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

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

Comparison of two methods of noise power spectrum determinations of medical radiography systems

Noise in medical images is recognized as an important factor that determines the image quality. Image noise is characterized by noise power spectrum (NPS). We compared two methods of NPS determination namely the methods of Wagner and Dobbins on Lanex Regular TMG screen-film system and Hologic Lorad Selenia full field digital mammography system, with the aim of choosing the better method to use. The methods differ in terms of various parametric choices and algorithm implementations. These parameters include the low pass filtering, low frequency filtering, windowing, smoothing, aperture correction, overlapping of region of interest (ROI), length of fast Fourier transform, ROI size, method of ROI normalization, and slice selection of the NPS. Overall, the two methods agreed to the practical value of noise power spectrum between 10 -3-10-6mm2 over spatial frequency range 0-10mm-1

Stability of Nucleic Acid Secondary Structures and Their Contribution to Gene Expression

Bacteriorhodopsin (bR) is a highly expressed transmembrane protein that acts as a light-driven proton pump converting light energy into a proton gradient. The extraordinary levels of expression achieved (15-30 mg per liter of culture) are a result of very efficient biogenesis that originates from molecular information encoded in the bacterio-opsin gene {bop) (1). DNA sequence analysis and predictive folding algorithms suggest that the first twenty-five bases of the bop gene mRNA can form a secondary structural element (a stem-loop ). Using biophysical methods, the goal was to determine if the stem-loop structure exists in solution conditions that mimic the in vivo biological environment (42°C and 4M KCl) (2-4). The salt-dependent thermal stability of a DNA model of the stem-loop sequence was obtained using temperature-controlled UVabsorption and Circular Dichroism (CD) spectroscopy and Differential Scanning Calorimetry (DSC). The combinatorial analysis indicates that an energetically favorable stem-loop structure forms in all solution conditions examined. The stem-loop structure is stabilized at very high salt concentrations, a requirement for a role in bop gene expressivity (AG= -1.13 kcal/mol, AH= -16.78 kcal/mol, AS= - 49.67 cal/mol/K). While the Tm values evaluated by all three physical techniques were comparable, comparison of the calorimetrie and van\u27t Hoff enthalpies indicate that the folding mechanism is not a two-state process. SVD analysis of the UV and CD spectral transitions confirm that formation of the stem-loop structure proceeds through a single significant folding intermediate. Similar analysis of the RNA sequence demonstrates that an RNA stem- loop structure can form and is significantly more stable than that of the DNA structure at all salt concentrations evaluated

Error Analysis: A Case Study of High Basic Stage Students in Latin Secondary School in Zarqa, Jordan

Errors made by Jordanian school students due to transfer from Arabic to English were analyzed in an attempt to help them overcome their weakness. The subjects of the study are private mixed school students in Zarqa. They are in the tenth grade and have been taught English mainly by Arab teachers. The study consists of 32 students who were asked to write a paragraph consists of 100 to 150 words. They were given sufficient time and asked to write freely and to express their points of view about the given topic. Errors from the scripts were analyzed on the basis of models given in literature. All types of errors were committed by the students which suggest that attention should be devoted to writing at high basic stage . Keywords: Error Analysis; Sources of Errors; Error Identification and Categorizatio

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

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