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authorbnewbold <bnewbold@robocracy.org>2017-01-16 16:24:09 -0800
committerbnewbold <bnewbold@robocracy.org>2017-01-16 16:28:35 -0800
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downloadmodelthing-6c9ec4f093ecfa48fe3a4a3fa99de16c5676d7dc.tar.gz
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-rw-r--r--examples/lotka_volterra/examples.toml11
-rw-r--r--examples/lotka_volterra/model.modelica12
-rw-r--r--examples/lotka_volterra/page.md35
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diff --git a/examples/lotka_volterra/examples.toml b/examples/lotka_volterra/examples.toml
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-
-[examples]
-
- [examples.mathworld]
- x = 10
- y = 5
- alpha = 1.5
- beta = 1
- gamma = 1
- t = [0, 20]
-
diff --git a/examples/lotka_volterra/model.modelica b/examples/lotka_volterra/model.modelica
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-model LotkaVolterra
- "Predator-Prey equations describing population dynamics of two biological species"
- parameter Real alpha;
- parameter Real beta;
- parameter Real delta;
- parameter Real gamma;
- Real x "population of prey";
- Real y "population of predator";
-equation
- der(x) = (alpha * x) - (beta * x * y);
- der(y) = (delta * x * y) - (gamma * y);
-end LotkaVolterra;
diff --git a/examples/lotka_volterra/page.md b/examples/lotka_volterra/page.md
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-
-The Lotka–Volterra equations, also known as the predator–prey equations, are a
-pair of first-order, [non-linear](https://en.wikipedia.org/wiki/Non-linear),
-differential equations frequently used to describe the dynamics of biological
-systems in which two species interact, one as a predator and the other as prey.
-
-The Lotka–Volterra system of equations is an example of a Kolmogorov
-model, which is a more general framework that can model the dynamics of
-ecological systems with predator-prey interactions, competition, disease, and
-mutualism.
-
-## Solutions to the equations
-
-The equations have periodic solutions and do not have a simple expression in
-terms of the usual trigonometric functions, although they are quite
-tractable.
-
-If none of the non-negative parameters α,β,γ,δ vanishes, three can be absorbed
-into the normalization of variables to leave but merely one behind: Since the
-first equation is homogeneous in x, and the second one in y, the parameters β/α
-and δ/γ, are absorbable in the normalizations of y and x, respectively, and γ
-into the normalization of t, so that only α/γ remains arbitrary. It is the only
-parameter affecting the nature of the solutions.
-
-A linearization of the equations yields a solution similar to simple harmonic
-motion with the population of predators trailing that of prey by 90° in the
-cycle.
-
-## References
-
-Body text taken from Wikipedia.
-
-* [Mathworld](http://mathworld.wolfram.com/Lotka-VolterraEquations.html)
-* [Wikipedia](https://en.wikipedia.org/wiki/Lotka%E2%80%93Volterra_equations)
-* [Population dynamics of fisheries](https://en.wikipedia.org/wiki/Population_dynamics_of_fisheries)