All articles starting with U
6,146 articles
Unscented Kalman filter
The unscented Kalman filter (UKF) is a derivative-free state-estimation algorithm for nonlinear dynamic systems that propagates a small set of sample points to approximate the state's mean and covariance.
Unschooling
Unschooling, also called natural learning or child-led home education, is homeschooling without an imposed curriculum, coined by John Holt in the 1970s; children learn through living, parents facilitate, and it is legally treated as homeschooling worldwide.
UNSCOM and UNMOVIC
UNSCOM and UNMOVIC were the United Nations commissions that verified the elimination of Iraq's weapons of mass destruction between 1991 and 2007 under Resolution 687.
Unseen character
Unseen character: also called absent or offstage character, a story figure who never appears to the audience but advances the plot, exemplified by Godot, Harvey, and Mr. Wingfield.
Unseen Warfare
Unseen Warfare (Ὁ Ἀόρατος Πόλεμος, Невидимая брань) is an Orthodox ascetic manual on the inner battle against the passions, drawn from Lorenzo Scupoli's 1589 Spiritual Combat.
Unshatter
"Unshatter" is a song by American rock band Linkin Park, released as a single on April 25, 2025 and included on the deluxe edition of their album From Zero.
Unshatter Film Soundtrack (Live in São Paulo)
Unshatter Film Soundtrack (Live in São Paulo) is Linkin Park's 2026 Warner Records live album, recorded November 2024 at Allianz Parque, São Paulo, companion to the Joe Hahn documentary Unshatter; 20 tracks, 65:27, released September 25, 2026.
Unshō Ishizuka (石塚運昇)
Unshō Ishizuka (石塚運昇) was a Japanese voice actor, narrator, and stage actor (1951–2018), Professor Oak in Pokémon and Jet Black in Cowboy Bebop; also dub voice of Liam Neeson and Kizaru in One Piece.
Unsi al-Haj
Unsi al-Haj (أنسي الحاج; 1937–2014) was a Lebanese poet and journalist, a pioneer of the Arabic prose poem whose first collection, Lan, appeared in 1960, and a leading contributor to the modernist magazine Shi'r.
Unsimulated sex
Unsimulated sex in film: real, non-imitated sex acts performed on screen in fiction and art cinema, from Warhol's Blue Movie and Gift (1966) to Romance, Intimacy, and Baise-Moi, governed by boards like the BBFC and now largely replaced by simulated scenes with intimacy coordinators.
Unsinkable (film)
Unsinkable, also titled Unsinkable: Titanic Untold, is a 2024 American historical drama directed by Cody Hartman about Senator William Alden Smith's inquiry into the Titanic sinking, starring Cotter Smith, Fiona Dourif, Karen Allen, and Jayne Wisener; distinct from the 2022 Irish documentary and 2023 Danish film of the same name.
Unsinkable Sam
Unsinkable Sam, also known as Oscar, was a ship's cat who, by a widely repeated Second World War story, survived the sinkings of three ships in 1941.
Unsloth
Unsloth is an open-source fine-tuning and quantization toolkit for large language models, released in 2023 by Daniel and Michael Han and reported to train about 2x faster.
Unsloth dynamic GGUF quants
Unsloth dynamic GGUF quants are offline, per-layer quantization recipes introduced by the Unsloth team in 2024 that assign different bit-widths to different tensors of open-weight models before GGUF export.
Unsolved Mysteries
Unsolved Mysteries is an American documentary TV series created by John Cosgrove and Terry Dunn Meurer, premiering on NBC in January 1987 with hosts Raymond Burr, Karl Malden, and Robert Stack; over 260 cases were solved through viewer tips, and Netflix revived it in 2020.
Unsolved problems in medicine
Unsolved problems in medicine: chronic disease causation (metaflammation), hidden infectious causes, Long COVID and ME/CFS, diagnostic error, personalized-medicine forecasting limits, antimicrobial resistance, and reproducibility, with key quantities from CDC, WHO, NIH, and journal sources.
Unsound Festival
Unsound Festival is an annual festival of experimental and avant-garde electronic music held each October in Kraków, Poland, founded in 2003, with satellite editions in New York, London, and other cities.
Unspeakable (YouTuber)
Unspeakable, also known as Nathan Johnson Graham, is an American YouTuber who built a family-friendly entertainment brand. He is known for his Minecraft gameplay and high-energy challenge videos.
Unspeakable Sins
Unspeakable Sins (Pecados inconfesables) is a 2025 Mexican Netflix telenovela-thriller, 18 episodes, created by Leticia López Margalli and Guillermo Ríos, starring Zuria Vega, Andrés Baida, and Erik Hayser in a blackmail plot gone wrong.
Unsplash
Unsplash: free stock-photo platform founded 2013 as a Tumblr blog, acquired by Getty Images in 2021. Unsplash License permits commercial use without attribution; paid Unsplash+ tier launched 2022.
Unsportsmanlike conduct
Unsportsmanlike conduct is a category of rule violations in sports covering taunting, violent or obscene gestures, abuse of officials, and unfair behavior, penalized by yardage, technical fouls, cards, ejections or fines across leagues such as the NFL, NCAA, NBA, IIHF, and IFAB.
Unstable
Unstable is a Netflix workplace comedy (2023-2024) co-created by and starring Rob Lowe and John Owen Lowe with Victor Fresco; Rob plays biotech CEO Ellis Dragon, John Owen his son Jackson, over two eight-episode seasons before cancellation.
Unstable angina
Unstable angina (also accelerating or crescendo angina): sudden chest pain at rest from transient myocardial ischemia with plaque rupture and thrombosis but no troponin rise; an ACS emergency treated with antiplatelets, anticoagulation, and revascularization, carrying lower mortality than NSTEMI but similar future MI risk.
Unstable beta globin chain variant disease
Unstable beta globin chain variant disease, also called dominant or inclusion body beta-thalassemia (ORPHA:231226), is a rare autosomal dominant hemolytic anemia caused by HBB mutations producing hyperunstable beta-globin that precipitates as Heinz bodies, causing ineffective erythropoiesis.
Unstable psoriasis
Unstable psoriasis is an inflammatory form of psoriasis marked by intense inflammation at plaque margins and new small papules, potentially preceding erythrodermic or pustular psoriasis.
Unstan Chambered Cairn
Unstan Chambered Cairn (Knowe of Onston), a 5,000-year-old Neolithic hybrid stalled/Maeshowe-type burial cairn by the Loch of Stenness, Orkney; excavated 1884 by Clouston, type site of Unstan Ware pottery.
Unstoppable
Unstoppable with NBK is a 2021 Indian Telugu-language celebrity talk show streaming on Aha, hosted by Nandamuri Balakrishna, with four seasons and 35 episodes as of January 2025.
Unstoppable (2010 film)
Unstoppable is a 2010 American action thriller directed by Tony Scott, starring Denzel Washington and Chris Pine as railroad workers stopping a runaway toxic freight train.
Unstoppable (2024 film)
Unstoppable (2024) is William Goldenberg's biographical sports drama about one-legged NCAA wrestling champion Anthony Robles, starring Jharrel Jerome and Jennifer Lopez, released by Amazon MGM on Prime Video January 16, 2025.
Unstoppable (Sia song)
Unstoppable: 2016 Sia song co-written with Christopher Braide, produced by Jesse Shatkin for This Is Acting; a 2022 TikTok-driven revival took it to US No. 28 and over 2 billion Spotify streams.