Problems and experiences in nuclear data processing in developing countries

This article offers a summary of many interesting experiences and problems the authors have come across while making attempts to develop RAMBHA, the Kalpakkam processing code system for multigrouping neutron interaction cross section data for fast reactor applications. Many of the problems are due to limitations arising from the nature of computer facility including memory restraints. Also offered here is an interesting comparison of non-adjusted ENDF/B-IV based RRC multigroup cross-section set with 1969 adjusted French set. An attempt is made to highlight the impact of processing uncertainties on reactor parameters by two examples.     

A reinforced movable boundary multiplexing scheme with adaptive interpolation: Modelling and performance evaluation

A novel multiplexing scheme for integrated networks characterized by the coexistence of circuitswitched and packet-switched traffic is described in this paper. The new scheme is realized by a reinforcement of the basic movable boundary hybrid-switching technique, by incorporating an adaptive interpolation within the circuit-switched subsystem. The adaptation mechanism is controlled by the level of congestion in the packet queue. A precise queueing model for the multiplexer is developed and an analytical evaluation of the key performance parameters of interest, namely the loss probability and expected delay of the packet-switched subsystem, and the freeze-out fraction of the circuit-switched subsystem, is conducted. The results of several numerical studies are presented to describe the performance of the multiplexer under different conditions. Of particular significance resulting from these studies is the trade-off between the freeze-out fraction of the circuit-switched subsystem and the loss probability of the packet-switched subsystem; this trade-off may be exploited in a systematic design of the interrated multiplexer tailored to specific applications.     

Experimental investigation of microwave-optoelectronic interactionsin a microstrip ring resonator

Microwave optoelectronic mixing on a semi-insulating gallium arsenide substrate performed by monolithically integrating Schottky diode photodetectors into a microstrip ring resonator is discussed. When operated in the resistive mixing mode, a low frequency difference signal is extracted from the bias pad of the circuit. In the parametric mode, both degenerate and non-degenerate parametric amplification of an optical carrier signal takes place. The circuit shows good potential for application in wide-band fiberoptic systems     

Mercury chalcogenides under pressure

The mercury chalcogenides, HgTe and Hg_1?x Cd _x Te, have received considerable attention in recent years because of their use in infrared photon detectors. This article is concerned with some recent experiments on the Γ₆-Γ₈ band crossover in these systems induced by pressure. It is shown that although the inverted band model is valid for HgTe, the conclusions of the earlier workers on the pressure induced Γ₆-Γ₈ crossover are erroneous. Experimental results show that it is difficult to observe the band crossover due to an intervening structural phase transition from cubic zinc blend to the cinnabar structure. However pressure experiments on the semiconductor alloy system Hg_0·9Cd_0·1 Te clearly indicate this crossover. New results on the zinc blend-cinnabar phase transformation are also presented. The striking behaviour of thermoelectric power in the high pressure cinnabar phase is correlated with the available experimental data on the structurally similar elemental semiconductors like selenium and tellurium.     

Selective ion-exchange in MAPO-36 and its application in toluene disproportionation

MAPO-36 was synthesized hydrothermally by isomorphic substitution of Mg²⁺ in the framework of AlPO-36 and ion-exchanged with Fe³⁺, Zn²⁺, La³⁺ and Ce³⁺ by wet method. The materials were characterized by XRD, TGA, TPD (ammonia) and SEM-EDX. XRD revealed absence of structural degradation after ion-exchange. TPD (ammonia) showed selective ion-exchange of strong acid sites in ion-exchanged MAPO-36. The weight loss around 550 °C in TGA for Fe, La and CeMAPO-36 suggested conversion of M(OH)₂⁺ to MO⁺. Toluene disproportionation was carried over all catalysts in which diphenyl methane derivative was suggested to be the principle intermediate in the formation of p-xylene and other products. The time on stream study showed exclusive formation of p-xylene after 6 h.     

Biohydrogen production from renewable agri-waste blend: Optimization using mixer design

Biohydrogen from untreated mixed renewable agri-waste using buffalo dung compost is reported. Corn husk (CH) supported 25% higher hydrogen (H₂) production and showed the maximum value (62.38%) with p value (1.2 × 10⁻⁶) revealing its significance at individual and interactive level, respectively, compared to ground nut shell (GNS) and rice husk (RH). Augmented-simplex-lattice design experimentation revealed that a partial supplementation of RH or GNS to CH improves H₂ yield. Multiple-linear-regression analysis indicated that a quadratic model (low p = 0.0023, high F value = 35.99 and R²_quadratic = 0.99) was more significant compared to other (linear, cubic and special cubic) models. Acetate and butyrate were accounted >80% of the volatile fatty acids (VFAs). A maximum accumulation of 65.78 ml H₂ g⁻¹ TVS was produced using agri-wastes in the ratio of CH:RH:GNS = 70:16:12.     

Process optimisation for a ready‐to‐serve breakfast smoothie from a composite milk–sorghum base

A composite milk and sorghum‐based smoothie containing varying levels of sorghum flour (2–4% w/w), sugar (9–11% w/w) and pectin (0.2–0.4% w/w) was optimised by response surface methodology on the basis of sensory (colour and appearance, flavour, consistency, sweetness and overall preference) and physical (viscosity, sedimentation and wheying off) attributes. Flour and pectin levels influenced the flavour, consistency, viscosity and sedimentation significantly. Sugar helped to increase the overall preference and had a positive correlation with sedimentation. An optimised smoothie composition of acceptable quality was obtained with 2.79% (w/w) germinated sorghum flour (GSF), 10.30% (w/w) sugar and 0.35% (w/w) pectin.     

媒染剂和染料用量对红土染料染色棉织物色牢度的影响

从红土中提取天然染料并将其应用于棉织物.改变媒染剂用量和染液用量进行染色试验.结果表明,与不使用媒染剂的试样相比,使用媒染剂的天然红土染色织物试样表现出较好的耐水洗、耐光和耐摩擦色牢度,且色牢度随着媒染剂用量的增加而提升.染料用量的增加未导致织物试样的色牢度明显提升.     

Assessment via the modified gompertz-model reveals new insights concerning the effects of ionic liquids on biohydrogen production

Lignocellulosic biofuel, in particular hydrogen gas production is governed by successful feedstock pretreatment, hydrolysis and fermentation. In these days, remarkable attention is paid to the use of ionic liquids to make the fermentable regions of lignocellulose biomass more accessible to the biocatalysts. Although these compounds have great potential for this purpose, their presence during the consecutive fermentation stage may pose a threat on process stability due to certain toxic effects. This, however, has not been specifically elaborated for dark fermentative biohydrogen generation. Hence, in this work, two common imidazolium-type ionic liquids (1-butyl-3-methylimidazolium acetate, ([bmim][Ac]) and 1-butyl-3-methylimidazolium chloride, ([bmim][Cl])) were employed in mixed culture biohydrogen fermentation to investigate the possible impacts related to their presence and concentrations. The batch assays were evaluated comparatively via the modified Gompertz-model based on the important parameters characterizing the process, namely the biohydrogen production potential, maximum biohydrogen production rate and lag-phase time.     

CuOCr2O3 core-shell structured co-catalysts on TiO2 for efficient photocatalytic water splitting using direct solar light

Synthesis of core-shell structured CuOCr₂O₃ nanoparticles as co-catalyst to improve the photocatalytic hydrogen evolution performance of TiO₂ was demonstrated. The effect of co-catalyst loading on TiO₂ and the nature of the reactor was found to be more significant for H₂ production under direct solar light. The formation of 9.3 nm Cr₂O₃ shell over CuO core in the CuOCr₂O₃ nanostructured co-catalyst was confirmed using transmission electron microscopy. A very high H₂ production rate of 82.39 and 70.4 mmol h^?1 g^?1_cat was observed with quartz and pyrex reactors under direct solar light of irradiation 96–100 mW/cm², respectively. This is almost three times higher than that of bare TiO₂ under similar experimental conditions. The core-shell co-catalyst loaded on TiO₂ by simple mechanical mixing method which is useful for bulk scale synthesis in practical applications. The observed high H₂ production was explained with plausible mechanism where the synergic effect of CuOCr₂O₃ co-catalyst loaded TiO₂ surface that reduces the effective charge carriers recombination and impeded backward reaction by the Cr₂O₃ thin layer. The presence of Cu²⁺ and absence of Cu⁺ and metallic Cu was confirmed using XPS analysis. The effect of co-catalyst loading and sacrificial agent concentration on the photocatalytic hydrogen production was also reported. The stability of the CuOCr₂O₃ core-shell NPs loaded TiO₂ photocatalyst under the direct solar light was examined by continuous cycling for three days and it was found to be 81 and 70% of photocatalyst activity is retained after 3 days in the quartz and pyrex reactor systems, respectively.