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1

Simulation of socio-ecological impacts: Modeling a fishing village  

NASA Astrophysics Data System (ADS)

The interrelationship of society and environment is addressed here through the study of a remote fishing village of 750 people. An interdisciplinary study evaluated demographic, economic, and social aspects of the community, and simulation modeling was used to integrate these societal characteristics with environmental factors. The population of the village had grown gradually until the 1960's, when a decline began. Out-migration correlated with declining fish harvests and with increased communications with urban centers. Fishing had provided the greatest economic opportunity, followed by logging. A survey was conducted to investigate the costs and revenues of village fishermen. Diversification characterized the local fleet, and analysis showed that rates of return on investment in the current year were equal between vessel types. The variable levels and rate parameters of the demographic, economic, and social components of the model were specified through static and time series data. Sensitivity analysis to assess the effects of uncertainty, and validation tests against known historical changes were also conducted. Forecast scenarios identified the development options under several levels of fish abundance and investment. The weight given to ecological versus economic resource management registered disproportionate effects due to the interaction between investment and migration rates and resource stochasticity. This finding argues against a “golden mean” rule for evaluating policy trade-offs and argues for the importance of using a dynamic, socio-ecological perspective in designing development policies for rural communities.

Miller, Philip C.

1982-03-01

2

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...

3

An ecological classification of forest landscape simulation models: tools and strategies for understanding broad-scale forested ecosystems  

Microsoft Academic Search

Computer models are increasingly being used by forest ecologists and managers to simulate long-term forest landscape change.\\u000a We review models of forest landscape change from an ecological rather than methodological perspective. We developed a classification\\u000a based on the representation of three ecological criteria: spatial interactions, tree species community dynamics, and ecosystem\\u000a processes. Spatial interactions are processes that spread across a

Robert M. Scheller; David J. Mladenoff

2007-01-01

4

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...

5

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

6

Simulation of Regionally Ecological Land Based on a Cellular Automation Model: A Case Study of Beijing, China  

PubMed Central

Ecological land is like the “liver” of a city and is very useful to public health. Ecological land change is a spatially dynamic non-linear process under the interaction between natural and anthropogenic factors at different scales. In this study, by setting up natural development scenario, object orientation scenario and ecosystem priority scenario, a Cellular Automation (CA) model has been established to simulate the evolution pattern of ecological land in Beijing in the year 2020. Under the natural development scenario, most of ecological land will be replaced by construction land and crop land. But under the scenarios of object orientation and ecosystem priority, the ecological land area will increase, especially under the scenario of ecosystem priority. When considering the factors such as total area of ecological land, loss of key ecological land and spatial patterns of land use, the scenarios from priority to inferiority are ecosystem priority, object orientation and natural development, so future land management policies in Beijing should be focused on conversion of cropland to forest, wetland protection and prohibition of exploitation of natural protection zones, water source areas and forest parks to maintain the safety of the regional ecosystem.

Xie, Hualin; Kung, Chih-Chun; Zhang, Yanting; Li, Xiubin

2012-01-01

7

Sensitivity of an ecological model to soil moisture simulations from two different hydrological models  

NASA Astrophysics Data System (ADS)

Although advanced land surface schemes have been developed in the past decade, many biosphere models still use the simple bucket model, partly due to its efficiency when it is coupled with an CGCM model. In this paper, we use a sophisticated land surface model, the Simulator for Hydrology and Energy Exchange at the Land Surface (SHEELS), including an explicit vegetation canopy and its physiological control on evapotranspiration and multiple, interactive subsurface soil layers. It is found that this model has potential for improving the carbon cycling description of a widely used biosphere model, the Carnegie-Ames-Stanford approach (CASA), especially for multiple seasonal integrations. Verifying with observations from Oklahoma Atmospheric Surface-layer Instrumentation System (OASIS) stations, we show that a bucket model as implemented in the CASA produces good simulations of the seasonal cycle of soil moisture content, but only for the upper 15-cm soil depth, no matter how it is initialized. This is partly due to its inability to include vegetation characteristics other than a fixed wilting point. Although only approximate, the soil depth to which CASA simulates storage of below-ground carbon is assumed to be about 30 cm depth, significantly deeper than the 15 cm depth. The bucket model cannot utilize the soil profile measurements that have recently been made widely available. A major finding of this study is that carbon fluxes are sensitive to the soil moisture simulations, especially the soil water content of the upper 30 cm. The SHEELS exhibits potential for simulating soil moisture, and hence the total soil water amount, accurately at every level. For the Net Primary Production (NPP) parameter, the differences between two hydrological schemes occur primarily during the growing seasons, when the land surface processes are more important for climate. However, soil microbial respiration is found to be sensitive all year round to soil moisture simulations at our 7 selected Oklahoma Mesonet stations. These suggest that for future implementing of interactive representation of soil carbon in CGCMs, the accompanying hydrological scheme should not be over-simplified.

Ren, D.; Leslie, L. M.; Karoly, D. J.

2008-08-01

8

Comparison of simulation modeling and satellite techniques for monitoring ecological processes  

NASA Technical Reports Server (NTRS)

In 1985 improvements were made in the world climatic data base for modeling and predictive mapping; in individual process models and the overall carbon-balance models; and in the interface software for mapping the simulation results. Statistical analysis of the data base was begun. In 1986 mapping was shifted to NASA-Goddard. The initial approach involving pattern comparisons was modified to a more statistical approach. A major accomplishment was the expansion and improvement of a global data base of measurements of biomass and primary production, to complement the simulation data. The main accomplishments during 1987 included: production of a master tape with all environmental and satellite data and model results for the 1600 sites; development of a complete mapping system used for the initial color maps comparing annual and monthly patterns of Normalized Difference Vegetation Index (NDVI), actual evapotranspiration, net primary productivity, gross primary productivity, and net ecosystem production; collection of more biosphere measurements for eventual improvement of the biological models; and development of some initial monthly models for primary productivity, based on satellite data.

Box, Elgene O.

1988-01-01

9

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

10

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

Microsoft Academic Search

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

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

2008-01-01

11

Individual-based models as tools for ecological theory and application: Understanding the emergence of organisational properties in ecological systems  

Microsoft Academic Search

Individual-based models offer a structurally unique (and unifying) approach to ecological applications. Model results also provide an important input into ecological theory. The approach operates on the lowest organisational level considered in ecology (i.e. activities of individuals). Simulating the actions of single organisms allows to study how the properties of higher level ecological entities like swarms, populations, trophic networks and

Broder Breckling; Ulrike Middelhoff; Hauke Reuter

2006-01-01

12

INTEGRATED MODELING AND ECOLOGICAL VALUATION  

Microsoft Academic Search

1. OBJECTIVES Understanding how anthropogenic and climate-induced changes alter ecological systems and evaluating the effects of alternative hydrologic profiles on these ecosystems are important concerns in the semi-arid West. The goal of the proposed research is to incorporate hydrologic, vegetation, avian, and economic models into an integrated framework to determine the value of changes in ecological systems that result from

David S. Brookshire; Bonnie Colby; David Goodrich; John Loomis; Holly Richter; Steven Stewart

13

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

14

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

15

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

16

Effects of changing anthropogenic pressures on water quality and plankton dynamics in three Swiss lakes - Long-term simulations with the biogeochemical-ecological lake model BELAMO  

NASA Astrophysics Data System (ADS)

Water quality and plankton dynamics, important indicators for the ecological state of a lake, are affected by many influence factors. To understand the behaviour of a lake under changing driving forces (such as nutrient loads or climatic change), modelling is an important resource. A model used for this purpose should represent the quantitative understanding of the dominant biogeochemical and ecological processes within a lake and be as universal as possible. With the Biogeochemical Ecologial LAke MOdel (BELAMO) it was tried to combine the description of biogeochemical processes in the lake with an ecological model. The results of its application to the lakes Greifensee (eutrophic), Lake Zurich (mesotrophic) and Walensee (oligotrophic) indicate that already a relatively simple plankton sub-model can lead to a quite high degree of universality (in the sense of applicability of the same model and parameter values to lakes of different trophic state). The box version of the model distinguishes the four mixed compartments epilimnion, hypolimnion and 2 sediment layers. It aims at a joint calculation of mass balances of nutrients, oxygen, organic particles, one group of phytoplankton and one group of zooplankton in a lake in all four compartments. The model was designed to explicitly describe the sediment processes, instead of considering their effect by source and sink terms at the bottom of the lake for substances exchanged between lake water and the sediment. Therefore the different mineralisation processes had to be quantified. Difficulties compassed the identification of aerobic, anoxic and anaerobic mineralisation rates while representing jointly the measured concentrations of oxygen, nitrate and organic material in the lake. The description of the lake by mixed compartments enhanced this difficulty, because the depth of the sediment layers determines maximal diffusion gradients for the entry of substances into the sediment. One further problem we had to cope with was the availability of concentration data only. The same concentrations can result from different fluxes that drive the dynamics in the lake. Different concentrations can have quite different sensitivities to external changes. An example for this are phosphate and algae. While the phosphate concentration responds quite fast to a decrease in phosphate input loading, the algae might not show this decrease directly. This is due to the ability of adaptation of the algal community and a parallel reaction of zooplankton. For this reason, the reduced turnover rates of phosphate do not necessarily lead to much smaller plankton concentrations. On a shorter time scale, phytoplankton and zooplankton can show faster variability than can be detected by monthly data. This makes it impossible to get a realistic description of short-term algal dynamics. To handle this problem when improving the model we conducted parameter calibrations that fit smoothed model results to smoothed data. This calibration technique avoids fitting the model to uncertain data peaks as well as rejecting parameter combinations resulting in model outputs that do not represent individual data peaks, but cover the main patterns of the measurements correctly. This pattern fitting technique led to a much better performance of the fit algorithm than fitting to the original data, which often resulted in simulations that covered some data peaks, but missed the basic annual and long-term pattern. In the end, long-term simulations for 20-30 years (depending on data availability for the different lakes) showed that good simulations are possible despite significantly changing driving forces. This is an indication of the good mechanistic representation of the processes in the lake. Nevertheless, as this behaviour depends critically on the chosen model parameter values, the predictive power of the model still needs further improvement.

Dietzel, A.; Mieleitner, J.; Reichert, P.

2009-04-01

17

Auto-calibration of a one-dimensional hydrodynamic-ecological model using a Monte Carlo approach: simulation of hypoxic events in a polymictic lake  

NASA Astrophysics Data System (ADS)

Automated calibration of complex deterministic water quality models with a large number of biogeochemical parameters can reduce time-consuming iterative simulations involving empirical judgements of model fit. We undertook auto-calibration of the one-dimensional hydrodynamic-ecological lake model DYRESM-CAEDYM, using a Monte Carlo sampling (MCS) method, in order to test the applicability of this procedure for shallow, polymictic Lake Rotorua (New Zealand). The calibration procedure involved independently minimising the root-mean-square-error (RMSE), maximizing the Pearson correlation coefficient (r) and Nash-Sutcliffe efficient coefficient (Nr) for comparisons of model state variables against measured data. An assigned number of parameter permutations was used for 10,000 simulation iterations. The 'optimal' temperature calibration produced a RMSE of 0.54 °C, Nr-value of 0.99 and r-value of 0.98 through the whole water column based on comparisons with 540 observed water temperatures collected between 13 July 2007 - 13 January 2009. The modeled bottom dissolved oxygen concentration (20.5 m below surface) was compared with 467 available observations. The calculated RMSE of the simulations compared with the measurements was 1.78 mg L-1, the Nr-value was 0.75 and the r-value was 0.87. The autocalibrated model was further tested for an independent data set by simulating bottom-water hypoxia events for the period 15 January 2009 to 8 June 2011 (875 days). This verification produced an accurate simulation of five hypoxic events corresponding to DO < 2 mg L-1 during summer of 2009-2011. The RMSE was 2.07 mg L-1, Nr-value 0.62 and r-value of 0.81, based on the available data set of 738 days. The auto-calibration software of DYRESM-CAEDYM developed here is substantially less time-consuming and more efficient in parameter optimisation than traditional manual calibration which has been the standard tool practiced for similar complex water quality models.

Luo, L.

2011-12-01

18

Modeling the coupling of ocean ecology and biogeochemistry  

Microsoft Academic Search

Abstract. 8 We examine the interplay between ecology and biogeochemical cycles in the context 9 of a global three-dimensional ocean model where self-assembling phytoplankton commu- 10 nities emerge from a wide set of potentially viable cell types. We consider the complex 11 model solutions in the light of resource competition theory. The simulations have clear 12 and plausible organization of

S. Dutkiewicz; M. J. Follows; J. G. Bragg

2009-01-01

19

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

20

Pattern-oriented modelling in population ecology  

Microsoft Academic Search

Ecological modelling should take its orientation more from real patterns observed in nature, than has been the case up to now, to overcome the deficiencies of the present strategies. Firstly, the orientation towards patterns provides guidelines about the manner and extent of the aggregation of biological information in the model. Modelling thereby loses much of its arbitrariness; secondly, pattern-oriented models

Volker Grimm; Karin Frank; Florian Jeltsch; Roland Brandl; Janusz Uchma?ski; Christian Wissel

1996-01-01

21

The Ecological Validity of Photographic Slides and Videotapes in Simulating the Service Setting  

Microsoft Academic Search

In the study of consumers' evaluation of the service setting, laboratory experiments using environmental simulations provide researchers with a level of control that can otherwise be difficult to achieve in field studies. This article demonstrates that photographic slides and videotapes, used as environmental simulations in testing a theory of crowding, have ecological validity. The same theoretical model is tested with

John E. G. Bateson; Michael K. Hui

1992-01-01

22

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

23

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

24

Individual-based models in ecology after four decades  

PubMed Central

Individual-based models simulate populations and communities by following individuals and their properties. They have been used in ecology for more than four decades, with their use and ubiquity in ecology growing rapidly in the last two decades. Individual-based models have been used for many applied or “pragmatic” issues, such as informing the protection and management of particular populations in specific locations, but their use in addressing theoretical questions has also grown rapidly, recently helping us to understand how the sets of traits of individual organisms influence the assembly of communities and food webs. Individual-based models will play an increasingly important role in questions posed by complex ecological systems.

Grimm, Volker

2014-01-01

25

Individual-based models in ecology after four decades.  

PubMed

Individual-based models simulate populations and communities by following individuals and their properties. They have been used in ecology for more than four decades, with their use and ubiquity in ecology growing rapidly in the last two decades. Individual-based models have been used for many applied or "pragmatic" issues, such as informing the protection and management of particular populations in specific locations, but their use in addressing theoretical questions has also grown rapidly, recently helping us to understand how the sets of traits of individual organisms influence the assembly of communities and food webs. Individual-based models will play an increasingly important role in questions posed by complex ecological systems. PMID:24991416

DeAngelis, Donald L; Grimm, Volker

2014-01-01

26

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

27

Using Student Generated Qualitative Ecological Models  

NSDL National Science Digital Library

As simplifications of real system, models can be used by students to improve their understanding of an ecosystem and to make predictions about what will happen after a disturbance or other change to the ecosystem. This activity guides students through the development of quantitative ecological models. Students use a model to explore how ecosystems work and to predict how disturbance can affect ecosystem function.

Dresner, Marion

2010-02-16

28

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

29

Systemic, Ecological Model for Rehabilitation Counseling.  

ERIC Educational Resources Information Center

Presents a reformulation of Hershenson's theoretical model for rehabilitation counseling in systemic and ecological terms. This macrosystem is organized by precipitating event of disability and is composed of four systems: consumer, functional, provider, and contextual. Discusses the use of the model for selecting rehabilitation interventions…

Hershenson, David B.

1998-01-01

30

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

31

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.

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

2013-01-01

32

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...

33

Social Ecological Model Analysis for ICT Integration  

ERIC Educational Resources Information Center

ICT integration of teacher preparation programmes was undertaken by the Australian Teaching Teachers for the Future (TTF) project in all 39 Australian teacher education institutions and highlighted the need for guidelines to inform systemic ICT integration approaches. A Social Ecological Model (SEM) was used to positively inform integration…

Zagami, Jason

2013-01-01

34

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

35

Spatial heterogeneity and ecological models. [Predation  

SciTech Connect

The role of natural enemies in the regulation of populations is one of the major questions facing population ecologists. Simplification have led to two theoretical ways of incorporating the role of natural enemies in single ecological models: diffusion models and patch-type models. The predictions of the models are different because of the way variability is incorporated. Three equations are presented for diffusion models and one for patch models. Since the two types of models apply at different combinations of spatial and temporal scales, the right model(s) to choose for a particular study requires careful assessment. A continuing dialogue between experimentalists and theoreticians will lead to a better understanding of natural systems such as those that occur in biological control.

Hastings, A. (Univ. of California, Davis (USA))

1990-04-01

36

Teaching About Landscape Ecology: Developing and Applying Neutral Models  

NSDL National Science Digital Library

This article emphasizes why it is important to teach landscape ecology in general ecology courses and describes the nature of landscape ecology. The laboratory exercise outlined employs percolation theory as a neutral model. It demonstrates how spatial characteristics of landscapes can change as a certain type of habitat changes. Additionally, it introduces students to threshold or nonlinear relationships and issues of scale.

Allen, Timothy F.

2010-02-16

37

Handbook of Scaling Methods in Aquatic Ecology: Measurement, Analysis, Simulation  

NASA Astrophysics Data System (ADS)

Researchers in aquatic sciences have long been interested in describing temporal and biological heterogeneities at different observation scales. During the 1970s, scaling studies received a boost from the application of spectral analysis to ecological sciences. Since then, new insights have evolved in parallel with advances in observation technologies and computing power. In particular, during the last 2 decades, novel theoretical achievements were facilitated by the use of microstructure profilers, the application of mathematical tools derived from fractal and wavelet analyses, and the increase in computing power that allowed more complex simulations. The idea of publishing the Handbook of Scaling Methods in Aquatic Ecology arose out of a special session of the 2001 Aquatic Science Meeting of the American Society of Limnology and Oceanography. The edition of the book is timely, because it compiles a good amount of the work done in these last 2 decades. The book is comprised of three sections: measurements, analysis, and simulation. Each contains some review chapters and a number of more specialized contributions. The contents are multidisciplinary and focus on biological and physical processes and their interactions over a broad range of scales, from micro-layers to ocean basins. The handbook topics include high-resolution observation methodologies, as well as applications of different mathematical tools for analysis and simulation of spatial structures, time variability of physical and biological processes, and individual organism behavior. The scientific background of the authors is highly diverse, ensuring broad interest for the scientific community.

Marrasé, Celia

2004-03-01

38

Implicit estimation of ecological model parameters  

NASA Astrophysics Data System (ADS)

We present a new methodology for data-based state and parameter estimation and results from its application to an ecological model. The method has a strong theoretical justification; it is appropriate when the model is nonlinear and for non-Gaussian distributions of the state conditioned on the observations; and it is able to estimate any number of parameters, including initial conditions and model error covariances. The ecological model describes the evolution of plankton, nutrients, and organic matter in the upper ocean. It depends on a set of parameters that determine the specific growth rates of the individual concentrations, their limiting due to crowding, and their interaction, whether it is consumption of one by another, or competition over a common resource. The true values of these parameters are rarely known precisely. Their estimation is essential to drawing accurate inferences about past, present, and future ecological states. In experiments with a simplified model and synthetically generated twin data, we show that the estimated parameters identify the correct asymptotic behavior of the model. In particular, we demonstrate that it is possible to detect whether the limit set of the state is a center, fixed point, or limit cycle. If the system has a Hopf bifurcation, the parameter estimation to recovers the correct dynamic behavior of the system, even when the initial guess and true parameters are on opposite sides of the bifurcation. We then examine the extent that real data from an in situ time series determines the dynamical properties of the full model. Under general assumptions on the tail decay of the conditional distribution, the parameter estimate shows no evidence of bias and its variance is comparable to the uniform minimum of any unbiased estimator. Our method is applicable in two forms: as a smoother estimate, which finds the best estimate for all the observations at once, and a filter estimate, which updates the parameter estimate with each new observation. The filter estimate is a method for the sequential continuation of the smoother estimate and is necessary when storage and time are limited. It is also a promising approach for the identification of the response of the state to a parameter that varies in time.

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

2011-12-01

39

An overview of the utility of population simulation software in molecular ecology.  

PubMed

Stochastic simulation software that simultaneously model genetic, population and environmental processes can inform many topics in molecular ecology. These include forecasting species and community response to environmental change, inferring dispersal ecology, revealing cryptic mating, quantifying past population dynamics, assessing in situ management options and monitoring neutral and adaptive biodiversity change. Advances in population demographic-genetic simulation software, especially with respect to individual life history, landscapes and genetic processes, are transforming and expanding the ways that molecular data can be used. The aim of this review is to explain the roles that such software can play in molecular ecology studies (whether as a principal component or a supporting function) so that researchers can decide whether, when and precisely how simulations can be incorporated into their work. First, I use seven case studies to demonstrate how simulations are employed, their specific advantage/necessity and what alternative or complementary (nonsimulation) approaches are available. I also explain how simulations can be integrated with existing spatial, environmental, historical and genetic data sets. I next describe simulation features that may be of interest to molecular ecologists, such as spatial and behavioural considerations and species' interactions, to provide guidance on how particular simulation capabilities can serve particular needs. Lastly, I discuss the prospect of simulation software in emerging challenges (climate change, biodiversity monitoring, population exploitation) and opportunities (genomics, ancient DNA), in order to emphasize that the scope of simulation-based work is expanding. I also suggest practical considerations, priorities and elements of best practice. This should accelerate the uptake of simulation approaches and firmly embed them as a versatile tool in the molecular ecologist's toolbox. PMID:24689878

Hoban, Sean

2014-05-01

40

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.

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

2014-01-01

41

Modeling the coupling of ocean ecology and biogeochemistry  

Microsoft Academic Search

We examine the interplay between ecology and biogeochemical cycles in the context of a global three-dimensional ocean model where self-assembling phytoplankton communities emerge from a wide set of potentially viable cell types. We consider the complex model solutions in the light of resource competition theory. The emergent community structures and ecological regimes vary across different physical environments in the model

S. Dutkiewicz; M. J. Follows; J. G. Bragg

2009-01-01

42

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.

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

2013-01-01

43

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...

44

A Conceptual Framework for Evaluating the Domains of Applicability of Ecological Models and its Implementation in the Ecological Production Function Library - International Society for Ecological Modelling Conference  

EPA Science Inventory

The use of computational ecological models to inform environmental management and policy has proliferated in the past 25 years. These models have become essential tools as linkages and feedbacks between human actions and ecological responses can be complex, and as funds for sampl...

45

Do simple models lead to generality in ecology?  

PubMed

Modellers of biological, ecological, and environmental systems cannot take for granted the maxim 'simple means general means good'. We argue here that viewing simple models as the main way to achieve generality may be an obstacle to the progress of ecological research. We show how complex models can be both desirable and general, and how simple and complex models can be linked together to produce broad-scale and predictive understanding of biological systems. PMID:23827437

Evans, Matthew R; Grimm, Volker; Johst, Karin; Knuuttila, Tarja; de Langhe, Rogier; Lessells, Catherine M; Merz, Martina; O'Malley, Maureen A; Orzack, Steve H; Weisberg, Michael; Wilkinson, Darren J; Wolkenhauer, Olaf; Benton, Tim G

2013-10-01

46

International Applications of Ecological Models: Implications for the Future.  

ERIC Educational Resources Information Center

Visits to 10 schools and residential centers in eight countries were made to investigate international applications of ecological models in the psychoeducational treatment of behavior disordered children. The ecological approach differs from other approaches because it views the problem as a disturbance in the relationship and reciprocity between…

Juul, Kristen D.

47

Adding Value to Ecological Risk Assessment with Population Modeling  

Microsoft Academic Search

Current measures used to estimate the risks of toxic chemicals are not relevant to the goals of the environmental protection process, and thus ecological risk assessment (ERA) is not used as extensively as it should be as a basis for cost-effective management of environmental resources. Appropriate population models can provide a powerful basis for expressing ecological risks that better inform

Valery E. Forbes; Peter Calow; Volker Grimm; Takehiko I. Hayashi; Tjalling Jager; Agnete Katholm; Annemette Palmqvist; Rob Pastorok; Dan Salvito; Richard Sibly; Julann Spromberg; John Stark; Richard A. Stillman

2011-01-01

48

A Complementary Ecological Model of the Coordinated School Health Program  

ERIC Educational Resources Information Center

Background: A complementary ecological model of the coordinated school health program (CSHP) reflecting 20 years of evolved changes is proposed. Ecology refers to the complex interrelationship between intrapersonal factors, interpersonal processes and primary groups, institutional factors, community factors, and public policy. Methods: Public…

Lohrmann, David K.

2010-01-01

49

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

50

Controlled Ecological Life Support System (CELSS) modeling  

NASA Technical Reports Server (NTRS)

Attention is given to CELSS, a critical technology for the Space Exploration Initiative. OCAM (object-oriented CELSS analysis and modeling) models carbon, hydrogen, and oxygen recycling. Multiple crops and plant types can be simulated. Resource recovery options from inedible biomass include leaching, enzyme treatment, aerobic digestion, and mushroom and fish growth. The benefit of using many small crops overlapping in time, instead of a single large crop, is demonstrated. Unanticipated results include startup transients which reduce the benefit of multiple small crops. The relative contributions of mass, energy, and manpower to system cost are analyzed in order to determine appropriate research directions.

Drysdale, Alan; Thomas, Mark; Fresa, Mark; Wheeler, Ray

1992-01-01

51

Revisions to the 1995 Map of Ecological Subregions that Affect Users of the Southern Variant of the Forest Vegetation Simulator.  

National Technical Information Service (NTIS)

The Southern Variant of the Forest Vegetation Simulator utilizes ecological units mapped in 1995 by the Forest Service, U.S. Department of Agriculture, to refine tree growth models for the Southern United States. The 2007 revision of the 1995 map resulted...

C. E. Keyser W. H. McNab

2011-01-01

52

TOWARD MODELING THE ECOLOGICAL EFFECTS OF CHEMICALS ACTING JOINTLY  

EPA Science Inventory

A physical basis is sought for modeling the ecological effects of neutral, hydrophobic chemicals acting jointly. It is assumed that these chemicals cross biological membranes passively, driven by gradients in chemical potential, and are distributed among chemical phases (types of...

53

Ammonia-oxidizing bacteria: a model for molecular microbial ecology.  

PubMed

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 nitrite as their sole energy source. Because of the importance of this functional group of bacteria, understanding of their ecology and physiology has become a subject of intense research over recent years. The monophyletic nature of these bacteria in terrestrial environments has facilitated molecular biological approaches in studying their ecology, and progress in this field has been rapid. The ammonia-oxidizing bacteria of the beta-subclass Proteobacteria have become somewhat of a model system within molecular microbial ecology, and this chapter reviews recent progress in our knowledge of their distribution, diversity, and ecology. PMID:11544365

Kowalchuk, G A; Stephen, J R

2001-01-01

54

Development and Application of Computer Simulation Tools for Ecological Risk Assessment  

Microsoft Academic Search

Based on a review of available models for ecological risk estimation, most are site-specific and their applications are limited. However, general models, which can be easily adapted to other sites, remain few, in addition, they are simple and associated with significant uncertainties. In this paper, an approach is introduced for an ecological risk assessment (ERA) model that can be modified

Haiyi Lu; Lisa Axe; Trevor A. Tyson

2003-01-01

55

Pattern-Oriented Modeling of Agent-Based Complex Systems: Lessons from Ecology  

Microsoft Academic Search

Agent-based complex systems are dynamic networks of many interacting agents; examples include ecosystems, financial markets, and cities. The search for general principles underlying the internal organization of such systems often uses bottom-up simulation models such as cellular automata and agent-based models. No general framework for designing, testing, and analyzing bottom-up models has yet been established, but recent advances in ecological

Volker Grimm; Eloy Revilla; Uta Berger; Florian Jeltsch; Wolf M. Mooij; Steven F. Railsback; Hans-Hermann Thulke; Jacob Weiner; Thorsten Wiegand; Donald L. DeAngelis

2005-01-01

56

Designing wetlands for controlling coal mine drainage: an ecologic-economic modelling approach  

Microsoft Academic Search

Baker, K.A., Fennessy, M.S. and Mitsch, W.J., 1991. Designing wetlands for controlling coal mine drainage: an ecologic-economic modelling approach. Ecol. Econ., 3: l-24. A simulation model is developed of the efficiency and economics of an application of ecotechnology - using a created wetland to receive and treat coal mine drainage. The model examines the role of loading rates of iron

Kimberly Anne Baker; M. Siobhan Fennessy; William J. Mitsch

1991-01-01

57

Ecologic Niche Modeling and Spatial Patterns of Disease Transmission  

PubMed Central

Ecologic niche modeling (ENM) is a growing field with many potential applications to questions regarding the geography and ecology of disease transmission. Specifically, ENM has the potential to inform investigations concerned with the geography, or potential geography, of vectors, hosts, pathogens, or human cases, and it can achieve fine spatial resolution without the loss of information inherent in many other techniques. Potential applications and current frontiers and challenges are reviewed.

2006-01-01

58

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

59

AQUATOX: Modeling environmental fate and ecological effects in aquatic ecosystems  

Microsoft Academic Search

AQUATOX combines aquatic ecosystem, chemical fate, and ecotoxicological constructs to obtain a truly integrative fate and effects model. It is a general, mechanistic ecological risk assessment model intended to be used to evaluate past, present, and future direct and indirect effects from various stressors including nutrients, organic wastes, sediments, toxic organic chemicals, flow, and temperature in aquatic ecosystems. The model

Richard A. Park; Jonathan S. Clough; Marjorie Coombs Wellman

2008-01-01

60

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

61

Cognitive Modeling for Agent-Based Simulation of Child Maltreatment  

NASA Astrophysics Data System (ADS)

This paper extends previous work to develop cognitive modeling for agent-based simulation of child maltreatment (CM). The developed model is inspired from parental efficacy, parenting stress, and the theory of planned behavior. It provides an explanatory, process-oriented model of CM and incorporates causality relationship and feedback loops from different factors in the social ecology in order for simulating the dynamics of CM. We describe the model and present simulation results to demonstrate the features of this model.

Hu, Xiaolin; Puddy, Richard

62

Modeling and simulation  

SciTech Connect

This book presents the papers given at a conference on computerized simulation. Topics considered at the conference included expert systems, modeling in electric power systems, power systems operating strategies, energy analysis, a linear programming approach to optimum load shedding in transmission systems, econometrics, simulation in natural gas engineering, solar energy studies, artificial intelligence, vision systems, hydrology, multiprocessors, and flow models.

Hanham, R.; Vogt, W.G.; Mickle, M.H.

1986-01-01

63

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

64

Guide for developing conceptual models for ecological risk assessments  

SciTech Connect

Ecological conceptual models are the result of the problem formulation phase of an ecological risk assessment, which is an important component of the Remedial Investigation process. They present hypotheses of how the site contaminants might affect the site ecology. The contaminant sources, routes, media, routes, and endpoint receptors are presented in the form of a flow chart. This guide is for preparing the conceptual models; use of this guide will standardize the models so that they will be of high quality, useful to the assessment process, and sufficiently consistent so that connections between sources of exposure and receptors can be extended across operable units (OU). Generic conceptual models are presented for source, aquatic integrator, groundwater integrator, and terrestrial OUs.

Suter, G.W., II

1996-05-01

65

A New Ecological Model Oriented Forest Plantation Map of China  

NASA Astrophysics Data System (ADS)

China has been implementing unprecedented afforestation programs since the middle 1980s to restore ecosystem services and mitigate climate change by sequestering carbon from atmosphere to biosphere. Over the past three decades, China has planted 120-160 million hectares of trees, accounting for about 70% of its current forested area. Planted forest ecosystems are different in biophysical and biochemical characteristics from natural forests. To accurately estimate regional carbon storage change in China, the spatio-temporal information of planted forests must be taken into account and distinguished from natural forests. The goal of this research is to create the first ecological model-oriented plantation map of China using coupled remote sensing data and statistical data. We divided our research into three steps. Firstly, to quantitatively characterize forest-plantation area, we proposed a Plantation Potential Index (PPI) that demonstrated the possibility of artificial forest establishment in a 1km by 1km grid. MODIS Vegetation Continuous Fields (VCF) data produced by the Global Land Cover Facility (GLCF) were employed to distinguish forest and non-forest area for each year from 2001-2010. Then time series of Normalized Differences Vegetation Index (NDVI) from MODIS were utilized to identify new growth forests and their establishment time by using a logistic growth function. With the identified new forests, Digital Elevation Model (DEM), NDVI variance, soil degradation level and the ratio of annual Land Surface Temperature maximum (LSTmax) to Enhanced Vegetation Index maximum (EVImax) were combined to construct PPI for each grid. Secondly, we built up a spatial allocation model to automatically assign statistical data from each province to map pixels based on their PPI values. Finally, we validated our plantation map at locations where independent field or documentary data were available and depicted plantation classification accuracy. After careful examination, we provided a layer of uncertainty map to quantify the varying range of each pixel value. With the new ecological model-oriented forest plantation map, we can better simulate the carbon budget in China and evaluate the afforestation programs. Results from this research can benefit land-use reconstructions and projections as well as the coupled human-earth system modeling study.

Ying, Q.; Hurtt, G. C.; Zhao, M.; Chini, L. P.; Fisk, J. P.; Liang, S.

2012-12-01

66

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...

67

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...

68

Ecological Niche Modeling of Cryptococcus gattii in British Columbia, Canada  

PubMed Central

Background Cryptococcus gattii emerged on Vancouver Island, British Columbia (BC), Canada, in 1999, causing human and animal illness. Environmental sampling for C. gattii in southwestern BC has isolated the fungal organism from native vegetation, soil, air, and water. Objectives Our aim was to help public health officials in BC delineate where C. gattii is currently established and forecast areas that could support C. gattii in the future. We also examined the utility of ecological niche modeling (ENM) based on human and animal C. gattii disease surveillance data. Methods We performed ENM using the Genetic Algorithm for Rule-set Prediction (GARP) to predict the optimal and potential ecological niche areas of C. gattii in BC. Human and animal surveillance and environmental sampling data were used to build and test the models based on 15 predictor environmental data layers. Results ENM provided very accurate predictions (> 98% accuracy, p-value < 0.001) for C. gattii in BC. The models identified optimal C. gattii ecological niche areas along the central and south eastern coast of Vancouver Island and within the Vancouver Lower Mainland. Elevation, biogeoclimatic zone, and January temperature were good predictors for identifying the ecological niche of C. gattii in BC. Conclusions The use of human and animal case data for ENM proved useful and effective in identifying the ecological niche of C. gattii in BC. These results are shared with public health to increase public and physician awareness of cryptococcal disease in regions at risk of environmental colonization of C. gattii.

Mak, Sunny; Klinkenberg, Brian; Bartlett, Karen; Fyfe, Murray

2010-01-01

69

Model organisms retain an "ecological memory" of complex ecologically relevant environmental variation.  

PubMed

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; Baliga, Nitin S

2014-03-01

70

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.

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

71

Wilderness Area Simulation Model.  

National Technical Information Service (NTIS)

The computer program for a simulation model for travel and encounters in wilderness areas is available to managers for testing alternative wilderness management strategies. Detailed technical information can be obtained from the U.S. Forest Service, Compu...

N. A. Heck D. B. Webster

1973-01-01

72

Mrbc Simulation Model.  

National Technical Information Service (NTIS)

A simulation was developed as a technique for analyzing and testing possible solutions for a centralized inventory control system for blood banking in the Chicago area. The model provides methods for studying the effects of different inventory techniques ...

T. R. Jobe

1969-01-01

73

Using satellite remote sensing analysis to evaluate a socio-economic and ecological model of deforestation in Rondônia, Brazil  

Microsoft Academic Search

The effectiveness of an integrated socio-economic and ecological simulation model for estimating patterns and rates of deforestation in Rondônia, Brazil is evaluated using Landsat data and landscape pattern metrics. The Percent Cleared, Contagion, and Fractal Dimension of image classifications are compared to those determined from model outputs. Results indicate that rates and spatial patterns of deforestation are similar between model

R. C. FROHN; K. C. McGWIRE; V. H. DALE; J. E. ESTES

1996-01-01

74

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...

75

Predicting population dynamics with analytical, simulation and supercomputer models  

Microsoft Academic Search

A set of epizootiological models describing the influence of a microsporidian disease on the population dynamics of an herbivorous insect demonstrate the similarities and differences between the three major approaches now available for ecological modeling. Simulation modeling allows the incorporation of randomness or the timing of discrete events in the temporal dynamics. More complex models incorporating both temporal and spatial

Onstad

1987-01-01

76

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...

77

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

78

Application of an Ecological Model for the Cibolo Creek Watershed  

Microsoft Academic Search

BACKGROUND: The U.S. Army Engineer District, Fort Worth (CESWF) is involved in demon- strating the utility of an ecological model in the performance and interpretation of a comprehensive General Investigations (GI) study of the Cibolo Creek watershed upstream of Interstate 10 near San Antonio, Texas. Partners to the District in this project are the Natural Resources Conservation Service (NRCS), U.S.

David Price; Terry McLendon; Cade Coldren

79

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...

80

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...

81

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...

82

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...

83

Advances in Violence and Trauma: Toward Comprehensive Ecological Models  

ERIC Educational Resources Information Center

The most important things learned about violence and trauma in the past 20 years are that interpersonal violence is prevalent, with different forms co-occurring, and that victims' reactions are complex. Researchers are called to consider models that include the ecological context within which victims experience violence and trauma to gain a better…

Hughes, Honore M.; Humphrey, Natalie N.; Weaver, Terri L.

2005-01-01

84

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...

85

Application of an Ecological Model for the Cibolo Creek Watershed.  

National Technical Information Service (NTIS)

The U.S. Army Engineer District, Fort Worth (CESWF) is involved in demon- strating the utility of an ecological model in the performance and interpretation of a comprehensive General Investigations (GI) study of the Cibolo Creek watershed upstream of Inte...

D. Price T. McLendon C. Coldren

2004-01-01

86

The Quality of Home Environment in Brazil: An Ecological Model  

ERIC Educational Resources Information Center

Based on Bronfenbrenner's (1999) ecological perspective, a longitudinal, prospective model of individual differences in the quality of home environment (Home Observation for Measurement of the Environment--HOME) was tested in a sample of 179 Brazilian children and their families. Perinatal measures of family socioeconomic status (SES) and child…

de Oliveira, Ebenezer A.; Barros, Fernando C.; Anselmi, Luciana D. da Silva; Piccinini, Cesar A.

2006-01-01

87

Trade in an Ecological-economic Integrated Model  

Microsoft Academic Search

This paper incorporates the concept of ecological pyramid into the John's specific factor model of trade to examine comparative advantages, gains from trade, terms of trade, and income distributional effects of trade in the presence of non-market ecosystem services. Our results show that the market price undervalues the opportunity cost of land-intensive goods. The terms of trade, pattern of trade,

Amy R. Hwang

2009-01-01

88

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...

89

POPULATION MODELS IN ECOLOGICAL RISK ASSESSMENT  

EPA Science Inventory

A SETAC Pellston Workshop on Population-Level Risk Assessment was held in Roskilde, Denmark on 23-27 August 2003. One aspect of this workshop focused on modeling approaches for characterizing population-level effects of chemical exposure. The modeling work group identified th...

90

Acute ecological toxicity and environmental persistence of simulants  

Microsoft Academic Search

The objectives of these studies are to establish the comparative environmental behavior and chemical fate of chemical simulants. Laboratory studies were undertaken to establish: (1) deposition efficiency (deposition velocities, Vd) for receptor surfaces including plant foliage and soils; (2) dose\\/response relationships for important environmental components including plants and soil microflora; and (3) the environmental persistence of the simulants. Chemical agent

D. A. Cataldo; M. W. Ligotke; B. D. McVeety; R. J. Fellows; H. Jr. Bolton; S. W. Li; P. Van Voris; R. S. Wentsel

1988-01-01

91

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

USGS Publications Warehouse

Abstract. 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 (2) 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.

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

2013-01-01

92

AQUATOX (Release 2) Modeling Environmental Fate and Ecological Effects in Aquatic Ecosystems. Volume 3: User's Manual for the Basins (Version 3.1) Extension to AQUATOX Release 2.  

National Technical Information Service (NTIS)

AQUATOX is a time-variable ecological risk assessment model that stimulates the fate and effects of various environmental stressors in aquatic ecosystems. It simulates the fate and transfer of pollutants from loads to the water, sediments, and biotic comp...

2004-01-01

93

Economic and Ecological Input-Output Model.  

ERIC Educational Resources Information Center

This documentation presents an input-output model which has been modified to include the environmental impact of economic operation. In lieu of market prices for the environmental factors, trade-offs with regional income and employment are estimated for use in regional planning. The program is written in FORTRAN IV with single precision for the…

Blaylock, James E.; Jones, Lonnie L.

94

An Ecological Process Model of Systems Change  

Microsoft Academic Search

In June 2007 the American Journal of Community Psychology published a special issue focused on theories, methods and interventions for systems change which included calls from the\\u000a editors and authors for theoretical advancement in this field. We propose a conceptual model of systems change that integrates\\u000a familiar and fundamental community psychology principles (succession, interdependence, cycling of resources, adaptation) and\\u000a accentuates

Leslea J. Peirson; Katherine M. Boydell; H. Bruce Ferguson; Lorraine E. Ferris

2011-01-01

95

Acute ecological toxicity and environmental persistence of simulants  

SciTech Connect

The objectives of these studies are to establish the comparative environmental behavior and chemical fate of chemical simulants. Laboratory studies were undertaken to establish: (1) deposition efficiency (deposition velocities, Vd) for receptor surfaces including plant foliage and soils; (2) dose/response relationships for important environmental components including plants and soil microflora; and (3) the environmental persistence of the simulants. Chemical agent simulants are employed for a range of testing and training activities where use of chemical agents is less than suitable from a safety and environmental standpoint. A variety of chemical simulant materials are used to simulate either nerve agents or blister agents. The following research describes the environmental effects and persistence of four simulants. These are the nerve agent stimulants diisopropyl methylphosphonate (DIMP), diisopropyl fluorophosphate (DFP), and bis (2-ethylhexyl) phosphonate (BIS), and the mustard stimulant 2-chloroethyl ethyl sulfide (CEES). The vapor pressures for DIMP, DFP, and CEES are relatively high, reported to be 0.17, 0.58 and 3.4 mm Hg, respectively; while that of BIS is substantially less at 5.8 /times/ 10/sup /minus/5/ mm Hg at 25/degree/C. The chemical characteristics of DFP and CEES are very similar to G/VX-agents and mustard, respectively, and are employed for materials evaluation under controlled conditions. However, their toxicity precludes their use in the environment. DIMP and BIS are currently used for testing in the open air. 3 figs., 3 tabs.

Cataldo, D.A.; Ligotke, M.W.; McVeety, B.D.; Fellows, R.J.; Bolton, H. Jr.; Li, S.W.; Van Voris, P.; Wentsel, R.S.

1988-06-01

96

Ecological prediction with nonlinear multivariate time-frequency functional data models  

USGS Publications Warehouse

Time-frequency analysis has become a fundamental component of many scientific inquiries. Due to improvements in technology, the amount of high-frequency signals that are collected for ecological and other scientific processes is increasing at a dramatic rate. In order to facilitate the use of these data in ecological prediction, we introduce a class of nonlinear multivariate time-frequency functional models that can identify important features of each signal as well as the interaction of signals corresponding to the response variable of interest. Our methodology is of independent interest and utilizes stochastic search variable selection to improve model selection and performs model averaging to enhance prediction. We illustrate the effectiveness of our approach through simulation and by application to predicting spawning success of shovelnose sturgeon in the Lower Missouri River.

Yang, Wen-Hsi; Wikle, Christopher K.; Holan, Scott H.; Wildhaber, Mark L.

2013-01-01

97

Realism and Relevance of Ecological Models Used in Chemical Risk Assessment  

Microsoft Academic Search

Ecological models have been developed and used in management of renewable natural resources, conservation biology, and assessments of ecological risks posed by toxic chemicals and other stressors. Because few models have been developed specifically for use in assessing chemical risks, this study examines the realism and relevance of a wide range of ecological models from the perspective of assessing toxicological

Steven M. Bartell; Robert A. Pastorok; H. Resit Akçakaya; Helen Regan; Scott Ferson; Christopher Mackay

2003-01-01

98

Modeling and simulation  

Microsoft Academic Search

Modeling and simulation (M&S) represents a fundamental change in the US Department of Defense (DOD), and has been identified as a critical technology that allows evaluation, testing, and training without building physical replicas. Although M&S can never replace actual hardware tests and exercises, savings come from testing borderline performance conditions with no risk to the hardware or human life. The

1992-01-01

99

Study of transportation and distribution of PCBs using an ecologically simulated growth chamber  

Microsoft Academic Search

This study was designed to investigate the transportation, distribution, and bioaccumulation of PCBs in various environmental media and compartments using an ecologically simulated growth chamber. Spatial and temporal trends of PCBs in the growth chamber were discussed. The release of PCB congeners in soil was affected by the amount of rainfall with the transporting direction moving away from PCBs contaminated

Yaw-Jian Lin; Hsiang-Chao Liu; Zeng-Yei Hseu; Wan-Jheng Wu

2006-01-01

100

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...

101

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

102

Spatial modelling of Bacillus anthracis ecological niche in Zimbabwe.  

PubMed

Anthrax continues to cause significant mortalities in livestock, wildlife and humans worldwide. In Zimbabwe, anthrax outbreaks have been reported almost annually over the past four decades. In this study we tested whether anthrax outbreak data and a set of environmental variables can be used to predict the ecological niche for Bacillus anthracis using maximum entropy modelling for species geographical distribution (Maxent). Confirmed geo-referenced anthrax outbreaks data for the period 1995-2010 were used as presence locations and a set of environmental parameters; precipitation, temperature, vegetation biomass, soil type and terrain as predictor variables. Results showed that the environmental variables can adequately predict the ecological niche of B. anthracis (AUC for test data=0.717, p<0.001), with soil type as the most important predictor followed by variance of vegetation biomass and maximum temperature. These results imply that the model we tested may be used by animal health authorities in devising better control strategies for anthrax. PMID:23726015

Chikerema, S M; Murwira, A; Matope, G; Pfukenyi, D M

2013-08-01

103

Towards a Broad Ecological Model of Fish Communities and Fisheries  

Microsoft Academic Search

The paper brings together major inferences from: (1) classical limnology—lake and stream typology, the role of major abiotic variables; (2) fisheries limnology—Ryder's morphoedaphic index, Jenkins' reservoir findings, concepts of habitat niches; (3) studies of ecological structure of communities—succession, diversity, stability, variability, regulation; (4) recent developments concerning the effects of major cultural stresses on fish communities. A model is proposed to

Henry A. Regier; H. Francis Henderson

1973-01-01

104

Research on agricultural ecology and environment analysis and modeling based on RS and GIS  

NASA Astrophysics Data System (ADS)

Analysis of agricultural ecology and environment is based on the data of agricultural resources, which are obtained by RS monitoring. The over-exploitation of farmlands will cause structural changes of the soil composition, and damage the planting environment and the agro-ecosystem. Through the research on the dynamic monitoring methods of multitemporal RS images and GIS technology, the crop growth status, crop acreage and other relevant information in agricultural production are extracted based on the monitor and analysis of the conditions of the fields and crop growth. The agro-ecological GIS platform is developed with the establishment of the agricultural resources management database, which manages spatial data, RS data and attribute data of agricultural resources. Using the RS, GIS analysis results, the reasons of agro-ecological destruction are analyzed and the evaluation methods are established. This paper puts forward the concept of utilization capacity of farmland, which describes farmland space for development and utilization that is influenced by the conditions of the land, water resources, climate, pesticides and chemical fertilizers and many other agricultural production factors. Assessment model of agricultural land use capacity is constructed with the help of Fuzzy. Assessing the utilization capacity of farmland can be helpful to agricultural production and ecological protection of farmland. This paper describes the application of the capacity evaluation model with simulated data in two aspects, namely, in evaluating the status of farmland development and utilization and in optimal planting.

Zhang, Wensheng; Chen, Hongfu; Wang, Mingsheng

2009-07-01

105

Mathematical Modeling of Plant Allelopathic Hormesis Based on Ecological-Limiting-Factor Models  

PubMed Central

Allelopathy arises from the release of chemicals by one plant species that affect other species in its vicinity, usually to their detriment. Allelopathic effects have been demonstrated to be limiting factors for species distributions and ecological processes in some natural or agricultural communities. Based on the biphasic hormetic responses of plants to allelochemicals, ecological-limiting-factor models were introduced into the An-Johnson-Lovett hormesis model to improve modelling the phenomenon of allelopathic hormesis and to better reflect the nature of allelopathy as a limiting factor in ecological processes. Outcomes of the models have been compared for several sets of experimental data from the literature and good agreement between the models and data was observed, which indicates that the new models give some insight into the ecological mechanisms involved and may provide more options for modelling the allelopathic phenomenon as well as platforms for further research on plant allelopathic hormesis.

Liu, Yinghu; Chen, Xiaoqiu; Duan, Shunshan; Feng, Yuanjiao; An, Min

2010-01-01

106

Opportunities for using the EOS Imaging Spectrometers and synthetic aperture radar in ecological models  

NASA Technical Reports Server (NTRS)

Several promising approaches to assessing biochemical and architectural properties of landscapes are outlined. Strategies for using new EOS sensors in ecological models are examined. Ways in which ecological and remote sensing models can utilize information provided by the new sensors to characterize ecological properties at coarse scales and to estimate within-ecosystem properties are addressed.

Ustin, Susan L.; Wessman, Carol A.; Curtiss, Brian; Kasischke, Eric; Way, Jobea; Vanderbilt, Vern C.

1991-01-01

107

Multi-Attribute Modelling of Economic and Ecological Impacts of Agricultural Innovations on Cropping Systems  

Microsoft Academic Search

Modeling of economic and ecological impacts of genetically modified crops is a demanding task. We present some models made for the purpose of the ECOGEN project Soil ecological and economic evaluation of genetically modified crops. One of the goals of the project is to develop a computer-based decision support system for the assessment of economic and ecological impacts of using

Sara SCATASTA; Justus WESSELER; Matty DEMONT

108

Gyrokinetic particle simulation model  

SciTech Connect

A new type of particle simulation model based on the gyrophase-averaged Vlasov and Poisson equations is presented. The reduced system, in which particle gyrations are removed from the equations of motion while the finite Larmor radius effects are still preserved, is most suitable for studying low frequency microinstabilities in magnetized plasmas. It is feasible to simulate an elongated system (L/sub parallel/ >> L/sub perpendicular/) with a three-dimensional grid using the present model without resorting to the usual mode expansion technique, since there is essentially no restriction on the size of ..delta..x/sub parallel/ in a gyrokinetic plasma. The new approach also enables us to further separate the time and spatial scales of the simulation from those associated with global transport through the use of multiple spatial scale expansion. Thus, the model can be a very efficient tool for studying anomalous transport problems related to steady-state drift-wave turbulence in magnetic confinement devices. It can also be applied to other areas of plasma physics.

Lee, W.W.

1986-07-01

109

Prediction of the environmental fate and aquatic ecological impact of nitrobenzene in the Songhua River using the modified AQUATOX model  

Microsoft Academic Search

An accidental discharge of nitrobenzene happened in November 2005 in the Songhua River, China. The AQUATOX model was modified and adapted to simulate the time-dependent nitrobenzene distribution in this multimedia aquatic system and its potential ecological impacts. Nitrobenzene concentrations in flowing water, sediment, and biota were predicted. Based on the initial concentrations of nitrobenzene observed in the field during the

Bingli LEI; Shengbiao HUANG; Min QIAO; Tianyun LI; Zijian WANG

2008-01-01

110

Model Predictive Control for Automobile Ecological Driving Using Traffic Signal Information  

NASA Astrophysics Data System (ADS)

This paper presents development of a control system for ecological driving of an automobile. Prediction using traffic signal information is considered to improve the fuel economy. It is assumed that the automobile receives traffic signal information from Intelligent Transportation Systems (ITS). Model predictive control is used to calculate optimal vehicle control inputs using traffic signal information. The performance of the proposed method was analyzed through computer simulation results. It was observed that fuel economy was improved compared with driving of a typical human driving model.

Yamaguchi, Daisuke; Kamal, M. A. S.; Mukai, Masakazu; Kawabe, Taketoshi

111

Land surface model (LSM version 1.0) for ecological, hydrological, and atmospheric studies: Technical description and user`s guide. Technical note  

SciTech Connect

This technical note describes version 1 of the LSM land surface model. In this model, land surface processes are described in terms of biophysical fluxes (latent heat, sensible heat, momentum, reflected solar radiation, emitted longwave radiation) and biochemical fluxes (CO2) that depend on the ecological and hydrologic state of the land. Consequently, ecological and hydrological sub-models are needed to simulate temporal changes in terrestrial biomass and water.

Bonan, G.B.

1996-01-01

112

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

113

Ecological forecasting under climatic data uncertainty: a case study in phenological modeling  

Microsoft Academic Search

Forecasting ecological responses to climate change represents a challenge to the ecological community because models are often site-specific and climate data are lacking at appropriate spatial and temporal resolutions. We use a case study approach to demonstrate uncertainties in ecological predictions related to the driving climatic input data. We use observational records, derived observational datasets (e.g. interpolated observations from local

Benjamin I. Cook; Adam Terando; Allison Steiner

2010-01-01

114

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

115

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

116

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.

Wang, Hui-Yu; Hook, Tomas O

2009-01-01

117

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

118

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

119

Modeling Ecologically Relevant Flow Metrics for Small Streams  

NASA Astrophysics Data System (ADS)

Western US river systems have experienced climate-driven shifts in hydrologic regime in recent decades, and are projected to undergo further changes in the future. This phenomenon has implications for the distributions of fish and other aquatic organisms adapted to specific flow regimes. The Variable Infiltration Capacity (VIC) macroscale hydrologic model has the potential to describe and forecast these changes, but to date has not been applied to small and medium-sized streams, which is the relevant scale for most freshwater species. We used a simple area-weighted sum approach to generate hydrographs from VIC model output for small and medium-sized streams the Pacific Northwest, USA (hydrologic region 17). We validated the approach using observed hydrographs at 55 USGS gaging stations. We found that for most streams, a number of ecologically relevant aspects of the hydrologic regime were accurately modeled, including the center of timing of the flow mass, mean annual and summer flow, and the frequency of high flows in the winter. The frequency of high flows and low flows in the summer were poorly predicted, however. Predictions were worse for sites with large groundwater influence or surface-groundwater connections, and some sites showed biases that may result from limitations in the weather station data that force the models. Running VIC models at 1/16th degree resolution provided only a small improvement over 1/8th degree resolution. We concluded that despite some limitations, the VIC model can successfully capture ecologically relevant characteristics of the hydrologic regime for most small and medium-sized streams, making it a useful tool for predicting effects of climate shifts on aquatic organisms.

Wenger, S.; Luce, C.; Hamlet, A. F.; Isaak, D.; Neville, H.

2009-12-01

120

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

121

An ecological risk assessment model for a pulsed contaminant emission into a wetland channel flow  

Microsoft Academic Search

As a continuation of the modelling on ecological degradation and hydraulic dispersion of pollutant emission into an idealized two-dimensional free-surface wetland flow (Zeng, L., Chen, G.Q., 2009b. Ecological degradation and hydraulic dispersion of contaminant in wetland. Ecol. Model., doi:10.1016\\/j.ecolmodel.2009.10.024), an ecological risk assessment model for the typical case of a pulsed contaminant emission into a realistic three-dimensional wetland channel flow

G. Q. Chen; L. Zeng; Z. Wu

2010-01-01

122

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

123

Integrating modelling architecture: a declarative framework for multi-paradigm, multi-scale ecological modelling  

Microsoft Academic Search

Multiple modelling paradigms are necessary to formulate crucial modelling problems in modern environmental science. Modelling paradigms help researchers to conceive, formulate and solve problems by providing semantic structures to organise their view of a system or process. An unusually large array of different paradigms is used in Ecology, reflecting the complexity and variety of the natural world. As a result

Ferdinando Villa

2001-01-01

124

An application of a computational ecology model to a routing method in computer networks  

Microsoft Academic Search

The paper proposes a network routing method based on a computational ecology model. The computational ecology model is a mathematical model proposed by B.A. Huberman and T. Hogg (1988), which represents a macro action of multi-agent systems. We formulate routing on a computer network as a resource allocation problem, where packets and links are regarded as agents and resources, respectively.

Tatsushi Yamasaki; Toshimitsu Ushio

2002-01-01

125

Rangeland Ecological and Physical Modeling in a Spatial Context  

Microsoft Academic Search

The Simulation of Production and Utilization of Rangelands (SPUR) model has been in use and revision since 1987 in diverse rangelands including Texas and the Great Plains. The model's applicability to semi-arid rangelands of the southwest is under evaluation at the USDA-ARS Southwest Watershed Research Center in Tucson, Arizona. As part of this effort, a spatially explicit implementation of SPUR

S. M. Skirvin; M. S. Moran

126

Conservation Models and Ecological Concerns of the Community: A Case-Based Biology Lesson Plan  

NSDL National Science Digital Library

In this activity, students will design a conservation model that will address the ecological concerns of a community. Students will obtain topographical map of an area and related data; research and analyze appropriate data as to deforestation; survey and select area for removal of trees and landscape according to water flow; and build and produce an ecologically balanced model that will address the concerns of the community. This case will involves the use of botany, environmental science, animal biology, ecology, forestry and mathematics.

Fouch, C.; Strong, T.

2007-08-31

127

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.

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

2014-01-01

128

An introduction to simulation modeling  

Microsoft Academic Search

This paper offers an introductory overview of discrete simulation, with emphasis on the simulation modeling process rather than on any specific simulation package. Examples are used to demonstrate the application of the methodology at each step of the process. An extensive list of additional readings is given for the reader who wishes to deepen his\\/her knowledge in a specific area.

Martha A. Centeno

1996-01-01

129

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

130

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

131

Social network models predict movement and connectivity in ecological landscapes  

USGS Publications Warehouse

Network analysis is on the rise across scientific disciplines because of its ability to reveal complex, and often emergent, patterns and dynamics. Nonetheless, a growing concern in network analysis is the use of limited data for constructing networks. This concern is strikingly relevant to ecology and conservation biology, where network analysis is used to infer connectivity across landscapes. In this context, movement among patches is the crucial parameter for interpreting connectivity but because of the difficulty of collecting reliable movement data, most network analysis proceeds with only indirect information on movement across landscapes rather than using observed movement to construct networks. Statistical models developed for social networks provide promising alternatives for landscape network construction because they can leverage limited movement information to predict linkages. Using two mark-recapture datasets on individual movement and connectivity across landscapes, we test whether commonly used network constructions for interpreting connectivity can predict actual linkages and network structure, and we contrast these approaches to social network models. We find that currently applied network constructions for assessing connectivity consistently, and substantially, overpredict actual connectivity, resulting in considerable overestimation of metapopulation lifetime. Furthermore, social network models provide accurate predictions of network structure, and can do so with remarkably limited data on movement. Social network models offer a flexible and powerful way for not only understanding the factors influencing connectivity but also for providing more reliable estimates of connectivity and metapopulation persistence in the face of limited data.

Fletcher, Jr. , R. J.; Acevedo, M. A.; Reichert, B. E.; Pias, K. E.; Kitchens, W. M.

2011-01-01

132

Statistical Predictive Models in Ecology: Comparison of Performances and Assessment of Applicability  

Microsoft Academic Search

Ecological systems are governed by complex interactions which are mainly nonlinear. In order to capture this complexity and nonlinearity, statistical models recently gained popularity. However, although these models are commonly applied in ecology, there are no studies to date aiming to assess the applicability and performance. We provide an overview for nature of the wide range of the data sets

Can Ozan Tan; Uygar Ozesmi; Meryem Beklioglu; Esra Per; Bahtiyar Kurt

2005-01-01

133

The Mondrian Propagation Simulation Model  

Microsoft Academic Search

We present a propagation simulation model developed at TELECOM-ParisTech to assess performance of mobile radio networks. This model is consistent with the typical propagation model OSLN (one slope with log normal shadowing propagation model) considered by most authors. The new scheme, called Mondrian model, presents several interesting features: (i) it introduces correlations between powers measured on two nearby points, (ii)

Philippe Godlewski

2011-01-01

134

Strategies for fitting nonlinear ecological models in R, AD Model Builder, and BUGS  

USGS Publications Warehouse

1. Ecologists often use nonlinear fitting techniques to estimate the parameters of complex ecological models, with attendant frustration. This paper compares three open-source model fitting tools and discusses general strategies for defining and fitting models. 2. R is convenient and (relatively) easy to learn, AD Model Builder is fast and robust but comes with a steep learning curve, while BUGS provides the greatest flexibility at the price of speed. 3. Our model-fitting suggestions range from general cultural advice (where possible, use the tools and models that are most common in your subfield) to specific suggestions about how to change the mathematical description of models to make them more amenable to parameter estimation. 4. A companion web site (https://groups.nceas.ucsb.edu/nonlinear-modeling/projects) presents detailed examples of application of the three tools to a variety of typical ecological estimation problems; each example links both to a detailed project report and to full source code and data.

Bolker, Benjamin M.; Gardner, Beth; Maunder, Mark; Berg, Casper W.; Brooks, Mollie; Comita, Liza; Crone, Elizabeth; Cubaynes, Sarah; Davies, Trevor; de Valpine, Perry; Ford, Jessica; Gimenez, Olivier; Kéry, Marc; Kim, Eun Jung; Lennert-Cody, Cleridy; Magunsson, Arni; Martell, Steve; Nash, John; Nielson, Anders; Regentz, Jim; Skaug, Hans; Zipkin, Elise

2013-01-01

135

Eco-hydrological modeling to integrate ecological processes and hydrological processes in a small forested catchment  

NASA Astrophysics Data System (ADS)

Ecological processes and hydrological processes are very tightly connected with each other. Especially, to estimate the amount of water outflow and water retention in forest, it is needed to quantify the role of vegetation in the forest. For this reason, Eco-hydrological modeling provides an useful tool to understand the forest ecosystem processes and services. But because the numerous processes is entangled each other, the model usually has a number of parameters but our ability to measure all necessary data at field condition is highly limited, which makes model calibration difficult. Therefore, we took a basic aim to estimate a water balance of forest ecosystem and studied an efficient methods to establish the relationship of ecological process and hydrological process and to find a significant parameters in the study site. A procedure of model calibration was separated by 5-steps according to time sequence of processes. (1) Initialize the Carbon, Nitrogen states based on the measured data. (2) Calibrate the maximum LAI and compute a rain interception parameter using the measured rain interception data. (3) Compute the long-term ET from the long-term streamflow and rainfall data and determine a canopy conductance parameter of ET algorithm. (4) Determine the soil parameter to separate a surface runoff and baseflow and (5) to estimate the pattern of outflow. By using the structured calibration process, we could independently assess the each hydrological and/or ecological process and provide analytical explanations of simulated results. Our improved modeling indicates that annual precipitation (1,329 mm) is partitioned to evapotranspiration, 486 mm (37 percent), and stream outflow, 843 mm (63 percent), respectively. The calibrated model was further applied to investigate spatial pattern of soil water content and evapotranspiration to support validation of satellite-driven estimations. - Keyword : Eco-hydrological model, calibration, parameterization, ecological process, hydrological process - Acknowledgements : This work was supported by the Sustainable Water Resources Research Center of the 21st Century Frontier Program (Project No. 1-8-2, Hydrokorea), Ministry of Environment (Carbokorea), Korea Forest Research Institute and Korean National Arboretum

Kim, E.; Kang, S.; Lee, A.; Kim, S.; Kim, K.; Kim, J.; Lee, D.

2006-12-01

136

Simulating Traffic with Queueing Models  

Microsoft Academic Search

Abstract: Queueing models for traffic simulations are interesting models for applications. They can be used to simulate up to 10^8 cars\\/s on completely standard hard-ware. Unfortunately, uptonow, there was a catch: they sometimes show weird results, most notably jams that do not run backward. This work shows how queueing models can be made as realistic as most car-following models. Two

Nils Eissfeldt; Peter Wagner

2003-01-01

137

Montreal MAPP training simulation model  

Microsoft Academic Search

Simulation is being used in the Montreal Metropolitain Area Postal Plant (MAPP) to train operating and supervisory staff to process the mail. A simulation model developed will initially be used to train the staff for the Letter Processing Plant (LPP) at St. Laurent. With some modifications the same model would be adapted to train staff for other LPP of Canada

Muhammed Naqi

1978-01-01

138

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

139

Agrobacterium -mediated transformation of Nicotiana attenuata , a model ecological expression system  

Microsoft Academic Search

Summary.   Research into the genetic basis of the ecological sophistication of plants is hampered by the availability of transformable\\u000a systems with a wealth of well-described ecological interactions. We present an Agrobacterium-mediated transformation system for the model ecological expression system, Nicotiana attenuata, a native tobacco that occupies the post-fire niche in the Great Basin Desert of North America. We describe a

Tamara Krügel; Michelle Lim; Klaus Gase; Rayko Halitschke; Ian T. Baldwin

2002-01-01

140

Numerical wind speed simulation model  

SciTech Connect

A relatively simple stochastic model for simulating wind speed time series that can be used as an alternative to time series from representative locations is described in this report. The model incorporates systematic seasonal variation of the mean wind, its standard deviation, and the correlation speeds. It also incorporates systematic diurnal variation of the mean speed and standard deviation. To demonstrate the model capabilities, simulations were made using model parameters derived from data collected at the Hanford Meteorology Station, and results of analysis of simulated and actual data were compared.

Ramsdell, J.V.; Athey, G.F.; Ballinger, M.Y.

1981-09-01

141

[Ecological characteristics of different Pseudosciaena crocea culture models].  

PubMed

A comparative study was conducted on the ecological characteristics of different Pseudosciaena crocea culture models including monoculture P. crocea (F) and polyculture P. crocea with seaweed Gracilaria lichevoides (FG), benthos Perinereis aibuhitensis (FP), and G. lichevoides plus P. aibuhitensis (FGP) in land-based enclosures, with the sediment and water environment condition, culture benefit, and nitrogen (N) and phosphorus (P) reclaim efficiency analyzed. G. lichevoides could effectively remove the N and P in the water body. The water N and P concentrations in FG and FGP were significantly lower than those in F and FP, and the P utilization efficiency reached 33.8% - 34.0% of the total P input. P. aibuhitensis improved sediment environment condition. The sediment N and P concentrations in FP and FGP were lower than those in F and FG, and had significant differences between surface sediment (1-2 cm) and subsurface sediment (2-4 cm). Comparing with those in F, the total N, total P, and inorganic P in FP and FGP reduced by 8.9% -9.2% , 6.1% -6.3% and 8.0% -8.1%, respectively. P. aibuhitensis had a higher efficiency in reclaiming sediment P (7.5% -7.8% of the total P input), being able to effectively mitigate the P accumulation in sediment. Among the test models, FGP had the best material utilization efficiency and optimal resource benefit. PMID:21812313

Lu, Guang-Ming; Xu, Yong-Jian; Lu, Hui-Xian

2011-05-01

142

Is it relevant to explicitly parameterize chlorophyll synthesis in marine ecological models?  

NASA Astrophysics Data System (ADS)

Oceanographers and modelers often relate chlorophyll concentrations with phytoplankton carbon invoking a suitable C:Chla ratio. However C:Chl ratios are not constant in natural systems, thus making chlorophyll a deceptive measure of true biomass. In this paper we report on the adaptation of an algorithm for chlorophyll synthesis to a complex ecological model for the marine environment. Based on this model we have developed several simulation experiments to assess the performance of the chlorophyll synthesis and the phytoplankton photoadaptation strategy. The model was applied to three distinct settings, comprising distinctive model geometries and ambient conditions: a schematic setting corresponding to a virtual mesocosm without any transport scheme (0D), a 1D vertical open-ocean application to a 150 m deep water-column, and an application to an estuary using a 2D configuration. Conditions vary from spatially stable in the first case to a strong spatial and temporal heterogeneity in the case of the estuary. Our results fall within the range and reproduce some of the trends found in published data, supporting the idea that when conditions have strong changes of nutrient availability and light conditions, a photoacclimation mechanism becomes an essential requirement for reliable chlorophyll biomass estimates. This is particularly relevant if model simulations are to be used to study natural systems complemented by data retrieved from direct measurements.

Mateus, M.; Leitão, P. C.; de Pablo, H.; Neves, R.

2012-06-01

143

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

National Technical Information Service (NTIS)

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...

J. R. Kercher

1994-01-01

144

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

145

A Conceptual Framework for Evaluating the Domains of Applicability of Ecological Models and its Implementation in the Ecological Production Function Library  

EPA Science Inventory

The use of computational ecological models to inform environmental management and policy has proliferated in the past 25 years. These models have become essential tools as linkages and feedbacks between human actions and ecological responses can be complex, and as funds for sampl...

146

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

147

Application of an integrative hydro-ecological model to study water resources management in the upper and middle parts of the Yellow River basin  

NASA Astrophysics Data System (ADS)

This study presents an application of a well-calibrated integrative hydro-ecological model to examine water resources management in the upper and middle parts of the Yellow River basin, an arid and semiarid area in northwestern China. The hydro-ecological model was developed to simulate dynamic and accumulative hydrologic, ecologic, and economic variables at different spatial units. Four water management scenarios based on water use priorities, a business-as-usual scenario, an ecological scenario, an irrigation use efficiency scenario and water use scenario were designed and modeled over the period of 2011-2020 to reflect alternative water management pathways to the future. Water resource conditions were assessed in terms streamflow, actual evapotranspiration, soil water, groundwater yield, overall water yield, and derived indicator of drought index. Unit crop yield was to assess ecological production, and monetary values of crop productivity and water productivity were used to assess economic output. Scenario analysis results suggested that water stress would continue in the study region under both current water use patterns and ecological scenarios of river flow being fully satisfied.Water use scenarios would result in decreased water availability and ecosystem degradation in the long run. Improving irrigation use efficiency would be the most efficient approach in securing long-term water and food supply. The simulation results from this study provided useful information for evaluating long-term water resources management strategies, and will contribute to the knowledge of interdisciplinary modeling for water resources management in the study region.

Li, Xianglian; Gao, Qiong; Lei, Tingwu; Yang, Xiusheng

2011-03-01

148

Nanorobot: Modelling and Simulation  

Microsoft Academic Search

This research addresses the state of the art in nanorobot design and simulation focusing on the leukemia disease as well as ongoing applications on addressing the challenges posed by cancer treatment, especially chemotherapy. Nanotechnology and cancer biology, along with a new concept to leukemia treatment are the basis for nanorobot design. Robot architecture consists of Body, Ultrasonic Sensors, Folate material

Arosha Senanayake; R. G. Sirisinghe; Phang Shih Mun

2007-01-01

149

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

150

A National Disturbance Modeling System to Support Ecological Carbon Sequestration Assessments  

NASA Astrophysics Data System (ADS)

The U.S. Geological Survey (USGS) is prototyping a methodology to fulfill requirements of Section 712 of the Energy Independence and Security Act (EISA) of 2007. At the core of the EISA requirements is the development of a methodology to complete a two-year assessment of current carbon stocks and other greenhouse gas (GHG) fluxes, and potential increases for ecological carbon sequestration under a range of future climate changes, land-use / land-cover configurations, and policy, economic and management scenarios. Disturbances, especially fire, affect vegetation dynamics and ecosystem processes, and can also introduce substantial uncertainty and risk to the efficacy of long-term carbon sequestration strategies. Thus, the potential impacts of disturbances need to be considered under different scenarios. As part of USGS efforts to meet EISA requirements, we developed the National Disturbance Modeling System (NDMS) using a series of statistical and process-based simulation models. NDMS produces spatially-explicit forecasts of future disturbance locations and severity, and the resulting effects on vegetation dynamics. NDMS is embedded within the Forecasting Scenarios of Future Land Cover (FORE-SCE) model and informs the General Ensemble Biogeochemical Modeling System (GEMS) for quantifying carbon stocks and GHG fluxes. For fires, NDMS relies on existing disturbance histories, such as the Landsat derived Monitoring Trends in Burn Severity (MTBS) and Vegetation Change Tracker (VCT) data being used to update LANDFIRE fuels data. The MTBS and VCT data are used to parameterize models predicting the number and size of fires in relation to climate, land-use/land-cover change, and socioeconomic variables. The locations of individual fire ignitions are determined by an ignition probability surface and then FARSITE is used to simulate fire spread in response to weather, fuels, and topography. Following the fire spread simulations, a burn severity model is used to determine annual changes in biomass pools. Vegetation succession among LANDFIRE vegetation types is initiated using burn perimeter and severity data at the end of each annual simulation. Results from NDMS are used to update land-use/land-cover layers used by FORE-SCE and also transferred to GEMS for quantifying and updating carbon stocks and greenhouse gas fluxes. In this presentation, we present: 1) an overview of NDMS and its role in USGS's national ecological carbon sequestration assessment; 2) validation of NDMS using historic data; and 3) initial forecasts of disturbances for the southeastern United States and their impacts on greenhouse gas emissions, and post-fire carbon stocks and fluxes.

Hawbaker, T. J.; Rollins, M. G.; Volegmann, J. E.; Shi, H.; Sohl, T. L.

2009-12-01

151

A Model for the Ecology of Avian Malaria.  

National Technical Information Service (NTIS)

Although studies on Plasmodium infections of wild birds have been reported frequently in the literature, our knowledge of the ecology of these parasites remains incomplete. A synthesis of data and ideas from these field studies, and recent experimental wo...

R. L. Beaudoin J. E. Applegate D. E. Davis R. G. McLean

1970-01-01

152

EPA ?s ECOLOGICAL MODELS FOR INTEGRATED WATERSHED MANAGEMENT  

EPA Science Inventory

Aquatic ecological populations and communities are affected by the nature and quality of the water in which they live. Specific factors that affect instream biota include chemical variables, biotic interactions, energy source, flow regime, and habitat structure. As watershed mana...

153

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.

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

2007-01-01

154

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

155

Modelling parasite aggregation: disentangling statistical and ecological approaches.  

PubMed

The overdispersion in macroparasite infection intensity among host populations is commonly simulated using a constant negative binomial aggregation parameter. We describe an alternative to utilising the negative binomial approach and demonstrate important disparities in intervention efficacy projections that can come about from opting for pattern-fitting models that are not process-explicit. We present model output in the context of the epidemiology and control of soil-transmitted helminths due to the significant public health burden imposed by these parasites, but our methods are applicable to other infections with demonstrable aggregation in parasite numbers among hosts. PMID:24703868

Yakob, Laith; Soares Magalhães, Ricardo J; Gray, Darren J; Milinovich, Gabriel; Wardrop, Nicola; Dunning, Rebecca; Barendregt, Jan; Bieri, Franziska; Williams, Gail M; Clements, Archie C A

2014-05-01

156

An Improved ASW Simulation Model.  

National Technical Information Service (NTIS)

Previous research demonstrated conclusively that significant improvements could be realized in existing ASW simulation models with the use of variance reduction schemes and improved random number generation procedures. Included in the report is a descript...

E. J. McGrath D. Feldman J. D. Wilson

1974-01-01

157

Validation process of simulation model.  

National Technical Information Service (NTIS)

It is presented a methodology on empirical about any detailed simulation model. This kind of validation it is always related with an experimental case. The empirical validation has a residual sense, because the conclusions are based on comparison between ...

M. J. San Isidro Pindado

1997-01-01

158

Container Stuffing Simulation Model (SIMCON).  

National Technical Information Service (NTIS)

The simulation model characterizes the operations of a cargo terminal that loads cargo into ocean going containers; it is oriented toward container freight stations operated by the Military Traffic Management Command (MTMC). General input data to the mode...

1974-01-01

159

Aircraft Maintenance Effectiveness Simulation (AMES) Model.  

National Technical Information Service (NTIS)

This report covers a project to develop and test a functional simulation model of aircraft maintenance. The model is called AMES, which means Aircraft Maintenance Effectiveness Simulation. AMES is a computer model that simulates the operation and maintena...

D. Gold B. Kleine F. Fuchs S. Ravo K. Inaba

1980-01-01

160

Comparing the ecological relevance of four wave exposure models  

NASA Astrophysics Data System (ADS)

Wave exposure is one of the main structuring forces in the marine environment. Methods that enable large scale quantification of environmental variables have become increasingly important for predicting marine communities in the context of spatial planning and coastal zone management. Existing methods range from cartographic solutions to numerical hydrodynamic simulations, and differ in the scale and spatial coverage of their outputs. Using a biological exposure index we compared the performance of four wave exposure models ranging from simple to more advanced techniques. All models were found to be related to the biological exposure index and their performance, measured as bootstrapped R2 distributions, overlapped. Qualitatively, there were differences in the spatial patterns indicating higher complexity with more advanced techniques. In order to create complex spatial patterns wave exposure models should include diffraction, especially in coastal areas rich in islands. The inclusion of wind strength and frequency, in addition to wind direction and bathymetry, further tended to increase the amount of explained variation. The large potential of high-resolution numerical models to explain the observed patterns of species distribution in complex coastal areas provide exciting opportunities for future research. Easy access to relevant wave exposure models will aid large scale habitat classification systems and the continuously growing field of marine species distribution modelling, ultimately serving marine spatial management and planning.

Sundblad, G.; Bekkby, T.; Isæus, M.; Nikolopoulos, A.; Norderhaug, K. M.; Rinde, E.

2014-03-01

161

Including overweight or obese students in physical education: a social ecological constraint model.  

PubMed

In this review, we propose a social ecological constraint model to study inclusion of overweight or obese students in physical education by integrating key concepts and assumptions from ecological constraint theory in motor development and social ecological models in health promotion and behavior. The social ecological constraint model proposes that constraints exist on five different levels and interact within and across levels to affect overweight students' engagement, learning, and physical activity in physical education. This model can provide a theoretical framework to guide and organize research on the inclusion of overweight students. It can also guide teachers in manipulating these constraints to create a culture for inclusion and provide instruction to meet the needs of overweight or obese students. PMID:23367820

Li, Weidong; Rukavina, Paul

2012-12-01

162

Composition and Analysis of a Model Waste for a Celss (Controlled Ecological Life Support System).  

National Technical Information Service (NTIS)

A model waste based on a modest vegetarian diet is given, including composition and elemental analysis. Its use is recommended for evaluation of candidate waste treatment processes for a Controlled Ecological Life Support System (CELSS).

T. Wydeven

1983-01-01

163

Composition and analysis of a model waste for a CELSS (Controlled Ecological Life Support System)  

NASA Technical Reports Server (NTRS)

A model waste based on a modest vegetarian diet is given, including composition and elemental analysis. Its use is recommended for evaluation of candidate waste treatment processes for a Controlled Ecological Life Support System (CELSS).

Wydeven, T. J.

1983-01-01

164

Predicting population dynamics with analytical, simulation and supercomputer models  

SciTech Connect

A set of epizootiological models describing the influence of a microsporidian disease on the population dynamics of an herbivorous insect demonstrate the similarities and differences between the three major approaches now available for ecological modeling. Simulation modeling allows the incorporation of randomness or the timing of discrete events in the temporal dynamics. More complex models incorporating both temporal and spatial dynamics in variable and heterogeneous environments require the use of supercomputers. Under a number of realistic circumstances, the qualitative predictions of the approaches may differ.

Onstad, D.W.

1987-07-01

165

Automated experimentation in ecological networks  

PubMed Central

Background In ecological networks, natural communities are studied from a complex systems perspective by representing interactions among species within them in the form of a graph, which is in turn analysed using mathematical tools. Topological features encountered in complex networks have been proved to provide the systems they represent with interesting attributes such as robustness and stability, which in ecological systems translates into the ability of communities to resist perturbations of different kinds. A focus of research in community ecology is on understanding the mechanisms by which these complex networks of interactions among species in a community arise. We employ an agent-based approach to model ecological processes operating at the species' interaction level for the study of the emergence of organisation in ecological networks. Results We have designed protocols of interaction among agents in a multi-agent system based on ecological processes occurring at the interaction level between species in plant-animal mutualistic communities. Interaction models for agents coordination thus engineered facilitate the emergence of network features such as those found in ecological networks of interacting species, in our artificial societies of agents. Conclusions Agent based models developed in this way facilitate the automation of the design an execution of simulation experiments that allow for the exploration of diverse behavioural mechanisms believed to be responsible for community organisation in ecological communities. This automated way of conducting experiments empowers the study of ecological networks by exploiting the expressive power of interaction models specification in agent systems.

2011-01-01

166

Predicting the Geography of Species' Invasions via Ecological Niche Modeling  

Microsoft Academic Search

Species' invasions have long been regarded as enormously complex processes, so complex as to defy predictivity. Phases of this process, however, are emerging as highly predictable: the potential geographic course of an invasion can be anticipated with high precision based on the ecological niche characteristics of a species in its native geographic distributional area. This predictivity depends on the premise

A. Townsend Peterson

2003-01-01

167

Simulation model for the closed plant experiment facility of CEEF  

NASA Astrophysics Data System (ADS)

The Closed Ecology Experiment Facilities (CEEF) is a testbed for Controlled Ecological Life Support Systems (CELSS) investigations. CEEF including the physico-chemical material regenerative system has been constructed for the experiments of material circulation among plants, breeding animals and crew of CEEF. Because CEEF is a complex system, an appropriate schedule for the operation must be prepared in advance. The CEEF behavioral Prediction System, CPS, that will help to confirm the operation schedule, is under development. CPS will simulate CEEFs behavior with data (conditions of equipments, quantity of materials in tanks, etc.) of CEEF and an operation schedule that will be made by the operation team everyday, before the schedule will be carried out. The result of the simulation will show whether the operation schedule is appropriate or not. In order to realize CPS, models of the simulation program that is installed in CPS must mirror the real facilities of CEEF. For the first step of development, a flexible algorithm of the simulation program was investigated. The next step was development of a replicate simulation model of the material circulation system for the Closed Plant Experiment Facility (CPEF) that is a part of CEEF. All the parts of a real material circulation system for CPEF are connected together and work as a complex mechanism. In the simulation model, the system was separated into 38 units according to its operational segmentation. In order to develop each model for its corresponding unit, specifications for the model were fixed based on the specifications of the real part. These models were put into a simulation model for the system.

Abe, Koichi; Ishikawa, Yoshio; Kibe, Seishiro; Nitta, Keiji

168

Integrating Edge Detection and Dynamic Modeling in Quantitative Analyses of Ecological Boundaries  

NSDL National Science Digital Library

This peer-reviewed article from BioScience about quantitative analysis of ecological boundaries. Habitat boundaries profoundly influence the structure and function of landscapes, influencing ecological processes both locally and over larger scales. In addition, boundaries themselves are dynamic entities whose changes can influence diverse populations, communities, and ecosystems by way of feedback effects. These two issues, scale dependence and spatiotemporal dynamics, underlie much of the now considerable attention that modelers and statisticians have devoted to the quantitative study of ecological edges and boundaries. We present the linkages between methods of delineating boundaries, monitoring boundary changes, and modeling edge-related dynamics. In the process, we clarify statistical and mathe-matical approaches to the study of ecological edges and boundaries, and we discuss important remaining issues in the area of quantitative edge research. In particular, we address conceptual and methodological problems faced by statisticians and modelers, while highlighting topics that would benefit from a collaborative approach.

WILLIAM F. FAGAN, MARIE-JOSÃÂE FORTIN, and CANDAN SOYKAN (;)

2003-08-01

169

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

170

The ecological effects of thermopeaking in Alpine streams in flume simulations  

NASA Astrophysics Data System (ADS)

In Alpine areas, the temporal patterns of hydropower plants operations can have consequences for the water bodies which receive downstream releases in the form of "hydropeaking", typically consisting in sharp releases of turbinated water in the river reaches below dams. Hydropeaking may significantly affect also the thermal regime of rivers: typically power plants fed by hypolimnetic releases from large dams cause a reduction in summer temperature and an increase in winter temperatures for long distances downstream. Very few studies have addressed the effects of the short-term temperature fluctuations related to hydropeaking (i.e., thermopeaking) on aquatic fauna, although they can be a major cause of riverine habitat degradation posing serious threats to aquatic communities. In the Adige River watershed, warm thermopeaking occurs from September to January and results in additional (up to 4°C) heating to the natural dial fluctuations; cold thermopeaking occurs from March to July and cools down the temperature (up to 6°C), in contrast with the natural trend that would result in heating during the day. The biological effects of thermopeaking are difficult to study in nature, because they are associated with hydropeaking, which is known to cause a high catastrophic drift due to the increased intensity of bed scour. However, controlled simulations of thermopeaking events could be performed in artificial flumes. We used artificial flumes which had proved to perform discharge manipulations which simulate hydropeaking events, and conducted four simulations, two warm thermopeakings in early and late winter, and two cold-thermopeakings, in early and late summer, respectively. The impact of thermopeaking on benthic macroinvertebrates was assessed by collecting those organisms which are displaced from the substrate and drift in the water column. Displacement can be active (i.e., part of the behavioural repertoire of certain insect species), or passive (i.e., catastrophic and generated by any disturbance). Drifting invertebrates were collected at time intervals before the simulation, and at continuous, short-time intervals during the simulation in order to follow the changes in drift over a short time period during the simulation. We assessed the effects of thermopreaking on the benthos community by answering to the following questions: 1) Do thermal alterations induce an increase in drift of benthic invertebrates? 3) Do a reduction or an increase in water temperature have different effects of invertebrate drift? Benthic invertebrates responded more to the cold thermopeaking simulations, with differences among taxa with different life strategies and ecological requirements.

Maiolini, Bruno; Carolli, Mauro; Bruno, M. Cristina; Siviglia, Annunziato

2010-05-01

171

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

172

Assessing uncertainties in a second-generation dynamic vegetation model caused by ecological scale limitations.  

PubMed

*Second-generation Dynamic Global Vegetation Models (DGVMs) have recently been developed that explicitly represent the ecological dynamics of disturbance, vertical competition for light, and succession. Here, we introduce a modified second-generation DGVM and examine how the representation of demographic processes operating at two-dimensional spatial scales not represented by these models can influence predicted community structure, and responses of ecosystems to climate change. *The key demographic processes we investigated were seed advection, seed mixing, sapling survival, competitive exclusion and plant mortality. We varied these parameters in the context of a simulated Amazon rainforest ecosystem containing seven plant functional types (PFTs) that varied along a trade-off surface between growth and the risk of starvation induced mortality. *Varying the five unconstrained parameters generated community structures ranging from monocultures to equal co-dominance of the seven PFTs. When exposed to a climate change scenario, the competing impacts of CO(2) fertilization and increasing plant mortality caused ecosystem biomass to diverge substantially between simulations, with mid-21st century biomass predictions ranging from 1.5 to 27.0 kg C m(-2). *Filtering the results using contemporary observation ranges of biomass, leaf area index (LAI), gross primary productivity (GPP) and net primary productivity (NPP) did not substantially constrain the potential outcomes. We conclude that demographic processes represent a large source of uncertainty in DGVM predictions. PMID:20618912

Fisher, Rosie; McDowell, Nate; Purves, Drew; Moorcroft, Paul; Sitch, Stephen; Cox, Peter; Huntingford, Chris; Meir, Patrick; Woodward, F Ian

2010-08-01

173

Dihydroergosine pharmacokinetic modelling and simulation.  

PubMed

For this study of dihydroergosine pharmacokinetic modelling and simulation, the data from our paper about 3H-DHESN plasma, bile, urine, and faeces concentrations after intravenous and oral administration were used (1). The model obtained with the identified parameters was in agreement with in vivo data. Certain special phenomena, such as the enterohepatic cycle and incomplete absorption, were taken into account. Analog-hybrid simulation and identification represents an effective tool for such studies. In spite of the limited validity of the available in vivo data, the work represents a first step in the introduction of DHESN into human medicine. PMID:6861792

Karba, R; Mrhar, A; Kozjek, F; Bremsak, F; Kopitar, Z; Lenardic, A

1983-01-01

174

a Model-Data Fusion Approach to Integrate National Ecological Observatory Network Observations Into AN Earth System Model  

NASA Astrophysics Data System (ADS)

Ecological observations, such as those from eddy covariance flux towers that provide direct measurements of the ecosystem exchange of water, carbon and energy, typically are made at small spatial scales but estimates of ecosystem processes at the regional and continental scale are required to diagnose, understand and predict the response of the global water and carbon cycles to a changing environment. The National Ecological Observatory Network (NEON) is a continental-scale facility that will collect ecological data, including eddy covariance flux observations, from 60 sites in the continental US, Alaska, Hawaii, and Puerto Rico over 30 years. However, despite the sample design and unprecedented spatial coverage of this new network, only a very small fraction of the US land area will be directly sampled. In order to meet NEON data product requirements to produce gridded data sets of carbon and water fluxes across the continent an approach is required that will allow spatial extrapolation from NEON sites and make temporal forecasting on decadal timescales possible. We are developing a model-data fusion framework in which NEON data will be combined with the Community Land Model (CLM) using a Bayesian approach to produce optimal solutions for model parameter values, states and fluxes. Here we briefly outline a methodology in which we have developed the Community Earth System Model (CESM) infrastructure to allow an ensemble of multiple instances of CLM to work simultaneously. This has allowed us to develop a model-data fusion framework in which we have coupled CLM with the National Center for Atmospheric Research's Data Assimilation Research Testbed (DART) Ensemble Kalman filter. We then discuss some initial results from an observing system simulation experiment in which we have attempted to optimize a limited subset of CLM parameters that a sensitivity analysis has shown strongly affect vegetation dynamics and land-atmosphere fluxes of carbon and water. We then describe some of the challenges of using this approach with complex land surface models, such as CLM, which require an extended "spin-up" run period to bring large pools of carbon and nitrogen into a quasi-equilibrium state for current climate drivers and model parameterizations. We also highlight the shortcomings of using carbon flux data alone, and the need for multiple types of ecosystem observations to effectively constrain model parameters over a variety of timescales.

Fox, A. M.; Hoar, T. J.; Moore, D. J.; Berukoff, S. J.; Schimel, D.

2011-12-01

175

Statistics and Deterministic Simulation Models: Why Not.  

National Technical Information Service (NTIS)

First deterministic simulation models are compared with random simulation models and real-life experiments. In deterministic simulation no mathematical statistics is needed in the experimental design and in the Least Squares curve fitting to the resulting...

J. P. C. Kleijnen

1990-01-01

176

Modelling forest ecosystem net primary production: the hybrid simulation approach used in forecast  

Microsoft Academic Search

In order to evaluate the impacts of alternative stand-level management scenarios on long-term site productivity, forest resource managers need ecologically based forest growth models. The forecast forest ecosystem management simulation model combines the traditional bioassay modelling approach with process-based simulation modelling to provide a method of projecting future forest biomass yield as well as a variety of other ecosystem variables

J. P. Kimmins; Daniel Mailly; Brad Seely

1999-01-01

177

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

178

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.

Skelly, Chris; Weinstein, Phil

2003-01-01

179

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

180

Expert Knowledge as a Basis for Landscape Ecological Predictive Models  

Microsoft Academic Search

\\u000a Defining an appropriate role for expert knowledge in science can lead to contentious debate. The professional experience of\\u000a ecologists, elicited as expert judgment, plays an essential role in many aspects of landscape ecological science. Experts\\u000a may be asked to judge the relevance of competing research or management questions, the quality and suitability of available\\u000a data, the best balance of complexity

C. Ashton Drew; Ajith H. Perera

181

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

182

A conceptual model for assessing ecological risk to water quality function of bottomland hardwood forests  

Microsoft Academic Search

Ecological risk assessment provides a methodology for evaluating the threats to ecosystem function associated with environmental\\u000a perturbations or stressors. This report documents the development of a conceptual model for assessing the ecological risk\\u000a to the water quality function (WQF) of bottomland hardwood riparian ecosystems (BHRE) in the Tifton-Vidalia upland (TVU) ecoregion\\u000a of Georgia. Previus research has demonstrated that mature BHRE

Richard Lowrance; George Vellidis

1995-01-01

183

Modeling and simulation of microturbine  

Microsoft Academic Search

In this work, modeling, simulation and analysis of load following behaviour of microturbine (MT) as a Distributed Energy Resource (DER) have been performed. The system comprises a MT interconnected to the utility grid. The MT is capable of operating in both islanded and grid-connected modes. This work considers that the MT supplies power to variable general and critical loads. The

A. K. Saha; S. Chowdhury

2010-01-01

184

Economic Analysis. Computer Simulation Models.  

ERIC Educational Resources Information Center

A multimedia course in economic analysis was developed and used in conjunction with the United States Naval Academy. (See ED 043 790 and ED 043 791 for final reports of the project evaluation and development model.) This volume of the text discusses the simulation of behavioral relationships among variable elements in an economy and presents…

Sterling Inst., Washington, DC. Educational Technology Center.

185

Ecological Modeling for the Extrapolation of Ecotoxicological Effects Measured during in Situ Assays in Gammarus.  

PubMed

Evaluating the effects of chemical contamination on populations and ecological communities still constitutes a challenging necessity in environmental management. However, the toxic effects of contaminants are commonly measured by means of organism-level responses. Linking such effects measures with ecological models is a promising way to determine population-level impacts. In this way, population models are currently increasingly used in predictive risk assessment procedures, but their use in environmental diagnostic framework remains limited due to their lack of ecological realism. The present study with the crustacean Gammarus fossarum, a sentinel species in freshwater monitoring, combines a dual field and laboratory experimental approach with a population modeling framework. In this way, we developed an ecologically relevant periodic matrix population model for Gammarus. This model allowed us to capture the population dynamics in the field, and to understand the particular pattern of demographic sensitivities induced by Gammarus life-history phenology. The model we developed provided a robust population-level assessment of in situ-based effects measures recorded during a biomonitoring program on a French watershed impacted by past mining activities. Thus, our study illustrates the potential of population modeling when seeking to decipher the role of environmental toxic contamination in ecological perturbations. PMID:24805228

Coulaud, Romain; Geffard, Olivier; Coquillat, Amandine; Quéau, Hervé; Charles, Sandrine; Chaumot, Arnaud

2014-06-01

186

From the Conceptual Change Model to the Productive Ecological Koinos Model: Learning that transcends  

NASA Astrophysics Data System (ADS)

This investigation presents the analysis of a model of teaching science called the Conceptual Change Model. This model stimulates students to identify their own and alternate science concepts, and to confront these concepts with dynamic situations that will incite a conceptual change and promote their ability to master and understand the conceptual systems that serve as foundations for scientific knowledge. During a previous research made by this investigator on the Conceptual Change Model, a proposal for a new teaching model came up which she called the Productive Ecological Koinos Model. This model incorporates, among other things, the teacher's reflection and inner thoughts about the concepts taught and the learning experiences achieved in concurrence with students. Using action research, an exploration and analysis was done that focused upon how students and teachers modified their perspective of science while testing the Productive Ecological Koinos Model during the teaching-learning processes that took place in a microbiology course. The action research design allows the researcher to analyze these points from the experiential perspective, while also allowing the researcher to participate in the study. The study employed qualitative research techniques such as reflective diaries, personal profiles of participants, document analysis, audio tape recordings and transcriptions. All of these techniques are accepted within action research (Elliot, 1991). The Wolcott Model was the data analysis method used in the research. The description, analysis and interpretation carried out allowed for the examination of the various components of the Productive Ecological Koinos Model with students and teachers as to the scientific terms virus and contagion, and their experiences during the learning process within and outside the classroom. From the analysis of the Model a modification cropped up which places emphasis on conscious introspection on the learning process. This new learning model has been named the Cognitive Reflection Model. Through this Model, an analysis and introspection is made on the cognitive foundations of the scientific concept from the perspectives of the experiences of both teachers and students. It proposes, among other things, scrutiny into what could be called "Reflexive Science" for the teaching of science subjects as a result of using the Cognitive Reflection Model.

Gelpi-Rodriguez, Phaedra

187

The construction of ecological logistics park based on network shape enterprises symbiotic relationship model  

Microsoft Academic Search

Based on the idea of environmental protection, with network shape enterprise symbiotic relationship model, and make an analysis about how to establish a stable symbiotic model among enterprises in the internal logistics park. Through the analysis, regard that the construction of the ecological logistics park in that is based on the model of network shape enterprises symbiotic relationship is the

Honglu Liu; Jiawei Zuo; Zhenji Zhang; Runtong Zhang

2008-01-01

188

Teaching Population Ecology Modeling by Means of the Hewlett-Packard 9100A.  

ERIC Educational Resources Information Center

The incorporation of mathematical modeling experiences into an undergraduate biology course is described. Detailed expositions of three models used to teach concepts of population ecology are presented, including introductions to major concepts, user instructions, trial data and problem sets. The models described are: 1) an exponential/logistic…

Tuinstra, Kenneth E.

189

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

190

Integrating human and natural systems in community psychology: an ecological model of stewardship behavior.  

PubMed

Community psychology (CP) research on the natural environment lacks a theoretical framework for analyzing the complex relationship between human systems and the natural world. We introduce other academic fields concerned with the interactions between humans and the natural environment, including environmental sociology and coupled human and natural systems. To demonstrate how the natural environment can be included within CP's ecological framework, we propose an ecological model of urban forest stewardship action. Although ecological models of behavior in CP have previously modeled health behaviors, we argue that these frameworks are also applicable to actions that positively influence the natural environment. We chose the environmental action of urban forest stewardship because cities across the United States are planting millions of trees and increased citizen participation in urban tree planting and stewardship will be needed to sustain the benefits provided by urban trees. We used the framework of an ecological model of behavior to illustrate multiple levels of factors that may promote or hinder involvement in urban forest stewardship actions. The implications of our model for the development of multi-level ecological interventions to foster stewardship actions are discussed, as well as directions for future research to further test and refine the model. PMID:22722897

Moskell, Christine; Allred, Shorna Broussard

2013-03-01

191

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

192

Assessment of Molecular Modeling & Simulation  

SciTech Connect

This report reviews the development and applications of molecular and materials modeling in Europe and Japan in comparison to those in the United States. Topics covered include computational quantum chemistry, molecular simulations by molecular dynamics and Monte Carlo methods, mesoscale modeling of material domains, molecular-structure/macroscale property correlations like QSARs and QSPRs, and related information technologies like informatics and special-purpose molecular-modeling computers. The panel's findings include the following: The United States leads this field in many scientific areas. However, Canada has particular strengths in DFT methods and homogeneous catalysis; Europe in heterogeneous catalysis, mesoscale, and materials modeling; and Japan in materials modeling and special-purpose computing. Major government-industry initiatives are underway in Europe and Japan, notably in multi-scale materials modeling and in development of chemistry-capable ab-initio molecular dynamics codes.

None

2002-01-03

193

Simulation Framework for Teaching in Modeling and Simulation Areas  

ERIC Educational Resources Information Center

Simulation is the process of executing a model that describes a system with enough detail; this model has its entities, an internal state, some input and output variables and a list of processes bound to these variables. Teaching a simulation language such as general purpose simulation system (GPSS) is always a challenge, because of the way it…

De Giusti, Marisa Raquel; Lira, Ariel Jorge; Villarreal, Gonzalo Lujan

2008-01-01

194

Conceptual ecological models to support detection of ecological change on Alaska National Wildlife Refuges  

USGS Publications Warehouse

More than 31 million hectares of land are protected and managed in 16 refuges by the U.S. Fish and Wildlife Service (USFWS) in Alaska. The vastness and isolation of Alaskan refuges give rise to relatively intact and complete ecosystems. The potential for these lands to provide habitat for trust species is likely to be altered, however, due to global climate change, which is having dramatic effects at high latitudes. The ability of USFWS to effectively manage these lands in the future will be enhanced by a regional inventory and monitoring program that integrates and supplements monitoring currently being implemented by individual refuges. Conceptual models inform monitoring programs in a number of ways, including summarizing important ecosystem components and processes as well as facilitating communication, discussion and debate about the nature of the system and important management issues. This process can lead to hypotheses regarding future changes, likely results of alternative management actions, identification of monitoring indicators, and ultimately, interpretation of monitoring results. As a first step towards developing a monitoring program, the 16 refuges in Alaska each created a conceptual model of their refuge and the landscape context. Models include prominent ecosystem components, drivers, and processes by which components are linked or altered. The Alaska refuge system also recognizes that designing and implementing monitoring at regional and ecoregional extents has numerous scientific, fiscal, logistical, and political advantages over monitoring conducted exclusively at refuge-specific scales. Broad-scale monitoring is particularly advantageous for examining phenomena such as climate change because effects are best interpreted at broader spatial extents. To enable an ecoregional perspective, a rationale was developed for deriving ecoregional boundaries for four ecoregions (Polar, Interior Alaska, Bering Coast, and North Pacific Coast) from the Unified Ecoregions of Alaska. Ecoregional models were then developed to illustrate resources and processes that operate at spatial scales larger than individual refuges within each ecoregion. Conceptual models also were developed for adjacent marine areas, designated as the North Pacific, Bering Sea, and Beaufort-Chukchi Sea Marine Ecoregions. Although many more conceptual models will be required to support development of a regional monitoring program, these definitions of ecoregions and associated conceptual models are an important foundation.

Woodward, Andrea; Beever, Erik A.

2011-01-01

195

Modelling Agent-Environment Interaction in Multi-Agent Simulations with Affordances.  

National Technical Information Service (NTIS)

A computational model of agent-environment interaction is presented that has been inspired by the theory of affordances from ecological psychology. The model is developed in the context of agent-environment interaction in multi- agent simulation in a virt...

M. Papasimeon

2010-01-01

196

An Extended Version of the Richardson Model for Simulating Daily Weather Variables  

Microsoft Academic Search

The Richardson model is a popular technique for stochastic simulation of daily weather variables, including precipitation amount, maximum and minimum temperature, and solar radiation. This model is extended to include two additional variables, daily mean wind speed and dewpoint, because these variables (or related quantities such as relative humidity) are required as inputs for certain ecological\\/vegetation response and agricultural management

Marc B. Parlange; Richard W. Katz

2000-01-01

197

Ongoing Ecological Divergence in an Emerging Genomic Model  

PubMed Central

Much of Earth’s biodiversity has arisen through adaptive radiation. Important avenues of phenotypic divergence during this process include the evolution of body size and life history (Schluter 2000). Extensive adaptive radiations of cichlid fishes have occurred in the Great Lakes of Africa, giving rise to behaviors that are remarkably sophisticated and diverse across species. In Tanganyikan shell-brooding cichlids of the tribe Lamprologini, tremendous intraspecific variation in body size accompanies complex breeding systems and use of empty snail shells to hide from predators and rear offspring. A study by Takahashi et al. (2009) in this issue of Molecular Ecology reveals the first case of genetic divergence between dwarf and normal-sized morphs of the same nominal lamprologine species, Telmatochromis temporalis. Patterns of population structure suggest that the dwarf, shell-dwelling morph of T. temporalis might have arisen from the normal, rock-dwelling morph independently in more than one region of the lake, and that pairs of morphs at different sites may represent different stages early in the process of ecological speciation. The findings of Takahashi et al. are important first steps toward understanding the evolution of these intriguing morphs, yet many questions remain unanswered about the mating system, gene flow, plasticity, and selection. Despite these limitations, descriptive work like theirs takes on much significance in African cichlids due to forthcoming resources for comparative genomics.

Arnegard, Matthew E.

2009-01-01

198

Simulation Validation Through Linear Model Comparison.  

National Technical Information Service (NTIS)

The Manned Flight Simulator at the Naval Air Warfare Center in Patuxent River, MD maintains high fidelity fixed and rotary wing simulation models. The aircraft simulations are utilized for a wide range of activities including flight test support, pilot tr...

K. Balderson D. P. Gaublomme J. W. Thomas

1996-01-01

199

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

200

INTEGRATION OF AN ECONOMY UNDER IMPERFECT COMPETITION WITH A TWELVE-CELL ECOLOGICAL MODEL  

EPA Science Inventory

This report documents the scientific research work done to date on developing a generalized mathematical model depicting a combined economic-ecological-social system with the goal of making it available to the scientific community. The model is preliminary and has not been tested...

201

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

202

Computational modeling for eco engineering: Making the connections between engineering and ecology (Invited)  

NASA Astrophysics Data System (ADS)

Ecological engineering, or eco engineering, is an emerging field in the study of integrating ecology and engineering, concerned with the design, monitoring, and construction of ecosystems. According to Mitsch (1996) 'the design of sustainable ecosystems intends to integrate human society with its natural environment for the benefit of both'. Eco engineering emerged as a new idea in the early 1960s, and the concept has seen refinement since then. As a commonly practiced field of engineering it is relatively novel. Howard Odum (1963) and others first introduced it as 'utilizing natural energy sources as the predominant input to manipulate and control environmental systems'. Mtisch and Jorgensen (1989) were the first to define eco engineering, to provide eco engineering principles and conceptual eco engineering models. Later they refined the definition and increased the number of principles. They suggested that the goals of eco engineering are: a) the restoration of ecosystems that have been substantially disturbed by human activities such as environmental pollution or land disturbance, and b) the development of new sustainable ecosystems that have both human and ecological values. Here a more detailed overview of eco engineering is provided, particularly with regard to how engineers and ecologists are utilizing multi-dimensional computational models to link ecology and engineering, resulting in increasingly successful project implementation. Descriptions are provided pertaining to 1-, 2- and 3-dimensional hydrodynamic models and their use at small- and large-scale applications. A range of conceptual models that have been developed to aid the in the creation of linkages between ecology and engineering are discussed. Finally, several case studies that link ecology and engineering via computational modeling are provided. These studies include localized stream rehabilitation, spawning gravel enhancement on a large river system, and watershed-wide floodplain modeling of the Sacramento River Valley.

Bowles, C.

2013-12-01

203

USING STRUCTURAL EQUATION MODELING TO INVESTIGATE RELATIONSHIPS AMONG ECOLOGICAL VARIABLES  

EPA Science Inventory

This paper gives an introductory account of Structural Equation Modeling (SEM) and demonstrates its application using LISREL< with a model utilizing environmental data. Using nine EMAP data variables, we analyzed their correlation matrix with an SEM model. The model characterized...

204

OCAM - A CELSS modeling tool: Description and results. [Object-oriented Controlled Ecological Life Support System Analysis and Modeling  

NASA Technical Reports Server (NTRS)

Controlled Ecological Life Support System (CELSS) technology is critical to the Space Exploration Initiative. NASA's Kennedy Space Center has been performing CELSS research for several years, developing data related to CELSS design. We have developed OCAM (Object-oriented CELSS Analysis and Modeling), a CELSS modeling tool, and have used this tool to evaluate CELSS concepts, using this data. In using OCAM, a CELSS is broken down into components, and each component is modeled as a combination of containers, converters, and gates which store, process, and exchange carbon, hydrogen, and oxygen on a daily basis. Multiple crops and plant types can be simulated. Resource recovery options modeled include combustion, leaching, enzyme treatment, aerobic or anaerobic digestion, and mushroom and fish growth. Results include printouts and time-history graphs of total system mass, biomass, carbon dioxide, and oxygen quantities; energy consumption; and manpower requirements. The contributions of mass, energy, and manpower to system cost have been analyzed to compare configurations and determine appropriate research directions.

Drysdale, Alan; Thomas, Mark; Fresa, Mark; Wheeler, Ray

1992-01-01

205

Entomopathogenic nematodes as a model system for advancing the frontiers of ecology.  

PubMed

Entomopathogenic nematodes (EPNs) in the families Heterorhabditidae and Steinernematidae have a mutualistic-symbiotic association with enteric ?-Proteobacteria (Steinernema-Xenorhabdus and Heterorhabditis-Photorhabdus), which confer high virulence against insects. EPNs have been studied intensively because of their role as a natural mortality factor for soil-dwelling arthropods and their potential as biological control agents for belowground insect pests. For many decades, research on EPNs focused on the taxonomy, phylogeny, biogeography, genetics, physiology, biochemistry and ecology, as well as commercial production and application technologies. More recently, EPNs and their bacterial symbionts are being viewed as a model system for advancing research in other disciplines such as soil ecology, symbiosis and evolutionary biology. Integration of existing information, particularly the accumulating information on their biology, into increasingly detailed population models is critical to improving our ability to exploit and manage EPNs as a biological control agent and to understand ecological processes in a changing world. Here, we summarize some recent advances in phylogeny, systematics, biogeography, community ecology and population dynamics models of EPNs, and describe how this research is advancing frontiers in ecology. PMID:23482825

Campos-Herrera, Raquel; Barbercheck, Mary; Hoy, Casey W; Stock, S Patricia

2012-06-01

206

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

207

Modeling discrete-variable stochastic dynamics: Ecological populations, gene networks, and a nanotube ion channel  

NASA Astrophysics Data System (ADS)

Many complex systems in both the physical and life sciences can be modeled as interacting elements with discrete-value variables. In most of these systems, stochasticity plays an important role. This paper examines an ecological population dynamics model, a simple model of a gene regulatory network, and a model for the conductance of a nanotube ion channel. The interplay of discrete-value variables, stochasticity, and nonlinear dynamics produces fascinating phenomena that are important in many areas of physics and biology.

Hilborn, Robert C.

2014-05-01

208

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

209

A comparison of simulation results from two terrestrial carbon cycle models using three climate data sets  

Microsoft Academic Search

This study addressed how different climate data sets influence simulations of the global terrestrial carbon cycle. For the period 1982-2001, we compared the results of simulations based on three climate data sets (NCEP\\/NCAR, NCEP\\/DOE AMIP-II and ERA40) employed in meteorological, ecological and biogeochemical studies and two different models (BEAMS and Sim-CYCLE). The models differed in their parameterizations of photosynthetic and

Akihiko Ito; Takahiro Sasai

2006-01-01

210

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

211

Predicting the Current and Future Potential Distributions of Lymphatic Filariasis in Africa Using Maximum Entropy Ecological Niche Modelling  

PubMed Central

Modelling the spatial distributions of human parasite species is crucial to understanding the environmental determinants of infection as well as for guiding the planning of control programmes. Here, we use ecological niche modelling to map the current potential distribution of the macroparasitic disease, lymphatic filariasis (LF), in Africa, and to estimate how future changes in climate and population could affect its spread and burden across the continent. We used 508 community-specific infection presence data collated from the published literature in conjunction with five predictive environmental/climatic and demographic variables, and a maximum entropy niche modelling method to construct the first ecological niche maps describing potential distribution and burden of LF in Africa. We also ran the best-fit model against climate projections made by the HADCM3 and CCCMA models for 2050 under A2a and B2a scenarios to simulate the likely distribution of LF under future climate and population changes. We predict a broad geographic distribution of LF in Africa extending from the west to the east across the middle region of the continent, with high probabilities of occurrence in the Western Africa compared to large areas of medium probability interspersed with smaller areas of high probability in Central and Eastern Africa and in Madagascar. We uncovered complex relationships between predictor ecological niche variables and the probability of LF occurrence. We show for the first time that predicted climate change and population growth will expand both the range and risk of LF infection (and ultimately disease) in an endemic region. We estimate that populations at risk to LF may range from 543 and 804 million currently, and that this could rise to between 1.65 to 1.86 billion in the future depending on the climate scenario used and thresholds applied to signify infection presence.

Slater, Hannah; Michael, Edwin

2012-01-01

212

Bjt Modeling for Circuit Simulation  

NASA Astrophysics Data System (ADS)

Physical models for transport mechanisms important in bipolar transistors are developed, implemented in SPICE3 for DC, AC, and transient analyses, and assessed with numerical device simulations. The analytical model of quasi-saturation, or base -push-out, is derived for all current levels. Deficiencies in previous quasi-saturation models are revealed and overcome. The quasi-saturation model is based on a derivation of the current-induced-base charge and the electric field in the collector for all bias conditions. Physical models for base-width modulation (BWM) at the collector-base (cb) junction and impact ionization in the collector are formulated as functions of the electric field; inclusion of these two effects greatly improves the accuracy in the output resistance. The impact ionization model gives a first -order description of avalanche breakdown, or snapback. The dynamic charge storage effects are investigated in detail with AC and transient analyses. The proper partitioning of the dynamic charging currents is made possible by the addition of an internal collector node and increases accuracy especially under quasi-saturation conditions. The cb junction capacitance and the cb junction transit time tau _{cv} are expressed as functions of the field E_1 at the cb junction. As E_1 decreases with increasing current due to the Kirk effect, the variable tau _{cv} and the BWM effect on the base-diffusion charge each can cause f_ {T} to fall-off at a current several times below that for the onset of quasi-saturation, which causes a more rapid f_{T} fall -off. The current-induced-base charge significantly reduces the effective base resistance as the dynamic base current flows laterally through the current-induced-base. Simulation results suggest that an AC emitter crowding model previously derived for low injection conditions is a good approximation even under base-push-out conditions. The delay time approach and the quasi-static charge-partition approach are compared; the former is found to be better in simulating the high frequency effects due to non-quasi-static conditions in the quasi-neutral base and current-induced-base regions. A non-quasi-static model for the charge in the quasi-neutral base region is developed and implemented in SPICE3 for transient analysis. The methodology to solve for the instantaneous carrier distribution by a series solution including all injection levels and the effect of the built-in field is presented. The solution applies for forward and reverse modes of operation. Analytic equations for the instantaneous base charge partitions are derived for the calculation of the instantaneous node currents. For switching times comparable to the base transit time, the non-quasi-static model is significantly more accurate than the Gummel-Poon model and previous quasi-static charge -partition models, as verified with numerical device simulations.

Szeto, Clement Keung

213

Coupled Human-Ecological Dynamics and Land Degradation in Global Drylands-A modelling approach (Invited)  

NASA Astrophysics Data System (ADS)

Drylands comprise one-third of the Earth’s land area. They pose research, management, and policy challenges impacting the livelihoods of 2.5 billion people. Desertification is said to affect some 10-20% of the drylands and is assumed to expand with climate change and population growth. Recent paradigms stress the importance of understanding linkages between human-ecological (H-E) systems in order to achieve sustainable management policies. Understanding coupled H-E systems is difficult at local levels. It represents an even greater challenge at regional scales to guide priorities and policy decisions at national and international levels. System dynamic modelling may help facilitating the probblem. Desertification and land degradation are often modelled and mathematically defined in terms of soil erosion. The soil erosion process is usually described as a function of vegetation ground cover, rainfall characteristics, topography, soil characteristics and land management. On-going research based on system dynamic modelling, focussing on elucidating the inherent complexity of H-E systems across multiple scales, enables an assessment of the relative roles that climate, policy, management, land condition, vulnerability and human adaptation may play in desertification and dryland development. An early approach (1995) to study desertification through an H-E coupled model considered desertification to be stress beyond resilience, i.e. irreversible, using a predator-prey system approach. As most predator-prey models, it was based on two linked differential equations describing the evolution of both a human population (predator) and natural resources (prey) in terms of gains, losses and interaction. A recent effort used a model approach to assess desertification risk through system stability condition analysis. It is based on the assumption that soil erosion and the soil sub-system play an overriding final role in the desertification processes. It is stressing the role and importance of economic units, production costs, investments and profitability in natural resources exploitation. This paper presents a recently developed coupled H-E system dynamic model to simulate and analyse desertification syndromes. The model integrates socio-economic drivers with bio-physical drivers of biomass production and land degradation. It is based on the UN and GEF definitions of desertification. It analyses and simulates dryland dynamics and desertification through differential equations and numeric simulation. The model relates population pressure and dynamics over time to the growth and availability of biomass resources. The human population stock is described as a function of growth rate, death rate and resources dependent migration of people. The relative growth rate of the stock of resources is modelled as a function of climate and human exploitation pressure affecting the removal of resources, soil erosion and water availability over time. The model is applied, demonstrated and discussed for combinations of time series of simulated and observed data referring to “desertification” cases in the Sahel, the Mediterranean and Inner Mongolia, China. The results are compared to existing land and population related statistics and remotely sensed observations opening for land system “carrying capacity” analysis and discussions.

Helldén, U.

2009-12-01

214

Automatic programming of AGVS simulation models  

Microsoft Academic Search

This paper presents a knowledge based modeling system that allows a manufacturing engineer who has very limited knowledge of simulation methodology to quickly and correctly, develop and run a simulation model of an automated guided vehicle system (AGVS). The modeling system is capable of guiding and assisting the engineer with a level of “expertise” comparable to a trained simulation specialist.

Mark K. Brazier; Robert E. Shannon

1987-01-01

215

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

216

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

217

Model Validation with Hybrid Dynamic Simulation  

SciTech Connect

Abstract—Model validation has been one of the central topics in power engineering studies for years. As model validation aims at obtaining reasonable models to represent actual behavior of power system components, it has been essential to validate models against actual measurements or known benchmark behavior. System-wide model simulation results can be compared with actual recordings. However, it is difficult to construct a simulation case for a large power system such as the WECC system and to narrow down to problematic models in a large system. Hybrid dynamic simulation with its capability of injecting external signals into dynamic simulation enables rigorous comparison of measurements and simulation in a small subsystem of interest. This paper presents such a model validation methodology with hybrid dynamic simulation. Two application examples on generator and load model validation are presented to show the validity of this model validation methodology. This methodology is further extended for automatic model validation and dichotomous subsystem model validation.

Huang, Zhenyu; Kosterev, Dmitry; Guttromson, Ross T.; Nguyen, Tony B.

2006-06-18

218

Conceptualizing Ecology: A Learning Cycle Approach.  

ERIC Educational Resources Information Center

Proposes a teaching strategy to teach ecological concepts and terminology through the use of games and simulations. Includes examples from physiological ecology, population ecology, and ecosystem ecology. (Author/SOE)

Lauer, Thomas E.

2003-01-01

219

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

220

mMWeb - An Online Platform for Employing Multiple Ecological Niche Modeling Algorithms  

PubMed Central

Background Predicting the ecological niche and potential habitat distribution of a given organism is one of the central domains of ecological and biogeographical research. A wide variety of modeling techniques have been developed for this purpose. In order to implement these models, the users must prepare a specific runtime environment for each model, learn how to use multiple model platforms, and prepare data in a different format each time. Additionally, often model results are difficult to interpret, and a standardized method for comparing model results across platforms does not exist. We developed a free and open source online platform, the multi-models web-based (mMWeb) platform, to address each of these problems, providing a novel environment in which the user can implement and compare multiple ecological niche model (ENM) algorithms. Methodology mMWeb combines 18 existing ENMs and their corresponding algorithms and provides a uniform procedure for modeling the potential habitat niche of a species via a common web browser. mMWeb uses Java Native Interface (JNI), Java R Interface to combine the different ENMs and executes multiple tasks in parallel on a super computer. The cross-platform, user-friendly interface of mMWeb simplifies the process of building ENMs, providing an accessible and efficient environment from which to explore and compare different model algorithms.

Qiao, Huijie; Lin, Congtian; Ji, Liqiang; Jiang, Zhigang

2012-01-01

221

An ecological model evaluation of two nutrient abatement strategies for the Baltic Sea  

NASA Astrophysics Data System (ADS)

The reduction of nutrient loads is the overriding strategy in order to abate eutrophication and to improve the ecological state of the Baltic Sea. A 3D-ecosystem model of the Baltic Sea was used to analyze the effects of two different 50% nitrogen and phosphorus load reduction scenarios. The first scenario assumed a proportional 50% load reduction in all riparian countries. The second was based on a cost-effective approach by Gren [I.-M. Gren, 2000. Managing a sea. Cost-Effective Nutrient Reduction To The Baltic Sea. Earthscan Publ., London. Ch. 43-56.] with significant regional differences in load reduction. The simulations suggest that a 50% reduction of nitrogen and phosphorus loads affect predominantly the coastal waters and favours cyanobacteria blooms in the central Baltic Sea. In the cost-effective approach, blooms of the potentially toxic cyanobacteria become even more pronounced in the northern part of the Baltic Proper. The comparison between the two 50% reduction scenarios reveals differences mainly in coastal waters. Near large rivers in the southern Baltic, like the Oder and the Vistula, the cost-effective scenario shows a greater decrease of nutrients and chlorophyll- a concentrations. Altogether the water quality in southern Baltic Sea, especially in Germany, Poland and the Baltic states benefits from a cost-effective approach. However, differences in nutrient and chlorophyll- a concentrations between the scenarios are small. Referring to our simulation results, in a medium-term perspective the measures to abate eutrophication in the Baltic Sea will be not very efficient concerning the central Baltic Sea and might generate undesirable summer blooms of nitrogen-fixing cyanobacteria. These are a result of nutrient imbalances in the system and may persist for several decades. A more pronounced and early reduction of the phosphorus loads might shorten the period of bloom persistence.

Neumann, Thomas; Schernewski, Gerald

2005-05-01

222

Ecological Neuropsychology: An Alternative to the Deficit Model for Conceptualizing and Serving Students with Learning Disabilities  

Microsoft Academic Search

The present paper contends that children with learning disabilities are better served when assessment and intervention are conceptualized within an ecological neuropsychology perspective than within the traditional deficit model perspective, which is the predominant approach to intervention in medical and educational settings. The deficit method conceptualizes problems as within the child, and the major consequence of this approach is that

Rik Carl D'Amato; Franci Crepeau-Hobson; Leesa V. Huang; Molly Geil

2005-01-01

223

Space To Grow: Creating an Ecology Model of Bi- and Multiracial Identity Development in College Students.  

ERIC Educational Resources Information Center

This study examined how campus peer culture influences the ways in which multiracial students make meaning of their racial identity, and applies Urie Bronfenbrenner's ecological model of cognitive development to analyze elements in the college environment that stimulate or inhibit identity development. Discussion of the situation of multiracial…

Renn, Kristen A.

224

Mathematical model of ecological disturbances in the oil rich Niger Delta region of Nigeria  

Microsoft Academic Search

An important class of interactions between biological species is the stability. We investigate the ecological, biological and economical impacts of petroleum exploration on the Niger Delta region of Southern Nigeria. A modified reaction-diffusion model describing the spread of the predators into the prey populations is adopted to establish the interaction between the parties involved. An attempt was made to explore

O. O. Ugbebor; P. O. K. Aiyelo

2009-01-01

225

DEVELOPMENT AND APPLICATION OF POPULATION MODELS TO SUPPORT EPA'S ECOLOGICAL RISK ASSESSMENT PROCESSES FOR PESTICIDES  

EPA Science Inventory

As part of a broader exploratory effort to develop ecological risk assessment approaches to estimate potential chemical effects on non-target populations, we describe an approach for developing simple population models to estimate the extent to which acute effects on individual...

226

FISSION RISK OR INERTIA? TOWARDS AN EVOLUTIONARY-ECOLOGICAL MODEL OF HUMAN CAPITAL DECISIONS  

Microsoft Academic Search

The evolutionary-ecological model presented here introduces a new concept, 'fission', in order to highlight the possibility of economically rational outcomes manifesting inert demand for human capital. The apparent paradox between the availability of skilled labour and an unresponsiveness of employers to its availability is shown to be the consequence of employer risk avoidance in the presence of 'fission', the dis-mantling

AURORA TEIXEIRA; Roberto Frias

227

An ecosystem model for assessing ecological risks in Québec rivers, lakes, and reservoirs  

Microsoft Academic Search

The comprehensive aquatic systems model (CASM) was adapted for estimating ecological risks posed by toxic chemicals in rivers, lakes, and reservoirs in Québec, Canada. Populations of aquatic plants, invertebrates, and fish characteristic of these aquatic ecosystems were identified and generic food webs were constructed. Bioenergetics parameters that determine the growth dynamics of these populations were derived from published values for

Steven M. Bartell; Guy Lefebvre; Grégoire Kaminski; Michel Carreau; Kym Rouse Campbell

1999-01-01

228

ECOLOGICAL ENDPOINT MODELING FOR TMDLS: EFFECTS OF SEDIMENT ON FISH POPULATIONS  

EPA Science Inventory

Sediment is one of the primary stressors of concern for Total Maximum Daily Loads (TMDLs) for streams, and often it is a concern because of its impact on ecological endpoints. A modeling approach relating sediment to stream fish population dynamics is presented. Equations are d...

229

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

Microsoft Academic Search

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

R Ekblom; J Galindo

2011-01-01

230

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...

231

Adaptation of Families with Mentally Retarded Children: A Model of Stress, Coping, and Family Ecology.  

ERIC Educational Resources Information Center

A critical review focused on parents, siblings, parent-child interactions, and family systems related to mental retardation is presented. A model is proposed that accounts for the range of possible familial adaptations and the family's coping resources and ecological environments as interactive systems that serve to mediate the family's response…

Crnic, Keith A.; And Others

1983-01-01

232

RIVPACS models for predicting the expected macroinvertebrate fauna and assessing the ecological quality of rivers  

Microsoft Academic Search

The European Union Water Framework Directive recognises the need for and value of biological monitoring. This paper reviews the modelling approach known as River Invertebrate Prediction and Classification System (RIVPACS) for assessing the ecological quality of river sites using macroinvertebrate sampling. The RIVPACS philosophy is to develop statistical relationships between the fauna and the environmental characteristics of a large set

Ralph T Clarke; John F Wright; Mike T Furse

2003-01-01

233

Integrated geographical assessment of environmental condition in water catchments: Linking landscape ecology, environmental modelling and GIS  

Microsoft Academic Search

Water catchments are functional geographical areas that integrate a variety of environmental processes and human impacts on landscapes. Integrated assessments recognize this interdependence of resources and components making up water catchments and are vital for viable long-term natural resource management. This paper couples eco-hydrological modelling with remote sensing, landscape ecological analyses and GIS to develop a series of indicators of

R Aspinall; D Pearson

2000-01-01

234

Social Ecological Model of Illness Management in High-Risk Youths with Type 1 Diabetes  

ERIC Educational Resources Information Center

In this study, the authors tested a social ecological model of illness management in high-risk, urban adolescents with Type 1 diabetes. It was hypothesized that management behaviors would be associated with individual adolescent characteristics as well as family, peer, and provider relationships. Questionnaires were collected from 96 adolescents…

Naar-King, Sylvie; Podolski, Cheryl-Lynn; Ellis, Deborah A.; Frey, Maureen A.; Templin, Thomas

2006-01-01

235

A CONCEPTUAL MODEL FOR EVALUATING RELATIVE POTENCY DATA FOR USE IN ECOLOGICAL RISK ASSESSMENTS  

EPA Science Inventory

For chemicals with a common mechanism of toxicity, relative potency factors (RPFs) allow dose and exposure measures to be normalized to an equivalent toxicity amount of a model chemical... In ecological risk assessments the large number of possible target species, variety of expo...

236

Ubiquitin: molecular modeling and simulations.  

PubMed

The synthesis and destruction of proteins are imperative for maintaining their cellular homeostasis. In the 1970s, Aaron Ciechanover, Avram Hershko, and Irwin Rose discovered that certain proteins are tagged by ubiquitin before degradation, a discovery that awarded them the 2004 Nobel Prize in Chemistry. Compelling data gathered during the last several decades show that ubiquitin plays a vital role not only in protein degradation but also in many cellular functions including DNA repair processes, cell cycle regulation, cell growth, immune system functionality, hormone-mediated signaling in plants, vesicular trafficking pathways, regulation of histone modification and viral budding. Due to the involvement of ubiquitin in such a large number of diverse cellular processes, flaws and impairments in the ubiquitin system were found to be linked to cancer, neurodegenerative diseases, genetic disorders, and immunological disorders. Hence, deciphering the dynamics and complexity of the ubiquitin system is of significant importance. In addition to experimental techniques, computational methodologies have been gaining increasing influence in protein research and are used to uncover the structure, stability, folding, mechanism of action and interactions of proteins. Notably, molecular modeling and molecular dynamics simulations have become powerful tools that bridge the gap between structure and function while providing dynamic insights and illustrating essential mechanistic characteristics. In this study, we present an overview of molecular modeling and simulations of ubiquitin and the ubiquitin system, evaluate the status of the field, and offer our perspective on future progress in this area of research. PMID:24113788

Ganoth, Assaf; Tsfadia, Yossi; Wiener, Reuven

2013-11-01

237

Using Teacher-Generated Ecological Models to Assess Knowledge Gained During Teacher Training  

NASA Astrophysics Data System (ADS)

Developing a capacity for systems thinking (ways to understand complex systems) requires both immersion in challenging, real-world problem contexts and exposure to systems analysis language, tools and procedures, such as ecosystem modeling. Modeling is useful as a means of conveying complex, dynamic interactions. Models of ecosystems can facilitate an ability to be attentive to whole systems by illustrating multiple factors of interaction, feedback, subsystems and inputs and outputs, which lead to a greater understanding of ecosystem functioning. Concept mapping, which uses models of students' ideas organized hierarchically is used in assessment, but it does not having any outside utility. Ecosystem models, on the other hand, are legitimate end-products in and of themselves. A change made in a learner-generated model that conforms to patterns observed in nature by the learner can be seen as reflections of his or her understanding. Starting with their own reflections on previous ecological knowledge, teachers will model components of the ecosystem they are about to study. 'Teaching models' will be used to familiarize learners with the symbolic language of models and to teach some basic ecology concepts. Teachers then work directly with ecologists in conducting research, using the steps of a straightforward study as a guide, and then observe and discuss patterns in the data they have collected. Higher-order thinking skills are practiced through the reflective use of ecological models. Through a series of questions including analysis, relational reasoning, synthesis, testing, and explaining, pairs of teacher describe the principles and theories about ecology that they think might be operating in their models to one another. They describe the consequences of human-caused impacts and possible causal patterns. They explain any differences in their understanding of ecosystem interactions before and after their research experiences

Dresner, M.; Moldenke, A.

2005-12-01

238

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

PubMed

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 to evaluate the effectiveness of drift-reduction measures in mitigating risks. The pesticides selected and the dosage, frequency, and timing of application were based on normal agricultural practices in the potato crop. Applications of prosulfocarb, metribuzin (both herbicides), lambda-cyhalothrin (insecticide), chlorothalonil, and fluazinam (both fungicides) were made in the sequence typical of the spray calendar for potatoes. A total of 15 treatments with the various compounds were made by spray application to the water surface at 0.2%, 1%, and 5% of the recommended label rates. Chemical fate and effects on ecosystem function and structure (phytoplankton, zooplankton, chlorophyll-a, macroinvertebrates, macrophytes, breakdown of plant litter) were investigated. To interpret the observed effects, treatment concentrations were also expressed in toxic units (TU), which describe the relative toxicity of the compounds with standard toxicity test organisms (Daphnia and algae). After treatment, each compound disappeared from the water phase within 2 d, with the exception of prosulfocarb, for which 50% dissipation time (DT50) values ranged between 6 and 7 d. At the 5% treatment level, an exposure peak of 0.9 TUalgae was observed, which resulted in short-term responses of pH, oxygen, and phytoplankton. At the 5% treatment level, exposure concentrations also exceeded 0.1 TUDaphnia, and this resulted in long-term effects on zooplankton and macroinvertebrates, some of which did not fully recover by the end of the present study. At the 1% treatment level, only slight transient effects were observed on a limited number of zooplankton and macro-invertebrate species and on pH. At the 0.2% level, no consistent treatment-related effects were observed. Most of the observed effects were consistent with the results from higher-tier and mesocosm studies with the individual compounds. Multi and repeated stress played a small role within the applied pesticide package, because of rapid dissipation of most substances and the absence of many simultaneous applications. This suggests that risk assessments based on the individual compounds would in this case have been sufficiently protective for their uses in a crop protection program. PMID:16646380

Arts, Gertie H P; Buijse-Bogdan, Laura L; Belgers, J Dick M; van Rhenen-Kersten, Caroline H; van Wijngaarden, Rene P A; Roessink, Ivo; Maund, Steve J; van den Brink, Paul J; Brockt, Theo C M

2006-04-01

239

Modeling of Army Research Laboratory EMP simulators  

SciTech Connect

Models are required that permit the estimation of emitted field signatures from EMP simulators to design the simulator antenna structure, to establish the usable test volumes, and to estimate human exposure risk. This paper presents the capabilities and limitations of a variety of EMP simulator models useful to the Army's EMP survivability programs. Comparisons among frequency and time-domain models are provided for two powerful US Army Research Laboratory EMP simulators: AESOP (Army EMP Simulator Operations) and VEMPS II (Vertical EMP Simulator II).

Miletta, J.R.; Chase, R.J.; Luu, B.B. (Army Research Lab., Adelphi, MD (United States)); Williams, J.W.; Viverito, V.J. (Science Applications International Corp., Germantown, MD (United States))

1993-12-01

240

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

241

Modeling and simulation of fire spreading through the activity tracking paradigm  

SciTech Connect

Modeling and simulation is essential for understanding complex ecological systems. However, knowledge of the structure and behavior of these systems is limited, and models must be revised frequently as our understanding of a system improves. Moreover, the dynamic, spatial distribution of activity in very large systems necessitates mapping natural mechanisms as logically as possible onto computer structures. This paper describes theoretical and algorithmic tools for building component-based models and simulations of dynamic spatial phenomena. These methods focus attention on and exploit the irregular distribution of activity in ecological processes. We use the DEVS formalism as the basis for a component based approach to modeling spatially distributed systems. DEVS is a mathematical theory of discrete-event systems that is well suited for describing large systems that are described by small parts with irregular, short-range interactions. This event-based approach to modeling leads naturally to efficient simulations algorithms which focus on the active parts of a large model. Ecological modeling benefits from these efficient the simulation algorithms and the reusability of the model s basic components. Our event-based method is demonstrated with a physics-based model of fire spread.

Muzy, [Laboratory UMR CNRS LISA, Università di Corsica-Pasquale Paoli; Nutaro, James J [ORNL; Zeigler, Bernard P [ORNL; Coquillard, [Laboratory UMR Biotic Interactions and Plant Health, AgroBiotech Center

2008-01-01

242

Tools from ecology: useful for evaluating infection risk models?  

Microsoft Academic Search

Despite the increasing number of models to predict infection risk for a range of diseases, the assessment of their spatial limits, predictive performance and practical application are not widely undertaken. Using the example of Schistosoma haematobium in Africa, this article illustrates how ecozonation and receiver–operator characteristic analysis can help to assess the usefulness of available models objectively.

Simon Brooker; Simon I. Hay; Don A. P. Bundy

2002-01-01

243

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.

244

An Ecological Perspective and Model for Campus Design  

ERIC Educational Resources Information Center

The authors introduce the concept of "ecosystems." An ecosystem is one in which there is a true transaction between mutually dependent partners, with the assumption on college campuses that either may change so that mutual benefit may result. A model for bringing about change is presented, and methodology for using the model is described.…

Banning, James H.; Kaiser, Leland

1974-01-01

245

Exploring ecological patterns with structural equation modeling and Bayesian analysis  

Microsoft Academic Search

Structural equation modeling is a multivariate statistical method that allows evaluation of a network of relationships between manifest and latent variables. In this statistical technique, preconceptualizations that reflect research questions or existing knowledge of system structure create the initial framework for model development, while both direct and indirect effects and measurement errors are considered. Given the interesting features of this

G. B. Arhonditsis; C. A. Stow; L. J. Steinberg; M. A. Kenney; R. C. Lathrop; S. J. McBride; K. H. Reckhow

2006-01-01

246

Verification and validation of simulation models  

Microsoft Academic Search

This paper surveys verification and validation of models, especially simulation models in operations research. For verification it discusses 1) general good programming practice (such as modular programming), 2) checking intermediate simulation outputs through tracing and statistical testing per module, 3) statistical testing of final simulation outputs against analytical results, and 4) animation. For validation it discusses 1) obtaining real-worl data,

Jack P. C. Kleijnen

1995-01-01

247

Modeling and simulation of power electronic converters  

Microsoft Academic Search

This paper reviews some of the major approaches to modeling and simulation in power electronics, and provides references that can serve as a starting point for the extensive literature on the subject. The major focus of the paper is on averaged models of various kinds, but sampled-data models are also introduced. The importance of hierarchical modeling and simulation is emphasized

DRAGAN MAKSIMOVIC ´; ALEKSANDAR M. STANKOVIC; V. JOSEPH THOTTUVELIL; GEORGE C. VERGHESE

2001-01-01

248

On identification in Bayesian disease mapping and ecological-spatial regression models.  

PubMed

We discuss identification of structural characteristics of the underlying relative risks ensemble for posterior relative risks inference within Bayesian generalized linear mixed model framework for small-area disease mapping and ecological-spatial regression. We revisit conditionally specified and locally characterized Gaussian Markov random field risks ensemble priors in univariate disease mapping and communicate insight into Gaussian Markov random field variance-covariance characteristics for representing disease risks variability and spatial risks interactions and for structural identification with respect to risks ensemble prior choices. Illustrative examples of identification in Bayesian disease mapping and ecological-spatial regression models are presented for Bayesian hierarchical generalized linear mixed Poisson models and zero-inflated Poisson models. PMID:22573502

MacNab, Ying C

2014-04-01

249

[Analysis on sustainable development of marine economy in Jiangsu Province based on marine ecological footprint correction model].  

PubMed

Based on the theories and methods of ecological footprint, the concept of marine ecological footprint was proposed. According to the characteristics of marine environment in Jiangsu Province, five sub-models of marine ecological footprints, including fishery, transporation, marine engineering construction, marine energy, and tidal flat, were constructed. The equilibrium factors of the five marine types were determined by using improved entropy method, and the marine footprints and capacities in Jiangsu Province from 2000 to 2008 were calculated and analyzed. In 2000-2008, the marine ecology footprint per capita in Jiangsu Province increased nearly seven times, from 36.90 hm2 to 252.94 hm2, and the ecological capacity per capita grew steadily, from 105.01 hm2 to 185.49 hm2. In 2000, the marine environment in the Province was in a state of ecological surplus, and the marine economy was in a weak sustainable development state. Since 2004, the marine ecological environment deteriorated sharply, with ecological deficit up to 109660.5 hm2, and the sustainability of marine economy declined. The high ecological footprint of fishery was the main reason for the ecological deficit. Tidal flat was the important reserve resource for the sustainable development of marine economy in Jiangsu Province. PMID:21657034

Yang, Shan; Wang, Yu-ting

2011-03-01

250

Hybrid simulation models of computer systems  

Microsoft Academic Search

This paper describes the structure and operation of a hybrid simulation model in which both discrete-event simulation and analytic techniques are combined to produce efficient yet accurate system models. In an example based on a simple hypothetical computer system, discrete-event simulation is used to model the arrival and activation of jobs, and a central-server queueing network models the use of

Herbert D. Schwetman; D. Siewiorek

1978-01-01

251

Adaptive spatio-temporal models for satellite ecological data  

Microsoft Academic Search

This article develops models for environmental data recorded by meteorological satellites. In general, such data are continuously\\u000a available for suitable space and time units and are intrinsically nonstationary. Space-time auto-regression (STAR) is a class\\u000a of models that can be used in monitoring and forecasting, but it must be adapted to nonstationary processes. A set of adaptive\\u000a recursive estimators is then

Carlo Grillenzoni

2004-01-01

252

Use of Ecological Risk Data in the Development of Visions, Conceptual Site Models and Maps for Department of Energy Lands: Ensuring Sustainability of Protecting Human and Ecological Health  

Microsoft Academic Search

Recent interest in understanding the human and ecological health risks of contaminants on lands in the United States has led some managers and public policy makers to use extensive narratives associated with maps and Conceptual Site Models (CSM) in their Vision statements. While narratives are descriptive, CSMs can graphically depict the sources, releases, transport and exposure pathways, and receptors, together

Joanna Burger

2005-01-01

253

A review and synthesis of late Pleistocene extinction modeling: progress delayed by mismatches between ecological realism, interpretation, and methodological transparency.  

PubMed

Late Pleistocene extinctions occurred globally over a period of about 50,000 years, primarily affecting mammals of > or = 44 kg body mass (i.e., megafauna) first in Australia, continuing in Eurasia and, finally, in the Americas. Polarized debate about the cause(s) of the extinctions centers on the role of climate change and anthropogenic factors (especially hunting). Since the late 1960s, investigators have developed mathematical models to simulate the ecological interactions that might have contributed to the extinctions. Here, we provide an overview of the various methodologies used and conclusions reached in the modeling literature, addressing both the strengths and weaknesses of modeling as an explanatory tool. Although late Pleistocene extinction models now provide a solid foundation for viable future work, we conclude, first, that single models offer less compelling support for their respective explanatory hypotheses than many realize; second, that disparities in methodology (both in terms of model parameterization and design) prevent meaningful comparison between models and, more generally, progress from model to model in increasing our understanding of these extinctions; and third, that recent models have been presented and possibly developed without sufficient regard for the transparency of design that facilitates scientific progress. PMID:24984323

Yule, Jeffrey V; Fournier, Robert J; Jensen, Christopher X J; Yang, Jinyan

2014-06-01

254

Hybrid simulation modelling of the software process  

Microsoft Academic Search

The paper proposes the combination of three traditional modelling methods (analytical, continuous and discrete-event), into a unique hybrid two-level modelling approach, to address software process simulation modelling issues. At the higher abstraction level,

Paolo Donzelli; Giuseppe Iazeolla

2001-01-01

255

Ecological genomics and process modeling of local adaptation to climate.  

PubMed

Locally adapted genotypes have higher fitness in their native site in comparison to foreign genotypes. Recent studies have demonstrated both local adaptation to and genomic associations with a range of climate variables. For climate adaptation, the most common genomic pattern is conditional neutrality, as proven by weak across-environment correlations, frequent SNP×environment interactions, and the topology of some developmental and physiological pathways potentially involved in local adaptation. Genomic association approaches readily translate to non-model systems, and genetically explicit climate envelope models will predict future species' distributions under changing climates. Here, we review recent evidence for local adaptation to climate, focusing primarily on the model system, Arabidopsis thaliana, and on studies incorporating genomic tools into field studies or climate analyses. PMID:24631846

Weinig, Cynthia; Ewers, Brent E; Welch, Stephen M

2014-04-01

256

Teaching and Learning Ecological Modeling over the Web: a Collaborative Approach  

NSDL National Science Digital Library

This online report, published in Conservation Ecology, describes the framework for web-based collaborative teaching, and provides the layout of an ecological modeling course as an example of how this method of teaching can be implemented. The course content consists of reading materials that describe the theory of systems analysis and modeling, guidelines on how models can be built, and numerous examples and illustrations. The interactive portion includes exercises that can be discussed with and evaluated by the instructor, and provides a means to mimic class discussions. In addition to the course content, the report also offers a discussion of the availability and relevance of other web-based tools, including links to those discussed.

Voinov, Alexy

2010-02-16

257

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

258

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

259

Applications of Ecological Niche Modeling for Species Delimitation: A Review and Empirical Evaluation Using Day Geckos (Phelsuma) from Madagascar  

Microsoft Academic Search

Although the systematic utility of ecological niche modeling is generally well known (e.g., concerning the recog- nition and discovery of areas of endemism for biogeographic analyses), there has been little discussion of applications concerning species delimitation, and to date, no empirical evaluation has been conducted. However, ecological niche mod- eling can provide compelling evidence for allopatry between populations, and can

CHRISTOPHER J. RAXWORTHY; COLLEEN M. INGRAM; Nirhy Rabibisoa; RICHARD G. PEARSON

2007-01-01

260

Use of a conceptual model of societal drivers of ecological change in South Florida: Implications of an ecosystem management scenario  

Microsoft Academic Search

Human-dominated ecosystems such as in South Florida's Everglades region are greatly affected by societal actions and choices, and efforts to restore degraded ecosystems must take into account the societal drivers of ecosystem change. A conceptual model of societal-ecological interactions within the region illustrates connections between major societal drivers, such as water management and land use, and ecological stressors, such as

Christine C. Harwell; Christopher W. Deren; George H. Snyder; William D. Solecki; James Wilson; Mark A. Harwell

1999-01-01

261

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

262

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

263

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.

Parsons, Peter A.

2006-01-01

264

Use of an integrated flow model to estimate ecologically relevant hydrologic characteristics at stream biomonitoring sites  

USGS Publications Warehouse

We developed an integrated hydroecological model to provide a comprehensive set of hydrologic variables representing five major components of the flow regime at 856 aquatic-invertebrate monitoring sites in New Jersey. The hydroecological model simulates streamflow by routing water that moves overland and through the subsurface from atmospheric delivery to the watershed outlet. Snow accumulation and melt, evapotranspiration, precipitation, withdrawals, discharges, pervious- and impervious-area runoff, and lake storage were accounted for in the water balance. We generated more than 78 flow variables, which describe the frequency, magnitude, duration, rate of change, and timing of flow events. Highly correlated variables were filtered by principal component analysis to obtain a non-redundant subset of variables that explain the majority of the variation in the complete set. This subset of variables was used to evaluate the effect of changes in the flow regime on aquatic-invertebrate assemblage structure at 856 biomonitoring sites. We used non-metric multidimensional scaling (NMS) to evaluate variation in aquatic-invertebrate assemblage structure across a disturbance gradient. We employed multiple linear regression (MLR) analysis to build a series of MLR models that identify the most important environmental and hydrologic variables driving the differences in the aquatic-invertebrate assemblages across the disturbance gradient. The first axis of NMS ordination was significantly related to many hydrologic, habitat, and land-use/land-cover variables, including the average number of annual storms producing runoff, ratio of 25-75% exceedance flow (flashiness), diversity of natural stream substrate, and the percentage of forested land near the stream channel (forest buffer). Modifications in the hydrologic regime as the result of changes in watershed land use appear to promote the retention of highly tolerant aquatic species; in contrast, species that are sensitive to hydrologic instability and other anthropogenic disturbance become much less prevalent. We also found strong relations between an index of invertebrate-assemblage impairment, its component metrics, and the primary disturbance gradient. The process-oriented watershed modeling approach used in this study provides a means to evaluate how natural landscape features interact with anthropogenic factors and assess their effects on flow characteristics and stream ecology. By combining watershed modeling and indirect ordination techniques, we were able to identify components of the hydrologic regime that have a considerable effect on aquatic-assemblage structure and help in developing short- and long-term management measures that mitigate the effects of anthropogenic disturbance in stream systems.

Kennen, J. G.; Kauffman, L. J.; Ayers, M. A.; Wolock, D. M.; Colarullo, S. J.

2008-01-01

265

Simulation and modeling of cohesive powder flow  

Microsoft Academic Search

Simulation and modeling of the flow behavior of cohesive powders are carried out through discrete element simulation (DES) and the kinetic theory of gas-based continuum model to gain a fundamental understanding of the cohesive powder flows. The cohesive forces between particles, such as van der Waal's forces, are accounted for by particle surface energy through a microscopic contact force model.

Hong Shang

1998-01-01

266

Assessing range management alternatives using simulation models  

Microsoft Academic Search

A methodology is proposed to assist land managers in decision making using simulation models as a tool. Two modes of analysis, point in time and time series, are presented, but all examples use the point in time technique. Examples used the EPIC model as the simulation model. The methodology allows land manager to use current technology in the decision making

1986-01-01

267

Verification, validation and accreditation of simulation models  

Microsoft Academic Search

The paper discusses verification, validation, and accreditation of simulation models. The different approaches to deciding model validity are presented; how model verification and validation relate to the model development process are discussed; various validation techniques are defined; conceptual model validity, model verification, operational validity, and data validity are described; ways to document results are given; a recommended procedure is presented;

Robert G. Sargent

2000-01-01

268

Theory, Modeling, and Simulation of Semiconductor Lasers  

NASA Technical Reports Server (NTRS)

Semiconductor lasers play very important roles in many areas of information technology. In this talk, I will first give an overview of semiconductor laser theory. This will be followed by a description of different models and their shortcomings in modeling and simulation. Our recent efforts in constructing a fully space and time resolved simulation model will then be described. Simulation results based on our model will be presented. Finally the effort towards a self-consistent and comprehensive simulation capability for the opto-electronics integrated circuits (OEICs) will be briefly reviewed.

Ning, Cun-Zheng; Saini, Subbash (Technical Monitor)

1998-01-01

269

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

270

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

271

Mathematics analysis and chaos in an ecological model with an impulsive control strategy  

NASA Astrophysics Data System (ADS)

In this paper, on the basis of the theories and methods of ecology and ordinary differential equation, an ecological model with an impulsive control strategy is established. By using the theories of impulsive equation, small amplitude perturbation skills and comparison technique, we get the condition which guarantees the global asymptotical stability of the lowest-level prey and mid-level predator eradication periodic solution. It is proved that the system is permanent. Further, influences of the impulsive perturbation on the inherent oscillation are studied numerically, which shows rich dynamics, such as period-doubling bifurcation, period-halving bifurcation, chaotic band, narrow or wide periodic window, chaotic crises,etc. Moreover, the computation of the largest Lyapunov exponent demonstrates the chaotic dynamic behavior of the model. At the same time, we investigate the qualitative nature of strange attractor by using Fourier spectra. All these results may be useful for study of the dynamic complexity of ecosystems.

Yu, Hengguo; Zhong, Shouming; Agarwal, Ravi P.

2011-02-01

272

Prediction of the environmental fate and aquatic ecological impact of nitrobenzene in the Songhua River using the modified AQUATOX model.  

PubMed

An accidental discharge of nitrobenzene happened in November 2005 in the Songhua River, China. The AQUATOX model was modified and adapted to simulate the time-dependent nitrobenzene distribution in this multimedia aquatic system and its potential ecological impacts. Nitrobenzene concentrations in flowing water, sediment, and biota were predicted. Based on the initial concentrations of nitrobenzene observed in the field during the accidental discharge, that is, 0.167-1.47 mg/L at different river segments, the predicted water concentrations of nitrobenzene would be lower than 0.02 and 0.002 mg/L after twenty days and one month, respectively. Both model prediction and field observation were in good agreement. The predicted nitrobenzene concentrations in sediments and aquatic organisms would be lower than 0.025 and 0.002 mg/kg, respectively, after two months. Among the environmental factors affecting nitrobenzene concentrations in water, inflow water dilution, water temperature, and initial concentration were the most important, by sensitivity analysis. Comparing the perturbed simulation and control simulation, the biomass changes for diatoms and mussel were significantly affected, whereas, no influence on other organisms could be predicted. Therefore the results indicated that nitrobenzene pollution in the Songhua River should have a limited impact on the benthos community. PMID:18814570

Lei, Bingli; Huang, Shengbiao; Qiao, Min; Li, Tianyun; Wang, Zijian

2008-01-01

273

Computer simulation and modeling in railway applications  

Microsoft Academic Search

An electrified railway system includes complex interconnections and interactions of several sub-systems. Computer simulation is the only viable means for system evaluation and analysis. This paper discusses the difficulties and requirements of effective simulation models for this specialized industrial application; and the development of a general-purpose multi-train simulator.

T. K. Ho; B. H. Mao; Z. Z. Yuan; H. D. Liu; Y. F. Fung

2002-01-01

274

Computer simulation and modeling in railway applications  

NASA Astrophysics Data System (ADS)

An electrified railway system includes complex interconnections and interactions of several sub-systems. Computer simulation is the only viable means for system evaluation and analysis. This paper discusses the difficulties and requirements of effective simulation models for this specialized industrial application; and the development of a general-purpose multi-train simulator.

Ho, T. K.; Mao, B. H.; Yuan, Z. Z.; Liu, H. D.; Fung, Y. F.

2002-02-01

275

The Social Ecological Model and Physical Activity in African American Women  

Microsoft Academic Search

Little is known about the social and contextual correlates (e.g., social norms, environment, social networks, and organizational\\u000a support) influencing the adoption and maintenance of regular physical activity among minority and underserved populations.\\u000a The purpose of this review was to apply the social ecological model to better understand physical activity among African American\\u000a women. A review of the literature pertaining to

Julie Fleury; Sarah M. Lee

2006-01-01

276

Ecological risk assessment of water environment for Luanhe River Basin based on relative risk model  

Microsoft Academic Search

The relative risk model (RRM) was applied in regional ecological risk assessments successfully. In this study, the RRM was\\u000a developed through increasing the data of risk source and introducing the source–stressor–habitat exposure filter (SSH), the\\u000a endpoint–habitat exposure filter (EH) and the stressor–endpoint effect filter (SE) to reflect the meaning of exposure and\\u000a effect more explicit. Water environment which include water

Jingling LiuQiuying ChenYongli Li; Qiuying Chen; Yongli Li

2010-01-01

277

A Generic Multibody Parachute Simulation Model  

NASA Technical Reports Server (NTRS)

Flight simulation of dynamic atmospheric vehicles with parachute systems is a complex task that is not easily modeled in many simulation frameworks. In the past, the performance of vehicles with parachutes was analyzed by simulations dedicated to parachute operations and were generally not used for any other portion of the vehicle flight trajectory. This approach required multiple simulation resources to completely analyze the performance of the vehicle. Recently, improved software engineering practices and increased computational power have allowed a single simulation to model the entire flight profile of a vehicle employing a parachute.

Neuhaus, Jason Richard; Kenney, Patrick Sean

2006-01-01

278

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

279

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...

280

Model Validation with Hybrid Dynamic Simulation  

SciTech Connect

Abstract—Model validation has been one of the central topics in power engineering studies for years. As model validation aims at obtaining reasonable models to represent actual behavior of power system components, it has been essential to validate models against actual measurements or known benchmark behavior. System-wide model simulation results can be compared with actual recordings. However, it is difficult to construct a simulation case for a large power system such as the WECC system and to narrow down to problematic models in a large system. Hybrid dynamic simulation with its capability of injecting external signals into dynamic simulation enables rigorous comparison of measurements and simulation in a small subsystem of interest. This paper presents such a model validation methodology with hybrid dynamic simulation. Two application examples on generator and load model validation are presented to show the validity of this model validation methodology. This methodology is further extended for automatic model validation and dichotomous subsystem model validation. A few methods to define model quality indices have been proposed to quantify model error for model validation criteria development.

Huang, Zhenyu; Kosterev, Dmitry; Guttromson, Ross T.; Nguyen, Tony B.

2006-06-22

281

Material Modeling for Terminal Ballistic Simulation.  

National Technical Information Service (NTIS)

Numerical simulation of terminal ballistic events requires quantitative modeling of the complex material responses which are observed to occur experimentally. This report discusses current deficiencies and future needs for material modeling in this contex...

G. Hauver, G. Randers-Pehrson, K. Kimsey, L. Magness, N. Huffington

1992-01-01

282

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

283

Simulation model for competitive bidding in construction  

Microsoft Academic Search

In this paper, bidding optimization procedures are summarized for the construction context, and a model design is proposed for use in simulating the bidding process and its complexities. Situations involving potentially large numbers of bidders are represented. The simulation model incorporates the variety typically representative of projects for which bids are submitted, as well as the tendency of bidders to

John Seydel

1994-01-01

284

Animation of Complex Construction Simulation Models  

Microsoft Academic Search

One of the major impediments in using computer simulation to model and optimize construction processes has been the fact that decision makers often do not have the training nor the time to check the validity of simulation models prepared by others and thus have little confidence in the results. Animation is an increasingly popular technique that can be used to

Photios G. Ioannou; Julio Martinez

285

Modelling and simulation in reactive polymer processing  

Microsoft Academic Search

Modelling and simulation in reactive polymer processing have been active research areas for the past decades in academic institutions as well as within the industry. Both areas have played a key role in advancing and optimizing reactive polymer processing operations. The objective of this paper is to review the two major classifications of models used to simulate polymer processes: physics

José M Castro; Mauricio Cabrera Ríos; Clark A Mount-Campbell

2004-01-01

286

Development of Multi Agent Simulation Modeling System \\  

Microsoft Academic Search

The mathematical model of multi agent resource conversion processes (RCP) is developed by the means of discrete-event simulation systems and expert systems. Within the framework of mathematical model RCP are defined: production system of the RCP structure, that taking into account conflicts origin. The discrete-event simulation and expert system \\

Konstantin A. Aksyonov; Elena F. Smoliy; Natalia V. Goncharova; Alexey A. Khrenov

2007-01-01

287

Resist profile simulation with fast lithography model  

NASA Astrophysics Data System (ADS)

A traditional approach to construct a fast lithographic model is to match wafer top-down SEM images, contours and/or gauge CDs with a TCC model plus some simple resist representation. This modeling method has been proven and is extensively used for OPC modeling. As the technology moves forward, this traditional approach has become insufficient in regard to lithography weak point detection, etching bias prediction, etc. The drawback of this approach is from metrology and simulation. First, top-down SEM is only good for acquiring planar CD information. Some 3D metrology such as cross-section SEM or AFM is necessary to obtain the true resist profile. Second, the TCC modeling approach is only suitable for planar image simulation. In order to model the resist profile, full 3D image simulation is needed. Even though there are many rigorous simulators capable of catching the resist profile very well, none of them is feasible for full-chip application due to the tremendous consumption of computational resource. The authors have proposed a quasi-3D image simulation method in the previous study [1], which is suitable for full-chip simulation with the consideration of sidewall angles, to improve the model accuracy of planar models. In this paper, the quasi-3D image simulation is extended to directly model the resist profile with AFM and/or cross-section SEM data. Resist weak points detected by the model generated with this 3D approach are verified on the wafer.

He, Yan-Ying; Chou, Chih-Shiang; Tang, Yu-Po; Huang, Wen-Chun; Liu, Ru-Gun; Gau, Tsai-Sheng

2014-03-01

288

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...

289

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

PubMed Central

Understanding factors that shape biodiversity and species coexistence across scales is of utmost importance in ecology, both theoretically and for conservation policies. Species-area relationships (SARs), measuring how the number of observed species increases upon enlarging the sampled area, constitute a convenient tool for quantifying the spatial structure of biodiversity. While general features of species-area curves are quite universal across ecosystems, some quantitative aspects can change significantly. Several attempts have been made to link these variations to ecological forces. Within the framework of spatially explicit neutral models, here we scrutinize the effect of varying the local population size (i.e. the number of individuals per site) and the level of habitat saturation (allowing for empty sites). We conclude that species-area curves become shallower when the local population size increases, while habitat saturation, unless strongly violated, plays a marginal role. Our findings provide a plausible explanation of why SARs for microorganisms are flatter than those for larger organisms.

Cencini, Massimo; Pigolotti, Simone; Munoz, Miguel A.

2012-01-01

290

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

291

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.

Petrovskii, Sergei; Petrovskaya, Natalia

2012-01-01

292

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.

Grimm, Volker; Railsback, Steven F.

2012-01-01

293

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

294

Forest Fire Ecology.  

ERIC Educational Resources Information Center

Presents a model that integrates high school science with the needs of the local scientific community. Describes how a high school ecology class conducted scientific research in fire ecology that benefited the students and a state park forest ecologist. (MKR)

Zucca, Carol; And Others

1995-01-01

295

A conceptual model for assessing ecological risk to water quality function of bottomland hardwood forests  

NASA Astrophysics Data System (ADS)

Ecological risk assessment provides a methodology for evaluating the threats to ecosystem function associated with environmental perturbations or stressors. This report documents the development of a conceptual model for assessing the ecological risk to the water quality function (WQF) of bottomland hardwood riparian ecosystems (BHRE) in the Tifton-Vidalia upland (TVU) ecoregion of Georgia. Previus research has demonstrated that mature BHRE are essential to maintaining water quality in this portion of the coastal plain. The WQF of these ecosystems is considered an assessment endpoit—an ecosystem function or set of functions that society chooses to value as evidenced by laws, regulations, or common usage. Stressors operate on ecosystems at risk through an exposure scenario to produce ecological effects that are linked to loss of the desired function or assessment end point. The WQF of BHRE is at risk because of the ecological and environmental quality effects of a suite of chemical, physical, and biological stressors. The stressors are related to nonpoint source pollution from adjacent land uses, especially agriculture; the conversion of BHRE to other land uses; and the encroachment of domestic animals into BHRE. Potential chemical, physical, and biological stressors to BHRE are identified, and the methodology for evaluating appropriate exposure scenarios is discussed. Field-scale and watershed-scale measurement end points of most use in assessing the effects of stressors on the WQF are identified and discussed. The product of this study is a conceptual model of how risks to the WQF of BHRE are produced and how the risk and associated uncertainties can be quantified.

Lowrance, Richard; Vellidis, George

1995-03-01

296

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

297

Numerical wind-speed simulation model  

SciTech Connect

A relatively simple stochastic model for simulating wind speed time series that can be used as an alternative to time series from representative locations is described in this report. The model incorporates systematic seasonal variation of the mean wind, its standard deviation, and the correlation speeds. It also incorporates systematic diurnal variation of the mean speed and standard deviation. To demonstrate the model capabilities, simulations were made using model parameters derived from data collected at the Hanford Meteorology Station, and results of analysis of simulated and actual data were compared.

Ramsdell, J.V.; Athey, G.F.; Ballinger, M.Y.

1981-09-01

298

Integrated Modeling for the Assessment of Ecological Impacts of Sea Level Rise  

NASA Astrophysics Data System (ADS)

Sea level rise (SLR) has the potential to affect a variety of coastal habitats with a myriad of deleterious ecological effects and to overwhelm human settlements along the coast. SLR should be given serious consideration when more than half of the U.S. population lives within 50 miles of the coast. SLR effects will be felt along coastal beaches and in estuarine waters, with consequences to barrier islands, submerged aquatic vegetation beds, sand and mud flats, oyster reefs, and tidal and freshwater wetlands. Managers of these coastal resources must be aware of potential consequences of SLR and adjust their plans accordingly to protect and preserve the resources under their care. The Gulf Coast provides critical habitats for a majority of the commercially important species in the Gulf of Mexico, which depend on inshore waters for either permanent residence or nursery area. The ecosystem services provided by these coastal habitats are at risk from rising sea level. Our team will assess the risk to coasts and coastal habitats from SLR in a 5-year project. We will apply existing models of circulation and transport from the watershed to the sea. The ultimate prediction will be of sediment loadings to the estuary as a result of overland flow, shoreline and barrier island erosion, and salinity transport, all of which will be used to model the evolution of intertidal marshes (MEM II). Over the five-year course of our research we will be simulating hydrodynamics and transport for all three NERRS reserves, including: Apalachicola, Weeks Bay and Grand Bay. The project will result in products whereby managers will be able to assess marshes, oyster reefs, submerged aquatic vegetation, predict wetland stability and indentify restoration locations for marsh and oyster habitats. In addition, we will produce Decision Support tools that will enable managers to predict future coastal erosion rates for management-specified shorelines. Project outcomes will enable the management community to prioritize risk management strategies, reformulate set back requirements, improve guidelines for construction of breakwaters and other coastal infrastructure, and assess water resources impacts and protection needs.

Hagen, S. C.; Lewis, G.; Bartel, R.; Batten, B.; Huang, W.; Morris, J.; Slinn, D. N.; Sparks, J.; Walters, L.; Wang, D.; Weishampel, J.; Yeh, G.

2010-12-01

299

Estimating population ecology models for the WWW market: evidence of competitive oligopolies.  

PubMed

This paper proposes adapting a particle filtering algorithm to model online Spanish real estate and job search market segments based on the Lotka-Volterra competition equations. For this purpose the authors use data on Internet information searches from Google Trends to proxy for market share. Market share evolution estimations are coherent with those observed in Google Trends. The results show evidence of low website incompatibility in the markets analyzed. Competitive oligopolies are most common in such low-competition markets, instead of the monopolies predicted by theoretical ecology models under strong competition conditions. PMID:23244754

de Cabo, Ruth Mateos; Gimeno, Ricardo

2013-01-01

300

An emergency medical system simulation model  

Microsoft Academic Search

This paper presents a SIMSCRIPT simulation model designed for general use by health systems planners in evaluating existing or proposed emergency medical systems. An extensive validation of the model was performed using actual data from the San Fernando Valley area of Los Angeles. Appropriate operating procedures for use of the model are discussed. In conclusion, an application of the model

James A. Fitzsimmons

1971-01-01

301

Modeling and simulation of blood collection systems.  

PubMed

This paper addresses the modeling and simulation of blood collection systems in France for both fixed site and mobile blood collection with walk in whole blood donors and scheduled plasma and platelet donors. Petri net models are first proposed to precisely describe different blood collection processes, donor behaviors, their material/human resource requirements and relevant regulations. Petri net models are then enriched with quantitative modeling of donor arrivals, donor behaviors, activity times and resource capacity. Relevant performance indicators are defined. The resulting simulation models can be straightforwardly implemented with any simulation language. Numerical experiments are performed to show how the simulation models can be used to select, for different walk in donor arrival patterns, appropriate human resource planning and donor appointment strategies. PMID:22048940

Alfonso, Edgar; Xie, Xiaolan; Augusto, Vincent; Garraud, Olivier

2012-03-01

302

Agent-based Modeling of Disrupted Market Ecologies: A Strategic Tool to Think and Learn With  

Microsoft Academic Search

For many years, computer modeling and simulations in business have been used for statistical analysis or for visual representations\\u000a of complex data. Recently, a new modeling approach has been developed—agent-based modeling—in which the agents in a complex simulated world interact with each other and the environment based on a set of often simple\\u000a rules. Agent-based models (ABM) were initially developed

Michael J. Jacobson; Mary Allison; Glen Ropella

303

Turning on the Heat: Ecological Response to Simulated Warming in the Sea  

PubMed Central

Significant warming has been observed in every ocean, yet our ability to predict the consequences of oceanic warming on marine biodiversity remains poor. Experiments have been severely limited because, until now, it has not been possible to manipulate seawater temperature in a consistent manner across a range of marine habitats. We constructed a “hot-plate” system to directly examine ecological responses to elevated seawater temperature in a subtidal marine system. The substratum available for colonisation and overlying seawater boundary layer were warmed for 36 days, which resulted in greater biomass of marine organisms and a doubling of space coverage by a dominant colonial ascidian. The “hot-plate” system will facilitate complex manipulations of temperature and multiple stressors in the field to provide valuable information on the response of individuals, populations and communities to environmental change in any aquatic habitat.

Smale, Dan A.; Wernberg, Thomas; Peck, Lloyd S.; Barnes, David K. A.

2011-01-01

304

Upscaling aquatic ecology: Pairing modern analytics with Big Data to simulate 2500 U.S. lakes  

NASA Astrophysics Data System (ADS)

Lakes are increasingly recognized as relevant engines in global processes, as recent estimates of the number of lakes and their contribution to biogeochemical cycles greatly exceed estimates from earlier assessments. Currently, our understanding of the diversity of physical controls on lake ecosystems is lacking, in part due to geographically limited observational campaigns and a failure to integrate Big Data products and informatics into modern limnological science practices. Momentum towards the interoperability of cyber-infrastructure in the fields of hydrology, climatology, remote sensing, and the geosciences has provided timely access to the pursuit of research aimed at upscaling our knowledge of the drivers of aquatic ecosystems. Here we share details of an open-source, standards-based data manipulation framework and one-dimensional model that were used to simulate water temperature dynamics for thousands of individual lakes. In addition to the automated scaling of gridded meteorological driver data, we integrated satellite estimates of water clarity and surrounding canopy heights in order to parameterize important lake-specific characteristics that influence lake physics. These methods keep terabyte-scale data off of the desktop through the use of web processing services, which performed many of our data-rich and computationally intensive tasks. We highlight results from a regional test-bed (the state of Wisconsin), as well as discuss opportunities for aquatic ecologists to leverage future pairings between Big Data and web-informatics. Supporting datasets include satellite imagery, space and airborne LIDAR, gridded climate reanalysis data, hydrography inventories, and citizen scientist measurements of water temperature; all components of the successful modeling of daily water temperature profiles for 2,500 lakes during 1979-2011. These results are being used to explain the long-term climate component of trends in the populations of two staples of the statewide fishery (bass and walleye). This framework can be used to capture hydrodynamic processes across the full distribution of lakes, removing many of the barriers to limnological research questions at global and continental scales. Future efforts could improve our estimates of greenhouse gas transfer, available thermal habitat, and the coupled physical-biogeochemical responses of lakes to climate change.

Read, J. S.; Winslow, L.; Hansen, G.; Van Den Hoek, J.; Markfort, C. D.; Booth, N.

2013-12-01

305

Forests, savannas and grasslands: bridging the knowledge gap between ecology and Dynamic Global Vegetation Models  

NASA Astrophysics Data System (ADS)

The forest, savanna, and grassland biomes, and the transitions between them, are expected to undergo major changes in the future, due to global climate change. Dynamic Global Vegetation Models (DGVMs) are very useful to understand vegetation dynamics under present climate, and to predict its changes under future conditions. However, several DGVMs display high uncertainty in predicting vegetation in tropical areas. Here we perform a comparative analysis of three different DGVMs (JSBACH, LPJ-GUESS-SPITFIRE and aDGVM) with regard to their representation of the ecological mechanisms and feedbacks that determine the forest, savanna and grassland biomes, in an attempt to bridge the knowledge gap between ecology and global modelling. Model outcomes, obtained including different mechanisms, are compared to observed tree cover along a mean annual precipitation gradient in Africa. Through these comparisons, and by drawing on the large number of recent studies that have delivered new insights into the ecology of tropical ecosystems in general, and of savannas in particular, we identify two main mechanisms that need an improved representation in the DGVMs. The first mechanism includes water limitation to tree growth, and tree-grass competition for water, which are key factors in determining savanna presence in arid and semi-arid areas. The second is a grass-fire feedback, which maintains both forest and savanna occurrences in mesic areas. Grasses constitute the majority of the fuel load, and at the same time benefit from the openness of the landscape after fires, since they recover faster than trees. Additionally, these two mechanisms are better represented when the models also include tree life stages (adults and seedlings), and distinguish between fire-prone and shade-tolerant savanna trees, and fire-resistant and shade-intolerant forest trees. Including these basic elements could improve the predictive ability of the DGVMs, not only under current climate conditions but also and especially under future scenarios.

Baudena, M.; Dekker, S. C.; van Bodegom, P. M.; Cuesta, B.; Higgins, S. I.; Lehsten, V.; Reick, C. H.; Rietkerk, M.; Scheiter, S.; Yin, Z.; Zavala, M. A.; Brovkin, V.

2014-06-01

306

Software-Engineering Process Simulation (SEPS) model  

NASA Technical Reports Server (NTRS)

The Software Engineering Process Simulation (SEPS) model is described which was developed at JPL. SEPS is a dynamic simulation model of the software project development process. It uses the feedback principles of system dynamics to simulate the dynamic interactions among various software life cycle development activities and management decision making processes. The model is designed to be a planning tool to examine tradeoffs of cost, schedule, and functionality, and to test the implications of different managerial policies on a project's outcome. Furthermore, SEPS will enable software managers to gain a better understanding of the dynamics of software project development and perform postmodern assessments.

Lin, C. Y.; Abdel-Hamid, T.; Sherif, J. S.

1992-01-01

307

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

2008-11-01

308

A mean field model for competition: from neutral ecology to the Red Queen.  

PubMed

Individual species are distributed inhomogeneously over space and time, yet, within large communities of species, aggregated patterns of biodiversity seem to display nearly universal behaviour. Neutral models assume that an individual's demographic prospects are independent of its species identity. They have successfully predicted certain static, time-independent patterns. But they have generally failed to predict temporal patterns, such as species ages or population dynamics. We construct a new, multispecies framework incorporating competitive differences between species, and assess the impact of this competition on static and dynamic patterns of biodiversity. We solve this model exactly for the special case of a Red Queen hypothesis, where fitter species are continually arising. The model predicts more realistic species ages than neutral models, without greatly changing predictions for static species abundance distributions. Our modelling approach may allow users to incorporate a broad range of ecological mechanisms. PMID:24924150

O'Dwyer, James P; Chisholm, Ryan

2014-08-01

309

Computer Simulation in Chemical Kinetics  

ERIC Educational Resources Information Center

Discusses the use of the System Dynamics technique in simulating a chemical reaction for kinetic analysis. Also discusses the use of simulation modelling in biology, ecology, and the social sciences, where experimentation may be impractical or impossible. (MLH)

Anderson, Jay Martin

1976-01-01

310

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...

311

Linking stressors and ecological responses  

USGS Publications Warehouse

To characterize risk, it is necessary to quantify the linkages and interactions between chemical, physical and biological stressors and endpoints in the conceptual framework for ecological risk assessment (ERA). This can present challenges in a multiple stressor analysis, and it will not always be possible to develop a quantitative stressor-response profile. This review commences with a conceptual representation of the problem of developing a linkage analysis for multiple stressors and responses. The remainder of the review surveys a variety of mathematical and statistical methods (e.g., ranking methods, matrix models, multivariate dose-response for mixtures, indices, visualization, simulation modeling and decision-oriented methods) for accomplishing the linkage analysis for multiple stressors. Describing the relationships between multiple stressors and ecological effects are critical components of 'effects assessment' in the ecological risk assessment framework.

Gentile, J.H.; Solomon, K.R.; Butcher, J.B.; Harrass, M.; Landis, W.G.; Power, M.; Rattner, B.A.; Warren-Hicks, W.J.; Wenger, R.

1999-01-01

312

Child Abuse: An Ecological Perspective.  

ERIC Educational Resources Information Center

Reviews various models for understanding, treating and preventing child abuse. Describes an ecological model of human behavior that provides a comprehensive perspective for integrating the diverse models. Discusses an ecological model of child abuse. (RJC)

Wiehe, Vernon R.

1989-01-01

313

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

314

Numerical Simulation of Unsteady Aerodynamic Models  

NASA Technical Reports Server (NTRS)

This report documents the results of the numerical simulations of unsteady aerodynamic models. The results focus on numerical accuracy and efficiency, and the robustness of the numerical methods. The aerodynamic models includes the classical Wagner and Kussner functions and the Leishman-Beddoes dynamic stall model. The simulations includes the numerical approximations of the Duhamel's integrals using both indicial (step) and impulse responses, the numerical integrations of the state-space models, and the exact solutions. The report also presents the conversion among different model representations.

Nguyen, Khanh Q.; Warmbrodt, William (Technical Monitor)

1997-01-01

315

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.

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

316

A Stochastic Simulation Model Of Family Income  

Microsoft Academic Search

This paper describes a stochastic simulation model of family income. Our goal is to implement a stochastic simulation experiment which provides an alternative view on the declining trend of U.S. real family income suggested in the joint study by The Children's Defense Fund and The Northeastern University's Center For Labor Studies. Thus, a major part of this paper is the

Jonathan Huntley; David Tepper; Thomas Wong

1993-01-01

317

A heteroskedastic error covariance matrix estimator using a first-order conditional autoregressive Markov simulation for deriving asympotical efficient estimates from ecological sampled Anopheles arabiensis aquatic habitat covariates  

PubMed Central

Background Autoregressive regression coefficients for Anopheles arabiensis aquatic habitat models are usually assessed using global error techniques and are reported as error covariance matrices. A global statistic, however, will summarize error estimates from multiple habitat locations. This makes it difficult to identify where there are clusters of An. arabiensis aquatic habitats of acceptable prediction. It is therefore useful to conduct some form of spatial error analysis to detect clusters of An. arabiensis aquatic habitats based on uncertainty residuals from individual sampled habitats. In this research, a method of error estimation for spatial simulation models was demonstrated using autocorrelation indices and eigenfunction spatial filters to distinguish among the effects of parameter uncertainty on a stochastic simulation of ecological sampled Anopheles aquatic habitat covariates. A test for diagnostic checking error residuals in an An. arabiensis aquatic habitat model may enable intervention efforts targeting productive habitats clusters, based on larval/pupal productivity, by using the asymptotic distribution of parameter estimates from a residual autocovariance matrix. The models considered in this research extends a normal regression analysis previously considered in the literature. Methods Field and remote-sampled data were collected during July 2006 to December 2007 in Karima rice-village complex in Mwea, Kenya. SAS 9.1.4® was used to explore univariate statistics, correlations, distributions, and to generate global autocorrelation statistics from the ecological sampled datasets. A local autocorrelation index was also generated using spatial covariance parameters (i.e., Moran's Indices) in a SAS/GIS® database. The Moran's statistic was decomposed into orthogonal and uncorrelated synthetic map pattern components using a Poisson model with a gamma-distributed mean (i.e. negative binomial regression). The eigenfunction values from the spatial configuration matrices were then used to define expectations for prior distributions using a Markov chain Monte Carlo (MCMC) algorithm. A set of posterior means were defined in WinBUGS 1.4.3®. After the model had converged, samples from the conditional distributions were used to summarize the posterior distribution of the parameters. Thereafter, a spatial residual trend analyses was used to evaluate variance uncertainty propagation in the model using an autocovariance error matrix. Results By specifying coefficient estimates in a Bayesian framework, the covariate number of tillers was found to be a significant predictor, positively associated with An. arabiensis aquatic habitats. The spatial filter models accounted for approximately 19% redundant locational information in the ecological sampled An. arabiensis aquatic habitat data. In the residual error estimation model there was significant positive autocorrelation (i.e., clustering of habitats in geographic space) based on log-transformed larval/pupal data and the sampled covariate depth of habitat. Conclusion An autocorrelation error covariance matrix and a spatial filter analyses can prioritize mosquito control strategies by providing a computationally attractive and feasible description of variance uncertainty estimates for correctly identifying clusters of prolific An. arabiensis aquatic habitats based on larval/pupal productivity.

Jacob, Benjamin G; Griffith, Daniel A; Muturi, Ephantus J; Caamano, Erick X; Githure, John I; Novak, Robert J

2009-01-01

318

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

319

Physical Modelling for Bipolar Device Simulation  

Microsoft Academic Search

Recent developments in physical models for device simulation are discussed. The dis­ cussion focusses on ihe incorporation of tunnelling effects in the generation-recombination of charge carriers, on the untried modelling of the majority and minority carrier mobility and on a resulting model for the bandgap narrowing valid for both n- and p-type silicon,

D. B. M. Klaassen

320

Contact Model for Haptic Medical Simulations  

Microsoft Academic Search

In surgery simulation, precise contact modeling is essential to obtain both realistic behavior and convincing haptic feedback. When instruments create deformations on soft tissues, they modify the bound- ary conditions of the models and will mainly modify their behavior. Yet, most recent work has focused on the more precise modeling of soft tissues while improving eciency; but this eort is

Guillaume Saupin; Christian Duriez; Stephane Cotin

2008-01-01

321

Modeling Human Tissues for Medical Simulators  

Microsoft Academic Search

Simulators could help to train practitioners for modern medicalprocedures. From this arises the need to model human anatomical structuresaccurately. We propose a methodology to model such structures in interactivetime. These techniques are then applied to model the heterogenous structure ofa human liver and non-linear behavior of the human thigh. The method usedfor parameter estimation is explained through the example of

C. Laugier; F. Boux De Casson

2000-01-01

322

Power Plant Models for Operator Training Simulators  

Microsoft Academic Search

Models for power plants have been developed over several decades for use in long term dynamic simulation of large power systems. These models are derived from, but are significantly simpler than, models used for studying power plants. This is because in system studies, as opposed to power plant studies, only the trajectories of the output variables of many plants are

Vani Kola; Anjan Bose; Paul M. Anderson

1989-01-01

323

Maintenance Personnel Performance Simulation (MAPPS) model  

SciTech Connect

A stochastic computer model for simulating the actions and behavior of nuclear power plant maintenance personnel is described. The model considers personnel, environmental, and motivational variables to yield predictions of maintenance performance quality and time to perform. The mode has been fully developed and sensitivity tested. Additional evaluation of the model is now taking place.

Siegel, A.I.; Bartter, W.D.; Wolf, J.J.; Knee, H.E.; Haas, P.M.

1984-01-01

324

Traffic simulation using agent-based models  

Microsoft Academic Search

In this paper we will build a computer traffic model simulating movement of each individual vehicle through the traffic network and the interactions of that vehicle with other vehicles and semaphores (an agent-based model). It will model a simple traffic network (a two-way coordinated semaphore system a.k.a. \\

V. Ljubovic

2009-01-01

325

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

326

Structural model uncertainty in stochastic simulation  

SciTech Connect

Prediction uncertainty in stochastic simulation models can be described by a hierarchy of components: stochastic variability at the lowest level, input and parameter uncertainty at a higher level, and structural model uncertainty at the top. It is argued that a usual paradigm for analysis of input uncertainty is not suitable for application to structural model uncertainty. An approach more likely to produce an acceptable methodology for analyzing structural model uncertainty is one that uses characteristics specific to the particular family of models.

McKay, M.D.; Morrison, J.D. [Los Alamos National Lab., NM (United States). Technology and Safety Assessment Div.

1997-09-01

327

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

328

Simulation of Solute Transport: A Multinomial Model.  

National Technical Information Service (NTIS)

A direct simulation method has been developed that uses a distribution function to model solute transport along a streamtube. During each timestep, the aqueous solution at each node is transported to the other downstream nodes according to the distributio...

C. J. Hostetler B. E. Opitz

1985-01-01

329

Building Fire Simulation Model, Volume 1.  

National Technical Information Service (NTIS)

The Building Fire Simulation Model (BFSM) provides information for improving fire tests and fire investigations. It provides a means of improving the quality of information used in code provision equipment and can assist in establishing equivalency for fi...

J.A. Swartz R.F. Fahy E.M. Connelly D.P. Demers

1983-01-01

330

Optimization of Multiple-Response Simulation Models.  

National Technical Information Service (NTIS)

This report describes several computerized multiple-variable, multiple-response optimization procedures for use in connection with computer simulation models. These procedures include complex search, a sequential first-order response surface approach, a s...

W. E. Biles

1978-01-01

331

Atmospheric Modeling and Sensor Simulation (AMASS) Study.  

National Technical Information Service (NTIS)

The capabilities of the atmospheric modeling and sensor simulation (AMASS) system were studied in order to enhance them. This system is used in processing atmospheric measurements which are utilized in the evaluation of sensor performance, conducting desi...

K. G. Parker

1984-01-01

332

Multiscale Modeling and Simulation of Material Processing.  

National Technical Information Service (NTIS)

This project is on the development of scaling laws for multiscale simulations from atomistic to continuum using material testing techniques, such as tension and indentation. The main objective is to address critical issues involved in modeling. Specific p...

H. Lu L. Raff R. Komanduri S. Roy

2006-01-01

333

Mathematical Modeling of Simulated Photochemical Smog.  

National Technical Information Service (NTIS)

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 ...

G. Z. Whitten H. Hogo

1977-01-01

334

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...

335

MODELING CONCEPTS FOR BMP/LID SIMULATION  

EPA Science Inventory

Enhancement of simulation options for stormwater best management practices (BMPs) and hydrologic source control is discussed in the context of the EPA Storm Water Management Model (SWMM). Options for improvement of various BMP representations are presented, with emphasis on inco...

336

Modeling and Simulation of Liquid Molding Processes.  

National Technical Information Service (NTIS)

Outline of presentation: LIMS simulation package development; changes and additions, LIMS UI extensions and development, and LIMS distribution made available; Addressing practical processing issues; Modeling issues, perform and distribution media deformat...

P. Simacek

2003-01-01

337

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

338

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...

339

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

340

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

341

Optimising the management of complex dynamic ecosystems. An ecological-economic modelling approach  

Microsoft Academic Search

Keywords: ecological-economic modelling; ecosystem services; resource use; efficient; sustainability; wetlands, rangelands.<\\/span><\\/o:p><\\/span>

Ecosystems supply a wide range of goods and services to mankind. This includes, for example, timber supplied by forests, and animal feed supplied by rangeland systems. In addition, ecosystems supply a range of essential life support services, such as the regulation of climatic

L. G. Hein

2005-01-01

342

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

343

Numerical simulation of direct injection gasoline engine model  

Microsoft Academic Search

Direct Injection Gasoline different numerical simulation models were analyzed. There are three kinds of the numerical simulation of turbulent: direct numerical simulation, large eddy simulation and Reynolds averaged simulation. Direct numerical simulation of turbulence modeling without using the numerical calculation solves the flow equations directly. Large eddy simulation of the main idea is: use of large-scale direct numerical solution of

Yongfeng Liu; Pucheng Pei; Yong Lu

2011-01-01

344

Adversary Modeling and Simulation in Cyber Warfare  

Microsoft Academic Search

Modeling and simulation provide many excellent benefits in preparation for successful cyber operations. Whether used for creating\\u000a realistic training environments, testing new cyber warfare techniques, or predicting possible adversary actions, it is critical\\u000a for such simulations to take into account the possibility of an active cyber adversary, able to adapt its plans to network\\u000a conditions. Without realtime high fidelity modeling

Samuel N. Hamilton; Wendy L. Hamilton

2008-01-01

345

Simulation models for terminal homing of KEW  

Microsoft Academic Search

Generic models for a realistic simulation of a kinetic energy weapon in the terminal homing mode are studied. While these models are functional in nature and do not describe the hardware characteristics, they do describe the input-output characteristics of the state-of-the-art tactical hardware which they represent. For terminal homing simulation, a KEW was designed in sufficient detail to compute masses

Gano B. Chatterji; Robert D. Curley; Richard A. Bortins

1988-01-01

346

NUMERICAL SIMULATION OF 2-DIMENSIONAL PROPERTY FOR ECOLOGICAL IMPACTS WITH GROWTH AND DECAY OF MACROPHYTES IN THE SOUTHERN LAKE BIWA  

NASA Astrophysics Data System (ADS)

Lake ecosystems can be viewed as complex systems where organisms and materials interact in many ways. The features of complex systems are two. One is nonlinear interaction, and another is effect of network formation between organisms and materials. A regime shift is a result of repetition by a chain of both effects. Water level operation of Lake Biwa causes serious concern with an influence on the ecosystem. Concretely, a state shift from turbid water to clear water may occur in response to thickness of macrophytes in the Southern Lake Biwa. It would appear that phenomenon of a regime shift occurred. In this paper, we predict a regime shift for the lake. Water quality analysis model is developed under a multi-layered model to predict 2-dimensional property of water quality through a year in the lake. This study illustrates ecological impacts of the water level operation through numerical experiments.

Nagamatsu, Yu; Kawaguchi, Tomoya; Ikari, Satoshi

347

Modeling post-fledging survival of lark buntings in response to ecological and biological factors  

USGS Publications Warehouse

We evaluated the influences of several ecological, biological, and methodological factors on post-fledging survival of a shortgrass prairie bird, the Lark Bunting (Calamospiza melanocorys). We estimated daily post-fledging survival (n = 206, 82 broods) using radiotelemetry and color bands to track fledglings. Daily survival probabilities were best explained by drought intensity, time in season (quadratic trend), ages a??3 d post-fledging, and rank given drought intensity. Drought intensity had a strong negative effect on survival. Rank was an important predictor of fledgling survival only during the severe drought of 2002 when the smallest fledglings had lower survival. Recently fledged young (ages a??3 d post-fledging) undergoing the transition from nest to surrounding habitat experienced markedly lower survival, demonstrating the vulnerable nature of this time period. Survival was greater in mid and late season than early season, corresponding to our assumptions of food availability. Neither mark type nor sex of attending parent influenced survival. The model-averaged product of the 22-d survival calculated using mean rank and median value of time in season was 0.360 A? 0.08 in 2001 and 0.276 A? 0.08 in 2002. Survival estimates that account for age, condition of young, ecological conditions, and other factors are important for parameterization of realistic population models. Biologists using population growth models to elucidate mechanisms of population declines should attempt to estimate species-specific of post-fledging survival rather than use generalized estimates.

Yackel Adams, A.A.; Skagen, S.K.; Savidge, J.A.

2006-01-01

348

An assessment of several of the historically most influential theoretical models used in ecology and of the data provided in their support  

Microsoft Academic Search

Hall, C.A.S., 1988. An assessment of several of the historically most influential theoretical models used in ecology and of the data provided in their support. Ecol. Modelling, 43: 5-31. Certain theoretical models (the logistic, Lotka-Volterra and density-dependent stock recruitment models in fisheries) and their mathematical representations are used pervasively in the teaching of ecology and in the application of ecology

CHARLES A. S. HALL

1988-01-01

349

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

350

A simulation model of an insect population  

NSDL National Science Digital Library

An insect life table simulation developed by Hein Bijlmakers. The above URL gets you to the introduction of the simulation model where various aspects of an insect population dynamics are explained. The link to the simulation brings you to the model itself with a myriad of variables including population development; egg; larval; pupal and adult mortality by parasitoids and predators amongst others. This is a great tool to investigate various aspects of insect population dynamics allowing one to investigate the impact of a number of variables on a population and may help students understand the function of insect life tables. Up to 40 generations can be iterated.

0002-11-30

351

European larch phenology in the Alps: can we grasp the role of ecological factors by combining field observations and inverse modelling?  

NASA Astrophysics Data System (ADS)

Vegetation phenology is strongly influenced by climatic factors. Climate changes may cause phenological variations, especially in the Alps which are considered to be extremely vulnerable to global warming. The main goal of our study is to analyze European larch ( Larix decidua Mill.) phenology in alpine environments and the role of the ecological factors involved, using an integrated approach based on accurate field observations and modelling techniques. We present 2 years of field-collected larch phenological data, obtained following a specifically designed observation protocol. We observed that both spring and autumn larch phenology is strongly influenced by altitude. We propose an approach for the optimization of a spring warming model (SW) and the growing season index model (GSI) consisting of a model inversion technique, based on simulated look-up tables (LUTs), that provides robust parameter estimates. The optimized models showed excellent agreement between modelled and observed data: the SW model predicts the beginning of the growing season (BGS) with a mean RMSE of 4 days, while GSI gives a prediction of the growing season length (LGS) with a RMSE of 5 days. Moreover, we showed that the original GSI parameters led to consistent errors, while the optimized ones significantly increased model accuracy. Finally, we used GSI to investigate interactions of ecological factors during springtime development and autumn senescence. We found that temperature is the most effective factor during spring recovery while photoperiod plays an important role during autumn senescence: photoperiod shows a contrasting effect with altitude decreasing its influence with increasing altitude.

Migliavacca, M.; Cremonese, E.; Colombo, R.; Busetto, L.; Galvagno, M.; Ganis, L.; Meroni, M.; Pari, E.; Rossini, M.; Siniscalco, C.; Morra di Cella, U.

2008-09-01

352

LAKE WATER TEMPERATURE SIMULATION MODEL  

EPA Science Inventory

Functional relationships to describe surface wind mixing, vertical turbulent diffusion, convective heat transfer, and radiation penetration based on data from lakes in Minnesota have been developed. hese relationships have been introduced by regressing model parameters found eith...

353

Dynamic modeling and simulation of planetary rovers  

NASA Technical Reports Server (NTRS)

This paper documents a preliminary study into the dynamic modeling and computer simulation of wheeled surface vehicles. The research centered on the feasibility of using commercially available multibody dynamics codes running on engineering workstations to perform the analysis. The results indicated that physically representative vehicle mechanics can be modeled and simulated in state-of-the-art Computer Aided Engineering environments, but at excessive cost in modeling and computation time. The results lead to the recommendation for the development of an efficient rover mobility-specific software system. This system would be used for vehicle design and simulation in planetary environments; controls prototyping, design, and testing; as well as local navigation simulation and expectation planning.

Lindemann, Randel A.

1992-01-01

354

Model simulations of DNA denaturation dynamics  

NASA Astrophysics Data System (ADS)

We present a model of DNA for use in computer simulations. This model is simple enough to allow long-time large-scale dynamics simulations, while, on the other hand, it is sophisticated enough to describe both double stranded and single stranded DNA and the transition between the two. We employed our simple model in the simulation of denaturation of double stranded DNA helices using Langevin dynamics. These are the first simulations of its kind of DNA denaturation. We have studied the melting behavior for several short double-stranded sequences of different composition. Duplexes of different lengths were considered, and also base pair mismatches were included in the study. Results are in good agreement with experimental data.

Drukker, Karen; Wu, Guosheng; Schatz, George C.

2001-01-01

355

Interactive communications systems simulation model (ICSSM)  

NASA Astrophysics Data System (ADS)

The Interactive Communication Systems Simulation Model (ICSSM) developed for Rome Air Development Center is capable of simulating a point-to-point communication system including its functional elements, components, propagation effects, and transmission media. The ICSSM is a flexible, expandable, sophisticated and easy-to-use computerized means to develop or configure communication system specific simulation models; specify and validate system requirements; evaluate new techniques and assess the performance of existing and proposed conventional and ECCM communications systems and equipment. The ICSSM's preconfigured programming structure frees the analyst from the burden of constructing a special simulation framework for each model effort, thus permitting him to concentrate on the model formulation itself. Further, the analyst may benefit from the legacy of previous modeling via the ICSSM library of communication model elements which are supported by computerized tutorials and guides. The development of the initial ICSSM concentrated on efficient system structure, a generalized simulation capability and on making the system easy to use. The ICSSM increases in utility with continued use as additional modeling elements are incorporated in the expandable library.

Paolicelli, J.; Griese, W. F.

1980-12-01

356

Interactive communication systems simulation model (ICSSM) extension  

NASA Astrophysics Data System (ADS)

The Interactive Communication System Simulation Model (ICSSM), developed for the Rome Air Development Center, is capable of simulating a point-to-point communication system including its functional elements, components, propagation effects, and transmission media. The ICSSM is a flexible, expandable, sophisticated and easy-to-use computerized means to develop or configure communication system specific simulation models; specify and validate system requirements; evaluate new techniques and assess the performance of existing and proposed conventional and ECCM communications systems and equipment. The ICSSM's preconfigured programming structure frees the analyst from the burden of constructing a special simulation framework for each model effort, thus permitting him to concentrate on the model formulation itself. Further, the analyst may benefit from the legacy of previous modeling via the ICSSM library of communication model elements which are supported by computerized tutorials and guides. The development of the initial ICSSM concentrated on efficient system structure, a generalized simulation capability and on making the system easy to use. The ICSSM increases in utility with continued use as additional modeling elements are incorporated into the expandable library.

Gerry, I.; Mammone, M.; Wade, W. D.

1983-07-01

357

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

358

Computer modeling of the biotic cycle formation in a closed ecological system.  

PubMed

The process of biotic turnover in a closed ecological system (CES) with an external energy flow was analyzed by mathematical modeling of the biotic cycle formation. The formation of hierarchical structure in model CESs is governed by energy criteria. Energy flow through the ecosystem increases when a predator is introduced into a "producer-reducer" system at steady state. Analysis of the model shows that under certain conditions the presence of the primary predator with its high mineralization ability accelerates the biotic turnover measured by primary production. We, therefore, conclude that for every system it is possible to find a suitable predator able to provide the system with a higher biotic turnover rate and energy consumption. Grant numbers: 99-04-96017/2000. PMID:11695440

Brilkov, A V; Ganusov, V V; Morozova, E V; Pechurkin, N S

2001-01-01

359

Perpest model, a case-based reasoning approach to predict ecological risks of pesticides.  

PubMed

The PERPEST model is a model that predicts the ecological risks of pesticides in freshwater ecosystems. This model simultaneously predicts the effects of a particular concentration of a pesticide on various (community) endpoints. In contrast to most effect models, PERPEST is based on empirical data extracted from the literature. This model is based on case-based reasoning, a technique that solves new problems (e.g., what is the effect of pesticide A?) by using past experience (e.g., published microcosm experiments). The database containing the past experience has been constructed by performing a review of freshwater model ecosystem studies. This review assessed the effects on various endpoints (e.g., community metabolism, phytoplankton, and macroinvertebrates) and classified them according to their magnitude and duration. The PERPEST model searches for analogous situations in the database, based on relevant (toxicity) characteristics of the compound. This allows the model to predict effects of pesticides for which no effects on a semifield scale have been published. The PERPEST model results in a prediction showing the probability of classes of effects (no, slight, or clear effects, plus an optional indication of recovery) on the various grouped endpoints. This paper discusses the scientific background of the model as well as its strengths, limitations, and possible applications. PMID:12389932

van den Brink, Paul J; Roelsma, Jan; Van Nes, Egbert H; Scheffer, Marten; Brock, Theo C M

2002-11-01

360

Agent-based Modeling and Simulation  

Microsoft Academic Search

Agent-based modeling and simulation (ABMS) is a new approach to modeling systems comprised of autonomous, interacting agents. Computational advances have made possible a growing number of agent-based models across a variety of application domains. Applications range from modeling agent behavior in the stock market, supply chains, and consumer markets, to predicting the spread of epidemics, mitigating the threat of bio-warfare,

Charles M. Macal; Michael J. North

2009-01-01

361

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

362

The causal pie model: an epidemiological method applied to evolutionary biology and ecology.  

PubMed

A general concept for thinking about causality facilitates swift comprehension of results, and the vocabulary that belongs to the concept is instrumental in cross-disciplinary communication. The causal pie model has fulfilled this role in epidemiology and could be of similar value in evolutionary biology and ecology. In the causal pie model, outcomes result from sufficient causes. Each sufficient cause is made up of a "causal pie" of "component causes". Several different causal pies may exist for the same outcome. If and only if all component causes of a sufficient cause are present, that is, a causal pie is complete, does the outcome occur. The effect of a component cause hence depends on the presence of the other component causes that constitute some causal pie. Because all component causes are equally and fully causative for the outcome, the sum of causes for some outcome exceeds 100%. The causal pie model provides a way of thinking that maps into a number of recurrent themes in evolutionary biology and ecology: It charts when component causes have an effect and are subject to natural selection, and how component causes affect selection on other component causes; which partitions of outcomes with respect to causes are feasible and useful; and how to view the composition of a(n apparently homogeneous) population. The diversity of specific results that is directly understood from the causal pie model is a test for both the validity and the applicability of the model. The causal pie model provides a common language in which results across disciplines can be communicated and serves as a template along which future causal analyses can be made. PMID:24963386

Wensink, Maarten; Westendorp, Rudi G J; Baudisch, Annette

2014-05-01

363

The causal pie model: an epidemiological method applied to evolutionary biology and ecology  

PubMed Central

A general concept for thinking about causality facilitates swift comprehension of results, and the vocabulary that belongs to the concept is instrumental in cross-disciplinary communication. The causal pie model has fulfilled this role in epidemiology and could be of similar value in evolutionary biology and ecology. In the causal pie model, outcomes result from sufficient causes. Each sufficient cause is made up of a “causal pie” of “component causes”. Several different causal pies may exist for the same outcome. If and only if all component causes of a sufficient cause are present, that is, a causal pie is complete, does the outcome occur. The effect of a component cause hence depends on the presence of the other component causes that constitute some causal pie. Because all component causes are equally and fully causative for the outcome, the sum of causes for some outcome exceeds 100%. The causal pie model provides a way of thinking that maps into a number of recurrent themes in evolutionary biology and ecology: It charts when component causes have an effect and are subject to natural selection, and how component causes affect selection on other component causes; which partitions of outcomes with respect to causes are feasible and useful; and how to view the composition of a(n apparently homogeneous) population. The diversity of specific results that is directly understood from the causal pie model is a test for both the validity and the applicability of the model. The causal pie model provides a common language in which results across disciplines can be communicated and serves as a template along which future causal analyses can be made.

Wensink, Maarten; Westendorp, Rudi G J; Baudisch, Annette

2014-01-01

364

Applying trait-based models to achieve functional targets for theory-driven ecological restoration.  

PubMed

Manipulating community assemblages to achieve functional targets is a key component of restoring degraded ecosystems. The response-and-effect trait framework provides a conceptual foundation for translating restoration goals into functional trait targets, but a quantitative framework has been lacking for translating trait targets into assemblages of species that practitioners can actually manipulate. This study describes new trait-based models that can be used to generate ranges of species abundances to test theories about which traits, which trait values and which species assemblages are most effective for achieving functional outcomes. These models are generalisable, flexible tools that can be widely applied across many terrestrial ecosystems. Examples illustrate how the framework generates assemblages of indigenous species to (1) achieve desired community responses by applying the theories of environmental filtering, limiting similarity and competitive hierarchies, or (2) achieve desired effects on ecosystem functions by applying the theories of mass ratios and niche complementarity. Experimental applications of this framework will advance our understanding of how to set functional trait targets to achieve the desired restoration goals. A trait-based framework provides restoration ecology with a robust scaffold on which to apply fundamental ecological theory to maintain resilient and functioning ecosystems in a rapidly changing world. PMID:24766299

Laughlin, Daniel C

2014-07-01

365

Empirical social-ecological system analysis: from theoretical framework to latent variable structural equation model.  

PubMed

The social-ecological system (SES) approach to natural resource management holds enormous promise towards achieving sustainability. Despite this promise, social-ecological interactions are complex and elusive; they require simplification to guide effective application of the SES approach. The complex, adaptive and place-specific nature of human-environment interactions impedes determination of state and trends in SES parameters of interest to managers and policy makers. Based on a rigorously developed systemic theoretical model, this paper integrates field observations, interviews, surveys, and latent variable modeling to illustrate the development of simplified and easily interpretable indicators of the state of, and trends in, relevant SES processes. Social-agricultural interactions in the Logone floodplain, in the Lake Chad basin, served as case study. This approach is found to generate simplified determinants of the state of SESs, easily communicable across the array of stakeholders common in human-environment interactions. The approach proves to be useful for monitoring SESs, guiding interventions, and assessing the effectiveness of interventions. It incorporates real time responses to biophysical change in understanding coarse scale processes within which finer scales are embedded. This paper emphasizes the importance of merging quantitative and qualitative methods for effective monitoring and assessment of SESs. PMID:18773239

Asah, Stanley Tanyi

2008-12-01

366

System Modeling to Improve the Hydro-Ecological Performance of Diked Wetlands  

NASA Astrophysics Data System (ADS)

Managing scarce water resources and invasive vegetation are common problems in wetlands. A systems model was developed to recommend water allocations and vegetation control actions among diked wetland units that will improve wetland habitat for bird species. Model recommendations are subject to constraints such as water availability, spatial connectivity of wetland units, hydraulic infrastructure capacities, vegetation growth and responses to management activities, plus financial and time resources available to manage water and invasive vegetation. Wetland habitat performance is quantified using two performance metrics. The first metric is a habitat suitability index (H) that represents the capacity of a given habitat attribute (such as water depth or vegetation cover) to support selected bird species. Suitability ranges from 0 (poor) to 1 (excellent) habitat quality. We combine the habitat suitability of water depth and vegetation coverage, weight by species and the wetted surface area to create the second metric defined as the weighted usable area for wetlands (WU). The WU represents the available surface area that provides suitable hydrological and ecological conditions for priority bird species. We apply the model at the Bear River Migratory Bird Refuge (the Refuge), which is the largest wetland complex on the Great Salt Lake, Utah. The Refuge provides important habitat for large populations of migratory birds that follow the North American Pacific and Central Flyways. Wetland managers and stakeholders participated throughout this study from identifying the problem, defining performance metrics, collecting data, through interpreting results. We ran the model for a base case representing hydrologic conditions in 2008 and eight scenarios that independently considered changes in water availability, financial budget, vegetation responses, and gate operation. Results of these analysis show that performance of wetland habitat are more affected by changes in vegetation response and water allocation than changes in gate operation or the financial budget available to reduce invasive vegetation. Also, comparison between the base case scenario of optimized management and past management activities show there are opportunities to increase by almost 2-fold the hydro-ecological performance of wetland habitat. This participatory modeling effort provides a general framework to develop and apply hydro-ecological performance metrics, model wetland habitat, and improve management in diked wetlands.

Alminagorta, O.; Rosenberg, D. E.; Kettenring, K.

2012-12-01

367

Using historical and projected future climate model simulations as drivers of agricultural and biological models (Invited)  

NASA Astrophysics Data System (ADS)

Climate model evaluation is frequently performed as a first step in analyzing climate change simulations. Atmospheric scientists are accustomed to evaluating climate models through the assessment of model climatology and biases, the models' representation of large-scale modes of variability (such as ENSO, PDO, AMO, etc) and the relationship between these modes and local variability (e.g. the connection between ENSO and the wintertime precipitation in the Southeast US). While these provide valuable information about the fidelity of historical and projected climate model simulations from an atmospheric scientist's point of view, the application of climate model data to fields such as agriculture, ecology and biology may require additional analyses focused on the particular application's requirements and sensitivities. Typically, historical climate simulations are used to determine a mapping between the model and observed climate, either through a simple (additive for temperature or multiplicative for precipitation) or a more sophisticated (such as quantile matching) bias correction on a monthly or seasonal time scale. Plants, animals and humans however are not directly affected by monthly or seasonal means. To assess the impact of projected climate change on living organisms and related industries (e.g. agriculture, forestry, conservation, utilities, etc.), derivative measures such as the heating degree-days (HDD), cooling degree-days (CDD), growing degree-days (GDD), accumulated chill hours (ACH), wet season onset (WSO) and duration (WSD), among others, are frequently useful. We will present a comparison of the projected changes in such derivative measures calculated by applying: (a) the traditional temperature/precipitation bias correction described above versus (b) a bias correction based on the mapping between the historical model and observed derivative measures themselves. In addition, we will present and discuss examples of various application-based climate model evaluations, such as: (a) agricultural crop yield estimates and (b) species population viability estimates modeled using observed climate data vs. historical climate simulations.

Stefanova, L. B.

2013-12-01

368

Revolutions in energy through modeling and simulation  

SciTech Connect

The development and application of energy technologies for all aspects from generation to storage have improved dramatically with the advent of advanced computational tools, particularly modeling and simulation. Modeling and simulation are not new to energy technology development, and have been used extensively ever since the first commercial computers were available. However, recent advances in computing power and access have broadened the extent and use, and, through increased fidelity (i.e., accuracy) of the models due to greatly enhanced computing power, the increased reliance on modeling and simulation has shifted the balance point between modeling and experimentation. The complex nature of energy technologies has motivated researchers to use these tools to understand better performance, reliability and cost issues related to energy. The tools originated in sciences such as the strength of materials (nuclear reactor containment vessels); physics, heat transfer and fluid flow (oil production); chemistry, physics, and electronics (photovoltaics); and geosciences and fluid flow (oil exploration and reservoir storage). Other tools include mathematics, such as statistics, for assessing project risks. This paper describes a few advancements made possible by these tools and explores the benefits and costs of their use, particularly as they relate to the acceleration of energy technology development. The computational complexity ranges from basic spreadsheets to complex numerical simulations using hardware ranging from personal computers (PCs) to Cray computers. In all cases, the benefits of using modeling and simulation relate to lower risks, accelerated technology development, or lower cost projects.

Tatro, M.; Woodard, J.

1998-08-01

369

Needle insertion modeling and simulation  

Microsoft Academic Search

Abstract—A methodology for estimating the force distribution that occurs along a needle shaft during insertion is described. An experimental system for measuring planar tissue phantom defor- mation during needle insertions has been developed and is pre- sented. A two-dimensional linear elastostatic material model, dis- cretised using the finite element method, is used to derive con- tact force information that is

Simon Peter DiMaio; Septimiu E. Salcudean

2003-01-01

370

Aquilegia as a model system for the evolution and ecology of petals  

PubMed Central

The ranunculid genus Aquilegia holds extraordinary promise as a model system for investigating a wide range of questions relating to the evolution and ecology of petals. New genetic and genomic resources, including an extensive EST database, BAC libraries and physical maps, as well as virus-induced gene silencing are facilitating this research on multiple fronts. At the developmental genetic level, Aquilegia has been important for elucidating the developmental programme for specifying petals and petaloid characteristics. Data suggest that duplication events among the petal and stamen identity genes have resulted in sub- and neofunctionalization. This expansion of gene function does not include the petaloidy of Aquilegia sepals, however, which does not depend on the same loci that control identity of the second whorl petals. Of special interest is the elaboration of the petal into a nectar spur, a major innovation for the genus. Intra- and interspecific variation in the shape and colour of petals, especially the spurs, has been shown to be adaptative for different pollinators. Thus, understanding the genetic basis of these traits will help us connect the ecological interactions driving speciation with the genetic changes responsible for remodelling morphology. Progress in this area has focused on the multiple, parallel transitions in flower colour and nectar spur length across the genus. For flower colour, upstream transcription factors appear to be primarily targets of natural selection. Thus research in Aquilegia spans the initial evolution of petals and petaloidy to the diversification of petal morphology to the ecological basis of petal form, thereby providing a comprehensive picture of the evolutionary biology of this critical angiosperm feature.

Kramer, Elena M.; Hodges, Scott A.

2010-01-01

371

Rotor systems research aircraft simulation mathematical model  

NASA Technical Reports Server (NTRS)

An analytical model developed for evaluating and verifying advanced rotor concepts is discussed. The model was used during in both open loop and real time man-in-the-loop simulation during the rotor systems research aircraft design. Future applications include: pilot training, preflight of test programs, and the evaluation of promising concepts before their implementation on the flight vehicle.

Houck, J. A.; Moore, F. L.; Howlett, J. J.; Pollock, K. S.; Browne, M. M.

1977-01-01

372

Regularization modeling for large-eddy simulation  

Microsoft Academic Search

A new modeling approach for large-eddy simulation (LES) is obtained by combining a ``regularization principle'' with an explicit filter and its inversion. This regularization approach allows a systematic derivation of the implied subgrid model, which resolves the closure problem. The central role of the filter in LES is fully restored, i.e., both the interpretation of LES predictions in terms of

Bernard J. Geurts; Darryl D. Holm

2003-01-01

373

Modeling, simulation and control of a spincopter  

Microsoft Academic Search

In this article we present a mathematical model of a spincopter - an inherently stable and easy to control unmanned aerial vehicle (UAV). Although the devised model represents only the first approximation of spincopter's physics, it captures basic phenomena that are sufficient for derivation and testing of a simple control algorithm. Results obtained by simulations in Simulink ® , presented

M. Orsag; S. Bogdan; T. Haus; M. Bunic; A. Krnjak

2011-01-01

374

How well do climate models simulate precipitation?  

Microsoft Academic Search

This study compares three different methods to evaluate the ability of Atmosphere Ocean General Circulation Models (AOGCMs) to simulate precipitation. Currently, AOGCMs are the most powerful tool to investigate the future climate but how to evaluate them is a relatively new research field. Thus, no standardized metric for defining a climate model's skill has been defined so far. The common

Nathalie Schaller; Irina Mahlstein; Reto Knutti; Jan Cermak

2010-01-01

375

Univariate input models for stochastic simulation  

Microsoft Academic Search

Techniques are presented for modeling and randomly sampling many of the multivariate probabilistic input processes that drive discrete-event simulation experiments. Emphasis is given to bivariate and trivariate extensions of the univariate beta, Johnson, and Bézier dist ribution families because of the flexibility of these families to model a wide range of shapes for the marginal distributions while also representing the

Michael E. Kuhl; Julie S. Ivy; Emily K. Lada; Natalie M. Steiger; Mary Ann Flanigan Wagner; James R. Wilson

2010-01-01

376

Advanced Chemical Modeling for Turbulent Combustion Simulations.  

National Technical Information Service (NTIS)

The goals of this project were the development of new sub-filter models for large eddy simulation of turbulent combustion and of chemical mechanisms for jet fuel surrogates. The sub-filter modeling work focuses on the development of a framework for descri...

H. Pitsch

2012-01-01

377

Modelling and Simulation of Power Plant Processes.  

National Technical Information Service (NTIS)

The first part of the paper deals with the basic aspects of modelling and simulation relating to power plant application, whereby the main emphasis is given to the systematic approach for obtaining an economical modelling. In the second part the results a...

H. J. Gebert H. Wilhelm H. Zimmermann

1976-01-01

378

Dynamic centrifugal compressor model for system simulation  

Microsoft Academic Search

A dynamic model of a centrifugal compressor capable of system simulation in the virtual test bed (VTB) computational environment is presented. The model is based on first principles, i.e. the dynamic performance including the losses is determined from the compressor geometry and not from the experimentally determined characteristic performance curves. In this study, the compressor losses, such as incidence and

Wei Jiang; Jamil Khan; Roger A. Dougal

2006-01-01

379

Oil market Simulation model documentation report. [OMS model  

Microsoft Academic Search

This report provides documentation of the Oil Market Simulation (OMS) Model, the principal model used by the Energy Information Administration (EIA) to project future world oil prices. The OMS model is continually being updated and improved. The methodological and technical discussions in this report document the version of the OMS model used in preparing forecasts for the Energy Information Administration's

Grillot

1983-01-01

380

How does floodplain width affect floodplain river ecology? A preliminary exploration using simulations  

Microsoft Academic Search

Hydraulic food chain models allow us to explore the linkages of river discharge regimes and river-floodplain morphology to the structure and dynamics of modeled food webs. Physical conditions (e.g. depth, width, velocity) that vary with river discharge affect the performance (birth, growth, feeding, movement, or death rates) of organisms or trophic groups. Their performances in turn affect their impacts on

Mary E. Power; Gary Parker; William E. Dietrich; Adrian Sun

1995-01-01

381

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

382

An ecological-transactional model of significant risk factors for child psychopathology in outer mongolia.  

PubMed

The present study examined significant risk factors, including child maltreatment, for child psychopathology in a cross-cultural setting. Ninety-nine Mongolian boys, ages 3-10 years, were assessed. Primary caregivers (PCG) completed structured interviews including the Emory Combined Rating Scale (ECRS) and the Mood and Feelings Questionnaire (MFQ). Structural equation modeling identifies eight risk factors affecting child psychopathology: Three with direct effects (severity of physical punishment, PCG's MFQ score, and PCG's education), three with indirect effects (cultural acceptance of violence as discipline, presence of community violence, and contact with extended family), and two with direct and indirect effects (quality of marriage/presence of spousal abuse, and household size). Results support the ecological-transactional theory of developmental psychopathology in a cross-cultural setting. Structural equation modeling provides a useful technique to isolate specific sites for intervention, while maintaining a comprehensive perspective of risk factor interaction. PMID:15577280

Kohrt, Holbrook E; Kohrt, Brandon A; Waldman, Irwin; Saltzman, Kasey; Carrion, Victor G

2004-01-01

383

Social-relational risk factors for predicting elder physical abuse: an ecological bi-focal model.  

PubMed

Annually in the United States, 1 to 5 million older adults, 65 and above, are physically or sexually injured or mistreated by their caregivers in family settings. This study examined the prevalence and risk factors involved in elder physical abuse by adult child caregivers, moving from the immediate elderly parent/adult child relationship context to more distal social support contexts, utilizing a subsample of 203 elderly participants from the Midlife Development in the United States study (MIDUS II, 2004-2006). LISREL modeling examined causal pathways between elderly demographic characteristics, physical/emotional health, and behavioral and contextual characteristics from an ecological perspective. Data modeling was accomplished using Mplus, PAXW, and SYSTAT statistical software packages. Results indicate that latent factors including older adult health, social isolation of the older adult, and adult child characteristics were significantly associated with elder physical abuse, as mediated by the quality of the elderly parent/adult child relationship. PMID:23115914

von Heydrich, Levente; Schiamberg, Lawrence B; Chee, Grace

2012-01-01

384

A three-level mixed-effects location scale model with an application to ecological momentary assessment data.  

PubMed

In studies using ecological momentary assessment (EMA), or other intensive longitudinal data collection methods, interest frequently centers on changes in the variances, both within-subjects and between-subjects. For this, Hedeker et al. (Biometrics 2008; 64: 627-634) developed an extended two-level mixed-effects model that treats observations as being nested within subjects and allows covariates to influence both the within-subjects and between-subjects variance, beyond their influence on means. However, in EMA studies, subjects often provide many responses within and across days. To account for the possible systematic day-to-day variation, we developed a more flexible three-level mixed-effects location scale model that treats observations within days within subjects, and allows covariates to influence the variance at the subject, day, and observation level (over and above their usual effects on means) using a log-linear representation throughout. We provide details of a maximum likelihood solution and demonstrate how SAS PROC NLMIXED can be used to achieve maximum likelihood estimates in an alternative parameterization of our proposed three-level model. The accuracy of this approach using NLMIXED was verified by a series of simulation studies. Data from an adolescent mood study using EMA were analyzed to demonstrate this approach. The analyses clearly show the benefit of the proposed three-level model over the existing two-level approach. The proposed model has useful applications in many studies with three-level structures where interest centers on the joint modeling of the mean and variance structure. PMID:22865663

Li, Xue; Hedeker, Donald

2012-11-20

385

Spatial ecology and artificial neural networks: modeling the habitat preference of the sea cucumber (Holothuria leucospilota) on Rarotonga, Cook Islands  

Microsoft Academic Search

In this paper we discuss the ability of artificial neural networks to predict the habitat preferences of the tropical sea cucumber (Holothuria leucospilota) in the reef-top ecosystem of Rarotonga, Cook Islands. We suggest that ANN's combined with geographic information systems (GIS) may provide an effective method for modeling spatial patterns in ecological data. The model that we have developed is

Darrin Drumm; Martin Purvis; Qingqing Zhou

386

Does Parenting Mediate the Effects of Exposure to Violence on Violent Behavior? An Ecological-Transactional Model of Community Violence  

ERIC Educational Resources Information Center

Three waves of longitudinal data from a high poverty sample of 1544 African American youth were used to test an ecological-transactional model of violence. SEM analyses were conducted to determine whether parenting (Time 2) mediated the effects of exposure to violence (Time 1) on violent behaviors (Time 3). Findings supported the specified model.…

Spano, Richard; Vazsonyi, Alexander T.; Bolland, John

2009-01-01

387

An Ecological Model for Education and Child Advocacy for Handicapped Children: The Role of the Residential Diagnostic Center.  

ERIC Educational Resources Information Center

An ecological model for service and advocacy for handicapped children through a residential diagnostic center is presented. Such a model is explained to provide a meaningful interrelationship of varied resources and agencies at the local, state, and federal level with a focus on the generic program. Four positive interfacing functions relating to…

Rankhorn, Barney; And Others

388

Candidate innate immune system gene expression in the ecological model Daphnia  

PubMed Central

The last ten years have witnessed increasing interest in host–pathogen interactions involving invertebrate hosts. The invertebrate innate immune system is now relatively well characterised, but in a limited range of genetic model organisms and under a limited number of conditions. Immune systems have been little studied under real-world scenarios of environmental variation and parasitism. Thus, we have investigated expression of candidate innate immune system genes in the water flea Daphnia, a model organism for ecological genetics, and whose capacity for clonal reproduction facilitates an exceptionally rigorous control of exposure dose or the study of responses at many time points. A unique characteristic of the particular Daphnia clones and pathogen strain combinations used presently is that they have been shown to be involved in specific host–pathogen coevolutionary interactions in the wild. We choose five genes, which are strong candidates to be involved in Daphnia–pathogen interactions, given that they have been shown to code for immune effectors in related organisms. Differential expression of these genes was quantified by qRT-PCR following exposure to the bacterial pathogen Pasteuria ramosa. Constitutive expression levels differed between host genotypes, and some genes appeared to show correlated expression. However, none of the genes appeared to show a major modification of expression level in response to Pasteuria exposure. By applying knowledge from related genetic model organisms (e.g. Drosophila) to models for the study of evolutionary ecology and coevolution (i.e. Daphnia), the candidate gene approach is temptingly efficient. However, our results show that detection of only weak patterns is likely if one chooses target genes for study based on previously identified genome sequences by comparison to homologues from other related organisms. Future work on the Daphnia–Pasteuria system will need to balance a candidate gene approach with more comprehensive approaches to de novo identify immune system genes specific to the Daphnia–Pasteuria interaction.

Decaestecker, Ellen; Labbe, Pierrick; Ellegaard, Kirsten; Allen, Judith E.; Little, Tom J.

2011-01-01

389

Global Patterns in Ecological Indicators of Marine Food Webs: A Modelling Approach  

PubMed Central

Background Ecological attributes estimated from food web models have the potential to be indicators of good environmental status given their capabilities to describe redundancy, food web changes, and sensitivity to fishing. They can be used as a baseline to show how they might be modified in the future with human impacts such as climate change, acidification, eutrophication, or overfishing. Methodology In this study ecological network analysis indicators of 105 marine food web models were tested for variation with traits such as ecosystem type, latitude, ocean basin, depth, size, time period, and exploitation state, whilst also considering structural properties of the models such as number of linkages, number of living functional groups or total number of functional groups as covariate factors. Principal findings Eight indicators were robust to model construction: relative ascendency; relative overhead; redundancy; total systems throughput (TST); primary production/TST; consumption/TST; export/TST; and total biomass of the community. Large-scale differences were seen in the ecosystems of the Atlantic and Pacific Oceans, with the Western Atlantic being more complex with an increased ability to mitigate impacts, while the Eastern Atlantic showed lower internal complexity. In addition, the Eastern Pacific was less organised than the Eastern Atlantic although both of these systems had increased primary production as eastern boundary current systems. Differences by ecosystem type highlighted coral reefs as having the largest energy flow and total biomass per unit of surface, while lagoons, estuaries, and bays had lower transfer efficiencies and higher recycling. These differences prevailed over time, although some traits changed with fishing intensity. Keystone groups were mainly higher trophic level species with mostly top-down effects, while structural/dominant groups were mainly lower trophic level groups (benthic primary producers such as seagrass and macroalgae, and invertebrates). Keystone groups were prevalent in estuarine or small/shallow systems, and in systems with reduced fishing pressure. Changes to the abundance of key functional groups might have significant implications for the functioning of ecosystems and should be avoided through management. Conclusion/significance Our results provide additional understanding of patterns of structural and functional indicators in different ecosystems. Ecosystem traits such as type, size, depth, and location need to be accounted for when setting reference levels as these affect absolute values of ecological indicators. Therefore, establishing absolute reference values for ecosystem indicators may not be suitable to the ecosystem-based, precautionary approach. Reference levels for ecosystem indicators should be developed for individual ecosystems or ecosystems with the same typologies (similar location, ecosystem type, etc.) and not benchmarked against all other ecosystems.

Heymans, Johanna Jacomina; Coll, Marta; Libralato, Simone; Morissette, Lyne; Christensen, Villy

2014-01-01

390

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

391

Ecological niche models reveal the importance of climate variability for the biogeography of protosteloid amoebae  

PubMed Central

Habitat availability and environmental preferences of species are among the most important factors in determining the success of dispersal processes and therefore in shaping the distribution of protists. We explored the differences in fundamental niches and potential distributions of an ecological guild of slime moulds—protosteloid amoebae—in the Iberian Peninsula. A large set of samples collected in a north-east to south-west transect of approximately 1000?km along the peninsula was used to test the hypothesis that, together with the existence of suitable microhabitats, climate conditions may determine the probability of survival of species. Although protosteloid amoebae share similar morphologies and life history strategies, canonical correspondence analyses showed that they have varied ecological optima, and that climate conditions have an important effect in niche differentiation. Maxent environmental niche models provided consistent predictions of the probability of presence of the species based on climate data, and they were used to generate maps of potential distribution in an ‘everything is everywhere' scenario. The most important climatic factors were, in both analyses, variables that measure changes in conditions throughout the year, confirming that the alternation of fruiting bodies, cysts and amoeboid stages in the life cycles of protosteloid amoebae constitutes an advantage for surviving in a changing environment. Microhabitat affinity seems to be influenced by climatic conditions, which suggests that the micro-environment may vary at a local scale and change together with the external climate at a larger scale.

Aguilar, Maria; Lado, Carlos

2012-01-01

392

Geographic Distribution of Chagas Disease Vectors in Brazil Based on Ecological Niche Modeling  

PubMed Central

Although Brazil was declared free from Chagas disease transmission by the domestic vector Triatoma infestans, human acute cases are still being registered based on transmission by native triatomine species. For a better understanding of transmission risk, the geographic distribution of Brazilian triatomines was analyzed. Sixteen out of 62 Brazilian species that both occur in >20 municipalities and present synanthropic tendencies were modeled based on their ecological niches. Panstrongylus geniculatus and P. megistus showed broad ecological ranges, but most of the species sort out by the biome in which they are distributed: Rhodnius pictipes and R. robustus in the Amazon; R. neglectus, Triatoma sordida, and T. costalimai in the Cerrado; R. nasutus, P. lutzi, T. brasiliensis, T. pseudomaculata, T. melanocephala, and T. petrocchiae in the Caatinga; T. rubrovaria in the southern pampas; T. tibiamaculata and T. vitticeps in the Atlantic Forest. Although most occurrences were recorded in open areas (Cerrado and Caatinga), our results show that all environmental conditions in the country are favorable to one or more of the species analyzed, such that almost nowhere is Chagas transmission risk negligible.

Gurgel-Goncalves, Rodrigo; Galvao, Cleber; Costa, Jane; Peterson, A. Townsend

2012-01-01

393

Incipient post-zygotic barrier in a model system of ecological speciation with gene flow.  

PubMed

The role of post-zygotic isolation in nonallopatric ecological speciation is still mostly unknown and information on the nature and strength of these barriers in well-known speciation models is essential for a deeper understanding of such processes. The Galician ecotypes of the marine snail Littorina saxatilis represent one of the best studied cases of nonallopatric ecological speciation. Here, we test the existence of incipient post-zygotic isolation by comparing the fertility of male hybrids with that of both pure forms [ridged and banded (RB) and smooth and unbanded (SU) ecotypes]. We analysed the degree of sperm DNA fragmentation (SDF) of individuals morphologically classified as RB, SU and hybrids, sampled from two locations. SDF analyses were chosen to study sperm quality because, in other animal species, SDF rates correlate with important parameters for speciation research, such as fertilization and abortion rates and viability of adult progeny. In the present work, hybrids showed significantly higher SDF rates than RB and SU males in one location and significantly higher variances in both locations. These results suggest the existence of an incipient post-zygotic barrier, the strength of which may vary across the Galician shore, and highlight the potential of SDF analyses for speciation research. PMID:24164692

Sá-Pinto, A; Martínez-Fernández, M; López-Fernández, C; Ferreira, Z; Pereira, R; Gosálvez, J; Rolán-Alvarez, E

2013-12-01

394

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

395

Modeling NAND Flash Memories for Circuit Simulations  

Microsoft Academic Search

In this paper, we will present the basic structure and the parameter extraction procedure for a compact model of a NAND Flash\\u000a memory string working in Spicelike circuit simulators. To the author knowledge, this is the first Spice-like model of a NAND\\u000a Flash memory string. This model is modular and simple to be implemented. It will allow accurately reproducing both

L. Larcher; A. Padovani; P. Pavan; I. Rimmaudo; A. Calderoni; G. Molteni; F. Gattel; P. Fantini

396

Ecological niche model of Phlebotomus alexandri and P. papatasi (Diptera: Psychodidae) in the Middle East  

PubMed Central

Background The purpose of this study is to create distribution models of two sand fly species, Phlebotomus papatasi (Scopoli) and P. alexandri (Sinton), across the Middle East. Phlebotomus alexandri is a vector of visceral leishmaniasis, while P. papatasi is a vector of cutaneous leishmaniasis and sand fly fever. Collection records were obtained from literature reports from 1950 through 2007 and unpublished field collection records. Environmental layers considered in the model were elevation, precipitation, land cover, and WorldClim bioclimatic variables. Models were evaluated using the threshold-independent area under the curve (AUC) receiver operating characteristic analysis and the threshold-dependent minimum training presence. Results For both species, land cover was the most influential environmental layer in model development. The bioclimatic and elevation variables all contributed to model development; however, none influenced the model as strongly as land cover. Conclusion While not perfect representations of the absolute distribution of P. papatasi and P. alexandri, these models indicate areas with a higher probability of presence of these species. This information could be used to help guide future research efforts into the ecology of these species and epidemiology of the pathogens that they transmit.

2010-01-01

397

The implications of model formulation when transitioning from spatial to landscape ecology.  

PubMed

In this article we compare and contrast the predictions of some spatially explicit and implicit models in the context of a thought problem at the interface of spatial and landscape ecology. The situation we envision is a one-dimensional spatial universe of infinite extent in which there are two disjoint focal patches of a habitat type that is favorable to some specified species. We assume that neither patch is large enough by itself to sustain the species in question indefinitely, but that a single patch of size equal to the combined sizes of the two focal patches provides enough contiguous favorable habitat to sustain the given species indefinitely. When the two patches are separated by a patch of unfavorable matrix habitat, the natural expectation is that the species should persist indefinitely if the two patches are close enough to each other but should go extinct over time when the patches are far enough apart. Our focus here is to examine how different mathematical regimes may be employed to model this situation, with an eye toward exploring the trade-off between the mathematical tractability of the model on one hand and the suitability of its predictions on the other. In particular, we are interested in seeing how precisely the predictions of mathematically rich spatially explicit regimes (reaction-diffusion models, integro-difference models) can be matched by those of ostensibly mathematically simpler spatially implicit patch approximations (discrete-diffusion models, average dispersal success matrix models). PMID:22229395

Cantrell, Robert Stephen; Cosner, Chris; Fagan, William F

2012-01-01

398

Distributed earth model/orbiter simulation  

NASA Technical Reports Server (NTRS)

Distributed Earth Model/Orbiter Simulation (DEMOS) is a network based application developed for the UNIX environment that visually monitors or simulates the Earth and any number of orbiting vehicles. Its purpose is to provide Mission Control Center (MCC) flight controllers with a visually accurate three dimensional (3D) model of the Earth, Sun, Moon and orbiters, driven by real time or simulated data. The project incorporates a graphical user interface, 3D modelling employing state-of-the art hardware, and simulation of orbital mechanics in a networked/distributed environment. The user interface is based on the X Window System and the X Ray toolbox. The 3D modelling utilizes the Programmer's Hierarchical Interactive Graphics System (PHIGS) standard and Raster Technologies hardware for rendering/display performance. The simulation of orbiting vehicles uses two methods of vector propagation implemented with standard UNIX/C for portability. Each part is a distinct process that can run on separate nodes of a network, exploiting each node's unique hardware capabilities. The client/server communication architecture of the application can be reused for a variety of distributed applications.

Geisler, Erik; Mcclanahan, Scott; Smith, Gary

1989-01-01

399

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

400

How does floodplain width affect floodplain river ecology? A preliminary exploration using simulations  

NASA Astrophysics Data System (ADS)

Hydraulic food chain models allow us to explore the linkages of river discharge regimes and river-floodplain morphology to the structure and dynamics of modeled food webs. Physical conditions (e.g. depth, width, velocity) that vary with river discharge affect the performance (birth, growth, feeding, movement, or death rates) of organisms or trophic groups. Their performances in turn affect their impacts on food webs and ecosystems in channel and floodplain habitats. Here we explore the impact of floodplain width (modeled as 1 ×, 10× and 40× the channel width) on a food web with two energy sources (detritus and vegetation), invertebrates that consume these, a size structured fish population which consumes invertebrates and in which larger fish cannibalize small fish, and birds which feed on large fish. Hydraulic linkages to trophic dynamics are assumed to be mediated in three ways: birds feed efficiently only in shallow water; plant carrying capacity varies non-linearly with water velocity, and mobile and drifting organisms are diluted and concentrated with spillover of river discharge to the floodplain, and its reconfinement to the channel. Aspects of this model are based on field observations of Junk and Bailey from the Amazon, of Sparks from the Mississippi, and on our observations of the Fly River in Papua New Guinea. The model produced several counter-intuitive results. Biomass of invertebrates and fish increased with floodplain width, but much more rapidly from 1 × to 10 × floodplains than from 10 × to 40 × floodplains. For birds, maximum biomass occurred on the 10× floodplain. Initially high bird biomass on the 40 × floodplain declined to extinction over time, because although favorable fishing conditions (shallow water) were most prolonged on the widest floodplain, this advantage was more than offset by the greater dilution of prey after spillover. Bird predation on large fish sometimes increased their biomass, by reducing cannibalism and thereby increasing the abundance of small fish available to grow into the larger size class. Sensitivity analyses indicated that model results were relatively robust to variation in parameter values that we chose, but much more exploration and calibration with field data are needed before we know how specific our results are to the structure and other assumptions of this model. We share with others the opinion that progress towards understanding complex dynamic systems like floodplain river ecosystems requires frequent feedback between modeling and field observations and experimentation. This understanding is crucial for river management and restoration. Organisms in real rivers have adapted to track and quickly exploit favorable conditions, and to avoid or endure adverse conditions. It is when we engineer away this environmental variability that we threaten the long term persistence of river-adapted biota.

Power, Mary E.; Parker, Gary; Dietrich, William E.; Sun, Adrian

1995-09-01

401

The ChimERA project: coupling mechanistic exposure and effect models into an integrated platform for ecological risk assessment.  

PubMed

Current techniques for the ecological risk assessment of chemical substances are often criticised for their lack of environmental realism, ecological relevance and methodological accuracy. ChimERA is a 3-year project (2013-2016), funded by Cefic's Long Range Initiative (LRI) that aims to address some of these concerns by developing and testing mechanistic fate and effect models, and coupling of these models into one integrated platform for risk assessment. This paper discusses the backdrop against which this project was initiated and lists its objectives and planned methodology. PMID:24532207

De Laender, F; van den Brink, Paul J; Janssen, Colin R; Di Guardo, Antonio

2014-05-01

402

Examples of Video to Communicate Scientific Findings to Non-Scientists-Bayesian Ecological Modeling  

NASA Astrophysics Data System (ADS)

The U.S Geological Survey (USGS) National Water-Quality Assessment Program (NAWQA) provides information about (1) water-quality conditions and how those conditions vary locally, regionally, and nationally, (2) water-quality trends, and (3) factors that affect those conditions. As part of the NAWQA Program, the Effects of Urbanization on Stream Ecosystems (EUSE) study examined the vulnerability and resilience of streams to urbanization. Completion of the EUSE study has resulted in over 20 scientific publications. Video podcasts are being used in addition to these publications to communicate the relevance of these scientific findings to more general audiences such as resource managers, educational groups, public officials, and the general public. An example of one of the podcasts is a film about the results of modeling the effects urbanization on stream ecology. The film describes some of the results of the EUSE ecological modeling effort and the advantages of the Bayesian and multi-level statistical modeling approaches, while relating the science to fly fishing. The complex scientific discussion combined with the lighter, more popular activity of fly fishing leads to an entertaining forum while educating viewers about a complex topic. This approach is intended to represent the scientists as interesting people with diverse interests. Video can be an effective scientific communication tool for presenting scientific findings to a broad audience. The film is available for access from the EUSE website (http://water.usgs.gov/nawqa/urban/html/podcasts.html). Additional films are planned to be released in 2012 on other USGS project results and programs.

Moorman, M.; Harned, D. A.; Cuffney, T.; Qian, S.

2011-12-01

403

Ecological niche modeling of potential West Nile virus vector mosquito species in Iowa.  

PubMed

Ecological niche modeling (ENM) algorithms, Maximum Entropy Species Distribution Modeling (Maxent) and Genetic Algorithm for Rule-set Prediction (GARP), were used to develop models in Iowa for three species of mosquito - two significant, extant West Nile virus (WNV) vectors (Culex pipiens L and Culex tarsalis Coquillett (Diptera: Culicidae)), and the nuisance mosquito, Aedes vexans Meigen (Diptera: Culicidae), a potential WNV bridge vector. Occurrence data for the three mosquito species from a state-wide arbovirus surveillance program were used in combination with climatic and landscape layers. Maxent successfully created more appropriate niche models with greater accuracy than GARP. The three Maxent species' models were combined and the average values were statistically compared to human WNV incidence at the census block group level. The results showed that the Maxent-modeled species' niches averaged together were a useful indicator of WNV human incidence in the state of Iowa. This simple method for creating probability distribution maps proved useful for understanding WNV dynamics and could be applied to the study of other vector-borne diseases. PMID:20874412

Larson, Scott R; DeGroote, John P; Bartholomay, Lyric C; Sugumaran, Ramanathan

2010-01-01

404

Dynamic creation and distribution of flexible climate indices for ecological modeling and climate change impact assessments  

NASA Astrophysics Data System (ADS)

Assessing the potential impacts of climate change on human-environment systems increasingly requires unique and non-standard derivative climate model products that are specific to the research or adaptation question being addressed. In addition, the analysis often requires data at a finer-scale than what is available from raw climate model output; necessitating some form of downscaling to address the information needs of the scientist or decision-maker. Finally, the use of climate model ensembles is becoming a standard practice in order to better quantify projection uncertainty and to take advantage of the proliferation of multi-model climate experiments. However, obtaining these data is a time-consuming and potentially difficult process if the user is unfamiliar with the data standards or lacks the computing resources to store or retrieve large amounts of raw climate model output. In response the U.S. Geological Survey has developed a data portal to provide pre-calculated and dynamically-derived indices of temperature and precipitation projections. The initial dataset consists of threshold summaries and temporal statistics for an ensemble of statistically downscaled climate models. This web visualization and data access portal is based on the Geo Data Portal Data Integration Framework leveraging numerous open standards and software implementations. As a result of standards adherence, very little to no customization is required to incorporate additional datasets into the portal; thus allowing for the inclusion of a wide variety of climatological or ecological data for assessment and planning purposes.

Terando, A. J.; Blodgett, D. L.; Kunicki, T.; Suftin, I.; Sibley, D.; Lewein, S.

2011-12-01

405

Ecological Niche Modeling of Potential West Nile Virus Vector Mosquito Species in Iowa  

PubMed Central

Ecological niche modeling (ENM) algorithms, Maximum Entropy Species Distribution Modeling (Maxent) and Genetic Algorithm for Rule-set Prediction (GARP), were used to develop models in Iowa for three species of mosquito — two significant, extant West Nile virus (WNV) vectors (Culex pipiens L and Culex tarsalis Coquillett (Diptera: Culicidae)), and the nuisance mosquito, Aedes vexans Meigen (Diptera: Culicidae), a potential WNV bridge vector. Occurrence data for the three mosquito species from a state-wide arbovirus surveillance program were used in combination with climatic and landscape layers. Maxent successfully created more appropriate niche models with greater accuracy than GARP. The three Maxent species' models were combined and the average values were statistically compared to human WNV incidence at the census block group level. The results showed that the Maxent-modeled species' niches averaged together were a useful indicator of WNV human incidence in the state of Iowa. This simple method for creating probability distribution maps proved useful for understanding WNV dynamics and could be applied to the study of other vector-borne diseases.

Larson, Scott R.; DeGroote, John P.; Bartholomay, Lyric C.; Sugumaran, Ramanathan

2010-01-01

406

Modeling Between- and Within-Subject Variance in Ecological Momentary Assessment (EMA) Data Using Mixed-Effects Location Scale Models  

PubMed Central

Ecological Momentary Assessment (EMA) and/or Experience Sampling (ESM) methods are increasingly used in health studies to study subjective experiences within changing environmental contexts. In these studies, up to thirty or forty observations are often obtained for each subject. Because there are so many measurements per subject, one can characterize a subject’s mean and variance, and specify models for both. In this article, we focus on an adolescent smoking study using EMA where interest is on characterizing changes in mood variation. We describe how covariates can influence the mood variances, and also extend the statistical model by adding a subject-level random effect to the within-subject variance specification. This permits subjects to have influence on the mean, or location, and variability, or (square of the) scale, of their mood responses. These mixed-effects location scale models have useful applications in many research areas where interest centers on the joint modeling of the mean and variance structure.

Hedeker, Donald; Mermelstein, Robin J.; Demirtas, Hakan

2013-01-01

407

Is the Mantel correlogram powerful enough to be useful in ecological analysis? A simulation study.  

PubMed

The Mantel correlogram is an elegant way to compute a correlogram for multivariate data. However, recent papers raised concerns about the power of the Mantel test itself. Hence the question: Is the Mantel correlogram powerful enough to be useful? To explore this issue, we compared the performances of the Mantel correlogram to those of other methods, using numerical simulations based on random, normally distributed data. For a single response variable, we compared it to the Moran and Geary correlograms. Type I error rates of the three methods were correct. Power of the Mantel correlogram was nearly as high as that of the univariate methods. For the multivariate case, the test of the multivariate variogram developed in the context of multiscale ordination is in fact a Mantel test, so that the power of the two methods is the same by definition. We devised an alternative permutation test based on the variance, which yielded similar results. Overall, the power of the Mantel test was high, the method successfully detecting spatial correlation at rates similar to the permutation test of the variance statistic in multivariate variograms. We conclude that the Mantel correlogram deserves its place in the ecologist's toolbox. PMID:22834387

Borcard, Daniel; Legendre, Pierre

2012-06-01

408

Methods for Detecting Early Warnings of Critical Transitions in Time Series Illustrated Using Simulated Ecological Data  

PubMed Central

Many dynamical systems, including lakes, organisms, ocean circulation patterns, or financial markets, are now thought to have tipping points where critical transitions to a contrasting state can happen. Because critical transitions can occur unexpectedly and are difficult to manage, there is a need for methods that can be used to identify when a critical transition is approaching. Recent theory shows that we can identify the proximity of a system to a critical transition using a variety of so-called ‘early warning signals’, and successful empirical examples suggest a potential for practical applicability. However, while the range of proposed methods for predicting critical transitions is rapidly expanding, opinions on their practical use differ widely, and there is no comparative study that tests the limitations of the different methods to identify approaching critical transitions using time-series data. Here, we summarize a range of currently available early warning methods and apply them to two simulated time series that are typical of systems undergoing a critical transition. In addition to a methodological guide, our work offers a practical toolbox that may be used in a wide range of fields to help detect early warning signals of critical transitions in time series data.

Dakos, Vasilis; Carpenter, Stephen R.; Brock, William A.; Ellison, Aaron M.; Guttal, Vishwesha; Ives, Anthony R.; Kefi, Sonia; Livina, Valerie; Seekell, David A.; van Nes, Egbert H.; Scheffer, Marten

2012-01-01

409

Modeling and Simulation of Mold Filling with LIMS.  

National Technical Information Service (NTIS)

Outline of presentation: What is the Computer Simulation (Modeling). Why do we need simulation. Computer modeling-Basics: experimental characterization; process modeling, analytic and numeric; Computer modeling-Advanced: control and sensing; optimization;...

P. Simacek

2003-01-01

410

Simulation and modeling for military air operations  

NASA Astrophysics Data System (ADS)

The Joint Forces Air Component Commander (JFACC) in military air operations controls the allocation of resources (wings, squadrons, air defense systems, AWACS) to different geographical locations in the theater of operations. The JFACC mission is to define a sequence of tasks for the aerospace systems at each location, and providing feedback control for the execution of these tasks in the presence of uncertainties and a hostile enemy. Honeywell Labs has been developing an innovative method for control of military air operations. The novel model predictive control (MPC) method extends the models and optimization algorithms utilized in traditional model predictive control systems. The enhancements include a tasking controller and, in a joint effort with USC, a probabilistic threat/survival map indicating high threat regions for aircraft and suggesting optimal routes to avoid these regions. A simulation/modeling environment using objected-oriented methodologies has been developed to serve as an aide to demonstrate the value of MPC and facilitate its development. The simulation/modeling environment is based on an open architecture that enables the integration, evaluation, and implementation of different control approaches. The simulation offers a graphical user interface displaying the battlefield, the control performance, and a probability map displaying high threat regions. This paper describes the features of the different control approaches and their integration into the simulation environment.

Kreichauf, Ruth D.; Bedros, Saad; Ateskan, Yusuf; Hespanha, Joao; Kizilocak, Hakan

2001-09-01

411

A groundwater-vegetation interaction model for assessing the impacts of water transfer on ecological restoration in the lower Tarim River  

NASA Astrophysics Data System (ADS)

The interactions between groundwater and vegetation is apparently important in hyper-arid area where groundwater is a vitally limiting factor for plants. Since the 1970s, the lower Tarim River (the largest inland basin of China) had suffered drying of river flow and ecosystem degradation. Water was released to the lower reaches to restore the ecosystem after 2000. It is important to understand the interactions between groundwater and vegetation for assessing the impacts of the water release on the ecological restoration. In this study a groundwater-vegetation interaction model was proposed which coupled the simulations of groundwater movement and vegetation dynamics. The model was used to simulate the changes of groundwater table and vegetation coverage at Yingsu section in the lower Tarim River from 2000 to 2006. The model was validated with groundwater observations and satellite-observed vegetation coverage. The effects of the water transfer on the ecological restoration were assessed. The results show that average groundwater raised 2.91 m and vegetation coverage increased from about 0.11 to 0.12-0.25 in the 40-1100 m belts aside the river because of the water release. Groundwater table. Solid line is ground surface. Dashed line is the simulated groundwater table on 2006-12-20. Circles are the observed groundwater table on 2006-12-20 at observation wells, i.e. C3, C4, C5, C6, C7. Vegetation coverage. Solid line is the simulated vegetation coverage on 2006-12-31. Circles are the observed vegetation coverage on 2000-2-18, derived from satellite-observed NDVI.

Liu, D.; Tian, F.; Hu, H.; Lin, M.; Cong, Z.

2010-12-01

412

Damage modeling for Taylor impact simulations  

NASA Astrophysics Data System (ADS)

G. I. Taylor showed that dynamic material properties could be deduced from the impact of a projectile against a rigid boundary. The Taylor anvil test became very useful with the advent of numerical simulations and has been used to infer and/or to validate material constitutive constants. A new experimental facility has been developed to conduct Taylor anvil impacts to support validation of constitutive constants used in simulations. Typically, numerical simulations are conducted assuming 2-D cylindrical symmetry, but such computations cannot hope to capture the damage observed in higher velocity experiments. A computational study was initiated to examine the ability to simulate damage and subsequent deformation of the Taylor specimens. Three-dimensional simulations, using the Johnson-Cook damage model, were conducted with the nonlinear Eulerian wavecode CTH. The results of the simulations are compared to experimental deformations of 6061-T6 aluminum specimens as a function of impact velocity, and conclusions regarding the ability to simulate fracture and reproduce the observed deformations are summarized.

Anderson, C. E., Jr.; Chocron, I. S.; Nicholls, A. E.

2006-08-01

413

Experimental Noise Injection in Simulated Model Signals  

NASA Astrophysics Data System (ADS)

Nondestructive testing methods have been routinely, designed, evaluated and optimized using simulation models developed using various computational techniques. The simulated signal using computational model differs from the true signal in that the signal does not simulated experimental noise. In order to use the computational models more effectively for signal processing algorithm development, experimental noise should be injected in the simulated signals. Experimental noise PDF (probability density function) can be numerically calculated from measured noise. The experimental signal PDF can then be generated by combining the simulation signal and measurement noise PDF. Sampling from experimental signal distribution is not a straight forward task as the distribution is generally not a standard parametric distribution. This paper presents a method that approximates experimental signal PDF as a mixture of Gaussian densities. Maximum-likelihood estimate of the parameters of Gaussian distributions from a given data set are computed using expectation-maximization (EM) technique. A sampling scheme from the mixture of Gaussian densities is also discussed. The overall algorithm is implemented on eddy current inspection data from steam generator (SG) tubing.

Khan, Tariq; Udpa, Lalita; Udpa, Satish

2011-06-01

414

Ecological Schoolyards.  

ERIC Educational Resources Information Center

Presents design guidelines and organizational and site principles for creating schoolyards where students can learn about ecology. Principles for building schoolyard ecological systems are described. (GR)

Danks, Sharon Gamson

2000-01-01

415

Catastrophic collapse can occur without early warning: examples of silent catastrophes in structured ecological models.  

PubMed

Catastrophic and sudden collapses of ecosystems are sometimes preceded by early warning signals that potentially could be used to predict and prevent a forthcoming catastrophe. Universality of these early warning signals has been proposed, but no formal proof has been provided. Here, we show that in relatively simple ecological models the most commonly used early warning signals for a catastrophic collapse can be silent. We underpin the mathematical reason for this phenomenon, which involves the direction of the eigenvectors of the system. Our results demonstrate that claims on the universality of early warning signals are not correct, and that catastrophic collapses can occur without prior warning. In order to correctly predict a collapse and determine whether early warning signals precede the collapse, detailed knowledge of the mathematical structure of the approaching bifurcation is necessary. Unfortunately, such knowledge is often only obtained after the collapse has already occurred. PMID:23593506

Boerlijst, Maarten C; Oudman, Thomas; de Roos, André M

2013-01-01

416

Catastrophic Collapse Can Occur without Early Warning: Examples of Silent Catastrophes in Structured Ecological Models  

PubMed Central

Catastrophic and sudden collapses of ecosystems are sometimes preceded by early warning signals that potentially could be used to predict and prevent a forthcoming catastrophe. Universality of these early warning signals has been proposed, but no formal proof has been provided. Here, we show that in relatively simple ecological models the most commonly used early warning signals for a catastrophic collapse can be silent. We underpin the mathematical reason for this phenomenon, which involves the direction of the eigenvectors of the system. Our results demonstrate that claims on the universality of early warning signals are not correct, and that catastrophic collapses can occur without prior warning. In order to correctly predict a collapse and determine whether early warning signals precede the collapse, detailed knowledge of the mathematical structure of the approaching bifurcation is necessary. Unfortunately, such knowledge is often only obtained after the collapse has already occurred.

Boerlijst, Maarten C.; Oudman, Thomas; de Roos, Andre M.

2013-01-01

417

Observation simulation experiments with regional prediction models  

NASA Technical Reports Server (NTRS)

Research efforts in FY 1990 included studies employing regional scale numerical models as aids in evaluating potential contributions of specific satellite observing systems (current and future) to numerical prediction. One study involves Observing System Simulation Experiments (OSSEs) which mimic operational initialization/forecast cycles but incorporate simulated Advanced Microwave Sounding Unit (AMSU) radiances as input data. The objective of this and related studies is to anticipate the potential value of data from these satellite systems, and develop applications of remotely sensed data for the benefit of short range forecasts. Techniques are also being used that rely on numerical model-based synthetic satellite radiances to interpret the information content of various types of remotely sensed image and sounding products. With this approach, evolution of simulated channel radiance image features can be directly interpreted in terms of the atmospheric dynamical processes depicted by a model. Progress is being made in a study using the internal consistency of a regional prediction model to simplify the assessment of forced diabatic heating and moisture initialization in reducing model spinup times. Techniques for model initialization are being examined, with focus on implications for potential applications of remote microwave observations, including AMSU and Special Sensor Microwave Imager (SSM/I), in shortening model spinup time for regional prediction.

Diak, George; Perkey, Donald J.; Kalb, Michael; Robertson, Franklin R.; Jedlovec, Gary

1990-01-01

418

Common challenges for ecological modelling: Synthesis of facilitated discussions held at the symposia organized for the 2009 conference of the International Society for Ecological Modelling in Quebec City, Canada, (October 6–9, 2009)  

Microsoft Academic Search

The eleven symposia organized for the 2009 conference of the International Society for Ecological Modelling (ISEM 2009) held in Quebec City, Canada, October 6–9, 2009, included facilitated discussion sessions following formal presentations. Each symposium focused on a specific subject, and all the subjects could be classified into three broad categories: theoretical development, population dynamics and ecosystem processes. Following discussions with

G. R. Larocque; D. Mailly; T.-X. Yue; M. Anand; C. Peng; C. Kazanci; M. Etterson; P. Goethals; S. E. Jørgensen; J. R. Schramski; E. J. B. McIntire; D. J. Marceau; B. Chen; G. Q. Chen; Z. F. Yang; B. Novotna; N. Luckai; J. S. Bhatti; J. Liu; A. Munson; A. M. Gordon; J. C. Ascough II

2011-01-01

419

Modeling and Simulation of Nuclear Fuel Materials  

SciTech Connect

We review the state of modeling and simulation of nuclear fuels with emphasis on the most widely used nuclear fuel, UO2. The hierarchical scheme presented represents a science-based approach to modeling nuclear fuels by progressively passing information in several stages from ab initio to continuum levels. Such an approach is essential to overcome the challenges posed by radioactive materials handling, experimental limitations in modeling extreme conditions and accident scenarios and small time and distance scales of fundamental defect processes. When used in conjunction with experimental validation, this multiscale modeling scheme can provide valuable guidance to development of fuel for advanced reactors to meet rising global energy demand.

Devanathan, Ram [Pacific Northwest National Laboratory (PNNL); Van Brutzel, Laurent [LSCE/CEA, Gif-sur-Yvette, France; Chartier, Alain [LSCE/CEA, Gif-sur-Yvette, France; Christine, Gueneau [LSCE/CEA, Gif-sur-Yvette, France; Mattsson, Ann [Sandia National Laboratories (SNL); Tikare, Veena [Sandia National Laboratories (SNL); Bartel, Timothy [Sandia National Laboratories (SNL); Besmann, Theodore M [ORNL; Stan, Marius [Los Alamos National Laboratory (LANL); Van Uffelen, Paul [Institute for Transuranium Elements, Germany

2010-01-01

420

Variation in grouping patterns, mating systems and social structure: what socio-ecological models attempt to explain  

PubMed Central

Socio-ecological models aim to predict the variation in social systems based on a limited number of ecological parameters. Since the 1960s, the original model has taken two paths: one relating to grouping patterns and mating systems and one relating to grouping patterns and female social structure. Here, we review the basic ideas specifically with regard to non-human primates, present new results and point to open questions. While most primates live in permanent groups and exhibit female defence polygyny, recent studies indicate more flexibility with cooperative male resource defence occurring repeatedly in all radiations. In contrast to other animals, the potential link between ecology and these mating systems remains, however, largely unexplored. The model of the ecology of female social structure has often been deemed successful, but has recently been criticized. We show that the predicted association of agonistic rates and despotism (directional consistency of relationships) was not supported in a comparative test. The overall variation in despotism is probably due to phylogenetic grade shifts. At the same time, it varies within clades more or less in the direction predicted by the model. This suggests that the model's utility may lie in predicting social variation within but not across clades.

Koenig, Andreas; Scarry, Clara J.; Wheeler, Brandon C.; Borries, Carola

2013-01-01

421

Variation in grouping patterns, mating systems and social structure: what socio-ecological models attempt to explain.  

PubMed

Socio-ecological models aim to predict the variation in social systems based on a limited number of ecological parameters. Since the 1960s, the original model has taken two paths: one relating to grouping patterns and mating systems and one relating to grouping patterns and female social structure. Here, we review the basic ideas specifically with regard to non-human primates, present new results and point to open questions. While most primates live in permanent groups and exhibit female defence polygyny, recent studies indicate more flexibility with cooperative male resource defence occurring repeatedly in all radiations. In contrast to other animals, the potential link between ecology and these mating systems remains, however, largely unexplored. The model of the ecology of female social structure has often been deemed successful, but has recently been criticized. We show that the predicted association of agonistic rates and despotism (directional consistency of relationships) was not supported in a comparative test. The overall variation in despotism is probably due to phylogenetic grade shifts. At the same time, it varies within clades more or less in the direction predicted by the model. This suggests that the model's utility may lie in predicting social variation within but not across clades. PMID:23569296

Koenig, Andreas; Scarry, Clara J; Wheeler, Brandon C; Borries, Carola

2013-05-19

422

Optimizing simulation models of agricultural systems  

Microsoft Academic Search

Agricultural systems vary widely in terms of scale, scope and purpose. Managers of thesereal-world systems are typically faced\\u000a with a multitude of alternative management optionsand strategies, and are turning more towards simulation models in an attempt\\u000a to evaluatethese and identify the optimal combination. From a modelling perspective, agriculturalsystems present a range of\\u000a problems which need to be addressed, and these

D. G. Mayer; J. A. Belward; K. Burrage

1998-01-01

423

Simulation of RTD using quantum hydrodynamic model  

Microsoft Academic Search

The quantum hydrodynamic model (QHD) can be derived from quantum Boltzmann equation (QBE) and classical hydrodynamics conservation laws. In this dissertation, a self-consistent solver for the partial differential equations of one-dimensional (1D) QHD model is implemented and simulation results of a 1D resonant tunneling diode (RTD) are presented that shows charge build-up in the quantum well and negative differential resistance

Lei Huang; Zhiping Yu; Cailan Xiang

2004-01-01

424

Min-Max-DEVS modeling and simulation  

Microsoft Academic Search

The representation of timing, a key element in modeling hardware behavior, is realized in hardware description languages including ADLIB-SABLE, Verilog, and VHDL, through delay constructs. The use of delays in the literature may be organized into four classes. Under the first category, the mean values are utilized as precise delay elements in the simulators. VHDL adopts this view to characterize

Maâmar El-amine Hamri; Norbert Giambiasi; Claudia S. Frydman

2006-01-01

425

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.

426

Building Fire Simulation Model, Volume 2: Appendices.  

National Technical Information Service (NTIS)

Twelve appendices comprise the second volume of this final report on the Building Fire Simulation Model (BFSM). The data base appendix consists of the data files used in the regression analyses for realm transition times and for the development and spread...

J.A. Swartz R.F. Fahy E.M. Connelly D.P. Demers

1983-01-01

427

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.

428

Monte Carlo simulation of CPN-1 models  

Microsoft Academic Search

Numerical simulations of two-dimensional CPN-1 models are performed at N=2, 10, and 21. The lattice action adopted depends explicitly on the gauge degrees of freedom and shows precocious scaling. Our tests of scaling are the stability of adimensional physical quantities (second moment of the correlation function versus inverse mass gap, magnetic susceptibility versus square correlation length) and rotation invariance. Topological