TIJUANA—Kaji Douša, the Senior Pastor at The Park Avenue Christian Church, stood on a pedestrian bridge over the Tijuana River on Tuesday, overlooking the concrete riverbed where American security forces had lobbed tear gas canisters at Central American migrants just two days before. Douša had come to Tijuana from New York City as part of the “Sanctuary Caravan,” a project aiming to recruit faith leaders to travel to the border to accompany migrants as they face their uphill battle to safely enter the United States and begin the asylum process. [ more › ] Gothamist https://ift.tt/2TZf95L November 28, 2018 at 10:05PM
Van der Pol’s differential equation is The equation describes a system with nonlinear damping, the degree of damping given by μ. If μ = 0 the system is linear and undamped, but for positive μ the system is nonlinear and damped. We will plot the phase portrait for the solution to Van der Pol’s equation in Python using SciPy’s new ODE solver ivp_solve . The function ivp_solve does not solve second-order systems of equations directly. It solves systems of first-order equations, but a second-order differential equation can be recast as a pair of first-order equations by introducing the first derivative as a new variable. Since y is the derivative of x , the phase portrait is just the plot of ( x , y ). If μ = 0, we have a simple harmonic oscillator and the phase portrait is simply a circle. For larger values of μ the solutions enter limiting cycles, but the cycles are more complicated than just circles. Here’s the Python code that made the plot. from scipy import linspace from ...
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