Hypersonic Velocity, Absorption and Relaxation in Molten CSNO3

1977 ◽  
Vol 32 (1) ◽  
pp. 57-60 ◽  
Author(s):  
H. E. Gunilla Knape ◽  
Lena M. Torell
Keyword(s):  
Relaxation Time ◽  
High Frequency ◽  
Viscosity Coefficient ◽  
Sound Waves ◽  
Frequency Range ◽  
Ultrasonic Velocities ◽  
Hypersonic Velocity ◽  
Frequency Shifts ◽  
Bulk Viscosity Coefficient ◽  
Good Agreement

Abstract Brillouin spectra of molten CSNO3 were investigated for scattering angles between 40 and 140° and in a temperature interval of 420-520 °C. An Ar+ singlemode laser was used for excitation and the total instrumental width was ~265 MHz. The measured frequency shifts and linewidths of the Brillouin components were used to determine velocities and attenuations of thermal sound waves in the frequency range 2.3-7.0 GHz. A dispersion of 4-5% was found between the present hyper­ sonic velocities and reported ultrasonic velocities. A considerable decrease in attenuation with frequency was observed in the investigated frequency range, with the value at high frequency ap­ proaching the classical attenuation. The results are in good agreement with Mountain's theory of a single relaxation time. The relaxation time of the bulk viscosity coefficient was calculated to 1.2×10-10S.

Approaches to Predicting the Vertical Transmissibility of a Suspension Seat With a Seated Subject

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Jun Wu ◽  
Meihuan Wang ◽  
Yi Qiu
Keyword(s):  
High Frequency ◽  
Dynamic Stiffness ◽  
The Other ◽  
Human Model ◽  
Apparent Mass ◽  
Frequency Range ◽  
Air Suspension ◽  
In Series ◽  
Inert Mass ◽  
Good Agreement

Abstract In this paper, four methods were put forward to predict the transmissibility of an air suspension seat with a seated subject. For characterizing the dynamics of the suspension seat, two of the methods were based on developing a model of the air suspension seat and calibrating the parameters using the transmissibilities of the suspension and complete seat respectively with an inert mass from the experiment. The other two methods substituted the detailed modeling of the seat by two dynamic stiffness connecting in series calculated from two same transmissibilities measured in the experiment. For characterizing the biodynamics of the human body, two of the methods took advantage of the normalized apparent mass from published papers to take the place of the human model, while the other two methods made use of one measured seat transmissibility with a subject to deduce the apparent masses of all the subjects. Good agreement was illustrated between the experiment and model prediction for all the four methods. In addition, it also exhibited that a large discrepancy can be resulted in, especially in the high-frequency range, if the seat model was substituted by one integrated dynamic stiffness.

scholarly journals Vibrational Cooling After Photo Isomerisation: First Application of a Novel Intramolecular Thermometer

1999 ◽  
Vol 19 (1-4) ◽  
pp. 45-49 ◽  
Author(s):  
P. Hamm ◽  
S. Ohline ◽  
M. Zurek ◽  
T. Röschinger
Keyword(s):  
Experimental Data ◽  
Schiff Base ◽  
Time Resolution ◽  
High Frequency ◽  
Low Frequency ◽  
Frequency Range ◽  
Frequency Shifts ◽  
Absorption Change ◽  
Vibrational System ◽  
Anharmonic Coupling

Femtosecond VIS-pump-IR-probe experiments (time resolution: 300fs, detectable absorption change: 5.10-5 , frequency range: 1000–1800 cm-1) were applied to the ultrafast photo isomerisation of azobenzene and the protonated Schiff base of retinal. The energy of the pump photon heats the vibrational system of the molecule, leading to pronounced anharmonic frequency shifts which are dominated by the anharmonic coupling between the investigated high frequency modes to hot low frequency modes. A model taking into account this intramolecular anharmonicity and assuming a well defined intramolecular temperature gives a good fit of the experimental data.

DECELERATING CAUSAL BULK VISCOUS COSMOLOGICAL MODELS

2000 ◽  
Vol 09 (02) ◽  
pp. 97-110 ◽  
Author(s):  
T. HARKO ◽  
M. K. MAK
Keyword(s):  
Relaxation Time ◽  
Bulk Viscosity ◽  
Viscosity Coefficient ◽  
State Equation ◽  
Cosmological Models ◽  
Boltzmann Gas ◽  
Bulk Viscous ◽  
Barotropic Equation ◽  
Bulk Viscosity Coefficient ◽  
The Universe

The dynamics of a causal bulk viscous cosmological fluid filled flat constantly decelerating noninflationary Robertson–Walker spacetime is considered. The matter component of the Universe is assumed to satisfy a linear barotropic equation of state and the state equation of the small temperature Boltzmann gas. The resulting cosmological models satisfy the condition of smallness of the viscous stress. The evolution of the relaxation time, temperature, bulk viscosity coefficient and comoving entropy of the dissipative cosmological fluid are obtained by assuming several bulk viscosity coefficient-relaxation time relations.

scholarly journals Electrostatically Tunable Nanomechanical Shallow Arches

2017 ◽  
Author(s):  
Syed N. R. Kazmi ◽  
Amal Z. Hajjaj ◽  
Pedro M. F. J. Costa ◽  
Mohammad I. Younis
Keyword(s):  
High Frequency ◽  
Room Temperature ◽  
Silicon On Insulator ◽  
Frequency Range ◽  
Shallow Arches ◽  
High Tunability ◽  
Band Pass ◽  
Dc Bias ◽  
Silicon Based ◽  
Good Agreement

We report an analytical and experimental study on the tunability of in-plane doubly-clamped nanomechanical arches under varied DC bias conditions at room temperature. For this purpose, silicon based shallow arches are fabricated using standard e-beam lithography and surface nanomachining of a highly conductive device layer on a silicon-on-insulator (SOI) wafer. The experimental results show good agreement with the analytical results with a maximum tunability of 108.14% for 180 nm thick arch with a transduction gap of 1 μm between the beam and the driving/sensing electrodes. The high tunability of shallow arches paves the ways for highly tunable band pass filtering applications in high frequency range.

scholarly journals Comparison of the fast Lyman-Alpha and LICOR hygrometers for measuring airborne turbulent fluctuations

2017 ◽  
Author(s):  
Astrid Lampert ◽  
Jörg Hartmann ◽  
Falk Pätzold ◽  
Lennart Lobitz ◽  
Peter Hecker ◽  
...  
Keyword(s):  
High Frequency ◽  
Frequency Noise ◽  
Closed Path ◽  
Mixing Ratio ◽  
Frequency Range ◽  
Absolute Value ◽  
Lyman Alpha ◽  
Airborne Measurements ◽  
Open Path ◽  
Good Agreement

Abstract. The properties of fast hygrometers, the Lyman-Alpha and different LICOR humidity sensors, are analysed in direct intercomparison flights on different airborne platforms. One vibration isolated closed-path and two non-isolated open path LICOR sensors were installed on the twin engine turbo-prop aircraft Dornier 128. The closed-path sensor provided absolute values and fluctuations of the water vapour mixing ratio in good agreement with the Lyman-Alpha. The signals of the two open-path sensors showed considerable high frequency noise, and the absolute value of the mixing ratio was observed to drift with time in this vibrational environment. On the helicopter-towed sonde Helipod with very low vibration level the open-path LICOR sensor agreed very well with the Lyman-Alpha over the entire frequency range up to 3 Hz. The results show that the LICOR sensors are well suited for airborne measurements of humidity fluctuations, provided that a vibrationsless environment is given, and this turns out to be more important than close sensor spacing.

scholarly journals Continuum perspective of bulk viscosity in compressible fluids

2017 ◽  
Vol 812 ◽  
pp. 966-990 ◽  
Author(s):  
Xin-Dong Li ◽  
Zong-Min Hu ◽  
Zong-Lin Jiang
Keyword(s):  
Relaxation Time ◽  
Bulk Viscosity ◽  
Viscosity Coefficient ◽  
Linear Increase ◽  
Compressible Fluids ◽  
Theoretical Formula ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Bulk Viscosity Coefficient ◽  
The Continuum

Kinetic theory and acoustic measurements have proven that the bulk viscosity associated with the expansion or compression effect cannot be ignored in compressible fluids except for monatomic gases. A new theoretical formula for the bulk viscosity coefficient (BVC) $\unicode[STIX]{x1D701}$ is derived by the continuum medium methodology, which provides a further understanding of the bulk viscosity, i.e. $\unicode[STIX]{x1D701}$ is equal to the product of the bulk modulus $K$ and the relaxation time $\unicode[STIX]{x1D70F}$ ($\unicode[STIX]{x1D701}=K\unicode[STIX]{x1D70F}$). The continuum and kinetic theories present consistent results from macro- and microperspectives respectively, only differing in terms of a coefficient. The theoretical predictions of the BVC in diatomic molecules, such as $\text{N}_{2}$, $\text{O}_{2}$ and CO, show good agreement with the experimental data over a wide range of temperature. In addition, the vibrational contributions to $\unicode[STIX]{x1D701}$ are controlled by a rapid exponential decrease at high temperatures, while at low temperatures a slow linear increase proceeds for the rotational cases. The relaxation time $\unicode[STIX]{x1D70F}$, collision number $Z$, BVC $\unicode[STIX]{x1D701}$ and ratio of bulk-to-shear viscosities $\unicode[STIX]{x1D701}/\unicode[STIX]{x1D707}$ in the vibrational mode are found to be several orders of magnitude larger than those in the rotational mode.

Winding Loss Simulation and Optimal Design of a High Frequency Coaxial Transformer

2012 ◽  
Vol 466-467 ◽  
pp. 567-571
Author(s):  
Xiao Guang Yang
Keyword(s):  
Magnetic Field ◽  
Proximity Effect ◽  
High Frequency ◽  
Coupling Efficiency ◽  
Analytical Calculation ◽  
Frequency Range ◽  
Voltage Ratio ◽  
Winding Loss ◽  
Split Winding ◽  
Good Agreement

A high frequency coaxial transformer (HFCT) with a split winding structure and litz wire has been developed for high frequency (HF) and high power DC/DC converter applications. A method combined numerical analysis of magnetic field and analytical calculation of litz wire winding losses, taking into account conduction losses and proximity effect losses, is proposed for the designed HFCT. The experimental results validate the winding loss calculation method. The measured results demonstrate that the voltage ratio has a good agreement with the turn ratio over the frequency range from 0.1MHz to 1MHz, indicating that the high coupling efficiency has been obtained.

scholarly journals Modeling High-Frequency Backscattering from a Mesh of Curved Surfaces Using Kirchhoff Approximation

2019 ◽  
Vol 27 (04) ◽  
pp. 1850057
Author(s):  
E. F. Lavia ◽  
J. D. Gonzalez ◽  
S. Blanc
Keyword(s):  
High Frequency ◽  
Complex Structure ◽  
Curved Surfaces ◽  
High Frequency Range ◽  
Frequency Range ◽  
Kirchhoff Approximation ◽  
Acoustic Backscattering ◽  
Iterative Integration ◽  
The One ◽  
Good Agreement

The Kirchhoff approximation (K-A) to calculate the acoustic backscattering of a complex structure can be evaluated using a discretized version of its surface (i.e, a mesh). From the computational viewpoint, the most handy approach is the one based on flat facets. However, in the high-frequency range, where the K-A provides good agreement and is therefore applicable, it requires a mesh with such a large number of facets that it turns impractical. To avoid these difficulties, a mesh of curved triangles can be used to model the scatterer’s complex structure. Previous computational implementations reported in the literature did not accomplish satisfactory results for high frequency. In this work, we propose a numerical model based upon an iterative integration using Gauss–Legendre rules. The model was validated against exact solutions and led us to achieve adequate results in the high-frequency range.

The Dynamic Response of Railway Track to High Frequency Vertical Excitation

1982 ◽  
Vol 24 (2) ◽  
pp. 77-90 ◽  
Author(s):  
S. L. Grassie ◽  
R. W. Gregory ◽  
D. Harrison ◽  
K. L. Johnson
Keyword(s):  
Dynamic Response ◽  
High Frequency ◽  
Dynamic Models ◽  
The Other ◽  
Dynamic Loads ◽  
Railway Track ◽  
Frequency Range ◽  
Vertical Excitation ◽  
Discrete Mass ◽  
Good Agreement

Two new dynamic models of railway track are presented, one continuous and the other incorporating the discrete mass of the sleepers. These models include the effect of the railpads which exist between rail and sleeper on modern track, and are used to calculate both the response of the track alone and the contact force between a moving wheel and the rail. There is good agreement between calculation and experiment in the frequency range from 50 to 1500 Hz, and it is shown that the railpad is of fundamental importance in attenuating dynamic loads in this frequency range.

Second Iteration of Slotted Fractal Log Periodic Dipole Antenna for UHF Digital TV Band Application

2021 ◽  
Vol 20 (3) ◽  
pp. 48-52
Author(s):  
Muhammad Hafeez Rosmin ◽  
Mohamad Kamal A Rahim ◽  
Nur Syahirah Yaziz ◽  
Muhammad Naeem Iqbal ◽  
Osman Ayop ◽  
...  
Keyword(s):  
Reflection Coefficient ◽  
Radiation Pattern ◽  
High Frequency ◽  
Dipole Antenna ◽  
Digital Tv ◽  
Wet Etching ◽  
Tangent Loss ◽  
Frequency Range ◽  
Etching Technique ◽  
Good Agreement

This paper discusses the simulations and measurements of the antenna with and without slot implementation in terms of reflection coefficient (S11) and radiation pattern. The slot implementation on each of the radiating elements on the 2nd iteration log periodic fractal Koch antenna (LPFKA) was described in this paper. This method is utilised to reduce the antenna's size while also preventing the lower designated frequencies from shifting to the higher band as the iteration increases. The antenna is designed to test and observe performance in the Ultra High Frequency (UHF) band, which ranges from 0.5 GHz to 3.0 GHz. Computer Simulation Technology (CST) software is used to design and model the antenna, which was then built using the wet etching technique. The antenna's substrate is made of FR-4 laminated board with a dielectric constant of 4.6, tangent loss of 0.019, and a thickness of 1.6mm. The results demonstrate good agreement, with a steady radiation pattern over the operational bandwidth and a reflection coefficient of less than -10 dB for the frequency range of interest. The antenna is being tested with Digital TV decoder and the result is observed towards the picture of the Digital TV.

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