• Journal of the Korean Geotechnical Society
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• v.28 no.4
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• pp.91-100
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• 2012

Soil-water characteristic curves (SWCCs), which represent a physical property in partially saturated soils, show the relation between volumetric water content and matric suction. The SWCCs exhibit hysteresis during wetting and drying, however experimental expressions used to describe SWCCs have generally ignored the hysteresis. In addition, the shape of SWCC may depend on the void ratio which is changed by soil skeleton deformations or hysteretic behavior under various loading conditions. Hence, it is necessary to understand, both empirically and analytically, the relationship between soil skeleton deformations and the SWCCs of various soils. The typical SWCCs experimentally have drying, wetting, and the second drying curve. The measurement of a complete set of hysteretic curves is severely time-consuming and difficult works, then the first drying curve of SWCC is generally determined to estimate the hydraulic conductivity and shear strength function of partially saturated soils. This paper presents the hydraulic-mechanical behavior of partially saturated soils (weathered soil and silty soil) for volume changes and hysteresis in SWCCs regarding the difference between the first drying and wetting curve.

• Journal of Korean Society of Transportation
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• v.32 no.5
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• pp.522-530
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• 2014

Spatio-temporal congestion evolution pattern can be reproduced using the VDS(Vehicle Detection System) historic speed dataset in the TMC(Traffic Management Center)s. Such dataset provides a pool of spatio-temporally experienced traffic conditions. Traffic flow pattern is known as spatio-temporally recurred, and even non-recurrent congestion caused by incidents has patterns according to the incident conditions. These imply that the information should be useful for traffic prediction and traffic management. Traffic flow predictions are generally performed using black-box approaches such as neural network, genetic algorithm, and etc. Black-box approaches are not designed to provide an explanation of their modeling and reasoning process and not to estimate the benefits and the risks of the implementation of such a solution. TMCs are reluctant to employ the black-box approaches even though there are numerous valuable articles. This research proposes a more readily understandable and intuitively appealing data-driven approach and developes an algorithm for identifying congestion patterns for recurrent and non-recurrent congestion management and information provision.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.668-669
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• 2009

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.4
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• pp.1-10
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• 1998

The magnitudes of historical earthquake records related with house collapses are estimated considering the magnitude, epicentral distance, soil condition and aging of a house. Eighteen artificial time histories for magnitudes 6-8, epicentral distances 5 km-350 km and hard and soft soil condition were generated. Nonlinear dynamic analyses were performed for a traditional three-bay-straw-roof house. The aging effect of the house was modeled as such that the lateral loading capacity of wooden frames represented by hysteretic stiffness was decreased linearly with time. The house was idealized by one degree-of-freedom lumped mass model and the nonlinear characteristics of wooden frames were modeled by the Modified Double-Target mode. For far field earthquakes, minor damages were identified regardless of magnitude, soil condition and aging of the house. For intermediate field earthquake, earthquake magnitude greater than 6.5 caused severe damages in soil sites. For near field earthquake, severe damages occurred for magnitude greater than 6.5 regardless of soil condition and aging of the house. It is estimated that the magnitude of historical earthquakes is about 6.2. An empirical equation of magnitude-intensity relationship suitable to Korea is suggested.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.2 s.54
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• pp.1-9
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• 2007

The method of generating the artificial acceleration time histories for seismic analysis based on genetic algorithms is presented. For applying to the genetic algorithms, the frequencies are selected as the decision variables eventually to be genes. An arithmetic average crossover operator and an arithmetic ratio mutation operator are suggested in this study. These operators as well as the typical simple crossover operator are utilized in generating the artificial acceleration time histories corresponding to the specified design response spectrum. Also these generated artificial time histories are checked whether their outward features are to be coincident with the recorded earthquake motion or not. The features include envelope shape, correlation condition between 2 horizontal components of motion, and the relationship of max. acceleration, max. velocity and max. displacement of ground.

• Magazine of the Korea Concrete Institute
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• v.9 no.4
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• pp.145-153
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• 1997

전단벽제 양단의 보강기둥은 비선형 휨거동에 주요 영향을 미치는 구조 요소이다. 본 연구에서는 전단 벽체에 일반적으로 사용되는 모델인 TVLEM에서, 수직 스프링 요소로 표현되는 보강기둥의 반복이력 모델을 제안하고 기존의 모델과 비교 검토하였다. 제안된 단순모델은 Vulcano의 모델 중 철근의 거동을 이중직선으로 가정하여 유도되었으며, 제안된 모델을 검증하기 위하여 Vulcano와 Kabeyasawa의 모델 사용시의 수치해석 값과 비교하였다. 비선형 해석은 자체 개발된 프로그램을 사용하였으며, Vallenas와 Bertero가 실험(1979)한 SP6의 모델에 대하여 수치해석을 수행하여 반복이력특성과 변위이력 및 발산에너지량을 비교하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.190-190
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• 2010

본 연구에서는 Ti이 도핑된 ZnO의 성장 및 후처리 과정에 따른 구조적, 전기적, 자기적 특성에 관하여 보고한다. ZnTiO 박막은 Pt/SiO2/Si기판에 $500^{\circ}C$, 20 mTorr에서 RF 마그네트론 스퍼터법과 DC 마그네트론 스퍼터법으로 코스퍼터링을 통하여 증착 하였다. 그리고 박막 성장 후 질소분위기에서 $600{\sim}900^{\circ}C$($50^{\circ}$ step)에서 급속 열처리 공정(RTA)을 이용하여 후열처리에 따른 특성변화를 관찰하였다. 구조적 특성변화를 확인하기 위하여 XRD 측정을 하였으며, Ti이 Zn와 치환되어 성장 한 것을 관측하였다. 한편 자기적 특성 확인을 위한 SQUID 측정 결과, ZnTiO 박막에서 강자성 특성인 자기-이력곡선을 확인하였다. 또한 강유전 특성 분석을 위한 I-V 측정에서 ZnTiO 박막에서 강유전 특성인 전류-이력 현상을 관측하였다.

• Cement Symposium
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• no.28
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• pp.179-186
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• 2001

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.3 s.55
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• pp.217-224
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• 2009

Many engineering researches are performed to ensuring structural safety from earthquake. In this study, the damping capacity of LRB(lead rubber bearing) with high lead-plug area ratio was examined by hysteresis loop from experiments. The displacement controlled tests were performed for 12 specimens designed in 2 types by lead-plug area ratio as main parameter. Each coupled specimens were tested by 3 times sinusoidal loads with different loading velocities. From the experimental results, LRB with high lead-plug area ratio has sufficient damping ratio for reducing horizontal seismic load to structures.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.277-285
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• 1997

To investigate the shear strength and hysteretic behavior of SRC column to H steel beam joints, seven cruciform specimens were fabricated and tested. The test specimens showed stable hysteresis behavior with a little pinching. The strength decreased with increase in deflection after the speciemens reached at the maximum strength. The shear strength of panel zones increased with increased in the concrete amount of SRC column sections. The shear strength may conservatively be estimated by the sum of shear yielding strength of steel column web, plastic bending strength of steel column flange and ultimate shear strength of concrete in the panel zone.