Surface analysis of a cold leg section of an SS316-lithium loop

Compatibility studies of austenitic stainless steel AISI 316 with liquid lithium for fusion application have shown that a porous ferritic layer is formed on the surface of the steel in the hot leg of a loop experiment due to depletion of alloying elements. The concentration profiles of the removed elements across the cross section of the tube reveal a pronounced step between the austenite matrix and the porous ferrite which is not expected in a normal diffusion process. The removed elements are partly deposited on the surface of the cold leg.In this study we looked at the boundary between the nickel rich deposit and the original matrix of a section of the cold (435 °C) leg. On the surface of the austenite, the expected grain boundary attack of lithium was observed. Additionally, to a depth of about one grain size, chromium and molybdenum were depleted and lithium seemed to also have attacked the bulk material, resulting in a splitting up into smaller grains with decomposed concentrations of the alloying elements, i.e. iron with large amounts of nickel and iron with chromium and small nickel amounts.In this paper a suggestion is put forward describing a reaction mechanism leading to the porous layer in the hot leg as a result of the instability of AISI 316 and its decomposition into two phases under the influence of liquid lithium.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Average growth-behavior and distribution properties of generalized weighted digit-block-counting functions

We introduce a generalized weighted digit-block-counting function on the nonnegative integers, which is a generalization of many digit-depending functions as, for example, the well known sum-of-digits function. A formula for the first moment of the sum-of-digits function has been given by Delange in 1972. In the first part of this paper we provide a compact formula for the first moment of the generalized weighted digit-block-counting function and show that a (weak) Delange type formula holds if the sequence of weights converges. The question, whether the converse is true as well, can only be answered partially at the moment. In the second part of this paper we study distribution properties of generalized weighted digit-block-counting sequences and their d-dimensional analogues. We give an if and only if condition under which such sequences are uniformly distributed modulo one.     

Computing finest mincut partitions of a graph and application to routing problems

Let G=(V,E,w) be an n-vertex graph with edge weights w>0. We propose an algorithm computing all partitions of V into mincuts of G such that the mincuts in the partitions cannot be partitioned further into mincuts. There are O(n) such finest mincut partitions. A mincut is a non-empty proper subset of V such that the total weight of edges with exactly one end in the subset is minimal. The proposed algorithm exploits the cactus representation of mincuts and has the same time complexity as cactus construction. An application to the exact solution of the general routing problem is described.