Sunday, June 27, 2010

3G vs Wi-Fi

3G and Wi-Fi are the two main mobile communications technologies today, but until recently they have been complementary services, the former offering users network access through cell phone masts forming a wide-area network (WAN), the latter based on hot-spot connections through a local-area network (LAN). Both then provide connectivity to the web, email and other services.

With the advent of Wi-Fi based municipal wireless networks, such as that launched by one telecommunications company in New York's Times Square and by a well-known supermarket chain across all its stores, there is, say Seungjae Shin of Mississippi State University -- Meridian and Martin Weiss of the University of Pittsburgh, Pennsylvania, a strong possibility that Wi-Fi will compete with the 3G cell phone network in city areas and perhaps even become a substitute.

Their study appears in theInternational Journal of Mobile Communications.

Shin and Weiss point out that substituting Wi-Fi for 3G would cut costs of peripatetic workers and others who need access to broadband internet services when not at devices connected directly to the internet, such as desktop computers. They have now used game theory to investigate how 3G and Wi-Fi would actually compete for users given a particular set of circumstances, costs, and availability. Their findings demonstrate which of the two technologies would be the winner in terms of market penetration and coverage percentages.

Their analysis shows that the 3G network would become more profitable as Wi-Fi coverage percentage increases, and that 3G is more favorable in areas of high population density. In contrast, Wi-Fi has the advantage when the market has a high penetration rate but a low coverage area. Until now, municipal wireless networks have not being active in big cities across the USA and the 3G cell phone service itself is relatively new and only being adopted as so-called smart phones become more prevalent and replaces old-style cell phones. As such, there has been little competition between the two wireless communications protocols.

The team suggests that as the market matures and competition increases between the two network service systems, the detailed results of the analysis will help to serve as a guideline for providers of either system to ensure ubiquitous mobile internet access.

Monday, February 1, 2010

Superconducting Hydrogen?

Superconducting Hydrogen? Researchers Model Three Hydrogen-Dense Metal Alloys

Physicists have long wondered whether hydrogen, the most abundant element in the universe, could be transformed into a metal and possibly even a superconductor -- the elusive state in which electrons can flow without resistance.

They have speculated that under certain pressure and temperature conditions hydrogen could be squeezed into a metal and possibly even a superconductor, but proving it experimentally has been difficult. High-pressure researchers, including Carnegie's Ho-kwang (Dave) Mao, have now modeled three hydrogen-dense metal alloys and found there are pressure and temperature trends associated with the superconducting state -- a huge boost in the understanding of how this abundant material could be harnessed.

The study is published in the January 25, 2010, early, on-line edition of theProceedings of the National Academy of Sciences.

All known materials have to be cooled below a very low, so-called, transition temperature to become superconducting, making them impractical for widespread application. Scientists have found that in addition to chemical manipulation to raise the transition temperature, superconductivity can also be induced by high pressure. Theoretical modeling is very helpful in defining the characteristics and pressures that can lead to high transition temperatures. In this study, the scientists modeled basic properties from first principles -- the study of behavior at the atomic level -- of three metal hydrides under specific temperature, pressure, and composition scenarios. Metal hydrides are compounds in which metals bind to an abundance of hydrogen in a lattice structure. The compounds were scandium trihydride (ScH3), yttrium trihydride (YH3) and lanthanum trihydride (LaH3).

"We found that superconductivity set in at pressures between roughly 100,000 to 200,000 times atmospheric pressure at sea level (10 to 20 GPa), which is an order of magnitude lower than the pressures for related compounds that bind with four hydrogens instead of three," remarked Mao, of Carnegie's Geophysical Laboratory. Lanthanum trihydride stabilized at about 100,000 atmospheres and a transition temperature of -- 423°F (20 Kelvin), while the other two stabilized at about 200,000 atmospheres and temperatures of -427 °F (18 K) and -387 °F (40 K) for ScH3 and YH3 respectively.

The researchers also found that two of the compounds, LaH3and YH3, had more similar distributions of vibrational energy to each other than to ScH3 at the superconducting threshold and that the transition temperature was highest at the point when a structural transformation occurred in all three. This result suggests that the superconducting state comes from the interaction of electrons with vibrational energy through the lattice. At pressures higher than 350,000 atmospheres (35 GPa) superconductivity disappeared and all three compounds became normal metals. In yttrium trihydride, the superconductivity state reappeared at about 500,000 atmospheres, but not in the others. The scientists attributed that effect to its different mass.

"The fact that the models predicted distinctive trends in the behavior for these three related compounds at similar temperatures and pressures is very exciting for the field," commented Mao. "Previous to this study, the focus has been on compounds with four hydrogens. The fact that superconductivity is induced at lower pressures in the trihydrides makes them potentially more promising materials with which to work. The temperature and pressures ranges are easily attainable in the lab and we hope to see a flurry of experiments to bear out these results." The team at Carnegie has embarked on their own experiments on this class of trihydrides to test these models.

Authors on the paper were Duck Young Kim, Ralph H. Scheicher, Ho-kwang Mao, Tae E. Kang, and Rajeev Ahuja. The work is supported by EFree, an Energy Frontier Research Center funded by the U. S. Department of Energy.

Wednesday, January 13, 2010

'Wet' Computing Systems to Boost Processing Power

'Wet' Computing Systems to Boost Processing Power

Sketch of artificial wet neuronal networks. (Credit: Image courtesy of University of Southampton)

ScienceDaily (Jan. 12, 2010) — A new kind of information processing technology inspired by chemical processes in living systems is being developed by researchers at the University of Southampton.

Dr Maurits de Planque and Dr Klaus-Peter Zauner at the University's School of Electronics and Computer Science (ECS) are working on a project which has just received €1.8 from the European Union's Future and Emerging Technologies (FET) Proactive Initiatives, which recognises ground-breaking work which has already demonstrated important potential.

The researchers, Dr de Planque, a biochemist, and Dr Zauner, a computer scientist, will adapt brain processes to a 'wet' information processing scenario by setting up chemicals in a tube which behave like the transistors in a computer chip

"What we are developing here is a very crude, minimal liquid brain and the final computer will be 'wet' just like our brain," said Dr Zauner. "People realise now that the best information processes we have are in our heads and as we are increasingly finding that silicon has its limitations in terms of information processing, we need to explore other approaches, which is exactly what we are doing here."

The project, entitled Artificial Wet Neuronal Networks from Compartmentalised Excitable Chemical Material, which is being co-ordinated by Friedrich Schiller University Jena with other project partners, the University of the West of England, Bristol and the Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, will run for three years and involves three complementary objectives.

The first is to engineer lipid-coated water droplets, inspired by biological cells, containing an excitable chemical medium and then to connect the droplets into networks in which they can communicate through chemical signals. The second objective is to design information-processing architectures based on the droplets and to demonstrate purposeful information processing in droplet architectures. The third objective is to establish and explore the potential and limitations of droplet architectures.

"Our system will copy some key features of neuronal pathways in the brain and will be capable of excitation, self-repair and self-assembly," said Dr de Planque.