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1500 questions
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Why does filter efficiency decrease with thickness?

I understand that the most important parameters for a filter are basically pressure drop and thickness, both of which affect efficiency. However why does thickness cause a change in efficiency? I'm particularly interested in the use of nanofibers as…
User2341
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Why does reducing the amount of emissions control improve the fuel economy of a car?

In addition to power and performance, one of the reasons VW cheated their emissions results was to improve the fuel economy of their cars. Why exactly does this happen? I'm familiar with cars and how cars work so feel free to get technical. And a…
Kevin
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How in Rankine cycle the turbine generates more power than the pump takes?

In Rankine cycle there's the boiler where water gets boiled into overheated steam. On input there's a pump that delivers more water, and on output there's a turbine that picks up the energy of the compressed steam. The steam pressure is roughly…
SF.
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How do I compute the force required to pierce HDPE?

I have a $2\text{ mm}$ sheet of HDPE at $280-320^{\circ}\text{ F}$. I want to pierce the skin of this sheet with a $2\text{ mm}$-high pin with a surface area of $3.33\text{ mm}^2$. The pin is also made of HDPE and has cooled completely. With the…
William B.
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How does pressure change with depth in earth?

I've learned in school that pressure in water changes like $$p(h) = \rho g h$$ where $h$ is depth in meters, $\rho$ is density (e.g. 1000 $\frac{\text{kg}}{\text{m}^3}$ for water) and $g$ is gravitation acceleration ($\approx 9.81…
Martin Thoma
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How should a bridge deck closure pour be positioned?

The Question: Where should a closure pour be located relative to centerline of girder and how should the closure pour width be detailed/designed? And now, a little background: When designing a steel girder bridge using phased construction with dead…
CableStay
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Steel selection for building a trailer

I'm thinking about building another trailer. I've built lots of smaller trailers in the past, but this time I'd like to build myself a small tandem axle gooseneck rated for 7,500 lbs. I am a certified welder, I have a Bachelor's degree in Physics,…
jp2code
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What is the practical limit on the number of storeys in residential buildings built with monolithic reinforced concrete?

I have recently bought a flat in a 25-storey building. I wonder what is the practical limit for the number of storeys in a mass-produced residential buildings built from monolithic reinforced concrete? Can we expect the number of storeys in typical…
Anixx
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Why is it unwise to choose cylindrical horizontal beam

I heard that it is unwise to choose cylindrical horizontal beam. My question is why?
Mohamed
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Can titanium be used as I-beams?

Is titanium capable of being used in I-beams....
LazyReader
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Motor for a hydraulic pump in a hydraulic system

I am a complete beginner to hydraulic systems, and I've wanted to learn more about this area. I'm designing a hydraulic system that involves using hydraulics to push/pull objects using pistons. I have looked at what the basic requirements are for a…
Tom
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Is there a way to make an air conditioner without venting heat outdoors?

Is there a way to make an air conditioner for when you can’t vent the heat outdoors? Can you trap the heat in an object or convert it to another form of energy? For example, could you transfer the heat through an electrical outlet? I would be…
1.21 gigawatts
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How to work on big CAD project in team?

I'm always confused on what is the effective way to work on CAD with multiple team members to make it efficient. So far, as I'm freshly graduated I only work on a project where I'm the only one using the CAD software. At best there's only two of us,…
el-cheapo
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Metric bolt shear strength for a layman

As a layman, how can I know the shear strength of a particular size bolt? For example, if I want to attach something to the internal wall of my van ( 1mm stainless steel ) using a rivnut and standard metric bolt and it should hold up to 50 kg, how…
Robert S. Barnes
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What is the effect of end diaphragms on prestressed girder forces/deflections?

I'm encasing the abutment ends of prestressed concrete bridge girders in concrete before the deck pour. (For lateral stability and to prevent the soil from spilling through.) Discussion of intermediate diaphragms for prestressed girders abounds, but…
CableStay
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