• Journal of Mechanical Science and Technology
• /
• 제14권1호
• /
• pp.113-120
• /
• 2000

This study has developed a new liquid crystal calibration technique using Neural networks with median filtering and applied this technique to heat transfer measurements. To verify the validity of this new measurement technique, the local Nusselt numbers on a flat plate surface subjected to an axisymmetric impinging jet were measured and compared with the results by the conventional Hue-temperature calibration technique under the same conditions. Because the Neural networks predict the non-linear relations between temperatures and corresponding R, G, B values, Neural networks-median filtering calibration technique can utilize a much wider color band in the experiment than the Hue-temperature calibration technique, resulting in a significant reduction in the experimental time.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제9권2호
• /
• pp.45-53
• /
• 2005

This paper investigates the influence of thermal conductivity and variable viscosity on the problem of micropolar fluid in the presence of suction or injection. The fluid viscosity is assumed to vary as an exponential function of temperature and the thermal conductivity is assumed to vary as a linear function of temperature. The governing fundamental equations are approximated by a system of nonlinear ordinary differential equations and are solved numerically by using shooting method. Numerical results are presented for the distribution of velocity, microrotation and temperature profiles within the boundary layer. Results for the details of the velocity, angular velocity and temperature fields as well as the friction coefficient, couple stress and heat transfer rate have been presented.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2009년도 추계학술대회 논문집
• /
• pp.850-854
• /
• 2009

Approximate analysis for a building installed with a friction damper is revisited to get insight of its dynamic behavior. Energy balance equation is used to have a closed analytical form solution of dynamic magnification factor (DMF) for the building with combined viscous and friction damping. It is found out that DMF is dependent on friction force ratio and resonance frequency. Linear transfer function from input external force to output building displacement is obtained by simplifying DMF equation. Root mean square of building displacement is derived under earthquake-like random excitation. Finally, design of friction damper is proposed by processing target control ratio, damping ratio factor, and friction force in sequence.

• International Journal of Control, Automation, and Systems
• /
• 제1권1호
• /
• pp.1-10
• /
• 2003

This paper presents a high-precision magnetically levitated (maglev) stage to meet demanding motion specifications in the next-generation precision manufacturing and nanotechnology. Characterization of dynamic behaviors of such a motion stage is a crucial task. In this paper, we address the issues related to the stochastic modeling of the stage including transfer function identification, and noise/disturbance analysis and prediction. Provided are test results on precision dynamics, such as fine settling, effect of optical table oscillation, and position ripple. To deal with the dynamic coupling in the platen, we designed and implemented a multivariable linear quadratic regulator, and performed time-optimal control. We demonstrated how the performance of the current maglev stage can be improved with these analyses and experimental results. The maglev stage operates with positioning noise of 5 nm rms in $\chi$ and y, acceleration capabilities in excess of 2g(20 $m/s^2$), and closed-loop crossover frequency of 100 Hz.

• Bulletin of the Korean Chemical Society
• /
• 제26권11호
• /
• pp.1735-1737
• /
• 2005

We obtain probabilities at a crossing of two linearly time-dependent potentials that are constantly coupled to the other by solving a time-dependent Schrödinger equation. We find that the system which was initially localized at one state evolves to split into both states at the crossing. The probability splitting depends on the coupling strength $V_0$ such that the system stays at the initial state in its entirety when $V_0$ = 0 while it is divided equally in both states when $V_0 \rightarrow {\infty}$ . For a finite coupling the probability branching at the crossing is not even and thus a complete probability transfer at $t \rightarrow {\infty}$ is not achieved in the linear potential crossing problem. The Landau-Zener formula for transition probability at $t \rightarrow {\infty}$ is expressed in terms of the probabilities at the crossing.

• Bulletin of the Korean Chemical Society
• /
• 제35권5호
• /
• pp.1329-1332
• /
• 2014

The kinetic studies on the reactions of O,O-diethyl Z-S-aryl phosphorothioates with X-pyridines have been carried out in dimethyl sulfoxide. The free energy correlations with X in the nucleophiles are biphasic concave upwards with a break point at X = H, while those for substituent Z variations in the leaving groups are linear. The negative sign of ${\rho}_{XZ}$ implies that the reaction proceeds through a concerted mechanism for both the strongly and weakly basic pyridines. The biphasic concave upward free energy relationships with X are rationalized by a change in the nucleophilic attacking direction from frontside with the strongly basic pyridines to backside with the weakly basic pyridines.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 하계학술대회 논문집 A
• /
• pp.184-186
• /
• 1996

This paper is a study on the analysis of normal zone propagating velocity in high Tc superconductor. Steady-state solution is analyzed based upon the one-dimensional heat transfer equation. This model incorporates the temperature and magnetic field dependent superconductor properties. The analytical results indicate that the propagation velocity is not a linear function of operating current, magnetic field and temperature.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
• /
• pp.265-268
• /
• 2005

A new method for measurement of the pore size in a nanohoneycomb structure using atomic force microscopy (AFM) was proposed. Porous type anodic aluminum oxide (AAO) was fabricated as a nanohoneycomb structure to measure the pore size. For measuring pore sizes from AFM images, a criterion was set in porous type AAO. The pore sizes from AFM images were compared with those from SEM images, and the results showed good agreement. The relationship between the pore size and widening time was found to be linear in the range of this study. It was understood as the synchronized effects of the impurity gradient in outer oxide of AAO, mechanical packing and mass transfer increase.

• Journal of Advanced Marine Engineering and Technology
• /
• 제17권1호
• /
• pp.26-32
• /
• 1993

The loads exerted on electro-hydraulic servo system are classified into inertial, viscous, and spring load. The additional load called disturbances is also exerted on system but is generally not modeled. To deal with these kinds of loads, it is necessary to maintain the continuous signal transfer, so we can construct compensator to satisfy control specifications using feedback signal such as displacement, velocity, acceleration and pressure known as state variables. In case of controlling the speed of hydraulic motor, we must keep up robust performance for the various loads and disturbances acted on the system. However, the load flow rate in the valve is characterized by nonlinearity so that traditional theory of linear control could not be expected to give the desired performance. In this paper, it is shown that speed controller of hydraulic motor gives a good command following and disturbance rejection performance by applying sliding mode theory as a way of robust control to the nonlinearity, variation of loads and disturbances.

• 대한기계학회논문집
• /
• 제16권7호
• /
• pp.1307-1313
• /
• 1992

본 연구에서는 유연한 조작기의 끝점 위치 제어를 위해 LQG/LTR 제어법을 적 용함으로서 기존의 고전적 제어방법과 비교하고자 한다.