• Proceedings of the KSME Conference
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• 2002.08a
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• pp.173-176
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• 2002

The purpose of this study is to develop a tool for the analysis of the cavitating flow around trans-cavitating marine propellers. In this study, a linearized super-cavitation theory was applied in order to analyze the performance of the 2-dimensional foils. The numerical results correlated very well with experimental data. The trans-cavitating propellers, manufactured and tasted in KRISO, is selected to validate the lifting surface procedure. For a TCP with a Johnson's five term section, the comparison between the numerical prediction and experiments is fairly good and promising. The new lifting surface procedure, developed and validated with 2-D foils and a TCP, is generally considered applicable to the practical design of the trans-cavitating propeller with Johnson's five term section

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.1 s.244
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• pp.41-47
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• 2006

High resolution dopant profiling in semiconductor devices has been an intense research topic because of its practical importance in semiconductor industry. Although several techniques have already been developed. it still requires very expensive tools to achieve nanometer scale resolution. In this study we demonstrated a novel dopant profiling technique with nanometer resolution using very simple setup. The newly developed technique measures the thermoelectric voltage generated in the contact point of the SPM probe tip and MOSFET surface instead of electrical signals widely adopted in previous techniques like Scanning Capacitance Microscopy. The spatial resolution of our measurement technique is limited by the size of contact size between SPM probe tip and MOSFET surface and is estimated to be about 10 nm in this experiment.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.1
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• pp.58-66
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• 2007

Genetic Algorithms (GA) have some difficulties in practical applications because of too many function evaluations. To overcome these limitations, an approximated modeling method such as Response Surface Modeling(RSM) is coupled to GAs. Original RSM method predicts linear or convex problems well but it is not good for highly nonlinear problems cause of the average effect of the least square method(LSM). So the locally approximated methods. so called as moving least squares method(MLSM) have been used to reduce the error of LSM. In this study, the efficient evolutionary GAs tightly coupled with RSM with MLSM are constructed and then a 2-dimensional inviscid airfoil shape optimization is performed to show its efficiency.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.209-214
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• 2003

This study presents the analysis of ball end milling machinability and its application to the determination of the optimum feedrate in the CNC machining process of sculptured surface. The methods which estimate the cutting force system is approached experimentally. The estimation strategy, named technological processor, was applied to the machining process of sculptured surface for finding optimum variable feedrate. From the result of practical implementation for the test model, it is ascertain that the technological processor have brought the dispersion of force profiles. As compared with conventional imposing of cutting conditions, the machining time has reduced by more than 60%.

• Journal of Ship and Ocean Technology
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• v.8 no.2
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• pp.13-19
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• 2004

Jet flows applied tangential to a foil surface near the leading and/or trailing edges increase the lift of the foil by delaying the separation also known as the Coanda effects. Many experimental and numerical studies have proven the effectiveness of Coanda effects on circulation control and the effects have been found to be useful in practical application in many aerodynamics fields. Most of the previous works have studied the effects of the jet blowing near the trailing edges and investigated the influence of jet momentum on lift. A few experimental studies, however, focused on the separation bubble that develops near the leading edge and applied jet flow the edge to remove the bubble but only to find decrease in lift. In the present paper, a Coanda foil of 20% thickness ellipse with modified rounded leading and trailing edges was investigated, and the flow around the foil was numerically studied. The blowing around the leading edge only decreased the lift, as the experiments showed, but the suction considerably increased the lift.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.12
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• pp.1253-1258
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• 2013

Ceramic particles as polishing abrasives are often used in a magnetic abrasive polishing process because they have strong wear resistance. Non-ferromagnetic ceramic abrasives should be mixed with ferromagnetic iron particles for controlling the mixture within a magnetic brush during the polishing process. This study describes the application of the ceramic particles for the magnetic abrasive polishing. The distribution of the magnetic abrasives attached on a tool varies with magnetic flux density and tool rotational speed. From the correlation between abrasive adhesion ratio in the tool and surface roughness produced on a workpiece, practical polishing conditions can be determined. A step-over for polishing a large sized workpiece is able to be selected by a S curve, and an ultrasonic vibration assisted MAP produces a better surface roughness and increases a polishing efficiency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.177-182
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• 2004

Electronic products are subjected to many different types of shock environment. As the Optical Disc Drive (ODD) market grows, the number of failures related to shock increases. Therefore, it is necessary to improve the performance of cushion package as well as the product design. Cushion materials such as expanded polystyrene are often used to protect electronic products from shock environment. In this paper, the drop analysis of the cushion package f3r optical disc drives was carried out with the explicit method of LS-DYNA and verified by the drop test. For the optimization of package, response surface approximation model was created using central composite design. As a result, cushioning performance was improved under the critical condition and practical design guidelines of cushion package were suggested.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.168-175
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• 2006

This paper presents surface matching algorithms that can be used to reconstruct the surface topography of an object scanned by an AFM. The essence of the algorithms is to match up neighboring images intentionally overlapped with others. Two performance indexes using the correlation coefficient and the sum of the squared differences are introduced. To compensate for the inaccuracy of the coarse stage implemented to AFM, all the six axes including the rotational degrees of freedom are successively matched so as to maximize the coefficients defined. The results show that the proposed algorithms are useful for measurement range extension of AFM. The results also show that a combined use of the two indexes is beneficial for practical cases.

• Journal of Ocean Engineering and Technology
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• v.11 no.1
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• pp.74-83
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• 1997

This study is to develop a practical calculation method of hydrodynamic force and motion response on very large floating structures of multiple legs. To investigate the effecr of hydrodynamic interfaction and of free surface on the reaponses of very large floating structures in regular waves, four kind of models are considered, ie. 1, 4, 64, 21248 column with footing. Based upon the results of this study, it is found that the middle parts of very large floating structures have small diffration effects. Therefore only out side parts are used to determine the hydrodynamic forcea for taking into account the effects of interaction.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2145-2149
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• 2007

This paper deals with optimum design criteria to minimize the torque ripple of a concentrated winding Synchronous Reluctance Motor (SynRM) using Response Surface Methodology (RSM). The feasibility of using RSM with the finite element method (FEM) in practical engineering problem is investigated with computational examples and comparison between the fitted response and the results obtained from an analytical solution according to the design variables of stator and rotor in concentrated winding SynRM (6slot).