• Communications for Statistical Applications and Methods
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• v.21 no.5
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• pp.387-393
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• 2014

Recurrent gap times are analyzed with diverse methods under several assumptions such as a marginal model or a frailty model. Several resampling techniques have been recently suggested to estimate the covariate effect; however, these approaches can be applied with a time-fixed covariate. According to simulation results, these methods result in biased estimates for a time-varying covariate which is often observed in a longitudinal study. In this paper, we extend a resampling method by incorporating new weights and sampling scheme. Simulation studies are performed to compare the suggested method with previous resampling methods. The proposed method is applied to estimate the effect of an educational program on traffic conviction data where a program participation occurs in the middle of the study.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.5
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• pp.101-107
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• 2001

This paper deals with the free vibrations of horizontally curved beams with mu1tiple elastic springs. Taking into account the effects of rotatory Inertia and shear deformation. differential equations governing the free vibrations of such beams are derived, In which each e1astic spring is modeled as a discrete Winkler foundation with very short longitudinal length. Differential equations are solved numerically to calculate natural frequencies and mode shapes. In numerical examples, the circular, Parabolic. sinusoidal and elliptic curved beams are considered. The parametric studies are conducted and the lowest four frequency parameters are reported In tables and figures as the non-dimensional forms. Also the typical mode shapes are presented.

• Journal of Biomedical Engineering Research
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• v.28 no.1
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• pp.102-107
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• 2007

In molecular imaging studies via magnetic resonance imaging, in vivo cell tracking is an important issue for the observation of cell therapy or disease behavior. High resolution imaging and longitudinal study are necessary to track the cell movement. Since the field inhomogeneity extends over several voxels, we have performed the numerical analysis using the sub-voxel method dividing a voxel of MR image into several elements and the information about the field inhomogeneity distribution around the micro-beads. We imbedded ferrite-composite micro-beads with the size of $20-150{\mu}m$ in the subject substituted for cells to induce local field distortion. In the phantom imaging with the isotropic voxel size of $200{\mu}m^3$, we could confirm the feasibility of sub-voxel tracking in a 3.0 T MRI.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.415-418
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• 2011

It is critical to assess the characteristics of flame response to pressure perturbations for the understanding of nonlinear combustion instabilities. Previous studies can be grouped into flame response upon perturbed, fresh air and fuel mixture, and flame response directly perturbed from longitudinal waves. The present study presents experimental methodology for the understanding of the flame response exposed to transverse acoustic waves generated by loud speakers.

• Structural Engineering and Mechanics
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• v.53 no.3
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• pp.455-479
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• 2015

This paper presents a numerical analysis of reinforced concrete slabs under missile impact loading. The specimen used for the numerical simulation was tested by the Technical Research Center of Finland. LS-DYNA, commercial available software, is used to analyze the model. The structural components of the reinforced concrete slab, missile, and their contacts are fully modeled. Included in the analysis is material nonlinearity considering damage and failure. The results of analysis are then verified with other research results. Parametric studies with different longitudinal rebar ratios, shear bar ratios, and concrete strengths are conducted to investigate their influences on the punching behavior of slabs under the impact of a missile. Finally, efficient designs are recommended.

• Journal of Distribution Science
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• v.10 no.8
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• pp.35-43
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• 2012

This study is designed to collaboratively investigate the influences of the characteristics of Internet shopping malls and the shopping traits of their users involved in e-commerce on shopping intention. With this in mind, the researchers take a look at the influences of such features of shopping malls on the web as the quality of the system, customer-support service, shopping-mall perception and security, the users' propensity to pursue pleasure and pragmatic interest on shopping intention. The study shows that all the variables suggested here have an influence on the purchase intent of Internet shopping-mall users. That is, this study cannot analyze how the purchase intent of the customers with regard to the features of Internet shopping malls has changed. Therefore it is necessary to conduct procedural researches taking longitudinal studies into consideration.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.3
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• pp.254-260
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• 2002

There have been many studies for the flow through internally finned tube, since the heat exchangers with fin device derive much attention in heat transfer enhance cent. In this study, analysis of laminar flow through the circular tube with longitudinal fins are investigated. The height and the number of fins are arbitrary. The flow field is assumed to be laminar and conformal mapping is used to obtain analytic solution. From the analytic solution, equi-velocity lines are shown, and the flow rate through the finned tube is calculated for various fin heights and numbers of fins. Darcy friction factor for this finned tube and shear stress distributions on the wall and fin are also considered.

• Wind and Structures
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• v.8 no.2
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• pp.135-146
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• 2005

Divergent galloping-like motion of a dry inclined cable has been observed in a limited number of experimental studies, which, due to the uncertainties in its onset conditions, has induced serious concerns in the bridge stay cable design. A series of dynamic and static model wind tunnel tests have been carried out to confirm the existence of the phenomenon and clarify its excitation mechanism. The present paper focuses on exploring the spatial flow structure around an inclined cable. The pattern of resultant aerodynamic forces acting at different longitudinal locations of the model and the spatial correlation of the forces are examined. The results lead one step closer in revealing the physical nature of the phenomenon.

• Transactions of the Korean hydrogen and new energy society
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• v.11 no.3
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• pp.127-136
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• 2000

Molecular dynamics simulations have been carried out to investigate the scattering and penetration properties of hydrogen ions with the normal incident angle to Ni (100) surface. The initial kinetic energies of hydrogen ions range from 100 to 1,600 eV. The simulation results are used to assess the applicabilities of theoretical predictions based on the binary collision approximation, and, in the high kinetic regime, theoretical results for scattering energies were shown to he a good agreement with molecular simulations. The angle dependencies on both scattering and penetration distributions were found in the longitudinal direction, but not in the azimuthal direction except for the high kinetic energy of 1,600 eV.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.250-253
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• 2006

This paper presents experimental studies on investigating the seismic retrofit performance of reinforced concrete circular columns with poor lap-splice details using GFRP wrapping. Four 1/2 scale-down model columns have been tested. The as-built column is expected to suffer brittle failure due to the bond failure of lap-spliced longitudinal reinforcement. The retrofitted columns using GFRP wrapping showed significant improvement of seismic performance.