• International Journal of Air-Conditioning and Refrigeration
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• v.15 no.4
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• pp.163-168
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• 2007

The feature of six existing condensation heat transfer correlations for microfin tubes were evaluated with the consideration of vapor quality, mass flux, geometries, and various refrigerants. The Kosky and Staub [15] and the Jaster and Kosky [16] correlations for smooth tube were used for the evaluation of the heat transfer enhancement factor (EF). For the prediction of zeotropic mixtures, most correlations show discrepancy with previous measurements. The Yu and Koyama [4] and the Shikazono et al. [8] correlations do not consider spiral angle effect. The Han and Lee [10] correlation shows fin height growth deteriorates heat transfer. Experimental verification to develop reliable condensation heat transfer correlation for microfin tubes is still needed with the consideration of geometrical effects and working conditions.

• The Journal of Korean Physical Therapy
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• v.18 no.1
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• pp.83-94
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• 2006

Purpose: This study conducts quantitative evaluation or structural and functional characteristics or normal skeletal muscle with ultrasound image and surface electromyography, and is to provide basic materials for utilizing ultrasound image analysis in physical therapy diagnosis and assessment of skeletal muscle. Methods: Measurement of three stages was conducted with 88 normal adults between their twenties and seventies, correlations and differences using collected data according to age and gender were compared and correlations among measured items were analyzed and then the following conclusions were obtained. Results: Analysis of ultrasound image of normal skeletal muscle showed that density, median frequency had the closest relations with age. In addition, it was found that there were high correlations between density explaining structural characteristics of skeletal muscle and median frequency explaining functional characteristics. Conclusion: Analysis of ultrasound image makes complex evaluation of structure and function of skeletal muscle possible when it is connected with functional evaluation method using physical measurement surface electromyography as well as quantitative evaluation of structural changes of skeletal muscle and is effective in complementing physical therapy diagnosis centering around functionality evaluation.

• The Journal of Korean Physical Therapy
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• v.20 no.1
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• pp.33-40
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• 2008

Purpose: This study was designed to investigate the correlations between muscle strength of the ankle and balance, walking in the elderly. Methods: Thirty-nine subjects were selected from a population of female volunteers. Measurement of balance ability included evaluation of timed "up and go", functional reach, and a one leg standing test. Measurement of walking analysis included evaluation of cadence, stride length, step length, and walking speed. Maximal voluntary isometric contraction (MVIC) of the ankle muscle strength was measured by use of a dynamometer. Results: For balance, there were significant negative correlations between timed "up and go" and the MVIC of the ankle dorsiflexor. There were significant positive correlations between one leg standing with the eyes closed and the MVIC of the ankle dorsiflexor. For walking, there were significant positive correlations between cadence, walking speed and the MVIC of the ankle dorsiflexor. Conclusion: This study showed that there were close relationships between muscle strength of the ankle dorsiflexor and walking and balance in the elderly.

• ETRI Journal
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• v.21 no.4
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• pp.83-93
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• 1999

This paper examines the correlations between user characteristics and their perferences for two selected features of Web-based OPAC systems. User characteristics identified in this study were age, gender, educational status, computer skills and OPAC experience. Usability features included interaction styles, character and image on screen, browsing and navigating style, screen layout, and ease of learning, whereas availability features attended to availability of information, quality of information and up-to-date information. Individual variables and features are described, and the correlation between the variables and the features are explored using Pearson's correlation coefficient(r). Although based on a small-scale sample survey, a considerably large number of statistically significant correlations were found between the users' characteristics and the selected evaluation features of interactive Web-based OPACs. From these observations, it seems to be suitable to recommend that system designers should make a more considered appraisal of the users' demographic characteristics in the design of the new generation of OPAC such as in user-tailored interactive Web-based OPAC systems.

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1100-1108
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• 2021

Supercritical water has great potential as a coolant for nuclear reactor. Its use will lead to higher thermal efficiency of Rankine cycle. However, in certain conditions heat transfer may get deteriorated which may lead to undesirable high clad surface temperature. It is necessary to estimate the operating conditions in which heat transfer deterioration (HTD) will take place, so as to establish thermal margins for safe reactor operation. In the present work, the heat flux corresponding to onset of HTD for vertically upward flow of supercritical water in a pipe is obtained over a wide range of system parameters, namely pressure, mass flux, and pipe diameter. This is done by performing large number of simulations using an in-house CFD code, which is especially developed and validated for this purpose. The identification of HTD is based on observance of one or more peak/s in the computed wall temperature profile. The existing correlations for predicting the onset of HTD are compared against the results obtained by present simulations as well as available sets of experimental data. It is found that the prediction accuracy of the correlation proposed by Dongliang et al. is best among the existing correlations.

• Journal of Mechanical Science and Technology
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• v.15 no.3
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• pp.403-409
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• 2001

The main objective of the present study is to perform an experimental evaluation of five existing correlations for the subchannel pressure drop analysis of a wire-wrapped fuel assembly. For this purpose, a series of water experiments have been performed using a helical wire-wrapped 19-pin fuel assembly for various test parameters. Four different test sections with different pitch to rod diameter ratios (P/D) and wire lead length to rod diameter ratios (H/D) have been fabricated. A series of pressure drop measurements were made to obtain friction factors for these four test sections. The new data along with existing data are used to evaluate existing correlations. Both the original and the simplified Cheng and Todreas correlations give the best agreement with experimental data for all flow regions.

• International Journal of Air-Conditioning and Refrigeration
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• v.15 no.4
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• pp.169-174
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• 2007

The characteristics of nine existing condensation frictional pressure drop correlations for microfin tubes were evaluated with geometries, vapor quality, mass flux, and refrigerants. The $M\ddot{u}ller-Steinhagen$ and Heck [17] smooth tube frictional pressure drop correlation was utilized to evaluate the pressure drop penalty factor (PF). Except the Nozu et al. [2], the Kedzierski and Goncalves [3], the Choi et al. [10], and the Cavallini et al. [7], other pressure drop correlations did not consider the effect of tube geometry. The prediction values for R407C by pressure drop correlations show discrepancy with previous researcher's experimental trend. Additional efforts on the development of reliable condensation pressure drop correlation for microfin tubes are still required with the systematic investigation of various effects like geometries and working conditions.

• Journal of ILASS-Korea
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• v.16 no.4
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• pp.176-185
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• 2011

The empirical correlations for the prediction of penetration height of liquid jet in crossflow are reviewed and classified in this study. Around thirty different correlations had been proposed by many investigators. It has generally known that the penetration height of a liquid jet in a cross-flow is a function of the liquid to air momentum flux ratio and the normalized downstream distance from the injector. However, several researchers incorporated the Weber number, liquid-to-water or air viscosity ratio, pressure ratio or Reynolds number, temperature ratio in the empirical correlations. The existing correlations can be grouped as correlations in a power-law, logarithmic, and exponential forms, respectively. Correlations in a power-law form can be further classified as three groups such as basic form, Weber number form and other parameters form. It should be pointed out that correlations in a logarithmic form in terms of Weber number or any other parameters could not be found. Universal correlation has still not been established due to the significant discrepancies between various correlations suggested to date. Several of the studies reported the significant discrepancies of predicted values by the existing correlations. The possible reasons for discrepancies will be summarized as measurement technique, assumptions made in defining terms in the liquid to air momentum flux ratio, difficulties in defining the boundaries of the liquid jets, and nozzle/injector geometry. Evaluation of validity for the correlations proposed recently by several investigators is essentially required. Those include eight power-law forms, two logarithmic forms, and one exponential form.

• Journal of ILASS-Korea
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• v.12 no.3
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• pp.146-153
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• 2007

The prediction of diesel spray penetration has been the subject of several works and intensive investigations are still underway by many researchers. It is required to summarize the correlations developed before 1990 days and to introduce the correlations reported recently in the literature. The existing zero-dimensional models for the prediction of diesel fuel spray penetration can be classified as theoretical and empirical correlations. Of various correlations, the models considered in this paper were selected as based on the evaluation results of previous reviews and the recently published works in the literature. The existing theoretical correlations can be classified into seven categories and the existing empirical ones as two categories in this review. According to the review of existing models, the dominating factors for the prediction of spray tip penetration are the spray angle, discharge coefficient, pressure drop across nozzle, ambient density and orifice diameter and time after the start of injection. Especially, the definition for the measurement of spray angle is different with researchers. It is required to evaluate the existing spray tip penetration models for the very high injection pressure and other fuel sprays such as DME. It is also required to evaluate the correlations for the prediction of diesel spray penetration with the connection of liquid-phase penetration.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.10
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• pp.1379-1383
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• 2006

A total of 6,804 records for Duroc breed were collected from three farms registered at the Korean Animal Improvement Association (KAIA) from 1998 to 2004 of which both records from two ultrasound modes (A and B) were analyzed to estimate the variance components of carcass traits. Three carcass traits backfat thickness (bf), loin eye muscle area (lma) and lean meat percentage (lmp) were measured. These traits were analyzed separately as bf1, lma1 and lmp1 for ultrasound mode A and bf2, lma2 and lmp2 for ultrasound mode B with multiple trait animal model by using MTDFREML (Boldman et al., 1993). All the traits revealed medium heritability values. Estimated heritabilities for bf1, bf2, lma1, lma2, lmp1 and lmp2 were 0.45, 0.39, 0.32, 0.25, 0.28 and 0.39, respectively. Estimated genetic correlations for traits bf1 and bf2, lma1 and lma2, lmp1 and lmp2 were positive but low. Specifically, genetic correlations between bf1 and bf2 was 0.30 while the estimates for lean traits between lma1 and lma2 and between lmp1 and lmp2 were 0.15 and 0.18, respectively. Conversely, high negative genetic correlations existed between bf1 and the lean traits lma2, lmp2. Likewise, the estimated genetic correlations between lma1 and lma2 and lmp1 and lmp2 were low.