|
Photon Doppler Velocimetry
Photon Doppler velocimetry (PDV) is a one-dimensional Fourier transform analysis of a heterodyne laser interferometry, used in the shock physics community to measure velocities in dynamic experiments with high temporal precision. PDV was developed at Lawrence Livermore National Laboratory by Oliver Strand. In recent years PDV has achieved popularity in the shock physics community as an adjunct or replacement for velocity interferometer system for any reflector (VISAR), another time-resolved velocity interferometry system. Modern data acquisition technology and off-the-shelf optical telecommunications devices now enable the assembly of PDV systems within reasonable budgets. Theory The fundamental mechanism of PDV is the interference pattern created by two electromagnetic waves with a small difference in frequency. Since most PDV systems are constructed with available telecommunications equipment, a standard laser source for a PDV system is centered at 1550 nm (or 193.4 THz). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fourier Transform
A Fourier transform (FT) is a mathematical transform that decomposes functions into frequency components, which are represented by the output of the transform as a function of frequency. Most commonly functions of time or space are transformed, which will output a function depending on temporal frequency or spatial frequency respectively. That process is also called ''analysis''. An example application would be decomposing the waveform of a musical chord into terms of the intensity of its constituent pitches. The term ''Fourier transform'' refers to both the frequency domain representation and the mathematical operation that associates the frequency domain representation to a function of space or time. The Fourier transform of a function is a complex-valued function representing the complex sinusoids that comprise the original function. For each frequency, the magnitude (absolute value) of the complex value represents the amplitude of a constituent complex sinusoid with that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterodyne
A heterodyne is a signal frequency that is created by combining or mixing two other frequencies using a signal processing technique called ''heterodyning'', which was invented by Canadian inventor-engineer Reginald Fessenden. Heterodyning is used to shift signals from one frequency range into another, and is also involved in the processes of modulation and demodulation. The two input frequencies are combined in a nonlinear signal-processing device such as a vacuum tube, transistor, or diode, usually called a '' mixer''. In the most common application, two signals at frequencies and are mixed, creating two new signals, one at the sum of the two frequencies , and the other at the difference between the two frequencies . The new signal frequencies are called ''heterodynes''. Typically, only one of the heterodynes is required and the other signal is filtered out of the output of the mixer. Heterodyne frequencies are related to the phenomenon of "beats" in acoustics. A major a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light which is ''coherent''. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers and lidar (light detection and ranging). Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum. Alternatively, temporal coherence can be used to produce ultrashort pulses of ligh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interferometry
Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy (and its applications to chemistry), quantum mechanics, nuclear and particle physics, plasma physics, remote sensing, biomolecular interactions, surface profiling, microfluidics, mechanical stress/strain measurement, velocimetry, optometry, and making holograms. Interferometers are devices that extract information from interference. They are widely used in science and industry for the measurement of microscopic displacements, refractive index changes and surface irregularities. In the case with most interferometers, light from a single source is split into two beams that travel in different optical paths, which are then combined again to produce interfer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lawrence Livermore National Laboratory
Lawrence Livermore National Laboratory (LLNL) is a federal research facility in Livermore, California, United States. The lab was originally established as the University of California Radiation Laboratory, Livermore Branch in 1952 in response to the detonation of the first atomic bomb by the Soviet Union during the Cold War. It later became autonomous in 1971 and was designated a national laboratory in 1981. A federally funded research and development center, Lawrence Livermore Lab is primarily funded by the U.S. Department of Energy and it is managed privately and operated by Lawrence Livermore National Security, LLC (a partnership of the University of California), Bechtel, BWX Technologies, AECOM, and Battelle Memorial Institute in affiliation with the Texas A&M University System. In 2012, the laboratory had the synthetic chemical element livermorium (element 116) named after it. Overview LLNL is self-described as a "premier research and development institution for sci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Velocity Interferometer System For Any Reflector
Velocity interferometer system for any reflector (VISAR) is a time-resolved velocity measurement system that uses laser interferometry to measure the surface velocity of solids moving at high speeds. For solids experiencing high velocity impact or explosive conditions, VISAR plots the free-surface velocity against time to show the shock wave profile of a material (See Figure). VISAR is a useful tool in determining the pressure-density relationship of a material known as the Rankine-Hugoniot conditions or simply the "Hugoniot". In recent years another time-resolved velocity measurement tool called laser Doppler velocimetry has achieved popularity in the shock physics community as an adjunct or replacement for VISAR. This device is essentially a displacement interferometer of the normal Michelson variety. As such it requires extremely fast data acquisition devices (digital oscilloscopes with bandwidths of 10 GHz or higher) and is limited in the range of velocities it can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VISAR
Veysar or Visar ( fa, ويسر) may refer to: * Visar, Kurdistan Visar ( fa, ويسر, also Romanized as Vīsar and Veysar; also known as Vesar) is a village in Zhavarud-e Gharbi Rural District, Kalatrazan District, Sanandaj County, Kurdistan Province, Iran. At the 2006 census, its population was 470, in 121 ... * Veysar, Mazandaran {{geodis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Texas At Austin
The University of Texas at Austin (UT Austin, UT, or Texas) is a public research university in Austin, Texas. It was founded in 1883 and is the oldest institution in the University of Texas System. With 40,916 undergraduate students, 11,075 graduate students and 3,133 teaching faculty as of Fall 2021, it is also the largest institution in the system. It is ranked among the top universities in the world by major college and university rankings, and admission to its programs is considered highly selective. UT Austin is considered one of the United States's Public Ivies. The university is a major center for academic research, with research expenditures totaling $679.8 million for fiscal year 2018. It joined the Association of American Universities in 1929. The university houses seven museums and seventeen libraries, including the LBJ Presidential Library and the Blanton Museum of Art, and operates various auxiliary research facilities, such as the J. J. Pickle Research Ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser Doppler Velocimetry
Laser Doppler velocimetry, also known as laser Doppler anemometry, is the technique of using the Doppler shift in a laser beam to measure the velocity in transparent or semi-transparent fluid flows or the linear or vibratory motion of opaque, reflecting surfaces. The measurement with laser Doppler anemometry is absolute and linear with velocity and requires no pre-calibration. Technology origin The development of the helium–neon laser (He-Ne) in 1962 at the Bell Telephone Laboratories provided the optics community with a continuous wave electromagnetic radiation source that was highly concentrated at a wavelength of 632.8 nanometers (nm) in the red portion of the visible spectrum. It was discovered that fluid flow measurements could be made using the Doppler effect on a He-Ne beam scattered by small polystyrene spheres in the fluid. At the Research Laboratories of Brown Engineering Company (later Teledyne Brown Engineering), this phenomenon was used to develop the first laser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Velocity Interferometer System For Any Reflector
Velocity interferometer system for any reflector (VISAR) is a time-resolved velocity measurement system that uses laser interferometry to measure the surface velocity of solids moving at high speeds. For solids experiencing high velocity impact or explosive conditions, VISAR plots the free-surface velocity against time to show the shock wave profile of a material (See Figure). VISAR is a useful tool in determining the pressure-density relationship of a material known as the Rankine-Hugoniot conditions or simply the "Hugoniot". In recent years another time-resolved velocity measurement tool called laser Doppler velocimetry has achieved popularity in the shock physics community as an adjunct or replacement for VISAR. This device is essentially a displacement interferometer of the normal Michelson variety. As such it requires extremely fast data acquisition devices (digital oscilloscopes with bandwidths of 10 GHz or higher) and is limited in the range of velocities it can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Measurement
Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. In other words, measurement is a process of determining how large or small a physical quantity is as compared to a basic reference quantity of the same kind. The scope and application of measurement are dependent on the context and discipline. In natural sciences and engineering, measurements do not apply to nominal properties of objects or events, which is consistent with the guidelines of the ''International vocabulary of metrology'' published by the International Bureau of Weights and Measures. However, in other fields such as statistics as well as the social and behavioural sciences, measurements can have multiple levels, which would include nominal, ordinal, interval and ratio scales. Measurement is a cornerstone of trade, science, technology and quantitative research in many disciplines. Historically, many measurement systems existed fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
