• Communications for Statistical Applications and Methods
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• v.11 no.2
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• pp.313-321
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• 2004

In this article we show that the tests of Robinson (1994) may have serious problems in distinguishing between fractionally integrated processes in the context of deterministic trends. The results are obtained via Monte Carlo experiments. A simple procedure, based on the t-values of the coefficients from the differenced regression, is presented to correctly specify the time series of interest and, an empirical application, using data of the US GNP is also carried out at the end of the article.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.105-106
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• 2003

The spectral eddy viscosity model is investigated through the large eddy simulation of the decaying and forced isotropic turbulence. It is shown that the widely accepted 'plateau and cusp' model overpredicts resolved kinetic energy due to the amplification of energy at intermediate wavenumbers. Whereas, the simple plateau model reproduces a correct energy spectrum. This result overshadows a priori tests based on the filtered DNS or experimental data. An alternative method for the validation of subgrid-scale model is discussed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.65-71
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• 1998

The superplastic deformation behaviors of 7075Al alloy have been characterized experimentally and analyzed by the internal variable theory of inelastic deformation. A simple rheological model including the grain boundary sliding has been used to interpret the superplastic deformation behaviors. A series of load relaxation and tensile tests have been carried out for 7075Al alloy at the various temperatures. The superplastic deformation of 7075Al alloy is confirmed to consist of the grain boundary sliding and accommodating grain matrix defprmation.

• Journal of the Korean Society of Safety
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• v.10 no.1
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• pp.41-49
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• 1995

A potable oil skimmer is in need to remove spilt oils before they spread, which is applicable to various situations of oil viscosity, spill location, current, tides, waves and wind. An air suction skimmer was selected to be developed because of its advantages such as simple structure, excellent transportability, and easy deployment. A prototype operating by a commercial vacuum cleaner was fabricated. Tests of the skimmer showed good performance : the maximum suction rate of water and suction head were 18㎥/h and 2.7m, respectively.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.10a
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• pp.178-184
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• 1995

A new combined isotropic/kinematic and orthotropic hardening viscoplastic model is proposed which can account for not only differential orientations but also preferred orientations of grains in n metal at finite plastic deformations with an introduction of multiple spin (rate of rotation) concept within the general framework of the model, the effects of anisotropy and constitutive spins will be discussed in conjunction with a closed-form solution for simple shear in n rigid-plastic material, which will be used to simulate experimental data of Montheillet, et al. (1984) for fixed-end tortion tests at finite plastic deformations.

• Journal of the Korean Data and Information Science Society
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• v.16 no.2
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• pp.227-236
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• 2005

A chi-squared test of spherical symmetry is suggested. This test is easy to apply in practice since it is easy to compute and has a limiting chi-squared distribution under spherical symmetry. The result of Park(1998) can be used to show that it has the limiting chi-squared distribution. A simulation study is conducted to study the accuracy, in finite samples, of the limiting distribution. Finally, a simulation study that compares the power of our test with those of other tests of spherical symmetry is performed.

• Journal of the Korean Data and Information Science Society
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• v.15 no.2
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• pp.423-430
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• 2004

We provide the exact form of a Rao-Robson version of the chi-squared test of multivariate normality suggested by Park(2001). This test is easy to apply in practice since it is easily computed and has a limiting chi-squared distribution under multivariate normality. A self-contained formal argument is provided that it has the limiting chi-squared distribution. A simulation study is provided to study the accuracy, in finite samples, of the limiting distribution. Finally, a simulation study in a nonnormal distribution is conducted in order to compare the power of our test with those of other popular normality tests.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.407-414
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• 2000

Recently the geogrids are being used in some large projects such as Inchon International Airport construction, highway construction, and Korean High-Speed Railway construction with not only the merit of simple construction but also reinforcing efficiency for the soft ground. Main function of roadbed is to provide a stable foundation in terms of bearing capacity and settlement for the subballast and ballsat layers. Differential settlement of the railroad should be avoided. The cyclic laboratory model tests were performed to investigate the settlement behavior of geogrid reinforced railroadbed. The ratio of settlement of roadbed under cyclic loading with three layers of geogrid reinforced is less than 1/2 of the roadbed thickness without reinforcement.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.101.1-101.1
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• 2012

Building a relativistic magnetohydrodynamic (RMHD) code based on upwind schemes has been a challenging project, because of the absence of analytic expressions of eigenvalues and eigenvectors. We found analytic expressions of eigenvalues and eigenvectors for adiabatic RMHD flows which are relatively simple and manageable. Especially, our eigenvectors can handle all degenerate points. Using these analytic forms, we built a code based on the total variation diminishing (TVD) scheme, and successfully performed one-dimensional shock tube tests.

• Proceedings of the KIEE Conference
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• summer
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• pp.1022-1024
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• 2004

This paper presents a design and characteristics analysis of an SRM drive for EPS application. A rack mounted EPS system is considered in this paper. In the unrestricted design conditions, motor parameters are determined for sufficient torque and speed with some restrictions. For the smooth torque generation and simple circuit of power system, 12/8 motor drive is considered. With FEM and magnetic circuit analysis, redesigned motor is simulated to meet the requirement of specifications. Effectiveness of the suggested SRM drive for EPS application is verified by redesigned motor drive tests.