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Low Emissivity
Low emissivity (low ''e'' or low thermal emissivity) refers to a surface condition that emits low levels of radiant thermal (heat) energy. All materials absorb, reflect, and emit radiant energy according to Planck's law but here, the primary concern is a special wavelength interval of radiant energy, namely thermal radiation of materials. In common use, especially building applications, the temperature range of approximately -40 to +80 degrees Celsius is the focus, but in aerospace and industrial process engineering, much broader ranges are of practical concern. Definition Emissivity is the value given to materials based on the ratio of heat emitted compared to a perfect black body, on a scale from zero to one. A black body would have an emissivity of 1 and a perfect reflector would have a value of 0. Kirchhoff's law of thermal radiation states that absorption equals emissivity opaque for every specific wavelength/frequency (materials often have quite different emissivities ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around 1 millimeter (300 GHz) to the nominal red edge of the visible spectrum, around 700 nanometers (430 THz). Longer IR wavelengths (30 μm-100 μm) are sometimes included as part of the terahertz radiation range. Almost all black-body radiation from objects near room temperature is at infrared wavelengths. As a form of electromagnetic radiation, IR propagates energy and momentum, exerts radiation pressure, and has properties corresponding to both those of a wave and of a particle, the photon. It was long known that fires emit invisible heat; in 1681 the pioneering experimenter Edme Mariotte showed that glass, though transparent to sunlight, obstructed radiant heat. In 1800 the astronomer Sir William Herschel discovere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around 1 millimeter (300 GHz) to the nominal red edge of the visible spectrum, around 700 nanometers (430 THz). Longer IR wavelengths (30 μm-100 μm) are sometimes included as part of the terahertz radiation range. Almost all black-body radiation from objects near room temperature is at infrared wavelengths. As a form of electromagnetic radiation, IR propagates energy and momentum, exerts radiation pressure, and has properties corresponding to both those of a wave and of a particle, the photon. It was long known that fires emit invisible heat; in 1681 the pioneering experimenter Edme Mariotte showed that glass, though transparent to sunlight, obstructed radiant heat. In 1800 the astronomer Sir William Herschel discove ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for servers, and Windows IoT for embedded systems. Defunct Windows families include Windows 9x, Windows Mobile, and Windows Phone. The first version of Windows was released on November 20, 1985, as a graphical operating system shell for MS-DOS in response to the growing interest in graphical user interfaces (GUIs). Windows is the most popular desktop operating system in the world, with 75% market share , according to StatCounter. However, Windows is not the most used operating system when including both mobile and desktop OSes, due to Android's massive growth. , the most recent version of Windows is Windows 11 for consumer PCs and tablets, Windows 11 Enterprise for corporations, and Windows Server 2022 for servers. Genealogy By marketing r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selective Surface
In solar thermal collectors, a selective surface or selective absorber is a means of increasing its operation temperature and/or efficiency. The selectivity is defined as the ratio of solar radiation absorption (αsol) to thermal infrared radiation emission (εtherm). Selective surfaces take advantage of the differing wavelengths of incident solar radiation and the emissive radiation from the absorbing surface: * Solar radiation covers approximately the wavelengths 350 nm to 4000 nm; UV-A, visible and near infrared ( NIR, or IR-A plus IR-B). * Thermal infrared radiation, from materials with temperatures approximately in the interval -40 to 100 °C, covers approximately the wavelengths 4000 nm to 40,000 nm = 4 um to 40 um; The thermal infrared radiation interval being named or covered by: MIR, LWIR or IR-C. Materials Normally, a combination of materials is used. One of the first selective surfaces investigated was a semico ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
R-value (insulation)
In the context of construction, the R-value is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists the conductive flow of heat. R-value is the temperature difference per unit of heat flux needed to sustain one unit of heat flux between the warmer surface and colder surface of a barrier under steady-state conditions. The ''R-value'' is the building industry term for thermal resistance "per unit area." It is sometimes denoted RSI-value if the SI units are used. An R-value can be given for a material (e.g. for polyethylene foam), or for an assembly of materials (e.g. a wall or a window). In the case of materials, it is often expressed in terms of R-value per metre. R-values are additive for layers of materials, and the higher the R-value the better the performance. The U-factor or U-value is the overall heat transfer coefficient and can be found by taking the inverse of the R-value. It is a property ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fiberglass
Fiberglass (American English) or fibreglass ( Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth. The plastic matrix may be a thermoset polymer matrix—most often based on thermosetting polymers such as epoxy, polyester resin, or vinyl ester resin—or a thermoplastic. Cheaper and more flexible than carbon fiber, it is stronger than many metals by weight, non- magnetic, non-conductive, transparent to electromagnetic radiation, can be molded into complex shapes, and is chemically inert under many circumstances. Applications include aircraft, boats, automobiles, bath tubs and enclosures, swimming pools, hot tubs, septic tanks, water tanks, roofing, pipes, cladding, orthopedic casts, surfboards, and external door skins. Other common names for fiberglass are glass-reinforced plastic (GRP), glass-fiber reinforced plastic (GFR ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Low-density Polyethylene
Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization. Its manufacture employs the same method today. The EPA estimates 5.7% of LDPE ( resin identification code 4) is recycled in the United States. Despite competition from more modern polymers, LDPE continues to be an important plastic grade. In 2013 the worldwide LDPE market reached a volume of about US$33 billion. Despite its designation with the recycling symbol, it cannot be as commonly recycled as No. 1 (polyethylene terephthalate) or 2 plastics (high-density polyethylene). Properties LDPE is defined by a density range of 917–930 kg/m3. At room temperature it is not reactive, except to strong oxidizers; some solvents cause it to swell. It can withstand temperatures of continuously and for a short time. Made in translucent and opaque ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RCR Wireless News
''RCR Wireless News'' is a digital wireless telecommunications industry trade publication. The core focus of the publisher are its news website, daily newsletters and editorial content, including reports and webinars. Alongside this, the organization also hosts digital and in-person industry events. History and profile ''RCR Wireless'' was started in 1982. ''RCR Wireless News''’ editorial team was led by Tracy Ford. The headquarters was in Golden, Colorado. On March 3, 2009, the magazine was shut down by Crain Communications. The publication was sold to Arden Media Company, and relaunched as an online publication in September 2009 with the same editorial team. Its headquarters is in Austin, Texas Austin is the capital city of the U.S. state of Texas, as well as the seat and largest city of Travis County, with portions extending into Hays and Williamson counties. Incorporated on December 27, 1839, it is the 11th-most-populous city .... References Business magaz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Phone Reception
A mobile phone signal (also known as reception and service) is the signal strength (measured in dBm) received by a mobile phone from a cellular network (on the downlink). Depending on various factors, such as proximity to a tower, any obstructions such as buildings or trees, etc. this signal strength will vary. Most mobile devices use a set of bars of increasing height to display the approximate strength of this received signal to the mobile phone user. Traditionally five bars are used. (see five by five) Generally, a strong mobile phone signal is more likely in an urban area, though these areas can also have some "dead zones", where no reception can be obtained. Cellular signals are designed to be resistant to multipath reception, which is most likely to be caused by the blocking of a direct signal path by large buildings, such as high-rise towers. By contrast, many rural or sparsely inhabited areas lack any signal or have very weak fringe reception; many mobile phone provide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distributed Antenna System
A distributed antenna system, or DAS, is a network of spatially separated antenna nodes connected to a common source via a transport medium that provides wireless service within a geographic area or structure. DAS antenna elevations are generally at or below the clutter level, and node installations are compact. A distributed antenna system may be deployed indoors (an iDAS) or outdoors (an oDAS). Concept As illustrated in the figure, the idea is to split the transmitted power among several antenna elements, separated in space so as to provide coverage over the same area as a single antenna but with reduced total power and improved reliability. A single antenna radiating at high power (a) is replaced by a group of low-power antennas to cover the same area (b). The idea was described in a paper by Saleh et al. in 1987. These antennas have recently been employed by several service providers in many areas around the United States. DAS is often used in scenarios where alternate te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CBS Los Angeles
KCBS-TV (channel 2) is a television station in Los Angeles, California, United States, serving as the West Coast flagship of the CBS network. It is owned and operated by the network's CBS News and Stations division alongside independent outlet KCAL-TV (channel 9). Both stations share studios at the CBS Studio Center on Radford Avenue in the Studio City section of Los Angeles, while KCBS-TV's transmitter is located on the western side of Mount Wilson near Occidental Peak. Aside from being affiliated with CBS News, since 2017, KCBS-TV has had no connection to KCBS radio (740 AM) in San Francisco. The 2017 sale to Entercom (now Audacy) of KCBS radio and KCBS-FM (93.1) in Los Angeles ended almost seven decades of co-ownership among the three stations under CBS. History Early years (1931–1948) KCBS-TV is the oldest continuously operating television station in the western United States. It was signed on by Don Lee Broadcasting, which owned a chain of radio stations on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
WCVB
WCVB-TV (channel 5) is a television station in Boston, Massachusetts, United States, affiliated with ABC and owned by Hearst Television. The station's studios are located on TV Place (off Gould Street near the I-95/ MA 128/Highland Avenue interchange) in Needham, Massachusetts, and its transmitter is located on Cedar Street, also in Needham, on a tower shared with several other television and radio stations. Nearby Manchester, New Hampshire, is considered part of the Boston media market, making WCVB-TV part of a nominal duopoly with WMUR-TV (channel 9), that city's ABC affiliate; however, the two stations maintain separate operations. WCVB is also one of six Boston television stations that are carried by satellite provider Bell Satellite TV and fiber optic television provider Bell Fibe TV in Canada. Since 2010, midday and weekend late newscasts, along with ''World News Now'', are overlaid with Canadian paid programming on those providers; however, the latter has car ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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