Clutter (radar) — Clutter is a term used for unwanted echoes in electronic systems, particularly in reference to radars. Such echoes are typically returned from ground, sea, rain, animals/insects, chaff and atmospheric turbulences, and can cause serious… … Wikipedia
David L. Fried — is a scientist, best known for his contributions to optics. Fried described what has come to be known as Fried s seeing diameter, or r0 (usually pronounced r naught). The seeing diameter is effectively a limiting aperture due to atmospheric… … Wikipedia
Convoy PQ 17 — Part of World War II, Atlantic Campaign Escorts and merchant ships at Hv … Wikipedia
Eyepiece — For the device for looking through a camera, see viewfinder. A collection of different types of eyepieces. An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is… … Wikipedia
dating — I In geology and archaeology, the process of determining an object s or event s place within a chronological scheme. Scientists may use either relative dating, in which items are sequenced on the basis of stratigraphic clues (see stratigraphy) or … Universalium
photography, technology of — Introduction equipment, techniques, and processes used in the production of photographs. The most widely used photographic process is the black and white negative–positive system (Figure 1 >). In the camera the lens projects an image of… … Universalium
TV and FM DX — TV DX and FM DX is the active search for distant radio or television stations received during unusual atmospheric conditions. The term DX is an old telegraphic term meaning long distance. VHF/UHF television and radio signals are normally limited… … Wikipedia
Transmission electron microscopy — A TEM image of the polio virus. The polio virus is 30 nm in size.[1] Transmission electron microscopy (TEM) is a microscopy technique whereby a beam of electrons is transmitted through an ultra thin specimen, interacting with the specimen as it… … Wikipedia
Redshift — This article is about the astronomical phenomenon. For other uses, see Redshift (disambiguation). Physical cosmology … Wikipedia
Positron emission tomography — (PET) is a nuclear medicine imaging technique which produces a three dimensional image or map of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron emitting radionuclide (tracer), which is… … Wikipedia
Revised Julian calendar — The Revised Julian calendar, also known as the Rectified Julian calendar, or, less formally, New calendar, is a calendar, originated in 1923, which effectively discontinued the 340 years of divergence between the naming of dates sanctioned by… … Wikipedia