Surface Integrity of SA508 Gr 3 Subjected to Abusive Milling Conditions

SA508 Gr 3, a bainitic forging steel employed in the fabrication of nuclear pressure vessels has been characterised after dry-milling to investigate extent of machining abuse on the surface. A detailed study of the evolution of residual stresses, microstructure, micro-hardness and roughness in relation to different milling parameters is presented. A central composite orthogonal (CCO) design of experiments (DoE) was used to generate a statistic model of the milling process. Deformation of the sub-surface layer was assessed via SEM BSE imaging. The developed statistical model is discussed aiming to illustrate availability of different cost-effective manufacturing techniques meeting the high standards required by the industry

Sawja: Static Analysis Workshop for Java

Static analysis is a powerful technique for automatic verification of programs but raises major engineering challenges when developing a full-fledged analyzer for a realistic language such as Java. This paper describes the Sawja library: a static analysis framework fully compliant with Java 6 which provides OCaml modules for efficiently manipulating Java bytecode programs. We present the main features of the library, including (i) efficient functional data-structures for representing program with implicit sharing and lazy parsing, (ii) an intermediate stack-less representation, and (iii) fast computation and manipulation of complete programs

Magnetism in a lattice of spinor Bose condensates

We study the ground state magnetic properties of ferromagnetic spinor Bose-Einstein condensates confined in a deep optical lattices. In the Mott insulator regime, the ``mini-condensates'' at each lattice site behave as mesoscopic spin magnets that can interact with neighboring sites through both the static magnetic dipolar interaction and the light-induced dipolar interaction. We show that such an array of spin magnets can undergo a ferromagnetic or anti-ferromagnetic phase transition under the magnetic dipolar interaction depending on the dimension of the confining optical lattice. The ground-state spin configurations and related magnetic properties are investigated in detail

Grain coarsening behaviour of solution annealed Alloy 625 between 600–800°C

As with all alloys, the grain structure of the nickel-base superalloy 625 has a significant impact on its mechanical properties. Predictability of the grain structure evolution in this material is particularly pertinent because it is prone to inter-metallic precipitate formation both during manufacture and long term or high temperature service. To this end, analysis has been performed on the grain structure of Alloy 625 aged isothermally at temperatures between 600 and 800 °C for times up to 3000 h. Fits made according to the classical Arrhenius equation describing normal grain growth yield an average value for the activation energy of a somewhat inhomogeneous grain structure above 700 °C of 108.3±6.6 kJ mol−1 and 46.6±12.2 kJ mol−1 below 650 °C. Linear extrapolation between 650 and 700 °C produces a significantly higher value of 527.7±23.1 kJ mol−1. This result is ultimately a consequence of a high driving force, solute-impeded grain boundary migration process operating within the alloy. Comparison of the high and low temperature values with the activation energy for volume self-diffusion and grain boundary diffusion identifies the latter as the principle governing mechanism for grain growth in both instances. A decrease in the value of the time exponent (n) at higher temperatures despite a reduction in solute drag is attributable to the Zener pinning imposed by grain boundary M6C and M23C6 particles identified from Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDXS) analysis. Vickers hardness results show the dominance of intermetallic intragranular precipitates in the governance of the mechanical properties of the material with grain coarsening being accompanied by a significant increase in hardness. Furthermore, the lack of any correlation with grain growth behaviour indicates these phases have no significant effect on the grain evolution of the material

Spinor condensates and light scattering from Bose-Einstein condensates

These notes discuss two aspects of the physics of atomic Bose-Einstein condensates: optical properties and spinor condensates. The first topic includes light scattering experiments which probe the excitations of a condensate in both the free-particle and phonon regime. At higher light intensity, a new form of superradiance and phase-coherent matter wave amplification were observed. We also discuss properties of spinor condensates and describe studies of ground--state spin domain structures and dynamical studies which revealed metastable excited states and quantum tunneling.Comment: 58 pages, 33 figures, to appear in Proceedings of Les Houches 1999 Summer School, Session LXXI

Modelling the nucleation, growth and coarsening kinetics of γ^″ (D0<inf>22</inf>) precipitates in the Ni-base Alloy 625

Alloy 625 is susceptible to significant precipitation hardening through the formation of γ″ (D022-NbNi3) particles. These precipitates can form both during manufacture and in high temperature service and, consequently, the accurate prediction of their behaviour is crucial. To this end, a model is presented here which describes γ″ precipitation in Alloy 625, encompassing the concurrent nucleation, growth and coarsening of different particles and allowing for the particles to be shape changing. This model is calibrated with respect to the experimentally measured aspect ratio evolution observed at 650 °C. The resultant outputs for interfacial energy, particle size distribution and number density are in agreement with experimental data for a simulation of 1000 h at 650 °C

Sound Control-Flow Graph Extraction for Java Programs with Exceptions

We present an algorithm to extract control-flow graphs from Java bytecode, considering exceptional flows. We then establish its correctness: the behavior of the extracted graphs is shown to be a sound over-approximation of the behavior of the original programs. Thus, any temporal safety property that holds for the extracted control-flow graph also holds for the original program. This makes the extracted graphs suitable for performing various static analyses, in particular model checking. The extraction proceeds in two phases. First, we translate Java bytecode into BIR, a stack-less intermediate representation. The BIR transformation is developed as a module of Sawja, a novel static analysis framework for Java bytecode. Besides Sawja’s efficiency, the resulting intermediate representation is more compact than the original bytecode and provides an explicit representation of exceptions. These features make BIR a natural starting point for sound control-flow graph extraction. Next, we formally define the transformation from BIR to control-flow graphs, which (among other features) considers the propagation of uncaught exceptions within method calls. We prove the correctness of the two-phase extraction by suitably combining the properties of the two transformations with those of an idealized control-flow graph extraction algorithm, whose correctness has been proved directly. The control-flow graph extraction algorithm is implemented in the \textsc{ConFlEx} tool. A number of test-cases show the efficiency and the utility of the implementation

Aqueous Methanol Extracts of Cochlospermum tinctorium (A. Rich) Possess Analgesic and Anti-inflammatory Activities

Cochlopermum tinctorium A. Rich. (Cochlospermaceae) is a commonly used medicinal plant in the West Africa sub-region for the management of various conditions including pain and inflammatory conditions. In the present study, we report the analgesic and anti-inflammatory activities of the aqueous methanol leaf (20–80 mg/kg), root (7.5–30 mg/kg), and root bark (20–80 mg/kg) extracts of the plant. The analgesic potentials of the extracts were studied using acetic acid induced writhing and hot plate tests in mice while the anti-inflammatory activity was investigated using carrageenan-induced paw edema in rats.The extracts significantly and dose dependently inhibited the acetic acid-induced writhing in mice. However, the highest protection against writhing was produced by aqueous methanol leaf extract at the dose of 80 mg/kg (96.65%) which even was greater than that of the standard agent, ketoprofen (82.30%). The extracts did not significantly increase mean latency of response in the hot plate test. However, aqueous methanol root bark extract at the dose of 20 mg/kg significantly (P < 0.05) increased the mean latency of pain response. While the extracts of the root and root bark extracts of the plant afforded non dose-dependent protection against carrageenan-induced edema, the aqueous methanol leaf extract significantly and dose-dependently inhibited carrageenan-induced hind paw edema at the end of the third hour.The present study suggests that the aqueous methanol leaf, root, and root bark extracts of Cochlopermum tinctorium possess analgesic and anti-inflammatory activities which lend some credence to the ethnomedical claim of the use of the plant in the management of pain and inflammatory conditions