33,306 research outputs found
Trellis-Based Equalization for Sparse ISI Channels Revisited
Sparse intersymbol-interference (ISI) channels are encountered in a variety
of high-data-rate communication systems. Such channels have a large channel
memory length, but only a small number of significant channel coefficients. In
this paper, trellis-based equalization of sparse ISI channels is revisited. Due
to the large channel memory length, the complexity of maximum-likelihood
detection, e.g., by means of the Viterbi algorithm (VA), is normally
prohibitive. In the first part of the paper, a unified framework based on
factor graphs is presented for complexity reduction without loss of optimality.
In this new context, two known reduced-complexity algorithms for sparse ISI
channels are recapitulated: The multi-trellis VA (M-VA) and the
parallel-trellis VA (P-VA). It is shown that the M-VA, although claimed, does
not lead to a reduced computational complexity. The P-VA, on the other hand,
leads to a significant complexity reduction, but can only be applied for a
certain class of sparse channels. In the second part of the paper, a unified
approach is investigated to tackle general sparse channels: It is shown that
the use of a linear filter at the receiver renders the application of standard
reduced-state trellis-based equalizer algorithms feasible, without significant
loss of optimality. Numerical results verify the efficiency of the proposed
receiver structure.Comment: To be presented at the 2005 IEEE Int. Symp. Inform. Theory (ISIT
2005), September 4-9, 2005, Adelaide, Australi
A Lyra2 FPGA Core for Lyra2REv2-Based Cryptocurrencies
Lyra2REv2 is a hashing algorithm that consists of a chain of individual
hashing algorithms and it is used as a proof-of-work function in several
cryptocurrencies that aim to be ASIC-resistant. The most crucial hashing
algorithm in the Lyra2REv2 chain is a specific instance of the general Lyra2
algorithm. In this work we present the first FPGA implementation of the
aforementioned instance of Lyra2 and we explain how several properties of the
algorithm can be exploited in order to optimize the design.Comment: 5 pages, to be presented at the IEEE International Symposium on
Circuits and Systems (ISCAS) 201
A Standalone FPGA-based Miner for Lyra2REv2 Cryptocurrencies
Lyra2REv2 is a hashing algorithm that consists of a chain of individual
hashing algorithms, and it is used as a proof-of-work function in several
cryptocurrencies. The most crucial and exotic hashing algorithm in the
Lyra2REv2 chain is a specific instance of the general Lyra2 algorithm. This
work presents the first hardware implementation of the specific instance of
Lyra2 that is used in Lyra2REv2. Several properties of the aforementioned
algorithm are exploited in order to optimize the design. In addition, an
FPGA-based hardware implementation of a standalone miner for Lyra2REv2 on a
Xilinx Multi-Processor System on Chip is presented. The proposed Lyra2REv2
miner is shown to be significantly more energy efficient than both a GPU and a
commercially available FPGA-based miner. Finally, we also explain how the
simplified Lyra2 and Lyra2REv2 architectures can be modified with minimal
effort to also support the recent Lyra2REv3 chained hashing algorithm.Comment: 13 pages, accepted for publication in IEEE Trans. Circuits Syst. I.
arXiv admin note: substantial text overlap with arXiv:1807.0576
Training a Convolutional Neural Network for Appearance-Invariant Place Recognition
Place recognition is one of the most challenging problems in computer vision,
and has become a key part in mobile robotics and autonomous driving
applications for performing loop closure in visual SLAM systems. Moreover, the
difficulty of recognizing a revisited location increases with appearance
changes caused, for instance, by weather or illumination variations, which
hinders the long-term application of such algorithms in real environments. In
this paper we present a convolutional neural network (CNN), trained for the
first time with the purpose of recognizing revisited locations under severe
appearance changes, which maps images to a low dimensional space where
Euclidean distances represent place dissimilarity. In order for the network to
learn the desired invariances, we train it with triplets of images selected
from datasets which present a challenging variability in visual appearance. The
triplets are selected in such way that two samples are from the same location
and the third one is taken from a different place. We validate our system
through extensive experimentation, where we demonstrate better performance than
state-of-art algorithms in a number of popular datasets
Status of the R&D activities for the upgrade of the ALICE TPC
After the Long Shutdown 2 the LHC will provide lead-lead collisions at
interaction rates as high as 50kz. In order to cope with such conditions the
ALICE Time Projection Chamber (TPC) needs to be upgraded. After the upgrade the
TPC will run in a continuous mode, without any degradation of the momentum and
dE/dx resolution compared to the performance of the present TPC. Since readout
by multi-wire proportional chambers is no longer feasible with these
requirements, new technologies have to be employed. In the new readout chambers
the electron amplification is provided by a stack of four Gas Electron
Multiplier (GEM) foils. Their high voltage settings and orientation have been
optimised to provide an energy resolution better then 12% at the photopeak of
55Fe. At the same settings the Ion BackFlow into the drift volume is less than
1% of the effective number of ions produced during gas amplification and the
primary ionisations. This is necessary to prevent the accumulation of space
charge, which eventually will distort the field in the drift volume. To ensure
stable operation at the high loads during LHC run 3 the chambers have to be
robust against discharges, too. With the selected configuration in a quadruple
GEM stack the discharge probability is kept at the level of
discharges per incoming hadron. An overview of the ALICE TPC upgrade activities
will be given in these proceedings and the optimised settings foreseen for the
GEM stacks of the future readout chambers are introduced. Furthermore the
outcome of two beam time campaigns at SPS and PS (at CERN) in the end of 2014
is shown. At this campaigns the stability against discharges and the dE/dx
performance of a full size readout chamber prototype was tested. In addition it
is reported on charging-up studies of 4GEM stacks and on tests of
electromagnetic sagging of large GEM foils.Comment: 4 pages, 3 figures, Proceedings of "4th Conference on Micro-Pattern
Gaseous Detectors
Quantum information cannot be completely hidden in correlations: implications for the black-hole information paradox
The black-hole information paradox has fueled a fascinating effort to
reconcile the predictions of general relativity and those of quantum mechanics.
Gravitational considerations teach us that black holes must trap everything
that falls into them. Quantum mechanically the mass of a black hole leaks away
as featureless (Hawking) radiation, but if the black hole vanishes, where is
the information about the matter that made it? We treat the states of the
in-fallen matter quantum mechanically and show that the black-hole information
paradox becomes more severe. Our formulation of the paradox rules out one of
the most conservative resolutions: that the state of the in-falling matter
might be hidden in correlations between semi-classical Hawking radiation and
the internal states of the black hole. As a consequence, either unitarity or
Hawking's semi-classical predictions must break down. Any resolution of the
black-hole information crisis must elucidate one of these possibilities.Comment: We first obtained this result two years ag
Real-Time MRI of Continent and Stress Incontinent Male Patients after Orthotopic Ileal Neobladder
Introduction: The aim of this study was to correlate anatomic differences with continence status in male patients after cystoprostatectomy and ileal neobladder using real-time magnetic resonance imaging. Patients and Methods: Anatomic differences of 14 male patients (7 daytime continent and 7 stress incontinent) with ileal neobladder were determined by measuring the orthogonal distance of the bladder neck to the pubococcygeal line (PCL) to correlate anatomic differences with continence status. Results: The median distance of the bladder neck to PCL was +5.4 mm in continent patients before voiding whereas in incontinent patients it was +2 mm (p = 0.012). During the Valsalva maneuver, the median distance in continent patients was +4 and in incontinent patients -3 mm (p = 0.003). At the end of micturition, the median distance was +2.3 mm in continent patients and -12 mm in incontinent patients (p = 0.002). Conclusions: The bladder neck in incontinent patients showed more pronounced mobility in relation to the PCL during micturition and the Valsalva maneuver as compared to continent patients. In addition, the ileal neobladder was positioned significantly lower in the pelvis of incontinent patients. These preliminary results suggest that a stable bladder neck may be an important factor to reach full continence in patients with ileal neobladder. Copyright (C) 2011 S. Karger AG, Base
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