• Structural Engineering and Mechanics
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• 제61권5호
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• pp.663-674
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• 2017

The determination of the fundamental period of vibration of a structure is essential to earthquake design. Current codes provide formulas for the approximate estimation of the fundamental period of earthquake-resistant building systems. These formulas are dependent only on the height of the structure or number of storeys without taking into account the presence of infill walls into the structure, despite the fact that infill walls increase the stiffness and mass of the structure leading to significant changes in the fundamental period. Furthermore, such a formulation is overly conservative and unable to account for structures with geometric irregularities. In this study, which comprises the companion paper of previous published research by the authors, the effect of the vertical geometric irregularities on the fundamental periods of masonry infilled structures has been investigated, through a large set of infilled frame structure cases. Based on these results, an attempt to quantify the reduction of the fundamental period due to the vertical geometric irregularities has been made through a proposal of properly reduction factor.

• 대한조선학회논문집
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• 제36권2호
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• pp.94-104
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• 1999

고장력강을 주로 사용하는 선체에서 좌굴은 중요한 설계기준이 된다. 판부재는 주로 면내강성을 갖는다. 만약 2차좌굴로 인하여 선체판의 면내강성이 저하한다면 선박전체의 종강도는 크게 저하한다. 그러므로, 판부재의 좌굴후거동과 같은 기하학적 비선형거동을 정확히 규명하여야 하는 것은 구조물 전체적으로 매우 필요하다. 이상과 같은 관점에서 본 논문에서는 에너지법을 이용하여 압축하중을 받는 단순지지판의 기하학적 비선형거동을 규명하였다. 에너지 법을 바탕으로 선체판의 탄성대변형해석을 수행하였고 분기점형좌굴과 극한점형좌굴에 대하여 규명하였다.

• Journal of the Korean Data and Information Science Society
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• 제21권6호
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• pp.1109-1115
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• 2010

본 연구는 질병자료나 사망자수 등과 관련된 자료의 분석에서 가장 많이 사용되는 초기하분포의 모수, 즉 성공의 확률에 대한 신뢰구간추정에 대하여 설펴보았다. 초기하분포의 성공의 확률에 대한 신뢰구간은 일반적으로 잘 알려져 있지 않으나 그 응용성과 활용성의 측면에서 신뢰구간의 추정은 상당히 중요하다. 본 논문에서는 초기하분포의 성공의 확률에 대한 정확신뢰구간을 소개하고 여러 가지 모집단의 크기와 표본수에 대하여, 그리고 몇가지 실현값에 대한 신뢰구간을 유도하고 소표본의 경우에 모의실험을 통하여 실제 포함확률의 측면에서 살펴보았다.

• ETRI Journal
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• 제30권6호
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• pp.774-782
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• 2008

An operational orbit determination (OD) and prediction system for the geostationary Communication, Ocean, and Meteorological Satellite (COMS) mission requires accurate satellite positioning knowledge to accomplish image navigation registration on the ground. Ranging and tracking data from a single ground station is used for COMS OD in normal operation. However, the orbital longitude of the COMS is so close to that of satellite tracking sites that geometric singularity affects observability. A method to solve the azimuth bias of a single station in singularity is to periodically apply an estimated azimuth bias using the ranging and tracking data of two stations. Velocity increments of a wheel off-loading maneuver which is performed twice a day are fixed by planned values without considering maneuver efficiency during OD. Using only single-station data with the correction of the azimuth bias, OD can achieve three-sigma position accuracy on the order of 1.5 km root-sum-square.

• 한국생산제조학회지
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• 제22권6호
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• pp.1018-1024
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• 2013

In the process of draw die design for stamping automotive press panels, the addendum surfaces generated in metal forming simulation software cannot be used in downstream processes such as machining and making draw dies because simulation tools use simple discrete models for the surface geometry. The downstream processes require more precise and continuous geometric models such as NURBS surfaces. Generally, automotive die engineers manually regenerate the addendum surface geometry using the discrete model. This paper presents an automated geometric modeling process for generating addendum surfaces using draft surface models. The design parameters of the section curve for the addendum surfaces are extracted automatically from the draft geometry. Using the extracted design parameters, smooth addendum surfaces are generated automatically as NURBS surfaces. The generated surfaces are $G^1$ continuous with the part surface and the binder surface, and can be used in downstream processes.

• 한국자동차공학회논문집
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• 제9권4호
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• pp.184-192
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• 2001

Cam/tappet wear is one of the critical concerns in valve train deign. Maximum contact stress and minimum oil film thickness between the cam and tappet are usually checked for the estimation of wear characteristics. If the two extreme cases arise simultaneously, there is a strong possibility of cam/tappet wear. In this paper, effects of valve train layout on the wear characteristics were studied. Especially for swinging arm type valve trains, initial geometric layout must be very carefully defined to avoid wear problems. The study was performed fur an end pivot type OHC valve train, which had severe wear problems. Analysis results show that some geometric parameter affect very sensitively on the wear characteristics. Experiments were also performed for the original and modified valve trains, which strongly support the analysis results.

• 대한의용생체공학회:의공학회지
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• 제21권2호
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• pp.189-201
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• 2000

Mechanical factors in the human body are considered to play a dominant role in low back problems. Various spinal structures. including muscles, act in unison to resist the external load. An estimation of the muscle forces in this structure requires a knowledge of the orientation, location and area of cross-section of the muscles to complete the formulation of a truly three-dimensional mathematical model of the spine. The geometric parameters which are calculated were the line of action, the centroid and physiologic area of cross-section of each muscle as a function of the spinal level. This geometric data were obtained from CT scans of 11 subjects participating in this study.

• Steel and Composite Structures
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• 제19권6호
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• pp.1467-1481
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• 2015

This paper presents a contribution to improving an analytical thermo-mechanical modeling of Oxley's machining theory of orthogonal metals cutting, which objective is the prediction of the cutting forces, the average stresses, temperatures and the geometric quantities in primary and secondary shear zones. These parameters will then be injected into the developed model of Karas et al. (2013) to predict temperature distributions at the tool-chip-workpiece interface. The amendment to Oxley's modified model is the reduction of the estimation of time-related variables cutting process such as cutting forces, temperatures in primary and secondary shear zones and geometric variables by the introduction the constitutive equation of Johnson-Cook model. The model-modified validation is performed by comparing some experimental results with the predictions for machining of 0.38% carbon steel.

• 소성∙가공
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• 제12권4호
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• pp.328-333
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• 2003

Ball indentation tests have been used to estimate the mechanical properties of materials by several investigators. In this study, load-depth curves from ball indentation tests were analyzed using the geometric conditions of the contact between ball and specimen. A series of numerical calculations and experimental results showed that the contact load-depth curves could be simplified by linear functions. Once we obtained the contact indentation depth from linearizing the experimental indentation curves, the estimation process of the flow properties became straight-forward and the scatter of results could be drastically reduced.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제12권4호
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• pp.275-287
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• 2005

Geometric invariants are basic tools for geometric processing and computer vision. In this paper, we give a linear approximation for the differentiation of the binormal vector field of a space curve by using the forward and backward differences of discrete binormal vectors. Two kind of discrete torsion, say, back-ward torsion $T_b$ and forward torsion $T_f$ can be defined by the dot product of the (backward and forward) discrete differentiation of binormal vectors that are linear approximations of torsion. Using Frenet formula and Taylor series expansion, we give error estimations for the discrete torsions. We also give numerical tests for a curve. Notably the average of $T_b$ and $T_f$ looks more stable in errors.