Mechanisms and empirical equations for deformation and some principles of alloy design

Some aspects of the deformation behaviour of solids at very high, moderately high and low strain rates are discussed. In the very high strain rate region, deformation equations and the physics of the shock front are analysed to propose a route to lower energy dissipation at the shock front. In the moderately high strain rate region, alloy design principles for maximizing the deformation resistance are outlined. In the low strain rate region, an analysis of the physical basis for the power law creep equation is presented. Some physical arguments are presented as a rationale for the high stress exponents and activation energies often observed in particle-strengthened alloys. The additivity of strain rates by various mechanisms is also briefly discussed.     

The NAL-ISRO acoustic test facility

The Indian Space Programme has the goals of launching a number of communication and remote sensing satellites for various uses. The acoustic exposure testing of such space bound components and systems on ground is mandatory to check their ability to withstand the extreme noise fields encountered during the trans-atmospheric flight to their final destinations in space. This paper outlines the nature and origin of this acoustic field, need for acoustic testing, establishment of a versatile groundbased high intensity acoustic-testing facility and its performance evaluation. The facility was set up as a joint project between the National Aeronautical Laboratory (nal) and the Indian Space Research Organisation (isro).     

Assessment of toxic content in Balanites aegyptiaca seed cake and use of enzymatic-catalysed biodiesel in diesel engine

The present study deals with the estimation of toxic phorbol esters in Balanites aegyptiaca seed cake and to evaluate the performance and combustion characteristics of different blends of biodiesel in a diesel engine. The seeds were manually collected from arid regions of Rajasthan, India and the oil extracted from the powdered kernel with Solvent extraction process. The extracted oil processed by enzymatic catalytic reactions are carried out at optimum operating conditions such as the molar ratio of 8:1 (methanol:oil), reaction temperature at 40°C for 4?h reaction time and xylanase 1% based on oil weight. The total conversion rate of extracted oil to methyl ester by enzymatic reactions yields up to 98.3%. The toxic content of seed cake was determined by high-performance liquid chromatography (HPLC, Shimadzu). The performance and combustion parameters such as BP, BTE and CP decreased, whereas BSFC and DP increased with biodiesel blends.     

MoSe2 nanoflowers as a counter electrode for quantum dots sensitized solar cells

Journal of Materials Science: Materials in Electronics - Layered transition metal dichalcogenides hold tunable and promising photoelectrochemical properties. MoSe2 is a potential candidate of the...     

Chemical,morphological, structural,optical, and magnetic properties of Zn<Subscript>1−x</Subscript>Nd<Subscript>x</Subscript>O nanoparticles

In the present investigation, we made an endeavor to fabricate the ZnO nanoparticles and achieved the tunable properties with Nd doping. The Nd-doped ZnO nanoparticles were characterized via X-ray diffraction (XRD), Raman, and X-ray photoelectron spectroscopy (XPS) studies that confirmed the successful doping of Nd ions in the ZnO crystal lattice without amending its hexagonal phase. The particle morphology revealed nearly spherical particles with uniform size distribution. The band gap of these samples was determined using diffuse-reflectance spectra (DRS) and was found to vary from 3.17 to 3.21 eV with increasing Nd concentration. A broad and intense emission band at 1083 nm for Nd doped ZnO nanoparticles is observed and is assigned to corresponding emission transition ⁴F_3/2?→?⁴I_11/2 of Nd³⁺ ions. Furthermore, the magnetic studies indicate that the Nd doping altered the magnetic behavior of nanocrystalline ZnO particles from diamagnetic to ferromagnetic at 300 K and that the magnetization of these samples decreased with increasing Nd concentration. The tunable optical band gap as well as room-temperature ferromagnetism of these samples may find applications in both optoelectronics and spintronics.     

Inverse Gaussian Autoregressive Models

A first-order autoregressive process with one-dimensional inverse Gaussian marginals is introduced. The innovation distributions are obtained in certain special cases. The unknown parameters are estimated using different methods and these estimators are shown to be consistent and asymptotically normal. Performance of the estimators is discussed using simulation experiments.     

Symmetric coupling of multi‐zone curved Galerkin boundary elements with finite elements in elasticity

The coupling of Finite Element Method (FEM) with a Boundary Element Method (BEM) is a desirable result that exploits the advantages of each. This paper examines the efficient symmetric coupling of a Symmetric Galerkin Multi‐zone Curved Boundary Element Analysis method with a Finite Element Method for 2‐D elastic problems. Existing collocation based multi‐zone boundary element methods are not symmetric. Thus, when they are coupled with FEM, it is very difficult to achieve symmetry, increasing the computational work to solve the problem. This paper uses a fully Symmetric curved Multi‐zone Galerkin Boundary Element Approach that is coupled to an FEM in a completely symmetric fashion. The symmetry is achieved by symmetrically converting the boundary zones into equivalent ‘macro finite elements’, that are symmetric, so that symmetry in the coupling is retained. This computationally efficient and fast approach can be used to solve a wide range of problems, although only 2‐D elastic problems are shown. Three elasticity problems, including one from the FEM‐BEM literature that explore the efficacy of the approach are presented. Copyright © 2000 John Wiley & Sons, Ltd.     

A fully symmetric multi‐zone Galerkin boundary element method

This paper examines the efficient integration of a Symmetric Galerkin Boundary Element Analysis (SGBEA) method with multi‐zone resulting in a fully symmetric Galerkin multi‐zone formulation. In a previous approach, a Galerkin multi‐zone method was developed where the interfacial nodes are assigned degrees of freedom globally so that the displacement and traction continuity across the zonal interfaces are addressed directly. However, the method was only block symmetric. In the present paper, two new approaches are derived. In the first approach, the degrees of freedom for a particular zone are assigned locally, independent of the other zones. The usual linear set of equations, from the symmetric Galerkin approach, are augmented with an additional set of equations generated by the Galerkin form of hypersingular boundary integrals along the interfaces. Zonal continuity is imposed externally through Lagrange's constraints. This approach is also only block symmetric. The second approach derived from the first, uses the continuity constraints at the zonal assembly level to achieve full symmetry. These methods are compared to collocation multi‐zone and an earlier formulation, on two elasticity problems from the literature. It was found that the second method is much faster than the collocation method for medium to large scale problems, primarily due to its complete symmetry. It is also observed that these methods spend marginally more time on integration than the previous Galerkin multi‐zone method but are better suited to parallel processing. Copyright © 1999 John Wiley & Sons, Ltd.     

Red palm oil supplementation: a feasible diet-based approach to improve the vitamin A status of pregnant women and their infants

This double-blinded, randomized, controlled study was designed to study the effect of dietary supplementation with red palm oil during pregnancy on maternal and neonatal vitamin A status. A total of 170 women were recruited at 16 to 24 weeks of gestation and randomly assigned to an experimental group that received red palm oil to supply approximately one recommended dietary amount (RDA) (2,400 micrograms) of beta-carotene or to a control group that received an equivalent volume of groundnut oil. The women received the oils for a period of 8 weeks, starting at 26 to 28 weeks of gestation and extending to 34 to 36 weeks of gestation. The mean postintervention (34 to 36 weeks) levels of serum retinol were 1.20 +/- 0.22 (SD) mumol/L (95% CI, 1.15-1.25) in women receiving red palm oil and 0.73 +/- 0.15 mumol/L (95% CI, 0.69-0.77) in their infants; these levels were significantly higher than those in women receiving groundnut oil (1.07 +/- 0.26 mumol/L; 95% CI, 1.01-1.13; p < .01) and their infants (0.62 +/- 0.17 mumol/L; 95% CI, 0.57-0.67; p < .001). A significantly lower proportion of women in the red palm oil group than in the control group had vitamin A deficiency (serum retinol levels < 0.7 mumol/L) after intervention (1.5% vs. 9.7%). The proportion of women having anemia was significantly lower (p < .01) in the red palm oil-supplemented group (80.6%) than in the control group (96.7%). The mean birthweight and gestational age of the infants did not differ significantly between the two groups. An increased risk of low birth-weight (p = .003) and preterm delivery (p = .000) was observed with decreasing serum retinol levels in the third trimester of pregnancy. These results show that red palm oil supplementation significantly improved maternal and neonatal vitamin A status and reduced the prevalence of maternal anemia. Maternal vitamin A status in the later part of pregnancy is significantly associated with fetal growth and maturation. Hence red palm oil, a rich source of bioavailable vitamin A, could be used as a diet-based approach for improving vitamin A status in pregnancy.