No abstract

Chemical relaxation experiments were conducted on sintered samples of calcium-doped lanthanum chromites by abruptly changing the oxygen partial pressure in the atmosphere and following the time change of conductivity. The re-equilibration kinetics was analyzed by fitting the relaxation data to the solutions of Fick's second law for appropriate boundary conditions. The diffusion equation ignoring the effect of surface reaction failed to describe the transient behavior especially for the initial stage, while that taking the surface effect into account gave a satisfactory interpretation of the overall relaxation process and allowed a precise determination of the two kinetic parameters: oxygen chemical diffusion coefficient and surface reaction rate constant. The chemical diffusion coefficients increased with a decrease of the oxygen partial pressure due to/he corresponding change in the concentration of the moving species. The activation energy was similar to that of oxygen vacancy diffusion coefficients in other monocrystalline perovskites, suggesting that the measured diffusion coefficients were attributable to lattice diffusion. The surface reaction rate constant increased with a decrease of the oxygen partial pressure similarly to the reported oxygen nonstoichiometry, which implies that the presence of oxygen vacancies plays an important role in the surface reaction kinetics.

We investigated the products of atomic oxygen reaction with ferrocene and nickelocene, comparing them with those of oxygen atom reaction with 1,3-cyclopentadiene. In the case of cyclopentadiene, important products were C4H6 isomers and in the case of metallocenes, vinylacetylene.

Electrical conductivity of calcium-doped lanthanum chromites, La,_xCaxCrO3_~, was determined as a function of composition, temperature, and oxygen partial pressure, Po,, to determine its defect structure and understand its redox behavior. The conductivity was independent of Po~ and was proportional to the dopant concentration at high Po.~. The activation energy of conductivity was 0.12 to 0.14 eV and the mobility was 0.066 to 0.075 cm~/V/s in the temperature range of 900 to 1050~ which was ascribable to small-polaron hopping. Under reducing conditions, the conductivity decreased ~1z4 relationship. A simple point-defect model, in exponentially with decreasing Po2 and asymptotically approached a -o2 which CaLa, h', and Vo" were assumed as predominating defect species, was proposed to elucidate the conductivity variation with Po~. The oxygen nonstoichiometry calculated based on the defect model was consistent with the reported thermogravimetric data, which verified the soundness of the model. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.194.20.173 Downloaded on 2015-02-03 to IP

Dedicated Short Range Communications (DSRC)-based communications enable novel automotive safety applications such as an Extended Electronic Brake Light or Intersection Collision Avoidance. These applications require reliable wireless communications even in scenarios with very high vehicle density, where these networks are primarily interference-limited. Given the uncertainties associated with current simulation models, particularly their interference models, it is critical to experimentally validate network performance for such scenarios.Towards this goal, we present a systematic, large-scale experimental study of packet delivery rates in a dense environment of 802.11 transmitters. We show that even with 100 transmitters in communication range with a frame size of 128 bytes and a bit-rate of 6Mbps, (a) most receivers can decode over 1500 pps in a saturated network, which corresponds to a packet delivery rate of 45% and (b) the mean packet delivery rate, for 10 pps per node workload that emulates vehicular safety applications, is about 95%. These results demonstrate that a COTS 802.11 implementation can correctly decode many packets under collision due to physical layer capture and can serve as a reference scenario for validation of network simulators.