3,175 research outputs found

    Homeownership is Still Out of Reach for Millions of Households

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    Homeownership has long been the leading source of household wealth in the U.S. However, the most recent housing crash stripped many Americans of much of their wealth, as home values plummeted and millions of homes went into foreclosure. These losses were especially painful for homeowners of color, who lost a greater share of wealth in the crash and have rebuilt their wealth more slowly in the recovery. Now, as the housing market recovers and interest rates remain low, many Americans find themselves without the savings or access to credit necessary to be able to purchase a home. Although homeownership is not the best option for every household, many Americans who could greatly benefit from it are still excluded

    Temporal distortion of annual modulation at low recoil energies

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    We show that the main features of the annual modulation of the signal expected in a WIMP direct detection experiment, i.e. its sinusoidal dependence with time, the occurrence of its maxima and minima during the year and (under some circumstances) even the one-year period, may be affected by relaxing the isothermal sphere hypothesis in the description of the WIMP velocity phase space. The most relevant effect is a distortion of the time-behaviour at low recoil energies for anisotropic galactic halos. While some of these effects turn out to be relevant at recoil energies below the current detector thresholds, some others could already be measurable, although some degree of tuning between the WIMP mass and the experimental parameters would be required. Either the observation or non-observation of these effects could provide clues on the phase space distribution of our galactic halo.Comment: 4 pages, 4 figures, typeset with ReVTeX4. The paper may also be found at http://www.to.infn.it/~fornengo/papers/distortion.ps.g

    Rural Facility Electric Power Quality Analysis

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    This report gives results of a recently completed data collection and analysis project investigating electric power quality of two isolated utility systems in Alaska. This is the second phase of a similar effort reported in 1984 which provided the first comprehensive power quality data from four small Alaskan communities. In this report, second generation instrumentation is described and comprehensive data and data analyses are presented. These data are important because of the increased use throughout Alaska of electrical and electronic equipment that may be damage by power system disturbances.Abstract - iv 1.0 Introduction - 1 1.1 Site descriptions - 1 1.2 Power quality definitions and disturbance analyzzer outputs - 2 2.0 Second Generation Instrumentation - 4 2.1 Hardware - 4 2.2 Software development and utilization - 8 3.0 Power System Disturbance Data - 9 3.1 Kotzebue site - 10 Figure Descriptions - 10 3.1.1 808: - 10 3.1.2 626: - 13 3.1.2.1 Impulse - 13 3.1.2.2 Sag - 16 3.1.2.3 Surge - 18 3.1.2.4 Frequency Disturbances - 21 3.1.2.5 Voltages - 23 Figures K1-K85 - 24-66 3.2 Tazlina site - 67 Figure Descriptions - 67 3.2.1 808: - 67 3.2.2 626: - 71 3.2.2.1 Impulse - 1 3.2.2.2 Sag - 74 3.2.2.3 Surge - 77 3.2.2.4 Frequency Disturbances - 81 3.2.2.5 Voltages - 83 Figures T1 - T102 - 85-135 3.3 Power system disturbance data summary - 136 3.3.1 Kotzebue site - 136 3.3.2 Tazlina site - 142 4.0 Conclusions - 147 5.0 Acknowledgements - 154 6.0 References - 154 7.0 Selected Bibliography - 155 8.0 Appendix

    Do current WIMP direct measurements constrain light relic neutralinos?

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    New upper bounds on direct detection rates have recently been presented by a number of experimental collaborations working on searches for WIMPs. In this paper we analyze how the constraints on relic neutralinos which can be derived from these results is affected by the uncertainties in the distribution function of WIMPs in the halo. Various different categories of velocity distribution functions are considered, and the ensuing implications for supersymmetric configurations derived. We conservatively conclude that current experimental data do not constrain neutralinos of small mass (below 50 GeV).Comment: 9 pages, 7 figures, typeset with ReVTeX4. The paper may also be found at http://www.to.infn.it/~fornengo/papers/constraints05.ps.gz or through http://www.astroparticle.to.infn.it/index.htm

    Effects of serum proteins on corrosion behavior of ISO 5832–9 alloy modified by titania coatings

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    Stainless steel ISO 5832–9 type is often used to perform implants which operate in protein-containing physiological environments. The interaction between proteins and surface of the implant may affect its corrosive properties. The aim of this work was to study the effect of selected serum proteins (albumin and γ-globulins) on the corrosion of ISO 5832–9 alloy (trade name M30NW) which surface was modified by titania coatings. These coatings were obtained by sol– gel method and heated at temperatures of 400 and 800 °C. To evaluate the effect of the proteins, the corrosion tests were performed with and without the addition of proteins with concentration of 1 g L−1 to the physiological saline solution (0.9 % NaCl, pH 7.4) at 37 °C. The tests were carried out within 7 days. The following electrochemical methods were used: open circuit potential, linear polarization resistance, and electrochemical impedance spectroscopy. In addition, surface analysis by optical microscopy and X-ray photoelectron spectroscopy (XPS) method was done at the end of weekly corrosion tests. The results of corrosion tests showed that M30NW alloy both uncoated and modified with titania coatings exhibits a very good corrosion resistance during weekly exposition to corrosion medium. The best corrosion resistance in 0.9 % NaCl solution is shown by alloy samples modified by titania coating annealed at 400 °C. The serumproteins have no significant effect onto corrosion of investigated biomedical steel. The XPS results confirmed the presence of proteins on the alloy surface after 7 days of immersion in proteincontaining solutions.The investigations were supported by the National Science Centre project No. N N507 501339. The authors gratefully acknowledge Dr. Janusz Sobczak and Dr. hab. Wojciech Lisowski from Institute of Physical Chemistry of PAS for XPS surface analyses

    Effect of Election Day Vote Centers on Voter Participation

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    In this article we study the effects of Election Day vote centers on voter turnout. Specifically we examine Texas and Colorado’s experience with alternative arrangements for the number and location of Election Day voting places and its impact on voter turnout in the 2006 and 2008 elections. We test our hypotheses at both the aggregate (i.e., county) and individual levels. We find evidence that vote centers increase voter turnout in presidential and midterm elections, and particularly among infrequent voters in midterms

    Displacements analysis of self-excited vibrations in turning

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    The actual research deals with determining by a new protocol the necessary parameters considering a three-dimensional model to simulate in a realistic way the turning process on machine tool. This paper is dedicated to the experimental displacements analysis of the block tool / block workpiece with self-excited vibrations. In connexion with turning process, the self-excited vibrations domain is obtained starting from spectra of two accelerometers. The existence of a displacements plane attached to the tool edge point is revealed. This plane proves to be inclined compared to the machines tool axes. We establish that the tool tip point describes an ellipse. This ellipse is very small and can be considered as a small straight line segment for the stable cutting process (without vibrations). In unstable mode (with vibrations) the ellipse of displacements is really more visible. A difference in phase occurs between the tool tip displacements on the radial direction and on the cutting one. The feed motion direction and the cutting one are almost in phase. The values of the long and small ellipse axes (and their ratio) shows that these sizes are increasing with the feed rate value. The axis that goes through the stiffness center and the tool tip represents the maximum stiffness direction. The maximum (resp. minimum) stiffness axis of the tool is perpendicular to the large (resp. small) ellipse displacements axis. FFT analysis of the accelerometers signals allows to reach several important parameters and establish coherent correlations between tool tip displacements and the static - elastic characteristics of the machine tool components tested

    Fitting functions for a disk-galaxy model with different LCDM-halo profiles

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    We present an adaptation of the standard scenario of disk-galaxy formation to the concordant LCDM cosmology aimed to derive analytical expressions for the scale length and rotation speed of present-day disks that form within four different, cosmologically motivated protogalactic dark matter halo-density profiles. We invoke a standard galaxy-formation model that includes virial equilibrium of spherical dark halos, specific angular momentum conservation during gas cooling, and adiabatic halo response to the gas inflow. The mean mass-fraction and mass-to-light ratio of the central stellar disk are treated as free parameters whose values are tuned to match the zero points of the observed size-luminosity and circular speed-luminosity relations of galaxies. We supply analytical formulas for the characteristic size and rotation speed of disks built inside Einasto r^{1/6}, Hernquist, Burkert, and Navarro-Frenk-White dark matter halos. These expressions match simultaneously the observed zero points and slopes of the different correlations that can be built in the RVL space of disk galaxies from plausible values of the galaxy- and star-formation efficiencies

    Mechanisms of the Vertical Secular Heating of a Stellar Disk

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    We investigate the nonlinear growth stages of bending instability in stellar disks with exponential radial density profiles.We found that the unstable modes are global (the wavelengths are larger than the disk scale lengths) and that the instability saturation level is much higher than that following from a linear criterion. The instability saturation time scales are of the order of one billion years or more. For this reason, the bending instability can play an important role in the secular heating of a stellar disk in the zz direction. In an extensive series of numerical NN-body simulations with a high spatial resolution, we were able to scan in detail the space of key parameters (the initial disk thickness z0z_0, the Toomre parameter QQ, and the ratio of dark halo mass to disk mass Mh/MdM_{\rm h} / M_{\rm d}). We revealed three distinct mechanisms of disk heating in the zz direction: bending instability of the entire disk, bending instability of the bar, and heating on vertical inhomogeneities in the distribution of stellar matter.Comment: 22 pages including 8 figures. To be published in Astronomy Letters (v.29, 2003
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