• 전기학회논문지
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• 제65권5호
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• pp.753-759
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• 2016

Power automation system to operate power distribution systems can be distinguished by distribution SCADA with remote monitoring and control; and distribution automation system with basic functions such as service restoration to the distribution SCADA; and distribution management system which is operated by various applications in order to enhance distribution system operation performance based on the distribution automation system. In the technological change, a technical boundary of information technology (IT) and operation technology (OT) is being blurred by that new concepts such as interoperability. In addtion, IT/OT convergence has been proposed by the improvement of ICT and power system technology. At the viewpoint, advanced distribution management system (ADMS) to have the new concepts and to increase distribution system operation efficiency through global information and functions from the other systems has been proposed. In order to implement the ADMS, IT and OT have to be employed together on the ADMS; and the concept-based IT/OT convergence concept has been presented. Therefore, this paper introduces ADMS and IT/OT convergence and proposes a design of IT/OT convergence based ADMS system design with configurations and functions.

• 한국유체기계학회 논문집
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• 제13권2호
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• pp.48-53
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• 2010

A computerized design system of axial fan is developed for constructing 3-D blade geometry and predicting both aerodynamic performance and noise. The aerodynamic blading design of fan is conducted by blade angle distribution, camber line determination, airfoil thickness distribution and blade element stacking along spanwise distance. The internal flow and the aerodynamic performance of designed fan are predicted by the through-flow modeling technique with flow deviation and pressure loss correlations. Based on the predicted internal flow field and performance data, fan noise is predicted by two models for discrete frequency and broadband noise sources. The present predictions of the flow distribution, the performance and the noise level of actual fans are well agreed with measurement results.

• Journal of Communications and Networks
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• 제6권2호
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• pp.182-191
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• 2004

In this paper, performances of different ultra-wideband (UWB) modulation schemes in the presence of timing jitter are evaluated and compared. Static and Rayleigh fading channels are considered. For fading channels, Oat and dispersive channels are assumed. First, bit error rate (BER) performances for each case are derived for a fixed value of timing jitter. Later, a uniform distribution of jitter is assumed to evaluate the performance of the system, and the theoretical results are verified by computer simulations. Finger estimation error is treated as timing jitter and an appropriate model is generated. Furthermore, a worst case distribution that provides an upper bound on the system performance is presented and compared with other distributions. Effects of timing jitter on systems employing different pulse shapes are analyzed to show the dependency of UWB performance on pulse shape. Although our analysis assumes uniform timing jitter, our framework can be used to evaluate the BER performance for any given probability distribution function of the jitter.

• Transactions on Electrical and Electronic Materials
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• 제18권5호
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• pp.303-309
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• 2017

The flexible AC transmission system (FACTS) provides a new advanced technology solution to improve the flexibility, controllability, and stability of a power system. The unified power flow controller (UPFC) is outstanding for regulating power flow in the FACTS; it can control the real power, reactive power, and node voltage of distribution networks. This paper investigates the performance of the UPFC for power flow control with a series of step changes in rapid succession in a power system steady state and the response of the UPFC to distribution network faults and islanding mode. Simulation was carried out using the MATLAB's simulink sim power systems toolbox. The results, which were carried out on a 5-bus test system and a 4-bus multi-machine electric power system, show clearly the effectiveness and viability of UPFC in rapid response and independent control of the real and reactive power flows and oscillation damping [6].

• 상하수도학회지
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• 제29권4호
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• pp.519-531
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• 2015

It has been widely accepted that the pressure management of water distribution systems using pressure reducing valves(PRVs) would be an effective method for controlling leakages. A pressure reducing valve (PRV) regulates outlet pressure regardless of fluctuating flow and varying inlet pressure, thereby reducing leakage and mitigating the stress on the water distribution system. However, the operation of a PRV is vulnerable to its mechanical condition and hydraulic operability. In this research, the effect of PRVs installed in water distribution system are evaluated in terms of hydraulic pressure reduction and mechanical performance by analyzing measured pressure data with statistical approach. A statistical approach using the moving average filter and frequency analysis based on fourier transform is presented to detect abnormally operated PRVs that have been densely installed in water distribution system. The result shows that the proposed approach can be a good performance evaluation method by simply measuring pressures for the PRVs.

• 오토저널
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• 제15권3호
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• pp.89-95
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• 1993

This paper presents the development of CAD system for the design of lens of the Turn Signal Lamp that can model and simulate its optical performance. The system consists of three main modules: skin surface modeling module, inner lens modeling module and optical performance simulation module. Skin surface geometry can be modeled by the input of data file and inner lens can be modeled by the input of only four parameter using its geometric characteristics. Also light distribution pattern, the barometer of optical performance is generated by means of finite ray tracing method. The system display modeled geometry, ray tracing and generated light distribution pattern.

• 한국항행학회논문지
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• 제19권3호
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• pp.207-216
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• 2015

SBAS 기준국의 배치는 시스템 성능에 영향을 미치는 가장 중요한 요소 중 하나이므로 기준국 배치가 주어진 성능 요구사항을 만족시킬 수 있는지 시스템 개발 초기에 신중하게 분석하여야 한다. 특히 한국형 SBAS로 개발이 진행 중인 KASS의 기준국은 대한민국 내에 설치될 예정이므로 기준국의 개수와 영역이 제한될 수밖에 없으며 이는 넓게 기준국을 배치할 수 있는 타 SBAS 시스템과 구별이 되는 부분이다. 본 논문에서는 이러한 한계로 인한 GPS 및 GEO에 대한 UDRE와 ${\delta}UDRE$ 성능 영향을 시뮬레이션을 통하여 분석하였으며 그 결과 UDRE 성능은 기준국이 얼마나 넓게 분포하는지에 크게 영향을 받으며 특히 GEO UDRE에 미치는 영향이 매우 심각한 것을 확인하였다. 이 결과를 바탕으로 기준국 배치 영향으로 인한 시스템 성능 위험을 최소화하기 위한 KASS설계 및 개발 고려 사항을 제시한다.

• 유통과학연구
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• 제19권7호
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• pp.19-27
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• 2021

Purpose: Former research has argued that organizations in distribution channels face several issues to make a better team-based system. The purpose of the present research is to measure between employee's job performance and three major issues which disturb a solid team system. Research design, data and methodology: Scant past studies are available to guide for team practitioners which elements should be eliminated to improve team performance. To achieve this goal, the present authors obtained 267 US workers in distribution channels and conducted ANOVA test to measure the relationship between three team issues (Free-rider, Trust, and Communication) and job performance. Results: Our statistical findings clearly suggests that there was a statistically recognizable difference at the significance level of probability between the mean value of employees' job performance and three major issues, showing the high degree of job performance can be occurred by eliminating three major team issues. Conclusions: Therefore, the present research concludes that it is necessary that team-based management in the supply chain should focus on removing free-rider issues and also adopt open communication lines to overcome team-building challenges due to communication. Above all else, the ability to increase trust can be enhanced via task delegation and more team members' engagement.

• KIEAE Journal
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• 제9권4호
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• pp.17-22
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• 2009

It is common to design the duct branches where to supply the required air flow for individual room in residential apartment house. However it is difficult to adjust the air volume adequately in small air duct branches in residential ventilation system. The purpose of this study is to figure out the performance of Multidrop chamber coupling system for the residential ventilation system. The experiments were designed to simulate apartment of $84m^2$ and established multidrop chamber duct and general duct on the ceiling of the apartment. Distribution performance of air supply rate were evaluated in this experiments. As a result, distribution performance of air supply rate in the general duct is different from designed air supply rate by about 35% ~ 50% and about 10% in the multidrop chamber system. In additional the sound insulation performance of the multidrop chamber system decreased about 20% compared with general duct system. Therefore, the multidrop chamber system is considered to satisfy proper air supply rate of each room and to improve the sound insulation performance in apartment Houses.

• 한국정보처리학회논문지
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• 제6권5호
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• pp.1189-1202
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• 1999

As compared with VOD data, NOD article data has the following characteristics: it is created at any time, has a short life cycle, is selected as not one article but several articles by a user, and has high access locality in time. Because of these intrinsic features, user access patterns of NOD article data are different from those of VOD. Thus, building NOD system using the existing techniques of VOD system leads to poor performance. In this paper, we analysis the log file of a currently running electronic newspaper, show that the popularity distribution of NOD articles is different from Zipf distribution of VOD data, and suggest a new popularity model of NOD article data MS-Zipf(Multi-Selection Zipf) distribution and its approximate solution. Also we present a life cycle model of NOD article data, which shows changes of popularity over time. Using this life cycle model, we develop LLBF (Largest Life-cycle Based Frequency) prefetching algorithm and analysis he performance by simulation. The developed LLBF algorithm supports the similar level in hit-ratio to the other prefetching algorithms such as LRU(Least Recently Used) etc, while decreasing the number of data replacement in article prefetching and reducing the overhead of the prefetching in system performance. Using the accurate user access patterns of NOD article data, we could analysis correctly the performance of NOD server system and develop the efficient policies in the implementation of NOD server system.