7,015 research outputs found

    Environmental test planning, selection and standardization aids available

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    Requirements for instrumentation, equipment, and methods to be used in conducting environmental tests on components intended for use by a wide variety of technical personnel of different educational backgrounds, experience, and interests is announced

    Range extension, habitat and conservation status of three rare mallees, Eucalyptus castrensis, Eucalyptus fracta and Eucalyptus pumila from the Hunter Valley, NSW

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    New populations of three threatened mallee species, Eucalyptus castrensis K.D.Hill, Eucalyptus fracta K.D.Hill and Eucalyptus pumila Cambage (all Myrtaceae), have recently been found in the Singleton Military Area in the Hunter Valley of New South Wales (32°45’S, 151°15’E). Each population is significant as they increase the known distribution and total numbers of three highly restricted species. Details of the habitat and size of each additional population are given and conservation notes provided

    Stabilizing the Dilaton in Superstring Cosmology

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    We address the important issue of stabilizing the dilaton in the context of superstring cosmology. Scalar potentials which arise out of gaugino condensates in string models are generally exponential in nature. In a cosmological setting this allows for the existence of quasi scaling solutions, in which the energy density of the scalar field can, for a period, become a fixed fraction of the background density, due to the friction of the background expansion. Eventually the field can be trapped in the minimum of its potential as it leaves the scaling regime. We investigate this possibility in various gaugino condensation models and show that stable solutions for the dilaton are far more common than one would have naively thought.Comment: 13 pages, LaTex, uses psfig.sty with 3 figure

    Constraints on string networks with junctions

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    We consider the constraints on string networks with junctions in which the strings may all be different, as may be found for example in a network of (p,q)(p,q) cosmic superstrings. We concentrate on three aspects of junction dynamics. First we consider the propagation of small amplitude waves across a static three-string junction. Then, generalizing our earlier work, we determine the kinematic constraints on two colliding strings with different tensions. As before, the important conclusion is that strings do not always reconnect with a third string; they can pass straight through one another (or in the case of non-abelian strings become stuck in an X configuration), the constraint depending on the angle at which the strings meet, on their relative velocity, and on the ratios of the string tensions. For example, if the two colliding strings have equal tensions, then for ultra-relativistic initial velocities they pass through one another. However, if their tensions are sufficiently different they can reconnect. Finally, we consider the global properties of junctions and strings in a network. Assuming that, in a network, the incoming waves at a junction are independently randomly distributed, we determine the r.m.s. velocities of strings and calculate the average speed at which a junction moves along each of the three strings from which it is formed. Our findings suggest that junction dynamics may be such as to preferentially remove the heavy strings from the network leaving a network of predominantly light strings. Furthermore the r.m.s. velocity of strings in a network with junctions is smaller than 1/\sqrt{2}, the result for conventional Nambu-Goto strings without junctions in Minkowski spacetime.Comment: 12 pages, 6 figures. Version to appear in PRD. (2 new references and slightly extended discussion in section VII

    Using State Merging and State Pruning to Address the Path Explosion Problem Faced by Symbolic Execution

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    Symbolic execution is a promising technique to discover software vulnerabilities and improve the quality of code. However, symbolic execution suffers from a path explosion problem where the number of possible paths within a program grows exponentially with respect to loops and conditionals. New techniques are needed to address the path explosion problem. This research presents a novel algorithm which combines the previously researched techniques of state merging and state pruning. A prototype of the algorithm along with a pure state merging and pure state pruning are implemented in the KLEE symbolic execution tool with the goal of increasing the code coverage. Each algorithm is tested over 66 of the GNU COREUTILS utilities. State merging combined with state pruning outperforms the unmodified version of KLEE on 53% of the COREUTILS. These results confirm that state merging with pruning has viability in addressing the path explosion problem of symbolic execution

    Outcome and Process Measure Feedback as They Effect Therapy Outcomes

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    In the study of treatment outcomes, a subset of effectiveness research, the client-focused approach is ideal, as it examines individual responses to therapy over time. The Life Status Questionnaire (LSQ) is designed to track therapy outcomes over time. Despite the emphasis on client outcomes, the process between a therapist and client may have the greatest impact on therapy outcomes and should be an inherent part of a client-focused approach. This study investigated the effects of simultaneous use of an outcome (LSQ) and two Empathy Scale-Revised process subscales, Positive (ES-P) and Negative (ES-N), to determine how these separately and collectively affect therapy process and outcomes. Procedures included administering the LSQ before the 15 \ 3rd, and 5th therapy sessions and both the ES-P and ES-Nat the end of sessions 2 and 4. Dependent variables of interest included (a) LSQ, (b) ES-P, and (c) ES-N. The primary independent variable in this study was the impact that feedback derived from these instruments, although several ancillary independent variables were considered. Feedback effects were measured by randomly assigning clients to one of four treatment conditions: (a) No Feedback, (b) LSQ Feedback, (c) ES Feedback (combined ES-P and ES-N), and (d) Both Feedback (feedback provided for all three instruments). Results found no evidence that feedback conditions impacted therapy outcomes. However, insufficient sample size may be responsible. The LSQ showed significant improvement from sessions 1 to 5. The ES-P showed positive changes in therapeutic relationship from sessions 2 to 4 despite a significant ceiling effect. An even more profound ES-N floor effect may explain why four sessions were necessary to show significant reduction in the negative therapeutic relationship. Findings suggest that clients\u27 overall mental health and in their positive and negative feelings toward their therapist improved over time, and that clients who terminated therapy generally had more improved LSQ scores compared to those who did not. These findings replicate that shown by, among others, Lambert et al., (2001)

    Use of LARS system for the quantitative determination of smoke plume lateral diffusion coefficients from ERTS images of Virginia

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    A technique for measuring smoke plume of large industrial sources observed by satellite using LARSYS is proposed. A Gaussian plume model is described, integrated in the vertical, and inverted to yield a form for the lateral diffusion coefficient, Ky. Given u, wind speed; y sub l, the horizontal distance of a line of constant brightness from the plume symmetry axis a distance x sub l, downstream from reference point at x=x sub 2, y=0, then K sub y = u ((y sub 1) to the 2nd power)/2 x sub 1 1n (x sub 2/x sub 1). The technique is applied to a plume from a power plant at Chester, Virginia, imaged August 31, 1973 by LANDSAT I. The plume bends slightly to the left 4.3 km from the source and estimates yield Ky of 28 sq m/sec near the source, and 19 sq m/sec beyond the bend. Maximum ground concentrations are estimated between 32 and 64 ug/cu m. Existing meteorological data would not explain such concentrations

    The Distribution of Information in Speculative Markets: A Natural Experiment

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    We use a unique natural experiment to shed light on the distribution of information in speculative markets. In June 2011, Betfair – a UK betting exchange – levied a tax of up to 60% on all future profits accrued by the top 0.1% of profitable traders. Such a move appears to have driven at least some of these traders off the exchange, taking their information with them. We investigate the effect of the new tax on the forecasting capacity of the exchange (our measure of the market's incorporation of information into the price). We find that there was scant decline in the forecasting capacity of the exchange – relative to a control market – suggesting that the bulk of information had hitherto been held by the majority of traders, rather than the select few affected by the rule change. This result is robust to the choice of forecasting measure, the choice of forecasting interval, and the choice of race type. This provides evidence that more than a few traders are typically involved in the price discovery process in speculative markets

    Influence of reheating on the trispectrum and its scale dependence

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    We study the evolution of the non-linear curvature perturbation during perturbative reheating, and hence how observables evolve to their final values which we may compare against observations. Our study includes the evolution of the two trispectrum parameters, \gnl and \taunl, as well as the scale dependence of both \fnl and \taunl. In general the evolution is significant and must be taken into account, which means that models of multifield inflation cannot be compared to observations without specifying how the subsequent reheating takes place. If the trispectrum is large at the end of inflation, it normally remains large at the end of reheating. In the classes of models we study, it is very hard to generate \taunl\gg\fnl^2, regardless of the decay rates of the fields. Similarly, for the classes of models in which \gnl\simeq\taunl during slow--roll inflation, we find the relation typically remains valid during reheating. Therefore it is possible to observationally test such classes of models without specifying the parameters of reheating, even though the individual observables are sensitive to the details of reheating. It is hard to generate an observably large \gnl however. The runnings, \nfnl and \ntaunl, tend to satisfy a consistency relation \ntaunl=(3/2)\nfnl, but are in general too small to be observed for the class of models considered regardless of reheating timescale
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