32,614 research outputs found

    Constraints of solar flare particle transport models from anisotropy observations at Voyager 1

    Get PDF
    In general a particle transport model for energetic solar flare particles contains a number of free parameters which are determined by fitting various features of observed particle events. Frequently the parameter values are not uniquely determined. In order to place tighter constraints on the models, the anisotropy of 1 and 25 MeV/nuc protons and helium nuclei were examined during the 22 November 1977 solar particle event using data from the LECP experiment on Voyager 1 at 1.6 AU. These observations were combined with the time intensity profiles at Voyager 1 and at 1 AU from ISEE-1 and IMP-8 to determine the magnitude and radial dependence of the interplanetary diffusion coefficient and the required injection duration at the sun. The first order anisotropy amplitudes for both 1 MeV and 25 MeV protons are observed to decrease from maximum values (approx. 1) during the event onset at Voyager 1 to values consistent with convection in the solar wind at about 3 days into the event decay phase. The intensity and anisotropy profiles at 1.6 AU are consistent with predictions of diffusive transport with a modest mean free path (lambda = approx. 0.1 AU)

    Old open clusters: UBGVRI photometry of NGC 2506

    Get PDF
    UBGVRI photometry for the open cluster NGC 2506 is presented. From comparison of the observed colour-magnitude diagrams with simulations based on stellar evolutionary models we derive in a self consistent way reddening, distance, and age of the cluster: E(B-V)=0-0.07, (m-M)o = 12.6, age = 1.5-2.2 Gyr. The cluster shows a well definite secondary sequence, suggesting that binary systems constitute about 20 % of the cluster members visible in the colour-magnitude diagram.Comment: 11 pages, 7 figures, MNRAS latex style, accepte

    Early History Of ISNA

    Get PDF
    The International Symposia on Nonlinear Acoustics, now referred to as ISNA, have convened regularly since 1968, bringing together scientists and engineers to report and discuss the latest developments in this branch of nonlinear physics. The fact that this series of symposia is still going strong after more than four decades is testimony that nonlinear acoustics has established itself as a distinct, important, and vibrant field of research. In this paper we take a look back at the early years of ISNA to recall how it all began and trace the evolution of the symposia into their current form.Applied Research Laboratorie

    A critical appraisal of WinEcon and its use in a first‐year undergraduate Economics programme

    Get PDF
    This is an extended review of WinEcon, a CAL package for introductory economics. Our comments are based on a survey of staff and students involved in the first large‐scale (n = 300+) attempt to integrate WinEcon into a teaching and assessment programme

    In the Wake of the Spill: Environmental Views Along the Gulf Coast

    Get PDF
    Abstract Objectives We analyze patterns in environmental views of Gulf Coast residents, in the wake of the 2010 oil spill. To what extent do spill-related and other environmental views vary with individual characteristics, personal experience with the spill, or characteristics of place? Methods About 2,000 residents of selected coastal regions in Louisiana and Florida were interviewed by telephone in late summer 2010. Results One-quarter of the respondents said that their environmental views had changed as a result of the spill. Despite reporting more change, more spill effects, and greater threats from climate-induced sea-level rise, Louisiana respondents were less likely to support a deepwater moratorium, alternative energy, or resource conservation. Conclusions Results are consistent with real effects from the spill. Differences between Louisiana and Florida respondents are not explained by spill effects or individual characteristics, however. The patterns reflect biophysical differences of the coastlines that shaped their socioeconomic development

    Reduction and scientific analysis of data from the charge-energy-mass (CHEM) spectrometer on the AMPTE/CCE spacecraft

    Get PDF
    The Charge-Energy-Mass (CHEM) spectrometer instrument on the AMPTE/Charge Composition Explorer (CCE) spacecraft is designed to measure the mass and charge-state abundance of magnetospheric and magnetosheath ions between 0.3 and 315 keV/e, an energy range that includes the bulk of the ring current and the dynamically important portion of the plasma sheet population. Continuing research is being conducted using the AMPTE mission data set, and in particular, that of the CHEM spectrometer which has operated flawlessly since launch and still provides excellent quality data. The requirted routine data processing and reduction, and software develpment continues to be performed. Scientific analysis of composition data in a number of magnetospheric regions including the ring current region, near-earth plasma sheet and subsolar magnetosheath continues to be undertaken. Correlative studies using data from the sister instrument SULEICA, which determines the mass and charge states of ions in the energy range of approximately 10 to 250 keV/e on the IRM, as well as other data from the CCE and IRM spacecraft, particularly in the upstream region and plasma sheet have also been undertaken

    Orbiter Landing Loads Math Model Description and Correlation with ALT Flight Data

    Get PDF
    Results of the space shuttle approach and landing test are examined in order to assess landing gear characteristics and performance and verify landing dynamic analyses. The landing gears were instrumented with load-calibrated strain gages, a wheel-speed sensor, and strut stroke measurement devices. The mathematical procedure used in predicting the shuttle touchdown loads and dynamics is presented together with the comparisons between measured flight data and the analytical predictions. Conclusions from these data are also presented

    The effect of low-energy ion-implantation on the electrical transport properties of Si-SiO2 MOSFETs

    Full text link
    Using silicon MOSFETs with thin (5nm) thermally grown SiO2 gate dielectrics, we characterize the density of electrically active traps at low-temperature after 16keV phosphorus ion-implantation through the oxide. We find that, after rapid thermal annealing at 1000oC for 5 seconds, each implanted P ion contributes an additional 0.08 plus/minus 0.03 electrically active traps, whilst no increase in the number of traps is seen for comparable silicon implants. This result shows that the additional traps are ionized P donors, and not damage due to the implantation process. We also find, using the room temperature threshold voltage shift, that the electrical activation of donors at an implant density of 2x10^12 cm^-2 is ~100%.Comment: 11 pages, 10 figure

    The Generalized Ricci Flow for 3D Manifolds with One Killing Vector

    Full text link
    We consider 3D flow equations inspired by the renormalization group (RG) equations of string theory with a three dimensional target space. By modifying the flow equations to include a U(1) gauge field, and adding carefully chosen De Turck terms, we are able to extend recent 2D results of Bakas to the case of a 3D Riemannian metric with one Killing vector. In particular, we show that the RG flow with De Turck terms can be reduced to two equations: the continual Toda flow solved by Bakas, plus its linearizaton. We find exact solutions which flow to homogeneous but not always isotropic geometries
    corecore