Kristopher Overholt

Python ImportError with backend_wx2.8 and wxPython when using Matplotlib

koverholt — Tue, 11 May 2010 04:42:18 +0000

For many months, since I upgraded to Snow Leopard (10.6), I’ve had the following error when trying to import matplotlib. When I issued the command “import pylab” or “from pylab import *” in iPython, Python, or any other tool that uses the Python shell, I got the following error:

ImportError: Matplotlib backend_wx and backend_wxagg require wxPython >=2.8

Well, after poking around this problem for the thousandth time, I finally fixed it for good. I did this by removing my ~/.matplotlib/matplotlibrc file. In this file, there was only one line:

backend : WXAgg

which I removed (and since it was the only line, I just removed the file). Now the error is gone, and matplotlib imports just fine, meaning that I can use it in any Python shell, including Sage.

Just thought I’d post this up in case any other Python/Snow Leopard users are having trouble.

Flammable antifreeze in fire sprinklers allegedly causes explosion

koverholt — Thu, 25 Feb 2010 04:02:03 +0000

In August of 2009 in Truckee, CA, a man was cooking on a stove when the pan caught fire, activating the fire sprinklers. Upon activation of the sprinklers, a violent explosion occurred which resulted in 1 death and 4 burn injuries to the family.

I came across this copy of a report (from the IAFSS mailing list) which details a report of a cooking fire turned explosive when the sprinklers were activated. Allegedly the propylene glycol used in the fire sprinkler system as an antifreeze aided in the explosive event, and another case is cited in which the antifreeze ignited and assisted in growing the fire from its ignition source.

The report can be found here: California –explosion– report (PDF)

While I have taken a few courses in fire sprinkler systems, I am not extremely familiar with the flammability of antifreeze such as propylene glycol, but allegedly the atomization of the droplets causing the liquid to become flammable was the cause of this explosion. More flammability and MSDS hazard info is cited in the report.

The report presents many questions at the end which would be useful in quantifying the relationship of the antifreeze in this case, especially since (to my understanding) propylene glycol is the most widely used antifreeze in sprinkler systems. I look forward to finding out more about this topic, and I think it’d be a great research project for a student or research firm to take on.

M.S. thesis paper published

koverholt — Wed, 24 Feb 2010 18:01:14 +0000

My M.S. in Fire Protection Engineering from WPI was recently confirmed and my M.S. thesis was released for publication. The title of the thesis is “Characterizing the Flammability of Storage Commodities Using an Experimentally Determined B-number”.

Link to thesis is here: http://www.wpi.edu/Pubs/ETD/Available/etd-121409-192436/

The abstract is as follows:

In warehouse storage applications, it is important to classify the burning behavior of commodities and rank them according to material flammability for early fire detection and suppression operations. In this study, the large-scale effects of warehouse fires are decoupled into separate processes of heat and mass transfer. As a first step, two nondimensional parameters are shown to govern the physical phenomena at the large-scale, a mass transfer number, and the soot yield of the fuel which controls the radiation observed in the large-scale. In this study, a methodology is developed to obtain a mass-transfer parameter using mass-loss (burning rate) measurements from bench-scale tests. Two fuels are considered, corrugated cardboard and polystyrene. Corrugated cardboard provides a source of flaming combustion in a warehouse and is usually the first item to ignite and sustain flame spread. Polystyrene is typically used as the most hazardous product in large-scale fire testing. A mixed fuel sample (corrugated cardboard backed by polystyrene) was also tested to assess the feasibility of ranking mixed commodities using the bench-scale test method. The nondimensional mass transfer number was then used to model upward flame propagation on 20-30 foot stacks of Class III commodity consisting of paper cups packed in corrugated cardboard boxes on rack-storage. Good agreement was observed between the model and large-scale experiments during the initial stages of fire growth.

Characterizing Flammability of Corrugated Cardboard Using a Cone Calorimeter

Plotting data on videos – A useful way to convey qualitative and quantitive information

koverholt — Wed, 25 Nov 2009 08:49:44 +0000

Every once in a while, someone makes an impression on you that lasts for a lifetime. It sticks with you every single time. This is one of those, although a bit on the nerdy side, it is one that can change the way you present information in a very meaningful way.

I was once sitting at the NIST annual fire conference, going about my business, and someone working on a project regarding the structural response aspect of buildings on fire showed a video in their presentation. No big deal, right? Normally, we get cool fire videos, then some plots, and so on. Sometimes the plots are interesting, sometimes they are default from Excel with the ugly legend and all – with no story to tell.

But not this guy. He showed a video with real-time plots superimposed over the video showing the exact real-time structural response of the structure overlaid on the video in a plot. “AMAZING!” I thought. And it stuck with me. A useful way to convey synchronous information. People love videos, why not tell the qualitative AND quantitative story at the same time?

So I started working in grad. school on fire problems, and naturally, soon thereafter, I was scheduled to give a presentation. As most of my real creative coding and writing work happens of hours between the hours of 1 AM and 6 AM, I wanted to make this happen. I REALLY wanted some real-time plotting action in my presentation. No Excel templates for me! So I stayed up for a couple nights and worked on a way to use MATLAB to make this plotting dream a reality: I worked on importing videos, messing with frame rates, tons of images, and so forth. And soon thereafter, it happened. I had a working script.

I used it to show plots of large-scale fire tests with actual and predicted flame heights vs. time as seen here:

And I used the script to show the predicted flame heights on a small-scale test in an amazing way that just about anyone can relate to, fire-crazed scientist or not:

From anyone who has seen the videos firsthand, the response has been amazing. This is a great teaching and communication tool, and surprisingly enough, I haven’t found any existing program or tool that does this. And so I am sharing the videos and script here for anyone to use to better convey information.

My next steps are: 1) to convert the script to Python (since I am now almost exclusively using Python+numpy+scipy for my graduate research and daily work instead of MATLAB, and 2) to make the script into a cross-platform and easy to use tool.

I’m providing the code in its raw and uncommented and unedited form. It generates a number of images with plots superimposed on them, and then it is trivial to use a program to stitch them together into a video. I used Quicktime’s built in method. Sorry, too much current work going on finishing my MS thesis and Master’s degree to clean up the code, but it’s a brutal use of the “release early, release often” ideal! Hopefully someone can make some use of it.

So, here are the linked .m files:

http://www.koverholt.com/scripts/ssPlotVideo.m
http://www.koverholt.com/scripts/fireplotVideo.m

Enjoy! And please leave your comments or ideas!

The human element in fire protection engineering

koverholt — Wed, 26 Aug 2009 11:29:07 +0000

What do a 3,700 acre fire in California, a 100,000 square foot warehouse fire in Texas, and the execution of a Texas man in 2004 have in common?

They were all events linked to arson and serve to show us the complicated relationship man has with fire, even with the modern day engineering tools and cutting edge analysis methods available to us.

Let me explore these three events in more detail:

Jesusita Fire; May 2009; Santa Barbara, CA

In May of 2009, a 300 foot high wall of fire burning through Santa Barbara, CA had 30,000 people running out of their city and wondering what they would return to, if anything more than an ashtray of their home’s contents. 3,700 acres were burned and it was marked as the most threatening natural disaster in the history of Santa Barbara. The cause? A campfire that got out of control from nearby marijuana growers.

40 MPH winds served to spread the fire as fast as it could towards the city. At the end of it all, 78 homes were destroyed, 29 firefighters were injured, and 15.5 million dollars were used. All from a campfire. From pot growers. This event reeks seriously of the complicated relationship between humans and fire – a relationship of utility, usefulness, crime, chaos, and control. A relationship that cannot be engineered out by even the best computational fluid dynamics code in the world.

Gallery Furniture Fire; May 2009; Houston, TX

Moving from wildland fires to warehouse fires: in May of 2009, an iconic Houston furniture warehouse burned to the ground as freeway traffic crawled by with worried onlookers in the late evening hours. After a long night of fighting the fire, the 100,000 square foot Gallery Furniture warehouse was no more and fell victim to to the 4-alarm fire. The Bureau of Alcohol, Tobacco, and Firearms stepped in and ruled the fire as arson, leading to the arrest of an employee who worked at the furniture store.

This fire hits me close to home since my Master’s thesis research involves warehouse storage and commodity fire protection and how it can be improved. I can formulate the best mathematical fire spread model for predicting fire spread along cardboard stacked to the ceiling, but will my math model account for a crazed man dumping gallons of gasoline in the warehouse and firing up a match? Absolutely not.

Willingham Residential Fire; Dec. 1991; Corsicana, TX

This last fire I’ll discuss was a residential fire in the city of Corsicana in Texas. In December of 1991, the home of Cameron Willingham was burned and his three children were killed in the fire. He was later arrested and imprisoned on the basis that he had set fire to his house and was responsible for the death of his children. The fire marshal’s investigative report backed this up. 12 years passed, and Cameron was executed in February of 2004 in Texas for murder charges.

Just a few days ago, in August of 2009, a report from Craig Beyler at Hughes Associates (one of many reports to check the validity of the fire investigations on Willingham’s residence) stated that the fire investigation seemed more like the work of psychics and mystics rather than scientific work. There are other human factors here at work – Cameron’s alleged abuse of his children is one example – but I am sticking to the discussion of the relationship between Cameron, the investigators, and fire. In the report, Beyler stated that the investigators had a poor understanding of fire science. And because of their poor understanding, a man was wrongly killed by the state.

Putting it all together: Humans, fire, and education

So the relationship of man vs. fire goes back to the first time someone discovered fire. It is very complicated. Now what? How can we use our understanding of this relationship to save lives?

While churning along my research path, I have learned that I favor fire research, fire dynamics, and fire forensics over alarm design, building construction work, or working with fire codes. The three fires that I discussed above are most interesting to me are all involving arson in some way – and humans in a big way. One fire came from clumsiness, one fire stemmed from passionate and crazed anger, and one fire put to death a wrongly accused person and killed three children. I don’t know about you, but to me, this serves to smack us fire protection engineers in the face with a reminder that the human element can never be ignored, or fully engineered out of the problem of fire. The consideration of the human element should be included in every thought, design, and fire model that is churned out.

And although a recent survey by the Society of Fire Protection Engineers showed that most people think that fire is the greatest likely event to cause harm to them, it also showed that only 18% of the respondents actually worried about the dangers of fire more than once a year. The solutions that fire protection engineering provides stem from years and years of exploring this relationship of people and fire: how crowds react in a building fire, how different residential occupants can be awoken in a fire, and how people respond to building fire alarms.

In my opinion, the best help in the impact of fire protection engineering is effective education of the public. Informing the public (in interesting and engaging ways!) about fire safety and what they can do in their homes and workplaces to stay safe. Informing college students about dorm fire safety. Moving on from stop, drop, and roll, and giving people more of the information and knowledge that they deserve. Informing residents about the benefits of fire sprinklers, and having a huge incentive to have them installed, even retroactively.

And who is responsible for all of these education efforts? Anyone and everyone in the fire protection field. From engineer to firefighter, fire librarian to professor, code official to fire marshal. Everyone can serve to help the big picture of educating the public by taking fire science courses, by working with code committees, by linking together agencies and people who need to be talking, but aren’t. Fire investigators can take fire science courses and fire scientists can run into burning buildings in training exercises. The more we know as professionals about the big picture, the more we can help and educate the public, and save lives in the process.

So again, I say that effective education of the public is the best tool in fire protection engineering. Because without an informed public, we can have the best fire models and investigators in the world, but we would only be putting a band-aid on the complex fire hose of man vs. fire.

Presentation for Cardboard B-number Research

koverholt — Wed, 27 May 2009 00:20:36 +0000

A previous news post linked to my completed paper for the 6th U.S. National Combustion Meeting through the CSSCI. The paper was titled â€œCharacterizing Flammability of Corrugated Cardboard Using a Cone Calorimeterâ€.

I have completed a presentation summarizing my research, and this was presented at the 6th U.S. National Combustion Conference on May 19, 2009, and the University of Michigan, Ann Arbor, MI.

The presentation can be downloaded or viewed in many different formats by using the links below:

Powerpoint format

HTML format

Quicktime format (.mov)

PDF Format

Cape Cod Weekend Escapade

koverholt — Fri, 08 May 2009 01:37:05 +0000

After 18 graduate hours down, another semester, two conferences, my first conference paper, Katie joining me up in Mass., and tons of other milestones for my life, it’s nice to sit back and just relax, reflecting on all that has happened.

On the last weekend in April, the weather went from 30 degrees to 85 degrees for a magical couple of days. Me and Katie capitalized on this and ran a 2 day random trip to the east coast of Massachusetts, to check out all of the hype around Cape Cod. The map below shows our roundabout route from Worcester to Plymouth, Sandwich, Provincetown, South Yarborough, New Bedford, Newport, Jamestown, Wickford, and back home.

To sum it up, it was amazing! Some pictures from the trip show the highlights! To view the full album, click here.

View Larger Map

From Cape Cod Weekend Escapade

Poster for Cardboard B-number Research

koverholt — Fri, 27 Mar 2009 21:15:17 +0000

The previous news post linked to my completed paper for the 6th U.S. National Combustion Meeting through the CSSCI. The paper was titled “Characterizing Flammability of Corrugated Cardboard Using a Cone Calorimeter”

I have completed a poster summarizing the research, which downloaded and viewed using the links below:

B number research poster

JPG copy of poster (1.4 MB)

Characterizing Flammability of Corrugated Cardboard Using a Cone Calorimeter

koverholt — Tue, 24 Mar 2009 21:32:03 +0000

My paper is now in press for the upcoming Central States Section of the Combustion Institute conference, the 6th U.S. National Combustion Meeting. The abstract is as follows:

In warehouse storage applications, it is important to classify the burning of cardboard because it provides a source of ï¬‚aming combustion and is usually the ï¬rst item to ignite and sustain ï¬‚ame spread. This study develops a methodology to obtain a non-dimensional mass transfer number (or Spaldingâ€™s B-number) by using the mass loss measurements from a cone calorimeter. The small-scale experimental measurements are used to model upward ï¬‚ame propagation on a 20-30 foot high rack-storage warehouse commodity packed in corrugated cardboard boxes. Good agreement is observed between the simple model and large scale experiments during the initial stages of ï¬re growth.

The paper can be seen here: Characterizing Flammability of Corrugated Cardboard Using a Cone Calorimeter

Cardboard flame spread tests

Not So Green Hill Park

koverholt — Sun, 15 Feb 2009 23:47:19 +0000

At Green Hill Park a mile or so from my house, where the hills are more white than green.

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View full album.