基于分层Arnold变换的置乱算法

针对数字图像信息隐藏存在的安全问题,提出一种基于按位分层Arnold变换的置乱算法。算法将秘密图像按位平面分层,同时考虑图像的位置迁移和像素的灰度变换,对每个位平面进行不同次数的Arnold变换,经像素交叉换位,相邻像素间按位异或得出置乱图像。实验结果表明,秘密图像分层置乱后直方图分布更加均匀,与白噪声相似度在0.962左右,置乱图像可近无损地还原和提取,提高了信息隐藏的鲁棒性。与其他置乱算法相比,置乱图像具有更高的置乱度、更强的抵御攻击能力,提高了空域信息隐藏的安全性。     

针对Kriging插值结果的空间查询方法

Kriging插值方法及其各种改进模型已被广泛应用,但由于其插值结果是栅格形式,因此不利于与矢量数据叠加分析。为了更加便捷地使用插值结果,在衡量Voronoi图和最小外接矩形特点的基础上,提出了适用于Kriging插值结果的数据结构及空间查询方法。查询某一点位的特征值时,先通过区域的最小外接矩形初步判断出该位置可能存在的区域,进而逐一判断点与所选区域的空间关系,根据点所在区域的属性值得到该点位的特征值。该方法实现了对Kriging插值结果的空间查询,其正确性通过某露天矿的实际运行数据得到了验证。实验结果表明,该方法的查询效率控制在毫秒级,能够满足矿区车载终端程序及类似应用的需求。     

角色群体协作中的层次感知模型研究

群体感知是群体协作有效进行的前提条件.在分析当前群体感知模型及群体协作模型研究现状的基础上,以角色为协作基础,根据任务相关度、协作者间组织结构的紧密程度来进行分层感知,提出了一种支持层次角色群体感知的模型(role based hierarchical awareness model,简称RHAM).RHAM 首先构建了一个群体协作环境(group cooperation environment,简称GCE),然后在GCE 的基础上扩展定义群体协作感知内容、感知层次及感知相关特性.最后对该模型的应用进行了     

Watershed scale temporal and spatial stability of soil moisture and its role in validating satellite estimates

Watershed scale soil moisture estimates are necessary to validate current remote sensing products, such as those from the Advanced Microwave Scanning Radiometer (AMSR). Unfortunately, remote sensing technology does not currently resolve the land surface at a scale that is easily observed with ground measurements. One approach to validation is to use existing soil moisture measurement networks and scale these point observations up to the resolution of remote sensing footprints. As part of the Soil Moisture Experiment 2002 (SMEX02), one such soil moisture gaging system in the Walnut Creek Watershed, Iowa, provided robust estimates of the soil moisture average for a watershed throughout the summer of 2002. Twelve in situ soil moisture probes were installed across the watershed. These probes recorded soil moisture at a depth of 5 cm from June 29, 2002 to August 19, 2002. The sampling sites were analyzed for temporal and spatial stability by several measures including mean relative difference, Spearman rank, and correlation coefficient analysis. Representative point measurements were used to estimate the watershed scale (∼25 km) soil moisture average and shown to be accurate indicators with low variance and bias of the watershed scale soil moisture distribution. This work establishes the validity of this approach to provide watershed scale soil moisture estimates in this study region for the purposes of satellite validation with estimation errors as small as 3%. Also, the potential sources of error in this type of analysis are explored. This study is a first step in the implementation of large-scale soil moisture validation using existing networks such as the Soil Climate Analysis Network (SCAN) and several Agricultural Research Service watersheds as a basis for calibrating satellite soil moisture products, for networks design, and designing field experiments.     

宁夏农田土壤耕层养分含量的时空变化特征

根据土壤普查资料和实际采样测定结果,探讨了宁夏山区和灌区农田土壤耕层有机质和氮磷钾养分含量的时空变化特征。结果表明,在1970年、1985年和2000年3个时段内,土壤有机质、有效磷和碱解氮含量呈显著或较显著增长态势,土壤速效钾含量近15年在灌区明显下降,土壤氮磷钾全量养分在30年间没有明显变化。从两个地区比较来看,除土壤全磷量外,土壤有机质和其它养分含量都是灌区显著高于山区,而变异系数除土壤全钾外都是山区显著大于灌区。     

主动授权规则实施支持空间特性的RBAC*

为满足安全策略或者角色定义的变化,系统或模型应该提供一种灵活的机制实施支持空间特性的RBAC。引入了OITE（on-if-then-else）主动授权规则实施支持空间特性的RBAC,定义了支持空间特性的RBAC中各基本元素与OITE之间的映射关系。使用OITE作为实施机制,可以在不同粒度上实施带有空间特性角色约束,并且可以将支持空间特性的RBAC应用在多个领域中。最后简要讨论了授权规则如何从支持空间特性的RBAC安全策略中自动产生。     

高安全属性价值设备威胁态势量化评估方法

传统的网络安全态势量化评估方法主要面向宏观网络安全态势,未针对安全价值较高的网络设备,给出了高安全属性价值设备的定义,设计了针对设备的威胁态势量化评估框架和评估指标,根据评估框架和指标提出了高安全属性价值设备威胁态势量化评估方法。对具体网络中实际设备的评估结果表明,该方法能够准确、有效地量化评估高安全属性价值设备的威胁态势。     

基于GIS的农村社会经济统计信息系统技术

将GIS技术应用于农村统计领域,通过制定统计行业空间信息化建设标准与规范,实现了系统与现有统计政务系统的数据共享。提出并研究了统计数据空间化处理、空间统计分析和多维可视化表达的技术方法体系,从农村统计业务流的角度进行系统数据库设计、框架搭建以及功能模块设计,在此基础上构建了系统原型并在国家统计局进行示范应用。实践证明,建立时空一体化的信息支撑平台,对于推动我国农村统计部门的政务信息化建设起到了积极作用。     

基于最大似然估计的空间谱测向技术

介绍了基于最大似然估计（简称ML）的空间谱测向,ML是一种高分辨算法,常用于空间测向和谱估计等方面。文中首先介绍了ML测向原理,由于ML是一个非线性、多维的极值问题,需要全局极值的多维搜索,其计算量非常的巨大,因此采用了AP算法进行ML算法的优化,最后通过均匀圆阵对非相干信号和相干信号进行了ML测向的计算机仿真,仿真结果表明：一个阵列对空间多个信号的分辨能力除了与信噪比有关外,还与入射信号是否相干以及两相干信号的相位差有关,ML算法可以直接对相干的入射信号进行测向,但是信号的相干性会影响ML算法测向的角度分辨率,在两信号相关的情况下,两信号间的相位差越大则测向精度越高。     

The role of metacognitive listening strategies awareness and podcast-use readiness in using podcasting for learning English as a foreign language

The aim of this study was to investigate the role of English as Foreign Language (EFL) learners’ metacognitive listening strategies awareness and podcast-use readiness in using podcasting technology for learning English as a foreign language. One hundred and forty-one EFL students completed Metacognitive Awareness Listening Questionnaire (MALQ) that assessed their awareness and perceived use of listening strategies in five components including planning-evaluation, directed attention, person knowledge, mental translation, and problem solving. They also completed a questionnaire that assessed their readiness to use podcasting in terms of familiarity, attitude, and experience. Information on participants’ frequency of podcast use for learning English, frequency of the internet use, and digital device ownership was also obtained. The result of the analysis revealed that podcasting use was significantly related to metacognitive listening strategies awareness in general and its entire components except mental translation strategies while the strongest correlation was found with problem solving strategies (r = .49, p < 0.01). Podcasting use was also found to be significantly related to perceived podcast-use readiness and internet use hours. Further, multiple regressions showed that perceived podcast-use readiness, problem solving, and person knowledge -in order of power prediction- were good predictors of podcasting use for learning English as a foreign language.