• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.9
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• pp.861-869
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• 2012

This paper presents a high performance position controller in a driving system using a time optimal control which is widely used to control driving systems to a desired reference position or velocity in minimum response time. The main purpose of this study is an improvement of transient response performance rather than steady-state response comparing with another various control strategies. In order to improve the performance of time optimal control, we tried to find the cause of the steady-state error in the driving system we have already made up and also suggest the newly modified type of time optimal control method in this paper.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.231-234
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• 1998

This study presents steady-state finite element analysis of three-dimensional hot extrusion of sections through square dies. The objective of this study is to develop a steady-state finite element method for hot extrusion through square dies, and to provide theoretical basis for the optimal die design and process control in the extrusion technology. In the present work, steady-state assumption is applied to both analyses of deformation and temperature. The analysis of temperature distribution includes heat transfer. Convection like element is adopted for the heat transfer analysis between billet and container, and also billet and die. Distributions of temperature, effective strain rate, velocity and mean stress are discussed to design extrusion die effectively.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.4
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• pp.42-49
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• 1997

A conventional adaptive noise canceller (ANC) using LMS algorithm suffers from the misadjustment of adaptive filter weights due to the gradient-estimate noise by input speech signal at steady state. In this paper, an ANC is proposed which uses the combination of VSLMS (variable step size LMS) and SA (sign algorithm) to improve steady state performance and convergence rate. SA algorithm is applied in speech region to prevent the weights from perturbing by output speech of ANC and VSLMS algorithm is applied to improve convergence rate and channel tracking ability in silence region and adaptive transient region. In compute rsimulation, the performance of the proposed VSLMS-SA combination algorithm is much better than LMS algorithm and the algorithm, recently proposed by greenberg, with adaptation step-size parameter determine dby sum method in convergence rate, channel tracking and steady state performance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.880-885
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• 2000

Flow patterns and steady flow characteristics of an intake 3valve cylinder head are not obviously declared. Thus, in the study, the characteristics and limitation of intake flow coefficient which applied to multi intake valve engine are introduced. The flow coefficient and tumble characteristics are investigated by means of the steady flow test and flow visualization method. As the results, it is found that the intake flow rate is dominated by effective valve open area. In addition, this paper shows that the mass flow rate of intake 3valve engine is greater than that of intake 2valve engine and tumble flow of intake 3valve engine is superior to that of intake 2valve engine.

• Management Science and Financial Engineering
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• v.16 no.1
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• pp.119-135
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• 2010

In this paper, we readdress the optimization problem for minimizing the inspection cost in a back-light unit inspection system, which forms a network including a K-stage inspection system, a source inspection shop, and a re-inspection shop. In order to formulate our objective function when the system is in a steady state, assuming that the number of nonconforming items in a lot follows a binomial distribution when a lot is formed for inspection, we make a steady-state network flow analysis between shops, and derive the steady-state amount of flows between nodes and the steady-state fraction defectives by solving a nonlinear balance equation. Finally we provide some fundamental properties and an enumeration method for determining an optimal value of K which minimizes our objective function. In addition, we compare our results numerically with previous ones.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.6
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• pp.89-102
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• 1997

In this study, the steady state cornering behavior of a vehicle is investigated by using a numerical model that has parameters associated with roll motion. The nonlinear characteristics of tire cornering forces and aligning torques are presented in analytical forms using the magic formula. The sets of nonlinear algebraic equations that govern the cornering motion are solved by the Newton-Raphson iteration method. The vehicle design parameters are measured by SPMD(Suspension Parameter Measuring Device), and its results are verified by carrying out a skid pad test. The design parameters that are most affecting the steady state cornering behavior are classified into four factors, and the contributions of the factors to understeer gradient are then calculated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.4
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• pp.764-770
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• 1989

This paper analyze the steady state performance of a self-acting air lubricated slider bearing in hard disk/head system. Modified Reynolds' equation is derived from the steady state compressible Navier-Stokes equation, under slip-flow conditions. Finite difference technique and numerical procedure are described by using Newton-Raphson iteration method to slove the non-linear equations. These techniques are applied to conventional slider bearings and the effects of molecular mean free path(MMFP) for a recording surface of hard disk are shown. The calculation procedure developed here, wide applicabilities in practical head design procedures, and converges rapidly.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.1
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• pp.88-96
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• 2015

This paper is the first investigation on the evaluation methods of flow characteristics in the steady bench. For this purpose, several assumptions used in the steady flow evaluation are examined, comparing the measured and/or processed results by the conventional impulse swirl meter with the ones by the real velocity through a particle image velocimetry. The results show that the most questionable assumption is the solid rotation of swirl. With regard to this assumption, the flow characteristics by the conventional methods are distorted seriously by both of the eccentricity of the swirl center and non-uniform velocity profile along the cylinder radial direction. In addition, the cylinder axial velocity distribution also has the great effect on the flow characteristics.

• Bulletin of the Korean Chemical Society
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• v.9 no.1
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• pp.36-40
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• 1988

The time correlation functions of concentration fluctuations due to the random forces near the steady state are evaluated for a general two-component nonlinear chemical system by solving the corresponding two dimensional Fokker-Planck equation. The approximate method of solving the Fokker-Planck equation is based on the eigenfunction expansion and the corresponding eigenvalues for both the linear and nonlinear Fokker-Planck operators are obtained near the steady state. The general results are applied to the Lotka model near the oscillatory marginal steady state and the comparison is made between linear and nonlinear cases.

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1454-1459
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• 2024

Researchers have applied theoretical and CFD models for years to analyze the fluidelastic instability (FEI) of tube arrays in steam generators and other heat exchangers. The accuracy of each approach has typically been evaluated using the discrepancy between the experimental critical flow velocity and the predicted value. In the best cases, the predicted critical flow velocity was within an order of magnitude comparable to the measured one. This paper revisits the quasi-steady approach for damping controlled FEI in a normal triangular array with a pitch ratio of P/d = 1.375. The method addresses the fluidelastic frequency at the stability threshold as an input parameter for the approach. The excellent agreement between the estimated stability thresholds and the equivalent experimental results suggests that the fluidelastic frequency must be included in the quasi-steady analysis, which requires minimal computing time and experimental data. In addition, the model allows a simple time delay analysis regarding flow convective and viscous effects.