A National Commodity Flow Model

1975 ◽  
Vol 2 (3) ◽  
pp. 292-304
Author(s):  
B. G. Hutchinson ◽  
W. B. O'Brien ◽  
I. N. Dawson
Keyword(s):  
Data Base ◽  
Flow Model ◽  
Urban Transport ◽  
Model Parameters ◽  
Model Structure ◽  
Commodity Flow ◽  
Commodity Flows ◽  
Development Patterns ◽  
Industry Sector ◽  
Independent Information

This paper describes a pilot study of the development of a national commodity flow model for Canada. The aim is to develop a modelling capability that can estimate the commodity movement implications of probable changes in development and in the transport system. The model described in this paper concentrates on estimating the implications of alternative development patterns. The basic inputs to the model are spatially disaggregated allocations of population and of employment by industry sector. The principal outputs from the model are the annual tonnages of freight on each link of each modal transport network. Data inputs to the model and the model parameters are derived principally from information collected and published by Statistics Canada.The structure of the model is similar to the model structure used in urban transport planning studies. It proceeds from the estimation of commodity productions and consumptions, through the estimation of commodity distributions patterns and modal split by mode to network assignment.Preliminary results from the commodity flow model using a 1971 data base are described along with a very limited appraisal of the model outputs using independent information on Canadian commodity flows. Plausible results were obtained from the model and the assembly of an improved data base should lead to a well-developed national commodity flow model for Canada. Such a model may then be used to examine the freight movement implications of alternative patterns of urbanization in Canada and to evaluate alternative transport supply decisions for the various modes of transport.

Dynamic Modeling of an Unmanned Helicopter From Flight Test Data

2011 ◽  
Author(s):  
Guanlin Wang ◽  
Jihong Zhu ◽  
Hui Xia
Keyword(s):  
Minimum Cost ◽  
Flight Test ◽  
Model Parameters ◽  
Model Structure ◽  
Unmanned Helicopter ◽  
Final Model ◽  
Identification Approach ◽  
Model Set ◽  
Partition Method ◽  
Approach Time

Accurately modeling the dynamic characteristics of a helicopter is difficult and time-consuming. This paper presents a new identification approach which applies the modes partition method and structure traversal (MPM/ST) algorithm. The dynamic modes, instead of model parameters of each model structure, are sequentially identified through MPM. The model with the minimum cost function (CF) is chosen from the best model set and is defined as the final model. Real flight tests of an unmanned helicopter are carried out to verify the identification approach. Time- and frequency-domain results of the identified models clearly demonstrate the potential of MPM/ST in modeling such complex systems.

scholarly journals The importance of vegetation to understand terrestrial water storage variations

2021 ◽  
Author(s):  
Tina Trautmann ◽  
Sujan Koirala ◽  
Nuno Carvalhais ◽  
Andreas Güntner ◽  
Martin Jung
Keyword(s):  
Soil Moisture ◽  
Large Scale ◽  
Water Storage ◽  
Model Parameters ◽  
Intermediate Water ◽  
Model Structure ◽  
Hydrological Models ◽  
Terrestrial Water Storage ◽  
Terrestrial Water

Abstract. So far, various studies aimed at decomposing the integrated terrestrial water storage variations observed by satellite gravimetry (GRACE, GRACE-FO) with the help of large-scale hydrological models. While the results of the storage decomposition depend on model structure, little attention has been given to the impact of the way how vegetation is represented in these models. Although vegetation structure and activity represent the crucial link between water, carbon and energy cycles, their representation in large-scale hydrological models remains a major source of uncertainty. At the same time, the increasing availability and quality of Earth observation-based vegetation data provide valuable information with good prospects for improving model simulations and gaining better insights into the role of vegetation within the global water cycle. In this study, we use observation-based vegetation information such as vegetation indices and rooting depths for spatializing the parameters of a simple global hydrological model to define infiltration, root water uptake and transpiration processes. The parameters are further constrained by considering observations of terrestrial water storage anomalies (TWS), soil moisture, evapotranspiration (ET) and gridded runoff (Q) estimates in a multi-criteria calibration approach. We assess the implications of including vegetation on the simulation results, with a particular focus on the partitioning between water storage components. To isolate the effect of vegetation, we compare a model experiment with vegetation parameters varying in space and time to a baseline experiment in which all parameters are calibrated as static, globally uniform values. Both experiments show good overall performance, but including vegetation data led to even better performance and more physically plausible parameter values. Largest improvements regarding TWS and ET were seen in supply-limited (semi-arid) regions and in the tropics, whereas Q simulations improve mainly in northern latitudes. While the total fluxes and storages are similar, accounting for vegetation substantially changes the contributions of snow and different soil water storage components to the TWS variations, with the dominance of an intermediate water pool that interacts with the fast plant accessible soil moisture and the delayed water storage. The findings indicate the important role of deeper moisture storages as well as groundwater-soil moisture-vegetation interactions as a key to understanding TWS variations. We highlight the need for further observations to identify the adequate model structure rather than only model parameters for a reasonable representation and interpretation of vegetation-water interactions.

scholarly journals Automated calibration of a two-dimensional overland flow model by estimating Manning's roughness coefficient using genetic algorithm

2017 ◽  
Vol 20 (2) ◽  
pp. 440-456
Author(s):  
J. Drisya ◽  
D. Sathish Kumar
Keyword(s):  
Genetic Algorithm ◽  
Flow Model ◽  
Overland Flow ◽  
Fitness Function ◽  
Roughness Coefficient ◽  
Model Parameters ◽  
Automatic Data ◽  
Automated Calibration ◽  
Manning’S Roughness Coefficient ◽  
Overland Flow Model

Abstract Calibration is an important phase in the hydrological modelling process. In this study, an automated calibration framework is developed for estimating Manning's roughness coefficient. The calibration process is formulated as an optimization problem and solved using a genetic algorithm (GA). A heuristic search procedure using GA is developed by including runoff simulation process and evaluating the fitness function by comparing the experimental results. The model is calibrated and validated using datasets of Watershed Experimentation System. A loosely coupled architecture is followed with an interface program to enable automatic data transfer between overland flow model and GA. Single objective GA optimization with minimizing percentage bias, root mean square error and maximizing Nash–Sutcliffe efficiency is integrated with the model scheme. Trade-offs are observed between the different objectives and no single set of the parameter is able to optimize all objectives simultaneously. Hence, multi-objective GA using pooled and balanced aggregated function statistic are used along with the model. The results indicate that the solutions on the Pareto-front are equally good with respect to one objective, but may not be suitable regarding other objectives. The present technique can be applied to calibrate the hydrological model parameters.

scholarly journals Interpreting the Estimates from the Full VECH Model with Asymmetry: The Case of US and Canadian Equity Prices

2017 ◽  
Vol 6 (4) ◽  
pp. 236
Author(s):  
Chikashi Tsuji
Keyword(s):  
Parameter Estimates ◽  
Model Parameters ◽  
Model Structure ◽  
Equity Prices ◽  
Related Research ◽  
Asymmetric Effects ◽  
Equity Index ◽  
Autoregressive Conditional Heteroscedasticity ◽  
Full Vector

This paper attempts to derive careful interpretation of the parameter estimates from one of the multivariate generalized autoregressive conditional heteroscedasticity (MGARCH) models, the full vector-half (VECH) model with asymmetric effects. We also consider and interpret the parameter estimates from a case study of US and Canadian equity index returns by applying this model. More specifically, we firstly inspect the model formula and derive general interpretation of the model parameters. We consider this is particularly useful for understanding not only the full VECH model structure but also similar MGARCH models. After the general considerations, we also interpret the case results that are derived from our application of the full VECH model to US and Canadian equity index returns. We consider that these concrete illustrations are also very helpful for future related research.

scholarly journals Back-calculation of the 2017 Piz Cengalo-Bondo landslide cascade with r.avaflow

2019 ◽  
Author(s):  
Martin Mergili ◽  
Michel Jaboyedoff ◽  
José Pullarello ◽  
Shiva P. Pudasaini
Keyword(s):  
Debris Flow ◽  
Flow Model ◽  
Rock Avalanche ◽  
Simulation Software ◽  
Process Models ◽  
Rock Fall ◽  
Model Parameters ◽  
Rock Slide ◽  
Glacier Ice ◽  
Initial Rock

Abstract. In the morning of 23 August 2017, around 3 million m3 of granitoid rock broke off from the east face of Piz Cengalo, SE Switzerland. The initial rock slide-rock fall entrained 0.6 million m3 of a glacier and continued as a rock(-ice) avalanche, before evolving into a channelized debris flow that reached the village of Bondo at a distance of 6.5 km after a couple of minutes. Subsequent debris flow surges followed in the next hours and days. The event resulted in eight fatalities along its path and severely damaged Bondo. The most likely candidates for the water causing the transformation of the rock avalanche into a long-runout debris flow are the entrained glacier ice and water originating from the debris beneath the rock avalanche. In the present work we try to reconstruct conceptually and numerically the cascade from the initial rock slide-rock fall to the first debris flow surge and thereby consider two scenarios in terms of qualitative conceptual process models: (i) entrainment of most of the glacier ice by the frontal part of the initial rock slide-rock fall and/or injection of water from the basal sediments due to sudden rise in pore pressure, leading to a frontal debris flow, with the rear part largely remaining dry and depositing mid-valley; and (ii) most of the entrained glacier ice remaining beneath/behind the frontal rock avalanche, and developing into an avalanching flow of ice and water, part of which overtops and partially entrains the rock avalanche deposit, resulting in a debris flow. Both scenarios can be numerically reproduced with the two-phase mass flow model implemented with the simulation software r.avaflow, based on plausible assumptions of the model parameters. However, these simulation results do not allow to conclude on which of the two scenarios is the more likely one. Future work will be directed towards the application of a three-phase flow model (rock, ice, fluid) including phase transitions, in order to better represent the melting of glacier ice, and a more appropriate consideration of deposition of debris flow material along the channel.

scholarly journals Calibration of physically based models: back to basics?

2003 ◽  
Vol 5 (4) ◽  
pp. 233-244 ◽  
Author(s):  
Vincent Guinot ◽  
Philippe Gourbesville
Keyword(s):  
Hydrological Model ◽  
Flash Flood ◽  
Model Parameters ◽  
Model Structure ◽  
Ungauged Catchments ◽  
Model Response ◽  
Physically Based ◽  
Physically Based Models ◽  
Extreme Hydrological Events ◽  
Main Factor

The modelling of extreme hydrological events often suffers from a lack of available data. Physically based models are the best available modelling option in such situations, as they can in principle provide answers about the behaviour of ungauged catchments provided that the geometry and the forcings are known with sufficient accuracy. The need for calibration is therefore limited. In some situations, calibration (seen as adjusting the model parameters so that they fit the calculation as closely to the measurements as possible) is impossible. This paper presents such a situation. The MIKE SHE physically based hydrological model is used to model a flash flood over a medium-sized catchment of the Mediterranean Alps (2820 km2). An examination of a number of modelling alternatives shows that the main factor of uncertainty in the model response is the model structure (what are the dominant processes). The second most important factor is the accuracy with which the catchment geometry is represented in the model. The model results exhibit very little sensitivity to the model parameters, and therefore calibration of these parameters is found to be useless.

scholarly journals Comparison of three Models of Avalanche Dynamics

1989 ◽  
Vol 13 ◽  
pp. 82-89 ◽  
Author(s):  
H. Gubler
Keyword(s):  
Differential Equation ◽  
Granular Flow ◽  
Flow Model ◽  
Model Parameters ◽  
Field Observations ◽  
Segmentation Method ◽  
Avalanche Dynamics ◽  
Flow Speeds ◽  
Avalanche Flow ◽  
Longitudinal Profiles

Results and characteristics of three models for estimating avalanche flow speeds, flow heights, and run-out distances are compared: (1) Voellmy–Salm equation used with the traditional release, track, and run-out segmentation method; (2) Voellmy–Salm differential equation solved numerically along longitudinal profiles of avalanche paths, combined with modified assumptions for the flow in the run-out zone; (3) a granular-flow model introduced by Salm and Gubler. Within the limits of the accuracy of the field observations, all models are able to predict run-out distances correctly, at least for large avalanches, but the Voellmy–Salm type models significantly underestimate flow speeds. Modelling different flow regimes (sliding and partial fluidization) increases the range of avalanche sizes for which correct run-out modelling is possible without recalibration of model parameters.

Analysis of parameter uncertainty of a flow and quality stormwater model

2009 ◽  
Vol 60 (3) ◽  
pp. 717-725 ◽  
Author(s):  
C. B. S. Dotto ◽  
A. Deletic ◽  
T. D. Fletcher
Keyword(s):  
Water Quality ◽  
Bayesian Methods ◽  
Flow Model ◽  
Model Parameters ◽  
Rainfall Runoff ◽  
Sources Of Uncertainty ◽  
Music Model ◽  
Rainfall Runoff Model ◽  
Water Quality Models ◽  
Runoff Model

Uncertainty is intrinsic to all monitoring programs and all models. It cannot realistically be eliminated, but it is necessary to understand the sources of uncertainty, and their consequences on models and decisions. The aim of this paper is to evaluate uncertainty in a flow and water quality stormwater model, due to the model parameters and the availability of data for calibration and validation of the flow model. The MUSIC model, widely used in Australian stormwater practice, has been investigated. Frequentist and Bayesian methods were used for calibration and sensitivity analysis, respectively. It was found that out of 13 calibration parameters of the rainfall/runoff model, only two matter (the model results were not sensitive to the other 11). This suggests that the model can be simplified without losing its accuracy. The evaluation of the water quality models proved to be much more difficult. For the specific catchment and model tested, we argue that for rainfall/runoff, 6 months of data for calibration and 6 months of data for validation are required to produce reliable predictions. Further work is needed to make similar recommendations for modelling water quality.

A Hydrostatic Bearing With Compressible Fluid for Broad Application

2001 ◽  
Author(s):  
John S. Jacob ◽  
Donald E. Bently ◽  
John J. Yu
Keyword(s):  
Compressible Fluid ◽  
Gas Flow ◽  
Flow Model ◽  
Compressible Fluids ◽  
Environmental Benefits ◽  
Model Parameters ◽  
Broad Application ◽  
Hydrostatic Bearing ◽  
Gas Bearing

The use of relatively inviscid, compressible fluids in externally-pressurized bearings has interesting possibilities for both OEM and retrofit applications. The chance to dramatically reduce mechanical losses and bearing heating, the elimination of oil from the process and installation, and the utilization of compressible process fluids as the supporting medium all have potential economic and environmental benefits. An experimental gas bearing rig was constructed to investigate the feasibility of some general applications. Clearance and orifice dimensions were selected based on a fairly simple gas flow model. Bently-Muszynska model parameters for the hydrostatic gas bearing were obtained through static-pull and non-synchronous perturbation testing.

scholarly journals Comparison of three Models of Avalanche Dynamics

1989 ◽  
Vol 13 ◽  
pp. 82-89 ◽  
Author(s):  
H. Gubler
Keyword(s):  
Differential Equation ◽  
Granular Flow ◽  
Flow Model ◽  
Model Parameters ◽  
Field Observations ◽  
Segmentation Method ◽  
Avalanche Dynamics ◽  
Flow Speeds ◽  
Avalanche Flow ◽  
Longitudinal Profiles

Results and characteristics of three models for estimating avalanche flow speeds, flow heights, and run-out distances are compared: (1) Voellmy–Salm equation used with the traditional release, track, and run-out segmentation method; (2) Voellmy–Salm differential equation solved numerically along longitudinal profiles of avalanche paths, combined with modified assumptions for the flow in the run-out zone; (3) a granular-flow model introduced by Salm and Gubler. Within the limits of the accuracy of the field observations, all models are able to predict run-out distances correctly, at least for large avalanches, but the Voellmy–Salm type models significantly underestimate flow speeds. Modelling different flow regimes (sliding and partial fluidization) increases the range of avalanche sizes for which correct run-out modelling is possible without recalibration of model parameters.

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