钱塘江河口涌潮强弱的历史变迁(1471-2001)

整理《中国近五百年旱涝分布图集》及其"续编""再续编"中1471-2000年间浙江金华与安徽屯溪两个站点的旱涝指数,将其作为反映钱塘江年径流量波动的指标,根据1950-2000年实测的钱塘江径流大小与海宁盐官站潮差和涌潮大小的相关关系,推断出五百余年来钱塘江涌潮强度变迁趋势。经检验,钱塘江流域旱涝指数特征与史料所载涌潮异常年份相符,且指数序列与同时期海宁盐官历年最大潮差值序列之间的相关系数具有较强相关性。将现代实测盐官历年最大潮差与旱涝指数拟合,得到函数关系式为y=-7.2x2+40.3x+580.1(其中x为旱涝指数,y为盐官年最大潮差)。又根据盐官潮差与涌潮高度间函数关系推出了明中期以后盐官历年涌潮最大强度,并绘制了1471-2001年间的钱塘江涌潮强弱变化曲线图。     

瘟疫何以肆虐?——一项医疗环境史的研究

"瘟疫何以肆虐"的问题,既与环境史相关,亦与医疗社会史不可分,但并不能用其中任何一者涵盖之;由此,我们提出"医疗环境史"的概念,以黑死病为个案,围绕瘟疫本身进行环境分析。在14世纪英国的聚落环境中,传染源普遍存在,鼠、蚤、人紧密共存,便于瘟疫的传播;交通运输的便利,利于瘟疫的跨聚落和跨地区流传;落后的医疗防治水平不能阻止瘟疫的肆虐,甚至会因不合理的举措而适得其反。上述病发、流传和应对环境还存在地区性的差异,从而导致瘟疫肆虐程度之不同。     

一部错冠其名的《湖州府志》

成化《湖州府志》和弘治《湖州府志》是明代湖州的两部府志。通过对现在通行本成化《湖州府志》的记述范围、记述下限、卷数、撰稿者署名、凡例、总目数、残本各卷卷首的“礼集”、“乐集”、“射集”、“书集”字样进行分析,可以判断通行本成化《湖州府志》实际是弘治《湖州府志》。     

地方志部门与高校的新型关系——兼谈地方志部门资政服务的可拓展空间

地方志部门与高校在新方志编纂、旧志整理、资源共享、人才培养、学科建设、资治辅政、社会服务等方面,有着非常好的互动合作共赢关系。这种互动合作,特别是修志对高校人才资源、信息资源、智力资源的利用,资政服务与高校的横向合作,以及共建社会实践基地等,是提高志书的资料性与学术性,有效开发利用志书资源,进一步拓展地方志部门资政服务空间和公共服务领域的重要举措。     

以书为画 形道混融：《心画》——王方宇的书法暨收藏作品展

12月8日题为《心画》的王方字捐法暨收藏作品展在北京大学赛克勒考古与艺术博物馆开幕,展出其创作的现代书法作品近50件,及其重要收藏品八大山人和现代齐白石的作品,展览并陈列其生前使用的文房用品笔墨砚、笔搁及部分自用印,还同时展出王方宇的部分英文著作,让观众从多个方面了解这位杰出华裔学者、艺术家在学术研究与艺术探索上的成就。     

IDENTIFICATION AND VERIFICATION OF SEISMIC DEMAND FROM DIFFERENT HYSTERETIC MODELS

The goal of this paper is to develop a modified Bouc-Wen hysteretic model from cyclic loading test data for reinforced columns, including the behavior of stiffness degradation, strength deterioration, pinching and softening effects of RC members. Seismic demands on this inelastic single degree of freedom system when subjected to both near-fault ground motion and far-field ground motion excitations were examined.

The cyclic loading test of reinforced concrete columns was experimentally observed and a system identification computer program was developed to solve each control parameter of the hysteretic model. A least-squared method for identifying parameters of the model is proposed in this paper. The hysteretic constitutive law produces a smoothly varying hysteresis such as the control-parameters for strength deterioration, stiffness degradation, pinching and softening effects. Two implementations of (1) flexure damage and (2) shear damage were conducted to provide better understanding of hysteretic behavior of RC structural members. A pseudo-dynamic experiment was also developed to verify the model parameters.

Based on the developed hysteretic model, the seismic demand of this inelastic model was investigated by using both near-fault ground motion data and far-field ground motion data as input motion. An R-μT inelastic response spectrum from different hysteretic models was generated.     

EVALUATION OF ACCIDENTAL ECCENTRICITY IN BUILDINGS DUE TO ROTATIONAL COMPONENT OF EARTHQUAKE

This study adopts a random procedure in the evaluation of the effect of the rotational component of earthquake on the accidental eccentricity of symmetric and asymmetric buildings. The spectral density function of the rotational component of earthquake acceleration (about the vertical axis) is obtained on the basis of the spectral density function of the horizontal component of earthquake acceleration. The rotational component of an earthquake can increase the response of the structure. The degree of the increase is highly dependent upon the dynamic characteristics of the system and the rotational component of the earthquake. To bring this increase under consideration, seismic codes represent a parameter referred to as accidental eccentricity, as a part of the design eccentricity. The purpose of the present study is to estimate the value of this increase and to make appropriate suggestions based on frequency domain analysis.     

AN UNCONDITIONALLY STABLE EXPLICIT METHOD FOR STRUCTURAL DYNAMICS

An explicit integration method with unconditional stability was proposed and presented in this paper. Numerical characteristics of this explicit method for linear elastic sys-tems are almost the same as those of the constant average acceleration method while for a nonlinear system it is more efficient in computing than for the constant average acceleration method. This explicit method integrates the most promising advantages possessed by the explicit and implicit methods. No limitation on the time step in satisfying the stability limit, which is the most important property for an implicit method, is theoretically proved for this explicit method. Furthermore, the avoidance of solving any implicit system or using any iterative procedure, which usually brings considerable simplification in practical applications for explicit methods, leads to the very low cost of one explicit step. Thus, the computational effort can be significantly reduced when compared to implicit methods in each time step. Consequently, this explicit method can be used to solve dynamic problems efficiently due to the unconditional stability and the very low cost of explicit steps. Rough guidelines with regards to the selection of a time step in achieving accurate solutions for the constant average acceleration method are also appropriate for the proposed explicit method.     

NONLINEAR SHAKE TABLE IDENTIFICATION AND CONTROL FOR NEAR-FIELD EARTHQUAKE TESTING

The primary focus of a structural shake table system is the accurate reproduction of acceleration records for testing. However, many systems deliver variable and less than optimal performance, particularly when reproducing large near-field seismic events that require extreme table performance. Improved identification and control methods are developed for large hydraulic servo-actuated shake table systems that can exhibit unacceptable tracking response for large, near-field seismic testing. The research is presented in the context of a 5-tonne shake table facility at the University of Canterbury that is of typical design. The system is identified using a frequency response approach that accounts for the actual magnitudes and frequencies of motion encountered in seismic testing. The models and methods developed are experimentally verified and the impact of different feedback variables such as acceleration, velocity and displacement are examined.

The methods show that shake table control in testing large near-field seismic events is often a trade off between accurate tracking and nonlinear velocity saturation of the hydraulic valves that can result in severe acceleration spikes. Control methods are developed to improve performance and include both acceleration and displacement feedback to reduce the acceleration spikes, and record modification, where the reference signal is modified to conform to the shake table's operational parameters. Results show record modification gives exact tracking for near-field ground motions, and optimal system response for reference signals with velocity components greater then the system capabilities. Overall, the research presents a methodology for simple effective identification, modelling, diagnosis and control of structural shake table systems that can be readily generalised and applied to any similar facility.