1,817 research outputs found

    Flux growth of ZnO microcrystals and growth of doped homoepitaxial ZnO films by liquid phase epitaxy

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    Zinc oxide is known as an outstanding material with desirable properties and a wide application range in optoelectronics, transparent electronics, etc. An increasingly important aspect is the fabrication of materials like ZnO by technologies which not only guarantee reproducibly high quality, but also facilitate one-step fabrication of the functional materials with a minimum effort in producing them by so-called green technologies. Moreover, mechanically untouched ZnO surfaces are desirable to exclude radiative losses due to a damaged surface layer. As the doping of hydrothermal grown bulk ZnO appears rather difficult and time consuming, LPE was employed to obtain high-quality single crystal films of several micrometer thickness. With the LPE growth technique the damaged surface layer is neutralized, at the same time doping can be realized and the sample surface is mechanically untouched. LPE is an advancement of the flux growth. Before growing films by LPE several flux experiments were done. Homoepitaxial ZnO films and microcrystals were grown from a LiCl solution at 640°C under ambient air conditions. ZnO is produced by a reaction of ZnCl2 with K2CO3, such way providing the feeding for continous growth. Doping and formation of solid solutions with ions such like Bi, Sb, Mo, and In was enabled through employment of the relevant pure metal, metal halogenide or metal oxide. The crystal quality has been investigated by SEM, EDX, XRD, DIC and PL

    Distinguishing low frequency mutations from RT-PCR and sequence errors in viral deep sequencing data

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    There is a high prevalence of coronary artery disease (CAD) in patients with left bundle branch block (LBBB); however there are many other causes for this electrocardiographic abnormality. Non-invasive assessment of these patients remains difficult, and all commonly used modalities exhibit several drawbacks. This often leads to these patients undergoing invasive coronary angiography which may not have been necessary. In this review, we examine the uses and limitations of commonly performed non-invasive tests for diagnosis of CAD in patients with LBBB

    Automated Simulation Updates based on Flight Data

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    A statistically-based method for using flight data to update aerodynamic data tables used in flight simulators is explained and demonstrated. A simplified wind-tunnel aerodynamic database for the F/A-18 aircraft is used as a starting point. Flight data from the NASA F-18 High Alpha Research Vehicle (HARV) is then used to update the data tables so that the resulting aerodynamic model characterizes the aerodynamics of the F-18 HARV. Prediction cases are used to show the effectiveness of the automated method, which requires no ad hoc adjustments by the analyst

    Synchronization Dynamics in the Presence of Coupling Delays and Phase Shifts

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    In systems of coupled oscillators, the effects of complex signaling can be captured by time delays and phase shifts. Here, we show how time delays and phase shifts lead to different oscillator dynamics and how synchronization rates can be regulated by substituting time delays by phase shifts at a constant collective frequency. For spatially extended systems with time delays, we show that the fastest synchronization can occur for intermediate wavelengths, giving rise to novel synchronization scenarios.This work was supported by spanish Ministry of Economy and Competitiveness (MINECO) through Grant PHYSDEV (No. FIS2012-32349) and from CSIC through the Junta para la Ampliación de Estudios program (JAEDOC014, 2010 call) cofunded by the European Social FundPublicad

    Development of a Low-Cost Sub-Scale Aircraft for Flight Research: The FASER Project

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    An inexpensive unmanned sub-scale aircraft was developed to conduct frequent flight test experiments for research and demonstration of advanced dynamic modeling and control design concepts. This paper describes the aircraft, flight systems, flight operations, and data compatibility including details of some practical problems encountered and the solutions found. The aircraft, named Free-flying Aircraft for Sub-scale Experimental Research, or FASER, was outfitted with high-quality instrumentation to measure aircraft inputs and states, as well as vehicle health parameters. Flight data are stored onboard, but can also be telemetered to a ground station in real time for analysis. Commercial-off-the-shelf hardware and software were used as often as possible. The flight computer is based on the PC104 platform, and runs xPC-Target software. Extensive wind tunnel testing was conducted with the same aircraft used for flight testing, and a six degree-of-freedom simulation with nonlinear aerodynamics was developed to support flight tests. Flight tests to date have been conducted to mature the flight operations, validate the instrumentation, and check the flight data for kinematic consistency. Data compatibility analysis showed that the flight data are accurate and consistent after corrections are made for estimated systematic instrumentation errors

    Collective modes of coupled phase oscillators with delayed coupling

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    We study the effects of delayed coupling on timing and pattern formation in spatially extended systems of dynamic oscillators. Starting from a discrete lattice of coupled oscillators, we derive a generic continuum theory for collective modes of long wavelength. We use this approach to study spatial phase profiles of cellular oscillators in the segmentation clock, a dynamic patterning system of vertebrate embryos. Collective wave patterns result from the interplay of coupling delays and moving boundary conditions. We show that the phase profiles of collective modes depend on coupling delays.Comment: 5 pages, 2 figure

    Development and Implementation of a Model-Driven Envelope Protection System for In-Flight Ice Contamination

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    Fatal loss-of-control (LOC) accidents have been directly related to in-flight airframe icing. The prototype system presented in this paper directly addresses the need for real-time onboard envelope protection in icing conditions. The combinations of a-priori information and realtime aerodynamic estimations are shown to provide sufficient input for determining safe limits of the flight envelope during in-flight icing encounters. The Icing Contamination Envelope Protection (ICEPro) system has been designed and implemented to identify degradations in airplane performance and flying qualities resulting from ice contamination and provide safe flight-envelope cues to the pilot. Components of ICEPro are described and results from preliminary tests are presented

    A categorification of Morelli's theorem

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    We prove a theorem relating torus-equivariant coherent sheaves on toric varieties to polyhedrally-constructible sheaves on a vector space. At the level of K-theory, the theorem recovers Morelli's description of the K-theory of a smooth projective toric variety. Specifically, let XX be a proper toric variety of dimension nn and let M_\bR = \mathrm{Lie}(T_\bR^\vee)\cong \bR^n be the Lie algebra of the compact dual (real) torus T_\bR^\vee\cong U(1)^n. Then there is a corresponding conical Lagrangian \Lambda \subset T^*M_\bR and an equivalence of triangulated dg categories \Perf_T(X) \cong \Sh_{cc}(M_\bR;\Lambda), where \Perf_T(X) is the triangulated dg category of perfect complexes of torus-equivariant coherent sheaves on XX and \Sh_{cc}(M_\bR;\Lambda) is the triangulated dg category of complex of sheaves on M_\bR with compactly supported, constructible cohomology whose singular support lies in Λ\Lambda. This equivalence is monoidal---it intertwines the tensor product of coherent sheaves on XX with the convolution product of constructible sheaves on M_\bR.Comment: 20 pages. This is a strengthened version of the first half of arXiv:0811.1228v3, with new results; the second half becomes arXiv:0811.1228v
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