Iphleandro-blog - Real

Apparently, Luzia’s section of the museum is ruined.

She was a fossil known as “the first brazilian”, because hers were the oldest homo sapiens remains found in brazilian soil. Her skull was discovered in Minas Gerais in the 70′s and anyone who visited the national museum from the 80′s until now has seen her face.

Descanse em paz, mais uma vez, Luzia.

The Bortle Scale and Light Pollution

The Bortle Scale is used by astronomers to rate the darkness of our skies. It ranges from 1 (darkest) to 9 (brightest). For most of us, our daily lives are spent beneath a radiance level of between 5 and 8 and rarely venture into areas ranked 3 or darker- and what a shame that is.

Light pollution, while a testament to our technological advances, has blanketed our view of the universe and decoupled our relationship with the cosmos. For the millions of people living in areas where less than 20 stars can be seen in the night sky, it is practically impossible to imagine a natural sky blanketed with upwards of 2,500 stars backed by great ribbons of billions of stars which can be found in our Galaxy: The Milky Way.

What are the effects of light pollution?

Continuar lendo

Here is a semester project in the 2012 Mechatronic control systems engineering module at San Jose State University. This is a Proportional-Integral-Derivative controlled (PID), 6 degree of freedom (6-DOF) Stewart platform, which basically means it has six axes on the top plate. This prototype uses 6 radio controlled servo motors instead of the traditional use of hydraulic jacks or electronic actuators. (this video has sound)

Proportional-Integral-Derivative:

A PID controller continuously calculates an error value as the difference between a measured process variable and a desired setpoint. The controller attempts to minimize the error over time by adjustment of a control variable, such as the position of a set of servo motors or actuators,  to a new value, given by a weighted sum:

where Kp ,Ki , and Kd, all non-negative, denote the coefficients for the proportional, integral, and derivative terms, respectively (sometimes denoted P, I, and D).

P accounts for present values of the error , and is determined by the direction and magnitude the correction needs to be applied (e.g. if the error is large and positive, the control variable will be large and negative),

I accounts for past values of the error (e.g. if the output is not sufficient to reduce the size of the error, the control variable will accumulate over time, causing the controller to apply a stronger action through P), and

D accounts for possible future values of the error, based on its current rate of change. This part determines when and at what rate it needs to reduce the magnitude of its action, e.g as the ball fast approaches the desired set point at the centre of the plate.

[source]

WHAT A JERK

When Trilobites Ruled the World

infographics by The New York Times

brought to you by Graphic Services for Science and Graphic Biology

Zany zebra facts: 1) Each zebra has a unique stripe pattern—no two are alike. 2) A zebra’s eyesight at night is thought to be about as good as that of an owl. 3) Zebras have a pad of fat under their mane that keeps it standing straight up.

Thanks to Todd Lahman for the stunning shot of Zari the zebra.

smithsoniannmnh When calcium leached out from this scallop some 40 million years ago, it formed a halo that solidified the sediment around it. Unearthed in Washington state, the specimen now resides in our research collections. Happy #FossilFridayfrom our Department of Paleobiology and @SIxDIGI, who are well on their way to digitizing #1MillionFossils!

Start the day off right… with a little code!