Optimum SHE for cascaded H-bridge multilevel inverters using: NR-GA-PSO, comparative study

Selective Harmonic Elimination (SHE) is very widely applied technique in the control of multilevel inverters that can be used to eliminate the low order dominant harmonics. This is considered a low frequency technique, in which the switching angles are predetermined based on solving a system of transcendental equations. Iterative techniques such as NR and Heuristic techniques such as GA and PSO have been used widely in literatures for the problem of SHE. This paper presents a detailed comparative study of these three techniques when applied for a 7-level CHB-MLI

Spin observables for pion photoproduction on the deuteron in the Δ\Delta(1232)-resonance region

Spin observables for the three charge states of the pion for the pion photoproduction reaction on the deuteron, $\gamma d\to\pi NN$, with polarized photon beam and/or oriented deuteron target are predicted. For the beam-target double-spin asymmetries, it is found that only the longitudinal asymmetries $T_{20}^{\ell}$ and $T_{2\pm 2}^{\ell}$ do not vanish, whereas all the circular and the other longitudinal asymmetries do vanish. The sensitivity of spin observables to the model deuteron wave function is investigated. It has been found that only $T_{21}$ and $T_{22}$ are sensitive to the model deuteron wave function, in particular in the case of $\pi^0$-production above the $\Delta$-region, and that other asymmetries are not.Comment: 16 pages, 8 figures, accepted for publication in J. Phys. G: Nucl. Part. Phy

Synthesis and characterisation of Fe₆ and Fe₁₂ clusters using bicine

Reaction of bicine {BicH3, N,N-bis(2-hydroxyethyl)glycine} with an Fe(III) oxo-centered pivalate triangle in MeCN in the presence of Et<sub>2</sub>NH yields [Et<sub>2</sub>NH<sub>2</sub>]<sub>2</sub>[Fe<sub>6</sub>O<sub>2</sub>(OH)<sub>2</sub>(Bic)<sub>2</sub>(O<sub>2</sub>CCMe<sub>3</sub>)<sub>8</sub>], which possesses an S = 5 ground state. Changing the base to NaOMe produces [Fe<sub>12</sub>O<sub>4</sub>(Bic)<sub>4</sub>(HBic)<sub>4</sub>(O<sub>2</sub>CCMe<sub>3</sub>)<sub>8</sub>], which contains two Fe6 units bridged by the carboxylate arms from the bicine ligands. The complex displays strong antiferromagnetic coupling leading to an S = 0 ground state

Polarization observables of the gamma d --> PiNN reaction in the Delta(1232)-resonance region

Polarization observables of the three charge states of the pion for the $\gamma d\to\pi NN$ reaction with polarized photon beam and/or oriented deuteron target are evaluated over the whole $\Delta$(1232)-resonance region adopting a nonrelativistic model based on time-ordered perturbation theory. Results for the $\pi$-meson spectra, linear photon asymmetry, vector and tensor target asymmetries are presented. Particular attention is given, for the first time, to double polarization asymmetries for which we present results for $T_{20}^{\ell}$ and $T_{2\pm 2}^{\ell}$. We found that all other double polarization asymmetries of photon and deuteron target are vanished.Comment: 17 Pages, 8 Figures, accepted for publication in Int. J. Mod. Phys.

Periodicities in geomagnetic-activity indices and solar-wind parameters, and their possible solar origin

We have examined the average behaviors of the solar-wind parameters and the geomagnetic-activity indices. There is a good correlation between the increasing pressure at the magnetopause and the intense magnetospheric disturbances. The ultra-low frequency power spectra for the geomagnetic disturbances have been analyzed and tested. Although the spectrum shows remarkable and stable peaks at the wavelengths 0.5, 0.7, 1.0, 1.3 years, additional significant peaks of 73 d, 1.5 y, 5.1 y and 9.2 y for Ap and 73 d and 1.4 y for the product BSV 2 are also found. However, the 73-d and 5.1-y variations correspond to a non-obvious physical process in the Sun. The Sun may reflect some irregular variations, basically not fundamental, which appear at different times. A comparison of both spectra for periods > 0.5 year suggests different solar origins. Both spectra have different power amplitudes and peaks at different locations. Our study confirmed 1.4–1.5 year oscillations in BSV 2 measurements between 1987 and 2000, and located slightly higher than the Kp peaks (∼ 1.3 y). Although many papers have discussed periodicities in the Ap index, a 9.2-year period has not been reported previously. There is some indication of an association with the coronal-hole variations in the southern hemisphere of the Sun. The conjunction of the Sun observations and SW measurements may be used to estimate the disturbances in the geomagnetic activity in the heliosphere