Mechanical and ablation properties of 2D-carbon/carbon composites pre-infiltrated with a SiC filler

In order to improve the mechanical and ablation properties of 2D-carbon/carbon composites, a SiC filler was added to a 2D-preform before isothermal chemical vapor infiltration densification by using a powder infiltration technique. Backscattered electron images showed that the SiC filler was mainly concentrated between the fiber bundles and between the layers. The tensile and flexural strengths of the composites were improved by the addition of the SiC filler because of the increase of interfacial surface areas between the bundles and between the layers, the less residual open porosity, and also the strong bonding between the SiC particles and the pyrocarbon matrix. The composites with filler experienced a 15.2% lower thickness erosion rate and a 51.7% lower mass erosion rate, compared to those C/C without filler. This was attributed to the low oxygen permeability of the SiO₂ shielding the exterior inter-bundle pores as well as to a thermal barrier effect.     

剑麻纤维／酚醛树脂复合材料研究

本文采用碱处理、硅烷偶联剂处理、化学接枝和热处理等物理化学方法，对剑麻纤维进行改性。研究了改性后短剑麻纤维／酚醛树脂复合材料的弯曲性能、无缺口冲击强度和布氏硬度，借助扫描电子显微镜观察了复合材料的弯曲断口形貌，并研究了剑麻纤维的不同处理方法对复合材料耐水浸泡性的影响。结果表明：剑麻纤维经硅烷偶联剂处理后，能有效改善刚性的剑麻纤维与脆性的酚醛树脂基体之间的粘结，从而提高了复合材料的综合力学性能，剑麻     

陕西秦岭山地体育旅游资源特征及开发模式分析＊

体育旅游作为一种新兴的旅游产品,正在慢慢走近人们的生活中。它将体育与旅游结合起来,在满足了人们休闲旅游需求的同时,也锻炼了身体,因此,受到了许多人的青睐。特别是山地体育旅游,它已经成为了广大旅游者的首要选择。在山地体育旅游蓬勃发展的大背景下,着重研究了陕西秦岭的山地体育旅游资源,分析了它的优势,并提出了合理的建议,以促进山地体育旅游的发展。     

国产软硬件环境下图像组织浏览构件设计

针对在国产软硬件环境下,应用系统读取、浏览大量图像数据的速度慢问题,设计了图像组织浏览构件。通过改进图像组织方式,将基础影像和目标对象图像分开组织管理,并对目标对象图像的属性和分层、分类进行探讨,实现图像信息的快速展现。对图像组织浏览构件进行了插件化设计与实现,利用QT跨平台开发工具,实现了应用集成框架,并通过实现统一集成接口,进行各业务插件的集成。     

Preparation and protein adsorption of hydrogel polysucrose microspheres

A series of novel hydrogel polysucrose microspheres with the mean size ranging from 200 to 500 μm were prepared via two‐step method. First, soluble polysucrose was synthesized by solution polymerization between sucrose and epichlorohydrin; second, a reversed phase suspension crosslinking reaction was performed to prepare polysucrose microspheres. The SEM images indicated that these spherical beads had smooth surface and hydrogel interior structure. FTIR was used to characterize the chemical structure of the beads. The hydrated and dry densities, equilibrium water content, and hydroxyl content of polysucrose microspheres were also investigated. The characteristic of high hydroxyl content (15.48–19.04 mmol/g) make these microspheres suitable for protein adsorption. Meanwhile, bovine serum albumin was used to examine the adsorption capacity of the microspheres. These microspheres had a capacity as high as 49.28 mg/g. The adsorption kinetics and recycling of the beads were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5934–5940, 2006     

Feeding pure docosahexaenoate or arachidonate decreases plasma triacylglycerol secretion in rats

Essential fatty acid (EFA)-deficient rats were fed highly purified methyl esters of docosahexaenoate (22∶6n−3), arachidonate (20∶4n−6), alpha-linolenate (18∶3n−3) or oleate (18∶1n−9) (100 mg/day, tube fed for 3–10 days), and their plasma triacylglycerol (TG) secretion rates were measured. Secretion rates of TG into plasma were reduced by tube-feeding 22∶6n−3, 20∶4n−6, 18∶3n−3, but not 18∶1n−9, to EFA-deficient rats. A significant reduction occurred after feeding 22∶6n−3 for only three days. Feeding 22∶6n−3 or 18∶3n−3 to EFA-deficient rats for three days also reduced the activities of liver lipogenic enzymes and sharply increased the proportions of 22∶6n−3 and 20∶5n−3 in liver phospholipid fractions. Mechanisms by which these EFA may reduce lipogenesis are discussed.     

Markov随机场与Gaussian曲线在MR图像分割中的应用

针对扫描的人脑组织MR图像边缘分辨率低、模糊性大的特点,本文提出了一种基于模糊Markov随机场和Gaussian曲线相结合的MR图像最佳阈值分割方法。该方法通过对图像的像素邻域属性的统计将模糊论引入其中,建立模糊Markov随机场,并利用Gaussian曲线对二维直方图最佳一维投影进行拟合,确定出图像中各脑组织的二维阈值点,在二维直方图上实现对脑组织的分割。通过实验表明,本算法能够有效提高脑组织的分辨率,对噪声的鲁棒性、结果区域的连通性相对于一维Otsu和二维Otsu算法都有了很大的提高。     

试议港口集卡调度算法模型分析

随着我国集装箱吞吐量的快速增长,集装箱港口对作业效率的要求也越来越高。在现有作业技术水平和硬件设备、设施的基础上实现作业效率的提高,已经成为集装箱港口发展所面临的重要问题。从集装箱港口作业的一个环节——集卡作业入手,分析提高集卡利用率,进而带动整个港口作业效率的提高。     

A non‐isothermal finite element model for injection stretch‐blow molding of PET bottles with parametric studies

A non‐isothermal finite element (FE) model for the injection stretch‐blow molding (ISBM) process of polyethylene terephthalate (PET) bottles is presented in this paper. The constitutive behavior of PET is modeled by the physically based Buckley glass‐rubber model in form of UMAT in ABAQUS. The heat transfer between the stretch rod, the preform, and the mold is modeled. Particular attention is paid to thermal and contact modeling, material model, and selection of proper element types. Extensive FE simulations are carried out to model ISBM of a 20 g‐330 ml bottle made in plant tests. Comparisons of numerical results with the measurements demonstrate that the model can satisfactorily predict the bottle thickness and material distributions. Significant nonlinear differentials are found in strain, temperature, and temperature reduction rate in both bottle thickness and length direction during the process. A volume approach is therefore necessary for accurate predictions of final bottle properties because they are governed by orientation and crystallinity, which are highly temperature and strain dependent. Parametric studies on contact modeling and heat transfer coefficient are also conducted and the results are discussed. Polym. Eng. Sci. 44:1379–1390, 2004. © 2004 Society of Plastics Engineers.     

马铃薯淀粉渣的羧甲基化研究

研究了马铃薯淀粉渣与氯乙酸进行羧甲基化反应的一般规律，考察了反应温度、反应时间、原料配比等因素对产物取代度的影响，通过正交试验，找到了最佳反应条件，并对产物性能进行了测试。