• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.421-427
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• 2013

The dependence between wind speeds in multiple wind sites has a considerable impact on the reliability of power systems containing wind energy. This paper presents a new method to generate dependent wind speed time series (WSTS) based on copulas theory. The basic feature of the method lies in separating multivariate WSTS into dependence structure and univariate time series. The dependence structure is modeled through the use of copulas, which, unlike the cross-correlation matrix, give a complete description of the joint distribution. An autoregressive moving average (ARMA) model is applied to represent univariate time series of wind speed. The proposed model is illustrated using wind data from two sites in Canada. The IEEE Reliability Test System (IEEE-RTS) is used to examine the proposed model and the impact of wind speed dependence between different wind regimes on the generation system reliability. The results confirm that the wind speed dependence has a negative effect on the generation system reliability.

• Journal of the Korean Operations Research and Management Science Society
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• v.39 no.2
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• pp.141-154
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• 2014

It is widely confirmed that online retailers can obtain crucial resources and greater growth potential by depending on the external web portal sites as it is explained in resource dependence theory. Nevertheless, recent studies show that the effect of dependence may not always be beneficial for firms and stress the importance of finding relevant contingent factors. In this study, we identify and suggest that firms' age and niche width strategy, whether generalist or specialist, are contributing factors on moderating the positive relationship between resource dependence and firm growth. To test our hypotheses based on the theory, we have collected monthly web traffic data of online retailers and portals from March 2000 and July 2008. The empirical results lend support to our theory of the firm age having a negative interaction effect on web traffic dependence. Moreover, results verified that positive effect of depending on the portals may become greater if the online retailer is a specialist in terms of niche width.

• Korean Journal of Human Ecology
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• v.24 no.6
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• pp.769-781
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• 2015

The purpose of this study was to examine the effects of self control and social support on the mobile phone dependence in elementary school students. The subjects were 392 children(187 boys, 205 girls) in 5, 6th grade from two elementary schools in Gyeonggi-do. The mobile phone dependence was assessed by the Mobile Phone Dependence Scale(Ko Seong-Ja, 2012), self control was measured by the Self-control Scale(Nam hyeon-mi, 1999) and social support was assessed by the Social Support Scale(Han mi hyun, 1996). Data were analyzed using descriptive statistics, t-test, Pearson correlations and hierarchical regressions. The major results of this study were as follows: First, there was no significant difference in mobile phone dependence by sex of the children. Second, children's mobile phone dependence were correlated with self control and social support. Finally, children's self control, family support and peer support significantly explained the mobile phone dependence. But peer support appeared to have negative corelation on mobile phone dependence, but appeared to have static effect in regression result by suppressor variables. So it needs to explore statistical function of suppressor variables in follow-up studies. Also research of this study indicate that self control enhancement program should be developed and parents should communicate more frankly and affectively with their children in order to prevent children's mobile phone dependence.

• Communications for Statistical Applications and Methods
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• v.23 no.3
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• pp.215-230
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• 2016

The powers of some tests for independence hypothesis against positive (negative) quadrant dependence in generalized Farlie-Gumbel-Morgenstern distribution are compared graphically by simulation. Some of these tests are usual linear rank tests of independence. Two other possible rank tests of independence are locally most powerful rank test and a powerful nonparametric test based on the $Cram{\acute{e}}r-von$ Mises statistic. We also evaluate the empirical power of the class of distribution-free tests proposed by Kochar and Gupta (1987) based on the asymptotic distribution of a U-statistic and the test statistic proposed by $G{\ddot{u}}ven$ and Kotz (2008) in generalized Farlie-Gumbel-Morgenstern distribution. Tests of independence are also compared for sample sizes n = 20, 30, 50, empirically. Finally, we apply two examples to illustrate the results.

• ETRI Journal
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• v.44 no.3
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• pp.504-511
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• 2022

Monte Carlo simulations show that, as temperature increases, the average kinetic energy of channel electrons in a GaN transistor first decreases and then increases. According to the calculations, the relative energy change reaches 40%. This change leads to a reduced barrier height due to quantum coupling among the three-dimensional motions of channel electrons. Thus, an analysis and physical model of the gate leakage current that includes drift velocity is proposed. Numerical calculations show that the negative and positive temperature dependence of gate leakage currents decreases across the barrier as the field increases. They also demonstrate that source-drain voltage can have an effect of 1 to 2 orders of magnitude on the gate leakage current. The proposed model agrees well with the experimental results.

• Journal of ILASS-Korea
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• v.7 no.3
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• pp.7-11
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• 2002

Comparison of the combustion characteristics of methane-air and gasoline-air mixtures has been conducted experimentally by a spherical bomb technique. The results indicate 1) the burning velocity of gasoline is slightly higher than that of methane, but their basic behavior of combustion characteristics, positive dependence on temperature and negative one on pressure, are the same, and 2) 20 vol.% addition of hydrogen to methane enhances the burning velocity by about 30%, but does not come to reverse the tendency of pressure dependence to that of pure hydrogen.

• Journal of Distribution Research
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• v.1 no.1
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• pp.109-127
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• 1996

The purpose of this study was to represent hypotheses of the interrelationship of the level of cooperation, conflict, and performance and to report the findings testing the hypotheses in car channels. This study provides some general guidance toward better cooperation, conflict, and performance management. The results indicate that noncoercive bases of power and dependence hale a positive effect on cooperation, while the proposed inverse relationship between coercive bases of power and cooperation is not statistically significant. Coercive bases of power have a positive effect on conflict, while conflict is not statistically significant for noncoercive bases of power, dependence, and cooperation. Finally, cooperation has a positive effect on dealer performance, but conflict has a negative effect on dealer performance.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.229-232
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• 1999

We have measured the temperature dependence of thermoelectric power (TEP) and resistivity for the Sr$_{1-x}K_xBiO_3$ superconductor (x=0.45-0.6). At T=10.2K, the resisitivity starts to increase from zero and a rather broad superconducting phase transition (${\Delta}$T ${\sim}$ 2.3K) is observed. TEP at room temperature has a small negative value ( S =-1.96${\mu}$V/K), characteristic of metallic-like TEP. The temperature dependence of TEP shows two distinct features. With decreasing temperature from room temperature, the absolute value of TEP decreases and the sign of TEP changes from negative to positive around 200k. Also, the negative slope of TEP(dS/dT) decreases substantially and becomes rather flat at around 160k, which is a feature already noted in Ba$_{1-x}K_xBiO_3$[1].

• Journal of Astronomy and Space Sciences
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• v.27 no.4
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• pp.329-335
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• 2010

We investigate the sources of the variation of the high-latitude thermospheric neutral mass density depending on the interplanetary magnetic field (IMF) conditions. For this purpose, we have carried out the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM) simulations for various IMF conditions under summer condition in the southern hemisphere. The NCAR-TIEGCM is combined with a new empirical model that provides a forcing to the thermosphere in high latitudes. The difference of the high-latitude thermospheric neutral mass density (subtraction of the values for zero IMF condition from the values for non-zero IMF conditions) shows a dependence on the IMF condition: For negative $B_y$ condition, there are significantly enhanced difference densities in the dusk sector and around midnight. Under the positive-$B_y$ condition, there is a decrease in the early morning hours including the dawn side poleward of $-70^{\circ}$. For negative $B_z$, the difference of the thermospheric densities shows a strong enhancement in the cusp region and around midnight, but decreases in the dawn sector. In the dusk sector, those values are relatively larger than those in the dawn sector. The density difference under positive-$B_z$ condition shows decreases generally. The density difference is more significant under negative-$B_z$ condition than under positive-$B_z$ condition. The dependence of the density difference on the IMF conditions in high latitudes, especially, in the dawn and dusk sectors can be explained by the effect of thermospheric winds that are associated with the ionospheric convection and vary following the direction of the IMF. In auroral and cusp regions, heating of thermosphere by ionospheric currents and/or auroral particle precipitation can be also the source of the dependence of the density difference on the IMF conditions.

• The Journal of the Korea Contents Association
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• v.18 no.12
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• pp.62-74
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• 2018

This study was proposed to examine the mediating effect of basic psychological needs on how parenting attitude affect middle school students with over-dependence on smart phone. This study utilized 2017 survey research by National Information Society Agency (NIA), namely a long-term follow-up study of 901 people with over-dependence on internet and smart phone. This study showed two findings. First, over-dependence on smart phone had correlations with basic psychological needs- autonomy(r=-.22, p<.001) and competence(r=-.13, p<.001); with parenting attitude- positive parenting(r=-.21, p<.001) and negative parenting(r=.15, p<.001). Second, both parenting attitude and basic psychological needs had a causal relationship with over-dependence on smart phone. These results can provide a basis to reconsider social awareness on over-dependence on smart phone among middle school students. This study proposed few research directions for further study to prevent over-dependence on smart phone and to educate parents.