基于移动窗口法的城市遥感生态质量评价研究

为进一步提高城市生态监测的精确度,在前人开展的城市生态遥感监测研究的基础上引入“区域尺度”的概念,充分考虑小区域范围内不同地物间的交互作用,并利用移动窗口模型(Moving Window-Remote Sensing Ecology Index, MW-RSEI)对沈阳市浑南区的遥感影像进行逐像元分析。实验结果表明,MW-RSEI模型和生态遥感监测模型（Remote Sensing Ecology Index, RSEI)在整体生态评价趋势上表现出一致性。但MW-RSEI模型对城市生态中的细节区域表征更明显。考虑到建筑及裸地周围植被的影响,其较差生态区域的占比仅为6%,生态评价为优的区域占比为11%。研究区生态评价结果表现得较为连续,并未出现明显的断层现象。该结果具有现实意义且与实际生态分布更为符合。MW-RSEI模型在城市生态监测中更为适用,可为相关部门提供一定的技术参考。     

DE-GMAW高速电弧焊工艺机理的研究

通过大量的工艺实验,找出了DE-GMAW双焊枪组合的匹配参数,测试了焊接电流波形,拍摄了熔滴过渡图像,并获得了无成型缺陷的焊缝照片.基于实验结果解释了高速焊接工艺的机理.建立了适用于DE-GMAW焊接工艺的有限元模型,并对该工艺条件下的温度场、应力-应变场进行了数值模拟.结果表明:计算出的DE-GMAW焊缝横断面形状尺寸与实验结果吻合良好;在通过焊丝的总电流相同时,DE-GMAW焊接时焊缝尺寸、热影响区宽度、应力、应变及变形均小于常规GMAW焊时的结果.这为DE-GMAW焊接工艺参数优化提供了基础数据.     

MICROSTRUCTURAL STUDY OF Fe-Cr-Al/Al COMPOSITE COATINGS DURING OXIDATION AND SULFIDATION AT 900 ℃

The microstructure of a composite coating system, which was composed of an inner layer of Fe-Cr-Al and an outer layer of aluminum, was studied after it was respectively oxidized and sulfurdized at elevated temperatures. Apart from the Al2O3 scale formed on the surface, the microstructure of the composite coatings exposed at 900℃ in air for 4h was a three-layer structure. The first layer consisted of a solid solution of Cr and Fe in α aluminum and an intermetallic compound FeAl3, while the second layer was a single phase of the aluminide and the third layer still remained the same appearance as the original Fe-Cr-Al coating.The microstructural observation of the specimen tested at 850-900 ℃ at low oxygen pressure and high sulfur pressure for 576h revealed that the surface coatings of the specimen had transformed into a duplex structure containing an outer layer and a thicker aluminide layer beneath. X-ray diffraction results showed that the out layer was composed of Al2S3 and Al2O3 and that AlCrFe2 was the main phase composition of the aluminide layer, with a few of Al2S3 and Al2O3 accompanied.     

催化剂组分对制取单壁碳纳米管的影响

采用温控电弧炉,以FeS,Ni,Mg的混和粉末作为催化剂,起弧电压为32V,放电时间为10min;研究了催化剂组成与成分对制取单壁碳纳米管的影响,确定了优化参数。在环境温度为600℃时,起弧电流为100A,催化剂FeS/Ni/Mg的组成和成分含量分别为2∶1∶2(%),5%,氦气气氛,气氛真空度为5.7×104Pa,单壁碳纳米管的产量和纯度都分别达到了12g/h和70%上,其管径为1.24～1.36nm。     

压缩感知理论中的广义不相关性准则

压缩感知理论（Compressed Sensing, CS）是对信号压缩的同时进行感知的新理论,而如何分析观测矩阵（Sensing Matrix）的稳定性是压缩感知理论中的一个非常重要研究方向。不相关性（Incoherence）准则是分析观测矩阵稳定性的一个重要准则,该准则的研究需要假设观测矩阵行向量是一组标准正交基的子集,这大大限制了不相关性准则的应用。本文针对这一局限性,提出了广义不相关性准则,即仅要求观测矩阵行向量是一组普通基的子集。首先推广了相关度定义,称为广义相关度;然后提出了广义不相关性准则,即推导并证明了压缩观测值（Compressive Measure）个数与广义相关度之间的满足某一关系式时,信号能够完全重构;最后把不相关性准则应用到高斯随机观测矩阵和随机±1构成的Rademacher矩阵的稳定性分析。数值仿真表明高斯随机观测矩阵和随机±1构成的Rademacher矩阵具有较好的稳定性。      

可变类谱聚类遥感影像分割

为实现遥感影像分割中类别数的准确、自动判别,提出了一种可变类谱聚类算法.根据影像的相似图构建权值矩阵和标准Laplacians矩阵,计算Laplacians矩阵较小特征值对应的特征向量生成特征向量矩阵,并视其与像素对应的向量行为像素特征点集;研究Laplacians矩阵处于不同（近似）块对角结构时类属同一目标类像素特征点的聚集性,定义聚类度指标,计算不同分割类别数对应聚类度;选择聚类度将发生最后一次较大跳变时的分割类别数作为算法估计类别数,并采用FCM（Fuzzy C-Means）算法划分该类别数对应像素特征点集实现影像分割.分别采用提出算法和基于特征间隙的算法分割合成及真实遥感影像.实验结果表明提出算法可准确地判别影像类别数.     

基于光纤光栅的机器人腕部多维力传感器

为实现机器人腕部等关节受力情况的测量,设计了一种十字型光纤光栅多维力传感器,该传感器由两个圆环及两环间呈90°分布的四个相同的等截面悬臂梁及粘贴于其上的光纤光栅组成.分析了传感器的传感原理并使用ANSYS对传感器进行力学仿真分析;研究了传感器不同部位受力时悬臂梁的应变情况;搭建了实验平台,进行了传感器的标定实验和温度补偿研究;通过对仿真数据和试验结果进行数学分析,得出了光纤光栅中心波长漂移量与传感器的受力关系.实验结果显示,该传感器能准确地测量腕部所受力的大小和位置,误差在1.6％以内,且抗干扰能力强,具有较好的稳定性,能在复杂环境中使用.     

一种计算有效的Nystrom特征子空间匹配主用户频谱感知新算法

针对核（kernel）空间下主用户频谱感知算法存在的计算任务繁重这一共性问题,提出一种低计算复杂度的Nystrom特征子空间匹配（NSM）新算法.该算法依据数据样本维的独立同分布特性随机地选择数据子集.在高维核空间下应用Nystrom近似获得主特征向量,用以分别构建主用户特征信号与次用户接收信号的Nystrom特征子空间.以此为基础计算相应的Frobenius距离,实现主用户检测.计算机仿真结果表明：与代表性的核空间下主用户频谱感知算法相比,所提算法在保证检测性能较为理想的前提下,可将相应的计算复杂度降低近66%.     

Growth-temperature-dependent optical and acetone detection properties of ZnO thin films

Zinc oxide (ZnO) thin films were prepared onto glass substrates at moderately low growth temperature by two-stage spray pyrolysis technique. The effects of growth temperature on structural, optical and acetone detection properties were investigated with X-ray diffractometry, a UV-visible spectrophotometer, photoluminescence (PL) spectroscopy and a homemade gas sensor testing unit, respectively. All the films are polycrystalline with a hexagonal wurtzite phase and exhibit a preferential orientation along [002] direction. The film crystallinity is gradually enhanced with an increase in growth temperature. The optical measurements show that all the films are physically highly transparent with a transmittance greater than 82% in the visible range. The band gap of the film is observed to exhibit a slight red shift with an increasing growth temperature. The PL studies on the films show UV/violet PL band at ～ 395 nm. Among all the films investigated, the film deposited at 250 ℃ demonstrates a maximum sensitivity of 13% towards 20 ppm of acetone vapors at 300 ℃ operating temperature.