Assessment of the MODIS LAI product for Australian ecosystems

The leaf area index (LAI) product from the Moderate Resolution Imaging Spectroradiometer (MODIS) is important for monitoring and modelling global change and terrestrial dynamics at many scales. The algorithm relies on spectral reflectances and a six biome land cover classification. Evaluation of the specific behaviour and performance of the product for regions of the globe such as Australia are needed to assist with product refinement and validation. We made an assessment of Collection 4 of the MODIS LAI product using four approaches: (a) assessment against a continental scale Structural Classification of Australian Vegetation (SCAV); (b) assessment against a continental scale land use classification (LUC); (c) assessment against historical field-based measurement of LAI collected prior to the Terra Mission; and (d) direct comparison of MODIS LAI with coincident field measurements of LAI, mostly from hemispherical photography. The MODIS LAI product produced a wide variety of geographically and structurally specific temporal response profiles between different classes and even for sub-groups within classes of the SCAV. Historical and concurrent field measurements indicated that MODIS LAI was giving reasonable estimates for LAI for most cover types and land use types, but that major overestimation of LAI occurs in some eastern Australian open forests and woodlands. The six biome structural land cover classification showed some significant deviations in class allocation compared to the SCAV particularly where grasslands are allocated to shrubland, savanna woodlands are allocated to shrubland, savanna and broadleaf forest, and open forests are allocated to savanna and broadleaf forest. The land cover and LAI products could benefit from some additional examination of Australian data addressing the structural representation of Eucalypt canopies in the “space of canopy realisation” for savanna and broadleaf forest classes.     

软件质量的模糊综合评判研究与应用

通过软件质量的模糊综合评估实践,首先分析了原模糊综合评判算法模型中以“取大取小”运算而使评估过程中产生大量有效信息丢失并导致评估结果出现过于简单化、绝对化的不足和缺陷,进而重点研究如何在保留原模糊综合评估算法良好结构的基础上将“取大取小”运算转变为矩阵乘法运算的改造,并以此建立适应现代软件质量综合评估需求的新算法模型实施软件质量的可计算化评估,提高了软件质量评估的准确性、实用性和可靠性。     

中文信息导航系统的关键软件技术分析

信息导航系统的设计与开发涉及广泛的技术问题。介绍了信息导航系统的特点和现状以及信息导行系统的总体设计，并主要就大规模中文信息导航系统设计中的关键软件技术进行了讨论，包括搜索引擎Robot、中文信息处理系统和导航系统相关服务的设计及其需要解决的主要技术问题，并提供了相应问题的解决方法。最后，简要提到了导航系统设计中需要解决的主要硬件技术问题。     

低折射率液芯光纤特性的研究

研究了以低折射率液体（ｎ≥１．３４６）及乙醇等水溶液的液芯光纤的传输特性和光谱特性，分析了影响芯光传输特性的因素及其对光强调制型芯光纤传感器的影响。     

密文数据库查询优化技术①

为了解决数据库加密后查询效率低的问题,针对数据库加密技术的实际应用,提出了一些解决方案。通过对数值型密文数据使用标志位,为字符型数据创建外存索引文本,缩小了查询范围,提高了数据查询效率。最后进行实验测试分析,证实了方法的有效性。     

Estimating aerodynamic resistance of rough surfaces using angular reflectance

Current wind erosion and dust emission models neglect the heterogeneous nature of surface roughness and its geometric anisotropic effect on aerodynamic resistance, and over-estimate the erodible area by assuming it is not covered by roughness elements. We address these shortfalls with a new model which estimates aerodynamic roughness length (z₀) using angular reflectance of a rough surface. The new model is proportional to the frontal area index, directional, and represents the geometric anisotropy of z₀. The model explained most of the variation in two sets of wind tunnel measurements of aerodynamic roughness lengths (z₀). Field estimates of z₀ for varying wind directions were similar to predictions made by the new model. The model was used to estimate the erodible area exposed to abrasion by saltating particles. Vertically integrated horizontal flux (F_h) was calculated using the area not covered by non-erodible hemispheres; the approach embodied in dust emission models. Under the same model conditions, F_h estimated using the new model was up to 85% smaller than that using the conventional area not covered. These F_h simulations imply that wind erosion and dust emission models without geometric anisotropic sheltering of the surface, may considerably over-estimate F_h and hence the amount of dust emission. The new model provides a straightforward method to estimate aerodynamic resistance with the potential to improve the accuracy of wind erosion and dust emission models, a measure that can be retrieved using bi-directional reflectance models from angular satellite sensors, and an alternative to notoriously unreliable field estimates of z₀ and their extrapolations across landform scales.     

DOG线条检测器在三维轮廓光切法测量中的应用

论文介绍了在三维轮廓光切法中提取二维轮廓光带中心线的传统方法,针对传统方法依赖于对轮廓光带精确分割的问题,提出了一种直接使用DOG(DifferenceofGaussian)线条检测器提取轮廓光带中心线的新方法。实验结果表明该方法具有好的准确性及较强的抗噪声能力。     

一种对等式存储系统的设计与实现

一方面信息量的爆炸式增长对传统的存储模型提出了严峻挑战,另一方面宽带广泛普及、计算机性能大幅度提升,在此背景下,以Pber-to-Peer的方式对存储资源进行管理成为可能。提出了系统的体系结构和模块组织,重点探讨存储资源的发布与发现以及数据的存取与维护,通过覆盖网的路由和定位机制均衡存储管理负载,通过数据分片与剐本机制增加系统可靠性,并对系统的设计与实现要点进行分析。结果表明对等式存储系统是可行的。     

警务绩效的模糊综合评价方法研究

警务绩效评估有利于强化警察机构的组织管理,提高警察的工作效能。针对警务绩效的综合评价问题,制定了警务绩效评估原则,建立了多因素、多层次的警务绩效评价指标体系,并基于模糊数学的评判理论,提出对警务绩效进行整体评价的多级模糊综合评价方法,最后通过一个应用实例,验证了该方法的有效性和实用性。     

质子交换膜燃料电池的连续模型预测控制器的设计

在对质子交换膜燃料电池(PEMFC)的工作原理进行研究分析的基础上,对其进行了数学描述,在Matlab/Simulink仿真平台下建立了质子膜燃料电池的动态仿真模型。维持PEMFC系统的正常运行需要良好的控制系统。通过将拉盖尔函数应用到连续模型预测控制(CMPC)算法中去,分析了CMPC的不足之处并通过指数权值函数进行了简单的修正,随后将两种控制策略与传统的离散预测控制(DMPC)施加到PEMFC系统中去并进行了仿真对比分析,仿真结果证明了CMPC算法的有效性以及优越性。