Seismic effectiveness of tuned mass dampers considering soil–structure interaction

This paper presents how soil–structure interaction affects the seismic performance of Tuned Mass Dampers (TMD) when installed on flexibly based structures. Previous studies on this subject have led to inconsistent conclusions since the soil and structure models employed considerably differ from each other. A generic frequency-independent model is used in this paper to represent a general soil–structure system, whose parameters cover a wide spectrum of soil and structural characteristics. The model structure is subjected to a stationary random excitation and the root-mean-square responses of engineering interest are used to measure the TMD's performance. Extensive parametric studies have shown that strong soil–structure interaction significantly defeats the seismic effectiveness of TMD systems. As the soil shear wave velocity decreases, TMD systems become less effective in reducing the maximum response of structures. For a structure resting on soft soil, the TMD system can hardly reduce the structural seismic response due to the high damping characteristics of soil–structure systems. The model structure is further subjected to the NS component of the 1940 El Centro, California earthquake to confirm the TMD's performance in a more realistic environment. Copyright © 1999 John Wiley & Sons Ltd.     

游客涉入对旅游目的地形象感知的影响——盎格鲁入境旅游者与国内旅游者的比较

本研究的主要目的是从维度层次探讨游客涉入对目的地形象感知的影响,并对盎格鲁入境旅游者(n = 349) 和国内旅游者(n = 292) 两个群体的影响模式进行比较。游客涉入测量使用Gursoy & Gavcar 修订的国际休闲旅游者游客涉入量表,包括娱乐/兴趣、风险可能性和风险后果3 个维度;目的地形象测量使用Baloglu 的目的地形象量表,包括认知形象和情感形象2 个成份。以桂林、阳朔作为案例地,使用多组结构模型分析方法比较两个群体的结构模型。研究发现：游客涉入对目的地形象感知有显著影响,具体表现为娱乐/兴趣显著正向影响认知和情感形象;风险后果显著负向影响认知和情感形象;风险可能性对情感形象无显著影响,国内旅游者风险可能性显著正向影响认知形象,但盎格鲁入境旅游者没有发现这种影响;2 个子样本只有娱乐/兴趣→认知形象和风险可能性→认知形象两个路径系数存在差异,其他路径系数均等值。     

绿色金融如何影响中国城市环境污染？——以雾霾污染为例

文章将绿色金融纳入环境规制的分析框架,以2016－2019年中国289个地级以上城市雾霾污染为例,使用空间杜宾模型探讨绿色金融、环境规制、产业结构、技术水平对雾霾治理的影响,侧重分析了绿色金融与其他因素的交互作用。结果表明：绿色金融具有空间溢出效应,本地绿色金融可以降低周边地区雾霾污染;绿色金融能够与环境规制协同互补,以优化产业结构、提升技术水平的方式促成雾霾治理。绿色金融的结构效应弱于环境规制,在中部地区并不显著;绿色金融的技术效应强于环境规制,能够激励不同地区技术创新。文章启示,绿色金融与环境规制能够相互增益,应建立区域间绿色金融合作机制,增强绿色金融的普惠性,助力区域产业转型和污染治理。     

地震作用下参数不确定系统的变结构控制

本文对结构参数具有有确定性的变结构控制系统设计方法进行了研究。首先采用摄动方法给出了结构参数具有确定性的控制系统的运动方程,证明了基于层间剪切模型的参数不确定受控系统与其标称系统具有相同的滑动模态,从而解决了系统切换函数的确定问题,并利用到达条件推导了控制律的表示式。算例分析结果表明,本文的控制方法能有效地减小结构的地震响应,对于结构系统建模存在误差或系统本身存在学确定性的情况,控制效果仍十分显著     

冻融作用下污泥固化轻质土动力特性及结构演化

冻融作用会影响污泥固化轻质土动力特性和结构特性。为研究不同冻融循环次数和冻结温度下的污泥固化轻质土动力特性及结构演化,对冻融循环作用后的污泥固化轻质土进行动三轴试验和固结试验。试验结果表明：在冻融循环作用下,污泥固化轻质土动应力-应变曲线呈弱应变硬化型。污泥固化轻质土动强度和变形随着冻融次数（n）的增加和冻结温度（T）的降低而减小。经历前4次冻融作用后,对固化土变形和动强度影响较大,经历8次冻融循环后基本趋于稳定。冻融循环对土体动力特性的影响本质上是对土体结构性的影响。固化土冻融结构势（mdσn）的变化规律与动强度类似,随冻融次数的增加和冻结温度的降低而下降。冻融循环次数是影响污泥固化轻质土动力特性和结构性的主要因素,冻结温度为次要因素。     

胶东金矿区夏甸金矿床矿化分布规律及构造控矿分析

夏甸金矿床是胶西北地区典型的蚀变岩型金矿床,金矿化主要受招平断裂带控制。本文对夏甸金矿床进行了野外地质调查,三维地质建模和构造空间分析,以期从三维空间和勘查数据中厘清矿化分布规律、探明构造控矿作用。研究结果显示,夏甸金矿床矿化主要为蚀变岩型和硫化物脉型,主要受招平断裂带及其次级构造控制,在空间中呈现出不均一分布的特征。夏甸金矿床的矿化侧伏规律,在空间中存在差异性,其中南部为NE侧伏,中段侧伏规律不明显但分支复合特征明显,而北段呈SE侧伏。这种侧伏规律与招平断裂带主裂面在走向方向的转折密切相关。进一步的空间分析显示,夏甸金矿床不同类型的矿体是不同空间范围内构造变形差异的结果。     

A method for evaluating the longitudinal functional connectivity of a river–lake–marsh system and its application in China

The longitudinal functional connectivity of a river–lake–marsh system (RLMS) refers to the actual water-mediated transport of material from upstream to downstream areas along a spatial gradient and is fundamental to understand hydrological and biogeochemical cycles. However, due to a lack of consensus on appropriate data and methods, the quantification of connectivity is still a challenge, especially at the catchment scale. We developed a new method to evaluate longitudinal functional connectivity based on fluxes of materials (water, sediment, and chemicals) along a RLMS. The calculation of fluxes is based on the longitudinal pattern of terrain gradient, which influences transport efficiency, and on contributions from hillslopes, which set the initial spatial template of material loading to the RLMS. We evaluate the contributions from hillslopes to RLMS based on a new modified version of the index of sediment connectivity (IC) proposed by Borselli et al. (2008) and revised by Chartin et al. (2017).We applied this method to the Baiyangdian Basin covering an area of 3.4 × 10⁴ km² in China and quantified longitudinal functional connectivity during normal, wet, and dry periods(April, July and December) in year 2016. We found that areas with good structural connectivity exhibited poor functional connectivity during the normal and dry periods. Modelling testing with discharge data from hydrological stations and measured chemicals from Baiyangdian Lake was satisfactory in test periods. We conclude that public data and Digital Elevation Model-derived information can be used to reliably map the longitudinal functional connectivity of RLMSs. The proposed method provides a useful tool for monitoring and restoring the longitudinal functional connectivity of RLMSs and our results indicate that efforts aimed at restoring functional connectivity in RLMSs should take into account landscape patterns that can greatly influence fluxes in the watershed.     

珠一坳陷始新世文昌组沉积期构造转换对源‒汇体系的控制

An obvious structural transformation between the early and the late stages of the middle Eocene rifting in the ZhuⅠ Depression, which has a significant impact on the formation and evolution of the Paleogene source-to-sink system, has recently been found. Based on comprehensive analysis of seismic, drilling and logging data in the study area, we argue that the structural transformation controls the basic elements of source-to-sink system, such as basin landscape, material source supply, transportation direction and sedimentary style, and affects the deep Paleogene reservoir conditions. Under the restriction of structural transformation, there are two typical source-to-sink models: source migration and fault transformation. Hydrocarbon accumulation related to structural transformation is commonly interpreted by two typical source-to sink models: source migration and fault transformation. The main source of the source migration model migrates under the influence of structural transformation, and the sedimentary boundary, accommodation space and depositional style change accordingly, forming a favorable superimposed and contiguous reservoir target;the supply, transportation and accumulation of provenance in the fault transformation model change orderly in time and space, forming the compound of co-existing fan-delta-beach sedimentary system and reservoir conditions have strong zonation. It is of great significance to explore the characteristics of source to sink system and sand-controlling model under the control of structural transformation in order to find high-quality reservoirs in Paleogene. © 2021, Science Press. All right reserved.     

豫西白术沟组的构造位态及时代问题

白术沟组以其独特的岩石物理特性而卷入到推覆构造带的特殊部位。本文研究了白术沟组的三种构造位态，确定其主要呈第一种构造位态广泛分布于推覆体内部某次一级逆冲滑脱断层的下部，其上覆逆冲岩席由震旦系栾川群及中元古界官道口群构成，下伏地层为下古生界陶湾群。前人将白术沟组置于栾川群的底部层位，笔者对此提出异议，认为以含磷、铀为特征的白术沟组碳质千枚岩层实与我省北部华北地台区早寒武世辛集组底部含磷铀的碳泥质层为同一层位，同样的地层也见于确山西部的“银洞沟组”及大别山的“商城群”石门冲组含磷层中。     

Nonstationary frequency effect of the ground motion upon the strength levels of the shear type RC structures

In order to investigate the influence of nonstationary frequency content variations, nonlinear response analysis for origin-oriented type hysteretic model is carried out and results are presented by applying two different S_I and S_II ensembles with varied frequency contents. The theoretical background of strong motion simulation is explained briefly depending on frequency parameters of stiff soil data. Based on models and applying Monte-Carlo's simulation mean values and standard deviations of displacement ductility demands for both ensembles are calculated. Required strength levels are investigated in probabilistic sense adopting light and heavy (but controlled) damage criteria. It is concluded that the nonlinear behaviour of the structure is greatly influenced by the nonstationary frequency content deviations as being shown that larger strength requirements for the S_I type strong ground motion ensemble than the S_II, although both ensembles have almost the same acceleration response spectra.