486,761 research outputs found
An improved negative selection algorithm based on the hybridization of cuckoo search and differential evolution for anomaly detection
The biological immune system (BIS) is characterized by networks of cells, tissues, and
organs communicating and working in synchronization. It also has the ability to learn,
recognize, and remember, thus providing the solid foundation for the development
of Artificial Immune System (AIS). Since the emergence of AIS, it has proved itself
as an area of computational intelligence. Real-Valued Negative Selection Algorithm
with Variable-Sized Detectors (V-Detectors) is an offspring of AIS and demonstrated
its potentials in the field of anomaly detection. The V-Detectors algorithm depends
greatly on the random detectors generated in monitoring the status of a system.
These randomly generated detectors suffer from not been able to adequately cover
the non-self space, which diminishes the detection performance of the V-Detectors
algorithm. This research therefore proposed CSDE-V-Detectors which entail the
use of the hybridization of Cuckoo Search (CS) and Differential Evolution (DE) in
optimizing the random detectors of the V-Detectors. The DE is integrated with CS
at the population initialization by distributing the population linearly. This linear
distribution gives the population a unique, stable, and progressive distribution process.
Thus, each individual detector is characteristically different from the other detectors.
CSDE capabilities of global search, and use of L´evy flight facilitates the effectiveness
of the detector set in the search space. In comparison with V-Detectors, cuckoo search,
differential evolution, support vector machine, artificial neural network, na¨ıve bayes,
and k-NN, experimental results demonstrates that CSDE-V-Detectors outperforms
other algorithms with an average detection rate of 95:30% on all the datasets. This
signifies that CSDE-V-Detectors can efficiently attain highest detection rates and
lowest false alarm rates for anomaly detection. Thus, the optimization of the randomly
detectors of V-Detectors algorithm with CSDE is proficient and suitable for anomaly
detection tasks
Three-dimensional imaging and detection efficiency performance of orthogonal coplanar CZT strip detectors
We report on recent three-dimensional imaging performance and detection efficiency measurements obtained with 5 mm thick prototype CdZnTe detectors fabricated with orthogonal coplanar anode strips. In previous work, we have shown that detectors fabricated using this design achieve both very good energy resolution and sub-millimeter spatial resolution with fewer electronic channels than are required for pixel detectors. As electron-only devices, like pixel detectors, coplanar anode strip detectors can be fabricated in the thickness required to be effective imagers for photons with energies in excess of 500 keV. Unlike conventional double-sided strip detectors, the coplanar anode strip detectors require segmented contacts and signal processing electronics on only one surface. The signals can be processed to measure the total energy deposit and the photon interaction location in three dimensions. The measurements reported here provide a quantitative assessment of the detection capabilities of orthogonal coplanar anode strip detectors
Measuring the influence of concept detection on video retrieval
There is an increasing emphasis on including semantic concept detection as part of video retrieval. This represents a modality for retrieval quite different from metadata-based and keyframe similarity-based approaches. One of the premises on which the success of this is based, is that good quality detection is available in order to guarantee retrieval quality. But how good does the feature
detection actually need to be? Is it possible to achieve good retrieval quality, even with poor quality concept detection and if so then what is the 'tipping point' below which detection accuracy proves not to be beneficial? In
this paper we explore this question using a collection of rushes video where we artificially vary the quality of detection of semantic features and we study the impact on the resulting retrieval. Our results show that the impact of improving or degrading performance of concept detectors is not directly reflected as retrieval performance and this raises interesting questions about how accurate concept
detection really needs to be
Niobium superconducting nanowire single-photon detectors
We investigate the performance of superconducting nanowire photon detectors
fabricated from ultra-thin Nb. A direct comparison is made between these
detectors and similar nanowire detectors fabricated from NbN. We find that Nb
detectors are significantly more susceptible than NbN to thermal instability
(latching) at high bias. We show that the devices can be stabilized by reducing
the input resistance of the readout. Nb detectors optimized in this way are
shown to have approximately 2/3 the reset time of similar large-active-area NbN
detectors of the same geometry, with approximately 6% detection efficiency for
single photons at 470 nm
Pixel Detectors
Pixel detectors for precise particle tracking in high energy physics have
been developed to a level of maturity during the past decade. Three of the LHC
detectors will use vertex detectors close to the interaction point based on the
hybrid pixel technology which can be considered the state of the art in this
field of instrumentation. A development period of almost 10 years has resulted
in pixel detector modules which can stand the extreme rate and timing
requirements as well as the very harsh radiation environment at the LHC without
severe compromises in performance. From these developments a number of
different applications have spun off, most notably for biomedical imaging.
Beyond hybrid pixels, a number of monolithic or semi-monolithic developments,
which do not require complicated hybridization but come as single sensor/IC
entities, have appeared and are currently developed to greater maturity. Most
advanced in terms of maturity are so called CMOS active pixels and DEPFET
pixels. The present state in the construction of the hybrid pixel detectors for
the LHC experiments together with some hybrid pixel detector spin-off is
reviewed. In addition, new developments in monolithic or semi-monolithic pixel
devices are summarized.Comment: 14 pages, 38 drawings/photographs in 21 figure
Acceleration-assisted entanglement harvesting and rangefinding
We study entanglement harvested from a quantum field through local
interaction with Unruh-DeWitt detectors undergoing linear acceleration. The
interactions allow entanglement to be swapped locally from the field to the
detectors. We find an enhancement in the entanglement harvesting by two
detectors with anti-parallel acceleration over those with inertial motion. This
enhancement is characterized by the presence of entanglement between two
detectors that would otherwise maintain a separable state in the absence of
relativistic motion (with the same distance of closest approach in both cases).
We also find that entanglement harvesting is degraded for two detectors
undergoing parallel acceleration in the same way as for two static, comoving
detectors in a de Sitter universe. This degradation is known to be different
from that of two inertial detectors in a thermal bath. We comment on the
physical origin of the harvested entanglement and present three methods for
determining distance between two detectors using properties of the harvested
entanglement. Information about the separation is stored nonlocally in the
joint state of the accelerated detectors after the interaction; a single
detector alone contains none. We also find an example of entanglement sudden
death exhibited in parameter space.Comment: 17 pages, 6 figures. Version 2 updated to address referee comments
and minor correction
Improved source localization with LIGO India
A global network of advanced gravitational wave interferometric detectors is
under construction. These detectors will offer an order of magnitude
improvement in sensitivity over the initial detectors and will usher in the era
of gravitational wave astronomy. In this paper, we evaluate the benefits of
relocating one of the advanced LIGO detectors to India.Comment: 7 pages, 3 figures, accepted for publication in proceedings of
ICGC2011 conference. Localization figures update
Multi Detector Fusion of Dynamic TOA Estimation using Kalman Filter
In this paper, we propose fusion of dynamic TOA (time of arrival) from
multiple non-coherent detectors like energy detectors operating at sub-Nyquist
rate through Kalman filtering. We also show that by using multiple of these
energy detectors, we can achieve the performance of a digital matched filter
implementation in the AWGN (additive white Gaussian noise) setting. We derive
analytical expression for number of energy detectors needed to achieve the
matched filter performance. We demonstrate in simulation the validity of our
analytical approach. Results indicate that number of energy detectors needed
will be high at low SNRs and converge to a constant number as the SNR
increases. We also study the performance of the strategy proposed using IEEE
802.15.4a CM1 channel model and show in simulation that two sub-Nyquist
detectors are sufficient to match the performance of digital matched filter
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