• Journal of Power Electronics
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• v.10 no.6
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• pp.762-768
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• 2010

This paper describes the development of a new islanding detection method for inverter-based distributed generation systems, which uses a signal cross-correlation scheme between the injected reactive current and the power frequency deviation. The proposed method injects 1% of the reactive current to the rated current which brings about a negligible degradation of the power quality. It discriminates the islanding state, when the calculated cross-correlation index is larger than 0.5. The operational feasibility was verified through computer simulations with PSCAD/EMTDC software and experimental research with a hardware prototype. The proposed method can detect the islanding state without degrading the power quality at the point of common connection. Further study is required to overcome the cancellation of the injected reactive current from multiple distributed generation units interconnected with the utility grid.

• Journal of Korean language education
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• v.29 no.4
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• pp.93-112
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• 2018

The purpose of this study is to deal with vocabulary in KFL. As a result of this study, learners learned vocabulary on average 43 points through contextual inference and introduction of the class to activate background knowledge. In particular, the implicit method showed the highest learning rate of 52 points, and the thematic method had a 41 point-learning rate. In contrast, the semantic method was the lowest with a 25 point-learning rate. There was no significant difference in the improvement rate of upper vocabulary learners, but in the case of the lower learner, there was significant difference in the improvement rate. The difference was not significant in the post-test relative gain rate of upper learners, but there was significant in lower learners. In the delayed test relative gain rate, the difference was significant in all groups. There was correlation between vocabulary difficulty and score, but there was no correlation with the thematic method. And there was no correlation between vocabulary difficulty, improvement rate and relative gain rate in all three classes. However, content understanding, lexical grade, improvement rate, and relative gain rate showed a significant correlation.

• The Journal of Korean Physical Therapy
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• v.22 no.1
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• pp.83-90
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• 2010

Purpose: This study aimed to determine the degree of job stress and self-esteem of physical therapists as well as the correlation between the two variables. Method: This study targeted 218 physical therapists of Busan City, and was carried out from July 16 to August 6, 2009 as survey research. A structured questionnaire referring to advance researches was used as a research tool. Job stress symptoms were measured one a 5 point scale, the higher the point total, the higher the job stress. Self-esteem was measured on a 4 point scale, the higher the point total, the lower the self-esteem. After data collection we determined descriptive statistics, and did reliability analysis, factor analysis, Spearman's correlation analysis, and regression analysis. Results: Reliability analysis indicated that reliability for the job stress questionnaire was 0.93 and for the self-esteem was 0.83. The average job stress score of physical therapists was 1.19 points which was not high. The average self-esteem score was 1.76 points, whichwas high. It appeared that the higher the self-esteem, the lower the job stress. Also, self-esteem had an influence on psychological symptoms among job stress factors. Conclusion: Job stress and self-esteem of physical therapists are well-correlated and influence each other. Accordingly, self-esteem can be used as a variable for adjusting job stress of physical therapists.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.67-76
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• 2009

The development of a variety of methods like AM1, PM3, PM5 and DFT now allows the calculation of atomic and molecular properties with high precision as well as the treatment of large molecules with predictive power. In this paper, these methods have been used to calculate a number of quantum chemical descriptors (like Klopman atomic softness in terms of $E_n^{\ddag}\;and\;E_m^{\ddag}$, chemical hardness, global softness, electronegativity, chemical potential, electrophilicity index, heat of formation, total energy etc.) for 75 alkanes to predict their boiling point values. The 3D modeling, geometry optimization and semiempirical & DFT calculations of all the alkanes have been made with the help of CAChe software. The calculated quantum chemical descriptors have been correlated with observed boiling point by using multiple linear regression (MLR) analysis. The predicted values of boiling point are very close to the observed values. The values of correlation coefficient ($r^2$) and cross validation coefficient ($r_{cv}^2$) also indicates the generated QSPR models are valuable and the comparison of all the methods indicate that the DFT method is most reliable while the addition of Klopman atomic softness $E_n^{\ddag}$ in DFT method improves the result and provides best correlation.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.95-104
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• 2016

Massive multiple-input multiple-output (MIMO) is a promising approach for cellular communication due to its energy efficiency and high achievable data rate. These advantages, however, can be realized only when channel state information (CSI) is available at the transmitter. Since there are many antennas, CSI is too large to feed back without compression. To compress CSI, prior work has applied compressive sensing (CS) techniques and the fact that CSI can be sparsified. The adopted sparsifying bases fail, however, to reflect the spatial correlation and channel conditions or to be feasible in practice. In this paper, we propose a new sparsifying basis that reflects the long-term characteristics of the channel, and needs no change as long as the spatial correlation model does not change. We propose a new reconstruction algorithm for CS, and also suggest dimensionality reduction as a compression method. To feed back compressed CSI in practice, we propose a new codebook for the compressed channel quantization assuming no other-cell interference. Numerical results confirm that the proposed channel feedback mechanisms show better performance in point-to-point (single-user) and point-to-multi-point (multi-user) scenarios.

• 한국가시화정보학회:학술대회논문집
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• 2003.11a
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• pp.63-66
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• 2003

A new algorithm, CBIR (Correlation Based Image Registration) was proposed to improve the resolution of image registration for PSP (Pressure Sensitive Paint). The local displacement vectors were obtained by finding the displacement which maximizes the cross-correlation between two interrogation windows of 'wind-off' and 'wind-on' images. A recursive multigrid processing was employed to increase the non-linear spatial resolutions. The variations of image were precisely measured without identifying the control points.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1778-1782
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• 2004

A new algorithm, CBIR (Correlation-Based Image Registration) was proposed to improve the resolution of image registration for PSP (Pressure-Sensitive Paint). The local displacement vectors were obtained by finding the displacement which maximizes the cross-correlation between two interrogation windows of 'wind-off' and 'wind-on' images. A recursive multigrid processing was employed to increase the non-linear spatial resolutions. The variations of image were precisely measured without identifying the control points.

• Journal of Environmental Science International
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• v.25 no.7
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• pp.1007-1016
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• 2016

Environmental policy implementation has been strengthened to protect the source waters in Korea and to improve their water quality. Increasing of non-point source caused water quality problem continuously. Research on runoff from forests, which occupy over 65% of the land in korea, is insufficient, and studies on the characteristics and influences of storm runoff are necessary. In this study, we chose to compare the effects of land use in the form of two types of forest distribution and then gathered data on storm characteristics and runoff properties during rainfall events in these areas. Furthermore, the significance and influences of the discharges were analyzed through correlation analysis, and multilateral runoff characteristics were examined by deducing a formula through $COD_{Mn}$ and TOC regression analysis. At two forest points, for which the basin areas differed from each other, flow changed according to storm quantity and intensity. The peak discharge at point A, where the basin area was big, was high, whereas water-quality fundamental items (BOD, $COD_{Mn}$, and SS) and TOC density were high at point B where the slope and storm intensity were high. Effects of dissolved organic matter were determined through correlation analysis, and the regression formulas for $COD_{Mn}$ and TOC were deduced by regression analysis. It is expected that the data from this study could be useful as basic information in establishing forest management measures.

• Journal of Korean Clinical Health Science
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• v.3 no.2
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• pp.311-319
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• 2015

Purpose. This study of purpose was to compare and analyze the relationship among the isokinetic trunk muscular functions, flexibility and low back pain of elite weight lifter with regard of sex. Methods. we measured the level of low back pain, isokinetic muscular functions according to gender, then analyzed the relationship between isokinetic functions and the level of low back pain, between flexibility and the level of pain, between Athletic Career and the level. Results. In this study, the gender, the VAS point was $2.6{\pm}2.3$ and the VRS point was $2.3{\pm}1.3$ in males. The other side, in females the VAS points was $3.6{\pm}1.7$ and the VRS was $3.2{\pm}1.1$. There was significant negative correlation(r=-0.826) between the VAS point and the maximal flexion muscular strength per kilogram of $30^{\circ}/sec$ isokinetic exercise in female. also there was negative correlation between the muscular flexion strength per kilogram and the VRS point in female, but there was no significant relationship in male. Conclusions. In current study, these results suggested that the higher muscular flexion strength per kilogram is, the lower the level of low back pain is in female athletes. this is caused by the imbalance between Abdominal Muscles and Back Extensor in weight lifter. Therefore, there is the need to apply the program to improve the balance of trunk.

• Journal of the East Asian Society of Dietary Life
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• v.19 no.4
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• pp.493-502
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• 2009

This study aimed to examine the relationship between nutrient intake and attention deficit hyperactivity (ADH) of children suffering atopic dermatitis. We examined clinical symptoms as well as the status of ADH and the dietary intake of 47 children with atopic dermatitis aged between 4 and 6 against 84 children in the control group. Family history of the atopic dermatitis group was significantly higher than the control group. There was no significant difference between the diet habit of the two groups. The daily energy intake of the atopic dermatitis group and the control group were 1,189.7 kcal and 1245.0 kcal, respectively. There was no significant difference between the nutrient intake of the two groups. In regards to the clinical symptom items, the point for 'anxieties' was 0.5 in the atopic dermatitis group, which was significantly higher than 0.3 of the control group (p<0.05). In terms of the detailed items in ADH assessed by kindergarten teachers, the point for 'changeable feeling' was 0.8 in the atopic dermatitis group, which was significantly higher than 0.5 of the control group (p<0.05). As for the correlation among nutrient intake, the ADH score and clinical symptoms, total fat intake (p<0.05) and animal fat intake (p<0.05) showed a significantly negative correlation with the point of ADH assessed by the teachers, while the intake of fiber (p<0.05) displayed a significantly negative correlation with the point of ADH assessed by the parents. Since atopic dermatitis and ADH may be caused by the same dietary factors, it will be necessary to conduct more studies in this field in the future. In addition, appropriate nutrition management will be necessary for children in the growing period who suffer from atopic dermatitis.