131 research outputs found
On Some Applications of Nonlinear Differential Equations in Image Processing: Concepts and Electronic Implementation
International audienc
Discrete instability in nonlinear lattices
The discrete multiscale analysis for boundary value problems in nonlinear
discrete systems leads to a first order discrete modulational instability above
a threshold amplitude for wave numbers beyond the zero of group velocity
dispersion. Applied to the electrical lattice [Phys. Rev. E, 51 (1995) 6127 ],
this acurately explains the experimental instability at wave numbers beyond
1.25 . The theory is also briefly discussed for sine-Gordon and Toda lattices.Comment: 1 figure, revtex, published: Phys. Rev. Lett. 83 (1999) 232
On dissipationless shock waves in a discrete nonlinear Schr\"odinger equation
It is shown that the generalized discrete nonlinear Schr\"odinger equation
can be reduced in a small amplitude approximation to the KdV, mKdV, KdV(2) or
the fifth-order KdV equations, depending on values of the parameters. In
dispersionless limit these equations lead to wave breaking phenomenon for
general enough initial conditions, and, after taking into account small
dispersion effects, result in formation of dissipationless shock waves. The
Whitham theory of modulations of nonlinear waves is used for analytical
description of such waves.Comment: 15 pages, 9 figure
Asymmetric gap soliton modes in diatomic lattices with cubic and quartic nonlinearity
Nonlinear localized excitations in one-dimensional diatomic lattices with
cubic and quartic nonlinearity are considered analytically by a
quasi-discreteness approach. The criteria for the occurence of asymmetric gap
solitons (with vibrating frequency lying in the gap of phonon bands) and
small-amplitude, asymmetric intrinsic localized modes (with the vibrating
frequency being above all the phonon bands) are obtained explicitly based on
the modulational instabilities of corresponding linear lattice plane waves. The
expressions of particle displacement for all these nonlinear localized
excitations are also given. The result is applied to standard two-body
potentials of the Toda, Born-Mayer-Coulomb, Lennard-Jones, and Morse type. The
comparison with previous numerical study of the anharmonic gap modes in
diatomic lattices for the standard two-body potentials is made and good
agreement is found.Comment: 24 pages in Revtex, 2 PS figure
GANDALF: Generative Adversarial Networks with Discriminator-Adaptive Loss Fine-tuning for Alzheimer's Disease Diagnosis from MRI
Positron Emission Tomography (PET) is now regarded as the gold standard for
the diagnosis of Alzheimer's Disease (AD). However, PET imaging can be
prohibitive in terms of cost and planning, and is also among the imaging
techniques with the highest dosage of radiation. Magnetic Resonance Imaging
(MRI), in contrast, is more widely available and provides more flexibility when
setting the desired image resolution. Unfortunately, the diagnosis of AD using
MRI is difficult due to the very subtle physiological differences between
healthy and AD subjects visible on MRI. As a result, many attempts have been
made to synthesize PET images from MR images using generative adversarial
networks (GANs) in the interest of enabling the diagnosis of AD from MR.
Existing work on PET synthesis from MRI has largely focused on Conditional
GANs, where MR images are used to generate PET images and subsequently used for
AD diagnosis. There is no end-to-end training goal. This paper proposes an
alternative approach to the aforementioned, where AD diagnosis is incorporated
in the GAN training objective to achieve the best AD classification
performance. Different GAN lossesare fine-tuned based on the discriminator
performance, and the overall training is stabilized. The proposed network
architecture and training regime show state-of-the-art performance for three-
and four- class AD classification tasks.Comment: Accepted for publication at the MICCAI 2020 conferenc
Human-Centered Design Components in Spiral Model to Improve Mobility of Older Adults
As humans grow older, their cognitive needs change more frequently due to distal and proximal life events. Designers and developers need to come up with better designs that integrate older users’ needs in a short period of time with more interaction with the users. Therefore, the positioning of human end users in the center of the design itself is not the key to the success of design artifacts while designing applications for older adults to use a smartphone as a promising tool for journey planner while using public transportation. This study analyzed the use of human-centered design (HCD) components, the spiral model, and the design for failure (DfF) approach to improve the interactions between older users and designers/developers in gathering usability needs in the concept stage and during the development of the app with short iterative cycles. To illustrate the importance of the applied approach, a case study with particular focus on older adults is presented.The results presented in this study are based on “Assistant” project funded by
AAL JP, co-funded by the European Union. The authors would like to thank Dr. Stefan Carmien,
my colleague in Assistant, for mentoring and for reading and making comments in the earlier
versions of this chapter; participating research institutes; funding agencies; and companies from
Finland, Spain, Austria, France, and the United Kingdom for their active support throughout the
project
Josephson Junctions and AdS/CFT Networks
We propose a new holographic model of Josephson junctions (and networks
thereof) based on designer multi-gravity, namely multi-(super)gravity theories
on products of distinct asymptotically AdS spacetimes coupled by mixed boundary
conditions. We present a simple model of a Josephson junction (JJ) that
exhibits the well-known current-phase sine relation of JJs. In one-dimensional
chains of holographic superconductors we find that the Cooper-pair condensates
are described by a discretized Schrodinger-type equation. Such non-integrable
equations, which have been studied extensively in the past in condensed matter
and optics applications, are known to exhibit complex behavior that includes
periodic and quasiperiodic solutions, chaotic dynamics, soliton and kink
solutions. In our setup these solutions translate to holographic configurations
of strongly-coupled superconductors in networks with weak site-to-site
interactions that exhibit interesting patterns of modulated superconductivity.
In a continuum limit our equations reduce to generalizations of the
Gross-Pitaevskii equation. We comment on the many possible extensions and
applications of this new approach.Comment: 39 pages, 11 figures; v2 clarified the nature and computation of the
Josephson current in subsec. 3.2 and specific properties of the two-site
system, analogous minor modifications in subsec. 4.4 and added a new subsec.
4.5 with a new fig.
Characteristics of subjective cognitive decline associated with amyloid positivity
Introduction: The evidence for characteristics of persons with subjective cognitive decline (SCD) associated with amyloid positivity is limited. Methods: In 1640 persons with SCD from 20 Amyloid Biomarker Study cohort, we investigated the associations of SCD-specific characteristics (informant confirmation, domain-specific complaints, concerns, feelings of worse performance) demographics, setting, apolipoprotein E gene (APOE) ε4 carriership, and neuropsychiatric symptoms with amyloid positivity. Results: Between cohorts, amyloid positivity in 70-year-olds varied from 10% to 76%. Only older age, clinical setting, and APOE ε4 carriership showed univariate associations with increased amyloid positivity. After adjusting for these, lower education was also associated with increased amyloid positivity. Only within a research setting, informant-confirmed complaints, memory complaints, attention/concentration complaints, and no depressive symptoms were associated with increased amyloid positivity. Feelings of worse performance were associated with less amyloid positivity at younger ages and more at older ages. Discussion: Next to age, setting, and APOE ε4 carriership, SCD-specific characteristics may facilitate the identification of amyloid-positive individuals
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