• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1693-1698
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• 2000

In operating test of medium speed diesel engine, the large noise over 110dBA would be occurred, and silencer should be needed to prevent the transmission of noise through exhaust duct. A near neighborhood of medium speed engine test shop, outbreak of low frequency noise was reported. From the result of noise measurement, it was found that the coupling of engine noise and air column between workshops was main cause of annoying low frequency noise. From this study, 3 ways of reformation methods were proposed; insertion of plenum chamber, placement of baffles, and alteration of direction of exhaust. As a result of these modification, low frequency noise was cancelled out.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.797-803
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• 2000

Recently, the singing phenomenon was encountered during the sea trials of high speed catamaran and 46,000 TDW product carrier and remedied after various treatments, which were based on the reduction of vortex shedding strength and the avoidance of resonance, respectively. And, the numerical approach for structure-acoustical problem like singing phenomenon was established using MSC/NASTRAN and SYSNOISE. In this paper, the effectiveness of numerical approach was verified through the control of singing noise. And the results according to the modification were also discussed. Finally, the future works were described to enhance the numerical approach pattern for singing phenomenon.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.157-162
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• 2012

A structural modification of baseframe is an effective method to avoid resonance in marine diesel generator (D/G) set which consists of diesel engine, generator and baseframe. However the reinforcement with thick plates or additional parts to increase the natural frequency can be less effective because of increased weight. Especially fine control of target mode based on the experience is difficult because the weight and interference of system have to be considered. In this paper, the design optimization of baseframe was performed to reduce the resonant vibration using a gradient descent method. The design parameters such as thickness, shape and location of baseframe parts are optimized to increase the torsional natural frequency of D/G set. From the actual test, the new designed baseframe reduced the vibration level in resonance by 55% without any increase of weight and interference. interference.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 추계학술발표대회 개요집
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• pp.24-26
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• 2003

In this study EB(Electron Beam) welder was modified to apply EB welder to micro-joining with solder ball and Pt wire. The power and beam current of EB welder is 6kW, 100mA and the minimum current was 1mA. The minimum current of EB welder was modified to decrease the amount of beam current to 0.0lmA and the monitoring system to observe materials was made up. The control system and CAD/CAM software for e-beam direct writing was developed and the deflection beam was controlled without moving workpieces. the possibility of applying EB welder to micro-joining with solder ball and Pt wire was studied through this experiments.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1648-1653
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• 2003

This paper predicts the modified proportional damping structural eigenvectors and eigenvalues due to the change in the mass and stiffness of a proportional damping structure by iterative calculation of the sensitivity coefficient using the original dynamic characteristics. The method is applied to examples of a cantilever and 3 degree of freedom lumped mass model by modifing the mass and stiffness. The predicted dynamic characteristics are in good agreement with these from the structural reanalysis using the modified mass and stiffness.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.36-36
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• 2010

Low-pressure fluorocarbon plasmas are widely used in microelectronics fabrication for a variety of surface modification purposes. In particular, fluorocarbon plasmas are used for the etching of dielectrics such as silicon dioxide and silicon nitride. Among the various fluorocarbons, this study focuses on C4F6 molecules (C4F6s) which are composed of hexafluorocyclobutene (c-C4F6), hexafluoro-1, 3-butadiene (1, 3-C4F6), and hexafluoro-2-butyne (2-C4F6). We have investigated the dissociation reactions of C4F6s, resulting in CF2, CF3, C2F3, and C3F3 fragments, by using the wB97X-D functional with various basis sets. In this presentation, the geometrical properties, energetics, and dissociation mechanisms of C4F6s will be suggested.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.197-199
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• 2006

The Proton Exchange Membrane Fuel Cells (PEMFCs) are being used in a variety of applications including portable power generation, transportation and back-up power systems. In this paper presents a novel circuit model for a PEMFC that can be used to design and analyze fuel-cell power system. The Pspice-based model uses BJTs, L and C elements available in the Pspice library with some modification. The model includes the phenomena like activation polarization, ohmic polarization and mass transport effect present in a PEM fuel cell. Simulated characteristics of the fuel cell were compared with the experimental results obtained on a commercial fuel cell.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권3호
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• pp.122-126
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• 2006

In this study, composite materials were put to dry interfacial treatment by use of plasma technology It has been presented that the optimum parameters for the best wettability of the samples at the time of generation of plasma were oxygen atmosphere, 0.1 Torr of system pressure, 100 W of discharge power, and 3 minutes of discharge time. The decrease in surface potential of charged samples by corona discharge indicates that the amount of accumulated electrical charges reduces and the charges that have been injected lessen rapidly when the duration of UV irradiation increases. The surface resistivity and the tensile strength of plasma treated samples, a longer UV irradiation time resulted in decreased insulation.

• 한국분말재료학회지
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• 제18권3호
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• pp.297-302
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• 2011

Colloidal stability is one of crucial factors for many applications of nanodiamond. Despite recent development, nanodiamonds available on the market often exhibit a high impurity content, wide size distribution of aggregates and low resistance to sedimentation. In the current study, four commercial nanodiamond powders synthesized by detonation synthesis were surface modified and then separated with respect to the size into six fractions by centrifugation. The fractions were evaluated by zeta potential, particle size distribution and elemental composition. The results showed that the modified nanodiamonds form stable colloidal suspensions without sedimentation for a long time.

• Communications for Statistical Applications and Methods
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• 제8권1호
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• pp.159-171
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• 2001

Shapiro and Wilk (1972) developed a test for exponentiality with origin and scale unknown. The procedure consists of comparing the generalized least squares estimate of scale with the estimate of scale given by the sample variance. However the test statistic is inconsistent ; that is, the power of the test will not approach 1 as the sample size increases. Hence we give a test based on the ratio of two asymptotically efficient estimates of scale. We also have conducted a power study to compare the test procedures, using Monte Carlo samples from a wide range of alternatives. It is found that the suggested statistics have higher power for the alternatives with the coefficient of variation greater that or equal to 1.