Analysis of design sensitivity of flow-reversal reactors: Simulations, approximations and oxidation experiments

The analysis of a flow-reversal reactor, constructed from a catalytic bed imbedded within two inert beds and catalysing an instantaneous reaction, shows that the main parameters that determine the maximal reactor temperature are the thermodynamic parameters, heat loss through the walls and the conductivity and length of the inert zones. We show how these parameters can be easily extracted from the experimental data of very fast reactions, and demonstrate it for ethylene and for propane oxidation. We also derive an approximation for the maximal temperature for fast or slow reactions. These approximations are compared with experimental results obtained during propane (with low feed concentration) or methane oxidation.     

Structured polyurethanes for oil uptake

In an attempt to develop a desirable resin formulation for spilled oil absorption, segmented polyurethanes of various types and lengths of hard and soft segments have been synthesized and tested for X‐ray diffraction, thermal, mechanical, and dynamic mechanical properties in addition to oil and water absorptions. Significant oil absorption was obtained with ether type polyol of high molecular weight, especially with short hard segments of long‐chain diamines. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2080–2087, 2005     

Behavior-state matching and synchrony in mother-infant interactions of nondepressed versus depressed dyads.

Behavior-state matching and synchrony in interactions were assessed in 48 depressed and nondepressed mother–infant dyads when the infants were 3 months old. Attentive/affective behavior states were coded for the infants and mothers on a negative to positive scale. The depressed mothers and their infants matched negative behavior states more often and positive behavior states less often than did the nondepressed dyads. The total percentage of time spent in matching behavior states was less for the depressed than for the nondepressed dyads. Cross-spectral analyses of the mothers' and the infants' behavior-state time series suggested only a trend for greater coherence or synchrony in the interactions of the nondepressed dyads. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transversal moving-front patterns: Criteria and simulations for two-bed and cylindrical shell packed-bed reactors

We show that a moving-front solution in a cylindrical shell packed-bed catalyzing a first-order activated reaction may bifurcate into transversal patterns when Pe_C/Pe_T<ΔT_ad/ΔT_m, i.e. when the ratio of the mass to heat Pe numbers is smaller than the ratio of the adiabatic to maximal temperature rises. This coincides with the previous condition of transversal patterns to emerge in stationary fronts [Pe_C/Pe_T<1 [Viswanathan, G., Bindal, A., Khinast, J., Luss, D., 2005. Stationary transversal hot zones in adiabatic packed-bed reactors. A.I.Ch.E. Journal 51, 3028-3038]] and extends the bifurcations condition to the case of moving fronts. The novel condition cannot be satisfied in a downstream propagating front (ΔT_m/ΔT_ad>1), but for an upstream propagating front (toward the cold reactor inlet) ΔT_m/ΔT_ad<1 and the symmetry breaking can be obtained within a feasible domain of operating conditions (Pe_C/Pe_T>1). It was also assumed that the axial and the transversal Pe numbers vary consistently, i.e. κ_C=Pe_C⊥/Pe_C=κ_T=Pe_T⊥/Pe_T. A similar condition was also obtained using a simplified model composed of two 1-D beds with heat and mass exchange between them.Bifurcation diagram showing domains of transversal patterns is constructed using a learning two-bed model. These predictions are verified by direct numerical simulations of the continuous 2-D cylindrical shell model showing various types of moving transversal patterns within a feasible domain of the state parameters with Pe_C>Pe_T. In the case of varying ratio (κ_C≠κ_T) the pattern domain can be significantly extended toward larger Pe_C/Pe_T.     

Distributed deadlock resolution in store-and-forward networks

We present a simple distributed algorithm that resolves store-and-forward deadlocks in data communication networks. The basic idea of the algorithm is to detect cycles of nodes that may cause store-and-forward deadlocks, and to rotate packets along these cycles. The algorithm uses a fixed amount of storage in each node for its execution, and, under reasonable assumptions upon the routing and packet handling, it ensures that packets that enter the network arrive at their destinations in finite time.Part of this work was done while this author was on sabbatical leave with IBM, Thomas J. Watson Research Center, Yorktown Heights, NY 10598, USA.     

Coding of temporal order information: An automatic process?

This article includes four experiments in which four criteria for testing the automaticity of coding of temporal order information are examined. Results show that memory for temporal order information is affected by intention to learn, competing task loads, encoding strategy, and subjects' age. The results, which generally hold for memory for absolute, as well as for relative temporal order information, do clarify the somewhat mixed pattern of results in previous studies, which was due, at least in part, to inappropriate testing methodologies. Such results, which are similar to recent tests of automaticity of frequency of occurrence and spatial location information, are at odds with the claim made by several researchers that memory for temporal order information is exclusively mediated by automatic processes. The concept of automaticity and the appropriateness of the testing criteria for it are discussed in light of the current results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A simple solution to the singular linear minimum-variance estimation problem

A simple expression is obtained for the transfer function matrix of the minimum-variance estimator for the states of a linear stationary continuous-time right invertible system whose output is measured perfectly. Using thes-domain approach, it is shown that the optimal estimator first finds the driving noise input that achieves, when applied on the minimum-phase image model of the system, an output spectrum which is identical to the measurement spectrum. This input is then applied on a state-space representation of the minimum-phase image to produce the optimal estimate.     

Mass transfer around oblate spheroidal drops at low Reynolds numbers

Steady and unsteady mass transfer in the continuous phase around slightly deformed oblate spheroidal drops at low (but not zero) Reynolds numbers was investigated theoretically. Asymptotic analytical solutions for short and long times, at large Peclet numbers, were obtained by the useful equations derived by Lochiel and Calderbank and by Favelukis and Mudunuri for axisymmetric drops of revolution, with the only requirements being the shape of the drop and the tangential velocity at the surface of the drop. As expected, the result, although complicated, represents a small correction to the classical problem of mass transfer around a spherical drop under creeping flow conditions, since the physical problem presented here requires both the Reynolds and the Weber number to be much smaller than one.     

Highly Efficient Ge-Rich Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Pb<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Te Thermoelectric Alloys

The search for alternative energy sources is presently at the forefront of applied research. In this context, thermoelectricity for direct energy conversion from thermal to electrical energy plays an important role. This paper is concerned with the development of highly efficient p-type Ge _x Pb_1−x Te alloys for thermoelectric applications, using spark plasma sintering. The carrier concentration of GeTe was varied by alloying of PbTe and/or by Bi₂Te₃ doping. Very high ZT values up to ~1.8 at 500°C were obtained by doping Pb_0.13Ge_0.87Te with 3 mol% Bi₂Te₃.