5,013 research outputs found
Data-efficient Neuroevolution with Kernel-Based Surrogate Models
Surrogate-assistance approaches have long been used in computationally
expensive domains to improve the data-efficiency of optimization algorithms.
Neuroevolution, however, has so far resisted the application of these
techniques because it requires the surrogate model to make fitness predictions
based on variable topologies, instead of a vector of parameters. Our main
insight is that we can sidestep this problem by using kernel-based surrogate
models, which require only the definition of a distance measure between
individuals. Our second insight is that the well-established Neuroevolution of
Augmenting Topologies (NEAT) algorithm provides a computationally efficient
distance measure between dissimilar networks in the form of "compatibility
distance", initially designed to maintain topological diversity. Combining
these two ideas, we introduce a surrogate-assisted neuroevolution algorithm
that combines NEAT and a surrogate model built using a compatibility distance
kernel. We demonstrate the data-efficiency of this new algorithm on the low
dimensional cart-pole swing-up problem, as well as the higher dimensional
half-cheetah running task. In both tasks the surrogate-assisted variant
achieves the same or better results with several times fewer function
evaluations as the original NEAT.Comment: In GECCO 201
Dynamical tunneling in mushroom billiards
We study the fundamental question of dynamical tunneling in generic
two-dimensional Hamiltonian systems by considering regular-to-chaotic tunneling
rates. Experimentally, we use microwave spectra to investigate a mushroom
billiard with adjustable foot height. Numerically, we obtain tunneling rates
from high precision eigenvalues using the improved method of particular
solutions. Analytically, a prediction is given by extending an approach using a
fictitious integrable system to billiards. In contrast to previous approaches
for billiards, we find agreement with experimental and numerical data without
any free parameter.Comment: 4 pages, 4 figure
Achenbach syndrome as a rare cause of painful, blue finger
Paroxysmal finger hematoma, also known as Achenbach syndrome, is an underdiagnosed condition that causes apprehension in patients owing to the alarming appearance. It usually presents as a blue-purple discoloration of the volar aspect of one or more digits and can be associated with pain and paresthesia. This condition is benign and is usually self-limiting
Development of improved semi-organic structural adhesives for elevated temperature applications Technical summary report, 1 ~JUL. 1964 - 29 ~FEB. 1968
Titanium chelate polymer adhesive formulation for aluminum joint curing in high temperature application
A STOL airworthiness investigation using a simulation of an augmentor wing transport. Volume 2: Simulation data and analysis
A simulator study of STOL airworthiness was conducted using a model of an augmentor wing transport. The approach, flare and landing, go-around, and takeoff phases of flight were investigated. The simulation and the data obtained are described. These data include performance measures, pilot commentary, and pilot ratings. A pilot/vehicle analysis of glide slope tracking and of the flare maneuver is included
Transport properties of anyons in random topological environments
The quasi one-dimensional transport of Abelian and non-Abelian anyons is
studied in the presence of a random topological background. In particular, we
consider the quantum walk of an anyon that braids around islands of randomly
filled static anyons of the same type. Two distinct behaviours are identified.
We analytically demonstrate that all types of Abelian anyons localise purely
due to the statistical phases induced by their random anyonic environment. In
contrast, we numerically show that non-Abelian Ising anyons do not localise.
This is due to their entanglement with the anyonic environment that effectively
induces dephasing. Our study demonstrates that localisation properties strongly
depend on non-local topological interactions and it provides a clear
distinction in the transport properties of Abelian and non-Abelian statistics.Comment: 9 pages, 5 figure
Rethinking the appraisal and approval of drugs for type 2 diabetes
The process for approving new drugs for type 2 diabetes illustrates the significant shortcomings of the regulatory standards for licensing, reimbursing, and adopting new drugs. Regulatory reform is needed to improve the real-world therapeutic value of anti-diabetic drugs
The Case for Learned Index Structures
Indexes are models: a B-Tree-Index can be seen as a model to map a key to the
position of a record within a sorted array, a Hash-Index as a model to map a
key to a position of a record within an unsorted array, and a BitMap-Index as a
model to indicate if a data record exists or not. In this exploratory research
paper, we start from this premise and posit that all existing index structures
can be replaced with other types of models, including deep-learning models,
which we term learned indexes. The key idea is that a model can learn the sort
order or structure of lookup keys and use this signal to effectively predict
the position or existence of records. We theoretically analyze under which
conditions learned indexes outperform traditional index structures and describe
the main challenges in designing learned index structures. Our initial results
show, that by using neural nets we are able to outperform cache-optimized
B-Trees by up to 70% in speed while saving an order-of-magnitude in memory over
several real-world data sets. More importantly though, we believe that the idea
of replacing core components of a data management system through learned models
has far reaching implications for future systems designs and that this work
just provides a glimpse of what might be possible
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