Category Archives: Tech

Adaptive Optics

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$20 Self Adjustable Pump-Action Glasses

The lenses comprise flexible membranes containing silicone oil. Using syringes (seen in the picture), the amount of oil can be adjusted and the refractive index of the lenses changed. The syringes are detachable.

This is big, because it means a single, uniform product can be mass produced and then tweaked at its destination without specialized equipment.

The goal is to distribute these in countries where ground glass (or plastic) lenses are too expensive and doctors are in short supply.

From The Telegraph,

His aim is to eventually reach 100 million people a year, with a target of one billion in total by 2020

Also see the writeup in the Washington Post

It's About Time, Part II

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Super clocks: More accurate than time itself

An article discussing the progression of atomic clock technology, and also relating to something I posted earlier, a discussion of what happens when the next generation of atomic clocks is deployed: the clocks won’t be the limiting factor in determining the time.

To tell the time consistently, all clocks need to be at a known height relative to Earth’s “geoid”, an imaginary surface that links points at which the gravitational field has the same strength. But the height of this geoid varies over time at any given place by up to 20 centimetres, because of effects such as tectonic movements, glacial melting and changes in ocean levels, and varying atmospheric pressure. Changes of that magnitude could wreak havoc with any attempt to establish a global time standard at an accuracy of 1 part in 1018 or better

One of the things that always glossed over in these discussions is that almost everything that is called a clock is actually a frequency standard, which is part of a clock. Clocks run continuously, because you are measuring a phase, and frequency standards don’t. Now, there’s a caveat here in “running continuously,” because even commercially-available clocks will skip measurement cycles to do self-diagnostics. During those skips in measurement, as with the time between measurements, the frequency is maintained with some oscillator. Usually this is a quartz crystal, which typically has excellent short-term stability. The important point becomes how long the clock is running on the “flywheel” oscillator and what kind of degradation that introduces. The latest generation of frequency standards run for several hours, but then are shut down for extended periods of time, which is not surprising for a cutting-edge kind of experiment. But while the frequency standard is not running, the clock’s performance approaches whatever the flywheel performance is, whether that’s cesium beam clocks or hydrogen masers, etc., or some ensemble made up of several clocks.

So when these stories appear touting the great performance of cutting-edge clocks, there’s an unwritten implication that we will be getting an improvement in the flywheel operation as well, to be able to leverage this improved frequency-standard performance.

Security and Usability

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Balancing Security and Usability in Authentication

In most cases, how an authentication system works when a legitimate user tries to log on is much more important than how it works when an impostor tries to log on. No security system is perfect, and there is some level of fraud associated with any of these authentication methods. But the instances of fraud are rare compared to the number of times someone tries to log on legitimately. If a given authentication system let the bad guys in one in a hundred times, a bank could decide to live with the problem—or try to solve it in some other way. But if the same authentication system prevented legitimate customers from logging on even one in a thousand times, the number of complaints would be enormous and the system wouldn’t survive one week.

Balancing security and usability is hard, and many organizations get it wrong. But it’s also evolving; organizations needing to tighten their security continue to push more involved authentication methods, and more savvy Internet users are willing to accept them. And certainly IT administrators need to be leading that evolutionary change.

In my experience, systems that have a captive audience, rather than a voluntary one (e.g. employee vs customer) are much less likely to care about usability in security but also in general, since they can go Nike on you and say, “Just do it.”

related:

Humans are incapable of securely storing high-quality cryptographic keys, and they have unacceptable speed and accuracy when performing cryptographic operations. (They are also large, expensive to maintain, difficult to manage, and they pollute the environment. It is astonishing that these devices continue to be manufactured and deployed. But they are sufficiently pervasive that we must design our protocols around their limitations.)

— Kaufman, Perlman, and Speciner

Peek-a-Boo

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Light Transmitting Concrete

Litracon is a combination of optical fibers and concrete. A wall made of Litracon has the strength of traditional concrete but thanks to an embedded array of optical glass fibers, which lets in the view of the outside world, such as the silhouette of trees, or passersby, that are displayed inside the building.

The glass fibers allow light to travel by points between the two sides of the blocks. Due to their parallel placement, the light-information on the brighter side of such a wall seems unchanged on the darker side. Also there is no change in the color of the light.

Looking for Energy Savings in All the Right Places

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Regenerative brakes recapture energy that conventional brakes dissipate as heat. What’s next? Shock absorbers.

New Shock Absorber Harvests Energy From Bumps In The Road, Increases Fuel Economy

Their prototype shock absorbers use a hydraulic system that forces fluid through a turbine attached to a generator. The system is controlled by an active electronic system that optimizes the damping, providing a smoother ride than conventional shocks while generating electricity to recharge the batteries or operate electrical equipment.

In their testing so far, the students found that in a 6-shock heavy truck, each shock absorber could generate up to an average of 1 kW on a standard road — enough power to completely displace the large alternator load in heavy trucks and military vehicles, and in some cases even run accessory devices such as hybrid trailer refrigeration units.