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UVAbbrev. for ultraviolet.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
UltraViolet(1) See ultraviolet light.
(2) A cloud-based storage locker for licensed content from the Digital Entertainment Content Ecosystem (see DECE). Under the Digital HD brand, purchases of Blu-ray discs with redeemable coupons and purchases of movies and TV shows (not rental) from participating online retailers entitles users to keep their content in the UltraViolet cloud and stream or download it as required.
Depending on the retailer's agreement, content might be sharable with friends and family, and parental access can be applied. A physical disc may also be obtainable. See Digital HD, Blu-ray Combo Pack and media locker.
ultraviolet lightAn invisible band of radiation at the upper end of the visible light spectrum. With wavelengths from 10 to 400 nm, ultraviolet (UV) starts at the end of visible light and ends at the beginning of X-rays. The primary source of ultraviolet light is the sun, and most of the UV that reaches earth is in the lower-frequency, longer-wavelength Ultraviolet "A" region (see below).
Although ultraviolet (UV) light is widely known as a disinfectant, it was also used to erase EPROM chips. After several minutes of exposure to UV light, the chip could be programmed again (see EPROM).
Ultraviolet for Chip Making
For a long time, chip lithography, which exposes the silicon to a pattern of light, has been using 193 nm far ultraviolet (FUV) as the source. However, because light cannot create a pattern smaller than its own wavelength, several photomasks are used, and complex chips require dozens of lithography steps.
After 10 nm process technology came into production, extreme ultraviolet (EUV) in the 13.5 nm range is considered the next-generation light source because its wavelength is closer to the feature size (see process technology).
Wavelength inUltraviolet Region Nanometers (nm) Long Wave "A" UVA 315-400 Medium Wave "B" UVB 280-315 Short Wave "C" UVC 100-280 Near NUV 300-400 Middle MUV 200-300 Far FUV 122-200 Vacuum VUV 10-200 Extreme EUV 10-121 Deep DUV Below 300
|Ultraviolet in the Spectrum|
|The ultraviolet band comes after visible light and ends at the beginning of X-rays.|
unique visitorsA count of how many different people access a website. For example, if a user leaves and comes back to the site five times during the measurement period, that person is counted as one unique visitor, but would count as five "user sessions."
Unique visitors are determined by the number of unique IP addresses on incoming requests that a site receives, but this can never be 100% accurate. Depending on configuration issues and type of ISP service, in some cases, one IP address can represent many users; in other cases, several IP addresses can be from the same user.
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