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본 연구에서는 2차원 NACA 0024 에어포일에서 앞전 슬릿흡입과 riblets이 경계층 구조에 미치는 영향에 대하여 실험적으로 고찰 하였다. 슬릿흡입(slit suction)에서 슬릿의 위치와 수, 자유흐름속도, 받음각 그리고 슬릿 흡입량이 중요한 변수이다. 슬릿흡입과 리블렛(riblets)이 설치된 2차원 에어포일의 양력계수와 항력계수 실험결과를 제시하였다. 에어포일에 슬릿 흡입을 적용하면 양력계수 항력계수가 다같이 증가된다. 원형 리블렛이 설치된 에어포일 모델에서는 양력계수가 증가되고 항력계수가 감소된다. An exprimental study on manipulation of the boundary layer of the two-dimensional NACA 0024 airfoil with slit suctions and riblets is presented. The slit locations, the number of slits, free stream velocity, angle of attack and the suction rate coefficient are variables. Exprimental results for the lift and drag coefficients of the two-dimensional airfoil with slit suctions and riblets are presented. When the slit suction is applied on the airfoil wall the lift and drag coefficients increase. Airfoil model with round riblets on the wall shows an increase of the lift coefficients and a decrease of the drag coefficient.
The aim of this study is to clarify regional characteristics by examining various factors having developed dispersed pattern of settlements on the Tae-An Peninsula, Choong Cheung Province. For the purpose of this study, intensive bibliographical studies of data concerned with this area were done and used actual field work. Results of this study may be summarized: (1) Tae-An peninsular, which belongs to Choongcheung Nam-Do and is bordered with the Gyeon gi Bay, has not been closely connected with the central area of the Gyeunggi Province for a long time. About 79% of the peninsula is made up of low mountains and hills. Plains and rivers are poorly developed, arable lands do not extend continuously in the peninsula. Ground water level is comparatively high and the entire land is well-drained. These physical characteristics supply foundations for the development of dispersed settlements. (2) Tae-An peninsular is one of places which have long been inhabited by men. For .a long time in its history, this peninsula was quite important for water transportation. In particular, in the Koryo and the Yi-Dynasties it was considered as a place of much importance on account of its water transportation of taxation rice. There were in this peninsula two attempts of constructing a canal accross it. (3) To defend the peninsula from the invasions of the Japanese pirate raiders and preserve human lives and properties, the inhabitants of this peninsula formed military villages and other villages surrounded with walls. At the end of the Koryo Dynasty, however, frequent invasions of the Japanese raiders forced the villagers to move to some .other places. The settlements which had been developed in the pre-historical era was since then devastated. (4) At the beginning of the Yi Dynasty these settlements were redeveloped. Since the majority of the villagers originally inhabited in this peninsula had moved to other regions, others who came into this peninsula formed new settlements. In addition to the common men who moved to this peninsula many noble men rusticated here from Seoul. These flows of population caused the number of population in this peninsula to increase with the result of maintaining. the lineage of the family. (5) It is estimated that tie dispersed villages of this peninsula were generally formed in the early Yi Dynasty. The villagers were for the most part composed of rusticated people and others flowed into this peninsula and villages had comparatively broad arable lands. These dispersed villages still remain almost as they were in the past. As suggested above, the development of these dispersed villages was not due to one single. factor, but to various factors such as the physical features, population outflows and inflows, the mode of choosing places for inhabitation in accordance with the theory of Poong-Soo, the relationship between the nobility and the common people, and tenant farming. These dispersed villages involve some factors which may interfere with the New Country Movement. For example, the difficulty incooperation between or among villages and in suppling electricity to all the villages. Besides, this peninsula is geographically vulnerable to the North Korean invasion: This is why the Government intends to bring together the small villages into larger ones. It is expected therefore that the traditionally dispersed villages in this peninsula will be grouped in the near future.
A wing moving through a fluid induces a differential pressure field between the upper and lower surfaces. The resultant spanwise movement of fluid combined with the free stream velocity generates a helical movement of fluid about the wing tip called trailing vortex. The induced drag of the wing is caused by this trailing vortex. This paper deals with an experimental results to decay such a trailing vortex int he recent years. The purpose of this investigation was to determined the effect of the wing geometry to decay a vortex in vortex flow such as propeller slip stream. The experimental investigation utilize a small vorticity meter to measure the vorticity strength behind the wing tip. The investigation considers the aspect ratio and taper ratio of the wing as a parameter that affect the strength of the trailing vortex. The following conclusions can be drawn. (1) The vorticity of the trailing vortex can be reduced to 0.5 by fitting a small wing in vortex flow line at the incidence angle of 10 detrees. (2) The vortex decay by the geometry of the wing are as follows. (3) The vorticity decrease with increasing aspect ratio and have its maximum value at A.R=4. (4) The vorticity of the trailing vortex decrease with increasing taper ratio.
A new variable wing that can be swept back and forward synchronously were developed to enhance the aerodynamic and stability characteristics of a high speed airplane. The configuration of the new variable wing changes in such a way that inner part of the wing sweeps forward and outer part of the wing sweeps backward, the shift of aerodynamic center of the wing is small, therfore the static margin that is required for the stability of a airplane is not affected. In this study, various configurations of wing models by combined swept back and forward were designed and a wind tunnel tests were conducted to investigate the aerodynamic characteristics of these variable wings. The experimental results showed that the variable wing by combined swept back and forward has no effect on the pitching moment coefficient affecting on an aircraft stability margin and enhance the aerodynamic characteristics for a given approach angle of attack.
An experimental study was performed on the time lag. lift and drag characteristics of a multi functional spoiler which is a device to increase lift and drag contrary to conventional spoiler which decrease lift and increase drag. In this study, a wind tunnel investigation was made of the effect of incidence angle, slot width, and chordwise location of multi functional spoiler on the time lag, lift and drag characteristics of a wing. The results indicate that the time lag of a multi functional spoiler is influenced mainly not only by the chordwise location of a spoiler but also by the slot width between spoiler and wing upper surface. Multi functional spoiler can reduce time lag effectively by slotting the trailing edge of spoiler with slot ratio(slot width devided by the wing chord length) between 0.05 and 0.1. Also, it shows that the lift and drag coefficients of the wing with the multi functional spoiler and trailing edge flap are increased by 20% and 80%. respectively, compared to the wing with trailing edge flap only.
산악이 많은 한국과 같은 지형적 조건에서 운용 가능한 지역 운송용 항공기를 설계하기 위한 임무 요구조건을 설정하고 유사기종에 대한 성능 분석을 하였다. 성능 분석에 따라 설계의 초기 파라미터를 결정하였고 초 단거리 이, 착륙 성능 구현을 위하여 새로운 개념의 고양력 장치인 고관성 Pre&Autorotating 로터를 도입하였다. 고관성 로터의 풍동실험 결과를 토대로 Prerotation에 의해 고관성 로터에 저장된 운동에너지를 발산시키는 방법에 의한 이륙 방식과 자동회전하는 로터를 이용하여 착륙하는 방식에 대하여 검토하였고 설계 파라미터간의 관계에 대해 고찰하였다. 가능성 검토의 결과 고관성 Pre&Autorotating 로터는 순항 성능을 훼손하지 않고 초단거리 이, 착륙 수송기를 설계하기 위한 보조 양력 증가장치로서 매우 유용할 수 있음을 알 수 있었다. Mission specifications were established for the regional transport aircraft which is operatable in the mountainous country like korea, and the performance of similar regional aircraft were analyzed. After that, for the research the initial design parameters were set simultaneously introducing the high inertia Pre&Autorotating rotor concept as a new high lift device. Feasibility research was made based on the wind tunnel test results of high inertia rotor for the ways of dissipating kinetic energy stored in the high inertia rotor for the take-off and of using autorotating rotor for the landing, correlations between design parameters were studied too. feasibility study indicated that the high inertia Pre&Autorotating rotor could be very useful augmented lift device in order to design super STOL transport not deteriorating cruising performance.