A Light Weight Secure Communication Scheme for Wireless Sensor Networks

Wireless Personal Communications - The majority of security systems for wireless sensor networks are based on symmetric encryption. The main open issue for these approaches concerns the...     

Cesium salt of a heteropolyacid in nanotubular channels and on the external surface of SBA-15 crystals: preparation and performance as acidic catalysts

The Cs-salt of heteropolyacid with stoichiometry Cs_2.5H_0.5PW₁₂O₄₀ (CsHPW) was deposited selectively at the external surface of the SBA-15 silica microcrystals, inside its mesoporous channels and simultaneously at both location modes. The structure, texture and performance of these CsHPW/SBA-15 composites were compared with that of a reference bulk salt of the same composition. Location of CsHPW salt on the external surface of SBA-15 microcrystals leads to disintegration of its agglomerates increasing acidity of the catalytic phase. A novel preparation strategy consisting of grafting the basic Cs-species at the internal pores surface of SBA-15 stabilized the CsHPW phase inside the channels in form of 5–8 nm nanocrystals at 30–70 wt.% loadings. The catalytic tests demonstrated that insertion of the CsHPW catalytic phase inside the nanotubular channels of SBA-15 in combination with location of an additional amount of this phase at the external surface of SBA-15 microcrystals allows to increase the specific activity of this phase in MTBE synthesis, propionylation of anisole and alkylation of catechol with t-butanol by a factor of 1.5–3. This level of specific activity in combination with high total loading of catalytic phase >60 wt.% permit to get composite catalytic materials with catalytic activity higher by a factor of 1.2–1.5 with respect to the bulk CsHPW catalyst and stabilizing the catalytic phase against colloidization in polar media.     

Extraction of anthocyanins from red cabbage and purification using adsorption

There is an increasing interest in anthocyanins, as natural food colorants, in food products and also in pharmaceutical products due to their antioxidative potential. The present study deals with extraction and purification of anthocyanins from red cabbage. Conventional extraction methods of anthocyanin from plant material are non-selective and yield pigment solutions with large amounts of byproducts such as sugars, organic acids and proteins. Some of these impurities may accelerate anthocyanin degradation. Different extracting media were used and the mixture of 50% (v/v) ethanol and acidified water resulted in maximum anthocyanin content (390.6 mg/L). In order to obtain anthocyanins in a purified form, adsorption was carried out with six different adsorbents. Among these, non-ionic acrylic ester adsorbent, namely Amberlite XAD-7HP, showed the highest adsorption capacity (0.84 mg/mL of resin) and desorption ratio (92.85%). Adsorption results were found to be correlated best using the Langmuir isotherm equation especially at low temperature. The resulting anthocyanin solution after purification was free from sugars, which are the major cause for degradation of anthocyanin. No browning was observed and chroma increased by 27% compared to crude anthocyanin.     

Design and analysis of low power high-speed 1-bit full adder cells for VLSI applications

This paper presents a low power and high speed two hybrid 1-bit full adder cells employing both pass transistor and transmission gate logics. These designs aim to minimise power dissipation and reduce transistor count while at the same time reducing the propagation delay. The proposed full adder circuits utilise 16 and 14 transistors to achieve a compact circuit design. For 1.2 V supply voltage at 0.18-μm CMOS technology, the power consumption is 4.266 μW was found to be extremely low with lower propagation delay 214.65 ps and power-delay product (PDP) of 0.9156 fJ by the deliberate use of CMOS inverters and strong transmission gates. The results of the simulation illustrate the superiority of the newly designed 1-bit adder circuits against the reported conservative adder structures in terms of power, delay, power delay product (PDP) and a transistor count. The implementation of 8-bit ripple carry adder in view of proposed full adders are finally verified and was observed to be working efficiently with only 1.411 ns delay. The performance of the proposed circuits was examined using Mentor Graphics Schematic Composer at 1.2 V single ended supply voltage and the model parameters of a TSMC 0.18-μm CMOS.     

Microstructure and residual stress distribution of similar and dissimilar electron beam welds – Maraging steel to medium alloy medium carbon steel

The influence of parent metal heat treatment condition on the residual stress distribution in dissimilar metal welds of maraging steel to quenched and tempered medium alloy medium carbon steel has been investigated. It has been observed that the residual stress distribution would be more compressive if the maraging steel is in soft condition. This is attributed to stress absorbing nature of highly yielding soft maraging steel.     

Synthesis and biological activity of novel thiazolidinediones

Novel compounds having a dual pharmacophore were synthesised and evaluated for their insulin sensitiser and anti-inflammatory properties in different animal models.     

Friction stir welding of thick section reduced activation ferritic–martensitic steel

Full penetration friction stir welding was conducted on 12?mm thick reduced activation ferritic–martensitic steel at tool rotational speeds of 500 and 900?rev?min^?1. Comparator welds at 500?rev?min^?1 were also produced in 6?mm thick reduced activation ferritic–martensitic steel plate to evaluate section thickness effects. Increase in section thickness led to an increase in heat input, which strongly influenced the microstructure evolution in stir zone (SZ), thermo-mechanical affected zone and the overall hardness in the SZ of this steel. In the as-welded condition, the base metal microstructure was significantly altered and resulted in carbide-free grain boundaries. The desirable microstructure and mechanical properties were achieved by subjecting the as-welded joints to appropriate post-weld heat treatments.     

An exact method for determining local solid fractions in discrete element method simulations

A novel solid fraction algorithm is presented which accounts for the partial volume of a sphere straddling cuboidal bin boundaries. The algorithm accounts for spheres intersecting a single plane (face), two perpendicular planes (edge), or three perpendicular planes (corner). Comparisons are made against the more common algorithm in which the solid fraction is determined by assigning the sphere's total volume to the bin in which the sphere's center of volume (COV) is located. Bin size‐to‐sphere diameter ratios >30 must be used to give errors <5% when using the traditional method when applied to simple cubic (SC) and hexagonal packing assemblies. Bin size‐to‐sphere diameter ratios larger than five are required for random sphere packings. Although time averaged solid fraction measurements are similar using either the exact or COV solid fraction schemes, the scatter in the COV method is much larger than for the exact method. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Microstructure and Mechanical Properties of Friction Stir Lap Welded Aluminum Alloy AA2014

Friction stir lap welds were produced in 3 mm thick Alclad sheets of Al alloy 2014-T4 using two different tools (with triangular and threaded taper cylindrical pins). The effects of tool geometry on weld microstructure, lap-shear performance and failure mode were investigated. The pin profile was found to significantly influence the hook geometry, which in turn strongly influenced the joint strength and the failure mode. Welds produced in alloy 2014-T4 Alclad sheets by using triangular and threaded taper cylindrical tools exhibited an average lap-shear failure load of 16.5 and 19.5 kN, respectively, while the average failure load for standard riveted joints was only 3.4 kN. Welds produced in alloy 2014-T6 Alclad sheets and in alloy 2014-T4 bare sheets (i.e., no Alclad) were comparatively evaluated with those produced in alloy 2014-T4 Alclad sheets. While the welds made (with threaded taper cylindrical tool) in T6 and T4 conditions showed very similar lap-shear failure loads, the joint efficiency of the welds made in T6 condition (43%) was considerably lower (because of the higher base material strength) than those made in T4 condition (51%). The Alclad layers were found to present no special problems in friction stir lap welding. Welds made with triangular tool in alloy 2014-T4 Alclad and bare sheets showed very similar lap-shear failure loads. The present work provides some useful insights into the use of friction stir welding for joining Al alloys in lap configuration.