Questions tagged [diffusion]
The diffusion tag has no usage guidance.
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Momentum Diffusivity without Mass Diffusion in Liquids
I have been reading about the differences between momentum and mass diffusivity. I understand that mass diffusion occurs because of the "random walk" of individual molecules which over time ...
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Diffusor for uniform illumination
I have an LED with a beam angle of 120° and I need to illuminate an area in the shape of a circle with a radius of 3.5 mm.
My objectives are as follows:
Achieve a uniform illumination of the circle (...
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Errors obtained in the numerical solution of the 1D convection-diffusion equation
I have been trying to solve the 1D convection-diffusion equation
In implementing the above, I have tried to follow closely the method described here: https://uk.mathworks.com/support/search.html/...
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Analytical solution for the 1D convection-diffusion equation
The Ogata and Banks analytical solution of the convection-diffusion equation for a continuous source of infinite duration and a 1D domain:
where C [mol/L] is the ...
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Will pressurizing container slow moisture permeation?
I have some electronics housed inside a sealed plastic enclosure, which will be used in a very humid environment. The environment can be assumed to be 100% humidity at a constant temperature, all the ...
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Is the silicone oil used in a diffusion pump oil special?
I have obtained two diffusion pump stages from a pair of very old Vacuubrand high vacuum pump. The rotary vane pump in one of them was dead and another overheating. So, I salvaged only the diffusion ...
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How the 3M Aura 9332+ masks filtrate airborne particles/virus?
The 3M Aura 9332+ mask is labeled FFP3 which means that it filters at least 99% of airborne particles.
This article mentions that N95 masks (which filtrate 95% of airborne particles) filtrate the ...
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P-N junction depletion region
Before I explain my problem I'd like to mention I'm still green and about 2 weeks into these topics. I learned most of it from youtube videos, wikipedia and other science sites, so I'll be explaining ...
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What is the difference between a diffuser and a duct in turbines?
I have been reading this paper, which addresses the advantages of diffusers in cross flow turbines.
The abstract says (emphasis is mine):
A CP’s extraordinary improving resulted when yaw increased ...
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Diffusion of miscible fluids
I was trying to model experimentally the interdiffusion of two miscible liquids. Is there an optical method to find out the extent of diffusion; the addition of fluorescing agent into any of the two ...
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How to calculate the Jacobi of electron/hole continuity equations for semiconductors with respect to potential when applying Newton's method?
These are the discretized drift diffusion equations as taken from the book "Analysis and Simulation of Semiconductor Devices" by Siegfried Selberherr. The electron continuity equation is:
$$\begin{...
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How is the reaction progress variable $c$ coupled with Temperature equation while solving the SIMPLE algorithm in CFD?
While solving the Navier-Stokes equation using SIMPLE algorithm, we solve the transport equation for additional scalar at the last step according to the SIMPLE's procedure.
We need to add a new ...
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Derivation of Overall Mass Transfer Coefficient
The flux in the gas can be written as:
$$N_{1}=k_{p}(p_{1}-p_{1i})$$
And the flux in the liquid can be written as:
$$N_{1}=k_{x}(x_{1i}-x_{1})$$
And we know that $$x^*_{1}=\frac{p_{1}}{H}$$
How ...
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Waterproof Case Time Limits
Some cell phone cases have a waterproof rating of IP-68, often specifying that they can tolerate immersion to 6 feet for 30 minutes or 3 feet for 60 minutes. My understanding, however, is that a good ...
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How long does it take for two initially seperate fluids to reach a certain homogenity across their container?
Imagine the following initial condition:
Two completely miscible fluids A and B with different dynamic viscosities $\eta_A$ and $\eta_B$ are seperated in a container with fixed Volume $V_0$ and ...
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