Estimation of the REV size for blockiness of fractured rock masses

The representative elementary volume (REV) is the premise of the continuous-media method of analysis, and the investigation of the REVs of fractured rock masses is a fundamental area of rock mechanics research. The existence of an REV can be determined based on a variety of physical parameters. This paper presents an analysis of the REV from the view of blockiness, which is defined as the percentage of the volume of isolated blocks formed by fractures in the total rock volume. Seventy-seven types of fractured rock mass models were developed based on 7 classes of fracture persistence and 11 classes of spacing that are suggested by the International Society for Rock Mechanics (ISRM) fracture classification. Rock blocks in each of the 77 types of fractured rock mass models were identified using GeneralBlock to determine the variation in blockiness with model domain sizes, which were changed from 2 to 20 times the fracture spacing. For each model domain size 9 random realizations were carried out to reduce the effects of randomness. The coefficient of variation (C_v) was then used to quantify the variability of the 9 random realizations. The fluctuation in blockiness with the variation in the scale of the model region was also investigated. In this way, the size of the REV in these models can be calculated using the average and the variance of the blockiness as indicators of the convergence. The blockiness of these fractured rock masses can be determined at the REV volume. The results indicate that of the 77 models, 76 REV sizes are between 2 and 20 times the fracture spacing. The fractured rock mass with a wide fracture spacing and very high persistence (WS2–VHP) has a REV size that exceeds 20 times the fracture spacing. Thus, the WS2–VHP model should be investigated further to validate this concept.     

Shared Socio-Economic Pathways of the Energy Sector – Quantifying the Narratives

Energy is crucial for supporting basic human needs, development and well-being. The future evolution of the scale and character of the energy system will be fundamentally shaped by socioeconomic conditions and drivers, available energy resources, technologies of energy supply and transformation, and end-use energy demand. However, because energy-related activities are significant sources of greenhouse gas (GHG) emissions and other environmental and social externalities, energy system development will also be influenced by social acceptance and strategic policy choices. All of these uncertainties have important implications for many aspects of economic and environmental sustainability, and climate change in particular. In the Shared-Socioeconomic Pathway (SSP) framework these uncertainties are structured into five narratives, arranged according to the challenges to climate change mitigation and adaptation. In this study we explore future energy sector developments across the five SSPs using Integrated Assessment Models (IAMs), and we also provide summary output and analysis for selected scenarios of global emissions mitigation policies. The mitigation challenge strongly corresponds with global baseline energy sector growth over the 21st century, which varies between 40% and 230% depending on final energy consumer behavior, technological improvements, resource availability and policies. The future baseline CO₂-emission range is even larger, as the most energy-intensive SSP also incorporates a comparatively high share of carbon-intensive fossil fuels, and vice versa. Inter-regional disparities in the SSPs are consistent with the underlying socioeconomic assumptions; these differences are particularly strong in the SSPs with large adaptation challenges, which have little inter-regional convergence in long-term income and final energy demand levels. The scenarios presented do not include feedbacks of climate change on energy sector development. The energy sector SSPs with and without emissions mitigation policies are introduced and analyzed here in order to contribute to future research in climate sciences, mitigation analysis, and studies on impacts, adaptation and vulnerability.     

基于共享社会经济路径的中国经济发展趋势及其影响要素分析

基于最新的经济和人口普查及逐年统计年鉴,采用柯布?道格拉斯(Cobb-Douglas)经济预测模型,分析了共享社会经济路径(SSPs)框架下中国“全面二孩”政策后2010—2100年经济发展趋势,并解析了劳动投入量、资本投入量和全要素生产率对经济发展的贡献率。研究发现：(1)不同的社会经济发展政策下,21世纪中国经济均呈增加趋势,GDP增速在2030年前基本维持在6%上下,但2030—2060年代迅速下降,2070年代起SSP1和SSP4路径下增幅低于0.5%,SSP2、SSP3和SSP5路径下增幅保持在0.5%~1.5%。(2)影响经济发展的三要素中,劳动投入量在SSP3路径下先减后增,于2060年代达到谷值;在其他路径下均先增后减,于2020年代达到峰值。资本投入量在SSP1路径下持续增加,2080年代起趋于平缓;其他路径下均呈持续增加趋势,但在SSP4路径下,在2060和2070年代有所下降。全要素生产率在所有路径下均呈增加趋势。(3)改革开放以来,资本投入量是影响我国经济增长最主要的因素。未来,SSP1和SSP2路径下,全要素生产率逐渐成为经济发展的主导因素;而SSP5路径下,资本投入量仍是影响经济发展的主要因素。     

2013—2016年海口市空气质量特征及典型个例污染物来源分析

根据海南省环境科学研究院提供的海口站2013—2016年逐日空气污染数据,统计分析了海口市空气质量状况。综合应用高低空环流场、AQI指数结合MODIS卫星蓝光气溶胶厚度图,采用HYSPLIT轨迹聚类分析法、潜在源贡献因子法和浓度权重轨迹分析方法,重点分析了2013年12月海口空气污染的的主要输送路径,并探讨了首要污染物PM_2.5和O₃的潜在源区。结果表明：冬夏季风风向转换是海口发生空气污染的最主要气象原因,且首要污染物为PM_2.5,其次是PM₁₀和O₃;海口市空气质量达标率在97.1%,总体较好,AQI指数呈逐年下降趋势;值得关注的是,O₃呈逐年稳定上升趋势。大气污染物浓度受污染物排放和环流场共同影响,海口污染日对应的地面天气形势主要有3种类型,冷高压、变暖高压脊和台风外围下沉气流。此次污染过程中污染源是来自北方地区污染物长距离输送影响的结果。污染物个例分析中,首要污染物PM_2.5潜在源区主要集中在湖南和江西的交界处、广东沿海地区、广西北部、江西和福建的交界处以及浙江中部地区,这些潜在源区气团沿着轨迹1、2和4通过长距离输送到海口。海口O₃质量浓度贡献较大的区域主要集中在湖南和江西的交界处、粤西一带,主要沿着轨迹2将内陆地区的污染源输送到海口。     

江苏风能资源代表年选择的方法比较

代表年法是风能资源计算中的重要方法,而对区域风能资源代表年的选取方法不一.以江苏省为例,对区域多站点的风能资源代表年选取的两种方法--"站点最大频数法"和"区域平均法"的比较分析表明,两种方法选取的江苏省风能代表年是一致的.本文的结果可以推广到其它多站点区域的风能资源代表年的选取上,其中站点最大频数法简便易操作,适用于较少站点数条件下的代表年选取和业务性运用;区域平均法适用于稠密站点条件下的代表年选取;在样本足够大条件下,上述两种方法的计算精度能够满足风能利用的业务和研究需要,并具有足够的区域一致性和代表性.     

Polychlorierte Dibenzo-p-dioxine, -furane (PCDD/F) und Analoga in Oberflächensedimenten und datierten aquatischen Sedimentkernen

Polychlorinated Dibenzo-p-dioxins, -furans (PCDD/F) and Analogues in Surface Sediments and Dated Aquatic Sediment Cores Aquatic sediments are the final sinks of unintentionally formed PCDD/Fs. Still not known are the conditions of formation of PCDD/Fs in the 8120 years old sediments in Japan and in 350 to 400 years old sediments in the Baltic. Sediments are means of source identification if transformation processes are taken into consideration in view of hydrological conditions. PCDD/Fs have been analysed 30 km from the source in sediments and over a distance of 50 km in benthos indicating a remarkable bioaccumulation potential. Elaborated data of the PCDD/F sediment contamination are missing as well as information on internal diagenetic processes, interactions at the sediment/water interface, and on the aerobic and anaerobic biodegradation and bioavailability of PCDD/Fs in sediments. Quality criteria for sediments and aquatic ecosystems remain to be elaborated.     

Transformation of debris flows into turbidity currents: mechanisms inferred from laboratory experiments

Three sets of lock exchange experiments were run to look at the generation of turbidity currents from debris flows. The flows ranged from reasonably dilute (4% volumetric concentration) to dense (40% volumetric concentration) with cohesive, non-cohesive and mixed cohesive/non-cohesive sediment. Concentration was measured at one height using an Ultrasonic High Concentration Meter. Velocity was measured using Ultrasonic Doppler Velocimetry Profiling at 10 different heights in each run. The resulting flows range from plug flows to well mixed flows. Comparison of the concentration profiles, velocity time–height plots and vertical profiles of downstream velocity and root mean square velocity showed several different transformation mechanisms. Depending on the concentration and composition of the flow, transformation took place through one or more of the following processes: erosion of material from the dense mass, breaking apart of the dense underflow, breaking of internal waves and turbulent mixing. The extent of transformation depends on the viscosity and density of the flow. Initially very dense and viscous flows experience minor transformation only at the surface, resulting in a dilute turbidity current. Flows that are initially not so dense and viscous are churned up entirely, undergoing the different transformation processes. For these flows, transformation processes work throughout the entire flow, not just at the surface. Transformation of the less-dense flows is efficient with all or most material ending up in the resulting turbidity current.     

Simulation of Time Series of Concentration Fluctuations in Atmospheric Dispersion Using a Correlation-distortion Technique

Short-duration fluctuations in the concentration of airborne substances can be important in a variety of atmospheric dispersion problems, especially when assessing the risks posed by harmful materials. This paper discusses a simulation technique for generating individual realisations of fluctuating concentration time series in dispersing plumes based on target probability distributions and spectral functions. The scheme uses a correlation-distortion approach to simulate these time series. Gaussian processes with modified spectral characteristics are generated and then transformed to yield non-Gaussian processes with the desired spectral characteristics. The simulation scheme is initially developed for a single receptor, and is then extended to model pairs of correlated time series at two receptors. In fact, the modelling technique can be generalised to an arbitrary number of receptors and this provides, in principal, an approach that is applicable to a wide class of similar problems (such as the modelling of instantaneous puff releases or the response of line-of-sight detection systems). The simulation technique is illustrated using observations made during recent field experiments, conducted both in the United Kingdom and in the U.S.A., investigating the short-range dispersion of a passive tracer.     

Some Simple Statistical Models For Relative And Absolute Dispersion

Observations of the dispersion of a contaminant plume in the atmospheric boundary layer, obtained using a Lidar, are analysed in the coordinate frame relative to the instantaneous centre of mass of the plume, as well as the absolute (or fixed) coordinate frame. The study extends the work presented in a previous article, which analysed the structure of the probability density function (pdf) of concentration within the relative coordinate frame. Firstly, the plume displacement component, or plume meander, is analysed and a simple parametric form for the pdf of the plume centreline position is suggested. This is then used to analyse the accuracy and applicability of absolute framework statistical quantities obtained by a convolution of the relative frame statistical quantity with the plume centreline pdf.     

滇东华力西期不整合面含金性

多年对滇东地质勘查和矿业开发研究中发现，区内各金矿床(体)的赋存部位，多沿被动大陆边缘华力西期不整合面分布。由于区内华力西期不整合面明显受到边缘NS两侧两条深大断裂控制，多期NE～SW向左行剪切挤压作用，使不整合面上下地块以其为差异变形轴，旋转产生多期构造剥离或错移，在不整合面上下层位中形成较发育的构造剥离空间、张裂带或板劈理带。这些略呈线型分布的构造挤压带，在地史发展过程中，卷入多期构造变形后演变成局限断裂陷槽或槽沟环境，沉积了一套有别于其它区域的岩性组合。边缘深大断裂多期次海底基性火山喷发或喷流作用。除提供了幔源、壳源含金物质和含矿热液的活化与迁移的通道外，再次卷入构造变形的这些局限断裂陷槽或槽沟又成为区域金成矿物质聚集的有利场所，含矿热液选择沉积其内或堆积其中的细碎屑岩、粘土质岩、含碳质泥质岩类、不纯碳酸盐岩进行交代与沉淀，不受层控的影响，形成了滇东沿华力西期不整合面或接触带金成矿带。