• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.7
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• pp.365-374
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• 2004

The relay measures the frequency of the power system in order to detect faults and separate them from the system. Many estimation algorithms for the relay have been proposed to accurately measure the frequency. This paper proposes a new frequency measurement method using the digital phase locked-loop(DPLL) for the relay of the power system. The proposed method is configured with a DPLL scheme and verified through computer simulations and experimental tests. In order to cope with noises in the power system, filters are included in the input signal processing part and the frequency comparator. MATLAB is used for computer simulations and an experimental setup with a CPU and an FPGA(Field Programmable Gate Array) is constructed. The loop filter of the DPLL is run in the CPU software In adjust parameters and others are in the FPGA. Experimental tests are performed lot a function generator and the power system. Results show that the proposed method is appropriate to the frequency measurement for the relay.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.112-115
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• 2001

This paper illustrates a new nodal effective load model for nodal probabilistic production cost simulation of the load point in a composite power system. The new effective load model includes capacities and uncertainties of generators as well as transmission lines. The CMELDC based on the new effective load model at HLII has been developed also. The CMELDC can be obtain from convolution integral processing of the outage capacity probabilistic distribution function of the fictitious generator and the original load duration curve given at the load point. It is expected that the new model for the CMELDC proposed. In this study will provide some solutions to many problems based on nodal and decentralized operation and control of an electric power systems under competition environment in future. The CMELDC based on the new model at HLII will extend the application areas of nodal probabilistic production cost simulation, outage cost assessment and reliability evaluation etc. at load points. The characteristics and effectiveness of this new model are illustrated by a case study of a test system.

• The Journal of the Korea Contents Association
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• v.8 no.4
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• pp.86-91
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• 2008

To present the design procedure of discretized 8-bit tent map executing the transformation of tent function which is one of the chaotic functions, first, the truth table of discretized tent map was written, and then according to the simplified Boolean algebra equations obtained from the truth table, the discretized map is implemented with the exclusive logic gate as a real hardware. The discretized tent map circuit which provides the feedback circuit for generating the period-8 states relevant to the 8-bit finite precision is also designed and presented in this paper. Furthermore, it might be used stream cipher system with a new key-stream circuit for generate of chaotic binary sequence.

• Korean Journal of Optics and Photonics
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• v.7 no.1
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• pp.1-8
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• 1996

Charge-coupled device(CCD) array detectors are widely used in real time modulation transfer function(MTF) measurement systems. This paper presents the characteristics of two-dimensional CCDs used in a real time MTF measurement system for copy lenses. The MTF characteristics of a copy lens measured by this equipment show different results according to the direction of shift register, shutter speed and the amplifier gain of CCDs. An object generator is fabricated to reduce the variation of MTF values for the irradiance nonuniformity in on-axis and off-axis image plane and this MTF equipment is calibrated by using a standard lens.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.87-90
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• 2003

This research examines the feasibility of using laboratory-synthesized nano scale zero-valent iron particles to remove arsenic from aqueous phase. Batch experiments were performed to determine arsenic sorption rates as a function of the nano scale zero-valent iron solution concentration. Rapid adsorption of arsenic was achieved with the nano scale zero-valent iron. Typically 1 mg $L^{-1}$ arsenic (III) was adsorbed by 5 g $L^{-1}$ nano scale zero-valent iron below the 0.01 g $L^{-1}$ concentration within 7min. The kinetics of the arsenic sorption followed pseudo-first-order reaction kinetics. Observed reaction rate constants ( $K_{obs}$) varied between 11.4 to 129.0 $h^{-1}$ with respect to different concentrations of nano scale zero-valent iron. A variety of analytical techniques were used to study the reaction products including HGAAS (hydride generator atomic adsorption spectrophotometer), SEM (scanning electron microscopy) and TEM (transmission electron microscopy). Our experimental results suggest novel method for efficient removal of arsenic Iron groundwater.r.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.10
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• pp.625-629
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• 2016

Electrical and optical properties of the AC voltage driven organic light-emitting diodes were investigated by measuring the electroluminescence of the device. Device structure of ITO(170 nm)/TPD(40 nm)/Alq3(60 nm)/LiF(0.5 nm)/Al(100 nm) was manufactured using a thermal evaporation. Sinusoidal and square-type AC voltage was applied to the device using a function generator. Amplitude of the applied voltage was 9.0 V, and a frequency was varied from 50 Hz to 50 kHz. Electroluminescence out of the device was measured in a Si photodetector simultaneously with the applied voltage together. An intensity and a delayed residual luminescence from the device were depended on the frequency of the sinusoidal voltage. It is thought to be due to a contribution of the capacitive nature in the equivalent circuit of the device. An electron mobility was estimated using a time constant obtained from the luminescence of the device driven by the square-type AC voltage.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.118-125
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• 2003

This paper presents a scheme for the placement of dispersed generator systems(DGs) based on load model in unbalanced systems. Groups of each individual load model consist of residential, industrial, commercial, official and agricultural load The main idea of solving fuzzy goal programming is to transform the original objective function and constraints into the equivalent multi-objectives functions with fuzzy sets to evaluate their imprecise nature for the criterion of power loss minimization, the number or total capacity of DGs and the bus voltage deviation, and then solve the problem using genetic algorithm The method proposed is applied to IEEE 13 bus unbalanced distribution systems to demonstrate its effectiveness.

• The Journal of the Acoustical Society of Korea
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• v.30 no.5
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• pp.249-254
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• 2011

Inquiring activities on the acoustic phenomena have been carried out by using a sound card installed in a personal computer. A sound card is cheaper and more accessible to the students than the precision equipment such as a function generator or an oscilloscope. The students record the sounds from various acoustic phenomena to the sound card. Then they analyze the frequency spectrums of that sounds by using a program. Inquired phenomena include beat by two tuning forks, sound from Rijke tube, pouring sound, breaking of a wine glass and pop-up sound of a wine bottle. Through these activities students perform quantitative analysis of various phenomena due to superposition, resonance and standing wave.

• Journal of Power Electronics
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• v.16 no.2
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• pp.786-797
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• 2016

This paper describes the design and development of a novel semiconductor-based solid-state switch for damped oscillating voltage test system. The proposed switch is configured as two identical series-connected switch stacks, each of which comprising 10 series-connected IGBT function units. Each unit consists of one IGBT, a gate driver, and an auxiliary voltage sharing circuit. A single switch stack can block 20 kV-rated high voltage, and two stacks in series are proven applicable to 30 kV-rated high voltage. The turn-on speed of the switch is approximately 250 ns. A flyback topology-based power supply system with a front-end power factor correction is built for the drive circuit by loosely inductively coupling each unit with a ferrite core to the primary side of a power generator to obtain the advantages of galvanic isolation and compact size. After the simulation, measurement, and estimation of the parasitic effect on the gate driver, a prototype is assembled and tested under different operating regimes. Experimental results are presented to demonstrate the performance of the developed prototype.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.891-894
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• 2002

We studied characteristics of polyimide (PI) about Liquid Crystal on Silicon (LCOS) microdisplay. In order to compare two kinds of PI and choose one PI, we measured some items. First, we measured thermal imidization of SE-7492, SE-5291 (Nissan) PI using FT-IR. The results of thermal imidization are same 85%for SE-7492 and 86% for SE-5291. The second, we measured voltage-holding ratio (VHR) of LCOS imager using two kinds PI and one liquid crystal (LC) that is a mixture developed by Merck. The third, we measured contrast ratio (C/R) of LCOS imager using function generator from ov to 4V. The results of VHR and C/R are higher LCOS imager using SE-7492 than LCOS imager using SE-5291. And last we measured response time and the result is same two types LCOS Imagers. So, we choose PI of LCOS imager and concluded that LC is much better matched of PI using SE-7492.