NH3-SCR of NO at low temperatures over sulphated vanadia on carbon-coated monoliths: Effect of H2O and SO2 traces in the gas feed

The objective of this research is to asses the impact of the addition of H₂O, SO₂, and both in the SCR of NO at low temperatures over sulphated vanadia on carbon-coated monoliths. The sulphated catalyst keeps a 100% conversion and total selectivity to N₂ in the low temperature range, i.e. 473–500 K, when either H₂O or SO₂ is added to the gas feed. However, a decline of steady state conversion and selectivity occurs when both H₂O and SO₂ are added simultaneously because H₂O speeds up the deposition of ammonium sulphate salts. This decrease of catalyst performance is reversed when the reaction is carried out under dry conditions at temperatures higher than 473 K but not at lower temperature (453 K). Thus, the catalyst has demonstrated to be a good candidate for the SCR of NO at low temperatures even in stack gases containing traces of undesired components.     

随机排列纤维过滤器颗粒捕集特性的数值研究

结合Matlab软件和数值计算前处理软件Gambit中的Journal文件建立了随机排列纤维过滤器模型,利用计算流体动力学(CFD)技术对4种随机排列纤维过滤器内部气-固两相流动特性进行数值研究,并将数值计算值和经典模型及实验关联式进行了比较。结果表明:利用论文提出的建模方法可以得到与实际纤维过滤器相似的模型。过滤器压力损失的数值计算预测值和实验关联式吻合较好,误差均在2%以内。不同结构过滤器收集效率的数值计算结果和理论模型的趋势基本一致,且不同粒径范围的颗粒收集机理也不同。对于小粒径颗粒(dp0.5μm),主要由布朗扩散起作用,dp1.5μm时,惯性碰撞贡献较大,当0.5μm≤dp≤1.5μm时,2种机理作用都较弱。另外,纤维直径和纤维填充密度分布会影响纤维过滤器的过滤性能,论文中,结构1(纤维直径和填充密度沿气流方向减小)的过滤器和结构3(纤维直径和填充密度沿气流方向增加)的收集效率高于结构2(在气流方向上纤维直径减小而填充密度增大)和4(在气流方向上纤维直径增大而填充密度减小),而压力损失则恰恰相反。结构1在大颗粒的收集上好于结构3,对于小颗粒则正好相反。结构4对于所有类型的颗粒的收集都要好于结构2。     

不饱和聚酯/海泡石纳米复合材料的制备及表征

以独特的松解方法对海泡石原矿进行分散,然后采用季胺盐对其进行有机改性处理,最后将有机海泡石纤维均匀分散到不饱和聚酯中,加入引发剂、促进剂和交联剂,使不饱和聚酯交联制得纳米复合材料。用SEM,FT-IR对复合体系的分散效果进行了分析和表征,并用差热分析方法对其热稳定性能进行了研究。结果表明,海泡石纤维以纳米级水平均匀分散在不饱和聚酯中,纳米复合材料的热分解温度也有所提高。     

Ultra‐High Pyridinic N‐Doped Porous Carbon Monolith Enabling High‐Capacity K‐Ion Battery Anodes for Both Half‐Cell and Full‐Cell Applications

An ultrahigh pyridinic N‐content‐doped porous carbon monolith is reported, and the content of pyridinic N reaches up to 10.1% in overall material (53.4 ± 0.9% out of 18.9 ± 0.4% N content), being higher than most of previously reported N‐doping carbonaceous materials, which exhibit greatly improved electrochemical performance for potassium storage, especially in term of the high reversible capacity. Remarkably, the pyridinic N‐doped porous carbon monolith (PNCM) electrode exhibits high initial charge capacity of 487 mAh g^?1 at a current density of 20 mA g^?1, which is one of the highest reversible capacities among all carbonaceous anodes for K‐ion batteries. Moreover, the K‐ion full cell is successfully assembled, demonstrating a high practical energy density of 153.5 Wh kg^?1. These results make PNCM promising for practical application in energy storage devices and encourage more investigations on a similar potassium storage system.     

无机胶凝成型活性炭的制备及性能研究

用水泥熟料作胶凝剂,探讨粉末活性炭的成型及性能。通过引入硅微粉与采取蒸压养护措施提高材料强度、缩短制备周期;用扫描电子显微镜(SEM)观察微观形貌,用抗压强度、碘吸附值、气孔率、吸水率、含炭量等指标评价试样的综合性能。研究结果表明,将70%(质量分数)活性炭粉末、25%(质量分数)水泥熟料粉末与5%(质量分数)硅微粉充分混合均匀后,造粒、成型,在195℃蒸压釜中养护6h,可制得性能良好的无机胶凝成型活性炭材料;试样的物理性能:碘吸附值为551.72mg/g,抗压强度为7.25MPa,炭含量为58.48%,气孔率为57.34%,吸水率为69.42%。     

Trilobal Polyimide Fiber Insulation for Cryogenic Applications

Recent measurements have shown a record-breaking low thermal conductivity λ_total of less than 0.25 × 10⁻³ W·m⁻¹·K⁻¹ at temperatures of 120 K for an evacuated sample consisting of polyimide fibers with a trilobal fiber cross section. Existing models for the heat transport in fiber insulations cannot sufficiently describe fiber insulations consisting of fibers with non-cylindrical cross sections. In this article, a modification for the model for cylindrical fibers will be presented. The modifications for the trilobal cross section of the fiber will be explained and compared to the original cylindrical model. The results of the theoretical calculations will be discussed in comparison to experimental results of measurements performed with a guarded hot-plate apparatus at temperatures in the range from 120 K to 420 K.     

Two analytical models for the study of periodic fibrous elastic composite with different unit cells

In this work, the effective elastic moduli of two-phase fibrous periodic composites are obtained by means of the Asymptotic Homogenization Method (AHM) and eigenfunction expansion-variational method (EEVM), for different types of parallelogram cells. The constituents exhibit transversely isotropic properties. A doubly periodic parallelogram array of cylindrical inclusions under longitudinal shear is considered. The behavior of the shear elastic coefficient for different geometry arrays of the cell related to the angle of the fibers is studied. Some numerical examples and comparisons with other theoretical results demonstrate that both methods (AHM and EEVM) are efficients for the analysis of composites with presence of rhombic cell. The effect of the configuration of the cells on the shear effective property is observed.     

Accelerated colorimetric immunosensing using surface-modified porous monoliths and gold nanoparticles

Abstract

A rapid and sensitive immunoassay platform integrating polymerized monoliths and gold nanoparticles (AuNPs) has been developed. The porous monoliths are photopolymerized in situ within a silica capillary and serve as solid support for high-mass transport and high-density capture antibody immobilization to create a shorter diffusion length for antibody–antigen interactions, resulting in a rapid assay and low reagent consumption. AuNPs are modified with detection antibodies and are utilized as signals for colorimetric immunoassays without the need for enzyme, substrate and sophisticated equipment for quantitative measurements. This platform has been verified by performing a human IgG sandwich immunoassay with a detection limit of 0.1 ng ml^?1. In addition, a single assay can be completed in 1 h, which is more efficient than traditional immunoassays that require several hours to complete.     

Micromechanical modeling of load transfer in fibrous composites

A unified analytical treatment is presented for the study of micromechanical stress distribution in unidirectional fibrous composites loaded with various thermal and mechanical loads. Two models are considered to represent the composite. Both use a concentric cylindrical system with the difference that one requires laterally free while the other requires laterally constrained outer boundaries, broadly describing situations of plane stress and plane strain, respectively. The present work has been motivated by the recent work of McCartney (McCartney, Proc. Roy. Soc. London, Ser. A 425 (1989) 215–244) who analyzed the laterally free system, and by our previous work (Nayfeh, Fibre Sci. Technol. 10 (1977)) in which we analyzed the laterally constrained one. For axisymmetric loading, and upon adopting some appropriate restrictions on the radial behavior of some field quantities, an elasticity-based procedure reduces the two-dimensional field equations, which hold in both the fiber and matrix components, together with the appropriate interface and boundary conditions, to a quasi-one-dimensional system. The resulting system is capable of identifying the stress distribution in each component as influenced by the other component via the readily identifiable interaction (transfer) terms. The model is general and applicable to a large variety of situations. These include situations of matrix cracking, fiber break and even regions of slip at the fiber–matrix interface. As a by-product, the model was capable of obtaining the classical Lamé solutions (the iso-strain case) as a degenerate case. Confidence in the modeling was gained when it identically reproduced all of the numerical examples presented by McCartney. Numerical results that parallel some of the ones presented by McCartney are included in the form of comparisons between results obtained based upon the laterally constrained and the laterally free systems.