• 한국전산유체공학회지
• /
• 제4권3호
• /
• pp.63-70
• /
• 1999

A Direct simulation Monte-Carlo (DSMC) code is developed, which employs the Monte-Carlo statistical sampling technique to investigate hypersonic rarefied gas flows accompanying chemical reactions. The DSMC method is a numerical simulation technique for analyzing the Boltzmann equation by modeling a real gas flow using a representative set of molecules. Due to the limitations in computational requirements. the present method is applied to a flow around a simple two-dimensional object in exit velocity of 7.6 km/sec at an altitude of 90 km. For the calculation of chemical reactions an air model with five species (O₂, N₂, O, N, NO) and 19 chemical reactions is employed. The simulated result showed various rarefaction effects in the hypersonic flow with chemical reactions.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1994년도 하계학술대회 논문집 A
• /
• pp.475-478
• /
• 1994

In this paper two methods of torque control for brushless DC motor with non-ideal trapezoidal back EMF are presented. One is the method of modulating the reference current so as to give a constant torque since the torque is given by the back EMF and the. phase currents. And the current control loop includes the feedforward control of back EMF and of the neutral voltage between the neutral points of the inverter and of the machine. The other is a direct voltage calculation algorithm for a given reference torque. In the two methods, the time delay due to the calculation is compensated by one sampling current prediction. The simulation results are presented to verify the proposed methods.

• 전기학회논문지
• /
• 제56권4호
• /
• pp.795-798
• /
• 2007

In this paper, we propose an image reconstruction method utilizing an optimized adaptive interpolation kernel along with a 2D M-channel perfect reconstruction filter bank (M-ch PR-FB) structure. In particular, the proposed approach leads to construction of a sharper image than a direct conversion, still preserving high frequency components of the original image through the subband processing of the 2D M-ch PR-FB. Finally, the image quality of the proposed approach is demonstrated by comparing with those of the direct methods using conventional interpolation kernels.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
• /
• pp.82-87
• /
• 2000

The direct simulation Monte Carlo (DSMC) method is applied to investigate the flow field of a disk-type drag pump. The pumping channels are cut on both sides of a rotating disk. The rotor has 10 Archimedes' spiral blades. In the present DSMC method, the variable hard sphere model is used as a molecular model, and the no time counter method is employed as a collision sampling technique. For simulation of diatomic gas flows, the Larsen-Borgnakke phenomenological model is adopted to redistribute the translational and internal energies.

• 한국전자파학회논문지
• /
• 제22권7호
• /
• pp.669-674
• /
• 2011

본 논문에서는 디지털 고주파 기억 장치(DRFM: Digital RF Memory)의 스퓨리어스 신호 저감 방법에 대하여 제안하였다. 스퓨리어스 특성은 디지털 고주파 기억 장치의 성능을 결정짓는 주요 요소이다. 제안한 방법은 입력되는 IF 신호에 랜덤 위상값을 가지는 LO 신호를 혼합하여 샘플링하여 스퓨리어스 신호를 저감하였으며, 랜덤 위상을 가지는 LO 신호는 직접 디지털 합성기(DDS: Direct Digital Synthesizer)의 고속 위상 제어 특성을 이용하여 생성하였다. 제안한 방법을 적용하여 5~10 dB의 스퓨리어스 특성이 향상됨을 확인하였다.

• 가족자원경영과 정책
• /
• 제3권2호
• /
• pp.33-50
• /
• 1999

The purpose of this study is to analyze the relationship of housewives’sense of ancestral service and behavior and to verify the how housewives’value orientation affects the sense of ancestral service and behavior. The data are collected from 393 housewives in urban. The statistics used for the analysis are Cronbach’$\alpha$, Frequency, Percentage, Mean, SD, and Multiple Regression Analysis. The results are summarized below: First, among the variables, degree of fate-control orientation is the most, on the contrary, material orientation is the lowest. Second, value orientation variables that affect sense and behavior of ancestral service are material orientation and gender equilibrium orientation. Third, the behavior of ancestral service is more traditional than sense of ancestral service. Fourth, cause-and-effect variable which affect behavior of ancestral service are education level, religion(Buddhism, Catholicism), employment status, number of children, health, daughter in -law’s ranking, sense of ancestral service, and value orientation, which affect the direct or direct and indirectly. Especially sense of ancestral service variable is the most important mediation one. We expect further studies on the sense of ancestral service and behavior with precise scale and sampling.

• 한국대기환경학회지
• /
• 제5권2호
• /
• pp.36-41
• /
• 1989

Concentrations of atmospheric asbestos at 5 sites in the central Seoul area, were determined by phase contrast microscopy. The observed numbers of asbestos per liter of air were: maximum 4.51, minimum 0.72 and average 2.20. The direct relationship between asbestos concentration at each sampling site and automobile traffics was not demonstrated. But the more there are automobile traffics, the higher asbestos concentratiof of total fibers is.

• 대한전기학회논문지
• /
• 제35권1호
• /
• pp.8-16
• /
• 1986

For digital process control, a low order discrete time modeling method is suggested and a direct digital control algorithm has been developed. The modeling method maintains process order of 3, while the sampling rate is doubled for fast response. With easy calculation it is possible to compute the model parameters and the controller gains. Controller tuning is possible on the spot. Simulation results show that this method has better performance than the deadbeat control agorithm.

• Toxicological Research
• /
• 제5권2호
• /
• pp.97-104
• /
• 1989

A new exposure system was developed to generate p-dinitrobenzene (p-DNB) containing atmosphere. A glass column was filled with small glass beads coated with the chemical. The p-DNB containing medium was heated to a temperature beyond the boiling point of p-DNB. A stream of air flow was forced to pass through the column and let it mixed with fresh air before introducing into an inhalation chamber. The concentration of p-DNB in the chamber air was measured by direct assaying the air directly and by sampling the chemical using a microfilter installed in the chamber.

• Bulletin of the Korean Chemical Society
• /
• 제19권7호
• /
• pp.766-770
• /
• 1998

On-line preconcentration by direct precipitation with hydroxide has been developed and applied for the analysis of Cd in Inductively Coupled Plasma Atomic Emission Spectrometry. Cadmium is continuously precipitated with hydroxide and dissolved by nitric acid in on-line mode. Currently, the enrichment factor is more than 90 times for 20.0 mL of sample and could be further increased very easily. For a large sample throughput, 1.0 mL of sample loop is used and the enrichment factor is 4.5 with the sampling speed of 15/hr. The method has been applied to the analysis of NIST reference sample and has yielded good results with the certified value.