• 한국데이터정보과학회:학술대회논문집
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• 2005.04a
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• pp.155-163
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• 2005

This paper applies Support Vector Regression (SVR) to estimate and forecast nonlinear autoregressive integrated (ARI) model of the daily exchange rates of four currencies (Swiss Francs, Indian Rupees, South Korean Won and Philippines Pesos) against U.S. dollar. The forecasting abilities of SVR are compared with linear ARI model which is estimated by OLS. Sensitivity of SVR results are also examined to kernel type and other free parameters. Empirical findings are in favor of SVR. SVR method forecasts exchange rate level better than linear ARI model and also has superior ability in forecasting the exchange rates direction in short test phase but has similar performance with OLS when forecasting the turning points in long test phase.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.42-48
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• 2004

Numerical simulation of viscous compressible flow in turbomachinery cascade involves many problems due to the complex geometry of blade but also flow phenomena. In the present study, numerical investigations have been performed to examine the three-dimensional flow characteristics inside the transonic linear turbine cascades using a commercial code, FLUENT. Multi-block H-type grids are applied to the high-turning turbine rotor blades and comparisons with the experimental data and the numerical results have been done. In addition, the effects of turbulence models on the prediction of the endwall flows are analyzed in the sense of the flow compressibility.

• Korean Institute of Interior Design Journal
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• v.14 no.5 s.52
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• pp.123-132
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• 2005

The 21th century is rapidly turning to the era of supernational competition aimed at global customers. Under these circumstances, applying the value innovation to space which will be in charge of value creation is recognized as being essential to life. This study aims to newly define the conception, the viewpoint, and types on applying the value innovation to space, which has not been established logically yet. The purpose of analyzing cases where the innovation was applied at home and abroad is to provide basic logic to establish these concepts in real space design. This study is prospected to be the core strategy of growth cause for maintaining our industrial development, so it is suggested that accepting, widening, and developing it may enable us to prepare for the continued innovation to space.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.523-525
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• 2008

Novel zero-voltage switching(ZVS) dual inductor-fed DC-DC converter integrating a conventional dual inductor-fed boost converter(DIFBC) and a parallel bidirectional boost converter has been proposed. Most of current-fed type boost topologies including dual inductor schemes have crucial defects such as a high voltage spike on the main switch when it comes to turning off, an unattainable soft start-up due to the limited range of duty ratio, above 50%, and considerable switching losses due to the hard switching. By adding two auxiliary switches and an output capacitor on the conventional DIFBC, the proposed circuit can solve mentioned problems and improve the efficiency with simple methods. The operational principle and theoretical analysis of the proposed converter have been included. Experimental results based on a 42V input, 400V/1A output and 50kHz prototype are shown to verify the proposed scheme.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.122-128
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• 2013

This paper describes the on-machine surface form evaluation of an ultra-precision cylinder for the fabrication by the compensation process. In this study, the surface form error of an ultra-precision cylinder, which was fabricated by the ultra-precision diamond turning machine with a single diamond cutting tool, was evaluated by using two capacitance-type displacement probes. Based on the measurement results, the compensation process was conducted. Since the measurement was carried out on the machine without re-mounting of the workpiece, additional fabrication for compensation process can be conducted precisely.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1203-1206
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• 2003

After the micro turning lathe was developed in the last year by AMR Laboratory, a micro-milling machine is developed for micro machining. This machine is integrated with PZT-driven micro-sliders, micro-linear encoders, air turbine spindle which has maximum 150.000 rpm. It is applicable to milling and drilling machining. This paper shows the possibility of micro machining and characteristics of micro end milling process by using micro machine. A machining of micro barrier ribs using 0.2 mm flat type end mill was achieved by micro-milling machine. As experimental results show the machining capability and positional accuracy of this machine is good enough for machining micro parts.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.3
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• pp.53-60
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• 1992

This paper deals with developing an Expert system for tool selection using knowledge base system approach, and its application. For the sake of building of knowledge base, the information from process through sensor, tool handbook and interview with expert are referrenced and managed. The system developed shows good application flexibility in providing the actual cutting process with the selection of tool(insert, holder) and cutting conditions(feed, speed, rake type, and so on), is found as a useful system for real-time machining process. The Expert system for tool selection is written in TURBO PROLOG ver. 2.0 for inference engine capability, and can be run in interactive mode for user friendliness. In order to apply the system developed in actual cutting process, more parameters should be considered and scrutinized, and the system should be further extended in modular basis.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.8
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• pp.115-121
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• 1997

The in-process detection of the tool wear is one of the most important technologies in completely auto- matic operation of machine tool. In this research, using the tools having flank wear, the dynamic compo- nent of cutting forces is considered to be available for identifying the cutting process. In order to investi- gate this relation in detail, the cutting forces in turning of workpiece made of aluminum were measured by dynamometer of piezoelectric type, and the dynamic components of cutting force were analyzed. The fre- quency analysis, probability density analysis and RMS analysis of the dynamic components were carried out independently. Through the experiments, the characteristics of the tool system have a large effect on the dynamic component of cutting forces. As a result, it is shown that the dynamic cutting force was able to detect flank wear accurately.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.523-528
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• 2000

In this paper, the new type biped walking robot which is composed of the minimum number or links just for walking and its appropriate gaits are proposed. The proposed new gaits for this robot are four-crossing, crawling, standing and turning gait. In designing the biped robot we propose the Performance Index which means the needed torque per a moving distance and generate foot trajectories by $3^{rd}$ order spline Interpolation. Among those, numerically we find the optimal conditions which minimize the Performance Index. Dynamically stable walking of the biped robot is realized by satisfying the stability condition of ZMP(zero moment point), which is related to maintaining the ZMP within the region of the supporting foot during the s1n91e leg support phase. We determine the region of mass center from the stability condition of ZMP and plan references which track the mass conte. trajectory of constant velocity. Finally we implement the gaits statically tracking the planned trajectories using PD control method.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.40-45
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• 1999

The demands for robotic and automatic system are continually increasing in manufacturing fields. There have been many studies to monitor and predict the system, but they have mainly focused upon measuring cutting force, and current of motor spindle, and upon using acoustic sensor, etc.In this study, time series sequence of cutting force was acquired by taking advantage of piezoelectric type tool dynamometer. Radial cutting force was obtained from it and was available for useful observation data. The parameter was estimated using PAA (parameter adaptation algorithm) from observation data. ARMA(auto regressive moving average) model was selected for system model and second order was decided according to parameter estimation. Uncorrelation test was also carried out to verify convergence of parameter.