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A measure of the attenuation caused by absorption of energy per unit of distance that occurs in an electromagnetic wave of given wavelength propagating in a material medium of given refractive index. Note: The value of the absorption index K' is given by the relation
#f01where K is the absorption coefficient, λ is the wavelength in vacuum, and n is the refractive index of the absorptive material medium. [After 2196] 2. The functional relationship between the Sun angle--at any latitude and local time--and the ionospheric absorption.
- Browse Related Terms: absorption, absorption band, absorption index, Absorptivity, F layer, material absorption, path loss, phonon absorption, Photoelectric Effect, photovoltaic effect, sudden ionospheric disturbance (SID)
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That part of the transmission loss caused by the dissipation or conversion of electrical, electromagnetic, or acoustic energy into other forms of energy as a result of its interaction with a material medium.
- Browse Related Terms: absorption loss, acoustics, acousto-optic effect, acousto-optics, anisotropic, magnetic circuit, magnetic tape, optically active material, photoconductive effect
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Amplitude modulation of the output of a radio transmitter by means of a variable-impedance circuit that is caused to absorb carrier power in accordance with the modulating wave.
- Browse Related Terms: absorption modulation, amplitude intensity modulation (AIM), amplitude modulation (AM), angle modulation, baseband local area network, carrier, carrier frequency, carrier noise level, class of emission, continuously variable slope delta (CVSD) modulation, envelope, fixed-reference modulation, Frequency Modulation (FM), modulation factor, modulation index, modulation rate, modulation suppression, off-the-air, on-the-air, optical repeater, overmodulation, percentage modulation, phase deviation, phase modulation (PM), plate modulation, precombining, predetection, pulse link repeater (PLR), quadrature modulation, radio telephony, single-sideband (SSB) emission, stereophonic crosstalk, subcarrier, two-tone keying, variable slope delta modulation
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1. The wavelength or frequency at which a particular substance absorbs the most power (or, where the attenuation of the propagated signal is the greatest) whenever the substance is bombarded or irradiated with audio, electromagnetic, or light waves. Note: Whenever a material is thus bombarded, there is reflection, transmission through the material, and absorption within the material. In the case of air, O2 has multiple absorption peaks. See figure. 2. In optical communications media, the specific wavelength at which a particular impurity absorbs the most power, i.e., causes a maximum attenuation of propagated lightwaves. Note: Absorption by these impurities at other wavelengths is less than that of the absorption peak. Glass quartz silica, and plastics used in optical fibers, slab dielectric waveguides, optical integrated circuits (OICs), and similar media, usually display absorption peaks. Impurities that cause absorption peaks include copper, iron, nickel, chromium, manganese, and hydroxyl ions. [From Weik]
- Browse Related Terms: absorption peak, anomalous propagation (AP), backscattering, Brillouin diagram, Brillouin scattering, forward scatter, material scattering, Mie Scattering, Rayleigh scattering, Scatter, Scattering, scattering center
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Of a material propagation medium, absorptance per unit path length.
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A Java keyword used in a class definition to specify that a class is not to be instantiated, but rather inherited by other classes. An abstract class can have abstract methods that are not implemented in the abstract class, but in subclasses.
- Browse Related Terms: abstract, aggregation, class inheritance, has-a relationship, Hash Function, hierarchy, implements clause, inheritance, inheritance hierarchy, interface inheritance, is-a relationship, multiple inheritance, sibling sub classes, single inheritance, sub class, Super, upcast
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A class that contains one or more abstract methods, and therefore can never be instantiated. Abstract classes are defined so that other classes can extend them and make them concrete by implementing the abstract methods.
A class with the
abstractreserved word in its header. Abstract classes are distinguished by the fact that you may not directly construct objects from them using thenewoperator. An abstract class may have zero or more abstract methods.- Browse Related Terms: abstract class, abstract method, const, declaration, definition, final class, final method, goto, keyword, method signature, reserved word, static initializer, static method, static nested class
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A method with the
abstractreserved word in its header. An abstract method has no method body. Methods defined in an interface are always abstract. The body of an abstract method must be defined in a sub class of an abstract class, or the body of a class implementing an interface.A method that has no implementation.
- Browse Related Terms: abstract class, abstract method, const, declaration, definition, final class, final method, goto, keyword, method signature, reserved word, static initializer, static method, static nested class
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- The part of an entity bean's deployment descriptor that defines the bean's persistent fields and relationships.
- Browse Related Terms: abstract schema, bean-managed persistence, cascade delete, container-managed persistence, conversational state, enterprise bean, Enterprise JavaBeans Query Language (EJB QL), entity bean, home interface, persistence, persistent field, primary key, reentrant entity bean, relationship field, stateful session bean, stateless session bean
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- A logical name that is referenced in EJB QL queries.
- Browse Related Terms: abstract schema name, activation, actor, bean-managed transaction, business logic, business method, caller principal, create method, EJB, EJB context, EJB home object, EJB module, EJB object, finder method, handle, message-driven bean, method permission, Passivation, remote interface, remove method, transaction attribute
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In open systems architecture, the specification of application-layer data or application-protocol control information by using notation rules that are independent of the encoding technique used to represent the information.
- Browse Related Terms: abstract syntax, abstract syntax notation one (ASN.1), Automatic Code Gap (ACG), Code, concrete syntax, packet format, Sequence, signatory
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A standard, flexible method that (a) describes data structures for representing, encoding, transmitting, and decoding data, (b) provides a set of formal rules for describing the structure of objects independent of machine-specific encoding techniques, (c) is a formal network-management Transmission Control Protocol/Internet Protocol (TCP/IP) language that uses human-readable notation and a compact, encoded representation of the same information used in communications protocols, and (d) is a precise, formal notation that removes ambiguities.
- Browse Related Terms: abstract syntax, abstract syntax notation one (ASN.1), Automatic Code Gap (ACG), Code, concrete syntax, packet format, Sequence, signatory
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A collection of graphical user interface (GUI) components that were implemented using native-platform versions of the components. These components provide that subset of functionality which is common to all native platforms. Largely supplanted by the Project Swing component set. See also Swing.
- Browse Related Terms: Abstract Window Toolkit (AWT), bootstrap classes, Java 2 Platform, Standard Edition (J2SE), Java Native Interface, JavaHQ, JDBC, JNDI, JNI, OS principal, POSE (Palm OS Emulator)
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Abstraction involves changing the interface of an object and exposing it in a more useful or appropriate form. This may be done by providing a layer of software, or whatever, which makes an object or collection of objects easier to manage by exposing a different object with a different interface. An example of this would be presenting the user with a tier of a service, for example of tier of web servers and their associated load balancer. The user would then manage the whole tier as a single object, including web tier attributes and load balancing policies, rather than managing each individual component.
Changing the interface of an object and exposing it in a more useful form. Abstraction may be done by providing a layer of software which makes an object or collection of objects easier to manage by exposing a different object with a different interface.
- Browse Related Terms: Abstraction, Commercial Enterprise Application, Decommissioning, GME (Grid Management Entity), GME Component, GRAM (Grid Resource Allocation and Management), Grid Component, Provisioning, Resource, Server Provisioning, Service, Software Provisioning, Storage Provisioning, Technical Enterprise Applications, Virtualization, VMM (Virtual Machine Monitor), VO (Virtual Organization)
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A simplified representation of something that is potentially quite complex. It is often not necessary to know the exact details of how something works, is represented or is implemented, because we can still make use of it in its simplified form. Object-oriented design often involves finding the right level of abstraction at which to work when modeling real-life objects. If the level is too high, then not enough detail will be captured. If the level is too low, then a program could be more complex and difficult to create and understand than it needs to be.
- Browse Related Terms: Abstraction, accessor method, coupling, divide and conquer, factory pattern, floating point number, inconsistent state, information hiding, locale, mutator method, object-oriented design, pattern, singleton pattern, state, wrapper
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Broadly, the use of specialized software, such as an application programming interface (API), as a means of shielding software from device dependencies or the complexities of underlying software. Note: For instance, hardware abstraction enables programs to focus on a task, such as communications, instead of on individual differences between communications devices. 2. In object-oriented programming, the process of reducing an object to its essence so that only the necessary elements are represented. Abstraction defines an object in terms of its properties (attributes), behaviors (functionality), and interface (means of communicating with other objects). [MS]
- Browse Related Terms: Abstraction, access category, application software, controlled access, explicit services, object oriented, opaque data objects, open system application program interface, platform, programming language API, resource controller (RC), transaction, transaction application program
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Abbreviation for alternating current.
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Telephone ringing that makes use of both ac and dc voltages and currents. Note: An alternating current may be used to operate a ringer and direct current to aid the relay action that stops the ringing when the called telephone is answered.
- Browse Related Terms: ac-dc ringing, alerting signal, audible ringing tone, call delay, extension bell, ring, ringback signal, ringdown signaling, selective ringing
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