• Journal of the Korean GEO-environmental Society
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• v.10 no.1
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• pp.49-54
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• 2009

The seismic slope stability is most often evaluated by the pseudo-static limit analysis, in which the earthquake loading is simplified as static inertial loads acting in horizontal and/or vertical directions. The transient loading is represented by constant acceleration via the pseudostatic coefficients. The result of a pseudostatic analysis is governed by the selection of the value of the pseudostatic coefficient. However, selection of the value is very difficult and often done in an ad hoc manner without a sound physical reasoning. In addition, the maximum acceleration is commonly estimated from the design guideline, which cannot accurately estimate the dynamic response of a slope. There is a need to perform a 2D dynamic analysis to properly define the dynamic response characteristics. This paper develops a new hybrid pseudostatic method that links the modified one-dimensional seismic site response analysis and the pseudostatic algorithm. The modified site response analysis adjusts the density of the layers to simulate the change in mass and weight of the layers of the slope with depth. Multiple analyses were performed at various locations within the slope to estimate the change in seismic response of the slope. The calculated peak acceleration profiles with depth from the developed procedure were compared to those by the two-dimensional analyses. Comparisons show that the two methods result in remarkable match. The calculated profiles are used to perform pseudostatic analysis. The results show that use of peak or a fraction of acceleration at the surface can seriously underestimate or overestimate the factor of safety, and that the proposed procedure significantly enhances the reliability of a standard procedure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.172-180
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• 2009

Normally in order to build a semi-active control system equipped with MR damper, the dynamic modeling of the damper is required to numerically predict its dynamic damping force and also its behavioral characteristics. For the dynamic modeling of the MR damper, this paper attempts to predict and evaluate its dynamic behavior by applying specifically both a power model and a Bingham model. Dynamic loading tests were performed on the squeeze type of damper specially designed for this research, and force-displacement hysteresis loops confirmed the effectiveness of the damper as a semi-active control device. In the meantime, in order to evaluate the effectiveness of each model applied, the model parameter for each model was identified. On the basis of the parameter, we derived the error ratio of the force-velocity relationship curve and the dynamic damping force, which was contrasted and compared with the experimental results of the squeeze type of damper. Finally, the squeeze type of MR damper developed in this research was proved to be valid as a semi-active control device, and also the evaluation of the two dynamic models showed they were working fine so that they were likely to be easily utilized to numerically predict the dynamic characteristics of any dampers with MR fluid as well as the squeeze type of MR damper.

• Journal of the Korean Society for Environmental Technology
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• v.18 no.2
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• pp.165-172
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• 2017

In current stage, it is hard to predict the scale of damage caused by natural disaster and it is hard to deal with it. However, in case of disaster planning level, if it is possible to predict the scale of disaster then quick reaction can be done which will reduce the damage. In the present study, therefore, function of wind wave damage estimation among various disaster is developed. Damage of wind wave and typhoon in eastern and Jeju coastal zone was collected from disaster report (1991~2014) published by Ministry of Public Safety and Security and to reflect inflation rate, 2014 damage cost was converted. Also, wave height, wind speed, wave direction, wave period, etc was collected from Meteorological Administration and Korea Hydrographic and Oceanographic Administration web site. To reflect the characteristic of coastal zone when wave damage occurs, CODI(Coastal Disaster Index), COSI(Coastal Sensitivity Index), CPII(Coastal Potential Impact Index) published by Korea Hydrographic and Oceanographic Agency in 2015 were used. When damage occurs, function predicting wind wave damage was developed through weather condition, regional characteristic index and correlation of damage cost.

• Journal of the Korean Geotechnical Society
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• v.17 no.5
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• pp.115-128
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• 2001

본 논문에서는 반복하중이나 지진하중을 받는 지반-구조물 시스템의 설계에 필수적인 변수인 전단탄성계수와 감쇠비에 대한 연구를 국내에 존재하는 비점성토 지반에 대하여 수행하였다. 국내 퇴적토지반 및 풍화토지반에서 채취된 자연시료와 입도분포를 조정하여 제작한 시료를 포함하여 총 60개의 시료에 대하여 20kPa에서 500kPa의 구속응력 범위에서 공진주 시험을 수행하고, 이를 조립질 사질토, 실트 및 실트질 모래, 풍화토의 3개의 그룹으로 나누어 결과를 정리하였다. 저변형률 영역의 변형특성인 최대전단탄성계수와 최소감쇠비에 대하여 구속응력의 영향을 확인하였다. 최대전단탄성계수를 예측하는 경험식을 3개의 그룹별로 제안하였다. 최소감쇠비는 구속응력에 따른 분포영역을 제시하였다. 세립분이 적은 조립질 사질토의 경우, 비선형 변형특성이 구속응력의 영향을 뚜렷이 받고 있어 이를 주요한 변수로 고려하여 대표곡선과 분포영역을 제안하였다. 구속응력의 영향을 적게 받는 실트 및 실트질 모래와 풍화토는 구속응력에 관계없이 대표곡선과 분포영역을 제안하였다. 제안된 각 시료의 대표곡선과 기존의 Vucetic-Dobry와 Seed-Idriss가 제안한 곡선과 비교하였다. 본 논문의 연구결과는 국내지반의 비점성토 지반에 대한 지진해석이나 동하중을 받는 시스템의 해석시 유용하게 사용될 것으로 판단된다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.7
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• pp.1869-1882
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• 1998

In this paper, we investigae convergence behaviors of a differential method for 2-D motion parameter estimation. While the differential method is widely studied for motion compensated prediction in video coding, little attention hs been paid to its convergence properties. Based on the nonseparable exponential covariance image model, we derive the estimates of update terms for the 2- and 6-parameter motion models. And, the effect of noise, spatial correlation, choice of spatial gradient measures, andthe size of a region, are quantitatively anlyzed in relation to the convergence speed. Some empirical results are presented to verify the analysis.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.676-684
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• 1990

This study is on the pulsating combustion of premixed gas in a Rijke type combustor made of a honeycomb flame holder in a tube. Modelling for the onset condition of the oscillation is made by the ratio of the acoustic power generation based on the analysis of heat transfer to the power loss due to the thermoviscous dissipation and radiation. Experiment is performed for the characteristics of acoustic, thermal and combustion. It is shown that the theoretical modelling for the oscillation may be used as a limit condition. And the combustion analysis for the acoustic power generation is needed for better prediction of the onset condition. Experimental result shows that, by pulsation, the flame length is shortened and the flame temperature is decreased with increase in the heat transfer coefficient. The NO$_{x}$ concentration in the exhaust gas is significantly reduced by pulsation and the concentration of unburned hydrocarbon shows a little increase.e.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.148-153
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• 2017

During natural ageing of HTPB propellant undergoes a series of slow physico-chemical degradation reactions. By using accelerated ageing conditions it is possible to simulate the material behaviour at different time-temperature conditions especially focused on the in-service conditions. Ageing behaviour of HTPB propellant were investigated using HFC(Micro-Heat Flow Calorimeter) is universal technique for measuring the rate of slow chemical and physical processes in long-term storage.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.130-130
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• 2019

최근 호내 조류문제가 심각해지고 있는 상황이다. 2017년도에는 남강댐의 조류경보 발령이 동절기인 12월까지 지속됨에 따라 지역 사회의 수질관리 불안이 커지고 있다. 본 연구에서는 호내 조류생장과 수심에 따라 수질에 관하여 연구하였다. 남강댐을 포함하고있는 남강댐 중권역은 경호강으로부터 남강댐까지 해당하며, 낙동강 전체 면적에 7.2%에 달하는 $2.293km^2$의 유역면적을 가지는 중권역이다. 남강댐 중권역에서 광역 및 지방을 포함하는 취수장이 총 10개 이며, 남강댐 중권역 내취수량의 95% 이상을 차지하는 남강 취수원과 진주 취수원이 남강댐 호소수에 의존하고 있으므로 남강댐 상수원의 수질 관리는 매우 중요하다. 그러므로 남강댐의 효과적인 수질관리를 위해 호내 조류 생장 구간의 특성을 파악하여 수질변화에 관한 연구가 필요하다. 본 연구에서는 남강댐 내의 조류 생장 구간인 오미천 유입부와 신풍리 지류 합류부 두 구간의 수심별 pH, DO, EC, 세포수, 클로로필을 측정하여 비교하였으며, 두 구간의 특성을 비교 분석 하였다. 본 연구는 조류 생장 구간인 두 지점의 특성을 파악에 비교 분석하며, 수심별 수질 변화를 예측하여 상수원으로 이용되고 있는 남강댐 호내의 수질관리에 필요한 선행 자료가 되고자 하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.59-65
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• 2018

During natural aging, hydroxyl-terminated polybutadiene(HTPB) propellant undergoes a series of slow physico-chemical degradation reactions. By using accelerated ageing conditions it is possible to simulate the material behavior at different time-temperatures focusing on in-service conditions. Aging behaviors of HTPB propellant are investigated using HFC(heat flow calorimeter), a universal technique for measuring the rate of slow chemical and physical processes in long-term storage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.6
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• pp.1297-1308
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• 2015

In Korea, the local traffic safety master plan has been established and implemented according to the Traffic Safety Act. Each local government is required to establish a customized traffic safety policy and share roles for improvement of traffic safety and this means that local governments lead and promote effective local traffic safety policies fit for local circumstances in substance. For implementing efficient traffic safety policies, which accord with many-sided characteristics of local governments, the prediction of community-based traffic accidents, which considers local characteristics and the analysis of accident influence factors must be preceded, but there is a shortage of research on this. Most of existing studies on the community-based traffic accident prediction used social and economic variables related to accident exposure environments in countries or cities due to the limit of collected data. For this reason, there was a limit in applying the developed models to the actual reduction of traffic accidents. Thus, this study developed a local traffic accident prediction model, based on smaller regional units, administrative districts, which were not omitted in existing studies and suggested a method to reflect traffic safety facility and policy variables that traffic safety policy makers can control, in addition to social and economic variables related to accident exposure environments, in the model and apply them to the development of local traffic safety policies. The model development result showed that in terms of accident exposure environments, road extension, gross floor area of buildings, the ratio of bus lane installation and the number of crossroads and crosswalks had a positive relation with accidents and the ratio of crosswalk sign installation, the number of speed bumps and the results of clampdown by police force had a negative relation with accidents.