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1500 questions
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How significant is a 8,500 lb concentrated load in a large (25+ floors) residential high-rise?

I'm thinking of installing a rather large aquarium on the 4th floor of a residential high-rise which has a total of 27 floors. I plan to place it directly against a concrete column with a diameter of around 4 feet. I think the main issues…
user3432
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Can redundancy be used instead of periodic calibration?

A lot of production equipment requires periodic calibration as part the documentation that the equipment is under control. The companies selling the equipment knows this and sometimes lowers the price of the equipment and offer an expensive service…
Norfeldt
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Is inviscid flow necessarily turbulent?

The Reynolds Number is defined as $Re = \frac{\rho v L}{\mu}$, where $\rho$ is the density, $v$ is the fluid velocity, $L$ is the characteristic length, and $\mu$ is the dynamic viscosity. By definition, inviscid flow implies that $\mu=0$. By this…
Paul
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BER peroformance of MPSK and MQAM in Rayleigh fading channel

I have a question regarding bit error rate (BER) performance over the Rayleigh channel. I observed BER performance over the AWGN channel using Simulink in MATLAB. I used to change the "SNR" parameter in the AWGN block to get the BER. What if I want…
Sara
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Looking for a loading code for use in the design of a small scale private bridge? (4.5m span, one lane)

I'm currently designing a small reinforced concrete bridge on private property. The project is in Scotland. It's very small scale, a single lane, with a span of around 4.5m. Service life is taken as 120 years. Using Eurocode design for standard…
Smeato
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Simplest way to reduce low frequency noise from windows

Could you please advise the simplest method to reduce low frequency noise from windows? The problem: Somewhere outside there is a source of noise with frequency of 166 Hz. I can’t neither find nor remove it. This could be ventilation hoods on other…
Damir Tenishev
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What development possibilities could yet exist in water desalination?

I am thinking mainly in $\frac{kWh}{m^3}$ and $\frac{\$}{m^3}$. In the past some decades a wide range of surprisingly efficient water desalination plants were built, mainly in desert regions (Middle East). These plants use reverse osmosis via a…
peterh
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How are blanking spades entered into gas pipelines?

I often see specifications for refurbishing works on gas pipelines calling for blanking spades, to separate the area worked on from the rest of the gas system. This is in addition to closing valves. Googling showed me some pictures of how blanking…
mart
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Are standard structural bolts acceptable for all cold climates?

The specifications for standard (ASTM A 325) bolts do not list minimum service temperatures. I am thinking of outdoor applications like Alaska or Canada (lows of -60F) and wondering if the cold temperatures would have an effect on the bolts. There…
hazzey
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How did this building's windows get like this?

I don't recall seeing the walls like this before, so I don't think it's just accumulated soilage. If it's wetness, what design flaw causes the windows to do that? Today was very hot and muggy so it's likely the AC was running all day.
Luke Sawczak
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6 answers

Is there such a thing as a sand-proof bearing?

I am working on a piece of art that has parts that rotate slowly, at about 1RPM, thanks to a couple of bearings. There is a possibility that it might be installed beside a beach for about a week. The problem is that sand and bearings do not play…
Steve
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5 answers

Why does a jumping rope have no bending stiffness and compression stiffness?

Can anyone just tell me that why doesn't a jumping rope, or any other kind of rope, have any bending stiffness? If I hold one end of the rope in my hand, the rest of the rope will just fall. It won't just keep itself straight. I know it is because…
Rameez Ul Haq
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Creating smooth shaft resistance

I am trying to emulate the resistance of a hand wheel which moves a table via a series of shafts and chains which turn an acme screw. I am switching to a CNC system that will allow the user to keep the old style crank for manual positioning. The…
Mister Tea
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Cutting mechanism for a robot in confined spaces

I'd like to build an exploratory robot that can fit within confined spaces1. As the robot moves along the inside of a 4" pipe, it's likely to encounter some obstacles that need to be removed. Typically, that will be tree roots up to 1/2" thick. …
user16
7
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2 answers

How do suction cups work?

These are suction-mounting hooks. I want to visualize and understand how do they stick on walls. After these hooks stick on wall. Like we compressed them. How? Since gases are compressible up to a good finite limit. What makes it difficult for them…
Rider
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