• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.116-118
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• 2004

송전선로 주변의 전자계 노출은 소아들의 암 발생/사망과 성인의 암 등 여러 가지 질병 발생 가능성이 항상 있으므로 전자계 노출을 장기간 계속적으로 받고 있는 환경을 관찰하는 것이 가장 중요하다. 따라서 본 연구에서는 이에 대한 연구기반을 형성하기 위해 송전 선로의 모델과 현장 실측을 통해 송전선로 자계치를 계산하여 시뮬레이션 하고자한다. 시뮬레이션을 통해 산출된 자계치를 이용하여 최근 효과적인 자계 저감책으로 보고되고 있는 수동루프에 의한 자계저감효과를 검토하고자 한다. 입력된 데이터는 765kV 실 송전선로를 모델로 사용하였으며, 자계의 계산 및 수동 루프에 의한 자계 저감 효과를 알아보기 위해서 미국 EPRI에서 개발한 자계 계산 전용 프로그램인 EMF Modeler를 이용하였다. 먼저 송전선로에 의해 발생되는 자계의 원리를 서술하였으며, 수동 루프를 통한 자계 감소 정도를 수식으로 유도하였고, EMF Modeler를 통하여 송전선 주변의 자계 분포 및 수동루프에 의한 자계 저감 효과를 각각 확인하였다.

• Journal of KIBIM
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• v.12 no.3
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• pp.30-38
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• 2022

Railway is compsed in various components, such as subgrade, track bed, sleeper, rail, and overhead line, on a linear space. Therefore, comprehensive work for various design standards and guidelines is required when designing a railway facility. For this reason, much time and effort are required to review the relevant design standards and guidelines. While, automatic legal check system for BIM models has been developed in the architectural engineering, it has not been developed in the railway engineering. This study reviews the korean design standard and the korean code for railway engineering, and suggests some rule items of logical information. Comparing the suggested rule items to the railway BIM library, items of logical information and additional attribute information are obtained. The analysis results of railway design standards and BIM library presented in this study would be utilized for defining rule-set items that is essential for development of the automatic legal check system for railway BIM models.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.505-508
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• 2016

In city, tracing of power transmission lines is difficult due to compound installation of overhead and underground lines, transposition, bad view caused by trees or big buildings. It is hard problem for electrical technician on site to trace power transformers or power lines to serve customers in 3 phase -4 wires power distribution systems. It is necessary that the correct and fast tracing method is required for load balancing among distribution lines. Old technology use to trace lines with high power impulse injection. Our proposed method uses to trace lines with very small power high frequency signal injection. Simulation models for 3-phase power transformers, 3-phase wire lines, and customer loads are described to investigate the transmission characteristics of high frequency power line carrier. Distribution lines have only a limited ability to carry higher frequencies. Typically power transformers in the distribution system prevent propagating the higher frequency carrier signal. The proposed method uses the limited propagation ability to identify the power transformer to serve customers. The system consists of a transmitter and a receiver with power-line communication module. Some experiments are conducted to verify the theoretical concepts in a big commercial building. Also some simulations are done to help and understand the concepts by using MATLAB Simulink simulator.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.4
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• pp.334-345
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• 2006

The objectives of this study were to analyze and compare 24 hrs personal exposure levels of MF at microenvironments such as home, school, educational institute, internet pc game room, transportation, and other places according to time activity patterns using various metrics for children attending the primary schools located near and away from the power lines, and to characterize the major microenvironments and impact factors attributed personal exposure level. The study was carried out for 44 children attending a primary school away from the lines(school A) and 125 children attending a school away from 154 kV power lines(school B), all who aged 12 years and were 6 grade, from July 2003 to December 2003. All participants filled in a questionnaire about characteristics, residence, use of electrical appliances and others. Children wore a small satchel in which EMDEX II and Lite (Enertech, Co. Ltd) and a diary of activity list for period of registration in 20 minutes blocks. All statistical calculations were made with the SAS System, Releas 6.12. The summary of results was presented below. First, about the characteristics of subjects, there no differences between two groups. The subject almost spent about 56 % of their time at home and about 20~25 % of their time at school. Fifty percent of children spent 2 hours at private educational institutes. Second, the personal exposure measurements of children in school B was statistically higher than those of children in school A by various metrics such as arithmetic mean, geometric mean, percentile(5, 25, 50, 75, 95), maximum, rate of change metric, constant field metric. The arithmetic and geometric mean magnetic fields during the time the children were at school B were 0.98 and $0.86{\mu}T$ and were about 23 times higher than those of children were at school A. In conclusion, the significant major determinants of personal exposure level is the distance from the power line to microenvironments.

• 대한공업교육학회지
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• v.33 no.2
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• pp.287-299
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• 2008

HTTP is one of the most widely used protocols of the WWW. Currently it uses TCP as the transport layer protocol to provide reliability. The HTTP uses separate TCP connection for each file request and adds unnecessary head-of-line blocking overhead for the file retrieval. The web application is short sized and affected by the increased handover latency of TCP in wireless environment. SCTP has attractive features such as multi-streaming and multi-homing. SCTP's multi-streaming and multi-homing avoid head-of-line blocking problem of TCP and reduce handover latency of TCP in wired and wireless environment. Mean response time is the important measure in most web application. In this paper, we present the comparison of mean response time between HTTP over SCTP with that of HTTP over TCP in wired and wireless environments using NS-2 simulator. We measured mean response time for varying packet loss rate, bandwidth, RTT, and the number of web objects in wired environment and mean response time and packet loss rate for varying moving speed and region size in wireless environment. Our experimental result shows that SCTP reduces the mean response time of TCP based web traffic.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.11_12
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• pp.541-556
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• 2005

The memory access latency of the system has been a primary factor of performance degradation in single-processor system and multi-processor system. The remote memory access latency takes a lot of overhead over the local memory access latency especially in the distributed shared-memory system. To resolve this problem, the multi-level cache architecture that contains a remote cache in the multi-processor system has been proposed. In this paper, we propose a new cache replacement policy that improves the performance of the multi-processor system with the remote cache. If the multi-level cache keeps the multi-level inclusion(MLI) property and uses the LRU(Least Recently Used) cache replacement policy, the LRU information of the higher-level cache(a processor cache) would be different with that of the lower-level cache(a remote cache). In this situation, the replacement of a remote cache line can induce the exchange of a processor cache line that is used by the processor. It is a main factor of performance degradation in a whole system. To alleviate this disadvantage of the LRU replacement polity, the new policy analyses tht processor's remote memory access pattern of each node and uses this information to reduce the number of invalidations of the useful cache line in the higher-level cache. The new replacement policy of the remote cache can improve the performance by $3.5\%$ in maximum and $2.5\%$ in average on SPLASH-2 benchmarks, compared to the general LRU cache replacement policy.

• Information Systems Review
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• v.5 no.1
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• pp.97-111
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• 2003

With the spread of electronic commerce on the Internet, comparison shopping sites with agent technique are getting popular for the best shopping. However, most consumers are still spending much time to search for the best price through the sites because each of them may show a different price even for the same goods or a site does not show any information about specific goods. Additionally, the search for the best price of the goods like books and CDs may cause the system to be overloaded and the response time to be long due to an on-line real-time search. In this paper, we have designed and implemented a meta-search system for comparison shopping sites with a local database and memory cache to resolve the above problems. The proposed system collects and maintains the price information of popular goods among the comparison shopping sites using several software agents. The experimental results show that our system is an efficient meta-comparison shopping engine and reduces the latency of the response time with little overhead.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.8
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• pp.674-682
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• 2013

Along with increasing of its subscribers and traffic for high-speed LTE service, it is widely expected to bring about the 2nd data explosion and results in any inconvenience of users. This paper proposes a smart traffic management scheme and its system design based on user's participating with the mobile application, in order to provide a fast and stable service for end users as well as to resolve the network overhead with increasing traffic. By making use of a time shift by users who want to reduce data usage amount and communication cost, the proposed scheme tries to reduce the peak traffic by shifting the delay-tolerant services, such as file sharing and software download, into the other time line. It also reduces the high volumed video traffics by transforming them into a user customized one. In addition, we suggest a mechanism to select video size and service time, then proposes an overall system design and its user service scenarios.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.3
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• pp.324-336
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• 2000

The paper proposes an efficient buffer management scheme to enhance performance of the disk I/O system. Without any user level information, the proposed scheme automatically detects the block reference patterns of applications by associating block attributes with forward distance of a block. Based on the detected patterns, the scheme applies an appropriate replacement policy to each application. We also present a new block allocation scheme to improve the performance of buffer cache when kernel needs to allocate a cache block due to a cache miss. The allocation scheme analyzes the cache hit ratio of each application based on block reference patterns and allocates a cache block to maximize cache hit ratios of system. These all procedures are performed on-line, as well as automatically at system level. We evaluate the scheme by trace-driven simulation. Experimental results show that our scheme leads to significant improvements in hit ratios of cache blocks compared to the traditional schemes and requires low overhead.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.191-201
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• 2013

In this paper, we propose a location based multicast routing protocol, called Geomulticast, in mobile ad-hoc wireless networks. The main features and contributions of the proposed geomulticast are as follows. First, support data transmission to only the specific mobile nodes within a target area. Second, establish stable routing route by using mobility information of nodes. Third, reduce control overhead, power for construction of routing route by using geomulticast guided line information. Fourth, present a theoretical model for establishing stable route. The performance evaluation of the proposed geomulticast is executed by using OPNET simulation and theoretical analysis, and the results of simulation and theoretical analysis have similar patterns. And we can see that data packets are efficiently transmitted to specific user groups within a specific area.