• The Journal of the Acoustical Society of Korea
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• 제20권3E호
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• pp.31-37
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• 2001

Finite element model of a cMUT is constructed using the commercial code ANSYS to analyze the cross talk mechanism. Calculation results of the complex load impedance seen by single capacitor cells are presented, and then followed by a calculation of the plane wave real load impedance seen by a parallel combination of many cells that are used to make a transducer. Cross talk between 1-D array elements is found to be due to two main sources: coupling through a Stoneley wave propagating at the transducer-water interface and coupling through Lamb waves propagating in the substrate. To reduce the cross talk level, the effect of various structural variations of the substrate are investigated, which include a change of its thickness and etched trenches or polymer walls between array elements.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2000년도 하계학술발표대회 논문집 제19권 1호
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• pp.51-54
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• 2000

This paper describes the fixed-point DSP implementation of a CELP(code-excited linear prediction)-based speech coder. The effective realization methodologies to maximize the utilization of the DSP's architectural features, specifically Parallel movement and pipelining are also presented together with the implementation results targeted for the ITU-T standard G.723.1 using Motorola DSP56309. The operation of the implemented speech coder is verified using the test vectors offered by the standard as well as using the peripheral interface circuits designed for the coder's real-time operation.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 제14회 신호처리 합동 학술대회 논문집
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• pp.821-824
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• 2001

본 논문에서는 TMS320C6701 을 이용하여 방대한 양의 데이터를 실시간으로 처리할 수 있는 병렬 DSP 시스템을 설계 및 구현한 것에 대하여 나타내었다. 이 병렬 DSP 시스템은 DSP 칩간의 통신과 보드간의 통신이 가능하며, DSP칩이 마스터가 되어 EMIF(External Memory Interface)포트를 통해 다른 DSP 칩의 지역메모리를 엑세스 할 수 있으며, 또한 외부의 호스트 프로세서가 보드 내의 DSP 칩에 프로그램을 다운로딩 할 수 있도록 설계하였다. DSP 칩에 의해 처리된 신호는 PCI 버스를 통하여 호스트로 전송되며, DSP 칩에서 DSP 칩 또는 지역메모리와의 통신은 지역버스를 통해 직접적으로 이루어진다. 병렬 DSP 시스템을 통하여 고속의 병렬신호처리를 수행 할 수 있다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 제13회 신호처리 합동 학술대회 논문집
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• pp.501-504
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• 2000

근본적으로 방대한 양의 실시간 연산을 요구하는 영상 신호처리, 소나, 레이다와 같은 시스템에서는 시스템의 성능을 최대화하기 위해 병렬 신호처리 시스템의 사용이 불가피하다. 본 논문은 방대한 양의 데이터를 실시간으로 처리할수 있는 병렬 신호처리보드를 설계 및 구현하였다. 이 보드는 DSP칩간의 통신과 보드간의 통신이 가능하며, DSP칩이 마스터가 되어 EMIF(External Memory Interface Port)포트를 통해 다른 DSP칩의 지역메모리를 액세스 할수 있다. 또한 외부의 호스트 프로세서가 보드 내의 DSP칩에 프로그램을 다운로딩 할수 있다. 보드간의 통신은 PCI 버스를 통하여 이루어지며, DSP칩간의 통신과 DSP칩과 그의 지역메모리와의 통신은 지역버스를 통해 직접적으로 이루어진다. 보드에서 가장 핵심인 DSP-to-PCI제어기는 하드웨어 언어인 VHDL로 설계하였으며, 시뮬레이션 환경은 Synopsys ＆ ALTERA MaxplusⅡ를 사용하여 검증하였으며, 최종적으로 CPLD(Complex Programable Logic Device)칩을 사용하여 구현하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.2252-2254
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• 1997

There are increasing demands on high accruacy DC power supplies for varous basic science reseach, such as accelerators and plasma applications, in Korea. In this paper, we present a study on 1kW class DC power supply using the parell operation method of the flyback converters. This DC power supply is equipped with a remote controller for computer interface. A Serial Communication Controller(SCC) is also developed for large scale scientific facilities which is capable of handling upto 32 power supplies simultaneously with one serial port in the host computer.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.321-325
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• 2001

Servo drives with microcomputer control provide the possibility of using modem and sophisticated control algorithms. As an additional feature it is possible to implement parallel and/or redundant software and hardware structures to realise safe motion or similar security functions. Unfortunately microcomputer control also has some impact on the behaviour of servo drives. Control algorithm, cycle time, sensors and interface have to be perfectly synchronised. Special control schemes are necessary on the line side (power supply) to meet the actual requirements concerning EMC. This contribution presents experiences and results obtained from a modem digital drive system pointing out the influences of low and high accuracy position sensors and the interdependencies mentioned above.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.168-171
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• 2001

Due to intrinsic load eccentricity, severe peel stress concentration occurs at both ends of the single-lap joint. To avoid load eccentricity as well as the singular tensile peel stress in the joint interface, composite wavy-lap joint is proposed. In this paper, refined 3-D stress analysis of wavy-lap joint is performed by finite element method using parallel mutifrontal solver. Analysis results show that the singular tensile peel stress concentration is totally avoided in wavy-lap joint, and that loads are more evenly transferred over the length of the joint. Therefore, the strength of wavy-lap joint is significantly higher than that of conventional single-lap joint. And it is believed that even higher strengths can be obtained by optimizing the new design configuration.

• 한국유체기계학회 논문집
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• 제1권1호
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• pp.72-80
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• 1998

Computational analysis of incompressible flows by numerically solving Navier-Stokes equations using multi-block finite volume method is conducted on a parallel computing system. Numerical algorithms adopted in this study $include^{(1)}$ QUICK upwinding scheme for convective $terms,^{(2)}$ central differencing for other terms $and^{(3)}$ the second-order Euler differencing for time-marching procedure. Structured grids are used on the body-fitted coordinate with multi-block concept which uses overlaid grids on the block-interfacing boundaries. Computational code is parallelized on the MPI environment. Numerical accuracy of the computational method is verified by solving a benchmark test case of the flow inside two-dimensional rectangular cavity. Computation in the axial compressor cascade is conducted by using 4 PE's md, as results, no numerical instabilities are observed and it is expected that the present computational method can be applied to the turbomachinery flow problems without major difficulties.

• Journal of electromagnetic engineering and science
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• 제10권3호
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• pp.166-170
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• 2010

To numerically calculate electromagnetic scattering from the electrical-large three-dimensional(3D) objects, the high-frequency approaches have been usually applied, but the accuracy and feasibility of these geometrical and physical optics(GO-PO) approaches, to some extent, are remained to be improved. In this paper, a new framework is developed for calculation of the near-field scattering field of an electrical-large 3D target by using a multilevel fast multipole algorithm(MLFMA) and generation of radar images by using a fast back-projection(FBP) algorithm. The MPI(Message Passing Interface) parallel computing is carried out to multiply the calculation efficiency greatly. Finally, a simple example of perfectly electrical conducting(PEC) patch and a canonical case of Fighting Falcon F-16 are presented.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.42-46
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• 1993

This paper presents development of a pratical tool deflection compensation system in order to reduce the machining error by the tool deflection in the end-milling process. The system is a tool adapter which includes 2-axis force sensor for detecting tool deflection and 2-axis tool tilting device for adjusting tool position through computer interface in on-line process. In experiments, it is revealed that the force sensor applying parallel plate principle and strain gauge is proper to obtain dynamic process signal, and the tilting device using stepping motor and cam drive mechanism is suitable to have necessary action. By the system and control algorithm, it is possible to get precise machining surface profile without excessive machining error and overcut generated due to increased cutting force in more productive machining condition.