scholarly journals M-Bonacci Zone Plates for Ultrasound Focusing

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4313 ◽  
Author(s):  
Sergio Pérez-López ◽  
José Miguel Fuster ◽  
Pilar Candelas
Keyword(s):  
Numerical Simulations ◽  
Design Process ◽  
Design Parameter ◽  
Industrial Applications ◽  
Experimental Measurements ◽  
Zone Plates ◽  
Wide Range ◽  
High Wavelength ◽  
Good Agreement

In this work, we present a thorough analysis on M-bonacci zone plates for ultrasound focusing applications. These planar lenses are capable of providing bifocal focusing profiles with equal intensity in both foci and become very appealing for a wide range of scenarios including medical and industrial applications. We show that in high-wavelength domains, such as acoustics or microwaves, the separation between both foci can be finely adjusted at the expense of slightly increasing the distortion of the focusing profile, and we introduce a design parameter to deal with this issue and simplify the design process of these lenses. Experimental measurements are in good agreement with numerical simulations and demonstrate the potential of M-bonacci lenses in ultrasound focusing applications.

Experimental Characterization of a T-Shaped Programmable Multistable Mechanism

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Mohamed Zanaty ◽  
Simon Henein
Keyword(s):  
Numerical Simulations ◽  
Reaction Force ◽  
Experimental Measurements ◽  
Experimental Characterization ◽  
Stable States ◽  
Stability Behavior ◽  
The Stability ◽  
Force Characteristics ◽  
Good Agreement

Programmable multistable mechanisms (PMM) exhibit a modifiable stability behavior in which the number of stable states, stiffness, and reaction force characteristics are controlled via their programming inputs. In this paper, we present experimental characterization for the concept of stability programing introduced in our previous work (Zanaty et al., 2018, “Programmable Multistable Mechanisms: Synthesis and Modeling,” ASME J. Mech. Des., 140(4), p. 042301.) A prototype of the T-combined axially loaded double parallelogram mechanisms (DPM) with rectangular hinges is manufactured using electrodischarge machining (EDM). An analytical model based on Euler–Bernoulli equations of the T-mechanism is derived from which the stability behavior is extracted. Numerical simulations and experimental measurements are conducted on programming the mechanism as monostable, bistable, tristable, and quadrastable, and show good agreement with our analytical derivations within 10%.

scholarly journals In Vitro Validation of Finite-Element Model of AAA Hemodynamics Incorporating Realistic Outlet Boundary Conditions

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Ethan O. Kung ◽  
Andrea S. Les ◽  
Francisco Medina ◽  
Ryan B. Wicker ◽  
Michael V. McConnell ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Numerical Simulations ◽  
In Silico ◽  
Physiological State ◽  
Patient Specific ◽  
Experimental Measurements ◽  
Windkessel Model ◽  
Measured Velocity ◽  
Good Agreement

The purpose of this study is to validate numerical simulations of flow and pressure in an abdominal aortic aneurysm (AAA) using phase-contrast magnetic resonance imaging (PCMRI) and an in vitro phantom under physiological flow and pressure conditions. We constructed a two-outlet physical flow phantom based on patient imaging data of an AAA and developed a physical Windkessel model to use as outlet boundary conditions. We then acquired PCMRI data in the phantom while it operated under conditions mimicking a resting and a light exercise physiological state. Next, we performed in silico numerical simulations and compared experimentally measured velocities, flows, and pressures in the in vitro phantom to those computed in the in silico simulations. There was a high degree of agreement in all of the pressure and flow waveform shapes and magnitudes between the experimental measurements and simulated results. The average pressures and flow split difference between experiment and simulation were all within 2%. Velocity patterns showed good agreement between experimental measurements and simulated results, especially in the case of whole-cycle averaged comparisons. We demonstrated methods to perform in vitro phantom experiments with physiological flows and pressures, showing good agreement between numerically simulated and experimentally measured velocity fields and pressure waveforms in a complex patient-specific AAA geometry.

Stiffness and Bond Strength of Rubber-Filled Hinges

1993 ◽  
Vol 66 (5) ◽  
pp. 733-741 ◽  
Author(s):  
A. N. Gent ◽  
Y-W. Chang
Keyword(s):  
Finite Element Analysis ◽  
Bond Strength ◽  
Direct Analysis ◽  
Test Method ◽  
Bond Rupture ◽  
Experimental Measurements ◽  
Element Analysis ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Good Agreement

Abstract The stiffness of rubber-filled hinges for small rotations of the hinge plates has been determined by finite element analysis (FEA). The rubber is assumed to be linearly elastic and virtually incompressible, and the hinge is assumed to be long enough for the rubber to be in a state of plane strain, i.e., prevented from any displacement parallel to the hinge. Results have been obtained for hinges of a wide range of unstrained angle, ranging from 5° up to 360°. The calculated stiffnesses for long hinges vary by over four orders of magnitude over this range. For small angles, an approximate solution has been obtained by direct analysis—it is in good agreement with the FEA solution for hinge angles up to about 40°. Experimental measurements on several rubber-filled hinges are also reported. The measured rotational stiffnesses are in satisfactory agreement with theoretical predictions. Because a rubber-filled hinge constitutes a possible test method for bond strength, conditions are derived for bond rupture as a hinge is strained open.

scholarly journals Actively modulated propagation of electromagnetic wave in hybrid metasurfaces containing graphene

2020 ◽  
Vol 7 ◽  
pp. 9
Author(s):  
Jiameng Nan ◽  
Ruisheng Yang ◽  
Jing Xu ◽  
Quanhong Fu ◽  
Fuli Zhang ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Fermi Level ◽  
Numerical Simulations ◽  
Sandwich Structure ◽  
Modulation Depth ◽  
Metallic Structure ◽  
Transmission Amplitude ◽  
Wide Range ◽  
Resonance Transmission ◽  
Good Agreement

Here we present the actively modulated transportation of electromagnetic wave through hybrid metasurfaces containing graphene. The hybrid metasurfaces are composed of patterned metallic layers of extraordinary transmission and backed with graphene-sandwich layers. With the designed metallic layer with perforated structure, we demonstrated effective modulation on the on-resonance transmission amplitude by increasing the bias voltage from 0 to 4 V to electrically tune the Fermi level as well as the sheet resistance of the graphene-sandwich structure. We also found that the modulation depth can be further improved by properly designing the perforated metallic structure. By change the geometry from cut-wire structure to the “butterfly”-like pattern we preliminarily achieved 19.2% improvement on the on-resonance transmission modulation. The measured transmittances of the active metasurfaces show good agreement with the numerical simulations with fitted graphene sheet resistances. The hybrid metasurfaces presented in this work may be deployed in a wide range of applications based on active electromagnetic or optical modulations.

scholarly journals Design and fabrication of a freeform mirror generating a uniform illuminance distribution in a rectangular region

2020 ◽  
Vol 44 (4) ◽  
pp. 540-546
Author(s):  
E.S. Andreev ◽  
E.V. Byzov ◽  
D.A. Bykov ◽  
М.А. Moiseev ◽  
L.L. Doskolovich
Keyword(s):  
Numerical Simulations ◽  
Assignment Problem ◽  
Transportation Problem ◽  
Design Method ◽  
Experimental Measurements ◽  
Mass Transportation ◽  
Rectangular Region ◽  
Linear Assignment Problem ◽  
Linear Assignment ◽  
Good Agreement

The design of a freeform mirror generating a uniform illuminance distribution in a rectangular region with angular dimensions of 30°x15° is presented. The design method is based on the formulation of the problem of calculating the "ray-mapping" as a Monge-Kantorovich mass transportation problem and its subsequent reducing to a linear assignment problem. We describe a mirror fabrication process with the use of milling technology and present results of experimental measurements of the light distribution generated by the mirror. The experimental results are in good agreement with the results of numerical simulations and thus confirm the manufacturability of mirrors designed by the method proposed.

Thermal study of clogging during filament-based material extrusion additive manufacturing: Experimental-numerical study

2021 ◽  
Author(s):  
Zahra Taheri ◽  
Ali Karimnejad Esfahani ◽  
Abas Ramiar
Keyword(s):  
Additive Manufacturing ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Thermal Conditions ◽  
Experimental Measurements ◽  
Clear Understanding ◽  
Material Extrusion ◽  
Series Of Experiments ◽  
Detailed Picture ◽  
Good Agreement

Abstract One of the major drawbacks of material extrusion additive manufacturing (AM) is hot-end clogging. This study aims to answer the question, “What thermal conditions lead to clogging during filament-based material extrusion?” Answering this question requires a clear understanding of temperature distribution inside the liquefier. However, this could not be achieved only through experimental measurements. Therefore, numerical simulations were also carried out by developing a 3D finite volume model of the hot-end. The results obtained from numerical simulations show good agreement with experimental measurements. They also give us a detailed picture of the temperature gradient near the nozzle. Moreover, a series of experiments were performed to determine when clogging occurs, and some criteria for avoiding clogging were presented. These results were also compared and combined with the numerical results to investigate the thermal condition leading to clogging. As the results show, overheating the heat barrier increases the length of the filament, whose temperature is above the glass transition temperature. As this length exceeds a critical value, the filament buckles under the extruder motor force and clogging occurs.

scholarly journals Three-dimensional multimode Rayleigh–Taylor and Richtmyer–Meshkov instabilities at all density ratios

2003 ◽  
Vol 21 (3) ◽  
pp. 327-334 ◽  
Author(s):  
D. KARTOON ◽  
D. ORON ◽  
L. ARAZI ◽  
D. SHVARTS
Keyword(s):  
Theoretical Model ◽  
Statistical Model ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Three Dimensional ◽  
3D Simulations ◽  
Analysis Scheme ◽  
Wide Range ◽  
Density Ratios ◽  
Good Agreement

The three-dimensional (3D) turbulent mixing zone (TMZ) evolution under Rayleigh–Taylor and Richtmyer–Meshkov conditions was studied using two approaches. First, an extensive numerical study was made, investigating the growth of a random 3D perturbation in a wide range of density ratios. Following that, a new 3D statistical model was developed, similar to the previously developed two-dimensional (2D) statistical model, assuming binary interactions between bubbles that are growing at a 3D asymptotic velocity. Confirmation of the theoretical model was gained by detailed comparison of the bubble size distribution to the numerical simulations, enabled by a new analysis scheme that was applied to the 3D simulations. In addition, the results for the growth rate of the 3D bubble front obtained from the theoretical model show very good agreement with both the experimental and the 3D simulation results. A simple 3D drag–buoyancy model is also presented and compared with the results of the simulations and the experiments with good agreement. Its extension to the spike-front evolution, made by assuming the spikes' motion is governed by the single-mode evolution determined by the dominant bubbles, is in good agreement with the experiments and the 3D simulations. The good agreement between the 3D theoretical models, the 3D numerical simulations, and the experimental results, together with the clear differences between the 2D and the 3D results, suggest that the discrepancies between the experiments and the previously developed models are due to geometrical effects.

On the tones and pressure oscillations induced by flow over rectangular cavities

1978 ◽  
Vol 89 (2) ◽  
pp. 373-399 ◽  
Author(s):  
Christopher K. W. Tam ◽  
Patricia J. W. Block
Keyword(s):  
Pressure Oscillation ◽  
Experimental Measurements ◽  
Pressure Oscillations ◽  
Resonance Mechanism ◽  
Acoustic Feedback ◽  
Oscillation Phenomenon ◽  
Wide Range ◽  
Mach Numbers ◽  
Tone Generation ◽  
Good Agreement

Experimental measurements of the frequencies of discrete tones induced by flow over rectangular cavities were carried out over a range of low subsonic Mach numbers to provide a reliable data base for (aircraft wheel well) cavity noise consideration. A mathematical model of the cavity tones and pressure oscillation phenomenon based on the coupling between shear layer instabilities and acoustic feedback is developed to help in understanding the tone generation mechanism. Good agreement is found between discrete tone frequencies predicted by the model and experimental measurements over a wide range of Mach numbers. Evidence of tones generated by the cavity normal mode resonance mechanism at very low subsonic Mach numbers is also presented.

Experimental and Numerical Investigation of a Centrifugal Compressor

2010 ◽  
Author(s):  
Hadi Karrabi ◽  
Ali Hajilouy-Benisi ◽  
Mahdi Nili-Ahmadabadi
Keyword(s):  
Numerical Simulation ◽  
Gas Turbine ◽  
Centrifugal Compressor ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Flow Parameters ◽  
Wide Range ◽  
Compressor Inlet ◽  
Sst Turbulence Model ◽  
Good Agreement

In this research, centrifugal compressor of a gas turbine is investigated experimentally and numerically. Operation line of the compressor as a component of the gas turbine is obtained experimentally by measurements of impeller rotational speed, and flow parameters at the compressor inlet and outlet during the gas turbine operation. The flow field inside the impeller and diffusers are analyzed numerically using a full 3D Navier-Stokes program with SST turbulence model. Boundary conditions for the numerical simulation are specified from the experimental measurements. The operation line of the compressor is obtained numerically, which is compared with that of the experimental results, and shows good agreement. Having validated the numerical results, the performance characteristic curves of the compressor are obtained numerically in a wide range.

A Novel Micro Capacitance Sensor for Studying Hydrodynamics of Particle Laden Flow

2000 ◽  
Author(s):  
Z. Pokusevski ◽  
I. G. Evans ◽  
T. A. York ◽  
T. Dyakowski
Keyword(s):  
Industrial Applications ◽  
Dynamic Tests ◽  
Capacitance Sensor ◽  
Particle Detection ◽  
Cfd Simulations ◽  
Static Tests ◽  
Dispersed Particles ◽  
Wide Range ◽  
Particle Laden Flow ◽  
Good Agreement

Abstract Particle laden flows occur in a wide range of industrial applications. Detection of dispersed particles and drops is of enormous importance since they may cause “erosion-corrosion effects” in industrial equipment. This paper presents a novel technique for particle detection. The results show 20 and 50 micron particles detected in the static tests. CFD simulations were carried out in order to design the sensor mounting and its optimal inclination to the flow. It was shown that sensor inclination of 5 or 10 degrees to the flow is highly beneficial. Dynamic tests were carried out and the full results show good agreement with the predicted particle tracks. 50 and 20 micron polyamide particles were detected at air velocities up to 12 metres per second.

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