Evaluation of Creep-fatigue Damage for Heat Exchangers in the Stella Sodium Test Loop

AbstractCreep-fatigue damage evaluation of DHX (Decay Heat Exchanger) and AHX(Air Heat Exchanger) in the sodium test facility has been performed. The sodium test loop of the STELLA-1 is for component performance tests of the main components, heat exchangers and mechanical pumps which are to be installed in an integral sodium test loop (STELLA-2) for simulating thermal hydraulic decay heat removal behaviour of the Korean demonstration Sodium-cooled Fast Reactor. High temperature design and fabrication of the DHX and AHX have been conducted and the components were installed at KAERI site. Evaluation of creep-fatigue damage at critical locations of the two heat exchangers were conducted according to the elevated temperature design codes of the ASME-NH and RCC-MR and the evaluation results were compared

Topology of iterated S1S^1-bundles

In this paper we investigate what kind of manifolds arise as the total spaces of iterated $S^1$-bundles. A real Bott tower studied in \cite{CMO}, \cite{KM} and \cite{KN} is an example of an iterated $S^1$-bundle. We show that the total space of an iterated $S^1$-bundle is homeomorphic to an infra-nilmanifold. A real Bott manifold, which is the total space of a real Bott tower, provides an example of a closed flat Riemannian manifold. We also show that real Bott manifolds are the only closed flat Riemannian manifolds obtained from iterated \bbr{P}^1-bundles. Finally we classify the homeomorphism types of the total spaces of iterated $S^1$-bundles in dimension 3

Universal factorization property of certain polycyclic groups

AbstractLet H be a torsion-free strongly polycyclic (torsion-free virtually polycyclic, resp.) group. Let G be any group with maximal condition. We show that there exists a torsion-free strongly polycyclic (torsion-free virtually polycyclic, resp.) group G˜ and an epimorphism ε:G→G˜ such that for any homomorphism ϕ:G→H, it factors through G˜, i.e., there exists a homomorphism ϕ˜:G˜→H such that ϕ=ϕ˜∘ε. We show that this factorization property cannot be extended to any finitely generated group G. As an application of factorization, we give necessary and sufficient conditions for N(f,g)=R(f,g) to hold for maps f,g:X→Y between closed orientable n-manifolds where π1(X) has the maximal condition, Y is an infra-solvmanifold, N(f,g) and R(f,g) denote the Nielsen and Reidemeister coincidence numbers, respectively