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George Ashley Campbell
George Ashley Campbell (November 27, 1870 – November 10, 1954) was an American engineer. He was a pioneer in developing and applying quantitative mathematical methods to the problems of long-distance telegraphy and telephony. His most important contributions were to the theory and implementation of the use of loading coils and the first wave filters designed to what was to become known as the image method. Both these areas of work resulted in important economic advantages for the American Telephone and Telegraph Company (AT&T). Education Campbell was educated at the McCollom Institute in New Hampshire and then at MIT, where he graduated in 1891. He then received a master's degree from Harvard University in 1893. He was awarded a fellowship which enabled him to spend three years on graduate work; one year studying advanced mathematics under Felix Klein at Göttingen, one year studying electricity and mechanics under Ludwig Boltzmann in Vienna, and one year studying under ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hastings, Minnesota
Hastings is a city mostly in Dakota County, Minnesota, of which it is the county seat, with a portion in Washington County, Minnesota. It is near the confluence of the Mississippi River, Mississippi, Vermillion, and St. Croix River (Wisconsin-Minnesota), St. Croix Rivers. Its population was 22,154 at the 2020 United States census, 2020 census. It is named for the first elected governor of Minnesota, Henry Hastings Sibley. The advantages of Hastings's location that led to its original growth are that it is well-drained, provides a good riverboat port, and is close to a hydropower resource at the falls of the Vermillion River (Minnesota), Vermillion River. Other sites closer to the river confluence are either too swampy (Dakota County) or too hilly (Washington County and Pierce County, Wisconsin). U.S. Route 61 in Minnesota, U.S. Highway 61 and Minnesota State Highways Minnesota State Highway 55, 55 and Minnesota State Highway 316, 316 are three of Hastings's main routes. Histor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AT&T Corp
AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company by revenue and the third largest provider of mobile telephone services in the U.S. , AT&T was ranked 13th on the ''Fortune'' 500 rankings of the largest United States corporations, with revenues of $168.8 billion. During most of the 20th century, AT&T had a monopoly on phone service in the United States. The company began its history as the American District Telegraph Company, formed in St. Louis in 1878. After expanding services to Arkansas, Kansas, Oklahoma and Texas, through a series of mergers, it became Southwestern Bell Telephone Company in 1920, which was then a subsidiary of American Telephone and Telegraph Company. The latter was a successor of the original Bell Telephone Company founded by Alexander Graham Bell in 1877. The American Bell Telephone Company formed the American Telep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lumped-element
The lumped-element model (also called lumped-parameter model, or lumped-component model) simplifies the description of the behaviour of spatially distributed physical systems, such as electrical circuits, into a Topology (electrical circuits), topology consisting of discrete entities that approximate the behaviour of the distributed system under certain assumptions. It is useful in electrical network, electrical systems (including electronics), mechanical multibody systems, heat transfer, acoustics, etc. This may be contrasted to distributed parameter systems or models in which the behaviour is distributed spatially and cannot be considered as localized into discrete entities. Mathematically speaking, the simplification reduces the State space (controls), state space of the system to a counting number, finite dimension, and the partial differential equations (PDEs) of the continuous (infinite-dimensional) time and space model of the physical system into ordinary differential equa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Attenuation
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable attenuation rates. Hearing protectors help reduce acoustic flux from flowing into the ears. This phenomenon is called acoustic attenuation and is measured in decibels (dBs). In electrical engineering and telecommunications, attenuation affects the propagation of waves and signals in electrical circuits, in optical fibers, and in air. Electrical attenuators and optical attenuators are commonly manufactured components in this field. Background In many cases, attenuation is an exponential function of the path length through the medium. In optics and in chemical spectroscopy, this is known as the Beer–Lambert law. In engineering, attenuation is usually measured in units of decibels per unit length of medium (dB/cm, dB/km, etc.) and is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Capacitance
Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are two closely related notions of capacitance: ''self capacitance'' and ''mutual capacitance''. An object that can be electrically charged exhibits self capacitance, for which the electric potential is measured between the object and ground. Mutual capacitance is measured between two components, and is particularly important in the operations of the capacitor, a device designed for this purpose as an elementary Linear circuit, linear electronic component. Capacitance is a function only of the geometry of the design of the capacitor, e.g., the opposing surface area of the plates and the distance between them, and the permittivity of the dielectric material between the plates. For many dielectric materials, the permittivity and thus the capaci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is equal to one event per second. The period is the interval of time between events, so the period is the reciprocal of the frequency. For example, if a heart beats at a frequency of 120 times a minute (2 hertz), the period, —the interval at which the beats repeat—is half a second (60 seconds divided by 120 beats). Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light. Definitions and units For cyclical phenomena such as oscillations, waves, or for examples of simple harmonic motion, the term ''frequency'' is defined as the number of cycles or vibrations per unit of time. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
West Newton, Massachusetts
West Newton is one of the thirteen villages within the city of Newton in Middlesex County, Massachusetts, United States. Among the oldest of the thirteen Newton villages, the West Newton Village Center is a National Register Historic District. The postal ("Zip") code 02465 roughly matches the village limits. Location West Newton is located in the north central part of Newton and is bordered by the town of Waltham on the north and by the villages of Auburndale on the west, Newton Lower Falls on the extreme southwest, Newtonville on the east, and Waban on the south. Railroad Station The West Newton train stop is located near an inn (now small shops) that served as a stagecoach stop. The original station structure was destroyed in the construction of the Massachusetts Turnpike, although the station itself still exists as a stop on the commuter rail. West Newton Square West Newton Square, the town center of West Newton, is home to many local businesses and venues. These in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jamaica Plain
Jamaica Plain is a neighborhood of in the City of Boston, Massachusetts, United States. Settled by Puritans seeking farmland to the south, it was originally part of the former Town of Roxbury, now also a part of the City of Boston. The community seceded from Roxbury as a part of the new town of West Roxbury in 1851, and became part of Boston when West Roxbury was annexed in 1874.Local Attachments : The Making of an American Urban Neighborhood, 1850 to 1920 (Creating the North American Landscape), by Alexander von Hoffman, The Johns Hopkins University Press (1996), In the 19th century, Jamaica Plain became one of the first streetcar suburbs in America and home to a significant portion of Boston's Emerald Necklace of parks, designed by Frederick Law Olmsted. In 2020, Jamaica Plain had a population of 41,012 according to the United States Census. History Colonial era Shortly after the founding of Boston and Roxbury in 1630, William Heath's family and three others settled o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distributed-element Model
: ''This article is an example from the domain of electrical systems, which is a special case of the more general distributed-parameter systems.'' In electrical engineering, the distributed-element model or transmission-line model of electrical circuits assumes that the attributes of the circuit ( resistance, capacitance, and inductance) are distributed continuously throughout the material of the circuit. This is in contrast to the more common lumped-element model, which assumes that these values are lumped into electrical components that are joined by perfectly conducting wires. In the distributed-element model, each circuit element is infinitesimally small, and the wires connecting elements are not assumed to be perfect conductors; that is, they have impedance. Unlike the lumped-element model, it assumes nonuniform current along each branch and nonuniform voltage along each wire. The distributed model is used where the wavelength becomes comparable to the physical dimensi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lumped-element Model
The lumped-element model (also called lumped-parameter model, or lumped-component model) simplifies the description of the behaviour of spatially distributed physical systems, such as electrical circuits, into a topology consisting of discrete entities that approximate the behaviour of the distributed system under certain assumptions. It is useful in electrical systems (including electronics), mechanical multibody systems, heat transfer, acoustics, etc. This may be contrasted to distributed parameter systems or models in which the behaviour is distributed spatially and cannot be considered as localized into discrete entities. Mathematically speaking, the simplification reduces the state space of the system to a finite dimension, and the partial differential equations (PDEs) of the continuous (infinite-dimensional) time and space model of the physical system into ordinary differential equations (ODEs) with a finite number of parameters. Electrical systems Lumped-matter disci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Stone Stone
John Stone Stone (September 24, 1869 – May 20, 1943) was an American mathematician, physicist and inventor. He initially worked in telephone research, followed by influential work developing early radio technology, where he was especially known for improvements in tuning. Despite his often advanced designs, the Stone Telegraph and Telephone Company failed in 1908, and he spent the remainder of his career as an engineering consultant. Biography Early years Stone was born in Dover (now Manakin) village, in Goochland County, Virginia, the son of Charles Pomeroy Stone, an American Civil War Union general and engineer, and Annie Jeannie toneStone. From 1870 until 1883, General Stone held the post of Chief of Staff to the khedive of Egypt, and, while growing up in Cairo, John Stone Stone became fluent in Arabic, French, German and Spanish in addition to English. His father tutored him in mathematics, and following the family's return to the United States, Stone attended Colum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heaviside Condition
The Heaviside condition, named for Oliver Heaviside (1850–1925), is the condition an electrical transmission line must meet in order for there to be no distortion of a transmitted signal. Also known as the distortionless condition, it can be used to improve the performance of a transmission line by adding loading to the cable. The condition A transmission line can be represented as a distributed-element model of its primary line constants as shown in the figure. The primary constants are the electrical properties of the cable per unit length and are: capacitance ''C'' (in farads per meter), inductance ''L'' (in henries per meter), series resistance ''R'' (in ohms per meter), and shunt conductance ''G'' (in siemens per meter). The series resistance and shunt conductivity cause losses in the line; for an ideal transmission line, \scriptstyle R=G=0. The Heaviside condition is satisfied when :\frac = \frac. This condition is for no distortion, but not for no loss. Backgro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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