Power loss investigation in HVDC for cascaded H-bridge multilevel inverters (CHB-MLI)

In the last decade, the use of voltage-source multilevel inverters in industrial and utility power applications has been increased significantly mainly due to the many advantages of multilevel inverters, compared to conventional two level inverters. These advantages include: 1) higher output voltage at low switching frequency, 2) low voltage stress (dv/dt), 3) lower total harmonic distortion (THD), 4) less electro-magnetic interference (EMI), 5) smaller output filter, and 6) higher fundamental output. However, the computation of multilevel inverter power losses is much more complicated compared to conventional two level inverters. This paper presents a detailed investigation of CHB-MLI losses for HVDC. Different levels, and IGBT switching devices have been considered in the study. The inverter has been controlled using selective harmonic elimination in which the switching angles were determined using the Genetic Algorithm (GA). MATLAB-SIMULINK is used for the modelling and simulation. This investigation should result in a deeper knowledge and understanding of the performance of CHB-MLI using different IGBT switching devices

Precise modelling of switching and conduction losses in cascaded h-bridge multilevel inverters

Nowadays, voltage source multilevel inverters are being used extensively in industry due to its many advantages, compared to conventional two level inverters, such as higher output voltage at low switching frequency, low voltage stress(dv/dt), lower total harmonic distortion (THD), less electro-magnetic interference (EMI), smaller output filter and higher fundamental output. However, the evaluation of multilevel inverter losses is much more complicated compared to two level inverters. This paper proposes an on-line model for precise calculation of conduction and switching losses for cascaded h-bridge multilevel inverter. The model is simple and efficient and gives clear process of loss calculation. A singlephase 7-level cascaded h-bridge with IGBT's as switching devices has been used as a case study of the proposed model. The inverter has been controlled using selective harmonic elimination in which the switching angles were determined using the Genetic Algorithm (GA). MATLAB-SIMULINK is used for the modelling and simulation

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

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.

CMS Software Distribution on the LCG and OSG Grids

The efficient exploitation of worldwide distributed storage and computing resources available in the grids require a robust, transparent and fast deployment of experiment specific software. The approach followed by the CMS experiment at CERN in order to enable Monte-Carlo simulations, data analysis and software development in an international collaboration is presented. The current status and future improvement plans are described.Comment: 4 pages, 1 figure, latex with hyperref

What Business Model is Suitable for Online Arab Newspapers? Journalists’ Perspectives

The study aimed to explore the journalists’ perspectives on ways to refinance Arab newspapers’ production and face the digital transformation challenges. The study found that Arab journalists have an ambiguous perception of the appropriate business models for newspapers in the digital age. The journalists ranking of the sources of revenue that newspapers can rely on are not well-suited with the appropriate business models for the digital environment, which could be explained by a lack of knowledge of business models. Most of the journalists’ experiences are derived from working under the conventional models. They do not trust public funding as a successful model and expect the continuity of the free model. The journalists still endorse the conventional business model, which depends on advertising, circulation, and external support. These types of models are difficult to be implemented in the digital era, with the decline of advertising revenue, the unwillingness of the governments to continue subsiding these newspapers, and the growing fall of the newspaper’s circulation. The journalists have some certain reluctance toward the new ecosyste

Quasi-free π0\pi^0 Photoproduction from the Bound Nucleon

Differential cross-sections for quasi-free $\pi^0$ photoproduction from the proton and neutron bound in the deuteron have been measured for $E_\gamma= 200 - 400$ MeV at $\theta^{\rm lab}_\gamma = 136.2^\circ$ usind the Glasgow photon tagger at MAMI, the Mainz 48 cm $\varnothing$ $\times$ 64 cm NaI(Tl) photon detector and the G\"ottingen SENECA recoil detector. For the proton measurements made with both liquid deuterium and liquid hydrogen targets allow direct comparison of "free" $\pi^0$ photoproduction cross-sections as extracted from the bound proton data with experimental free cross sections which are found to be in reasonable agreement below 320 MeV. At higher energies the "free" cross sections extracted from quasifree data are significantly smaller than the experimental free cross sections and theoretical predictions based on multipole analysis. For the first time, "free" neutron cross sections have been extracted in the $\Delta$-region. They are also in agreement with the predictions from multipole analysis up to 320 MeV and significantly smaller at higher photon energies

Photoproduction of mesons off nuclei

Recent results for the photoproduction of mesons off nuclei are reviewed. These experiments have been performed for two major lines of research related to the properties of the strong interaction. The investigation of nucleon resonances requires light nuclei as targets for the extraction of the isospin composition of the electromagnetic excitations. This is done with quasi-free meson photoproduction off the bound neutron and supplemented with the measurement of coherent photoproduction reactions, serving as spin and/or isospin filters. Furthermore, photoproduction from light and heavy nuclei is a very efficient tool for the study of the interactions of mesons with nuclear matter and the in-medium properties of hadrons. Experiments are currently rapidly developing due to the combination of high quality tagged (and polarized) photon beams with state-of-the-art 4pi detectors and polarized targets

Study of the B +→ J / ψ Λ ¯ p decay in proton-proton collisions at √s = 8 TeV

A study of the B +→ J / ψ Λ ¯ p decay using proton-proton collision data collected at s = 8 TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.6 fb−1, is presented. The ratio of branching fractions B(B+→J/ψΛ¯p)/B(B+→J/ψK∗(892)+) is measured to be (1.054 ± 0.057(stat) ± 0.035(syst) ± 0.011(B))%, where the last uncertainty reflects the uncertainties in the world-average branching fractions of Λ ¯ and K*(892) + decays to reconstructed final states. The invariant mass distributions of the J / ψ Λ ¯ , J/ψp, and Λ ¯ p systems produced in the B +→ J / ψ Λ¯ p decay are investigated and found to be inconsistent with the pure phase space hypothesis. The analysis is extended by using a model-independent angular amplitude analysis, which shows that the observed invariant mass distributions are consistent with the contributions from excited kaons decaying to the Λ ¯ p system. [Figure not available: see fulltext.