Characterisation of interfaces in nanocrystalline palladium

Structures of grain boundaries and triple line junctions in nanocrystalline materials are of interest owing to large fractions of atoms in nanocrystalline materials being at these interfacial positions. Grain boundary and triple line junction structures in nanocrystalline palladium have been studied using high-resolution transmission electron microscopy (HRTEM). The main micro structural features observed include the varying atomic structures of grain boundaries and the presence of disordered regions at triple line junctions. Also, there is variation in lattice parameters in different nanocrystalline grains. Geometric phase analysis is used to quantify atomic displacements within nanocrystalline grains. Displacement fields thus detected indicate links to the interface structures.     

A study of the energy consumption characteristics of cryptographic algorithms and security protocols

Security is becoming an everyday concern for a wide range of electronic systems that manipulate, communicate, and store sensitive data. An important and emerging category of such electronic systems are battery-powered mobile appliances, such as personal digital assistants (PDAs) and cell phones, which are severely constrained in the resources they possess, namely, processor, battery, and memory. This work focuses on one important constraint of such devices-battery life-and examines how it is impacted by the use of various security mechanisms. In this paper, we first present a comprehensive analysis of the energy requirements of a wide range of cryptographic algorithms that form the building blocks of security mechanisms such as security protocols. We then study the energy consumption requirements of the most popular transport-layer security protocol: Secure Sockets Layer (SSL). We investigate the impact of various parameters at the protocol level (such as cipher suites, authentication mechanisms, and transaction sizes, etc.) and the cryptographic algorithm level (cipher modes, strength) on the overall energy consumption for secure data transactions. To our knowledge, this is the first comprehensive analysis of the energy requirements of SSL. For our studies, we have developed a measurement-based experimental testbed that consists of an iPAQ PDA connected to a wireless local area network (LAN) and running Linux, a PC-based data acquisition system for real-time current measurement, the OpenSSL implementation of the SSL protocol, and parameterizable SSL client and server test programs. Based on our results, we also discuss various opportunities for realizing energy-efficient implementations of security protocols. We believe such investigations to be an important first step toward addressing the challenges of energy-efficient security for battery-constrained systems.     

Prototype test on X-bracing panels using cold-formed lipped angles

The behavior and suitability of cold-formed lipped angle members for X-bracing with redundant have been studied. For the purpose, two full-scale panel tests were carried out. The first panel was designed so that the compression member would fail by buckling in flexural mode and the second panel in flexural-torsional mode. The members were designed using ASCE Manual No. 52. Theoretical aspects of least radius of gyration and buckling behavior of this bracing system have been discussed. The investigation on first panel, revealed that the member would buckle only in the flexural-torsional mode although flexural buckling would govern the design. The second panel test result showed that, the buckling mode and strength of the system for lipped angle sections can be predicted reasonably well.     

A simple route for synthesis of a bi-epitaxial junction in thin films of YBa2Cu3O7 − x

A two-step fabrication process for the creation of a bi-epitaxial junction in thin films of YBa₂Cu₃O_{7 – x} is described. The junction has been fabricated on (100) SrTiO₃ substrate using a buffer layer of CeO₂. Polarized light optical microscopy indicates a regular basket-weave microstructure and a granular structure on either side of the junction. The junction shows Josephson critical currents at temperatures upto 74 K and the critical current increases linearly with decreasing temperature.     

High voltage 4H-SiC Schottky barrier diodes

Characteristics of 4H-SiC Schottky barrier diodes with breakdown voltages up to 1000 V are reported for the first time. The diodes showed excellent forward I-V characteristics, with a forward voltage drop of 1.06 V at an on-state current density of 100 A/cm². The specific on-resistance for these diodes was found to be low (2×10 ^-3 Ω-cm² at room temperature) and showed a T ^1.6 variation with temperature. Titanium Schottky barrier height was determined to be 0.99 eV independent of the temperature. The breakdown voltage of the diodes was found to decrease with temperature     

Formation of Nanocrystalline Calcia by the Decomposition of Calcite

Formation of nanocrystalline calcia from calcite has been studied in situ via transmission electron microscopy. The crystallographic transformation occurred via two mechanisms: the first is by distortion of the cleaved rhombohedron of calcite, formed by {104} planes in hexagonal coordinates, into a cube. This produced a microstructure of oriented, elongated nanocrystals of calcia with planar boundaries. In the second mechanism, the micrometer-sized parent calcite particles broke up into nano-sized grains as the decomposition began, leading to irregularly shaped, randomly oriented nanocrystals of calcia.     

Study of transformation behavior in a Ti–4.4 Ta–1.9 Nb alloy

An alloy of composition Ti–4.4 wt.% Ta–1.9 wt.% Nb is being developed as a structural material for corrosion applications, as titanium and its alloys possess excellent corrosion resistance in many oxidizing media. The primary physical metallurgy database for the Ti–4.4 wt.% Ta–1.9 wt.% Nb alloy is being presented for the first time. Determination of the β transus, M_s temperature and classification of the alloy have been carried out, employing a variety of microscopy techniques, X-ray diffraction (XRD), micro-hardness and differential scanning calorimetry (DSC). The β transition temperature or β transus determined using different experimental techniques was found to agree very well with evaluations based on empirical calculations. Based on chemistry and observed room temperature microstructure, the alloy has been classified as an + β titanium alloy. The high temperature β transforms to either ′ or + β by a martensitic or Widmanstatten transformation. The mechanisms of transformation of β under different conditions and characteristics of different types of have been studied and discussed in this paper.     

Improved device performance based on crosslinking of poly (3-hexylthiophene)

Diode devices (glass/ITO/polymer/Al) have been fabricated using poly (3-hexylthiophene) (P3HT) crosslinked with two different biaryl crosslinkers. Crosslinking was performed by exposing the thin films with different wt% of crosslinker to UV irradiation and progress of crosslinking was monitored by IR spectroscopy. An increase in hole mobility of two orders of magnitude has been observed after crosslinking.     

<Emphasis Type="Italic">In-Situ</Emphasis> Synchrotron Characterization of Transformation Sequences in TiNi-Based Shape Memory Alloys during Thermal Cycling

In-situ synchrotron radiation has been used to provide direct analysis of the transformation sequences in TiNi-based shape memory alloys during thermal cycling. The high resolution, narrow peak width Debye–Scherrer diffraction spectra enabled positive identification and quantification of the phase transformation sequences, which is not possible through normal laboratory studies. The results facilitate a clearer understanding of the development and influence of intermediate phases such as R or B19 on sequential martensitic transformations. Ti_50.2Ni_49.8 transformed predominately via a single-step B2 ↔ B19′ transformation, although evidence of the R phase was found during cooling in every cycle. The martensitic start temperature was depressed by ~0.6 °C per cycle, while the R-phase start temperature was found to be unaffected. Ti₅₀Ni₄₁Cu₉ transformed through a two-step B2 ↔ B19 ↔ B19′ sequence, with the B2 → B19 transformation reaching completion prior to the formation of any B19′. The transformation temperatures of Ti₅₀Ni₄₁Cu₉ were found to be insensitive to thermal cycling, remaining constant over the studied cycle range.     

Evaluation of antioxidant and anti-initiating activities of crude polyphenolic extracts from seedless and seeded Indian grapes

The extracts of crude polyphenols (seeds, pulp + skin, whole) from four different cultivars of Indian grapes were used in this study. The total polyphenolic contents of grape polyphenolic extracts (GPEs) were determined and their in vitro antioxidant and anti-initiating activities evaluated. The total polyphenolic contents, expressed in terms of gallic acid/catechin/procyanidin B3 equivalents, were found to vary significantly. Antioxidant activity of GPEs, particularly the seedless variety, was evident from significant dose-dependent inhibition of lipid peroxidation and DPPH activity. GPEs and catechin inhibited the microsome-catalysed activity of cytochrome P450 isozymes (1A1, 1A2, 2B1) in a dose-dependent manner, by the decreased formation of resorufin. The inhibitory activity of GPEs on nitrite-mediated N-nitrosation of dimethylamine and N-methylaniline appears to correlate significantly with the total polyphenolic contents. Furthermore, six individual polyphenols present in GPEs were quantitated by HPLC, wherein procyanidin B3 was a major constituent.