Itcanbeshown.com

• I finally graduated!

• I decided to take a hiatus from my doctoral pursuits. I hope to locate a job where I may build on my research experience for the short term (1.5 - 2 years) to feel things out and the venture down different avenues. Notwithstanding, the career-track jobs I see during my inchoate jobsearch insofar still informs that the jobs I hope to attain someday do require a Ph.D. So, I do still have steadfast intent to return to graduate school to earn a Ph.D., but at least for now I think is a convenient and sensible time to see what is out there before I start full on towards a Ph.D.. After this, maybe in the end I might not even desire a doctoral degree, I am just saying these are my intents at the moment, to return for further studies, but who knows what will develop in the next couple years. I am familiar with the strong caution regarding taking a break from school, with the major concern being to never return, but maybe (although unfathomable to me evenstill) that is what might be best for me and what I might even want someday. Ultimately, what I mean to say is I am super excited to walk down a new pathway in my life, and wherever I end up is fine with me. But, I think this investigative period will be thoroughful fruitful in a number of regards, and will perhaps provide more clarity.

I had updated minimally throughout the semester, but since then I have a number of updates to catch up on. As usual, I am only publishing on this website work that I typesetted. I took two courses during my final semester. And, although I never announce matters like this I am happy, and do not see it too improper, to acknowledge that I ended up my final semester ("ever") on a high note, in that I 4.0'd this semester! Specific updates since last time include:

NEEP 548 -- Engineering Analysis II

Homework 4: Green's functions

• Green's functions solutions to various ordinary differential equations. The problems are an adaption of those from Haberman problem 9.3.12.

Homework 5: Multiple-scale Analysis

• Bender & Orszag 11.11
• Bender & Orszag 11.14

Homework 6: Method of Images

• Method of images solutions to Poisson's equation in semi-infinite domains in two and three dimensions with mixed boundary conditions

Take-home exam 2

• Method of images solutions to the heat equation, finite domain, Neumann boundary conditions
• Method of characteristics solutions to the wave equation, semi-infinite domain

NEEP 741-- Interaction of Radiation with Matter, aka "the second half of Jackson"

Homework 5

• Frame invariance of electric and magnetic fields
• Quadratic Lorentz invariants in electric/magnetic fields
• 4-vector solution to a kinematics problem

  Take-home Final Exam

• Energy loss of alpha particles in a carbon medium
• Jackson 14.4
• Energy spectrum of a linear antenna with a prescribed current
• Jackson 14.9
• Jackson 15.9
• Classical lifetime of an electron in a Bohr atom.

EMA 201 -- Statics

• My career as a TA has come to a close, I have uploaded many materials I have assembled and/or developed over the years so that it may be of use to any future students or TAs. Materials include a number of problems, detailed solutions, slideshow presentations, a sample design report, design report/technical writing advice, and more. I purposefully did not upload any of the design project solutions. While the solution manual has been leaked, this manual does not contain solutions for these problems. If you are a TA/instructor, and would like a copy of my solutions, please send me an email and I would be happy to provide you with any of them. These solutions are in a number of forms: typesetted documents with accompanying plots, excel spreadsheets, and/or matlab scripts.

Guest contribution: Law of Averages proof

• Kyle Herrity provides a proof to a classic law of large numbers, that is, that for a sufficiently large sample size the sample mean converges to the expected mean. Thank you Kyle!

Those two take-home finals from the top two classes were the very last works I produced as a graduate student at the University of Wisconsin - Madison. Remember what kind of students we used to be? Really, the difference between these two works and my nascent efforts as an undergraduate student speaks so much on the behalf of the effect of education. Especially in that 741 final exam, I remember being at the age and phase when some elementary physics problems that took but a few lines of algebra seemed laborious, and to now knock out a 34 page writeup of nontrivial problems in but a few days is certainly something meaningful. I really am thankful to all my professors, and institutions for so actively steer me on this course. I am learning much more every day and by no means do I mean to insinuate that I have reached a finish line by any means, I just mean to take a pause and juxtapose levels of progress while I veer down a different avenue.

Thanks everyone for reading and visiting. This break from academia will surely not mark a simultaneous hiatus from updates, I will still be around, but the updates may take a more blog-like turn as opposed to the usual academic works I am able to post by way of assignment. Over the years since this site's inception I have received so many kind emails from students around the world, professors, and even researchers who I am thankful to who have taken time out of their day to forward me papers or links regarding clearing up uncertainties I may have expressed throughout miscellaneous documentation posted on here, or questioning how I obtained particular plots, or even challenging interpretations I have put forth. I really find it encouraging and warming to see the candidness in communication, that people would not only benefit from anything they find on this site, but that they could be so friendly as to let me know how it helped and even upload these documents on share sites to spread them around. Others have taken the time to correct me, pose discussion points via email about tenets I have pushed forth in my work, or to provide me with citations that may elucidate something that maybe even I was confused on. I really feel a sense of community from making this site that I never imagined would reach me just by me publishing some of my works somewhere in an odd corner of the internet. How awesome is it to receive emails from researchers around the world, with oftentimes no intent but to help *me* learn more? Thank you to each and every one of your who have contacted me over the years, I appreciated every email, each discussion point, paper, link, etc. that has come my way. I have had tremendous trouble locating research experience throughout my graduate career, and it is part of the reason why I am taking a break and apprehend this issue directly by seeking research experience in a job, but I have felt like this website has contributed towards filling some of that deficit by allowing me interaction with a global community.

I am traveling to Latin America in a couple days for a duration of 15 days. Otherwise I am on the job hunt for principally a plasma physics research position in fusion sciences. I have upgraded my resume from a usual ms word document to a TeX version at long last. Thanks is deserving to Derek Hildreth who was generous enough to provide his source .tex file.

Outside of that, peace out Madison. Thanks for the times, education, friends, relationships, and mentors. I will miss you grad school (kind of), see you again someday (maybe). Take care everyone, and all the best.

- David

• Oh grad school...

Figure lol - "Looking for a more compact answer"? That makes two of us.
(full size answer, problem statement [NEEP 741, Hegna])

• Nick Touran's (University of Michigan, Nuclear Engineering and Radiological Sciences Department) article on the Fukushima Nuclear Power Plant (福島第一原子力発電所) incident [whatisnuclear]


• Some assignments/exams that I have typed my solutions for have been uploaded to the Graduate work section.


• NEEP 548 (Spring 2011, Engineering Analysis II) --

Asymptotic and perturbation methods for solving partial and ordinary differential equations (boundary layer theory, WKB approximations, etc.) are discussed in this class. The course follows the text by Bender & Orszag (BO).

• Homework 1 (partial assignment, covers chapter 3 ["Approximate solution of linear differential equations"] of BO)


• Bender & Orszag problem 3.8


• Take-home exam 1 (boundary layer theory and WKB methods)


• The problems in this course are short enough that I will try to typeset most of my assignments (as opposed to the course below), so stay tuned.

• NEEP 741 (Spring 2011, Interaction of Radiation with Matter)

This course covers the second half Jackson's electrodynamics text including dynamic electromagnetic fields, gauge potentials, relativistic electromagnetic theory, covariant/contravariant formulations, 4-vectors, d'Alembertian operators, electromangetic tensors, Cerenkov, Bremsstrahlung, and synchrotron radiation, thomson scattering, Raman scattering, etc. My first homework assignment has been uploaded (missing one problem, which I submitted handwritten). I do not forsee typesetting most of my assignments in this course, as Dr. Hegna informs, his assignments can get pretty "beefy," and regrettably enough the interesting problems are usually the beefiest. In all it would require too much time in all likelihood for me to be able to keep up with typing up these assignments. This will probably be the first and last assignment I include on this site for this course, unless I get super motivated somehow to typeset subsequent assignments.

• New problems and solutions have been added to the For Students section regarding material for a statics course I TA for as well.


• Happy spring break!

• The slideshow presentation relating to my research at Lawrence Livermore National Laboratory (LLNL, Summer 2009) has been uploaded under Graduate Work.


• My research involved computational excursions using LLNL's 3D multi-physics radiation hydrodynamics code for inertial confinement fusion apt towards national ignition facility simulations. Specifically, I worked on analyzing opacity calculations in HYDRA in both the local and nonlocal thermodynamic equilibrium (LTE/NLTE) regime. The analysis was furnished by developing a representative test problem that involved high energy laser bombardment of a titanium doped (0%-6% atom percent) underdense SiO₂ (0.1% of STP density, 2.04 mg/cc) target. Laser interactions with the underdense target generated a plasma that essentially had each numerical zone described as NLTE. LTE calculations were determined as a benchmark with HYDRA, and compared with the commercially available HYADES and HELIOS codes under identical conditions.


• NLTE comparison was performed with a newly developed Detailed Configuration Accounting (DCA) package that used realistic atom models capable of tracking kinetic rate transitions (10 ~ 20 levels per ionization stage) described by superconfigutations labeled by principal quantum number. DCA was shown preliminarily to agree with the popular averaged-atom package, XSN, used for NLTE calculations. Further comparison of opacities showed that the LTE computations, XSN, and DCA showed the overall curvature in parameter space, yet DCA showed a fine-structure in quantities such as emissitivty, opacities, radiation energy density, etc. Before the end of my term, we were investigating effects on the results by using different (more detailed) atomic models (generated by CRETIN), and by adjusting quantities such as the ionization fraction, and the LTE-to-DCA transition temperature. Noticeable fluctuations were observed in the followed parameters of interest, suggesting that while the results of the DCA package (as of Summer 2009) show significant agreement with established codes (XSN, CRETIN) in providing accurate calculations, additional variation is seen depending on how DCA is incorporated into simulations. A compromise between computational expense and fine-detailed calculations is then understood to be met on a case-by-case basis depending on the particular aims of each numerical investigation.


• I had a surreal summer here, and it was a dream come true to actually work at this lab. Thanks so much to everyone involved at LLNL, especially my mentor Mehul Patel and Marty Marinak who helped me out tremendously throughout the summer. I really appreciate evertyhing, take care~.

Merhaba arkadaşlar~

I just came back from a fantastic summer interning at Lawrence Livermore National Lab in California, I will publish documentation relating to my work there whenever it gets cleared by security.

As is evident and expected, I was a little bit more than a little busy during the summer, and ended up not fulfilling any of the numerous ambitions I had in mind for this website (as discussed in the previous update). However, I do still intend to produce these materials in the future. I am here in Madison for my second year of graduate school. Anyway, I am not sure how I feel about these updates becoming slightly blog-like, so I am going to stop now and think about it later, where later = winter break or some other time.

To all of my students this year: please refer to section 'For Students' on the menu bar on the left for materials related to discussion sections. This section will be updated with more material as we progress in the semester. You may find my contact information on the left as well.

Also, thanks very much to everyone who has sent me such kind emails about how itcanbeshown.com has been useful for them, or how they enjoyed it, or for whatever other reason. It has been really nice to hear from you all