日照市土地利用变化对生态环境的影响

日照是生物多样性的地区,生态环境较好,但近年来,随着工业化、城市化的发展,土地利用结构与布局发生了较大变化,土地生态环境总体上也在不断恶化。该文通过分析日照市不同土地利用类型的变化,探讨其对生态环境的影响,对日照市土地利用结构与布局调整具有指导意义。     

西南某水利枢纽废旧煤洞的工程效应研究

通过对西南某水利枢纽工程坝区煤系地层的系统研究,揭示了在坝区左右岸煤洞的展布特征,结合工程,分析了煤洞的存在及其变形的工程效应。最后,对煤洞的变形提出了针对性的处理建议。     

青藏高原的主要环境效应

作为地球的"第三极",青藏高原越来越受到世界的关注,本文就青藏高原的环境效应问题进行了研究和探讨.青藏高原的隆起和抬升,形成了其自身独特的自然环境特征,促成了独特的高原季风系统,造就了中国现代季风格局,影响着全球气候的变化和亚洲植被格局的分布,导技致了亚洲干旱地带的北移和植被地带的不对称分布,形成了世界上著名的高原地带性植被格局.对中国东部、西北干旱区、亚洲的气候和植被格局乃至全球气候变化都具有深刻的影响.     

中国城市化过程及其资源与生态环境效应机制

目前中国城市化进程表现为速度过快、地域差异显著以及城乡二元结构明显等特征.城市化带来了显著的生态效应,使城市生态系统的结构、过程和功能受到影响或发生不可逆转的变化,出现了耕地资源流失、水资源稀缺、能源压力、城市环境污染严重以及城市区域生态占用扩大等资源与生态环境问题.目前国内外学者研究了城市热岛效应、城市地表覆被变化、城市生物多样性损失以及城市水土资源等问题,但多侧重单要素、单城市、单学科研究,缺乏多尺度机理性的研究.鉴于此,提出若干未来城市化及其生态环境效应研究的方向与议题,归纳为:(1)中国城市化过程多尺度定量模拟与监测研究;(2)阐明城市化影响下地表自然过程和人文过程相互作用的机理;(3)资源与生态环境约束下中国未来城市化的可能情景及其风险评估等.     

Cumulative impact mapping: Advances,relevance and limitations to marine management and conservation,using Canada's Pacific waters as a case study

Analysis of cumulative human impacts in the marine environment is still in its infancy but developing rapidly. In this study, existing approaches were expanded upon, aiming for a realistic consideration of cumulative impacts at a regional scale. Thirty-eight human activities were considered, with each broken down according to stressor types and a range of spatial influences. To add to the policy relevance, existing stressors within and outside of conservation areas were compared. Results indicate the entire continental shelf of Canada's Pacific marine waters is affected by multiple human activities at some level. Commercial fishing, land-based activities and marine transportation accounted for 57.0%, 19.1%, and 17.7% of total cumulative impacts, respectively. Surprisingly, most areas with conservation designations contained higher impact scores than the mean values of their corresponding ecoregions. Despite recent advances in mapping cumulative impacts, many limitations remain. Nonetheless, preliminary analyses such as these can provide information relevant to precautionary management and conservation efforts.     

全球变暖背景下东亚对流层顶高度演变特征的研究

研究了1948～2004年东亚增暖背景下对流层顶高度的演变特征,重点分析对流层温度、平流层中下部温度与对流层顶高度变化之间的关系。结果表明：东亚地区对流层顶高度在1970年代后呈现波动上升趋势,其上升趋势不如南半球显著;东亚对流层温度与对流层顶高度呈显著正相关,特别是对流层中上部温度与对流层顶高度的正相关最显著,这说明对流层中上部的增温对对流层顶高度的抬升贡献较大;东亚平流层中下层温度与对流层顶高度基本呈显著负相关,70hPa层上的负相关最显著;近20年来东亚对流层温度上升了约0．2℃,平流层中下部温度下降了约1．2℃,对流顶高度上升了约86m,对流层的增暖和平流层的冷却作用共同导致了东亚对流层顶高度的变化。     

地方集群网络、信息溢出效应与中国ICT产品出口地理网络扩张

研究中国ICT产品的出口贸易扩张有助于理解"全球-地方"互动视角下国际贸易与国内产业地理的相互作用。本文构建地方集群网络和信息溢出效应促进产品出口扩张的机制分析框架,利用2000—2016年中国海关库数据,探究中国ICT产品出口地理网络扩张机制。研究发现:(1)中国ICT产品出口源地从沿海地区向内陆地区扩张,出口目的地扩张重点在不同时间段存在差异。(2)中东部省份出口到东亚和北美、西部省份出口到北美和西欧的贸易扩张较为显著。(3)面板Probit模型分析表明,地方集群网络和信息溢出效应能够增加出口源地-目的地层面ICT产品出口额,提升出口专业化程度。     

Numerical modeling of dynamic rock fracture with a combined 3D continuum viscodamage‐embedded discontinuity model

This paper deals with numerical modeling of dynamic failure phenomena in rate‐sensitive quasi‐brittle materials, such as rocks, with initial microcrack populations. To this end, a continuum viscodamage‐embedded discontinuity model is developed and tested in full 3D setting. The model describes the pre‐peak nonlinear and rate‐sensitive hardening response of the material behavior, representing the fracture‐process zone creation, by a rate‐dependent continuum damage model. The post‐peak response, involving the macrocrack creation accompanied by exponential softening, is formulated by using an embedded displacement discontinuity model. The finite element implementation of this model relies upon the linear tetrahedral element, which seems appropriate for explicit dynamic analyses involving stress wave propagation. The problems of crack locking and spreading typical of embedded discontinuity models are addressed in this paper. A combination of two remedies, the inclusion of viscosity in the spirit of Wang's viscoplastic consistency approach and introduction of isotropic damaging into the embedded discontinuity model, is shown to be effective in the present explicit dynamics setting. The model performance is illustrated by several numerical simulations. In particular, the dynamic Brazilian disc test and the Kalthoff–Winkler experiment show that the present model provides realistic predictions with the correct failure modes and rate‐dependent tensile strengths of rock at different loading rates. The ability of initial embedded discontinuity populations to model the initial microcrack populations in rocks is also successfully tested. Copyright © 2016 John Wiley & Sons, Ltd.     

Stormwater management network effectiveness and implications for urban watershed function: A critical review

Deleterious effects of urban stormwater are widely recognized. In several countries, regulations have been put into place to improve the conditions of receiving water bodies, but planning and engineering of stormwater control is typically carried out at smaller scales. Quantifying cumulative effectiveness of many stormwater control measures on a watershed scale is critical to understanding how small‐scale practices translate to urban river health. We review 100 empirical and modelling studies of stormwater management effectiveness at the watershed scale in diverse physiographic settings. Effects of networks with stormwater control measures (SCMs) that promote infiltration and harvest have been more intensively studied than have detention‐based SCM networks. Studies of peak flows and flow volumes are common, whereas baseflow, groundwater recharge, and evapotranspiration have received comparatively little attention. Export of nutrients and suspended sediments have been the primary water quality focus in the United States, whereas metals, particularly those associated with sediments, have received greater attention in Europe and Australia. Often, quantifying cumulative effects of stormwater management is complicated by needing to separate its signal from the signal of urbanization itself, innate watershed characteristics that lead to a range of hydrologic and water quality responses, and the varying functions of multiple types of SCMs. Biases in geographic distribution of study areas, and size and impervious surface cover of watersheds studied also limit our understanding of responses. We propose hysteretic trajectories for how watershed function responds to increasing imperviousness and stormwater management. Even where impervious area is treated with SCMs, watershed function may not be restored to its predevelopment condition because of the lack of treatment of all stormwater generated from impervious surfaces; non‐additive effects of individual SCMs; and persistence of urban effects beyond impervious surfaces. In most cases, pollutant load decreases largely result from run‐off reductions rather than lowered solute or particulate concentrations. Understanding interactions between natural and built landscapes, including stormwater management strategies, is critical for successfully managing detrimental impacts of stormwater at the watershed scale.     

Modelling the optical turbulence boiling and its effect on finite-exposure differential image motion

It is usually accepted that whenever dealing with astronomical observation through the atmosphere, the optical turbulence temporal evolution can be sufficiently described with the so-called frozen turbulence hypothesis. In this model, turbulence is supposed to be equivalent to a series of solid phase screens that slide horizontally in front of the observation field of view. Experimental evidence shows, however, that an additional physical process must be taken into account when describing the temporal behaviour of the optical turbulence. In fact, while translating above the observer, turbulence undergoes a proper temporal evolution and affects differently the astronomical and, more specifically, the astrometric observations. The proper temporal evolution of the turbulence-induced optical turbulence observable quantities is here called the optical turbulence boiling. We are proposing through this paper a theoretical approach to the modelling of the optical turbulence temporal evolution when the turbulent layer horizontal translation and the optical turbulence boiling are both involved. The model we propose, as a working hypothesis though, has a direct relevance to differential astrometry because of its explicit dependence upon the optical turbulence temporal evolution. It can also be generalized to other techniques of high angular resolution astronomical observation through the atmospheric turbulence.