Featured Author

John Hayward

I am a Visiting Research Fellow in Mathematics at the University of South Wales. Before my retirement, I was a senior lecturer at the university, teaching specialist courses in system dynamics, mathematical modelling and agent-based methods. I was awarded a BSc in astrophysics, and a PhD in applied mathematics, from the University of London, and then spent my career as a lecturer in mathematics. My research is in mathematical sociology with applications to the spread of social phenomena, such as ... Read more

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We found 40 items
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#1

Information Processing and Neurophysiology Model

by Jon Darkow
The main dependent variable measured in the model is the membrane potential (millivolts) of two diff ... Read more
The main dependent variable measured in the model is the membrane potential (millivolts) of two different neurons in a series. You will be able to add excitatory and inhibitory neurotransmitters, and compare how these modulate electrical impulses of the two neurons. Additionally, you will be able to compare the effects of three neurotoxins: Tetrodotoxin, botulinum toxin, and sarin nerve gas. While extremely lethal, these toxins are very instructive in understanding neurons because of the specific way the toxins act. Each toxin modifies or inhibits a specific molecule in neurons that help process and transmit information.
sim ⋮ 15,232 runs
infromation processing neurophysiology biology
22447.559
#2

Lactase Enzyme Simulation with Data Analysis

by Jon Darkow
sim ⋮ 77,574 runs
20154.04
#3

Photosynthesis Model

by Jon Darkow
sim ⋮ 29,097 runs
7550.02
#4

Cellular Respiration Accounting Model

by Jon Darkow
The purpose of the model is to understand how glucose is metabolized, and how the energy stored in i ... Read more
The purpose of the model is to understand how glucose is metabolized, and how the energy stored in its chemical bonds is transfered.
sim ⋮ 5,903 runs
cellular respiration aerobic respiration ATP biology
6533.886
#5

Population dynamics of white footed mouse

by Jon Darkow
sim ⋮ 14,165 runs
3667.7
#6

Lactose Operon: An Inducible System

by Jon Darkow
In this simulation users explore the negative feedback system of the Lactose Operon found in bacteri ... Read more
In this simulation users explore the negative feedback system of the Lactose Operon found in bacteria. Lactose induces the system by inhibiting and inhibitor.
sim ⋮ 3,142 runs
Inhibition negative feedback biology lactose operon
3612.3625
#7

Apterous Genetics

by Jon Darkow
Apterous is an allele that results in a fly without wings. Wild-type variants have normally function ... Read more
Apterous is an allele that results in a fly without wings. Wild-type variants have normally functioning wings. The goal of this simulation is to determine the pattern of inheritance for the apterous phenotype. Is apterous dominant or recessive? Sex-linked or autosomal? Complete, incomplete, or codominant?
sim ⋮ 6,011 runs
Genetics
2721.42
#8

Growth Factors, Cyclins, and Cancer

by Jon Darkow
Explores the feedback loops that regulate the cell cycle. Model focuses on manipulating stimuli (gro ... Read more
Explores the feedback loops that regulate the cell cycle. Model focuses on manipulating stimuli (growth factors), to stimulate the cell cycle feedback loops.
sim ⋮ 2,857 runs
growth factors cyclins cell cycle cancer
2661.6624
#9

Evolution and Natural Selection

by Jon Darkow
sim ⋮ 7,046 runs
1816.76
#10

Evolution of LAP Allele in Mussels

by Jon Darkow
sim ⋮ 2,799 runs
Evolution Natural Selection Cline
1741.5067
#11

zFourth Position - don't move

by Automated Tests
sim ⋮ 5,952 runs
1532.32
#12

White-Eyed Genetics

by Jon Darkow
White-eyed is an allele that results in a fly white eyes. Wild-type variants have red eyes. The ... Read more
White-eyed is an allele that results in a fly white eyes. Wild-type variants have red eyes. The goal of this simulation is to determine the pattern of inheritance for the white-eyed phenotype. Is yellow body dominant or recessive? Sex-linked or autosomal? Complete, incomplete, or codominant?
sim ⋮ 2,935 runs
Genetics
1285.4567
#13

Zombie Apocalypse

by isee systems
This is our first model in the From Imagination to Simulation series. It is a nod to the Halloween s ... Read more
This is our first model in the From Imagination to Simulation series. It is a nod to the Halloween season and investigates a zombie apocalypse! Our fascination with zombies continually grows with the help of movies, TV shows, and books that give a wide range of zombie possibilities. But what are the dynamics behind a zombie epidemic? This model will specifically look at the spread of a zombie outbreak and examine some of the variables that help and hinder the rate of infection. We hope you will continue to see the benefits and versatility of Systems Thinking and enjoy our new series, From Imagination to Simulation! Continue to ponder those out-of-the-ordinary problems. They may seem unrealistic, but perhaps some of their dynamics may resonate with reality. Check out our zombie apocalypse model to see if there is any chance for human survival!
sim ⋮ 579 runs
Systems Thinking zombies epidemic disease susceptible
1188.248
#14

Trp Operon

by Jon Darkow
Tryptophan is an amino acid that is synthesized by plants and bacteria from other molecules in a bio ... Read more
Tryptophan is an amino acid that is synthesized by plants and bacteria from other molecules in a biochemical pathway (see diagram below). The trypophan operon is a series of sequential genes found on a bacterial genome. The genes of the operon produce the enzymes that direct the synthesis of tryptophan. In this model you will experiment with the negative feedback loop of the repressible system.
sim ⋮ 671 runs
Feedback loop operon biology tryptophan repressible
937.06
#15

Evolution

by Jon Darkow
Evolution of Populations: Genetic Drift, Natural Selection, and Mutations
sim ⋮ 1,105 runs
evolution natural selection genetic drift
907.455
#16

Water Potential and Osmosis

by Jon Darkow
Factors that affect the flow across a semi-permeable membrane.
sim ⋮ 3,021 runs
773.41
#17

HPV and Adaptive Immune Response

by Jon Darkow
sim ⋮ 930 runs
HPV Antibodies feedback loops vaccine
666.26666
#18

Limits to Growth Archetype

by John Hayward
Shifting loop dominance in a limits-to-growth archetype is examined using the Hayward/Boswell Loop I ... Read more
Shifting loop dominance in a limits-to-growth archetype is examined using the Hayward/Boswell Loop Impact Method.
sim ⋮ 418 runs, 4 downloads
Download Model
Loop dominance Limits to Growth archetype loop impact
596.06934
#19

Vacation

by isee systems
Do you ever feel like work is taking over your life? Burnout is generally characterized as a state o ... Read more
Do you ever feel like work is taking over your life? Burnout is generally characterized as a state of mental and physical exhaustion resulting in low productivity and de-personalization and is most likely caused by prolonged stress that does not dissipate. There are many different aspects that affect both the building and dissipation of burnout. This model focuses on workloads and vacations to see how they contribute to both your level of burnout and productivity. Use this model to ask questions about your workload and any benefits you would receive from taking a vacation. What happens when you suddenly have a bigger workload? What happens when work piles up? Does vacation increase or decrease your stress levels?
sim ⋮ 297 runs
Vacation burnout stress productivity workload
590.4633
#20

PCU-curso-VSN

by Armando Izquierdo
Este modelo es un primer intento de utilizar el "Business Canvas" desarrollado por Alexander Osterwa ... Read more
Este modelo es un primer intento de utilizar el "Business Canvas" desarrollado por Alexander Osterwalder e Yves Pigneur, para explicar su carácter sistémico mediante la simulación de un modelo de negocio genérico utilizando Stella Architect. El objetivo principal es mostrar el vínculo entre los conceptos del pensamiento sistémico y la práctica del "Systems Dynamics" con el ampliamente difundido "Business Canvas". En la narrativa utilizada para describir la construcción del diagrama "Stock & Flow", se denomina entre parentesis el tipo de componente (Stock, Flow, Converter, o Conector) correspondiente a los principales elementos del modelo de negocio. La simulación permite visualizar la naturaleza sistémica de un modelo de negocio representado mediante el "Business Canvas".
sim ⋮ 174 runs
Stella Architect Business Canvas Modelos de Negocios Alex Osterwalder Simulación
573.51733
#21

Steady State in Freshwater Ecosystems

by Jon Darkow
sim ⋮ 2,249 runs
569.54
#22

mse-litsim

by Lorenzo Andrade
Modelo de Simulación de Escenarios MSE-LITSIM
sim ⋮ 511 runs
gestión áreas litorales eutrofización estuarios humedales
549.805
#23

macrolab

by David Wheat
macrolab
sim ⋮ 2,156 runs
545.76
#24

Transformation Simulation

by Jon Darkow
Simulation allows students to test the transformation principle. Two major goals of the experiment a ... Read more
Simulation allows students to test the transformation principle. Two major goals of the experiment are: 1. Allow users to see that supernatant from heat-killed bacteria can transform the genes of another bacterium. 2. What transforms the inheritance of the bacteria is DNA, not RNA or proteins.
sim ⋮ 660 runs
transformation DNA biology
530.64
#25

MNH Strategic Model

by Peter Hovmand
Strategic model of country-level policies to reduce maternal and neonatal mortality.
sim ⋮ 534 runs
global health maternal survival neonatal survival
524.24664
#26

Recombination and Gene Linkage

by Jon Darkow
sim ⋮ 1,882 runs
474.12
#27

Macromodel

by Pervin Dadashova
Model for the public policy testing
sim ⋮ 1,831 runs
462.61
#28

Health Policy Management Flight Simulator

by Shamim
This is a basic health policy simulator that allows the user a policy lever on where to prioritise h ... Read more
This is a basic health policy simulator that allows the user a policy lever on where to prioritise health care spending.
sim ⋮ 707 runs
health systems shifting boat
433.81
#29

Salmon Simulator

by James Pratt
Simulation of salmon populations with harvesting using the Tucannon River (WA) as an example. Simul ... Read more
Simulation of salmon populations with harvesting using the Tucannon River (WA) as an example. Simulation accompanies the text Modeling the Environment, 2nd ed. by Andrew Ford. Used with permission.
sim ⋮ 440 runs
salmon harvesting maximum sustainable yield
426.73
#30

Campus sexual assault

by Peter Hovmand
A very simple, one stock, simulation of campus sexist attitudes toward rape and initimate partner vi ... Read more
A very simple, one stock, simulation of campus sexist attitudes toward rape and initimate partner violence. The model was originally developed in 1998 and later translated into Stella. The model has a number of modeling errors, but at the time, proved useful for gaining insight into the dynamics of the system and developing an innovative prevention program.
sim ⋮ 421 runs, 4 downloads
Download Model
campus sexual assault community norms
422.11667
#31

Salmon Hypoxia Modeling Lab

by Ryan Bellmore
This model simulates the influence of spawning salmon on dissolved oxygen in southeast Alaskan River ... Read more
This model simulates the influence of spawning salmon on dissolved oxygen in southeast Alaskan Rivers.
sim ⋮ 243 runs
Pacific salmon water quality dissolved oxygen hypoxia ecological modeling
371.13232
#32

Weight Loss Sim

by Corne
This simulation gives the user the ability to specify their own current condition (weight, age, heig ... Read more
This simulation gives the user the ability to specify their own current condition (weight, age, height etc.), choose their exercise regime and eating plans. The simulator then gives a projection for the user's weight for the next year (at a weekly resolution). Please take note that most of the pictures are navigation buttons to different screens, so remember to click on the pictures. I have personally used this simulator to successfully lose more than 20 kg. Hope you find this as valuable as I did. Good luck with your weight journey!
sim ⋮ 390 runs
Weight loss Health
367.55334
#33

The Laundry Detergent Game

by Billy Schoenberg
Congratulations! You've just been hired by the major grocery chain The Price Shopper as head of mark ... Read more
Congratulations! You've just been hired by the major grocery chain The Price Shopper as head of marketing. Your job is to turn around The Price Shopper's dismal sales of laundry detergent. The big-wigs have given you 12 months and a marketing budget of up to $10,000 per month to spend as you please. They'll decide to keep you, or send you to the cleaners based on how much profit you bring in over the year. Do you think you can make the big MONEY?
sim ⋮ 252 runs, 11 downloads
Download Model
system dynamics bass diffusion model marketing
355.37668
#34

Product Development Simulator

by Billy Schoenberg
The Bass Model or Bass Diffusion Model was developed by Frank Bass and it consists of a simple diffe ... Read more
The Bass Model or Bass Diffusion Model was developed by Frank Bass and it consists of a simple differential equation that describes the process of how new products get adopted in a population. The model presents a rationale of how current adopters and potential adopters of a new product interact.
sim ⋮ 211 runs
product development game simulator bass diffusion marketing
328.60367
#35

Feebates

by James Pratt
Model of fees and rebates for air pollution control based on differing vehicle types. Model orginal ... Read more
Model of fees and rebates for air pollution control based on differing vehicle types. Model orginally developed by Andrew Ford to accompany Modeling the Environment, 2nd Ed., Island Press (2010) . Used with permission.
sim ⋮ 498 runs
air pollution rebates
314.57867
#36

Phenology of the Karner Blue Butterfly

by Jon Darkow
Karner Blue butterfly is an endangered species. Habitat loss and climate change are contributing fac ... Read more
Karner Blue butterfly is an endangered species. Habitat loss and climate change are contributing factors to the reduction in the butterflies' population sizes. Climate change can alter the timing of lifecycles. When climate change disproportionally affects the timing of life cycles of species in an ecosystem asynchrony within a food web occurs.
sim ⋮ 190 runs
asynchrony timing phenology climate change butterfly
314.48666
#37

macrolab2016

by David Wheat
sim ⋮ 1,123 runs
276.78
#38

Urban Stream Rainfall

by Samuel Austin
A simple example of streamflow response to rainfall and basin percent urban area.
sim ⋮ 172 runs
rainfall-runoff modeling simulation urban peak-flow streamflow
268.54868
#39

Extinction Vortex

by Jon Darkow
sim ⋮ 918 runs
223.48
#40

General Practice Advanced skill simulator

by Whole Systems Partnership
A model to explore changing roles within the advanced skilled workforce for General Practice in the ... Read more
A model to explore changing roles within the advanced skilled workforce for General Practice in the UK.
sim ⋮ 186 runs
Primary care workforce skills level strategic workforce planning
222.57466
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Uploading a Bundle from Zip

Instead of creating bundles, categories, and assemblies one by one, you can upload a single zip file that contains all of your bundle's content. To create your zipped bundle, make a folder with your bundle's name and add subfolders with your categories' names. The folder tree should have the same structure that you want the categories to have in your bundle. Place your assembly .stmx files in the appropriate category folders, then zip your bundle folder and upload it using the Upload Bundle from Zip link above.

Assemblies, Bundles, and Categories

Assemblies are self contained models that demonstrate common ways to connect together building blocks and that can be used as parts of other models. This is analogous to using prefabricated wall and roof pieces to construct a house.

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Categories are subgroups of assemblies within a bundle. For example, a Health Care bundle might contain a Funding category for assemblies related to the management of hospital funds. All assemblies must be assigned to a category—they cannot be assigned to the root of a bundle.

Assemblies, bundles, and categories can be created and uploaded to the isee Exchange™ via the options on the Manage My Assemblies page. To learn more, visit our help pages, or take our assemblies tutorial.

Sim App (Sim)

An interface that allows users to interact with a model.

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Sim apps allow users to interact with a model using buttons, sliders, knobs, tables, graphs, and storytelling. These interactions help users understand how parts of a system interact.

Interfaces are created by model authors in the Stella desktop software and can be uploaded to the isee Exchange™.

Model

A diagram that represents how elements in a system influence one another.

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Models are mathematical representations of how elements in a system are connected and interact (e.g., ecosystems, organizations, supply chains). When running models on the isee Exchange™, results can be viewed in output devices like graphs and tables.

Models appear in the isee Exchange™ directory when authors upload them from the Stella® desktop software or create them with Stella Online™.

Causal Loop Diagram (CLD)

A map that represents the feedback structure of a system.

Image of a CLD

CLDs are high-level maps that represents the feedback structure of a system and easily communicate the essence of a model. They appear in the isee Exchange™ when authors upload them from the Stella desktop software or create them with Stella Online™.