• Proceedings of the Korea Society for Simulation Conference
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• 1999.10a
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• pp.24-29
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• 1999

Proposed in this paper is a modeling and simulation methodology for a virtual manufacturing environment. Based on DEVS formalism[Zeigler 76], the proposed model, so called GKDEVS, is designed to descript the geometrical knematic structure as well as event-driven and continuous state dynamics. In terms of abstract simulation algorithm[Zeigler 84], the simulation method of GKDEVS is proposed for combined discrete-continuous simulation. Using the GKDEVS, and FMS model consisting of a turing machine, a 3-axis machine and a RGV-mounted robot is constructed and simulated.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.59.5-59
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• 2001

Multi-agent robot system is the system which executes by cooperating with each robots and controlling several robots. Capability and function of each robot must be considered for cooperation behavior. Furthermore, it is necessary to analyze the given environment and to replace complex task with some simple tasks. Analysis of the given environment and role assignment for the given tasks are composed of discret event. In this paper, the hierarchical controller for multi-agent robot system using the petri-net state diagram is proposed. The proposed modeling method is implemented for soccer robot system. The effectiveness of proposed modeling method is shown through experiment.

• Nuclear Engineering and Technology
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• v.48 no.5
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• pp.1162-1173
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• 2016

In this paper, we describe a physicomathematical model of the processes that occur in a sodium circuit with a variable flow cross-section in the case of a water leak into sodium. The application area for this technique includes the possibility of analyzing consequences of this leak as applied to sodium-water steam generators in fast neutron reactors. Hydrodynamic processes that occur in sodium circuits in the event of a water leak are described within the framework of a one-dimensional thermally nonequilibrium three-component gas-liquid flow model (sodium-hydrogen-sodium hydroxide). Consideration is given to the results of a mathematical modeling of experiments involving steam injection into the sodium loop of a circulation test facility. That was done by means of the computer code in which the proposed model had been implemented.

• Korean Journal of Health Education and Promotion
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• v.24 no.3
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• pp.21-34
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• 2007

Objectives: This study aims to examined whether physical activity prevent the negative effect of psychological stress on cardiovascular reactivity by reducing stress induced sympathetic output and preventing norepinephrine depletion negative psych-affective responses. It is assumed that physical activity reduces the magnitude of cardiovascular responses and psychological responses to stress which threaten individuals' physical and mental health. The result of investigating the effect of physical activity on reducing negative physiological and psychological responses would suggest useful information health for practitioners who want to prevent stress-induced diseases, especially coronary heart disease. Methods: participants of this study were 30 students (10 males & 20 females), whose mean age was 21.30 (SD=2.29). Fifteen students (5 males & 10 females) were assigned for in each group, treatment and control groups. They were interviewed and given a survey that included a consent form, demographics sheet and psychological tests, such as State-Trait Anger Expression Inventory and State-Trait Anxiety Inventory. Before the application of psychological stress, participants in treatment group were going through with a course of physical exercise, running on treadmill 15minutes, while participants in control group were not physically active. After exercise, there was 15 minutes resting period before applying cognitive stress. During the experiment, all participants performed challenging cognitive tasks for 20minutes in situations that were designed to experience learned helplessness and measured their cardiovascular reactivity including blood pressure and heart rate every 5 minutes, until 10 minutes after finishing the application of psychological stress(recovering state). In the end of experiment, they were given some psychological test again. Results: Heart rates of exercise group were significantly higher than non-exercise group, especially, five minute after applying cognitive stress and at the end of recovery, in other word 10 minutes after stressful event. Systolic blood pressures of exercise group were lower than those of non-exercise group during the stressful event, but this differences in borderline level of significance. state anger level of exercise group decreased even experiencing stress, while those of non-exercise group increase. And state anxiety level of exercise group decreased in borderline level of significance. Conclusion: This study reiterate health benefits of physical activity and suggest that regular moderate exercise may regulate cardiovascular reactivity and psycho-affective responses from stress by reducing stress induced sympathetic output.

• ETRI Journal
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• v.30 no.2
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• pp.275-281
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• 2008

A 40 Gb/s clock and data recovery (CDR) module for a fiber-optic receiver with improved phase-locked loop (PLL) circuits has been successfully implemented. The PLL of the CDR module employs an improved D-type flip-flop frequency acquisition circuit, which helps to stabilize the CDR performance, to obtain faster frequency acquisition, and to reduce the time of recovering the lock state in the event of losing the lock state. The measured RMS jitter of the clock signal recovered from 40 Gb/s pseudo-random binary sequence ($2^{31}-1$) data by the improved PLL clock recovery module is 210 fs. The CDR module also integrates a 40 Gb/s D-FF decision circuit, demonstrating that it can produce clean retimed data using the recovered clock.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.56-59
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• 2003

As electric power systems grow to supply the increasing electric power demand short-circuit current tends to increase and impose a severe burden on circuit breakers and power system apparatuses. Thus, all electric equipment in a power system has to he designed to withstand the mechanical and thermal stresses of potential short-circuit currents. Among current limiting devices, Fault Current Limiter (FCL) is expected to reduce the short-circuit current. Especially, Superconducting Fault Current Limiters (SFCL) offer ideal performance: in normal operation the SFCL is in its superconducting state and has negligible impedance, in the event of a fault, the transition into the normal conducting state passively limits the current. The SFCL using high-temperature superconductors offers a positive resolution to controlling fault-current levels on utility distribution and transmission networks. This study contributes to the EMTDC based modeling and simulation method of DC Reactor type SFCL. Single and three phase faults in the utility system with DC reactor type SFCLs have been simulated using EMTDC in order to coordinate with other equipments, and the results are discussed in detail.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.330-335
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• 1993

This paper presents an efficient solution for a class of forbidden state problems by introducing a cyclic timed controlled marked graphs (TCMG's), a special class of timed controlled Petri nets (TCPN's) as a model of a class of discrete event systems (DES's). The state feedback control is synthesized, which is maximally permissive while guaranteeing the forbidden states will be avoided. The practical applications or tire theoretical results for an automated guided vehicle (ACV) coordination problem in a flexible manufacturing facility is illustrated.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.10
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• pp.967-973
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• 2009

The model matching problem of asynchronous sequential machines is to design a corrective controller such that the stable-state behavior of the closed-loop system matches that of a prescribed model. In this paper, we address model matching when the external input set consists of controllable inputs and uncontrollable ones. Like in the frame of supervisory control of Discrete-Event Systems (DES), uncontrollable inputs cannot be disabled and must be transmitted to the plant without any change. We postulate necessary and sufficient conditions for the existence of a corrective controller that solves model matching despite the influence of uncontrollable events. Whenever a controller exists, the algorithm for its design is outlined. To illustrate the physical meaning of the proposed problem, the closed-loop system of an asynchronous machine with the proposed control scheme is implemented in VHDL code.

• Journal of the Korean Home Economics Association
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• v.27 no.4
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• pp.51-58
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• 1989

The purpose of this study was to investigate the state of eating out and the food preference of college students in Seoul. This survey was carried out through questionaires, and the subjects were 158 male and 159 female students. The results obttained were summarized as follows; 1) Students who took late evening meal at home after eating out were 35.7% and most of the reasons were to custom. 2) During eating out, 30% of students had drinking. Male students had Soju (45.6%), and female had Beer (56.0%). 3) The most cases in date time, eating out cost were 5,000w. They were fond of Western Restaurant and the favorite food were Dongas. 4) Freqency of eating out with family had more than once a month (35%), because of a memorial day and event day, and the most favorite food was Sogalbigui. 5) Male and female students's choice in food at restaurant type were very different.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.757-763
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• 2003

웹서비스 기술이 발전함에 따라 분산환경의 웹기반 서비스들을 조합한 복잡한 비즈니스 프로세스를 구현할 수 있게 되었다. 이러한 비즈니스 프로세스는 일반적으로 비즈니스 활동(activity)들의 순서와 로직을 포함딴 이벤트 기반 모델(event-driven model)로 표현되고 있다. 하지만 비즈니스 활동을 수행하기 위해서는 불특정 다수의 대안 서비스들 중 하나를 런타임-바인딩(runtime binding)하여 해당 비즈니스 활동을 수행해야 하는 경우가 빈번히 일어나는데. 이는 기존의 이벤트 기반 모델링 기법만을 이용해서 해결하기 어렵다. 따라서 본 논문에서는 비즈니스 프로세스를 동적으로 통합할 수 있도록 상태 기반 협상 모델링(state-,driven brokering modeling SDBM)을 기존 모델링 기법에 확장한 아키텍쳐를 제안한다. SDBM은 이벤트 기반 모델링에서 표현하기 힘든 대안 서비스들의 동적 런타임-바인딩을 가능하게 하는데. 이는 대화 정잭(conversation policy)을 구현함으로써 가능해 진다. 본 논문에서는 핵심 비즈니스 프로세스에 독립적이며 웹기반의 분산 비즈니스 프로세스 간의 유연한 통합과 자동화된 협업을 수행랄 수 있는 확장된 메커니즘을 웹서비스 기술로 구현하였다.