The paper generalizes the two-step approach to estimating a first-order spatial autoregressive model with spatial autoregressive disturbances in a cross-section with heteroscedastic innovations.
Commerce international ; Céréale ; Géographie humaine ; Marché mondial ; Modèle ; Oligopole ; Prix agricole
In the first section, the two duopoly models are reviewed. The second section discusses the evidence for the formation of the triopoly, and the third section develops a model of triopoly pricing. Price determination and the implications
of the triopoly for the future wheat prices are discussed in the final two sections. (INRA).
The present article is confined to the development of a model of the beef and pork market of the RFA. In section 1, a model is specified to explain the functionning of the German beef and pork market. In section 2, the unknown structural
coefficients of the model are estimated and different multipliers are derived there from. (INRA).
California ; Fluvial dynamics ; Fluvial processes ; Model ; River bed ; Stream flow ; United States
measured flow-depth data to assist in model calibration and calculation of cross-sectional area and mean (section average) flow velocity. It is implicit in the discussion that there is a direct relation between near-bed velocities measured and mean (section
The purpose of this paper is to re-evaluate the riffle-pool sequence in Dry Creek near Winters, California, and to test the velocity-reversal hypothesis by hydraulic modelling using detailed channel topography surveyed at Dry Creek. The AA. also use
provide a basic framework toward the understanding of hillslope scale erosion processes that would eventually be used to build a physically based erosion prediction model.
The A. discusses a two-dimensional depth-averaged model, various meander models and a model for the braided Brahmaputra-Jamuna River in Bangladesh. Emphasis is placed on the need for future research rather than on model applications. The models help
Modelling stage-discharge relationships in anastomosed bedrock-influenced sections of the Sabie River system
Afrique du Sud ; Chenal anastomosé ; Cours d'eau ; Dynamique fluviale ; Débit ; Géométrie hydraulique ; Hydrologie fluviale ; Modèle
Braided channel ; Channel geometry ; Discharge ; Fluvial dynamics ; Fluvial hydrology ; Model ; South Africa ; Stream
distributaries with varying water surface elevations across a cross-section. A Multiple Stage model was developed to predict hydraulic conditions in each distributary, using a single measured rating curve and knowledge of individual distributary water surface
elevations at a low flow. This model has enabled realistic prediction of channel geometry and hydraulic variables, that accounts for the different stages found in bedrock-influenced sections.
The AA. investigated the effects of cross-section spacing on flow properties simulated with 2D modeling at low, medium and high discharges in 2 morphologically different reaches, a simple (almost featureless with low sinuosity) and a complex
. Conversely, models generated with cross-sections spaced at 0.5 and 1 W have stream flow properties, sediment mobility and spatial habitat distribution similar to those of the complete bathymetry. Furthermore, differences in flow properties between
(presenting pools, riffles, runs, contractions and expansions) reach of the Snake River (Idaho). They compared the results from 2D models developed with complete channel bathymetry acquired with multibeam sonar data and photogrammetry, with 2D model results
that were developed using interpolated topography from uniformly distributed transects. Results indicate that cross-sections spaced equal to or greater than 2 times the average channel width (W) smooths the bathymetry and suppresses flow structures
interpolated and complete topography models generally increase with discharge and with channel complexity.
pendant un intervalle de temps. Autre approche: estimation avec le choix de la destination la plus fréquentée. Les deux modèles prédisent correctement le choix du magasin.
The purpose of this paper is to use the power law or quadratic equations in studying the morphology of glacial valley cross-sections in the middle and western Tian Shan Mountains, to further examine the evolution patterns of glacial valley form
A numerical model with grid resolution 500 m has been used to simulate tides on this section of the shelf off the coast in western Norway. The fine spatial resolution resolves important fine scale features of the bottom topography on the shelf
and the complex coastline with fjords and islands. Boundary conditions at the oceanic sides of the model domain are obtained by interpolation from a larger scale tidal model covering the Nordic Sea. Duscussion of the results.
la transformation du profil longitudinal d'un ravin, 5) la vérification du modèle sur la base des données d'observation du développement du ravin Brouk Krik de 1838 à 1992 (bassin du fleuve Yass dans le sud-est de l'Australie).
Geomorphology ; Mathematical model ; Model ; Programming ; Research technique ; Slope
The C program is operational under either the DOS or UNIX environment, depending on how it is compiled. This program is designed to detect slope forms in three dimensions that include both the profile and cross-section directions based on elevation
The present paper uses results from a Froude scale laboratory model in consideration of the relationship between bedload transport rates measured at a single cross-section and channel morphology measured at two scales. The first scale
is that of the cross-section at which the bedload transport rate was measured, which is two-dimensional. The second scale is that of the river reach extending about 10 channel widths upstream of this section and is three dimensional.
Erodibility ; Glacial erosion ; Glacial valley ; Lithology ; Model ; New Zealand ; Slope gradient ; Spatial variation ; Valley
A simulation model that examines the development of valley cross-profiles as a result of glacial erosion has been constructed by placing a finite-element model for ice flow within an iterative program that modifies channel cross-section form
on the basis of an erosion equation. The simulation model has previously been used to examine how different flow laws, erosion laws and ice discharge histories affect medium-scale landform development. This allows to better understand the development of glacial
Glacial erosion ; Glacial features ; Glacier ; Glaciology ; Global change ; Ice sheet;Ice cap;Inlandsis ; Modelling ; Numerical model
The first section of this paper provides a very brief overview of the main trends in Anglo-American glacial geomorphology from 1900 to the present. The A. then discusses more detail work on process modeling of glacial landform development, an area
Accuracy assessment for a simulation model of Amazonian deforestation
Amazonie ; Brésil ; Dynamique du paysage ; Déboisement ; Foncier ; Modèle ; Paysage ; Simulation ; Utilisation du sol
Amazon Basin ; Brazil ; Deforestation ; Land ; Land use ; Landscape ; Landscape dynamics ; Model ; Simulation
Evaluation quantitative du résultat d'un modèle comportemental de paysage qui simule la configuration spatiale du déboisement. Dix-huit étapes pour une section de l'autoroute amazonienne, qui résultent d'une combinaison unique des paramètres de
trois modèles. A l'intérieur des lotissements familiaux, le déboisement intervient à proximité des routes.
of an experiment to intercompare a range of precipitation models used for downscaling. The final section examines ongoing challenges to the future development of climate downscaling.
General circulation models (GCMs) suggest that rising concentrations of greenhouse gases may have significant consequences for the global climate. This article reviews the present generation of downscaling tools and go on to summarize the results
Erosion ; Mathematical model ; Model ; Rill wash ; Sediment transport ; Watershed
Treating the dynamics of sediment transport as two-dimensional on interrill-areas and as one-dimensional in rill sections, areally averaged sheet sediment transport (SST) equations are developed. The two-dimensional SST equation is averaged over
an individual interrill-area width and then along the interrill-area length to obtain local-scale areally averaged interrill-area sheet sediment transport equation (local-scale areal averaging). Similarly, the cross-sectional-averaged rill sediment transport