傅海棠的大蒜交易是从840元/吨价格买入的，4000元/吨价格卖出，历时4个月。

This model compares exponential growth vs logistic growth of a Quokka population. Quokka's are a small creature which are native to the Australian continent. This population increases due to addition of joey's that enter the initial quokka population through each quokka mother that gives birth. The loss of numbers is the quokka's leaving the population by death. This whole system keeps the quokka population in equilibrium and can also act as a guide to sustainability, as it allows us to view birth and death rates of a population. We can then work with the numbers of this model to decide how we want to approach this population with sustainability in mind. For example, a high birth rate means we would need to find methods to control the population to create a sustainable environment which is able to maintain this population. 

Developed by Maurice Karsten (Bielefeld University) as part of a doctoral research in chemistry education.  

Overview:

This System Dynamics model operationalizes the dynamic, reciprocal relationships between Subjective Culture, Self-construal, and Goal Orientation across developmental time.

Key Pathways Tested:

1. Culture→Goals & Self→Goals: Goal Orientation is calculated as a weighted composite where Alignment determines whether goals are internally or externally generated.

2. Culture→Self: Macro-level direct cultural socialization pulls Self-Construal toward cultural norms over developmental time (tmacro​=18).

3. Goals→Self: Reciprocal feedback from goal pursuit reshapes Self-Construal, with the feedback rate moderated by Alignment ( cultural goodness-of-fit).

A simplified Science Olympiad trial model for comparing lake-restoration strategies. Adjust wastewater treatment, water-hyacinth removal, and wetland-buffer effort, then run the simulation to compare pollution load, pathogen risk, and hyacinth coverage over time. Values are normalized challenge indices, not field measurements or a real-world safety forecast.

The World3 model is a detailed simulation of human population growth from 1900 into the future. It includes many environmental and demographic factors.

Use the sliders to experiment with the initial amount of non-renewable resources to see how these affect the simulation. Does increasing the amount of non-renewable resources (which could occur through the development of better exploration technologies) improve our future? Also, experiment with the start date of a low birth-rate, environmentally focused policy.