473 research outputs found
Fast, Preisach-like characterization of hysteretic systems
Proposed is a substantially simplified, Preisach-like model for
characterization of hysteretic systems, in particular magnetic systems. The
main idea is to replace a two-dimensional Preisach density with just two real
functions, describing in a {\em unique way} the reversible and irreversible
processes. As a byproduct of our model we prove, that the major hysteresis loop
alone is insufficient to produce the unique Preisach map. Keywords: magnetic
hysteresis; magnetization processes; materials testing; modeling.Comment: 7 double spaced pages, 4 figures. Presented at 5th International
Symposium on Hysteresis and Micromagnetic Modeling, Budapest, Hungary, May
30th - June 1st, 200
Synthesis of H<sub>x</sub>Li<sub>1-x</sub>LaTiO<sub>4</sub> from quantitative solid-state reactions at room temperature
The layered perovskite HLaTiO4 reacts stoichiometrically with LiOH·H2O at room temperature to give targeted compositions in the series HxLi1-xLaTiO4. Remarkably, the Li+ and H+ ions are quantitatively exchanged in the solid state and this allows stoichiometric control of ion exchange for the first time in this important series of compounds
Convolutional State Space Models for Long-Range Spatiotemporal Modeling
Effectively modeling long spatiotemporal sequences is challenging due to the
need to model complex spatial correlations and long-range temporal dependencies
simultaneously. ConvLSTMs attempt to address this by updating tensor-valued
states with recurrent neural networks, but their sequential computation makes
them slow to train. In contrast, Transformers can process an entire
spatiotemporal sequence, compressed into tokens, in parallel. However, the cost
of attention scales quadratically in length, limiting their scalability to
longer sequences. Here, we address the challenges of prior methods and
introduce convolutional state space models (ConvSSM) that combine the tensor
modeling ideas of ConvLSTM with the long sequence modeling approaches of state
space methods such as S4 and S5. First, we demonstrate how parallel scans can
be applied to convolutional recurrences to achieve subquadratic parallelization
and fast autoregressive generation. We then establish an equivalence between
the dynamics of ConvSSMs and SSMs, which motivates parameterization and
initialization strategies for modeling long-range dependencies. The result is
ConvS5, an efficient ConvSSM variant for long-range spatiotemporal modeling.
ConvS5 significantly outperforms Transformers and ConvLSTM on a long horizon
Moving-MNIST experiment while training 3X faster than ConvLSTM and generating
samples 400X faster than Transformers. In addition, ConvS5 matches or exceeds
the performance of state-of-the-art methods on challenging DMLab, Minecraft and
Habitat prediction benchmarks and enables new directions for modeling long
spatiotemporal sequences
The Non-Destructive and Nano-Microstructural Characterization of Thermal-Barrier Coatings
The durability of thermal barrier coatings (TBCs) plays an important role in the service reliability and maintainability of hot-section components in advanced turbine engines for aerospace and utility applications. Photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) are being concurrently developed as complimentary nondestructive evaluation (NDE) techniques for quality control and liferemain assessment of TBCs. This paper discusses recent achievements in understanding the residual stress, phase constituents, and electrochemical resistance (or capacitance) of TBC constituents—with an emphasis on the thermally grown oxide. Results from NDE by PSLS and EIS are correlated to the nano- and microstructural development of TBCs
The Non-Destructive and Nano-Microstructural Characterization of Thermal-Barrier Coatings
The durability of thermal barrier coatings (TBCs) plays an important role in the service reliability and maintainability of hot-section components in advanced turbine engines for aerospace and utility applications. Photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) are being concurrently developed as complimentary nondestructive evaluation (NDE) techniques for quality control and liferemain assessment of TBCs. This paper discusses recent achievements in understanding the residual stress, phase constituents, and electrochemical resistance (or capacitance) of TBC constituents—with an emphasis on the thermally grown oxide. Results from NDE by PSLS and EIS are correlated to the nano- and microstructural development of TBCs
Of Potions, Poisons, Polygonum and Pre‐emptive Polymorphism
There are scores of references to plants and herbs in William Shakespeare's plays; he was obviously very knowledgeable about their perceived effects. The secret to the highly potent love potion Oberon asks Puck to find, lies in the purple, yellow and white flower, ‘love‐in‐idleness’, a folk name for the wild pansy (Viola tricolour). When scientists from Royal Society of Chemistry and Quest International put this to the test 400 years later, they concluded that ‘Wild pansies were noted in herbal folklore medicine
Chemical Accident Hazard Assessment by Spatial Analysis of Chemical Factories and Accident Records in South Korea
This study identified the potential chemical accident occurrence in Korea by analyzing the spatial distribution of chemical factories and accidents. The number of chemical factories and accidents in 25-km2 grids were used as the attribute value for spatial analysis. First, semi-variograms were conducted to examine spatial distribution patterns and to identify spatial autocorrelation of chemical factories and accidents. Semi-variograms explained that the spatial distribution of chemical factories and accidents were spatially autocorrelated. Second, the results of the semi-variograms were used in Ordinary Kriging to estimate chemical hazard levels. The level values were extracted from the Ordinary Kriging result and their spatial similarity was examined by juxtaposing the two values with respect to their location. Six peaks were identified in both the factory hazard and accident hazard estimation result, and the peaks correlated with major cities in Korea. Third, the estimated two hazard levels were classified with geometrical interval and could be classified into four quadrants: Low Factory and Low Accident (LFLA), High Factory and Low Accident (HFLA), Low Factory and High Accident(LFHA), and High Factory and High Accident (HFHA). The 4 groups identified different chemical safety management issues in Korea; safe LFLA group, many chemical reseller factories were found in HFLA group, chemical transportation accidents were in the LFHA group, and an abundance of factories and accidents were in the HFHA group. Each quadrant represented different safety management obstacles in Korea, and studying spatial differences can support the establishment of an efficient risk management plan
Weighted Sobolev spaces of radially symmetric functions
We prove dilation invariant inequalities involving radial functions,
poliharmonic operators and weights that are powers of the distance from the
origin. Then we discuss the existence of extremals and in some cases we compute
the best constants.Comment: 38 page
Semiclassical stationary states for nonlinear Schroedinger equations with fast decaying potentials
We study the existence of stationnary positive solutions for a class of
nonlinear Schroedinger equations with a nonnegative continuous potential V.
Amongst other results, we prove that if V has a positive local minimum, and if
the exponent of the nonlinearity satisfies N/(N-2)<p<(N+2)/(N-2), then for
small epsilon the problem admits positive solutions which concentrate as
epsilon goes to 0 around the local minimum point of V. The novelty is that no
restriction is imposed on the rate of decay of V. In particular, we cover the
case where V is compactly supported.Comment: 22 page
Development of Improved Methods for Low Template DNA Analysis
We investigated on the crystallographic, morphological and magnetic characteristics of barium ferrite-SiO2/Si films prepared by sol-gel dip coating method. It is found that the sol obtained at 80°C for 90 min. is the most suitable for coating. The particles formed in the films prepared by heat treatment at 800°C for 3 hours exhibits needle-like particles placing parallel to substrate. The saturation magnetization increases as thickness increases, and its maximum value is 260 emu/cm3. The direction of easy-magnetization in the films has tendency to vary from perpendicular to parallel to substrate as thickness increases
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