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Lookahead maths predicts credit risk

It usually appears in the small print: “The company will contact credit rating agencies in its consideration of your application.” For older products it is easy for lenders to compare your profile against historical data to rate your suitability. Mathematicians have now devised a credit scoring technique for newly launched products where little data is available for analysis.

“There are basically two classes of customer,” notes Professor David Hand from the Department of Mathematics at Imperial College, London. “There are the ‘bads’ – those that default in some way before the end of the loan term – and the ‘goods’ who keep up their payments. Once you have accumulated a body of data for a loan product, you can build some sort of model that uses application form data and credit bureau ratings to classify applicants as good or bad.”

But for new products no data are available. Worse still, you normally have to wait until the end of the loan term before you know that a customer really is ‘good’. Professor Hand has applied a branch of statistics called survival analysis to borrowers’ records that should help banks score applicants more accurately.

“Survival analysis takes into account customers who are likely to default before the end of the loan term,” Professor Hand explains, “not just the customers who have actually defaulted at by the time of the calculation. When we used our survival analysis for lookahead scoring far fewer accepted customers turned bad.”

Professor Hand hopes to further refine his methods. For instance, he wants to allow for the low probability of borrowers going ‘bad’ when reaching the end of the loan term. “Already we have shown that survival analysis, using just a small body of data, is a powerful technique to improve applicant credit scoring for new loan products. It should help lenders accept few ‘bad’ customers and develop more comprehensive predictive models faster.”

Carbon makes electricity from the sun

Carbon makes electricity from the sun

The sun is our ultimate source of energy, but capturing its rays using solar cells is unsatisfactory. First solar cells are expensive, and even when the sun shines brightly, the amount of electricity produced is small. Research now suggests that carbon, the main constituent of all organic compounds on the earth, at last makes the sun an economical electrical powerhouse.

Solar cells produce electricity when the sun’s energy is absorbed to move electrons into higher energy states. In these excited states, the electrons move through the cell material towards an electrode, generating an electric current.

Today’s commercial solar cells are made from inorganic semiconductor materials, where there is a good match between the energy in sunlight and the energy which can be absorbed by electrons. Recently, though, scientists have discovered that some plastic-like organic materials can also be used to absorb solar light and convert into electricity.

In these organic polymers the absorbed light is converted to an excited, negatively charged electron bound to a positive ‘hole’. This bound electron-hole pair is termed a ‘exciton’.

“In normal solar cells the electron and the hole are not bound as an exciton, and can drift apart to opposite electrodes to develop a voltage. This is the origin of the classical photovoltaic effect exploited in solar cells,” explains Professor Gehan Amaratunga, who leads a research team in Cambridge University. “Therefore, to have a polymer solar cell it is essential that the exciton is split or disassociated so that electron and hole can drift apart to form the negative and positive terminals of the cell. Exciton dissociation takes place best at the junction between the polymer and a metal which accepts the electrons.”

Professor Amaratunga’s group in the Department of Engineering thought that carbon could make a good electron acceptor in the polymer. “We introduced carbon into the body of the polymer in the form of tiny channels which could accept the electrons and allow them to travel to the electrode. It is as if there were electron acceptor sites throughout the entire polymer, and not just at its surface. We used a form of carbon called single wall nanotubes, where carbon atoms arranged in a flat sheet are rolled up to form a tube.”

The researchers sandwiched the polymer-carbon nanotube blend between a layer of aluminium on one side and indium-tin oxide on the other to act as the electrodes.

They found that when illuminated, the cells produced an electric current around two orders of magnitude larger than for a more typical cell made with only the polymer. “These results are very exciting,” says Professor Amaratunga. “It appears that the nanotubes improve the transport of free electrons to the electrodes, opening the way for a new class of photocell with improved performance. You get more electricity for the size of your cell, and being much cheaper, they make solar power more of an economical option.”

These organic solar cells have an energy payback time of as little as three months. In other words, in three months they convert the same amount of energy that is needed for their manufacture. Even though their energy efficiency is only 2-3%, the best solar cells have an energy payback time of five to six years and are far more expensive.

“These new organic cells could be especially important in less developed countries where the initial investment available for developing an electric power infrastructure is limited,” notes Professor Amaratunga.

Perhaps carbon, all too condemned for its polluting effects in soot and greenhouse gases, could contribute to renewable energy production too.

The right (and left) way to design packaging

Forget about food safety and hygiene. Just opening a packet of sandwiches or a tin of sweetcorn can be a hazard – especially if you are left-handed, stubborn or poor at making decisions under pressure. Anyone can slip when opening a jar of pickle, but recent research puts the onus on package designers and engineers to cater for different consumer characteristics and personality traits in their designs.

Dr Belinda Winder and her colleagues from the Department of Mechanical Engineering at Sheffield University asked 200 shoppers about their experiences with different types of food packaging. The shoppers also completed personality questionnaires.

The results show that ‘natural born worriers’ and those who have already suffered a serious injury on packaging complain the most about designs. “This group of consumers is most anxious about opening packets,” says Dr Winder. “However, those scoring highly in neuroticism were actually no more likely to injure themselves than anyone else.”

While the worriers are prone to complain, left-handed consumers suffer the most. “This is a world dominated by right-handed people, designed by them and, perhaps more to the point,” notes Dr Winder, “designed for them too. Although there are no differences in the types of accidents that left-handed people reported, it seems that left-handers are at a disadvantage when trying to open every type of packaging.”

Certain personality traits can also lead to a consumer’s comeuppance, the researchers found. In particular, fuzzy decision making under pressure appears to contribute to injuries. Moreover, ‘socially resistant’ individuals – those who do not ask for help – tend to suffer the most severe accidents. These people are probably the ones who will not be beaten; they resort to sharp knives, ‘home remedies’ and extreme measures to get at their food.

“The results of this study indicate that accidents and injuries from food and drink packaging cannot be attributed simply to poor designs,” says Dr Winder. “Individual differences and attitudes to products affect the way we try to open them. But it is important for designers to recognise the broad spectrum of consumers and take into account their characteristics and behaviour when planning new packaging designs.”

Researchers discover that our windows are cleaner than previously thought – Good news for energy efficiency

Researchers discover that our windows are cleaner than previously thought – Good news for energy efficiency

Britain’s windows are cleaner than they were originally thought to be, researchers have discovered. The finding is important because it will allow architects to design buildings that are more energy-efficient.

The research has been carried out by a team led by Peter Tregenza and Steve Sharples in the School of Architecture at the University of Sheffield. The project was funded by the Engineering and Physical Sciences Research Council.

An important factor in building design is the amount of daylight that will enter through the windows. To calculate this, one of the things that architects must take into account the likelihood of dirt building up on the glass, obscuring some of the light.

‘The amount of light coming through a window can be reduced by as much as half,’ says Professor Tregenza. ‘A lot of this loss is due to things like overhangs and blinds, but a significant amount can be lost because of accumulation of dirt on the window pane.’

A web of desire

Why have cotton when you can have silk? Perhaps the real question should be: why reel it off the silkworm cocoon when you could make it in a factory?

Professor Fritz Vollrath and a team of researchers in the Department of Zoology at Oxford University are investigating techniques for producing artificial silk. Instead of the silkworm, the scientists have focused their attention on another silk producer – spiders.

Web spider silks have many exciting properties. They can be incredibly tough, with a capacity to absorb energy that equals the nylon filaments in bullet-proof vests. Yet spider silk is extremely eco-friendly: fully biodegradable, it is produced at ambient temperatures from water soluble, renewable materials.

“Spider silk is an amazing material, and I think we can copy it in the very near future,” asserts Professor Vollrath.