古地图复原与校正方法实验研究

在中国古代地图绘制中,计里画方和山水形象画法是2个显著特色。然而,由于没有数学基础或没有明确的数学基础,使得地图定位精度大大降低,给古地图的处理和地理配准工作带来很大困难。本文将古地图的定位基准现状,分为完全没有地理参考、有部分地理参考和有较精确地理参考进行分析,从资料选取、预处理、辐射校正和图面信息复原角度探讨古地图的修复方法,并以部分近代地图为例进行地图拼接实验。最后,针对不同定位基准类型的古地图,分别采用特征点校正、分块（网格）匹配和相对位置转移等方法,完成古地图与现代地图的地理匹配,研究了计里画方地图与不同地理参考系、投影之间的数理关系。在古地图数字化、编辑、纠正和配准的基础上,尝试研究和建立校正后的古地图和现代地图的数理关系,探究古代舆图坐标基准和坐标体系与现代地图系统的关系,为建立古今坐标体系对照的数理关系打下基础。     

北京地震台gPhone重力仪对尼泊尔M8.1强震所激发地球自由振荡的探测

利用北京地震台gPhone重力仪观测资料,采用功率谱密度估计方法,检测2015-04-25尼泊尔M8.1地震激发的0S0～0S60之间的地球球型自由振荡,并与地球初步参考模型(PREM)的理论自由振荡周期进行对比。结果表明,0S2～0S56基频自由振荡的实测周期值与PREM 模型的理论值基本一致,证实了gPhone重力仪能有效检测出地球自由振荡信号。     

剩余地形模型高程异常计算的积分法及精度分析

以构建剩余地形模型高程异常的数字地形模型的分辨率及其参考面的选择为研究对象,系统分析两者对剩余地形模型高程异常计算效率及精度的影响。实验结果表明：1）将DTM2006.0模型作为参考面时,在海岸带区域产生较大的误差,而在陆地与RET2012和RET2014模型的计算结果相差不大;2）在构建我国东部地区剩余地形模型高程异常时,为保证计算效率及精度,计算时内外圈的积分半径分别取50 km和200 km,SRTM数据的分辨率分别采用7.5″和15″,参考面模型使用RET2012。     

山东省生态地球化学调查与评价综述

自2002年开展生态地球化学调查以来,山东省生态地球化学调查已覆盖全省陆域和部分近岸海域,面积161370km2。该文介绍了山东省生态地球化学调查评价的基本情况和方法技术,并以获取的海量地球化学数据为基础,对多目标区域地球化学调查、区域生态地球化学评价成果进行了系统总结,为山东省社会经济发展提供了基础平台。     

利用数字图像相关方法实现高速相机序列影像运动目标的快速跟踪

以数字图像相关方法为核心设计了一套应用于高速相机序列影像运动目标的跟踪方案,该方案首先在基准窗口周围以局域搜索方法获取目标点的整像素位移值,然后联合使用梯度算法和最小二乘算法估计目标点的亚像素位移值,从而获得目标点的像素坐标,实现对目标点的自动跟踪。本文应用该技术方案处理了构筑物振动台实验的高速相机视频测量影像数据,与商用软件PhotoModeler Scanner 相比,跟踪结果具有同等精度,在计算速度上有优势。     

Hargreaves公式在塔克拉玛干沙漠腹地的适用性

对运用Hargreaves公式计算参考作物蒸散量(ET0)在干旱区的适用性存在不同观点。为了求证Hargreaves公式在极端干旱区塔克拉玛干沙漠腹地的适用性,利用2005-2010年塔克拉玛干沙漠研究站的气象资料,以利用Penman-Monteith公式计算的结果为标准,对利用Hargreaves公式计算的ET0进行了对比分析,并对两种计算结果差异的成因进行了阐释。结果表明:在年时间尺度上,利用Hargreaves公式计算的结果略大于利用Penman-Monteith公式计算的结果,标准差介于32.86~35.00 mm,年参考作物蒸散量计算结果呈现弱变异程度;在月时间尺度上,用两种方法计算的参考作物蒸散量呈现中等变异程度,蒸散量绝对偏差介于-3.26~8.73 mm,相对偏差介于-12.20%~29.02%,除了10月与11月,其余月份相对偏差均保持在10%之内。用两种方法计算的10月与11月份ET0产生差异的最主要原因在于有较高的温度较差。最后,经过对年、月参考作物蒸散量进行t-检验及建立回归方程,表明Hargreaves公式适用于极端干旱的塔克拉玛干沙漠腹地。     

Fractional order intensity measures for probabilistic seismic demand modeling applied to highway bridges

Probabilistic seismic analysis of structures involves the construction of seismic demand models, often stated as probabilistic models of structural response conditioned on a seismic intensity measure. The uncertainty introduced by the model is often a result of the chosen intensity measure. This paper introduces the concept of using fractional order intensity measures (IMs) in probabilistic seismic demand analysis and uses a single frame integral concrete box‐girder bridge class and a seismically designed multispan continuous steel girder bridge class as case studies. The fractional order IMs considered include peak ground response and spectral accelerations at 0.2 and 1.0 s considering a single degree of freedom system with fractional damping, , as well as a linear single degree of freedom system with fractional response, . The study reveals the advantage of fractional order IMs relative to conventional IMs such as peak ground acceleration, peak ground velocity, or spectral acceleration at 0.2 and 1.0 s. Metrics such as efficiency, sufficiency, practicality, and proficiency are measured to assess the optimal nature of fractional order IMs. The results indicate that the proposed fractional order IMs produce significant improvements in efficiency and proficiency, whereas maintaining practicality and sufficiency, and thus providing superior demand models that can be used in probabilistic seismic demand analysis. Copyright © 2011 John Wiley & Sons, Ltd.     

A practice‐oriented estimation of the failure probability of building structures

In the presented practice‐oriented probabilistic approach for the seismic performance assessment of building structures, the SAC‐FEMA method, which is a part of the broader PEER probabilistic framework and permits probability assessment in closed form, is combined with the pushover‐based N2 method. The most demanding part of the PEER probabilistic framework, that is incremental dynamic analysis, is replaced by the much simpler N2 method, which requires considerably less input data and much less computational time, but which can, nevertheless, often provide: acceptable estimates for the mean values of the structural response. Using some additional simplifying assumptions that are consistent with seismic code procedures, an explicit equation for a quick estimation of the annual probability of “failure” (i.e. the probability of exceeding the near collapse limit state) of a structure can be derived, which is appropriate for practical applications, provided that predetermined default values for the dispersion measures are available. In the paper, this simplified approach is summarized and applied to the estimation of the “failure” probability of reinforced concrete frame buildings representing both old structures, not designed for earthquake resistance, and new structures designed according to Eurocode 8. The results of the analyses indicate a high probability of the “failure” of buildings, which have not been designed for seismic loads. For a building designed according to a modern code, the conservatively determined probability of “failure” is about 30 times less but still significant (about 1% over the lifetime of the structure). Copyright © 2011 John Wiley & Sons, Ltd.     

Rocking isolation of low‐rise frame structures founded on isolated footings

This paper explores the effectiveness of a new approach to foundation seismic design. Instead of the present practice of over‐design, the foundations are intentionally under‐dimensioned so as to uplift and mobilize the strength of the supporting (stiff) soil, in the hope that they will thus act as a rocking–isolation mechanism, limiting the inertia transmitted to the superstructure, and guiding plastic ‘hinging’ into soil and the foundation–soil interface. An idealized simple but realistic one‐bay two‐story reinforced concrete moment resisting frame serves as an example to compare the two alternatives. The problem is analyzed employing the finite element method, taking account of material (soil and superstructure) and geometric (uplifting and P–Δ effects) nonlinearities. The response is first investigated through static pushover analysis. It is shown that the axial forces N acting on the footings and the moment to shear (M/Q) ratio fluctuate substantially during shaking, leading to significant changes in footing moment‐rotation response. The seismic performance is explored through dynamic time history analyses, using a wide range of unscaled seismic records as excitation. It is shown that although the performance of both alternatives is acceptable for moderate seismic shaking, for very strong seismic shaking exceeding the design, the performance of the rocking‐isolated system is advantageous: it survives with no damage to the columns, sustaining non‐negligible but repairable damage to its beams and non‐structural elements (infill walls, etc.). Copyright © 2011 John Wiley & Sons, Ltd.     

Pin‐supported walls for enhancing the seismic performance of building structures

An application of a pin‐supported wall‐frame system in retrofitting an eleven‐story steel reinforced concrete frame is introduced. The retrofit aims at enhancing integrity and avoiding weak story failure in an existing moment‐resisting frame. Seismic performance of the building before and after the retrofit is assessed through nonlinear dynamic analysis. The results show that the pin‐supported walls are effective in controlling the deformation pattern of the ductile frame and hence in avoiding weak story failure. With the well‐controlled deformation pattern, carefully arranged energy dissipating devices are able to concentrate energy dissipations so that damage to the rest of the structure can be significantly reduced. Copyright © 2012 John Wiley & Sons, Ltd.