Two way shape memory loss in Cu---Zn---Al alloy

Investigation is carried out to understand the reasons behind the degradation of two way shape memory effect in Cu---Zn---Al alloy which exhibits a complete loss in its two way memory effect after a finite number of transformation cycles. It is observed that the two-way memory loss is attributable to a chemical effect viz. the precipitation of intermetallics at the martensite plate boundaries. Since repetitive thermal cycling is related to some kind of ageing effects, the present investigation also includes the study on the ageing behaviour of the alloys. The ageing effects are finally co-related with the observed two-way shape memory loss to describe the transformation fatigue found in the Cu---Zn---Al alloy.     

Note on axis-symmetric jet mixing of compressible dusty fluid

Summary Laminar jet mixing of a compressible dusty fluid issuing from a circular opening has been considered. Assuming that the jet mixing is under full expansion, the governing equations have been linearised and solved by successively using Hankel and Laplace transform techniques. Numerical computations of the integrals giving velocity, temperature and density of both the fluid and particle phase have been made to discuss results. The increase in the concentration of dust particles results in width of the jet is greater for compressible flow. The compressible dusty jet does not cool as fast as a compressible jet of clear fluid. The particle concentration decreases along the axial direction but increases towards the free jet boundary.     

Data Compression Limit for an Information Source of Interacting Qubits

A system of interacting qubits can be viewed as a non-i.i.d quantum information source. A possible model of such a source is provided by a quantum spin system, in which spin-1/2 particles located at sites of a lattice interact with each other. We establish the limit for the compression of information from such a source and show that asymptotically it is given by the von Neumann entropy rate. Our result can be viewed as a quantum ana-logue of Shannon's noiseless coding theorem for a class of non-i.i.d. quantum informa-tion sources. From the probabilistic point of view it is an analog of the Shannon-McMillan-Breiman theorem considered as a cornerstone of modern Information Theory. PACS: 03.67-a; 03.67.Lx     

On finding eigenvalue distribution of a matrix in several regions of the complex plane

A direct method is proposed for determining eigenvalue distribution of a matrix with respect to several important regions of the complex plane. These regions include half planes, shifted half planes, hyperbolas, sectors, quadrants, imaginary axis, region contained within two straight lines that pass through the orgin, etc. The method neither requires computation of the characteristic polynomial of the given matrix nor solution of any matrix equations. The method seems to be more efficient than the eigenvalue and matrix equations methods.     

Thermal transformation in a chrysotile asbestos

Structural changes accompanying thermal transformation in a chrysotile asbestos sample of Indian origin upto a temperature of 900°C have been investigated by x-ray method. The changes in lattice parameters have been systematically measured by applying a least square refinement technique and the crystallite size and strain defects at different stages have been estimated by line profile analysis of the diffraction peaks. The present study also confirms the earlier results on stepwise transformation of chrysotile fibres. This sequence of transformation has been explained assuming two different types of crystallites as reported in kaolinite.     

Properties of YIG-based magnetic glass-ceramics with different nucleating agents

The effect of bismuth, silver oxide and palladium on the crystallization of yttrium iron garnet in Na₂O-SiO₂-Y₂O₃-Fe₂O₃ glass-ceramics has been investigated by X-ray diffraction thermal analysis, magnetic measurements and optical microscopy. It is found that the magnetic properties of these glass-ceramics can be altered significantly by a change in the nucleating agents and the heat treatment schedule. This behaviour is explained on the basis of the microstructure and the volume fraction of the different magnetic phases crystallized within the glasses.     

Aluminide coating formation on nickel-base superalloys by pack cementation process

A detailed study was carried out to investigate the effects of pack powder compositions, coating temperature and time on the aluminide coating formation process on a superalloy CMSX-4 by pack cementation. With the aid of recently developed thermodynamic analytical tools, powder mixtures that are activated by a series of fluoride and chloride salts were analysed and the effectiveness of these activators in transferring and depositing Al was evaluated at a range of coating temperatures. The Al chloride vapours formed at coating temperatures from 900°C to 1100°C were also analysed thermodynamically as a function of Al concentration in the original pack for the powder mixtures activated by 4 wt% CrCl₃·6H₂O. Based on the thermochemical calculations, a series of coating experiments was carried out. Aluminide coatings were formed at temperatures from 850°C to 1100°C for periods varying from 4 hours to 8 hours using powder mixtures activated by NH₄Cl, NaCl and CrCl₃·6H₂O and AlF₃. The effects of changing Al concentration as well as adding small quantities of Cr in the powder mixtures on the coating formation process were also investigated. The aluminide coatings were analysed using a range of techniques including SEM, EDX and XRD. The relationships between the mass gain and coating thickness and structure were investigated. The experimental results were compared with the predictions from thermochemical calculations. Based on the understandings established, an effective approach to control the aluminide coating parameters and structures was identified, which made it possible to optimise powder mixture compositions and coating conditions for different coating requirements.     

ADVANCED CHEMICAL OXIDATION OF 2,4,6 TRICHLOROPHENOL IN AQUEOUS PHASE BY FENTON'S REAGENT-PART II: EFFECTS OF VARIOUS REACTION PARAMETERS ON THE TREATMENT REACTION

Part I of this paper examined the effects of the amounts of oxidant and catalyst on the rates and extents of oxidation of 2,4,6-Trichlorophenol (TCP), in aqueous phase, by Fenton's Reagent. In this part the effects of various reaction parameters, e.g. temperature, pH, oxidation state of catalyst (ferrous versus ferric), mode of addition of oxidant to the reactor (single batch versus multiple increments), and the presence of dissolved oxygen (D.O.) have been examined. The progress of each reaction has been monitored by the rate and extent of release of free chloride ions in the aqueous solution. All the experiments were conducted using optimum molar ratios of the oxidant (hydrogen peroxide) to the substrate (TCP), and the catalyst (ferrous ions) to the oxidant of 5.5:1 and 0.10:1 respectively, as defined in Part I.     

Determination of compounding formulation of cured rubber by reverse engineering

The present work deals with reverse engineering on four rubber formulations. Information about the material composition of the compounding formulations was obtained by using techniques such as acetone extract, thermogravimetric analysis, energy dispersive X‐ray fluorescence studies, and Fourier transform infrared (FTIR) spectroscopy in attenuated total reflection mode. The reverse engineered formulations were compared on a qualitative and quantitative basis with the initial formulations. The aim was to ascertain the validity of the methodology, which may be used as reverse engineering of rubber compounds to quantitatively analyze unknown ground tire rubber in future. The state of the art was based on a fractional mass transfer from acetone extract to the rubbers detected in TGA. Through this new approach, the formulations calculated were very consistent with the formulations employed, thus establishing the validity of the methodology used. POLYM. ENG. SCI., 55:1450–1458, 2015. © 2015 Society of Plastics Engineers     

Effect of Alumina Reactivity on the Densification and Properties of Al2O3–Cr2O3 Refractories

Alumina‐chrome (Al₂O₃–Cr₂O₃) refractories with Al₂O₃:Cr₂O₃ molar ratio 1:1 were synthesized in the temperature range of 1400–1700°C by conventional solid–oxide reaction route. The effect of different aluminas (viz., hydrated and calcined) on the densification, microstructure, and properties of Al₂O₃–Cr₂O₃ refractories was investigated without changing the Cr₂O₃ source. The starting materials were analyzed to determine the chemical composition, mineralogy, density, surface area, and particle size. Sintered materials were characterized in terms of densification, phase assemblage, and mechanical strength at room temperature and at higher temperatures. Microstructural evolution at different sintering temperature was correlated with sintering characteristics. It can be concluded that the Al₂O₃–Cr₂O₃ refractories prepared with hydrated alumina as Al₂O₃ source show better densification and hot mechanical strength than corresponding calcined variety.