微米六方BN-KH550/聚丁二酸丁二醇酯耐热性复合膜的制备及性能

为进一步改善聚丁二酸丁二醇酯(PBS)的力学性能和耐热性能,采用硅烷偶联剂KH550改性微米六方氮化硼(h-BN),对PBS进行共混改性,通过熔融共混与开炼压延工艺制备了具有较高耐热性的h-BN-KH550/PBS复合膜。对h-BN-KH550粒子结构和复合膜的力学性能、聚集态结构、断面形貌、结晶性能及热稳定性进行了测试和表征。结果表明:与PBS相比,h-BN-KH550/PBS复合膜的力学性能得到改善,当KH550与h-BN质量比为2∶50、h-BN-KH550与PBS质量比为3∶50时,综合力学性能最优;h-BN-KH550粒子可在PBS中均匀分散;在PBS结晶过程中,h-BN-KH550作为成核剂,使PBS的结晶速率加快,结晶度增大;h-BN-KH550/PBS复合膜的热稳定性显著提高,当h-BN-KH550与PBS质量比为3∶50时,复合膜热分解过程中质量损失为5%、10%、50%时的温度(T5d、T10d、T50d)和热分解峰值温度(Tp)分别提高了30.0、22.6、9.5和10.0℃。     

校正源条件下基于双星序列观测量的地面运动目标定位算法及理论性能分析

The method for locating a moving source on earth using a sequence of time difference of arrival(TDOA)and frequency difference of arrival(FDOA)measurements pairs obtained by dual-satellites was presented in the presence of calibration sources with accurate positions.First,the difference calibration(DC)location algorithm aiming to the mobile target was derived,and its theoretical performance was also analytically derived.The result demonstrates that the DC localization variance could not reach the CRB,although it could eliminate the location bias produced by the position and velocity errors of the dual-satellites.For this reason,a two-step optimal association location algorithm was proposed,and its theoretical performance was proved to be equal to the CRB.Finally,a variety of numerical experiments are performed to corroborate the superiority of the geolocation algorithms and the effectiveness of the performance analysis.     

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 对E550探伤不合格试样进行了分析,发现探伤不合格是由于连铸卷渣引起。但在保护渣与钢基的结合处存在厚度为200～300 μm的纯铁素体带异常组织。应用光学显微镜、电子探针等对缺陷周围的异常组织进行了详细探讨。结果表明：探伤不合格是由于连铸卷渣引起;保护渣周围的异常组织是由于保护渣中存在非晶态的SiO2,在钢液凝固时硅扩散到钢中形成富硅区域,导致钢从液态直接进入α相区,形成只有铁素体+极少量珠光体组织,而不是回火索氏体组织。     

RT550型越野轮胎起重机

在全球高端市场中,越野轮胎起重机占移动式起重机40%的市场份额。在国内工程机械领域,越野轮胎起重机是一个极具增长潜力的产品。介绍RT550型越野轮胎起重机主要技术参数、系统构成及技术特点。     

未知频偏下直扩信号的扩频序列估计

针对未知频偏下的直扩信号, 通过将载频吸收至扩频波形中, 提出了一种有效的基于协方差矩阵子空间分解的扩频序列估计算法. 通过信号子空间分解, 提高了含有未知频偏信息的扩频波形估计的信噪比, 从而降低了载频估计难度. 在随机信号模型条件下, 还推导了扩频波形估计器的克拉美劳界. 在低信噪比条件下, 仿真验证了该算法的有效性.     

基于双L阵的双基地MIMO雷达多目标角度估计

提出了发射和接收均为L阵配置下的双基地MIMO雷达多目标角度估计的方法.基于ESPRIT算法,分别提取出发射、接收端的方位和俯仰旋转不变因子,构造了2个配对复矩阵并对其特征分解,根据特征值的实部和虚部分别估计出发射方位和俯仰角,接收方位和俯仰角,并实现了各角度间的自动配对.推导了双L阵配置下双基地MIMO雷达角度估计的克拉美罗界.仿真结果验证了本文算法的有效性.     

数据辅助的时域自相关与互相关联合频偏估计方法

针对数据辅助下突发数据通信中频偏估计精度低和复杂度高的问题,提出了一种数据辅助的时域自相关与互相关联合频偏估计方法。首先,推导出基于通用数据帧结构的频偏估计克拉美劳界（CRB）,同时引入一个形式上更为简单的近似CRB作为估计算法的性能界;然后,在自相关估计中,利用自相关算子和复信号指数化近似得到具有较大范围和较低信噪比门限的自相关算法;在互相关估计中,借鉴自相关估计原理,利用互相关算子获得兼顾低复杂度和高精度的互相关算法。仿真结果表明,所提方法可估计出接近符号速率一半的载波频偏且达到了近似CRB性能;与经典的M&M算法相比,所提方法的估计精度提高了5倍,且从实乘运算来看还具有与导频长度相关的线性复杂度,适用于突发数据通信的工程应用。     

Cramér-Rao Bounds for Estimating the Position and Width of 3D Tubular Structures and Analysis of Thin Structures with Application to Vascular Images

In this work we derive analytic lower bounds for estimating the position and width of 3D tubular structures. Based on a continuous image model comprising blur and noise introduced by an imaging system we analyze three different intensity models of 3D tubular structures with increasing complexity. The derived formulas indicate that quantification of 3D tubular structures can be performed with very high precision under certain assumptions. We also determine conditions under which the model parameters are coupled or uncoupled. For uncoupled parameters the lower bounds are independent of prior knowledge about other parameters, and the derivation of the bounds is simplified. The theoretical results are substantiated by experimental investigations based on discretized and quantized 3D image data. Moreover, we study limits on estimating the width of thin tubular structures in 3D images. We use the derived lower bound of the width estimate as a benchmark and compare it with three previously proposed accuracy limits for vessel width estimation.

高层建筑抗震钢板的轧制工艺与组织性能

采用光学显微镜和万能拉伸试验机等研究了轧制过程中的开冷温度和终冷温度对Q550D钢板的显微组织、铁素体和M/A岛占比以及室温拉伸性能的影响.结果表明,不同开冷温度和终冷温度下,试样中M/A岛的形态主要为颗粒状、块状和断续分布的长条状,且M/A岛主要分布在贝氏体或者铁素体的相界处;试样中M/A岛体积分数会随着开冷温度或终...     

KH550修饰纳米莫来石对聚脲润滑脂摩擦学性能的影响

目的 研究硅烷偶联剂表面修饰纳米莫来石(Mullite)(Al2O3-SiO2体系)作为添加剂,对聚脲润滑脂摩擦学性能的影响。方法 用硅烷偶联剂(KH550)对纳米Mullite表面进行修饰,分别制备质量分数为0.03%的纳米Mullite和KH-mullite的聚脲润滑脂。采用四球摩擦试验机测试纳米Mullite和KH-mullite作为添加剂对聚脲润滑脂摩擦学性能的影响,利用扫描电子显微镜(SEM)和三维表面形貌仪观察磨损表面形貌,通过X射线能量色散能谱仪(EDS)分析磨损表面的元素分布,使用X射线光电子能谱(XPS)分析磨损表面润滑膜的元素价态,探究添加剂在聚脲润滑脂中的作用机理。结果 经过修饰后,纳米KH-mullite在聚脲润滑脂中的减摩抗磨性能较优,摩擦因数和磨斑直径分别降低了22.4%、15.6%。通过SEM和三维表面轮廓仪观察磨损表面发现,KH-mullite添加剂能够有效降低磨损表面的粗糙度,修复磨损表面。KH-mullite聚脲润滑脂优良的摩擦学性能归功于两点,首先KH-mullite能够沉积并吸附在磨损表面,在起到修复作用的同时促进了润滑膜的形成;其次,KH-mullite能够进入润滑膜中,将摩擦副之间的摩擦方式变为滚动摩擦。结论 Mullite和KH-mullite都具有提升聚脲润滑脂润滑性能的作用,经硅烷偶联剂修饰后的KH-mullite在减摩抗磨性能方面表现更优越。