• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.557-560
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• 2000

The Purpose of this study is analysis of kinematic for a modified manipulator and experimental test to certify auto-balancing operation. The test is carried out as follows. First, we solve the inverse kinematics and then do a closed loop control. Second we confirm translation displacement and rotation angle of a manipulator.

• Journal of the Korean Data and Information Science Society
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• 제23권2호
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• pp.403-409
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• 2012

We consider a life testing experiment in which several two-component shared parallel systems are put on test, and the test is terminated at a predesigned experiment time. In this thesis, the maximum likelihood estimators for parameters of Freund's bivariate exponential distribution under the system level life testing are obtained. Results of comparative studies based on Monte Carlo simulation are presented.

• Geomechanics and Engineering
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• 제15권5호
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• pp.1047-1059
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• 2018

This paper focuses on the cracking and fragmentation process in rock materials containing a pair of non-parallel flaws, which are through the specimen thickness, under vertical compression. Several numerical experiments are conducted with varying flaw arrangements that affect the initiation and tensile wing cracks, shear crack growth, and crack coalescing behaviors. To obtain realistic numerical results, a parallelized peridynamics formulation coupled with a finite element method, which is able to capture arbitrarily occurring cracks, is employed. From previous studies, crack initiation and propagation of tensile wing cracks, horsetail cracks, and anti-wing cracks are well understood along with the coalescence between two parallel flaws. In this study, the coalescence behaviors, their fragmentation sequences, and the role of an x-shaped shear band in rock material containing two non-parallel flaws are discussed in detail on the basis of simulation results strongly correlated with previous experimental results. Firstly, crack initiation and propagation of tensile wing cracks and shear cracks between non-parallel flaws are investigated in time-history and then sequential coalescing behavior is analyzed. Secondly, under the effect of varying inclination angles of two non-parallel flaws and overlapping ratios between a pair of non-parallel flaws, the cracking patterns including crack coalescence, fragmentation, and x-shaped shear band are investigated. These numerical results, which are in good agreement with reported physical test results, are expected to provide insightful information of the fracture mechanism of rock with non-parallel flaws.

• Journal of Mechanical Science and Technology
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• 제16권6호
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• pp.799-809
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• 2002

In order to utilize a parallel mechanism as a machine tool component, it is important to estimate the errors of its end-effector due to the uncertainties in parts. This study proposes an error analysis for a new parallel device, a cubic parallel mechanism. For the parallel device, we consider two kinds of errors. One is a static error due to link stiffness and the other is a dynamic error due to clearances in the parts. In this study, we propose a stiffness model for the cubic parallel mechanism under the assumption that the link stiffness is a linear function of the link length. Also, from the fact that the errors of u-joints and spherical joints are changed with the direction of force acting on the link, they are regarded as a part of link errors, and then the error model is derived using forward kinematics. Lastly, both the error models are integrated into the total error, which is analyzed with a test example that the platform moves along a circular path. This analysis can be used in predicting the accuracy of other parallel devices.

• Journal of the Korean Data and Information Science Society
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• 제10권2호
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• pp.473-483
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• 1999

Linux 운영체계를 기반으로 한 PC 시스템을 고가의 상용 워크스테이션에 필적하도록 성능을 극대화하고, 각 단위 Linux PC 시스템을 네트워크를 통해 CPU와 memory를 공유하게 하는 병렬가상장치(PVM: Parallel Virtual Machine) 방식의 소프트웨어를 사용하여 군집(clustering)함으로써 슈퍼 컴퓨터급 기능을 발휘하는 분산형 PC 시스템을 시험 구축하였다. 구축된 시스템의 성능을 PVM 방식의 병렬프로그램을 사용하여 벤치마킹 해본 결과, 병렬효율 (parallel efficiency)이 90%급에 접근함을 확인하였다.

• 대한원격탐사학회지
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• 제9권2호
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• pp.7-19
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• 1993

In stereo vision, when we use two parallel axis images, small portion of object is contained and B/H(Base-line to Height) ratio is limited due to the size of object and depth information is inaccurate. To overcome these difficulities we take a non-parallel axis image which is rotated $\theta$ about y-axis and match other parallel-axis image. Epipolar lines of non-parallel axis image are not same as those of parallel-axis image and we can't match these two images directly. In this paper, we transform the non-parallel axis image geometrically with camera parameters, whose epipolar lines are alingned parallel. NCC(Normalized Cross Correlation) is used as match measure, area-based matching technique is used find correspondence and 9$\times$9 window size is used, which is chosen experimentally. Focal length which is necessary to get depth information of given object is calculated with least-squares method by CCD camera characteristics and lenz property. Finally, we select 30 test points from given object whose elevation is varied to 150 mm, calculate heights and know that height RMS error is 7.9 mm.

• 문화기술의 융합
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• 제6권2호
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• pp.467-472
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• 2020

일반적인 보통 등급의 지반(ground) 상 구조물의 안정성 확보를 위한 설계입력정수(input-parameters) 도출방법들은 보편적으로 잘 알려져 있다. 연구지역과 같은 습곡된(folded) 변성암(metamorphic rocks) 지반은 엽리가(foliation) 촘촘히 발달해 있고, 엽리에 평행한 소규모 단층들(faults)이 분포하고 있어 설계입력정수 도출을 위한 특별한 조사방법 및 시험, 등이 요구된다. 수 mm 간격의 엽리가 발달한 변성암 지반은 엽리면 직접전단강도시험(direct shear test), 엽리의 배향(strike/dip)과 맵핑(mapping), 엽리의 지하 연속성 파악을 위한 시추조사, 변성암반의 암반분류(rock mass rating), 등이 필요하다. 특정 엽리면을 따라 발달한 소규모의 엽리평행단층(foliation-parallel faults)이 다수 발달한 지반은 선구조선 분석, 단층 추적을 위한 지표지질맵핑, 단층면 직접전단강도시험, 등이 필수적이다. 습곡지반은 지질구조구(structural domain) 분석, 불연속면의 평사투영(stereonet)해석, 습곡축을 따른 전기비저항탐사, 등의 추가조사로 설계입력정수 도출이 합리적이다.

• 한국소음진동공학회논문집
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• 제16권4호
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• pp.355-365
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• 2006

The coupled time-integration method with a staggered algorithm based on computational structural dynamics (CSD), finite element method (FEM) and computational fluid dynamics (CFD) has been developed in order to demonstrate physical vibration phenomena due to dynamic aeroelastic excitations. Virtual flutter tests for the spanwise curved ing model have been effectively conducted using the present advanced computational method with high speed parallel processing technique. In addition, the present system can simultaneously give a recorded data file to generate virtual animation for the flutter safety test. The results for virtual flutter test are compared with the experimental data of wind tunnel test. It is shown from the results that the effect of spanwise curvature have a tendency to decrease the flutter dynamic pressure for the same flight condition.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.806-809
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• 2007

SRAM cell array and peripheral circuits on display panel are designed using LTPS process. To overcome low yield of SOP, high speed parallel fault detection circuitry for memory cells is designed at local I/O lines with minimal overhead for efficient memory cell redundancy replacement. Normal read/write and parallel test read/write are simulated and verified.

• Structural Engineering and Mechanics
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• 제26권1호
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• pp.99-109
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• 2007

A cracked composite specimen, comprised of an epoxy and an aluminium plate, was fractured under a tensile load. In this paper, two crack configurations were investigated. The first was an artificial center crack positioned in the epoxy plate parallel to the material interface. The other was for two edge cracks in the epoxy plate, again, parallel to the interface. A tensile test was carried out by gradually increasing the applied load and it was verified that the cracks always moved suddenly in an outward direction from the interface. The d/a ratio was gradually reduced to zero, and it was confirmed that the maximum stress intensity factor value for the artificial center crack, $K_{{\theta}{\theta}}^{max}$, approached that of an artificial interface crack,$K_{{\theta}{\theta}}^{ifc\;max}$ (where: 2a is the crack length and d is the offset between the crack and interface). The same phenomenon was also verified for the edge cracks. Specifically, when the offset, d, was reduced to zero, the maximum stress intensity factor value, $K_{{\theta}{\theta}}^{max}$, approached that of an artificial interface edge crack.