• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1489-1498
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• 2013

The monolithically coupled finite element analysis for a deformable unsaturated soil slope is performed to investigate the effect of antecedent rainfall which is assumed by initial conditions varying degree of saturation (36, 51, 77%) in finite element analysis. The distributions of matric suction and deformation on slope surface obtained from numerical simulation show the instability of antecedent rainfall-induced unsaturated soil slope. Moreover, the numerical analysis using Drucker-Prager model can be checked if a soil slope has reached failure (trial failure criterion $f^{tr}$ >0, plastic behavior) or not (trial failure criterion $f^{tr}$ < 0, elastic behavior). It is found that displacement of slope surface layer increases and the matric suction on soil slope decreases with an increase of initial degree of saturation by antecedent rainfall. Especially, the matric suction of the soil slope in dry condition (S=36%) rapidly decreases rather than that in wet condition (S=51%) at the same rainfall duration. The results of the trial failure criterion ($f^{tr}$ > 0) show slope instability in the toe region and surface of the slopes.

• Journal of the Korean GEO-environmental Society
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• v.4 no.1
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• pp.5-10
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• 2003

The solids and the fluids in porous media have a relative velocity to each other. Due to physically and chemically different material properties and their relative velocity, the behavior of saturated porous media is extremely complicated. Thus, in order to describe and clarify the deformation behavior of saturated porous media, constitutive models for deformation of porous media coupling several effects need to be developed in frame of Arbitrary Lagrangian Eulerian(ALE) description. The aim of ALE formulations is to maximize the advantages of Lagrangian and Eulerian elements, and to minimize the disadvantages. Therefore, this method is appropriate for the analysis of porous media which are considered for the behavior of the solids and the fluids. For this reason, mass balance equations for saturated porous media are derived here in ALE description frames. ALE formulations of mass conservation for the solid phase and the fluid phase are expressed. Then, linear momentum balance equation for porous media as multiphase media is expressed.

• Journal of the Korean Society for Railway
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• v.15 no.3
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• pp.257-265
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• 2012

Since the collapse of MSE walls frequently occurs due to the rainfall, it is necessary to analyze the behavior of MSE wall depending on the characteristics of rainfall and the properties of permeability of backfill. In order to understand the behavior of MSE wall depending on the characteristics of rainfall and the properties of permeability of backfill, finite element analyses were performed on the typical MSE wall. With varying ratio of saturated permeability to rainfall intensity, porepressures, displacements and factor of safety were analyzed. As the ratio of the saturated permeability to rainfall intensity increases, the global factor of safety is found to increase. Based on the analyses, the use of permeability of backfill with $2.56{\times}10^{-5}m/sec$ is desirable considering the characteristics of rainfall in Korea.

• Journal of the Korean Solar Energy Society
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• v.31 no.2
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• pp.1-7
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• 2011

PEM 연료전지에 있어서 수분의 균형이 연료전지의 시스템 성능에 현저한 영향을 미친다. 그래서 수분 균형은 가장 중요한 요소 중의 일부가 되었으며, 이에 관한 연구가 광범위하게 이루어지고 있다. 적절한 수분 균형을 유지하기 위해서는 적당한 멤브레인 수화작용(membrane hydration)이 필요하며, 반대로 촉매층(catalyst layer)에서의 익수(water flooding)현상이 없어져야 한다. 따라서 이와 같은 동적 상태에서 PEM 연료전지 내의 수분 균형을 유지하기 위해서는, 고도의 동적 수분 조정 기술이 확보되어야 한다. 현재의 연구는 이러한 특성을 고려하여 PEM 연료전지에서 동적부하 상태에서의 수분 이동에 관한 일차원 해석 모델에 관한 것이다. 금번 모델링의 결과, 양극촉매층(CCL, cathode catalystlayer)에서의 수분 상태는 거의 포화 단계에 이르고 있음을 보여주고 있으며, 이 모델링은 연료전지가 작동되는 동안의 CCL에 나타나는 수분의 양상을 예측하는데 활용될 수 있다. 본 논문에서는 수분 이동 모델이 국제규격에 따라 다양한 수송기관이 가동될 때, 동적부하 상태에서 서로 다른 차이점을 발견하기 위한 시뮬레이션 결과에 초점이 맞추어져 있다. 이 모델링을 적용한 결과, 수분 포화도가 상태에 따라 상이하게 나타남을 알 수 있었고, 또한 정적 수분 조절 요소에 따라 최적 상태가 모든 동적 분포에 따라 달라짐을 알 수 있었다.

• Tuberculosis and Respiratory Diseases
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• v.41 no.2
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• pp.103-110
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• 1994

To find out the predictors of nocturnal arterial oxygen desaturation in patients with respiratory diseases, transcutaneous oxygen saturation($StcO_2$) monitoring studies using a pulse oximeter were performed during sleep in 20 patients. $StcO_2$ was decreased more than 4% from the baseline value in 18 patients(90%) and more than 10%("Desaturator") in 8(40%). Five of the seven patients(71.4%) with awake $PaO_2$<60mmHg and three of the thirteen patients(23.1%) with awake $PaO_2{\geq}60mmHg$ were "desaturators". The awake $PaO_2/FIO_2$ and $PaO_2/PAO_2$ could distinguish "desaturator" from "nondesaturator", and $PaO_2,\;SaO_2$ or $StcO_2$ could not. These results suggest that the nocturnal oxygen desaturation depends on the severity of the underlying disease rather than the baseline $PaO_2$. Anthropomorphic and lung function factors could not separate between "desaturator" and "non-desaturator", and about a quater of patients with a wake $PaO_2{\geq}60mmHg$ developed significant desaturation. Therefore, it is necessary to monitor the nocturnal arterial oxygen saturation in patients with respiratory diseases regardless of their severity of airflow obstruction or awake $PaO_2$.

• Journal of the Korean GEO-environmental Society
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• v.6 no.3
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• pp.55-61
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• 2005

Dynamic compaction is a ground improvement technique which is particularly effective for loose granular soils. It has also been used successfully to the cohesive soils with high void ratio, and wastes and fills. For the design of dynamic compaction method, prediction of depth of improvement is very important. The depth of improvement is influenced not only by compaction energy but also by many parameters such as grid spacing, soil property, degree of saturation and site conditions. Based on the test results, the depth of improvement were evaluated with considering compaction energy, soil type and ground water level.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.6
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• pp.1-5
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• 2010

We propose an algorithm which can classify the system should use a PI controller, which have a weak high frequency attenuation characteristics near the critical frequency. To classify the system, we use a time delay element to calculate a gain attenuation rate near the critical frequency. The proposed algorithm also can design PI controller with the given magnitude margin and phase margin specification. The proposed algorithm uses time delay element and saturation function to identify the one point information in frequency domain. We justify the proposed algorithm via the simulation.

• Journal of Korean Society of Transportation
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• v.12 no.2
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• pp.5-30
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• 1994

다이아몬드형 인터체인지는 고속도로와 노면가로가 교차할 경우 방향별 교통류를 처리하는데 보편적으로 사용하는 인터체인지이다. 인터체인지에 교통량의 부하가 과도해지 면 인터체인지내부의 교차로에서 발생한 대기차량이 종종 고속도로본선으로 역류하여 본선 의 교통소통에 문제를 야기하며 특히 고속도로의 안전에도 큰 위험요소가 된다. 본 논문은 과포화상태의 다이아몬드형 인터체인지의 교통신호제어를 다루며, 신호시간계획을 산출하는 동적 최적화모형(dynamic optimization model)을 제시한다. 최적화 모형은 지체도최소화를 목적함수로 하며, 함수계측법의 형태가 된다. 본 모형의 핵심은 신호제어에 따라 발생하는 대기차량길이를 모형화하여 대기차량길이가 정해진 상한치를 초과하지 않도록 하는 신호시 간계획을 산출하는데 있다. 제시된 동적모형은 다이아몬드형 인터체인지의 신호시간을 위하 여 널리 사용되는 PASSER III와 최적해를 상호 비교한다. TRAF-NETSIM을 통한 시뮬레이 션의 결과에 따르면 동적 모형이 우수한 결과를 보이며, 대기차량의 길이를 효과적으로 제 어하는 것으로 판명된다.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.05a
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• pp.346-349
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• 2013

화질향상에 큰 영향을 주는 요소 중의 하나는 명암대비 향상이다. 영상의 명암대비를 향상시키는 대표적인 방법으로 히스토그램 평활화(Histogram Equalization) 방법이 있으며, 히스토그램 평활화의 변형된 방법에 대한 다양한 연구가 이루어지고 있다. 그러나 기존의 방법들은 평균 밝기의 급격한 변화로 인하여 부자연스러운 결과영상을 얻거나, 대비 향상 효과가 낮은 결과를 얻는 단점이 종종 발생한다. 본 논문에서는 히스토그램 압축방법을 통해서 개선된 명암대비 향상 기법을 제안한다. 제안한 방법은 과도한 명암대비 증가로 인한 과포화 현상을 억제하기 위하여 히스토그램의 빈도수에 따라 히스토그램을 차등 압축시키도록 설계되어 있다. 실험결과 제안방법은 기존 방법에 비해 과포화 현상 없이 좋은 명암대비 향상 효과를 보였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.6
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• pp.67-86
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• 2009

In this study, a 3D transmitting boundary in water-saturated transversely isotropic soil strata has been developed based on u-w formulation for application to general 3D analysis. Behavior in the far field region is expanded in the Fourier series, and dynamic stiffness for each term is obtained based on the u-w formulation. Transformation of the dynamic stiffness is presented to combine the transmitting boundary with the 3D finite elements for the near field region formulated in a 3D Cartesian coordinate system. The developed transmitting boundary is verified through a comparison of the dynamic behavior of a rigid circular foundation with the results from the existing numerical method. In addition, the developed transmitting boundary is applied to the analysis of the dynamic behavior of rigid foundations of diverse shapes, and the effects of the level of the groundwater table on the dynamic stiffness of a rigid rectangular foundation in the water-saturated transversely isotropic layered stratum are studied.