• Journal of Advanced Marine Engineering and Technology
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• v.35 no.7
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• pp.891-898
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• 2011

The present work was conducted to get the best geometric information for the optimum design of the complex heat exchanger. The objective function for optimal design was expressed as a combination of pressure drop and heat transfer rate. The geometric parameters for the variables of louver pitch and height, tube width, etc., were limited to ranges set by manufacturing conditions. The optimum geometric parameters were calculated by using empirical correlations and theory. The sensitivity of the parameters and optimum values are shown and discussed. The weighting factor in the objective function is important in the selection of the louver fin-tube heat exchanger.

• International Journal of High-Rise Buildings
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• v.4 no.4
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• pp.227-239
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• 2015

This paper discusses the design parameters that are required for the design of high-rise building foundations, and suggests that the method of assessment for these parameters should be consistent with the level of complexity involved for various stages in the design process. Requirements for effective ground investigation are discussed, together with relevant in-situ and laboratory test techniques for deriving the necessary strength and stiffness parameters. Some empirical correlations are also presented to assist in the early stages of design, and to act as a check for parameters that are deduced from more detailed testing. Pile load testing is then discussed and a method of interpreting bi-directional tests to obtain pile design parameters is outlined. Examples of the application of the assessment process are described, including high-rise projects in Dubai and Saudi Arabia.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.6
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• pp.538-545
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• 2004

This paper presents the experimental data for the heat transfer and pressure drop characteristics obtained during the gas cooling process of carbon dioxide in a horizontal tube. The tube in which carbon dioxide flows is made of copper with an inner diameter of 7.73 mm. Experiments were conducted for various mass fluxes and inlet pressures of carbon dioxide. Mass fluxes are controlled at 225, 337 and 450 kg/$m^2$s and inlet pressures are adjust-ed from 7.5 to 8.8 ㎫. The experimental results in this study are compared with the existing correlations for the supercritical heat transfer coefficient, which generally under-predict the measured data. Pressure drop data agree very well with those calculated by the Blasius' equation. Based on the experimental data, a new empirical correlation to estimate the near-critical heat transfer coefficients has been developed.

• Journal of Mechanical Science and Technology
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• v.18 no.8
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• pp.1428-1434
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• 2004

This paper presents the mean streamline analysis using the empirical loss correlations for performance prediction of cross-flow fans. Comparison of overall performance predictions with test data of a cross-flow fan system with a simplified vortex wall scroll casing and with the published experimental characteristics for a cross-flow fan has been carried out to demonstrate the accuracy of the proposed method. Predicted performance curves by the present mean streamline analysis agree well with experimental data for two different cross-flow fans over the normal operating conditions. The prediction method presented herein can be used efficiently as a tool for the preliminary design and performance analysis of general-purpose cross-flow fans.

• Journal of the Korean Society of Combustion
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• v.4 no.1
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• pp.59-65
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• 1999

Ignition of $NH_3-O_2-Ar$ mixtures have been studied behind reflected shock waves over the temperature range of 1600-2300 K and the pressures in the range of 1.1-1.6 atm. The pressure profile and the radiation emitted behind the shock waves have been monitored to give empirical correlations between ignition delay times and the mixture concentrations with the experimental conditions. On the basis of this data, several kinetic mechanisms proposed for ammonia oxidation at high temperatures have been tested. The ignition delay times obtained from the mechanism proposed by Miller and Smook were in good agreement with our experimental results.

• Journal of ILASS-Korea
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• v.16 no.1
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• pp.15-26
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• 2011

In this article, spray characteristics in CI engines fuelled with vegetable oils and its derivatives will be reviewed. Of edible vegetable oils, soybean oil and rapeseed oil were mainly investigated. Of inedible vegetable oils, jatropha oil and used frying oil were main concern on the research on the spray characteristics in CI engine. Spray angle and spray penetration were mainly examined among the macroscopic spray characteristics and Sauter mean diameter was only investigated among the microscopic spray characteristics. There exist six different definitions of spray angle which should be examined. Neat vegetable oil and biodiesel fuels show smaller spray angle than diesel fuel. Biodiesel fuel and vegetable oils and its blend have a longer spray penetration than diesel fuel. However, biodiesel blends with diesel shows the similar spray penetration with diesel fuel. SMDs in the biodiesel spray, vegetable oils and its blends spray are higher than that in the diesel spray.

• Journal of the Korean Data and Information Science Society
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• v.17 no.4
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• pp.1099-1106
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• 2006

This study is an analysis of the stock trading value in terms of investor types in the Korean stock market for recent 12 years. We examined the characteristics in stock trading value variation according to each investor type and the interactive relationship in the trading value between types of investors. The results show that the trading value scale of every investor type increases overall while the proportion of the trading value by each investor type in the market exhibits variation. In addition, a statistically significant interactive relationship in the trading value between types of investors exists: the correlations are formed differently before and after events which largely influence the stock market.

• Journal of Environmental Science International
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• v.27 no.8
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• pp.701-709
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• 2018

Few prior studies investigated the correlation between corporate ownership structure and environmental information disclosure. Using environmental index disclosure in GRI (Global Reporting Initiative) reports of the Korean companies, the study examines the effects of ownership structure on the magnitude of environmental information disclosure. A total of 220 firm-years during 2013-2016 period are analyzed. The empirical results of the study indicate that the institutional and foreign investors' ownership have positive correlations with environmental information disclosure, while the executives' within board of directors has a negative correlation. The ownership by largest shareholders including those with special interests shows no significant relationship with the environmental information disclosure.

• Management Science and Financial Engineering
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• v.3 no.2
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• pp.45-70
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• 1997

The objectives of this study are to suggest and empirically prove the relationship model for investigating influence factors on the use of EDP audit techniques, and to identify moderating effects of the task types of EDP audit on the relationships between the influence factors and the use of EDP audit techniques. The results of the empirical test suggested that there are significant (positive or negative) correlations between the use of some EDP audit techniques and the influence factors, such as audit education, auditor's familiarity and age, and effectiveness of the technique, etc. The significant differences in the use of EDP audit techniques were empirically proved in the ratio of audit fees and the audit structure. It was also proved that the relationships between the use of techniques and the influence factors are different according to the task types of EDP audit. This study proposed the technique and the auditor related implications of these findings for the successful fulfilment of EDP audit.

• Journal of Computing Science and Engineering
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• v.5 no.3
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• pp.169-182
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• 2011

Privacy preserving microdata publication has received wide attention. In this paper, we investigate the randomization approach and focus on attribute disclosure under linking attacks. We give efficient solutions to determine optimal distortion parameters, such that we can maximize utility preservation while still satisfying privacy requirements. We compare our randomization approach with l-diversity and anatomy in terms of utility preservation (under the same privacy requirements) from three aspects (reconstructed distributions, accuracy of answering queries, and preservation of correlations). Our empirical results show that randomization incurs significantly smaller utility loss.