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RISS 인기검색어
- 검색키워드
- 저자 : 김동흔 (검색결과 4 건)
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김동흔 성균관대학교 산업과학대학원 1998 국내석사
The characteristics of the inter-modulation (IMD) and the reason causing the IMD in the RF passive components are described. The method for the measurement of the inter-modulation (IMD) is introduced. One may show, based on the measurement result, that the main factors causing the IMD are the contact resistance and the surface roughness between the connector and the other components. One may also show that the co-currency of the IMD in passive components is all restituted above 15 percentage after substituting a silver and a brass coating by a nickel coating and improving the surface roughness. The IMD value (Iv) is improved to - 140dBc < Iνc - 159dBc from - 117dBc < Iν < - 135dBc after the nickel coating for connector is replaced by the silver and brass Coating. In case of arrester, Iν is improved to - 151 dBc < Iν< - 162 dBc from - 117dBc Iν -135dBc after N type connector is replaced by DIN type. In case of antenna, Iu is improved to -14ldBc < Iν < -159 dBc from -122dBc < Iν< -135dBc after the connection between antenna and reflector is strengthened by chemical material and nickel coating is replaced by silver coating on the connector part contacted with antenna.
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목초액과 살충제를 혼합함으로써 벼멸구와 애멸구에서 나타나는 시너지 효과에 대해서 연구하였다. 본 실험에서 사용된 목초액은 대표적인 멸구류 살충제, 곤충성장조절제가 함유된 살충제, 다른 해충의 살충제 그리고 천연물 추출 살충제의 4개의 그룹의 총 14종의 살충제와 혼합을 하였다. 목초액 단독 처리 실험에서는 멸구류에 대해 살충력이 없는 것으로 나타났다. 그리고 목초액과 혼합된 대부분의 살충제들은 높은 살충력을 나타내지 않았다. 하지만 목초액이 carbosulfan과 혼합되었을 때, 그 효과는 carbosulfan 단독의 살충력 보다 훨씬 높게 나타났다. 그리고, carbosulfan의 target molecule인 acetylcholinesterase 의 활성을 측정한 결과 목초액과 혼합된 처리구에서 그 활성이 아주 낮게 나타났다. 본 실험의 결과를 토대로 목초액의 시너지 효과는 대부분의 살충제에 공통적으로 나타나는 것이 아니라, 특정 살충제와 혼합했을 때만 살충력을 향상 시켜준다고 판단된다. 다양한 살충제와 목초액을 혼합해 실험을 하여 그 특징을 밝힘으로써 궁극적으로 보다 친환경적인 멸구류 방제법 개발에 기여할 수 있을 것으로 판단된다.
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충북대학교 천문대는 2008년 개관하여 1m R-C형 망원경과 60cm 광시야 망원경을 이용한 변광성의 시계열관측을 수행해 왔다. 그러나 관측 자료 중 20일 이상 관측된 영역이 많음에도 관측 대상에 대한 분석을 제외하고는 다른 별들에 대한 연구가 전무한 실정이어서 이에 대한 활용 방안 모색이 필요한 실정이다. 시계열 관측된 자료 활용 방안의 하나로 변광성 후보군 검출 알고리즘을 개발하는 것이 본 연구의 주된 목표이다. 이 목표를 달성하기 위해 관측영상이 회전을 보정할 수 있고 관측영역에 포함된 별에 대해 동일한 ID를 부여하기 위해 USNO-B1.0 항성목록을 이용한 WCS tools를 사용하였다. ID가 부여된 관측영역의 천체들의 변광 및 주기분석은 Shin & Byun(2004)의 방법을 이용하여 수행하였다. 개발된 변광성 찾기 알고리즘을 충북대학교 천문대가 모니터링하고 있는 몇몇 자기격변변광성의 시계열관측 자료에 적용해 보았다. 개발된 알고리즘이 DO Dra, TT Ari, RXSJ1803 그리고 MU Cam 영역에서 변광하는 천체들의 존재를 확인하고 해당 변광성들의 주기를 잘 찾아내는 것을 확인하였다. 또한 2K CCD 와 4K CCD로 관측된 영역에서도 동일한 작업을 수행 가능함을 별의 인식률계산을 통해 확인하였다. 개발된 알고리즘은 향 후 시계열 관측을 하는 천문대들의 관측이미지를 재분석하여 많은 변광성들을 찾아내는데 활용될 전망이다. Chungbuk National University Observatory Jincheon Station are monitoring many variable stars with 1m R-C telescope and 0.6m wide field telescope. The time series observation data of these variable stars are analysed only for the variability study of these stars till now. It is highly needed to use such time series data in order to find some variable stars in same field. The main purpose of this work is to develop an algorithm detecting new variable star candidates in the variable star field as one of application of the time series data. The developed algorithm has two steps; the first step is to identify the stars in the observed filed. Some fields of time series data, which contain observation data more than 20 day with R filter at Jincheon station, are selected, and tried to identify all stars in selected field using WCS tools with USNO-B1.0 star catalog as well as to give an ID for each identified star. The WCS method has an advantage to compensate the rotation of the observation image and to give a same ID for identified star. The second step is to find the period for each stars if this star is confirmed as a variable star. The period analysis algorithm developed by Shin & Byun (2004) has been used for this purpose. The developed algorithm are applied to the time series data of some magnetic cataclysmic variables being monitored at Chungbuk National University Observatory now. As a result, 12 variable star candidates have been detected from the time series data of DO Dra for 67 days, TT Ari for 48 days, RXSJ1803 for 39 days and MU Cam for 30 days, which are observed using 2K CCD and 4K CCD. Five of these 12 variable stars are new variables not reported as variable star yet. Comparison of the matching ratio between DAOfind and our method shows that the developed algorithm can be used in the time series data even if the field of view are changed. The developed algorithm will be applied to find new variables in time series data at different observatories in the future.
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Size controlled Synthesis and Assembly of Gold Nanoparticles and Their Applications
The synthesis of shape and size controlled gold nanoparticles was carried out in an aqueous environment via the reduction of HAuCl4 by ascorbic acid with the addition of NaOH in the presence of cetyltrimethylammonium bromide (CTAB). The different method of precursor injection has successfully provided the different shape of octahedral and cubic gold nanoparticles. All the products were composed of monodisperse nanoparticles with a well-defined octahedral and cubic shape. The size of the octahedral gold nanoparticles can be readily controlled by varying the reaction temperature. The average edge lengths of the octahedral gold nanoparticles prepared at 25, 30, 40, and 50 °C were 38.4 ± 1.7, 34.8 ± 1.6, 28.5 ± 1.7, and 23.1 ± 1.8 nm, respectively. The efficient surface-enhanced Raman spectroscopy (SERS) properties of nanoparticles dependent on the minute size of product was observed. The edge lengths of the gold nanocubes were 68 ± 2 nm. The gold nanocubes were assembled on the faces of the gold nanoplates. The gold nanoplates were prepared by reduction of HAuCl4 through photochemical reduction in the presence of cetyltrimethylammonium chloride (CTAC). The gold nanocubes were attached to the gold nanoplate surface with 1,4-benzenedithiol self assembled monolayers as a molecular linker. We have observed that single-crystalline nanocubes are feasibly assembled on the different single-crystalline nanoplates with well-defined geometries. These products can be applied in the field of surface-enhanced Raman spectroscopy (SERS). The obtained products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis spectroscopy, atomic force microscopy (AFM), and X-ray diffraction (XRD).
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