Non-uniform illumination in concentrating solar cells

After a gap of more than two decades, Concentrator Photovoltaics (CPV) technology is once again under spotlight for making use of the best available solar cell technologies and improving the overall performance. CPV finds its use in a number of applications ranging from building integration to huge power generation units. Although the principles of solar concentration are well understood, many practical design, operation, control issues require further understanding and research. A particular issue for CPV technology is the non-uniformity of the incident flux which tends to cause hot spots, current mismatch and reduce the overall efficiency of the system. Understanding of this effect requires further research, and shall help to employ the most successful means of using solar concentrators. This study reviews the causes and effects of the non-uniformity in the CPV systems. It highlights the importance of this issue in solar cell design and reviews the methods for the solar cell characterization under non-uniform flux conditions. Finally, it puts forward a few methods of improving the CPV performance by reducing the non-uniformity effect on the concentrator solar cells.     

A low complexity hardware architecture of K-means algorithm for real-time satellite image segmentation

Multimedia Tools and Applications - The Real time monitoring of forest area, coastal regions, sea, river basins, nation borders etc. helps in quick determination of devastations caused by natural...     

Antimicrobial,mechanical, barrier,and thermal properties of starch–casein based,neem (Melia azardirachta) extract containing film

The Starch–Casein‐based edible films containing with or without neem (Melia azadirachta) extract was prepared. The neem based free films were also heat pressed and all of them were assessed for inhibition of pathogenic organisms namely E. coli, Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Pseudomonas spp., and Salmonella, using disc diffusion assay. The Glass‐transition temperature (T_g) and thermal properties of the films were determined with the help of DSC and DMA. Tensile strength (TS), elongation at break (EAB), water vapor transmission rate (WVTR), and oxygen transmission rate (OTR) of the films were also determined. Incorporation of neem extract to edible film did not affect any of the physical properties except microbial, and the films were effective in inhibiting the growth of pathogens, since the inhibition zones varied from 15 mm as large as 24 mm. However, the heat‐pressed films containing neem extract led higher the T_g, TS, and modulus, while the EAB was marginally affected, indicating the toughening of the film and as expected, the heat pressing of films decreased the WVTR and marginally affected OTR. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3948–3954, 2006     

Differential scanning calorimetry and wide-angle X-ray scattering studies of bread staling

Wide angle X-ray scattering (WAXS) was used to follow the development of crystal size and strain during the staling of bread containing different additives. In this it was observed that one can classify the good anti-staling additives as gelatin, propylene glycol, maltodextrin and anti-staling enzyme corresponding to the order of increasing crystal size for a particular Bragg reflection in all the samples and correlate using DSC (differential scanning calorimetry) studies of all the bread compositions containing different additives. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1597–1603, 1998     

Studies on the potential of coal fly ash as a heterogeneous catalyst in oxidation of aqueous sodium sulfide solutions with hydrogen peroxide

The potential of fly ash procured form coal-fired thermal power plants was studied as a heterogeneous catalyst in the oxidation of aqueous sodium sulfide solutions with hydrogen peroxide in the temperature range of 303–323 K. The effects of various parameters (source of fly ash, fly ash loading, initial concentrations of sodium sulfide and hydrogen peroxide, electrolyte and deactivation of catalytic effect of fly ash) were studied. For an initial sodium sulfide and hydrogen peroxide concentration of 26·98×10⁻² kmol m⁻³ and 24·28×10⁻² kmol m⁻³ respectively, only 4% (w/v) fly ash loading intensified the rate of oxidation by a factor of 4·52 over that without fly ash at 303 K. The deactivation of the catalytic effect of fly ash was found to be less than 20% even after six repeated uses. The kinetics of aqueous phase decomposition of hydrogen peroxide was also studied in the presence of fly ash in alkaline medium. ©1997 SCI     

Characterization of microstructure and corrosion properties of cold worked Alloy 800

X-ray diffraction studies indicated that cold worked (∼50%) Alloy 800 was austenitic and transmission electron microscopy revealed the presence of a small volume fraction of hexagonal ε-martensite along with deformation bands, high dislocation density and primary TiN particle with a few dislocations within it. The passivity of cold worked alloy was very stable in H₂SO₄ solution but unstable in HCl solution at room temperature. The exposure of cold worked alloy in 673 K steam (initial pH of water was 10.1) for a period of 264 h showed almost nil corrosion rate. Scanning electron microscopy revealed a number of small oxide particles on the surface exposed in steam indicating initiation of oxide formation. Energy dispersive X-ray analyses of the surface containing small oxide particles indicated that the surface composition was similar to bulk composition of the alloy. X-ray photoelectron spectroscopy revealed that the alloy surface exposed in steam contained mixed oxides of iron and chromium as well as elemental form of iron, nickel and chromium.     

Differential scanning calorimetric and free volume study of reactive compatibilization by EPM‐g‐MA of poly(trimethylene terephthalate)/EPDM blends

Differential scanning calorimetry (DSC) and positron annihilation lifetime measurements have been carried out to study the effect of the compatibilizer maleic anhydride grafted ethylene propylene copolymer (EPM‐g‐MA) in poly trimethylene terephthalate and ethylene propylene diene monomer (PTT/EPDM) immiscible blends. The DSC results for the blends of 50/50 and 30/70 compositions show two clear glass transition temperatures, indicating that the blends are two‐phase systems. With the addition of compatibilizer, the separation between the two glass transitions decreased, suggesting an increased interaction between the blend components with compatibilizer. At 5 wt % of compatibilizer, the separation between the T_gs reduced in both 50/50 and 30/70 blends. The positron results for the blends without compatibilizer showed an increase in relative fractional free volume, as the EPDM content in the blend is increased. This suggests the coalescence of free volume of EPDM with the free volumes of PTT due to phase separation. However, the effect of compatibilizer in the blends was clearly seen with the observed minimum in free volume parameters at 5% of the compatibilizer, further suggesting that this percent of compatibilizer seems to be the optimum value for these blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 740–747, 2006     

Complete clinical remission and subsequent relapse of bronchiectasis-related (AA) amyloid induced nephrotic syndrome

Systemic amyloidosis normally has a dismal prognosis. However, there are several case reports of protracted survival, usually as a response to measures designed to retard the further deposition of amyloid fibrils. In AA amyloid, most commonly associated with inflammatory rheumatological, bowel, and chest diseases, such interventions have had some success, but the dramatic response of complete resolution of nephrotic syndrome as a result of the regular institution of postural chest drainage and antibiotic therapy, in the clinical context of bronchiectasis, has been previously reported only once. In both of our cases, after protracted remission, such therapy was abandoned by the patients, leading both to recurrence of nephrotic syndrome and also eventually to end-stage renal failure requiring dialysis.     

Selective oxidation of benzaldehyde by molecular oxygen over molybdovanadophosphoric acid supported MCM-41

A series of molybdovanadophosphoric acid (MVPA) supported on mesoporous silica was synthesized by an incipient wetness impregnation method. The catalysts were characterized by nitrogen adsorption?Cdesorption, X-ray powder diffraction, Fourier-Transform Infra red spectroscopy (FT-IR), UV?CVis Diffused reflectance spectroscopy (UV?CVis DRS), Temperature programmed reduction (TPR) and ³¹P MAS Nuclear magnetic resonance(NMR) study. The characterization data reveals the incorporation of vanadium in phosphomolybdic acid and retention of intact Keggin ion on the support. The catalytic activities were evaluated for oxidation of benzaldehyde using molecular oxygen as oxidant as the new green reaction system. Among all the promoted catalysts, 50wt% molybdovanadophosphoric acid supported on MCM-41 exhibits highest catalytic activity in oxidation of benzaldehyde, giving 95% conversion. Other oxidants like H₂O₂ and tert-butyl hydrogen peroxide (TBHP) were also tested for benzaldehyde oxidation reaction.