• Progress in Superconductivity and Cryogenics
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• v.5 no.2
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• pp.66-70
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• 2003

Transient magnetic diffusion process in a melt-cast Bi2Sr2CaCu20X(Bi-2212) tube was studied by experimental and numerical analyses. The transient diffusion partial differential equation is transformed into an ordinary differential equation by integral method. The penetration depth of magnetic field into a superconducting tube is obtained by solving the differential equation numerically. The results show that the penetration depth as a function of time which is somewhat different from the results by Bean's critical state model. The reason of the difference between the present results and that of Bean's model is discussed and compared in this paper. This experiment measure the magnetic flux density in the supercondutor after supply direct-current of Bi-2212 rounded by copper coil. This study was discussed of valid of a previous numerical solution which is compared by the penetrate time and the magnetic flux density difference of between the present results and the numerical solution.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.11
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• pp.991-996
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• 2002

Transient magnetic diffusion process in a melt-cast BSCCO-2212 tube is analyzed by an analytical method. The transient diffusion partial differential equation is transformed into an ordinary differential equation by integral method. The penetration depth of magnetic field into a superconducting tube is obtained by solving the differential equation numerically. The results show that the penetration depth as a function of time which is somewhat different from the results by Bean's critical state model. The reason of the difference between the present results and that of Bean's model is discussed and compared in this paper.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.366-370
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• 1997

This paper descibes a micro groove machining process on the polyurethane biopolymer by KrF excimer laser. To investigate the etch charcteristics of polyurethane biopolymer quantitatively,laser system for ablation was installed with high precison moter and then polymer ablation experiment, in which paramteters were fluence,pulse repetition rate,numbers of pulses and assist gas, was carred out. In this experiment, we found out that the value of critical energy density for ablation is 30mJ/cmsup2/ and the etching rate is more dependent on the pulse number and fluence than any other pamameter. Finally, we machined micro grooves for fiexibility as width 300.mu.m depth 100.mu.m and port for micro-devices mounting as length 100.mu.m width 300.mu.m depth .mu.m on the outer wallof polyurethane biopolymer tube which is used as medical device.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.1053-1057
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• 1997

Laser thin film process with a Q-switch pulsed YAG laser was performed for micro machining. In this research, we performed basic Cr thin film on glass substrates removal machining experiments. Form experiments, it happens not only evaporration of thin film but also spatter and cohesion of melting substance in working region, when machining a Cr thin film by Q-switch YAG laser beam irradiation. Critical energy of surface irradiation type by irradiation direction of laser in a face composing thin film on the glass is higher than that of back irradiation type, but the latter is favorable because of spatter appearance. In case of image formation position when laser beam is irradiated, the defocus is permitted to a certain extent within forcus depth. Ifexceeds focus depth, formation of pattern is vanishing step by step.

• Special Issue of the Society of Naval Architects of Korea
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• 2006.09a
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• pp.71-76
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• 2006

Preliminary conceptual design of hulls is developed and a theoretical evaluation study performed for the comparison of the hull concepts. Systematic variation of the side hull location is carried out to find an optimum position of side hulls for a trimaran by CFD computation. In order to compare computed results, the model test of trimaran was carried out. Shallow water effect is considered due to the route which has critical water depth of 20m for the design speed and investigated on the condition of different speeds and water depth by the numerical computations.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.4
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• pp.65-72
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• 1990

After observing grinding characteristics according to variable grinding condition in order to raise the grinding effect without making worse the grinding quality by using general grinding machine, main conclusions of this study are as follows; 1) When grinding quality is constant, grinding effect is changed according to the speed of the workpiece. But the rapidly increasing critical speed of table is($V_w{\leq}4m/min$). 2) As grinding effect is equal, the lower the speed of the workpiece becomes, the lower the grinding force and surface roughness obtains good results. 3) In terms of grinding method, the down cut grinding method produces good grinding surface royghness in case of little grinding depth;otherwise, the up cut method in case of more grinding depth.

• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.1
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• pp.43-51
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• 2006

80-nm self-aligned n-and p-channel I-MOS devices were demonstrated by using a novel fabrication method featuring double sidewall spacer, elevated drain structure and RTA process. The fabricated devices showed a normal transistor operation with extremely small subthreshold swing less than 12.2 mV/dec at room temperature. The n- and p-channel I-MOS devices had an ON/OFF current of 394.1/0.3 ${\mu}A$ and 355.4/8.9 ${\mu}A$ per ${\mu}m$, respectively. We also investigated some critical issues in device design such as the junction depth of the source extension region and the substrate doping concentration.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.8
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• pp.828-832
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• 2015

This study is conducted for the evaluation of corrosion and lifetime prediction of fire extinguishing pipelines in residential buildings. The fire extinguishing pipeline is made of carbon steel. Twenty-four samples were selected among all the fire extinguishing pipelines in a building; the selection was based on specimenspositions, pipeline diameters, and pipeline thickness. Analysis was conducted by using the results of visual inspection, electrochemical potentiodynamic anodic polarization test, pitting depth measurements, and extreme value statistics with the Gumbel distribution. The maximum pitting depth and remaining life were statistically predicted using extreme value statistics. During visual inspection, pitting corrosion was observed in several samples. In addition, extreme value statistics demonstrated that there were several pipelines that were very sensitive to pitting corrosion. However, the pitting corrosion was not critical in all the pipelines; thus, it was necessary to change only those pipelines that were severely corroded.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.491-492
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• 2006

In the microstereolithography which can make 3-D microstructures, curing depth is different according to exposure energy. Curing depth has to be controlled to fabricate complex 3-D microstructures with overhang shape. It becomes increases when the exposure energy increases. And photocurable resin is cured when the exposure energy is bigger than critical energy. So optimal exposure energy has to be found to fabricate overhang structures without being gel. To make thinner layer, UV absorber is used and exposure pattern is changed. In this paper, we find curing characteristics according to exposure energy, and fabricate microstructures with overhang shape.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04a
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• pp.41-45
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• 2002

Transient magnetic diffusion process in a melt-cast BSCCO-2212 tube is analyzed by an analytical method. The transient diffusion equation is transformed into an ordinary differential equation by integral method. The penetration depth of magnetic field into a superconducting tube is obtained by solving the differential equation numerically. The results show that the penetration depth as a function of time which is somewhat different from the results by Bean's critical current model. The reason of the difference between the present results and that of Bean's model is discussed and compared in this paper.