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The improvement of a regional climate model by coupling a land surface model with eco-physiological processes: A case study in 1998

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CLIMATIC CHANGE 2015年第3-4期129卷 457-470页

作者： Dan, Li Cao, Fuqiang Gao, Rong Chinese Acad Sci Inst Atmospher Phys Key Lab Reg Climate Environm Temperate East Asia Beijing 100029 Peoples R China China Meteorol Adm Natl Climate Ctr Beijing 100081 Peoples R China

The Atmospheric-Vegetation Interaction Model (AVIM) is coupled with a Regional Integrated Environment modeling System (RIEMS) to improve the regional simulation of climate variables. A case study in 1998 is implemented to study the improvement mechanism through land-air interaction in East Asia, especially in Asian summer monsoon regions. The coupled model reduces the warming bias in July in East China through the surface heat fluxes changes. Compared to the original model of RIEMS, the strong precipitation of eastern China in July is weakened by coupling of the interactive vegetation. The surface heat flux in uncoupled model is remarkably overestimated in these regions, and the enhanced heating from land surface, particularly with latent heat flux in July, will produce the overestimated temperature and precipitation in East China. Through coupling AVIM with RIEMS, the simulated area-averaged latent heat flux of two key regions decreases (e.g. from 132.36 to 103.13 W/m(2) over the region 1 between 105-125A degrees E and 20-40A degrees N) in July, which makes the overestimated temperature and precipitation declined, respectively.

关键词： Case studies Climate change computer based modeling

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Simulation of Aerosol Coagulation and Deposition Under Multiple Flow Regimes with Arbitrary Computational Precision

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AEROSOL SCIENCE AND TECHNOLOGY 2013年第5期47卷 530-542页

作者： Geng, J. Park, H. Sajo, E. Univ Massachusetts Lowell Dept Phys & Appl Phys Lowell MA 01854 USA Los Alamos Natl Lab Div Theoret Los Alamos NM USA

In computational aerosol coagulation models, a widely used technique is the sectional treatment of the particle size distribution. This approach is used in many first- and second-generation computer codes, where the section boundaries are selected to obey a geometric constraint. While this technique improves computational efficiency, it introduces a number of limitations, including poor representation of the initial size distribution and loss of resolution in the coagulated or final distribution. A robust and versatile computer model, SEROSA, has been developed, which permits an arbitrary number of sections with arbitrary size boundaries to simulate the temporal evolution of coagulation and deposition under multiple flow-regimes and coagulation types. The code permits a large number of parameter combinations and what-if scenarios under user control. Results are benchmarked against an analytical model as well as three coagulation models using coincident section boundaries and coagulation mechanisms. The comparison shows excellent agreement in cases where other computer models are known to perform well. The test cases also included scenarios where previously published computational coagulation models lack capabilities or exhibit numerical difficulties. Computational time varies depending on the number of sections, ageing, and coagulation types from a few seconds to minutes. The software is distributed by the Radiation Safety Information Computational Center of Oak Ridge National Laboratory as Code Package PSR 573. Copyright 2013 American Association for Aerosol Research

关键词： Coagulation Aerosols Simulation computer based modeling

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computer modeling of Geoelectromagnetic Fields in Three-Dimensional Media by the Finite Element Method

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IZVESTIYA-PHYSICS OF THE SOLID EARTH 2011年第2期47卷 79-89页

作者： Persova, M. G. Soloveichik, Yu. G. Trigubovigh, G. M. Novosibirsk State Tech Univ Novosibirsk Russia Siberian Res Inst Geol Geophys & Mineral Resource Novosibirsk Russia

This work describes the basic approaches to the solution of three-dimensional (3D) problems of geoelectromagnetism with the use of the finite element method and the possibilities of the GeoEM program complex for its implementation. The methods of modeling geoelectromagnetic fields for the most widely known types of controllable sources and the mathematical apparatus for the solution of problems of magnetotelluric soundings are considered. Examples of the calculations of 3D fields for the horizontal and vertical electric lines in planning electric exploration works on the shelf are presented, as well as an example of the 3D interpretation of array transient electromagnetic sounding data during the search for deep-seated target objects in conditions of a mostly heterogeneous upper part of the section.

关键词： Electromagnetism Finite element analysis computer based modeling Geophysics

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Skill of regional and global model forecast over Indian region

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THEORETICAL AND APPLIED CLIMATOLOGY 2016年第3-4期123卷 629-636页

作者： Kumar, Prashant Kishtawal, C. M. Pal, P. K. Space Applicat Ctr ISRO EPSA Atmospher & Ocean Sci Grp Ahmadabad 380015 Gujarat India

The global model analysis and forecast have a significant impact on the regional model predictions, as global model provides the initial and lateral boundary condition to regional model. This study addresses an important question whether the regional model can improve the short-range weather forecast as compared to the global model. The National Centers for Environmental Prediction (NCEP) Global Forecasting System (GFS) and the Weather Research and Forecasting (WRF) model are used in this study to evaluate the performance of global and regional models over the Indian region. A 24-h temperature and specific humidity forecast from the NCEP GFS model show less error compared to WRF model forecast. Rainfall prediction is improved over the Indian landmass when WRF model is used for rainfall forecast. Moreover, the results showed that high-resolution global model analysis (GFS4) improved the regional model forecast as compared to low-resolution global model analysis (GFS3).

关键词： Analysis Boundary layer computer based modeling Weather forecasting

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Computational prediction of the chromosome-damaging potential of chemicals

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CHEMICAL RESEARCH IN TOXICOLOGY 2006年第10期19卷 1313-1319页

作者： Rothfuss, Andreas Steger-Hartmann, Thomas Heinrich, Nikolaus Wichard, Joerg Schering AG Expt Toxicol D-13342 Berlin Germany Schering AG Computat Chem D-13342 Berlin Germany FMP Mol Modeling Grp D-13125 Berlin Germany

We report on the generation of computer- based models for the prediction of the chromosome-damaging potential of chemicals as assessed in the in Vitro chromosome aberration (CA) test. On the basis of publicly available CA-test results of more than 650 chemical substances, half of which are drug-like compounds, we generated two different computational models. The first model was realized using the (Q) SAR tool MCASE. Results obtained with this model indicate a limited performance (53%) for the assessment of a chromosome-damaging potential (sensitivity), whereas CA- test negative compounds were correctly predicted with a specificity of 75%. The low sensitivity of this model might be explained by the fact that the underlying 2D-structural descriptors only describe part of the molecular mechanism leading to the induction of chromosome aberrations, that is, direct drug-DNA interactions. The second model was constructed with a more sophisticated machine learning approach and generated a classification model based on 14 molecular descriptors, which were obtained after feature selection. The performance of this model was superior to the MCASE model, primarily because of an improved sensitivity, suggesting that the more complex molecular descriptors in combination with statistical learning approaches are better suited to model the complex nature of mechanisms leading to a positive effect in the CA- test. An analysis of misclassified pharmaceuticals by this model showed that a large part of the false-negative predicted compounds were uniquely positive in the CA- test but lacked a genotoxic potential in other mutagenicity tests of the regulatory testing battery, suggesting that biologically nonsignificant mechanisms could be responsible for the observed positive CA- test result. Since such mechanisms are not amenable to modeling approaches it is suggested that a positive prediction made by the model reflects a biologically significant genotoxic potential. An integration of the

关键词： Subject Headings drug development chemical compounds computer based modeling Machine Learning Descriptors

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Role reversal in geomagnetism

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NATURE 1999年第6756期401卷 861-862页

作者： Buffett, B Univ British Columbia Dept Earth & Ocean Sci Vancouver BC V6T 1Z4 Canada

What drives the erratic reversal of Earth's magnetic field? Simulations that allow for variations in heat flow at the core-mantle boundary now implicate events in the mantle.

关键词： Magnetism Geology computer based modeling Temperature

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A GENERALIZED NEURONAL ACTIVATION FUNCTION DERIVED FROM ION-CHANNEL CHARACTERISTICS

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NETWORK-COMPUTATION IN NEURAL SYSTEMS 1995年第3期6卷 389-401页

作者： CARTLING, B Department of Theoretical Physics The Royal Institute of Technology S-100 44 Stockholm Sweden

An abstract model neuron, simple enough to be used in analytical studies of neural networks, is defined. It incorporates neuronal adaptation, i.e. the coupling between neuronal activity and excitability, which can control the complexity of neural network dynamics. A generalized neuronal activation function is defined as the output activity, i.e. the firing rate of action potentials, as a function of an input and an excitability variable. For a biological neuron, the intracellular concentration of Ca ions is shown to be a useful excitability variable. The principal features of the generalized activation function are derived by means of a multicompartment model neuron with ionic currents described by Hodgkin-Huxley-type equations. As a relevant neuron type for investigations of cortical associative memory, a neocortical pyramidal cell of the regularly-spiking type is selected. An approximate analytical consideration suggests a simple form of independent variable of the generalized activation function. The complete numerical treatment verifies this form and displays a threshold character of the activation function. The derivation thereby provides an interpretation of dynamic threshold models of neuronal adaptation in terms of ionic mechanisms. The threshold with respect to the input has well-defined dynamics directly given by the intracellular Ca dynamics. A comparison of the response of the Hodgkin-Huxley-type and reduced-model neurons to a varying input variable indicates that the reduced model is a useful approximation even for the detailed behaviour of the firing rate. The generalized activation function also accounts for the dependence on neuromodulation via an adaptability parameter. An abstract model neural network of units thus defined has the capacity to describe complex network dynamics and the simplicity to allow elucidation of mechanisms and applications to large-scale systems.

关键词： computer-based model Neural networks Associative memory Realistic simulations Hippocampal-neurons Olfactory cortex Modulation Receptors Conductances Excitation Olfactory Cortex Associative memory Action Potentials Activation Neural network Conductance computer based modeling Excitability Receptor Excitation Neurons realistic simulation

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LOW SPIKING RATES IN A POPULATION OF MUTUALLY EXCITING PYRAMIDAL CELLS (VOL 6, PG 271, 1995)

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NETWORK-COMPUTATION IN NEURAL SYSTEMS 1995年第3期6卷 511-511页

作者： FRANSEN, E LANSNER, A SANS — Studies of Artificial Neural Systems Department of Numerical Analysis and Computing Science Royal Institute of Technology S-100 44 Stockholm Sweden

In a recurrent artificial neural network, the units active in an attractor state typically reach their maximum activity value while the others are quiescent. In contrast, recordings of cortical cell activity in vivo rarely reveal cells firing at their maximum rate. This discrepancy has been one of the main arguments against using attractor networks as models of cortical associative memory. In this study we show that low-rate sustained after-activity can be obtained in a simulated network of mutually exciting pyramidal cells. This is achieved by assuming that the synapses in the network are of a saturating type. When the application of a monoamine neuromodulator is simulated, after-activity with firing rates around 60?s^?1 can be produced. The firing pattern of the network was found to be similar to that of the experimentally most comparable system, the disinhibited hippocampal slice. The results obtained are robust against simulated biological variation and background noise.

关键词： Primate temporal cortex computer-based model Neural networks Visual-cortex Realistic simulations Neuronal correlate Dendritic spines Cortical-neurons Firing rates Term-memory FIRING RATE Attractor Neural network computer based modeling cell activity ignition sequence Network Dendritic Spines realistic simulation Visual Cortex

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Nonlinear dynamics of ice-wedge networks and resulting sensitivity to severe cooling events

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NATURE 2002年第6892期417卷 929-933页

作者： Plug, LJ Werner, BT Univ Calif San Diego Cecil & Ida Green Inst Geophys & Planetary Phys Complex Syst Lab La Jolla CA 92093 USA

Patterns of subsurface wedges of ice that form along cooling-induced tension fractures, expressed at the ground surface by ridges or troughs spaced 10-30 m apart, are ubiquitous in polar lowlands(1). Fossilized ice wedges, which are widespread at lower latitudes, have been used to infer the duration(2-4) and mean temperature(5,6) of cold periods within Proterozoic(2) and Quaternary climates(3-13), and recent climate trends have been inferred from fracture frequency in active ice wedges(14). Here we present simulations from a numerical model for the evolution of ice-wedge networks over a range of climate scenarios, based on the interactions between thermal tensile stress, fracture and ice wedges. We find that short-lived periods of severe cooling permanently alter the spacing between ice wedges as well as their fracture frequency. This affects the rate at which the widths of ice wedges increase as well as the network's response to subsequent climate change. We conclude that wedge spacing and width in ice-wedge networks mainly reflect infrequent episodes of rapidly falling ground temperatures rather than mean conditions.

关键词： Ice Fossils Climate computer based modeling

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Three Rivers Water Filtration Plant: Architectural Beauty and Operations Optimization

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JOURNAL AMERICAN WATER WORKS ASSOCIATION 2015年第4期107卷 82-87页

作者： Yavich, Alex Shastri, Chet Zehr, Vicky Schipper, Andrew Wirtz, Matthew Optimizat Solut Environm LLC Grand Rapids MI 49506 USA Three Rivers Water Filtrat Plant Ft Wayne IN USA City Ft Wayne City Util Water Program Ft Wayne IN USA City Ft Wayne City Util Engn Ft Wayne IN USA

The Three Rivers Water Filtration Plant, which faces the challenge of extremely variable raw water conditions, combines operational effectiveness with architectural beauty. The plant's history includes several physical additions and an innovative, multiyear process-improvement project that included implementing computer modeling for the management and optimization of its entire treatment operation.

关键词： Rivers Water filtration Water treatment plants computer based modeling Project management Optimization

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