Empirical Dynamic Modeling

2020 ◽  
pp. 251-268
Author(s):  
Michael J. Fogarty ◽  
Jeremy S. Collie
Keyword(s):  
Dynamic Modeling ◽  
Nearest Neighbor ◽  
Wide Spectrum ◽  
Species Abundance ◽  
Mechanistic Modeling ◽  
Parametric Models ◽  
Ecological Processes ◽  
Regression Methods ◽  
Modeling Approaches ◽  
Dynamical Behaviors

Empirical Dynamic Modeling offers a flexible complement to standard mechanistic modeling approaches. Because it makes no assumptions concerning the structural form of ecological processes, it can provide an effective approach to dealing with model uncertainty. The method uses non-linear, non-parametric models. It can accommodate a wide spectrum of dynamical behaviors and makes no equilibrium assumptions. The approach is predicated on the idea that within a time series of observations of an ecological variable (e.g. population or species abundance) is encoded information on the factors that have affected that variable over time (e.g. the effects of predators or prey, competitors, environmental change, etc.). The method employs state-space reconstruction to decode this embedded information, and applies nearest-neighbor and kernel regression methods of forecasting. Forecast skill is used directly as a criterion for model selection and validation. It has been proven effective in application to fisheries forecasting problems, often outperforming standard modeling approaches.

scholarly journals Developing Practical Models of Complex Salts for Molten Salt Reactors

Thermo ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 168-178
Author(s):  
Theodore M. Besmann ◽  
Juliano Schorne-Pinto
Keyword(s):  
Molten Salt ◽  
Nearest Neighbor ◽  
System Modeling ◽  
Model Parameters ◽  
Calphad Approach ◽  
Coordination Numbers ◽  
Regression Methods ◽  
Complex Salts ◽  
Salt Systems ◽  
Fitting Model

Molten salt reactors (MSRs) utilize salts as coolant or as the fuel and coolant together with fissile isotopes dissolved in the salt. It is necessary to therefore understand the behavior of the salts to effectively design, operate, and regulate such reactors, and thus there is a need for thermodynamic models for the salt systems. Molten salts, however, are difficult to represent as they exhibit short-range order that is dependent on both composition and temperature. A widely useful approach is the modified quasichemical model in the quadruplet approximation that provides for consideration of first- and second-nearest-neighbor coordination and interactions. Its use in the CALPHAD approach to system modeling requires fitting parameters using standard thermodynamic data such as phase equilibria, heat capacity, and others. A shortcoming of the model is its inability to directly vary coordination numbers with composition or temperature. Another issue is the difficulty in fitting model parameters using regression methods without already having very good initial values. The proposed paper will discuss these issues and note some practical methods for the effective generation of useful models.

scholarly journals The Relative Importance of Niche Process and Neutral Process in the Community Assembly of Subtropical Karst Forest: A Perspective on the Changes of Species Distribution Patterns at Different Scales

2021 ◽  
Author(s):  
Yan He ◽  
Yong Jiang ◽  
Hongling Lin ◽  
Yuanfang Pan ◽  
Shichu Liang ◽  
...  
Keyword(s):  
Community Assembly ◽  
Variation Partitioning ◽  
Species Abundance ◽  
Distribution Patterns ◽  
Relative Importance ◽  
Ecological Processes ◽  
Abundance Pattern ◽  
Karst Forest ◽  
Neutral Processes ◽  
Neutral Process

Abstract Background and aimsThe importance of niche processes and neutral processes to community assembly has been affirmed by most studies, although their relative importance needs to be determined in many systems. Moreover, as the spatial scale changes, the ecological processes that determine the community pattern may differ. We tested these ideas in subtropical karst forest in southwestern China in order to aid efforts of community reconstruction.MethodsTo test the importance of niche-based and neutral mechanisms we compared the fit six models to the observed SAD of the plot at three different sampling scales (10 m × 10 m, 20 m × 20 m, 50 m × 50 m). We also used spatial autocorrelation and distance-based Moran's eigenvector maps (dbMEM) combined with variation partitioning to further determine the relative contribution of the niche process and the neutral process under different sampling scales.ResultsThe neutral theoretical and statistical models fit the observed species abundance distribution curve best at each sampling scale. And variation partitioning showed that although the contribution of spatial structure was lower at larger sampling scales, it was still important, suggesting that neutral processes drive community structure at all sampling scales. In contrast, habitat filtering and interspecies competition may lead to a net weakening of the contribution of the niche process to the species abundance pattern of the community because they act in opposite directions. ConclusionsIn the restoration and reconstruction of local karst forest communities, environmental heterogeneity, inter-species relationships, and geographic spatial differences should all be considered.

scholarly journals Dynamic Modeling and Experimental Verification of A Cable-Driven Continuum Manipulator With Cable-Constrained Synchronous Rotating Mechanisms

2021 ◽  
Author(s):  
Xudong Zheng ◽  
Taiwei Yang ◽  
Xianjin Zhu ◽  
Zhang Chen ◽  
Xueqian Wang ◽  
...  
Keyword(s):  
Dynamic Modeling ◽  
Friction Model ◽  
Modeling Method ◽  
Stick Slip ◽  
Dynamical Behaviors ◽  
Ale Formulation ◽  
Two Factors ◽  
New Type ◽  
Continuum Manipulator ◽  
Coulomb Friction Model

Abstract The cable-driven segmented manipulator with cable-constrained synchronous rotating mechanisms (CCSRM) is a new type of continuum manipulator, which has large stiffness and less motors, and thus exhibits excellent comprehensive performance. This paper presents a dynamic modeling method for this type of manipulator to analyze the friction and deformation of the cables on the dynamical behaviors of the system. First, the driving cables are modeled based on the ALE formulation, the strategies for detecting stick-slip transitions are proposed by using a trial-and-error algorithm, and the stiff problems of the dynamic equations are released by a model smoothing method. Second, the dynamic modeling method for rigid links is presented by using quaternion parameters. Third, the connecting cables are modeled by torsional spring-dampers and the frictions between the connecting cables and the conduits are considered based on a modified Coulomb friction model. Finally, the numerical results are presented and verified by comparing with experiment results. The study shows that the friction and cable deformation play an important role in the dynamical behaviors of the manipulator. Due to these two factors, the constant curvature bending of the segments does not remain.

scholarly journals Developing Practical Models of Complex Salts for Molten Salt Reactors

2021 ◽  
Author(s):  
Theorore M. Besmann ◽  
Juliano Schorne-Pinto
Keyword(s):  
Molten Salts ◽  
Nearest Neighbor ◽  
System Modeling ◽  
Model Parameters ◽  
Quasichemical Model ◽  
Coordination Numbers ◽  
Regression Methods ◽  
Complex Salts ◽  
Salt Systems ◽  
Fitting Model

olten salt reactors (MSRs) utilize salts as coolant or as the fuel and coolant together with fissile isotopes dissolved in the salt. It is necessary to therefore understand the behavior of the salts to effectively design, operate, and regulate such reactors, and thus there is a need for thermodynamic models for the salt systems. Molten salts, however, are difficult to represent as they exhibit short range order that is dependent on both composition and temperature. A widely useful approach is the modified quasichemical model in the quadruplet approximation that provides for consideration of first and second nearest neighbor coordination and interactions. Its use in the CALPHAD ap-proach to system modeling requires fitting parameters using standard thermodynamic data such as phase equilibria, heat capacity, and others. Shortcoming of the model is its inability to directly vary coordination numbers with composition or temperature. Another issue is the difficulty in fitting model parameters using regression methods without already having very good initial values. The proposed paper will discuss these issues and note some practical methods for the effective genera-tion of useful models.

scholarly journals Putting the Biophysical (Back) in Economics: A Taxonomic Review of Modeling the Earth-Bound Economy

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
John Sherwood ◽  
Michael Carbajales-Dale ◽  
Becky Roselius Haney
Keyword(s):  
Wide Spectrum ◽  
Future Research ◽  
Research Papers ◽  
Dynamic Interactions ◽  
Biophysical Models ◽  
Modeling Approaches ◽  
Research Areas ◽  
Biophysical Economics ◽  
Research Questions ◽  
Active Research

Abstract Economists rarely model the economy as explicitly bound by earth’s ecological systems. Modeling the dynamic interactions of both human and non-human systems is admittedly a challenging task, as it requires expertise from multiple disciplines. Within the last 10 years, a wide variety of research papers have been published that include some biophysical aspects in a model of the economy. These papers all have one thing in common: the model of the economy includes physical and/or energetic exchanges, as well as monetary exchange. This theme is what defines the emerging sub-discipline of biophysical economics, BPE. BPE models of the economy originate from a variety of disciplines, and thus BPE research articles are published across a wide spectrum of academic journals. As inter-disciplinary researchers ourselves, we want to understand what BPE modeling approaches have been used so far. In this paper, we examine and classify over one hundred published articles that use biophysical models of the economy. Although BPE modeling approaches are quite varied, grouping the research by common characteristics reveals several active research areas. We highlight recent papers that are helpful examples of the most popular BPE modeling strategies. Gaps also exist. Several modeling approaches have not been used in published works yet. We identify which of those gaps could be promising avenues for future research. We conclude by suggesting which BPE modeling approach might be particularly appropriate for a variety of research questions.

Supervised Learning in Game Data Science

2021 ◽  
pp. 179-218
Author(s):  
Magy Seif El-Nasr ◽  
Truong Huy Nguyen Dinh ◽  
Alessandro Canossa ◽  
Anders Drachen
Keyword(s):  
Data Science ◽  
Nearest Neighbor ◽  
Support Vector ◽  
Classification Methods ◽  
K Nearest Neighbor ◽  
Linear Discriminant ◽  
Regression Methods ◽  
Vector Machines ◽  
Pros And Cons ◽  
Classification And Regression

This chapter discusses several classification and regression methods that can be used with game data. Specifically, we will discuss regression methods, including Linear Regression, and classification methods, including K-Nearest Neighbor, Naïve Bayes, Logistic Regression, Linear Discriminant Analysis, Support Vector Machines, Decisions Trees, and Random Forests. We will discuss how you can setup the data to apply these algorithms, as well as how you can interpret the results and the pros and cons for each of the methods discussed. We will conclude the chapter with some remarks on the process of application of these methods to games and the expected outcomes. The chapter also includes practical labs to walk you through the process of applying these methods to real game data.

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