3,862 research outputs found

    Embracing complexity in international forest governance: a way forward; Policy Brief

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    This Policy Brief summarizes the findings of a comprehensive assessment of scientific information about international forest governance carried out by an Expert Panel of over 30 of the world's leading scientists working in the areas of environmental governance and international forest law. It aims to provide policy and decision makers with essential knowledge and building blocks required for a more effective and inclusive governance of the world's forest

    Computer simulation of diffusion processes in tilt spatio-periodic potentials

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    Нещодавно було показано, що в істотно нерівноважних системах коефіцієнт дифузії може вести себе немонотонно з температурою. Одним із прикладів таких систем з аномальною температурної залежністю є рух броунівських часток в просторово-періодичних структурах. Метою статті було дослідження зміни температурної залежності дифузії в недодемпфованих системах з низьким коефіцієнтом тертя. В роботі методами комп'ютерного моделювання вивчено зміна коефіцієнта дифузії частинок в широкому діапазоні температур в нахилених просторово-періодичних потенціалах для різних значень коефіцієнта тертя. Показано, що дифузія досягає максимуму при певній величині зовнішньої сили. Її значення залежить від величини коефіцієнта тертя. Показано, що на відміну від звичайної залежності Аррениуса, в разі нахиленого періодичного потенціалу, максимальний коефіцієнт дифузії зростає, а не зменшується з пониженням температури експоненціальним чином. Встановлено, що така залежність характерна для всіх недодемпфованих систем. Показано, що для просторово-періодичних структур існує обмежена ділянка сил, в якому спостерігається зростання коефіцієнта дифузії зі зменшенням температури. Це область так званої температурно-аномальної дифузії (ТАД). Визначено ширина і положення області ТАД в залежності від коефіцієнта тертя γ і параметрів системи. Показано, що зі зменшенням γ, ширина області ТАД зменшується пропорційно γ. При цьому коефіцієнт дифузії в області ТАД, навпаки зростає ~γ. Отримані дані про температурно-аномальної дифузії мають важливе значення для різних областей фізики і техніки та відкривають перспективи створення новітніх технологій управління процесами дифузії.It was recently shown that in essentially nonequilibrium systems, the diffusion coefficient can behave nonmonotonically with temperature. One example of such systems with anomalous temperature dependence is the motion of Brownian particles in spatially periodic structures. The aim of the article was to study the change in the temperature dependence of diffusion in underdamped systems with a low coefficient of friction. In this paper, computer simulation methods are used to study the change in the diffusion coefficient of particles in a wide range of temperatures in oblique spatially periodic potentials for different values of the friction coefficient. It is shown that diffusion reaches a maximum at a certain external force. Its value depends on the coefficient of friction. It is shown that, in contrast to the usual Arrhenius dependence, in the case of an inclined periodic potential, the maximum diffusion coefficient increases while temperature is decreasing exponentially. It is established that such a dependence is common to all underdamped systems. It is shown that for spatially periodic structures there is a limited portion of forces in which an increase in the diffusion coefficient while decreasing temperature is observed. This is the area of the so-called temperature-anomalous diffusion (TAD). The width and position of the TAD region are determined depending on the friction coefficient γ and the system parameters. It has been shown that a decrease in γ, width TAD region decreases proportionally γ. In this case, the diffusion coefficient in the TAD region, on the contrary, increases ~γ. The data obtained on the temperature and the anomalous diffusion are important for various fields of physics and engineering, and opens new prospects for a diffusion process control technology

    Simplifying Contract-Violating Traces

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    Contract conformance is hard to determine statically, prior to the deployment of large pieces of software. A scalable alternative is to monitor for contract violations post-deployment: once a violation is detected, the trace characterising the offending execution is analysed to pinpoint the source of the offence. A major drawback with this technique is that, often, contract violations take time to surface, resulting in long traces that are hard to analyse. This paper proposes a methodology together with an accompanying tool for simplifying traces and assisting contract-violation debugging.Comment: In Proceedings FLACOS 2012, arXiv:1209.169

    Online and offline representations of biocultural diversity: A political ecology perspective on nature-based tourism and indigenous communities in the Brazilian Pantanal

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    The concept of biocultural diversity is confronted with contemporary changes that impact on local communities, such as globalization and digital transformations. Engaging the conceptual flexibility of ‘biocultural diversity’, we studied nature-based tourism at the intersection of indigenous communities and the digital realm. We employed a political ecology perspective to examine online and offline representations of biocultural diversity in the Brazilian Pantanal, one of the biggest wetlands in the world, and home to groups of peoples known as the Pantaneiros. Data from interviews with 48 stakeholders in the tourist sector were structured along three ‘myths’—the Uncivilised, Unrestrained, and Unchanged—for which we have also constructed counter narratives. Each myth denoted the primacy of biodiversity, and ignored broader dimensions of the Pantanal as a bioculturally diverse landscape. The relationships of the Pantaneiros with their environment were found to be intricate and had clear repercussions for tourism, but ironically, reference to the Pantaneiro culture in nature-based tourism was superficial. Moreover, thriving on the myths, this form of tourism perpetuates skewed power structures and social inequalities. Lower-class Pantaneiros likely suffer most from this. We recommend stakeholder engagement with a biocultural design that facilitates the integration of other-than-biodiversity values, and that thereby promotes sustainability of the entire social-ecological system

    Saline Aquifer CO2 Storage (SACS2). Final report, geological characterisation of the Utsira Sand reservoir and caprocks (Work Area 1)

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    This report summarises the results and highlights the main findings of SACS Work Area 1, the geological and reservoir characterisation of the Utsira Sand and its caprock. For more detailed technical information on each topic, the reader is directed to the relevant SACS Technical Reports and, in particular, two earlier Work Area 1 interim reports, Holloway et al. (1999) and Chadwick et al. (2000). The Utsira Sand comprises a basinally-restricted deposit of Mio-Pliocene age forming a clearly defined seismic unit, pinching out to east and west, and seismically distinct from overlying and underlying strata.The reservoir is highly elongated, extending for more than 400 km from north to south and between 50 and 100 km from east to west, with an area of some 26100 km2. Its eastern and western limits are defined by stratigraphical lap-out, to the southwest it passes laterally into shaly sediments, and to the north it occupies a narrow channel deepening towards the More Basin. Locally, particularly in the north, depositional patterns are quite complex with some isolated depocentres, and lesser areas of non-deposition within the main depocentre. The top Utsira Sand surface generally varies relatively smoothly, mainly in the range 550 to 1500 m, but mostly from 700 to 1000 m. The base of the sand is more irregular, disturbed by diapirism of the underlying shales. Isopachs of the reservoir sand show two main depocentres. One is in the south, around Sleipner, where thicknesses range up to more than 300 m. The second depocentre lies some 200 km to the north of Sleipner. Here the Utsira Sand is locally 200 m thick, with an underlying sandy unit adding further to the total reservoir thickness. Macroscopic and microscopic analysis of core and cuttings samples of the Utsira Sand show that it consists of a largely uncemented fine-grained sand, with medium and occasional coarse grains. The grains are predominantly angular to sub-angular and consist primarily of quartz with some feldspar and shell fragments. Sheet silicates are present in small amounts (a few percent). The sand is interpreted as being deposited by mass flows in a marine environment in water depths of 100 m or more. The porosity of the Utsira Sand core ranges generally from 27% to 31%, but reaches values as high as 42% Regional log porosities are quite uniform, in the range 35 to 40% over much of the reservoir. Geophysical logs show a number of peaks on the -ray, sonic and neutron density logs, and also on some induction and resistivity logs. These are interpreted as mostly marking thin (~1m thick) intrareservoir shale layers. The shale layers constitute important permeability barriers within the reservoir sand, and have proved to have a significant effect on CO2 migration through, and entrapment within, the reservoir. The proportion of clean sand in the total reservoir thickness varies generally from about 0.7 to nearly 1.0. The caprock succession overlying the Utsira reservoir is rather variable, and can be divided into three main units. The Lower Seal forms a shaly basin-restricted unit, some 50 to 100 m thick. The Middle Seal mostly comprises prograding sediment wedges of Pliocene age, dominantly shaly in the basin centre, but coarsening into a sandier facies both upwards and towards the basin margins. The Upper Seal comprises Quaternary strata, mostly glacio-marine clays and glacial tills. The Lower Seal extends well beyond the area currently occupied by the CO2 injected at Sleipner and seems to be providing an effective seal at the present time. Cuttings samples comprise dominantly grey clay silts or silty clays. Most are massive although some show a weak sedimentary lamination. XRD analysis typically reveal quartz (30%), undifferentiated mica (30%), kaolinite (14%), K-feldspar (5%), calcite (4%), smectite (4%), albite (2%), chlorite (1%), pyrite (1%) and gypsum (1%) together with traces of drilling mud contamination. The clay fraction is generally dominated by illite with minor kaolinite and traces of chlorite and smectite. The cuttings samples are classified as non-organic mudshales and mudstones. Although the presence of small quantities of smectite may invalidate its predictions, XRD-determined quartz contents suggest displacement pore throat diameters in the range 14 to 40 nm. Such displacement pore throat diameters are consistent with capillary entry pressures of between about 2 and 5.5 MPa capable of trapping a CO2 column several hundred metres high. In addition, the predominant clay fabric with limited grain support resembles caprocks which are stated in the literature to be capable of supporting a column of 35 API oil greater than 150 m in height. Empirically, therefore, the caprock samples suggest the presence of an effective seal at Sleipner, with capillary leakage of CO2 unlikely to occur. Around and east of the injection point, a layer of sand, 0 - 50 m thick, lies close to the base of the Lower Seal and is termed the Sand-wedge. The geometry of this unit is likely to prove important in determining the long-term migration behaviour of the CO2. Fluid flow in the Utsira Sand, based on limited pressure measurements and basin-modelling, is likely to be low, in the range 0.3 – 4 metres per year, depending on assumed permeabilities. The total pore-space within the Utsira Sand is estimated at 6.05 x 1011 m3. However not all of this can necessarily be utilised for CO2 storage. The simplest assumption is that long-term storage of CO2 can only be accomplished in structural traps at the top of the reservoir. A detailed study around Sleipner indicates that 0.3% of the reservoir porosity is actually situated within structural closures such as this. In practical terms moreover, with a small number of injection wells, it is unlikely that all of the small traps could be utilised in any case. Around Sleipner the most realistic estimate of the pore-space situated within accessible closed structures is just 0.11% of the total pore-volume. On the other hand, trapping of CO2 beneath the intra-reservoir shales could significantly increase realisable storage volumes, particularly if it encouraged dissolution of CO2 into the groundwater. Similarly trapping of CO2 in the Sand-wedge, as well as beneath the top of the Utsira Sand, will increase the overall storage capacity significantly. In conclusion, the theoretical storage capacity of the Utsira Sand is very high, but how much of this can be utilised in reality is uncertain, and a function of several complex parameters. Migration models have been constructed with 30 x 106 m3 of CO2, injected into the Utsira Sand (approximating to the expected final injected mass of 20 million tonnes). They show that if the CO2 is trapped at the top of the Utsira Sand it will migrate generally northwestward, reaching a maximum distance from the injection site of about 12 km. However, if the CO2 is trapped within the Sand-wedge, migration is less well constrained, being northwards then northeastwards. Data limitations to the east of the injection point preclude quantitative estimates of the maximum migration distance in this case

    Copyright Notice

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    The Routing Over Low-Power and Lossy (ROLL) networks Working Group has been chartered to work on routing solutions for Low-Power and Lossy Networks (LLNs) in various markets: industrial, commercial (building), home, and urban networks. Pursuant to this effort, this document defines the IPv6 routing requirements for building automation. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained a

    Broedresultaten van kokmeeuwen in Nederland in 1997 = Reproductive success of Black-Headed gulls in the Netherlands in 1997

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    The Black-headed Gull population in The Netherlands, as in other parts of Europe, has seriously declined since the 1980s. The decline has been noted both at coastal and mainland breeding sites. The reasons for the general decline are not known. Therefore a monitoring programme was established to measure breeding results of Black-headed Gulls in six Dutch colonies in 1997. Remarkable differences were found in hatching success and breeding success. Hatching success was high (75- 90%) in the three northern colonies situated in or near the Wadden Sea, whereas in all other colonies hatching success was extremely low (0-43%). Most eggs were lost through flooding, trampling by geese, depredation or nest desertion. Only in the colony at Griend, fledging success was high (66%) and some young fledged in Julianapolder. In all other colonies, most chicks died of starvation or depredation. In those colonies the food mainly consisted of marine prey (e.g. fish, shrimps and lugworms), whereas in the other colonies the chicks were fed with a large proportion of insects and other invertebrates

    Aperture array development for future large radio telescopes

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    We present the design of a phased array system for future radio telescopes. This includes a system overview and recent results of the designed and implemented system, the Electronic Multi-Beam Radio Astronomy Concept (EMBRACE). Furthermore, simulations with a full-EM antenna simulator, combined with measurements on actual hardware, will provide information for the next design step, the Aperture Array Verification System (AAVS). With AAVS, we will prove design readiness of this novel array technology
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