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  • Articles  (33)
  • Springer  (28)
  • Blackwell Publishing Ltd  (5)
  • American Physical Society
  • American Physical Society (APS)
  • Computer Science  (22)
  • Geography  (11)
Collection
  • Articles  (33)
Journal
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 5 (1987), S. 0 
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 35 (1999), S. 0 
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Data from seven Management Systems Evaluation Areas (MSEA) were used to test the sensitivity of a leaching model, Pesticide Root Zone Model-2, to a variety of hydrologic settings in the Midwest. Atrazine leaching was simulated because it was prevalent in the MSEA studies and is frequently detected in the region's groundwater. Short-term simulations used site specific soil and chemical parameters. Generalized simulations used data avail. able from regional soil databases and standardized variables. Accurate short-term simulations were precluded by lack of antecedent atrazine concentrations in the soil profile and water, suggesting that simulations using data for less than five years underestimate atrazine leaching. The seven sites were ranked in order of atrazine detection frequency (concentration 〉 0.2 μg L-1) in soil water at 2 m depth in simulations. The rank order of the sites based on long-term simulations were similar to the ranks of sites based on atrazine detection frequency from groundwater monitoring. Simulations with Map Unit Use File (MUUF) soils data were more highly correlated with ranks of observed atrazine detection frequencies than were short-term simulations using site-specific soil data. Simulations using the MIJUIF data for soil parameters were sufficiently similarity to observed atrazine detection to allow the credible use of regional soils data for simulating leaching with PRZM-2 in a variety of Midwest soil and hydrologic conditions. This is encouraging for regional modeling efforts because soil parameters are among the most critical for operating PRZM-2 and many other leaching models.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 31 (1995), S. 0 
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : Evaluation criteria for reservoir and stream resources were developed to provide decision makers with feedback on environmental consequences of water allocation decisions under conditions of severe sustained drought within the Colorado River Basin by using the AZCOL gaming simulation model. Seven categories of flow dependent resources were identified which highlight resource states associated with reservoirs or river reaches within the AZCOL model. AZCOL directly simulates impact of water management decisions on five resource categories: threatened, endangered or sensitive fish; native nonlisted fish; wetland and riparian elements; national or state wildlife refuges; and hatcheries or other flow dependent facilities. Two additional categories - cold and warm water sport fish - are not modeled explicitly but are incorporated in the evaluation of monetary benefits from recreation on Colorado River waters. Each resource category was characterized at each time step in the simulation according to one of four environmental states: stable, threatened, endangered, or extirpated. Changes in resource states were modeled by time and flow-dependent decision criteria tied to either reservoir level or stream flows within the AZCOL model structure. Gaming results using the AZCOL model indicate environmental impacts would be substantial and that water allocation decisions directly impacted environmental resource states.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 37 (2001), S. 0 
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : The fate of pesticides entering the Riparian Buffer Strips (RBS) has not been well documented. This study compared the transport and fate of atrazine in soil of three-, five-, and nine-year-old switchgrass (Panicum virgatum L.) RBS to that in adjacent soils cropped to a corn-soybean rotation or a grass-alfalfa pasture. Undisturbed soil columns were collected from the RBS and cropped areas within the Bear Creek watershed, near Roland, Iowa. Atrazine and bromide breakthrough curves obtained using intact soil columns under saturated conditions were described by a two-region, mobile-immobile transport model. Preferential flow of bromide and atrazine was evident in five-and nine-year-old RBS soil, but there was little difference in transport characteristics between these two RBS soils and the adjacent cropped soils. There was a trend towards an increase in dispersion coefficients between the five-and nine-year-old RBS sites, which suggests an increased degree of preferential flow with increasing RBS age. Despite similar texture and organic C contents, atrazine sorption was significantly greater in RBS soil than the adjacent cropped soil. Cropped soil degraded atrazine faster than the RBS soil. The rapid degradation of atrazine in the corn-soybean soil adjacent to the five-year-old RBS (atrazine half-life of 19 days) appeared to be due to a larger population of atrazine-degrading microorganisms. Atrazine-degrading microorganisms in the corn-soybean soil were 50,940 cells g-1 soil compared with 2,970 cells g-4 soil in 5-year-old RBS soil which resulted in 60 percent mineralization of [14C-UL-atrazine] in the corn-soybean soil.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 27 (1991), S. 0 
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : The spatial and temporal variability of hydroclimatic elements were investigated in the central and northern Rocky Mountains (Colorado, Idaho, Montana, Utah, and Wyoming) during the 1951–1985 period. The three hydroclimatic elements studied were total water-year (October 1-September 30) streamflow (ST), winter (October 1-March 31) accumulated precipitation (PR), and April 1 snowpack (SN). An analysis of 14 virgin watersheds showed wide spatial djfferences in the temporal variability of SN, PR, and ST, and these were found to be caused largely by basin exposure to moist air flows. The more stable (low variability) basins were those exposed to prevailing northerly to westerly flow, while unstable (high variability) basins were exposed to occasional southwesterly to southeasterly moist flow. Snowpack was the better indicator of ST in 11 of the 14 watersheds, explaining 37 to 87 percent of the ST variance.Analysis of the spatial variability, based on all SN and PR data from across the study area, revealed 11 discrete climatic regions. Both SN and PR exhibited coherent regions of stable and unstable temporal variability. The average variability between stable and unstable regions differed by a factor of two, and the differences were best explained by the exposure of the mountain barrier to moist air flows.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 26 (1977), S. 39-50 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Im Dezember 1975 wurden durch eine Fesselballonsonde die vertikalen Temperatur- und Windprofile im Gore River Valley im westlichen Colorado ermittelt. Aus Beobachtungen an einem wolkenlosen Morgen bei einer anfangs starken Inversion im Tal zeigte sich, daß die Inversionsobergrenze stetig um 120 m Std−1. absank und nach ungefähr vier Stunden den Talgrund erreichte. Schwache Talabwinde wehten innerhalb der Inversionsschicht. während stärkere Talaufwinde oberhalb derselben herrschten. Eine Hypothese wird vorgeschlagen, um diese Beobachtungen zu erklären. Die Abkühlung am späten Nachmittag und am Abend, wobei die Bildung einer Inversion einsetzte, deren Schichtdicke in weniger als zwei Stunden 175 m betrug, ist Gegenstand einer gesonderten Untersuchung. Winde innerhalb der Inversionsschicht wurden nicht mehr von den Winden in der freien Atmosphäre beeinflußt und blieben im Laufe der Nacht sehr schwach. Bewölkung während der Erwärmungsperiode an einem Morgen hatte zur Folge, daß das Temperaturprofil sich Isothermie näherte, indem Erwärmung gleichmäßig im ganzen Luftraum des Tales sich fortsetzte.
    Notes: Summary A tethered balloon sounder was used to collect vertical temperature and wind structure data in the Gore River Valley of Western Colorado during December, 1975. Observations taken on a clear morning in which a deep inversion was initially present in the valley showed that the inversion top descended at a steady rate of ∼120 m hr−1. reaching the valley bottom after approximately 4 hours. Weak down-valley winds were present within the inversion layer while stronger up-valley winds prevailed above. A hypothesis is presented to account for these observations. A case study is presented for afternoon and evening cooling in which a ground-based inversion developed to a depth of 175 m in less than 2 hours. Winds within the inversion became decoupled from the synoptic-scale winds and remained very weak during the night. The effect of cloud cover during a morning heating cycle was to make the temperature soundings approach isothermal while sensible heating continued throughout the valley volume.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of intelligent and robotic systems 7 (1993), S. 233-254 
    ISSN: 1573-0409
    Keywords: Quadratic half-plane ; positive quadratic space ; model and parameter mismatch ; constraint analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The stability of the PUMA-560 robot manipulator is investigated under model mismatch using PD and PID controllers. Craig's quadratic half-plane constraint analysis is applied, and conditions are found in terms of calculated position and velocity error upper bounds to guarantee the stability of the robot arm under PD control. The theory is extended to guarantee stability under PID control using the modified positive quadratic space constraint analysis. Dynamic model mismatch is assumed to result from incomplete knowledge of the link masses, centers of mass and radii of gyration. The results indicate stability regions under different percentages of individual and combined parameter mismatch in the model.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of intelligent and robotic systems 29 (2000), S. 349-387 
    ISSN: 1573-0409
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Current learning approaches to computer vision have mainly focussed on low-level image processing and object recognition, while tending to ignore high-level processing such as understanding. Here we propose an approach to object recognition that facilitates the transition from recognition to understanding. The proposed approach embraces the synergistic spirit of soft computing, exploiting the global search powers of genetic programming to determine fuzzy probabilistic models. It begins by segmenting the images into regions using standard image processing approaches, which are subsequently classified using a discovered fuzzy Cartesian granule feature classifier. Understanding is made possible through the transparent and succinct nature of the discovered models. The recognition of roads in images is taken as an illustrative problem in the vision domain. The discovered fuzzy models while providing high levels of accuracy (97%), also provide understanding of the problem domain through the transparency of the learnt models. The learning step in the proposed approach is compared with other techniques such as decision trees, naïve Bayes and neural networks using a variety of performance criteria such as accuracy, understandability and efficiency.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 70 (1994), S. 397-405 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. An important step in visual processing is the segregation of objects in a visual scene from one another and from the embedding background. According to current theories of visual neuroscience, the different features of a particular object are represented by cells which are spatially distributed across multiple visual areas in the brain. The segregation of an object therefore requires the unique identification and integration of the pertaining cells which have to be “bound” into one assembly coding for the object in question. Several authors have suggested that such a binding of cells could be achieved by the selective synchronization of temporally structured responses of the neurons activated by features of the same stimulus. This concept has recently gained support by the observation of stimulus-dependent oscillatory activity in the visual system of the cat, pigeon and monkey. Furthermore, experimental evidence has been found for the formation and segregation of synchronously active cell assemblies representing different stimuli in the visual field. In this study, we investigate temporally structured activity in networks with single and multiple feature domains. As a first step, we examine the formation and segregation of cell assemblies by synchronizing and desynchronizing connections within a single feature module. We then demonstrate that distributed assemblies can be appropriately bound in a network comprising three modules selective for stimulus disparity, orientation and colour, respectively. In this context, we address the principal problem of segregating assemblies representing spatially overlapping stimuli in a distributed architecture. Using synchronizing as well as desynchronizing mechanisms, our simulations demonstrate that the binding problem can be solved by temporally correlated responses of cells which are distributed across multiple feature modules.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 66 (1992), S. 381-387 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract We present a scheme for systematically reducing the number of differential equations required for biophysically realistic neuron models. The techniques are general, are designed to be applicable to a large set of such models and retain in the reduced system as high a degree of fidelity to the original system as possible. As examples, we provide reductions of the Hodgkin-Huxley system and the A-current model of Connor et al. (1977).
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