Elastic Displacement Spectrum-Based Design Approach for Buckling-Restrained Braced Frames

The design focus for a buckling-restrained braced frame (BRBF) is that the buckling-restrained braces (BRBs) dissipate most of the seismic energy while the main frame retains a degree of elastic stiffness under a major earthquake. An elastic displacement spectrum based design method is presented in this article, which can directly determine the sectional area of the BRBs. The yield displacement in the roof of the main frame is taken as the target displacement under a major earthquake. An elastic displacement design spectrum is used to solve the target period of the BRBF. To validate this method, a six-story buckling-restrained braced steel frame is designed using the proposed method, and a series of nonlinear response history analyses (RHAs) are performed to verify the design result. The example shows that the required BRB area can be simply and accurately determined by the proposed method. The error between the given target displacement and the RHA results is 4.0% and 21.3% for BRBFs designed with BRB yield strength of 235 Mpa and 100 Mpa, respectively.     

Characterization of dyes in ancient textiles from Yingpan,Xinjiang

In this paper we analyzed the natural dyes in well-preserved, ancient textiles from Yingpan, an important archaeological site on the Silk Road, using high-performance liquid chromatography with diode array and mass spectrometric detection. Dyes were removed from textile fibers using a soft extraction method (pyridine, water and oxalic acid). Two species of madder-type plants, Rubia tinctorum and Rubia cordifolia were identified as the dye sources in red and brown samples. We also were able to detect unusual flavonoid glycosides in yellow and green woolen yarns, although we have not been able to pinpoint with certainty a specific plant that may have been used to produce this dye(s). On the other hand, we found that yellow and green silk threads had been colored with protoberberine-type dyes, probably obtained from species of cork tree, Phellodendron spp., and/or other protoberberine producing plant. We propose that the textile dyes found at Yingpan reflect a merging of Eastern and Western practices and technologies during the 800-year period (206 BCE–618 CE) encompassing the early years of the Silk Road.     

Spatial–temporal distribution and geographic context of Neolithic cultural sites in the Hanjiang River Basin,Southern Shaanxi,China

Understanding how to live successfully within our environment is among the most pressing challenges facing contemporary society. This paper probes the problem based on comparative analysis and discusses the relationship between the spatial–temporal distribution of the Neolithic cultural sites and the geographic context in the Hanjiang River Basin in the south of Shaanxi Province, China. Archaeological studies have identified 175 Neolithic cultural sites in the study area, with a sequence of Laoguantai (¹⁴C age 8–7 ka BP), Yangshao (¹⁴C age 7–5 ka BP) and the late period of the Neolithic Age (¹⁴C age 5–4 ka BP). The total number of archaeological sites, the distribution area and the density all showed an early ascending and later descending trend, but the proportion of the number of archaeological sites in the study area to the corresponding value of the entire Shaanxi Province declined sharply. Spatially, these sites were concentrated on the terraces of the Hanjiang River and its main tributaries with an altitude of 400–800 m. Multiple data were integrated to clarify the critical effects of tectonic and geomorphologic conditions on the distribution of the Neolithic sites. Further comparisons revealed the correlation of Holocene climate change and environmental evolution with the Neolithic cultural succession in the study area that ameliorated conditions to generally promote the development of the primitive culture while degeneration coincided with the culture's transition or interruption. The discussion on the origin of the primitive culture and the temporal–spatial distribution corresponding to the regional culture differentiation sheds light on the complex and dynamic human–nature interaction system during the Neolithic Age, thus emphasising the wider field-based investigation and high-resolution reconstruction works of the palaeoclimate and palaeoenvironment in the future.     

Discovery of late Changhsingian (latest Permian) brachiopod Attenuatella species from South China

Cretaceous polar dinosaur faunas were taxonomically diverse, which suggests varied strategies for coping with the climatic stress of high latitudes. Some polar dinosaurs, particularly larger taxa such as the duckbill Edmontosaurus Lambe, 1917 Lambe, L. M. 1917. A new genus and species of crestless hadrosaur from the Edmonton Formation of Alberta. Ottawa Naturalist, 31: 65–73.  [Google Scholar], were biomechanically and energetically capable of migrating over long distances, up to 2600 km. However, current evidence strongly suggests many polar dinosaurs (including sauropods, large and small theropods, and ankylosaurs of New Zealand) overwintered in preference to migration. Certain groups also appear more predisposed to overwintering based on their physical inability (related to biomechanics, natural history, or absolute size) to migrate, such as ankylosaurs and many small taxa, including hypsilophodontids and troodontids. Low-nutrient subsistence is found to be the best overwintering method overall, although the likelihood that other taxa employed alternative means remains plausible. Despite wide distribution of some genera, species-level identification is required to assess the applicability of such distributions to migration distances. Presently, such resolution is not available or contradicts the migration hypothesis.     

生态旅游概念内涵、原则与演进

生态旅游是21世纪国际旅游业发展的主导形式,自1980年正式提出后迅速在学术界和实业界引起了巨大的反响。本文着重分析了生态旅游的概念由来、体系构成和要素内涵,并对其发展演进进行了深入的研究,探讨了在可持续思想下生态旅游的提升,以及对旅游业健康发展的作用。     

长江三角洲大都市区划分研究——兼论中美大都市区界定指标体系的比较

本文运用中国大都市区界定指标体系,根据2002年数据对长江三角洲大都市区进行了重新划分。从划分的结果看,后者与前者相比发生较大变化。而中国大都市区界定指标体系对这种变化表现出了一定的不适应性,因此本文试图通过中美大都市区界定指标体系的比较研究为中国大都市区界定指标体系的修订提供参考。     

中国城市流动人口的空间结构

利用中国公安部1996年流动人口统计数据,采用空间统计分析方法和断裂点法,对中国城市流动人口的空间结构进行研究发现,中国城市流动人口主要集中在沿海地带,而且客观存在着三大城市流动人口圈:①京津连流动人口圈。为中国第三大的城市流动人口圈,具有性别比高、来自圈外的流动人口比重大、以亲缘、地缘为纽带聚居等特点。②沪宁杭流动人口圈。为中国第二大的城市流动人口圈,具有来自省内的流动人口比重高、暂住时间差距大等特点。③广深厦流动人口圈。为中国最大的城市流动人口圈,具有女性流动人口比重高、来自外省的流动人口比重大等特点。     

省域城市网络中心性测度及比较研究——以江苏省和广东省的对比分析为例

城市网络中心性是衡量城市地位、分析城市体系的重要概念.本文在剖析中心性理论内涵的演化后,提出网络中心性应当同时体现规模等级和要素流动的水平.通过区分静态网络和联系网络,论文构建了基于规模数据和流动数据的网络中心性评价体系,并以江苏、广东为例进行实证分析.研究发现:①从规模和联系两类城市网络中心性的视角识别首位城市是有效...     

北宋御辽战略的演变与"澶渊之盟"的产生及影响

北宋初确定了通过北伐收复燕云地区,以扭转被动局面的御辽战略思想。宋太宗在两次北伐失败后,放弃以往的主动战略,转而实施全面防御的部署。宋真宗朝继承了“守内虚外”的思想,因此最终与辽达成“澶渊之盟”。“澶渊之盟”的订立,固然维持了长期的北部和平局面,但却给宋朝的国防战略带来了极大的消极影响,使宋廷过分依赖议和的手段,轻视了武备建设,从而令边防陷入长期被动挨打的境地。     

真实性视角下乡村旅游经济可持续开发研究

作为推进新农村建设的重要经济力量,乡村旅游经济如何在快速发展过程中实现可持续竞争力的维持与提升已经成为地方政府经济管理过程中关注的焦点。本文基于对旅游真实性文献的回顾与分析,认为保持与宏扬真实性是旅游体验的根源与旅游开发的要义,据此,从多元层面,着重探讨了真实性在乡村可持续旅游经济开发中的作用机理,从真实性出发,有针对性地提出了促进乡村旅游经济发展的若干管理策略。