• Composites Research
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• 제17권3호
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• pp.29-37
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• 2004

본 연구에서는 대변형 보이론을 이용하여 정지 비행 시 복합재 무베어링 로우터 시스템의 공력탄성학적 안정성 해석을 수행하였다. 무베어링 로우터 시스템은 유연보, 토오크 튜브, 피치 링크, 그리고 메인 블레이드로 구성된다. 유연보, 토오크 튜브, 그리고 메인 블레이드를 각각 플랩 굽힘, 리드-래그 굽힘, 비틀림 그리고 축 방향 변형의 탄성 운동을 하는 보로 가정하고, 1차원 보 요소로 모델링을 하였다. 또한, 유연보를 복합재료 적층판으로 구성된 비틀림에 유연한 직사각형 단면을 갖는 보로 모델링 하여, 1차원 보 해석에 필요한 유효 단면 상수를 얻었다. 외력으로는 2차원 준-정상 공기력 모델을 적용하였으며, 보의 유한 요소 지배방정식은 헤밀턴 원리(Hamilton's principle)를 이용하여 얻었다. 공력 탄성학적 안정성 해석을 수행하기 위하여 p-k 방법을 이용하였으며, 유연보의 적층각과 적층 순서에 따른 구조적 연성이 무베어링 로우터 시스템의 공란성 안정성에 미치는 영향을 알아보았다.

• 한국안전학회지
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• 제31권5호
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• pp.89-94
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• 2016

The objective of this study was to estimate the dynamic behavior of a personal rapid transit(PRT) track system using a rail of rectangular tube section and a rail joint of sliding type, and to compare the results with the normal rail and rail joint of a PRT track system by performing field measurements using actual vehicles running along the service lines. The measured vertical displacement of rail and sleeper, and vertical acceleration of rail for the normal rail and rail joint section were found to be similar, and the rail joint of sliding type satisfied the design specifications of the track impact factor for a conventional railway track. The experimental results showed that the overall dynamic response of the rail joint were found to be similar to or less than that of the normal rail, therefore the rail joint of sliding type for PRT track system was sufficient to ensure a stability and safety of PRT track system.

• 대한기계학회논문집A
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• 제32권1호
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• pp.63-69
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• 2008

A fatigue test on the steel welded L-shaped frame was conducted. The frame was consisted with carbon steel tube and reinforced bracket. The four type reinforced brackets were fabricated. They were two rectangular plate reinforced bracket, two sided pentagon plate reinforced bracket, triangular plate reinforced bracket and fully reinforced bracket. The fatigue test of frame was conducted with axial tension loading. The fatigue simulation of the steel welded L-shaped frame was also performed by the finite element method with code FEMFAT. The frame of fully reinforced bracket had the highest fatigue life and reinforced quality factor.

• 대한기계학회논문집
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• 제1권1호
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• pp.17-25
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• 1977

관벽의 영향을 무시할 수 있는 요기내의 액체중을 상승하는 단일공기포의 상승속도, 형산, 경로를 명확히 하고 원주형관, 정방형관, 평행평판간의 액체중을 상승하는 단일기포의 상승속도에 미치는 관벽영향을 구하였다. 원주형관을 상승하는 공기포는 dimensionless plot로 실험치를 통 적으로 표현할 수가 있었으며 관벽영향을 받지않고 관중을 상승할 수 있는 공기포에 대한 최저의 관경을 결정할 수가 있었다.

• Steel and Composite Structures
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• 제3권3호
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• pp.199-212
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• 2003

An experimental investigation of lightweight aggregate and foamed concrete contribution to the ultimate strength capacity of square and rectangular steel tube sections is presented in this study. Thirty-four simply supported beam specimens, 1000-mm long, filled with lightweight aggregate and foamed concretes were tested in pure flexural bending to calculate the ultimate moment capacity. Normal concrete-filled steel tubular and bare steel sections of identical dimensions were also tested and compared to the filled steel sections. Theoretical values of ultimate moment capacity of the beam specimens were also calculated in this study for comparison purposes. The test results showed that lightweight aggregate and foamed concrete significantly enhance the load carrying capacity of steel tubular sections. Furthermore, it can be concluded from this study that lightweight aggregate and foamed concretes can be used in composite construction to increase the flexural capacity of the steel tubular sections.

• Structural Monitoring and Maintenance
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• 제5권3호
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• pp.391-416
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• 2018

The purpose of this article is to strengthen concrete structures using buckling and non-buckling braces. Connection plates are modeled in three shapes including the effect of 1.5t hinge zone length, 2t one and without the zone (1.5t-CP, 2t-CP and WCP). According to the verification performed with ABAQUS software, the connection plates which are superior in ductility and strengthening are found. The results show adding steel braces in concrete moment frames increase the strength and stiffness of the structures up to about 12 and 3 times, respectively. The frame strength increased about 21 and 25 percent with considering the effect of 2t hinge length in connection plates compared to 1.5t-CPs and WCPs. Also the ductility of retrofitted frames with 2t-CP improved 2.06 times more than WCP ones. Thus, 2t-CP sample is the best choice for connecting steel braces to concrete moment frames for retrofitting them. Afterwards, optimum conditions for elemental coating in braces with no buckling are assessed. The length of concrete coatings could be reduced about 30 percent, and buckling did not occur. Therefore, the weight of restraining coating decreased, and its performance improved. It is worth noting that BRBs could be constructed with only steel materials, which have outer steel tubes too. In fact, only the square cross sections of the tube profiles are appropriate for removing the filler concrete, and the rectangular ones are prone to buckle around their weak axis.

• 한국전자파학회지:전자파기술
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• 제4권3호
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• pp.3-10
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• 1993

전파흡수체의 전파흡수능 측정방법은 기본적으로 다양한 마이크로파 측정법이 이용될 수 있지만, 레이다용 전파흡수체의 경우, 전파의 주파수가 높기 때문에 파장이 짧아서 측정오차가 큰 문제점이 있다. 따라서, 지금까지는 $20mm\Phi$동축관 및 구형도파관을 이용한 재료정수측정법과 전파흡수능측정기법에 관하여 검토하여 왔다. 본 논문에서는 그동안 실험실적으로 설계하여 온 X-Barn Radar용 전파홉수체를 실용의 상태에 가까운 반사 전력법에 의하여 그 성능을 예비평가하고, 실제의 target를 제작하여 X-Band Radar로 실장실험한 결과에 관하여 보고한다.

• 대한기계학회논문집B
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• 제40권9호
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• pp.613-620
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• 2016

유체의 전도율(conductivity)이 전자기유량계의 특성에 미치는 영향을 평가하기 위해 소형 전자기 유량계를 설계 제작하였다. 유량계의 측정관(measuring tube)은 $4mm{\times}3mm$의 직사각형 단면을 가지며 길이는 9 mm이다. 전극은 직경이 1.5 mm인 점전극과 단면이 $2mm{\times}3mm$인 면전극으로 설계하였다. 코일의 열 발생에 영향을 미치는 자화주파수, 회전수 및 굵기를 변화시키면서 최적값을 찾았다. 최적화된 측정관은 자속밀도(magnetic flux density) 0.04 T (400 gauss)를 발생시키며 안정되고, 선형적인 유량신호를 얻을 수 있었다. 유량계를 특성을 평가하기 위해 중량식 유량계 교정 장치를 제작하였다. 유동율 범위는 최대 $1.17{\times}10^{-5}m^3/s$(700 cc/min)이며 ISO규격에 따라 유동량 결정의 불확도를 평가하였으며 크기는 0.06 % 이내이었다. 유체의 전도율은 $3-11{\mu}S/cm$ 사이에서 조절하였다.

• 설비공학논문집
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• 제16권9호
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• pp.828-837
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• 2004

The present study investigated two-phase flow distribution, phase separation and pressure drop in multi-microchannel tubes under adiabatic condition. The test section consisted of inlet and outlet headers with the inner diameter of 19.4㎜ and 15 parallel microchannel tubes. Each microchannel tube brazed to the inlet and outlet headers and had 8 rectangular ports with the hydraulic diameter of 1.32㎜. The key experimental parameters were orientation of header (horizontal and vertical), flow direction of refrigerant into the inlet header (in-line, parallel and cross flow) and inlet quality (0.1, 0.2 and 0.3). It was found that the orientation of the header had relatively large effect on the flow distribution and phase separation, while the inlet quality didn't affect much on them. The horizontal header showed the better flow distribution and phase separation characteristics than the vertical one. The parallel flow condition with the horizontal header showed the best performance for the flow distribution and phase separation characteristics under the test conditions. Two-phase pressure drops through the microchannel tubes with the horizontal header were higher than those of the microchennel tubes with the vertical header due to gravitational effect.

• 복식
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• 제63권5호
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• pp.35-50
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• 2013

This thesis is based on the study of formativeness and versatility of Sarong. For the aim of the research, Sarongs were classified into two types: rectangular and tube, using its original form as the basis. These two types of Sarongs were divided into more detailed groups depending on the purposes of attire, such as skirts, dresses, and capes. To look into the formativeness and versatility of Sarong, the usage of wear and expression methods were observed based on these categories. The following results were found regarding the versatility of Sarong: First, Sarong has a wide degree of versatility in terms of usage. It can be worn as a skirt, a head scarf, a dress, a cape, or used as a carrier or even a sleeping bag, based on one's intention. The change of usage is often accompanied with the change of forms, as can be shown by the longyi of Myanmar, the tube type Sarong, which is used as briefs. Second, Sarong has a wide degree of versatility in terms of function. Variations of instrumental and expressive function of Sarong are observed simultaneously. The physical function sometimes coincides with the changes of usage as mentioned above. The way that Sarong's are expressed in different social situations changes depending on the wearer's social status, religion, or origin. So by looking at the way a Sarong is worn, others can tell if a person is going to social events such as festivals and weddings. Third, Sarong has a wide degree of versatility in terms of design. However, even if same usage and function is pursued, the design can be different based on an individual. This is because the external change of Sarong is affected by individuality or aesthetic sense of the wearer.