Technology and the built world

Direct detection (optical communications)

Direct detection in optical communications is a receiver technique in which a photodiode converts received optical power straight into electrical current, measuring only the light's intensity.

Direct distance dialing

Direct distance dialing is a North American telephone service feature letting callers dial long-distance numbers, such as area codes, without operator assistance, introduced by the Bell System in 1951.

Direct download link

A direct download link is a URL that delivers a file to the device for saving rather than displaying a hosted page, also known as a DD link.

Oct 22, 2026

Direct energy conversion of field-reversed configuration exhaust

Direct energy conversion of field-reversed configuration exhaust turns the energy of an expanding FRC fusion plasma directly into electricity by electromagnetic induction, without a steam cycle.

Oct 22, 2026

Direct formic acid fuel cell

A direct formic acid fuel cell is a fuel cell that converts liquid formic acid directly into electricity, studied since the early 2000s for portable power.

Direct impingement

Direct impingement is a gas operation for self-loading firearms in which propellant gas cycles the action directly, without a piston; it is best known from the AR-15.

Direct injection

Direct injection is an engine fuel-delivery method that sprays fuel directly into the combustion chamber, used in both diesel engines and, as gasoline direct injection, in spark-ignited cars.

Oct 22, 2026

Direct ink writing of liquid crystal elastomers

Direct ink writing of liquid crystal elastomers is an extrusion-based 3D printing method in which shear aligns the ink during extrusion, so the printed path programs molecular orientation and actuation.

Direct kinematics of parallel manipulators

Direct kinematics of parallel manipulators, also known as forward kinematics, computes a platform's position and orientation from actuator leg lengths; the general six-degree-of-freedom problem has up to 40 solutions.

Direct laser deposition

Direct laser deposition, also called laser directed energy deposition, is an additive manufacturing method that melts metal powder or wire to build parts layer by layer.

Direct laser interference patterning

Direct laser interference patterning (DLIP) is a laser surface texturing method that splits one beam into coherent sub-beams, structuring surfaces at interference maxima without photoresist.

Direct liquefaction of biomass

Direct liquefaction of biomass is the family of thermochemical processes that turn biomass directly into biocrude, mainly by fast pyrolysis and hydrothermal liquefaction, then upgrade it to fuels.

Direct lithium extraction

Direct lithium extraction (DLE) is a family of chemical processes that extracts lithium from brines without solar evaporation, cutting brine-to-carbonate time from about a year to around a day.

Direct memory access

Direct memory access (DMA) is a transfer strategy in which hardware moves data to or from memory without using the processor, freeing it for other tasks.

Direct metal deposition

Direct metal deposition (DMD) is a laser-based additive manufacturing process that melts powder or wire to build parts layer by layer and repair existing components.

Direct metal laser sintering

Direct metal laser sintering (DMLS) is an additive manufacturing process that uses a laser to fuse thin layers of metal powder into dense parts from CAD data.

Direct multiple shooting

Direct multiple shooting, also called parallel shooting, is an optimal control transcription method that divides the trajectory into segments tied by continuity constraints and solved as one nonlinear program.

Direct normal irradiance

Direct normal irradiance (DNI), also called beam radiation, is the rate at which direct sunlight reaches a surface perpendicular to the Sun's beam, measured in watts per square meter.

Direct part marking

Direct part marking (DPM) physically alters a part's surface to form a machine-readable Data Matrix symbol, using methods such as dot peen, laser marking, or etching.

Direct potable reuse

Direct potable reuse is the introduction of highly treated reclaimed wastewater directly into a drinking water system without an environmental buffer, pioneered in Windhoek, Namibia, in 1968.

Direct preference optimization

Direct preference optimization (DPO) is a method for aligning large language models, introduced by Rafael Rafailov and colleagues in 2023 and used in Llama 3 and Qwen2.

Direct recycling

Direct recycling is a lithium-ion battery recycling method that recovers and regenerates cathode material intact, preserving its crystal structure and avoiding energy-intensive metal extraction and resynthesis.

Direct reduced iron

Direct reduced iron, also called sponge iron or hot-briquetted iron when compacted, is metallic iron made by removing oxygen from iron ore in the solid state without melting.

Direct Rendering Manager

The Direct Rendering Manager (DRM) is the Linux kernel subsystem that coordinates access to graphics hardware, letting multiple 3D applications, a display server, and the kernel share one GPU safely.

Direct shear test

The direct shear test is a laboratory test that measures the shear strength of soil or rock by sliding one half of a specimen past the other.

Direct Sparse Odometry

Direct Sparse Odometry (DSO) is a visual odometry method that estimates camera motion by directly minimizing photometric error, proposed by Engel, Koltun, and Cremers in 2016.

Direct steam generation

Direct steam generation (DSG) is a concentrating solar power technology that produces steam directly in collector receiver tubes, removing the oil loop and heat exchangers for higher efficiency and simpler plants.

Direct stiffness method

The direct stiffness method is a matrix-based structural analysis technique that assembles element stiffness relations into global equations, the basis of most finite element software.

Direct Stream Digital

Direct Stream Digital (DSD) is a one-bit audio encoding method developed by Sony and Philips for the Super Audio CD, standardized in the 1999 Scarlet Book.