Effect of support modification on the chlorobenzene hydrodechlorination activity on Pt/Al2O3 catalysts

Al₂O₃ was modified with TiO₂ and ZrO₂ using organometallic precursors and is used in the preparation of supported platinum catalysts. The catalysts have been characterised by nitrogen adsorption, hydrogen chemisorption and X-ray diffraction and were tested for their activity in the hydrodechlorination of chlorobenzene. The investigations show that support modification controls the catalyst deactivation remarkably and the catalysts were found to be highly active and selective. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evaluation and Predictive Model Development of Oxidative Stability of Biodiesel on Storage

Biodiesel comprises mono-alkyl esters of long-chain fatty acid methyl esters (FAME) derived from a renewable lipid feedstock. A major technical issue with the use of biodiesel is that it is more prone to oxidation during storage, when compared to petroleum fuel, due to the high content of polyunsaturated methyl esters that are easily oxidizable to compounds such as acids, aldehydes, and alcohols. Biodiesel (Jatropha and Pongamia) and antioxidants (Turmeric and butylated hydroxytoulene) were used for this study. We found that the acid value and viscosity for pongamia biodiesel increased significantly by 41.17% and 44.0% and that for jatropha biodiesel increased by 31.5% and 37.0%, respectively, after being stored for 3 months. The impact of antioxidants on the storage stability of biodiesel was examined according to the ASTM D4625 12-week procedure, and best results were found at a concentration level of 2500 ppm. The specific objective of this investigation is to develop models to determine the viscosity of biodiesel at any time “t” during long-term storage based on these experimental trials for upto 12 weeks. In addition, the models were used to predict the level of antioxidants that are to be added to biodiesel in order to minimize the effects of oxidative degradation during storage. The developed model recorded an adjusted R² of 0.86 and a modeling efficiency of 0.88.     

Nanoengineered biocomposite tricomponent polymer based matrices for bone tissue engineering

Nanoengineered biodegradable constructs based on synthetic and natural polymers enriched with hydroxyapatite (HA) nanoparticles have been found to mimic the extracellular matrix of bone tissue. The main objective of this study was to create biocomposite nanostructured scaffolds by incorporating collagen and HA nanoparticles into poly(L-lactic acid)-co-poly(?-caprolactone) by electrospinning. The fiber diameter of the composite PLCL/Col and PLCL/Col/HA fibers was smaller compared to PLCL. In vitro biocompatibility of the scaffolds studied using human fetal osteoblasts and EDX analysis showed high deposition of calcium on PLCL/Col/HA. The results shows that PLCL/Col/HA nanofibrous constructs have huge potential as substrates for bone regeneration.     

A basic experimental study of sandwich injection molding with sequential injection

An experimental study of sandwich injection molding is reported which involves sequential injection of polymer melts with differing melt viscosity into a mold. In isothermal injection molding the relative viscosity of the two melts is the primary variable determining the phase distribution in the mold. Generally the most uniform skin-core structure occurs when the second melt entering the mold has a slightly higher viscosity than the first melt injected. Large viscosity inequalities lead to nonuniform skin thicknesses. The influence of blowing agents and non-uniform temperature fields on the extent of encapsulation is described. Temperature fields are very important especially if the first polymer melt injected has a greater activation energy of viscous flow (or a greater temperature dependence of the viscosity function).     

纳米石墨/聚丙烯酸甲酯复合乳液的合成工艺研究

采用自由基乳液聚合方法合成了纳米石墨/聚丙烯酸甲酯复合乳液,并用紫外及可见分光光度计和扫描电子显微镜对乳液进行了表征.结果表明:运用丙烯酸甲酯对纳米石墨进行聚合包覆的改性方法实现了纳米石墨在水基液中的稳定分散,并确定最佳聚合条件为:5 h,70℃.     

Bayesian uncertainty analysis with applications to turbulence modeling

In this paper, we apply Bayesian uncertainty quantification techniques to the processes of calibrating complex mathematical models and predicting quantities of interest (QoI's) with such models. These techniques also enable the systematic comparison of competing model classes. The processes of calibration and comparison constitute the building blocks of a larger validation process, the goal of which is to accept or reject a given mathematical model for the prediction of a particular QoI for a particular scenario. In this work, we take the first step in this process by applying the methodology to the analysis of the Spalart-Allmaras turbulence model in the context of incompressible, boundary layer flows. Three competing model classes based on the Spalart-Allmaras model are formulated, calibrated against experimental data, and used to issue a prediction with quantified uncertainty. The model classes are compared in terms of their posterior probabilities and their prediction of QoI's. The model posterior probability represents the relative plausibility of a model class given the data. Thus, it incorporates the model's ability to fit experimental observations. Alternatively, comparing models using the predicted QoI connects the process to the needs of decision makers that use the results of the model. We show that by using both the model plausibility and predicted QoI, one has the opportunity to reject some model classes after calibration, before subjecting the remaining classes to additional validation challenges.     

Electrical and magnetic properties of nanocrystalline BiFeO3 prepared by high energy ball milling and microwave sintering

A new synthesis route with high energy ball milling and microwave sintering is used to obtain nanocrystalline BiFeO3 with improved dielectric and magnetic properties. Electrical and magnetic properties are compared with a conventionally sintered microcrystalline BiFeO3. It is found that the dielectric constant is increased more than one order of magnitude, electrical resistivity by six orders of magnitude and remnant polarization value is increased by 4-5 times for nanocrystalline BiFeO3 in comparison to conventionally sintered microcrystalline BiFeO3. Nanocrystalline BiFeO3 is seen to have ferromagnetic behavior whereas microcrystalline BiFeO3 is known to be antiferromagnetic.     

Heat capacity and thermal expansion of samarium titanate

Samarium titanate (Sm₂TiO₅) was prepared by solid-state synthesis and characterized by X-ray diffraction (XRD). Heat capacity measurements were carried out by differential scanning calorimeter (DSC) in the temperature range 298-800 K. Thermal expansion characteristics have been studied by high temperature X-ray diffraction technique (HTXRD) in the temperature range 298-1573 K. The heat capacity value at 298 K is 170 J K^− 1 mol^− 1. The percentage linear thermal expansion in the temperature range 298-1573 K along a, b and c axes are 0.96, 0.89 and 1.07 respectively. The average coefficient of thermal expansion value obtained in the present study for samarium titanate up to 1573 K is 10.8 × 10^− 6 K^− 1.