任意三角网格模型体积的快速精确计算方法

三角网格是使用最为广泛的网格模型。提出了一种仅根据三角网格模型的三角面片集合计算模型体积的方法。该方法通过指定投影平面,计算每个三角面片及其在投影平面上的投影所围成的凸五面体的带符号体积（必要时对三角面片进行细分）,整个模型的体积为所有凸五面体带符号体积的代数和。所提出的三角网格模型体积计算方法能实现模型体积的快速准确计算。在大型水电工程施工模拟中施工单元的方量计算测试和不同规模的三角网格模型体积计算测试都证实了该方法的有效性。     

三维模型两点连通概率函数的快速计算

三维数字岩心模型的连通性分析中,两点连通概率函数是一个重要的统计参数。针对该函数由于计算复杂度过于庞大而造成计算时间过长的问题,提出了使用基于均匀分布的随机函数的空间随机采样法,缩小待计算数据集的规模,同时进行并行优化,达到缩短计算时间的目的。通过实验对比,结果表明,这种采样方法在平均相对误差较小的情况下,能够达到缩短计算时间数百倍,具有良好的稳定性。     

pH精算及酸碱滴定曲线绘制通用软件的开发

以Microsoft.NET Framework为开发平台,使用面向对象的C#语言,开发pH计算及滴定曲线绘制的软件。该软件利用分布系数计算各种形态的平衡浓度,根据酸碱质子理论归纳出通用方程后,利用二分法求解氢离子浓度计算pH。软件收集了常见酸碱的离解常数,用户只要输入浓度后就可精算pH值、绘制酸碱滴定曲线,同时提供Excel数据输出、图像保存等功能。如果需要考虑活度,可根据德拜-休克尔公式计算活度系数,使用浓度常数代替活度常数,使所得pH更接近体系真实值。软件计算结果准确、界面友好、容易操作,可广泛应用于各种体系。     

Fast facial shape recovery from a single image with general, unknown lighting by using tensor representation

In this paper, we propose a fast 3-D facial shape recovery algorithm from a single image with general, unknown lighting. In order to derive the algorithm, we formulate a nonlinear least-square problem with two parameter vectors which are related to personal identity and light conditions. We then combine the spherical harmonics for the surface normals of a human face with tensor algebra and show that in a certain condition, the dimensionality of the least-square problem can be further reduced to one-tenth of the regular subspace-based model by using tensor decomposition (N-mode SVD), which greatly speeds up the computations. In order to enhance the shape recovery performance, we have incorporated prior information in updating the parameters. In the experiment, the proposed algorithm takes less than 0.4 s to reconstruct a face and shows a significant performance improvement over other reported schemes.     

Consideration of illumination effects and optimization of window size for accurate calculation of depth map for 3D shape recovery

Obtaining an accurate and precise depth map is the ultimate goal for 3D shape recovery. For depth map estimation, one of the most vital parts is the initial selection of the focus measure and processing the images with the selected focus measure. Although, many focus measures have been proposed in the literature but not much attention has been paid to the factors affecting those focus measures as well as the manner the images are processed with those focus measures. In this paper, for accurate calculation of depth map, we consider the effects of illumination on the depth map as well as the selection of the window size for application of the focus measures. The resulting depth map can further be used in techniques and algorithms leading to recovery of three-dimensional structure of the object which is required in many high-level vision applications. It is shown that the illumination effects can directly result in incorrect estimation of depth map if proper window size is not selected during focus measure computation. Further, it is shown that the images need some kind of pre-processing to enhance the dark regions and shadows in the image. For this purpose, an adaptive enhancement algorithm is proposed for pre-processing. In this paper, we prove that without such pre-processing for image enhancement and without the use of proper window size for the estimation of depth maps, it is not possible to obtain the accurate depth map.     

Fast and Accurate 3D Face Recognition

In this paper we present a new robust approach for 3D face registration to an intrinsic coordinate system of the face. The intrinsic coordinate system is defined by the vertical symmetry plane through the nose, the tip of the nose and the slope of the bridge of the nose. In addition, we propose a 3D face classifier based on the fusion of many dependent region classifiers for overlapping face regions. The region classifiers use PCA-LDA for feature extraction and the likelihood ratio as a matching score. Fusion is realised using straightforward majority voting for the identification scenario. For verification, a voting approach is used as well and the decision is defined by comparing the number of votes to a threshold. Using the proposed registration method combined with a classifier consisting of 60 fused region classifiers we obtain a 99.0% identification rate on the all vs first identification test of the FRGC v2 data. A verification rate of 94.6% at FAR=0.1% was obtained for the all vs all verification test on the FRGC v2 data using fusion of 120 region classifiers. The first is the highest reported performance and the second is in the top-5 of best performing systems on these tests. In addition, our approach is much faster than other methods, taking only 2.5 seconds per image for registration and less than 0.1 ms per comparison. Because we apply feature extraction using PCA and LDA, the resulting template size is also very small: 6 kB for 60 region classifiers.     

快速三维人耳提取与识别

针对现有三维人耳提取与识别算法中存在处理时间长、识别率低的问题,提出一种快速三维人耳提取方法和2种三维人耳识别方法.三维人耳提取时,使用不变特征迭代最近点算法使人耳与平均耳对齐,完成位置和姿态的归一化,然后用掩膜提取出三维人耳.第一种=三维人耳识别方法结合人耳深度和曲率信息,采用主元分析算法进行降维.然后用最近邻分类完成识别;第二种三维人耳识别方法则使用不变特征迭代最近点算法对齐测试耳与原型耳,利用配准误差完成人耳识别.实验结果表明,第一种人耳识别方法识别率较高、计算速度很快,第二种人耳识别方法可达到很高的识别率.     

Method for a Fast and Simple Dynamic Analysis of 2D and 3D Mechanisms

Here, an approach to describe the dynamics of 2D and 3D mechanisms that leads to a simpleand fast analysis is presented. Any position of an elastic mechanism may be defined usingonly rotations. Because in space the finite angles are not vectors, the Euler–Rodriguesparameters were adopted to describe the 3D rotations. The assembling process of the links intothe whole mechanism is natural and follows the standard finite element scheme. Lagrange multipliersare used only to impose the closed loop conditions. The approach developed in this work can be applied to 3D mechanisms composed by beams and having internal hinges as kinematics pairs, but itcan be generalized to other link shapes. The method is used either for mechanisms with rigid links,or with elastic ones, even for very deformable links that completely change the initial configuration.Both the floating and the absolute reference frame approach may be used, depending on the problem;passing from one formulation to the other is quite natural.If the links may be considered beams, the method starts from the exact equations written forthe deformed shape of each link and this provides a good accuracy. In this paper, a special finiteelement is presented: the unknowns of the problems being the nodal rotations or nodal Euler–Rodriguesparameters. Few nodes are requested for good accuracy. In general, as the number degrees of freedomper node is smaller than in the classical finite element approach, an important reducing of the totalnumber of nodal unknowns is obtained leading to an important reducing of the computer time. TheEuler–Bernoulli beam model was adopted, but the implementation of the Timoshenko beam model thattakes the shear efforts into account, is not difficult.     

Topological lines in 3D tensor fields and discriminant Hessian factorization

This paper addresses several issues related to topological analysis of 3D second order symmetric tensor fields. First, we show that the degenerate features in such data sets form stable topological lines rather than points, as previously thought. Second, the paper presents two different methods for extracting these features by identifying the individual points on these lines and connecting them. Third, this paper proposes an analytical form of obtaining tangents at the degenerate points along these topological lines. The tangents are derived from a Hessian factorization technique on the tensor discriminant and leads to a fast and stable solution. Together, these three advances allow us to extract the backbone topological lines that form the basis for topological analysis of tensor fields.     

Quick and accurate estimation of human 3D hand posture

We propose a three-dimensional hand posture estimation system that can retrieve a hand posture image most similar to the input data from a non-multilayer database. Our system uses, at the first stage, coarse screening by the proportional information on the hand images, which roughly correspond to forearm rotation or bending of the thumb or four fingers; then, at the second stage, performs a detailed search for similarity for selected candidates. To describe forearm rotation, and wrist’s internal and external rotations, bending and stretching, no separate processes were used for estimating the corresponding joint angles. By estimating the sequential images of the finger shape using this method, we successfully realized a process involving a joint angle estimation error within two or three degrees, a processing time of approximately 80 fps or more, using only one Note PC and high-speed camera, even when the wrist was freely rotating. Since the image information and the joint angle information are paired in the database, as well as the wrist joint, the system can generate the imitative motions as those of the fingers and wrist of a human being with no time delay by means of a robot, by outputting the estimation results to the robot hand.     

3D-ARNet: An accurate 3D point cloud reconstruction network from a single-image

Multimedia Tools and Applications - Generating a more realistic 3D reconstruction point cloud is an ill-posed problem. It is a challenging task to infer 3D shape from a single image. In this paper,...     

Fast method for calculation of mutual coupling in planar microwave circuits on general multilayer substrates

In this article a new fast method for the calculation of mutual coupling in planar microwave circuits is described. The circuit is divided into three component classes: lines, small discontinuities and larger, meshed, structures. Modules are proposed to calculate the intra‐ and inter class couplings. The first two models take full advantage of the specific properties of lines and small discontinuities to speed up calculations. For lines, this means using the traveling waves and for small discontinuities the radiation behavior is approximated by that of an elementary dipole. The third module is the regular method of moments (MoM), which has been altered in such a way that solving the integral equation matrix immediately yields the S‐parameters on the lines that feed the structure. The new method uses far less unknowns and needs far less CPU time than the traditional MoM. The advantage over other circuit simulators such as Advanced Design System (ADS) and Microwave Design System (MDS) is that the new method includes the parasitical coupling effects in the entire circuit that are ignored in these commercial packages. These parasitical couplings can sometimes have a large effect upon the circuit. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 378–388, 2003.     

Shape-based detail-preserving exaggeration of extremely accurate 3D faces

We present an approach to automatically exaggerate the distinctive features of extremely detailed 3D faces. These representations comprise several million triangles and capture skin detail down to the pores. Despite their high level of realism, their size makes visualization difficult and real-time mesh manipulation infeasible. The premise of our methodology is to first remove the detail to obtain low resolution shape information, then perform shape-based exaggeration on a low resolution model and finally reapply the detail onto the exaggeration to recover the original resolution. We also present the results of applying this methodology to a small set of faces.     

三维组态软件设计中场景快速组态及交互方法研究

针对三维组态软件三维监控场景组态困难以及人机交互复杂的问题,提出一种基于本体的三维场景快速组态方法以及分层三维交互模型。在三维组态软件设计中给监控设备模型加入语义信息,使组态过程智能化,从而使监控场景的组态更加简便,人机交互更加自然。采用分层的人机交互模型,实现了高层交互的设备无关性,有利于系统的扩展。采用以上方法增强了三维组态软件开发及使用的有效性。     

Fast and accurate mining of correlated heavy hitters

The problem of mining correlated heavy hitters (CHH) from a two-dimensional data stream has been introduced recently, and a deterministic algorithm based on the use of the Misra–Gries algorithm has been proposed by Lahiri et al. to solve it. In this paper we present a new counter-based algorithm for tracking CHHs, formally prove its error bounds and correctness and show, through extensive experimental results, that our algorithm outperforms the Misra–Gries based algorithm with regard to accuracy and speed whilst requiring asymptotically much less space.     

3D BEM for the general piezoelectric solids

In this paper we present a new scheme of three-dimensional boundary element method for the general anisotropic piezoelectric solids. We use the Radon transform representation of the three-dimensional fundamental solutions of piezoelectricity and integrate them analytically over the triangular boundary element with the linear interpolation. This reduces the computation for the system matrices G and H from the standard singular surface integrations to the simple regular line integrations and enables a drastic reduction of the computation time. The integrand of the line integral consists of the product of a function dependent and another function independent on the location vectors representing the source and observation points. The latter function depends only on the material and element properties and thus calculated only once for each element and saved for a repeated use in the calculation of G and H matrices and in the post-processing. Exploitation of this favorable structure results in the further reduction of the computation time for very large systems. The implementation of the proposed method with numerical examples will be presented.     

The operator method of the bandwidth calculation in a composite multimode optical fibre line

In this paper has been considered the new operator method which makes the calculation of a composite optical fiber bandwidth possible with taking into account an inhomogeneity’s type and scale. As an example of usage of the method the broadening compensation effect has been considered in details and was shown the possibility of the bandwidth increase in composite fiber with specially matched profile gradients.