1,963 research outputs found
Computer control study for a manned centrifuge Final technical report
Analog simulation of manned centrifuge capability for production of various gravity levels - centrifuge control syste
Few-Shot Bayesian Imitation Learning with Logical Program Policies
Humans can learn many novel tasks from a very small number (1--5) of
demonstrations, in stark contrast to the data requirements of nearly tabula
rasa deep learning methods. We propose an expressive class of policies, a
strong but general prior, and a learning algorithm that, together, can learn
interesting policies from very few examples. We represent policies as logical
combinations of programs drawn from a domain-specific language (DSL), define a
prior over policies with a probabilistic grammar, and derive an approximate
Bayesian inference algorithm to learn policies from demonstrations. In
experiments, we study five strategy games played on a 2D grid with one shared
DSL. After a few demonstrations of each game, the inferred policies generalize
to new game instances that differ substantially from the demonstrations. Our
policy learning is 20--1,000x more data efficient than convolutional and fully
convolutional policy learning and many orders of magnitude more computationally
efficient than vanilla program induction. We argue that the proposed method is
an apt choice for tasks that have scarce training data and feature significant,
structured variation between task instances.Comment: AAAI 202
Graph Element Networks: adaptive, structured computation and memory
We explore the use of graph neural networks (GNNs) to model spatial processes
in which there is no a priori graphical structure. Similar to finite element
analysis, we assign nodes of a GNN to spatial locations and use a computational
process defined on the graph to model the relationship between an initial
function defined over a space and a resulting function in the same space. We
use GNNs as a computational substrate, and show that the locations of the nodes
in space as well as their connectivity can be optimized to focus on the most
complex parts of the space. Moreover, this representational strategy allows the
learned input-output relationship to generalize over the size of the underlying
space and run the same model at different levels of precision, trading
computation for accuracy. We demonstrate this method on a traditional PDE
problem, a physical prediction problem from robotics, and learning to predict
scene images from novel viewpoints.Comment: Accepted to ICML 201
Development of an Epileptic Seizure Detection Application based on Parallel Computing
Abstract—Epileptic seizure detection in a large database of Electroencephalography (EEG) signals needs to be a time constrained process for real-time analysis. Epileptic seizure detection algorithms are designed to obtain and analyze a group of neural signals and recognize the presence of seizure occurrence. The computational cost of the algorithms should be minimized to reduce the processing time and memory consumption. Automated epileptic seizure detection using optimized feature selection improves the classification accuracy, but it occupies more processing time during the Artifact Removal (AR) stage. So, the execution time is greatly reduced by introducing task parallelism in the artifact removal stage. By harnessing parallel computing the computational overhead and processing time are decreased. An epileptic seizure detection application is developed and analyzed with respect to execution time, speedup, and parallel efficiency. The application was developed in Intel Pentium(R) Dual-core CPU with processor clock rate of 2.60 GHz, memory of 1.96 GB, and operating system of Windows X
Time-dependent wave-packet approach for fusion reactions of halo nuclei
The fusion reaction of a halo nucleus 11Be on 208Pb is described by a
three-body direct reaction model. A time-dependent wave packet approach is
applied to a three-body reaction problem. The wave packet approach enables us
to obtain scattering solutions without considering the three-body scattering
boundary conditions. The time evolution of the wave packet also helps us to
obtain intuitive understanding of the reaction dynamics. The calculations
indicate a decrease of the fusion probability by the presence of the halo
neutron.Comment: 7 pages, 3 figures, use espcrc1.sty, Talk at the International
Symposium on "Physics of Unstable Nuclei (ISPUN02)", Halong Bay, Vietnam,
November 20-25, 200
Petrogenesis of rift-related tephrites, phonolites and trachytes (Central European Volcanic Province, Rhön, FRG): Constraints from Sr, Nd, Pb and O isotopes
Highlights:
• Some differentiated alkaline rocks may evolve by FC or AFC but not both
• Analyses of acid-leached samples necessary to detect unsupported 87Sr
• Crustal contamination hardly detectable in high-Sr lavas but obvious in low-Sr lavas
• Deep crustal contamination confirmed by high-precision Pb double-spike data
• Positively correlated 87Sr/86Sr ratios - δ18O values also indicate crustal contamination
The volcanic rocks of the Rhön area (Central European Volcanic Province, Germany) belong to a moderately alkali basaltic suite that is associated with minor tephriphonolites, phonotephrites, tephrites, phonolites and trachytes. Based on isotope sytematics (87Sr/86Sr: 0.7033-0.7042; 143Nd/144Nd: 0.51279-0.51287; 206Pb/204Pb: 19.1-19.5), the inferred parental magmas formed by variable degrees of partial melting of a common asthenospheric mantle source (EAR: European Asthenospheric Reservoir of Cebria and Wilson, 1995). Tephrites, tephriphonolites, phonotephrites, phonolites and trachytes show depletions and enrichments in some trace elements (Sr, Ba, Nb, Zr, Y) indicating that they were generated by broadly similar differentiation processes that were dominated by fractionation of olivine, clinopyroxene, amphibole, apatite and titaniferous magnetite ± plagioclase ± alkalifeldspar. The fractionated samples seem to have evolved by two distinct processes. One is characterized by pure fractional crystallization indicated by increasing Nb (and other incompatible trace element) concentrations at virtually constant 143Nd/144Nd ~ 0.51280 and 87Sr/86Sr ~ 0.7035. The other process involved an assimilation-fractional crystallization process (AFC) where moderate assimilation to crystallization rates produced evolved magmas characterized by higher Nb concentrations at slightly lower 143Nd/144Nd down to 0.51275. Literature data for some of the evolved rocks show more variable 87Sr/86Sr ranging from 0.7037-0.7089 at constant 143Nd/144Nd ~ 0.51280. These features may result from assimilation of upper crustal rocks by highly differentiated low-Sr (< 100 ppm Sr) lavas. However, based on the displacement of the differentiated rocks from this study towards lower 143Nd/144Nd ratios and modeled AFC processes in 143Nd/144Nd vs. 87Sr/86Sr and 207Pb/204Pb vs. 143Nd/144Nd space assimilation of lower crustal rocks seems more likely. The view that assimilation of lower crustal rocks played a role is confirmed by high-precision double-spike Pb isotope data that reveal higher 207Pb/204Pb ratios (15.62-15.63) in the differentiated rocks than in the primitive basanites (15.58-15.61). This is compatible with incorporation of radiogenic Pb from lower crustal xenoliths (207Pb/204Pb: 15.63-15.69) into the melt. However, 206Pb/204Pb ratios are similar for the differentiated rocks (19.13-19.35) and the primitive basanites (19.12-19.55) implying that assimilation involved an ancient crustal end member with a higher U/Pb ratio than the mantle source of the basanites. In addition, alteration-corrected δ18O values of the differentiated rocks range from c. 5 to 7 ‰ which is the same range as observed in the primitive alkaline rocks. This study confirms previous interpretations that highlighted the role of AFC processes in the evolution of alkaline volcanic rocks in the Rhön area of the Central European Volcanic Province
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