| slovo | definícia |
spectrum
(encz) | spectrum,spektrum Pavel Machek; Giza |
Spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
spectrum
(wn) | spectrum
n 1: an ordered array of the components of an emission or wave
2: a broad range of related objects or values or qualities or
ideas or activities |
spectrum
(foldoc) | ZX Spectrum
Spectrum
Sinclair's first personal computer with a colour
display. The Spectrum used the Zilog Z80 processor like its
predecessors the ZX-80 and ZX-81. It was originally
available in 16k and 48k versions using cassette tape and
later grew to 128k and sprouted floppy disks. It had a
wider and more solid case and a marginally better "dead flesh"
keyboard. Unlike the earlier models, it didn't require the
presence of a cold carton of milk to prevent it overheating.
It was possibly the most popular home computer in the UK for
many years.
The TK-90X was a clone.
(1995-11-04)
|
| | podobné slovo | definícia |
broad-spectrum
(encz) | broad-spectrum,široké spektrum Zdeněk Brož |
color spectrum
(encz) | color spectrum, n: |
electromagnetic spectrum
(encz) | electromagnetic spectrum, n: |
emission spectrum
(encz) | emission spectrum, n: |
infrared spectrum
(encz) | infrared spectrum, n: |
line spectrum
(encz) | line spectrum, n: |
mass spectrum
(encz) | mass spectrum, n: |
microwave spectrum
(encz) | microwave spectrum, n: |
radio spectrum
(encz) | radio spectrum, n: |
radio-frequency spectrum
(encz) | radio-frequency spectrum, n: |
sound spectrum
(encz) | sound spectrum, n: |
spectrum analysis
(encz) | spectrum analysis, n: |
spectrum line
(encz) | spectrum line, n: |
speech spectrum
(encz) | speech spectrum, n: |
ultraviolet spectrum
(encz) | ultraviolet spectrum, n: |
visible spectrum
(encz) | visible spectrum, n: |
x-ray spectrum
(encz) | x-ray spectrum,rentgenové spektrum n: [tech.] mammx-ray spectrum,spektrum rentgenového záření n: [tech.] mamm |
Absorption spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
Chemical spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
Chromatic spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
Continous spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
Diffraction spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster]Diffraction \Dif*frac"tion\, n. [Cf. F. diffraction.] (Opt.)
The deflection and decomposition of light in passing by the
edges of opaque bodies or through narrow slits, causing the
appearance of parallel bands or fringes of prismatic colors,
as by the action of a grating of fine lines or bars.
[1913 Webster]
Remarked by Grimaldi (1665), and referred by him to a
property of light which he called diffraction.
--Whewell.
[1913 Webster]
Diffraction grating. (Optics) See under Grating.
Diffraction spectrum. (Optics) See under Spectrum.
[1913 Webster] |
Gaseous spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
Normal spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
Ocular spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
ocular spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
Prismatic spectrum
(gcide) | Prismatic \Pris*mat"ic\, Prismatical \Pris*mat"ic*al\, a. [Cf.
F. prismatique.]
1. Resembling, or pertaining to, a prism; as, a prismatic
form or cleavage.
[1913 Webster]
2. Separated or distributed by a prism; formed by a prism;
as, prismatic colors.
[1913 Webster]
3. (Crystallog.) Same as Orthorhombic.
[1913 Webster]
Prismatic borax (Chem.), borax crystallized in the form of
oblique prisms, with ten molecules of water; --
distinguished from octahedral borax.
Prismatic colors (Opt.), the seven colors into which light
is resolved when passed through a prism; primary colors.
See Primary colors, under Color.
Prismatic compass (Surv.), a compass having a prism for
viewing a distant object and the compass card at the same
time.
Prismatic spectrum (Opt.), the spectrum produced by the
passage of light through a prism.
[1913 Webster]Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
Solar spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
Spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
Spectrum analysis
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster] |
Thermal spectrum
(gcide) | Spectrum \Spec"trum\, n.; pl. Spectra. [L. See Specter.]
1. An apparition; a specter. [Obs.]
[1913 Webster]
2. (Opt.)
(a) The several colored and other rays of which light is
composed, separated by the refraction of a prism or
other means, and observed or studied either as spread
out on a screen, by direct vision, by photography, or
otherwise. See Illust. of Light, and Spectroscope.
(b) A luminous appearance, or an image seen after the eye
has been exposed to an intense light or a strongly
illuminated object. When the object is colored, the
image appears of the complementary color, as a green
image seen after viewing a red wafer lying on white
paper. Called also ocular spectrum.
[1913 Webster]
Absorption spectrum, the spectrum of light which has passed
through a medium capable of absorbing a portion of the
rays. It is characterized by dark spaces, bands, or lines.
Chemical spectrum, a spectrum of rays considered solely
with reference to their chemical effects, as in
photography. These, in the usual photogrophic methods,
have their maximum influence at and beyond the violet
rays, but are not limited to this region.
Chromatic spectrum, the visible colored rays of the solar
spectrum, exhibiting the seven principal colors in their
order, and covering the central and larger portion of the
space of the whole spectrum.
Continous spectrum, a spectrum not broken by bands or
lines, but having the colors shaded into each other
continously, as that from an incandescent solid or liquid,
or a gas under high pressure.
Diffraction spectrum, a spectrum produced by diffraction,
as by a grating.
Gaseous spectrum, the spectrum of an incandesoent gas or
vapor, under moderate, or especially under very low,
pressure. It is characterized by bright bands or lines.
Normal spectrum, a representation of a spectrum arranged
upon conventional plan adopted as standard, especially a
spectrum in which the colors are spaced proportionally to
their wave lengths, as when formed by a diffraction
grating.
Ocular spectrum. See Spectrum, 2
(b), above.
Prismatic spectrum, a spectrum produced by means of a
prism.
Solar spectrum, the spectrum of solar light, especially as
thrown upon a screen in a darkened room. It is
characterized by numerous dark lines called Fraunhofer
lines.
Spectrum analysis, chemical analysis effected by comparison
of the different relative positions and qualities of the
fixed lines of spectra produced by flames in which
different substances are burned or evaporated, each
substance having its own characteristic system of lines.
Thermal spectrum, a spectrum of rays considered solely with
reference to their heating effect, especially of those
rays which produce no luminous phenomena.
[1913 Webster]Thermal \Ther"mal\, a. [L. thermae hot springs, fr. Gr. ?, pl.
of ? heat, fr. ? hot, warm, ? to warm, make hot; perhaps akin
to L. formus warm, and E. forceps.]
1. Of or pertaining to heat; warm; hot; as, the thermal unit;
thermal waters.
[1913 Webster]
The thermal condition of the earth. --J. D.
Forbes.
[1913 Webster]
2. caused by or affected by heat; as, thermal springs.
[PJC]
3. designed to retain heat; as, thermal underwear.
[PJC]
Thermal conductivity, Thermal spectrum. See under
Conductivity, and Spectrum.
Thermal unit (Physics), a unit chosen for the comparison or
calculation of quantities of heat. The unit most commonly
employed is the amount of heat necessary to raise the
temperature of one gram or one pound of water from zero to
one degree Centigrade. See Calorie, and under Unit.
[1913 Webster] |
Vampyrus spectrum
(gcide) | Vampire \Vam"pire\, n. [F. vampire (cf. It. vampiro, G. & D.
vampir), fr. Servian vampir.] [Written also vampyre.]
1. A blood-sucking ghost; a soul of a dead person
superstitiously believed to come from the grave and wander
about by night sucking the blood of persons asleep, thus
causing their death. This superstition was once prevalent
in parts of Eastern Europe, and was especially current in
Hungary about the year 1730. The vampire was often said to
have the ability to transform itself into the form of a
bat, as presented in the novel depicting the legend of
Dracula published by Bram Stoker in 1897, which has
inspired several movies.
[1913 Webster + PJC]
The persons who turn vampires are generally wizards,
witches, suicides, and persons who have come to a
violent end, or have been cursed by their parents or
by the church, --Encyc. Brit.
[1913 Webster]
2. Fig.: One who lives by preying on others; an extortioner;
a bloodsucker.
[1913 Webster]
3. (Zool.) Either one of two or more species of South
American blood-sucking bats belonging to the genera
Desmodus and Diphylla; also called vampire bat.
These bats are destitute of molar teeth, but have strong,
sharp cutting incisors with which they make punctured
wounds from which they suck the blood of horses, cattle,
and other animals, as well as man, chiefly during sleep.
They have a caecal appendage to the stomach, in which the
blood with which they gorge themselves is stored.
[1913 Webster]
4. (Zool.) Any one of several species of harmless tropical
American bats of the genus Vampyrus, especially
Vampyrus spectrum. These bats feed upon insects and
fruit, but were formerly erroneously supposed to suck the
blood of man and animals. Called also false vampire.
[1913 Webster]
Vampire bat (Zool.), a vampire, 3.
[1913 Webster]
[1913 Webster]False \False\, a. [Compar. Falser; superl. Falsest.] [L.
falsus, p. p. of fallere to deceive; cf. OF. faus, fals, F.
faux, and AS. fals fraud. See Fail, Fall.]
1. Uttering falsehood; unveracious; given to deceit;
dishnest; as, a false witness.
[1913 Webster]
2. Not faithful or loyal, as to obligations, allegiance,
vows, etc.; untrue; treacherous; perfidious; as, a false
friend, lover, or subject; false to promises.
[1913 Webster]
I to myself was false, ere thou to me. --Milton.
[1913 Webster]
3. Not according with truth or reality; not true; fitted or
likely to deceive or disappoint; as, a false statement.
[1913 Webster]
4. Not genuine or real; assumed or designed to deceive;
counterfeit; hypocritical; as, false tears; false modesty;
false colors; false jewelry.
[1913 Webster]
False face must hide what the false heart doth know.
--Shak.
[1913 Webster]
5. Not well founded; not firm or trustworthy; erroneous; as,
a false claim; a false conclusion; a false construction in
grammar.
[1913 Webster]
Whose false foundation waves have swept away.
--Spenser.
[1913 Webster]
6. Not essential or permanent, as parts of a structure which
are temporary or supplemental.
[1913 Webster]
7. (Mus.) Not in tune.
[1913 Webster]
False arch (Arch.), a member having the appearance of an
arch, though not of arch construction.
False attic, an architectural erection above the main
cornice, concealing a roof, but not having windows or
inclosing rooms.
False bearing, any bearing which is not directly upon a
vertical support; thus, the weight carried by a corbel has
a false bearing.
False cadence, an imperfect or interrupted cadence.
False conception (Med.), an abnormal conception in which a
mole, or misshapen fleshy mass, is produced instead of a
properly organized fetus.
False croup (Med.), a spasmodic affection of the larynx
attended with the symptoms of membranous croup, but
unassociated with the deposit of a fibrinous membrane.
False door or False window (Arch.), the representation of
a door or window, inserted to complete a series of doors
or windows or to give symmetry.
False fire, a combustible carried by vessels of war,
chiefly for signaling, but sometimes burned for the
purpose of deceiving an enemy; also, a light on shore for
decoying a vessel to destruction.
False galena. See Blende.
False imprisonment (Law), the arrest and imprisonment of a
person without warrant or cause, or contrary to law; or
the unlawful detaining of a person in custody.
False keel (Naut.), the timber below the main keel, used to
serve both as a protection and to increase the shio's
lateral resistance.
False key, a picklock.
False leg. (Zool.) See Proleg.
False membrane (Med.), the fibrinous deposit formed in
croup and diphtheria, and resembling in appearance an
animal membrane.
False papers (Naut.), documents carried by a ship giving
false representations respecting her cargo, destination,
etc., for the purpose of deceiving.
False passage (Surg.), an unnatural passage leading off
from a natural canal, such as the urethra, and produced
usually by the unskillful introduction of instruments.
False personation (Law), the intentional false assumption
of the name and personality of another.
False pretenses (Law), false representations concerning
past or present facts and events, for the purpose of
defrauding another.
False rail (Naut.), a thin piece of timber placed on top of
the head rail to strengthen it.
False relation (Mus.), a progression in harmony, in which a
certain note in a chord appears in the next chord prefixed
by a flat or sharp.
False return (Law), an untrue return made to a process by
the officer to whom it was delivered for execution.
False ribs (Anat.), the asternal rebs, of which there are
five pairs in man.
False roof (Arch.), the space between the upper ceiling and
the roof. --Oxford Gloss.
False token, a false mark or other symbol, used for
fraudulent purposes.
False scorpion (Zool.), any arachnid of the genus
Chelifer. See Book scorpion.
False tack (Naut.), a coming up into the wind and filling
away again on the same tack.
False vampire (Zool.), the Vampyrus spectrum of South
America, formerly erroneously supposed to have
blood-sucking habits; -- called also vampire, and {ghost
vampire}. The genuine blood-sucking bats belong to the
genera Desmodus and Diphylla. See Vampire.
False window. (Arch.) See False door, above.
False wing. (Zool.) See Alula, and Bastard wing, under
Bastard.
False works (Civil Engin.), construction works to
facilitate the erection of the main work, as scaffolding,
bridge centering, etc.
[1913 Webster] |
absorption spectrum
(wn) | absorption spectrum
n 1: the spectrum of electromagnetic radiation that has passed
through a medium that absorbed radiation of certain
wavelengths |
acoustic spectrum
(wn) | acoustic spectrum
n 1: the distribution of energy as a function of frequency for a
particular sound source [syn: sound spectrum, {acoustic
spectrum}] |
action spectrum
(wn) | action spectrum
n 1: the efficiency with which electromagnetic radiation
produces a photochemical reaction plotted as a function of
the wavelength of the radiation |
atomic spectrum
(wn) | atomic spectrum
n 1: (physics) a spectrum of radiation caused by electron
transitions within an atom; the series of spectrum lines is
characteristic of the element |
color spectrum
(wn) | color spectrum
n 1: the distribution of colors produced when light is dispersed
by a prism [syn: visible spectrum, color spectrum] |
electromagnetic spectrum
(wn) | electromagnetic spectrum
n 1: the entire frequency range of electromagnetic waves |
emission spectrum
(wn) | emission spectrum
n 1: spectrum of electromagnetic radiation emitted by a self-
luminous source |
infrared spectrum
(wn) | infrared spectrum
n 1: the spectrum of infrared radiation |
line spectrum
(wn) | line spectrum
n 1: a spectrum in which energy is concentrated at particular
wavelengths; produced by excited atoms and ions as they
fall back to a lower energy level |
mass spectrum
(wn) | mass spectrum
n 1: a distribution of ions as shown by a mass spectrograph or a
mass spectrometer |
microwave spectrum
(wn) | microwave spectrum
n 1: the part of the electromagnetic spectrum corresponding to
microwaves |
radio spectrum
(wn) | radio spectrum
n 1: the entire spectrum of electromagnetic frequencies used for
communications; includes frequencies used for radio and
radar and television [syn: radio spectrum, {radio-
frequency spectrum}] |
radio-frequency spectrum
(wn) | radio-frequency spectrum
n 1: the entire spectrum of electromagnetic frequencies used for
communications; includes frequencies used for radio and
radar and television [syn: radio spectrum, {radio-
frequency spectrum}] |
sound spectrum
(wn) | sound spectrum
n 1: the distribution of energy as a function of frequency for a
particular sound source [syn: sound spectrum, {acoustic
spectrum}] |
spectrum analysis
(wn) | spectrum analysis
n 1: the use of spectroscopes to analyze spectra [syn:
spectroscopy, spectrometry, spectroscopic analysis,
spectrum analysis, spectrographic analysis] |
spectrum line
(wn) | spectrum line
n 1: an isolated component of a spectrum formed by radiation at
a uniform frequency |
speech spectrum
(wn) | speech spectrum
n 1: the average sound spectrum for the human voice |
ultraviolet spectrum
(wn) | ultraviolet spectrum
n 1: the spectrum of ultraviolet radiation |
visible spectrum
(wn) | visible spectrum
n 1: the distribution of colors produced when light is dispersed
by a prism [syn: visible spectrum, color spectrum] |
frequency-hopping spread spectrum
(foldoc) | Frequency-Hopping Spread Spectrum
FHSS
(FH, FHSS) A variation of {spread spectrum
communications} in which a sequence of pseudo random numbers
control a frequency synthesizer, generating different
carrier frequencies that "hop around" in the desired frequency
range. The receiver tunes to the same sequence of carrier
frequencies in synchronisation with the transmitter.
Frequency hopping spread spectrum was invented by Hedy Lamarr
("the most beautiful girl in the world", Samson and Delilah
etc.) and the composer George Antheil. They held a patent
filed in 1942.
(2009-07-01)
|
spread spectrum communications
(foldoc) | spread spectrum communications
(Or "spread spectrum") A technique by which a
signal to be transmitted is modulated onto a pseudorandom,
noise-like, wideband carrier signal, producing a
transmission with a much larger bandwidth than that of the
data modulation.
Reception is accomplished by cross correlation of the
received wide band signal with a synchronously generated
replica of the carrier.
Spread-spectrum communications offers many important benefits:
Low probability of detection, interception or determination of
the transmitter's location. To an observer who does not
possess information about the carrier, the transmission is
indistinguishable from other sources of noise.
High immunity against interference and jamming (intentional
interference). The presence of (narrowband) interference
signals only decreases the channel's signal-to noise ratio
and therefore its error rate, which can be dealt with by
using error correcting codes. A jammer would have to use
wideband interference signals, which would require very high
power (again assuming that the jammer does not know the
characteristics of the carrier).
High immunity against adverse effects of multipath
transmission. In the presence of multiple paths between
transmitter and receiver (e.g. by reflected signals), signals
of certain frequencies can be cancelled at certain locations
when the difference in path delays between multiple
propagation paths cause the signals to arrive out of phase.
This effect is particularly troublesome in narrowband mobile
communications, where it causes "blind spots" - locations
where no signal can be received.
Transmitter/receiver pairs using independent random carriers
can operate in the same frequency range with minimal
interference. These are called {Code Division Multiple
Access} (CDMA) systems. Increasing the number of T/R pairs
again only gradually increases each channel's error rate. In
contrast, narrowband systems can only accomodate a fixed
number of channels determined by available bandwidth and
channel width (data rate).
When the data modulation cannot be distinguished from the
carrier modulation, and the carrier modulation is random to an
unwanted observer, the spread spectrum system assumes
cryptographic capabilities, with the carrier modulation taking
on the function of a key in a cipher system.
The most important practical modes of spread spectrum coding
are Direct Sequence (DS) and {Frequency-Hopping Spread
Spectrum} (FH).
In DS, a pseudo random sequence is phase-shift-keyed (PSK)
onto the carrier.
Spread Spectrum development began during World War II, with
the earliest studies dating from the 1920s. Most papers
remained classified until the 1980s.
Direct sequence spread spectrum was invented by Paul Kotowski
and Kurt Dannehl at Telefunken.
The technique is used extensively in military communications
today. Commercial applications include mobile telephony
and mobile networking.
["Spread Spectrum Communications", Charles E. Cook et al
(Ed.), IEEE Press, New York, 1983. ISBN 0-87942-170-3].
Hedy Lamarr (http://sirius.be/lamarr.htm),
(http://ncafe.com/chris/pat2/).
(2001-08-08)
|
zx spectrum
(foldoc) | ZX Spectrum
Spectrum
Sinclair's first personal computer with a colour
display. The Spectrum used the Zilog Z80 processor like its
predecessors the ZX-80 and ZX-81. It was originally
available in 16k and 48k versions using cassette tape and
later grew to 128k and sprouted floppy disks. It had a
wider and more solid case and a marginally better "dead flesh"
keyboard. Unlike the earlier models, it didn't require the
presence of a cold carton of milk to prevent it overheating.
It was possibly the most popular home computer in the UK for
many years.
The TK-90X was a clone.
(1995-11-04)
|
|