• Journal of the Korean Society for Precision Engineering
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• v.21 no.9
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• pp.103-110
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• 2004

Pressure ripples yield noise and vibration in hydraulic pipelines, which are inevitably generated by a fluctuation of flow rate in the pump mechanism, and such noise and vibration deteriorate the stability and accuracy of hydraulic systems. To reduce the pressure ripples, accumulator and hydraulic attenuator are normally used. In this study, parallel pipeline with a bent-axis piston pump is introduced to a hydraulic pipe system as a method for reducing the pressure ripples and using the transfer matrix method, the dynamic characteristics of the pipe system are analysed and compared with experimental results. The results show that the phase interference using parallel pipeline with a bent-axis piston pump is effective to reduce the pressure ripples in the hydraulic pipelines.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.333-338
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• 1997

A hollow crankshaft is considered as part of an effort to reduce the weight of the automobile powertrain. Since the resulting mass reduction alters both the inertia and stiffness properties of the crankshaft, the vibration characteristics of the hollow crankshaft needs to be investigated in comparison with the original solid crankshaft. The crankshafts are modeled by 38 lumped mass and stiffness elements, in which the dynamic parameters for each lumped element are obtained by the finite element calculation. The fluid-film bearings supporting the crankshaft give rise to linear spring and damping elements that can be derived from the hydrodynamic bearing model. The transfer matrix method is applied to yield the natural frequencies and mode shapes of the crankshaft vibration. The natural frequencies of the hollow crankshaft are founded to be greater than that of the solid crankshaft, and the incorporation of the bearing stiffness tends to accentuate the difference.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1062-1066
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• 2004

In this study, refrigerant noise at connection of capillary tube and evaporator is investigated. Mechanism of refrigerant noise generation is examined in side-by-side type home refrigerator with two evaporators. It is found that the refrigerant noise is generated during refrigeration room fan-off (R-fan of) for that type refrigerator. The reason is that mass flow rate gets down during R-fan of and flow pattern is changed at outlet of capillary tube. We suggest designs for reduction of refrigerant noise with horizontal double expansion device, muffler, and accumulator. To evaluate those improved designs, sound quality index is used.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.301-306
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• 2000

Small passenger and car carrier ships are mainly used as a connection way between land and small islands. And these ships should be designed to enlarge the capacity of passenger and car loading within limited space and draft. So the resonances of various vibrations exist in normal operation range of engine and propulsion shafting. In this paper, hull's superstructure vibration which was especially induced by the 1st order excitation of whirling vibration on the 2-engines and 2-propulsion shafting systems is introduced. Also these are verified via the theoretical analysis using transfer matrix method and FEA software ANSYS and its vibration measurement.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.2
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• pp.93-102
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• 2005

The Nyquist robust stability margin is proposed as a measure of robust stability for systems with Affine TFM(Transfer Function Matrix) parametric uncertainty. The parametric uncertainty is modeled through a Affine TFM MIMO (Multi-Input Multi-Output) description with dead-time, and the unstructured uncertainty through a bounded perturbation of Affine polynomials. Gershgorin's theorem and concepts of diagonal dominance and GB(Gershgorin Bands) are extended to include model uncertainty. Multiloop PI/PID controllers can be tuned by using a modified version of the Ziegler-Nichols (ZN) relations. Consequently, this paper provides sufficient conditions for the robustness of Affine TFM MIMO uncertain systems with dead-time based on Rosenbrock's DNA. Simulation examples show the performance and efficiency of the proposed multiloop design method for Affine uncertain systems with dead-time.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.87.1-87
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• 2001

For a plant subject to several kinds of disturbances in the plant input side, we consider a problem of designing a controller based on the disturbance cancellation. The conventional loop transfer recovery (LTR) technique can not be used since the extended system consisting of the plant and the disturbance model is not necessarily stabilizable. We propose a new LTR technique that can be applied for our problem. As a target of the LTR, we choose a state feedback controller using a disturbance estimator. We find an LTR procedure based on the Riccati equation formalism where the stochastic model contains the filter gain matrix of the disturbance estimator in the target. The procedure recovers the target feedback ...

• Earthquakes and Structures
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• v.2 no.4
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• pp.323-336
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• 2011

The problem of reconstruction of complete building response from a limited number of response measurements is considered. The response at the intermediate degrees of freedom is reconstructed by using piecewise cubic Hermite polynomial interpolation in time domain. The piecewise cubic Hermite polynomial interpolation is preferred over the spline interpolation due to its trend preserving character. It has been shown that factorization of response data in variable separable form via singular value decomposition can be used to derive the complete set of normal modes of the structural system. The time domain principal components can be used to derive empirical transfer functions from which the natural frequencies of the structural system can be identified by peak-picking technique. A reduced-rank approximation for the system flexibility matrix can be readily constructed from the identified mass-orthonormal mode shapes and natural frequencies.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.2
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• pp.29-37
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• 1994

In this paper the modelling procedure and analysis technique for the prediction of accurate critical speeds of marine propeller shafts are suggested. As a solution method the transfer matrix method is employed to calculate the critical speeds, which are correspond to natural frequencies of the shaft in lateral vibration, and whirling responses. Furthermore, in order to check the validity of the simple prediction formulae, such as Jasper's formula and Panagopulos's formula, numerical calculations were performed. From the numerical results it was found that the critical speed of the propeller shaft is sensitive to the position and the supporting conditions of journal bearings.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1096-1101
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• 2008

Concrete is shown the time dependent behavior after placing. The time dependent behavior of normal strength concrete that is used usually in present, were already examined closely lots of parameters by several investigators. however, high strength concrete is that the material characteristics are not definite and the experimental data are lacking. So, The goal of this study is to propose the material characteristics models, and to develop the routine of the time dependent behavior above 60 MPa. The thermal conductivity, the specific heat, the moisture diffusion coefficient, and the surface coefficient are proposed the suitable models through the parametric study. The structural element is used the 8-node solid element. The matrix equation is developed considering the transient heat transfer and moisture diffusion theory. The application of the time dependent behavior is used the finite differential method.

• Steel and Composite Structures
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• v.32 no.4
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• pp.537-548
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• 2019

This paper introduces an improved numerical model which can consider the bond-slip effect in steel-concrete composite structures without taking double nodes to minimize the complexity in constructing a finite element model. On the basis of a linear partial interaction theory and the use of the bond link element, the slip behavior is defined and the equivalent modulus of elasticity and yield strength for steel is derived. A solution procedure to evaluate the slip behavior along the interface of the composite flexural members is also proposed. After constructing the transfer matrix relation at an element level, successive application of the constructed relation is conducted from the first element to the last element with the compatibility condition and equilibrium equations at each node. Finally, correlation studies between numerical results and experimental data are conducted with the objective of establishing the validity of the proposed numerical model.