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Topic Review
UN-SPIDER
UN-SPIDER ("United Nations Platform for Space-based Information for Disaster Management and Emergency Response") is a platform which facilitates the use of space-based technologies for disaster management and emergency response. It is a programme under the auspices of the United Nations Office for Outer Space Affairs (UNOOSA).
  • 202
  • 18 Oct 2022
Topic Review
UC Berkeley College of Natural Resources
The College of Natural Resources (CNR), a college of the University of California, Berkeley, is the oldest college in the UC system and home to several internationally top-ranked programs. CNR's Department of Agriculture & Economics is considered to be one of the most prestigious schools in agricultural economics in the world, ranking #1 according to the Journal of Agricultural and Applied Economics, #1 by the Chronicle of Higher Education, #1 by Perry for its Ph.D. programs and in International Trade, #1 by the National Research Council in Agricultural & Resource Economics, and #1 by U.S. News in Environmental/Environmental Health. In environmental disciplines, QS World Rankings recognizes the University of California, Berkeley, as the world's leading university in Environmental Studies with 100 points in Academic Reputation. U.S. News also ranks it as the best global university for environment and ecology. A study of AJAE authors and their university affiliations found it to have the highest number of pages per research faculty member. Established in 1868 as the College of Agriculture under the federal Morrill Land-Grant Acts, CNR is the first state-run Agricultural Experiment Station. The college is home to four academic departments: Agriculture and Resource Economics; Environmental Science, Policy, and Management; Nutritional Sciences and Toxicology; and Plant and Microbial Biology, and one interdisciplinary program, Energy and Resources Group. Faculty include 40 Fulbright Fellows, 30 American Association for the Advancement of Science Fellows, 19 National Academy of Sciences members, 12 Guggenheim Fellows, 9 American Academy of Arts and Sciences members, 7 MacArthur Fellows, 4 Nobel Laureates, 3 Wolf Prize winners, and 2 World Food Prize winners. The Dean of the College is Prof. David Ackerly.
  • 344
  • 01 Nov 2022
Topic Review
True Range Multilateration
True range multilateration is a method to determine the location of a movable vehicle or stationary point in space using multiple ranges (distances) between the vehicle/point and multiple spatially-separated known locations (often termed 'stations'). True range multilateration is both a mathematical topic and an applied technique used in several fields. A practical application involving a fixed location is the trilateration method of surveying. Applications involving vehicle location are termed navigation when on-board persons/equipment are informed of its location, and are termed surveillance when off-vehicle entities are informed of the vehicle's location. Two slant-ranges from two known locations can be used to locate a third point in a two-dimensional Cartesian space (plane), which is a frequently applied technique (e.g., in surveying). Similarly, two spherical ranges can be used to locate a point on a sphere, which is a fundamental concept of the ancient discipline of celestial navigation — termed the altitude intercept problem. Moreover, if more than the minimum number of ranges are available, it is good practice to utilize those as well. This article addresses the general issue of position determination using multiple ranges. In two-dimensional geometry, it is known that if a point lies on two circles, then the circle centers and the two radii provide sufficient information to narrow the possible locations down to two – one of which is the desired solution and the other is an ambiguous solution. Additional information often narrow the possibilities down to a unique location. In three-dimensional geometry, when it is known that a point lies on the surfaces of three spheres, then the centers of the three spheres along with their radii also provide sufficient information to narrow the possible locations down to no more than two (unless the centers lie on a straight line). True range multilateration can be contrasted to the more frequently encountered (pseudorange) multilateration, which employs range differences to locate a (typically, movable) point. Pseudo range multilateration is almost always implemented by measuring times-of-arrival (TOAs) of energy waves. True range multilateration can also be contrasted to triangulation, which involves the measurement of angles. Multiple, sometimes overlapping and conflicting terms are employed for similar concepts – e.g., multilateration without modification has been used for aviation systems employing both true ranges and pseudo ranges. Moreover, different fields of endeavor may employ different terms. In geometry, trilateration is defined as the process of determining absolute or relative locations of points by measurement of distances, using the geometry of circles, spheres or triangles. In surveying, trilateration is a specific technique. The term true range multilateration is accurate, general and unambiguous. Authors have also used the terms range-range and rho-rho multilateration for this concept.
  • 634
  • 25 Oct 2022
Topic Review
Tropical Ecology
Tropical ecology is the study of the relationships between the biotic and abiotic components of the tropics, or the area of the Earth that lies between the Tropic of Cancer and the Tropic of Capricorn (23.4378° N and 23.4378° S, respectively). The tropical climate experiences hot, humid weather and rainfall year-round. While many might associate the region solely with the rainforests, the tropics are home to a wide variety of ecosystems that boast a great wealth of biodiversity, from exotic animal species to seldom-found flora. Tropical ecology began with the work of early English naturalists and eventually saw the establishment of research stations throughout the tropics devoted to exploring and documenting these exotic landscapes. The burgeoning ecological study of the tropics has led to increased conservation education and programs devoted to the climate. This climatic zone offers numerous advantages to ecologists conducting a wide array of studies, from rich biodiversity to vast lands untainted by man.
  • 764
  • 14 Oct 2022
Topic Review
Trindade and Martin Vaz
Trindade and Martin Vaz (Portuguese: Trindade e Martim Vaz, pronounced [tɾĩˈdadʒi i mɐʁˈtʃĩ ˈvas]) is an archipelago located in the South Atlantic Ocean about 1,100 kilometres (680 miles) east of the coast of the Brazilian state of Espírito Santo, of which it forms a part. The archipelago has a total area of 10.4 square kilometres (4.0 square miles) and a population of 32 (Brazilian Navy personnel).The archipelago consists of five islands and several rocks and stacks; Trindade is the largest island, with an area of 10.1 square kilometres (3.9 square miles); about 49 kilometres (30 miles) east of it are the tiny Martin Vaz islets, with a total area of 0.3 square kilometres (30.0 hectares). The islands are of volcanic origin and have rugged terrain. They are largely barren, except for the southern part of Trindade. They were discovered in 1502 by Portuguese explorer Estêvão da Gama and stayed Portuguese until they became part of Brazil at its independence in 1822. From 1895 to 1896, Trindade was occupied by the United Kingdom until an agreement with Brazil was reached. During the period of British occupation, Trindade was known as South Trinidad. The islands are situated some 2,100 kilometres (1,300 miles) southwest of Ascension Island and 2,550 kilometres (1,580 miles) west of Saint Helena, and the distance to the west coast of Africa is 4,270 kilometres (2,650 miles).
  • 432
  • 31 Oct 2022
Topic Review
Travertine
Travertine (/ˈtrævərˌtiːn/ TRA-vər-teen) is a form of limestone deposited by mineral springs, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and even rusty varieties. It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot spring or in a limestone cave. In the latter, it can form stalactites, stalagmites, and other speleothems. It is frequently used in Italy and elsewhere as a building material. Travertine is a terrestrial sedimentary rock, formed by the precipitation of carbonate minerals from solution in ground and surface waters, or geothermally heated hot-springs. Similar (but softer and extremely porous) deposits formed from ambient-temperature water are known as tufa.
  • 724
  • 02 Nov 2022
Topic Review
Transfer of Natural Radionuclides in Terrestrial Food Chains
From the radiation protection point of view, less important natural radionuclides are 238U, 226Ra, 40K, and Th isotopes. However, 238U is a long-lived (t½ = 4.5 × 109 a) alpha emitter whose chemical toxicity exceeds its radiological toxicity. Although isotope 238U is not considered to cause significant radiation exposure, it is still the mother nuclide of a whole uranium decay series, producing isotopes of astatine, bismuth, lead, polonium, protactinium, radium, radon, thallium, and thorium while decaying. 40K also has a very long half-life (t½ = 1.28 × 109 a).
  • 377
  • 14 Feb 2023
Topic Review
Transcaucasia
Transcaucasia, also known as the South Caucasus, is a geographical region on the border of Eastern Europe and Western Asia, straddling the southern Caucasus Mountains. Transcaucasia roughly corresponds to modern Armenia, Georgia and Azerbaijan, and are sometimes collectivelly known as the Caucasian States. The total area of these countries measures about 186,100 square kilometres (71,850 square miles). Transcaucasia and Ciscaucasia (North Caucasus) together comprise the larger Caucasus geographical region that divides Eurasia.
  • 3.4K
  • 23 Nov 2022
Topic Review
Tier-Scalable Reconnaissance
Tier-Scalable Reconnaissance is the term for an approach to deploying and controlling vehicles in multiple areas of interest, such as in the exploration of planets or diverse regions on Earth. It is not a rigid or fixed paradigm, but is infinitely extensible. It uses hierarchical levels of oversight called tiers, each tier commanding or controlling the vehicles within the tier beneath it. The size of each tier can be scaled from one to many vehicles.
  • 582
  • 09 Oct 2022
Topic Review
Theodore Roosevelt National Park
Theodore Roosevelt National Park is an American national park comprising three geographically separated areas of badlands in western North Dakota. The park was named for U.S. President Theodore Roosevelt. The park covers 70,446 acres (110.072 sq mi; 28,508 ha; 285.08 km2) of land in three sections: the North Unit, the South Unit, and the Elkhorn Ranch Unit. The park's larger South Unit lies alongside Interstate 94 near Medora, North Dakota. The smaller North Unit is situated about 80 mi (130 km) north of the South Unit, on U.S. Highway 85, just south of Watford City, North Dakota. Roosevelt's Elkhorn Ranch is located between the North and South units, approximately 20 mi (32 km) west of US 85 and Fairfield, North Dakota. The Little Missouri River flows through all three units of the park. The Maah Daah Hey Trail connects all three units. The park received 708,003 recreational visitors in 2017. It is the only American national park named directly after a single person.
  • 639
  • 22 Nov 2022
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