• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.3
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• pp.156-160
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• 1992

The evolution of leading waves generated by a wavemaker in a two-dimensional tank has been studied. The front of wave trains can be described in general by the Schrodinger equation. In particular, when the slope of the carrier waves is steep, and hence nonlinearity becomes important, the cubic Schrodinger equation is proved to be an appropriate mathematical model. Computations are made by using the Crank-Nicolson algorithm and compared with experimental data. It is found that the numerical result predicts the evolution of leading waves fairly well and the evolution is significantly affected by nonlinearity for steep waves when kh＞1.36.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.33-43
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• 1998

Dynamic behavior of a scroll compressor has been investigated analytically. The equations of motion of moving elements of the scroll compressor such as the orbiting scroll, anti-rotation device, slider bush, and the crank shaft with eccentric crank pin have been set up. As the solutions of these equations, reaction forces between the moving elements, and also between the moving elements and the compressor frame have been calculated. The reaction forces from the moving elements to the frame are the unbalanced forces, which produce accelerations of the compressor body. These accelerations can be used as a measure of the compressor vibration. The major contributions to the unbalanced forces come from the orbiting movement of the orbiting scroll.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.545-546
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• 2006

A problem of oil supply for a reciprocating compressor is very significant for an evaluation of reliability. Since a rotational motion of a crank shaft for the reciprocating compressor with small capacity is used for a power source of oil supply, a centrifugal force of the rotational shaft provides a stroke of oil inside the shaft like a centrifugal pump. The pumped oil rises following an inner wall and provided to a bearing passed through an oil supply hole at the side of the shaft for lubrication of the bearing. In this study, the amount of oil supply has been investigated by a numerical analysis for various conditions such as a shape of a groove, rpm of the compressor, and a shape of a flow channel. Also, a method of increasing oil supply for a low rpm has been studied so that the function can be improved for a variable condition.

• Journal of applied mathematics & informatics
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• v.8 no.3
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• pp.773-793
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• 2001

The explicit expressions for the 2n+1 primitive idempotents in R/sub pⁿ/ = F[x]/< x/sup pⁿ/ -1>, where F is the field of prime power order q and the multiplicative order of q modulo pⁿ is ø(pⁿ)/2(n≥1 and p is an odd prime), are obtained. An algorithm for computing the generating polynomials of the minimal QR cyclic codes of length pⁿ, generated by these primitive idempotents, is given and hence some bounds on the minimum distance of some QR codes of prime length over GF(q)(q=2, 3, ...) are obtained.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.1
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• pp.133-140
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• 2012

In this study, a reliable control scheme with PID combined controller will be considered. The combined controller in this study is PID algorithm with parameters tuned by using ILC (iterative learning control) approach. The controller was applied to the vibration isolator using an induction motor which works as an actuator. This isolator is developed to eliminate the influence of vibration from rotating machineries on the small ship. The NI cRIO real time controller with FPGA is loaded to get or generate control signals. Crank mechanism which converts rotating energy into translational force is adopted and the relation between control force and torque generated from actuator is also analyzed. A Labview program is composed for controlling practice. Experimental results will be described to show the effectiveness of the proposed control schemes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.346.1-346
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• 2002

There have been many studies to visualize the vibration and noise of rotary compressor. Most of these studies assumed that the signal is stationary and the time-averaged signal is used for visualization. However, the noise and vibration signals generated during one cycle of crank shaft vary continuously. In this paper, the noise and vibration of rotary compressor which vary continuously are visualized by short time fourier transform method. (omitted)

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1369-1374
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• 2007

We carried out a vibration test to analyze causes of the damage in the plate of Bell Crank of the high speed Line turnout, at the section where the plate of high speed railway turnout get damaged from May 8th to 9th in 2006. In addition, through a test of the material quality, we performed an analysis of the qualities (of the components) composing the plate. The result indicates that the main cause of faults of the high speed line turnout, which is installed in the section of Chil-gok IEC, is the vibration. In this paper, effects on track-side equipments from vibration, and measurements to protect them from it are mainly analyzed and checked.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.17 no.4
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• pp.295-306
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• 2013

In this paper, we consider the adaptive multigrid method for solving the Black-Scholes equation to improve the efficiency of the option pricing. Adaptive meshing is generally regarded as an indispensable tool because of reduction of the computational costs. The Black-Scholes equation is discretized using a Crank-Nicolson scheme on block-structured adaptively refined rectangular meshes. And the resulting discrete equations are solved by a fast solver such as a multigrid method. Numerical simulations are performed to confirm the efficiency of the adaptive multigrid technique. In particular, through the comparison of computational results on adaptively refined mesh and uniform mesh, we show that adaptively refined mesh solver is superior to a standard method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.157-166
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• 1995

A large crank shaft for ship engine consists of several components, such as throw, jornal, pin and flange. These compoents are individually made by open-die forging followed by machining and they are thermally fitted to form the crankshaft. In the present investigation, it was attempted to design an optimum preform for the throw by use of the spread coefficient. The spread coefficient found in the literature was confirmed by comparison with experimental results using plasticine. However, the preform designed by the spread coefficient was unable to produce the final product. The reason was found that the spread coefficient differs distinctly for the magnitude of bite ratio. Therefore, another spread coefficient, especially for low bite ratios, was proposed and the preform was redesigned. It was found that the new preform was able to produce the final product.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.653-656
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• 2002

This paper presents the development of 15G(Integrate Starter Generator). The ISG is the crank shaft mount type and it is installed at tile flywheel. The wide operating range of ISG requires large constant power speed ratio, good overload performance and high efficiency. High saliency ratio permanent magnet motor is developed for the ISG applications and 500A MOSFET inverter is designed to derive the ISG. The characteristic of developed ISG is investigated using the special test-bed for the 42V PowerNet and the detailed results is presented