277 research outputs found
Query-Based Learning for Aerospace Applications
Models of real-world applications often include a large number of parameters with a wide dynamic range, which contributes to the difficulties of neural network training. Creating the training data set for such applications becomes costly, if not impossible. In order to overcome the challenge, one can employ an active learning technique known as query-based learning (QBL) to add performance-critical data to the training set during the learning phase, thereby efficiently improving the overall learning/generalization. The performance-critical data can be obtained using an inverse mapping called network inversion (discrete network inversion and continuous network inversion) followed by oracle query. This paper investigates the use of both inversion techniques for QBL learning, and introduces an original heuristic to select the inversion target values for continuous network inversion method. Efficiency and generalization was further enhanced by employing node decoupled extended Kalman filter (NDEKF) training and a causality index (CI) as a means to reduce the input search dimensionality. The benefits of the overall QBL approach are experimentally demonstrated in two aerospace applications: a classification problem with large input space and a control distribution problem
Vibration Analysis Via Neural Network Inverse Models to Determine Aircraft Engine Unbalance Condition
This paper describes the use of artificial neural networks (ANNs) with the vibration data from real flight tests for detecting engine health condition - mass imbalance herein. Order-tracking data, calculated from time series is used as the input to the neural networks to determine the amount and location of mass imbalance on aircraft engines. Several neural network methods, including multilayer perceptron (MLP), extended Kalman filter (EKF) and support vector machines (SVMs) are used in the neural network inverse model for the performance comparison. The promising performances are presented at the end
Fluoropyrimidine sensitivity of human MCF-7 breast cancer cells stably transfected with human uridinehosphorylase
The relationship between uridine phosphorylase (UP) expression level in cancer cells and the tumour sensitivity to fluoropyrimidines is unclear. In this study, we found that UP overexpression by gene transfer, and the subsequent efficient metabolic activation of 5-fluorouracil (5-FU) by the ribonucleotide pathway, does not increase the fluoropyrimidine sensitivity of MCF-7 human cancer cells. © 2001 Cancer Research Campaign http://www.bjcancer.co
Aircraft Cabin Noise Minimization Via Neural Network Inverse Model
This paper describes research to investigate an artificial neural network (ANN) approach to minimize aircraft cabin noise in flight. The ANN approach is shown to be able to accurately model the non-linear relationships between engine unbalance, airframe vibration, and cabin noise to overcome limitations associated with traditional linear influence coefficient methods. ANN system inverse models are developed using engine test-stand vibration data and on-airplane vibration and noise data supplemented with influence coefficient empirical data. The inverse models are able to determine balance solutions that satisfy cabin noise specifications. The accuracy of the ANN model with respect to the real system is determined by the quantity and quality of test stand and operational aircraft data. This data-driven approach is particularly appealing for implementation on future systems that include continuous monitoring processes able to capture data while in operation
Vehicle Base Station
A system to load and unload material from a vehicle comprises a vehicle base station and an assembly to autonomously load and unload material from the vehicle
Wilson line correlators in two-dimensional noncommutative Yang-Mills theory
We study the correlator of two parallel Wilson lines in two-dimensional
noncommutative Yang-Mills theory, following two different approaches. We first
consider a perturbative expansion in the large-N limit and resum all planar
diagrams. The second approach is non-perturbative: we exploit the Morita
equivalence, mapping the two open lines on the noncommutative torus (which
eventually gets decompacted) in two closed Wilson loops winding around the dual
commutative torus. Planarity allows us to single out a suitable region of the
variables involved, where a saddle-point approximation of the general Morita
expression for the correlator can be performed. In this region the correlator
nicely compares with the perturbative result, exhibiting an exponential
increase with respect to the momentum p.Comment: 21 pages, 1 figure, typeset in JHEP style; some formulas corrected in
Sect.3, one reference added, results unchange
On the invariance under area preserving diffeomorphisms of noncommutative Yang-Mills theory in two dimensions
We present an investigation on the invariance properties of noncommutative
Yang-Mills theory in two dimensions under area preserving diffeomorphisms.
Stimulated by recent remarks by Ambjorn, Dubin and Makeenko who found a
breaking of such an invariance, we confirm both on a fairly general ground and
by means of perturbative analytical and numerical calculations that indeed
invariance under area preserving diffeomorphisms is lost. However a remnant
survives, namely invariance under linear unimodular tranformations.Comment: LaTeX JHEP style, 16 pages, 2 figure
Two-dimensional non-commutative Yang-Mills theory: coherent effects in open Wilson line correlators
A perturbative calculation of the correlator of three parallel open Wilson
lines is performed for the U(N) theory in two non-commutative space-time
dimensions. In the large-N planar limit, the perturbative series is fully
resummed and asymptotically leads to an exponential increase of the correlator
with the lengths of the lines, in spite of an interference effect between lines
with the same orientation. This result generalizes a similar increase occurring
in the two-line correlator and is likely to persist when more lines are
considered provided they share the same direction.Comment: 22 pages, 1 figure, typeset in JHEP styl
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