Survey of grid-connected photovoltaic inverters and related systems

Grid-connected photovoltaic (PV) inverter technology has advanced since it first attracted the attention of policy makers. The objective of this article is to present a survey of grid-connected PV inverters and their present technology in Malaysia. Surveyed here are 186 PV inverter products from 22 manufacturers, their power factors, system THDs, efficiencies, power inputs (from PV array), costs, sizes, and protections investigated, and their datasheets collected from various manufacturers in Europe, North America, and Asia. The data are compared within regions and subject headings. Discussed are the lowering of cost, the raising of efficiency levels, and reliability improvement.     

Unique stimuli responsive characteristics of electron beam synthesized bacterial cellulose/acrylic acid composite

The formation and swelling behavior of bacterial cellulose/acrylic acid hydrogel prepared from aqueous mixture consists of 20 : 80 (v/v) acrylic acid (AAc) and 1% bacterial cellulose dispersion under accelerated electron beam was investigated. Gel fraction of hydrogel increased with the increasing dose suggesting a denser composite at 50 kGy compared to 35 kGy. SEM photomicrographs revealed a homogenous pores distribution at higher dose with pore sizes ranging from 1 to 5 μm. Hydrogel synthesized at lower dose of electron beam exhibited higher swelling ability and the degree of swelling increased as the pH of surrounding medium increased and it reached the optimum swelling at pH 7. While swelling of the hydrogel decreased with the increasing ionic strength of solution, swelling at different temperatures ranging from 25 to 50°C revealed a unique character where the hydrogel shrunk at 37°C. Moreover, hydrogel synthesized at higher dose exhibited a higher degree of swelling in methanol with respect to water. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Geochemistry of the sediments of the El-Kabir River and Akkar watershed in Syria and Lebanon

A total of 39 sediment samples were collected from the El‐Kabir River and its major tributaries during the low‐flow period of August/September 2001. Of these samples, six were selected for a scan for pesticide residues, polychlorinated biphenyls and polycyclic aromatic hydrocarbons (PAHs). An additional seven samples were analysed for major elements and trace elements. Despite the limited number of samples analysed, it can be concluded that major elements reflect the distribution and chemistry of major rock types in the watershed, the sodium oxide concentrations indicate an early onset of salinization in the coastal plain, dichlorodiphenyltrichloroethane is currently in use in the watershed despite being a banned substance, the PAH contamination is directly linked to an old, disused railway track, and chromium and nickel are the two trace elements showing anthropogenic enrichment, being attributed to leather tanning and metal plating by small‐scale industries in the watershed.     

Synthesis and properties of poly(arylenevinylene)s comprising of an electron-donating carbazole unit and an electron-accepting 2,1,3-benzothiadiazole (or fluorenone) unit in the main chain

Two new soluble arylenevinylene-based polymers comprising of an electron-donating carbazole unit and an electron-accepting 2,1,3-benzothiadiazole (or fluorenone) unit in the main chain were synthesized by Heck polycondensation between 3,6-divinylene-9-decyl carbazole and 4,7-dibromo-2,1,3-benzothiadiazole (or 2,7-dibromofluorenone). In the toluene solution, a polymer with benzothiadiazole unit showed strong red photoluminescence, whereas the polymer with fluorenone unit showed white-yellow photoluminescence. The polymers had good thermal stability with 5 wt% loss temperature of more than 430 °C. Electrochemically, the polymers appeared to be reversible under reduction.     

An Abbreviated Synthesis of 7,12-Dimethylbenz[ a ]anthracene and Benzo[ c ]chrysene Metabolites Using the Suzuki Reaction

Efficient syntheses of important metabolites of 7,12-dimethylbenz[ a ]anthracene (DMBA) and benzo[ c ]chrysene (B[ c ]C), via Suzuki coupling reaction are described. This approach provides an excellent method for the preparation of 3-methoxy-DMBA 5 , 10-methoxy-B[ c ]C 14 and 2-methoxy B[ c ]C 20 , and hence for the corresponding dihydrodiols 6 , 15 , and 21 . Following a similar Suzuki reaction, DMBA-6(5 H )-one 8 was also synthesized in high yield.     

Surface roughness and dispersion parameters of indium doped amorphous As2Se3 thin films

Both a binary amorphous system of composition As₂Se₃ and a ternary amorphous system of composition amorphous (As₂Se₃)_0.99In_0.01 with thickness in the range 150–250 nm have been prepared by thermal evaporation technique. Indium doping and thickness effects on the features of As₂Se₃ thin films have investigated. The optical transmission spectra of these films have been measured in the range 200–1200 nm where the absorption coefficient and the optical energy gap Eg are evaluated. The refractive index and surface roughness of the prepared films are found to be highly dependent on film thickness and indium doping, using Swanepoel method.The single oscillator energy (E_o) and the energy dispersion parameter (E_d) have been calculated and discussed in terms of the Wemple and DiDomenico model. The results reveal that, they are thickness dependent—both E_o and E_d being higher for the undoped samples than that for the doped films.     

Blind source separation based on time-frequency signalrepresentations

Blind source separation consists of recovering a set of signals of which only instantaneous linear mixtures are observed. Thus far, this problem has been solved using statistical information available on the source signals. This paper introduces a new blind source separation approach exploiting the difference in the time-frequency (t-f) signatures of the sources to be separated. The approach is based on the diagonalization of a combined set of “spatial t-f distributions”. In contrast to existing techniques, the proposed approach allows the separation of Gaussian sources with identical spectral shape but with different t-f localization properties. The effects of spreading the noise power while localizing the source energy in the t-f domain amounts to increasing the robustness of the proposed approach with respect to noise and, hence, improved performance. Asymptotic performance analysis and numerical simulations are provided     

Roof-harvested rainwater for potable purposes: Application of solar collector disinfection (SOCO-DIS)

The efficiency of solar disinfection (SODIS), recommended by the World Health Organization, has been determined for rainwater disinfection, and potential benefits and limitations discussed. The limitations of SODIS have now been overcome by the use of solar collector disinfection (SOCO-DIS), for potential use of rainwater as a small-scale potable water supply, especially in developing countries. Rainwater samples collected from the underground storage tanks of a rooftop rainwater harvesting (RWH) system were exposed to different conditions of sunlight radiation in 2-L polyethylene terephthalate bottles in a solar collector with rectangular base and reflective open wings. Total and fecal coliforms were used, together with Escherichia coli and heterotrophic plate counts, as basic microbial and indicator organisms of water quality for disinfection efficiency evaluation. In the SOCO-DIS system, disinfection improved by 20–30% compared with the SODIS system, and rainwater was fully disinfected even under moderate weather conditions, due to the effects of concentrated sunlight radiation and the synergistic effects of thermal and optical inactivation. The SOCO-DIS system was optimized based on the collector configuration and the reflective base: an inclined position led to an increased disinfection efficiency of 10–15%. Microbial inactivation increased by 10–20% simply by reducing the initial pH value of the rainwater to 5. High turbidities also affected the SOCO-DIS system; the disinfection efficiency decreased by 10–15%, which indicated that rainwater needed to be filtered before treatment. The problem of microbial regrowth was significantly reduced in the SOCO-DIS system compared with the SODIS system because of residual sunlight effects. Only total coliform regrowth was detected at higher turbidities. The SOCO-DIS system was ineffective only under poor weather conditions, when longer exposure times or other practical means of reducing the pH were required for the treatment of stored rainwater for potable purposes.     

Antioxidant capacity of methanolic and water extracts prepared from food‐processing by‐products

This study aims to evaluate the antioxidant capacity of mango peel, roselle seed, okara (by‐product of soya milk industry), cocoa shell and pink guava (by‐product of pink guava industry) in comparison to 6‐hydroxy‐2,5,7,8‐tetramethylchroman‐2‐carboxylic acid (Trolox). The β‐carotene bleaching, 1,1‐diphenyl‐2‐picrylhydrazyl and reducing power assays were used to determine the antioxidant capacity of selected by‐products by measuring the absorbance at 470, 520 and 700 nm, respectively. The results showed that methanolic extracts of pink guava and cocoa shell exhibited the highest antioxidant activity and free radical scavenging activity compared to other studied samples. Roselle seed water extract exhibited the highest antioxidant activity and free radical scavenging when extracted with water. Pink guava possessed the highest reducing power in methanolic extract at a concentration of 0.16 mg mL^?1. At the same concentration, mango peel exhibited the highest reducing power when extracted with water. The present study shows that pink guava, roselle seed and cocoa shell are potential sources of antioxidant components that can be exploited as food preservative agents or nutraceuticals. Copyright © 2006 Society of Chemical Industry