• Journal of Electrical Engineering and Technology
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• 제6권4호
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• pp.466-473
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• 2011

This paper proposes a protection algorithm for a wind turbine generator (WTG) in a large wind farm. To minimize the outage section, a protection relay for a WTG should operate instantaneously for an internal fault or a connected feeder fault, whereas the relay should not operate for an internal fault of another WTG connected to the same feeder or an adjacent feeder fault. In addition, the relay should operate with a delay for an inter-tie fault or a grid fault. An internal fault of another WTG connected to the same feeder or an adjacent feeder fault, where the relay should not operate, is determined based on the magnitude of the positive sequence current. To differentiate an internal fault or a connected feeder fault from an inter-tie fault or a grid fault, the phase angle of the negative sequence current is used to distinguish a fault type. The magnitude of the positive sequence current is then used to decide either instantaneous operation or delayed operation. The performance of the proposed algorithm is verified under various fault conditions with EMTP-RV generated data. The results indicate that the algorithm can successfully distinguish instantaneous operation, delayed operation, or non-operation depending on fault positions and types.

• ETRI Journal
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• 제36권5호
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• pp.835-840
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• 2014

New ways of achieving small, multiband, multifunctional, and standard solutions for mobile handset antennas are demanded in the current wireless market. A non-resonant element of $5mm{\times}5mm{\times}5mm$, a matching network, and a $100mm{\times}40mm$ slotted ground plane are proposed to satisfy mobile market demands that require multiband operation and small antenna solutions. The main advantage of the proposed design is that with only one non-resonant element of considerably small size ($0.015{\lambda}$, 900 MHz), the handset is capable of providing operation at mobile bands.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 학술대회 논문집 전문대학교육위원
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• pp.147-153
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• 2006

Voltage unbalance will be generated by the load unbalance operation such as combination operation of single & three phase load and current unbalance will be more severe by the deteriorated voltage quality. Under the these unbalance conditions, all power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. it may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration. This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system by the unbalance and harmonic components. It was able to confirm that the number of torque pulsation decreased and torque ripple values increased by the harmonics that reduction was difficult by five harmonics filters at additional driving time of single-phase non-linear load.

• 한국해양학회지:바다
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• 제4권2호
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• pp.93-100
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• 1999

금강 하구역의 해수면 변화에 미치는 하구언 수문 작동의 영향을 알아보기 위하여 군산 내항과 외항의 조석자료를 분석하여 비조석 해수면, 평균해수면 및 주요분조의 조화상수를 구하였다. 비조석 및 평균해수면은 하구언 수문 작동이후 내항과 외항에서 낮아졌고 특히 내항에서 급격한 비조석 해수면의 하강을 보였다. 이러한 비조석 해수면의 감소로 내항과 외항사이의 평균해수면 구배가 변화되었으며 이는 주로 하구언으로부터 담수유출량이 감소하여 발생한 것으로 해석되었다. $M_2$와 $S_2$ 분조의 진폭은 내항에서 수분작용 후 급격히 증가하였고, 위상은 다소 감소하였다. $O_1$과 $K_1$ 분조의 위상과 진폭은 변화가 미약하였다 이러한 반일주조 진폭의 큰 변화는 입사파와 하구언에서 반사된 파의 중첩에 의한 것으로 해석된다.

• 전력전자학회논문지
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• 제21권4호
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• pp.283-289
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• 2016

Islanding protection of a grid-connected photovoltaic (PV) inverter is a key function for standards compliance. Unintentional islanding results in safety hazards, reliability, and many other issues. Therefore, many anti-islanding schemes have been examined. However, existing anti-islanding schemes have poor power quality and non-detection zone issues. Moreover, most schemes have problems that deteriorate the performance of islanding detection under parallel operation. Therefore, this paper proposes a novel anti-islanding scheme that has negligible power quality degradation and has no non-detection zone and islanding detection under a parallel operation. Both simulation and experimental results validate the proposed scheme.

• 한국멀티미디어학회논문지
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• 제19권6호
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• pp.1014-1023
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• 2016

In this study, we presented a method for non-square Differential LBP operation that can well describe the micro pattern in the horizontal and vertical component. We proposed a way to represent a LBP operation with various direction components as well as the diagonal component. In order to verify the validity of the proposed operation, Differential LBP was investigated with respect to accuracy, sensitivity, and specificity for the classification of facial expression. In accuracy comparison proposed LBP operation obtains better results than Square LBP and LBP-CS operations. Also, Proposed Differential LBP gets better results than previous two methods in the sensitivity and specificity indicators 'Neutral', 'Happiness', 'Surprise', and 'Anger' and excellence Differential LBP was confirmed.

• 대한수학회지
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• 제54권6호
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• pp.1699-1731
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• 2017

In this note, we define and compare some closures which behave somewhat like the radical closure. Using these closures as a starting point allows us to classify all semiprime closures on the nodal curve. Several examples provided show how these closures can differ significantly in the non-Noetherian setting.

• 한국항공운항학회지
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• 제22권4호
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• pp.87-92
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• 2014

In spite of ICAO's effort to ensure the safety of flight operation by requiring crews, controllers, and other ground aviation staffs to use unified system for units, SI (System International of units), there are still many aircrafts designed, manufactured, and operated based on non-SI units, and many crew training in airline companies are also conducted based on non-SI. Due to this confusion of using different unit systems in international flight operation, many crew members and passengers are exposed to danger. International flights pilots may have confusion while flying different airspaces of different countries that use different unit systems, and this may cause human errors causing accidents and incidents. Due to these reasons, it is needed to establish the standards to reflect non-SI that many countries practically use to SI, which is international standard.

• International Journal of Internet, Broadcasting and Communication
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• 제15권1호
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• pp.195-202
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• 2023

This study is a comparative survey study conducted to explore the differences in learners' learning flow and learning satisfaction according to the non-face-to-face class operation methods implemented at universities. After implementing different class management methods for the same subject taught by the same instructor non-face-to-face for 15 weeks, each learning flow and learning satisfaction were compared and analyzed, and the collected data were analyzed with IBM SPSS 21.0. As a result of the study, learning flow was high in the order of lectures using real-time ZOOM and recorded lectures using self-studio(3.41±0.91, 3.28±1.01), and learning satisfaction was high in the order of lectures using real-time ZOOM and lectures using the automatic recording system of classes(3.40±0.80, 3.30±0.74). The item with the lowest score was the PPT audio recording lecture in both areas of learning flow and learning satisfaction(2.72±1.04, 1.73±1.04). Considering that system errors such as sound in the smart lecture environment operated for the first time in this study affected the research results, it is suggested that future research should be conducted by supplementing the corresponding part.

• 임상간호연구
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• 제16권2호
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• pp.85-93
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• 2010

Purpose: The purpose of this study was to investigate the effect of the SMS(Short Message Service) informing patients' surgical operation status to his or her family members on their nursing satisfaction. Methods: A non-equivalent control group non-synchronized design was used. The subjects were the family members of patients underwent spine surgery operation at a general hospital in B city. Twenty five subjects in the experimental group received SMS services whereas the other twenty five subjects in the control group received no intervention. Results: There was a significant difference in the level of nursing satisfaction in the experimental group compared to that of the control group(t=7.14, p=.001). Conclusion: The result above indicates that the level of nursing satisfaction of family members of the patients under surgical operation can be raised by providing SMS informing surgical operational status during the operation. This finding leads to the conclusion that such information service can be used as one of the efficient interventions for improving patient and family satisfactions with nursing care in a surgical unit.