Hygrothermal bending of laminated composite plates with a cutout

Bending of laminated composite plates with a cutout subjected to moisture and temperature is investigated. An eight-noded isoparametric element, which takes transverse shear deformation into account, is used in the present analysis. Three types of cutouts are considered, namely, circular, rounded corner square, and square. The distribution of deflection and moment resultants are studied in anti-symmetric laminates for simply supported and clamped boundary conditions, subjected to uniform moisture and temperature.     

Axisymmetric vibration of bimodulus thick circular and annular plates

The fundamental natural frequencies of axisymmetric circular and annular plates subjected to a combination of a pure bending stress and extensional stress in the plane of the plate are investigated. The thick plate ring element model which includes the effect of transverse shear deformation is created for axisymmetric free vibration problems. The obtained results of non-dimensional natural frequency coefficient compared with the closed form solutions for ordinary plates are shown to be very good. The effects of various parameters on the natural frequency and neutral surface locations are studied. The bimodulus properties are shown to have significant influence on the natural frequency.     

Asymmetric vibration and dynamic stability of bimodulus thick annular plates

The free vibration and dynamic stability problems of asymmetric bimodulus thick annular plates are studied. The annular element with Lagrangian polynomials and trigonometric functions as shape function is developed. The element is based on the Mindlin plate theory so that the effect of transverse shear deformation is included. The dynamic stability of an annular plate subjected to a combination of a pure dynamic bending and a uniform dynamic extensional stress in the plane of the plate is investigated. The non-axisymmetric modes are shown to have significant effects in the annular bimodulus plates.     

Optimization of the reinforcement of a 3D medium with thin composite plates

The reinforcement with a thin composite plate of a 3D linear elastic medium on its external boundary or inside is considered. A linear analysis of the 3D problem leads to a variational formulation in which the reinforcement is modelled by a Kirchhoff–Love plate. Considering the sum of the compliance and a cost as the design objective, a numerical example of the optimization of this reinforcement is performed taking into account the in-plane membrane rigidity only (i.e. the bending aspects are not treated numerically).     

一种覆岩弯曲带三维建模方法

针对三棱柱模型无法准确表示不规则地层结构尤其是钻孔偏斜情况的问题,提出了一种基于广义三棱柱模型的覆岩弯曲带三维建模方法。该方法首先利用钻孔等原始信息,结合广义三棱柱模型,构建采动前覆岩地质三维模型;然后通过判别关键层位置确定弯曲带范围;最后通过估计覆岩弯曲带变形参数对采动前覆岩地质三维模型进行修正,建立采动后覆岩弯曲带地质三维模型。实例分析结果验证了该方法的有效性。     

Non-linear bending of annular sector plates using a matrix method

This paper deals with the large-deflection analysis of isotropic annular sector plates clamped at the edges. The plate is subjected to a uniformly distributed lateral load. The non-linear governing equations are converted into a set of algebraic equations using integral equations associated with beam theory. These equations are solved by the modified Newton-Raphson method. The results are compared to those available for a clamped square plate by taking suitable values of sector angle and inner radius of the annular sector plate. For parametric study, the sector angle and radii ratio are varied. The results are presented in the form of graphs.     

Free vibration of laminated plates using a high-order element

Free vibration analysis of laminated composite plates using the finite element method has been presented. A high-order quadratic isoparametric element has been employed in the analysis. Both the eight-node serendipity and the nine-node Lagrangian shape functions have been used and their performances have been compared. Various schemes for the generation of the mass matrix have been discussed and a comparative study of these schemes has been presented. The results from the present method have been compared with the closed form solutions and experimental observations of the previous investigators.     

Free vibration analysis of laminated composite plates based on FSDT using one-dimensional IRBFN method

This paper presents a new effective radial basis function (RBF) collocation technique for the free vibration analysis of laminated composite plates using the first order shear deformation theory (FSDT). The plates, which can be rectangular or non-rectangular, are simply discretised by means of Cartesian grids. Instead of using conventional differentiated RBF networks, one-dimensional integrated RBF networks (1D-IRBFN) are employed on grid lines to approximate the field variables. A number of examples concerning various thickness-to-span ratios, material properties and boundary conditions are considered. Results obtained are compared with the exact solutions and numerical results by other techniques in the literature to investigate the performance of the proposed method.     

3D woven composite design using a flattening simulation

Fiber composite materials have unique, advantageous mechanical properties that have made them highly desirable in a range of industries. In particular, 3D woven-fiber composites are highly resistant to delamination compared with laminated 2D woven-fiber composites and have been adopted in various advanced products. This paper focuses on the design of 3D woven-fiber composite products and proposes a flattening simulation method for designed 3D models with constant thickness. The proposed method estimates the shape of a flat material and the fiber directions in the 3D model design; deformation phenomena of 3D woven-fiber materials are also considered in order to improve the accuracy of the proposed method. CT images are used to compare the simulation results with the actual deformation of 3D woven-fiber materials and confirm the ability of our method to effectively design the fiber direction base on the 3D model and to estimate the shape of flat materials.     

An element for static, vibration and buckling analysis of thick laminated plates

A conforming finite element formulation of the equations governing composite multilayered plates using Reddy's higher-order theory is presented. The element has eight degrees of freedom, u₀, v₀, w, ∂w/∂x, ∂w/∂y, ∂²w/∂x∂y, γ_x, γ_y, per node. The transverse displacement of the present element is described by a modified bicubic displacement function while the in-plane displacements and shear-rotations are interpolated quadraticly. The element is evaluated for its accuracy in the analysis of static, vibration, and buckling of anisotropic rectangular plates with different lamination schemes and boundary conditions. The conforming finite element described here for the higher-order theory gives fairly accurate results for displacements, stresses, buckling loads, and natural frequencies.     

Dynamic fire 3D modeling using a real-time stereovision system

This work presents a new framework for three-dimensional modeling of dynamic fires present in unstructured scenes. The proposed approach addresses the problem of segmenting fire regions using information from YUV and RGB color spaces. Clustering is also used to extract salient points from a pair of stereo images. These points are then used to reconstruct 3D positions in the scene. A matching strategy is proposed to deal with mismatches due to occlusions and missing data. The obtained data are fitted in a 3D ellipsoid in order to model the enclosing fire volume. This form is then used to compute dynamic fire characteristics like its position, dimension, orientation, heading direction, etc. These results are of great importance for fire behavior monitoring and prediction.     

Three-dimensional vibration analysis of thick, circular and annular plates with nonlinear thickness variation

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of thick, circular and annular plates with nonlinear thickness variation along the radial direction. Unlike conventional plate theories, which are mathematically two-dimensional (2-D), the present method is based upon the 3-D dynamic equations of elasticity. Displacement components u_s, u_z, and u_θ in the radial, thickness, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in θ, and algebraic polynomials in the s and z directions. Potential (strain) and kinetic energies of the plates are formulated, and the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four-digit exactitude is demonstrated for the first five frequencies of the plates. Numerical results are presented for completely free, annular and circular plates with uniform, linear, and quadratic variations in thickness. Comparisons are also made between results obtained from the present 3-D and previously published thin plate (2-D) data.     

矩形中厚板自由振动问题的哈密顿体系与辛几何解法

以矩形中厚板的胡海昌方程为基础,将中厚板自由振动问题导入哈密顿体系,然后利用辛几何中的分离变量和本征函数展开的方法求出了对边简支板自由振动的精确解．文中采用的辛方法不必事先人为地引入试函数,而是通过完全理性的推导,从而突破了传统半逆解法的限制,使得问题的求解更加合理,易于推广．计算实例证明了本文推导结果的正确性．     

Stability of moderately thick rectangular plates using a high precision triangular finite element

Stability of moderately thick rectangular plates is studied in this paper. A high precision triangular finite element is used in the present formulation. Explicit expressions for elastic stiffness and geometric stiffness matrices are presented; the use of numerical integration is avoided. The effect of transverse shear on the critical loads is brought out through two typical examples.     

Multiple reconstruction and dynamic modeling of 3D digital objects using a morphing approach

Organ segmentation and motion simulation of organs can be useful for many clinical purposes such as organ study, diagnostic aid, therapy planning or even tumor destruction. In this paper we present a full workflow starting from a CT-Scan resulting in kidney motion simulation and tumor tracking. Our method is divided into three major steps: kidney segmentation, surface reconstruction and animation. The segmentation is based on a semi-automatic region-growing approach that is refined to improve its results. The reconstruction is performed using the Poisson surface reconstruction and gives a manifold three-dimensional (3D) model of the kidney. Finally, the animation is accomplished using an automatic mesh morphing among the models previously obtained. Thus, the results are purely geometric because they are 3D animated models. Moreover, our method requires only a basic user interaction and is fast enough to be used in a medical environment, which satisfies our constraints. Finally, this method can be easily adapted to magnetic resonance imaging acquisition because only the segmentation part would require minor modifications.     

A multimodal approach for 3D face modeling and recognition using 3D deformable facial mask

We present a multimodal approach for face modeling and recognition. The algorithm uses three cameras to capture stereo images, two frontal and one profile, of the face. 2D facial features are extracted from one of the frontal images and a dense disparity map is computed from the two frontal images. Using the extracted 2D features and their corresponding disparities, we compute their 3D coordinates. We next align a low resolution 3D mesh model to the 3D features, re-project its vertices onto the frontal 2D image and adjust its profile silhouette vertices using the profile view image. We increase the resolution of the resulting 2D model at its center region to obtain a facial mask model covering distinctive features of the face. The 2D coordinates of the vertices, along with their disparities, result in a deformed 3D mask model specific to a given subject’s face. Our method integrates information from the extracted facial features from the 2D image modality with information from the 3D modality obtained from the stereo images. Application of the models in 3D face recognition, for 112 subjects, validates the algorithm with a 95% identification rate and 92% verification rate at 0.1% false acceptance rate.

Coupled 3D master equation and 1D drift‐diffusion approach for advanced OLED modeling

A novel simulation approach for excitonic organic light‐emitting diodes (OLEDs) is established by combining a continuous one‐dimensional (1D) drift‐diffusion (DD) model for the charge carrier dynamics with a three‐dimensional (3D) master equation (ME) model describing the exciton dynamics in a multilayer OLED stack with an additional coupling to a thin‐film optics solver. This approach effectively combines the computational efficiency of the 1D DD solver with the physical accuracy of a discrete 3D ME model, where excitonic long‐range interactions for energy transfer can be taken into account. The coupling is established through different possible charge recombination types as well as the carrier densities themselves. We show that such a hybrid approach can efficiently and accurately describe steady‐state and transient behavior of optoelectronic devices reported in literature. Such a tool will facilitate the optimization and characterization of multilayer OLEDs and other organic semiconductor devices.     

Free vibration analysis of symmetric laminated composite plates by FSDT and radial basis functions

In this paper, we use the first-order shear deformation theory in the multiquadric radial basis function (MQRBF) procedure for predicting the free vibration behavior of moderately thick symmetrically laminated composite plates. The transverse deflection and two rotations of the laminate are independently approximated with the MQRBF approximation. The natural frequencies of vibration are computed for various laminated plates and compared with some available published results. Through numerical experiments, the capability and efficiency of the MQRBF method for eigenvalue problems are demonstrated, and the numerical accuracy and convergence are thoughtfully examined.     

Parallel electromagnetic modeling of 3D microstrip discontinuities using FEM and PML

An approach is developed for 3D microstrip discontinuities using the finite element method (FEM) and the perfectly matched layers (PML). It is shown that iterative solvers are not suitable for this problem since the matrix equations from the PML‐used FEM modeling are rather ill‐conditioned and lead to a very slow or nonconvergent result. A newly developed package SuperLU of the sparse LU decomposition solver is incorporated into our developed approach running on a PC‐based parallel platform. Various implementation techniques are detailed. Numerical experiments clearly show that the developed approach is reliable, efficient, and suitable for modeling 3D microstrip discontinuities. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 38–47, 2001     

High-quality as-is 3D thermal modeling in MEP systems using a deep convolutional network

With the growing need for automated condition monitoring and analysis in existing buildings, significant effort has been spent on the development of three-dimensional (3D) thermal models. However, little attention has been paid to ensuring the quality of these 3D thermal models, which can directly impact the accuracy of condition monitoring and analysis results. This study aims to propose a method to generate a high-quality 3D thermal model for mechanical, electrical, and plumbing (MEP) systems by bridging the quality discrepancy between high-resolution laser scan data and low-resolution thermal images using a deep convolutional neural network. The proposed method consists of two main parts: (1) improving the resolution of thermal images based on a deep convolutional network and (2) generating a high-quality 3D thermal model by mapping improved thermal images. The performance of the thermal image resolution improvement was validated using a dataset consisting of 312 thermal images. The results demonstrated that the quality of the improved thermal images based on a deep convolutional network was higher than conventional bicubic interpolation in terms of root mean square error (RMSE), peak signal-to-noise ratio (PSNR), and structural similarity (SSIM). Qualitative analysis of a 3D thermal model utilizing the resolution-improved thermal images was also conducted. This was further qualitatively analyzed to have resulted in improved overall quality of the 3D thermal model. The ability to generate a high-quality 3D thermal model can help auditors to perform automated condition monitoring and analysis in buildings based on objective and accurate data.