Experimental Evaluation of the Mechanical Properties of Steel Reinforcement at Elevated Temperature

This paper describes an experimental investigation into the influence of elevated temperatures on the mechanical properties of steel reinforcement. The study includes tests carried out at ambient temperature as well as under steady-state and transient elevated temperature conditions. A complementary test series, in which the residual post-cooling properties of reinforcing bars were examined, is also described. The experimental study focussed on assessing the performance of reinforcement of 6 and 8 mm diameter, although 10 mm bars were also considered in some cases. The specimens included both plain and deformed bars. After providing an outline of the experimental set-up and loading procedures, a detailed account of the test results is presented and discussed. Apart from the evaluation of stress–strain response and degradation of stiffness and strength properties, particular emphasis is given to assessing the influence of temperature on enhancing the ductility of reinforcement. The findings of this study have direct implications on procedures used for predicting the ultimate behaviour of structural floor elements and assemblages during, and following, exposure to elevated temperatures

Experimental and analytical assessment of ductility in lightly reinforced concrete members

This is the post-print version of the final paper published in Engineering Structures. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2010 Elsevier B.V.This paper is concerned with the ultimate behaviour of lightly reinforced concrete members under extreme loading conditions. Although the consideration given to the assessment of ductility is of general relevance to various applications, it is of particular importance to conditions resembling those occurring during severe building fires. The main purpose of the investigation is to examine the failure of idealised members representing isolated strips within composite floor slabs which become lightly reinforced in a simulated fire situation due to the early loss of the steel deck. An experimental study, focusing on the failure state associated with rupture of the reinforcement in idealised concrete members, is presented. The tests enable direct assessment of the influence of a number of important parameters such as the reinforcement type, properties and ratio on the ultimate response. The results of several tests also facilitate a detailed examination of the distribution of bond stresses along the length. After describing the experimental arrangements and discussing the main test results, the paper introduces a simplified analytical model that can be used to represent the member response up to failure. The model is validated and calibrated through comparisons against the test results as well as more detailed nonlinear finite element simulations. The results and observations from this investigation offer an insight into the key factors that govern the ultimate behaviour. More importantly, the analytical model permits the development of simple expressions which capture the influence of salient parameters such as bond characteristics and reinforcement properties, for predicting the ductility of this type of member. With due consideration of the findings from other complementary experimental and analytical studies on full slab elements under ambient and elevated temperatures, this work represents a proposed basis for developing quantified failure criteria.Engineering and Physical Sciences Research Council (EPSRC

Non-extensive Random Matrix Theory - A Bridge Connecting Chaotic and Regular Dynamics

We consider a possible generalization of the random matrix theory, which involves the maximization of Tsallis' $q$-parametrized entropy. We discuss the dependence of the spacing distribution on $q$ using a non-extensive generalization of Wigner's surmises for ensembles belonging to the orthogonal, unitary and symplectic symmetry universal classes.Comment: Accepted for publication in Physics Letters

Precise Tight-binding Description of the Band Structure of MgB2

We present a careful recasting of first-principles band structure calculations for MgB2 in a non-orthogonal sp-tight-binding (TB) basis. Our TB results almost exactly reproduce our full potential linearized augmented plane wave results for the energy bands, the densities of states and the total energies. Our procedure generates transferable Slater-Koster parameters which should be useful for other studies of this important material.Comment: REVTEX, 2 Encapsulated PostScript Figure

Китайско-российское инвестиционное сотрудничество: современное состояние, проблемы и перспективы развития

In process of growth of investments of the Chinese enterprises to Russia variety of problems has gradually come to light. Sometimes there were simply failures to an investment of financial assets. Authors of article have tried to find an explanation and ways of the decision of similar failures. Stimulus of the Chinese direct investments to Russia, working out of system investment strategy can serve by the government of China, at simultaneous acceptance by the Russian government of measures for maintenance of the Chinese enterprises in Russia.По мере роста инвестиций китайских предприятий в Россию постепенно выявился целый ряд проблем, в частности, неудачи с вложением финансовых средств. Авторы статьи попытались найти объяснение и пути решения подобных ситуаций. Стимулом китайских прямых инвестиций в Россию, по мнению авторов, может послужить разработка правительством Китая системной инвестиционной стратегии при одновременном принятии российским правительством мер для поддержания китайских предприятий в России

Gravitational Collapse of Phantom Fluid in (2+1)-Dimensions

This investigation is devoted to the solutions of Einstein's field equations for a circularly symmetric anisotropic fluid, with kinematic self-similarity of the first kind, in $(2+1)$-dimensional spacetimes. In the case where the radial pressure vanishes, we show that there exists a solution of the equations that represents the gravitational collapse of an anisotropic fluid, and this collapse will eventually form a black hole, even when it is constituted by the phantom energy.Comment: 10 page

Note on invariant properties of a quantum system placed into thermodynamic environment

The analysis conducted in this work indicates that interactions of a CP-violating (and CPT-preserving) quantum system with a thermodynamic environment can produce the impression of a CPT violation in the system. This conclusion is reasonably consistent with the results reported for decays of neutral K-mesons

Alternatives to Quintessence Model Building

We discuss the issue of toy model building for the dark energy component of the universe. Specifically, we consider two generic toy models recently proposed as alternatives to quintessence models, known as Cardassian expansion and the Chaplygin gas. We show that the former is enteriely equivalent to a class of quintessence models. We determine the observational constraints on the latter, coming from recent supernovae results and from the shape of the matter power spectrum. As expected, these restrict the model to a behaviour that closely matches that of a standard cosmological constant $\Lambda$.Comment: RevTex4; 7 pages, 4 figures. v2: Improved discussion of constraints on Chaplygin gas models. Other clarifications added. Phys Rev. D (in press

Evidence for phase formation in potassium intercalated 1,2;8,9-dibenzopentacene

We have prepared potassium intercalated 1,2;8,9-dibenzopentacene films under vacuum conditions. The evolution of the electronic excitation spectra upon potassium addition as measured using electron energy-loss spectroscopy clearly indicate the formation of particular doped phases with compositions K$_x$dibenzopentacene ($x$ = 1,2,3). Moreover, the stability of these phases as a function of temperature has been explored. Finally, the electronic excitation spectra also give insight into the electronic ground state of the potassium doped 1,2;8,9-dibenzopentacene films.Comment: 6 pages, 5 figures. arXiv admin note: text overlap with arXiv:1201.200

First-Principles Calculation of the Superconducting Transition in MgB2 within the Anisotropic Eliashberg Formalism

We present a study of the superconducting transition in MgB2 using the ab-initio pseudopotential density functional method and the fully anisotropic Eliashberg equation. Our study shows that the anisotropic Eliashberg equation, constructed with ab-initio calculated momentum-dependent electron-phonon interaction and anharmonic phonon frequencies, yields an average electron-phonon coupling constant lambda = 0.61, a transition temperature Tc = 39 K, and a boron isotope-effect exponent alphaB = 0.31 with a reasonable assumption of mu* = 0.12. The calculated values for Tc, lambda, and alphaB are in excellent agreement with transport, specific heat, and isotope effect measurements respectively. The individual values of the electron-phonon coupling lambda(k,k') on the various pieces of the Fermi surface however vary from 0.1 to 2.5. The observed Tc is a result of both the raising effect of anisotropy in the electron-phonon couplings and the lowering effect of anharmonicity in the relevant phonon modes.Comment: 4 pages, 3 figures, 1 tabl