• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
• /
• pp.324-324
• /
• 2008

Piezoelectric ceramics is an active element that makes stator to vibrate to generate rotational force in ultrasonic motors. In drive of ultrasonic motors, many factors that affect to the resonance characteristics of piezoelectric ceramics exist. For example, those factors are bonding condition with elastic body, the magnitude of electric field, the normal force for frictional drive and the emission of heat due to vibration and friction and so on. Therefore, it is important to research the inclination of property variation of piezoelectric ceramics in circumstance that has complex elements. In this paper, we focused and analyzed the resonance characteristics of ultrasonic motor due to the magnitude of the driving voltage and normal force.

• 한국전기전자재료학회논문지
• /
• 제16권7호
• /
• pp.557-563
• /
• 2003

SiC has been an useful material for the high voltage, high temperature, and high frequency devices, however, the required high process temperature to activate the implanted p-type dopants has hindered further developments. In this study, we report, for the first time, on the laser activation of implanted Al and non-alloyed Mo ohmic contacts and its application to MOSFET fabrication. The contact and sheet resistance measured from CTLM patterns have decreased by increasing laser power, and the lowest values are 3.9 $K\Omega$/$\square$ and 1.3 $\times$ 10$^{-3}$ $\Omega$-cm$^2$, respectively, at the power density of 1.45 J/cm$^2$ The n-MOSFETs fabricated on laser activated p-well exhibit well-behaved I-V characteristics and threshold voltage reduction by reverse body voltage. These results prove that the laser process for implant activation is an alternative low temperature technology applicable to SiC devices.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2006년도 춘계종합학술대회
• /
• pp.906-909
• /
• 2006

본 논문은 저 전압 및 저 왜곡 스위치형 커패시터 (switched-capacitor, SC)를 적용한 새로운 형태의 몸체효과 보상형 스위치 구조를 제안한다 제안된 회로는 저 전압 SC 회로를 위해서 rail-to-rail 스위칭을 허용하며 기존의 부트스트랩된 회로 (19dB) 보다 더 우수한 총 고조파 왜곡을 가진다. 설계된 2-1 캐스케이드 시그마 델타 변조기는 통신 송수신시스템내의 오디오 코덱을 위한 고해상도 아날로그-디지털변환을 수행한다. 1단 폴드형 캐스코드 연산증폭기 및 2-1 캐스케이드 시그마 델타 변조기는 0.25 마이크론 이중 폴리 3-금속 표준 CMOS 공정으로 제작되었으며, 2.7V에서 동작한다.

• Journal of Power Electronics
• /
• 제15권4호
• /
• pp.910-919
• /
• 2015

The use of a PV grid-connected inverter with non-isolated topology and without a transformer is good for improving conversion efficiency; however, this inverter has become increasingly complicated for eliminating leakage current. To simplify the complicated architecture of traditional three-level dual buck inverters, a new dual Buck three-level PV grid-connected inverter topology is proposed. In the proposed topology, the voltage on the grounding stray capacitor is clamped by large input capacitors and is equal to half of the bus voltage; thus, leakage current can be eliminated. Unlike in the traditional topology, the current in the proposed topology passes through few elements and does not flow through the body diodes of MOSFET switches, resulting in increased efficiency. Additionally, a multi-loop control method that includes voltage-balancing control is proposed and analyzed. Both simulation and experimental results are demonstrated to verify the proposed structure and control method.

• 대한방사선기술학회지:방사선기술과학
• /
• 제11권2호
• /
• pp.3-15
• /
• 1988

When X-rays were projected into a patient, there occured the phenomena such as penetration, absorption and scattering etc. The penetrating rays were recorded on films as X-ray image used for diagnosis but scattered rays caused the radiation hazard both to the patient, specialist and technicians. The soft tissue includes many organs which are sensitive to the radiation and in may occupy $40{\sim}50%$ of body weight. Therefore X-rays should be carefully projected to the patient and it is strongly recommended to analyse the distribution of X-rays, when ever the patient is exposed to X-rays. In this study, the distribution of X-ray according to the thickness, the radiation field and the tube voltages (kVp) in soft tissue, the following results were obtained: 1. Total transmitted rays which kept the step with X-ray tube voltage (kVp) increased in proportion to the increasing of X-ray tube voltage. 2. The scattered ray rate in the total transmitted ray was not significantly found with X-ray tube voltage. 3. The affecting factors of the scattered ray rate in total transmitted ray were shown through the radiation field and the thickness. 4. The dose of scattered ray by the angle was observed more in direction of primary ray ($0^{\circ}$) and back scattering ($160^{\circ}$) than in direction of $90^{\circ}$. 5. The more the distance from phantom to the patient should be less distribution of scattered ray.

• 소성∙가공
• /
• 제13권7호
• /
• pp.586-593
• /
• 2004

A terminal pin, which is a part of high-voltage capacitors, has a plate-shaped head section with thickness of 0.8mm. The current manufacturing process, in which the head section is welded on the body part, has given wide deviations of part qualities such as geometrical accuracy, mechanical strength and electrical stability. In this study, a cold forging process sequence was designed in order to produce the terminal pin as one piece. The plate-shaped head section requires an upsetting in the lateral direction of a cylindrical billet, which is followed by a blanking process. The deformed geometry of the lateral upsetting, however, could not be predicted precisely by intuition since metal flows of an axial and a lateral direction of the cylindrical billet would occur simultaneously. Therefore, in this study, three dimensional finite element analyses were applied to the lateral upsetting process in order to determine a proper diameter and height of the cylindrical billet. Once the geometry of the initial billet was determined, intermediate forging processes were designed by applying cold forging guidelines and the designed process sequence was verified by two dimensional finite element analysis. In addition, cold forging tryouts were conducted by using a die set, which was manufactured based on the designed process and finally we found that the part qualities were improved by the proposed cold forging process.

• 한국전자통신학회논문지
• /
• 제14권1호
• /
• pp.137-146
• /
• 2019

다수의 초음파 트랜스듀서를 이용한 초음파 위상 배열은 초점제어에 의해 인체 내 종양을 치료하는 목적 등으로 사용되고 있다. 초점제어에 의해 결정된 각 초음파 트랜스듀서 표면음압의 크기와 위상은 각 초음파 트랜스듀서에 인가되는 전압의 크기와 위상을 제어하여 구현 가능하다. 본 논문에서는 초음파 트랜스듀서의 인가전압과 표면음압 사이의 관계를 모델링하고, 요구되는 초음파 트랜스듀서의 표면음압을 생성하기 위한 인가전압을 PWM 기법으로 제어하는 방법을 제안한다. 제안한 방법의 타당성은 61개의 초음파 트랜스듀서로 구성된 초음파 위상배열의 초점제어를 예로 들어 시뮬레이션으로 검증하였다.

• 한국재료학회지
• /
• 제29권2호
• /
• pp.106-115
• /
• 2019

Recently, metal cases are widely used in smart phones for their luxurious color and texture. However, when a metal case is used, electric shock may occur during charging. Chip capacitors of various values are used to prevent the electric shock. However, chip capacitors are vulnerable to electrostatic discharge(ESD) generated by the human body, which often causes insulation breakdown during use. This breakdown can be eliminated with a high-voltage chip varistor over 340V, but when the varistor voltage is high, the capacitance is limited to about 2pF. If a chip capacitor with a high dielectric constant and a chip varistor with a high voltage can be combined, it is possible to obtain a new device capable of coping with electric shock and ESD with various capacitive values. Usually, varistors and capacitors differ in composition, which causes different shrinkage during co-firing, and therefore camber, internal crack, delamination and separation may occur after sintering. In addition, varistor characteristics may not be realized due to the diffusion of unwanted elements into the varistor during firing. Various elements are added to control shrinkage. In addition, a buffer layer is inserted in the middle of the varistor-capacitor junction to prevent diffusion during firing, thereby developing a co-fired product with desirable characteristics.

• 전기전자학회논문지
• /
• 제26권1호
• /
• pp.124-128
• /
• 2022

기존 LDO 레귤레이터 외부 커패시터는 오버슈트 및 언더슈트와 같은 과도 응답 특성을 줄일 수 있다. 그러나 본 연구에서 제안한 Capless LDO 레귤레이터는 과도 응답을 개선하고 우수한 전류 구동 능력을 제공하기 위해 패스 트랜지스터에 바디 기술을 적용하였다. 제안하는 LDO 레귤레이터의 동작 조건은 3.3V ~ 4.5V 범위의 입력 전압, 최대 부하 전류 200mA, 출력 전압 3V로 설정하였다. 측정 결과, 부하 전류가 100mA일 때 전압은 언더슈트 상태에서 95 mV, 오버슈트 상태에서 105 mV임을 확인 할 수 있었다.

• 전기학회논문지
• /
• 제57권3호
• /
• pp.344-353
• /
• 2008

To apply the appropriate new grounding system to domestic power system, safety has to be guaranteed under the given circumstances. It is not possible to decide the safety of grounding systems by the experimental test because safety experiments directly relate to the human life and the installed electric machines. Therefore, the computer simulation program to decide the safety of grounding systems based on the IEC standard systems, has to be developed. This paper proposes the computer simulation based method to decide the safety of grounding system with the concepts of touch voltage, step voltage, human resistivity, and applied electric current according to the several conditions of human body located in the corresponding grounding systems. The proposed method is implemented by Matlab/Simulink and Visual C++ programming tools for its visualization.