• Journal of the Korean Operations Research and Management Science Society
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• v.34 no.1
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• pp.61-83
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• 2009

This study developed a variable demand traffic assignment model by stable dynamics. Stable dynamics, suggested by Nesterov and do Palma[19], is a new model which describes and provides a stable state of congestion in urban transportation networks. In comparison with the user equilibrium model, which is based on the arc travel time function in analyzing transportation networks, stable dynamics requires few parameters and is coincident with intuitions and observations on congestion. It is therefore expected to be a useful analysis tool for transportation planners. In this study, we generalize the stable dynamics into the model with variable demands. We suggest a three stage optimization model. In the first stage, we introduce critical travel times and dummy links and determine variable demands and link flows by applying an optimization problem to an extended network with the dummy links. Then we determine link travel times and path flows in the following stages. We present a numerical example of the application of the model to a given network.

• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.3
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• pp.63-80
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• 2007

This study is a generalization of 'stable dynamics' recently suggested by Nesterov and de Palma[29]. Stable dynamics is a new model which describes and provides a stable state of congestion in urban transportation networks. In comparison with user equilibrium model that is common in analyzing transportation networks, stable dynamics requires few parameters and is coincident with intuitions and observations on the congestion. Therefore it is expected to be an useful analysis tool for transportation planners. An equilibrium in stable dynamics needs only maximum flow in each arc and Wardrop[33] Principle. In this study, we generalize the stable dynamics into the model with multiple traffic classes. We classify the traffic into the types of vehicle such as cars, buses and trucks. Driving behaviors classified by age, sex and income-level can also be classes. We develop an equilibrium with multiple traffic classes. We can find the equilibrium by solving the well-known network problem, multicommodity minimum cost network flow problem.

• Journal of the Korean Operations Research and Management Science Society
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• v.34 no.4
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• pp.123-138
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• 2009

This study examined the first- and second-best pricing by stable dynamics in congested transportation networks. Stable dynamics, suggested by Nesterov and de Palma (2003), is a new model which describes and provides a stable state of congestion in urban transportation networks. The first-best pricing in user equilibrium models introduces user-equilibrium in the system-equilibrium by tolling the difference between the marginal social cost and the marginal private cost on each link. Nevertheless, the second-best pricing, which levies the toll on some, but not all, links, is relevant from the practical point of view. In comparison with the user equilibrium model, the stable dynamic model provides a solution equivalent to system-equilibrium if it is focused on link flows. Therefore the toll interval on each link, which keeps up the system-equilibrium, is more meaningful than the first-best pricing. In addition, the second-best pricing in stable dynamic models is the same as the first-best pricing since the toll interval is separately given by each link. As an effect of congestion pricing in stable dynamic models, we can remove the inefficiency of the network with inefficient Braess links by levying a toll on the Braess link. We present a numerical example applied to the network with 6 nodes and 9 links, including 2 Braess links.

• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.4
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• pp.19-35
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• 2007

This study is for detecting the Braess Paradox by stable dynamics in general transportation networks. Stable dynamics, suggested by Nesterov and de Palma[18], is a new model which describes and provides a stable state of congestion in urban transportation networks. In comparison with user equilibrium model based on link latency function in analyzing transportation networks, stable dynamics requires few parameters and is coincident with intuitions and observations on the congestion. Therefore it is expected to be an useful analysis tool for transportation planners. The phenomenon that increasing capacity of a network, for example creating new links, may decrease its performance is called Braess Paradox. It has been studied intensively under user equilibrium model with link latency function since Braess[5] demonstrated a paradoxical example. However it is an open problem to detect the Braess Paradox under stable dynamics. In this study, we suggest a method to detect the Paradox in general networks under stable dynamics. In our model, we decide whether Braess Paradox will occur in a given network. We also find Braess links or Braess crosses if a network permits the paradox. We also show an example how to apply it in a network.

• Journal of Agricultural Extension & Community Development
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• v.18 no.3
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• pp.631-664
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• 2011

As agricultural companies encounter number of risks in their business, it is very important to control the risks for their stable management. So we examine the agricultural business risks and propose the risk management strategies for the agricultural companies. For these purpose, we analyze the agricultural business risks with which agricultural companies are confronted, and propose the agricultural companies' the risk management strategies. The results of this study are as follows : First, Changing the risk environment of agricultural business, we have to realize the importance of the agricultural risks and risk management in it. Second, When we choose the risk management strategies which are risk retention, risk avoidance, risk control, risk transfer and insurance, etc., we should always consider the frequency of loss and the severity of loss. Third, If we don't control the agricultural risks, we will be in a position to very difficult situation. So, Agricultural companies should lead to stronger effort to manage the risks for their stable business.

• ETRI Journal
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• v.21 no.4
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• pp.23-28
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• 1999

In this paper, we analyze the performance benefits of broadband ATM networks when the call control and management flows are separated from user data flows. The virtual path tunneling concept for control and management flows are applied to the same physical ATM networks. The behaviors of channel throughput and transfer delay are analyzed. It results that the proposed virtual short-cut paths can maintain the network being stable with acceptable bandwidth. They are very useful to provide the stable control and management capabilities for Internet and mobile applications in the broadband ATM networks. In our numerical results, the effective throughputs of the proposed virtual shout-ut channel are about three times than those of end-to-end user data channels with hop distances of 10, and about two times than those with hop distance of 5 when the link blocking probability increases to 0.1. It concludes that the effective channel bandwidth are greatly reduced down while physical links are not stable and user traffic flows are occasionally overflowed.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1992.04b
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• pp.171-179
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• 1992

본고에서는 그래프를 이용하여 stable law분포의 index, skewness, scale, location 모수들에 대한 추정방법을 제시한다. 먼저, order statistics의 함수인 tail length statistic $K_{t}$ , skewness statistic $K_{s}$ 를 이용하여 index .alpha., scale .betha.를 추정한다. 다음에는, 추정된 .alpha., .betha.를 index로 하여 개발된 그래프들로 부터 scale .sigma., location .mu.추정에 필요한 order statistics의 함수를 결정한다. 몇가지 예를 마지막에 예시한다.

• Korean Journal of Human Ecology
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• v.8 no.1
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• pp.15-27
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• 1999

This study investigated characteristics of H.T.P test responses according to home environment variables. The subjects were 183 children in the fifth grade at an elementary school in Taejon. SAS was utilized in order to analyze data using x2 technique. The result of the study were as follows. The more home environment stimuli the children were provided by parents, the more stable in emotion they were. Especially four out of six home environment variables were found significant in helping children become emotionally stable, confident, well-adjusted, and high in achievement. These four variables were language stimulus, social maturity educational resources, and housing environment. It is concluded that children used to be provided with good home environment including language stimulus, social maturity, educational resource, housing environment, and plenty of family activities in order to become emotionally stable, confident, high in achievement, and adjustment.

• Journal of the Korean Operations Research and Management Science Society
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• v.1 no.1
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• pp.139-145
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• 1976

To evaluate the composite composed of Shell-Oil Co. itself and its sub-sidiary companies, the account data for 10 years from 1964 to 1973 was analyzed. Before analyzing, the formula needed to it was deduced and by synthesizing the deduced formula, the price earning ratio (R) was computed as the trial and error method. Resultantly the earning power (ic) was less than 5% ie. R=17.03. So this company showed the normal company earnings and allotment from 1964 to 1968. From 1968 to 1970, the allotment was increased but the earnings was decreased. And in spite of the successive increase of the allotment from 1970 to 1973, the company showed that it was the stable and profitable one with stable increase of earnings. In conclusion, this company showed the stable trend of increase in the allotment of earnings and earnings itself.

• Management Science and Financial Engineering
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• v.2 no.1
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• pp.103-122
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• 1996

This paper presents an easily used graphical procedure for simultaneous estimation of the index, skewness, scale, and location parameters of the stable laws. First, the index $\alpha$ and skewness $\beta$ are estimated through the joint use of a tail length statistic $\widetilde{K_t}$ and a skewness statistic $\widetilde{K_s}$, both of which are functions of order statistics. Next, the function of order statistics needed for estimation of scale $\sigma$ and location $\mu$ are determined from a nomogram indexed on the estimates of $\alpha$ and $\beta$. Some applications and examples are provided.