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71.
72.
An indirect boundary element method (IBEM) is developed to study the dynamic impedance functions (stiffness coefficients) of a rigid strip foundation embedded in a multi-layered viscoelastic transversely isotropic (TI) half-space. The proposed IBEM using half-space Green’s functions of distributed loads as fundamental solutions have the merits of fictitious loads being directly applied on the real boundaries without the problem of singularity and of the discretization effort restricted to local boundaries. In addition, the accuracy of the proposed method is not affected by the thickness of the discrete TI layers, as the exact dynamic stiffness matrix is employed. The presented algorithm is verified via comparisons with published results for the isotropic medium. By taking a rigid strip foundation embedded in a homogeneous half-space, a single-layered half-space, and a multi-layered half-space as examples, the effects of material anisotropy, frequency of excitation, and soil layer on the impedance functions are studied in detail. Numerical results show that impedance functions for the TI medium can be significantly different from those of the isotropic case. The variation of TI parameters alters the dynamic characteristics of the TI layered site, which in turn alters the dynamic interaction between the soil and foundation. In addition, the soil sedimentary sequence also has a remarkable influence on the impedance functions. 相似文献
73.
The displacement ductility limit for seismic design of concrete piles is determined for the range of cohesionless soils expected in practice. The curvature ductility capacity associated with specified performance limit states, namely, the “serviceability” and “damage-control” limits, is determined based on the current provisions for confining steel. An analytical model is applied to assess the displacement ductility factor at the specified curvature ductility level. The investigated parameters include the soil stiffness, pile diameter, longitudinal reinforcement ratio, axial force level, and pile above-ground height. A set of design displacement ductility factors is recommended and verified to ensure the satisfactory seismic performance. 相似文献
74.
Qifang Xie Long Wang Peijun Zheng Lipeng Zhang Weibing Hu 《International Journal of Architectural Heritage》2018,12(1):125-136
This article presents the results of an experimental study on the rotational behavior of degraded Chinese traditional mortise-tenon joints with different degradation types and different degradation degrees. Six joint specimens degraded through artificially simulated method, were tested by reversed cyclic loading, from which the moment-rotation curves were obtained. The results indicated that the rotational behavior of these joints is semi-rigid, the hysteretic curve shapes of degraded joints are same to that of joint without degradation. The maximum moment, yield moment, and initial rotational stiffness of degraded joints decreases as the degraded degree increases, whose empirical degradation relationships were obtained based on the test data. A hysteretic model for degraded traditional mortise tenon joints was proposed. Experimental results were used to validate the proposed hysteretic model. Good agreement between predictions and tests was observed. 相似文献
75.
空铁型综合交通枢纽是将航空枢纽和高铁枢纽有机整合而形成的航空高铁一体化综合交通枢纽,具有较强的经济社会带动作用,对区域空间演化产生重要影响。根据复杂适应系统理论,选取上海虹桥综合交通枢纽地区为案例地,分析了空铁型综合交通枢纽地区地域空间演化阶段性特征。结果表明:交通枢纽地区地域系统通过多个适应性主体之间非线性相互作用形成复杂适应系统,该地域系统演化过程可划分为枢纽地区空间形成阶段、枢纽地区空间生长阶段和枢纽地区空间涌现阶段。上海虹桥综合交通枢纽地区在三个阶段特征不同,配套设施建设、要素集聚与流动、城市功能形成与发展、区域品牌形成等方面不断深化。研究有助于认知综合交通枢纽地域系统空间演化规律,为深化研究和实践发展提供科学借鉴。 相似文献
76.
战后天津暨华北地区日俘日侨遣返研究 总被引:1,自引:1,他引:0
本文依据大量的档案资料,全面考察了抗战胜利后华北各地约34万日俘日侨经天津遣返的基本情况.笔者以为,中国政府在这次遣返过程中的举措总体而言是值得肯定的,它对华北战后的社会安定和民众情绪的抚慰产生了十分积极的影响,体现出中华民族与人为善、宽宏大量的民族性格. 相似文献
77.
媒介形式和媒介内容的日趋多样化,使作为重要知识储备群体的大学生面临着空前复杂的媒介环境。在这一形势下,依托高校图书馆服务功能的拓展,开展大学生媒介素养教育具有重要的现实意义。 相似文献
78.
Diagenesis and elemental geochemistry under varying reservoir oil saturation in the Junggar Basin of NW China: implication for differentiating hydrocarbon‐bearing horizons
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In this paper, we attempt to differentiate hydrocarbon‐bearing reservoir horizons of the Junggar Basin of NW China based on the characteristics of diagenesis and associated elemental geochemistry. Reservoirs at this site have varying levels of oil saturation that correlate with the degree of dissolution in minerals (e.g., calcite and feldspar). Four different horizons with varying diagenetic mineral assemblages were observed, including (i) kaolinite‐rich, oil‐dominated horizons, (ii) kaolinite–pyrite–hematite‐rich, oil–water‐dominated horizons, (iii) siderite–chlorite‐rich, water‐dominated horizons, and (iv) chlorite‐rich horizons with negligible hydrocarbon production. The mean MnO content of the representative diagenetic mineral (e.g., calcite) in each of the above horizons is >2.5, 2.0–2.5, 1.5–2.0, and <1.0 wt%, respectively. We propose that the above methodology can be used for the identification of reservoir hydrocarbon‐bearing horizons. We argue that the indicators presented here can be applied in oil exploration across the Junggar Basin. 相似文献
79.
"义赈"一词最晚在16世纪已经产生。在其后数百年中,该词的流布情况,以及与之相关联的实践内容,都出现了重大变化。起初,该词主要被作为捐赈活动的一个褒称,使用频率十分有限。到19世纪前半期,该词开始被用来指称一种特定的地方性赈灾活动,其名声得到较为广泛的传播。从19世纪70年代起,该词又成为新兴民间赈灾活动的专名,并风行于海内外。这种名称不变而实践内容发生剧烈转换的状况,体现的正是一种既传承又超越的新陈代谢进程。而结合社会史和文化史来充分理解这一进程,也可以为考察中国民间赈灾事业的演变提供一条有益的线索。 相似文献
80.
X‐L. Chen Y‐M. Fang Y‐W. Hu Y‐F. Hou P. Lü J. Yuan G‐D. Song B. T. Fuller M. P. Richards 《International Journal of Osteoarchaeology》2016,26(5):808-817
During the late Longshan period (ca. 4200–3900 BP) settlements on the Central Plains of China underwent a diversification in food production technologies, which set the stage for rapid economic and social development. The introduction of novel domesticates such as rice, wheat, cattle, and sheep not only provided more food choices, but also changed ideas concerning land use, farming techniques, and the use and mobilization of large scale labor forces. To better understand the contribution that these new dietary items and practices made to shaping the late Longshan period societies, a stable isotope ratio study of humans (n = 12) and animals (n = 42) was conducted at the late Longshan period site of Wadian. The human δ13C and δ15N values are clustered into two distinct groups. One group of nine individuals (δ13C = −9.9 ± 0.7‰; δ15N = 7.5 ± 0.5‰) had a predominately C4 diet based on millet grains with little protein input from the domestic animals. The other group of three individuals (δ13C = −14.3 ± 0.8‰; δ15N = 10.2 ± 0.3‰) had a mixed C3/C4 diet of millets and rice and were consuming sheep and cattle. The animals also displayed dietary diversity with the pigs (δ13C = −11.3 ± 2.5‰; δ15N = 6.9 ± 1.0‰, n = 10) and dogs (δ13C = −10.1 ± 1.0‰; δ15N = 7.2 ± 1.1‰, n = 7) having mostly a C4 plant based diet (millets). In contrast, the cattle (δ13C = −12.8 ± 2.1‰; δ15N = 7.6 ± 0.7‰, n = 9), sheep (δ13C = −16.7 ± 0.9‰; δ15N = 7.6 ± 0.1‰, n = 2), and cervids (δ13C = −20.8 ± 0.9‰; δ15N = 5.0 ± 1.2‰, n = 10) had diets with a greater contribution from C3 sources such as rice and wild plants. The discovery that humans and animals had different subsistence patterns indicates dietary complexity at Wadian and that rice agriculture, and cattle and sheep husbandry practices were already an important part of the local economy by the late Longshan period in the southern region of the Central Plains of China. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献