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.

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.

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.

Horizontal Vibration of Pile Considering Pile-Soil Separation

2013 ◽  
Vol 838-841 ◽  
pp. 685-689
Author(s):  
Hong Xia Han ◽  
Wu Wen Cui ◽  
Yan Yan Li
Keyword(s):  
Mixed Boundary ◽  
Dynamic Stiffness ◽  
Expansion Method ◽  
The Other ◽  
Infinite Plane ◽  
Theory Of Computation ◽  
Horizontal Vibration ◽  
Circular Holes ◽  
Stiffness And Damping ◽  
Good Agreement

Taken into account the effect of pile partially separated from soils, the dynamic stiffness and damping of pile in horizontal vibration is caculated by using the theory of computation about the mixed boundary value problem of circular holes radiation stress at an infinite plane and the theory of elastic waves, and the Fourier expansion method. The calculated results based on this paper are compared with the calculated results of the other literature. It is showed that the calculated results considering the influence of pile-soil separation are less than that of the other literature, which the bonding of the pile to the soil was assumed, and are in good agreement with experiments.

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 Modifikasi Permukaan Elemen Peredam Bising Dengan Profil Berbentuk Prisma

2016 ◽  
Vol 6 (01) ◽  
Author(s):  
Hanif Azimut
Keyword(s):  
High Frequency ◽  
Sound Absorption ◽  
Coupling Effect ◽  
Low Frequency ◽  
The Other ◽  
Frequency Range ◽  
Closed Type ◽  
Wave Resonance ◽  
Half Wave ◽  
Absorption Performance

<p class="AbstractText">The influence of surface modification by using prism shaped profile on the sound absorption of absorber element was investigated experimentally. A prime number based configuration of the two types opened and closed type rism shaped profile inclusion was tested by using impedance tube according ASTM E1050 standard. The result shows that sound absorption at low frequency band below 200 Hz increased with the increasing of closed prism number. It is related to the coupling effect between the cavities of the absorber element and the prisms that changes reactance of the coupled structure. In the other side, a half wave resonance like effect occur on the use of opened prisms inclusion, which is increase the sound absorption performance at mid to high frequency range between 800 Hz to 1,25 kHz.  </p>

scholarly journals Methods of Testing of Sound Insulation Properties of Barriers Intended for High Frequency Noise and Ultrasonic Noise Protection

2018 ◽  
Vol 68 (4) ◽  
pp. 55-64
Author(s):  
Pleban Dariusz ◽  
Mikulski Witold
Keyword(s):  
High Frequency ◽  
Test Chamber ◽  
Test Stand ◽  
The Other ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Frequency Range ◽  
High Frequency Noise

AbstractTwo test stands for determining sound insulation in the frequency range above 5 kHz were made. One consisted of two horizontally adjacent reverberation rooms and a special source of high frequency sounds and ultrasounds. The other test stand consisted of a miniaturized test chamber and a special source of ultrasounds. The paper presents results of the preliminary measurements of sound insulation properties of different barriers in the frequency range above 5 kHz.

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.

scholarly journals Calculation of Site Attenuation for Calculable Dipole Antennas

2020 ◽  
Vol 20 (2) ◽  
pp. 145-154
Author(s):  
Ki-Chai Kim ◽  
Hyuk-Jun Seo ◽  
Tae-Weon Kang ◽  
Jae-Yong Kwon ◽  
Jeong-Hwan Kim
Keyword(s):  
Half Space ◽  
Measurement System ◽  
Power Loss ◽  
Test Site ◽  
The Other ◽  
Open Area ◽  
Frequency Range ◽  
Dipole Antennas ◽  
Dissipative Loss ◽  
Good Agreement

This paper presents a method for calculating the site attenuation (SA) of an open-area test site (OATS) for a pair of calculable dipole antennas with a 3-dB hybrid balun in the frequency range of 30 MHz to 1 GHz. The SA was directly derived using the concept of power mismatch and dissipative loss from the SA measurement system instead of the concept of substitution loss. Two types of SA formulas using the power loss concept on the treatment of the OATS are presented. The first is the SA formula related to knowing only the value of the SA. The other is the SA formula that analyzed the effects of each part of the SA. Additionally, the constituent losses of the SA measurement system are discussed using the derived SA formula. The analysis of the results showed that the SA could be successfully characterized individually from the loss of the OATS. It also showed that SA is expressed as two kinds of losses: the balanced portmismatch losses of transmit and receive baluns and the half-space dissipative loss. The resultant SA showed good agreement with the results calculated from the S-parameters as well as with the measured results.

Sign in / Sign up

Export Citation Format

Share Document