Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

COLD safer than HOT

27.02.2002


Fires can devastate HOT forests.
© Getty Images


New theory shows that high performance needn’t mean high risk.

For man-made systems such as machines and markets, catastrophe lurks somewhere between high risk and high performance. US physicists may have found a way to strike the optimal balance1.

This trade-off is familiar to the financial world. Brokers develop investment portfolios to provide the best returns within a specified level of risk. Mark Newman and co-workers at the Santa Fe Institute in New Mexico have borrowed some ideas from the economic theories of risk aversion to create a general prescription for avoiding ruin.



As a simple model of a system where productivity is coupled to risk, the researchers considered forest management. A forester wants to plant trees densely enough to produce a high timber yield. But the denser the trees, the more susceptible a forest is to devastating fires. So forests include open spaces to limit fires.

In 1999, researchers showed that complex systems like this often have states of ’highly optimized tolerance’ or HOT2,3. In a HOT state, performance (tree yield, in this case) is as good as it can be, in the face of influences (such as forest fires) that potentially undermine it.

But a HOT system has an Achilles’ heel. It is typically fragile under perturbations for which it was not designed. For example, if the distribution of fire breaks or sparks alters slightly, a forest can become highly susceptible to fires and give a poor yield.

Newman’s team now points out that HOT designs have another drawback. The cost of an optimal performance is a high chance of a ruinous collapse. Catastrophic fires that burn nearly all the trees are rare, but not as rare as one would expect if fire size were random. The optimal state is a high-risk state: it gives good returns at the price of possible ruin.

Most engineers don’t want to run this risk. So Newman’s group has calculated how to design a system to optimize performance and almost eliminate the probability of ruinous events. They call this design principle ’constrained optimization with limited deviations’, or COLD.

Surprisingly, a COLD state can completely remove the danger of total ruin while sacrificing only a few per cent of the average yield relative to a HOT state. Newman and colleagues say that, as we are generally risk-averse, we are more likely to prefer COLD designs than HOT ones.

Nature, apparently, is more short-sighted. Ecosystems, for example, are often in HOT states They are catastrophically susceptible to rare disturbances not accounted for by natural selection - such as meteorite impacts.

References

  1. Newman, M. E. J., Girvan, M. & Farmer, J. D. Optimal design, robustness, and risk aversion. Preprint, (2002).
  2. Carlson, J. M. & Doyle, J. Highly optimized tolerance: a mechanism for power laws in designed systems. Physical Review E, 60, 1412 - 1427, (1999).
  3. Carlson, J. M. & Doyle, J. Highly optimized tolerance: robustness and design in complex systems. Physical Review Letters, 84, 2529 - 2532, (2000).

    PHILIP BALL | © Nature News Service
    Further information:
    http://www.nature.com/nsu/020225/020225-3.html

More articles from Physics and Astronomy:

nachricht Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials
17.01.2018 | Universität des Saarlandes

nachricht Black hole spin cranks-up radio volume
15.01.2018 | National Institutes of Natural Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Polymers Based on Boron?

18.01.2018 | Life Sciences

Bioengineered soft microfibers improve T-cell production

18.01.2018 | Life Sciences

World’s oldest known oxygen oasis discovered

18.01.2018 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>