92,114 research outputs found
ImageSig: A signature transform for ultra-lightweight image recognition
This paper introduces a new lightweight method for image recognition.
ImageSig is based on computing signatures and does not require a convolutional
structure or an attention-based encoder. It is striking to the authors that it
achieves: a) an accuracy for 64 X 64 RGB images that exceeds many of the
state-of-the-art methods and simultaneously b) requires orders of magnitude
less FLOPS, power and memory footprint. The pretrained model can be as small as
44.2 KB in size. ImageSig shows unprecedented performance on hardware such as
Raspberry Pi and Jetson-nano. ImageSig treats images as streams with multiple
channels. These streams are parameterized by spatial directions. We contribute
to the functionality of signature and rough path theory to stream-like data and
vision tasks on static images beyond temporal streams. With very few parameters
and small size models, the key advantage is that one could have many of these
"detectors" assembled on the same chip; moreover, the feature acquisition can
be performed once and shared between different models of different tasks -
further accelerating the process. This contributes to energy efficiency and the
advancements of embedded AI at the edge
Best network chirplet-chain: Near-optimal coherent detection of unmodeled gravitation wave chirps with a network of detectors
The searches of impulsive gravitational waves (GW) in the data of the
ground-based interferometers focus essentially on two types of waveforms: short
unmodeled bursts and chirps from inspiralling compact binaries. There is room
for other types of searches based on different models. Our objective is to fill
this gap. More specifically, we are interested in GW chirps with an arbitrary
phase/frequency vs. time evolution. These unmodeled GW chirps may be considered
as the generic signature of orbiting/spinning sources. We expect quasi-periodic
nature of the waveform to be preserved independent of the physics which governs
the source motion. Several methods have been introduced to address the
detection of unmodeled chirps using the data of a single detector. Those
include the best chirplet chain (BCC) algorithm introduced by the authors. In
the next years, several detectors will be in operation. The joint coherent
analysis of GW by multiple detectors can improve the sight horizon, the
estimation of the source location and the wave polarization angles. Here, we
extend the BCC search to the multiple detector case. The method amounts to
searching for salient paths in the combined time-frequency representation of
two synthetic streams. The latter are time-series which combine the data from
each detector linearly in such a way that all the GW signatures received are
added constructively. We give a proof of principle for the full sky blind
search in a simplified situation which shows that the joint estimation of the
source sky location and chirp frequency is possible.Comment: 22 pages, revtex4, 6 figure
Extracting information from the signature of a financial data stream
Market events such as order placement and order cancellation are examples of
the complex and substantial flow of data that surrounds a modern financial
engineer. New mathematical techniques, developed to describe the interactions
of complex oscillatory systems (known as the theory of rough paths) provides
new tools for analysing and describing these data streams and extracting the
vital information. In this paper we illustrate how a very small number of
coefficients obtained from the signature of financial data can be sufficient to
classify this data for subtle underlying features and make useful predictions.
This paper presents financial examples in which we learn from data and then
proceed to classify fresh streams. The classification is based on features of
streams that are specified through the coordinates of the signature of the
path. At a mathematical level the signature is a faithful transform of a
multidimensional time series. (Ben Hambly and Terry Lyons \cite{uniqueSig}),
Hao Ni and Terry Lyons \cite{NiLyons} introduced the possibility of its use to
understand financial data and pointed to the potential this approach has for
machine learning and prediction.
We evaluate and refine these theoretical suggestions against practical
examples of interest and present a few motivating experiments which demonstrate
information the signature can easily capture in a non-parametric way avoiding
traditional statistical modelling of the data. In the first experiment we
identify atypical market behaviour across standard 30-minute time buckets
sampled from the WTI crude oil future market (NYMEX). The second and third
experiments aim to characterise the market "impact" of and distinguish between
parent orders generated by two different trade execution algorithms on the FTSE
100 Index futures market listed on NYSE Liffe
Detecting early signs of depressive and manic episodes in patients with bipolar disorder using the signature-based model
Recurrent major mood episodes and subsyndromal mood instability cause
substantial disability in patients with bipolar disorder. Early identification
of mood episodes enabling timely mood stabilisation is an important clinical
goal. Recent technological advances allow the prospective reporting of mood in
real time enabling more accurate, efficient data capture. The complex nature of
these data streams in combination with challenge of deriving meaning from
missing data mean pose a significant analytic challenge. The signature method
is derived from stochastic analysis and has the ability to capture important
properties of complex ordered time series data. To explore whether the onset of
episodes of mania and depression can be identified using self-reported mood
data.Comment: 12 pages, 3 tables, 10 figure
Fourteen candidate RR Lyrae star streams in the inner Galaxy
We apply the GC3 stream-finding method to RR Lyrae stars (RRLS) in the
Catalina survey. We find two RRLS stream candidates at confidence
and another 12 at confidence over the Galactocentric distance
range . Of these, only two are associated with known
globular clusters (NGC 1261 and Arp2). The remainder are candidate `orphan'
streams, consistent with the idea that globular cluster streams are most
visible close to dissolution. Our detections are likely a lower bound on the
total number of dissolving globulars in the inner galaxy, since many globulars
have few RRLS while only the brightest streams are visible over the Galactic
RRLS background, particularly given the current lack of kinematical
information. We make all of our candidate streams publicly available and
provide a new GALSTREAMS Python library for the footprints of all known streams
and overdensities in the Milky Way.Comment: 18 pages, 4 figures. Accepted for publication at MNRAS. GALSTREAMS
Milky Way Streams Footprint Library are available at
https://github.com/cmateu/galstreams . All RRL data and code used in the
paper are available at
https://cmateu.github.io/Cecilia_Mateu_WebPage/CatalinaGC3_Streams.htm
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