Author Archives: Marcus

Microsoft Project Lessons

Here are some tips for using MS Project in par­tic­u­lar and project man­age­ment in gen­er­al that I picked up, which have either proven use­ful or which sound rea­son­able and which I plan to try out in the future. Feel free to add yours in the com­ments. Leave Buffers Since no project ever goes accord­ing to […]

Adventures in JavaScript: Number Bases

Here’s just a quick lit­tle JavaScript that will con­vert num­bers between dif­fer­ent bases. It grew out of the idea that num­bers in a sys­tem based on π would be much more use­ful in engi­neer­ing that the reg­u­lar old ones. Well, just because one can do it doesn’t mean it’s a good idea, but it was […]

Adventures in JavaScript: Humidity

You thor­ough­ly air out your rooms dur­ing win­ter time and watch the humid­i­ty inside drop in the process (pro­vid­ed you own a hygrom­e­ter). But where will it stop? This lit­tle gad­get will tell you. Just enter the out­side tem­per­a­ture and humid­i­ty and the tem­per­a­ture the air will be heat­ed up to inside.   Ref­er­ences [1] […]


The pre­vi­ous post on the Gauss­ian beam not­ed that this beam is a solu­tion to the parax­i­al wave equa­tion and thus only accu­rate for small diver­gence angles. The lim­it giv­en in [1] was $w_0 \gt 2\lambda/\pi$ or $\theta \lt 0.5\mathrm{rad}$ or $\approx 29^\circ$. The Gauss­ian beam mod­el is of course not exact up to that […]

the Gaussian beam (interactive)

The Gauss­ian beam “is a con­ve­nient, wide­spread mod­el in laser optics.” [1] It is indeed con­ve­nient that such a math­e­mat­i­cal­ly rel­a­tive­ly sim­ple mod­el can describe the evo­lu­tion of laser light in free space so well. Giv­en the wave­length of the laser, it can be described by a sin­gle para­me­ter. This can be either the beam […]

TiddlyWiki – EditSectionPlugin Keyboard Shortcuts

Like so many of his plu­g­ins, Eric Shulman’s Edit­Sec­tion­Plu­g­in for Tid­dly­Wi­ki is quite awe­some. Espe­cial­ly in long tid­dlers it can save you a lot of scrolling and search­ing. One thing I was miss­ing, though, were the key­board short­cuts ESC to can­cel edit­ing and CTRL+ENTER to fin­ish edit­ing, like the ones you have when edit­ing the […]

The Coupon (Sticker) Collector

Super­mar­ket chain Ede­ka cur­rent­ly runs this stick­er col­lect­ing rack­et – which used to be smurf col­lect­ing – where you get four stick­ers with ani­mal pic­tures for every €10 spent. The kids are col­lect­ing like crazy, I am told, even though the pic­tures are mediocre at best. Any­way, as geeks we don’t care much about the […]

Summer of Code

Dab­bling in JavaScript has been my new past­time for the last few weeks. After a lot of pok­ing in the dark try­ing to cus­tomize my Tid­dly­Wi­ki, I thought that I could use my new­found JavaScript pow­ers to make more use­ful stuff. So I sat down and wrote a bunch of scripts that add fea­tures to […]

shopping for a NAS

So I have this inter­nal 500GB HDD dri­ve that holds the back­up for my per­son­al data and pho­tos and what­not. Not only is it 98 per­cent full, but also very noisy, even when spin­ning idly. Since some Win­dows process always seems to access it reg­u­lar­ly, it also nev­er spins down. To get some peace of […]

the Doppler effect (relativistic)

Chris­t­ian Doppler in 1942 pre­dict­ed the Doppler effect for all kinds of waves, not only sound waves. The Doppler effect for light was demon­strat­ed in 1948 by Fizeau. In con­junc­tion with the arti­cle on the clas­si­cal Doppler effect, as it occurs e.g. for sound waves, we will here exam­ine the rel­a­tivis­tic Doppler effect which is […]