车牌识别预处理优化的研究与实现

车牌识别包括车牌图像的预处理、车牌定位、字符分割和字符识别等重要的部分,其中车牌图像预处理和定位的优劣直接决定着车牌识别准确率的高低。提出了图像预处理的优化方法和步骤,并且在计算机中进行了实现;同时给出和比较了一些典型定位的方法。     

Corning® 384 Well Low Volume Microplate Performance in Miniaturized Assays

In response to the ever-increasing demand for microplates that facilitate assay miniaturization without compromising assay integrity, Corning's new 384 well Low Volume (384 LV) microplates were evaluated using a homogenous, fluorescence polarization protease assay. Fluorescently labeled casein substrate was incubated over time with dilutions of protease at working volumes that range from 1 to 20 μL and reagent concentrations that range from 0.125 to 50 pg/μL. Four types of plates were evaluated:

• Corning 384 well LV black medium bind

• Corning 384 well LV black non-binding surface (NBS™)

• Corning 1536 well black medium bind

• Competitor 384 well small volume

Protease activity was detected as a decrease in polarized fluorescence resulting from substrate degradation over time. Following assay miniaturization to 20 μL working volumes and protease concentration reduction from 25 to 0.25 pg/μL, Corning 384 well LV medium bind and NBS coated assay plates maintained superior signal to noise ratios compared to competitor's 384 well small volume assay plates. At even lower 10 μL working volumes, Corning 384 well LV medium bind assay plates maintained signal to noise ratios comparable to the competitor's assay plates. However as the reagent concentrations were further reduced to 2.5 pg/μL, Corning 384 well LV medium bind and NBS coated assay plates had significantly greater signal to noise ratios compared to the competitor's assay plates. As working volumes were reduced even further to 5 μL and 1 μL, Corning 384 well LV medium bind and NBS coated assay plates had significantly greater signal to noise ratios than the competitor's 384 well small volume assay plates. Furthermore, at 1 μL working volumes, Corning 384 well LV NBS coated assay plates had significantly greater signal to noise ratios than the competitor's assay plates and standard 1536 well assay plates.These results suggest that Corning 384 well LV medium bind and NBS coated assay plates facilitate assay miniaturization while maintaining assay integrity. Furthermore, as working volumes were significantly reduced to those typically found in 1536 deep well and standard 1536 well assay plates (5 and 1 μL, respectively), Corning's 384 well LV NBS coated assay plates provided superior assay performance.     

Free vibrations of laminated composite plates using second-order shear deformation theory

A complete set of linear equations of the second-order theory of laminated composite plates are obtained. A generalized Levy type solution in conjunction with the state space concept is used to analyze the free vibration behavior of cross-ply and antisymmetric angle-ply laminated plates. Exact fundamental frequencies of cross-ply plate strips are obtained for arbitrary boundary conditions. The exact analytical solutions are obtained for thick and moderately thick plates as well as for thin plates and plate strips. It is shown that the results of the second-order theory are very close to the results of the first-order and third-order theories reported in the literature, and different from those of the classical Kirchhoff’s theory for thick laminates.     

Fundamental frequencies of annular plates with internal cracks

The Rayleigh method with a simple sub-sectioning technique has been used to obtain fundamental frequencies of annular plates with internal concentric cracks. Single-term deflection functions which satisfy the respective boundary conditions for the bending of an annular plate are used as admissible functions. The predicted fundamental frequencies are in good agreement with the reported analytical results for annular plates without any internal cracks. Numerical results for fundamental frequencies are presented for annular plates with internal cracks simply supported and clamped on both the outside and inside edges of the plates.     

Natural vibrations of shear deformable cantilevered skewed trapezoidal and triangular thick plates

In a recent companion paper, the efficacy of higher-order shear deformable, C⁰ continuous, Lagrangian isoparametric plate finite element analyses has been demonstrated on cantilevered skewed (parallelogram) thick plates. The present work extends the method to include skewed thick plates having trapezoidal and triangular planforms, and is the first known vibrational study of such plates. Extensive and accurate nondimensional frequency tables and graphical charts are presented for a series of trapezoidal plates showing the effect of aspect ratio, chord ratio, thickness ratio, and skew angle. The need for the present higher-order shear deformable plate finite element method for skewed trapezoidal plate vibrations increases as the skew angle increases and as the aspect ratio, chord ratio, and thickness ratio decreases. Some theoretical and experimental data hitherto published for delta and skewed triangular cantilevered plates are compared with results obtained using the present finite element method. No published theoretical results for cantilevered skewed trapezoidal and triangular thick plates are known to exist.     

Elastic stability of orthotropic plates using the conjugate load/displacement method

It is shown that the conjugate load/displacement method which has been used for the elastic stability analysis of isotropic plates can also be used for orthotropic plates. Results are presented for a range of plates of various rectangular configurations and boundary conditions, as well as for different values of the material modular ratios. A range of loadings is covered; in particular the case of concentrated loads is dealt with. For this loading case the conjugate load/displacement method has been found to be particularly useful.     

Synthesis of waffle plates in the post buckled domain

Typical of many structural elements, plates retain a considerable amount of strength and stiffness in the post-buckled domain. Utilizing the latent strength and stiffness of the plate, this paper reports on the synthesis of metal and composite waffle plates under mechanical and thermal loads with weight as the objective function. The weight of the waffle plate is reduced as the out-of-plane displacement of a panel of the waffle plate is increased. Several examples under various mechanical and thermal loads are presented to illustrate the synthesis of waffle plates in the linear post-buckled domain.     

Performance evaluation of 3D polystyrene 96-well plates with human neural stem cells in a calcium assay

In this study, we have generated a high-throughput screening (HTS)-compatible 3D cell culture platform by chemically "welding" polystyrene scaffolds into standard 2D polystyrene 96-well plates. The variability of scaffolds was minimized by introducing automation into the fabrication process. The fabricated 3D cell culture plates were compared with several commercially available 3D cell culture platforms with light and scanning electron microscopy. Voltage-gated calcium channel functionality was used to access the Z' factors of all plates, including a 2D standard plate control. It was found that with the No-Wash Fluo-4 calcium assay and neural progenitor cells, all plates display acceptable Z' factors for use in HTS. The plates with "welded" polystyrene scaffolds have several advantages, such as being versatile and economical, and are ready to use off the shelf. These characteristics are especially desired in HTS preclinical drug discovery applications.     

On the design and analysis of simply supported and clamped thick rectangular plates

The finite difference method, although well known as an efficient numerical method, was applied in the past, in the case of plate problems, only for the solution of thin plates. In the present study, the suitability of the method for problems involving thick plates is studied. The finite difference method as applied here is a modified finite difference approach to the ordinary finite difference method generally used for the solution of thin plate problems. Thin plates are treated as a particular case of the corresponding thick plates. The method is first applied to investigate the behaviour of clamped, square isotropic homogeneous thick plates. After the validity of the method is established, it is then extended to the solution of similar problems for simply supported square plates. Once the solution for a thick plate with a particular plate aspect ratio and boundary condition is obtained using a limited number of mesh sizes, a more refined solution to investigate the accuracy and convergence of the problem is then extended by providing more detailed functions satisfying the mesh sizes generated automatically by a computer program.

Whenever possible results of the present method are compared with existing solutions in the technical literature obtained by much more laborious numerical techniques, and close agreements are found. The submatrices involved in the formation of the finite difference equations from the governing differential equations are generated directly by the computer program. Simplicity in formulation and quick convergence are the obvious advantages of the method in comparison with other numerical methods requiring extensive computer facilities.     

Free vibration analysis of plates using least-square-based finite difference method

In this paper, we apply the two-dimensional least-square-based finite difference (LSFD) method for solving free vibration problems of isotropic, thin, arbitrarily shaped plates with simply supported and clamped edges. Using the chain rule, we show how the fourth-order derivatives of the plate governing equation can be discretized in two or three steps as well as how the boundary conditions can be implemented directly into the governing equation. By analyzing vibrating plates of various shapes and comparing the solutions obtained against existing results, we clearly demonstrate the effectiveness of LSFD as a mesh-free method for computing vibration frequencies of generally shaped plates accurately.     

Vibration of stiffened skew plates by using B-spline functions

This paper presents a general procedure for calculating the free vibration of stiffened skew plates by the Rayleigh-Ritz method with B-spline functions as coordinate functions. The stiffened skew plates are modelled as the skew plate with a number of stiffening beams.The results are compared with existing values based on other numerical methods. Vibration characteristics of stiffened skew plates are also studied with changing the arrangements of stiffening beams, the stiffness parameters of beams, skew angle and aspect ratio.     

Hybrid-interface element for thick laminated composite plates

A novel 27-node three-dimensional hexahedral hybrid-interface finite element (FE) model has been presented to analyze laminated composite plates and sandwich plates using the minimum potential energy principle. Fundamental elasticity relationship between components of stress, strain and displacement fields are maintained throughout the elastic continuum as the transverse stress components have been invoked as nodal degrees of freedom. Continuity of the transverse stresses at lamina interface has been maintained. Each lamina is modeled by using hybrid-interface elements at the top and the bottom interfaces and conventional displacement based elements sandwiched between these interfaces. Results obtained from the present formulation have found to be in excellent agreement with the elasticity solutions for thin and thick composite cross-ply, angle-ply laminates, as well as sandwich plates. Additional results have also been presented on the variation of the transverse strains to highlight magnitude of discontinuity in these quantities due to difference in properties of face and core materials of sandwich plates. Present formulation can be used effectively to interface hybrid formulation that uses transverse stresses and displacements as degrees of freedom with conventional purely displacement based formulation for realistic estimates of the transverse stresses.     

An incremental galerkin method for plates and stiffened plates

In order to perform a detailed analysis of large deflection behavior of a rectangular plate or stiffened plate, an efficient semi-analytical method is developed. First, incremental forms of the governing differential equations of plates and stiffened plates with initial deflection are derived. These equations are linearized and may be easily solved. Secondly, these equations are solved for each load increment by the Galerkin method with a special consideration of simply supported boundaries.A procedure of equilibrium correction at intermediate load steps is presented such that good accuracy of the solution may be maintained with larger load steps.This method is successfully applied to plates with initial deflection subjected to in-plane as well as out-of-plane loads to obtain the whole histories of the behavior of these plates. Application of this method to stiffened plates with initial deflection is also presented. Comparisons of results obtained by this method with those obtained by other methods are made and the validity of the method is demonstrated.This incremental version of the Galerkin method is found to be extremely advantageous in certain types of plate and stiffened plate problems. These types are identified and the efficiency of the method is demonstrated.     

Analysis of multibody systems with flexible plates using variational graph-theoretic methods

This work treats the problem of modelling multibody systems with structural flexibility. By combining linear graph theory with the principle of virtual work and finite elements, a dynamic formulation is obtained that extends graph-theoretic (GT) modelling methods to the analysis of thin flexible plates for multibody systems. The system is represented by a linear graph, in which nodes represent reference frames on flexible plates, and edges represent components that connect these frames. To generate the equations of motion with elastic deformations, the flexible plates are discretized using a triangular thin shell finite element based on the discrete Kirchhoff criterion and can be used to discretize bidirectional bodies such as satellite panels, flatbed trailers, and mechanisms with plates. Three flexible systems with plates are analyzed to illustrate the performance of this new variational graph-theoretic formulation and its ability to generate directly a set of motion equations for flexible multibody systems (FMS) without additional user input.     

Self Assembly of Polymer Structures Induced by Electric Field

A method has been developed for fabricating polymer microstructures based on electric field induced self assembly and pattern formation. A dielectric fluid placed in between two conductive plates experience a force in an applied electric field gradient across the plates, which can induce a diffusive surface instability and self construction of the fluid surface. This process is exploited for the fabrication of self assembled polymer microstructures as well as replicated patterns through the use of pre-patterned plates or electrodes. FEM simulation is used to decide the minimum wavelength and electric gradient distribution of polymer structures. A variety of structures in the micron and nanometer scales including bio-fluidic MEMS, polymer optoelectronic devices can be fabricated using this method.     

Linear and non-linear deflection analysis of thick rectangular plates—II. Numerical applications

Variational methods are widely used for the solution of complex differential equations in mechanics for which exact solutions are not possible. The finite difference method, although well known as an efficient numerical method, was applied in the past only for the analysis of linear and non-linear thin plates. In this paper the suitability of the method for the analysis of non-linear deflection of thick plates is studied for the first time. While there are major differences between small deflection and large deflection plate theories, the former can be treated as a particular case of the latter, when the centre deflection of the plate is less than or equal to 0.2–0.25 of the thickness of the plate. The finite difference method as applied here is a modified finite difference approach to the ordinary finite difference method generally used for the solution of thin plate problems. In this analysis thin plates are treated as a particular case of the corresponding thick plate when the boundary conditions of the plates are taken into account. The method is first applied to investigate the deflection behaviour of clamped and simply supported square isotropic thick plates. After the validity of the method is established, it is then extended to the solution of rectangular thick plates of various aspect ratios and thicknesses. Generally, beginning with the use of a limited number of mesh sizes for a given plate aspect ratio and boundary conditions, a general solution of the problem including the investigation of accuracy and convergence was extended to rectangular thick plates by providing more detailed functions satisfying the rectangular mesh sizes generated automatically by the program. Whenever possible results obtained by the present method are compared with existing solutions in the technical literature obtained by much more laborious methods and close agreements are found. The significant number of results presented here are not currently available in the technical literature. The submatrices involved in the formation of the finite difference equations from the governing differential equations are generated directly by the computer program. The subroutine SOLINV using the change of variable technique illustrated elsewhere takes care of the solution of the general system. Simplicity in formulation and quick convergence are the obvious advantages of the finite difference formulation developed to compute small and large deflection analysis of thick plates in comparison with other numerical methods requiring extensive computer facilities.     

受限于平行硅板中水的分子动力学模拟

采用分子动力学模拟方法研究了不同间距(16.6,13.6,和11.8 A)两硅平板之间水分子的结构性质,模拟结果显示:受限水呈现出与体态水完全不同的结构性质,即水分子的分布依赖于两板间距.间距为16.6 A时,硅壁的吸引力造成了其附近形成两个明显的水层,其中的水分子的O-H平行于壁面形成氢键.随着间距的减小,第二层水分子中的O-H键由平行于壁面转向垂直于壁面,与临近的水层通过氢键相连.此外,模拟结果表明,在不同上下板间距情况下,被壁面吸引所形成的水层中水分子的结构取向基本没有变化.     

An improved finite-difference analysis of bending of thin rectangular elastic plates

A finite-difference formulation that gives accurate bending moments for thin elastic plates is presented. The biharmonic equation is replaced with two deflection-normal bending moment relations and the equilibrium equation in terms of the moments. Isotropic as well as orthotropic rectangular plates under various loadings and edge conditions are analyzed to demonstrate the accuracy of the present formulation.     

双参数弹性地基上板的自由振动

建立了双参数弹性地基上的正交异性矩形薄板自由振动位移函数微分方程,并得到其一般解．这可用以精确地求解板在任意边界条件下的自由振动问题．以四边固定的正方形板为例进行了分析,计算过程简单,便于实际应用．亦适用于求解单参数弹性地基和各向同性板情形。