• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.51-56
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• 2010

There are two main software in COMS ground station at the normal mode operation - stationkeeping and wheel off-loading. In this paper, ground software validation test for wheel off-loading is summarized and described. The wheel off-loading was performed the design change from E3000 heritage and analyzed. The wheel off-loading of ground software has two part; one is wheel off-loading management for parameters change at the thruster set switching time and the other is wheel off-loading set-point being sent to satellite for the reference momentum.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.2
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• pp.66-70
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• 2006

Various kind of structural defects are observed to be present on the oxidized surface of the silicon crystal which was previously damaged mechanically. The formation of such defects was found to depend on the amount of damage induced and the temperature of thermal oxidation. It was confirmed by the measurement of minority carrier life time that gettering capability decreases as the size of the defects increase. The strained layer which is formed due to smaller amount of damage or lower oxidation temperature believed to has higher capability of gettering over defects like dislocation loops or stacking faults.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.66-71
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• 2016

Reducing the wafer breakage rate and sawing thinner wafers will decrease the cost of solar cells. This study was carried out in order to identify ways to achieve this goal. In this study, the cutting force characteristics using an ingot tilting-type diamond multi wire-sawing machine were analyzed. The cutting force was analyzed while varying the tilting angles and wire speed. The obtained data were analyzed by classifying the tangential cutting force and the normal cutting force. In this cutting force experiment, the difference between the forces was confirmed; it was found that it rises with increasing the tilting angles and decreases when the wire speed elevates. The resulting value can be utilized as basic data for the determination of an ideal cutting recipe.

• Journal of Energy Engineering
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• v.11 no.3
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• pp.216-223
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• 2002

Generation facilities of the power system are mainly classified into large-scale concentrated generation and small-scale dispersed generation, but generation planning of the Korea power system has been focusing on the large-scale generation so far. Recently, however, applications of dispersed generation sources including solar cell, fuel cell, wind power, etc. have been rapidly increasing and being strongly promoted, and such generation sources should be comprehensively considered in both planning and operating. Since it is not always possible that the dispersed generation alone meets all the load interconnected to it is especially when a fault occurs, interconnection into the existing utility is desirable and recommended. In relation to wind power generation systems interconnected at the low and extra high voltage levels, this paper performs the simulation and analysis of the system protection and suggests protection coordination plans on various faults which possibly occur.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.11
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• pp.54-60
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• 2006

This paper discusses wheel offloading approaches of the COMS which has a single solar array system for the accommodation of the optical payloads. First of all, in an effort to reduce fuel consumption and reflect practical implementation point of view, thruster sets for wheel offloading are proposed based on numerical analyses taking into account the COMS configuration. In this analysis, it is assumed that the wheel offloading is conducted twice a day. Secondly, in order to evaluate the effectiveness of the proposed thruster sets, orbit simulations are conducted for several wheel offloading approaches and compared.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1832-1836
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• 2009

우리나라 수위관측소에 설치되어 있는 수위표는 야간 시인성 부족으로 야간이나 우천시 수위관측을 수행하는데 있어 많은 어려움이 있다. 특히 유량측정 전후 수위관측이 반드시 필요하지만 야간일 경우 눈으로 확인하는 것이 쉽지 않다. 야간 수위관측시 시인성을 높이기 위해 일부 관측소에서 야광도료를 이용하거나 빛의 반사효과를 높인 수위표를 설치하는 등의 노력을 하고 있으나 그 효과는 크지 않다. 이에 본 연구에서는 야간 수위관측시 수위 식별이 어려운 문제를 해결하기 위해 첨단 소자인 LED(Light Emitting Diode)를 이용한 수위표를 개발하고 동시에 전류식 수위센서를 이용하여 자동 수위측정이 가능한 수위표를 개발하였다. 이는 기존의 눈으로 확인하는 수위표와 로거에 저장되는 수위측정장치를 하나로 통합한 것이며 주야간을 가리지 않는 탁월한 시인성과 정확한 수위측정 및 수위자료의 저장이 특징이다. LED는 최근 각광받고 있는 첨단 소자로서 각종 전광판 등에 다양하게 활용되고 있으며 전력을 크게 소비하지 않는 것이 특징이다. 또한 전기장치를 수중에 설치하는 것이므로 방수를 위해 실리콘을 이용하여 완벽 방수구조를 갖추었으며 홍수시 하천 유하물에 의한 파손을 방지하기 위해 내구성을 갖춘 구조로 설계 제작하였다. LED를 이용한 수위표는 야간이나 홍수시 수위관측을 수행할 때 많은 장점이 있을 것으로 판단되며 저전력 구조로 상용전원을 이용할 수 없는 위치에서 태양열 전지판을 이용한 배터리 기반 시스템으로 구성할 수 있으므로 측정의 정확도, 활용도 측면뿐만 아니라 설치의 편리성 문제도 큰 장점을 가질 것으로 판단된다.

• Current Industrial and Technological Trends in Aerospace
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• v.7 no.1
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• pp.97-104
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• 2009

Successful separation of satellites from launch vehicles and release its appendages such as solar arrays and antennas are one of the most important tasks for mission accomplishment during in-orbit maneuver. Especially, specific release devices called NEA(Non-Explosive Actuator) have been widely adopted to perform safe separation and release due to its outstanding performance of low functional shock (below 500g), no contamination and easy handing as opposed to the pyroshock device. In the paper, various kinds of NEA and its history of development are reviewed along with a summary on the domestic research trend.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1714-1715
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• 2011

In this work, highly conductive organic solvent-based polyaniline(PANI) was used as an anode in organic photovoltaic cells (OPV) based on poly - (3-hexylthiophene) and [6,6] - phenyl - C60 - butyricacid methyl ester (P3HT : PCBM). The transmittance of the used PANI film were 87.67% and 86.57% at 550nm, and its sheet resistance were 454 ${\Omega}/{\Box}$ and 298 ${\Omega}/{\Box}$. We fabricated ITO-free OPV cells using PANI as an anode, which exhibited an external power conversion efficiency of 2.28% with a result of Jsc of 6.922mA/cm2, Voc of 0.6093V, and FF of 54.10% under an illumination of air mass(AM) 1.5G (100mW/$cm^2$). We used ink-jet printing to deposit buffer layer and active layer on a glass substrate.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.61-61
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• 2003

다결정 실리콘 박막은 박막 트랜지스터와 실리콘 태양전지등에 응용되며, 비정질 실리콘을 재결정화 하여 얻어지는 다결정 실리콘 박막이 주로 이용되고 있다. 비정질 실리콘 박막을 금속 원소와 접촉시킨 상태에서 열처리할 경우 결정화 온도가 낮아지고 결정화에 필요한 열처리 시간이 짧아지게 된다. 금속을 실리콘 박막 표면에 가하는 방법은 진공증착법등으로 비정질 실리콘 박막 위에 금속원소 층을 형성하는 방법이 주로 이용되었다. 본 연구에서는 AlCl$_3$와 NiCl$_2$ 금속화합물 분위기에서 LPCVD 비정질 실리콘 박막을 열처리하여 결정화 거동을 관찰하였다. 금속화합물과 결정화할 비정질 실리콘 박막을 각각 다른 온도로 가열해 줄 수 있는 노를 이용하여 열처리를 시행하였다. AlCl$_3$와 NiCl$_2$ 분말을 혼합하여 소스로 이용한 경우 48$0^{\circ}C$ 5시간 열처리로 결정화가 완료되었으며, 박막 전체에 걸친 균일도와 재현성이 우수하였다. AlCl$_3$와 NiCl$_2$를 이용한 결정화 초기 상태에는 박막 전면에 걸쳐 등근 형태의 결정립이 균일한 핵 생성으로 나타났다. 이와 같은 결과는 Al과 Ni이 고상결정화에 동시에 작용하면서 나타난 것으로, Al이 가해진 비정질 실리콘으로 인해 결정화 속도가 빨라지고 결함이 작은 결정립을 얻을 수 있었으며, Ni로 인해 결정화의 균일성과 재현성을 높일 수 있었다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.10
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• pp.1694-1696
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• 2016

Present thin film solar cells with hydrogenated amorphous silicon oxide (a-SiO:H) as an absorber suffer from low fill factor(FF) of 61~64 [%] in spite of its benefits related to high open circuit voltage ($V_{oc}$). Since degraded quality of a-SiO:H absorber by alloying with oxygen can affect the FF, we aimed to achieve high photosensitivity by minimizing $CO_2$ gas addition. Improving optical gap($E_{opt}$) has been attained by strong hydrogen dilution combined with lowering substrate temperature down to 100 [$^{\circ}C$]. Small amount of the $CO_2$ was added in order to disturb microcrystalline formation by high hydrogen dilution. The developed a-SiO:H has high photosensitivity (${\sim}2{\times}10^5$) and high $E_{opt}$ of 1.85 [eV], which contributed to attain remarkable FF of 74 [%] and high $V_{oc}$ (>1 [V]). As a result, high power conversion efficiency of 7.18 [%] was demonstrated by using very thin absorber layer of only 100 [nm], even though we processed all experiment at extremely low temperature of 100 [$^{\circ}C$].