• Journal of Power Electronics
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• v.14 no.3
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• pp.598-607
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• 2014

This paper proposes a frequency-locked loop (FLL) scheme for a single-phase grid-connected converter. A second-order generalized integrator (SOGI) based on fuzzy logic (FL) is applied to this converter to achieve precise phase angle detection. The use of this method enables the compensation of the nonlinear characteristic of the frequency error, which is defined in the SOGI scheme as the variation of the central frequency through the self-tuning gain. With the proposed scheme, the performance of the SOGI-FLL is further improved at the grid disturbances, which results in the stable operation of the grid converter under grid voltage sags or frequency variation. The PSIM simulation and experimental results are shown to verify the effectiveness of the proposed method.

• Korean Journal of Community Nutrition
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• v.13 no.5
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• pp.701-712
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• 2008

The purpose of the present study was aimed to identify dish items applicable in developing dish?based food frequency questionnaire (DFFQ) for a hypertension study of Koreans. The 24-hour recall data of 4,401 subjects aged $20{\sim}65$ years from the 2001 Korean National Health and Nutrition Examination Survey were used for the analysis. Logistic regression model was used to identify the nutrient related with hypertension. Energy, fiber, sodium, calcium, carotene, vitamin B1 and vitamin C were associated with hypertension. Selection the top 30 dish items for these seven nutrients was performed based on their degree of contribution in supplying nutrients in terms of the cumulative percent contribution (cPC), as well as on their degree of explanation for between?person variation, in terms of the cumulative regression coefficient (cMRC). Rice supplied 43% of total energy consumption. Korean cabbage and radish kimchi were two major sources of sodium and it also covered the 27% of between person variation of sodium intake. Soybean paste soup and single item of orange?colored fruits supplied 43% of total vitamin C intake for Koreans and it covered the almost 79% of between person variation among the Korean population. Korean cabbage kimchi was the major source of fiber, calcium, sodium, carotene, and vitamin C for Koreans. In summary, the top 30 selected dish items supplying the 78% to 89% of the 7 nutrients. Those items also covered the 79% to 94% of between person variation of the 7 nutrients consumption. Therefore, the selected 30 dish items in each categories of nutrient could be applicable in developing dish based food frequency questionnaire for hypertension study.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.9
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• pp.813-821
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• 2013

In this paper, a vital signal sensor based on impedance variation of resonator is presented. Proposed vital signal sensor can detect the vital signal, such as respiration and heart-beat signal. System is composed of resonator, oscillator, surface acoustic wave (SAW) filter, and power detector. The cyclical movement of a dielectric such as a human body, causes the impedance variation of resonator within the near-field range. So oscillator's oscillation frequency variation is effected on resonator's resonant frequency. SAW filter's skirt characteristic of frequency response can be transformed a small amount of frequency deviation to a large variation. Aim to enhance the existing sensor detection range, proposed sensor operates in 870 MHz ISM band, and detect respiration and heart-beat signal at distance of 120 mm.

• Phonetics and Speech Sciences
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• v.2 no.4
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• pp.19-28
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• 2010

The purpose of this study was to increase the current understanding of the acoustic characteristics of voices with advancing age. The relationship between age-related changes in body physiology and certain acoustic characteristics of voice was studied in a sample of 80 men representing four chronological age groupings (20-29, 50-59, 60-69, 70-79) who were all of good physical condition. Each subject was asked to phonate the vowel /a/, /i/, and /u/ for as long as possible at comfortable frequency and intensity level and read the sentence. A promising voice analysis program (Multi-Dimensional Voice $Program^{TM}$) was used to measure the fundamental frequency ($f_0$), jitter, shimmer, $f_0$ variation, peak-amplitude variation, smoothed pitch perturbation quotient, smoothed amplitude perturbation quotient, soft phonation index, $f_0$-tremor intensity index, amplitude tremor intensity index, and noise-to-harmonics ratio from the samples.

• Journal of Wetlands Research
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• v.4 no.2
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• pp.43-56
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• 2002

About 12 rain gauge stations of Korea, annual maximum rainfall series of before and after 1980 whose durations are 1, 2, 3, 6, 12, 24, 48, 72 hours respectively were composed and statistical characteristics of those time series were calculated and probability rainfall were estimated by L-moment frequency analysis method and compared each other in order to investigate the recent quantitative rainfall variations. And also, distribution curves of each statistical variations for each duration were constructed by using Kigging method to look into spacial rainfall variation aspects. As a result, We could confirm recent rainfall increase in the South Korea. And spatial increase pattern of standard deviation and frequency rainfall appeared analogously each other. 1n the cases of comparatively short rainfall duration, we could see relatively low increase or decrease tendency in Chungchong Province, Cholla-bukdo, Cholla-namdo eastern part, Kyongsang-namdo western part area. While, variations happened great1y in seaside district of east coast, southwest seashore, Inchon area etc. In the cases of longer durations relatively low increase was showed in southern seashore such as Yeosoo area and as distance recedes from this area, showed gradually augmented tendency. The aspect of mean looks similar tendency of above except that the variation rate of almost seaside district are big in the case of shorter durations. In addition, rainfall increases of short durations which became the center of hydrologist and meteorologist are unconfirmed in this study.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.11
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• pp.1584-1589
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• 2012

The grid-interconnected microgrid can be able to operate with and without the utility microgrid to supply electricity. when the microgrid operates in grid-connected mode, the frequency of the microgrid synchronizes with the system frequency. In this case, the frequency of the microgrid has small variation which is able to change the output of distributed generation with a droop controller. Thus, the small variation of frequency can make the distributed generation generate unnecessary electricity consistently. In this paper, we propose a frequency droop control with a dead band so as to prevent the distributed generations from generating unnecessary output while in grid-interconnected mode. In addition, a distributed generation can have a restoration control to restore the frequency changed by a droop control as a rated frequency. Also, we state the problem of restoration control with a dead band, and propose its solution when the microgrid operates in stand alone mode. We simulate the proposed droop control using PSCAD/EMTDC to verify the validity of the control.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.27-35
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• 1998

An experimental study was performed to investigate the optimum cycle of an inverter heat pump as a function of frequency. The performance of the inverter heat pump with the rated cooling capacity of 4,141 W(3,550kcal/h) was measured with a variation of frequency, indoor and outdoor temperature, and length of capillary tube in the psychrometric test room. As a base case, the inverter heat pump with the standard capillary length of l,000mm(optimum size for the frequency of 60Hz) and ASHRAE Test condition "A" was tested by varying frequency from 30Hz to 80Hz. Then, the optimum cycles were investigated by varying the length of capillary tube at each frequency level of 30, 60 and 80Hz. Based on the experimental data, the change of system characteristics between the optimum and the base case were analyzed for each selected frequency level. Generally, for low frequency level(30Hz), the longer length of the capillary tube compared with the standard size showed the higher energy efficiency ratio(EER), while for high frequency level(80Hz) the shorter length of the capillary tube showed the higher EER.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.1
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• pp.64-72
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• 1997

An experiment study was performed to investigate the optimum cycle of an inverter heat pump as a function of frequency. The performance of the inverter heat pump with the rated cooling capacity of 4141W(3550kcal/h) was measured with a variation of frequency, indoor and outdoor temperature, and length of capillary tube in the psychrometric test room. As a base case, the inverter heat pump with the standard capillary length of 1000mm which was optimum size for the frequency of 60Hz and ARHRAE Test condition A was tested by varying frequency from 30Hz to 80Hz. Then, the optimum cycle was invesigated by varying the length of capillary tube at each frequency levels of 30, 60 and 80Hz. Based on the experimental data, the change of system characteristics between the optimum and the base case were analyzed for each selected frequency levels. Generally, for low frequency level(30Hz), the longer length of the capillary tube compared with the standard size showed the higher EER, while for high frequency level(80Hz) the shorter length of the capillary tube showed the higher EER.

• Journal of the Korean Magnetics Society
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• v.19 no.1
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• pp.5-11
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• 2009

The Explosive Magnetic Generator of Frequency (EMGF) has been studied as a method to generate a strong microwave effectively through converting the explosion powder energy into the electromagnetic energy. However, the generated high frequency electromagnetic wave has not been explained clearly yet, for it is known to be difficult to analyze the high frequency electromagnetic wave oscillation using a simple time-varying equivalent circuit model. In this paper, we analyze the problems of the widely used inductance model with an exponential decreasing pattern and investigate the tendency of a more accurate inductance variation model using the finite element method of EMGF inductance by considering the magnetic compression effect. And we have shown via an EMGF output simulation that the new inductance variation model proposed here has an negative effect on EMGF output.

• The Research Journal of the Costume Culture
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• v.29 no.3
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• pp.388-405
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• 2021

This study classifies the compositional methods of power shoulder jackets from 1980 to the present. It analyzes the relevance of jacket details according to how the power shoulder changes and its compositional methods by era. The research subdivides shoulder compositional techniques into seven, based on shoulder variation, sleeve variation, and the body and sleeve combination. The researcher investigates the frequency and trends of composing shoulders and analyzes details pertaining to the silhouette, jacket length, collar shape, and front closure. The most common method of shoulder composition is an angular shoulder variation. The others are a rounded shoulder variation, puffed sleeve, sleeve variation using pattern incision, raglan and kimono sleeves, and a shoulder variation that expanded the angle and width. The frequency differs slightly for each era. The relationship between shoulder compositional methods and details of power shoulder jackets is statistically significant, showing period-related differences. The homogeneity analysis results reveal that the shoulder composition of power shoulder jackets, the times, and details fall into distinct groups. This analysis shows that the silhouette, length, collar, and front closure of the power shoulder jacket differ depending on the power shoulder's compositional methods. Moreover, the shape of the power shoulder jacket is distinctly different. One can use this data to help develop the power shoulder jacket design by reflecting the details of shoulder compositional methods and changing trends over time.