[en] Particle size and specific surface area measurements are conventional characterization techniques for ceramic powders to predict sintering behaviour. Dilatometry is one of the most popular techniques in ceramics to study the sintering characteristics for optimization of firing processes. Uranium dioxide (UO_2) powders from different sources were characterized by conventional techniques and these characteristics were correlated with sintering behaviour, as measured with a dilatometer. The suitability of dilatometry to correlate the sintering characteristics of UO_2 powder with variations in the O/U ratio, particle size and green density was discussed. Explanations of features in the sintering profiles for UO_2 powders have been presented. (author)

[en] In SverdNIIkhimmash series of units are created for reprocessing of different materials initial particle sizes of which reach 1.5 m and finished product sizes are some micrometers. Realized on the basis of hydraulic presses, jaw, knife, roller and cone crushers, abrasive discs, ball, vibratory, vapart, and jet-type mills with equipping of part of them by screen or pneumatic classifiers these units are combined into one ore some stages and work in open or closed cycle

[en] Mathematical simulation on basis of Stock law has been done for wet sizing process on cylinder equipment of laboratory and semi-industrial scale. The model consists of mathematical equations describing relations between variables, such as: - Resident time distribution function of emulsion particles in the separating zone of the equipment depending on flow-rate, height, diameter and structure of the equipment. - Size-distribution function in the fine and coarse parts depending on resident time distribution function of emulsion particles, characteristics of the material being processed, such as specific density, shapes, and characteristics of the environment of classification, such as specific density, viscosity. - Experimental model was developed on data collected from an experimental cylindrical equipment with diameter x height of sedimentation chamber equal to 50 x 40 cm for an emulsion of zirconium silicate in water. - Using this experimental model allows to determine optimal flow-rate in order to obtain product with desired grain size in term of average size or size distribution function. (author)

No abstract available

No abstract available

[en] In 1979, 21 years after the moratorium on nuclear testing in the Marshall Islands, surface sediment samples (to depths of 2 and 4 cm) were collected from 87 locations over the floor of Bikini lagoon. The main purpose for the collections was to map the distribution of long- lived man-made radionuclides associated with the bottom material. In addition the samples were processed to estimate the fraction of fine and coarse components to show what modifications occurred since the sediment composition was first described in samples collected before testing in 1946. In this report a comparison is made of the amount and distribution of fine material associated with the lagoon surface sediment before and after the testing of nuclear devices. Nuclear testing produced more finely divided material in-the surface sediment layer over large areas of the lagoon and especially in regions of the lagoon and reef adjacent to test sites. Five cratering events at Bikini Atoll generated sufficient material to account for the inventory of new fine material found over the bottom surface of the lagoon. Although the fraction of fine material in the bottom sediments was altered by the nuclear events, the combined processes of formation, transport and deposition were not sufficiently dynamic to alter the geographical features of the major sedimentary components over most of the lagoon floor

[en] The shapes of particles and apertures have significant effects on the screening process. Experiments employing slotted screens were performed to determine the influence of screening parameters on mass recovery and flakiness index of the oversize particles. Response surface methodology was employed for modelling and analysis of data. It was shown that the mass recovery and flakiness index of the screen oversize could be predicted from the operating parameters. This study should provide a basis for optimising the screening conditions to obtain maximum mass recovery at low flakiness index. (author)

[en] We analyse the combinatorial aspect of global optimisation for multicomponent systems, which involves searching for the optimal chemical ordering by permuting particles corresponding to different species. The overall composition is presumed fixed, and the geometry is relaxed after each permutation in order to relieve local strain. From ideas used to solve graph partitioning problems we devise a deterministic search scheme that outperforms (by orders of magnitude) conventional and self-guided basin-hopping global optimisation. The search is guided by the energy gain from either swapping particles i and j (ΔE_ij) or changing the identity of particles i (ΔE_i). These quantities are derived from the underlying (arbitrary) energy function, hence not constituting external bias, and for site-separable force fields each ΔE_i can be approximated simply and efficiently. In our self-guided variant of basin-hopping, particles are weighted by an approximate ΔE_i when randomly selected for an exchange, yielding a significant improvement for segregated multicomponent systems with modest particle size mismatch

[en] Measurements of mass transfer rates in open bubble columns; studies of oxidation of tritium as it permeates fusion reactor containment, flooding studies in columns filled with Goodloe packing, studies of mass transfer rates between water and mercury, preparation of small particles, and development of equipment are reported. (MCG)

[en] Pinched flow fractionation is a simple method for separating micron-sized particles by size, but has certain intrinsic limitations, e.g. requirement of a pinched segment similar to particle size and limited separation distance. In this paper, we developed an acoustic bubble enhanced pinched flow fractionation (PFF) method for microparticle separation. The proposed technique utilized microbubble streaming flows to overcome the limitations of conventional PFF. Our device has demonstrated separation of different sized microparticles (diameters 10 and 2 μm) with a larger pinched segment (60 μm) and at different buffer/particle solution flow rate ratios (5–25). The separation distances between particles are larger (as much as twice as large) than those achieved with conventional PFF. In addition, the separation position and distance can be adjusted by changing the driving voltage. The robust performance is due to the unique features of the flow field inside the pinched segment. We investigated several factors, including flow rate ratio, total flow rate and driving voltage, that affect the separation performance. (paper)