• Journal of Magnetics
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• v.18 no.1
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• pp.65-73
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• 2013

In this paper, design and performance analysis of robust and inexpensive permanent magnet-assisted synchronous reluctance generators (PMa-SynRG) for tactical and commercial generator sets is studied. More specifically, the optimal design approach is investigated for minimizing volume and maximizing performance for the portable generator. In order to find optimized PMa-SynRG, stator winding configurations and rotor structures are analyzed using the lumped parameter model (LPM). After comparisons of stator windings and rotor structure by LPM, the selected stator winding and rotor structure are optimized using a differential evolution strategy (DES). Finally, output performances are verified by finite element analysis (FEA) and experimental tests. This design process is developed for the optimized design of PMa-SynRG to achieve minimum magnet and machine volume as well as maximum efficiency simultaneously.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1006-1010
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• 2010

This paper discusses the numerical study on the stability of the high-speed EMU by developing its lumped parameter model including the effect of the creepage. The 6, 10 and 14 degrees-of-freedom (DOF) lumper parameter dynamic models are developed and the critical hunting speeds calculated from each model via Matlab software are analyzed and compared. It is demonstrated that the critical hunting speeds decrease while the degrees-of-freedom increase. In addition, the parametric study is conducted to extract major design parameters to influence on the stability of the high-speed EMU.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.901-906
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• 1989

A robust stability problem for time delay systems is discussed by using a property of Lyapunov type operator equation. We propose a method to check the robust stability against the parameter perturbations occurring in both lumped parameter part and distributed delay element.

• Journal of Ocean Engineering and Technology
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• v.27 no.6
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• pp.22-26
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• 2013

The purpose of this study was to improve the design of a mooring line by attaching a lumped mass to it on the seabed. A numerical analysis of the redesigned mooring system is performed to analyze the effect of the weight of the attached lumped mass using the commercial software Orcaflex. The ultimate tension of the mooring system with the lumped mass is compared with that of a bare mooring line in the original design. An appropriately designed weight for the lumped mass is found to induce a critical lifted point in the mooring line by floater motion in the ultimate condition to move toward the floater position from the anchor point, while maintaining a similar safety factor for the mooring line. On the other hand, it is shown that excess weight for the lumped mass induces snapping in a mooring line, resulting in low safety factor for the mooring system. The distance between lumped weights is shown to be a minor parameter affecting the safety of a mooring line, although a shorter line has an advantage from an economic point of view. Using the optimal weight for the lumped mass attached to the mooring line on a seabed reduces the mooring line length and installation area occupied by a mooring system under real sea conditions.

• Computational Structural Engineering
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• v.10 no.3
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• pp.217-223
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• 1997

This paper deals with the basic concepts of sensitivity analysis in a time domain for the transient response of a lumped mass system. Sensitivity analysis methods in thme domain for determining the effects of parameter changes on the response of a dynamic system by external excitation are presented. The parametric sensitivity of a lumped mass system in time domain can be investigated using different types of sensitivity functions, including first order standard and percentage sensitivity functions. These sensitivity functions are determined as a function of partial derivatives of system variables taken with respect to system parameters. In addition, we compared the results of the analytical method by direct method and those of numerical methods.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.269-272
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• 2005

In order to prevent a router machine feed drive system from transient operational vibration, this paper presents vibration analysis of a rack and pinion typed feed drive system for a router machine. The feed drive system was mathematically idealized as a 5-degree-of-freedom lumped parameter model. Stiffness parameters of motor-shaft, rack and pinion gears, and machine structure were appropriately considered in the modeling. Computational experiment was carried out to obtain vibrations of the feed drive system during its transient speed operation.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.721-722
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• 2002

The aim of this work is to analyze changes in cerebral hemodynamics and intracranial pressure mediated by cerebral blood flow challenges in patients with acute heart arrest. Lumped parameter model with feedback mechanism is utilized to simulate the hemodynamics of brain blood flow in case 40 min T-PLS operation is applied to patients of cardiac arrest. Numerical solutions show that cerebral blood flow and perfusion pressure in patients of cardiac arrest are sharply recovered in the initial state of T-PLS operation.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.465-470
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• 2009

This paper discusses the numerical study on the dynamics of the high-speed EMU by developing the 34 degrees-of-freedom (DOF) lumped parameter model including the effect of the creepage. In order to reflect the creepage, the Kalker's wheel-rail contact theory is introduced in the proposed model. The dynamic analysis using $Matlab^{(R)}$ software is conducted, and its results are compared with those from ADAMS/Rail to investigate the validity of the proposed 34-DOF lumped parameter model. It is demonstrated that the results from the numerical study are similar to those from ADAMS/Rail. In addition, the critical design parameters of high-speed EMU are examined, and the design guidelines for reducing vibration and enhancing ride quality are proposed.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1900-1908
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• 2014

This paper establishes a compact and practical model for a water-wall system comprising supercritical once-through boilers, which can be used for automatic control or simple analysis of the entire boiler-turbine system. Input and output variables of the water-wall system are defined, and balance equations are applied using a lumped parameter method. For practical purposes, the dynamic equations are developed with respect to pressure and temperature instead of density and internal energy. A comparison with results obtained using APESS, a practical thermal power plant simulator developed by Doosan Heavy Industries and Construction, is presented with respect to steady state and transient responses.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.216-221
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• 2000

In this study, two mathematical models are first constructed to analyze vibration characteristics of a gear train - spindle system of an NC lathe gear box. One is a lumped parameter model which is used for calculating natural frequencies of the torsional vibration, the other is a finite element model for analyzing lateral vibration and critical speeds of the spindle system. In addition, this study examines some possible resonance conditions such as gear mesh frequencies, 1X shaft rpm frequencies over whole operating speed range, and so on. The results may be helpful to design a machine tool gear box with low noise and vibration.