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Prototype Fast Breeder Reactor
The Prototype Fast Breeder Reactor (PFBR) is a 500 MWe sodium-cooled fast breeder reactor at Kalpakkam, Tamil Nadu, India, designed by IGCAR and built by BHAVINI.
Prototype Fast Reactor
The Prototype Fast Reactor (PFR) was a sodium-cooled fast reactor at Dounreay, Scotland, built by the UK Atomic Energy Authority and operated from 1974 to 1994.
Prototype filter
A prototype filter is a normalized low-pass filter with a 1 rad/s corner frequency and 1 Ω impedances, serving as the template for deriving practical low-pass, high-pass, band-pass, and band-stop filters.
Prototype-based programming
Prototype-based programming is a style of object-oriented programming in which objects reuse behavior by delegating to prototype objects instead of classes, as in JavaScript and Self.
Prototypical network
A prototypical network is a metric-based few-shot learning method that classifies examples by comparing their embeddings to one prototype per class, introduced by Snell, Swersky, and Zemel at NIPS 2017.
Prototypical networks
Prototypical networks are a metric-based meta-learning method for few-shot classification, introduced by Jake Snell, Kevin Swersky, and Richard Zemel at NIPS 2017, which classifies queries by distance to class prototypes.
Protura
Protura is a six-degrees-of-freedom robotic patient positioning couch used in radiotherapy, made by CIVCO Radiotherapy of Coralville, Iowa, that moves and rotates patients on a linear accelerator with sub-millimeter precision.
PROV-O
PROV-O, the PROV Ontology, is a W3C Recommendation published in 2013 that expresses provenance, the documented history of how entities were produced, as an OWL ontology.
Proved reserves
Proved reserves are oil and gas quantities demonstrated with reasonable certainty to be commercially recoverable from known reservoirs, the most conservative tier of petroleum reserve classification.
Provincial Electricity Authority
The Provincial Electricity Authority (การไฟฟ้าส่วนภูมิภาค; PEA) is a Thai state enterprise, established in 1960, that buys bulk electricity and distributes it to over 20 million customers across 74 of Thailand's 77 provinces.
Provisional Measure No. 1,340
Provisional Measure No. 1,340 (Medida Provisória nº 1.340) was a 2026 Brazilian measure subsidizing road diesel at R$ 0.32 per liter; it lapsed in July 2026.
Proxemics in robotics
Proxemics in robotics is the application of proxemics, the study of how humans use space, to human-robot interaction, defining comfortable approach distances for social robots.
Proxima (film)
Proxima is a 2019 French-German drama directed by Alice Winocour, starring Eva Green as astronaut Sarah Loreau, a single mother training with ESA for a year-long ISS mission; filmed at real ESA, Star City, and Baikonur facilities; San Sebastián Special Jury Prize winner.
Proxima Fusion
Proxima Fusion is a Munich-based fusion startup founded in 2023 as the first spin-out of the Max Planck Institute for Plasma Physics, developing stellarator power plants.
Proximal gradient method
The proximal gradient method, also known as proximal gradient methods, is a first-order algorithm minimizing smooth plus nonsmooth objectives, popularized as ISTA for l1-regularized problems.
Proximal point algorithm
The proximal point algorithm, or proximal point method, is an iterative optimization method that repeatedly minimizes a convex objective plus a quadratic penalty centered at the current iterate.
Proximal Policy Optimization
Proximal Policy Optimization (PPO) is a family of reinforcement learning algorithms introduced at OpenAI in 2017, later the training engine of RLHF pipelines behind ChatGPT.
Proximity operations
Proximity operations, usually paired with rendezvous as RPO, are spacecraft maneuvers in which one vehicle flies near another space object to observe, inspect, service, or capture it.
Proximity Query Package
The Proximity Query Package (PQP) is a C++ library for collision detection, distance computation, and tolerance verification on triangle meshes, written at UNC Chapel Hill and released in 1999.
Proximus
Proximus is Belgium's largest telecommunications company, headquartered in Brussels and listed on Euronext Brussels. It descends from the state operator RTT, became Belgacom in 1992, and took the Proximus name in 2015.
Proximus Group
Proximus Group, known as Belgacom until its 2015 renaming, is a Belgian telecommunications and digital services company headquartered in Brussels that operates fixed, mobile, and ICT services in Belgium and Luxembourg.
Proxmox Virtual Environment
Proxmox Virtual Environment, known as Proxmox VE, is an open-source server virtualization platform from Vienna, Austria, combining KVM virtual machines and LXC containers under a single web-based interface.
Proxy auto-config
A PAC file, or Proxy.pac, is a JavaScript function named FindProxyForURL that a web browser evaluates for each request to decide whether traffic goes direct or through a proxy server.
Proxy list
A proxy list is a published set of proxy server addresses, written as IP:port, that clients configure so requests appear to come from the proxy.
Proxy pattern
The proxy pattern, or proxy design pattern, is a structural design pattern in which a proxy object controls access to another object with the same interface.
Proxy re-encryption
Proxy re-encryption is a public-key encryption scheme in which a semi-trusted proxy, using a re-encryption key, retargets ciphertexts to new recipients without learning the plaintext.
Proxy server
A proxy server, also called an Internet proxy, is an intermediary between a client and a destination server that forwards, modifies, blocks, or answers requests itself.
PRQL
PRQL (Pipelined Relational Query Language, "Prequel") is an open-source pipelined query language that compiles to SQL for any database. Launched January 2022 by Maximilian Roos; Rust compiler prqlc; 10.9k GitHub stars; 0.13.14 (2026).
PrSM
The Precision Strike Missile (PrSM) is a Lockheed Martin surface-to-surface guided missile for the US Army, replacing ATACMS with a range of up to 499 kilometers.
Prudhoe Bay Oil Field
Prudhoe Bay Oil Field is a giant oil field on Alaska's Arctic coast, discovered in 1968 by ARCO and Humble Oil; it is the largest oil field in North America.