SWDC数码航摄区域网控制点布设的精度试验

介绍了SWDC数码航摄影像的技术基础和其应用于航空摄影测量的优越性,鉴于SWDC像幅的特殊性,在保证量测精度的前提下,为减少外业作业的工作量,通过以不同基线的区域网像片控制点布设方案的精度试验,证明了控制点按照8条基线布设可满足内业生产及大比例尺地形图的需要。     

大比例尺数字测图质量控制方法探讨

大比例尺数字测图正以其测图精度高、成图速度快等优势逐步取代传统的以平板为主的模拟测图.与传统的模拟测图相比,数字测图的质量控制关键点更多、内容与方法更为复杂.结合厦门市西北部测区2003年大比例尺数字图测绘工程的实施情况,就如何在数字测图的各个环节实施质量控制,确保最终数字测绘产品成果(DLG)的数据质量,进行探讨.     

空间信息技术是防洪减灾现代化的基础

我国洪涝灾害频繁,洪灾损失严重,防洪减灾将是一项长期而艰巨的任务。在防洪减灾研究中,必须积极引进当今最新科学技术成果,以高新技术改造水利这一传统产业,以水利信息化推动水利现代化。以遥感、地理信息系统和全球导航定位系统为支撑的空间信息技术可以广泛地应用于防洪减灾中,是防洪减灾现代化的基础。本文分析了空间信息技术在防洪减灾中的作用,并对空间信息技术在防洪减灾中的应用趋势作出展望。     

GIS中曲线综合平差模型的建立

针对大中比例尺地图中的行政界线、地块权属界线的制图综合问题,利用Douglas Peuker算法,提出距离阈值自适应求解算法对图形进行综合;将平差理论应用于综合后图形的处理中,保证图形的综合质量。讨论了面积、长度、固定点、直角/直线条件的建立,结合实例,研究了综合、平差的算法框架与实施步骤。     

城市基础地理空间数据建库中的质量控制研究

基础空间数据库是数字城市的核心,而数据质量的高低又是数据库建设成功与否的关键。本文在简要分析数字城市基础空间数据库构建过程的前提下,详细论述了数字城市基础空间数据建库中需进行的质量控制内容及方法。     

EXTERNAL CONTROL OF NONMETROPOLITAN INDUSTRY IN KENTUCKY

The organizational separation of management and other quaternary activities from production operations in American manufacturing has resulted in a divergent pattern of production and headquarter locations. We examine the external control relationships that arise from this separation between headquarter location and branch plant operations in nonmetropolitan Kentucky. Although corporate headquarters have diffused to the Sunbelt, no shift was found in the corporate control of branch plants in Kentucky. Nonmetropolitan manufacturing in Kentucky was oriented toward the metropolitan centers of the traditional manufacturing belt rather than the newer corporate centers of the South. Also control relationships are more likely to be local among smaller factories. Large plants having more autonomy in production or producing finished goods were more likely to be owned by a distant firm located in a large SMSA.     

雪崩防治工程研究与应用现状

雪崩是对高寒山区房屋、设施、道路安全威胁最大的自然灾害之一.在目前雪崩监测预警技术还很不完善的情况下,发展灾害防治工程技术是避免或减轻雪崩对人类生命财产损失的重要措施.对国际上常用雪崩防治工程进行分类,重点按作用手段分别阐述了各种防治工程的研究与应用现状,对防治工程研究进展、适用范围、设计要求、应用情况等关键问题进行了总结和探讨.研究认为,目前的雪崩灾害防护工程存在修筑标准欠缺、雪崩机理不明确、工程设计参数计算不合理、试验模拟不理想、基础理论研究落后于实践活动等不足,并建议从工程综合配置、雪崩与防护结构相互作用、工程设计参数定量化研究、开发积雪清理技术、构建监测预警系统等方面开展先行工作.     

Vegetative succession and controlled fire in a glades ecosystem A geographical information system approach

Abstract

A geographical information system (GIS) approach was used successfully on a federal wilderness area in southwestern Missouri to examine vegetative succession relative to fire management in a glades ecosystem. Maps of vegetation were obtained by interpreting aerial photographs taken in 1938, 1958, 1966, 1975 and 1986. Maps of topography, streams, soils and the location of fires which burned during the period 1938 to 1986 were also procured from a variety of public agencies. All maps were digitized and incorporated into a raster-based GIS with 25 m pixels. It was concluded that (1) both glades and oak-hickory forest have an affinity for distinct physiographic areas and (2) fire can help decrease the rate of processes of natural succession which cause glades to convert to forest. The probable effects of controlled fire on three areas proposed by the Forest Service were evaluated and summarized.     

Effective force testing using a robust loop shaping controller

Effective force testing (EFT) is one of the force‐based experimental methods used for performance evaluation of structures that incorporate dynamic force control using hydraulic actuators. Although previous studies have shown successful implementations of force control, controllable frequency ranges are limited to low frequencies (10 Hz). This study presents the EFT method using a robust loop shaping force feedback controller that can extend the frequency range up to 25 Hz or even higher. Unlike the conventional PID controllers, loop shaping controllers can provide robustness for a high level of force measurement noise. This study investigates the dynamic properties of hydraulic actuators and the design of a loop shaping controller that compensates for control–structure interaction and suppresses the effect of oil‐column resonance. The designed loop shaping controller was successfully implemented into an EFT setup at the Johns Hopkins University. An experimental investigation of the loop shaping controller was performed under step, random, and earthquake force loadings. Experimental results showed that the loop shaping controller provided excellent force tracking performance and robustness for dynamic force loadings. It was also shown that the loop shaping controller had the gain margin of 9.54 dB at the frequency of 28 Hz. Copyright © 2012 John Wiley & Sons, Ltd.     

Seismic response of steel structures with seesaw systems using viscoelastic dampers

Vibration control systems are being used increasingly worldwide to provide enhanced seismic protection for new and retrofitted buildings. This paper presents a new vibration control system on the basis of a seesaw mechanism with viscoelastic dampers. The proposed vibration control system comprises three parts: brace, seesaw member, and viscoelastic dampers. In this system, only tensile force appears in bracing members. Consequently, the brace buckling problem is negligible, which enables the use of steel rods for bracing members. By introducing pre‐tension in rods, long steel rods are applicable as bracing between the seesaw members and the moment frame connections over some stories. Seesaw mechanisms can magnify the damper deformation according to the damper system configuration. In this paper, first, the magnification factor, that is, the ratio of the damper deformation to the story drift, is delivered, which includes the rod deformation. Results of a case study demonstrate that the magnification factor of the proposed system is greater than unity for some cases. Seismic response analysis is conducted for steel moment frames with the proposed vibration control system. Energy dissipation characteristics are examined using the time‐history response results of energy. The maximum story drift angle distributions and time‐history response results of displacement show that the proposed system can reduce the seismic response of the frames effectively. Copyright © 2012 John Wiley & Sons, Ltd.