Global spatial sampling with isotropic virtual planes: estimators of length density and total length in thick, arbitrarily orientated sections

Existing design-based direct length estimators require random rotation around at least one axis of the tissue specimen prior to sectioning to ensure isotropy of test probes. In some tissue it is, however, difficult or even impossible to define the region of interest, unless the tissue is sectioned in a specific, nonrandom orientation. Spatial uniform sampling with isotropic virtual planes circumvents the use of physically isotropic or vertical sections. The structure that is contained in a thick physical section is investigated with software-randomized isotropic virtual planes in volume probes in systematically sampled microscope fields using computer-assisted stereological analysis. A fixed volume of 3D space in each uniformly sampled field is probed with systematic random, isotropic virtual planes by a line that moves across the computer screen showing live video images of the microscope field when the test volume is scanned with a focal plane. The intersections between the linear structure and the virtual probes are counted with columns of two dimensional disectors.
Global spatial sampling with sets of isotropic uniform random virtual planes provides a basis for length density estimates from a set of parallel physical sections of any orientation preferred by the investigator, i.e. the simplest sampling scheme in stereology. Additional virtues include optimal conditions for reducing the estimator variance, the possibility to estimate total length directly using a fractionator design and the potential to estimate efficiently the distribution of directions from a set of parallel physical sections with arbitrary orientation.
Other implementations of the basic idea, systematic uniform sampling using probes that have total 3D × 4π freedom inside the section, and therefore independent of the position and the orientation of the physical section, are briefly discussed.     

一种通用的三维有限元前置处理软件

提供了一个适用于三维有限元（包括二维问题）的前置处理软件。利用该软件,可生成三维八节点六面体单元,同时也可生成二维三角形和四边形单元。在数据自动检查中,提出了数组维数检查法。在三维网格可视化中,采用了逐步消隐法进行消隐。适当修改相应的形状函数,还可将其扩充生成其它的单元网格。该软件包括友好的用户界面,从而为用户提供了良好的操作环境。     

刀尖圆弧半径对圆锥零件加工精度的影响

主要分析了数控车削加工中刀具刀尖圆弧对圆锥类零件表面加工精度的影响,并提出了相应措施。对在数控车削加工中正确选择加工工艺、选择刀具参数和编制加工程序提供了依据,对在实际生产中提高零件加工精度提供了保证。     

任意分布参数平面连杆机构运动精度可靠性灵敏度设计

将可靠性设计理论与灵敏度分析方法相结合,讨论了任意分布参数平面连杆机构运动精度可靠性灵敏度设计问题。首先,结合机构精确度理论和可靠性理论,提出任意分布参数平面机构运动精度可靠性评估方法。然后,引入灵敏度设计理论,推导出任意分布参数平面机构运动精度可靠性灵敏度设计方法。最后,以平面四杆机构为例,详细阐述了设计参数的改变对平面连杆机构运动精度可靠性的影响,为平面连杆机构的运动精度可靠性设计和可靠性维护提供了理论依据。     

计算机辅助三维装配顺序规划

针对三维空间装配顺序推理问题,应用方向包围盒和分离轴定理,对装配几何约束分析方法进行了扩展完善,提出三维几何约束分析方法,并开发出相应的计算机辅助分析系统.通过实例表明,该方法可以在三维装配环境中自动推理出正确完备的装配优先关系和几何可行的装配顺序.     

Statistical analysis of labelling patterns of mammary carcinoma cell nuclei on histological sections

It is of central interest for tumour biology to explore the mechanisms of tumour cell proliferation. In this study, methods of spatial statistics were used to study the spatial distribution of proliferating cells within tumour tissue quantitatively and objectively. Mammary cancer tissue was studied as an example. It was attempted to clarify whether cell division occurs entirely at random (random labelling), i.e. the process of division occurs at random, independently from the state of the neighbouring nuclei, or whether the spatial distribution of proliferation is more complex, e.g. in the form of actively proliferating clusters alternating with relatively silent zones. In the case of random labelling, the reduced second moment functions K(r) of the labelled and the unlabelled nuclei would be identical. The same would hold for the pair correlation functions g(r) . The alternative hypothesis is that the second‐order properties of the processes of the labelled and the unlabelled nuclei are different. Twenty cases of invasive ductal mammary carcinomas were studied. The nuclei of proliferating cells were stained immunohistochemically with the monoclonal antibody MIB‐1, which detects specifically the proliferation‐associated nuclear antigen Ki 67. The planar coordinates of the tumor cell nucleus profiles from two rectangular visual fields per case were recorded. For each visual field, the following investigations were performed: estimation of the explorative summary characteristics K(r) and g(r) , fitting of the parameters of a stationary Strauss hard‐core model to the observed point patterns, estimation of two distance‐dependent Simpson indices and Monte Carlo tests of all individual patterns on the null hypothesis of random labelling. Significant differences between the mean K‐functions and the mean g‐functions of the labelled and the unlabelled nuclei were found. Moreover, the mean interaction parameter γ of the stationary Strauss hard‐core model was significantly higher for the labelled nuclei than for the unlabelled nuclei. The estimates of the two distance‐dependent Simpson indices showed a tendency of points with the same label towards a positive spatial correlation. In the Monte Carlo tests, the null hypothesis of random labelling was rejected for the majority of the visual fields. These four lines of investigation led to the concordant conclusion that the labelling of mammary carcinoma nuclei by MIB‐1 is not simply random. The data suggest that the second‐order properties of the point process of the labelled nuclei are significantly different from those of the unlabelled nuclei. In particular, the process of the labelled nuclei shows a higher degree of clustering (increased strength of interaction) than the process of the unlabelled points.     

基于FPGA的科氏质量流量计数字闭环系统设计

设计一种科氏质量流量计(Coriolis mass flowmeter,CMF)数字闭环系统,实现CMF稳定闭环工作条件.采用高速数字电路以及现代信号处理技术取代了传统的模拟正反馈系统来实现CMF闭环控制,使CMF测量管稳定维持在简谐振荡状态.利用模拟数字转换电路(A/D)将传感器输出的信号完整采样,借助现场可编程器件(FPGA,Field Programmable Gate Array)对信号进行分析与处理,根据信号特性进行相应的数字滤波、幅值解算,实现CMF闭环系统的幅值增益和相位的精确控制.实验结果表明:该数字闭环系统具有动态特性好、稳定性好等优点.     

一种基于STL几何模型的有限元三角形网格的自动生成方法

有限元网格划分是有限元分析的关键技术之一。本文利用CAD软件导出的STL几何模型,用自行开发的几何基本工具库对其进行几何信息提取,然后通过网格优化后,自动生成合格的三角形有限元网格,最后输出商业化有限元分析软件所需的前处理文件,为有限元分析提供了一个快速建模工具。     

驾驶员疲劳检测系统

通过人眼图像来检测驾驶员疲劳驾驶是目前的主流方向,面部及眼睛定位是其中关键的环节。针对驾驶员疲劳检测系统,结合图像处理和模式识别技术,提出一种基于人脸面部特征的人眼定位方法。经实验验证:该方法实时性好,可用于不同背景、光照、旋转和偏转角度,以及睁闭眼、戴眼镜等多种复杂条件下的眼睛定位。     

基于几何非线性大型带式输送机动力学仿真

用离散单元模型建立了基于胶带悬垂度的带式输送机非线性运动微分方程，推导了胶带等效刚度表达式，分析其非线性特性及对运动微分方程的影响。提出并建立了三台电动机和液力偶合器组成的驱动系统的数学模型，并据此设计动态仿真软件BDS。对一条带式输送机的动态性能进行了数值计算，其结果与国外软件计算结果进行比较，发现两者比较接近；对离散单元模型和连续介质模型等三个模型之间的张力波波动速度进行比较，结果十分吻合。最后分析了数值解和步长之间的关系。