Accelerating subsurface scattering using Cholesky factorization

In this paper we present a simplified subsurface scattering model that exploits a diffusion mechanism to provide a simpler solution to the transport equation. Our model is based on numerical analysis techniques that are amenable to Cholesky factorization. We treat the factorization as a precomputed scattering quantity which can be used to significantly speed up multiple scattering calculations as the global light source changes. On low resolution meshes, we have been able to achieve real-time solutions of the subsurface scattering while still maintaining good visual quality of the solution.     

Improved performance of iron-based redox flow batteries using WO3 nanoparticles decorated graphite felt electrode

Iron flow batteries are having tremendous attraction because of their economic feasibility and environmentally favorable electrolytes. Electrode and electrolyte used in iron-based redox flow batteries (IRFBs) have a vital role in the performances of electrochemical energy storage devices. Therefore designing a suitable electrode and optimization of electrolyte composition is highly needed. Graphite is one of the appropriate electrodes used in flow batteries but they have to be modified to improve the electrical performance. Here, for the first time, WO₃ nanoparticles (WONs) were used to modify graphite felt electrode for IRFBs applications. The effect of loading mass per unit cm² of electrochemically active material has been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (Tafel) studies. The ligand based iron-electrolyte along with anion exchange membrane has been selected for the studies. The performance of the modified graphite felt electrode (3 mg/cm²) assembled in 132 cm² cell results in a peak power density of 53 mW/cm² at 40 mA/cm². This study provides information about the improvement in the electrochemical performance of IRFBs.     

Influence of a pore-forming agent on swelling,network parameters,and permeability of poly(ethylene glycol)-crosslinked poly(methyl vinyl ether-co-maleic acid) hydrogels: Application in transdermal delivery systems

We characterized hydrogels, prepared from aqueous blends of poly(methyl vinyl ether-co-maleic acid) (PMVE/MA) and poly(ethylene glycol) (PEG 10,000 Daltons) containing a pore-forming agent (sodium bicarbonate, NaHCO₃). Increase in NaHCO₃ content increased the equilibrium water content (EWC) and average molecular weight between crosslinks (M_c) of hydrogels. For example, the %EWC was 731, 860, 1109, and 7536% and the M_c was 8.26, 31.64, 30.04, and 3010.00 × 10⁵ g/mol for hydrogels prepared from aqueous blends containing 0, 1, 2, and 5% w/w of NaHCO₃, respectively. Increase in NaHCO₃ content also resulted in increased permeation of insulin. After 24 h, percentage permeation was 0.94, 3.68, and 25.71% across hydrogel membranes prepared from aqueous blends containing 0, 2, and 5% w/w of NaHCO₃, respectively. Hydrogels containing the pore-forming agent were fabricated into microneedles (MNs) for transdermal drug delivery applications by integrating the MNs with insulin-loaded patches. It was observed that the mean amount of insulin permeating across neonatal porcine skin in vitro was 20.62% and 52.48% from hydrogel MNs prepared from aqueous blends containing 0 and 5% w/w of NaHCO₃. We believe that these pore-forming hydrogels are likely to prove extremely useful for applications in transdermal drug delivery of biomolecules. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Analysis of composite ENF specimen using higher order beam theories

Mathematical modelling, for the stress analysis of symmetric composite end notch flexure (ENF) specimen, has been presented using classical beam theory, first, second, and third order shear deformation beam theories to determine the strain energy release rate (SERR) for symmetric composites under mode II interlaminar fracture. In the present formulation, appropriate matching conditions have been applied at the crack tip and these matching conditions at the crack tip have been derived by enforcing the displacement continuity at the crack tip in conjunction with the variational equation. Compliance method has been used to calculate the SERR. Beam models under plane stress and plane strain conditions agree with each other with good performance to analyze the unidirectional and cross-ply composite ENF specimens, whereas for multidirectional composite ENF specimen, only the beam model under plane strain condition appears to be applicable with moderate performance. Third order shear deformation beam model of ENF specimen has been found to be better than other beam models in determining the SERR for unidirectional, cross-ply and multidirectional composites under mode II interlaminar fracture.     

Analysis of unidirectional (0°) fiber-reinforced laminated composite double cantilever beam specimen using higher order beam theories

Mathematical models, for the stress analysis of unidirectional (0°) fiber-reinforced laminated composite double cantilever beam (DCB) specimen using classical beam theory, first and higher order shear deformation beam theories, have been developed to determine the mode I strain energy release rate (SERR) for unidirectional composites. In the present study, appropriate matching conditions at the crack tip of the DCB specimen have been derived by using variational principles. SERR has been calculated using compliance method. In general, the performance of shear deformation beam models of DCB specimen with variationally derived matching conditions at the crack tip is good in determining the SERR for medium to long crack lengths. Performance of higher order shear deformation beam model (having quadratically varying transverse displacement over the thickness) of DCB specimen, with non-variationally derived matching conditions at the crack tip, is good in determining the SERR for all the crack lengths in comparison with the available theoretical and finite element solutions in the literature. Higher order shear deformation beam theories having varying transverse displacement over the thickness are more appropriate to analyze DCB specimen as they predict the appropriate nature of the interlaminar normal stress at the crack tip and its distribution ahead of the crack tip.     

Kinetics studies of ketazine formation: Effect of temperature and catalyst concentration

Formation of methyl ethyl ketazine is a distinct case of homogeneous catalyzed gas–liquid–liquid reactions. Kinetics studies of methyl ethyl ketazine formation has been carried out in a semi‐batch reactor. The effects of temperature and catalyst concentration on the percentage yield of ketazine have been studied extensively. The yield of ketazine is found to increase with increase in temperature and then levels off. Increase in catalyst concentration favours the formation of ketazine. The conversion of peroxide is found to increase with increase in temperature thus indicating that chemical reaction is rate‐limiting step in the system. The desired temperature for carrying out the reaction is found to be 60°C and the required catalyst to peroxide ratio is 2.5. The activation energy for the reaction is 24.5 kJ/mol.     

Dietary ligands as determinants of iron-zinc interactions at the absorptive enterocyte

Iron and zinc interact at the enterocyte and influence the absorption of one another. We have previously reported that zinc noncompetitively inhibits iron uptake in Caco-2 cells, a widely accepted model of the absorptive enterocyte. However, the determinants of this interaction, such as the effect of dietary ligands, remain uncharacterized. Dietary ligands selectively chelate iron and zinc in definite stoichiometric proportions and thus alter the bioavailability from food matrices. Here, we have used common dietary ligands, such as ascorbic acid, phytic acid, tannic acid, tartaric acid, cysteine, histidine, and methionine to characterize iron, zinc uptake individually and in combination, using Caco-2 cells. Selective chelation of zinc, using cysteine, decreased the magnitude of inhibition of iron uptake but could not reverse the inhibition. On the other hand, selective increase in iron uptake in the presence of methionine resulted in increased zinc uptake, rather than inhibition. Taken together, these in vitro results suggest that dietary ligands can modulate iron-zinc interaction and that zinc cannot competitively inhibit iron uptake.     

Mechanical Behavior of Commercial Purity Titanium Processed by Equal Channel Angular Pressing Followed by Cold Rolling

Equal channel angular pressing (ECAP) has been widely shown to be able to produce ultrafine grained microstructures in a variety of metals and alloys. In this study, the ECAP process has been used as an intermediate processing step prior to cold rolling to achieve superior mechanical properties. Commercial purity (CP) titanium was processed by ECAP at 400 °C and subsequently the ECAPed specimens were subjected to a post deformation process by conventional cold rolling. Microstructure and mechanical property characterization of CP titanium billets subjected to ECAP alone and ECAP plus cold rolling were carried out. 98 % reduction in thickness (from 15 to 0.2 mm thickness) was possible by cold rolling. Post-deformation by cold rolling significantly increased the strength of CP titanium while retaining considerable ductility. TEM images after ECAP show deformation induced dislocation networks and the disintegration of the initial coarse grained microstructure giving rise to lamellar structures 0.3–0.5 μm in width.     

Online control using integrated moving average model for manufacturing errors

We propose a protocol for online control using an Integrated Moving Average (IMA) model for manufacturing errors. This model is suitable for manufacturing processes that are mildly to moderately non-stationary. The protocol is similar to that of the Shewhart X-bar chart. After some number N of the units of product have been manufactured, the ( N + 1)th unit is sampled and its error relative to the target value is checked and recorded. At each check, the observed absolute error is compared against a benchmark, called the correction limit denoted by D to assess the state of errors. When errors are excessive, the system is stopped for correction. Our objective is to determine the ideal settings for N and D from engineering economic and statistical viewpoints. We use root expected mean square error (REMSE) as a measure of the dispersion of errors subject to online control. We use the IMA model to approximate REMSE as a simple function of N and D . Next, we use the approximate REMSE to define a loss function due to manufacturing error. We then determine explicit expressions for N and D that minimize the loss function. The expressions for N and D are simple functions of the engineering economic parameters (manufacturer's cost per unit of product due to errors, cost of checking, cost of correction, and product tolerance) and the two statistical parameters of IMA. We discuss estimation of these parameters and propose how this approach may be used for multiple product characteristics.     

Comparative performance of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) across populations,resource types and structural forms of those resources

The significance of Tribolium castaneum (Herbst) as a pest of stored grains will likely be influenced by the relative availability of different resources regionally and the beetles’ ability to utilize each of them. Therefore the performance across the life cycle of laboratory and field populations of T. castaneum on commonly available structural forms of wheat and sorghum, as conventional resources, was quantified and compared to that on cotton seed. The latter is not usually associated with T. castaneum, but large beetle infestations have been recorded commonly in cotton gins in Australia. The highest number of individuals of each stage (from a given number of eggs) developed on wheat and sorghum flour and kibbled seeds. Cotton seed did not support the development of laboratory population beetles and all neonate larvae died before pupation. In contrast, some of the field population larvae did develop on cotton flour, but their number was significantly lower in comparison to development on wheat and sorghum. Field population beetles produced significantly more eggs than did laboratory population beetles, on both the whole seed and flour. Field population females had a consistently higher fecundity (～78% more eggs) than the laboratory population females, at least over the first three weeks of adult life. These results suggest that field populations of T. castaneum should be used in experiments if we are to develop a more realistic understanding of the field ecology of this species. The relative rate at which these insects infest available resources in the field also warrants further investigation.