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Archive for August, 2014

Listening to Meteors

Sunday, August 31st, 2014

The View from the Front Yard 3:30 AM, August 30, 2014

Texas A&M, hot on the heels of their newfound football success has upgraded Kyle Field, their legendary football stadium where undergrads aren’t allowed to sit.  They’re allowed into the stadium mind you, it’s just considered poor form to sit.   We found out early one morning last week that a portion of the upgrade was a brand new jumbotron.  This became somewhat blindingly apparent when the pup and I were treated to technicolor clouds on our morning walk.  The jumbotron sits atop the newly refurbished end zone bleachers over a mile away from our house.  We wouldn’t be treated to such displays if it wasn’t for Johnny Football, and of course, our rather persistent low-lying early morning cloud cover that wafts in from the gulf.  The same circumstance that made for our polychromatic morning walk , (the cloud cover, not Johnny Football), obscured most of the Perseids meteor shower a few weeks ago.  As it turns out though, we could have listened to the meteor shower uninhibited.

When meteors hurtle through the atmosphere they leave a column of ionized gas in their trail.  Radio signals are reflected by this column, and so, while listening to a far-away mostly unintelligible TV or radio station, using a shortwave AM radio receiver, you can actually hear meteors whistle as they fly overhead.   The whistle is caused by the falling meteor Doppler shifting the frequency of the station you are listening to.  Most people are familiar with audio frequency Doppler shifts like the change in pitch of a moving fire engine siren.  As a source of waves, (sound waves in the case of the fire engine siren), moves, the frequency of the waves  changes with respect to a stationary listener.  Thus, as a fire engine approaches its siren goes first up in pitch, and then down as it passes by, and drives away.  Radio waves bouncing off the ion cloud created by a falling meteor exhibit the same effect.  Their frequency changes in proportion to the speed of the meteor.

Dr. .William Lonc of St. Mary’s University in Halifax, Canada[1] suggests listening for the video carrier of a television channel using an AM shortwave radio.  See Wikipedia for a list of television channel frequencies.  As a meteor cruises by, the Doppler shifted television signal will heterodyne with the local oscillator signal in your radio, and create a beat signal, or whistle in your speaker with a frequency determined by the speed of the meteor,

During a meteor shower like the Leonids, coming up in November, you should hear several pings, (in the older literature, they’re called whistlers), per minute.  Give it a try and please let me know how it goes.  I’ll try to do the same here at A&M and keep you posted.

 

References:

1.  William Lonc,Meteors by radio: Getting started,The Physics Teacher 37, 123 (1999); doi: 10.1119/1.880168

 

 

 

Math for Nothing and Refactoring for Free

Wednesday, August 20th, 2014

With all the requests by scientists and the government for money lately, here, finally, is something you can get from the government… for free.  Yes, that’s right, applicable scientific and engineering tools that are the result of NSF funding that your taxes paid for and that you can actually use… today… really!  If, like many engineers, you find yourself in need of the functionality Mathematica provides, but you’re reluctant to ask your boss for the money to purchase a license, sagemath might be for you.  Sage provides a lot of the same functionality that Mathematica does, and you don’t have to pay for it.  You can even use this Python based tool without making an install, with a cloud based version of Sage.  If you’ve ever played with Python, then you’re already most of the way to using Sage.

 

Functional Verification and Software Development, Brothers from a Different Mother

Verification Process Advise In Disguise as a Software Development Forum

Do you need better insights on improving your verification processes?  Are you running into issues like these?

  • Revision control nightmares
  • Blindingly and debilitatingly fast feature changes from marketing
  • Difficult to follow information trails on code verification history
  • Days and hours spent fixing broken designs after “No one changed anything” or only added “Correct By Design” fixes

As it turns out, the software industry had all these problems and beat the functional verification automation gang to the punch by several years.  While there is an ever growing cadre of EDA tools available to cure the above woes, there are also simple process steps, identified by the software folks, (as well as my own humble offering along with Shankar Hemady and a host of industry luminaries), that you can take to improve things now.  One of the beautiful things about the software industry  is that lots of its denizens love to share.  Checkout http://programmers.stackexchange.com, a forum that regularly discuss project management, debug, and code refactoring, (known as ‘garshdarned feature creep’ in our lingo).  As I was writing this, a question appeared on the board:

Develop in trunk and then branch off, or in release branch and then merge back?

Sound familiar?  Don’t let the name of the site fool you.  It’s not about how to program, it’s about how to be a programmer.  In addition to revision control, you’ll find posts about how to best change code, without destroying the code around it, and, equally importantly, with the advent of UVM, questions about design patterns, (think factory pattern).  Don’t worry about having to share in kind.  Stackexchange seems to have realized that your design, and or processes may actually be unique and beautiful snowflakes, in which cases, they’re quite happy with folks ‘just’ reading.

In the same vein, Coverity, a software verification company regularly publishes a software testing blog.  If you remember to squint your eyes, and say to yourself, ‘hardware systems’, or ‘embedded systems’, everywhere the blog says ‘software systems’, there are many good tricks and processes just waiting there for the taking.