Computer simulation of electron diffraction studies of GdCo crystalline compounds

The interference function, the diffraction intensity and the radial distribution function for Gd₁₀Co₉₀, Gd₂Co₁₇ and GdCo₅ compounds are studied by computer simulation. It is found that the position of the maxima of the radial distribution function in all the cases are same and the curves nearly coincide with the experimental curves. The first peak in all the cases are nearly equal at r ≈ 3.8 Å. The effect of strain on the interference function is studied.     

A new method for the measurement of the diffusivity of carbon in alpha-iron using an electrochemical cell

A new method has been employed to measure the diffusivity of carbon in alpha iron. The method involves the measurement of ionic current of a carbon concentration cell which employs an iron cylinder as the anode. The design of the cell is such that when a constant external potential is applied, the ionic current is determined by the concentration polarization of carbon in the two electrodes. From the values of ionic current, the diffusivity of carbon (D _c) is calculated by the application of Fick's law. The results in the temperature range 854–975 K have been fitted by regression analysis to obtain the expression:D _c = 2.448 × 10^–5 exp(–102900.7/RT) withD _c in m² s^–1 andR in JK^–1 mol^–1. The results agree well with data in the literature.     

A spline strip kernel particle method and its application to two‐dimensional elasticity problems

In this paper we present a novel spline strip kernel particle method (SSKPM) that has been developed for solving a class of two‐dimensional (2D) elasticity problems. This new approach combines the concepts of the mesh‐free methods and the spline strip method. For the interpolation of the assumed displacement field, we employed the kernel particle shape functions in the transverse direction, and the B₃‐spline function in the longitudinal direction. The formulation is validated on several beam and semi‐infinite plate problems. The numerical results of these test problems are then compared with the existing solutions obtained by the exact or numerical methods. From this study we conclude that the SSKPM is a potential alternative to the classical finite strip method (FSM). Copyright © 2003 John Wiley & Sons, Ltd.     

Antiviral properties of the seed extract of an Indian medicinal plant, Pongamia pinnata, Linn., against herpes simplex viruses: in-vitro studies on Vero cells

Pyoderma gangrenosum in a twenty-nine-year-old woman with associated long-standing Crohn's disease was treated with topical 5-aminosalicylic acid cream. Significant improvement in the ulceration occurred despite progressive deterioration of the inflammatory bowel disease. The possible mode of action is reviewed. The efficacy, together with the lack of side effects, warrants further study into the therapeutic role of topical 5-aminosalicylic acid.     

Effect of Aluminizing and Nitridation on the Oxidation Behavior of AISI 316LN SS

The application of stainless steel at temperatures above 973 K is rendered difficult by the chromium loss due to generation of volatile CrO₃ species and the consequent reduction in the capacity to maintain protective scale. We have attempted a method to circumvent this problem by modifying the surface. The surface was modified by three techniques each suiting a particular application. The first two methods involved aluminizing the surface by physical vapor deposition as the initial step. The pre-treatments were carried out in two ways viz. (i) high temperature diffusion-annealing and (ii) laser annealing of the surface. In the third method the specimen was modified by ion-nitriding. The oxidation behavior of these modified steels was compared with stainless steel in the as-received condition to exactly gauge the effect of surface modification. The oxidation experiment was carried out at 1123 K for 3.6 Ms. The oxidation was interrupted at specific time intervals to examine the mass change of the specimen and mass of the spalled oxide. The results indicated that aluminizing followed by heat-treatment and laser-treatment showed significant improvement in the adherence of the scale. On the other hand the bare and nitrided specimens showed similar behavior characterized by intermittent spallation and poor adherence. Nitriding resulted in the increase in the surface hardness. The post-oxidation examinations were carried out using SEM, EDAX and GIXRD. The uncoated specimen showed the presence of uniform oxide layer and contained oxides of iron and chromium. The aluminum-coated specimen showed the presence of adherent scale. The surface showed a nodular structure due to the formation of pits and zones of enhanced oxidation. The major part of the oxide was alumina with small fractions of chromium and iron oxides. The nodular region was enriched in the oxide of iron. The analysis of the surface by GIXRD revealed the nature of different phases formed on the surface. The oxide on the oxidized bare metal was Cr₂O₃, aluminized (non-oxidized) AlFe and Al₂Fe, aluminized and oxidized Al₂O₃ and FeCr₂O₄, aluminized and laser-treated Al₂O₃, FeCr₂O₄, Fe₂O₃ and Fe₃O₄, nitrided Fe₂O₃ and FeCr₂O₄. In the light of the above results the mechanism of scale failure has been proposed.     

Lightweight Bio-Chaos Crypt to Enhance the Security of Biometric Images in Internet of Things Applications

In recent times, numerous Internet of Things (IoT) applications have begun to use biometric identity for authentication purposes. The integrity and confidentiality of biometric templates during storage and transmission is crucial as it contains key information on the physical identity of the users. Encryption is an effective template protection technique. However, most of the edge side gadgets in the IoT environment require lightweight encryption schemes due to constraints in available power and memory space. Conventional cryptosystems are expensive because of their complexity and multiple rounds for encryption. In the present work, a lightweight bio-cryptosystem is developed to ensure security while storing and transmitting biometric templates. The proposed bio-crypto architecture has three stages—key generation, confusion and diffusion. A two-dimensional logistic sine map is used for key generation. A novel method of diffusion using DNA encoding and ciphering is proposed to decrease the complexity of the encryption process considerably and achieve desirable integrity. Simulations and security analysis indicate that the proposed cryptosystem has sufficient level of security and robustness, involves lesser computational complexity and has the potential of satisfying the requirements of IoT applications.

     

Energy-efficient CMOS voltage level shifters with single- $$\hbox {V}_{{DD}}$$ V DD for multi-core applications

Analog Integrated Circuits and Signal Processing - The never-ending demands for battery-powered applications are driven by technological advances in the field of low power digital CMOS circuits....     

Identification of Added Mass in the Composite Plate Structure Based on Wavelet Packet Transform

A new concept has been introduced that the combination of rotational mode shape with two‐dimensional wavelet packet transform to detect the added mass (damage) in a glass fibre reinforced polymer composite plate structure. Wavelet packet transform is an advanced signal processing tool that can magnify the abnormality features in the signal. Rotational mode shapes are sensitive to damage in beam and plate structures. The proposed method employs an added mass, which slides to different locations to alter the local and global dynamic characteristics of the structure. Finite element analysis is carried out to obtain the first three rotational bending mode shapes, from the damaged plate structure, then used as input to two‐dimensional wavelet packet transform. The numerical results of normalised diagonal detail wavelet packet coefficients show a peak at single or multiple added mass (damage) locations of a plate structure for two different boundary conditions. This method seems to be sensitive to relatively small amount of damage to the plate structure. A simple parametric study is carried out for the damage extent quantification. In addition, investigation with noise‐contaminated signals shows its feasibility in the real applications.     

Influence of precursor molar concentration on the electrical and magnetic properties of synthesized MnS nanocrystals

MnS Nanocrystals have been synthesized with 1:1, 1:2 and 2:1 molar ratio of precursors using wet chemical method. The electrical and magnetic properties of as-synthesized MnS nanocrystals have been investigated using the impedance spectroscopy and vibrating sample magnetometer respectively. An increase in dielectric constant from 68.5 to 87.9 with increasing Mn content and decrease to 54.1 with increase in the sulfur content was observed. Both the dielectric constant and the loss factor increased with temperature due to the Maxwell–Wagner type interfacial space-charge polarization. The Cole–Cole plot confirmed that the conduction in as-synthesized samples are through the grain and grain boundaries. The resistance and capacitance of grain and grain boundaries have been calculated. The grain resistance varies from 248 to 199 Ω whereas the grain boundary resistance varies from 16 to 6.7 KΩ over the temperature ranges of 323–473 K for 1:1 sample. It endorsed the NTCR type behavior in all the samples. The electric modulus representation revealed the well-defined relaxation peaks. The relaxation time versus temperature behavior revealed that the relaxation time decreases with increase in temperature. AC-conductivity (σ_ac) increases with increasing frequency and temperature. σ_ac increases from 1.58 × 10^?5 to 1.51 × 10^?3 S cm^?1 with the increase of Mn content and then decreases to 1.22 × 10^?8 S cm^?1 with increase of sulfur content. The activation energy is found to be 0.35 eV (1:1), 0.64 eV (1:2) and 0.28 eV (2:1) at 3 kHz. The chemically modified MnS nanocrystals exhibit paramagnetic behavior. A typical saturation magnetization of 0.56, 0.38, and 0.57 emu/g and coercivity of 2.31, 8.42, and 5.57 Oe at room temperature for 1:1, 1:2 and 2:1 sample respectively.     

Crystallization of a coprecipitated mullite precursor during heat treatment

Powder of mullite composition (3Al₂O₃·2SiO₂) has been made by a coprecipitation method. The evolution of mullite in this precursor powder during heat treatment has been studied using differential thermal analysis, electron microscopy and X-ray diffraction techniques. It is shown that during calcination below 1100°C the coprecipitate develops -Al₂O₃ and perhaps cristobalite crystallites within the basic grains, whose morphology is otherwise invariant with temperature. Mullite forms above 1100°C by reaction of these -Al₂O₃ and SiO₂ crystallites, and the grain morphology changes markedly. Small exothermic events occur at 1000 and 1250 °C. The former is associated with the decomposition of a small content of aluminosilicate or perhaps with the conversion of - to -Al₂O₃, and the latter with mullite formation. For comparison, the behaviour of a polymeric mullite precursor during calcination is also examined. This material showed a large exothermic event at 1000°C which could be associated with the decomposition of the (amorphous) aluminosilicate to crystalline -Al₂O₃ and SiO₂, and a small exothermic event at 1250° C due to mullite formation.