• Structural Engineering and Mechanics
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• 제28권4호
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• pp.373-386
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• 2008

In this study stochastic analysis of non-linear dynamical systems under ${\alpha}$-stable, multiplicative white noise has been conducted. The analysis has dealt with a special class of ${\alpha}$-stable stochastic processes namely sub-Gaussian white noises. In this setting the governing equation either of the probability density function or of the characteristic function of the dynamical response may be obtained considering the dynamical system forced by a Gaussian white noise with an uncertain factor with ${\alpha}/2$- stable distribution. This consideration yields the probability density function or the characteristic function of the response by means of a simple integral involving the probability density function of the system under Gaussian white noise and the probability density function of the ${\alpha}/2$-stable random parameter. Some numerical applications have been reported assessing the reliability of the proposed formulation. Moreover a proper way to perform digital simulation of the sub-Gaussian ${\alpha}$-stable random process preventing dynamical systems from numerical overflows has been reported and discussed in detail.

• 대한전기학회논문지
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• 제36권9호
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• pp.660-669
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• 1987

Routh approximation method is the most computationally attractive. But this method may cause time-response error because this method does not match the time-response directly. In this paper a new mixed method for obtaining stable reduced-order models for high-order continuous-time systems is proposed. It makes use of the advantages of the Routh approximation method and the Minimization of Integral Squared Error(MISE) criterion approach. In this mixed method the characteristic polynomial of the reduced-order model is first obtained from that of original system by using the Auxiliary Denominator Polynomial(ADP). The numerator polynomial is then determined so as to minimize the intergral squared-error of unit step responses. The advantages of the propsed method are that the reduced models are always stable if the original system are stable and the frequency domain and time domain characteristic of the original system will be preserved in the reduced models.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제17권2호
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• pp.129-138
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• 2013

A spatio-temporal models as systems of ODE which describe two-species Beddington - DeAngelis type predator-prey system living in a habitat of two identical patches linked by migration is investigated. It is assumed in the model that the per capita migration rate of each species is influenced not only by its own but also by the other one's density, i.e. there is cross diffusion present. We show that a standard (self-diffusion) system may be either stable or unstable, a cross-diffusion response can stabilize an unstable standard system and destabilize a stable standard system. For the diffusively stable model, numerical studies show that at a critical value of the bifurcation parameter the system undergoes a Turing bifurcation and the cross migration response is an important factor that should not be ignored when pattern emerges.

• 한국산학기술학회논문지
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• 제3권4호
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• pp.280-284
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• 2002

본 논문에서는 임의형상제작시스템을 위한 적층 및 이송장치의 컴퓨터 시뮬레이션을 보여주고 있다. 적층 및 이송 장치는 임의형상제작시스템의 필수적인 요소로서 절단된 슬라이스의 일관된 적층을 위해 안정된 작동을 하는 것이 매우 중요하다. 적층 및 이송장치는 공압장치로 모델링될 수 있다. 공압장치는 공압컴푸레서, 제어밸브 및 실린더 둥으로 구성되어있다. 설계변수를 변화시켜가면서 행한 시뮬레이션 결과로부터 시간응답을 예측할 수 있다. 결과에서 알 수 있는 것은 일부 설계변수를 변화시키면 안정된 동특성을 얻을 수 있다는 것이다.

• The Journal of the Acoustical Society of Korea
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• 제21권2E호
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• pp.56-62
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• 2002

This paper describes a new method of stability evaluation for an estimated impulse response of a plant. It is difficult for the conventional stability evaluation equation to be used in an adaptive feedforward control system which uses an immeasurable acoustic transfer system of a real plant, because the equation requires an exact true impulse response of the plant. Therefore, the usefulness of the conventional equation is limited in a computer simulation. The proposed method is applicable to not only a computer simulation but also a real feedforward adaptive control system. It is found that the system is stable when the value of misadjustment is below -10 dB through computer simulations and experiments. And also, it is proved that the error signal is stable through the verification using filtered reference and filtered error LMS methods.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.277-283
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• 2003

It is well known that the natural frequencies of the pipe come to be lower as internal fluid velocity and pressure increase, and the pipe will be unstable if the fluid velocity is higher than critical velocity. But even if the velocity of the fluid below the critical velocity, resonance will be caused by pulsation of the fluid. So it should be also taken into consideration that the effect of pulsating fluid in pipe design. The research of the piping system vibration due to a fluid pulsation has been studied by many people. But almost is dealt with determining the boundary between stable and unstable region without analyzing forced response in the stable region. In this study, not only stability analysis but also forced response analysis, which is caused by harmonically excited fluid especially, is conducted.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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• pp.457-459
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• 2005

Low viscosity LCs have been developed for fast response time improvement of the TFT-LCD Monitors based on TN mode. This low viscosity characteristic s cause the pretilt angle to be changed and the uniformity to degrade. We have studied on the pretilt angle effect by the various components used for low viscosity LCs. We prepared the panels by using these various components and measured pretilt angle for this research. As a result of this research, we have found out that each low viscosity component has the different pretilt angle level and uniformity. For good display quality, it is important to keep the stable pretilt angle. The low viscosity LCs with this stable pretilt angle make it possible to prepare the high performance TFT-LCD Monitor with both fast response time characteristics and good display quality

• 한국군사과학기술학회지
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• 제8권1호
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• pp.81-91
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• 2005

It is well known that the natural frequencies of the pipe come to be lower as internal fluid velocity and pressure increase, and the pipe will be unstable if the fluid velocity is higher than critical velocity. But even if the velocity of the fluid below the critical velocity, resonance will be caused by pulsation of the fluid. So the effects of pulsating fluid in pipe should be also taken into consideration for better analysis. The research of the vibration of piping system due to a fluid pulsation has been studied by many people. But most of them are dealt with determining the boundary between stable and unstable region without analyzing forced response in the stable region. In this study, not only stability analysis but also forced response analysis, which is caused by harmonically excited fluid especially, is conducted. In order to analyze the system numerically, the descretized equation is formulated by using FEM(Finite Element Method). And the results of this method are compared with those of AMM(Assumed Mode Method) which were used by many researcher earlier.

• 대한약침학회지
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• 제11권2호
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• pp.13-19
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• 2008

Objectives To investigate the therapeutic effects of intravenous cultivated wild ginseng(Panax ginseng C.A. Meyer) pharmacopuncture(CWGP) in treating patients with non-small cell lung cancer(NSCLC). Design Prospective case series. Setting This study was conducted at the East-West Cancer Center of Dunsan Oriental Hospital, Daejeon University. Patients Two non-small cell lung cancer patients. Intervention Two non-small cell lung cancer patients were injected CWGP(20mL/day) mixed with 0.9% normal saline(100mL) intravenously. Each patient received a total of 16 and 9 cycles, respectively. One cycle is composed of 14 days. Outcome Measures The effect of intravenous CWGP was measured by scanning with computed tomography(CT) after every 2 cycle and Positron emission tomography- computed tomography(PET/CT) after every 6 cycles. Response and progression was evaluated using the Response Evaluation Criteria in Solid Tumors(RECIST) Committee classification of complete response(CR), partial response(PR), progressive disease(PD) and stable disease(SD). Results They were treated with intravenous CWGP for 8 and 5 months respectively. time later, each tumor remains stable disease(SD). Conclusion These cases may give us a possibility that intravenous CWGP offers potential benefits for non-small cell lung cancer patients.

• 상하수도학회지
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• 제33권4호
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• pp.269-279
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• 2019

This study would present a risk analysis method to evaluate stable tap water supply in a multi-regional water supply system and propose a measure for the evaluation of the effect of the conjunctive operation of the multi-regional water supply system using this. Judging from the vulnerability for the crisis response of the entire N. multi-regional water supply system, as compared to the result of Scenario 1 in which no conjunctive pipes were operated, it was found that in Scenario 2, in which conjunctive pipes were partially operated, the vulnerability of crisis response decreased by about 30.6%, and as compared to Scenario 3, the vulnerability of crisis response decreased by 86.2%. In setting a plan for stable tap water supply in N multi-regional water supply system, using the estimated value and the method for the evaluation of the vulnerability of crisis response by pipe, by interval and by line, it is judged that this can be utilized as a basis for the judgment of the evaluation of the operation or the additional installation of conjunctive pipes.