fiber), the signal-carrying portion of an optical fiber * Core, the central part of a fruit * Hydrophobic core, the interior zone of a protein * Nuclear reactor core, a portion containing the fuel components * Pit (nuclear weapon) or core, the fissile material in a nuclear weapon * Semiconductor intellectual property core (IP core), is a unit of design in ASIC/FPGA electronics and IC manufacturing * Atomic core, an atom with no valence electrons Geology and astrophysics * Core sample, in Earth science, a sample obtained by coring ** Ice core * Core, the central part of a galaxy; see Mass deficit * Core (anticline), the central part of an anticline or syncline * Planetary core, the center of a planet ** Earth's inner core ** Earth's outer core * Stellar core, the region of a star where nuclear fusion takes place ** ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Core (anatomy)
The core or trunk is the axial (central) part of an organism's body. In common parlance, the term is broadly considered to be synonymous with the torso, but academically it also includes the head and neck. Functional movements are highly dependent on this part of the body, and lack of core muscular development can result in a predisposition to injury. The major muscles of the core reside in the area of the belly and the mid and lower back (not the shoulders), and peripherally include the hips, the shoulders and the neck. Muscles Major muscles included are the pelvic floor muscles, transversus abdominis, multifidus, internal and external obliques, rectus abdominis, erector spinae (sacrospinalis) especially the longissimus thoracis, and the diaphragm. The lumbar muscles, quadratus Lumborum (deep portion), deep rotators, as well as cervical muscles, rectus capitus anterior and lateralis, longus coli may also be considered members of the core group. Minor core muscles includ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Core
The core of the Sun is considered to extend from the center to about 0.2 to 0.25 of solar radius (140,000 - 170,000 kilometres (86,000 - 110,000 miles)). It is the hottest part of the Sun and of the Solar System. It has a density of 150 g/cm3 at the center, and a temperature of 15 million kelvins (15 million degrees Celsius, 27 million degrees Fahrenheit). The core is made of hot, dense plasma (ions and electrons), at a pressure estimated at 265 billion bar (3.84 trillion psi or 26.5 petapascals (PPa)) at the center. Due to fusion, the composition of the solar plasma drops from 68–70% hydrogen by mass at the outer core, to 34% hydrogen at the core/Sun center. The core inside 20% of the solar radius contains 34% of the Sun's mass, but only 0.8% of the Sun's volume. Inside 24% of the solar radius is the core which generates 99% of the fusion power of the Sun. There are two distinct reactions in which four hydrogen nuclei may eventually result in one helium nucleus: the pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unbounded Operator
In mathematics, more specifically functional analysis and operator theory, the notion of unbounded operator provides an abstract framework for dealing with differential operators, unbounded observables in quantum mechanics, and other cases. The term "unbounded operator" can be misleading, since * "unbounded" should sometimes be understood as "not necessarily bounded"; * "operator" should be understood as "linear operator" (as in the case of "bounded operator"); * the domain of the operator is a linear subspace, not necessarily the whole space; * this linear subspace is not necessarily closed; often (but not always) it is assumed to be dense; * in the special case of a bounded operator, still, the domain is usually assumed to be the whole space. In contrast to bounded operators, unbounded operators on a given space do not form an algebra, nor even a linear space, because each one is defined on its own domain. The term "operator" often means "bounded linear operator", but in the con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triangulated Category
In mathematics, a triangulated category is a category with the additional structure of a "translation functor" and a class of "exact triangles". Prominent examples are the derived category of an abelian category, as well as the stable homotopy category. The exact triangles generalize the short exact sequences in an abelian category, as well as fiber sequences and cofiber sequences in topology. Much of homological algebra is clarified and extended by the language of triangulated categories, an important example being the theory of sheaf cohomology. In the 1960s, a typical use of triangulated categories was to extend properties of sheaves on a space ''X'' to complexes of sheaves, viewed as objects of the derived category of sheaves on ''X''. More recently, triangulated categories have become objects of interest in their own right. Many equivalences between triangulated categories of different origins have been proved or conjectured. For example, the homological mirror symmetry conj ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Core (group Theory)
In group theory, a branch of mathematics, a core is any of certain special normal subgroups of a group. The two most common types are the normal core of a subgroup and the ''p''-core of a group. The normal core Definition For a group ''G'', the normal core or normal interiorRobinson (1996) p.16 of a subgroup ''H'' is the largest normal subgroup of ''G'' that is contained in ''H'' (or equivalently, the intersection of the conjugates of ''H''). More generally, the core of ''H'' with respect to a subset ''S'' ⊆ ''G'' is the intersection of the conjugates of ''H'' under ''S'', i.e. :\mathrm_S(H) := \bigcap_. Under this more general definition, the normal core is the core with respect to ''S'' = ''G''. The normal core of any normal subgroup is the subgroup itself. Significance Normal cores are important in the context of group actions on sets, where the normal core of the isotropy subgroup of any point acts as the identity on its entire orbit. Thus, in ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Core (graph Theory)
In the mathematical field of graph theory, a core is a notion that describes behavior of a graph with respect to graph homomorphisms. Definition Graph C is a core if every homomorphism f:C \to C is an isomorphism, that is it is a bijection of vertices of C. A core of a graph G is a graph C such that # There exists a homomorphism from G to C, # there exists a homomorphism from C to G, and # C is minimal with this property. Two graphs are said to be homomorphism equivalent or hom-equivalent if they have isomorphic cores. Examples * Any complete graph is a core. * A cycle of odd length is a core. * A graph G is a core if and only if the core of G is equal to G. * Every two cycles of even length, and more generally every two bipartite graphs are hom-equivalent. The core of each of these graphs is the two-vertex complete graph ''K''2. * By the Beckman–Quarles theorem, the infinite unit distance graph on all points of the Euclidean plane or of any higher-dimensional Euclidean s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Core (game Theory)
In cooperative game theory, the core is the set of feasible allocations that cannot be improved upon by a subset (a ''coalition'') of the economy's agents. A coalition is said to ''improve upon'' or ''block'' a feasible allocation if the members of that coalition are better off under another feasible allocation that is identical to the first except that every member of the coalition has a different consumption bundle that is part of an aggregate consumption bundle that can be constructed from publicly available technology and the initial endowments of each consumer in the coalition. An allocation is said to have the ''core property'' if there is no coalition that can improve upon it. The core is the set of all feasible allocations with the core property. Origin The idea of the core already appeared in the writings of , at the time referred to as the ''contract curve''. Even though von Neumann and Morgenstern considered it an interesting concept, they only worked with zero-sum ga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Server Core
Server Core is a minimalistic Microsoft Windows Server installation option, debuted in Windows Server 2008. Server Core provides a server environment with functionality scaled back to core server features, and because of limited features, it has reduced servicing and management requirements, attack surface, disk and memory usage. Andrew Mason, a program manager on the Windows Server team, noted that a primary motivation for producing a Server Core variant of Windows Server 2008 was to reduce the attack surface of the operating system, and that about 70% of the security vulnerabilities in Microsoft Windows from the prior five years would not have affected Server Core. Most notably, no Windows Explorer shell is installed. All configuration and maintenance is done entirely through command-line interface windows, or by connecting to the machine remotely using Microsoft Management Console (MMC), remote server administration tools, and PowerShell. Configuration levels As Server Core ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multi-core Processor
A multi-core processor is a microprocessor on a single integrated circuit with two or more separate processing units, called cores, each of which reads and executes program instructions. The instructions are ordinary CPU instructions (such as add, move data, and branch) but the single processor can run instructions on separate cores at the same time, increasing overall speed for programs that support multithreading or other parallel computing techniques. Manufacturers typically integrate the cores onto a single integrated circuit die (known as a chip multiprocessor or CMP) or onto multiple dies in a single chip package. The microprocessors currently used in almost all personal computers are multi-core. A multi-core processor implements multiprocessing in a single physical package. Designers may couple cores in a multi-core device tightly or loosely. For example, cores may or may not share caches, and they may implement message passing or shared-memory inter-core communica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Central Processing Unit
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, and input/output (I/O) operations specified by the instructions in the program. This contrasts with external components such as main memory and I/O circuitry, and specialized processors such as graphics processing units (GPUs). The form, design, and implementation of CPUs have changed over time, but their fundamental operation remains almost unchanged. Principal components of a CPU include the arithmetic–logic unit (ALU) that performs arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that orchestrates the fetching (from memory), decoding and execution (of instructions) by directing the coordinated operations of the ALU, registers and other co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic-core Memory
Magnetic-core memory was the predominant form of random access, random-access computer memory for 20 years between about 1955 and 1975. Such memory is often just called core memory, or, informally, core. Core memory uses toroids (rings) of a hard magnetic material (usually a Ferrite (magnet)#Semi-hard ferrites, semi-hard ferrite) as transformer cores, where each wire threaded through the core serves as a transformer winding. Two or more wires pass through each core. Magnetic Magnetic hysteresis, hysteresis allows each of the cores to "remember", or store a state. Each core stores one bit of information. A core can be magnetized in either the clockwise or counter-clockwise direction. The value of the bit stored in a core is zero or one according to the direction of that core's magnetization. Electric current pulses in some of the wires through a core allow the direction of the magnetization in that core to be set in either direction, thus storing a one or a zero. Another wire ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Core
A magnetic core is a piece of magnetic material with a high magnetic permeability used to confine and guide magnetic fields in electrical, electromechanical and magnetic devices such as electromagnets, transformers, electric motors, generators, inductors, magnetic recording heads, and magnetic assemblies. It is made of ferromagnetic metal such as iron, or ferrimagnetic compounds such as ferrites. The high permeability, relative to the surrounding air, causes the magnetic field lines to be concentrated in the core material. The magnetic field is often created by a current-carrying coil of wire around the core. The use of a magnetic core can increase the strength of magnetic field in an electromagnetic coil by a factor of several hundred times what it would be without the core. However, magnetic cores have side effects which must be taken into account. In alternating current (AC) devices they cause energy losses, called core losses, due to hysteresis and eddy currents in applic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
