平面美术图案形成的新探讨：可调Z样条曲线设计

本文介绍了可调Ｚ样条曲线的定义和特点，将Ｚ样曲线应用于计算机辅助平面美术图案设计系统中，可以采用统一的数据结构对平面设计图案进行存储，便于计算机对图形进行几何编辑处理和形图形数据文件，以实现平面主图案设计的自动化。     

复杂模型的建模技术

本通过规划复杂模型的特征线,利用坐标测量机实测数据,采用UGⅡ软件构成样条曲线、拟合模型、反复修正样条,直至拟合模型样条光顺,即采用逆向工程和正向设计结合的方法进行建模。     

C-B样条旋转曲面造型研究

论文提出利用C-B样条来构造工程中常见的旋转曲面。在介绍C-B样条曲线理论的基础上,讨论了圆及椭圆弧的C-B样条表示及用C-B样条构造旋转曲面体的建模方法。构造了形状可调,母线可以包含圆弧、椭圆弧等的旋转曲面。该方法结构简单,造型速度快,形状在一定范围内可调,表示圆弧、椭圆弧时,参数的几何意义明确。同时由于C-B样条和均匀B样条有相同的结构,该方法可以方便地应用于CAD/CAM建模系统。     

船体箱形截面梁设计及抗爆性能分析

在船体构件上应用箱形梁设计,能提高结构的纵向强度,具有利于保护重要管道和线缆、提高建造速度、利于质量控制和方便维修等优点。但是,国内外目前都是局部运用箱形梁结构,并未全船性设计使用,在此以某常规船体为基础,针对提高船舶抗爆性能和保持生命力的设计要求,全船性使用箱形梁。这种船体结构使钢制箱形梁承担全部的总强度,而船体型线和必要的使用刚度由轻质高强的复合材料板材来保证,实现局部强度与总体强度的解耦。在ABAQUS软件中基于声固耦合法,对船体水下爆炸响应进行分析,证实箱形梁结构具有较好的抗爆性能。最后对船体箱形梁进行优化设计,进一步提高抗爆能力。     

AutoCAD软件中样条曲线实现技术剖析

通过对AutoCAD软件中各类样条曲线的功能及其DXF组码深入分析，并用objectARX二次开发环境进行编程验算，反求出了AutoCAD中的双圆弧样条曲线、NURBS样条曲线以及B样条曲线的具体实现技术及教学模型，并对AutoCAD环境下各类样条曲线的数控加工编程进行了讨论。这些为更好地、准确地应用这些样条曲线功能来从事设计、制造及CAD／CAM软件系统开发提供了理论基础。     

上海轨道交通三号线列车运行图自动生成系统的设计与实现

基于对上海地铁三号线列车运行管理业务流程的分析,介绍了一个基于数据库和矢量图形的列车运行图自动生成系统的设计和实现。系统实现了数据的输入、修改,并根据数据的更新自动生成地铁列车运行图。     

CAPP工序图生成子系统的设计与讨论

工序图是工艺文件中清楚表达加工信息的辅助手段,具有直观、简洁的特点,是CAPP中不可缺少的组成部分。由于图形生成系统的复杂性,目前,国内的CAPP一般采用AUTOCAD来设计生成工序图,利用AUTOCAD等专用软件,节约了开发图系统的开销,但是由于开发语言与AUTOCAD连结接口以及数据加工处理与共享等存在着一些问题,往往需要设计专用的接口程序。本文所述的CAPP工序图生成子系统正是针对这一困境而设计的。由于开发语言与工序图生成子系统之间的兼容性,保证了CAPP工艺生成与CAPP工序图子系统之间的数据共享。本系统采用了覆盖(OVERLAY)与对策技术,减轻了系统对内存的开销。在图形处理方面,设计实现了交互能力较强的弹拉式菜单并实现了汉字字符的矢量化,综合利用了BGI较强的绘图功能。用户使用这个图形编辑器可以很方便地对需要局部修改的工序图进行编辑操作,图形数据库的结构也比较简单,一般情况下用户无需设计图形数据库,由系统自动实现数据库的有关操作,但用户可方便的查寻图形的有关信息。总之,本文所述的CAPP工序图生成子系统的设计有一些特色。     

活塞裙部纵向型线的拟合

本文对用多项式拟合活塞裙部纵向型线的最佳拟合阶次进行了分析讨论。提出用三次样条函数拟合裙部纵向型线的新方法。     

B样条轴映射模型的构造方法

将轴变形方法引入B样条造型,以促进多肢物体如人体的建模。基本轴映射模型主要针对简单形体造型。为方便用户操作,它将B样条曲面的表面关键点分组映射至轴线上,而关键点被用来定义和操纵轴线及曲面的形状。为适应复杂的造型需求,将基本轴映射模型组合为复合轴映射模型,定义了模型间的连接关系和过渡曲面。测试表明,B样条轴映射模型可以实现简易、直观的多肢物体实时交互造型,并具有通用性和复用性。     

曲线的光滑处理与仿真组合测量

仿真组合测量方法适合测量具有复杂轮廓的零件,首先需要根据零件图样绘出理论轮廓的CAD图形和公差带,然后测量出零件轮廓上的点坐标,同样转换为CAD图形,以其实测轮廓是否超出理论图形的公差带进行合格性判断。对于以离散点表达的复杂曲线,图样上要求光滑连接各离散点,绘制CAD理论图形时一般以二维多线段格式读人数据点,CAD提供了两种使其光滑连接的方法,就是修改二维多线段为拟合曲线或样条曲线。另外,零件轮廓的实测数据转换为CAD图形后也同样需要光滑连接,采用拟合曲线还是样条曲线,本文将根据不同情况进行分析。     

大深度载人潜器耐压壳极限强度的简化算法

深潜器耐压壳极限强度分析是设计深海载人潜水器的关键技术。基于切线模量理论, 引入切线模量因子的参数并结合材料的力学性能试验数据, 可以建立工程常用的多种合金材料的切线模量因子曲线。观察材料曲线的特性, 推导出计算耐压壳极限强度的简化数学表达式。利用该表达式计算深海载人潜水器常用的某种钛合金耐压球壳和TC4合金试验球壳的极限强度, 并将计算结果与有限元数值计算结果, 以及实验结果进行比较, 发现该简化方法具有良好的适用性。应用表明, 该方法简便实用, 可以作为耐压壳极限承载力的简化算法, 在初步设计阶段使用。     

基于边缘曲线光顺的图像放大算法

针对常规插值方法在图像放大时图像轮廓模糊的问题,提出了一种基于边缘的图像放大算法。算法包括边缘曲线光顺和插值放大两个步骤。第1步使用能量优化方法,从离散的边缘曲线数据恢复成连续而光顺的边缘曲线,这些曲线将图像分为若干个区域;第2步基于这些光顺曲线,针对不同的区域分别进行图像插值放大计算。使用该方法得到的放大图像边缘清晰光顺,实例证明该算法产生的图像质量高于常规算法。     

The effect of thin deployable construction elements of the international space station on the probability of its hull penetration by meteoroids and orbital debris

When calculating the probability of hull penetration by meteoroid and orbital debris (M/OD) for some of the International Space Station (ISS) modules (e.g. FGB, Service module, cargo vehicle “Progress”), one has to take into account their additional shielding produced by ISS deployable construction elements (such as solar panels, radiators), which decrease M/OD penetrating probabilities. The lack of developed calculation methods of accounting for this effect has arisen the necessity to investigate the law— governed nature of particle fragmentation process accompanying high velocity penetration of thin barriers, as well as to elaborate techniques for correct calculation of the probability of no penetration (PNP) of module pressure wall. The results of thorough analysis of the theoretical and experime ntal published data as well as of data obtained in joint NASA and RSA experimental program on particle fragmentation are presented in this report in the form of normalized analytical correlation between the fragment maximum size and impact parameters. On the basis of above mentioned particle fragmentation law, the method of module hull ballistic limit curves (BLC's) recalculation is determined, which include the effect of thin barriers greatly distanced from the module hull. This BLC's are used for module PNP calculations with the help of modified version of NASA BUMPER code. The special subroutines accounting for PNP changes due to the particle collisions with ISS deployable construction elements are introduced in the BUMPER algorithm. The results of the Service module PNP calculations with account for its “shadowing” by solar panels and radiators are presented.     

Numerical investigations of collision experiments considering weld joints

The design of double hull structures is investigated through two collision experiments with different large-scale specimens. The experiments were performed with a design of a typical double hull structure and a design with an alternative stiffening system (English: plate strengthened stiffeners, German: Plattenverstärkte Profilsteifen – PVPS) invented by Röhr and Heyer (2007) [1]. In contrast to the typical double hull design the alternative stiffening system is characterized by an additional trapezoidal sheet metal which is welded on the bulb profiles of the outer shell. The focus of this investigation is to reproduce the experimental results in terms of the force–displacement curves and failure mechanisms in numerical analyses. For this purpose, true stress–strain relations are determined from tension and compression tests of the different steel batches and the weld metal of the large-scale specimens. The RTCL and Lou–Kõrgesaar–Romanoff failure criteria are calibrated using tension tests and applied to the numerical analyses of the experiments. Both failure criteria lead to nearly identical force–displacement curves as well as failure mechanisms and they are capable of reproducing the experimental results. In the finite element model, an analogous model of fillet welds is implemented by assigning a fictitious thickness and material behavior of the weld metal shell elements at the location of weld joints. It is necessary to consider weld joints with the analogous model in the numerical analyses to predict the maximum reaction forces in the force–displacement curves. Furthermore, the impact velocity in the numerical analyses is investigated and it is concluded that an impact velocity of 10 m/s is appropriate to balance the accuracy and the simulation time.     

The construction and use of convex hulls in limited-angle computerized tomography

A method is developed to construct the convex hull of an object and make use of it in limited-angle x-ray computerized tomography (CT). The convex hull of an object is the smallest convex region containing the object, and therefore it can serve as boundary information in the reconstruction of the object from limited-angle data. Two methods, the intersection version and the superimposition version, of constructing the convex hull of an object from x-ray data are presented. It is shown that the intersection version is very efficient when the noise is very low, whereas the superimposition version is more stable with respect to noise. The usefulness and the construction of the convex hulls of embedded flaws in industrial x-ray CT are also studied. It is demonstrated with simulated data that the use of convex hulls makes it possible to reconstruct high-quality images from limited-angle data.     

Reliability assessment for ultimate longitudinal strength of ship hulls in composite materials

A method for reliability assessment of the ultimate longitudinal strength of ship hulls in composite materials is described. The ultimate longitudinal strength of a ship hull is predicted by a progressive collapse analysis based on load–average strain curves of stiffened composite panels that are developed by a progressive failure nonlinear finite element analysis. Sagging, hogging and slamming conditions are regarded as three extreme loading conditions and the corresponding limit state functions are established with an appropriate stochastic modeling of the basic design variables, such as the modeling uncertainties, the materials properties, the lamina thickness, the lamination angle, the still-water moment, the wave-induced moment, and the slamming-induced moment. The reliability estimation is achieved by an improved first-order reliability algorithm. The sensitivities of the reliability estimates with respect to model parameters are determined and those parameters with small sensitivity factors are replaced by deterministic values to improve the computational efficiency in the prediction of the ultimate longitudinal strength of ship hull. An all-composite ship is analyzed for demonstration.     

一种新的曲线曲面

给出了由任意n（n≥3）个函数构成的混合函数组,这些函数组具有非负性、规范性、对称性,以及特殊的端点性质.由这些函数组定义的曲线具有凸包性、几何不变性、对称性等基本性质.曲线的起点、终点分别为控制多边形首、末边的中点,曲线在起点处的一阶、二阶导矢都平行于控制多边形的首边,在终点处的一阶、二阶导矢都平行于控制多边形的末边.对于任意给定的m（m＞3）个控制顶点,可以由之定义一条曲线段,也可以由之定义由多条曲线段构成的组合曲线,而各条曲线段可以由不同数量的控制顶点来定义,因此由同一组控制顶点可以定义出多种不同的形状.另外,组合曲线在分段连接点处均G2连续,可以满足工程实际中大多数的需求.由函数组定义的张量积曲面具有类似于曲线的诸多良好性质.     

平流层飞艇气动阻力的数值模拟及公式拟合

该文以某中间有圆柱段的平流层飞艇为研究对象,在验证数值模拟方法的基础上,分析了尾翼、长细比、高度及雷诺数对飞艇气动阻力的影响。基于参数分析,采用TableCurve3D软件拟合给出了该艇型在水平姿态下的气动阻力系数估算公式,且给出攻角对公式的修正。研究表明:水平姿态下,平均风压系数沿着艇体头部逐渐减小,中间圆柱段保持稳定,沿着尾部逐渐增加;沿着艇体方向,风压系数曲线斜率拐点出现在各段连接附近。尾翼及艇体对阻力系数的贡献值随着俯仰角的增大而增加,但艇体是主要的贡献者;气动阻力系数随着长细比和高度的增加呈现先减小后增加趋势,随着Re数（1.0×107~2.0×108）的增加而递减。     

服装产业布料裁剪CAD／CAM系统

介绍了我们正在研制开发的服装产业布料裁剪ＣＡＤ／ＣＡＭ系统。该系统由服装板数据输入、缩放、排料及裁剪控制系统软件服装自动裁剪机本体组成，它适应当今服务行业“短、快、多”的发展潮流，将推动我国的服装行业从手工作业向现代化方向迈进，提高企业的效益和竞争力。     

A Method for Assessing the Fairness of Health Resource Allocation Based on Geographical Grid

The assessment of the fairness of health resource allocation is an important part of the study for the fairness of social development. The data used in most of the existing assessment methods comes from statistical yearbooks or field survey sampling. These statistics are generally based on administrative areas and are difficult to support a fine-grained evaluation model. In response to these problems, the evaluation method proposed in this paper is based on the query statistics of the geographic grid of the target area, which are more accurate and efficient. Based on the query statistics of hot words in the geographic grids, this paper adopts the maximum likelihood estimation method to estimate the population in the grid region. Then, according to the statistical yearbook data of Hunan province, the estimated number and actual number of hospitals in each grid are analyzed and compared to measure the fairness of health resource allocation in the target region. Experiments show that the geographical grid population assessment based on hot words is more accurate and close to the actual value. The estimated average error is only about 17.8 percent. This method can assess the fairness of health resource allocation in any scale, and is innovative in data acquisition and evaluation methods.