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1.
A. N. Volkovich 《Pattern Recognition and Image Analysis》2008,18(4):716-719
Methods for the automatic construction of a three-dimensional model based on stereoimages are described in the report. Algorithms
of the construction of disparity maps are described. Approaches to their parallel implementation are discussed. Additionally,
results from computing experiments on the comparison of the efficiency of the execution of sequential and parallel implementations
of algorithm are presented.
The text was submitted by the author in English.
Alexander Nikolaevich Volkovich. Born in 1982 in Grodno. Received the high distinction diploma of High Education in 2005 in Yanka Kupala State University
of Grodno. Now he is a PhD student at the United Institute of Informatics Problems of the National Academy of Sciences of
Belarus. His research interests include stereovision and 3D-reconstructing. 相似文献
2.
Michael J. Pratt Author Vitae Bill D. Anderson Author Vitae Author Vitae 《Computer aided design》2005,37(12):1251-1265
The paper describes the status of work aimed at extending the international standard ISO 10303 (STEP) to permit the exchange of parameterized feature-based models between different CAD systems, in terms of the constructional history of the models concerned. Such procedural models have the advantage of being easy to edit following an exchange, by contrast with the models that can be exchanged using current STEP methodology, which prove to be difficult or impossible to edit in the receiving system. The use of the approach described has already been demonstrated in the exchange of realistic procedural shape models of mechanical parts, and the paper includes a brief account of some of the tests performed and the projected benefits of the use of this extension of STEP technology. 相似文献
3.
Fitting mixtures of exponentials to long-tail distributions to analyze network performance models 总被引:7,自引:0,他引:7
Traffic measurements from communication networks have shown that many quantities charecterizing network performance have long-tail probability distributions, i.e., with tails that decay more slowly than exponentially. File lengths, call holding times, scene lengths in MPEG video streams, and intervals between connection requests in Internet traffic all have been found to have long-tail distributions, being well described by distributions such as the Pareto and Weibull. It is known that long-tail distributions can have a dramatic effect upon performance, e.g., long-tail service-time distributions cause long-tail waiting-time distributions in queues, but it is often difficult to describe this effect in detail, because performance models with component long-tail distributions tend to be difficult to analyze. We address this problem by developing an algorithm for approximating a long-tail distribution by a hyperexponential distribution (a finite mixture of exponentials). We first prove that, in prinicple, it is possible to approximate distributions from a large class, including the Pareto and Weibull distributions, arbitrarily closely by hyperexponential distributions. Then we develop a specific fitting alogrithm. Our fitting algorithm is recursive over time scales, starting with the largest time scale. At each stage, an exponential component is fit in the largest remaining time scale and then the fitted exponential component is subtracted from the distribution. Even though a mixture of exponentials has an exponential tail, it can match a long-tail distribution in the regions of primary interest when there are enough exponential components. When a good fit is achieved, the approximating hyperexponential distribution inherits many of the difficulties of the original long-tail distribution; e.g., it is still difficult to obtain reliable estimates from simulation experiments. However, some difficulties are avoided; e.g., it is possible to solve some queueing models that could not be solved before. We give examples showing that the fitting procedure is effective, both for directly matching a long-tail distribution and for predicting the performance in a queueing model with a long-tail service-time distribution. 相似文献
4.
ACRONYM is a comprehensive domain independent model-based system for vision and manipulation related tasks. Many of its submodules and representations have been described elsewhere. Here the derivation and use of invariants for image feature prediction is described. Predictions of image features and their relations are made from three-dimensional geometric models. Instructions are generated which teli the interpretation algorithms how to make use of image feature measurements to derive three-dimensional size, structural, and spatial constraints on the original three-dimensional models. Some preliminary examples of ACRONYM's interpretations of aerial images are shown. 相似文献
5.
Two dimensional and three dimensional noise reduction techniques are used on real 3D images and compared. The comparison is based on the busyness of the resulting images and on their fidelity to the original images. The following methods, each with 2D and 3D versions, are reviewed: mean filtering, median filtering, nearest neighbor smoothing, selective averaging and maximum likelihood smoothing. The results suggest that the 3D techniques are more effective at removing noise and retaining image information content than the 2D techniques. The methods that produced the highest quality images were the nearest neighbor and maximum likelihood smoothing techniques. The mean and median filtering methods removed the most noise, but blurred the images. The selective averaging method provided intermediate results. 相似文献
6.
A computer program is described for implementing and fitting Gaussian statistical models of proton binding or metal binding (at constant pH) to complex mixtures of binding sites, such as humic substances. Both unimodal and bimodal continuous ligand distribution models are incorporated, providing fitting capability for data corresponding to either one or two classes of binding sites. Turbo Pascal source code is given along with an example of program usage. 相似文献
7.
《Ergonomics》2012,55(11):1268-1272
Three-dimensional image (3-D image) was experimentally generated by the binocular disparity principle, and psychological tests were performed in relation to the state of accommodation. An image of a square formed by the time-sharing system using liquid crystal (LC) shutter glasses was displayed before the CRT screen (forward image) by the crossed visual-line method and behind the monitor screen (backward image) by the non-crossed visual-line method. The subjects were requested to subjectively compare each image with the original image on the CRT screen in relation to the size. The forward image displayed by the crossed visual lines looked smaller than the original image, while the backward image displayed by the non-crossed visual lines looked larger. In consideration of the developmental mechanism of micropsia occurring in patients with accommodative palsy or paresis of accommodation and macropsia occurring in patients with accommodative spasm, it was surmised that, in the generation of 3-D image due to binocular disparity, accommodation works so that the original image position is maintained. 相似文献
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9.
Chuang Wang Xiaojun Gu Jihong Zhu Han Zhou Shaoying Li Weihong Zhang 《Structural and Multidisciplinary Optimization》2020,61(3):869-894
In this work, a novel design and modeling method is proposed to obtain hierarchical structures with non-uniform lattice microstructures based on density-ba 相似文献
10.
Zhixue Wu 《Structural and Multidisciplinary Optimization》2009,37(6):625-634
The goal of this work is to obtain optimal hole shape for minimum stress concentration in two-dimensional finite plates using
parameterized geometry models. The boundary shape for a hole is described by two families of smooth curves: one is a “generalized
circular” function with powers as two parameters; the other one is a “generalized elliptic” function
a and b are ellipse axes) with powers as two parameters and one of the ellipse axes as the third parameter. Special attention is
devoted to the practicability of parameterized equations and the corresponding optimal results under the condition with and
without the curvature radius constraint. A number of cases were examined to test the effectiveness of the parameterized equations.
The numerical examples show that extremely good results can be obtained under the conditions with and without curvature radius
constraint, as compared to the known solutions in the literature. The geometries of the optimized holes are presented in a
form of compact parametric functions, which are suitable for use and test by designers. It is anticipated that the implementation
of the suggested parameterized equations would lead to considerable improvements in optimizing hole shape with high quality. 相似文献
11.
The problem of estimating the parameters of a noncausal autoregressive signal model from noisy observations is considered. The signal is assumed to be non-Gaussian. The measurement noise is allowed to be non-Gaussian. Two techniques that use both autocorrelations and third-order autocumulants of the data are presented for parameter estimation. Knowledge of the probability distribution of the driving noise is not required. Several simulation examples are presented to illustrate the two methods. The problem of model order selection is also addressed. 相似文献
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Marco Cesati 《Journal of Computer and System Sciences》2003,67(4):654-685
We propose a general proof technique based on the Turing machine halting problem that allows us to establish membership results for the classes W[1], W[2], and W[P]. Using this technique, we prove that Perfect Code belongs to W[1], Steiner Tree belongs to W[2], and α-Balanced Separator, Maximal Irredundant Set, and Bounded DFA Intersection belong to W[P]. 相似文献
15.
Wayne J. Dunstan Robert R. Bitmead Sergio M. Savaresi 《Control Engineering Practice》2001,9(12):1301-1317
Tools for fitting low-complexity nonlinear models based on experimental data are examined through the example problem of finding a reduced-order model suitable for control of a combustion instability operating in a limit cycle. This proceeds in four parts; physical modeling, linear system identification, nonlinear analysis, and validation test design. It is shown how the nonlinear tools of describing functions, bifurcation methods and manifold analysis assist in developing a simple nonlinear model capable of describing the data and consistent with physical understanding. The system being modeled is a lean gas turbine combustor which exhibits a sustained mid-range (100–1000 Hz) limit cycle instability. The closed-loop experimental data does not contain a sufficiently rich spectrum for confident modeling in the first linear system identification phase. Despite the paucity of information quality, a grey-box nonlinear model is created and parametrized which provides an explanation both of the limit-cycle fundamental oscillation and of a high frequency nonharmonic signal also present. The model structure is explored and various operating conditions simulated to understand the model better.
The validation and/or refinement of this model is then considered. The model validation problem is important because of the poor information content of the periodic limit cycle data. The challenge is to provide a practically feasible, small excitation to the loop to improve identifiability and to provide qualitative tests of model performance. We examine this problem by considering the nonlinear dynamics of the model class and feasible excitation mechanisms. 相似文献
16.
In a generalised linear model the mean of each observation is assumed to be related to its linear predictor by a known link function. In some cases this link function may not be known exactly, but can be assumed to be of some general ‘parametric’ form. We show how generalised linear models can be extended to fit models with such link functions. Examples given include the two-parameter logistic and estimating the exponent of the Box-Cox link. GLIM-3 coding is supplied. 相似文献
17.
A truncated Levenberg-Marquardt algorithm for the calibration of highly parameterized nonlinear models 总被引:1,自引:0,他引:1
We propose a modification to the Levenberg-Marquardt minimization algorithm for a more robust and more efficient calibration of highly parameterized, strongly nonlinear models of multiphase flow through porous media. The new method combines the advantages of truncated singular value decomposition with those of the classical Levenberg-Marquardt algorithm, thus enabling a more robust solution of underdetermined inverse problems with complex relations between the parameters to be estimated and the observable state variables used for calibration. The truncation limit separating the solution space from the calibration null space is re-evaluated during the iterative calibration process. In between these re-evaluations, fewer forward simulations are required, compared to the standard approach, to calculate the approximate sensitivity matrix. Truncated singular values are used to calculate the Levenberg-Marquardt parameter updates, ensuring that safe small steps along the steepest-descent direction are taken for highly correlated parameters of low sensitivity, whereas efficient quasi-Gauss-Newton steps are taken for independent parameters with high impact. The performance of the proposed scheme is demonstrated for a synthetic data set representing infiltration into a partially saturated, heterogeneous soil, where hydrogeological, petrophysical, and geostatistical parameters are estimated based on the joint inversion of hydrological and geophysical data. 相似文献
18.
Delzanno Giorgio 《International Journal on Software Tools for Technology Transfer (STTT)》2016,18(5):475-493
International Journal on Software Tools for Technology Transfer - We give a unified view of different parameterized models of concurrent and distributed systems with broadcast communication based... 相似文献
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Knowledge about the relationship between morphology and the function of neurons is an important instrument in understanding the role that neurons play in information processing in the brain. In paricular, the diameter and length of segments in dendritic arborization are considered to be crucial morphological features. Consequently, accurate detection of morphological features such as centre line position and diameter is a prerequisite to establish this relationship. Accurate detection of neuron morphology from confocal microscope images is hampered by the low signal to noise ratio of the images and the properties of the microscope point spread function (PSF). The size and the anisotropy of the PSF causes feature detection to be biased and orientation dependent. We deal with these problems by utilizing Gaussian image derivatives for feature detection. Gaussian kernels provide for image derivative estimates with low noise sensitivity. Features of interest such as centre line positions and diameter in a tubular neuronal segment of a dendritic tree can be detected by calculating and subsequently utilizing Gaussian image derivatives. For diameter measurement the microscope PSF is incorporated into the derivative calculation. Results on real and simulated confocal images reveal that centre line position and diameter can be estimated accurately and are bias free even under realistic imaging conditions. 相似文献