Secure CLS and CL-AS schemes designed for VANETs

The Journal of Supercomputing - Vehicular Ad hoc Network (VANET) is a part of intelligent transport system facing the problem of limited bandwidth. Certificateless aggregate signature (CL-AS)...     

Trajectory Tracking Control with Heterogeneous Input Delay in Multi-Agent System

In this paper we present a protocol to track a general trajectory for a multi-agent system in the presence of heterogeneous constant finite input delays. We consider two different multi-agent cases: agents with single-integrator and double-integrator dynamics. For the single-integrator case, we assume that the velocity along the desired trajectory is known to all agents for all time. Similar assumption is made only for the acceleration along the desired trajectory for the double-integrator case. It is assumed that at least one agent has the complete information about the desired trajectory for all time. The tracking strategy comprises of a consensus-based estimator and a simple independent tracking controller for each agent in the system. Only the state estimates are exchanged among the agents. The communication graph for the multi-agent system along with the desired trajectory has a rooted directed spanning tree with the desired trajectory being the root. The proposed tracking strategy ensures asymptotic convergence of the multi-agent system. The controller and estimator gains do not depend on the edge weights of the graph. The chosen controller gains of individual agent are bounded by their respective input delays. We present a particular form of control gains in order to achieve a desired possible exponential convergence rate and maximize the upper bound of the convergence rate for these selective gains. Finally, we present simulation results to substantiate the effectiveness of the proposed methodology. Comparison of the proposed strategy with the existing work in the literature show a better performance.     

Intelligent Physical Layer Secure Relay Selection for Wireless Cooperative Networks with Multiple Eavesdroppers

Wireless Personal Communications - The modern and emerging wireless communication technologies are benefiting from relaying techniques, which is already adopted in long term evolution (LTE) Release...     

Wear and friction characteristics of atmospheric plasma sprayed Cr3C2–NiCr coatings

ABSTRACT

The present work focuses on investigating the wear and friction characteristics of the Atmospheric Plasma Sprayed Cr₃C₂-NiCr coatings deposited onto the surface of die steel material. The as-sprayed specimens were characterized. The coating porosity, bond strength and microhardness values were evaluated. Wear tests were performed on the high-temperature pin-on-disc tribometer at room temperatures, 400°C and 800°C under two loads as 25N and 50N in the laboratory. The wear mechanisms of all the worn-out samples were studied by scanning electron microscopy (SEM) technique. The specific wear rates and the coefficient of friction values were analyzed. The developed coating showed better wear resistance than its uncoated counterpart. The coefficient of friction values for coated specimens decreased at elevated temperatures. At room temperatures, the wear mode was observed to be adhesive and further at elevated temperatures of testing, the wear mode was observed to be the combination of oxidative, adhesive and abrasive.     

Does the length of the short chain branch affect the mechanical properties of linear low density polyethylenes? An investigation based on films of copolymers of ethylene/1-butene, ethylene/1-hexene and ethylene/1-octene synthesized by a single site metallocene catalyst

Three nearly identical linear low density polyethylene resins based on copolymers of ethylene with 1-butene (B), 1-hexene (H) and 1-octene (O) were utilized to investigate the effect of short chain branch length on the mechanical properties of blown and compression molded (quenched and slow cooled) films. The content of short chain comononer in the three copolymers was ca. 2.5-2.9 mol% that corresponded to a density of 0.917-0.918 g/cm³. Within a given series, the tensile properties of these films do not show any significant difference at slow deformation rates (up to 510 mm/min), even though the DSC and TREF profiles of ‘H’ and ‘O’ differed slightly in comparison to ‘B’. However, at higher deformation rates (ca. 1 m/s), the breaking strength of these films was found to increase with increasing short chain branch length. In addition, the Spencer impact and Elmendorf tear strength of the blown films were also observed to increase with increasing short chain branch length. Further, dart impact strength and high-speed puncture resistance (5.1 m/s) of 1-octene and 1-hexene based samples was also observed to be higher than that based on 1-butene. The blown films displayed low and comparable levels of equivalent in-plane birefringence and crystalline orientation by wide angle X-ray scattering. This confirms that the differences in mechanical properties in the blown film series are not attributable to differences in molecular orientation. The deformation behavior of both the compression molded and blown films were also investigated in a well-defined controlled regime by analyzing their essential work of fracture. It was found that the essential work of fracture of films based on 1-hexene and 1-octene was higher than that of films based on 1-butene. While the origin of these differences in mechanical properties with increasing short chain branch length is not fully understood, the present investigation confirms this effect to be pronounced at high deformation rates for both the blown and compression molded quenched films.     

Demand sensing in e-business

In this paper, we identify various models from the optimization and econometrics literature that can potentially help sense customer demand in the e-business era. While modelling reality is a difficult task, many of these models come close to modelling the customer's decision-making process. We provide a brief overview of these techniques, interspersing the discussion occasionally with a tutorial introduction of the underlying concepts.     

Synthesis of nanocomposite gold-semiconductor materials by seed-growth method

Gold-semiconductor nanocomposite hybrid materials were synthesized by applying the seed-growth approach. Citrate stabilized gold nanoparticles were prepared by the reduction of HAuCl₄ with borohydride and used as seeds. The structural and morphological features of semiconductor materials i.e. CdS, CuS, NiS, and PbS in the presence of Au NP were examined with the help of UV-Visible spectroscopy, phase contrast microscopy, transmission electron microscopy (TEM) and X-ray diffraction measurements. The experimental results revealed that a network of semiconductor-Au NP nanocomposite material is formed in each case.     

Extended Release of Theophylline Through Sodium Alginate Hydrogel Beads: Effect of Glycerol on Entrapment Efficiency,Drug Release

Theophylline is the most useful bronchodilators for the treatment of severe reversible bronchospasm. The fluctuations of serum theophylline level in clinical practice and associated central nervous system side effects necessitate the development of an extended release formulation. In the present study, theophylline-loaded beads were prepared by extruding the dispersion of theophylline, sodium alginate, and glycerol into the cationic crosslinking solution of calcium chloride. The effect of the addition of glycerol was determined by entrapment efficiency, drug release, and morphology of beads. Absence of chemical interaction between drug, polymer, and counterions after production of beads was confirmed by Fourier transform infrared spectroscopy. Theophylline entrapment of up to 72% was achieved in beads with almost spherical shape and size ranging from 0.67 to 1.12 mm. Percentage entrapment of theophylline found to be more and release was extended up to the eleventh hour from the glycerol containing sodium alginate beads. Hence, sodium alginate glycerol beads could represent a promising oral drug delivery system to extend the release of theophylline.     

Low Thermal Conductivity and High Thermoelectric Performance in In<Subscript>4</Subscript>Se<Subscript>3−<Emphasis Type="Italic">x</Emphasis></Subscript> with Phase-Separated Indium Inclusions

We report the thermoelectric properties of undoped hot-pressed In₄Se_3?x (x = 0.05). Stoichiometric imbalance due to selenium deficiency in In₄Se₃ was found to create a secondary phase of elemental indium in the host material. Heat treatment drove grain growth and increased the indium solubility in In₄Se₃. Indium-rich domains at grain surfaces/boundaries in untreated samples were found to redistribute inside the grains and their junctions after heat treatment. Due to enhanced phonon scattering by secondary phase of indium, very low values of thermal conductivity were observed for all samples, leading to a maximum thermoelectric figure of merit (zT) of 1.13 at 723 K along the hot-pressing direction for the heat-treated sample.     

On the decision fusion for cooperative spectrum sensing in cognitive radio networks

Cooperation among different cognitive radios is used to enhance the sensing performance by exploiting the multiuser diversity. Soft and Hard decision fusion schemes are usually employed at the fusion center to detect the presence or absence of primary user. Soft decision fusion schemes perform better than hard fusion schemes but at the cost of increased bandwidth burden on the control channel. In this context, we propose a semi-soft fusion scheme to achieve a tradeoff between sensing performance and bandwidth cost. Under this scheme, each cognitive radio makes a local decision and sends one or two-bit data to the fusion center based on the observed test statistics. On the basis of received data, fusion center estimates the global test statistics which are then compared to a predetermined threshold to make the final decision. Furthermore, a closed form expression for average bandwidth cost for the proposed scheme is also derived. MATLAB simulation demonstrates that the performance of the proposed semi-soft fusion approaches to that of soft fusion scheme with a remarkable reduction in the bandwidth cost of control channel.