The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform
M. Gallerani - One of the best experts on this subject based on the ideXlab platform.
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An experimental comparison of different methods of measuring wave propagation in viscoelastic tubes
Journal of biomechanics, 1994Co-Authors: Mauro Ursino, E. Artioli, M. GalleraniAbstract:In this work the values of wave attenuation and phase velocity in a 6 x 9 latex rubber tube closed at the distal end were measured by means of different Equations, and varying the distance between transducers. Three Equations are based on two simultaneous pressure measurements and on the knowledge of the terminal reflection coefficient (two-point methods). The Fourth Equation is based on three simultaneous pressure measurements (three-point method). In all cases small amplitude pressure signals (20 mmHg peak-to-peak) were employed. The results of our experiments were then compared with those computed using a classic linear model of wave propagation, and with the high-frequency asymptotic values obtained experimentally using an original method recently developed by the authors. The results obtained with 40 cm between transducers demonstrate that phase velocity (about 15 m/s) and wave attenuation (about 0.003 Neper/cm at 10 Hz) are in agreement with the predictions of classic linear theories in the frequency range 1-15 Hz, provided wall tethering and viscoelasticity are taken into account. Only at certain critical frequencies, which depend on the particular Equation employed, does the estimation of wave attenuation become inaccurate owing to an insufficient signal-to-noise ratio. Moreover, wave propagation measurements become inaccurate also at very low frequencies (< 1 Hz). The results obtained using a small distance between transducers (10 cm) demonstrate that the two-point methods maintain greater accuracy than the three-point one. In particular, when reducing the separation between transducers, the three-point attenuation values become 3-4 times greater than the attenuation obtained using the two-point Equations. This finding might explain the large differences between propagation values observed in recent in vivo experiments. Finally, asymptotic estimations of the high-frequency phase velocity and attenuation per wave-length turn out rather robust and insensitive to a reduction in the transducer distance. These estimations might, therefore, be usefully adopted during in vivo experiments performed in difficult conditions.
Mauro Ursino - One of the best experts on this subject based on the ideXlab platform.
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An experimental comparison of different methods of measuring wave propagation in viscoelastic tubes
Journal of biomechanics, 1994Co-Authors: Mauro Ursino, E. Artioli, M. GalleraniAbstract:In this work the values of wave attenuation and phase velocity in a 6 x 9 latex rubber tube closed at the distal end were measured by means of different Equations, and varying the distance between transducers. Three Equations are based on two simultaneous pressure measurements and on the knowledge of the terminal reflection coefficient (two-point methods). The Fourth Equation is based on three simultaneous pressure measurements (three-point method). In all cases small amplitude pressure signals (20 mmHg peak-to-peak) were employed. The results of our experiments were then compared with those computed using a classic linear model of wave propagation, and with the high-frequency asymptotic values obtained experimentally using an original method recently developed by the authors. The results obtained with 40 cm between transducers demonstrate that phase velocity (about 15 m/s) and wave attenuation (about 0.003 Neper/cm at 10 Hz) are in agreement with the predictions of classic linear theories in the frequency range 1-15 Hz, provided wall tethering and viscoelasticity are taken into account. Only at certain critical frequencies, which depend on the particular Equation employed, does the estimation of wave attenuation become inaccurate owing to an insufficient signal-to-noise ratio. Moreover, wave propagation measurements become inaccurate also at very low frequencies (< 1 Hz). The results obtained using a small distance between transducers (10 cm) demonstrate that the two-point methods maintain greater accuracy than the three-point one. In particular, when reducing the separation between transducers, the three-point attenuation values become 3-4 times greater than the attenuation obtained using the two-point Equations. This finding might explain the large differences between propagation values observed in recent in vivo experiments. Finally, asymptotic estimations of the high-frequency phase velocity and attenuation per wave-length turn out rather robust and insensitive to a reduction in the transducer distance. These estimations might, therefore, be usefully adopted during in vivo experiments performed in difficult conditions.
Renato Spigler - One of the best experts on this subject based on the ideXlab platform.
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Geometric effects in the design of catalytic converters in car exhaust pipes
Mathematics-in-Industry Case Studies, 2018Co-Authors: Matteo Laurenzi, Renato SpiglerAbstract:Introduction We solve the gas dynamics (Euler) Equations, augmented by adding a Fourth Equation governing the fraction of unburnt gas, in a number of cylindrically symmetric configurations of the pipe system. Case description The purpose is to test several duct profiles to see which one favors a higher reduction of the residual noxious gases, at the end of a car’s exhaust pipe. Discussion and evaluation It is found that this purely geometric factor does play a role in the environment’s purification accomplished by the catalytic converter. This is possibly due to the longer time spent by the noxious gases resident inside the device when this has certain profiles, though at the price of a little higher temperature attained. Conclusions It seems that geometric factors play a role in reducing cars’ noxious gases by means of catalytic converters. A more precise analysis should be formulated as a mathematical inverse problem.
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Geometric effects in the design of catalytic converters in car exhaust pipes
Mathematics-in-Industry Case Studies, 2018Co-Authors: Matteo Laurenzi, Renato SpiglerAbstract:We solve the gas dynamics (Euler) Equations, augmented by adding a Fourth Equation governing the fraction of unburnt gas, in a number of cylindrically symmetric configurations of the pipe system. The purpose is to test several duct profiles to see which one favors a higher reduction of the residual noxious gases, at the end of a car’s exhaust pipe. It is found that this purely geometric factor does play a role in the environment’s purification accomplished by the catalytic converter. This is possibly due to the longer time spent by the noxious gases resident inside the device when this has certain profiles, though at the price of a little higher temperature attained. It seems that geometric factors play a role in reducing cars’ noxious gases by means of catalytic converters. A more precise analysis should be formulated as a mathematical inverse problem.
Andrew Beckwith - One of the best experts on this subject based on the ideXlab platform.
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Using “Enhanced Quantization” to Bound the Cosmological Constant, and Computing Quantum Number N for Production of 100 Relic Mini Black Holes in a Spherical Region of Emergent Space-Time
viXra, 2018Co-Authors: Andrew BeckwithAbstract:We are looking at comparison of two action integrals and we identify the Lagrangian multiplier as setting up a constraint Equation (on cosmological expansion). This is a direct result of the Fourth Equation of our manuscript which unconventionally compares the action integral of General relativity with the second derived action integral, which then permits Equation 5, which is a bound on the Cosmological constant. What we have done is to replace the Hamber Quantum gravity reference-based action integral with a result from John Klauder’s “Enhanced Quantization”. In doing so, with Padamabhan’s treatment of the inflaton, we then initiate an explicit bound upon the cosmological constant. The other approximation is to use the inflaton results and conflate them with John Klauder’s Action principle for a way to, if we have the idea of a potential well, generalized by Klauder, with a wall of space time in the Pre Planckian-regime to ask what bounds the Cosmological constant prior to inflation. And, get an upper bound on the mass of a graviton. We conclude with a redo of a multiverse version of the Penrose cyclic conformal cosmology to show how this mass of a heavy graviton is consistent from cycle to cycle. All this is possible due to Equation 4. And we compare all this with results of reference [1] in the conclusion. While showing its relevance to early universe production of black holes, and the volume of space producing 100 black holes of say 10^2 times Planck Mass. Initially in radii of 10^3 Planck length, of space-time for say entropy of about 1000 initially speaking. Key words: Inflaton, action integral, Cosmological Constant, Penrose cyclic cosmology, black holes, massive gravitons, enhanced quantization
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Using “Enhanced Quantization” to Bound the Cosmological Constant, (For a Bound-on Graviton Mass), by Comparing Two Action Integrals(one Being from General Relativity) at the Start of Inflation
viXra, 2018Co-Authors: Andrew BeckwithAbstract:We are looking at comparison of two action integrals and we identify the Lagrangian multiplier as setting up a constraint Equation (on cosmological expansion). This is a direct result of the Fourth Equation of our manuscript which unconventionally compares the action integral of General relativity with the second derived action integral, which then permits Equation 5, which is a bound on the Cosmological constant. What we have done is to replace the Hamber Quantum gravity reference-based action integral with a result from John Klauder’s “Enhanced Quantization” . In doing so, with Padamabhan’s treatment of the inflaton, we then initiate an explicit bound upon the cosmological constant. The other approximation is to use the inflaton results and conflate them with John Klauder’s Action principle for a way to, if we have the idea of a potential well, generalized by Klauder, with a wall of space time in the Pre Planckian-regime to ask what bounds the Cosmological constant prior to inflation. And, get an upper bound on the mass of a graviton. We conclude with a redo of a multiverse version of the Penrose cyclic conformal cosmology to show how this mass of a heavy graviton is consistent from cycle to cycle. All this is possible due to Equation 4. And we compare all this with results of reference [1] in the conclusion.
E. Artioli - One of the best experts on this subject based on the ideXlab platform.
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An experimental comparison of different methods of measuring wave propagation in viscoelastic tubes
Journal of biomechanics, 1994Co-Authors: Mauro Ursino, E. Artioli, M. GalleraniAbstract:In this work the values of wave attenuation and phase velocity in a 6 x 9 latex rubber tube closed at the distal end were measured by means of different Equations, and varying the distance between transducers. Three Equations are based on two simultaneous pressure measurements and on the knowledge of the terminal reflection coefficient (two-point methods). The Fourth Equation is based on three simultaneous pressure measurements (three-point method). In all cases small amplitude pressure signals (20 mmHg peak-to-peak) were employed. The results of our experiments were then compared with those computed using a classic linear model of wave propagation, and with the high-frequency asymptotic values obtained experimentally using an original method recently developed by the authors. The results obtained with 40 cm between transducers demonstrate that phase velocity (about 15 m/s) and wave attenuation (about 0.003 Neper/cm at 10 Hz) are in agreement with the predictions of classic linear theories in the frequency range 1-15 Hz, provided wall tethering and viscoelasticity are taken into account. Only at certain critical frequencies, which depend on the particular Equation employed, does the estimation of wave attenuation become inaccurate owing to an insufficient signal-to-noise ratio. Moreover, wave propagation measurements become inaccurate also at very low frequencies (< 1 Hz). The results obtained using a small distance between transducers (10 cm) demonstrate that the two-point methods maintain greater accuracy than the three-point one. In particular, when reducing the separation between transducers, the three-point attenuation values become 3-4 times greater than the attenuation obtained using the two-point Equations. This finding might explain the large differences between propagation values observed in recent in vivo experiments. Finally, asymptotic estimations of the high-frequency phase velocity and attenuation per wave-length turn out rather robust and insensitive to a reduction in the transducer distance. These estimations might, therefore, be usefully adopted during in vivo experiments performed in difficult conditions.
