• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2548-2550
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• 2000

RTP(Rapid Thermal Processing)은 IC제조 공정과 관련된 열처리 과정에 사용되는 단일 웨이퍼프로세스 기술이다. 반도체 웨이퍼를 고속 열처리할 때 웨이퍼별로 작은 반응실에서 가열, 가공, 냉각된다. 현재 사용되는 반도체 열처리장비는 고온로(furnace)에의해 대부분 이루어지지만, 시간이 많이 걸려서 주문형반도체 생산과 같은 다양한 종류의 웨이퍼를 소량 생산하는데는 부적절하다. 이에 매우 적은 시간이 소요되는 RTP장비가 많이 연구되고 있다. 그러나 RTP는 예기치 못한 몇 가지의 문제점을 일으킨다. 그중 하나는 웨이퍼 표면에 분포된 온도의 불 균일성이다. 이러한 불 균일성은 웨이퍼의 표면에 심각한 왜곡(distortion)을 일으켜 좋지 못한 결과를 가져오게 한다. 이번 논문의 목적은 RTP시스템을 수학적으로 모델링하고, 이를 이용하여 멀티 램프 시스템의 입력값을 조절하여 이미 배치된 램프에 대한 최적의 온도 균일도에 알맞은 각 램프입력을 구하여 램프 입력 프로파일을 만들고 또한 이를 이용하여 외란에 대한 PID 제어기 설계를 목표로 한다.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.219.1-219.1
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• 2012

우주물체 전자광학 감시체계(OWL: Optical Wide-field Patrol)의 50cm급 자동망원경 마운트 시스템은 인공위성 관측을 위해 고속으로 움직이면서도 안정적인 추적이 가능해야 하며, 무엇보다 해외설치를 위한 경량화 및 무인 운영을 위한 신뢰성 있는 시스템이어야 한다. 우리가 개발한 경위대식 마운트는 웜기어가 아닌 마찰구동 방식으로 백래쉬가 없고 소음 및 진동을 최소화할 수 있다. 마운트의 자체 중량은 약 400kg이며 최대 가반하중은 250kg까지 가능하다. 지향정밀도와 밀접한 연관이 있는 절대 반복도는 warm start의 경우 5 acrsec, cold start의 경우 10 arcsec이며, 별관측을 통한 추적오차는 10분동안 2 arcsec이내의 값을 가지는 것으로 확인되었다. 마운트의 최대속도는 약 20deg/sec이며, 해외 환경에서의 작동을 위해 내부 온도제어를 통하여 이슬 및 결빙을 방지하도록 하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.2
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• pp.28-33
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• 2007

In this paper, we are studied on the direction and formation of carbonized conductive path according to surface leakage current between electrodes. The characteristics of the tracking as surface is broken down between exposed live parts. Using the HSIS(high speed imaging system. 100,000[fps], redlake ltd., USA), it took photographs by arc growth mechanism occurred in on/off surge, ground fault and discharge between electrodes. Then the results was analyzed. Hereafter, it expected effects that application of energy utility technology through the arc control.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1259-1261
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• 2003

고정밀 와이어컷 방전가공기는 높은 정밀도를 갖는 금형제작에 사용되고 있는 공작기계로서 최근 나노단위의 가공기술이 요구되는 산업추세에 발맞추어 고속, 고정밀 가공특성을 갖추도록 전반적인 성능개선이 이루어지고 있다. 본 논문에서는 기존 Thyristor를 이용한 위상제어 방식보다 우수한 특성을 갖는 스위칭모드 방식의 10kW급 직류 전원장치의 개발에 대해 기술하고있다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.223-223
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• 2010

InSb 물질은 다른 III-V족 물질들과 비교해서 bandgap이 낮고 전자 이동도가 높아, 소자 구현 시 낮은 전압으로도 고속 동작 특성을 제어할 수 있다는 장점이 있다. 그러나 Si, GaAs 또는 InP 등 쉽게 구할 수 있는 기판과 격자 부정합이 커서 상기 기판에 성장시 많은 defect가 존재하는 단점이 있다. 그러므로 이를 상기 기판에 성장하는데 meta-morphic이라 불리는 성장 기술이 요구되는 어려움이 있다. 본 발표에서 Semi-insulating GaAs 기판위에 고품질의 InSb 박막을 성장하기 위해 grading buffer technique을 도입하며 이에 대한 여러 가지 비교실험과 함께 최적의 성장 방법과 기술에 대해 논의 한다. GaAs와 InSb 물질사이의 bandgap과 격자 부정합을 고려하여 AlSb 물질을 먼저 성장하면서 동시에 InxAl1-xSb로 변화를 주어 InSb 박막이 성장되도록 하였다. ($x=0{\rightarrow}1$). 성장 온도 변화 및 In과 Al의 조성비에 변화를 주어 grading 기법으로 성장하였고 상기 grading buffer위에 InSb 박막을 0.65um 성장하였다. $10um{\times}10um$ AFM 측정결과 2.2nm 정도의 표면 거칠기를 가지며 상온에서의 전자 이동도는 약 46, 300 cm2/Vs 이고 sheet electron density는 9.47(e11) /cm2의 결과를 확인하였다. 실험결과 InSb 박막을 올리는데 있어 가장 고려할 사항인 GaAs 기판과 InSb 박막 사이에 존재하는 격자 부정합을 어떻게 해결하는가에 대해서, 기존의 여러가지 방법과 비교해서 grading buffer 기술이 유효하다는 것을 증명하였다.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.1
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• pp.73-77
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• 2007

In this paper, we propose a VLSI architecture of an LMS filter based on a Cyclo-static scheduler for fast computation of LMS filteing algorithm which is widely used in adptive filtering area. This process is composed of two steps: scheduling and circuit synthesis. The scheduling step accepts a fully specified flow graph(FSFG) as an input, and generates an optimal Cyclo-static schedule in the sense of the sampling rate, the number of processors, and the input-output delay. Then the generated schedule is transformed so that the number of communication edges between the processors. The circuit synthesis part translates the modified schedule into a complete circuit diagram by performing resource allocations. The VLSI layout generation can be performed easily by an existing silicon compiler.

• Investigative Magnetic Resonance Imaging
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• v.7 no.1
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• pp.12-21
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• 2003

Purpose : In order to overcome limitations in the existing conventional spectrometer, a new spectrometer with advanced functionalities is designed and implemented. Materials and Methods : We designed a spectrometer using the TMS320C6701 DSP capable of 1 giga floating point operations per second (GFLOPS). The spectrometer can generate continuously varying complicate gradient waveforms by real-time calculation, and select image plane interactively. The designed spectrometer is composed of two parts: one is DSP-based digital control part, and the other is analog part generating gradient and RF waveforms, and performing demodulation of the received RF signal. Each recover board can measure 4 channel FID signals simultaneously for parallel imaging, and provides fast reconstruction using the high speed DSP. Results : The developed spectrometer was installed on a 1.5 Tesla whole body MRI system, and performance was tested by various methods. The accurate phase control required in digital modulation and demodulation was tested, and multi-channel acquisition was examined with phase-array coil imaging. Superior image quality is obtained by the developed spectrometer compared to existing commercial spectrometer especially in the fast spin echo images. Conclusion : Interactive control of the selection planes and real-time generation of gradient waveforms are important functions required for advanced imaging such as spiral scan cardiac imaging. Multi-channel acquisition is also highly demanding for parallel imaging. In this paper a spectrometer having such functionalities is designed and developed using the TMS320C6701 DSP having 1 GFLOPS computational power. Accurate phase control was achieved by the digital modulation and demodulation techniques. Superior image qualities are obtained by the developed spectrometer for various imaging techniques including FSE, GE, and angiography compared to those obtained by the existing commercial spectrometer.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.217-222
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• 2016

This study investigates the design, analysis, and implementation of the square-root extended Kalman filter by using an algorithm derived by combining the Potter or Carlson algorithm with the modified Gram-Schmidt algorithm, for sensorless speed control of a permanent-magnet synchronous motor. The sensitivity of the Kalman filter to round-off errors is a well-known problem. A possible way to address this limitation is by combining the square-root concept and Kalman filter that can improve the numerical performance and solve instability-related problems such as divergence. This paper presents the design and analysis of the implementation of such a square-root extended Kalman filter. To demonstrate the performance of the proposed filter, experimental results under several operating conditions, such as high and low speeds, reversal rotation, detuned parameters and load test, have been analyzed. Further, code sizes and operation times have been compared. Experimental results establish the performance of the proposed square-root extended Kalman filter-based estimation technique for sensorless speed control of a permanent-magnet synchronous motor.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.10
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• pp.52-63
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• 1998

In this paper, several improvements to a copy network proposed previously for multicast packet switching are described. The improvements provide a solution to some problems inherent in multicasting. The input fairness problem caused by overf low is solved by a dynamic starting point decider(DSD), which can calculate running sums of copy requests starting from any input port. The starting point is changed adaptively in every time slot based on both the fill level of the input buffers in current time slot and the overflow situations of the previous time slot. Using the fill level of the conventional network. The DSD also provides the function of regulating overall copy requests according to the amount of input traffics. This is an essential function in improving overall throughputs of the copy networks. The throughput of a multicast switch can be improved substantially if partial service of copy request is implemented when overflow occurs. Call-splitting can also be implemented by the DSD in a straightforward manner. The hardware for the DSD is derived with the objective of simple architectures for the high speed operation. Simulation study of the copy network under various traffic conditions is presented to evaluate its performance.

• Journal of Astronomy and Space Sciences
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• v.25 no.4
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• pp.481-490
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• 2008

Reaction wheel is one of the actuators for spacecraft attitude control, which generates torque by changing an inertial rotor speed inside of the wheel. In order to generate required torque accurately and estimate an accurate angular momentum, wheel speed should be measured as close to the actual speed as possible. In this study, two conventional speed detection methods for high speed motor with digital tacho pulse (Elapsed-time method and Pulse-count method) and their resolutions are analyzed. For satellite attitude maneuvering and control, reaction wheel shall be operated in bi directional and low speed operation is sometimes needed for emergency case. Thus the bias error at low speed with constant acceleration (or deceleration) is also analysed. As a result, the speed detection error of elapsed-time method is largely influenced upon the high-speed clock frequency at high speed and largely effected on the number of tacho pulses used in elapsed time calculation at low speed, respectively.