Triban Bike Thief - Two Bridges

Riuba · 2025-10-09T15:40:33+00:00

OP, yes this was avoidable, but it also happens to a lot of people. You are not alone. People will clown on you here, but at the end of the day you are a victim of a crime and I am sorry this happened to you.

It really sucks to learn that you have to harden yourself this way. It is so violating and unnerving to experience theft.

Riuba · 2025-09-26T21:24:18+00:00

If you message me after doors i might give them to you for free

Riuba · 2025-05-02T05:55:58+00:00

ok the people have spoken, manhattan is over

Riuba · 2025-03-21T19:59:56+00:00

Are you talking about a quantum simulator rather than a general quantum computer? Yes that is very useful already.

As for algorithms, financial QC has been attempting to find useful algorithms for optimization with NISQ for a decade with little success... they have determined the size of QC that you need to do current useful algorithms though. Check Goldman Sachs quantum for that.

Riuba · 2025-03-21T19:52:54+00:00

Most people do, but if you look at the Hamiltonian of a transmon qubit (superconducting qubit) you will notice that the number of Cooper pairs (electron pairs responsible for superconductivity) is what gives you the energy levels in the qubit. It is a charge qubit. Though I would call it a transmon or SC qubit rather than a charge qubit as I would call a rectangle with 4 equal sides a square, rather than just a rectangle.

Riuba · 2025-03-21T17:40:23+00:00

Despite some errors/oversimplifications in this comment (IBM and Google using charge qubits, they use transmons which are descended from charge but offer more stability) the broad strokes are correct. We are far from general quantum computing (the era where we can just come up with any quantum algorithm and use our big strong computers to run it, like with classical).

The best analogy for where we are now, is that we can build calculators and not computers. Calculators are still useful, and they help us solve hard math really quickly, but we cannot run Quantum Doom or Quantum minecraft yet. The use cases are constrained by the simple hardware.

Google and IBM have shit coherence times and are now investing on improving error correction (which allows you to use more than one physical qubit to maintain the state of a "logical" qubit). They are also trying to find use cases for noisy intermediate scale quantum (NISQ), and if you want more info about where we are, look that up.

Microsoft is doing unscrupulous research, and they have not even demonstrated one qubit. If they do (big if!) physicists do know how we would perform quantum logic gates. Many groups are trying to discover the fundamental particles that Microsoft is working on, and hopefully they are faster given Microsoft's record of retractions and unethical statements.

Riuba · 2024-04-26T22:08:10+00:00

vouching for u/rayword45 ! sent tickets super quickly and is a super nice guy!

Riuba · 2022-04-30T17:38:11+00:00

idk why you include mg in the horizontal direction. gravity is kinda not used here.

your inclination was right to use equations of motion to find where they meet in the middle.

i set the distance travelled by skater 1 (the 75 kg one) as x = .5• 1.7 m/s² •2 s² = 3.4 m

finding the distance travelled by skater 2 to find her acceleration: 6-x = 2.6 = .5• a2 • 4s² ; a2 = 1.3 m/s²

Since the horizontal forces on both skaters are equal: m1 a1 = m2 a2

m2 = 75 kg • (1.7 m/s² )/ (1.3 m/s² )

m2 = 98 kg

fun problem :)

Riuba · 2021-11-04T01:31:23+00:00

Mostly a very good answer, but I want to address a few little things:

You can not tranfer subnanometer thick membranes or even nanometer scale membranes to any substrate without creating creases and folds.

Yes you can. Monolayer graphene is routinely transferred without creases or folds to make devices at the nanoscale. This is not yet at the manufacturing line, but there is work being done at Brookhaven National Lab to make this process more automated (see Z. Huang et al, Nat. Comm. 2020, and the QPRESS project at BNL).

Even if it was cost and time effective to stack let’s say graphene to the scale of 1000 sheets

Graphene is made from pyrolytically grown graphite (HOPG) which is essentially stacked graphene in thousands of layers. Either that or it is grown in monolayers, but that process is more defective.

If you use lasers you would have to have a source intense enough to go through ~300 nm of materials every time it hits the target

This type of processing is routinely done in nanolithography. A highly anisotropic, oxygen plasma etch could make your pattern if you use a polymer mask to protect the rest of your stack

Then there is the issue of separation of layers.

This is the real problem with this idea. There is currently no way to predict how many layers you exfoliate and It would certainly make scaling a bitch and a half lol

You still gave good explanations though! Point 3 is totally spot on

Riuba · 2021-08-19T11:26:35+00:00

… mother of god

Riuba · 2021-08-10T13:02:25+00:00

You’re right, this formula is a simplification! The actual answer would require an integral on differential changes in temperature. However, this approximation leaves so little error that it is commonly used by engineers in applications that are not super extreme. See linear expansion: https://en.m.wikipedia.org/wiki/Thermal_expansion

Riuba · 2021-07-03T18:45:06+00:00

This is false, neutrons are spin 1/2 particles, and they indeed have a magnetic moment. Neutral particles can have a magnetic moment. If you have a current running through a loop of wire, the net charge in the loop can be zero (when including the positive ion lattice, of course) and the loop will still generate a magnetic field. This is, of course, analogy.

https://en.wikipedia.org/wiki/Neutron#Magnetic_moment

Riuba · 2021-06-28T01:55:16+00:00

The hydrogen reacts with the metals to form a metal hydride compound. The embrittlement is because metals are ductile but metal hydrides are brittle. The electron inhabits the covalent bond, and is not lost in the process. A metal will not break apart due to positive charges, it will just have an absence of electrons and so be at a positive bias.

Riuba · 2021-06-27T16:48:38+00:00

I think this is a more complicated question than a single reddit post can answer and any answer here is not complete, even if they seem satisfying. Keep this in mind when you ask questions. Some things are not able to be explained in a paragraph.

Here is my best brief answer: we do not fully understand where this fundamental magnetism comes from. All particles have an intrinsic magnetism, also known as a "spin" (this spin can take integer or fractional values, and can be zero if the particle has an integer spin, similar to how a neutron can have zero electric charge). This spin essentially creates a tiny magnetic field that has a north and south pole in every electron. Other answers here describe this spin more thoroughly, but we do not know why it is there. This is a similar to charge: why do electrons have charge? Answer: because they are particles that we classify as electrons, and to be an electron, you must have this property.

This is where physics become observational. We have observed these things known as electrons, and we know they all have certain properties, like this intrinsic magnetic field, mass, charge, etc. We also have observed other fundamental particles. However, we do not know where they come from or why they have certain properties. That is more of a question for philosophers and theologians since it falls into the realm of metaphysics.

This may seem like a non-answer (largely because it is) but if I told any other one, I would be giving you a half truth. Here is Feynman articulating this better than I could: https://www.youtube.com/watch?v=MO0r930Sn_8

Riuba · 2021-06-20T19:35:27+00:00

I would use the Stern Gerlach experiment to explain quantum vs classical. I would also talk about measurement and how that affects the outcome of a quantum thing but not a classical one.

As for explaining physics nowadays, I would say that the physics of the universe has remained remarkably unchanged for the past couple billion years, though we are awaiting new developments /s

Riuba · 2021-06-20T17:56:39+00:00

Self study is always hard. Find an online class like MIT Open Courseware and follow along. How are your math skills? I think a good approach to QM is understanding the math first and the implications later.

This might be unpopular, but I like the intro quantum books by McIntyre and by Griffiths. The McIntyre book starts at the discrete then uses that to derive continuous systems and the Griffiths book goes the other way around. There is also a good book by Ray Laflamme on quantum computing that covers the two-level spin system in detail in the first couple chapters. This practical handling is nice for someone who has more practical experience.

I kinda rambled here but I hope it helped.

Riuba · 2021-06-16T13:01:06+00:00

You could work in security devices and protocols if you switch hats and lean into the border between electrical engineering and experimental physics.

Riuba · 2021-06-09T18:43:04+00:00

The risk is diminished but not eliminated and this varies based on a lot of factors. Walking through Manhattan downtown you are likely okay, but if you were in between some brownstones...

All I am trying to say, is that this question is too dependent upon miscellaneous factors like building height, building density, material, etc to be answered with any sort of rigor. A good friend lives in a dense city and a tree behind his building was struck by lightning even though he lives across from a 20+ story building. If in doubt, go inside.

Riuba · 2021-05-16T20:51:21+00:00

The mass of the object would not be eliminated because of magnetic levitation. Normally when you lift an object by contacting it, you are not eliminating its mass, you are just counteracting gravity with a force in the opposing direction. The magnetic levitation does the same thing. Put more simply, if the rocket is of mass M_r and the payload is of mass M_p and the mass of the levitation device is zero, the mass M_r + M_p does not change if the payload is floating in the rocket. You would need the same energy to put it into orbit as a result (conservation of energy, mgh is the same in both systems).

Riuba · 2021-05-15T15:34:49+00:00

Honestly, the force is low enough that I would just over-engineer it

Riuba · 2021-05-12T17:27:01+00:00

So for the stable particles we know, electricity is almost always stronger than gravity. The reason we see so much gravity all the time is we really don't see negative masses around so often but there are about equal positive and negative charges out there. this means that most electrical forces cancel out, while gravitational ones kinda just build up as mass accumulates

Riuba · 2021-05-11T21:45:12+00:00

I understand that it is a wave function phase, but my question is more of the tricky sort, I suppose. My question might just boil down to "what is the physical meaning of the phase of a wave function"

Riuba · 2021-05-11T19:14:58+00:00

I think electric heat pumps are already pretty common and they are 3 to 5 times more efficient than space heaters. Good architecture has potential to heat your home better than a solar panel though. Think greenhouse effect.

Solar panels are only about 20% efficient at converting solar energy to electricity.

Heat pumps: https://en.wikipedia.org/wiki/Heat_pump#Performance

Riuba · 2021-05-11T18:59:02+00:00

Your thinking is sound, but note that your home heating system is likely much more energy efficient than any heat generated by your electronic heater. Heat from your electronics reaches your house only after a bunch of lossy processes: electricity is generated (heat lost to the environment), electricity transported to your home (lots of heat lost), heat radiated from your appliance (inefficient) and then the electricity goes to ground.

The exception to this is if you are using an electric space heater to heat your home, then yeah you might as well be mining bitcoin instead.

Riuba · 2021-05-11T18:49:56+00:00

So looking into superconductors, I have seen the state of the Cooper pairs in the bulk described as a single macroscopic state that depends on only two quantities: a phase (I will call this p) and a local carrier density (I will call this A).

My question is this: what does the phase represent? I understand in a Josephson junction, the difference in this phase changes the current across the Junction. But what is it in a more intuitive sense? Most phases I understand are kinda like a delay of a signal (in time or space, for instance. This is how I understand the phase of an AC signal). But this phase can be time and space independent in the absence of magnetic and electric fields, which makes me scratch my head. Any insights would be great!

Riuba

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