Search results for "Amplitude"
showing 10 items of 1169 documents
Wavefront Recovery: Shack-Hartmann Aberrometry vs PhaseLift Using a Single Binary Amplitude Modulating Mask
2019
We investigate whether a wavefront can be recovered by using a single mask rotated in four different positions. Results show that PhaseLift can recover the wavefront from intensity measurements using such a kind of modulation.
Ship Roll Motion under Stochastic Agencies Using Path Integral Method
2009
The response of ship roll oscillation under random ice impulsive loads modeled by Poisson arrival process is very important in studying the safety of ships navigation in cold regions. Under both external and parametric random excitations the evolution of the probability density function of roll motion is evaluated using the path integral (PI) approach. The PI method relies on the Chapman-Kolmogorov equation, which governs the response transition probability density functions at two close intervals of time. Once the response probability density function at an early close time is specified, its value at later close time can be evaluated. The PI method is first demonstrated via simple dynamica…
Innovative Computational Approach to Harmonic Mitigation for Seven-level Cascaded H-Bridge Inverters
2020
Low frequency modulation strategies are a good solution to increase the energy conversion efficiency in high power applications. The paper is devoted to presents an innovative way to low order harmonics mitigation for seven-level Cascaded H-Bridge Inverters. In particular, this approach is based on the mitigation of selected harmonics without solve non-linear equations for an extended range of the fundamental amplitude. In fact, in real-Time operation to evaluate the control angles the polynomial equations have been identified. Through circuit simulation analysis in MatLab/PLECS environment, the effectiveness of the harmonic mitigation method has been tested and compared with theoretical re…
Selective harmonic mitigation with asymmetrical staircase voltage waveform for a three-phase five-level Cascaded H-Bridge Inverter
2020
Selective harmonics elimination or mitigation strategies are used in all applications where it is necessary to rise the efficiency and reliability of the overall system. This paper presents a simple approach to reduce the low order harmonics amplitude of an asymmetrical staircase voltage waveform for a five-level, three-phase Cascaded H-Bridge Inverter without solving non-linear equations. Through this simple approach, polynomial equations to evaluate the control angels in real-time operations have been found. The effectiveness of the harmonic mitigation method has been tested through the simulation analysis in MatLab/PLECS environment.
Measurement of the decay rate and form factor parameter in the decay KL→e+e−γ
1999
Abstract The decay rate of the neutral K meson KL→e+e−γ has been measured with the NA48 detector at the CERN SPS. A total of 6864 events has been observed with an estimated background of 10 events. The branching ratio is Γ(KL→e+e−γ)/Γ(KL→all) = (1.06±0.02stat±0.02sys±0.04calc)×10−5. The parameter α K ∗ describing the relative strength of the two contributing amplitudes to this decay through intermediate pseudoscalar or vector mesons was measured to be α K ∗ =−0.36±0.06stat±0.02sys.
A powerful thyristor modulator for a microtron
1980
Abstract The circuit of a powerful modulator is illustrated and a detailed description is given of the modulator construction and in particular of the components employed. The main parameters are: length of shaped pulse 2 μs; amplitude of the output voltage 30 kV; pulse repetition frequency 50–200 Hz. The compactness of this device, its comparatively low cost and its good performance, as illustrated in the attached photographs, make it suitable for use in accelerator engineering (microtron).
Combining super-orthogonal space-frequency trellis coding, constellation shaping by shell mapping, and OFDM for high data rate broadband mobile commu…
2014
In this paper, we seamlessly combine three transmission techniques to design an improved performance broadband mobile communication system with two transmit antennas. In so doing, we took inspiration from the V.34 data modem toolbox designed for public switched telephone network. We modified the constellation shaping by shell mapping algorithm to apply it only to the orthogonal frequency division multiplexing (OFDM) frame sent by the first antenna, in such a way that the peak-to-average power ratio (PAPR) is also reduced for the second antenna. We use a 24-point quadrature amplitude modulation (QAM) signal constellation on each subcarrier, while the reference system employs 16 QAM for the s…
Performance Analysis of Cooperative Communication Systems with Imperfect Channel Estimation
2009
This paper investigates the effects of channel estimation errors on the symbol-error-rate (SER) performance of a cooperative communication system operating in an amplify-and- forward (AF) mode. A pilot symbol assisted modulation scheme with linear minimum mean square estimation (LMMSE) is used for the channel estimation. An accurate and easy-to-evaluate SER expression is presented for uncoded cooperative communication systems with quadrature amplitude modulation (QAM) and phase-shift keying (PSK) constellations. Numerical simulations are conducted to verify the correctness of the proposed analytical formulation. It is shown that the performance loss caused by channel estimation errors incre…
Reducing the peak and average power for OFDM systems using QAM by constellation shaping
2009
In this paper, we present a shell mapping scheme to reduce the peak and average power of orthogonal frequency division multiplexing (OFDM) signals using quadrature amplitude modulation (QAM) by constellation shaping. Our approach can be considered as an extension of the shell mapping technique introduced originally in the V.34 recommendation of ITU-T. The shell mapping method uses multiple cost functions, each having the OFDM block length N as a parameter. The cost functions are presented in closed form for any N. The main advantage of the proposed scheme is that the peak and average power can be reduced without sacrificing the data rate, and no side information is needed at the receive sid…
Inter- and intramolecular motions in proteins
1992
The use of 57 Fe Mossbauer radiation allows the study of protein crystal dynamics by a time-resolved analysis of X-ray scattering. In myoglobin crystals, the main source of the root mean squared amplitude of motions come from intramolecular protein dynamics. Segments of the size of an α-helix move collectively. Long-range correlated motions give only a minor contribution. Comparison with Mossbauer absorption spectroscopy shows that protein-specific dynamics is frozaen out below 200 K and the lattice dynamics in mainly responsible for the low-temperature behavior