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1

Computer simulation models : applications to the study of ecological systems  

Microsoft Academic Search

Tho role of state-space and feedback concepts in the dovolopmont of simulation models for ecological systems is discussedThe modelling process as applied to ecology is illustrated by the development of models for three ecological systems ; the growth of a single species limited by food supply, the competition between two species for a common food supply and a predator–prey relationship.

LLOYD E. PEPPARD

1975-01-01

2

Ecological Modelling 193 (2006) 271294 A simulation model of sustainability of coastal communities  

E-print Network

Ecological Modelling 193 (2006) 271­294 A simulation model of sustainability of coastal communities. / Ecological Modelling 193 (2006) 271­294 Fig. 1. Total aquaculture production (EU + EFTA) (FAO Fish Stat). EU and played its part in satisfying an increasing consumer demand for marine fish (Fig. 1). It has been argued

Pierce, Graham

3

ERROR AND UNCERTAINTY ANALYSIS FOR ECOLOGICAL MODELING AND SIMULATION  

EPA Science Inventory

The main objectives of this project are a) to develop a general methodology for conducting sensitivity and uncertainty analysis and building error budgets in simulation modeling over space and time; and b) to apply that methodology to the assessment of soil erosion through the RU...

4

Ecological Modelling 177 (2004) 193208 Simulating the effects of wolf-elk population  

E-print Network

Ecological Modelling 177 (2004) 193­208 Simulating the effects of wolf-elk population dynamics,butitisunclearwhetherthisrepresentsatransientorpermanenteffectofwolfreintroduction.Herewepresent a wolf-elk model with human elk harvest and use it to investigate the long-term consequences of predator of carrion is shifted from reliance on winter severity and elk density to dependence on the strength of wolf

Wilmers, Chris

5

Simulation Models for Potato Late Blight Management and Ecology  

Microsoft Academic Search

Late blight of potato has been one of the most widely studied diseases and particular attention has been given to the mathematical\\u000a description of disease development. Several process based simulation models have been developed and this paper focuses primarily\\u000a on several versions developed at Cornell University, and later through collaboration between that University, the International\\u000a Potato Center and the Volcani

G. A. Forbes; W. E. Fry; J. L. Andrade-Piedra; D. Shtienberg

6

Simulating pesticides in ditches to assess ecological risk (SPIDER): I. Model description.  

PubMed

Risk assessment for pesticides in the aquatic environment relies on a comparison between estimated exposure concentrations in surface water bodies and endpoints from a series of effect tests. Many field- and catchment-scale models have been developed, ranging from simple empirical models to comprehensive, physically-based, distributed models that require complex parameterisation, often through inverse modelling methods. Routine use of catchment models for assessment and management of pesticides requires a tool that is comprehensive in being able to address all major routes of entry of pesticides into surface water and that has reasonable parameter requirements. Current models either focus primarily on transport of pesticides in surface runoff or are restricted in application because they require calibration against data from detailed monitoring programmes. SPIDER (Simulating Pesticides In Ditches to assess Ecological Risk) was developed to address the gap in models available to simulate pesticide exposure within networks of small surface water bodies (ditches and streams) in support of ecological risk assessment for pesticides. SPIDER is a locally distributed, capacitance-based model that accounts for pesticide entry into surface water bodies via spray drift, surface runoff, interlayer flow and drainflow and that can be used for small agricultural catchments. This paper provides a detailed description of the model. PMID:18275984

Renaud, Fabrice G; Bellamy, Pat H; Brown, Colin D

2008-05-01

7

A FUNCTIONAL DESCRIPTION OF THE ECOLOGICAL DYNAMICS SIMULATION (EDYS) MODEL, WITH APPLICATIONS FOR ARMY AND OTHER FEDERAL LAND MANAGERS  

EPA Science Inventory

A key component of this capability package is the Ecological Dynamics Simulation (EDYS) model. The model provides the capability to predict responses of training lands to both military and non-military stressors and facilitates linking the cost of training and testing land mainte...

8

Adding ecology to particle capture models: Numerical simulations of capture on a moving cylinder in crossflow.  

PubMed

The particle capture efficiency, ?, of systems that remove suspended particles from ambient flow (e.g. suspension feeding, abiotic pollination) has been studied using static collectors in steady flows. Particle deposition on collectors moving due to fluid flow remains largely unknown, despite its ecological relevance. We used numerical modeling to simulate particle deposition on a 2D circular cylinder subject to flow-induced oscillation in a cross flow. Using parameter values relevant to wind pollination and other natural biological systems, we examined the influence of the direction, amplitude and frequency of the oscillation, the Stokes number (Stk=0.01-5, characterizing particle behavior), as well as the Reynolds number (Re=662 and 3309, characterizing flow regime) in steady and unsteady flow, on ?. The numerical model was validated with empirical results for parts of the parameter space. Particle capture occurred via "inertial impaction", "direct interception" and "leeward deposition", as well as via a new mechanism, "collector chasing" for moving collectors. The ? of an oscillating cylinder varied significantly relative to a static cylinder, depending on the parameters used, and on the magnitude of a numerical error that caused loss of particles. This variance of ? was due to a change in relative momentum between the particle and the moving collector, which depends on Re, Stk and the oscillation parameters. Collector oscillation transverse to oncoming flow direction strongly increased ?, whereas collector motion parallel to flow had little effect on capture efficiency. The oscillation also changed leeward capture significantly in some cases. For most conditions, however, leeward deposition was small. Results suggest that collector motion could have significant influence on the particle capture efficiency of natural systems, which indicates the need to incorporate these ecologically more relevant findings into current models. Empirical studies, however, are still necessary to validate these results and provide reliable data. PMID:25496731

Krick, Julian; Ackerman, Josef Daniel

2015-03-01

9

The use of typed lambda calculus for comprehension and construction of simulation models in the domain of ecology  

NASA Technical Reports Server (NTRS)

We are concerned with two important issues in simulation modelling: model comprehension and model construction. Model comprehension is limited because many important choices taken during the modelling process are not documented. This makes it difficult for models to be modified or used by others. A key factor hindering model construction is the vast modelling search space which must be navigated. This is exacerbated by the fact that many modellers are unfamiliar with the terms and concepts catered to by current tools. The root of both problems is the lack of facilities for representing or reasoning about domain concepts in current simulation technology. The basis for our achievements in both of these areas is the development of a language with two distinct levels; one for representing domain information, and the other for representing the simulation model. Of equal importance, is the fact that we make formal connections between these two levels. The domain we are concerned with is ecological modelling. This language, called Elklogic, is based on the typed lambda calculus. Important features include a rich type structure, the use of various higher order functions, and semantics. This enables complex expressions to be constructed from relatively few primitives. The meaning of each expression can be determined in terms of the domain, the simulation model, or the relationship between the two. We describe a novel representation for sets and substructure, and a variety of other general concepts that are especially useful in the ecological domain. We use the type structure in a novel way: for controlling the modelling search space, rather than a proof search space. We facilitate model comprehension by representing modelling decisions that are embodied in the simulation model. We represent the simulation model separately from, but in terms of a domain mode. The explicit links between the two models constitute the modelling decisions. The semantics of Elklogic enables English text to be generated to explain the simulation model in domain terms.

Uschold, Michael

1992-01-01

10

Simulating pesticides in ditches to assess ecological risk (SPIDER): II. Benchmarking for the drainage model.  

PubMed

SPIDER (simulating pesticides in ditches to assess ecological risk) is a locally distributed, capacitance-based model that accounts for pesticide entry into surface water bodies via spray drift, surface runoff, interlayer flow and drainage. SPIDER was developed for application to small agricultural catchments. Transport of pesticide from site of application to surface water via subsurface field drains is one of the major routes of entry to surface water. Several pesticide fate models describe transfer of pesticide via drainflow, notably MACRO which has been evaluated against field data in several studies. The capacity of SPIDER to simulate drainflow and pesticide concentration in drain water was evaluated against two datasets that had been used previously to evaluate MACRO independently of this study: a plot experiment at Cockle Park and a field experiment at Maidwell, both located in the UK. In both circumstances, SPIDER was able to reproduce drain hydrographs relatively well with no or limited calibration. At Cockle Park, simulated and observed drainflow over the season were 240 and 278 mm, respectively with a Nash and Sutcliffe model efficiency (NSME) coefficient of 0.32 whilst at Maidwell they were 259 and 296 mm, respectively with a NSME coefficient of 0.55. Prediction of maximum isoproturon concentration at Cockle Park by SPIDER and MACRO were 5.3 and 13.1 microg L(- 1) respectively compared to the 3.8 microg L(- 1) measured in the field, whilst pesticide load to drains over the season were 0.22 and 1.53 g, respectively, compared to an observed load of 0.35 g. Maximum sulfosulfuron concentration at Maidwell were 2.3, 3.9 and 5.4 microg L(- 1) for observed and as simulated by SPIDER and MACRO, respectively and pesticide loading to drains of the season was 0.77, 5.61, 4.77 g, respectively. Results from the sensitivity analysis showed that the sensitivity of SPIDER compared favourably to that of several other capacity models but was more sensitive than MACRO to variations in input parameters. SPIDER is currently being tested at the catchment scale. PMID:18280538

Renaud, Fabrice G; Brown, Colin D

2008-05-01

11

A Simulated Stream Ecology Study.  

ERIC Educational Resources Information Center

Describes a simulated field experience to study stream ecology in the classroom. Secondary students determine the composition of the stream community, describe the distribution of the benthic invertebrates, and design a food web. (Author/MA)

Zampella, Robert A.

1979-01-01

12

Linking Bayesian and Agent-Based Models to Simulate Complex Social-Ecological Systems in the Sonoran Desert  

NASA Astrophysics Data System (ADS)

Interdependencies of ecologic, hydrologic, and social systems challenge traditional approaches to natural resource management in semi-arid regions. As a complex social-ecological system, water demands in the Sonoran Desert from agricultural and urban users often conflicts with water needs for its ecologically-significant riparian corridors. To explore this system, we developed an agent-based model to simulate complex feedbacks between human decisions and environmental conditions. Cognitive mapping in conjunction with stakeholder participation produced a Bayesian model of conditional probabilities of local human decision-making processes resulting to changes in water demand. Probabilities created in the Bayesian model were incorporated into the agent-based model, so that each agent had a unique probability to make a positive decision based on its perceived environment at each point in time and space. By using a Bayesian approach, uncertainty in the human decision-making process could be incorporated. The spatially-explicit agent-based model simulated changes in depth-to-groundwater by well pumping based on an agent's water demand. Depth-to-groundwater was then used as an indicator of unique vegetation guilds within the riparian corridor. Each vegetation guild provides varying levels of ecosystem services, the changes of which, along with changes in depth-to-groundwater, feedback to influence agent behavior. Using this modeling approach allowed us to examine resilience of semi-arid riparian corridors and agent behavior under various scenarios. The insight provided by the model contributes to understanding how specific interventions may alter the complex social-ecological system in the future.

Pope, A.; Gimblett, R.

2013-12-01

13

Modelling the Geomorphological and Ecological Dynamics of River Corridors: Developing a Simulation Tool for River Management  

NASA Astrophysics Data System (ADS)

Interest in the integrated restoration of managed river corridors has arisen in response to falling levels of riparian and floodplain biodiversity due to flood control works including channalization and flow regulation by headwater impoundments. This decline is in part, a direct response to the impact of engineering works on the geomorphological dynamics of rivers and in particular, upon rates of channel migration. Channel instability, through the processes of bank erosion, avulsion and cutoff, and within and overbank sedimentation, continuously renews the floodplain creating virgin territory for plant colonization. The varying age of alluvial surfaces, in combination with differences in topography and sediment calibre influence plant succession pathways and gives rise to a mosaic of floodplain plant communities. This geomorphological influence underpins the `intermediate disturbance hypothesis' which suggests a non-linear relationship between floodplain turnover rates and biodiversity, which is low in both highly stable and unstable rivers regimes. In the former case, diversity is limited as stable regimes promote succession towards relatively uniform stands of floodplain forest while the in the later case, extreme instability results in the sole dominance of early coloniser species. By contrast, diversity is maximized for intermediate levels of disturbance, which result in a range of habitats at varying positions along successional pathways. While conceptually satisfying, calibration and validation of this perceptual model is confounded by the differing local conditions and environmental history of individual rivers, which complicates simple empirical inter-comparisons. Prescription of the appropriate levels of disturbance necessary to optimise habitat and biological diversity therefore remains unclear and difficult to translate into practical frameworks for river management. This paper presents an alternative approach to investigate this interdependence through the development of a numerical model which captures the primary geomorphological and ecological dynamics of river systems at appropriate levels of complexity tuned to reach and decadal space and time scales. Here a prototype model is presented for braided rivers, in which a simplified flow routing procedure is used to drive predictions of sediment transport and sorting based on a cellular spatial discretization, a force-balance entrainment model and a step-length advection and grain sorting procedure. This sub-model provides the topographic and sedimentological boundary conditions for a stochastic plant succession model which simulates colonization and community development on the evolving braidplain. The model is parameterised and validated against distributed datasets from the braided River Feshie, Scotland. A Monte-Carlo based sensitivity analysis is used to explore the one-way interaction between channel migration and habitat development, with an emphasis placed on the structure of the evolving timeseries of reach-scale biodiversity indicators. Importantly however, the framework also permits full coupling of this interrelationship by modelling the influence of vegetation on bank stability so that feedback can occur to affect channel migration and floodplain turnover. Such feedback is critical in understanding the autogenic switching between channel planform types (meandering and braiding) and a new computational framework for simulating this behaviour is presented.

Brasington, J.; Richards, K.; Bithell, M.

2002-12-01

14

Simulated ecology-driven sympatric speciation  

NASA Astrophysics Data System (ADS)

We introduce a multilocus genetically acquired phenotype, submitted to mutations and with selective value, in an age-structured model for biological aging. This phenotype describes a single-trait effect of the environment on an individual, and we study the resulting distribution of this trait among the population. In particular, our simulations show that the appearance of a double phenotypic attractor in the ecology induces the emergence of a stable polymorphism, as observed in the Galapagos finches. In the presence of this polymorphism, the simulations generate short-term speciation, when mating preferences are also allowed to suffer mutations and acquire selective value.

Sá Martins, J. S.; Moss de Oliveira, S.; de Medeiros, G. A.

2001-08-01

15

Simulating fire-induced ecological succession with the dynamically coupled fire-vegetation model, ED-SPIFTIRE  

NASA Astrophysics Data System (ADS)

The simulation of fire-vegetation feedbacks is crucial for determining fire-induced changes to ecosystem structure and function, and emissions of trace gases and aerosols under future climate change. A new global fire model SPITFIRE (SPread and InTensity of FIRE) has been designed to overcome many of the limitations in existing fire models set within DGVM frameworks (Thonicke et al. 2008). SPITFIRE has been applied in coupled mode globally (Thonicke et al. 2008) and northern Australia (Spessa et al. unpubl.) as part of the LPJ DGVM. It has also been driven with MODIS burnt area data applied to sub-Saharan Africa (Lehsten et al. 2008) as part of the LPJ-GUESS vegetation model (Smith et al. 2001). Recently, Spessa & Fisher (unpubl.) completed the coupling of SPIFTIRE to the Ecosystem Demography (ED) model (Moorecroft et al. 2001), which has been globalised by Dr R. Fisher as part of the development of the new land surface scheme JULES (Joint UK Environment Simulator) within the QUEST Earth System Model (http://www.quest-esm.ac.uk/). In contrast to the LPJ DGVM, ED is a ‘size and age structured' approximation of an individual based gap model. The major innovation of the ED-SPITFIRE model compared with LPJ-SPITFIRE is the categorisation of each climatic grid cell into a series of non-spatially contiguous patches which are defined by a common ‘age since last disturbance'. In theory, the age-class structure of ED facilitates ecologically realistic processes of succession and re-growth to be represented. By contrast, LPJ DGVM adopts an ‘area-based approach' that implicitly averages individual and patch differences across a wider area and across ‘populations' of PFTs. This presentation provides an overview of SPITFIRE, and provides preliminary results from ED-SPITFIRE applied to northern Australian savanna ecosystems which, due to spatio-temporal variation in fire disturbance, comprise a patchwork of grasses and trees at different stages of post-fire succession. Comparisons with similar simulations undertaken with LPJ-SPITFIRE are also presented.

Spessa, A.; Fisher, R.

2009-04-01

16

Fire-BGC: A mechanistic ecological process model for simulating fire succession on coniferous forest landscapes of the northern Rocky Mountains. Forest Service research paper  

SciTech Connect

An ecological process model of vegetation dynamics mechanistically simulates long-term stand dynamics on coniferous landscapes of the Northern Rocky Mountains. This model is used to investigate and evaluate cumulative effects of various fire regimes, including prescribed burning and fire exclusion, on the vegetation and fuel complex of a simulation landscape composed of many stands. Detailed documentation of the model FIRE-BGC (a FIRE BioGeoChemical succession model) with complete discussion of all model parameters is followed with results of an application of the FIRE-BGC to a whitebark pine landscape in the Bob Marshall Wilderness Complex. Simulation results of several management scenarios are contrasted to predict the fate of whitebark pine over 200 years. Model testing reveals predictions within 10 to 30 percent of observed values.

Keane, R.E.; Morgan, P.; Running, S.W.

1996-03-01

17

Modeling & Simulation  

NSDL National Science Digital Library

Modeling & Simulation is a journal published by The Society for Modeling and Simulation International. The Society has made its 2004 Modeling and Simulation Resource Guide available free to download. The directory provides descriptions and contact information for the many modeling and simulation software packages currently available, as well as listings for various modeling and simulation organizations worldwide. Two guest articles describe techniques for the application of real-time simulation in simulations that are complex. Previously published articles are also posted in the online archive.

18

Long-term impacts of selective logging on two Amazonian tree species with contrasting ecological and reproductive characteristics: inferences from Eco-gene model simulations.  

PubMed

The impact of logging and subsequent recovery after logging is predicted to vary depending on specific life history traits of the logged species. The Eco-gene simulation model was used to evaluate the long-term impacts of selective logging over 300 years on two contrasting Brazilian Amazon tree species, Dipteryx odorata and Jacaranda copaia. D. odorata (Leguminosae), a slow growing climax tree, occurs at very low densities, whereas J. copaia (Bignoniaceae) is a fast growing pioneer tree that occurs at high densities. Microsatellite multilocus genotypes of the pre-logging populations were used as data inputs for the Eco-gene model and post-logging genetic data was used to verify the output from the simulations. Overall, under current Brazilian forest management regulations, there were neither short nor long-term impacts on J. copaia. By contrast, D. odorata cannot be sustainably logged under current regulations, a sustainable scenario was achieved by increasing the minimum cutting diameter at breast height from 50 to 100?cm over 30-year logging cycles. Genetic parameters were only slightly affected by selective logging, with reductions in the numbers of alleles and single genotypes. In the short term, the loss of alleles seen in J. copaia simulations was the same as in real data, whereas fewer alleles were lost in D. odorata simulations than in the field. The different impacts and periods of recovery for each species support the idea that ecological and genetic information are essential at species, ecological guild or reproductive group levels to help derive sustainable management scenarios for tropical forests.Heredity advance online publication, 15 January 2014; doi:10.1038/hdy.2013.146. PMID:24424164

Vinson, C C; Kanashiro, M; Sebbenn, A M; Williams, T Cr; Harris, S A; Boshier, D H

2014-01-15

19

Simulating fire-induced ecological succession with the dynamically coupled fire-vegetation model, ED-SPIFTIRE  

Microsoft Academic Search

The simulation of fire-vegetation feedbacks is crucial for determining fire-induced changes to ecosystem structure and function, and emissions of trace gases and aerosols under future climate change. A new global fire model SPITFIRE (SPread and InTensity of FIRE) has been designed to overcome many of the limitations in existing fire models set within DGVM frameworks (Thonicke et al. 2008). SPITFIRE

A. Spessa; R. Fisher

2009-01-01

20

Register of Ecological Models, The (REM)  

NSDL National Science Digital Library

The Register of Ecological models is a a meta-database for existing mathematical models in ecology. It is a cooperative service of the University of Kassel and the GSF - National research center for Environment and Health

21

QUALITATIVE ECOLOGICAL MODELING  

Technology Transfer Automated Retrieval System (TEKTRAN)

Students construct qualitative models of an ecosystem and use the models to evaluate the direct and indirect effects that may result from perturbations to the ecosystem. Qualitative modeling is described for use in two procedures, each with different educational goals and student backgrounds in min...

22

Ecologic simulation of warm water aquaculture ponds  

SciTech Connect

A generalized ecologic model of a fertilized warm-water aquaculture pond is under development. The model is intended to represent the pond ecosystem and its response to external stimuli. The major physical, chemical and biological processes and parameters are included in the model. A total of 19 state variables are included in the model (dissolved oxygen, alkalinity, pH, ammonia, phytoplankton, etc.). The model is formulated as a system of mass balance equations. The equations include stimulatory and inhibitory effects of environmental parameters on processes taking place in the pond. The equations may be solved for the entire growth period and diurnal as well as seasonal fluctuations may be identified. The ultimate objective of the model is to predict the fish biomass that can be produced in a pond under a given set of environmental conditions.

Piedrahitu, R.H.; Brune, D.E.; Orlob, G.T.; Tchobanoglous, G.

1983-06-01

23

Spatial uncertainty and ecological models  

SciTech Connect

Applied ecological models that are used to understand and manage natural systems often rely on spatial data as input. Spatial uncertainty in these data can propagate into model predictions. Uncertainty analysis, sensitivity analysis, error analysis, error budget analysis, spatial decision analysis, and hypothesis testing using neutral models are all techniques designed to explore the relationship between variation in model inputs and variation in model predictions. Although similar methods can be used to answer them, these approaches address different questions. These approaches differ in (a) whether the focus is forward or backward (forward to evaluate the magnitude of variation in model predictions propagated or backward to rank input parameters by their influence); (b) whether the question involves model robustness to large variations in spatial pattern or to small deviations from a reference map; and (c) whether processes that generate input uncertainty (for example, cartographic error) are of interest. In this commentary, we propose a taxonomy of approaches, all of which clarify the relationship between spatial uncertainty and the predictions of ecological models. We describe existing techniques and indicate a few areas where research is needed.

Jager, Yetta [ORNL; King, Anthony Wayne [ORNL

2004-07-01

24

CollageMachine: Model of ``Interface Ecology''  

E-print Network

CollageMachine: Model of ``Interface Ecology'' By Andruid Kerne dissertation submitted partial addresses browsing creatively, been co­developed with the metadisciplinary framework interface ecology, in addition inside them, open process without definite bounds. a metadiscipline, interface ecology brings

Mohri, Mehryar

25

An ecological economic simulation model of a non-selective grazing system in the Nama Karoo, South Africa  

Microsoft Academic Search

The Nama Karoo region of South Africa is characterized by low (?200 mm) and variable annual rainfall, which results in grass and shrub biomass production, which is low and highly variable in space and time. These characteristics of Nama Karoo rangelands challenge the ability of the region's livestock farmers to make a sustainable living. In this paper we model a

P. C. Beukes; R. M. Cowling; S. I. Higgins

2002-01-01

26

A dynamic ecological–economic modeling approach for aquaculture management  

Microsoft Academic Search

This paper presents a Modeling Approach to Resource economics decision-maKing in EcoaquaculTure (MARKET model). The MARKET model was developed as a scenario-testing tool to provide insights on the ecological and economic interactions, which is a critical issue for sustainable aquaculture management. As a case study, the model was applied to simulate shellfish production in an embayment located in the East

A. M. Nobre; J. K. Musango; M. P. de Wit; J. G. Ferreira

2009-01-01

27

Ecological Impacts of the Cerro Grande Fire: Predicting Elk Movement and Distribution Patterns in Response to Vegetative Recovery through Simulation Modeling October 2005  

SciTech Connect

In May 2000, the Cerro Grande Fire burned approximately 17,200 ha in north-central New Mexico as the result of an escaped prescribed burn initiated by Bandelier National Monument. The interaction of large-scale fires, vegetation, and elk is an important management issue, but few studies have addressed the ecological implications of vegetative succession and landscape heterogeneity on ungulate populations following large-scale disturbance events. Primary objectives of this research were to identify elk movement pathways on local and landscape scales, to determine environmental factors that influence elk movement, and to evaluate movement and distribution patterns in relation to spatial and temporal aspects of the Cerro Grande Fire. Data collection and assimilation reflect the collaborative efforts of National Park Service, U.S. Forest Service, and Department of Energy (Los Alamos National Laboratory) personnel. Geographic positioning system (GPS) collars were used to track 54 elk over a period of 3+ years and locational data were incorporated into a multi-layered geographic information system (GIS) for analysis. Preliminary tests of GPS collar accuracy indicated a strong effect of 2D fixes on position acquisition rates (PARs) depending on time of day and season of year. Slope, aspect, elevation, and land cover type affected dilution of precision (DOP) values for both 2D and 3D fixes, although significant relationships varied from positive to negative making it difficult to delineate the mechanism behind significant responses. Two-dimensional fixes accounted for 34% of all successfully acquired locations and may affect results in which those data were used. Overall position acquisition rate was 93.3% and mean DOP values were consistently in the range of 4.0 to 6.0 leading to the conclusion collar accuracy was acceptable for modeling purposes. SAVANNA, a spatially explicit, process-oriented ecosystem model, was used to simulate successional dynamics. Inputs to the SAVANNA included a land cover map, long-term weather data, soil maps, and a digital elevation model. Parameterization and calibration were conducted using field plots. Model predictions of herbaceous biomass production and weather were consistent with available data and spatial interpolations of snow were considered reasonable for this study. Dynamic outputs generated by SAVANNA were integrated with static variables, movement rules, and parameters developed for the individual-based model through the application of a habitat suitability index. Model validation indicated reasonable model fit when compared to an independent test set. The finished model was applied to 2 realistic management scenarios for the Jemez Mountains and management implications were discussed. Ongoing validation of the individual-based model presented in this dissertation provides an adaptive management tool that integrates interdisciplinary experience and scientific information, which allows users to make predictions about the impact of alternative management policies.

S.P. Rupp

2005-10-01

28

Simulating evolutionary responses of an introgressed insect resistance trait for ecological effect assessment of transgene flow: a model for supporting informed decision-making in environmental risk assessment  

PubMed Central

Predicting outcomes of transgene flow from arable crops requires a system perspective that considers ecological and evolutionary processes within a landscape context. In Europe, the arable weed Raphanus raphanistrum is a potential hybridization partner of oilseed rape, and the two species are ecologically linked through the common herbivores Meligethes spp. Observations in Switzerland show that high densities of Meligethes beetles maintained by oilseed rape crops can lead to considerable damage on R. raphanistrum. We asked how increased insect resistance in R. raphanistrum – as might be acquired through introgression from transgenic oilseed rape – would affect seed production under natural herbivore pressure. In simulation experiments, plants protected against Meligethes beetles produced about twice as many seeds as unprotected plants. All stages in the development of reproductive structures from buds to pods were negatively affected by the herbivore, with the transition from buds to flowers being the most vulnerable. We conclude that resistance to Meligethes beetles could confer a considerable selective advantage upon R. raphanistrum in regions where oilseed rape is widely grown. PMID:23467842

Meier, Matthias S; Trtikova, Miluse; Suter, Matthias; Edwards, Peter J; Hilbeck, Angelika

2013-01-01

29

WASP TRANSPORT MODELING AND WASP ECOLOGICAL MODELING  

EPA Science Inventory

A combination of lectures, demonstrations, and hands-on excercises will be used to introduce pollutant transport modeling with the U.S. EPA's general water quality model, WASP (Water Quality Analysis Simulation Program). WASP features include a user-friendly Windows-based interfa...

30

Spatial Uncertainty Analysis of Ecological Models  

SciTech Connect

The authors evaluated the sensitivity of a habitat model and a source-sink population model to spatial uncertainty in landscapes with different statistical properties and for hypothetical species with different habitat requirements. Sequential indicator simulation generated alternative landscapes from a source map. Their results showed that spatial uncertainty was highest for landscapes in which suitable habitat was rare and spatially uncorrelated. Although, they were able to exert some control over the degree of spatial uncertainty by varying the sampling density drawn from the source map, intrinsic spatial properties (i.e., average frequency and degree of spatial autocorrelation) played a dominant role in determining variation among realized maps. To evaluate the ecological significance of landscape variation, they compared the variation in predictions from a simple habitat model to variation among landscapes for three species types. Spatial uncertainty in predictions of the amount of source habitat depended on both the spatial life history characteristics of the species and the statistical attributes of the synthetic landscapes. Species differences were greatest when the landscape contained a high proportion of suitable habitat. The predicted amount of source habitat was greater for edge-dependent (interior) species in landscapes with spatially uncorrelated(correlated) suitable habitat. A source-sink model demonstrated that, although variation among landscapes resulted in relatively little variation in overall population growth rate, this spatial uncertainty was sufficient in some situations, to produce qualitatively different predictions about population viability (i.e., population decline vs. increase).

Jager, H.I.; Ashwood, T.L.; Jackson, B.L.; King, A.W.

2000-09-02

31

Jan 16 Conceptual models of ecological systems Why is Integration Needed in Ecology?  

E-print Network

Jan 16 Conceptual models of ecological systems #12;Why is Integration Needed in Ecology? Great advances have been made by dividing ecology into subdisciplines. But too much focus on subdisciplines has also hindered ecology · too little study of the interface between disciplines · tended to narrow focus

Hansen, Andrew J.

32

An Interdisciplinary Model for Teaching Evolutionary Ecology.  

ERIC Educational Resources Information Center

Describes a general systems evolutionary model and demonstrates how a previously established ecological model is a function of its past development based on the evolution of the rock, nutrient, and water cycles. Discusses the applications of the model in environmental education. (MDH)

Coletta, John

1992-01-01

33

Predictive habitat distribution models in ecology  

Microsoft Academic Search

With the rise of new powerful statistical techniques and GIS tools, the development of predictive habitat distribution models has rapidly increased in ecology. Such models are static and probabilistic in nature, since they statistically relate the geographical distribution of species or communities to their present environment. A wide array of models has been developed to cover aspects as diverse as

Antoine Guisan; Niklaus E. Zimmermann

2000-01-01

34

Exploring the Realized Niche: Simulated Ecological Mapping with a Microcomputer.  

ERIC Educational Resources Information Center

Describes a computer program based upon field observations of littoral zonation modified by a small stream. The program employs user-defined color graphic characters to display simulated ecological maps representing the patterning of organisms in response to local values of niche limiting factors. (Author/JN)

Kent, J. W.

1983-01-01

35

Ecological Modelling xxx (2005) xxxxxx Modelling carbon and water cycles in a beech forest  

E-print Network

Ecological Modelling xxx (2005) xxx­xxx Modelling carbon and water cycles in a beech forest Part II A forest ecosystem model (CASTANEA) simulating the carbon balance (canopy photosynthesis, autotrophic and heterotrophic respirations, net ecosystem exchange, wood and root growth) and the water cycle (transpiration

Boyer, Edmond

36

A Global Lake Ecological Observatory Network (GLEON) for synthesising high-frequency sensor data for validation of deterministic ecological models  

USGS Publications Warehouse

A Global Lake Ecological Observatory Network (GLEON; www.gleon.org) has formed to provide a coordinated response to the need for scientific understanding of lake processes, utilising technological advances available from autonomous sensors. The organisation embraces a grassroots approach to engage researchers from varying disciplines, sites spanning geographic and ecological gradients, and novel sensor and cyberinfrastructure to synthesise high-frequency lake data at scales ranging from local to global. The high-frequency data provide a platform to rigorously validate process- based ecological models because model simulation time steps are better aligned with sensor measurements than with lower-frequency, manual samples. Two case studies from Trout Bog, Wisconsin, USA, and Lake Rotoehu, North Island, New Zealand, are presented to demonstrate that in the past, ecological model outputs (e.g., temperature, chlorophyll) have been relatively poorly validated based on a limited number of directly comparable measurements, both in time and space. The case studies demonstrate some of the difficulties of mapping sensor measurements directly to model state variable outputs as well as the opportunities to use deviations between sensor measurements and model simulations to better inform process understanding. Well-validated ecological models provide a mechanism to extrapolate high-frequency sensor data in space and time, thereby potentially creating a fully 3-dimensional simulation of key variables of interest.

David, Hamilton P; Carey, Cayelan C; Arvola, Lauri; Arzberger, Peter; Brewer, Carol A.; Cole, Jon J; Gaiser, Evelyn; Hanson, Paul C.; Ibelings, Bas W; Jennings, Eleanor; Kratz, Tim K; Lin, Fang-Pang; McBride, Christopher G; de Motta Marques, David; Muraoka, Kohji; Nishri, Ami; Qin, Boqiang; Read, Jordan S.; Rose, Kevin C.; Ryder, Elizabeth; Weathers, Kathleen C.; Zhu, Guangwei; Trolle, Dennis; Brookes, Justin D

2014-01-01

37

Simulating the effects of fire and climate change on northern Rocky Mountain landscapes using the ecological process model FIRE-BGC  

SciTech Connect

A mechanistic successional model, FIRE-BGC (a FIRE BioGeoChemical succession model), has been developed to investigate the role of fire and climate on long-term landscape dynamics in northern Rocky Mountain coniferous forests. This FIRE-BGC application explicitly simulates fire behavior and effects on landscape characteristics. Predictions of evapotranspiration are contrasted with and without fire over 200 years of simulation for the McDonald Drainage, Glacier National Park under current climate conditions are provided as an example of the potential of FIRE-BGC.

Keane, R.E.; Ryan, K. [Intermountain Fire Sciences Lab., Missoula, MT (United States); Running, S.W. [Univ. of Montana, Missoula, MT (United States). School of Forestry

1995-12-31

38

OVERVIEW OF CLIMATE INFORMATION NEEDS FOR ECOLOGICAL EFFECTS MODELS  

EPA Science Inventory

Atmospheric scientists engaged in climate change research require a basic understanding of how ecological effects models incorporate climate. This report provides an overview of existing ecological models that might be used to model climate change effects on vegetation. ome agric...

39

Model selection in ecology and evolution  

Microsoft Academic Search

Recently, researchers in several areas of ecology and evolution have begun to change the way in which they analyze data and make biological inferences. Rather than the traditional null hypothesis testing approach, they have adopted an approach called model selection, in which several competing hypotheses are simultaneously confronted with data. Model selection can be used to identify a single best

Jerald B. Johnson; Kristian S. Omland

2004-01-01

40

Simulating Ecological Complexity Using the Example of Pesticides in Ecosystems.  

ERIC Educational Resources Information Center

Describes a simulation exercise developed for an introductory biology course for nonmajors. The simulation focuses on the control of western spruce budworms in forests of the western United States. A nonlinear, multivariate simulation model is used. (PR)

Muir, Patricia S.; McCune, Bruce

1993-01-01

41

Social Ecological Model of Multilevel Influences on Diet  

Cancer.gov

Social Ecological Model of Multilevel Influences on Diet Social ecological model of multilevel influences on diet: A graphic depicting concentric spheres, with the innermost sphere representing the Individual level and text labels corresponding to key

42

Applications of Individual-Based Modelling in Microbial Ecology  

E-print Network

Individual-based modelling (IbM) allows description of differences between individuals in a spatially heterogeneous environment - the typical case in microbial ecology. We present the prototype of the first spatially explicit individual-based model of bacterial growth. The simulation reproduced the desired bacterial growth properties correctly. In order to describe the dependence of cell size on growth rate at the single cell level, we implemented a mechanistic version of Donachie's conceptual model of cell division. Surprisingly, it appeared incomplete and had to be replaced by a descriptive version. Random variation of cellular parameters as well as spatial heterogeneity of substrate concentration each led to a complete loss of synchrony of the simulated culture. We propose new measures for growth synchrony and spatial heterogeneity. The model prototype shows the feasibility of this novel approach. It will be extended to become a generic tool for simulating all aspects of microbial g...

Bell Cr; Brylinsky M; Johnson-green P (eds; J. -u. Kreft; G. Booth; J. W. T. Wimpenny

2000-01-01

43

Big questions, small worlds: microbial model systems in ecology  

E-print Network

Big questions, small worlds: microbial model systems in ecology Christine M. Jessup1 , Rees Kassen2, the explicit use of microbial com- munities as model systems in ecology has traditionally been more restricted. It is the simpli- city of microbial model systems that makes them such powerful tools for the study of ecology

Buckling, Angus

44

Implicit assimilation for marine ecological models  

NASA Astrophysics Data System (ADS)

We use a new data assimilation method to estimate the parameters of a marine ecological model. At a given point in the ocean, the estimated values of the parameters determine the behaviors of the modeled planktonic groups, and thus indicate which species are dominant. To begin, we assimilate in situ observations, e.g., the Bermuda Atlantic Time-series Study, the Hawaii Ocean Time-series, and Ocean Weather Station Papa. From there, we estimate the parameters at surrounding points in space based on satellite observations of ocean color. Given the variation of the estimated parameters, we divide the ocean into regions meant to represent distinct ecosystems. An important feature of the data assimilation approach is that it refines the confidence limits of the optimal Gaussian approximation to the distribution of the parameters. This enables us to determine the ecological divisions with greater accuracy.

Weir, B.; Miller, R.; Spitz, Y. H.

2012-12-01

45

Spatially-Explicit Simulation Modeling of Ecological Response to Climate Change: Methodological Considerations in Predicting Shifting Population Dynamics of Infectious Disease Vectors  

PubMed Central

Poikilothermic disease vectors can respond to altered climates through spatial changes in both population size and phenology. Quantitative descriptors to characterize, analyze and visualize these dynamic responses are lacking, particularly across large spatial domains. In order to demonstrate the value of a spatially explicit, dynamic modeling approach, we assessed spatial changes in the population dynamics of Ixodes scapularis, the Lyme disease vector, using a temperature-forced population model simulated across a grid of 4 × 4 km cells covering the eastern United States, using both modeled (Weather Research and Forecasting (WRF) 3.2.1) baseline/current (2001–2004) and projected (Representative Concentration Pathway (RCP) 4.5 and RCP 8.5; 2057–2059) climate data. Ten dynamic population features (DPFs) were derived from simulated populations and analyzed spatially to characterize the regional population response to current and future climate across the domain. Each DPF under the current climate was assessed for its ability to discriminate observed Lyme disease risk and known vector presence/absence, using data from the US Centers for Disease Control and Prevention. Peak vector population and month of peak vector population were the DPFs that performed best as predictors of current Lyme disease risk. When examined under baseline and projected climate scenarios, the spatial and temporal distributions of DPFs shift and the seasonal cycle of key questing life stages is compressed under some scenarios. Our results demonstrate the utility of spatial characterization, analysis and visualization of dynamic population responses—including altered phenology—of disease vectors to altered climate. PMID:24772388

Dhingra, Radhika; Jimenez, Violeta; Chang, Howard H.; Gambhir, Manoj; Fu, Joshua S.; Liu, Yang; Remais, Justin V.

2014-01-01

46

Spatially-Explicit Simulation Modeling of Ecological Response to Climate Change: Methodological Considerations in Predicting Shifting Population Dynamics of Infectious Disease Vectors.  

PubMed

Poikilothermic disease vectors can respond to altered climates through spatial changes in both population size and phenology. Quantitative descriptors to characterize, analyze and visualize these dynamic responses are lacking, particularly across large spatial domains. In order to demonstrate the value of a spatially explicit, dynamic modeling approach, we assessed spatial changes in the population dynamics of Ixodes scapularis, the Lyme disease vector, using a temperature-forced population model simulated across a grid of 4 × 4 km cells covering the eastern United States, using both modeled (Weather Research and Forecasting (WRF) 3.2.1) baseline/current (2001-2004) and projected (Representative Concentration Pathway (RCP) 4.5 and RCP 8.5; 2057-2059) climate data. Ten dynamic population features (DPFs) were derived from simulated populations and analyzed spatially to characterize the regional population response to current and future climate across the domain. Each DPF under the current climate was assessed for its ability to discriminate observed Lyme disease risk and known vector presence/absence, using data from the US Centers for Disease Control and Prevention. Peak vector population and month of peak vector population were the DPFs that performed best as predictors of current Lyme disease risk. When examined under baseline and projected climate scenarios, the spatial and temporal distributions of DPFs shift and the seasonal cycle of key questing life stages is compressed under some scenarios. Our results demonstrate the utility of spatial characterization, analysis and visualization of dynamic population responses-including altered phenology-of disease vectors to altered climate. PMID:24772388

Dhingra, Radhika; Jimenez, Violeta; Chang, Howard H; Gambhir, Manoj; Fu, Joshua S; Liu, Yang; Remais, Justin V

2013-09-01

47

Aviation Safety Simulation Model  

NASA Technical Reports Server (NTRS)

The Aviation Safety Simulation Model is a software tool that enables users to configure a terrain, a flight path, and an aircraft and simulate the aircraft's flight along the path. The simulation monitors the aircraft's proximity to terrain obstructions, and reports when the aircraft violates accepted minimum distances from an obstruction. This model design facilitates future enhancements to address other flight safety issues, particularly air and runway traffic scenarios. This report shows the user how to build a simulation scenario and run it. It also explains the model's output.

Houser, Scott; Yackovetsky, Robert (Technical Monitor)

2001-01-01

48

An Ecological Model for Premature Infant Feeding  

PubMed Central

Premature infants are at increased risk for poor health, feeding difficulties, and impaired mother-infant interaction leading to developmental delay. Social-environmental risks, such as poverty or minority status, compound these biologic risks, placing premature infants in double jeopardy. Guided by an ecological model, the Hospital-Home Transition: Optimizing Prematures’ Environment (H-HOPE) intervention combines the Auditory, Tactile, Visual, and Vestibular intervention with participatory guidance provided by a nurse and community advocate to address the impact of multiple risk factors on premature infants’ development. PMID:19614884

White-Traut, Rosemary; Norr, Kathleen

2013-01-01

49

Turing Machine as an ecological model for Task Analysis  

E-print Network

1 Turing Machine as an ecological model for Task Analysis Thierry Morineau, Emmanuel Frénod.morineau@univ-ubs.fr #12;2 Abstract: We present a new model for task analysis based on the ecological approach initiated by Cognitive Work Analysis (CWA). This model aims to improve the implementation of the theoretical principles

Frénod, Emmanuel

50

Theory Modeling and Simulation  

SciTech Connect

Los Alamos has a long history in theory, modeling and simulation. We focus on multidisciplinary teams that tackle complex problems. Theory, modeling and simulation are tools to solve problems just like an NMR spectrometer, a gas chromatograph or an electron microscope. Problems should be used to define the theoretical tools needed and not the other way around. Best results occur when theory and experiments are working together in a team.

Shlachter, Jack [Los Alamos National Laboratory

2012-08-23

51

The Centre for Statistics at Goettingen University, Germany, is inviting applications for 1 PhD Position in Ecological Modelling  

E-print Network

, Forest Inventory and Remote Sensing, Genetic Epidemiology, Mathematical Stochastics, Statistics with skills/ knowledge in simulation modelling, statistics, and ecological concepts. Very good knowledgeThe Centre for Statistics at Goettingen University, Germany, is inviting applications for 1 Ph

Munk, Axel

52

Ecological Modelling 149 (2002) 297311 Risk assessment of the harvested pike-perch population of  

E-print Network

resulting from different harvesting strategies (i.e. combinations of harvesting efforts on yearlingsEcological Modelling 149 (2002) 297­311 Risk assessment of the harvested pike-perch population by the consideration of optimal harvesting. The problem is therefore multicriteria. A stochastic simulation model

Jost, Christian

53

AGRICULTURAL SIMULATION MODEL (AGSIM)  

EPA Science Inventory

AGSIM is a large-scale econometric simulation model of regional crop and national livestock production in the United States. The model was initially developed to analyze the aggregate economic impacts of a wide variety issues facing agriculture, such as technological change, pest...

54

AN INTRODUCTION TO THE PRACTICE OF ECOLOGICAL MODELING  

EPA Science Inventory

No abstract. Modeling has become an important tool in the study of ecological systems, as a scan of the table of contents of any major ecological journal makes abundently clear. The development of a conceptual model can be an integral part of designing and carrying out any resear...

55

Ecological Niche Modeling of Bacillus anthracis on Three Continents: Evidence for Genetic-Ecological Divergence?  

PubMed Central

We modeled the ecological niche of a globally successful Bacillus anthracis sublineage in the United States, Italy and Kazakhstan to better understand the geographic distribution of anthrax and potential associations between regional populations and ecology. Country-specific ecological-niche models were developed and reciprocally transferred to the other countries to determine if pathogen presence could be accurately predicted on novel landscapes. Native models accurately predicted endemic areas within each country, but transferred models failed to predict known occurrences in the outside countries. While the effects of variable selection and limitations of the genetic data should be considered, results suggest differing ecological associations for the B. anthracis populations within each country and may reflect niche specialization within the sublineage. Our findings provide guidance for developing accurate ecological niche models for this pathogen; models should be developed regionally, on the native landscape, and with consideration to population genetics. Further genomic analysis will improve our understanding of the genetic-ecological dynamics of B. anthracis across these countries and may lead to more refined predictive models for surveillance and proactive vaccination programs. Further studies should evaluate the impact of variable selection of native and transferred models. PMID:23977300

Mullins, Jocelyn C.; Garofolo, Giuliano; Van Ert, Matthew; Fasanella, Antonio; Lukhnova, Larisa; Hugh-Jones, Martin E.; Blackburn, Jason K.

2013-01-01

56

The Evolutionary Ecology of Model Microbial Communities William Russell Harcombe, B.S.  

E-print Network

The Evolutionary Ecology of Model Microbial Communities by William Russell Harcombe, B version of the following dissertation: The Evolutionary Ecology of Model Microbial Communities Committee their advice. #12;iv The Evolutionary Ecology of Model Microbial Communities William Russell Harcombe, Ph

Hillis, David

57

Equilibrium and nonequilibrium concepts in ecological models  

SciTech Connect

Mathematical models and empirical studies have revealed two potentially disruptive influences on ecosystems; (1) instabilities caused by nonlinear feedbacks and time-lags in the interactions of biological species, and (2) stochastic forcings by a fluctuating environment. Because both of these phenomena can severely affect system survival, ecologists are confronted with the question of why complex ecosystems do, in fact, exist. The authors study analyzes the basic theme of this research and identifies five general hypotheses that, in recent years, theoretical ecologists have built into models to increase their stability against disruptive feedback and stochasticity. To counter feedback instabilities, theoreticians have considered (1) functional interactions between species that act as stabilizers, (2) disturbance patterns that interrupt adverse feedback effects, and (3) the stabilizing effect of integrating small-spatial-scale systems into large landscapes. To decrease the influence of stochasticity, modelers have hypothesized (4) compensatory mechanisms operating at low population densities, and (5) the moderating effect of spatial extent and heterogeneity. They show that modeling based on these ideas can be organized in a systematic way. They also show that the stable equilibrium state should not be viewed as a fundamental property of ecological systems, but as a property that can emerge asymptotically from extrapolation to sufficiently large spatial scales.

DeAngelis, D.L.; Waterhouse, J.C.

1987-03-01

58

Ecological Modelling 189 (2005) 151167 Habitat and exposure modelling for ecological risk assessment: A  

E-print Network

information system (GIS)-based Monte Carlo simulation model. The model was applied to the raccoons (Procyon lotor) on the Savannah River Site (SRS), a former nuclear production and current research facility

Hodgson, Michael E.

59

Hydrodynamic and Ecological Assessment of Nearshore Restoration: A Modeling Study  

SciTech Connect

Along the Pacific Northwest coast, much of the estuarine habitat has been diked over the last century for agricultural land use, residential and commercial development, and transportation corridors. As a result, many of the ecological processes and functions have been disrupted. To protect coastal habitats that are vital to aquatic species, many restoration projects are currently underway to restore the estuarine and coastal ecosystems through dike breaches, setbacks, and removals. Information on physical processes and hydrodynamic conditions are critical for the assessment of the success of restoration actions. Restoration of a 160- acre property at the mouth of the Stillaguamish River in Puget Sound has been proposed. The goal is to restore native tidal habitats and estuary-scale ecological processes by removing the dike. In this study, a three-dimensional hydrodynamic model was developed for the Stillaguamish River estuary to simulate estuarine processes. The model was calibrated to observed tide, current, and salinity data for existing conditions and applied to simulate the hydrodynamic responses to two restoration alternatives. Responses were evaluated at the scale of the restoration footprint. Model data was combined with biophysical data to predict habitat responses at the site. Results showed that the proposed dike removal would result in desired tidal flushing and conditions that would support four habitat types on the restoration footprint. At the estuary scale, restoration would substantially increase the proportion of area flushed with freshwater (< 5 ppt) at flood tide. Potential implications of predicted changes in salinity and flow dynamics are discussed relative to the distribution of tidal marsh habitat.

Yang, Zhaoqing; Sobocinski, Kathryn L.; Heatwole, Danelle W.; Khangaonkar, Tarang; Thom, Ronald M.; Fuller, Roger

2010-04-10

60

Ocean Biogeochemistry and Phytoplankton Ecology in a Global Simulation  

NASA Astrophysics Data System (ADS)

A coupled Biogeochemistry/Ecosystem/Circulation (BEC) model is used to examine ocean biogeochemistry and phytoplankton ecology at the global scale. Phytoplankton groups represented in the model include diatoms, diazotrophs, coccolithophores and picoplankton. The groups experience differential grazing pressure and compete for light and the potentially growth-limiting nutrients iron, nitrate, ammonium, phosphate, and silicate. The model includes several key aspects of the global nitrogen cycle including nitrogen fixation (by the diazotrophs), water column denitrification under low oxygen conditions, and atmospheric nitrogen deposition to the oceans. We examine how these nitrogen fluxes influence ecosystem structure and also how light and nutrient availability restrict phytoplankton growth rates over seasonal timescales. Atmospheric deposition of mineral dust also inputs dissolved iron to the ocean model. These iron additions modify phytoplankton community composition, and rates of production and export in the iron-limited High Nitrate, Low Chlorophyll regions, and indirectly modify ecosystem dynamics by altering rates of nitrogen fixation in nitrogen-depleted, tropical and subtropical regions. We will examine the links between dust/iron deposition and nitrogen cycling in the oceans.

Moore, J. K.; Doney, S. C.; Lindsay, K.

2005-05-01

61

1 NUMERICAL MODELS OF SALT MARSH 2 EVOLUTION: ECOLOGICAL, GEOMORPHIC,  

E-print Network

1 NUMERICAL MODELS OF SALT MARSH 2 EVOLUTION: ECOLOGICAL, GEOMORPHIC, 3 AND CLIMATIC FACTORS 4 2011. 8 [1] Salt marshes are delicate landforms at the boundary 9 between the sea and land that 13 quantify the formation and evolution of salt marshes under 14 different physical and ecological

62

QUANTITATIVE ECOLOGY A Simple Numerical Model of the Flight Behavior of Small Insects in  

E-print Network

QUANTITATIVE ECOLOGY A Simple Numerical Model of the Flight Behavior of Small Insects of rising air, and that the insects in those plumes oppose the updrafts at a rate that increases as the updrafts become stronger. In this paper, a simple numerical simulation of the airÃ?ow Ã?eld and insect

Geerts, Bart

63

Documentation of the Ecological Risk Assessment Computer Model ECORSK.5  

SciTech Connect

The FORTRAN77 ecological risk computer model--ECORSK.5--has been used to estimate the potential toxicity of surficial deposits of radioactive and non-radioactive contaminants to several threatened and endangered (T and E) species at the Los Alamos National Laboratory (LANL). These analyses to date include preliminary toxicity estimates for the Mexican spotted owl, the American peregrine falcon, the bald eagle, and the southwestern willow flycatcher. This work has been performed as required for the Record of Decision for the construction of the Dual Axis Radiographic Hydrodynamic Test (DARHT) Facility at LANL as part of the Environmental Impact Statement. The model is dependent on the use of the geographic information system and associated software--ARC/INFO--and has been used in conjunction with LANL's Facility for Information Management and Display (FIMAD) contaminant database. The integration of FIMAD data and ARC/INFO using ECORSK.5 allows the generation of spatial information from a gridded area of potential exposure called an Ecological Exposure Unit. ECORSK.5 was used to simulate exposures using a modified Environmental Protection Agency Quotient Method. The model can handle a large number of contaminants within the home range of T and E species. This integration results in the production of hazard indices which, when compared to risk evaluation criteria, estimate the potential for impact from consumption of contaminants in food and ingestion of soil. The assessment is considered a Tier-2 type of analysis. This report summarizes and documents the ECORSK.5 code, the mathematical models used in the development of ECORSK.5, and the input and other requirements for its operation. Other auxiliary FORTRAN 77 codes used for processing and graphing output from ECORSK.5 are also discussed. The reader may refer to reports cited in the introduction to obtain greater detail on past applications of ECORSK.5 and assumptions used in deriving model parameters.

Anthony F. Gallegos; Gilbert J. Gonzales

1999-06-01

64

INVASIVE SPECIES: PREDICTING GEOGRAPHIC DISTRIBUTIONS USING ECOLOGICAL NICHE MODELING  

EPA Science Inventory

Present approaches to species invasions are reactive in nature. This scenario results in management that perpetually lags behind the most recent invasion and makes control much more difficult. In contrast, spatially explicit ecological niche modeling provides an effective solut...

65

Groundwater Management Model to Meet the Goals of Water Supply and Ecological Baseflow  

NASA Astrophysics Data System (ADS)

Groundwater is important for water supply and stream baseflow during dry period in Taiwan. Ecological baseflow is an essential element to maintain the sustainability of the stream ecosystem. How to maintain ecological baseflow and to estimate allowable groundwater withdraws for water supply system becomes an essential issue. On the premise that satisfies both ecological baseflow and water supply, a simulation-optimization model is developed to allocate groundwater pumpings among an area which is divided into several zones. This study will apply MODFLOW model to construct a pumping-drawdown response matrix, and further develop an optimization model to optimize maximal pumping and to determine allowable withdraw for each zone. Both land uses and equality are considered in the discussion. In this study, we expect that through the research process, it can allocate and utilize the surplus groundwater resource in the study area, and then achieve effective management of groundwater resource.

Huang, S.; Tung, C.; Hsu, C.; Tan, C.

2007-12-01

66

Boechera, a model system for ecological genomics  

PubMed Central

The selection and development of a study system for evolutionary and ecological functional genomics (EEFG) depends on a variety of factors. Here we present the genus Boechera as an exemplary system with which to address ecological and evolutionary questions. Our focus on Boechera is based on several characteristics: 1) native populations in undisturbed habitats where current environments reflect historical conditions over several thousand years; 2) functional genomics benefitting from its close relationship to Arabidopsis thaliana; 3) inbreeding tolerance enabling development of recombinant inbred lines, near-isogenic lines, and positional cloning; 4) interspecific crosses permitting mapping for genetic analysis of speciation; 5) apomixis (asexual reproduction by seeds) in a genetically tractable diploid; and 6) broad geographic distribution in North America, permitting ecological genetics for a large research community. These characteristics, along with the current sequencing of three Boechera species by the Joint Genome Institute, position Boechera as a rapidly advancing system for EEFG studies. PMID:22059452

Rushworth, Catherine A.; Song, Bao-Hua; Lee, Cheng-Ruei; Mitchell-Olds, Thomas

2011-01-01

67

Power resource simulation model  

SciTech Connect

The Power Resource Simulation Model (PRSM) was developed by Black & Veatch for the Southwestern Power Administration (Southwestern). Southwestern, one of five power marketing agencies for the US Department of Energy, markets the power and energy generated at 24 US Army Corps of Engineers hydroelectric power plants. PRSM simulates the operation of multipurpose, multireservoir systems and operates the reservoirs to meet user-specified demands (water and electrical) while staying within established operating limits. PRSM is equipped with a graphical user-interface which allows the user to enter and modify input data, initiate the Run program, and view and print simulation results with user-defined tables and graphs. PRSM is operated by specifying demands at each reservoir and for the system as a whole. Once all the individual project demands have been addressed, PRSM operates the reservoirs to meet the system electrical load demands which are input in the form of load duration curves. If the hydropower resources are not capable of meeting the entire system electrical load demand, PRSM will use nonhydro (thermal) resources to meet the remaining system load.

Bultsma, M.L.; Arroyo, J.A. [Black & Veatch, Kansas City, MO (United States); Herrold, B.J. [Southwestern Power Administration, Tulsa, OK (United States)] [and others

1995-12-31

68

[Removal of nitrogen in simulated rivers embanked by ecological concrete].  

PubMed

The removal of nitrogen was studied in four types of pilot-scale rivers. The embankment for rivers No. 1, 2 and 3 consisted of respectively spheriform ecological-concrete prefab-bricks, rectangular ecological-concrete prefab-bricks and square ecological-concrete prefab-bricks with 4 hemispheroids. The embankment for river No. 4 was made of concrete C25. The results show that the removal rates of NH4+ -N, NO2- -N, NO3- -N and TN of river 1 are 83.6%, 75.2%, 37.1% and 47.5% under hydraulic retention time of 2 days, 83.4%, 53.0%, 30.6% and 40.4% for river 2, 88.1%, 72.4%, 33.0% and 40.9% for river 3. Under the same condition, NH4+ -N, TN of river 4 decreasesby 61.1%, 9.1%, while NO2- -N, NO3- -N increase by 7.4%, 3.4% due to the transformation of NH4+ -N. It indicates that ecological embankment rivers can effectively remove nitrogen. Besides, the addition of pore rate in embankment structure and more rate of plant coverage are good for the removal of nitrogen in ecological embankment rivers. PMID:18839568

Chen, Yang-hui; Lü, Xi-wu; Wu, Yi-feng

2008-08-01

69

Comparison of Ecological Validity of Learning Disabilities Diagnostic Models  

ERIC Educational Resources Information Center

The purpose of this article is to examine models designed for the determination of a learning disability and compare them to specific criteria to determine whether the given diagnostic process is ecological in nature. The traditional child-centered deficit model (CCD), Relative Achievement Discrepancy model (RAD), and Responsiveness to…

Dean, Vincent J.; Burns, Matthew K.; Grialou, Tina; Varro, Patrick J.

2006-01-01

70

Ecological Modelling 146 (2001) 263273 Applications of symbolic machine learning to ecological  

E-print Network

algal growth in lagoons and lakes (e.g. in the Venice lagoon) to predicting biodegradation rates for chemicals. This paper gives an overview of machine learning applications to ecological modelling, focussing antelopes, brown bears, and Collembola. This paper gives an overview of machine learn- ing applications

Dzeroski, Saso

71

State of the art of ecological modelling in limnology  

Microsoft Academic Search

An overview of modelling in limnology is given by presentation of core problems and milestones of ecological modelling. The history of modelling can be presented by five generations of models, from Lotka-Volterra and Streeter-Phelps to the structural dynamic models of today. The three major problems of modelling in the 1970s are discussed. They are: how do we build a reliable

Sven Erik Jørgensen

1995-01-01

72

Meeting in Korea: WASP Transport Modeling and WASP Ecological Modeling  

EPA Science Inventory

A combination of lectures, demonstrations, and hands-on excercises will be used to introduce pollutant transport modeling with the U.S. EPA's general water quality model, WASP (Water Quality Analysis Simulation Program). WASP features include a user-friendly Windows-based interfa...

73

Meeting in Turkey: WASP Transport Modeling and WASP Ecological Modeling  

EPA Science Inventory

A combination of lectures, demonstrations, and hands-on excercises will be used to introduce pollutant transport modeling with the U.S. EPA's general water quality model, WASP (Water Quality Analysis Simulation Program). WASP features include a user-friendly Windows-based interfa...

74

Aggregate dynamic economic - ecological models for sustainable development  

Microsoft Academic Search

The aim of the paper is to formulate a general integrated aggregate dynamic model for sustainable development, that will be both simple in structure and able to deal with the main objectives, processes, and constraints applying to sustainable development in closed economic - ecological systems. General characteristics of models to be used for sustainable development are discussed. It turns out

J C J M van den Bergh; P Nijkamp

1991-01-01

75

Cellular Automata as a Paradigm for Ecological Modeling Bioinfnmutica  

E-print Network

's work on "self-reproduction" and Ulam's work on "cellular auxology" (1962, reprinted in [6]), whichCellular Automata as a Paradigm for Ecological Modeling P. Hogeweg Bioinfnmutica Paduulaan 8 Utrecht, The Netherlands ABSTRACT We review cellular automata as a modeling formalismand discusshow it can

Utrecht, Universiteit

76

PLACE PRIORITIZATION FOR BIODIVERSITY REPRESENTATION USING SPECIES' ECOLOGICAL NICHE MODELING  

Microsoft Academic Search

Place prioritization for biodiversity representation is essential for conservation planning, particularly in megadiverse countries where high deforestation threatens biodiversity. Given the collecting biases and uneven sampling of biological inventories, there is a need to develop robust models of species' distributions. By modeling species' ecological niches using point occurrence data and digitized environmental feature maps, we can predict potential and extant

Víctor Sánchez-Cordero; Verónica Cirelli; Mariana Munguía; Sahotra Sarkar

2005-01-01

77

Dense and sparse aggregations in complex motion: Video coupled with simulation modeling  

Technology Transfer Automated Retrieval System (TEKTRAN)

In censuses of aggregations composed of highly mobile animals, the link between image processing technology and simulation modeling remains relatively unexplored despite demonstrated ecological needs for abundance and density assessments. We introduce a framework that connects video censusing with ...

78

Distribution of phytoplankton functional types in high-nitrate, low-chlorophyll waters in a new diagnostic ecological indicator model  

NASA Astrophysics Data System (ADS)

Modeling and monitoring plankton functional types (PFTs) is challenged by the insufficient amount of field measurements of ground truths in both plankton models and bio-optical algorithms. In this study, we combine remote sensing data and a dynamic plankton model to simulate an ecologically sound spatial and temporal distribution of phyto-PFTs. We apply an innovative ecological indicator approach to modeling PFTs and focus on resolving the question of diatom-coccolithophore coexistence in the subpolar high-nitrate and low-chlorophyll regions. We choose an artificial neural network as our modeling framework because it has the potential to interpret complex nonlinear interactions governing complex adaptive systems, of which marine ecosystems are a prime example. Using ecological indicators that fulfill the criteria of measurability, sensitivity and specificity, we demonstrate that our diagnostic model correctly interprets some basic ecological rules similar to ones emerging from dynamic models. Our time series highlight a dynamic phyto-PFT community composition in all high-latitude areas and indicate seasonal coexistence of diatoms and coccolithophores. This observation, though consistent with in situ and remote sensing measurements, has so far not been captured by state-of-the-art dynamic models, which struggle to resolve this "paradox of the plankton". We conclude that an ecological indicator approach is useful for ecological modeling of phytoplankton and potentially higher trophic levels. Finally, we speculate that it could serve as a powerful tool in advancing ecosystem-based management of marine resources.

Palacz, A. P.; St. John, M. A.; Brewin, R. J. W.; Hirata, T.; Gregg, W. W.

2013-11-01

79

Distribution of phytoplankton functional types in high-nitrate low-chlorophyll waters in a new diagnostic ecological indicator model  

NASA Astrophysics Data System (ADS)

Modeling and monitoring plankton functional types (PFTs) is challenged by insufficient amount of field measurements to ground-truth both plankton models and bio-optical algorithms. In this study, we combine remote sensing data and a dynamic plankton model to simulate an ecologically-sound spatial and temporal distribution of phyto-PFTs. We apply an innovative ecological indicator approach to modeling PFTs, and focus on resolving the question of diatom-coccolithophore co-existence in the subpolar high-nitrate and low-chlorophyll regions. We choose an artificial neural network as our modeling framework because it has the potential to interpret complex nonlinear interactions governing complex adaptive systems, of which marine ecosystems are a prime example. Using ecological indicators that fulfill the criteria of measurability, sensitivity and specificity, we demonstrate that our diagnostic model correctly interprets some basic ecological rules similar to ones emerging from dynamic models. Our time series highlight a dynamic phyto-PFT community composition in all high latitude areas, and indicate seasonal co-existence of diatoms and coccolithophores. This observation, though consistent with in situ and remote sensing measurements, was so far not captured by state-of-the-art dynamic models which struggle to resolve this "paradox of the plankton". We conclude that an ecological indicator approach is useful for ecological modeling of phytoplankton and potentially higher trophic levels. Finally, we speculate that it could serve as a powerful tool in advancing ecosystem-based management of marine resources.

Palacz, A. P.; St. John, M. A.; Brewin, R. J. W.; Hirata, T.; Gregg, W. W.

2013-05-01

80

Ecological Niche Modelling of Bank Voles in Western Europe  

PubMed Central

The bank vole (Myodes glareolus) is the natural host of Puumala virus (PUUV) in vast areas of Europe. PUUV is one of the hantaviruses which are transmitted to humans by infected rodents. PUUV causes a general mild form of hemorrhagic fever with renal syndrome (HFRS) called nephropathia epidemica (NE). Vector-borne and zoonotic diseases generally display clear spatial patterns due to different space-dependent factors. Land cover influences disease transmission by controlling both the spatial distribution of vectors or hosts, as well as by facilitating the human contact with them. In this study the use of ecological niche modelling (ENM) for predicting the geographical distribution of bank vole population on the basis of spatial climate information is tested. The Genetic Algorithm for Rule-set Prediction (GARP) is used to model the ecological niche of bank voles in Western Europe. The meteorological data, land cover types and geo-referenced points representing the locations of the bank voles (latitude/longitude) in the study area are used as the primary model input value. The predictive accuracy of the bank vole ecologic niche model was significant (training accuracy of 86%). The output of the GARP models based on the 50% subsets of points used for testing the model showed an accuracy of 75%. Compared with random models, the probability of such high predictivity was low (?2 tests, p < 10?6). As such, the GARP models were predictive and the used ecologic niche model indeed indicates the ecologic requirements of bank voles. This approach successfully identified the areas of infection risk across the study area. The result suggests that the niche modelling approach can be implemented in a next step towards the development of new tools for monitoring the bank vole’s population. PMID:23358234

Amirpour Haredasht, Sara; Barrios, Miguel; Farifteh, Jamshid; Maes, Piet; Clement, Jan; Verstraeten, Willem W.; Tersago, Katrien; Van Ranst, Marc; Coppin, Pol; Berckmans, Daniel; Aerts, Jean-Marie

2013-01-01

81

A dynamic ecological-economic model as a tool for conflict resolution in an invasive-alien-plant, biological control and native-plant scenario  

Microsoft Academic Search

The release of biological control agents for the control of environmental weeds is often resisted by parties which utilize these plants. This conflict is difficult to resolve because of the social, economic and ecological complexities involved. We construct an ecological-economic model to simulate the complex dynamics of the release of a biological control agent with the aim of developing a

Steven I. Higgins; Esteban J. Azorin; Richard M. Cowling; Mike J. Morris

1997-01-01

82

ELSEVIER EcologicalModelling95 (1997)95-111 Using machine learning techniques in the construction of models.  

E-print Network

ELSEVIER EcologicalModelling95 (1997)95-111 E(OL061(I monBun6 Using machine learning techniques the acquisition of ecological knowledge, i.e., automate the construction of ecological models. This paper analysis in several ecological domains. These include the biological classification of British rivers based

Dzeroski, Saso

83

Model Organisms Retain an “Ecological Memory” of Complex Ecologically Relevant Environmental Variation  

PubMed Central

Although tractable model organisms are essential to characterize the molecular mechanisms of evolution and adaptation, the ecological relevance of their behavior is not always clear because certain traits are easily lost during long-term laboratory culturing. Here, we demonstrate that despite their long tenure in the laboratory, model organisms retain “ecological memory” of complex environmental changes. We have discovered that Halobacterium salinarum NRC-1, a halophilic archaeon that dominates microbial communities in a dynamically changing hypersaline environment, simultaneously optimizes fitness to total salinity, NaCl concentration, and the [K]/[Mg] ratio. Despite being maintained under controlled conditions over the last 50 years, peaks in the three-dimensional fitness landscape occur in salinity and ionic compositions that are not replicated in laboratory culturing but are routinely observed in the natural hypersaline environment of this organism. Intriguingly, adaptation to variations in ion composition was associated with differential regulation of anaerobic metabolism genes, suggesting an intertwined relationship between responses to oxygen and salinity. Our results suggest that the ecological memory of complex environmental variations is imprinted in the networks for coordinating multiple cellular processes. These coordination networks are also essential for dealing with changes in other physicochemically linked factors present during routine laboratory culturing and, hence, retained in model organisms. PMID:24413600

Beer, Karlyn D.; Wurtmann, Elisabeth J.; Pinel, Nicolás

2014-01-01

84

A New Approach to Ecological Risk Assessment: Simulating Effects of Global Warming on Complex Ecological Networks  

NASA Astrophysics Data System (ADS)

The field of Ecological Risk Assessment (ERA) has been under development since the 1970s. Early ERA borrowed basic concepts from human health risk assessment (HRA) methodology [NAS 1983]. However, because of the nature of an ecosystem, there is a fundamental difference between HRA and ERA. In an HRA, the only receptor is a single human being and the concerned endpoints are always associated with human health issues, such as the risk of cancer. In ERA, however, entire populations, communities and ecosystems are at risk, and ERA must rigorously assess these more complex and larger scaled concerns. Many investigators have attempted to develop a new paradigm for ERA that can deal with this intrinsic distinction. Currently, a six-step framework is now widely used by the U.S. EPA and its contractors. This new paradigm is characterized by: (1) receptor identification, (2) hazard identification, (3) endpoint identification, (4) exposure assessment, (5) doseresponse assessment and (6) risk characterization [Lipton et al. 1993, Suter 1993]. The six-step framework identifies receptors at risk, possible hazards related to certain receptors, and chooses appropriate assessment and measurement endpoints [Suter 1990]. While the additional receptor and endpoint identifications improve on the traditional framework, single-species laboratory toxicity tests typically estimate ecological responses simply by predicting an environmental concentration associated with a certain stressor divided by the no-observed effect concentration (NOEC) for that stressor. This "Hazard Quotient" (HQ) approach ignores interactions between species that are critical to the functioning of communities and ecosystems.

Zhou, Yun; Brose, Ulrich; Kastenberg, William; Martinez, Neo D.

85

INTERPRETING ECOLOGICAL DIVERSITY INDICES APPLIED TO T-RFLP DATA: INSIGHTS FROM SIMULATED MICROBIAL COMMUNITIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Ecological diversity indices are frequently applied to molecular profiling methods, such as terminal restriction fragment length polymorphism (T-RFLP), in order to detect differences in diversity of the microbial communities sampled. We performed simulations to determine whether diversity indices c...

86

SIMULATION OF ECOLOGICALLY CONSCIOUS CHEMICAL PROCESSES: FUGITIVE EMISSIONS VERSUS OPERATING CONDITIONS: JOURNAL ARTICLE  

EPA Science Inventory

NRMRL-CIN-1531A Mata, T.M., Smith*, R.L., Young*, D., and Costa, C.A.V. "Simulation of Ecologically Conscious Chemical Processes: Fugitive Emissions versus Operating Conditions." Paper published in: CHEMPOR' 2001, 8th International Chemical Engineering Conference, Aveiro, Portu...

87

Assessing the Effectiveness of a Computer Simulation for Teaching Ecological Experimental Design  

ERIC Educational Resources Information Center

Designing manipulative ecological experiments is a complex and time-consuming process that is problematic to teach in traditional undergraduate classes. This study investigates the effectiveness of using a computer simulation--the Virtual Rocky Shore (VRS)--to facilitate rapid, student-centred learning of experimental design. We gave a series of…

Stafford, Richard; Goodenough, Anne E.; Davies, Mark S.

2010-01-01

88

Ecological impact in ditch mesocosms of simulated spray drift from a crop protection program for potatoes  

Microsoft Academic Search

Outdoor aquatic ditch mesocosms were treated with a range of pesticides to simulate various spray drift rates resulting from a typical crop protection program used in the cultivation of potatoes in The Netherlands. The main experimental aims of the present study were to provide information on the fate and ecological effects of drift of the pesticides into surface water and

Gertie HP Arts; Laura L Buijse-Bogdan; J Dick M Belgers; Rhenen-Kersten van C. H; Wijngaarden van R. P. A; Ivo Roessink; Steve J Maund; Brink van den P. J; Theo CM Brock

2006-01-01

89

Inferential consequences of modeling rather than measuring snow accumulation in studies of animal ecology.  

PubMed

It is increasingly common for studies of animal ecology to use model-based predictions of environmental variables as explanatory or predictor variables, even though model prediction uncertainty is typically unknown. To demonstrate the potential for misleading inferences when model predictions with error are used in place of direct measurements, we compared snow water equivalent (SWE) and snow depth as predicted by the Snow Data Assimilation System (SNODAS) to field measurements of SWE and snow depth. We examined locations on elk (Cervus canadensis) winter ranges in western Wyoming, because modeled data such as SNODAS output are often used for inferences on elk ecology. Overall, SNODAS predictions tended to overestimate field measurements, prediction uncertainty was high, and the difference between SNODAS predictions and field measurements was greater in snow shadows for both snow variables compared to non-snow shadow areas. We used a simple simulation of snow effects on the probability of an elk being killed by a predator to show that, if SNODAS prediction uncertainty was ignored, we might have mistakenly concluded that SWE was not an important factor in where elk were killed in predatory attacks during the winter. In this simulation, we were interested in the effects of snow at finer scales (< 1 km2) than the resolution of SNODAS. If bias were to decrease when SNODAS predictions are averaged over coarser scales, SNODAS would be applicable to population-level ecology studies. In our study, however, averaging predictions over moderate to broad spatial scales (9-2200 km2) did not reduce the differences between SNODAS predictions and field measurements. This study highlights the need to carefully evaluate two issues when using model output as an explanatory variable in subsequent analysis: (1) the model's resolution relative to the scale of the ecological question of interest and (2) the implications of prediction uncertainty on inferences when using model predictions as explanatory or predictor variables. PMID:23734491

Brennan, Angela; Cross, Paul C; Higgs, Megan; Beckmann, Jon P; Klaver, Robert W; Scurlock, Brandon M; Creel, Scott

2013-04-01

90

Locating Pleistocene Refugia: Comparing Phylogeographic and Ecological Niche Model Predictions  

Microsoft Academic Search

Ecological niche models (ENMs) provide a means of characterizing the spatial distribution of suitable conditions for species, and have recently been applied to the challenge of locating potential distributional areas at the Last Glacial Maximum (LGM) when unfavorable climate conditions led to range contractions and fragmentation. Here, we compare and contrast ENM-based reconstructions of LGM refugial locations with those resulting

Eric Waltari; Robert J. Hijmans; A. Townsend Peterson; Árpád S. Nyári; Susan L. Perkins; Robert P. Guralnick

2007-01-01

91

Author's personal copy Ecological Modelling 243 (2012) 1832  

E-print Network

caribou (Rangifer tarandus) are classified as threatened in Canada, and the Little Smoky herd in west. Introduction Woodland caribou (Rangifer tarandus caribou) in Alberta are cur- rently designated as threatened behavioral­ecological strategies in pattern-oriented modeling of caribou habitat use in a highly

Hebblewhite, Mark

92

A Novel Integrated Ecological Model for the study of Sustainability  

EPA Science Inventory

In recent years, there has been a growing interest among various sections of the society in the study of sustainability. Recently, a generalized mathematical model depicting a combined economic-ecological-social system has been proposed to help in the formal study of sustainabili...

93

A Model of Practice in Special Education: Dynamic Ecological Analysis  

ERIC Educational Resources Information Center

Dynamic Ecological Analysis (DEA) is a model of practice which increases a teams' efficacy by enabling the development of more effective interventions through collaboration and collective reflection. This process has proved to be useful in: a) clarifying thinking and problem-solving, b) transferring knowledge and thinking to significant parties,…

Hannant, Barbara; Lim, Eng Leong; McAllum, Ruth

2010-01-01

94

Development of stable isotope mixing models in ecology - Perth  

EPA Science Inventory

More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

95

Modeling clonal plant growth: from ecological concepts to mathematics  

E-print Network

influenced by plant horizontal growth Effect and response to environmental variability is strongly linkedModeling clonal plant growth: from ecological concepts to mathematics Workshop MODECOL 7-8 June, rhizomes in the shoot basis Resource storage Clonal properties #12;Intraclonal plasticity Clonal

Azevedo, Ricardo

96

Development of stable isotope mixing models in ecology - Dublin  

EPA Science Inventory

More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

97

Development of stable isotope mixing models in ecology - Fremantle  

EPA Science Inventory

More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

98

Historical development of stable isotope mixing models in ecology  

EPA Science Inventory

More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

99

Development of stable isotope mixing models in ecology - Sydney  

EPA Science Inventory

More than 40 years ago, stable isotope analysis methods used in geochemistry began to be applied to ecological studies. One common application is using mathematical mixing models to sort out the proportional contributions of various sources to a mixture. Examples include contri...

100

ASSESSMENT OF SPATIAL AUTOCORRELATION IN EMPIRICAL MODELS IN ECOLOGY  

EPA Science Inventory

Statistically assessing ecological models is inherently difficult because data are autocorrelated and this autocorrelation varies in an unknown fashion. At a simple level, the linking of a single species to a habitat type is a straightforward analysis. With some investigation int...

101

Author's personal copy Ecological Modelling 222 (2011) 144153  

E-print Network

8 October 2010 Keywords: Forest harvesting Harvest intensity Biofuels Soil organic carbonDirect Ecological Modelling journal homepage: www.elsevier.com/locate/ecolmodel The effects of forest harvest harvesting substantially affects C dynamics; these effects may be amplified if forest harvesting

Mladenoff, David

102

Representing and managing uncertainty in qualitative ecological models  

Microsoft Academic Search

Ecologists and decision makers need ways to understand systems, test ideas, and make predictions and explanations about systems. However, uncertainty about causes and effects of processes and parameter values is pervasive in models of ecological systems. Uncertainty associated with incomplete knowledge of a phenomenon–and incomplete knowledge of the limits of one's knowledge–is referred to as epistemic uncertainty. Here, we illustrate

Tim Nuttle; Bert Bredeweg; Paulo Salles; Michael Neumann

2009-01-01

103

INTEGRATION OF AN ECONOMIC WITH AN ECOLOGICAL MODEL  

EPA Science Inventory

We summarize our work on integration of an economy under imperfect competition with a simple Lotka-Volterra type ecological model. Firms and households operate within a single period planning horizon, thus there is no savings or investment. Wages are set by a dominant employer. P...

104

Ecological Models: Family Systems and Beyond. A Symposium.  

ERIC Educational Resources Information Center

There has been a resurgence of interest in human ecosystems, attributable to the growth of community mental health centers and public sector funding. The first of two papers discusses human ecology models based on this resurgence. Implications for future development of the mental health area are presented with the challenge to integrate…

Jasnoski, M. L.; O'Connor, William A.

105

Silene as a model system in ecology and evolution  

Microsoft Academic Search

The genus Silene, studied by Darwin, Mendel and other early scientists, is re-emerging as a system for studying interrelated questions in ecology, evolution and developmental biology. These questions include sex chromosome evolution, epigenetic control of sex expression, genomic conflict and speciation. Its well-studied interactions with the pathogen Microbotryum has made Silene a model for the evolution and dynamics of disease

G. Bernasconi; J. Antonovics; A. Biere; D. Charlesworth; L. F. Delph; D. Filatov; T. Giraud; M. E. Hood; G. A. B. Marais; D. McCauley; J. R. Pannell; J. A. Shykoff; B. Vyskot; L. M. Wolfe; A. Widmer

2009-01-01

106

Ecology.  

ERIC Educational Resources Information Center

This set of teaching aids consists of nine Audubon Nature Bulletins, providing teachers and students with informational reading on various ecological topics. The bulletins have these titles: Schoolyard Laboratories, Owls and Predators, The Forest Community, Life in Freshwater Marshes, Camouflage in the Animal World, Life in the Desert, The…

National Audubon Society, New York, NY.

107

Relationship of stream ecological conditions to simulated hydraulic metrics across a gradient of basin urbanization  

USGS Publications Warehouse

The relationships among urbanization, stream hydraulics, and aquatic biology were investigated across a gradient of urbanization in 30 small basins in eastern Wisconsin, USA. Simulation of hydraulic metrics with 1-dimensional unsteady flow models was an effective means for mechanistically coupling the effects of urbanization with stream ecological conditions (i.e., algae, invertebrates, and fish). Urbanization, characterized by household, road, and urban land density, was positively correlated with the lowest shear stress for 2 adjacent transects in a reach for the low-flow summer (p < 0.001) and autumn (p < 0.01) periods. Urbanization also was positively correlated with Reynolds number and % exposed stream bed during months with moderate to low flows. Our study demonstrated the value of temporally and spatially explicit hydraulic models for providing mechanistic insight into the relationships between hydraulic variables and biological responses. For example, the positive correlation between filter-feeding invertebrate richness and minimum 2-transect shear stress observed in our study is consistent with a higher concentration of water-column particulates available for filtration. The strength of correlations between hydraulic and biological metrics is related to the time period (annual, seasonal, or monthly) considered. The hydraulic modeling approach, whether based on hourly or daily flow data, allowed documentation of the effects of a spatially variable response within a reach, and the results suggest that stream response to urbanization varies with hydraulic habitat type. ?? North American Benthological Society.

Steuer, J.J.; Bales, J.D.; Giddings, E.M.P.

2009-01-01

108

Ecology, 00(0), 0000, pp. 000000 0000 by the Ecological Society of America  

E-print Network

ecology; simulation modeling; sustain- ability. Why are starfish like an atomic bomb? The answer, according to the co-authors of Complexity in landscape ecology, is that like the chain reaction of atomic

Turner, Monica G.

109

ECOLOGICAL MODEL TESTING: VERIFICATION, VALIDATION OR NEITHER?  

EPA Science Inventory

Consider the need to make a management decision about a declining animal population. Two models are available to help. Before a decision is made based on model results, the astute manager or policy maker may ask, "Do the models work?" Or, "Have the models been verified or validat...

110

Predicting species’ geographic distributions based on ecological niche modeling  

E-print Network

types of error enter into such niche modeling and geographic prediction ef- forts (Fielding and Bell 1997). First, omission of areas actually inhabited represents a failure of the modeling effort to extend to all ecological conditions under which... on their high species richness, distribution in regions well covered by the North American Breeding Bird Survey (http://www.mbr-pwrc.usgs.gov/ bbs/bbs.html), and ease of detection in visual/ auditory surveys. The Breeding Bird Survey data offer relatively...

Peterson, A. Townsend

2001-08-01

111

Automatic programming of simulation models  

NASA Technical Reports Server (NTRS)

The objective of automatic programming is to improve the overall environment for describing the program. This improved environment is realized by a reduction in the amount of detail that the programmer needs to know and is exposed to. Furthermore, this improved environment is achieved by a specification language that is more natural to the user's problem domain and to the user's way of thinking and looking at the problem. The goal of this research is to apply the concepts of automatic programming (AP) to modeling discrete event simulation system. Specific emphasis is on the design and development of simulation tools to assist the modeler define or construct a model of the system and to then automatically write the corresponding simulation code in the target simulation language, GPSS/PC. A related goal is to evaluate the feasibility of various languages for constructing automatic programming simulation tools.

Schroer, Bernard J.; Tseng, Fan T.; Zhang, Shou X.; Dwan, Wen S.

1988-01-01

112

Modeling hydrologic and ecologic responses using a new eco-hydrological model for identification of droughts  

NASA Astrophysics Data System (ADS)

severely damages water and agricultural resources, and both hydrological and ecological responses are important for its understanding. First, precipitation deficit induces soil moisture deficiency and high plant water stress causing agricultural droughts. Second, hydrological drought characterized by deficit of river discharge and groundwater follows agricultural drought. However, contributions of vegetation dynamics to these processes at basin scale have not been quantified. To address this issue, we develop an eco-hydrological model that can calculate river discharge, groundwater, energy flux, and vegetation dynamics as diagnostic variables at basin scale within a distributed hydrological modeling framework. The model is applied to drought analysis in the Medjerda River basin. From model inputs and outputs, we calculate drought indices for different drought types. The model shows reliable accuracy in reproducing observed river discharge in long-term (19 year) simulation. Moreover, the drought index calculated from the model-estimated annual peak of leaf area index correlates well (correlation coefficient r = 0.89) with the drought index from nationwide annual crop production, which demonstrates that the modeled leaf area index is capable of representing agricultural droughts related to historical food shortages. We show that vegetation dynamics have a more rapid response to meteorological droughts than river discharge and groundwater dynamics in the Medjerda basin because vegetation dynamics are sensitive to soil moisture in surface layers, whereas soil moisture in deeper layers strongly contributes to streamflow and groundwater level. Our modeling framework can contribute to analyze drought progress, although analyses for other climate conditions are needed.

Sawada, Yohei; Koike, Toshio; Jaranilla-Sanchez, Patricia Ann

2014-07-01

113

Spatiotemporal modelling of ecological and evolutionary problems  

E-print Network

III.3. A spatial model of the evolution of quorum sensing...............................................90 III.4.Quorum sensing: the evolutionary benefit of dishonest signalling.........................103

Czárán, Tamás

114

Metamorphic Modelling: Simulating Metamorphic Processes  

NSDL National Science Digital Library

These activities are aimed at simulating metamorphic rock formation, and explain how increased pressure and heat affect such formation. The first activity, which can also be performed as a teacher demonstration, simulates the idea of contact metamorphism by investigating the effect of heat from a beaker of hot water on egg white. The other two laboratory activities simulate the formation of slate and simulate the distortion of fossils under pressure using plaster of Paris models. The lesson also discusses differences between igneous and metamorphic rocks.

115

Development of a zoning-based environmental-ecological coupled model for lakes: a case study of Baiyangdian Lake in northern China  

NASA Astrophysics Data System (ADS)

Environmental/ecological models are widely used for lake management as they provide a means to understand physical, chemical, and biological processes in highly complex ecosystems. Most research has focused on the development of environmental (water quality) and ecological models, separately. Limited studies were developed to couple the two models, and in these limited coupled models, a lake was regarded as a whole for analysis (i.e. considering the lake to be one well-mixed box), which is appropriate for small-scale lakes but is not sufficient to capture spatial variations within middle-scale or large-scale lakes. In response to this problem, this paper seeks to establish a zoning-based environmental-ecological coupled model for a lake. Hierarchical cluster analysis was adopted to determine the number of zones in a given lake based on hydrological, water quality, and ecological data analysis. The MIKE 21 model was used to construct 2-D hydrodynamics and water quality simulations. STELLA software was used to create a lake ecological model that can simulate the spatial variations of ecological condition based on flow field distribution results generated by MIKE 21. Baiyangdian Lake, the largest freshwater lake in northern China, was adopted as the study case. The results showed that the new model is promising for predicting spatial variations of ecological conditions in response to changes in lake water quantity and quality, and could be useful for lake management.

Zhao, Y. W.; Xu, M. J.; Xu, F.; Wu, S. R.; Yin, X. A.

2014-06-01

116

Modeling and Simulation at NASA  

NASA Technical Reports Server (NTRS)

This slide presentation is composed of two topics. The first reviews the use of modeling and simulation (M&S) particularly as it relates to the Constellation program and discrete event simulation (DES). DES is defined as a process and system analysis, through time-based and resource constrained probabilistic simulation models, that provide insight into operation system performance. The DES shows that the cycles for a launch from manufacturing and assembly to launch and recovery is about 45 days and that approximately 4 launches per year are practicable. The second topic reviews a NASA Standard for Modeling and Simulation. The Columbia Accident Investigation Board made some recommendations related to models and simulations. Some of the ideas inherent in the new standard are the documentation of M&S activities, an assessment of the credibility, and reporting to decision makers, which should include the analysis of the results, a statement as to the uncertainty in the results,and the credibility of the results. There is also discussion about verification and validation (V&V) of models. There is also discussion about the different types of models and simulation.

Steele, Martin J.

2009-01-01

117

A CONCEPTUAL MODEL FOR MULTI-SCALAR ASSESSMENTS OF ESTUARINE ECOLOGICAL INTEGRITY  

EPA Science Inventory

A conceptual model was developed that relates an estuarine system's anthropogenic inputs to it's ecological integrity. Ecological integrity is operationally defined as an emergent property of an ecosystem that exists when the structural components are complete and the functional ...

118

CONCEPTUAL MODEL FOR ASSESSING ECOLOGICAL RISK TO WATER QUALITY FUNCTION OF BOTTOMLAND HARDWOOD FORESTS  

EPA Science Inventory

Ecological risk assessment provides a methodology for evaluating the threats of ecosystem function associated with environmental perturbations or stressors. his report documents the development of a conceptual model for assessing the ecological risk to the water quality function ...

119

System dynamic modelling to assess economic viability and risk trade-offs for ecological restoration in South Africa.  

PubMed

Can markets assist by providing support for ecological restoration, and if so, under what conditions? The first step in addressing this question is to develop a consistent methodology for economic evaluation of ecological restoration projects. A risk analysis process was followed in which a system dynamics model was constructed for eight diverse case study sites where ecological restoration is currently being pursued. Restoration costs vary across each of these sites, as do the benefits associated with restored ecosystem functioning. The system dynamics model simulates the ecological, hydrological and economic benefits of ecological restoration and informs a portfolio mapping exercise where payoffs are matched against the likelihood of success of a project, as well as a number of other factors (such as project costs and risk measures). This is the first known application that couples ecological restoration with system dynamics and portfolio mapping. The results suggest an approach that is able to move beyond traditional indicators of project success, since the effect of discounting is virtually eliminated. We conclude that systems dynamic modelling with portfolio mapping can guide decisions on when markets for restoration activities may be feasible. PMID:23524327

Crookes, D J; Blignaut, J N; de Wit, M P; Esler, K J; Le Maitre, D C; Milton, S J; Mitchell, S A; Cloete, J; de Abreu, P; Fourie nee Vlok, H; Gull, K; Marx, D; Mugido, W; Ndhlovu, T; Nowell, M; Pauw, M; Rebelo, A

2013-05-15

120

Eco-genetic model to explore fishing-induced ecological and evolutionary effects on growth and maturation schedules  

PubMed Central

Eco-genetic individual-based models involve tracking the ecological dynamics of simulated individual organisms that are in part characterized by heritable parameters. We developed an eco-genetic individual-based model to explore ecological and evolutionary interactions of fish growth and maturation schedules. Our model is flexible and allows for exploration of the effects of heritable growth rates (based on von Bertalanffy and biphasic growth patterns), heritable maturation schedules (based on maturation reaction norm concepts), or both on individual- and population-level traits. In baseline simulations with rather simple ecological trade-offs and over a relatively short time period (<200 simulation years), simulated male and female fish evolve differential genetic growth and maturation. Further, resulting patterns of genetically determined growth and maturation are influenced by mortality rate and density-dependent processes, and maturation and growth parameters interact to mediate the evolution of one another. Subsequent to baseline simulations, we conducted experimental simulations to mimic fisheries harvest with two size-limits (targeting large or small fish), an array of fishing mortality rates, and assuming a deterministic or stochastic environment. Our results suggest that fishing with either size-limit may induce considerable changes in life-history trait expression (maturation schedules and growth rates), recruitment, and population abundance and structure. However, targeting large fish would cause more adverse genetic effects and may lead to a population less resilient to environmental stochasticity. PMID:25567890

Wang, Hui-Yu; Höök, Tomas O

2009-01-01

121

Structural Equation Modeling: Applications in Ecological and Evolutionary Biology Research  

USGS Publications Warehouse

This book presents an introduction to the methodology of structural equation modeling, illustrates its use, and goes on to argue that it has revolutionary implications for the study of natural systems. A major theme of this book is that we have, up to this point, attempted to study systems primarily using methods (such as the univariate model) that were designed only for considering individual processes. Understanding systems requires the capacity to examine simultaneous influences and responses. Structural equation modeling (SEM) has such capabilities. It also possesses many other traits that add strength to its utility as a means of making scientific progress. In light of the capabilities of SEM, it can be argued that much of ecological theory is currently locked in an immature state that impairs its relevance. It is further argued that the principles of SEM are capable of leading to the development and evaluation of multivariate theories of the sort vitally needed for the conservation of natural systems. Supplementary information can be found at the authors website, http://www.jamesbgrace.com/. ? Details why multivariate analyses should be used to study ecological systems ? Exposes unappreciated weakness in many current popular analyses ? Emphasizes the future methodological developments needed to advance our understanding of ecological systems.

Pugesek, Bruce H.; von Eye, Alexander; Tomer, Adrian

2003-01-01

122

Equilibrium and nonequilibrium concepts in ecological models  

Microsoft Academic Search

Mathematical models and empirical studies have revealed two potentially disruptive influences on ecosystems; (1) instabilities caused by nonlinear feedbacks and time-lags in the interactions of biological species, and (2) stochastic forcings by a fluctuating environment. Because both of these phenomena can severely affect system survival, ecologists are confronted with the question of why complex ecosystems do, in fact, exist. The

D. L. DeAngelis; J. C. Waterhouse

1987-01-01

123

Ornithopter modeling for flight simulation  

Microsoft Academic Search

This paper presents the flight simulation of flapping-wing air vehicles (ornithopters) based on a refined flapping-wing aerodynamic model; the modified strip theory (MST). Compared with conventional types of micro air vehicles (MAVs), flapping MAVs show more complicated flight behaviors due to their complex wing motions and aerodynamics. In this paper, a flight dynamic model of an ornithopter is presented to

Jae-Hung Han; Jin-Young Lee; Dae-Kwan Kim

2008-01-01

124

Ecological niche modeling and differentiation of populations of *Triatoma brasiliensis* Neiva, 1911, the most important Chagas disease vector in northeastern Brazil (Hemiptera, Reduviidae, Triatominae)  

E-print Network

Ecologic niche modeling has allowed numerous advances in understanding the geographic ecology of species, including distributionalpredictions, distributionalchange and invasion, and assessment of ecologic differences. We ...

Costa, Jane; Peterson, A. Townsend; Beard, C. Ben

2002-11-01

125

Functional genomics of a model ecological species, Daphnia pulex.  

E-print Network

??Determining the molecular basis of heritable variation in complex, quantitative ecologically important traits will provide insight into the proximate mechanisms driving phenotypic and ecological variation,… (more)

Malcom, Jacob Wesley

2013-01-01

126

On the specification of structural equation models for ecological systems  

USGS Publications Warehouse

The use of structural equation modeling (SEM) is often motivated by its utility for investigating complex networks of relationships, but also because of its promise as a means of representing theoretical concepts using latent variables. In this paper, we discuss characteristics of ecological theory and some of the challenges for proper specification of theoretical ideas in structural equation models (SE models). In our presentation, we describe some of the requirements for classical latent variable models in which observed variables (indicators) are interpreted as the effects of underlying causes. We also describe alternative model specifications in which indicators are interpreted as having causal influences on the theoretical concepts. We suggest that this latter nonclassical specification (which involves another variable type-the composite) will often be appropriate for ecological studies because of the multifaceted nature of our theoretical concepts. In this paper, we employ the use of meta-models to aid the translation of theory into SE models and also to facilitate our ability to relate results back to our theories. We demonstrate our approach by showing how a synthetic theory of grassland biodiversity can be evaluated using SEM and data from a coastal grassland. In this example, the theory focuses on the responses of species richness to abiotic stress and disturbance, both directly and through intervening effects on community biomass. Models examined include both those based on classical forms (where each concept is represented using a single latent variable) and also ones in which the concepts are recognized to be multifaceted and modeled as such. To address the challenge of matching SE models with the conceptual level of our theory, two approaches are illustrated, compositing and aggregation. Both approaches are shown to have merits, with the former being preferable for cases where the multiple facets of a concept have widely differing effects in the system and the latter being preferable where facets act together consistently when influencing other parts of the system. Because ecological theory characteristically deals with concepts that are multifaceted, we expect the methods presented in this paper will be useful for ecologists wishing to use SEM. ?? 2010 by the Ecological Society of America.

Grace, J.B.; Michael, Anderson T.; Han, O.; Scheiner, S.M.

2010-01-01

127

Modeling abundance using N-mixture models: the importance of considering ecological mechanisms.  

PubMed

Predicting abundance across a species' distribution is useful for studies of ecology and biodiversity management. Modeling of survey data in relation to environmental variables can be a powerful method for extrapolating abundances across a species' distribution and, consequently, calculating total abundances and ultimately trends. Research in this area has demonstrated that models of abundance are often unstable and produce spurious estimates, and until recently our ability to remove detection error limited the development of accurate models. The N-mixture model accounts for detection and abundance simultaneously and has been a significant advance in abundance modeling. Case studies that have tested these new models have demonstrated success for some species, but doubt remains over the appropriateness of standard N-mixture models for many species. Here we develop the N-mixture model to accommodate zero-inflated data, a common occurrence in ecology, by employing zero-inflated count models. To our knowledge, this is the first application of this method to modeling count data. We use four variants of the N-mixture model (Poisson, zero-inflated Poisson, negative binomial, and zero-inflated negative binomial) to model abundance, occupancy (zero-inflated models only) and detection probability of six birds in South Australia. We assess models by their statistical fit and the ecological realism of the parameter estimates. Specifically, we assess the statistical fit with AIC and assess the ecological realism by comparing the parameter estimates with expected values derived from literature, ecological theory, and expert opinion. We demonstrate that, despite being frequently ranked the "best model" according to AIC, the negative binomial variants of the N-mixture often produce ecologically unrealistic parameter estimates. The zero-inflated Poisson variant is preferable to the negative binomial variants of the N-mixture, as it models an ecological mechanism rather than a statistical phenomenon and generates reasonable parameter estimates. Our results emphasize the need to include ecological reasoning when choosing appropriate models and highlight the dangers of modeling statistical properties of the data. We demonstrate that, to obtain ecologically realistic estimates of abundance, occupancy and detection probability, it is essential to understand the sources of variation in the data and then use this information to choose appropriate error distributions. PMID:19425427

Joseph, Liana N; Elkin, Ché; Martin, Tara G; Possinghami, Hugh P

2009-04-01

128

Recovery system simulation - Link modelization  

NASA Astrophysics Data System (ADS)

In the frame of the preliminary design studies, the dynamic analysis of the recovery system has to be done with a simulator which gives rapidly realistic results. This paper points out the importance of the modelization of the link between the parachute and the load by showing its contribution in the dynamic behavior of this complex system . An eight Degrees of Freedom (DOF) model is presented with its sensitivity to the driving parameters, based on physical considerations. All these considerations are illustrated by results of simulations done in the frame of MARSNET program.

Moulin, J.

129

An overview of APSIM, a model designed for farming systems simulation  

Microsoft Academic Search

The Agricultural Production Systems Simulator (APSIM) is a modular modelling framework that has been developed by the Agricultural Production Systems Research Unit in Australia. APSIM was developed to simulate biophysical process in farming systems, in particular where there is interest in the economic and ecological outcomes of management practice in the face of climatic risk. The paper outlines APSIM's structure

B. A. Keating; P. S. Carberry; G. L. Hammer; M. E. Probert; M. J. Robertson; D. Holzworth; N. I. Huth; J. N. G. Hargreaves; H. Meinke; Z. Hochman; G. McLean; K. Verburg; V. Snow; J. P. Dimes; M. Silburn; E. Wang; S. Brown; K. L. Bristow; S. Asseng; S. Chapman; R. L. McCown; D. M. Freebairn; C. J. Smith

2003-01-01

130

Ecological Modelling xxx (2005) xxxxxx Modelling carbon and water cycles in a beech forest  

E-print Network

Ecological Modelling xxx (2005) xxx­xxx Modelling carbon and water cycles in a beech forest Part I to assess the role of forested areas in the global carbon cycle and in the continental water balance. During with a carbon allocation model and coupled with a soil model. CASTANEA describes canopy photosynthesis

Boyer, Edmond

131

Automatic programming of simulation models  

NASA Technical Reports Server (NTRS)

The concepts of software engineering were used to improve the simulation modeling environment. Emphasis was placed on the application of an element of rapid prototyping, or automatic programming, to assist the modeler define the problem specification. Then, once the problem specification has been defined, an automatic code generator is used to write the simulation code. The following two domains were selected for evaluating the concepts of software engineering for discrete event simulation: manufacturing domain and a spacecraft countdown network sequence. The specific tasks were to: (1) define the software requirements for a graphical user interface to the Automatic Manufacturing Programming System (AMPS) system; (2) develop a graphical user interface for AMPS; and (3) compare the AMPS graphical interface with the AMPS interactive user interface.

Schroer, Bernard J.; Tseng, Fan T.; Zhang, Shou X.; Dwan, Wen S.

1990-01-01

132

Spray Dryers: Modeling and Simulation  

Microsoft Academic Search

This work presents a simulation study of the spray dryer operation using the whole milk suspension as the emulsion to be dried. Two approaches are used to obtain a general description of this operation. The first approach comprises a population balance model, in which drops and particles make up the discrete phase and are distributed into temporal compartments following their

V. S. Birchal; L. Huang; A. S. Mujumdar; M. L. Passos

2006-01-01

133

Recovery system simulation - Link modelization  

Microsoft Academic Search

In the frame of the preliminary design studies, the dynamic analysis of the recovery system has to be done with a simulator which gives rapidly realistic results. This paper points out the importance of the modelization of the link between the parachute and the load by showing its contribution in the dynamic behavior of this complex system . An eight

J. Moulin

1993-01-01

134

Process model of fire ecology and succession in a mixed-conifer forest  

SciTech Connect

A forest succession simulator, SILVA, has been developed for the mixed-conifer forest (seven major species) of the Sierra Nevada, California, to simulate the effects of fire on forest dynamics. SILVA is an extensive modification of a simulator for forests of the northeastern United States. The simulation includes the time development of the growth in tree diameter, tree height, and leaf-area index. Recruitment and mortality are modeled stochastically. Modifications include fire ecology, temporal seed-crop patterns, and seedling-survival factors unique to Sierra Nevada forests. The probability of mortality from fire is determined by the height of crown scorch (a function of fire intensity, diameter at breast height, and bark thickness). The model simulates the dynamic and structural responses of communities to many factors. For 500-yr simulations from an initial clear-cut condition, the time-averaged basal-area ratios of Pinus ponderosa to Abies concolor were 5.2:1 and 1:16 for elevations of 1524 m and 1829 m, respectively. At 1524 m, the ratio of P. ponderosa to A. concolor decreased 59% when fire suppression was introduced. Fire provides P. ponderosa with a strong competitive advantage. Its growth form and growth rate are significant factors in its ability to evade fire. Rank correlations of species were compared with data for stands of ponderosa pine and white fir. Correlations were significant at 1% and 10% levels, respectively.

Kercher, J.R.; Axelrod, M.C.

1984-01-01

135

Advanced Space Shuttle simulation model  

NASA Technical Reports Server (NTRS)

The effects of atmospheric turbulence in horizontal and near-horizontal flight during the return of the Space Shuttle are important for determining design, control, and pilot-in-the-loop effects. A nonrecursive model (based on vonKarman spectra) for atmospheric turbulence along the flight path of the Shuttle Orbiter has been developed which provides for simulation of instantaneous vertical and horizontal gusts at the vehicle center-of-gravity and also for simulation of instantaneous gust gradients. Based on this model the time series for gusts and gust gradients have been generated and stored on a series of magnetic tapes which are entitled Shuttle Simulation Turbulence Tapes (SSTT). The time series are designed to represent atmospheric turbulence from ground level to an altitude of 120,000 meters. A description of the turbulence generation procedure is provided, the results of validating the simulated turbulence are described, and conclusions and recommendations are presented. Appendices provide tabulated one-dimensional vonKarman spectra, a discussion of the minimum frequency simulated, and the results of spectral and statistical analyses of the SSTT.

Tatom, F. B.; Smith, S. R.

1982-01-01

136

From actors to agents in socio-ecological systems models  

PubMed Central

The ecosystem service concept has emphasized the role of people within socio-ecological systems (SESs). In this paper, we review and discuss alternative ways of representing people, their behaviour and decision-making processes in SES models using an agent-based modelling (ABM) approach. We also explore how ABM can be empirically grounded using information from social survey. The capacity for ABM to be generalized beyond case studies represents a crucial next step in modelling SESs, although this comes with considerable intellectual challenges. We propose the notion of human functional types, as an analogy of plant functional types, to support the expansion (scaling) of ABM to larger areas. The expansion of scope also implies the need to represent institutional agents in SES models in order to account for alternative governance structures and policy feedbacks. Further development in the coupling of human-environment systems would contribute considerably to better application and use of the ecosystem service concept. PMID:22144388

Rounsevell, M. D. A.; Robinson, D. T.; Murray-Rust, D.

2012-01-01

137

Ecologic niche modeling and spatial patterns of disease transmission  

E-print Network

algorithm, and the bottom panel shows the ability of ecologic niche modeling approaches to detect unknown patterns in biologic phenomena based on the relationship between known occurrences and spatial patterns in environmental parameters. GIS, geographic... spatial dynamics of vector insects and human dengue cases. Trans R Soc Trop Med Hyg. 2005;99:647–55. 18. Lopez-Cardenas J, González-Bravo FE, Salazar-Schettino PM, Gallaga-Solorzano JC, Ramírez-Barba E, Martínez-Mendez J, et al. Fine-scale predictions...

Peterson, A. Townsend

2006-12-01

138

Modelling dendritic ecological networks in space: anintegrated network perspective  

USGS Publications Warehouse

the context of stream ecology. Within this context, we summarise the key innovations of a new family of spatial statistical models that describe spatial relationships in DENs. Finally, we discuss how different network analyses may be combined to address more complex and novel research questions. While our main focus is streams, the taxonomy of network analyses is also relevant anywhere spatial patterns in both network and 2-D space can be used to explore the influence of multi-scale processes on biota and their habitat (e.g. plant morphology and pest infestation, or preferential migration along stream or road corridors).

Peterson, Erin E.; Ver Hoef, Jay M.; Isaak, Dan J.; Falke, Jeffrey A.; Fortin, Marie-Josée; Jordon, Chris E.; McNyset, Kristina; Monestiez, Pascal; Ruesch, Aaron S.; Sengupta, Aritra; Som, Nicholas; Steel, E. Ashley; Theobald, David M.; Torgersen, Christian E.; Wenger, Seth J.

2013-01-01

139

Modeling and Simulation for Safeguards  

SciTech Connect

The purpose of this talk is to give an overview of the role of modeling and simulation in Safeguards R&D and introduce you to (some of) the tools used. Some definitions are: (1) Modeling - the representation, often mathematical, of a process, concept, or operation of a system, often implemented by a computer program; (2) Simulation - the representation of the behavior or characteristics of one system through the use of another system, especially a computer program designed for the purpose; and (3) Safeguards - the timely detection of diversion of significant quantities of nuclear material. The role of modeling and simulation are: (1) Calculate amounts of material (plant modeling); (2) Calculate signatures of nuclear material etc. (source terms); and (3) Detector performance (radiation transport and detection). Plant modeling software (e.g. FACSIM) gives the flows and amount of material stored at all parts of the process. In safeguards this allow us to calculate the expected uncertainty of the mass and evaluate the expected MUF. We can determine the measurement accuracy required to achieve a certain performance.

Swinhoe, Martyn T. [Los Alamos National Laboratory

2012-07-26

140

Multiscale Stochastic Simulation and Modeling  

SciTech Connect

Acceleration driven instabilities of fluid mixing layers include the classical cases of Rayleigh-Taylor instability, driven by a steady acceleration and Richtmyer-Meshkov instability, driven by an impulsive acceleration. Our program starts with high resolution methods of numerical simulation of two (or more) distinct fluids, continues with analytic analysis of these solutions, and the derivation of averaged equations. A striking achievement has been the systematic agreement we obtained between simulation and experiment by using a high resolution numerical method and improved physical modeling, with surface tension. Our study is accompanies by analysis using stochastic modeling and averaged equations for the multiphase problem. We have quantified the error and uncertainty using statistical modeling methods.

James Glimm; Xiaolin Li

2006-01-10

141

Ecological Modelling 190 (2006) 231259 Maximum entropy modeling of species geographic distributions  

E-print Network

characteristic (ROC) analyses. The area under the ROC curve (AUC) was almost always higher for Maxent, indicating better discrimination of suitable versus unsuitable areas for the species. The Maxent modeling approachEcological Modelling 190 (2006) 231­259 Maximum entropy modeling of species geographic

Anderson, Robert P.

142

Ecological Modelling 167 (2003) 97114 Modeling white sturgeon movement in a reservoir  

E-print Network

Ecological Modelling 167 (2003) 97­114 Modeling white sturgeon movement in a reservoir: the effect and survival of white sturgeon (Acipenser transmontanus) in a reservoir subject to large spatial and temporal-QUAL-W2 model of Brownlee Reservoir, Idaho for a typical wet, normal, and dry hydrologic year. We compared

Jager, Henriette I.

143

Homogenization of Large-Scale Movement Models in Ecology  

USGS Publications Warehouse

A difficulty in using diffusion models to predict large scale animal population dispersal is that individuals move differently based on local information (as opposed to gradients) in differing habitat types. This can be accommodated by using ecological diffusion. However, real environments are often spatially complex, limiting application of a direct approach. Homogenization for partial differential equations has long been applied to Fickian diffusion (in which average individual movement is organized along gradients of habitat and population density). We derive a homogenization procedure for ecological diffusion and apply it to a simple model for chronic wasting disease in mule deer. Homogenization allows us to determine the impact of small scale (10-100 m) habitat variability on large scale (10-100 km) movement. The procedure generates asymptotic equations for solutions on the large scale with parameters defined by small-scale variation. The simplicity of this homogenization procedure is striking when compared to the multi-dimensional homogenization procedure for Fickian diffusion,and the method will be equally straightforward for more complex models. ?? 2010 Society for Mathematical Biology.

Garlick, M.J.; Powell, J.A.; Hooten, M.B.; McFarlane, L.R.

2011-01-01

144

Ecological Modelling 145 (2001) 197210 Modelling long-term peatland dynamics. I. Concepts,  

E-print Network

the existing conceptual and simulation models for peatlands and develops a model framework for simulating peatland dynamics in boreal regions. Clymo's peat bog growth model has been used as the conceptual foundation in published simulation models, but in these models the structural and functional layers of litter

Yu, Zicheng

145

Process-Driven Ecological Modeling for Landscape Change Analysis  

NASA Astrophysics Data System (ADS)

Landscape pattern is an important driver in ecosystem dynamics and can control system-level functions such as nutrient cycling, connectivity, biodiversity and carbon sequestration. However, the links between process, pattern and function remain ambiguous. Understanding the quantitative relationship between ecological processes and landscape pattern across temporal and spatial scales is vital for successful management and implementation of ecosystem-level projects. We used remote sensing imagery to develop critical landscape metrics to understand the factors influencing landscape change. Our study area, a coastal area in southwest Florida, is highly dynamic with critically eroding beaches and a range of natural and developed land cover types. Hurricanes in 2004 and 2005 caused a breach along the coast of North Captiva Island that filled in by 2010. We used a time series of light detection and ranging (lidar) elevation data and hyperspectral imagery from 2006 and 2010 to determine land cover changes. Landscape level metrics used included: Largest Patch Index, Class Area, Area-weighted mean area, Clumpiness, Area-weighted Contiguity Index, Number of Patches, Percent of landcover, Area-weighted Shape. Our results showed 1) 27% increase in sand/soil class as the channel repaired itself and shoreline was reestablished, 2) 40% decrease in the mudflat class area due to conversion to sand/soil and water, 3) 30% increase in non-wetland vegetation class as a result of new vegetation around the repaired channel, and 4) the water class only slightly increased though there was a marked increase in the patch size area. Thus, the smaller channels disappeared with the infilling of the channel, leaving much larger, less complex patches behind the breach. Our analysis demonstrated that quantification of landscape pattern is critical to linking patterns to ecological processes and understanding how both affect landscape change. Our proof of concept indicated that ecological processes can correlate to landscape pattern and that ecosystem function changes significantly as pattern changes. However, the number of links between landscape metrics and ecological processes are highly variable. Extensively studied processes such as biodiversity can be linked to numerous landscape metrics. In contrast, correlations between sediment cycling and landscape pattern have only been evaluated for a limited number of metrics. We are incorporating these data into a relational database linking landscape and ecological patterns, processes and metrics. The database will be used to parameterize site-specific landscape evolution models projecting how landscape pattern will change as a result of future ecosystem restoration projects. The model is a spatially-explicit, grid-based model that projects changes in community composition based on changes in soil elevations. To capture scalar differences in landscape change, local and regional landscape metrics are analyzed at each time step and correlated with ecological processes to determine how ecosystem function changes with scale over time.

Altman, S.; Reif, M. K.; Swannack, T. M.

2013-12-01

146

Application of QUAL2K Model to Assess Ecological Purification Technology for a Polluted River.  

PubMed

Industrialization and urbanization have caused water pollution and ecosystem degradation, especially in urban canals and rivers in China; accordingly, effective water quality improvement programs are needed. In this study, the Tianlai River in Jiangsu, China was taken as a research site, and a combination of ecological purification technologies consisting of biological rope, phytoremediation, and activated carbon were applied in a laboratory-scale study to examine degradation coefficients under dynamic water conditions. Coefficients were then input into the QUAL2K model to simulate various hypothetical scenarios and determine the minimum density of ecological purification combination and hydraulic retention time (HRT) to meet Grade V or IV of the China standard for surface water. The minimum densities for Grade V and IV were 1.6 times and 2 times the experimental density, while the minimum HRTs for Grade V and IV were 2.4 day and 3 day. The results of this study should provide a practical and efficient design method for ecological purification programs. PMID:25689997

Zhu, Wenting; Niu, Qian; Zhang, Ruibin; Ye, Rui; Qian, Xin; Qian, Yu

2015-01-01

147

Modeling socioeconomic and ecologic aspects of land-use change  

SciTech Connect

Land use change is one of the major factors affecting global environmental conditions. Prevalent types of land-use change include replacing forests with agriculture, mines or ranches; forest degradation from collection of firewood; and forest logging. A global effect of wide-scale deforestation is an increase in atmospheric carbon dioxide concentration, which may affect climate. Regional effects include loss of biodiversity and disruption of hydrologic regimes. Local effects include soil erosion, siltation and decreases in soil fertility, loss of extractive reserves, and disruption of indigenous people. Modeling land use change requires combining socioeconomic and ecological factors because socioeconomic forces frequently initiate land-use change and are affected by the subsequent ecological degradation. This paper describes a modeling system that integrates submodels of human colonization and impacts to estimate patterns and rates of deforestation under different immigration and land use scenarios. Immigration which follows road building or paving is a major factor in the rapid deforestation of previously inaccessible areas. Roads facilitate colonization, allow access for large machines, and provide transportation routes for mort of raw materials and produce.

Dale, V.H.; Pedlowski, M.A.; O'Neill, R.V.; Southworth, F.

1992-01-01

148

Ecological Footprint Model Using the Support Vector Machine Technique  

PubMed Central

The per capita ecological footprint (EF) is one of the most widely recognized measures of environmental sustainability. It aims to quantify the Earth's biological resources required to support human activity. In this paper, we summarize relevant previous literature, and present five factors that influence per capita EF. These factors are: National gross domestic product (GDP), urbanization (independent of economic development), distribution of income (measured by the Gini coefficient), export dependence (measured by the percentage of exports to total GDP), and service intensity (measured by the percentage of service to total GDP). A new ecological footprint model based on a support vector machine (SVM), which is a machine-learning method based on the structural risk minimization principle from statistical learning theory was conducted to calculate the per capita EF of 24 nations using data from 123 nations. The calculation accuracy was measured by average absolute error and average relative error. They were 0.004883 and 0.351078% respectively. Our results demonstrate that the EF model based on SVM has good calculation performance. PMID:22291949

Ma, Haibo; Chang, Wenjuan; Cui, Guangbai

2012-01-01

149

Simulating spin models on GPU  

NASA Astrophysics Data System (ADS)

Over the last couple of years it has been realized that the vast computational power of graphics processing units (GPUs) could be harvested for purposes other than the video game industry. This power, which at least nominally exceeds that of current CPUs by large factors, results from the relative simplicity of the GPU architectures as compared to CPUs, combined with a large number of parallel processing units on a single chip. To benefit from this setup for general computing purposes, the problems at hand need to be prepared in a way to profit from the inherent parallelism and hierarchical structure of memory accesses. In this contribution I discuss the performance potential for simulating spin models, such as the Ising model, on GPU as compared to conventional simulations on CPU.

Weigel, Martin

2011-09-01

150

A model based on Biomimicry to enhance ecologically sustainable design  

Microsoft Academic Search

Sustainable development has become a central part of the agenda in the building design professions; however, in recent years, the concept of ecologically sustainable development has gained ground which aims to balance both economic and environmental facets of sustainability. This has necessitated new approaches to ecological sustainable design that includes ecological facets to design. Such a design approach that draws

Arosha Gamage; Richard Hyde

2012-01-01

151

Evolutionary model on market ecology of investors and investments  

NASA Astrophysics Data System (ADS)

The interactions between investors and investments are of significant importance to understand the dynamics of financial markets. An evolutionary model is proposed to investigate the dynamic behaviors of investors and investments in a market ecology. The investors are divided into two groups, active ones and passive ones, distinguished by different selection capabilities based on the partial information, while the investments are simply categorized as good ones and bad ones. Without external influence, the system consisting of both investors and investments can self-organize to a quasi-stationary state according to their own strategies associating with the gains of market information. The model suggests that the partial information asymmetry of investors and various qualities of investments commonly give rise to a diverse dynamic behavior of the system by quantifying the fraction of active investors and of good investment at the quasi-stationary state.

Gao, Ya-Chun; Cai, Shi-Min; Lü, Linyuan; Wang, Bing-Hong

2013-08-01

152

Healthcare Policy Modeling, Simulation, and Analysis: COMPARE  

E-print Network

Healthcare Policy Analysis Modeling, Simulation, and Analysis: COMPARE Challenge Decision and Information Sciences Division Modeling, Simulation, and Visualization Group Healthcare and possible healthcare reform are important issues for the American public, the healthcare industry, policy analysts

153

Predicting the distribution of Sasquatch in western North America: anything goes with ecological niche modelling  

Microsoft Academic Search

The availability of user-friendly software and publicly available biodiversity databases has led to a rapid increase in the use of ecological niche modelling to predict species distributions. A potential source of error in publicly available data that may affect the accuracy of ecological niche models (ENMs), and one that is difficult to correct for, is incorrect (or incomplete) taxonomy. Here

J. D. Lozier; P. Aniello; M. J. Hickerson

2009-01-01

154

Spatial Modeling of Seedbed Microclimate and the Utility of Ecological Site Descriptions for Rangeland Restoration Planning  

E-print Network

for Rangeland Restoration Planning Alex R. Boehm1, Stuart P. Hardegree1, Nancy F. Glenn2 and Gerald NSpatial Modeling of Seedbed Microclimate and the Utility of Ecological Site Descriptions Seedbed Modeling Hydrothermal Germination Response Ecological indices of seasonal and annual variability

155

Research on the sustainable development capacity based on ecological footprint model in the Northeast of China from 1999?2008  

Microsoft Academic Search

Taking the Northeast as the example, this paper put forward a model for evaluating regional sustainable development capacity which was based on ecological footprint method. The result was shown that ecological footprint per capita, ecological carrying capacity per capita and ecological deficit per capita were still rising up, it indicated that the Northeast was in unsustainable development. But GDP footprint

Wu Di; Chunyou Wu; Dawei Xu

2010-01-01

156

SEMI Modeling and Simulation Roadmap  

SciTech Connect

With the exponential growth in the power of computing hardware and software, modeling and simulation is becoming a key enabler for the rapid design of reliable Microsystems. One vision of the future microsystem design process would include the following primary software capabilities: (1) The development of 3D part design, through standard CAD packages, with automatic design rule checks that guarantee the manufacturability and performance of the microsystem. (2) Automatic mesh generation, for 3D parts as manufactured, that permits computational simulation of the process steps, and the performance and reliability analysis for the final microsystem. (3) Computer generated 2D layouts for process steps that utilize detailed process models to generate the layout and process parameter recipe required to achieve the desired 3D part. (4) Science-based computational tools that can simulate the process physics, and the coupled thermal, fluid, structural, solid mechanics, electromagnetic and material response governing the performance and reliability of the microsystem. (5) Visualization software that permits the rapid visualization of 3D parts including cross-sectional maps, performance and reliability analysis results, and process simulation results. In addition to these desired software capabilities, a desired computing infrastructure would include massively parallel computers that enable rapid high-fidelity analysis, coupled with networked compute servers that permit computing at a distance. We now discuss the individual computational components that are required to achieve this vision. There are three primary areas of focus: design capabilities, science-based capabilities and computing infrastructure. Within each of these areas, there are several key capability requirements.

Hermina, W.L.

2000-10-02

157

A tutorial view of simulation model development  

Microsoft Academic Search

Working from the background of simulation language developments, we develop an understanding of the current status of simulation model development. Factors characterizing the current status include a shift in emphasis from program to model, more commitment to modeling tools, and the lingering impedance of simulation language isolation. Current and future needs are identified. Specific approaches to meeting these needs are

Richard E. Nance

1983-01-01

158

Collective philanthropy: describing and modeling the ecology of giving.  

PubMed

Reflective of income and wealth distributions, philanthropic gifting appears to follow an approximate power-law size distribution as measured by the size of gifts received by individual institutions. We explore the ecology of gifting by analysing data sets of individual gifts for a diverse group of institutions dedicated to education, medicine, art, public support, and religion. We find that the detailed forms of gift-size distributions differ across but are relatively constant within charity categories. We construct a model for how a donor's income affects their giving preferences in different charity categories, offering a mechanistic explanation for variations in institutional gift-size distributions. We discuss how knowledge of gift-sized distributions may be used to assess an institution's gift-giving profile, to help set fundraising goals, and to design an institution-specific giving pyramid. PMID:24983864

Gottesman, William L; Reagan, Andrew James; Dodds, Peter Sheridan

2014-01-01

159

Collective Philanthropy: Describing and Modeling the Ecology of Giving  

PubMed Central

Reflective of income and wealth distributions, philanthropic gifting appears to follow an approximate power-law size distribution as measured by the size of gifts received by individual institutions. We explore the ecology of gifting by analysing data sets of individual gifts for a diverse group of institutions dedicated to education, medicine, art, public support, and religion. We find that the detailed forms of gift-size distributions differ across but are relatively constant within charity categories. We construct a model for how a donor's income affects their giving preferences in different charity categories, offering a mechanistic explanation for variations in institutional gift-size distributions. We discuss how knowledge of gift-sized distributions may be used to assess an institution's gift-giving profile, to help set fundraising goals, and to design an institution-specific giving pyramid. PMID:24983864

Gottesman, William L.; Reagan, Andrew James; Dodds, Peter Sheridan

2014-01-01

160

Ecological Engineering 20 (2003) 379387 Engineering role models: do non-human  

E-print Network

the answers? A.D. Rosemond, C.B. Anderson Institute of Ecology, University of Georgia, 18 Ecology Building-mail address: rosemond@sparc.ecology.uga.edu (A.D. Rosemond). have positive role models. Seeing an alternative Elsevier B.V. All rights reserved. doi:10.1016/j.ecoleng.2003.09.002 #12;380 A.D. Rosemond, C.B. Anderson

Rosemond, Amy Daum

161

Operations planning simulation: Model study  

NASA Technical Reports Server (NTRS)

The use of simulation modeling for the identification of system sensitivities to internal and external forces and variables is discussed. The technique provides a means of exploring alternate system procedures and processes, so that these alternatives may be considered on a mutually comparative basis permitting the selection of a mode or modes of operation which have potential advantages to the system user and the operator. These advantages are measurements is system efficiency are: (1) the ability to meet specific schedules for operations, mission or mission readiness requirements or performance standards and (2) to accomplish the objectives within cost effective limits.

1974-01-01

162

Simulation, Modelling and Visualisation: Toolkits for Building Simulated Worlds.  

E-print Network

planted at the centre of the image is gradually grown by releasing "walker" particles around about it of on-going simulation projects making use of field equation models, micro- scopic entity models to simulate real world textures and patterms that arise from physical processes and systems. The background

Hawick, Ken

163

Georeferenced model simulations efficiently support targeted monitoring  

NASA Astrophysics Data System (ADS)

The European Water Framework Directive (WFD) demands the good ecological and chemical status of surface waters. To meet the definition of good chemical status of the WFD surface water concentrations of priority pollutants must not exceed established environmental quality standards (EQS). Surveillance of the concentrations of numerous chemical pollutants in whole river basins by monitoring is laborious and time-consuming. Moreover, measured data do often not allow for immediate source apportionment which is a prerequisite for defining promising reduction strategies to be implemented within the programme of measures. In this context, spatially explicit model approaches are highly advantageous because they provide a direct link between local point emissions (e.g. treated wastewater) or diffuse non-point emissions (e.g. agricultural runoff) and resulting surface water concentrations. Scenario analyses with such models allow for a priori investigation of potential positive effects of reduction measures such as optimization of wastewater treatment. The geo-referenced model GREAT-ER (Geography-referenced Regional Exposure Assessment Tool for European Rivers) has been designed to calculate spatially resolved averaged concentrations for different flow conditions (e.g. mean or low flow) based on emission estimations for local point source emissions such as treated effluents from wastewater treatment plants. The methodology was applied to selected pharmaceuticals (diclofenac, sotalol, metoprolol, carbamazepin) in the Main river basin in Germany (approx. 27,290 km²). Average concentrations of the compounds were calculated for each river reach in the whole catchment. Simulation results were evaluated by comparison with available data from orienting monitoring and used to develop an optimal monitoring strategy for the assessment of water quality regarding micropollutants at the catchment scale.

Berlekamp, Jürgen; Klasmeier, Jörg

2010-05-01

164

Integrated Bayesian network framework for modeling complex ecological issues.  

PubMed

The management of environmental problems is multifaceted, requiring varied and sometimes conflicting objectives and perspectives to be considered. Bayesian network (BN) modeling facilitates the integration of information from diverse sources and is well suited to tackling the management challenges of complex environmental problems. However, combining several perspectives in one model can lead to large, unwieldy BNs that are difficult to maintain and understand. Conversely, an oversimplified model may lead to an unrealistic representation of the environmental problem. Environmental managers require the current research and available knowledge about an environmental problem of interest to be consolidated in a meaningful way, thereby enabling the assessment of potential impacts and different courses of action. Previous investigations of the environmental problem of interest may have already resulted in the construction of several disparate ecological models. On the other hand, the opportunity may exist to initiate this modeling. In the first instance, the challenge is to integrate existing models and to merge the information and perspectives from these models. In the second instance, the challenge is to include different aspects of the environmental problem incorporating both the scientific and management requirements. Although the paths leading to the combined model may differ for these 2 situations, the common objective is to design an integrated model that captures the available information and research, yet is simple to maintain, expand, and refine. BN modeling is typically an iterative process, and we describe a heuristic method, the iterative Bayesian network development cycle (IBNDC), for the development of integrated BN models that are suitable for both situations outlined above. The IBNDC approach facilitates object-oriented BN (OOBN) modeling, arguably viewed as the next logical step in adaptive management modeling, and that embraces iterative development. The benefits of OOBN modeling in the environmental community have not yet been fully realized in environmental management research. The IBNDC approach to BN modeling is described in the context of 2 case studies. The first is the initiation of blooms of Lyngbya majuscula, a blue-green algae, in Deception Bay, Australia where 3 existing models are being integrated, and the second case study is the viability of the free-ranging cheetah (Acinonyx jubatus) population in Namibia where an integrated OOBN model is created consisting of 3 independent subnetworks, each describing a particular aspect of free-ranging cheetah population conservation. PMID:21853523

Johnson, Sandra; Mengersen, Kerrie

2012-07-01

165

Identifying Droughts by Modeling the Hydrologic and Ecologic Responses in the Medjerda River Basin, Tunisia  

NASA Astrophysics Data System (ADS)

Drought brings severe damage to water and agricultural resources, and both of hydrological and ecological responses are important for understanding droughts. However, the ecological contributions to drought characteristics at the basin scale have not been quantified. To address this issue, we developed an eco-hydrological model that can calculate vegetation dynamics as a diagnostic valuable in a distributed-hydrological modeling framework and identified different drought types in the Medjerda River Basin where drought is a predominant issue. From the inputs and outputs of the model, we calculate drought indices for different drought types. The model shows reliable accuracy in reproducing the observed river discharge and the satellite observed leaf area index in the long-term (19-year) simulation. Moreover, the drought index calculated from model estimated annual peak of leaf area index is well correlated (correlation coefficient; r = 0.89; see Figure) with drought index from nationwide annual crop production, which show the modeled leaf area index has enough capacity to reproducing agricultural droughts that can be related with historical food shortage on 1988-1989 and 1993-1995. Our model can estimate vegetation dynamics and water cycle simultaneously in the enough accuracy to analyze the basin-scale agricultural and hydrological droughts separately. We clarify that vegetation dynamics has quicker response to meteorological droughts than river discharge and groundwater dynamics in Medjerda River Basin because vegetation dynamics is sensitive to soil moisture in surface layers while soil moisture in deeper layers strongly contributes to stream flow and depth of groundwater level. Therefore, historical agricultural droughts predominantly occurred prior to hydrological droughts and in the 1988-1989 drought, the hydrological drought lasted much longer even after crop production recovered. Standardized anomaly index (SA) for estimated annual maximum leaf area index (green line) from model and observed annual crop production in Tunisia (orange line).

Sawada, Y.; Koike, T.; Jaranilla-sanchez, P. A.

2013-12-01

166

Theoretically exploring direct and indirect chemical effects across ecological and exposure scenarios using mechanistic fate and effects modelling.  

PubMed

Predicting ecosystem response to chemicals is a complex problem in ecotoxicology and a challenge for risk assessors. The variables potentially influencing chemical fate and exposure define the exposure scenario while the variables determining effects at the ecosystem level define the ecological scenario. In absence of any empirical data, the objective of this paper is to present simulations by a fugacity-based fate model and a differential equation-based ecosystem model to theoretically explore how direct and indirect effects on invertebrate shallow pond communities vary with changing ecological and exposure scenarios. These simulations suggest that direct and indirect effects are larger in mesotrophic systems than in oligotrophic systems. In both trophic states, interaction strength (quantified using grazing rates) was suggested a more important driver for the size and recovery from direct and indirect effects than immigration rate. In general, weak interactions led to smaller direct and indirect effects. For chemicals targeting mesozooplankton only, indirect effects were common in (simple) food-chains but rare in (complex) food-webs. For chemicals directly affecting microzooplankton, the dominant zooplankton group in the modelled community, indirect effects occurred both in food-chains and food-webs. We conclude that the choice of the ecological and exposure scenarios in ecotoxicological modelling efforts needs to be justified because of its influence on the prevalence and magnitude of the predicted effects. Overall, more work needs to be done to empirically test the theoretical expectations formulated here. PMID:25454235

De Laender, F; Morselli, M; Baveco, H; Van den Brink, P J; Di Guardo, A

2015-01-01

167

Sensitivity analysis as an aid in modelling and control of (poorly-defined) ecological systems. [closed ecological systems  

NASA Technical Reports Server (NTRS)

A literature review of the use of sensitivity analyses in modelling nonlinear, ill-defined systems, such as ecological interactions is presented. Discussions of previous work, and a proposed scheme for generalized sensitivity analysis applicable to ill-defined systems are included. This scheme considers classes of mathematical models, problem-defining behavior, analysis procedures (especially the use of Monte-Carlo methods), sensitivity ranking of parameters, and extension to control system design.

Hornberger, G. M.; Rastetter, E. B.

1982-01-01

168

Hydro-Ecological Modeling of Lower Mississippi River  

NASA Astrophysics Data System (ADS)

The Mississippi River is one of largest rivers in the world and has major economic, environmental, ecological, and industrial values not only to Louisiana but also to the entire United States. At present, the Mississippi River Delta area of coastal Louisiana is being deprived of practically all the sediment (about 220 million tons annually) that the river is transporting to the Gulf of Mexico. Therefore, alternative solutions to recover or re-direct portion of this massive amount of valuable sediment to benefit the restoration of Louisiana coastal lands should be carefully investigated. In order for such investigation to be successful, the impact of management and restoration projects on the conditions of the River (supply side) and on the surrounding wetland and water bodies (demand side) should be considered. The objective of this study is to develop a three-dimensional (3D) model for portion of the Lower Mississippi River. The model should provide detailed information on the spatial and temporal patterns of the river's hydrodynamics, salinity, sediment, and water quality parameters. The model will serve as an excellent overall management and analysis tool for the Lower Mississippi River. The model will provide detailed information on the availability of fresh water and sediment for diversion to surrounding wetlands; and determine quantitatively the impact of exiting and planned diversion projects on the dynamics of the river.

Meselhe, E. A.; Habib, E. H.; Griborio, A.; McCorquodale, J. A.; Georgiou, I. Y.; Stronach, J.; Campanella, R.

2005-05-01

169

A modular BLSS simulation model  

NASA Technical Reports Server (NTRS)

A bioregenerative life support system (BLSS) for extraterrestrial use will be faced with coordination problems more acute than those in any ecosystem found on Earth. A related problem in BLSS design is providing an interface between the various life support processors, one that will allow for their coordination while still allowing for system expansion. A modular model is presented of a BLSS that interfaces system processors only with the material storage reservoirs, allowing those reservoirs to act as the principal buffers in the system and thus minimizing difficulties with processor coordination. The modular nature of the model allows independent development of the detailed submodels that exist within the model framework. Using this model, BLSS dynamics were investigated under normal conditions and under various failure modes. Partial and complete failures of various components, such as the waste processors or the plants themselves, drive transient responses in the model system, allowing the examination of the effectiveness of the system reservoirs as buffers. The results from simulations help to determine control strategies and BLSS design requirements. An evolved version could be used as an interactive control aid in a future BLSS.

Rummel, John D.; Volk, Tyler

1987-01-01

170

Improving ecological niche models by data mining large environmental datasets for surrogate models  

Microsoft Academic Search

WhyWhere is a new ecological niche modeling (ENM) algorithm for mapping and explaining the distribution of species. The algorithm uses image processing methods to efficiently sift through large amounts of data to find the few variables that best predict species occurrence. The purpose of this paper is to describe and justify the main parameterizations and to show preliminary success at

David R. B. Stockwell

2005-01-01

171

Improving ecological niche models by data mining large environmental datasets for surrogate models  

Microsoft Academic Search

WhyWhere is a new ecological niche modeling (ENM) algorithm for mapping and explaining the distribution of species. The algorithm uses image processing methods to efficiently sift through large amounts of data to find the few variables that best predict species occurrence. The purpose of this paper is to describe and justify the main parameterizations and to show preliminary success at

David R. B. Stockwell

2006-01-01

172

A primer for data assimilation with ecological models using Markov Chain Monte Carlo (MCMC).  

PubMed

Data assimilation, or the fusion of a mathematical model with ecological data, is rapidly expanding knowledge of ecological systems across multiple spatial and temporal scales. As the amount of ecological data available to a broader audience increases, quantitative proficiency with data assimilation tools and techniques will be an essential skill for ecological analysis in this data-rich era. We provide a data assimilation primer for the novice user by (1) reviewing data assimilation terminology and methodology, (2) showcasing a variety of data assimilation studies across the ecological, environmental, and atmospheric sciences with the aim of gaining an understanding of potential applications of data assimilation, and (3) applying data assimilation in specific ecological examples to determine the components of net ecosystem carbon uptake in a forest and also the population dynamics of the mayfly (Hexagenia limbata, Serville). The review and examples are then used to provide guiding principles to newly proficient data assimilation practitioners. PMID:21874332

Zobitz, J M; Desai, A R; Moore, D J P; Chadwick, M A

2011-11-01

173

The Future of Eurasian Boreal Forests: Ecological Modeling Projections in the Russian Federation  

NASA Astrophysics Data System (ADS)

Ecological modeling is one of the primary methodologies for making predictions on future changes in forested ecosystems such as those occurring in Northern Eurasia and Siberia. In particular, combining ecological modeling with global circulation model simulation outputs is a method in which scientists can forecast the impact of climate change on biodiversity (Thuiller, 2007) as well as the forested landscape. Dynamic global vegetation models (DGVMs) have been designed for specifically this purpose, however, these vegetation models run at large spatial scales and as a result make predictions that are highly uncertain (Purves and Pacala, 2008). In previous papers, we discussed the FAREAST forest gap model and its ability to accurately predict boreal forest dynamics at smaller scales and higher resolution than DGVMs. This presentation investigates the use of the FAREAST gap model, modified for spatial expansion to cover the entire country of Russia, to predict future land cover trends under different warming scenarios. The poster provides the initial framework for the project, as well as some initial results. The collection of input variables needed by FAREAST to model the Russian continent will involve collaboration with the Russian Academy of Sciences (CEPF). Together we have developed a framework in which to amalgamate both original (temperature, precipitation, soil values) parameters as well as new parameters (fire probability, logging probability) into a GIS database that can be integrated with the FAREAST model. This framework will be capable of providing visual and graphical output for interpretation of large model runs. In order to ensure accuracy in FAREAST's ability to simulate the current environment, a run of the model under current-day conditions will be compared to recent remote sensing land cover maps. The GLC2000 land cover classification project (EU JRC) will be the primary validation method with additional validation through other biophysical variables extracted by remote sensing such as biomass and LAI. These steps will ensure that the model's predictions of forests under future climate will be acceptable. The updated and expanded version of FAREAST will be run for several future climate scenarios using projections from the PCMDI. Comparison between future and present FAREAST runs of the Russian federation will provide information regarding potential changes of the region's forests and land cover. Implications for biodiversity and climate interactions from these results will be analyzed, as well as socio-economic impacts for regional and local economies.

Lutz, D.; Shugart, H.

2008-12-01

174

Simulation model development in information security education  

Microsoft Academic Search

The value of modeling and simulation for education, training, and testing in information security has been documented in several studies. In this paper, we suggest that it is important not only to include the general use of simulation in various courses of the security curriculum, but also to include the theory and development of simulation models. We describe briefly the

Jose M. Garrido; Tridib Bandyopadhyay

2009-01-01

175

Noise Simulation Modeling for Airport Noise Analysis  

Microsoft Academic Search

Noise simulation modeling is now feasible for assessing the noise impacts of airports since computational capabilities have increased. The current aviation noise models use integrated exposure assumptions to calculate the overall noise exposure. However, this assumption greatly restricts the ability to model the effects of terrain, barriers, weather, and aircraft directivity. Noise simulation models, such as NMSim, provide more accurate

J. Micah Downing

176

Use of enclosed model ecosystems in soil ecology: a bias towards laboratory research  

Microsoft Academic Search

Enclosed model ecosystems, or microcosms, have become a major research tool in soil ecology. Due to the speed, statistical power and mechanistic insights attainable with laboratory-based microcosm experiments, these have added considerably to our ecological knowledge. However, soil ecologists agree that, due to problems of scale and artificiality, microcosm research should be carried out in the context of appropriately scaled

C. Kampichler; A. Bruckner; E. Kandeler

2001-01-01

177

Testing Natureserve's ecological integrity assessment model in Michigan and Indiana  

EPA Science Inventory

NatureServe, in partnership with member programs from the Natural Heritage Network and federal agencies, has developed an assessment of ecosystems condition, structured around the concept of ecological integrity. Our multi-metric approach for our Ecological Integrity Assessment m...

178

Interdisciplinary Industrial Ecology Education: Recommendations for an Inclusive Pedagogical Model  

ERIC Educational Resources Information Center

Industrial ecology education is being developed and delivered predominantly within the domains of engineering and management. Such an approach could prove somewhat limiting to the broader goal of developing industrial ecology as an integrated knowledge base inclusive of diverse disciplines, contributing to sustainable development. This paper…

Sharma, Archana

2009-01-01

179

Propulsion System Modeling and Simulation  

NASA Technical Reports Server (NTRS)

The Aerospace Systems Design Laboratory at the School of Aerospace Engineering in Georgia Institute of Technology has developed a core competency that enables propulsion technology managers to make technology investment decisions substantiated by propulsion and airframe technology system studies. This method assists the designer/manager in selecting appropriate technology concepts while accounting for the presence of risk and uncertainty as well as interactions between disciplines. This capability is incorporated into a single design simulation system that is described in this paper. This propulsion system design environment is created with a commercially available software called iSIGHT, which is a generic computational framework, and with analysis programs for engine cycle, engine flowpath, mission, and economic analyses. iSIGHT is used to integrate these analysis tools within a single computer platform and facilitate information transfer amongst the various codes. The resulting modeling and simulation (M&S) environment in conjunction with the response surface method provides the designer/decision-maker an analytical means to examine the entire design space from either a subsystem and/or system perspective. The results of this paper will enable managers to analytically play what-if games to gain insight in to the benefits (and/or degradation) of changing engine cycle design parameters. Furthermore, the propulsion design space will be explored probabilistically to show the feasibility and viability of the propulsion system integrated with a vehicle.

Tai, Jimmy C. M.; McClure, Erin K.; Mavris, Dimitri N.; Burg, Cecile

2002-01-01

180

Editorial article Industrial ecology in the strategic sustainable development model: strategic applications of industrial ecology  

Microsoft Academic Search

In a recent article of this journal, Robert et al. (Journal of Cleaner Production 10 (2002) 197) define five hierarchical and inter- dependent levels for a systems approach for strategic sustainable development (SSD) to move toward the desired outcome, the state of sustainability. This paper evaluates the concept of industrial ecology (IE) by considering its application and use in terms

Jouni Korhonen

181

Industrial ecology in the strategic sustainable development model: strategic applications of industrial ecology  

Microsoft Academic Search

In a recent article of this journal, Robert et al. [Journal of Cleaner Production 10 (2002) 197] define five hierarchical and interdependent levels for a systems approach for strategic sustainable development (SSD) to move toward the desired outcome, the state of sustainability. This paper evaluates the concept of industrial ecology (IE) by considering its application and use in terms of

Jouni Korhonen

2004-01-01

182

Multi-Model Investigation of Ecological Response to Extreme Events  

NASA Astrophysics Data System (ADS)

Extreme events such as droughts and heat waves have serious and damaging impacts on terrestrial processes. Under climate change, these extreme weather events are likely to shift in both magnitude and frequency at regional and local scales. The resulting interactions and feedbacks between the terrestrial and atmosphere systems could lead to non-linear and/or threshold responses in the eco-climate system, and raise a concern as to the resiliency of natural as well as managed ecosystems under extreme changes. This study investigates the response of ecosystem to droughts at different time scales and magnitudes. Four land surface models with different bio-geophysical parameterizations and representations are used to simulate soil-canopy processes, such as evapotranspiration, during these extreme events. The Terrestrial Ecosystem Model (TEM) is a process-based ecosystem model that uses spatially referenced information on climate, elevation, soils, vegetation and water availability to make monthly estimates of vegetation and soil carbon and nitrogen fluxes and pool sizes. There are two versions of TEM model, the TEM-Hydro daily model and the TEM monthly model. The Advanced Canopy-Atmosphere-Soil Algorithm (ACASA) is a multi-layered land surface model based on eddy-covariance theory to calculate the biosphere-atmosphere exchanges of carbon dioxide, water, and momentums. The Community Land Model (CLM) is a community-based model consists of biogeophysics, hydrological cycle, biogeochemistry and dynamic vegetation. Model simulations are evaluated using the biogeophysical and micrometeorological field observations from the AmeriFlux sites across the US. Preliminary results indicate that during a severe drought the link between evapotranspiration and Net Ecosystem Productivity (NEP) in the models is weaker than what observations indicate. This and other interpretations are presented and discussed.

Xu, L.; Kicklighter, D. W.; Felzer, B. S.; Schlosser, C. A.; Chang, K.; Paw U, K.

2013-12-01

183

Assessing the trophic position and ecological role of squids in marine ecosystems by means of food-web models  

NASA Astrophysics Data System (ADS)

We synthesized available information from ecological models at local and regional scales to obtain a global picture of the trophic position and ecological role of squids in marine ecosystems. First, static food-web models were used to analyze basic ecological parameters and indicators of squids: biomass, production, consumption, trophic level, omnivory index, predation mortality diet, and the ecological role. In addition, we developed various dynamic temporal simulations using two food-web models that included squids in their parameterization, and we investigated potential impacts of fishing pressure and environmental conditions for squid populations and, consequently, for marine food webs. Our results showed that squids occupy a large range of trophic levels in marine food webs and show a large trophic width, reflecting the versatility in their feeding behaviors and dietary habits. Models illustrated that squids are abundant organisms in marine ecosystems, and have high growth and consumption rates, but these parameters are highly variable because squids are adapted to a large variety of environmental conditions. Results also show that squids can have a large trophic impact on other elements of the food web, and top-down control from squids to their prey can be high. In addition, some squid species are important prey of apical predators and may be keystone species in marine food webs. In fact, we found strong interrelationships between neritic squids and the populations of their prey and predators in coastal and shelf areas, while the role of squids in open ocean and upwelling ecosystems appeared more constrained to a bottom-up impact on their predators. Therefore, large removals of squids will likely have large-scale effects on marine ecosystems. In addition, simulations confirm that squids are able to benefit from a general increase in fishing pressure, mainly due to predation release, and quickly respond to changes triggered by the environment. Squids may thus be very sensitive to the effects of fishing and climate change.

Coll, Marta; Navarro, Joan; Olson, Robert J.; Christensen, Villy

2013-10-01

184

BOTTOMLAND HARDWOODS IN THE TIFTON-VIDIALIA UPLAND OF GEORGIA: A CONCEPTUAL MODEL FOR ECOLOGICAL RISK ASSESSMENT  

EPA Science Inventory

Ecology risk assessment provides a methodology for evaluating threats to ecosystem function associated with environmental perturbations or stressors. his report documents the development of a conceptual model for assessing the ecological risk to the water quality function (WQF) o...

185

A model intercomparison for stochastic simulation of temporal precipitation  

NASA Astrophysics Data System (ADS)

Stochastic models, based on diverse stochastic processes, have been applied in the last decades for the simulation of precipitation time series. Different models target a good reproduction of statistical properties of precipitation across a specific range of temporal scales. The choice of the statistical properties and the respective range of scales are frequently dictated by the purpose for which each model is built. Despite the large variety of stochastic precipitation modeling tools, an intercomparison has been rarely attempted. Moreover, a common practice is to validate a stochastic model only for the statistical properties for which it has been developed to perform well. It is our opinion that this practice may have negative implications, especially when stochastic models are used in hydrology as a black box. In this study we present an extensive comparison among some of the most widely applied stochastic precipitation models. Models based on point processes (e.g. Neyman-Scott rectangular pulses model, Bartlett-Lewis rectangular pulses model), Mutiplicative Random Cascades (e.g. canonical and microcanonical MRC), Markov chains, scaling processes and their combinations (e.g. Paschalis et al., 2013, Advances in Water resources) are used in order to assess their efficiency for a number of stations belonging to different climates, spanning from semiarid to wet oceanic. A complete model validation is performed, taking into account all the essential statistical properties of precipitation (e.g. probability distribution, extremes, autocorrelation, intermittency, etc.) for a wide range of temporal scales relevant for hydrological and ecological applications. The overall goal is to identify the general patterns of the strengths and weaknesses of the various modeling tools, and to provide insights for generally applicable guidelines in the model selection dependent on the specific hydrological/ecological application.

Paschalis, Athanasios; Molnar, Peter; Fatichi, Simone; Burlando, Paolo

2014-05-01

186

Aeroacoustic simulation for phonation modeling  

NASA Astrophysics Data System (ADS)

The phonation process occurs as air expelled from the lungs creates a pressure drop and a subsequent air flow across the larynx. The fluid-structure interaction between the turbulent air flow and oscillating vocal folds, combined with additional resonance in the oral and nasal cavities, creates much of what we hear in the human voice. As many voice-related disorders can be traced to irregular vocal tract shape or motion, it is important to understand in detail the physics involved in the phonation process. To numerically compute the physics of phonation, a solver must be able to accurately model acoustic airflow through a moving domain. The open-source CFD package OpenFOAM is currently being used to evaluate existing solvers against simple acoustic test cases, including an open-ended resonator and an expansion chamber, both of which utilize boundary conditions simulating acoustic sources as well as anechoic termination. Results of these test cases will be presented and compared with theory, and the future development of a three-dimensional vocal tract model and custom-mode acoustic solver will be discussed.

Irwin, Jeffrey; Hanford, Amanda; Craven, Brent; Krane, Michael

2011-11-01

187

Model simulations for Europa's atmosphere  

NASA Astrophysics Data System (ADS)

Europa's tenuous atmosphere is thought to be produced from sputtering of surface species (predominantly H2O ice ) by heavy ions in the Jovian magnetosphere. Because of its low residence time at Europa's surface temperature, O2, a stable decomposition product of H2O, has been predicted to exist in a significant amount in Europa's atmosphere [Johnson et al. 1982, Eviatar et al. 1985, Johnson 1990]. Recent HST observations have confirmed that and suggested an O2 atmospheric column of 1015 cm-2 on Europa [Hall et al. 1995]. Recent theoretical studies applied to modeling of pure oxygen atmospheres on Europa [Ip et al. 1996, Saur et al. 1998, Shematovich and Johnson 2000] have produced results that are consistent with the above scenerio. In addition to water products, recent observations from Galileo NIMS instruments have suggested the existence of hydrated salt minerals and sulfuric acid on Europa's surface [McCord et al. 1999, Carlson et al. 1999]. Therefore, it is expected that decomposition of these materials by magnetospheric ions can produce volatile species such as H2S, SO2, CO2 and Na in Europa's atmosphere. In fact, Na has been identified in the extended atmosphere of Europa [Brown and Hill, 1996]. In this paper, we will use a kinetic model to study the fate and abundance of these volatile species in addition to simulating the formation of an oxygen atmosphere on Europa.

Wong, M. C.; Carlson, R. W.; Johnson, R. E.

2000-10-01

188

Designing for ecology : the ecological park  

E-print Network

This thesis aims to define a) what an ecological park is, and b) whether it is a new model in park design. Reference to the literature on landscape ecology is used to analyze the natural ecological merit of these parks, ...

Power, Andres M

2006-01-01

189

Coastal environmental assessment and management by ecological simulation in Yeoja Bay, Korea  

Microsoft Academic Search

An eco-hydrodynamic model was used to estimate the carrying capacity of pollutant loads and response of water quality to environmental change in Yeoja Bay, Korea. An energy-system model also was used to simulate the fluctuation in nutrients and organic matter in the bordering wetland. Most water quality factors showed a pulsed pattern, and the concentrations of nutrients and organic matter

Dae-In Lee; Jeong-Min Choi; Yeon-Gyu Lee; Moon-Ock Lee; Won-Chan Lee; Jong-Kyu Kim

2008-01-01

190

Locating Pleistocene Refugia: Comparing Phylogeographic and Ecological Niche Model Predictions  

PubMed Central

Ecological niche models (ENMs) provide a means of characterizing the spatial distribution of suitable conditions for species, and have recently been applied to the challenge of locating potential distributional areas at the Last Glacial Maximum (LGM) when unfavorable climate conditions led to range contractions and fragmentation. Here, we compare and contrast ENM-based reconstructions of LGM refugial locations with those resulting from the more traditional molecular genetic and phylogeographic predictions. We examined 20 North American terrestrial vertebrate species from different regions and with different range sizes for which refugia have been identified based on phylogeographic analyses, using ENM tools to make parallel predictions. We then assessed the correspondence between the two approaches based on spatial overlap and areal extent of the predicted refugia. In 14 of the 20 species, the predictions from ENM and predictions based on phylogeographic studies were significantly spatially correlated, suggesting that the two approaches to development of refugial maps are converging on a similar result. Our results confirm that ENM scenario exploration can provide a useful complement to molecular studies, offering a less subjective, spatially explicit hypothesis of past geographic patterns of distribution. PMID:17622339

Waltari, Eric; Hijmans, Robert J.; Peterson, A. Townsend; Nyári, Árpád S.; Perkins, Susan L.; Guralnick, Robert P.

2007-01-01

191

Modeling the ecological impacts of Flaming Gorge Dam operations  

SciTech Connect

Hydropower operations at Flaming Gorge Dam on the Green River in Utah, US, can produce rapid downstream changes in flow and stage during a day. These changes can, in turn, affect ecological resources below the dam, including riparian vegetation, trout, and endangered fish. Four hydropower operational scenarios featuring varying degrees of hydropower-induced flow fluctuation were evaluated with hydrologic models and multispectral aerial videography of the river. Year-round high fluctuations would support the least amount of stable spawning habitat for trout and nursery habitat for endangered fish, and would have the greatest potential for reducing growth and over winter survival of fish. Seasonally, adjusted moderate fluctuation and seasonally adjusted steady flow scenarios could increase food production and over winter survival and would provide the greatest amount of spawning and nursery habitat for fish. The year-round high fluctuation, seasonally adjusted high fluctuation, and seasonally adjusted moderate fluctuation scenarios would result in a 5% decrease in upper riparian zone habitat. the seasonally adjusted steady flow scenario would result in an 8% increase in upper riparian zone habitat. Lower riparian zone habitat would increase by about 17% for year-round and seasonally adjusted high fluctuating flow scenarios but decrease by about 24% and 69% for seasonally adjusted moderate fluctuating and steady flow scenarios, respectively.

Yin, S.C.L.; LaGory, K.E.; Hayse, J.W.; Hlohowskyj, I.; Van Lonkhuyzen, R.A.; Cho, H.E. [Argonne National Lab., IL (United States). Environmental Assessment Div.

1996-05-01

192

Towards a catchment-scale macro-ecological model to support integrated catchment management in Europe  

NASA Astrophysics Data System (ADS)

In Europe, the Water Framework Directive (WFD) is providing a powerful regulatory driver to adopt integrated catchment management, and so pressurizing researchers to build suitable supporting tools. The WFD requires agencies to drive towards `good ecological quality' by 2015. After the initial step of characterising water bodies and the pressures on them, the next substantive step is the preparation of river basin management plans and proposed programmes of measures by 2009. Ecological quality is a complex concept and poorly defined, unless it is taken as a simple measure such as the abundance of a particular species of organism. There is clearly substantial work to do to build a practical but sound definition of ecological quality; practical in the sense of being easy to measure and explain to stakeholders, and sound in the sense that it reflects ecological complexity within catchments, the variability between catchments, and the conflicts demands for goods and services that human society places upon the ecological system. However ecological quality is defined, it will be driven by four interacting groups of factors. These represent the physical, chemical, ecological and socio-economic environments within and encompassing the catchment. Some of these groupings are better understood than others, for example hydrological processes and the transport of solutes are reasonably understood, even though they remain research areas in their own right. There are much larger gaps in our understanding at the interfaces, i.e. predicting how, for example, hydrological processes such as flow and river morphology influence ecological quality. Overall, it is clear we are not yet in a position to build deterministic models of the overall ecological behaviour of catchment. But we need predictive tools to support catchment management agencies in preparing robust plans. This poster describes our current exploration of soft modelling options to build a comprehensive macro-ecological model of UK catchments. This is taking place within the Catchment Science Centre, a joint venture between the University of Sheffield and the Environment Agency.

Lerner, R. N.; Lerner, D. N.; Surridge, B.; Paetzold, A.; Harris, B.; Anderson, C. W.

2005-12-01

193

Using the ODD Protocol for Describing Three Agent-Based Social Simulation Models of Land-Use Change  

Microsoft Academic Search

This article describes three agent-based social simulation models in the area of land-use change using a model documentation protocol, ODD, from the ecological literature. Our goal is to evaluate how well fitted it is to social simulations and how successful it might be in increasing communication between individual- and agent-based modellers. Such shared protocols can facilitate model review, comparison, and

J. Gary Polhill; Dawn C. Parker; Daniel G. Brown; Volker Grimm

2008-01-01

194

Modelling and simulation of a heat exchanger  

NASA Technical Reports Server (NTRS)

Two models for two different control systems are developed for a parallel heat exchanger. First by spatially lumping a heat exchanger model, a good approximate model which has a high system order is produced. Model reduction techniques are applied to these to obtain low order models that are suitable for dynamic analysis and control design. The simulation method is discussed to ensure a valid simulation result.

Xia, Lei; Deabreu-Garcia, J. Alex; Hartley, Tom T.

1991-01-01

195

Resistive companion battery modeling for electric circuit simulations , R. Dougalb  

E-print Network

Resistive companion battery modeling for electric circuit simulations B. Wua , R. Dougalb , R for electric circuit simulations. With a RC numerical solver, simulations of complex electric systems can reserved. Keywords: Battery modeling; Battery simulation; Electric circuit simulation; Resistive companion

196

Fuzzy comprehensive evaluation model of ecological demonstration area  

Microsoft Academic Search

Ecological demonstration area (EDA) is an authorized nomination, which should be assessed from several aspects, including\\u000a ecological, social, environmental, economic ones and so on. It is difficult to advance an exact developing level index of\\u000a EDA due to its indieator system’s complexity and disequilibrium. In this paper, a framework of indicators was set to evaluate,\\u000a monitor and examine the comprehensive

Ya-juan Yu; Huai-cheng Guo; Young Liu; Shu-tong Wang; Jin-feng Wang

2005-01-01

197

Modeling patch occupancy: Relative performance of ecologically scaled landscape indices  

Microsoft Academic Search

In fragmented landscapes, the likelihood that a species occupies a particular habitat patch is thought to be a function of\\u000a both patch area and patch isolation. Ecologically scaled landscape indices (ESLIs) combine a species’ ecological profile,\\u000a i.e., area requirements and dispersal ability, with indices of patch area and connectivity. Since their introduction, ESLIs\\u000a for area have been modified to incorporate

Carol E. Rizkalla; Jeffrey E. Moore; Robert K. Swihart

2009-01-01

198

Guidelines for developing and updating Bayesian belief networks applied to ecological modeling and conservation1  

Microsoft Academic Search

Bayesian belief networks (BBNs) are useful tools for modeling ecological predictions and aiding resource- management decision-making. We provide practical guidelines for developing, testing, and revising BBNs. Primary steps in this process include creating influence diagrams of the hypothesized \\

Bruce G. Marcot; J. Douglas Steventon; Glenn D. Sutherland; Robert K. McCann

199

Ecological Modelling 147 (2002) 291307 The kin facilitation hypothesis for red grouse population  

E-print Network

Ecological Modelling 147 (2002) 291­307 The kin facilitation hypothesis for red grouse population grouse population cycles to the formation of spatial assemblages comprising related territory holders clusters; Kinship; Ordinary differential equations; Population cycles; Red grouse (Lagopus lagopus scoticus

Lambin, Xavier

200

Monte Carlo Simulations of Model Nonionic Surfactants  

E-print Network

Monte Carlo Simulations of Model Nonionic Surfactants A.P. Chatterjee and A.Z. Panagiotopoulos was studied by histogram reweight- ing grand canonical Monte Carlo simulations. Two di erent sets of site volume fractions using lattice Monte Carlo simulations performed in the canonical constant NV T ensemble

201

Spatially explicit ecological exposure models: a rationale for and path toward their increased acceptance and use.  

PubMed

Spatially explicit wildlife exposure models have been developed to integrate chemical concentrations dispersed in space and time, heterogeneous habitats of varying qualities, and foraging behaviors of wildlife to give more realistic wildlife exposure estimates for ecological risk assessments. These models not only improve the realism of wildlife exposure estimates, but also increase the efficiency of remedial planning. However, despite being widely available, these models are rarely used in baseline (definitive) ecological risk assessments. A lack of precedent for their use, misperceptions about models in general and spatial models in particular, non-specific or no enabling regulations, poor communication, and uncertainties regarding inputs are all impediments to greater use of such models. An expert workshop was convened as part of an Environmental Security Technology Certification Program Project to evaluate current applications for spatially explicit models and consider ways such models could bring increased realism to ecological exposure assessments. Specific actions (e.g., greater accessibility and innovation in model design, increased communication with and training opportunities for decision makers and regulators, explicit consideration during assessment planning and problem formulation) were discussed as mechanisms to increase the use of these valuable and innovative modeling tools. The intent of this workshop synopsis is to highlight for the ecological risk assessment community both the value and availability of a wide range of spatial models and to recommend specific actions that may help to increase their acceptance and use by ecological risk assessment practitioners. PMID:21442731

Wickwire, Theodore; Johnson, Mark S; Hope, Bruce K; Greenberg, Marc S

2011-04-01

202

SSA Modeling and Simulation with DIRSIG  

NASA Astrophysics Data System (ADS)

We describe and demonstrate a robust, physics-based modeling system to simulate ground and space-based observations of both LEO and GEO objects. With the DIRSIG radiometry engine at its core, our system exploits STK, adaptive optics modeling, and detector effects to produce high fidelity simulated images and radiometry. Key to generating quantitative simulations is our ability to attribute engineering-quality, faceted CAD models with reflective and emissive properties derived from laboratory measurements, including the spatial structure of such difficult materials as MLI. In addition to simulated video imagery, we will demonstrate a computational procedure implementing a position-based dynamics approach to shrink wrap MLI around space components.

Bennett, D.; Allen, D.; Dank, J.; Gartley, M.; Tyler, D.

2014-09-01

203

VHDL simulation with access to transistor models  

NASA Astrophysics Data System (ADS)

Hardware description languages such as VHDL have evolved to aid in the design of systems with large numbers of elements and a wide range of electronic and logical abstractions. For high performance circuits, behavioral models may not be able to efficiently include enough detail to give designers confidence in a simulation's accuracy. One option is to provide a link between the VHDL environment and a transistor level simulation environment. The coupling of the Vantage Analysis Systems VHDL simulator and the NOVA simulator provides the combination of VHDL modeling and transistor modeling.

Gibson, J.

204

Computational Modeling and Simulation of Infectious Diseases  

E-print Network

Computational Modeling and Simulation of Infectious Diseases May 21­July 27, 2012 Receive a 10-week of Public Health Models of Infectious Disease Agent Study (MIDAS) National Center of Excellence #12;

Sibille, Etienne

205

Next generation dynamic global vegetation models: learning from community ecology (Invited)  

NASA Astrophysics Data System (ADS)

Dynamic global vegetation models are a powerful tool to project past, current and future vegetation patterns and the associated biogeochemical cycles. However, most models are limited by their representation of vegetation by using static and pre-defined plant functional types and by their simplistic representation of competition. We discuss how concepts from community assembly theory and coexistence theory can help to improve dynamic vegetation models. We present a trait- and individual-based dynamic vegetation model, the aDGVM2, that allows individual plants to adopt a unique combination of trait values. These traits define how individual plants grow, compete and reproduce under the given biotic and abiotic conditions. A genetic optimization algorithm is used to simulate trait inheritance and reproductive isolation between individuals. These model properties allow the assembly of plant communities that are adapted to biotic and abiotic conditions. We show (1) that the aDGVM2 can simulate coarse vegetation patterns in Africa, (2) that changes in the environmental conditions and disturbances strongly influence trait diversity and the assembled plant communities by influencing traits such as leaf phenology and carbon allocation patterns of individual plants and (3) that communities do not necessarily return to the initial state when environmental conditions return to the initial state. The aDGVM2 deals with functional diversity and competition fundamentally differently from current models and allows novel insights as to how vegetation may respond to climate change. We believe that the aDGVM2 approach could foster collaborations between research communities that focus on functional plant ecology, plant competition, plant physiology and Earth system science.

Scheiter, S.; Higgins, S.; Langan, L.

2013-12-01

206

Effects of Changes in Lugu Lake Water Quality on Schizothorax Yunnansis Ecological Habitat Based on HABITAT Model  

NASA Astrophysics Data System (ADS)

Schizothorax Yunnansis is an unique fish species only existing in Lugu Lake, which is located in the southwestern China. The simulation and research on Schizothorax Yunnansis habitat environment have a vital significance to protect this rare fish. With the development of the tourism industry, there bring more pressure on the environmental protection. The living environment of Schizothorax Yunnansis is destroyed seriously because the water quality is suffering the sustaining pollution of domestic sewage from the peripheral villages. This paper analyzes the relationship between water quality change and Schizothorax Yunnansis ecological habitat and evalutes Schizothorax Yunnansis's ecological habitat impact based on HABITAT model. The results show that when the TP concentration in Lugu Lake does not exceed Schizothorax Yunnansis's survival threshold, Schizothorax Yunnansis can get more nutrients and the suitable habitat area for itself is increased. Conversely, it can lead to TP toxicity in the Schizothorax Yunnansis and even death. Therefore, unsuitable habitat area for Schizothorax Yunnansis is increased. It can be seen from the results that HABITAT model can assist in ecological impact assessment studies by translating results of hydrological, water quality models into effects on the natural environment and human society.

Huang, Wei; Mynnet, Arthur

207

Monte Carlo Simulation of Interacting Electron Models  

E-print Network

Monte Carlo Simulation of Interacting Electron Models by a New Determinant Approach by Mucheng discusses the calculation of determinants and Monte Carlo simulation of Hub- bard models by a new and a Monte Carlo summation algorithm to evaluate the relevant diagram determinant sums. Index words: Monte

Robinson, Robert W.

208

Scaling strength in human simulation models  

Microsoft Academic Search

Introduction: Simulating human movement, with multi-body models, enables virtual experiments that are too difficult, costly or dangerous to perform in reality. When simulation models are used for subject specific goals, like planning a rehabilitation intervention, it is important that they are based on subject-specific data. Therefore, accurate strength scaling, accounting for subject specific differences, is required. Unfortunately, current strength scaling

Annegarn J; Rasmussen J; Savelberg HHCM; Verdijk LB; Meijer K

209

Crop Simulation Models and Decision Support Systems  

Technology Transfer Automated Retrieval System (TEKTRAN)

The first computer simulation models for agricultural systems were developed in the 1970s. These early models simulated potential production for major crops as a function of weather conditions, especially temperature and solar radiation. At a later stage, the water component was added to be able to ...

210

SIMULATION MODELLING OF DEMENTIA PATIENT PATHWAYS  

E-print Network

SIMULATION MODELLING OF DEMENTIA PATIENT PATHWAYS Mohsen Jahangirian, Julie Eatock School of Information Systems, Computing and Mathematics Brunel University, London, UK MalesFemales DEMENTIA `DISEASE-diagnosed patients Disease Progression Disease Onset Community Care DEMENTIA PATHWAY SIMULATION HIGH- LEVEL MODEL

Oakley, Jeremy

211

Submarine landslide flows simulation through centrifuge modelling  

E-print Network

SUBMARINE LANDSLIDE FLOWS SIMULATION THROUGH CENTRIFUGE MODELLING by Chang Shin GUE A dissertation submitted for the degree of Doctor of Philosophy at the University of Cambridge Churchill College January... “Continuous effort – not strength or intelligence – is the key to unlocking our potential” - Winston Churchill ABSTRACT SUBMARINE LANDSLIDE FLOWS SIMULATION THROUGH CENTRIFUGE MODELLING Chang Shin GUE Landslides occur both onshore...

Gue, Chang Shin

2012-05-08

212

Ecological Modelling 154 (2002) 263288 Forest canopy hydraulic properties and catchment water  

E-print Network

Ecological Modelling 154 (2002) 263­288 Forest canopy hydraulic properties and catchment water observed. However, mid-day leaf water potentials and the leaf area-specific canopy hydraulic conductance canopy model with a 1-D soil column model and TOPMODEL hydrologic formulations. The SPA model was used

213

Graphical simulation environments for modelling and simulation of integrative physiology.  

PubMed

Guyton's original integrative physiology model was a milestone in integrative physiology, combining significant physiological knowledge with an engineering perspective to develop a computational diagrammatic model. It is still used in research and teaching, with a small number of variants on the model also in circulation. However, though new research has added significantly to the knowledge represented by Guyton's model, and significant advances have been made in computing and simulation software, an accepted common platform to integrate this new knowledge has not emerged. This paper discusses the issues in the selection of a suitable platform, together with a number of current possibilities, and suggests a graphical computing environment for modelling and simulation. By way of example, a validated version of Guyton's 1992 model, implemented in the ubiquitous Simulink environment, is presented which provides a hierarchical representation amenable to extension and suitable for teaching and research uses. It is designed to appeal to the biomedical engineer and physiologist alike. PMID:20576310

Mangourova, Violeta; Ringwood, John; Van Vliet, Bruce

2011-06-01

214

Modeling low-flow bedrock springs providing ecological habitats with climate change scenarios  

NASA Astrophysics Data System (ADS)

Groundwater discharge areas, including low-flow bedrock aquifer springs, are ecologically important and can be impacted by climate change. The development of and results from a groundwater modeling study simulating fractured bedrock spring flow are presented. This was conducted to produce hydrological data for an ecohydrological study of an endangered species, Allegheny Mountain Dusky Salamanders (Desmognathus ochrophaeus), in southern Quebec, Canada. The groundwater modeling approach in terms of scale and complexity was strongly driven by the need to produce hydrological data for the related ecohydrological modeling. Flows at four springs at different elevations were simulated for recent past conditions (2006-2010) and for reference (1971-2000) and future (2041-2070) periods using precipitation and temperature data from ten climate scenarios. Statistical analyses of spring flow parameters including activity periods and duration of flow were conducted. Flow rates for the four simulated springs, located at different elevations, are predicted to increase between 2% and 46% and will be active (flowing) 1-2% longer in the future. A significant change (predominantly an increase) looking at the seasonality of the number of active days occurs in the winter (2-4.9%) and spring seasons (-0.6-6.5%). Greatest flow rates were produced from springs at elevations where sub-horizontal fractures intersect the ground surface. These results suggest an intensification of the spring activity at the study site in context of climate change by 2050, which provides a positive habitat outlook for the endangered salamanders residing in the springs for the future.

Levison, J.; Larocque, M.; Ouellet, M. A.

2014-07-01

215

Target modelling for SAR image simulation  

NASA Astrophysics Data System (ADS)

This paper examines target models that might be used in simulations of Synthetic Aperture Radar imagery. We examine the basis for scattering phenomena in SAR, and briefly review the Swerling target model set, before considering extensions to this set discussed in the literature. Methods for simulating and extracting parameters for the extended Swerling models are presented. It is shown that in many cases the more elaborate extended Swerling models can be represented, to a high degree of fidelity, by simpler members of the model set. Further, it is shown that it is quite unlikely that these extended models would be selected when fitting models to typical data samples.

Willis, Chris J.

2014-10-01

216

Modeling and simulation of friction  

Microsoft Academic Search

Two new models for 'slip-stick' friction are presented. One, called the 'bristle model,' is an approximation designed to capture the physical phenomenon of sticking. This model is relatively inefficient numerically. The other model, called the 'reset integrator model,' does not capture the details for the sticking phenomenon, but is numerically efficient and exhibits behavior similar to the model proposed by

David A. Haessig; Bernard Friedland

1991-01-01

217

Pathogen survival trajectories: an eco-environmental approach to the modeling of human campylobacteriosis ecology.  

PubMed Central

Campylobacteriosis, like many human diseases, has its own ecology in which the propagation of human infection and disease depends on pathogen survival and finding new hosts in order to replicate and sustain the pathogen population. The complexity of this process, a process common to other enteric pathogens, has hampered control efforts. Many unknowns remain, resulting in a poorly understood disease ecology. To provide structure to these unknowns and help direct further research and intervention, we propose an eco-environmental modeling approach for campylobacteriosis. This modeling approach follows the pathogen population as it moves through the environments that define the physical structure of its ecology. In this paper, we term the ecologic processes and environments through which these populations move "pathogen survival trajectories." Although such a modeling approach could have veterinary applications, our emphasis is on human campylobacteriosis and focuses on human exposures to Campylobacter through feces, food, and aquatic environments. The pathogen survival trajectories that lead to human exposure include ecologic filters that limit population size, e.g., cooking food to kill Campylobacter. Environmental factors that influence the size of the pathogen reservoirs include temperature, nutrient availability, and moisture availability during the period of time the pathogen population is moving through the environment between infected and susceptible hosts. We anticipate that the modeling approach proposed here will work symbiotically with traditional epidemiologic and microbiologic research to help guide and evaluate the acquisition of new knowledge about the ecology, eventual intervention, and control of campylobacteriosis. PMID:12515674

Skelly, Chris; Weinstein, Phil

2003-01-01

218

Assessment of ecological security in Changbai Mountain Area, China based on MODIS data and PSR model  

NASA Astrophysics Data System (ADS)

The assessment of ecological security is to identify the stability of the ecosystem, and to distinguish the capacity of sustainable health and integrity under different kinds of risks. Using MODIS time series images from 2000 to 2008 as the main data source, the derived parameters including NDVI, the ratio of NPP and GPP, forest coverage, landscape diversity and ecological flexibility etc. are integrated to depict the properties of the ecological system. The pressure and response indicators such as population density, industrial production intensity, arable land per capita, fertilizer consumption, highway density, agricultural mechanization level and GDP per capita are also collected and managed by ArcGIS. The `pressure-state-response' (PSR) conceptual model and a hierarchical weighted model are applied to construct an evaluation framework and determine the state of ecological security in Changbai Mountain area. The results show that the ecological security index (ESI) values in 2000 and 2008 were 5.75 and 5.59 respectively, indicating the ecological security state in Changbai Mountain area degraded. In 2000, the area of in good state of ecological security was 21901km2, occupying 28.96% of the study region. 48201 km2 of the land were with moderate level. The grades of ESI in Dunhua, Longjing and Antu decreased from moderate to poor. Though the ESI value of Meihekou increased by 0.12 during 2000-2008, it was still in a very poor state of ecological security induced by intensive human activities. The ecological security situation of Changbai Mountain region was not optimistic on the whole.

Huang, Fang; Wang, Ping; Qi, Xin

2014-11-01

219

The ecological footprint: a non-monetary metric of human consumption applied to North America  

Microsoft Academic Search

This paper employs ecological footprint analysis as a potential non-monetary metric of human consumption and ecological productivity in a simulation-modeling framework, applied to North America. The ecological footprint provides an indirect basis for considering the long-term ecological risk and sustainability of human settlements, regions or, in this case, a continent. We examine several scenarios for human consumption, ecological productivity and

Maged Senbel; Timothy McDaniels; Hadi Dowlatabadi

2003-01-01

220

Gecko: a continuous 2D world for ecological modeling.  

PubMed

An individual-based simulation system, named Gecko, is presented for modeling multiple species at multiple trophic levels, on a spatially explicit, continuous two-dimensional landscape. Biologically motivated rules are specified at an individual level, and resulting behaviors are observed at an ecosystem level. Individuals are represented by circles with free range on a resource-producing plane. These circles grow allometrically with biomass of fixed resources. Resource acquisition behaviors include competition by area overlap for producers, and movement based on perception and intent. Individual-level energetics are explicitly modeled with inefficient assimilation, resource transformation, and allometrically specified metabolic costs. Individual growth and reproduction requires a history of successful resource acquisition. Terrestrial producer, herbivore, and carnivore species classes are included, extensible to further classes. A grassland food chain model of "plants," "grasshoppers," and "spiders" is used to demonstrate ecosystem-level results of given individual-level behaviors. Ecosystem-level behaviors include a trophic cascade of indirect carnivore-producer interaction effects; stable persistence of all populations; a near-realistic biomass pyramid; and spatial competition and coexistence of multiple producer species. Initial Gecko results show promise for application in both theoretical and natural ecosystem modeling. PMID:9385732

Booth, G

1997-01-01

221

Ecological niche modelling and prioritizing areas for species reintroductions  

Microsoft Academic Search

Species reintroduction programmes, in prior- itizing areas for reintroductions, have traditionally used tools that include measures of habitat suitability and evaluations of area requirements for viable populations. Here we add two tools to this approach: evaluation of ecological requirements of species and evaluation of future suitability for species facing changing climates. We demonstrate this approach with two species for which

Enrique Martínez-Meyer; A. Townsend Peterson; Jorge I. Servín; Lloyd F. Kiff

2006-01-01

222

Author's personal copy Ecological Modelling 265 (2013) 113  

E-print Network

, Calle Ofra s/n, E-38320 La Laguna, Tenerife, Islas Canarias, Spain b Área de Ecología, Departamento de (C.I.M.A.), C/Arzobispo Elías Yanes n 44, E-38206 La Laguna, Tenerife, Spain d Escuela Técnica

223

Simulating Runoff from a Grid Based Mercury Model: Flow Comparisons  

EPA Science Inventory

Several mercury cycling models, including general mass balance approaches, mixed-batch reactors in streams or lakes, or regional process-based models, exist to assess the ecological exposure risks associated with anthropogenically increased atmospheric mercury (Hg) deposition, so...

224

Using observation-level random effects to model overdispersion in count data in ecology and evolution  

PubMed Central

Overdispersion is common in models of count data in ecology and evolutionary biology, and can occur due to missing covariates, non-independent (aggregated) data, or an excess frequency of zeroes (zero-inflation). Accounting for overdispersion in such models is vital, as failing to do so can lead to biased parameter estimates, and false conclusions regarding hypotheses of interest. Observation-level random effects (OLRE), where each data point receives a unique level of a random effect that models the extra-Poisson variation present in the data, are commonly employed to cope with overdispersion in count data. However studies investigating the efficacy of observation-level random effects as a means to deal with overdispersion are scarce. Here I use simulations to show that in cases where overdispersion is caused by random extra-Poisson noise, or aggregation in the count data, observation-level random effects yield more accurate parameter estimates compared to when overdispersion is simply ignored. Conversely, OLRE fail to reduce bias in zero-inflated data, and in some cases increase bias at high levels of overdispersion. There was a positive relationship between the magnitude of overdispersion and the degree of bias in parameter estimates. Critically, the simulations reveal that failing to account for overdispersion in mixed models can erroneously inflate measures of explained variance (r2), which may lead to researchers overestimating the predictive power of variables of interest. This work suggests use of observation-level random effects provides a simple and robust means to account for overdispersion in count data, but also that their ability to minimise bias is not uniform across all types of overdispersion and must be applied judiciously. PMID:25320683

2014-01-01

225

Supervision in School Psychology: The Developmental/Ecological/Problem-Solving Model  

ERIC Educational Resources Information Center

Effective supervision models guide the supervisory relationship and supervisory tasks leading to reflective and purposeful practice. The Developmental/Ecological/Problem-Solving (DEP) Model provides a contemporary framework for supervision specific to school psychology. Designed for the school psychology internship, the DEP Model is also…

Simon, Dennis J.; Cruise, Tracy K.; Huber, Brenda J.; Swerdlik, Mark E.; Newman, Daniel S.

2014-01-01

226

An Ecological Model of Developing Researcher Competence: The Case of Software Technology in Doctoral Research  

ERIC Educational Resources Information Center

This paper presents an ecological model of developing researcher competence, with a particular focus on doctoral students' use of research software. The model extends on theoretical work done by Young et al. ("Instructional Science 30"(1): 47-63, 2002), modelling the intentional dynamics of technological learning contexts. The development of the…

Stelma, Juup

2011-01-01

227

Ecological Modelling 153 (2002) 131142 Temperature sensitivity of soil respiration and its effects on  

E-print Network

Ecological Modelling 153 (2002) 131­142 Temperature sensitivity of soil respiration and its effects of the nonlinearity in temperature sensitivity of soil respiration, several commonly used ecosystem models produce substantially different estimates of soil respiration with the same or similar model input. In this paper we

Wu, Jianguo "Jingle"

228

Metabolic ecology.  

PubMed

Ecological theory that is grounded in metabolic currencies and constraints offers the potential to link ecological outcomes to biophysical processes across multiple scales of organization. The metabolic theory of ecology (MTE) has emphasized the potential for metabolism to serve as a unified theory of ecology, while focusing primarily on the size and temperature dependence of whole-organism metabolic rates. Generalizing metabolic ecology requires extending beyond prediction and application of standardized metabolic rates to theory focused on how energy moves through ecological systems. A bibliometric and network analysis of recent metabolic ecology literature reveals a research network characterized by major clusters focused on MTE, foraging theory, bioenergetics, trophic status, and generalized patterns and predictions. This generalized research network, which we refer to as metabolic ecology, can be considered to include the scaling, temperature and stoichiometric models forming the core of MTE, as well as bioenergetic equations, foraging theory, life-history allocation models, consumer-resource equations, food web theory and energy-based macroecology models that are frequently employed in ecological literature. We conclude with six points we believe to be important to the advancement and integration of metabolic ecology, including nomination of a second fundamental equation, complementary to the first fundamental equation offered by the MTE. PMID:24028511

Humphries, Murray M; McCann, Kevin S

2014-01-01

229

Modeling Physics with Easy Java Simulations  

NSDL National Science Digital Library

The paper Modeling Physics with Easy Java Simulations describes the use of the Easy Java Simulations (Ejs) modeling and authoring tool and shows how this tool can be used to teach mechanics concepts using computer modeling. Although the modeling method can be used without computers, the use of computers allows students to study problems that are difficult and time consuming, to visualize their results, and to communicate their results with others. The combination of computer modeling with theory and experiment can achieve insight and understanding that cannot be achieved with only one approach. Journal article available from http://scitation.aip.org/tpt/

Christian, Wolfgang; Franciscouembre

2008-05-30

230

Fusion Simulation Project (Whole Tokamak Plasma Modeling)  

E-print Network

;PSACI June 7-8, 2007 PPPL FSP Objective and Motivation · Primary objective of Fusion Simulation is expected to cost about a million dollars · Whole device computer simulations needed to optimize discharge Integration Initiatives · Coupling pairs of components before moving to whole device modeling · OFES formed

231

Modeling and Simulating Electronic Textile Applications  

E-print Network

1 Modeling and Simulating Electronic Textile Applications Thomas Martin, Mark Jones, Joshua Edmison@vt.edu Abstract-- This paper describes our experiences with a simulation environment for electronic textiles to the design of electronic textiles, including the physical environment they will be used in, the behavior

232

Agent-based modeling to simulate the dengue spread  

NASA Astrophysics Data System (ADS)

In this paper, we introduce a novel method ABM in simulating the unique process for the dengue spread. Dengue is an acute infectious disease with a long history of over 200 years. Unlike the diseases that can be transmitted directly from person to person, dengue spreads through a must vector of mosquitoes. There is still no any special effective medicine and vaccine for dengue up till now. The best way to prevent dengue spread is to take precautions beforehand. Thus, it is crucial to detect and study the dynamic process of dengue spread that closely relates to human-environment interactions where Agent-Based Modeling (ABM) effectively works. The model attempts to simulate the dengue spread in a more realistic way in the bottom-up way, and to overcome the limitation of ABM, namely overlooking the influence of geographic and environmental factors. Considering the influence of environment, Aedes aegypti ecology and other epidemiological characteristics of dengue spread, ABM can be regarded as a useful way to simulate the whole process so as to disclose the essence of the evolution of dengue spread.

Deng, Chengbin; Tao, Haiyan; Ye, Zhiwei

2008-10-01

233

Carbon sequestration by patch fertilization: A comprehensive assessment using coupled physical-ecological-biogeochemical models  

SciTech Connect

This final report summarizes research undertaken collaboratively between Princeton University, the NOAA Geophysical Fluid Dynamics Laboratory on the Princeton University campus, the State University of New York at Stony Brook, and the University of California, Los Angeles between September 1, 2000, and November 30, 2006, to do fundamental research on ocean iron fertilization as a means to enhance the net oceanic uptake of CO2 from the atmosphere. The approach we proposed was to develop and apply a suite of coupled physical-ecological-biogeochemical models in order to (i) determine to what extent enhanced carbon fixation from iron fertilization will lead to an increase in the oceanic uptake of atmospheric CO2 and how long this carbon will remain sequestered (efficiency), and (ii) examine the changes in ocean ecology and natural biogeochemical cycles resulting from iron fertilization (consequences). The award was funded in two separate three-year installments: • September 1, 2000 to November 30, 2003, for a project entitled “Ocean carbon sequestration by fertilization: An integrated biogeochemical assessment.” A final report was submitted for this at the end of 2003 and is included here as Appendix 1. • December 1, 2003 to November 30, 2006, for a follow-on project under the same grant number entitled “Carbon sequestration by patch fertilization: A comprehensive assessment using coupled physical-ecological-biogeochemical models.” This report focuses primarily on the progress we made during the second period of funding subsequent to the work reported on in Appendix 1. When we began this project, we were thinking almost exclusively in terms of long-term fertilization over large regions of the ocean such as the Southern Ocean, with much of our focus being on how ocean circulation and biogeochemical cycling would interact to control the response to a given fertilization scenario. Our research on these types of scenarios, which was carried out largely during the first three years of our project, led to several major new insights on the interaction between ocean biogeochemistry and circulation. This work, which is described in the following Section II on “Large scale fertilization,” has continued to appear in the literature over the past few years, including two high visibility papers in Nature. Early on in the first three years of our project, it became clear that small "patch-scale" fertilizations over limited regions of order 100 km diameter were much more likely than large scale fertilization, and we carried out a series of idealized patch fertilization simulations reported on in Gnanadesikan et al. (2003). Based on this paper and other results we had obtained by the end of our first three-year grant, we identified a number of important issues that needed to be addressed in the second three-year period of this grant. Section III on “patch fertilization” discusses the major findings of this phase of our research, which is described in two major manuscripts that will be submitted for publication in the near future. This research makes use of new more realistic ocean ecosystem and iron cycling models than our first paper on this topic. We have several major new insights into what controls the efficiency of iron fertilization in the ocean. Section IV on “model development” summarizes a set of papers describing the progress that we made on improving the ecosystem models we use for our iron fertilization simulations.

Jorge L. Sarmiento - Princeton PI, Anand Gnanadesikan - Princeton Co-I, Nicolas Gruber - UCLA PI, Xin Jin - UCLA PostDoc, Robert Armstrong - SUNY/Stony Brook Consultant

2007-06-21

234

SIMULATION MODELING OF GASTROINTESTINAL ABSORPTION  

EPA Science Inventory

Mathematical dosimetry models incorporate mechanistic determinants of chemical disposition in a living organism to describe relationships between exposure concentration and the internal dose needed for PBPK models and human health risk assessment. Because they rely on determini...

235

Digital elevation models in numerical rockfall simulations  

NASA Astrophysics Data System (ADS)

The current state of the art in rigid body rockfall modelling permits full three-dimensional simulation of real rock shapes and their interactions with the terrain. The terrain is represented by digital elevation models DEM, providing the geometric terrain information on which the spatial model parameters are assigned. This is fundamental to numerical simulations of mass movements. DEM's can be obtained from a number of sources and offer spatial resolutions ranging from centimetres up to 90m. The spatial resolution representing the terrain morphology can have a strong bearing on modelling results. In particular if finer scale morphologies (centimetres to meters) such as the terrain roughness of a scree slope or boulder field are included in the DEM. The issue occurs if the meso- to micro- scale roughness is included that would normally be loose surface material, because in the modelling domain the terrain surface is a rigid body. It is at these scales a crossover between representing terrain properties as either model parameters or terrain geometry occurs. Little is known about the optimal resolution to represent terrain in rockfall simulations. In this contribution we present the results of numerical simulations with different DEM resolutions. We sampled the terrain morphology of a highly rockfall active area in Matter valley in Switzerland using LiDAR with a maximum resolution of 50cm. The DEM was resampled at resolutions of 1m, 5m and 20m and rockfall simulations were performed where the model ground impact parameters were held constant. To induce the naturally stochastic initial conditions of rock fall release we vary the rock shapes and release orientation, while the potential energy was held constant. We compare the different simulation results and discuss the influence of the DEM resolution on fully three dimensional rockfall simulations. We find the DEM resolution has a strong influence on the simulation results demonstrating that the selection of the DEM is a crucial step in numerical simulation of rockfalls.

Bühler, Yves; Glover, James; Christen, Marc; Bartelt, Perry

2014-05-01

236

Computer simulations and physical modelling of erosion  

E-print Network

Computer simulations and physical modelling of erosion C.S. Stuetzle, J. Gross, Z. Chen, B. Cutler in 2 disciplines. 2 / 10 #12;Problem and goals Validation of Erosion Models for Levee Overtopping Levee terrain, a.k.a. soil, · better modeling of local erosion in terrain and earthen structures such as levees

Franklin, W. Randolph

237

Theory, modeling, and simulation annual report, 1992  

SciTech Connect

This report briefly discusses research on the following topics: development of electronic structure methods; modeling molecular processes in clusters; modeling molecular processes in solution; modeling molecular processes in separations chemistry; modeling interfacial molecular processes; modeling molecular processes in the atmosphere; methods for periodic calculations on solids; chemistry and physics of minerals; graphical user interfaces for computational chemistry codes; visualization and analysis of molecular simulations; integrated computational chemistry environment; and benchmark computations.

Not Available

1993-05-01

238

Aggregate calibration of microscopic traffic simulation models  

E-print Network

The problem of calibration of microscopic simulation models with aggregate data has received significant attention in recent years. But day-to-day variability in inputs such as travel demand has not been considered. In ...

Mahanti, Bhanu Prasad, 1981-

2004-01-01

239

Transportation Analysis, Modeling, and Simulation (TAMS) Application  

E-print Network

Transportation Analysis, Modeling, and Simulation (TAMS) Application Center for Transportation Passenger Flows Supply Chain Efficiency Transportation: Energy Environment Safety Security Vehicle Technologies T he Center for Transportation Analysis (CTA) TAMS application is a web-based tool that supports

240

A Simulation To Model Exponential Growth.  

ERIC Educational Resources Information Center

Describes a simulation using dice-tossing students in a population cluster to model the growth of cancer cells. This growth is recorded in a scatterplot and compared to an exponential function graph. (KHR)

Appelbaum, Elizabeth Berman

2000-01-01

241

MATHEMATICAL MODELING OF SIMULATED PHOTOCHEMICAL SMOG  

EPA Science Inventory

This report deals with the continuing effort to develop a chemical kinetic mechanism to describe the formation of photochemical smog. Using the technique of computer modeling to simulate smog chamber data, several explicit kinetic mechanisms for specific hydrocarbons were analyze...

242

DEVELOPMENT OF THE ADVANCED UTILITY SIMULATION MODEL  

EPA Science Inventory

The paper discusses the development of the Advanced Utility Simulation Model (AUSM), developed for the National Acid Precipitation Assessment Program (NAPAP), to forecast air emissions of pollutants from electric utilities. USM integrates generating unit engineering detail with d...

243

Mathematical Model Development and Simulation Support  

NASA Technical Reports Server (NTRS)

This report summarizes the work performed in support of the Contact Dynamics 6DOF Facility and the Flight Robotics Lab at NASA/ MSFC in the areas of Mathematical Model Development and Simulation Support.

Francis, Ronald C.; Tobbe, Patrick A.

2000-01-01

244

A New Animal Model for Merging Ecology and Evolution  

Microsoft Academic Search

\\u000a The theory of evolution has recently been in turmoil, with great interest in applying empirical information from EvoDevo,\\u000a genomics, and ecology into the framework of quantitative genetic studies of evolution. Ciona is a small genus of sea squirts within the class Ascidiacea of the subphylum Tunicata, the sister group of vertebrates, a\\u000a phylogenetic position that has contributed to fuel the

Gabriele Procaccini; Ornella Affinito; Francesco Toscano; Paolo Sordino

245

Using Species Distribution Models for Conservation Planning and Ecological Forecasting  

Microsoft Academic Search

\\u000a Conservation practitioners and resource managers must often work with limited data to answer critical, time-sensitive questions.\\u000a In many regions of the world, even the most basic information about the distribution of species is lacking. Knowing the geographic\\u000a extent of a given species or ecological system is the first step in planning for its management or conservation. The sustainable\\u000a management of

Josh J. Lawler; Yolanda F. Wiersma; Falk Huettmann

246

Ammonia-oxidizing bacteria: A model for molecular microbial ecology  

Microsoft Academic Search

The eutrophication of many ecosystems in recent decades has led to an increased interest in the ecology of nitrogen transformation. Chemolitho-autotrophic ammonia-oxidizing bacteria are responsible for the rate-limiting step of nitrification in a wide variety of environments, making them important in the global cycling of nitrogen. These organisms are unique in their ability to use the conversion of ammonia to

George A. Kowalchuk; John R. Stephen

2001-01-01

247

Modeling the growth dynamics of four candidate crops for Controlled Ecological Life Support Systems (CELSS)  

NASA Technical Reports Server (NTRS)

The production of food for human life support for advanced space missions will require the management of many different crops. The research to design these food production capabilities along with the waste management to recycle human metabolic wastes and inedible plant components are parts of Controlled Ecological Life Support Systems (CELSS). Since complete operating CELSS were not yet built, a useful adjunct to the research developing the various pieces of a CELSS are system simulation models that can examine what is currently known about the possible assembly of subsystems into a full CELSS. The growth dynamics of four crops (wheat, soybeans, potatoes, and lettuce) are examined for their general similarities and differences within the context of their important effects upon the dynamics of the gases, liquids, and solids in the CELSS. Data for the four crops currently under active research in the CELSS program using high-production hydroponics are presented. Two differential equations are developed and applied to the general characteristics of each crop growth pattern. Model parameters are determined by closely approximating each crop's data.

Volk, Tyler

1987-01-01

248

Modeling & Simulation Data Analysis and Modeling & Simulation for the  

E-print Network

, and designing pulsed detonation propulsion systems. · Worked with Proctor and Gamble on computer codes used - conditions. KIVA applications include performing low and combustion modeling in spark-ignition diesel engines

249

Model abstraction and the simulation sandbox  

Microsoft Academic Search

The Air Force Hierarchy of Models, often referred to as the Great Pyramid, depicts the four disparate levels of resolution in which models are typically categorized. These levels range from an Engineering\\/Component level at the bottom, to Theater\\/Campaign level at the apex of the pyramid. Today, the landscape of simulations has evolved from uni-purpose, stove-piped simulations to those that provide

Dawn A. Trevisani; Alex F. Sisti; Michael J. Mayhew

2002-01-01

250

Verification validation and accreditation of simulation models  

Microsoft Academic Search

This paper presents guidelines for conducting verifica- tion, validation and accreditation (VV&A) of simulation models. Fifteen guiding principles are introduced to help the researchers, practitioners and managers better com- prehend what VV&A is all about. The VV&A activities are described in the modeling and simulation life cycle. A taxonomy of more than 77 V&V techniques is provided to assist simulationists

Osman Balci

1997-01-01

251

Minimum-complexity helicopter simulation math model  

NASA Technical Reports Server (NTRS)

An example of a minimal complexity simulation helicopter math model is presented. Motivating factors are the computational delays, cost, and inflexibility of the very sophisticated math models now in common use. A helicopter model form is given which addresses each of these factors and provides better engineering understanding of the specific handling qualities features which are apparent to the simulator pilot. The technical approach begins with specification of features which are to be modeled, followed by a build up of individual vehicle components and definition of equations. Model matching and estimation procedures are given which enable the modeling of specific helicopters from basic data sources such as flight manuals. Checkout procedures are given which provide for total model validation. A number of possible model extensions and refinement are discussed. Math model computer programs are defined and listed.

Heffley, Robert K.; Mnich, Marc A.

1988-01-01

252

Functional response as a component of dynamic simulation models in biological control: the Catolaccus-boll weevil system  

Microsoft Academic Search

A simulation model using Time Varying Distributed Delays was created on the HERMES (Hierarchical Environment for Research Modelling of Ecological Systems) of the USDA\\/ARS with the purpose of evaluating different forms of functional response components in dynamic simulations of biological control systems. The specific host-parasitoid life system used in the evaluation was the boll weevil-Catolaccus grandis system. Four forms of

B. C. Legaspi; R. I. Carruthers; J. A. Morales-Ramos

1996-01-01

253

Integrating ecological risk assessments across levels of organization using the Franklin-Noss model of biodiversity  

SciTech Connect

Wildlife toxicologists pioneered methodologies for assessing ecological risk to nontarget species. Historically, ecological risk assessments (ERAS) focused on a limited array of species and were based on a relatively few population-level endpoints (mortality, reproduction). Currently, risk assessment models are becoming increasingly complex that factor in multi-species interactions (across trophic levels) and utilize an increasingly diverse number of ecologically significant endpoints. This trend suggests the increasing importance of safeguarding not only populations of individual species, but also the overall integrity of the larger biotic systems that support them. In this sense, ERAs are in alignment with Conservation Biology, an applied science of ecological knowledge used to conserve biodiversity. A theoretical conservation biology model could be incorporated in ERAs to quantify impacts to biodiversity (structure, function or composition across levels of biological organization). The authors suggest that the Franklin-Noss model for evaluating biodiversity, with its nested, hierarchical approach, may provide a suitable paradigm for assessing and integrating the ecological risk that chemical contaminants pose to biological systems from the simplest levels (genotypes, individual organisms) to the most complex levels of organization (communities and ecosystems). The Franklin-Noss model can accommodate the existing ecotoxicological database and, perhaps more importantly, indicate new areas in which critical endpoints should be identified and investigated.

Brugger, K.E.; Tiebout, H.M. III [DuPont Agricultural Products, Wilmington, DE (United States). Experimental Station; [West Chester Univ., West Chester, PA (United States). Dept. of Biology

1994-12-31

254

Biological soil crusts (biocrusts) as a model system in community, landscape and ecosystem ecology  

USGS Publications Warehouse

Model systems have had a profound influence on the development of ecological theory and general principles. Compared to alternatives, the most effective models share some combination of the following characteristics: simpler, smaller, faster, general, idiosyncratic or manipulable. We argue that biological soil crusts (biocrusts) have unique combinations of these features that should be more widely exploited in community, landscape and ecosystem ecology. In community ecology, biocrusts are elucidating the importance of biodiversity and spatial pattern for maintaining ecosystem multifunctionality due to their manipulability in experiments. Due to idiosyncrasies in their modes of facilitation and competition, biocrusts have led to new models on the interplay between environmental stress and biotic interactions and on the maintenance of biodiversity by competitive processes. Biocrusts are perhaps one of the best examples of micro-landscapes—real landscapes that are small in size. Although they exhibit varying patch heterogeneity, aggregation, connectivity and fragmentation, like macro-landscapes, they are also compatible with well-replicated experiments (unlike macro-landscapes). In ecosystem ecology, a number of studies are imposing small-scale, low cost manipulations of global change or state factors in biocrust micro-landscapes. The versatility of biocrusts to inform such disparate lines of inquiry suggests that they are an especially useful model system that can enable researchers to see ecological principles more clearly and quickly.

Bowker, Matthew A.; Maestre, Fernando T.; Eldridge, David; Belnap, Jayne; Castillo-Monroy, Andrea; Escolar, Cristina; Soliveres, Santiago

2014-01-01

255

Right model, wrong prediction: Model-free vs Mechanistic forecasting for nonlinear ecological systems  

NASA Astrophysics Data System (ADS)

As environmental time series have grown, and computer-intensive statistical methods have become more convenient, fitting mechanistic models that incorporate both process and observation error (i.e. state-space models) has become increasingly popular. It has been suggested that such models are more robust to noise due to their inclusion of a process-error term, however their out-of-sample forecast ability remains largely untested. Therefore, it is important to determine how various forecasting strategies perform under realistic levels of noise and forcing. We compared the forecast accuracy of a model-free forecasting approach based on nonlinear state-space reconstruction (SSR) against a suite of mechanistic models fit to their own time series with realistic levels of noise added. To further favor the mechanistic approach, these models were fit using a Bayesian adaptive MCMC algorithm actually initiated on the correct parameter values. Surprisingly, we found that the SSR forecasts were more accurate than the correct mechanistic models despite being fit to only one time series of a multivariate system. This was true for four different ecological models, and for experimental data from a series of flour beetle experiments. Our results suggest that for forecasting real ecosystems, where the correct model is never known, a robust model-free approach such as SSR may be a more practical alternative to complex fitted models containing many free parameters.

Perretti, C.; Munch, S. B.; Deyle, E. R.; Ye, H.; Sugihara, G.

2012-12-01

256

Ecological Modelling 171 (2004) 2133 Bottom-up and top-down effects in food chains  

E-print Network

Ecological Modelling 171 (2004) 21­33 Bottom-up and top-down effects in food chains depend analysis of trophic-level interactions within the standard energy-based linear food-chain model, or (2) 21­33 Section 3: General analytical approach for a press-perturbed food chain. Section 4: Response

Vermont, University of

257

The Role of Models in (Population) Ecology "Populations grow, but only to a point".  

E-print Network

1 The Role of Models in (Population) Ecology TYPES: ·Verbal "Populations grow, but only to a point for applied problems! Empirical Predict system behavior, compare with data of actual system behavior Model elements of a given problem They can be verbal, graphical, or mathematical; purpose can be heuristic

Gervais, Jennifer

258

Ecological Modelling 185 (2005) 105131 Tropical deforestation in Madagascar: analysis using hierarchical,  

E-print Network

Ecological Modelling 185 (2005) 105­131 Tropical deforestation in Madagascar: analysis using­effect relationships for deforestation at various scales has proven difficult even when rates of deforestation appear approach to develop a novel deforestation model for the eastern wet forested zone of Madagascar, a global

Silander Jr., John A.

259

Reconstruction of fire regimes through integrated paleoecological proxy data and ecological modeling  

PubMed Central

Fire is a key ecological process affecting vegetation dynamics and land cover. The characteristic frequency, size, and intensity of fire are driven by interactions between top-down climate-driven and bottom-up fuel-related processes. Disentangling climatic from non-climatic drivers of past fire regimes is a grand challenge in Earth systems science, and a topic where both paleoecology and ecological modeling have made substantial contributions. In this manuscript, we (1) review the use of sedimentary charcoal as a fire proxy and the methods used in charcoal-based fire history reconstructions; (2) identify existing techniques for paleoecological modeling; and (3) evaluate opportunities for coupling of paleoecological and ecological modeling approaches to better understand the causes and consequences of past, present, and future fire activity. PMID:25657652

Iglesias, Virginia; Yospin, Gabriel I.; Whitlock, Cathy

2015-01-01

260

Forest Productivity and Diversity: Using Ecological Theory and Landscape Models to Guide Sustainable Forest Management  

SciTech Connect

Sustainable forest management requires maintaining or increasing ecosystem productivity, while preserving or restoring natural levels of biodiversity. Application of general concepts from ecological theory, along with use of mechanistic, landscape-based computer models, can contribute to the successful achievement of both of these objectives. Ecological theories based on the energetics and dynamics of populations can be used to predict the general distribution of individual species, the diversity of different types of species, ecosystem process rates and pool sizes, and patterns of spatial and temporal heterogeneity over a broad range of environmental conditions. This approach requires subdivision of total biodiversity into functional types of organisms, primarily because different types of organisms respond very differently to the spatial and temporal variation of environmental conditions on landscapes. The diversity of species of the same functional type (particularly among plants) tends to be highest at relatively low levels of net primary productivity, while the total number of different functional types (particularly among animals) tends to be highest at high levels of productivity (e.g., site index or potential net primary productivity). In general, the diversity of animals at higher trophic levels (e.g., predators) reaches its maximum at much higher levels of productivity than the diversity of lower trophic levels (e.g., plants). This means that a single environment cannot support high diversity of all types of organisms. Within the framework of the general patterns described above, the distributions, population dynamics, and diversity of organisms in specific regions can be predicted more precisely using a combination of computer simulation models and GIS data based on satellite information and ground surveys. Biophysical models that use information on soil properties, climate, and hydrology have been developed to predict how the abundance and spatial distribution of various plants and animals. These models can be, used to predict the patterns of forest type and structure that develop in response to variation in productivity and disturbance across complex landscapes, as well as species diversity and the distribution and population fluctuations of threatened species in specific regions.

Huston, M.A.

1998-11-01

261

Modelling and simulation of a distributed battery management system  

Microsoft Academic Search

This paper discusses the modelling and simulation of a distributed battery management system with a continuous and discrete-event simulation environment. The simulation model focuses on replicating the generic components within the system into model blocks to provide a structured approach in simulating battery networks. The simulation model also deals with three key network levels, which are the process level, the

Darren LIM; A. Anbuky

2004-01-01

262

Assessment of water ecological carrying capacity under the two policies in Tieling City on the basis of the integrated system dynamics model.  

PubMed

Considering the limitation of the traditional method to assess the ecological carrying capacity and the complexity of the water ecological system, we used system dynamics, ANN, and CA-Markov to model a water ecological system. The social component was modeled according to Granger causality test by system dynamics. The natural component consists of the water resource and water environmental capacity, which were forecasted through the prediction of precipitation and change in land use cover. The interaction of the social component and the natural component mainly reflected environmental policies, such as the imposition of an environmental fee and environmental tax based on their values. Simulation results showed the different assessments on water ecological carrying capacity under the two policies. The population grew (2.9 million), and less pollution (86,632.37 t COD and 2854.5 t NH4N) was observed with the imposition of environmental tax compared with the imposition of an environmental fee (2.85 million population, 10,8381 t COD and 3543 t NH4N) at the same GDP level of 585 billion CNY in 2030. According to the causality loop, we discussed the different states under the policies and the reasons that caused the differences in water ecological carrying capacity state. According to game theory, we explained the limitation of the environmental fee policy on the basis of marginal benefit and cost. The externality was cleared up by the environmental tax policy. PMID:24361570

Wang, Shuo; Xu, Ling; Yang, Fenglin; Wang, He

2014-02-15

263

Chapter 4 Modeling and Simulation  

Microsoft Academic Search

Quantitative Modeling has been the basis of most of the initial research in operations, labeled as Operational Research in Europe, and was the basis of initial management consulting and Operations Research in the USA. Initially, quantitative modeling in Operational Research was oriented very much towards solving real-life problems in operations management rather than towards developing scientific knowledge. Later however, especially

Duane S. Boning; Okumu Ouma

1999-01-01

264

Trimming an aircraft model for flight simulation  

NASA Technical Reports Server (NTRS)

Real-time piloted aircraft simulations with digital computers have been performed at Ames Research Center (ARC) for over two decades. For the simulation of conventional aircraft models, the establishment of initial vehicle and control orientations at various operational flight regimes has been adequately handled by either analog techniques or simple inversion processes. However, exotic helicopter configurations have been introduced recently that require more sophisticated techniques because of their expanded degrees of freedom and environmental vibration levels. At ARC, these techniques are used for the backward solutions to real-time simulation models as required for the generation of trim points. These techniques are presented in this paper with examples from a blade-element helicopter simulation model.

Mcfarland, Richard E.

1987-01-01

265

Chemical Potentials by Monte Carlo Simulations Model  

NSDL National Science Digital Library

The Chemical Potentials by Monte Carlo Simulations Model performs canonical (NVT) and isothermal-isobaric (NPT) Monte Carlo simulations focusing the calculation of chemical potentials, for the fluid phases of the Lennard-Jones system, by using the virtual particle insertion method of Widom. Although it can not determine phase-equilibrium directly, the gas-liquid line can be approached as illustrated in the included case study. The model paves the way to uVT and Gibbs Ensemble simulations, and shows the limitation of Widom's method at high fluid densities. The Chemical Potentials by Monte Carlo Simulations Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Fernandes, Fernando S.

2013-10-30

266

Towards a coupled hydro-ecological catchment modeling approach Pt.2: water quality model  

NASA Astrophysics Data System (ADS)

Fine sediments are a key constraint for the functions of a river. On the one hand they impact the light and heat regime and, consequently, the primary production. On the other hand they control the hydraulic connectivity of the hyporheic zone, determining residence time and oxygen availability and, hence, bio-geochemical reactions and habitat suitability. In turn, fine sediment delivery to and its fate in the aquatic system is a matter of catchment hydrology and erodability as well as transport capacity and load, respectively. This study aims to assess the influence of fine sediments on the aquatic system and the responses thereupon. The holistic modeling of fine sediment dynamics at catchment scale is challenging because of a lack of available information (input data), knowledge gaps in mathematical descriptions and the large range of spatiotemporal resolutions. In order to face these problems we approach to link distributed overland transport to in stream processes. Study site is the Kharaa river in northern Mongolia that shows a gradual degradation from pristine headwaters to disturbed lower reaches impacted by agricultural practices. Besides effects of climate change and population growth there are several pressures enhancing soil erosion from land surface or bank structures: deforestation and wildfires at headwater hill slopes, intensive grazing at floodplains, diminishing of riparian vegetation from downstream the mid reaches on and irrigated agriculture on vast stretches. Former investigations revealed deficits in benthic communities developed within the middle region and an increase in fine sediment colonisers. The part presented here concerns the water quality modeling using a compartmentalisation approach that describes the water column and sediment compartment at the same time. This is done according to the compendium described within the River Water Quality Model No.1 (RWQM1) and implemented through the AQUASIM Program for Identification and Simulation of Aquatic Systems which includes simplified submodels for sediment transport and oxygen balance. Water quality and hydraulic parameters of water column and hyporheic zone are in focus for a distinct intensive monitoring program at three different reaches along the main river course. This concept of measures contains 24 hour physicochemical measurements as well as recording of water constituents in surface and pore water (extracted via interstitial probes). Further techniques include the analysis of subsurface temperature records and freeze coring for studies on hyporheic flow as well as the examination of biomass of benthic and pelagic phytoplankton for the estimation of production and respiration parameters. Macroinvertebrates and meiofauna communities are investigated at the same time to facilitate the calibration of an ecological submodel. We expect to see effects by colmation of the upper sediment layer in dependency of space (reach) and time (hydrology). This blocking of interstices causes changes in the benthic community composition as well as it seals the lower sediment layers where oxygen depletion and anaerobic biogeochemical processes like denitrification or the mobilization of phoshorus are able to evolve.

Hartwig, Melanie; Borchardt, Dietrich

2010-05-01

267

Architecting a Simulation Framework for Model Rehosting  

NASA Technical Reports Server (NTRS)

The utility of vehicle math models extends beyond human-in-the-loop simulation. It is desirable to deploy a given model across a multitude of applications that target design, analysis, and research. However, the vehicle model alone represents an incomplete simulation. One must also replicate the environment models (e.g., atmosphere, gravity, terrain) to achieve identical vehicle behavior across all applications. Environment models are increasing in complexity and represent a substantial investment to re-engineer for a new application. A software component that can be rehosted in each application is one solution to the deployment problem. The component must encapsulate both the vehicle and environment models. The component must have a well-defined interface that abstracts the bulk of the logic to operate the models. This paper examines the characteristics of a rehostable modeling component from the perspective of a human-in-the-loop simulation framework. The Langley Standard Real-Time Simulation in C++ (LaSRS++) is used as an example. LaSRS++ was recently redesigned to transform its modeling package into a rehostable component.

Madden, Michael M.

2004-01-01

268

Multibody Simulation Model of Human Walking  

Microsoft Academic Search

A three-dimensional simulational model of a human walking is presented. The biped is anthropomorphic, i.e., its inertial and kinematical properties are similar to human ones. The biped consists of eight rigid bodies. Each leg consists of three parts: thigh, shank, and foot. The trunk is modeled as two rigid bodies connected by a revolute joint. The inertia properties of head

Marek Wojtyra

2003-01-01

269

Transient fault modeling and fault injection simulation  

E-print Network

An accurate transient fault model is presented in this thesis. A 7-term exponential current upset model is derived from the results of a device-level, 3-dimensional, single-event-upset simulation. A curve-fitting algorithm is used to extract...

Yuan, Xuejun

2012-06-07

270

Can we reach consensus between marine ecological models and DEB theory? A look at primary producers  

NASA Astrophysics Data System (ADS)

In the last decades we have witnessed an explosion in marine modeling efforts, both at the development and application levels. A general agreement is expected between ecological models and metabolic theories, and one should be able to use ideas and principles from both views. Nevertheless, there are marked differences that can vary from differences in formulation of processes to baseline assumptions. So far, efforts to reconcile these models of natural systems have been limited. Here, we critically compare ERSEM (European Regional Seas Ecosystem Model), a state of the art ecological model in marine biogeochemical modeling, with a DEB (Dynamic Energy Budget) model (based on the metabolic theory DEB), highlighting similarities and showing where the approaches differ. This study focuses on primary producers and is driven by two main questions: (1) Is it possible to harmonize the philosophy and structure of models like ERSEM with the general scope of unifying metabolic theories such as DEB? (2) Can we bring the current paradigms in ecological modeling for marine communities to consensus with metabolic theories? We analyze the links between the underling processes in the DEB and ERSEM models. We found that the processes of assimilation and mobilization are the most difficult to reconcile between the two models. However, we also find a number of clear analogies between the parameters, state variables and fluxes of the two models, which allow for the transference of knowledge between them.

Marques, Gonçalo M.; Mateus, Marcos; Domingos, Tiago

2014-11-01

271

PIXE simulation: Models, methods and technologies  

SciTech Connect

The simulation of PIXE (Particle Induced X-ray Emission) is discussed in the context of general-purpose Monte Carlo systems for particle transport. Dedicated PIXE codes are mainly concerned with the application of the technique to elemental analysis, but they lack the capability of dealing with complex experimental configurations. General-purpose Monte Carlo codes provide powerful tools to model the experimental environment in great detail, but so far they have provided limited functionality for PIXE simulation. This paper reviews recent developments that have endowed the Geant4 simulation toolkit with advanced capabilities for PIXE simulation, and related efforts for quantitative validation of cross sections and other physical parameters relevant to PIXE simulation.

Batic, M. [INFN Sezione di Genova, Via Dodecaneso 33, 16146 Genova, Italy and Jozef Stefan Institute, Jamova cesta 39, Ljubljana 1000 (Slovenia); Pia, M. G.; Saracco, P. [INFN Sezione di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Weidenspointner, G. [Max-Planck-Institut Halbleiterlabor, Otto-Hahn-Ring 6, 81739 Muenchen (Germany) and Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, Garching 85748 (Germany)

2013-04-19

272

Mars Smart Lander Parachute Simulation Model  

NASA Technical Reports Server (NTRS)

A multi-body flight simulation for the Mars Smart Lander has been developed that includes six degree-of-freedom rigid-body models for both the supersonically-deployed and subsonically-deployed parachutes. This simulation is designed to be incorporated into a larger simulation of the entire entry, descent and landing (EDL) sequence. The complete end-to-end simulation will provide attitude history predictions of all bodies throughout the flight as well as loads on each of the connecting lines. Other issues such as recontact with jettisoned elements (heat shield, back shield, parachute mortar covers, etc.), design of parachute and attachment points, and desirable line properties can also be addressed readily using this simulation.

Queen, Eric M.; Raiszadeh, Ben

2002-01-01

273

Abstracts and program proceedings of the 1994 meeting of the International Society for Ecological Modelling North American Chapter  

SciTech Connect

This document contains information about the 1994 meeting of the International Society for Ecological Modelling North American Chapter. The topics discussed include: extinction risk assessment modelling, ecological risk analysis of uranium mining, impacts of pesticides, demography, habitats, atmospheric deposition, and climate change.

Kercher, J.R.

1994-06-01

274

Nutrient and plankton dynamics in an intermittently closed\\/open lagoon, Smiths Lake, south-eastern Australia: An ecological model  

Microsoft Academic Search

A spatially resolved, eleven-box ecological model is presented for an Intermittently Closed and Open Lake or Lagoon (ICOLL), configured for Smiths Lake, NSW Australia. ICOLLs are characterised by low flow from the catchment and a dynamic sand bar blocking oceanic exchange, which creates two distinct phases – open and closed. The process descriptions in the ecological model are based on

Jason D. Everett; Mark E. Baird; Iain M. Suthers

2007-01-01

275

Nutrient and plankton dynamics in an intermittently closed\\/open lagoon, Smiths Lake, south-eastern Australia: An ecological model  

Microsoft Academic Search

A spatially resolved, eleven-box ecological model is presented for an Intermittently Closed and Open Lake or Lagoon (ICOLL), configured for Smiths Lake, NSW Australia. ICOLLs are characterised by low flow from the catchment and a dynamic sand bar blocking oceanic exchange, which creates two distinct phases open and closed. The process descriptions in the ecological model are based on a

Jason D. Everett; Mark E. Baird; Iain M. Suthers

2007-01-01

276

Ecological Niche Model used to examine the distribution of an invasive, non-indigenous coral.  

PubMed

All organisms have a set of ecological conditions (or niche) which they depend on to survive and establish in a given habitat. The ecological niche of a species limits its geographical distribution. In the particular case of non-indigenous species (NIS), the ecological requirements of the species impose boundaries on the potential distribution of the organism in the new receptor regions. This is a theoretical assumption implicit when Ecological Niche Models (ENMs) are used to assess the potential distribution of NIS. This assumption has been questioned, given that in some cases niche shift may occur during the process of invasion. We used ENMs to investigate whether the model fit with data from the native range of the coral Tubastraea coccinea Lesson, 1829 successfully predicts its invasion in the Atlantic. We also identified which factors best explain the distribution of this NIS. The broad native distributional range of T. coccinea predicted the invaded sites well, especially along the Brazilian coast, the Caribbean Sea and Gulf of Mexico. The occurrence of T. coccinea was positively related to calcite levels and negatively to eutrophy, but was rather unaffected to other variables that often limit other marine organisms, suggesting that this NIS has wide ecological limits, a trait typical of invasive species. PMID:25465286

Carlos-Júnior, L A; Barbosa, N P U; Moulton, T P; Creed, J C

2015-02-01

277

The Ecological Model Web Concept: A Consultative Infrastructure for Decision Makers and Researchers  

NASA Astrophysics Data System (ADS)

Rapid climate and socioeconomic changes may be outrunning society's ability to understand, predict, and respond to change effectively. Decision makers want better information about what these changes will be and how various resources will be affected, while researchers want better understanding of the components and processes of ecological systems, how they interact, and how they respond to change. Although there are many excellent models in ecology and related disciplines, there is only limited coordination among them, and accessible, openly shared models or model systems that can be consulted to gain insight on important ecological questions or assist with decision-making are rare. A "consultative infrastructure" that increased access to and sharing of models and model outputs would benefit decision makers, researchers, as well as modelers. Of course, envisioning such an ambitious system is much easier than building it, but several complementary approaches exist that could contribute. The one discussed here is called the Model Web. This is a concept for an open-ended system of interoperable computer models and databases based on making models and their outputs available as services ("model as a service"). Initially, it might consist of a core of several models from which it could grow gradually as new models or databases were added. However, a model web would not be a monolithic, rigidly planned and built system--instead, like the World Wide Web, it would grow largely organically, with limited central control, within a framework of broad goals and data exchange standards. One difference from the WWW is that a model web is much harder to create, and has more pitfalls, and thus is a long term vision. However, technology, science, observations, and models have advanced enough so that parts of an ecological model web can be built and utilized now, forming a framework for gradual growth as well as a broadly accessible infrastructure. Ultimately, the value of a model web lies in the increase in access to and sharing of both models and model outputs. By lowering access barriers to models and their outputs there is less reinvention, more efficient use of resources, greater interaction among researchers and across disciplines, as well as other benefits. The growth of such a system of models fits well with the concept and architecture of the Global Earth Observing System of Systems (GEOSS) as well as the Semantic Web. And, while framed here in the context of ecological forecasting, the same concept can be applied to any discipline utilizing models.

Geller, G.; Nativi, S.

2011-12-01

278

Water system modeling for dispatcher training simulators  

SciTech Connect

This paper addresses the existing need for training dispatchers in the operation of power systems where it involves managing large water systems. The problem formulation and implementation of water system modeling for the Dispatcher Training Simulators (DTS) are presented in this paper. The method systematically builds the water network descriptions. The model periodically calculates the water system flows, storage values, and currently available hydro generation capacities. The model is controllable by the instructor and provides the simulated telemetry of water system data to the control center functions in the DTS. The water system modeling enhances the power system modeling subsystem of the DTS. The method is validated on a large water system and power system data. The results and the benefits of water system modeling are discussed.

Rajagopal, S.; Sigari, P.G. (Empros Systems International, Minneapolis, MN (United States)); Allen, J.E.; Assadian, M. (Pacific Gas and Electric, San Francisco, CA (United States))

1993-08-01

279

Simulation Modeling of Software Development Processes  

NASA Technical Reports Server (NTRS)

A simulation modeling approach is proposed for the prediction of software process productivity indices, such as cost and time-to-market, and the sensitivity analysis of such indices to changes in the organization parameters and user requirements. The approach uses a timed Petri Net and Object Oriented top-down model specification. Results demonstrate the model representativeness, and its usefulness in verifying process conformance to expectations, and in performing continuous process improvement and optimization.

Calavaro, G. F.; Basili, V. R.; Iazeolla, G.

1996-01-01

280

Integrating Empirical-Modeling Approaches to Improve Understanding of Terrestrial Ecology Processes  

SciTech Connect

Recent decades have seen tremendous increases in the quantity of empirical ecological data collected by individual investigators, as well as through research networks such as FLUXNET (Baldocchi et al., 2001). At the same time, advances in computer technology have facilitated the development and implementation of large and complex land surface and ecological process models. Separately, each of these information streams provides useful, but imperfect information about ecosystems. To develop the best scientific understanding of ecological processes, and most accurately predict how ecosystems may cope with global change, integration of empirical and modeling approaches is necessary. However, true integration - in which models inform empirical research, which in turn informs models (Fig. 1) - is not yet common in ecological research (Luo et al., 2011). The goal of this workshop, sponsored by the Department of Energy, Office of Science, Biological and Environmental Research (BER) program, was to bring together members of the empirical and modeling communities to exchange ideas and discuss scientific practices for increasing empirical - model integration, and to explore infrastructure and/or virtual network needs for institutionalizing empirical - model integration (Yiqi Luo, University of Oklahoma, Norman, OK, USA). The workshop included presentations and small group discussions that covered topics ranging from model-assisted experimental design to data driven modeling (e.g. benchmarking and data assimilation) to infrastructure needs for empirical - model integration. Ultimately, three central questions emerged. How can models be used to inform experiments and observations? How can experimental and observational results be used to inform models? What are effective strategies to promote empirical - model integration?

McCarthy, Heather [University of Oklahoma; Luo, Yiqi [University of Oklahoma; Wullschleger, Stan D [ORNL

2012-01-01

281

Incorporation of RAM techniques into simulation modeling  

SciTech Connect

This work concludes that reliability, availability, and maintainability (RAM) analytical techniques can be incorporated into computer network simulation modeling to yield an important new analytical tool. This paper describes the incorporation of failure and repair information into network simulation to build a stochastic computer model represents the RAM Performance of two vehicles being developed for the US Army: The Advanced Field Artillery System (AFAS) and the Future Armored Resupply Vehicle (FARV). The AFAS is the US Army`s next generation self-propelled cannon artillery system. The FARV is a resupply vehicle for the AFAS. Both vehicles utilize automation technologies to improve the operational performance of the vehicles and reduce manpower. The network simulation model used in this work is task based. The model programmed in this application requirements a typical battle mission and the failures and repairs that occur during that battle. Each task that the FARV performs--upload, travel to the AFAS, refuel, perform tactical/survivability moves, return to logistic resupply, etc.--is modeled. Such a model reproduces a model reproduces operational phenomena (e.g., failures and repairs) that are likely to occur in actual performance. Simulation tasks are modeled as discrete chronological steps; after the completion of each task decisions are programmed that determine the next path to be followed. The result is a complex logic diagram or network. The network simulation model is developed within a hierarchy of vehicle systems, subsystems, and equipment and includes failure management subnetworks. RAM information and other performance measures are collected which have impact on design requirements. Design changes are evaluated through ``what if`` questions, sensitivity studies, and battle scenario changes.

Nelson, S.C. Jr.; Haire, M.J.; Schryver, J.C.

1995-07-01

282

Combining correlative and mechanistic habitat suitability models to improve ecological compensation.  

PubMed

Only a few studies have shown positive impacts of ecological compensation on species dynamics affected by human activities. We argue that this is due to inappropriate methods used to forecast required compensation in environmental impact assessments. These assessments are mostly descriptive and only valid at limited spatial and temporal scales. However, habitat suitability models developed to predict the impacts of environmental changes on potential species' distributions should provide rigorous science-based tools for compensation planning. Here we describe the two main classes of predictive models: correlative models and individual-based mechanistic models. We show how these models can be used alone or synoptically to improve compensation planning. While correlative models are easier to implement, they tend to ignore underlying ecological processes and lack accuracy. On the contrary, individual-based mechanistic models can integrate biological interactions, dispersal ability and adaptation. Moreover, among mechanistic models, those considering animal energy balance are particularly efficient at predicting the impact of foraging habitat loss. However, mechanistic models require more field data compared to correlative models. Hence we present two approaches which combine both methods for compensation planning, especially in relation to the spatial scale considered. We show how the availability of biological databases and software enabling fast and accurate population projections could be advantageously used to assess ecological compensation requirement efficiently in environmental impact assessments. PMID:24837691

Meineri, Eric; Deville, Anne-Sophie; Grémillet, David; Gauthier-Clerc, Michel; Béchet, Arnaud

2015-02-01

283

A review of models for estimating terrestrial ecological receptor exposure to chemical contaminants  

Microsoft Academic Search

In instances where empirical measurements are not practicable, ecological risk assessments may rely on site-specific exposure models for estimating uptake of chemical contaminants. This paper presents, based on a review of the literature, a compilation of relatively simple quantitative models that can be combined to produce site- and species-specific first-order estimates of uptake of chemicals from abiotic media. These models

Bruce K. Hope

1995-01-01

284

An approach to the mathematical modelling of a controlled ecological life support system  

NASA Technical Reports Server (NTRS)

An approach to the design of a computer based model of a closed ecological life-support system suitable for use in extraterrestrial habitats is presented. The model is based on elemental mass balance and contains representations of the metabolic activities of biological components. The model can be used as a tool in evaluating preliminary designs for closed regenerative life support systems and as a method for predicting the behavior of such systems.

Averner, M. M.

1981-01-01

285

Common modeling system for digital simulation  

NASA Technical Reports Server (NTRS)

The Joint Modeling and Simulation System is a tri-service investigation into a common modeling framework for the development digital models. The basis for the success of this framework is an X-window-based, open systems architecture, object-based/oriented methodology, standard interface approach to digital model construction, configuration, execution, and post processing. For years Department of Defense (DOD) agencies have produced various weapon systems/technologies and typically digital representations of the systems/technologies. These digital representations (models) have also been developed for other reasons such as studies and analysis, Cost Effectiveness Analysis (COEA) tradeoffs, etc. Unfortunately, there have been no Modeling and Simulation (M&S) standards, guidelines, or efforts towards commonality in DOD M&S. The typical scenario is an organization hires a contractor to build hardware and in doing so an digital model may be constructed. Until recently, this model was not even obtained by the organization. Even if it was procured, it was on a unique platform, in a unique language, with unique interfaces, and, with the result being UNIQUE maintenance required. Additionally, the constructors of the model expended more effort in writing the 'infrastructure' of the model/simulation (e.g. user interface, database/database management system, data journalizing/archiving, graphical presentations, environment characteristics, other components in the simulation, etc.) than in producing the model of the desired system. Other side effects include: duplication of efforts; varying assumptions; lack of credibility/validation; and decentralization in policy and execution. J-MASS provides the infrastructure, standards, toolset, and architecture to permit M&S developers and analysts to concentrate on the their area of interest.

Painter, Rick

1994-01-01

286

Ecological niche modelling of an invasive alien plant and its potential biological control agents  

Microsoft Academic Search

Invasive alien plants are of concern in South Africa. Pompom weed (Campuloclinium macrocephalum) is currently invading the Grassland and Savannah biomes of South Africa and is likely to continue spreading in the southern African sub- region. Two possible biological control agents (Liothrips tractabilis and Cochylis campuloclinium) have been identified for control of pompom weed. We used ecological niche modelling to

P. D. Trethowan; M. P. Robertson; A. J. McConnachie

2011-01-01

287

Genetic and ecological effects of salmon farming on wild salmon: modelling from experimental results  

Microsoft Academic Search

Hindar, K., Fleming, I. A., McGinnity, P., and Diserud, O. 2006. Genetic and ecological effects of salmon farming on wild salmon: modelling from experimental results. ? ICES Journal of Marine Science, 63: 1234e1247. Cultured salmonids are released or escape into the wild in large numbers and may make up significant proportions of wild salmonid populations in fresh- and saltwater, causing

Kjetil Hindar; Ian A. Fleming; Philip McGinnity; Ola Diserud

2006-01-01

288

SPATIAL FOREST SOIL PROPERTIES FOR ECOLOGICAL MODELING IN THE WESTERN OREGON CASCADES  

EPA Science Inventory

The ultimate objective of this work is to provide a spatially distributed database of soil properties to serve as inputs to model ecological processes in western forests at the landscape scale. The Central Western Oregon Cascades are rich in biodiversity and they are a fascinati...

289

What Ecological Factors Shape Species-Area Curves in Neutral Models?  

E-print Network

What Ecological Factors Shape Species-Area Curves in Neutral Models? Massimo Cencini1 , Simone structure of biodiversity. While general features of species-area curves are quite universal across) and the level of habitat saturation (allowing for empty sites). We conclude that species-area curves become

Cencini, Massimo

290

The Primate Community of Cachoeira (Brazilian Amazonia): A Model to Decipher Ecological Partitioning  

E-print Network

The Primate Community of Cachoeira (Brazilian Amazonia): A Model to Decipher Ecological, Villeurbanne, France Abstract Dental microwear analysis is conducted on a community of platyrrhine primates from South America. This analysis focuses on the primate community of Cachoeira Porteira (Para, Brazil

Paris-Sud XI, Université de

291

Ecological Modelling 178 (2004) 349356 Growth dilution in multilevel food chains  

E-print Network

Ecological Modelling 178 (2004) 349­356 Growth dilution in multilevel food chains Robert A of growth dilution in all trophic levels of a food chain. We are concerned with concentration as well by Elsevier B.V. Keywords: Growth dilution; Bioaccumulation; Biomagnification; Food chain 1. Introduction

Vermont, University of

292

ecological modelling 1 9 5 ( 2 0 0 6 ) 6171 available at www.sciencedirect.com  

E-print Network

ecological modelling 1 9 5 ( 2 0 0 6 ) 61­71 available at www.sciencedirect.com journal homepage University, Busan (Pusan) 609-735, Republic of Korea d Division of Biological Sciences, Pusan National to the treat- ments of carbofuran, an anticholinesterase insecticide, at a low concentration (0.1 mg/l) in semi

Chon, Tae-Soo

293

COMMUNITY AND ECOSYSTEM ECOLOGY Modeling Temporal Trends in Aphid Vector Dispersal and Cucumber  

E-print Network

COMMUNITY AND ECOSYSTEM ECOLOGY Modeling Temporal Trends in Aphid Vector Dispersal and Cucumber trends to the incidence of CMV. Alates were monitored weekly using water pan traps in 74 snap bean Ã?elds facilities and are harvested over a 2-mo period, typi- cally beginning in mid-July. Processing demands

Nault, Brian

294

Ecological Modelling 185 (2005) 513529 Air quality prediction in Milan: feed-forward neural networks,  

E-print Network

December 2004; accepted 3 January 2005 Abstract Ozone and PM10 constitute the major concern for air qualityEcological Modelling 185 (2005) 513­529 Air quality prediction in Milan: feed-forward neural as state-of-the-art approach for statistical prediction of air quality, are compared with two alternative

Corani, Giorgio

295

Ecological Modelling 152 (2002) 205211 The effectiveness of various rabies spatial vaccination  

E-print Network

Ecological Modelling 152 (2002) 205­211 The effectiveness of various rabies spatial vaccination, periodic episodes of rabies epidemics erupt every 5­7 years despite low densities of the main reservoir species of rabies in this area. Canids in this desert are spread non-uniformly over space, with high

Bohrer, Gil

296

Scale-dependent foraging ecology of a marine top predator modelled using passive acoustic data  

E-print Network

Scale-dependent foraging ecology of a marine top predator modelled using passive acoustic data especially challenging in marine predators, but passive acoustic techniques provide opportunities to study and Environmental Sciences, University of Aberdeen, Cromarty IV11 8YL, UK; and 3 Plymouth Marine Laboratory

Aberdeen, University of

297

USING A NEW DISPERSED OIL MODEL TO SUPPORT ECOLOGICAL RISK ASSESSMENT  

Microsoft Academic Search

A new model is being used to support dispersant Ecological Risk Assessment (ERA) workshops. User-driven output includes trajectory maps for both chemically dispersed and undispersed oil, and concentration isopleths reported by depth and over time. To help make toxicological sense of the output, oil concentration isopleths were nominally fixed at concentrations and exposure times of concern developed by consensus during

Alan Mearns; Glen Watabayashi; Caitlin O'Connor

298

Integrating Evolution into Ecological Modelling: Accommodating Phenotypic Changes in Agent Based Models  

PubMed Central

Evolutionary change is a characteristic of living organisms and forms one of the ways in which species adapt to changed conditions. However, most ecological models do not incorporate this ubiquitous phenomenon. We have developed a model that takes a ‘phenotypic gambit’ approach and focuses on changes in the frequency of phenotypes (which differ in timing of breeding and fecundity) within a population, using, as an example, seasonal breeding. Fitness per phenotype calculated as the individual’s contribution to population growth on an annual basis coincide with the population dynamics per phenotype. Simplified model variants were explored to examine whether the complexity included in the model is justified. Outputs from the spatially implicit model underestimated the number of individuals across all phenotypes. When no phenotype transitions are included (i.e. offspring always inherit their parent’s phenotype) numbers of all individuals are always underestimated. We conclude that by using a phenotypic gambit approach evolutionary dynamics can be incorporated into individual based models, and that all that is required is an understanding of the probability of offspring inheriting the parental phenotype. PMID:23940700

Moustakas, Aristides; Evans, Matthew R.

2013-01-01

299

Islands as model systems in ecology and evolution: prospects fifty years after MacArthur-Wilson.  

PubMed

The study of islands as model systems has played an important role in the development of evolutionary and ecological theory. The 50th anniversary of MacArthur and Wilson's (December 1963) article, 'An equilibrium theory of insular zoogeography', was a recent milestone for this theme. Since 1963, island systems have provided new insights into the formation of ecological communities. Here, building on such developments, we highlight prospects for research on islands to improve our understanding of the ecology and evolution of communities in general. Throughout, we emphasise how attributes of islands combine to provide unusual research opportunities, the implications of which stretch far beyond islands. Molecular tools and increasing data acquisition now permit re-assessment of some fundamental issues that interested MacArthur and Wilson. These include the formation of ecological networks, species abundance distributions, and the contribution of evolution to community assembly. We also extend our prospects to other fields of ecology and evolution - understanding ecosystem functioning, speciation and diversification - frequently employing assets of oceanic islands in inferring the geographic area within which evolution has occurred, and potential barriers to gene flow. Although island-based theory is continually being enriched, incorporating non-equilibrium dynamics is identified as a major challenge for the future. PMID:25560682

Warren, Ben H; Simberloff, Daniel; Ricklefs, Robert E; Aguilée, Robin; Condamine, Fabien L; Gravel, Dominique; Morlon, Hélène; Mouquet, Nicolas; Rosindell, James; Casquet, Juliane; Conti, Elena; Cornuault, Josselin; Fernández-Palacios, José María; Hengl, Tomislav; Norder, Sietze J; Rijsdijk, Kenneth F; Sanmartín, Isabel; Strasberg, Dominique; Triantis, Kostas A; Valente, Luis M; Whittaker, Robert J; Gillespie, Rosemary G; Emerson, Brent C; Thébaud, Christophe

2015-02-01

300

The spatial optimism model research for the regional land use based on the ecological constraint  

NASA Astrophysics Data System (ADS)

The study focuses on the Yunnan-Guizhou (i.e. Yunnan province and Guizhou province) Plateau in China. Since the Yunnan-Guizhou region consists of closed basins, the land resources suiting for development are in a shortage, and the ecological problems in the area are quite complicated. In such circumstance, in order to get the applicable basins area and distribution, certain spatial optimism model is needed. In this research, Digital Elevation Model (DEM) and land use data are used to get the boundary rules of the basins distribution. Furthermore, natural risks, ecological risks and human-made ecological risks are integrated to be analyzed. Finally, the spatial overlay analysis method is used to model the developable basins area and distribution for industries and urbanization. The study process can be divided into six steps. First, basins and their distribution need to be recognized. In this way, the DEM data is used to extract the geomorphology characteristics. The plaque regions with gradient under eight degrees are selected. Among these regions, the total area of the plaque with the area above 8 km2 is 54,000 km2, 10% of the total area. These regions are selected to the potential application of industries and urbanization. In the later five steps, analyses are aimed at these regions. Secondly, the natural risks are analyzed. The conditions of the earthquake, debris flow and rainstorm and flood are combined to classify the natural risks. Thirdly, the ecological risks are analyzed containing the ecological sensibility and ecosystem service function importance. According to the regional ecologic features, the sensibility containing the soil erosion, acid rain, stony desertification and survive condition factors is derived and classified according to the medium value to get the ecological sensibility partition. The ecosystem service function importance is classified and divided considering the biology variation protection and water conservation factors. The fourth step is the man-made ecological risks analysis. The mineral resources exploitation, forest resources developing, farming, tourism, industrialization and urbanization are integrated to derive the potential ecological risks made by human activities. The risks weight are given using the expert marking method, Then the man-made ecological risks are classified and divided among the regions. In the fifth step, the comprehensive ecological controlling divisions are obtained based on the above factors classification. At last, the applicable regions and distribution are derived using the spatial overlay analysis removing the higher ecological risks area and considering the land use status. In conclusion, based on the above comprehensive analyses, the applicable basins area are 2,575 km2 and 1,011 km2 respectively for the Yunnan province and Guizhou province. The amount is less than 1% of the perspective province total area focusing on the central part of the two provinces.

XU, K.; Lu, J.; Chi, Y.

2013-12-01

301

A tree hollow dynamics simulation model  

Microsoft Academic Search

This paper describes a deterministic computer model for simulating forest dynamics. The model predicts the long-term dynamics of hollow-bearing trees which occur in a single-species (monotypic) forest stand under an array of different timber harvesting regimes over a time scale of centuries. It is applied to a number of different timber harvesting scenarios in the mountain ash (Eucalyptus regnans F.

I. R. Ball; D. B. Lindenmayer; H. P. Possingham

302

Byrd Polar Research Center Climate Model Simulation  

NSDL National Science Digital Library

This set of animations and interactive simulations from the Byrd Polar Research Center at Ohio State University helps students develop an understanding of models used to understand the Earth System. Students consider the types of data that need to be included in a climate model, looking at inputs and outputs as well as variables, such as land surface, and how to measure changes of different parts of Earth's surface over time.

Center, Byrd P.; University, Ohio S.

303

Volumetric object modeling for surgical simulation  

Microsoft Academic Search

Surgical simulation has many applications in medical education, surgical training, surgical plan- ning and intra-operative assistance. However, extending current surface-based computer graphics methods to model phenomena such as the deformation, cutting, tearing or repairing of soft tissues poses significant challenges for real-time interactions. This paper discusses the use of volumetric methods for modeling complex anatomy and tissue interactions. New techniques

Sarah Gibson; Christina Fyock; Eric Grimson; Takeo Kanade; Ron Kikinis; Hugh Lauer; Neil McKenzie; Andrew Mor; Shin Nakajima; Hide Ohkami; Randy Osborne; Joseph Samosky; Akira Sawada

1997-01-01

304

Modeling and Simulation of Count Data  

PubMed Central

Count data, or number of events per time interval, are discrete data arising from repeated time to event observations. Their mean count, or piecewise constant event rate, can be evaluated by discrete probability distributions from the Poisson model family. Clinical trial data characterization often involves population count analysis. This tutorial presents the basics and diagnostics of count modeling and simulation in the context of pharmacometrics. Consideration is given to overdispersion, underdispersion, autocorrelation, and inhomogeneity. PMID:25116273

Plan, E L

2014-01-01

305

WATER SUPPLY SIMULATION MODEL. VOLUME 3. DOCUMENTATION  

EPA Science Inventory

This three-volume report describes the development of a water supply simulation model (WSSM), a system of computer programs that allows for a systematic evaluation of the physical and economic characteristics of a water distribution system in a spatial framework. The WSSM concept...

306

Love Kills:. Simulations in Penna Ageing Model  

NASA Astrophysics Data System (ADS)

The standard Penna ageing model with sexual reproduction is enlarged by adding additional bit-strings for love: Marriage happens only if the male love strings are sufficiently different from the female ones. We simulate at what level of required difference the population dies out.

Stauffer, Dietrich; Cebrat, Stanis?aw; Penna, T. J. P.; Sousa, A. O.

307

Robust three-body water simulation model  

Microsoft Academic Search

The most common potentials used in classical simulations of liquid water assume a pairwise additive form. Although these models have been very successful in reproducing many properties of liquid water at ambient conditions, none is able to describe accurately water throughout its complicated phase diagram. The primary reason for this is the neglect of many-body interactions. To this end, a

C. J. Tainter; P. A. Pieniazek; Y.-S. Lin; J. L. Skinner

2011-01-01

308

Models, Simulations, and Games: A Survey.  

ERIC Educational Resources Information Center

A Rand evaluation of activity and products of gaming, model-building, and simulation carried out under the auspices of the Defense Advanced Research Projects Agency aimed not only to assess the usefulness of gaming in military-political policymaking, but also to contribute to the definition of common standards and the refinement of objectives for…

Shubik, Martin; Brewer, Garry D.

309

Center for Advanced Modeling and Simulation Intern  

ScienceCinema

Some interns just copy papers and seal envelopes. Not at INL! Check out how Vanessa Gertman, an INL intern working at the Center for Advanced Modeling and Simulation, spent her summer working with some intense visualization software. Lots more content like this is available at INL's facebook page http://www.facebook.com/idahonationallaboratory.

Gertman, Vanessa

2013-05-28

310

Center for Advanced Modeling and Simulation Intern  

SciTech Connect

Some interns just copy papers and seal envelopes. Not at INL! Check out how Vanessa Gertman, an INL intern working at the Center for Advanced Modeling and Simulation, spent her summer working with some intense visualization software. Lots more content like this is available at INL's facebook page http://www.facebook.com/idahonationallaboratory.

Gertman, Vanessa

2010-01-01

311

Modeling and Simulation Information Analysis Center  

NSDL National Science Digital Library

The Modeling and Simulation Information Analysis Center (MSIAC) assists the Department of Defense (DoD) in meeting its M&S needs "by providing scientific, technical, and operational support information and services." Through the Help Desk, MSIAC also answers technical inquiries from non-DoD customers, who agree to pay for their service beyond the first two hours. The group has experience in weapons technology including WMD, information management, modeling and simulation, operations analysis, chemical and explosive sciences, material sciences, spectrum engineering, wireless communication, life sciences, medical informatics and telemedicine, transportation systems, and reliability, availability, and maintainability. A wealth of resources are available from this website, including the Modeling & Simulation Resource Repository (MSRR), which is described as "the first place to go for answers to M&S" and Glossary of Modeling and Simulation (M&S) Terms, information on special topics of interest within M&S, and links to related websites. The MSIAC's M&S Journal Online offers quarterly articles of interest to the M&S community free of charge. This site is also reviewed in the March 25, 2005_NSDL MET Report_.

312

Modeling and simulation of aquifer storage energy systems  

Microsoft Academic Search

Computer simulation model AQSYST for simulating energy systems employing thermal energy storage in aquifers, or groundwater basins, is described. Aquifers offer a potential and economical way of storing solar heat for long periods of time. The simulation model AQSYST features a modular energy system, in which subsystems and their connections are accurately simulated. The storage simulation in AQSYST is accomplished

M. T. Kangas; P. D. Lund

1994-01-01

313

Estimating Environmental Drivers for Broad-Scale Ecological Models: Comparing Performance of Modeled Stream Flow and Meteorological Observations  

NASA Astrophysics Data System (ADS)

Fisheries ecologists are charged with assessing the impact of climate and land use changes on wild fish populations. Their ecological population models require estimates of environmental drivers, stream flow and stream temperature, across broad spatial scales. Observation data is frequently not available at that scale, especially for smaller streams and headwaters that are the habitat for target species. As estimates at a coarse temporal resolution are sufficient for many ecological population models, it is possible to develop regionalized models across the broad spatial scale required with the limited observations available. It may also be possible to use measures of air temperature and precipitation, for which meteorological observations are more readily available, as proxy metrics for stream flow and stream temperature. Since additional sources of model uncertainty are avoided by using the proxy measures, it is important to evaluate whether modeled stream flow provides enough improvement to the ecological models to justify this introduction of uncertainty. We employ wild brook trout occupancy models to evaluate these different environmental inputs. We present a regionalized model for estimating stream flow at the seasonal time-step, and a model of summary statistics. Performance of fish occupancy models using each of these estimates is then compared to the performance of a fish occupancy model using meteorological measures as the environmental driver.

Rosner, A.; Letcher, B. H.; Kanno, Y.

2013-12-01

314

Adaptive System Modeling for Spacecraft Simulation  

NASA Technical Reports Server (NTRS)

This invention introduces a methodology and associated software tools for automatically learning spacecraft system models without any assumptions regarding system behavior. Data stream mining techniques were used to learn models for critical portions of the International Space Station (ISS) Electrical Power System (EPS). Evaluation on historical ISS telemetry data shows that adaptive system modeling reduces simulation error anywhere from 50 to 90 percent over existing approaches. The purpose of the methodology is to outline how someone can create accurate system models from sensor (telemetry) data. The purpose of the software is to support the methodology. The software provides analysis tools to design the adaptive models. The software also provides the algorithms to initially build system models and continuously update them from the latest streaming sensor data. The main strengths are as follows: Creates accurate spacecraft system models without in-depth system knowledge or any assumptions about system behavior. Automatically updates/calibrates system models using the latest streaming sensor data. Creates device specific models that capture the exact behavior of devices of the same type. Adapts to evolving systems. Can reduce computational complexity (faster simulations).

Thomas, Justin

2011-01-01

315

Computational Spectrum of Agent Model Simulation  

SciTech Connect

The study of human social behavioral systems is finding renewed interest in military, homeland security and other applications. Simulation is the most generally applied approach to studying complex scenarios in such systems. Here, we outline some of the important considerations that underlie the computational aspects of simulation-based study of human social systems. The fundamental imprecision underlying questions and answers in social science makes it necessary to carefully distinguish among different simulation problem classes and to identify the most pertinent set of computational dimensions associated with those classes. We identify a few such classes and present their computational implications. The focus is then shifted to the most challenging combinations in the computational spectrum, namely, large-scale entity counts at moderate to high levels of fidelity. Recent developments in furthering the state-of-the-art in these challenging cases are outlined. A case study of large-scale agent simulation is provided in simulating large numbers (millions) of social entities at real-time speeds on inexpensive hardware. Recent computational results are identified that highlight the potential of modern high-end computing platforms to push the envelope with respect to speed, scale and fidelity of social system simulations. Finally, the problem of shielding the modeler or domain expert from the complex computational aspects is discussed and a few potential solution approaches are identified.

Perumalla, Kalyan S [ORNL

2010-01-01

316

Video Modeling: Combining Dynamic Model Simulations with Traditional Video Analysis  

NSDL National Science Digital Library

The Tracker video analysis program allows users to overlay simple dynamic particle models on a video clip. In a typical video modeling experiment students capture and open a digital video file, calibrate the scale, and define appropriate coordinate axes just as for traditional video analysis. But instead of tracking objects with the mouse, students define theoretical force expressions and initial conditions for a dynamic model simulation that synchronizes with and draws itself on the video. The behavior of the model is thus compared directly with that of the real-world motion. Tracker uses the Open Source Physics code library so sophisticated models are possible. Video modeling offers advantages over both traditional video analysis and simulation-only modeling. This paper includes video modeling experiments produced by students in an Introductory Mechanics course.

Brown, Douglas

2008-08-16

317

Ecological Modelling 187 (2005) 179200 Eutrophication model for Lake Washington (USA)  

E-print Network

--model calibration and system dynamics analysis George B. Arhonditsis, Michael T. Brett Department of Civil patterns of the system and results in a good fit be- tween simulated and observed monthly values the meteorological forcing (air temperature, solar radiation, precipitation and subsequent river inflows

Arhonditsis, George B.

318

Requirements for psychological models to support design: Towards ecological task analysis  

NASA Technical Reports Server (NTRS)

Cognitive engineering is largely concerned with creating environmental designs to support skillful and effective human activity. A set of necessary conditions are proposed for psychological models capable of supporting this enterprise. An analysis of the psychological nature of the design product is used to identify a set of constraints that models must meet if they can usefully guide design. It is concluded that cognitive engineering requires models with resources for describing the integrated human-environment system, and that these models must be capable of describing the activities underlying fluent and effective interaction. These features are required in order to be able to predict the cognitive activity that will be required given various design concepts, and to design systems that promote the acquisition of fluent, skilled behavior. These necessary conditions suggest that an ecological approach can provide valuable resources for psychological modeling to support design. Relying heavily on concepts from Brunswik's and Gibson's ecological theories, ecological task analysis is proposed as a framework in which to predict the types of cognitive activity required to achieve productive behavior, and to suggest how interfaces can be manipulated to alleviate certain types of cognitive demands. The framework is described in terms, and illustrated with an example from the previous research on modeling skilled human-environment interaction.

Kirlik, Alex

1991-01-01

319

Author's personal copy Ecological Modelling 222 (2011) 11291138  

E-print Network

a powerful tool. We develop an agent-based model of urban growth for the Phoenix metropolitan region regression model is employed to predict the future urban development of the Phoenix metropolitan region a better understanding of urban dynam- ics, researchers have developed different kinds of modeling

Wu, Jianguo "Jingle"

320

Statistical simulation models for Rayleigh and Rician fading  

Microsoft Academic Search

New simulation models are proposed for Rayleigh and Rician fading channels. First, the statistical properties of Clarke's fading model with a finite number of sinusoids are analyzed. An improved Clarke's model is then proposed for the simulation of Rayleigh fading channels. Based on this improved Rayleigh fading model, a novel simulation model is proposed for Rician fading channels. The new

Chengshan Xiao; Yahong R. Zheng; Norman C. Beaulieu

2003-01-01

321

Computational model for protein unfolding simulation  

NASA Astrophysics Data System (ADS)

The protein folding problem is one of the fundamental and important questions in molecular biology. However, the all-atom molecular dynamics studies of protein folding and unfolding are still computationally expensive and severely limited by the time scale of simulation. In this paper, a simple and fast protein unfolding method is proposed based on the conformational stability analyses and structure modeling. In this method, two structure-based conditions are considered to identify the unstable regions of proteins during the unfolding processes. The protein unfolding trajectories are mimicked through iterative structure modeling according to conformational stability analyses. Two proteins, chymotrypsin inhibitor 2 (CI2) and ? -spectrin SH3 domain (SH3) were simulated by this method. Their unfolding pathways are consistent with the previous molecular dynamics simulations. Furthermore, the transition states of the two proteins were identified in unfolding processes and the theoretical ? values of these transition states showed significant correlations with the experimental data (the correlation coefficients are >0.8). The results indicate that this method is effective in studying protein unfolding. Moreover, we analyzed and discussed the influence of parameters on the unfolding simulation. This simple coarse-grained model may provide a general and fast approach for the mechanism studies of protein folding.

Tian, Xu-Hong; Zheng, Ye-Han; Jiao, Xiong; Liu, Cai-Xing; Chang, Shan

2011-06-01

322

Electronic continuum model for molecular dynamics simulations  

PubMed Central

A simple model for accounting for electronic polarization in molecular dynamics (MD) simulations is discussed. In this model, called molecular dynamics electronic continuum (MDEC), the electronic polarization is treated explicitly in terms of the electronic continuum (EC) approximation, while the nuclear dynamics is described with a fixed-charge force field. In such a force-field all atomic charges are scaled to reflect the screening effect by the electronic continuum. The MDEC model is rather similar but not equivalent to the standard nonpolarizable force-fields; the differences are discussed. Of our particular interest is the calculation of the electrostatic part of solvation energy using standard nonpolarizable MD simulations. In a low-dielectric environment, such as protein, the standard MD approach produces qualitatively wrong results. The difficulty is in mistreatment of the electronic polarizability. We show how the results can be much improved using the MDEC approach. We also show how the dielectric constant of the medium obtained in a MD simulation with nonpolarizable force-field is related to the static (total) dielectric constant, which includes both the nuclear and electronic relaxation effects. Using the MDEC model, we discuss recent calculations of dielectric constants of alcohols and alkanes, and show that the MDEC results are comparable with those obtained with the polarizable Drude oscillator model. The applicability of the method to calculations of dielectric properties of proteins is discussed. PMID:19256627

Leontyev, I. V.; Stuchebrukhov, A. A.

2009-01-01

323

Robust three-body water simulation model.  

PubMed

The most common potentials used in classical simulations of liquid water assume a pairwise additive form. Although these models have been very successful in reproducing many properties of liquid water at ambient conditions, none is able to describe accurately water throughout its complicated phase diagram. The primary reason for this is the neglect of many-body interactions. To this end, a simulation model with explicit three-body interactions was introduced recently [R. Kumar and J. L. Skinner, J. Phys. Chem. B 112, 8311 (2008)]. This model was parameterized to fit the experimental O-O radial distribution function and diffusion constant. Herein we reparameterize the model, fitting to a wider range of experimental properties (diffusion constant, rotational correlation time, density for the liquid, liquid/vapor surface tension, melting point, and the ice Ih density). The robustness of the model is then verified by comparing simulation to experiment for a number of other quantities (enthalpy of vaporization, dielectric constant, Debye relaxation time, temperature of maximum density, and the temperature-dependent second and third virial coefficients), with good agreement. PMID:21568515

Tainter, C J; Pieniazek, P A; Lin, Y-S; Skinner, J L

2011-05-14

324

Robust three-body water simulation model  

NASA Astrophysics Data System (ADS)

The most common potentials used in classical simulations of liquid water assume a pairwise additive form. Although these models have been very successful in reproducing many properties of liquid water at ambient conditions, none is able to describe accurately water throughout its complicated phase diagram. The primary reason for this is the neglect of many-body interactions. To this end, a simulation model with explicit three-body interactions was introduced recently [R. Kumar and J. L. Skinner, J. Phys. Chem. B 112, 8311 (2008), 10.1021/jp8009468]. This model was parameterized to fit the experimental O-O radial distribution function and diffusion constant. Herein we reparameterize the model, fitting to a wider range of experimental properties (diffusion constant, rotational correlation time, density for the liquid, liquid/vapor surface tension, melting point, and the ice Ih density). The robustness of the model is then verified by comparing simulation to experiment for a number of other quantities (enthalpy of vaporization, dielectric constant, Debye relaxation time, temperature of maximum density, and the temperature-dependent second and third virial coefficients), with good agreement.

Tainter, C. J.; Pieniazek, P. A.; Lin, Y.-S.; Skinner, J. L.

2011-05-01

325

Compressible homogeneous shear: Simulation and modeling  

NASA Technical Reports Server (NTRS)

Compressibility effects were studied on turbulence by direct numerical simulation of homogeneous shear flow. A primary observation is that the growth of the turbulent kinetic energy decreases with increasing turbulent Mach number. The sinks provided by compressible dissipation and the pressure dilatation, along with reduced Reynolds shear stress, are shown to contribute to the reduced growth of kinetic energy. Models are proposed for these dilatational terms and verified by direct comparison with the simulations. The differences between the incompressible and compressible fields are brought out by the examination of spectra, statistical moments, and structure of the rate of strain tensor.

Sarkar, S.; Erlebacher, G.; Hussaini, M. Y.

1992-01-01

326

Flight Simulation Model Exchange. Volume 2; Appendices  

NASA Technical Reports Server (NTRS)

The NASA Engineering and Safety Center Review Board sponsored an assessment of the draft Standard, Flight Dynamics Model Exchange Standard, BSR/ANSI-S-119-201x (S-119) that was conducted by simulation and guidance, navigation, and control engineers from several NASA Centers. The assessment team reviewed the conventions and formats spelled out in the draft Standard and the actual implementation of two example aerodynamic models (a subsonic F-16 and the HL-20 lifting body) encoded in the Extensible Markup Language grammar. During the implementation, the team kept records of lessons learned and provided feedback to the American Institute of Aeronautics and Astronautics Modeling and Simulation Technical Committee representative. This document contains the appendices to the main report.

Murri, Daniel G.; Jackson, E. Bruce

2011-01-01

327

A parallel computational model for GATE simulations.  

PubMed

GATE/Geant4 Monte Carlo simulations are computationally demanding applications, requiring thousands of processor hours to produce realistic results. The classical strategy of distributing the simulation of individual events does not apply efficiently for Positron Emission Tomography (PET) experiments, because it requires a centralized coincidence processing and large communication overheads. We propose a parallel computational model for GATE that handles event generation and coincidence processing in a simple and efficient way by decentralizing event generation and processing but maintaining a centralized event and time coordinator. The model is implemented with the inclusion of a new set of factory classes that can run the same executable in sequential or parallel mode. A Mann-Whitney test shows that the output produced by this parallel model in terms of number of tallies is equivalent (but not equal) to its sequential counterpart. Computational performance evaluation shows that the software is scalable and well balanced. PMID:24070545

Rannou, F R; Vega-Acevedo, N; El Bitar, Z

2013-12-01

328

Flight Simulation Model Exchange. Volume 1  

NASA Technical Reports Server (NTRS)

The NASA Engineering and Safety Center Review Board sponsored an assessment of the draft Standard, Flight Dynamics Model Exchange Standard, BSR/ANSI-S-119-201x (S-119) that was conducted by simulation and guidance, navigation, and control engineers from several NASA Centers. The assessment team reviewed the conventions and formats spelled out in the draft Standard and the actual implementation of two example aerodynamic models (a subsonic F-16 and the HL-20 lifting body) encoded in the Extensible Markup Language grammar. During the implementation, the team kept records of lessons learned and provided feedback to the American Institute of Aeronautics and Astronautics Modeling and Simulation Technical Committee representative. This document contains the results of the assessment.

Murri, Daniel G.; Jackson, E. Bruce

2011-01-01

329

Advanced Modeling, Simulation and Analysis (AMSA) Capability Roadmap Progress Review  

NASA Technical Reports Server (NTRS)

Contents include the following: NASA capability roadmap activity. Advanced modeling, simulation, and analysis overview. Scientific modeling and simulation. Operations modeling. Multi-special sensing (UV-gamma). System integration. M and S Environments and Infrastructure.

Antonsson, Erik; Gombosi, Tamas

2005-01-01

330

Effects of stream topology on ecological community results from neutral models  

EPA Science Inventory

While neutral theory and models have stimulated considerable literature, less well investigated is the effect of topology on neutral metacommunity model simulations. We implemented a neutral metacommunity model using two different stream network topologies, a widely branched netw...

331

Advancing Material Models for Automotive Forming Simulations  

NASA Astrophysics Data System (ADS)

Simulations in automotive industry need more advanced material models to achieve highly reliable forming and springback predictions. Conventional material models implemented in the FEM-simulation models are not capable to describe the plastic material behaviour during monotonic strain paths with sufficient accuracy. Recently, ESI and Corus co-operate on the implementation of an advanced material model in the FEM-code PAMSTAMP 2G. This applies to the strain hardening model, the influence of strain rate, and the description of the yield locus in these models. A subsequent challenge is the description of the material after a change of strain path. The use of advanced high strength steels in the automotive industry requires a description of plastic material behaviour of multiphase steels. The simplest variant is dual phase steel consisting of a ferritic and a martensitic phase. Multiphase materials also contain a bainitic phase in addition to the ferritic and martensitic phase. More physical descriptions of strain hardening than simple fitted Ludwik/Nadai curves are necessary. Methods to predict plastic behaviour of single-phase materials use a simple dislocation interaction model based on the formed cells structures only. At Corus, a new method is proposed to predict plastic behaviour of multiphase materials have to take hard phases into account, which deform less easily. The resulting deformation gradients create geometrically necessary dislocations. Additional micro-structural information such as morphology and size of hard phase particles or grains is necessary to derive the strain hardening models for this type of materials. Measurements available from the Numisheet benchmarks allow these models to be validated. At Corus, additional measured values are available from cross-die tests. This laboratory test can attain critical deformations by large variations in blank size and processing conditions. The tests are a powerful tool in optimising forming simulations prior to larger scale industrial validation.

Vegter, H.; An, Y.; ten Horn, C. H. L. J.; Atzema, E. H.; Roelofsen, M. E.

2005-08-01

332

Component-basedComponent based Modeling and SimulationModeling and Simulation  

E-print Network

­ grid, p2p, cloud computing, etc. Advance simulation models and knowledge sharing on· Advance simulation Meng Teo and Claudia Szabo** Department of Computer Science National University of Singapore email: teoym@comp.nus.edu.sg ** Department of Computer Science** Department of Computer Science University

Teo, Yong-Meng

333

Coastal environmental assessment and management by ecological simulation in Yeoja Bay, Korea  

NASA Astrophysics Data System (ADS)

An eco-hydrodynamic model was used to estimate the carrying capacity of pollutant loads and response of water quality to environmental change in Yeoja Bay, Korea. An energy-system model also was used to simulate the fluctuation in nutrients and organic matter in the bordering wetland. Most water quality factors showed a pulsed pattern, and the concentrations of nutrients and organic matter of seawater increased when input loads of nutrients increased due to freshwater discharge. The well-developed tidal zones and wetlands in the northern area of the bay were highly sensitive to input loads. Residence times of water, chemical oxygen demand (COD), and dissolved inorganic nitrogen (DIN) within the bay were estimated to be about 16 days, 43.2 days, and 50.2 days, respectively. Water quality reacted more sensitively to the effects of nitrogen and phosphorus input than to COD. A plan to reduce the present levels of COD and dissolved inorganic phosphorus (DIP) by 20-30% and DIN by at least 50% in pollutant loads is needed for satisfying the target water quality criteria. The natural removal rate of nutrients in wetlands by reeds was assessed to be approximately 10%.

Lee, Dae-In; Choi, Jeong-Min; Lee, Yeon-Gyu; Lee, Moon-Ock; Lee, Won-Chan; Kim, Jong-Kyu

2008-12-01

334

Study on ecological impact evaluation for land consolidation based on cloud model: a case study of Miaotan town  

NASA Astrophysics Data System (ADS)

Combining the basic theory of cloud model and the process of ecological impact evaluation for land consolidation, the author constructs the rule of ecological impact evaluation and the cloud models of the antecedent and the consequent, by translating the uncertain factor conditions into quantitative values with the uncertain illation based on cloud model, computes the evaluation factor scores and comprehensive scores of MiaoTan, and then, comparing the results with composite index computation method and fuzzy comprehensive assessment, a feasible method used in Ecological Impact Evaluation for Land Consolidation is proposed.

Liu, Yao-lin; Fan, Min; Yang, Xiao-yu; Liu, Hui

2008-10-01

335

An online database for informing ecological network models: http://kelpforest.ucsc.edu  

USGS Publications Warehouse

Ecological network models and analyses are recognized as valuable tools for understanding the dynamics and resiliency of ecosystems, and for informing ecosystem-based approaches to management. However, few databases exist that can provide the life history, demographic and species interaction information necessary to parameterize ecological network models. Faced with the difficulty of synthesizing the information required to construct models for kelp forest ecosystems along the West Coast of North America, we developed an online database (http://kelpforest.ucsc.edu/) to facilitate the collation and dissemination of such information. Many of the database's attributes are novel yet the structure is applicable and adaptable to other ecosystem modeling efforts. Information for each taxonomic unit includes stage-specific life history, demography, and body-size allometries. Species interactions include trophic, competitive, facilitative, and parasitic forms. Each data entry is temporally and spatially explicit. The online data entry interface allows researchers anywhere to contribute and access information. Quality control is facilitated by attributing each entry to unique contributor identities and source citations. The database has proven useful as an archive of species and ecosystem-specific information in the development of several ecological network models, for informing management actions, and for education purposes (e.g., undergraduate and graduate training). To facilitate adaptation of the database by other researches for other ecosystems, the code and technical details on how to customize this database and apply it to other ecosystems are freely available and located at the following link (https://github.com/kelpforest-cameo/data?baseui).

Beas-Luna, Rodrigo; Tinker, M. Tim; Novak, Mark; Carr, Mark H.; Black, August; Caselle, Jennifer E.; Hoban, Michael; Malone, Dan; Iles, Alison C.

2014-01-01

336

An Online Database for Informing Ecological Network Models: http://kelpforest.ucsc.edu  

PubMed Central

Ecological network models and analyses are recognized as valuable tools for understanding the dynamics and resiliency of ecosystems, and for informing ecosystem-based approaches to management. However, few databases exist that can provide the life history, demographic and species interaction information necessary to parameterize ecological network models. Faced with the difficulty of synthesizing the information required to construct models for kelp forest ecosystems along the West Coast of North America, we developed an online database (http://kelpforest.ucsc.edu/) to facilitate the collation and dissemination of such information. Many of the database's attributes are novel yet the structure is applicable and adaptable to other ecosystem modeling efforts. Information for each taxonomic unit includes stage-specific life history, demography, and body-size allometries. Species interactions include trophic, competitive, facilitative, and parasitic forms. Each data entry is temporally and spatially explicit. The online data entry interface allows researchers anywhere to contribute and access information. Quality control is facilitated by attributing each entry to unique contributor identities and source citations. The database has proven useful as an archive of species and ecosystem-specific information in the development of several ecological network models, for informing management actions, and for education purposes (e.g., undergraduate and graduate training). To facilitate adaptation of the database by other researches for other ecosystems, the code and technical details on how to customize this database and apply it to other ecosystems are freely available and located at the following link (https://github.com/kelpforest-cameo/databaseui). PMID:25343723

Beas-Luna, Rodrigo; Novak, Mark; Carr, Mark H.; Tinker, Martin T.; Black, August; Caselle, Jennifer E.; Hoban, Michael; Malone, Dan; Iles, Alison

2014-01-01

337

Using Mechanistic Models to Scale Ecological Processes across Space and Time  

NSDL National Science Digital Library

This peer-reviewed article from BioScience is about using mechanistic models to scale ecological processes. Human activities affect the natural environment at local to global scales. To understand these effects, knowledge derived from short-term studies on small plots needs to be projected to much broader spatial and temporal scales. One way to project short-term, plot-scale knowledge to broader scales is to embed that knowledge in a mechanistic model of the ecosystem. The National Science Foundation's Long Term Ecological Research (LTER) Network makes two vital contributions to this type of modeling effort: (1) a commitment to multidisciplinary research at individual sites, which results in a broad range of mutually consistent data, and (2) long-term data sets essential for estimating rate constants for slow ecosystem processes that dominate long-term ecosystem dynamics. In this article, we present four examples of how a mechanistic approach to modeling ecological processes can be used to make projections to broader scales. The models are all applied to sites in the LTER Network.

EDWARD B. RASTETTER, JOHN D. ABER, DEBRA P. C. PETERS, DENNIS S. OJIMA, and INGRID C. BURKE (;)

2003-01-01

338

GLAST Burst Monitor Instrument Simulation and Modeling  

SciTech Connect

The GLAST Burst Monitor (GBM) is designed to provide wide field of view observations of gamma-ray bursts and other fast transient sources in the energy range 10 keV to 30 MeV. The GBM is composed of several unshielded and uncollimated scintillation detectors (twelve NaI and two BGO) that are widely dispersed about the GLAST spacecraft. As a result, reconstructing source locations, energy spectra, and temporal properties from GBM data requires detailed knowledge of the detectors' response to both direct radiation as well as that scattered from the spacecraft and Earth's atmosphere. This full GBM instrument response will be captured in the form of a response function database that is derived from computer modeling and simulation. The simulation system is based on the GEANT4 Monte Carlo radiation transport simulation toolset.

Hoover, A. S.; Kippen, R. M.; Wallace, M. S. [Los Alamos National Laboratory, Los Alamos, NM (United States); Pendleton, G. N. [Dynetics, Inc., Huntsville, AL (United States); Fishman, G. J.; Meegan, C. A.; Kouveliotou, C.; Wilson-Hodge, C. A. [NASA/National Space Science Technology Center, Huntsville, AL (United States); Bissaldi, E.; Diehl, R.; Greiner, J.; Lichti, G. G.; Kienlin, A. von; Steinle, H. [Max-Planck-Institut fur Extraterrestrische Physik, Garching (Germany); Bhat, P. N.; Briggs, M. S.; Connaughton, V.; Paciesas, W. S.; Preece, R. D. [University of Alabama at Huntsville/National Space Science Technology Center, Huntsville, AL (United States)

2008-05-22

339

A simulation model for material accounting systems  

SciTech Connect

A general-purpose model that was developed to simulate the operation of a chemical processing facility for nuclear materials has been extended to describe material measurement and accounting procedures as well. The model now provides descriptors for material balance areas, a large class of measurement instrument types and their associated measurement errors for various classes of materials, the measurement instruments themselves with their individual calibration schedules, and material balance closures. Delayed receipt of measurement results (as for off-line analytical chemistry assay), with interim use of a provisional measurement value, can be accurately represented. The simulation model can be used to estimate inventory difference variances for processing areas that do not operate at steady state, to evaluate the timeliness of measurement information, to determine process impacts of measurement requirements, and to evaluate the effectiveness of diversion-detection algorithms. Such information is usually difficult to obtain by other means. Use of the measurement simulation model is illustrated by applying it to estimate inventory difference variances for two material balance area structures of a fictitious nuclear material processing line.

Coulter, C.A.; Thomas, K.E.

1987-01-01

340

Modeling Active Galactic Nuclei in Cosmological Simulations  

NASA Astrophysics Data System (ADS)

It is generally accepted that black holes play an essential role in the formation and evolution of galaxies. Resolving galaxies and AGN feedback in cosmological simulations allows us to investigate the current understanding of galaxy formation, black hole growth, gas accretion and the origin of AGN. Due to the limited resolution of the simulations, a simplified sub-scale model for AGN feedback is commonly used. Such a model usually depends on various parameters, for which true values are highly uncertain. I present a new advanced model and a more detailed description of AGN feedback, where such nuisance parameters reflect recent observations. The model takes into account the dependency of these parameters on the properties of the black hole and describes a continuous transition between the feedback processes acting in the so called radio-mode and quasar-mode. I will show that with these new implementations, our simulations are now very successful in reproducing observed properties of AGN and their host galaxies, such as the relation between the black hole mass and the stellar mass of the bulge, the stellar mass function and the black hole luminosity function.

Bachmann, L.; Dolag, K.; Hirschmann, M.

2014-07-01

341

Theory, modeling and simulation: Annual report 1993  

SciTech Connect

Developing the knowledge base needed to address the environmental restoration issues of the US Department of Energy requires a fundamental understanding of molecules and their interactions in insolation and in liquids, on surfaces, and at interfaces. To meet these needs, the PNL has established the Environmental and Molecular Sciences Laboratory (EMSL) and will soon begin construction of a new, collaborative research facility devoted to advancing the understanding of environmental molecular science. Research in the Theory, Modeling, and Simulation program (TMS), which is one of seven research directorates in the EMSL, will play a critical role in understanding molecular processes important in restoring DOE`s research, development and production sites, including understanding the migration and reactions of contaminants in soils and groundwater, the development of separation process for isolation of pollutants, the development of improved materials for waste storage, understanding the enzymatic reactions involved in the biodegradation of contaminants, and understanding the interaction of hazardous chemicals with living organisms. The research objectives of the TMS program are to apply available techniques to study fundamental molecular processes involved in natural and contaminated systems; to extend current techniques to treat molecular systems of future importance and to develop techniques for addressing problems that are computationally intractable at present; to apply molecular modeling techniques to simulate molecular processes occurring in the multispecies, multiphase systems characteristic of natural and polluted environments; and to extend current molecular modeling techniques to treat complex molecular systems and to improve the reliability and accuracy of such simulations. The program contains three research activities: Molecular Theory/Modeling, Solid State Theory, and Biomolecular Modeling/Simulation. Extended abstracts are presented for 89 studies.

Dunning, T.H. Jr.; Garrett, B.C.

1994-07-01

342

University of Michigan scientists modeling cancer using ecological principles:  

Cancer.gov

The invasion of a new species into an established ecosystem can be directly compared to the steps involved in cancer metastasis. New [University of Michigan] research published in BioMed Central's open access journal Theoretical Biology and Medical Modelling uses the Tilman model of competition between invasive species to study the metastasis of prostate cells into bone.

343

Computational ecology as an emerging science  

PubMed Central

It has long been recognized that numerical modelling and computer simulations can be used as a powerful research tool to understand, and sometimes to predict, the tendencies and peculiarities in the dynamics of populations and ecosystems. It has been, however, much less appreciated that the context of modelling and simulations in ecology is essentially different from those that normally exist in other natural sciences. In our paper, we review the computational challenges arising in modern ecology in the spirit of computational mathematics, i.e. with our main focus on the choice and use of adequate numerical methods. Somewhat paradoxically, the complexity of ecological problems does not always require the use of complex computational methods. This paradox, however, can be easily resolved if we recall that application of sophisticated computational methods usually requires clear and unambiguous mathematical problem statement as well as clearly defined benchmark information for model validation. At the same time, many ecological problems still do not have mathematically accurate and unambiguous description, and available field data are often very noisy, and hence it can be hard to understand how the results of computations should be interpreted from the ecological viewpoint. In this scientific context, computational ecology has to deal with a new paradigm: conventional issues of numerical modelling such as convergence and stability become less important than the qualitative analysis that can be provided with the help of computational techniques. We discuss this paradigm by considering computational challenges arising in several specific ecological applications. PMID:23565336

Petrovskii, Sergei; Petrovskaya, Natalia

2012-01-01

344

Simulation model of clastic sedimentary processes  

SciTech Connect

This dissertation describes SEDSIM, a computer model that simulates erosion, transport, and deposition of clastic sediments by free-surface flow in natural environments. SEDSIM is deterministic and is applicable to sedimentary processes in rivers, deltas, continental shelves, submarine canyons, and turbidite fans. The model is used to perform experiments in clastic sedimentation. Computer experimentation is limited by computing power available, but is free from scaling problems associated with laboratory experiments. SEDSIM responds to information provided to it at the outset of a simulation experiment, including topography, subsurface configuration, physical parameters of fluid and sediment, and characteristics of sediment sources. Extensive computer graphics are incorporated in SEDSIM. The user can display the three-dimensional geometry of simulated deposits in the form of successions of contour maps, perspective diagrams, vector plots of current velocities, and vertical sections of any azimuth orientation. The sections show both sediment age and composition. SEDSIM works realistically with processes involving channel shifting and topographic changes. Example applications include simulation of an ancient submarine canyon carved into a Cretaceous sequence in the National Petroleum Reserve in Alaska, known mainly from seismic sections and a sequence of Tertiary age in the Golden Meadow oil field of Louisiana, known principally from well logs.

Tetzlaff, D.M.

1987-01-01

345

Common Challenges for Ecological Modelling: Synthesis of Facilitated Discussions Held at the Symposia Organized for the Conference of the International Society for Ecological Modelling in Quebec City, Canada (October 6-9, 2009)  

EPA Science Inventory

The symposia organized for the conference of the International Society for Ecological Modelling (ISEM 2009) included facilitated discussion sessions following formal presentations. Each symposium focused on a specific subject, and all the subjects could be classified into three b...

346

An ecological model of the impact of sexual assault on women's mental health.  

PubMed

This review examines the psychological impact of adult sexual assault through an ecological theoretical perspective to understand how factors at multiple levels of the social ecology contribute to post-assault sequelae. Using Bronfenbrenner's (1979, 1986, 1995) ecological theory of human development, we examine how individual-level factors (e.g., sociodemographics, biological/genetic factors), assault characteristics (e.g., victim-offender relationship, injury, alcohol use), microsystem factors (e.g., informal support from family and friends), meso/ exosystem factors (e.g., contact with the legal, medical, and mental health systems, and rape crisis centers), macrosystem factors (e.g., societal rape myth acceptance), and chronosystem factors (e.g., sexual revictimization and history of other victimizations) affect adult sexual assault survivors' mental health outcomes (e.g., post-traumatic stress disorder, depression, suicidality, and substance use). Self-blame is conceptualized as meta-construct that stems from all levels of this ecological model. Implications for curbing and/or preventing the negative mental health effects of sexual assault are discussed. PMID:19433406

Campbell, Rebecca; Dworkin, Emily; Cabral, Giannina

2009-07-01

347

A Transmission Model for the Ecology of an Avian Blood Parasite in a Temperate Ecosystem  

PubMed Central

Most of our knowledge about avian haemosporidian parasites comes from the Hawaiian archipelago, where recently introduced Plasmodiumrelictum has contributed to the extinction of many endemic avian species. While the ecology of invasive malaria is reasonably understood, the ecology of endemic haemosporidian infection in mainland systems is poorly understood, even though it is the rule rather than the exception. We develop a mathematical model to explore and identify the ecological factors that most influence transmission of the common avian parasite, Leucocytozoonfringillinarum (Apicomplexa). The model was parameterized from White-crowned Sparrow (Zonotrichialeucophrys) and S. silvestre / craigi black fly populations breeding in an alpine ecosystem. We identify and examine the importance of altricial nestlings, the seasonal relapse of infected birds for parasite persistence across breeding seasons, and potential impacts of seasonal changes in black fly emergence on parasite prevalence in a high elevation temperate system. We also use the model to identify and estimate the parameters most influencing transmission dynamics. Our analysis found that relapse of adult birds and young of the year birds were crucial for parasite persistence across multiple seasons. However, distinguishing between nude nestlings and feathered young of the year was unnecessary. Finally, due to model sensitivity to many black fly parameters, parasite prevalence and sparrow recruitment may be most affected by seasonal changes in environmental temperature driving shifts in black fly emergence and gonotrophic cycles. PMID:24073288

Murdock, Courtney C.; Foufopoulos, Johannes; Simon, Carl P.

2013-01-01

348

Ecological interpretation of short-term toxicity results: Development of a population model for Arbacia  

SciTech Connect

The Arbacia punctulata fertilization and larval development tests are used extensively in regulatory and research programs to evaluate toxicity associated with contaminants in aqueous media. These short-term assays are inexpensive, easy to use, and provide information regarding the effects of environmental contaminants on critical life history stages of the sea urchin. Despite substantial consideration of the precision of assay methods, and a clear understanding of the statistical significance of treatment differences, an appreciation of the ecological significance of treatment effects is lacking. To address this problem, a stage classified population projection model was developed to relate short-term test endpoints to potential effects at the population level. The model was applied to evaluate population-level effects using short-term toxicity data obtained in an estuarine ecological risk assessment conducted for Portsmouth Naval Shipyard, Kittery, Maine. The model also was used to examine which test endpoints provide useful information relative to population growth dynamics. Population modeling approaches can be extremely valuable in extrapolating single species toxicity information to higher level ecological endpoints and for identifying appropriate measurement endpoints during toxicity test development.

Munns, W.R. Jr.; Nacci, D.E. [SAIC, Narragansett, RI (United States); Walker, H.A. [Environmental Protection Agency, Narragansett, RI (United States); Johnston, R.K. [NCCOSC, Narragansett, RI (United States). RDTE Division

1994-12-31

349

Ecological Modelling 165 (2003) 209220 Implications of fetal sex ratio hypotheses in endangered  

E-print Network

Key deer (Odocoileus virginianus clavium). Several general hypotheses have been proposed that describe rights reserved. Keywords: Key deer; Odocoileus virginianus clavium; Fetal sex ratio; Simulation model

Peterson, M. Nils

350

Theory, Modeling and Simulation Annual Report 2000  

SciTech Connect

This annual report describes the 2000 research accomplishments for the Theory, Modeling, and Simulation (TM and S) directorate, one of the six research organizations in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory (PNNL). EMSL is a U.S. Department of Energy (DOE) national scientific user facility and is the centerpiece of the DOE commitment to providing world-class experimental, theoretical, and computational capabilities for solving the nation's environmental problems.

Dixon, David A; Garrett, Bruce C; Straatsma, TP; Jones, Donald R; Studham, Scott; Harrison, Robert J; Nichols, Jeffrey A

2001-11-01

351

Theory, Modeling and Simulation Annual Report 2000  

SciTech Connect

This annual report describes the 2000 research accomplishments for the Theory, Modeling, and Simulation (TM&S) directorate, one of the six research organizations in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory (PNNL). EMSL is a U.S. Department of Energy (DOE) national scientific user facility and is the centerpiece of the DOE commitment to providing world-class experimental, theoretical, and computational capabilities for solving the nation's environmental problems.

Dixon, David A.; Garrett, Bruce C.; Straatsma, Tp; Jones, Donald R.; Studham, Ronald S.; Harrison, Robert J.; Nichols, Jeffrey A.

2001-11-01

352

Model Reduction for RF MEMS Simulation  

Microsoft Academic Search

Radio-frequency (RF) MEMS resonators, integrated into CMOS chips, are of great interest to engineers planning the next generation of com- munication systems. Fast simulations are necessary in order to gain insights into the behavior of these devices. In this paper, we discuss two structure-preserving model-reduction techniques and apply them to the frequency-domain analysis of two proposed MEMS resonator designs.

David S. Bindel; Zhaojun Bai; James W. Demmel

2004-01-01

353

A statistical simulation model for mobile radio fading channels  

Microsoft Academic Search

Recently, a Clarke's model-based simulator was proposed for Rayleigh fading channels. However, that model, as shown in this paper, may encounter statistic deficiency. Therefore, an improved model is presented to remove the statistic deficiency. Furthermore, a new simulation model is proposed for Rician fading channels. This Rician fading simulator with finite number of sinusoids plus a zero-mean stochastic sinusoid as

Chengshan Xiao; Yahong R. Zheng

2003-01-01

354

Closed loop models for analyzing engineering requirements for simulators  

NASA Technical Reports Server (NTRS)

A closed loop analytic model, incorporating a model for the human pilot, (namely, the optimal control model) that would allow certain simulation design tradeoffs to be evaluated quantitatively was developed. This model was applied to a realistic flight control problem. The resulting model is used to analyze both overall simulation effects and the effects of individual elements. The results show that, as compared to an ideal continuous simulation, the discrete simulation can result in significant performance and/or workload penalties.

Baron, S.; Muralidharan, R.; Kleinman, D.

1980-01-01

355

Closed loop models for analyzing the effects of simulator characteristics. [digital simulation of human operators  

NASA Technical Reports Server (NTRS)

The optimal control model of the human operator is used to develop closed loop models for analyzing the effects of (digital) simulator characteristics on predicted performance and/or workload. Two approaches are considered: the first utilizes a continuous approximation to the discrete simulation in conjunction with the standard optimal control model; the second involves a more exact discrete description of the simulator in a closed loop multirate simulation in which the optimal control model simulates the pilot. Both models predict that simulator characteristics can have significant effects on performance and workload.

Baron, S.; Muralidharan, R.; Kleinman, D. L.

1978-01-01

356

Population dynamics simulations of functional model proteins  

NASA Astrophysics Data System (ADS)

In order to probe the fundamental principles that govern protein evolution, we use a minimalist model of proteins to provide a mapping from genotype to phenotype. The model is based on physically realistic forces of protein folding and includes an explicit definition of protein function. Thus, we can find the fitness of a sequence from its ability to fold to a stable structure and perform a function. We study the fitness landscapes of these functional model proteins, that is, the set of all sequences mapped on to their corresponding fitnesses and connected to their one mutant neighbors. Through population dynamics simulations we directly study the influence of the nature of the fitness landscape on evolution. Populations are observed to move to a steady state, the distribution of which can often be predicted prior to the population dynamics simulations from the nature of the fitness landscape and a quantity analogous to a partition function. In this paper, we develop a scheme for predicting the steady-state population on a fitness landscape, based on the nature of the fitness landscape, thereby obviating the need for explicit population dynamics simulations and providing some insight into the impact on molecular evolution of the nature of fitness landscapes. Poor predictions are indicative of fitness landscapes that consist of a series of weakly connected sublandscapes.

Blackburne, Benjamin P.; Hirst, Jonathan D.

2005-10-01

357

Modeling Hydrology, Phosphorus and Ecology in the Hampshire Avon Catchment to Assess Alternative Strategies to Improve Water Quality  

NASA Astrophysics Data System (ADS)

Phosphorus (P) enrichment is a worldwide issue of fresh river systems that causes algae blooms, oxygen decline and eutrophication. Therefore, controlling the input of nutrients especially P into aquatic ecosystems is a crucial management focus across much of the world. For example, approximately 70% of water bodies in the Hampshire Avon catchment (UK) are considered not in a good ecological condition due to excess soluble reactive phosphorus (SRP) in the water. In this work, we explored the issues of diffuse and point source P pollution in the Hampshire Avon catchment using an integrated catchment model (INCA) and further we used the model to assess different management options for P reduction. A multi-branch, process based, dynamic water quality model (INCA-P) has been applied to the whole Hampshire Avon river system to simulate water fluxes, concentrations of total phosphorus (TP) and SRP, and ecology. The model has been used to assess impacts of both agricultural runoff and point sources from Waste Water Treatment Plants (WWTPs) on water quality. The results showed that agriculture contributes approximately 40% of the P load and point sources contribute the other 60%. A set of scenarios have been investigated to assess the impacts of alternative P reduction strategies and results suggest that a combined strategy of agricultural P reduction through either fertilizer reductions or better P management together with improved treatment at WWTPs would reduce the SRP concentrations in the river to acceptable levels to meet the European legislation e.g. Water Framework Directive requirements. A seasonal strategy for P reductions from WWTPs would achieve significant benefits at reduced cost.

Jin, L.; Whitehead, P. G.; Crossman, J.

2013-12-01

358

Model for minerals activity and decision simulation  

SciTech Connect

The foundation is provided for an integrated computerized system that can be used to model the long-range supply of minerals in a region. The system consists of a set of individual models that represent major elements of the supply process: geologic endowment, exploration, discovery, development, production, and transportation. Each is represented by a set of submodels and computer subroutines that differ depending on the mineral. The output consists of estimated quantities of resources to be discovered, proved reserves, and production at each point in time over some given time horizon. The results are obtained through Monte Carlo simulation. 34 references, 11 figures.

Lee, R.

1984-01-01

359

Simulated lights for an airfield model  

NASA Technical Reports Server (NTRS)

A light at an aircraft landing site is simulated on a model board by the protruding output end of a precision cut optical fiber. The fiber is secured within a counterbore of a counterbored hole in the model board. The length of the precision cut fiber and the depth of the counterbore are closely controlled to ensure that the output end of the fiber protrudes a desired distance. The input end of the precision cut fiber is optically coupled to a collimated light source by a second optical fiber extending through the smaller diameter bore of the counterbored hole.

Gdovin, David P. (Inventor); Lusk, Frank J. (Inventor)

1982-01-01

360

An Ecological Risk Model for Early Childhood Anxiety: The Importance of Early Child Symptoms and Temperament  

Microsoft Academic Search

Childhood anxiety is impairing and associated with later emotional disorders. Studying risk factors for child anxiety may\\u000a allow earlier identification of at-risk children for prevention efforts. This study applied an ecological risk model to address\\u000a how early childhood anxiety symptoms, child temperament, maternal anxiety and depression symptoms, violence exposure, and\\u000a sociodemographic risk factors predict school-aged anxiety symptoms. This longitudinal, prospective

Nicholas D. Mian; Laurel Wainwright; Margaret J. Briggs-Gowan; Alice S. Carter

2011-01-01

361

Implications of Simulation Conceptual Model Development for Simulation Management and Uncertainty Assessment  

NASA Technical Reports Server (NTRS)

A simulation conceptual model is a simulation developers way of translating modeling requirements (i. e., what is to be represented by the simulation or its modification) into a detailed design framework (i. e., how it is to be done), from which the software, hardware, networks (in the case of distributed simulation), and systems/equipment that will make up the simulation can be built or modified. A conceptual model is the collection of information which describes a simulation developers concept about the simulation and its pieces. That information consists of assumptions, algorithms, characteristics, relationships, and data. Taken together, these describe how the simulation developer understands what is to be represented by the simulation (entities, actions, tasks, processes, interactions, etc.) and how that representation will satisfy the requirements to which the simulation responds. Thus the conceptual model is the basis for judgment about simulation fidelity and validity for any condition that is not specifically tested. The more perspicuous and precise the conceptual model, the more likely it is that the simulation development will both fully satisfy requirements and allow demonstration that the requirements are satisfied (i. e., validation). Methods used in simulation conceptual model development have significant implications for simulation management and for assessment of simulation uncertainty. This paper suggests how to develop and document a simulation conceptual model so that the simulation fidelity and validity can be most effectively determined. These ideas for conceptual model development apply to all simulation varieties. The paper relates these ideas to uncertainty assessments as they relate to simulation fidelity and validity. The paper also explores implications for simulation management from conceptual model development methods, especially relative to reuse of simulation components.

Pace, Dale K.

2000-01-01

362

Computer Modeling and Simulation of Communications Satellite Channels  

Microsoft Academic Search

Computer modeling of satellite communications channels is a valuable adjunct to analytical modeling and hardware simulation for predicting and verifying communications link performance. In the computer simulation approach, sampled signals are created in the computer and operated on by algorithms that simulate the effects of filtering, channel nonlinearities, interference, and noise. After passage through the simulated channel, the distorted signals

LARRY C. PALMER

1984-01-01

363

Modelling the ecological consequences of whole tree harvest for bioenergy production  

NASA Astrophysics Data System (ADS)

There is an increasing demand for energy from biomass as a substitute to fossil fuels worldwide, and the Norwegian government plans to double the production of bioenergy to 9% of the national energy production or to 28 TWh per year by 2020. A large part of this increase may come from forests, which have a great potential with respect to biomass supply as forest growth increasingly has exceeded harvest in the last decades. One feasible option is the utilization of forest residues (needles, twigs and branches) in addition to stems, known as Whole Tree Harvest (WTH). As opposed to WTH, the residues are traditionally left in the forest with Conventional Timber Harvesting (CH). However, the residues contain a large share of the treés nutrients, indicating that WTH may possibly alter the supply of nutrients and organic matter to the soil and the forest ecosystem. This may potentially lead to reduced tree growth. Other implications can be nutrient imbalance, loss of carbon from the soil and changes in species composition and diversity. This study aims to identify key factors and appropriate strategies for ecologically sustainable WTH in Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) forest stands in Norway. We focus on identifying key factors driving soil organic matter, nutrients, biomass, biodiversity etc. Simulations of the effect on the carbon and nitrogen budget with the two harvesting methods will also be conducted. Data from field trials and long-term manipulation experiments are used to obtain a first overview of key variables. The relationships between the variables are hitherto unknown, but it is by no means obvious that they could be assumed as linear; thus, an ordinary multiple linear regression approach is expected to be insufficient. Here we apply two advanced and highly flexible modelling frameworks which hardly have been used in the context of tree growth, nutrient balances and biomass removal so far: Generalized Additive Models (GAMs) and Random Forests. Results obtained for GAMs so far show that there are differences between WTH and CH in two directions: both the significance of drivers and the shape of the response functions differ. GAMs turn out to be a flexible and powerful alternative to multivariate linear regression. The restriction to linear relationships seems to be unjustified in the present case. We use Random Forests as a highly efficient classifier which gives reliable estimates for the importance of each driver variable in determining the diameter growth for the two different harvesting treatments. Based on the final results of these two modelling approaches, the study contributes to find appropriate strategies and suitable regions (in Norway) where WTH may be sustainable performed.

Skår, Silje; Lange, Holger; Sogn, Trine

2013-04-01

364

Development of stressor-response models for an ecological risk assessment case study  

SciTech Connect

An estuarine ecological risk assessment for the Portsmouth Naval Shipyard (Kittery, ME) is being conducted following the US EPA`s Framework for Ecological Risk Assessment (ERA). As part of the Analysis phase of the ERA, laboratory studies were conducted to develop stressor-response models for lead, the primary contaminant of concern. Thirty-day exposures to adult sea urchins, Arbacia punctulata, occurred via food or suspended sediment. Exposure media were amended with lead sulfate to 10--100 or 100--300 times uncontaminated levels for the Feeding or Sediment Experiments, respectively. The sea urchin experimental model was selected because it permitted the measurement of biological endpoints with significance at the population level (e.g., adult survival and reproduction success), including those used in standard marine bioassays (i.e., fertilization and larval development). Feeding Experiment treatments produced few effects. Sediment Experiment treatments resulted in reductions in survival, growth and reproductive output of exposed adults and were directly toxic to early lifestages. However, in uncontaminated sea water, gametes from Sediment Experiment adults fertilized and completed larval development normally. Data from these experimental systems will be used to produce models relating lead exposure to specific biological responses and, ultimately, ecological risk.

Nacci, D.E.; Munns, W.R.; Cayula, S.; Serbst, J. [Science Applications International Corp., Narragansett, RI (United States); Johnston, R.K.; Walker, H.A. [Environmental Protection Agency, Narragansett, RI (United States)

1994-12-31

365

Cognitive Niches: An Ecological Model of Strategy Selection  

ERIC Educational Resources Information Center

How do people select among different strategies to accomplish a given task? Across disciplines, the strategy selection problem represents a major challenge. We propose a quantitative model that predicts how selection emerges through the interplay among strategies, cognitive capacities, and the environment. This interplay carves out for each…

Marewski, Julian N.; Schooler, Lael J.

2011-01-01

366

Understanding the Codevelopment of Modeling Practice and Ecological Knowledge  

ERIC Educational Resources Information Center

Despite a recent focus on engaging students in epistemic practices, there is relatively little research on how learning environments can support the simultaneous, coordinated development of both practice and the knowledge that emerges from and supports scientific activity. This study reports on the co-construction of modeling practice and…

Manz, Eve

2012-01-01

367

Author's personal copy Ecological Modelling 221 (2010) 23742387  

E-print Network

wolf behavior in Banff and Kootenay National Parks, Canada Marco Musiania , Sk. Morshed Anwarb-based model Human­wildlife interaction Wolf Banff National Park Kootenay National Park Human impact Recreation to investi- gate how varying levels of human presence could affect elements of wolf behavior, including

Hebblewhite, Mark

368

Ecological Modelling 177 (2004) 129142 Dynamic trophic cascade  

E-print Network

-function) perturbations on food chains [Ecol. Model. 171 (2004) 21]. The method allows explicit variation is to multiply the previous press result by a factor that diminishes both up and down the food chain. The factor; Bottom-up; Top-down; Food chain; Dynamic; Periodic perturbation 1. Introduction In a food chain

Vermont, University of

369

Author's personal copy Ecological Modelling 221 (2010) 27602768  

E-print Network

and Railsback, 2005). ABMs were early criticized as generally being so poorly doc- umented that the models could struc- ture by which all ABMs could be documented. The primary purpose of ODD is to make writing as unscientific. In the few years it has existed, ODD has been used in more than 50 publications. ODD was also

Tesfatsion, Leigh

370

Ecological utilization of leather tannery waste with circular economy model  

Microsoft Academic Search

Circular economy (CE) focuses on resource-productivity and eco-efficiency improvement in a comprehensive way, especially on the industrial structure optimization of new technology development and application, equipment renewal and management renovation. The leather industry on the one side boosts the local economic development, on the other side however leads to the tremendous environment pollution and biological chains destruction. The CE model

Jing Hu; Zuobing Xiao; Rujun Zhou; Weijun Deng; Mingxi Wang; Shuangshuang Ma

2011-01-01

371

Management of marine construction works using ecological modelling  

NASA Astrophysics Data System (ADS)

A system of bridges and tunnels between Denmark and Sweden is being constructed. The environmental management of the dredging and reclamation work includes planning using a mathematical model which can forecast the effect of different spill scenarios in order to minimize adverse effects on eelgrass beds. To develop the model, plots of eelgrass beds (4 m 2) were covered with nets excluding 30, 60 and 90% of the light. Shoot density, leaf and root/rhizome biomass, and soluble carbohydrates in roots and rhizomes were observed in order to determine the response of the plants to shading. In selected plots, all aboveground biomass was harvested to assess the re-growth potential. The minimum level of soluble carbohydrates necessary for securing re-growth was 60-90 mg g -1. The inclusion of the subsediment parts of the eelgrass permits model runs beyond one growth season, and the prediction of re-growth after subsequent shading and winter dormancy. The model has been satisfyingly calibrated and validated. A feedback monitoring system has been developed based on field studies of eelgrass variables, a set of pre-fixed environmental criteria and forecasting of the effects of the construction works. The system facilitates planning and management of the dredging and reclamation operations, and mitigating actions during the progression of the work.

Bach, H. K.; Jensen, K.; Lyngby, J. E.

1997-01-01

372

Beyond Cultural Relativism: An Ecological Model for Rhetorical Ethics.  

ERIC Educational Resources Information Center

A model intended to overcome the cultural relativism of determining what is an ethical act draws an analogy to environmental studies. Beginning with the concepts of "telos" (final purpose) and "archai" (priority), the notion of an ecosystem of ethics avoids limitation to a particular historical definition of good. Since the telos of human life is…

Mackin, Jim

373

Great Basin land management planning using ecological modeling.  

PubMed

This report describes a land management modeling effort that analyzed potential impacts of proposed actions under an updated Bureau of Land Management Resource Management Plan that will guide management for 20 years on 4.6 million hectares in the Great Basin ecoregion of the United States. State-and-transition models that included vegetation data, fire histories, and many parameters (i.e., rates of succession, fire return intervals, outcomes of management actions, and invasion rates of native and nonnative invasive species) were developed through workshops with scientific experts and range management specialists. Alternative restoration scenarios included continuation of current management, full fire suppression, wildfire use in designated fire use zones, wildfire use in resilient vegetation types only, restoration with a tenfold budget increase, no restoration treatments, and no livestock grazing. Under all the scenarios, cover of vegetation states with native perennial understory declined and was replaced by tree-invaded and weed-dominated states. The greatest differences among alternative management scenarios resulted from the use of fire as a tool to maintain native understory. Among restoration scenarios, only the scenario assuming a tenfold budget increase had a more desirable outcome than the current management scenario. Removal of livestock alone had little effect on vegetation resilience. Rather, active restoration was required. The predictive power of the model was limited by current understanding of Great Basin vegetation dynamics and data needs including statistically valid monitoring of restoration treatments, invasiveness and invasibility, and fire histories. The authors suggest that such computer models can be useful tools for systematic analysis of potential impacts in land use planning. However, for a modeling effort to be productive, the management situation must be conducive to open communication among land management agencies and partner entities, including nonprofit organizations. PMID:16514478

Forbis, Tara A; Provencher, Louis; Frid, Leonardo; Medlyn, Gary

2006-07-01

374

Integration of environmental simulation models with satellite remote sensing and geographic information systems technologies: case studies  

USGS Publications Warehouse

Environmental modelers are testing and evaluating a prototype land cover characteristics database for the conterminous United States developed by the EROS Data Center of the U.S. Geological Survey and the University of Nebraska Center for Advanced Land Management Information Technologies. This database was developed from multi temporal, 1-kilometer advanced very high resolution radiometer (AVHRR) data for 1990 and various ancillary data sets such as elevation, ecological regions, and selected climatic normals. Several case studies using this database were analyzed to illustrate the integration of satellite remote sensing and geographic information systems technologies with land-atmosphere interactions models at a variety of spatial and temporal scales. The case studies are representative of contemporary environmental simulation modeling at local to regional levels in global change research, land and water resource management, and environmental simulation modeling at local to regional levels in global change research, land and water resource management and environmental risk assessment. The case studies feature land surface parameterizations for atmospheric mesoscale and global climate models; biogenic-hydrocarbons emissions models; distributed parameter watershed and other hydrological models; and various ecological models such as ecosystem, dynamics, biogeochemical cycles, ecotone variability, and equilibrium vegetation models. The case studies demonstrate the important of multi temporal AVHRR data to develop to develop and maintain a flexible, near-realtime land cover characteristics database. Moreover, such a flexible database is needed to derive various vegetation classification schemes, to aggregate data for nested models, to develop remote sensing algorithms, and to provide data on dynamic landscape characteristics. The case studies illustrate how such a database supports research on spatial heterogeneity, land use, sensitivity analysis, and scaling issues involving regional extrapolations and parameterizations of dynamic land processes within simulation models.

Steyaert, Louis T.; Loveland, Thomas R.; Brown, Jesslyn F.; Reed, Bradley C.

1993-01-01

375

Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation  

E-print Network

Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation Aljoscha Rheinwalt 14. Januar 2009 Betreuender Professor: Prof. M. M¨uller-Preu�ker #12;Das Ising-Modell und Monte-Carlo-Simulation Gliederung Gliederung Ising-Modell Definition Anwendungen Numerische Analyse Statistische Beschreibung Monte-Carlo

376

Spatial modeling of ecological areas by fitting the limiting factors for As in the vicinity of mine, Serbia.  

PubMed

Elevated arsenic (As) concentrations in soil are often found in the vicinity of certain mineral deposits that have been, or are currently, under exploitation, regardless of the target resource. Detailed study of such areas for safe agriculture requires considerable financial costs and long periods of time. Application of an appropriate spatial model that describes the behavior of arsenic in soil and plants can significantly ease the whole investigation process. This paper presents a model of ecological security of an area that, in the past, was an antimony mine and has a naturally high content of arsenic. For simulation and modeling the geographic information science (GIS) technology with the inserted predictors influencing the accessibility of As and its content in plants was used. The results obtained were the following: (1) a categorization of contaminated soils according to soil properties was developed; (2) the proposed methodology allows focusing on particular suspect area saving an energy and human resource input; and (3) new safe areas for growing crops in contaminated area were modeled. The application of the proposed model of As solubility to various crops grown around a former antimony mine near the village of Lisa, southwest Serbia showed that significant expansion of the areas suitable for growing potato, raspberry, and pasture was possible. PMID:24281676

Cakmak, Dragan; Perovic, Veljko; Saljnikov, Elmira; Jaramaz, Darko; Sikiric, Biljana

2014-03-01

377

Radiation, Ecology and the Invalid LNT Model: The Evolutionary Imperative  

PubMed Central

Metabolic and energetic efficiency, and hence fitness of organisms to survive, should be maximal in their habitats. This tenet of evolutionary biology invalidates the linear-nothreshold (LNT) model for the risk consequences of environmental agents. Hormesis in response to selection for maximum metabolic and energetic efficiency, or minimum metabolic imbalance, to adapt to a stressed world dominated by oxidative stress should therefore be universal. Radiation hormetic zones extending substantially beyond common background levels, can be explained by metabolic interactions among multiple abiotic stresses. Demographic and experimental data are mainly in accord with this expectation. Therefore, non-linearity becomes the primary model for assessing risks from low-dose ionizing radiation. This is the evolutionary imperative upon which risk assessment for radiation should be based. PMID:18648598

Parsons, Peter A.

2006-01-01

378

Coupling Ecology and River Dynamics using a Simplified Interaction Model  

NASA Astrophysics Data System (ADS)

Quantifying how changes in streamflow and sediment affect riverine life is an important component of river basin management and stream restoration efforts, especially under human and climate-induced changes affecting many basins around the world. In the Midwestern US, drastic changes in mussel populations have been witnessed over the past decade begging quantitative understanding of cause and effect and attribution of these changes to the concurrent changes in streamflow and sediment loads to the rivers. Previous empirical analyses have attempted to explore mussel abundance with habitat associations and bulk hydrologic and geomorphic attributes as predictors but results showed relatively weak relationships and low predictive power. In this work, we developed a process-based model that incorporates water-sediment-mussel interactions using functional relationships and predicts the long-term trends of suspended-sediment, chlorophyll-a and mussel population using a daily streamflow record. We applied the model to the Minnesota River Basin, which has experienced significant changes in precipitation and runoff, increased sediment delivery, and decreasing mussel populations. Our model captures the general dynamics of the system and provides a better predictor of mussel populations than predictions based on geomorphic (e.g. upstream drainage area, slope) and hydraulic variables (e.g. 2-year recurrence interval peak streamflow, depth, width, cross sectional area, velocity, and Froude number) alone. To highlight the utility of our model, we tested possible scenarios that illustrate (1) how climate and land-use change may undermine the resilience of mussel populations and (2) how management efforts can allow mussel populations to recover.

Longjas, A.; Czuba, J. A.; Schwenk, J.; Danesh Yazdi, M.; Hansen, A.; Foufoula-Georgiou, E.

2013-12-01

379

Best Practices for Crash Modeling and Simulation  

NASA Technical Reports Server (NTRS)

Aviation safety can be greatly enhanced by the expeditious use of computer simulations of crash impact. Unlike automotive impact testing, which is now routine, experimental crash tests of even small aircraft are expensive and complex due to the high cost of the aircraft and the myriad of crash impact conditions that must be considered. Ultimately, the goal is to utilize full-scale crash simulations of aircraft for design evaluation and certification. The objective of this publication is to describe "best practices" for modeling aircraft impact using explicit nonlinear dynamic finite element codes such as LS-DYNA, DYNA3D, and MSC.Dytran. Although "best practices" is somewhat relative, it is hoped that the authors' experience will help others to avoid some of the common pitfalls in modeling that are not documented in one single publication. In addition, a discussion of experimental data analysis, digital filtering, and test-analysis correlation is provided. Finally, some examples of aircraft crash simulations are described in several appendices following the main report.

Fasanella, Edwin L.; Jackson, Karen E.

2002-01-01

380

Nutritional models for a Controlled Ecological Life Support System (CELSS): Linear mathematical modeling  

NASA Technical Reports Server (NTRS)

The NASA Controlled Ecological Life Support System (CELSS) Program is involved in developing a biogenerative life support system that will supply food, air, and water to space crews on long-duration missions. An important part of this effort is in development of the knowledge and technological capability of producing and processing foods to provide optimal diets for space crews. This involves such interrelated factors as determination of the diet, based on knowledge of nutrient needs of humans and adjustments in those needs that may be required as a result of the conditions of long-duration space flight; determination of the optimal mixture of crops required to provide nutrients at levels that are sufficient but not excessive or toxic; and consideration of the critical issues of spacecraft space and power limitations, which impose a phytomass minimization requirement. The complex interactions among these factors are examined with the goal of supplying a diet that will satisfy human needs while minimizing the total phytomass requirement. The approach taken was to collect plant nutritional composition and phytomass production data, identify human nutritional needs and estimate the adjustments to the nutrient requirements likely to result from space flight, and then to generate mathematical models from these data.

Wade, Rose C.

1989-01-01

381

EDITORIAL: Modelling and simulation in polymer and composites processing  

NASA Astrophysics Data System (ADS)

The general theme of this special section is modelling and simulation in polymer and composite processing. Composite processing in general involves reactive processing. During the last decade there have been numerous advances in modelling and simulation in both thermoplastic and reactive processing. This fact, coupled with the enormous advances in computing capability, has made Computer Aided Engineering (CAE) a reality. Industry nowadays depends on CAE to improve and/or develop new processes. There is no excuse not to take advantage of modelling and simulation. Another tendency is a clear move towards environmentally benign manufacturing; thus several papers in this issue discuss environmentally benign alternatives to traditional manufacturing for both composite and thermoplastics. The first two papers are a review of modelling and simulation; the first paper by Castro, Cabrera Rios and Mount-Campbell focuses on reactive processing, while the second by Kim and Turng discusses thermoplastics moulding. Another important issue is the need to use empirical modelling for cases where physics-based models are not available or are too cumbersome to use. For that reason the paper by Castro et al focuses on empirical modelling and the paper by Kim and Turng discusses exclusively physics-based modelling. The next three papers, two by Advani and collaborators and the third by Srinivasagupta and Kardos, refer to composite manufacturing. Advani's papers cover recent advances in Reactive Liquid Moulding, a process that has gained great acceptance as an environmentally benign alternative to open moulding. The paper by Srinivasagupta and Kardos covers the important issue of addressing simultaneously both environmental and economical design. In general the environmental optimum does not coincide with the economic optimum; this gives rise to the need to compromise. The Data Envelopment Analysis (DEA) technique, discussed in the first paper, can be used to identify the best set of compromises. The exergy approach used by Srinivasagupta and Kardos to evaluate the ecological impact has shown great potential for measuring the effect of processes in the environment. The process they discuss is an environmentally friendly alternative to the standard pultrusion process. The sixth paper, by Chensong Dong and collaborators, focuses on modelling and optimizing dimensional variation in composites, and offers a good complement to Advani's papers. Papers seven by Lilly et al, and eight by Lyytikainen et al, focus on thermoplastic moulding. The last paper, by Chen et al, discusses the modelling of a technology that has the potential to be the environmentally friendly alternative to painting. I would like to thank Dr Mauricio Cabrera Rios, who obtained his PhD under my supervision and is now a professor at the Universidad Autonoma de Nuevo Leon, Mexico, for his help in coordinating the paper reviews. Also, the willingness of the authors to go through several review iterations where needed is greatly appreciated. Finally I would like to thank Ms Judith Adams (editor), without whose help this issue would not have been possible. She was instrumental in securing some papers and in obtaining the proper evaluations of others.

Castro, Josè M.

2004-05-01

382

Modeling and simulation of climate and climate change  

Microsoft Academic Search

Introduction Energy balance models Formulation Governing equations Calibration: simulation of the present-day seasonal cycle Simulation of 2 × CO2-induced temperature and sea-level - changes Radiative-convective models Formulation Governing equations Surface convection Convective adjustment Model specification and initialization Simulation of the present-day temperature Simulation of the temperature change induced by doubling the CO2 - concentration General circulation models Formulation of atmospheric

M. E. Schlesinger; N. G. Andronova; B. Entwistle; A. Ghanem; N. Ramankutty; W. Wang; F. Yang

1997-01-01

383

A methodology for eliciting, representing, and analysing stakeholder knowledge for decision making on complex socio-ecological systems: From cognitive maps to agent-based models.  

PubMed

This paper aims to contribute to developing better ways for incorporating essential human elements in decision making processes for modelling of complex socio-ecological systems. It presents a step-wise methodology for integrating perceptions of stakeholders (qualitative) into formal simulation models (quantitative) with the ultimate goal of improving understanding and communication about decision making in complex socio-ecological systems. The methodology integrates cognitive mapping and agent based modelling. It cascades through a sequence of qualitative/soft and numerical methods comprising: (1) Interviews to elicit mental models; (2) Cognitive maps to represent and analyse individual and group mental models; (3) Time-sequence diagrams to chronologically structure the decision making process; (4) All-encompassing conceptual model of decision making, and (5) computational (in this case agent-based) Model. We apply the proposed methodology (labelled ICTAM) in a case study of viticulture irrigation in South Australia. Finally, we use strengths-weakness-opportunities-threats (SWOT) analysis to reflect on the methodology. Results show that the methodology leverages the use of cognitive mapping to capture the richness of decision making and mental models, and provides a combination of divergent and convergent analysis methods leading to the construction of an Agent Based Model. PMID:25622296

Elsawah, Sondoss; Guillaume, Joseph H A; Filatova, Tatiana; Rook, Josefine; Jakeman, Anthony J

2015-03-15

384

Using structural equation modeling to investigate relationships among ecological variables  

USGS Publications Warehouse

Structural equation modeling is an advanced multivariate statistical process with which a researcher can construct theoretical concepts, test their measurement reliability, hypothesize and test a theory about their relationships, take into account measurement errors, and consider both direct and indirect effects of variables on one another. Latent variables are theoretical concepts that unite phenomena under a single term, e.g., ecosystem health, environmental condition, and pollution (Bollen, 1989). Latent variables are not measured directly but can be expressed in terms of one or more directly measurable variables called indicators. For some researchers, defining, constructing, and examining the validity of latent variables may be the end task of itself. For others, testing hypothesized relationships of latent variables may be of interest. We analyzed the correlation matrix of eleven environmental variables from the U.S. Environmental Protection Agency's (USEPA) Environmental Monitoring and Assessment Program for Estuaries (EMAP-E) using methods of structural equation modeling. We hypothesized and tested a conceptual model to characterize the interdependencies between four latent variables-sediment contamination, natural variability, biodiversity, and growth potential. In particular, we were interested in measuring the direct, indirect, and total effects of sediment contamination and natural variability on biodiversity and growth potential. The model fit the data well and accounted for 81% of the variability in biodiversity and 69% of the variability in growth potential. It revealed a positive total effect of natural variability on growth potential that otherwise would have been judged negative had we not considered indirect effects. That is, natural variability had a negative direct effect on growth potential of magnitude -0.3251 and a positive indirect effect mediated through biodiversity of magnitude 0.4509, yielding a net positive total effect of 0.1258. Natural variability had a positive direct effect on biodiversity of magnitude 0.5347 and a negative indirect effect mediated through growth potential of magnitude -0.1105 yielding a positive total effects of magnitude 0.4242. Sediment contamination had a negative direct effect on biodiversity of magnitude -0.1956 and a negative indirect effect on growth potential via biodiversity of magnitude -0.067. Biodiversity had a positive effect on growth potential of magnitude 0.8432, and growth potential had a positive effect on biodiversity of magnitude 0.3398. The correlation between biodiversity and growth potential was estimated at 0.7658 and that between sediment contamination and natural variability at -0.3769.

Malaeb, Z.A.; Kevin, Summers J.; Pugesek, B.H.

2000-01-01

385

Vertical eddy heat fluxes from model simulations  

NASA Technical Reports Server (NTRS)

Vertical eddy fluxes of heat are calculated from simulations with a variety of climate models, ranging from three-dimensional GCMs to a one-dimensional radiative-convective model. The models' total eddy flux in the lower troposphere is found to agree well with Hantel's analysis from observations, but in the mid and upper troposphere the models' values are systematically 30 percent to 50 percent smaller than Hantel's. The models nevertheless give very good results for the global temperature profile, and the reason for the discrepancy is unclear. The model results show that the manner in which the vertical eddy flux is carried is very sensitive to the parameterization of moist convection. When a moist adiabatic adjustment scheme with a critical value for the relative humidity of 100 percent is used, the vertical transports by large-scale eddies and small-scale convection on a global basis are equal: but when a penetrative convection scheme is used, the large-scale flux on a global basis is only about one-fifth to one-fourth the small-scale flux. Comparison of the model results with observations indicates that the results with the latter scheme are more realistic. However, even in this case, in mid and high latitudes the large and small-scale vertical eddy fluxes of heat are comparable in magnitude above the planetary boundary layer.

Stone, Peter H.; Yao, Mao-Sung

1991-01-01

386

Pattern-oriented modelling: a ‘multi-scope’ for predictive systems ecology  

PubMed Central

Modern ecology recognizes that modelling systems across scales and at multiple levels—especially to link population and ecosystem dynamics to individual adaptive behaviour—is essential for making the science predictive. ‘Pattern-oriented modelling’ (POM) is a strategy for doing just this. POM is the multi-criteria design, selection and calibration of models of complex systems. POM starts with identifying a set of patterns observed at multiple scales and levels that characterize a system with respect to the particular problem being modelled; a model from which the patterns emerge should contain the right mechanisms to address the problem. These patterns are then used to (i) determine what scales, entities, variables and processes the model needs, (ii) test and select submodels to represent key low-level processes such as adaptive behaviour, and (iii) find useful parameter values during calibration. Patterns are already often used in these ways, but a mini-review of applications of POM confirms that making the selection and use of patterns more explicit and rigorous can facilitate the development of models with the right level of complexity to understand ecological systems and predict their response to novel conditions. PMID:22144392

Grimm, Volker; Railsback, Steven F.

2012-01-01

387

Modeling And Simulation Tools For Education Reform  

NSDL National Science Digital Library

Created by the Shodor Education Foundation, Inc., the Modeling And Simulation Tools for Education Reform (MASTER) provide useful educational tools that help students and teachers learn through observation and modeling activities. The Shodor Foundation worked in tandem with the National Center for Supercomputing Applications, George Mason University, and other educational organizations to craft these tools and visitors can access all eight of them here. The Fractal Modeling Tools are a good place to start as visitors can download the required software or take in some instructional materials, such as the interactive fractal microscope and the snowflake fractal generator. Other notable areas here include The Pit and the Pendulum, which offers the work of Edgar Allan Poe as a way to learn about better reading through computation.

388

Applications of next generation sequencing in molecular ecology of non-model organisms  

PubMed Central

As most biologists are probably aware, technological advances in molecular biology during the last few years have opened up possibilities to rapidly generate large-scale sequencing data from non-model organisms at a reasonable cost. In an era when virtually any study organism can ‘go genomic', it is worthwhile to review how this may impact molecular ecology. The first studies to put the next generation sequencing (NGS) to the test in ecologically well-characterized species without previous genome information were published in 2007 and the beginning of 2008. Since then several studies have followed in their footsteps, and a large number are undoubtedly under way. This review focuses on how NGS has been, and can be, applied to ecological, population genetic and conservation genetic studies of non-model species, in which there is no (or very limited) genomic resources. Our aim is to draw attention to the various possibilities that are opening up using the new technologies, but we also highlight some of the pitfalls and drawbacks with these methods. We will try to provide a snapshot of the current state of the art for this rapidly advancing and expanding field of research and give some likely directions for future developments. PMID:21139633

Ekblom, R; Galindo, J

2011-01-01

389

A coupled geomorphic and ecological model of tidal marsh evolution.  

PubMed

The evolution of tidal marsh platforms and interwoven channel networks cannot be addressed without treating the two-way interactions that link biological and physical processes. We have developed a 3D model of tidal marsh accretion and channel network development that couples physical sediment transport processes with vegetation biomass productivity. Tidal flow tends to cause erosion, whereas vegetation biomass, a function of bed surface depth below high tide, influences the rate of sediment deposition and slope-driven transport processes such as creek bank slumping. With a steady, moderate rise in sea level, the model builds a marsh platform and channel network with accretion rates everywhere equal to the rate of sea-level rise, meaning water depths and biological productivity remain temporally constant. An increase in the rate of sea-level rise, or a reduction in sediment supply, causes marsh-surface depths, biomass productivity, and deposition rates to increase while simultaneously causing the channel network to expand. Vegetation on the marsh platform can promote a metastable equilibrium where the platform maintains elevation relative to a rapidly rising sea level, although disturbance to vegetation could cause irreversible loss of marsh habitat. PMID:17389384

Kirwan, Matthew L; Murray, A Brad

2007-04-10

390

A coupled geomorphic and ecological model of tidal marsh evolution  

PubMed Central

The evolution of tidal marsh platforms and interwoven channel networks cannot be addressed without treating the two-way interactions that link biological and physical processes. We have developed a 3D model of tidal marsh accretion and channel network development that couples physical sediment transport processes with vegetation biomass productivity. Tidal flow tends to cause erosion, whereas vegetation biomass, a function of bed surface depth below high tide, influences the rate of sediment deposition and slope-driven transport processes such as creek bank slumping. With a steady, moderate rise in sea level, the model builds a marsh platform and channel network with accretion rates everywhere equal to the rate of sea-level rise, meaning water depths and biological productivity remain temporally constant. An increase in the rate of sea-level rise, or a reduction in sediment supply, causes marsh-surface depths, biomass productivity, and deposition rates to increase while simultaneously causing the channel network to expand. Vegetation on the marsh platform can promote a metastable equilibrium where the platform maintains elevation relative to a rapidly rising sea level, although disturbance to vegetation could cause irreversible loss of marsh habitat. PMID:17389384

Kirwan, Matthew L.; Murray, A. Brad

2007-01-01

391

WATER SUPPLY SIMULATION MODEL. VOLUME 1. MODEL DEVELOPMENT  

EPA Science Inventory

This three-volume report describes the development of a water supply simulation model (WSSM), a system of computer programs that allows for a systematic evaluation of the physical and economic characteristics of a water distribution system in a spatial framework. The WSSM concept...

392

Modeling and Simulation of Incident Management for Homeland Security Applications  

E-print Network

i Modeling and Simulation of Incident Management for Homeland Security Applications DRAFT in the breakout track on Incident Management at the workshop on Homeland Security Modeling & Simulation Organized For discussion at DHS/NIST Workshop on Homeland Security Modeling & Simulation June 14-15, 2011 Proposed matter

Magee, Joseph W.

393

Integrating realtime project progress input into a construction simulation model  

Microsoft Academic Search

Computer simulation has been widely applied in modeling construction operation to gain insight into project performance. However, simulation models are rarely used after the project planning and design stage. One main constraint is the time and effort needed for collecting pertinent and correct information and processing it for input into the model. As projects progress and project circumstances change, simulation

Hua Xie; Siri Fernando; Simaan AbouRizk

2011-01-01

394

Conceptual simulation model for strategic decision evaluation in project management  

Microsoft Academic Search

This paper focuses on a conceptual methodology for an integrated simulation model dubbed as dynamic simulation modelling system (DSMS) for proactive and optimal decision making within a project management framework. Due to the uncertainties in project environment, the technical and operational functionality of a facility needs to be assessed during development and operation phases of the project. The simulation model

Hemanta Doloi; Ali Jaafari

2002-01-01

395

Ecology and evolution simulation and quest design for an educational massive multiplayer online game  

E-print Network

In this design-based research project, I developed two simulations to be used as student tools in a massively multiplayer online game targeted at STEM education, the Radix Endeavor. I designed both the underlying agent-based ...

Zhang, Mark (Mark A.)

2013-01-01

396

Modelling the ecological vulnerability to forest fires in mediterranean ecosystems using geographic information technologies.  

PubMed

Forest fires represent a major driver of change at the ecosystem and landscape levels in the Mediterranean region. Environmental features and vegetation are key factors to estimate the ecological vulnerability to fire; defined as the degree to which an ecosystem is susceptible to, and unable to cope with, adverse effects of fire (provided a fire occurs). Given the predicted climatic changes for the region, it is urgent to validate spatially explicit tools for assessing this vulnerability in order to support the design of new fire prevention and restoration strategies. This work presents an innovative GIS-based modelling approach to evaluate the ecological vulnerability to fire of an ecosystem, considering its main components (soil and vegetation) and different time scales. The evaluation was structured in three stages: short-term (focussed on soil degradation risk), medium-term (focussed on changes in vegetation), and coupling of the short- and medium-term vulnerabilities. The model was implemented in two regions: Aragón (inland North-eastern Spain) and Valencia (eastern Spain). Maps of the ecological vulnerability to fire were produced at a regional scale. We partially validated the model in a study site combining two complementary approaches that focused on testing the adequacy of model's predictions in three ecosystems, all very common in fire-prone landscapes of eastern Spain: two shrublands and a pine forest. Both approaches were based on the comparison of model's predictions with values of NDVI (Normalized Difference Vegetation Index), which is considered a good proxy for green biomass. Both methods showed that the model's performance is satisfactory when applied to the three selected vegetation types. PMID:23052472

Duguy, Beatriz; Alloza, José Antonio; Baeza, M Jaime; De la Riva, Juan; Echeverría, Maite; Ibarra, Paloma; Llovet, Juan; Cabello, Fernando Pérez; Rovira, Pere; Vallejo, Ramon V

2012-12-01

397

Modelling the Ecological Vulnerability to Forest Fires in Mediterranean Ecosystems Using Geographic Information Technologies  

NASA Astrophysics Data System (ADS)

Forest fires represent a major driver of change at the ecosystem and landscape levels in the Mediterranean region. Environmental features and vegetation are key factors to estimate the ecological vulnerability to fire; defined as the degree to which an ecosystem is susceptible to, and unable to cope with, adverse effects of fire (provided a fire occurs). Given the predicted climatic changes for the region, it is urgent to validate spatially explicit tools for assessing this vulnerability in order to support the design of new fire prevention and restoration strategies. This work presents an innovative GIS-based modelling approach to evaluate the ecological vulnerability to fire of an ecosystem, considering its main components (soil and vegetation) and different time scales. The evaluation was structured in three stages: short-term (focussed on soil degradation risk), medium-term (focussed on changes in vegetation), and coupling of the short- and medium-term vulnerabilities. The model was implemented in two regions: Aragón (inland North-eastern Spain) and Valencia (eastern Spain). Maps of the ecological vulnerability to fire were produced at a regional scale. We partially validated the model in a study site combining two complementary approaches that focused on testing the adequacy of model's predictions in three ecosystems, all very common in fire-prone landscapes of eastern Spain: two shrublands and a pine forest. Both approaches were based on the comparison of model's predictions with values of NDVI (Normalized Difference Vegetation Index), which is considered a good proxy for green biomass. Both methods showed that the model's performance is satisfactory when applied to the three selected vegetation types.

Duguy, Beatriz; Alloza, José Antonio; Baeza, M. Jaime; De la Riva, Juan; Echeverría, Maite; Ibarra, Paloma; Llovet, Juan; Cabello, Fernando Pérez; Rovira, Pere; Vallejo, Ramon V.

2012-12-01

398

Modeling galactic chemical evolution in cosmological simulations  

NASA Astrophysics Data System (ADS)

The most fundamental challenges to models of galactic chemical evolution (GCE) are uncertainties in the basic inputs, including the properties of the stellar initial mass function (IMF), stellar nucleosynthetic yields, and the rate of return of mass and energy to the interstellar and intergalactic medium by Type Ia and II supernovae and stellar winds. In this dissertation, we provide a critical examination of widely available stellar nucleosynthetic yield data, with an eye toward modeling GCE in the broad scope of cosmological hydrodynamical simulations. We examine the implications of uncertain inputs for the Galactic stellar IMF, and nucleosynthetic yields from stellar-evolution calculations, on our ability to ask detailed questions regarding the observed Galactic chemical-abundance patterns. We find a marked need for stellar feedback data from stars of initial mass 8 to 12 Msun and above 40 M sun, and for initial stellar metallicities above and below solar, Z sun=0.02. We find the largest discrepancies amongst nucleosynthetic yield calculations are due to various groups' treatment of hot bottom burning, formation of the 13C pocket in asymptotic giant-branch (AGB) stars, and details of mass loss, rotation, and convection in all stars. Our model of GCE is used to post-process simulations to explore in greater detail the nucleosynthetic evolution of the stellar populations and interstellar/intergalactic medium, and to compare directly to the chemical abundances of the Milky Way stellar halo and dwarf spheroidal galaxy stellar populations.

Peruta, Carolyn Cynthia

399

Toy models for galaxy formation versus simulations  

NASA Astrophysics Data System (ADS)

We describe simple useful toy models for key processes of galaxy formation in its most active phase, at z > 1, and test the approximate expressions against the typical behaviour in a suite of high-resolution hydro-cosmological simulations of massive galaxies at z=4-1. We address in particular the evolution of (a) the total mass inflow rate from the cosmic web into galactic haloes based on the EPS approximation, (b) the penetration of baryonic streams into the inner galaxy, (c) the disc size, (d) the implied steady-state gas content and star formation rate (SFR) in the galaxy subject to mass conservation and a universal star formation law, (e) the inflow rate within the disc to a central bulge and black hole as derived using energy conservation and self-regulated Q ˜ 1 violent disc instability (VDI) and (f) the implied steady state in the disc and bulge. The toy models provide useful approximations for the behaviour of the simulated galaxies. We find that (a) the inflow rate is proportional to mass and to (1 + z)5/2, (b) the penetration to the inner halo is ˜50 per cent at z=4-2, (c) the disc radius is ˜5 per cent of the virial radius, (d) the galaxies reach a steady state with the SFR following the accretion rate into the galaxy, (e) there is an intense gas inflow through the disc, comparable to the SFR, following the predictions of VDI and (f) the galaxies approach a steady state with the bulge mass comparable to the disc mass, where the draining of gas by SFR, outflows and disc inflows is replenished by fresh accretion. Given the agreement with simulations, these toy models are useful for understanding the complex phenomena in simple terms and for back-of-the-envelope predictions.

Dekel, A.; Zolotov, A.; Tweed, D.; Cacciato, M.; Ceverino, D.; Primack, J. R.

2013-10-01

400

ETEKOS experimental ecological system  

NASA Technical Reports Server (NTRS)

The problem of changes in the ecology resulting, for example, in increases in water temperature because of discharges from large thermal power plants is considered. An experiment creating a model of such an ecological system is described.

Alekseyev, V. V.; Geogiyev, A. A.; Gorbatov, Y. I.; Lyamin, M. Y.; Maksimov, V. N.; Sapozhnikov, V. V.; Shinkar, G. G.; Shirokova, Y. L.

1980-01-01

401

Coarse-grained models for biological simulations  

NASA Astrophysics Data System (ADS)

The large timescales and length-scales of interest in biophysics preclude atomistic study of many systems and processes. One appealing approach is to use coarse-grained (CG) models where several atoms are grouped into a single CG site. In this work we describe a new CG force field for lipids, surfactants, and amino acids. The topology of CG sites is the same as in the MARTINI force field, but the new model is compatible with a recently developed CG electrostatic water (Big Multiple Water, BMW) model. The model not only gives correct structural, elastic properties and phase behavior for lipid and surfactants, but also reproduces electrostatic properties at water-membrane interface that agree with experiment and atomistic simulations, including the potential of mean force for charged amino acid residuals at membrane. Consequently, the model predicts stable attachment of cationic peptides (i.e., poly-Arg) on lipid bilayer surface, which is not shown in previous models with non-electrostatic water.

Wu, Zhe; Cui, Qiang; Yethiraj, Arun

2011-03-01

402

Modelling and simulation of gyrotrons for ITER  

NASA Astrophysics Data System (ADS)

Powerful gyrotrons of the megawatt class will be used for electron cyclotron resonance heating (ECRH) and current drive (ECCD) of magnetically confined plasma in the thermonuclear reactor ITER. For computer-aided design (CAD), analysis and optimization of their performance numerical experiments based on adequate physical models are used. In this paper, we outline and illustrate the current status of both the available software tools for numerical simulation of such gyrotrons, as well as the novel computer codes of the problem oriented GYREOSS software package which is under development now.

Damyanova, M.; Kern, S.; Illy, S.; Thumm, M.; Sabchevski, S.; Zhelyazkov, I.; Vasileva, E.

2014-06-01

403

Integrating fundamental concepts of ecology, biogeography, and sampling into effective ecological niche modeling and species distribution modeling  

E-print Network

, see below). The literature taking advantage of this novel analytical functionality has increased massively (Figure 1), and two book-length syntheses have now appeared (Franklin 2010, Peterson et al. 2011). Two recent papers have seen massive... was easy to implement. Niche modeling, however, has seen the opposite evolutionary trajectory: tools that, in effect, estimate niches have been around for decades (Nix 1986, Austin et al. 1990, Stockwell and Noble 1992), yet a conceptual framework...

Peterson, A. Townsend; Soberó n, Jorge

2012-10-30

404

Ecological Acclimation and Hydrologic Response: Problem Complexity and Modeling Challenges  

NASA Astrophysics Data System (ADS)

Elevated CO2 in the atmosphere leads to a number of acclimatory responses in different vegetation types. These may be characterized as structural such as vegetation height or foliage density, ecophysiological such as reduction in stomatal conductance, and biochemical such as photosynthetic down-regulation. Furthermore, the allocation of assimilated carbon to different vegetation parts such as leaves, roots, stem and seeds is also altered such that empirical allometric relations are no longer valid. The extent and nature of these acclimatory responses vary between C3 and C4 vegetation and across species. These acclimatory responses have significant impact on hydrologic fluxes both pertaining to water and energy with the possibility of large-scale hydrologic influence. Capturing the pathways of acclimatory response to provide accurate ecohydrologic response predictions requires incorporating subtle relationships that are accentuated under elevated CO2. The talk will discuss the challenges of modeling these as well as applications to soybean, maize and bioenergy crops such as switchgrass and miscanthus.

Kumar, P.; Srinivasan, V.; Le, P. V. V.; Drewry, D.

2012-04-01

405

Grand challenges in modeling and simulation  

NASA Astrophysics Data System (ADS)

Few argue with the need for modeling and simulation (M&S) to better or more completely represent current and expected military operations. The challenge is to decide where to make specific improvements in M&S representation and functionality within time, funding, technology, and research limitations. So, it is natural to select key areas - Grand Challenges - for a significant evolution in M&S where a major effort of many at considerable cost is needed to deal with the critical issues ahead. This paper selects three proposed and related Grand Challenges. First, M&S Depiction of Information and Effects-Based Operations, as a Grand Challenge, will assist in creating sufficiently realistic battlespaces for M&S users. Second, M&S Support to Crisis Response and Military Operations, as a Grand Challenge, is a key area that will help the Department of Defense meet transformation goals. Third, Effective Development of Future Simulations, as a Grand Challenge, will set the standards by which future M&S improvements and new M&S programs will be acquired to ensure needed simulations are delivered on time and at desired cost.

Gordon, Steven C.

2002-07-01

406

Orion Landing Simulation Eight Soil Model Comparison  

NASA Technical Reports Server (NTRS)

LS-DYNA finite element simulations of a rigid Orion Crew Module (CM) were used to investigate the CM impact behavior on eight different soil models. Ten different landing conditions, characterized by the combination of CM vertical and horizontal velocity, hang angle, and roll angle were simulated on the eight different soils. The CM center of gravity accelerations, pitch angle, kinetic energy, and soil contact forces were the outputs of interest. The simulation results are presented, with comparisons of the CM behavior on the different soils. The soils analyzed in this study can be roughly categorized as soft, medium, or hard, according to the CM accelerations that occur when landing on them. The soft group is comprised of the Carson Sink Wet soil and the Kennedy Space Center (KSC) Low Density Dry Sand. The medium group includes Carson Sink Dry, the KSC High Density In-Situ Moisture Sand and High Density Flooded Sand, and Cuddeback B. The hard soils are Cuddeback A and the Gantry Unwashed Sand. The softer soils were found to produce lower peak accelerations, have more stable pitch behavior, and to be less sensitive to the landing conditions. This investigation found that the Cuddeback A soil produced the highest peak accelerations and worst stability conditions, and that the best landing performance was achieved on the KSC Low Density Dry Sand.

Mark, Stephen D.

2009-01-01

407

Multiple Time Series Ising Model for Financial Market Simulations  

NASA Astrophysics Data System (ADS)

In this paper we propose an Ising model which simulates multiple financial time series. Our model introduces the interaction which couples to spins of other systems. Simulations from our model show that time series exhibit the volatility clustering that is often observed in the real financial markets. Furthermore we also find non-zero cross correlations between the volatilities from our model. Thus our model can simulate stock markets where volatilities of stocks are mutually correlated.

Takaishi, Tetsuya

2015-01-01

408

Modeling and visual simulation of Microalgae photobioreactor  

NASA Astrophysics Data System (ADS)

Microalgae is a kind of nutritious and high photosynthetic efficiency autotrophic plant, which is widely distributed in the land and the sea. It can be extensively used in medicine, food, aerospace, biotechnology, environmental protection and other fields. Photobioreactor which is important equipment is mainly used to cultivate massive and high-density microalgae. In this paper, based on the mathematical model of microalgae which grew under different light intensity, three-dimensional visualization model was built and implemented in 3ds max, Virtools and some other three dimensional software. Microalgae is photosynthetic organism, it can efficiently produce oxygen and absorb carbon dioxide. The goal of the visual simulation is to display its change and impacting on oxygen and carbon dioxide intuitively. In this paper, different temperatures and light intensities were selected to control the photobioreactor, and dynamic change of microalgal biomass, Oxygen and carbon dioxide was observed with the aim of providing visualization support for microalgal and photobioreactor research.

Zhao, Ming; Hou, Dapeng; Hu, Dawei

409

VISION: Verifiable Fuel Cycle Simulation Model  

SciTech Connect

The nuclear fuel cycle is a very complex system that includes considerable dynamic complexity as well as detail complexity. In the nuclear power realm, there are experts and considerable research and development in nuclear fuel development, separations technology, reactor physics and waste management. What is lacking is an overall understanding of the entire nuclear fuel cycle and how the deployment of new fuel cycle technologies affects the overall performance of the fuel cycle. The Advanced Fuel Cycle Initiative’s systems analysis group is developing a dynamic simulation model, VISION, to capture the relationships, timing and delays in and among the fuel cycle components to help develop an understanding of how the overall fuel cycle works and can transition as technologies are changed. This paper is an overview of the philosophy and development strategy behind VISION. The paper includes some descriptions of the model and some examples of how to use VISION.

Jacob J. Jacobson; Abdellatif M. Yacout; Gretchen E. Matthern; Steven J. Piet; David E. Shropshire

2009-04-01

410

VISION: Verifiable Fuel Cycle Simulation Model  

SciTech Connect

The nuclear fuel cycle consists of a set of complex components that work together in unison. In order to support the nuclear renaissance, it is necessary to understand the impacts of changes and timing of events in any part of the fuel cycle system. The Advanced Fuel Cycle Initiative’s systems analysis group is developing a dynamic simulation model, VISION, to capture the relationships, timing, and changes in and among the fuel cycle components to help develop an understanding of how the overall fuel cycle works. This paper is an overview of the philosophy and development strategy behind VISION. The paper includes some descriptions of the model components and some examples of how to use VISION.

Jacob Jacobson; A. M. Yacout; Gretchen Matthern; Steven Piet; David Shropshire; Tyler Schweitzer

2010-11-01

411

Simulating Complex Modulated Phases Through Spin Models  

NASA Astrophysics Data System (ADS)

We extend the computational approach for studying striped phases on curved surfaces, presented in the previous talk, to two new problems involving complex modulated phases. First, we simulate a smectic liquid crystal on an arbitrary mesh by mapping the director field onto a vector spin and the density wave onto an Ising spin. We can thereby determine how the smectic phase responds to any geometrical constraints, including hybrid boundary conditions, patterned substrates, and disordered substrates. This method may provide a useful tool for designing ferroelectric liquid crystal cells. Second, we explore a model of vector spins on a flat two-dimensional (2D) lattice with long-range antiferromagnetic interactions. This model generates modulated phases with surprisingly complex structures, including 1D stripes and 2D periodic cells, which are independent of the underlying lattice. We speculate on the physical significance of these structures.

Selinger, Jonathan V.; Lopatina, Lena M.; Geng, Jun; Selinger, Robin L. B.

2009-03-01

412

Plasma simulation studies using multilevel physics models  

SciTech Connect

The question of how to proceed toward ever more realistic plasma simulation studies using ever increasing computing power is addressed. The answer presented here is the M3D (Multilevel 3D) project, which has developed a code package with a hierarchy of physics levels that resolve increasingly complete subsets of phase-spaces and are thus increasingly more realistic. The rationale for the multilevel physics models is given. Each physics level is described and examples of its application are given. The existing physics levels are fluid models (3D configuration space), namely magnetohydrodynamic (MHD) and two-fluids; and hybrid models, namely gyrokinetic-energetic-particle/MHD (5D energetic particle phase-space), gyrokinetic-particle-ion/fluid-electron (5D ion phase-space), and full-kinetic-particle-ion/fluid-electron level (6D ion phase-space). Resolving electron phase-space (5D or 6D) remains a future project. Phase-space-fluid models are not used in favor of delta f particle models. A practical and accurate nonlinear fluid closure for noncollisional plasmas seems not likely in the near future.

Park, W.; Belova, E.V.; Fu, G.Y. [and others

2000-01-19

413

At the Biological Modeling and Simulation Frontier  

PubMed Central

We provide a rationale for and describe examples of synthetic modeling and simulation (M&S) of biological systems. We explain how synthetic methods are distinct from familiar inductive methods. Synthetic M&S is a means to better understand the mechanisms that generate normal and disease-related phenomena observed in research, and how compounds of interest interact with them to alter phenomena. An objective is to build better, working hypotheses of plausible mechanisms. A synthetic model is an extant hypothesis: execution produces an observable mechanism and phenomena. Mobile objects representing compounds carry information enabling components to distinguish between them and react accordingly when different compounds are studied simultaneously. We argue that the familiar inductive approaches contribute to the general inefficiencies being experienced by pharmaceutical R&D, and that use of synthetic approaches accelerates and improves R&D decision-making and thus the drug development process. A reason is that synthetic models encourage and facilitate abductive scientific reasoning, a primary means of knowledge creation and creative cognition. When synthetic models are executed, we observe different aspects of knowledge in action from different perspectives. These models can be tuned to reflect differences in experimental conditions and individuals, making translational research more concrete while moving us closer to personalized medicine. Electronic supplementary material The online version of this article (doi:10.1007/s11095-009-9958-3) contains supplementary material, which is available to authorized users. PMID:19756975

Ropella, Glen E. P.; Lam, Tai Ning; Tang, Jonathan; Kim, Sean H. J.; Engelberg, Jesse A.; Sheikh-Bahaei, Shahab

2009-01-01

414

Detailed simulation of morphodynamics: 1. Hydrodynamic model  

NASA Astrophysics Data System (ADS)

We present a three-dimensional high-resolution hydrodynamic model for unsteady incompressible flow over an evolving bed topography. This is achieved by using a multilevel Cartesian grid technique that allows the grid to be refined in high-gradient regions and in the vicinity of the river bed. The grid can be locally refined and adapted to the bed geometry, managing the Cartesian grid cells and faces using a hierarchical tree data approach. A ghost-cell immersed-boundary technique is applied to cells intersecting the bed topography. The governing equations have been discretized using a finite-volume method on a staggered grid, conserving second-order accuracy in time and space. The solution advances in time using the fractional step approach. Large-eddy simulation is used as turbulence closure. We validate the model against several experiments and other results from literature. Model results for Stokes flow around a cylinder in the vicinity of a moving wall agree well with Wannier's analytical solution. At higher Reynolds numbers, computed trailing bubble length, separation angle, and drag coefficient compare favorably with experimental and previous computational results. Results for the flow over two- and three-dimensional dunes agree well with published data, including a fair reproduction of recirculation zones, horse-shoe structures, and boiling effects. This shows that the model is suitable for being used as a hydrodynamic submodel in the high-resolution modeling of sediment transport and formation and evolution of subaqueous ripples and dunes.

Nabi, M.; de Vriend, H. J.; Mosselman, E.; Sloff, C. J.; Shimizu, Y.

2012-12-01

415

Modeling Ecologic and Geomorphic Change in Semi-Arid New Mexico  

NASA Astrophysics Data System (ADS)

A record of grazing, fire suppression and drought in the semi-arid American south-west since the 1800s has left a mark on the landscape. In the Pajarito Plateau, New Mexico, pinyon-juniper woodlands have expanded at the expense of ponderosa pine forest, giving rise to increased erosion rates - a concern to the sustainability of the soil resource and of vegetation. Soil loss also risks human exposure to contaminants from Los Alamos National Laboratory. The dynamics of this water-controlled environment arise from the complex interplay of climate, hydrology, ecology and geomorphology, an understanding of which is fundamental to solution of the environmental challenges. In an effort to predict the course of ecological and geomorphic change in the region, and to provide a tool for land-use planners in averting possible human health and environmental hazards, a numerical landscape evolution model is developed. It assimilates research encompassing plant physiology, ecology, hydrology, and geomorphology, highlights weaknesses in process understanding, and provides a prediction of the future environmental state on the time-scale of 100s of years.

Collins, D. B.; Bras, R. L.

2004-12-01

416

Ecological input-output modeling for embodied resources and emissions in Chinese economy 2005  

NASA Astrophysics Data System (ADS)

For the embodiment of natural resources and environmental emissions in Chinese economy 2005, a biophysical balance modeling is carried out based on an extension of the economic input-output table into an ecological one integrating the economy with its various environmental driving forces. Included resource flows into the primary resource sectors and environmental emission flows from the primary emission sectors belong to seven categories as energy resources in terms of fossil fuels, hydropower and nuclear energy, biomass, and other sources; freshwater resources; greenhouse gas emissions in terms of CO2, CH4, and N2O; industrial wastes in terms of waste water, waste gas, and waste solid; exergy in terms of fossil fuel resources, biological resources, mineral resources, and environmental resources; solar emergy and cosmic emergy in terms of climate resources, soil, fossil fuels, and minerals. The resulted database for embodiment intensity and sectoral embodiment of natural resources and environmental emissions is of essential implications in context of systems ecology and ecological economics in general and of global climate change in particular.

Chen, Z. M.; Chen, G. Q.; Zhou, J. B.; Jiang, M. M.; Chen, B.

2010-07-01

417

Dimensions of Credibility in Models and Simulations  

NASA Technical Reports Server (NTRS)

Based on the National Aeronautics and Space Administration's (NASA's) work in developing a standard for models and simulations (M&S), the subject of credibility in M&S became a distinct focus. This is an indirect result from the Space Shuttle Columbia Accident Investigation Board (CAIB), which eventually resulted in an action, among others, to improve the rigor in NASA's M&S practices. The focus of this action came to mean a standardized method for assessing and reporting results from any type of M&S. As is typical in the standards development process, this necessarily developed into defming a common terminology base, common documentation requirements (especially for M&S used in critical decision making), and a method for assessing the credibility of M&S results. What surfaced in the development of the NASA Standard was the various dimensions credibility to consider when accepting the results from any model or simulation analysis. The eight generally relevant factors of credibility chosen in the NASA Standard proved only one aspect in the dimensionality of M&S credibility. At the next level of detail, the full comprehension of some of the factors requires an understanding along a couple of dimensions as well. Included in this discussion are the prerequisites for the appropriate use of a given M&S, the choice of factors in credibility assessment with their inherent dimensionality, and minimum requirements for fully reporting M&S results.

Steele, Martin J.

2008-01-01

418

Modeling ecological drivers in marine viral communities using comparative metagenomics and network analyses.  

PubMed

Long-standing questions in marine viral ecology are centered on understanding how viral assemblages change along gradients in space and time. However, investigating these fundamental ecological questions has been challenging due to incomplete representation of naturally occurring viral diversity in single gene- or morphology-based studies and an inability to identify up to 90% of reads in viral metagenomes (viromes). Although protein clustering techniques provide a significant advance by helping organize this unknown metagenomic sequence space, they typically use only ?75% of the data and rely on assembly methods not yet tuned for naturally occurring sequence variation. Here, we introduce an annotation- and assembly-free strategy for comparative metagenomics that combines shared k-mer and social network analyses (regression modeling). This robust statistical framework enables visualization of complex sample networks and determination of ecological factors driving community structure. Application to 32 viromes from the Pacific Ocean Virome dataset identified clusters of samples broadly delineated by photic zone and revealed that geographic region, depth, and proximity to shore were significant predictors of community structure. Within subsets of this dataset, depth, season, and oxygen concentration were significant drivers of viral community structure at a single open ocean station, whereas variability along onshore-offshore transects was driven by oxygen concentration in an area with an oxygen minimum zone and not depth or proximity to shore, as might be expected. Together these results demonstrate that this highly scalable approach using complete metagenomic network-based comparisons can both test and generate hypotheses for ecological investigation of viral and microbial communities in nature. PMID:25002514

Hurwitz, Bonnie L; Westveld, Anton H; Brum, Jennifer R; Sullivan, Matthew B

2014-07-22

419

Modeling ecological drivers in marine viral communities using comparative metagenomics and network analyses  

PubMed Central

Long-standing questions in marine viral ecology are centered on understanding how viral assemblages change along gradients in space and time. However, investigating these fundamental ecological questions has been challenging due to incomplete representation of naturally occurring viral diversity in single gene- or morphology-based studies and an inability to identify up to 90% of reads in viral metagenomes (viromes). Although protein clustering techniques provide a significant advance by helping organize this unknown metagenomic sequence space, they typically use only ?75% of the data and rely on assembly methods not yet tuned for naturally occurring sequence variation. Here, we introduce an annotation- and assembly-free strategy for comparative metagenomics that combines shared k-mer and social network analyses (regression modeling). This robust statistical framework enables visualization of complex sample networks and determination of ecological factors driving community structure. Application to 32 viromes from the Pacific Ocean Virome dataset identified clusters of samples broadly delineated by photic zone and revealed that geographic region, depth, and proximity to shore were significant predictors of community structure. Within subsets of this dataset, depth, season, and oxygen concentration were significant drivers of viral community structure at a single open ocean station, whereas variability along onshore–offshore transects was driven by oxygen concentration in an area with an oxygen minimum zone and not depth or proximity to shore, as might be expected. Together these results demonstrate that this highly scalable approach using complete metagenomic network-based comparisons can both test and generate hypotheses for ecological investigation of viral and microbial communities in nature. PMID:25002514

Hurwitz, Bonnie L.; Westveld, Anton H.; Brum, Jennifer R.; Sullivan, Matthew B.

2014-01-01

420

SPECIAL ISSUE PAPER Modeling social behaviors in an evacuation simulator  

E-print Network

SPECIAL ISSUE PAPER Modeling social behaviors in an evacuation simulator Mei Ling Chu1 *, Paolo simulation; egress simulation; social agents; social behavior; simulated perception *Correspondence Mei Ling@stanford.edu 1. INTRODUCTION During evacuation, people often observe the behaviors of their social peers

Stanford University

421

Ecology of testate amoebae (Protista) in south-central Alaska peatlands: building transfer-function models for palaeoenvironmental studies  

Microsoft Academic Search

Testate amoebae are valuable indicators of peatland hydrology and have been used in many palaeoclimatic studies in peatlands. Because the species' ecological optima may vary around the globe, the development of transfer function models is an essential prerequisite for regional palaeoclimatic studies using testate amoebae. We investigated testate amoebae ecology in nine peatlands covering a 250-km north-south transect in south-central

Richard J. Payne; Keiko Kishaba; Jeff J. Blackford; Edward A. D. Mitchell

2006-01-01

422

Ecological niche modeling as a new paradigm for large-scale investigations of diversity and distribution of birds  

E-print Network

for endangered spe- cies. Although for some species and regions the answer is straightforward (e.g., wherever there is forest!), in other cases it is not at all clear. A preliminary explor- ation of this functionality focused on the Mexican Wolf (Canis lupus..., the ecological niche modeling approach has been able to identify key additions to protected areas systems via addition of critical suites of species to the reserve system. Invasions and Reintroductions An early observation indicated that species’ ecological...

Peterson, A. Townsend; Kluza, Daniel A.

2005-01-01

423

Simulation: Transactions of the Society for Modeling and Simulation International  

E-print Network

by discussing how PMAP may be applicable in the stock markets, using a simplified order book simulation- fied neural spike trains via loudspeakers as a method of navigating the location of an electrode

Miranda, Eduardo Reck

424

MODELING LAND USE CHANGE AND ITS ECOLOGICAL CONSEQUENCES IN THE PHOENIX METROPOLITAN REGION Jianguo Wu, John David, Darrel Jenerette, Matt Luck, and Sheryl Berling-Wolff  

E-print Network

MODELING LAND USE CHANGE AND ITS ECOLOGICAL CONSEQUENCES IN THE PHOENIX METROPOLITAN REGION Jianguo land use change, multiple-scale analysis of the current urban landscape, spatial ecological footprint), (2) Land Use and Land Cover Change Modeling (a CA-Markov-GA model, a rule-based urban growth model

Hall, Sharon J.

425

Complexity and evolutionary simulation models in cognitive science Epistemology of synthetic bottom-up simulation modelling  

Microsoft Academic Search

In complex adaptive systems, where internal and external non-linear interactions give rise to an emergent functionality, analytic decomposition of component and isolated functional evaluation of them is not a viable methodological practice. More recently, embodied bottom-up synthetic methodological approaches have been proposed to solve this problem. Evolutionary simulation modelling (specifically evolutionary robotics) provides an explicit research methodology in this direction.

Xabier Barandiaran

426

Model-guided fieldwork: practical guidelines for multidisciplinary research on wildlife ecological and epidemiological dynamics  

PubMed Central

Infectious disease ecology has recently raised its public profile beyond the scientific community due to the major threats that wildlife infections pose to biological conservation, animal welfare, human health and food security. As we start unravelling the full extent of emerging infectious diseases, there is an urgent need to facilitate multidisciplinary research in this area. Even though research in ecology has always had a strong theoretical component, cultural and technical hurdles often hamper direct collaboration between theoreticians and empiricists. Building upon our collective experience of multidisciplinary research and teaching in this area, we propose practical guidelines to help with effective integration among mathematical modelling, fieldwork and laboratory work. Modelling tools can be used at all steps of a field-based research programme, from the formulation of working hypotheses to field study design and data analysis. We illustrate our model-guided fieldwork framework with two case studies we have been conducting on wildlife infectious diseases: plague transmission in prairie dogs and lyssavirus dynamics in American and African bats. These demonstrate that mechanistic models, if properly integrated in research programmes, can provide a framework for holistic approaches to complex biological systems. PMID:22809422

Restif, Olivier; Hayman, David T S; Pulliam, Juliet R C; Plowright, Raina K; George, Dylan B; Luis, Angela D; Cunningham, Andrew A; Bowen, Richard A; Fooks, Anthony R; O'Shea, Thomas J; Wood, James L N; Webb, Colleen T

2012-01-01

427

Ecological forecasting in Chesapeake Bay: Using a mechanistic-empirical modeling approach  

NASA Astrophysics Data System (ADS)

The Chesapeake Bay Ecological Prediction System (CBEPS) automatically generates daily nowcasts and three-day forecasts of several environmental variables, such as sea-surface temperature and salinity, the concentrations of chlorophyll, nitrate, and dissolved oxygen, and the likelihood of encountering several noxious species, including harmful algal blooms and water-borne pathogens, for the purpose of monitoring the Bay's ecosystem. While the physical and biogeochemical variables are forecast mechanistically using the Regional Ocean Modeling System configured for the Chesapeake Bay, the species predictions are generated using a novel mechanistic-empirical approach, whereby real-time output from the coupled physical-biogeochemical model drives multivariate empirical habitat models of the target species. The predictions, in the form of digital images, are available via the World Wide Web to interested groups to guide recreational, management, and research activities. Though full validation of the integrated forecasts for all species is still a work in progress, we argue that the mechanistic-empirical approach can be used to generate a wide variety of short-term ecological forecasts, and that it can be applied in any marine system where sufficient data exist to develop empirical habitat models. This paper provides an overview of this system, its predictions, and the approach taken.

Brown, C. W.; Hood, R. R.; Long, W.; Jacobs, J.; Ramers, D. L.; Wazniak, C.; Wiggert, J. D.; Wood, R.; Xu, J.

2013-09-01

428

Case studies and mathematical models of ecological speciation. 4. Hybrid speciation in butterflies in a jungle.  

PubMed

We build a spatial individual-based multilocus model of homoploid hybrid speciation tailored for a tentative case of hybrid origin of Heliconius heurippa from H. melpomene and H. cydno in South America. Our model attempts to account for empirical patterns and data on genetic incompatibility, mating preferences and selection by predation (both based on coloration patterns), habitat preference, and local adaptation for all three Heliconius species. Using this model, we study the likelihood of recombinational speciation and identify the effects of various ecological and genetic parameters on the dynamics, patterns, and consequences of hybrid ecological speciation. Overall, our model supports the possibility of hybrid origin of H. heurippa under certain conditions. The most plausible scenario would include hybridization between H. melpomene and H. cydno in an area geographically isolated from the rest of both parental species with subsequent long-lasting geographic isolation of the new hybrid species, followed by changes in the species ranges, the secondary contact, and disappearance of H. melpomene-type ecomorph in the hybrid species. However, much more work (both empirical and theoretical) is necessary to be able to make more definite conclusions on the importance of homoploid hybrid speciation in animals. PMID:19545268

Duenez-Guzman, Edgar A; Mavárez, Jesus; Vose, Michael D; Gavrilets, Sergey

2009-10-01

429

Using Computational Simulations to Confront Students' Mental Models  

ERIC Educational Resources Information Center

In this paper we show an example of how to use a computational simulation to obtain visual feedback for students' mental models, and compare their predictions with the simulated system's behaviour. Additionally, we use the computational simulation to incrementally modify the students' mental models in order to accommodate new data,…

Rodrigues, R.; Carvalho, P. Simeão

2014-01-01

430

VisiGarp: Graphical Representation of Qualitative Simulation Models  

E-print Network

research, we use GARP as our qualitative simulation engine (Bredeweg 1992). The GARP framework containsVisiGarp: Graphical Representation of Qualitative Simulation Models Anders Bouwer & Bert Bredeweg, The Netherlands E-mail: {anders, bert}@swi.psy.uva.nl Abstract Qualitative simulation models can play a useful

Bouwer, Anders

431

Dynamic wind turbine models in power system simulation tool  

E-print Network

Dynamic wind turbine models in power system simulation tool DIgSILENT Anca D. Hansen, Florin Iov models in power system simulation tool DIgSILENT Department: Wind Energy Department Risø-R-1400(ed.2)(EN system simulation tool PowerFactory DIgSILENT for different wind turbine concepts. It is the second

432

Fuzzy Model for a Computer Simulation of Bird Flocking  

E-print Network

Fuzzy Model for a Computer Simulation of Bird Flocking A PHD DISSERTATION BY Iztok LEBAR BAJEC #12;Fuzzy Model for a Computer Simulation of Bird Flocking Bird Flocks [line formations] High degree for a Computer Simulation of Bird Flocking Bird Flocks [cluster formations] Large flocks wheeling and turning

Bajec, Iztok Lebar

433

Chemistry climate model simulations of1 spring Antarctic ozone  

E-print Network

Chemistry climate model simulations of1 spring Antarctic ozone 1234567 89A64BC7DEF72B4 19B34EE3293C climate model simulations of spring Antarctic ozone John Austin,1,2 H. Struthers,3 J. Scinocca,4 D. A) and Intergovernmental Panel on Climate Change A1b Scenario. The simulations of the Antarctic ozone hole are compared

Wirosoetisno, Djoko

434

Using computational simulations to confront students’ mental models  

NASA Astrophysics Data System (ADS)

In this paper we show an example of how to use a computational simulation to obtain visual feedback for students’ mental models, and compare their predictions with the simulated system’s behaviour. Additionally, we use the computational simulation to incrementally modify the students’ mental models in order to accommodate new data, and receive visual feedback for those modifications.

Rodrigues, R.; Simeão Carvalho, P.

2014-03-01

435

A taxonomy for simulation modeling based on programming language principles  

E-print Network

A taxonomy for simulation modeling based on programming language principles PAUL A. FISHWICK many diverse areas employ simulation models, no agreed-upon taxonomy has been developed to categorize than the design structure of the model. We present a uniform model design taxonomy whose categories

Mukherjee, Amlan

436

The distribution, dominance patterns and ecological niches of plankton functional types in Dynamic Green Ocean Models and satellite estimates  

NASA Astrophysics Data System (ADS)

We compare the spatial and temporal representation of phytoplankton functional types (pPFTs) in four different Dynamic Green Ocean Models (DGOMs; CCSM-BEC, NEMURO, PISCES and PlankTOM5) to derived phytoplankton distributions from two independent satellite estimates, with a particular focus on diatom distributions. Global annual mean surface biomass estimates for diatoms vary between 0.23 mmol C m-3 and 0.77 mmol C m-3 in the models, and are comparable to a satellite-derived estimate (0.41 mmol C m-3). All models consistently simulate a higher zonal mean diatom biomass contribution in the high latitudes than in the low latitudes, but the relative diatom contribution varies substantially between models with largest differences in the high latitudes (20% to 100% of total biomass). We investigate phytoplankton distribution in terms of annual and monthly mean dominance patterns, i.e. the distribution of locations where a given PFT contributes more than 50% to total biomass. In all models, diatoms tend to dominate large areas of the high latitudes of both hemispheres, and the area of the surface ocean dominated by diatoms is significantly higher in the models than in the satellite estimates. We estimate the realized ecological niches filled by the dominant pPFT at each location as a function of annual mean surface nitrate concentration (NO3), sea surface temperature (SST), and mixed layer depth. A general additive model (GAM) is used to map the probability of dominance of all pPFTs in niche and geographic space. Models tend to simulate diatom dominance over a wider temperature and nutrient range, whereas satellites confine diatom dominance to a narrower niche of low-intermediate annual mean temperatures (annual mean SST < 10 °C), but allow for niches in different ranges of surface NO3 concentrations. For annual mean diatom dominance, the statistically modelled probability of dominance explains the majority of the variance in the data (65.2-66.6%). For the satellite estimates, the explained deviance is much lower (44.6% and 32.7%). The differences in the representation of diatoms among models and compared to satellite estimates highlights the need to better resolve phytoplankton succession and phenology in the models. This work is part of the marine ecosystem inter-comparison project (MAREMIP).

Vogt, M.; Hashioka, T.; Payne, M. R.; Buitenhuis, E. T.; Le Quéré, C.; Alvain, S.; Aita, M. N.; Bopp, L.; Doney, S. C.; Hirata, T.; Lima, I.; Sailley, S.; Yamanaka, Y.

2013-11-01

437

Ecological Resilience, Biodiversity, and Scale  

Microsoft Academic Search

We describe existing models of the relationship between species diversity and ecological function, and propose a conceptual model that relates species richness, ecological resilience, and scale. We suggest that species interact with scale-dependent sets of ecological structures and processes that determine functional opportunities. We propose that ecologi- cal resilience is generated by diverse, but overlap- ping, function within a scale

Garry Peterson; Craig R. Allen; C. S. Holling

1998-01-01

438

Identifying hazards in complex ecological systems. Part 3: Hierarchical Holographic Model for herbicide tolerant oilseed rape.  

PubMed

This paper is the third in a series designed to demonstrate the application of rigorous, systematic hazard identification techniques to ecological systems. Here we use Hierarchical Holographic Modelling to identify the potential ecological hazards associated with the commercial release of herbicide tolerant oilseed rape. Hierarchical Holographic Models decompose complex systems into a series of sub-systems and consider interactions between the components and processes of these sub-systems in order to identify hazards. In this example we considered 1356 potential interactions between the biological, chemical and physical components and processes of the herbicide tolerant oilseed rape environment, and identified 152 potential hazards, grouped into 14 categories. The hazards were subsequently scored for degree of concern and plausibility, and then compared with an equivalent list of hazards generated independently by a checklist approach. The incidence of herbicide tolerant volunteers (and weeds) both on and off the farm had the highest average score of all the ecological hazard categories. The checklist based approach identified or implied 44% of the hazards identified in the Hierarchical Holographic Model, including nine of the ten hazards ranked most important. The checklist approach focussed almost exclusively on the phenotypic and genotypic hazards associated with herbicide tolerant oilseed rape and largely ignored the hazards associated with the circumstances surrounding its use. As a result the checklist identified only 6 out of the 79 potential hazards associated with changes to farming practice. The commercial release of herbicide tolerant oilseed rape will be associated with changes in tillage and the application of post-emergent herbicides. It may also lead to changes in spray schedules of insecticide and fungicide. Many of the environmental hazards identified with these changes are plausible and may warrant further investigation or targeted monitoring. PMID:15612508

Hayes, Keith R; Gregg, Peter C; Gupta, V V S R; Jessop, R; Lonsdale, W M; Sindel, B; Stanley, J; Williams, C K

2004-01-01

439

A Theoretical Reassessment of Microbial Maintenance and Implications for Microbial Ecology Modeling  

SciTech Connect

We attempted to reconcile three microbial maintenance models (Herbert, Pirt, and Compromise) through a critical reassessment. We provided a rigorous proof that the true growth yield coefficient (YG) is the ratio of the specific maintenance rate (a in Herbert) to the maintenance coefficient (m in Pirt). Other findings from this study include: (1) the Compromise model is identical to the Herbert for computing microbial growth and substrate consumption, but it expresses the dependence of maintenance on both microbial biomass and substrate; (2) the maximum specific growth rate in the Herbert ( max,H) is higher than those in the other two models ( max,P and max,C), and the difference is the physiological maintenance factor (mq = a); and (3) the overall maintenance coefficient (mT) is more sensitive to mq than to the specific growth rate ( G) and YG. Our critical reassessment of microbial maintenance provides a new approach for quantifying some important components in soil microbial ecology models.

Wang, Gangsheng [ORNL; Post, Wilfred M [ORNL

2012-01-01

440

Modeling and Simulation of Electric and Hybrid Vehicles  

Microsoft Academic Search

This paper discusses the need for modeling and simulation of electric and hybrid vehicles. Different modeling methods such as physics-based Resistive Companion Form technique and Bond Graph method are presented with powertrain component and system modeling examples. The modeling and simulation capabilities of existing tools such as Powertrain System Analysis Toolkit (PSAT), ADvanced VehIcle SimulatOR (ADVISOR), PSIM, and Virtual Test

David Wenzhong Gao; Chris Mi; Ali Emadi

2007-01-01

441

Using Simulation Models for District Chilled Water Distribution Systems Design  

E-print Network

Using Simulation Models for District Chilled Water Distribution Systems Design Case Study ? University of Texas at San Antonio 1604 Campus Qiang Chen Chen Xu Song Deng David E. Claridge W. Dan Turner Energy Systems Laboratory Texas A...). The simulation model appeared to be reliable, consistent, and conservative (Chen et al. 2002) by comparing with an earlier report (Smith 1997). The finished simulation model is illustrated in Figure 1. This mode is called the base model. All...

Chen, Q.; Xu, C.; Deng, S.; Claridge, D. E.; Turner, W. D.

2004-01-01

442

Dangers of using global bioclimatic datasets for ecological niche modeling. Limitations for future climate projections  

NASA Astrophysics Data System (ADS)

Global bioclimatic datasets are being widely used in ecological research to estimate the potential distribution of species using Climate Envelope Models (CEMs). These datasets are easily available and offer high resolution information for all land areas globally. However, they have not been tested rigorously in smaller regions, and their use in regional CEM studies may pose problems derived from their poor representation of local climate features. Moreover, these problems may be enhanced when using CEMs for future climate projections—a topic of current active research—due to the uncertainty derived from the future altered climate scenarios.

Bedia, Joaquín; Herrera, Sixto; Gutiérrez, José Manuel

2013-08-01

443

Ecological modelling of convergence patterns between European and African `whip' snakes  

NASA Astrophysics Data System (ADS)

The concept of evolutionary convergence in morphological traits among phylogenetically unrelated organisms because of their ecological similarities is one of the most venerable in evolutionary ecology, and indeed has attracted the attention of ecologists for a long time. The 'whip snakes' are phylogenetically unrelated, morphologically and ecologically convergent species, which are characterized by slender bodies, long tails, large eyes, alertness, diurnality, saurophagy, oviparity, and rapid movement. It has been hypothesized that their morphology has evolved as a response preying on quick-running diurnal prey, mainly lizards. Here I compared two species of saurophagous whip snakes, the European Coluber ( Hierophis) viridiflavus and the African Psammophis phillipsii. I explored whether the proximate factors which influence the presence of the two species in their natural habitat are the same in both Mediterranean central Italy ( Coluber viridiflavus) and in tropical Nigeria ( Psammophis phillipsii). I also used as control two other species of colubrids, Natrix natrix in Italy and Lamprophis fuliginosus in Nigeria. I selected 11 independent variables that are general for both study systems, and that are easily identified for their presence/absence in/around the site of capture of each snake specimen, and then explored the effects of these variables on the presence of the two species using a robust statistical design, i.e. a forward stepwise logistic regression model. My modelling analyses indicated that two variables influenced positively (i.e. the presence of lizards (LIZ) and of tall grass (GRS)), and one influenced negatively (the presence of water bodies (WBS)), the African species' presence. With regard to the European species, only two variables influenced positively and significantly the snakes presence, i.e. LIZ and GRS. Overall, the comparison of the two models clearly showed that both species' presence was influenced exactly by the same variables, despite the different continents and environmental conditions. The two control species were influenced by entirely different variables. Hence, robust modelling statistics revealed a extreme ecological similarity between the phylogenetically unrelated Psammophis and Coluber, clearly indicating that their peculiar morphologies have evolved to prey a rapid moving type of diurnal prey (lizards) in a specific type of microhabitat (tall grass). As there was no significant correlation between LIZ and GRS, hence the positive influence of GRS on both the snake species' presence cannot be considered as a mere correlate of the LIZ variable, but is likely that the peculiar morphological adaptations of these snakes are particularly efficient in this type of microhabitat compared to others.

Luiselli, Luca

2006-07-01

444

Revisiting the catastrophic die-off of the urchin Diadema antillarum on Caribbean coral reefs: Fresh insights on resilience from a simulation model  

Microsoft Academic Search

In 1983, the dominant urchin of Caribbean coral reefs (Diadema antillarum) experienced massive disease-induced mortality and its functional extinction persists to this day. Concurrently, reports of coral disease, coral bleaching and nutrification began to appear and many Caribbean reefs have deteriorated in the last two decades. Here, we describe a spatial simulation model of physical and ecological processes occurring on

Peter J. Mumby; John D. Hedley; Kamila Zychaluk; Alastair R. Harborne; Paul G. Blackwell

2006-01-01

445

LADEE Satellite Modeling and Simulation Development  

NASA Technical Reports Server (NTRS)

As human activity on and around the Moon increases, so does the likelihood that our actions will have an impact on its atmosphere. The Lunar Atmosphere and Dust Environment Explorer (LADEE), a NASA satellite scheduled to launch in 2013, will orbit the Moon collecting composition, density, and time variability data to characterize the current state of the lunar atmosphere. LADEE will also test the concept of the "Modular Common Bus" spacecraft architecture, an effort to reduce both development time and cost by designing reusable, modular components for use in multiple missions with similar requirements. An important aspect of this design strategy is to both simulate the spacecraft and develop the flight code in Simulink, a block diagram-style programming language that allows easy algorithm visualization and performance testing. Before flight code can be tested, however, a realistic simulation of the satellite and its dynamics must be generated and validated. This includes all of the satellite control system components such as actuators used for force and torque generation and sensors used for inertial orientation reference. My primary responsibilities have included designing, integrating, and testing models for the LADEE thrusters, reaction wheels, star trackers, and rate gyroscopes.

Adams, Michael; Cannon, Howard; Frost, Chad

2011-01-01

446

Improving the Algae Bloom Prediction through the Assimilation of the Remotely Sensed Chlorophyll-A Data in a Generic Ecological Model in the North Sea  

NASA Astrophysics Data System (ADS)

Harmful algae can cause damage to co-existing organisms, tourism and farmers. Accurate predictions of algal future composition and abundance as well as when and where algal blooms may occur could help early warning and mitigating. The Generic Ecological Model, GEM, [Blauw et al 2008] is an instrument that can be applied to any water system (fresh, transitional or coastal) to calculate the primary production, chlorophyll-a concentration and phytoplankton species composition. It consists of physical, chemical and ecological model components which are coupled together to build one generic and flexible modeling tool. For the North Sea, the model has been analyzed to assess sensitivity of the simulated chlorophyll-a concentration to a subset of ecologically significant set of factors. The research led to the definition of the most significant set of parameters to the algae blooming process in the North Sea [Salacinska et al 2009]. In order to improve the prediction of the model, the set of parameters and the chlorophyll-a concentration can be further estimated through the use of data assimilation. In this research, the Ensemble Kalman Filter (EnKF) data assimilation technique is used to assimilate the chlorophyll-a data of the North Sea, retrieved from MEdium Resolution Imaging Sensor (MERIS) spectrometer data [Peters et al 2005], in the GEM model. The chlorophyll-a data includes concentrations and error information that enable their use in data assimilation. For the same purpose, the uncertainty of the ecological generic model, GEM has been quantified by means of Monte Carlo approach. Through a study covering the year of 2003, the research demonstrates that both data and model are sufficiently robust for a successful assimilation. The results show that through the assimilation of the satellite data, a better description of the algae bloom has been achieved and an improvement of the capability of the model to predict the algae bloom for the North Sea has been confirmed. Blauw A.N., Los F.J., Bokhorst M., Erftemeijer P.L.A., (2009), GEM: a Generic Ecological Model for estuaries and coastal waters. Journal of Hydrobiologia, Volume 618, Number 1, 175-198. Peters, S.W.M., Eleveld, M. Pasterkamp, R., Woerd, H. van der, Devolder, M., Jans, S., Park, Y., Ruddick, K., Block, T., Brockmann, C., Doerffer, R., Krasemann, H., Röttgers, R., Schönfeld, W., Jørgensen, P.V., Tilstone, G., Martinez-Vicente, V., Moore, G., Sørensen, K., Høkedal, J., Johnsen, T.M., Lømsland, E.R., Aas, E. (2005). Atlas of Chlorophyll-a concentration for the North Sea based on MERIS imagery of 2003. IVM report, Vrije Universiteit Amsterdam, 117 pp. ISBN 90-5192-026-1. Salacinska K., El Serafy G.Y., Blauw A., Los F.J., (2009) Sensitivity analysis of the two dimensional application of the Generic Ecological Model (GEM) to algal bloom prediction in the North Sea, Journal of Ecological Modeling, volume 221, 7, pp 178-190, DOI: 10.1016/j.ecolmodel.2009.10.001

El Serafy, Ghada

2010-05-01

447

Simulation Models for Socioeconomic Inequalities in Health: A Systematic Review  

PubMed Central

Background: The emergence and evolution of socioeconomic inequalities in health involves multiple factors interacting with each other at different levels. Simulation models are suitable for studying such complex and dynamic systems and have the ability to test the impact of policy interventions in silico. Objective: To explore how simulation models were used in the field of socioeconomic inequalities in health. Methods: An electronic search of studies assessing socioeconomic inequalities in health using a simulation model was conducted. Characteristics of the simulation models were extracted and distinct simulation approaches were identified. As an illustration, a simple agent-based model of the emergence of socioeconomic differences in alcohol abuse was developed. Results: We found 61 studies published between 1989 and 2013. Ten different simulation approaches were identified. The agent-based model illustration showed that multilevel, reciprocal and indirect effects of social determinants on health can be modeled flexibly. Discussion and Conclusions: Based on the review, we discuss the utility of using simulation models for studying health inequalities, and refer to good modeling practices for developing such models. The review and the simulation model example suggest that the use of simulation models may enhance the understanding and debate about existing and new socioeconomic inequalities of health frameworks. PMID:24192788

Speybroeck, Niko; Van Malderen, Carine; Harper, Sam; Müller, Birgit; Devleesschauwer, Brecht

2013-01-01

448

Modeling Propellant Combustion Using Molecular Dynamics Simulations  

NASA Astrophysics Data System (ADS)

Currently, a first-principles theoretical model of self-sustained combustion of solid energetic materials does not exist and consequently the development of new propellants has to be approached from a strictly empirical viewpoint. Without a theoretical framework to guide it, this method remains expensive and time consuming and therefore inefficient. The benefits of a theoretical model are numerous. Primarily, it would offer a systematic way of understanding the seemingly unapproachable combination of physical and chemical reactions inherent in all combustion phenomena. The resulting predictive capabilities would serve as the underlying methods in the development of new propellants. Our model involves the three states of matter as frozen ozone(M.S. Miller, Materials Research Society, Fall meeting (1995).) melts and eventually vaporizes giving oxygen upon decomposition. However, much of the needed thermodynamic and transport properties are unavailable from experiments and therefore, we have appealed to molecular dynamics simulations. Using a Lennard-Jones potential we have been able to obtain thermodynamic and transport properties about the pure components and various mixtures of ozone and oxygen in each phase as well as at the interfaces.

Bembenek, Scott D.; Rice, Betsy M.; Miller, Martin S.

1998-03-01

449