The ZX81 was designed to be small, simple, and above all, inexpensive, with as few components as possible. Video output is to a television set rather than a dedicated monitor. Programs and data are loaded and saved onto compact audio cassettes. It uses only four silicon chips and a mere 1 KB of memory. There is no power switch or any moving parts with the exception of a VHF TV channel selector switch present in some models. It has a pressure-sensitive membrane keyboard. The ZX81's limitations prompted a market in third-party peripherals to improve its capabilities. Its distinctive case and keyboard brought designer Rick Dickinson a Design Council award. (Full article...)
Remains of the Alconétar Bridge with its flattened arches
The almost 300 m long Alconétar Bridge served as a crossing point for the Roman Via de la Plata, the most important north-south connection in western Hispania, over the Tagus, the longest river of the Iberian peninsula. It presumably remained in service until the Reconquista, after which numerous early modern reconstruction attempts by Spanish engineers failed. The ruins, which were mainly to be found on the right river bank, were relocated from their original position in 1970 when the Alcántara reservoir was created. (Full article...)
"Big Pete" Ramagos, rigger at work on Douglas Dam, Tennessee, June 1942. A rigger is a person or company which specializes in the lifting and/or moving of extremely large and/or heavy objects. Riggers use equipment expressly designed for moving and lifting objects where ordinary material handling equipment cannot go.
An animated cut-away diagram of a typical fuel injector, which is used to spray controlled amounts of petrol (gasoline) into an internal combustion engine. A solenoid is activated when fuel is intended to be delivered to the engine, causing the plunger to become pulled toward the solenoid by magnetic force. This uncovers the valve opening, allowing fuel to flow into the atomiser and out the spray tip. The route of fuel is shown in orange; grey/blue indicates no fuel present.
This photograph, showing five of the Australia Telescope Compact Array's dishes, was taken around 1984, in the late phase of the construction process. It is a long-exposure photograph taken in darkness in the late evening; during the exposure, the photographer, John Masterson, walked around the dishes firing off over 130 flashes using a hand-held flash gun.
The Wiesen Viaduct is a single-track railway viaduct (concrete blocks with dimension stone coverage) which spans the Landwasser southwest of the hamlet of Wiesen, Switzerland. Designed by Henning Friedrich, then the chief engineer of the Rhaetian Railway, it was built between 1906 and 1909 by the contractor G. Marasi (Westermann & Cie, Zürich) under the supervision of P. Salaz and Hans Studer (RhB). The Rhaetian Railway still owns and uses the viaduct today for regular service with 29 passenger trains per day. An important element of the Davos–Filisur railway, the viaduct is 88.9 metres (292 ft) high, 210 metres (690 ft) long, and has a main span of 55 metres (180 ft). In 1926, the viaduct was the inspiration for Ernst Ludwig Kirchner's painting Brücke bei Wiesen.
A diagram of a typical turbojet engine. Air is compressed as it enters the engine, and is mixed with fuel that burns in the combustion section. Released through the exhaust, the resulting hot gases provide forward thrust and turn the turbines that drive the fan blades of the compressor.
A thermoplastic-sheathed cable consists of a toughened outer thermoplastic sheath of polyvinyl chloride, covering one or more individual annealed copper conductors. Each of the current-carrying conductors in the "core" is insulated by an individual thermoplastic sheath, coloured to indicate the purpose of the conductor concerned. The protective earth conductor may also be covered with insulation, although, in some countries, this conductor may be left as bare copper. The type of thermoplastic, the dimensions of the conductors and the colour of their individual insulation are specified by the regulatory bodies in the various countries concerned.
A hybrid-propellant rocket is a rocket with an engine that uses propellants in two different phases, one solid and the other gaseous or liquid. The concept can be traced back to at least the 1930s.
This picture shows a transparent 3D-printed hybrid-rocket fuel grain with dual helical fuel ports, a post-combustion chamber, and a de Laval nozzle, photographed prior to the hot-fire test. The motor used nitrous oxide as the oxidizer and Pyrodex pellets for the igniter.
Two Jet Propulsion Laboratory engineers stand with three vehicles, providing a size comparison of three generations of Mars rovers. Front and center is the flight spare for the first Mars rover, Sojourner, which landed on Mars in 1997 as part of the Mars Pathfinder Project. On the left is a Mars Exploration Rover test vehicle, a working sibling to Spirit and Opportunity, which landed on Mars in 2004. On the right is a test rover for the Mars Science Laboratory, which landed Curiosity on Mars in 2012.
The SOCATA TBM (now Daher TBM) is a family of high-performance single-engine turboprop business and utility light aircraft manufactured by Daher. This SOCATA TBM 900 was photographed in flight during the 2015 EAA AirVenture Oshkosh airshow in the U.S. state of Wisconsin. The aircraft features a Pratt & Whitney Canada PT6A-64 engine, and a five-blade carbon-fiber propeller, which increases performance and decreases cabin noise. In a passenger configuration, the pressurized cabin is typically fitted with highly finished interiors, featuring luxury materials such as leather and wood veneers.
This diagram of four pulley systems illustrates how increasing the number of pulleys increases the mechanical advantage, making the load easier to lift. MA is the factor by which a mechanism multiplies the force put into it. In this diagram, 100 newtons is required to lift the weight off the ground. Each additional pulley increases the MA such that the four-pulley system only needs 25 newtons to accomplish the same task, but the rope must be pulled four times as far.
The Commodore 64 is an 8-bit home computer introduced in 1982 by Commodore International. Its low retail price and easy availability led to the system becoming the market leader for three years. It remains the best-selling single personal computer model of all time.
A test firing of twin linear XRS-2200 aerospike engines, originally built for the Lockheed Martin X-33, a next-generation, commercially operated reusable launch vehicle. The aerospike engine is a type of rocket engine that maintains its efficiency across a wide range of altitudes through the use of an aerospike nozzle. A vehicle with an aerospike engine uses 25-30% less fuel at low altitudes, where most missions have the greatest need for thrust.
An escalator is a moving staircase for carrying people between floors of a building. The device consists of a motor-driven chain of individual, linked steps that move up or down on tracks, allowing the step treads to remain horizontal.
Image 4The wheel, invented sometime before the 4th millennium BC, is one of the most ubiquitous and important technologies. This detail of the "Standard of Ur", c. 2500 BCE., displays a Sumerian chariot (from History of technology)
Image 18A rare 1884 photo showing the experimental recording of voice patterns by a photographic process at the Alexander Graham Bell Laboratory in Washington, D.C. Many of their experimental designs panned out in failure. (from Invention)
John David McAfee (/ˈmækəfiː/MAK-ə-fee; 18 September 1945 – 23 June 2021) was a British-American computer programmer, businessman, and two-time presidential candidate who unsuccessfully sought the Libertarian Party nomination for president of the United States in 2016 and in 2020. In 1987, he wrote the first commercial anti-virus software, founding McAfee Associates to sell his creation. He resigned in 1994 and sold his remaining stake in the company. McAfee became the company's most vocal critic in later years, urging consumers to uninstall the company's anti-virus software, which he characterized as bloatware. He disavowed the company's continued use of his name in branding, a practice that has persisted in spite of a short-lived corporate rebrand attempt under Intel ownership. (Full article...)
YouTube Premium (formerly Music Key and YouTube Red) is a subscription service offered by the video platform YouTube. The service provides ad-free access to content across the service, as well as access to premium YouTube Originals programming produced in collaboration with the site's creators, downloading videos and background playback of videos on mobile devices, and access to the YouTube Music music streaming service. (Full article...)