Claude Elwood Shannon (April 30, 1916 – February 24, 2001) was an American mathematician, electrical engineer, and cryptographer known as "the father of information theory". Shannon is noted for having founded information theory with a landmark paper, "A Mathematical Theory of Communication", that he published in 1948.
He is also well known for founding digital circuit design theory in 1937, when—as a 21-year-old master's degree student at the Massachusetts Institute of Technology (MIT)—he wrote his thesis demonstrating that electrical applications of Boolean algebra could construct any logical numerical relationship. Shannon contributed to the field of cryptanalysis for national defense during World War II, including his fundamental work on codebreaking and secure telecommunications.
- "Claude Shannon" | 2009-12-03 | 25 Upvotes 12 Comments
A human-powered helicopter (HPH) is a helicopter powered solely by one or more humans carried on board. As in other human-powered aircraft, the power is usually generated by pedalling. It remains a considerable engineering challenge to obtain both the power-to-weight ratio and rotor efficiency required to sustain a helicopter in flight.
On 13 June 2013, the AeroVelo Atlas was the first to complete a flight that lasted 64 seconds and reached an altitude of 3.3 metres, thus winning the American Helicopter Society (AHS) International's Igor I. Sikorsky Human Powered Helicopter Competition.
- "Human-powered helicopter" | 2018-05-23 | 28 Upvotes 6 Comments
The Twike (a portmanteau of the words twin and bike) is a human-electric hybrid vehicle (HEHV) designed to carry two passengers and cargo. Essentially a velomobile with an electrical hybrid engine, it can be driven in electric-only mode or electric + pedal power mode. Pedaling warms the user, making electric heating in winter unnecessary, extends the range of the vehicle but does not substantially add to the vehicle's top speed.
Constructed of lightweight materials such as aluminium (frame) and plastic (shell), the 246 kg (542 lb) (unladen, varying with battery weight) tricycle vehicle first used NiCd batteries, later Li-Mn, LiFePO4 and LiIon. Typically ranges reach from 50 to over 500 km depending on battery size, type, status on one side and speed and altitude profile and load on the other. Energy is reclaimed while driving through regenerative braking, and load is removed from the electric system by use of the pedalling system which transfers its input directly to the drivetrain (i.e., both systems operate in parallel, not in series).
- "Twike" | 2021-07-21 | 275 Upvotes 195 Comments
Countersteering is used by single-track vehicle operators, such as cyclists and motorcyclists, to initiate a turn toward a given direction by momentarily steering counter to the desired direction ("steer left to turn right"). To negotiate a turn successfully, the combined center of mass of the rider and the single-track vehicle must first be leaned in the direction of the turn, and steering briefly in the opposite direction causes that lean. The rider's action of countersteering is sometimes referred to as "giving a steering command".: 15
The scientific literature does not provide a clear and comprehensive definition of countersteering. In fact, "a proper distinction between steer torque and steer angle ... is not always made."
- "Countersteering" | 2022-09-14 | 105 Upvotes 137 Comments
The Idaho stop is the common name for laws that allow cyclists to treat a stop sign as a yield sign, and a red light as a stop sign. It first became law in Idaho in 1982, but was not adopted elsewhere until Delaware adopted a limited stop-as-yield law, the "Delaware Yield", in 2017. Arkansas was the second state to legalize both stop-as-yield and red light-as-stop in April 2019. Studies in Delaware and Idaho have shown significant decreases in crashes at stop-controlled intersections.
- "Idaho Stop" | 2022-11-05 | 131 Upvotes 293 Comments