LYCOS RETRIEVER 
Lightning (High Voltage)
built 639 days ago
Lightning (High Voltage) also shows up in the Retriever categories:
Lightning (Hockey Team) , and more.
Lightning (Hockey Team) , and more.
Lightning is a major cause of building fires, even though highly effective protection against this threat has long been available. In the 1700s Benjamin Franklin proposed a method of protecting structures from the effects of lightning. His method was based on observations that suggested (a) lightning preferentially strikes elevated objects and (b) lightning currents can be carried to and dissipated in earth by a suitable network of conductors and grounding electrodes. Various approaches aimed at providing protection against lightning, similar to Franklin's method of elevated rods and down-conductors, have been tried over the past 250 years; the more successful designs have been described and published as standards for guidance and protection of the public. In 1904, The National Fire Protection Association of Quincy, MA, established the American standard for installation of lightning protection systems. Now known as NFPA 780, The Standard for the Installation of Lightning Protection Systems (available for purchase through http://www.nfpa.org/Codes/index.asp) is revised periodically by an NFPA technical committee to incorporate new knowledge about the physics of lightning and advances in technology.
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The National Lightning Safety Institute is an independent, non-profit consulting, education and research organisation based in Louisville, CO, USA. The institute's website hosts a large collection of reference information, including: a lightning safety discussion group; a quiz (in PowerPoint format); a glossary; middle and high school lesson plans; lightning maps for Australia, France, UK, India, Japan and the USA; lightning accidents and injuries; FAQs and other lightning information.
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Lightning discharges generate electromagnetic pulses, known as sferics, that propagate through the waveguide formed by the earth and the ionosphere. The energy in the VLF band of the sferic can propagate over great distances ($\sim$10,000 km) with low loss (3 dB/Mm) and can therefore be detected far from the source lightning location. Using sferic measurements from VLF receivers located at three globally separated sites (Palmer Station, Antarctica; Upland, Indiana; Sde Boker, Israel) the locations of individual lightning discharges are triangulated. Both time of arrival (TOA) and magnetic direction finding (MDF) data are used in the location algorithm. The very large distances between receiver sites and a high global sferic rate ($\sim$100 per second) create space-time complications in the correlation of data between sites causing ambiguities in the pairing of sferics detected at one site to their corresponding sferics detected at the other two sites. These complications sometimes result in the detection of ``ghost'' lightning discharges which occurs when physically inconsistent (not originating from the same lightning discharge) yet statistically consistent (acceptable arrival times and azimuths) sferics are used in the location algorithm.
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Lightning is more than light and noise: It's an intense chemical factory that affects both local air quality and global climate. But how big is the effect? Researchers aren't sure. To answer the question they're developing a new technique to estimate the factory's output.
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Lightning has been identified as a potentially important natural source of nitrogen oxides (NOx =NO+NO2) and ... several laboratory experiments have been conducted to measure the NOx production as a function of energy dissipated in sparks and laser plasma discharges. Chameides et al. [1977] measured NOx production in air subjected to a centimetre long spark by chemiluminescenc and derived a yield of (61) 1016 molecule J-1. The sparks were generated by a 35 kV electrostatic generator, yielding an energy of 36 mJ per spark. Levine et al. [1981] measured NOx production in air using chemiluminescent technique from several centimetre long sparks having a discharge energy of 12 kJ, which is more than a five order of magnitude energy increase compared to the energy produced in Chemeides experiment and derived a yield of (52) 1016 molecule J-1. Hill et al. [1988] investigated also the production of NO in atmospheric coronas using a specially designed plasma reactor operated at a pressure of 0.1 MPa and a temperature of 300 K and found a yield of NO to be (1.40.7)1016 molecule J-1. Wang et al. [1998] employed sparks with lightning like peak currents of up to 30kA, a spark of 4 cm long at atmospheric pressure and found that the production was about (15-401016) molecule J-1.
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Lightning strikes cause tremendous losses each year and pose threat to property. For instance, in Charlotte, North Carolina, from 1993 to 1995, eleven lightning strikes caused over $100,000 damages. Also, everyone could have the chance of damaging strikes. It has been estimated that a home owner can expect a damaging strike once every 100 to 200 years.
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Lightning (High Voltage)