Dynamic simulation modelers are particularly interested in understanding and being able to distinguish between the behavior of stocks and flows that result from internal interactions and those that result from external forces acting on a system.  For some time modelers have been particularly int

Dynamic simulation modelers are particularly interested in understanding and being able to distinguish between the behavior of stocks and flows that result from internal interactions and those that result from external forces acting on a system.  For some time modelers have been particularly interested in internal interactions that result in stable oscillations in the absence of any external forces acting on a system.  The model in this last scenario was independently developed by Alfred Lotka (1924) and Vito Volterra (1926).  Lotka was interested in understanding internal dynamics that might explain oscillations in moth and butterfly populations and the parasitoids that attack them.  Volterra was interested in explaining an increase in coastal populations of predatory fish and a decrease in their prey that was observed during World War I when human fishing pressures on the predator species declined.  Both discovered that a relatively simple model is capable of producing the cyclical behaviors they observed.  Since that time, several researchers have been able to reproduce the modeling dynamics in simple experimental systems consisting of only predators and prey.  It is now generally recognized that the model world that Lotka and Volterra produced is too simple to explain the complexity of most and predator-prey dynamics in nature.  And yet, the model significantly advanced our understanding of the critical role of feedback in predator-prey interactions and in feeding relationships that result in community dynamics.The Lotka–Volterra model makes a number of assumptions about the environment and evolution of the predator and prey populations:

1. The prey population finds ample food at all times.
2. The food supply of the predator population depends entirely on the size of the prey population.
3. The rate of change of population is proportional to its size.
4. During the process, the environment does not change in favour of one species and genetic adaptation is inconsequential.
5. Predators have limitless appetite.
As differential equations are used, the solution is deterministic and continuous. This, in turn, implies that the generations of both the predator and prey are continually overlapping.[23]

Prey
When multiplied out, the prey equation becomes
dx/dtαx - βxy
 The prey are assumed to have an unlimited food supply, and to reproduce exponentially unless subject to predation; this exponential growth is represented in the equation above by the term αx. The rate of predation upon the prey is assumed to be proportional to the rate at which the predators and the prey meet; this is represented above by βxy. If either x or y is zero then there can be no predation.

With these two terms the equation above can be interpreted as: the change in the prey's numbers is given by its own growth minus the rate at which it is preyed upon.

Predators

The predator equation becomes

dy/dt =  - 

In this equation, {\displaystyle \displaystyle \delta xy} represents the growth of the predator population. (Note the similarity to the predation rate; however, a different constant is used as the rate at which the predator population grows is not necessarily equal to the rate at which it consumes the prey). {\displaystyle \displaystyle \gamma y} represents the loss rate of the predators due to either natural death or emigration; it leads to an exponential decay in the absence of prey.

Hence the equation expresses the change in the predator population as growth fueled by the food supply, minus natural death.


Model presented by Jeff Klemens at GC3 conference, Cincinnati,  OH on May 15th 2018 as part of keynote address "Active learning spaces as a catalyst for institution-wide change in teaching and learning"    Feel free to clone and modify this model, but please share your modifications and discoveries
Model presented by Jeff Klemens at GC3 conference, Cincinnati,  OH on May 15th 2018 as part of keynote address "Active learning spaces as a catalyst for institution-wide change in teaching and learning"

Feel free to clone and modify this model, but please share your modifications and discoveries with me! I can be contacted via my university homepage: https://sites.philau.edu/KlemensJ/  
  ​S-Curve + Delay for Bell Curve Showing Erlang Distribution      Generation of Bell Curve from Initial Market through Delay in Pickup of Customers     This provides the beginning of an Erlang distribution model      The  Erlang distribution  is a two parameter family of continuous  probability dis
​S-Curve + Delay for Bell Curve Showing Erlang Distribution

Generation of Bell Curve from Initial Market through Delay in Pickup of Customers

This provides the beginning of an Erlang distribution model

The Erlang distribution is a two parameter family of continuous probability distributions with support . The two parameters are:

  • a positive integer 'shape' 
  • a positive real 'rate' ; sometimes the scale , the inverse of the rate is used.

  object is projected with an initial velocity u at an angle to the horizontal direction.  We assume that there is no air resistance .Also since the body first goes up and then comes down after reaching the highest point , we will use the Cartesian convention for signs of different physical quantiti

object is projected with an initial velocity u at an angle to the horizontal direction.

We assume that there is no air resistance .Also since the body first goes up and then comes down after reaching the highest point , we will use the Cartesian convention for signs of different physical quantities. The acceleration due to gravity 'g' will be negative as it acts downwards.

h=v_ox*t-g*t^2/2

l=v_oy*t
 Perceptual Control Theory Model of Balancing an Inverted Pendulum. See  Kennaway's slides  on Robotics. as well as PCT example WIP notes. Compare with  IM-1831  from Z209 from Hartmut Bossel's System Zoo 1 p112-118

Perceptual Control Theory Model of Balancing an Inverted Pendulum. See Kennaway's slides on Robotics. as well as PCT example WIP notes. Compare with IM-1831 from Z209 from Hartmut Bossel's System Zoo 1 p112-118

Modelling the rate of school dropout 
Modelling the rate of school dropout 
           Despite a mature field of inquiry, frustrated educational policy makers face a crisis characterized by little to no clear research-based guidance and significant budget limitations --  in the face of too often marginal or unexpectedly deleterious achievement impacts. As such, education pe
Despite a mature field of inquiry, frustrated educational policy makers face a crisis characterized by little to no clear research-based guidance and significant budget limitations --  in the face of too often marginal or unexpectedly deleterious achievement impacts. As such, education performance has been acknowledged as a complex system and a general call in the literature for causal models has been sounded. This modeling effort represents a strident first step in the development of an evidence-based causal hypothesis: an hypothesis that captures the widely acknowledged complex interactions and multitude of cited influencing factors. This non-piecemeal, causal, reflection of extant knowledge engages a neuro-cognitive definition of students.  Through capture of complex dynamics, it enables comparison of different mixes of interventions to estimate net academic achievement impact for the lifetime of a single cohort of students. Results nominally capture counter-intuitive unintended consequences: consequences that too often render policy interventions effete. Results are indexed on Hattie Effect Sizes, but rely on research identified causal mechanisms for effect propagation. Note that the net causal interactions have been effectively captured in a very scoped and/or simplified format.  Relative magnitudes of impact have been  roughly adjusted to Hattie Ranking Standards (calibration): a non-causal evidence source. This is a demonstration model and seeks to exemplify content that would be engaged in a full or sufficient model development effort.  Budget & time constraints required significant simplifying assumptions. These assumptions mitigate both the completeness & accuracy of the outputs. Features serve to symbolize & illustrate the value and benefits of causal modeling as a performance tool.
 Effect of rewards on the selection promotion and retirement of scholars in universities. Based on Geoffrey Brennan's Selection and the Currency of Reward chapter10 in The Theory of Institutional Design ed. RG Goodwin Cambridge University Press 1996 See also  IM-2016

Effect of rewards on the selection promotion and retirement of scholars in universities. Based on Geoffrey Brennan's Selection and the Currency of Reward chapter10 in The Theory of Institutional Design ed. RG Goodwin Cambridge University Press 1996 See also IM-2016

A modified version of a cloned model for my Env. Sci. class.
A modified version of a cloned model for my Env. Sci. class.
Crea un modelo de propagación de una epidemia en una población constante. Acople de Bucles Universidad del Cauca.  Profesor: Miguel Angel Niño Zambrano  curso:  Enlace Curso en Moodle   Videos ejemplos:  Enlace a la lista de videos del curso youtube
Crea un modelo de propagación de una epidemia en una población constante. Acople de Bucles
Universidad del Cauca. 
Profesor: Miguel Angel Niño Zambrano
This is to help understand the way a modern university system works.
This is to help understand the way a modern university system works.
Crea un modelo de propagación de una epidemia en una población constante. Acople de Bucles Universidad del Cauca.  Profesor: Miguel Angel Niño Zambrano  curso:  Enlace Curso en Moodle   Videos ejemplos:  Enlace a la lista de videos del curso youtube
Crea un modelo de propagación de una epidemia en una población constante. Acople de Bucles
Universidad del Cauca. 
Profesor: Miguel Angel Niño Zambrano
The critical potential leverage points for the future of dynamic education and the learning experience.
The critical potential leverage points for the future of dynamic education and the learning experience.