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Forensic Ballistics
Ballistics is the field of mechanics concerned with the launching, flight behaviour and impact effects of projectiles, especially ranged weapon munitions such as bullets, unguided bombs, rockets or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance. A ballistic body is a free-moving body with momentum which can be subject to forces such as the forces exerted by pressurized gases from a gun barrel or a propelling nozzle, normal force by rifling, and gravity and air drag during flight. A ballistic missile is a missile that is guided only during the relatively brief initial phase of powered flight and the trajectory is subsequently governed by the laws of classical mechanics; in contrast to (for example) a cruise missile which is aerodynamically guided in powered flight like a fixed-wing aircraft. History and prehistory The earliest known ballistic projectiles were stones and spears, and the throwing stick. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Missile Guidance
Missile guidance refers to a variety of methods of guiding a missile or a guided bomb to its intended target. The missile's target accuracy is a critical factor for its effectiveness. Guidance systems improve missile accuracy by improving its Probability of Guidance (Pg). These guidance technologies can generally be divided up into a number of categories, with the broadest categories being "active", "passive", and "preset" guidance. Missiles and guided bombs generally use similar types of guidance system, the difference between the two being that missiles are powered by an onboard engine, whereas guided bombs rely on the speed and height of the launch aircraft for propulsion. History The concept of unmanned guidance originated at least as early as World War I, with the idea of remotely guiding an airplane bomb onto a target, such as the systems developed for the first powered drones by Archibald Low (The Father of Radio Guidance). In World War II, guided missiles were first d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hamburg
(male), (female) en, Hamburger(s), Hamburgian(s) , timezone1 = Central (CET) , utc_offset1 = +1 , timezone1_DST = Central (CEST) , utc_offset1_DST = +2 , postal_code_type = Postal code(s) , postal_code = 20001–21149, 22001–22769 , area_code_type = Area code(s) , area_code = 040 , registration_plate = , blank_name_sec1 = GRP (nominal) , blank_info_sec1 = €123 billion (2019) , blank1_name_sec1 = GRP per capita , blank1_info_sec1 = €67,000 (2019) , blank1_name_sec2 = HDI (2018) , blank1_info_sec2 = 0.976 · 1st of 16 , iso_code = DE-HH , blank_name_sec2 = NUTS Region , blank_info_sec2 = DE6 , website = , footnotes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of The Witwatersrand
The University of the Witwatersrand, Johannesburg (), is a multi-campus South African public research university situated in the northern areas of central Johannesburg. It is more commonly known as Wits University or Wits ( or ). The university has its roots in the mining industry, as do Johannesburg and the Witwatersrand in general. Founded in 1896 as the South African School of Mines in Kimberley, it is the third oldest South African university in continuous operation. The university has an enrolment of 40,259 students as of 2018, of which approximately 20 percent live on campus in the university's 17 residences. 63 percent of the university's total enrolment is for undergraduate study, with 35 percent being postgraduate and the remaining 2 percent being Occasional Students. The 2017 Academic Ranking of World Universities (ARWU) places Wits University, with its overall score, as the highest ranked university in Africa. Wits was ranked as the top university in South Africa in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lyn Wadley
Lyn Wadley is an honorary professor of archaeology, and also affiliated jointly with the Archaeology Department and the Institute for Evolution at the University of the Witwatersrand in Johannesburg, South Africa. Education Wadley received her master's degree from the University of Cape Town in 1977, and her PhD from the University of the Witwatersrand in 1986. Career Wadley taught in the School of Geography, Archaeology and Environmental Studies and the Evolutionary Studies Institute, University of the Witwatersrand from 1982 to 2004. Wadley began her career researching social and ecological issues in the Later Stone Age in South Africa. This included the first considerations of gender in the archaeological record of Southern Africa, as articulated by Mazel "this has firmly placed the study of gender on the South African archaeological map". She directed excavations at multiple Holocene sites in Magaliesberg and then began working on older, Pleistocene sites. Professor Wadley ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South Africa
South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the north by the neighbouring countries of Namibia, Botswana, and Zimbabwe; and to the east and northeast by Mozambique and Eswatini. It also completely Enclave and exclave, enclaves the country Lesotho. It is the southernmost country on the mainland of the Old World, and the List of countries and dependencies by population, second-most populous country located entirely south of the equator, after Tanzania. South Africa is a biodiversity hotspot, with unique biomes, plant and animal life. With over Demographics of South Africa, 60 million people, the country is the world's List of countries and dependencies by population, 24th-most populous nation and covers an area of . South Africa has three capital cities, with the executive, judicial and le ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sibudu Cave
Sibudu Cave is a rock shelter in a sandstone cliff in northern KwaZulu-Natal, South Africa. It is an important Middle Stone Age site occupied, with some gaps, from years ago to years ago. Evidence of some of the earliest examples of modern human technology has been found in the shelter (although the earliest known spears date back years). The evidence in the shelter includes the earliest bone arrow ( years old), and the earliest stone arrows (64,000 years old), the earliest needle ( years old), the earliest use of heat-treated mixed compound gluing ( years ago), and an example of the use of bedding ( years ago) which for a while was the oldest known example (an older example from years ago was recently discovered at Border Cave, South Africa).Wadley L, Sievers C, Bamford M, Goldberg P, Berna F, Miller C. (2011)Middle Stone Age Bedding Construction and Settlement Patterns at Sibudu, South Africa Science 9 December 2011: Vol. 334 no. 6061 pp. 1388–1391. An older example is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spear-thrower
A spear-thrower, spear-throwing lever or ''atlatl'' (pronounced or ; Nahuatl ''ahtlatl'' ) is a tool that uses leverage to achieve greater velocity in dart or javelin-throwing, and includes a bearing surface which allows the user to store energy during the throw. It may consist of a shaft with a cup or a spur at the end that supports and propels the butt of the spear. It's usually about as long as the user's arm or forearm. The user holds the spear-thrower in one hand, gripping near the end farthest from the cup. The user puts the butt end of the spear, or dart, in the cup, or grabs the spur with the end of the spear. The spear is much longer than the thrower. The user holds the spear parallel to the spear-thrower and going in the other direction. The user can hold the spear, with the index and thumb, with the same hand as the thrower, with the other fingers. The user reaches back with the spear pointed at the target. Then they make an overhand throwing motion with the thrower ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Throwing Stick
The throwing stick or throwing club is a wooden rod with either a pointed tip or a spearhead attached to one end, intended for use as a weapon. A throwing stick can be either straight or roughly boomerang-shaped, and is much shorter than the javelin. It became obsolete as slings and bows became more prevalent, except on the Australian continent, where the native people continued refining the basic design. Throwing sticks shaped like returning boomerangs are designed to fly straight to a target at long ranges, their surfaces acting as airfoils. When tuned correctly they do not exhibit curved flight, but rather they fly on an extended straight flight path. Straight flight ranges greater than 100 meters have been reported by historical sources as well as in recent research. Distribution The ancient Egyptians used throwing sticks to hunt small game and waterfowl, as seen in several wall paintings. The 18th-dynasty pharaoh Tutankhamun was a known lover of duck hunting and us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fixed-wing Aircraft
A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane, which is capable of flight using wings that generate lift caused by the aircraft's forward airspeed and the shape of the wings. Fixed-wing aircraft are distinct from rotary-wing aircraft (in which the wings form a rotor mounted on a spinning shaft or "mast"), and ornithopters (in which the wings flap in a manner similar to that of a bird). The wings of a fixed-wing aircraft are not necessarily rigid; kites, hang gliders, variable-sweep wing aircraft and airplanes that use wing morphing are all examples of fixed-wing aircraft. Gliding fixed-wing aircraft, including free-flying gliders of various kinds and tethered kites, can use moving air to gain altitude. Powered fixed-wing aircraft (airplanes) that gain forward thrust from an engine include powered paragliders, powered hang gliders and some ground effect vehicles. Most fixed-wing aircraft are flown by a pilot on board the craf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerodynamics
Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dynamics and its subfield of gas dynamics. The term ''aerodynamics'' is often used synonymously with gas dynamics, the difference being that "gas dynamics" applies to the study of the motion of all gases, and is not limited to air. The formal study of aerodynamics began in the modern sense in the eighteenth century, although observations of fundamental concepts such as aerodynamic drag were recorded much earlier. Most of the early efforts in aerodynamics were directed toward achieving heavier-than-air flight, which was first demonstrated by Otto Lilienthal in 1891. Since then, the use of aerodynamics through mathematical analysis, empirical approximations, wind tunnel experimentation, and computer simulations has formed a rational basis fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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