descent

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descent,

in anthropology, method of classifying individuals in terms of their various kinship connections. Matrilineal and patrilineal descent refer to the mother's or father's sib (or other group), respectively. Bilateral descent refers to descent derived from both sibs equally. Descent groups are of basic significance in the social structure of most nonindustrial societies. They constitute a series of social groups that dominate the domestic organization and the process of socialization, the use and transfer of property, the settlement of disputes, religious activities such as ancestor worship, and certain political relationships. Some lineage systems extend to the limits of the society itself. The Tiv of E Nigeria, for example, all consider themselves descendants in the male line of an eponymous ancestor, and the genealogy of this progeny defines the complete outline of descent group structure.

descent

(ANTHROPOLOGY) the means by which individuals are allocated to specific ancestral groups. If a society has descent rules, they will specify the basis of the construction of LINEAGES, with all the rights and obligations which go with such membership. Descent may be based on PATRILINEAL, MATRILINEAL, BILATERAL or NON-UNILINEAL principles, and its discussion was central to postwar British SOCIAL ANTHROPOLOGY.

Descent

 

in astronautics, the downward trajectory of a spacecraft or descent vehicle through dense layers of an atmosphere or in a vacuum prior to landing on the surface of a celestial body. During descent onto the surface of a planet that possesses an atmosphere, the velocity of a spacecraft is reduced by any force of resistance to the spacecraft’s motion, for example, by aerodynamic drag. Descent with atmospheric braking is most useful for landing spacecraft on the surface of a planet with a rather dense atmosphere. In this case, only a descent vehicle is usually involved, not the entire spacecraft. Atmospheric braking reduces the velocity of the descent vehicle to 150–250 m/sec. Further deceleration and the landing are usually accomplished by means of parachute and other braking systems.

Descent with atmospheric braking may have either a ballistic or a glide trajectory. During a glide descent, the descent vehicle is subject to lift as well as the force of gravity and any resistance forces. The vehicle is subjected to less load in a glide descent than in a ballistic descent, and maneuvering is also possible. If descent in the atmosphere is not preceded by retrorocket braking—using a rocket engine that generates thrust opposite in direction to the motion of the spacecraft—the spacecraft will enter the atmosphere with a high velocity (of the order of orbital velocity for a spacecraft orbiting relatively near a planet or escape velocity for a spacecraft approaching a planet from a great distance). In this case, deceleration is accompanied by overloads and heating of the spacecraft. The reduction of these and other effects at velocities greater than orbital velocity is possible only in a controlled descent or as a result of gradual braking of the landing craft upon multiple passes of the craft through the atmosphere of the planet. Retrorocket braking is used for the descent of a spacecraft onto a celestial body without an atmosphere.

The first return to earth at orbital velocity after an orbital flight was accomplished by the American satellite Discoverer 13 on Aug. 11,1960. The first earth landing of a satellite after an orbital flight was accomplished by the second Soviet orbital spacecraft on Aug. 20, 1960. The first return to earth of a spacecraft with escape velocity was accomplished by the American spacecraft Apollo 4 on Nov. 9, 1967, and the first return to earth of a spacecraft with escape velocity after orbiting the moon was accomplished by the Soviet spacecraft Zond 5 on Sept. 21,1968 (ballistic descent). The first descent and landing on a celestial body when lacking an atmosphere was accomplished on Feb. 3, 1966, when the Soviet space probe Luna 9 landed on the moon. The first descent from escape velocity in the atmosphere of another planet (Venus) was accomplished by the Soviet space probe Venera 4 on Oct. 18, 1967. The first landing on another planet (Venus) was achieved by the Soviet space probe Venera 7 on Dec. 15, 1970, and the first descent and landing on Mars was accomplished by the Soviet space probe Mars 3 on Dec. 2, 1971.

What does it mean when you dream about a descent?

A dream of descending in an elevator—or by any other means—may indicate a decline in energy or status. Alternatively, it may symbolize descent into the unconscious in a journey of self-discovery.

descent

[di′sent]
(aerospace engineering)
Motion of a craft in which the path is inclined with respect to the horizontal.

descent

1. derivation from an ancestor or ancestral group; lineage
2. (in genealogy) a generation in a particular lineage
3. Property law (formerly) the transmission of real property to the heir on an intestacy
References in periodicals archive ?
One shouldn't ask for precision in speed and descent rate but casually consider where the approach should begin.
Increased signage and emphasis on requirement for heavy vehicles to use low gear not brakes on descent from Crafers,
We obtain generating functions for the descents occurring immediately after the first and the last maxima, by splitting these compositions into blocks that occur before and after these maxima.
The memories and images of the last few days bring smiles to our faces: the almost blind descent through thick fog, over the gently curved glacier at Piz Calderas; the snow hole at the cornice of Piz Traunter-Ovas, where we waited for a break in the weather; the lively banter we enjoyed over a glass of wine in the warm bothy; the ascent through the couloirs at Piz d'Err in powdery snow; the astonished faces of a ski touring group, as they watched us shoot out of the couloirs, right over the glacier and down into the north face; the detour we took, where parts of the glacier had broken off; the endless north face, wide and covered in fresh snow; the solitude and the warm sun--these are just some of the elements that made this such an extraordinary and special adventure.
THE DESCENT PART 2 (18) Verdict: WRITER-director Neil Marshall's original hit The Descent (2005) remains one of the most claustrophobic British horror films of the decade.
Conversely, descents in the physical world are characterised by "displacement" (tajf).
Most people go to the theme park, and they don't look at what's going on behind the scenes,'' said Luan, who worked alongside fellow classmate Tony Jiang to determine how close the steepest descent on the Scream ride comes to free fall.
Thus, songs which have in them three descents have the form Type I followed by Type II followed by Type I--I II I.
The descent is usually made to rescue someone either abducted or rightfully dead, to find the answer to a question or discover a secret from the ruler of the underworld, or to seize some treasure.
SAS estimates from a potential 36,000 optimized descents yearly into Stockholm alone, annual benefits could reach $6 million in fuel savings with an additional $4 million in cost avoidance due to the increased efficiency and punctuality of aircraft using GE's FMS.
We've talked about constant angle descents for months, but have you flown one?