C颗粒对Cp/AZ91D复合材料铸态显微组织的影响

通过复合铸造工艺制备了C_p/AZ91D复合材料，研究了C颗粒含量和保温时间等参数对该复合材料显微组织和力学性能的影响。结果表明，与保温时间相比，C_p的晶粒细化作用更为显著。当添加C_p质量分数为1.5%，保温时间15 min时，C_p/AZ91D复合材料铸锭平均晶粒尺寸由176 μm降低至32 μm，组织整体细化均匀，增强相C颗粒在复合材料基体中均匀分布，并且硬度值最高，达到89.07 HV。     

某电厂主蒸汽管道SA335P91制造质量分析

本文通过对电厂SA335P91主蒸汽管道的现场检验和试验室取样综合分析,指出该批管道由于制造加工或热处理过程控制不当,导致管道内、外壁表面及近表面出现块状铁素体,金相组织异常,表面硬度值偏低.     

A test case for time-dependent density functional theory calculations of electronic circular dichroism: 2-chloro-4-methoxy-6- [(R)-1-phenylethylamino]-1,3,5- triazine

The three-dimensional structure of an optically active substituted s-triazine derivative, 2-chloro-4-methoxy-6-[(R)-1-phenylethylamino]-1,3,5-triazine, has been studied by conformational analysis using density functional theory (DFT) both in vacuo and in acetonitrile solution in the polarizable continuum model integral equation formalism framework. Time-dependent DFT methods have been used to investigate the molecular electronic CD and absorption UV spectra. Comparison with experimental results allowed the reliability of the theoretical predictions to be enhanced and suggested a possible interpretation of the measured data. Electronic Supplementary Material The online version of this article doi:contains supplementary material, which is available to authorized users.     

Bounds for Asian basket options

In this paper we propose pricing bounds for European-style discrete arithmetic Asian basket options in a Black and Scholes framework. We start from methods used for basket options and Asian options. First, we use the general approach for deriving upper and lower bounds for stop-loss premia of sums of non-independent random variables as in Kaas et al. [Upper and lower bounds for sums of random variables, Insurance Math. Econom. 27 (2000) 151–168] or Dhaene et al. [The concept of comonotonicity in actuarial science and finance: theory, Insurance Math. Econom. 31(1) (2002) 3–33]. We generalize the methods in Deelstra et al. [Pricing of arithmetic basket options by conditioning, Insurance Math. Econom. 34 (2004) 55–57] and Vanmaele et al. [Bounds for the price of discrete sampled arithmetic Asian options, J. Comput. Appl. Math. 185(1) (2006) 51–90]. Afterwards we show how to derive an analytical closed-form expression for a lower bound in the non-comonotonic case. Finally, we derive upper bounds for Asian basket options by applying techniques as in Thompson [Fast narrow bounds on the value of Asian options, Working Paper, University of Cambridge, 1999] and Lord [Partially exact and bounded approximations for arithmetic Asian options, J. Comput. Finance 10 (2) (2006) 1–52]. Numerical results are included and on the basis of our numerical tests, we explain which method we recommend depending on moneyness and time-to-maturity.     

F91与12Cr1MoV异种钢焊接工艺研究

介绍了电厂2×600 MW超临界火电机组锅炉二级减温水管道设计中的F91和12 Cr1MoV的焊接工艺.本文从生产实际出发,分析了该异种钢的焊接性,从焊接材料、工艺参数、焊接规范等几个方面对F91/12Cr1MoV异种钢接头的焊接工艺进行了深入研究,使用结果表明该焊接工艺规范合理、质量控制方法切实可行.     

Local times of ranked continuous semimartingales

Given a finite collection of continuous semimartingales, we derive a semimartingale decomposition of the corresponding ranked (order-statistics) processes. We apply the decomposition to extend the theory of equity portfolios generated by ranked market weights to the case where the stock values admit triple points.     

Representable topologies and locally connected spaces

The objective of this paper is to study certain order-theoretic properties of locally connected topologies. In the main theorem we prove that the assertion that a locally connected topology which satisfies the countable chain condition has the continuous representability property is undecidable in ZFC set theory. Some related problems and generalizations are also included.     

Real, complex and quaternionic equivariant vector fields on spheres

The equivariant real, complex and quaternionic vector fields on spheres problem is reduced to a question about the equivariant J-groups of the projective spaces. As an application of this reduction, we give a generalization of the results of Namboodiri [U. Namboodiri, Equivariant vector fields on spheres, Trans. Amer. Math. Soc. 278 (2) (1983) 431-460], on equivariant real vector fields, and Önder [T. Önder, Equivariant cross sections of complex Stiefel manifolds, Topology Appl. 109 (2001) 107-125], on equivariant complex vector fields, which avoids the restriction that the representation containing the sphere has enough orbit types.     

A singular control model with application to the goodwill problem

We consider a stochastic system whose uncontrolled state dynamics are modelled by a general one-dimensional Itô diffusion. The control effort that can be applied to this system takes the form that is associated with the so-called monotone follower problem of singular stochastic control. The control problem that we address aims at maximising a performance criterion that rewards high values of the utility derived from the system’s controlled state but penalises any expenditure of control effort. This problem has been motivated by applications such as the so-called goodwill problem in which the system’s state is used to represent the image that a product has in a market, while control expenditure is associated with raising the product’s image, e.g., through advertising. We obtain the solution to the optimisation problem that we consider in a closed analytic form under rather general assumptions. Also, our analysis establishes a number of results that are concerned with analytic as well as probabilistic expressions for the first derivative of the solution to a second-order linear non-homogeneous ordinary differential equation. These results have independent interest and can potentially be of use to the solution of other one-dimensional stochastic control problems.     

C颗粒对Cp /AZ91D复合材料铸态显微组织的影响

通过复合铸造工艺制备了C_p/AZ91D复合材料，研究了C颗粒含量和保温时间等参数对该复合材料显微组织和力学性能的影响。结果表明，与保温时间相比，C_p的晶粒细化作用更为显著。当添加C_p质量分数为1.5%，保温时间15 min时，C_p/AZ91D复合材料铸锭平均晶粒尺寸由176 μm降低至32 μm，组织整体细化均匀，增强相C颗粒在复合材料基体中均匀分布，并且硬度值最高，达到89.07 HV。