• Tunnel and Underground Space
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• v.10 no.3
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• pp.355-365
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• 2000

As large underground projects such as radioactive waste disposal, hot water and heat storage, and geothermal energy become influential, the study, which consider all aspects of thermics, hydraulics and mechanics would be needed. Thermo-Hydro-Mechanical coupling analysis is one of the most complex numerical technique because it should be implemented with the combined three governing equations to analyze the behavior of rock mass. In this study, finite element code, which is based on Biot's consolidation theory, was developed to analyze the thermo-hydro-mechanical coupling in continuum rock mass. To verify the implemented program, one-dimensional consolidation model under the isothermal and non-isothermal conditions was analyzed and was compared with the analytic solution. The parametric study on two-dimensional consolidation was also performed and the effects of several factors such as poisson's ratio and hydraulic anisotropy on rock mass behavior were investigated. In the future, this program would be revised to be used for analysis of general discontinuous media with incorporating discrete joint model.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.211-213
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• 2004

차세대 인터넷 사용자들을 위해서는 이동하면서 연속적으로 인터넷에 접속하고 통신할 수 있도록 지원하는 것이 필수적이다. 현재까지 Mobile IT를 기점으로 다양한 네트워크 계층에서의 이동성 지원 프로토콜들이 제안되어 왔다. 그런데 최근에는 네트워크 계층에서의 이동성 지원과는 전혀 다른 접근 방식으로서, 트랜스포트 계층에서 이동성을 지원하는 방안이 언급되고 있다. 트랜스포트 계층에서의 이동성 지원은 기존 네트워크 계층에서의 이동성 지원 방안처럼 코어 네트워크에 홈 에이전트나 외부 에이전트와 같은 특별한 엔터티들의 추가를 요구하지 않기 때문에 디플로이가 상대적으로 용이하며, 종단 간 이동성을 지원할 수 있기 때문에 네트워크 계층에서의 이동성 지원 방안에서 발생하는 터널링 오버헤드나 비효율적인 라우팅 문제를 피할 수 있다. 이에 본 논문에서는 차세대 인터넷 환경인 IPv6 네트워크에서 WLAN 기반의 트랜스포트 계층 이동성 지원 방안을 제안한다 시뮬레이션을 통하여 제안하는 방안이 네트워크 계층에서의 이동성 지원과 대등한 성능을 보임을 확인하였고, 특히 이동 노드의 속도가 빠를 때 새로운 네트워크에서의 IT 주소 획득 시간이 길 때, 네트워크 계층에서의 이동성 지원 방안보다 더 좋은 성능을 제공함을 볼 수 있었다.

• Proceedings of the KAIS Fall Conference
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• 2009.05a
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• pp.821-824
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• 2009

고속도로를 주행 중인 차량에 강풍이 작용할 경우 차량의 주행안정성 저하와 운전자의 상황에 따른 치명적인 교통사고로 이어질 수 있다. 특히, 최근에 건설되거나 추진 중인 고속도로는 교량과 터널의 연속적인 조합으로 강풍발생위험에 노출되어 있어 적극적인 강풍저감 대책이 필요하다. 효과적인 방풍 시설 설치나 사전예고 시스템의 도입을 위해서는 차량의 동역학적 거동 분석, 주행 중인 차량의 위험도 판단기준 연구, 강풍위험지역의 정확한 풍속 추정기법 연구, 지능화된 방풍벽 개발, 방풍시설 설치판단 기준 제시, 합리적인 차량 속도 규제정책 등의 연구 개발이 수행되어야 한다. 본 연구에서는 강풍 발생 구간을 주행하는 차량의 동역학적 거동모델을 제시하고, 이를 기반으로 기존에 제안된 위험도 판단기준의 합리성을 제고하였으며, 운전자의 상황을 고려한 현실적인 차량주행위험도 판단기준 제시를 목표로 하였다.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1119-1120
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• 2006

고속철도 운행 및 급증하는 철도교통 수요에 대처하기 위해 기존선 속도향상이 요구됨에 따라 180km/h급 틸팅차량을 개발 중에 있다. 일반적으로 곡선부에서 승객들의 승차감을 위해 열차의 통과속도를 제한하지만 틸팅차량은 대차에 틸팅장치를 장착하여 차량의 곡선 통과속도를 향상시킬 수 있다. 곡선부에서 증가된 속도로 이 열차를 주행할 수 있도록 허용할 뿐만 아니라, 운전자의 실수, 고속주행으로 인한 탈선을 예방하기 위해 연속적으로 열차속도를 감시하는 것이 필요하다. 게다가, 기존선의 어떤 구간에서는 엄격한 틸팅의 승인이 있어야 하는 구간이 존재할지도 모른다. 틸팅열차가 열차간 충돌, 터널, 다리, 반대편의 열차와 충돌을 피해만 한다. 이러한 문제점의 해결은 TASS장치의 개발과 설치로 해결될 수 있다. 본 논문은 EMU 타입 틸팅열차에 적합한 TASS 장치의 적용방안을 제시한다.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1089-1094
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• 2004

Numerical methods to estimate behaviors of jointed rock mass can be roughly divided into two method : discontinuous model and continuum model. Generally, distinct element method (DEM) is applied in discontinuous model, and finite element method (FEM) or finite difference method (FDM) is utilized in continuum model. To predict a behavior of discontinuous model by DEM, it is essential to understand characteristics of joints developed in rock mass through field tests. However, results of field tests can not provide full information about rock mass because field tests is conducted in limited area. In this paper, discontinuous analysis by UDEC and continuous analysis by FLAC is utilized to estimate a behavior of a tunnel in jointed rock mass. For including discontinuous analysis in continuous analysis, joints in rock mass is considered by reducing rock mass properties obtained by RMR and decreasing shear strength of rock mass. By comparing and revising two analysis results, analysis results similar with practical behavior of a tunnel can be induced and appropriate support system is decided.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.05a
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• pp.614-617
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• 2013

DDoS 대피소 시스템은 백본 네트워크의 연동구간에서 공격 대상 서버로 유입되는 DDoS 트래픽의 경로를 변경하여 공격성 패킷은 차단하고 정상적인 패킷은 원래의 경로로 전송함으로써 서비스의 연속성을 보장하는 보안 시스템이다. 본 논문에서는 일반적인 DDoS 대피소 시스템의 구성에 L7 스위치와 웹 캐시서버를 추가적으로 구성하고 클라이언트의 요청을 웹 캐시서버에서 처리하도록 하여 소규모 트래픽을 이용한 웹 어플리케이션 계층 세션 고갈형 DDoS(Web DDoS) 공격을 효과적으로 방어할 수 있으며, IP 터널링 없이도 서비스를 지속할 수 있는 L7 계층 Web DDoS 대피소 시스템을 제안한다.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.161-176
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• 1999

A powerful numerical method that can be used for modeling rock-structure interaction is the Discontinuous Deformation Analysis (D D A) method developed by Shi in 1988. In this method, rock masses are treated as systems of finite and deformable blocks. Large rock mass deformations and block movements are allowed. Although various extensions of the D D A method have been proposed in the literature, the method is not capable of modeling water-block interaction, sequential loading or unloading and rock reinforcement; three features that are needed when modeling surface or underground excavation in fractured rock. This paper presents three new extensions to the D D A method. The extensions consist of hydro-mechanical coupling between rock blocks and steady water flow in fractures, sequential loading or unloading, and rock reinforcement by rockbolts, shotcrete or concrete lining. Examples of application of the D D A method with the new extensions are presented. Simulations of the underground excavation of the \ulcornerUnju Tunnel\ulcorner in Korea were carried out to evaluate the influence of fracture flow, excavation sequence and reinforcement on the tunnel stability. The results of the present study indicate that fracture flow and improper selection of excavation sequence could have a destabilizing effect on the tunnel stability. On the other hand, reinforcement by rockbolts and shotcrete can stabilize the tunnel. It is found that, in general, the D D A program with the three new extensions can now be used as a practical tool in the design of underground structures. In particular, phases of construction (excavation, reinforcement) can now be simulated more realistically.

• Journal of the Korean Geotechnical Society
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• v.23 no.11
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• pp.87-98
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• 2007

For the quick rehabilitation of a fire-damaged tunnel structure, it is the most important procedure to investigate the fire-induced damaged zone rapidly. This study aims to propose a new drilling resistance testing method by which mechanical properties of tunnel concrete lining altered by high temperature can be estimated easily and continuously. Especially, it alms to derive the relationships to estimate mechanical properties of mortar and concrete materials from drilling parameters. To obtain the optimum testing condition, a series of drilling resistance tests were carried out for mortar specimens. When the rotation per minute of drill bit, tile penetration rate and the bit diameter were 1,300 rpm, 1.40 mm/sec, and 10 mm respectively, the deviation of measured drilling resistance forces was minimal. Under the optimum testing condition, the relationships between drilling resistance and mechanical properties of mortar specimens were shown to be very favorable. The concept of replacing a mean value of resistance farces measured during drilling with the resistance energy was proposed to consider the effects of randomly distributed aggregates inside a concrete material on drilling resistance. When the concept was applied to concrete materials, a favorable relationship between actual compressive strength and drilling resistance energy was also successfully derived.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.2
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• pp.129-142
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• 2016

The underground cavity known as one of the reasons of ground surface settlement is a discontinuous character. Therefore, it is limited to analyze with continuum analysis. In this research, The spherical underground cavity affecting the ground surface settlement is studied with Discrete Element Method. Ground properties, depth and diameter of the spherical underground cavity are chosen as factors of the spherical underground cavity and the effect of the each factor variations on the ground surface settlement is analyzed. Relative depth to the diameter of the spherical underground cavity is also studied. The result of the research suggests the basis of underground cavity collapse prediction and standard of support.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.1
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• pp.31-41
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• 2010

This paper presents both numerical and physical modeling approaches for the dilation and spalling of rock recognized as typical process of rock around an underground opening at depth. For physical approach, laboratory testing of rectangular beams using a synthetic rock was used to investigate the onset of dilation and spalling. The beams are axially compressed and subjected to 4-point bending to provide non-uniform compressive stresses which are similar to the maximum tangential stress distribution around circular openings. Discrete element numerical analyses using commercial code $PFC^{2D}$ (Particle Flow Code) were performed to evaluate the stress path at various locations in the beams. The findings from these approaches suggest that the onset of dilation in laboratory tests appears to be a good indicator for assessing the stress magnitudes required to initiate spalling.