• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.12
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• pp.609-615
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• 2005

A 30kW electrical power conversion system is developed for a variable speed wind turbine. In the wind energy conversion system(WECS) a synchronous generator with field current excitation converts the mechanical energy into electrical energy. As the voltage and the frequency of the generator output vary according to the wind speed, a 6-bridge diode rectifier and a PWM boost chopper is utilized as an ac-dc converter maintaining the constant dc-link voltage with only single switch control. An input current control algorithm for maximum power generation during the variable speed operation is proposed without any usage of speed sensor. Grid connection type PWM inverter converts dc input power to ac output currents into the grid. The active power to the grid is controlled by q-axis current and the reactive power is controlled by d-axis current with appropriate decoupling. The phase angle of utility voltage is detected using software PLL(Phased Locked Loop) in d-q synchronous reference frame. Experimental results from the test of 30kW prototype wind turbine system show that the generator power can be controlled effectively during the variable speed operation without any speed sensor.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.12
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• pp.138-146
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• 2010

On wind turbine generators, the speed and volume of the wind affect the turbine angle speed which finally determines the output level of the electric power. However it is very difficult to forecast correctly the future power output and quality based on previous fixed sampling methods. This paper proposes a variable sampling method based on Buneman frequency estimation algorithm to reflect the variations of the frequency and amplitude on wind power outputs. The proposed method is also verified through the performance test by comparing with the results from previous fixed sampling methods and the real measurement data.

• Journal of ILASS-Korea
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• v.14 no.2
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• pp.65-70
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• 2009

An experimental study was performed to explore the atomization characteristics as the drop formation and the liquid breakup of an ethanol fuel using an electrohydrodynamic atomizer. A developed electrohydrodynamic atomizer controlled by a high AC power, a variable frequency, and a liquid feeding was used for the experiments. The test had been considered a disperse atomization processing at $450{\sim}4200V$ applied power, $200{\sim}400\;Hz$ frequency, and $1{\sim}3\;ml/min$ ethanol feeding to achieve an uniformed droplet formation. The goal of the research was to investigate the possibility of the liquid breakup for an ethanol fuel in an electrohydrodynamic atomizer. The results showed that the mean droplet radius decreased as the applied voltage increased or as the applied AC frequency increased. The whipping motion had been grown at the specified voltages due to the applied frequency.

• Journal of Broadcast Engineering
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• v.18 no.1
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• pp.106-114
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• 2013

This paper deals with the effect of the internal sampling frequency and core band down sampling ratio on the overall performance of the MPEG USAC. Here, the internal sampling frequency is the sampling frequency of a signal actually coded. The core band down sampling ratio is the ratio of the width of the core band over that of the coded band. The performance was measured on 6 different test sound sources by the MUSHRA test with 10 subjects. The experiments showed that 1/3 or 1/4 core band down sampling ratio could yield the better performance than the conventional 1/2 ratio, especially at low rates.

• Journal of Korean Physical Therapy Science
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• v.6 no.2
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• pp.1007-1017
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• 1999

The purpose of this study was to evaluate the factors influencing the ambulatory status in hemiplegia with intracerebral hemorrhage after rehabilitation. Thirty patients with stroke who was admitted in the Chosun University Hospital, between from January 1st' 1998 and December 31st' 1998, were included in this study. The following variables as a potential predictors for ambulation were evaluated at treatment of the stroke onset; 1) general characteristics including age and sex, and 2) clinical characteristics including frequency and onset time of the stroke, affected side, duration of the treatment, time interval between onset and rehabilitation, manual muscle test of paretic limb, sitting and standing balance, proprioception, perception, cognitive function. We compared and analyzed the these variables to the two type of ambulatory status at the time of the discharge by Modified Barthel Index, independent, dependent. The data were analyzed by student t-test, Fisher-exact test, Mann Whitney-U test, $X^{2}$-test, correlation analysis(spearman's). The results were as follows; 1. Were no significantly inflenced independent ambulatory status among general characteristics. 2. Frequency of the stroke and proprioception (p<0.05), muscle strength of the lower limb, cognitive function and standing balance (p<0.01), perception and sitting balance (p<0.001) were significantly inflenced independent ambulatory status among clinical characteristics. 3. Independent Variable correlated with the ambulatory status were muscle strength of the lower limb, proprioception and sitting balance (p<0.05), standing balance, frequency of the stroke, perception and cognitive function (p<0.01). Therefore the muscle strength of the lower limb, proprioception, sitting balance, standing balance, frequency of the stroke, perception, cognitive function were the most significant influencing factors of ambulatory status after rehabilitation.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1175-1182
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• 2021

The receiver of each radio telescope of KVN, has a sampler that converts astronomical radio signal to digital data. The ability of this sampler (the bandwidth, sampling frequency, and sampling bits) is improved by sqrt(n), if the bandwidth is increased by n times, and the number of observable objects increases exponentially in the case of continum spectrum radio sources. As the bandwidth increases, there are the more spectrum lines that can be simultaneously monitored in the radio source. This will greatly expand the research area in astronomical radio observation. For this reason, we are trying to independently develop the technology of the fast digital sampler. Therefore, based on the research experience and technology accumulated so far, An ability of sampling up to 3.5 GHz, that can vary the sampling frequency and can observe in a wider band, was designed and made for proto-type. In this study, we introduce the development details and test results for new sampling system.

• The Research Journal of the Costume Culture
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• v.20 no.4
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• pp.515-528
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• 2012

The purpose of this study was to classify appearance management attitudes into groups and analyze the difference of self-efficacy and body satisfaction by the groups. Questionnaires were administered to 255 college students living in Deagu Metropolitan City and Kyungbook province. The data collected were analyzed by using frequency, factor analysis, cluster analysis, correlation analysis, ANOVA, Duncan-test, t-test, and ${\chi}^2$-test. The findings were as follows. Appearance management attitudes of college students were classified into three groups such as group health body, low body interest group, emphasizes collective body. The appearance management attitudes showed significant correlation with the sub-variables of self-efficacy and body satisfaction. Male students showed no significant difference in self-efficacy by the groups while female students showed a significant one in task performance which was a sub-variable of self-efficacy. Both of the male and female students showed a significance of difference in the gap between actual and ideal weight which was a sub-variable of body satisfaction by the groups. Gender of college students showed distinction between the sub-variables of self-efficacy factors such as task performance, and anxiety and body satisfaction such as BMI, the difference between current height and ideal height, the difference between current weight and ideal weight.

• Korean Institute of Interior Design Journal
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• no.20
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• pp.3-9
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• 1999

The purpose of this study was to verify the stability of environmental disposition through analyzing the short term effect of the 'Interior Design History' course on students environmental dispositions, especially their interior image preferences toward traditional/modern, female/masculine, and simple/complex characteristics. The pre-test post-test control group experimental design was used. The independent variable was the experience of the Interior Design History course, and the dependent variable was environmental disposition measured by IIPS(Interior Image Preference Scale). The measurements were done at both beginning and end of fall semester, 1997. Subjects were using 71 undergraduate students of Drafting course (control group) and 35 undergraduate students of Interior Design History course (experimental group) at Y University. Data were analyzed using frequency, percentage, mean, and F-test through ANOCOVA. This research revealed no effect of the Interior Design History course on students interior environmental dispositions. The stability of those environmental dispositions and also the validity of the IIPS were proved.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.5
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• pp.417-425
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• 2000

The underlying mechanism commonly applicable for both the positive and negative force-frequency relationships (FFR) was pursued in left atria (LA) of rat and rabbit. The species differences in the roles of $Na^+/Ca^{2+}$ exchanger and sarcoplasmic reticulum (SR), which are major intracellular $Ca^{2+}$ regulatory mechanisms in the heart, were examined in the amplitude accommodation to the frequency that changed from 3 Hz to the variable test frequencies for 5 minutes in the electrically field stimulated left atria (LA) of rat and rabbit. Norepinephrine strongly increased the frequency-related amplitude accommodation in both of rat and rabbit LA, while monensin, oubain or the reduced $Na^+$ and 0 mM $Ca^{2+}$ containing Tyrode solution increased the frequency-related amplitude accommodation only in the rabbit LA. Monenisn was also able to increase the frequency-related amplitude accommodation only in 1-day old rat LA but not in 4-week old rat LA that had 75% less $Na^+/Ca^{2+}$ exchanger with 97% higher SR than 1-day old rat LA. Taken together, it is concluded that the differences in the prevalence between myocardial $Na^+/Ca^{2+}$ exchanger and SR in the amplitude accommodation to the frequency-change determine the difference in the FFR between rat and rabbit heart.

• Journal of the Korean Society of Clothing and Textiles
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• v.29 no.6
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• pp.885-895
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• 2005

The purpose of this study was to find out the most pursuasive social stratification variables affecting the attitude toward foreign luxury goods and the purchase frequency and examined the difference in the attitude toward foreign luxury goods and the purchase frequency among groups divided by age and social stratification variables. The subjects were 521 married women over 25 years old living in Seoul and Kyong-gi province areas. The data were analyzed by multiple regression, ANOVA, Duncan's multiple range test, frequency and percentage. Social stratification was measured by family's monthly income, educational and occupational levels of married women's and their husbands' for an objective method while economic levels, social status, consumption levels, and cultural levels were used fer a subjective method. The results were as follows; first, the most explainable variables influencing the attitude toward foreign luxury goods and the purchase frequency were age and women's educational levels examined by the objective method of social stratification. Second, according to the subjective method of social stratification, the attitude toward foreign luxury goods and the purchase frequency were affected by age, economic levels, consumption levels, and cultural levels. Consumption levels which showed actual expense per family were the most explainable variable in the purchase frequency.