• Computers and Concrete
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• 제4권5호
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• pp.331-346
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• 2007

A computer program was developed to analyze the non-linear, cyclic flexural performance of reinforced concrete structural members under various types of loading paths including non-sequential variations in axial load. This performance is significantly affected by the loading history. Different monotonic material models as well as hysteresis rules for confined and unconfined concrete and steel, some developed and calibrated against test results on material samples, were implemented in a fiber-based moment-curvature and in turn force-deflection analysis. One of the assumptions on curvature distribution along the member was based on a method developed to address the variation of the plastic hinge length as a result of loading pattern. Functionality of the program was verified by reproduction of analytical results obtained by others for several cases, and accuracy of the analytical process and the implemented models were evaluated against the experimental results from large-scale reinforced concrete columns tested under the analyzed loading cases. While the program can be used to predict the response of a member under a certain loading pattern, it can also be used to examine various analytical models and methods or refine a custom material model against test data.

• 한국자동차공학회논문집
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• 제6권6호
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• pp.155-165
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• 1998

The resistance coefficient and heat transfer performance are studied for the turbulent water flow in a smooth coiled tube having variable curvature ratios and a corrugated-coiled tube having a ratio of coil to tube diameter of 22. Experiments are carried out for the fully developed turbulent flow of water in tube coils on the uniform wall temperature condition. This work is limited to tube coils of R/a between 22 and 60 and Reynolds numbers from 13000 to 53000. The tube having a ratio of coil to tube diameter of 27 among the 3 smooth tube coils shows the best heat transfer performance. A corrugated-coiled tube(R/a=60) shows more excellent performance than a smooth coiled tub (R/a=60) at a similar curvature ratio. The friction factor f is sensitive to changes in the velocity profile caused by a temperature gradient. Allowance was made for the pressure loss in the short inlet and outlet lengths and due to the presence of the thermocouple inlet and outlet as a result of separate experimental on a straight tube. It is to be expected that the allowance at the exit will be somewhat too low because of secondary flow effects carried over from the coil.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1480-1486
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• 2002

In this study, the cross-coupling control (CCC) with three new features is proposed to maintain contour precision in high-speed nonlinear contour machining. One is an improved contour error model that provides almost exact calculation of the errors. Another is the utilization of variable controller gains based on the instantaneous curvature of the contour and the variable command. For this scheme, a stability is analyzed. As a result, the stability region is obtained, and the variable gains are decided within that region. The other scheme in the proposed CCC is a real-time feedrate adaptation module to regulate cutting force fur better surface finish through regulation of material removal rate (MRR). The simulation results show that the proposed CCC system can provide better precision than the existing method particularly in high-speed machining of nonlinear contours.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.265-268
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• 2008

The safety of a tunnel under seismic motion is most often evaluated by ovalling deformation of tunnel. This paper research about tunnel's longitudinal deformation. Because of spatial variation of seismic ground motion, the longitudinal structures like tunnel are likely to experience relative displacements along longitudinal direction. The spatially variable ground motion can be estimated by coherency function obtained empirically, and can be considered from different arrival times of ground motion. As a result of estimating tunnel's relative displacements at maximum curvature of tunnel, the displacements and curvatures estimated by coherency function affect the tunnel's safety more than different arrival times. However, if tunnel's displacements by coherency function superpose on displacements by different arrival times, the relative displacements and curvatures of tunnel will be more severe. Therefore, to estimate accurately tunnel's deformation in longitudinal direction has to consider both coherency and wave passage effects.

• Advances in aircraft and spacecraft science
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• 제9권2호
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• pp.103-117
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• 2022

In this paper, a novel morphing mechanism using a deployable scissor structure was proposed for a variable camber morphing wing. The mechanism was designed through the optimization process so that the rib can form the target airfoils with different cambers. Lastly, the morphing wing was manufactured and its performance was successfully evaluated. The mechanism of the morphing wing rib was realized by a set of deployable scissor structure that can form diverse curvatures. This characteristic of the structure allows the mechanism to vary the camber that refers to the airfoil's curvature. The mechanism is not restrictive in defining the target shapes, allowing various airfoils and overall morphing wing shape to be implemented.

• 한국정보과학회논문지:소프트웨어및응용
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• 제32권1호
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• pp.22-33
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• 2005

본 논문에서는 얼굴 형태와 유사한 타원체형 모델의 가변적 블록크기를 기반으로 하는 영상정렬 알고리즘을 제안한다. 블록정합 수행 시 좌우 곡률만을 고려한 기존의 실린더형 원형모델 방법은 좌우 영상에 대하여 정확한 정렬을 수행하지만 상하 영상에 대해서는 사람의 두상모양이나 턱 구조의 특징을 반영하지 않았기 때문에 정렬오류가 발생한다. 본 논문에서 제안한 알고리즘은 타원체형 얼굴 모델의 상하 좌우의 곡률에 따라 가변적인 블록크기를 사용하는 블록정합 알고리즘으로서 영상의 상관관계를 이용하여 정확한 정렬을 할 수 있다. 그리고 정렬된 영상으로부터 얼굴 텍스쳐 영상을 생성하기 위하여 영상 모자익 기법을 사용한다. 이때 중첩된 영역에 따라 선형적인 가중치를 부여하여 영상을 스티칭하고 부분적으로 나타나는 고스트 효과를 제거함으로써 더 실감 있는 텍스쳐를 생성한다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.34-37
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• 2006

Accoarding as a specimen for reinforced concrete bridge deck was designed by each researcher's opinions, its size and shape was variable. Therefore, it makes difficult to comparison with other experiments. In the result of researching papers for design method of reinforced concrete bridge deck specimens, there is hardly found. The target of this study is introduction of the design method of a reinforced concrete bridge deck specimen. The most important point for the specimen design is materialization of the curvature of the real bridge deck. The result of this study appears that the specimens thickness effects highly to fit for the real reinforced concrete bridge deck's curvature.

• 동력기계공학회지
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• 제3권3호
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• pp.54-59
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• 1999

The purpose of the present study was to develop the numerical method for predicting the on-design and off-design performance of multistage axial-flow compressors. The aerodynamic properties in blade rows were analyzed by incorporating the streamline curvature method as a quasi 3D analysis with the imperical modeling of exit flow angle and loss coefficients. The present calculation procedure has been tested by applying to 5-stage compressors and good agreement with experiments has been found. The detail analysis of aerodynamic performances has been done on the compression part of the bench-scaled gas turbine engines. The predicted performance map at the variable speedline and flow rates could be used as a guide of the engine operation.

• Steel and Composite Structures
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• 제46권4호
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• pp.513-523
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• 2023

Buckling and post-buckling behaviors of geometrically perfect double-curvature shells made from smart composites have been investigated. The shell has been supposed to be exposed to transverse mechanical loading and magneto-electro-elastic (MEE) coupling. The composite shell has been made of two constituents which are piezoelectric and magnetic ingredients. Thus, the elastic properties might be variable based upon the percentages of the constituents. Incorporating small scale impacts in regard to nonlocal theory leads to the establishment of the governing equations for the double-curvature nanoshell. Such nanoshell stability will be shown to be affected by composite ingredients. More focus has been paid to the effects of small scale factor, electric voltage and magnetic intensity on stability curves of the nanoshell.

• 한국재난정보학회 논문집
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• 제19권3호
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• pp.572-581
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• 2023

연구목적:이력형 댐퍼에 하중이 작용할 때 편심에 의해서 부재가 면외 방향으로 거동하는 것을 방지하여 응력-변형율 곡선의 불규칙성을 개선하고 감쇠효과의 계산 시 정확성을 기하고자 하는 것이 본 연구의 목적이다. 연구방법:본 연구에서 사용하는 강재 스트립의 제원은 동일하게 하되 각각의 댐퍼를 구성할 스트립의 곡률은 다르게 한다. 곡률이 다른 각각의 강재 스트립을 댐퍼 1개당 3개씩 정삼각형으로 배치하여 곡률이 다른 5개의 댐퍼를 제작한 후 반복하중 실험을 수행하고, 에너지 소산량을 계산하여 댐퍼의 감쇠성능을 측정하였다. 연구결과: 시험 결과, 댐퍼 중에서 초기곡률이 조금이라도 있는 경우는 없는 경우보다 에너지 소산량은 상당히 감소하지만, 곡률의 크기에 따른 에너지 소산량의 변화는 크지 않으며, 곡률의 유무가 중요한 변수로 사료된다. 결론:댐퍼를 적용한 해석적 검토에서 주기는 T=0.3sec에서 T=0.536sec로 약 78.7% 정도 장주기화 되었고, 응답 스펙트럼 가속도는 Sa=0.54g에서 Sa =0.229g로 줄었으므로 댐퍼의 감쇠효과는 충분히 존재한다.