SO2与水分综合影响下的云冈石窟砂岩劣化研究

气体污染物SO₂是造成云冈石窟文物本体劣化的重要因素之一。为厘清SO₂与水分耦合作用下的云冈砂岩劣化规律，开展不同SO₂浓度、相对湿度以及降水条件下的室内模拟风化试验，测定试样质量、表面特征和化学成分变化。结果表明：SO₂易与砂岩中的碳酸盐矿物(如方解石)和长石发生化学反应，产物包括CaSO₄·2H₂O、MgSO₄·7H₂O和高岭石等，且随着相对湿度增加，反应程度增大，造成试样的质量、色差值、可溶盐含量上升及硅铝比下降；液态水的参与能显著加快SO₂与砂岩的相互作用过程，不但增加了各项指标的变化幅度，还加大了SO₂入侵深度。研究成果可为砂岩质文物的科学认知和预防性保护提供参考。     

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.     

榆阳区明长城典型遗址的雨蚀破坏模式分析

现有的夯土遗址雨蚀病害分类方式关注的是多次降雨后遗址破坏的静态结果,以识别病害、辨明病因为主要目的。为进一步研究水土作用方式在夯土雨蚀病害发育过程中的作用,明确雨蚀病害的动态发育过程,在现场调查的基础上对榆阳区明代夯土长城的雨蚀病害进行分类、统计、分析,综合考虑侵蚀模式、雨蚀动态响应过程和劣化程度三个方面提出雨蚀破坏模式,分别为干湿破坏、冲刷破坏和降雨导致的重力侵蚀三种,三种破坏模式的提出为研究夯土遗址雨蚀和降雨间的响应关系提供新思路。     

降雨对陕西省榆林市榆阳区明长城破坏的初步分析

降雨是陕西省榆林市榆阳区明长城的主要破坏因素之一。调查中发现,降雨对遗址破坏严重。为了研究降雨对遗址的破坏,在对遗址详细调查的基础上,结合遗址特征与遗址区降雨特点,并参考土壤侵蚀学等方面理论,分析了降雨对遗址的破坏形式及影响因素。结果表明,降雨对遗址的破坏形式可分为直接破坏和间接破坏两大类。其中,主要破坏形式为冲沟侵蚀、片流面蚀和雨蚀剥离。影响因素包括降雨特点、遗址形态、土的性质、植物生长状况和地幔层等,不同破坏形式的主要影响因素各有不同。本结果不仅丰富了降雨对土遗址破坏方面的研究,还为后续陕西榆阳区明长城保护加固措施的选择提供了依据。     

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。     

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。     

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.