Temporal scaling in river flow: can it be chaotic? / L’invariance d’échelle de l’écoulement fluvial peut-elle être chaotique?     

《水文科学杂志》2013,58(3)

Abstract

Abstract Identification of the presence of scaling in the river flow process has been a challenging problem in hydrology. Studies conducted thus far have viewed this problem essentially from a stochastic perspective, because the river flow process has traditionally been assumed to be a result of a very large number of variables. However, recent studies employing nonlinear deterministic and chaotic dynamic concepts have reported that the river flow process could also be the outcome of a deterministic system with only a few dominant variables. In the wake of such reports, a preliminary attempt is made in this study to investigate the type of scaling behaviour in the river flow process (i.e. chaotic or stochastic). The investigation is limited only to temporal scaling. Flow data of three different scales (daily, 5-day and 7-day) observed in each of three rivers in the USA: the Kentucky River in Kentucky, the Merced River in California and the Stillaguamish River in Washington, are analysed. It is assumed that the dynamic behaviour of the river flow process at these individual scales provides clues about the scaling behaviour between these scales. The correlation dimension is used as an indicator to distinguish between chaotic and stochastic behaviours. The results are mixed with regard to the type of flow behaviour at individual scales and, hence, to the type of scaling behaviour, as some data sets show chaotic behaviour while others show stochastic behaviour. They suggest that characterization (chaotic or stochastic) of river flow should be a necessary first step in any scaling study, as it could provide important information on the appropriate approach for data transformation purposes.  相似文献   

Formulation of a three‐dimensional constitutive model for unsaturated soils incorporating mechanical–water retention couplings     

Martí Lloret‐Cabot  Marcelo Sánchez  Simon J. Wheeler 《国际地质力学数值与分析法杂志》2013,37(17):3008-3035

Wheeler, Sharma and Buisson proposed an elasto‐plastic constitutive model for unsaturated soils that couples the mechanical and water retention behaviours. The model was formulated for isotropic stress states and adopts the mean Bishop's stress and modified suction as stress state variables. This paper deals with the extension of this constitutive model to general three‐dimensional stress conditions, proposing the generalized stress–strain relationships required for the numerical integration of the constitutive model. A characteristic of the original model is the consideration of a number of elasto‐plastic mechanisms to describe the complex behaviour of unsaturated soils. This work presents the three‐dimensional formulation of these coupled irreversible mechanisms in a generalized way including anisotropic loading. The paper also compares the results from the model with published experiments performed under different loading conditions. The response of the model is very satisfactory in terms of both mechanical and water retention behaviours. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

A comprehensive model of the psychology of environmental behaviour—A meta-analysis     

Christian A. Klöckner 《Global Environmental Change》2013,23(5):1028-1038

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Synergies and tradeoffs in how managers,scientists, and fishers value coral reef ecosystem services     

Christina C. Hicks  Nicholas A.J. Graham  Joshua E. Cinner 《Global Environmental Change》2013,23(6):1444-1453

Managing ecosystems in a changing environment faces the challenge of balancing diverse competing perspectives on which ecosystem services – nature's benefits – to prioritize. Consequently, we measured and compared how different stakeholders (managers, scientists and fishers) prioritize specific coral reef ecosystem services. Managers’ priorities were more aligned with scientists’ priorities but all stakeholder groups agreed that fishery, education, and habitat were high priorities. However, stakeholder groups differed in the extent to which they prioritized certain services. Fishers tended to assigned greater estimates to fishery and education, managers to culture, and scientists to coastal protection. Furthermore, using network analysis to map the interactions between stakeholders’ priorities, we found distinct synergies and trade-offs in how ecosystem services were prioritized, representing areas of agreement and conflict. In the fishers’ network, trade-offs emerged between two services, both of a higher priority, such as fishery and habitat. Conversely, in the scientists’ network, trade-offs emerged between services of a higher and lower priority, such as habitat and culture. The trade-offs and synergies that emerged in the managers’ network overlap with both fishers’ and scientists’ suggesting a potential brokering role that managers can play in balancing both priorities and conflicts. We suggest that measuring ecosystem service priorities can highlight key areas of agreement and conflict, both within and across stakeholder groups, to be addressed when communicating and prioritizing decisions.  相似文献   

Proportional stress and strain paths in barodesy          下载免费PDF全文

Gertraud Medicus  Dimitrios Kolymbas  Wolfgang Fellin 《国际地质力学数值与分析法杂志》2016,40(4):509-522

Asymptotic behaviour of soil deserves particular attention: If soil is deformed with a proportional strain path, the resulting stress path approaches asymptotically a proportional stress path. In this arcticle, we review existing experimental evidence on this phenomenon and discuss it in the frame of barodesy. Here, the presented relation is a modification of a barodetic expression and includes Jáky's relation, inhibits tensile stress and is able to predict asymptotic stress ratios based on experimental findings. The proposed relation is compared with experimental data as well as with the so‐called stress‐dilatancy relations and other constitutive relations proposed so far. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Abrupt changes in the discharge and sediment load of the Pearl River,China     

Qiang Zhang  Chong‐Yu Xu  Xiaohong Chen  Xixi Lu 《水文研究》2012,26(10):1495-1508

The abrupt changes in the streamflow and sediment load at nine hydrological stations of the Pearl River basin were systematically analysed by using the simple two‐phase linear regression scheme and the coherency analysis technique. Possible underlying causes were also discussed. Our study results indicated that abrupt changes in the streamflow occurred mainly in the early 1990s. The change points were followed by significant decreasing streamflow. Multiscale abrupt behaviour of the sediment load classified the hydrological stations into two groups: (1) Xiaolongtan, Nanning and Liuzhou; and (2) Qianjiang, Dahuangjiangkou, Wuzhou, Gaoyao, Shijiao and Boluo. The grouped categories implied obvious influences of water reservoirs on the hydrological processes of the Pearl River. On the basis of analysis of the locations and the construction time of the water reservoirs, and also the time when the change points occurred, we figured out different ways the water reservoirs impacted the hydrological processes within the Pearl River basin. As for the hydrological variation along the mainstream of the Pearl River, the water reservoirs have considerable influences on both the streamflow and sediment load variations; however, more influences seemed to be exerted on the sediment load transport. In the North River, the hydrological processes seemed to be influenced mainly by climate changes. In the East River, the hydrological variations tended to be impacted by the water reservoirs. The study results also indicated no fixed modes when we address the influences of water reservoirs on hydrological processes. Drainage area and regulation behaviour of the water reservoirs should be taken into account. The results of this study will be of considerable importance for the effective water resources management of the Pearl River basin under the changing environment. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Sustainable energy transition in developing countries: the role of energy aid donors     

Jung Eun Kim 《Climate Policy》2019,19(1):1-16

Dialogues on global climate policy are increasingly discussing the sustainable energy transition, with Goal 7 of the UN’s Sustainable Development Goals highlighting the importance of affordable and clean energy. This study looks at foreign aid as a carrier of global climate policy and examines donor behaviour in the energy sector. By examining donor behaviour when giving energy aid, one can grasp how the donor community helps recipients achieve a sustainable energy transition. A panel of donor–recipient pairs, covering 29 donors and 99 recipients, was constructed for the period between 1996 and 2013, using data from Organisation for Economic Co-operation and Development Creditor Reporting System (OECD CRS), International Energy Agency (IEA) and World Development Indicators (WDI). The pair-year panel data were empirically analysed using a two-part model to test whether energy aid donors respond to recipients’ needs with regard to renewable energy and residential electricity. The findings demonstrate that donors respond to recipients’ sustainable energy needs, both renewable and residential, when selecting recipients. Moreover, donors tend to increase the amount of aid based on renewable energy needs. The findings also highlight the significant role of international climate policy, as donors have changed their energy aid-giving patterns since the start of the Kyoto Protocol. Contrary to the common belief in the aid-giving literature, this study shows that, with regard to energy aid, donor interests are more weakly related to recipient selection than are recipient needs.

Key policy insights

• Donors are influenced by the residential energy needs of recipients when giving energy aid, which aligns with the Sustainable Development Goals.

• Donors’ energy aid-giving patterns changed between the periods before and after entry into force of the Kyoto Protocol, highlighting the significant role of international climate change policy.

• Policy makers and aid practitioners can steer donors to continue to allocate resources to the development of recipients’ energy policy and to help recipients prepare institutional structures to attract private investment in sustainable energy.

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Laboratory simulations of prebiotic molecule stability in the jarosite mineral group; end member evaluation of detection and decomposition behavior related to Mars sample return     

J. Michelle Kotler  C. Doc Richardson  Jill R. Scott 《Planetary and Space Science》2009,57(12):1381-1388

Recently, the prebiotic amino acid glycine has been found associated with natural jarosite samples from locations around the world. Since the discovery of jarosite on Mars, extensive research focuses on linking this mineral group with possible detection of biosignatures in the geologic record on Earth and Mars. Multiple analytical methods, including extraction and mass spectrometry techniques, have identified glycine and other biomolecules in jarosite samples. The jarosite end members jarosite (sensu stricto-potassium jarosite), natrojarosite (sodium jarosite), and ammoniojarosite (ammonium jarosite) have different thermodynamic stabilities, decompose at different rates, and have potentially different susceptibilities to substitution. The relationship between the thermodynamic stability of the jarosite end members and the effect that glycine has on the thermal decomposition behavior of each end member was investigated using thermal gravimetric analysis. Introducing glycine into the synthesis procedure (75 ppm) of the potassium, sodium, and ammonium jarosite end member has elucidated the effects that glycine has on the thermal stability of the mineral group. Potassium jarosite appears to be the least susceptible to the effects of glycine, with the sodium and ammonium end members showing marked changes in thermal decomposition behavior and decomposition rates. These results suggest that the sodium and ammonium jarosites are more suitable targets for identifying signs of prebiotic or biotic activity on Mars and Earth than the potassium jarosites. These results have implications for current in situ investigations of the martian surface and future sample return missions.  相似文献   

Ecophysiology of atmospheric moisture in the Namib Desert     

Joh R. Henschel  Mary K. Seely   《Atmospheric Research》2008,87(3-4):362

Although the Namib Desert is classified as hyperarid, with rainfall extremely rare, there are several other sources of atmospheric moisture, namely, humidity, dew and fog, which make it possible for organisms to live there. Methods to use these sources include locating moist micro-climates, drinking from wet surfaces, consuming moist food, collecting water on the body, and absorbing water vapour. In describing these mechanisms from published sources, we highlight the work of Professor Gideon Louw, to whom we dedicate this paper. Louw's pioneering work on water relations and economy, which includes osmoregulation in desert plants and animals such as grass, beetles, and springbok, established a foundation that inspired numerous studies by colleagues and students. Ecophysiology provides many more lessons that have potential to be mimicked and applied in the occult collection of water in arid regions.  相似文献   

Experimental analysis of kaolinite particle orientation during triaxial path     

Mahdia Hattab  Jean‐Marie Fleureau 《国际地质力学数值与分析法杂志》2011,35(8):947-968

The goal of this study was to analyze the relation between the behaviour of a clayey material at the macroscopic scale and its microfabric evolution. This may lead to a better understanding of macroscopic strain mechanisms especially the contractancy and dilatancy phenomena. The approach proposed in this paper is based on the study of clay particles orientation by SEM picture analysis after different phases of triaxial loading. In the initial state of the samples (one‐dimensional compression), the SEM observations highlight a microstructural anisotropy with a preferential orientation of the particles normal to the loading direction. During isotropic loading, densification of the clayey matrix occurs related to a random orientation of particles indicated by the term ‘depolarization’. In the earlier stages of constant σ₃ drained triaxial path on slightly overconsolidated specimens, the microstructural depolarization seems to persist inside a macroscopic domain, in which only the volumetric strains due to the isotropic part of the stress tensor evolve. Then, a rotation mechanism of the particles towards preferred directions seems to be activated. The phenomenon appears directly linked to the evolution of the deviatoric part of the stress tensor. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献