The pleasure of finding things (out).   Leave a comment

Scholarship can be a tedious activity. Specifically, searching the existing literature to determine the context for my own research activities.

There’s a few ways to simplify the process. First (and foremost), is that literature more than a few years old is less relevant than current literature. That is, a research paper from 1925 is likely to be less useful than one written in 2009 on the same topic. Also, there are periodic review papers that survey the literature, so locating a few review papers will allow me to sort through several hundred papers to find the (say) dozen or so that are directly relevant. There are others, as well.

However, research has always been a rich person’s game. Journals charge for papers, for example. Without access to an academic (or equivalent) library, there would be no practical way to stay abreast of the literature: if I had to personally pay for every article I read, I would probably spend more than $5000 per year. The business of scientific publishing is beyond the scope of this post.

It used to be a *lot* harder to stay current- before electronic access to 99% of the papers worth reading became commonplace, whole areas of publishing were seldom available to a larger audience. An obvious example is the Russian scientific literature prior to perestroika. Although much was translated by an American Publisher (the Consultants Bureau Enterprises) and the Foreign Technology Division of the U.S. Air Force, by and large Russian results were unknown to the West.

Another example is the Defense Technical Information Center (DTIC) library. Generally catering to the U.S. military and government research programs, the technical documents contain important and useful results that were generally unobtainable, even by academics. I spent many hours in the basement of NASA’s library, going through mountains of microfiche to locate interesting work not in the ‘open scientific literature’.

Who cares? Honestly, not many people do- that’s why the microfiche is relegated to the basement, in the back. But sometimes it’s the thrill of the chase- to locate some primary source, lost to time. It’s easier now, since most materials have been made available online. The experience of being in the bowels of a library, just you, the microfiche reader and huge banks of motorized storage cabinets is memorable, and unfortunately becoming less common.

I am not referring to “landmark” papers- those are trivially easy to obtain copies of, even ones that go back to 1805 or earlier, through JSTOR. I am referring to articles, while just as influential, are far more obscure.

The chase starts when I read an assertion in a current paper, the assertion does not make sense to me, and the paper is just quoting some *other* paper rather than justifying the assertion. I retrieve the referenced paper and usually, that clears up my confusion.

Sometimes, the referenced paper is *also* just quoting an earlier reference. Again, I get the ‘grandfather’ paper and see what *that* one says. Sometimes, I’ve traced back 4 or 5 times before getting to the original justifcation.

If I have to go back 5 generations or so (which can represent a paper published in the 1950’s or early 1960’s), the paper trail tends to go off the scientific journal path. Sometimes it ends in a conference proceedings, sometimes a PhD dissertation, but usually it goes to the DTIC archive.

Here’s a few examples:

1) Sandford, Brian P., “Infrared Reflectances of Aircraft Paints”. AFGL-IR-84-0307, Accession # AD-B092 172 (November 21, 1984).

I dug this one up when I was at Nichols Research. The code we were developing was a ‘synthetic scene generator’. The goal was to generate images that would be identical to that obtained by a weapons sensor (say an infrared camera or a LADAR guidance system). In a way, it was a lot like video games, and in fact we hired people with video game experience to do some of the work. Video games use a lot of the techniques the military pioneered- fast and accurate rendering of photorealistic surfaces.

In order to generate realistic scenes, we need the object geometry, the lighting conditions (for example, by specifying the latitude, longitude, date, and time to generate the position of the sun and a program like MODTRAN or LOWTRAN to generate atmospheric conditions), and the detector characteristics (waveband, signal-to-noise ratio, etc.). We also needed information about the materials the object was made of- how they reflect or emit light.

Some basic data can be found easily enough- the emissivity for building materials in the infrared, for example. But that’s not good enough- we needed the BRDF of materials to generate realistic scenes, and those measurements are hard to come by. There are some databases of materials (for example here), but there wasn’t anything we could use. Until I started digging around and came up with the report listed above: BRDF measurements from 0.3 to 25 microns of military paint samples. This sort of measured data is precious.

2) Ufimtsev, P. Ya., “Method of edge waves in the physical theory of diffraction”, Accession # AD733203 (1962).

This unclassified translated Russian work (you can get any of the references I am posting here- just give your librarian the reference and turn them loose) is the basis for stealth aircraft. Once the work was translated, Lockheed and Boeing used the results to develop aircraft with very small reflectances- that’s correct; stealth aircraft were under development since the mid 1960’s.

Those two were very obscure works, but give a good ‘flavor’ for the sheer volume of results *not* contained in peer-reviewed literature. The next two have much more interesting stories:

3) G. G. Slyusarev, “On the possible and impossible in optics”, FTD-TT-62-175/1+2, Accession # AD-281847. (July 16, 1962).

More people should have copies of this. The first 10 pages of this report clearly demolishes a major ‘urban legend’: Archimedes’ death ray. Additional portions of the text decisively refute solar concentrators that violate the second law of thermodynamics and imaging systems that violate basic principles of optics. Just for busting Myth #1 (Archimedes’ death ray), this should be required reading in any optics class.

I’ll end with the following:
Parke, Nathan Grier., “Matrix Optics” (Ph.D. dissertation, MIT, 1948)
Parke, N. G., “Matric Algebra of Electromagnetic Waves” (MIT Research Laboratory of Electronics, Technical Report #70, June 30, 1948)
Parke, N. G., “Statistical Optics: I. Radiation”, (MIT Research Laboratory of Electronics, Technical Report #95, January 31, 1949)
Parke, N. G., “Statistical Optics: II. Mueller Phenomenological Algebra”, (MIT Research Laboratory of Electronics, Technical Report #119, June 15, 1949)

Here’s the primary sources for the ‘Mueller calculus’ representation of polarized light. The Mueller calculus (Mueller matrices and Stokes vectors) is completely different than the Jones calculus- it’s based on entirely different concepts- but is infinitely more useful. The Mueller calculus allows us to describe light that is not completely polarized (which is 99% of the light in the universe), in contrast to the Jones calculus which treats light as 100% polarized. The Mueller formalism is rarely taught and few are familiar with it. Even so, the Mueller calculus has allowed the development of very sophisticated techniques in telecommunications (both fiber and wireless) as well as LCD displays.

Parke’s dissertation references a technical report by Mueller (Mueller, H. “Theory of Polarimetric Investigations of Light Scattering”, Parts I, II. Contract W-18-035-CWS-1304. D.I.C. 2-6467. MIT (1946-1947)), but I have been so far unable to locate a printed copy of this report- most likely, the attribution has a typographical error. If you happen to come across this, I would appreciate a copy!

Hans Mueller never actually wrote a paper discussing his own invention- there is only a single paragraph, the abstract of a presentation, in the ‘official’ literature (H. Mueller, “The Foundations of Optics”, J. Opt. Soc. Am. 38, 661 (1948)). Apparently, Hans Mueller did not write *any* papers at all- at least, I haven’t found any. Let’s pause for a moment to contemplate the case of a faculty member at MIT making tenure and full Professor without having written a single peer-reviewed paper, and how that contrasts with academia today.


Posted December 29, 2010 by resnicklab in Pedagogy, Science

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