车身曲面逆向设计投影法参数化方法的应用

针对在汽车车身曲面逆向设计中很难由散落数据点云构造出合适光顺曲面的问题，提出了一种以Hoschek方法确定散乱数据点云的边界线、以基面投影法确定其他散乱数据点云参数值的逆向算法：给出了一种重构曲面的拟合方法，结合车身部件上散乱数据点云的特点，建立了该算法的数学模型，并通过VC＋＋6．0进行了编程实现。与通过UG得到的插值曲面比较可以看出，该拟合方法能够更好地对原曲面进行再现。     

基于BIM技术的涵洞一体化设计应用研究

为了实现涵洞设计的计算、出图、工程量统计一体化,依托MicroStation CONNECT Edition平台,研发了铁路涵洞一体化设计程序。(1)根据铁路BIM联盟相关规范,对铁路涵洞构件进行颗粒度分类和编码,并对构件非几何属性进行细化,形成结构化、便于检索的涵洞模型信息数据库;(2)根据涵洞构件几何特点,通过二次开发,建立涵洞构件及附属构件全参数化模型库,并根据构件间约束关系,将各涵洞构件装配为整体三维模型;(3)对构件编码与数据库进行关联,输出涵洞的主要工程数量,实现涵洞的一体化设计。基于本程序,可实现涵洞的三维可视化和参数化批量设计,减少铁路工程中涵洞设计人力资源投入,提高涵洞的设计生产效率。     

钢桁架加劲PC连续箱梁桥的BIM建模技术

简述BIM技术的含义和特点,利用Autodesk Revit软件平台,通过建立参数化桥墩、箱梁、钢筋等族库,实现族模型的自动修改,构建钢桁架加劲PC连续箱梁桥的模型。探讨BIM模型的图形格式转换方法,并利用Lumion软件平台实现模型的动态漫游展示,为该类桥梁结构的细部展示提供三维可视化手段和新理念。     

轿车底盘三维参数化总布置设计系统集成研究

介绍了起始于设计需求和技术,包括选型、匹配、性能计算和评估、三维参数化总布置、干涉检查、运动校核以及性能仿真等全过程轿车底盘设计系统集成的开发思路。阐述了基于Pro／E二次开发建立轿车底盘三维参数化总布置设计系统的开发过程,详细描述了该系统开发的基本原理和关键技术。     

断面结构刚度性能参数化应用

文章以某车型B柱断面为例,详细介绍了Hypermesh软件计算获得复杂断面结构刚度性能的过程,并通过定义尺寸参数为设计变量、性能参数为响应,运用试验设计和多项式拟合建立了复杂断面刚度性能与其结构尺寸之间的函数关系,且与实际断面性能对比拟合计算结果平均误差在5%以内。基于建立的断面结构刚度性能函数关系,实现无网格过程的复杂断面结构刚度性能快速评估,同时为断面结构尺寸、性能与白车身刚度性能之间的关联提供支撑。     

汽车底盘设计中参数化技术的运用分析

文章通过分析汽车底盘设计中参数化技术的相关运用,首先从汽车底盘设计中参数化技术的优势入手,紧接着着重介绍了汽车底盘设计中参数化技术的应用,希望通过这些分析能更好地提升汽车底盘设计的质量。     

Re-parameterization of Bézier Curves by Square Approximation with Endpoint Constraints

In order to get an approximation with better effect of parameterization of Bozier curves, we proposed a method for arc-length parameterization and the corresponding algorithms by square approximation for the discrete even de-parameterization of the curves. This method is simple and easy to implement, and the property of the approximation has no change compared with the original curve. A quantitative criterion for estimating the effect of parameterization is also built to quantitatively characterize the parameterization effect of the algorithms. As a result, the nearly arc-length parameterized curve has a smaller relative deviation using either the algorithm with point constraint at endpoints or the algorithm with point constraint plus the first derivative constraint at endpoints. Experiments show that after re-parameterization with our algorithms, the relative deviation will have at least a 20% reduction.     

CATIAV5环境下的零件参数化建模方法

为改善系列化零件的常规建模方法存在重复建模和零件的修改步骤繁琐的缺点,文章对CATIAV5相关选项进行设置,以环形抱箍为例建立了零件的模型和参数,并将参数与尺寸关联,实现了通过修改参数来修改模型的功能。表明零件的参数化建模方法简化了系列化零件的建模步骤及修改零件的操作,提高了设计工作的效率。     

Parameterization of air–sea gas fluxes at extreme wind speeds

Air–sea flux measurements of O₂ and N₂ obtained during Hurricane Frances in September 2004 [D'Asaro, E. A. and McNeil, C. L., 2006. Measurements of air–sea gas exchange at extreme wind speeds. Journal Marine Systems, this edition.] using air-deployed neutrally buoyant floats reveal the first evidence of a new regime of air–sea gas transfer occurring at wind speeds in excess of 35 m s^− 1. In this regime, plumes of bubbles 1 mm and smaller in size are transported down from near the surface of the ocean to greater depths by vertical turbulent currents with speeds up to 20−30 cm s^− 1. These bubble plumes mostly dissolve before reaching a depth of approximately 20 m as a result of hydrostatic compression. Injection of air into the ocean by this mechanism results in the invasion of gases in proportion to their tropospheric molar gas ratios, and further supersaturation of less soluble gases. A new formulation for air–sea fluxes of weakly soluble gases as a function of wind speed is proposed to extend existing formulations [Woolf, D.K, 1997. Bubbles and their role in gas exchange. In: Liss, P.S., and Duce, R.A., (Eds.), The Sea Surface and Global Change. Cambridge University Press, Cambridge, UK, pp. 173–205.] to span the entire natural range of wind speeds over the open ocean, which includes hurricanes. The new formulation has separate contributions to air–sea gas flux from: 1) non-supersaturating near-surface equilibration processes, which include direct transfer associated with the air–sea interface and ventilation associated with surface wave breaking; 2) partial dissolution of bubbles smaller than 1 mm that mix into the ocean via turbulence; and 3) complete dissolution of bubbles of up to 1 mm in size via subduction of bubble plumes. The model can be simplified by combining “surface equilibration” terms that allow exchange of gases into and out of the ocean, and “gas injection” terms that only allow gas to enter the ocean. The model was tested against the Hurricane Frances data set. Although all the model parameters cannot be determined uniquely, some features are clear. The fluxes due to the surface equilibration terms, estimated both from data and from model inversions, increase rapidly at high wind speed but are still far below those predicted using the cubic parameterization of Wanninkhof and McGillis [Wannikhof, R. and McGillis, W.R., 1999. A cubic relationship between air–sea CO₂ exchange and wind speed. Geophysical Research Letters, 26:1889–1892.] at high wind speed. The fluxes due to gas injection terms increase with wind speed even more rapidly, causing bubble injection to dominate at the highest wind speeds.