• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 추계학술대회 논문집
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• pp.14-17
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• 2004

A purpose of this visual experiment is to investigate the effect of reduced frequency qualitatively by examining wake pattern change for insect flying motion. Insect is composed of two pair wing with forewing and hindwing, flying motion of insect is performed pitching and plunging so it makes a separation over the wings. The separation affects at the wake pattern and changed wake pattern has an influence on lift, drag and propulsion. This experiment is conducted by using a smoke wire technique and a camera is fixed at hindwing to take a photograph of wake. An electronic device is mounted below test section to find exact the mean positional angle of wing. The reduced frequency in experiment is 0.15, 0.3 and 0.45. We obtained the result which that reduced frequency is closely related to wake pattern that determines flight efficiency.

• 한국의류산업학회지
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• 제11권3호
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• pp.445-452
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• 2009

This study aims to improve the fit of high school girls' uniforms. This study researched on the fit of the recent high school girls' uniforms and developed a sizing system that adequately reflects their body figures. The results are as follows. First, the research showed that over 50% of the highschool girls wore their blouses too tight, whereas over 60% of the girls wore skirts that were appropriately fitted. Second, to classify the high school girls' figures, factor analysis and cluster analysis were conducted. 5 factors were extracted for upper body and 3 factors for the lower body. The girls were then divided into 3 groups for the upper body and 4 groups for the lower body. Third, KS size intervals were used for frequency distribution of height and bust for the bodice, height and waist for the lower body. Sizing system of the uniform company and the frequency distribution of sizes were compared. As a result, sizing system of the uniform company and the frequency distribution slightly overlapped. Fourth, sizing system considering body type distribution and high frequency distribution section of sizes was suggested. As a result, for the upper body, when 6 sizes were suggested, 43.9% of the population was covered and when 11 sizes were suggested, 58.3% was covered. For the lower body, when 6 sizes were suggested, 32.2% was covered, and when 11 sizes were suggested 58.9% of the population was covered.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1360-1364
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• 2014

In this paper, RCS characteristics on defect pattern of crossed dipole slot FSS having a finite size have been analyzed. To analyze RCS, we applied the electric field integral equation analysis which applies BiCGSTab algorithm with iterative method and uses RWG basis function. To verify the validity of this paper, RCS of PEC sphere has been compared to the theoretical results and FSSs with defect patterns are fabricated and measured. As defect patterns in FSS, missing one column, missing some elements, and discontinuity in surfaces are simulated and compared with the measurement results. Resonant frequency shifts in pass band and changes in bandwidth are observed. From the results, precisely predicting and designing frequency characteristics over defect patterns are essential when applying FSS structures such as FSS radomes.

• 한국전자파학회논문지
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• 제12권4호
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• pp.651-658
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• 2001

본 논문에서는 마이크로파대 광대역 다단 평면형 전력분배기의 설계방법과 구조를 새로이 제안하였다. 제시된 마이크로파 광대역 전력분배기의 설계과정은 평면형 다단 3-포트 하이브리드와 도파관트랜스포머 설계로 구성되었다. 다단 전력분배기는 최적화된 λ/4 트랜스포머 설계이론에 근거를 두고 있다. 두 인접 출력포드의 광대역 격리 특성을 얻기위해, 기모드 등기회로는 저항 같은 손실소자를 사용하여 정합되어야 한다. 기모드 정합소자 값을 계산하기 위한 설계공식은 단일 종단 여파기 설계이론으로부터 유도하였다. 도파관 트랜스포머단의 형상은 하우징 금속전계벽의 영향으로 인한 도파관 모드와 같은 고차모드의 전파를 억제하기 위해 설계되었다. 따라서, 설계된 각각의 도파관 트랜스포머단에서는 제안된 마이크로파 광대역 전력 분배기의 동작주파수 영역에서 모두 감쇄모드(evanescent mode)로 동작하여야 한다. 본 논문에서는 제안된 마이크로파 광대역 전력분배기의 검증을 위해, 다단 전력 분배기의 시뮬레이션과 실험 결과들을 제시하였다. 시뮬에이션과 실험 결과는 다단 전력분배기의 우수한 성능을 보여준다.

• 한국연소학회지
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• 제3권1호
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• pp.59-69
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• 1998

The results of study on the active control of naturally occurring combustion oscillations with a single dominant frequency in an atmospheric dump combustor are presented. Control was achieved by an oscillatory infection of secondary fuel at the dump plane. A high speed solenoid valve with a maximum frequency of 250Hz was used as the actuator and a sound level meter, located at the combustor exit, measured the pressure fluctuations which served as the feedback signal for the control loop. Instability characteristics were mapped over a range of mean mixing section velocities from 6.7 m/s-9.3 m/s and with three mixing conditions. Different fuel/air mixing conditions were investigated by introducing varying percentages of primary fuel at two locations, one at the entrance to the mixing section and one 6 mixing tube diameters upstream of the dump plane. Control studies were conducted at a mean velocity of 9.3 m/s, with an air temperature of $415^{\circ}C$, and from flame blowout to the stoichiometric condition.

• 한국공간구조학회논문집
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• 제5권4호
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• pp.101-108
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• 2005

고층건물의 진동응답을 저감시키기 위한 다양한 방법들이 연구되고 있다. 이들 진동응답의 저감 연구는 건물의 외관을 병화 시키는 방법과 건물에 부가감쇠장치를 설치하는 방법들이 있는데 본 논문에서는 고층 건물의 형태의 변화에 다른 진동변위응답의 특성을 파악하고자 한다. 고층건물의 형태변화 중에서도 외관에 테이퍼를 수는 방법을 사용하였다. 기류의 특성은 도심 및 교외지역을 중심으로 풍동실험을 실시하였다.

• 대한전자공학회논문지
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• 제11권6호
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• pp.38-43
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• 1974

임의의 전원임피이던스와 임의의 부하임피이던스 사이에 삽입할 때 입력반사계수가 가급적 넓은 주파수범위에서 최소가 되는 임피이던스 정합용 불균일선로 섹션을 설계하는 문제를 고찰하였다. 고려대상의 불균일선로는 수학적으로는 특수한 종류에 속하는 것이나 실제적으로는 완만하게 변하는 거의 모든 전송선로를 포괄할 수 있다. 입력반사 계수의 계산에서는 선로의 ABCD 파라미터의 테일러 급수전관식을 이용하였다. 그리고 설계문제를 비선형 구속조건을 가진 비선형 프로그래밍 문제로서 수식화하였으며 이것을 수차적비구속 최소법(Sequential Unconstrained Minimigation Technique)과 Fletcher-Powell 방법을 병용하여 풀었다. 결과적으로 이제까지 광대역 임피이던시 정합편 전송선제로서 발표된 가장 우수한 것보다 훨씬 특성이 개선된 것을 얻을 수 있었다.

• ETRI Journal
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• 제15권3_4호
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• pp.1-26
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• 1994

Simulated annealing is an attractive, but expensive, heuristic method for approximating the solution to combinatorial optimization problems. Attempts to parallel simulated annealing, particularly on distributed memory multicomputers, are hampered by the algorithm's requirement of a globally consistent system state. In a multicomputer, maintaining the global state S involves explicit message traffic and is a critical performance bottleneck. To mitigate this bottleneck, it becomes necessary to amortize the overhead of these state updates over as many parallel state changes as possible. By using this technique, errors in the actual cost C(S) of a particular state S will be introduced into the annealing process. This paper places analytically derived bounds on this error in order to assure convergence to the correct optimal result. The resulting parallel simulated annealing algorithm dynamically changes the frequency of global updates as a function of the annealing control parameter, i.e. temperature. Implementation results on an Intel iPSC/2 are reported.

• Steel and Composite Structures
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• 제2권3호
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• pp.223-236
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• 2002

An analytical procedure based on the transfer matrix method to estimate not only the natural frequencies but also vibration mode shapes of the thin-walled members composed of interconnected cylindrical shell panels is presented. The transfer matrix is derived from the differential equations for the cylindrical shell panels. The point matrix relating the state vectors between consecutive shell panels are used to allow the transfer procedures over the cross section of the members. As a result, the interactions between the shell panels of the cross sections of the members can be considered. Although the transfer matrix method is naturally a solution procedure for the one-dimensional problems, this method is well applied to thin-walled members by introducing the trigonometric series into the governing equations of the problem. The natural frequencies and vibration mode shapes of the thin-walled members composed of number of interconnected cylindrical shell panels are observed in this analysis. In addition, the effects of the number of shell panels on the natural frequencies and vibration mode shapes are also examined.

• 아시안잔디학회지
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• 제13권4호
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• pp.181-190
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• 1999

This study was carried out to survey green system, area, green slope, green turfgrass variety, green section, and particle size of green construction materials, and to investigate and evaluate the characteristics of Design and Construction in Korean golf course green for improving the quality of Korean golf course into that of the international golf course held international tournament. The results were as follows. 1. The greens of 129 Korean golf courses consisted of 2(two) green system and 1(one) green system. 2(two) green system was 50.8%, 1(one) green system was 40.7%, and 1+2 green system was 8.5% of them. 2. In 48 Korean golf courses, the green area of 2(two) green system was mostly 400~$600\m^2$(56.5%) and the green area of 1(one) green system was mostly 600~$800\m^2$(47.8%). In 48 Korean golf courses, 1.5~3% green slope appeared the highest frequency(50.0%) and the next was 3~5%(29.4%). 3. Penncross variety was the highest frequency(71.2%). The next was mixed variety (Penncross+Crenshaw, Penn A-1, Pennlinks, or Penneagle/SR 1020+SR 1019) and the frequency of mixed variety was 7.6%. 4. In 48 Korean golf courses, 70~80cm total thickness of green appeared the highest frequency(36.1%), 10~20cm thickness of green mixed sandy layer appeared the highest frequency(43.6%), and 10~20cm thickness of green coarse sandy layer appeared the highest frequency(55.6%). 0~10cm thickness of green gravel layer appeared the highest frequency(67.6%), 20~30cm thickness of green drain layer appeared the highest frequency(52.8%), and 20~30cm width of green drain layer appeared the highest frequency(44.4%). Below 1mm sand diameter used in green mixed sandy layer appeared the highest frequency(46.2%), below 2mm or over 2mm sand diameter used in green coarse sandy layer appeared the highest frequency(31.4%). 20~40mm coarse gravel diameter used in green gravel layer appeared the highest frequency(43.2%) and 0~20mm fine gravel diameter used in green gravel layer appeared the highest frequency(65.8%). 20~40mm gravel diameter used in green drain layer appeared the highest frequency(64.1%).