CCD光谱层析技术重建氩等离子束射流三维温度场

根据谱线相对强度法,提出了利用正交面阵CCD光谱层析技术,实时重建氩等离子束射流三维温度场的方法.通过CCD获得的待测场图像与没有射流射出时在待测场处放置的坐标纸图像进行比对,测最了实际待测场的大小;利用步进电机带动光纤探针对待测场进行扫描,通过光谱仪获得了待测场的光强分布.根据谱线相对强度法中谱线选取的原则,选择了696.5和763.5 nm两条谱线作为研究对象.为防止CCD接收光强过饱和及待测场边缘光谱信息的损失,根据待测场的大小和光强分布设计了梯度衰减片,再通过窄带滤波片获得了待测场的光谱信息.结果表明与光纤光谱扫描法获得的结果吻合较好,不确定度为3.3%.系统满足了实时重建三维温度场的要求,为等离子束射流后续的密度场、压力场和速度场的实时诊断提供了坚实基础.     

3D打印贝壳仿生复合材料的拉伸力学行为

采用硬质和软质双组分材料,通过调控两种基体材料的装配夹角,采用光固化3D打印技术制备了不同装配方式的仿贝壳珍珠层复合材料,开展了准静态拉伸实验,结合扫描电镜观察,分析了其拉伸力学性能、断裂及能量耗散机理。研究结果表明,保持胞元边长不变,随着面内装配角度增加,仿贝壳珍珠层复合材料的强度呈线性增加趋势,断裂应变呈线性减小的趋势;随着面外装配角度增大,断裂应变呈线性减小趋势,而强度在面外装配角小于45°时呈增强趋势,超过45°时趋于稳定;面外装配角度为45°时,材料的强度达到最大值。试样在断裂前主要通过硬质材料的拔出、软/硬相界面处微裂纹的生成及微裂纹在扩展过程中的合并和偏转等方式耗散能量。     

计算机3D立体图的设计和制造

介绍了计算机３Ｄ立体图的分类和基本原理，给出了计算机３Ｄ立体图的设计制造过程，讨论了计算机３Ｄ立体图的应用前景和发展方向     

非接触三维测量全场结构关系模型分析及系统开发

研究开发了一种基于光栅投影和主动式三角法的高精度三维测量系统。分析了系统的全场结构关系模型及镜头失真对系统的影响,给出了空间三维坐标的详细算法。试验结果表明,系统的测量误差小于0.04mm,测量精度约为0.03mm。多视角测量的拼合结果表明,系统具有良好的360°测量精度,测量精细表面纹理效果好。该系统在反求工程及质量控制等领域具有良好的工业应用前景。     

Design and characterization of a 3D encapsulation with silicon vias for radio frequency micro-electromechanical system resonator

In this paper, we present a three-dimensional(3D) vacuum packaging technique at a wafer level for a radio frequency micro-electromechanical system(RF MEMS) resonator, in which low-loss silicon vias is used to transmit RF signals.Au–Sn solder bonding is adopted to provide a vacuum encapsulation as well as electrical conductions. A RF model of the encapsulation cap is established to evaluate the parasitic effect of the packaging, which provides an effective design solution of 3D RF MEMS encapsulation. With the proposed packaging structure, the signal-to-background ratio(SBR) of 24 dB is achieved, as well as the quality factor(Q-factor) of the resonator increases from 8000 to 10400 after packaging.The packaged resonator has a linear frequency–temperature( f –T) characteristic in a temperature range between 0℃ and 100℃. And the package shows favorable long-term stability of the Q-factor over 200 days, which indicates that the package has excellent hermeticity. Furthermore, the average shear strength is measured to be 43.58 MPa among 10 samples.     

影响条纹图形拼接法测量精度的主要误差因素

通过对计算机模拟和实验结果的分析表明，影响条纹图形拼接法测量精度的主要因素是子孔径面形测量精度，重叠区的大小，面形拟合阶次和拼接模式等。     

Performance analysis of a 3D full-field sensor based on fringe projection

This article analyzes the measurement performance of a 3D full-field imaging system based on the projection of grating and active triangulation. We first explore the exact mathematical relationship that exists between the height of an object's surface, the phase and the parameters of the experimental setup, which relationship can be used to obtain the precise shape of an object. We then investigate in detail the influence on the measurement results of the introduction of an inaccuracy into the determination of the system's parameters. Finally, using simulated data, we conduct experiments to evaluate the measurement performance.     

3D shape reconstruction of teeth by shadow speckle correlation method

This paper presents a new method for 3D shape reconstruction in computer-aided dental prosthetics. A specklegram is projected onto the tooth to be measured. This shadow speckle image is recorded and then processed by a digital image correlation method, which enables the computation of 2D shapes based on the similar principle of shadow moiré method. By repeating the procedure for all the sides, i.e., one crown and several side surfaces, local 2D shapes can be measured precisely. Afterwards, these local 2D profiles are merged to form a 3D model, during which certain constraints such as the widths along perpendicular directions are introduced to guide the process. As the height information within an entire image field is recorded instantly, it has the potential to be employed in an intra-oral environment, which would make the patient feel more comfortable during the restoration process. In vitro experiments were carried out on gypsum teeth models and the results proved the effectiveness of the proposed method.     

Reconstruction of 3D ultrasound images based on Cyclic Regularized Savitzky-Golay filters

This paper presents a new three-dimensional (3D) ultrasound reconstruction algorithm for generation of 3D images from a series of two-dimensional (2D) B-scans acquired in the mechanical linear scanning framework. Unlike most existing 3D ultrasound reconstruction algorithms, which have been developed and evaluated in the freehand scanning framework, the new algorithm has been designed to capitalize the regularity pattern of the mechanical linear scanning, where all the B-scan slices are precisely parallel and evenly spaced. The new reconstruction algorithm, referred to as the Cyclic Regularized Savitzky-Golay (CRSG) filter, is a new variant of the Savitzky-Golay (SG) smoothing filter. The CRSG filter has been improved upon the original SG filter in two respects: First, the cyclic indicator function has been incorporated into the least square cost function to enable the CRSG filter to approximate nonuniformly spaced data of the unobserved image intensities contained in unfilled voxels and reduce speckle noise of the observed image intensities contained in filled voxels. Second, the regularization function has been augmented to the least squares cost function as a mechanism to balance between the degree of speckle reduction and the degree of detail preservation. The CRSG filter has been evaluated and compared with the Voxel Nearest-Neighbor (VNN) interpolation post-processed by the Adaptive Speckle Reduction (ASR) filter, the VNN interpolation post-processed by the Adaptive Weighted Median (AWM) filter, the Distance-Weighted (DW) interpolation, and the Adaptive Distance-Weighted (ADW) interpolation, on reconstructing a synthetic 3D spherical image and a clinical 3D carotid artery bifurcation in the mechanical linear scanning framework. This preliminary evaluation indicates that the CRSG filter is more effective in both speckle reduction and geometric reconstruction of 3D ultrasound images than the other methods.     

The 3D solitons and vortices in 3D discrete monatomic lattices with cubic and quartic nonlinearity

By virtue of the method of multiple-scale and the quasi-discreteness approach, we have discussed the nonlinear vibration equation of a 3D discrete monatomic lattice with its nearest-neighbours interaction. The 3D simple cubic lattices have the same localized modes as a 1D discrete monatomic chain with cubic and quartic nonlinearity. The nonlinear vibration in the 3D simple cubic lattice has 3D distorted solitons and 3D envelop solitons in the direction of $k_{x}=k_{y}=k_{z}=k$ and $k=\pm \pi$/6$a_{0}$ in the Brillouin zone, as well as has 3D vortices in the direction of $k_{x}=k_{y}=k_{z}=k$ and $k=\pm \pi$/$a_{0}$ in the Brillouin zone.     

三维超声驻波场的数字全息测量与重建研究

利用数字全息干涉术研究了超声驻波场的三维分布特征,由所记录的不同角度的超声驻波场的数字全息图,经数值再现,得到了超声驻波场的强度和相位差分布图,进而由迭代重建算法重建出超声驻波场的三维分布曲线。结果表明,数字全息干涉术与迭代重建算法相结合是测量与重建三维超声驻波场的一种方便有效方法。     

纯永磁波荡器磁场计算的三维修正

 用归一化量对纯永磁波荡器的磁场进行三维计算分析,讨论了一般情况下有限磁极宽度的三维修正以及对好场区的影响,给出了磁极宽度对通常二维近似的修正曲线以及在不同磁极宽度下相对场强的横向变化曲线。     

基于物体特征有效提取和离散点三维重建的3D扫描系统原型研究

针对3D扫描技术的近期发展情况,以及市场关于被摄物体特征有效提取的迫切需求,通过系统的对照相机和投影仪测量的方法与计算,利用离散点三维重建算法、标准化算法详细分析了,作为3D扫描原型系统的关键技术,并深入的对三维坐标重复演算的过程,进行了实践研究与计算,论证了基于投影光编码技术的3D扫描仪原型系统,在物体特征有效提取和离散点三维重建中完全可以高效应用;同时,使用焦距标准化运算、逆向倾角变形运算、逆向扭曲变形运算三种方法,综合论述了物体特征有效提取和离散点三维重建过程的相关内容,测试了原型系统对真实文物的扫描情况,展开了该原型系统可应用于不同材料,不同种类物体的扫描,并能有效的进行数字化物体特征识别的研究结论。     

Whole 3D shape reconstruction of vascular segments under pressure via fringe projection techniques

Understanding and modelling vascular wall mechanics is a primary issue in the study of circulatory diseases. Although theoretical and numerical studies on arteries compliance are continuously increasing, relatively little work has been documented on the use of non-invasive imaging techniques for monitoring 3D vascular wall deformations. Usually, 2D video dimension analyzer (VDA) systems recover diameter and length variations during inflation/extension tests by tracking position changes of few markers put on the blood vessel surface. Then, strain determination relies on the assumption of axisymmetric deformations. However, more rigorous evaluations of whole wall deformation map are required for properly modelling the highly anisotropic and inhomogeneous vascular tissue mechanical response.

This paper describes the development and application of a fringe projection (FP)-based procedure for the 360° 3D shape reconstruction of tubular samples subjected to internal pressure. A specially designed fixture for mounting and inflating the tubular segment allows specimen rotation about its axis. Movement is controlled by a high-precision rotational stage. This yields accurate positioning of the surface to be investigated with respect to the viewing direction. Data point clouds obtained from multiple recorded images are then processed and merged in a CAD environment, thus providing the whole shape of the sample with very high spatial resolution.

The entire procedure has successfully been applied to latex specimens and porcine vascular segments. Further improvements will make the present procedure suitable for in vitro tests under more closely reproduced physiological conditions.     

三维点云物体频谱获取方法

为了简化三维物体计算全息数据和加快计算时间,提出了一种三维点云物体频谱获取方法.在分析频谱获取方法模型的基础上,由不同视角的投影图像(视图)与对应的平面波因子相乘积分的方法得到了三维点云物体频谱;介绍了视图获取算法,使用Matlab并行计算得到了一个三维‘鸟’的视图序列;根据实际物体频谱分布情况,采用高阶高斯概率分布减少视图获取数量;通过视图序列得到三维物体的频谱,采用傅里叶逆变换得到物空间内一个平面的复振幅分布,将其衍射一段距离,编码为菲涅尔全息,并进行了模拟再现和实验验证.模拟再现和实验结果表明:只需要原总视图的17.75%可以获得高质量的再现效果,验证了频谱获取方法的可行性及视图获取简化模型的正确性.所获取的三维物体频谱可以通过一定方式编码成多种全息进行三维显示,拓宽了该频谱获取方法的应用范围.     

BGK方法在三维非结构网格上的初步应用

将BGK计算方法从二维拓展到三维并且应用于三维非结构网格,具有重要的理论价值和实用价值.采用旋转局部座标的方法,发展了一种针对三维非结构网格的BGK计算方法.在计算过程中,将最小二乘法应用于三维非结构网格的导数计算.对三维激波管和三维欠膨胀垂直冲击射流等两个算例进行了细致分析.这两个算例的计算结果表明,该方法在三维非结构网格上的初步应用是成功的 关键词： 气动BGK方法 三维 非结构网格     

采用二元光学元件的三维轮廓测量方法

提出了采用二元光学元件(BOE)进行三维形貌测量的新方法。设计二元光学元件产生空间二维点阵结构光,经物面调制后的点阵信息被相机一次获取,利用三角测量法得到物体的三维空间坐标。按该方法处理得到的结果与实际物体的形貌特征吻合。结果表明,按该测量系统具有便捷式功能,适用于三维照相等应用领域。     

基于3维实体重建的直线加速器加速管热稳定性的优化设计

 行波电子直线加速器运行时加速管腔体因铜损会产生不均匀的热变形和腔频率偏移。因无法获知腔频率的准确偏移值,设计加速管冷却系统的一种经验设计方法是控制管体温度离散度在3 ℃之内。提出并实现了一种以直接控制加速管腔体频率离散度为设计目标的方法。采用插值蒙皮曲面造型理论,依据温度场和热变形的有限元仿真结果,高精度重建出变形后的腔体3维实体模型。将其导入到电磁场分析软件微波工作室,解算出不均匀温度分布造成的热变形引起的各腔频率偏移,实现了热-结构-电磁场的耦合分析。以加速管腔体频率离散度最小为设计目标,获得冷却系统优化参数。相对于经验设计方法,可大大减小冷却水流量和水压差,节约运行成本。     

The effect of out-of-plane motion on 2D and 3D digital image correlation measurements

The effect of out-of-plane motion (including out-of-plane translation and rotation) on two-dimensional (2D) and three-dimensional (3D) digital image correlation measurements is demonstrated using basic theoretical pinhole image equations and experimentally through synchronized, multi-system measurements. Full-field results obtained during rigid body, out-of-plane motion using a single-camera vision system with (a-1) a standard f55mm Nikon lens and (a-2) a single Schneider–Kreuznach Xenoplan telecentric lens are compared with data obtained using a two-camera stereovision system with standard f55mm Nikon lenses.Results confirm that the theoretical equations are in excellent agreement with experimental measurements. Specifically, results show that (a) a single-camera, 2D imaging system is sensitive to out-of-plane motion, with in-plane strain errors (a-1) due to out-of-plane translation being proportional to ΔZ/Z, where Z is the distance from the object to the pin hole and ΔZ the out-of-plane translation displacement, and (a-2) due to out-of-plane rotation are shown to be a function of both rotation angle and the image distance Z; (b) the telecentric lens has an effective object distance, Z_eff, that is 50× larger than the 55 mm standard lens, with a corresponding reduction in strain errors from 1250 μs/mm of out-of-plane motion to 25 μs/mm; and (c) a stereovision system measures all components of displacement without introducing measurable, full-field, strain errors, even though an object may undergo appreciable out-of-plane translation and rotation.