Damping and Bandgap Characteristics of a Viscoelastic Tensegrity Damper

2021 ◽  
pp. 1-47
Author(s):  
Mohamed Raafat ◽  
Amr Baz
Keyword(s):  
Mathematical Model ◽  
Material Characterization ◽  
Structural Vibrations ◽  
New Class ◽  
Structural Applications ◽  
Theoretical Predictions ◽  
Specific Frequency ◽  
The Mathematical Model ◽  
Theory And Experiments

Abstract A theoretical and experimental investigation of a new class of a tensegrity-based structural damper is presented. The damper is not only capable of attenuating undesirable structural vibrations, as all conventional dampers, but also capable of completely blocking the transmission of vibration over specific frequency bands by virtue of its periodicity. Such dual functionality distinguishes the tensegrity damper over its counterparts of existing structural dampers. Particular emphasis is placed here in presenting the concept and developing the mathematical model of the dynamics of a unit cell the damper. The model is then coupled with a Floquet-Bloch analysis in order to identify the bandgap characteristics of the damper. The predictions of the mathematical model are validated experimentally using a prototype of the damper which is built using 3D printing. A comprehensive material characterization of the damper is performed followed by a detailed extraction of the static and dynamic behavior of the damper in order to validate the theoretical predictions. Close agreement is observed between theory and experiments. The developed theoretical and experimental techniques provide invaluable means for the design of this new class of dampers particularly for critical structural applications.

scholarly journals Modelling Degradation and Replication Kinetics of the Zika Virus In Vitro Infection

Viruses ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 547
Author(s):  
Veronika Bernhauerová ◽  
Veronica V. Rezelj ◽  
Marco Vignuzzi
Keyword(s):  
Mathematical Model ◽  
Viral Infection ◽  
Host Cell ◽  
Decay Time ◽  
Zika Virus ◽  
Infectious Virus ◽  
Numerical Characterization ◽  
The Mathematical Model

Mathematical models of in vitro viral kinetics help us understand and quantify the main determinants underlying the virus–host cell interactions. We aimed to provide a numerical characterization of the Zika virus (ZIKV) in vitro infection kinetics, an arthropod-borne emerging virus that has gained public recognition due to its association with microcephaly in newborns. The mathematical model of in vitro viral infection typically assumes that degradation of extracellular infectious virus proceeds in an exponential manner, that is, each viral particle has the same probability of losing infectivity at any given time. We incubated ZIKV stock in the cell culture media and sampled with high frequency for quantification over the course of 96 h. The data showed a delay in the virus degradation in the first 24 h followed by a decline, which could not be captured by the model with exponentially distributed decay time of infectious virus. Thus, we proposed a model, in which inactivation of infectious ZIKV is gamma distributed and fit the model to the temporal measurements of infectious virus remaining in the media. The model was able to reproduce the data well and yielded the decay time of infectious ZIKV to be 40 h. We studied the in vitro ZIKV infection kinetics by conducting cell infection at two distinct multiplicity of infection and measuring viral loads over time. We fit the mathematical model of in vitro viral infection with gamma distributed degradation time of infectious virus to the viral growth data and identified the timespans and rates involved within the ZIKV-host cell interplay. Our mathematical analysis combined with the data provides a well-described example of non-exponential viral decay dynamics and presents numerical characterization of in vitro infection with ZIKV.

Spectral characterization of ciliary beating: variations of frequency with time

1985 ◽  
Vol 249 (1) ◽  
pp. C160-C165 ◽  
Author(s):  
D. Eshel ◽  
Y. Grossman ◽  
Z. Priel
Keyword(s):  
Mathematical Model ◽  
Power Spectra ◽  
Ciliary Beating ◽  
Isolated Lung ◽  
Ciliary Cell ◽  
The Mathematical Model ◽  
Beating Frequency ◽  
Over Time ◽  
Dominant Frequencies

Ciliary beating frequency in tissue culture from frog palate and isolated lung was optically examined using instrumentation that was adjusted to measure a fraction of the surface area of a single ciliary cell. Consecutive 1-s segments of the analogue signal were fast Fourier transformed (FFT) to obtain a power spectrum. At room temperature, these power spectra changed over time from 1 s to the next. Each spectrum contained several dominant frequencies of similar intensities. Cooling the preparation resulted in a single-peak spectrum that was constant over time. A mathematical model is proposed to simulate these findings. The results and the mathematical model support the hypothesis that ciliary beating frequency fluctuates over short periods of time.

Optimal H∞ Control of Structural Vibrations Using Shape Memory Alloy Actuators

1999 ◽  
Author(s):  
Jian Sun ◽  
Ali R. Shahin
Keyword(s):  
Mathematical Model ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Model Uncertainty ◽  
High Frequency ◽  
Structural Vibrations ◽  
Design Procedures ◽  
Sma Actuators ◽  
Temperature Dynamics ◽  
The Mathematical Model

Abstract This paper investigates robust control problem of structural vibrations using shape memory alloy (SMA) wires as actuators. The mathematical model for these SMA actuators is derived with emphasis in model uncertainty. The linearization of the relation between stress and temperature dynamics of SMA actuators is analyzed for active control. To handle the uncertainties caused by the linearization and the neglected high frequency dynamics, optimal H∞ control was employed to design a controller. An example is used to demonstrate the design procedures and the control system is tested in a nonlinear environment.

Thermal Modeling of a Reversing Valve in a Refrigeration System

2003 ◽  
Author(s):  
Shirish Raichintala ◽  
Manohar Kulkarni
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Heat Pump ◽  
Pressure Losses ◽  
Heat Leakage ◽  
Theoretical Predictions ◽  
Work Input ◽  
Compressor Work ◽  
Mass Leakage ◽  
The Mathematical Model

A mathematical model of a reversing valve was developed in order to evaluate the losses and for determining the effects of a reversing valve, on the performance of a heat pump. This mathematical model of the reversing valve was tested using the experimental data of Fang and Nutter (1999). The theoretical predictions made by this model agreed with that of the experimental data. Further, the mathematical model isolated the pressure losses due to friction; pipe-fittings, mass-leakage and heat transfer from the total losses. The evaluation of constituent losses assisted in detecting a faculty reversing valve, and also determining the effect of mass leakage and heat leakage on the compressor work input and COP of the heat pump.

Gas-Tight Oxides - Reality or Just a Hope

2006 ◽  
Vol 522-523 ◽  
pp. 93-102 ◽  
Author(s):  
C. Anghel ◽  
Gunnar Hultquist ◽  
Qian Dong ◽  
J. Rundgren ◽  
Isao Saeki ◽  
...  
Keyword(s):  
Mathematical Model ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Gas Content ◽  
Molar Ratio ◽  
Protection Measure ◽  
Straightforward Method ◽  
Gas Tight ◽  
The Mathematical Model

A better understanding of the transport properties of gases in oxides is certainly very important in many applications. In the case of metals, a general protection measure against corrosion implies formation of a dense metal oxide scale. The scale should act as a barrier against gas transport and consequently it needs to be gas-tight. This is often assumed but rarely, if ever, confirmed. Hence there is a need for characterization of micro- and/or meso- pores formed especially during the early oxidation stage of metallic materials. This paper presents a novel and relatively straightforward method for characterization of gas release from an oxide previously equilibrated in a controlled atmosphere. The geometry of the sample is approximated to be a plate. The plate can be self-supporting or constitute a scale on a substrate. A mathematical model for calculation of diffusivity and gas content is given for this geometry. A desorption experiment, involving a mass spectrometer placed in ultra high vacuum, can be used to determine diffusivity and amount of gas released with aid of the mathematical model. The method is validated in measurements of diffusivity and solubility of He in quartz and applied in characterization of two Zroxides and one Fe oxide. From the outgassed amounts of water and nitrogen the H2O/N2 molar ratio can be used to estimate an effective pore size in oxides.

scholarly journals Evaporation of a thin droplet in a shallow well: theory and experiment

2021 ◽  
Vol 927 ◽  
Author(s):  
Hannah-May D'Ambrosio ◽  
Teresa Colosimo ◽  
Brian R. Duffy ◽  
Stephen K. Wilson ◽  
Lisong Yang ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Light Emitting Diode ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Aspect Ratios ◽  
Physical Experiments ◽  
Industrial Manufacture ◽  
Before And After ◽  
Theoretical Predictions ◽  
The Mathematical Model

Motivated by the industrial manufacture of organic light-emitting-diode displays, we formulate and analyse a mathematical model for the evolution of a thin droplet in a shallow axisymmetric well of rather general shape both before and after touchdown that accounts for the spatially non-uniform evaporation of the fluid, perform physical experiments using three cylindrical wells with different small aspect ratios, and validate the mathematical model by comparing the present experimental results with the corresponding theoretical predictions for a cylindrical well.

Measuring the Pressure Distribution along the Surfaces of the Blades in a Francis Turbine Runner

1975 ◽  
Vol 189 (1) ◽  
pp. 213-220 ◽  
Author(s):  
B. Opelt ◽  
A. H. Khalifa
Keyword(s):  
Mathematical Model ◽  
Pressure Distribution ◽  
Static Pressure ◽  
Francis Turbine ◽  
Experimental Procedure ◽  
Static Pressure Distribution ◽  
Scale Models ◽  
Turbine Runner ◽  
Theoretical Predictions ◽  
The Mathematical Model

Measurements were made of the static pressure distribution along the surfaces of the blades of a Francis turbine runner operating near its optimum efficiency and at the extremes of unit speeds where incidences stretched from + 80° to −54°. The paper describes equipment and experimental procedure aimed at accuracy and compares the results against theoretical predictions furnished by computer programmes available at GEC Power Engineering Ltd. The correlation between curves was good in the optimum efficiency region and it was concluded that the mathematical model was a valuable aid to design and development and, subject to some restrictions, could reduce the need for scale models.

Characterization of Automotive Shock Absorbers Using Random Excitation

1995 ◽  
Vol 209 (4) ◽  
pp. 239-248 ◽  
Author(s):  
S Cafferty ◽  
K Worden ◽  
G Tomlinson
Keyword(s):  
Mathematical Model ◽  
Dynamic Properties ◽  
Test Procedure ◽  
Random Excitation ◽  
Fixed Frequency ◽  
Restoring Force ◽  
Shock Absorbers ◽  
The Mathematical Model ◽  
Clear Method

In a previous paper [see reference (4)], it was shown that the restoring force surface (RFS) procedure provides a direct and clear method for characterizing the dynamic properties of automotive shock absorbers or dampers. The procedure was based on repetitive harmonic testing of the absorbers at fixed frequency but with varying amplitude. The current paper describes how the surfaces can be obtained from tests using random excitation. The merits and demerits are discussed relative to the harmonic test procedure. It is shown that the random excitation approach offers a useful alternative but produces force surfaces which are corrupted by small stochastic components; an explanation of the distortion is given in terms of the mathematical model proposed in the previous paper. The implications for identification of shock absorbers are discussed

Modeling and Experimental Characterization of a Permanent Magnet Linear Alternator for Free-Piston Engine Applications

2009 ◽  
Author(s):  
Hans T. Aichlmayr ◽  
Peter Van Blarigan
Keyword(s):  
Mathematical Model ◽  
Permanent Magnet ◽  
Experimental Validation ◽  
Experimental Characterization ◽  
Piston Engine ◽  
Free Piston ◽  
Free Piston Engine ◽  
Linear Alternator ◽  
The Mathematical Model

Sandia National Laboratories is developing a prototype 30kW free-piston internal-combustion-based linear generator for vehicular applications. This paper describes the development and experimental validation of a mathematical model for the permanent magnet linear alternator that will be used by the prototype. A magnetic-flux versus mover-position function is used to correlate individual coil fluxes to the motion of the mover. This function is derived from a finite element electromagnetic simulation of the linear alternator. The mathematical model of the alternator is compared to experiments with prototype hardware driving 0.5–2kW loads; excellent correspondence to measured voltage and current waveforms is found.

scholarly journals Modeling and Hourly Time-Scale Characterization of the Main Energy Parameters of Parabolic-Trough Solar Thermal Power Plants Using a Simplified Quasi-Dynamic Model

Energies ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 221
Author(s):  
Ignacio Arias ◽  
Eduardo Zarza ◽  
Loreto Valenzuela ◽  
Manuel Pérez-García ◽  
José Alfonso Romero Ramos ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Power Plants ◽  
Thermal Power ◽  
Thermal Power Plants ◽  
Parabolic Trough ◽  
Solar Thermal Power ◽  
Simulation Results ◽  
Solar Field ◽  
The Mathematical Model

A simplified mathematical model of parabolic-trough solar thermal power plants, which allow one to carry out an energetic characterization of the main thermal parameters that influence the solar field performance, was evaluated through a comparison of simulation results. Two geographical locations were selected to evaluate the mathematical model proposed in this work—one in each hemisphere—and design considerations according with the practical/operational experience were taken. Furthermore, independent simulations were performed using the System Advisor Model (SAM) software, their results were compared with those obtained by the simplified model. According with the above, the mathematical model allows one to carry out simulations with a high degree of flexibility and adaptability, in which the equations that allow the plant to be energetically characterized are composed of a series of logical conditions that help identify boundary conditions between dawn and sunset, direct normal irradiance transients, and when the thermal energy storage system must compensate the solar field energy deficits to maintain the full load operation of the plant. Due to the above, the developed model allows one to obtain satisfactory simulation results; referring to the net electric power production, this model provides results in both hemispheres with a relative percentage error in the range of [0.28–8.38%] compared with the results obtained with the SAM, with mean square values of 4.57% and 4.21% for sites 1 and 2, respectively.

Sign in / Sign up

Export Citation Format

Share Document