双随机相位加密全息标识防伪技术研究

在输入面和频谱面上分别放置随机相位加密模板对图像数据进行加密是一种高密级的有效数据加密技术。在研究双随机相位数据加密技术的基础上,结合数字全息技术和印刷技术的特点,提出了一种新的双随机相位加密同轴相位全息标识(简称同轴相位全息标识)印刷防伪方法。理论分析证明了同轴相位全息标识方法能有效地恢复原始图像数据,仿真实验证明了该方法具有强抗随机干扰能力和抗位压缩性能。通过打印和扫描实验验证了同轴相位全息标识可以通过普通的数字印刷技术印制在证件等印刷品中作为防伪标识,印刷品中的同轴相位全息标识可以通过扫描输入计算机,变换生成数字图像,通过解密模板可从中恢复出原始图像数据。     

掌上分光光度计的开发及应用

基于Arduino技术,利用AS7341传感器、全彩 LED灯珠、聚光透镜、蓝牙芯片搭配3D打印技术设计出一款掌上分光光度计。介绍了掌上分光光度计的应用实例:对不同颜色的食用色素标准液进行测定,在测定范围内,吸光度与待测样品浓度具有良好的线性拟合关系;运用于菠菜中铁元素含量的测定,所得实验数据具有良好的一致性;运用于绘制待测溶液的吸光度时间曲线,取得了良好的实验效果。结果表明自制的掌上分光光度计完全可以代替传统的分光光度计,且进一步拓展了分光光度计的功能。     

快速三维MR血管壁成像评估急性脑梗死及颈动脉粥样硬化的研究

本研究探讨在脑梗死及颈动脉粥样硬化斑块评估中,快速三维MR血管壁成像技术的应用价值。选取颈动脉粥样硬化斑块患者78例,共计斑块112个,其中发生脑梗死患者36例,未发生脑梗死患者42例。与病理结果比较,快速三维MR血管壁成像评估颈动脉斑块性质一致性Kappa值为0.790(P<0.05);不稳定性斑块MR积分明显高于稳定性斑块(P<0.05);脑梗死患者甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)和平均MR积分明显高于无脑梗死患者(P<0.05),而高密度脂蛋白胆固醇(HDL-C)明显低于无脑梗死患者(P<0.05);平均MR积分预测脑梗死的ROC曲线下面积为0.852(P<0.05)。因此,快速三维MR血管壁成像技术能有效评估颈动脉粥样硬化斑块性质,对预测脑梗死有一定应用价值。     

带槽平板的三维应力集中效应

本文提供了用电阻应变片方法测量一组不同厚度的带有对称圆槽的拉伸平板在应力集中部位的应力分布情况。实验结果表明,应力集中系数不仅与板平面的几何尺寸有关,而且与板的厚度有关。     

A Three-Dimensional Hybrid LES-Acoustic Analogy Method for Predicting Open-Cavity Noise

A three-dimensional (3D) hybrid LES-acoustic analogy method for computational aeroacoustics (CAA) is presented for the prediction of open-cavity noise. The method uses large-eddy simulation (LES) to compute the acoustic source while the Ffowcs Williams-Hawkings (FW-H) acoustic analogy is employed for the prediction of the far-field sound. As a comparison, a two-dimensional (2D) FW-H analogy is also included. The hybrid method has been assessed in an open-cavity flow at a Mach number of 0.85 and a Reynolds number of Re=1.36×10⁶, where some experimental data are available for comparison. The study has identified some important technical issues in the application of the FW-H acoustic analogy to cavity noise prediction and CAA in general, including the proper selection of the integration period and the modes of sound sources in the frequency domain. The different nature of 2D and 3D wave propagation is also highlighted, which calls for a matching acoustic solver for each problem. The developed hybrid method has shown promise to be a feasible, accurate and computationally affordable approach for CAA.     

On the stability of finite difference method for solving three-dimensional unsteady gasdynamic equations with artificial viscosity terms

The artificial viscosity method for three—dimensional unsteady gas flow is developed. The stability of finite difference scheme in this case is investigated. The necessary and sufficient conditions for the stability are obtained; these conditions formally agree with the two-dimensional result in Rusanov's paper.     

3D打印中的优化设计

3D打印技术的兴起在许多领域掀起了新的研究热点,《3D打印中的优化设计》应用课题针对几何处理领域中的许多相关问题做了系统性的研究,其中包括在3D打印中通过几何模型的结构优化以节省打印材料和打印时间的问题,三维几何模型保持特征的去噪和构建问题,以及三维几何模型的序贯重建和多余分支去除问题.相关问题中多涉及含有复杂约束的优化问题,以及压缩感知和稀疏优化问题.本文简要总结了上述问题的研究方法,并从几何优化的角度阐述了其中运筹学原理与方法的运用,表明了运筹学工具在相关领域研究中的重要性和有效性.     

计算机图形学中3D打印研究进展

3D打印是一种加法加工制造技术,它改变了传统的减式加工技术,实现了许多传统加工制造技术无法完成的任务.3D打印不仅为给计算机图形学提出了新的研究内容与挑战,也有力地推动了计算机图形学相关技术的发展.文中首先介绍3D打印技术相对于传统制造技术的优势同时,简要介绍3D打印技术的分类、原理与过程.在此基础上,对3D打印在计算机图形学的研究进展进行综述,包括:结构强度分析、大物体打印、打印方向优化、自平衡优化、支撑结构设计与优化、降低打印成本、提高打印效率和质量等.最后对3D打印在计算机图形学领域的发展情况进行展望.     

Long‐Term Stable Poly(acrylamide) Brush Modified Transparent Microwells for Cell Attachment Studies in 3D

The fabrication of 3D cell microenvironments exploiting versatile, long‐term stable passivating poly(acryl amide) brushes in a microwell format and the study of the behavior of fibroblast and pancreatic tumor cells in wells of systematically varied shape and size is reported. The microwells, which are obtained by combining micromolding in capillaries with microcontact printing of initiator monolayers for subsequent surface‐initiated polymerization of acrylamide and controlled functionalization with fibronectin (FN), expose cell adhesive areas inside the wells and protein and cell resistant brushes on the topside plateaus. NIH 3T3 fibroblast and pancreatic tumor (Patu 8988T) cells adhere and remain viable in the FN coated microwells for more than 1 week. Compared to 2D patterns, both cell lines are observed to attach to the bottom as well as the sidewalls of the microwells. The cytoskeleton alignment is found to be less pronounced compared to 2D patterned substrates, independent of microwell size and geometry.

     

THEORETICAL STUDY OF THREE-DIMENSIONAL NUMERICAL MANIFOLD METHOD

IntroductionNumerical manifold method is a new numerical method established on the basis of finitecover of manifold[1,2].By using continuous and non-continuous finite cover system,thenumerical manifold method includes the continuous and non-continuous as …