Microstructural and mechanical assessment of transient liquid phase bonded commercially pure titanium

Diffusion joining of commercially pure titanium was successfully prepared via transient liquid phase bonding in vacuum environment. The process was carried out using AMS 4772 silver-based filler alloy at 900–1000°C for various holding time under the vacuum of 6?×?10^?7?Torr. Optical and scanning electron microscopy equipped with an EDS analyzer was conducted for microstructural evaluations. Mechanical properties were also investigated by shear test, fractographic assessment and X-ray diffraction analyses. The tendency to achieve isothermally solidified joint increased by increasing bonding time. No sign of athermal solidification was detected of sample bonded at 1000°C for 90?min. Consequently, the bonding condition of a high quality joint was obtained. Elemental analyses revealed that filler alloy’s elements (Ag, Cu) distributed more uniformly in fully isothermal solidified bond, whereas the aggregation of these elements is considerable in athermally solidified bond. Shear test results represented that the highest shear strength attributed to the sample bonded in isothermal solidified condition (bonded at 1000°C for 90?min).     

Using weighted pseudo‐inverse method for reconstruction of reflectance spectra and analyzing the dataset in terms of normality

Most of spectral estimation methods are based on improving the learning‐based procedures which mainly modify the training sets used by the basic methods. In this article, a new method is developed for analyzing of superiority of these modified processes to the basic methods in terms of normality of datasets. Hence, two qualitative terms, named generality and similarity are introduced to interpret the recovery achievements of different databases and their roles as training and testing sets. Also, a simple technique based on dataset modification of pseudo‐inverse method is introduced for the recovery of reflectance spectra of samples from their corresponding colorimetric data. The method modifies the training dataset according to the color specifications of test sample. In fact, different weighting matrices are employed as dynamic modifiers to improve the pseudo‐inverse estimation as a simple recovery method. The employed datasets are examined in the self as well as cross test conditions and the results are spectrally and colorimetrically evaluated. The root mean square errors between the reconstructed and actual spectra along with the corresponding color difference values under different illuminants decrease by employing the suggested modification method in comparison to classical pseudo‐inverse technique as well as the recently improved version named optimized adaptive Wiener method. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2010     

The influence of depth of cut on the machinability of an alloyed austempered ductile iron

The volume fraction of high carbon austenite present in the microstructure of austempered ductile iron (ADI) is one of the important factors that influence the mechanical and physical properties of the alloy. Formation of martensite by TRIP (transformation induced plasticity) mechanism during the machining operation in which a large amount of stress is applied to the microstructure results in a decrease in machinability of austempered ductile iron which has affected the expansion of ADI in industry. In this article, the effect of depth of cut as a machining variable is assessed in an alloyed austempered ductile iron containing Cu, Ni and Mo. The measurements of mechanical properties including impact energy, tensile strength, hardness and microhardness along the cross-section of samples are reported for samples austenitized at 870 °C followed by austempering at 375, 340 and 300 °C. Results indicate that contrary to the behavior of many alloys, in austempered ductile iron, reducing the depth of cut will not improve the machinability. In the case of studied composition, cutting with depths of 0.5 and 0.1 mm had the best and worst results, respectively.     

Tuning parallel applications in parallel

In this paper, we present and evaluate a parallel algorithm for parameter tuning of parallel applications. We discuss the impact of performance variability on the accuracy and efficiency of the optimization algorithm and propose a strategy to minimize the impact of this variability. We evaluate our algorithm within the Active Harmony system, an automated online/offline tuning framework. We study its performance on three benchmark codes: PSTSWM, HPL and POP. Compared to the Nelder–Mead algorithm, our algorithm finds better configurations up to seven times faster. For POP, we were able to improve the performance of a production sized run by 59%.     

Statistical optimization for oxidation of ethyl benzene over Co-Mn/SBA-15 catalyst by Box-Behnken design

A series of cobalt and manganese catalysts supported on SBA-15 with different loading of Mn⁺² and Co⁺² were synthesized. These samples were characterized by SEM and XRD techniques. The catalytic activity of these samples was evaluated in the oxidation of ethylbenzene (EB) to produce acetophenone (AP) and benzoic acid (BA) in the liquid phase using tert-butylhydroperoxide (TBHP) as an oxidant. The effects of Co-Mn loading, TBHP: EB molar ratio and temperature on acetophenone and benzoic acid yields were studied by Box-Behnken experimental design to optimize the production of acetophenone and benzoic acid in liquid system.     

Effect of Cu2+ Ions and Buffering Capacity on Smectite Microstructure and Performance

Smectite is usually used as buffer clay for contaminant of high level nuclear waste canisters. Corrosion of the canisters will expose the buffer clay to Cu2+ ions as one of the corrosion products. This study investigates the effect of Cu2+ cations in a smectite, with and without addition of sodium carbonate in the clay, on its consolidation behavior and transmission characteristics. Characterization experiments conducted in the study included determination of changes in the buffering capacity and permeability properties of the clay in relation to the presence of varying concentrations of Cu2+, and consolidation experiments. Double-layer swelling forces and buffering capacity are seen to be dominant factors in the performance of the clays—apparently through their influence on formation and restructuring of microstructures in the overall smectite clay mixtures.     

Three-dimensional free vibration of variable thickness thick circular and annular isotropic and functionally graded plates on Pasternak foundation

This paper describes a study of three-dimensional free vibration analysis of thick circular and annular isotropic and functionally graded (FG) plates with variable thickness along the radial direction, resting on Pasternak foundation. The formulation is based on the linear, small strain and exact elasticity theory. Plates with different boundary conditions are considered and the material properties of the FG plate are assumed to vary continuously through the thickness according to power law. The kinematic and the potential energy of the plate-foundation system are formulated and the polynomial-Ritz method is used to solve the eigenvalue problem. Convergence and comparison studies are done to demonstrate the correctness and accuracy of the present method. With respect to geometric parameters, elastic coefficients of foundation and different boundary conditions some new results are reported which may be used as benchmark solutions for future researches.     

Energy advantages of microprocessor platforms with on-chip configurable logic

System chips that incorporate configurable logic can reduce the energy consumed in executing software. The key is to use the configurable logic to execute performance-critical loops, producing average energy savings of 25% to 71% for embedded-system benchmarks.