一类C2连续可调控的交错B样条曲面

提出一类C^2连续可调控的带参数ε的交错B样条曲面的生成方法,这种曲面具有普通3次B样条曲面的主要性质,在控制点固定时,改变参数ε的值能调控曲面的位置,当ε→0时曲面整体地逼近于控制多面体网。     

B样条曲线曲面降阶综述

B样条曲线曲面的降阶是样条曲线和曲面造型中的关键技术之一,为了实现不同CAD系统之间的数据交换,常用到这一技术,它已成为热点问题,得到越来越多的研究.结合作者在该领域的研究成果,文章综述了近年来国内外专家学者关于B样条曲线曲面的降阶逼近研究的方法、理论成果及实际应用情况,并对各种不同的方法进行了分析比较.     

基于九叉树分割的曲面片上点的快速反解算法

本文针对曲面造型中，”由参数样条曲面上点的笛卡尔坐标，反求其对应参数“的反解问题，提出了一种通过曲面快速分割来逼近最终解的快速，简单，可靠的反解算法；并以Ｂ样条参数曲面为例，介绍了算法的实现过程。     

基于九叉树分割的曲面片上点的快速反解算法

本文针对曲面造型中，“由参数样条曲面上点的笛卡尔坐标，反求其对应参数”的反解问题，提出了一种通过曲面快速分割来逼近最终解的快速、简单、可靠的反解算法；并以Ｂ样条参数曲面为例，介绍了算法的实现过程。     

P-nary细分多层B样条算法及曲面拟合

多层B样条方法在曲面的拟合中提供了新的途径.在证明均匀B样条基函数P-nary细分方程基础上,给出了均匀B样条曲线的P-nary细分控制点之间的计算公式,进而讨论了B样条曲面的P-nary细分问题,并将其用于层次B样条曲面拟合.提出了基于P-nary细分多层B样条曲面拟合算法.该算法加快了层次B样条曲面拟合中网格加细后曲面控制点的计算,数值实例显示所给算法的有效性.     

有理三次Hemite插值样条及其逼近性质

提高插值曲线曲面的逼近性是计算辅助几何设计中的一个重要问题.本文构建了一种带单参数的分段有理三次Hermite插值样条.讨论了该样条的逼近性,给出了一种提高插值曲线曲面逼近性的方法,并且给出数值例子.结果表明,对于给定的插值条件,通过选择合适的参数,依本文方法所生成的插值曲线曲面在逼近效果上好于标准三次Hermite插...     

B样条曲线的小波光顺法

本文研究了B样条曲线的小波光顺法。首先介绍了利用准均匀B样条曲线逼近具有任意节点矢量的B样条曲线的方法，从而将任意B样条曲线转化为多分辨率表示，进而提出了基于小波的曲线光顺误差控制算法。小波光顺法在光顺曲线的同时具有减少控制顶点的作用，兼具简单性和通用性的优点。     

有理B样条方法的工程应用

1946年,Schoenberg发表了长篇文章讨论等距节点的逼进问题,最早提出了B样条的概念。二十余年后,Riesenfeld研究了B样条逼近在计算机辅助几何设计中的应用,并于1973年发表了博士论文。随即B样条曲线曲面在几何设计中获得了广泛的应用。翌年,Versprille完成了“有理B样条在计算机辅助设计中的应用”的博士论文,首先研究了有理B样条问题。由于有理B样条方法的独特优点,已为若干系统如SDRC公司的GEOMOD、波音公司的系统以及Evans＆Sutherland公司的PS300智能图形终端等采用,但公开发表的文献很少。为了进一步完善我们正在发展的三维造型系统,使其具有更强的造型功能,并能精确表达园锥曲线、曲面,我们对有理B样条方法作了初步研究,并设计了试验程序。本文根据我们的研究成果依次阐述有理B样条的特点,有理B样条曲线曲面的表达和形状控制,有理B样条曲线和有理Be＇Zier曲线的转换,最后简述当前正在进行的研究。文中也涉及Versprille曾经研究过而很少应用的若干问题。     

基于改进粒子群算法的复杂曲面轮廓度误差评定及可视化

针对复杂曲面轮廓度误差的求解是一个复杂的非线性寻优问题,将改进的粒子群算法与细分曲面逐次逼近的方法相结合,实现了复杂曲面轮廓度误差值的精确计算和评定结果可视化。利用双3次B样条曲面进行理论廓面的拟合,从最小条件准则出发,建立了曲面轮廓度误差的数学模型;通过细分曲面逐次逼近的方法,计算出点到曲面的最小距离。在对基本粒子群算法分析的基础上,引入了非线性动态惯性权重系数和杂交算子,提高了算法的精度和效率。以VRML作为三维展示平台、Java Applet作为控制核心,实现了面轮廓度误差评定的可视化、网络化。     

B-样条曲面的局部形状改进算法

提出了一种双三次B-样条曲面局部形状改进算法。首先根据节点处三阶不连续性的近似局部光顺准则，选择曲面待光顺的节点；然后利用约束的最小二乘逼近法修改相应的局部控制顶点网，从而降低曲面局部的三阶不连续性，使局部形状得到改进。在详细描述算法原理后，给出了算法的实现步骤。     

基于SCFNA法的FSS吸波材料设计及制备

目的 设计并制备一种与单元电导率匹配、电磁性能优异的柔性频率选择表面吸波材料。方法 首先选择空间限域强制组装法（SCFNA）制造具有优异导电性能的片材,再按圆形谐振单元裁剪并周期性排布在有机介质层内。完成频率选择表面（FSS）的制备后测试其电磁波性能,并与仿真模型优化的结果进行对比。结果 制备的柔性选择表面样件在频率为18～40GHz时吸收率达到96.22%以上。结论 使用空间限域强制组装法设计制备了导电单元,通过调整工艺参数实现对单元电导率的精准调控,成功制备出了一种在18～40 GHz频段下电磁性能优异的高柔性吸波体材料。     

In vitro Biological Effects of Ti2448 Alloy Modified by Micro-arc Oxidation and Alkali Heatment

The purpose of this study was to test the hypothesis that the combination of micro-arc oxidation and alkali heatment (MAH) would improve the cytocompatibility of a newly designed Ti-24Nb-4Zr-8Sn alloy.In this study,commercially pure titanium (cp Ti) and Ti-24Nb-4Zr-8Sn were used.Surface modification of Ti-24Nb4Zr-8Sn by a two-step treatment of micro-arc oxidation (MAO) and alkali heatment was reported.Surface characterizations were performed by scanning electron microscopy (SEM),thin film X-ray diffraction (TF-XRD) and X-ray photoelectron spectroscopy (XPS).The MAH layer consisted of finer crystals and possessed a higher degree of crystallity and stability than the MAO layer.A biocompatibility study on treated and untreated Ti24Nb-4Zr-8Sn in comparison with cp Ti was carried out to investigate the effect of the different surfaces on the bone integration property in vitro.The cellular assays revealed that the MAO and MAH layer favored the initial adhesion of MC3T3-E1 cells and that the growth rate of MC3T3-E1 cells on MAH layer was significantly higher than that on the conventional MAO-treated layer after 3-day and 5-day incubation,demonstrating the greater potential of the hybrid treatment of micro-arc oxidation followed with alkali heatment as a novel surface modification method for implanting materials.     

The Role and the Effect of Calcium Ion Content of Photographic Gelatins on Coating Defects

The influence of the calcium ion content of some photographic gelatins on the adhesion of gelatin solutions to emulsion layers was investigated by surface tension, pH and viscosity measurements and by coating using the dip method.

Adhesion of the gelatin layers was examined in the coating process under the following conditions:

Surface tension at varying wetting agent concentrations, for gelatin solutions which contain calcium ions from 0 to 5760 ppm concentration.

Surface tension at varying gelatin concentrations.

Surface tension at varying pH values of the gelatin solutions used in the coating process.

The experimental results demonstrate that, at gelatin concentrations between 2 and 4%, the adhesion ability of a gelatin solution on a dry or wet gelatin (emulsion) layer depends on the Ca2* content of the coating solution. It is necessary to have at least 1000 ppm Ca2* concentration to guarantee a perfect adhesion and a perfect coating. Gelatin source, pH and the viscosity of the system are unimportant.     

Dose measurement for medical staff with glass dosemeters and thermoluminescence dosemeters during 125I brachytherapy for prostate cancer

Photoluminescence glass dosemeters (PLDs) and thermoluminescence dosemeters (TLDs) are commonly used as a personal monitoring dosemeter. PLDs and TLDs were used for surface dose monitoring of medical staff involved in (125)I brachytherapy for prostate cancer because these dosemeters have a wide dose-response linearity and high sensitivity for low photon energy. Surface doses measured with PLDs agreed with those with TLDs within ～20 % except for a few cases. Surface doses at a surgeon's left hand and arm were higher than those at the other measuring points. A surgeon received a maximum dose of 650 μGy at the back of left hand. Surface doses to an assistant were <100 μGy. Surface doses to a nurse, a radiologist, an anaesthesiologist and a radiological technologist were <10 μGy. The occupational exposure to a surgeon could be reduced by the adjustment of fluoroscopic parameters and the use of lead gloves.     

Evaluating High-Frequency Visco-Elastic Moduli in Asphalt Concrete

Spectral Analysis of Surface Wave (SASW) testing was used to evaluate an improvement in the source generation repeatability of surface waves when a sheet metal couplant strip was used compared to the exposed asphalt surface, plus the increase in maximum coherent frequency achieved using a wire spring impactor compared to a solenoid driven steel striker plate. Both SASW and Multichannel Analysis of Surface Waves (MASW) were used to evaluate the high-frequency visco-elastic dynamic modulus of asphalt concrete plate specimens vs. a master curve constructed from standard dynamic modulus tests. The master curve was used to temperature and frequency shift the high-frequency moduli to an 18°C, 25 Hz reference value for comparison. SASW results tended to overestimate the 25 Hz reference modulus obtained from the master curve. MASW results agreed well with the reference modulus, when shifted using the master curve equations, but overestimated the reference modulus when shifted using a power function approximation of the linear portion of the master curve.     

Surface properties of poly(ethylene terephthalate) foils of different thicknesses

Surface properties of commercially available poly(ethylene terephthalate) (PET) foils of different thicknesses (3, 13, 23, 50, and 100 μm) were characterized using different analytical methods. Surface roughness and morphology were determined by atomic force microscopy, goniometry was used for determination of contact angle (wettability of surface) and electrokinetical analysis (zeta potential) for characterization of surface polarity and conductivity. X-ray photoelectron spectroscopy was used for characterization of PET surface chemistry. Infrared spectroscopy and differential scanning calorimetry (DSC) were used for determination of crystallinity portion. By DSC analysis, it was confirmed that the crystallinity portion depends on the foil thickness. Most important result of this study is that the surface properties of PET foils depend not only on the foil thickness but also on the foil side under study. This finding may be of importance for future experiments performed on PET foils and for their application in tissue engineering or microelectronics.     

Investigation of vibratory bowl finishing

Although vibratory finishing has been in commercial use for over 40 years, relatively little fundamental information is known about the process, and industrial practice remains largely based on empiricism and trial and error. An experimental investigation into the vibratory bowl finishing process was conducted using material removal rate and surface roughness as the dependent variables. Bowl performance can best be described in terms of acceleration and depends primarily on the feed weights used, while bowl loading has a relatively minor effect. Furthermore, small changes in bowl loading resulting from normal media wear can be neglected. Results showed that material removal rates were constant over time for aluminium, brass and steel and were sensitive to hardness and bowl acceleration. Surface roughness saturated after a fixed period and was primarily a function of material composition. Surface roughness did not appear to be sensitive to bowl acceleration.     

基于功能模式的概念结构生长型设计研究

为解决功能-结构映射问题,首先提出了功能表面映射模型。功能表面作为功能-结构映射的信息载体,可分为定位表面和使定表面,进而提出了基于功能表面的功能传递链。通过对生物个体与产品的类比,提出了概念结构生长型设计方法,依据广义定位原理和分解重构理论,建立了基于功能表面的功能模式,具体包括执行模式、传动模式和定位模式,得到了基于功能模式的概念结构生长型设计过程模型。最后,以偶件滚字夹具设计为例,说明了基于功能模式的生长型设计过程。     

Oberflächenenergetische Charakterisierung

Surface Energetic Characterization of Nanoscale Fillers and Elastomers Almost any technically used rubber material is filled with particles in nanometer size, by which the properties of the material can be specific controlled. In modern car tires the used fillers have crucial influence on driving security (wet grip and ice grip), on fuel consumption (rolling resistance) and on the cost‐effectiveness (life time of the tire) [1].The first fillers used in rubber application were carbon blacks; actually in passenger car tires mostly surface modified silica is applied. The implementation of novel filler systems like organophilic modified layered silicates (organo‐clays) or carbon nanotubes is subject of intense research [2,3]. Surface energy and –polarity of the filler surface is a crucial, but often underestimated determining factor. All surface properties of rubber and filler have to be well balanced to get the nanoscale filler particles finely dispersed in the rubber matrix and also to obtain a good adhesion between polymer and filler surface.     

Improvement of adhesion properties of polypropylene substrates by methyl methacrylate UV photografting surface treatment

Polypropylene is a widely used commodity plastic from an industrial point of view. Typical applications include both low and high technological content, as it has a good balance between overall properties, processability and cost. However, it is important to remark its intrinsic low surface energy which leads to high chemical inertness. This has an important restriction on some technical applications that require joining and/or finishing processes such as painting. Therefore, the use of polypropylene in these applications requires previous surface modification in order to increase surface activity. Surface modification can be carried out by physical processes such as plasmas or by chemical ways. Surface chemical modification is characterized by relatively low cost and easy implementation at industrial scale. In this work, we have used a chemical process to improve adhesion properties on polypropylene substrates. The selected method has been ultraviolet photografting of methyl methacrylate (MMA) monomer. This process allows increasing surface activity and this has a positive effect on polypropylene–polypropylene adhesion joints. Surface changes have been followed by contact angle measurements and subsequent surface free energy calculation. The evolution of mechanical properties of adhesion joints (T-peel and shear conditions) in terms of the previous exposure time to UV radiation has been evaluated. Optical microscopy (OM) and scanning electron microscopy (SEM) have been used to characterize adhesion fracture type.