• Atmosphere
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• v.26 no.1
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• pp.127-140
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• 2016

In this study, the correlations between AST850 and precipitation, and those between WDT and precipitation in the Yeongdong coastal region under the direct/indirect influence of the expansion of cP (continental polar air mass) high were quantitatively analyzed based on the winter season data for the last 20 years, according to surface pressure patterns such as Type 1 (cP high expansion type), Type 2 (cP high expansion + trough type), Type 4 (South trough type), and Type 5 (East Sea trough type). Here, AST850 represents 'sea surface temperature minus temperature on 850 hPa level' and WDT represents 'a speed of 1000 hPa wind projected onto a certain wind direction times precipitation duration in hour'. First, the correlation coefficients between AST850 and precipitation in Type 1, Type 2, and Type 5 cases were 0.253, 0.384, and 0.398 respectively, indicating that a tendency of increasing precipitation linearly with the value of AST850 is slightly presented. In the case of Type 4, however, the coefficient was -0.15, representing almost no linear correlation between AST850 and precipitation. In the correlation between WDT and precipitation, there was the largest correlation coefficient (0.464) between WDT along a direction of $90^{\circ}$ and at EN1 in Type 1 cases. In the case of Type 2, there was the largest correlation coefficient (0.767) between WDT along a direction of $67.5^{\circ}$ and at ES1. In the case of Type 4, there was the largest correlation coefficient (0.559) between WDT along a direction of $22.5^{\circ}$ and at EN2. Finally, in the case of Type 5, there was the largest correlation coefficient (0.945) between WDT along a direction of $315^{\circ}$ and at SE1, representing the largest coefficient among the types. It was found that surface wind directions with the highest correlations to precipitation in the Yeongdong coastal area on winter season were varied according to surface pressure patterns, and that the correlations between WDT and precipitation were higher than those between AST850 and precipitation.

• Journal of Ocean Engineering and Technology
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• v.29 no.1
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• pp.1-8
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• 2015

An analytical model of liquid sloshing is developed to consider the energy-loss effect through a partially submerged porous baffle in a horizontally oscillating rectangular tank. The nonlinear boundary condition at the porous baffle is derived to accurately capture both the added inertia effects and the energy-loss effects from an equivalent non-linear drag law. Using the eigenfunction expansion method, the horizontal hydrodynamic force (added mass, damping coefficient) on both the wall and baffle induced by the fluid motion is assessed for various combinations of porosity, submergence depth, and the tank's motion amplitude. It is found that a negative value for the added mass and a sharp peak in the damping curve occur near the resonant frequencies. In particular, the hydrodynamic force and free surface amplitude can be largely reduced by installing the proper porous baffle in a tank. The optimal porosity of a porous baffle is near P=0.1.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.5
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• pp.337-345
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• 2003

In the case of heat exchangers operating under frosting condition, the growth of frost layer causes the heat exchanger to increase the thermal resistance and pressure loss of the air flow. In this paper, a transient characteristic prediction model of the heat transfer for multi inverter heat pump with frosting on its surface was presented taking into account the change of the fin efficiency due to the growth of the frost layer. In this dynamic simulation program, which was peformed for a basic air conditioning system model, such as evaporator, condenser, compressor, linear electronic expansion valve (LEV) and bypass circuit. The theoretical model was driven from the obtained heat transfer coefficient and mass transfer coefficient, independently. And we consider heat transfer performance was only affected by a decrease of the wind flow area. The calculated results were compared with some cases of experiments for frosting conditions.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.3
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• pp.183-187
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• 2016

Recently, power demand has been increasing every year according to variation of electrical equipments and temperature rise in summer season. So, much more overhead line is being demanded to copy with increasing power demand and operate reliable power system. This paper analysis the characteristics of long span overhead transmission line using special high-tension wire in such as a safety factor, coefficient of elasticity, and the coefficient of linear expansion. Based on the analysis, we proposed the effectiveness of special high-tension wire having much more advantages with respect to height of steel tower and dip compared with conventional ACSR in long span overhead transmission line.

• Composites Research
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• v.26 no.1
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• pp.60-65
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• 2013

A nanolaminate consisting of alternate layers of aluminium oxide ($Al_2O_3$) (5 nm) and zirconium oxide ($ZrO_2$) (20 nm) was deposited at an optimized oxygen partial pressure of $3{\times}10^{-2}$ mbar by pulsed laser deposition. The nanolaminate film was analysed using high temperature X-ray diffraction (HTXRD) to study phase transition and thermal expansion behaviour. The surface morphology was investigated using field emission scanning electron microscopy (FE-SEM). High temperature X-ray diffraction indicated the crystallization temperature of tetragonal zirconia in the $Al_2O_3/ZrO_2$ multilayer-film was 873 K. The mean linear thermal expansion coefficient of tetragonal $ZrO_2$ was $4.7{\times}10^{-6}\;K^{-1}$ along a axis, while it was $13.68{\times}10^{-6}\;K{-1}$ along c axis in the temperature range 873-1373 K. The alumina was in amorphous nature. The FESEM studies showed the formation of uniform crystallites of zirconia with dense surface.

• Progress in Superconductivity and Cryogenics
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• v.14 no.4
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• pp.24-27
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• 2012

The measurement of the coefficient of thermal expansion (CTE) of polypropylene laminated paper (PPLP) as electric insulating material is important for its practical superconducting device application. The thermal strain induced to HTS tapes and its insulating material during cooling from room temperature might largely affect the critical current ($I_c$) of HTS tapes. In this study, the thermal contraction of PPLP material was measured during cooling from 300 K to 77 K using double extensometers. Initially, the CTE of a brass tape was measured and it was compared with a reference data. It was found that the measured thermal expansion data of the brass material approaches that of the reference one. Based on the results, it was then confirmed that the measurement technique could be applied to thin and flexible samples. Therefore, the same measurement procedure was applied to PPLP material using double extensometers. As a result, the linear CTE of the PPLP at 77 K has been measured to be ${\sim}15.3{\times}10^{-6}/K$. Also, it was found that the thermal contraction characteristics of PPLP was dominated by polypropylene on the cross direction (higher thermal contraction) while it was dominated by Kraft paper on the machine direction (lower thermal contraction). Overall, this measurement procedure could be adopted for the determination of CTE of flexible materials such as PPLP.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.2
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• pp.387-413
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• 1998

Image resampling is of particular interest in digital radiology. When resampling an image to a new set of coordinate, there appears blocking artifacts and image changes. To enhance image quality, interpolation algorithms have been used. Resampling is used to increase the number of points in an image to improve its appearance for display. The process of interpolation is fitting a continuous function to the discrete points in the digital image. The purpose of this study was to determine the effects of the seven interpolation functions when image resampling in digital periapical images. The images were obtained by Digora, CDR and scanning of Ektaspeed plus periapical radiograms on the dry skull and human subject. The subjects were exposed to intraoral X-ray machine at 60kVp and 70 kVp with exposure time varying between 0.01 and 0.50 second. To determine which interpolation method would provide the better image, seven functions were compared; (1) nearest neighbor (2) linear (3) non-linear (4) facet model (5) cubic convolution (6) cubic spline (7) gray segment expansion. And resampled images were compared in terms of SNR(Signal to Noise Ratio) and MTF(Modulation Transfer Function) coefficient value. The obtained results were as follows ; 1. The highest SNR value(75.96dB) was obtained with cubic convolution method and the lowest SNR value(72.44dB) was obtained with facet model method among seven interpolation methods. 2. There were significant differences of SNR values among CDR, Digora and film scan(P<0.05). 3. There were significant differences of SNR values between 60kVp and 70kVp in seven interpolation methods. There were significant differences of SNR values between facet model method and those of the other methods at 60kVp(P<0.05), but there were not significant differences of SNR values among seven interpolation methods at 70kVp(P>0.05). 4. There were significant differences of MTF coefficient values between linear interpolation method and the other six interpolation methods (P< 0.05). 5. The speed of computation time was the fastest with nearest -neighbor method and the slowest with non-linear method. 6. The better image was obtained with cubic convolution, cubic spline and gray segment method in ROC analysis. 7. The better sharpness of edge was obtained with gray segment expansion method among seven interpolation methods.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.04a
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• pp.37-46
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• 1998

Several researchers have developed a number of theoretical time factors to determine the coefficient of consolidation by biezocone excess pore water dissipation test in soft clay deposits. However, depending on the assumptions and analytical techniques, the estimated coefficient of consolidation could be in a considerably wide range even for a specific degree of consolidation. These solutions are obtained from an initial excess porewater pressure distribution which can be determined from. either the cavity expansion theory or the strain path method. The 야ssipation of the initial excess porelvater pressure has been usally simulated by means of linear-uncoupled consolidation analysis and then the dissipation curve is normalized by the initial excess porewater pressure for easy use. However. since there is no guidelines or rules on which method gives the best solution for obtaining the coefficient of consolidation from the dissipation curve, the final selection was only based on engineer's extrience and Judgements. Thus, such an arbitrary selection might be inappropriate for a specific site to characterize the consolidation behavior. In this paper, we reviewed various theoretical time factors and, based on this consideration, we mentioned needs for researches in selecting a specific solution that is compatible for Korean clays. Also we listed some source of errors that can be encountered in the procedure of dissipation analysis.

• Journal of Environmental Science International
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• v.8 no.4
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• pp.431-441
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• 1999

In this study, the regional frequency analysis is used to determine each subbasin drought frequency with reliable monthly precipitation and the L-Moments method which is almost unbiased and has very nearly a normal distribution is used for the parameter estimation of monthly precipitation time series in Nakdong river basin. As the result of this study, the duration of '93-'94 is most severe drought year than any other water year and the drought frequency is established as compared the regional frequency analysis result of cumulative precipitation of 12th duration months in each subbasin with that of 12th duration months in the major drought duration. The Linear regression equation is induced according to linear regression analysis of drought frequency between Nakdong total basin and each subbasin of the same drought duration. Therefore, as the foundation of this study, it can be applied proposed method and procedure of this study to the water budget analysis considering safety standards for the design of impounding facilities large-scale river basin and for this purpose, above all, it is considered that expansion of reliable preciptation data is needed in watershed rainfall station.

• Steel and Composite Structures
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• v.47 no.6
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• pp.693-707
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• 2023

This article investigates the static thermo-mechanical response of anisotropic thick laminated composite plates on Visco-Pasternak foundations under various thermal load conditions (linear, non-linear, and uniform) along the transverse direction (thickness) of the plate, while keeping the mechanical load constant. The governing equations, which represent the thermo-mechanical behavior of the composite plate, are derived from the principle of virtual displacements. Using Navier's type solution, these equations are solved for the composite plate with simply supported condition. The Visco-Pasternak foundation type is included by considering the impact of the damping on the classical foundation model, which is modeled by Winkler's linear modulus and Pasternak's shear modulus. The excellent accuracy of the present solution is confirmed by comparing the results with those available in the literature. The study investigates the impact of geometric ratios, thermal expansion coefficient ratio, damping coefficient and foundation parameters on the thermo-mechanical flexural response of the composite plate. Overall, this article provides insights into the behavior of composite plates on visco-Pasternak foundations and may be useful for designing and analyzing composite structures in practical applications.