Analytical study of surface and bulk oxidation of Astroloy

Nickel-base alloys, such as Astroloy, used for aeronautical turbine disks, are sensitive to time-dependent cracking in environments containing oxygen. The q155364980607100/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">mosaicq155364980607100/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> structure of the alloy consisting q155364980607100/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">q155364980607100/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0"> islands (200 nm average size) surrounded by the q155364980607100/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-phase (100 nm thick) induces complex oxidation phenomena. Various analytical approaches allow the delineation of all the steps from segregation to oxidation occurring on the surface of such a duplex structure. The protection of Astroloy by its outer oxide layer against oxygen penetration was studied also, using alternative ¹⁶O₂ then ¹⁸O₂ oxidation. In association with STEM studies, it is shown that the outer oxide scale is not a real barrier against oxygen penetration and that inner precipitation of chronium (+ aluminium and titanium)-enriched oxides, takes place especially in the q155364980607100/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0"> structure.     

On numerical solution of arbitrary symmetric linear systems by approximate orthogonalization

A very important class of inverse problems are those modelled by integral equations of the first kind. These equations are usually ill-conditioned, such that any discretization technique will produce an ill-conditioned system, in classical or least-squares formulation. For such kind of symmetric problems, we propose in this paper a stable iterative solver based on an approximate orthogonalization algorithm introduced by Z. Kovarik. We prove convergence of our algorithm for general symmetric least-squares problems and present some numerical experiments ilustrating its good behaviour on problems concerned with the determination of charge distribution generating a given electric field and gravity surveying, both modelled by first kind integral equations.     

A mathematical programming approach to a problem in variance penalised Markov decision processes

In this paper we present three algorithms for solving a problem in which it is required to get an optimal compromise between the average expected reward per unit time and the variance of the reward per unit time. The algorithms lead to anq56221tx02/xxlarge603.gif" alt="epsiv" align="BASELINE" BORDER="0">-optimal solution, whereq56221tx02/xxlarge603.gif" alt="epsiv" align="BASELINE" BORDER="0">>0 is arbitrary.quote>     

On several concepts for ɛ-efficiency

We introduce two new concepts for?-efficiency and investigate these and some known concepts under the following aspects: (1) What are the relationships between the efficient and the?-efficient point set? (2) If the sequence (v ^?) of?-efficient points converges forε → 0, is the limit efficient, or weakly efficient? (3) Can the distance between the?-efficient and the efficient point set be estimated in terms ofε?     

一种新型的BoD带宽请求分配算法

BoD协议中 可以 通过充分利用按需分配后剩余的带宽来降低时延。首先针对如何高效地利用剩余带宽及其对反馈控制的影响,提出了一种新型的基于预测和星上反馈控制的BoD带宽请求分配算法。其次根据网络流量同时呈现长相关和短相关特性,提出采用ARFIMA(p,d,q)模型进行流量建模与预测,该模型根据参数d的取值不同既能表示长相关又能表示短相关。最后利用OPNET软件建立仿真系统。仿真结果表明,对于长相关和短相关业务流,基于ARFIMA(p,d,q)模型预测和星上反馈控制的BoD带宽请求分配方案能够最高效地利用剩余带宽来降低时延。     

Tuples of Disjoint $\mathsf{NP}$ -Sets

Disjoint q/224_2007_9023_Article_IEq2.gif" alt="$\mathsf{NP}$" align="middle" border="0"> -pairs are a well studied complexity-theoretic concept with important applications in cryptography and propositional proof complexity. In this paper we introduce a natural generalization of the notion of disjoint q/224_2007_9023_Article_IEq3.gif" alt="$\mathsf{NP}$" align="middle" border="0"> -pairs to disjoint k-tuples of q/224_2007_9023_Article_IEq4.gif" alt="$\mathsf{NP}$" align="middle" border="0"> -sets for k≥2. We define subclasses of the class of all disjoint k-tuples of q/224_2007_9023_Article_IEq5.gif" alt="$\mathsf{NP}$" align="middle" border="0"> -sets. These subclasses are associated with a propositional proof system and possess complete tuples which are defined from the proof system. In our main result we show that complete disjoint q/224_2007_9023_Article_IEq6.gif" alt="$\mathsf{NP}$" align="middle" border="0"> -pairs exist if and only if complete disjoint k-tuples of q/224_2007_9023_Article_IEq7.gif" alt="$\mathsf{NP}$" align="middle" border="0"> -sets exist for all k≥2. Further, this is equivalent to the existence of a propositional proof system in which the disjointness of all k-tuples is shortly provable. We also show that a strengthening of this conditions characterizes the existence of optimal proof systems. An extended abstract of this paper appeared in the proceedings of the conference CSR 2006 (Lecture Notes in Computer Science 3967, 80–91, 2006). Supported by DFG grant KO 1053/5-1.     

On a quasiorder on the class of monounary algebras

In the paper we introduce a relation q5601832622161h3/MediaObjects/s00500-005-0520-xflb1.gif" alt="MediaObjects/s00500-005-0520-xflb1.gif" align="middle"> on the class of monounary algebras q5601832622161h3/MediaObjects/s00500-005-0520-xflb2.gif" alt="MediaObjects/s00500-005-0520-xflb2.gif" align="middle"> by means of q5601832622161h3/MediaObjects/s00500-005-0520-xflb3.gif" alt="MediaObjects/s00500-005-0520-xflb3.gif" align="middle">-homomorphisms. It is a quasiorder. We take a subclass q5601832622161h3/MediaObjects/s00500-005-0520-xflb4.gif" alt="MediaObjects/s00500-005-0520-xflb4.gif" align="middle"> of q5601832622161h3/MediaObjects/s00500-005-0520-xflb2.gif" alt="MediaObjects/s00500-005-0520-xflb2.gif" align="middle"> containing monounary algebras q5601832622161h3/MediaObjects/s00500-005-0520-xflb5.gif" alt="MediaObjects/s00500-005-0520-xflb5.gif" align="middle"> satisfying the property q5601832622161h3/MediaObjects/s00500-005-0520-xflb6.gif" alt="MediaObjects/s00500-005-0520-xflb6.gif" align="middle"> We characterize algebras in q5601832622161h3/MediaObjects/s00500-005-0520-xflb4.gif" alt="MediaObjects/s00500-005-0520-xflb4.gif" align="middle"> by the notions of a degree and properties of their q5601832622161h3/MediaObjects/s00500-005-0520-xflb3.gif" alt="MediaObjects/s00500-005-0520-xflb3.gif" align="middle">-endomorphisms. We apply the results to finite monounary algebras. Supported by grant VEGA 1/0161/03     

The historical workstation project

Since 1978 research in the development of software dedicated to the specific problems of historical research has been undertaken at the Max-Planck-Institute für Geschichte in Göttingen. From a background of practical experiences during these years, a concept of what an appropriate q821/xxlarge8216.gif" alt="lsquo" align="BASELINE" BORDER="0">workstationq821/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> for an historian would be has been derived. It stresses the necessity of three components: (a) software, derived from a detailed analysis of what differentiates information contained in historical sources from such present in current material, (b) databases which are as easily available as printed books and (c) knowledge bases which allow software and data bases to draw upon the information contained in historical reference works. A loose network of European research projects, dedicated to the realization of such a setup, is described.Manfred Thaller has a Ph.D. (1975) in Modern and Medieval History and held a post-doctoral fellowship in sociology at the Institute for Advanced Studies (Vienna). Since 1978 he has been at the Max-Planck-Institute for History, where he is a research fellow for Historical Information Science.     

关于IV-(∈,∈Ⅴq)模糊格蕴涵子代数

运用区间值模糊集的思想对IV-(∈,∈Ⅴq)-模糊格蕴涵子代数概念作进一步研究。给出了IV-(∈,∈Ⅴq)-模糊格蕴涵子代数的若干新的性质与刻画;获得了IV-(∈,∈Ⅴq)-模糊格蕴涵子代数的象与原象成为IV-(∈,∈Ⅴq)-模糊格蕴涵子代数的条件;讨论了IV-(∈,∈Ⅴq)-模糊格蕴涵子代数的直积特征。     

银川市城市环境质量状况及污染防治

运用环境科学的基本理论，分析了银川市的环境空气质量状况，城市噪声功能区的划分与噪声源的现状，银川市水环境的状况和主要排水沟的现状及固体废弃物的排放、利用情况。指出银川市环境空气质量中的主要污染物质是总悬浮颗粒物，及造成此种污染的原因；说明银川市的城市噪声源是随着城区面积的扩大，活动人群的密集，噪声幅度的增加而小幅增加的。由于水资源的需求快速增长，污染物的排放及措施的不力，使水资源面临多方压力。造成水质的主要污染因子是氨氮；水质污染类型为有机污染、无机盐类污染；银川市固体废弃物的产生量为全区第三位，工业固体废弃物综合利用率为全区首位。提出了银川市环境质量污染的防治措施。