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Rectifier transformer
A rectifier transformer is a specialized power transformer that supplies AC from the grid to a rectifier converting it to DC, serving electrolysis, plating, and DC drives.
Recumbent bicycle
A recumbent bicycle is a bicycle with the rider in a reclined, feet-forward seat instead of a saddle; its lower aerodynamic drag makes it the basis of the fastest human-powered vehicles.
Recurrent AI arbitration
The Recurrent AI arbitration is a Hong Kong arbitration filed in November 2024 by investors in Recurrent AI against Moonshot AI founders Yang Zhilin and Zhang Yutao.
Recurrent convolutional neural network
A recurrent convolutional neural network, also called a convolutional recurrent network, combines convolutional layers with recurrent connections to process data structured in space and time, such as video and speech.
Recurrent Memory Transformer
The Recurrent Memory Transformer (RMT), introduced at NeurIPS 2022 by Bulatov, Kuratov, and Burtsev, processes long sequences in segments linked by memory tokens, reaching two million tokens.
Recurrent neural network
A recurrent neural network (RNN) is a neural network that processes sequences one step at a time while keeping an internal hidden state that carries information forward.
Recurrent neural network channel decoder
A recurrent neural network channel decoder is a neural network that recovers transmitted information bits from noisy channel outputs by reusing the same weights across decoding iterations.
Recursion (computer science)
Recursion in computer science is a method of solving a problem in which a function calls itself on a smaller version of the same problem, ending at a base case.
Recursive acronym
A recursive acronym, also called a self-referential or circular acronym, is an acronym that refers to itself, a hacker tradition best known through GNU, "GNU's Not Unix!"
Recursive filtering
A recursive filter computes each output from the current measurement and the previous estimate, matching full-history accuracy with fixed cost, as in IIR filters and the Kalman filter.
Recursive neural network
A recursive neural network is a neural architecture that applies the same composition function recursively over structured inputs such as parse trees, producing hierarchical vector representations used in natural language processing.
Recursive Newton–Euler algorithm
The recursive Newton–Euler algorithm (RNEA) computes a robot's inverse dynamics: given joint positions, velocities, and accelerations, it calculates the required joint forces and torques in linear time.
Recursive reward modeling
Recursive reward modeling (RRM) is an AI alignment method proposed by Jan Leike and colleagues at DeepMind in 2018, in which AI agents help humans evaluate more capable agents.
Recursive self-improvement
Recursive self-improvement, also known as Seed AI, is a proposed capability in which an AI autonomously designs and develops its own successor; it has not yet been achieved.
Recursive Superintelligence
Recursive Superintelligence, branded Recursive, is a frontier AI startup in San Francisco and London founded by Richard Socher, launched in May 2026 with $650 million in funding.
Recycled aluminium
Recycled aluminum, also called secondary aluminum, is aluminum recovered from scrap and remelted, using about 5% of the energy of producing it from bauxite ore.
Recycling
Recycling is the reprocessing of waste materials into new products or substances, from composting to metals and plastics, with the US recycling about 32% of its municipal waste in 2018.
Recycling codes
Recycling codes, also called recycling numbers, are the numbered triangle marks on plastics, developed in 1988, that identify the resin a plastic item is made of rather than its recyclability.
Red Adair
Red Adair, born Paul Neal Adair, was a Texan oil well firefighter who pioneered techniques and equipment for controlling oil and gas well fires, notably in Kuwait in 1991.
Red Arrows
The Red Arrows, officially the Royal Air Force Aerobatic Team, are the RAF's aerobatic display team, flying red, white and blue Hawk T1 jets since 1965.
Red Beard (nuclear weapon)
Red Beard was the first British tactical nuclear weapon, an unboosted fission gravity bomb carried by RAF and Royal Navy aircraft from about 1960 to the early 1970s.
Red Bull Ford V6 hybrid Formula One power unit
The Red Bull Ford V6 hybrid Formula One power unit, named DM01, is a 1.6-liter turbocharged V6 hybrid built by Red Bull Powertrains with Ford for the 2026 season.
Red Bull Racing RB20
The Red Bull Racing RB20 is the Formula 1 car with which Red Bull Racing competed in the 2024 season, winning 9 races and the drivers' title with Max Verstappen.
Red Bull Racing RB21
The Red Bull Racing RB21 is the Formula 1 car Oracle Red Bull Racing used in 2025, carrying Max Verstappen to second in the drivers' championship.
Red Bull Racing RB22
The Red Bull Racing RB22 is a Formula One car built by Red Bull Racing for the 2026 season, powered by its own DM01 engine and driven by Max Verstappen and Isack Hadjar.
Red Bull RB17
The Red Bull RB17 is a track-only, two-seat hypercar designed by Adrian Newey and built by Red Bull Advanced Technologies, revealed in 2024 with a Cosworth V10 hybrid.
Red Bull Stratos
Red Bull Stratos was a privately funded program whose Austrian skydiver Felix Baumgartner jumped from a balloon at 38,969 meters in 2012, breaking the sound barrier in freefall.
Red dot sight
A red dot sight, also called a red dot reflex sight, is a non-magnifying firearm sight superimposing an illuminated LED dot on the target; the first commercial model launched in 1975.
Red Eléctrica de España
Red Eléctrica de España (REE) is the sole transmission system operator of Spain, running the national high-voltage grid since 1985 as the first company in the world dedicated exclusively to electricity transmission.
Red Fort
The Red Fort, or Lal Qila, is a 17th-century Mughal palace fortress in Old Delhi built by Shah Jahan, completed in 1648 and a UNESCO World Heritage Site since 2007.