Photoinduced Anisotropy in Poly(Methyl Methacrylate)/Sudan Red III Thin Films

The dynamic behavior of photoinduced optical anisotropy of amorphous PMMA/Sudan Red III thin films has been investigated using the pump-probe method. The results showed that the anisotropy increased rapidly in an exponential fashion in the first seconds of pumping, so that a photostationary state was reached as a result of the photoisomerization process cycles. The anisotropy relaxation phase decreased exponentially in a slow manner, which means the anisotropy did not disappear instantaneously when the irradiation was switched off. Evidence of the existence of the Angular Hole Burning (AHB) and the Angular Redistribution (AR) effects in the Sudan Red III molecules in the PMMA polymeric host is presented. The relative photoinduced optical anisotropy was calculated. The results showed that, at room temperature, the thermal isotropic relaxation of the photoisomer was negligible compared to the anisotropic reverse photoisomerization that occurred as soon as the pump beam was cut-off.     

Laminar and turbulent burning velocities of propane in spherical vessels

Laminar and turbulent burning velocities of C₃H₈/air mixtures under moderately elevated temperature and pressure conditions have been determined experimentally using spherical combustion bombs. The results are reported here and the effects of temperature, pressure, turbulence intensity and stoichiometric ratio are included. The results obtained are compared with those of other researchers. The laminar burning velocity obtained from the pressure-time curves without compensation for the reaction zone thickness is lower than those determined using burners. A reaction zone thickness correction which reduces the difference is suggested and this relies on an assessment based on the different histories found experimentally when different initial temperatures were used for the isentrope through the standard state. For mixtures with initially low turbulence levels, both the turbulent burning velocity and the burning velocity ratio, turbulent to laminar, increase as the combustion progresses. The rate of increase becomes larger with increase in the initial and instantaneous turbulence intensity, temperature and stoichiometric ratio. Deviation from the Damköhler relationship is noted.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

A simplified method for levoglucosan quantification in wintertime atmospheric particulate matter by high performance anion-exchange chromatography coupled with pulsed amperometric detection

Levoglucosan, a tracer for the assessment of the biomass burning contribution to atmospheric particulate matter (PM) concentrations, was determined by means of high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD). In this work we propose a modification in the instrumental set-up aiming at an improvement in the detector response by adding NaOH after chromatographic separation to increase the pH. The comparison between this technique and the gas chromatography/mass spectrometry (GC/MS) method commonly used showed good agreement. Repeatability is 4.8% RSD, limits of detection for pevoglucosan, mannosan and galactosan are in the range 0.001–0.002 µg mL^?1 in solution, corresponding to 3–4 ng m^?3 for 24 m³ of air sampled. PM10 samples were characterised for levoglucosan and for organic and elemental carbon contents. The preliminary results reported here for five sites in the Lombardy region (Northern Italy) are, as far as we know, the first data on levoglucosan contribution to OC in Italy. The levoglucosan concentrations observed in Lombardy vary in the range 173–963 ng m^?3 with an average levoglucosan-C to OC ratio ranging from 1.5% to 2.5%.     

Impact of rice crop residue burning on levels of SPM,SO2 and NO2 in the ambient air of Patiala (India)

Ground-based ambient air monitoring was conducted at five different locations in and around Patiala city (29°49′–30°47′N Latitude, 75°58′–76°54′E Longitude) in Northern India in order to determine the impact of open burning of rice (Oriza sativa) crop residues on concentration levels of suspended particulate matter (SPM), sulphur dioxide (SO₂) and nitrogen dioxide (NO₂). Covering sensitive, residential, agricultural, commercial and urban areas, sampling of these pollutants was organised during August 2006 to January 2007 and August 2007 to January 2008 casing two rice crop residue burning periods (October–November) using a high volume sampling technique combined with gaseous sampling systems. Gravimetric analysis was used in the estimation of total suspended particulate matter (TSPM) whereas SO₂ and NO₂ concentration was determined using spectrophotometer (Specord205, Analytikjena). Monthly average concentrations of SPM, SO₂ and NO₂ have shown significant up and down features at all the selected sampling sites during the study period. Monthly average concentrations (24 hour) of SPM, SO₂ and NO₂ varied from 100 ± 11 µg m^?3 to 547 ± 152 µg m^?3, 5 ± 4 µg m^?3 to 55 ± 34 µg m^?3 and 9 ± 5 µg m^?3 to 91 ± 39 µg m^?3. Substantially higher concentrations were recorded at the commercial area site as compared to the other sampling sites for all the targeted air pollutants. Levels of SPM, SO₂ and NO₂ showed clear increase during the burning months (October–November) incorporated with the effect of meteorological parameters especially wind direction, precipitation and atmospheric temperature.     

富燃料丙烷/空气预混火焰特性的微重力实验研究

地面常重力(1g)条件下,丙烷/空气预混火焰向上传播的富燃极限为9.2%C_3H_8,而向下传播时的富燃极限仅为6.3%C_3H_8,二者之间存在明显差距。利用微重力条件下的实验,对燃料浓度从6.5%到8.6%(微重力实验中测定的可燃极限)范围内的丙烷/空气预混火焰特性进行了研究。实验发现,重力对近极限丙烷/空气火焰的传播有显著影响,影响程度随着当量比的增加而增大。微重力下丙烷/空气的富燃极限为8.6%C_3H_8(φ=2.24),明显高于1g条件下向下传播火焰的可燃极限,略低于向上传播火焰的可燃极限。随着当量比的增大,根据压力变化曲线计算的火焰层流燃烧速度从8.5cm/s逐渐减小到2.7 cm/s,可燃极限处的层流燃烧速度与前人实验数据一致。     

频域中固体多重光谱烧孔研究

报道固体选通光谱多重光谱烧孔研究的新进展，分析影响多生烧孔形成的一些主要因素，首次报道了在有机材料ＺｎｔｂＰ／ＣＡ／ＰｈＲ的非均匀加宽线内获得一次连续烧出１００多光谱孔的结果，还进一步报道用穿带激光获得更窄线宽的光谱烧孔的情况。     

BaSO4Sm^2＋晶体的光谱及光子选通烧孔效应

首次报道—种新的无机光子造通光谱烧孔材料——BaSO_4:Sm~ (2+)的烧孔效应.并给出了有关光谱性质的实验结果.     

Zone conditional analysis of a freely propagating one-dimensional turbulent premixed flame

The zone conditional conservation equations are derived and validated against the DNS data of a freely propagating one-dimensional turbulent premixed flame. Conditional flow velocities are calculated by the conditional continuity and momentum equations, and a modeled transport equation for the Reynolds average reaction progress variable. An asymptotic formula for turbulent burning velocity is obtained with the effects of a finite Damköhler number accounted for as an additional factor. It is shown that flame generated turbulence is primarily due to correlations between fluctuating gas velocities and fluctuating unit normal vector on a flame surface. More investigation is required to validate general predictive capability of the derived conditional conservation equations and the relationships modeled for closure.     

堆芯等离子体燃烧和控制

本工作描述我们编制的零维三流体粒子和功率平衡的等离子体动力学时关模拟程序。在物理上我们把等离子体动力学与新经典轮运理论结果结合起来,通过辅助加热、燃料粒子注入速率和纵场纹波控制堆芯等离子体燃烧。数值结果表明,通过控制完全可以实现堆芯等离子体的稳定燃烧和排灰要求。