• Korean Journal of Mathematics
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• v.29 no.2
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• pp.371-386
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• 2021

This paper investigates two discrete time queueing inventory models with positive service time and lead time. Customers arrive according to a Bernoulli process and service time and lead time follow geometric distributions. The first model under discussion based on replenishment of order upto S policy where as the second model is based on order placement by a fixed quantity Q, where Q = S - s, whenever the inventory level falls to s. We analyse this queueing systems using the matrix geometric method and derive an explicit expression for the stability condition. We obtain the steady-state behaviour of these systems and several system performance measures. The influence of various parameters on the systems performance measures and comparison on the cost analysis are also discussed through numerical example.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.87-90
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• 1990

We compare the reflectivity spectrum and phase change of Bragg reflectors obtained by the matrix method and the coupled wave method. We show that the results obtained by the two methods agree well generally and the discrepancy between the results obtained by the two methods increases as the fractional refractive index difference between adjacent layers increases and/or the absorption loss increases, due to the approximations inherent in the coupled wave method for the analysis of multiple dielectric layers.

• Journal of applied mathematics & informatics
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• v.29 no.5_6
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• pp.1067-1074
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• 2011

In this paper, a preconditioned mixed-type splitting iterative method for solving the linear systems Ax = b is presented, where A is a Z-matrix. Then we also obtain some results to show that the rate of convergence of our method is faster than that of the preconditioned AOR (PAOR) iterative method and preconditioned SOR (PSOR) iterative method. Finally, we give one numerical example to illustrate our results.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.963-968
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• 2002

This paper will review the driving methods and issues of driving circuitry for passive matrix organic electro-luminescent displays(PM-OELDs). And it will shows the proposed one-chip and two-chip solution for driving the PM-OELDs and also the pixel structure and driving methods of active matrix (AM-OELDs). We will discuss the proper applications of OELDs with its power consumption by comparison with that of LCD.

• Journal of Applied Reliability
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• v.1 no.1
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• pp.17-33
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• 2001

The characteristics of Weibull distribution are investigated as a function of shape parameter. The statistical estimation methods of the shape parameter and statistical comparison methods of two or more shape parameters are studied. Assuming Weibull distribution, statistical analysis of bending-strength data of alumina titanium carbide ceramic matrix composites machined two different methods are performed.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.124-128
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• 2009

In this study, the effect of multi-step purification or functionalization on physicochemical properties of multi-walled carbon nanotubes (MWNTs)/epoxy (EP) nanocomposites was investigated. The nanocomposites containing multi-step purified MWNTs showed a stronger influence on $T_g$ and increased in mechanical properties in comparison to nanocomposites containing the same amount of only purified MWNTs. Consequently, the multi-step purification of MWNTs led to an improvement of thermomechanical properties of nanocomposites, resulting from improving the intermolecular interaction of MWNTs in epoxy matrix resins.

• Smart Structures and Systems
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• v.29 no.3
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• pp.387-393
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• 2022

This paper presents the vibration analysis of cracked ceramic-reinforced aluminum composite beams by using a method based on changes in modal strain energy. The crack is considered to be straight. The effective properties of composite materials of the beams are estimated through Mori-Tanaka micromechanical model. Comparison study and numerical simulations with various parameters; ceramic volume fraction, reinforcement aspect ratio, ratio of the reinforcement Young's modulus to the matrix Young's modulus and ratio of the reinforcement density to the matrix density are taken into investigation. Results demonstrate the pronounced effects of these parameters on intact and cracked ceramic aluminum beams.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.1362-1365
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• 1993

Fuzzy mathematics is used to elicit and evaluate human psychophysical responses in panel tests. The fundamental instrument used is a bar graph whose data is then converted to a paired comparison matrix. Form this matrix we use the theory of Perron and Froebenius to obtain an eigenvalue and eigenvector which indicates not only the panelist's comparitive responses but also the consistency of the responses from that panelist. Tests were done to evaluate the procedure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.509-510
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• 2010

• Transactions of the Society of Information Storage Systems
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• v.5 no.1
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• pp.47-52
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• 2009

Most hard disk drives that apply the ramp load/unload technology unload the heads at the outer edge of the disk while the disk is rotating. The load/unload includes the benefits as like an increased areal density, a reduced power consumption and an improved shock resistance. A lot of papers investigating the effects of the various load/unload parameters such as a suspension tab, a limiter, a ramp and air-bearing surface designs have been published. However, in previous researches, an effect of the suspension is not considered at each load/unload step. In this paper, we focus that a variation of the state matrix affects the load/unload performance on based on a state matrix that is a stiffness matrix of the suspension. Because the state matrix is related to the suspension at each load/unload step, to change the state matrix means the structural change of the suspension. Therefore, we investigated a range of a pitch static attitude(PSA) and a roll static attitude(RSA) for load/unload performance. We also analyzed an effect of the variation of the state matrix a range of load/unload velocity occurred a slider-disk contact. We determined the variation of the state matrix to improve the load/unload performance through comparison of each factor of state matrix.