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1500 questions
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2 answers

Deriving the amplitude of a coulomb (dry friction) damped spring

This is my first time posting anything, but I could not figure out the derivation of the amplitude of the spring for the 4 first oscillations. I am not acquainted with the effect and calculations of damping since I am only in high school. This is…
Sam
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Do liquid hydrogen-based cooling devices exist and what are they used for?

Liquid hydrogen cooling could be some intermediate solution between helium and liquid nitrogen based cooling. For example, some type of superconductors could be cooled by liquid H2, and this could be much cheaper than the liquid He. What are their…
peterh
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Why do electric trains arc at high speeds?

When I watch videos of high speed trains I always see explosions of electricity near the top, or arcing. Why does that happen? I know that the Acela does it a lot but other high speed trains have it, too.
user3831089
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Design of transverse reinforcement in a wide beam

Besides satisfying nominal bar provision in the code, is there any special requirement in the provision of transverse reinforcement to ensure that the longitudinal reinforcement is fully effective in a wide beam design? That is, can I use the full…
Rebar Lor
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Why do some high speed trains have long noses, while others do not?

Why do some high speed trains like the Shinkansen E5 and E6, have really long noses while other trains, like the Eurostar and Javelin, have shorter noses? How does the shape of the nose affect the train?
user3831089
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Why is it impossible to create an observer for this not fully observable system?

Consider a 1D point-mass moving along an axis. A force $u$ is applied as control. There is no gravity or other forces involved. The system can be described in state space equations as: $$\begin{align} A &= \begin{bmatrix} 0 & 1 & 0 \\ …
FirefoxMetzger
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Torque converter torque multiplication

I keep reading all over the internet that a torque converter multiplies torque at stall speed. Every explanation I have found sounded more like hand-waving than quantitative physical explanation. Essentially, the argument goes that the stator…
gsimard
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How can I calculate the stresses and limits for the physical lowering of in-service pipelines?

Sometimes underground pipelines are exposed due to vertical scour or lateral migration of streams (or other erosion). One option is to lower the (in-service) pipeline to a new depth that provides sufficient ground cover. How can I determine the…
JustInTheWoods
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Can I reduce the column moment due to beam, by setting the beam end to pin?

I have a structure, which contains only frame elements ( beam and column). From what I know, if I apply point load at the columns on both left and right hand side,and if the beam-column joint is rigid, then the column at the center will experience…
Graviton
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Computing error dynamics from state space deadbeat observer

I'm trying to solve this problem: Given the transfer function: $$ G(z) = \frac{z^{2}+2z+1}{z^{3}-z^{2}-5z+1} $$ Design a deadbeat observer for this transfer function and compute the error dynamics $e(0)=e$. I know that to design a deadbeat…
John
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Line balancing - How far do companies go?

I understand that the concept of line balancing is such that each station takes exactly the same amount of time to process one unit. Clearly, this is an idealization and real manufacturing plants will have bottleneck stations and underutilized…
user1936752
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How can we prevent/detect hydrogen embrittlement?

There has recently been a series of high profile bolt failures on 'The Cheesegrater' in London, which have been attributed to hydrogen embrittlement. What can engineers do to ensure that hydrogen embrittlement doesn't effect their structures?
thomasmichaelwallace
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Adding a lubricant to an already lubricious material, how is CoF affected?

I have a dry film moly-graphite lubricant (CoF=.075) and a lubricious CVD coating (CoF=.05). The CoF of each of these lubricious materials was determined using the same ASME standardized test. The standardized test consists of: a plain steel object…
CBRF23
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2 answers

What is a PD pump that I can use as an immersion pump for a slurry?

I need to pump a thick slurry from a tank. The slurry can be pumped, but won't flow well enough that I can use a suction pump from outside the tank. Normally, I'd use a centrifugal immersion pump that can be drawn from the tank for service. But with…
mart
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What does it mean when actual member reaction is 100% of allowed?

I received construction documents for an extensive residential remodel and looking at the engineering there's a glulam drop beam with a calculated member reaction that is 100% of allowed (3965 lbs @ 5 1/2"). No other member comes close to 100%.…
user5867
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