• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.11
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• pp.1019-1025
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• 2004

The X-band 10${\times}$10 waveguide slot array antenna for SAR is designed, fabricated and measured. The array antenna is designed using the equivalent circuit model based on the field distribution of the dominant mode, TE$\sub$10/, and EM simulation. The method to decide optimum angle of the centered inclined slot(coupling slot) and the optimum of offset of the longitudinal slot(radiating slot) is provided. The designed antenna structure is EM simulated and fabricated. The measured return loss bandwidth is 180 MHz at 9.15 GHz , the side lobe level is below -25 dB, HPBW is about 9$^{\circ}$, and the gain is 25.5 dB. These results are similar to the simulation data.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.4
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• pp.439-449
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• 2002

Experimental investigations of the flow structure and heat transfer enhancement in a channel with a built-in circular cylinder and a wing-let type vortex generator are presented. Without any vortex generators, relatively low heat transfer takes place in the downstream of the circular cylinder where is a recirculation region with low velocity fluid is formed. However with a wing-let type longitudinal vortex generator in the wake region behind the cylinder, heat transfer in the region can be enhanced. In order to control the strength of longitudinal vortices, the angle of attack of the vortex generators is varied from $20^{circ} to 45^{\circ}$, but spacings between the vortex generations are fixed to be 5 mm. The 3-dimensional mean velocity field downstream of the vortex generator is measured by a five-hole pressure probe, and the hue-capturing method using thermochromatic liquid crystals has been used to provide the local distribution of the heat transfer coefficient. The vorticity field and streamwise velocity contour are obtained from the velocity field. Streamwise distributions of averaged Stanton number on the measurement planes show very similar trends for all the experimental cases($\beta=20^{circ}, 30^{circ} and 45^{\circ}$). Circulation strength and heat transfer coefficient have the maximum values when the angle of attack($\beta$) is $30^{\circ}$.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.2
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• pp.149-154
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• 2004

Results of a numerical simulation of a flowing of the underwater vehicles hull with the pump-jet nozzle are presented. It was calculate velocity distributions coefficients of the lift force the longitudinal moment of the hull with the pump-jet nozzle and isolated hull for some values of angle of attack. It was shown that the area of the influence of the nozzle on the velocities distribution of the hull and character of changing of coefficients of the lift force and the longitudinal moment and their derivatives depending on angle of attack.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.731-740
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• 1998

Orthogonally stiffened steel plates are used for orthotropic steel decks of long-span bridges because of high degree of flexural and torsional resistances and good load-distribution behavior. An analytic study is presented for evaluating the buckling strength of orthogonally stiffened plates subjected to uniaxial compression. By using the plate theory, the buckling stress under overall and partial buckling modes, is derived. Parametric studies are performed to show the effects of the stiffness and the number of transverse and longitudinal ribs on the buckling strength. The results show quantitatively strong influence of stiffness and spacing of longitudinal and transverse ribs.

• Journal of Welding and Joining
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• v.4 no.2
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• pp.30-39
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• 1986

In manufacturing of pipe walls for boiler units, distortion can result in pipe-web-pipe joints from the nonuniform expansion and contraction of the weld metal and the adjacent base metal during heating and cooling cycle of the welding process. In this study, the stresses and strains during longitudinal welding of the plate-to-pipe joint were investigated. Using the method of successive elastic solution, longitudinal stresses and strains during and after welding were calculated from the information of temperature distributions obtained by Rosenthal's equations. In order to confirm the validity of the numerical results, the temperature and residual stress distributions were measured and compared with the calculated results. In spite of some assumptions, the one-dimensional analytical results of residual stresses were in fairly good agreement with the experimental ones. The residual stresses due to welding of plate-to-pipe joints are tensile near the weld line and compressive in the base metal as in the welding of plates. the amount and distribution of residual stresses were deeply dependent on the heat input ratio of the plate and pipe.

• The Korean Journal of Applied Statistics
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• v.28 no.6
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• pp.1121-1131
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• 2015

Logistic models with a random intercept are useful to analyze longitudinal binary data. Traditionally, the random intercept of the logistic model is assumed to be parametric (such as normal distribution) and is also assumed to be independent to variables. Such assumptions are very strong and restricted for application to real data. Recently, Garcia and Ma (2015) derived semiparametric efficient estimators for logistic model with a random intercept without these assumptions. Their estimator shows the consistency where we do not assume any parametric form for the random intercept. In addition, the method is computationally simple. In this paper, we apply this method to analyze toenail infection data. We compare the semiparametric estimator with maximum likelihood estimator, penalized quasi-likelihood estimator and hierarchical generalized linear estimator.

• Journal of Mechanical Science and Technology
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• v.16 no.9
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• pp.1054-1064
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• 2002

Numerical prediction of welding-induced residual stresses using the finite element method has been a common practice in the development or refinement of welded product designs. Various researchers have studied several thermal models associated with the welding process. Among these thermal models, ramp heat input and double-ellipsoid moving source have been investigated. These heat-source models predict the temperature fields and history with or without accuracy. However, these models can predict the thermal characteristics of the welding process that influence the formation of the inherent plastic strains, which ultimately determines the final state of residual stresses in the weldment. The magnitude and distribution of residual stresses are compared. Although the two models predict similar magnitude of the longitudinal stress, the double-ellipsoid moving source model predicts wider tensile stress zones than the other one. And, both the ramp heating and moving source models predict the stress results in reasonable agreement with the experimental data.

• Journal of Korean Society of Disaster and Security
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• v.8 no.1
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• pp.29-37
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• 2015

This study is concerned with the estimation of fluctuation wind velocity spectrum and turbulence characteristics in the major cities reflecting the recent meteorological with typhoon wind velocity about 2003 (Maemi) 2010 (Kompasu) 2012 (Tembin). The purpose of this paper is to present spectral analysis for longitudinal component fluctuating velocity. In the processes of analysis, the longitudinal velocity spectrums are compared widely used spectrum models with horizontal wind velocity observations data obtained at Korea Meteorological Adminstration (KMA) and properties of the atmospheric air for typhoon fluctuating wind data are estimated to parameters with turbulency intensity, shear velocity and roughness length.

• The Journal of the Acoustical Society of Korea
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• v.22 no.1
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• pp.78-87
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• 2003

High-frequency (126-㎑) bottom backscattering measurements with various bottom types were conducted at the water tank in Ocean Acoustic Laboratory, Hanyang University. For the purpose of investigating the energy distribution of bottom scattering with various bottom types, the sediment was varied with gravel, sand, sandy mud and mixed bottoms. To examine the anisotropic nature of the scattering due to the orientations of bottom ripple, the footprints were made transverse and longitudinal to the direction of incident wave. The total scattering characteristics are that the larger grazing angles the larger backscattering strengths become and backscattering strengths for a transverse ripple case are higher than those of longitudinal ripple case. finally, the variations of scattering strength depend mainly on the ripple's orientation.

• Journal of Oral Medicine and Pain
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• v.39 no.3
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• pp.107-114
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• 2014

Purpose: This study want to draw conclusion based on data taken from national health insurance and determined the distribution and direction of patients treated at private clinics. Methods: The author's research spanned and compared the nationally insured patients by sexes, diagnoses, age groups and cases per year (2005, 2009, and 2013). Subjects were 3,536 patients of a private clinic in Seoul that were covered under national insurance. Results: There was no disparity across sexes nor cases, but both were on the decline. The most common dental conditions were pulpitis and dental caries at 38.4% and 16.4%, respectively. Both have decreased. Despite a drop in overall patients, the percentage of patients under 10 years old jumped substantially. Of overall age groups, teens were most prevalent at 33.5%, second and third being those in their forties and fifties (14.2% and 12.0%, respectively). Conclusions: The major illnesses that plague patients are pulpitis, dental caries, eruption disorder, gingivitis and periodontitis: the wane of pulpitis cases (a considerable percentage) and the actual numbers of patients has contributed to the general decrease in cases.