• Journal of Korea Multimedia Society
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• v.7 no.11
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• pp.1515-1520
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• 2004

In this paper, a new continuous-time bandpass active filter for lour-voltage applications is proposed. The active filter is composed of the CMOS complementary cascode circuit which can increase trans-conductance of an active element. These results are verified through the 0.25$\mu\textrm{m}$ CMOS n-well parameter hspice simulation. As a result, the gain and the unity gain frequency is 42dB and 200MHz respectively in the integrator. Additionally, center frequency of the bandpass active filter is 747kHz. And also bandwidth of the filter is 649kHz on 2V supply voltage.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.235-235
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• 2011

진단용 또는 의료용 동위원소들은 안정한 표적물질에 높은 에너지의 양성자가 조사 될 때 핵반응에 의해서 생성된다. 양성자를 충분한 에너지로 가속하기 위해서 이용되는 사이클로트론의 주요 부분은 (1) 진공시스템, (2) 자석시스템, (3) RF 시스템, (4) 외부 이온원, (5) 수직 축 방향빔의 수평방향 전환 시스템, (6) 빔 인출 장치, 그리고 빔전송과 표적장치로 구성된다. 인출된 빔은 표적까지 손실 없이 전송 될 수 있도록 빔 라인에 설치된 광학적 요소에 의해 집속되어 전송된다. 방사성동위원소의 생산량은 양성자 빔의 특성과 표적 물질의 종류에 따라 결정된다. 즉, 표적 물질에 조사하는 입자의 종류, 적절한 핵반응 선택, 최소량의 불순핵종과 원하는 방사핵종의 최대수율을 얻을 수 있는 최적 에너지 범위결정, 표적 물질의 냉각능력과 입자전류의 세기 등을 고려 하여야 한다. 동위원소 생산에 있어서 예측되는 수율은 입자전류와 비례하며, 에너지에 대한 핵반응 단면적 즉, 여기함수를 적분하여 아래와 같이 얻을 수 있다. 주 생성핵종의 생산 효율을 최대로 높이고 불순 핵종의 생성량을 최소로 감소시키기 위해서는 정확한 여기 함수 자료를 바탕으로 최적 입자를 결정하여야 한다. 또한 이론적인 생산 수율은 입자 전류에 정비례하지만, 입자 전류가 클경우 생산수율은 이론적인 수율보다 적다. 입자빔의 불균일성, 표적의 방사선 피폭에 의한 손상, 높은 입자전류에 의해 발생하는 열로 인하여 생성 핵종이 증발하여 생산 수율이 감소된다. 본 발표에서 방사핵종 C-11과 Tc-99m을 개발하기 위한 최적 조건에 관한 연구결과를 보고하고자 한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.5
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• pp.640-647
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• 1998

Microstrip patch antennas are analyzed by a multiresolution wavelet method. The spectral Green's dyad of the structure is obtained and its joint spatial-spectral domain representations are presented. Based on the joint spatial-spectral domain representation, we show that the spectral-domain wavelets are useful in the analysis of this problem. We obtain the matrix equations of the integral equations of this Green's dyad by using the method of moment(MoM), and efficiently solve the problem using the spectral domain wavelet transform concepts in conjuction with the conjugate gradient method. The results for a single-layered square patch are compared with those of conventional MoM and CG-FFT.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.7
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• pp.1424-1428
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• 2004

In this paper, CMOS analog filters for use in the Analog front End of digital subscriber loop(DSL) chip set are proposed. Designed filters contain receiver continuous-time filters which are composed of lowpass and highpass functions. And their cutoff frequency are 138H1z and 1.1MHz respectively. A low-voltage gm-c integrator is improved and used to design filters. Desisned filters are verified by HSPICE simulation with the 0.25${\mu}m$ CMOS n-well parameter.

• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.256-261
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• 2013

Power conversion efficiency of the red and green phosphors was measured and analyzed. Two different samples of phosphors of thickness 50 ${\mu}m$ were prepared: one was the phosphor layer coated on the transparent substrate and the other was prepared on the reflective substrate. The 445 nm blue laser diode beam was used as the exciting beam. The conversion efficiencies of the red and green phosphor layers were 41.4% and 46%, respectively. The quantum efficiencies of the red and green phosphors were 60.4% and 53.5%, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.5
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• pp.989-998
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• 2012

A ratio type of capacitance measurement circuit is proposed to measure an extremely small value of the fF capacitance on this paper. This measurement circuit is formed with a switched-capacitor integrator, a comparator, and logic circuit blocks to control the switches. It converts the measured ratio value between the known value of on-chip capacitor and the unknown value of capacitor to the digital signal. The fF capacitance with minimized error can be obtained by calculating this ratio. This proposed circuit is designed with standard CMOS $0.18{\mu}m$ process, and various HSpice simulations prove that this capacitance measurement circuit is able to measure the capacitance under 5fF with less than ${\pm}0.3%$ error rate.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.3
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• pp.266-274
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• 1994

Two-dimensional numerical analysis is performed for the simulation of tidal characteristics related to various development projects in Incheon coastal waters along the west coast of Korea. Field observation of tides and currents was made in order to provide the input boundary and validation data set to the numerical modelling. For the simulation of changes of tides and currents a depth-integrated two-dimensional shallow water model of Flather and Heaps (1975) has been used herein. Tidal model is set up with open boundary sea level from observed two major constituents, M$_2$ and S$_2$. Subsequently the established model is utilized to investigate the effect of two development projects in this region. It has been found that in spring tide the changes of tidal amplitude are small, however, those of tidal current are locally significant.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.1
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• pp.34-42
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• 1990

The tides in the Saemanguem Area, the western coast of Korea have been examined based on simulations with barotropic depth-integrated model. As a first step tidal computations were performed with open-boundary sea level forcing from four major constitutents ($M_2$, $S_2$, $K_1$, and $O_1$). Subsequently the established model was utilized to investigate the effect of construction of tidal barriers for Saemanguem development plan on the existing tidal regime. It has been shown that tide of semi-diurnal constituents may be reduced to 2-7 cm in amplitude along the frontal area of proposed barrier. In connection with above changes the tidal current regime may be subjected to significant reduction in intensity. thus suggesting the high possibility of sedimentation along the frontal region of tidal barrier.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.132-141
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• 1998

Particle image velocimetry(PIV), a planar measuring technique, is an efficient tool for studying the complicated flow field such as in-cylinder flow, and intake port flow. PIV can be also used for analyzing the integral length scale of turbulence, which is a measure of the size of the large eddies that contain most of the turbulence kinetic energy. In this study, dual color scanning PIV was designed and demonstrated by using a rotating mirror and a beam splitter. This PIV system allowed enlargement of flexibility in the intensity of vectors to be calculated by spatial filtering technique, even in combustion chamber with high velocity gradient and high vorticity$({\sim}1000s^{-1})$. A new color image processing algorithm was developed, which was used to find the direction of particle movement directly from the digital image. These measuring techniques were successfully applied to obtaining the turbulence intensity (~0.1m/s) and the turbulent integral length scale of vorticity(~1mm).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.4
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• pp.685-695
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• 1997

In this paper, a new CMOS continuous-time fully-differential current-mode integrator is proposed as a basic building block of the low-voltage high frequency current-mode active filter. The proposed integrator is composed of the CMOS complementary circuit which can extend transconductance of an integrator. Therefore, the unity gain frequency which is determined by a small-signal transconductance and a MOSFET gate capacitance can be expanded by the complementary transconductance of the proposed integrator. And also the magnitude of pole and zero are increased. The unity gain frequency of the proposed integrator is increased about two times larger than that of the conventional continuous-time fully-differential integrator with NMOS-gm. These results are verified by the small signal analysis and the SPICE simulation. As an application circuit of the proposed fully-differential current-mode integrator, the three-pole Chebyshev lowpass filter is designed using 0.8.$\mu$m CMOS processing parameters. SPICE simulation predicts a 3-dB bandwidth of 148MHz and power dissipation of 4.3mW/pole for the three-pole filter with 3-V power supply.