• Title/Summary/Keyword: High-C waveforms

Search Result 25, Processing Time 0.026 seconds

Development of MRI gradient waveform generator using DSP (DSP를 이용한 자기공명영상의 경사자계 파형 발생기 개발)

  • Ko, K.H.;Kwon, E.S.;Song, Y.C.;Kim, H.J.;Yim, C.Y.;Ahn, C.B.
    • Proceedings of the KIEE Conference
    • /
    • 1999.07g
    • /
    • pp.3147-3149
    • /
    • 1999
  • In this paper, we develop a TMS320C31- 60 DSP board to generate spiral gradient waveforms for Spiral imaging, one of the ultra fast MRI methods. In Spiral imaging, accurate gradient waveforms are very important to acquire high quality image. For this purpose, sampling rate for generating the gradient waveforms is set twice as high as the data sampling rate. With the developed DSP board accurate gradient waveforms are obtained. Ultra fast MR image with the developed DSP board is currently under development.

  • PDF

A Study of the Effect of Stress Waveform on the Behavior of High Temp. Fatigue Crack Propagation Using J Parameters (J파라미터를 이용한 고온피로균열전파 거동에 미치는 응력파형 영향의 연구)

  • Hur, Chung-Weon;Park, Won-Jo
    • Journal of the Korean Society of Safety
    • /
    • v.15 no.2
    • /
    • pp.8-12
    • /
    • 2000
  • The fatigue crack propagation tests were performed in triangular and holding-time stress waveforms at $650^{\circ}C$. The behavior of fatigue crack propagation was investigated according to waveform. The analysis of high temperature fatigue crack propagation by the stress intensity factor range ${\Delta}K$, elastic fracture mechanics parameter, was not available. The behaviors of high temperature fatigue crack propagation by the J-integral(${\Delta}J_f$, J' and ${\Delta}J_c$), elasto-plastic fracture mechanics parameter, were investigated in a number of stress waveforms. The fast-fast waveform exhibited cycle-dependent(fatigue type), the slow-fast and the hold time with 500sec waveforms appear to be time-dependent(creep type) and the fast-slow and the hold time with 5, 25sec waveforms exhibited conbined behavior of both types(fatigue-creep conbined type).

  • PDF

The Current and Power Waveform Improvement of a $3{\Phi}$ Induction Motor with LC Filter Driven by a Digital Bridge Inverter (디지탈 브리지형 인버터로 구동되는 3상유도전동기의 LC 필터에 의한 전류 및 전력 파형 개선)

  • Chung, J.Y.;Park, J.G.;Kang, C.N.
    • Proceedings of the KIEE Conference
    • /
    • 1996.07a
    • /
    • pp.553-555
    • /
    • 1996
  • This paper concerns with a method to improve the current and power waveforms of the variable speed $3{\Phi}$ AC motor system driven by the single-pulse PWM, and the current waveforms and $3{\Phi}$ power waveforms are analyzed by FFT under various running conditions. By the performance analysis through the experiments, the following results have been obtained. AC source of pseudo sine waveform can be obtained from the modulated alternating square voltage by means of the well designed LC filter. It is confirmed that current waveforms and $3{\Phi}$ power waveforms can be improved by utilizing the high order low pass LC filter than that of lower order. Especially, current waveforms and $3{\Phi}$ power waveforms tan be much improved at low frequency domain. $3{\Phi}$ power waveforms have a smatter ripple and bigger power by utilizing the high order low pass LC filter than that of lower order. Also, the running condition of $3{\Phi}$ AC motor is good at low frequency domain.

  • PDF

A Study of Strain Waveform Effect on Fatigue Life in High Temperature Low Cycle Fatigue Test (고온저사이클 피로시험에서 변형률파형이 피로수명에 미치는 영향에 대한 연구)

  • 유재환
    • Journal of the Korean Society of Safety
    • /
    • v.14 no.1
    • /
    • pp.41-48
    • /
    • 1999
  • The fatigue life tests were performed in strain control with triangular and hole-time wave-forms at $650^{\circ}C$. The fatigue lifes were investigated according to waveform examining damage mechanisms, which could be used to predict the fatigue life and estimate the remaining life. The results obtained are as follows; The fatigue lifes were in order of the fast-fast>the fast-slow>the slow-fast in the triangular waveforms, and the fatigue lifes in slow-fast waveforms got shorter in the hold-time waveforms. The damage mechanisms of the fracture surfaces were transgranular fracture in the fast-fast, the fast-slow waveforms and intergranular fracture in the slow-fast waveform.

  • PDF

Gradient Waveform Synthesizer in Magnetic Resonance Imaging System using Digital Signal Processors (DSP를 이용한 자기공명영상시스템의 경사자계 파형 발생기)

  • Go, Gwang-Hyeok;Gwon, Ui-Seok;Kim, Chi-Yeong;Kim, Hyu-Jeong;Kim, Sang-Muk;An, Chang-Beom
    • The Transactions of the Korean Institute of Electrical Engineers D
    • /
    • v.49 no.1
    • /
    • pp.48-53
    • /
    • 2000
  • In this paper, we develop a TMS320C31 (60MHz) digital signal processor (DSP) board to synthesize gradient waveforms for Spiral Scan Imaging (SSI), which is one of the ultra fast magnetic resonance imaging (MRI) methods widely used. In SSI, accurate gradient waveforms are very essential to high quality magnetic resonance images. For this purpose, sampling rate for synthesizing the gradient waveforms is set twice as high as the data sampling rate. With the developed DSP boards accurate gradient waveforms are obtained. Ultra fast spiral scan imaging with the developed with the developed DSP board is currently under development.

  • PDF

Long-Term Forecasting by Wavelet-Based Filter Bank Selections and Its Application

  • Lee, Jeong-Ran;Lee, You-Lim;Oh, Hee-Seok
    • The Korean Journal of Applied Statistics
    • /
    • v.23 no.2
    • /
    • pp.249-261
    • /
    • 2010
  • Long-term forecasting of seasonal time series is critical in many applications such as planning business strategies and resolving possible problems of a business company. Unlike the traditional approach that depends solely on dynamic models, Li and Hinich (2002) introduced a combination of stochastic dynamic modeling with filter bank approach for forecasting seasonal patterns using highly coherent(High-C) waveforms. We modify the filter selection and forecasting procedure on wavelet domain to be more feasible and compare the resulting predictor with one that obtained from the wavelet variance estimation method. An improvement over other seasonal pattern extraction and forecasting methods based on such as wavelet scalogram, Holt-Winters, and seasonal autoregressive integrated moving average(SARIMA) is shown in terms of the prediction error. The performance of the proposed method is illustrated by a simulation study and an application to the real stock price data.

Real-time Interactive Control of Magnetic Resonance Imaging System Using High-speed Digital Signal Processors (고속 DSP를 이용한 실시간 자기공명영상시스템 제어)

  • 안창범;김휴정;이흥규
    • Journal of the Institute of Electronics Engineers of Korea SC
    • /
    • v.40 no.5
    • /
    • pp.341-349
    • /
    • 2003
  • A real time interactive controller (spectrometer) for magnetic resonance imaging (MRI) system has been developed using high speed digital signal processors (DSP). The controller generates radio frequency (rf) waveforms and audio frequency gradient waveforms and controls multiple receivers for data acquisition. By employing DSPs having high computational power (e.g., TMS320C670l) real time generation of complicated gradient waveforms and interactive control of selection planes are possible, which are important features in real-time imaging of moving organs, e.g., cardiac imaging. The spectrometer was successfully implemented at a 1.5 Tesla whole body MRI system for clinical application. Performance of the spectrometer is verified by various experiments including high- speed imaging such as fast spin echo (FSE) and echo planar imaging (EPI). These high-speed imaging techniques reduce measurement time, however, usually intensify artifact if there is any systematic phase error or jitter in the synchronization between the transmitter, receiver, and gradients.

Junction, Circuit and System Developments for a High-$T_c$ Superconductor Sampler

  • Hidaka, M.;Satoh, T.;Tahara, S.
    • Progress in Superconductivity
    • /
    • v.1 no.2
    • /
    • pp.81-84
    • /
    • 2000
  • A Josephson sampler circuit using high-Tc superconductor (HTS) ramp-edge junctions has been designed, fabricated, and experimentally tested. It consists of five ramp-edge junctions with a stacked groundplane and is based on single-flux-quantum (SFQ) operations. The sampler was used to measure current waveforms at picosecond and microampere resolutions. We are developing a system based on the sampler for measuring the current waveform in a room-temperature sample. And measuring current flowing through wiring in a semiconductor large-scale integrated circuit is a promising application for the HTS sampler system.

  • PDF

A Study on the Efficiency Characteristics of the Interleaved CRM PFC using GaN FET (GaN FET를 적용한 인터리브 CRM PFC의 효율특성에 관한 연구)

  • Ahn, Tae-Young;Jang, Jin-Haeng;Gil, Yong-Man
    • The Transactions of the Korean Institute of Power Electronics
    • /
    • v.20 no.1
    • /
    • pp.65-71
    • /
    • 2015
  • This paper presents the efficiency analysis of a critical current mode interleaved PFC rectifier, in which each of three different semiconductor switches is employed as the active switch. The Si FET, SiC FET, and GaN FET are consecutively used with the prototype PFC rectifier, and the efficiency of the PFC rectifier with each different semiconductor switch is analyzed. An equivalent circuit model of the PFC rectifier, which incorporates all the internal losses of the PFC rectifier, is developed. The rms values of the current waveforms main circuit components are calculated. By adapting the rms current waveforms to the equivalent model, all the losses are broken down and individually analyzed to assess the conduction loss, switching loss, and magnetic loss in the PFC rectifier. This study revealed that the GaN FET offers the highest overall efficiency with the least loss among the three switching devices. The GaN FET yields 96% efficiency at 90 V input and 97.6% efficiency at 240 V, under full load condition. This paper also confirmed that the efficiency of the three switching devices largely depends on the turn-on resistance and parasitic capacitance of the respective switching devices.

A DSP based Three Phase Power Quality Analyzer for Motor Drives (모터 구동장치를 위한 DSP기반 3상 전력품질분석 시스템)

  • 정영국
    • Proceedings of the KIPE Conference
    • /
    • 2000.07a
    • /
    • pp.661-664
    • /
    • 2000
  • This paper presents a digital instrument for the power quality analysis in three phase power system where current waveform is non-sinusoidal. It is based on C31 DSP and on a special high-speed data acquisition system. Voltage and current waveforms are acquired and processed by using a simple average power algorithm, The paper also goes on to discuss the performance of an instrument prototype both in terms of accuracy and speed of measurement.

  • PDF