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1500 questions
11
votes
1 answer
Detailed dimensions of an aircraft engine compressor blade
I am working on rub-induced vibrations in compressor stages of aircraft engines. The work is carried out in partnership with a company, therefore there is a limited amount of it that could be published openly.
Is it feasible to release open source…
Nicolas
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11
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1 answer
What does "$\pm$ 0.5% F.S." mean?
I've seen it in several data sheets - it is a measure of error of some kind, of course. The problem is I dont know the exact meaning. I've seen it in the context of repeatability, accuracy and linearity.
An example is the following data sheet: smc…
JHK
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11
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2 answers
Is a chair with N+1 wheels ever less stable than a chair with N wheels?
My workplace has a policy to provide standing desks upon request, but no policy to provide chairs of matching height. (I work for the government...) We can buy our own, or build our own. However they added a stipulation that the chairs must be…
Dennis
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11
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6 answers
What fundamentally distinguishes cavitation and boiling as different phenomena?
Cavitation and boiling are names for phenomenon that both involve sudden appearance of bubbles of vapor within a liquid, and in both cases they happen when the local hydrostatic pressure is lower than the vapor pressure of the fluid, but that…
uhoh
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11
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3 answers
Why would a bearing plate that further concentrates load onto small surface be used?
Here's a photo of a bearing plate where a bridge reinforced concrete beam meets the earthfill
The bridge span is about 20 meters long and consists of two reinforced concrete beams each resting on two bearing plates like the one shown - one plate…
sharptooth
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10
votes
2 answers
Best way to get rid of turbulent flows?
I am making a testing facility for pumps. This facility has to be able to handle 500 m3/h with at little turbulence as possible. The basin itself is 5 meters long, 2,5 meters wide and 2 meters tall. The water level in the basin is kept at 1,9…
Arjo
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10
votes
1 answer
How to calculate Power of motor when used as a generator?
How can you calculate how much power can be generated by a motor when used as a generator (like a motor used in a wind turbine)?
Does the power depend on how fast the magnet is rotated? If so, is there a equation that lets you know given the rpm,…
user510
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10
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1 answer
Where did I go wrong conceptually when attempting to calculate the maximum force on a truss at a given joint?
In the problem statement below, the question states to find the maximum load $\vec{P}$ that the truss can support. My method of approach was:
Draw a FBD for the entire structure.
Generally I would identify all external forces, however for this…
Hunter
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10
votes
1 answer
MIMO (multi input - multi output) system decoupling method
A MIMO system with 2 input and 2 output decoupling method to a SISO system is described in many articles and books. How about m*n size transfer functions systems? How can we generalize the method for example to 3*3 or 3*7 MIMO systems?
Here is a 2*2…
lahidj
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10
votes
3 answers
How do you determine the accuracy of a measurement device?
Lets say you have a measurement device of which you do not know the accuracy, and a reference measurement device. Both measure a variable $x$. The range of interest is $x_0
JHK
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10
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1 answer
Response of a system to a step function (Heaviside function)
I'd like to compute the response to a step function of a electrical/thermal system. Generally I can "easily" compute the transfer function $H$:
$$H(\omega) = \frac{V_{out}(\omega)}{V_{in}(\omega)}$$
Since the Fourier transform ($\mathcal{F}$) of the…
Worldsheep
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10
votes
5 answers
What do you call the difference between the on and off temperatures in a simple thermostat?
A simple thermostat will turn on at one temperature and off at a higher temperature. This keeps the thermostat from cycling on and off too quickly. The difference between these values is sometimes called dead band and sometimes called hysteresis.…
ericnutsch
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10
votes
2 answers
How are wind tunnel models used when designing supersonic aircraft?
There are two things involved: wave drag and boundary layer separation. The wave drag depends on the Mach number while the latter depends on the Reynolds number of the flow. It's easy to maintain the incoming Mach number as it is independent of the…
Subodh
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10
votes
2 answers
How to calculate permittivity for higher frequencies?
In many books the permittivity of a material is only listed as dielectric constant for one or a couple of frequencies. 1 kHz is used often (for example in the Plastics Technology Handbook, 4th ed, ISBN-13: 978-0-8493-7039-7), but I'm looking for the…
Mast
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10
votes
2 answers
Are small car engines designed to tolerate a higher duty cycle than large car engines?
For simplicity we're going to ignore aerodynamics and vehicle mass for a moment...
Are small (around 1 litre) car engines designed to tolerate a higher duty cycle than large (2+ litre) car engines?
Cars are usually all travelling at roughly the…
squigbobble
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