• Design & Manufacturing
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• 제7권1호
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• pp.55-59
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• 2013

A Light Emitting Diode(LED) is a semiconductor device which converts electricity into light. LEDs are widely used in a field of illumination, LCD(Liquid Crystal Display) backlight, mobile signals because they have several merits, such as low power consumption, long lifetime, high brightness, fast response, environment friendly. In general, LEDs production does die bonding and wire bonding on board, and do silicon and phosphor dispensing to protect LED chip and improve brightness. Then lens molding process is performed using mixed liquid silicon rubber(LSR) by resin and hardener. A mixture of resin and hardener affect the optical characteristics of the LED lens. In this paper, computational design of static mixer was performed for mixing of liquid silicon. To evaluate characteristic of mixing efficiency, finite element model of static mixer was generated, and fluidic analysis was performed according to length of mixing element. Finally, optimal condition of length of mixing element was applied to static mixer from result of fluidic analysis.

• 한국태양에너지학회 논문집
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• 제30권4호
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• pp.9-14
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• 2010

The main cause of global warming is carbon dioxide generated from the use of fossil fuels, and active research on the reduction of carbon is in progress to slow down the increasing global warming. Wind turbines generate electricity from kinetic energy of wind and are considered as representative for an energy source that helps to reduce carbon emission. Since the kinetic energy of wind is proportional to the cube of the wind speed, the intensity of wind affects wind farm construction validity the most. Therefore, to organize a wind farm, validity analysis should be conducted first through measurement of the wind resources. To facilitate the approval and permission and reduce installation cost, measuring sensors should be installed at locations below the actual wind turbine hub. Wind conditions change in shape with air density, and air density is most affected by the variable sterrain and surface type. So the magnitude of wind speed depends on the ground altitude. If wind conditions are measured at a location below the wind turbine hub, the wind speed has to be extrapolated to the hub height. This correction of wind speed according to height is done with the Deacon equation used in the statistical analysis of previously observed data. In this study, the optimal Deacon equation parameter was obtained through the analysis of the correction of the wind speed error with the Deacon equation based on the characteristics of terrain.

• 한국수소및신에너지학회논문집
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• 제7권1호
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• pp.29-37
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• 1996

Alkaline water electrolysis has been commercialized as the only large-scale method for a long time to produce hydrogen and the technology is superior to other methods such as photochemical, thermochemical water splitting, and thermal decomposition method in view of efficiency and related technical problem. However, such conventional electrolyzer do not have high electric efficiency and productivity to apply to large scale hydrogen production for energy or chemical feedstocks. Solid polymer electrolyte water electrolysis using a perfluorocation exchange membrane as an $H^+$ ion conductor is considered to be a promising method, because of capability for operating at high current densities and low cell voltages. So, this is a good technology for the storage of electricity generated by photovoltaic power plants, wind generators and other energy conversion systems. One of the most important R&D topics in electrolyser is how to minimize cell voltage and maximize current density in order to increase the productivity of the electrolyzer. A commercialized technology is the hot press method which the film type electrocatalyst is hot-pressed to soild polymer membrane in order to eliminate the contact resistance. Various technologies, electrocatalyst formed over Nafion membrane surface by means of nonelectrolytic plating process, porous sintered metal(titanium powder) or titanium mesh coated with electrocatalyst, have been studied for preparation of membrane-electrocatalyst composites. In this study some experiments have been conducted at a solid polymer electrolyte water electrolyzer, which consisted of single cell stack with an electrode area of $25cm^2$ in a unipolar arrangement using titanium mesh coated with electrocatalyst.

• KIEAE Journal
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• 제13권4호
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• pp.43-48
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• 2013

The effect of climate change has influenced humanity and ecosystem with tremendous changes in temperature. For the past 150 years, the national annual average temperature is 0.6 degree increased and the heating degree day reduced from April to November. However, December to January, the climate change was generated and the heating degree day increased. The blackout occured in 2011 and 2012 by increasing electricity consumption of heating and cooling equipment to the effects of climate change. That is because heating load accounted for 20% of building electric use. In this study, strengthening measures to reduce heating energy consumption is presented due to climate change in winter since 1980 to prevent blackout and reliable power supply for the building energy-saving design standards by Meteorological data provided by the National Weather Service were calculated using the heating degree days in order to present eighteen cities from 1980 to 2012. Insulation standards are presented to prevent black-out by the heating degree days. the heating energy demand was reduced almost 6% including 10% in Central, 5% in South and Jeju area based on strengthening of the insulation. It is applied to the entire country an annual economic effect of 250 billion won, and black-out can be prevented.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권4호
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• pp.210-220
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• 2002

We analysised the effect of harmonics on electric machines of substation power system barred on quantitatively measured harmonics and proposed the methods for prevention of harmonics through checking on transformer, rectifier and cable's capacities against harmonics with reference to KEPCO's electricity service standard. In order to analysis harmoninics of silicon rectifier that is power source in DC substation, computer simulations for a substation with TR of high voltage distribution switchboard are performed. Simulation results show that the total harmonic distortion factor becomes smaller for TR primary and receiving points in order rather than silicon rectifier which is harmonic generation source so that the harmonics generated frets each rectifier are outflowed to power supply and high voltage distribution switchboard The result of higher distortion factors of voltage and current for rectifier with 100% load than those with 50 % and 30% indicates that the waveform of voltage and current for the real substation power system at the office-going and the closing hours with heavy loads might be more distorted. As proposed methods for harmonic reduction, the conventional 6 pulse-type for substation is required to be replaced by 12 pulse-type for reduction of 5th and 7th harmonics. The active filter rather than the passive filter is more effective due to severe variance of rectifier loads, but the high cost is price to be paid. In view of installation area and costs, the use of 12 pulse-type transformer is desirable and then the parallel transformer and the rectifier within the substation must be replaced at the same time. Other substations with parallel feeder can use 6 pulse-type transformer.

• 전기학회논문지
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• 제65권1호
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• pp.97-102
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• 2016

In this paper, a bidirectional power supply charger is proposed. This system used a solar cell panel to generate electricity and used super capacitors to store these energies, which can be used for the robot cleaner or some other electronic products. This system include a phase-shift controlled bidirectional dual active bridge (DAB) converter, solar panel super capacitors and DSP controller. In the daytime it can charge to the super capacitors to store the energy generated by the solar cell panel and in the night it will release the energy stored in the super capacitors to loads. A prototype of the proposed bidirectional power supply charger system was designed which can achieve 18V to 30V input, 10V/20W output to super capacitors and 9V/6.5W output when it acts as a charger for the robot cleaner. The system is verified to be sTable and reliable by both the simulation and experimental results.

• 한국해양공학회지
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• 제23권5호
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• pp.25-31
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• 2009

The most important component of wind turbine is rotor blades. The developing method of wind turbine was focused on design of rotor blade. By the way, the design of a rotating body is more decisive process in order to adjust the performance of wind turbine. For instance, the design allows the designer to specify the wind characteristics derived by topographical map. The iterative solver is then used to adjust one of the selected inputs so that the desired rotating performance which is directly related to power generating capacity and efficiency is achieved. Furthermore, in order to save the money for manufacturing the rotor blades and to decrease the maintenance fee of wind power generation plant, while decelerating the cut-in speed of rotor. Therefore, the design and manufacturing of rotating body is understood as a substantial technology of wind power generation plant development. The aiming of this study is building-up the profitable approach to designing of rotating body as a system for the wind power generation plant. The process was conducted in two steps. Firstly, general designing and it’s serial testing of rotating body for voltage measurement. Secondly, the serial test results above were examined with the CFD code. Then, the analysis is made on the basis of amount of electricity generated by rotor-blades and of cut-in speed of generator.

• 한국전산구조공학회논문집
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• 제29권5호
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• pp.413-419
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• 2016

지진시 사회 인프라시설물의 피해는 시설물 자체의 피해보다 사회 전반에 걸친 2차 피해를 야기한다. 그 중, 지하 공동구 구조물은 통신, 가스, 전기 등 사회의 라이프라인에 해당하여 지진에 대한 취약성을 정확히 평가하여야 할 필요가 있다. 따라서, 본 연구에서는 지하 공동구의 지진 발생 지반가속도에 따른 파괴가능성을 평가하였다. 평가를 위한 입력지반운동은 해외 실측 지진데이터와 한반도에서 발생가능한 인공지진파를 차용하였으며, 지진해석 방법은 응답변위법과 시간이력해석법을 사용하였다. 파괴여부를 판별하는 한계상태는 휨모멘트와 전단 파괴를 바탕으로 하였다. 취약도 함수 도출을 위한 방법은 최우도법이 사용되었으며, 그 분포함수는 대수정규분포로 가정하였다. 이는 지진시 지하 공동구 시설물의 피해 평가는 물론 지하 공동구 시설물의 내진설계를 위한 기초자료로 활용될 수 있다.

• 한국전기전자재료학회논문지
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• 제25권6호
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• pp.439-444
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• 2012

For the application of photo-detector as active layer, we have studied how to deposit SiGe thin film using an independent Si target and Ge target, respectively. Both targets were synthesized by purity of 99.999%. Plasma generators were generated by radio frequency (rf, 13.56 MHz) and direct current (dc) power. When Ge and Si targets were sputtered by dc and rf power, respectively, we could observe the growth of highly crystalline Ge thin film at the temperature of $400^{\circ}C$ from the result of raman spectroscopy and X-ray diffraction method. However, SiGe thin film did not deposit above method. Inversely, we changed target position like that Ge and Si targets were sputtered by rf and dc power, respectively. Although Ge crystalline growth without Si target sputtering deteriorated considerably, the growth of SiGe thin film was observed with increase of Si dc power. SiGe thin film was evaluated as microcrystalline phase which included (111) and (220) plane by X-ray diffraction method.

• 한국산학기술학회논문지
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• 제12권10호
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• pp.4288-4295
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• 2011

본 논문에서는 고주파 용접기의 가변 리엑터 및 커패시터를 해석하여 최적화 설계 하였다. 고주파 용접기의 극판 부분은 콘덴서의 역할을 하기 때문에 큰 정전 용량의 콘덴서를 만들기 위해서는 유전율이 큰 재료의 선택과 극판의 면적을 크게 하고, 극판의 간격을 얇게 하여야 한다. 하지만 많은 전류가 흐르기 때문에 저항이 발생하여 열이 발생하게 된다. 이러한 극판의 열 변형을 막기 위하여 냉각수 등을 이용한 방법으로 극판의 열을 식힌다. 이때 극판의 변형 및 온도에 따른 냉각수의 속도를 최적화 하였다.