二重组织织物计算机三维模拟的实现

探讨利用计算机进行二重组织织物三维模拟的实现方法.在建立二重组织织物计算机设计模型的基础上,依据其整数矩阵中各组织点的性质,基于织物结构的Peirce模型,利用虚拟现实建模语言(VRML),构建了二重组织织物结构的三维仿真模型.进一步结合Java语言编程,实现了表、里组织纱线颜色、光照等参数的网络交互设计.以经二重组织为例,进行了计算机三维模拟及网络交互设计.     

三维单纱的计算机模拟

为了缩短产品开发周期,实现纱线仿真效果,采用基于织物结构的Peirce模型和非圆形纱线的几何结构参数,探讨三维纱线结构中纱线截面的变化和纱线中心轴线的空间位置,以建立真实的纱线三维结构模型.借助于Visual C 与Open GL开发工具,把光照和纱线材质因素引入纱线三维结构模型中,实现计算机纱线三维模拟.     

基于DirectX 3D技术的织物三维模拟仿真

介绍了DirectX 3D的技术原理,给出了基于该技术和三次样务插值算法实现织物三维模拟仿真的具体实施办法,为进一步实现服装的三维模拟仿真提供现实和理论依据.     

纬编针织物三维仿真系统的开发

针对现有电脑横机花型准备系统缺乏三维花型模拟和针织物仿真功能等问题,将虚拟现实技术应用于针织物三维仿真研究,开发了纬编针织物三维仿真系统.系统以建立的三维线圈模型为基础,运用参数化设计方法和VRML语言,实现了织物组织的三维参数化仿真设计,仿真图像可多视角观察,任意平移、旋转或缩放.运用Java语言和VRML的EAI接...     

基于WebGL的纬编提花织物三维仿真

为了实现纬编提花织物的三维结构仿真和虚拟仿真,在深入研究各提花类型编织原理的基础上总结其仿真结构特点。通过数学建模的方法,建立提花织物中常用的线圈几何模型、线圈型值点模型和平移模型,借助矩阵运算可根据织物组织快速计算线圈的空间坐标位置。采用WebGL技术和三维图形引擎库Three.js,根据型值点空间坐标实现了三维线圈结构的绘制和颜色渲染,截取提花织物三维仿真图作为纹理材质,利用纹理映射技术实现纬编提花织物三维虚拟仿真。以各类提花效应的三维仿真效果为例对仿真方法进行检验,结果表明矩阵模型可以实现线圈型值点坐标快速转换与计算,WebGL技术可实现三维结构仿真可视化从而准确描述提花织物结构特征,增强服装虚拟仿真的真实感。     

三维纵横步进编织预成型件的计算机仿真

针对三维纵横步进编织物的建模仿真问题,基于三维纵横步进编织的基本编织原则,引入编织图对其编织模式进行描述,将编织过程转换为数学置换运算过程,通过计算机模拟纵横步进编织运动,并采用Bézier曲线对纱线运动轨迹进行拟合,利用计算机图形技术对三维编织结构进行显示,获得了一种设计与实现三维纵横步进编织预成型件的计算机仿真方法,从而解决了各种纵横步进编织工艺预成型件的仿真问题。同时针对规则截面以及异型截面的预成型件结构进行了仿真分析,仿真结果表明所提出的仿真方法有效、可行。     

基于数字单元法的三维正交织物微观几何结构建模

为了反映织物内部纱线的空间构型和微观几何结构,针对在织物建模过程中,因忽略纤维间的相互作用而引起的纱线截面形状变化的问题,基于数字单元法理论,提出了一种计算纤维间摩擦力的方法。通过纱线纤维化离散,用数值模拟和仿真方法模拟三维正交织物成型过程,建立了5种精度递进的微观几何结构数值模型。5种模型中的每根纱线分别由4、7、12、19和37根数字纤维表征。研究结果表明:随着纱线纤维化离散程度的提高,仿真时间延长,织物厚度减小,纤维体积分数增大,节点平均作用力下降速度变缓,势能变小;当每根纱线由19根数字纤维组成时,所建织物的微观几何结构数值模型与真实织物样本在显微镜下的内部切片图像较为吻合。     

基于Rhino-Python的多圈高簇绒地毯三维仿真

为解决空间结构复杂的多圈高簇绒地毯在实现其外观三维仿真时缺乏真实感的问题,利用Rhino环境下的PythonScript实现了簇绒地毯外观的三维仿真。将绒圈中心线及截面曲线分段后局部求解相关控制点坐标,再由B样条曲线对二者进行拟合。同时考虑到地毯绒圈之间的相互挤压导致绒圈发生了随机偏转变形,通过设计算法模拟了绒圈产生形变后的状态。在此基础上添加绒圈表面纹理及光照模型,进一步渲染输出仿真结果。测试结果表明:利用B样条曲线拟合原理并借助于Rhino-Python平台的簇绒地毯三维仿真方法是可行的,且易于实现;与实际地毯样品相比,能够较为真实地模拟不同排纱规律下多种花型图案、绒圈高度变化的簇绒地毯。     

三维编织物的计算机仿真系统研制

介绍三维编织物计算机仿真系统的结构和主要功能。以四步法矩形三维编织物为例 ,研究实现三维编织物计算机动画仿真的方法。给出了各种编织结构和编织工艺的三维编织物计算机仿真实例。     

基于Web的织物结构三维参数化仿真

为实现基于网络的织物结构三维参数化仿真,运用虚拟现实建模语言(VRML)构建了织物的三维仿真模型,研究了Java Applet通过VRML的外部编程接口EAI对织物仿真场景进行交互控制的原理、方法和实现过程,并给出了运行实例.为进一步研究织物异地协同设计提供一种思路.     

Virtual characterization of MDF fiber network

A virtual design method for medium density fiberboards (MDF) is proposed with the aim to optimize the fiber orientation and lay-up of MDF. The new method estimates the stiffness and strength by using microstructure models of the MDF fiber network. The virtual design is used to improve the manufacturing technology of MDF plates with multilayer oriented fiber structure. Experimental investigations of the mechanical behavior of MDF microstructure for various fiber geometries, glue content and distribution are complicated, time consuming and expensive. On the other side, virtual microstructure design allows to develop a new wood fiber based material with less experimental work. Microstructure models help to better understand the non-linear damage mechanical behavior of a wood fiber network depending on fiber geometrical parameters. Such parameters as crack distribution and fiber deformation on micro-scale level are complicated to experimentally measure, but possible to model using computer simulations. The virtual design tool requires less empirical data. The model takes into account information on average wood fiber orientation, fiber diameter, fiber length and mechanical properties of wood fiber cell wall and glue. The numerical method for strength and stiffness analysis of MDF microstructure was calibrated using standard MDF with non-oriented fibers. It turned out that this method gives precise results for MDF with oriented fibers and even with multilayer structure. The proposed virtual microstructure design tool can significantly improve and speed-up the optimization manufacturing technology of MDF and other wood fiber based composites.     

纤维尺度下数码纱仿真方法

为解决因配色复杂多变,数码纱外观难以直观预测的问题,提出基于纤维单元的模拟方法,用于实现数码纱外观的仿真。依据纤维原料颜色数值,构建纤维级别的纹理模型;根据纺纱工艺参数计算数码纱上的区域色块参数,构建色块排列模型;利用不同组分纤维间渐变规律,同时结合光照模型仿真亮度信息构建颜色渐变模型;采集真实数码纱的直径数据,仿真纱线的直径形态。实验中分别保持颜色和组分不变,模拟出不同组分和颜色的数码纱。结果证明所提出的纱线仿真方法可较快地模拟出数码纱的外观,并且与实际数码纱的外观视觉十分接近,为数码纱的设计开发以及织物仿真奠定了基础。     

Water transfer of Masson pine lumber during high temperature drying

This paper presents a mathematical model developed to simulate moisture movement in lumber of Masson pine during high temperature drying. It is based on the three types of water transport in softwood during high temperature drying: (1) Liquid water movement through cell lumens and pits above fiber saturation point is assumed to be a consequence of capillary action between liquid and gas phases inside the capillary; (2) Bound water diffusion through cell-wall below the fiber saturation point is the result of the moisture content gradient across cell-wall; (3) Water vapor that moves towards the surface of wood under a partial vapor pressure gradient through the whole moisture content range during drying. The model was solved numerically to predict moisture content profiles. Experiments were undertaken to measure the moisture content gradient and used to verify the model.     

准静态仓储粮堆温度场的CFD模拟

现有仓储粮堆数学模型难以有效模拟实际粮堆温度的变化过程.本试验应用计算流体力学(CFD)方法模拟研究了仓储粮堆在不通风情况下温度场的变化情况,根据粮仓结构和仓外环境条件,通过确定模拟区域、网格划分、模型选择,确定了合理的CFD模拟方案,得到并分析了两种不同尺度粮仓内仓储粮堆温度随季节变化过程的模拟结果.通过对准静态仓储粮堆内部温度随环境温度变化过程的分析,为仓储通风系统的优化设计提供了有价值的参考依据,为进一步的模拟研究奠定了良好基础.     

人体着装传热传质过程的数学模型(二)--模型的数值求解

对人体着装传热传质过程的数学模型进行了三维离散，并利用完全隐式差分格式和MATLAB软件进行了数值求解，得到了较为满意的结果。通过与实验结果的比较，验证了模型的正确性，为利用计算机技术对人体热湿舒适性的仿真分析奠定了基础。     

Mathematical modeling and numerical simulation of heat and moisture transfer in a porous textile medium

The moisture accumulation within clothing is a serious problem for sportswear and clothing in cold climate. There are several experimental methods available to measure moisture build up in insulate materials. However, information on parameters such as temperature, relative humidity and vapor pressure can be obtained through simulation using a predictive mathematical model. The focus of this study is the development of a mathematical model to simulate heat and moisture transfer in a sample of fabric, coated to provide insulation, which is in contact with human skin on one side and with the external environment on the other. To numerically simulate the mathematical model, the finite volume method is used and a computational procedure for the solution of the model is designed. The simulation results are analyzed to verify whether they are consistent with the physical reality.     

胶原纤维和植物纤维混合抄片吸水性的研究

从浆料的种类、配比和抄片的微观结构等方面,研究了对胶原纤维和植物纤维混合抄片吸水性的影响。结果表明：胶原纤维和木浆纤维混合抄片的吸水性大于胶原纤维和草浆纤维混合抄片的吸水性。浆料配比对混合抄片吸水性影响较大,调节胶原纤维和纸浆纤维的用量比例,可以控制混合抄片吸水性的大小。     

基于数学方法的流行几何图案设计

为了拓展传统印花图案设计的思路,为设计师和工艺师提供更多各类的设计方法和途径。从数学艺术图形角度对服装印花图案的生成方法进行了研究和探讨,主要阐述了准规则斑图和均匀随机网形成流行几何图案的原理和方法。首先,在对几何图案特点研究的基础上,根据对准规则斑图和均匀随机网的数学原理,结合计算机图形技术,进行了其生成图案方法的算法研究;其次调整其数学模型的不同参数,生成一系列具有一定流行度和审美需求的几何图案。结果表明,利用数学方法来进行流行图案设计具有实用性和优越性。本文的目的在于拓展传统印花图案设计的思路,为设计师和工艺师提供更多种类的设计方法和途径。     

On the modelling of colour changes of wood surfaces

Colour has an influence on the aesthetic properties of wood surfaces, and changes in colour have an impact on each individual’s perception of wood construction materials. This study examines an approach to model the discolouration of wood during natural weathering. A novel mathematical model was used to estimate colour changes of two softwoods during natural weathering. The surface colour of fir and larch samples was determined according to the CIEL*a*b* system during natural weathering over a period of one year. In order to demonstrate the value of the model, two different weathering sites were chosen. The data collected from each site was smoothed using a local regression method, and the corresponding parameters were used to generate the confidence intervals around the smoothed curves. The results show that all three colour parameters exhibit varying differences during the weathering trial. The locally weighted regression method seems to be an appropriate approach for modelling weathering effects and could be used to simulate colour change in wood in exterior applications in the future.     

无损检测阔叶材纤维长度的近红外光谱法

比较了近红外光谱分析技术测量木材纤维长度与传统的测量方法的优缺点并详细介绍了应用近红外光谱分析技术测量木材纤维长度,其中包括木材样品选择及制备、近红外光谱采集及纤维长度真值测量、多变量数据分析与模型建立的实验方法与操作步骤.实验表明近红外光谱分析技术可以快速准确地预测阔叶材纤维长度.