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김현곤,이동희 경성대학교 공학기술연구소 2012 공학기술연구지 Vol.18 No.-
본 논문에서는 전력 용량 10kW급의 새로운 양방향 PWM Sepic/Zeta 회로를 사용한 컨버터를 제안한다. 이 회로를 설계하고, 이 컨버터의 설계가 동작 가능한지에 Matlab의 Simulink를 사용하여 시뮬레이션 하였다.
탄소섬유 프리프레그 외부 표면 적층방법에 따른 하이브리드 샤프트 진동특성
홍동표,김현식,홍용,고유곤,유청환 한국공작기계학회 2009 한국공작기계학회 춘계학술대회논문집 Vol.2009 No.-
Studies on carbon fiber epoxy composite is being conducted broadly in industries because of its specific stiffness, specific strength and good fatigue resistance. Because carbon fiber epoxy composite has high vibration characteristics, if existing metal material is alternated by carbon fiber epoxy composite, structure will be low weight, satisfy 1st bending natural frequency and have high fatigue resistance. In this study, research on to manufacture hybrid propeller-shaft using carbon fiber epoxy composite instead of current steel propeller shaft of rear wheel drive vehicle. For this, change of 1st bending natural frequency by the number of layers of carbon fiber epoxy composite on the outer surface of aluminum shaft was observed. Compared the change of 1st bending natural frequency by FEA with computer simulation and vibration test. Through this, the amount of increase in 1st bending natural frequency of hybrid shaft by the increase in number of layers of carbon fiber epoxy composite and high vibration characteristics of hybrid shaft was acknowledged.
異方性 Ba-ferrife의 磁性에 미치는 SrCO₃의 添加效果
全鶴坤,吉炳龍,李東熙 연세대학교 산업기술연구소 1982 논문집 Vol.14 No.1
The effect of SrCO₃addition on the improvement of magnetic properties of anisotropic Ba-ferrite was studied by employing the crystallographic investgation into the change of structural orientation due to the addition and subsequent treatment. From the results obtained in these experiments, the followings were concluded; Ba-farrite containing 1.3wt. % Sr, i.e. (Ba0)₁(Sro)??- 5.45 Fe₂O₃,has showed the highest improvement of magnetic properties when sintered at 1250℃ for one hour, where the measured Br,??H?? and (B·H)???were respectively 3,500G, 2,600 Oe and 3.4 MG Oe. The orientaion parameter of this composite was 0.71, and an linear relationship, q=6x10? Br+0.502, was also found between the orentation parameter q and remanence Br. The reasons for these could be attributed to the facts that; (1) this content of Sr falls into the reported optimum range (5.2-5.8) of the mloe ratio of FeOł涍/(BaO)-(SrO). The proper amount of Sr is believed to enhance the formation of a complex ferrite, (BaO)??(SrO)??-n Fe₂O₃, through the diffusional process replacing some of Ba????ions by Sr????ions in the ferrite structure. (2) The possible eutectic reaction between SrO and BaO could be occured at as low as 1250 ˚C and may result in the impoved sinterability of the compacts through the liquid-phase like sintering. ·
김언곤,신동일,조성준 한국항공대학교 1986 論文集 Vol.24 No.-
Uplink와 downlink 가우스성 잡음이 존재하는 존재하에서 비선형 위성 트랜스폰더(transponder)를 통과하는 DS-BPSK(Direct Sequence-Binary Phase Shift Keying)신호의 오율식을 구했다. 위성 트랜스폰더의 TWT(traveling wave tube)전력 증폭기의 비선형 특성은 이상적인 하드리미터(hard limiter)로 모델링하였다. 구해진 오율식에 의해 컴퓨터 계산을 행하고, 그 결과를 반송파 대 uplink잡음전력비(uplink CNR), 반송파 대 downlink잡음 전력비(downlink CNR) 및 확산 스펙트럼의 처리 이득을 파라미터로 하여 그래프로 나타내고 선형시스템의 경우와 비교ㆍ분석했다. 그 결과 uplink CNR 이 O[dB] 이상일 경우는 비선형시스템이 선형시스템에 비해 downlink CNR 면에서 0.4[dB] 정도의 이득이 있었고, 선형시스템에 대한 비선형시스템의 개선도에 있어서 처리 이득은 그다지 영향을 미치지 못함을 알 수 있었다. The error rate equation of DS-BPSK(Direct Sequence-Binary Phase Shift Keying) signal transmitted through the nonlinear satellite transponder has been derived in the up link and downlink Gaussian noise environment. The nonlinearity of TWT(traveling wave tube) in satellite transponder is modeled as an ideal hard limiter. The numerical results of the derived equations have been shown in figures in terms of carrier to uplink noise power ratio(uplink CNR), carrier to downlink noise power ratio(downlink CNR) and process gain, and compared with those of the linear system. In the analysis, we have known that when the uplink CNR is below -5[dB] the hard-limited system degrades the error rate performance compared with the linear system, however, when the uplink CNR is above O[dB] the hard-limited system can gain 0.4[dB] improvement in downlink CNR to maintain a fixed error rate Pe=10(??) compared with the linear system. Even though the process gain can improve the error rate performance of both systems-the hard-limited system and the linear system, it does not affect seriously the improvements of the hard-limite system performance over the linear system performance.
김일곤,유동선 昌原大學校 基礎科學硏究所 2001 基礎科學硏究所論文集 Vol.13 No.-
We have measured the absorption spectrum of CuBr quantum dots at 8.5K. Z1.2 exciton peak moves toward the shorter wavelength relative to the bulk CuBr. After a selective excitation by the dye laser, we could find the spectral hole in the absoprption spectrum. The depth and width of spectral hole depends on the optical fluence of dye laser. There are two process in the hole burning of quantum dots. The rising times of hole depth are 1.2 sec and 250 sec respectively. We think that the fast process is the result of the reduction of quantum dots which have the specific mean diameter, the second process is caused by the variation of a environment of matrix.
김동백,강대호,구인선,김봉곤 경상대학교 과학교육연구소 1996 科學敎育硏究所報 Vol.16 No.1
This study treats of the comparative analysis of the science textbooks in relation to the inquiry learning ability and STS viewpoint in order to offer some aids that help teaching/learning in class. The major findings of the study are summarized below. 1. The textbooks on the 6th curriculum contain more variety of inquiry process than those on the 5th, which makes students get interested in their learning and get the result of experiments without making experiments. 2. The pictures on the 6th rose 27 percent compared with 5th. It can help students reduce the burden of learning and understand science more easily. 3. The textbooks on the 6th are intended to develop a balanced and varied inquiry ability, while the textbooks on the 5th are rather biased to several items. 4. The textbooks on the 6th have more contents and pictures connected with everyday science than those on the 5th.
UV/Cl₂(g)에 의한 Si-wafer 표면금속 오염물의 건식세정에 관한 연구
손동수,정광진,최성호,천희곤,조동율 울산대학교 1998 공학연구논문집 Vol.29 No.2
본 연구에서는 실리콘 웨이퍼 표면에 존재하는 미량의 Zn, Fe, Ti 금속 오염물들이 UV-excited chlorine radical을 이용한 건식세정 방법으로 제거되는 반응과정을 연구 하였다. 실리콘 웨이퍼 상에 진공증착법으로 원형패턴이 있는 Zn, Fe, Ti 박막을 증착시켜 상온 및 200℃에서 UV/CI₂세정하였을 때, 염소 래디컬(CI*)이 Fe, Zn, Ti와 반응하여 제거되는 것을 반응 전후 광학현미경과 SEM을 통해 표면 형상 변화를 관찰하였고, in-line으로 연결된 XPS를 통해서 반응 후 웨이퍼 표면에 남아있는 화합물의 화학적 결합상태를 관찰하였으며, UV/CI₂세정 후 실리콘 기판이 손상받는 정도를 알기 위해 AFM으로 표면 거칠기를 측정하였다. 광학현미경과 SEM의 분석에 의하면 Zn와 Fe는 쉽게 제거되는 반면 염화물을 형성하기 보다는 휘발성이 적은 산화물을 형성하는 경향이 강한 Ti은 약간만 제거되는 것을 확인하였다. XPS 분석을 통해서 이들 금속 오염물들이 chlorine radical과 반응하여 웨이퍼 표면에 금속 염화물을 형성하고 있는 것을 확인하였고, UV/CI₂세정처리를 하였을 때 실리콘 웨이퍼의 표면 거칠기가 약간 증가하는 것을 알 수 있었다. 지금까지의 결과를 통해 볼 때, 습식세정과 UV/CI₂건식세정을 병행하면 플라즈마 및 레이저를 사용하는 다른 건식세정 방법에 비하여 보다 저온에서 실리콘 기판의 큰 손상 없이 비교적 용이하게 금속 오염물을 제거할 수 있음을 알수 있었다. The reaction mechanisms of dry cleaning of Zn, Fe and Ti trace contaminants on the Si wafer using UV/CI₂ have been studied by SEM, AFM and XPS analyses. The patterned Zn, Fe and Ti films were deposited on the Si wafer surface by thermal evaporation and changes in the surface morphology after dry cleaning using CI₂and UV/CI₂at 200℃ were studied by optical microscopy and SEM. In addition changes in surface roughness of Si wafer by the cleaning was observed by AFM. The chemical bonding states of the Zn, Fe and Ti deposited silicon surface were observed with in-line XPS analysis. Zn and Fe were easily cleaned in the form of volatile zinc-chloride and iron-chloride as verified by the surface morphology changes. Ti which forms involatile oxides was not easily removed at room temperature but was slightly removed by UV/CI₂at elevated temperature of 200℃. It was also found that the surface roughness of the Si wafer increased after CI₂and UV/CI₂cleaning. Therefore, the metallic contaminants on the Si wafer can be easily removed at lower temperature by continuous processes of wet cleaning followed by UV/CI₂dry cleaning.
오동석,이병곤 한국산업안전학회 2002 한국안전학회지 Vol.17 No.4
In this study, the fracture characteristics of carbonized silicon grinding wheels were examined with tensile, compression, impact and bending test. The experiment was performed for the various grinding wheels with grain size #46, #80, and grade H, L, P, and one vitrified bond and one structure No. 7. Also the centrifugal fracture rpm of carbonized silicon grinding wheels were measured and compared with the calculated values for the various wheel diameters and thicknesses. The results showed that the fracture tensile strength was 1.5~2.0㎏/㎟, and it was increased by decreasing grain size and increasing grade. The fracture compression loads were 1,600~3,000㎏_f, and the inner stress was higher than outer's. And the abosrption energy of impact test was 3.3~4.7 J, and it was increased by decreasing grain size but it was not effected by grade. The fracture bending stress was 0.1~0.2㎏/㎟, and it was increased by decreasing grain size and increasing grade. The centrifugal fracture rpm of carbonized silicon grinding wheel was about 8,500~12,000 and agreed well with the calculated value, and it was increased by decreasing diameter. However, it was almost constant for the reduction of wheel thickness.