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    Earth's Internal Heat Source

    This is a response to a question in Scientific American given by Dr. Quentin Williams who specializes in the deep interior. I searched "Why is the earth's core so hot" on Duckduckgo. (I'm not sure if current posting guidelines allows me to give links to periodicals?)
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    Automotive Random Vibration and PSD spectrum profiles

    There is a great article by Tom Irvine on why the units are unusual. I have myself wondered this for some time, working in this field. The units are generally motivated by the practical considerations of signal processing, viz., getting a meaningful measure of amplitude that is free from the...
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    News Stephen Hawking has Died - March 14th, 2018

    RIP Dr. Hawking! I have seen him as a source of inspiration for years. I think he is still scientifically underrated.
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    Earth's Internal Heat Source

    I've been wondering about this question for some time now. There are the following two contributors: ~~~~~~~~~~~~~~ 1. Heat left over from the planet's initial formation. In the early 19th century Lord Kelvin estimated the temperature based on a homogenous sphere of uniform initial temperature...
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    How much lb could an average person push?

    This is really a question of two related parameters: 1. How heavy is the average person? 2. What is the average coefficient of static friction (for all combination of surfaces), i.e., what is 'typical'? When you answer these two, you should be able to extract an answer.
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    Subjects needed in High School for Aerospace Engineering

    Remember how to do calculus, matrices, and all that. Math is an indispensable tool, but HowlerMonkey also underscores an equally important point: we need to be able to communicate effectively, succinctly, and with proper grammar and spelling.
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    Stress Calculation on trailer legs

    There are quite a few other corrosion-resistant materials out there, some of them non-ferrous. Even within the family of austenitic steels you can consider 304L or 316L in the 1/2-hard 3/4-hard or full hard or extruded Cond. F grades as alternatives. I can also see where Chris is going... those...
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    Coefficient of friction in soap?

    What are the static and dynamic friction values for dry and wet soap? I can't find these things anywhere on the net, except for an assumption of the kinetic value of 0.06. If someone has access to an extensive data sheet on frictional values, then that would help greatly. Thanx
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    Use of steel powder in composites

    How effective is using steel powder in a polymer/ceramic composite matrix? I am wondering this from observing this product called Faststeel which is one of those epoxy putty sticks that claims to be steel-reinforced. I actually think that it will make a material stronger than the matrix...
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    Material with best tensile strength to weight ratio?

    Kevlar and basalt fiber are two contenders on the practical scale; carbon nanotubes are the strongest on the laboratory/R&D world. But while there are many fibers that exist with high tensile strength, I still think man has not found any composite, polymer, ceramic, or metal that can come...
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    Space Density

    If I remember correctly, the average density of space is something on the order of one atom per cubic centimeter.
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    Can a nuke power plant just blow up?

    You can have a steam explosion. But a nuclear one? No. The uranium used in reactors is not enriched enough.
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    Rust Production

    Or better yet : find an old alley. There are dumpsters with lots of rust chips that can be taken from the ground.
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    Material Choice: Durability, Cost, Weight

    I would aluminum alloy is your best bet if you're making a robot. Normally its pneumatic operations and small motors that power it would want less burden on the weight. But it depends. If you want strength per volume, steel. Simply put, if you have to handle cyclic loads on small parts...
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    Heat-resistant materials

    Yes. This is exactly what I want to find out. Is there something wrong with the mechanical behavior of MgO at high temperatures?
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    Heat-resistant materials

    Great links, but I'm still puzzled as to why MgO isn't as used as often as alumina or zirconia in high-tech refractories. Currently most engineering is focused on ceramic coatings on a metal substrate. Is this due to the high cost of the ceramic? If I remember correctly there is a lot of...
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    Heat-resistant materials

    Zirconia has a very high melting point, about 2700C. This is the primary reason why it is used as a refractory. However, after some preliminary searches, I found another common ceramic material with a melting point higher than that of zirconia - magnesia (MgO), with a melting temperature of...
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    Rust Production

    Yes. Put many small pieces of scrap steel in salt water.
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    Heat Absorbing Materials

    The space shuttle ceramic... but I don't know what it is.
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    World Jump Day

    Yes. I meant to imply that. How come it doesn't work?
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    Strongest bond?

    I really don't know, and that's a pretty darn good question. I'd like to know myself from some of the experts. You can probably tell the bond strength roughly by the melting temperature of the solid, which is where interatomic interactions partially break loose. In this case, tungsten is the...
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    World Jump Day

    The situation might be more complex than a simple analysis with conservation of momentum. Imagine two containers in free space connected by a spring. One consists of viscoelastic tissue like human tissue and the other consists of cold tar, like earth's magma. Which direction would the system...
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    Helium question

    For argon the answer must be yes. The atmosphere is about 0.7% argon (which is quite a bit if you think about it) by volume, meaning you can distill this gas right out of the air. The cost definitely makes sense here.
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    Best oxidizing and reducing agent in periodic table

    If I understood your question correctly, I think the two extremes would be francium and flourine.
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    Helium question

    Graham's law explains the relation between molar masses on the rate of diffusion. It should be the the inverse square root of the molar masses if I remember correctly, meaning Helium diffuses roughly 3.2 times as fast as argon (turns out that it has around 40 daltons of mass). However, I need...
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    Helium question

    I suppose, then, that it can probably diffuse through a thick glass wall, but I'll have to look that up sometime with regards as to how much slower.
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    Helium question

    I have a question about helium : If it is the most inert substance, why isn't it used more than krypton or argon for high-temperature incandescent bulbs? I don't see neon in light bulbs too often either.
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    Potassium oxide question

    Does any potassium nitride form? The superoxide might make sense, but would it be a gas as described above?
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    Potassium oxide question

    Just what, exactly, is its melting point? I came across a ICSC website saying it decomposes at 350 degrees Celsius. Now how is that supposed to make sense, when it is itself a by-product of wood fires?
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    Flywheel materials

    It's come upon my interest that besides capacitors, flywheels can also be used to store considerable amounts of energy at impressive levels. The best material is supposedly carbon fiber, since it can spin at high speeds. But what about other materials like steel fibers or fiberglass? Those...
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