• Journal of Broadcast Engineering
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• v.18 no.3
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• pp.455-462
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• 2013

This paper introduces the Spatially Preprocessed Speech Distortion Weighted Multi-channel Wiener Filter (SP-SDW-MWF) for multi-microphone noise reduction and proposes a method to determine the speech distortion weights. The SP-SDW-MWF is known as a robust noise reduction algorithm against the error caused by the mismatch in microphones. The SP-SDW-MWF adopts weights which determine the amount of noise reduction at the expense of introducing speech distortion in the noise-suppressed speech. In this paper, we use the error of power spectral density between the estimated signal and the desired signal as the evaluation measure. Thus the a priori SNR is used to control the speech distortion weights in the frequency domain. In the experimental results, the proposed method yields better result in terms of MFCC distortion compared to the conventional method.

• The Journal of Korean Society for Radiation Therapy
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• v.32
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• pp.73-83
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• 2020

Purpose: The purpose of this study is to confirm the matching of the electron density between tissue and gas due to variation of abdominal gas volume in MRgART (Magnetic Resonance-guided Adaptive Radiation Therapy) for pancreatic cancer patients, and to confirm the effect on the dose change and treatment time. Materials and Methods: We compared the PTV and OAR doses of the initial plan and the AGC(Abdominal gas correction) plans to one pancreatic cancer patient who treated with MRgART using the ViewRay MRIdian System (Viewray, USA) at this clinic. In the 4fx AGC plans, Beam ON(%) according to the patient's motion error was checked to confirm the effect of abdominal gas volume on treatment time. Results: Comparing the Initial plan with the average value of AGC plan, the dose difference was -7 to 0.1% in OAR and decreased by 0.16% on average, and in PTV, the dose decreased by 4.5% to 5.5% and decreased by 5.1% on average. In Adaptive treatment, as the abdominal gas volume increased, the Beam ON(%) decreased. Conclusion: Abdominal gas volume variation causes dose change due to inaccurate electron density matching between tissue and gas. In addition, if the abdominal gas volume increases, the Beam ON(%) decreases, and the treatment time may increase due to the motion error of the patient. Therefore, in MRgART, it is necessary to check the electron density matching and minimize the variability of the abdominal gas.

• Journal of computational fluids engineering
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• v.1 no.1
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• pp.142-149
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• 1996

이차원 노즐을 통하여 저밀도 환경으로 팽창하는 희박류의 분석에 있어서 불연속좌표법과 결합된 유한차분법(finite-difference method coupled with the discrete-ordinate method, FDDO)과 직접모사법(direct-simulation Monte-Carlo method, DSMC)이 비교되었다. FDDO를 이용한 분석에서는 충돌적분모델을 도입하여 간단해진 볼츠만식(Boltzmann equation)이 불연속좌표법을 이용하여 물리적 공간에서는 연속이나 분자속도 공간에서는 불연속좌표로 표시되는 편미분방정식군으로 변환되어 유한차분법에의하여 수치해석 되었다. 직접모사법에서는 분자모델로 가변강구모델(variable hard sphere model, VHS)이, 충돌샘플링모델로는 비시계수법(no time counter method, NTC)이 채택되었다. 전혀 다른 두 가지 방법에 의한 노즐 내부에서의 유체흐름 해석결과는 매우 잘 일치하였으며, 노즐 외부의 plume 영역에서는 FDDO에 의한 해석결과가 직접모사법에 의한 해석결과에 비하여 약간 느린 팽창을 보였다.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.1
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• pp.23-29
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• 2001

Cylindrical type of self-controlled restrictor are designed for hydrostatic bearing of grinding wheel spindle. Typical hydrostatic journal bearing with the designed restrictor is analytically model. According to the model, the affect of oper-ation parameters, such as, initial cross distance, supply pressure, diameter of two supply holes, pre-load of spring, and clearance between spindle and housing, on bearing stiffness are analyzed. From the results of the analysis, the optimum conditions of operation parameters that maximize the bearing stiffness are estimated.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.425-431
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• 1999

Nowadays development of electric and optical devices needs precision more and more. This study focuses on hydrostatic journal bearing of grinding wheel spindle. It presents theoretical analysis about cylinder type self-controlled restrictor to control flux of oil flowing into pockets around the hydrostatic journal bearing. As a result of this analysis, optimal properties to maximize bearing stiffness such as initial cross distance, supply pressure, diameter of two supply holes, pre-load of spring and clearance between spindle and housing can be obtained. Therefore, by using them it is possible to estimate bearing stiffness and the performance of grinding wheel spindle can be improved.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.423-425
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• 1998

In this paper, a novel Programmable Signal Conditioner(PSC) for Thermo Couple(T/C) without variable-resistance is proposed. It is fabricated by using a fully digitalized error-correction and calibration algorithm. In signal processing of T/C, since the output voltage of T/C is nonlinear and its level is very low, the circuitry become very complicated to reduce the converting error and identify the true thermal voltage signal. The newly proposed PSC has compensation and calibration algorithm not using variable resistor. Moreover structure can be very simple and it has highly precise output characteristics.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.1
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• pp.117-124
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• 2012

In this paper, we propose a simple H parity check matrix from the CPM(circulant permutation matrix), which can easily avoid the cycle-4, and approach to flexible code rates and lengths. As a result, the operations of the submatrices will become the multiplications between several CPMs, the calculations of the LDPC(low density parity check) encoding could be simplest. Also we consider the fast encoding problem for LDPC codes. The proposed constructions could lead to fast encoding based on the simplest matrices operations for both regular and irregular LDPC codes.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2224-2226
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• 2003

서보시스템은 공작 기계, 자동화기계용 등의 제어에 사용되고 있는 대표적인 제어 시스템으로서 관성 디스크를 교환하기도 하며 전자가변 포화도와 히스테리시스등을 사용하여 고정밀 연구용에도 이용가능하다. 그러나 모델의 불확실성이나 외부외란이 필연적으로 존재할 수 밖에 없으므로 이를 분석하고 규명하여 원하는 목적의 제어를 위한 제어기를 설계해야만 할 것이다. 따라서, 본 연구에서는 제어대상 시스템의 불화실성을 극복할 수 있고 비선형항의 소거를 통한 선형화가 아닌 비선형 제어기의 설계를 가능하게 하는 Backstepping 제어기법을 사용하여 서보시스템의 정밀한 제어와 시스템 안정성을 보장하고자 한다. Backstepping 제어기를 설계하여 다양한 조건하에서의 시뮬레이션을 수행하여 제안하는 제어기의 최적 수행 능력을 보이고자 한다.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.73-80
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• 1993

There and two important variables in machining process control, which are feed and cutting speed. It is possible to improve the machining accuracy and the productivity by maintaining the optimal feed and cutting speed. In this work, a controller is designed to achieve on-line cutting force control based on the modeling of cutting process dynamics established through step response test. Two schemes are proposed and implemented. The first is feed control under the constant spindle speed and the second is spindle speed control under the constant feed. Finally, both are proved to work properly through simulation and experimentation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.58-61
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• 1995

Instead of using CCl$_4$CCl$_2$F$_2$ gases, we used a alternative reaction gas of CFCs which we have developed, for the experiment of laser induced dry etching of laser induced dry etching of GaAs, and compared with the etch profile of a usual reation gas. Laser powers(power density) on the sample surface were varied from 100 mW(12.7 MW/$\textrm{cm}^2$) to 210mW(27 MW/$\textrm{cm}^2$) The laser beam was scanned over the sample by moving the cell with a speed raging from 8.3$\mu\textrm{m}$/sec and the gas pressure also was varied form 260 Torr to 760 Torr, High etching rates up to 136 $\mu\textrm{m}$/sec and an aspect ratio of 2.6 have been achieved by single scan of laser beam. The chemical compositions of the reaction products deposited on the etched groove were measured by Auger electron spectroscopy(AES) Etch profiles, including depth and width were observed by scanning electron microscopy(SEM)