Enhanced magnetic behavior of Al substituted LaFeO3 (La(1 − x)AlxFeO3, x = 0.10 and 0.30)

La_(1 − x)Al_xFeO₃ (x = 0, 0.1, 0.3) has been prepared by solid state reaction method. The formation of pure crystallographic phase of LaFeO₃ and the substitution of Al³⁺ in all the doped samples have been confirmed by Rietveld analysis. The magnetic measurements viz., magnetization curves, hysteresis loops etc. in the temperature range 300-5 K showed that magnetization of the doped samples has been appreciably enhanced compared to that of the pristine LaFeO₃. The maximum enhancement factor of ~ 19 for saturation magnetization measured at room temperature has been found in La_0.7Al_0.3FeO₃.     

On Cutter Deflection Profile Errors in End Milling: Modeling and Experimental Validation

In the present paper three dimensional cutter deflections and the corresponding profile errors during end milling are predicted by finite element and bond graph modeling approach. The deflections have been modeled considering the cutter as a cantilever beam fixed at the collet end. Rayleigh beam model is used for modeling to consider the shear force effect, and Castigliano's theorem of strain energy is used to predict the deflections due to radial, tangential, and axial cutting forces. The tool-workpiece contact region is sliced into small elements to apply the forces on the entire contact region and predict deflections more accurately. The predicted deflections at different parametric settings are compared with experimental measurements by measuring the geometric accuracy of the cut profiles. The depth of cut has the most significant influence on profile deviations, while feed and speed have marginal effects. The results reveal that the predictions by finite elements and the bond graph closely matches with the experimental results, and errors of the machined profile are significantly influenced by the radial and tangential deflections. The axial deflection is negligible and leads to insignificant deviation in depth of the cut profile. The proposed model shows that the bond graph simulation takes significantly less computational time and space as compared to the finite element technique.     

A new model for estimating End-of-Life disassembly effort during early stages of product design

Clean Technologies and Environmental Policy - In this paper, a new model for estimating disassembly effort during early stages of product design is proposed. The model has been developed by...     

Photoconductivity of Cu(In, Ga) Se2 films

Polycrystalline CuIn_{1 − x}Ga_xSe₂ (0 ≤ x < 0.3) films (CIGS) were deposited by coevaporating the elements from appropriate sources onto glass substrates (substrate temperature 720 to 820 K). Photoconductivity of the polycrystalline CIGS films with partially depleted grains were studied in the temperature range 130–285 K at various illumination levels (0–100 mW/cm²). The data at low temperature (T < 170 K) were analyzed by the grain boundary trapping model with monovalent trapping states. The grain boundary barrier height in the dark and under illumination were obtained for different x-values of CuIn_1−xGa_xSe₂ films. Addition of Ga in the polycrystalline films resulted in a significant decrease in the barrier height. Variation of the barrier height with incident intensity indicated a complex recombination mechanism to be effective in the CIGS films.     

Instability of plastic flow in the directions of pure shear: II. Experimental

Two aspects of the phenomenon of plastic instability in direction of pure shear are examined, namely that the condition dσ = 0 (maximum in true flow stress) is necessary for localization of flow along characteristics as defined in continuum plasticity, and that fracture is initiated and propagates along characteristics. Two types of sheet specimens were employed, the standard-type flat sheet specimens, and specimens simulating both plane stress and plane strain. Grids were placed on gage sections and photographs were taken successively in the plastic range to enable strains to be calculated and instabilities to be observed and recorded. The principal variable in the flat specimen test was theW/T ratio (width to thickness). In the plane* strain specimens, both the gage length (constantW/T) and the strength level of the material (quenched and tempered AISI 4340 steel) were varied. A maximum in true flow stress is found consistently at the onset of instabilities. Fracture propagated consistently along the instability band-matrix interface. Variations in specimen geometry produces significant changes in stress state, directions of characteristics, and ductility. For a given specimen geometry, plane strain is more closely approached the higher the strength level of the material. In mixed mode fracture paths slant fracture is associated with the more embrittling stress state. Formerly with Metals and Ceramics Laboratory, Aerospace Research Laboratories, Wright-Patterson AFB     

Instability of plastic flow in the directions of pure shear: I. Theory

The localization of plastic flow (plastic instability) is a prelude to fracture initiation. Prior treatments are based mainly on the phenomenon of necking (load maximum) which has for its basis fluctuations in cross-sectional area. A second basic mode of localization has been confirmed experimentally. This is the localization of flow within a plastic zone along characteristic directions (direction of pure shear or zero extensional strain). The localization is effected by the activation of tangential velocity discontinuities along the characteristics. A necessary condition is that the material simulate the ideal plastic state. The conditions for this second mode of localization are formulated. A general condition for instability involving both modes is derived. In situations in which both modes are possible, necking is always expected to precede the localization along characteristics.     

Hydrogen production by Chlamydomonas reinhardtii in a two-stage process with and without illumination at alkaline pH

This work presents the results of a two-stage (carbon fixation and hydrogen production) experimental study for hydrogen production from microalgae using optical fiber as an internal light source. Effect of absence and presence of light on Chlamydomonas reinhardtii culture’s pH shift is also evaluated. The culture pH value is a function of light intensity; the pH in the alkaline range changes from 7.5 to 9.5 in the presence and absence of optical fiber respectively. The maximum rate of hydrogen production in the presence of exogenic glucose and optical fiber is 6 mL/L_cult/hour, which is higher than other reported values. This study has also revealed that the presence of light reduces the lag time for hydrogen production from 12 to 5 h.     

Auto-desulphurization of coal

The effect of atmospheric oxidation or weathering on different forms of sulphur in coal has been studied using a coal sample ground to <63 μm and kept exposed to the atmosphere for up to 228 days. Occasionally, samples were taken from the exposed coal for analysis of total-, sulphate-, pyritic- and organic sulphur. Significant amounts of total-, pyritic- and organic sulphur were reduced up to 106 days of exposure, resulting in a total sulphur content within the permissible limits of utilization. Thus, commercial desulphurization of coal may be possible by using the simple process of atmospheric weathering.