Siliconcarbide Embedded Hybrid Nanocomposites as Abrasion Resistant Coating

Siliconcarbide (SiC) ceramic powder incorporated inorganic–organic nanocomposites were prepared by sol–gel spin coating method. Coating properties and abrasion resistance of the hybrid polymers were examined by scanning electron microscopy (SEM), EDX analysis, FT-IR spectroscopy, thermogravimetric differential thermal analysis (TG-DTA). Mechanical tests like surface static corrosion analysis, abrasion test, scratch-tape test, adhesion test, chemical and solvent resistance, surface hardness were performed in order to evaluate the coatings for possible industrial applications. Prepared polymers were applied onto the aluminium substrates. Results revealed that industrially available SiC ceramic powder incorporated inorganic–organic nanocomposites can be prepared with an easy and controlled way using sol–gel method and applied onto the aluminium surfaces by spin coating without using primer solution and shows excellent abrasion resistance.     

Silicon carbide particle reinforced mullite composite foams

Silicon carbide particle reinforced mullite composite foams were produced by the polymer replica method using alumina and kaolin to form in situ mullite matrix. Up to 20 wt.% silicon carbide particles (SiCp) were added to aqueous ceramic slurry to explore its effect on the rheological behaviour of ceramic slurries and also properties of as sintered products. By means of solid loading optimisation and sintering enhancement by silicon carbide, mullite based ceramic composite foams of higher strength were obtained. The strength of the as sintered foams was found to depend greatly on the phase composition, relative density of the structures and the amount of SiCp addition. By studying the effect of the additive concentration, on the mechanical properties of the ceramic matrix, it is found that the optimal silicon carbide addition is 20 wt.%.     

Arbitrary Lagrangian–Eulerian methods for analysis of regressing solid domains and interface tracking

We present the details of the formulation and implementation of the arbitrary Lagrangian–Eulerian (ALE) finite element method for three-dimensional problems involving regressing solid domains and moving boundaries. An example of such problems is the simulation of solid-propellant rockets in which the evolution of a fluid–solid interface is governed by a combustion law and the transfer of mass and momentum across it. The ALE method, while providing a means to track the location of the interface, allows the adaptation of the finite element mesh to the constantly changing solid domain. In this study, the mesh adaptation is achieved via a novel smoothing technique in which the shape of finite elements with smaller volumes, which are more susceptible to mesh-entanglement, are better preserved compared to those with larger volumes. An analysis of the stability of the ALE computations, under certain simplifying assumptions, is also performed. The stability limits determined from this analysis can be utilized as constraints for adjusting mesh velocities or time increments in the convective mesh-motion phase of the ALE computations. In addition, a method is provided for generating verification problems with moving interfaces from those with known solutions on stationary material domains. A problem in which the prescribed growth of a cavity in an infinite medium under a time-varying pressure loading is used to verify the implementation and to demonstrate the verification technique.     

A novel hash function based fragile watermarking method for image integrity

In recent years, tampering and altering of digital images have become easier with the rapid development of computer technologies such as digital image editing tools. Therefore, verification of image integrity and tamper detection of digital images have become a great challenge. Fragile watermarking is the most widely used method for protecting the integrity and content authenticity of the image. In this paper, by using SHA-256 hash function, a novel block based fragile watermark embedding and tamper detection method is proposed. In watermark embedding phase, host image is divided into 32?×?32 non-overlapped blocks. Each 32?×?32 block is then divided into four 16?×?16 nonoverlapped sub-blocks. The entire hash value of the first three sub-blocks is generated as a watermark using SHA-256 hash function. The generated 256-bit binary watermark is embedded into the least significant bits (LSBs) of the fourth sub-block and watermarked image is obtained. In tamper detection phase, the detection of tampered block has been performed by comparing the hash value obtained from the three sub-blocks with the extracted watermark from the fourth sub-block of the watermarked image. The performance of the proposed method has been evaluated by applying linear and nonlinear attacks to the different regions of the watermarked images. Experimental results show that the proposed method detects all the tampered regions of the attacked images and high visual quality of watermarked images has been obtained.

     

A new algorithm for sensorless operation of permanent magnet motors

In this paper, the authors propose and investigate a new algorithm for shaft position sensorless operation of permanent magnet motors, based on flux linkage and line current estimation. Measured line current and terminal voltage are used to estimate the flux linkage of the motor. The algorithm has a two current-loop structure, with the outer loop used to correct the position, and the inner loop utilised to correct the estimated flux linkage. The theoretical basis of the algorithm and individual definition of the system blocks is explained. Dependencies on motor parameters and measurement errors are discussed to show the effectiveness of the method using real data. As well as giving a detailed explanation of the new algorithm, the paper presents a wide range of computed and experimental results, demonstrating the reliability of the method even during acceleration of the motor from rest     

Ratios of internal conversion coefficients

We present here a database of available experimental ratios of internal conversion coefficients for different atomic subshells measured with an accuracy of 10% or better for a number of elements in the range 26 ? Z ? 100. The experimental set involves 414 ratios for pure and 1096 ratios for mixed-multipolarity nuclear transitions in the transition energy range from 2 to 2300 keV. We give relevant theoretical ratios calculated in the framework of the Dirac-Fock method with and without regard for the hole in the atomic subshell after conversion. For comparison, the ratios obtained within the relativistic Hartree-Fock-Slater approximation are also presented. In cases where several ratios were measured for the same transition in a given isotope in which two multipolarities were involved, we present the mixing ratio δ² obtained by a least squares fit.     

Synthesis and characterization of conducting copolymers of poly(vinyl alcohol) with thiophene side‐groups and pyrrole

Graft copolymers of poly(vinyl alcohol) with thiophene side‐groups and pyrrole were synthesized by electrochemical polymerization methods. Poly(vinyl alcohol) with thiophene side‐groups (PVATh) was obtained from the reaction between poly(vinyl alcohol) (PVA) and thiophene‐3‐acetic acid. The syntheses of copolymers of PVATh and pyrrole were achieved electrochemically by using three different supporting electrolytes, p‐toluene sulfonic acid (PTSA), sodium dodecyl sulfate (SDS) and tetrabutylammonium tetrafluoroborate (TBAFB). Characterization of PVATh and graft copolymers was performed by a combination of techniques including cyclic voltammetry, scanning electron microscopy, thermal gravimetry, differential scanning calorimetry, size‐exclusion chromatography, ¹H NMR and FT‐IR. The conductivities were measured by the four‐probe technique. Copyright © 2004 Society of Chemical Industry     

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Journal of Materials Science: Materials in Electronics -     

Wood and bark volatile compounds of Laurus nobilis L.

Wood and bark parts of Laurus nobilis L. were extracted with two different methods to determine the volatile compounds. They were analyzed with GC/MS. Monoterpenes were determined as the principal group of the bark volatiles whereas sesquiterpenes are the main components in wood extractives. The main compounds in bark are 1.8-cineol and eugenol, while dehydrocostunolide in the wood extract.