• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.2
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• pp.153-161
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• 2009

A domain/boundary decomposition method is applied for efficient analyses of thermo-elasto-viscoplastic damage and contact problems under the assumption of infinitesimal deformation. For the decomposition of a whole domain and contact boundaries, all the equality constraints on the interface and contact interfaces are restated with simple penalty functional. Therefore, the non-linearity of the problem is localized within finite element matrices in a few subdomains and on contact interfaces. By setting up suitable solution algorithms, the computational efficiency can be improved considerably. The general tendency of the computational efficiency is illustrated with some numerical experiments.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.2
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• pp.213-220
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• 2016

The needs for the utilization of space in the urban ara due to the increasing population and traffic volume. A Double-deck tunnel can be an appropriate solution. Geosynthetics are inevitably installed between ground and tunnel lining, therefore, geosynthetic-soil interface is also comprises. Dynamic shear behavior of geosynthetic-soil interface affects the dynamic behavior of tunnel, and experimental study is required since the behavior is very complicated. In this study, chemical factors such as acid and basic element in the groundwater and temperature are considered in the laboratory test. Multi-purpose Interface Apparatus(M-PIA) is utilized and submerging periods are 60 and 960 days. Consequently, dynamic shear degradation of geosynthetic-soil interface considering chemical and thermal factors are verified.

• Journal of Biomedical Engineering Research
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• v.21 no.3 s.61
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• pp.295-301
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• 2000

It is known that among many factors, relative micromotion at bone/implant interfaces can hinder bone ingrowth into surface pores of an implant. Loading conditions, mechanical properties of spinal materials, friction coefficients at the interfaces and geometry of spinal segments would affect the relative micromotion and spinal stability. A finite clement model of the human lumbar spine segments (L4-L5) was constructed to investigate the mechanical sensitivity at the interfaces between bone and cage. Relative micromotion. Posterior axial displacement. bone stress, cage stress and friction force were predicted in changes of friction coefficients, loading conditions. bone density and age-related material/geometric properties of the spinal segments. Relative micromotion (slip distance in a static loading means relative micromotion in routine activity) at the interfaces increased significantly as the mechanical properties of cancellous bone, annulus fibers or/and ligaments decrease or/and as the friction coefficient at the interfaces decreases. The contact normal force at the interfaces decreased as cancellous bone density decreases or/and as the friction coefficient increases A significant increase of slip distance at anterior annulus occurred with an addition of torsion to compressive preload. Relative micromotion decreased with an increase of disc area. In conclusion. relative micromotion, stress response. Posterior axial displacement and contact normal force are sensitive to the friction coefficient of the interfaces, bone density, loading conditions and age-related geometric/material changes.

• Defense and Technology
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• no.10 s.176
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• pp.44-49
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• 1993

인간공학은 인간-체계 접촉면(Human-System Interfaces)을 가장 중요시하는 학문으로서 대부분의 무기체계에서 인간체계 접촉면은 그 무기체계의 응용적 효율성에 핵심이 됩니다 무기체계에서 강조되는 인간은 무기체계 성능의 최적화에 핵심요소이고, 이러한 무기체계 구조하에서 인간공학 기술투자는 미래에 보다 더 개선가능한 한국형 무기체계의 효율성을 증대시키고, 보다 높은 이익을 가져올 수 있습니다

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.12
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• pp.1021-1030
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• 2017

This paper describes the algorithm of computing thermal contact conductance between unmatched grid interfaces for finite element thermal analysis. Because grid interfaces should be coincident with adjacent meshes for finite element method, large amount of man hours and huge computations are required to match interfaces between many numbers of complex subdomains. A novel method that distributes feasibly the conductances to interface nodes is proposed. The aims of the method are described, and details of the nodal conductance distribution algorithm with less dependency on meshes are represented. The algorithm can be applied both the flat and curved interfaces in 3 dimensional space, and proposed method can combined with many finite element application including thermal analysis.

• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.81-91
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• 2012

This paper mainly deals with the analysis of probabilistic characteristics of the disturbed function proposed to predict dynamic behavior of Geosynthetic-soil interface as the lining and cover systems used in waste landfills. Calibration and statistical property estimation of the parameters in the disturbed function model were first performed using many experimental data obtained from a new multi-purpose interface apparatus (M-PIA). In order to analyze the effect due to changes in chemical degradation and normal loads condition, probabilistic properties such as mean, coefficient of variation and distribution type of the disturbed function were evaluated using both the LHS method known to be a very efficient sampling scheme and the estimated statistical property of A and Z. As a result, variation of the disturbed function is found to range approximately from 10~28% according to the level of ${\xi}_D$ and Weibull appears to be the most adequate distribution type at almost all levels of ${\xi}_D$. It is concluded that a probabilistic safety assessment method for Geosynthetic-soil interface considering uncertainty in shear strength can be developed by utilizing probabilistic properties of the disturbed function obtained in this study.

• Journal of the Korean Geosynthetics Society
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• v.5 no.3
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• pp.25-30
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• 2006

Large-scale direct shear tests were conducted in order to evaluate both the shear strength of soil itself and the interface shear strength between soil and woven geotextile. Two types of soil (sand and clay) with a woven geotextile were used in the experimental program. Total nine tests were conducted in this study. It has been found from the experimental results that the friction angle of sand itself were $30^{\circ}$. Interface friction angle between woven geotextile and sand showed $26^{\circ}$ indicating an efficiency of 87%. Similarly, interface friction angle between woven geotextile and clay showed $7.7^{\circ}$.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2138-2139
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• 2011

본 논문에서는 44V AC 및 DC전원에서 직렬아크에 의한 전선 접속부에서의 산화물 성장 특성에 대하여 실험, 분석하였다. 실험에 사용된 전선은 동전선과 황동선으로 각각 지름 1.0mm을 사용하였으며, 교류의 경우 3가지 접속조건, 직류의 경우 4가지의 접속 조건으로 하여 전선 접촉면에서 직렬아크가 발생하였을 때 2A, 3A, 4A의 전류에서 산화물의 성장 특성과 접촉면 양단의 전압강하 변화, 산화물의 성장 길이 및 방향, 온도 분포 등에 대하여 분석하였다. 실험, 분석결과, 동전선과 동전선의 접속에서 가장 산화물의 성장이 잘 이루어짐을 볼 수 있었으며, 교류에서는 접촉면을 중심으로 좌우로, 직류에서는 접촉면을 중심으로 +극(양극) 방향으로만 산화물이 성장함을 볼 수 있었다. 본 연구 결과는 AC 및 DC 전원에서의 전기안전을 위한 기술 자료로 활용할 수 있을 것으로 기대된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.178-185
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• 2010

This paper presents the evaluation of foundation stability according to decrease of the foundation contact area on the ground. In order to carry out this research, the experimental and numerical studies are performed. In the experimental study, the carefully controled laboratory model tests are carried out with different foundation size and types. The model test results are analyzed and interpreted by analytical and numerical calculation in order to verify both results obtained from experimental and numerical studies. It is clearly found from the results that the foundation stability is considerably reduced when the foundation contact area ratio is less than 75%. This research may be very useful to develop the economical foundation type.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.664_665
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• 2009

초음파모터의 동작은 기본적으로 기계적인 마찰에 의지하기 때문에, 이를 해석하기 위해서는 복잡하고 비선형적인 접촉 메커니즘에 대한 고찰이 필요하다. 본 논문에서는 타원형 접촉면 모델을 이용하여 이러한 접촉 메커니즘을 설명하고, 또한 회전자가 가하는 압력에 의해 발생하는 고정자의 변형도 고려하는 회전형 초음파 모터의 해석법을 제시한다.