GIS中3维空间圆曲线的不确定性εσ模型

随着GIS向3维领域的不断发展,对3维空间元素的不确定性研究日趋重要.基于不确定性理论及概率统计理论,研究GIS中3维空间圆曲线的不确定性模型.首先建立3维空间圆曲线上任意点坐标的微分关系式,然后得到圆曲线上任意点坐标的方差, 进而获得3维空间圆曲线的εσ模型.实际算例表明,3维空间圆曲线误差分布呈现出"两端大,中间小"的趋势.     

Beyond the epsilon band: polygonal modeling of gradation/uncertainty in area-class maps

A spatial modeling technique is proposed to represent boundary uncertainty or gradation on area-class maps using a simple polygon tessellation with designated zones of indeterminacy or transition zones. The transition zone can be conceptualized as a dual of the epsilon band, but is more flexible and allows for a wide range of polygonal configurations, including polygons with sinuous boundaries, spurs, three-way transition zones, and null polygons. The model is specified using the medial axis to capture the general shape characteristics of a transition zone. Graph theoretic representation of an extended version of the medial axis captures key junctions in both shape and classification and is used to identify well-formed transition zones that can be logically and unambiguously handled by the model. A multivariate classification surface is specified by first defining degrees or probabilities of membership at every point on the medial axis and transition zone boundary. Degrees or probabilities of membership at all other points are defined by linear interpolation. The technique is illustrated with an example of a complex transition zone, and a simple isoline representation that can be derived from the model is presented. The proposed modeling technique promises to facilitate expert characterization of soil formations, ecological systems, and other types of areal units where gradation and/or boundary uncertainty are prevalent.     

基于高灵敏度检波器数据的分频匹配滤波方法及其应用(英文)

具有较高自然频率的高灵敏度检波器在采集数据时可以通过压制低频信号来相对提高高频能量,但这也造成了其低频响应差的问题,如果将高灵敏度数据与常规数据进行优势组合,就可以达到拓宽频带的目的。为此,本文提出分频段匹配滤波的方法,即在保持常规数据低频优势的前提下,对其高频端进行匹配滤波,实现不同频带范围内的优势互补,从而改善地震记录。通过引入不同主频的雷克子波模拟得到具有常规数据和高灵敏度数据特点的理论模型,论证了分频匹配滤波方法的可行性。在对野外单炮地震记录处理中发现,分频匹配滤波方法拓宽了地震记录的有效频带宽度,提高了地震记录的分辨率。     

Residual drift demands in moment‐resisting steel frames subjected to narrow‐band earthquake ground motions

This paper presents the main results of the evaluation of residual inter‐story drift demands in typical moment‐resisting steel buildings designed accordingly to the Mexican design practice when subjected to narrow‐band earthquake ground motions. Analytical 2D‐framed models representative of the study‐case buildings were subjected to a set of 30 narrow‐band earthquake ground motions recorded on stations placed in soft‐soil sites of Mexico City, where most significant structural damage was found in buildings as a consequence of the 1985 Michoacan earthquake, and scaled to reach several levels of intensity to perform incremental dynamic analyses. Thus, results were statistically processed to obtain hazard curves of peak (maximum) and residual drift demands for each frame model. It is shown that the study‐case frames might exhibit maximum residual inter‐story drift demands in excess of 0.5%, which is perceptible for building's occupants and could cause human discomfort, for a mean annual rate of exceedance associated to peak inter‐story drift demands of about 3%, which is the limiting drift to avoid collapse prescribed in the 2004 Mexico City Seismic Design Provisions. The influence of a member's post‐yield stiffness ratio and material overstrength in the evaluation of maximum residual inter‐story drift demands is also discussed. Finally, this study introduces response transformation factors, T_p, that allow establishing residual drift limits compatible with the same mean annual rate of exceedance of peak inter‐story drift limits for future seismic design/evaluation criteria that take into account both drift demands for assessing a building's seismic performance. Copyright © 2013 John Wiley & Sons, Ltd.     

地震模拟振动台三参量控制技术的研究

针对电液伺服振动台单纯的以位移控制为基础存在着使用频率狭窄和系统阻尼小的缺陷而不能很好地实现波形复现的问题,本文根据地震模拟振动台振动控制系统的工作性能,在对液压系统进行一定线性化处理的基础之上,搭建了系统的数学模型.在单纯位移控制的基础上,增加了加速度和速度环节设计三参量控制器,分别用PID控制和三参量控制的方法对电液振动台进行仿真研究,比较了PID控制和三参量控制的优缺点.仿真结果表明,三参量的方法能有效地增大系统阻尼防止共振破坏,增强了系统的稳定性.     

宅基地使用权登记发证工作探讨与思考

农村宅基地管理是土地管理的重要组成部分,涉及千家万户,关系到农民切身利益。在宅基地使用权确权、登记和发证工作中,应当积极思考和探索符合当地特定条件的方法和做法。规范管理和合理使用宅基地能够有效维护农民利益和社会稳定。     

一种气象卫星云图的坐标转换与配准方法研究

设计了气象卫星云图坐标转换与范围截取的算法,并基于ArcEngine组件实现了卫星云图的自动配准。实验证明,本文提出的方法可以快速有效地实现卫星云图的位置校正以及与基础地理数据的准确叠加,减少分析过程中的误差,提高气象卫星云图的使用效率,对天气监测及分析预报等工作提供了及时、有效、科学的辅助决策支持。     

Error analysis of satellite attitude determination using a vision-based approach

Improvements in communication and processing technologies have opened the doors to exploit on-board cameras to compute objects’ spatial attitude using only the visual information from sequences of remote sensed images. The strategies and the algorithmic approach used to extract such information affect the estimation accuracy of the three-axis orientation of the object.This work presents a method for analyzing the most relevant error sources, including numerical ones, possible drift effects and their influence on the overall accuracy, referring to vision-based approaches. The method in particular focuses on the analysis of the image registration algorithm, carried out through on-purpose simulations. The overall accuracy has been assessed on a challenging case study, for which accuracy represents the fundamental requirement. In particular, attitude determination has been analyzed for small satellites, by comparing theoretical findings to metric results from simulations on realistic ground-truth data. Significant laboratory experiments, using a numerical control unit, have further confirmed the outcome.We believe that our analysis approach, as well as our findings in terms of error characterization, can be useful at proof-of-concept design and planning levels, since they emphasize the main sources of error for visual based approaches employed for satellite attitude estimation. Nevertheless, the approach we present is also of general interest for all the affine applicative domains which require an accurate estimation of three-dimensional orientation parameters (i.e., robotics, airborne stabilization).     

空间信息服务管理机制研究

针对UDDI、CSW、Clearinghouse等空间信息服务注册与查找方式存在的不足,提出了空间信息服务管理机制,集成实现空间信息服务的搜索、描述、分类、组织、存储、发布、发现为一体的空间信息服务管理架构。基于此,实现了空间信息服务描述与注册、服务发现与调用等服务活动过程,为空间信息服务共享与增值应用奠定基础。     

Riegl VZ-400三维激光扫描仪数据的建模的研究

三维激光扫描技术是近年来发展起来的一门新技术,其在众多领域中有非常广阔的应用前景。本文介绍了三维激光扫描仪目前的应用现状,以及原理和数据后处理方法。最后通过青海玉树山体建模实例叙述了Riegl VZ-400扫描仪如何获取数据、点云数据的拼接及三维模型的建立。