Tag Archives: uncertainty

Models as fables

moel arthurIn his book, ‘Economic Rules – Why economics works, when it fails and how to tell the difference‘, Dani Rodrik describes models as fables – short stories that revolve around a few principal characters who live in an unnamed generic place and whose behaviour and interaction produce an outcome that serves as a lesson of sorts.  This seems to me to be a healthy perspective compared to the almost slavish belief in computational models that is common today in many quarters.  However, in engineering and increasingly in precision medicine, we use computational models as reliable and detailed predictors of the performance of specific systems.  Quantifying this reliability in a way that is useful to non-expert decision-makers is a current area of my research.  This work originated in aerospace engineering where it is possible, though expensive, to acquire comprehensive and information-rich data from experiments and then to validate models by comparing their predictions to measurements.  We have progressed to nuclear power engineering in which the extreme conditions and time-scales lead to sparse or incomplete data that make it more challenging to assess the reliability of computational models.  Now, we are just starting to consider models in computational biology where the inherent variability of biological data and our inability to control the real world present even bigger challenges to establishing model reliability.

Sources:

Dani Rodrik, Economic Rules: Why economics works, when it fails and how to tell the difference, Oxford University Press, 2015

Patterson, E.A., Taylor, R.J. & Bankhead, M., A framework for an integrated nuclear digital environment, Progress in Nuclear Energy, 87:97-103, 2016

Hack, E., Lampeas, G. & Patterson, E.A., An evaluation of a protocol for the validation of computational solid mechanics models, J. Strain Analysis, 51(1):5-13, 2016.

Patterson, E.A., Challenges in experimental strain analysis: interfaces and temperature extremes, J. Strain Analysis, 50(5): 282-3, 2015

Patterson, E.A., On the credibility of engineering models and meta-models, J. Strain Analysis, 50(4):218-220, 2015

Unexpected bad news for turkeys

http://www.penguin.co.uk/books/the-black-swan/9780141034591/Risk is defined as the probability of something happening multiplied by consequences of its occurrence.  Engineers expend considerable time and effort in reducing the consequences of the quite probable such as ensuring the passenger compartment of a car will remain largely intact during a crash.  The installation of automatic breaking systems on some cars is also an attempt to reduce the probability of an impact, i.e. the occurrence of a crash.  It is difficult to anticipate the very low probability event with catastrophic consequences and so cars are not designed to deal with meteors dropping out the sky or even elevated highways collapsing in an earthquake.   These are what Nassim Taleb, labels Black Swan events but would perhaps be better named after another bird, the more humble turkey.  An American turkey is fed daily by a friendly human and has no idea in November that Thanksgiving is about happen with fatal consequences, or substitute December and Christmas for a British turkey.  From the turkey’s perspective everything is fine down on the farm until it isn’t; in other words, the very low probability event with catastrophic consequences occurs.  From the farmer’s perspective, turkey for dinner at Thanksgiving is close to a certainty, i.e. a probability of one.  The problem for engineers designing machines is to have the perspective of the farmer and not the turkey.

Happy Thanksgiving to my American readers!

Source:

Nassim Nicholas Taleb, The Black Swan – the impact of the highly probable, London: Penguin Books, 2008.

Greed overwhelms ethics

My car but not my house!

My car but not my house!

The scandal about Volkswagen emissions has already caused journalists and others to wring their hands or to preach sermons, or both, about the ethical standards of the engineering profession, see for example the Editor’s blog in Professional Engineer where he reminds us that professional engineers should conduct their professional work and relationships with “integrity and objectivity and with due regard for the welfare of the people, the organisations and the environment with which they interact”. The quotation is from the Royal Charter of the Institution of Mechanical Engineers. Fine words written to induce good intentions that rarely survive in the face of greed or simply the need to keep your job so that you can feed and house your family.

In my view, the emissions scandal seems to have parallels with the banking scandals of the past decade, in which corporate greed has trampled over ethics and morals in the pursuit of ever larger profits while government regulators through incompetence or acquiescence have allowed it to continue. Volkswagen were wrong to design a device to cheat the Government emission tests, but Government regulators were naive to design a test in which it was so easy to cheat. Senior executives at Volkswagen have blamed their employees following other recent examples.  These company leaders were paid gigantic salaries to provide both leadership and management and, in my opinion, they have failed in both by blaming the people they are supposed to be leading and by allowing the scandals to happen in the first place.

The evidence would suggest that we can trust neither corporations nor governments to take care of the environment. One solution is for all vehicles to provide real-time information on the dashboard about NOX and Carbon emissions as well fuel consumption then we can make our own choices. When I moved to the US more than a decade ago, I was surprised to find that fuel consumption data was not available on the dashboard of most cars as it was already commonplace in Europe. Perhaps its presence was a factor in the development of fuel efficient cars in Europe although clearly higher fuel prices play a large role.  However, in the absence of a tax on emissions, real-time emission data on the dashboard would motivate engineering ingenuity to compete to produce lower emission designs instead of wasting creativity on cheating in useless Government tests.

Here are some of facts to support my statements above about large profits and gigantic salaries:

Volkswagen profits rose 21% in 2014 to more than $12billion on an annual turnover of $230 billion which is comparable to the GDP of Portugal.

The CEO of Volkswagen was paid almost $18million per year which is about 250 times the average salary of a Volkswagen engineer.

Sources:

Hibbert, L., Editor’s comment: October 2015 The Volkswagen emissions testing scandal has put the issue of professional ethics in the spotlight, Professional Engineer, October 07, 2015.

Wall Street Journal, Feb 27th, 2015

Volkswagen AG Annual Report 2014

World Bank Data Bank

Reuters, March 12th, 2012

glassdoor.com

 

Safety first!

cornerMost of us walk up and down stairs at home without a second thought and often without holding the handrail. It’s a personal choice to hold the handrail or not. However, for some when you are at work it is no longer a personal choice but a health and safety rule. You must hold the handrail and in many organisations you are expected to politely ask visitors to do so. This is justified on the basis that trips/slips and falls are the most common sources of workplace injuries accounting for 40% of serious injuries. For managers it is about managing risk and reducing costs.

Risk is the probability of something happening multiplied by the consequences when it does happen. Many of us subconsciously calculate risk when we make decisions in everyday life. The consequences of the aircraft crashing on the way to your holiday destination is very serious, if not fatal, but the probability is extremely small so that overall the risk is acceptably low. We make lots of risk assessments in our personal life but as soon as an organisation gets involved and feels that it might be liable for the consequences then our freedom of choice is eroded quickly. Hence, the instruction to hold the handrail on the stairs. However, the equation is changed when the cost of reducing the risk involved in an essential or profitable activity is too high or perceived to be so. A simple example would be being free to stand on a platform within half a metre of a passing express train. It would be too expensive and probably impractical to install railings or remove everyone from the platform. However, at least we have platforms and are not allowed to wander around on the track; that would be really dangerous with both a high probability of being hit and fatal consequences as the Liverpool MP William Huskisson found out at the inauguration of the first scheduled passenger train service on September 15, 1830. When the train stopped on the way from Liverpool to Manchester, he got out and walked down the track to the Prime Minister who was in the next carriage to enthuse about the service and he was killed by the train going the other way. There are easier ways to get a street named after you, not to mention a town in Australia!

Source: http://www.workplacesafetyadvice.co.uk/common-injuriescauses-accidents-work.html.  BTW – according to this website, the finance is the safest sector in which to work and agriculture the most dangerous sector.

Photo credits: Sarah & CharlesPicture8