An overheating‐tolerant space vector modulation algorithm for multilevel inverters

As promising and suitable candidates for high‐power applications, multilevel inverters have become one of the most promising solutions in various applications. However, power switching devices are highly subjected to thermal overheating, which leads to shortened lifetime and reduced reliability. Thermal overheating may result from the degradation of power switching devices due to continuous overloading and power cycling. In addition, degradation and faults in the cooling system of power switching devices may cause thermal stresses as well. A new overheating‐tolerant space vector modulation algorithm is proposed in this paper to alleviate thermal stresses from overheated power switching device. The proposed algorithm relies on using the redundancy property between switching states in multilevel inverters to continuously evaluate a cost function of the junction temperature of the overheated device for all possible switching sequence sets and then selects the optimal switching sequence. In addition, the proposed algorithm preserves the DC‐link capacitor voltage without reduction in the output current of the inverter. The proposed algorithm is general, which can be applied to n‐level inverters. Both simulation and experimental results reveal the efficient performance of the proposed algorithm using a three‐level T‐type inverter as a case study. Accordingly, the lifetime and reliability of the inverter are enhanced considerably using the proposed algorithm. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Degradation of bromoxynil and trifluralin in natural water by direct photolysis and UV plus H2O2 advanced oxidation process

The degradation of two pesticides, bromoxynil and trifluralin, was investigated in ultrapure and natural water solutions under ultraviolet (UV) light and a combination of UV and hydrogen peroxide (H₂O₂). The effect of pH on the photooxidation of the pesticides was also studied. The results indicated that under direct photolysis with monochromatic light at 253.7 nm and different conditions, the photochemical rates followed first-order kinetics, with fluence-based rate constants ranging from 9.15 × 10⁻⁴ to 6.37 × 10⁻³ cm² mJ⁻¹ and 7.63 × 10⁻³ to 1.47 × 10⁻² cm² mJ⁻¹ for bromoxynil and trifluralin, respectively. Quantum yields, in the range of 0.08-0.25 for bromoxynil and 0.12-0.72 for trifluralin, were observed in experiments using ultrapure water. The study also found that the UV/H₂O₂ process enhanced the oxidation rate in comparison to direct photolysis. A 90% degradation with UV dose of 333 and 188 mJ cm⁻² was achieved for bromoxynil and trifluralin, respectively, in natural water, in presence of 8.8 × 10⁻⁴ M H₂O₂. To assess the aquatic toxicity, the Microtox^® 81.9% screening test protocol was used before and after treatment. The test results indicated a decrease in the acute toxicity of the samples after treatment for both pesticides.     

Water resistance,mechanical properties,and biodegradability of poly(3‐hydroxybutyrate)/starch composites

Composites of poly(3‐hydroxybutyrate), P(3HB), and starch were prepared by solution casting technique. To improve adhesion of starch to P(3HB), stearic acid was added as a compatibilizer and glycerol as a plasticizer. The water resistance, mechanical, and biodegradable properties of the P(3HB)/starch composites were studied. Diffusion and penetration coefficients of water increased with increasing starch content in the composites. The results showed that the elastic modulus and strain at rupture of the P(3HB)/starch composites were enhanced by increasing starch content upto 10 wt % and the tensile strength increased from 21.2 to 93.9 MPa. The presence of starch content higher than 10 wt % had an adverse effect on the mechanical properties of the investigated composites. The biodegradation rate using Actinomycetes increased proportionally to the starch content in the composite and accelerated in a culture medium of pH ≈ 7.0 at 30°C. Enzymatic degradation experiments showed that lipase produced by Streptomyces albidoflavus didnot degrade P(3HB)/starch composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

PIV/PLIF Study of Impinging Jet Ozone Bubble Column with Mixing Nozzles

This paper introduces the results obtained from a particle image velocimetry/planer laser-induced fluorescence (PIV/PLIF) system used in characterizing an impinging jet ozone bubble column with mixing nozzles. This research aims at evaluating the mixing effect resulting from the nozzle diffusers attached to the outlets of the impinging jets' injectors. The PIV system was used to study the flow patterns of the liquid and gas phases under different superficial gas and liquid velocities (u_G and u_L, respectively) values (from 0.002 to 0.017 m/s and from 0.008 to 0.024 m/s, respectively). Furthermore, a particle dynamics analyzer (PDA) system was used to characterize the bubble sizes under the same operating conditions. The PLIF system was used to determine the liquid axial dispersion coefficient (D_L, m²/s) for the mentioned range of operating conditions. The column average gas hold-up (?_G) and specific interfacial area (a) were then determined in order to evaluate the column's mass transfer efficiency. The results showed that higher mass transfer rates can be obtained by using this column, as high ?_G, and were achieved.     

CuII Pyrazolyl-Benzimidazole Dinuclear Complexes with Remarkable Antioxidant Activity

Three dinuclear coordination complexes generated from 1-n-butyl-2-((5-methyl-1H-pyrazole-3-yl)methyl)-1H-benzimidazole ( L ), have been synthesized and characterized spectroscopically and structurally by single crystal X-ray diffraction analysis. Reaction with iron(II) chloride and then copper(II) nitrate led to a co-crystal containing 78 % of [Cu(NO₃)(μ-Cl)( L’ )]₂ ( C₁ ) and 22 % of [Cu(NO₃)(μ-NO₃)( L’ )]₂ ( C₂ ), where L was oxidized to a new ligand L^’ . A mechanism is provided. Reaction with copper chloride led to the dinuclear complex [Cu(Cl)(μ-Cl)( L) ]₂ ( C₃ ). The presence of N−H⋅⋅⋅O and C−H⋅⋅⋅O intermolecular interactions in the crystal structure of C₁ and C₂ , and C−H⋅⋅⋅N and C−H⋅⋅⋅Cl hydrogen bonding in the crystal structure of C₃ led to supramolecular structures that were confirmed by Hirshfeld surface analysis. The ligands and their complexes were tested for free radical scavenging activity and ferric reducing antioxidant power. The complex C₁ / C₂ shows remarkable antioxidant activities as compared to the ligand L and reference compounds.     

US Foreign Affiliates,Technology Diffusion and Host Country Human Development: Human Development Index versus Human Capital

In this study, we use a cross-sectionally correlated and timewise autoregressive model and panel data for the period 1966–2000 to investigate human development as a measure of host country absorptive capacity in 30 developed and developing countries. The results suggest that technology diffusion from US foreign affiliates has a positive and significant impact on labor productivity only if host countries have a minimum level of human development. This condition may partially explain why previous studies show mixed support for the hypothesis that foreign affiliates have a positive effect on productivity in developing countries. Although the results have to be interpreted with caution, the policy implication is that human development enhances the capacity of countries to reap the benefits of foreign direct investments.     

Photo- and bio-degradation of poly(ester-urethane)s films based on poly[(R)-3-Hydroxybutyrate] and poly(ε-Caprolactone) blocks

Biodegradable segmented poly(ester-urethane)s derived from telechelic dihydroxy-poly[(R)-3-hydroxybutyrate], acting as hard segments, and poly(ε-caprolactone)-diols, acting as soft segments, using 1,6-hexamethylene diisocyanate, as non toxic connecting agent, were synthesized. The copolymers were characterized with regard to their molecular weight by GPC and their main thermal transitions by DSC. These copolymers as well as PHB were exposed to UV-irradiation for different time intervals and the changes in the chemical structure were analyzed by FTIR spectroscopy. Under our experimental conditions, it was found that the increase of irradiation time was accompanied by increase of the proportion of the gel fraction and the decrease of the intrinsic viscosity of the soluble fraction of the investigated copolymers. The biodegradability of PHB and poly(ester-urethane) sample containing ~40 wt% PHB before and after UV-irradiation was investigated under soil burial. The results showed that the photolysis in air prior to biodegradation increased the rate of degradation.     

Effect of frozen storage of hake,sardine and mixed minces on natural actomyosin extracted in salt solutions

Natural actomyosin extracted in salt solutions from mixtures of hake and sardine minces (3:1; 1:1 and 1:3 w/w) stored frozen for up to 1 year differed in the amount extracted and in the characteristics of the extracts. In the mixed minces the amount of natural actomyosin extracted decreased during frozen storage at a higher rate than that theoretically corresponding to the amount of hake in the mixes. With increasing storage time and proportion of sardine a lower percentage of myosin heavy chain and actin was observed by electrophoresis. An increased size of aggregates was also observed by electrophoresis and transmission electron microscopy. The stability of emulsions was enhanced when aggregates appeared in the extracts. The decrease in the amount of natural actomyosin extracted does not explain the changes observed in the texture of the minces during frozen storage. This may indicate that the size of the aggregates unextractable in salt solutions, independently of the type of bonds that bind the proteins in the aggregates, plays an important role in the textural changes observed. Copyright © 2003 Society of Chemical Industry