Kinetic study of chlorine behavior in the waste incineration process

The waste incineration atmosphere was simulated as HCl/H₂O/O₂/CO₂/N₂ in order to experimentally study chlorine behavior as temperature ranges from 1173 to 1473 K and residence time varies. The results show that Cl radicals, produced by the decomposition of HCl at high temperature, mainly recombine to form Cl₂ and HCl at the quenching section. It was found that temperature, residence time, cooling rate and feeding gas composition influence Cl₂ concentration. To thoroughly understand this reaction system, a kinetic model was developed and validated against experimental results. The key reactions and main pathway were found out with the use of sensitivity and rate of production analysis (ROP). The reaction HCl + O₂ → Cl + HO₂ was shown to initiate the reaction system, and it was found that a significant amount of Cl₂ was simultaneously produced by the following high temperature reaction: Cl + HOCl → Cl₂ + OH. In the cooling process, the main consumption reactions of Cl radicals were H₂O + Cl → HCl + OH, OH + Cl → HCl + O and Cl + Cl + M → Cl₂ + M. Among these, the first two reactions can be used to explain the effect of H₂O on the concentration of Cl radical at high temperature. In addition, the influence of the quenching rate on the distribution of chlorine was found to occur because of the varying effects that temperature change causes to the different Cl radical consumption reactions.     

A porous media theory for characterization of membrane blood oxygenation devices

A porous media theory has been proposed to characterize oxygen transport processes associated with membrane blood oxygenation devices. For the first time, a rigorous mathematical procedure based a volume averaging procedure has been presented to derive a complete set of the governing equations for the blood flow field and oxygen concentration field. As a first step towards a complete three-dimensional numerical analysis, one-dimensional steady case is considered to model typical membrane blood oxygenator scenarios, and to validate the derived equations. The relative magnitudes of oxygen transport terms are made clear, introducing a dimensionless parameter which measures the distance the oxygen gas travels to dissolve in the blood as compared with the blood dispersion length. This dimensionless number is found so large that the oxygen diffusion term can be neglected in most cases. A simple linear relationship between the blood flow rate and total oxygen transfer rate is found for oxygenators with sufficiently large membrane surface areas. Comparison of the one-dimensional analytic results and available experimental data reveals the soundness of the present analysis.     

Enhancement of high energy proton yield with a polystyrene-coated metal target driven by a high-intensity femtosecond laser

We present experimental results on protons accelerated up to 950 keV from a 3-μm thick tantalum foil with a 133-nm thick polystyrene layer on its rear surface, irradiated with a laser pulse having the duration of 70 fs and the intensity of 2.7×10¹⁸ W/cm². The energy distribution of fast protons was measured simultaneously with that of the hot-electrons from the rear surface. The proton yield from the polystyrene-coated target is about 10 times as high as that from the uncoated metal target. This enhancement of the proton yield is roughly proportional to the increase of hydrogen atoms given by the 133-nm thick polystyrene layer, assuming a contaminant layer of ∼10-nm thickness is on the metal surface without coating. This result shows that the polystyrene layer contributes to the yield enhancement. PACS 52.38.Kd; 52.50.Jm; 52.59.-f     

Surface enhanced Raman scattering of organic sample powders spread over vacuum-evaporated silver thin film

Surface enhanced Raman scattering (SERS) from samples prepared by spreading para-nitrobenzoic acid (PNBA) and adenosine powders over silver thin films was achieved. The SERS intensities of the ionized PNBA on the silver film increase with increased applied pressure through a cover-glass and reach a maximum at 0.6 MPa. In contrast, the signals caused by adenosine remain nearly unchanged under applied pressures of 0-0.6 MPa. Beyond 0.6 MPa, the signals attributable to samples decrease in intensity. Atomic force microprobe images reveal that nanometer-scale surface morphology is changed by 0.8 MPa pressure, suggesting that the decrease in SERS intensity is related to pressure-induced morphological changes. Results obtained in this study indicate that SERS spectra are obtainable easily, without solvents, under ambient conditions using dispersion of the sample powder.     

Noise-intensity fluctuation in Langevin model and its higher-order Fokker-Planck equation

In this paper, we investigate a Langevin model subjected to stochastic intensity noise (SIN), which incorporates temporal fluctuations in noise-intensity. We derive a higher-order Fokker-Planck equation (HFPE) of the system, taking into account the effect of SIN by the adiabatic elimination technique. Stationary distributions of the HFPE are calculated by using the perturbation expansion. We investigate the effect of SIN in three cases: (a) parabolic and quartic bistable potentials with additive noise, (b) a quartic potential with multiplicative noise, and (c) a stochastic gene expression model. We find that the existence of noise-intensity fluctuations induces an intriguing phenomenon of a bimodal-to-trimodal transition in probability distributions. These results are validated with Monte Carlo simulations.     

Surface Plasmon Resonance of Au Nanoparticles Fabricated by Negative Ion Implantation and Grid Structure toward Plasmonic Applications

Optical properties of Au nanoparticle composites and a grid structure of Cu nanoparticle composite were studied. Negative ion implantation was applied to synthesize Au and Cu nanoparticles in amorphous SiO₂ and Al₂O₃. Au nanoparticles were embedded within a depth of 30 nm by 60keV Au⁻ implantation. The surface plasmon resonance (SPR) of Au:SiO₂ and Au: Al₂O₃ composites shifted to red and to blue, respectively, compared to calculated ones by the Mie theory. Optical nonlinearity was measured with pump-probe femtosecond spectroscopy and the transient spectrum of Au: Al₂O₃ composite presented a large red shift from the SPR peak. Image mapping of far-field transmitted intensity of Cu-implanted SiO₂ with a fine grid structure drawn by laser-lithography was observed by a scanning near-field optical microscopy (SNOM) system.     

China ASON Network Migration Scenarios and Their Quantitative Analysis

This paper proposes two migration scenarios from China rin g networks to ASON mesh networks . In our quantitative analysis with ASON/GMPLS simulator, a subnetwork protection scheme achieved best balanced performance in resource utilization and restoration time.     

Optical precursors in coupled-resonator-induced transparency

We experimentally examined the propagation of temporally square modulated optical pulses through a coupled ring resonator. Sharp transient spikes appeared as the square pulses entered the system. The main signal gradually grew up through coupled-resonator-induced transparency (CRIT), with the time constant determined by a second resonator. Transient spikes were attributed to the higher and lower spectral components of the incident pulse, to which the resonators cannot respond; hence, they were interpreted as optical precursors. The experiments, therefore, demonstrated that precursors and the main signal can be observed separately, with amplitudes comparable to that of the incident step in CRIT.     

Spectral diffusion in nitride quantum dots: Emission energy dependent linewidths broadening via giant built‐in dipole moments

We present a study about the origin of the huge emission linewidths broadening commonly observed for wurtzite GaN/AlN quantum dots. Our analysis is based on a statistically significant number of quantum dot spectra measured by an automatized µ‐photoluminescence mapping system applying image recognition techniques. A clear decrease of the single quantum dot emission linewidths is observed with rising overall exciton emission energy. 8‐band k · p based model calculations predict a corresponding decrease of the built‐in exciton dipole moments with increasing emission energy in agreement with the measured behavior for the emission linewidths. Based on this proportionality we explain the particular susceptibility of nitride quantum dots to spectral diffusion causing the linewidth broadening via the linear quantum‐confined Stark effect. This is the first statistical analysis of emission linewidths that identifies the giant excitonic dipole moments as their origin and estimates the native defect‐induced electric field strength to ～2 MV/m. Our observation is in contrast to less‐polar quantum dot systems as e.g. arsenides that exhibit a naturally lower vulnerability to emission linewidth broadening due to almost negligible exciton dipole moments. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)