4,038 research outputs found

    Enhancement of the Deuteron-Fusion Reactions in Metals and its Experimental Implications

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    Recent measurements of the reaction d(d,p)t in metallic environments at very low energies performed by different experimental groups point to an enhanced electron screening effect. However, the resulting screening energies differ strongly for divers host metals and different experiments. Here, we present new experimental results and investigations of interfering processes in the irradiated targets. These measurements inside metals set special challenges and pitfalls which make them and the data analysis particularly error-prone. There are multi-parameter collateral effects which are crucial for the correct interpretation of the observed experimental yields. They mainly originate from target surface contaminations due to residual gases in the vacuum as well as from inhomogeneities and instabilities in the deuteron density distribution in the targets. In order to address these problems an improved differential analysis method beyond the standard procedures has been implemented. Profound scrutiny of the other experiments demonstrates that the observed unusual changes in the reaction yields are mainly due to deuteron density dynamics simulating the alleged screening energy values. The experimental results are compared with different theoretical models of the electron screening in metals. The Debye-H\"{u}ckel model that has been previously proposed to explain the influence of the electron screening on both nuclear reactions and radioactive decays could be clearly excluded.Comment: 22 pages, 12 figures, REVTeX4, 2-column format. Submitted to Phys. Rev. C; accepte

    The construction of social housing pathways across Australia

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    This report examines the formal social housing pathways set out in policy and how these differ across jurisdictions. It uses a systems thinking approach to examine how actors, levers, feedback loops, incentives and disincentives influence formal social housing pathways. The discussion presents evidence from a comprehensive policy review, as well as data from interviews and a workshop with key stakeholders, including government representatives and community housing managers

    Quantitative Risk Assessment as Applied to Natural Terrain Landslide Hazard Management in a Mid-levels Catchment, Hong Kong

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    This paper presents a case study of the application of quantitative risk assessment techniques to a site-specific natural terrain hazard study in Hong Kong. The development of the landslide hazard and susceptibility models is described and salient details of the consequence model are given, including the assessment of debris flowpaths and runout using state-of-the-art Geographic Information System (GIS) tools and debris runout computer models. A synthesis of the risk quantification process and schematic design of risk mitigation works is presented

    Influence of dissipation on the extraction of quantum states via repeated measurements

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    A quantum system put in interaction with another one that is repeatedly measured is subject to a non-unitary dynamics, through which it is possible to extract subspaces. This key idea has been exploited to propose schemes aimed at the generation of pure quantum states (purification). All such schemes have so far been considered in the ideal situations of isolated systems. In this paper, we analyze the influence of non-negligible interactions with environment during the extraction process, with the scope of investigating the possibility of purifying the state of a system in spite of the sources of dissipation. A general framework is presented and a paradigmatic example consisting of two interacting spins immersed in a bosonic bath is studied. The effectiveness of the purification scheme is discussed in terms of purity for different values of the relevant parameters and in connection with the bath temperature.Comment: 10 pages, 3 figure

    Energy dissipation in soil samples during drained triaxial shearing

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    The discrete-element method was used to simulate drained triaxial compression of large-scale, polydisperse numerical samples at a range of void ratios while tracing all relevant energy components. The frictional dissipation and boundary work are almost equal regardless of sample density. The volumetric work reaches a steady value at large strain. However, the distortional work increases continually as sample deformation continues post-critical state. There is a preferential orientation for frictional dissipation at around 45° to the major principal stress direction. This matches the orientation at which there is the largest number of sliding contacts. The work equations, which are fundamental in most commonly used constitutive models, are linear when plotted against deviatoric strain. The modified Cam Clay work equation substantially over-predicts the frictional dissipation for dense samples. An alternative, thermodynamically consistent work equation gives a much better description of frictional dissipation and is therefore recommended to ensure accuracy in modelling

    Identification of the Beutler-Fano formula in eigenphase shifts and eigentime delays near a resonance

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    Eigenphase shifts and eigentime delays near a resonance for a system of one discrete state and two continua are shown to be functionals of the Beutler- Fano formulas using appropriate dimensionless energy units and line profile indices. Parameters responsible for the avoided crossing of eigenphase shifts and eigentime delays are identified. Similarly, parameters responsible for the eigentime delays due to a frame change are identified. With the help of new parameters, an analogy with the spin model is pursued for the S matrix and time delay matrix. The time delay matrix is shown to comprise three terms, one due to resonance, one due to a avoided crossing interaction, and one due to a frame change. It is found that the squared sum of time delays due to the avoided crossing interaction and frame change is unity.Comment: 17 pages, 3 figures, RevTe
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