System Bits: Jan. 21

Metamaterial modeling
Metamaterials — artificial materials engineered to have properties that are not normally found in nature and being explored in a number of technologies such as perfect lenses, antennas and terahertz devices – are becoming more important to model. Modeling them is a difficult task considering their unconventional nature and delicate properties but researchers from Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland have found a way to create computational models that can be applied to a large range of metamaterials.

Designing new metamaterials to meet technological demands requires an increased understanding of structural possibilities and the best way to predict the full spectrum of metamaterial properties is through computer modeling, which requires a certain degree of mathematical abstraction. This presents metamaterial designers with the problem of how to develop accurate and efficient tools to model non-standard materials.

EPFL researchers have developed a computational approach that seeks to address this problem using an approach called the discontinuous Galerkin method, which is a class of numerical methods for solving differential equations – equations that describe how one variable changes in relation to another, such as the speed of a car changing over time.

Metamaterial modeling involves a set of differential equations known as Maxwell’s equations, which describe how electromagnetic waves propagate in space and time and detailed models for how the metamaterials react to electromagnetic waves. But in order for a computer model to work, it is necessary to translate these equations from continuous functions into discrete or non-continuous ones – a common practice for conventional materials, but more complex for the exotic metamaterials.

Building on previous efforts, the researchers were able to develop a custom-made way of solving Maxwell’s equations specifically for metamaterials and test their method and demonstrate its applicability on certain models of metamaterials with different structures.

They believe the new method can greatly improve computer modeling of metamaterials to allow faster discovery, design and manufacturing of new forms and structures.

Saving lives with cell phones
Researchers at the Technische Universitaet Muenchen have developed a technique that enables driver assistance systems in cars to pinpoint pedestrians and cyclists – even while they are hidden from view – whereby the cell phones of the pedestrians and cyclists could serve as transponders.

In this method, on-board positioning systems would compute the projected trajectory of the transponders and initiate an emergency braking sequence in case a pedestrian or cyclist moves into the path of a car.

In the context of this “cooperative transponder” research project, the researchers created a completely new approach to distance measurement. The distance to an object can be determined to an accuracy of a few centimeters within just a few microseconds (millionths of a second). The on-board positioning system achieves this by sending a unique series of codes to a transponder. The transponder, in turn, modifies the code sequence and returns it in a very precise temporal pattern.