• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.1
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• pp.3-9
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• 2009

Although Active matrix organic light emitting diode (AMOLED) display has a better image quality in terms of viewing angle, contrast ratio, and response time than liquid crystal displays (LCDs), it still has some critical issues such as lifetime, residual images, and brightness non-uniformity due to non-uniformity in electrical characteristics of driving TFTs and IR drops on supplied power line. Among them, we improved irrecoverable residual images of AMOLED displays which is mainly related to the hysteresis characteristics of driving TFTs. We consider four kinds of surface treatment conditions before gate oxide deposition for improving hysteresis characteristics. We can reduce the hysteresis level of p-channel TFT to 0.23 V, interface trap states between the poly-Si layer and gate insulator to $3.11{\times}10^{11}cm^{-2}$, and output current variation of p-channel TFT to 3.65 % through the surface treatment using ultraviolet light and H2 plasma. Therefore, the recoverable residual image problem of AMOLED displays can be improved by surface treatment using ultraviolet light and $H_2$ plasma.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.5
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• pp.433-441
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• 1999

This paper presents a S-FES(Superconducting magnetic becuing Flywheel Energy Storage System) for the p purpose of replacing battery used to store the energy. Especially, the design elements of FES, such as the b beming, wheel mateηaI, and power converter, etc., are described. The design and manufacturing techniques of t the controllable IXlwer converter are proposed to generate the sinusoidal output current in the high speed operation and to get the const빠synchronous motor with halbach cuTay of high coesive I\d-Fe-B permanent magnet is used as the driver of F FES. The proposed S-FES system shows the stable rotation characteristics at high speed range about l 10,000[rpm]. To verify the validity of proposed system, the comparative study with the conventional ball b beming s~rstem is proceeded and it is well confirmed with the result of the lower friction losses of S-FES S system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1092-1098
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• 2007

Since one decade, the detection of HFPD (High frequency Partial Discharge) has been proposed as one of the effective method for the diagnosis of the power component under service in power grids. As a tool for HFPD detection, Metal Foil sensor based on the embedded technology has been commercialized for mainly power cable due to its advantages. Recently, for the on-site noise discrimination, several PA (Pulse analysis) methods have been reported and the related software, such as Neural Network and Fuzzy, have been proposed to separate the PD (Partial Discharge) signals from the noises since their wave shapes are completely different from each other. On the other hand, the relevant fundamental investigation has not yet clearly made while it is reported that the effectiveness of the current methods based on PA is dependant on the types of sensors. Moreover, regarding the identification of the vital defects introducible into the Power Cable, the direct identification of the nature of defects from the PD signals through Metal Foil coupler has not yet been realized. As a trial for solving above shortcomings, different types of software have been proposed and employed without any convincing probability of identification. In this regards, our novel algorithm 'PA Map' based on the pulse analysis is suggested to identify directly the defects inside the power cable from the HFPD signals which is output of the HFCT and metal foil sensors. This method enables to discriminate the noise and then to make the data analysis related to the PD signals. For the purpose, the HFPD detection and PA (Pulse Analysis) system have been developed and then the effect of noise discrimination has been investigated by use of the artificial defects using real scale mockup. Throughout these works, our system is proved to be capable of separating the small void discharges among the very large noises such as big air corona and ground floating discharges at the on-site as well as of identifying the concerned defects.

• Journal of the Korea Convergence Society
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• v.9 no.4
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• pp.161-167
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• 2018

The amount of CNG was measured using a pressure sensor in the case of CNG vehicles. However, the current measurement method causes anxiety to the driver because it is difficult to measure the detailed amount of CNG according to various environmental conditions. This study was performed to measure the amount of CNG in CNG fuel system, and presented the method of measurement by simulating the detection system of CNG. In this experiment, a detection simulator with an ultrasonic sensor in CNG tank of Type-3 was designed, and the reception signal of the ultrasonic sensor was verified by reducing the pressure from 100 bars to 0 bars (increment=5 bars) using compressed air. As a result, the output signal voltage of the ultrasonic sensor decreased as the pressure in the tank decreased, and the it was verified that the shape of the graph was linearity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.10
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• pp.907-913
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• 2015

This work presents a method to predict the near magnetic field distribution on the digital switching circuit mounted on PCB using co-simulation of circuit and electromagnetic fields. The proposed method first obtains the normalized near field distribution by exciting the signal and power ports of the switching circuit using sinusoidal sources. Then the real near magnetic field distribution is determined by weighting the normalized field distribution using the current spectrum of the switching circuit. To confirm the proposed method, a switching IC with a ring oscillator and a output buffer is fabricated and measured in the form of chip-on-board. The surface magnetic field distribution is measured using a magnetic probe above the PCB and compared with the simulation results. Experimental results show the correspondence between simulation and measurement results within 10 dB up to fifth harmonics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.10
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• pp.1107-1113
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• 2009

In this paper, the design and implementation of K-Band frequency dividers using 130 nm CMOS process are presented. A Miller frequency divider is presented, which realizes a division range from 20 to 25 GHz with 7.2 mW power consumption from 1.2 V supply. The layout size of the core circuit is about $315{\times}246\;um^2$. In addition, a CML frequency divider which divides the output signal of the Miller frequency divider is also presented, which realizes a division range from 8.5 to 13 GHz with 5.7 mW power consumption. The layout size of the CML core is about $91{\times}98\;um^2$. Cascading the Miller and CML frequency dividers, we confirmed the divide-by-4 operation for the input signal from 20 to 25 GHz.

• ETRI Journal
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• v.36 no.3
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• pp.352-360
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• 2014

This paper presents a 900 MHz zero-IF RF transceiver for IEEE 802.15.4g Smart Utility Networks OFDM systems. The proposed RF transceiver comprises an RF front end, a Tx baseband analog circuit, an Rx baseband analog circuit, and a ${\Delta}{\Sigma}$ fractional-N frequency synthesizer. In the RF front end, re-use of a matching network reduces the chip size of the RF transceiver. Since a T/Rx switch is implemented only at the input of the low noise amplifier, the driver amplifier can deliver its output power to an antenna without any signal loss; thus, leading to a low dc power consumption. The proposed current-driven passive mixer in Rx and voltage-mode passive mixer in Tx can mitigate the IQ crosstalk problem, while maintaining 50% duty-cycle in local oscillator clocks. The overall Rx-baseband circuits can provide a voltage gain of 70 dB with a 1 dB gain control step. The proposed RF transceiver is implemented in a $0.18{\mu}$ CMOS technology and consumes 37 mA in Tx mode and 38 mA in Rx mode from a 1.8 V supply voltage. The fabricated chip shows a Tx average power of -2 dBm, a sensitivity level of -103 dBm at 100 Kbps with PER < 1%, an Rx input $P_{1dB}$ of -11 dBm, and an Rx input IP3 of -2.3 dBm.

• Journal of KIBIM
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• v.3 no.3
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• pp.9-18
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• 2013

In case of applying the BIM method in the civil engineering of irregularly shaped structure, BIM method began to be introduced in the current building engineering area compared with the expected effects of the relatively high construction productivity has been recognized. In this paper, I have developed quantity calculation algorithms applying it to earthwork and bridge construction, tunnel construction, retaining wall construction, culvert construction and implemented BIM based 3D-BIM Modeling quantity calculation. Structure work in which errors occurred in range between -6.28% ~ 5.17%. Especially, understanding of the problem and improvement of the existing 2D-CAD based of quantity calculation through rock type quantity calculation error in range of -14.36% ~ 13.07% of earthwork quantity calculation. It's benefit and applicability of BIM method in civil engineering. In addition, routine method for quantity of earthwork has the same error tolerance negligible for that of structure work. But, rock type's quantity calculated as the error appears significantly to the reliability of 2D-based volume calculation shows that the problem could be. Through the estimating quantity of earthwork based 3D-BIM, proposed method has better reliability than routine method. BIM, as well as the design, construction, maintenance levels of information when you consider the benefits of integration, the introduction of BIM design in civil engineering and the possibility of applying for the effectiveness was confirmed. In addition, as the beginning phase of information integration, quantity document automation program has been developed for activation of BIM. And automatically enter the program code number, linkage and manual volume calculation program, quantity document automation programs, such as the development is now underway, and step-by-step procedures and methods are presented.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1050-1060
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• 2012

As an approach to high-efficiency of SOFC system, SOFC/GT Hybrid system is effective. However, if the output size of the system belongs to the marine class of dozens MWs, the introduction of the cooling system of GT system, which is used as sub-system, makes its related devices complicated and also makes its control difficult. Accordingly, for the marine use, SOFC/GT (non-cooling)Hybrid system looks more suitable than SOFC/GT(cooling)Hybrid system. This study established the SOFC/GT (non-cooling)Hybrid system, and examined the operating temperature & current density of the stack for the system, pressure ratio of the gas turbine, the influence of TIT(Turbine Inlet Temperature) on system performance, etc. through the simulation process. Through this research process, this study was able to confirm that electrical efficiency rises in spite of the increase in the required power for the air compressor, and there exists a limited range of temperatures for operation in TIT.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.1
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• pp.57-62
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• 2017

The purpose of this study is to develop a method for diagnosing the degree of gradual degradation of a reciprocating pump caused by continuous use as a water supply pump in a nuclear power plant. Normally, the progress of such degradation is too slow to be noticed. Hence, it is difficult to determine the degree of degradation using the existing diagnostic methods. In this paper, we propose a new method by which the normal state and the degraded state of the pump can be differentiated, so that the degree of degradation can be identified. First, an emulator was developed using FPGA by providing the parameters of the pump under normal state, so that the emulator generates the information of the pump in the healthy state. Then, by comparing this information with the parameters received from various output sensors of the emulator during the current state, it is possible to identify and measure the degree of gradual degradation. This paper presents some of the results obtained during the development process, and results that show how the emulator operates, by comparing the data collected from an actual pump.