一种典型钒钛系SCR催化剂SO3生成特性研究

选择性催化还原（SCR）技术由于脱硝效率高、选择性好而被广泛应用于烟气氮氧化物排放控制;然而,目前广泛采用的钒钛系SCR脱硝催化剂会使烟气中SO₂氧化成SO₃,烟气中过高的SO₃对电厂安全运行会造成严重影响,也会对环境造成污染。以典型V₂O₅-WO₃/TiO₂催化剂为研究对象,系统研究了SCR脱硝过程中烟气流量、温度、O₂浓度、SO₂浓度等对催化剂表面SO₃生成特性的影响,并进一步对SO₃生成的反应动力学特性进行了分析。研究表明：催化剂表面SO₃生成反应中SO₂的反应级数为0.59,当O₂浓度大于3%时,O₂的反应级数为0,该反应的表观活化能为70.39 kJ/mol;实验条件下,烟气中SO₂浓度增加会使SO₃生成的反应速率提高;O₂浓度对催化剂表面SO₃生成影响并不显著;烟气温度对催化剂表面SO₃生成具有显著影响,高温会促进SO₃的生成。     

基于CO2稀释的旋流无焰燃烧理论判别方法

基于温度判据和时间判据,本文建立了考虑旋流入口条件和CO₂稀释的无焰燃烧理论判别方法并进行验证,进而讨论了结构参数和操作参数对燃烧模式和火焰稳定性的影响。模型预测的旋流无焰燃烧临界氧浓度与文献中实验数据相比,最大相对误差不超过8%。降低氧浓度、减小当量比或提高入口流量时,温度判据1变化不大,而时间判据更易满足,因此有利于实现无焰燃烧;低旋流数条件下,无焰燃烧稳定性较差。增大燃烧室高度时,温度判据1更易满足,而时间判据更难满足,温度判据1分界线下移更快,有利于形成无焰燃烧;减小燃烧室截面积时,温度判据1变化不大,而时间判据更易满足,有利于实现无焰燃烧;增大燃烧器出口面积时,温度判据1和时间判据均更难满足,且时间判据分界线下移更快,不利于形成无焰燃烧。     

硫酸盐干湿循环作用下CFRP-黏土砖界面粘结性能退化规律分析

碳纤维增强复合材料(CFRP)与黏土砖界面的粘结性能是外贴CFRP加固技术的关键,为了解CFRP-黏土砖界面粘结性能在硫酸盐侵蚀下的退化规律,对硫酸盐干湿循环不同周期下的加固试件进行了单面剪切试验,结果表明：硫酸盐侵蚀对CFRP片材与浸渍胶性能影响并不明显,但对CFRP-黏土砖界面粘结性能影响较大,CFRP-黏土砖界面剪应力、承载力均随循环次数呈先小幅上升后明显下降的趋势;在试验基础上,根据已有的理论,提出硫酸盐干湿循环作用下CFRP-黏土砖界面粘结-滑移模型,通过与试验值对比分析发现,模型能够很好地反映CFRP-黏土砖界面的粘结性能退化规律。基于ABAQUS软件,利用内聚力本构关系模型对界面力学行为进行数值模拟,结果表明,内聚力模型可以很好地模拟界面的非线性力学行为,数值模拟值与试验值吻合较好。     

Microstructural characterization of rapidly solidified Al-Ta alloys

Two Al-rich Al-Ta alloys containing by weight 3 and 6 pct Ta have been rapidly solidified from the melt using the ‘gun’ technique. The microstructures and the crystal structures of the phases in the as-solidified as well as those formed on subsequent decomposition of the supersaturated solid solution have been characterized. A supersaturated solid solution was obtained in both the alloys in the as-solidified condition indicating a solid solubility extension of Ta in Al to almost 6 wt pct. The supersaturated solid solutions formed in both the alloys have been found to be quite stable up to 673 K (for 1 hour). Annealing at higher temperatures resulted in the formation of rod-shaped precipitates inside the grains and massive precipitates along grain boundaries. The rod-shaped precipitates arranged in a regular pattern constitute a new metastable intermediate phase Al₇Ta having an ordered structure. The massive precipitates which form along grain boundaries constitute the equilibrium Al₃Ta phase with a tetragonal crystal structure. The transformation behavior and the morphology of the transformation products are detailed in this paper.     

Thermodynamic Analysis of Ag_3Ge Phase Formation

In the present work a thermodynamic model is presented for the nucleation of metastable Ag3Ge phase from the undercooled melt in Ag-Ge alloy system. It is shown that under kinetically induced favourable condition, nucleation of a single phase compound with an approximate stoichiometry Ag3Ge has greater affinity for nucleation over Ag and Ge based phases requiring diffusion in the liquid.     

Transformations in a Ti-24Al- 15Nb alloy: Part II. a composition invariant βo → O transformation

This article explores the nature of a composition invariant phase transformation fromβ _o(B2, Ti₂AlNb) to an orthorhombic O phase (Cmcm) on aging aβ quenched Ti-24Al-15Nb alloy. The transformation product is shown to contain a variety of defect structures whose origins are analyzed and explained. The orthorhombic phase is shown in exist in two forms: (1) in which the Nb atoms occupy a specific sublattice and (2) in which the Nb and Ti atoms randomly occupy the same sublattice. The subsequent decomposition of the metastable O product into the equilibrium phases is also described.     

Preparation of 3-dimentional skeletal polymer via control of reaction-induced phase separation in epoxy/poly(ethylene glycol) blends

Summary  In order to prepare 3D skeletal polymer with low cross-linking density and high hydrophilicity bisphenol A epoxy was cured with diethylenetriamine in the PEG1000/PEG2000 mixing medium. The reaction-induced phase separation of this system was controlled by changing the weight ratio of PEG1000 and PEG2000. The morphology observation of the resulted polymers showed that the connectivity of epoxy phase strongly depended on the content of PEG2000 and was also influenced by the curing temperature. A 3D skeletal polymer with well-controlled macro-through-pores was prepared by using a mixture of PEG1000 and PEG2000 in 7/1 weight ratio as reaction medium and porogen. A unique light-filtrating effect was found in the prepared 3D skeletal polymer that filled with high refractive liquids. The effect most likely resulted from a total reflection mechanism of light in 3D macro-through-pores.     

Spinodal decomposition of a Co-Ti-Nb alloy

The microstructural evolution on aging a Co-3 wt pct Ti-2 wt pct Nb alloy has been followed by transmission electron microscopy and diffraction to show that the solid solution decomposed by the spinodal mode. The strengthening observed has been correlated with the differences in lattice parameters of the coexisting phases. The several stages of coarsening have been documented to yield information about their kinetics and morphological changes. Formerly Visiting Assistant Professor, Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, IL 61801, is with .     

Estimation of complex concentration in a regular associated solution

Novel procedures have been developed to estimate the concentration ofA _pB –type clusters in liquid alloys with the aid of regular associated solution model utilizing activity coefficients of the components at infinite dilution and activity data at any one other composition. The equilibrium constant for the dissociation of clusters as well as the nature and magnitude of pairwise interaction energies between unassociated atoms and clusters have been evaluated without making any assumptions whatsoever. These enable estimation of thermodynamic properties of the liquid alloys at any other desired composition. The utility of the procedures has been demonstrated with respect to the thermodynamics of association in molten Mg-Sn and In-Sb alloys. The calculated activities, enthalpies and free energies are shown to be in excellent agreement with experimental values.     

High-dose methotrexate with "RESCUE" plus cyclophosphamide as initial chemotherapy in ovarian adenocarcinoma. A randomized trial with observations on the influence of C parvum immunotherapy

In a prospective randomized study, the chemotherapeutic combination of high-dose methotrexate-citrovorum factor rescue plus cyclophosphamide (MECY) has been shown to be statistically significantly superior to the combination of 5-fluorouracil plus cyclophosphamide (FUCY) in the treatment of Stage III-IV ovarian adenocarcinoma. With MECY, an overall objective remission rate of 67% and a complete remission rate of 48% were achieved. All patients had undergone no treatment except for surgery. In addition to the chemotherapy, patients were randomly allocated to receive or not receive nonspecific immunotherapy with Corynebacterium parvum; this immunotherapy had no apparent effect on the chemotherapeutic response. The study demonstrates a high degree of activity for the MECY regimen, and a comparison between the results with MECY in this study and melphalan in an earlier prospective randomized study provides statistical evidence favoring MECY over single-agent melphalan in the treatment of this disease.