• 전기학회논문지
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• 제63권5호
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• pp.713-718
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• 2014

DC urban railway power system consists of DC power network and AC power network. The DC power network supplies electric power to railway vehicles and the AC power network supplies electric power to station electric equipment. Recently, because of power consumption reduction and peak load shaving, intelligent measurement of regenerative energy and renewable energy adapted on DC urban railway is required. For this reason, DC smart metering system for DC power network shall be developed. Therefore, in this paper, DC voltage sensor, current sensor, and DC smart meter were developed and evaluated by performance test. DC voltage sensor was developed for measuring standard voltage range of DC urban railway, and DC current sensor was developed as hall effect split core type in order to install in existing system. DC smart meter possesses function of general intelligent electric power meter, such as measuring electricity and wireless communication etc. And, DC voltage sensor showed average 0.17% of measuring error for 2,000V/50mA, and current sensor showed average 0.21% of measuring error for ${\pm}2,000V/{\pm}4V$ in performance test. Also DC smart meter showed maximum 0.92% of measuring error for output of voltage sensor and current sensor. In similar environment for real DC power network, measuring error rate was under 0.5%. In conclusion, accuracy of DC smart metering system was confirmed by performance test, and more detailed performance will be verified by further real operation DC urban railway line test.

• 전기학회논문지
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• 제65권12호
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• pp.2127-2137
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• 2016

In this paper, characteristic tests for current transformers with maximum mA secondary current of 250 mA is performed. The purpose of this paper is not only to test the mA current transformers by following the IEEE Draft Standard for Current Transformers with Maximum mA Secondary Current of 250mA, but also to take into consideration certain applications in the use of the mA CTs for billing purposes.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.443-450
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• 2017

Nowadays, Power Line Communication (PLC) is gaining high attention from industry and electric supply companies for the services like demand response, demand side management and Advanced Metering Infrastructure (AMI). The reliable services to consumers using PLC can be provided by utilizing an efficient PLC channel for which sophisticated channel modeling is very important. This paper presents characterization of a Low Voltage (LV) access network for Narrowband Power Line Communications (NB-PLC) using transmission line (TL) theory and a Simulink model. The TL theory analysis not only includes the constant parameters but frequency selectivity is also introduced in these parameters such as resistance, conductance and impedances. However, the proposed Simulink channel model offers an analysis and characterization of capacitive coupler, network impedance and channel transfer function for NB-PLC. Analysis of analytical and simulated results shows a close agreement of the channel transfer function. In the absence of a standardized NBPLC channel model, this research work can prove significant in improving the efficiency and accuracy of NB-PLC communication transceivers for Smart Grid communications.

• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.572-580
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• 2013

Power metering and monitoring system is a basic element of Smart Grid technology. This paper proposes a new Non-Intrusive Load Monitoring (NILM) method for a residential buildings sector using the measured total active power consumption. Home electrical appliances are classified by ON/OFF state models, Multi-state models, and Composite models according to their operational characteristics observed by experiments. In order to disaggregate the operation and the power consumption of each model, an algorithm which includes a switching function, a truth table matrix, and a matching process is presented. Typical profiles of each appliances and disaggregation results are shown and classified. To improve the accuracy, a Time Lagging (TL) algorithm and a Permanent-On model (PO) algorithm are additionally proposed. The method is validated as comparing the simulation results to the experimental ones with high accuracy.

• 한국측량학회지
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• 제29권3호
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• pp.303-309
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• 2011

일상생활에 미치는 영향이 확산되고 있는 상황인식서비는 위치기반서비스와 소셜네트워크서비스로 분류되며, 스마트폰의 GPS 및 전자나침반 기술의 정확도에 따라 상황인식서비스 품질이 달라질 수 있다. 본 연구에서는 상황인식서비스를 이용할 때 가장 중요한 단초가 될 수 있는 GPS, 전자나침반(Digital Compass), 무선통신, 공간정보(Geospatial Web)를 활용함에 있어서의 위치적 정확도에 대하여 분석하였다. 스마트폰을 이용한 위치 및 방향 결정 정확도 실험 결과 실외에 비하여 낮은 실내 위치 및 방향 정확도와 플랫폼으로 활용되는 공간정보가 갖고 있는 오차에 의해 상황인식서비스 이용 시 정확한 정보를 제공 받지 못하는 문제점이 발생하는 것으로 나타났다. 실내 위치 결정 정확도 향상 방안으로 Wi-Fi를 이용한 측위 방법 등이 있으나 실외에서 사용하는 GPS에 비해 많은 보완 사항이 있는 것으로 나타났으며, 상황인식서비스의 플랫폼으로 활용되는 공간정보의 품질 향상을 위하여 DSM을 이용해 폐색영역을 보정한 실감 정사영상의 제작이 필요한 것으로 판단된다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권2호
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• pp.146-153
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• 2006

A passive microfluidic delivery system using hydrophobic valving and pneumatic control was devised for microfluidic handling on a chip. The microfluidic metering, cutting, transport, and merging of two liquids on the chip were correctly performed. The error range of the accuracy of microfluid metering was below 4% on a 20 nL scale, which showed that microfluid was easily manipulated with the desired volume on a chip. For a study of the feasibility of biochemical reactions on the chip, a single enzymatic reaction, such as ${\beta}-galactosidase$ reaction, was performed. The detection limit of the substrate, i.e. fluorescein $di-{\beta}-galactopyranoside$ (FDG) of the ${\beta}-galactosidase$ (6.7 fM), was about 76 pM. Additionally, multiple biochemical reactions such as in vitro protein synthesis of enhanced green fluorescence protein (EGFP) were successfully demonstrated at the nanoliter scale, which suggests that our microfluidic chip can be applied not only to miniaturization of various biochemical reactions, but also to development of the microfluidic biochemical reaction system requiring a precise nano-scale control.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.761-767
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• 1993

A precision planting system using computer controlled technology for mulching cultivation was developed and tested . The system consisting of a micro-computer, several optical fiber sensors and control actuators realized the mechanization of the precision planting operation. The film hole positions, existences of a seed on shutter were detected and the planting speed was measured. The shutter opening mechanism and a seed metering device driven by a stepping motor were controlled, automatically . The planting timing of the shutter opening mechanism were analyzed from a video camera motion analysis, theoretically. The results showed a sufficient accuracy of a seed planted into the center a film hole with a variety of planting speeded. The gravity point positions in film hole of seeds planted by the system just were within the area of +-5mm of the hole center when the hole diameter was 40mm.

• 정보보호학회논문지
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• 제26권3호
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• pp.757-767
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• 2016

패스워드 인증은 가장 대표적인 사용자 인증 기법이며 그 중에서 특히 문자 기반 패스워드가 가장 많이 사용되고 있다. 그러나 사용자들이 선택하는 패스워드가 갖는 취약성으로 인하여 사용자로 하여금 강한 패스워드 생성을 유도하기 위해 많은 웹사이트에서는 패스워드 강도를 측정하는 패스워드 미터를 제공하고 있다. 하지만 여기에는 패스워드 미터결과가 일관되지 않고, 정확하지 않은 강도로 피드백하는 문제가 있다. 이에 본 논문에서는 패스워드 미터의 문제점에 대해 알아보며 패스워드 미터의 개선 방향을 제시하고자 한다.

• 한국안전학회지
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• 제22권4호
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• pp.20-25
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• 2007

Instrument transformers are a safe measurement device designed to measure high voltage and large current. A current transformer(CT) is a type of instrument transformer designed to provide a current in its secondary winding proportional to the current flowing in its primary. It is commonly used in metering and protective relaying in the electrical power industry where it facilitates the safe measurement of large current. But, care must be taken that the secondary of a current transformer is not disconnected from its load while current is flowing in the primary, as this will produce a dangerously high voltage across the open secondary, and may permanently affect the accuracy of the transformer. Especially, industrial disaster such as an electric shock and/or a burn accident occurs occasionally by disregard of warning or attention. In this paper, we developed the detector for open of current transformer secondary terminal, and which was tested by the Korea Electrotechnology Research Institute. Test results show that Current Transformer secondary Open Detector(CTOD) interrupted within one second electronically when the 2nd terminal of current transformer opened.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 추계학술대회 논문집 전력기술부문
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• pp.12-14
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• 2007

A voltage transformer (VT) is used to transform a high voltage into a low voltage as an input for a metering device or a protection relay. VTs use an iron core which maximizes the flux linkage. The primary current of the VT has non-fundamental components caused by the hysteresis characteristics of the iron core. It causes a voltage drop in the winding impedances resulting in the error of the VT. This paper describes a compensation algorithm for the VT. The proposed algorithm can compensate the secondary voltage of VT by calculating the primary current from the exciting current of the hysteresis loop in the voltage transformer. In this paper, the exciting branch was divided into a non-linear core loss resistor and a non-linear magnetizing inductor. The performance of the proposed algorithm was validated under various conditions using EMTP generated data. Test results show that the proposed compensation algorithm can improve the accuracy of the VT significantly.