The Experts below are selected from a list of 82383 Experts worldwide ranked by ideXlab platform

Sanjay Saini - One of the best experts on this subject based on the ideXlab platform.

  • comparison of z axis automatic tube current Modulation Technique with fixed tube current ct scanning of abdomen and pelvis
    Radiology, 2004
    Co-Authors: Mannudeep K Kalra, Michael M Maher, Thomas L Toth, Ravi S Kamath, Elkan F Halpern, Sanjay Saini
    Abstract:

    PURPOSE: To compare image quality, diagnostic acceptability, and radiation exposure associated with 16-section multi–detector row computed tomographic (CT) examinations of abdomen and pelvis performed with z-axis Modulation Technique of automatic tube current Modulation and with manual selection of fixed tube current. MATERIALS AND METHODS: Sixty-two consecutive subjects (mean age, 60 years; age range, 19–84 years; male-to-female ratio, 35:27) underwent follow-up CT of abdomen and pelvis with use of a 16-section multi–detector row scanner and z-axis Modulation Technique (10.5–12.0-HU noise index, 10–380 mA). Scanning parameters included 140 kVp, 0.5–1.0-second gantry rotation time, 0.938:1 beam pitch, and 5-mm reconstructed section thickness. For each subject, images obtained with z-axis Modulation were compared with previous images obtained with fixed tube current (200–300 mA) and with other parameters identical. Images were compared for noise and diagnostic acceptability by two subspecialty radiologists...

Tony K M Chan - One of the best experts on this subject based on the ideXlab platform.

  • an active Modulation Technique for single phase grid connected csi
    IEEE Transactions on Power Electronics, 2007
    Co-Authors: Henry Shuhung Chung, Tony K M Chan
    Abstract:

    Due to the interaction between the rectified voltage appearing on the dc side of the grid-connected current source inverter (CSI) and the dc inductor, the input current on the dc side inherently consists of the second-order harmonic of the grid frequency. This harmonic component will be modulated by the pulsewidth Modulation (PWM) signal that results in generating low-order harmonics at the output and thus injecting into the grid. This paper presents an active nonlinear Modulation Technique for reducing the low-order harmonics. The method requires simple analog circuitry to modify the Modulation function of the sinusoidal PWM (SPWM) scheme. It is based on measuring the dc and ac components of the dc inductor current to compensate the Modulation effect from the dc side to the ac side of the CSI. Apart from reducing the harmonic content, this method can also reduce the required value of the dc inductor. Modeling, design, and analysis of the method are given. The proposed method has been tested with a 1 kW, 220 V, 50 Hz prototype, powered by a dc voltage of 80 V. The results are favorably compared with the performance of the CSI with the SPWM scheme.

  • an active Modulation Technique for single phase grid connected csi
    Power Electronics Specialists Conference, 2006
    Co-Authors: Henry Shuhung Chung, Tony K M Chan
    Abstract:

    Due to the interaction between the rectified voltage appeared on the dc side of the grid-connected current source inverter (CSI) and the buffer inductor, the input current on the dc side inherently consists of a second-order harmonic of the grid frequency. This harmonic component will be modulated by the pulsewidth Modulation (PWM) signal that results in generating low-order harmonics at the output and thus injecting into the grid. This paper presents an active nonlinear Modulation Technique for reducing the low-order harmonics. The method requires a simple analog circuitry to modify the Modulation function of sinusoidal PWM (SPWM) scheme. It is based on measuring the dc and ac components of the buffer inductor current to compensate the Modulation effect from the dc side to the ac side of the CSI. Apart from reducing the harmonic content, the method can also reduce the required value of the buffer inductor. Modeling, design, and analysis of the method are given. The proposed method has been tested with a 1kW, 220V, 50Hz prototype, powered by a dc voltage of 80V. The results are favorably compared with the performance of the CSI with the SPWM scheme.

Paolo Tomasin - One of the best experts on this subject based on the ideXlab platform.

  • High-performance hysteresis Modulation Technique for active filters
    IEEE Transactions on Power Electronics, 1997
    Co-Authors: L Malesani, Paolo Mattavelli, Paolo Tomasin
    Abstract:

    A new, substantial improvement of the hysteresis current control method for voltage source inverters is presented. A simple and fast prediction of the hysteresis band is added to a linearized version of the phase-locked loop control, thus ensuring constant switching frequency and tight control of the position of Modulation pulses. This allows high accuracy in tracking highly distorted current waveforms and minimizes the ripple in multiphase systems. The implementation of this Technique is very simple and robust, employing only a small number of conventional inexpensive analog and logic components. It does not require trimmings or tunings, giving the control the capability to adjust itself to the different operating conditions. The proposed method is compared with the most diffused Modulation Techniques, demonstrating its superior performance in responding to the most demanding conditions met in active filters. The behavior of the method has been fully verified by simulation and by experimental tests.

  • High-performance hysteresis Modulation Technique for active filters
    Proceedings of Applied Power Electronics Conference. APEC '96, 1996
    Co-Authors: L Malesani, Paolo Mattavelli, Paolo Tomasin
    Abstract:

    A new, substantial improvement of the hysteresis current control method for voltage source power converters is presented. A simple and fast prediction of the hysteresis band is added to a linearized version of the phase-locked-loop control, thus ensuring constant switching frequency and tight control of the position of Modulation pulses. This allows high accuracy in tracking highly distorted current waveforms, and minimizes the ripple in multi-phase systems. The Technique implementation is very simple and robust, employing only a small number of conventional, inexpensive analog and logic components. It does not require trimmings or tunings, giving the control the capability to adjust itself to the different operating conditions. The proposed method is compared with the most diffused Modulation Techniques, demonstrating its superior performance in responding to the most demanding conditions met in active filters. The behaviour of the method has been fully verified by simulation and by experimental tests.

C. Krismadinata - One of the best experts on this subject based on the ideXlab platform.

  • Five-level inverter with dual reference Modulation Technique for grid-connected PV system
    Renewable Energy, 2010
    Co-Authors: Nasrudin Abd Rahim, Jeyraj Selvaraj, C. Krismadinata
    Abstract:

    Abstract This paper presents a single-phase five-level grid-connected PV inverter with a novel dual reference Modulation Technique. Two reference signals identical to each other with an offset equivalent to the amplitude of the triangular carrier signal were used to generate PWM signals. The inverter consists of a full-bridge inverter and an auxiliary circuit comprising four diodes and a switch. The inverter produces output voltage in five levels: zero, +1/2 V dc , V dc , −1/2 V dc and − V dc . A digital PI current control algorithm is implemented in DSP TMS320F2812 to keep the current injected into the grid sinusoidal and to have high dynamic performance with low THD. The validity of the proposed inverter is verified through simulation and implemented in a prototype. The experimental results are compared with conventional single-phase three-level grid-connected PWM inverter in terms of THD.

Mannudeep K Kalra - One of the best experts on this subject based on the ideXlab platform.

  • comparison of z axis automatic tube current Modulation Technique with fixed tube current ct scanning of abdomen and pelvis
    Radiology, 2004
    Co-Authors: Mannudeep K Kalra, Michael M Maher, Thomas L Toth, Ravi S Kamath, Elkan F Halpern, Sanjay Saini
    Abstract:

    PURPOSE: To compare image quality, diagnostic acceptability, and radiation exposure associated with 16-section multi–detector row computed tomographic (CT) examinations of abdomen and pelvis performed with z-axis Modulation Technique of automatic tube current Modulation and with manual selection of fixed tube current. MATERIALS AND METHODS: Sixty-two consecutive subjects (mean age, 60 years; age range, 19–84 years; male-to-female ratio, 35:27) underwent follow-up CT of abdomen and pelvis with use of a 16-section multi–detector row scanner and z-axis Modulation Technique (10.5–12.0-HU noise index, 10–380 mA). Scanning parameters included 140 kVp, 0.5–1.0-second gantry rotation time, 0.938:1 beam pitch, and 5-mm reconstructed section thickness. For each subject, images obtained with z-axis Modulation were compared with previous images obtained with fixed tube current (200–300 mA) and with other parameters identical. Images were compared for noise and diagnostic acceptability by two subspecialty radiologists...