• Journal of Power Electronics
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• 제19권2호
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• pp.519-528
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• 2019

The unified power quality conditioner (UPQC) is an effective custom power device that is used at the point of common coupling to protect loads from voltage and current-related PQ issues. Currently, most researchers have studied series unit and parallel unit models and an idealized transformer model. However, the interactions of the series and parallel converters in AC-link are difficult to analyze. This study utilizes an equivalent transformer model to accomplish an electric connection of series and parallel converters in the AC-link and to establishes a precise unified mathematical model of the UPQC. The strong coupling interactions of series and parallel units are analyzed, and they show a remarkable dependence on the excitation impedance of transformers. Afterward, a feed-forward decoupling method based on a unified model that contains the uncertainty components of the load impedance is applied. Thus, this study presents an adaptive method to estimate load impedance. Furthermore, simulation and experimental results verify the accuracy of the proposed modeling and decoupling algorithm.

• Journal of Biosystems Engineering
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• 제13권4호
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• pp.9-19
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• 1988

The threshing of head-feed combine may be accomplished mainly by the action of impact between threshing teeth and rice. In this study, it was attempted to assess threshing performance characteristics of head-feed threshing teeth. And the characteristics of threshing teeth will be applied to the method which could analyze the time and order of impact between teeth and the rice, which was used as a basis for predicting the threshing performance and determining the optimum design parameters. The results of the study are summarized as follows: 1. About 50% of threshed material were threshed by the beginning 7 impacts on the rice bundle. Threshing torque decreased until 25 impacts and did not change thereafter. 2. There was significant difference in the threshability according to the shape of threshing teeth. The triangular-shaped tooth was the most efficient in threshability ratio and the semicircle-shaped tooth was the lowest. There was no significant difference in specific energy requirement for the varied teeth design. Torn-head ratio being generated by the semicircle-shaped and the triangular-shaped teeth in series was less than that by a single tooth with the triangular-shaped and the double setting of the triangular-shaped. Chaff generation ratio by the triangular-shaped and the semicircle-shaped teeth was less than the others tried. 3. The triangular-shaped teeth in series, which was newly designed for this study, showed an intermediate characteristics between the double setting of the triangular-shaped and the semicircle- shaped teeth. Threshability ratio of the triangular-shaped teeth in series was higher than that of the semicircle and lower than the double setting of the triangular-shaped tooth. Torn-head generation ratio for it was about same as that of the semicircle. Chaff being generated by the triangular-shaped teeth in series was about same as the double setting of the triangular-shaped teeth. 4. About 40% of threshed grains which passed through concave were concentrated under the threshing tooth and the rest of grains displayed a skew distribution toward the inlet of threshing chamber.

• Journal of information and communication convergence engineering
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• 제18권3호
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• pp.162-166
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• 2020

The present paper presents an array antenna of a microstrip patch for 5G applications. Four rectangular microstrip patch elements are arranged in parallel and series to form an array antenna. Two insets are made on both sides of each patch element to achieve a wide frequency bandwidth of 23.97-31.60 GHz. To attain a high gain and wider bandwidth, the microstrip patch antenna is fed using series and corporate feeding networks. Further, three director elements on top of the top-most patch elements, and one reflector element at the open end of each patch element, are added. The addition of the Yagi elements improved the overall gain and acquired a higher radiation efficiency throughout the operating frequency bandwidth, with the array antenna achieving a maximum peak gain of 8.7 dB. The proposed antenna is built on a low-loss and low-cost substrate of FR4-eproxy. The proposed antenna design with a simple structure is suitable for Internet of Things and 5G applications.

• 멤브레인
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• 제9권3호
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• pp.163-169
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• 1999

투과증발 공정을 이용한 알코올/물 혼합물의 분리 시 투과성분/투과성분, 투과성분/막간의 상호인력이 전체적인 투과거동에 어떠한 영향을 미치는지 연구하였다. 사용한 막은 poly(vinyl alcohol)을 glutaraldehyde 로 가교한 막을 사용하였다. 일련의 알코올은 분자량 크기 순서대로 methanol, ethanol, 1-propanol, 1-butanol을 사용하였으며, 조성은 70~97 wt% , 온도는 30, 40, 5$0^{\circ}C$로 변화시키면서 실험하였다. 투과속도는 알코올 함량이 높은 영역에서는 methanol 수용액이 가장 높았으며 ethanol, 1-propanol, 1-butanol 수용액 순으로 감소하였다. 그러나 물의 함량이 어느 정도 높아지면 이런 현상은 완전히 역전되어 1-butanol 수용액의 투과속도가 가장 높으며 1-propanol, ethanol, methanol 수용액 순으로 투과속도 크기를 보였다. 이러한 현상을 공급액의 조성에 따른 막과 투과성분간의 상호인력, 투과성분과 투과성분간의 상호인력 등의 영향의 관점에서 분석하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.201-205
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• 1998

In this paper, the charge control with the input voltage feed forward is proposed for the input series-output parallel connected converter configuration for high voltage power conversion applications. This control scheme accomplishes the output current sharing for the output-parallel connected modules as well as the input voltage sharing for the input-series connected modules for all operating conditions including the transients. It also offers the robustness for the component value mismatches among the modules.

• 한국가금학회지
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• 제30권2호
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• pp.107-112
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• 2003

하절기에 산란피크기간의 대부분이 해당되는 육용종계 산란기의 적정 에너지공급체계를 구명하기 위하여 강원도 홍천군 북방면소재 홍천종계에서 케이지 사양형태의 로스 육용종계 400를 공시하여 2002년 4월부터 2003년 l월까지 40주간 (24∼64주령 ) Table 2 와 같은 4 가지 에너지공급체계 사양시험을 실시한 결과를 요약하면 다음과 같다. 1) 총 산란율, 종란 산란율, 평균난중 및 성계 생존율은 모두 처리간에 유의적인 차이가 인정되지 않았으나, 산란율은 l 일 에너지공급량이 많을수록 오히려 저하하는 경향을 보였다. 2) 사료요구율, ME 및 CP요구량과 사료비는 모두 l일 에너지공급량이 증대함에 따라서 증가하는 경향을 보였다 (P<0.05) 본 연구의 결과 l일 ME공급량을 24주령에 280kcal로부터 30∼34주령에 400kcal 까지 증가시키고 35주령 이후 380kcal를 공급한 Tl 처리가 가장 우수한 성적을 보였다.

• 한국기계가공학회지
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• 제7권3호
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• pp.55-60
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• 2008

Until a recent date, the surface finish generated in turning by the conventional cutting tool is directly related to the feed rate and the size of the tool nose radius. With this tool a large feed rate will give poorer surface finish and a large nose radius will generate a better surface finish. Recently a new concept in the tool design is introduced to achieve a better surface finish at a higher feed rate. This is the wiper tool, which has the portion of nose with infinite radius. This can remove the ridges left when the conventional tool is used. In this study two series of cutting tests with the wiper tool and the conventional tool are carried out under the various cutting conditions of cutting depth, feed rate and cutting speed. The effects of the wiper design and the cutting conditions on the surface roughness resulted are carefully examined and compared.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.413-417
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• 2003

In this paper, a series-fed microstrip array antenna utilized a sub-array with a waveguide slot feeding is presented. This sub-array can reduce the feed loss compared with a full microstrip feed network. The sub-array has been designed both for a broad reflection bandwidth and a flat gain bandwidth from 40.5 GHz to 43.5 GHz. The $24{\times}24$ array antenna has been implemented with the maximum gain of 32.4 dBi.

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.2062-2069
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• 2015

In the series hybrid active power filter (SHAPF) with magnetic flux compensation (MFC), the system current oscillate in the experimental results when adding the same phase harmonic current command in current control block. This condition endangers the security of the SHAPF. Taking the digit period average arithmetic as example, this paper explains the inter-harmonics current oscillation in the experiment. The conclusion is that the SHAPF is unstable to the inter-harmonics current in theory. Limited by the capacity of the inverter, the system current and the inverter output current do not increase to infinite. At last, some methods are proposed to solve this problem. From the practical viewpoint, the voltage feed-forward control is easy to achieve. It can suppress the current oscillation problems, and also improve the filtering effect. The feasibility of the methods is validated by both the emulation and experiment results.

• 한국정밀공학회지
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• 제27권7호
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• pp.79-86
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• 2010

The environment-friendly abrasive materials of starch series has a wide range of application value such as deburring of plastic injection products, paint exfoliation and surface treatment of painted products and polishing, etc. In this study, an experiment of paint exfoliation was performed by using the environment-friendly abrasive materials made of cheap starch, and its performance was reviewed. By adjusting the grit size of abrasive materials, nozzle pressure, nozzle feed and number of nozzle repetition, paint could be exfoliated effectively. In this experiment, it was found that the most suitable condition was grit size 0.75~1.0 mm, nozzle pressure 0.4 MPa, nozzle feed 5 mm/min and number of processing repetition 2 times.