Unreferenced date December 2009 Acoustics Acoustic absorption is that property of any material that changes the acoustic energy of Sound sound waves into another form, often heat , which it to some extent retains, as opposed to that sound energy that material reflects or conducts. Acoustic absorption is represented by the symbol A in calculations. Absorption is not a single mechanism of sound attenuation propagation through a heterogeneous system is affected by scattering as well. The absorptive of a given material is frequency dependent and is affected by size, shape, location and the mounting method used. Porous insulative materials such as mineral wool or glass wool are effective sound absorbers compared with good conductors such as metals. Micro perforated plate s, however, supply hard absorptive surfaces. Acoustic absorption is important in the analysis of sonar . The primary substance in seawater that is responsible for absorption is magnesium sulfate . The secondary substance is boric acid . The most common sea salt, sodium chloride has virtually no effect on sound absorption. See also Acoustic attenuation Acoustic board Attenuation coefficient Anechoic chamber DEFAULTSORT Absorption Acoustics Category Acoustics ca Absorci so da Lydabsorption de Schallabsorption es Absorci n sonido gl Absorci n son nl Geluidsabsorptie nn Absorpsjon i akustikk pl Poch anianie akustyka pt Absor o ac stica sv Ljudabsorption ... more details
The ITU Terrestrial Model for One Terminal in Woodland is a Radio propagation model belonging to the class of Foliage models. This model is a successor of the Early ITU Model . Applicable To Under Conditions Applicable to the scenario where one terminal of a link is inside foliage and the other end is free. Coverage Frequency Below 5 GHz Depth of Foliage Unspecified Mathematical Formulation The mathematical formulation of the model is math A v A 1 e frac d gamma A math Where, A sub v sub Attenuation due to Vegetation. Unit Decibel dB A Maximum Attenuation for one terminal caused by a certain foliage. Unit Decibel dB d Depth of Foliage along the path. Unit Meter m math gamma math Specific Attenuation for short vegetations. Unit Decibel meter dB m Points to Note The value of math gamma math is dependent on frequency and is an empirical constant. The model assumes that exactly one of the terminals is located inside some forest or plantation and the term depth applies to the distance from the terminal inside the plantation to the end of plantation along the link. Further reading Introduction to RF propagation, John S. Seybold, 2005, John Wiley and Sons. See also Early ITU Model Weissberger s Model Single Vegetative Obstruction Model Category Radio frequency propagation ... more details
Refimprove date October 2007 K edge describes a sudden increase in the attenuation coefficient of photon s occurring at a photon energy just above the binding energy of the K Electron shell shell electron of the atom s interacting with the photons. The sudden increase in attenuation is due to photoelectric absorption of the photons. For this interaction to occur, the photons must have more energy than the binding energy of the K shell electrons. A photon having an energy just above the binding energy of the electron is therefore more likely to be absorbed than a photon having an energy just below this binding energy. Use The two X ray contrast medium contrast media iodine and barium have ideal K shell binding energies for absorption of X rays, 33.2 keV and 37.4 keV, respectively, which is close to the mean energy of most diagnostic X ray beams. Similar sudden increases in attenuation may also be found for other inner shells than the K shell the general term for the phenomenon is absorption edge . ref http physics.nist.gov PhysRefData XrayMassCoef intro.html NIST data for full tabulation ref References reflist Category X rays atomic physics stub ... more details
A stopband is a Band radio band of frequencies, between specified limits, through which a electrical circuit circuit , such as a Filter signal processing filter or telephone circuit, does not allow signals to pass, or the attenuation is above the required stopband attenuation level. Depending on application, the required attenuation within the stopband may typically be a value between 20 and 120 decibel dB higher than the nominal passband attenuation, which often is 0 dB. The lower and upper limiting frequencies , also denoted lower and upper stopband corner frequency corner frequencies , are the frequencies where the stopband and the transition band s meet in a filter specification. The stopband of a low pass filter is the frequencies from the stopband corner frequency which is slightly higher than the passband 3 dB cut off frequency up to the infinite frequency. The stopband of a high pass filter consists of the frequencies from 0 hertz to a stopband corner frequency slightly lower than the passband cut off frequency . A band stop filter has one stopband, specified by two non zero and non infinite corner frequencies. The difference between the limits in the band stop filter is the stopband Bandwidth signal processing bandwidth , which usually is expressed in hertz . A bandpass filter typically has two stopbands. The shape factor of a bandpass filter is the relationship between the 3dB bandwidth, and the difference between the stopband limits. See also Passband Band stop filter Band gap in solid state physics Band rejection References FS1037C MS188 Category Filter theory Category Electronics terms electronics stub telecomm term stub ru sv Stoppband ... more details
Unreferenced date December 2006 Sensitivity Time Control STC is used to attenuate the very strong signals returned from nearby ground clutter targets in the first few range gate s of a Radar receiver. Without this signal attenuation , the receiver would routinely saturate due to the strong signals. Category Radar signal processing Electronics stub de Sensitivity Time Control ... more details
unreferenced date July 2011 A line filter is the kind of electronic filter that is placed between an electronic equipment and a line external to it, to attenuate conducted radio frequencies Radio frequency interference RFI , also known as electromagnetic interference EMI between the line and the equipment. In particular, an AC Line Filter is used between the AC power line and the equipment. Types of line filters A Line Filter may be incorporated in a connector. For example An AC Line Filter may be incorporated in a modular IEC power inlet connector or Power entry module Power Entry Module A telephone line filter may be incorporated in a modular RJ11 connector A line filter may be mounted on a PCB An AC line filter may be a stand alone device, chassis mounted inside the equipment A facility AC Line Filter is mounted inside a room or cabinet, at the point where the AC power comes in Characteristics of line filters A line filter may be used to attenuate EMI in either direction. For example Emissions It may be used to reduce the unintentional conducted emission from the equipment, to a level sufficiently low to pass regulatory limits such as FCC part 15 . For example, in switching power supplies. Immunity It may be used to reduce the level of EMI entering the equipment, to a level sufficiently low not to cause any undesired behavior. For example, in equipment used in Radio Transmitter facilities The attenuation of Line filters is measured in 2 areas Common Mode attenuation to signals that appear identically on each of the wires going through the filter Differential Mode attenuation to signals that appear on just one of the lines For each Mode, the attenuation is characterized over the frequency spectrum, and measured in dB References Reflist DEFAULTSORT Line Filter Category Electrical power connectors Category Wireless tuning and filtering Category Tone, EQ and filter de Netzfilter pt Filtro de linha ... more details
orphan date February 2012 Third party date February 2012 The Vienna II Au is a FET condenser microphone made by ADK Microphones. It includes a switchable low frequency cut off 1st order, 3dB 100 Hz or 160 Hz and a switchable attenuation pad 8dB or 16dB . ref http adkmic.com catalog customshop ViennaII AU Edition.php ref References reflist http adkmic.com catalog customshop ViennaII AU Edition.php Adkmic.com Category Microphones ... more details
wiktionary extinction wikiquote Extinction Extinction may refer to Extinction peerage , in the United Kingdom In science Bird s eye extinction , in optical mineralogy Extinction , in biology and palaeontology Extinction another word for attenuation , in physical sciences Extinction astronomy Extinction angle , in optical mineralogy Extinction coefficient another term for mass attenuation coefficient , in physical sciences Undulose extinction , a geological term In medicine Extinction psychology Extinction neurology In books Extinction novel Extinction novel , a fantasy novel by Lisa Smedman Extinction , a science fiction novel by Ray Hammond In entertainment Extinction , a song by Stigmata from the album Hollow Dreams Extinction Star Trek Enterprise Extinction Star Trek Enterprise , television episode Extinction Smallville episode Extinction Smallville episode , television episode Aliens versus Predator Extinction , a video game for PlayStation 2 and Xbox Resident Evil Extinction , a 2007 film starring Milla Jovovich See also Extinct disambiguation disambig de Extinktion es Extinci n desambiguaci n fr Extinction pl Ekstynkcja sv Extinktion ... more details
Impact Insulation Class or IIC is an integer number rating of how well a building floor attenuates impact sounds, such as footsteps. A larger number means more attenuation. The scale, like the decibel scale for sound, is logarithm ic. The IIC is derived from ASTM method E989, which in turn uses a tapping machine specifed in ASTM method E492. ref National Research Council of Canada Institute for Research in Construction, http irc.nrc cnrc.gc.ca pubs ctus 35 e.html ref The IIC number is derived from sound attenuation values tested at sixteen standard frequencies from 100 to 3150 Hertz Hz . Unfortunately, real world footstep noise is also generated at frequencies below 100 Hz, so the IIC value may not accurately describe the complete noise attentuation profile of a floor. ref Described in California Building Code, Section 1207.9, Sound Transmission Tested Assemblies . ref References reflist 1 Category Sound measurements ... more details
speed and attenuation of ultrasound for a set of frequencies in the megahertz range. These measurable ... into fluid compressibility . Attenuation determines M , which is a measure of viscous properties ... liquid attenuation yields information on the volume viscosity . Stokes law sound attenuation provides relationship among attenuation , dynamic viscosity and volume viscosity of the Newtonian fluid ... more details
Other uses Attenuator disambiguation Cleanup date February 2008 Attenuation is a regulatory feature found ... transcription . ref name Merino2005 Merino E, Yanofsky C 2005 . Transcription attenuation a highly ... of transcription. ref name Naville2010 Naville M, Gautheret, D 2009 . Transcription attenuation ... attenuation, these are now considered to be variants of the same phenomena ref name Naville2010 and are included in this article. Attenuation is an ancient regulatory system, prevalent in many bacterial ... the change in RNA structure. It is likely that transcription attenuation mechanisms developed early ... in different organisms. ref name Merino2005 Small molecule mediated attenuation Riboswitches Riboswitch ... but are significantly more complex than the previous class of attenuators. Protein mediated attenuation .... ref name Merino2005 Ribosome mediated attenuation In this situation RNA polymerase is dependent on lagging ... proteins in E. coli . ref name Naville2010 Discovery Attenuation was first observed by Charles Yanofsky in the trp operon of E. coli . ref name Yanofsky C. Yanofsky, Attenuation in the control of expression ... attenuation of the trp operon. An example is the trp operon trp gene in bacteria . When there is a high ... in later tryptophan synthesis. Attenuation is a second mechanism of negative feedback in the trp operon. While the TrpR repressor decreases transcription by a factor of 70, attenuation can further decrease it by a factor of 10, thus allowing accumulated repression of about 700 fold. Attenuation ..., a key element in attenuation. A similar attenuation mechanism regulates the synthesis of histidine ... alternate secondary structures form. Other operons controlled by attenuation The discovery of this type ... RNA motif Attenuation in Eukaryotes Research conducted on microRNA processing showed an evidence of attenuation process in Eukaryote s. After co transcriptional endonucleolitical cleavage by Drosha ... 2011 DEFAULTSORT Attenuator Genetics Category Gene expression de Attenuation Genexpression et ... more details
The mathematical basis for tomographic imaging was laid down by Johann Radon . It is applied in Computed Tomography to obtain cross sectional images of patients. This article applies in general to tomographic reconstruction for all kinds of tomography , but some of the terms and physical descriptions refer directly to X ray computed tomography. Image Tomographic fig1.png thumb Figure 1 Parallel beam geometry. Each projection is made up of the set of line integrals through the object. The projection of an object at a given angle math theta math is made up of a set of line integrals . In X ray CT, the line integral represents the total attenuation of the beam of x rays as it travels in a straight line through the object. As mentioned above, the resulting image is a 2D or 3D model of the attenuation coefficient . That is, we wish to find the image math mu x,y math . The simplest and easiest way to visualise method of scanning is the system of parallel projection , as used in the first scanners. For this discussion we consider the data to be collected as a series of parallel rays, at position math r math , across a projection at angle math theta math . This is repeated for various angles. Attenuation occurs exponential decay exponentially in tissue math I I 0 exp left int mu x,y ,ds right math where math mu x math is the attenuation coefficient at position math x math along the ray path. Therefore generally the total attenuation math p math of a ray at position math r math , on the projection at angle math theta math , is given by the line integral math p r, theta ln I I 0 int mu x,y ,ds math Image Ct skull.jpg thumb right 250px Projected X rays are clearly visible on this slice taken with a CT scan Using the coordinate system of Figure 1, the value of math r math onto which the point math x,y math will be projected at angle math theta math is given by math x cos theta y sin theta r math So the equation above can be rewritten as math p r, theta int infty infty int infty ... more details
Image Ionospheric absorption en .svg thumb right 350px Attenuation diagram, day and night Ionospheric absorption or ISAB is the scientific name for absorption electromagnetic radiation absorption occurring as a result of the interaction between various types of Electromagnetic radiation electromagnetic waves and the free electrons in the ionosphere , which can interfere with radio transmissions. Description Ionosphere absorption is of critical importance when radio network s, telecommunication systems or interlinked radio systems are being planned, particularly when trying to determine Radio propagation propagation conditions. ref name walk Walker, J.K. Bhatnagar, V.P. Ionospheric absorption, typical ionization, conductivity, and possible synoptic heating parameters in the Earth s atmosphere upper atmosphere . Geological Survey of Canada.http www.osti.gov energycitations product.biblio.jsp?osti id 6068491 ref The ionosphere can be described as an area of the atmosphere in which Radio frequency radio waves on shortwave bands are refracted or reflected back to earth. As a result of this reflection, which is often key in the long distance propagation of radio waves,some of the shortwave signal strength is decreased. In this regard, ISAB is the primary limiting factor in radio propagation. ref name dav Davies, Kenneth. Ionospheric Radio. ISBN 086341186X ref Attenuation mechanics Image RIOM2.JPG thumb right 400px Chart of Attenuation ISAB is only a factor in the period of the day where radio signals travel through the portion of the ionosphere facing the sun. The solar wind and radiation cause the ionosphere to become charged with electrons in the first place. At night, the atmosphere becomes drained of its charge, and radio signals can go much further with less loss of signal ... amount of attenuation can be derived as a function of the Inverse square law . The lower the frequency, the greater the attenuation. ref name dav See also Radio horizon Sudden Ionospheric Disturbance ... more details
The optical power budget in a fiber optic communication data link link is the allocation of available optical Power physics power launched into a given fiber by a given source among various loss producing mechanisms such as launch coupling loss , fiber attenuation electromagnetic radiation attenuation , splice losses, and fiber optic connector connector losses, in order to ensure that adequate Signalling telecommunication signal strength optical power is available at the receiver. The optical power budget is usually specified or expressed in decibel s dB . The amount of optical power launched into a given fiber by a given transmitter depends on the nature of its active optical source LED or laser diode and the type of fiber, including such parameters as core diameter and numerical aperture . Manufacturers sometimes specify an optical power budget only for a fiber that is optimum for their equipment or specify only that their equipment will operate over a given distance, without mentioning the fiber characteristics. The user must first ascertain, from the manufacturer or by testing, the transmission telecommunications transmission losses for the type of fiber to be used, and the required signal strength for a given level of performance. In addition to transmission loss , including those of any splices and connectors, allowance should be made for at least several dB of optical power margin losses, to compensate for electronic component component aging and to allow for future splices in the event of a severed optical fiber cable cable . LT L Lc Ls LT Total Loss Fiber Attenuation L Length of fiber Lc Connector Loss Ls Splice Loss References FS1037C Category Telecommunications terms ... more details
Dispersion shifted fiber DSF is a type of optical fiber made to optimize both low dispersion optics dispersion and low attenuation . Dispersion Shifted Fiber is a type of single mode optical fiber with a core clad index profile tailored to shift the zero dispersion wavelength from the natural 1300 Nanometer nm in silica glass fibers to the minimum loss window at 1550 nm. The group velocity or intramodal dispersion which dominates in single mode fibers includes both material and waveguide dispersion. Waveguide dispersion can be made more negative by changing the index profile and thus be used to offset the fixed material dispersion, shifting or flattening the overall intramodal dispersion. This is advantageous because it allows a communication system to possess both low dispersion and low attenuation. However, when used in wavelength division multiplexing systems, dispersion shifted fibers can suffer from four wave mixing which causes intermodulation of the independent signals. As a result nonzero dispersion shifted fiber is often used. Dispersion shifted fiber is specified in ITU T G.653. References L.G. Cohen, C. Lin, and W. G. French, Electron. Lett. , 15 , 334 1979 . optics stub Category Optical fiber ... more details
Infobox rfam Name Plasmid RNAIII image RF00235.jpg width caption Predicted secondary structure and sequence conservation of Plasmid RNAIII Symbol Plasmid RNAIII AltSymbols Rfam RF00235 miRBase miRBase family RNA type Gene Tax domain Bacteria GO SO SO 0000233 CAS number EntrezGene HGNCid OMIM PDB RefSeq Chromosome Arm Band LocusSupplementaryData Plasmid RNAIII is a non coding RNA found in bacterial plasmid s including pIP501. RNAIII acts by Transcription genetics transcription al attenuation of the essential repR mRNA. RNAIII is composed of four stem loop s with loops L3 and L4 that interact with the RNA target. ref cite journal last Heidrich first N coauthors Brantl S year 2003 title Antisense RNA mediated transcriptional attenuation importance of a U turn loop structure in the target RNA of plasmid pIP501 for efficient inhibition by the antisense RNA journal J Mol Biol volume 333 pages 917 929 pmid 14583190 doi 10.1016 j.jmb.2003.09.020 issue 5 ref References reflist 1 External links Rfam id RF00235 name Plasmid RNAIII Category Non coding RNA molecular cell biology stub ... more details
medium, for example The absorption coefficient, and some closely related derived quantities The attenuation ... by molarity see also Beer Lambert law . The mass attenuation coefficient , also called mass extinction coefficient , which is the absorption coefficient divided by density see also mass attenuation ... and attenuation coefficients, respectively. Extinction astronomy Extinction in astronomy is equivalent to the attenuation coefficient. Penetration depth and skin effect , Propagation constant , Propagation constant Attenuation constant attenuation constant , Propagation constant Phase ... example is the Computation of radiowave attenuation in the atmosphere used in satellite link ... more details
In telecommunications , a cutback technique is a destructive technique for determining certain optical fiber transmission characteristic s, such as attenuation electromagnetic radiation attenuation and Bandwidth computing bandwidth . Procedure The measurement technique consists of performing the desired measurements on a long length of the fiber under test, cutting the fiber under test at a point near the launching end, repeating the measurements on the short length of fiber, and subtracting the results obtained on the short length to determine the results for the residual long length. The cut should be made to retain 1 meter or more of the fiber, in order to establish equilibrium mode distribution conditions for the second measurement. In a multimode fiber , the lack of an equilibrium mode distribution could introduce errors in the measurement due to output coupling effects. In a single mode fiber , measuring a shorter cutback fiber could result in significant transmission of cladding modes light carried in the cladding rather than the core of the optical fiber , distorting the measurement. The errors introduced will result in conservative results i.e. , higher transmission losses and lower bandwidths than would be realized under equilibrium conditions. Benefits The benefit of this technique is that it allows measurement of the fiber characteristics without introducing errors due to variation in the launch conditions. For example, the Coupling loss coupling efficiency of the light source is kept consistent between the initial and the cutback measurements. Several characteristics may be determined using the same test fiber. Attenuation measurement Since the attenuation is defined as proportional to the logarithm of the ratio between math P x math and math P y math , where math P math is the Radiant power power at point math x math and math y math respectively. Using the cutback technique, the power transmitted through a fiber of known length is measured and com ... more details
Forward echo In a transmission line , a reflection electrical reflection propagating in the same direction as the original wave and consisting of energy reflected back by one discontinuity and then forward again by another discontinuity. Forward echoes can be supported by reflections caused by splices or other discontinuities in the transmission medium e.g. optical fiber , twisted pair, or coaxial tube . In metal lic lines, they may be supported by Impedance matching impedance mismatches between the source or Electrical load load and the characteristic impedance of the transmission medium. They may cause attenuation distortion . References FS1037C MS188 Category Telecommunications engineering Category Telephony telecomm stub ... more details
Hydroxyl ion absorption is the Absorption optics absorption in optical fiber s of electromagnetic wave s, including the near infrared , due to the presence of trapped hydroxyl ions remaining from water as a contaminant. The hydroxyl OH sup sup ion can penetrate glass during or after product fabrication, resulting in significant attenuation of discrete optical wavelengths, e.g. , centred at 1.383 m, used for telecommunication communications via optical fibres. See also Water absorption References FS1037C Category Fiber optics Category Glass engineering and science analytical chemistry stub optics stub ... more details
Image EQ parametrique.jpg thumb 250px Digital domain parametric equalisation Unreferenced date December 2009 An audio filter is a frequency dependent amplifier circuit, working in the audio frequency range, 0 Hz to beyond 20 kHz. Many types of filters exist for applications including equalizer graphic equalizer s, synthesizer s, sound effect s, Compact disc CD players and virtual reality systems. Being a frequency dependent amplifier, in its most basic form, an Audio frequency audio filter is designed to amplify, pass or attenuate negative amplification some frequency ranges. Common types include low pass, which pass through frequencies below their cutoff frequencies, and progressively attenuates frequencies above the cutoff frequency. A high pass filter does the opposite, passing high frequencies above the cutoff frequency, and progressively attenuating frequencies below the cutoff frequency. A bandpass filter passes frequencies between its two cutoff frequencies, while attenuating those outside the range. A band reject filter, attenuates frequencies between its two cutoff frequencies, while passing those outside the reject range. An all pass filter , passes all frequencies, but affects the phase of any given sinusoidal component according to its frequency. In some applications, such as in the design of equalizer graphic equalizer s or CD players, the filters are designed according to a set of objective criteria such as pass band , pass band attenuation, stop band, and stop band attenuation, where the pass bands are the frequency ranges for which audio is attenuated less than a specified maximum, and the stop bands are the frequency ranges for which the audio must be attenuated by a specified minimum. In more complex cases, an audio filter can provide a audio feedback feedback loop, which introduces resonance ringing alongside attenuation. Audio filters can also be designed to provide gain boost as well as attenuation. In other applications, such as with synth ... more details
Extinction coefficient refers to several different measures of the absorption of light in a medium In chemistry, biochemistry, molecular biology, or microbiology, the mass attenuation coefficient mass extinction coefficient and the molar absorptivity molar extinction coefficient are parameters defining how strongly a substance absorbs light at a given wavelength, per density mass density or per molar concentration , respectively. In physics, the extinction coefficient is the imaginary part of the complex index of refraction , which also relates to light absorption. For the quantitative relationship between the chemistry and physics definitions, see Mathematical descriptions of opacity . disambig ca Coeficient d extinci de Extinktionskoeffizient es Coeficiente de extinci n fr Absorptivit molaire ... more details
Wideband material refers to material that can convey Microwave signals light sound over a variety of wavelength s. These materials possess exemplary attenuation and dielectric constants, and are excellent dielectric s for semiconductor gate s. Examples of such material include gallium nitride GaN and silicon carbide SiC . SiC has been used extensively in the creation of laser s for several years. However, it performs poorly providing limited brightness because it has an indirect band gap . GaN has a wide band gap 3.4 eV , which usually results in high energies for structures which possess electron s in the conduction band . References Empty section date July 2010 External links http my.ece.ucsb.edu yorklab Projects GaN widebandgap semicons and circuits.htm UCSB.edu &ndash Wideband Gap Semiconductors Category Materials science condensedmatter stub chem stub ... more details
A land treatment unit LTU is a location in which land is treated, usually through bioremediation processes, to reduce the toxicity of the soil . LTUs are becoming more common as more sites needing clean up are identified. Land treatment units are areas where hazardous waste is applied or incorporated into the soil surface. Land treatment units are typically units consisting of natural soils where natural biological and chemical degradation and attenuation processes immobilize, transform, or degrade hazardous constituents over time. ref http www.epa.gov compliance resources policies civil rcra wasteanalygman rpt.pdf Waste Analysis at Facilities that Generate, Treat, Store, and Dispose of Hazardous Waste, A Guidance Manual US EPA OSWER 9938.4 03 ref See also Land disposal unit Notes references Category Waste treatment technology ... more details
TRAP is an abbreviation that may refer to Tartrate resistant acid phosphatase , a metalloenzyme involved in bone formation. Translocon associated protein Telomeric Repeat Amplification Protocol , a method for detecting telomerase activity. TNF related activation protein , also known as CD40 ligand. Mediator coactivator Thyroid Hormone Receptor associated Proteins , a transcriptional coactivator genetics coactivator . Tripartite ATP independent periplasmic transporter , a family of prokaryotic solute transporters. Attenuator genetics trp RNA binding attenuation protein , a RNA binding protein regulating the biosynthetis of tryptophan TRAP processor instruction Tactical Recovery of Aircraft and Personnel , also known as a TRAP team is U.S. Marine Corps capability to rescue, recover both downed air crews and aircraft. disambig ... more details
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