Model for large strain consolidation under constant rate of strain     

He‐Fu Pu  Patrick J. Fox  Yong Liu 《国际地质力学数值与分析法杂志》2013,37(11):1574-1590

A numerical model, called CCRS1, is presented for one‐dimensional large strain consolidation under constant rate of strain loading conditions. The algorithm accounts for vertical strain, general constitutive relationships, relative velocity of fluid and solid phases, changing compressibility and hydraulic conductivity during consolidation, and an externally applied hydraulic gradient acting across the specimen. Soil compressibility is rate independent, and as such, the current model is most appropriate for less‐structured clays. Verification checks show excellent agreement with analytical and numerical solutions for small and large strain conditions. A series of numeric examples indicates that compressibility and hydraulic conductivity constitutive relationships can have an important effect on constant rate of strain consolidation response. Results also indicate that analytical solutions obtained using small strain theory can be in significant error for large strain conditions with changing coefficient of consolidation. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Deep groundwater mediates streamflow response to climate warming in the Oregon Cascades     

Christina Tague  Gordon Grant  Mike Farrell  Janet Choate  Anne Jefferson 《Climatic change》2008,86(1-2):189-210

Recent studies predict that projected climate change will lead to significant reductions in summer streamflow in the mountainous regions of the Western US. Hydrologic modeling directed at quantifying these potential changes has focused on the magnitude and timing of spring snowmelt as the key control on the spatial–temporal pattern of summer streamflow. We illustrate how spatial differences in groundwater dynamics can also play a significant role in determining streamflow responses to warming. We examine two contrasting watersheds, one located in the Western Cascades and the other in the High Cascades mountains of Oregon. We use both empirical analysis of streamflow data and physically based, spatially distributed modeling to disentangle the relative importance of multiple and interacting controls. In particular, we explore the extent to which differences in snow accumulation and melt and drainage characteristics (deep ground water vs. shallow subsurface) mediate the effect of climate change. Results show that within the Cascade Range, local variations in bedrock geology and concomitant differences in volume and seasonal fluxes of subsurface water will likely result in significant spatial variability in responses to climate forcing. Specifically, watersheds dominated by High Cascade geology will show greater absolute reductions in summer streamflow with predicted temperature increases.  相似文献   

Studying hot gas using the ultraviolet: High ions in galactic halos     

Andrew J. Fox  Patrick Petitjean  Cédric Ledoux  Raghunathan Srianand 《Astrophysics and Space Science》2009,320(1-3):27-30

Among the many spectral lines falling in the ultraviolet are the resonance doublets of the highly ionized species O VI, N V, C IV, and Si IV. By using both space-based UV observations and ground-based optical observations, these lines can be used to trace diffuse astrophysical plasma over a large fraction of the age of the Universe. In this paper we discuss observations of these absorption lines in damped Lyman-α systems at z≈2–3, using the UVES spectrograph on the VLT in Chile.  相似文献   

Toward cyberinfrastructure to facilitate collaboration and reproducibility for marine integrated ecosystem assessments     

Stace E. Beaulieu  Peter A. Fox  Massimo Di Stefano  Andrew Maffei  Patrick West  Jonathan A. Hare  Michael Fogarty 《Earth Science Informatics》2017,10(1):85-97

There is a growing need for cyberinfrastructure to support science-based decision making in management of natural resources. In particular, our motivation was to aid the development of cyberinfrastructure for Integrated Ecosystem Assessments (IEAs) for marine ecosystems. The IEA process involves analysis of natural and socio-economic information based on diverse and disparate sources of data, requiring collaboration among scientists of many disciplines and communication with other stakeholders. Here we describe our bottom-up approach to developing cyberinfrastructure through a collaborative process engaging a small group of domain and computer scientists and software engineers. We report on a use case evaluated for an Ecosystem Status Report, a multi-disciplinary report inclusive of Earth, life, and social sciences, for the Northeast U.S. Continental Shelf Large Marine Ecosystem. Ultimately, we focused on sharing workflows as a component of the cyberinfrastructure to facilitate collaboration and reproducibility. We developed and deployed a software environment to generate a portion of the Report, retaining traceability of derived datasets including indicators of climate forcing, physical pressures, and ecosystem states. Our solution for sharing workflows and delivering reproducible documents includes IPython (now Jupyter) Notebooks. We describe technical and social challenges that we encountered in the use case and the importance of training to aid the adoption of best practices and new technologies by domain scientists. We consider the larger challenges for developing end-to-end cyberinfrastructure that engages other participants and stakeholders in the IEA process.  相似文献   

Mapping rubber tree growth in mainland Southeast Asia using time-series MODIS 250 m NDVI and statistical data   总被引：5，自引：0，他引：5  

Zhe Li  Jefferson M. Fox 《Applied geography (Sevenoaks, England)》2012,32(2):420-432

Expanding global and regional markets are driving the conversion of traditional subsistence agricultural and occupied non-agricultural lands to commercial-agricultural purposes. In many parts of mainland Southeast Asia rubber plantations are expanding rapidly into areas where the crop was not historically found. Over the last several decades more than one million hectares of land have been converted to rubber trees in areas of China, Laos, Thailand, Vietnam, Cambodia and Myanmar, where rubber trees were not traditionally grown. This expansion of rubber plantations has replaced ecologically important secondary forests and traditionally managed swidden fields and influenced local energy, water and carbon fluxes. Accurate and up-to-date monitoring and mapping of rubber tree growth is critical to understanding the implications of this changing ecosystem. Discriminating rubber trees from second-growth forests and fallow land has proven challenging. Previous experiments using machine-learning approaches with hard classifications on remotely sensed data, when faced with the realities of a heterogeneous plant-life mixture and high intra-class variance, have tended to overestimate the areas of rubber tree growth. Our current research sought to: 1) to investigate the potential of using a Mahalanobis typicality model to deal with mixed pixels; and 2) to explore the potential for combining MOderate Resolution Imaging Spectroradiometer (MODIS) imagery with sub-national statistical data on rubber tree areas to map the distribution of rubber tree growth across this mainland Southeast Asia landscape. Our study used time-series MODIS Terra 16-day composite 250 m Normalized Difference Vegetation Index (NDVI) products (MOD13Q1) acquired between March 2009 and May 2010. We used the Mahalanobis typicality method to identify pixels where rubber tree growth had the highest probability of occurring and sub-national statistical data on rubber tree growth to quantify the number of pixels of rubber tree growth mapped per administrative unit. We used Relative Operating Characteristic (ROC) and error matrix analysis, respectively, to assess the viability of Mahalanobis typicalities and to validate classification accuracy. High ROC values, over 0.8, were achieved with the Mahalanobis typicality images of both mature and young rubber trees. The proposed method greatly reduced the commission errors for the two types of rubber tree growth to 1.9% and 2.8%, respectively (corresponding to user’s accuracies of 98.1% and 97.2%, respectively). Results indicate that integrating Mahalanobis typicalities with MODIS time-series NDVI data and sub-national statistics can successfully overcome the earlier overestimation problem.  相似文献   

QuakeSim and the Solid Earth Research Virtual Observatory     

Andrea Donnellan  John Rundle  Geoffrey Fox  Dennis McLeod  Lisa Grant  Terry Tullis  Marlon Pierce  Jay Parker  Greg Lyzenga  Robert Granat  Margaret Glasscoe 《Pure and Applied Geophysics》2006,163(11-12):2263-2279

We are developing simulation and analysis tools in order to develop a solid Earth Science framework for understanding and studying active tectonic and earthquake processes. The goal of QuakeSim and its extension, the Solid Earth Research Virtual Observatory (SERVO), is to study the physics of earthquakes using state-of-the-art modeling, data manipulation, and pattern recognition technologies. We are developing clearly defined accessible data formats and code protocols as inputs to simulations, which are adapted to high-performance computers. The solid Earth system is extremely complex and nonlinear, resulting in computationally intensive problems with millions of unknowns. With these tools it will be possible to construct the more complex models and simulations necessary to develop hazard assessment systems critical for reducing future losses from major earthquakes. We are using Web (Grid) service technology to demonstrate the assimilation of multiple distributed data sources (a typical data grid problem) into a major parallel high-performance computing earthquake forecasting code. Such a linkage of Geoinformatics with Geocomplexity demonstrates the value of the Solid Earth Research Virtual Observatory (SERVO) Grid concept, and advances Grid technology by building the first real-time large-scale data assimilation grid.  相似文献   

iSERVO: Implementing the International Solid Earth Research Virtual Observatory by Integrating Computational Grid and Geographical Information Web Services     

Mehmet Aktas  Galip Aydin  Andrea Donnellan  Geoffrey Fox  Robert Granat  Lisa Grant  Greg Lyzenga  Dennis McLeod  Shrideep Pallickara  Jay Parker  Marlon Pierce  John Rundle  Ahmet Sayar  Terry Tullis 《Pure and Applied Geophysics》2006,163(11-12):2281-2296

We describe the goals and initial implementation of the International Solid Earth Virtual Observatory (iSERVO). This system is built using a Web Services approach to Grid computing infrastructure and is accessed via a component-based Web portal user interface. We describe our implementations of services used by this system, including Geographical Information System (GIS)-based data grid services for accessing remote data repositories and job management services for controlling multiple execution steps. iSERVO is an example of a larger trend to build globally scalable scientific computing infrastructures using the Service Oriented Architecture approach. Adoption of this approach raises a number of research challenges in millisecond-latency message systems suitable for internet-enabled scientific applications. We review our research in these areas.  相似文献   

Biodiversity of the wetlands of the Kakadu Region, northern Australia     

C. Max Finlayson  John Lowry  Maria Grazia Bellio  Suthidha Nou  Robert Pidgeon  Dave Walden  Chris Humphrey  Gary Fox 《Aquatic Sciences - Research Across Boundaries》2006,68(3):374-399

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Constrained iterative deconvolution applied to SeaMARC I sidescansonar imagery     

Fox  C.G. Jones  F.J. Lau  T.-K. 《Oceanic Engineering, IEEE Journal of》1990,15(1):24-31

Images collected by any sidescan sonar system represent the convolution of the acoustic beam pattern of the instrument with the true echo amplitude distribution over the seafloor. At typical low speeds, the 1.7° beam width of SeaMARC I (seafloor mapping and remote characterization) results in multiple insonification of individual targets, particularly at the outside of the swath. A nonlinearly constrained iterative deconvolution technique developed for radar applications can be applied to SeaMARC I imagery to reduce the effect of the beam pattern and equalize the spectral content of the image across the swath. Since the deconvolution is implemented in the along-track direction, the registration of individual scan lines must be precisely corrected before the operator is applied. The deconvolution operator must be modeled to account for beam shape, vehicle speed, swath width, slant range, and ping rate. The method is numerically stable and increases the effective resolution of the image, but results in some loss of dynamic range. The technique is applied to target recognition and imagery from volcanic terrains of the central Juan de Fuca Ridge  相似文献   

Nutrient budget of a montane evergreen broad‐leaved forest at Ailao Mountain National Nature Reserve,Yunnan, southwest China     

Wenyao Liu  John E. D. Fox  Zaifu Xu 《水文研究》2003,17(6):1119-1134

Hydrological fluxes and associated nutrient budget were studied during a 2 year period (1998–99) in a montane moist evergreen broad‐leaved forest at Ailao Mountain, Yunnan. Water samples of rainfall, throughfall, and stemflow, and of surface runoff, soil water, and stream flow were collected bimonthly to determine the concentration and fluxes of nutrients. Soil budgets were determined from the difference between precipitation input (including nutrient leaching from canopy) and output via runoff and drainage. The forest was characterized by low canopy interception and surface runoff, and high percolation and stream flow. Concentrations of nutrients were increased in throughfall and stemflow compared with precipitation. Surface runoff and drainage water had higher nutrient concentrations than precipitation and stream water. Total nitrogen and NH₄⁺‐N concentrations were higher in soil water than stream water, whereas K⁺, Ca²⁺, and Mg²⁺ concentrations were lower in the former than the latter. Annual nutrient fluxes decreased with soil depth following the pattern of water flux. Annual losses of most nutrient elements via stream flow were less than the corresponding inputs via throughfall and stemflow, except for calcium, for which solute loss was greater than the inputs via precipitation. Leaching losses of that element may be compensated by weathering. Losses of nitrogen, phosphorus, potassium, magnesium, sodium, and sulphur could be replaced through atmospheric inputs. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献