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Measuring the distance to an object with RF resonance

Assume I put an RF antenna in front of an object (typically the face of someone sitting in a chair, so able to move about +/- 10cm in all directions) at a typical distance of 1m. If I consider the system antenna/face as a resonant cavity, I'd get a…
Julien
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How do cyclonic vacuum cleaners maintain collection efficiency with constant motion and changes in orientation?

Anyone used to doing housework has probably noticed that vacuum cleaners come in both "bagged" and "bagless" varieties. If you're of a certain age, you may have noticed when these "bagless" vacuums appeared back in the 1990s. Though I didn't…
Air
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What is the accuracy of direct metal laser sintering (DMLS)?

They've printed jet engines with it that work after polishing. So how is the accuracy measured and how accurate is the DMLS process? I can't find the required info anywhere.
Daniel Donnelly
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Difference between continuous wave laser and a pulsed laser

I understand the difference between the two in terms of how they function; one will release all of it's energy in small pulses with the other creates a constant stream of radiation. My question is for materials processing such as marking or cutting.…
Jonny Flowers
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How small can you get a stream of molten steel to be at low pressure?

I'm designing a crucible / extruder, and right now it has a .6mm hole to extrude from. Will this work? A chart with various metals listed would be nice. Pictures: Click to expand
Daniel Donnelly
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Efficient 3D mesh topology for CFD simulation of turbine blade

I´m developing a tool to generate an openFoam wind tunnel case of a wind turbine. I already have the blade geometry constructed, but I'm really new to CFD and parametric meshing. I found some articles where they mention a C topology to mesh the…
efirvida
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Bend allowances when making a C-shape plate

I am trying to find the formulas for making bends in sheet metal. I understand there are formulas for bend allowances. My issue is how do I determine where to bend if I want the inside dimension to be an exact number and if I want the outside to be…
BrianB
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How an airfoil works

I have read on many sites that for lift to occur, the pressure below a wing must be higher than the pressure above it. This happens by somehow moving air faster over the top of the air foil so the pressure above the wing decreases. What I can't…
Fady basem
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How much stronger than the bare minimum should a motor be?

A motor gives its strength in N-cm or oz-in, but how do you know how much you require? I know you can just calculate the minimum torque you need to move the load, but is there a typical amount over that minimum that is standard? Like 20% or…
Zephyr
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How to extract a building's heat isolation and thermal inertia based on temperature curves?

So imagine we have a house with some isolation and some thermal inertia. This house also has a heating system that turns on (starts heating) when the observed temperature curve goes below some predefined temperature threshold. I figured that in the…
Samy Geronymos
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What is the reason for the instant loss of a vaccum through the sealed glass tube after shuting off a pump?

A pump is connected to a glass tube to evacuate it. The reading shows 0.4 mbar when the pump is on because of a vacuum. As soon as the pump is turned off, the pressure in the tube becomes equal to atmospheric pressure.
Rahul
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Understanding pressure drop and mass average values

While studying some papers, I didn't understand the following sentences: deltP the pressure drop across the turbine, evaluated using the mass average values at the inlet and outlet sections of the computational domain, respectively. What is the…
user19061
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Penetration depth and weld deposition rate in Welding

What factors affect the penetration depth and weld deposition rate in arc welding? How does polarity affect the penetration depth and weld deposition rate? My lecturer said that penetration depth is higher when using straight polarity when compared…
M.Tarun
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Is it feasible to forge multiple, smaller parts in the same forging operation?

Let us assume you have a large forging press or drophammer, and drawings for a set of smaller parts that all need to be forged from the same material. Would it be feasible to construct a forging die so that all the parts could be forged from a…
ThreePhaseEel
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Why aren't these spokes radial?

Have a look at this water wheel (located at Hama, Syria). Most spoked wheels seem to be designed with spokes that radiate outward from the center of the hub (bicycle wheels being the notable exception). All of the spokes in this wheel are offset…
ConanTheGerbil
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