• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.64 no.3
• /
• pp.498-504
• /
• 2015

This paper proposed an Spread Spectrum Time Domain Reflectometry (SSTDR) using time-frequency correlation analysis in order to have more accurate fault determination and location detection than classical SSTDR despite increased signal attenuation due to the long distance to cable fault location. The proposed method was validated through comparison with classical SSTDR methods in open- and short-circuit fault detection experiments of low-voltage power cables. The experimental results showed that the proposed method can detect correlation coefficients at fault locations accurately despite reflected signal attenuation so that cable faults can be detected more accurately and clearly in comparison to existing methods.

• Structural Engineering and Mechanics
• /
• v.57 no.2
• /
• pp.369-387
• /
• 2016

In this work, random homogenization analysis for the effective thermal properties of a three-dimensional composite material with unidirectional fibers is presented by combining the equivalent inclusion method with Random Factor Method (RFM). The randomness of the micro-structural morphology and constituent material properties as well as the correlation among these random parameters are completely accounted for, and stochastic effective thermal properties as thermal expansion coefficients as well as their correlation are then sought. Results from the RFM and the Monte-Carlo Method (MCM) are compared. The impact of randomness and correlation of the micro-structural parameters on the random homogenized results is revealed by two methods simultaneously, and some important conclusions are obtained.

• International Journal of Internet, Broadcasting and Communication
• /
• v.10 no.3
• /
• pp.65-72
• /
• 2018

The purpose of this study was to assess the intra-tester and inter-tester reliability and validity of elbow flexion range of motion using a smart phone used by the general public. Thirty-one general people participated in this study. The range of motion in active elbow flexion was measured with a goniometer and smart phone over two times by two observers. The intra-taster and inter-tester reliability were evaluated using the intraclass correlation coefficient(ICC). The validity was measured by Pearson's correlation coefficient. The intra-observer reliability was good in all measured items ICC>0.900. The inter-observer reliability was high with ICC>0.806. All correlation coefficients of android app and goniometer were greater than 0.868 and showed a significant positive correlation (p<0.01). The range of motion measurement with a smart phone showed acceptable reliability. Therefore, using a smartphone to measure the range of motion of the elbow joint could provide convenience and economic benefits.

• YAKHAK HOEJI
• /
• v.43 no.5
• /
• pp.577-583
• /
• 1999

Concentrations of heavy metals, including As, Cd, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se, Si, Sn, V and Zn in the internal organs (liver, kidney, heart, lung, spleen, cerebrum and bone) of Korean obtained from 91 forensic medical autopsy cadavers, with an age range of 12-87 years, were determined by inductively coupled plasma atomic emission spectrometry. From the results, positive correlation with age was observed in the following cases : Cd in liver, kidney and cerebrum; Fe in cerebrum and bone; Pb in bone; v in lung. Copper in heart, Hg in bone and Mn in kidney correlated negatively with age. A significantly positive correlation between Se and Hg was only observed in heart. Significant correlation coefficients between Se and As were observed in liver, kidney, heart spleen and bone. The correlation between Cd and Zn was significant in liver and kidney, indicating that the distribution of Cd is similar to that of Zn in the liver and kidney.

• IE interfaces
• /
• v.14 no.1
• /
• pp.79-83
• /
• 2001

In this paper, we propose a simple method to reduce categorical variables into smaller, but significant numbers, and also demonstrate how the proposed method can be applied to the problem of reduction that empirical research often faces in the course of data processing. For the purpose, we introduce a concept of pseudo-correlation coefficient to make it possible to use factor analysis (FA) as a tool for reducing variables. The main idea of the concept is to deal with the measures of association of categorical variables in the sense of the concept of Pearson's correlation coefficient in order to meet the input requirement of FA. Upon examination of existing measures that could play as pseudo-correlation coefficients, Cramer's V coefficient is selected for the best result among them. To show the detailed procedure of the proposed method, a specific demonstration with the data from 329 R&D projects conducted in 18 private laboratories in electric and electronics industry is presented.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.3 no.3
• /
• pp.157-165
• /
• 1999

The nondestructive testing methods are commonly used to determine the in-situ compressive strength of concrete. The correlation curves to evaluate the effect of aging on the development of concrete strength was proposed. Thirty two ${\Phi}10{\times}20cm$ cylinder specimens were cast from 5 batches having different strength levels. The correlation curves for rebound hammer method, ultrasonic pulse velocity method and combined method were derived from the laboratory tests and multiple regression analysis. To account for the change of condition such as surface hardness, internal moisture contents, the aging coefficients are applied to the correlation curves. From the comparison the nondestructive strength with the core strength taken from the existing reinforced concrete structures, the validity of the proposed correlation curves are verified.

• International conference on construction engineering and project management
• /
• 2005.10a
• /
• pp.791-795
• /
• 2005

A simulation model is proposed to evaluate the effect of correlations between activity durations on the overall project duration. The proposed model incorporates NORTA, a recent developed statistical method, into the simulation process to allow arbitrarily specified marginal distributions for activity durations and any desired correlation structure. The generality is of practical value when systematic data is not available and planners have to rely on arbitrary experts' estimation, which may involve a mixed situation when some activity durations are continuously distributed whereas others are discrete outcomes. The proposed model is validated by showing that the correlation coefficients of the simulation results are close to the originally specified ones. The simulation results are compared to two conventional approaches: PERT and simulation without correlation. The comparisons illustrate that the proposed model can provide important management information, which would otherwise be distorted due to the neglect of the correlations between activity durations.

• Journal of Advanced Marine Engineering and Technology
• /
• v.25 no.3
• /
• pp.552-562
• /
• 2001

Measurement of average of heat transfer and friction coefficients were obtained with air flowing through electrically heated ducts having square, rectangular(aspect ration, 5), and triangular cross section for range of surface temperature from $540^{\circ}$to $1780^{\circ}$ R and Reynolds number from 1000 to 330,000. The results indicates that the effect of heat flux on correlations of the average heat transfer and friction coefficients is similar to that obtained for circular tubes in previous investigation and was nearly eliminated by evaluating the physical properties and density of the air a film temperature halfway between the average surface and fluid bulk temperatures, With the Nusselt and Reynolds numbers on the hydraulic diameter of the ducts, the data for the noncircular ducts could be represented by the same equations obtained in the previous investigation for circular tubes. Correlation of the average difference between the surface corner and midwall temperatures for the square duct was in agreement with predicted values from a previous analysis. However, for the rectangular and triangular ducts, the measured corner temperature was greater by approximately 20 and 35 percent, respectively, than the values predicted by analysis.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.9 no.3
• /
• pp.10-17
• /
• 2001

This study investigated the condensation heat transfer coefficients of R-22, R-290 and R-600a inside horizontal tube. Heat transfer measurements were performed for smooth tube with inside diameter of 10.07 mm and outside diameter of 12.07 mm and inner grooved tube having 75 fins whose height is 0.25 mm. Condensation temperatures and mass velocity were ranged from 308K to 323 K and $51kg/m^2s$ to $250kg/m^2s$, respectively. The test results showed that the local condensation heat transfer coefficients increased as the mass flux increased, and also the effects of mass velocity on heat transfer coefficients of R-290 and R-600a were less than those of R-22. Average condensation heat transfer coefficients of natural refrigerants were superior to that of R-22. The present results had a good agreement with Cavallini-Zecchin's correlation for smooth and inner grooved tubes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.8 no.1
• /
• pp.140-150
• /
• 1996

CFC-12, which has been used most widely in automobile air conditioners and household refrigerators is scheduled to be phased out soon because of its high ozone depletion potential. Now HFC-134a is suggested as an alternative refrigerant for CFC-12. In this Study, we intended to investigate how PAG oil influence evaporation heat transfer and flow pattern, using R-134a and PAG oil influences evaporation heat transfer and flow pattern, using R-134a and PAG oil in the horizontal miro-fin evaporation tube. Experiments were conducted under the flowing est conditions : mass velocity 86-250kg/$m^2$s, heat flux 5-30 ㎾/$m^2$, oil concentration 0-21 wt.% and saturation temperature 5$^{\circ}C$. Local evaporation heat transfer coefficients were found to be higher at the top, side and bottom of the tube in this order. Average heat transfer coefficients turned out to increase with oil concentration increment up to 3 wt.% oil concentration, whereas heat transfer coefficients gradually decreased over 3 wt.% oil concentration, because of oil-rich liquid film was formed on the heat transfer surface. Flow patterns were rapidly transitioned to annular regimes up to 3 wt.% oil concentration. In case of pure refrigerant, measured heat transfer coefficients in the experiments were similar to those of Kandlikar＇s correlation.