• Educational Technology International
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• 제9권2호
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• pp.79-95
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• 2008

This paper aims to investigate modeling scripts based on the mode of group interaction in a computer-supported collaborative learning environment. Based on a literature review, this paper assumes that group interaction and its mode would have strong influence on the online collaborative learning process, and furthermore lead learners to create and share significant knowledge within a group. This paper deals with two different modes of group interaction- distributed and shared interaction. Distributed interaction depends on the external representation of individual knowledge, while shared interaction is concerned with sharing knowledge in group action. In order to facilitate these group interactions, this paper emphasizes the utilization of appropriate CSCL scripts, and then proposes the conceptual framework of CSCL scripts which integrate the existing scripts such as implicit, explicit, internal and external scripts. By means of the model regarding CSCL scripts based on the mode of group interaction, the implications for research on the design of CSCL scripts are explored.

• Journal of Electrical Engineering and Technology
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• 제7권4호
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• pp.459-467
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• 2012

In this paper, a grid connected microgrid with multiple inverter-based distributed generators (DGs) is considered. DG in FFC mode regulates the microgrid as a controllable load from the utility point of view as long as its output is within the capacity limit. The transition mode causes a change in frequency of microgrid due to the loss of power transferred between main grid and microgrid. Frequency deviation from the nominal value can exceed the limit if the loss of power is large enough. This paper presents a coordinated control method for inverter-based DGs so that the microgrid is always regulated as a constant load from the utility viewpoint during grid connected mode, and the frequency deviation in the transition mode is minimized. DGs can share the load by changing their control modes between UPC and FFC and stabilize microgrid during transition.

• Journal of Power Electronics
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• 제9권1호
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• pp.26-35
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• 2009

A high efficiency active clamp sepic-flyback converter is presented for fuel cell generation systems. The proposed converter is a superposition of a sepic converter mode and. flyback converter mode. The output voltages of the sepic converter mode and flyback converter mode can be regulated by the same PWM technique with constant frequency. By merging the sepic and flyback topologies, they can share the transformer, power MOSFET and active clamp circuit. The result has outstanding advantages over conventional active clamp DC-DC converters: high efficiency, high power density, and component utilization. Simulation results and experimental results are presented to verify the principles of operation for the proposed converter.

• 전력전자학회논문지
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• 제21권3호
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• pp.200-206
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• 2016

In the microgrid, inverters for energy storage system are generally constructed in a parallel structure because of capacity expandability, convenience of system maintenance, and reliability improvement. Parallel inverters are required to provide stable voltage to the critical load in PCC and to accurately share the current between each inverter. Furthermore, when islanding occurs, the inverters should change its operating mode from grid-connected mode to stand-alone mode. However, during clearing time and control mode change, the conventional control method has a negative impact on the critical load, that is, severe fluctuating voltage. In this study, a parallel operation control method is proposed. This method provides seamless mode transfer for the entire transition period, including clearing time and control mode change, and has accurate current sharing between each inverter. The proposed control method is validated through simulation and experiment.

• 조명전기설비학회논문지
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• 제22권12호
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• pp.157-163
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• 2008

다상 교호 컨버터에서 인덕턴스가 불일치 할 때 첨두전류 제어기를 사용하는 경우에 각 상의 평균 전류는 동일하지 않다. 본 논문에서는 각 상의 인덕턴스가 불일치한 경우에 첨두전류 모드에서 평균전류가 동일해지는 전류분배 제어기를 제안한다 제어기는 과도상태에서도 전류의 평형이 잘 이루어질 수 있도록 설계한다. 제안된 방법을 2상과 4상 교호 승압컨버터에 적용시켰으며, 실험 결과를 통해 인덕턴스가 불일치한 경우에도 첨두전류 모드에서 전류평형이 잘 이루어짐을 보인다.

• 대한토목학회논문집
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• 제33권2호
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• pp.667-677
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• 2013

신교통수단의 도입은 통행 대안 간의 수단분담률에 영향을 미친다. 그러나 수단분담률을 추정하는 데에 일반적으로 사용되는 다항로짓 모형은 통행자 선택의 다양성을 반영하기 어렵기 때문에 수단선택 특성을 정확하게 파악하는 데에 한계가 있다. 이러한 문제는 교통수단의 도입 효과를 과다 또는 과소추정하는 결과를 야기하며, 이는 심각한 사회적 손실을 초래할 수 있다. 본 연구는 선호의 동질성 문제를 극복할 수 있는 방법론을 모색하는 것을 목적으로 한다. 전체모집단을 직접수혜자와 간접수혜자로 구분하는 시장분할 구조를 적용하여 선호의 이질성을 반영할 수 있도록 한다. 제주도의 조사 자료를 활용하여 수단 선택 모형이 추정되며, 통계적 검정이 수행된다. 분석 결과, 신교통수단의 통행특성이 고급화됨에 따라 도심부에 거주하는 직접수혜자의 수단 전환율이 증가하는 것으로 확인되었다. 본 연구는 수단전환 패턴의 다양성을 반영함으로써 신교통수단 도입시 수요예측의 정확성을 제고하는 데에 기여할 것으로 사료된다.

• Macromolecular Research
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• 제10권5호
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• pp.273-277
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• 2002

Ultra-thin polymer films containing cobalt(II) meso-tetraphenylporphyrin(CoTPP) have been prepared by vacuum codeposition of the metal complex and trans-2-butene as an organic monomer using an inductively coupled RF glow discharge operating at 7-9 Watts. The polymer films were characterized by sorption measurements. Sorption data obtained for polymer films containing CoTPP indicate that the CoTPP molecules are capable of reversibly binding oxygen molecules. It was found that the adjacent CoTPP molecules in the aggregated metal complex phase could irreversibly share the oxygen molecules. A dispersion of the metal complex molecules in the polymer matrix was made to maintain the reversible reactivity of the metal complex molecules with oxygen in the polymer films via vacuum evaporation process. The Henry mode solubility constant, the Langmuir mode capacity constant, the amount of binding oxygen, and the dissociation equilibrium in the dual mode sorption theory were discussed.

• Clinical Pain
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• 제20권1호
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• pp.7-14
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• 2021

Musculoskeletal ultrasound has evolved as the essential tool to diagnose and guide intervention procedures in people with neuromusculoskeletal conditions. Image optimization and understanding device operations are core components for ultrasound guided intervention procedure training. All ultrasound machines share the common operative features and there are various buttons for the features in the device control panel. Ultrasound "knobology" refers to the thorough understanding of imaging optimization. This review addressed basic information for the transducers, depth setting, gain and focus control, different modes focusing on brightness and doppler modes.

• 한국실내디자인학회논문집
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• 제21권2호
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• pp.174-185
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• 2012

The purpose of this study is to suggest planning strategy of tenant mix for UEC based on the final result of tenant mix analysis of five different research cases. The following is the comprehensive explanation about the result of tenant mix planning strategy for UEC currently in operation and when planning a new facility. First, overall research cases in this study show the tendency of following an old tradition, which stresses direct sales focusing on retail and dining adaptation. In order to compensate the defect, it is suggested to adopt new type of tenants with the functional mix of retail and dining with entertainment rather than decreasing the proportion of retail and dining tenant and increasing it of entertainment tenant. Second, the floorplan of UEC should adopt racetrack or circuit form that can stimulate shoppers' circular movement so to expose them to as much tenants as possible. Service consumption mode related tenants are required to place on the side or the edge of UEC, while retail consumption mode related tenants should be planned in the center. Among dining consumption mode related tenants, impulse dining tenants like a coffee shop should be placed at the turning point or at the end of the pathway, destination tenants like a restaurant and a food court, on the other hand, is needed to be placed in the center of the space. In case of Entertainment related tenants, destination tenants like bookstore or multiplex should also be placed at the end of the pathway, and on the way to those tenants, it is required to place general tenants that can share target customers with them. On the contrary, game center or record shop like tenants that can stimulate impulse sales should be placed on the visitor's main move or near the other destination tenants. Third, anchor tenants play an important role in gathering people to the UEC, and then induce them to visit the other tenants that are located near the anchors. Thus it is suggested to plan to place general tenants on the same floor as anchor tenants are placed so they can share the characteristics of target customers which create synergy effect.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 춘계학술발표대회 논문집
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• pp.43-48
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• 2008

Through simulations and field experiment on A.C. parallel operation of both Utility Interactive Photovoltaic System and Diesel Engine Revolving Field Type Synchronous Generator, following factors have been found. First, the inverter should be operated in three modes of frequency(mode.1: ${\pm}$0.3Hz, mode.2: ${\pm}$1Hz, mode.3: ${\pm}$2Hz) as default, considering properties of operating Synchronous Generator. Second, as a result of supplying 13.5kW of residual power, it has been found that Synchronous Generator takes the power input only as reactive power, because it was electrically stable with frequency of 60.14Hz and high voltage of 222.3V even when power factor was -0.94. Besides, it was mechanically stable, too, because the quake, noise, and temperature of Synchronous Generator in this case were 7.5mm/s, 97dB, and $6^{\circ}C$ respectively, which were lower than normal load connection of 145.6kW; 11.03mm/s. Thus, load share of Revolving Field Type Synchronous Generator reduces according to the supply of Photovoltaic System to the load power. In this experiment, 200kW of Synchronous Generator and 40kW of Photovoltaic System were operated in parallel. The load share was 20% in maximum. and 11.1lit/hr of fuel was saved.