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  • Modelling
  • Seismics (controlled source seismology)
  • Waves
  • 1990-1994  (382)
  • 1970-1974  (68)
  • 1960-1964  (35)
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Keywords
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Aluminium electrolytic cells: A computer simulator for training and supervision (1994)
    Springer
    Engineering with computers 10 (1994), S. 12-21 
    Details
    ISSN: 1435-5663
    Keywords: Aluminium electrolysis ; Expert systems ; Modelling ; Simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A workstation-based simulator of an aluminium electrolytic cell has been constructed. A mathematical model of the cell is integrated with a database and a knowledge base, and the simulator serves as a tool for the training of personnel and for research related to cell dynamics and cell control. When used in conjunction with an expert system, it provides a powerful decision-making tool or an efficient supervisory system. The mathematical model, the simulator itself, the user environment, the interactive simulation procedure as well as examples of the use of the simulator are presented in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206536
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  • 2
    Electronic Resource
    Electronic Resource
    A thermal appraisal of the ablation process in canine aorta in vivo using a 100 μm pulsed Nd-YAG laser (1991)
    Springer
    Lasers in medical science 6 (1991), S. 373-378 
    Details
    ISSN: 1435-604X
    Keywords: Heat necrosis ; Modelling ; Nd-YAG laser ; Dog aorta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract A model has been developed to calculate distal tissue necrosis in vascular tissue after application of a 100μ laser pulse from a Nd-YAG laser (5 kW peak pulse power on a 0.13 mm2 spot size). The model assumes that the temperature profile in the tissue is proportional to the laser light fluence rate and that the distal tissue necrosis depth is that depth in the tissue where there is a temperature increase of 42 °C minus the etch rate (ablation depth per laser pulse). The fluence rate has been calculated using the diffusion approximation to the radiative transport equation. The tissue optical parameters (absorption and reduced scattering coefficients) have been derived from published data. The etch rate used (10μm per pulse) is derived from in vivo experimental results. The model predicts a damage depth varying between 0 and 2.33 mm (mean 1.10 mm) and this is compared with an experimental result (0.77 mm) in dog aorta.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02042459
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  • 3
    Electronic Resource
    Electronic Resource
    Interconnected games and international environmental problems, II (1994)
    Springer
    Annals of operations research 54 (1994), S. 97-117 
    Details
    ISSN: 1572-9338
    Keywords: Modelling ; interconnection ; side payments ; game theory ; environment ; transboundary pollution ; multiple objective games ; repeated games ; tensor games ; tradeoff ; Pareto equilibrium ; Nash equilibrium ; Folk theorem ; prisoners' dilemma ; JEL C70 ; Q28
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract Some features of international environmental problems are considered. A basic problem is to induce countries to adopt a cooperative approach. One of the instruments to induce countries to cooperate is an exchange of concessions in fields of relative strengths, such as swapping trade concessions for cooperation on international environmental problems. This instrument will be modelled in this paper with tensor games. Both tradeoff and non-tradeoff tensor games will be addressed, with emphasis on tradeoff tensor games with linear strict weights. The relationship between the Pareto equilibria of a non-tradeoff tensor game and the Nash equilibria of the associated tradeoff tensor games will be studied. Due to structural similarities between tensor games and repeated multiple objective games, some attention will also be paid to the latter. Relationships between objects related to Folk theorems for the tradeoff tensor game with completely additive weights and the corresponding objects for its constituting isolated games will be studied. Since many international environmental problems have prisoners' dilemma characteristics, it is analyzed how interconnection may enhance cooperation in prisoners' dilemma games.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02031729
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  • 4
    Electronic Resource
    Electronic Resource
    On optimality, physiology and honeybees — a reply to Varjú and Núñez (1993)
    Springer
    Journal of comparative physiology 172 (1993), S. 251-256 
    Details
    ISSN: 1432-1351
    Keywords: Foraging ; Optimality ; Modelling ; Energetics ; Apis mellifera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The analysis of foraging behaviour with optimization models has been used widely in recent years. Studies on nectar collection in the honeybee have been among the examples cited repeatedly in favour of the approach. These studies (based on the “energy-maximizing” hypothesis) have now been challenged in a recent paper by Varjú and Núñez (1991). These authors claim that the observed behaviour can be explained without reference to this hypothesis and even without energetic considerations. Moreover, they maintain that the observations support the “information-exchange” hypothesis, an alternative preferred by the authors. In this paper the arguments used by Varjú and Núñez (1991) are shown to be erroneous in several respects. A recurrent problem results from confusing causal and functional questions. In addition, their analysis fails to distinguish between statistically inferred and normative models, misinterprets the nature of observations and misrepresents the predictions of the energy-maximizing hypothesis. Whereas the information-exchange hypothesis is a plausible alternative, the evidence cited by the authors cannot distinguish between the two competing explanations but rather suggests that energy is important. Varjú and Núñez (1991) do not specify the meaning of “information” so that their hypothesis cannot generate specific predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189401
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  • 5
    Electronic Resource
    Electronic Resource
    Modelling and forecasting industrial innovations via the transfer function S-shaped learning curve (1993)
    Springer
    The international journal of advanced manufacturing technology 8 (1993), S. 329-343 
    Details
    ISSN: 1433-3015
    Keywords: S-shaped learning curve ; Industrial innovations ; Modelling ; Forecasting ; Simulation modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Algorithms are derived for the four-parameter transfer function S-shaped curve, using a least-squared-error (LSE) method for an exponential function. The S-shaped curve is just one in a family of industrial dynamics learning-curve models of increasing complexity which may be used to replicate and forecast the start-up of industrial innovations. Controlled experiments are undertaken, via simulation of “message” and “noise”, to test the modelling and forecasting capabilities of the algorithms. A number of strategies are introduced to improve forecasting performance, such as “boots-trapping”, sequential and parallel adaptation, and alternatively adopting the simplified three-parameter S-curve model. Four examples of modelling industrial innovations via the transfer function learning curve models are presented. The paper concludes that although there is now the capability to model the general four-parameter S-curve, its applications are limited. This is because simpler (and hence less accurate) transfer function models tend to be more robust.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01783617
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  • 6
    Electronic Resource
    Electronic Resource
    Node splitting: A constructive algorithm for feed-forward neural networks (1993)
    Springer
    Neural computing & applications 1 (1993), S. 17-22 
    Details
    ISSN: 1433-3058
    Keywords: Adaptive architecture ; Construction ; Modelling ; Neural networks ; Pruning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract A constructive algorithm is proposed for feed-forward neural networks which uses node-splitting in the hidden layers to build large networks from smaller ones. The small network forms an approximate model of a set of training data, and the split creates a larger, more powerful network which is initialised with the approximate solution already found. The insufficiency of the smaller network in modelling the system which generated the data leads to oscillation in those hidden nodes whose weight vectors cover regions in the input space where more detail is required in the model. These nodes are identified and split in two using principal component analysis, allowing the new nodes to cover the two main modes of the oscillating vector. Nodes are selected for splitting using principal component analysis on the oscillating weight vectors, or by examining the Hessian matrix of second derivatives of the network error with respect to the weights.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01411371
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  • 7
    Electronic Resource
    Electronic Resource
    Neuromodels of analytic dynamic systems (1993)
    Springer
    Neural computing & applications 1 (1993), S. 268-279 
    Details
    ISSN: 1433-3058
    Keywords: Neural nets ; Dynamic systems ; Modelling ; Euler equations ; Chaos ; Prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In contrast to recent work aimed at using neural networks for relatively ‘long term’ prediction of time series, this paper examines how neural networks designed for short term prediction can form very good approximation models, valid over a large region of the phase space, after having been trained on as few as 500 pointsfrom a single trajectory of the underlying dynamic system. This is illustrated using four dynamic systems of increasing complexity, including a simple chaotic system and a more realistic system describing rigid body rotation using orthogonal torques under a chaotic control regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02098745
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  • 8
    Electronic Resource
    Electronic Resource
    Neuro-genetic adaptive attitude control (1994)
    Springer
    Neural computing & applications 2 (1994), S. 183-204 
    Details
    ISSN: 1433-3058
    Keywords: Neural nets ; Genetic algorithms ; Attitude control ; Euler equations ; Adaptive control ; Satellites ; Modelling ; Prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract It has previously been demonstrated that for smooth dynamic systems, using relatively few sample points from a single trajectory, a neural network can be trained to perform very accurate short-term prediction over a large part of the phase space. In this paper, we exploit the capability of a Locally Predictive Network (LPN) to derive an adaptive control architecture for a satellite equipped with controllable, bidirectional thrusters on each of the three principal axes. It is assumed that a hardware implementation of the neural network is available. The inputs for the network are a small history of system states up to the present time and a set of current control inputs, the outputs are the next system state. Once the LPN has been trained successfully, at each time step a genetic algorithm searches the space of hypothetical control inputs. Given a set of control signals, the LPN is used to predict the state of the system at the next sample point. This enables the ‘fitness’ of each set of hypothetical control torques to be evaluated very rapidly. In effect, the genetic algorithm determines a satisfactory solution to the inverse kinematic problem in time to apply the solution (set of control torques) at the next control point. With the exception of the neuromodelling (which is repeated only when the system dynamics change), the whole process is then repeated. The results presented indicate that such an architecture is easily able to master the attitude control problem for arbitrary slew angles, with arbitrary a priori unknowndynamics and noise in the sensor system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01414807
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  • 9
    Electronic Resource
    Electronic Resource
    Modelling manufacturing systems: A birth-death approach (1990)
    Springer
    Journal of intelligent and robotic systems 3 (1990), S. 379-392 
    Details
    ISSN: 1573-0409
    Keywords: Modelling ; manufacturing systems ; approximate method ; queuing network ; birth-death approach ; queues
    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 An approximation method for modelling a manufacturing system is introduced. The system is considered as a queueing network, where each queue is limited in size, and interarrival and processing times are exponentially distributed. The birth-death approach is considered and an approximation method to reduce the dimension of the model is developed. The results are the marginal probability distribution of the number of units in each queue; other performance indices, such as mean queue lengths, utilizations of the working stations, and throughput can be easily obtained. The general procedure is applied to model, for example, queues in tandem, a split node, and a more complex network of queues. Simulation and, when possible, comparison with the exact solution show an acceptable error level of the proposed method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00439425
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  • 10
    Electronic Resource
    Electronic Resource
    Modelling water flow, nitrogen transport and root uptake including physical non-equilibrium and optimization of the root water potential (1991)
    Springer
    Nutrient cycling in agroecosystems 27 (1991), S. 215-231 
    Details
    ISSN: 1573-0867
    Keywords: Modelling ; water flow ; nitrogen transport ; nitrogen cycle ; root uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A model is presented for the simulation of water flow, heat flow, and nitrate and ammonium transport. Two approaches are used for modelling plant water uptake as well as for plant nitrogen uptake. Nitrogen transformations are accounted for in a very simple way. This paper focuses mainly on water flow modelling, solute transport, and water uptake. Richards' equation is used to model water flow in layered soil profiles with a great variety of boundary conditions. Solute transport is simulated with either a simple convection dispersion equation or with a two-region physical non-equilibrium model to distinguish between mobile and immobile water and solute exchange between these two regions. A macroscopic sink term is added to Richards' equation to account for plant water uptake. This term can be calculated along two different approaches, one of which is based on the concept of root water potential. The root water potential is then continuously optimized to minimize the difference between the climatic demand and the uptake rate. Simulation results are compared with field data from the Netherlands to illustrate the degree to which the model is able to predict water flow, solute transport and plant water uptake. The root water potential optimization model seems to provide the best prediction of water distribution. In particular the shape of the profile, revealing uptake patterns, is quite well reproduced with this model. Comparison of simulated and observed water content profiles seems also to reveal the presence of preferential pathways. The comparisons show also how predicted solute distributions can be improved by using a two-region approach rather than a simple convection-dispersion model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01051129
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