Local and remote climatic impacts due to land use degradation in the Amazon “Arc of Deforestation”     

Maria Elisa Siqueira Silva  Gabriel Pereira  Rosmeri Porfírio da Rocha 《Theoretical and Applied Climatology》2016,124(3-4):609-620

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The inner core thermodynamics of the tropical cyclone boundary layer     

Gabriel J. Williams 《Meteorology and Atmospheric Physics》2016,128(5):545-564

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Novel evaluation metrics for sparse spatio-temporal point process hotspot predictions - a crime case study     

Monsuru Adepeju  Gabriel Rosser 《International journal of geographical information science》2016,30(11):2133-2154

Many physical and sociological processes are represented as discrete events in time and space. These spatio-temporal point processes are often sparse, meaning that they cannot be aggregated and treated with conventional regression models. Models based on the point process framework may be employed instead for prediction purposes. Evaluating the predictive performance of these models poses a unique challenge, as the same sparseness prevents the use of popular measures such as the root mean squared error. Statistical likelihood is a valid alternative, but this does not measure absolute performance and is therefore difficult for practitioners and researchers to interpret. Motivated by this limitation, we develop a practical toolkit of evaluation metrics for spatio-temporal point process predictions. The metrics are based around the concept of hotspots, which represent areas of high point density. In addition to measuring predictive accuracy, our evaluation toolkit considers broader aspects of predictive performance, including a characterisation of the spatial and temporal distributions of predicted hotspots and a comparison of the complementarity of different prediction methods. We demonstrate the application of our evaluation metrics using a case study of crime prediction, comparing four varied prediction methods using crime data from two different locations and multiple crime types. The results highlight a previously unseen interplay between predictive accuracy and spatio-temporal dispersion of predicted hotspots. The new evaluation framework may be applied to compare multiple prediction methods in a variety of scenarios, yielding valuable new insight into the predictive performance of point process-based prediction.  相似文献   

The soft X-ray polychromator for the Solar Maximum Mission     

L. W. Acton  J. L. Culhane  A. H. Gabriel  R. D. Bentley  J. A. Bowles  J. G. Firth  M. L. Finch  C. W. Gilbreth  P. Guttridge  R. W. Hayes  E. G. Joki  B. B. Jones  B. J. Kent  J. W. Leibacher  R. A. Nobles  T. J. Patrick  K. J. H. Phillips  C. G. Rapley  P. H. Sheather  J. C. Sherman  J. P. Stark  L. A. Springer  R. F. Turner  C. J. Wolfson 《Solar physics》1980,65(1):53-71

The 1.4–22.4 Å range of the soft X-ray spectrum includes a multitude of emission lines which are important for the diagnosis of plasmas in the 1.5–50 million degree temperature range. In particular, the hydrogen and helium-like ions of all abundant solar elements with Z > 7 have their primary transitions in this region and these are especially useful for solar flare and active region studies. The soft X-ray polychromator (XRP) is a high resolution experiment working in this spectral region. The XRP consists of two instruments with a common control, data handling and power system. The bent crystal spectrometer is designed for high time resolution studies in lines of Fe i-Fe xxvi and Ca xix. The flat crystal scanning spectrometer provides for 7 channel polychromatic mapping of flares and active regions in the resonance lines of O viii, Ne ix, Mg xi, Si xiii, S xv, Ca xix, and Fe xxv with 14 spatial resolution. In its spectral scanning mode it covers essentially the entire 1.4–22.5 Å region.This paper summarizes the scientific objectives of the XRP experiment and describes the characteristics and capabilities of the two instruments. Sufficient technical information for experiment feasibility studies is included and the resources and procedures planned for the use of the XRP within the context of the Solar Maximum Mission is briefly discussed.  相似文献   

Effects of currents on interpretation of sub-surface pressure spectra     

D. W. Gabriel  T. S. Hedges 《Coastal Engineering》1986,10(4)

Ocean waves are often measured using sub-surface pressure transducers. The transfer function, relating pressure fluctuations to variations in water-surface elevation, is usually based on linear wave theory, with an empirical correction factor being applied to account for non-linearities.This paper is concerned with the determination of surface-elevation spectra from pressures recorded beneath irregular waves travelling on a current. Predicted spectra are compared with spectral densities calculated from measurements using a surface-piercing wave gauge. Results show that significant errors arise if the Doppler effect, associated with the presence of the current, is ignored. The importance of selecting appropriate values of the empirical correction factor is also demonstrated.  相似文献   

Cadmium uptake and accumulation by the decapod crustacean Penaeus indicus     

Nuñez-Nogueira G  Rainbow PS 《Marine environmental research》2005,60(3):339-354

Juveniles of the dendrobranchiate decapod Penaeus indicus take up radiolabelled cadmium from solution over the exposure concentration range of 1.8-31.5 microg L(-1), with an uptake rate constant of 0.090 L g(-1)d(-1) at 15 salinity and 25 degrees C. New cadmium taken up is added to the existing cadmium content of the prawn with no significant excretion, and the rate of accumulation of radiolabelled cadmium is a measure of the absolute cadmium uptake rate from solution. Moulting had no significant effect on the accumulation of cadmium. Newly accumulated cadmium is distributed to all organs with the highest proportions of body content being found in the hepatopancreas, exoskeleton, gills and remaining soft tissues, the hepatopancreas and gills containing the highest labelled cadmium concentrations. Like other crustaceans, penaeid prawns inhabiting anthropogenically contaminated coastal waters with raised cadmium bioavailabilities can be expected to contain raised body concentrations of cadmium. Cadmium concentrations of most field-collected adult penaeids are relatively low, as a probable consequence of the growth dilution of their cadmium contents as a result of the rapid growth rates of penaeid prawns.  相似文献   

Predicting the optical properties of the West Florida Shelf: resolving the potential impacts of a terrestrial boundary condition on the distribution of colored dissolved and particulate matter   总被引：1，自引：0，他引：1  

W. Paul Bissett  Robert Arnone  Sharon DeBra  Dwight A. Dieterle  Daniel Dye  Gary J. Kirkpatrick  Oscar M. Schofield  Gabriel A. Vargo 《Marine Chemistry》2005,95(3-4):199-233

Predicting the distribution of Inherent Optical Properties (IOPs) in the water column requires predicting the physical, chemical, biological, and optical interactions in a common framework that facilitates feedback responses. This work focuses on the development of ecological and optical interaction equations embedded in a 2D hindcast model of the shallow water optical properties on the West Florida Shelf (WFS) during late summer/fall of 1998. This 2D simulation of the WFS includes one case with a Loop Current intrusion above the 40-m isobath and one with the Loop Current intrusion in addition to a periodic terrestrial nutrient supply below the 10-m isobath. The ecological and optical interaction equations are an expansion of a previously developed model for open ocean conditions (Bissett, W.P., Carder, K.L., Walsh, J.J., Dieterle, D.A., 1999a. Carbon cycling in the upper waters of the Sargasso Sea: II. Numerical simulation of apparent and inherent optical properties. Deep-Sea Research, Part I: Oceanographic Research Papers, 46 (2), 271–317; Bissett, W.P., Walsh, J.J., Dieterle, D.A., Carder, K.L., 1999b. Carbon cycling in the upperwaters of the Sargasso Sea: I. Numerical simulation of differential carbon and nitrogen fluxes. Deep-Sea Research, Part I: Oceanographic Research Papers, 46 (2), 205–269). The expansion includes an increase in the number of elemental pools to include silica, phosphorus, and iron, an increase in the number of phytoplankton functional groups, and a redevelopment of the Dissolved Organic Matter (DOM) and Colored Dissolved Organic Matter (CDOM) interaction equations. It was determined from this simulation that while the Loop Current alone was able to predict the water column conditions present during the summer, the Loop Current alone was not enough to simulate the magnitude of optical constituents present in the fall of 1998 when compared to satellite imagery. Simulating terrestrial inorganic and organic nutrients and CDOM pulses coinciding with significant meteorological events and high freshwater pulses released from the major rivers feeding the WFS were required to accurately predict the distribution and scale of the inherent optical properties at the surface during the fall months. Modeling the in situ light field for phytoplankton growth and community competition requires addressing the CDOM optical constituent explicitly. The majority of the annually modeled CDOM on WFS was created via in situ production; however, it was also rapidly removed via advection and photochemical destruction. A pulse of terrestrial nutrient and organic color was required to simulate the dramatic changes in surface color seen in satellite imagery on the WFS. The dynamics of the biogeochemical portion of the simulation demonstrate the importance of nonstoichiometric supplies of terrestrial nutrients on the WFS to the prediction of nutrient and CDOM fluxes.  相似文献   

Analytical solution for the response of a flexible retaining structure with an elastic backfill     

Chulmin Jung  Antonio Bobet  Gabriel Fernández 《国际地质力学数值与分析法杂志》2010,34(13):1387-1408

An extension of an existing analytical solution for the response of a flexible retaining wall subjected to seismic loading is presented. The solution is based on the assumption that the wall and the soil remain elastic and that there are no shear stresses at the wall–soil interface while the contact remains tied. In addition to the wall displacements due to bending, the wall can experience rigid‐body motions due to rotation and horizontal and vertical movements. The solution is verified by comparing its results with those of a finite element method. Results from the analytical solution together with those of the (FEM) are used to identify and quantify the relative importance of key parameters on the seismic response of a wall. The study shows that wall flexibility and horizontal rigid‐body motions of the wall and frequency content of the seismic input have a significant effect on the wall loads. The pressures behind a rigid wall decrease as the wall rotates about its base, whereas for a flexible wall, the soil pressures decrease as the friction between the backfill and the wall increases. The rigid‐body vertical movements of a wall have little impact on the dynamic pressures induced in the wall, except for a flexible wall where, when prevented, the dynamic loads may be reduced. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

An Innovative Post Grouting Technique for Soil Nails     

Barbosa  Max Gabriel Timo  de Assis  André Pacheco  da Cunha  Renato Pinto 《Geotechnical and Geological Engineering》2022,40(11):5539-5546

This study presents an innovative technique of executing soil nails called sectorized post grouting (SPG). The most utilized technique of soil nail grouting is gravity grouting, with the literature reporting advances in pressurized grouting. Although obtaining higher pullout resistance of soil nails, pressurized grouting, mostly done in single-stage grouting, does not compensate for exudation and its use in higher nail lengths is difficult. Thus, a technique has been developed that compensates for exudation, with easier application in lengthier nails. The technique was qualitatively assessed to evaluate its surface roughness and later applied in seven real soil nailing works, where it could be quantitatively assessed. The results show that sectorized post-grouted nails obtained greater pullout resistances than gravity grouted and single-stage grouted nails. Although similar improvement was found in tube-à-manchette (TAM) grouted nails, this method presents lower economic efficiency than sectorized post grouting. The pullout resistance results obtained in this study can be utilized in future soil nailing works executed utilizing SPG.

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Nutrient dynamics at the sediment-water interface in a Mediterranean lagoon (Thau, France): influence of biodeposition by shellfish farming activities   总被引：2，自引：0，他引：2  

Mesnage V  Ogier S  Bally G  Disnar JR  Lottier N  Dedieu K  Rabouille C  Copard Y 《Marine environmental research》2007,63(3):257-277

The Thau Lagoon, a French Mediterranean shallow lagoon, is a site where extensive shellfish farming occurs. The aim of the present work is to evaluate the role of this activity on nutrient exchange at the sediment-water interface in relation to organic matter (OM) sedimentation and degradation. Two stations inside (C5) and outside (C4) of the shellfish farming areas were sampled at three seasons. Porewater chemistry surveys and calculated diffusive fluxes were used to evaluate the trophic status of the Thau lagoon. Quantitative (Particulate Organic Carbon) as well as qualitative OM (Hydrogen Index, Carbohydrates) analyses were performed on sediments to assess OM characteristics. Results emphasized that surficial sediments at C5 are always more enriched in OM. Porewater nutrient concentrations are 10-20 times higher at C5 than at C4. In June 2003, the porewater profiles exhibit a sharp gradient at the bottom waters, indicating a hypereutrophic status, leading to an anoxic crisis.  相似文献