Wednesday, July 20, 2011
The Digger D-3 is a mine-clearing robot with a unique approach. Instead of poking around to locate mines and explosives, it shreds that area and eats them. It is a land tiller on steroids (and lots of them). At the front of the D-3 is a giant spinning metal pulverizer, which has tungsten hammers that beat down a quarter meter into the ground, turning everything into mulch. The mines do blow up but don't seem to damage the Digger at all. It is designed to width stand antitank mines and unexploded shells of sizes up to 81 mm and has been able to successfully ingest mines containing as much as 8 kilograms of explosive.
Here is the Digger D-2 in action:
An operator commands this beast from a safe distance using a remote control unit. The hull of the robot is made up of hardened steel plates in a "V" shape to help limit any damage from explosions. The only potentially vulnerable spots are the air intakes, which are protected from flying shrapnel by special grates. At full throttle, the D-3 can reliably clear a comforting 100 percent of landmines from the ground at a rate of 1,000 square meters per hour (about 10,000 square feet per hour), while also divesting the land of any unwanted shrubbery (I guess you can plant the field it leaves behind). I can't wait to try one in my back yard so I can plant new grass!
A very controversial subject is whether RF radiation from cell phones is dangerous to our health. There are studies showing that it might be and others that show is not dangerous. Many people do not realize that RF radiation at these frequencies is non-ionizing so it cannot damage the cell structure on the molecular level like solar radiation does. However, it can heat the cells (as a microwave oven does to food) but cell phones are relatively low power so does it do any damage to us? Nothing conclusive to date has shown that it is dangerous at the power limits set by the FCC or other international organizations. Below is a recent release about the subject.
The International Journal of Hyperthermia has unveiled a new special issue which addresses the thermal aspects of RF exposure on human health. This special issue resulted from a workshop born out of the controversies surrounding huge growth and use of wireless communication. In the issue, invited experts further refine a quantitative assessment of the effects of thermal energy on tissue damage, fetal development, immune function and neurocognitive behaviour. The special issue papers are available on: http://informahealthcare.com/toc/hth/27/4.
One of the key findings of the workshop and research papers is that while RF exposure standards can surely be refined further, it is fair to say that the present exposure limits set for the general public are far more protective against thermal hazards than recommended limits for the temperature of hot water in the home.
“The purpose of the workshop – and the resulting special issue – was to review current knowledge of the effects of heat on the body that are of potential relevance to setting limits for human exposure to RF,” explains the lead review author, Kenneth R Foster, of the Department of Bioengineering at the University of Pennsylvania. “Thermal damage to the body is clearly a very large topic; our discussion and this special issue focuses on thermal effects that are likely to be relevant to setting RF exposure limits.”
“We examined the most appropriate health endpoints for a given tissue or system, appropriate time periods for acute and chronic exposure, time-temperature thresholds for adverse effects, as well as cost effective and targeted research to help us better understand and define human exposure standards,” continued Foster.
“The upshot was that current RF limits, as recommended by the WHO and adopted by the majority of the world’s governments, are – in thermal terms – far below temperatures that could harm the body,” says Foster. “Indeed, under ordinary environmental conditions, exposure at the whole body limits for the general public, will lead to no detectable increase in core body temperature due to thermoregulatory responses.
That said, both sets of current guidelines on exposure to radiofrequency are subject to limitations, despite the fact that they form the basis for exposure guidelines throughout most of the world. The IEEE (Institute of Electrical and Electronics Engineers) and the ICNIRP (International Commission on Non-Ionizing Radiation Protection) limits set out basic restrictions in terms of power absorbed in tissue. However, the biologically significant quantity is the thermal exposure (increase in temperature and duration of exposure to elevated temperature).
Within the human body, time-temperature functions for thermal damage to different tissue types varies widely and current limit definitions are complex and difficult to explain to the public. In addition, new technologies employing high-power mmWave sources are coming into use and the possibility of human exposure to such energy at potentially injurious levels is increasing.“If the limiting hazards of RF energy are indeed thermal, several questions must be addressed,” says Mark Dewhirst, Professor of Radiation Oncology, Pathology and Biomedical Engineering at Duke University. “Are current limits adequate to protect diverse tissues from thermal injury? Would it make sense to move to a time-temperature based limit? Are present standards adequately protective for exposures to the types of energy employed by modern electronic devices?”
I am sure there will be more to come on this subject. What do you think?
Monday, July 18, 2011
This was published from Ga Tech a week or so ago - interesting research on energy scavenging:
Researchers have discovered a way to capture and harness energy transmitted by such sources as radio and television transmitters, cell phone networks and satellite communications systems. By scavenging this ambient energy from the air around us, the technique could provide a new way to power networks of wireless sensors, microprocessors and communications chips.
Georgia Tech School of Electrical and Computer Engineering professor Manos Tentzeris displays an inkjet-printed rectifying antenna used to convert microwave energy to DC power. This grid was printed on flexible Kapton material and is expected to operate with frequencies as high as 10 gigahertz when complete. (Click image for high-resolution version. Credit: Gary Meek).
“There is a large amount of electromagnetic energy all around us, but nobody has been able to tap into it,” said Manos Tentzeris, a professor in the Georgia Tech School of Electrical and Computer Engineering who is leading the research. “We are using an ultra-wideband antenna that lets us exploit a variety of signals in different frequency ranges, giving us greatly increased power-gathering capability.”
Tentzeris and his team are using inkjet printers to combine sensors, antennas and energy-scavenging capabilities on paper or flexible polymers. The resulting self-powered wireless sensors could be used for chemical, biological, heat and stress sensing for defense and industry; radio-frequency identification (RFID) tagging for manufacturing and shipping, and monitoring tasks in many fields including communications and power usage.
A presentation on this energy-scavenging technology was given July 6 at the IEEE Antennas and Propagation Symposium in Spokane, Wash. The discovery is based on research supported by multiple sponsors, including the National Science Foundation, the Federal Highway Administration and Japan’s New Energy and Industrial Technology Development Organization (NEDO).
Communications devices transmit energy in many different frequency ranges, or bands. The team’s scavenging devices can capture this energy, convert it from AC to DC, and then store it in capacitors and batteries. The scavenging technology can take advantage presently of frequencies from FM radio to radar, a range spanning 100 megahertz (MHz) to 15 gigahertz (GHz) or higher.
Georgia Tech School of Electrical and Computer Engineering professor Manos Tentzeris holds a sensor (left) and an ultra-broadband spiral antenna for wearable energy-scavenging applications. Both were printed on paper using inkjet technology. (Click image for high-resolution version. Credit: Gary Meek)
Scavenging experiments utilizing TV bands have already yielded power amounting to hundreds of microwatts, and multi-band systems are expected to generate one milliwatt or more. That amount of power is enough to operate many small electronic devices, including a variety of sensors and microprocessors.
And by combining energy-scavenging technology with super-capacitors and cycled operation, the Georgia Tech team expects to power devices requiring above 50 milliwatts. In this approach, energy builds up in a battery-like supercapacitor and is utilized when the required power level is reached.
The researchers have already successfully operated a temperature sensor using electromagnetic energy captured from a television station that was half a kilometer distant. They are preparing another demonstration in which a microprocessor-based microcontroller would be activated simply by holding it in the air.
Exploiting a range of electromagnetic bands increases the dependability of energy-scavenging devices, explained Tentzeris, who is also a faculty researcher in the Georgia Electronic Design Center at Georgia Tech. If one frequency range fades temporarily due to usage variations, the system can still exploit other frequencies.
The scavenging device could be used by itself or in tandem with other generating technologies. For example, scavenged energy could assist a solar element to charge a battery during the day. At night, when solar cells don’t provide power, scavenged energy would continue to increase the battery charge or would prevent discharging.
Georgia Tech graduate student Rushi Vyas (front) holds a prototype energy-scavenging device, while School of Electrical and Computer Engineering professor Manos Tentzeris displays a miniaturized flexible antenna that was inkjet-printed on paper and could be used for broadband energy scavenging. (Click image for high-resolution version. Credit: Gary Meek)
Utilizing ambient electromagnetic energy could also provide a form of system backup. If a battery or a solar-collector/battery package failed completely, scavenged energy could allow the system to transmit a wireless distress signal while also potentially maintaining critical functionalities.
The researchers are utilizing inkjet technology to print these energy scavenging devices on paper or flexible paper-like polymers – a technique they already using to produce sensors and antennas. The result would be paper-based wireless sensors that are self-powered, low-cost and able to function independently almost anywhere.
To print electrical components and circuits, the Georgia Tech researchers use a standard materials inkjet printer. However, they add what Tentzeris calls “a unique in-house recipe” containing silver nanoparticles and/or other nanoparticles in an emulsion. This approach enables the team to print not only RF components and circuits, but also novel sensing devices based on such nanomaterials as carbon nanotubes.
When Tentzeris and his research group began inkjet printing of antennas in 2006, the paper-based circuits only functioned at frequencies of 100 or 200 MHz, recalled Rushi Vyas, a graduate student who is working with Tentzeris and graduate student Vasileios Lakafosis on several projects.
“We can now print circuits that are capable of functioning at up to 15 GHz — 60 GHz if we print on a polymer,” Vyas said. “So we have seen a frequency operation improvement of two orders of magnitude.”
The researchers believe that self powered, wireless paper-based sensors will soon be widely available at very low cost. The resulting proliferation of autonomous, inexpensive sensors could be used for applications that include:
· Airport security: Airports have both multiple security concerns and vast amounts of available ambient energy from radar and communications sources. These dual factors make them a natural environment for large numbers of wireless sensors capable of detecting potential threats such as explosives or smuggled nuclear material.
· Energy savings: Self-powered wireless sensing devices placed throughout a home could provide continuous monitoring of temperature and humidity conditions, leading to highly significant savings on heating and air conditioning costs. And unlike many of today’s sensing devices, environmentally friendly paper-based sensors would degrade quickly in landfills.
· Structural integrity: Paper or polymer based sensors could be placed throughout various types of structures to monitor stress. Self powered sensors on buildings, bridges or aircraft could quietly watch for problems, perhaps for many years, and then transmit a signal when they detected an unusual condition.
· Food and perishable material storage and quality monitoring: Inexpensive sensors on foods could scan for chemicals that indicate spoilage and send out an early warning if they encountered problems.
· Wearable bio-monitoring devices: This emerging wireless technology could become widely used for autonomous observation of patient medical issues.