电影蜜桃成熟时

Pollution-Free Hydrogen SUV Hits the Driveway

Like many of her neighbors, Maria Recchia-O'Neill has a sport utility vehicle sitting in her driveway in Rye Brook, just north of New York City. She drives it to work and around town to run errands. But although her vehicle looks like any other SUV, her Chevrolet Equinox gets excellent gas mileage -- and it doesn't emit any pollutants or climate change-promoting carbon dioxide. That is because it is a hydrogen fuel cell electric vehicle -- one of 40 such automobiles that U.S. carmaker General Motors provided for motorists to road test. [ScientificAmerican.com, 20 Mar 2008] Read more

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Prototype Plane Uses Composites in New Way

In a high-security compound where some of the world's most exotic aircraft were born, engineers and technicians are building a prototype for a new Air Force cargo plane that may change aviation. Lockheed Martin is building the first military cargo jet in which the craft's structure will be made of fibers, resins and epoxy, replacing metals such as aluminum and titanium that have been in use in aircraft for decades. [USATODAY.com, accessed 24 Mar 2008]Read more

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Most Vehicles Will Be Hybrid by 2020

General Motors vice chairman Bob Lutz said today that the automaker would have produce 80 percent of its vehicles as some type of hybrid by 2020 in order to meet new tougher fuel economy standards. "Ultimately by 2020, we figure that 80 percent of vehicles are going to require some sort of level of hybridization," Lutz said in an interview today. "We cannot get to 35 miles per gallon with anything resembling the current product portfolio with conventional technology." Automakers must average a combined 35 miles per gallon by 2020 for passenger cars and light trucks, a 40 percent increase. Lutz said in order to meet the first increases in the requirements, GM would build about one-third of its vehicles as hybrids by 2015 -- when new fuel economy standards "really start to bite."[Detroit News (online), 19 Mar 2008 ]Read more

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Big Incentive for Fuel-Efficient Vehicle

The X Prize Foundation, best known for its competitions promoting space flights, is offering $10 million to the teams that can produce the most production-ready vehicles that get 100 miles per gallon or more. The foundation was to announce the size of the purse and its sponsor, Progressive Casualty Insurance Co., on Thursday at the New York International Auto Show. More than 60 teams from nine countries have signed up for the competition so far, including California electric car-makers Aptera Motors and Tesla Motors, German diesel car-maker Loremo and a team from Cornell University.[Chicago Tribune (online), 20 Mar 2008 ]Read more

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电影蜜桃成熟时

Generating Power from Kites

by N. MartinelliWired News, 10 Oct 2006Researchers in Italy have high hopes for a new wind-power generator that resembles a backyard drying rack on steroids.Despite its appearance, the Kite Wind Generator, or KiteGen for short, could produce as much energy as a nuclear power plant.Read more

Methods of Using Existing Wire Lines for Totally Secure Classical Communication

by L.B. KisharXiv.org E-print Archive, 2 Oct 2006We outline some general solutions to use already existing and currently used wire lines, such as power lines, phone lines, internet lines, etc, for the unconditionally secure communication method based on Kirchoff's Law and Johnson-like Noise.Two different methods are shown.One is based on filters used at single wires and the other one utilizes a common mode voltage superimposed on a three-phase powerline.Read more

Engineers Study 'Morphing Aircraft' Idea

PhysOrg.com, accessed 11 Oct 2006Modern materials are enabling engineers to take a fresh look at the idea of aircraft that can flex, twist or change shape to make them more maneuverable.NASA and the Defense Department are funding research programs to explore ideas.Scientists hope to gain a better understanding of the basic physics of the components and subsystems that will be needed for the next generation of aircraft.The research includes evaluating flexible-skin concepts that have been proposed to enable wings to change shape, improving tools for simulating how morphing structures behave in flight, and looking at using devices within the wing skins to recover or "harvest" energy as the wings move.Read more

New All-Optical Modulator Paves the Way to Ultrafast Communications and Computing

PhysOrg.com, accessed 11 Oct 2006In the 1950s, a revolution began when glass and metal vacuum tubes were replaced with tiny and cheap transistors.Today, for the cost of a single vacuum tube, you can buy a computer chip with literally millions of transistors.Today, physicists and engineers are looking to accomplish a similar shrinking act with the components of optical systems -- lasers, modulators, detectors, and more -- that are used to manipulate light.The goal: designing ultrafast computing and communications devices that use photons of light, instead of electrons, to transmit information and perform computations, all with unprecedented speed.Read more

Sensing of Distributed Strain and Damage for Life Prediction and Self Healing

by E.T. Thostenson & T.-W. ChouAdvanced Materials, 2 Oct 2006 (online)Composite materials are made by weaving together strong fibres of carbon or glass and embedding them in a matrix of epoxy or other polymer.They are widely used in the construction of aircraft because they offer an unmatched combination of strength and lightness.Their downside is that internal defects that can lead to catastrophic structural failure can be hard to detect.Now engineers at the University of Delaware have shown that carbon nanotubes embedded in composite materials can be used to spot these hidden internal flaws.Read more

Mathematical Parallels between Packet Switching and Information Transmission

by T.T. LeearXiv.org E-print Archive, 10 Oct 2006All communication networks comprise of transmission systems and switching systems, even though they are usually treated as two separate issues.Communication channels are generally disturbed by noise from various sources.In circuit switched networks, reliable communication requires the error-tolerant transmission of bits over noisy channels.In packet switched networks, however, not only can bits be corrupted with noise, but resources along connection paths are also subject to contention.Thus, quality of service is determined by buffer delays and packet losses.The theme of this paper is to show that transmission noise and packet contention actually have similar characteristics and can be tamed by comparable means to achieve reliable communication, and a number of analogies between switching and transmission are identified.The sampling theorem of bandlimited signals provides the cornerstone of digital communication and signal processing.Recently, the Birkhoff-von Neumann decomposition of traffic matrices has been widely applied to packet switches.With respect to the complexity reduction of packet switching, we show that the decomposition of a doubly stochastic traffic matrix plays a similar role to that of the sampling theorem in digital transmission.We conclude that packet switching systems are governed by mathematical laws that are similar to those of digital transmission systems as envisioned by Shannon in his seminal 1948 paper, "A Mathematical Theory of Communication."Read more

Pipelined Feed-Forward Cyclic Redundancy Check Calculation

by M. WalmaarXiv.org E-print Archive, 5 Oct 2006This paper discusses a method for pipelining the calculation of Cyclic Redundancy Checks (CRCs), such as ITU/CCITT CRC32, into a mostly feed-forward architecture.This method allows several benefits such as independent scaling of circuit frequency and data throughput.Additionally it allows calculation over packet tails.Finally it offers the ability to update a CRC where a subset of data in the packet has changed.Read more

Boosting Internet Speeds without Fiber-Optics

CNN.com, 10 Oct 2006A group of technology and telecoms companies, including Spanish giant Telefonica, joined forces on Tuesday to boost the Internet speeds of copper telephone wires to almost equal that of fiber-optic cable.The new technology, dubbed Dynamic Spectrum Management, promises speeds to rival those of fibre-optic networks, much faster than currently available on broadband.Read more

Future of the Hard Drive Secure

by Chris LongBBC News, 6 Oct 2006With all the developments in memory technology you could be forgiven for thinking that the lowly hard drive is dead.But although the hard drive is 50 this year, we have seen yet more growth in the technologies around it.The one terabyte drive is more or less here, we have perpendicular recording and they are getting smaller all the time.Read more

Friday, October 06, 2006

Long-Term Power-Law Fluctuation in Internet Traffic

by S. TadakiarXiv.org E-print Archive, 29 Sep 2006Scale-free properties of observed Internet packet flow are discussed.The data is obtained by a multi-router traffic grapher system for 9 months.Internet packet flow is analyzed using the detrended fluctuation analysis.By extracting the average daily trend, the data shows clear power-law fluctuations.The exponents of the fluctuation for the incoming and outgoing flow are almost unity.Internet traffic can be understood as a daily periodic flow with power-law fluctuations.Read more

Hybrids with a Power Cord

by Jim MotavalliNew York Times, 1 Oct 2006Are there plug-in hybrid vehicles in America’s future?Such hybrids could travel 10 to 20 additional miles on battery power alone, but until recently automakers have said -- more or less unanimously -- that it was not practical to add a larger battery pack and plug-in chargers to hybrid vehicles because of the added weight, complexity and cost.The public is already confused about hybrids, they say, with many people still believing that these cars (whose batteries are charged by their internal-combustion engines) need to be plugged in.So now hybrids really will have a power cord?Read more

Quantum Teleportation between Light and Matter

by J.F. Sherson et al.Nature, 5 Oct 2006Quantum teleportation is an important ingredient in distributed quantum networks, and can also serve as an elementary operation in quantum computers.Teleportation was first demonstrated as a transfer of a quantum state of light onto another light beam; later developments used optical relays 7 and demonstrated entanglement swapping for continuous variables.The teleportation of a quantum state between two single material particles has now also been achieved.Here we demonstrate teleportation between objects of a different nature -- light and matter, which respectively represent 'flying' and 'stationary' media.A quantum state encoded in a light pulse is teleported onto a macroscopic object.Deterministic teleportation is achieved for sets of coherent states with mean photon number (n) up to a few hundred.The fidelities are 0.58 ± 0.02 for n = 20 and 0.60 ± 0.02 for n = 5 -- higher than any classical state transfer can possibly achieve.Besides being of fundamental interest, teleportation using a macroscopic atomic ensemble is relevant for the practical implementation of a quantum repeater.An important factor for the implementation of quantum networks is the teleportation distance between transmitter and receiver; this is 0.5 metres in the present experiment.As our experiment uses propagating light to achieve the entanglement of light and atoms required for teleportation, the present approach should be scalable to longer distances.Read more

Robot Cars Will Race in Real Traffic

by W. KnightNewScientist.com, 3 Oct 2006The first 11 teams for a race in which robot cars will jostle with real ones along mocked-up city streets have been announced.The teams must construct autonomous vehicles to navigate an unfamiliar urban environment in the shortest time possible.The robot racers will face a "simulated" urban course 60 miles in length in November 2007.The course will feature urban obstacles, such as trees and buildings, traffic signs and other moving vehicles.Its location is yet to be disclosed.Read more

'Airblade' Hand Dryer Could Improve Hygiene

by T. SimoniteNewScientist.com, 3 Oct 2006A hand dryer that uses "blades" of air and bacteria-killing filters is more effective and hygienic than conventional drying machines, its inventors claim.Conventional hand dryers use a heater and a motorised fan to evaporate water from a person's hands.The Dyson dryer uses a motor to force unheated air through two thin slots at 400 miles per hour.These jets form so-called "air blades" that force water off a user's hands, as they slowly withdraw them past the blades.Read more

Method Could Help Carbon Nanotubes Become Commercially Viable

Northwestern UniversityPress Release, 4 Oct 2006Carbon nanotubes are intriguing new materials which have been highly touted for their exceptional mechanical, thermal, optical and electrical properties.Researchers worldwide are striving to apply these nanostructures in electronics, high-resolution displays, high-strength composites and biosensors.A fundamental problem relating to their synthesis, however, has limited their widespread use.Current methods for synthesizing carbon nanotubes produce mixtures of tubes that differ in their diameter and twist.Variations in electronic properties arise from these structural differences, resulting in carbon nanotubes that are unsuitable for most proposed applications.Now, a new method developed at Northwestern University for sorting single-walled carbon nanotubes promises to overcome this problem.Read more

Cooperative Processes for Scientific Workflows

by K. Gaaloul, F. Charoy, & C. GodartarXiv.org E-print Archive, 4 Oct 2006The work described in this paper is a contribution to the problems of managing in data-intensive scientific applications.First, we discuss scientific workflows and motivate there use in scientific applications.Then, we introduce the concept of cooperative processes and describe their interactions and uses in a flexible cooperative workflow system called Bonita.Finally, we propose an approach to integrate and synthesize the data exchanged by the mapping of data-intensive science into Bonita, using a binary approach, and illustrate the endeavors done to enhance the performance computations within a dynamic environment.Read more

Network Calculus Based FDI Approach for Switched Ethernet Architecture

by B. Brahimi, C. Aubrun, & E. RondeauarXiv.org E-print Archive, 5 Oct 2006Networked Control Systems are complex systems which integrate information provided by several domians such as automatic control, computer science, communication network.The work presented in this paper concerns fault detection, isolation and compensation of communication network.The proposed method is based on the classical approach of Fault Detection and Isolation and Fault Tolerant Control currently used in diagnosis.The modelling of the network to be supervised is based on both couloured petri nets and network calculus theory often used to represent and analyse the network behaviour.The goal is to implement inside network devices algorithms enabling to detect, isolate and compensate communication faults in an autonomous way.Read more

Robotic Whiskers Used to Sense Features

byJ.H. Solomon & M.J. HartmannNature, 5 Oct 2006Several species of terrestrial and marine mammals with whiskers use them to sense and navigate in their environment -- for example, rats use their whiskers to discern the features of objects, and seals rely on theirs to track the hydrodynamic trails of their prey.Here we show that the bending moment -- sometimes referred to as torque -- at the whisker base can be used to generate three-dimensional spatial representations of the environment, and we use this principle to construct robotic whisker arrays that extract precise information about object shape and fluid flow.Our results will contribute to the development of versatile tactile-sensing systems for robotic applications, and demonstrate the value of hardware models in understanding how sensing mechanisms and movement control strategies are interlocked.Read more

Cricket Machine Masters Bowling

BBC News, 6 Oct 2006A machine that can replicate the spin and swing of bowlers has been developed at a U.K. university.The robotic bowler has been created at Loughborough University as part of a virtual reality project to improve match training for cricket."Cricketers want to be able to face bowlers like Shane Warne," said project lead Dr Andy West."The machine is helping us to figure out the science of bowling and the mysteries of spin and swing."Read more

NSF Funding Opportunity - Biophotonics

The goal of the Biophotonics Program is to continue exploitation of the power of photonics to advance biomedical engineering.Developing molecularly specific sensing, imaging, and monitoring systems with high optical sensitivity, and resolution would be an enormous accomplishment with powerful applications to both biology and medicine.Low cost diagnostics will require novel integration of photonics, molecular biology, and material science.Complex biosensors capable of detecting and discriminating among large classes of biomolecules could be important not only to biology and medicine, but also to environmental sensing and homeland defense.Read more

NSF Funding Opportunity - Environmental Sustainability

The Environmental Sustainability program supports engineering research with the goal of promoting sustainable engineered systems that support human well-being and that also are compatible with sustaining natural systems, which provide ecological services vital for human survival.The long-term viability of natural capital is critical for many areas of human endeavor, including agriculture, industry, and tourism.Research in Environmental Sustainability considers long time horizons and incorporates contributions from the social sciences and ethics.This program supports engineering research that seeks to balance society’s need to provide ecological protection and maintain stable economic conditions.Research is encouraged to advance the next generation of water and wastewater treatment that will decrease material and energy use, consider new paradigms for delivery of services, and promote longer life for engineered systems.Read more

NSF Funding Opportunity - Environmental Engineering

The Environmental Engineering Program supports research and educational activities across the broad field it serves, with the goal of applying engineering principles to understand and reduce adverse effects of solid, liquid, and gaseous discharges into land, inland and coastal waters, and air that result from human activity and that impair the ecological and economic value of those resources.It fosters cutting-edge research based on fundamental science and four types of engineering tools -- measurement, analysis, synthesis, and design.Read more

NSF Funding Opportunity - Environmental Technology

The Environmental Technology Program provides support to develop and test new technologies across the range of sub-areas and activities in the field of environmental engineering.These include new devices and systems for more effective pollutant removal from air and water, as well as new technologies that minimize or avoid the pollutant generation inherent in older commercial and domestic processes and activities.The program also supports research on the development and refinement of sensors and sensor network technologies that can be used to measure a wide variety of physical, chemical, and biological properties of interest in characterizing environmental systems.The program emphasizes engineering principles underlying pollution avoidance as well as pollution treatment and remediation.Innovative production processes, waste reduction, recycling, and industrial ecology technologies are important to this program.The program supports research on innovative techniques to restore polluted land, water, and air resources.Read more

A Few Powerful Nodes Enhance Mobile Network Connectivity

by X. Shi, C. Adams, & A. KondozSPIE Newsroom, accessed 6 Oct 2006A mobile ad hoc network (MANET) is a temporary collection of wireless nodes communicating without the benefit of infrastructure.A connection between two nodes may involve several others in what is known as multi-hop routing.MANET can be used in situations in which, for example, soldiers relay and share information on a battlefield or relief workers coordinate efforts during an emergency.A basic requirement of a MANET is that it must maintain higher network connectivity, loss of which could entail severe consequences.Therefore, a principal task is to set up a route that connects source and destination nodes.Due to the dynamic shifts in network topology, multi-hop routing is neither stable nor pre-established.Strategically positioned nodes with extra transmission power can maintain system-wide connectivity in ad hoc networks.Read more

Sandia Releases Optimization Software Free to the Public

Sandia National LaboratoryNews Release, 4 Oct 2006Acro 1.0 optimization software, developed by a Sandia National Laboratories team led by Bill Hart, has recently been released to the public and is available at no charge.“Acro puts together different optimization software applications into one large package, making it easier to solve large-scale engineering and scientific problems,” Hart says.Read more

Phase Diagram of Water Revised

Sandia National LaboratoriesNews Release, 3 Oct 2006Supercomputer simulations by two Sandia researchers have significantly altered the theoretical diagram universally used by scientists to understand the characteristics of water at extreme temperatures and pressures.The new computational model also expands the known range of water’s electrical conductivity.The Sandia theoretical work showed that phase boundaries for “metallic water” -- water with its electrons able to migrate like a metal’s -- should be lowered from 7,000 to 4,000 kelvin and from 250 to 100 gigapascals.Read more

Wednesday, October 04, 2006

New Wood-Plastic Composites to Boost Industry

Oregon State UniversityPress Release, 2 Oct 2006Wood science researchers in the College of Forestry at Oregon State University have developed new wood-plastic composites that are stronger and less expensive than any similar products now available -- a major breakthrough for this growing industry.The new wood-plastic composites use superior compatibilizers and an innovative technology for mixing wood and thermoplastics such as nylons, in which the melting temperature of the plastic is higher than the wood degradation temperature.With this approach, the new wood-plastic composites can use very inexpensive plastics such as those found in old carpet fibers -- about 4.4 billion pounds of which are now wasted every year, going into landfills where they are extremely slow to biodegrade and pose a significant waste disposal problem.Read more

Musical Robot Composes, Performs, and Teaches

by M. AbshireCNN.com, 3 Oct 2006A professor of musical technology at Georgia Tech, Gil Weinberg, enlisted the support of graduate student Scott Driscoll to create Haile -- the first truly robotic musician.In this way, he became a sort of Geppetto creating his musical Pinocchio.Read more

Robots to Race through Traffic for Pentagon Prize

CNN.com, 2 Oct 2006The winners of last year's Pentagon-sponsored robot race are back to take on another challenge -- this time to develop a vehicle that can drive through congested city traffic all by itself.Read more

Friday, September 29, 2006

NSF Funding Opportunity - Research and Evaluation on Education in Science and Engineering

The Division of Research, Evaluation and Communication in the Directorate for Education and Human Resources of the National Science Foundation (NSF) supports basic and applied research and evaluation that enhances science, technology, engineering and mathematics (STEM) learning and teaching.This solicitation calls for two types of proposals -- synthesis and empirical.For either type of proposal, areas of interest include behavioral, cognitive, social, and technological aspects of learning and education; learning in formal and informal settings; diffusion, implementation, and the role of context in educational and learning innovations; and theoretical, methodological, and statistical issues of importance in advancing research and evaluation.Investigators from across the broad range of disciplines supported by the NSF are invited to submit proposals.Interdisciplinary proposals are particularly welcome.Read more

High-Tech Fabric Lights Up the Catwalk

ZDNet News, 27 Sep 2006It's one thing to light up the catwalk with innovative design, but what about producing designs that actually light up the catwalk?Philips, the Dutch electronics giant, and German fashion designer Anke Loh aim to try.Loh this week launched a new collection, "Dressing Light," in which each garment incorporates Philips' new photonic fabric -- which has arrays of light-emitting diodes that can display text, graphics and animation.Read more

Balanced Vehicular Traffic at a Bottleneck

by F. Siebel et al.arXiv.org E-print Archive, 27 Sep 2006The balanced vehicular traffic model is a macroscopic model for vehicular traffic flow.We use this model to study the traffic dynamics at highway bottlenecks either caused by the restriction of the number of lanes or by on-ramps or off-ramps.The coupling conditions for the Riemann problem of the system are applied in order to treat the interface between different road sections consistently.Our numerical simulations show the appearance of synchronized flow at highway bottlenecks.Read more

Fabry-Perot Otical Binary Switch for Aircraft Applications

by Z. Xie & H.F. TaylorOptics Letters, September 2006An optical binary switch for aircraft applications is demonstrated.A fiber Fabry-Perot interferometer (FFPI) bonded to a cantilever is used as the sensing element.A white-light interferometry system with two bulk Michelson interferometers sharing the same motor-driven translation stage is utilized to monitor the elongation of the FFPI.The system exhibits excellent linearity as a force sensor; the experimental results are in good agreement with theoretical calculated values.With a properly set threshold value, the system produces a binary output.Read more

The Ascent of Wind Power

by K. BradsherNew York Times, 28 Sep 2006Dilip Pantosh Patil uses an ox-drawn wooden plow to till the same land as his father, grandfather and great-grandfather.But now he has a new neighbor: a shiny white wind turbine taller than a 20-story building, generating electricity at the edge of his bean field.Wind power may still have an image as something of a plaything of environmentalists more concerned with clean energy than saving money.But it is quickly emerging as a serious alternative not just in affluent areas of the world but in fast-growing countries like India and China that are avidly seeking new energy sources.Read more

Carbon Nanotube Forests: A Non-Stick Workbench for Nanomanipulation

by K. Gjerde et al.Nanotechnology, 14 Oct 2006The ubiquitous static friction (stiction) and adhesion forces comprise a major obstacle in the manipulation of matter at the nanoscale.In this work it is shown that a surface coated with vertically aligned carbon nanotubes -- a nanotube forest -- acts as an effective non-stick workbench for the manipulation of micro-objects and fibres/wires with one or more dimensions in the nano-range.These include organic nanofibres and microsized latex beads, which adhere strongly even to a conventional low surface-energy material like Teflon.Although organic nanofibres are attractive as device components due to their chemical adaptability, adhesion forces nearly always rule out manipulation as a route to assembly of prototype devices based on such materials, because organic materials are soft and fragile, and tend to stick to any surface.We demonstrate here that the nanotube forest due to its roughness not only exhibits very low stiction and dynamic friction; it also acts as a springy and mechanically compliant surface, making it possible to lift up and manipulate delicate nanostructures such as organic nanofibres in ways not possible on planar, rigid surfaces.Read more

Modelling and Simulation of Scheduling Policies Implemented in Ethernet Switch

by B. Brahimi, C. Aubrun, & E. RondeauarXiv.org E-print Archive, 27 Sep 2006The objective of this paper is to propose models enabling to study the behaviour of Ethernet switch for Networked Control Systems.Two scheduler policies are analyzed: the static priority and the Weighted Round Robin.The modelling work is based on Coloured Petri Nets.A temporal validation step based on the simulation of these modelling, shows that the obtained results are near to the expected behaviour of these scheduler policies.Read more

Wednesday, September 27, 2006

Technologies That Will Shape Our Future

What technologies are most likely to have the greatest impact over the next 20 years?This month, IEEE Spectrum teams up with The Institute for the Future to survey over 700 IEEE fellows to find out what scientific and technological innovations can be expected to have the greatest impact on the way we live in future years since they have so much to do with making them come about.Included in the list of influential technologies are a commercially available universal language translator, lifelike interactive computer graphics, and routine global video conferencing.Read more

Amplification and Increased Duration of Earthquake Motion on Uneven Stress-Free Ground

by A. Wirgin & J.-P. GrobyarXiv.org E-print Archive, 22 Sep 2006When a flat stress-free surface separating air from a isotropic, homogeneous or horizontally-layered, solid substratum is solicited by a shear horizontal plane body wave incident in the substratum, the response in the substratum is a single specularly-reflected body wave.When the stress-free condition, equivalent to vanishing surface impedance, is relaxed by the introduction of a spatially-constant, non-vanishing surface impedance, the response in the substratum is again a single reflected body wave whose amplitude is less than the one in the situation of a stress-free ground.When the stress-free condition is relaxed by the introduction of a spatially-modulated surface impedance, which simulates the action of an uneven ground, the frequency-domain response takes the form of a spectrum of plane body waves and surface waves and resonances are produced at the frequencies of which one or several surface wave amplitudes can become large.It is shown, that at resonance, the amplitude of one, or of several, components of the motion on the surface can be amplified with respect to the situation in which the surface impedance is either constant or vanishes.Also, when the solicitation is pulse-like, the integrated time history of the square of surface displacement and of the square of velocity can be larger, and the duration of the signal can be considerably longer, for a spatially-modulated impedance surface than for a constant, or vanishing, impedance surface.Read more

Seismic Motion in Urban Sites

by J.-P. Groby & A. WirginarXiv.org E-print Archive, 26 Sep 2006We address the problem of the response to a seismic wave of an urban site consisting of N non-identical, non-equispaced blocks overlying a soft layer underlain by a hard substratum.The results of a theoretical analysis, appealing to a space-frequency mode-matching technique, are compared to those obtained by a space-time finite element technique.The two methods are shown to give rise to the same prediction of the seismic response for N=1 and N=2 blocks.The mechanism of the interaction between blocks and the ground, as well as that of the mutual interaction between blocks, are studied.It is shown that the presence of a small number of blocks modifies the seismic disturbance in a manner which evokes qualitatively, but not quantitatively, what was observed during the 1985 Michoacan earthquake in Mexico City.Read more

Even on the Ground, Space Elevators May Have Uses

by K. YoungNewScientist.com, 26 Sep 2006Balloon-borne platforms developed as precursors to space elevators could be used as high-altitude relay stations for wireless communications, a 60-day field test suggests.The hope is that one day a space elevator, comprised of a robot that will climb a strong tether about 60,000 miles long, will be able to send humans or other cargo cheaply into space.Read more

MIT's Intelligent Aircraft Fly and Cooperate Autonomously

Massachusetts Institute of TechnologyPress Release, 26 Sep 2006The U.S. military depends on small, unmanned aerial vehicles (UAVs) to perform such tasks as serving as "eyes in the sky" for battalion commanders planning maneuvers.While some of these UAVs can be easily carried in a backpack and launched by hand, they typically require a team of trained operators on the ground, and they perform only short-term tasks individually rather than sustained missions in coordinated groups.MIT researchers, in collaboration with Boeing's advanced research and development arm, Phantom Works, are working to change that.Read more

UNH Space Scientists to Build Sensor for Next-Generation Weather Satellites

University of New HampshirePress Release, 26 Sep 2006With an award in excess of $10 million, scientists from the University of New Hampshire's Space Science Center have been selected to build an instrument for the National Oceanic and Atmospheric Administration's third-generation weather satellites under the Geostationary Operational Environmental Satellite Program.The principal parties involved in the mission will hold their first operational meeting next week.UNH scientists and engineers will design and build the Energetic Heavy Ion Sensor for the Space Environment In-Situ Suite, which will monitor potentially dangerous energetic atomic nuclei and electrons as they hurtle through space near Earth.Read more

Intel Tips Teraflops Programmable Processor

by M. LaPedusEE Times, 26 Sep 2006Intel Corp. revealed the first details of its terascale research silicon program, including the development of the world's first programmable processor said to deliver 1 trillion floating point operations per second.They also tipped an SRAM and a silicon laser chip, as part of its ongoing research into terascale technology.Earlier this year, the company disclosed details about its internal terascale research program that promises to usher in the next wave of computing.Read more

Intel Offers Prize for Sexiest PC

BBC News, 27 Sep 2006Intel is offering $1m in prizes to designers and manufacturers who can come up with sexier alternatives to the "big, beige box."The Intel Core Processor Challenge is looking for smaller, more stylish multimedia PCs.The only condition is that entries must be powered by Intel Viiv technology, using the chip giant's Core 2 Duo processors.Beyond that, Intel urges potential applicants to "think outside the box."Read more

'Tower of Babel' Technology Nears

BBC News, 27 Sep 2006The problem of compatibility between wireless devices is being addressed at an international conference this week.Scientists will be discussing what has been dubbed "Tower of Babel" technology -- software that can converge different wireless gadgets into a single device.The aim for Software Defined Radio (SDR) is to be able to translate and understand any kind of radio wave signal, such as 3G or Wi-Fi.Researchers say SDR gadgets could become commonplace in five to 10 years.Read more

Tuesday, September 26, 2006

Quick and Easy Enrichment of Metallic Carbon Nanotubes

by H. Kataura & Y. MiyataSPIE Newsroom, accessed 26 Sep 2006A carbon nanotube (CNT) can exhibit either metal or semiconductor electronic behavior, depending on the molecule's chirality.The metallic variety is used in conductive films and transparent electrodes, while the semiconducting type is in great demand for high-performance field effect transistors (FETs).Unfortunately, current synthesis methods can't produce pure batches of either type, probably because of structural similarities, and instead generally produce twice as many semiconducting nanotubes as metallic nanotubes.This mixture can degrade application performances.For example, metallic CNTs reduce an FET's on/off current ratio, while semiconducting CNTs lower a thin film's overall conductivity.Thus, it is essential to have an effective way to separate the two types in order to better realize CNT potential.Read more

Stochastic Model for Power Grid Dynamics

by M. Anghel, K.A. Werley, & A.E. MotterarXiv.org E-print Archive, 24 Sep 2006We introduce a stochastic model that describes the quasi-static dynamics of an electric transmission network under perturbations introduced by random load fluctuations, random removing of system components from service, random repair times for the failed components, and random response times to implement optimal system corrections for removing line overloads in a damaged or stressed transmission network.We use a linear approximation to the network flow equations and apply linear programming techniques that optimize the dispatching of generators and loads in order to eliminate the network overloads associated with a damaged system.We also provide a simple model for the operator's response to various contingency events that is not always optimal due to either failure of the state estimation system or due to the incorrect subjective assessment of the severity associated with these events.This further allows us to use a game theoretic framework for casting the optimization of the operator's response into the choice of the optimal strategy which minimizes the operating cost.We use a simple strategy space which is the degree of tolerance to line overloads and which is an automatic control parameter that can be adjusted to trade off automatic load shed without propagating cascades versus reduced load shed and an increased risk of propagating cascades.The tolerance parameter is chosen to describes a smooth transition from a risk averse to a risk taken strategy.Read more

A Unifying Approach to Left Handed Material Design

by J. Zhou et al.arXiv.org E-print Archive, 23 Sep 2006In this letter we show that equivalent circuits offer a qualitative and even quantitative simple explanation for the behavior of various types of left-handed (or negative index) meta-materials.This allows us to optimize design features and parameters, while avoiding trial and error simulations or fabrications.In particular we apply this unifying circuit approach in accounting for the features and in optimizing the structure employing parallel metallic bars on the two sides of a dielectric film.Read more

Google to Push for More Electrical Efficiency in PC’s

by J. MarkoffNew York Times, 26 Sep 2006Google is calling on the computer industry to create a simpler and more efficient power supply standard that it says will save billions of kilowatt-hours of energy annually.In a white paper to be presented Tuesday on the opening day of the Intel Developer Forum here, two leading data center designers at Google will argue that the industry is mired in inefficiency for historical reasons, dating to the introduction of the first I.B.M. PC in 1981.Read more

Prequel to a Hydrogen Future: Driving G.M.’s Fuel Cell Prototype

by L. BrookeNew York Times, 24 Sep 2006If an afternoon behind the wheel of General Motors’ latest prototype hydrogen fuel cell vehicle, the Sequel, is any indication, automotive powertrains of the future will not feel much different from the engines that drive today’s cars and trucks.By a seat-of-the-pants evaluation, the Sequel feels reasonably peppy; acceleration is smooth and nearly silent. And it is capable of reaching 90 miles an hour.Read more

IEEE Developing Lithium-Ion Battery Standard

EE Times, 25 Sep 2006The IEEE is developing a standard to enhance performance for lithium-ion and lithium-ion polymer batteries used in digital cameras and camcorders.Designated IEEE P1825, the standard will set uniform criteria for the design, production and evaluation of lithium-ion and lithium-ion polymer batteries.Read more

Motion Primitives for Robotic Flight Control

by B.E. Perk & J. J. E. SlotinearXiv.org E-print Archive, 25 Sep 2006We introduce a simple framework for learning aggressive maneuvers in robotic flight control.Standard movement primitive techniques are analyzed and extended using nonlinear contraction theory.Accordingly, dynamic primitives, approximated and regenerated from an observed movement, can be stably combined or concatenated for various purposes.We demonstrate our results experimentally on the Quanser Helicopter, in which we first imitate aggressive maneuvers performed by a human, and then use these primitives to achieve new maneuvers that can pass an obstacle.Read more

Cooperative Wireless Systems

by M. Yuksel & E. ErkiparXiv.org E-print Archive, 21 Sep 2006We consider a general multiple antenna network with multiple sources, multiple destinations and multiple relays in terms of diversity-multiplexing tradeoff (DMT).We examine several projections of this most general problem taking into account the network geometry, the processing capability of the relays, and the number of antennas the nodes have.We first study a system with a single source-destination pair and multiple relays, each node with a single antenna, and show that even under idealistic assumptions, this virtual multi-input multi-output (MIMO) system can never fully mimic a real MIMO DMT.We provide communication strategies that achieve the best DMT of this relay system.We extend our work to cover cooperative systems with multiple sources and multiple destinations.We next study the relay channel with multiple antenna nodes for full-duplex relays to understand the effect of increased degrees of freedom in the direct link.We find DMT upper bounds and investigate the achievable performance of decode-and-forward, and compress-and-forward (CF) protocols.As having a full-duplex relay is an idealistic assumption, we also study the multiple antenna relay channel with half-duplex relays.We also study the multiple-access relay channel (MARC) as a subproblem of the most general network, and evaluate how CF works in MARC.Read more

Device Seeks to Detect Concussions during Games

CNN.com, 25 Sep 2006Concussions in football, and sports in general, are a relatively common injury.According to Dr. David Wright, a researcher at Emory University in Atlanta, "There's 1.2 million concussions [in this country] every year, and the problem is they are very difficult to diagnose."Wright and Michelle LaPlaca, an associate professor at Georgia Tech, are trying to make it easier to detect possible concussions.They are working on a device that could be used on the sidelines of a football game or in the locker room.Read more

Internet's Future in 2020 Debated

BBC News, 4 Sep 2006The Pew report on the future internet surveyed 742 experts in the fields of computing, politics and business.More than half of respondents had a positive vision of the net's future but 46% had serious reservations.Almost 60% said that a counter culture of Luddites would emerge, some resorting to violence.The Pew Internet and American Life report canvassed opinions from the experts on seven broad scenarios about the future internet, based on developments in the technology in recent years.Read more