• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1072-1077
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• 2004

This paper provides a new approach to analyze the stability of a general multi-link TCP Vegas, which is a kind of feedback-based congestion algorithm. Whereas the conventional approaches use the approximately linearized model of the TCP Vegas along equilibrium pints, this approach models a multi-link TCP Vegas network in the form of a piecewise linear multiple time-delay system. And then, based on the exactly characterized dynamic model, this paper presents a new stability criterion via a piecewise and multiple delay-dependent Lyapunov-Krasovskii function. Especially, the resulting stability criterion is formulated in terms of linear matrix inequalities (LMIs).

• Journal of applied mathematics & informatics
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• v.29 no.5_6
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• pp.1097-1115
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• 2011

We consider the global stability of a general tuberculosis model with two differential infectivity, n classes of latent individuals and mass action incidence. This system exhibits the traditional threshold behavior. There is always a globally asymptotically stable equilibrium state. Depending on the value of the basic reproduction ratio $\mathcal{R}_0$, this state can be either endemic ($\mathcal{R}_0$ > 1), or infection-free ($\mathcal{R}_0{\leq}1$). The global stability of this model is derived through the use of Lyapunov stability theory and LaSalle's invariant set theorem. Both the analytical results and numerical simulations suggest that patients should be strongly encouraged to complete their treatment and sputum examination.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.10
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• pp.748-754
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• 1987

A robustness analysis for model reference adaptive control(MRAC) system with plant uncertainty is discussed in this paper. The adaptive control system is designed under assumptions that the controlled plant is represented by a lst order nominal model and that the system is drived by a constant reference signal. When using general gradient method(GGM), it is shown that unmodelled dynamics in plant model can cause the instability of the overall control loop during the adaptation process. However, as the algorithm of least square method(LSM) is introduced, the global stability of the system can be hold. And it is also given that the boundedness of adjustable parameters may be verified using the concept of an equilibrium point analysis.

• KDI Journal of Economic Policy
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• v.37 no.3
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• pp.1-30
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• 2015

Based on a quantitative, heterogeneous agent general equilibrium model, we compute the optimal tax rates for labor and capital incomes for the Korean economy. According to our model, a more progressive income tax schedule along with a higher capital tax rate can increase average welfare by as much as 0.86% of permanent consumption. Approximately 64% of house-holds, those with low assets and low productivity, are better off when a more progressive optimal tax schedule is adopted. Despite the potentially significant welfare gains, our calculation should be interpreted with caution because our benchmark model does not take into account possible capital outflows or the increased administrative costs associated with high taxes.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.309-309
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• 2000

The main objective of this study is to understand the regeneration step of the PTSA(Pressure and thermal swing adsorption) process below the atmospheric pressure by rigorous dynamic simulation. This target process is to recover toluene using activated carbon as an adsorbent. To do this, the dynamic simulations for the regeneration step are performed at 360, 490, 590mmHg and at high temperature after the simulation of the adsorption step at latm and 298K. A mathematical model was developed to simulate the column dynamics of the adsorption systems. This model is based on non-equilibrium, non-isothermal and non-adiabatic conditions, and axial dispersion and heat conduction are also considered. Heat transfer resistances are considered in gas-solid, gas-column wall and column wall-outside air. The LDF(Linear Driving Force) approximation model describes the mass transfer rate between the gas and solid phase. This study shows that the recovery of toluene by PTSA is more preferable than that by general TSA.

• Journal of the Korean Regional Science Association
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• v.13 no.2
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• pp.75-92
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• 1997

This paper is concerned with an estimation of optimal investment of road sector in 1996-2005. The main method is a Computable General Equilibrium (CGE) Model for Korea in which the optimal solution is derived in a recursively dynamic path. The model is composed of three main modules: the supply, the demand and the price. In this paper, the investment demand for the road is optimized with subject to national economic growth and price inflation. If the annual inflation level and the economic growth rate during 1996-2005 are set to 4.5%-5.0% and 6.0%-6.5% respectively, the optimal demand for the road investment is estimated as 155.1-180.1 trillion Won or 3.33%-3.89% of the GDP for ten years. It implies that the additional increase of the road investment by 0.61%-1.15% of the GDP is required for sustainable economic development, since the share of the road investment in the GDP of the latest 5 years has stayed around 2.27%. However, it is necessary to reduce construction investments on housing as well as to promote private financing of the road in order to maximize an efficiency of resource allocation.

• Journal of Power Electronics
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• v.17 no.4
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• pp.884-891
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• 2017

The improved transfer functions of the modified Sheppard-Taylor (MS-T) converter, which is capable of regulating output voltage under a wide range of input voltage and load variations, negligible current ripple, and fewer components in comparison to the Sheppard-Taylor (S-T) converter, operating in continuous conduction mode (CCM) are investigated in this study. Its DC equilibrium point, small signal model, and transfer functions are derived and analyzed. Then, the voltage controller is applied for this MS-T converter. The comparisons between the derived model and the existing model are presented. The hardware circuit is designed and the circuit experiments are provided for validation. The results show that the improved transfer functions of the MS-T converter are more effective and general than the previous ones for describing its real characteristics.

• Structural Engineering and Mechanics
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• v.78 no.5
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• pp.573-583
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• 2021

This paper presents a theoretical approach of the structures reinforced with bonded FRP composites, taking into account loading model, shear lag effect and the thermal effect. These composites are used, in particular, for rehabilitation of structures by stopping the propagation of the cracks. They improve rigidity and resistance, and prolong their lifespan. In this paper, an original model is presented to predict and to determine the stresses concentration at the FRP end, with the new theory analysis approach. The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened beam, i.e., the concrete beam, the FRP plate and the adhesive layer. The theoretical predictions are compared with other existing solutions. The numerical resolution was finalized by taking into account the physical and geometric properties of materials that may play an important role in reducing the stress values. This solution is general in nature and may be applicable to all kinds of materials.

• Honam Mathematical Journal
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• v.44 no.3
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• pp.402-418
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• 2022

Noise is a fundamental factor to increased validity and regularity of spike propagation and neuronal firing in the nervous system. In this paper, we examine the stochastic version of the Izhikevich-FitzHugh neuron dynamical model. This approach is based on techniques presented by Luo and Guo, which provide a general framework for the bifurcation and stability analysis of two dimensional stochastic dynamical system as an Itô averaging diffusion system. By using largest lyapunov exponent, local and global stability of the stochastic system at the equilibrium point are investigated. We focus on the two kinds of stochastic bifurcations: the P-bifurcation and the D-bifurcations. By use of polar coordinate, Taylor expansion and stochastic averaging method, it is shown that there exists choices of diffusion and drift parameters such that these bifurcations occurs. Finally, numerical simulations in various viewpoints, including phase portrait, evolution in time and probability density, are presented to show the effects of the diffusion and drift coefficients that illustrate our theoretical results.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.6
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• pp.713-721
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• 1998

In this paper a new modeling and an optimal pole-placement control for the suspension system of Macpherson type are investigated. The rotational motion of the unsprung mass is emphasized in the new modeling. The two generalized coordinates selected in the new model are the vortical displacement of sprung mass and the angular displacement of control arm. Both variables are measured from their static equilibrium points. It is shown that the conventional model is a special case of the new model since the transfer function of the new model coincides with that of the conventional one if the lower support point of the shock absorber is located at the mass center of the unsprung mass. It is also shown that the resonance frequencies of the new model agree better with experimental results. Therefore, the new model is more general in the sense that it Provides an extra degree of freedom in determining the plant model for control system design. An optimal pole-placement control which combines LQ control and pole-placement technique is applied to the new model. Simulations are provided.