• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.51-54
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• 2005

Generator efficiency optimization is important for economic saving and environmental pollution reduction. In general, the machine loss can be reduced by the decreasing the flux level, resulting in the significant reduction of the core loss. This paper proposesan model-based controller is used to decrement the excitation current component on the basis of measured stator current and machine parameters and the q-axis current component controls the generator torque, by which the speed of the induction generator iscontrolled according to the variation of the wind speed in order to produce the maximum output power. The generator reference speed is adjusted according to the optimum tip-speed ratio. The generated power flows into the utility grid through the back-to-back PWM converter. The grid-side converter controls the dc link voltage and the line-side power factor by the q-axis and the d-axis current control, respectively. Experimental results are shown to verify the validity of the proposed scheme.

• 동서간호학연구지
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• 제11권1호
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• pp.58-64
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• 2005

The purpose of this study was to examine impact of hospital computerization on the nursing practice. The study was conducted using the repeated measured design. The subjects were 166 nurses working at surgical nursing care units in a tertiary teaching hospital. A questionnaire was developed based on the Burke's study, and reviewed by a committee for content validity. Eighty-eight nurses responded the questionnaire throughout the study. Indirect nursing care time significantly decreased(p<0.05) after the computerization. These decrease related to time saving in checking physicians' order and writing nursing records. However, the change in direct nursing care time was not clear. In conclusion, the computerization led to the decrease in indirect nursing care time but it did not link to increase in direct nursing care time. Therefore, nurse managers should take into account redesign of the nursing works after computerization.

• ETRI Journal
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• 제42권3호
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• pp.341-350
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• 2020

In a wireless sensor network (WSN), the data transmission technique based on the cooperative multiple-input multiple-output (CMIMO) scheme reduces the energy consumption of sensor nodes quite effectively by utilizing the space-time block coding scheme. However, in networks with high node density, the scheme is ineffective due to the high degree of correlated data. Therefore, to enhance the energy efficiency in high node density WSNs, we implemented the distributed source coding (DSC) with the virtual multiple-input multiple-output (MIMO) data transmission technique in the WSNs. The DSC-MIMO first compresses redundant source data using the DSC and then sends it to a virtual MIMO link. The results reveal that, in the DSC-MIMO scheme, energy consumption is lower than that in the CMIMO technique; it is also lower in the DSC single-input single-output (SISO) scheme, compared to that in the SISO technique at various code rates, compression rates, and training overhead factors. The results also indicate that the energy consumption per bit is directly proportional to the velocity and training overhead factor in all the energy saving schemes.

• 통상정보연구
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• 제10권2호
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• pp.23-43
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• 2008

Requirement of facilitating electronic trade transactions and efforts to platform on the electronic trade in major countries are link to the interest of Bill of Lading, the major transportation document, to be electronic, namely interest in Electronic Bill of Lading. Regardless of the benefits from replacing paper based Bill of Lading to the electronic form, which are eliminating of the Crisis of Bill of Lading and cost saving of international trade community, it has not been successful so far. Among the three functions of Bill of Lading, evidence of contracts and receipt of goods can be easily transferable to the electronic form. However the most important function, Document of Title, became the hardest work to replicate in electronic form. The purpose of this paper is to clarify what kind of conditions shall be prepared to ensure the transfer of right and negotiability of the Electronic Bill of Lading and propose to ensure the use of electronic bill of lading and its transfer of right and negotiability in the era of the electronic transactions.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 춘계 학술논문 발표대회
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• pp.21-23
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• 2012

The process of building project for planning, designing, construction, maintenance, and waste disposal are related with each other. However, we have a difficulty for estimating building's LCC due not to be flexible each other. Therefore, we analyzed the boundary condition between the process of construction and maintenance, and analyzed the factor of segment. We also suggested the Link System for flexible relation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권6호
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• pp.1116-1132
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• 2010

In this paper, a new forward error correction (FEC) protocol is proposed for point-to-multipoint satellite links. Link-layer error control protocols in point-to-multipoint satellite links impose several problems such as unreliability and receiver-heterogeneity. To resolve the problem of heterogeneous error rates at different receivers, the proposed scheme exploits multiple multicast channels to which each receiver tunes. The more channels a receiver tunes to, the more powerful error correcting capability it achieves. Based on its own channel condition, each receiver tunes to as many channels as it needs, which prevents from receiving unwanted parities. Furthermore, each receiver saves the decoding time, processing overhead, and processing energy. Performance evaluation shows that the proposed scheme guarantees the target PER while saving energy. The proposed technique is highly adaptive to the channel variation with respect to the throughput efficiency, and provides scalable PER and throughput efficiency.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.467-469
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• 2001

An investigation into power conditioners that interface with photovoltaic array and utilities has been completed. The rating for this investigation is residential system(3-5kW) that interface with a 220V single phase utility connection. As the result of this investigation, a 3kW high frequency PWM IGBT inverter feeding a high frequency isolation transformer with a sinusoidal current wave was selected. The output of the transformer rectified with a diode bridge rectifier, four IGBT, used as 60Hz switched, reverse the polarity of the rectified current on every other half cycle of the utility voltage. Even though the high frequency link system used more power semiconductors, a net size, weight, and parts cost saving result compared to the other systems due to elimination of 60Hz transformer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 G
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• pp.2473-2475
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• 1998

In this paper, we implemented RS232C serial communication by the 2 wires(Data,GND), and multiple access, by the applying Collision Sensing Multiple Access(CSMA) Protocol. Multiple access is implemented by assigning a unique ID to each controller. The multiple access control operation starts by sending a command packet from a host to another host and the command packet is composed of ID bytes of source and target host computer, data bytes and the check sum, byte. In host computer, after sending command packet, the collision from loop back data. If collision is detected, it means a command packet was collided with another command packet for another host. The packet communication of the controller enables the multiple acces of the controller through the common serial data link. The application of this serial communication through CSMA protocol and the usage of two wires, have an effect on saving the wires and convenient of layout work.

• Asia pacific journal of information systems
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• 제12권3호
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• pp.213-233
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• 2002

Recently, a lot of companies intend to make spin-offs as the Internet usage is proliferating in the business area. A spin-off means a small but autonomous company which is thought to show higher profitability rather than it stays under the influence of a mother enterprise. To prove our hypotheses, we collected questionnaire data from 104 companies considering spin-offs. From experiments with Factor Analysis, we found that there exist four factors which decision-makers should consider before deciding spin-offs such as competence of unit, competence of mother company, competence of spin-off company, and support of mother company. After massive experiments with Regression Analysis we also found that there are significant three performance factors such as competence of unit, competence of spin-off company, and support of mother company. The survey also asked about three potential strategies that they may have been following for achieving business objectives: Cost leadership, Focus, and Differentiation, Six benefits factors emerged from this study: External competitiveness, Internal competency, Productivity, Change, Cost saving, and Improvement. External competitiveness was the most important benefit, and it predicted a Differentiation and Focus strategy. Productivity and Improvement also predicted a Differentiation strategy. External competitiveness, Change, and Cost saving predicted a Cost leadership strategy. However, organizations followed Differentiation and Focus strategies significantly more than Cost leadership. The assessment thus sheds light on the link between information strategy and spin off. We hope that based on our results, many companies considering a spin-off can make a right decision and expect higher performance in a turbulent business environment.

• 한국정보과학회논문지:시스템및이론
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• 제32권11_12호
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• pp.654-662
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• 2005

무선 네트워크는 한정된 배터리 전원에 의존하는 이동 휴대 기기를 사용하기 때문에 무선 통신 프로토콜을 설계하는데 있어서 에너지 효율에 대한 고려가 필요하게 되었다. 무선 환경에서 대표적인 TCP 성능 향상 연구 중에 하나인 TCP-Westwood는 ACK를 이용한 샘플링 기법으로 가용 대역폭을 측정한다. 측정한 가용 대역폭을 이용해서 효과적인 데이타 전송을 할 수 있다는 장점을 갖는 반면에, TCP-Westwood 송신단이 무선 구간에 있을 경우에 대한 고려가 미흡하다. 본 논문에서는 TCP-Westwood의 송신단이 무선 구간에 있을 경우에 발생하는 문제점을 보완하기 위해서 새로운 전송 프로토콜인 E2TP(Energy Efficient Transport Protocol)를 제안한다. 제안한 E2TP는 패킷 손실이 발생할 경우에는 일시적인 전송 단위 조절을 이용한 재전송 방법을 사용하여 보다 효과적인 데이타 전송을 수행한다. E2TP의 성능을 검증하기 위한 실험 결과, E2TP가 전송률 및 에너지 효율 측면에서 TCP와 TCP-Westwood보다 성능이 향상됨을 확인할 수 있었다.