Studies on cold upsetting behaviour of AA2014-based metal matrix composites, FEM simulation, and comparison with experimental results

Cold upsetting experiments under unlubricated conditions were carried out on as cast and homogenized AA2014/SiC/10p composite billets having dispersoids in size range of 20–40 μm. The study was aimed to evaluate the effect of homogenization on their deformation behaviour. Optical and scanning electron micrographic examination of the samples was also undertaken. Hardness measurements were carried out to observe changes, if any, before and after the forging. Ring compression tests were also carried out to determine the coefficient of friction between the platens and the work piece, which is a necessary requirement to carry out simulation studies. FEM simulation analysis of the forging of composite cylinders was then undertaken using MSC-Marc software with a specified diameter-to-height ratio. Detailed comparisons of the experimental variables with the finite element method (FEM) results were carried out to ascertain the accuracy with which the deformation process can be modelled. Predictions from the simulation results were found to be in good agreement with the actual experimentation.     

Design process for nanomaterials

This article begins by discussing the concept of deign process of nanomaterials and their importance in this era. Several methods which are reported earlier are discussed here for the synthesis of different dimensions (0D, 1D, 2D, and 3D) of nanoparticles. Their application in future and how they are bifacial for the society is also discussed.     

Stereochemical assignments of the nuclear magnetic resonance spectra of isobornyl acrylate/methacrylonitrile copolymers

Isobornyl acrylate (B)/methacrylonitrile (N) copolymers with different compositions were synthesized by the free‐radical bulk polymerization with azobisisobutyronitrile as the initiator under a nitrogen atmosphere at 70°C. The copolymer compositions were calculated from quantitative ¹³C(¹H)NMR spectra. The reactivity ratios of the comonomers in the B/N copolymers determined from the linear Kelen–Tudos method and nonlinear error‐in‐variable method were r_B = 0.66 ± 0.11 and r_N = 1.54 ± 0.22 and r_B = 0.74 and r_N = 1.65, respectively. The complete spectral assignments of the ¹H‐NMR and ¹³C(¹H)‐NMR spectra were carried out with the help of distortionless enhancement by polarization transfer, two‐dimensional (2D) heteronuclear single quantum coherence, and 2D total correlation spectroscopy. The nitrile carbon of the N unit and the methine and OCH carbons of the B unit were assigned to triad compositional sequences, whereas the β‐methylene carbons of the B and N units were assigned to the tetrad compositional and configurational sequences. The α‐methyl carbon of the N unit was also assigned to the triad level of configurational and compositional sequences. Similarly, the nitrile and quaternary carbon resonances with the methine, methylene, and methyl protons were studied in detail with 2D heteronuclear multiple‐bond correlation spectra. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

An impact of bias and structure dependent L_\mathrm{SD} variation on the performance of GaN HEMTs based biosensor

In this paper, we discussed the effect of different bias and structures in relation to S-D distance variation on the device electrical and expected biosensing performance. Devices with source to drain length ( \(L_{SD})\) variations from 3.5, 5.0, 8.0, 14.0, 26.0 to \(52~\upmu \) m were simulated at low and high bias voltages. Different structures having gate recess and finger variations were investigated for the complete range of \(L_{SD}\) variations. Small and very large \(L_{SD}\) variations in non-recessed structure showed good values of drain current \((I_{ds})\) and transconductances \((g_{m})\) at different low and high bias voltages respectively. Therefore expected response time and sensitivity could be improved by choosing a proper bias condition for different biosensing \(L_{SD}\) lengths. A gate recess structure showed better \(g_{m}\) values at low bias conditions for all \(L_{SD}\) lengths. However, \(I_{ds}\) degraded for these structures and hence the expected response time. The non-recessed structure variations in terms of number of fingers and gate width did not change the effective trends in \(L_{SD}\) variation.     

Constitutive calcium-independent release of Toxoplasma gondii dense granules occurs through the NSF/SNAP/SNARE/Rab machinery

The signals and the molecular machinery mediating release of dense matrix granules from pathogenic protozoan parasites are unknown. We compared the secretion of the endogenous dense granule marker GRA3 in Toxoplasma gondii with the release of a stably transfected foreign reporter, beta-lactamase, that localizes to parasite dense granules. Both proteins were released constitutively in a calcium-independent fashion, as shown using both intact and streptolysin O-permeabilized parasites. N-Ethylmaleimide and recombinant bovine Rab-guanine dissociation inhibitor inhibited beta-lactamase secretion in permeabilized parasites, whereas recombinant hamster N-ethylmaleimide-sensitive fusion protein and bovine alpha-SNAP augmented release. Guanosine 5'-3-O-(thio)triphosphate, but not cAMP, augmented secretion in the presence but not in the absence of ATP. The T. gondii NSF/SNAP/SNARE/Rab machinery participates in dense granule release using parasite protein components that can interact functionally with their mammalian homologues.     

Differential scanning calorimetry studies of Se85Te15−x Pb x (x = 4, 6, 8 and 10) glasses

Results of differential scanning calorimetry (DSC) studies of Se₈₅Te_15−x Pb _x (x = 4, 6, 8 and 10) glasses have been reported and discussed in this paper. The results have been analyzed on the basis of structural relaxation equation, Matusita’s equation and modified Kissinger’s equation. The activation energies of structural relaxation lie in between 226 and 593 kJ/mol. The crystallization growth is found to be onedimensional for all compositions. The activation energies of crystallization are found to be 100–136 kJ/mol by Matusita’s equation while 102–139 kJ/mol by modified Kissinger’s equation. The Hruby number (indicator of ease of glass forming and higher stability) is the highest for Se₈₅Te₉Pb₆ glass while S factor (indicator of resistance to devitrification) is highest for Se₈₅Te₇Pb₈ glass at all heating rates in our experiment. Further the highest resistance to devitrification has the highest value of structural activation energy and the activation energy of crystallization is maximum for the most stable glass by both Matusita’s equation and the modified Kissinger’s equation.     

Microstructural response of an Al-modified Ni–Cr–Fe ternary alloy during thermal processing

A thermodynamic package was used to predict the phase transformations that occurred during thermal processing of a superalloy based on the composition of a ternary Ni–Cr–Fe alloy. The effect of the addition of 6 w/o Al on phase transformation in the material sintered were estimated and compared with results obtained experimentally by X-ray diffraction and metallography, while the transformation temperature of the modified alloy was corroborated by differential scanning calorimetry (DSC). Mechanical property of the alloy was estimated in terms of Vickers hardness. These results suggest that despite potential problems encountered in high-temperature powder processing of superalloys that often tend to influence the feasibility of using thermodynamic predictions to model such alloy systems, the software and predictions used in this study offer a way to simulate both design and characterisation of the experimental alloy.     

Construction of turbo code interleaves from 3-regular Hamiltonian graphs

In this letter, we present a new construction of interleavers for turbo codes from 3-regular Hamiltonian graphs. The interleavers can be generated using a few parameters, which can be selected in such a way that the girth of the interleaver graph (IG) becomes large, inducing a high summary distance. The size of the search space for these parameters is derived. The proposed interleavers themselves work as their de-interleavers.     

On enhancing the mechanical properties of aluminum P/M alloys

Sintered aluminum alloys are an attractive material for the automobile industry, both because of the low specific gravity and high strength-to-weight ratio of aluminum itself, and the fabrication advantages associated with a powder metallurgy process. However, properties such as impact, stiffness, corrosion and wear resistance are often poor, thereby restricting the widespread use of these materials. Recent work by the authors has shown that hardness, wear resistance and tensile properties of a P/M Al–Cu–Mg ternary master alloy can be improved using a novel diffusion/supersolidus liquid phase sintering process. Improvements were due to in-situ microalloying during sintering, in particular, the influence of Ag and Sn. To complement this work, the present investigation addresses the response of a commercial alloy, AA2014, to the microalloying process. Results show that sintered densities for the commercial alloy were relatively unaffected by the presence of either Ag or Sn, and were superior to the ternary master alloy. Hardness and tensile properties were also improved relative to those obtained for the ternary, and were comparable to wrought 2014. Examination of final microstructure of Ag modified AA2014 using TEM showed the presence of Ω as the principal precipitate, but only after extended sintering times. This particular precipitate is believed to contribute to enhanced hardness. The apparent absence of Ω for short sintering times was due to the presence of silicon in the commercial product. However, the corrosion behavior of the P/M AA2014 was superior to the wrought product and thus the process is presented as a potential P/M alternative to using ingot metallurgy techniques for microalloying.     

A trend in the C-O bond strength ofCH3O(ad) on NiAl(100), FeAl(100) andTiAl(010). Effect of the alloy Fermi level

Research is presented that investigates the C-O bond stability of surface methoxy bound on Al-terminated NiAl(100), FeAl(100), and TiAl(010).Temperature-programmed desorption suggests that a fraction of methoxy individually bound on the Al component of all three surfaces undergoes C-O bond cleavage to evolve gaseous methyl radicals. The trend in the temperature of maximum methyl ejection rate, T_m, is as follows :T_m(NiAl)>T_m(FeAl)>T_m(TiAl), suggesting that the nature of the transition metal in the underlying layer affects of the C-O bond energy. Results are shown that suggest that the position of the Fermilevel in these materials plays a role in determining the C-O bond strength, consistent with the prediction of recent theory by Shiller and Anderson. This revised version was published online in July 2006 with corrections to the Cover Date.