• Journal of applied mathematics & informatics
• /
• v.28 no.1_2
• /
• pp.153-162
• /
• 2010

The finite buffer GI/G/1/K system is set up by using an unconventional arrangement of the state space, in which the remaining interarrival time or service time is chosen as the level. The stationary distributions of resulting Markov chain can be explicitly determined, and the chain is positive recurrent without any restriction. This is an advantage of this method, compared with that using the elapsed time approach [2].

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.710-712
• /
• 2004

Generation companies(Genco) submit the supply functions as a bidding function to a bid market in a competitive electricity market. The profits of Gencos vary in accordance with the bid functions, so the selection of a bidding function plays a key role in increasing their profits. This paper presents an analysis of the selection of the supply function from the viewpoint of Nash equilibrium(NE). Four types of bidding function parameters are used for analizing the electricity market. The competition of selecting bidding parameters is modeled as subgame and overall game in this research. The NEs in both game are computed by using analytic method and payoff matrix method. It is verified in case studies for the NE of overall game to satisfy the equilibrium condition.

• Journal of applied mathematics & informatics
• /
• v.38 no.3_4
• /
• pp.351-373
• /
• 2020

There is an extensive literature on retrial queueing models. While a majority of the literature on retrial queueing models focuses on the retrial times to be exponentially distributed (so as to keep the state space to be of a reasonable size), a few papers deal with nonexponential retrial times but with some additional restrictions such as constant retrial rate, only the customer at the head of the retrial queue will attempt to capture a free server, 2-state phase type distribution, and finite retrial orbit. Generally, the retrial queueing models are analyzed as level-dependent queues and hence one has to use some type of a truncation method in performing the analysis of the model. In this paper we study a retrial queueing model with threshold-type policy for orbiting customers in the context of nonexponential retrial times. Using matrix-analytic methods we analyze the model and compare with the classical retrial queueing model through a few illustrative numerical examples. We also compare numerically our threshold retrial queueing model with a previously published retrial queueing model that uses a truncation method.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.11
• /
• pp.2664-2675
• /
• 1993

In this paper, the effects of chip breaker configuration on cutting forces for various cutting conditions are investigated and a method for predicting cutting forces effectively for chip breaker insert in milling is described. Based on the shear plane model and the relevant equations already existing for the relation among the parameters, the method makes use of the analytic geometric approach considering the configuration of cutting too by a 3-dimensional coordinate transformation matrix. The groove type chip breaker insert is modeled to be a double rake insert, represented by the first radial rake angle, the second radial rake angle and the length of land, and the program analyzing the cutting forces is developed. The program capability is verified by comparing the results with the experimental ones for a single cutter; and in case of primary cutting forces, the results of simulation and experiments agree very well showing 2%~16.7% difference within the feed rate range investigated.

• 한국전산유체공학회:학술대회논문집
• /
• 1998.05a
• /
• pp.43-48
• /
• 1998

The development of unsteady three-dimensional incompressible viscous solver based on unsteady physical curvilinear coordinate system is presented. A 12-point finite analytic scheme based on local uniform grid spacing is extended for nonuniform grid spacing. The formulation of a condition is suggested to avoid the oscillation of the series summations produced by the application of the method of separation of variables. SIMPLER and pressure Poisson equation techniques are used for solving a velocity-pressure coupled problem. The matrix is solved using the Generalized Minimal RESidual (GMRES) method to enhance the convergence rate of unsteady flow solver and the Kinematic boundary condition of a free surface flow. It is demonstrated that the numerical solutions of these equations are less mesh sensitive.

• Journal of KSNVE
• /
• v.10 no.6
• /
• pp.977-984
• /
• 2000

Vibration of disk drive spindle is one of the major limiting factors in achieving higher track densities in hard disk drives. Vibration of a BLDC motor is a coupled phenomenon between mechanical characteristics and magnetic origins through the motor air-gap. In this paper, radial magnetic forces for symmetric and asymmetric BLDC motor are calculated with respect to the various rotor eccentricity using analytic method. Based on the results of the radial magnetic forces, transient whirl responses of the spindle motor are analyzed using finite element and transfer matrices. Results show that an asymmetric motor has a worse effects on unbalanced magnetic forces and vibration when mechanical and magnetic coupling exists.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.669-672
• /
• 2006

Recently, large efforts have been made to develop and understand the behavior of Fiber Reinforced Concrete. As in the static loading cases, many researches have been done. However, a few studies have been conducted in cyclic behaviors of FRC. The main objective of the present work is to investigate the cyclic behavior of fiber reinforced concrete with theoretical method. First, cyclic constitutive relations which describe the crack bridging stress considering non-uniform interfacial bond degradation in short randomly oriented fiber reinforced matrix composites under uniaxial cyclic tension were considered. A cyclic degradation model of single fiber based on micromechanics also taken into consideration. As an example, fatigue analysis for ECC with PVA fiber was conducted using proposed equations. Results shows that proposed method can establish a basis for analyzing cyclic behavior of fiber reinforced composites.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.32 no.10
• /
• pp.335-340
• /
• 1983

The analysis of static power converter circuit using state-space method is presented. Semiconductors are modeled in two-state resistors depending on their ON or OFF states. Then the modes of circuit are determined according to the conducting states of semiconductors and different describing matrices are given automatically for each mode. Newton-Raphson algorithm is used as an iterative method for obtaining steady-state solution and an adjoint network is introduced for the efficient and accurate evaluation of the Jacobi matrix in the algorithm. Using the porogram exploited from the above algorithm, it is shown through examples that the results are in good agreement with the analytic solutions and computation time is considerably reduced for obtaining the steady-state solutions.

• Proceedings of the KIEE Conference
• /
• 1993.07b
• /
• pp.683-685
• /
• 1993

Semiconductor switches are modelled as binary inductors, as a very low value of inductance during conduction, and infinite value of inductance otherwise. The system matrix is partitioned in such a manner as to permit efficient handling of switch status. The backward Euler method of integration is used for the solution of equation to ensure convergence. The application of thristor switching to induction motor speed control has resulted in a number of unconventional supply systems. In this paper, an analytic method for predicting the steady-state of performance of system is presented.

• Journal of Korea Technology Innovation Society
• /
• v.14 no.1
• /
• pp.60-84
• /
• 2011

This study accomplished technology improvement assessment of Gashydrate R&D project using ANP method which can deal with the sophisticated decisions involving a variety of interactions and dependencies. Criteria were selected by consultation and questionnaires with experts in four technology parts of gas hydrate project, and then the network was formed from relation with criteria and alternatives. As the result of analysis, the weight matrix was derived and the various relation in the network was able to be verified. The analysis was accomplished with four technology parts - geophysical exploration technology, geological and geochemical technology, analysis of deep-drill cores and stability technology, production technology - and the 'reliability' criterion ranked the highest of all parts. The rank of other criteria and the result of technology improvement assessment reflected the level of each technology. Thus, the result of this study will contribute to policy decision-making for developing and evaluating gas hydrate technology and other R&D projects.