• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.694-699
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• 2007

The spacer grid set is a part of a nuclear fuel assembly. The set has a spring and the spring supports the fuel rods safely. Although material nonlinearity is involved in the deformation of the spring,nonlinearity has not been considered in design of the spring. Recently a nonlinear response structural optimization method has been developed using equivalent loads. It is called nonlinear response optimization equivalent loads (NROEL). In NROEL, the external loads are teansformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response no EL. The objective function is defined by minimizing the maximum stress in the spring while is limited and the support force of the spring is larger than a certain value. The results are verified by nonlinear. ABAQUS is used for nonlinear response analysis and GENESIS is employed for linear response optimization.

• 대한기계학회논문집A
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• 제31권11호
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• pp.1059-1068
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• 2007

Nonlinear response structural optimization is performed using equivalent loads (NROEL). Nonlinear response optimization is extremely cost because many nonlinear analyses are required. In NROEL, the external loads are transformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response field of linear analysis as that of nonlinear analysis. The primitive from of theory has been published. In this research, the theory is investigated with large scale example problems. Four examples are solved by using NROEL. Conventional optimization with sensitivity analysis using the finite difference method (FDM) is also applied to the same examples. Moreover, response surface optimization method is applied to the last two examples. The results of the optimizations are compared. In nonlinear response optimization of large scale problems, hundreds (or even thousands) of nonlinear analyses are expected to satisfy the convergence criteria. However, in nonlinear response optimization using equivalent loads, only tens of nonlinear analyses are required. The results are discussed and the usefulness of NROEL is presented.

• Earthquakes and Structures
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• 제8권5호
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• pp.957-976
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• 2015

Recently, two energy-based response parameters, i.e., the absolute and the relative elastic input energy equivalent velocity, have been receiving a lot of research attention. Several studies, in fact, have demonstrated the potential of these intensity measures in the prediction of the seismic structural response. Although some ground motion prediction equations have been developed for these parameters, they only provide marginal distributions without information about the joint occurrence of the spectral values at different periods. In order to build new prediction models for the two equivalent velocities, a large set of ground motion records is used to calculate the correlation coefficients between the response spectral values corresponding to different periods and components of the ground motion. Then, functional forms adopted in models from the literature are calibrated to fit the obtained data. A new functional form is proposed to improve the predictions of the considered models from the literature. The components of the ground motion considered in this study are the two horizontal ones only. Potential uses of the proposed equations in addition to the prediction of the correlation coefficients of the equivalent velocity spectral values are shown, such as the prediction of derived intensity measures and the development of conditional mean spectra.

• 정보관리학회지
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• 제21권4호
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• pp.27-47
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• 2004

본 연구에서는 다국어 시소러스에 수록된 디스크립터간의 관계를 온톨로지 언어로 표현하는 실험을 수행하였다. 대등관계는 equivalentClass와 equivalentProperty, sameAS 등으로, 그리고 연관관계는 ObjectProperty을 비롯하여 DatatypeProperty, inverseOf 등으로 표현할 수 있었다. 이러한 언어를 기반으로 실제 AAT에 배정된 디스크립터와 ICCD에서 구축한 다국어 시소러스의 디스크립터를 대상으로 디스크립터의 한글화 작업이 수행되었으며, 다국어간 개념일치를 위해 패싯개념이 시소러스 구조에 이용되었다. 본 연구를 통한 실험의 결과 다국어 시소러스를 온톨로지로 표현하기 위해서는 속성관련 온톨로지 언어를 사용하는 것이 가장 효과적임을 확인할 수 있었다.

• 대한방사선치료학회지
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• 제1권1호
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• pp.47-51
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• 1985

Authors describe some useful data when constructing tissue-equivalent compensators which would compensate tissue deficit in the treatment field of high energy electromagnetic radiation Tissue equivalent compensator is made of lucite. The ratio of compensator thickness to the thickness of tissue deficit depends on radiation energy, field size and the distance from the compensator to patient skin. When the compensator is separated from skin surface, the thickness ratio is always smaller than 1.0. This means that the larger the separation, the contribution to the total dose by means of scattered radiation from a tissue equivalent compensator is smaller. Authors propose that the thickness of lucite as tissue equivalent compensator is 0.57 times tissue deficit and the separation between compensator and skin is at least 15m for Co-60 gamma ray and 25cm for 10MV X-ray.

• Steel and Composite Structures
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• 제13권1호
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• pp.47-70
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• 2012

To enhance cable stiffness, this paper proposed a combined application of carbon fiber reinforced polymers (CFRP) and steel materials, resulting in a novel type of hybrid stay cable system especially for the cable-stayed bridges with main span lengths of 1400~2800 m. In this combination, CFRP materials can conserve all their advantages such as light weight and high strength; while steel materials help increase the equivalent stiffness to compensate for the low elastic modulus of CFRP materials. An increase of the equivalent stiffness of the hybrid stay cable system could be further obtained with a reasonable increase of its safety factor. Following this concept, a series of parametric studies for the hybrid stay cable system with the consideration of stiffness and cost were carried out. Three design strategies/criteria, namely, best equivalent stiffness with a given safety factor, highest ratio of equivalent stiffness to material cost with a given safety factor, and best equivalent stiffness under a given cost were proposed from the stiffness and cost viewpoints. Finally, a comprehensive design procedure following the proposed design strategies was suggested. It was shown that the proposed hybrid stay cable system could be a good alternative to the pure CFRP or traditional steel stay cables in the future applications of super long span bridges.

• 전산구조공학
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• 제10권3호
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• pp.203-216
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• 1997

본 논문에서는 실무에서 이동 집중하중에 대한 별도의 복잡한 구조해석을 수행하지 않고도 등분포하중에 대한 부재력으로부터 손쉽게 차량하중의 영향을 고려한 거더와 보 부재의 설계 부재력을 구할 수 있도록 등가차량하중계수를 제안하였다. 먼저 국내에서 생산되는 중,소형 차량의 조사와 외국의 주차장 관련 설계규준의 비교, 검토를 통해 주차장 구조물의 한계 활하중인 총중량 2.4ton의 설계기준차량을 설정하였으며, 이를 토대로 설계 활하중인 등분포하중(500kg/m/sup 2/)과 집중하중(P=2.4ton)에 대한 구조부재의 거동 특성을 분석하고 회귀분석을 통해 상호 관계식을 부재 길이의 함수로 구성하였다. 나아가 제안된 등가차량하중계수를 대표적인 보와 거더 부재에 적용시켜 그 효율성과 신뢰성을 검증하였다.

• 전자공학회논문지SC
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• 제40권1호
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• pp.30-38
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• 2003

Verilog HDL의 UDP(User Defined Primitive) 라이브러리는 디지털 회로 설계 과정에서 시뮬레이션을 위해 사용된다. 그러나 합성이 되지 않는 특성으로 인해 이와 등가의 게이트수준 라이브러리를 따로 만드는 데에 많은 시간과 노력이 소요된다. 등가의 게이트수준 모델이 존재하지 않을 경우 이는 테스트 과정에서 고장 검출율을 낮추는 요인이 되므로 등가 게이트수준 모델 생성은 필수적이며 이의 자동화가 필요하다. 이를 위해 매우 복잡한 알고리즘이 발표되기는 했지만 Verilog UDP library의 특성상 보다 더 간단한 알고리즘으로 구현이 가능하다. 알고리즘이 간략해짐에 따라 이를 구현하는 데에 걸리는 시간과 노력이 절약되고 프로그램 실행시간도 크게 줄일 수 있다.

• 한국전자파학회논문지
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• 제21권10호
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• pp.1121-1127
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• 2010

본 논문에서는 X-대역 Radant lens 4-bit 위상 변위기 설계에 필요한 $11.25^{\circ}$, $22.5^{\circ}$, $45^{\circ}$ 위상 변위 레이어(layer) 중에서 $45^{\circ}$ 레이어의 등가회로에 관하여 기술한다. $45^{\circ}$ 위상 변위 레이어에 대한 CST사의 MWS (Microwave Studio)와 Agilent사의 ADS(Advanced Design System) 시뮬레이션을 비교 분석하여 등가회로를 추출하고, 등가회로를 통해 얻을 수 있는 이론치와 측정치를 비교한다. 또한, 추출된 등가회로를 활용하여, 4-bit Radant lens의 위상 bit 시뮬레이션 결과도 제시한다.

• 대한기계학회논문집
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• 제14권2호
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• pp.339-348
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• 1990

Techniques which are able to predict and control dynamic characteristics, not affecting the vibrational characteristics on the modification of structural design, are being studied. As one of these techniques, experimental modal analysis is widely applied by many researchers. In this study, modal analysis is performed using transfer matrix method by a macro computer. The developed program would estimate the structural modal parameters precisely, and the validity of this program is certified by comparing with the experimental results of .GAMMA A. structure. Estimated modal parameters(natural frequency, vibrational mode, equivalent mass, etc.) are in accord with the experimental results. Also, the optimal location of the additive mass is determined by the evaluation of the vibrational mode and the equivalent mass. The relation between the additive mass and the equivalent mass is specified, and we come to know that the ratio of equivalent mass to additive mass alter linearly within the range of 20%.