• Journal of Communications and Networks
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• v.8 no.1
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• pp.70-84
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• 2006

We propose a new distributed QoS routing scheme called pre-computation based selective probing (PCSP). The PCSP scheme is designed to provide an exact solution to the constrained optimization problem with moderate overhead, considering the practical environment where the state information available for the routing decision is not exact. It does not limit the number of probe messages, instead, employs a qualitative (or conditional) selective probing approach. It considers both the cost and QoS metrics of the least-cost and the best-QoS paths to calculate the end-to-end cost of the found feasible paths and find QoS-satisfying least-cost paths. It defines strict probing condition that excludes not only the non-feasible paths but also the non-optimal paths. It additionally pre-computes the QoS variation taking into account the impreciseness of the state information and applies two modified QoS-satisfying conditions to the selection rules. This strict probing condition and carefully designed probing approaches enable to strictly limit the set of neighbor nodes involved in the probing process, thereby reducing the message overhead without sacrificing the optimal properties. However, the PCSP scheme may suffer from high message overhead due to its conservative search process in the worst case. In order to bound such message overhead, we extend the PCSP algorithm by applying additional quantitative heuristics. Computer simulations reveal that the PCSP scheme reduces message overhead and possesses ideal success ratio with guaranteed optimal search. In addition, the quantitative extensions of the PCSP scheme turn out to bound the worst-case message overhead with slight performance degradation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.603-606
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• 2013

Mobile and wireless communication technologies to the development of a variety of next-generation mobile networks such as smart phones, tablet PC and mobile terminals will coexist various access networks. In a variety of network service continuity and quality of service degradation due to network conditions, and the EPC network traffic overload phenomenon still remains a problem. In this paper, the EPC network traffic overload in distributed cloud servers is proposed to select. Our proposed scheme using an efficient network handover can provide optimal service according to the network condition.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.13 no.4
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• pp.73-85
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• 2014

Approaching to aging society with increasing transportation vulnerable, most developed countries has positively promote low-floor bus. Such circumstance in Korea has plan to introduce low-floor bus to intra-city bus system which accounted for 30 percent of total number of buses however there is no specific operating plan for this matter. According to the revealed preference study on bus service, the study shows that the efficiency of low-floor is relatively low than that of other buses, therefore, it is necessary to establish feasible plan for bus route selection. Thus, this study is to conduct research on analyzing trip characteristics of transportation vulnerable and establish bus route selection measures for low-floor bus. The result from the survey in Jeollabuk-do Province reveals that the trip purpose of transportation vulnerable is mainly for welfare and medical service, which was made less than 6 times a week. Futhermore, 37.6 percent of transportation vulnerable use buses, thus, it is essential to improve its service quality for enhancing user's convenience and safety. In that transportation vulnerable O-D needs to be established and forecasts future demand for selecting optimal bus route. According to the estimation, route passing through densely populated areas with transportation vulnerable should take the first priority, city circular and other route would be next. Moreover, it is economically efficient that areas populated more than 200,000 with fixed route and less than 200,000 with limited route responsive to demands would be feasible plans. This study will have greater an impact on transportation planning and further research on transportation vulnerable.

• Journal of Korea Port Economic Association
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• v.38 no.3
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• pp.15-28
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• 2022

Bunkering refers to the supply of bunker fuel necessary for the ship operation, as well as minimizing the price and supply cost of fuel itself, and includes supplying good quality fuel oil in a timely manner and at the optimal port. Bunkering is an important criterion in terms of cost for shipping companies because bunkering involves a significant cost to the purchaser of bunkering from the time of initial purchase. This study aims to prioritize selection criteria for tramper companies to call port for bunkering. For this study, the variables were selected by analyzing the common criteria such as price, location, bunker quality and service and infrastructure etc. employed in previous studies. The AHP method was employed to prioritize the criteria in order. As a result of the analysis, the high level factors appeared in the order of price, location, bunkering quality and port service and infrastructure factors. The importance of price criterion and location criterion was found to be high. In the low level criterion of price, the bunker price per MT was ranked first in importance. In terms of location criteria, the location on the main trade route was high. In the low criteria of bunker quality and port service, the bunkering available types and bunker quality were found to be important factors, and in the low level criteria of infrastructure, anchorage and availability of bunkering during loading and discharging and port security factors were found to be important criteria. This study provides the guidelines for research designed to compare the bunkering port selection factors and to derive their importance suggesting the ways to enhance competitiveness as a bunkering port.

• Journal of the Korea Society of Computer and Information
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• v.18 no.10
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• pp.141-148
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• 2013

This paper proposes an EMS algorithm designed to determine the optimal locations for Emergency Medical Service centers that both satisfy the maximum ambulance response time T in case of emergency and cover the largest possible number of residents given a limited number of emergency medical services p in a city divided into different zones. This methodology generally applies integer programming whereby cases are categorized into 1 if the distance between two zones is within the response time and 0 if not and subsequently employs linear programming to obtain the optimal solution. In this paper, where p=1, the algorithm determines a node with maximum coverage. In cases where $p{\geq}2$, the algorithm selects top 5 nodes with maximum coverage. Based on inclusion-exclusion method, this selection entails repeatedly selecting a node with the maximum coverage when nodes with lower numbers are deleted. Among these 5 selected nodes, the algorithm selects a single node set with the greatest coverage and thereby as the optimal EMS location. The proposed algorithm has proven to accurately and expeditiously obtain the optimal solutions for 12-node network, 21-node network, and Swain's 55-node network.

• The Journal of the Korea Contents Association
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• v.18 no.5
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• pp.191-214
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• 2018

This research empirically analyzed the selection factors and the locational selection factors of the medical service facilities according to the gradual increase of the importance of the selection factors and the locational selection factors regarding the establishments of the small- and medium-sized hospitals according to the rapid changes of the socio-economic conditions. By analyzing the priority order according to the levels of the importance of each evaluation item factor through a research related to the selection factors and the locational selection factors of the small- and medium-sized hospitals and by drawing what the important factors that have the influences on the competitiveness of the pre-existent small- and medium-sized hospitals are through the classification of the real estate locational factors and the non-locational factors, the purpose lies in utilizing them as the basic data and materials for the opening strategies of the small- and medium-sized hospitals considering the special, locational characteristics according to the important factors of the selection factors of the small- and medium-sized hospitals, regarding the medical suppliers that have been preparing, for opening the new, small- and medium-sized hospitals. Based on the results of the preceding researches and the researches on the case examples, 28 evaluation factors were arrived at in terms of the level of the medical treatment, the medical services, the accessibilities of the hospitals, the conveniences of the hospitals, and the physical environment. And, regarding the 28 detailed evaluation factors that had been collected, through the interviews with the related experts, the 5 factors of the medical level, the medical service, the expertise of the hospital, the convenience of the hospital, and the physical environment were selected as the upper class evaluation factors. And, according to each upper class, a total of 28 low-part evaluation factors were selected. Regarding the optimal evaluation factors that were selected, the optimal locational factors were selected by carrying out an AHP questionnaire survey investigation with 200 medical experts as the subjects. Regarding the AHP analysis results, similarly with the case examples of the precedent researches, the levels of the importance appeared in the order of the medical level, the medical services, the accessibility of the hospital, the physical environment, and the convenience. And the factors that were related to the facilities of a hospital appeared low. The results of this research can be applied in providing the basis for the decision-makings regarding the selections of the locations of the small- and medium-sized hospitals in the future.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.10
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• pp.1999-2007
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• 2017

In this paper, we implement a multi-band network selection (MNS) system based on Linux operating system which determines the optimal communication link for given network conditions among the available LTE, very high frequency (VHF), and high frequency (HF). The implemented software consists of a network interface, an MNS server, and a user GUI. We perform indoor test to verify the function of the implemented MNS system using two sets of MNS system. To this end, two types of VHF communication links that follow ITU-R M.1842-1 Annex 1 and Annex 4 are emulated in software. In addition, the HF transmission (reception) port of one MNS is directly connected to the HF reception (transmission) port of another MNS. We demonstrate through indoor tests that the implemented MNS system can support seamless maritime communication service in spite of artificial disconnection or re-connection of LTE, VHFs, and HF. The implemented MNS system is applicable to various maritime communication services including e-navigation.

• Journal of Distribution Science
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• v.12 no.1
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• pp.13-19
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• 2014

Purpose - This study investigated relationship quality and/or loyalty, from the viewpoint that merchants and consumers could develop the traditional market. It reorganized variables to find the conditions of values that could stimulate consumers' motives to revive the traditional market. Research Design, data, and methodology - This study employed 202 copies of effective questionnaires, based on the data of Yang & Ju (2012), to conduct correlation, regression, and structured equation modeling (SEM). Results - The results emphasized product and store atmosphere as store selection attributes to consider in the minimum error correction (MEC) model; service factor was not significant. Further, consumers valued relationship quality in the test of mediated effects of the sub-factors of store selection attributes, including consumers' social and emotional value. The relationship quality significantly influenced consumers' value in traditional markets that needed to improve and develop using several variables. Conclusions - This study revealed connections between attributes, consequences, and values using the causal relation model, to generate an optimal model based on a practical and theoretical background and proposed ways to obtain consumer-related information easily.

• Journal of the Korean Society for Railway
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• v.10 no.2 s.39
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• pp.112-116
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• 2007

In this paper, we proposed a selection and application recommendations of ZnO arresters for DC electric traction vehicles. To decide the Continuous Operating Voltage($U_C$), the Rated Voltage($U_r$), and the Nominal Discharge Current(In), we measured and analyzed system voltages and surge currents flowing the arrester installed on a DC electric traction vehicle under running state. System voltages measured up to 1,800 V in 1,500 V-system, and surge currents were recorded up to 3 times per a running-service-route and their magnitudes were ranges of $150A{\sim}2kA$. From these results and a standard EN50163, we could proposed $U_C$, $U_r$, and In available for the 1,500 VDC electric traction vehicles.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10C
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• pp.983-991
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• 2009

While H.264/AVC is in wide use for multimedia applications such as DMB and IPTV service, we have limited usage cases for embedded real-time applications due to its high computational demand. The paper provides judicious guide line for optimization method selection, by presenting the detailed experiments data through the development process of a real time H.264 software encoder on embedded DSP. The experimental analysis includes an intensive profiling analysis, fast algorithm application, optimal memory assignment, and intrinsic-based instruction selection. We have realized a real-time software that encodes CIF resolution videos 15 fps on TMS320DM64x processors.