• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.58-68
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• 1998

A computer-controlled system for measuring dielectric hysteresis has been developed. This system consists of the wave generation par\, the high voltage amplifier part, the measurement part, the data acquisition part and the related controll circuits and is interfaced to P.C(personal computer). The applied voltage and its frequency are controlled by P.C . Since the measured datas can be saved in the RAM of P.C, the analysis and the graphics of the datas are very convenient. As a accuracy test, the capcitances of the commercial mica and styroll capacitors were measured by applying high voltage and the results were good agreement with the rating values. In the test of PZT ceramic sample, the typical D-E hysteresis loops were obtained by applying a single frequency voltage to the sample, and $\varepsilon-E$ and D-E hysteresis loops could be measured at the same time by applying a double frequency voltage to the sample.sample.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.72-81
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• 2009

This paper presents quasi-resonant type high power factor ac power supply for atmospheric pressure plasma cleaning system adopting three phase PFC boost converter and it's control method. The presented ac power supply consists of single phase H-bridge inverter, step-up transformer for generating high voltage and three phase PFC boost converter for high power factor on source utility. Unlikely to the traditional LC resonant converter, the propose one has an inductor inside only. A single resonant takes place through the inside inductor and the capacitor from the plasma load modeled into two series capacitor and one resistance. The quasi-resonant can be achieved by cutting the switching signal when the load current decrease to zero. To obtain power control ability, the propose converter controlled by two control schemes. One is the changing output pulse period scheme in the manner of PFM(Pulse Frequency Modulation) control. On the other, to provide more higher power to load, the DC rail voltage is directly controlled by the 3-phase PFC boost converter. The significant merits of the proposed converter are the uniform power providing capability for high quality plasma generation and low reactive power in AC and DC side. The proposed work is verified through digital simulation and experimental implementation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.4
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• pp.74-80
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• 2003

Ionic wind is produced by a corona discharge when a DC high voltage is applied across the point-to-plane gap geometry. The corona discharge phenomena have been investigated in several beneficial application fields such as electrostatic cooling, ozone generation, electrostatic precipitation and electrostatic spraying. Recently ionic wind might be used in aerodynamic, for example, heat transfer, airflow modification, and etc. In this work, in order to analyze the control behavior of the velocity and amount of ionic wind produced by the positive DC corona discharges. The ionic wind velocity was measured as a function of the applied voltage, diameter of the punched hole on plate electrode and separation between the point-to-plate electrodes. As a results, the airflow is generated from the tip of needle to the plate electrode in the needle-to-punched-plate electrode systems. The ionic wind velocity is linearly increased with an increase in applied voltage and ranges from 1 to 3 m/sec at the locations of 100-200 mm from the punched-plate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.1926-1938
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• 2009

In this study, detection system of the blood flow variation rate was implemented using the variation effect of bio electric impedance at time of the blood pressure measurement by means of impedance method. The blood pressure measurement was performed by the oscillometric method. The mean arterial pressure was calculated using maximum amplitude algorithm. The systolic and diastolic pressure were estimated by establishment of the various characteristic ratio according to mean arterial pressure range. Alternative static current source and lock_in amplifier were introduced to impedance measurement. The variation of blood volume was measured using variation bio impedance according to induced cuff pressure at measuring area.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.349-356
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• 2017

OH radical generation is one of the common method to evaluate photocatalytic activity. In many of previous studies, only the UV(Ultraviolet) light was applied to test photocatalytic ability of $TiO_2$ nanotubes by studying probe compound(4-Chlorobenzoic acid) concentration change in solution. Also, $TiO_2$ nanotubes were found to show some electrochemical characteristics when the flow of electric current was applied. In this study, the flow of electric current and UV light were applied at the same time to determine whether electrochemical characteristics of $TiO_2$ nanotube plate can give synergetic effect on the photocatalytic activity. $TiO_2$ nanotube was grown on Ti by anodic oxidation to create $TiO_2$ nanotube plate which can be used as a photocatalyst and a electrode that can undergo AOP(Advanced Oxidation Process) for water treatment. Probe compound solution was prepared using 4-chlorobenzoic acid and $H_2O$ as a solvent. NaCl was added to give conductivity to work as electrolyte. As a result, enough level of electric current flow was found to give synergetic photocatalytic effect which can be used for efficient AOP water treatment method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.643-648
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• 2010

Portable fuel cells are commonly operated in the dead-end mode because of such as high fuel utilization. However, the performance of such systems deteriorates continuously with an increase in the amount of by-products such as water vapor and nitrogen. In this study, to verify the effect of water vapor on Proton Exchange Membrane Fuel Cells (PEMFCs), constant-load experiments were carried out for a current density of 600 mA/cm2 and a voltage of 0.4 V, respectively. The performance of the cell was more stable under constant voltage conditions than under constant current density conditions. Condensed water accumulated in the anode channel near the cell outlet. The experimental results show how the relative humidity (RH = 0.15, 0.4 and 0.75) of air at the cathode side affect the performance of PEMFCs with dead-end anode. At RH values higher than 0.15, the mean power density increased by up to 51% and the mean purge duration decreased by up to 25% compared to the corresponding initial values.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.4
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• pp.577-582
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• 2016

This Study focused on the development of SMPS (Switching Mode Power Supply) to supply the constant votage and current nevertheless LED fluorescent Light generated the electric noise (with Harmonics) and Inrush current at instant time of turn-on and off. Recently, according to the Green policy in government, the LED fluorescent Lighter showed the rapidly increasing tend as indoor and outdoor Lighter. But, because of costs, LED fluorescent Light not considered and neglected the following items; power factor, efficiency, Harmonics and Inrush current. So, we are developed the SMPS about 3 key issues as follows: 1st, power factor and efficiency is 85%. 2nd, the switching noisy by harmonic is minimized. 3rd, the Inrush current at turn on and off time is reduced the minimum 0.3 A after $100{\mu}sec$ on turnon time. The proposed SMPS adjusted by LNK 409 driver (included the high frequency modulation function). Although, the developed SMPS maintained the about 85% of power factor and efficiency. but, the SMPS must be generated low heat by the variation of minute load current at switching timing. To improve the above weak point, the developed SMPS have the feedback monitoring circuit between input side and output side to maintain the power factor and efficiency. Also, we are studied the time-constant of control circuit to output the constant voltage and current nevertheless the load disturbance of LED lighting. The LED fluorescent Light of 46W is checked the above items.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.448-448
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• 2013

최근 생물학적 분석 기구에서 시료를 처리, 분리, 검출, 샘플링 또는 분석하기 위해 사용되는 마이크로펌프(Micropump)에 대한 관심이 높아지고 있다. 또한 전자소자의 성능과 신뢰성의 증진을 위한 전자소자의 열 문제를 해결하기 위해 냉각장치로 마이크로 펌프가 적용되기도 한다. 그 외에도 마이크로펌프는 다양한 분야에 응용이 가능하다. 마이크로펌프는 작동 방식에 따라 압전형, 공압형, 열공압형, 연동형 등의 여러 종류로 분류되고 있다. 그중에서도 최근에는 연동형 마이크로 펌프의 개발이 각광받고 있다. 기존의 연동형 펌프들은 다중 챔버를 가지고 있으며, 각각의 챔버 내에서 Dead volume이 많이 발생할 뿐만 아니라 이상적인 연동운동과는 차이가 많이 나는 문제점을 가지고 있다. 또한 압전방식과 열공압방식은 느린 응답성으로 인해 효율적인 유체 이동이 어렵다. 본 논문에서는 이상적인 연동운동을 구현하기 위하여 기존의 연동형 펌프의 단점을 보완하고, 하나의 챔버에 다중전극 구조를 가지는 정전기력방식의 연동형 펌프를 개발하였다. 정전기력방식으로 펌프를 구동함으로써, 저전력으로 펌프구동이 가능하며, 하나의 챔버에 다중전극을 설치함으로써 이상적인 연동운동을 재현하였다. 그리고 Dead volume을 최소화 하였다. 또한, 빠른 반응속도로 인해 효율적인 유체 이동을 실현시킬 수 있었다. 본 연구에서 제안된 마이크로 펌프의 구성은 크게 챔버, 박막, Inlet/outlet hole으로 구성되었다. 챔버는 Si-wafer에 wet etching 공정으로 제작 하였고 그 위에 알루미늄 박막을 200 nm 증착시켰다. 챔버는 가로 32 mm, 세로 5 mm, 깊이는 $15{\mu}m$, 부피는 $200{\mu}l$으로 제작되었다. 박막은 폴리이미드(polyimide)를 사용하여 $3{\mu}m$의 두께로 제작 되었으며, 폴리이미드 박막 사이에는 200 nm 두께의 4개의 알루미늄 박막 전극을 삽입시켰다. 삽입된 4개의 전극에 개별적인 전기신호를 보냄으로써 연동운동이 가능하다. Inlet/outlet hole은 직경 2 mm의 크기로 제작되었으며, 튜브를 연결하여 유체가 흐를 수 있는 체널을 형성하였다. 제작된 마이크로 펌프의 구동전압은 115 V이며, 인가되는 주파수를 1 Hz~100 KHz까지 변화시켜 유량을 측정하였다. 작동 유체는 공기이며, 유량측정은 튜브 내에 물방울을 삽입하여 시간에 따른 이동거리를 관측하였다. 측정결과 2.2 KHz에서 2.4 mm/min의 가장 높은 유량을 확인할 수 있었다. 본 연구를 통해 제안된 연동형 마이크로펌프는 이상적인 연동운동이 가능함으로써 기존의 연동형 방식의 문제점을 보완하였으며, 생명과학, 의학, 화학 등의 분야에서 적용이 가능하리라 기대된다.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.1
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• pp.29-33
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• 2011

The current density in copper electroplating is directly related with the productivity and then to increase the productivity, the increase in current density is required. To obtain the high mass flow rate, rotating disk electrode(RDE) was employed. High rotational speed in RDE can increase the mass flow rate and then high speed electroplating was possible using RDE to control mass flow. Two types of cathode were used. One is RDE and another is rotating cylindrical electrode(RCE). A constant-current, constant-voltage and linear sweep voltammetry were applied to investigate current and voltage relationship. The maximum current density without evolution of hydrogen gas was increased with rotational speed. Over 400 rpm, maximum current density was higher than 1000 A/$m^2$. The diffusion coefficients of copper calculated from the slope of the plots are $5.5{\times}10^6\;cm^2\;s^{-1}$ at $25^{\circ}C$ and $10.5{\times}10^6\;cm^2\;s^{-1}$ at $62^{\circ}C$. The stable voltage without evolution of hydrogen gas was -0.05 V(vs Ag/AgCl). Additives were added to prevent dendritic growth on cathode deposits. The surface roughness was analyzed with UV-Vis Spectrophotometer. The reflectance of the copper surface over 600 nm was measured and was related with the surface roughness. As the surface roughness improved, the reflectance was also increased.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.83-83
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• 2017

생체재료의 표면은 이식과 동시에 생체계면의 역할을 하게 되어, 일련의 생물학적 반응이 시작되고 진행되는 중요한 장소가 된다. 초기에 생체계면에서 일어나는 단백질 흡착이나 염증반응을 비롯한 생물학적 반응들은 궁극적으로 임플란트의 성패를 좌우할 만큼 중요하다. 골융합을 개선하기 위한 다른 방법으로 생체불활성의 타이타늄 (Ti)과 골조직의 능동적인 반응을 이루기 위해 생체활성 표면을 부여함으로서 계면에서의 골형성 반응을 증진시키는 방법이 이용된다. 생체불활성의 Ti과 Ti합금은 골조직과 직접적인 결합을 이루지 못하므로, 골조직과의 반응을 향상하기 위해 여러 종류의 생체활성 재료를 코팅하는 방법이 연구되어 왔고, 이 중 생체의 변화와 가장 유사한 하이드록시아파타이트 코팅이 가장 대중적인 방법으로 사용되었으며 이는 초기 골형성을 촉진하는 것으로 알려졌다. 치과용 임플란트의 표면형상과 화학조성이 골 융합에 영향을 미치는 가장 중요한 인자이므로 최근의 연구동향은 이들 두 가지 표면특성을 결합함으로서 결과적으로 최적의 골세포반응을 유도하고, 골융합 후 골조직과의 micromechanical interlocking에 의해 임플란트의 안정성에 중요한 역할을 하는 마이크론 단위의 표면조도와 표면 구조를 유지하면서, 부가적으로 골 조직 반응을 능동적으로 개선할 수 있는 생체활성 성분을 부여하여 골 융합에 상승효과를 이루기 위한 표면처리법에 관해 많은 연구가 요구되어지고 있다. 따라서 골을 구하는 원소인 망간과 실리콘으로 치환된 하이드록시아파타이트를 플라즈마 전해 산화법으로 코팅하여 세포와 잘 결합할 수 있는 표면을 제공함으로써 골 융합과 치유기간을 단축시킬 수 있을 것으로 사료된다. 실험방법은 시편은 치과 임플란트 제작 합금인 Ti-6Al-4V ELI disk (grade 5, Timet Co., USA; diameter, 10 mm, thickness, 3 mm)이며, calcium acetate monohydrate, calcium glycerophosphate, manganese(II) acetate tetrahydrate, sodium metasilicate을 설계조건에 따라 혼합 제조된 전해질 용액을 이용하여 플라즈마 전해 산화법으로 표면 코팅을 실시하였다. 각 시편의 플라즈마 전해시 전압은 280V로 인가하였고, 전류밀도는 70mA로 정전류를 공급하여 해당 인가전압 도달 후 3분 동안 정전압 방식을 유지하였다. 코팅된 피막 표면을 주사전자현미경과 X-선 회절분석을 통하여 미세구조 및 결정상을 관찰하였다. 또한 코팅된 표면의 생체활성 평가는 정량적으로 평가하기 위해 동전위시험과 AC 임피던스를 통하여 시행하였다. 분극거동을 확인하기 위해 potentiostat (Model PARSTAT 2273, EG&G, USA)을 이용하여 구강 내 환경과 유사한 $36.5{\pm}1^{\circ}C$의 0.9 wt.% NaCl에서 실시하였다. 전기화학적 부식 거동은 potentiodynamic 방법으로 조사하였고 인가전위는 -1500 mV에서 2000 mV까지 분당 1.67 mV/min 의 주사속도로 인가하여 시험을 수행하였다. 임피던스 측정은 potentiostat (Model PARSTAT 2273, EG&G, USA)을 이용하였으며, 측정에 사용한 주파수 영역은 10mHz ~ 100kHz 까지의 범위로 하여 조사하였고 ZSimWin(Princeton applied Research, USA) 소프트웨어를 사용하여 용액의 저항, 분극 저항 값을 산출하였다. 망간의 함량이 증가할수록 불규칙한 기공을 보였으며, 실리콘은 $TiO_2$ 산화막 형성을 저해하는 경향을 확인할 수 있었다. 단독으로 표면을 처리한 경우보다 두 가지 원소를 이용해 복합 표면처리를 시행한 경우가 내식성이 좋아 임플란트과의 골 유착에 긍정적인 영향을 미칠 것으로 사료된다.