水热温度对玻璃纤维增强HAp-CS涂层的影响

为了制备出结合强度较好的生物涂层,采用水热电泳法在碳/碳复合材料表面成功制备了玻璃微纤维增强的羟基磷灰石——壳聚糖(g(f)/HAp-CS)复合涂层,用x-射线衍射仪、透射电子显微镜、扫描电子显微镜、能谱分析仪、红外傅里叶变换分析仪等测试手段对涂层进行了测试和表征,主要研究了水热沉积温度对复合涂层中HAp晶相和涂层显微结构的影响以及HAp涂层的沉积动力学.结果表明:采用玻璃微纤维增强的HAp-CS涂层,致密性和均匀性有了很大提高,显著减少了复合涂层表面的裂纹;随着水热温度的升高,涂层中HAp的衍射峰逐渐增强,表面形貌得到了有效改善,涂层的致密性和均匀性显著提高;涂层的沉积速率随水热温度的升高而加快,其沉积活化能为14.63kJ/mol.     

培养小学生自主作文途径探究

正众所周知,作文教学是一项综合、系统工程。有人认为,要想大面积提高小学作文教学质量,必须从作文教学的各个方面,各个环节入手,进行综合治理,优化作文教学。这种观点不无道理。可依我拙见,它还没有说到点子上。要想真正提高小学生的作文水平,首先必须激发小学生的作文兴趣,使小学生对作文产生一种内驱力,变老师要我作文为我要作文。培养写作兴趣,让小学生自主作文,要讲究方法。本文从"下水"示范、讲究策略、重视修改、创造成功四方面加以探讨。     

MVQ海绵拉伸和压缩过程的SEM原位观察

利用扫描电子显微镜对甲基乙烯基硅橡胶（MVO）海绵拉伸和压缩过程进行原位观察。结果发现，MVQ海绵的微观结构表现为大泡孔内嵌套有众多小泡孔；拉伸时MVO海绵微裂纹萌生于泡孔壁微缺陷处，裂纹扩展方向垂直于加载方向，随着拉伸应变的增大，裂纹变长变宽并与另一泡孔连通，形成许多大小不一且平行分布的沟槽；压缩时MVQ海绵泡孔主要发生两种破坏，一种是泡孔的变形使相邻泡孔之间的泡孔壁受到拉伸应力的作用而发生断裂，另一种是相邻泡孔之间的泡孔壁发生相互折叠。     

An algorithm and observability research of autonomous navigation and joint attitude determination in asteroid exploration descent stage

In this paper, an autonomous relative navigation and joint attitude determination algorithm in asteroid exploration descent stage is researched based on feature point information of perpendicular asteroid surface image observed by optical navigation camera, distance vectors from spacecraft to asteroid measured by three angled installed lidars and relative velocity increment measured by accelerometer when the relative distance vector to the centroid of asteroid can not be obtained. The inertial attitude of spacecraft is determined by sun vector, star vectors and inertial angular velocity respectively measured by sun sensor, star trackers and inertial reference unit. Also, in order to obtain measurement error model transferred from sensor noise, a covariance matrix solver considering error correlation is presented via the error model of normalized vector to first order. Numerical simulation and improved observability evaluation of filtering are undertaken to discuss the results of complete sensor observation and weak observation of lidars, and verify the effectiveness of the presented relative navigation and attitude determination algorithm.     

活化煤矸石对硬化水化浆体性能的影响

采用化学结合水、SEM、XRD对掺有活化煤矸石的硬化水泥浆体的性能和微观结构进行了研究.研究发现,煅烧后的煤矸石具有火山灰活性,掺有煤矸石的水泥浆体的结合水量低于不掺煤矸石的硅酸盐水泥,但后期增长较快;掺有煤矸石的水泥浆体结构较疏松,孔隙较多;煤矸石掺量的增加促进了水泥熟料矿物的水化,而且掺量越大,越有利于熟料矿物的水化.     

基于改进LLE算法的手势特征提取研究

在人机交互领域中,基于视觉的手势特征提取成为研究的热点,但手势存在较大范围的变化,很难实现对手势的有效分类.研究了一种基于LLE改进算法的手势特征提取方法.先将手势特征数据中的某个数据点与邻近数据点组成局部线性关系,对重构误差进行拉格朗日乘子算法优化处理,求出新的局部重建权值矩阵,为了使局部线性关系能够满足低维度空间,通过求解映射矩阵的方法,将手势特征样本数据的目标特征空间映射到低维度空间中.采用稀疏观察手势描述法对手势特征进行提取,根据手势参数对手势轨迹数据进行归一化处理,为了提高手势特征提取的实时性,采用支持向量分类器的方法将手势从难以分类的空间映射到高维度的手势空间中.实验结果表明,所提方法对手势的查准率和召回率较高,泛化性较好,即使在样本数据很少的情况下,也具有较好的识别效果.     

胶凝砂砾石含泥量对其强度的影响

胶凝砂砾石骨料多为现场开挖料,含泥量较普通混凝土高得多,对混凝土的工作性能有较大的不利影响。为了给工程设计提供参考依据,进行了水胶比为1.0、1.1、1.2、1.3、1.4的情况下含泥量为0%～50%的胶砂试块强度试验和SEM电镜扫描,通过试验数据分析和微观SEM图像分析,研究了含泥量对胶凝砂砾石强度的影响。结果表明:泥在胶砂试块内部影响胶凝材料的水化反应,导致试块整体结构性变差、密实度和强度降低;随着含泥量的增加,胶砂试块强度降低,当含泥量在10%以下、水胶比为1.0左右时对胶砂试块强度影响最小,即含泥量小于10%时才能保证试块强度。     

基于SEM的干湿循环蚀变花岗岩分形特征与力学特性演化规律

分形维数是对岩石裂隙、破碎程度和损伤等细观特征的定量描述,岩石的细观结构往往会对宏观强度特征产生较大的影响。为了研究干湿循环侵水对蚀变花岗岩细观特征的影响,基于电镜扫描(SEM)试验,得到了经历不同干湿循环次数的蚀变花岗岩的细观图像,并通过盒维数法计算得到各岩样的分形维数,建立基于分形维数的细观损伤演化方程;其次,通过室内单轴抗压强度和抗拉强度试验,获得不同干湿循环次数下蚀变花岗岩的力学特性。通过试验数据,得到了干湿循环次数及分形维数分别与岩石强度特性和弹性参数的关系。研究表明:岩石干湿循环次数的增加在宏观上表现为抗拉强度、单轴抗压强度以及弹性模量的减小;在细观上表现为分形维数的增大;泊松比不受此影响。分形维数将岩石细观特征量化、建立了细观和宏观的联系。研究结果可为衡量蚀变花岗岩强度特性的指标提供依据。     

Characterization of polyhydroxyalkanoates synthesized in activated sludge using three carbon sources

Polyhydroxyalkanoates(PHAs) were synthesized in activated sludge using three types of carbon sources (sodium acetate,sodium propionate and sodium butyrate), and their characterization were studied. It was shown that the content of PHA synthesized by microorganisms in activated sludge were different. The biggest synthetic amount up to 36.7% of VSS was obtained when sodium acetate was used as carbon source. The polymer yield was lower when using sodium propionate as the carbon source than when using others, with 25.1% of VSS, while resulted in an increase of hydroxyvalerate(HV) units produced. The structure and thermal properties of extracted biopolymers were analyzed by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and themo-gravimetry (TG).     

Application of image analysis based on SEM and chemical mapping on PC mortars under sulfate attack

The degradation mechanisms of cementitious materials exposed to sulfate solutions have been controversial, despite considerable research. In this paper, two methodologies of image analysis based on scanning electron microscope and chemical mapping are used to analyse Portland cement mortars exposed to sodium sulfate solution. The effects of sulfate concentration in solution and water to cement ratio of mortar, which are considered as the most sensitive factors to sulfate attack, are investigated respectively by comparing the macro expansion with microstructure analysis. It is found that the sulfate concentration in pore solution, expressed as sulfate content in C-S-H, plays a critical role on the supersaturation with respect to ettringite and so on the expansion force generated.