Charging of one or several cylindrical particles by monopolar ions in electric fields

In many electrostatic processes (precipitation of dust, separation of granular mixtures, spraying of powders) insulating particles are subjected to unipolar charging in the presence of other bodies. The present paper addresses this problem from both a computational and an experimental point of view, with the aim to extend an original numerical method of unipolar charge computation to the case of two or more particles, relatively close to each other. The charge acquired by cylinders of various dielectric constants was evaluated with a computer program based on the boundary element method of field analysis. The experimental setup simulated the charging conditions of millimeter-size calibrated cylinders of polyvinyl chloride in a roll-type electrostatic separator, the unipolar space charge being generated by a wire-type electrode. The experimental results, which were in good agreement with the theoretical predictions, put forward that the relative spacing between the particles changes the value of the saturation charge, an effect, which is stronger for particles of higher dielectric constant. These facts should be taken into account in the design of any electrostatic technology based on the corona charging of granular matter.     

On implementation of the extended interior penalty function

The extended interior penalty function formulation is implemented. A rational method for determining the transition between the interior and extended parts is set forth. The formulation includes a straightforward method for avoiding design points with some negative components, which are physically meaningless in structural analysis. The technique, when extended to problems involving parametric constraints, can facilitate closed form integration of the penalty terms over the most important parts of the parameter interval. The method lends itself well to the use of approximation concepts, such as design variable linking, constraint deletion and Taylor series expansions of response quantities in terms of design variables. Examples demonstrating the algorithm, in the context of planar orthogonal frames subjected to ground motion, are included.     

The prediction of the ternary liquid-liquid equilibrium by means of the NRTL-equation

The prediction of ternary liquid-liquid equilibria by means of the NRTL-equation and using the parameters obtained by the correlation of the limiting binary systems is examined. The predicted data are compared with experimental data for systems composed of an aromatic and an aliphatic hydrocarbon and sulpholane. The number of sets of binary parameters obtained from the correlation of the binary systems is infinite. For any value of the non-randomness parameter a corresponding pair of energy parameters can be determined, giving rise to a set fitting the data equally well. Limits to the value of the parameters can only vaguely be determined on the basis of their physical meaning. The upper limit of the non-randomness parameter related to the heterogeneous binary system is more precisely defined. Some general conclusions for the selection of the parameters could be reached. The predicted heterogeneous area is in general too large but decreases with increasing values of the non-randomness parameter of the heterogeneous binary system. The value of the parameters of the homogeneous binary system has only a small influence on the position of the binodal. The slope of the tie lines is mainly determined by the non-ideality of the homogeneous binary systems.     

Microstructural effects of heat treatment on the bond interface of explosively welded metals

The microstructure and composition of the interface of nickel-to-copper, copper-to-steel, and tantalum-to-steel explosion welds which had been subjected to heat treatments between 500° and 1100°C was investigated by electron microscopy and electron probe microanalysis. The results confirmed that explosive welding establishes continuous and practically diffusionless metallurgical bonds. Diffusion induced by heat treatment causes characteristic microstructural changes along the bond zone which depend on the type of binary phase diagram to which the specimen belongs. The diffusion penetration in nickel explosively welded to copper is noticeably more extensive than in the similar electroplated couple. In all three metal pairs the diffusion rate varies cyclically along the weld interface. These latter effects appear to be related to the unique concentration and distribution of lattice defects characterizing explosively bonded metals.     

Introduction des notions de fiabilité et de disponibilité au CCITT et au CCIR

After having recalled to mind the historic evolument of the introduction of such conceptions as reliability and availability at the CCIR and CCITT, and more particularly at the joint study group, the anthors review current studies and results already achieved, then look into what the future development of these studies could be, within the fromework of a more general concept about quality of service.     

Optimum control of irrigation water application

The problem of controlling soil water within the root zone of irrigated crops to minimize the expected loss is examined. Control is accomplished by scheduling the amount of and timing irrigations to replenish the soil water reservoir depleted by the crop's water consumption. Actual evapo-transpiration rates are a function of the prevailing soil water level and the evaporative demand, which may be considered to be either deterministic or probabilistic. For crops grown on a particular soil, an optimum soil water level is defined as the lowest soil water level above which crops are not stressed. The reduced yield of a crop is related to its growth stage and to the amount and duration that the soil water content is below this optimum value.Existing inventory models are adapted for the purpose of determining the optimal irrigation policy, that is, the timing and amount of water application that result in the minimum irrigation cost to the farmer. Solutions to complex decision-making problems are currently available for a variety of irrigation situations.