Priority based efficient data scheduling technique for VANETs

As vehicular networks are gaining popularity, large number of vehicles want to take advantage of these networks, by utilizing the information they have, in order to take decision. Vehicle receives data from other vehicles or from the road side units (RSUs) available across the road. Since RSUs act as router to connect with the external world as well as it is a high capacity storage place where important data (e.g. data used in traffic safety, location dependent query, etc.) can be stored for download purpose for other vehicles moving through the service area. Since the RSUs have limited communication range and vehicles usually moves at very high speed in the service area, they have limited time to serve data to vehicles moving in the service area. For this purpose RSUs have to schedule data in such a way that maximum vehicles can get benefit from the data available with the RSUs. There are many algorithms proposed in the past to schedule data at RSUs. This paper proposes a mechanism to schedule data of those vehicles which are in the coverage range of the RSU. The proposed algorithm outperforms to serve requests whose deadline is about to expire i.e. vehicles which have left the service area after forwarding request to RSU. This scheme performs well in dense network and has good results in highway scenario.     

The Effect of Nanoparticle Morphology on the Measurement Accuracy of Mobility Particle Sizers

The influence of particle morphology on the accuracy of nanoparticle size distributions measured by the engine exhaust particle sizer spectrometer (EEPS, TSI Model 3090) was studied using the scanning mobility particle sizer (SMPS, TSI Model 3936) as a reference. The EEPS shows higher total number concentrations with the maximum relative difference up to 67 % and smaller number median mobility diameters for polydisperse silver nanoparticles generated in the laboratory. To provide a quantitative explanation of the difference, generated polydisperse nanoparticles were classified as monodisperse particles with the initial equivalent mobility diameter (d _m1) and sintered in the second furnace at different temperatures (room temperature to 600 °C), to change their morphologies for the comparison tests. Without sintering (room temperature), results show that the measured mobility diameter (d _m2) of the EEPS is smaller than that measured by the SMPS when d _m1 is larger than 30 nm and the difference increases as d _m1 is increased from 30 to 300 nm. But the difference decreases as the morphology of particles is changed from branched chain agglomerates to spheres for d _m1 less than 80 nm and the sintering temperature higher than 200 °C. Theoretical analysis shows that the mean charge per agglomerates is more than that of spheres resulting in overestimation of the electrical mobility and underestimation of the d _m2 by the EEPS.     

Effect of UV irradiation on PC membrane and use of Pd nanoparticles with/without PVP for H2 selectivity enhancement over CO2 and N2 gases

The hydrogen-based economy is one of the possible approaches toward to eliminate the problem of global warming, which are increases because of the gathering of greenhouse gases. Palladium (Pd) is well-known material having a strong affinity to the hydrogen absorbing property and thus appropriate material to embed in the membrane for the improvement of selective permeation of hydrogen gas. In present work, we have functionalized polycarbonate (PC) membranes with the help of UV irradiation to embed the Pd nanoparticles in pores as well as on the surface of the PC membrane. Use of Pd Nanoparticles is helpful to enhance the H₂ selectivity over other gases (CO₂, N_2, etc.). Also, the UV based modification of membrane increases the attachment of Pd Nanoparticles. Further to enhance the Pd nanoparticles attachment, we used PVP binder with Pd nanoparticles solution. Gas permeability measurements of functionalized PC membranes have been carried out, and better selectivity of hydrogen has been found in the functionalized and Pd nanoparticle binded membrane. PC membrane with 48 h UV irradiated and Pd NPs with PVP have been found to have maximum selectivity and permeability for H₂ gas. All the samples being characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy and UV–Vis spectroscopy for their morphological and structural investigation.     

Iron molybdates as electrocatalysts for O2 evolution reaction in alkaline solutions

Iron molybdates with [Mo]/[Fe] ratios 1.0, 1.5 and 3.0 have been prepared by a co-precipitation method and produced in the form of thin films on a Ni support. These oxides follow the monoclinic crystal geometry. The study shows that the new oxide is highly active towards the oxygen evolution reaction in alkaline solutions and that its activity seems to depend upon the molar ratio of Mo and Fe in the oxide. The oxide with [Mo]/[Fe] = 1.0 is observed to exhibit the greatest electrocatalytic activity. The reaction order with respect to OH⁻ concentration has been found to be fractional (0.8–1.6). The Tafel slopes at low potentials were close to 35 mV.     

Design framework for dimethyl ether (DME) production from coal and biomass-derived syngas via simulation approach

A comprehensive thermodynamic study was conducted to evaluate the comparative efficacy of methanol and dimethyl ether (DME) synthesis using CO₂ rich syngas feed. The first part of our study included assessing the relative performances of the methanol synthesis system, two step DME synthesis system, and one step DME synthesis system in terms of the CO_x conversion and product yield (methanol/DME) based on the Gibbs free energy minimization approach. The wide range of composition of CO₂-enriched syngas feed produced by the coal and biomass gasification was simulated using Aspen Plus and the following evaluation parameters were analyzed for a broad parameter range: reaction temperature (180–280°C), reaction pressure (10–80 bar), stoichiometry number (SN) (0–11), and CO₂/(CO₂ + CO) molar feed ratio (0–1) for isothermal as well as adiabatic conditions. Based on the equilibrium yield, one-step DME synthesis was discovered as the most viable process to utilize the co-gasification derived syngas effectively. In the second part of our study, the overall process efficiency was inspected through the process design of 1 tonnes per day (TPD) DME plant inclusive of heat integration, resulting in significant CO₂ abatement and DME production with high product purity and minimum energy consumption. Consequently, one-step DME production via CO₂-enriched syngas obtained through the coal or biomass gasification process is identified as the leading technology based on energy utilization and CO₂ abatement.     

Stability analysis between two concentric rotating cylinders with heat and mass transfer

The stability of the liquid/vapor interface between two concentric revolving cylinders is examined. The transfer of heat/mass is allowed at the interface. Both the cylinders rotate with different angular velocities. The fluids inside the annular region are taken as incompressible and viscous. The theory of viscous potential flow analysis is used to add the viscous effects. The normal mode technique is used to calculate the growth of perturbations. If we rotate the inner cylinder, it is seen that asymmetric disturbances have a destabilizing character at the interface but the rotation of the outer cylinder has a stabilizing effect. We found that an asymmetric disturbance destabilizes the interface if the inner cylinder rotates. It is found that the arrangement gets destabilized on rotating of the inner cylinder but rotation of the outer cylinder induces stability, and the most stable case is found when the inner cylinder is stationary and the outer cylinder is rotating.     

Effect of sinusoidal cylindrical surface of PCM on melting performance

Journal of Mechanical Science and Technology - A numerical analysis was conducted to examine the effect of capsule shape on phase change material (PCM) melting speed. The surface parameters of the...     

Design of Fresnel lens with spherical facets for concentrated solar power applications

In this paper, a ray-tracing model is developed using MATLAB based on mathematical formulations used in the design of Fresnel lens with spherical facets. Further, a design chart for Fresnel lens with spherical facets is developed to determine aperture radius and design angle for a given focal length and focus size. Concentration ratio and spherical aberration for Fresnel lens with spherical facets are also compared with those of plano-convex lens and conventional Fresnel lens with triangular facets. Furthermore, the present mathematical model is validated with SolTrace model and with the experimental study conducted on a prototype of Fresnel lens with spherical facets fabricated using CO₂ laser cutting machine. Focal length for the proposed Fresnel lens with spherical facets is found to be the same. However, concentration ratio computed from the present ray-tracing model is in fair agreement with SolTrace model and experimental data with percentage deviations at focal length 5.4% and 12.4%, respectively.     

Optimal Sensing and Transmission of Energy Efficient Cognitive Radio Networks

Wireless Personal Communications - The issue of spectrum scarcity can be alleviated by the cognitive radio technology with efficient spectrum sensing and allocation of free spectrum bands....