12,373 research outputs found
Evaluation of MEMS Structures with Directional Characteristics Based on FRAT and Lifting Wavelet
Steps and grooves, which have typical directional characteristic, are two main functional structures of MEMS (Micro-Electro-Mechanical Systems). This paper proposes a method for analysis and evaluation of MEMS steps and grooves based on finite radon transform (FRAT) and lifting wavelet. The method consists of three steps. Firstly, FRAT is adopted to detect the directional characteristic of a MEMS structure. Secondly, on the basis of the directional characteristic obtained, the profiles of the MEMS structure are analyzed by lifting wavelet. Finally, Histogram-fitting is employed for areal evaluation of a MEMS structure. Simulated and experimental results show that MEMS structures with directional characteristic can be extracted and evaluated by the method effectively
Graph Spectral Image Processing
Recent advent of graph signal processing (GSP) has spurred intensive studies
of signals that live naturally on irregular data kernels described by graphs
(e.g., social networks, wireless sensor networks). Though a digital image
contains pixels that reside on a regularly sampled 2D grid, if one can design
an appropriate underlying graph connecting pixels with weights that reflect the
image structure, then one can interpret the image (or image patch) as a signal
on a graph, and apply GSP tools for processing and analysis of the signal in
graph spectral domain. In this article, we overview recent graph spectral
techniques in GSP specifically for image / video processing. The topics covered
include image compression, image restoration, image filtering and image
segmentation
Implicit Methods for Equation-Free Analysis: Convergence Results and Analysis of Emergent Waves in Microscopic Traffic Models
We introduce a general formulation for an implicit equation-free method in
the setting of slow-fast systems. First, we give a rigorous convergence result
for equation-free analysis showing that the implicitly defined coarse-level
time stepper converges to the true dynamics on the slow manifold within an
error that is exponentially small with respect to the small parameter measuring
time scale separation. Second, we apply this result to the idealized traffic
modeling problem of phantom jams generated by cars with uniform behavior on a
circular road. The traffic jams are waves that travel slowly against the
direction of traffic. Equation-free analysis enables us to investigate the
behavior of the microscopic traffic model on a macroscopic level. The standard
deviation of cars' headways is chosen as the macroscopic measure of the
underlying dynamics such that traveling wave solutions correspond to equilibria
on the macroscopic level in the equation-free setup. The collapse of the
traffic jam to the free flow then corresponds to a saddle-node bifurcation of
this macroscopic equilibrium. We continue this bifurcation in two parameters
using equation-free analysis.Comment: 35 page
Coarse Grained Computations for a Micellar System
We establish, through coarse-grained computation, a connection between
traditional, continuum numerical algorithms (initial value problems as well as
fixed point algorithms) and atomistic simulations of the Larson model of
micelle formation. The procedure hinges on the (expected) evolution of a few
slow, coarse-grained mesoscopic observables of the MC simulation, and on
(computational) time scale separation between these and the remaining "slaved",
fast variables. Short bursts of appropriately initialized atomistic simulation
are used to estimate the (coarse-grained, deterministic) local dynamics of the
evolution of the observables. These estimates are then in turn used to
accelerate the evolution to computational stationarity through traditional
continuum algorithms (forward Euler integration, Newton-Raphson fixed point
computation). This "equation-free" framework, bypassing the derivation of
explicit, closed equations for the observables (e.g. equations of state) may
provide a computational bridge between direct atomistic / stochastic simulation
and the analysis of its macroscopic, system-level consequences
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