• Journal of the Korean Operations Research and Management Science Society
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• v.30 no.4
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• pp.99-115
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• 2005

For an analysis of the performance of a computer system, the minimum cycle time method has been widely used. The minimum cycle time method is a mathematical technique with which we can find the minimum duration time needed to fire all the transitions at least once and coming back to the Initial marking in a timed net. A timed net is a modified version of a Petri net where a transition is associated with a delay time. In the real world, an event is associated with a probability of occurrence. However, a timed net is not equipped with any facility of specifying probability of event occurrence. Therefore, the minimum cycle time method applied on a timed net can easily overlook probabilities of occurrences of events and yield a wrong result. We are proposing 'Timed Net with Probabilities of Choices' where a transition can be associated with both delay time and a probability of occurrence. We also introduce an algorithm for minimum cycle time analysis on a 'Timed Net with Probabilities of Choices'. As an example of application, we are performing an analysis of the location based service system using 'Timed Net with Probabilities of Choices'.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.4
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• pp.323-329
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• 2015

For the design guide of a vessel operating in cold region, numerical analysis was carried out to evaluate the ice class louver which installed the heating cables by using ANSYS 13.0 CFX. The numerical analysis was performed by considering Unsteady Reynolds Averaged Navier Stokes (RANS) equation. This study based on the experimental results of ‘The Cryogenic Performance Evaluation for the Excellent De-icing Ice Class Louver’ in KRISO. For validation of the numerical analysis results, the cold chamber experimental data measured by the heat sensors in certain location of the ice class louver was used. The external environmental temperature which varies from 0℃ to –30℃ was considered in numerical analysis. Also the design guide for optimum de-icing presented through heating cable power capacity(33 W/m, 45 W/m, 66 W/m), location of the heating cable(front, center, behind on the blade) and relative velocity(1 m/s, 4 m/s, 7 m/s).

• Korean journal of food and cookery science
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• v.29 no.6
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• pp.637-645
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• 2013

The purpose of this study was to investigate the consumers' selection attributes of social enterprises type cafe by IPA(Importance-Performance Analysis). Data were collected through a self-administered questionnaire by 309 random consumers in several social enterprises type cafes in Seoul and Gyonggi area. The data was analyzed using SPSS windows(ver. 17.0) for descriptive analysis, t-test, one-way ANOVA and factor analysis. The importance of cafe's selection attributes were divided into five factors including 'promotion and menu', 'service quality and atmosphere', 'location', 'taste', and 'brand name'. The mean scores of importance and performance for cafe selection attributes were 4.01 and 3.68 out of 5, showing a significant difference between importance and performance. According to the IPA results of 17 selection attributes for social enterprises type cafe, the selection attributes with relatively low performance but high importance(II quadrant) was 'easy accessibility'. The factor to be improved through the IPA was accessibility factor, showing that the consumers had a low satisfaction compared to the significance of cafe's location.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.150-159
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• 2018

The present research deals with a finite element analysis and fatigue evaluation of a steam separator of a high-pressure evaporator for the Heat Recovery Steam Generator (HRSG). The fatigue during the expected life of the HRSG was evaluated according to the ASME Boiler and Pressure Vessel Code Section VIII Division 2 (ASME Code). First, based on the eight transient operating conditions prescribed for the HRSG, temperature distribution of the steam separator was analyzed by a transient thermal analysis. Results of the thermal analysis were used as a thermal load for the structural analysis and used to determine the mean cycle temperature. Next, a structural analysis for the transient conditions was carried out with the thermal load, steam pressure, and nozzle load. The maximum stress location was found to be the riser nozzle bore, and hence fatigue was evaluated at that location, as per ASME Code. As a result, the cumulative usage factor was calculated as 0.00072 (much less than 1). In conclusion, the steam separator was found to be safe from fatigue failure during the expected life.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.2
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• pp.123-129
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• 2012

It was previously suggested the design sensitivity analysis based on transmissibility function to identify the most sensitive response location over a small design modification. On the other hand, energy isoclines were used to predict the fatigue damage with acceleration response only. Both of previous studies commonly tackle the engineering problem using the acceleration response alone such that it may be possible to investigate the relationship between sensitivity analysis and accumulated fatigue damage. In this paper, it is suggested the novel method of vibration fatigue prediction using design sensitivity analysis to enhance the accuracy of predicted accumulated fatigue. Uni-axial vibration testing is performed with a simple notched specimen and the prediction of fatigue damage is conducted using accelerations measured at different locations. It can be concluded that the accuracy of predicted fatigue damage is proportional to the sensitivity index of the responsible location.

• International Journal of Automotive Technology
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• v.7 no.3
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• pp.329-336
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• 2006

The resistance spot-welded region in most current finite element crash models is characterized as a rigid beam at the location of the welded spot. The region is modeled to fail with a failure criterion which is a function of the axial and shear load at the rigid beam. The calculation of the load acting on the rigid beam is important to evaluate the failure of the spot-weld. In this paper, numerical simulation is carried out to evaluate the calculation of the load at the rigid beam. At first, the load on the spot-welded region is calculated with the precise finite element model considering the residual stress due to the thermal history during the spot welding procedure. And then, the load is compared with the one obtained from the model used in the crash analysis with respect to the element size, the element shape and the number of imposed constraints. Analysis results demonstrate that the load acting on the spot-welded element is correctly calculated by the change of the element shape around the welded region and the location of welded constrains. The results provide a guideline for an accurate finite element modeling of the spot-welded region in the crash analysis of vehicles.

• Journal of Korea Planning Association
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• v.53 no.7
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• pp.23-37
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• 2018

In recent years, there has been a proliferation of commercial uses in the area where Gentrification occurs. In order to cope with such a diffusion phenomenon, it is necessary to derive the diffusion area accurately. Gentrification has a feature that occurs locally in a short time. Therefore, this study used the space-time pattern analysis to derive the diffusion area of commercial uses in Bukchon, a typical gentrified area in Seoul. Among the space-time pattern analysis, space time permutation statistics used in this study can derive the convergence phenomenon of time and space in a particular case with only the location information. The results confirmed that there has been three proliferation area in Bukchon, one started in 2007, other in 2013 and the other in 2014. In the earliest area, independent shops were the most popular, and the majority of them were restaurants. However in latter areas, there has been more chain stores and clothing stores than earlier area. The findings of this study indicate that space time pattern analysis can be used as a tool to analyze the proliferation by gentrification because it can derive accurate location and timing of the diffusion.

• Journal of the Society of Disaster Information
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• v.20 no.2
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• pp.339-350
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• 2024

Purpose: This study analyzes accessibility of 10 hydrogen charging stations in Seoul and identifies areas that were difficult to access. The purpose is to re-analyze accessibility by adding a new location in terms of equity and safety of location placement, and then draw implications by comparing the improvement effects. Method: By applying the location-allocation model and the service area model based on network analysis of the ArcGIS program, areas with weak access were identified. The location selection method applied the 'Minimize Facilities' method in consideration of the need for rapid arrival to insufficient hydrogen charging stations. The limit distance for arrival within a specific time was analyzed by applying the average vehicle traffic speed(23.1km/h, Seoul Open Data Square) in 2022 to three categories: 3,850m(10minutes), 5,775m(15minutes), 7,700m(20minutes). In order to minimize conflicts over the installation of hydrogen charging stations, special standards of the Ministry of Trade, Industry and Energy applied to derive candidate sites for additional installation of hydrogen charging stations among existing gas stations and LPG/CNG charging stations. Result: As a result of the analysis, it was confirmed that accessibility was significantly improved by installing 5 new hydrogen charging stations at relatively safe gas stations and LPG/CNG charging stations in areas where access to the existing 10 hydrogen charging stations is weak within 20 minutes. Nevertheless, it was found that there are still areas where access remains difficult. Conclusion: The location allocation model is used to identify areas where access to hydrogen charging stations is difficult and prioritize installation, decision-making to select locations for hydrogen charging stations based on scientific evidence can be supported.

• Journal of Korea Port Economic Association
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• v.24 no.4
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• pp.199-217
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• 2008

Many studies have identified the determinants of shippers' selection of ports, and of these, a number have repetitively cited major elements. However, different researchers came up with somewhat different research results depending on the position and preference of research targets. Accordingly, to deduce the determinants of shippers' selection of Gwangyang Port, appropriate research and analysis is required in addition to literature study. This study first deduced from previous studies the determinants that have influence on shippers when selecting a port and positively analyzed the effects of those determinants on the shippers using Gwangyang Port. In this regard, whether shippers using Gwangyang Port have continuously used the port was set as a dependent variable, and port service, port facilities, location of ports, port costs, and other determinants for port selection deduced in the previous studies were set as independent variables. This study's analysis finds shippers using Gwangyang Port are all influenced by the elements of port service, port facilities, location of ports, and port costs in their selection of Gwangyang Port. Their degree of importance is in the order of port costs, location of ports, port service and port facilities. This indicates that shippers consider port costs and location of ports more important than port facilities in their selection of a port.

• Journal of the Korean Regional Science Association
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• v.34 no.2
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• pp.21-34
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• 2018

The purpose of this study is to analyze the spatial-temporal proliferation of individual factories in the Seoul Metropolitan Area and to provide policy implications. The location of the factory is divided into individual locations and planned locations. In the case of individual locations, it takes a long time to establish factories. Also, due to high cost and regulation, the establishment of individual factories is not easy. However, since the establishment process is simple and the price of land is low, the establishment of individual factories has led to an increase in the number of individual factories. The problem of the undeveloped factories is that the lack of infrastructure such as the road and environmental pollution treatment facilities around the factory deteriorates the pleasant environment and the cityscape and deteriorates the health of the residents in the surrounding area. In this study, we analyzed the location of individual factories established in the Seoul metropolitan area from 2001 to 2016 by using ArcGIS Pro. The results of the analysis are as follows. First, individual location factories are formed around existing industrial complexes and industrial sites. The reason for this is considered to be the external effect that can be obtained from the surrounding area. Secondly, since the Seoul city's individual location factories are established in many residential areas, it shows the conflicting result of the mixture of residence and factory. Third, the Gyeonggi province's individual location factories have a high proportion of non-urban areas. This is because the Gyeonggi province's management area occupies a larger proportion than other areas in Gyeonggi province. This study analyzed the spatial - temporal spreading process of individual factories and the unfolding of individual factories in the metropolitan area, and it can provide policy implications to control the over development of individual factories in the future.