3,786 research outputs found
How New York City Reduced Mass Incarceration: A Model for Change?
In this report, leading criminologists examine the connection between New York City's shift in policing strategies and the dramatic decrease in the City's incarcerated and correctional population
Look No Further: Adapting the Localization Sensory Window to the Temporal Characteristics of the Environment
Many localization algorithms use a spatiotemporal window of sensory
information in order to recognize spatial locations, and the length of this
window is often a sensitive parameter that must be tuned to the specifics of
the application. This letter presents a general method for environment-driven
variation of the length of the spatiotemporal window based on searching for the
most significant localization hypothesis, to use as much context as is
appropriate but not more. We evaluate this approach on benchmark datasets using
visual and Wi-Fi sensor modalities and a variety of sensory comparison
front-ends under in-order and out-of-order traversals of the environment. Our
results show that the system greatly reduces the maximum distance traveled
without localization compared to a fixed-length approach while achieving
competitive localization accuracy, and our proposed method achieves this
performance without deployment-time tuning.Comment: Pre-print of article appearing in 2017 IEEE Robotics and Automation
Letters. v2: incorporated reviewer feedbac
Feature Map Filtering: Improving Visual Place Recognition with Convolutional Calibration
Convolutional Neural Networks (CNNs) have recently been shown to excel at
performing visual place recognition under changing appearance and viewpoint.
Previously, place recognition has been improved by intelligently selecting
relevant spatial keypoints within a convolutional layer and also by selecting
the optimal layer to use. Rather than extracting features out of a particular
layer, or a particular set of spatial keypoints within a layer, we propose the
extraction of features using a subset of the channel dimensionality within a
layer. Each feature map learns to encode a different set of weights that
activate for different visual features within the set of training images. We
propose a method of calibrating a CNN-based visual place recognition system,
which selects the subset of feature maps that best encodes the visual features
that are consistent between two different appearances of the same location.
Using just 50 calibration images, all collected at the beginning of the current
environment, we demonstrate a significant and consistent recognition
improvement across multiple layers for two different neural networks. We
evaluate our proposal on three datasets with different types of appearance
changes - afternoon to morning, winter to summer and night to day.
Additionally, the dimensionality reduction approach improves the computational
processing speed of the recognition system.Comment: Accepted to the Australasian Conference on Robotics and Automation
201
Practical improvements to class group and regulator computation of real quadratic fields
We present improvements to the index-calculus algorithm for the computation
of the ideal class group and regulator of a real quadratic field. Our
improvements consist of applying the double large prime strategy, an improved
structured Gaussian elimination strategy, and the use of Bernstein's batch
smoothness algorithm. We achieve a significant speed-up and are able to compute
the ideal class group structure and the regulator corresponding to a number
field with a 110-decimal digit discriminant
Rhythmic Representations: Learning Periodic Patterns for Scalable Place Recognition at a Sub-Linear Storage Cost
Robotic and animal mapping systems share many challenges and characteristics:
they must function in a wide variety of environmental conditions, enable the
robot or animal to navigate effectively to find food or shelter, and be
computationally tractable from both a speed and storage perspective. With
regards to map storage, the mammalian brain appears to take a diametrically
opposed approach to all current robotic mapping systems. Where robotic mapping
systems attempt to solve the data association problem to minimise
representational aliasing, neurons in the brain intentionally break data
association by encoding large (potentially unlimited) numbers of places with a
single neuron. In this paper, we propose a novel method based on supervised
learning techniques that seeks out regularly repeating visual patterns in the
environment with mutually complementary co-prime frequencies, and an encoding
scheme that enables storage requirements to grow sub-linearly with the size of
the environment being mapped. To improve robustness in challenging real-world
environments while maintaining storage growth sub-linearity, we incorporate
both multi-exemplar learning and data augmentation techniques. Using large
benchmark robotic mapping datasets, we demonstrate the combined system
achieving high-performance place recognition with sub-linear storage
requirements, and characterize the performance-storage growth trade-off curve.
The work serves as the first robotic mapping system with sub-linear storage
scaling properties, as well as the first large-scale demonstration in
real-world environments of one of the proposed memory benefits of these
neurons.Comment: Pre-print of article that will appear in the IEEE Robotics and
Automation Letter
Graph Saturation in Multipartite Graphs
Let be a fixed graph and let be a family of graphs. A
subgraph of is -saturated if no member of
is a subgraph of , but for any edge in , some element of
is a subgraph of . We let and
denote the maximum and minimum size of an
-saturated subgraph of , respectively. If no element of
is a subgraph of , then .
In this paper, for and we determine
, where is the complete balanced -partite
graph with partite sets of size . We also give several families of
constructions of -saturated subgraphs of for . Our results
and constructions provide an informative contrast to recent results on the
edge-density version of from [A. Bondy, J. Shen, S.
Thomass\'e, and C. Thomassen, Density conditions for triangles in multipartite
graphs, Combinatorica 26 (2006), 121--131] and [F. Pfender, Complete subgraphs
in multipartite graphs, Combinatorica 32 (2012), no. 4, 483--495].Comment: 16 pages, 4 figure
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