Category Archives: Classical mechanics and electromagnetism

Using metamaterials to transmit magnetic fields

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MIT Technology Review: Metamaterials have already been used to guide and direct electromagnetic waves in unusual ways. Now Carles Navau of the Autonomous University of Barcelona and his colleagues have shown that a static magnetic field can be manipulated in a similar way. Their design consists of a 7-cm-long tube made of a series of concentric rings, which was filled with a ferromagnetic alloy. At one end of the tube they generated a 1.3-mT magnetic field. A crack farther down the tube allowed the magnetic field to escape. When they measured the field escaping, they found it to be 0.8 mT in strength. That was significantly greater than the field strength at that distance from the source without the tube. Navau suggests that the ability to project magnetic fields over longer distances might be useful in quantum computing, where they are needed for manipulating quantum bits.

Passive electric grid stabilization prevents automatic generator syncing

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Ars Technica: For an energy grid with a network of electrical generators to remain stable, the generators must balance their contribution or else one generator will become overloaded. When the system is stable, much of that balancing is done automatically; when one generator is slowed by an increased load, the others speed up. However, the coupling can result in other generators responding to the adjustments and compounding the instability. When the system is less stable, operators actively adjust the generators’ output to return to stability. Adilson Motter of Northwestern University in Illinois and his colleagues examined several real-world power systems to determine if there was a way to allow more passive maintenance of the system stability. They found that by incorporating banks of capacitors and inductors that are automatically activated when the load on the generator increases, the phase of the current could be reestablished, thereby ensuring that the generator remains synchronized with the others in the network and decreasing the likelihood of spreading instability. The researchers believe that could work in the real world as well, since they applied the system to models of actual power grids.

Three-body problem admits 13 new solutions

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Science: When Isaac Newton defined his law of gravity, he used it to determine that two bodies orbiting each other will create an ellipse. It took more than 200 years before a German mathematician, Heinrich Bruns, determined that there was no general solution to describe the path of three bodies orbiting each other in a repeated pattern: Only specific solutions are possible. Since Bruns’s first solution, only two other families of orbits that solve the “three-body problem” have been found. Now, Milovan Šuvakov and Veljko Dmitrašinović of the University of Belgrade in Serbia have used computer simulations to define an additional 13 unique solutions. Starting their simulations with the known solutions, they systematically adjusted the initial conditions until a new solution was found. Surprised by how many solutions they discovered, they had to create a new classification system for the solutions. They developed a “shape-sphere” that depicts where the bodies cannot go in their orbits and determines the relative distances between the bodies. Then the bodies were sorted based on symmetry and other characteristics. The next step will be to determine the stability of the solutions to see if any of the systems may be seen in observations of astronomical objects.

Nanoscale silicon wires resist quantum predictions

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Nature: New research indicates that not everything on a quantum level exhibits quantum behavior. Wires just a few nanometers wide have now been shown to conduct electricity in the same way as the larger components of existing devices. Michelle Simmons, a physicist and director of the Centre for Quantum Computation and Communication Technology at the University of New South Wales in Sydney, Australia, and her colleagues made atomic-scale wires of phosphorous-doped silicon in which the phosphorous provided the extra electrons needed to generate a current, writes Edwin Cartlidge for Nature. Although the width of the wires varied from 1.5 to 11 nm, the resistivity did not differ substantially, thus obeying Ohm’s law of classical electronics. David Ferry, an electrical engineer at Arizona State University in Tempe, noted the importance of the finding to such devices as transistors, which every two years have been shrinking in size yet yielding ever-better performance—a trend known as Moore’s law. If quantum coherence came into play, he said, the transistors wouldn’t turn on and off as expected. Therefore, the new research could have significant implications for the microchip industry. What the implications will be for quantum computing, however, remains to be seen.

Researchers build spherical dynamo to mimic Earth’s interior

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Nature: Although self-sustaining dynamos occur readily in stars and planets, none has yet been achieved in the lab. That may change next year when a project at the University of Maryland, College Park, is scheduled to go on line. Housed in a cavernous warehouse at the university, the Three Meter Experiment consists of a 3-meter-diameter ribbed sphere, inside of which is a 1-meter sphere surrounded by thousands of kilograms of liquid sodium heated to about 105 °C. When the device is turned on, it will whirl around and churn the electrically conducting fluid, which researchers hope will generate a self-sustaining electromagnetic field similar to Earth’s. The project could shed light on how rotational forces in Earth’s core deflect flows of electrically conducting liquid into a configuration that produces a magnetic field with north and south poles, writes Susan Young for Nature.

LEDs could multitask as data transmitters

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Guardian: Light bulbs could soon be used to broadcast wireless internet. Harald Haas of the UK’s Edinburgh University has been working on a revolutionary method of data transmission that makes use of light waves rather than wires or radio waves. Using LEDs, which are more efficient than standard light bulbs and can be switched on and off very quickly, he has found that he can vary the intensity of their output and pick up the signals with a simple receiver. With data rates of 100 megabits per second, Haas’s system relies on the fact that the human eye cannot detect the rapid flickering on and off of the LEDs—instead they appear to maintain a normal steady glow. Besides faster transmission capabilities, such a device would also have applications in the oil and gas industries, where radio waves can cause sparks, and for underwater robotic vehicles and submarines, where the electrically conductive salt water stifles radio waves.

US builds strongest split magnet

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BBC: Scientists have achieved a huge engineering feat by building the world’s most powerful “split magnet,” made in two halves with holes in the middle for observing experiments. Operating at 25 tesla, which is equivalent to 500 000 times the strength of Earth’s magnetic field, the magnet is 43% stronger than its predecessor, built in 1991, and has 1500 times more space inside to carry out tests. “The split magnet is essentially like two magnets brought close together, but kept a few centimeters apart to provide open pathways to the sample,” said Gregory Boebinger, head of the National High Magnetic Field Laboratory at Florida State University. “The spectacular engineering achievement with the magnet is the ability to maintain the very high magnetic field without having the two halves slam together.” Another of the researchers, Eric Palm, added, “Discoveries made here will enable researchers to improve their materials and use them to make improved products such as solar cells or semiconductors for the next generation of computers.”