Category Archives: Thermodynamics

Productive cheating?

2 Replies

I cut out a Dilbert cartoon from the New York Times a few weeks ago that I found amusing and shared it with my new Head of School.  Dilbert informs his boss that he will be taking advantage of the new unlimited vacation policy by being away for 200 days in the coming year but will still double his productivity.  His boss replies that there is no way to measure productivity for engineers.

Of course, bosses are very interested in measuring productivity and marketing executives like to brag about the productivity or efficiency of whatever it is they are selling.  Engineers know that it is easy to cheat on measures of productivity and efficiency, for instance, by carefully drawing the boundaries of the system to exclude some inputs or some wasteful outputs [see my post on ‘Drawing Boundaries’ on December 19th, 2012 ].  So claims of productivity or efficiency that sound too good to be true probably aren’t what they seem.

Also in the New York Times [on October 15th, 2013] Mark Bittman discussed the productivity of the two food production systems found in the world, i.e. industrial agriculture and one based on small landholders, what the ETC group refers to as peasant food webs.  He reports that the industrial food chain uses 70% of agricultural resources to provide 30% of the world’s food while peasant farming produces the remaining 70% with 30% of the resources.  The issue is not that industrial agriculture’s claims for productivity in terms of yields per acre are wrong but that the industry measures the wrong quantity.  Efficiency is defined as desired output divided by required input [see my post entitled ‘National efficiency‘ on May 29th, 2013].  In this case the required output is people fed not crop yield and a huge percentage of the yield from industrial agriculture never makes to people’s mouths [see my post entitled ‘Food waste’ on January 23rd, 2013].

Sources:

http://www.nytimes.com/2013/10/15/opinion/how-to-feed-the-world.html?ref=markbittman&_r=0

http://www.etcgroup.org/content/poster-who-will-feed-us-industrial-food-chain-or-peasant-food-webs

Year of Air: 2013

2 Replies

I mentioned some time ago (Noise Transfer on 3rd April, 2013) that we are privileged to have magnificent views of the river and hills beyond from our city centre house.  From the back bedroom window you can just about see the sea and we are certainly aware of it in most days due to the almost constant sea breeze (or gale).  So despite living in a city centre we are not amongst the 95 percent of EU city dwellers who are exposed to fine particles levels that exceed WHO guidelines.  However, the EU levels are well below those in Beijing that are 300 times the guidelines and probably comparable to those in London during the Great Smog of 1952 that caused cows to choke to death and contributed to the death of about 3000 people.  London has come a long way in the intervening 60 years with current levels of fine particles at about half the WHO guideline, which is 25 micrograms per cubic metre, whereas Beijing has recorded levels of 400. it has been estimated that 13,000 people die prematurely in the UK due to combustion related pollution compared to 1.2 million in China

In my post entitled ‘Extraordinary Technical Intelligence’ on 10th April, 2013 I wrote about the process of urbanisation and industrialisation that has been seen repeatedly across the world.  The progress of this process in a region can also be measured in the levels and type of pollution being generated.  The West has been where China is now, and where India and Africa are likely to go next.  Air pollution on this scale effects the neighbours of the polluter so we have an incentive to help alleviate the problem.  We should also feel a moral obligation because much of the pollution is associated with factories producing goods that we buy and probably don’t repair or recycle at the end their useful life [see ‘Old is Beautiful’ posted on May 1st, 2013] .  If we drew the system boundaries more appropriately then the pollution generated during the manufacture of these goods is as much our responsibility as the manufacturer’s [see my post on 19th December, 2012 about ‘Drawing Boundaries’].

This is the Year of Air, maybe it should have been called the Year of Clean Air to make it absolutely clear what it is all about, i.e. giving everyone on the planet the chance to live and breathe clean air!

BTW, a fine particle is one of diameter less than 2.5 microns or 1/30th diameter of one of your hairs.  One my PhD students is working on tracking nano-particles about a hundred times smaller as they interact with biological structures such as human cells, but that’s another story [see last week’s post].

Sources:

‘Under a Cloud’ by Pilita Clark in the Financial Times, July 13/14, 2013 [ http://www.ft.com/cms/s/0/83ef4b78-eae5-11e2-9fcc-00144feabdc0.html#axzz2cgRhFXMs ].

Yim SHL and Barrett SRH. Public Health Impacts of Combustion Emissions in the United Kingdom. Environmental Science and Technology, 2012, 46 (8), pp 4291–4296.

‘Air Pollution Linked to 1.2 Million Premature Deaths in China’ by Edward Wong in the New York Times on April 1, 2013 http://www.nytimes.com/2013/04/02/world/asia/air-pollution-linked-to-1-2-million-deaths-in-china.html?_r=0

Silva, R.A., et al., 2013, Global premature mortality due to anthropogenic outdoor air pollution and the contribution of past climate change, Environmental Research Letters, 8:034005. http://iopscience.iop.org/1748-9326/8/3/034005/pdf/1748-9326_8_3_034005.pdf

Sweeping Kinetics

Leave a reply

Last week I left the rubbish on the streets and encouraged you to make a mess in the classroom.  Partly because kinematics does not help us to analyse the forces involved in sweeping rubbish or, more glamorously, an ice hockey puck.  This is the realm of kinetics in which we need to consider the forces acting on objects to cause or impede their motion, such as the push from a broom and the friction against the pavement.  See the 5E lesson plan attached for more details on how Newton’s laws of motion can be applied in these situations.

You might be thinking ‘why should engineers be interested in forces involved in sweeping rubbish?’  Well, it might not be as glamorous as designing sports equipment but someone has to design street sweeping machines that keep our towns and cities clean and it is arguably more beneficial to society and the environment.  Of course, it would be better for the environment if we didn’t drop rubbish that needed sweeping but that’s another post…

5EplanNoD2_force&acceleration

For more on 5E lesson plans see: my post entitled ‘Disease of the modern age’ on June 26th, 2013 and ‘Sizzling Sausages’ on July 3rd, 2013.

For a set of videos on kinetics try: http://www.khanacademy.org/science/physics/forces-newtons-laws

Kinematics leaves rubbish

Leave a reply

On the street outside my house leaves are being swirled into piles against the railings that guard the light-well for our basement.  In other streets, not graced by trees, discarded packaging from take-away meals eaten in the street is being blown around eluding the best efforts of the city’s refuse collectors.  This phenomenon is an ‘everyday experience’ for the vast majority of people although the content of the wind-blown detritus may vary depending on where you live.  It is not difficult to reproduce similar conditions in the classroom using the contents of the recycling bin and to use the motion of sheets of paper, screwed up balls of paper and paper airplanes to discuss the kinematics of motion and the limitations of its assumptions, i.e. that the geometry of an object has no influence on its motion, which restricts the cases we can consider using kinematics.  Think particles with mass but negligible size and shape plus objects that can be approximated in this way.  The 5E lesson plan attached below expands on this theme for instructors interested in using this Everyday Example.

5EplanNoD1_rectilinear&curvilinear_motion

For more on 5E lesson plans see: my post entitled ‘Disease of the modern age’ on June 26th, 2013 and ‘Sizzling Sausages’ on July 3rd, 2013.

If you want more on kinematics try: http://www.khanacademy.org/science/physics/one-dimensional-motion