基于位平面特征的SAR图像筛选

为了获取含有感兴趣特定目标的SAR图像,根据SAR图像目标的成像特性,提出了一种基于位平面特征的SAR图像筛选方法。在对图像适当的灰度预处理基础上,分析特定目标的先验知识,利用对位平面的复杂度度量、游程度量以及频谱度量,定义了位平面价值度量准则,同时结合图像的灰度直方图特征对图像进行筛选。实验以机场目标为对象对SAR图像进行快速筛选,并对机场目标进行提取,效果良好,能够满足预期的要求。     

Augmented 3D arrows for visualizing off-screen Points of Interest without clutter

When navigating through 3D environments from a first-person perspective, the limited field-of-view poses challenges in locating off-screen Points Of Interest (POIs), particularly when using the compact screen of a mobile phone. Existing techniques for visualizing off-screen POIs tend to clutter the screen, negatively affecting the visualization’s overall effectiveness. To resolve this problem, we propose a method for displaying off-screen POIs in high-density settings (with over 15 POIs). The proposed approach uses 3D arrows placed along the edges of the smartphone screen to point to the POIs. To minimize clutter, a cluster of POIs is represented by a single 3D arrow pointing to the cluster’s centroid. A model known as the cluttering threshold has also been developed to determine the number of POIs to include in a cluster while maintaining direction information. Additionally, a distance filter is implemented to reduce clutter in dense environments. The effectiveness of the proposed system was evaluated using a within-subject study involving 16 participants. The results indicate that our approach is considerably more efficient and accurate than the current state-of-the-art systems, namely, 3DWedge+ and Halo3D, particularly when the number of POIs in the environment is high.     

基于Agent的用户兴趣学习算法及其实现

通过对用户兴趣学习上的Bayesian算法和向量空间法的对比，提出了采用ID3算法实现用户兴趣学习，并介绍了其在智能引擎中的应用和具体实现方法。     

基于概率密度的兴趣点检测算法

针对基于亮度兴趣点检测算法存在对纹理敏感和兴趣点分布不均匀(集中于高对比度区域)问题, 提出了一种新颖的基于概率密度的兴趣点检测算法. 该算法在经典的Harris角点检测算法基础上, 利用亮度的概率密度梯度代替亮度的梯度构建二阶矩矩阵, 进行兴趣点检测. 与基于亮度的Harris检测算法相比, 新算法不仅具有同样的几何不变性, 还有效地抑制了纹理中的``噪声'兴趣点, 并且兴趣点分布的均匀性明显优于基于亮度算法的检测结果.     

Joint maximum likelihood estimation of unit root testing equations and GARCH processes: Some finite-sample issues

In recent research [B. Seo, Distribution theory for unit root tests with conditional heteroskedasticity, J. Econometrics 91 (1999) 113–144] has suggested that the examination of the unit root hypothesis in series exhibiting GARCH behaviour should proceed via joint maximum likelihood (ML) estimation of the unit root testing equation and GARCH process. The results presented show the asymptotic distribution of the resulting ML t-test to be a mixture of the Dickey–Fuller and standard normal distributions. In this paper, the relevance of these asymptotic arguments is considered for the finite samples encountered in empirical research. In particular, the influences of sample size, alternative values of the parameters of the GARCH process and the use of the Bollerslev–Wooldridge covariance matrix estimator upon the finite-sample distribution of the ML t-statistic are explored. It is shown that the resulting critical values for the ML t-statistic are similar to those of the Dickey–Fuller distribution rather than the standard normal, unless a large sample size and empirically unrealistic values of the volatility parameter of the GARCH process are considered. Use of the Bollerslev–Wooldridge standard covariance matrix estimator exaggerates this finding, causing a leftward shift in the finite-sample distribution of the ML t-statistic. The results of the simulation analysis are illustrated via an application to U.S. short term interest rates.     

星载SAR图像机场兴趣区检测算法

提出一种解决低信噪比、大尺寸的星载合成孔径雷达(SAR)图像机场兴趣区(ROI)自动检测问题的方法。对图像进行基于马尔可夫场的分割,由目标标记方法确定ROI的候选区。用Hough变换检测跑道平行线,滤除部分伪ROI。计算ROI候选区的跑道方向投影直方图及目标的宽、高、宽高比、目标背景面积比和目标背景灰度比5个参数,用支持向量机对样本参数进行学习,完成ROI的最终判定。用实际星载SAR图像进行试验,结果表明了该方法的有效性和可靠性。     

无线传感器网络路由协议分析与改进

定向扩散(directed diffusion,DD)协议的兴趣扩散和发送探测分组数据阶段,采用的洪泛方式能量开销较大.先对定向扩散协议进行研究分析,提出利用节点的区域信息控制兴趣数据包的转发和通过最佳跳数值控制探测数据的扩散范围.最后通过仿真验证改进的定向扩散协议具有更好的节能性和适应性.     

信息过滤系统中用户文档更新策略研究

信息过滤系统(IF Systems)的目的是为了帮助用户查找用户感兴趣的信息。IF系统的用户文档(User Profiles)表示用户的兴趣，用来匹配网络上的信息。当用户的兴趣发生变化时，用户文档就变得不精确，过滤质量下降。用户的兴趣变化不定，IF系统如何及时快速地更新用户文档以缩短系统性能下降的时间就变得非常的重要。通过对现有IF系统用户文档更新方法的研究，分析了它们的独到之处和存在的不足。     

地铁出行模式下的城市时空可达性研究

传统的空间可达性不能反映不同OD间可达程度的差异,为此,研究提出了在地铁出行模式下的城市时空可达性表达模型。该模型以地铁站点的服务范围作为研究的基本单元,各服务范围包含了不同种类与数量的兴趣点,模型以兴趣点的可自由活动时间作为时间约束,以可达范围作为空间约束,研究地铁两站点在时间和空间的共同约束下相对于整个区域的时空可达情况。通过对广州市地铁网的实例研究与分析,证明了该模型可以实现面向个人的可达性表达,提高了时空可达性研究的实用价值与应用水平,丰富了城市交通规划的理论依据。     

多方博弈下的城中村改造利益均衡模式探讨——以郑州市冉屯村改造控制性详细规划为例

随着城镇化进程的持续推进,城中村如何融入城市、外来人口如何真正落脚城市,已成为困扰各大城市经济社会发展的迫切问题。研究从梳理城中村改造中六个利益主体的自身诉求入手,分析三大主要利益主体之间及与次利益主体之间的博弈关系,构建多方博弈下的城中村改造利益均衡模式,在政府角色承担、开发强度确定、廉租群体利益保障等方面给出相应的方法。最后通过郑州市冉屯村改造控制性详细规划,解释这一模式在具体案例中的应用,实践如何通过博弈实现最终的多方共赢。