• Advanced Composite Materials
• /
• v.17 no.4
• /
• pp.373-407
• /
• 2008

This paper will examine the possibilities of the virtual tests of composite structures by simulating mechanical behaviors by using supercomputing technologies, which have now become easily available and powerful but relatively inexpensive. We will describe mainly the applications of large-scale finite element analysis using the direct numerical simulation (DNS), which describes composite material properties considering individual constituent properties. DNS approach is based on the full microscopic concepts, which can provide detailed information about the local interaction between the constituents and micro-failure mechanisms by separate modeling of each constituent. Various composite materials such as metal matrix composites (MMCs), active fiber composites (AFCs), boron/epoxy cross-ply laminates and 3-D orthogonal woven composites are selected as verification examples of DNS. The effective elastic moduli and impact structural characteristics of the composites are determined using the DNS models. These DNS models can also give the global and local information about deformations and influences of high local in-plane and interlaminar stresses induced by transverse impact loading at a microscopic level inside the materials. Furthermore, the multi-scale models based on DNS concepts considering microscopic and macroscopic structures simultaneously are also developed and a numerical low-velocity impact simulation is performed using these multi-scale DNS models. Through these various applications of DNS models, it can be shown that the DNS approach can provide insights of various structural behaviors of composite structures.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.11 no.5
• /
• pp.15-26
• /
• 2012

Government agencies including the national police agency have executed diverse efforts including continuous improvements of traffic facilities and operation methods, education, enforcements in order to improve traffic operation systems; nevertheless there have been continuous criticisms on irrationality in traffic signal and road facility operation. One of the reasons may be the lack of systematic preliminary evaluations on various alternatives. However, there was no appropriate tool to evaluate the mobility and safety of thus alternatives in a systematic way. Therefore, this study proposes the systematic use of microscopic traffic simulation models as a comprehensive evaluation tool. In addition, this study verified the potential of using a microscopic traffic simulation model using the case of operating an overlap phase on a shared-left-turn lane through a systematic way where the evaluation was conducted through data collection, building networks, calibrating microscopic simulation models, producing performance measures, evaluating mobility and safety, and so on. As a result, the operation of overlap phase on a shared-left-turn lane showed no big difference from other operation scenarios such as leading left-turn on exclusive left turn lane in terms of mobility. However the operation of overlap phase on a shared-left-turn lane decreased safety by increasing potential conflicts.

• Journal of the Korean Wood Science and Technology
• /
• v.40 no.5
• /
• pp.352-362
• /
• 2012

Mass transfer behavior in wood was estimated through its microscopic structure. The diffusion coefficients which were decided by theoretical equations are influenced by different anatomical properties of wood. From the experiment, the moisture flux was linear to the square root of time. The diffusion coefficients had a regular tendency during the time elapse. During the modeling, it is necessary to understand the limitation of parameters and consider the particular situation to be simulated. In hardwood, because the apertures were not considered, tangential mass transfer simulation was totally different from experiment. As a result, a hardwood model design should consider the apertures which are even on the fiber walls.

• Proceedings of the Korea Society for Simulation Conference
• /
• 2001.05a
• /
• pp.106-106
• /
• 2001

네트웍의 용량의 개념이 없는 미세한 교통혼잡 도구로서 Microscopic시뮬레이션 모형인 Paramics가 소개된다. 모형의 기본구조가 설명되고, 특히 응용사례로서 서울시 교통관리 시스템을 설치함에 있어서 대안의 평가에 따른 제반 결과의 척도를 이끌어 내는 절차가 소개되었고, 아울러 결과가 분석되어 제시되었다. 이는 미시적 교통 시뮬레이션을 위한 고성능의 소프트웨어로서 각 차량들은 상세한 속성들을 가지고, ITS와 운전자와의 인터페이스를 모델링 할 뿐만 아니라 정확한 교통류, 대중교통 시간, 혼잡정보를 시뮬레이션 할 수 있는 장점이 있는바 적용 분야로서 여기까지가 있으나 혼잡이 있는 도로 네트워크 및 일반도로 네트워크와 ITS 인프라의 존재상황에서 제반 모델링이 가능한바 이를 통한 도시고속도로 관리시스템의 효과를 분석하였다. 신호의 영향, 첨단신호제어, 램프 미터링, 루프 검지기, 다양한 속도 표지, VMS 정보전략 등의 기능을 소개하고 금번 서울시의 사례를 통한 모형의 장단점을 보고한다. 아울러 이 시뮬레이션 모형의 한계도 함께 지적되었다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.2D
• /
• pp.119-125
• /
• 2010

Transportation system improved with rapid economic growth has helped human being a lot. However, the system has been also created social problems. The fast increasing auto ownership has not only increased transportation accidents but decreased air quality rapidly. One of the serious problems in transportation is that transportation policies have disregarded human factor, especially pedestrian environment. This research has developed microscopic pedestrian simulation with Netlogo. Netlogo is a very useful program for simulating complex systems such as pedestrian movements. The simulated pedestrian movements has been compared with actual surveyed pedestrian movements on a sidewalk. The comparison has been showed that the simulation program can be used for analyzing various pedestrian environments. Also, the impacts of bollard on the sidewalks have been analyed with the simulation program.

• Transportation Technology and Policy
• /
• v.12 no.1
• /
• pp.51-56
• /
• 2015

• Journal of Korean Society of Transportation
• /
• v.10 no.3
• /
• pp.7-20
• /
• 1992

The common cycle time for the linded signals is usually determined for the critical intersecion, just because the cpacity of a signalized intersection depends on the cycle time. This may not be optimal since the interactions between the flow and the spatial structure of the route or the area are disregarded in this case. It is common to separate the total delay incurred at signals into two parts, a deterministic or uniform delay and a stochastic or random delay. The deterministic delays and the stochastic delays on the artery particularly related to signal cycle time. For this purpose a microscopic simulation technique is used to evaluate deterministic delays, and a macroscopic simulation technique based on the principles of Markov chains is used to evaluate stochastic delays with over flow queue. As a result of investigating the relations between deterministic delays and cycle time in the various circumstances of spacing of signals and traffic volume. As for stochastic delays the resalts of comparisons of the macroscopic simulation and Newell's approximation with the microscopic simulation indicate that the former is valid for the degree of saturation less than 0.95 and the latter is for that above 0.95. Newell's argument that the total stochastic delay on an arterial is dominated by that at or caused by critical intersection is certified by the simulation experiments. The comprehensive analyses of the values of optimal cycle time with various conditions lead to a model. The cycle time determined by this model shows to be approximately 70% of that calculated by Webster's.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.21 no.6
• /
• pp.70-86
• /
• 2022

An autonomous demand-responsive bus with mobility-on-demand service is an innovative transport compensating for the disadvantages of an autonomous bus and a demand-responsive bus with mobility-on-demand service. However, less attention has been paid to the quantitative impact assessment of the autonomous demand-responsive bus due to the technological complexity of the autonomous demand-responsive bus. This study simulates autonomous demand-responsive bus trips by reinforcement learning on a microscopic traffic simulation to quantify the impact of the autonomous demand-responsive bus. The Chungju campus of the Korea National University of Transportation is selected as a testbed. Simulation results show that the introduction of the autonomous demand-responsive bus can reduce the wait time of passengers, average control delay, and increase the traffic speed compared to the results with fixed route bus service. This study contributes to the quantitative evaluation of the autonomous demand-responsive bus.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1487-1491
• /
• 2008

Detailed knowledge on the motion of blood cells flowing in micro-channels under simple shear flow and the influence of blood flow is essential to provide a better understanding on the blood rheological properties and blood cell aggregation. The microscopic behavior of red blood cell (RBCs) is numerically investigated using a fluid-structure interaction (FSI) method based on the Arbitrary-Lagrangian-Eulerian (ALE) approach and the dynamic mesh method (smoothing and remeshing) in FLUENT (ANSYS Inc., USA). The employed FSI method could be applied to the motions and deformations of a single blood cell and multiple blood cells, and the primary thrombogenesis caused by platelet aggregation. It is expected that, combined with a sophisticated large-scale computational technique, the simulation method will be useful for understanding the overall properties of blood flow from blood cellular level (microscopic) to the resulting rheological properties of blood as a mass (macroscopic).

• Proceedings of the Korean Society for Language and Information Conference
• /
• 2007.11a
• /
• pp.459-470
• /
• 2007

This study explores the textual characteristics, more precisely the quantity and diversity of nouns, of Japanese prime ministers' Diet addresses. In the field of stylistics, textual characteristics independent of the content have been examined with the aim on detecting the authors, genres, and chronological variations of texts. This study focuses instead on textual characteristics related to the content of texts, namely the quantity and diversity of nouns, because our aim is to analyze texts to better understand two political phenomena: (a) the difference between the two types of Diet addresses delivered by Japanese prime ministers, and (b) the perceived changes made to these addresses by two powerful prime ministers. It is a case study of the microscopic characterization of texts, which has become more and more important with the expansion in the scope of stylistics and the production of a wide variety of new types of texts following the advent of the Web.