167 research outputs found
Tuning crack pattern by phase separation in the drying of binary colloid-polymer suspension
No full textDrying the colloidal suspension leads to the versatile crack patterns, where the microstructure formed during the drying process determines crack patterns. Here, the polymer is introduced into a silica suspension to tune the crack arrangement in the drying deposit. Five dominated types of crack patterns are defined by varying the ratio of nanoparticles to polymer. Two phase separation processes are proposed to explain the spatial characteristics of the crack patterns: the depletion-induced phase separation of particles and polymer in their mixture; and the separation of water and particle (or polymer) clusters by the water drainage. (C) 2014 Elsevier B.V. All rights reserved,http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000334989700026&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Physics, MultidisciplinarySCI(E)[email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]
Reversible Resampling of Integer Signals
No full textExcept some extremely special cases, signal resampling was generally considered to be irreversible because of strong attenuation of high frequencies after interpolation. In this paper, we prove that signal resampling based on polynomial interpolation can be reversible even for integer signals, i.e., the original signal can be reconstructed losslessly from the resampled data. By using matrix factorization, we also propose a reversible method for uniform shifted resampling and uniform scaled and shifted resampling. The new factorization yields three elementary integer-reversible matrices. The method is actually a new way to compute linear transforms and a lossless integer implementation of linear transforms with the factor matrices. It can be applied to integer signals by in-place integer-reversible computation, which needs no auxiliary memory to keep the original sample data for the transformation during the process or for "undo" recovery after the process. Some examples of low-order resampling solutions are also presented in this paper and our experiments show that the resampling error relative to the original signal is comparable to that of the traditional irreversible resampling.Engineering, Electrical & ElectronicSCI(E)EI1ARTICLE2516-5255
Customizable Triangular Factorizations of Matrices
No full textCustomizable triangular factorizations of matrices find their applications in computer graphics and lossless transform coding. In this paper, we prove that any N nonsingular matrix A can be factorized into 3 triangular matrices, A PLUS, where P is a permutation matrix, L is a unit lower triangular matrix, U is an upper triangular matrix of which the diagonal entries are customizable and can be given by all means as long as its determinant is equal to that of A up to a possible sign adjustment, and S is a unit lower triangular matrix of which all but N 1 off-diagonal elements are set zeros and the positions of those N elements are also flexibly customizable, such as a single-row, a single-column, a bidiagonal matrix or other specially patterned matrices. A pseudo-permutation matrix, which is a simple unit upper triangular matrix with off-diagonal elements being 0, 1 or can take the role of the permutation matrix P as well. In some cases, P may be the identity matrix. Besides PLUS, a customizable factorization also has other alternatives, LUSP, PSUL or SULP for lower S, and PULS, ULSP, PSLU, SLUP for upper S
Regional wind power ramp forecasting using real-time Mesonet measurements
No full textWind power has been increasingly integrated into electricity grid as renewable
power supply through worldwide power system year by year. The intermittent and
variable characteristics of wind energy will be pronounced in large-area wind power
integrated power systems. When a large amount of wind power production changes, it
would have significant impact on the stable operation of power systems because of the
significant power imbalance introduced by large-area wind generation. Since current
power system is more prepared to handle small variations of wind power, the above
situation would pose a significant yet new challenge for power system operators to
maintain the stability and reliability of system operations, schedule power planning,
prepare non-spinning reserves, make unit commitment, and also manage economic
market. Large wind power ramps are the especially critical events which are sudden
and significant change in wind power generation in a relatively short time period. This
makes large-area wind power ramp forecasting extremely important for power system
operators. Since wind power ramps occurs very stochastically, it would be much
useful and reliable to forecast them in a short time horizon.
Normally, the wind speed data from local measurement site can be used for
forecasting wind power ramps of individual wind turbine or wind farm. However,
when forecasting large-area wind power ramps, there are multiple wind speed data
available from different measurement sites covered over the corresponding
geographical region which should be considered to predict more accurately. NWP
(Numerical Weather Prediction) models can also be used for wind power ramp
forecasting, whereas it is not accurate when predicting hourly and intra-hour wind
power ramps because of its low refreshing rate of output data which typically updates
only every 3 or 6 hours limited by their computational complexity and complicated
postprocessing. This issue should be resolved to make it possible for NWPs to provide
timely predictions of wind power ramps.
This dissertation would be focused on addressing the above-mentioned issues,
which would be predicting the large-scale wind power ramps in an extended region
with hourly ahead forecast results. Three innovative methodologies have been proposed for the forecasting purpose in a timely manner. First, the ordinal levels of
wind power ramp events have been defined as the forecasting information for power
system operators. Multinomial logistic regression has been developed based on the
discovery of the correlation of real-time meso-scale wind speed measurements from
multiple Mesonet sites with regional wind power data. Further, the probabilistic output
of individual multinomial logistic regressive models been combined to an aggregate
model formed with different weights which are calculated by minimizing the Brier
skill score (BSS) on the individual models. Based on the observation of the
multivariate wind speed measurements from diverse locations in the extended region,
those measurements are highly correlated. Thus, sparse primary component analysis
(PCA) has been developed to utilize the above correlation information for further data
fusion and feature extraction to improve the performance of forecasting models.
Besides, ensemble NWP model has been developed with the weighted linear
combination of several individual NWPs based on ensemble learning method. This
method calculates the weights by minimizing the difference between forecast values
and real-time wind speed measurements through gradient boosting algorithm. All the
above developed models can be trained offline and carried out for online wind power
ramp forecasting. The developed methods been tested and evaluated with real-world
data using several metrics compared with other currently proposed methods. The
results have shown the effectiveness and outperformance of these methods for
improving wind power ramp event forecasting.Embargo status: Restricted until 06/2022. To request the author grant access, click on the PDF link to the left
INFINITY-NORM ROTATION FOR REVERSIBLE DATA HIDING
No full textIn this paper, we propose a novel transform that preserves the dynamic range—infinity-norm rotation. This transform is perfectly reversible and piecewise linear, and keeps the maximum value unchanged. We apply the transform to reversible data hiding, which can be utilized for fragile data hiding and covert communication. After the inverse transform applied to the image with hidden data, no overflow or underflow occurs to the pixel values, and small changes of the coefficients in the transform domain result in small changes of the corresponding pixel values after reconstruction. With progressive symmetrical histogram expansion, we obtain very high embedding capacity for data hiding in the transform domain of infinity-norm rotation. Furthermore, the embedding capacity can be further expanded with blocked coefficients and low-frequency coefficients, which is demonstrated by our experiments. Index Terms—Dynamic range preservation, histogram expansion, infinity-norm rotation, pyramidal hierarchy, reversible data hiding. 1
A general iterative method for spatial resolution improvement of digital images in spatial domain
No full textSpatial resolution improvement of digital images has significant applications in remote sensing and computer vision. In this paper, a general iterative method is proposed to improve the spatial resolution from low-resolution images in spatial domain. The general method of interpolation and simulated sampling is formed based on the iterative methods for signal reconstruction from nonuniform sampling and the methods of projection onto convex sets (POCS) by defining convex sets of the sampled images and projection onto the sets, and using a general parallel projection method to find the common points of the sets. The method can be applied to multiframe images with different spatial resolution, various image radiance, relative geometric distortion, additive random noise, and some other general imaging style. Some experiments with resolution test pattern and multiangular remote sensing images performed the convergence and the effectiveness of the algorithms.Computer Science, Software EngineeringCPCI-S(ISTP)
Nuclear chiral and magnetic rotation in covariant density functional theory
No full textExcitations of chiral rotation observed in triaxial nuclei and magnetic and/or antimagnetic rotations (AMR) seen in near-spherical nuclei have attracted a lot of attention. Unlike conventional rotation in well-deformed or superdeformed nuclei, here the rotational axis is not necessary coinciding with any principal axis of the nuclear density distribution. Thus, tilted axis cranking (TAC) is mandatory to describe these excitations self-consistently in the framework of covariant density functional theory (CDFT). We will briefly introduce the formalism of TAC-CDFT and its application for magnetic and AMR phenomena. Configuration-fixed CDFT and its predictions for nuclear chiral configurations and for favorable triaxial deformation parameters are also presented, and the discoveries of the multiple chiral doublets in Ce-133 and Rh-103 are discussed.Major State 973 Program of China [2013CB834400]; National Natural Science Foundation of China [11175002, 11335002, 11461141002]; US Department of Energy (DOE), Office of Science, Office of Nuclear Physics [DE-AC02-06CH11357]SCI(E)[email protected]; [email protected]
Fingerprint indexing based on LAS registration
No full textFingerprint indexing is an efficient technique that greatly improves the performance of fingerprint based person authentication systems by reducing the number of comparison. In this paper, we propose an indexing method based on fingerprint registration with a novel feature called local axial symmetry (LAS). The location and direction estimation of reference point are achieved in a straightforward way after the LAS field is achieved. Then the registered orientation field is utilized as a feature vector to perform the following indexing. A new scheme of the experiment is introduced and satisfactory experimental results are achieved on FVC2000 DB2 that the average search space is only 2.34% of all fingers in the condition of equal-sized training set and testing set.Computer Science, Artificial IntelligenceComputer Science, Information SystemsComputer Science, Software EngineeringImaging Science & Photographic TechnologyRadiology, Nuclear Medicine & Medical ImagingEICPCI-S(ISTP)
Fingerprint reference point detection based on local axial symmetry
No full textReference point detection is an important process for fingerprint analysis. In this paper, we propose a novel feature which is named local axial symmetry (LAS) and present an algorithm to calculate reference point of a fingerprint based on this kind of feature. Experimental results demonstrate its feasibility, validity and the ability to detect reference points of all classes of fingerprints including arch-type fingerprints which is difficult to locate a stable reference point with other methods.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000240678200251&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Computer Science, Artificial IntelligenceEICPCI-S(ISTP)
A BLIND VIDEO WATERMARK DETECTION METHOD BASED ON 3D-DWT TRANSFORM
No full textIn this paper, we propose a new blind video watermark detection method which is based on 3D-DWT transform. We find that the coefficients in the high frequency band of temporal wavelet transform (TWT) are nearly orthogonal to the normally-distributed watermark, which is the basis of our proposed extraction method. The watermarking procedure is similar to the former 3D-DWT method, first 2D-DWT in the spatial domain, then 1D-DWT in the temporal domain (TWT). The difference is that we do not use the low frequency band in the 1D-DWT procedure, for the property of the TWT high frequency band that we have found in the detection procedure. We also propose to use two zero-mean normally-distributed watermarks in embedding to avoid block effects. Finally, an absolute value detection scheme is proposed. Using this scheme our scheme can resist frame dropping attack and temporal frame averaging attack, because the TWT high frequency band reflects the changing parts along the temporal axis.Engineering, Electrical & ElectronicImaging Science & Photographic TechnologyEICPCI-S(ISTP)
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