54,424 research outputs found
Dynamic Programming for Optimal Control of Set-Up Scheduling with Neural Network Modifications
This paper demonstrates an optimal control solution to change of machine set-up scheduling based on dynamic programming average cost per stage value iteration as set forth by Cararnanis et. al. [2] for the 2D case. The difficulty with the optimal approach lies in the explosive computational growth of the resulting solution. A method of reducing the computational complexity is developed using ideas from biology and neural networks. A real time controller is described that uses a linear-log representation of state space with neural networks employed to fit cost surfaces.Defense Advanced Research Projects Agency (90-0083
Fast Simulation of Gaussian-Mode Scattering for Precision Interferometry
Understanding how laser light scatters from realistic mirror surfaces is
crucial for the design, com- missioning and operation of precision
interferometers, such as the current and next generation of gravitational-wave
detectors. Numerical simulations are indispensable tools for this task but
their utility can in practice be limited by the computational cost of
describing the scattering process. In this paper we present an efficient method
to significantly reduce the computational cost of optical simulations that
incorporate scattering. This is accomplished by constructing a near optimal
representation of the complex, multi-parameter 2D overlap integrals that
describe the scattering process (referred to as a reduced order quadrature). We
demonstrate our technique by simulating a near-unstable Fabry-Perot cavity and
its control signals using similar optics to those installed in one of the LIGO
gravitational-wave detectors. We show that using reduced order quadrature
reduces the computational time of the numerical simulation from days to minutes
(a speed-up of ) whilst incurring negligible errors. This
significantly increases the feasibility of modelling interferometers with
realistic imperfections to overcome current limits in state-of-the-art optical
systems. Whilst we focus on the Hermite-Gaussian basis for describing the
scattering of the optical fields, our method is generic and could be applied
with any suitable basis. An implementation of this reduced order quadrature
method is provided in the open source interferometer simulation software
Finesse.Comment: 15 pages, 11 figure
A Comparative Analysis of Phytovolume Estimation Methods Based on UAV-Photogrammetry and Multispectral Imagery in a Mediterranean Forest
Management and control operations are crucial for preventing forest fires, especially in Mediterranean forest areas with dry climatic periods. One of them is prescribed fires, in which the biomass fuel present in the controlled plot area must be accurately estimated. The most used methods for estimating biomass are time-consuming and demand too much manpower. Unmanned aerial vehicles (UAVs) carrying multispectral sensors can be used to carry out accurate indirect measurements of terrain and vegetation morphology and their radiometric characteristics. Based on the UAV-photogrammetric project products, four estimators of phytovolume were compared in a Mediterranean forest area, all obtained using the difference between a digital surface model (DSM) and a digital terrain model (DTM). The DSM was derived from a UAV-photogrammetric project based on the structure from a motion algorithm. Four different methods for obtaining a DTM were used based on an unclassified dense point cloud produced through a UAV-photogrammetric project (FFU), an unsupervised classified dense point cloud (FFC), a multispectral vegetation index (FMI), and a cloth simulation filter (FCS). Qualitative and quantitative comparisons determined the ability of the phytovolume estimators for vegetation detection and occupied volume. The results show that there are no significant differences in surface vegetation detection between all the pairwise possible comparisons of the four estimators at a 95% confidence level, but FMI presented the best kappa value (0.678) in an error matrix analysis with reference data obtained from photointerpretation and supervised classification. Concerning the accuracy of phytovolume estimation, only FFU and FFC presented differences higher than two standard deviations in a pairwise comparison, and FMI presented the best RMSE (12.3 m) when the estimators were compared to 768 observed data points grouped in four 500 m2 sample plots. The FMI was the best phytovolume estimator of the four compared for low vegetation height in a Mediterranean forest. The use of FMI based on UAV data provides accurate phytovolume estimations that can be applied on several environment management activities, including wildfire prevention. Multitemporal phytovolume estimations based on FMI could help to model the forest resources evolution in a very realistic way
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