301 research outputs found
Keith Gendreau, Mark Bautz, George Ricker
No full textWe report measurements of effects of 2.1 MeV and 40 MeV protons on Charge Coupled Device X-ray detectors of a type soon to be launched on several astronomical research satellites. We discuss ground performance characterization techniques and compare our measurements to simple models of the detector damage mechanism. We predict detector peformance degradation rates in low-earth orbit. We plan to compare these predictions to early flight data obtained from the Solid State Imaging Spectrometer (SIS) focal plane instrument mounted on the Japan/US X-ray astronomy satellite Asuka launched on February 20, 1993. Introduction At MIT, we are developing photon counting imaging x-ray spectrometers using Charge Coupled Device (CCD) detectors for several astronomical research satellites. The first of these, the Japan/US mission Asuka, has been developed jointly by the Japanese Institute for Space and Aeronautical Science (ISAS) and the National Aeronautics and Space Administration (NASA) (Ricker e..
Simulation-based optimization of agent scheduling in multiskill call centers.
No full textWe examine and compare simulation-based algorithms for solvingthe agent scheduling problem in a multiskill call center.This problem consists in minimizing the total costs of agents underconstraints on the expected service level per call type,per period, and aggregated.We propose a solution approach that combines simulation withinteger or linear programming, with cut generation.In our numerical experiments with realistic problem instances,this approach performs better than all other methods proposedpreviously for this problem.We also show that the two-step approach, which is the standard methodfor solving this problem, sometimes yield solutions that arehighly suboptimal and inferior to those obtained by our proposed method.<br/
Optimizing daily agent scheduling in a multiskill call center
No full textWe examine and compare simulation-based algorithms for solving the agent scheduling problem in a multiskill call center. This problem consists in minimizing the total costs of agents under constraints on the expected service level per call type, per period, and aggregated. We propose a solution approach that combines simulation with integer or linear programming, with cut generation. In our numerical experiments with realistic problem instances, this approach performs better than all other methods proposed previously for this problem. We also show that the two-step approach, which is the standard method for solving this problem, sometimes yield solutions that are highly suboptimal and inferior to those obtained by our proposed method.<br/
X-ray CCDs for space applications : calibration, radiation hardness, and use for measuring the spectrum of the cosmic X-ray background
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1995.Includes bibliographical references (200-202).by Keith Charles Gendreau.Ph.D
Moral rights and industrial design
No full textThe chapter examines moral rights arising from the creation of industrial design works. The author observes how, in the European Union, the overlap between the registered design law and the copyright law, which also applies to industrial designs, raises problems of harmonisation between the rules of one discipline and those of the other, while at the same time allowing a considerable extension of the moral rights available to the author. However, the attribution to the author of an industrial design of all the moral rights recognised by copyright law raises non-trivial problems of balancing interests against the need to protect the reasonable expectations of the authors' successors in title
La civilisation du droit d'auteur au Canada
No full textAt a time when the information society requires that copyright be increasingly harmonised, the author describes how the two main copyright traditions meet in Canada. The distinction between common law and civil law also exists in copyright law ; one then talks about « the copyright tradition » and about the author's right tradition, the continental tradition or the civil law tradition. The first half of this article deals with the characteristics of each System in light of the law s of four countries, two per system, which represent the major trends within each System. One of the goals of this exercise is thus to show how each tradition can include various tendencies.
Canadian copyright law is examined in the second halfofthe article. The Canadian Copyright Act, which has grown out of the British copyright tradition, has undergone important changes on the occasion of its revision in 1988 and 1997. Some of the modifications resulted in the introduction of several author's rights notions. Other legislative and case law developments contribute to the understanding of the special nature of Canadian copyright law.A l'heure où le droit d'auteur doit être de plus en plus harmonisé pour répondre aux impératifs de la société de l'information, l'auteur dresse le portrait de la rencontre au Canada des deux grandes traditions de cette matière. En effet, l'opposition entre le droit civil et la common law existe en droit d'auteur sous les noms de « tradition de droit d'auteur », tradition continentale ou tradition civiliste, et de tradition de copyright. Dans la première partie sont exposées les caractéristiques des deux traditions à la lumière, pour chacune d'entre elles, des lois de deux pays qui représentent des tendances lourdes à l'intérieur de chaque système. L'un des objectifs est ici de démontrer que chaque tradition n'est pas aussi homogène qu'il n'y paraît.
La seconde partie de l'article est consacrée à l'examen du droit d'auteur canadien. Issue de la tradition britannique et donc appartenant à la famille du copyright, la loi canadienne a subi des modifications importantes lors des révisions de 1988 et 1997. Ces modifications ont introduit plusieurs éléments de la conception continentale du droit d'auteur. D'autres éléments législatifs et jurisprudentiels permettent également de mieux comprendre le caractère particulier de ce droit;Gendreau Ysolde. La civilisation du droit d'auteur au Canada. In: Revue internationale de droit comparé. Vol. 52 N°1, Janvier-mars 2000. pp. 101-123
Neutron Star Interior Composition Explorer X-ray timing of the radio and gamma-ray quiet pulsars PSR J1412+7922 and PSR J1849-0001
No full textWe present new timing and spectral analyses of PSR J1412+7922 (Calvera) and PSR J1849-0001, which are only seen as pulsars in X-rays, based on observations conducted with the Neutron Star Interior Composition Explorer (NICER). We obtain updated and substantially improved pulse ephemerides compared to previous X-ray studies, as well as spectra that can be well-fit by simple blackbodies and/or a power law. Our refined timing measurements enable deeper searches for pulsations at other wavelengths and sensitive targeted searches by LIGO/Virgo for continuous gravitational waves from these neutron stars. Using the sensitivity of LIGO's first observing run, we estimate constraints that a gravitational wave search of these pulsars would obtain on the size of their mass deformation and r-mode fluid oscillation
Pulsar Navigation and X-ray Communication Demonstrations with the NICER Payload on the ISS
No full textNo abstract availabl
Evolution of the Inner Accretion Flow and the White Dwarf Spin Pulse during the 2023 Outburst in GK Persei
No full textWe present our X-ray and optical observations performed by NICER, NuSTAR, and Tomo-e Gozen during the 2023 outburst in the intermediate polar GK Persei. The X-ray spectrum consisted of three components: blackbody (BB) emission of several tens of eVs from the irradiated white dwarf (WD) surface, a source possibly including several emission lines around 1 keV, and multitemperature bremsstrahlung emission from the accretion column. The 351.3 s WD spin pulse was detected in X-rays, and the observable X-ray flux from the column drastically decreased at the off-pulse phase, which suggests that the absorption of the column by the accreting gas, called the curtain, was the major cause of the pulse. As the system became brighter in the optical, the column became fainter, the pulse amplitude became higher, and the energy dependence of pulses became weaker at <8 keV. These phenomena could be explained by the column’s more pronounced absorption by the denser curtain as mass-accretion rates increased. The BB and line fluxes rapidly decreased at the optical decline, which suggests the expansion of the innermost disk edge with decreasing accretion rates. The electron scattering or the column geometry may be associated with the almost no energy dependence of high-energy pulses. The irradiated vertically thick structure at the disk may generate optical quasi-periodic oscillations with a period of ∼5700 s
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