The Photo‐Stability of Polymer Solar Cells: Contact Photo‐Degradation and the Benefits of Interfacial Layers

The organic/electrode interfaces in organic solar cells are systematically studied for their light, heat, and electrical stability in an inert atmosphere. Various extraction layers are examined for their effect on device stability, including poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and MoO₃ for hole extraction layers, as well as LiF, Cs₂CO₃, and lithium acetylacetonate (Liacac) for electron extraction layers. The organic/metal interface is shown to be inherently photo‐unstable, resulting in significant losses in device efficiency with irradiation. X‐ray photoelectron spectroscopy measurements of the organic/aluminum interface suggest that the photo‐induced changes are chemical in nature. In general, interfacial layers are shown to substantially reduce photo‐degradation of the active layer/electrode interface. In spite of their photo‐stability, several interfacial layers present at the active layer/cathode interface suffer from thermal degradation effects due to temperature increases under exposure to light. Electrical aging effects are proven to be negligible in comparison to other major modes of degradation.     

Insulation the Saudi way

Attention focuses on the growing building market in Saudi Arabia. This article from the Materials Testing Laboratory in Riyadh on some local building techniques explains the theoretical approach which seems to favour the use of suspended gypsum plasterboard for thermal insulation in the prevailing climatic conditions.     

Optimisation of reaction conditions for the synthesis of single‐walled carbon nanotubes using response surface methodology

The effects of three preparation variables, i.e. reaction temperature, reaction time and reaction gas (methane/nitrogen) flow rate, on the ratio of the intensity of the Raman D band to the intensity of the G band (I_D/I_G), carbon mass and the presence of radial breathing mode (RBM) peaks were investigated by using a central composite design to develop two linear models. The most influential factor in each experimental design‐response was identified using the analysis of variance. The predicted I_D/I_G ratio, carbon mass and presence of RBM peaks determined during the process optimisation were found to agree satisfactorily with the experimental values. The optimum conditions for synthesising single‐walled carbon nanotubes were determined to be a reaction temperature of 900°C, a reaction time of 59 min and a reaction gas flow rate of 54 mL/min. © 2011 Canadian Society for Chemical Engineering     

MCNPX Modeling of BN-600 Full MOX Fast Reactor Core

The BN-600 full mixed oxide fueled core is modeled using MCNPX code. A three dimensional model typical of the core is prepared which includes 6 radial zones, low enrichment zone, medium enrichment zone and high enrichment zone, two zones of steel shielding assemblies, and a radial blanket in addition to shim and scram rods. The twelve axial zones are also modeled. The model calculates core parameters such as reactor multiplication factor, power distribution through reactor core, and control rod worth. An estimation of isotope transmutation through various reactor zones and analysis of internal breeding zone were presented. The results are compared with previously published results which indicated good agreement. Typical results of the present model for reactor multiplication factor are !.00832 compared with transport model （1.00664） and diffusion model （1.00131）. The high enrichment zone dominates power production. The results also estimate the isotope variation due to burnup in the MOX core.     

A comparative study of numerical integration based on Haar wavelets and hybrid functions

A quadrature rule based on uniform Haar wavelets and hybrid functions is proposed to find approximate values of definite integrals. The wavelet-based algorithm can be easily extended to find numerical approximations for double, triple and improper integrals. The main advantage of this method is its efficiency and simple applicability. Error estimates of the proposed method alongside numerical examples are given to test the convergence and accuracy of the method.     

Hydrogen production by Chlamydomonas reinhardtii in a two-stage process with and without illumination at alkaline pH

This work presents the results of a two-stage (carbon fixation and hydrogen production) experimental study for hydrogen production from microalgae using optical fiber as an internal light source. Effect of absence and presence of light on Chlamydomonas reinhardtii culture’s pH shift is also evaluated. The culture pH value is a function of light intensity; the pH in the alkaline range changes from 7.5 to 9.5 in the presence and absence of optical fiber respectively. The maximum rate of hydrogen production in the presence of exogenic glucose and optical fiber is 6 mL/L_cult/hour, which is higher than other reported values. This study has also revealed that the presence of light reduces the lag time for hydrogen production from 12 to 5 h.     

Comparative assessment of proximate composition,physicochemical parameters,fatty acid profile and mineral content in farmed and wild rainbow trout (Oncorhynchus mykiss)

This study was conducted to determine differences between farmed and wild rainbow trout in terms of proximate and fatty acid composition, physicochemical parameters and mineral content. Fat content of farmed fish fillets was higher, while moisture content was lower than wild fish. However, wild fish had higher pH value and water‐holding capacity comparing to farmed fish. The muscle lipids of farmed fish contained higher proportions of 20:0, 18:1n‐9 and 20:1n‐9; and lower proportions of 18:2n‐6, 20:2cis, 18:3n‐3, 20:3n‐6, 20:4n‐6, 20:5n‐3 and 22:6n‐3 fatty acids than wild fish. The percentage of total saturated fatty acids (SFAs) was similar in both fish. Total polyunsaturated fatty acids (PUFAs), n‐3 PUFAs and n‐3/n‐6 PUFAs ratio were higher in the wild fish comparing to farmed fish, whereas its total monounsaturated fatty acids (MUFAs) and n‐6 PUFAs contents were lower. Among the seventeen minerals analysed in fish flesh, differences existed between farmed and wild rainbow trout in Ca and Fe contents. Moreover, toxic trace minerals (As, Cd, Pb and Hg) were all present in amounts below their toxic levels. The differences observed between farmed and wild fish may be attributed to the diet constituents and environmental conditions of the fish.     

Structural and Optical Properties of Lead-Boro-Tellurrite Glasses Induced by Gamma-Ray

Spectrophotometric studies of lead borotellurite glasses were carried out before and after gamma irradiation exposure. The increasing peak on the TeO₄ bi-pyramidal arrangement and TeO₃₊₁ (or distorted TeO₄) is due to augmentation of irradiation dose which is attributed to an increase in degree of disorder of the amorphous phase. The structures of lead tellurate contain Pb₃TeO₆ consisting of TeO₃ trigonal pyramid connected by PbO₄ tetragonal forming a three-dimensional network. The decrease of glass rigidity is due to irradiation process which is supported by the XRD diffractograms results. The decreasing values of absorption edge indicate that red shift effect occur after irradiation processes. A shift in the optical absorption edge attributed to an increase of the conjugation length. The values of optical band gap, E_opt were calculated and found to be dependent on the glass composition and radiation exposure. Generally, an increase and decrease in Urbach’s energy can be considered as being due to an increase in defects within glass network.     

Time-averaged heat transfer correlation for direct injection hydrogen fueled engine

This paper presents the development of an empirical correlation for the prediction of time-averaged heat transfer for a direct-injection hydrogen fueled engine. Computer simulation based on one-dimensional gas dynamics approach was used to perform the time-averaged analysis for the in-cylinder heat transfer. Simulation was performed for 1800 ≤ rpm ≤ 5000, 0.2 ≤ φ ≤ 1.2 and 130 deg before top dead center (BTDC) ≤ SOI ≤ 70 deg BTDC. Experimental measurements were used to verify the developed model, during which the engine performance could be determined to a reasonable accuracy of 10%. The equivalence ratio (φ) was considered as a governing variable, through the new correlation for the time-averaged heat transfer. A nonlinear regression approach was used to develop the new correlations. In the case of all the simulation data, the proposed correlations have a satisfactory performance with the determination coefficient (R²) of about 0.99. A relative error of 10% was found in more than 95% of the simulation data. However, the relative error was reduced to about 50% in the newly developed correlations, which increased its reliability to more than the Taylor's correlation for representing the actual data. Due to the general form, hydrocarbon fuel is suitable for the newly developed correlations that are theoretically made.