• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2597-2615
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• 2013

This paper proposes a dynamic downlink load control scheme that jointly employs dynamic load threshold management and virtual coverage management schemes to reduce the degree of performance degradation due to traffic overload in two-tier femtocell networks. With the proposed scheme, the downlink load in a serving macrocell is controlled with a load threshold which is adjusted dynamically depending on the varying downlink load conditions of neighboring macrocells. In addition, traffic overloading is alleviated by virtually adjusting the coverage of the overloaded serving macrocell, based on the adjusted load threshold of the serving macrocell. Simulation results show that the proposed scheme improves the performance of two-tier femtocell networks in terms of the outage probability and sum throughput. This improvement is significantly increased with appropriate values of load thresholds and with an intermediate-level adjustment of the virtual coverage area (i.e., handover hysteresis margin: HOM). Furthermore, the proposed scheme outperforms both a previously proposed load control scheme with a static load threshold and the LTE system without a HOM adjustment.

• Journal of Korean Society of Transportation
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• v.4 no.1
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• pp.3-11
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• 1986

One important element of a systematic approach to the management and control of the flow of people over an urban street network is the monitoring and evaluation of system performance. The nature of TSM strategies that, in part, differentiates them from traditional long-range transportation improvement alternatives is that they are less costly, are more quickly implemented and modified, and are often oriented toward sub-area problems which must be addressed at a more microscopic level of analysis. These factors suggest that pre-implementation evaluations of alternative TSM actions will often have to rely on quick-turn around, manual methods of analysis to guide the choice of which management action should be implemented. This paper was prepared to focus on the definition and importance of TSM, specifically associated with monitoring and evaluating traffic performance in the context of TSM startegies. A simple case study of reversible lane technique was presented. The purposes of the case study is to illustrate the methodology of evaluating TSM strategies and demonstrate to identify the benefit from the reversible lane technique, which may otherwise be overlooked in real world. Applying the reversible lane technique to Sam-Il elevate highway, it was found to be a very promising low cost alternative to reduce total travel time(or delay) and fuel consumption.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2261-2266
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• 2012

The general bus system architecture consists of masters, slaves, arbiter, decoder and so on in shared bus. As several masters can't use a bus concurrently, arbiter plays an role in bus arbitration. In compliance with the selection of arbitration method, The efficiency of bus usage can be determined. Fixed Priority, Round-Robin, TDMA, Lottery arbitration are studied in conventional arbitration method. In this paper, we draw the performance analysis of Fixed Priority, Round Robin, TDMA and Lottery bus arbitration policies due to the data traffic concentration and propose the methods of performance improvement.

• Journal of the Korean Society of Safety
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• v.21 no.6 s.78
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• pp.55-63
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• 2006

Rapid economic growth in Korea, on the other side, has generated increase of multiple complex dangers. To take off dangers scattered in the Korean society and to conduct safe society for better life, it is needed to develop social safety index. Social safety index analyzed by time series could compare and estimate various social disasters, thus it act as the foundation to set up safety policy. The research has focused on 8 social safety indexes; natural disaster, fire, traffic accident, crime, industry accident, forest fire, collapse and explosion, and environmental pollution. To find out Korean society safety index analyzed by time series, the research analyzed changes of each safety indexes in 10 years since 1994. Looking at the changes of each indexes, traffic accident showed the most improvement overall the nation, with industrial accident and collapse and explosion rating second and third place. However, crime, fire and natural disaster get worse, and especially crime has turned worsened than any other divisions.

• The Journal of the Korea Contents Association
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• v.21 no.1
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• pp.139-146
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• 2021

Ahead of the commercialization of autonomous vehicles, it's application should be considered into the current transportation infrastructure. Under limited traffic circumstances, effective set of lane change rules alone could bring benefits to the autonomous driving system. In this study, a cooperative movement (local platooning) plan with limited vehicles associated as pocket driving, aiming at effective movement between vehicles in urban environment was proposed. Under congested roadway condition, the gaussian gap between vehicles was introduced to secure gap acceptance for safe lane change maneuver. Proposed lane change method showed 86.6% delay reduction along with traffic volume improvement. This result could be considered as a crucial factor in designing a next-generation roadway infrastructure with autonomous driving.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.277-283
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• 2017

In recent years, earthquakes and volcanic activity have been occurring actively in Japan, China, and Southeast Asia in the central Pacific Rim, and the cycle interval is shortening. In addition, there is Baekdu mountain, which is a large active volcano in Korea. On the other hand, the legal system and guidelines related to volcanic ash are very limited to counteract volcanic disasters. The volcano manual does not present specific countermeasures against volcanic disasters. The preparation of systematic disaster prevention measures against an eruption of Mt. Baekdu and the volcanic activity in Japan and China, which are occurring continuously, is necessary. Therefore, this study suggests an improvement to the relevant laws and regulations against volcanic disasters to analyze the aviation safety manual and relevant legal system. The problems with the current legal system are improved by modifying the legal system related to the air traffic sector when volcanic disaster occurs, and it is expected that more efficient manuals and guidelines will form the basis for the smooth operation of the manual at a disaster site.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.6
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• pp.1302-1310
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• 1997

In this paper, we propose a dynamic code allocation strategy using voice activity detection and evaluate the performance of a dynamic code allocation strategy using voice activeity detection in DS-CDMA system. Proposed method allocates code to mobile terminal according to the residual capacity computed by SIR in the base station. In hot spot traffic loading cell, we find that the performance of proposed method is better than that of a fixed code assignment strategy using voice activity detection. Also, we find that the proposed method provide much improvement in blocking probability against the dynamic code assignment strategy withoug voice activity detection.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.125-128
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• 2002

One of ultimate purpose that performance to information society been going recently festinately intends is in human's welfare improvement. Also, research about assist for disabled person that belong on category that is disabled persons' cloth elevation estranged in the past according to disabled person population's increase and change of advanced human rights consciousness to ruins of industrial society and traffic civilization is afoot abuzz. Guidance robot of sight obstacle can speak as its part. This research is thing about voice system about location set and search in guidance robot that is embodying to make sight disabled person can visit schedule place smoothly.

• Proceedings of the Korean Society of Computer Information Conference
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• 2010.07a
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• pp.137-140
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• 2010

교통사고의 발생은 교통 혼잡의 주요 원인으로 작용되어 교통사고에 의한 직 간접적 손해비용까지 지출되고 있다. 따라서 교통사고를 사전에 예방하거나 사고가 발생한 후 신속하게 처리할 수 있는 실시간 교통사고 대처 시스템이 요구되고 있다. 즉, 교통사고 자동검지 시스템의 필요성은 가 피해자의 구분에 활용하는 것 이외에 신속한 인명구조와 사고처리 등의 교차로 유고관리가 가능하며, 교통사고로 발생할 수 있는 교통 혼잡을 최소화 할 수 있다. 본 논문에서는 다양한 형태의 충돌 및 추돌 사고를 검지하는 시스템의 성능을 개선하기 위한 것으로 영상 또는 소리라는 매체에 기반을 둔 시스템에서 자동 검지의 한계성을 도출하고 개선하고자 하였다. 테스트 베드를 기반으로 자동검지 실패의 원인을 분석하고 그 원인에 따른 오인식의 문제점을 개선하여 운전자 단독사고로 인하여 차량 추적이 불가능한 경우, 소리 없이 발생한 사고, 야간에 발생한 사고 등의 문제점들을 극복함과 동시에 성능을 개선하는데 그 목적이 있다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.5
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• pp.1-13
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• 2010

In this paper, we describe the result of the test-bed on Nation-wide Interoperable Transportation System connected with Interoperable Traffic Information Collection System, which was developed by Korea Financial Telecommunications & Clearings, KOREAIL NETWORKS, HiPlusCard and Samsung SDS. we constructed Nation-wide Interoperable Transportation System on 4 downtown bus routes, 20 stations on line 1 subway, 2 stations of a train and 2 sections of the Honam highway in Gwangju and Interoperable Traffic Information Collection System in Seoul University IC Card Center. So we operated that by 480 Several staff were given a test card and asked to try it for about 6 months. This test-bed is for demonstrates the accuracy, safety and credibility of the Nation-wide Interoperability standard technology and it can be applied to all of transportation practically. When the staffs contact the card to Purchase terminal, the card performs transaction with Purchase SAM in the terminal, then transactions ara used to calculate in Settlement system and Interoperable Traffic Information Collection System. Through the test-bed, we examined this process and found unexpected problems happening during the test operation and have successfully solved them. In addition, the results of the test-bed let us know what additional improvement might be required for System. The successful run of the test-bed was verified by an evaluation of the test-bed staff and a public survey.