Efficient and Reliable Cluster-Based Data Transmission for Vehicular Ad Hoc Networks

Vehicular ad hoc network (VANET) is an emerging technology for the future intelligent transportation systems (ITSs). The current researches are intensely focusing on the problems of routing protocol reliability and scalability across the urban VANETs. Vehicle clustering is testified to be a promising approach to improve routing reliability and scalability by grouping vehicles together to serve as the foundation for ITS applications. However, some prominent characteristics, like high mobility and uneven spatial distribution of vehicles, may affect the clustering performance. Therefore, how to establish and maintain stable clusters has become a challenging problem in VANETs. This paper proposes a link reliability-based clustering algorithm (LRCA) to provide efficient and reliable data transmission in VANETs. Before clustering, a novel link lifetime-based (LLT-based) neighbor sampling strategy is put forward to filter out the redundant unstable neighbors. The proposed clustering scheme mainly composes of three parts: cluster head selection, cluster formation, and cluster maintenance. Furthermore, we propose a routing protocol of LRCA to serve the infotainment applications in VANET. To make routing decisions appropriate, we nominate special nodes at intersections to evaluate the network condition by assigning weights to the road segments. Routes with the lowest weights are then selected as the optimal data forwarding paths. We evaluate clustering stability and routing performance of the proposed approach by comparing with some existing schemes. The extensive simulation results show that our approach outperforms in both cluster stability and data transmission

A novel thermal-insulating film incorporating microencapsulated phase-change materials for temperature regulation and nano-TiO2 for UV-blocking

Phase-change materials (PCMs) have promising applications in the fields of solar energy storage, energy conservation in buildings, thermal insulation, and thermal regulation. In this study, novel multifunctional composite films were prepared via a thermosetting process using poly(vinyl chloride) (PVC) as a film matrix, microencapsulated PCMs (micro-PCMs) as a temperature-regulating additive and TiO2 nanoparticles (nano-TiO2) as a UV-blocking additive. The latent heat of the film fabricated with 6 wt% micro-PCMs and 6 wt% nano-TiO2 is 9.226 J/g. The film also shows high thermal stability, with no obvious change in thermal performance after 100 heating-cooling cycles. The temperature of a space enclosed by the film fabricated with 6 wt% micro-PCMs and 6 wt% nano-TiO2 can be controlled in the range 25-28 degrees C for 3298 s. The composite films exhibit a significantly decreased UV transmittance due to the UV absorption of nano-TiO2. Furthermore, the thermal conductivity of the sample fabricated with 6 wt% micro-PCMs and 6 wt% nano-TiO2 is 0.2356 W/(m K), which is comparable with that of a pure PVC film. These findings indicate that the novel thermal-insulating film is promising for use in energy-efficient building and automobile applications. (C) 2015 Elsevier B.V. All rights reserved

Nitrogen-doped porous carbons with high performance for hydrogen storage

Hydrothermally carbonized chitosan has been successfully used as a carbon source for the preparation of highly porous carbons via chemical activation. The porous carbons with different nitrogen contents (0.56-6.53 wt%) have high surface area (1362-3009 m(2) g(-1)) and large pore volume (0.670-1.497 cm(3) g(-1)). These properties can be varied from modifying the activation parameters (i.e., amount of activation agent and activation temperature). We observed hydrogen storage capacity of up to 2.71 wt% at 77 K and 1 bar, and 6.77 wt% at 20 bar, for PC-2-800 porous carbons. This result indicates that the hydrogen uptake of porous carbons mainly depends on the high micropore surface area related to optimum pore size. Furthermore, one found that high N-doping is beneficial for hydrogen storage at low pressure but it is detrimental at high pressure according to the analysis of hydrogen uptake isotherms. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

Improvement on Hydrogen Desorption Performance of Calcium Borohydride Diammoniate Doped with Transition Metal Chlorides

Calcium borohydride diammoniate with a molecular formula of Ca(BH4)(2).2NH(3) is a novel complex hydride for hydrogen storage. However, it suffers from high temperature and sluggish kinetics for hydrogen desorption. In this work, the temperature and kinetics for hydrogen desorption of calcium borohydride diammoniate were effectively improved through doping transition metal chlorides (such as CoCl2, NiCl2, and FeCl3) in a closed vessel. Three additives could effectively decrease the temperature for hydrogen desorption of Ca(BH4)(2).2NH3. Among them, CoCl2-doped Ca(BH4)(2).2NH3 could desorb hydrogen even at a low temperature of 170 degrees C, and at 200 degrees C, 7.6 wt % hydrogen with high purity is released, which shows superior performance for hydrogen desorption than that of pristine Ca(BH4)(2).2NH(3.) For CoCl2-doped Ca(BH4)(2).2NH(3), X-ray absorption fine structure (XAFS) revealed that the improvements could be ascribed to the catalytic function of well-dispersed cobalt particles, which results in a much lower activation energy (86.1 kJ/mol) for hydrogen desorption of calcium borohydride diammoniate

Influence of Zr Addition on Structure and Performance of Rare Earth Mg-Based Alloys as Anodes in Ni/MH Battery

In this study, the substitution of Mg with Zr in La0.7Mg0.3(Ni0.85Co0.15)3.5 was carried out with the purpose of improving the electrochemical performances. The structural and hydrogen storage properties in both gas-solid reaction and the electrochemical system were systematically studied on La0.7(Mg0.3−xZrx)(Ni0.85Co0.15)3.5 (x = 0.05, 0.1, 0.2, 0.3) alloys. Each tested alloy is composed of LaNi3 phase, LaNi5 phase and ZrNi3 phase with different phase abundances. The electrochemical studies indicated that all Zr-substituted anodes possessed a much higher cycling capacity retention than pristine La0.7Mg0.3(Ni0.85Co0.15)3.5. However, the maximum discharge capacity was reduced with the increase of Zr content. The potential-step tests showed that the diffusion of hydrogen atoms inside the anodes was decelerated after the introduction of Zr