A simulation model to evaluate the impact of environmental programmes on dairy farms

A simulation model has been developed to determine the impact of the implementation of environmental programmes putting restrictions on fertiliser use and mowing date on dairy farms. In the paper, the simulation model is described and results showing the trade-offs between the economic, environmental and nature protection criteria are given. Finally, the optimal compromise is found using multi-criteria analysis.     

A computer program for the simulation of landform erosion

A computer implementation of a stochastic model describing changes in a landform during lithologically controlled erosion is described. The model is a Markov chain in two dimensions where the noise component depends upon the underlying lithologies. A surface at any elevation above the present level can be reconstructed according to the characteristics of any of four generally accepted geomorphic theories. Erosion then proceeds until the desired reduction in elevation is achieved. The resulting surface then can be compared to an expected surface, such as the present one, and a measure of fit obtained. About 4096 geomorphically significant option combinations are available, including: isostatic adjustment to erosion, epeirogenic uplift, treatment of the landform parameters as random variables, and criteria for ending the simulation. A technique for validation based upon the random topology model of R. L. Shreve is included. An example covering about 5000 km² in the central Appalachians is described.     

A computer simulation in surgery for a human hip joint

For patients who have early signs of hip joint disease resulting from a structural abnormality, various surgeries for correcting abnormal stress distribution can be useful to prevent the progression of the disease. However, it is difficult to confirm the optimal procedure for surgery. To deal with this problem, we devised a computer program to support preoperative planning. Hip images obtained by computed tomography were loaded into our program, and a three-dimensional voxel model was created. Then the pressure distribution on the hip joint was analyzed with a rigid-body spring analysis (computational nonlinear mechanical analysis). This system has a module for performing virtual surgery. This program allows the hip joint mechanics to be evaluated easily, so that the advantages and disadvantages of various surgical methods can be examined biomechanically prior to surgery. However, this system has several problems that should be solved in the near future. This work was presented in part at the 12th International Symposium on Artifi cial Life and Robotics, Oita, Japan, January 25–27, 2007     

A computer simulation game of the locational decision process

A method of representing the locational-decision processes of home and workplace for a household as a game has been developed on a microcomputer. A 10-year period is represented, and each year rail fares, house values and incomes rise by a different amount. The player is able to request information on the houses and jobs available, and can then make decisions to meet a pre-defined objective and to avoid bankruptcy and, if desired, to accumulate capital or savings. On some occasions the player is forced to find a new job because of redundancy or a new home because of demolition. Furthermore, each year a proportion of savings is spent on furnishings and house repairs. These events of redundancy and house demolition, as well as the fares, income and house values are all generated by the computer using stochastic functions.The game is being used to increase understanding of the processes at work as the cost of travel increases and to demonstrate the complexities of the decisions. Extension of the methodology into simulation of the transport and location interaction process will be discussed.     

A computer simulation of turbulent jet flow

The evolution of a round turbulent jet is simulated numerically under the constraint of axial symmetry. The vortex sheet shed from the orifice is represented by vortex ring elements, with a velocity field cut-off to control close encounters. Large-scale vortex clusters form in the model jet, similar to those inferred from laboratory flow visualization experiments. However, comparisons of statistical properties reveal significant differences between the axisymmetric model flow and real turbulent jets.     

Electrocardiogram simulation using a personal computer

A personal computer with a digital-to-analog converter is used as an electrocardiogram simulator. A TurboPascal procedure, given the heart rate, rhythm, and ST segment levels, generates the voltages for Leads II and V5. A simple circuit reduces the voltages to the physiologic range and smoothes the waveforms, removing the staircase effects of digitalization. The procedure can be manually controlled using a software interface or driven by other programs for use in a full-scale operating room simulator.     

GTSIM A computer simulation of music perception

GTSIM is a computer simulation model of human perception of rhythm, based on Lerdahl and Jackendoff'sA Generative Theory of Tonal Music. GTSIM, a rule-based model with a neural network component, simulates the metric and grouping stages of Lerdahl and Jackendoff's theory. Using a rule-based production system, GTSIM simulates parallel processing, operating left-to-right without backtracking. GTSIM identifies the key of the piece of music and produces hierarchical representations of the metric and grouping structure which conform to Lerdahl and Jackendoff. Jacqueline A. Jones, assistant professor of Computer Science at Brooklyn College of CUNY, is currently working on a project applying genetic algorithms to inductive learning of music. She is the co-author of Problem Solving Using Turbo Pascaland the Schaum's Outline of Programming with Assembly Language.With Scarborough and Miller, she has published several articles using computers to do music analysis. She sings with the Dessoff Choirs. Don Scarborough is professor in the Department of Psychology at Brooklyn College. His research interests include: memory, perception, bilingualism, machine learning, neural networks, genetic algorithms, induction. His publications include On the perception of meter in Understanding Music with AI: Perspectives on Music Cognition. Ben Miller is currently assistant professor of psychology at Simmons College in Boston. His research interests are in mental representation and computer simulation of cognitive processes. He is particularly interested in how listeners perceive musical meter.     

Alveolar flooding: a computer simulation

A validated computer simulation of pulmonary microvascular exchange (J.L. Bert and K.L. Pinder, Microvasc. Res., 27 (1984) 51-70) has been extended to include exchange with the air space (alveoli). Equations which hypothetically describe characteristics associated with this additional compartment and the exchange of both fluid and plasma proteins between the lung tissue and the alveolar space are presented. These are incorporated into the simulation which has been used to predict the behavior of the pulmonary microvascular exchange system including alveolar flooding. The predicted trends associated with alveolar flooding are reasonable. However, due to the lack of specific experimental or clinical findings, the simulation remains essentially unvalidated. The effect on alveolar flooding and interstitial edema of the parameters associated with the additional relationships is presented and discussed. Primarily, results for perturbations in circulatory pressure are presented. Additionally, changes in permeability characteristics are shown and discussed.     

A wideband data link computer simulation model

This paper describes a computer simulation model capable of predicting the performance of a high data rate end-to-end communication system for biphase and quadriphase CPSK transmission. Simulation results are compared with laboratory measurements in order to verify the simulation procedure. Ultimately, the simulation model is utilized to conduct a parameter sensitivity analysis for the purpose of evaluating the effect of different signal distortion phenomena on link performance.     

QDENSITY—A Mathematica quantum computer simulation

This Mathematica 6.0 package is a simulation of a Quantum Computer. The program provides a modular, instructive approach for generating the basic elements that make up a quantum circuit. The main emphasis is on using the density matrix, although an approach using state vectors is also implemented in the package. The package commands are defined in Qdensity.m which contains the tools needed in quantum circuits, e.g., multiqubit kets, projectors, gates, etc.

New version program summary

Program title: QDENSITY 2.0Catalogue identifier: ADXH_v2_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXH_v2_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 26 055No. of bytes in distributed program, including test data, etc.: 227 540Distribution format: tar.gzProgramming language: Mathematica 6.0Operating system: Any which supports Mathematica; tested under Microsoft Windows XP, Macintosh OS X, and Linux FC4Catalogue identifier of previous version: ADXH_v1_0Journal reference of previous version: Comput. Phys. Comm. 174 (2006) 914Classification: 4.15Does the new version supersede the previous version?: Offers an alternative, more up to date, implementationNature of problem: Analysis and design of quantum circuits, quantum algorithms and quantum clusters.Solution method: A Mathematica package is provided which contains commands to create and analyze quantum circuits. Several Mathematica notebooks containing relevant examples: Teleportation, Shor's Algorithm and Grover's search are explained in detail. A tutorial, Tutorial.nb is also enclosed.Reasons for new version: The package has been updated to make it fully compatible with Mathematica 6.0Summary of revisions: The package has been updated to make it fully compatible with Mathematica 6.0Running time: Most examples included in the package, e.g., the tutorial, Shor's examples, Teleportation examples and Grover's search, run in less than a minute on a Pentium 4 processor (2.6 GHz). The running time for a quantum computation depends crucially on the number of qubits employed.     

A homogeneous computer network Analysis and simulation

A network of minicomputers to support transaction processing against a distributed data base is described. This paper gives a brief overview of the design based on a loop communications subnetwork and then describes analytic and simulation models that have been used to predict performance.Service demands in this network are assumed to have the following characteristics.Transaction: Users at on-line terminals enter messages that invoke short computations, a few accesses to the data base and a response message that is then sent back to the terminal.Locality of reference: Transactions entering at one node in the network can almost always be serviced locally, the fraction requiring remote service is expected to be in the 10% to 30% range.The network has been modelled analytically as a network queues. The predictions of this model have been compared to those of a large simulation of the network in an attempt to validate that simulation model. Agreement is good for a two host network over a broad range of network loading. The simulation program has been used to study a large number of problems where we varied: transaction characteristics, remote traffic fraction, host configuration and communications subnetwork speed. One such experiment is described here in detail.     

A computer simulation of medical decision strategy performance

This study demonstrates a computer model which can be used to compare the effects of errors in probability and utility estimation on the performance of Bayesian and alternative medical decision strategies. The model task requires choosing one of three treatments for a patient with one of three diseases based on the patient's state with respect to five binary cues and estimates of the prior probabilities of disease, the conditional probabilities of the cues and the utilities of the treatments. A classic decision analytic strategy uses Bayes' formula to calculate posterior probabilities of disease and chooses treatments based on maximization of expected value. Alternative strategies use likelihood ratios to calculate disease scores for each patient state and choose the treatment with highest payoff for the disease with the highest score. Two strategies with different cutoffs for the ratios are compared with a random strategy and a classic decision analytic strategy. The simulation results show that the payoffs for all strategies except the random strategy decline with increasing estimation error. The decision analytic strategy has the highest mean payoff at all levels of error. The differences between this optical strategy and the alternatives, however, decrease as estimation error increases, and the frequency with which the strategies based on simple diagnostic scoring rules outperform the formal Bayesian strategy increases.     

A finite difference model for air pollution simulation

A 3-D model for atmospheric pollutant transport is proposed considering a set of coupled convection–diffusion–reaction equations. The convective phenomenon is mainly produced by a wind field obtained from a 3-D mass consistent model. In particular, the modelling of oxidation and hydrolysis of sulphur and nitrogen oxides released to the surface layer is carried out by using a linear module of chemical reactions. The dry deposition process, represented by the so-called deposition velocity, is introduced as a boundary condition. Moreover, the wet deposition is included in the source term of the governing equations using the washout coefficient. Before obtaining a numerical solution, the problem is transformed using a terrain conformal coordinate system. This allows to work with a simpler domain in order to build a mesh that provides finite difference schemes with high spatial accuracy. The convection–diffusion–reaction equations are solved with a high order accurate time-stepping discretization scheme which is constructed following the technique of Lax and Wendroff. Finally, the model is tested with a numerical experiment in La Palma Island (Canary Islands).     

Dynamic computer simulation and energy absorption of foam-filled conical tubes under axial impact loading

This paper treats the dynamic response and energy absorption of aluminum foam-filled conical tubes under axial impact loading using non-linear finite element techniques. The influence of geometrical, material and loading parameters on the impact response is investigated using validated numerical models. Results are quantified in terms of important impact response parameters and indicate that the foam filler stabilizes the crushing process and thus improves the energy absorption capacity. The superior performance of foam-filled conical tubes as impact energy absorbers is evident from the results. The research information generated will be useful in developing guidance towards the design of these devices in impact applications.