An Investigation of the Ground Motion Scaling Procedures for the Nonlinear Seismic Analyses of Concrete Gravity Dams

Seismic assessment of gravity dams is generally carried out using time history analyses. Scaling of the motions is commonly used; however, in contrast to buildings, the performance of scaling procedures at predicting the mean and reducing the dispersion in engineering demand parameters (EDPs) is not known. The main goal of this study is to assess the performance of different scaling procedures in predicting seismic demands on dams. The performance regarding the prediction of the damage and the required number of motions for effective analysis was investigated. The results show that techniques commonly used for moment frames should not readily be applied to these structures.     

Bayesian Parameter Identification and Model Selection for Normalized Modulus Reduction Curves of Soils

This work develops a procedure that involves the use of Bayesian approach to quantify data scatterness, estimates the optimal values of model parameters, and selects the most appropriate model for the construction of normalized modulus reduction curves of soils. The proposed procedure is then demonstrated using real observation data based on a set of comprehensive resonant column tests on coarse-grained soils conducted in the study.     

Effects of Different Record Selection Methods on the Transverse Seismic Response of a Bridge in South Western British Columbia

The seismic response of a continuous 4-span bridge designed according to the current Canadian seismic provisions is investigated using Incremental Dynamic Analysis (IDA). Different earthquake types, including shallow crustal events, interface Cascadia subduction, and deep inslab subduction are considered. The median collapse capacities calculated using different record selection methods including Conditional Mean Spectrum (CMS)-based, Uniform Hazard Spectrum (UHS)-based, and epsilon-based methods are compared. The use of the epsilon-based method generally resulted in the highest collapse capacity predictions, but the CMS-based method was less sensitive to the number of records considered in the IDA.     

A Method for Selecting Ground Motions that Considers Target Response Spectrum Mean and Variance as Well as Correlation Structure

This study proposes a method for selecting ground motions from a ground motion library with response spectra that match the target response spectrum mean, variance, and correlation structures. The proposed method is conceptually simple and straightforward. In this method, a desired number of ground motions are sequentially selected from first to last. The accuracy and consistency of the proposed method are verified through comparisons of the ground motions selected using the proposed method with those selected using conventional methods. This study shows that the seismic responses of the frames vary according to ground motion selection and correlation structures.     

从文学视角看《零售商菲化案》对华侨社会的影响——以《二十世纪五十年代商报小说选》为主的分析

论文通过对《二十世纪五十年代商报小说选》作品的分析,介绍了《零售商菲化案》产生的背景和主要内容;展示了《零售商菲化案》对菲律宾华侨零售商的冲击和在此背景下菲律宾华侨的悲惨命运,并对这段历史进行了客观理性的分析评价。一方面,菲律宾独立建国以后,为了发展经济,建设国家,必然要通过各种手段整合社会力量与有关资源。遗憾的是,菲律宾政府在经济危机面前,舍本求末,把危机转嫁在华侨身上,造成了20世纪50年代菲华社会的惶惑与动荡;另一方面,菲律宾华侨也必须经过一个转型期,才能更好地在当地生存发展。或许说,正是因为有了20世纪50年代的惶惑与动荡,才加速了菲华社会与当地社会的融合。     

修昔底德选用史料方法刍议

修昔底德的史著以叙述伯罗奔尼撒战争为主要内容,涉及希腊世界主要城邦的政治、军事、经济、外交以及海陆交通等方面丰富多样的史料。修昔底德按照自己处理史料的原则,对于战前史和战争史本身的史料分别采取了不同的处理方法。对于战前史料的选择和考信方法主要采用比较考异法和反溯法;对于当代史料的选用及考信方法主要采取实录法、辨异法、推测法、纠错法、隐微法等五种。修昔底德貌似如实直书的表象背后,隐含着名副其实的“修昔底德陷阱”。     

Variable Selection in Artefact Compositional Studies

In artefact compositional studies, the selection of variables to use in analysis is unavoidable. Given this ubiquity, surprisingly little attention has been paid to ways in which variables might be selected. After arguing the case for the importance of variable selection, two systematic approaches to making a choice, which have had little or no application in archaeometry, are discussed and illustrated. One, based on the use of principal components, is appropriate if structure in the data is not known. The other, based on the use of classification trees, is applicable when there are known or assumed groups in the data.     

Technical Note: Practical Challenges Facing the Selection of Conditional Spectrum-Compatible Accelerograms

There are various possibilities for the selection and scaling of ground motions for advanced seismic assessment of buildings using nonlinear response-history analyses. As part of an on-going project looking at building-specific loss assessment in Italy, this article highlights a number of challenges currently facing the use of conditional spectra for ground motion selection in practice, essentially related to the limited amount of seismic hazard information that is publicly available. To illustrate the points being made, the challenges faced when trying to develop conditional spectra and select spectrum-compatible accelerograms for a rock site in Napoli, Italy, are described and the seismic assessment results obtained for a number of reinforced concrete wall structures are presented. Aside from providing practitioners with an appreciation of the potential difficulty associated with using conditional spectra for record selection, this technical note should also motivate national authorities to provide more background information on national seismic hazard data and detailed guidance for record selection.     

Acheulean variation and selection: does handaxe symmetry fit neutral expectations?

It has been suggested that the property of symmetry observed in Acheulean handaxes was selected for functional, adaptive or social and aesthetic reasons. However, selectionist accounts of variation may be contrasted with the approach taken by population geneticists to molecular variation. Population geneticists always first assume a neutral pattern of variation for molecular data, and only look to non-neutral (e.g., selective) scenarios for pattern and variation in the face of strong evidence against this null model of neutral expectation. Here, using a combination of cultural transmission theory, morphometrics, and the principles of population genetics, (null) neutral expectations for Acheulean handaxe symmetry are tested. The results of the analyses are inconsistent with a null hypothesis of neutral expectation for patterns of handaxe symmetry variation. Rather, the results imply that the property of symmetry in Acheulean handaxes was subject to selection for functional, adaptive or social reasons.     

乡村旅游对农户农林业生产和外出务工影响研究——基于陕西22个旅游扶贫村农户调查数据

利用课题组2017年6-8月在陕西安康、商洛、汉中、宝鸡4市9县22个旅游扶贫村收集的841个农户调查数据，采用双重选择模型（DSM）等分析了农户参与旅游对家庭农林业劳动时间、外出务工时间的影响。研究发现，参与旅游有助于增加调查地的农户收入，旅游兼营型农户收入更高。在全样本中，参与旅游对农户农林业生产时间具有显著负向作用，但在参与了旅游的农户样本中，农户参与旅游一些特征或形式，如土特产销售，对农林业生产则有显著正向作用；在多个模型中，农户从事旅游对家庭外出务工活动具有显著的负向作用。提出了延长农业产业链、发展“旅游+农业”、促进农村一二三产业融合，提高景区带村作用、完善旅游扶贫政策等对策建议。