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  • 20 votes cast
Sep
10
comment Need a logistic like function with y=0 at x=0
The trend is changed by doing so. The logistic growth has a property that I need, it is bending downward (lower-right) at the beginning and then bending upward (upper-left) after a certain point.
Sep
10
comment Need a logistic like function with y=0 at x=0
@avid19 Yes, I hope so. Is it possible to further drive down the $y$ value at the beginning? i.e., around $x=0$?
Sep
10
asked Need a logistic like function with y=0 at x=0
Sep
2
awarded  Popular Question
Dec
22
awarded  Caucus
Mar
14
comment Looking for a function
Thanks, I found $\frac{\tanh(Cx)}{\tanh(C)}$ satisfies my needs.
Mar
14
revised Looking for a function
added 12 characters in body
Mar
14
revised Looking for a function
added 50 characters in body
Mar
14
asked Looking for a function
Jan
14
comment Navier-Stokes Equation and turbulence, current status of research?
Thanks. I have already bookmarked it. I've been following this news for many days. :)
Jun
11
accepted Looking for a 3D smooth step function
Jun
11
comment Looking for a 3D smooth step function
I am just using the region between -1<x<+1. I should say, it is just step-like function, not a perfect alternative for step function though.
Jun
11
revised Looking for a 3D smooth step function
added 78 characters in body
Jun
11
asked Looking for a 3D smooth step function
Jun
10
awarded  Supporter
May
30
asked Navier-Stokes Equation and turbulence, current status of research?
May
29
accepted How to apply chain rule to this term $\vec a \cdot \nabla \cdot \nabla \vec b$?
May
29
awarded  Commentator
May
29
comment How to apply chain rule to this term $\vec a \cdot \nabla \cdot \nabla \vec b$?
So, if I understand correctly, you do not suggest using notation like "$\left( {\nabla \vec b} \right) \cdot \left( {\nabla \vec a} \right)$", because they are not well defined and is not powerful enough to represent the tensor calculus. Please correct me if I am wrong. But if I do use the notation of $\left( {\nabla \vec b} \right) \cdot \left( {\nabla \vec a} \right)$ to represent $\vec\nabla a_i)(\vec\nabla b_i$, then it is OKAY to write $$\vec a\cdot\nabla\cdot\nabla\vec b=\nabla \cdot \left({\vec a\cdot\nabla\vec b}\right) - \left({\nabla \vec b} \right)\cdot\left({\nabla\vec a}\right)$$?
May
29
comment How to apply chain rule to this term $\vec a \cdot \nabla \cdot \nabla \vec b$?
$\vec a$ and $\vec b$ are both velocities, in fluid dynamics, so they are vectors, and the gradient of the vector field is a tensor field, and I am wondering what it would mean by dot product of two tensor field ($\left( {\nabla \vec b} \right) \cdot \left( {\nabla \vec a} \right)$)?