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  • Articles  (15)
  • simulation  (15)
  • 1985-1989  (15)
  • 1950-1954
  • Geosciences  (13)
  • Architecture, Civil Engineering, Surveying  (5)
  • Political Science
  • 1
    Electronic Resource
    Electronic Resource
    Stochastic analysis of estuarine hydraulics (1989)
    Springer
    Stochastic environmental research and risk assessment 3 (1989), S. 71-84 
    Details
    ISSN: 1436-3259
    Keywords: Hydraulics ; quasilinearization ; simulation ; stochastic ; estuarine system ; Monte Carlo methods ; random differential equations ; parameter uncertainty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A new methodology is presented for the solution of the stochastic hydraulic equations characterizing steady, one-dimensional estuarine flow. The methodology is predicated on quasi-linearization, perturbation methods, and the finite difference approximation of the stochastic differential operators. Assuming Manning's roughness coefficient is the principal source of uncertainty in the model, stochastic equations are presented for the water depths and flow rates in the estuarine system. Moment equations are developed for the mean and variance of the water depths. The moment equations are compared with the results of Monte Carlo simulation experiments. The results confirm that for any spatial location in the estuary that (1) as the uncertainty in the channel roughness increases, the uncertainty in mean depth increases, and (2) the predicted mean depth will decrease with increasing uncertainty in Manning'sn. The quasi-analytical approach requires significantly less computer time than Monte Carlo simulations and provides explicit
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01544073
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  • 2
    Electronic Resource
    Electronic Resource
    An adaptable microcomputer model for evacuation management (1989)
    Springer
    Fire technology 25 (1989), S. 291-307 
    Details
    ISSN: 1572-8099
    Keywords: evacuation management ; model-based support systems ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract A simulation method is presented which enables a modeler to identify dangerous bottlenecks for emergency building evacuation and to test the sensitivity of occupant exit behavior to evacuation improvement strategies. The modeling method is tested against landmark evacuation data of Pauls and Jones, and used to predict problems and solutions for a complex evacuation situation involving a large university building with multiple exit choices. Some concluding remarks are addressed to a future research agenda for this method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01040378
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  • 3
    Electronic Resource
    Electronic Resource
    The use of renormalization for calculating effective permeability (1989)
    Springer
    Transport in porous media 4 (1989), S. 37-58 
    Details
    ISSN: 1573-1634
    Keywords: Heterogeneity ; effective permeability ; scaling ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract There is a need in the numerical simulation of reservoir performance to use average permeability values for the grid blocks. The permeability distributions to be averaged over are based on samples taken from cores and from logs using correlations between permeabilities and porosities and from other sources. It is necessary to use a suitable ‘effective’ value determined from this sample. The effective value is a single value for an equivalent homogeneous block. Conventionally, this effective value has been determined from a simple estimate such as the geometric mean or a detailed numerical solution of the single phase flow equation. If the permeability fluctuations are small then perturbation theory or effective medium theory (EMT) give reliable estimates of the effective permeability. However, for systems with a more severe permeability variation or for those with a finite fraction of nonreservoir rock all the simple estimates are invalid as well as EMT and perturbation theory. This paper describes a real-space renormalization technique which leads to better estimates than the simpler methods and is able to resolve details on a much finer scale than conventional numerical solution. Conventional simulation here refers to finite difference (or element) techniques for solving the single phase pressure equation. This requires the pressure and permeability at every grid point to be stored. Hence, these methods are limited in their resolution by the amount of data that can be stored in core. Although virtual memory techniques may be used they increase computer time. The renormalization method involves averaging over small regions of the reservoir first to form a new ‘averaged permeability’ distribution with a lower variance than the original. This pre-averaging may be repeated until a stable estimate is found. Examples are given to show that this is in excellent agreement with computationally more expensive numerical solution but significantly different from simple estimates such as the geometric mean.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00134741
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  • 4
    Electronic Resource
    Electronic Resource
    Real-time application of an oil spill movement prediction system (1989)
    Springer
    Natural hazards 2 (1989), S. 31-44 
    Details
    ISSN: 1573-0840
    Keywords: Oil spill ; pollution ; simulation ; Canada ; emergency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This paper deals with the prediction, in real time, of the motion of experimental oil slicks. The experiments were conducted during September 1983 offshore near Halifax on the east coast of Canada. The objectives of the experiments were (i) to determine the suitability of oil spill dispersants as countermeasures and (ii) the testing and verification of oil spill trajectory models and systems. The Atmospheric Environment Service (AES) participated in the experiments to test the capability of its oil spill motion prediction system in providing real-time trajectory forecasts. The experiment consisted of three sets of spills. Each set had a control slick and a test slick. Sixteen barrels of crude oil were used in each spill. The test slicks were used to test the effectiveness of various dispersants, the control slicks were used to verify trajectory forecasts. The spill trajectories and oil weathering information obtained from the system during the experiments demonstrated the relative ease with which the system could handle the required input and provide timely forecasts. The accuracy of these forecast trajectories was confirmed by observations, and their utility was demonstrated by their application in the operational decision-making process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00124756
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  • 5
    Electronic Resource
    Electronic Resource
    Simulation of the time-space evolution of an extratropical cyclonic precipitation field over USA (1988)
    Springer
    Stochastic environmental research and risk assessment 2 (1988), S. 281-294 
    Details
    ISSN: 1436-3259
    Keywords: precipitation field ; stochastic time-space evolution ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The time-space evolution of an extratropical cyclonic precipitation field over U S A is simulated in a stochastic setting as outlined in Kavvas et al. (1988). The birth of a cyclonic storm is characterized by the simultaneous birth of a cyclone center and births of subsynoptic precipitation areas (SPA) at preferred locations around the cyclone center. The precipitation cores and cells which are used as the fundamental building blocks of the SPAs are approximated by circular precipitation areas (CPA) of different sizes. The time space evolution of the precipitation field after the birth is governed by (1) the movement of the synoptic cyclone described by the cyclone center trajectory, (2) independent nonidentically distributed random velocities of the individual CPAs relative to the cyclone center, (3) the births of new CPAs in time and space relative to the cyclone center, (4) the independent evolution in time of the individual spatially uniform intensities of the existing CPAs, (5) the expansion and shrinkage of the existing CPAs in the course of movement and (6) the dissipation (death) of a random number of existing CPAs within the cyclonic system. The computer simulation, the results of which are presented in this paper, successfully reproduced the general mesoscale and synoptic scale features of the radar detected cyclonic rain fields as observed by Austin and Houze (1972), Houze et al. (1976), Hobbs (1978), Hobbs and Locatelli (1978), Houze (1981), Houze and Hobbs (1982) and others.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01544041
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  • 6
    Electronic Resource
    Electronic Resource
    Saltwater transport in a heterogeneous formation: A case study (1988)
    Springer
    Transport in porous media 3 (1988), S. 217-256 
    Details
    ISSN: 1573-1634
    Keywords: Salinity ; advection ; dispersion ; aquifers ; flow model ; transport model ; simulation ; sea water ; connate water ; leakage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Historical information of the hydraulic and salinity aspect, detailed geological information, and information on the physical characteristics of the different layers comprising the formation, are needed for simulating the saltwater transport process in aquifers. In most simulation studies of field situations, there is an inadequacy of data and the modeller has to make justifiable assumptions to analyze a particular situation in order to provide an insight into the problem. A quasi-three-dimensional solute transport model is used to analyze the saltwater encroachment phenomena in aquifers underlying the City of Bangkok; first by calibrating the model's performance with available historical data and then by assessing the extent of future saltwater encroachment with the implementation of the regulatory pumpage to be followed in order to restrict the alarming rate of land subsidence. Model simulation indicates a substantial reduction in the rate of encroachment of the saltwater front with a reduction of pumpage after 1987.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235330
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  • 7
    Electronic Resource
    Electronic Resource
    Dynamics of C, N, P and S in grassland soils: a model (1988)
    Springer
    Biogeochemistry 5 (1988), S. 109-131 
    Details
    ISSN: 1573-515X
    Keywords: soil organic matter ; nitrogen ; phosphorus ; sulfur ; simulation ; grasslands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We have developed a model to simulate the dynamics of C, N, P, and S in cultivated and uncultivated grassland soils. The model uses a monthly time step and can simulate the dynamics of soil organic matter over long time periods (100 to 10,000 years). It was used to simulate the impact of cultivation (100 years) on soil organic matter dynamics, nutrient mineralization, and plant production and to simulate soil formation during a 10,000 year run. The model was validated by comparing the simulated impact of cultivation on soil organic matter C, N, P, and S dynamics with observed data from sites in the northern Great Plains. The model correctly predicted that N and P are the primary limiting nutrients for plant production and simulated the response of the system to inorganic N, P, and S fertilizer. Simulation results indicate that controlling the C:P and C:S ratios of soil organic matter fractions as functions of the labile P and S levels respectively, allows the model to correctly simulate the observed changes in C:P and C:S ratios in the soil and to simulate the impact of varying the labile P and S levels on soil P and S net mineralization rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02180320
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  • 8
    Electronic Resource
    Electronic Resource
    Simulation of the movement and dispersion of oil slicks in the Arabian Gulf (1988)
    Springer
    Natural hazards 1 (1988), S. 197-219 
    Details
    ISSN: 1573-0840
    Keywords: Arabian Gulf ; oil ; oil ; simulation ; meteorology ; tides ; residual currents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The extensive oil drilling and transportation activities in the Arabian Gulf increased the possibility of oil spills and the consequent threat of oil pollution to the regional ecology. The available literature concerning the main aspects of the physical oceanographic characteristics affecting the movement and spreading of oil spill in the Gulf are reviewed. It is concluded that evaporation, wind-driven currents, and sandfall are important as weathering processes, while tidal currents cause lateral spreading of the slick. Oil spill modelling has shown some usefulness in estimating the trajectories of few major spills illustrated by reference to three models developed for the Gulf. The performance of these models, their capabilities and limitations are reviewed. Recommendations are made to gather more data on the behavior of oil spills in this particular environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00126615
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  • 9
    Electronic Resource
    Electronic Resource
    On a stochastic description of the time-space behaviour of extratropical cyclonic precipitation fields (1987)
    Springer
    Stochastic environmental research and risk assessment 1 (1987), S. 37-52 
    Details
    ISSN: 1436-3259
    Keywords: Cyclonic precipitation ; mathematical modeling ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A stochastic description is developed for extratropical cyclonic precipitation fields at synoptic and meso scales as they are typically observed by radars over the Earth. This description attempts to account I) for the synoptic scale behavior of a cyclonic storm (its birth, its synoptic scale motion trajectory, and its dissipation) II) for the synoptic-scale organizational structure of subsynoptic precipitation areas (rainbands, precipitation cores and raincells) within a cyclonic storm; and III) for the behavior of subsynoptic precipitation areas, in terms of their births, their spatial configuration evolutions, their motions, and their deaths (dissipation). The precipitation cores and the raincells are taken as the building blocks of the subsynoptic precipitation, areas within a cyclonic rainfield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01543908
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of leaching on mixing in porous media with a single heterogeneity (1987)
    Springer
    Transport in porous media 2 (1987), S. 3-18 
    Details
    ISSN: 1573-1634
    Keywords: Dispersion ; heterogeneity ; leaching ; regimes ; scales ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This paper presents an exploratory study of the effect of leaching on mixing in a porous medium containing a single heterogeneity to investigate the effect of the heterogeneity and time-dependent pore structure on dispersion. A percolation-convection simulation (PCS) model is used along with laboratory model experiments to study the mixing. The results show that mixing changes when the pores of the models are leached and that there is a change in regime influence during leaching. The simulation represents the mixing through a first leach for homogeneous media and for heterogeneous media with significant changes in permeability. If the pore structure is changing with time, prediction of mixing must include effects of heterogeneity and regime influence. Although the experimental results are representative of idealized laboratory sized systems they provide insight into the effects of leaching in heterogeneous media. Further the simulation may be useful on a field scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208533
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  • 11
    Electronic Resource
    Electronic Resource
    Generating large stochastic simulations—The matrix polynomial approximation method (1987)
    Springer
    Mathematical geology 19 (1987), S. 99-107 
    Details
    ISSN: 1573-8868
    Keywords: geostatistics ; simulation ; Toeplitz matrices ; block Toeplitz matrices ; matrix polynomial approximation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract An algorithm for producing a nonconditional simulation by multiplying the square root of the covariance matrix by a random vector is described. First, the square root of a matrix (or a function of a matrix in general) is defined. The square root of the matrix can be approximated by a minimax matrix polynomial. The block Toeplitz structure of the covariance matrix is used to minimize storage. Finally, multiplication of the block Toeplitz matrix by the random vector can be evaluated as a convolution using the fast Fourier transform. This results in an algorithm which is not only efficient in terms of storage and computation but also easy to implement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00898190
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  • 12
    Electronic Resource
    Electronic Resource
    Development and testing of soil water regime simulation models (1987)
    Springer
    Water resources management 1 (1987), S. 293-303 
    Details
    ISSN: 1573-1650
    Keywords: Soil water regime ; modelling ; simulation ; evapotranspiration ; drainage ; soil water resources ; irrigation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Four soil water balance simulation models corresponding to specific soil-crop relations were developed for application to irrigation planning and management. The forms of the models were inferred from 18 months of weekly and bi-weekly soil water data and daily meteorological data. Soil water change is computed by budgeting of the water inputs and outputs, namely precipitation, evapotranspiration, drainage, and runoff. Actual evapotranspiration was found to be dependent on both potential evapotranspiration and soil water content. Empirical drainage functions were developed, but semi-empirical ones inferred from theoretical knowledge of soil hydraulic properties performed at least as well. Runoff functions were required to explain only exceptional conditions of very heavy rainfall. A quantitative assessment of each model's prediction accuracy was performed. The uncertainty that can be expected for any predicted value with a cumulative probability of 0.95 is in all cases within an interval of 1% of the soil water content in average conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00421881
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  • 13
    Electronic Resource
    Electronic Resource
    Spectral-type simulation of spatially correlated fracture set properties (1985)
    Springer
    Mathematical geology 17 (1985), S. 41-52 
    Details
    ISSN: 1573-8868
    Keywords: fracture set ; simulation ; spectral density ; Fourier transform
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Fracture set properties such as orientation, spacing, trace length, and waviness tend to be spatially correlated. These properties can be efficiently simulated by spectral analysis procedures that take advantage of the computational speed of the fast Fourier transform. The covariance function of each property to be simulated is obtained from the variogram function estimated from mapped fracture set data and is typically referenced to the mean vector of the set. Simulation procedures for normally and exponentially distributed data involve generating uncorrelated Fourier coefficients that are assigned proper variance according to the spectral density, which is the Fourier transform of the covariance function. These coefficients are then reverse Fourier transformed to produce simulated set properties that have the desired variance and variogram function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01030366
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  • 14
    Electronic Resource
    Electronic Resource
    Two-dimensional simulation by turning bands (1985)
    Springer
    Mathematical geology 17 (1985), S. 81-90 
    Details
    ISSN: 1573-8868
    Keywords: simulation ; turning bands ; covariance ; semivariogram ; geostatistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Journel (1974) developed the turning-bands method which allows a three-dimensional data set with specified covariance to be obtained by the simulation of several one-dimensional realizations which have an intermediate covariance. The relationship between the threedimensional and one-dimensional covariance is straightforward and allows the one-dimensional covariance to be obtained immediately. In theory a dense uniform distribution of lines in three-dimensional space is required along which the one-dimensional realizations are generated; in practice most workers have been content to use the fifteen axes of the regular icosahedron. Many mining problems may be treated in two dimensions, and in this paper a turning-bands approach is developed to generate two-dimensional data sets with a specified covariance. By working in two dimensions, the area on which the data is simulated may be divided as finely as desired by the lines on which the one-dimensional realizations are first generated. The relationship between the two-dimensional and one-dimensional covariance is derived as a nontrivial integral equation. This is solved analytically for the onedimensional covariance. The method is applied to the generation of a two-dimensional data set with spherical covariance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01030369
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  • 15
    Electronic Resource
    Electronic Resource
    The Bi-Gaussian approach: A simple method for recovery estimation (1985)
    Springer
    Mathematical geology 17 (1985), S. 625-644 
    Details
    ISSN: 1573-8868
    Keywords: recoveries ; multi-Gaussian ; bi-Gaussian ; simulation ; disjunctive kriging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A new and simple method is proposed to obtain estimates of recovery functions: the Bi-Gaussian approach. Existing methods estimate recovery functions with conditional distributions where the conditioning set is all the data available. Here instead the simple kriging estimate of the Gaussian transform is proposed to be used. Results in the point recovery case are identical to the multi-Gaussian approach of Verly (1983, 1984), whereas in the non-point-support situation, an approximation is derived which saves computer time as compared to employing the strict multi-Gaussian hypothesis. Two examples compare favorably with the well-established disjunctive kriging method (discrete Gaussian model).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01030857
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