382 research outputs found
Determination of the Indigenous Microflora of Men in Controlled Environments Final Report, Jul. 1964 - Nov. 1965
Determination of indigenous microflora in man during simulated space travel for establishing personal hygiene and sanitation criteri
Pre-Congestion Notification (PCN) Architecture
This document describes a general architecture for flow admission and termination based on pre-congestion information in order to protect the quality of service of established, inelastic flows within a single Diffserv domain.\u
Selectively oxidised vertical cavity surface emitting lasers with 50% power conversion efficiency
Includes bibliographical references (page 209).Index-guided vertical cavity top-surface emitting laser diodes have been fabricated from an all epitaxial structure with conducting mirrors by selective lateral oxidation of AlGaAs. Low voltage, a 78% slope efficiency, and a 350μA threshold current in a single device combine to yield a maximum power conversion efficiency of 50% at less than a 2mA drive current. The device operates in a single mode up to 1.5mW
High-frequency modulation of oxide-confined vertical cavity surface emitting lasers
Includes bibliographical references (page 458).High-speed studies of packaged, submilliampere threshold, oxide-confined vertical cavity surface emitting lasers show modulation bandwidths > 16GHz. Very high modulation current efficiency factors occur at low bias but decrease as the modulation bandwidth and frequency of the relative intensity noise peak saturate at higher currents
Fabrication and performance of selectively oxidized vertical-cavity lasers
Includes bibliographical references.We report the high yield fabrication and reproducible performance of selectively oxidized vertical-cavity surface emitting lasers. We show that linear oxidation rates of AlGaAs without an induction period allows reproducible fabrication of buried oxide current apertures within monolithic distributed Bragg reflectors. The oxide layers do not induce obvious crystalline defects, and continuous wave operation in excess of 650 h has been obtained. The high yield fabrication enables relatively high laser performance over a wide wavelength span. We observe submilliamp threshold currents over a wavelength range of up to 75 nm, and power conversion efficiencies at 1 mW output power of greater than 20% over a 50-nm wavelength range.The work at Sandia National Laboratories was supported in part by the United States DOE under contract No. DE-AC04-94AL85000
A New Model of Plan Recognition
We present a new abductive, probabilistic theory of plan recognition. This
model differs from previous plan recognition theories in being centered around
a model of plan execution: most previous methods have been based on plans as
formal objects or on rules describing the recognition process. We show that our
new model accounts for phenomena omitted from most previous plan recognition
theories: notably the cumulative effect of a sequence of observations of
partially-ordered, interleaved plans and the effect of context on plan
adoption. The model also supports inferences about the evolution of plan
execution in situations where another agent intervenes in plan execution. This
facility provides support for using plan recognition to build systems that will
intelligently assist a user.Comment: Appears in Proceedings of the Fifteenth Conference on Uncertainty in
Artificial Intelligence (UAI1999
Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides
Abstract Two new fates of imine intermediates formed on radical cyclizations of ene-sulfonamides have been identified, reduction and hydration/fragmentation. Tin hydride-mediated cyclizations of 2-halo-N-(3-methyl-N-sulfonylindole)anilines provide spiro[indoline-3,3'-indolones] or spiro-3,3'-biindolines (derived from imine reduction), depending on the indole C2 substituent. Cyclizations of 2-haloanilide derivatives of 3-carboxy-N-sulfonyl-2,3-dihydropyrroles also presumably form spiro-imines as primary products. However, the lactam carbonyl group facilitates the ring-opening of these cyclic imines by a new pathway of hydration and retroClaisen-type reaction, providing rearranged 2-(2'-formamidoethyl)oxindoles. 164
Data-driven Identification of Parametric Governing Equations of Dynamical Systems Using the Signed Cumulative Distribution Transform
This paper presents a novel data-driven approach to identify partial
differential equation (PDE) parameters of a dynamical system. Specifically, we
adopt a mathematical "transport" model for the solution of the dynamical system
at specific spatial locations that allows us to accurately estimate the model
parameters, including those associated with structural damage. This is
accomplished by means of a newly-developed mathematical transform, the signed
cumulative distribution transform (SCDT), which is shown to convert the general
nonlinear parameter estimation problem into a simple linear regression. This
approach has the additional practical advantage of requiring no a priori
knowledge of the source of the excitation (or, alternatively, the initial
conditions). By using training data, we devise a coarse regression procedure to
recover different PDE parameters from the PDE solution measured at a single
location. Numerical experiments show that the proposed regression procedure is
capable of detecting and estimating PDE parameters with superior accuracy
compared to a number of recently developed machine learning methods.
Furthermore, a damage identification experiment conducted on a publicly
available dataset provides strong evidence of the proposed method's
effectiveness in structural health monitoring (SHM) applications. The Python
implementation of the proposed system identification technique is integrated as
a part of the software package PyTransKit
(https://github.com/rohdelab/PyTransKit)
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