• 한국통신학회논문지
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• 제17권1호
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• pp.38-46
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• 1992

본 논문에서, 63_88MHz 밴드폭에서 25MHz 채널 스페이싱을 갖는 1023 채널과 100 hops/sec 호핑율을 가진 주파수 호핑 송수신기에 적용할 수 있는 고속 동기 회로를 수행했다. 동기과정(초기 동기와 트래킹)은 두 스텝으로 구성된다. Short hopping frequencies, synchronization prefix에 정합된 두개의 채널 수동 correlators를 사용한 변황된 정합 필터는 초기동기를 위해 제시되었다. 초기 동기의 확률을 증가 시키기 위해 prefix는 반복적으로 전송된다. correlator의 출력은 동기 결정회로로 보내지고 코드 시작 시간은 동기 결정회로에 대해서 알아낸다. 변형된 정합 필터 방법은 하드웨어의 복잡성을 줄이고 코드 획득을 빠르게 얻는 것은 가능하게 했다. 쿨럭 회복 회로는 tracking을 위해 PN코드를 발생했다.

• 한국생산제조학회지
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• 제25권6호
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• pp.410-420
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• 2016

The geometric dimension and shape of microchannels that are formed during surface texturing are widely studied for applications in flow control, and drag and friction reduction. In this research, a new method for controlling the deformation of U channels during micro-rolling-based surface texturing was developed. Since the width of the U channels is almost constant, controlling the depth is essential. A calibration procedure of initial rolling gap, and proportional-integral PI controllers and a linear interpolation have been applied simultaneously to control the depth. The PI controllers drive the position of the pre-U grooved roll as well as the rolling gap. The relationship between the channel depth and rolling gap is linearized to create a feedback signal in the depth control system. The depth of micro channels is studied on A2021 aluminum lamina surfaces. Overall, the experimental results demonstrated the feasibility of the method for controlling the depth of microchannels.

• 한국정밀공학회지
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• 제23권5호
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• pp.190-196
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• 2006

Transparent materials are widely used in the fields of optic parts and bio industry. We have experiment to find out the characteristics of the micromachining inside transparent materials using femtosecond laser pulses. With its non-linear effects by very high peak intensity, filament (plasma channel) was formed by the cause of the self-focusing and the self-defocusing. Physical damage could be found when the intensity is high enough to give rise to the thermal stress or evaporation. At the vicinity of the power which makes the visible damage or modification, the structural modification occurs with the slow scanning speed. According to the polarization direction to the scanning direction, the filament quality is quite different. There is a good quality when the polarization direction is parallel to the scanning direction. For fine filament, we could suggest the conditions of the high numerical aperture lens, the short shift of focusing point, the low scanning speed and the low power below 20 mW. As the examples of optics parts, we fabricated the fresnel zone plate with the $225{\mu}m$ diameter and Y-bend optical wave guide with the $5{\mu}m$ width.

• 상하수도학회지
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• 제22권6호
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• pp.619-625
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• 2008

Urban sewer systems are designed to operate in open-channel flow regime and energy loss at square manholes is usually not significant. However, the energy loss at surcharged manholes is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharged flow. Hydraulic experimental apparatus which can change the manhole inner profile(CASE I, II, III, and IV) and the invert types(CASE A, B, C) were installed for this study. The experimental discharge was $16{\ell}/sec$. As the ratio of b/D(manhole width/inflow pipe diameter) increases, head loss coefficient increases due to strong horizontal swirl motion. The head loss coefficients for CASE I, II, III, and IV were 0.46, 0.38, 0.28 and 0.37, respectively. Side covers increase considerably drainage capacity at surcharged square manhole when the ratio of d/D(side cover diameter/inflow pipe diameter) was 1.0. The head loss coefficients for CASE A, B, and C were 0.45, 0.37, and 0.30, respectively. Accordingly, U-invert is the most effective for energy loss reduction at surcharged square manhole. This head loss coefficients could be available to evaluate the urban sewer system with surcharged flow.

• 펄프종이기술
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• 제35권2호
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• pp.33-38
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• 2003

In order to design the high strength corrugated fiberboard containers for agricultural products that can be used for the cold chain system, a large number of individual boxes were placed in various humidity environments at two different temperature of 5 and $20^{\circ}C$. The results indicated that temperature changes do not effect on physical strength of corrugated fiberboard containers as much as humidity changes did. The main conclusion from this study was that compression strength of corrugated fiberboard containers dropped significantly at high humidity condition, but the rates varied depending on the number of walls, temperature, and perimeter of containers. The packaging designer must consider the corrugated fiberboard boxes are also greatly affected by dimensional variations such as the length versus width ratio. Based on this study, water-resistant board would not be necessary if the ambient relative humidity does not reach to a critical point, 85 percent in the cold chain system. However, the designer must count for the unexpected fluctuation of rotative humidity resulting in severe loss of the compression strength of corrugated fiberboard container.

• 천문학회보
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• 제36권2호
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• pp.110.1-110.1
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• 2011

오리온 A 분자운은 별탄생이 활발하게 일어나는 영역이다. 때문에 분자운 연구를 통해서 별탄생을 연구하기에는 최적의 곳이다. 특기할 것은 Orion A에는 필라멘트 구조가 있다는 점이다. 필라멘트는 전형적으로는 길이 4.8pc, 너비 1.4 pc 로 제시되었다(Nagahama et al. 1998). 많은 미지의 조건들 가운데 필라멘트 구조는 별탄생에 대한 새로운 조명을 던져주는 데, 가령 분자운이 수축, 분열하며 작은 덩어리를 만드는 과정에 이런 기다란 구조가 별탄생에 어떤 과정에서 나타나며 이것이 별탄생이 어떤 효과를 발생하는지 연구되어야 하는 문제들이다. 대덕전파안테나의 1분의 분해능(Channel resolution 63 KHz/ Band Width 25 MHz) 의 12CO, 13CO(J=1-0) 분자선 관측으로 필라멘트를 이전 연구보다 자세하게 관측하여 이것 안에 있을 것으로 보이는 substructure들 연구하고자 한다. 관측영역은 적경: 5h 32m ~ 5h 37m, 적위: $-5^{\circ}$ 14' ~ $-5^{\circ}$ 37'으로 ($1^{\circ}{\times}1^{\circ}$) 영역을 관측하였다. 그 결과 필라멘트구조를 확인할 수 있었으며 약 0.7pc,약 $1000\;M_{\odot}$의 덩어리들이 이전관측에서 보여진 X자형태가 아니라 일자형태로 분포되어있는 것을 알 수 있었다. 관측된 최소덩어리는 star cluster mass이고 stellar size 의 덩어리는 별탄생 과정 이후 소멸된 것으로 보인다. 관측으로 확인된 덩어리들의 물리적인 성질과 분포를 깊이 연구해 보고자 한다. 향후 Orion A 전체를 추가로 관측하고자 한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
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• pp.446-448
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• 2000

Organic semiconductors based on vacuum-deposited films of fused-ring polycyclic aromatic hydrocarbon have great potential to be utilized as an active layer for electronic and optoelectronic devices. In this study, pentacene thin films and electrode materials were deposited by Organic Molecular Beam Deposition (OMBD) and vacuum evaporation respectively. For the gate dielectric layer, OPTMER PC403 photo acryl (JSR Coporation.) was spin-coated and cured at $220^{\circ}C$. Electrical characteristics of the devices were investigated, where the channel length and width was $50{\mu}m$ and 5 mm. It was found that field effect mobility was $0.039\;cm^2V^{-1}s^{-1}$, threshold voltage was -7 V, and on/off current ratio was $10^6$.

• 대한조선학회논문집
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• 제29권1호
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• pp.55-60
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• 1992

본 논문에서는 선형포턴셜이론을 이용하여 제한수로에 놓인 2차원 주상체에 작용하는 동유체력과 운동응답의 특성을 고찰하였다. 유체영역을, 수로입구영역 그리고 수로영역으로 구분하여 우선 각 영역에서 해를 독립적으로 구한 다음 이를 인접영역의 해와 정합시켜 완전해를 구하였다. 수로의 길이보다 대략 4배가 긴 파장의 입사파는 수로내 유동을 공진시킨다. 이때 주상체에 작용하는 부가질량은 음의 값을 갖게 되며 동유체감쇠력은 급격한 변화를 보이고 주상체의 수평운동은 최대가 됨을 밝혔다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.359-364
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• 2005

In dehumidification evaporation cooling system. the regeneratie evaporative cooler(REC) makes an important role to reduce the sensible cooling load in the system through evaporative cooling, By this reason, many studies about increasing the cooling capacity of the REC were undertook. In this paper, we analyzed the cooling characteristics of the REC due to the structures of the REC and determined the best structure for the REC's effectiveness and cooling capacity. From the study. we could obtain some important results: at first. corrugated type has the benefit to expand the channel width of the REC, But because the type has some weak points about the size and weight. there is almost no benefit to improve the performance of the REC. Through these reasons. we decided that finned type is the best structure to improve the performance of the REC.

• Archives of Pharmacal Research
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• 제28권3호
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• pp.319-324
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• 2005

The present study was designed to study the difference effects between nicardipine and its two enantiomers on thoracic artery of rabbit. A high-performance liquid chromatographic method was used to prepare the two enantiomers of nicardipine. The thoracic artery of rabbit was removed. The vessels were cut into 3 mm in width and 15 mm in length spiral strips and immersed into tissue baths. The concentration-response curves of nicardipine and its enantiomers were obtained by cumulative administration of the vasoconstrictors. Nicardipine and the enantiomers could shift the dose-response curves of NE, KCI or CaCl$_2$ to right in a nonparallel manner and decrease the maximum effective in a concentration-depended manner, respectively. The pD$_2$' value of R-(-)-nicardipine showed significantly effective than that of nicardipine and S-(+)-nicardipine (P<0.01). There was not obviouse difference between the pD$_2$' value of nicardipine and S-(+)-nicardipine (P>0.05). The results demonstrate that the stereoselective interaction between R-(-)-nicardipine and L-calcium channel receptor is more stronger than that of S-(+)-nicardipine.