2W/nm Peak-power All-Fiber Supercontinuum Source and its Application to the Characterization of Periodically Poled Nonlinear Crystals

We demonstrate a uniform high spectral brightness and peak power density all-fiber supercontinuum source. The source consists of a nanosecond Ytterbium fiber laser and an optimal length PCF producing a continuum with a peak power density of 2 W/nm and less than 5 dB of spectral variation between 590 to 1500 nm. The Watt level per nm peak power density enables the use of such sources for the characterization of nonlinear materials. Application of the source is demonstrated with the characterization of several periodically poled crystals.Comment: 8 pages 4 figures v2 includes revisions to the description of the continuum formatio

The Kentucky Noisy Monte Carlo Algorithm for Wilson Dynamical Fermions

We develop an implementation for a recently proposed Noisy Monte Carlo approach to the simulation of lattice QCD with dynamical fermions by incorporating the full fermion determinant directly. Our algorithm uses a quenched gauge field update with a shifted gauge coupling to minimize fluctuations in the trace log of the Wilson Dirac matrix. The details of tuning the gauge coupling shift as well as results for the distribution of noisy estimators in our implementation are given. We present data for some basic observables from the noisy method, as well as acceptance rate information and discuss potential autocorrelation and sign violation effects. Both the results and the efficiency of the algorithm are compared against those of Hybrid Monte Carlo. PACS Numbers: 12.38.Gc, 11.15.Ha, 02.70.Uu Keywords: Noisy Monte Carlo, Lattice QCD, Determinant, Finite Density, QCDSPComment: 30 pages, 6 figure

Low temperature oxidation of biphenyl in an alumina reactor: Possible initiation by O2 (1Δ)

Oxidation of biphenyl (as a prototype model compound for polychlorinated biphenyls) in an alumina reactor at 490°C yields the initial products dibenzofuran and benzaldehyde which have been confirmed in GC/MS studies. It is postulated that 0 2 O2 (1Δ) whose formation is catalysed by the reactor surfaces, initiates the reaction at this low temperature. Quantum chemical computations of the reaction potential energy surfaces suggest low energy pathways to the observed initial products

Controlling NOx emission from post-blast process gases

This study investigates effect of the pH on nitric oxides (NOx) removal. A spray tower has been used to study the absorption of nitrogen oxides in both acidic and alkaline solution of sodium chlorite (NaClO2). Sodium chlorite was used as an oxidant in order to oxidise NO to NO2, which is highly soluble in aqueous phase. NO was oxidized to NO2 followed by NO2- and ClO2 to ClO2- in liquid phase respectively. The latter was found to be reduced to Cl- and ClO- . Varying pH of the solution form acidic and alkaline phases, pH (4-12), which is influential in the efficiency of NOx removal, was studied. According to the experiments carried out in this study, alkaline medium was found to be more reliable than acidic one, and 100% NO with 86% NOx removal was observed in ambient conditions. The main reason is attributed to hydrolysis of N2O4 in higher pH (basic). Experimental results demonstrate the feasibility of the aqueous solution of sodium chlorite for NOx removal

Comparative study on the formation of toxic species from 4-chlorobiphenyl in fires: Effect of catalytic surfaces

This contribution compares the formation of toxic species, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) and their precursors such as polychlorobenzenes (PCBz) and polychlorophenols (PCP), during oxidation of 4-chlorobiphenyl (4-CB) in a laboratory-scale apparatus, under conditions similar to those that occur in fires and waste combustion. The experiments were conducted using two gas flow reactors made of 99.5% alumina and high purity quartz, respectively. A sampling system intercepted the gaseous products leaving the reactors, trapping the volatile organic compounds (VOC; i.e., PCBz and PCP) and PCDD/F on a XAD-2 cartridge. The analysis of VOC involved high resolution gas chromatography (HRGC) – quadrupole mass spectrometry (QMS) while HRGC – ion trap (IT) MS/MS quantitated the PCDD/F produced. For the experiments using the alumina reactor, VOC analysis revealed the formation of PCBz and PCP, commencing at temperatures as low as 400 °C. Other products included benzaldehyde, naphthalene, 3- ethylbenzaldehyde, 1-chloro-4-ethynylbenzene and benzofuran. Gaseous species such as CO, CO2 and HCl were detected and quantitated either by Fourier transform infra-red spectroscopy (FTIR) or ion chromatography (IC). Similar products were found to form in the quartz reactor, however, their formation commenced at 500 °C, with their yields significantly lower than those found for the alumina reactor. The present measurements indicate that surface reactions govern the oxidation of 4-CB between 300 and 650 °C for the alumina reactor, and between 450 and 600 °C for the quartz reactor. At 700 °C, both reactors operate similarly, with the oxidation process dominated by the gas phase reactions. With respect to dibenzo-p-dioxins and dibenzofurans, only isomers of chlorinated monochlorodibenzofuran (MCDF) and chlorinated dichlorodibenzofuran (DCDF) were found at low temperatures (300 to 450 °C), with 3-MCDF as the dominant congener. In our system, they appear to form in gas phase reactions involving 4-CB and singlet oxygen (1Δg O2), the latter generated on the reactor walls. The present results indicate that the combustion of 4-CB in fires will be dominated by catalytic surfaces of fly ash below 600 °C, and by gas-phase kinetics above 700 °C