• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.63.3-64
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• 2020

수소 라이먼 알파선은 관측이 어려운 외부은하의 성간 물질이나 성운 주위의 물질의 운동학적, 기하학적 상태를 알려주는 지표이다. 특히 라이먼 알파 방출 스펙트럼의 두 최고점에서 측정한 선속도 차이는 물질의 수축, 팽창 여부에 영향을 받기 때문에 은하의 역학적 특성을 연구하는 데에 있어 새로운 도구로서 각광받고 있다. 관측에서 얻어지는 은하들의 선속도 차이는 100km/s에서 800km/s까지 넓은 영역에서 존재한다. 선행 분자구름 규모의 연구에서 얻어진 선속도 차이는 상대적으로 작은 선속도 차이(148.54km/s)를 가진다. 그래서 이 연구에서는 더 큰 규모인 은하에서 라이먼 알파 선속도 차이를 확인하고 은하내 물리량의 영향을 알아보았다. 이 연구에서는 복사유체역학 시뮬레이션 코드 RAMSES-RT를 활용한, 각각 다른 물리량을 가진 은하 시뮬레이션 결과를 활용하였다. 은하 내 가스의 비율, 금속함량비를 다르게 하였으며, 각 시뮬레이션들은 몬테- 카를로 공진선 복사전달 코드 RASCAS를 이용하여 라이먼 알파선의 복사 과정을 계산하였다. 첫 번째로 기준 은하 시뮬레이션과 분자구름 시뮬레이션(Kimm+19)의 결과를 비교한 결과 148.54km/s에서 221.76km/s로 선속도 차이의 평균 값이 상승한 것을 확인하였다. 이는 성간 물질의 존재 유무의 차이로 인한 것이다. 은하 내 가스의 금속함량비를 증가시킨 경우, 은하 내 먼지량과 젊은 별들이 별 생성 구름에 머무는 시간이 증가하기 때문에 기준 은하와 비교하여 선속도 차이가 작아졌다.(206.9km/s) 반면 은하의 가스량을 증가시켯을 때는 산란 횟수 증가로 인한 상대적으로 큰 선속도 차이(298.51km/s)를 확인할 수 있었다. 또한 기준은하에 대해, 난류의 효과를 포함하여 선속도 차이를 비교한 결과, 선속도 차이는 (308.8km/s)상승하였다. 이를 통해 성간 물질의 물리량 차이만으로는 400km/s 이상의 큰 선속도 차이를 만드는 것은 어렵다. 관측에서 보이는 400km/s 이상의 몇몇 큰 선속도 차이의 은하를 위해서는 이 시뮬레이션에 포함되지 않은 성운 주위의 물질과 같은 부분이나, 은하 합병과 같은 극한의 상황이 필요할 것이다.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.25-31
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• 1989

Two-dimensional large-amplitude motions in regular harmonic wave are treated in time domain, by satisfying the exact body boundary condition and the linear free surface condition. For the present numerical calculation, the method of free-surface spectral representation with simple source distribution on the instantaneous body surface has been extended to include the effect of the incident wave. Calculations of the wave exciting force are performed for a submerged circular cylinder fixed or oscillating with large amplitude. Especially, nonlinear effects on the time-mean forces are studied in detail. It is shown that relative motion between the body and the fluid particle gives a significant effect on the lift and drift forces. Also, large-amplitude motion of a submerged circular cylinder and that of a floating Lewis-form cylinder are directly simulated in time domain. In the calculation results, some nonlinear effects are shown.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.418-424
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• 2014

In this paper, we propose a boundary input method for video surveillance systems. Since intrusion of a moving object is decided by comparition of its position and the surveillance boundary, the boundary input method is a basic function in video surveillance. Previous methods are difficult to adapt to the change of surveillance environments such as the size of surveillance area, the number of cameras, and the position of cameras because those build up the surveillance boundary using the captured image in the center of each camera. In our approach, the whole surveillance boundary is once defined in the form of polygon based on the satellite map and transformed into each camera environment. Its characteristics is that the boundary input is independent from the surveillance environment. Given the position of a moving object, the time complexity of its intrusion detection shows O(n), where n is the number of polygon vertices. To verify our method, we implemented a 3D simulation and assured that the input boundary can be reused in each camera without any redefinition.

• Journal of the Korea Society of Computer and Information
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• v.3 no.2
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• pp.77-84
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• 1998

The continuous time signal system by development of CMOS technology have been receiving consideration attention. In this paper, Low pass filter using CMOS floating resistor have been designed with cut off frequency for speech signal processing. Especially a new floating resistor consisting entirely of CMOS devices in saturation has been developed. Linearity within $\pm$0.04% is achieved through nonlineartiy via current mirrors over an applied range of $\pm$1V. The frequency response exceeds 10MHz, and the resistors are expected to be useful in implementing integrated circuit active RC filters. The low pass filter designed using this method has simpler structure than switched capacitor filter. So reduce the chip area. The characteristics of the designed low pass filter using this method are simulated by pspice program.

• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.82-86
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• 2001

In this Paper, we Propose synthetic aperture technique for twin-line may. Sin91e-line way is required long aperture size in order to achieve high SNR and angular resolution in shallow water Ultra low frequency signal from far-field has left-right ambiguity at sing1e-line array. To resolve these Problems, we'd like to adopt the synthetic aperture technique to twin-line array. The synthetic aperture method adopts coherent processing of sub-aperture signals at successive tine intervals in the beam domain. The proposed method shows low nile error and improved angular resolution. In simulation result, average sidelobe level is reduced about 7〔dB〕when the array Peformed 5-synthesis.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.1
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• pp.32-39
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• 1998

A numerical analysis for large amplitude motions of submerged circular cylinder is presented. The method is based on potential theory and two-dimensional motions in regular harmonic waves are tented as an initial value problem. The fully nonlinear free surface boundary condition is assumed in an inner domain and this solution is matched along an assumed an assumed common boundary to a linear solution in outer domain. Calculations of the large amplitude motion of a submerged circular cylinder are directly simulated in time domain. It is shown that relative motion between the body and fluid particle gives a significant effect on the lift and drift motions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.2
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• pp.184-191
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• 1993

Continuous-time integrated filters, implemented in MOS VLSI technology, have been receiving considerable attention. In this paper, a continuous-time fifth order elliptic low-pass MOSFET-C filter has been designed with a cutoff frequency 3,400Hz. First an active RC filter is designed using cascade method which each block can be tunable. And then the resistors of an active RC network are replaced by a linear resistor using NMOS depletion transistors operated in the triode region. This continuous-time MOSFET filter have simpler structure than switched-capacitor filter, so reduce the chip area. The designed MOSFET-C filter characteristics are simulated by PSPICE program.

• Journal of the Korea Computer Industry Society
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• v.5 no.5
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• pp.721-728
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• 2004

OCSP (Online Certificate Status Protocol) server which checks the certificate status provides the real time status verification in the PKI (Public Key Infrastructure) system which is the essential system of certificate. However, OCSP server need the message authentication with the server and client, so it has some shortcomings that has slow response time for the demands of many clients concurrently and has complexity of the mathematical process in the public encryption system. In this research, simulation model of the certificate status vertification server is constructed of the DEVS (Discrete EVent system Specification) formalism. This sever model is constructed to practice the authentication with hash function when certificate is checked. Simulation results shows the results of increase of the certificate status verification speed and decrease of the response time to the client.

• Child Health Nursing Research
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• v.19 no.1
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• pp.1-11
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• 2013

Purpose: This study was done to develop a scenario and evaluate student performance in simulation learning of care for children with respiratory distress syndrome in neonatal intensive care units. Methods: To test the application effect, a one group pre-test design was applied. The scenario based on actual patients and textbook material was developed through several meetings of experts. The scenario was used with 17 groups of 55 senior nursing students who participated voluntarily. Results: Contents were organized focusing on the nursing process for simulation learning. In the application of knowledge and skills, nursing students had high scores in the contents of observation of oxygen saturation, and care to relieve dyspnea. Participants' ability, especially in suction and oxygen supply in the evaluation of objective structured clinical examination was not adequate. There was a significant positive correlation between problem-solving ability and satisfaction in learning. Conclusion: The respiratory distress syndrome simulation scenario developed in this study was an effective tool to give students experience in problem solving and critical thinking ability under conditions similar to reality. The development of various scenarios for child nursing care is needed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.3
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• pp.213-224
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• 1992

An encoding technique based on region splitting and vector quantization is proposed for the lower level Laplacian pyramid images. The lower level Laplacian pyramid images have lower variance than higher levels but a great influence on compression ration due to large spatial area. And so from data compression viewpoint, we subdivide them with variance thresholding into two regions such as one called : flat region” and the other “edge region”, and encode the flat region with its mean value and the edge region as vector quantization method. The edge region can be reproduced faithfully and significant improvement on compression ratio can be accomplished with a little degradation of PSNR in spite of the effect of large flat region since the codebook used is generated from the edge region only on from the entire image including the flat region. It can be verified by computer simulation results that proposed method is more efficient in compression ratio and processing time than the conventional encoding technique of vector quantization.