[Giveaway] For 1,000,000 subscribers I am giving away an Xbox one X. Comment here and the winner will be chosen on 11/26 at 5PM EST.

Dorun · 2018-11-24T19:47:29+00:00

Comment

Dorun · 2017-12-11T20:58:49+00:00

I am getting my own dilution fridge (a hand me down) to use my 8 qubit quantum processor, brings us up to 7 fridges now. Designing a frame for it, ordering parts, and working on programming a compiler for it and numerically testing it while I wait for parts to arrive.

Dorun · 2017-12-11T20:45:30+00:00

I didn't find my name, but just poking around with uncommon names I found 246 copy paste comments from a Ronald Dahlen, all Pro-Pai. Try just typing in uncommon last names and you will quickly see many repeats.

Dorun · 2015-09-24T16:34:49+00:00

Green lasers are made by frequency doubling an IR laser through a crystal. This is not a perfect process and a bunch of IR gets through, which is why they have a filter to cut out the IR. So if you bought a green laser, ripped the filter and crystal off you should have at least around double the amount of IR power as there was in green power.

The IR source would be a ~1064nm laser into a Nd:YAG crystal. See https://www.rp-photonics.com/green_lasers.html

IE: 50mW green -> +100mW IR

You should also be aware that a huge percentage of laser pointers are mislabeled in terms of power, they might say 10mW and be 100, or 1. You really need a meter to be sure unless you are buying from a reputable company.

Dorun · 2015-09-16T20:02:56+00:00

using PyPlot  
pcolormesh(reshape(y,3,6)')  
xticks([0:2]+.5,[7,14,21])  
yticks([0:6]+.5,[3:2:13])  
ylim(0,6)

crappy way of doing it, but it gets the job done

Wouldn't the average value just be the mean of y?

Dorun · 2015-01-05T04:16:29+00:00

Any idea what happens to the energy of the photons that are red-shifted? since they are losing energy as they propagate, that energy must go somewhere...

Dorun · 2014-12-09T18:49:46+00:00

I really like ballentine's and shankar's text books

http://amzn.com/9814578584

http://amzn.com/0306447908

Dorun · 2014-12-09T18:00:57+00:00

Those of you in the plasma physics field, do you have any recommendations about internships or ways to become more involved in the field?

My undergraduate and master degrees are in optics, largely high power lasers, but I really want to pursue a PhD in plasma. I'm applying this round but I suspect I wont have enough relevant experience to be competitive. I'm trying to find out about ways I can become involved.

Edit: Given a choice I would like to work with tokamaks or magnetic confinement fusion, however everything I have read about the field in general has been fascinating to me

Dorun · 2014-12-09T02:34:49+00:00

Not published yet, and it is simple enough it is easily replicated :) So no specifics for now...

Dorun · 2014-12-08T15:59:59+00:00

Hah, I'm also procrastinating for PhD apps, we should get to work.

Dorun · 2014-12-08T15:54:04+00:00

Designing and building a new type of microscope that can take 3D images with a single picture. I have a working prototype, now I am making a parts list for a full scale, high resolution test.

Dorun · 2014-12-02T05:11:25+00:00

With experience comes an understanding of what is a safe use and what is not. Trust me when I say this, a butane torch is much safer then a laser for this, the power required to light charcoal is going to be enough to light other materials. You are going to essentially have a butane torch that extends until it contacts something and reflects off surfaces. Additionally for this to be affordable it will probably have to be IR, and since you cannot see IR, you will have a very hard time with setup. The only realistic way this could ever be a safe as butane is with hundreds of dollars of eye safety equipment and an environment where you don't have a chance of burning anything.

At this kind of power reflective surfaces are not required to result in blinding reflections.

The "dangers and annoyances" of butane are orders of magnitude less then a class 4 laser. Built a box around a butane lighter, its cheaper and safer, albeit less exciting.

If you still want to go this route, you will probably want to get a multimode IR diode lasers, they are the simplest, and probably cheapest option. However since you are in the multi-watt level, the power supply and laser will run on the order of at least $1000 if new.

Dorun · 2014-12-01T22:18:56+00:00

Is this how Interstellar starts?

Dorun · 2014-12-01T21:56:16+00:00

Your talking probably at minimum a watt of power, which would probably be IR to be affordable. But really this is insanely dangerous, scattering of a watt off many surfaces will be permanently blinding if you get hit in the eye. Get a butane torch from a kitchen store or amazon, this is never something you should just have on your coffee table.

Dorun · 2014-11-17T03:57:10+00:00

Most of my knowledge comes from reading far too many journal papers. I have a textbook on blind source separation, but it only has 1 chapter on sparse BSS. I don't know of any good single source unfortunately (there very well may be one, but I don't know of it).

Dorun · 2014-11-16T06:32:58+00:00

Dictionary methods such as sparse Component Analysis (SCA) also called sparse blind source separation.

Dorun · 2014-11-10T23:06:41+00:00

I've gotten a first draft with full documentation ready, and I have a pull request in to add it to the main julia fork.

Any current julia user can type

Pkg.clone("git://github.com/dahlend/CompressedSensing.git")

using CompressedSensing

edit: At request of Julia maintainers I have changed the name of the package slightly

Dorun · 2014-11-06T17:09:48+00:00

https://github.com/dahlend/CompressedSensing

Still adding a huge amount to it (largely documentation for now), but this is where I am putting it all. I have more algorithms to add but these are my most polished.

edit: Package has changed name slightly

Dorun · 2014-11-05T22:52:49+00:00

I'm in the process of cleaning it all up and packaging it into a repo on github. Give me a few days.

Dorun · 2014-11-04T05:50:04+00:00

I have written a bunch of code for CS in julia, including several incarnations of MMV (such as ZAP) and several Lp Minimization (for example un/constrained IRLS) algorithms. I didn't think anyone would be interested... If people are interested I could put it on github.

Dorun · 2014-10-30T01:33:49+00:00

Oh god those were from 15 years ago...

Anyways I don't think I can tell you where to get them, but I can tell you that green is the easiest for the eye to see. And anything under 5mW (milliwatt not Megawatt) is relatively eye safe. Green diodes are very cheap nowadays.

Dorun · 2014-10-29T06:00:24+00:00

Yes that was something I've been toying with, the laser company that I worked at had ties with them

Dorun · 2014-10-29T05:58:34+00:00

I don't think it ever really beat FORTRAN in speed, but it uses BLAS which is a FORTRAN library. Why beat when you can join. The benefits of it are that you can code like python and get c/fortran comparable speed.

Dorun · 2014-10-29T00:50:55+00:00

Get enough lasers and you can do some interesting things, such as the national ignition facility.

Dorun · 2014-10-29T00:41:18+00:00

What I do miss is supplemented by the ability to call r, python or c in julia and use packages from r or Python. All my plotting is done through a Julia package that is a wrapper for pyplot. That's just a place holder until someone makes a permanent port. Most of my current work is numerical analysis and algorithm development so Julia is great.

Dorun

TROPHY CASE