Low Expectations

The other day, I asked M whether she is sometimes fed up about her students. She said no, she just has low expectations.

Same with flying in the U.S. I didn't even take off for the first leg to Philadelphia, and we're already 15min late.
It's just a farce that the only PA broadcasts are Dept of Homeland Security threat level advisories.
Threat level is orange. Same as always. No news about the delay.

Lost in modulo 360

Finally somebody expressed the reason why I have difficulties to intuitively navigate in America.



(If anybody knows who to credit for this, please drop me a note. Tun, thanks for the quote origin.)

LED Abuse

Another fancy application which was news to me (I am not an electrical engineer, but rather a computing "scientist")... one can use LEDs for sensing.



I was made aware of this by two students of ours, wondering how this is achieved. We explored several ideas and finally came up with a concept that probably is exactly how it works in reality: LED as light sensor.

Fancy.

Magnetic Field Torque

Last week, Edward Cheung from the NASA Goddard Space Flight Center, one of the engineers for the Hubble Space Telescope, visited the LCSR and gave a talk. Given that the Space Shuttle is to be retired after the next half-dozen flights, the talk scope changed to focus on the Shuttle technology. However, there were still some interesting details about the Hubble to be learned.



One of these details concerned the actuation of the telescope. As the Hubble has to stay operational for very long periods of time without any servicing missions, it doesn't have thrusters or boosters for orienting the telescope that would use up fuel. Instead, it uses inertial reaction wheel assemblies (that was what I expected), but also magnetic torquers (which was news to me). To keep the rotational speed of the RWAs within certain limits, the telescope can use metal bars that are extended and oriented into the magnetic field of the Earth as the Hubble traverses it, generating eddy currents in circuits through the bars and thus generating torque that turns the whole telescope (EDIT: or maybe not eddy currents, but rather a capacitor is discharged into the rod, cf. the link below?). The proper term seems to be "RWA momentum desaturation".



Properly awesome principle.
(For more info, look here. In fact, one control center for the Hubble is at the Space Telescope Science Institute just down the road, on my morning way to the parking lot.)



Strangely enough, these insights always come in pairs. Today, I saw an automatic tabletop globe in a catalog. Since it was an "organic" catalog (what is called "Öko" in German), it doesn't use batteries for rotation, but instead has a built-in photovoltaic cell. So far, so good; but the interesting part is that the globe sphere is embedded in an outer glass sphere that completely encases it, and there is no axis connecting the two spheres. In fact, the inner globe sphere is suspended in a thin layer of water within the outer sphere. And yet it moves. (10pts for proper quote attribution without googling.)



The catalog description claimed it uses "Earth magnetic field torque". Of course, having read up to here, the reader knows how it works, but I have to admit at first I thought "what a load of bull". Only then did I remember the magnetic torquers on the Hubble. Probably there is a magnetic rod similar to a compass needle mounted inside the globe sphere, and a photovoltaically powered motor inside the sphere torques the globe sphere against said rod. Voila, completely encapsulated torque actuation. Not a bad idea.

First Snow

Saturday, first snow in Baltimore.

Saftiges Nierchen

Hier ist ein Zwischenstand des Nierchenprojekts. Nicht das Ergebnis (3D-B-Mode-Ultraschall) ist entscheidend, sondern das Funktionieren der gesamten Modul-Pipeline bis dahin...

Noise Emissions

When I came to the U.S., I wondered every day how people tolerate the continuous noise everywhere. Loud cars, air conditioners running all the time, trucks big and small on and off the campus... only very rarely is one of those particularly atrocious transport vehicles on the campus replaced by an electric one. Somehow, silence is not a value here.

(In fact, during my last visit to British Columbia in 2008 I invested two or three days just looking for a place that has no other noises but nature itself. It didn't work. Even in the most remote valleys I tried, there was always at least the hum of some distant plane.)

So I wondered whether there is any country anywhere that has noise emissions regulations, any rules that would govern how machines and devices are to be constructed in a noise-minimizing fashion, sanctioning their operation licenses. Indeed, Germany (and probably some other countries, too) has some laws that regulate noise immissions for workers and in habitated areas (workers have to wear protective gear, and home residents can force noise sources to be shut down), but this doesn't protect the average pedestrian on the street. I don't know of any place that has laws that apply to the engineering side of the equation - making devices quiet before they're built, instead of banning loud ones.

Now it seems that even places like Kenia have noticed that people need to be protected from excessive noise levels. I would not be surprised if neither Germany nor other European places, not to mention the U.S., actually cared about or legislated noise reduction in public places.

Breakthrough

Today was one of those rare breakthrough days.

After many months of work, about 90% of the modules on our side of our Hopkins/Fraunhofer cooperation project that I am working on started working together.
The system consists of lots of separate reusable executables that "run anywhere" (meaning on any of our four or five project machines) and communicate with each other using mostly TCP/IP or shared memory. And over the course of the last two or three days, I figured out (with some help) the last remaining stumbling block to get the data constructed that the Fraunhofer people need.

It's about 8:20pm, so that means I can go home early.