Salt and ice crystallisation in porous sandstones   总被引：1，自引：0，他引：1  

Joerg Ruedrich  Siegfried Siegesmund 《Environmental Geology》2007,52(2):225-249

Salt and ice crystallisation in the pore spaces causes major physical damage to natural building stones. The damaging effect of these processes can be traced back to physically induced stress inside of the rock while crystallizing. The increasing scientific research done during the past century has shown that there are numerous parameters that have an influence on the weathering resulting from these processes. However, the working mechanisms of the stress development within the rock and its material dependency are still subject to discussion. This article gives an overview of salt and ice weathering. Additionally, laboratory results of various sandstones examined are presented. Salt crystallisation tests and freeze/thaw tests were done to obtain information about how crystallisation weathering depends on material characteristics such as pore space, water transportation, and mechanical features. Simultaneous measuring of the length alternating during the salt and ice crystallisation has revealed detailed information on the development of crystal in the pore spaces as well as the development of stress. These findings can help to understand the damaging mechanisms.  相似文献   

Living radiolarian feeding mechanisms: new light on past marine ecosystems     

Atsushi Matsuoka 《Swiss Journal of Geoscience》2007,100(2):273-279

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Irreversible thermodynamic and viscoelastic model for power-law relaxation and attenuation of rocks     

Yusuke Kawada  Hiroyuki Nagahama  Hiroaki Hara 《Tectonophysics》2006,427(1-4):255

A constitutive law for viscoelastic behaviour of rocks is derived from irreversible thermodynamics. To this model, two specific parameters are introduced; one is an internal state variable which is a variable concerning the microstructures such as defects in crystals or microcracks, and the other is a temperature reduced time obtained by normalizing the various temperature behaviours. A large number of internal state variables have the respective relaxation times and show the respective time evolutions, while a set of the time evolutions generates temporal power-law behaviour of rocks. The time evolutions of internal states are regarded as dynamics of elements of the generalized Maxwell model, and the stress–strain relation is represented by a response function following a temporal power-law in terms of linear system theory. This relation is inversely formulated to investigate the source field from output data. This model enables us to explain experimentally-based constitutive laws for transient and steady-state behaviour of rocks (e.g., lherzolite) following a temporal power-law and for attenuation behaviour of polycrystals (e.g., olivine) represented by a relation between the quality factor and frequency. Both laws show power-laws on deformation time or frequency depending on the fractal structure in polycrystals or rocks, and the experimental high-temperature behaviours can be extrapolated to long deformation time or high frequency behaviour.  相似文献   

Assessing the EU ETS with a bottom-up,multi-sector model     

Pablo Pintos  Pedro Linares 《Climate Policy》2018,18(4):413-424

The European Emissions Trading System (EU ETS) is the central pillar of the EU response against climate change. This trading mechanism is considered, from the theoretical point of view, as the most cost-effective method to reduce GHG. However, previous studies show that the agents who participate in these markets may behave in a way that may lead to inefficient CO₂ prices, creating doubts about the static and dynamic efficiency of the system. This article analyses these possible anomalies by first trying to model the ETS in a more realistic way, addressing some of the limitations of previous models, and second, by comparing the results with real market transactions. For this, a bottom-up, multi-sector model has been built, which represents the EU ETS in an integrated, cross-sectoral way, paying particular attention to the interactions among the most emissions intensive industries. The results show the benefits of this modelling approach and how it better reflects real market conditions. Some preliminary conclusions regarding the behaviour of the agents in the ETS market are also presented.

POLICY RELEVANCE

Low allowance prices in the EU ETS have put into question the dynamic efficiency of the EU ETS system, prompting various ideas for structural reform. However, determining the right reform also requires estimating correctly how agents will respond to it. This article proposes a tool to realistically simulate the EU ETS under the assumption of rational agents, and compare it to real market outcomes, in order to understand better the behaviour of agents in this carbon market, and therefore how to design better policies.  相似文献   

轨道站点合理步行可达范围建成环境与轨道通勤的关系研究——以北京市44个轨道站点为例   总被引：4，自引：1，他引：3  

申犁帆  王烨  张纯  姜冬睿  李赫 《地理学报》2018,73(12):2423-2439

轨道站点步行可达范围内建成环境因素与轨道交通通勤行为之间的关系越来越受到人们的重视。从潜在通勤者的角度出发,划定轨道站点的合理步行可达范围,以北京市44个轨道站点为例,利用大数据方法从“宜出行”程序中提取站点合理步行范围内的相对人口数据,结合2017年9月10个工作日早高峰时段的轨道站点刷卡数据得到该站点的相对乘车率。基于数据的非正态分布特征构建GARCH模型,分析早高峰站点合理步行范围内建成环境因素与站点相对乘车率的关系。结果表明：① 始发轨道站点与站点乘车率存在显著正向关系,而站点所在线路的换乘概率与站点乘车率具有非常明显的负相关性;② 轨道站点的出入口数量与乘车率显著正相关;③ 小区—站点的路径转折数和步行范围内的交叉路口数等可步行性特征对轨道交通通勤行为无显著影响,步行范围的公交车站密度与站点乘车率正相关;④ 合理步行范围内的用地混合度与乘车率存在显著的负相关性;⑤ 合理步行范围内的路网密度以及早高峰拥堵道路比与乘车率之间在不同程度上呈现正向关系;⑥ 共享单车订单数与轨道交通通勤行为之间的关系并不明确;⑦ 相比手机信令数据,“宜出行”定位数据的精度更高,适用于分析微观尺度下的实时人口分布及变化。  相似文献   

从物联网到人迹网:理论、技术与应用     

陈戈  张小垒  韩勇  马纯永 《中国海洋大学学报(自然科学版)》2014,44(10):148-154

近几年,物联网快速发展,建立了物质环境在网络数字世界中的映射;移动互联网和智能终端的发展,使人类的日常行为信息越来越多的映射到了网络数字世界中。这些信息与人们在传统网络中的行为数据相比,最大的变革就是有了空间和时间属性,用一个形象的词来描述这类信息那就是"人迹",人迹通过时空互联形成的一种网络,本文叫做"人迹网"。在人迹网出现之前,对于人类社会行为的研究缺乏大规模的实验环境,无法获取完善的人类行为数据。人迹网承载了关于人类社会行为和交互的大规模、客观、实时、连续、动态的现场数据,为人类行为理解和交互规律认识的研究提供坚实基础。同时对人类社会行为的研究,可以为城市、社会、个人等提供科学的行为指导,具有良好的应用和社会意义。本文描述了人迹网的形成,从理论体系、技术方法和和应用实例等方面对人迹网进行了阐述和设计。  相似文献   

Do suburban residents prefer the fastest or low-carbon travel modes? Combining public participation GIS and multimodal travel time analysis for daily mobility research     

《Applied geography (Sevenoaks, England)》2014

Sustainability of urban transportation and residents' daily mobility is increasingly important for the future of urban regions. In this paper, we present a novel methodology combining mapped survey responses (gathered using public participation GIS) and sophisticated multimodal routing analysis to understand patterns of suburban residents' daily mobility. Our particular focus is on residents' mode choices and their optimality in terms of travel time. We also examine the carbon-intensity of potential mode choice mismatches where a comparatively slower travel mode is chosen for a particular trip. This paper shows how the combination of the two data sources create new possibilities for analysing daily mobility by enabling the comparison of self-reported, geographically referenced mobility patterns and modelled, objectively “optimal” patterns. Our case study results from a rapidly growing metropolitan area, Greater Helsinki in Finland, indicate that people have rather sustainable daily mobility practices. Their daily trips are typically short (median 1.8 km), and non-motorised travel modes are the most popular. Also the share of car travel is significant. While public transport clearly has the lowest modal share, it is frequently used on longer trips to destinations where public transport connections are good (particularly the city centre). In 44% of trips, the respondents choose the fastest travel mode. When a comparatively slower travel mode is chosen, it most often produces less CO₂ emissions than the fastest mode. However, particularly on shopping trips – the most commonly reported type of trip – car driving dominates as the fastest means of transportation. When a slower mode is chosen on a shopping trip, it is typically more carbon-intensive than the fastest mode would have been in that case. The methodology presented here can be used to support local decision making, particularly when daily services and transport infrastructure are planned or reorganised.  相似文献   

Photo-identification and habitat use of Atlantic humpback dolphins Sousa teuszii around the Río Nuñez Estuary in Guinea,West Africa     

CR Weir 《African Journal of Marine Science》2015,37(3):325-334

Ecological data for the Atlantic humpback dolphin Sousa teuszii are scant. Six on-effort Sousa teuszii sightings were recorded during 817.6?km of boat-based effort in the Río Nuñez region of Guinea during October and November 2013. Two incidental sightings were also reported. Groups comprised 1–25 animals. Photo-identification produced a minimum population estimate of 47 animals. Most sightings (n = 5) were located close (<1?km) to shore along a 5.7?km stretch of coast on the west side of Île de Taïdi, primarily over shallow, sand–mud habitat. Two very distinctive individuals were present in all four Taïdi photo-identification encounters, suggesting high site fidelity and stable associations. Two sightings occurred in the outer Río Nuñez Estuary much farther from the coast (5–12?km) but in relatively shallow water (≤15?m) over sand–mud sediment. Focal follows (n = 5: 0.2–3.8?h duration) produced 9.02?h of behavioural data. Travel (51%), foraging (39%) and feeding (9.2%) dominated, with Taïdi dolphins spending more time foraging and feeding than the outer estuary groups. Three individuals had linear-severed dorsal fins consistent with injuries from fishing line. Some management implications of variation in habitat, site fidelity and movements of Sousa teuszii groups are discussed.  相似文献   

Movement patterns of surf-zone fish species in a subtropical marine protected area on the east coast of South Africa     

BQ Mann  PD Cowley  ST Fennessy 《African Journal of Marine Science》2015,37(1):99-114

A long-term mark-recapture study was used to assess the movement patterns of surf-zone fishes in the St Lucia Marine Reserve, a marine protected area within the iSimangaliso Wetland Park, a World Heritage Site on the east coast of South Africa. Between 2001 and 2013, 6 613 fish from 71 species, caught by hook and line, were tagged at four sites within and adjacent to a no-take marine sanctuary area. A total of 1 004 (15.2%) recaptures were made from 17 species. The majority (82.4%) of these species displayed station-keeping behaviour, whereas only three were classified as wider-ranging species, and no species with discernible migratory behaviour was observed. Findings for five species with the highest recapture rates, namely Pomadasys furcatus, Epinephelus andersoni, E. marginatus, Dinoperca petersi and Lutjanus rivulatus, are presented in greater detail. Recapture rates ranged from 7% to 50% and time at liberty from 0 to 3 163 days. Individuals of all five species displayed station-keeping behaviour, with the 95th percentile of intra-study-site movements varying between 200 and 1 025 m (linear distance). However, four of the five species also displayed some ranging behaviour and made exploratory excursions ranging from 3.5 to 125 km, in both northerly and southerly directions. The dominance of station-keeping behaviour suggests that the St Lucia Marine Reserve sanctuary zone provides an important refuge for these species, with some export to adjacent areas.  相似文献   

How the response spectrum of non-liquefied loose-to-medium sand deposits is affected by the groundwater level     

《Computers and Geotechnics》2014

This study examines the water level influence on the seismic response of sand deposits. The seismic ground response of a sand deposit for two cases was computed: groundwater level near the surface and at great depth. The ratio of soil factors computed for both cases evaluates the influence of having the water table near the surface. This parameter is small when the full range of periods is considered, but rises to ∼1.15 when narrowing the range of periods to 0.2–0.6 s, corresponding to the plateau of Eurocode 8 ground type C response spectrum. So, the water level effect is of the same magnitude of the existing soil factor in seismic codes.  相似文献