Flapping micro air vehicles inspired by swifts

Flapping micro air vehicles inspired by swifts

  3:50:00 PM    Science Lover

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Scientists have designed a micro aircraft that will be able to flap, glide and hover like a bird.

This shows the wake of a swift in slow forward flight, the new design mimics these birds to improve MAV performance. Credit: William Thielicke

Researchers from the Biomimetics-Innovation-Centre in Germany have been inspired by birds to produce a new versatile design of Micro air vehicle (MAV) that combines flapping wings, which allow it to fly at slow speeds and hover, with the ability to glide, ensuring good quality images from any on-board camera.

"In birds, the combination of demanding tasks like take-off, travelling long distances, manoeuvring in confined areas and landing is daily practice," explains PhD researcher Mr. William Thielicke, who is presenting this work at the Society for Experimental Biology Annual Conference in Glasgow on the 2nd of July.

Micro air vehicles (MAVs) are small unmanned
aircraft, often used for rescue or reconnaissance
missions in areas where it would be dangerous
or impractical for humans to go. Credit: William
Thielicke

This innovative design was inspired by one bird in particular, the swift. "We know that swifts are very manoeuvrable and they can glide very efficiently. So we thought these birds would be a very good starting point for an energy efficient flapping-wing MAV," says Mr. Thielicke.

While fixed wing MAVs are energy efficient, their manoeuvrability is low. The new design would allow the flapping wing MAV to glide, improving energy efficiency and ensuring good images but when needed it can also slow its flight and manoeuvre in confined spaces.

"Although the models are not yet ready to be used, initial tests are positive and we hope that this design will combine the best of both worlds," says Mr. Thielicke.

Provided by Society for Experimental Biology

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Scientists Find Universal Rules For Food-web Stability

Scientists Find Universal Rules For Food-web Stability

  8:11:00 PM    Science Lover

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New findings, published in the journal Science, conclude that food-web stability is enhanced when many diverse predator-prey links connect high and intermediate trophic levels. The computations also reveal that small ecosystems follow other rules than large ecosystems: differences in the strength of predator-prey links increase the stability of small webs, but destabilize larger webs.

A Juvenile African Bush Viper (Atheris chlorechis) with a small frog, at night.
Researchers found that food-web stability is enhanced when many diverse predator-prey links connect high and intermediate trophic levels. (Credit: iStockphoto/Mark Kostich)

Natural ecosystems consist of interwoven food chains, in which individual animal or plant species function as predator or prey. Potential food webs not only differ by their species composition, but also vary in their stability. Observable food webs are stable food webs, with the relationships between their species remaining constant over relatively long periods of time.

Understanding complex systems such as food webs present major challenges to science. They can either be examined by observing natural environments, or by computer simulations. To enable computer simulations of such systems, scientists often have to make simplifying assumptions, keeping the number of model parameters as low as possible. Yet, the computational demands of such simulations are high and their relevance is often limited.

Innovative methodology

Scientists from the Max Planck Institute for the Physics of Complex Systems (MPIPKS) in Dresden, Germany, have developed a new method that allows them to efficiently analyze the impact of innumerable parameters on complex systems.

"By using a method called generalized modeling, we examine whether a given food web can, in principle, be stable, i.e., whether its species can coexist in the long term," says Thilo Gross from MPIPKS. Complex ecosystems can thus be simulated and analyzed under almost any conditions. "In this way we can estimate which parameters will keep ecosystems stable and which will upset their balance."

The method can also be used for examining other complex systems, such as human metabolism or gene regulation.

Generalists stabilize, specialists destabilize

Applying this innovative modeling approach together with colleagues at the International Institute for Applied Systems Analysis (IIASA) in Laxenburg, Austria, and Princeton University, USA, the scientists have succeeded in discovering not just one, but several universal rules in the dynamics of ecosystems.

"Food-web stability is enhanced when species at high trophic levels feed on multiple prey species and species at intermediate trophic levels are fed upon by multiple predator species," says Ulf Dieckmann of IIASA.

The scientists have also identified additional stabilizing and destabilizing factors within ecosystems. Ecosystems with high densities of predator-prey links are less likely to be stable, while a strong dependence of predation on predator density destabilizes the system. On the other hand, a strong dependence of predation on prey density has a stabilizing impact on food webs.

Differences between small and large systems

A further important finding is that food webs consisting of only a few species behave qualitatively different from webs consisting of many species.

"Small ecosystems apparently follow different rules than large ecosystems," says Ulf Dieckmann. "Systems with fewer species are more stable if there are strong interactions between some species, but only weak interactions between others. For food webs with many species, exactly the opposite is true. Extremely strong or weak predator-prey links in nature should therefore be the rarer the more species a food web contains," he concludes.

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Watchful windows

Watchful windows

  10:20:00 PM    Science Lover

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New light-sensitive sensor technology could enable your windows to detect intruders and sound an alarm

Ever had that sinking feeling that someone is sneaking around in front of your window, probably trying to break in? With new technology crafted by researchers in Germany, windows and doors might soon be able to detect whether there’s suspicious activity outside your house, and accordingly, sound an alarm.

A novel motion sensor developed by the Fraunhofer Institutes for Applied Polymer Research (IAP) in Potsdam-Golm enables window panes and glass doors to detect movements, thanks to a special coating.

If anything changes in front of a pane, or someone sneaks up to it, an alarm is soon sounded.

“The glass is coated with a fluorescent material,” explains IAP group manager Dr Burkhard Elling. “The coating contains nanoparticles that convert light falling on the window into fluorescent radiation.”

How it works

The principle is as follows: The invisible light of an ultraviolet (UV) lamp “illuminates” the window panes, and generates fluorescent radiation in the coating. Sensors in the edges of the window detect this radiation, and thus keep a tab on activities.

A single sensor can perform simple applications: For example, if someone steps into the light of the lamp, less light reaches the coating and less fluorescent radiation is produced – thus triggering the sensor.

If several sensors are installed on all four sides of the window frame, conclusions can be drawn from the data as to how fast and in what direction an object is moving. Its size, too, can be estimated by the sensors.

The invisible light of a UV lamp ‘illuminates’ the window panes and generates fluorescent radiation in the coating. This radiation is detected by sensors in the edges of the window

“This is especially useful in warding off false alarms. For instance, by setting a threshold for the alarm, moving objects that are the size of birds do not set off any sirens,” Elling says.

Likewise, the smart sensors do not react to light from passing cars, as the researchers have developed a software application that can interpret different light signals. This enables the system to easily distinguish between a UV lamp and the slowly changing light from a passing headlight.

“The system has further advantages: For one, it does not infringe on anybody’s personal rights, as it only detects the change in radiation, and not who triggered it,” Elling points out.

“It is also cost-efficient, because the coating can be sprayed onto the windows by airbrush or glued on as a film,” he adds.

A demonstrator system has already been made, and the boffins are aiming to market it at places such as museums.

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