A design procedure for “liquid to air” type atomisers based on air and water mixture outflow velocity

The paper proposes a procedure which enables to determine selected geometric and operating parameters for twin-fluid liquid-to-air atomisers with internal mixing. The presented approach assumes that in order to ensure proper operation of an atomiser it is necessary to design its structure and flow parameters in such a way so that the flow inside the mixing chamber has a dispersive character. In order to calculate a required exhaust cross-section for the analysed atomiser, conditions within the exhaust plane: pressure, density and outflow velocity were estimated. In order to determine diameter and number of orifices supplying the liquid to the mixing chamber of the investigated atomiser type, a multi-parameter analysis based on numerical fluid mechanics was performed. The final part of the paper presents selected results obtained from experimental stand measurements made on an atomiser designed according to the presented procedure.

Thermal and Optical Stretched Exponentials in Defect Kinetics in a-Si:H

Dispersive description of defect generation in a-Si:H that leads to stretched-exponential transients is extended by relaxing the assumption that light-induced processes and thermally induced processes have the same dispersive character. This is done by separating the rate equation for the defect density into two parts, one thermal and one optical, each with its own dispersion parameter. The solutions of this new equation — which must be obtained numerically — generally have two distinct parts: there may be a two-part rise or a peak, depending on the relative values of the two stretch parameters. Using this formulation we have readily simulated the recently observed peak in relaxation of a previously heavily degraded solar cell while exposed to a weak light. We find no way to explain other reports in similar two-part experiments that relaxation is faster under weak excitation than without.

The Influence of the Void Structure on Deuterium Diffusion in a-Si:H

ABSTRACTWe have used small-angle X-ray scattering (SAXS) and Doppler-broadening measurements of positron-annihilation radiation to study changes in the microvoid distribution in PECVD a-Si:H films during annealing. From a comparison of data on deuterium diffusion with information obtained from SAXS we conclude that changes, during annealing, in the dispersive character of deuterium diffusion are likely to be caused by void formation through clustering of smaller structural defects.

Protection of the Pleistocene Sediments along the rim of the San Jacinto reservoir in Bolivia

Quaternary tectonic and volcanic activity, and glaciation, have created conditions in the Andes which have complicated the engineering of many dams. A notorious feature often encountered is the “paleocauce”, a former river bed blocked during Quaternary times and now filled with thick sediments, subsequent erosion having formed a new, displaced river bed. In many cases more severe problems have been caused by the presence of a paleocauce, particularly when this was only detected at an advanced stage of studies, than have arisen from the damming of the new river course,The paper describes a particular problem which arose during design of the San Jacinto project in southern Bolivia, and was due to the dispersive character of the Pleistocene deposits filling the paleocauce of the river Tolomosa.To fully evaluate the phenomenon of dispersivity, the Standard “pinhole test” has to be per formed, in conjunct ion with two other tests, on a large selection of samples. The results of these tests on samples from San Jacinto suggested that Classification diagrams for dispersive soils may have to be modified from case to case to reflect specific properties of the soil of the respective sedimentary facies.