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Continuous Scan Laser Doppler Vibrometry
Continuous-scan laser Doppler vibrometry (CSLDV) is a method of using a laser Doppler vibrometer (LDV) in which the laser beam is swept across the surface of a test subject to capture the motion of a surface at many points simultaneously. This is different from scanning laser vibrometry (SLDV) in which the laser beam is kept at a fixed point during each measurement and quickly moved to a new position before acquiring the next measurement. Advantages and disadvantages CSLDV can allow one to capture the mode shapes of a structure with high resolution much more quickly than would be possible with SLDV. Allen & Sracic show results where measurements were acquired with CSLDV in a hundredth of the time that would be required for LDV. Allen & Aguilar postulated that the additional detail available from CSLDV might provide important information when validating structural dynamic models. CSLDV also makes testing with an instrumented hammer practical with LDV, and some have speculated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser Doppler Vibrometer
A laser Doppler vibrometer (LDV) is a scientific instrument that is used to make non-contact vibration measurements of a surface. The laser beam from the LDV is directed at the surface of interest, and the vibration amplitude and frequency are extracted from the Doppler shift of the reflected laser beam frequency due to the motion of the surface. The output of an LDV is generally a continuous analog voltage that is directly proportional to the target velocity component along the direction of the laser beam. Some advantages of an LDV over similar measurement devices such as an accelerometer are that the LDV can be directed at targets that are difficult to access, or that may be too small or too hot to attach a physical transducer. Also, the LDV makes the vibration measurement without mass-loading the target, which is especially important for MEMS devices. Principles of operation A vibrometer is generally a two beam laser interferometer that measures the frequency (or phase) dif ... [...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 coherence (physics), ''coherent''. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and Photolithography#Light sources, lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimated light, 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 frequency spectrum, spectru ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scanning Laser Vibrometry
The scanning laser vibrometer or scanning laser Doppler vibrometer, was first developed by the British loudspeaker company, Celestion, around 1979, further developed in the 1980s,Stoffregen, B., Felske, A., “Scanning Laser Doppler Analysis System,” SAE Paper No. 850327, 1985. and commercially introduced by Ometron, Ltd around 1986. It is an instrument for rapid non-contact measurement and imaging of vibration. Fields where they are applied include automotive, medical, aerospace, micro system and information technology as well as for quality and production control. The optimization of vibration and acoustic behavior are important goals of product development in all of these fields because they are often among the key characteristics that determine a product's success in the market. They are also in widespread use throughout many universities conducting basic and applied research in areas that include structural dynamics, modal analysis, acoustic optimization and non-destr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Normal Mode
A normal mode of a dynamical system is a pattern of motion in which all parts of the system move sinusoidally with the same frequency and with a fixed phase relation. The free motion described by the normal modes takes place at fixed frequencies. These fixed frequencies of the normal modes of a system are known as its natural frequencies or resonant frequencies. A physical object, such as a building, bridge, or molecule, has a set of normal modes and their natural frequencies that depend on its structure, materials and boundary conditions. The most general motion of a system is a superposition of its normal modes. The modes are normal in the sense that they can move independently, that is to say that an excitation of one mode will never cause motion of a different mode. In mathematical terms, normal modes are orthogonal to each other. General definitions Mode In the wave theory of physics and engineering, a mode in a dynamical system is a standing wave state of exci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structural Dynamics
Structural dynamics is a type of structural analysis which covers the behavior of a structure subjected to dynamic (actions having high acceleration) loading. Dynamic loads include people, wind, waves, traffic, earthquakes, and blasts. Any structure can be subjected to dynamic loading. Dynamic analysis can be used to find dynamic displacements, time history, and modal analysis. Structural analysis is mainly concerned with finding out the behavior of a physical structure when subjected to force. This action can be in the form of load due to the weight of things such as people, furniture, wind, snow, etc. or some other kind of excitation such as an earthquake, shaking of the ground due to a blast nearby, etc. In essence all these loads are dynamic, including the self-weight of the structure because at some point in time these loads were not there. The distinction is made between the dynamic and the static analysis on the basis of whether the applied action has enough acceleration ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speckle Noise
Speckle, speckle pattern, or speckle noise is a granular noise texture degrading the quality as a consequence of interference among wavefronts in coherent imaging systems, such as radar, synthetic aperture radar (SAR), medical ultrasound and optical coherence tomography. Speckle is not external noise; rather, it is an inherent fluctuation in diffuse reflections, because the scatterers are not identical for each cell, and the coherent illumination wave is highly sensitive to small variations in phase changes. Although scientists have investigated this phenomenon since the time of Newton, speckles have come into prominence since the invention of the laser. Such reflections may occur on materials such as paper, white paint, rough surfaces, or in media with a large number of scattering particles in space, such as airborne dust or in cloudy liquids. They have been used in a variety of applications in microscopy, imaging, and optical manipulation. The vast majority of surfaces, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Imperial College
Imperial College London (legally Imperial College of Science, Technology and Medicine) is a public research university in London, United Kingdom. Its history began with Prince Albert, consort of Queen Victoria, who developed his vision for a cultural area that included the Royal Albert Hall, Victoria & Albert Museum, Natural History Museum and royal colleges. In 1907, Imperial College was established by a royal charter, which unified the Royal College of Science, Royal School of Mines, and City and Guilds of London Institute. In 1988, the Imperial College School of Medicine was formed by merging with St Mary's Hospital Medical School. In 2004, Queen Elizabeth II opened the Imperial College Business School. Imperial focuses exclusively on science, technology, medicine, and business. The main campus is located in South Kensington, and there is an innovation campus in White City. Facilities also include teaching hospitals throughout London, and with Imperial College Healthca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Wisconsin – Madison
A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. ''University'' is derived from the Latin phrase ''universitas magistrorum et scholarium'', which roughly means "community of teachers and scholars". Universities typically offer both undergraduate and postgraduate programs. The first universities in Europe were established by Catholic Church monks. The University of Bologna (), Italy, which was founded in 1088, is the first university in the sense of: *being a high degree-awarding institute. *using the word ''universitas'' (which was coined at its foundation). *having independence from the ecclesiastic schools and issuing secular as well as non-secular degrees (with teaching conducted by both clergy and non-clergy): grammar, rhetoric, logic, theology, canon law, notarial law.Hunt Janin: "The university in medieval life, 1179–1499", McFarland, 2008, , p. 55f.de Ridder-Symoens, Hilde''A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Maryland, Baltimore County
The University of Maryland, Baltimore County (UMBC) is a public research university in Baltimore County, Maryland. It has a fall 2022 enrollment of 13,991 students, 61 undergraduate majors, over 92 graduate programs (38 master, 25 doctoral, and 29 graduate certificate programs) and the first university research park in Maryland. It is classified among "R1: Doctoral Universities – Very High Research Activity". Established as a part of the University System of Maryland in 1966, the university became the first public college or university in Maryland to be inclusive of all races. UMBC has the fourth highest enrollment of the University System of Maryland, specializing in natural sciences and engineering, as well as programs in the liberal arts and social sciences. Athletically, the UMBC Retrievers have 17 NCAA Division I teams that participate in the America East Conference. History The planning of the University of Maryland, Baltimore County was first discussed in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser Applications
Many scientific, military, medical and commercial laser applications have been developed since the invention of the laser in 1958. The coherency, high monochromaticity, and ability to reach extremely high powers are all properties which allow for these specialized applications. Scientific In science, lasers are used in many ways, including: * A wide variety of interferometric techniques'' * Raman spectroscopy * Laser induced breakdown spectroscopy * Atmospheric '' remote sensing'' * Investigating nonlinear optics phenomena * Holographic techniques employing lasers also contribute to a number of measurement techniques. * Laser based lidar (LIght raDAR) technology has application in geology, seismology, remote sensing and atmospheric physics. * Lasers have been used aboard spacecraft such as in the Cassini-Huygens mission. * In astronomy, lasers have been used to create artificial '' laser guide stars'', used as reference objects for adaptive optics telescopes. Lasers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Measuring Instruments
A measuring instrument is a device to measure a physical quantity. In the physical sciences, quality assurance, and engineering, measurement is the activity of obtaining and comparing physical quantities of real-world objects and events. Established standard objects and events are used as units, and the process of measurement gives a number relating the item under study and the referenced unit of measurement. Measuring instruments, and formal test methods which define the instrument's use, are the means by which these relations of numbers are obtained. All measuring instruments are subject to varying degrees of instrument error and measurement uncertainty. These instruments may range from simple objects such as rulers and stopwatches to electron microscopes and particle accelerators. Virtual instrumentation is widely used in the development of modern measuring instruments. Time In the past, a common time measuring instrument was the sundial. Today, the usual measu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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