复合镁质添加剂对球团生产影响的试验分析

球团矿作为一种优质的高炉炼铁原料,其配比不断增加.试验采用复合镁质添加剂代替膨润土,提高球团矿中的MgO含量,考察其对生球质量和球团冶金性能的影响规律和作用机理.试验结果表明,采用复合镁质添加剂代替膨润土后,生球抗压强度略有降低,落下次数变化不大,爆裂温度均高于600℃;球团矿的低温还原粉化指数(RDI+3.15)变化...     

Improvement of Gold to Reducibility of La-Ce-Mn Catalyst under Lean Combustion

The effect of Au on the reducibility of La-Ce-Mn catalyst was studied in the synthetic exhaust gas mixture containing 10% oxygen. The characteristics of samples were analyzed by BET, SEM, XRD and activity evaluation. The resuits show that, in lean combustion, the performance of perovskite-type catalysts is evidently enhanced through adding Au, and specially a satisfying reducibility for NOx is demonstrated between 300～500℃. The catalytic activity of samples increases with the loading amount of Au, and the maximum conversion rate for NOx decomposition reaches up to 47% in 360～400℃. Moreover, the dispersivity and uniformity of the surface distribution of perovskite with Au have an important influence on the catalytic activity.     

Effect of calcination temperature on catalyst reducibility and hydrogenation reactivity in rice husk ash–alumina supported nickel systems

Nickel catalysts supported on rice husk ash–alumina (Ni/RHA–Al₂O₃) were prepared by an incipient wetness impregnation method. Characterization included TGA, DSC, TPR, XRD, and BET. Results show that the decomposition of the nickel compound to nickel oxide was complete above 500 °C. The TPR analysis revealed a strong interaction between nickel and support, and a decrease in reducibility of NiO with increasing calcination temperature. The XRD analysis of Ni/RHA–Al₂O₃ catalyst precursors demonstrated the presence of spinel. It also showed that the size of crystallites in the supported NiO first decreased with increase in calcination temperature up to 700 °C, and then increased due to phase transformation of nickel oxide to spinel. The pores are mesopores and their meshy surface structure was not affected by calcination temperature in the range investigated. The catalytic activity was tested by CO₂ hydrogenation with an H₂/CO₂ ratio of 4/1 at 500 °C. The CO₂ conversion and CH₄ yield for CO₂ hydrogenation over 15 wt% Ni/RHA–Al₂O₃ catalyst were almost independent of calcination and reduction temperatures. Copyright © 2004 Society of Chemical Industry     

Average Floquet factorisations in linear continuous-time periodic systems

The paper examines existence and properties about average Floquet factorisations, determined via average integration instead of matrix logarithms, for the transition matrices of finite-dimensional linear continuous-time periodic (FDLCP) systems. We talk about the following aspects about average Floquet factorisations: existence conditions, properties and relationships with the conventional Floquet factorisations. We reveal that average scaling and modelling may be incomplete or even incorrect for reflecting dynamics in general FDCLP systems, compared to the Floquet factorisations defined through matrix logarithms.     

Classification and characteristics of Floquet factorisations in linear continuous-time periodic systems

This article has two purposes. Firstly, the article is devoted to collecting basic facts about the Floquet theorem and various Floquet factorisation algorithms claimed for finite-dimensional linear continuous-time periodic (FDLCP) systems. Secondly, the article presents a unified representation framework for various Floquet factorisations in FDLCP systems, while structural and analytic characteristics about them are examined as well. More precisely, the following aspects are considered: (i) algorithms for Floquet factorisations; (ii) characteristics of Floquet factors; (iii) relationships and properties among Floquet factorisations. Most results are reported for the first time, while the others are generalised versions of existing ones.     

Undecidability in Some Structures Related to Computation Theory

We show that many of the so called discrete weak semilatticesconsidered earlier in a series of author's publications havehereditary undecidable first-order theories. Since such structuresappear naturally in some parts of computation theory, we obtainseveral new undecidability results. This applies e.g. to thestructures of complete numberings, of m-degrees of index setsand of the Wadge degrees of k-partitions in the Baire spaceand -algebraic domains. Whenever possible, we try to determinealso the exact degrees of undecidability of the theories underdiscussion.     

CeO2改性对CuO/SBA-15催化剂结构及其催化活性的影响

采用浸渍法在Ce-SBA-15载体上负载活性组分CuO,制备一系列不同配比的CuO/Ce-SBA-15催化剂,运用XRD、TEM、N2吸附、TPR、CO-IR等手段考察催化剂CuO/Ce-SBA-15的物理化学性质,并对其进行CO氧化催化活性的测试。活性测试结果表明,CeO2对SBA-15载体的改性有效地提高了CuO/SBA-15催化剂在CO氧化反应中的催化活性。XRD结果表明:CeO2对SBA-15载体的改性可以促进氧化铜在载体表面的分散;进一步结合H2-TPR、CO-IR表征结果,CeO2促进了CuO在载体表面的还原,这些都有利于催化活性的提高。     

Enumeration Order Equivalence in Rational Numbers

The enumeration of elements of c.e. sets in the theory of computability and computational complexity has already been investigated. However, the order of this enumeration has received less attention. The enumeration orders of elements of c.e. sets by means of Turing machines on natural numbers are investigated. In this paper, we consider the enumeration orders of elements of c.e. sets on rational numbers. We present enumeration order reducibility and enumeration order equivalence on rational numbers and propose some lemmas and theorems on these concepts. Also, we show that the theories here hold for Rc and we could repeat the same theories in this domain, in a same way.     

Observations on complete sets between linear time and polynomial time

There is a single set that is complete for a variety of nondeterministic time complexity classes with respect to related versions of m-reducibility. This observation immediately leads to transfer results for determinism versus nondeterminism solutions. Also, an upward transfer of collapses of certain oracle hierarchies, built analogously to the polynomial-time or the linear-time hierarchies, can be shown by means of uniformly constructed sets that are complete for related levels of all these hierarchies. A similar result holds for difference hierarchies over nondeterministic complexity classes. Finally, we give an oracle set relative to which the nondeterministic classes coincide with the deterministic ones, for several sets of time bounds, and we prove that the strictness of the tape-number hierarchy for deterministic linear-time Turing machines does not relativize.     

广义严格对角占优矩阵的一组新判据

广义严格对角占优矩阵在科学和工程实际中有广泛的应用,因此研究这类矩阵的判定问题是非常重要的．本文利用细分区域的思想给出了判定广义严格对角占优矩阵的几个新条件,推广和改进了已有的结果,并通过数值算例说明了这些条件的有效性．