http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : 김선철 (검색결과 265 건)
- 무료
- 기관 내 무료
- 유료
-
-
-
THE MOTION OF POINT VORTEX DIPOLE ON THE ELLIPSOID OF REVOLUTION
김선철 대한수학회 2010 대한수학회보 Vol.47 No.1
A pair of point vortices of the same strength but opposite sign is called a vortex dipole. We consider the limiting case where two vortices approach infinitely close while the ratio of the strength to the distance kept constant. The motion of such {\em point} vortex dipole on the ellipsoid of revolution is investigated geometrically to conclude that the trajectory draws a geodesic up to the leading order of perturbation, whose direction is determined by the initial orientation of the dipole. Related issues are also remarked.
-
Fractional-N PLL (Phase-Locked Loop) 주파수 합성기 설계
김선철,원희석,김영식,Kim Sun-Cheo,Won Hee-Seok,Kim Young-Sik 대한전자공학회 2005 전자공학회논문지TC (Telecommunications) Vol.42 No.7
This paper proposes a fractional-N phase-locked loop (PLL) frequency synthesizer using the 3rd order ${\Delta}{\sum}$ modulator for 900MHz medium speed wireless link. The LC voltage-controlled oscillator (VCO) is used for the good phase noise property. To reduce the lock-in time, a charge pump has been developed to control the pumping current according to the frequency steps and the reference frequency is increased up to 3MHz. A 36/37 fractional-N divider is used to increase the reference frequency of the phase frequency detector (PFD) and to reduce the minimum frequency step simultaneously. A 3rd order ${\Delta}{\sum}$ modulator has been developed to reduce the fractional spur VCO, Divider by 8 Prescaler, PFD and Charge pump have been developed with 0.25um CMOS, and the fractional-N divider and the third order ${\Delta}{\sum}$ modulator have been designed with the VHDL code, and they are implemented through the FPGA board of the Xilinx Spartan2E. The measured results show that the output power of the PLL is about -lldBm and the phase noise is -77.75dBc/Hz at 100kHz offset frequency. The minimum frequency step and the maximum lock-in time are 10kHz and around 800us for the maximum frequency change of 10MHz, respectively.
-
김선철,김영호,Kim, Sun-Chul,Kim, Youngh-Ho 한국마이크로전자및패키징학회 2012 마이크로전자 및 패키징학회지 Vol.19 No.1
Recently, flip chip interconnection has been increasingly used in microelectronic assemblies. The common Flip chip interconnection is formed by reflow of the solder bumps. Lead-Tin solders and Tin-based solders are most widely used for the solder bump materials. However, the flip chip interconnection using these solder materials cannot be applied to temperature-sensitive components since solder reflow is performed at relatively high temperature. Therefore the development of low temperature bonding technologies is required in these applications. A few bonding techniques at low temperature of $150^{\circ}C$ or below have been reported. They include the reflow soldering using low melting point solder bumps, the transient liquid phase bonding by inter-diffusion between two solders, and the bonding using low temperature curable adhesive. This paper reviews various low temperature bonding methods.
-
H.264/AVC 복호기를 위한 고성능 연산처리 인트라 예측기 설계
김선철,류광기,Jin, Xianzhe,Ryoo, Kwangki 한국정보통신학회 2012 한국정보통신학회논문지 Vol.16 No.11
This paper proposes a parallel operation intra predictor for H.264/AVC decoder. In previous intra predictor design, common operation units were designed for 17 prediction modes in order to compute more effectively. However, it was designed by analyzing the equation applied to one pixel. So, there are four operation units for computing 16 pixels in a $4{\times}4$ block and they need four cycles. In this paper, the proposed intra predictor contains T3(Three Type Transform) operation unit for parallel operation. It divides 17 modes into 3 types to calculate 16 pixels of a $4{\times}4$ block in only one cycle and needs 16 cycles minimum in 16x16 block. As the result of the experiment, in terms of processing cycle, the performance of proposed intra predictor is 58.95% higher than the previous one.
-
-
김선철,권미영,황연신,Kim Seoncheol,Kwon Mi-yeong,Hwang Yoen-Shin 대한음성학회 2004 말소리 Vol.50 No.-
The aim of this paper is to show what are the sociolinguistic variables of word-initial length loss in Seoul dialect. 350 people were inquired to pronounce 40 words. Among the informants, 152 were male, and 198 were female. In terms of their age, 49 were twenties, 70 were thirties, 69 were forties, 71 were fifties, and 91 were above sixties. According to our statistics, 18 words show sociolinguistic variation by age, and sex was not a variable. So we can conclude that Seoul dialect is undergoing length loss by age at least. But we need to enlarge the number of words and informants and we also need to adopt other variables like social level, education etc for better understanding of Seoul dialect.
-
Vortex Motion on Riemann Surfaces
김선철 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.1
Vortex motion of an incompressible inviscid flow on a infinitely thin curved shell specified as a Riemann surface is studied. The intrinsic dynamical equations are derived and compared on two conformally equivalent Riemann surfaces. In particular, the relations for the streamfunction, velocity, and vorticity are found by using explicit computations. Then, the result is applied to the problem of motion of point vortex dipoles on Riemann surfaces whose trajectories in time turn out to be a geodesic. Also, the case of more complicated surfaces with a boundary, is discussed with an example.
-
김선철,최윤수,한충규,조경호,김형원,Kim, Sun-Cheol,Choi, Yoon-Soo,Han, Chung-Kyu,Cho, Kyung-Ho,Kim, Hyoung-Won 한국군사과학기술학회 2011 한국군사과학기술학회지 Vol.14 No.6
A high power laser beam focused on a small area accelerates a thin material that flies and hits other target material in which a shock wave may be induced. This laser induced shock experimental method is more repeatable and cheaper but worse than other experimental method using gas gun or other apparatus. An optical system including a phase zone plate reduces the interference and also makes the focused-beam-intensity distribution uniform. We wrote a computer code that calculates light ray traces. Using the code we designed and fabricated an optical system including a phase zone plate and improved the laser-beam uniformity. We introduce preliminary experimental results of laser induced shock of the samples such as aluminum and other materials.
ScienceON연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
