• 전자공학회논문지A
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• 제31A권1호
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• pp.1-8
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• 1994

In this paper, we have analyzed the performance of a BRAM (The Broadcasting Recognizing Access Method) protocol, as a CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) scheme, which is widely used in wireles LAN systems. We have selected a Fair BRAM protocol among CSMA/CA schemes, considering the fairness of channel usage and the simplicity of the protocol. We have compared the performance of BRAM protocol to that of CSMA/CD. to research the characteristics of BRAM in wireless LAN system. In order to analyze the performance of this system, we have set up an imbedded Markov chain and calculated state transition probabilities. Then we have calculated steady state probabilities and finally derived the throughput of a Fair BRAM moder. To verify our analysis, we have simulated practical models. Then, we have found that analytic results are very close to simulation ones. Our analysis of the BRAM protocol will be expected to be very helpful to design and evaluate a MAC (Media Access Control) protocol in wireless LAN systems.

• 한국시뮬레이션학회논문지
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• 제14권4호
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• pp.77-86
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• 2005

[ $IP^2$ ] (IP-based IMT Network Platform) is a ubiquitous platform supporting mobility using two step If address IPha (IP host address) and IPra (IP routing address) - in a backbone network. MN (Mobile Node) in $IP^2$ maintains either Active or Dormant state, which is transferred to Active state through Paging process when communication is required. In this paper, we proposed a Paging method using proxy to resolve the problem of the conventional Paging method which transmits the Paging messages to all cells in LA (Location Area) resulting in the excessive use of network resources. Performanceevaluation of the proposed method using NS-2 showed that the usage of network resources becomes more efficient by reducing paging loads, especially under the condition of increased nodes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
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• pp.147-149
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• 2006

We designed an intelligent intrusion detection scheme that works based on target system's operational states and doesn't depend on humans' analysis. As a prior work, we presents a scheme to describe computer system's operational states. For this, Hidden Markov Model is used. As input to modeling, huge amount of system audit trail including data on events occurred in target system connected to network and target system's resource usage monitoring data is used. We can predict system's future state based on current events' sequence using developed model and determine whether it would be in daniel or not.

• 대한조선학회지
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• 제52권2호
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• pp.19-24
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• 2015

A reliable assessment and analysis of the condition of high pressure and temperature steam pipelines requires defining stress state, which will take into consideration not just the impact of internal pressure and temperature but all applied loads. For that, usage of modeling and numerical methods for calculation and analysis of stress state is essential. The main aim of piping stress analysis is to check the design of piping layout, which will allow simple, efficient and economical piping supports and provide flexibility to the piping system for loads and stresses. The piping stress analysis is carried out using CAESER II software. By using this software we can evaluate stresses, stress ratios, flange condition, support loads, element forces and displacements at each node and points. In this paper, only the maximum and minimum displacement results are tabulated, which is also shown in detail by an example of main steam pipelines of UST Main Engine System [1].

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.817-819
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• 1996

This paper presents an algorithm for calculation of harmonic distribution in distribution systems. In distribution systems, most state variables are not given explicitly. To calculate the harmonic distribution in distribution systems, state estimation is necessary. In this paper, power usage and harmonic current injection is estimated for each node from practically available data. The estimating procedure is illustrated by examples.

• International Journal of Air-Conditioning and Refrigeration
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• 제15권4호
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• pp.182-190
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• 2007

Refrigeration and air-conditioning equipments are indispensable products in this civilized society. However, discharged refrigerants used in the equipments and exhausted carbon dioxide to drive the refrigeration and air-conditioning equipments are related to serious environmental problems and energy problems. Especially, the destroyed ozonosphere by the discharged refrigerants and the increased normal temperature by carbon dioxide and fluorocarbon refrigerants (green house gases) are sounded as serious global problems. For alleviating these problems, environmental-friendly refrigeration and air-conditioning equipments must be developed and will spread soon. To develop new equipment, a suitable refrigerant for each usage must be presented. In this paper, the current state of refrigerants was introduced. And, thermophysical properties of the refrigerants were introduced briefly. From the properties, the refrigerants and refrigeration cycles are promising to be used in the future, were proposed

• Advances in Energy Research
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• 제8권3호
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• pp.145-153
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• 2022

Recent concerns about rising fuel prices and greenhouse gas emissions have focused attention on alternative energy sources, particularly in the transport sector. Transportation consumes 40% of overall fuel usage. As a result, a growing majority of researches on Electric Vehicles (EVs) and their Energy Management Systems (EMS) have been done. In order to enhance the performance and to meet the needs of drivers, more information regarding the EMS is needed. A new Energy Management System is proposed using a FOPID controller. To put the concept into practice, state equations are utilised. The fifth-order state-space model under study is a linked model with several inputs and outputs and the transfer matrices are calculated for decoupling the system. Utilizing these transfer matrices to decouple the system and FOPID controller is used to tune the system. The tuned parameters are minimized using a Particle Swarm Optimization (PSO) approach with Integral Time Absolute Error (ITAE) as the goal. When the suggested FOPID system's results are compared to those of PID-controlled systems, a sizable improvement is observed, which is explained by the results.

• 한국통신학회논문지
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• 제29권11B
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• pp.956-966
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• 2004

향후 NGN(Next Generation Network)은 패킷 기반의 QoS가 제공되는 네트웍으로 발전하고 있다. 본 논문에서는 MPLS 네트웍에서의 보다 효율적인 경로 선택에 관한 기법으로 Service interruption time을 줄이는 복구방법을 제안한다. 장애복구의 주요 성능 중의 하나인 복구자원사용의 효율성을 높이기 위해서 각 노드들 간의 state information을 fault detector 와 bandwidth broker가 서로 공유하여 장애 발생 시 복구를 위한 message transmission time을 줄였다. 또한 트래픽양의 변화에 따라 망 전체의 필요한 대역폭을 효과적으로 관리하고 변화시킴으로써 대역폭 사용의 효율성을 개선하였다. 그리고 우선순위 서비스를 제공할 수 있는 MPLS 망에서 우선순위에 따른 트래픽에 대해서도 전체 망에 도메인을 나눔으로써 우선순위가 높은 트래픽에 대한 종단간 복구방법에 대해 효율적인 자원 할당을 하며 낮은 우선순위의 트래픽에 대해서 장애가 발생한 도메인 내에서만 경로 복구를 하여 재설정을 위한 시간을 줄일 수 있고, 불필요한 메시지의 전달을 줄일 수 있다

• 한국식생활문화학회지
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• 제20권5호
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• pp.525-531
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• 2005

This study was carried out to establish the consumer-centric food labeling system by investigating usage state, importance evaluation, problems and satisfaction, etc. on the current food labeling system by consumer. For usage state of checking the food label, 50.2% of respondents were replied ‘mostly check the label’, and they were indicated a significant difference on ‘education level(p<.05)’, and in case of married respondents, most were relied 'absolutely check the label', For the reason to check the food label, 61.8% of respondents were replied 'to determine whether it is stable or not', and they were indicated a significant difference on age(p<.01), marital status(p<.01), and job(p<.01). For the item considered as important things on the label of the whole food, 49.8% of respondents were replied that 'expiration and manufacture date is important', and they were indicated a significant difference(p<.001) on age, marital status, job. For item considered as important things on the label of each food, it was indicated that they considered food company as important thing in case of snack, soft drink, edible oils, and noodles, and food company in case of ice cream, and expiration and manufacture date in case of milk product and meat product. For the problems on the current food labeling system, the clauses 'Poor marking on food additives and materials contents' and 'untrue marking of nutrition contents' were indicated a significant difference on age(p<0.05, p<0.001), and the clause 'untrue marking of nutrition contents' were indicated a significant difference on marital status(p<.01) and job(p<.01).

• 한국조경학회지
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• 제27권5호
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• pp.181-190
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• 2000

The purpose of this paper is to promote the usage of facade greenery in order to improve the quality of life in cities and to improve their ecological worth. It is necessary to find out what people think about facade greenery, what problems they think, they might encounter and to promote the use of facade greenery. The survey was grouped according to three housing types; family house, tenement house and apartment. We distributed questionnaires individually to 140 people in each of the three housing types. All 420 people answered. The major questions in the questionnaire relate to the following issues: opinions about facade greenery, opinions regarding reasons to install facade greenery and expected problems, favourite plants, and to provide an analysis of the current usage of facade greenery. The results of this study show that most people like facade greenery and revealed that there was a significant difference in the kinds of responses from the three types of housing. The most important factor to affect respondents' positive preference for facade greenery is that it provides opportunities to experience nature near the housing and the improvement of the aesthetic appeal of facades for those living in apartment housing. Negative responses were based on the inhabitation of insects, and the difficulties in maintaining facade greenery. The favourite plants are parthenocissus and climbing rose. Generally people were lacking in an understanding of the ecological value of facade greenery. Most of the respondents indicated a liking for facade greenery and so the situation is now suitable to promote it.