• 컴퓨터교육학회논문지
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• 제16권1호
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• pp.97-110
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• 2013

본 연구는 교육정보공유체제의 이용 활성화를 위한 방안을 제안하고자 주 사용자인 교사들의 요구사항을 분석하였다. 교사들이 생각하는 현행 시스템의 문제점과 개선점 및 희망 컨텐츠가 무엇인지에 대한 세 가지 연구과제를 설정하고, 구체적인 의견 수렴을 위해 개방형 설문을 실시하였으며 NVivo 10 프로그램으로 분석하였다. 현 시스템은 기능적 문제, 자료의 신뢰성 부족 문제, 공유 및 활용을 위한 체제 문제를 갖고 있으며, 교사들은 개인의 상황에 맞는 매우 다양한 자료들을 요구하였다. 이에 본 연구에서는 맞춤형 검색이 가능한 새로운 검색엔진 도입, 컨텐츠 저작 도구 탑재 등의 웹사이트 기능 개선을 제안하였다. 또한 다양한 교사의 요구를 만족하기 위하여 교사가 주도적으로 컨텐츠를 생산 공유 유통할 수 있는 오픈마켓 서비스 체제를 제안하였고, 교사들의 교육정보공유체제 이용을 활성화하기 위해 저작권의 문제가 선결되어야 함을 강조하였다.

• Journal of Power Electronics
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• 제11권3호
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• pp.360-368
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• 2011

This paper proposes an active frequency with a positive feedback in the d-q frame anti-islanding method suitable for a robust phase-locked loop (PLL) algorithm using the FFT concept. In general, PLL algorithms for grid-connected PV PCS use d-q transformation and controllers to make zero an imaginary part of the transformed voltage vector. In a real grid system, the grid voltage is not ideal. It may be unbalanced, noisy and have many harmonics. For these reasons, the d-q transformed components do not have a pure DC component. The controller tuning of a PLL algorithm is difficult. The proposed PLL algorithm using the FFT concept can use the strong noise cancelation characteristics of a FFT algorithm without a PI controller. Therefore, the proposed PLL algorithm has no gain-tuning of a PI controller, and it is hardly influenced by voltage drops, phase step changes and harmonics. Islanding prediction is a necessary feature of inverter-based photovoltaic (PV) systems in order to meet the stringent standard requirements for interconnection with an electrical grid. Both passive and active anti-islanding methods exist. Typically, active methods modify a given parameter, which also affects the shape and quality of the grid injected current. In this paper, the active anti-islanding algorithm for a grid-connected PV PCS uses positive feedback control in the d-q frame. The proposed PLL and anti-islanding algorithm are implemented for a 250kW PV PCS. This system has four DC/DC converters each with a 25kW power rating. This is only one-third of the total system power. The experimental results show that the proposed PLL, anti-islanding method and topology demonstrate good performance in a 250kW PV PCS.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.183-186
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• 2007

The injection molding process has high accuracy and good reproducibility that are essential for mass production at low cost. Conventional molding processes typically use the water-based mold heating and air cooling methods. However, in the nano injection molding processes, this semi-active mold temperature control results in the several defects such as air-flow mark, non-fill, sticking and tearing, etc. Therefore, in order to control temperature of the molds actively and improve the quality of the molded products, the novel nano injection molding system, which uses active heating and cooling method, has been introduced. By using the Peltier devices, the temperature of locally adiabatic molds can be controlled dramatically and the quality of the molded patterns can be improved.

• Journal of Power Electronics
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• 제13권2호
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• pp.287-295
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• 2013

The use of LCL filters in pulse width modulation voltage source converters is a standard solution for providing proper attenuation of high-order grid-current harmonics. However, these filters can cause the undesired effect of resonance. This paper proposes an active damping strategy with harmonics compensation. It can alleviate the harmonics around the resonance frequency caused by the LCL filters. The proposed strategy is attractive since it is simple, does not depend on grid parameters and does not increase the number of sensors. Simulation and experimental results verify the effectiveness of the proposed active damping strategy.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.903-908
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• 2006

As environmental vibration requirements on precision equipment become more stringent. use of pneumatic isolators has become more popular and their performance is subsequently required to be further improved. Dynamic performance of passive pneumatic isolators is related to various design parameters in a complicated manner and, hence, is very limited especially in low frequency range by volume of chambers. In this study, an active control technique, so called time delay control which is considered to be adequate for a low frequency or nonlinear system, is applied to a single chamber pneumatic isolator. The procedure of applying the time delay control law to the pneumatic isolator is presented and its effectiveness in enhancement of transmissibility performance is shown based on simulation and experiment. Comparison between passive and active pneumatic isolators is also presented.

• 융복합기술연구소 논문집
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• 제3권1호
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• pp.45-49
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• 2013

Spherical active carbon materials have been used for the removal of pollutants in the area of food processing, water treatment, air purification, oral administration. Moreover, they are now expected to make an epoch in the areas of electronics, life science, environmental technology, and so on due to their superior physical properties. Carbon particles should be requested for the edgeless spherical shapes in order to minimize the loss due to the abrasion during the process and/or practical use, but the carbon particles manufactured from petroleum-based pitch do not meet these needs. Nowadays, thus, the spherical active carbon particles carbonized from various spherical polymer beads are studied with thermoplastic and/or thermosetting polymers. In this paper, the synthesis of spherical phenolic beads and furan beads, which are thermosetting polymers, and their carbonization techniques are examined.

• 대한음성학회지:말소리
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• 제66호
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• pp.87-103
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• 2008

We describe a new active learning method in conditional random fields (CRFs) framework for keyphrase extraction. To save elaboration in annotation, we use diversity and representative measure. We select high diversity training candidates by sentence confidence value. We also select high representative candidates by clustering the part-of-speech patterns of contexts. In the experiments using dialog corpus, our method achieves 86.80% and saves 88% training corpus compared with those of supervised method. From the results of experiment, we can see that the proposed method shows improved performance over the previous methods. Additionally, the proposed method can be applied to other applications easily since its implementation is independent on applications.

• 한국실내디자인학회논문집
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• 제19호
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• pp.20-29
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• 1999

We live now in information society. High-tech communication technique of information came up to our daily life thoroughly. Then, what will happen to change the field of architecture in information society\ulcorner This study realized architecture in virtual reality by choosing technique in virtual reality that was able to alternate architecture in reality. The result of this study: 1. We promoted some shopping malls by making use of 'an active world' that is one of the virtual reality programs. As a result, we could know that we were able to find out goods faster than reality economically and purchase them in virtual reality. 2. There are many fields that we can adapt the architecture in virtual reality beside the shopping malls. For example, they can be a museum, an art gallery, and educational facility, a movie theater, a government and public office, and a recreation facility. 3. The architecture in virtual reality will cause to change our lifestyles and environments and to coexist architecture in reality.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 D
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• pp.2528-2530
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• 2005

In this paper, a study on the analysis and design of an electro-hydraulic pressure reducing valve for active suspension system of car is fulfilled. Also, the structurally improved direct-acting electro-hydraulic pressure reducing valve is proposed to satisfy the performance that active suspension system requires. To prove the possibility whether the proposed valve can be used for active suspension system or not, the mathematical modeling and analysis for this valve is fulfilled and the experiment of response to controlled pressure is achieved. Here we conformed the response speed to controlled pressure of the structurally improved valve changed for the better by modifying the shape of spool such as the structure which make use of the power of controlled pressure derived from the area difference between two section areas of valve spool.

• 약학회지
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• 제6권2호
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• pp.1-6
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• 1962

Clinical tests revealed that the extracts of Gelidium amansii (Gelidiaceae) had a anthelmintic action and further examinations were made on the anthelmintic components of this seaweed. This anthelmintic principle is absorbed on alumina and eluted from it by alkali solution. The active principle is absorbed on activated carbon from aqueous extract and eluted from it by methanol and it is not adsorbed on Amberite IR-120(H-form). This anthelmintic effective fraction was prepared by the use of this properties. Action of the active principle of Gelidium amansii was examined pharmacologically. The active principle of Gelidium amansii was found to decrease the tensity, tonus and mobility of Eisenia foetida(Savigny) nerve muscles. The active principle of this effective fraction was submitted to paper chromatography and spots to ninhydrin were detected at Rf; 0.30-0.31(yellow), 0.26(violet), 0.2(violet), 0.14-0.13(violet), 0.9(orange) and 0.04(violet).