带双参数四次Said-Ball曲线的扩展

为了使曲线易于实现光滑拼接,同时具有对应于相同控制顶点的不同形状,定义了具有凸包性、对称性、形状可调性等基本性质的新曲线.文中分析了基函数及曲线的性质和2个形状参数的几何意义,给出了2条Said-Ball型曲线的G0,G1,G2连续拼接条件.类似构造了局部形状可调的组合曲面.数值实例说明了所给方法的正确性和有效性.     

翻领成型器曲面几何形状研究

翻领成型器曲面为可展曲面,用微分几何方法描述了翻领成型器曲面的数学模型,推出了肩曲面为左右对称顶点不同的锥面时的圆形料管翻领成型器的交接曲线以及边界曲线的数学模型,并用Pro/E建立其三维曲面参数化数字模型,为翻领成型器其他截面形状、其他曲面形状的研究提供新的研究方法,为翻领成型器设计制造提供一定的理论依据。     

应用3D打印技术的运动文胸模杯个性化定制

为了使运动文胸模杯更加合体舒适,探索了基于逆向工程对运动文胸模杯建模,运用3D打印技术制作模杯的方法,首先通过三维人体扫描仪扫描人台获取点云数据,再运用Geomagic Studio软件优化点云数据,构造胸部NURBS曲面,根据模杯款式及体表曲率,运用UG软件截取模杯轮廓并对截取曲面进行厚度设计,3D打印运动文胸模杯模型过程中,首先对创建的模型切片,再运用光固化原理对模型进行3D打印,最终制得3D打印运动文胸模杯。同时分析了3D打印运动文胸模杯内表面与人台体表曲面之间存在的误差,其中曲面重构平均偏差为0.01mm,3D打印机精度为0.03mm。结果表明,结合逆向工程,运用3D打印技术,可以生产出合体的模杯,实现女性运动文胸模杯的个性化定制。     

青年男性肩点横截面曲线及其体型细分

为建立基于横截面曲线形态指标细分青年男性肩部体型的方法,选取了年龄在18~26周岁的213名在校青年男性,用三维人体扫描仪测量获得其肩部数据,借助IMAGEWARE 12.0与Mat Lab R2012b软件,利用冒泡排序算法实现了肩点的自动准确提取,且肩高相对误差控制在(0,0.011)之间;通过分析肩点横截面形态特征,提取了曲线曲率半径及矢额径比作为分类指标,对比曲率半径均值,确定了5个特征点角度为-50°、-35°、0°、50°与90°;应用K-Means聚类方法及方差分析,将肩部体型划分为4类,建立了依据特征点曲率半径与矢额径比细分肩部体型的方法,通过对比肩点截面曲线形态,进一步定性描述了4类肩部截面的曲线变化特征。     

水平动线犁体曲面解析

水平动线犁体曲面的工作性能,主要决定于水平动线的曲导线和动线与沟壁夹角θ的控制曲线。本文试图用解析法分析这两条曲线的几何性质对犁体曲面工作性能的影响,为两条曲线的选择提供一点理论分析的依据,同时建立犁体曲面及有关曲线的方程,供设计研究参考。     

带有2个形状参数的Ball曲线和曲面的扩展

构造了一组带有2个参数的四次多项式基函数,分析了这组基函数的性质.基于基函数定义了带有2个参数的多项式曲线.所定义的曲线不仅具有Ball曲线的特性,而且在控制顶点不变的情况下,随着参数的取值不同,可产生不同的逼近控制多边形的曲线.三次Ball曲线和相关文献中的曲线均是该文所定义的曲线的特例.运用张量积的方法,将曲线推广到曲面.应用实例表明,定义的曲线和曲面为曲线曲面设计提供了一种有效地方法.     

NURBS曲线反算不同参数取值法在纬平针织物仿真中的比较

为精准模拟和灵活控制纬平针组织三维仿真效果，通过分析纬平针织物的几何结构改进成圈线圈模型，建立纬平针组织三维结构模型，获得线圈中心线型值点数据和纱线的结构特征。使用Code::Blocks开发环境、C++语言和OpenGL函数库，基于非均匀有理B样条(NURBS)曲线原理，采用均匀参数化法、弦长参数化法和向心参数化法3种不同的节点矢量计算方法，反算控制点，之后拟合曲线模拟线圈中心线，比较使用不同节点矢量计算方法时线圈中心线结构的模拟效果，最终得到合理通用的仿真效果，并可根据型值点的选取情况以及各方法的特性选择合适的节点矢量计算方法。基于NURBS曲面原理可模拟纬平针组织纱线表面，并增加光照与材质效果，实现纬平针组织三维实体仿真。     

基于点模型的织物平整性能分析

为客观评价织物的平整度等级,给出一个基于点模型的织物平整性能分析流程。首先以三维高精度激光扫描仪上获取的织物离散数据点为研究对象,引入点模型的分析方法,筛选出反映织物表面起伏与否的特征点及其邻域点集,并在特征点邻域重构MLS曲面。然后,依据离散微分几何中的曲面理论,计算特征点在重构曲面上的高斯曲率和平均曲率,用曲率值的大小客观表达特征点处局部曲面的屈曲类型和弯曲程度。实验数据表明,织物点模型特征点处的曲率值揭示了点模型所代表的织物表面的褶皱起伏程度和尖锐程度,合理反映了织物的平整性能,可以为客观评价织物的平整度等级提供依据。     

楦体测量的新方法LAM—100型鞋楦三维面形自动测量系统

鞋楦是各种鞋类设计、制作与成型的基础模具。鞋楦源于脚型。但又不同于脚型,它适应人体生理结构要求,又是造型艺术的产物,脚型中各特征部位点都合理地分布在鞋楦这个不规则几何曲面体之中。我们有了鞋楦并开始进行帮、底样设计时,总要通过很多特定的部位点对楦体进行测量:长度、围度、宽度、高度和各种曲线     

基于机器视觉的曲面枕个性化定制方法

为有效扩展曲面枕个体适应性,满足大规模个性化定制需求,提出了基于机器视觉的曲面枕个性化定制方法。采用MINet显著性目标检测实现人像的自动分割与轮廓提取。在此基础上,对人像中的4个关键参考点、32个特征点进行提取,实现轮廓曲线的快速拟合与尺寸测量,以此方式构建头部样本数据集。通过数据聚类,将65个样本划分成12类,使用三维建模软件绘制出适合个体头、颈、肩部尺寸需求,满足仰、侧睡姿需求的曲面枕。实验得到12种曲面枕关键尺寸参数,包括侧卧区域高度、仰卧贴合区域曲线峰值和谷值。该方法进一步扩展了曲面枕形态适应性,为曲面枕定制提供分类方法参考。     

Peirce平纹机织物结构模型的计算精确度

为提出一种可估计任意机织物结构理论模型精度的思路,利用Peirce织物结构理论计算平纹织物纱线的几何形态。用Keyence数码显微镜非破坏性地实际测量织物的关键点位置,并利用保形3次B样条曲线模拟织物结构。采用离散Fréchet距离进行判别理论计算的纱线构形曲线和实测模拟的纱线构形曲线的相似性程度。计算两条曲线上对应波峰点、波谷点及相邻波峰点与波谷点的离散Fréchet距离差的绝对值,得到一个可认为曲线相似时的阈值 ,并与织物厚度相比较,提出纱线中心线形状相似度的概念。阈值 越小,则相似度越高,织物结构模型计算的精确度越高。通过MatLab应用程序,对两种平纹组织三维重建织物结构模型的相似性进行了分析并计算出样品1和样品2经、纬纱的相似度值分别为90%,86%,82%,94%。     

应用响应面优化法的文胸泡沫模杯模压厚度变化趋势研究

为减少文胸泡沫模杯模压技术中试错法的次数并建立定量分析方法,采用3因素3水平响应面优化（Box-Behnken）方法,设计出15种实验组合,通过回归方程和响应曲面探索模压工艺之间的关系并进行预测,同时评估交互作用。结果表明：对于模杯厚度,模压温度较模压时间有显著影响,从响应曲面看出模压温度不够即使再增加模压时间,模杯的厚度也不能保持稳定;对于不同杯深的模压头,在指定模压后模杯厚度的情况下,该方法可快速准确地确定出合适的模压温度、模压时间,效率是没有采用试验设计的3.6倍;通过试验验证了回归模型的有效性。     

Using geometric morphometrics for the genetics analysis of shape and size of lactation curves in Israeli first-parity Holstein cattle

Our objective was to combine the methods of geometric morphometrics and multivariate quantitative genetics to genetic evaluation of the size and shape of lactation curves of milk of 3,492 Israeli first-parity Holstein cattle. Lactation records were treated as morphological data, for which 2 different lactation shape functions were evaluated, one depicted by a line graph and the other by an orbital graph. The lactation curves from both shape functions were represented by 2-dimensional Cartesian landmark coordinates. The 2 sets of landmarks were then analyzed individually for each shape function with geometric morphometrics to separate variation into components of size and shape. The analysis yielded 2 size measures and 2 sets of shape variables, and they were the inputs to estimate variance components using the MTC REML individual animal model program. Variance components were also estimated for the 305-d lactation production as a reference. Shape variables showed negligible correlation with 305-d production, providing evidence of size and shape of lactation curve as separate characters. The size measure derived from the orbital-depicted lactation curve had equal heritability (0.39 ± 0.01; ± standard error) and complete genetic and environmental correlations with 305-d production, whereas the size measure derived from the line-depicted lactation curve showed low heritability (0.09 ± 0.01) and environmental correlation (0.02 ± 0.004) and relative high genetic correlation with 305-d production (0.48 ± 0.04). This may validate both the orbital graph to depict lactation records and the use of geometric morphometrics to split variation of lactation curve into size and shape components. The maximal heritability for shape of lactation curve was 0.55 for orbital- and 0.56 for line-depicted lactation curves. The respective patterns of variations were visualized as shape changes from the mean shape in the data set. Geometric morphometrics are well grounded within the theory of shape analysis and can be paired with conventional methods in the field to characterize the patterns of phenotypic and genetic variation of shape and size of lactation curve in dairy cattle.     

基于图像的人体颈肩部三维模型构建

为实现个性化服装在线设计和虚拟试衣,提出一种基于人体正侧面照片的尺寸测量及建模方法.首先结合202名青年女性的三维点云数据确定与人体颈肩部形态相关的8个特征截面层,以各截面层中心点为基准点每隔10°测量角度半径并分析其与截面厚度、宽度之间的关系,建立各截面层的曲线形态规则.然后基于人体正侧面照片进行图像分割以提取人体轮...     

Genetic parameters derived from using a biological model of lactation on records of commercial dairy cows

The object of this study was to investigate the genetics of lactation curve parameters derived from a biological model of lactation and the relationships among them. This biological model fitted 2 logistic curves to mimic the initial increase in milk secretory cell numbers in early lactation and the progression of apoptosis in late lactation. Records from 82,255 Holstein-Friesian heifers from commercial dairy herds in the United Kingdom, recorded from 1994 to 2003, were analyzed. The heritabilities of 2 lactation curve parameters, maximum secretion potential and relative cell death rate, were 0.27 and 0.08 respectively. Maximum secretion potential was highly genetically correlated with peak yield (0.99), and relative cell death rate was highly correlated with persistency of lactation (0.84). Heritability values for the traits analyzed showed a characteristic pattern. Total milk yield traits, maximum secretion potential, and peak yield had similar and moderate heritabilities (∼0.3). Traits associated with late lactation had lower heritability values (∼0.1), whereas day of peak yield and early lactation traits had little genetic variation. The permanent environmental variance of the various traits ranged from 0.08 to 0.26 of the phenotypic variance. Parameters from the 2 logistic curves were not highly correlated, suggesting that selection programs could be devised to exploit genetic variation in both aspects of lactation independently.     

Detection of different shapes of lactation curve for milk yield in dairy cattle by empirical mathematical models

The study of relationships between mathematical properties of functions used to model lactation curves is usually limited to the evaluation of the goodness of fit. Problems related to the existence of different lactation curve shapes are usually neglected or solved drastically by considering shapes markedly different from the standard as biologically atypical. A deeper investigation could yield useful indications for developing technical tools aimed at modifying the lactation curve in a desirable fashion. Relationships between mathematical properties and lactation curve shapes were analyzed by fitting several common functions (Wood incomplete gamma, Wilmink's exponential, Ali and Schaeffer's polynomial regression, and fifth-order Legendre polynomials) to 229,518 test-day records belonging to 27,837 lactations of Italian Simmental cows. Among the best fits (adjusted r(2) higher than 0.75), the 3-parameter models (Wood and Wilmink) were able to detect 2 main groups of curve shape: standard and atypical. Five-parameter models (Ali and Schaeffer function and the Legendre polynomials) were able to recognize a larger number of curve shapes. The higher flexibility of 5-parameter models was accompanied by increased sensitivity to local random variation as evidenced by the bias in estimated test-day yields at the beginning and end of lactation (border effect). Meaning of parameters, range of their values and of their (co) variances are clearly different among groups of curves. Our results suggest that analysis based on comparisons between parameter values and (co)variances should be done carefully. Comparisons among parameter values and (co)variances could yield more robust, reliable, and easy to interpret results if performed within groups based on curve shape.     

三维服装仿真中人体左右剖面的构造

针对三维服装仿真人体变形严重失真的情况,提出一种构造人体左右剖面的算法,将人体分成前后2 个部分分别进行变形。首先,对处理过的扫描人体进行特征识别,选取肩线和体侧线上的点,指定为特征点,标识并获取其三维坐标信息;其次,对这些特征点的坐标数据进行分析,构造空间二次曲面方程作为左右剖面模型;然后,利用逆向工程的曲面重构,将获取的指定特征点的三维坐标数据代入二次曲面方程,构成非齐次线性方程组,通过反求方程组的参数,获得二次曲面方程的系数;最后,将构成左右剖面的二次曲面方程应用到仿真人体上,形成包含特征点的冠状面。研究结果表明,该方法精准地构造了人体冠状面,将仿真人体分成前后2 个部分,并应用到服 装仿真人体的变形,效果良好。     

基于混合韦伯分布的碳纤维针刺毡结构表征

为研究碳纤维针刺毡的结构并对其参数化表征,基于混合（Weibull）分布分析了3种碳纤维针刺毡的结构参数。对碳纤维针刺毡的纤维长度分布进行了拟合,并分析了造成纤维长度分布规律不同的原因。采用纯弯梁模型模拟碳纤维在针刺毡中的弯曲状态,并对弯曲参数进行了统计分析。结果表明,采用混合Weibull分布模型分析碳纤维针刺毡的内部结构,可真实反映参数指标的分布规律。无论是纤维长度还是纤维的弯曲参数,拟合曲线都有较高的拟合度。此外,采用纯弯梁模型模拟弯曲的碳纤维,不仅可以模拟纤维在针刺毡中的弯曲形貌,还可以将测量结果用于碳纤维针刺毡的参数化建模。     

基于三维人体测量的文胸模杯定制系统研究

采用正向工程设计方法,利用三维人体测量技术获得定制文胸模杯的人体数据,通过对乳房细部特征尺寸数据和乳房形态分析,应用Pro／E软件构造出三堆女性乳房的基;位体系,利用样条曲线技术和模杯造型中的关键点（Pro／E软件中的技术）,生成三维的模杯内、外表面,从而设计出完全贴舍个体乳房的文胸模杯,实现文胸的量身定制。