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Topic Review
PXL-2000
The PXL-2000 (also known as Fisher-Price PXL2000, Fisher-Price PixelVision, Sanwa Sanpix1000, KiddieCorder, and Georgia) is a toy black-and-white camcorder produced in 1987 that uses a compact audio cassette as its recording medium. The PXL-2000 was created by a team of inventors led by James Wickstead, who sold the rights to Fisher-Price in 1987 at the American International Toy Fair in Manhattan. Surviving on the market for merely a year, only around 400,000 units were ever produced, resulting in the PXL-2000's eventual present status as a sought-after cult object among many artists and media historians.
  • 575
  • 02 Nov 2022
Topic Review
Safe Mode (Spacecraft)
Safe mode is an operating mode of a modern unmanned spacecraft during which all non-essential systems are shut down and only essential functions such as thermal management, radio reception and attitude control are active. Safe mode is entered automatically upon the detection of a predefined operating condition or event that may indicate loss of control or damage to the spacecraft. Usually the trigger event is a system failure or detection of operating conditions considered dangerously out of the normal range. Cosmic rays penetrating spacecraft electrical systems can create false signals or commands and thus cause a trigger event. The central processor electronics are especially prone to such events. Another trigger is the lack of a received command within a given time window. Lack of received commands can be caused by hardware failures or mis-programming of the spacecraft, as in the case of the Viking 1 lander. The process of entering safe mode, sometimes referred to as safing, involves a number of immediate physical actions taken to prevent damage or complete loss. Power is removed from non-essential subsystems. Regaining attitude control, if lost, is the highest priority because it is necessary to maintain thermal balance and proper illumination of the solar panels. A tumbling or cartwheeling spacecraft can quickly roast, freeze or exhaust its battery power and be lost forever.
  • 1.6K
  • 02 Nov 2022
Topic Review
Armor-Piercing Shell
An armor-piercing shell, armour-piercing shell in Commonwealth English, AP for short, is a type of ammunition designed to penetrate armor. From the 1860s to 1950s, a major application of armor-piercing projectiles was to defeat the thick armor carried on many warships and cause damage to the lightly-armored interior. From the 1920s onwards, armor-piercing weapons were required for anti-tank missions. AP rounds smaller than 20 mm are typically known as "armor-piercing ammunition", and are intended for lightly-armored targets such as body armor, bulletproof glass and light armored vehicles. The AP shell is now seldom used in naval warfare, as modern warships have little or no armor protection. In the anti-tank role, as tank armor improved during World War II newer designs began to use a smaller but dense penetrating body within a larger shell. These lightweight shells were fired at very high muzzle velocity and retained that speed and the associated penetrating power over longer distances. An armor-piercing shell must withstand the shock of punching through armor plating. Shells designed for this purpose have a greatly strengthened body with a specially hardened and shaped nose. One common addition to later shells is the use of a softer ring or cap of metal on the nose known as a penetrating cap. This lowers the initial shock of impact to prevent the rigid shell from shattering, as well as aiding the contact between the target armor and the nose of the penetrator to prevent the shell from bouncing off in glancing shots. Ideally, these caps have a blunt profile, which led to the use of a further thin aerodynamic cap to improve long-range ballistics. AP shells may contain a small explosive charge known as a "bursting charge". Some smaller-caliber AP shells have an inert filling or an incendiary charge in place of the bursting charge. Designs using newer technologies no longer look like the classic artillery shell and have displaced it. Instead the penetrator is a long rod of dense material like tungsten or depleted uranium (DU) that further improves the terminal ballistics. Whether these modern designs are considered to be AP rounds depends on the definition. Accordingly reference sources vary in whether they include or exclude them.
  • 8.1K
  • 02 Nov 2022
Topic Review
Bongo Drum
Bongos (Spanish: bongó) are an Afro-Cuban percussion instrument consisting of a pair of small open bottomed hand drums of different sizes. They are struck with both hands, most commonly in an eight-stroke pattern called martillo (hammer). They are mainly employed in the rhythm section of son cubano and salsa ensembles, often alongside other drums such as the larger congas and the stick-struck timbales. Bongo drummers (bongoseros) emerged as the only drummers of son cubano ensembles in eastern Cuba toward the end of the 19th century. The instrument remained important as son groups evolved into larger conjuntos and orchestras in Havana in the 1940s, at which point they began to share the stage with congas. Bongos later reached the United States, where they are commonly played in salsa, Afro-Cuban jazz, Latin rock and other genres. Bongo drums are about 20 centimetres (8 in) high and have diameters of approximately 20 centimetres (8 in) and 25 centimetres (10 in) (the smaller drum is called macho, male, and the larger drum, hembra, female). They are the smallest drums in Latin percussion, some models being only 15 centimetres (6 in) in diameter. The shells of the drums and the bridge (the small block that joins them) are usually made of wood, although fiberglass is also common. The heads are typically made of calfskin and attached to the shells via steel hardware that enables their tuning. Originally, metal tacks were used, so tuning had to be done by heating the skins.
  • 2.9K
  • 02 Nov 2022
Topic Review
Mac Transition to Apple Silicon
The Mac transition to Apple Silicon is the planned two-year process of introducing ARM64-based Apple silicon to, and deprecating Intel's x86-64 from, Apple's Macintosh line of computers. CEO Tim Cook announced the plan in his WWDC keynote address on June 22, 2020. The transition is the third time Apple has migrated Macintosh to a new instruction set architecture (ISA). The first was the switch from the Mac's original Motorola 68000 series architecture to the new PowerPC platform in 1994, and the second was the transition from PowerPC to Intel x86, which was formally announced in June 2005. Apple first utilized the ARM architecture in 1993 in its Newton personal digital assistant, and since then has extensively deployed it throughout other product lines including iPhone, iPad, iPod, and Apple Watch. Apple has designed its own custom ARM chips since 2009.
  • 1.1K
  • 02 Nov 2022
Topic Review
Thermal Inkjet Printing
Inkjet printing technologies have advanced significantly and found several applications in the pharmaceutical and biomedical sector. Thermal inkjet printing is one of the most widely used techniques due to its versatility in the development of bioinks for cell printing or biosensors, and the potential to fabricate personalized medications of various forms such as films and tablets.
  • 1.6K
  • 02 Nov 2022
Topic Review
Picture Exchange Communication System
The Picture Exchange Communication System (PECS) is an augmentative and alternative communication system developed and produced by Pyramid Educational Consultants, Inc. PECS was developed in 1985 at the Delaware Autism Program by Andy Bondy, PhD, and Lori Frost, MS, CCC-SLP. The developers of PECS noticed that traditional communication techniques, including speech imitation, sign language, and picture point systems, relied on the teacher to initiate social interactions and none focused on teaching students to initiate interactions. Based on these observations, Bondy and Frost created a functional means of communication for individuals with a variety of communication challenges. Although PECS was originally developed for young children with autism spectrum disorder (ASD), its use has become much more widespread. Through the years, PECS has been successfully implemented with individuals with varying diagnoses across the aged span. PECS is an evidence-based practice that has been highly successful with regard to the development of functional communication skills.
  • 597
  • 02 Nov 2022
Topic Review
Gee Bee Model R
The Gee Bee Model R Super Sportster was a special purpose racing aircraft made by Granville Brothers Aircraft of Springfield, Massachusetts at the now-abandoned Springfield Airport (Massachusetts). Gee Bee stands for Granville Brothers.
  • 460
  • 02 Nov 2022
Topic Review
Panzer II Variants
The Panzerkampfwagen II (Pz.Kpfw.II) light tank, produced in Germany in the late 1930s and early 1940s had a wide array of variants, both as development of the light tank and for specialised tasks.
  • 3.4K
  • 02 Nov 2022
Topic Review
Transmission (Mechanics)
A transmission is a machine in a power transmission system, which provides controlled application of power. Often the term 5-speed transmission refers simply to the gearbox, that uses gears and gear trains to provide speed and torque block conversions from a rotating power source to another device. The term transmission properly refers to the whole drivetrain, including clutch, gearbox, prop shaft (for rear-wheel drive vehicles), differential, and final drive shafts. In the United States the term is sometimes used in casual speech to refer more specifically to the gearbox alone, and detailed usage differs. The most common use is in motor vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. Such engines need to operate at a relatively high rotational speed, which is inappropriate for starting, stopping, and slower travel. The transmission reduces the higher engine speed to the slower wheel speed, increasing torque in the process. Transmissions are also used on pedal bicycles, fixed machines, and where different rotational speeds and torques are adapted. Often, a transmission has multiple gear ratios (or simply "gears") with the ability to switch between them as the speed varies. This switching may be done manually (by the operator) or automatically (by a control unit). Directional (forward and reverse) control may also be provided. Single-ratio transmissions also exist, which simply change the speed and torque (and sometimes direction) of motor output. In motor vehicles, the transmission generally is connected to the engine crankshaft via a flywheel or clutch or fluid coupling, partly because internal combustion engines cannot run below a particular speed. The output of the transmission is transmitted via the driveshaft to one or more differentials, which drive the wheels. While a differential may also provide gear reduction, its primary purpose is to permit the wheels at either end of an axle to rotate at different speeds (essential to avoid wheel slippage on turns) as it changes the direction of rotation. Conventional gear/belt transmissions are not the only mechanism for speed/torque adaptation. Alternative mechanisms include torque converters and power transformation (e.g. diesel-electric transmission and hydraulic drive system). Hybrid configurations also exist. Automatic transmissions use a valve body to shift gears using fluid pressures in response to engine RPM, speed, and throttle input.
  • 2.3K
  • 01 Nov 2022
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