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Extremely Low Frequency
Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz.Liemohn, Michael W. and A. A. CHAN,Unraveling the Causes of Radiation Belt Enhancements. . EOS, TRANSACTIONS, AMERICAN GEOPHYSICAL UNION, Volume 88, Number 42, 16 October 2007, pages 427–440. Republished by NASA and accessed online, 8 February 2010. Adobe File, page 2. In the related magnetosphere science, the lower-frequency electromagnetic oscillations (pulsations occurring below ~3 Hz) are considered to lie in the ULF range, which is thus also defined differently from the ITU radio bands. ELF radio waves are generated by lightning and natural disturbances in Earth's magnetic field, so they are a subject of research by atmospheric scientist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base units is 1/s or s−1, meaning that one hertz is one per second or the Inverse second, reciprocal of one second. It is used only in the case of periodic events. It is named after Heinrich Hertz, Heinrich Rudolf Hertz (1857–1894), the first person to provide conclusive proof of the existence of electromagnetic waves. For high frequencies, the unit is commonly expressed in metric prefix, multiples: kilohertz (kHz), megahertz (MHz), gigahertz (GHz), terahertz (THz). Some of the unit's most common uses are in the description of periodic waveforms and musical tones, particularly those used in radio- and audio-related applications. It is also used to describe the clock speeds at which computers and other electronics are driven. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communication With Submarines
Communication with submarines is a field within military communications that presents technical challenges and requires specialized technology. Because radio waves do not travel well through good electrical conductors like salt water, submerged submarines are cut off from radio communication with their command authorities at ordinary radio frequencies. Submarines can surface and raise an antenna above the sea level, or float a tethered buoy carrying an antenna, then use ordinary radio transmissions; however, this makes them vulnerable to detection by anti-submarine warfare forces. Early submarines during World War II mostly travelled on the surface because of their limited underwater speed and endurance, and dived mainly to evade immediate threats or for stealthy approach to their targets. During the Cold War, however, nuclear-powered submarines were developed that could stay submerged for months. In the event of a nuclear war, submerged ballistic missile submarines have to be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charged Particle
In physics, a charged particle is a particle with an electric charge. For example, some elementary particles, like the electron or quarks are charged. Some composite particles like protons are charged particles. An ion, such as a molecule or atom with a surplus or deficit of electrons relative to protons are also charged particles. A Plasma (physics), plasma is a collection of charged particles, atomic nuclei and separated electrons, but can also be a gas containing a significant proportion of charged particles. Charged particles are labeled as either '' positive'' (+) or ''negative'' (-). The designations are arbitrary. Nothing is inherent to a positively charged particle that makes it "positive", and the same goes for negatively charged particles. Examples Positively charged particles * protons * positrons (antielectrons) * positively charged pions * alpha particles * ion, cations Negatively charged particles * electrons * antiprotons * muons * tauons * negative charged ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Very Low Frequency
Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3–30 kHz, corresponding to wavelengths from 100 to 10 km, respectively. The band is also known as the myriameter band or myriameter wave as the wavelengths range from one to ten myriameters (an obsolete metric unit equal to 10 kilometers). Due to its limited bandwidth, audio (voice) transmission is highly impractical in this band, and therefore only low- data-rate coded signals are used. The VLF band is used for a few radio navigation services, government time radio stations (broadcasting time signals to set radio clocks) and secure military communication. Since VLF waves can penetrate at least into saltwater, they are used for military communication with submarines. Propagation characteristics Because of their long wavelengths, VLF radio waves can diffract around large obstacles and so are not blocked by mountain ranges, and they can propagate as ground wave ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Curvature Of The Earth
Spherical Earth or Earth's curvature refers to the approximation of the figure of the Earth as a sphere. The earliest documented mention of the concept dates from around the 5th century BC, when it appears in the writings of Greek philosophers. In the 3rd century BC, Hellenistic astronomy established the roughly spherical shape of Earth as a physical fact and calculated the Earth's circumference. This knowledge was gradually adopted throughout the Old World during Late Antiquity and the Middle Ages, displacing earlier beliefs in a flat earth.Adoption by China via European science: and A practical demonstration of Earth's sphericity was achieved by Ferdinand Magellan and Juan Sebastián Elcano's circumnavigation (1519–1522). The realization that the figure of the Earth is more accurately described as an ellipsoid dates to the 17th century, as described by Isaac Newton in '' Principia''. In the early 19th century, the flattening of the earth ellipsoid was determined to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffraction
Diffraction is the deviation of waves from straight-line propagation without any change in their energy due to an obstacle or through an aperture. The diffracting object or aperture effectively becomes a secondary source of the Wave propagation, propagating wave. Diffraction is the same physical effect as Wave interference, interference, but interference is typically applied to superposition of a few waves and the term diffraction is used when many waves are superposed. Italian scientist Francesco Maria Grimaldi coined the word ''diffraction'' and was the first to record accurate observations of the phenomenon in 1660 in science, 1660. In classical physics, the diffraction phenomenon is described by the Huygens–Fresnel principle that treats each point in a propagating wavefront as a collection of individual spherical wavelets. The characteristic pattern is most pronounced when a wave from a Coherence (physics), coherent source (such as a laser) encounters a slit/aperture tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schumann Resonance Spectrum
Robert Schumann (; ; 8 June 181029 July 1856) was a German composer, pianist, and music critic of the early Romantic music, Romantic era. He composed in all the main musical genres of the time, writing for solo piano, voice and piano, chamber music, chamber groups, orchestra, choir and the opera. His works typify the spirit of the Romantic era in German music. Schumann was born in Zwickau, Saxony, to an affluent middle-class family with no musical connections, and was initially unsure whether to pursue a career as a lawyer or to make a living as a pianist-composer. He studied law at the universities of Leipzig University, Leipzig and Heidelberg University, Heidelberg but his main interests were music and Romantic literature. From 1829 he was a student of the piano teacher Friedrich Wieck, but his hopes for a career as a virtuoso pianist were frustrated by a worsening problem with his right hand, and he concentrated on composition. His early works were mainly piano pieces, inclu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World Health Organization
The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Geneva, Switzerland, and has 6 regional offices and 150 field offices worldwide. Only sovereign states are eligible to join, and it is the largest intergovernmental health organization at the international level. The WHO's purpose is to achieve the highest possible level of health for all the world's people, defining health as "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity." The main functions of the World Health Organization include promoting the control of epidemic and endemic diseases; providing and improving the teaching and training in public health, the medical treatment of disease, and related matters; and promoting the establishment of international standards for biologic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NeuroToxicology (journal)
''NeuroToxicology'' is a peer-reviewed scientific journal covering research on the toxicology of the nervous system. It was established in 1979 and originally published by Intox Press, until it was acquired by Elsevier in 2001. The editor-in-chief is Joan Marie Cranmer (University of Arkansas for Medical Sciences). Abstracting and indexing The journal is abstracted and indexed in: According to the ''Journal Citation Reports'', the journal has a 2014 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a type of journal ranking. Journals with higher impact factor values are considered more prestigious or important within their field. The Impact Factor of a journa ... of 3.379, ranking it 20th out of 87 journals in the category "Toxicology". References External links * Elsevier academic journals Academic journals established in 1979 Toxicology journals Bimonthly journals Neuroscience journals English-language journals< ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peer Review
Peer review is the evaluation of work by one or more people with similar competencies as the producers of the work (:wiktionary:peer#Etymology 2, peers). It functions as a form of self-regulation by qualified members of a profession within the relevant Field of study, field. Peer review methods are used to maintain quality standards, improve performance, and provide credibility. In academia, scholarly peer review is often used to determine an academic paper's suitability for publication. Peer review can be categorized by the type and by the field or profession in which the activity occurs, e.g., #Medical, medical peer review. It can also be used as a teaching tool to help students improve writing assignments. Henry Oldenburg (1619–1677) was a German-born British philosopher who is seen as the 'father' of modern scientific peer review. It developed over the following centuries with, for example, the journal ''Nature (journal), Nature'' making it standard practice in 1973. The t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Times Of India
''The Times of India'' (''TOI'') is an Indian English-language daily newspaper and digital news media owned and managed by the Times Group. It is the List of newspapers in India by circulation, third-largest newspaper in India by circulation and List of newspapers by circulation, largest selling English-language daily in the world. It is the oldest English-language newspaper in India, and the second-oldest Indian newspaper still in circulation, with its first edition published in 1838. It is nicknamed as "The Old Lady of Bori Bunder", and is a newspaper of record. Near the beginning of the 20th century, Lord Curzon, the Viceroy of India, called ''TOI'' "the leading paper in Asia". In 1991, the BBC ranked ''TOI'' among the world's six best newspapers. It is owned and published by Bennett, Coleman & Co. Ltd. (BCCL), which is owned by the Sahu Jain family. In the Brand Trust Report India study 2019, ''TOI'' was rated as the most trusted English newspaper in India. In a 2021 surve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jane's Information Group
Janes is a global open-source intelligence company specialising in military, national security, aerospace and transport topics, whose name derives from British author Fred T. Jane. History Jane's Information Group was founded in 1898 by Fred T. Jane, who had begun sketching ships as an enthusiast naval artist while living in Portsmouth. This gradually developed into an encyclopedic knowledge, culminating in the publishing of Jane's Fighting Ships, ''All the World's Fighting Ships'' (1898). The company then gradually branched out into other areas of military expertise. The books and trade magazines published by the company are often considered the ''de facto'' public source of information on warfare and transportation systems. Based in Greater London for most of its existence, the group was owned by the Thomson Corporation, the Woodbridge Company, then IHS Markit, before being acquired by Montagu Private Equity in 2019. In March 2022, Janes acquired Washington, D.C.-based RWR Ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
