• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1229-1231
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• 2003

We considered of the efficiency for the Buck+Half bridge converter, this converter has advantages of applications for a low output voltage, a high output current and a wide input voltage. Developed the Buck+Half Bridge converter ratings are of $36{\sim}72V$ input and 3.3V/30A output. In Half Bridge converter the $86{\sim}96.4%$ of the efficiency is measured at 100kHz switching frequency with PQI core. In the case of synchronized the Buck+Half Bridge converter, the measured efficiency is higher than the unsynchronized converter. In the synchronized Buck+Half Bridge, the maximum efficiency is up to 92.3% with PQI core at 100kHz, 7A output.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1232-1234
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• 2003

The push pull forward converter is a very suitable circuit for low output voltage, high output current applications with a wide input voltage range. This converter can be miniaturized by integrate magnetic components such as the output inductor, the transformer and the input inductor. We considered of the efficiency for the push pull forward converter. Developed the push pull forward converter rating are of $36{\sim}72V$ input and 3.3V/30A output. In this converter. the efficiency was measured by 76.4% at full load and 82.95% at half load. The maximum efficiency is up to 83.% at 200kHz, 11A output.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.451-454
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• 2008

Potential tsunamis which may occur near Ryukyu Islands were simulated. Propagation characteristics of the potential tsunamis over the southwestern sea and the influence of tsunamis on the southwestern coast of Korean Peninsula were analyzed. The shallow water area in the east sea of China and the deep water Okinawa Trough play an important role in wave transformation and propagation of the potential tsunamis. The propagation characteristics of the potential tsunamis generated near Ryukyu Islands can be described as in followings : In the first stage after generation, the tsunamis propagate with high speed both northeastward and southwestward along the Okinawa Trough. As a result the waves are elongated and the tsunami height is significantly reduced. The elongated crest of tsunamis spans the whole distance of the Okinawa Trough and lines up toward the edge of the continental shelf of East China Sea. Then, the tsunamis are propagating towards the southeast coast of China. Thus, the influence of tsunamis on the Korean coasts becomes weak.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.169-170
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• 2014

본 논문에서는 넓은 영전압 스위칭 범위를 가지며 클램프 다이오드와 클램프 스위치를 이용하여 비대칭 하프 브릿지 컨버터의 정상 입력 시 최적 설계가 가능하게 하여 모든 부하 조건에서 효율을 상승 시킬 수 있는 회로를 제안한다. Hold-up 조건 만족을 위하여 입력 전압이 낮은 경우에, 클램프 스위치를 동작시켜 변압기의 턴 비를 바꾸어 주어 출력 전압을 유지해준다. 정상 상태 동작에서는 클램프 스위치를 키지 않음으로써 클램프 다이오드 역할을 하여 2차 측 정류기의 전압 스트레스를 줄여주며, 보조 턴을 이용하여 클램프 다이오드에서의 도통 손실을 줄여 정상 상태에서의 비대칭 하프 브릿지 컨버터의 효율 최적화를 달성한다. 본 논문에서는 제안하는 회로의 이론적 해석 및 설계방법을 설명하고 실험결과를 통해 회로의 동작을 검증한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.1 s.232
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• pp.81-87
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• 2005

A fracture of hand held device, such as radio, TV and CD-RW drive, mainly occurs due to drop situation. For CD-RW drive, the need of high reading/writing speed in conjunction with low price accelerates the fracture of the device. Computer simulation can reduce the period of development and enhance impact characteristic of device. In this study, the detailed finite element model of CD-RW drive was developed to predict the damage under drop conditions. Material property for shock absorbing damper was obtained from tensile test of raw material. A MOONEY-RIVLIN type rubber in LS-DYNA was used as the material model of damper. To assess the reliability of the developed model, drop test at 200G-2msec and 150G-10msec condition was conducted and acceleration at pick-up was compared.

• Progress in Superconductivity and Cryogenics
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• v.24 no.2
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• pp.23-26
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• 2022

A lossless transport of an arbitrary waveform in a frequency range of 10⁶-10⁹ Hz through a conduction channel in a cryogenic temperature is of importance for a high-speed operation of quantum device. However, it is hard to use a commercial oscilloscope to directly detect the waveform travelling in a device located in a cryogenic system. Here, we developed a cryogenic voltage sampling technique by using a Schottky barrier gate prepared on a surface of a GaAs/AlGaAs device, which revealed that an incident rectangle waveform can transport through a 1 mm long two-dimensional conduction channel without waveform deformation up to 20 MHz, while further study is needed to increase the detection frequency.

• Journal of the Semiconductor & Display Technology
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• v.22 no.1
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• pp.88-93
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• 2023

In software engineering, requirement analysis is an important task throughout the process and takes up a high proportion. However, factors that fail to analyze requirements include communication failure, different understanding of the meaning of requirements, and failure to perform requirements normally. To solve this problem, we derived actors and behaviors using morpheme analysis and BERT algorithms in the Korean requirement document and constructed them as ontologies. A chatbot system with ontology data is constructed to derive a final system event list through Q&A with users. The chatbot system generates the derived system event list as a requirement diagram and a requirement specification and provides it to the user. Through the above system, diagrams and specifications with a level of coverage complied with Korean requirement documents were created.

• The Korean Journal of Food And Nutrition
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• v.30 no.6
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• pp.1245-1251
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• 2017

The objective of this study is to investigate the satisfaction of elementary, middle and high school nutrition teachers in the Chungnam province concerning the free school food service. We surveyed satisfaction related to policies on school food service and the school food service center. Satisfaction on the school food service center was separated according to four dimensions; perception, food materials, operational system and service. Furthermore, we analyzed factors that affect satisfaction with the school food service center with a multiple regression model. First, satisfaction about the free school food service and dietary life education are higher than the total average of satisfaction with the policy about the school food service. Second, satisfaction about a variety of food materials and reasonable prices are lower than total average of satisfaction with the school food service center. Third, when more teachers have a high level of a positive perception and have higher satisfaction with the operational system of the school food service center, then they also subsequently display higher satisfaction with the school food service center. Therefore it is necessary to improve or make up for pricing and diversity on food materials by the school food service center.

• Archives of Plastic Surgery
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• v.37 no.5
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• pp.702-704
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• 2010

Purpose: Chordoma is a rare primary osseous tumor arising from the remnants of the primitive notochord. It occurs once in 2,000,000. It is characterized by its slow growth, high frequency to invade destroy bone by direct extension. We experienced giant sacral chordoma and reconstructed with gluteal advancement flap. Methods: A 52-year-old woman presented with a 2-years history of gluteal pain. In the biopsy study revealed sacral chordoma. MRI study showed $13{\times}12{\times}10\;cm$ sized m0cs. We approached anterior and posterior resection and reconstructed with bilateral gluteus maximus advancement flap. Results: After the operation, blader and anal function were slightly decreased. But, 4 months later those were almost fully recovered. There was no significant complication and recurrence after 2-years follow-up. Conclusion: Chordoma is characterized by its slow growth, high frequency to invade and destroy bone by direct extension. Wide surgical resection is the only curative procedure. We report a ase of giant sacral chordoma which was successfully treated by anterior and posterior approach and reconstructed with bilateral gluteal advancement flap.

• The Plant Pathology Journal
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• v.20 no.2
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• pp.110-114
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• 2004

Through in vitro screening for biocontrol agents (BCAs) against Streptomyces scabiei causing potato (Solanum tuberosum) common scab, 19 streptomycete and 17 fungal isolates with antagonistic activity were selected as BCA candidates. For the selection of BCA candidates which are highly resistant to 10 kinds of antibiotics or pesticides, chemical susceptibility testing was initially performed in vitro. A remarkable degree of variation in susceptibility to antibiotics or pesticides was observed among the isolates tested. Streptomycete A020645 isolate was highly resistant to all the tested chemicals except neomycin up to 5,000 ppm. On the other hand, out of 36 antagonistic microbes subjected to in vivo pot tests using cultivar Daejima, four streptomycete isolates namely, A020645, A010321, A010564, and A020973, showed high antagonistic activity with >60% and 55% control value, respectively, and high chemical resistance to 10 kinds of chemicals. Therefore, these isolates were selected as potential BCAs for the control of potato common scab.