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61.
机载高光谱成像是一种快速、无损的检测技术,具有光谱分辨率高、波段窄而多和图谱合一的特点。国内小型化的机载高光谱成像仪主要依赖进口,价格昂贵,且高性能的高光谱设备进口困难,限制了高光谱技术在国内的推广和普及。中国地质调查局南京地质调查中心在国家重大仪器开发专项和国家重点研发计划支持下,成功研制出以推扫式小型化成像光谱仪HMS400/1000为核心的轻型机载高光谱成像系统SSMap,建立了机载高光谱遥感综合调查技术方法和作业流程,形成了一套可靠的地物分类方法和水土污染光谱定量反演模型。本文在介绍机载高光谱成像技术基本原理和分析国内外研究现状的基础上,以自主研发的机载高光谱成像系统SSMap为例,结合长江经济带生态环境的需求,详细探讨了总面积4500余km2的航空高光谱遥感作业方法、信息提取与调查应用。通过长江经济带江苏、安徽、浙江等地区的生态环境地质调查应用示范,取得了高质量的机载遥感数据,获得了一批重要调查成果。研究表明,机载高光谱成像技术在生态环境调查、水体监测、土地利用和土地质量评价等方面具广阔应用前景。具有自主知识产权的国产化机载高光谱成像仪降低了采购成本,推动了机载高光谱技术普及,服务了国家重大区域发展战略,具有显著的经济和社会效益。 相似文献
62.
Successful development of approaches to quantify impacts of diverse landuse and associated agricultural management practices on ecosystem services is frequently limited by lack of historical and contemporary landuse data. We hypothesized that ground truth data from one year could be used to extrapolate previous or future landuse in a complex landscape where cropping systems do not generally change greatly from year to year because the majority of crops are established perennials or the same annual crops grown on the same fields over multiple years. Prior to testing this hypothesis, it was first necessary to classify 57 major landuses in the Willamette Valley of western Oregon from 2005 to 2011 using normal same year ground-truth, elaborating on previously published work and traditional sources such as Cropland Data Layers (CDL) to more fully include minor crops grown in the region. Available remote sensing data included Landsat, MODIS 16-day composites, and National Aerial Imagery Program (NAIP) imagery, all of which were resampled to a common 30 m resolution. The frequent presence of clouds and Landsat7 scan line gaps forced us to conduct of series of separate classifications in each year, which were then merged by choosing whichever classification used the highest number of cloud- and gap-free bands at any given pixel. Procedures adopted to improve accuracy beyond that achieved by maximum likelihood pixel classification included majority-rule reclassification of pixels within 91,442 Common Land Unit (CLU) polygons, smoothing and aggregation of areas outside the CLU polygons, and majority-rule reclassification over time of forest and urban development areas. Final classifications in all seven years separated annually disturbed agriculture, established perennial crops, forest, and urban development from each other at 90 to 95% overall 4-class validation accuracy. In the most successful use of subsequent year ground-truth data to classify prior year landuse, an overall 57-class accuracy of 75% was achieved despite the omission of 10 entire classes, most of which were annually disturbed or perennial crops grown on very few fields. Synthetic ground-truth data for the 2004 harvest year based on the most common landuse classes over the following 7 years classified 49 of 57 categories at an overall accuracy of 96% in a final version that included CLU polygon majority rule, default smoothing and aggregation, and forcing of urban development and forest from multi-year majority-rule. 相似文献
63.
文章研究了时滞 Markovian 跳变系统的稳定性和镇定问题.首先,运用一个新的积分不等式,得到了保守性更小的稳定性判据;其次,基于此判据,获得了一个状态反馈控制器存在的充分条件,使得闭环系统具有随机稳定性并满足扩展耗散性;最后,两个实际例子说明了设计方法的可行性和有效性. 相似文献
64.
近年来,超材料打破了传统材料或结构的物理极限,为高效率发射天线的发展开辟了崭新的研究空间,获得了愈来愈广泛的关注.首先介绍了超材料的理论和结构研究概况,然后针对几种新型超材料技术在提高平面天线单元效率的研究工作进行了详细介绍和分析,包括非周期超材料技术、超材料作为新型辐射元或低剖面反射板等方面.最后,针对无线能量收集系统对高效率天线阵列的需求,介绍了高次模激励技术和新型低损耗传输线技术,以此降低阵列馈电网络的损耗,从而提高系统的整体效率. 相似文献
65.
在稠油热采地震监测中，储层特性的变化主要是通过弹性波参数的变化才最终表现为地层速度和实际地震响应的变化.因此，在一定条件下，弹性波参数应当是储层特定变化最直接和灵敏的标志.本文详细叙述了弹性波阻抗反演的方法，并将其应用于稠油热采地震资料的反演和解释中，结果表明弹性波阻抗反演用于稠油热采地震监测是切实可行的. 相似文献
66.
《International Journal of Mineral Processing》2005,78(1):22-30
The paper presents a method for separating the small metallic nonferrous particles from two component nonferrous mixtures using a new type of dynamic eddy-current separator with permanent magnets. The so called Angular Drum Eddy-Current Separator (ADECS) consists of a horizontal rotary drum covered with permanent magnets, alternately N–S and S–N oriented. The rotor is placed oblique, under the superior part of a horizontal conveyor belt, coplanar with its surface. The axis of the drum and the direction of displacement of the belt make a certain angle, depending on the physical properties of the particles subjected to the separation process. The separator functions on the basis of the jump effect of the strongly conducting particles which assume different trajectories in the active zone of the field, namely, upper part of the drum. The experimental results and comments regarding the values obtained for grade and recovery for wastes consisting in Cu–Pb and Cu–Al mixtures are given. 相似文献
67.
传统上都是使用基于常规波束形成(CBF)输出功率的不同进行声源的被动检测和定位。广义相关波束形成,是一种旨在将平均Toep litz相关函数用于估计波束形成的输出功率。从线性矢量水听器阵出发,分析了常规波束形成,对广义相关波束形成(GCBF)进行了深入研究,通过对广义相关波束形成器进行“W ilson”和“Bartlett”加权,可以分别得到FIM(WFIM)和CBF,对这三种波束形成器进行了理论分析和计算机仿真,结果表明三个波束形成器的分辨能力从高到低依次是:FIM、WFIM、CBF。 相似文献
68.
When a high-speed body with cavity passes through water-air free surface and exits water, its mechanical environment and dynamic characteristics change significantly due to the great difference in density and viscosity between water and air. With focusing on this problem, the Computational Fluid Dynamics (CFD) method is applied to perform numerical calculation on the process of this vapor-liquid-gas flow during the water exit of a high-speed cylinder, with the Volume of Fraction (VOF) multiphase flow interface-capturing techniques and the overset grid technology. After the verification and validation of the CFD model through mesh convergence study and a water-entry experiment, cavity evolution and flow characteristics including pressure and velocity distribution during the water exit are analyzed. The effects of different initial velocities on the pressure distribution and drag characteristics of the cylinder are investigated. Calculated results show that the cavity collapse during water exit causes strong pressure fluctuation on the cylinder; when the cylinder exits water enveloped in a supercavity, the pressure distribution on its wall surface and surrounding water region is relatively uniform, and the drag changes gently, and thus the cylinder has good motion stability.
相似文献69.
在中国经济和城镇化都逐步迈入高质量发展阶段的背景下,厘清经济发展对城市宜居性的影响规律具有重要的学术价值和应用价值。本文将宜居性作为一项“要素”引入生产函数研究框架,构建了经济发展对城市宜居性影响的理论模型,并基于2005—2019年中国40个大中城市的面板数据,利用系统GMM、面板门槛模型等方法对其进行实证检验。结果表明：① 2005—2019年中国大中城市的宜居性水平总体呈上升态势,但存在明显的维度分异和空间分异特征。② 总体上经济发展对城市宜居性的提高具有抑制效应,但这种效应在不同时间阶段和不同城市规模中呈现出明显的异质性。对于进入经济新常态阶段前,以及规模较大的直辖市和部分经济发达的省会城市,这种抑制作用比较显著;而进入新常态阶段后,经济发展对城市宜居性提升具有明显的促进作用。③ 经济发展对城市宜居性的影响还存在门槛效应,随着居民收入水平的提高,其影响效应呈现出显著的倒“N”型门槛特征。当经济发展使职工平均工资处于6万元至8万元时,经济发展能明显提高城市宜居度。经济发展本身对城市宜居性的影响表现出显著的单一门槛抑制效应,但其负向影响呈现出边际效率递减规律。最后,根据本文的研究发现从“宏观指引”和“微观行动”两个层面提出相应的政策启示。 相似文献
70.
现有研究缺乏对城市群空间尺度下借用规模问题的关注。为弥补这一不足,论文基于2008—2019年地级以上城市数据,从功能和绩效维度对中国14个城市群借用规模的存在性,以及借用规模发生的空间条件和形成机制展开研究。结果表明：① 从城市群层面看,长株潭、珠三角、武汉、辽中南、哈长、北部湾和京津冀7个城市群存在借用规模;从城市层面看,大城市更有可能同时借用功能和借用绩效,即存在借用规模,而中小城市更有可能借用功能,成渝、中原、山东半岛、粤闽浙沿海和长三角5个城市群存在集聚阴影。② 借用规模更频繁发生于多中心结构的城市群,大、中、小城市均能通过嵌入多中心结构城市群实现借用功能,但只有中等城市和大城市可以在多中心结构城市群中实现借用绩效,多中心结构对中等城市借用功能和借用绩效的影响最为明显。③ 增强城市的地理邻近程度将会降低借用功能,但可以提高借用绩效;增强城市的网络关联程度可以提高借用功能和借用绩效;对于借用功能而言,网络关联与地理邻近之间存在替代效应,对于借用绩效而言,网络关联与地理邻近之间存在互补效应;网络关联对借用功能和借用绩效的促进作用仅在大城市中能够显现。 相似文献