Constitutive response of Rene 80 under thermal mechanical loads

The applicability of a classical constitutive model for stress-strain analysis of a nickel base superalloy, Rene' 80, in the gas turbine thermomechanical fatigue (TMF) environment is examined. A variety of tests were conducted to generate basic material data and to investigate the material response under cyclic thermomechanical loading. Isothermal stress-strain data were acquired at a variety of strain rates over the TMF temperature range. Creep curves were examined at 2 temperature ranges, 871 to 982 C and 760 to 871 C. The results provide optimism on the ability of the classical constitutive model for high temperature applications

Contribution of integrated farm management (IFM) to Defra objectives

A farming system comprises a complex of interrelated and interacting factors. Any study of an isolated part of the system will not provide adequate understanding of the behaviour of the entire system and interactions may be equally or more important than individual components. There is therefore a requirement for the development of integrated approaches and practices to help farming systems adapt to, eliminate or reduce the negative impacts of production on the environment. This must be achieved whilst maintaining the economic viability of the farm enterprise. Our analysis has confirmed that IFM techniques generally have far more beneficial than adverse effects on current Defra policy objectives. However, there are some notable ‘conflicts’ where a technique that has a large beneficial effect in one policy area has a large negative effect in another. Carbon footprinting is used to quantify the impact of some integrated farming practices

Mobilising communities to address alcohol harm : an Alcohol Health Champion approach

In this article, Cathy Ure et al. look at engaging communities in order to reduce alcohol harms. By training Alcohol Health Champions, individuals can support vulnerable friends and family, and work within their communities to influence policy and promote change

Testing a Simplified Version of Einstein's Equations for Numerical Relativity

Solving dynamical problems in general relativity requires the full machinery of numerical relativity. Wilson has proposed a simpler but approximate scheme for systems near equilibrium, like binary neutron stars. We test the scheme on isolated, rapidly rotating, relativistic stars. Since these objects are in equilibrium, it is crucial that the approximation work well if we are to believe its predictions for more complicated systems like binaries. Our results are very encouraging.Comment: 9 pages (RevTeX 3.0 with 6 uuencoded figures), CRSR-107

Implementing an apparent-horizon finder in three dimensions

Locating apparent horizons is not only important for a complete understanding of numerically generated spacetimes, but it may also be a crucial component of the technique for evolving black-hole spacetimes accurately. A scheme proposed by Libson et al., based on expanding the location of the apparent horizon in terms of symmetric trace-free tensors, seems very promising for use with three-dimensional numerical data sets. In this paper, we generalize this scheme and perform a number of code tests to fully calibrate its behavior in black-hole spacetimes similar to those we expect to encounter in solving the binary black-hole coalescence problem. An important aspect of the generalization is that we can compute the symmetric trace-free tensor expansion to any order. This enables us to determine how far we must carry the expansion to achieve results of a desired accuracy. To accomplish this generalization, we describe a new and very convenient set of recurrence relations which apply to symmetric trace-free tensors.Comment: 14 pages (RevTeX 3.0 with 3 figures

Computing the Similarity Between Moving Curves

In this paper we study similarity measures for moving curves which can, for example, model changing coastlines or retreating glacier termini. Points on a moving curve have two parameters, namely the position along the curve as well as time. We therefore focus on similarity measures for surfaces, specifically the Fr\'echet distance between surfaces. While the Fr\'echet distance between surfaces is not even known to be computable, we show for variants arising in the context of moving curves that they are polynomial-time solvable or NP-complete depending on the restrictions imposed on how the moving curves are matched. We achieve the polynomial-time solutions by a novel approach for computing a surface in the so-called free-space diagram based on max-flow min-cut duality

Gravitational waves from black hole-neutron star binaries I: Classification of waveforms

Using our new numerical-relativity code SACRA, long-term simulations for inspiral and merger of black hole (BH)-neutron star (NS) binaries are performed, focusing particularly on gravitational waveforms. As the initial conditions, BH-NS binaries in a quasiequilibrium state are prepared in a modified version of the moving-puncture approach. The BH is modeled by a nonspinning moving puncture and for the NS, a polytropic equation of state with $\Gamma=2$ and the irrotational velocity field are employed. The mass ratio of the BH to the NS, $Q=M_{\rm BH}/M_{\rm NS}$, is chosen in the range between 1.5 and 5. The compactness of the NS, defined by ${\cal C}=GM_{\rm NS}/c^2R_{\rm NS}$, is chosen to be between 0.145 and 0.178. For a large value of $Q$ for which the NS is not tidally disrupted and is simply swallowed by the BH, gravitational waves are characterized by inspiral, merger, and ringdown waveforms. In this case, the waveforms are qualitatively the same as that from BH-BH binaries. For a sufficiently small value of Q \alt 2, the NS may be tidally disrupted before it is swallowed by the BH. In this case, the amplitude of the merger and ringdown waveforms is very low, and thus, gravitational waves are characterized by the inspiral waveform and subsequent quick damping. The difference in the merger and ringdown waveforms is clearly reflected in the spectrum shape and in the "cut-off" frequency above which the spectrum amplitude steeply decreases. When an NS is not tidally disrupted (e.g., for Q=5), kick velocity, induced by asymmetric gravitational wave emission, agrees approximately with that derived for the merger of BH-BH binaries, whereas for the case that the tidal disruption occurs, the kick velocity is significantly suppressed.Comment: 25 pages, 3 jpg figures, accepted for publication in PRD; erratum is added on Jul 23. 201