12,485 research outputs found

    Optical Turbulence Measurements and Models for Mount John University Observatory

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    Site measurements were collected at Mount John University Observatory in 2005 and 2007 using a purpose-built scintillation detection and ranging system. Cn2(h)C_n^2(h) profiling indicates a weak layer located at 12 - 14 km above sea level and strong low altitude turbulence extending up to 5 km. During calm weather conditions, an additional layer was detected at 6 - 8 km above sea level. V(h)V(h) profiling suggests that tropopause layer velocities are nominally 12 - 30 m/s, and near-ground velocities range between 2 -- 20 m/s, dependent on weather. Little seasonal variation was detected in either Cn2(h)C_n^2(h) and V(h)V(h) profiles. The average coherence length, r0r_0, was found to be 7±17 \pm 1 cm for the full profile at a wavelength of 589 nm. The average isoplanatic angle, θ0\theta_0, was 1.0±0.11.0 \pm 0.1 arcsec. The mean turbulence altitude, h0ˉ\bar{h_0}, was found to be 2.0±0.72.0\pm0.7 km above sea level. No average in the Greenwood frequency, fGf_G, could be established due to the gaps present in the \vw\s profiles obtained. A modified Hufnagel-Valley model was developed to describe the Cn2(h)C_n^2(h) profiles at Mount John, which estimates r0r_0 at 6 cm and θ0\theta_0 at 0.9 arcsec. A series of V(h)V(h) models were developed, based on the Greenwood wind model with an additional peak located at low altitudes. Using the Cn2(h)C_n^2(h) model and the suggested V(h)V(h) model for moderate ground wind speeds, fGf_G is estimated at 79 Hz.Comment: 14 pages; accepted for publication in PAS

    Navigation systems for approach and landing of VTOL aircraft

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    The formulation and implementation of navigation systems used for research investigations in the V/STOLAND avionics system are described. The navigation systems prove position and velocity in a cartestian reference frame aligned with the runway. They use filtering techniques to combine the raw position data from navaids (e.g., TACAN, MLS) with data from onboard inertial sensors. The filtering techniques which use both complementary and Kalman filters, are described. The software for the navigation systems is also described

    Modification of nuclear transitions in stellar plasma by electronic processes: K-isomers in 176Lu and 180Ta under s-process conditions

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    The influence of the stellar plasma on the production and destruction of K-isomers is studied for the examples 176Lu and 180Ta. Individual electromagnetic transitions are enhanced predominantly by nuclear excitation by electron capture, whereas the other mechanisms of electron scattering and nuclear excitation by electron transition give only minor contributions. It is found that individual transitions can be enhanced significantly for low transition energies below 100 keV. Transitions with higher energies above 200 keV are practically not affected. Although one low-energy transition in 180Ta is enhanced by up to a factor of 10, the stellar transition rates from low-K to high-K states via so-called intermediate states in 176Lu and 180Ta do not change significantly under s-process conditions. The s-process nucleosynthesis of 176Lu and 180Ta remains essentially unchanged.Comment: 10 pages, 10 figures, Phys. Rev. C, accepte

    The Conflicts Between Female Inmates\u27 Needs And Prisoners\u27 Goals

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    A comparison of the purposes behind the existence of male and female institutions reveals that several common goals exist: custody, deterrence, and rehabilitation. An examination of these goals of women\u27s prisons can be best understood in the context of whom they are aimed to serve. If the goals are to serve society alone, then the custody of female offenders is undoubtedly viewed as an accomplished goal, since society is protected and secure from the infliction of criminal acts by these female offenders. However, if the goals are directed at the inmates as well, deterrence of further criminal activity and rehabilitation have failed both the society and the inmates as workable goals. Women sentenced to prison frequently return; in fact, it has been estimated that anywhere from fifty to eighty-five percent are recidivists. Furthermore, the women are generally not rehabilitated. Upon release, they are ill-prepared to cope with life on the outside. One former inmate stated, You just come out BAMB. And you don\u27t know how to deal with it. You don\u27t have a family to go to half the time. You don\u27t have a home or job. . . . A lot of times the only thing left for a person to do is commit new crime. If one agrees with Herbert Packer that the goal of rehabilitation is justified by the desire to reform the offender so further criminal activity will cease, and that each offender must be treated individually according to her needs then one must ask, why are not female offenders rehabilitated? This study attempts to develop an answer to this question by first researching the crimes committed by female offenders. The crimes committed reveal problems of which the prisons fail to take account. This leads to an inevitable conflict of prison goals with inmate needs. This conflict raises two alternatives: (1) one can work from the assumption that prisons will long continue in existence, so that any attempt to bring goals and needs closer together will have to be developed by working with the prison system, or (2) one can work from the assumption that alternatives to prison, as it is now known, must be found in order to effectuate the goals of prison and society and yet accommodate the needs of the female offenders

    The Southern Debate Over Slavery

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    Primary Sources on American Slavery The Southern Debate over Slavery, Vol. I, Petitions to Southern State Legislatures, 1778-1864. Vol. II, Petitions to Southern County Courts, 1775-1867. The two volumes under review have their origin in the “Race and Slavery Petitions Projec...

    Fragment Approach to Constrained Density Functional Theory Calculations using Daubechies Wavelets

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    In a recent paper we presented a linear scaling Kohn-Sham density functional theory (DFT) code based on Daubechies wavelets, where a minimal set of localized support functions is optimized in situ and therefore adapted to the chemical properties of the molecular system. Thanks to the systematically controllable accuracy of the underlying basis set, this approach is able to provide an optimal contracted basis for a given system: accuracies for ground state energies and atomic forces are of the same quality as an uncontracted, cubic scaling approach. This basis set offers, by construction, a natural subset where the density matrix of the system can be projected. In this paper we demonstrate the flexibility of this minimal basis formalism in providing a basis set that can be reused as-is, i.e. without reoptimization, for charge-constrained DFT calculations within a fragment approach. Support functions, represented in the underlying wavelet grid, of the template fragments are roto-translated with high numerical precision to the required positions and used as projectors for the charge weight function. We demonstrate the interest of this approach to express highly precise and efficient calculations for preparing diabatic states and for the computational setup of systems in complex environments

    Lamb Shift of 3P and 4P states and the determination of α\alpha

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    The fine structure interval of P states in hydrogenlike systems can be determined theoretically with high precision, because the energy levels of P states are only slightly influenced by the structure of the nucleus. Therefore a measurement of the fine structure may serve as an excellent test of QED in bound systems or alternatively as a means of determining the fine structure constant α\alpha with very high precision. In this paper an improved analytic calculation of higher-order binding corrections to the one-loop self energy of 3P and 4P states in hydrogen-like systems with low nuclear charge number ZZ is presented. A comparison of the analytic results to the extrapolated numerical data for high ZZ ions serves as an independent test of the analytic evaluation. New theoretical values for the Lamb shift of the P states and for the fine structure splittings are given.Comment: 33 pages, LaTeX, 4 tables, 4 figure

    Flight instrumentation specification for parameter identification: Program user's guide

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    A set of four digital computer programs is presented which can be used to investigate the effects of instrumentation errors on the accuracy of aircraft and helicopter stability-and-control derivatives identified from flight test data. The programs assume that the differential equations of motion are linear and consist of small perturbations about a quasi-steady flight condition. It is also assumed that a Newton-Raphson optimization technique is used for identifying the estimates of the parameters. Flow charts and printouts are included

    QED self-energy contribution to highly-excited atomic states

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    We present numerical values for the self-energy shifts predicted by QED (Quantum Electrodynamics) for hydrogenlike ions (nuclear charge 60Z11060 \le Z \le 110) with an electron in an n=3n=3, 4 or 5 level with high angular momentum (5/2j9/25/2\le j \le 9/2). Applications include predictions of precision transition energies and studies of the outer-shell structure of atoms and ions.Comment: 20 pages, 5 figure
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