Synergistic effect of carbon black and nanoclay fillers in styrene butadiene rubber matrix: Development of dual structure

Styrene butadiene rubber (SBR) based hybrid nanocomposites containing carbon black (CB) and organo-modified nanoclay (NC) was prepared. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed the presence of intercalated, aggregated, and partially exfoliated structures. Incorporating 10 phr NC to the control SBR containing 20 phr CB resulted 153% increase in tensile strength, 157% increase in elongation at break and 144% stress improvement at 100% strain, which showed synergistic effect between the fillers. The dynamic modulus reinforcement of nanocomposites was examined by the Guth, Modified Guth, and Halpin–Tsai equations. For predicting CB filled nanocomposite modulus, the contribution of modified intercalated structure of clay and the ‘nano-unit’ (dual structure) comprising CB–NC should be considered.     

Parameters controlling supersaturation by DELOS using carbon dioxide

The present work pertains to estimation of the maximum degree of supersaturation that can be attained in an organic solution by the DELOS process using carbon dioxide (CO₂) as a cosolvent. The paper analyzes the effects of initial mole fraction of carbon dioxide, temperature and pressure on the degree of supersaturation of cholesterol in a CO₂—acetone—cholesterol solution. It has been observed that owing to liberation of large amounts of CO₂ very large temperature drops may be attained by depressurization, resulting in attainment of very high supersaturation. Within the ranges of the parameters studied in this work, the degree of supersaturation is higher with higher values of initial temperature and initial CO₂ mole fraction of the solution due to inverse interdependence of the final temperature and the residual CO₂ mole fraction in the depressurized solution. Copyright © 2006 Society of Chemical Industry     

Investigation of hydrodynamics in bubble column with internals using radioactive particle tracking (RPT)

Even though many experimental investigations are reported on this subject of liquid velocity patterns in bubble columns, most of the reported work is restricted to measurements at the near wall regions, columns without internals, and in low dispersed phase hold‐ups. In the present work, a non‐invasive radioactive particle tracking technique was employed to quantify the hydrodynamic parameters in 120 mm diameter bubble column with, and without vertical rod internals, using air/water system as the working fluids. The superficial air velocities cover a wide range of flow regimes: from 14 to 265 mm/s. Experiments were performed for two internals configurations with percentage obstruction area varied from 0 (without internals) to 11.7%. We report that the liquid phase hydrodynamics depends strongly on superficial gas velocity and internals. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Queries and materialized views on probabilistic databases

We review in this paper some recent yet fundamental results on evaluating queries over probabilistic databases. While one can see this problem as a special instance of general purpose probabilistic inference, we describe in this paper two key database specific techniques that significantly reduce the complexity of query evaluation on probabilistic databases. The first is the separation of the query and the data: we show here that by doing so, one can identify queries whose data complexity is #P-hard, and queries whose data complexity is in PTIME. The second is the aggressive use of previously computed query results (materialized views): in particular, by rewriting a query in terms of views, one can reduce its complexity from #P-complete to PTIME. We describe a notion of a partial representation for views, and show that, once computed and stored, this partial representation can be used to answer subsequent queries on the probabilistic databases. evaluation.     

An extension of the Wagner theory of alloy oxidation and sulfidation

The recent Wagner theory of binary alloy oxidation applies to situations in which an alloy of metals Aand Breacts with nonmetal Xto form a scale consisting of a solid solution of the corresponding compounds, i.e., A(X)and (X).This theory has been modified in two respects. First, the mathematics have been simplified somewhat by establishing an explicit expression for the average equivalent fraction of each compound in the scale. Second, the Wagner analysis has been generalized to allow for transport of nonmetal Xin the alloy. This latter modification involved permitting the dissociation reaction to take place at the scale-alloy interface. The nonmetal thus released into the alloy was assumed to diffuse interstitially inward.     

New conductive polymeric materials: Cofacial assembly of mixed valent metallomacrocycles

This paper reports on an approach to control molecular stacking interactions in low-dimensional mixed valence materials by locking partially oxidized metallomacrocycles together in a cofacial orientation. Iodine doping of the face-to-face linked oligomers [M(Pc)O]_n (M = Si, Ge, Sn; Pc = phthalocyaninato) produces electrically conductive polymers {[M(Pc)O]I_xn with a wide range of x stoichiometries. Resonance Raman spectroscopy indicates that the iodine has oxidized the polymer chain. Polymer structure has been studied by X-ray powder diffraction, and it is possible to estimate interplanar spacings. Halogen doping of the [M(Pc)O]_n materials is accompanied by electrical conductivity increases as large 10⁷ (ohm cm)^?1; the general trend is $\text{σ}{}_{\mathrm{<mtext>Si</mtext>}}\text{? σ}{}_{\mathrm{<mtext>Ge</mtext>}}\text{> σ}{}_{\mathrm{<mtext>Sn</mtext>}}$. Variable temperature conductivity and magnetic susceptibility data are reported.     

A contact‐point based approach for the analysis of reactions among solid particles

The contact‐point framework, 1 which replaces the picture of continuous contact between the reactants by contact at a finite number of points, has been proposed as a rational one for treating reactions among particulate solids. However, available models suffer from various drawbacks, the main one being that they do not show the right asymptotic behavior for large number of contact points. A model is presented here, that corrects these deficiencies. The results show that the contact‐point model approaches particle‐continuum behavior whenever the number of contact points exceeds 500. The model predictions have been compared with some data from our previous work on calcia‐alumina system in the temperature range 1,150–1,300°C. The model fits the data well, with the fitted values of diffusivity (of calcia through alumina) being of the order of 10^?16 m²/s. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Pipelining in multi-query optimization

Database systems frequently have to execute a set of related queries, which share several common subexpressions. Multi-query optimization exploits this, by finding evaluation plans that share common results. Current approaches to multi-query optimization assume that common subexpressions are materialized. Significant performance benefits can be had if common subexpressions are pipelined to their uses, without being materialized. However, plans with pipelining may not always be realizable with limited buffer space, as we show. We present a general model for schedules with pipelining, and present a necessary and sufficient condition for determining validity of a schedule under our model. We show that finding a valid schedule with minimum cost is NP-hard. We present a greedy heuristic for finding good schedules. Finally, we present a performance study that shows the benefit of our algorithms on batches of queries from the TPCD benchmark.