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Simulation Runs (simulation + run)
Selected AbstractsRainfall distribution is the main driver of runoff under future CO2 -concentration in a temperate deciduous forestGLOBAL CHANGE BIOLOGY, Issue 1 2010SEBASTIAN LEUZINGER Abstract Reduced stomatal conductance under elevated CO2 results in increased soil moisture, provided all other factors remain constant. Whether this results in increased runoff critically depends on the interaction of rainfall patterns, soil water storage capacity and plant responses. To test the sensitivity of runoff to these parameters under elevated CO2, we combine transpiration and soil moisture data from the Swiss Canopy Crane FACE experiment (SCC, 14 30,35 m tall deciduous broad-leaved trees under elevated CO2) with 104 years of daily precipitation data from an adjacent weather station to drive a three-layer bucket model (mean yearly precipitation 794 mm). The model adequately predicts the water budget of a temperate deciduous forest and runoff from a nearby gauging station. A simulation run over all 104 years based on measured sap flow responses resulted in only 5.5 mm (2.9%) increased ecosystem runoff under elevated CO2. Out of the 37 986 days (1 January 1901,31 December 2004), only 576 days produce higher runoff in the elevated CO2 scenario. Only 1 out of 17 years produces a CO2 -signal >20 mm a,1, which mostly depends on a few single days when runoff under elevated CO2 exceeds runoff under ambient conditions. The maximum signal for a double preindustrial CO2 -concentration under the past century daily rainfall regime is an additional runoff of 46 mm. More than half of all years produce a signal of <5 mm a,1, because trees consume the ,extra' moisture during prolonged dry weather. Increased runoff under elevated CO2 is nine times more sensitive to variations in rain pattern than to the applied reduction in transpiration under elevated CO2. Thus the key driver of increased runoff under future CO2 -concentration is the day by day rainfall pattern. We argue that increased runoff due to a first-order plant physiological CO2 -effect will be very small (<3%) in a landscape dominated by temperate deciduous forests, and will hardly increase flooding risk in forest catchments. Monthly rainfall sums are unsuitable to realistically model such CO2 effects. These findings may apply to other ecosystems with comparable soil water storage capacity. [source] Morphology of Symmetric Diblock Copolymers Confined Between Two Stripe-Patterned Surfaces , Tilted Lamellae and MoreMACROMOLECULAR THEORY AND SIMULATIONS, Issue 2 2005Qiang Wang Abstract Summary: We report the first Monte Carlo simulations on the thin-film morphology of symmetric diblock copolymers confined between either symmetrically or antisymmetrically stripe-patterned surfaces. Under suitable surface configurations (where the lamellae can comply with the surface patterns and can have a period close to the bulk lamellar period L0), tilted lamellae are observed for film thicknesses D,,,2L0; the checkerboard morphology is obtained for smaller film thicknesses. The A-B interfaces in the tilted lamellae are basically perpendicular to the surfaces in their immediate vicinity, and exhibit undulations away from them. In some cases, the severe frustration imposed by the two patterned surfaces leads to irregular or unexpected morphologies, which represent locally stable states. The efficient sampling of our expanded grand-canonical Monte Carlo technique enables us to observe more than one locally stable morphologies and the flipping between them during a single simulation run. Tilted lamellae between symmetrically patterned surfaces (perpendicular to z) with a surface pattern period of 1.5L0 and a film thickness of 2.67L0. L0 is the bulk lamellar period and the black curves mark the A-B interfaces. [source] Structure and development of decision-support systems and their use by the State Plant Protection Services in Germany,EPPO BULLETIN, Issue 1 2000B. Kleinhenz To ensure continuing work on decision-support systems (DSSs) and the elaboration of new systems according to the needs of the Plant Protection Services of the federal states of Germany, these services have installed ZEPP (Central Institution for Decision Support Systems and Programmes in Crop Protection). At the national level, ZEPP guarantees a permanent supply of meteorological data, organizes and co-ordinates trials, incorporates scientific progress into the existing DSSs and, in close co-operation with universities and federal research stations, develops new systems for important pests. The PASO desktop system includes a data bank that administers all relevant meteorological files and field data. It allows for automated simulation runs and forecasts, serving as input for timely warnings by different media. Depending on the individual decision-support modules, results are presented as tables and/or graphs. [source] Information theoretical measures to analyze trajectories in rational molecular designJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 16 2007K. Hamacher Abstract We develop a new methodology to analyze molecular dynamics trajectories and other time series data from simulation runs. This methodology is based on an information measure of the difference between distributions of various data extract from such simulations. The method is fast as it only involves the numerical integration/summation of the distributions in one dimension while avoiding sampling issues at the same time. The method is most suitable for applications in which different scenarios are to be compared, e.g. to guide rational molecular design. We show the power of the proposed method in an application of rational drug design by reduced model computations on the BH3 motif in the apoptosis inducing BCL2 protein family. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Rate-based nonisothermal LLX model and its experimental validationAICHE JOURNAL, Issue 2 2004Debjit Sanpui Abstract Most of the current open literature handles liquid,liquid extraction (LLX) using equilibrium and/or isothermal models. However, in most industrial applications, the assumption of equilibrium and isothermal operation is not reasonable. A rate-based nonequilibrium model for both the mass and energy transfer in LLX during the three distinct stages of drop formation,drop, fall or rise, and drop coalescence,has been developed. These three hydrodynamic phenomena affect the mass transfer between dispersed and continuous phases for which a parallel,parallel mass-transfer resistance model has been incorporated. Because of the very large number of computations associated with repeated calculations of mass-transfer coefficients a local model has been proposed. We have compared our rate-based simulator with two other commercial simulators and our bench-scale experiments have been done for toluene,acetone,water and methyl isobutyl ketone,acetic acid,water systems. Stagewise mass and energy transfer and the hydrodynamics features have been compared between the experimental and the simulation runs. Relative-error square analysis (for the concentration profiles) shows that our simulation results are two orders of magnitude better in comparison to other commercial simulators. © 2004 American Institute of Chemical Engineers AIChE J, 50: 368,381, 2004 [source] Serotonergic Agents and Alcoholism Treatment: A SimulationALCOHOLISM, Issue 12 2003Scott F. Stoltenberg Background: Those with early-onset alcoholism may better respond to ondansetron (a 5-HT3 receptor antagonist) than to selective serotonin reuptake inhibitor (SSRI) treatment, whereas those with late-onset alcoholism may present the reverse response pattern. Johnson and colleagues proposed a model that attempts to explain the observed treatment response patterns of those with early and late alcoholism onset by focusing on the influence of a common genetic variant in the serotonin transporter regulatory region (5-HTTLPR) on serotonin (5-HT) and dopamine (DA) system function. Methods: The present study formalizes and extends Johnson's descriptive model into a computer simulation consisting of differential equations. For each of 16 conditions defined by genotype, drinking status, diagnostic status, and drug treatment, data were generated by 100 simulation runs. Results: In every condition, the S/_ genotype (S/S and S/L) had higher extracellular 5-HT levels than did the L/L genotype. The S/_ genotype also had higher rates of postsynaptic DA firing than did the L/L genotype with the exception of the SSRI treatment condition, where the firing rates were similar. Drinking generally increased levels of extracellular 5-HT, reduced rates of presynaptic 5-HT firing, and increased rates of postsynaptic DA firing. Drinking produced increases in DA activation that were greater for the L/L genotype in the SSRI treatment condition and for the S/_ genotype in the ondansetron treatment condition. Conclusions: Genotype at 5-HTTLPR may influence relative reward of drinking alcohol while a person is under pharmacological treatment for alcoholism. Alternatively, 5-HTTLPR genotype may influence pathways of alcohol craving. Clinical studies should examine these hypotheses. [source] Design and analysis for the Gaussian process model,QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 5 2009Bradley Jones Abstract In an effort to speed the development of new products and processes, many companies are turning to computer simulations to avoid the time and expense of building prototypes. These computer simulations are often complex, taking hours to complete one run. If there are many variables affecting the results of the simulation, then it makes sense to design an experiment to gain the most information possible from a limited number of computer simulation runs. The researcher can use the results of these runs to build a surrogate model of the computer simulation model. The absence of noise is the key difference between computer simulation experiments and experiments in the real world. Since there is no variability in the results of computer experiments, optimal designs, which are based on reducing the variance of some statistic, have questionable utility. Replication, usually a ,good thing', is clearly undesirable in computer experiments. Thus, a new approach to experimentation is necessary. Published in 2009 by John Wiley & Sons, Ltd. [source] The role and impact of mental simulation in designAPPLIED COGNITIVE PSYCHOLOGY, Issue 3 2009Bo T. Christensen Although theories of mental simulations have used different formulations of the premises of ,thought experiments', they can be fitted under a minimalist hypothesis stating that mental simulations are run under situations of uncertainty to turn that uncertainty into approximate answers. Three basic assumptions of mental simulations were tested by using naturalistic data from engineering design. Results from the design protocols showed (1) initial representations in mental simulation had higher than base-rate uncertainty, (2) uncertainty in mental simulations were lowered after simulation runs, (3) resulting representations had more approximations than base-rate or initial representations. Further, the reference to external representational systems (sketches and prototypes) was examined. It was found that prototypes had fewer technical/functional simulations compared to sketches or unsupported cognition. Although prototypes were associated with more approximation than unsupported cognition, the different external representation categories did not differ in information uncertainty. The results support the minimalist hypothesis of mental simulations. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||