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Hie Shrine
Hie Shrine (日枝神社, Hie-jinja) is a major Shinto shrine in Nagatacho, Tokyo, founded in 1478 as the guardian shrine of Edo Castle and known for its Sanno Matsuri.
Hierarchical and recursive queries in SQL
Hierarchical and recursive queries in SQL are queries that traverse tree or graph data in relational tables, using recursive CTEs from SQL:1999 or Oracle's CONNECT BY.
Hierarchical clustering
Hierarchical clustering, also known as agglomerative clustering, is a family of cluster analysis methods that merge or split clusters to build a nested hierarchy shown as a dendrogram.
Hierarchical Data Format
Hierarchical Data Format (HDF) is a set of file formats and libraries for storing large scientific datasets, created at NCSA in 1987 and best known through its successor HDF5, implemented in 1998.
Hierarchical database model
The hierarchical database model is a data model that organizes records as a tree, enforcing one-to-many relationships, and formed the basis of IBM's IMS, released in 1968.
Hierarchical federated learning
Hierarchical federated learning (HFL) is a distributed machine learning method in which model updates are aggregated at edge servers between clients and the cloud, cutting communication.
Hierarchical modulation
Hierarchical modulation, also called layered modulation, is a transmission technique that superimposes two data streams of different priority on a single carrier, protecting one better against noise.
Hierarchical navigable small world
Hierarchical navigable small world (HNSW) is a fully graph-based index for approximate nearest-neighbor search, introduced by Yu. A. Malkov and D. A. Yashunin in a 2018 IEEE paper.
Hierarchical reinforcement learning
Hierarchical reinforcement learning (HRL) structures an agent into layers of policies or subgoals so complex tasks decompose into reusable subtasks, using frameworks such as options, MAXQ, and HAMs.
Hierarchical routing
Hierarchical routing is a network routing approach that organizes routers into levels or regions so each keeps detailed state only for its own region, letting large networks scale.
Hierarchy of hazard controls
The hierarchy of hazard controls, or hierarchy of controls, ranks workplace safeguards from most to least effective: elimination, substitution, engineering controls, administrative controls, and PPE.
HIF Global
HIF Global (Highly Innovative Fuels) is a multinational e-fuels developer, structured as a US holding company originated in Chile, operating the first e-fuels plant, Haru Oni, in Punta Arenas.
HIFI (Herschel instrument)
HIFI, the Heterodyne Instrument for the Far Infrared, was a spectrometer aboard the European Space Agency's Herschel Space Observatory, covering 480 to 1910 GHz and identifying individual molecules in space.
HiFi-GAN
HiFi-GAN is a generative adversarial network vocoder introduced in 2020 by Jungil Kong and colleagues at Kakao Enterprise, converting mel-spectrograms into speech waveforms at high quality and speed.
Higashi Niigata LNG Terminal
The Higashi Niigata LNG Terminal is an LNG import terminal in Seiro, Niigata Prefecture, Japan, opened in 1984 and serving the Higashi Niigata Thermal Power Station.
Higashi Niigata thermal power station
Higashi Niigata thermal power station (東新潟火力発電所) is an LNG-fired power station of Tohoku Electric Power in Seiro Town, Niigata Prefecture, Japan, with a capacity of about 4,160 MW.
Higashi Ohgishima LNG Terminal
Higashi Ohgishima LNG Terminal (東扇島LNG基地) is an LNG import terminal in Kawasaki, Japan, on Tokyo Bay, opened in 1984 to supply TEPCO's Higashi-Ohgishima Thermal Power Station with an import capacity of 13.2 Mtpa.
Higashi-Ohgishima thermal power station
Higashi-Ohgishima thermal power station (東扇島火力発電所) is a 2,000 MW liquefied natural gas-fired power station in Kawasaki, Japan, owned and operated by JERA and supplying the Tokyo-area grid.
Higgins Armory Museum
The Higgins Armory Museum was a museum in Worcester, Massachusetts, devoted to arms and armor; for most of its life it was the only such museum in the United States.
Higgs Audio
Higgs Audio is a family of open audio-language models released by Boson AI in 2025, combining audio understanding and expressive speech generation, with version 3 following in 2026.
Higgsfield
Higgsfield is a subscription-based AI video and image creation platform launched in 2025, offering cinematic camera control and models like Sora and Veo under one subscription.
Higgsfield AI
Higgsfield AI is a San Francisco startup founded in 2023 by Alex Mashrabov, formerly of Snap, offering an application-layer platform for AI video and image generation.
High Average Power Laser program
The High Average Power Laser program (HAPL) was a United States multi-institution research program, managed at the Naval Research Laboratory, that developed laser-driven inertial fusion energy from 1999 to 2008.
High Bandwidth Memory
High Bandwidth Memory (HBM) is a type of computer memory in which stacked DRAM dies deliver very high bandwidth, the dominant memory in AI accelerators and HPC systems.
High Definition Compatible Digital
High Definition Compatible Digital (HDCD) is a proprietary process that improves 16-bit CD sound while remaining playable on any standard CD player, developed by Keith Johnson and Michael Pflaumer.
High Earth orbit
High Earth orbit (HEO) is defined as an orbit around Earth above 35,786 kilometers or 2,000 kilometers. It covers geostationary and highly elliptical orbits used for communications and astronomy.
High Efficiency Image File Format
High Efficiency Image File Format (HEIF) is an ISO standard container for storing images and image sequences with metadata, best known through its HEIC variant.
High Efficiency Video Coding
High Efficiency Video Coding (HEVC), also known as MPEG-H Part 2 and ITU-T H.265, is a video compression standard that cuts bitrate about 50 percent versus H.264.
High fidelity
High fidelity, often shortened to hi-fi, is the faithful reproduction of recorded music through wide frequency response, wide dynamic range, low noise, and minimal distortion; it boomed after World War II.
High Flux Reactor
The High Flux Reactor (HFR) is a 45 MW materials-testing research reactor in Petten, Netherlands, operated by NRG and supplying about 65 percent of European medical isotope demand.