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  • Articles  (8)
  • Other Sources
  • Articles: DFG German National Licenses  (8)
  • simulation  (8)
  • Springer  (8)
  • 1995-1999  (8)
  • Architecture, Civil Engineering, Surveying  (8)
  • 1
    Electronic Resource
    Electronic Resource
    A new formulation for the stochastic control of systems with bounded state variables: An application to a single reservoir system (1996)
    Springer
    Stochastic environmental research and risk assessment 10 (1996), S. 167-186 
    Details
    ISSN: 1436-3259
    Keywords: Reservoir stochastic theory ; reliability ; mean ; variance ; indicator function ; storage bounds ; nonlinear programming ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A new formulation is presented for the analysis of reservoir systems synthesizing concepts from the traditional stochastic theory of reservoir storage, moments analysis and reliability programming. The analysis is based on the development of the first and second moments for the stochastic storage state variable. These expressions include terms for the failure probabilities (probabilities of spill or deficit) and consider the storage bounds explicitly. Using this analysis, expected values of the storage state, variances of storage, optimal release policies and failure probabilities — useful information in the context of reservoir operations and design, can be obtained from a nonlinear programming solution. The solutions developed from studies of single reservoir operations on both an annual and monthly basis, compare favorably with those obtained from simulation. The presentation herein is directed to both traditional reservoir storage theorists who are interested in the design of a reservoir and modern reservoir analysts who are interested in the long term operation of reservoirs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581462
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  • 2
    Electronic Resource
    Electronic Resource
    Kernel bandwidth selection for a first order nonparametric streamflow simulation model (1998)
    Springer
    Stochastic environmental research and risk assessment 12 (1998), S. 33-52 
    Details
    ISSN: 1436-3259
    Keywords: Keywords: Streamflow ; simulation ; nonparametric
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A new approach for streamflow simulation using nonparametric methods was described in a recent publication (Sharma et al. 1997). Use of nonparametric methods has the advantage that they avoid the issue of selecting a probability distribution and can represent nonlinear features, such as asymmetry and bimodality that hitherto were difficult to represent, in the probability structure of hydrologic variables such as streamflow and precipitation. The nonparametric method used was kernel density estimation, which requires the selection of bandwidth (smoothing) parameters. This study documents some of the tests that were conduced to evaluate the performance of bandwidth estimation methods for kernel density estimation. Issues related to selection of optimal smoothing parameters for kernel density estimation with small samples (200 or fewer data points) are examined. Both reference to a Gaussian density and data based specifications are applied to estimate bandwidths for samples from bivariate normal mixture densities. The three data based methods studied are Maximum Likelihood Cross Validation (MLCV), Least Square Cross Validation (LSCV) and Biased Cross Validation (BCV2). Modifications for estimating optimal local bandwidths using MLCV and LSCV are also examined. We found that the use of local bandwidths does not necessarily improve the density estimate with small samples. Of the global bandwidth estimators compared, we found that MLCV and LSCV are better because they show lower variability and higher accuracy while Biased Cross Validation suffers from multiple optimal bandwidths for samples from strongly bimodal densities. These results, of particular interest in stochastic hydrology where small samples are common, may have importance in other applications of nonparametric density estimation methods with similar sample sizes and distribution shapes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004770050008
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  • 3
    Electronic Resource
    Electronic Resource
    Simulation assessment of incident detection by cellular phone call-in programs (1999)
    Springer
    Transportation 26 (1999), S. 399-416 
    Details
    ISSN: 1572-9435
    Keywords: cellular telephones ; incident detection ; simulation ; traffic modeling ; wireless communications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract This research study was designed to assess by simulation the efficacy of incident detection by cellular phone call-in programs. The assessment was conducted by varying the proportion of drivers with cellular phones on the highway so as to mirror the cellular industry statistics that show a continued growth of ownership of cellular phones in the United States. An analytical model, which combined simulation and the limited field data available in the literature, was used to determine measures of effectiveness of the cellular phone-based detection system. The results showed that a cellular phone detection system offers fast incident detection times and higher detection rates for both shoulder and lane blocking incidents. For example, in moderate traffic flow (i.e. 1,550 vehicles per hour per lane), 90 percent of incidents blocking two lanes were detected in 1.5 minutes when the proportion of drivers with cellular phones was one out of 10 drivers, even with only 20 percent of them willing to report incidents. When the current proportion of cellular ownership, i.e. 1 out of 3, was used in the simulation, the detection time improved to 0.8 minutes. The simulation analysis of incident detection by cellular phones also showed that there is a direct relationship between the probability of detection and the detection time; that is, the specification of a higher detection rate resulted in slower detection times. This is in sharp contrast with the results of field study of automatic incident detection (AID) systems which demonstrated an inverse relationship between probability of detection and detection time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005283307060
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  • 4
    Electronic Resource
    Electronic Resource
    Technical Communication: Two-Phase Stochastic Dynamic Programming Model for Optimal Operation of Irrigation Reservoir (1997)
    Springer
    Water resources management 11 (1997), S. 395-406 
    Details
    ISSN: 1573-1650
    Keywords: irrigation reservoirs ; operation ; water deficit ; yield response ; multicrop environment ; stochastic dynamicprogramming ; soil moisture ; water allocation ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract A two-phase stochastic dynamic programming model is developed for optimal operation of irrigation reservoirs under a multicrop environment. Under a multicrop environment, the crops compete for the available water whenever the water available is less than the irrigation demands. The performance of the reservoir depends on how the deficit is allocated among the competing crops. The proposed model integrates reservoir release decisions with water allocation decisions. The water requirements of crops vary from period to period and are determined from the soil moisture balance equation taking into consideration the contribution of soil moisture and rainfall for the water requirements of the crops. The model is demonstrated over an existing reservoir and the performance of the reservoir under the operating policy derived using the model is evaluated through simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007914019102
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  • 5
    Electronic Resource
    Electronic Resource
    Water Drainage in Layered Soils. Laboratory Experiments and Numerical Simulation (1997)
    Springer
    Water resources management 11 (1997), S. 437-444 
    Details
    ISSN: 1573-1650
    Keywords: water first and second drainage ; layered unsaturated soil ; experiment ; γ-radiation ; simulation ; finite differences ; periodically changing head
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Experimental results during first and second drainage in a vertical column of saturated layered soil were compared to those predicted from simulation. The sample was composed of a sandyloam soil overlying a fine sand. The soil water content was measured by using γ-ray absorption method (241Am) and the water pressure through tensiometers, arranged vertically along the column and connected to pressure transducers. From the evaluation of moisture and pressure versus time, the characteristic curves Ψ(θ) of the layers were obtained and approximated by van Genuchten's analytical equation. The relationship K(θ) between hydraulic conductivity and moisture was estimated by van Genuchten's prediction model. Ψ(θ) and K(θ) equations were used as inputs in the numerical model. The drainage of water was simulated by Richard's partial differential equation, which was solved with the finite differences computational scheme type Laasonen. The upper and lower boundary conditions were zero flux and a periodically changing head respectively. Numerical results show a good agreement with experimental data, with small deviations for certain hours.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007900415561
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  • 6
    Electronic Resource
    Electronic Resource
    Performance Risk Analysis for Fukuoka Water Supply System (1998)
    Springer
    Water resources management 12 (1998), S. 13-30 
    Details
    ISSN: 1573-1650
    Keywords: risk ; reliability ; resiliency ; vulnerability ; drought risk index ; drought damage index ; simulation ; water supply ; reservoir operation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract In this study, simulation is used to evaluate the performance of the municipal water system in Fukuoka city. In combination with daily simulation model, a kind of risk model incorporating water demand prediction is presented. This model applies five risk indices: reliability, resiliency, vulnerability, drought risk index (DRI) and drought damage index (DDI). They aid in the identification of operation policies for the municipal water system, and the planning and operational policies obtained are aimed at achieving minimum risk for a given scenario of operation. In this paper, the performance risk of the municipal water system is investigated under three alternatives: (1) the existing system operation when available supply from the Chikugo river is decreased; (2) water restrictions for different percentages of reduction are implemented; and (3) available water supply increases when desalination of sea water is implemented. The results obtained show that savings of between 5 and 12% of water consumption from May 1, or increasing of daily desalination of sea water about 30 000 m3 or more, may efficiently decrease the performance risk of the Fukuoka water supply system. Potentials also exist for further increase of reservoir storage by more rational operation. The measure that more attention should be paid to increasing the water supply from stable sources is recommended as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007951806144
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  • 7
    Electronic Resource
    Electronic Resource
    A Comparative Study of Two Methods for Modeling Soil Water Regime in Agricultural Fields (1998)
    Springer
    Water resources management 12 (1998), S. 285-293 
    Details
    ISSN: 1573-1650
    Keywords: agrometeorological models ; PRZM ; simulation ; SWATRER ; water balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Two methods widely used in agrometeorogical simulation models for describing field soil water regimes are compared and evaluated based on their ability to predict experimental data from a single field study. The first method is based on a numerical solution to the Richards' equation for describing water movement in the soil profile, while the second method is based on soil-water capacity terms. The evaluation of the performance of the two methods is based on goodness-of-fit statistics and graphical analysis. Results indicate that the first method is more accurate for both the upper and the lower soil zones; the second method, despite its low performance in the upper soil zone can adequately describe soil moisture conditions in the lower soil zones. Recommendations are made for model use based on comparison results, the intended model use, and the difficulty in the acquisition of required model inputs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008073824019
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  • 8
    Electronic Resource
    Electronic Resource
    A Planning Model for the Fuerte-Carrizo Irrigation System, Mexico (1997)
    Springer
    Water resources management 11 (1997), S. 165-184 
    Details
    ISSN: 1573-1650
    Keywords: optimization ; linear programming ; simulation ; irrigation planning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract A methodology is presented for planning the operation of the Fuerte-Carrizo irrigation system in northwest Mexico. The system has two storage dams, two irrigation districts, and water transfer capabilities between both dams. The methodology uses a combination of linear programming (LP) and simulation. The LP model maximizes the net return of the farmers, subject to restrictions of the system, availability of water and land, and water transfer relationships. The simulation model is programmed as a microcomputer interactive package simulating the performance of the system. The methodology has proven to be a useful tool to assist those responsible for the operation of the irrigation system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007910530591
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