• Journal of Mechanical Science and Technology
• /
• 제15권9호
• /
• pp.1281-1291
• /
• 2001

The hereditary integral form of a quasi-linear viscoelastic law has been employed. Four new concepts have been employed: 1. a reduced relaxation function with a non-linear exponential function of time, 2. an inverse method to determine the scale factor of the elastic response, 3. an instant elastic recovery strain during unloading, and 4. the results of a constitutive model for cyclic tests may be a function of the Heavyside class. These concepts have been supported by agreement between measured and predicted responses of soft connective tissue to three types of multiple cyclic tests which include rest periods of no extension and alternations between different strain levels. Such agreement has not been attained in the previous studies. Chun and Hubbard (2001) is our companion experimental analysis paper.

• 수산경영론집
• /
• 제43권1호
• /
• pp.35-48
• /
• 2012

Inverse demand models are well established as market demands in theory and practice of the existing literature. However, the derivation and its interpretation of individual demands from the market demands are not well known in the literature. This paper analyzes the fish market in Korea by the inverse demand model and shows how we deduce the consumer's responses from the market responses when the markets determine the prices by the quantities demanded. It illustrates empirically how this can be done applying to the korean fish market data. The empirical results show that all fishes are price inflexible and mackerels and hairtails are scale flexible in the market demand while mackerels, hairtails, and croakers are price elastic and mackerels and hairtails are income inelastic in the individual demand. The methodology and empirics used in the paper will make a contribution to the existing literature especially for the purpose of recovering consumer's demand from the market demand, thus implementing the policies to administer the fish markets.

• Journal of Electrical Engineering and information Science
• /
• 제2권6호
• /
• pp.82-89
• /
• 1997

In this paper, an adaptive speed controller with an FNN(Feedforward Neural Network) is proposed for servo motor drives. Generally, the motor system has nonlinearities in friction, load disturbance and magnetic saturation. It is necessary to treat the nonlinearities for improving performance in servo control. The FNN can be applied to control and identify a nonlinear dynamical system by learning capability. In this study, at first, a robust speed controller is developed by Lyapunov stability theory. However, the control input has discontinuity which generates an inherent chattering. To solve the problem and to improve the performances, the FNN is introduced to convert the discontinuous input to continuous one in error boundary. The FNN is applied to identify the inverse dynamics of the motor and to control the motor using coordination of feedforward control combined with inverse motor dynamics identification. The proposed controller is developed for an SR motor which has highly nonlinear characteristics and it is compared with an MRAC(Model Reference Adaptive Controller). Experiments on an SR motor illustrate te validity of the proposed controller.

• Structural Engineering and Mechanics
• /
• 제76권3호
• /
• pp.413-420
• /
• 2020

Considering inverse cotangential shear strain function, the present paper studies nonlinear stability of nonlocal higher-order refined beams made of metal foams based on Chebyshev-Ritz method. Based on inverse cotangential beam model, it is feasible to incorporate shear deformations needless of shear correction factor. Metal foam is supposed to contain different distributions of pores across the beam thickness. Also, presented Chebyshev-Ritz method can provide a unified solution for considering various boundary conditions based on simply-supported and clamped edges. Nonlinear effects have been included based upon von-karman's assumption and nonlinear elastic foundation. The buckling curves are shown to be affected by pore distribution, geometric imperfection of the beam, nonlocal scale factor, foundation and geometrical factors.

• 충청수학회지
• /
• 제24권2호
• /
• pp.247-252
• /
• 2011

We study some properties of the Riemann-Stieltjes integrals with respect to the Riesz-$N\acute{a}gy$-$Tak\acute{a}cs$ distribution $H_{a,p}$ and its inverse $H_{p,a}$ on the unit interval satisfying the equation 1 - a = $a^2$ and p = 1 - a. Using the properties of the dual distributions $H_{a,p}$ and $H_{p,a}$, we compare the Riemann-Stieltjes integrals of $H_{a,p}$ over some essential intervals with that of its inverse $H_{p,a}$ over the related intervals.

• Nuclear Engineering and Technology
• /
• 제53권2호
• /
• pp.414-422
• /
• 2021

The aim of this work considers a second order point reactor kinetics model based on the P1 approximation of transport theory, called in this work as P1 point reactor model. The P1 point reactor model implicitly considers the time derivative of the neutron source which has not been thus considered previously. The inverse method to calculate the reactivity in nuclear reactors -chosen because its high accuracy- Matrix Formulation. The numerical results shown that the Matrix Formulation for the reactivity estimation constitutes a method with insignificant calculation errors.

• 대한수학회논문집
• /
• 제39권1호
• /
• pp.149-160
• /
• 2024

In this paper, we give sufficient conditions for the generalized Ornstein-Uhlenbeck operators perturbed by regular potentials and inverse square potentials A_Φ,G,V,c=∆-∇Φ·∇+G·∇-V+c|x|^-2 with a suitable domain generates a quasi-contractive, positive and analytic C₀-semigroup in L^p(ℝ^N , e^-Φ(x)dx), 1 < p < ∞. The proofs are based on an L^p-weighted Hardy inequality and perturbation techniques. The results extend and improve the generation theorems established by Metoui [7] and Metoui-Mourou [8].

• 한국소음진동공학회논문집
• /
• 제21권11호
• /
• pp.1043-1050
• /
• 2011

This paper presents practical results for the estimation of vibration level inside a powertrain based on the rigid body theory and measurement. The vibration level of inside powertrain has been used for the calculation of excitation force of an engine indirectly. However it was difficult to estimate or measure the vibration level inside of a powertrain when a powertrain works on the driving condition of a vehicle. To do this work, the rigid body theory is employed. At the first, the vibration on the surface of a powertrain is measured and its results are secondly used for the estimation the vibration level inside of powertrain together with rigid body theory. Also did research on how to decrease the error rate when the rigid body theory is applied. This method is successfully applied to the estimation of the vibration level on arbitrary point of powertrain on the driving condition at the road.

• 한국지반공학회논문집
• /
• 제24권8호
• /
• pp.5-12
• /
• 2008

Biot는 균질하며 등방성인 포화된 물질에서의 혼합체 연동이론(coupled theory mixtures)을 이용하여 탄성파 전파의 진동수 의존성에 관한 이론을 제시하였다. Biot의 이론에 의하면 포화된 지반을 전파하는 탄성파의 진동수는 지반의 투수계수에 관한 정보를 가지고 있음을 보여주고 있다. 지반의 투수계수 산정에 사용되는 특정 진동수는 '특성 진동수 (characteristic frequency)'라 불리며, 특성 진동수는 진동수의 연속변화를 통한 I/Q(inverse quality factor)와 진동수의 관계도에 의하여 구할 수 있으며, 지반의 투수계수는 Biot의 식을 이용하여 산정할 수 있다. 본 연구에서는 시험상자 (test box)를 이용한 실내 시험을 미시시피 주립대학에서 수행함으로써 특성 진동수를 측정하였으며, 또 이를 이용하여 투수계수를 계산하였다. 모르타르 모래 시료에 대하여 시험한 결과 특성 진동수는 3500Hz에서 나타났으며 이를 Biot 식을 이용하여 시료의 투수계수를 산정한 결과 투수계수는 2.01 $10^{-4}m/sec$로 나타났다. 이는 실내 정 수두 투수계수 시험 값인 1.49 $10^{-4}m/sec$ 와 비교했을 때 다소 크게 나타났다 그러나 이 차이는 투수계수의 통상적인 오차범위를 고려할 때 매우 합리적인 것으로 나타났다. 따라서, 본 연구는 음파를 이용하여 보다 쉽고 빠른게 지반의 투수계수를 산정할 수 있는 가능성이 있음을 보여 주었다. 본 논문에서는 특별히 고안된 장치를 통하여 시료의 특성 진동수를 실험적으로 결정하는 세부적인 방법과 그 이론적인 배경을 기술하였다.

• Structural Engineering and Mechanics
• /
• 제73권2호
• /
• pp.109-121
• /
• 2020

This study aims to estimate crack location and crack length in damaged beam structures using transfer matrix formulations, which are based on analytical solutions of governing equations of motion. A single variable shear deformation theory (SVSDT) that considers parabolic shear stress distribution along beam cross-section is used, as well as, Timoshenko beam theory (TBT). The cracks are modelled using massless rotational springs that divide beams into segments. In the forward problem, natural frequencies of intact and cracked beam models are calculated for different crack length and location combinations. In the inverse approach, which is the main concern of this paper, the natural frequency values obtained from experimental studies, finite element simulations and analytical solutions are used for crack identification via plots of rotational spring flexibilities against crack location. The estimated crack length and crack location values are tabulated with actual data. Three different beam models that have free-free, fixed-free and simple-simple boundary conditions are considered in the numerical analyses.