THE EFFECTIVE DURATION OF EARTHQUAKE STRONG MOTION

The duration of strong ground shaking during earthquakes can play an important role in the response of foundation materials and structures, particularly when strength or stiffness degradation is encountered. A thorough seismic hazard assessment should therefore include an estimation of the expected duration of strong motion, which first requires criteria to define the part of an accelerogram considered to represent the duration of strong ground motion. Some 30 different definitions of strong motion duration are reviewed and classified into generic groups. Problems that arise with the use of these definitions for duration are highlighted. A new definition of duration is presented using a previously unexplored option which identifies the part of the record where the main energy is contained and constrains this strong shaking phase by absolute criteria. This new definition is shown to give consistently meaningful durations for strong earthquake accelerograms from an engineering viewpoint. The correlations between the new definition of duration and magnitude, soil conditions and distance are explored as a first step towards the development of predictive equations.     

A PROCEDURE FOR ESTIMATING INPUT ENERGY SPECTRA FOR SEISMIC DESIGN

In this paper, the damage potential of an earthquake ground motion is evaluated in terms of the total power of the acceleration of the ground motion. By assuming an appropriate spectral shape for the input energy spectrum, and using the well-known Parseval theorem for evaluating the total power of a random signal, the peak amplification factor for the equivalent input energy velocity spectrum can be determined. It is shown that the peak amplification factor for the input energy spectrum depends on the peak-ground-acceleration to peak-ground-velocity ratio and duration of the strong motion phase of the ground motion. Values for the equivalent input energy velocity amplification factor vary from about 2 to 10 for most of the recorded ground motions used in this study. Although a considerable scatter of data is observed in this study, the peak amplification factor predicted by the Fourier amplitude spectrum of the ground acceleration provides a fairly good estimate of the mean value of the peak input energy compared to that determined from inelastic dynamic time history analyses, particularly for systems with high damping and low lateral strength. The peak amplification factor derived in this paper provides a more consistent approach for estimation of seismic demand when compared to an earlier empirical expression used for the formulation of duration-dependent inelastic seismic design spectra, even though only a slight difference in the required lateral strength results from the use of the new formula.     

流动人口居留稳定性的群体分异与空间格局

利用2015年全国1%人口抽样调查数据,本文分析了流动人口居留稳定性的总体特征、群体分异和空间差异性,并对流动人口居留稳定性的影响因素进行了探讨。结果表明：①我国跨市流动人口在当前城市的平均居住时间约为5年,新生代流动人口的居留稳定性与老一代并没有显著差异,从事工业行业的流动人口居留稳定性明显低于各类服务业从业者;②省内流动人口的居留稳定性低于省际流动人口,且有更大的可能离开当前城市,转向省际流动;③城市流动人口的规模和居留稳定性在空间格局和影响因素方面均存在明显差异,虽然收入水平和就业机会依然是吸引流动人口的主要因素,但公共服务、住房市场和环境等城市宜居性因素对提高流动人口的居留稳定性更为重要。     

Elderly widowhood in China

As population ageing accelerates in China, the number of elderly widowed individuals are expected to increase. Using 2010 census data we estimate widowhood indices for rural and urban areas, and for men and women in China. The indices show that the probability of elderly widowhood to be higher for females (0.68) than males (0.32)—with no rural and urban difference. An average marriage in China lasts about 47 years. After the death of a spouse, the average duration of widowhood is about 11 years for males and about 15 years for females. Spousal age difference has a significant impact on widowhood indices. Rural populations have the shortest marriage duration and the youngest widowhood age, and longer widowhood duration.     

Distinctive Places, Suitable Spaces: Conceptualizing Mobile Group Occupational Duration and Landscape Use

While extreme mobility and ensconced sedentism can be easily distinguished in the archeological record, effective means are lacking of discriminating between degrees of mobility that may range from seasonal shifts by farmers to recurrent moves across the landscape as a way of life. Fortunately, site layout and the way space is used are related to expectations regarding length of stay, and though they are not quantifiable measures, they provide linkages between the active and material realms. Short stays elicit a search for distinctive characteristics of a place rather than investing in the modification of a place. The quest for suitable spaces is a matter of fact among mobile groups, whereas sedentary groups, or those expecting to stay in one place for an extended period, tend to build their environment to suit their needs, even formalizing spaces in consistent ways from place to place. By understanding the ramifications of these concepts it is possible to distinguish between differing degrees of mobility of groups occupying similar environmental zones in the southern portion of the American Southwest in the protohistoric and early historic periods and to apply these to wider contexts.     

略论西方铜版画艺术在中国明清时期的传播

本文从西方铜版画艺术在明清时期传入中国引发的西画东渐入手,分析了西方铜版画在华从传播到出版的历程,最终揭示了外来文化艺术熔融于中国社会的关键所在：即必须建立在适合的社会生活和社会基础之上。     

War and city size: The asymmetric effects of the Spanish Civil War

Populations are affected by shocks of different kinds, and wars, a priori, may be among the most prominent. This article studies the effect of the Spanish Civil War (1936–1939) shock on the distribution of population, especially on cities. One of the main contributions of this study is that it underlines the importance of distinguishing between winning and losing sides, an aspect which until now has been largely overlooked. While previous research on war shocks has also tended to be concerned with inter-state wars, this paper concentrates on a civil war. We take advantage of a new, long-term, annual data set. Our results show that, overall, the Spanish Civil War did not have a significant effect on city growth. However, we also find a significant and negative effect in the growth of cities that aligned themselves with the losing side. These results are robust to heterogeneity in the effect of the war shock, measured as war severity and duration. Although short lived, the temporary effect on growth results in a permanent effect on the size of cities on the losing side.     

Latinos in the USA: Changing socio-economic patterns

This paper aims to provide an overview of socio-economic inequality experienced by Latinas and Latinos, suggesting that the increase in numbers and their dispersal throughout the country disrupts the traditional black–white paradigm used in race relations theory. Instead, I argue that the particular historical and geographical experiences of Latinas/os portend complex changes within labour markets and neighbourhoods and across families, ultimately challenging how we think about race relations in the USA.     

降雨时长对土壤结皮发育性能的影响研究

室外土遗址经常因遭遇降雨、水淹等发生结皮,造成土遗址表层性能改变,影响土遗址的进一步保护。以定量纯净黄土在等降雨大小下,通过控制不同降雨时长,试验了不同降雨时长下土壤结皮发育的过程,分别测试了降雨前后的结皮厚度、密度、硬度及孔隙结构。结果表明,在降雨量未达到饱和状态时,随降雨量增大,结皮层的厚度、密度、硬度迅速增大,表皮土壤颗粒被击碎,孔隙迅速减小;在降雨量达到饱和状态时,随降雨量增大,结皮层的厚度、密度、硬度缓慢增大,但表皮土壤裂缝迅速发育,由周围向中心形成同心圆状或辐射状裂隙。研究结论可为室外土遗址的保护提供参考。     

SEISMIC HAZARD IN GREECE BASED ON DIFFERENT STRONG GROUND MOTION PARAMETERS

The available Greek strong ground motion records to date are used in order to study the duration of strong-motion in Greece, covering magnitudes between 4.5 and 6.9 and distances from 1 km to 128 km. An attenuation relation of strong-motion duration is calculated and compared to earlier existing similar relations proposed for Greece and Japan. Furthermore, the seismic hazard for the area of Greece is assessed, using the strong-motion parameters of duration and peak ground acceleration. The results are presented in the form of a map according to which Greece is classified in four different categories of equal seismic hazard.