EN Numerical modeling of a hydrocyclone in the system of technical water supply under the conditions of the UAE

The article is devoted to solving a practical problem: the choice of equipment for pre-treatment of salt water that feeds the desalination plant. The preliminary stage of desalination is the purification of water from sand particles, which can significantly reduce productivity and even damage the desalination plant, which is situated at the next stage. For pre-treatment, settling tanks, hydrocyclones, sand filters, etc. are used. The main dimensions of hydrocyclones of standard designs are calculated based on well-known recommendations. Modern computer simulation systems allow you to create three-dimensional models of the apparatus being studied, and then calculate the velocity and pressure fields in them. It was necessary to estimate the amount of sand contained in the feed water. To solve this problem, an experimental hydrocyclone was developed and manufactured. The hydrocyclone was numerically simulated and the sand capture coefficient was estimated under various operating conditions. It has been established that an experimental hydrocyclone reliably captures grains of sand 50 microns in size and above. The average daily mass of trapped sand was experimentally determined. Numerical modeling made it possible with reasonable accuracy to estimate the sand capture coefficient by an experimental hydrocyclone. During the tests, the mass of sand entering the pipeline per day was determined. The hydrocyclone reliably captures sand particles of 50 microns or more. At the same time, a significant part of particles less than 50 microns is not captured by the hydrocyclone, which is why a sand filter was chosen for industrial use. In the future, it is advisable to use a serial connection of a hydrocyclone and a sand filter, but such a solution requires additional technical and economic calculation. It is concluded that in the case under consideration, it is advisable to use a sand filter for preliminary water treatment

Формирование ускоренного электронного пучка с высоким коэффициентом захвата в ускоряющей структуре с параллельной связью

An electron beam with a high (close to 100%) coefficient of electron capture into the regime of acceleration has been obtained in a linear electron accelerator based on a parallel coupled slow-wave structure, electron gun with microwave-controlled injection current, and permanent-magnet beam-focusing system. The high capture coefficient was due to the properties of the accelerating structure, beam-focusing system, and electron-injection system. Main characteristics of the proposed systems are presented.

Recombination at Oxide Precipitates in Silicon

Transient and quasi-steady-state photoconductance methods were used to measure minority carrier lifetime in p-type Czochralski silicon processed in very clean conditions to contain oxide precipitates. Precipitation treatments were varied to produce a matrix of samples, which were then characterised by chemical etching and transmission electron microscopy to determine the density and morphology of the precipitates. The lifetime component associated with the precipitates was isolated by preventing or factoring out the effects of other known recombination mechanisms. The lifetime component due to unstrained precipitates could be extremely high (up to ~4.5ms). Recombination at unstrained precipitates was found to be weak, with a capture coefficient of ~8 x 10-8cm3s-1at an injection level equal to half the doping level. Strained precipitates and defects associated with them (dislocations and stacking faults) act as much stronger recombination centres with a capture coefficient of ~3 x 10-6cm3s-1at the same level of injection. The lifetime associated with strained precipitates increases with temperature with a ~0.18eV activation energy over the room temperature to 140°C range. The shape of the injection level dependence of lifetime was similar for all the specimens studied, with the magnitude of the lifetime being dependent on the precipitate density, strain state and temperature, but independent of precipitate size.

Light Intensity Exponents as Sensitive Tools for the Detection of Impurities in a-Si:H

ABSTRACTWe have shown recently that the temperature dependence of the phototransport properties can yield information regarding the state distribution in the forbidden gap of semiconductors. Of these properties the light intensity exponents of both, the majority carriers, γe, and the minority carriers, γh, were found to be very sensitive to the details of this distribution. In particular, noting that sub 1/2 values of the exponents are very unusual we have studied their origin in some a-Si:H materials. Finding experimentally such sub 1/2 values of γh and running computer simulations of the recombination processes in a-Si:H led us to the conclusion that these low values are due to acceptor-like centers which have a relatively high capture coefficient for the holes. We attribute these centers to the unintentional oxygen doping in a-Si:H. We will show that the oxygen presence, usually ignored in the discussions of the phototransport properties of a-Si:H, appears to be, in many cases, the dominant factor in the properties of “intrinsic” a-Si:H.