Search found 363 matches

by Mavrisa
Mon Feb 24, 2014 10:09 pm UTC
Forum: Hardware
Topic: Laptop/phone's headphone jack as a DAC
Replies: 8
Views: 6259

Laptop/phone's headphone jack as a DAC

So my friends and I are doing a project, and we need a DAC which has fairly good resolution between 0 and 0.3V (~100 values). First option we were looking at was a cheap arduino, but we found that it only had PWM outputs. Sure, you could voltage divide and then use an RC lowpass to get roughly the r...
by Mavrisa
Thu Jan 30, 2014 11:55 pm UTC
Forum: Science
Topic: Type of aurora?
Replies: 4
Views: 2264

Type of aurora?

One week ago, at about 2 am on Friday the 24th, I was walking outside and up in the sky I saw a number of bands of very faint greenish blue light. They were vertical, covering 3-5 degrees of the sky. There were 4 in a group like claw marks in the sky to my north. One more was to the northeast and a ...
by Mavrisa
Mon Oct 28, 2013 7:55 pm UTC
Forum: Science
Topic: Turtle/Amphibian eyes
Replies: 2
Views: 1618

Turtle/Amphibian eyes

My friend has a turtle, and it got me thinking... how do its eyes work? When diving underwater, I have extremely poor vision, which I assume is because the refractive index difference between water and the various parts of my eye are much smaller than in air. Do turtles and other amphibians suffer t...
by Mavrisa
Sat Jul 27, 2013 2:57 am UTC
Forum: Science
Topic: Material Selection
Replies: 6
Views: 3828

Re: Material Selection

Yeah I suppose that would help, wouldn't it... I need the material to be a conductor (actual conductivity shouldn't matter too much), relatively cheap, low density, not violently reactive with water, and a melting point between roughly 200C and 500C. To me it sounds like a metal or alloy would fit t...
by Mavrisa
Sat Jul 27, 2013 1:29 am UTC
Forum: Science
Topic: Material Selection
Replies: 6
Views: 3828

Material Selection

Hi, I was wondering if anyone knew of a database or some software that would help me to find a material for a specific application I'm looking into. I need information like conductivity, density, melting point, cost, etc.

Thank you!
by Mavrisa
Thu Mar 14, 2013 5:18 pm UTC
Forum: Science
Topic: Neat and tidy charges - An unanswered question or not?
Replies: 27
Views: 5264

Neat and tidy charges - An unanswered question or not?

I was wondering: do we know why it is that subatomic particles all have charges of 0, +/- e, or in the case of quarks, +/- 1/3 or 2/3 e?
Seems awfully convenient... Why isn't there a particle with 0.7982364 e as its charge, for instance?
by Mavrisa
Sat Feb 02, 2013 11:45 pm UTC
Forum: Science
Topic: What if c was smaller?
Replies: 21
Views: 3808

Re: What if c was smaller?

speising wrote:This is pretty nice, but deals only with one aspect of a lower c. It ignores the end of all the known universe which would probably occur when someone changes c. (cf. "well-tuned universe")

This is more along the lines that I was thinking of. Why, or in what ways would the universe end?
by Mavrisa
Fri Jan 25, 2013 9:21 pm UTC
Forum: Science
Topic: What if c was smaller?
Replies: 21
Views: 3808

Re: What if c was smaller?

So there would be no other noticeable differences in the universe, other than things would behave relativistically much more easily? That's a much more boring answer than I was expecting. :?
The fact that ε0 and μ0 are larger does nothing? The fact that gravity is slower has no effect?
by Mavrisa
Fri Jan 25, 2013 7:17 pm UTC
Forum: Science
Topic: What if c was smaller?
Replies: 21
Views: 3808

What if c was smaller?

What if c was a smaller value? For our purposes, let c be both the cosmic speed... barrier, and the speed of light/massless particles. I get the feeling our universe would change dramatically at some point. I wonder at what point that would be. What if it was one 10th the speed, or one 1000th? Or a ...
by Mavrisa
Sun Dec 02, 2012 9:52 pm UTC
Forum: Science
Topic: That feeling you get in your chest...
Replies: 2
Views: 6481

That feeling you get in your chest...

When in love, or upon experiencing emotional pain or excitement, many people will report a sensation in their chest, one which I can't find the words to describe, but I assume everyone knows the one I'm talking about. I imagine this is where the association of love and the heart came from. What I wa...
by Mavrisa
Fri Nov 16, 2012 1:27 am UTC
Forum: Science
Topic: Methods for Selective Precipitation of Metal Ions Needed
Replies: 8
Views: 2174

Re: Methods for Selective Precipitation of Metal Ions Needed

Electroplating: I don't have access to the required equipment unfortunately, and I'm not sure, but it may be too expensive to scale up. Thanks for the suggestion though. Calcining: I can calcine up to 800 C, which is good enough for ZrO2 at least (the oxide is the goal in fact, the hydroxide and sul...
by Mavrisa
Wed Nov 14, 2012 3:55 pm UTC
Forum: Science
Topic: Name 3 famous living scientists (no cheating!) ;)
Replies: 39
Views: 11159

Re: Name 3 famous living scientists (no cheating!) ;)

Neil deGrasse Tyson, Brian Cox, Craig Venter
by Mavrisa
Wed Nov 14, 2012 7:00 am UTC
Forum: Science
Topic: Methods for Selective Precipitation of Metal Ions Needed
Replies: 8
Views: 2174

Methods for Selective Precipitation of Metal Ions Needed

I've been trying to do this for a few weeks now and it's frustrating as hell... I'm looking for a way to get relatively pure zirconium (sulphate, oxide or hydroxide forms are all okay) out from an aqueous solution of: 70 g/L Zr 40 g/L Mg 60 g/L S (as SO4) Free acid around 1 normal Addition of base f...
by Mavrisa
Tue Oct 16, 2012 12:23 am UTC
Forum: Mathematics
Topic: Why is calculus such a big deal?
Replies: 11
Views: 3132

Re: Why is calculus such a big deal?

it seems like most of the stuff you have to do in calculus (in undergrad anyway) a computer can do much much better than you. In fact, it seemed like the higher up I went with Calculus at university, the less I learned about actually doing maths, and the more I learned about how to use Maple TM . I...
by Mavrisa
Mon Oct 15, 2012 4:22 am UTC
Forum: Mathematics
Topic: Why is calculus such a big deal?
Replies: 11
Views: 3132

Re: Why is calculus such a big deal?

She's starting a business degree now. I'm not sure which applications that would suggest. Optimization as ThirdParty mentioned must surely be in there, though.
Thanks for your feedback!
by Mavrisa
Sun Oct 14, 2012 2:52 am UTC
Forum: Mathematics
Topic: Why is calculus such a big deal?
Replies: 11
Views: 3132

Why is calculus such a big deal?

Okay. I love math, calculus especially, because it is so handy in so many ways, and so many fields use it extensively. It is no stretch to say that we wouldn't be anywhere near as advanced as we are today without the development of calculus. My friend doesn't see it that way. She took it once in hig...
by Mavrisa
Sat Jun 16, 2012 6:06 pm UTC
Forum: Science
Topic: Modelling an interesting quantum phenomenon
Replies: 0
Views: 1202

Modelling an interesting quantum phenomenon

Hi, I'm taking a course on quantum mechanics, and we have a project which involves modelling some sort of quantum phenomenon using the numerical methods we've learned about. Basically, we've discretized the hamiltonian in the 1D case, and we've used Matlab to solve for eigenenergies and eigenfunctio...
by Mavrisa
Sun Jun 10, 2012 12:27 am UTC
Forum: Science
Topic: Phase difference resulting in elliptically polarized light
Replies: 4
Views: 2336

Re: Phase difference resulting in elliptically polarized lig

Hmmm. I think I'm beginning to grasp it, but it's still unclear to me why it's possible to slow down one component of a wave relative to the other..
Is there any analogous situation which I might be more familiar with that I could draw parallels to?
by Mavrisa
Sat Jun 09, 2012 9:18 pm UTC
Forum: Science
Topic: Phase difference resulting in elliptically polarized light
Replies: 4
Views: 2336

Phase difference resulting in elliptically polarized light

I'm reading up on polarized light microscopy for one of my courses, and I am getting really confused by linear vs. elliptical polarization. Before when I was taught about PLM, what I got out of it was that light was polarized linearly, went into an anisotropic sample, its polarization was changed, i...
by Mavrisa
Wed Nov 30, 2011 9:50 am UTC
Forum: Fictional Science
Topic: Some mechanism to locally reverse time
Replies: 22
Views: 8682

Re: Some mechanism to locally reverse time

This could allow you some interesting plot devices to use as well... For example, receiving these memories would mean that the chip (or a replica?) must exist at the point in time in the future in order to send those memories back to itself, or there would be a time paradox which the universe doesn...
by Mavrisa
Tue Nov 29, 2011 10:06 pm UTC
Forum: Fictional Science
Topic: Some mechanism to locally reverse time
Replies: 22
Views: 8682

Re: Some mechanism to locally reverse time

Indeed - you can even play with the fact that to the reader it might appear the characters were travelling backwards in time in an explicable way before dropping the bombshell... Another problem/interesting bit is the question of how these newtonian flash-forwards interact with each other... imagin...
by Mavrisa
Sun Nov 27, 2011 9:17 am UTC
Forum: Fictional Science
Topic: Some mechanism to locally reverse time
Replies: 22
Views: 8682

Re: Some mechanism to locally reverse time

It's not that they are going back in time, it's that they get to see forward in time and then get a chance to change stuff. i.e. "show me what will happen if I didn't know what was going to happen." The only problem/difference is this requires you to decide before any particular event tha...
by Mavrisa
Sat Nov 26, 2011 9:37 pm UTC
Forum: Fictional Science
Topic: Some mechanism to locally reverse time
Replies: 22
Views: 8682

Re: Some mechanism to locally reverse time

Well at this point, they have knowledge in their heads about what happened once before, so this pretty much ensures that the course of events will not be the exact same as last time. But yeah, they're pretty much free to do what they want once time resumes its usual direction.
by Mavrisa
Sat Nov 26, 2011 8:55 am UTC
Forum: Fictional Science
Topic: Some mechanism to locally reverse time
Replies: 22
Views: 8682

Re: Some mechanism to locally reverse time

Awesome, questions. This is very similar to the time-turner idea (I don't know why I never made that parallel... especially since I just reread all of them a couple of months ago), but in my mind, they would be able to see time play in reverse for a brief... period... of time? Though unlike in Harry...
by Mavrisa
Sat Nov 26, 2011 3:13 am UTC
Forum: Fictional Science
Topic: Some mechanism to locally reverse time
Replies: 22
Views: 8682

Some mechanism to locally reverse time

Okay so this is going to be far-fetched, but I can't think of anything that sounds remotely reasonable. For a story I'm writing, I need something which can be activated, and will reverse time to a set point in the past, but at the same time, will preserve all of the information in the user's brain. ...
by Mavrisa
Sat Nov 12, 2011 5:37 pm UTC
Forum: Coding
Topic: Dijkstra's Algorithm
Replies: 2
Views: 1468

Dijkstra's Algorithm

It's been a long time since I've had a good programming task to sink my teeth into, and I wanted to get into something different from what I've normally done. So I made some vector copies of the blueprints to each building in my university and I'm hoping to make a Google-maps type thing that will be...
by Mavrisa
Tue Nov 08, 2011 4:59 pm UTC
Forum: Science
Topic: Equivalent capacitance
Replies: 7
Views: 2421

Re: Equivalent capacitance

I believe some of the numbers in the OP's spoilered image where added by the OP, and others by the original problem. There is a bunch of verbage about "first quarter", "second quarter" in half-passive voice that I couldn't be bothered to decode that leads me to that conclusion. ...
by Mavrisa
Tue Nov 08, 2011 8:15 am UTC
Forum: Science
Topic: Equivalent capacitance
Replies: 7
Views: 2421

Equivalent capacitance

I have a question on an assignment which I've been working on for a while with a friend. We also have access to a copy of the solutions manual, but we disagree with it completely. It's not the first time that it's been wrong. Essentially we're given a section of circuit made up of only capacitors an...
by Mavrisa
Wed Oct 26, 2011 4:42 pm UTC
Forum: Science
Topic: [Rather long] Reciprocal lattice -> band structure?
Replies: 6
Views: 3879

Re: [Rather long] Reciprocal lattice -> band structure?

Awesome. Thank you again. I think I just have one more: 3) No, you aren't restricted to k values where n*lambda. So far we've used such wavevectors as examples because in those cases the real space situation is easy to visualise. But k can take any value. So how does it look when k corresponds to a ...
by Mavrisa
Tue Oct 25, 2011 3:10 pm UTC
Forum: Science
Topic: Is anyone as desperate to find life as I am?
Replies: 76
Views: 8852

Re: Is anyone as desperate to find life as I am?

How long would it take to engineer super-intelligent animals, perhaps an ape, crow, or dolphin? And when will we make a machine with human-like intelligence? Perhaps we don't need to go to other worlds to meet an alien intelligence. I view this as cheating. For me, this would be like discovering mi...
by Mavrisa
Mon Oct 24, 2011 11:01 pm UTC
Forum: Science
Topic: Is anyone as desperate to find life as I am?
Replies: 76
Views: 8852

Re: Is anyone as desperate to find life as I am?

I feel your pain, OP. But we can't . ... Our only hope is that of strings of future events, conceivable, yet so improbable such as to be, by any other name, a fiction. That was beautiful. In response to the OP, I'm not sure I feel as strongly about it as you do, but I would definitely feel an absen...
by Mavrisa
Mon Oct 24, 2011 5:10 am UTC
Forum: Science
Topic: Is this real?
Replies: 25
Views: 5318

Re: Is this real?

Eternal Questionner wrote:Do you mean this video

Yup, that's the one. Thank you.
by Mavrisa
Sun Oct 23, 2011 3:58 am UTC
Forum: Science
Topic: Is this real?
Replies: 25
Views: 5318

Re: Is this real?

From what I've heard, this is slightly different from the usual Meissner-effect demo's we've all seen. In one video (I'll post the link if I can find it) they explain that the superconductor is a few hundred nanometers thick and has dopants introduced into it so that it allows some flux to penetrate...
by Mavrisa
Sat Oct 22, 2011 5:09 pm UTC
Forum: Science
Topic: Hydrophobicity looked at from a non-entropic point of view
Replies: 5
Views: 1014

Re: Hydrophobicity looked at from a non-entropic point of vi

I'm confused slightly about what you mean by the universe "caring." In my mind, to accept that physics can exist is to accept the universe "cares." It seems to me what you know and your intuition are at odds. I mean the universe has no concept of entropy, or lowering a system's ...
by Mavrisa
Sat Oct 22, 2011 4:57 am UTC
Forum: Science
Topic: Hydrophobicity looked at from a non-entropic point of view
Replies: 5
Views: 1014

Hydrophobicity looked at from a non-entropic point of view

Sooo... as far as I know, the universe doesn't give a shit about what entropy is, it's just something that happens because it ought to. It's ridiculously unlikely for all of the air in a room to be in one half of it, so it probably isn't. And if somehow it's made to be, it soon won't be. This makes ...
by Mavrisa
Sat Oct 22, 2011 4:39 am UTC
Forum: Science
Topic: [Rather long] Reciprocal lattice -> band structure?
Replies: 6
Views: 3879

Re: [Rather long] Reciprocal lattice -> band structure?

Alright so both of those really helped . I'm going to address both answers separately as best as I can. Okay, well I don't think I can summarize a whole semester's class in one post (or want to!), but maybe I can help with the big picture. It sounds like you don't really have any physics background,...
by Mavrisa
Sat Oct 08, 2011 6:59 am UTC
Forum: Science
Topic: [Rather long] Reciprocal lattice -> band structure?
Replies: 6
Views: 3879

[Rather long] Reciprocal lattice -> band structure?

In one of my courses, we have been introduced to the concept of reciprocal space in order to figure out the band structure of crystal lattices. Between 98 and 100 % of the class does not understand what the hell is going on, and I'm not sure if it's the concepts being too hard, or that our professor...
by Mavrisa
Fri Aug 19, 2011 5:04 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0026: "Fourier"
Replies: 1
Views: 1364

Re: 0026: "Fourier"

Bahhh! This is one of my favourites.
by Mavrisa
Sat Aug 13, 2011 8:36 am UTC
Forum: Mathematics
Topic: The Tau Manifesto
Replies: 165
Views: 42513

Re: The Tau Manifesto

... The reason not to slowly change from pi to tau is that the only benefit is dropping a factor of 2 sometimes. This is such a small benefit that it's effectively outweighed by even a very small cost or inconvenience of changing it. ... All of those changes would actually offer significant improve...

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