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1500 questions
6
votes
1 answer
Why prefer plain pipes over corrugated pipes for storm sewage and culverts?
Recently I observed installing new storm sewage along a city street. Pipes have plain surface (not corrugated) and are made of some plastic looking like HDPE (polyethylene) and their diameter is around 0,5 meters and the walls are around 40…
sharptooth
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6
votes
4 answers
Is a circle the strongest 2D shape for containing internal pressure?
I understand how a circle (or sphere if you want 3D) is the best shape for holding a vacuum inside a container, but what if you wanted to have a large positive pressure inside of the container instead of outside? Would a circle/sphere still be the…
user2813274
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6
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2 answers
When is DC power generation superior over AC power generation?
If the goal is to transmit power over a large distance, I can see the advantage of an alternator over a generator: more power, less loss. If the target DC load is small and very close by, would an alternator still be more advantageous in terms of…
Paul
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6
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2 answers
What is this pan-tilt system called?
Based on the description of friend I drew this small example of a specific pan-tilt mechanism I'd like more information on, but as I'm not an engineer I don't really know what terms to use and can't seem to find anything.
I think I might have seen…
Jasper
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6
votes
1 answer
controlled depositing of goo with a syringe
I was thinking about this kickstarter project where they print circuit boards, and later they show it printing solder paste. I've seen other liquid or paste dispensing systems like this too, maybe for medical or chemical uses.
My question is how do…
confused
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6
votes
2 answers
Shape of chain saw teeth
Looking at the teeth of a chain saw, I believe the chain moves from right to left while cutting.
It has two wedges A and B.
I've never owned a chain saw, so I've been trying to visualize how these two wedges work.
And I feel stuck because the…
sadhvika
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6
votes
1 answer
How deep are utilities typically buried?
What are the recommended or relevant standards for US city planning with regards to depth ranges for various utilities such as water, natural gas, and power, as well as for subway or rail, etc...?
For example, water and gas lines should be buried…
Atomiklan
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6
votes
1 answer
How does corrosion occur at a temperature below 0 degrees Celsius?
The ISO 9223 standard indicates that there should be no corrosion at temperatures below 0 degrees celsius. Independent researchers have however proposed to lower the minimun temperature stated in the standard to lower values in order to account for…
user1164
6
votes
5 answers
Forged carbon fibre finish
I'm currently looking around for a new bike and I've noticed lots of load-bearing carbon parts (frames, cranksets, forks etc.) with an interesting finish like this:
and I was wondering what this type of carbon cloth is called and why it's used.…
HJCee
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6
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3 answers
How does the strength of a square tube depend on the side size?
There are two square tubes of the same length, material and wall thickness, one being 40x40mm, the other 20x20mm. How does their strength against bending compare?
On the one hand, the cross-sectional area of the 40mm tube is 4 times bigger. On the…
Greendrake
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6
votes
6 answers
Can vacuum balloon become possible with this idea?
As it is well known, a vacuum balloon using the materials we have at our disposal is not possible, because of the sheer force they have to resist from the air outside.
I asked this question on Physics stack exchange and haven't got an answer yet.
I…
Moj
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6
votes
2 answers
Why does AN-94 have higher burst fire than its cyclic rate?
AN-94 is an assault rifle of Russian design chambered in 5.45 caliber. It is claimed to be state-of-art in Russian small arms development.
The most important design differences (relative to common designs like AKM) include:
Internal receiver,…
eimyr
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6
votes
1 answer
Second order system with additional pole
Why is it that a second order system with an additional pole or zero can be approximated into the general second order system for analysis?
This was asked during our lecture and I am still looking for the answer.
In my reading I've only learned that…
magicianiam
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6
votes
2 answers
How do I invert a system in state space form?
Suppose I have a system described in state-space form. Can I invert the system (swapping the roles of the input $u$ and output $y$)?
If we start with:
\begin{align}
\dot{x} &= A\,x + B\,u \\
y &= C\,x + D\,u
\end{align}
and $D$ is invertible, then…
nibot
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6
votes
4 answers
Is it possible to fire a ball of water that holds its shape?
Background
I participate every year in a huge water balloon battle. The clash happens between two universities so you can imagine that the commitment, at least for some people, is quite high. To give you an idea last year some 40000 (thats 40e3)…
Vladimir Cravero
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