• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.987-993
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• 1996

This report suggests a new non-linear friction compensation for digital control systems. This control adopts a hysteric nonlinear clement which can introduce the phase lead of the control system to compensate the phase delay comes from the inherent time delay of a digital control. The Lyapunov direct method is used to prove the asymtotic stability of the suggested control, and the stability and the effectiveness are verified analytically and experimentally on a single axis servo driving system.

• Multiscale and Multiphysics Mechanics
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• 제1권2호
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• pp.171-188
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• 2016

Gradient enhanced theories of crystal plasticity enjoy great research interest. The focus of this work is on thermodynamically consistent modeling of grain size dependent hardening effects. In this contribution, we develop a model framework for damage coupled to gradient enhanced crystal thermoplasticity. The damage initiation is directly linked to the accumulated plastic slip. The theoretical setting is that of finite strains. Numerical results on single-crystalline metal showing the development of damage conclude the paper.

• Journal of Mechanical Science and Technology
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• 제20권8호
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• pp.1302-1308
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• 2006

The unsteady Hartmann flow of an electrically conducting, viscous, incompressible fluid bounded by two parallel non-conducting porous plates is studied with heat transfer taking the Hall effect into consideration. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to an exponential decaying pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the ion slip and the uniform suction and injection on both the velocity and temperature distributions is examined.

• 한국음향학회지
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• 제35권3호
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• pp.183-191
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• 2016

자동차의 저소음 보기류 구동 시스템을 개발하는 체계적인 방법론이 전산해석과 리그 실험을 통해 제시되었다. 벨트 구동 소음 예측의 두 가지 난제는 1) 벨트와 풀리 접촉면에서의 스틱-슬립 비선형성과 2) 벨트 구동 시스템과 파워트레인 회전진동계와의 연성이다. 본 연구에서는 최근 개발된 해석 방법을 이용하여 벨트 구동시스템과 엔진 회전진동계를 통합한 해석 모델을 구축하였고, 다양한 파워트레인 운전 조건에서 정합성을 확보하였다. 통합 모델을 이용하여 스틱-슬립 소음이 발생하는 벨트 시스템을 개선할 수 있음을 확인하였다. 또한 새로운 방법론을 통해 신엔진 개념설계에서 NVH (Noise, Vibration and Harshness), 기능, 연비 등을 고려한 개념 설계안을 제시하였다.

• 대한토목학회논문집
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• 제14권1호
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• pp.171-178
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• 1994

본 연구에서는 연약지반에 시공한 단독말뚝에서 발생하는 주변마찰력과 이로 인해 유발되는 축하중 해석방법을 개발하고 해석결과를 유한요소해석 프로그램에 의한 예측결과 및 현장 실험값과 비교 분석하였다. 이때 말뚝과 지반의 접촉면에 국부파괴가 발생하는 경우(slip case)와 발생하지 않는 경우(no slip case)에 대해 고려하였다. 본 연구에서 말뚝의 지지층은 암반인 경우를 고려하였고 해석모형의 물성으로는 말뚝, 연약 지반, 암반층에 대하여 모두 일반적인 값들을 적용하였다. 해석결과를 유한요소해석 및 현장 실측값과 비교 분석한 결과, 말뚝에 발생하는 주면마찰력은 압밀도가 커짐에 따라 증가하며, 주면마찰력에 의해 유발되는 축하중은 압밀이 완료되는 시기에 최대의 값을 갖는다는 결론을 얻었다. 또한 복잡한 2차원 또는 3차원 비선형 거동 해석외에 간단한 1차원 압밀 이론을 적용한 해석 역시 비교적 정확한 결과를 얻을 수 있음을 알았다.

• 지질공학
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• 제2권2호
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• pp.155-165
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• 1992

본 연구는 한반도의 지진지체구조 특성에 부합되는 내진설계용 부지응답 스펙트럼 작성을 위한 유사지진 선정에 관한 연구이다. Seismic Moment Tensor를 이용 파형을 Inversion한 결과에 의하면 지진원 특성상, Kern Conty 지진(1952년 7월 21일, 리히터 규모 ML = 7.2)은 한반도 지진지체구조 특성에 부합되는 현실적으로 유사한 외국의 지진들 중의 하나로서, 선정된 Kern Conty 지진으로 부터 발생한 강지진동 자료를 전산처리하여 표준응답 스펙트럼과 일반적 특성을 비교하여 보는 일도 의미있는 일이라고 할 수 있다.

• Nutrition Research and Practice
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• 제6권4호
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• pp.366-374
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• 2012

In order to create a worker-friendly environment for institutional foodservice, facilities operating with a dry kitchen system have been recommended. This study was designed to compare the work safety and work environment of foodservice between wet and dry kitchen systems. Data were obtained using questionnaires with a target group of 303 staff at 57 foodservice operations. Dry kitchen facilities were constructed after 2006, which had a higher construction cost and more finishing floors with anti-slip tiles, and in which employees more wore non-slip footwear than wet kitchen (76.7%). The kitchen temperature and muscular pain were the most frequently reported employees' discomfort factors in the two systems, and, in the wet kitchen, "noise of kitchen" was also frequently reported as a discomfort. Dietitian and employees rated the less slippery and slip related incidents in dry kitchens than those of wet kitchen. Fryer area, ware-washing area, and plate waste table were the slippery areas and the causes were different between the functional areas. The risk for current leakage was rated significantly higher in wet kitchens by dietitians. In addition, the ware-washing area was found to be where employees felt the highest risk of electrical shock. Muscular pain (72.2%), arthritis (39.1%), hard-of-hearing (46.6%) and psychological stress (47.0%) were experienced by employees more than once a month, particularly in the wet kitchen. In conclusion, the dry kitchen system was found to be more efficient for food and work safety because of its superior design and well managed practices.

• 플랜트 저널
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• 제18권3호
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• pp.52-61
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• 2022

본 연구는 실제 운영중인 영동에코발전본부 1호기 125 MW 우드펠릿 발전소를 대상으로 탈질설비 운전조건이 NOx 발생량에 미치는 영향을 시험하였다. SNCR 요소 유량 증가에 따라 NOx 농도는 점차 감소하였으나 SCR 후단 암모니아 슬립은 상승하였다. 시험대상 보일러는 고온의 내부온도로 인해 SNCR 운영에 불리한 구조이며 노즐의 최적위치 검토가 필요할 것이다. SCR 희석공기 온도변화는 NOx 발생량에 영향을 미치지 않았다. SCR 암모니아 유량 증가는 SCR 후단 NOx 농도를 감소시켰고 NOx 제거효율도 증가시켰다. 다만 암모니아 슬립 자체 기준치를 초과하지 않는 암모니아 유량 111 kg/h가 최대 운전기준으로 추정된다. SCR 믹서 압력 상승은 NOx 농도를 감소시키고 제거효율도 최대로 측정되어 NOx 생성을 가장 효과적으로 억제하는 변수로 파악되었다.

• Structural Engineering and Mechanics
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• 제22권3호
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• pp.263-278
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• 2006

Starting with the geometrically non-linear formulation and the subsequent linearization, this paper presents a consistent formulation of the exact mechanical analysis of geometrically and materially linear three-layer continuous planar beams. Each layer of the beam is described by the geometrically linear beam theory. Constitutive laws of layer materials and relationships between interlayer slips and shear stresses at the interface are assumed to be linear elastic. The formulation is first applied in the analysis of a three-layer simply supported beam. The results are compared to those of Goodman and Popov (1968) and to those obtained from the formulation of the European code for timber structures, Eurocode 5 (1993). Comparisons show that the present and the Goodman and Popov (1968) results agree completely, while the Eurocode 5 (1993) results differ to a certain degree. Next, the analytical solution is used in formulating a general procedure for the analysis of layered continuous beams. The applications show the qualitative and quantitative effects of the layer and the interlayer slip stiffnesses on internal forces, stresses and deflections of composite continuous beams.

• Computers and Concrete
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• 제3권1호
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• pp.65-77
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• 2006

This study reports the details of the finite element analysis of eleven shear critical partially prestressed concrete T-beams having steel fibers over partial or full depth. Prestressed concrete T-beams having a shear span to depth ratio of 2.65 and 1.59 and failing in the shear have been analyzed using 'ANSYS'. The 'ANSYS' model accounts for the nonlinear phenomenon, such as, bond-slip of longitudinal reinforcements, post-cracking tensile stiffness of the concrete, stress transfer across the cracked blocks of the concrete and load sustenance through the bridging of steel fibers at crack interface. The concrete is modeled using 'SOLID65'-eight-node brick element, which is capable of simulating the cracking and crushing behavior of brittle materials. The reinforcements such as deformed bars, prestressing wires and steel fibers have been modeled discretely using 'LINK8' - 3D spar element. The slip between the reinforcement (rebar, fibers) and the concrete has been modeled using a 'COMBIN39'-non-linear spring element connecting the nodes of the 'LINK8' element representing the reinforcement and nodes of the 'SOLID65' elements representing the concrete. The 'ANSYS' model correctly predicted the diagonal tension failure and shear compression failure of prestressed concrete beams observed in the experiment. The capability of the model to capture the critical crack regions, loads and deflections for various types of shear failures in prestressed concrete beam has been illustrated.