• 한국ITS학회 논문지
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• 제10권6호
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• pp.84-90
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• 2011

본 논문은 이중대역 Pseudo-combline 협대역 대역통과 여파기를 제안한다. 제안한 이중대역 대역통과 여파기의 특징은 개방형 공진 스터브를 사용하고 있으며 ITS와 X-밴드 위성 시스템에 적용이 가능하다. 이중대역 대역통과 여파기는 첫번째 운용 주파수 대역의 중심 주파수 5.8 GHz 그리고 대역폭 3.6 %에서 삽입 및 반사 손실이 각각 1.72 dB 및 15.5 dB 이다. 또한 두 번째 운용 주파수 대역의 중심 주파수 8.5 GHz 그리고 대역폭 3%에서 삽입 및 반사 손실은 각각 1.92 dB 및 16.3 dB 이다.

• 전력전자학회논문지
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• 제13권5호
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• pp.396-402
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• 2008

본 논문에서는 영전압 스위칭 풀브릿지 컨버터에 적용할 수 있는 새로운 방식의 복합 변압기(Integrated magnetics) 구조를 제안하고 시험용 컨버터에 적용하여 실험 결과를 보고한 것이다. 제안된 복합변압기의 권선 방법은 두 개의 1차측 권선을 병렬로 하고 2차측 권선은 중앙에 탭이 있는 배전압 방식으로 구성이 된다. 복합변압기의 구조는 기본적으로 EE, EI 코어를 이용하며 코어 양쪽 다리에 변압기의 1, 2차 권선이 각각 위치하고, 중앙의 다리에는 출력 필터용 인덕터 권선을 구성한다 제안된 복합변압기의 성능을 평가하기 위해서 100kHz의 스위칭 주파수, 12V 출력전압과 최대출력 720W급의 컨버터를 제작하였으며 복합변압기는 전 범위에서 동작이 안정되었으며 컨버터는 최대 92%의 전력변환효율을 나타내었다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제27권6호
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• pp.570-575
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• 2001

This study evaluated the short-term outcome of treating fractures of the mandible with bioabsorbable plates. Thirty-four fractures of the mandible in 27 patients were treated by open reduction and internal fixation using bioabsorbable plates and 2.4-mm, 2.0-mm, and 1.5-mm pre-tapped screws. The duration of intermaxillary fixation ranged from 0 to 23 days, with a mean of 5.3 days. Patients were evaluated for complications during the follow-up period, which ranged from 2 to 18 months. Five patients(18.5%) experienced complications. These included infection (four patients), and premature occlusal contact(one patient). Except for one case, all complications were minor and adequately managed with incision and drainage, elastic traction, and medication. Delayed infection (osteomyelitis) developed in a symphysis fracture and was treated by saucerization and antibiotics. The fracture line subsequently showed complete consolidation. Bioabsorbable plates can be selectively used for internal fixation in mandibular fractures with the advantage that they do not need to be removed.

• 마이크로전자및패키징학회지
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• 제11권1호
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• pp.71-76
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• 2004

무선 이동 통신에 응용할 수 있는 소형의 집적된 형태의 여파기를 LTCC기술과 인터디지털 커패시터 (Interdigital capacitor)를 가진 컴라인 타입(Combline type)의 구조를 이용해 구현했다. 또한 T 패턴을 가지는 마이크로스트립(Microstrip)타입의 공진기를 이용해 LTCC 기판의 전기적 성능을 측정했다. 구현된 여파기는 인터디지털과 컴라인 구조를 이용해 2.7mm${\times}$2.03mm의 비교적 소형으로 구현할 수 있었고 5.09 GHz의 중심주파수에서 1.8 dB의 삽입손실, 37.6 dB의 반사손실, 그리고 280 MHz의 대역폭을 가졌다. 제안된 여파기는 작은 크기와 간단한 구조로 인해 여러 가지 LTCC기판의 집적형 여파기로 응용될 수 있을 것이다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.39-44
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• 2009

Geothermal energy is the heat contained in the earth and its internal fluids. Geothermal energy is stored as sensible or latent heat. Supplied by both internal and external sources, it represents a vast supply which is only started to be tapped for generation of electric power. In general, this is natural dry or wet medium to high enthalpy steam at temperatures above $150^{\circ}C$. For some time, binary systems employing substances with a lower boiling point than water in a secondary circuit have been used to generate vapor for driving turbines at a lower temperature level. The utilization of binary plants and the possibility of production from enhanced geothermal systems can expand its availability on a worldwide basis. The geothermal electricity installed capacity is approaching the 10,000GW threshold. Geothermal energy is not present everywhere, but its baseload capability is a very important factor for its success.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1296-1308
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• 2014

This paper presents a new zero voltage switching (ZVS) converter for medium power and high input voltage applications. Three three-level pulse-width modulation (PWM) circuits with the same power switches are adopted to clamp the voltage stress of MOSFETs at $V_{in}/2$ and to achieve load current sharing. Thus, the current stresses and power ratings of transformers and power semiconductors at the secondary side are reduced. The resonant inductance and resonant capacitance are resonant at the transition interval such that active switches are turned on at ZVS within a wide range of input voltage and load condition. The series-connected transformers are adopted in each three-level circuit. Each transformer can work as an inductor to smooth the output current or a transformer to achieve the electric isolation and power transfer. Thus, no output inductor is needed at the secondary side. Three center-tapped rectifiers connected in parallel are used at the secondary side to achieve load current sharing. Compared with the conventional parallel three-level converters, the proposed converter has less switch counts. Finally, experiments based on a 1.44kW prototype are provided to verify the operation principle of proposed converter.

• Journal of Power Electronics
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• 제14권4호
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• pp.661-670
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• 2014

A new DC/DC converter with zero voltage switching is proposed for applications with high input voltage and high load current. The proposed converter has two circuit modules that share load current and power rating. Interleaved pulse-width modulation (PWM) is adopted to generate switch control signals. Thus, ripple currents are reduced at the input and output sides. For high-voltage applications, each circuit module includes two half-bridge legs that are connected in series to reduce switch voltage rating to $V_{in}/2$. These legs are controlled with the use of asymmetric PWM. To reduce the current rating of rectifier diodes and share load current for high-load-current applications, two center-tapped rectifiers are adopted in each circuit module. The primary windings of two transformers are connected in series at the high voltage side to balance output inductor currents. Two series capacitors are adopted at the AC terminals of the two half-bridge legs to balance the two input capacitor voltages. The resonant behavior of the inductance and capacitance at the transition interval enable MOSFETs to be switched on under zero voltage switching. The circuit configuration, system characteristics, and design are discussed in detail. Experiments based on a laboratory prototype are conducted to verify the effectiveness of the proposed converter.

• 전력전자학회논문지
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• 제26권3호
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• pp.237-240
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• 2021

This research proposes a new rectifier circuit to reduce the circulating current of a phase-shifted full bridge converter. The proposed circuit is a structure in which the output inductor of the secondary rectifier circuit is changed to a coupled inductor in the phase-shifted full bridge with the existing center-tapped rectifier. The parts are rearranged after adding a diode. After applying the proposed circuit, the circulating current to the primary current of the transformer and the voltage stress of the rectifier diode on the secondary side of the transformer are reduced. Accordingly, the snubber loss of the rectifier is improved. By reducing the circulating current and snubber loss, the circuit achieves higher efficiency than conventional circuits. In this research, we present the structure of the proposed circuit, its strengths, and the analysis results from experiments. Furthermore, its effectiveness is verified through the experimental results of a prototype converter with an input of 300-400 V and an output of 50 V/1 kW.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.127-130
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• 2004

For the quality control of the industrial products, an automatic hole measuring system has been developed. The measurement device allows X-Y movement due to contact forces between a hole and its own circular cone and the device is attached to an industrial robot. Its measurement accuracy is about 0.04mm. This movement of the plate is measured by two LVDT sensor system. But this system using the LVDT sensors is restricted by high cost and precision of measurement and correspondence of environment so particularly, a vision system with CCD-Camera is discussed in this paper for the above mentioned purpose. The device consists of two of two links jointed with hinge pins basically and, they guarantee free movement of the touch prove attached on the second link in the same plane. These links are returned to home position by the spring plungers automatically after each process for the next one. On the surface of the touch prove, it has a circular white mark for camera recognition. The system detect and notify the center coordinate of capture mark image through the image processing. Its measuring accuracy has been proved to be about $\pm$0.01mm through the repeated implementation over 200 times. This technique will shows the advantage of touch-indirect image capture idea using cone-shaped touch prove in various symmetrical shaped holes particulary, like tapped holes, chamfered holes, etc As a result, we attained our object in a view of the accuracy, economical efficiency, and functionality

• 대한치과교정학회지
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• 제41권6호
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• pp.423-430
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• 2011

Objective: To evaluate the extent and aspect of stress to the cortical bone after application of a lateral force to a two-component orthodontic mini-implant (OMI, mini-implant) by using three-dimensional finite element analysis (FEA). Methods: The 3D-finite element models consisted of the maxilla, maxillary first molars, second premolars, and OMIs. The screw part of the OMI had a diameter of 1.8 mm and length of 8.5 mm and was placed between the roots of the upper second premolar and the first molar. The cortical bone thickness was set to 1 mm. The head part of the OMI was available in 3 sizes: 1 mm, 2 mm, and 3 mm. After a 2 N lateral force was applied to the center of the head part, the stress distribution and magnitude were analyzed using FEA. Results: When the head part of the OMI was friction fitted (tapped into place) into the inserted screw part, the stress was uniformly distributed over the surface where the head part was inserted. The extent of the minimum principal stress suggested that the length of the head part was proportionate with the amount of stress to the cortical bone; the stress varied between 10.84 and 15.33 MPa. Conclusions: These results suggest that the stress level at the cortical bone around the OMI does not have a detrimental influence on physiologic bone remodeling.