Comments on the shortcomings of predicting the precision of Cavalieri volume estimates based upon assumed measurement functions

It is well known that the estimation of an object's volume by means of serial cross-sections, the so-called Cavalieri method, yields an unbiased estimate. But by itself it provides no means by which to estimate how precise this estimate is unless the shape of the volume is fully known beforehand. This knowledge can only be partially determined from the serial section information that is collected. Methods have been developed that claim to surmount this difficulty by using the serial section data to create a mathematical model of the volume's shape properties. The model then is used to estimate (predict) the precision of the volume estimate (its CE) from the single set of data available. Unfortunately, the theory underlying the model is flawed and so the model itself amounts to no more than an unsubstantiated guess about the shape of the volume. Therefore, the precision of the volume estimates that one obtains from the method is only as good as the model and this cannot be ascertained from the single set of acquired data. In this letter I explain the inadequacies of the modelling method. I suggest that it be used only with caution, if at all. Instead I suggest two alternative ways to predict the CE, one that is based upon a rule-of-thumb approach to the object's shape, and another that is based upon spectral analysis of the measurement function and that is easy to implement with available computer software.     

Precision of the fractionator from Cavalieri designs

A popular procedure to predict the variance of the fractionator consists in splitting the initial collection of fragments into two subsets, in order to use the corresponding particle counts (or any other pertinent measure), in the calculation. The current formula does not account for local or ‘nugget’ errors inherent in the estimation of fragment contents, however. Moreover, it does not account for the fact that the contribution of the variability between fragments or slices should rapidly decrease as the sampling fraction increases. For these reasons, an update to the formula is overdue. It should be stressed, however, that the formula applies to Cavalieri slices designs – its application for arbitrary partition designs is therefore not warranted.     

基于INGA的电容层析成像图像重建算法的研究

电容层析成像图像重建是一个具有典型的病态问题,在分析遗传算法基础上,针对小生境遗传算法易于早熟、收敛速度慢以及局部寻优能力较差等缺点,提出了一种引入梯度算子的改进小生境遗传算法(INGA)用于ECT图像重建.仿真和实验结果表明,对于简单流型该算法与LBP、Landweber算法相比满足收敛速度快且重建图像误差小,并能以较高的精度重构出两相流体的截面成像,为ECT图像重建算法的研究提供了一个新的思路.     

Response of the excitation condition to electromagnetic tomography

Electromagnetic tomography (EMT) has potential practical value in the fields of industrial and biomedical detection. The sensitivity, stability and accuracy of the sensor system are significant in the detection of EMT. In this paper, the EMT excitation condition is analyzed through the COMSOL Multiphysics finite element analysis software. The effects on a sensor array of 8 equally spaced inductive coils are discussed in terms of two effects: the direct effect on the received signals due to the change of the excitation condition and the effect of variations on the sensitivity, which is calculated through the received signals. The relationship between the exciting frequency and the received signal is discussed both in the simulation and the experiment; a multi-coil excitation strategy is proposed, and the comparisons are presented. The results clearly show that the higher exciting frequency led to the higher received signal. The selection of the excitation strategy should be considered based on the object field distribution, and it is necessary to increase the coil number for the multi-coil excitation strategy to obtain a better performance. This paper estimates the sensing field status according to the simulation results and provides a theoretical foundation for image reconstruction optimization.     

数据挖掘聚类算法研究

聚类是数据挖掘中用来发现数据分布和隐含模式的一项重要技术.全面总结了大部分常用聚类算法的主要特点,对一些经典聚类算法进行比较,并提出了相关结论,最后对几种新型的聚类算法进行基本概括.     

基于遗传算法的机械零部件可靠性优化设计

针对机械可靠性优化设计，提出一种自适应最优化保存的模拟退火遗传算法，建立了基于遗传算法的机械零部件可靠性优化设计的数学模型，并通过算例与传统优化方法进行了比较，说明了遗传算法在机械可靠性优化设计方面，具有广泛的应用前景。     

基于WSN的两种气体源定位算法研究

本文基于气体污染源浓度衰减模型，首次采用极大似然预估算法、直接三边测距算法对气体污染源定位进行了对比研究。仿真实验对比了两种算法在不同数量传感器节点以及背景噪声情况下对预估定位误差的影响。仿真表明：在环境背景噪声较大的情况下，采用极大似然算法比采用直接三边测距算法有着更强的鲁棒性；而直接三边测距算法简单，在背景噪声较小时，定位效果同样有效。     

基于HE-SVDD的航空发动机工作状态识别*

针对人工识别航空发动机工作状态的复杂性和耗时性,提出一种基于超椭球分类面支持向量数据描述(HESVDD)的快速识别方法。首先构建了一个根据训练样本分布特征可调的HE-SVDD分类器,使之具有从大规模飞行数据中快速识别发动机工作状态的能力;然后研究了航空发动机状态识别的参数选取和样本生成问题;最后采用HE-SVDD对两个飞行架次的发动机工作状态进行了识别。结果表明,该方法能快速准确地识别出发动机的工作状态,可应用于发动机状态的在线或离线监控。     

基于区块链的服务质量综合评估框架与算法

企业为了保证自己业务的灵活性与高效性,经常需要购买外部服务来执行业务流程中的活动,然而现有服务评价体系很难保证评价的真实性与准确性.区块链技术凭借其分布式存储、共识机制以及智能合约等优势可以替代第三方来对服务进行评价.有研究者提出了一个基于区块链的框架来解决该问题,然而,该框架只存储用户反馈的服务质量(QoS)值,没有...     

基于代价参考的粒子滤波算法研究

针对非线性模型滤波问题,分别研究了代价参考粒子滤波器和标准粒子滤波器.分析了两者在算法结构和算法思路中的相同点和不同点,并利用Matlab工具分析和比较了在同一单变量非静态增长模型下两者的滤波效果.研究结果表明基于数理统计的滤波方法在解决非线性问题中优于基于概率统计的滤波方法.     

基于粒子滤波的彩色图像跟踪算法的研究

摘 要;在以往的视频跟踪中,目标检测和跟踪常常需要两个计算法则,过程比较复杂,实现耗时较多。为了实现序列彩色图像的实时检测与跟踪,本文以目标有无信息和目标位置信息为变量建立联合状态向量,利用粒子滤波方法实现目标检测及跟踪。此外为了减少计算量并且充分考虑到跟踪区域各像素的权重,建立基于颜色信息的特征直方图作为观测向量,用于后验估计。实验证明本文提出的方法能够在14.37ms内检测并跟踪目标,并且对目标的旋转变化和尺度变化具有一定的鲁棒性     

基于多维矢量矩阵的离散余弦变换快速算法

为了提高彩色视频流压缩变换的速度,缩短变换时间,将基于多维矢量离散余弦变换(DCT)正交矩阵的视频流压缩算法同现有的快速DCT算法相结合,提出了基于多维矢量矩阵DCT的快速算法.首先,对一种实用性较强的一维快速DCT算法进行部分校正与补充,并将两种极具代表性的二维快速DCT算法,即行列分解法和线性组合法拓展到了多维层面.然后,结合多维矢量矩阵理论,推导出了两种DCT快速算法及其蝶形示意图,并分析了算法的乘法运算次数.最后,将这两种基于多维矢量矩阵的DCT快速算法应用在标准视频库中测试视频的压缩编码中,同时做了对比实验.实验结果表明:两种算法在DCT时所需的时间均小于0.25 s,满足视频实时性的要求.该算法在保证重建视频质量的同时降低了运算时间,并将DCT快速算法从低维扩展到了多维,可以处理更多维数的视频.     

基于Rough集的遥感影像增强方法研究

通过对Rough集理论特点和遥感影像信息的不确定特性分析,基于对Rough集理论的不可分辨关系、近似集合和分类概念的分析,研究实现了一种保护图像边缘的遥感图像滤波和增强的算法,并通过实验证明了该算法的效果和有效性.     

基于线性插值的图像分块分割算法

图像分割是图像处理中的一个重要问题,全局阈值法和局部阈值法是图像分割中广泛采用的两类方法。全局阈值法效率高,但是对局部信息不敏感;局部阈值法对局部信息保存较好,但是计算效率不高。针对这一问题,该文提出一种基于分块的图像分割算法。首先将图像分块,然后,每块内采用最大类间方差法计算阈值,最后,块与块之间采用线性插值的方式平滑分割图像。实验表明,该文提出的算法和全局阈值法相比能较好地保存局部信息,和局部阈值法相比有更高的运行效率,在实际中推荐使用。     

基于遗传算法的多PID控制器参数整定

为了解决多入多出系统和采用状态控制的单入单出系统的多PID控制器参数整定困难的问题，本文提出了基于遗传算法的多PID控制器参数整定方法，该方法只需给出大概的PID参数范围即可得到控制性能最优的PID参数，本文结合实例证实了该方法的有效性。     

基于灰色理论的电厂设备状态趋势预测研究

本文提出了基于灰色预测理论的机械设备状态监测方法,重点介绍了灰色预测理论的内容及其应用;其根据设备自身历史数据建立动态微分方程,并预测自身的发展,具有数据量小、计算简单、预测准确的特点.通过实例证明,该方法是有效的.     

基于混联机床立卧转换加T的机床运动控制算法研究

介绍了一种新型立卧转换式三杆混联机床-3-TPS混联机床,对该机床的结构进行了分析.文中给出了该机床在实现立卧转换加工时的坐标变换过程及变换方程,给出了实现立卧转换加工时的后置处理算法及数学模型,并分析了该机床在两种不同加工方式下所能够实现的三轴联动加工、四轴联动加工.文中所给的算法简单、直观、实用,方程为显示.     

Unbiased estimation of human body composition by the Cavalieri method using magnetic resonance imaging

The classical methods for estimating the volume of human body compartments in vivo (e.g. skin-fold thickness for fat, radioisotope counting for different compartments, etc.) are generally indirect and rely on essentially empirical relationships — hence they are biased to unknown degrees. The advent of modern non-invasive scanning techniques, such as X-ray computed tomography (CT) and magnetic resonance imaging (MRI) is now widening the scope of volume quantification, especially in combination with stereological methods. Apart from its superior soft tissue contrast, MRI enjoys the distinct advantage of not using ionizing radiations. By a proper landmarking and control of the scanner couch, an adult male volunteer was scanned exhaustively into parallel systematic MR ‘sections’. Four compartments were defined, namely bone, muscle, organs and fat (which included the skin), and their corresponding volumes were easily and efficiently estimated by the Cavalieri method: the total section area of a compartment times the section interval estimates the volume of the compartment without bias. Formulae and nomograms are given to predict the errors and to optimize the design. To estimate an individual's muscle volume with a 5% coefficient of error, 10 sections and less than 10min point counting (to estimate the relevant section areas) are required. Bone and fat require about twice as much work. To estimate the mean muscle volume of a population with the same error contribution, from a random sample of six subjects, the workload per subject can be divided by √6, namely 4 min per subject. For a given number of sections planimetry would be as accurate but far more time consuming than point counting.     

基于CBR和遗传算法的模具智能CAD系统

在分析和总结当前智能设计方法的基础上，采用CBR与遗传算法这两种智能技术，用C Builder和SQL Server开发了一个模具智能CAD系统，集成人机智能进行模具结构方案优化设计。     

基于 V-ResNet 的电阻抗层析成像方法

电阻抗层析成像技术(EIT)因其非侵入和可视化等特性为人体肺部空间特性的监测提供了一种有效的方法。但是EIT的逆问题具有严重的非线性、病态性和欠定性,使得图像重建结果含有严重的伪影。针对上述问题,提出了一种由预映射、特征提取、深度重建以及残差去噪四个模块构成的V-ResNet的深度网络成像算法,实现对场域空间位置和电导率参数分布的重建。该算法有效地增加了前馈信息的多重传递并解决了深度网络的梯度消失问题,同时残差去噪模块有效地平滑了图像边界。采用相对误差(RE)和结构相似度(SSIM)来衡量成像质量,实验得出RE的平均值为0.14,SSIM平均值为0.96。仿真与实验结果表明,基于V-ResNet的成像算法与传统的成像算法相比,图像重建结果边界清晰,空间分辨率高。