Technology and the built world

Spillway

A spillway, or overflow channel, is a structure at or beside a dam that releases excess reservoir water so the dam is never overtopped and eroded.

Spillway bridge

A spillway bridge is a bridge deck carried on or across a dam spillway crest or gate structure, providing roadway access, gate-hoist support, and operator access over the flow surface.

Spillway hydraulics and safety

Spillway hydraulics and safety is the engineering analysis of whether a dam's spillway and outlet works can pass extreme floods without overtopping the dam or failing.

Spin (aerodynamics)

A spin, also called a tailspin, is an aggravated stall in which an airplane descends in a corkscrew path while rotating, with at least one wing stalled.

SPIN (Self-Play Fine-Tuning)

SPIN (Self-Play fIne-tuNing) is a post-training method for large language models, introduced at UCLA in 2024, that improves a model using its own generated responses.

Sep 29, 2026

Spin coating

Spin coating is a thin-film deposition technique in which a liquid on a rapidly spinning substrate spreads into a thin, uniform layer, used for photoresists and solar cells.

Spin Hall nano-oscillator

A spin Hall nano-oscillator (SHNO) is a nanoscale spintronic device in which spin Hall effect spin currents drive magnetic precession, generating tunable microwave signals for neuromorphic computing.

Spin image

A spin image is a 3D surface shape descriptor, a 2D histogram around an oriented point introduced by Johnson and Hebert at Carnegie Mellon in 1999.

Spin recovery

Spin recovery is the set of control actions a pilot uses to return an airplane to normal flight after a spin, stopping rotation and reducing the angle of attack below stall.

Spin stabilization

Spin stabilization is a passive spacecraft attitude-control technique in which the whole vehicle spins, so its angular momentum stays fixed and gyroscopic stiffness resists disturbance torques.

Spin-orbit torque

Spin-orbit torque (SOT) is a physical effect in which current flowing through a heavy metal exerts torque on an adjacent ferromagnet, switching its magnetization direction.

Spin-torque oscillator

A spin-torque oscillator (STO) is a nanoscale device that generates microwave signals, used in hard disk drive write heads to lower the field needed to record data.

Spin-wave majority gate

A spin-wave majority gate is a spintronic logic device whose output, set by spin-wave interference, returns the majority of input phases; first demonstrated experimentally in 2017 in a YIG waveguide.

Spindletop

Spindletop, an oil field south of Beaumont, Texas, marked the birth of the modern petroleum industry when the Lucas Gusher blew in on January 10, 1901.

SpinLaunch is a California-based space company founded in 2014 that uses a large electric centrifuge in a vacuum chamber to launch projectiles, with suborbital test flights from Spaceport America in New Mexico since 2021.

Spinlock

A spinlock is a mutual exclusion lock where a waiting thread busy-waits by repeatedly checking the lock, efficient for critical sections shorter than a context switch.

Spinnaker

A spinnaker is a large, light, three-cornered downwind sail set flying from the masthead on a sailing yacht, in symmetric and asymmetric types, first recorded in 1866.

Spinner (robot)

Spinner is an unmanned ground combat vehicle prototype developed for DARPA by Carnegie Mellon University's NREC with Boeing, known for driving while upside down and serving as the base for its successor, Crusher.

Spinning (textiles)

Spinning, also known as hand spinning or wool spinning, is the textile process of converting staple fiber into yarn by drawing and twisting it; ring spinning has dominated since the early 1800s.

Spinning reserve

Spinning reserve is the portion of operating reserve from generators already synchronized to the grid and running below full output, able to increase production within about 10 minutes.

Spinning Up in Deep RL

Spinning Up in Deep RL is an educational resource released by OpenAI in 2018, combining RL theory, a reading list, and minimal implementations of six core algorithms.

Spintronic artificial neurons

Spintronic artificial neurons are nanoscale magnetic devices, typically magnetic tunnel junctions, that reproduce the integrating and spiking behavior of biological neurons for low-power neuromorphic computing.

Spiral antenna

A spiral antenna is a wideband, frequency-independent antenna with conductive arms wound in a spiral, radiating circularly polarized waves; it is used in direction finding, electronic warfare, and GPS.

Spiral bevel gear

A spiral bevel gear is a bevel gear with curved, oblique teeth that transmit power between intersecting shafts, most often at 90 degrees, more smoothly than straight bevel gears.

Spiral model

The spiral model, or Boehm spiral, is a risk-driven software development process model described by Barry Boehm of TRW in 1988, best suited to large, high-risk projects.

Spiral phase plate

A spiral phase plate is a transparent optical element whose thickness varies with angle, twisting a laser beam into a vortex beam that carries orbital angular momentum.

Spiral search

Spiral search is a blind robotic strategy for peg-in-hole assembly in which a peg winds outward in a spiral, pressing down until it drops into the hole.

Spiral staircase

A spiral staircase is a stair whose wedge-shaped treads wind in a helix around a central column, letting the flight climb in a tight circular footprint; a helical stair winds around a central void instead.

Spire

A spire is a tall, slender, pointed structure that crowns a tower or roof, most often on a church, and is especially prominent in Gothic architecture.