Grain boundary motion and grain growth in zinc in a high magnetic field

The motion of grain boundaries in zinc bicrystals (99.995 %) driven by the “magnetic” driving force was measured. An in situ technique for observations and continuous recording the boundary migration was applied. Planar symmetrical and asymmetrical $ \left\langle {10\overline{1} 0} \right\rangle $ tilt grain boundaries with rotation angles in the range between 60° and 90° were studied. The boundary migration was measured in the temperature regime between 330 and 415 °C. The mobility of $ \left\langle {10\overline{1} 0} \right\rangle $ tilt boundaries in zinc and its temperature dependence were found to depend on the misorientation angle and the inclination of the boundary plane. An application of a magnetic field during the annealing of cold rolled (90 %) zinc–1.1 % aluminum alloy sheet specimens substantially affected the texture and microstructure evolution. This effect is attributed to the additional magnetic driving force for grain growth arising due to the magnetic anisotropy of zinc.     

Silicon multi-branch nanostructures for decent field emission and excellent electrical transport

We report on the synthesis, field electron emission and electric transport properties of a novel nanomaterial: ordered arrays of crystallized silicon multi-branch nanostructures. A decent field electron emission with relatively low turn-on field of 3.16 V μm?1 and high field-enhancement factor of 1252 was received for the silicon nanobranches. The relevancies between field-emission current-voltage characteristic, turn-on field, threshold field and sample-anode distance have been thoroughly analyzed. In addition, electrical transport measurements revealed a small electrical resistance of 0.51 MΩ for as-prepared silicon nanobranches. In contrast, by improving the silicon nanobranch-electrode contact, vacuum annealing dramatically reduced the electrical resistance, by a factor approaching two, while thermal oxidation resulted in a much higher resistance due to the amorphous oxide coating of the silicon nanobranches, both of the current versus voltage curves became more linear and symmetrical, and the transport stability was obviously improved.     

Topology optimization of resonating structures using SIMP method

The present paper is concerned with the layout optimization of resonating actuators using topology optimization techniques. The goal of the optimization is a maximization of the magnitude of steady‐state vibrations for a given excitation frequency. The problem formulation includes an external viscous damper at the output port which models a working load on the structure. Copyright © 2002 John Wiley & Sons, Ltd.     

On the influence of fatigue on machine part wear

The main aspects of the relationship between fatigue and machine part wear are considered and the relevant problem is formulated. The results of an investigation of the influence of the fatigue process on machine part wear are given for diesel engine piston rings. As the results show, the solution of the problem could open up new prospects in the development of the theory of machine part cyclic wear and the details of the technology of cyclic straining treatments for increasing fatigue wear resistance.     

Removing of light hydrocarbons from gas mixtures using polymeric composite membranes based on poly(1-trimethylsilylpropyne)

Usually the methodologies used to analyse the feasibility of water reuse projects are focused on the internal costs. The aim of this paper is to show a methodology to assess the feasibility of a water reuse project taking into account not just the internal impact, but also the external impact (environmental and social, for example) and the opportunity cost derived from the project. Internal benefit is obtained from the difference between internal income and internal costs. Internal income is obtained by multiplying the selling price of reclaimed water and the volume obtained. Internal costs are made up of the sum of investment costs, operating costs, financial costs and taxes. While some of these factors identified can be calculated directly in terms of money, biophysical and social aspects demand the definition of units of measurement. In order to homogenize results, an annual reference is proposed. A monetary value can be obtained from the calculation of each impact. However, there are a series of externalities for which no explicit market exists. In these cases economic valuation methods are used, based on hypothetical scenarios or patterns observed in related markets.     

Mathematical modelling of the transient behaviour of cstrs with reactive particulates: Part 2 — Application to pyrite pressure oxidation

A population balance based transient reactor model is applied to a particulate process employed in the hydrometallurgical industry. The process is the pressure oxidation of pyritic concentrates, pertinent to the treatment of refractory gold materials. The chemical reaction system involves first an oxygen gas to aqueous mass transfer step, followed by a chemical reaction on the surface of mineral particles. The chemical reactor stimulated is a multi-stage continuous autoclave with variable compartment size. The model accounts for recycling oxidized solids, as well as for venting the gas phase. A complex system of partial and non-linear ordinary differential equations is rendered dimensionless and solved by a method developed previously using the Mathematica® software. The transient response of the reactor to different modes of reactor start-up, as well as the response to a step change of a key variable, are examined. The validity of the steady-state solution is assessed by comparing it to previous modelling attempts.     

Mathematical modelling of the transient behaviour of cstrs with reactive particulates: Part 1 — The population balance framework

The population balance model appears to be the best approach to model particulate systems where multiple heterogeneous reactions occur. This work demonstrates a mathematical formulation that is based on the population balance model, and aims at simulating the non steady-state behaviour of a single-stage CSTR under isothermal operation. The chemical reaction system is a typical example from the field of hydrometallurgy with two parallel reactions, one being leaching, the other precipitation with simultaneous reactant regeneration. The solution of the resulting system of the partial and ordinary differential equations is achieved by combining the moment transformation of the population balance equations with the numerical method of lines, using the Mathematica® software. Finally, examples are given for a reactor startup in two cases: a single leaching reaction, and simultaneous leaching and precipitation reactions. In the first case, the difference between simultaneous and sequential feeding in achieving steady-state is also discussed.