Micromagnetic analysis of a magnetic domain wall in 2-d and 3-d nanocontacts

We have performed micromagnetic calculations of magnetic domain walls in two-dimensional (2-D) and three-dimensional (3-D) nanocontacts and estimate the domain wall widths. The magnetic domain wall in a 3-D nanocontact is smaller than that in a 2-D nanocontact due to the larger magnetic volume available to pin the magnetization in the antiparallel configuration of the electrodes. Therefore, 3-D nanocontacts are more suitable than 2-D nanocontacts for domain wall confinement and large magnetoresistance effects.     

Motion estimation of elastic articulated objects from image contours

Abstract

This paper presents a new model of elastic articulated objects based on revolving conic surface. The model includes three-dimensional object skeleton and deformable surfaces that can represent the deformation of human body surfaces. In each limb, surface deformation is represented by adjusting only two deformation parameters. Then, the deformation parameters are determined by corresponding two-dimensional image contours from a sequence of stereo images. The three-dimensional motion parameters are estimated based on the skeleton points. The algorithm presented in this paper includes skeleton-based parameter estimation of motion and parameter determination of deformable surfaces.     

等离子喷涂ZrO2涂层显微结构表征和热导率分析（英文）

利用大气等离子喷涂制备了ZrO2涂层,采用扫描电子显微镜结合图像分析的方法对涂层的显微结构特征(总气孔率和大气率)进行了量化表征.同时利用扫描电子显微镜附带X射线扫描成像对涂层内部的微裂纹和大的分隔裂纹的三维分布进行了表征.据此建立了ZrO2涂层显微结构与热导率之间的关系.室温下,涂层N2的热导率较N1的低,因为涂层N2内气孔和微裂纹数较多;在1000℃,由于微裂纹的烧结作用导致热导率增大,所以涂层N2的热导率较N1反而高.高温下,涂层内由微裂纹汇聚而形成的大的分隔裂纹的存在则可以有效地抑制烧结,降低涂层的热导率.     

Two-dimensional inverse born approximation in ultrasonic flaw characterization

A method is developed to characterize flaws of arbitrary shape by using ultrasound pulse echoes at multiple coplanar incident directions. The three-dimensional image reconstruction problem is reduced to a series of two-dimensional image reconstructions, thereby avoiding the difficulties associated with three-dimensional image reconstructions, such as taking and processing a large amount of data, and the complications associated with three-dimensional image reconstructions, such as three-dimensional interpolation, long computing time, etc. The reconstructed two-dimensional images represent the two-dimensional projections or shadows of the three-dimensional flaw characteristic function. Each projection image is reconstructed independently using well-developed computerized tomography reconstruction techniques. If the shape of the flaw is not too irregular, or if the fine details of the shape are not of interest, only a few of these projection images suffice to characterize the flaw. The magnitude scaling problem and the alignment problem of the echoes at different incident directions can be handled easily in the algorithm. Simulation studies yielded encouraging results.     

一种双目立体视觉系统的校准方法

基于双目立体视觉系统的图像分析以及人工神经网络的三维空间建模算法,设计了一种针对双目立体视觉相机的校准方法,并可应用于运动目标点的轨迹追踪。将均匀分布目标点的校准平面放置在有效视野内的不同位置,通过双目立体视觉系统来捕获处于不同位置的校准平面图像。在图像处理之后,使用校准点中心的二维坐标作为人工神经网络训练的输入样本集,通过建立人工神经网络模型结构,实现目标点二维平面坐标到三维空间坐标的映射关系。采用这种具有通用性的方法,可以有效修正系统中存在的失真因子,获得目标三维位置信息,而无需进行复杂的相机校准操作。实验表明,提出的方案具有良好的可行性和鲁棒性。     

从序列图像计算二次曲线的光流

提出一种二次曲线的整体表示法：空间二次曲线和平面二次曲线的坐标表示法，建立了基于动态灰度图像和基于序列灰度图像的二次曲线光流概念，采用边缘检测、边缘细化和轮廓跟踪等技术，获得了具有单像素宽的边缘点集，提出有分段二次曲线描述边缘，计算得到了二次曲线的光流。     

Uniform bicubic B-splines applied to boundary element formulation for 3-D scalar problems

In this work, uniform bicubic B-spline functions are used to represent the surface geometry and interpolation functions in the formulation of boundary-element method (BEM) for three-dimensional problems. This is done as a natural generalization of cubic B-spline curves, introduced by Cabral et al, for two-dimensional problems. Three-dimensional scalar problems, with particular applications to Laplace and Helmholtz equations, are considered.     

一种含特定微裂纹缺陷三维编织复合材料弹性常数预报方法

本文将细观力学的Eshelby和Mori-Tanaka理论与刚度体平均化方法相结合,对含圆币型基体微裂纹的三维编织复合材料弹性常数进行了理论预报,分析了纤维体积含量、微裂纹密度、编织特征参数变化的影响,与文献[3]的实验结果进行了比较。     

Shape assessment of particles in concrete technology: 2D image analysis and 3D stereological extrapolation

A survey is given of stereology-based two-dimensional (2D) and three-dimensional (3D) approaches to shape assessment of embedded or non-embedded particles. Firstly, the development is outlined of global parameters characterizing geometric structure of cementitious materials. Secondly, these parameters are combined to yield effective shape estimators to be applied to section images of embedded particles or to projection images of non-embedded particles. This application can be just 2D, denoted as quantitative image analysis, giving information on what is displayed of the particle(s) in the section or projection image plane only. However, the researcher should strive for geometrical–statistical (stereological) extrapolation of the 2D observations to the real world’s third dimension. This is demonstrated superior over the 2D approach, however, requires a careful sampling strategy for providing representative information on structure.     

Optical shifter for a three-dimensional image by use of a gradient-index lens array

We propose a new function of the two-dimensional lens array that is composed of many gradient-index lenses. The array forms three-dimensional (3D) images. The characteristics of the 3D images depend on the length of the gradient-index lens. Especially, if the length of the lens is an odd-integer multiple of the half period of the optical path, 3D images are pseudoscopic with a reversed depth. The two lens arrays are positioned at a suitable distance, so that orthoscopic 3D images with the correct depth are formed in front of the lens array.     

Microcracks in chromium electrodeposits

The internal stress in chromium deposits plated using a sulphate catalyst was determined using a bent cathode method. Chromium deposits exhibited a high internal tensile stress which decreased with increasing deposit thickness. Surface structures and microcrack patterns were studied using secondary electron and y-modulation techniques and atomic force microscopy (AFM). Y-modulation images revealed some three-dimensional information about microcracks. AFM analysis provided quantitative information about microcrack widths and depths. This revised version was published online in November 2006 with corrections to the Cover Date.     

Real object recognition using moment invariants

Moments and functions of moments have been extensively employed as invariant global features of images in pattern recognition. In this study, a flexible recognition system that can compute the good features for high classification of 3-D real objects is investigated. For object recognition, regardless of orientation, size and position, feature vectors are computed with the help of nonlinear moment invariant functions. Representations of objects using two-dimensional images that are taken from different angles of view are the main features leading us to our objective. After efficient feature extraction, the main focus of this study, the recognition performance of classifiers in conjunction with moment-based feature sets, is introduced     

Projection display for the generation of two orthogonal polarized images using liquid crystal on silicon panels and light emitting diodes

We present a projection system that is capable of two-dimensional and three-dimensional image display. A novel projection architecture is discussed that can simultaneously generate two linear polarized full-color images with orthogonal states of polarization using only one optical system. Both images are modulated by using two high-resolution liquid crystal on silicon panels that are illuminated with high-power light emitting diodes. The optical core and the illumination system are simulated, characterized, and optimized with nonsequential ray tracing software. A proof-of-concept demonstrator of the entire projection system is built and characterized. Important component specifications are discussed to improve the system performance.     

自适应Chirplet信号分解用于ISAR目标三维转动检测

当ISAR目标作复杂的三维转动时,目标上各散射点的相位误差将与它们在目标上所处的位置有关,传统的相位聚焦方法难以采用统一的相位校正函数来进行补偿。为解决此问题,论文提出了一种基于自适应Chirplet信号分解的ISAR目标三维转动检测方法,该方法使用自适应Chirplet信号分解的快速算法来估计散射点子回波的相位信息,并根据两个散射点相位之间的非线性度来判断目标是否存在三维转动,从而只选择那些仅具有二维转动的数据段进行成像。仿真实验结果表明了它的有效性。     

Calibration of High-Resolution X-Ray Tomography With Atomic Force Microscopy

For two-dimensional x-ray imaging of thin films, the technique of scanning transmission x-ray microscopy (STXM) has achieved images with feature sizes as small as 40 nm in recent years. However, calibration of three-dimensional tomographic images that are produced with STXM data at this scale has not yet been described in the scientific literature, and the calibration procedure has novel problems that have not been encountered by x-ray tomography carried out at a larger scale. In x-ray microtomography, for example, one always has the option of using optical imaging on a section of the object to verify the x-ray projection measurements; with STXM, on the other hand, the sample features are too small to be resolved by light at optical wavelengths. This fact implies that one must rely on procedures with higher resolution, such as atomic force microscopy (AFM), for the calibration. Such procedures, however, generally depend on a highly destructive sectioning of the sample, and are difficult to interpret because they give surface information rather than depth information. In this article, a procedure for calibration is described that overcomes these limitations and achieves a calibration of an STXM tomography image with an AFM image and a scanning electron microscopy image of the same object.A Ge star-shaped pattern was imaged at a synchrotron with a scanning transmission x-ray microscope. Nineteen high-resolution projection images of 200 × 200 pixels were tomographically reconstructed into a three-dimensional image. Features in two-dimensional images as small as 40 nm and features as small as 80 nm in the three-dimensional reconstruction were resolved. Transverse length scales based on atomic force microscopy, scanning electron microscopy, x-ray transmission and tomographic reconstruction agreed to within 10 nm. Toward the center of the sample, the pattern thickness calculated from projection images was (51 ± 15) nm vs (80 ± 52) nm for tomographic reconstruction, where the uncertainties are evaluated at the level of two standard deviations.     

Long-wave Marangoni Convection in Two-layer Films Under the Action of Gravity Modulation

The influence of the gravity on the long-wave Marangoni patterns in two-layer films is considered. The numerical analysis is carried out in the lubrication approximation. Periodic boundary conditions have been applied on the boundaries of the computational region. The development of instabilities is investigated by means of nonlinear simulations. The cases of a constant gravity and a time-periodic gravity modulation are considered. In the case of a constant gravity, non-stationary three-dimensional and two-dimensional structures have been found. It is shown that the periodic modulations of the gravity force lead to the development of new three-dimensional spatially-periodic patterns. Outside the region of parameters, corresponding to three-dimensional structures, dynamical regime of two-dimensional traveling waves have been observed.     

Three-dimensional reconstruction of the statistics of heterogeneous objects from a collection of one projection image of each object

An estimation problem for statistical reconstruction of heterogeneous three-dimensional objects from two-dimensional tomographic data (single-particle cryoelectron microscope images) is posed as the problem of estimating class probabilities, means, and covariances for a Gaussian mixture where both the mean and covariance are stochastically structured. Both discrete (i.e., classes) and continuous heterogeneity is included. A maximum likelihood solution computed by a generalized expectation-maximization algorithm is presented and demonstrated on experimental images of Flock House Virus.     

Evaluation of the characteristics of cracks according to the images of the surfaces of materials

We consider the problem of three-dimensional reconstruction of the surface according to its two-dimensional images. The results of this reconstruction are applied to the analysis of the images of materials with cracks. We describe each step of the algorithm used for the analysis of the characteristics of cracks in the material according to their images. It is shown that the data on the profile and volume of the cracks can be obtained with the help of the proposed methods. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 4, pp. 107–111, July–August, 2007.     

Recognition and classification of three-dimensional phase objects by digital Fresnel holography

We demonstrate the validity of wavelet-based processing for recognition and classification of three-dimensional phase objects. One Fresnel digital hologram of each of the three-dimensional (3-D) phase objects to be classified is recorded. The electronic holograms are processed digitally to permit 3-D object information to be retrieved as two-dimensional digital complex images. We use a Mexican-hat wavelet- matched filter (WMF) to enhance the correlation peak and discriminate between the objects. The WMF performs a wavelet transform (WT) to enhance the significant features of the images and the correlation of the WT coefficients thus obtained. We compare the feasibility of a WMF-based object classifier with the matched-filter-based classifier to classify our four 3-D phase objects in a 3-D scene into true or false classes with minimal error.     

Three- and Four-dimensional Filter Operations by Coherent Optics

Three- and four-dimensional signals can be replaced by two-dimensional sequences of sectional images if sampling in one or two dimensions is practicable. The convolution of such sequences yields, under certain conditions, the sequence representation of the three- or four-dimensional convolution result. Thus higher-dimensional filter operations can be performed by means of two-dimensional filter methods, e.g. coherent optics, whose parallel computing power matches the usually high space-bandwidth products (SBP) of such sequences. The possible throughput of coherent-optical setups is estimated. Experimental results for three-dimensional filter operations are shown.