Seventh Semester at College

How did I become a senior? It doesn't feel like orientation and freshman year happened that long ago.
Tomorrow is the first day of class for the 2013 fall semester. I'll be taking 8.07 — Electromagnetism II, 8.09 — Classical Mechanics III, 8.333 — Statistical Mechanics I (a graduate class), and 14.12 — Economic Applications of Game Theory. I'm looking forward to all of these classes along with continuing my UROP (which may transition sooner or later into a new project as I wrap up my current one). The bigger things I have to deal with though are graduate school applications and the Physics GRE. The latter will be over in a few weeks. The former will be going on until around the beginning of December, but I hope to be done a while before that. Hopefully this semester goes well. Good luck to everyone else for the start of their school year/job/whatever else!

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Reflection: 2013 Summer UROP

Wow. This summer has been incredibly busy, productive, and fun all at once. I can't believe it's already over!

So what did I do this summer?
My primary concern this summer was my UROP. I have been able to bring it very close to an end point; I wasn't able to finish it up completely, but I guess that was an unrealistic expectation because that's just not how science works. It doesn't wrap up cleanly; it's an ongoing process. I learned a whole lot more about Scheme and MEEP in the process, though, which was great.
On a related note, another UROP project fell by the wayside (as I wrote about earlier this summer) once I realized it was based on flawed calculations. To be honest, I'm not really sure if I want to pick up that project again and try to bring it to some sort of conclusion or if that's really worth my time.
My secondary concern was preparing for graduate school. I took the GRE this past Tuesday, and I am happy to say that went quite well. I have also been studying for the Physics GRE, along with making my list of graduate schools/programs/professors that I want to further investigate and send applications.
My tertiary concern was making another video for the MIT-K12 project. That went off successfully as well.

Apart from that, not being around my usual set of friends for the summer had a silver lining. While I would have certainly liked to have been able to hang out with them more, I was able to become a lot closer to a few people who usually live on my floor during the semester and hang out with them a lot more. Compared to the end of last semester, where I would basically just say "hi" to them but not a whole lot more, I now intend to hang out with them significantly more during this coming semester.

What didn't I do? These things didn't happen because I didn't have the time or energy to carry them out.
I wasn't able to edit and publish all the videos I took of 8.033 lectures from 2 years ago. In fact, I couldn't really look at those at all.
I wasn't able to do much work for OCW as I had planned.
(Actually, that's mostly it.)

I'm excited for the coming semester. My classes all look quite exciting, and I'm still deciding what I want to do regarding my UROP once my current project can truly said to be concluded. That said, I feel a bit sad that this has been my last summer at MIT, and it is already over. After that, I only have 9 more months at this place. I hope I can make those 9 months really special. Before that, though, I'll be going on a vacation with my family for a few days and then spending the remaining 1.5 weeks of August at home. Yay!

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Skepticism in My Photonics UROP

I've mentioned here on several occasions that I've been doing a UROP regarding nanophotonics/photonic crystals. Specifically, my first project was in determining whether particular types of photonic structures might enhance absorptivity of light, which would help solar cells that convert that light into electricity. The goal is that the absorptivity enhancement (versus no texturing over the solar cell) should be over as broad of a frequency band as possible, because it is difficult to manufacture many different kinds of photonic structures just to satisfy performance demands over many narrow frequency bands. I worked on this project for about 4 months, because that was the time that my postdoctoral UROP supervisor was around (he moved after that). I was able to get some really nice-looking results in that time, and I figured there wasn't much more I needed to do to wrap it up, so I felt comfortable generally moving on to a new project (which I have been working on since 2012 February or so). The enhancement results looked great compared to existing designs, so I thought we might be on to something here. Recently, things started gearing up for a publication submission.

Today, it all came crashing down. Why? Another postdoctoral UROP supervisor (who I have worked with since last year primarily on my more current project but recently joined in to help progress of the older project, which is the subject of this post) asked me some hard questions about what I was really doing. Because of this, I realized that one of the parameter choices in my calculations that were giving such nice results was fatally flawed. When I fixed that issue, the results I was getting suddenly looked significantly less compelling; with that, any dreams of publication were dashed.

Why did this happen? It boils down to me not being skeptical enough about what was going on. A large part of this has to do with the fact that because this was my first UROP, I didn't have a great idea of what was going on in terms of details. And because that time I spent was only about 4 months and was followed immediately by a new project, I didn't spend much more time on that project after that. Ultimately I got complacent in more ways than one. Because the code I was using was based on existing code for similar calculations, I figured it must have been written to work even with the modifications I was making. I also figured that because I had been getting consistently good results from what I had done over those 4 months, I just needed to worry about those results on the surface and not the fundamentals operation of the code. Those two assumptions combined such that even though I had seen the results of not being careful in my second UROP project and had become much more careful about checking that code as a result, I didn't think I needed to apply the same level of care in checking the code used for the first project.

After realizing the implications of this, I did a few more calculations in a significantly more mopey mood. But then I thought about this and I realize that I shouldn't feel so bad about this. Why is that? Here are a few reasons in no particular order.

1. I've made similar mistakes before, and I've really come to learn from them. One example of something that I thought was going great but turned out badly has to do with email. People who know me may have heard this story, and people who have known me for a while may have actually been there to see me do this, but I won't share the story now; I believe it is sufficient to say that I am now a lot more careful when sending emails especially to large groups of people. A reverse example actually comes from my second UROP project: for a while I was making a mistake in my code that was giving garbage, but after many months of trying various fixes, one particular fix solved all the other issues. Since then I have been a lot more careful about checking my code for that project (though I guess I was confident enough about the code used in the first project that I thought such a high level of care might be unnecessary).

2. I didn't think I would be in the position of having my work for both projects on paper until very recently. Now I can go back to thinking that in any case my second project work would be more likely to go on paper (especially as I know that I have taken a lot more care in checking my code for that project).

3. Several months ago, when my second project was stalling, I was asking myself why it wasn't going as smoothly or quickly as my first project. Now I know that the first project should have in fact gone as slowly as the second project for the work to become as solid and carefully checked. The other part of this issue is that I have been working on the second project continuously, so I have been able to make continuous adjustments to the code and work progressively higher levels of care in checking the code in a smooth manner. Because I essentially stopped working on the first project after those first four months, if I adopt more careful code-checking now, it'll feel more like I'm starting over from scratch, which makes the process feel a lot more frustrating.

4. With all this, I feel like I have already learned a lot more from this lesson than I would have if everything was fine and dandy and this work did get submitted for publication.

5. If nothing else, I hold out hope that I may be able to salvage some good results with the fixes I have made to the code of the first project.

There are two morals to this story. The first is that I shouldn't just check the code I run; I should check it in an actively skeptical manner, always questioning each and every line. The second is that C++ is way more painful to read and (to a lesser extent) write than Scheme is for the kinds of calculations I run.

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Done with 6th Semester!

I'm done with junior year! The spring semester was a bit more manageable than the fall semester, but was still challenging nevertheless. I intentionally chose to take only 3 classes: 8.06 — Quantum Physics III, 8.14 — Experimental Physics II, and 14.03 — Microeconomic Theory and Public Policy. I did this so that I could spend more time on each of those classes (especially 8.14 — Experimental Physics II) as well as on my UROP. Speaking of my UROP, things were progressing rather slowly in the beginning of the semester and only slowed further from there, until just after spring break, at which point progress went extremely quickly. I'm really looking forward to being able to make more such progress in the summer; plus, I may even be able to start on a new project about the Casimir effect, about which I wrote a paper for 8.06 — Quantum Physics III. Before that, I'm spending two weeks at home. For these next few days, I'm just going to relax and spend time and travel with family. After that, I'll probably be able to start work again on my UROP; a few weeks into the summer, I intend to start looking seriously into graduate programs in physics. Anyway, at last, it is summer!

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Long-Term Review: Chakra 2013.02 "Benz"

I did this long-term review on my normal UROP desktop computer with the 64-bit edition of the OS. Follow the jump to see how it fared. Also do note that there are more days logged because I intend to use it for about 60-80 full hours of work, which is the equivalent of 7-10 full days in the summer, though now I am working on a part-time basis as classes have started.

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Nonzero Electromagnetic Fields in a Cavity

The class 8.06 — Quantum Physics III requires a final paper, written essentially like a review article of a certain area of physics that uses quantum mechanics and that is written for the level of 8.06 (and not much higher). At the same time, I have also been looking into other possible UROP projects because while I am quite happy with my photonic crystals UROP and would be pleased to continue with it, that project is the only one I have done at MIT thus far, and I would like to try at least one more thing before I graduate. My advisor suggested that I not do something already done to death like the Feynman path integrals in the 8.06 paper but instead to do something that could act as a springboard in my UROP search. One of the UROP projects I have been investigating has to do with Casimir forces, but I pretty much don't know anything about that, QED, or [more generally] QFT. Given that other students have successfully written 8.06 papers about Casimir forces, I figured this would be the perfect way to teach myself what I might need to know to be able to start on a UROP project in that area. Most helpful thus far has been my recitation leader, who is a graduate student working in the same group that I have been looking into for UROP projects; he has been able to show me some of the basic tools in Casimir physics and point me in the right direction for more information. Finally, note that there will probably be more posts about this in the near future, as I'll be using this to jot down my thoughts and make them more coherent (no pun intended) for future reference.

Anyway, I've been able to read some more papers on the subject, including Casimir's original paper on it as well as Lifshitz's paper going a little further with it. One of the things that confused me in those papers (and in my recitation leader's explanation, which was basically the same thing) was the following. The explanation ends with the notion that quantum electrodynamic fluctuations in a space with a given dielectric constant, say in a vacuum surrounded by two metal plates, will cause those metal plates to attract or repel in a manner dependent on their separation. This depends on the separation being comparable to the wavelength of the electromagnetic field (or something like that), because at much larger distances, the power of normal blackbody radiation (which ironically still requires quantum mechanics to be explained) does not depend on the separation of the two objects, nor does it really depend on their geometries, but only on their temperatures. The explanation of the Casimir effect starts with the notion of an electromagnetic field confined between two infinite perfectly conducting parallel plates, so the fields form standing waves like the wavefunctions of a quantum particle in an infinite square well. This is all fine and dandy...except that this presumes that there is an electromagnetic field. This confused me: why should one assume the existence of an electromagnetic field, and why couldn't it be possible to assume that there really is no field between the plates?

Then I remembered what the deal is with quantization of the electromagnetic field and photon states from 8.05 — Quantum Physics II. The derivation from that class still seems quite fascinating to me, so I'm going to repost it here. You don't need to know QED or QFT, but you do need to be familiar with Dirac notation and at least a little comfortable with the quantization of the simple harmonic oscillator.

Let us first get the classical picture straight. Consider an electromagnetic field inside a cavity of volume $\mathcal{V}$. Let us only consider the lowest-energy mode, which is when $k_x = k_y = 0$ so only $k_z > 0$, stemming from the appropriate application of boundary conditions. The energy density of the system can be given as \[H = \frac{1}{8\pi} \left(\vec{E}^2 + \vec{B}^2 \right)\] and the fields that solve the dynamic Maxwell equations \[\nabla \times \vec{E} = -\frac{1}{c} \frac{\partial \vec{B}}{\partial t}\] \[\nabla \times \vec{B} = \frac{1}{c} \frac{\partial \vec{E}}{\partial t}\] as well as the source-free Maxwell equations \[\nabla \cdot \vec{E} = \nabla \cdot \vec{B} = 0\] can be written as \[\vec{E} = \sqrt{\frac{8\pi}{\mathcal{V}}} \omega Q(t) \sin(kz) \vec{e}_x\] \[\vec{B} = \sqrt{\frac{8\pi}{\mathcal{V}}} P(t) \cos(kz) \vec{e}_y\] where $\vec{k} = k_z \vec{e}_z = k\vec{e}_z$ and $\omega = c|\vec{k}|$. The prefactor comes from normalization, the spatial dependence and direction come from boundary conditions, and the time dependence is somewhat arbitrary. I think this is because the spatial conditions are unaffected by time dependence if they are separable, and the Maxwell equations are linear so if a periodic function like a sinusoid or complex exponential in time satisfies Maxwell time evolution, so does any arbitrary superposition (Fourier series) thereof. That said, I'm not entirely sure about that point. Also note that $P$ and $Q$ are not entirely arbitrary, because they are restricted by the Maxwell equations. Plugging the fields into those equations yields conditions on $P$ and $Q$ given by \[\dot{Q} = P\] \[\dot{P} = -\omega^2 Q\] which looks suspiciously like simple harmonic motion. Indeed, plugging these electromagnetic field components into the Hamiltonian [density] yields \[H = \frac{1}{2} \left(P^2 + \omega^2 Q^2 \right)\] which is the equation for a simple harmonic oscillator with $m = 1$; this is because the electromagnetic field has no mass, so there is no characteristic mass term to stick into the equation. Note that these quantities have a canonical Poisson bracket $\{Q, P\} = 1$, so $Q$ can be identified as a position and $P$ can be identified as a momentum, though they are actually neither of those things but are simply mathematical conveniences to simplify expressions involving the fields; this will become useful shortly.

Quantizing this yields turns the canonical Poisson bracket relation into the canonical commutation relation $[Q, P] = i\hbar$. This also implies that $[E_a, B_b] \neq 0$, which is huge: this means that states of the photon cannot have definite values for both the electric and magnetic fields simultaneously, just as a quantum mechanical particle state cannot have both a definite position and momentum. Now the fields themselves are operators that depend on space and time as parameters, while the states are now vectors in a Hilbert space defined for a given mode $\vec{k}$, which has been chosen in this case as $\vec{k} = k\vec{e}_z$ for some allowed value of $k$. The raising and lowering operators $a$ and $a^{\dagger}$ can be defined in the usual way but with the substitutions $m \rightarrow 1$, $x \rightarrow Q$, and $p \rightarrow P$. The Hamiltonian then becomes $H = \hbar\omega \cdot \left(a^{\dagger} a + \frac{1}{2} \right)$, where again $\omega = c|\vec{k}|$ for the given mode $\vec{k}$. This means that eigenstates of the Hamiltonian are the usual $|n\rangle$, where $n$ specifies the number of photons which have mode $\vec{k}$ and therefore frequency $\omega$; this is in contrast to the single particle harmonic oscillator eigenstate $|n\rangle$ which specifies that there is only one particle and it has energy $E_n = \hbar \omega \cdot \left(n + \frac{1}{2} \right)$. This makes sense on two counts: for one, photons are bosons, so multiple photons should be able to occupy the same mode, and for another, each photon carries energy $\hbar\omega$, so adding a photon to a mode should increase the energy of the system by a unit of the energy of that mode, and indeed it does. Also note that these number eigenstates are not eigenstates of either the electric or the magnetic fields, just as normal particle harmonic oscillator eigenstates are not eigenstates of either position or momentum. (As an aside, the reason why lasers are called coherent is because they are composed of light in coherent states of a given mode satisfying $a|\alpha\rangle = \alpha \cdot |\alpha\rangle$ where $\alpha \in \mathbb{C}$. These, as opposed to energy/number eigenstates, are physically realizable.)

So what does this have to do with quantum fluctuations in a cavity? Well, if you notice, just as with the usual quantum harmonic oscillator, this Hamiltonian has a ground state energy above the minimum of the potential given by $\frac{1}{2} \hbar\omega$ for a given mode; this corresponds to having no photons in that mode. Hence, even an electrodynamic vacuum has a nonzero ground state energy. Equally important is the fact that while the mean fields $\langle 0|\vec{E}|0\rangle = \langle 0|\vec{B}|0\rangle = \vec{0}$, the field fluctuations $\langle 0|\vec{E}^2|0\rangle \neq 0$ and $\langle 0|\vec{B}^2|0 \rangle \neq 0$; thus, the electromagnetic fields fluctuate with some nonzero variance even in the absence of photons. This relieves the confusion I was having earlier about why any analysis of the Casimir effect assumes the presence of an electromagnetic field in a cavity by way of nonzero fluctuations even when no photons are present. Just to tie up the loose ends, because the Casimir effect is introduced as having the electromagnetic field in a cavity, the allowed modes are standing waves with wavevectors given by $\vec{k} = k_x \vec{e}_x + k_y \vec{e}_y + \frac{\pi n_z}{l} \vec{e}_z$ where $n_z \in \mathbb{Z}$, assuming that the cavity bounds the fields along $\vec{e}_z$ but the other directions are left unspecified. This means that each different value of $\vec{k}$ specifies a different harmonic oscillator, and each of those different harmonic oscillators is in the ground state in the absence of photons. You'll be hearing more about this in the near future, but for now, thinking through this helped me clear up my basic misunderstandings, and I hope anyone else who was having the same misunderstandings feels more comfortable with this now.

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More on My Photonic Crystal UROP

In my post at the end of the summer, I talked a bit about what I actually did in that UROP. Upon rereading it, I have come to realize that it is a little jumbled and technical. I'd like to basically rephrase it in less technical terms, along with providing more context on what I did in the 2011 fall semester. Follow the jump to see more.

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Sixth Semester at College

Today is the first day of my sixth semester at college. I'll be taking 8.06 — Quantum Physics III, 8.14 — Experimental Physics II (also known colloquially as "J-Lab"), and 14.03 — Microeconomic Theory & Public Policy. I feel like taking three classes apart from J-Lab was too much last semester, so taking two this semester should make my schedule feel a lot more sane and manageable. Plus, now I have a handle on what J-Lab expects, so striving to meet that should be easier now. Finally, I did this because my UROP sort of fell to the wayside last semester, and I don't want that to happen this semester, so now I should be able to spend more time on both classes and that. Hopefully this semester will be a good one; good luck to all my fellow classmates out there!

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Reflection: 2013 IAP

This IAP was a ton of fun, and I was also able to get quite a bit done. The highlight was in my UROP, which is a continuation of what I was doing in the past semester. In late November, there was a power outage that reintroduced a previously-fixed bug into the computing cluster that I used, which caused various issues for my photonic crystal calculations. After trying several different workarounds, it wasn't until two weeks ago that I figured out how to properly route around the issue; when that happened, I was quite happy to have sensible, working flux spectrum calculations. Some people from the main UROP office also came to chat with me about what I am doing for my UROP, which was cool. At the same time, I was able to start wrapping up my project from the 2011 fall semester by creating more proper figures for the work I did then.
On the side, I worked on a video for the MIT-K12 initiative, which is a partnership between MIT and the Khan Academy. I was able to create a video about friction aimed at middle school students, and I'm fairly pleased with how it turned out. It should become official in a few weeks, at which point I will have either an update to this post or a separate follow-up post to include links to that and the result of the UROP chat (whenever that gets finalized).
I was also able to start typesetting lecture notes for 8.04 — Quantum Physics I for use by MIT OCW. I'm working with two other friends on that as well to get it done more efficiently.
The last week of IAP was particularly hectic. Along with the UROP chat, I was able to participate at the Diversity Summit as part of a panel of students with disabilities. Also, I helped to organize the SPS and UWIP joint Physics Lightning Lectures event.
There were a few things I was not able to do, but those can be done later, and I am glad that I gave myself enough time to rest and take life at a more relaxed pace compared to that of the semester. That said, this blog will likely reenter a sort of hibernation once the semester starts next Tuesday (and another post on that will likely occur on Monday or Tuesday of this coming week). Anyway, for this weekend, I am just going to relax and enjoy the large televised football game tomorrow!

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Done with 5th Semester!

Wow. This semester was longer and far more difficult than any previous one here. Most of that is courtesy 8.13, though 8.231 and 14.04 were certainly contributing factors. Final exams were also fairly challenging as well this time. My only regret is that my UROP somewhat fell by the wayside as a consequence. I really enjoyed learning what I did in my classes, and the experiences I gained were immensely rewarding in the end, but I am so glad that I am done with it now. Right now, I'm just focusing on going home in a few hours and spending quality winter break time with family and friends. I will be back over IAP to continue my UROP. After that, in the spring semester, I intend to take fewer classes, because I realize that I may have bitten off a little more than I could chew this semester. Anyway, happy holidays everyone!

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Long-Term Review: openSUSE 12.2 KDE

I did this long-term review on my normal UROP desktop computer with the 64-bit edition of the OS. Follow the jump to see how it fared. Also do note that there are more days logged because I intend to use it for about 60-80 full hours of work, which is the equivalent of 7-10 full days in the summer, though now I am working on a part-time basis as classes have started. Finally, for some reason Blogger decided to delete the content of what I had here, so everything up until "Day 2" is very much paraphrased from memory.

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Fifth Semester at College

Well, it has indeed happened. I am now a junior! Wait, what? When did this happen all of a sudden?
Classes start tomorrow, and this semester I'm taking 8.05 (Quantum Physics II), 8.13 (Experimental Physics I, also known as "J-Lab"), 8.231 (Physics of Solids), and 14.04 (Intermediate Microeconomic Theory); in addition, I am continuing my UROP from the summer. I'm most scared about J-Lab, because I've seen other friends take it in the past and I've seen how they have had essentially no time to do anything else (often even to the detriment of other classwork). Well, I'll see how it goes; while 4 classes and a UROP will be quite a time-crunch, I think I'll make it through OK. That said, this blog will probably see many fewer posts over the course of the semester. I guess I'll wait and see how that goes too.

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Featured Comments: Week of 2012 August 5

There is no "Featured Comments" post for this past week because there were no posts that week, but the one for the previous week is this one because I was out of town last weekend and couldn't write this post at that time.

Review: Stella 6.3

An anonymous reader supported the puns: "I know what you mean about Tennessee Williams, I been perfecting my Marlin Brando Stanley Kowalski impression since I first heard the name. I know there's a pun headline there somewhere, but I just can't seem to capture my 'Stel-la!' impression in text."
Commenter crabbos said, " This one sounded interesting until you mentioned it has 2 panels. That just killed any interest I had right there. Still waiting for a look at Voyager too hehe ^_^"
Reader Nux, who is also the developer of Stella, had this to say: "Thanks for trying out Stella. Glad you liked the name, at least. :-) The remix is intentionally kept simple, I didn't want to create the new **insert random ubuntu remix here**, I just wanted Centos (EL) fans a hassle free installation, hence just a few small modifications here and there as you noticed: - nautilus uses the browser mode by default - the default fonts differ - totem should load subs automatically and also resume playing files (a la smplayer) - Bluecurve: this theme was one of the graphical landmarks of RedHat linux, old redhatters know. Using it was my own way to give credit, if you like, to this great distro. I also happen to think it's one of the most beautiful themes, but that's just me. :-) * And a tip for those who have it installed: add yourself to the "wheel" group and you will be able to use sudo and install/update software (via gui or pkcon) without the root password."
An anonymous commenter had this bit of support for a decision in the distribution: "I actually like the bluecurve theme a lot and hope you will continue to atleast have that as one of the optional themes even if you decide to change the main theme."

Reflection: 2012 Summer UROP

Reader Chenyu Zhao said, "Scheme is great! You must read SICP if you haven't already: http://mitpress.mit.edu/sicp/"

Long-Term Review: Linux Mint 13 LTS "Maya" KDE

Commenter Erno had this experience to share: "I found Amorok as painfully bad working with Mint 13 KDE. So i uninstalled it and replaced it with much better working Banshee. Perhaps one of the reasons might have been my old cd/dvd device. However with Banshee in both Lubuntu, Mint 13 MATE and Mint 13 KDE it has worked very well."
An anonymous reader asked in response, "Curious to know how you got Banshee to work in Mint 13 KDE. Tried it and 1st time it dissapeared. Restarted the app and it crashed again.
I have a Sony Vaio VPCF234FD which reverts to HDMI audio at the slightest provocation and Amarok keep switching phonon to the HDMI audio (quite annoying), So for me it has been back to good 'ol Gmusicbrowser. Frankly I'd like to know your secret to make Banshee work in KDE."
Commenter crabdog also responded, "I've become rather fond of Clementine of late. So much so that it's now my default music player in Windows 7 as well as my various Linux distros. As for Mint, I've tried all flavors of Maya and didn't find anything compelling enough for me to stick with it. I'm currently running Voyager 12.04 xfce, a Zorin 6 respin and BigLinux KDE."
Reader Rudy Hartmann shared this tip: "I had a few crashes in Linux Mint 13 KDE too. I think it has better polish than Kubuntu also. But I upgraded Mint 13 KDE to KDE 4.9 and all the bad stuff stopped happening. sudo apt-add-repository ppa:kubuntu-ppa/backports -y sudo apt-get update sudo apt-get dist-upgrade Try it! Works good!"

Thanks to all those who commented on the previous week's posts. There were no posts this past week as I was relaxing with family and friends at home. That will continue to be true for this coming week and the following week, meaning that posts may or may not happen during that time. Anyway, if you like what I write, please continue subscribing and commenting!

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Long-Term Review: Linux Mint 13 LTS "Maya" KDE

I recently reviewed Linux Mint 13 LTS "Maya" KDE, and I was quite pleased with it. My long-term review of the Xfce edition just ended, so this one will go for another 8 days. This will be the last such long-term review of the summer, because after this I am going home and won't be back until just before the semester starts, at which point I probably will not be able to continue this.

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Reflection: 2012 Summer UROP

The long-term reviews I have been doing this summer have been on the desktop that I have been using for my UROP work this summer. Most of my thoughts about that have basically been along the lines of "UROP work went fine today". But I've realized that I haven't properly discussed what I've done this summer, I figured that I should share a little bit about that today because tomorrow is my last day here for the summer before I go home for a few weeks' break.

Let us start with the basics. A dielectric is essentially any material medium that changes the average speed at which light propagates due to the interaction of the electromagnetic field with the atoms and molecules constituting the dielectric. A photonic crystal is a periodic array of dielectric, and this periodicity can be found in 1, 2, or 3 dimensions. The photonic crystals that I was modeling this summer are in 2 dimensions; specifically, they are rectangular slabs of dielectric material with cylindrical holes of air/vacuum punched through the center along one axis. These sorts of periodic structures are special because they have certain bands of natural resonant frequencies at which the electromagnetic field is very well supported and other bands of frequencies where the field basically can't exist in the structure at all. This allows for very efficient manipulation of light at various frequencies. For instance, last fall, I was looking at optimizing photonic crystals to absorb the most light at various angles of incidence given a range of frequencies. This summer, I have been characterizing the electromagnetic energy flux from the photonic crystal structure that I mentioned before as a function of frequency and wavevector; the energy flux comes from localized current sources embedded in the dielectric material, and this models spontaneous emission. Such spectra should and do show peaks near the resonant frequencies. I was working closely with a postdoctoral associate and graduate student who had previously determined the functional dependence of the flux spectrum analytically and verified it experimentally. I was essentially providing a third method of verification through numerical analysis in MEEP. I have also asked the graduate student with whom I work about the ultimate applications of these flux spectrum modeling techniques, and the closest thing I have gotten to a good answer is that many macromolecules look like photonic crystals locally, so knowing the resonant frequencies and wavevectors for the flux spectrum makes imaging said macromolecules much easier.

In the process, I've become much more accustomed to using MEEP. I'm no longer scared of Scheme despite my C++/JAVA programming background; in fact I'm almost used to using Scheme. I've gotten a better handle on the tricks of the Linux terminal. And this was the first time that I was able to have a good level of appreciation for what I was doing, because this was the first full term that I was able to UROP after the lecture in my 8.04 (Quantum Physics I) class in 2012 May about photonics. Overall, I would say that my UROP was a success in that I really enjoyed every bit of it!

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Long-Term Review: Linux Mint 13 LTS "Maya" Xfce

If you've read my very recent review of Linux Mint 13 LTS "Maya" Xfce, you'll know how pleased I was with it. Given that my latest long-term review of Kubuntu 12.04 LTS "Precise Pangolin" just ended, I needed something new, so this was going to be it. Follow the jump to see what this is like over the course of 7-10 days.

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Long-Term Review: Kubuntu 12.04 LTS "Precise Pangolin"

This is the second of a handful of long-term reviews I will be doing this summer. The initial subject of this was the 64-bit edition of #! 11 "Waldorf", so follow the jump to see how that turned out.

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Long-Term Review: Chakra 2012.05 "Archimedes"

For those of you who don't know what this is about, this post should clear things up. Essentially, I now have another computer upon which I can do tests of installed distribution sessions for several days at a time. There will be three more posts like this one this summer; I may or may not be able to continue it through the semester. For reference, I used the 64-bit minimal CD for live testing and installation. Follow the jump to read my experiences with Chakra over more than a week of use.

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Long-Term Review: Because Now I Can

I am doing a UROP on campus this summer (as opposed to last summer, when I interned at NIST), and it is a continuation of my UROP from the last two semesters concerning photonic crystals. This summer, my ultimate goal is to be able to use MEEP finite-difference method simulations to recreate the spontaneous emission spectrum of a particular photonic crystal structure of great interest to the research group in which I am working.

To do that, I create the simulations as programs written in the Scheme programming language (a derivative of Lisp) and executed through MEEP. These actual steps are done on a cluster of computers, so the laptop computer that I have been using at my office is merely a terminal for the cluster. Because that laptop runs Microsoft Windows XP, there is no built-in way to SSH into the cluster, so I have to use a UNIX-like terminal emulator for Microsoft Windows; in my case, I use SecureCRT combined with XWin32 for graphical programs like Gedit and Geeqie. Unfortunately, that laptop is at least 7 years old (judging from its hardware specifications and thickness), and with Microsoft Windows XP, it is certainly showing its age; last semester it worked just fine, but a few days ago, it started choking trying to run Mozilla Firefox/Adobe Reader, LibreOffice Calc, and SecureCRT simultaneously. I asked my UROP faculty advisor if I could use a much newer desktop in the office that I use that no one else seems to be using, and he was fine with that; I even asked him if I could run Linux on it, and given that my previous UROP postdoc advisor (in the same research group) ran Ubuntu and helped other people set up Linux for work computers, he was fine with that too.

This presents a unique opportunity for me this summer with regard to this blog, and that's where the title comes in. One of the most common complaints about the reviews I do here is that they use the live session without trying the installation on real hardware at all. Also, because I usually only test the live session, the actual amount of time I spend is not more than a few hours spread over two days or so. Now, I have finally secured the official go-ahead to do with the computer whatever I feel is useful, so I will attempt to take more time to test some distributions (now as an installed session on real hardware) that I have said before that I would have no problem installing, because I want to see just how true of a statement that is. The computer in question is probably not more than 3 years old; it is a Dell desktop with a 64-bit Intel Core i5 processor, 4 GB of RAM, a 320 GB hard drive, and an ATI graphics card (though I am not sure if the graphics card is integrated or dedicated).

Given the amount of time I have left this summer to work, I intend to test each distribution for between 7-10 days of work, though that may change depending on my schedule and if a given distribution really does not work out. I have already installed Chakra 2012.05 "Archimedes", so that will be the subject of the first real "Long-Term Review" post. Each of these posts will be updated with a daily label detailing any changes, bugs, or other things that I notice. Each post will also have a "Day 0" label at the top sort of revisiting the live session like I normally do to set up my ideal desktop once more. At the end of the testing session (again, 7-10 days), I will publish the full post. While the "Day 0" section will basically be like a full review all over again, the following days' sections will be shorter. It doesn't take a long time to see if my favorite applications work or not, but it does take longer to really feel comfortable with the desktop, look for bugs and quirks, and make sure that upgrades go smoothly. So in these posts, I will really be looking out for details like how well the file manager and panel do stuff that I want them to do on a daily basis, how stable the system is, et cetera, as opposed to simply seeing once if something like Skype works; at my UROP, I only really need a web browser to see some web pages and check email, a PDF viewer to read papers, and a terminal emulator to SSH into the cluster, so I could theoretically settle for something like Ubuntu, but I don't want to waste this opportunity.

Again, I have already started with Chakra. I've always been fond of #!, so I might give that a go too. I'll also give Sabayon a run given that version 9 seemed to work so incredibly well. All of these will be the 64-bit editions because the computer has a 64-bit processor and 4 GB of RAM, so I want to make use of that. That leaves room for a fourth distribution (but probably not more than that); I will have to think about what I want to save for last, and I certainly welcome any comments and suggestions on the matter. Do look out for these posts along with my usual reviews and other random posts.

(UPDATE: Duh. I just realized I could do a long-term test of a prerelease version of SolusOS at the end of summer, and that would be the fourth distribution to test. Hopefully by then a 64-bit beta edition will have been released. I haven't written about it formally, but I have checked out SolusOS 2 Alpha 4, and I'm quite pleased with what I see, especially for an alpha release. Now, I will be able to see if that is really true over a longer period of use on an installed system instead of just a shorter period of use on a live system.)

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Done with 4th Semester!

Oh my goodness. I am done with half of my undergraduate career at MIT. This is crazy!
This past semester was even more crazy than the one before that. The great thing was that my classes this semester were way more interesting on the whole and will be far more useful especially towards the UROP that I will be doing over the summer.
For now, though, I'm not thinking much about my UROP. I'm thinking about what I'll do to relax and unwind at home. And by the way, one of the things I had originally intended to do was write a few more reviews, but because I stupidly forgot my USB flash drives in my dormitory room, that will not be happening until I get back to campus. Oh well. I'll find other stuff to do too!

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