• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1341-1345
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• 2010

본 연구에서는 부산시 44개 지방하천을 대상으로 하여 홍수량 산정지점을 기준으로 175개의 소단위지구의 한계유출량을 산정하기 위하여 지형상관인자를 소단위지구별로 조사하였다. 한편, 한계유효강우는 한계홍수량에 해당하는 돌발홍수능(FFG, Flash Flood Guidance)을 산정하기 위한 전단계로 김홍태(2009) 등이 지형수문단위도 개발에서 제시한 KGCUH 공식을 이용하여 유역규모 $50km^2$을 기준으로 구분하여 적용하였다. 빈도별 지속시간별 한계유효강우를 산정하였으며, SCS유효우량 산정법을 이용하여 부산시 44개 지방하천 175개의 소단위지구별 및 빈도별(2, 10, 30, 50, 80, 100년) 돌발홍수능을 산정하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.997-1000
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• 2008

기상 레이더와 지상강우계를 이용한 실시간 강우산정기법은 전형적인 Marshall-Palmer(M-P) 방법, geostatistic 접근법을 이용한 방법, 회귀분석에 의한 방법, Kalman filter를 이용한 방법 및 실시간 weight mask를 이용한 보정 등 여러 형태가 존재한다. 본 연구에서는 실시간 강우산정을 위한 각 방법의 장단점 및 적용성을 분석하였다. 전형적인 M-P 방법은 잘 알려진 바와 같이 호우사상을 과소 추정하는 단점을 가졌으며 기존 연구자들이 제시한 바와 같이 층운형, 대류형과 같은 강우형태에 따라 다른 Z-R관계식을 가지므로 단일 Z-R관계식으로 강수를 산정함에 있어 한계를 가진다. Geostatistic 기법을 이용한 실시간 강수 산정의 경우, 지상 강우계 정보를 활용하여 강우공간분포를 개선하는 여러 기법 즉 cokriging, external drift 기법 등이 존재함에도 불구하고 과다한 계산시간, 실시간 variogram 산정과 적용상의 문제 등을 내포하고 있다. 실시간 회귀분석을 이용한 강우산정은 실제 적용에 있어 지상 강우계와 레이더 반사도사이의 선형 상관관계에 대한 결정계수가 매우 낮아 기법 적용이 간단한 장점에도 불구하고 적용에 한계를 가진다. Kalman filter기법을 이용한 실시간 레이더 강수산정은 계산시간이 여타 기법보다 많이 소요되어 실시간성을 유지하는데 한계를 가진다. 실시간 weight mask를 이용한 보정기법은 지상강우계 강우강도와 기상레이더 강우강도가 선형상관관계를 가진다는 가정이 대상지역 전체에 균일하게 적용될 수 없음에도 불구하고 기법의 적용이 간편하며 실시간 강우 공간분포를 실제 강우 관측인 지상 강우계 공간 분포 특성을 간접 강우 관측인 기상 레이더 반사도 분포와 결합하여 공간 변화 특성을 잘 나타낸다는 장점을 가지므로 실용적 적용에 있어 장점을 가진다.

• Review of KIISC
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• v.29 no.1
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• pp.34-37
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• 2019

지난 5년동안 전통적인 차량에 적용된 CAN 버스 상에서의 침입탐지시스템에 대한 연구가 활발히 진행되고 있다. 초기에 rule-base 로 탐지하거나, 단순한 경량 알고리즘을 통해 침입탐지를 하는 알고리즘이 주를 이루었다면, 최근에는 machine learning을 적용한 탐지 알고리즘들 역시 많이 개발되고 있다. CAN 용 침입탐지시스템이 그간 학계에서 주로 연구가 이루어 졌었다면 2019년 이후에는 상용차량들에 침입탐지시스템을 실제 탑재하여 출시될 예정에 있기 때문에, 이제는 산업계 주도적인 개발과 적용이 이루어질 것으로 보여진다. 다만, CAN 버스의 설계 구조상 공격 노드를 특정하기 어렵다는 한계와 전송량 대역폭의 제한으로 인해 기술적인 한계가 있어 왔기 때문에, 최근에는 IP 체계가 적용되고 automotive ethernet 기반으로 차량 네트워크가 빠르게 적용될 예정에 있다. 이에, 본 기고문에서는 automotive ethernet 의 보안기술에 대해 살펴보고, automotive ethernet 상에서 침입탐지시스템을 개발하기 위해 필요한 사항들은 어떤 것들이 있을지 살펴보고자 한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1B
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• pp.1-11
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• 2011

Channel network delineation from DEM (Digital Elevation Model) is a fundamental pre-process for hydrologic model application since it determines the drainage system in a watershed. This study aims to propose an effective and efficient channel network delineation process and assess the effects of DEM-based channel networks on the watershed drainage system. For these objectives, we applied two methods to generate the channel networks of the Jinan-cheon catchment with $18.28km^2$ from the 20 m resolution DEM: a widely-used area-threshold method and a slope-area threshold method based on the relationship between contributing areas and local slopes. The results showed that the area-threshold method led to unreliable drainage system, which did not satisfy geomorphological laws with respect to drainage density and source area representation whereas the slope-area threshold method provided acceptable results under the geomorphological laws. Our suggestions in this study can give valuable pre-processing information in DEM-based hydrologic modeling.

• Journal of the Korean GEO-environmental Society
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• v.20 no.11
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• pp.11-22
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• 2019

Limit state design (LSD) and allowable stress design (ASD) are two main types of soil nailing design methodologies. In the LSD method, stability is determined by applying individual coefficients to ground strength, working load and etc. The ASD method calculates the safety factor and compares it with the minimum safety factor to determine the stability. The global design trend of soil nailing system is changing from the ASD method to the LSD method. The design method in Korea still adopts the ASD philosophy while others mostly do the limit state design. In this study, four soil nail design methods, 'FHWA GEC 7' in U.S. (2015), 'Clouterre' in France (1991), 'Soil nailing - best practice guidance' in U.K. (2005), 'Geoguide 7' in Hongkong (2008), and 'Design guide for slope in construction work' in Korea (2016) were applied to the evaluation of the stability and the results were analyzed comparatively in brief. It is revealed that the design method of 'the overall stability of soil nail walls' in Korea is the most conservative and next those by FHWA, Clouterre and CIRIA become more conservative in order. However, the difference of results obtained from FHWA and Clouterre is negligible. Also, this study found out that efforts to improve domestic design criterion are needed.

• Journal of Korean Society of Steel Construction
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• v.22 no.6
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• pp.581-588
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• 2010

Recently the requirements of the buildings built with structural steel were increased in terms of structural stabilities and fire resistance at severe fire conditions. To meet the building regulations of fire resistance, a fire design is needed. This is of a prescriptive method and a performance engineering based method. Recently a simple calculation method as one of performance based engineering method is very popular because of its ease for an application in building built with structural steel. But, in Korea the performance based engineering method is not allowed yet. Thus it is needed to make a guideline for the performance based engineering method. The purpose of this study is to establish the limit temperature derived from structural beams made with both a H-section and a H-section filled with concrete at the web and derived the limit temperatures from beams made with H-sections and found out that the limit temperatures from two kinds of specimens depended on the applied loads and the specimens filled with the concrete represented 3 hour fire resistance in the range of 80%, 60%, and 50% of the maximum load.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.99-118
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• 2018

Recently, the limit state design method in the design of the structure is in global trend, but it is limited to a few structures in Korea. Since the introduction of the limit state design method has recently been attempted for tunnels, which are the main underground structures, it is surely necessary to understand the latest limit state design method. Therefore, based on the recently published AASHTO LRFD Road Tunnel Design and Construction Guide Specification (2017), structural load factors and load combinations were reviewed, and various factors which should be applied for the review of structures have been analyzed. In this study, utility tunnel section and subway tunnel sections used in Korea were analyzed by the limit state design method, and we have analyzed the direction of application of limit state design method through studying the tendency of member force by various influential factors such as ground conditions, load modifier and joint stiffness.

• Membrane Journal
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• v.6 no.4
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• pp.203-212
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• 1996

The operating parameters influencing on limiting flux was investigated in the ultrafiltration of PVA, and a new model, which is based on the Amiar model using the concept of heat transfer coefficient, was devised to overcome the limitation of gel-layer model. Using polysulfone plate-unit membrane (MWCO=20,000) and hollow-fiber membrane (MWCO= 30,000), ultrafiltration characteristics of PVA was examined with the variation of operating parameters such as cross flow velocity, transmembrane pressure, temperature, and PVA concentration. According to experimental results, the ultrafiltration of PVA through polysulfone membrane is mainly controlled by well-known phenomena of concentration polarization caused by gel-layer formation. On the contrary, in hollow fiber membrane was observed upward limiting flux which can not be explained by gel-layer model. New model was applied to predict the upward limiting flux behavior with partial satisfaction. The application of new model including viscosity correction factor, however, revealed that PVA ultrafiltration is closely related to the viscosity of permeating fluid.

• Journal of the Korean Geotechnical Society
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• v.20 no.1
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• pp.121-129
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• 2004

In this study, a slope stability chart for assessing stability of homogeneous simple soil slopes is proposed. Most existing slope stability charts are based on limit equilibrium method, which is not rigorous in mechanical standpoint. Meanwhile, limit analysis based on the principle of virtual work and the bound theorems of plasticity is suitable for evaluating the stability of geotechnical structures such as slope due to its simplicity in computation and mechanical rigor. Numerical limit analysis taking advantage of finite elements and linear programming can consider various slope conditions and, in addition, find the optimum stability solution with effeciency. In this study, a numerical limit analysis program in terms of effective stress is developed and a mechanically rigorous slope stability chart is proposed by performing stability analyses for various slope conditions. Pore pressure ratio, commonly used in stability charts, is applied to consider the effects of pore pressure for effective stress analysis. As a result of comparison between proposed stability chart and Spencer's stability chart, it was found that Spencer's chart solutions are biased to lower bound which means conservative in design.

• Proceedings of the Korean Association for Survey Research Conference
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• 2000.11a
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• pp.93-107
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• 2000

본 연구에서는 횡단면 즉 지방자치단체별로 "고정된 효과"를 가지고 있다는 전제하에 시의 공무원 정원을 산정하였다. 본 연구에서 주장하는 시의 공무원 정원은 시 공무원 1인당 업무량에 기준한 적정정원에 대한 산출은 아니나 도시형태별로 - 일반시와 도농복합행태의 시 - 동종 시가 평균적으로 고용하고 있는 현정원에 가까운 평균 인력규모를 타단체와의 비교를 통하여 평균적인 추세를 파악했다는 점에서 의의 있는 일이다. 그러나 공무원 정원산정의 거시적 모델을 학문적으로 논의하는 것은 가능할 지 모르지만 계량적 방법의 한계가 있기 때문에 이를 현실에 적용하는 것은 정치적.사회적으로 타당성에 한계가 있다.성에 한계가 있다.