Molecular Dynamics Simulations of Dislocation Activity in Single-Crystal and Nanocrystalline Copper Doped with Antimony

Recent experimental and simulation results have indicated that high-temperature grain growth in nanocrystalline (NC) materials can be suppressed by introducing dopant atoms at the grain boundaries. However, the influence of grain boundary dopants on the mechanical behavior of stabilized NC materials is less clear. In this work, molecular dynamics (MD) simulations are used to study the impact of very low dopant concentrations (<1.0 at. pct Sb) on plastic deformation in single-crystal and NC Cu. A new interatomic potential for low Sb concentration Cu-Sb solid-solution alloys is used to model dopant/host and dopant/dopant interatomic interactions within the MD framework. In single-crystal models, the strained regions around the Sb atoms act as heterogeneous sources for partial dislocation nucleation; the stress associated with this process decreases with increasing Sb concentration. In NC models, MD simulations indicate that Sb dopants randomly dispersed at the grain boundaries cause an increase in the flow stress in NC Cu, implying that Sb atoms at the grain boundaries retard both grain boundary sliding and dislocation nucleation from grain boundary regions.     

ELECTROOSMOTIC DEWATERING (EOD) OF CLAYS AND SUSPENSIONS: COMPONENTS OF VOLTAGE IN AN ELECTROOSMOTIC CELL

In the electroosmotic dewatering (EOD) of clays, suspensions and fines, a continuous or interrupted DC voltage, V, is applied between the anode and the cathode. In the previous literature on this subject the components of V have not been completely clarified.

Following a brief outline of the EOD that emphasizes the central role of the electrochemical double layer, we provide an analysis of the components of V, Three case are distinguished

(1)Threshold voltage V-n, for initiating the EOD and its connection to the so-called open-circuit voltage;

(2)EOD at very low voltages viz. around IV;

(3)EOD at very high rates for prolonged times where electrodes such as Al can form barrier oxides and some “caking” is also observed near the a node, This attempt to define the components of V under different conditions of EOD is aimed to identify parameters and processes that arc involved in the effect of V on EOD; RT for example, it is generally not recognized that —pH can form a significant part of V F under some conditions of EOD     

Table of three-quasiparticle rotational bands in deformed nuclei, 153 ? A ? 187

The experimentally observed level structures based on three-quasiparticle (3qp) states are classified according to their intrinsic structures, and other properties are deduced from measurements such as B(M1)/B(E2) ratios, |g_K − g_R| values, lifetimes, etc. The present table lists data for a total of 168 such structures which have been extracted from the literature for 55 nuclides in the mass region A = 153-187 (Z = 63-78, N = 88-112), with the majority of these bands in the A = 180 region (28 bands in seven Re isotopes alone). Nuclear models used for the interpretation of 3qp structures, generalization of the Gallagher-Moszkowski (GM) rules to 3qp states, and high-spin features such as t-bands, high-K isomers, signature splitting, signature inversion, alignment, etc., are discussed briefly. The literature cutoff date for extraction of data for known 3qp structures is July 15, 2005.     

PEPA Queues: Capturing Customer Behaviour in Queueing Networks

Queueing network formalisms are very good at describing the spatial movement of customers, but typically poor at describing how customers change as they move through the network. We present the PEPA Queues formalism, which uses the popular stochastic process algebra PEPA to represent the individual state and behaviour of customers and servers. We offer a formal semantics for PEPA Queues, plus a direct translation to PEPA, allowing access to the existing tools for analysing PEPA models. Finally, we use the ipc/DNAmaca tool-chain to provide passage-time analysis of a dual Web server example.     

Design of a Pumping Main Considering Pipeline Failure

Cost and reliability are two diametrically opposite objectives in a pumping main design as the objective of an uninterrupted supply of water will increase the system cost. In this investigation, a methodology for pumping main design is presented by considering the costs of pumping main and pipeline breakage. Although it has been found that there is no clear-cut optimum point in such a design objective, there is however, a set of non-dominated points called Pareto-optimal front which can be used to optimize pipe diameter. It is hoped that this methodology will be useful to design engineers engaged in the design of pumping mains and will also result in the cost savings to water service providers.     

Macroporous interpenetrating cryogel network of poly(acrylonitrile) and gelatin for biomedical applications

Cryogels are supermacroporous gel network formed by cryogelation of appropriate monomers or polymeric precursors at subzero temperature. The beneficial feature of this system is a unique combination of high porosity with adequate mechanical strength and osmotic stability, due to which they are being envisaged as potential scaffold material for various biomedical applications. One of the important aspect of cryogel is simple approach by which they can be synthesized and use of aqueous solvent for their synthesis which make them suitable for different biological applications. Various modifications of the cryogels have been sought which involves coupling of various ligands to its surfaces, grafting of polymer chain to cryogel surface or interpenetrating networks of two or more polymers to form a cryogel which provides diversity of its applications. In the following work we have synthesized full interpenetrating network of polyacrylonitrile (PAN)-gelatin with varied gelatin concentration. The PAN-gelatin cryogel interpenetrating network is macroporous in nature and has high percentage swelling equlibirium in the range of 862–1,200 with a flow rate greater than 10 ml/min, which characterizes the interconnectivity of pores and convective flow within the network. PAN-gelatin interpenetrating cryogel network has good mechanical stability as determined by Young’s modulus which varies from 123 kPa to 819 kPa depending upon the polymer concentration. Moreover they are shown to be biocompatible and support cell growth within the scaffolds.     

Low-fat Fried Foods with Edible Coatings: Modeling and Simulation

We studied the use of edible films to reduce fat absorption in fried foods. A mathematical model was developed incorporating heat, moisture and fat transfer in the food and the film. Moisture diffusivities of the food and the film were 0.33×10^?7 m²/s and 0.25×10^?7m²/s, respectively. Fat diffusivities were 0.103×10^?8m²/s for the food and 0.604×10^?9m²/s for the film. Thermal diffusivities were 0.102×10^?6m²/s for the food and 0.156×10^?6m²/s for the film. Film diffusivities were determined for gellan gum films at a thickness of 2.0 mm during frying.     

Finite element computation of unsteady viscous transonic flows past stationary airfoils

Results are presented for computations of unsteady viscous transonic flows past a stationary NACA0012 airfoil at various angles of attack. The Reynolds number, based on the chord-length of the airfoil, is 10,000 and the Mach number is 0.85. Stabilized finite-element formulations are employed to solve the compressible Navier-Stokes equations. The equation systems, resulting from the discretization, are solved iteratively by using the preconditioned GMRES technique. Time integration of the governing equations is carried out for large values of the non-dimensional time to understand the unsteady dynamics and long-term behavior of the flows. The results show interesting flow patterns and a complex interaction between the boundary/shear layers, shock/expansion waves and the lateral boundaries of the computational domain. For transonic flow past an airfoil at various angles of attack in a narrow channel/wind-tunnel one can observe solutions that are qualitatively different from each other. At low angles of attack an unsteady wake is observed. At moderate angles of attack the interaction between the shock system and the lateral walls becomes significant and the temporal activity in the wake decreases and eventually disappears. At high angles of attack a reflection shock is formed. Hysteresis is observed at an angle of attack 8^∘. For the flow in a domain with the lateral boundaries located far away, the unsteadiness in the flow increases with an increase in the angle of attack. Computations for a Mach 2, Re 106 flow past an airfoil at 10^∘ angle of attack compare well with numerical and experimental results from other researchers