• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.691-696
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• 2004

Recently, it is required that the automotive air conditioning system must keep the cabin temperature comfortable in spite of engine speed, and Improve the fuel consumption during all the seasons. To satisfy these requirements, the variable displacement swash plate type compressor with control pressure valve is developed. In this study, the effects of two type valves, suction pressure control valve and differential pressure control valve, on the performance of swash plate type compressor has been investigated experimentally.

• Proceedings of the Korean Reliability Society Conference
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• 2000.04a
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• pp.213-222
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• 2000

In present study, a stochastic model is developed for the low cycle fatigue life prediction and reliability assessment of 316L stainless steel under variable multiaxial loading. In the proposed model, fatigue phenomenon is considered as a Markov process, and damage vector and reliability are defined on every plane. Any low cycle fatigue damage evaluating method can be included in the proposed model. The model enables calculation of statistical reliability and crack initiation direction under variable multiaxial loading, which are generally not available. In present study, a critical plane method proposed by Kandil et al., maximum tensile strain range, and von Mises equivalent strain range are used to calculate fatigue damage. When the critical plane method is chosen, the effect of multiple critical planes is also included in the proposed model. Maximum tensile strain and von Mises strain methods are used for the demonstration of the generality of the proposed model. The material properties and the stochastic model parameters are obtained from uniaxial tests only. The stochastic model made of the parameters obtained from the uniaxial tests is applied to the life prediction and reliability assessment of 316L stainless steel under variable multiaxial loading. The predicted results show good accordance with experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.374-378
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• 2003

This paper presents investigation of damping characteristics of squeeze mode type MR (Magneto-Rheological) mount experimentally. Since damping property of the MR fluid is changed by variation of the applied magnetic field strength, squeeze mode type MR mount proposed in the study has variable damping characteristics according to the applied magnetic field s strength. In the present work, the performance of the mount was experimentally investigated according to the magnetic field strength and exciting frequencies. The experimental results present that the MR mount can effectively reduce the vibration in a wide range of frequency by controlling the applied electromagnetic filed strength. Viscous damping and stiffness coefficients of the MR mount tend to be changed according to the variation of the applied currents in this study and MR effect is reduced by increasing exciting frequency.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.3
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• pp.251-259
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• 1998

Environmental control facilities are used to simulate an environment or combination of environments under which many kinds of research and tests can be performed. The design of the control system to maintain desired environmental conditions is essential to proper operation of the facility. A simulation model of the facility has been developed by analyzing each component of the system thermodynamically with necessary properties and heat transfer relations. Using the system simulation model, the required characteristics of the control system has been investigated. PI controller is considered as the most probable controller for this kind of the facility, and electric heater power is shown as the Proper manipulated variable for temperature control.

• International Journal of Air-Conditioning and Refrigeration
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• v.8 no.1
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• pp.62-72
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• 2000

Environmental control facilities are used to simulate an environment or combination of environments under which many kinds of research and tests can be performed. The design of the control system to maintain desired environmental conditions is essential to proper operation of the facility. A simulation model of the facility has been developed by analyzing each component of the system thermodynamically. with necessary properties and heat transfer relations. Using the system simulation model, the required characteristics of the control system has been investigated. PI controller is considered as the most probable controller for this kind of the facility, and electric heater power is shown as the proper manipulated variable for temperature control.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.5
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• pp.809-818
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• 1994

In this paper , the author proposed FLVSC (Fuzzy Logic Variable Structure Controller),of which control rules are extracted from the concepts of VSC(Variable Structure Control). FLC(Fuzzy Logic Controller) based on linguistic rules has the advantages of not needing of some exact mathematical model for plant to be controlled. The proposed method has the characteristics which are viewed in conventional VSC, e.g. insensitivity to a class of disturbances, parameter variations and uncertainties in sliding mode. In addition, the method has the properties of FLC-noise rejection capability etc. The computer simulations have been carried out for position control of DC servo motor to show the usefulness of the proposed method and the effects of disturbances and parameter variations are considered.

• The Korean Journal of Applied Statistics
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• v.20 no.3
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• pp.597-604
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• 2007

There are many uses of control charts in health-care monitoring and in public-health surveillance. For example, control charts are used in monitoring and improvement of hospital performance, in monitoring chronic diseases and infectious diseases, and so on. We introduce the Variable Life-Adjusted Display (VLAD) chart and propose the method for choosing control limits of the VLAD chart to give specified in-control properties.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.6
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• pp.490-495
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• 2003

This paper presents investigation of damping characteristics of squeeze mode type MR (magneto-rheological) mount experimentally. Since damping property of the MR fluid is changed by variation of the applied magnetic field strength, squeeze mode type MR mount proposed in the study has variable damping characteristics according to the applied magnetic field strength. In the present work, the performance of the mount was experimentally Investigated according to the magnetic field strength and exciting frequencies. The experimental results present that the MR mount can effectively reduce the vibration in a wide range of frequency by controlling the applied electromagnetic field strength. Viscous damping and stiffness coefficients of the MR mount tend to be changed according to the variation of the applied currents in this study and MR effect is reduced by increasing exciting frequency.

• Steel and Composite Structures
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• v.33 no.1
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• pp.133-142
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• 2019

In the present study, microstructure-dependent static stability analysis of inhomogeneous tapered micro-columns is performed. It is considered that the micro column is made of functionally graded materials and has a variable cross-section. The material and geometrical properties of micro column vary continuously throughout the axial direction. Euler-Bernoulli beam and modified couple stress theories are used to model the nonhomogeneous micro column with variable cross section. Rayleigh-Ritz solution method is implemented to obtain the critical buckling loads for various parameters. A detailed parametric study is performed to examine the influences of taper ratio, material gradation, length scale parameter, and boundary conditions. The validity of the present results is demonstrated by comparing them with some related results available in the literature. It can be emphasized that the size-dependency on the critical buckling loads is more prominent for bigger length scale parameter-to-thickness ratio and changes in the material gradation and taper ratio affect significantly the values of critical buckling loads.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.597-601
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• 2008

Three-dimensional structures of detonation wave propagating in circular tube were investigated. Inviscid fluid dynamics equations coupled with a conservation equation of reaction progress variable were analyzed by a MUSCL-type TVD scheme and four stage Runge-Kutta time integration. Variable-$\gamma$ formulation was used to account for the variable properties between unburned and burned states and the chemical reaction was modeled by using a simplified one-step irreversible kinetics model. The computational code was parallelized based on domain decomposition technique using MPI-II message passing library. The computations were carried out using a home made Windows based PC cluster having 160 AMD AthloxXP and Athlon64 processor. The computational domain consisted of through a roundshaped tube with wall conditions. As an initial condition, analytical ZND solution was distributed over the computational domain with disturbances. The disturbances has circumferential large gradient. The unsteady computational results in three-dimension show the detailed mechanisms of multi-cell mode of detonation wave instabilities resulting diamond shape in smoked-foil record.