Asymptotic Expansions of the Heat Kernel of the Laplacian for General Annular Bounded Domains with Robin Boundary Conditions：Further Results

The asymptotic expansions of the trace of the heat kernel θ(t)=∑^∞v=1^exp(-tλv) for small positive t,where {λv} are the eigenvalues of the negative Laplacian -△n=-∑^ni=1(D/Dx^1)^2 in R^2(n=2 or 3),are studied for a general annular bounded domain Ω with a smooth inner boundary DΩ1 and a smooth outer boundary DΩ2,where a finite number of piecewise smooth Robin boundary conditions(D/Dnj γh)Ф=0 on the components Гj(j= 1,...,m) of (DΩ1 and on the components Гj (j=k 1,…,m) of of DΩ2 are considered such that DΩl=U^kj=lГj and DΩ2= U^m=k 1Гj and where the coefficients γj(j=1,...,m) are piecewise smooth positive functions. Some applications of θ(t) for an ideal gas enclosed in the general annular bounded domain Ω are given. Further results are also obtained.     

Metastable systems driven by colored noise: The stationary state

The influence of the Bardeen-Herring back-jump correlations on the Fermi-Dirac statistics of the one-dimensional nonhomogeneous fermionic lattice gas is studied by the Monte Carlo simulation technique and semianalytically. The resulting distribution is obtained, exhibiting increased population of the lower levels in comparison to the Fermi-Dirac statistics.     

A lattice gas model for thermohydrodynamics

The lattice gas model is extended to include a temperature variable in order to study thermohydrodynamics, the combination of fluid dynamics and heat transfer. The compressible Navier-Stokes equations are derived using a Chapman-Enskog expansion. Heat conduction and convection problems are investigated, including Bénard convection. It is shown that the usual rescaling procedure can be avoided by controlling the temperature.     

双电极对双脉冲激光器结构分析

本文对双电极对双脉冲激光器的谐振腔结构进行了分析,结果表明采用双非稳腔和增大反射镜的曲率半径可分别获得单纵模和基横模输出。为使输出能量稳定,则双电极对的间距有一最小值的限制。     

烧结烟气脱硫脱硝用活性炭混合钢渣复合材料的光谱学分析

钢渣是冶金工业中产生的主要固体废弃物,其产量约为每年粗钢产量的15%~20%。由于技术的局限,导致我国钢渣利用率较低,仅为年钢渣产量的10%,同时加之管理制度的不健全,导致钢渣大量露天堆放,对土地资源、地下水源,以及空气质量形成严重影响。固体废弃物再利用是资源可持续发展的重要途径之一,钢渣的主要化学成分为CaO, SiO2, Al2O3, MgO, Fe2O3, MnO, f-CaO等。面对上述问题,利用冶金固体废弃物与活性炭开发一种价格低廉且性能优越的活性炭混合钢渣复合材料,既是冶金固体废弃物的高附加值利用与资源可持续发展的重要途径之一,也是大幅降低改性活性炭生产成本与提高经济效益的重要途径之一。该研究创新性以活性炭与钢渣为研究对象,利用钢渣中含有的金属氧化物对活性炭进行改性处理制备用于烧结烟气脱硫脱硝的活性炭混合钢渣复合材料,通过搭建实验反应装置对活性炭混合钢渣复合材料的脱硫脱硝性能进行测试。利用X射线荧光光谱仪(XRF)对钢渣的化学成分进行测试与分析,比表面积及孔径测定仪(BET)对活性炭混合钢渣复合材料的孔结构进行测试与分析,傅里叶变换红外光谱仪(FTIR)对钢渣的结构组成进行测试与分析,扫描电子显微镜(SEM)对活性炭混合钢渣复合材料的微观结构进行测试与分析,以揭示活性炭与钢渣制备活性炭混合钢渣复合材料的机理,以及活性炭混合钢渣复合材料对烧结烟气脱硫脱硝的机理。结果表明:当钢渣为电炉热泼渣、钢渣与活性炭质量比为2∶4、钢渣与活性炭细度为400目时,活性炭混合钢渣复合材料具有良好的脱硫脱硝性能与合理的经济性,即脱硫效率为100%、脱硝效率为58%。活性炭混合钢渣复合材料具有的多孔结构对SO2和NO进行有作用,钢渣中Fe2O3与MnO2促使活性炭官能团进行催化还原反应提高脱硫脱硝性能,其中吸附作用是主导与前提,催化还原反应是辅助与协同。以期为高附加值的钢渣利用提供新途径,实现钢铁企业以废治废、以废增效的目的。     

强点火作用下C3HF7对甲烷-空气爆炸的抑制

为解决瓦斯输送过程中的爆炸安全问题,探索寻找绿色环保且阻火性能优越的新型抑爆剂,开展了当量比下甲烷-空气预混气体爆炸传播过程中的七氟丙烷抑爆效果研究。实验采用长径比L/D=108的水平管道爆炸特性测试系统,研究了在强点火作用下不同体积分数的七氟丙烷对9.5%甲烷-空气预混气体最大爆炸压力、最大压力上升速率和火焰传播速度的影响。实验结果显示:将2.5 m长的管段作为七氟丙烷抑爆区时,七氟丙烷阻断9.5%甲烷-空气预混气体爆炸火焰传播的最小体积分数为5%;当七氟丙烷的体积分数为1%~4%时,不仅无法阻断爆炸火焰的传播,而且与对照组相比,会使火焰传播速度加快;当七氟丙烷的体积分数为1%~6%时,爆炸源及管道末端处的爆炸压力峰值随着七氟丙烷体积分数的增加而逐渐减小;当七氟丙烷的体积分数为3%时,抑爆区处的爆炸压力峰值与对照组相比增幅为10.9%。     

Methane dissolution inside bulk or porous-medium-confined water at near-hydrate equilibrium conditions

In this study, we perform a series of mass-balance-type calculations, in order to estimate the minimum volume of liquid water required to dissolve completely a single methane gas bubble, located inside different types of domains that are near or under hydrate equilibrium pressure/temperature conditions. We examine the case of methane bubble dissolution in the bulk, along with the cases of methane bubble dissolution within simple/regular networks of pores, where all pores have the same size. In our calculations, we consider experimental values for the equilibrium solubilities of methane in water, along the hydrate-forming line, as well as, values obtained from predictive tools that are based on different thermodynamic models. The effect of aqueous NaCl solutions on the results is also investigated. As a result of the relatively low solubility of methane in water, large volumes of water are required for complete dissolution of a methane bubble.     

A rapid,spatially dispersive frequency comb spectrograph aimed at gas phase chemical reaction kinetics

This New Views article will highlight some recent advances in high sensitivity gas detection using direct infrared absorption frequency comb laser spectroscopy, with a focus on frequency comb use in chemical reaction kinetics and our own contribution to this field. Our recently implemented detection technique uses a combination of a 12.9?GHz free spectral range virtually imaged phased array and diffraction grating to spatially disperse the mid-infrared frequency comb onto a camera. Individual frequencies or ‘comb teeth’ of a 250?MHz repetition-rate frequency comb are able to be resolved. High molecular sensitivity is achieved by increasing the interaction path length using a Herriott multipass cell. High spectral resolution, broadband spectral coverage, and high molecular sensitivity are all achieved on an adjustable 1–50 µs timescale, making this frequency comb apparatus ideal for measuring chemical reaction kinetics where multiple absorbing species can be monitored simultaneously. This New Views article will also discuss some of the challenges and decisions that chemists might face in implementing this advanced physics technology in their own laboratory.

Spatially dispersed 250 MHz mid-infrared frequency comb laser, with absorption of some frequencies by a dilute sample of methane.     

可溶性离子对煅烧烟气脱硫石膏水化的影响

本文主要研究了不同水溶性离子对煅烧烟气脱硫石膏水化过程,也就是对大块煅烧石膏向石膏转化的相变过程的影响. 研究表明,在煅烧石膏向石膏转化的相变过程中,所有的阳离子都能加速煅烧石膏的水化作用,其中Ca²⁺的加速效应最弱. 对于最终沉淀得到的晶体,除了钠离子外,晶体尺寸不受不同种类盐的影响. 而在钠离子中,可以观察到长度大于130 μm的巨型结晶. 本研究阐明了不同离子对煅烧石膏水化的影响,为原始的烟气脱硫石膏在实际应用前的预处理提供了充分的指导.     

轮背空腔-密封气对CAES向心涡轮变工况流动损失的影响

本文以国内首套MW级压缩空气储能(CAES)系统末级向心涡轮为研究对象,通过数值模拟分析了变工况条件下轮背空腔-密封气对等熵效率和流场结构的影响.结果表明:在求解中考虑轮背空腔-密封气结构能够使等熵效率数值解的偏差减小0.7%;随涡轮进口压力增加,轮背空腔泄漏流由叶片吸力面中部叶高区域逐渐向轮毂转移,流动损失先增加后减小;合理降低轮背空腔泄漏气体的轴向速度,能够减弱轮背空腔-密封气结构对等熵效率的负面影响,使向心涡轮在较宽的变工况范围内都保持高效运行.