2,481 research outputs found

    The role of the Treaty of Waitangi in contemporary public law : does the Treaty have to be incorporated into municipal law to be of effect?

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    Recent work on Al-Cu-Mg based alloys with Cu:Mg atomic ratio close to unity is reviewed to clarify the mechanisms for age hardening. During the first stage of hardening a substantial exothermic heat evolution occurs whilst the microstructural change involves the formation of initially Cu-rich / Mg-rich clusters and later Cu-Mg co-clusters. The data show that the first stage of the age hardening is due to the formation of Cu-Mg co-clusters. The combined experimental methods show the second stage hardening is dominated by formation of S phase, which forms a dense precipitation at the peak hardness stage, whilst no significant amounts of other phases or zones are detected. S phase strengthens the alloy predominantly through the Orowan looping mechanism. These findings are incorporated into a multi-phase, multi-mechanism model for yield strength of Al-Cu-Mg based alloys

    Hardening mechanism of commercially pure Mg processed by high pressure torsion at room temperature

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    Coarse-grained Mg in the as-cast condition and fine-grained Mg in the extruded condition were processed by high pressure torsion (HPT) at room temperature for up to 16 turns. Microstructure observation and texture analysis indicate that to fulfil the Von Mises criterion, the non-basal slip is activated in the as-cast Mg and tension twinning is activated in the as-extruded Mg. Although the deformation mechanism is different in the as-cast Mg and the as-extruded Mg during HPT, their hardening evolutions are similar, i.e. after 1/8 turn of HPT, microhardness of the as-cast Mg and the extruded Mg both show a significant increase and further HPT processing does not significantly further increase the microhardness. Texture strengthening can explain the rapid hardening. Hardness anisotropy and texture data results suggest that texture strengthening plays an important role for both types of samples. Texture strengthening weakens with decreasing grain size

    Multiaxial Kitagawa analysis of A356-T6

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    Experimental Kitagawa analysis has been performed on A356-T6 containing natural and artificial defects. Results are obtained with a load ratio of R = -1 for three different loadings: tension, torsion and combined tension-torsion. The critical defect size determined is 400 \pm 100 \mum in A356-T6 under multiaxial loading. Below this value, the microstructure governs the endurance limit mainly through Secondary Dendrite Arm Spacing (SDAS). Four theoretical approaches are used to simulate the endurance limit characterized by a Kitagawa relationship are compared: Murakami relationships [Y Murakami, Metal Fatigue: Effects of Small Defects and Nonmetallic Inclusions, Elsevier, 2002.], defect-crack equivalency via Linear Elastic Fracture Mechanics (LEFM), the Critical Distance Method (CDM) proposed by Susmel and Taylor [L. Susmel, D. Taylor. Eng. Fract. Mech. 75 (2008) 15.] and the gradient approach proposed by Nadot [Y. Nadot, T. ~Billaudeau. Eng. Fract. Mech. 73 (2006) 1.]. It is shown that the CDM and gradient methods are accurate; however fatigue data for three loading conditions is necessary to allow accurate identification of an endurance limit.Comment: 27 pages, 11 figure

    p-wave phase shift and scattering length of 6^6Li

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    We have calculated the p-wave phase shifts and scattering length of 6^6Li. For this we solve the pp partial wave Schr\"odinger equation and analyze the validity of adopting the semiclassical solution to evaluate the constant factors in the solution. Unlike in the ss wave case, the semiclassical solution does not provide unique value of the constants. We suggest an approximate analytic solution, which provides reliable results in special cases. Further more, we also use the variable phase method to evaluate the phase shifts. The p-wave scattering lengths of 132^{132}Cs and 134^{134}Cs are calculated to validate the schemes followed. Based on our calculations, the value of the pp wave scattering length of 6^6Li is −45ao-45a_o.Comment: 10 figure

    A New Model for Void Coalescence by Internal Necking

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    A micromechanical model for predicting the strain increment required to bring a damaged material element from the onset of void coalescence up to final fracture is developed based on simple kinematics arguments. This strain increment controls the unloading slope and the energy dissipated during the final step of material failure. Proper prediction of the final drop of the load carrying capacity is an important ingredient of any ductile fracture model, especially at high stress triaxiality. The model has been motivated and verified by comparison to a large set of finite element void cell calculations.

    Extracting Br(omega->pi^+ pi^-) from the Time-like Pion Form-factor

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    We extract the G-parity-violating branching ratio Br(omega->pi^+ pi^-) from the effective rho-omega mixing matrix element Pi_{rho omega}(s), determined from e^+e^- -> pi^+ pi^- data. The omega->pi^+ pi^- partial width can be determined either from the time-like pion form factor or through the constraint that the mixed physical propagator D_{rho omega}^{mu nu}(s) possesses no poles. The two procedures are inequivalent in practice, and we show why the first is preferred, to find finally Br(omega->pi^+ pi^-) = 1.9 +/- 0.3%.Comment: 12 pages (published version

    Gravitational-wave Detection With Matter-wave Interferometers Based On Standing Light Waves

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    We study the possibility of detecting gravitational-waves with matter-wave interferometers, where atom beams are split, deflected and recombined totally by standing light waves. Our calculation shows that the phase shift is dominated by terms proportional to the time derivative of the gravitational wave amplitude. Taking into account future improvements on current technologies, it is promising to build a matter-wave interferometer detector with desired sensitivity.Comment: 7 pages, 3 figures. To be published in General Relativity and Gravitatio

    Local channels preserving maximal entanglement or Schmidt number

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    Maximal entanglement and Schmidt number play an important role in various quantum information tasks. In this paper, it is shown that a local channel preserves maximal entanglement state(MES) or preserves pure states with Schmidt number rr(rr is a fixed integer) if and only if it is a local unitary operation.Comment: 10 page

    (Twisted) Toroidal Compactification of pp-Waves

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    The maximally supersymmetric type IIB pp-wave is compactified on spatial circles, with and without an auxiliary rotational twist. All spatial circles of constant radius are identified. Without the twist, an S1^1 compactification can preserve 24, 20 or 16 supercharges. T2T^2 compactifications can preserve 20, 18 or 16 supercharges; T3T^3 compactifications can preserve 18 or 16 supercharges and higher compactifications preserve 16 supercharges. The worldsheet theory of this background is discussed. The T-dual and decompactified type IIA and M-theoretic solutions which preserve 24 supercharges are given. Some comments are made regarding the AdS parent and the CFT description.Comment: 22 pages REVTeX 4 and AMSLaTeX. v3: References and a paragraph on nine dimensional Killing spinors were added. v4: A few typos corrected and a footnote was modifie
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