• Structural Engineering and Mechanics
• /
• 제16권6호
• /
• pp.731-748
• /
• 2003

In this paper a thick cylindrical shell with varying thickness which is subjected to static non-uniform internal pressure is analyzed. At first, equilibrium equations of the shell have been derived by the energy principle and by considering the first order theory of Mirsky-Herrmann which includes transverse shear deformation. Then the governing equations which are, a system of differential equations with varying coefficients have been solved analytically with the boundary layer technique of the perturbation theory. In spite of complexity of modeling the conditions near the boundaries, the method of this paper is very capable of providing a closed form solution even near the boundaries. Displacement predictions are in a good agreement with the calculated finite elements and other analytical results. The convergence of solution is very fast and the amount of calculations is less than the Frobenius method.

• Journal of the Korean Data and Information Science Society
• /
• 제28권5호
• /
• pp.1167-1177
• /
• 2017

The censored regression using the pseudo-response variable proposed by Buckley and James has been one of the most well-known models. Recently, the varying coefficient regression model has received a great deal of attention as an important tool for modeling. In this paper we propose a censored varying coefficient regression model using Buckley-James method to consider situations where the regression coefficients of the model are not constant but change as the smoothing variables change. By using the formulation of least squares support vector machine (LS-SVM), the coefficient estimators of the proposed model can be easily obtained from simple linear equations. Furthermore, a generalized cross validation function can be easily derived. In this paper, we evaluated the proposed method and demonstrated the adequacy through simulate data sets and real data sets.

• 제어로봇시스템학회논문지
• /
• 제5권5호
• /
• pp.521-528
• /
• 1999

The nth-order, scalar, linear time-varying (LTV) systems can be dealt with operators on a differential ring. Using this differential algebraic structure and a classical result on differential operator factorizaitons developed by Floquet, a novel eigenstructure(eigenvalues, eigenvectors) concepts for linear time0varying systems are proposed. In this paper, Necessary and sufficient conditions for the existence of well-defined(free of finite-time singularities) SD- and PD- spectra for SPDOs with complex- and real-valued coefficients are also presented. Three numerical examples are presented to illustrate the proposed concepts.

• 대한수학회지
• /
• 제48권2호
• /
• pp.223-240
• /
• 2011

In this paper, the problem on periodic solutions of the bidirectional associative memory neural networks with both periodic coefficients and periodic time-varying delays is discussed. By using degree theory, inequality technique and Lyapunov functional, we establish the existence, uniqueness, and global asymptotic stability of a periodic solution. The obtained results of stability are less restrictive than previously known criteria, and the hypotheses for the boundedness and monotonicity on the activation functions are removed.

• Structural Engineering and Mechanics
• /
• 제9권2호
• /
• pp.141-152
• /
• 2000

Based on the discussion about some empirical coherency models resulted from earthquake-induced ground motion recordings at the SMART-1 array in Taiwan, and a heuristic model of the coherency function from elementary notions of stationary random process theory and a few simplifying assumptions regarding the propagation of seismic waves, a practical coherency model for spatially varying ground motions, which can be applied in aseismic analysis and design, is proposed, and the regressive coefficients are obtained using least-square fitting technique from the above recordings.

• 대한전기학회논문지
• /
• 제37권12호
• /
• pp.884-893
• /
• 1988

Adaptive controllers for linear unknown coefficient system, that is corrupted by disturbance, are designed by parameter adaptation model reference adaptive control(MRAC). This design is stemmed from the Lyapunov direct method. To reduce the model following error and to improve the convergence rate of the design, an indirect-suboptimal control law is derived. Proper compensation for the effects of time-varying coefficients and plant disturbance are suggested. In the design procedure no complete identification of unknown coefficients are required.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1992년도 추계학술대회
• /
• pp.79-82
• /
• 1992

Under the assumption that the EMG signal was used as the reference signal for driving a prosthetic arm, function discrimination of EMG signal from the biceps and triceps of subject was achived with LPC CEPSTRUM coefficients. By varying the number of coefficients, the types of windows, window size, and window overlaping rates, the best conditions for the function discrimination of EMG signal were obtained.

• 한국음향학회지
• /
• 제32권2호
• /
• pp.116-123
• /
• 2013

본 논문은 시변 해수면을 생성하고 KA(Kirchhoff Approximation) 기반으로 산란계수를 시뮬레이션하여 결정론적 모델인 벨홉 임펄스 응답에 적용함으로써 시변동성 채널을 생성한다. 1D Pierson-Moskowitz 해수면 스펙트럼과 가우시안 상관 함수를 이용하여 일정한 속도로 변화하는 시 변동성 해수면을 사용하였다. 산란계수는 벨홉의 채널 임펄스 응답의 신호 응답 강도에 적용한다. 실제 실측 데이터에서 해수면 반사 성분을 분리하여 시 변동성 특성에 대한 도플러 파워 스펙트럼을 구하고, 해수면 산란계수 시뮬레이션의 결과와 비교하여 해수면에 사용된 가우시안 상관 함수의 상관 시간을 추정하였다. 최종적으로 생성된 시변동성 채널에 수동 시역전 통신 시나리오를 가정하고 기법을 적용하여 비트에러율 및 채널응답 상관계수 시뮬레이션을 수행하였다.

• 한국소음진동공학회논문집
• /
• 제13권4호
• /
• pp.247-257
• /
• 2003

This paper presents an analytical method to Investigate the stability of a hydrodynamic journal bearing with rotating herringbone grooves. The dynamic coefficients of the hydrodynamic Journal bearing are calculated using the FEM and the perturbation method. The linear equations of motion can be represented as a parametrically excited system because the dynamic coefficients have time-varying components due to the rotating grooves, even in the steady state. Their solution can be assumed as a Fourier series expansion so that the equations of motion can be rewritten as simultaneous algebraic equations with respect to the Fourier coefficients. Then, stability can be determined by solving Hill's infinite determinant of these algebraic equations. The validity of this research is proved by the comparison of the stability chart with the time response of the whirl radius obtained from the equations of motion. This research shows that the instability of the hydrodynamic journal bearing with rotating herringbone grooves increases with increasing eccentricity and with decreasing groove number, which play the major roles in increasing the average and variation of stiffness coefficients, respectively. It also shows that a high rotational speed is another source of instability by increasing the stiffness coefficients without changing the damping coefficients.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 춘계학술대회논문집
• /
• pp.166-174
• /
• 2002

This paper presents an analytical method to Investigate the stability of a hydrodynamic journal bearing with rotating herringbone grooves. The dynamic coefficients of the hydrodynamic journal bearing are calculated using the FEM and the perturbation method. The linear equations of motion can be represented as a parametrically excited system because the dynamic coefficients have time-varying components due to the rotating grooves, even in the steady state. Their solution can be assumed as a Fourier series expansion so that the equations of motion can be rewritten as simultaneous algebraic equations with respect to the Fourier coefficients. Then, stability can be determined by solving Hill's infinite determinant of these algebraic equations. The validity of this research is proved by the comparison of the stability chart with the time response of the whirl radius obtained from the equations of motion. This research shows that the instability of the hydrodynamic journal bearing with rotating herringbone grooves increases with increasing eccentricity and with decreasing groove number, which play the major roles in increasing the average and variation of stiffness coefficients, respectively. It also shows that a high rotational speed is another source of instability by increasing the stiffness coefficients without changing the damping coefficients.