• The KIPS Transactions:PartC
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• v.8C no.6
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• pp.847-854
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• 2001

The Web continues to grow fast rate in both a large aclae volume of traffic and the size and complexity of Web sites. Along with growth, the complexity of tasks such as Web site design Web server design and of navigating simply through a Web site have increased. An important input to these design tasks is the analysis of how a web site is being used. The is paper proposes a Page logging System(PLS) identifying reliably user sessions required in Web mining system PLS consists of Page Logger acquiring all the page accesses of the user Log processor producing user session from these data, and statements to incorporate a call to page logger applet. Proposed PLS abbreviates several preprocessing tasks which spends a log of time and efforts that must be performed in Web mining systems. In particular, it simplifies the complexity of transaction identification phase through acquiring directly the amount of time a user stays on a page. Also PLS solves local cache hits and proxy IPs that create problems with identifying user sessions from Web sever log.

• Journal of Korean Society of Transportation
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• v.35 no.3
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• pp.197-209
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• 2017

With the advent of age that people spend more time and money on leisure activities, there is increasing interest in professional sport games. The location of large scale sport facilities has substantial impacts on existing transportation pattern because the facility attracts and generates massive traffic volume within a short period of time. This study aims to develop a mode choice model of leisure trips of which the destinations are a sport facility. A structured SP (stated preference) survey questionnaires were developed through an experimental design, and professional sport spectators were asked to state their preference in the choice of transport mode to the sport facility. The survey results show that public transportation is preferred to passenger cars for their trip to big sports event, implying that the convenience of back home trip after the event is an important factor of their mode choice. This study is a rare research on the trip pattern to sports complex in Korea, which provides policy implications on the provision of mass transit including subway system to large scale sport complexes. And it is also expected that this study contributes to future researches on leisure trip pattern.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.887-895
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• 2018

This paper presents a braking model that can be used to design the safety distance of a train control system and a train braking system to increase the volume of traffic. For the braking model, a train set (electric multiple unit composed 6 cars) was tested. The factors that can affect the braking characteristics include the friction coefficient, braking pressure, and regenerative braking. The braking pressure was classified into service and emergency braking and reflected the characteristics of the vehicle. The external force acting on the running railway car was tested in accordance with KS R 9217, and the running resistance of the train is presented in the form of a polynomial. The dynamic behavior of the train running on a straight flat line was simulated using UM 8.3. The results were validated with experimental data, and the results were reasonable. With the validated model, a stopping distance was determined according to the initial braking speed and compared with the deceleration braking model. In addition, a safety distance for the train control system could be changed according to the frictional coefficient limits. These results are expected to be useful for analyzing the dynamic behavior of trains, and for analyzing various railway environments and improving the braking performance.

• Korea Trade Review
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• v.43 no.5
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• pp.159-177
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• 2018

The container shipping sector is an important international logistics operation that connects open economies. Freight rates rapidly change as the market fluctuates, and staff related to the shipping market are interested in factors that determine freight rates in the container market. This study uses the Vector Error Correction Model(VECM) to estimate the impact of factors affecting container freight rates. This study uses data published by Clarksons. The analysis results show a 4.2% increase in freight rates when world container traffic increases at 1.0%, a 4.0% decrease in freight rates when volume of container carriers increases by 1.0%, a 0.07% increase in freight rates when bunker price increases by 1.0%, and a 0.04% increase in freight rates accompanying 1.0% increase in libor interests rates. In addition, if the current freight rate is 1.0% higher than the long-term equilibrium rate, the freight rate will be reduced by 3.2% in the subsequent term. In addition, if the current freight rate is 1.0% lower than the long-term equilibrium rate, the freight rate will decrease by 0.12% in the following term. However, the adjusting power in a period of recession is not statistically significant which means that the pressure of freight rate increase in this case is neglectable. This research is expected to contribute to the utilization of scientific methods in forecasting container freight rates.

• Journal of Korean Society of Transportation
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• v.22 no.7 s.78
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• pp.155-159
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• 2004

Recently, there are many trials about Artificial neural networks : ANNs structure and studying method of researches for forecasting traffic volume. ANNs have a powerful capabilities of recognizing pattern with a flexible non-linear model. However, ANNs have some overfitting problems in dealing with a lot of parameters because of its non-linear problems. This research deals with the application of a variety of model selection criterion for cancellation of the overfitting problems. Especially, this aims at analyzing which the selecting model cancels the overfitting problems and guarantees the transferability from time measure. Results in this study are as follow. First, the model which is selecting in sample does not guarantees the best capabilities of out-of-sample. So to speak, the best model in sample is no relationship with the capabilities of out-of-sample like many existing researches. Second, in stability of model selecting criterion, AIC3, AICC, BIC are available but AIC4 has a large variation comparing with the best model. In time-series analysis and forecasting, we need more quantitable data analysis and another time-series analysis because uncertainty of a model can have an effect on correlation between in-sample and out-of-sample.

• Journal of Korean Society of Transportation
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• v.35 no.4
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• pp.360-373
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• 2017

The BTO-a projects is the types, which has a demand risk among the type of PPP projects in Korea. When demand risk is realized, private investor encounters financial difficulties due to lower revenue than its expectation and the government may also have a problem in stable infrastructure operation. In this regards, the government has applied various risk sharing policies in response to demand risk. However, the amount of government's risk sharing is the government's contingent liabilities as a result of demand uncertainty, and it fails to be quantified by the conventional NPV method of expressing in the text of the concession agreement. The purpose of this study is to estimate the value of investment risk sharing by the government considering the demand risk in the profit sharing system (BTO-a) introduced in 2015 as one of the demand risk sharing policy. The investment risk sharing will take the form of options in finance. Private investors have the right to claim subsidies from the government when their revenue declines, while the government has the obligation to pay subsidies under certain conditions. In this study, we have established a methodology for estimating the value of investment risk sharing by using the Black - Scholes option pricing model and examined the appropriateness of the results through case studies. As a result of the analysis, the value of investment risk sharing is estimated to be 12 billion won, which is about 4% of the investment cost of the private investment. In other words, it can be seen that the government will invest 12 billion won in financial support by sharing the investment risk. The option value when assuming the traffic volume risk as a random variable from the case studies is derived as an average of 12.2 billion won and a standard deviation of 3.67 billion won. As a result of the cumulative distribution, the option value of the 90% probability interval will be determined within the range of 6.9 to 18.8 billion won. The method proposed in this study is expected to help government and private investors understand the better risk analysis and economic value of better for investment risk sharing under the uncertainty of future demand.

• The Korean Journal of Air & Space Law and Policy
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• v.30 no.2
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• pp.337-371
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• 2015

In recent years, aviation safety has been facing new hazards due to the rapidly changing environment in which aircraft operation increasingly finds. Continuously increasing air traffic volume, integration of various cultures from many States, and many other changes are the causal factors of the new risks. To identify such new hazards and risks, the government of the Republic of Korea (ROK) established aviation safety reporting systems in accordance with the international standards of the Convention on International Civil Aviation. However, there are some misunderstandings by the government in operating and by the personnel who take part in these reporting systems. Everybody should understand that aviation safety reporting system is not a punitive measure but a tool for collecting data in order to improve safety. In addition, such a system can be utilized further to promote an improved awareness on the need for a proper safety culture on the part of both the government, the industry and the personnel. This paper includes studies on international standards, relevant regulations in the United States and the United Kingdom. Moreover, this paper proposes to the government of ROK several points to improve their own system, including integration of the existing reporting systems, improvement of reporting items, implementation of safety data taxonomy and the establishment of safety data protection.

• Korean Journal of Heritage: History & Science
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• v.43 no.1
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• pp.190-211
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• 2010

The purpose of this paper is to provide the preliminary data for maintenance of old trees of natural monuments and establishing protection projects. Accordingly, growth conditions, location circumstances, environment and protection management were analyzed for old trees at 34 sites in Gyeongsangbuk-do. Tree forms, crown, trunk and trees' health, leaves volume were analyzed in survey sites. As the results, the growth of Picrasma quassioides in Songsadong, Andong-si and Catalpa ovata in Hongwon-ri, Cheongsong-gun were not in good condition, along with other old trees of 6 cities (Quercus variabilis in Susan-ri, Uljin-gun, Juniperus chinensis in Hujeong-ri, Uljin-gun, Pyrus ussuriensis in Ssangjeon-ri, Uljin-gun, Salix glandulosa var. pilosa in Deokchon-ri, Cheongdo-gun, Pinus densiflora for. multicaulis in Hwasan-ri, Mungyeong-si, Pinus densiflora in Daeha-ri, Mungyeong-si). Accoding to these results, protection project and consistent monitoring are necessary. The analysis results of growth conditions per location circumstances showed that the old trees in the small spaces with large traffic of people were in bad condition. Therefore, it is necessary to secure sufficient space and soil improvement for such trees. The analysis results of growth conditions per species showed that Zelkova serrata, Quercus spp., Pinus densiflora are in good condition while Salix koreensis and others, i.e. a singular tree, are in poor condition. Thus, relatively smaller individuals and separately situated trees need careful management in their protection. The analysis results of trunk's growth ratio showed that Pinus densiflora, Ginkgo biloba, Zelkova serrata are in good condition whereas Juniperus chinensis, Quercus variabilis, Salix koreensis are not. It is a recent trend that tree surgeries are gradually decreasing; there are a number of damaged trees with no maintenance/management, and several sites requiring mend trunks management and cabling, bracing in protection and management projects. Hence, in the future, local government and management organizations should plan for systematic management and establish a protection plan for the natural monument trees. Also, 12 sites were found to be in need to purchase lands in order to secure the growth spaces, and since most of these areas are available for purchase, it is needed to promote a budget and purchase those areas through persuasion of the owner. These areas seems crucial in order to maximize the effect of conservation efforts and budgets for the preservation and restoration of the old trees.