• The KIPS Transactions:PartA
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• v.16A no.6
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• pp.481-488
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• 2009

GIS is used to isolate large power electrical equipment using SF6 gas. While GIS has simple structure, it has few break down, relatively high reliability. But it is hard to check up faults for reason of pressure. Faults of GIS should have a ripple effect on community and be hard to recovery. Consequently, GIS imports a preventive diagnostic system to find internal faults in advance. It is most important that reliability on the GIS preventive diagnostic system, because it estimates abnormality of system by analysis result of collected data. But, exist system which used central data management is low efficiency, and hard to guarantee timeliness and accuracy of data. To guarantee timeliness and accuracy, the GIS preventive diagnostic system needs accordingly to use a real-time middleware. So, in this paper, to improve reliability of the GIS preventive diagnostic system, we use a middleware based on TMO for guaranteeing timeliness of real-time distributed computing. And we propose an improved GIS preventive diagnostic system applying data acquisition, monitoring and control methods based on the TMO model. The presented system uses the Communication Control Unit(CCU) for distributed data handling which is supported by TMO. CCU can improve performance of the GIS preventive diagnostic system by guaranteeing timeliness of data handling process and increasing reliability of data through the TMO middleware. And, it has designed to take full charge of overload on a data acquisition task had been processed in an exist server. So, it could reduce overload of the server and apply distribution environment from now. Therefore, the proposed system can improve performance and reliability of the GIS preventive diagnostic system and contribute to stable operation of GIS.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.348-351
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• 1999

We investigated current limiting properties for an SFCL of YBCO thin film coated with an Au layer. The YBCO film of 1 mm wide and 400 nm thick could carry the current 9.6 A$_{peak}$ without quench. The SFCL limited the fault current below 7.6 A$_{peak}$, which otherwise increases above 65 A$_{peak}$ and melted down at the potential fault current of about 100 A$_{peak}$ which is 10 times greater than the quench current. This means that the Au layer successfully protected the superconducting film by dispersing the heat generated at hot spots and electrically shunting the YBCO film.

• Journal of the Korea Society for Simulation
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• v.25 no.2
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• pp.21-29
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• 2016

Indoor location system has been used Wi-Fi to get a location. After the development of BLE(Bluetooth Low Energy), the interest in the method of a indoor positioning had been move on. It has more advantages than using Wi-Fi. Easy installation, low power consumption, low signal interference and changeable setting(Advertising interval, tx power, etc.). These things can improve efficiency or accuracy in a indoor positioning system. For this reason, recent indoor positioning system uses BLE rather than Wi-Fi. Accordingly, error factors of BLE beacon based indoor positioning should be studying for high accuracy of indoor positioning. In this research, set up few experiment scenarios and keep a close watch on how technological, environmental factor is affecting positioning accuracy. When a application uses largest signal strength to get the indoor location, the mean error of experimental results was decreased compare to using received signal strength in real-time. The result was same when the application applied average and standard deviation to get the indoor location. Changing advertising interval had an effect on the mean error of indoor positioning. Short advertising interval makes the lower mean error than large advertising interval.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.159-166
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• 2009

This study has been attempted to generate electricity, while simultaneously treating artificial organic wastewater using both batch and continuous microbial fuel cells (MFCs). In the batch MFC, current-voltage curve showed an onset potential of -0.69 V vs. Ag/AgCl. The potential range between this potential and 0 potential displayed an available voltage for an automatic production of electric energy and glucose, which was oxidized and treated at the same time. The 486 mg/L glucose solution showed the maximum power of $30mW/m^2$ and the maximum current density of $75mA/m^2$ shown in the power curve. As a result, discharging of the cell containing COD 423 mg/L at the constant current density of $60mA/m^2$ showed a continuous electricity generation for about 22 hours that dropped rapidly due to dissipating of organic material. Total electric energy production was 18.0 Wh. While discharging, the pH change was low and dropped from pH 6.53 to 6.20 then increased to 6.47, then stabilized at this charge. The COD treatment efficiency was found to be 72%. In the continuous MFC, COD removal tends to increase as the hydraulic retention time is increased. At one day of hydraulic retention time as the maximum value reaches the COD removal efficiency, power production rate and power production rate per COD removal that were obtained were 68.8%, $14mW/m^2$, and $20.8mW/m^2/g$ CODrm, respectively. In the continuous MFC, the power production rate per COD removal increases as the hydraulic retention time is increased and decreases as the organic loading rate is increased. At the values lower than an organic loading rate of $1kgCOD/m^3/d$, the values higher than about $18.1mW/m^2/g$ CODrm could be obtained.

• Journal of the Korean Vacuum Society
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• v.21 no.1
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• pp.29-35
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• 2012

The Hydrogenated silicon nitride (SiNx:H) using plasma enhanced chemical vapor deposition is widely used in photovoltaic industry as an antireflection coating and passivation layer. In the high temperature firing process, the $SiN_x:H$ film should not change the properties for its use as high quality surface layer in crystalline silicon solar cells. Initially PECVD-$SiN_x:H$ film trends were investigated by varying the deposition parameters (temperature, electrode gap, RF power, gas flow rate etc.) to optimize the process parameter conditions. Then by varying gas ratios ($NH_3/SiH_4$), the hydrogenated silicon nitride films were analyzed for its optical, electrical, chemical and surface passivation properties. The $SiN_x:H$ films of refractive indices 1.90~2.20 were obtained. The film deposited with the gas ratio of 3.6 (Refractive index=1.98) showed the best properties in after firing process condition. The single crystalline silicon solar cells fabricated according to optimized gas ratio (R=3.6) condition on large area substrate of size $156{\times}156mm$ (Pseudo square) was found to have the conversion efficiency as high as 17.2%. Optimized hydrogenated silicon nitride surface layer and high efficiency crystalline silicon solar cells fabrication sequence has also been explained in this study.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.1 s.343
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• pp.27-36
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• 2006

Conventional delay-insensitive (DI) data encodings usually require 2N+1 wires for transferring N-bit. To reduce complexity and power dissipation of wires in designing a large scaled chip, an encoder and a decoder circuits, where N-bit data transfer can be peformed with only N+l wires, are proposed. These circuits are based on a quasi delay-insensitive (QDI) model and designed by using current-mode multiple valued logic (CMMVL). The effectiveness of the proposed data transfer mechanism is validated by comparisons with conventional data transfer mechanisms using dual-rail and 1-of-4 encodings through simulation at the 0.25 um CMOS technology. In general, simulation results with wire lengths of 4 mm or larger show that the CMMVL scheme significantly reduces delay-power product ($D{\ast}P$) values of the dual-rail encoding with data rate of 5 MHz or more and the 1-of-4 encoding with data rate of 18 MHz or more. In addition, simulation results using the buffer-inserted dual-rail and 1-of-4 encodings for high performance with the wire length of 10 mm and 32-bit data demonstrate that the proposed CMMVL scheme reduces the D*P values of the dual-rail encoding with data rate of 4 MHz or more and 1-of-4 encoding with data rate of 25 MHz or more by up to $57.7\%\;and\;17.9\%,$ respectively.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.148-156
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• 2013

This paper suggests a multi-level and multi-output SMPS based on a shared digital logic controller through independently operating in each dedicated time periods. Although the shared architecture can be devised with small area and high efficiency, it has critical drawbacks that real-time control of each DPWM generators are impossible and its output voltage can be unstable. To solve these problems, a real-time current compensation scheme is proposed as a solution. A current consumption of the core block and entire block with four driver buffers was simulated about 4.9mA and 30mA at 10MHz switching frequency and 100MHz core operating frequency. Output voltage ripple was 11 mV at 3.3V output voltage. Over/undershoot voltage was 10mV/19.6mV at 3.3V output voltage. The noise performance was simulated at 800mA and 100KHz load regulation. Core circuit can be implemented small size in $700{\mu}m{\times}800{\mu}m$ area. For the verification of proposed circuit, the simulations were carried out with Dong-bu Hitek BCD $0.35{\mu}m$ technology.

• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.279-288
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• 2014

Nuclear energy is expected to meet the growing energy demand while avoiding CO2 emission. However, the problem of accumulating spent fuel from current nuclear power plants which is mainly composed of uranium oxides should be addressed. One of the most practical solutions is to reduce the spent oxide fuel and recycle it. Next-generation fuel cycles demand innovative features such as a reduction of the environmental load, improved safety, efficient recycling of resources, and feasible economics. Pyroprocessing based on molten salt electrolysis is one of the key technologies for reducing the amount of spent nuclear fuel and destroying toxic waste products, such as the long-life fission products. The oxide reduction process based on the electrochemical reduction in a LiCl-$Li_2O$ electrolyte has been developed for the volume reduction of PWR (Pressurized Water Reactor) spent fuels and for providing metal feeds for the electrorefining process. To speed up the electrochemical reduction process, the influences of the feed form for the cathode and the type of anode shroud on the reduction rate were investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.304-304
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• 2010

최근 생활에 편리하며 휴대하기 좋은 전자기기들이 개발되고 있다. 휴대폰이나 MP3와 같은 전자기기들은 거의 필수품이라고 할 정도로 우리의 일상생활에 근접하여 있다. 그 종 대표적으로 휴대폰의 종류로 스마트폰과 같은 터치스크린을 이용한 사례는 점차 상승하고 있으며 시간이 지날수록 그 수요는 더욱 많아지고 있다. 때문에 몰입감 제공을 위하여 햅틱장치의 채용이 일반화 되고 있다. 햅틱장치란 가상환경이나 원거리에 있는 환경과 사용자가 상호 작용할 때 사용자에게 촉감이나 힘의 정보를 전달하여 주는 장치로 진동 및 회동 저항에 의해 사용자로 하여금 촉감들 느낄 수 있도록 하는 장치를 뜻한다. 즉, 현실감을 전달을 중점으로 하는 햅틱장치는 빠른 응답 속도와, 진동의 주파수와 크기는 독립적으로 제어가 가능해야 하며 기계적 수용기들을 직접적으로 자극할 수 있어야 한다. 하지만 모바일 햅틱장치의 경우 크기 및 소비전력의 문제로 모든 스펙을 만족하기에는 어려워 좀 더 한정적인 느낌을 제공할 수 없다. 현재까지 모바일 장치에서 햅틱 피드백을 위하여 진동모터나, 솔레노이드, 압전 액츄에이터 등이 많이 사용되어 지고 있다. 그 중 압전 액츄에이터는 입력에너지를 기계적 출력에너지로 변환되는 효과를 이용 한 것으로 압력 센서, 초음파 센서 등 많은 분야에서 응용되고 있으며 변위 범위는 작지만, 크기가 매우 작고 변위 정밀도가 높으며 발생력과 응답속도가 빠르다는 장점이 존재한다. 이를 이용한 햅틱 압전 엑츄에이터의 제작에 사용되는 압전 세라믹스는 높은 전기적 특성을 가질수록 더 졸은 효율을 가지며 이로 인하여 보다 좋은 전기적 특성을 가지는 압전 세라믹스를 필요로 한다. 현재 많이 사용되는 PZT계 세라믹스는 우수한 전기적 특성으로 많이 사용되고 있지만 Pb의 유독성으로 인한 환경문제로 Pb가 포함된 제품을 제한하고 있어 현재 Lead-free의 연구가 이루어지고 있다. Lead-free중 Ba$(Ti_{0.8}Zr_{0.2})O_3$(BZT)는 PZT계 세라믹스를 대체할 차세대 압전 재료로 주목받고 있다. 일반적으로 Lead-free의 압전계수($d_{33}$=100~300pC/N)는 비교적 낮은 값을 보이지만 BZT의 압전계수(BZT $d_{33}$~620pC/N)는 PZT계 세라믹스의 압전계수($d_{33}$=500~600pC/N)와 비교하여 부족하지 않은 압전계수를 보여주며 PZT를 대체할 재료로 주목받고 있다. 본 실험은 햅틱 압전 엑츄에이터용 무연 압전세라믹스의 제작을 위하여 Ba$(Ti_{0.8}Zr_{0.2})O_3-(Ba_{0.7}Ca_{0.3})-TiO_3$(BZT -BCT)의 조성으로 유전 및 압전 특성을 조사하였다.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.840-847
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• 2003

Recently, the coal-ash production has been increased by increase of consumption of electric power. So it is important to secure a reclaimed land and treatment utility for coal-ash. This is an experimental study to compare and analyze the engineering properties of concrete according to W/C and replacement ratio of bottom ash. For this purpose, the mix proportions of concrete according to W/C(40, 50, 60%) and replacement ratio of bottom ash(0, 10, 20, 35, 50%) were established, and then tested for slump, chloride content, setting time, bleeding content, compressive strength. Also the durability test of concrete with W/E 60% was performed. According to test results, it was found that the bleeding content of concrete decreased as the replacement ratio of bottom ash increased. And the chloride content of concrete using the bottom ash increased as the replacement ratio of bottom ash increased, but it is satisfied with the chloride content of fresh concrete $0.30kg/m^3$ below("concrete standard specification" regulation value). The compressive strength of concrete using the bottom ash was similar to that of BA0 concrete after 28 days of curing and the carbonation depth of concrete was increased according to increase of the replacement ratio of bottom ash.