Sunday, 29 July 2012

Physics stuff from the week 23-29/7/12

[video] All objects fall equally fast, under gravity, right?
Then how does one beat the other, in this experiment, then?

[video] 'Lightning Captured at 7,207 Images per Second'

'Engineering students race first 3-D printed boat in Milk Carton Derby'
"Faculty adviser Mark Ganter, professor of mechanical engineering, experiments with unconventional methods and ingredients for 3-D printing (including ceramics, glass and cookie dough) in the UW's Open3DP Lab, which he operates with colleague Duane Storti, associate professor of mechanical engineering."
"Frankly, milk jug material is an awful material to work with," he said. "It shrinks, it curls, it doesn't want to stick to itself. Overcoming all those parts of the problem was part of the achievement."

"Functional coatings, for example with highly water-resistant or antibacterial properties, have at their surface nano-sized molecular groups that provide these specific properties. But up to now, these molecular groups are easily and irreversibly damaged by minor contact with their surface (such as by scratching), quickly causing their properties to be lost."
"[They have designed] surfaces with special ‘stalks’ carrying the functional chemical groups at their ends, and mixing these through the coating. If the outer surface layer is removed by scratching, the ‘stalks’ in the underlying layer re-orient to the new surface, thereby restoring the function."
"products like mobile phones, solar panels or even aircraft will remain clean for a longer time. For aircraft a cleaner surface means less air resistance, which in turn reduces fuel consumption. Other applications are contact lenses that self-repair their scratches, and coatings that resist the formation of algae, which is an advantage for ships. A limitation of the new technology is that it only works with superficial scratches that do not completely penetrate the coating."

[video] An electric aircraft, powered by two 35-horsepower motors and lithium polymer batteries has achieved 202.6 mph in level flight!
Top speeds certainly grabs people's attention, but the team acknowledges that stamina is the system's downfall - their record-setting flight lasted just 16 minutes.

"NASA and the Interior Department Monday marked the 40th anniversary of the Landsat program, the world's longest-running Earth-observing satellite program. The first Landsat satellite was launched July 23, 1972, from Vandenberg Air Force Base in California."
"The 40-year Landsat record provides global coverage that shows large-scale human activities such as building cities and farming. The program is a sustained effort by the United States to provide direct societal benefits across a wide range of human endeavors, including human and environmental health, energy and water management, urban planning, disaster recovery and agriculture."

'Terahertz radiation can induce insulator-to-metal change of state in some materials'
Boston University researchers have used Terahertz radiation to 'convince' VO2 (vanadium oxide) to stop being an insulator, and to start conducting electrical current!
Terahertz-frequency radiation lies at the boudnary between the Infrared and Microwave classifications of electromagnetic radiation.
"“Sub-picosecond THz pulses can allow us to initiate strong changes in a material. In the case of VO2, the THz pulse actually distorts the potential in which electrons lie, freeing them up to make the material a better conductor.” However, to do this requires very strong THz fields: In this case, the researchers used an antenna-like structure called a split ring resonator to concentrate the electric field of a THz pulse in a small area, increasing the electric field from hundreds of kilovolts per centimeter to about 4 megavolts per centimeter."
That's a monstrous energy density, by the way.

'High speed camera study shows why boiling drops take off'
Water droplets race around the pan uncontrollably because they sit on a cushion of evaporated water, which means there is very little friction between them and the pan's surface.
Any force can cause them to ping off in one direction, or another, until they eventually fizzle out.
With a hot enough surface, the vapour produced by boiling of the underside of the droplet causes enough upthrust to ping the droplet into the 3rd dimension - away from the pan's surface.
With ethanol, the researchers found that droplets could just bounce straight out of the pan!
But there are ways to control a water drop:

What does a pile of gold look like?
Well, if there are only 20 atoms in it -- like this:

'Sumatran zigzag earthquake answers seismology puzzle'
"Meng says the findings show that quakes can grow to large, potentially dangerous magnitudes far from subduction zones by jumping from fault to fault. The oceanic crust is riddled with seemingly dormant faults."

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