19,606 research outputs found
Hardware Considerations for Signal Processing Systems: A Step Toward the Unconventional.
As we progress into the future, signal processing algorithms are becoming more computationally intensive and power hungry while the desire for mobile products and low power devices is also increasing. An integrated ASIC solution is one of the primary ways chip developers can improve performance and add functionality while keeping the power budget low. This work discusses ASIC hardware for both conventional and unconventional signal processing systems, and how integration, error resilience, emerging devices, and new algorithms can be leveraged by signal processing systems to further improve performance and enable new applications. Specifically this work presents three case studies: 1) a conventional and highly parallel mix signal cross-correlator ASIC for a weather satellite performing real-time synthetic aperture imaging, 2) an unconventional native stochastic computing architecture enabled by memristors, and 3) two unconventional sparse neural network ASICs for feature extraction and object classification. As improvements from technology scaling alone slow down, and the demand for energy efficient mobile electronics increases, such optimization techniques at the device, circuit, and system level will become more critical to advance signal processing capabilities in the future.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/116685/1/knagphil_1.pd
Optimized auxiliary oscillators for the simulation of general open quantum systems
A method for the systematic construction of few-body damped harmonic
oscillator networks accurately reproducing the effect of general bosonic
environments in open quantum systems is presented. Under the sole assumptions
of a Gaussian environment and regardless of the system coupled to it, an
algorithm to determine the parameters of an equivalent set of interacting
damped oscillators obeying a Markovian quantum master equation is introduced.
By choosing a suitable coupling to the system and minimizing an appropriate
distance between the two-time correlation function of this effective bath and
that of the target environment, the error induced in the reduced dynamics of
the system is brought under rigorous control. The interactions among the
effective modes provide remarkable flexibility in replicating non-Markovian
effects on the system even with a small number of oscillators, and the
resulting Lindblad equation may therefore be integrated at a very reasonable
computational cost using standard methods for Markovian problems, even in
strongly non-perturbative coupling regimes and at arbitrary temperatures
including zero. We apply the method to an exactly solvable problem in order to
demonstrate its accuracy, and present a study based on current research in the
context of coherent transport in biological aggregates as a more realistic
example of its use; performance and versatility are highlighted, and
theoretical and numerical advantages over existing methods, as well as possible
future improvements, are discussed.Comment: 23 + 9 pages, 11 + 2 figures. No changes from previous version except
publication info and updated author affiliation
SuperpixelGraph: Semi-automatic generation of building footprint through semantic-sensitive superpixel and neural graph networks
Most urban applications necessitate building footprints in the form of
concise vector graphics with sharp boundaries rather than pixel-wise raster
images. This need contrasts with the majority of existing methods, which
typically generate over-smoothed footprint polygons. Editing these
automatically produced polygons can be inefficient, if not more time-consuming
than manual digitization. This paper introduces a semi-automatic approach for
building footprint extraction through semantically-sensitive superpixels and
neural graph networks. Drawing inspiration from object-based classification
techniques, we first learn to generate superpixels that are not only
boundary-preserving but also semantically-sensitive. The superpixels respond
exclusively to building boundaries rather than other natural objects, while
simultaneously producing semantic segmentation of the buildings. These
intermediate superpixel representations can be naturally considered as nodes
within a graph. Consequently, graph neural networks are employed to model the
global interactions among all superpixels and enhance the representativeness of
node features for building segmentation. Classical approaches are utilized to
extract and regularize boundaries for the vectorized building footprints.
Utilizing minimal clicks and straightforward strokes, we efficiently accomplish
accurate segmentation outcomes, eliminating the necessity for editing polygon
vertices. Our proposed approach demonstrates superior precision and efficacy,
as validated by experimental assessments on various public benchmark datasets.
A significant improvement of 8% in AP50 was observed in vector graphics
evaluation, surpassing established techniques. Additionally, we have devised an
optimized and sophisticated pipeline for interactive editing, poised to further
augment the overall quality of the results
The wavefunction reconstruction effects in calculation of DM-induced electronic transition in semiconductor targets
The physics of the electronic excitation in semiconductors induced by sub-GeV
dark matter (DM) have been extensively discussed in literature, under the
framework of the standard plane wave (PW) and pseudopotential calculation
scheme. In this paper, we investigate the implication of the all-electron (AE)
reconstruction on estimation of the DM-induced electronic transition event
rates. As a benchmark study, we first calculate the wavefunctions in silicon
and germanium bulk crystals based on both the AE and pseudo (PS) schemes within
the projector augmented wave (PAW) framework, and then make comparisons between
the calculated excitation event rates obtained from these two approaches. It
turns out that in process where large momentum transfer is kinetically allowed,
the two calculated event rates can differ by a factor of a few. Such
discrepancies are found to stem from the high-momentum components neglected in
the PS scheme. It is thus implied that the correction from the AE wavefunction
in the core region is necessary for an accurate estimate of the DM-induced
transition event rate in semiconductors.Comment: A missing factor associated with the Fourier
transformation is added to both the AE and PS event rates in this version.
The ratio between the AE and PS event rates is not affecte
A Comprehensive Overview of Computational Nuclei Segmentation Methods in Digital Pathology
In the cancer diagnosis pipeline, digital pathology plays an instrumental
role in the identification, staging, and grading of malignant areas on biopsy
tissue specimens. High resolution histology images are subject to high variance
in appearance, sourcing either from the acquisition devices or the H\&E
staining process. Nuclei segmentation is an important task, as it detects the
nuclei cells over background tissue and gives rise to the topology, size, and
count of nuclei which are determinant factors for cancer detection. Yet, it is
a fairly time consuming task for pathologists, with reportedly high
subjectivity. Computer Aided Diagnosis (CAD) tools empowered by modern
Artificial Intelligence (AI) models enable the automation of nuclei
segmentation. This can reduce the subjectivity in analysis and reading time.
This paper provides an extensive review, beginning from earlier works use
traditional image processing techniques and reaching up to modern approaches
following the Deep Learning (DL) paradigm. Our review also focuses on the weak
supervision aspect of the problem, motivated by the fact that annotated data is
scarce. At the end, the advantages of different models and types of supervision
are thoroughly discussed. Furthermore, we try to extrapolate and envision how
future research lines will potentially be, so as to minimize the need for
labeled data while maintaining high performance. Future methods should
emphasize efficient and explainable models with a transparent underlying
process so that physicians can trust their output.Comment: 47 pages, 27 figures, 9 table
Floquet theory for temporal correlations and spectra in time-periodic open quantum systems: Application to squeezed parametric oscillation beyond the rotating-wave approximation
Open quantum systems can display periodic dynamics at the classical level
either due to external periodic modulations or to self-pulsing phenomena
typically following a Hopf bifurcation. In both cases, the quantum fluctuations
around classical solutions do not reach a quantum-statistical stationary state,
which prevents adopting the simple and reliable methods used for stationary
quantum systems. Here we put forward a general and efficient method to compute
two-time correlations and corresponding spectral densities of time-periodic
open quantum systems within the usual linearized (Gaussian) approximation for
their dynamics. Using Floquet theory we show how the quantum Langevin equations
for the fluctuations can be efficiently integrated by partitioning the time
domain into one-period duration intervals, and relating the properties of each
period to the first one. Spectral densities, like squeezing spectra, are
computed similarly, now in a two-dimensional temporal domain that is treated as
a chessboard with one-period x one-period cells. This technique avoids
cumulative numerical errors as well as efficiently saves computational time. As
an illustration of the method, we analyze the quantum fluctuations of a damped
parametrically-driven oscillator (degenerate parametric oscillator) below
threshold and far away from rotating-wave approximation conditions, which is a
relevant scenario for modern low-frequency quantum oscillators. Our method
reveals that the squeezing properties of such devices are quite robust against
the amplitude of the modulation or the low quality of the oscillator, although
optimal squeezing can appear for parameters that are far from the ones
predicted within the rotating-wave approximation.Comment: Comments and constructive criticism are welcom
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