Krishna Palem is a heretic. In the world of microchips, precision and perfection have always been imperative. Every step of the fabrication process involves testing and retesting and is aimed at ensuring that every chip calculates the exact answer every time. But Palem, a professor of computing at Rice University, believes that a little error can be a good thing.

Palem has developed a way for chips to use significantly less power in exchange for a small loss of precision. His concept carries the daunting moniker "probabilistic complementary metal-oxide semiconductor technology"--PCMOS for short. Palem's premise is that for many applications--in particular those like audio or video processing, where the final result isn't a number--maximum precision is unnecessary. Instead, chips could be designed to produce the correct answer sometimes, but only come close the rest of the time. Because the errors would be small, so would their effects: in essence, Palem believes that in computing, close enough is often good enough.

Every calculation done by a microchip depends on its transistors' registering either a 1 or a 0 as electrons flow through them in response to an applied voltage. But electrons move constantly, producing electrical "noise." In order to overcome noise and ensure that their transistors register the correct values, most chips run at a relatively high voltage. Palem's idea is to lower the operating voltage of parts of a chip--specifically, the logic circuits that calculate the least significant bits, such as the 3 in the number 21,693. The resulting decrease in signal-to-noise ratio means those circuits would occasionally arrive at the wrong answer, but engineers can calculate the probability of getting the right answer for any specific voltage. "Relaxing the probability of correctness even a little bit can produce significant savings in energy," Palem says.

Every time you use your cell phone, you leave behind a few bits of information. The phone pings the nearest cell-phone towers, revealing its location. Your service provider records the duration of your call and the number dialed.

Some people are nervous about trailing digital bread crumbs behind them. Sandy Pentland, however, revels in it. In fact, the MIT professor of media arts and sciences would like to see phones collect even more information about their users, recording everything from their physical activity to their conversational cadences. With the aid of some algorithms, he posits, that information could help us identify things to do or new people to meet. It could also make devices easier to use--for instance, by automatically determining security settings. More significant, cell-phone data could shed light on workplace dynamics and on the well-being of communities. It could even help project the course of disease outbreaks and provide clues about individuals' health. Pentland, who has been sifting data gleaned from mobile devices for a decade, calls the practice "reality mining."

Reality mining, he says, "is all about paying attention to patterns in life and using that information to help [with] things like setting privacy patterns, sharing things with people, notifying people--basically, to help you live your life."

Researchers have been mining data from the physical world for years, says Alex Kass, a researcher who leads reality-mining projects at Accenture, a consulting and technology services firm. Sensors in manufacturing plants tell operators when equipment is faulty, and cameras on highways monitor traffic flow. But now, he says, "reality mining is getting personal."

Within the next few years, Pentland predicts, reality mining will become more common, thanks in part to the proliferation and increasing sophistication of cell phones. Many handheld devices now have the processing power of low-end desktop computers, and they can also collect more varied data, thanks to devices such as GPS chips that track location. And researchers such as Pentland are getting better at making sense of all that information.

Solar Broadband Radio Spectrometer

A new radio spectrometer, Solar Broadband Radio Spectrometer (SBRS) with characteristics of high time resolution, high-frequency resolution, high sensitivity, and wide frequency coverage in the microwave region is described. Its function is to monitor solar radio bursts in the frequency range of 0.7–7.6 GHz with time resolution of 1–10 ms. SBRS consists of five `component spectrometers' which work in five different wave bands (0.7–1.5 GHz, 1.0–2.0 GHz, 2.6–3.8 GHz, 4.5–7.5 GHz, and 5.2–7.6 GHz, respectively). A combination of multi-channel and scanning techniques is adopted. The component spectrometers are attached to different antennas which are separately located at Beijing, Kunming, and Nanjing. Close attention was paid to solve the problems of sensitivity, dynamic range, interference-resistance, data acquisition, and handling a large amount of data. The SBRS was put into operation in the 23th solar maximum activity period, and has proved itself to be a valuable instrument for the study of solar bursts in microwaves.