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isaacsas committed Jun 7, 2024
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4 changes: 2 additions & 2 deletions docs/pages.jl
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Expand Up @@ -19,7 +19,7 @@ pages = Any[
"model_creation/examples/basic_CRN_library.md",
"model_creation/examples/programmatic_generative_linear_pathway.md",
"model_creation/examples/hodgkin_huxley_equation.md",
#"model_creation/examples/smoluchowski_coagulation_equation.md"
"model_creation/examples/smoluchowski_coagulation_equation.md"
]
],
"Model simulation" => Any[
Expand All @@ -32,7 +32,7 @@ pages = Any[
"Steady state analysis" => Any[
"steady_state_functionality/homotopy_continuation.md",
"steady_state_functionality/nonlinear_solve.md",
"steady_state_functionality/steady_state_stability_computation.md",
"steady_state_functionality/steady_state_stability_computation.md",
"steady_state_functionality/bifurcation_diagrams.md",
"steady_state_functionality/dynamical_systems.md"
],
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3 changes: 1 addition & 2 deletions docs/src/assets/Project.toml
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Expand Up @@ -5,7 +5,6 @@ CairoMakie = "13f3f980-e62b-5c42-98c6-ff1f3baf88f0"
Catalyst = "479239e8-5488-4da2-87a7-35f2df7eef83"
DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
DiffEqParamEstim = "1130ab10-4a5a-5621-a13d-e4788d82bd4c"
DifferentialEquations = "0c46a032-eb83-5123-abaf-570d42b7fbaa"
Distributions = "31c24e10-a181-5473-b8eb-7969acd0382f"
Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
DynamicalSystems = "61744808-ddfa-5f27-97ff-6e42cc95d634"
Expand Down Expand Up @@ -38,7 +37,7 @@ Symbolics = "0c5d862f-8b57-4792-8d23-62f2024744c7"

[compat]
BenchmarkTools = "1.5"
BifurcationKit = "0.3"
BifurcationKit = "0.3.4"
CairoMakie = "0.12"
Catalyst = "13"
DataFrames = "1.6"
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111 changes: 64 additions & 47 deletions docs/src/model_creation/examples/smoluchowski_coagulation_equation.md
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Expand Up @@ -4,72 +4,88 @@ This tutorial shows how to programmatically construct a [`ReactionSystem`](@ref)
The Smoluchowski coagulation equation describes a system of reactions in which monomers may collide to form dimers, monomers and dimers may collide to form trimers, and so on. This models a variety of chemical/physical processes, including polymerization and flocculation.

We begin by importing some necessary packages.
```julia
```@example smcoag1
using ModelingToolkit, Catalyst, LinearAlgebra
using DiffEqBase, JumpProcesses
using JumpProcesses
using Plots, SpecialFunctions
```
Suppose the maximum cluster size is `N`. We assume an initial concentration of monomers, `Nₒ`, and let `uₒ` denote the initial number of monomers in the system. We have `nr` total reactions, and label by `V` the bulk volume of the system (which plays an important role in the calculation of rate laws since we have bimolecular reactions). Our basic parameters are then
```julia
## Parameter
N = 10 # maximum cluster size
Vₒ = (4π/3)*(10e-06*100)^3 # volume of a monomers in cm³
Nₒ = 1e-06/Vₒ # initial conc. = (No. of init. monomers) / bulk volume
uₒ = 10000 # No. of monomers initially
V = uₒ/Nₒ # Bulk volume of system in cm³

integ(x) = Int(floor(x))
n = integ(N/2)
nr = N%2 == 0 ? (n*(n + 1) - n) : (n*(n + 1)) # No. of forward reactions
```@example smcoag1
# maximum cluster size
N = 10
# volume of a monomers in cm³
Vₒ = (4π / 3) * (10e-06 * 100)^3
# initial conc. = (No. of init. monomers) / bulk volume
Nₒ = 1e-06 / Vₒ
# No. of monomers initially
uₒ = 10000
# Bulk volume of system in cm³
V = uₒ / Nₒ
n = floor(Int, N / 2)
# No. of forward reactions
nr = ((N % 2) == 0) ? (n*(n + 1) - n) : (n*(n + 1))
nothing #hide
```
The [Smoluchowski coagulation equation](https://en.wikipedia.org/wiki/Smoluchowski_coagulation_equation) Wikipedia page illustrates the set of possible reactions that can occur. We can easily enumerate the `pair`s of multimer reactants that can combine when allowing a maximal cluster size of `N` monomers. We initialize the volumes of the reactant multimers as `volᵢ` and `volⱼ`

```julia
```@example smcoag1
# possible pairs of reactant multimers
pair = []
for i = 2:N
push!(pair, [1:integ(i/2) i .- (1:integ(i/2))])
halfi = floor(Int, i/2)
push!(pair, [(1:halfi) (i .- (1:halfi))])
end
pair = vcat(pair...)
vᵢ = @view pair[:,1] # Reactant 1 indices
vⱼ = @view pair[:,2] # Reactant 2 indices
volᵢ = Vₒ*vᵢ # cm⁻³
volⱼ = Vₒ*vⱼ # cm⁻³
vᵢ = @view pair[:, 1] # Reactant 1 indices
vⱼ = @view pair[:, 2] # Reactant 2 indices
volᵢ = Vₒ * vᵢ # cm⁻³
volⱼ = Vₒ * vⱼ # cm⁻³
sum_vᵢvⱼ = @. vᵢ + vⱼ # Product index
nothing #hide
```
We next specify the rates (i.e. kernel) at which reactants collide to form products. For simplicity, we allow a user-selected additive kernel or constant kernel. The constants(`B` and `C`) are adopted from Scott's paper [2](https://journals.ametsoc.org/view/journals/atsc/25/1/1520-0469_1968_025_0054_asocdc_2_0_co_2.xml)
```julia
```@example smcoag1
# set i to 1 for additive kernel, 2 for constant
i = 1
if i==1
B = 1.53e03 # s⁻¹
kv = @. B*(volᵢ + volⱼ)/V # dividing by volume as its a bi-molecular reaction chain
if i == 1
B = 1.53e03 # s⁻¹
# dividing by volume as it is a bimolecular reaction chain
kv = @. B * (volᵢ + volⱼ) / V
elseif i==2
C = 1.84e-04 # cm³ s⁻¹
kv = fill(C/V, nr)
C = 1.84e-04 # cm³ s⁻¹
kv = fill(C / V, nr)
end
```
We'll store the reaction rates in `pars` as `Pair`s, and set the initial condition that only monomers are present at ``t=0`` in `u₀map`.
```julia
# unknown variables are X, pars stores rate parameters for each rx
We'll set the parameters and the initial condition that only monomers are present at ``t=0`` in `u₀map`.
```@example smcoag1
# k is a vector of the parameters, with values given by the vector kv
@parameters k[1:nr] = kv
# create the vector of species X_1,...,X_N
t = default_t()
@species k[1:nr] (X(t))[1:N]
pars = Pair.(collect(k), kv)
@species (X(t))[1:N]
# time-span
if i == 1
tspan = (0. ,2000.)
tspan = (0.0, 2000.0)
elseif i == 2
tspan = (0. ,350.)
tspan = (0.0, 350.0)
end
# initial condition of monomers
u₀ = zeros(Int64, N)
u₀[1] = uₒ
u₀map = Pair.(collect(X), u₀) # map variable to its initial value
u₀map = Pair.(collect(X), u₀) # map species to its initial value
nothing #hide
```
Here we generate the reactions programmatically. We systematically create Catalyst `Reaction`s for each possible reaction shown in the figure on [Wikipedia](https://en.wikipedia.org/wiki/Smoluchowski_coagulation_equation). When `vᵢ[n] == vⱼ[n]`, we set the stoichiometric coefficient of the reactant multimer to two.
```julia
```@example smcoag1
# vector to store the Reactions in
rx = []
for n = 1:nr
Expand All @@ -82,19 +98,20 @@ for n = 1:nr
end
end
@named rs = ReactionSystem(rx, t, collect(X), collect(k))
rs = complete(rs)
```
We now convert the [`ReactionSystem`](@ref) into a `ModelingToolkit.JumpSystem`, and solve it using Gillespie's direct method. For details on other possible solvers (SSAs), see the [DifferentialEquations.jl](https://docs.sciml.ai/DiffEqDocs/stable/types/jump_types/) documentation
```julia
```@example smcoag1
# solving the system
jumpsys = convert(JumpSystem, rs)
dprob = DiscreteProblem(jumpsys, u₀map, tspan, pars)
jprob = JumpProblem(jumpsys, dprob, Direct(), save_positions=(false,false))
jsol = solve(jprob, SSAStepper(), saveat = tspan[2]/30)
jumpsys = complete(convert(JumpSystem, rs))
dprob = DiscreteProblem(rs, u₀map, tspan)
jprob = JumpProblem(jumpsys, dprob, Direct(), save_positions = (false, false))
jsol = solve(jprob, SSAStepper(), saveat = tspan[2] / 30)
```
Lets check the results for the first three polymers/cluster sizes. We compare to the analytical solution for this system:
```julia
```@example smcoag1
# Results for first three polymers...i.e. monomers, dimers and trimers
v_res = [1;2;3]
v_res = [1; 2; 3]
# comparison with analytical solution
# we only plot the stochastic solution at a small number of points
Expand All @@ -114,15 +131,15 @@ elseif i == 2
end
# plotting normalised concentration vs analytical solution
default(lw=2, xlabel="Time (sec)")
scatter(ϕ, jsol(t)[1,:]/uₒ, label="X1 (monomers)", markercolor=:blue)
default(lw = 2, xlabel = "Time (sec)")
scatter(ϕ, jsol(t)[1,:] / uₒ, label = "X1 (monomers)", markercolor = :blue)
plot!(ϕ, sol[1,:]/Nₒ, line = (:dot,4,:blue), label="Analytical sol--X1")
scatter!(ϕ, jsol(t)[2,:]/uₒ, label="X2 (dimers)", markercolor=:orange)
plot!(ϕ, sol[2,:]/Nₒ, line = (:dot,4,:orange), label="Analytical sol--X2")
scatter!(ϕ, jsol(t)[2,:] / uₒ, label = "X2 (dimers)", markercolor = :orange)
plot!(ϕ, sol[2,:] / Nₒ, line = (:dot, 4, :orange), label = "Analytical sol--X2")
scatter!(ϕ, jsol(t)[3,:]/uₒ, label="X3 (trimers)", markercolor=:purple)
plot!(ϕ, sol[3,:]/Nₒ, line = (:dot,4,:purple), label="Analytical sol--X3",
scatter!(ϕ, jsol(t)[3,:] / uₒ, label = "X3 (trimers)", markercolor = :purple)
plot!(ϕ, sol[3,:] / Nₒ, line = (:dot, 4, :purple), label = "Analytical sol--X3",
ylabel = "Normalized Concentration")
```
For the **additive kernel** we find
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