• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.235-238
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• 1998

In this study, the cymbal actuators with brass and bronze endcap at various endcap thickness were fabricated, and then the displacement vs applied voltage relation and position from the center of endcap relation were investigated The displacement values of all cymbal actuator were measured using laser vibrometer. The displacement of the cymbal actuator was increased linearly with increasing applied voltage. The cymbal actuator with 0.15mm thick brass endcap show approximately 1.3$\mu\textrm{m}$ displacement more than cymbal actuator with uniformly thick bronze endcap. The displacement about 3mm in diameter at the center of the endcap was uniform and rapidly decreased away from 3mm in diameter at the center of the endcap.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.844-846
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• 1998

In this study, Brass endcap with 2, 3, 5, and 7mm contact surface and 0.6, 0.9, 1.2, 1.5mm conical cavity depths was fabricated by the punch die while keeping the cavity diameter constant 9.25mm then displacement characteristics of the cymbal actuators with each of brass endcap thickness were measured under an applied voltage $60V_{max}$. Dispacement increased with increasing contact surface and resonant frequency decreased with increasing contact surface, cymbal actuator with 7mm contact surface and 1.5mm endcap cavity depth exhibits $35.89{\mu}m$ displacement and 18.8kHz resonant frequency, displacement increased with increasing endcap cavity depth while contact surface was kept constant at 3mm and Below a endcap thickness of 0.2mm, Differences in displacement between 1.2mm and 1.5mm cavity depth appeared at $0.18{\mu}m$. that is, displacement of cymbal actuator with 1.2mm over cavity depth saturated nearly.

• Investigative Magnetic Resonance Imaging
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• 제7권2호
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• pp.137-143
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• 2003

목적 : 자기공명영상(MRI)에서 두부영상촬영을 위하여 가장 많이 사용되는 birdcage RF (Radiofrequency) 코일의 RF B1 필드가 코일 중앙부에서 endring영역으로 갈수록 줄어드는 것을 볼 수 있다. Birdcage RF 코일에서 endcap 쉴드가 코일 중앙부에서 endring영역으로 갈수록 RF B1 필드 균질성에 얼마나 영향을 주는지에 대하여 분석하였다. 대상 및 방법 : Lowpass, highpass, hybrid birdcage RF 코일들에 대해 각각 FDTD (Finite Difference Time Domain) 모의실험으로 RF B1 자속밀도 분포를 비교하였다. 모의 실험결과 RF Bl 필드가 가장 높은 조건인 highpass birdcage RF코일을 선택하여 RF코일 endring 근처에 endcap 쉴드를 적용함으로써 RF B1 균질성에 얼마나 영향이 있는 지 조사하였다. 결과 : FDTD모의실험결과 highpass birdcage RF코일은 코일 내부에서 RF B1 필드가 lowpass나 hybrid 형태의 birdcage RF 코일들 보다 우수하나 코일 중앙부에서 endring 영역까지의 균질성은 떨어졌다. 그러나 highpass birdcage RF 코일에 endcap 쉴드를 적용하면 hybrid birdcage RF 코일의 RF B1 필드와 비슷한 수준이면서 sagittal 방향의 전체적인 RF B1 균질성은 우수하였다. 결론 : 본 논문에서 제안한 방법은 임상에서 MRI자장의 세기가 커질수록 RF코일 내부의 RF B1 균질성이 현저히 떨어지는 문제점이 있는데 이를 개선하는데 적용 할 수 있다고 사료된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1500-1503
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• 2002

In this paper, we proposed windmill type ultrasonic motor which has modified shape of Endcap. The motor was especially designed by FEM for high speed. As results, displacements of the windmill and the clover type motor was compared. Using clover type motor, more smooth rotation of rotor was achieved. If Z component of the displacement of the clover type motor can be applied for linear motor.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1377-1380
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• 2008

An irradiation test of a nuclear fuel rod having external and internal tube structure was planned for a performance. To establish fabrication process satisfying the requirements of irradiation test, micro-TIG welding system for fuel rods was developed, and preliminary welding experiments for optimizing process conditions of fuel rod was performed. Fuel rods with 15.9mm diameter and 0.57mm wall thickness of cladding tubes and end caps have been used and optimum conditions of endcap welding have been selected. In this experiment, the qualification test was performed by tensile tests, helium leak inspections, and metallography examinations to qualify the endcap welding procedure. The soundness of the welds quality of a dual cooled fuel rods has been confirmed by mechanical tests and microstructural examinations.

• 한국정밀공학회지
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• 제25권12호
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• pp.13-19
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• 2008

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.636-640
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• 2003

As industrial technology was developed, necessity for small size motor was increased on various fields such as medical treatment and robotics. The motor should be simple structure, and it has easy process of manufacture to overcome the limit of miniaturization. So, "the windmill type ultrasonic motor" is enough to satisfy these conditions. In this paper, windmill type ultrasonic motor which was proposed by B.Koc and K.Uchino, was analyzed and fabricated with modified endcap shape. Displacements of arms of the proposed endcap were compared with the previous endcap, using the finite element analysis program (ANSYS). Better rotational characteristics was expected in proposed model as result of FEA. Experimentally, rotary motors of 3.5 [cm] diameter were fabricated, and the speed and torque of the motor were measured. As a result, speed and torque were changed in proportion to the electrical input voltages. And low efficiency which was different from an expectation was obtained in this motor. So, various problems should be improved for practical use.

• 대한기계학회논문집B
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• 제22권4호
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• pp.510-519
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• 1998

Recently, computer modelling is increasingly used as a design tool, which requires more detailed data for heat transfer coefficients in various regions of the induction motor. But there are little information about those of rotor fan and endring because of difficulty in measuring signals in rotating bodies. In the present studies, the temperature signals were precisely measured with self-developed telemetry system, which had multi-channels and high rotational speed. After some losses were compensated, the heat transfer coefficients of the rotor endring and fan surfaces were measured. Minimum heat transfer region was existed with endcap plate distance and maximum heat transfer was found at some rotor fan width. It was also studied that how the guide plate and endcap inside rib effected on the rotor heat transfer. The higher heat transfer were obtained with decreasing guide plate distance, increasing the number and height of endcap inside rib. The correlation equations of the results were obtained and compared with others. Above results of the heat transfer coefficients can be used as basic data for cooling design of the various kind of motors.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2000년도 하계학술발표대회 논문집 제19권 1호
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• pp.373-376
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• 2000

기존의 Push-Pull 트랜스듀서보다 간단한 구조를 가지며 출력을 한층 더 높이기 위해서 실린더 중앙에 구동부를 둔 새로운 구조의 Push-Pull 트랜스듀서를 설계하고자 한다. 유한 요소 상용 Package인 ANSYS를 이용하여 트랜스듀서의 모델을 구성한 후, 분석 시 고려되어 지는 길이, 반경, Endcap Edge 형상에 대해 변수로 설정, 변수들의 변화에 대한 음압의 변화 경향을 조사하여 최대 음압을 구현하기 위한 최적 길이, 반경, Endcap Edge 형상을 설정하였다. Endcap의 형상이 수직, 삼각형 형태의 트랜스듀서에서 나타난 결과에서 힘의 전달이 Edge형상이 수직일 때보다는 삼각형일 때가 더 좋은 것을 볼 수가 있었다. 또한 기존의 트랜스듀서를 유한 요소로 설계를 하여서 분석을 하였고, 기존의 트랜스듀서와 비교해 본 결과, 최적 설계한 트랜스듀서가 구조적으로 더 단순한 구조임에도 불구하고 더 큰 음압을 구현할 수 있는 고출력 트랜스듀서라는 것을 입증하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권3호
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• pp.105-109
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• 2001

In this paper, the windmill type ultrasonic motors with 11.35 mm diameter, 2.87 mm thickness of metal endcap and 1.47 g weight were fabricated. Effects of slots and thickness on torque characteristic in the windmill type ultrasonic motor were investigated, when stator's slots were changed from 4, 6, 8 and thickness 0.15 mm, respectively. Specially designed metal endcaps with windmill shaped cutting can provide longitudinal and torsional displacements simultaneously as the ceramic disk vibrates radically. The windmill type ultrasonic motor has only three components: a stator element with windmill shape slotted metal endcap, a rotor and bearing. Ultrasonic motor stimulated to ultrasonic oscillations by piezoelectrics to drive a rotor via friction contact. The ultrasonic motor fabricated here was the windmill type ultrasonic motor operated by single-phase AC source. Bidirectional revolution using single-phase high frequency for driving the ultrasonic motor was presented.