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931.
车牌识别是智能交通系统中的关键技术。而车牌定位是识别的先决工作。本文在定位过程中提出了根据梯度的变化方向，对图像的目标部分增强明暗的对比．克服了图像目标局部灰度变化差异性而引起的二值图像中字符笔划缺失或粘连问题．为车牌定位和字识别提供更为可靠二值图像； 相似文献
932.
Ya-xiang Yuan Zhen-zhen Zheng 《计算数学(英文版)》2006,24(3):357-364
In this paper, disturbed sparse linear equations over the 0-1 finite field are considered.Due to the special structure of the problem, the standard alternating coordinate methodcan be implemented in such a way to yield a fast and efficient algorithm. Our alternatingcoordinate algorithm makes use of the sparsity of the coefficient matrix and the currentresiduals of the equations. Some hybrid techniques such as random restarts and geneticcrossovers are also applied to improve our algorithm. 相似文献
933.
In this paper, we consider a chemical reaction–diffusion model with Degn–Harrison reaction scheme under homogeneous Neumann boundary conditions. The existence of Hopf bifurcation to ordinary differential equation (ODE) and partial differential equation (PDE) models are derived, respectively. Furthermore, by using the center manifold theory and the normal form method, we establish the bifurcation direction and stability of periodic solutions. Finally, some numerical simulations are shown to support the analytical results, and to reveal new phenomenon on the Hopf bifurcation. 相似文献
934.
Lourdes Gómez-Valle Miguel Ángel López-Marcos Julia Martínez-Rodríguez 《Mathematical Methods in the Applied Sciences》2020,43(14):7993-8005
In this paper, we consider a two-factor interest rate model with stochastic volatility, and we assume that the instantaneous interest rate follows a jump-diffusion process. In this kind of problems, a two-dimensional partial integro-differential equation is derived for the values of zero-coupon bonds. To apply standard numerical methods to this equation, it is customary to consider a bounded domain and incorporate suitable boundary conditions. However, for these two-dimensional interest rate models, there are not well-known boundary conditions, in general. Here, in order to approximate bond prices, we propose new boundary conditions, which maintain the discount function property of the zero-coupon bond price. Then, we illustrate the numerical approximation of the corresponding boundary value problem by means of an alternative direction implicit method, which has been already applied for pricing options. We test these boundary conditions with several interest rate pricing models. 相似文献
935.
Gang Luo & Qingzhi Yang 《高等学校计算数学学报(英文版)》2020,13(1):200-219
In recent years, alternating direction method of multipliers (ADMM) and its variants are popular for the extensive use in image processing and statistical learning. A variant of ADMM: symmetric ADMM, which updates the Lagrange multiplier twice in one iteration, is always faster whenever it converges. In this paper, combined with Nesterov's accelerating strategy, an accelerated symmetric ADMM is proposed. We prove its $mathcal{O}(frac{1}{k^2})$ convergence rate under strongly convex condition. For the general situation, an accelerated method with a restart rule is proposed. Some preliminary numerical experiments show the efficiency of our algorithms. 相似文献
936.
Jules K. Djoko Jonas Koko Radek Kucera 《Mathematical Methods in the Applied Sciences》2019,42(5):1488-1511
For the power law Stokes equations driven by nonlinear slip boundary conditions of friction type, we propose three iterative schemes based on augmented Lagrangian approach and interior point method to solve the finite element approximation associated to the continuous problem. We formulate the variational problem which in this case is a variational inequality and construct the weak solution of the continuous problem. Next, we formulate two alternating direction methods based on augmented Lagrangian formalism in order to separate the velocity from the symmetric part the velocity gradient and tangential part of the velocity. Thirdly, we present some salient points of a path‐following variant of the interior point method associated to the finite element approximation of the problem. Some numerical experiments are performed to confirm the validity of the schemes and allow us to compare them. 相似文献
937.
This paper addresses the problem of robust angle of arrival (AOA) target localization in the presence of uniformly distributed noise which is modeled as the mixture of Laplacian distribution and uniform distribution. Motivated by the distribution of noise, we develop a localization model by using the -norm with as the measurement error and the -norm as the regularization term. Then, an estimator for introducing the proximal operator into the framework of the alternating direction method of multipliers (POADMM) is derived to solve the convex optimization problem when . However, when , the corresponding optimization problem is nonconvex and nonsmoothed. To derive a convergent method for this nonconvex and nonsmooth target localization problem, we propose a smoothed POADMM estimator (SPOADMM) by introducing the smoothing strategy into the optimization model. Eventually, the proposed algorithms are compared with some state-of-the-art robust algorithms via numerical simulations, and their effectiveness in uniformly distributed noise is discussed from the perspective of root-mean-squared error (RMSE). The experimental results verify that the proposed method has more robustness against outliers and is less sensitive to the selected parameters, especially the variance of the measurement noise. 相似文献
938.
Kamran Ahmad Khan Gul Majid Khan Muhammad Muzammal Mohammed Al Mohaini Abdulkhaliq J. Alsalman Maitham A. Al Hawaj Ashfaq Ahmad Zahid Rasul Niazi Kifayat Ullah Shah Arshad Farid 《Molecules (Basel, Switzerland)》2022,27(3)
Controlled release matrices have predictable drug release kinetics, provide drugs for an extended period of time, and reduce dosing frequency with improved patient compliance as compared with conventional tablet dosage forms. In the current research work, losartan potassium controlled release matrix tablets were fabricated and prepared with rate altering agents; that is, Ethocel grade 100 combined with Carbopol 934PNF. Various drug to polymer ratios were used. HPMC, CMC, and starch were incorporated in some of the matrices by replacing some amount of filler (5%). The direct compression method was adopted for the preparation of matrices. In phosphate buffer (pH 6.8), the dissolution study was conducted by adopting the USP method-I as the specified method. Drug release kinetics was determined and dissolution profiles were also compared with the reference standard. Prolonged release was observed for all matrices, but those with Ethocel 100FP Premium showed more extended release. The co-excipient (HPMC, CMC, and starch) exhibited enhancement in the drug release rates, while all controlled release matrices released the drug by anamolous non-Fickian diffusion mechanism. This combination of polymers (Ethocel grade 100 with Carbopol 934PNF) efficiently extended the drug release rates up to 24 h. It is suggested that these matrix tablets can be given in once a day dosage, which might improve patient compliance, and the polymeric blend of Ethocel grade 100 with Carbopol 934PNF might be used in the development of prolonged release matrices of other water-soluble drugs. 相似文献
939.
Dr. Ling Zhang Laicheng Zhou Na Xu Zhenjie Ouyang 《Angewandte Chemie (International ed. in English)》2017,56(28):8191-8195
It is challenging to prepare co-organized nanotube systems with controlled nanoscale chirality in an aqueous liquid flow field. Such systems are responsive to a bubbled external gas. A liquid vortex induced by bubbling carbon dioxide (CO2) gas was used to stimulate the formation of nanotubes with controlled chirality; two kinds of achiral cationic building blocks were co-assembled in aqueous solution. CO2-triggered nanotube formation occurs by formation of metastable intermediate structures (short helical ribbons and short tubules) and by transition from short tubules to long tubules in response to chirality matching self-assembly. Interestingly, the chirality sign of these assemblies can be selected for by the circulation direction of the CO2 bubble-induced vortex during the co-assembly process. 相似文献
940.
Corona discharges in flowing gas are of technological significance for a wide range of applications, ranging from plasma reactors to lightning protection systems. Numerous experimental studies of corona discharges in wind have confirmed the strong influence of wind on the corona current. Many of these studies report global electrical characteristics of the gaseous discharge but do not present details of the spatial structure of the potential field and charge distribution. Numerical simulation can help clarify the role of wind on the ion redistribution and the electric field shielding. In this work, we propose a methodology to solve numerically for the drift region of a DC glow corona using the usual approach of collapsing the ionization region to the electrode surface, but allowing for strong inhomogeneities in the electrical and flow setup. Numerical results for a grounded wire in the presence of an ambient electric field and wind are presented. The model predicts that the effect of the wind is to reduce the extension of the corona over the wire and to shift the center of the ion distribution upstream of the flow. In addition, we find that, even though the near-surface ion distribution is strongly affected by the ion injection law used, the current characteristics and the far field solution remain pretty much unaffected. 相似文献