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131.
Short‐term prediction of environmental variables such as stream flow rate is useful to members of the general public and environmental scientists alike, providing the ability to predict environmental disasters or scientifically interesting events. Here, a neural‐network based method is presented, which is capable of providing advance flood warnings or the prediction of high stream flow events for research purposes in a small upland headwater in NE Scotland. This method relies on training from past time series data acquired in the field, and provides the ability to predict a range of hydrological and meteorological variables up to 24 h ahead using feedback of predicted values at time t as new inputs for the next time step t + 1. The system is rapid and effective, relies on standard neural network training methods, and has the potential to be implemented in a web‐based monitoring and prediction package. The model design could be implemented at any study site where time series data has been gathered, and is sufficiently flexible to accept whatever data is available. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
132.
Prem Chhetri Robert Stimson Jim Cooper Jonathan Corcoran Martin Bell David Pullar 《Transactions in GIS》2007,11(4):597-619
This article presents a GIS‐based methodology to integrate a measure of geographic attractiveness of localities in the process of allocating potential dwellings in the context of a large urban region. The methodology was developed for a study area in Brisbane‐South East Queensland (SEQ), known as the Sunbelt Region, a rapidly growing region and a popular tourist destination in Australia. In this article, we have used a multivariate technique to develop a set of parameterised linear equations to define underlying dimensions that drive residential location decision choices. Aesthetic and accessibility factors were identified in the factor analysis from data collected via a survey of Quality of Life. Spatial measures were based on a combination of network distance and kernel density estimation to calculate ‘aesthetic’ and ‘accessibility’ scenarios, which were then overlaid and multiplied by their subjective weights to create an ‘overall attractiveness scenario’. These development scenarios were integrated as a set of criteria to control the allocation of potential dwelling capacity over the next 25 years at a grid cell level. 相似文献
133.
We identify and assess the relative importance of the principal factors influencing the release of dissolved organic carbon (DOC) and dissolved forms of nitrogen (N) from a small upland headwater dominated by podzolic soils during a sequence of autumn runoff events. We achieve this by subjecting high‐resolution hydrometeorological and hydrochemical data to an R‐mode principal component factor analysis and a stepwise multivariate regression analysis. We find that the release of DOC and N is influenced by four principal factors, namely event magnitude, soil water flow through the Bs horizon, the length of time since the soil profile was last flushed, and rewetting of the H horizon. The release of DOC and dissolved organic nitrogen (DON) is most strongly influenced by the combination of event magnitude and soil water flow through the Bs horizon, and to a lesser extent by the length of time since the soil profile was last flushed. Rewetting of the H horizon also influences the release of DOC, but this is not the case for DON. The release of nitrate (NO3‐N) is most strongly influenced by the combination of the length of time since the soil profile was last flushed and rewetting of the H horizon, and to a lesser extent by event magnitude. Soil water flow through the Bs horizon does not influence the release of NO3‐N. We argue that the mechanisms by which the above factors influence the release of DOC and N are probably strongly associated with moisture‐dependent biological activity, which governs the turnover of organic matter in the soil and limits the availability of NO3‐N in the soil for leaching. We conclude that the release of DOC and N from upland headwaters dominated by podzolic soils is largely controlled by the variable interaction of hydrometeorological factors and moisture‐dependent biological processes, and that a shift in climate towards drier summers and wetter winters may result in the release of DOC and N becoming increasingly variable and more episodic in the future. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
134.
Catherine Lalande Jacqueline M. Grebmeier Paul Wassmann Lee W. Cooper Mikhail V. Flint Valentina M. Sergeeva 《Continental Shelf Research》2007
Drifting sediment traps were deployed at 9 stations in May-June (ice-covered conditions) and July-August (ice-free conditions) 2004 in the Chukchi Sea to investigate the variability in export fluxes of biogenic matter in the presence and absence of sea ice cover. Measurements of chlorophyll-a (Chl-a), particulate organic carbon (POC), particulate nitrogen (PN), phytoplankton, zooplankton fecal pellets, and the stable carbon isotope composition (δ13C) of the sinking material were performed along Barrow Canyon (BC) and a parallel shelf-to-basin transect from East Hanna Shoal (EHS) to the Canada Basin. POC export fluxes were similarly high in the presence (378±106 mg C m−2 d−1) and in the absence of ice cover (442±203 mg C m−2 d−1) at the BC stations, while fluxes were significantly higher in the absence (129±98 mg C m−2 d−1) than in the presence of ice cover (44±29 mg C m−2 d−1) at the EHS stations. The C/N ratios and δ13C values of sinking organic particles indicated that POC export fluxes on the Chukchi continental shelf were mostly composed of freshly produced labile material, except at the EHS stations under ice cover where the exported matter was mostly composed of refractory material probably advected into the EHS region. Chl-a fluxes were higher under ice cover than in ice-free water, however, relatively low daily loss rates of Chl-a and similar phytoplankton carbon fluxes in ice-covered and ice-free water suggest the retention of phytoplankton in the upper water column. An increase in fecal pellet carbon fluxes in ice-free water reflected higher grazing pressure in the absence of ice cover. Elevated daily loss rates of POC at the BC stations confirmed other indications that Barrow Canyon is an important area of carbon export to the basin and/or benthos. These results support the conclusion that there are large spatial and temporal variations in export fluxes of biogenic matter on the Chukchi continental shelf, although export fluxes may be similar in the presence and in the absence of ice cover in highly productive regions. 相似文献
135.
Predation is often the largest source of mortality for juvenile fish and the risk of predation can influence growth rates
by either forcing young fish into suboptimal foraging habitats or reducing the amount of time spent foraging. We used field
experiments to test effects of predation risk by gulf flounder (Paralichthys albigutta) on juvenile pinfish (Lagodon rhomboides) growth rates by measuring changes in length and weight in three habitats (sand, low density, and high density shoalgrass,Halodule wrightii) in Perdido Key, Florida. Benthic cores, seagrass samples, and stomach contents were also analyzed to examine differences
in pinfish prey densities, grass densities and epiphyte coverage, and diet, respectively, among habitat and predator treatments.
Both length and weight growth rates were determined and showed similar results. We found that pinfish inhabiting seagrass
habitats, particularly low densityHalodule displayed the fastest growth rates in the beginning of the growing season (June) and those in sand had the fastest growth
rates later in the season (October). These differences in growth rates did not appear to be influenced by densities of pinfish
prey items since the treatment having the highest density of prey was not that in which growth rates were the greatest. This
seasonal shift may be attributed to increasing pinfish size. Larger pinfish in October may have been inhibited by high density
grass, reducing foraging efficiency. These results demonstrate how occupying a suboptimal foraging habitat can affect juvenile
pinfish growth rates. Predation risk significantly reduced length and weight growth rates of pinfish in June, but not October.
This suggests that smaller pinfish early in the season traded time spent foraging for predator avoidance, while larger pinfish
were likely to have reached a size refuge from predation. This study demonstrates that nonlethal effects from predation are
also important influences on juvenile pinfish. 相似文献
136.
137.
As technology matures, Real Time Kinematic (RTK) global positioning system (GPS) receivers are providing increased performance
in accuracy, on-the-fly (OTF) initialization times, measurement speed, and latency. Leica's Dozer 2000 machine guidance system
combines an MC1000 GPS sensor, graphic intensive guidance software, a digital terrain model, and a digital site plan. Figure
1 shows the operator's view of the system. The end results is a highly accurate, extremely responsive local navigation system.
Engineers can easily upload design information onto a touch-screen machine guidance personal computer (PC) and greatly reduce
earthmoving costs while simultaneously recording “as-built” inspection data.
The Leica MC1000 machine control sensor is a true 10-Hz, centimeter-level-accuracy, open-architecture GPS sensor specifically
designed for machine guidance and control. At the heart of the MC1000's performance are a very stable oven-controlled oscillator
(3 × 10−11/s short-term stability), a low-power Intel 486-DX4-80 processor, and four user-configurable input/output (I7O) ports. Special
algorithms mitigate the effects of multipath and Selective Availability (SA) while providing centimeter accuracy up to 10
times per second with only 30 milliseconds' latency. The high update rate and low latency are essential for machine guidance
and control.
The MC1000 GPS reference station is capable of outputting RTK and Differential GPS (DGPS) data simultaneously, providing and
entire site with GPS information for machine guidance and control, tracking and dispatching of vehicles, and support of survey
crews.
This article describes how recent advances in technology have combined to produce the Leica Dozer 2000 – a machine guidance
system that is ideal for a wide range of earthmoving and inspection applications. ? 2000 John Wiley & Sons, Inc. 相似文献
138.
Alan F. Cooper Durmus Boztuğ J. Michael Palin Candace E. Martin Mihoko Numata 《Contributions to Mineralogy and Petrology》2011,161(5):811-828
The late Cretaceous A-type Karaçay?r pluton in Central Anatolia, Turkey, intrudes and entrains xenoliths of Palaeozoic limestone. Carbonatitic magmatic rocks within the syenite have been previously interpreted (Schuiling in Nature, 192:1280, 1961) to result from metasomatic alteration and syntectic melting of marble. Carbonatites and associated calcite-syenites exhibit mineralogical characteristics (Ab-rich plagioclase, Ba-rich K-feldspar, low-Mg# biotite) that are petrogenetically more evolved than the host syenitic suite. Geochemically, carbonate-rich magmatic rocks are greatly enriched in Sr, Ba, Th, and REE and have higher LREE/HREE ratios than either syenites or marbles. In terms of O-C-Sr-Pb isotope ratios, the carbonatite/calcite-syenite suite form a consistent and geochemically coherent group that is distinct from the marble country rock and xenolith population, but similar to some of the syenitic, and particularly the nepheline syenite components of the Karaçay?r pluton. Other silicate magmatic rocks are geochemically, isotopically, and geochronologically different, suggesting the pluton is composite. Overall, the mineralogical and geochemical characteristics of the carbonatites are incompatible with binary mixing of syenite and marble but are consistent with derivation of carbonatite from petrogenetically evolved foid syenite. Carbonate–silicate rock types have modal variations compatible with an origin by fractional crystallisation, rather than by liquid immiscibility. 相似文献
139.
D. W. T. Jackson J. H. M. Beyers K. Lynch J. A. G. Cooper A. C. W. Baas I. Delgado‐Fernandez I 《地球表面变化过程与地形》2011,36(8):1113-1124
The behaviour of offshore‐directed winds over coastal dune and beach morphology was examined using a combination of modelling (3‐D computational fluid dynamics (CFD)) and field measurement. Both model simulations and field measurements showed reversal of offshore flows at the back beach and creation of an onshore sediment transport potential. The influence of flow reversals on the beach‐dune transport system and foredune growth patterns has previously received little attention. Detailed wind flow measurements were made using an extensive array of mast‐mounted, 3‐D ultrasonic anemometers (50 Hz), arranged parallel to the dominant incident wind direction. Large eddy simulation (LES) of the offshore wind flow over the dune was conducted using the open‐source CFD tool openFOAM. The computational domain included a terrain model obtained by airborne LiDAR and detailed ground DGPS measurements. The computational grid (~22 million cells) included localized mesh refinement near the complex foredune terrain to capture finer details of the dune morphology that might affect wind flows on the adjacent beach. Measured and simulated wind flow are presented and discussed. The CFD simulations offer new insights into the flow mechanics associated with offshore winds and how the terrain steering of wind flow impacts on the geomorphological behaviour of the dune system. Simulation of 3‐D wind flows over complex terrain such as dune systems, presents a valuable new tool for geomorphological research, as it enables new insights into the relationship between the wind field and the underlying topography. The results show that offshore and obliquely offshore winds result in flow reversal and onshore directed winds at distances of up to 20 m from the embryo dune toe. The potential geomorphological significance of the findings are discussed and simple calculations show that incoming offshore and obliquely offshore winds with mean velocities over 13 m s?1 and 7 m s?1, respectively, have the potential to create onshore‐directed winds at the back beach with mean velocities above 3.3 m s?1. These are above the threshold of movement for dry sand and support previous conclusions about the significance of offshore winds in dune and beach budget calculations. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
140.
Observations of tidal trapping in a channel connected to large volumes along its perimeter showed that the exchange between
them is driven by advection due to tidal flows. Therefore, quantifying the longitudinal dispersion of scalars in the channel
that results from tidal trapping was not possible using traditional frameworks, which assume that the exchange is a diffusive
process. This study uses the concentration moment method to solve analytically for the dispersion coefficient of a solute
in a tidal channel which exchanges advectively with volumes along its edges. This constitutes a new framework for analyzing
the longitudinal dispersion that results from tidal trapping in systems such as a branching tidal channel or the breached
salt ponds of San Francisco Bay. A comparison of dispersion coefficients from traditional, diffusion-driven frameworks for
tidal trapping, the new advective framework derived in the present study, and observations show that the new formulation is
best suited to this environment. 相似文献