10,679 research outputs found

    g-elements, finite buildings and higher Cohen-Macaulay connectivity

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    The main result is a proof that the g-vector of a simplicial complex with a convex ear decomposition is an M-vector. This is a generalization of similar results for matroid complexes. We also show that a finite building has a convex ear decomposition. This leads to connections between higher Cohen-Macaulay connectivity and increasing h-vectors.Comment: To appear in JCT A. 20 page

    Sensor Simulation and position calibration for the CMS pixel detector

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    In this paper a detailed simulation of irradiated pixel sensors was used to investigate the effects of radiation damage on charge sharing and position determination. The simulation implements a model of radiation damage by including two defect levels with opposite charge states and trapping of charge carriers. We show that charge sharing functions extracted from the simulation can be parameterized as a function of the inter-pixel position and used to improve the position determination. For sensors irradiated to Phi=5.9x10^14 n/cm^2 a position resolution below 15 um can be achieved after calibration.Comment: Presented at the 14th Int. Workshop on Vertex Detectors (Vertex 2005), November 7-11 2005, Chuzenji Lake, Nikko, Japan. 4 pages, 1 figur

    Signal processor architecture for backscatter radars

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    Real time signal processing for backscatter radars which requires computational throughput and I/O rates is discussed. The operations that are usually performed in real time are highly repetitive simple accumulations of samples or of products of samples. The control logic does not depend on the values of the data and general purpose computers are not required for the initial high speed processing. The implications of these facts on the architectures of preprocessors for backscatter radars are explored and applied to the design of the Radar Signal Compender

    Micro-fluid exchange coupling apparatus

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    In a macro-fluid exchange, a hollow needle, such as a syringe needle, is provided for penetrating the fluid conduit of the animal. The syringe needle is coupled to a plenum chamber having an inlet and outlet port. The plenum chamber is coupled to the syringe needle via the intermediary of a standard quick disconnect coupling fitting. The plenum chamber is carried at the end of a drive rod which is coupled to a micrometer drive head. The micrometer drive head is slidably and pivotably coupled to a pedestal for adjusting the height and angle of inclination of the needle relative to a reference base support. The needle is positioned adjacent to the incised trachea or a blood vessel of a small animal and the micrometer drive head is operated for penetrating the fluid conduit of the animal

    Temperature and intensity dependence of the performance of an electron-irradiated (AlGa)As/GaAs solar cell

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    The performance of a Hughes, liquid-phase epitaxial 2 centimeter-by-2 centimeter, (AlGa)As/GaAs solar cell was measured before and after irradiations with 1 MeV electrons to fluences of 1 x 10 to the 16th power electrons/sq cm. The temperature dependence of performance was measured over the temperature range 135 to 415 K at each fluence level. In addition, temperature dependences were measured at five intensity levels from 137 to 2.57 mW/sq cm before irradiation and after a fluence of 1 x 10 to the 16th power electrons/sq cm. For the intermediate fluences, performance was measured as a function of intensity at 298 K only

    Performance and temperature dependencies of proton irradiated n/p GaAs and n/p silicon cells

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    The n/p homojunction GaAs cell is found to be more radiation resistant than p/nheteroface GaAs under 10 MeV proton irradiation. Both GaAs cell types outperform conventional silicon n/p cells under the same conditions. An increase temperature dependency of maximum power for the GaAs n/p cells is attributed largely to differences in Voc between the two GaAs cell types. These results and diffusion length considerations are consistent with the conclusion that p-type GaAs is more radiation resistant than n-type and therefore that the n/p configuration is possibly favored for use in the space radiation environment. However, it is concluded that additional work is required in order to choose between the two GaAs cell configurations

    World Politics and the Evolution of War

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    A proposed generalized constitutive equation for nonlinear para-isotropic materials

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    Finite element models of varying complexities were used to solve problems in solid mechanics. Particular emphasis was given to concrete which is nonisotropic at any level of deformation and is also nonlinear in terms of stress-strain relationships
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