609 research outputs found

    Learning to Live With Wolves: Community-based Conservation in the Blackfoot Valley of Montana

    Get PDF
    We built on the existing capacity of a nongovernmental organization called the Blackfoot Challenge to proactively address wolf (Canis lupus)-livestock conflicts in the Blackfoot Valley of Montana. Beginning in 2007, wolves started rapidly recolonizing the valley, raising concerns among livestock producers. We built on an existing program to mitigate conflicts associated with an expanding grizzly bear population and worked within the community to build a similar program to reduce wolf conflicts using an integrative, multi-method approach. Efforts to engage the community included one-on-one meetings, workshops, field tours, and regular group meetings as well as opportunities to participate in data collection and projects. Initial projects included permanent electric fencing of calving areas and livestock carcass removal to address the threat of grizzly bears and, later, wolves. Subsequently we used intensive livestock and wolf monitoring through range riders in an attempt to reduce the frequency of encounter rates among wolves and livestock. Although we cannot claim causation from our efforts, results are encouraging. Confirmed livestock losses to wolves from 2006-2015 have been 2.2 confirmed depredations per year across nearly 50 ranches on about 3,240 km2 that are annually grazed by 16,000-18,000 head of livestock. Fewer than three wolves per year have been removed (2.4 wolves per year) due to these depredations for the same period as the population increased from one confirmed pack to approximately twelve. Our collaborative approach and prior experience with grizzly bears was key in building a proactive program to help reduce conflict with wolves in a community adjusting to an increasing large carnivore presence over a short period

    Tomographic analysis of jammed ellipsoid packings

    Get PDF
    Disordered packings of ellipsoidal particles are an important model for disordered granular matter. Here we report a way to determine the average contact number of ellipsoid packings from tomographic analysis. Tomographic images of jammed ellipsoid packings prepared by vertical shaking of loose configurations are recorded and the positions and orientations of the ellipsoids are reconstructed. The average contact number can be extracted from a contact number scaling (CNS) function. The size of the particles, that may vary due to production inaccuracies, can also be determined by this method

    Numerical solutions of the algebraic matrix Riccati equation.

    Get PDF
    Abstract The linear-quadratic control model is one of the most widely used control models in both empirical and theoretical economic modeling. In order to obtain the equilibrium solution of this control model, the so-called algebraic matrix Riccati equation has to be solved. In this note we present a numerical solution method for solving this equation. Our method solves the Riccati equation as a multidimensional fixed-point problem. By establishing the analytical derivative of the Riccati equation we have been able to construct a very efficient Newton-type solution method with quadratic convergence properties. Our method is an extension for the Newton-Raphson method described in Kwakemaak and Sivan ( 1972) and does not require any special conditions on the transition rn3 as inthe nonrecursive method o

    Analytical expression of the magneto-optical Kerr effect and Brillouin light scattering intensity arising from dynamic magnetization

    Full text link
    Time-resolved magneto-optical Kerr effect (MOKE) and Brillouin light scattering (BLS) spectroscopy are important techniques for the investigation of magnetization dynamics. Within this article, we calculate analytically the MOKE and BLS signals from prototypical spin-wave modes in the ferromagnetic layer. The reliability of the analytical expressions is confirmed by optically exact numerical calculations. Finally, we discuss the dependence of the MOKE and BLS signals on the ferromagnetic layer thickness

    Near-Equilibrium Dynamics of Crystalline Interfaces with Long-Range Interactions in 1+1 Dimensional Systems

    Full text link
    The dynamics of a one-dimensional crystalline interface model with long-range interactions is investigated. In the absence of randomness, the linear response mobility decreases to zero when the temperature approaches the roughening transition from above, in contrast to a finite jump at the critical point in the Kosterlitz-Thouless (KT) transition. In the presence of substrate disorder, there exists a phase transition into a low-temperature pinning phase with a continuously varying dynamic exponent z>1z>1. The expressions for the non-linear response mobility of a crystalline interface in both cases are also derived.Comment: 14 Pages, Revtex3.0, accepted to be published in Phys. Rev. E Rapid Communicatio

    Tomographic analysis of jammed ellipsoid packings

    No full text
    Disordered packings of ellipsoidal particles are an important model for disordered granular matter. Here we report a way to determine the average contact number of ellipsoid packings from tomographic analysis. Tomographic images of jammed ellipsoid packings prepared by vertical shaking of loose configurations are recorded and the positions and orientations of the ellipsoids are reconstructed. The average contact number can be extracted from a contact number scaling (CNS) function. The size of the particles, that may vary due to production inaccuracies, can also be determined by this method

    Micromagnetic simulations of spinel ferrite particles

    Full text link
    This paper presents the results of simulations of the magnetization field {\it ac} response (at 22 to 1212 GHz) of various submicron ferrite particles (cylindrical dots). The ferrites in the present simulations have the spinel structure, expressed here by M1−n_{1-n}Znn_{n}Fe2_2O4_4 (where M stands for a divalent metal), and the parameters chosen were the following: (a) for n=0n=0: M = \{ Fe, Mn, Co, Ni, Mg, Cu \}; (b) for n=0.1n=0.1: M = \{ Fe, Mg \} (mixed ferrites). These runs represent full 3D micromagnetic (one-particle) ferrite simulations. We find evidences of confined spin waves in all simulations, as well as a complex behavior nearby the main resonance peak in the case of the M = \{ Mg, Cu \} ferrites. A comparison of the n=0n=0 and n=0.1n=0.1 cases for fixed M reveals a significant change in the spectra in M = Mg ferrites, but only a minor change in the M = Fe case. An additional larger scale simulation of a 33 by 33 particle array was performed using similar conditions of the Fe3_3O4_4 (magnetite; n=0n=0, M = Fe) one-particle simulation. We find that the main resonance peak of the Fe3_3O4_4 one-particle simulation is disfigured in the corresponding 3 by 3 particle simulation, indicating the extent to which dipolar interactions are able to affect the main resonance peak in that magnetic compound.Comment: 35 pages, 11 figures, Journal of Magnetism and Magnetic Materials, in press

    Magnetic Vortex Core Reversal by Excitation of Spin Waves

    Get PDF
    Micron-sized magnetic platelets in the flux closed vortex state are characterized by an in-plane curling magnetization and a nanometer-sized perpendicularly magnetized vortex core. Having the simplest non-trivial configuration, these objects are of general interest to micromagnetics and may offer new routes for spintronics applications. Essential progress in the understanding of nonlinear vortex dynamics was achieved when low-field core toggling by excitation of the gyrotropic eigenmode at sub-GHz frequencies was established. At frequencies more than an order of magnitude higher vortex state structures possess spin wave eigenmodes arising from the magneto-static interaction. Here we demonstrate experimentally that the unidirectional vortex core reversal process also occurs when such azimuthal modes are excited. These results are confirmed by micromagnetic simulations which clearly show the selection rules for this novel reversal mechanism. Our analysis reveals that for spin wave excitation the concept of a critical velocity as the switching condition has to be modified.Comment: Minor corrections and polishing of previous versio
    • 

    corecore