4,151 research outputs found
Filamentary Switching: Synaptic Plasticity through Device Volatility
Replicating the computational functionalities and performances of the brain
remains one of the biggest challenges for the future of information and
communication technologies. Such an ambitious goal requires research efforts
from the architecture level to the basic device level (i.e., investigating the
opportunities offered by emerging nanotechnologies to build such systems).
Nanodevices, or, more precisely, memory or memristive devices, have been
proposed for the implementation of synaptic functions, offering the required
features and integration in a single component. In this paper, we demonstrate
that the basic physics involved in the filamentary switching of electrochemical
metallization cells can reproduce important biological synaptic functions that
are key mechanisms for information processing and storage. The transition from
short- to long-term plasticity has been reported as a direct consequence of
filament growth (i.e., increased conductance) in filamentary memory devices. In
this paper, we show that a more complex filament shape, such as dendritic paths
of variable density and width, can permit the short- and long-term processes to
be controlled independently. Our solid-state device is strongly analogous to
biological synapses, as indicated by the interpretation of the results from the
framework of a phenomenological model developed for biological synapses. We
describe a single memristive element containing a rich panel of features, which
will be of benefit to future neuromorphic hardware systems
A novel fast fractal image compression method based on distance clustering in high dimensional sphere surface
Fractal encoding method becomes an effective image compression method because of its high compression ratio and short decompressing time. But one problem of known fractal compression method is its high computational complexity and consequent long compressing time. To address this issue, in this paper, distance clustering in high dimensional sphere surface is applied to speed up the fractal compression method. Firstly, as a preprocessing strategy, an image is divided into blocks, which are mapped on high dimensional sphere surface. Secondly, a novel image matching method is presented based on distance clustering on high dimensional sphere surface. Then, the correctness and effectiveness properties of the mentioned method are analyzed. Finally, experimental results validate the positive performance gain of the method
Detrended fluctuation analysis for fractals and multifractals in higher dimensions
One-dimensional detrended fluctuation analysis (1D DFA) and multifractal
detrended fluctuation analysis (1D MF-DFA) are widely used in the scaling
analysis of fractal and multifractal time series because of being accurate and
easy to implement. In this paper we generalize the one-dimensional DFA and
MF-DFA to higher-dimensional versions. The generalization works well when
tested with synthetic surfaces including fractional Brownian surfaces and
multifractal surfaces. The two-dimensional MF-DFA is also adopted to analyze
two images from nature and experiment and nice scaling laws are unraveled.Comment: 7 Revtex pages inluding 11 eps figure
Texture Analysis of Diffraction Enhanced Synchrotron Images of Trabecular Bone at the Wrist
The purpose of this study is to determine the correlation between texture features of Di raction
Enhanced Imaging (DEI) images and trabecular properties of human wrist bone in the assessment
of osteoporosis. Osteoporosis is a metabolic bone disorder that is characterized by reduced bone
mass and a deterioration of bone structure which results in an increased fracture risk. Since the
disease is preventable, diagnostic techniques are of major importance. Bone micro-architecture and
Bone mineral density (BMD) are two main factors related to osteoporotic fractures. Trabecular
properties like bone volume (BV), trabecular number (Tb.N), trabecular thickness (Tb.Th), bone
surface (BS), and other properties of bone, characterizes the bone architecture. Currently, however,
BMD is the only measurement carried out to assess osteoporosis. Researchers suggest that bone
micro-architecture and texture analysis of bone images along with BMD can provide more accuracy
in the assessment.
We have applied texture analysis on DEI images and extracted texture features. In our study,
we used fractal analysis, gray level co-occurrence matrix (GLCM), texture feature coding method
(TFCM), and local binary patterns (LBP) as texture analysis methods to extract texture features.
3D Micro-CT trabecular properties were extracted using SkyScanTM CTAN software. Then, we
determined the correlation between texture features and trabecular properties. GLCM energy fea-
ture of DEI images explained more than 39% of variance in bone surface by volume ratio (BS/BV),
38% of variance in percent bone volume (BV/TV), and 37% of variance in trabecular number
(Tb.N). TFCM homogeneity feature of DEI images explained more than 42% of variance in bone
surface (BS) parameter. LBP operator - LBP 11 of DEI images explained more than 34% of vari-
ance in bone surface (BS) and 30% of variance in bone surface density (BS/TV). Fractal dimension
parameter of DEI images explained more than 47% of variance in bone surface (BS) and 32% of
variance in bone volume (BV). This study will facilitate in the quanti cation of osteoporosis beyond
conventional BMD
Fast Search Approaches for Fractal Image Coding: Review of Contemporary Literature
Fractal Image Compression FIC as a model was conceptualized in the 1989 In furtherance there are numerous models that has been developed in the process Existence of fractals were initially observed and depicted in the Iterated Function System IFS and the IFS solutions were used for encoding images The process of IFS pertaining to any image constitutes much lesser space for recording than the actual image which has led to the development of representation the image using IFS form and how the image compression systems has taken shape It is very important that the time consumed for encoding has to be addressed for achieving optimal compression conditions and predominantly the inputs that are shared in the solutions proposed in the study depict the fact that despite of certain developments that has taken place still there are potential chances of scope for improvement From the review of exhaustive range of models that are depicted in the model it is evident that over period of time numerous advancements have taken place in the FCI model and is adapted at image compression in varied levels This study focus on the existing range of literature on FCI and the insights of various models has been depicted in this stud
Characterizing the structure of diffuse emission in Hi-GAL maps
We present a study of the structure of the Galactic interstellar medium
through the Delta-variance technique, related to the power spectrum and the
fractal properties of infrared/sub-mm maps. Through this method, it is possible
to provide quantitative parameters which are useful to characterize different
morphological and physical conditions, and to better constrain the theoretical
models. In this respect, the Herschel Infrared Galactic Plane Survey carried
out at five photometric bands from 70 to 500 \mu m constitutes an unique
database for applying statistical tools to a variety of regions across the
Milky Way. In this paper, we derive a robust estimate of the power-law portion
of the power spectrum of four contiguous 2{\deg}x2{\deg} Hi-GAL tiles located
in the third Galactic quadrant (217{\deg} < l < 225{\deg}, -2{\deg} < b <
0{\deg}). The low level of confusion along the line of sight testified by CO
observations makes this region an ideal case. We find very different values of
the power spectrum slope from tile to tile but also from wavelength to
wavelength (2 < \beta < 3), with similarities between fields attributable to
components located at the same distance. Thanks to the comparison with models
of turbulence, an explanation of the determined slopes in terms of the fractal
geometry is also provided, and possible relations with the underlying physics
are investigated. In particular, an anti-correlation between ISM fractal
dimension and star formation efficiency is found for the two main distance
components observed in these fields. A possible link between the fractal
properties of the diffuse emission and the resulting clump mass function is
discussed.Comment: Accepted by Ap
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