• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2208-2218
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• 2017

To resolve overload in a distribution system, a distribution system operator (DSO) often performs a load transfer using normally open tie points and switches in the distribution line. During this process, the distribution system is momentarily operated in closed-loop operation. A closed-loop current in the distribution system can cause a power failure due to excess breaking current in the circuit breakers and reclosers. Therefore, it is necessary to calculate the closed-loop current exactly. However, if there are a large number of distributed generation (DG) systems in the distribution system, such as energy storage systems (ESS), they might obstruct the closed-loop operation based on bidirectional power flow. For quick and precise operation of a closed-loop system, the ESS has to regulate the power generation while satisfying closed-loop operation in the worst cases. We propose a strategy for balanced power regulation of an ESS. Simulations were carried out using PSCAD/EMTDC, and the results were compared with calculation results.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권11호
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• pp.720-728
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• 2000

This paper describes the calculation of the equivalent circuit parameters and the characteristic analysis of a capacitor-run type single-phase induction motor by means of the finite element method in coupled with the conventional equivalent circuit model. The circuit parameters of the stator are calculated form the lumped parameter and the slot leakage reactance of the rotor with the closed slot can be obtained by the use of slot pitch boundary condition. From the analysis result this combined equivalent circuit and finite element method which is used slot pitch boundary condition is compared with the experimental results, the validity of the method is proved.

• 한국광물학회지
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• 제23권4호
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• pp.297-303
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• 2010

본 연구에서는 파쇄 메커니즘이 상이한 파쇄기(함마 크럿셔와 롤 크럿셔)와 파쇄회로(개회로 및 폐회로)를 사용하여 각각의 파쇄기 종류에 따른 백운석 파쇄산물의 입도분포와 파쇄특성에 대해 알아보았다. 함마 크럿셔로 파쇄한 경우, 100 mesh 이하의 미분이 약 34 wt.%로 롤 크럿셔로 파쇄한 경우보다 약 3 배 이상 높았다. 또한 14~25 mesh 산물은 롤 크럿셔로 파쇄할 경우, 함마 크럿셔로 파쇄한 경우에 비하여 약 20 wt.% 이상 많이 생성되었다. 35 mesh 이하의 산물은 함마 크럿셔로 파쇄 시 전체의 약 80 wt.% 정도였다. 두 파쇄기 모두 개회로에 비해 폐회로 파쇄 시 미분의 발생률이 감소하였다. 광석에 따른 적절한 파쇄기 및 파쇄회로의 선택에 따라 목적하는 입도의 산물을 효율적으로 얻을 수 있다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.864-870
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• 2005

Hydraulic excavators have been popular devices in construction field because of its multi-workings and economic efficiency. The mathematical models of excavators have many nonlinearities because of nonlinear opening characteristics and dead zone of main control valve, oil temperature variation, etc. The objective of this paper is to develop a simulator for hydraulic excavator using AMESim. Components and whole circuit are expressed graphically. Parameters and nonlinear characteristics are inputted in text style. From the simulation results, fixed spring stiffness of MCV can't satisfy accuracy of spool displacement under whole P-Q diagrams. Closed loop type MCV containing proportional gain is proposed in this paper that can reduce displacement error. The ability of closed loop MCV is verified through comparing with normal type MCV using AMESim simulator. The simulator can be used to forecastexcavator behavior when new components, new mechanical attachments, hydraulic circuit changes, and new control algorithm are applied. The simulator could be a kind of development platform for various new excavators.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.531-536
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• 2008

This paper presents experimental result of characteristics about Closed circuit Cooling Tower having a rated 2RT. The experimental apparatus has been set-up with a conventional type system. The test section is heat exchangers of cooling tower that consist of different vertical tubes, 15.88mm with 10 rows and columns and 19.05 mm with 8 rows and 12 columns. The main results were summarized as follows : The values of heat and mass transfer coefficients of cooling tower operating with two paths are higher than these with one path. Cooling capacity per unit volume using 15.88mm tubes are higher than 19.05mm tubes.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1701-1705
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• 2004

This paper presents a design and analysis of electromechanical sigma-delta modulator for MEMS gyroscope, which enables us to control the proof mass and to obtain an exact digital output without additional A/D conversion. The system structure and the circuit realization of the sigma-delta modulation are simpler than those of the analog sensing and feedback circuit. Based on the electrical sigma-delta modulator theory, a compensator is designed to improve the closed loop resolution of the sensor. With the designed compensator, we could obtain enhanced closed-loop performances of the gyroscope such as larger bandwidth, lower noise, and digital output comparing with the results of analog open-loop system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.718-719
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• 2011

Lately, the demand for electrical power has been significantly increased. As a result a power transmission system has been improved. On the other hand fault current increased more than past. Superconducting fault current limiter (SFCL) is one of the solutions to limit fault current. However, SFCL's research has not advanced in a power transmission system fully. Therefore, we studied effect of SFCL in a power transmission system. The power distribution system is open-loop circuit, but a power transmission system is closed-loop system. Consequently, Fault current in a power transmission system is larger than fault current in a power distribution system. we exerimented a simple closed-loop power transmission system circuit.

• Journal of Biosystems Engineering
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• 제14권2호
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• pp.104-114
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• 1989

The most important subject in developing agricultural robots for fruit harvesting is to detect accurately the location of a fruit about the given coordinate system. This study was carried out to develop an image processing algorithm which enables finding out the three dimensional locations of a fruit. The digital image processing device consisted of an optosensor (Closed-circuit TV camera), image processing interface board (Digitizer) and microcomputer (IBM PC/AT). A stereo-image processing method using the two cameras attached to the manipulator was evaluated through experiment with apples. The accuracy and quickness of detecting the location of apples by this method was not satisfactory. The maximum errors of the detected locations by the stereo-image processing method in x-, Y-, and z- directions were 3, 4 and 4 cm, respectively. The maximum time required to get the rectangular coordinate data of a fruit was about 2 minutes.

• Journal of Multimedia Information System
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• 제7권3호
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• pp.205-214
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• 2020

Crime has become one of the major problems in modern society. Even though visual surveillances through closed-circuit television (CCTV) is extensively used for solving crime, the number of crimes has not decreased. This is because there is insufficient workforce for performing 24-hour surveillance. In addition, CCTV surveillance by humans is not efficient for detecting dangerous situations owing to accuracy issues. In this paper, we propose the autonomous detection of dangerous situations in CCTV scenes using a deep learning model with relational inference. The main feature of the proposed method is that it can simultaneously perform object detection and relational inference to determine the danger of the situations captured by CCTV. This enables us to efficiently classify dangerous situations by inferring the relationship between detected objects (i.e., distance and position). Experimental results demonstrate that the proposed method outperforms existing methods in terms of the accuracy of image classification and the false alarm rate even when object detection accuracy is low.

• Journal of Preventive Medicine and Public Health
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• 제3권1호
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• pp.17-22
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• 1970

By using Siregnost FD 91 body plethysmograph, we measured thoracic gas volume (TGVe) at end of expiration in 19 healthy subjects aged 20-43 years in order to compare with functional residual capacity (FRC) measured by closed circuit method. The results obtained were as follows 1. Mean values of TGVe and FRC were $3.395{\pm}0.5851{\ell},\;and\;3.393{\pm}0.618{\ell}$, respectively. 2. A advantage of the body phethysmographic method for measuring thoracic gas volume was that it were rapid, safe, and easy to perform, requires no gas sample for chemical analysis, and measured TGVe several times.