42,434 research outputs found

    Keldysh-Rutherford model for attoclock

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    We demonstrate a clear similarity between attoclock offset angles and Rutherford scattering angles taking the Keldysh tunnelling width as the impact parameter and the vector potential of the driving pulse as the asymptotic velocity. This simple model is tested against the solution of the time-dependent Schr\"odinger equation using hydrogenic and screened (Yukawa) potentials of equal binding energy. We observe a smooth transition from a hydrogenic to 'hard-zero' intensity dependence of the offset angle with variation of the Yukawa screening parameter. Additionally we make comparison with the attoclock offset angles for various noble gases obtained with the classical-trajectory Monte Carlo method. In all cases we find a close correspondence between the model predictions and numerical calculations. This suggests a largely Coulombic origin of the attoclock offset angle and casts further doubt on its interpretation in terms of a finite tunnelling time

    Investigation of the enhanced spatial density of submicron lunar ejecta between L values 1.2 and 3.0 in the earth's magnetosphere: Theory

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    Initial results from the measurement conducted by the dust particle experiment on the lunar orbiting satellite Lunar Explorer 35 (LE 35) were reported with the data interpreted as indicating that the moon is a significant source of micrometeroids. Primary sporadic and stream meteoroids impacting the surface of the moon at hypervelocity was proposed as the source of micron and submicron particles that leave the lunar craters with velocities sufficient to escape the moon's gravitational sphere of influence. No enhanced flux of lunar ejecta with masses greater than a nanogram was detected by LE 35 or the Lunar Orbiters. Hypervelocity meteoroid simulation experiments concentrating on ejecta production combined with extensive analyses of the orbital dynamics of micron and submicron lunar ejecta in selenocentric, cislunar, and geocentric space have shown that a pulse of these lunar ejecta, with a time correlation relative to the position of the moon relative to the earth, intercepts the earth's magnetopause surface (EMPs). As shown, a strong reason exists for expecting a significant enhancement of submicron dust particles in the region of the magnetosphere between L values of 1.2 and 3.0. This is the basis for the proposal of a series of experiments to investigate the enhancement or even trapping of submicron lunar ejecta in this region. The subsequent interaction of this mass with the upper-lower atmosphere of the earth and possible geophysical effects can then be studied

    Balancing Efficiency, Equity, and Voice in Workplace Resolution Procedures

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    Systems for resolving workplace disputes are very important to workers and firms, and have been the subject of much debate. In the United States, traditional unionized grievance procedures, emerging nonunion dispute resolution systems, and the court-based system for resolving employment law disputes have all been criticized. Much of the existing debate on workplace dispute resolution, however, has been atheoretical, with a focus on techniques of dispute resolution rather than the goals of the system. What is missing from the debate are fundamental standards for comparing and evaluating dispute resolutions systems. In this paper, we develop efficiency, equity, and voice as these standards. Unionized, nonunion, and employment law procedures are then evaluated against these three standards.

    Indenture as a Self-Enforced Contract Device: An Experimental Test

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    We experimentally test the efficacy of indenture as a self-enforced contract device. In an indenture game, the principal signals the intention of payment-on-delivery, by tearing a banknote and giving the agent half of it as "prepayment"; the agent receives the completing half after delivering the service. By forward induction, cooperation is incentive-compatibly self-enforcing. The indenture performs very well, inducing a significantly higher level of cooperation than that in a three-stage centipede game, which we use to benchmark the natural rate of cooperation. The difference between cooperation rates in both games increases over time.Cooperation, experiment, contracts, indenture, reciprocity

    The Economics of Solidarity: A Conceptual Framework

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    For many people "solidarity" has become a meaningless word used in slogans - too often used without leading to any economic consequences. We show in this paper conditions under which solidarity can be a powerful instrument. In a solidary action, an individual in a group contributes to a series of actions that aims for a reallocation of scarce resources. The willingness to contribute is mainly influenced by the efficiency of the objective of the solidary action, and is enhanced by feelings of mutual exchange (solidarity) within a group. --solidarity,altruism,dynamic,mutual

    X-56A Structural Dynamics Ground Testing Overview and Lessons Learned

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    The X-56A Multi-Utility Technology Testbed (MUTT) is a subscale, fixed-wing aircraft designed for high-risk aeroelastic flight demonstration and research. Structural dynamics ground testing for model validation was especially important for this vehicle because the structural model was directly used in the development of a flight control system with active flutter suppression capabilities. Structural dynamics ground tests of the X-56A MUTT with coupled rigid-body and structural modes provided a unique set of challenges. An overview of the ground vibration test (GVT) and moment of inertia (MOI) test setup and execution is presented. The series of GVTs included the wing by itself attached to a strongback and complete vehicle at two mass conditions: empty and full fuel. Two boundary conditions for the complete-vehicle test were studied: on landing gear and suspended free-free. Pitch MOI tests were performed using a compound pendulum method and repeated with two different pendulum lengths for independent verification. The original soft-support test configuration for the GVT used multiple bungees, resulting in unforeseen coupling interactions between the soft-support bungees and the vehicle structural modes. To resolve this problem, the soft-support test setup underwent multiple iterations. The various GVT configurations and boundary-condition modifications are highlighted and explained. Lessons learned are captured for future consideration when performing structural dynamics testing with similar vehicles

    Thermodynamics of Photon Gas with an Invariant Energy Scale

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    Quantum Gravity framework motivates us to find new theories in which an observer independent finite energy upper bound (preferably Planck Energy) exists. We have studied the modifications in the thermodynamical properties of a photon gas in such a scenario where we have an invariant energy scale. We show that the density of states and the entropy in such a framework are less than the corresponding quantities in Einstein's Special Relativity (SR) theory. This result can be interpreted as a consequence of the deformed Lorentz symmetry present in the particular model we have considered.Comment: 17 pages, 3 figure files, some addition in text as well as in references, the scaling of figures have been modifie
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