基于PowerBuilder的信息系统的权限控制     

罗卫敏 《成都信息工程学院学报》2004,19(2):209-213

针对信息系统安全的考虑,介绍在PowerBuilder环境中对用户权限的具体控制.  相似文献   

GALILEO系统局域完备性监测设计与实现     

赵春梅  程鹏飞  高星伟 《测绘学报》2008,37(1):0-113

根据GALILEO系统局域完备性概念和网络RTK的基本理论,建立导航系统局域网络完备性监测理论和算法。算法主要包括网络系统完备性算法和用户完备性算法,内容包括网络误差模型的建立、插值算法的选择、误差改正数完备性指标的计算、完备性指标的验证和用户保护水平的计算等。仿真结果表明,采用网络RTK技术和完备性监测算法,飞机的平面保护水平和垂直保护水平均小于完备性告警门限值,可以满足飞机Ⅱ类和Ⅲ类精密进近的完备性要求,为卫星导航系统在民航中的应用提供完备性理论基础。  相似文献   

宽带接入用户认证技术分析与比较   总被引：2，自引：0，他引：2  

张卫锋  郭科  李加华 《物探化探计算技术》2003,25(2):173-177

给出了一个宽带接入用户认证系统的基本模型，并基于此模型对目前被广泛应用的PPPoE、WEB、DHCP等用户认证技术进行了分析与比较。最后，简单介绍了用户认证技术的新成员-802．1x(Port Based Network Access Control Protoco1)协议。  相似文献   

GPS广播星历参数拟合算法   总被引：25，自引：2，他引：25  

崔先强焦文海  贾小林尹豫疆 《测绘学院学报》2004,21(4):244-246

介绍了GPS广播星历参数的最小二乘估计方法。推导了相应的计算公式。计算结果表明。文中给出的公式是正确的，其拟合精度以用户距离误差(URE)示时，对预报轨道的损失小于1cm。  相似文献   

Enhancement of backtracking search algorithm for identifying soil parameters     

Yin-Fu Jin  Zhen-Yu Yin 《国际地质力学数值与分析法杂志》2020,44(9):1239-1261

In this paper, an enhanced backtracking search algorithm (so-called MBSA-LS) for parameter identification is proposed with two modifications: (a) modifying the mutation of original backtracking search algorithm (BSA) considering the contribution of current best individual for accelerating convergence speed and (b) novelly incorporating an efficient differential evolution (DE) as local search for improving the quality of population. The proposed MBSA-LS is first validated with better performance than the original BSA and some other typical state-of-the-art optimization algorithms on a benchmark of soil parameter identification in terms of effectiveness, efficiency, and robustness. Then, the efficiency of the MBSA-LS is further illustrated by two representative cases: identifying soil parameters from both laboratory tests and field measurements. All comparisons demonstrate that the proposed MBSA-LS algorithm can give accurate results in a short time. Finally, to conveniently solve the problems of parameter identification, a practical tool ErosOpt for parameter identification is developed by integrating the proposed MBSA-LS and some other efficient algorithms for readers to conduct the parameter identification using optimisation algorithms.  相似文献   

Measured and perceived visual complexity: a comparative study among three online map providers     

Susan Schnur  Kenan Bektaş 《制图学和地理信息科学》2018,45(3):238-254

We present a study on human perception of map complexity, with the objective of better understanding design decisions that may lead to undesirable levels of complexity in web maps. We compare three complexity metrics to human ratings of complexity obtained through a user survey. Specifically, we use two algorithmic approaches published by others, which measure feature congestion (FC) and subband entropy (SE), as well as our own approach of counting object types rather than individual objects. We compare these metrics with each other as well as with human complexity ratings for three maps of the same area from map providers Google Maps, Bing Maps, and OpenStreetMap. Each map design is assessed at three different scales (levels of detail). We find that (1) the FC and SE metrics appear to be adequate predictors of what humans consider complex; (2) object-type counts are slightly less successful at predicting human-rated complexity, implying that clutter is more important in perceived complexity than diversity of symbology; and (3) generalization choices do impact human complexity ratings. These findings contribute to our understanding of what makes a map complex, with implications for designing maps that are easy to use.  相似文献   

The effects of visual realism,spatial abilities,and competition on performance in map-based route learning in men     

Arzu Çöltekin  Rebecca Francelet  Kai-Florian Richter  John Thoresen  Sara Irina Fabrikant 《制图学和地理信息科学》2018,45(4):339-353

We report on how visual realism might influence map-based route learning performance in a controlled laboratory experiment with 104 male participants in a competitive context. Using animations of a dot moving through routes of interest, we find that participants recall the routes more accurately with abstract road maps than with more realistic satellite maps. We also find that, irrespective of visual realism, participants with higher spatial abilities (high-spatial participants) are more accurate in memorizing map-based routes than participants with lower spatial abilities (low-spatial participants). On the other hand, added visual realism limits high-spatial participants in their route recall speed, while it seems not to influence the recall speed of low-spatial participants. Competition affects participants’ overall confidence positively, but does not affect their route recall performance neither in terms of accuracy nor speed. With this study, we provide further empirical evidence demonstrating that it is important to choose the appropriate map type considering task characteristics and spatial abilities. While satellite maps might be perceived as more fun to use, or visually more attractive than road maps, they also require more cognitive resources for many map-based tasks, which is true even for high-spatial users.  相似文献   

适用于遥感领域的交互式图像处理系统     

余旭初 《测绘学院学报》1995,(2)

数字图像处理技术的广泛应用使很多与图像相关的领域产生了根本性的变革。反过来，这些变革也对数字图像处理提出更高的要求，而计算机和人工智能技术的迅速发展为建立新的、面向具体应用的图像处理系统提供了现实的可能性。本文展示了一个基于Ｕｎｉｘ工作站的、适用于遥感领域的交互式图像系统的设计框架和主要功能。  相似文献   

基于用户星精密轨道的TDRS卫星定轨     

李敏  施闯 《测绘信息与工程》2006,31(6):29-31

分析了TDRS卫星的轨道特性及传统的地基测距跟踪技术定轨精度不高的现状,研究了基于空基的用户星精密轨道的TDRS卫星定轨,解决了基于空基的一般GEO卫星定轨问题。  相似文献   

USERS′ PERCEPTION OF KOWLOON PARK, HONG KONG： VISITING PATTERNS AND SCENIC ASPECTS   总被引：1，自引：0，他引：1  

Wong Koon-kwai  Manfred Domroes 《中国地理科学(英文版)》2004,14(3):269-275

Hong Kong is a hyper-dense city with 7×10⁶ people living in an area of 1100km². One way to improve the livability of compacted and congested cities like Hong Kong is through the provision of urban parks, an aspect that has largely been under-researched. This study focuses on how users perceive and utilize various facilities in the Kowloon Park. The findings revealed that the Kowloon Park is one of the most preferred parks in Hong Kong for both local residents and tourists. Users were quite satisfied with the park’s facilities. Notably, the most important component of an urban park is its greenery. This is followed by water elements, seating places, and facilities for various recreational activities. The improvements users would like to see in urban parks include good design and management, meeting users’ needs, overcoming barriers to use, and providing a high quality and varied experience for different groups in the community. The findings of this study provide a good basis to address park management issues from the users’ perspective. In particular, parks should provide easy access, encourage optimum usage and enable complimentary improvements to the environment. Foundation item: Under the auspices of the Germany-Hong Kong Joint Research Scheme (No.GER/99-00/01) and the Faculty Research Grant of the Hong Kong Baptist University (No.FRG/00-01/I-38) Biography: WONG Koon-kwai (1950—), male, a native of Guangdong Province, Ph.D., associate professor, specialized in the analysis of human-environment interaction. E-mail: kenwong@hkbu.edu.hk  相似文献