Comments for The Daily Photon http://dawes.wordpress.com optics, photonics, electronics, and computing Wed, 09 Jul 2008 16:53:04 +0000 http://wordpress.org/?v=MU Comment on Walk Score by Tommi http://dawes.wordpress.com/2008/06/29/walk-score/#comment-156 Tommi Tue, 08 Jul 2008 11:50:38 +0000 http://dawes.wordpress.com/?p=150#comment-156 Yes, walk score is real a good idea! But why only walk score? How often do we walk nowadays? More and more people drive cars.I have also tried one more service at http://drivescore.fizber.com/. It is called Drive Score. With the help of it you can see how close establishments are by car. It's really a perfect idea! Yes, walk score is real a good idea! But why only walk score?
How often do we walk nowadays? More and more people drive cars.I have also tried one more service at
http://drivescore.fizber.com/. It is called Drive Score.
With the help of it you can see how close establishments
are by car. It’s really a perfect idea!

]]> Comment on SVN and LaTeX by Subversion and mac bundles « The Daily Photon http://dawes.wordpress.com/2008/04/26/svn-and-latex/#comment-155 Subversion and mac bundles « The Daily Photon Tue, 01 Jul 2008 19:27:51 +0000 http://dawes.wordpress.com/?p=137#comment-155 [...] 1, 2008 by adawes I wrote earlier about using SVN and LaTeX for document management. While this has continued to work well for me, I [...] [...] 1, 2008 by adawes I wrote earlier about using SVN and LaTeX for document management. While this has continued to work well for me, I [...]

]]> Comment on Waves and Optics by adawes http://dawes.wordpress.com/2008/06/26/waves-and-optics/#comment-150 adawes Fri, 27 Jun 2008 01:52:19 +0000 http://dawes.wordpress.com/?p=149#comment-150 Ok, sorry for the misunderstanding. The end effect you refer to can be described via impedance, or also by a reflection that is 180 degrees out of phase. I like the animations shown here: http://www.phys.unsw.edu.au/jw/flutes.v.clarinets.html In particular, the pulses traveling in partially-open and fully-open pipes. The diffusion of the pressure wave as it exits, leaves the inverse wave to propagate back down the pipe. This also explains why the reflection occurs slightly past the end... and also why diameter matters. When the pipe is larger, the diffusion takes place over a longer length scale (the constant between the extra length and diameter is something like 0.6). Ok, sorry for the misunderstanding. The end effect you refer to can be described via impedance, or also by a reflection that is 180 degrees out of phase. I like the animations shown here:

http://www.phys.unsw.edu.au/jw/flutes.v.clarinets.html

In particular, the pulses traveling in partially-open and fully-open pipes. The diffusion of the pressure wave as it exits, leaves the inverse wave to propagate back down the pipe. This also explains why the reflection occurs slightly past the end… and also why diameter matters. When the pipe is larger, the diffusion takes place over a longer length scale (the constant between the extra length and diameter is something like 0.6).

]]> Comment on Waves and Optics by flamendialis http://dawes.wordpress.com/2008/06/26/waves-and-optics/#comment-149 flamendialis Fri, 27 Jun 2008 01:13:54 +0000 http://dawes.wordpress.com/?p=149#comment-149 Thanks for the reply. What I am looking for is why the end effect is proportional to the diameter of the pipe. I have seen explanations based on the impedance on both sides, but that is perhaps overkill for this application. I used to explain it as waves radiating out in a hemisphere from the pipe, but now I am not so convinced. As to your explanation, my question would be why molecules vibrate at a small distance away from the end rather than _at_ the end of the pipe. Thanks for the reply. What I am looking for is why the end effect is proportional to the diameter of the pipe. I have seen explanations based on the impedance on both sides, but that is perhaps overkill for this application. I used to explain it as waves radiating out in a hemisphere from the pipe, but now I am not so convinced. As to your explanation, my question would be why molecules vibrate at a small distance away from the end rather than _at_ the end of the pipe.

]]> Comment on Waves and Optics by adawes http://dawes.wordpress.com/2008/06/26/waves-and-optics/#comment-148 adawes Thu, 26 Jun 2008 19:59:41 +0000 http://dawes.wordpress.com/?p=149#comment-148 Yes, it tends toward optics, mostly by virtue of the large number of wave phenomena that optics can demonstrate. Based on the older set of notes I have (from the version that was taught in 2003-4), the first few weeks included some sound waves and other types of waves. The second half of the course is entirely optics: polarization, interference, diffraction, reflection, refraction, etc. The final weeks covered optical systems and devices, lasers, and current topics. As to your question about the "end effect" perhaps it is understandable from the perspective of an air molecule. Recall that sound waves are regions of high and low density: compression and rarefaction, respectively. From the perspective of an air molecule, this means that as a sound wave goes by, you first get pulled one way, and then you get pushed the other way (as opposed to a water wave where you would get pushed up and then slide down). Imagine the group of air molecules that lives at the closed end of a pipe. They hit the wall if they try to go one way, so the only way that a standing wave can be established is if those molecules are at a node: the point in the standing wave that does not oscillate. That way the end molecules simply stay put. Conversely, since an open-ended pipe does not have the barrier, the molecules at the end are free to oscillate and so that is what they do.Some of the confusion arises when drawing a standing wave in a pipe. Typically people draw a wavy string-like line inside the tube. This isn't how the molecules vibrate, this is more like a plot of the density at each point in the tube (for one instant in time).Let me know if that helped or hurt your picture of the end effect :-) Yes, it tends toward optics, mostly by virtue of the large number of wave phenomena that optics can demonstrate. Based on the older set of notes I have (from the version that was taught in 2003-4), the first few weeks included some sound waves and other types of waves. The second half of the course is entirely optics: polarization, interference, diffraction, reflection, refraction, etc. The final weeks covered optical systems and devices, lasers, and current topics.
As to your question about the “end effect” perhaps it is understandable from the perspective of an air molecule. Recall that sound waves are regions of high and low density: compression and rarefaction, respectively. From the perspective of an air molecule, this means that as a sound wave goes by, you first get pulled one way, and then you get pushed the other way (as opposed to a water wave where you would get pushed up and then slide down). Imagine the group of air molecules that lives at the closed end of a pipe. They hit the wall if they try to go one way, so the only way that a standing wave can be established is if those molecules are at a node: the point in the standing wave that does not oscillate. That way the end molecules simply stay put. Conversely, since an open-ended pipe does not have the barrier, the molecules at the end are free to oscillate and so that is what they do.Some of the confusion arises when drawing a standing wave in a pipe. Typically people draw a wavy string-like line inside the tube. This isn’t how the molecules vibrate, this is more like a plot of the density at each point in the tube (for one instant in time).Let me know if that helped or hurt your picture of the end effect :-)

]]> Comment on Waves and Optics by flamendialis http://dawes.wordpress.com/2008/06/26/waves-and-optics/#comment-147 flamendialis Thu, 26 Jun 2008 17:10:43 +0000 http://dawes.wordpress.com/?p=149#comment-147 Is this more of an optics course? I am not an expert, but I see that college courses don't have much of classical physics, something along the lines of "Theory of Sound". In particular, I haven't seen any non-mathematical (physics based) justification for the "end effect" in pipes. Is this more of an optics course? I am not an expert, but I see that college courses don’t have much of classical physics, something along the lines of “Theory of Sound”. In particular, I haven’t seen any non-mathematical (physics based) justification for the “end effect” in pipes.

]]> Comment on SVN and LaTeX by adawes http://dawes.wordpress.com/2008/04/26/svn-and-latex/#comment-145 adawes Sat, 14 Jun 2008 15:48:58 +0000 http://dawes.wordpress.com/?p=137#comment-145 My files are still on google code in the repository: http://code.google.com/p/dawes-phd-thesis I started out with a local repository, but I found it much easier to just use the google one since it is off-site and then I can upload versions from my laptop, and then sync any other computers to the google version. This removed the requirement that I maintain my own server (and maintain access to it). I'm happy to answer any questions about it, but I was an svn newbie when I started, and I just followed the instructions google has for it's code database. It worked really well, and I think I'll do a similar thing in the future for grant proposals and papers (although maybe not a public repository!). -Andy My files are still on google code in the repository:

http://code.google.com/p/dawes-phd-thesis

I started out with a local repository, but I found it much easier to just use the google one since it is off-site and then I can upload versions from my laptop, and then sync any other computers to the google version. This removed the requirement that I maintain my own server (and maintain access to it).

I’m happy to answer any questions about it, but I was an svn newbie when I started, and I just followed the instructions google has for it’s code database. It worked really well, and I think I’ll do a similar thing in the future for grant proposals and papers (although maybe not a public repository!).

-Andy

]]> Comment on SVN and LaTeX by Allen H. http://dawes.wordpress.com/2008/04/26/svn-and-latex/#comment-144 Allen H. Fri, 06 Jun 2008 04:19:59 +0000 http://dawes.wordpress.com/?p=137#comment-144 Very interesting! I've been doing all my writing in latex as well, in the hopes that going into Thesis.sty for my university will lead to easy submission. I'm interested in version control, but haven't ever used it, and the beast is a bit big and scary. :) My Prof. will never use it, of course... he tried a latex a couple times, and it just didn't work. BTW, did you remove your files from the repository, or are they still there? I'm not sure I want to run a gcode repository myself... may try to set it up on my server, or run it in local mode only. Any pointers greatly appreciated. :) Cheers! -Allen Very interesting! I’ve been doing all my writing in latex as well, in the hopes that going into Thesis.sty for my university will lead to easy submission. I’m interested in version control, but haven’t ever used it, and the beast is a bit big and scary. :) My Prof. will never use it, of course… he tried a latex a couple times, and it just didn’t work.

BTW, did you remove your files from the repository, or are they still there? I’m not sure I want to run a gcode repository myself… may try to set it up on my server, or run it in local mode only.

Any pointers greatly appreciated. :)

Cheers!
-Allen

]]> Comment on Mac Apps, round 1 by Whew. « metadatta. http://dawes.wordpress.com/2007/12/01/mac-apps-round-1/#comment-143 Whew. « metadatta. Tue, 03 Jun 2008 20:24:53 +0000 http://dawes.wordpress.com/2007/12/02/mac-apps-round-1/#comment-143 [...] program, and now that I’m doing more on the front it makes a lot of sense. Andrew has a post on some mac apps that he uses - similar to my previous post on the subject, and presumably with [...] [...] program, and now that I’m doing more on the front it makes a lot of sense. Andrew has a post on some mac apps that he uses - similar to my previous post on the subject, and presumably with [...]

]]> Comment on DrDawes.wordpress.com by skullsinthestars http://dawes.wordpress.com/2008/04/11/drdaweswordpresscom/#comment-138 skullsinthestars Fri, 18 Apr 2008 15:45:52 +0000 http://dawes.wordpress.com/?p=132#comment-138 Let me say congratulations again! I hope you don't get too bored with all the free time you'll find yourself (temporarily) with! :) Let me say congratulations again! I hope you don’t get too bored with all the free time you’ll find yourself (temporarily) with! :)

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