Fabrication and microstructure of the AlSi11 matrix composite containing 10 % volume fraction of CrFe30C8 particles were presented in this paper. Composite suspension was manufactured by using mechanical stirring. During stirring process the temperature of liquid metal, time of mixing and rotational speed of mixer were fixed. After stirring process composite suspension was gravity cast into shell mould. The composites were cast, applying simultaneously an electromagnetic field. The aim of the present study was to determine the effect of changes in the frequency of the current power inductor on the morphology of the reinforcing phase in the aluminum matrix. The concept is based on the assumption that a chromium-iron matrix of CrFe30C8 particles dissolves and residual carbide phases will substantially strengthen the composite. The microstructure and interface structure of the AlSi11/CrFe30C8 composite has been studied by optical microscopy, scanning microscopy and X-ray diffraction.
Horizontal centrifugal casting is an effective method for the production of hollow metal with good mechanical properties, low defect, cast
to size and relatively cheap. The ability of a metal to satisfy the above requirements highly depends on its microstructure. In this study, the
relationship between microstructural parameters such as grain size and the amount of phases with bulk hardness of SnCu4Pb3 is concerned
in three areas of the product. Consequently, to achieve the desired hardness of the product in a particular area, the interaction of two
factors of the microstructure including, grain size and particles amount of the hard intermetallic compositions (Cu6Sn5) should be noted.
Effects of confinement on mechanical, structural and thermodynamic properties of uniform fluids are very well understood. In contrast, a general theory based on statistical thermodynamics for confined nonuniform and non-isotropic phases, such as the lamellar phase, is in its infancy. In this review we focus on the lamellar phase confined in a slit or in a pipe in order to illustrate various effects of confinement. We limit ourselves to the results obtained by M. Tasinkevych, V. Babin and the author for lamellar phases in oil-water-surfactant mixtures within a generic semi-microscopic model, using a mean-field approximation. We show that compared to isotropic fluids the excess grand potential contains additional terms associated with structural deformations. These terms depend on the type of the confining walls, the shape of the container and on the thickness of the lamella. As a result of the dependence of the structure of the confined lamellar phase on the shape of the container, capillary lamellarization and capillary delamellarization is found in slits and in pipes respectively.
In the present paper it is proposed to consider the computer cooling capacity using the thermosyphon loop. A closed thermosyphon loop consists of combined two heaters and a cooler connected to each other by tubes. The first heater may be a CPU processor located on the motherboard of the personal computer. The second heater may be a chip of a graphic card placed perpendicular to the motherboard of personal computer. The cooler can be placed above the heaters on the computer chassis. The thermosyphon cooling system on the use of computer can be modeled using the rectangular thermosyphon loop with minichannels heated at the bottom horizontal side and the bottom vertical side and cooled at the upper vertical side. The riser and a downcomer connect these parts. A one-dimensional model of two-phase flow and heat transfer in a closed thermosyphon loop is based on mass, momentum, and energy balances in the evaporators, rising tube, condenser and the falling tube. The separate two-phase flow model is used in calculations. A numerical investigation for the analysis of the mass flux rate and heat transfer coefficient in the steady state has been accomplished.
Structures and characteristics ofwideband small-size phase shiftersmade with the use of single parallel stubs are presented in this paper. The stubs can be short-circuited or open-circuited on termination. Such devices arewell known, but are primarily used as components of filters ormatching circuits. The novelty, then, comes from the establishment of simple, but helpful formulae, which enable to describe the insertion phase shift and differential phase shift of a line with short and open stubs connected in parallel. These equations can be very useful for designing complex microwave multi-ports. The results of simulations and measurements of the devices, which were designed and made, are shown herein. It was also proved that the presented devices have several usable operating frequency sub-bands, and that the differential phase shift values in the higher sub-bands are greater than those in the lower operating frequency ranges. Thanks to this, the described phase shifters can be used in more than one frequency sub-band. It was stated that in the conditions under analysis, larger phase shifts can be achieved using open-circuited stubs rather than short-circuited stubs. However, the phase shifters with shorted parallel stubs can operate in a wider frequency band.
The exact measurement of multiphase flow is an important and essential task in the oil and petrochemical related industries. Several methods have already been proposed in this field. In the existing methods, flow rate measurement depends on the fluid flow pattern. Flow pattern recognition requiring calibration has created instability in such systems. In this paper, a imple and reliable method is proposed which is based on ultrasonic tomography. It is free from calibration and instability problems that existing methods have. The obtained data from a 32-digit array of ultrasonic sensors have been used and the two-phase flow rate including liquid and gas phases have been calculated through a simple algebraic algorithm. Simulation results show that while applying this method the measurement technique is independent from the fluid flow pattern and the system error is decreased. For the proposed algorithm, the average amount of the spatial imaging error (SIE) for a bubble at different positions inside the pipe is about 5%.
To obtain anti-corrosive thermo-diffusion zinc coatings, the authors use highly effective zinc saturating mixtures. This technology makes it possible to obtain coatings with a high zinc content in the δ-phase as well as a zinc-rich phase of FeZn13 (ζ-phase) on the coating surface. As a result of long-term studies into the corrosion properties of thermo-diffusion zinc (TDZ) coatings conducted by the authors, a number of features of their corrosive behavior have been established. The corrosion rate of those coatings in desalted and chloride-containing media is lower than those of galvanic or hot-dip zinc coatings. The corrosion behavior depends on the content of zinc on the surface and the texture features of the coating. The results showed that on the surface of thermo-diffusion coatings in the corrosion on media containing chloride ions, zinc hydroxychloride (simonkolleite – Zn5Cl2[OH]8[H2O]) has been formed. Compared to coatings obtained by other methods, the rate of simonkolleite formation was higher on TDZ coatings, which might have a positive effect on their resistance in aggressive atmospheres.
Although the phenomenon of otoacoustic emission has been known for nearly 30 years, it has not been fully explained yet. One kind of otoacoustic emission is distortion product of the otoacoustic emission (DPOAE). New aspects of this phenomenon are constantly discovered and attempts are made to interpret correctly the obtained results. This paper discusses a new method of measuring DPOAE signals based on double phase-sensitive detection, which makes possible a real-time measurement of the DPOAE signal amplitude and phase. The method was applied for measurements of DPOAE signals in guinea pigs. Sample records are presented and the obtained results are discussed.