Spatio-temporal Characteristics of Urban Land Cover Structures in Prefecture-level Cities of Inner Mongolia Autonomous Region based on Remote Sensing Imagery

The urban land cover structures play an important role in providing urban ecological service and altering the quality of human settlements environment.In this study,2000~2015 Landsat TM series satellite data along with fine resolution remote sensing images were used to capture information of each 5-year land cover structures in 12 prefecture-level cities of Inner Mongolia Autonomous Region.Subsequently,there land cover information was used to monitor and analyze the spatiotemporal dynamics of urban expansion,and differences of land cover structures and expansion types.The results showed that：in 2000~2015,the overall changes of land cover structures in 12 prefecture level cities of Inner Mongolia Autonomous Region were rapid.Specifically,the urban area expanded by 278.93 km².By comparison,the proportion of urban area expansion in 2010~2015 was 1.61 times and 1.91 times than that of the first two periods (in 2000~2005 and in 2005~2010).Since 2010,the most dramatic changes has been observed.Particularly,obvious urban impervious surface expansion was found.Also urban vegetation showed obviously increased with varying degrees.At the past decade,urban expansion has undergone three stages.Specifically,the main process experienced from urban interior filling to urban interior filling and then to urban extension,of which Baotou and Hulunbeier belonging to the internal filling city.Population growth and socio-economic development are responsible for these differences.     

Designment and Assessment of Far-Red Solar-Induced Chlorophyll Fluorescence Retrieval Method for the Terrestrial Ecosystem Carbon Inventory Satellite

Solar-Induced Chlorophyll Fluorescence (SIF),which is emitted by photosystem during photosynthesis under natural illumination,carries important information of actual photosynthesis of plants.Spaceborne remote sensing of SIF provides an unprecedented opportunity for monitoring global photosynthesis at regional to global scales.Up to date,in-orbit operational spaceborne sensors that are available for SIF retrieval are originally designed for atmosphere monitoring.The hyperspectral sensor onboard Chinese Terrestrial Ecosystem Carbon Inventory Satellite (CTECS) is expected to be the first operational spaceborne sensor that is specifically designed for sensing SIF from space (scheduled to be launched around 2020,2 years before the Fluorescence Explorer (FLEX) Mission).Data-driven approach has been selected as the main algorithm for far-red SIF retrieval for CTECS,but is to be refined and assessed according to sensor specifications (e.g.spectral resolution and signal-to-noise ratio).In this context,this study aims to improve the designment of far-red SIF retrieval method for CTECS.based on end-to-end simulation,we evaluate the precision and accuracy of SIF retrieval in several potential windows.We then analyze the sensitivity of SIF retrieval to number of features (nv) and fluorescence spectral shape function (hF) in the forward model in different windows.Results show that a broader fitting window increases retrieval precision,but is accompanied with lower accuracy and stronger sensitivity to nv and hF.Considering both retrieval precision and accuracy,the window of 735~758 nm with nv set to 6 and hFset as single peak Gaussian function (μ=740 nm and σ=30 nm) is selected as optimal fitting window for CTECS.SIF retrieval results based on proximal and airborne remote sensing data demonstrate the feasibility and reasonability of the designed method.Our results provide an important reference for far-red SIF retrieval for CTECS.     

基于视频确认的变电站顺控操作系统

目前变电站的顺控操作都需要人为干预,工作效率低,自动化程度不高。由于电网对变电站顺控操作的准确性要求高,目前顺控操作防止误操作机制单一,因此无法满足电网对安全性的高要求。本文在原有防误逻辑的基础上提出一种通过模板特征匹配视频分析算法来视频识别设备当前运行状态的方法,对顺控操作中刀闸、翻字牌等设备状态进行高精度可靠识别,实现了顺控操作不同源信号双确认,增加了防止误操作的途径,大大降低了顺控操作中系统误判率,也减少了顺控操作人工参与,提高了变电站顺控操作的工作效率和自动化程度,为电网安全运行提供了保障。     

椭圆形泡沫填充薄壁管斜向冲击吸能特性仿真研究

为了提高汽车在斜向碰撞中的防撞性,提出了一种新型的椭圆形泡沫填充管。以比吸能和冲击力峰值作为评价指标,采用有限元仿真的方法分析了椭圆向心率、壁厚和泡沫铝密度等参数对其斜向冲击吸能特性的影响。结果表明:向心率的减小,在小角度冲击时,可降低冲击力峰值,大角度冲击时,能提高比吸能量;比吸能和冲击力峰值与壁厚近似为线性关系;泡沫铝密度为0.153 g/cm~3时,泡沫填充管的综合比吸能最小,而冲击力峰值则随着泡沫密度的增大而增大。因此,合理地设计椭圆形泡沫填充管参数有利于提高汽车的防撞性,从而提高乘员安全性能。     

振动环境下压力传感器失效机理分析

在复杂的振动环境中,一种特定结构的压力传感器经常出现内引线断裂的失效现象。通过对内引线断截面及断口侧面的观察,确定为振动疲劳断裂。应用机械振动和模态分析理论,将转接引线的力学模型简化为伯努利-欧拉梁,通过自由振动偏微分方程计算其基频,与有限元软件计算的结果进行比对,证明建立的有限元模型能够准确反映传感器的动力学状态。应用该有限元模型,进行模态和振型的计算,寻求致使内引线断裂失效的原因,并将计算结果与试验结果对比,证明寻找的失效原因的正确性。     

基于拟合误差最小化原则的奇异值分解降噪有效秩阶次确定方法

为了最大限度地提高旋转机械设备故障振动信号的信噪比,研究了奇异值分解降噪的原理,提出了一种新的奇异值分解降噪有效秩阶次的确定方法。首先,对振动信号进行相空间重构,对吸引子轨迹矩阵进行奇异值分解;然后,按不同的阶数,将奇异值分成信号组和噪声组,对每次分组的结果,以阶数为自变量、以奇异值为因变量,拟合成信号特征奇异值曲线和噪声特征奇异值曲线,并求拟合误差;最后,将拟合误差最小值对应的奇异值阶数确定为有效秩阶次,并进行奇异值分解降噪。通过数值仿真和实际齿轮故障数据分析,表明该方法可以有效地提高信号的信噪比,为后期的故障特征提取创造有利条件。     

室内爆炸与火灾联合作用下约束钢柱损伤评估

结构体系提供的约束刚度和附加质量会显著影响钢柱在爆炸下的动力响应,同时火灾下结构对热膨胀的约束会导致钢柱内产生附加轴力,受力特性与无约束柱明显不同。采用引入损伤的Johnson-Cock强度模型分析了约束钢柱在室内爆炸荷载作用下的损伤情况,建立了评估约束钢柱在爆炸与火灾联合作用下破坏情况的压力-冲量-时间曲面图及表达式。为了说明结构约束的影响,将计算结果与无约束钢柱在爆炸与火灾联合作用下的破坏时间进行对比,并进一步分析了超压时程曲线形状、约束刚度及钢柱几何尺寸对P-I-t曲面图的影响。结果表明,当爆炸荷载强度较小时,约束钢柱的破坏时间早于无约束钢柱,当爆炸荷载强度较大时,约束钢柱的破坏时间晚于无约束钢柱;超压时程曲线形状参数越大,约束钢柱在爆炸作用下越易破坏;约束刚度对钢柱在爆炸与火灾联合作用下的破坏时间基本无影响;当爆炸损伤较小时,钢柱壁厚对破坏时间影响很小,当爆炸损伤较大时,钢柱壁厚度越大,钢柱越易破坏,但在压力-冲量-时间空间中,仍为壁厚越小、柱高越高的钢柱越易破坏。     

带挠性附件卫星转动惯量的在轨辨识

针对大型卫星的挠性附件振动会影响质量特性参数辨识精度和准确性的问题,提出了带挠性附件卫星转动惯量参数在轨辨识的递推算法。基于带挠性附件卫星动力学模型,导出了转动惯量参数辨识的最小二乘描述形式;与挠性附件振动模态估计的卡尔曼滤波算法相结合,提出了一种适用于带挠性附件卫星转动惯量参数辨识的并发递推算法。通过仿真算例验证了卫星挠性附件振动对转动惯量参数辨识的影响和文中递推算法的有效性。     

基于小波包能量特征向量的光纤布拉格光栅低速冲击定位

光纤布拉格光栅(FBG)传感器在飞行器的实时冲击定位监测中具有广阔的应用前景。根据两次冲击位置距离越近接收到信号幅频特性相似度越高的关系,提出基于小波包能量特征向量与相似度匹配算法共同实现冲击定位的研究,构建了一套由光纤布拉格光栅传感器和复合材料层合板组成的冲击定位监测系统。首先通过遍布冲击建立能量特征向量数据库。然后通过试验点的能量特征向量与数据库中各点的能量特征向量进行相似度计算实现冲击定位。实验表明,对480 mm×480 mm的复合材料层合板的16次冲击定位实验中,该方法的最大误差为40 mm。