• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1994.04a
• /
• pp.181-188
• /
• 1994

Generally, the structural material shows rate dependent behaviors, which require to constitute different strain-stress relations according to strain rates. Conventional rate- independent constitutive equations used in general purpose finite analysis programs are inadequate for dynamic finite strain problems. In this paper, a rate dependent constitutive equation for elastic-plastic material was developed. The plastic stretch rate was modeled based on slip model with dislocation velocity and density so that there is no yielding condition, and no loading conditions. Non-linear hardening rule was also introduced for finite strain. Material constants of present constitutive equation were determined by experimental data of mild steel. The constitutive equation was applied to uniaxile tension. It was appeared that the present constitutive equation well simulates rate dependent behaviors of mild steel.

• Journal of Korean Society for Quality Management
• /
• v.25 no.3
• /
• pp.22-38
• /
• 1997

In a traditional sequential acceptance sampling plan, it is assumed that the sampled items are independent each other. In this paper, stochastically dependent sequential acceptance sampling plans are dealt when there exists dependency between sampled items. Monte-Calro algorithm is used to find the acceptance and rejection probabilities of a lot. The number of defectives for the test to be accepted and rejected in probability ratio sequential test can be found by using these probabilities. The formula for measures of performance of these sampling plans is developed. Type I and II error probabilities are estimated by simulation. This research can be a, pp.ied to sequential sampling procedures in place of control charts where there is a recognized and necessary dependency during the production processes. Also, dependent multiple acceptance sampling plans can be derived by extending this sequential sampling procedure. As a numerical example, a Markov dependent process model is given, and the characteristics of the sampling plans are examined according to the change of the dependency factor.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.27 no.2
• /
• pp.80-88
• /
• 2017

In this research a time dependent thermal and solutal convection was computationally investigated for the physical vapor transport of the mixture of $Hg_2Cl_2-I_2$ system with for the convective regime from thermal Rayleigh number of $2.16{\times}10^6$ up to $1.7{\times}10^7$ with marching time to a steady state problem. With time marching, the convective cells are decreased for the thermal Rayleigh number of $2.16{\times}10^6$, and increased for the thermal Rayleigh number of $1.7{\times}10^7$. The convective flow structures are found to be essentially time independent on the horizontal orientation of the enclosure with respect to the gravity vector, and on the other hand, time dependent on the vertical orientation of the enclosure with respect to the gravity vector.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.8 s.227
• /
• pp.968-975
• /
• 2004

Nanofluids have anomalously high thermal conductivities at very low fraction, strongly temperature-dependent and size-dependent conductivities, and three-fold higher critical heat flux than that of base fluids. Traditional conductivity theories such as the Maxwell or other macroscale approaches cannot explain why nanofluids have these intriguing features. So in this paper, we devise a theoretical model that accounts for the fundamental role of dynamic nanoparticles in nanofluids. The proposed model not only captures the concentration and temperature-dependent conductivity, but also predicts strongly size-dependent conductivity. Furthermore, we physically explain the new phenomena for nanofluids. In addition, based on a proposed model, the effects of various parameters such as the ratio of thermal conductivity of nanofluids to that of a base fluid, volume fraction, nanoparticle size, and temperature on the thermal conductivities of nanofluids are investigated.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.8
• /
• pp.1141-1151
• /
• 1998

An effective thermal conductivity measurement for suspensions of microparticles in oil mixture is conducted in order to evaluate the shear rate-dependence of the thermal conductivity of suspensions. Measurements are made for rotating Couette flows between two concentric cylinders. The rotating outer cylinder is immersed into a constant temperature water bath while the stationary inner cylinder is subject to a uniform heat fluff. Test fluids are made to be homogeneous suspensions, in which neutrally buoyant microparticles ($d=25{\sim}300{\mu}m$) are uniformly dispersed. The present measurements show strong shear-rate dependent thermal conductivities for the suspensions, which are higher than those at zero shear rate. The shear rate dependent thermal conductivity increases with the particle size and volume concentration.4 new model for shear rate-dependent thermal conductivity of microparticle suspensions is proposed; the correlation covers from zero shear rate value to asymptotic plateau value at moderately high shear rates.

• Biomolecules & Therapeutics
• /
• v.6 no.1
• /
• pp.25-30
• /
• 1998

The roles of dopamine(DA) and N-methyl-D-aspartate(NMDA) system in the development and expression of morphine dependence were investigated by monitoring the concentrations of extracellular DA and its metabolites by in vivo microdialysis and simultaneous observation of behavioral changes in morphine dependent rats. Extracellular DA level in caudate putamen of morphine-dependent rat was decreased and the concentrations of its metabolites, dihydroxy phenylacetic acid(DOPAC) and homovanillic acid(HVA), were increased during naloxone-precipitated withdrawal. DA contents were recovered to normal levels by pretreatment of MK-801, a noncompetitive NMDA receptor antagonist, which may explain the mechanism of diminishing effect of MK-801 on withdrawal symptoms in morphine-dependent rats. MK-801(0.3 mg/tg, i.p.) induced the untoward hamful neurological signs such as ataxia and severe rotations, which may be produced by hyperactivation of dopaminergic system. These results suggest that MK-801 may inhibit the expression of mophine dependence by altering the dopamine release.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.11
• /
• pp.2041-2046
• /
• 2008

A frequency-dependent slow-wave factor (SWF) and equivalent circuit model of transmission line with defected ground structures (DGS) is described. Once S-parameters of a DGS transmission line are given, the conventional frequency -independent equivalent circuit elements are extracted using 3dB cutoff and resonant frequencies (Fc and Fo) as the first step. Using the initial equivalent elements and simple transmission line theories, a frequency-dependent equivalent transmission line model is established through an analytical method, and finally the frequency dependent SWF is calculated. The proposed equivalent circuit model and SWF are frequency-dependent and more reliable because even small insertion loss within available passband is considered, while they have been independent of frequency.

• Journal of Korean Institute of Industrial Engineers
• /
• v.25 no.1
• /
• pp.8-20
• /
• 1999

In this paper, a design and estimation procedure for the stochastically dependent nonstationary multiple acceptance sampling plans is developed. At first, the rough-cut acceptance and rejection numbers are given as an initial solution from the corresponding sequential sampling plan. A Monte-Carlo algorithm is used to find the acceptance and rejection probabilities of a lot. The conditional probability formula for a sample path is found. The acceptance and rejection probabilities are found when a decision boundary is given. Several decision criteria and the design procedure to select optimal plans are suggested. The formula for measuring performance of these sampling plans is developed. Type I and II error probabilities are also estimated. As a special case, by setting the stage size as 1 in a dependent sampling plan, a sequential sampling plan satisfying type I and II error probabilities is more accurate and a smaller average sample number can be found. In a numerical example, a Polya dependent process is examined. The sampling performances are shown to compare the selection scheme and the effect of the change of the dependency factor.

• Journal of the Korean Mathematical Society
• /
• v.46 no.4
• /
• pp.827-840
• /
• 2009

Let {$X_{ni}$ | $1{\leq}i{\leq}n,\;n{\geq}1$} be an array of rowwise negatively dependent (ND) random variables. We in this paper discuss the conditions of ${\sum}^n_{t=1}a_{ni}X_{ni}{\rightarrow}0$ completely as $n{\rightarrow}{\infty}$ under not necessarily identically distributed setting and the strong law of large numbers for weighted sums of arrays of rowwise negatively dependent random variables is also considered.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.05a
• /
• pp.693-695
• /
• 2003

In this paper, we have investigated temperature-dependent characteristics of current-voltage for double gate MOSFET with main gate and side gate. DG MOSFET has the main gate length of 50nm and the side gate length of 70nm. We have investigated the temperature-dependent characteristics of current-voltage and drain voltage is changed from 0V to 5.0V at $V_{mg}$ =1.5V and $V_{sg}$ =3.0V. We have obtained a very good characteristics of current-voltage for 77K. We have simulated using ISE-TCAD tool for characteristics analysis of device.