XRD, Magnetic and M?ssbauer Spectral Studies of?Ag x Ni1?x Fe2O4 Ferrite Nanoparticles

Nanophase Ag _x Ni_1?x Fe₂O₄ (x=0,0.2) ferrites were prepared by glycothermal method. The NiFe₂O₄ (x=0) nanosized sample was also produced by high-energy ball milling for comparison of properties. Structural investigations of the samples were carried out by X-ray diffraction. The experiment reveals that pure Ag-Ni ferrite materials with grain sizes of about 8 nm can be obtained after annealing at relatively low temperature of about 500?°C. The nanosized compounds produced by glycothermal reaction indicate superparamagnetic behavior. A higher value of coercive field (910 Oe) is observed in x=0 milled sample with similar particle size. The zero field cooled (ZFC) and field cooled (FC) magnetization measurements reveals spin glass like behavior of the nanosized compounds.     

Anatomical and joint dissection studies of tissue weight distribution in buffalo bulls and cows: Part 1-Distribution of muscle and bone

Carcasses from six buffalo bulls (slaughtered between 430 and 560 kg liveweight) and six buffalo cows (slaughtered between 405 and 583 kg liveweight) were dissected, the left sides by the anatomical approach, the right sides being jointed and the joints being dissected into fat, muscle, bone and other tissues. Weights of the anatomically dissected muscles and bones, and weights of muscle and bone dissected from each cut, were regressed on weight of the respective tissue in the side. The influence of the animals' sex on tissue distribution was investigated using a one-way analysis of covariance. Results were consistent with those reported on cattle in that (i) sex had no influence on the amount of total muscle occurring in the distal parts of limbs or surrounding the spinal column and connecting the fore limb to the thorax and neck, (ii) females had more of their total muscle in the flank or abdominal wall and less in the loin than males, and (iii) females tended to have less of their total side bone in the appendicular skeleton and more in the axial skeleton than males. However, the influence of the animal's sex on the amount of total muscle in the proximal parts of its limbs was significant in buffaloes but not in cattle; the reverse was true for the muscle group of the thorax and neck. The overall sex differences in bone-weight distribution for buffaloes were as small as previously reported for cattle, sheep and pigs. Features of better muscle-weight distribution in buffalo males as compared with females and in Egyptian buffaloes as compared with Australian buffaloes and British cattle breed types are discussed.     

Direct-writing of PbS nanoparticles inside transparent porous silica monoliths using pulsed femtosecond laser irradiation

Pulsed femtosecond laser irradiation at low repetition rate, without any annealing, has been used to localize the growth of PbS nanoparticles, for the first time, inside a transparent porous silica matrix prepared by a sol-gel route. Before the irradiation, the porous silica host has been soaked within a solution containing PbS precursors. The effect of the incident laser power on the particle size was studied. X-ray diffraction was used to identify the PbS crystallites inside the irradiated areas and to estimate the average particle size. The localized laser irradiation led to PbS crystallite size ranging between 4 and 8 nm, depending on the incident femtosecond laser power. The optical properties of the obtained PbS-silica nanocomposites have been investigated using absorption and photoluminescence spectroscopies. Finally, the stability of PbS nanoparticles embedded inside the host matrices has been followed as a function of time, and it has been shown that this stability depends on the nanoparticle mean size.     

Polyamide 66 nanocomposites based on organoclays treated with thermally stable phosphonium salts

Purification of bentonite clays and their modification with two thermally stable (alkyl and aryl) phosphonium organic salts were investigated. The organoclays were subsequently melt compounded with Polyamide 66 (PA66), with and without the use of an elastomeric compatibilizer. The morphology, melt flow, thermal stability, and mechanical properties of the binary and ternary nanocomposites were studied. The bentonite clay was purified by sedimentation, resulting in higher cation exchange capacity and thermal stability in comparison with unpurified clay. These were then used in the synthesis of two thermally stable organoclays by replacing the interlayer sodium cations with two (alkyl and aryl) phosphonium surfactant cations to circumvent the problem of low temperature decomposition of quaternary ammonium organoclays usually used in polymer nanocomposites. The organoclay with aliphatic groups showed more compatibility with PA66 in comparison with the organoclay with aromatic groups. Thus, the use of organoclay with aliphatic groups resulted in nanocomposites with higher tensile strength, higher modulus, higher elongation at break, and higher impact strength in comparison with the nanocomposites produced from the organoclay with aromatic groups. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The Effect of Non Ionic Surfactants Containing Triazole, Thiadiazole and Oxadiazole as Inhibitors of the Corrosion of Carbon Steel in 1M Hydrochloric Acid

In the present investigation novel nonionic surfactants were synthesized, characterized and tested as inhibitors of the corrosion of carbon steel in 1M HCl solution. The inhibition action of these surfactants was studied by weight loss, galvanostatic polarization and electrochemical impedance spectroscopy. The adsorption of the inhibitors was well described by the Langmuir adsorption isotherm and the adsorption isotherm parameters were determined at different temperatures. The inhibition efficiency was found to rise when increasing the concentration of these compounds and decreasing the temperature. The effect of temperature on the inhibition efficiency of the corrosion process was studied and the values of some activated thermodynamic parameters were calculated to elaborate the mechanism of inhibition. The synthesized nonionic surfactants exhibit good surface and antimicrobial properties.     

Efficient Decoding for Generalized Quasi-Orthogonal Space–Time Block Codes

Space–time coding can achieve transmit diversity and power gain over spatially uncoded systems without sacrificing bandwidth. There are various approaches in coding structures, including space–time block codes. A class of space–time block codes namely quasi-orthogonal space–time block codes can achieve the full rate, but the conventional decoders of these codes experience interference terms resulting from neighboring signals during signal detection. The presence of the interference terms causes an increase in the decoder complexity and a decrease in the performance gain. In this article, we propose a modification to the conventional coding/decoding scheme that will improve performance, reduce decoding complexity, and improve robustness against channel estimation errors as well.     

Hydrodynamic lubrication of porous journal bearings using a modified Brinkman-extended Darcy model

A numerical solution for the hydrodynamic lubrication of finite porous journal bearings considering the flexibility of the liner is introduced. The Brinkman-extended Darcy equations and the Stokes' equations are utilized to model the flow in the porous region and fluid film region, respectively. A stress jump boundary condition at the porous media/fluid film interface and effects of viscous shear are included into the lubrication analysis. Elrod's cavitation algorithm, which automatically predicts film rupture and reformation in the bearing, is implemented in the solution scheme. The present analysis predictions for pressure distributions, load carrying capacity, and friction factor are in good agreement with three different sets of experimental results available in the literature. Furthermore, the effects of dimensionless permeability parameter, and stress jump parameter on performance parameters such as load carrying capacity, side leakage, friction factor, and attitude angle, are presented and discussed.     

On the link between intrinsic catalytic reactions kinetics and the development of catalytic processes: Catalytic dehydrogenation of ethylbenzene to styrene

A procedure linking kinetic modeling of catalytic reactions to reactor modeling for different configurations is developed and applied to the catalytic dehydrogenation of ethylbenzene to styrene. The procedure is applied to four configurations, namely fixed bed with/without hydrogen selective membranes and bubbling fluidized beds with/without selective membranes. The kinetic data for the industrial catalyst are extracted from industrial fixed bed data using a rigorous heterogeneous model. The kinetic data for the three in-house prepared catalysts are obtained from the laboratory scale experiments using pseudo-homogeneous models.     

Effect of grinding forces on the vibration of grinding machine spindle system

In this paper the effects of dynamic changes in the grinding force components due to changes in the grinding wheel wear flat area and the workpiece material on the vibration behavior of the grinding spindle are studied. The steady-state dynamics and vibration behavior of the grinding machine spindle is simulated by a five degree of freedom model. The results indicate that when grinding different materials using a grinding wheel with fixed wear flat area, different vibration behavior is noticed. As the grinding wheel flat area increases, the level of vibration increases for all the degrees of freedom, which indicates that there is an upper limit for the level of wear on the grinding wheel that can be tolerated, and after that level dressing operation must be conducted on the grinding wheel.     

The Effect of Annealing Temperature on the Magnetic Properties of Mn x Co1?x Fe2O4 Ferrites Nanoparticles

Mn _x Co_1?x Fe₂O₄ ferrites compounds (0??x??0.6) have been synthesized by a glycol-thermal method from high-purity metals chlorides. Single phase spinel structure of the nanoparticles has been confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The diameters of the as-prepared powders were estimated from XRD and TEM and were found to be in the range: 7 to 13?nm. Room temperature magnetizations were obtained using a vibrating sample magnetometer (VSM) on the as-prepared samples and on samples annealed at 500 and 700?°C. The variation of coercive fields, saturation and remnant magnetizations as a function of composition (x) and grain size have been investigated. ⁵⁷Co M?ssbauer spectra for as-prepared samples were also measured at different temperatures (27, 100, and 200?°C). Significant changes in magnetization properties and M?ssbauer parameters are observed across the composition range studied. The variation of coercive fields and saturation magnetizations appear to critically depend on the particle sizes as the compounds evolve from single domain to multidomain structure.