• Journal of applied mathematics & informatics
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• v.26 no.5_6
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• pp.889-900
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• 2008

The problem of scheduling n jobs on a single machine is considered when the machine is subject to stochastic breakdowns. The objective is to minimize the weighted squared deviation of job completion times from a common due date. Two versions of the problem are addressed. In the first one the common due date is a given constant, whereas in the second one the common due date is a decision variable. In each case, a general form of deterministic equivalent of the stochastic scheduling problem is obtained when the counting process N(t) related to the machine uptimes is a Poisson process. It is proved that an optimal schedule must be V-shaped in terms of weighted processing time when the agreeable weight condition is satisfied. Based on the V-shape property, two dynamic programming algorithms are proposed to solve both versions of the problem.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.39-40
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• 2005

Photovoltaic Power Generation system occupies an important position as an alternative energy source, converting directly sunlight into electricity,using a photovoltaic cell. The Purpose of this research is to present and confirm the effectiveness of concentration and tracking of sun in photovoltaic power generation. Comparative experiments were carried outwith two rating 75 watt solar modules in $25^{\circ}$ under condition of various times concentration, tracking and plain normal measuring generated voltages, currents and temperatures of back sheet of modules by internet monitoring system to find out which is best in economic sense. The experiments show that output power of concentration and tracking photovoltaic power generation is over 180% more then that of plain normal system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.498-503
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• 2009

This paper presents the vibration problem of the Engine Casing (E/C) "B" deck in the handymax vessel and describes a method to avoid resonance. The first ship of the series did not have any vibration issue on the "B" deck. However, resonance condition occurred when additional machine was installed to the following vessels. To understand the dynamic characteristics of the deck, the normal mode analysis and impact test have been performed. Within the normal operating range of the vessel, the $1^{st}$ natural frequency of the E/C "B" deck is close to the main engine's $6^{th}$ order. Based on these analysis, a reinforcement on the deck was suggested and it proved to be effective. Since actual impact test after the reinforcement also confirmed the resonance avoidance.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.1020-1024
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• 1997

Recently the use of ceramic materals has been greatly increased in the industries. But machining of the ceramics is quite unproductive because of their high stength,high hardness,and brittleness. The efficiency of the grinding operation of ceramics depends on the preparation of diamond grinding wheel, i.e.,truning and dressing. This paper describes some experimental results on the dressing conditions of diamond grinding wheel. The dressing performance is evaluated by the magnitude of normal grinding force. The better dressed wheels result in the lower normal grinding forces. The dressing performances of copper plate and aluminum oxide dressing stick are compared. The optimum dressing conditions including the grit size of dressing sticks, the depth of the dressing operation, and the dressing speed qre determined.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.661-665
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• 1996

An inverse kinemetics problem of a reclaimer which digs and transports ironstones or coals in the raw yard is investigated. Because of the special features of the reclaimer of which scooping buckets are attached around the rotating drum at the end of boom, kinematic redundancy occurs in determining the joint varialbes For a given reclaiming point in space the forward kinematics yields 3 equations, however the number of involved variables in the equations are four. A plane equation approximating the surface near a reclaiming point is obtained by considering 8 adjacent points surrounding the reclaiming point. One extra equation to overcome redunduncyis further obtained from the condition that the normal vector at a reclaiming point is perpendicular to the plane. An approximate solution for a simplified problem is first discussed, Numerical solution for the oritinal nonlinear porblem with a constraint equation is also investigated. Finally a closed form solution which is not exact but sufficiently close enough is proposed by exploiting geometric constraint.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.9
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• pp.707-712
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• 2008

The fatigue characteristics of a material or a structure are generally derived from fatigue tests of standard specimens. However, test results of standard specimens are different from those of real structures or components. Therefore, to calculate more accurate fatigue life, the geometrical effect and surface condition must be considered by comparing test results of standard specimens with those of real structures or components. Thus the object of this paper is to evaluate the fatigue characteristics of a real waterwork pipe. Also, to evaluate fatigue characteristic based on life distribution, the statistical fatigue characteristics were analyzed by the normal distribution and related data of P-S-N curve.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.453-457
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• 2007

AGT system is a kind of light railway train. AGT system use of concrete track and rubber tire, so it can be reduce the noise and vibration, compare to the normal train system. And, the dynamic responses of normal bridge are influenced by the dynamic characteristics of bridge, the speed of vehicle and the surface roughness of railway. But the AGT system bridge is influenced not only the above facts but also the guiderail unevenness, because, AGT vehicle steered by guiderail. So, in this study, optimized service condition is suggested for the design and operation of AGT system, by the means of experimental study. The experiments are executed for PSC bridge with length of 30m, at the AGT test line in Kyongsan. The test results are compared and investigated according to the prominence. In the test result, the guiderail prominence influenced on the dynamic response of bridge. It shows a increase as compared with no guiderail prominence in the dynamic response value acceleration, displacement, stain.

• KSTLE International Journal
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• v.3 no.1
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• pp.49-53
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• 2002

Inconel 690 for nuclear steam generator tube has more chromium than the conventionally used Inconel 600 in order to increase the corrosion resistance. TD evaluate the tribological characteristics under fretting condition the fretting tests as well as sliding tests were carried out in elevated temperature water environment. Fretting tests of the cross-cylinder type were done under various vibrating amplitudes and applied normal loads in order to measure the friction forces and wear volumes. Also, the conventional sliding tests of pin-en-disk type were carried out to compare the test results. In fretting, the friction was very sensitive to the load and the amplitude. The friction coefficient decreased with increasing load and decreasing amplitude. Also, the wear of Inconel 690 can be predictable using the work rate model. Depending on normal loads and vibrating amplitudes, distinctively different wear mechanisms and of ten drastically different wear rates can occur. It was fecund that the fretting wear coefficients in water were increased as increasing the temperature of water.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.140-143
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• 1997

The present study is concerned with the hydrostatic extrusion process of copper-clad aluminium bar to investigate the basic flow characteristics. Considering the bonding mechanism of bi-metal contact surface as cold pressure welding, the normal pressure and the contact surface expansion are selected as process parameters governing the bonding condition. The critical pressure required for the bonding at the interface is obtained by solving a "local extrusion" using a slip line meyhod. A viscoplastic finite element method is used to analyze the steady state extrusion process. The boundary profile of bi-metal rod is predicted by tracking a particle path adjacent to interface surface. The variations of contact surface area and the normal pressure along the interface profile are predicted and compared to those by experiments.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.10a
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• pp.265-270
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• 2000

AESTRACI: The shmr behior of sawtoothed artrjicial joints grouted with cement milk rm investiguted in the lahotconstant normal stress conditions. Tests were amducted on joints with asperities h i n g inclinations cf 16.7" and 26.6" ,strengths h i n g 15MPa and 47MPa under a given nmge of n o d stresses wrying frcm 0.76 to 1.g MPa md at a freepitching, rolling and dihtmuy. Results show that the gect of asperities on shmr strength increme is signifamt up to as,to grout thidness (t/a) mtio 4 0.3-1.0. Increme of ahesim is the nmn muse cf shmr strength increme in cemmtoothed artificial iointsed artificial ioints