A New Imaging Method for Arterial Tubes Based on Vibration Measurement

2003 ◽  
Author(s):  
Xiaoming Zhang ◽  
Mostafa Fatemi ◽  
James F. Greenleaf
Keyword(s):  
Focal Point ◽  
Single Point ◽  
Vibration Measurement ◽  
Ultrasound Transducer ◽  
Imaging Method ◽  
Large Artery ◽  
Large Radius ◽  
Modal Shape ◽  
Measured Velocity ◽  
Gel Phantom

A new method for imaging and detecting modal shapes of vessels is introduced. Theory is developed that predicts the measured velocity is proportional to the value of the mode shape at the focal point of the ultrasound beam. Experimental a cylindrical gel phantom of large radius. This model simulates approximately a large artery and the surrounding body. The fundamental frequency was measured 83 Hz for the tube-phantom system. At this frequency the ultrasound transducer was scanned across the vessel plane with velocity measurement at one single point on the vessel and on the phantom by laser. The images obtained show clearly the interior tube and the modal shape of the tube.

scholarly journals Hydrodynamics of Regular Breaking Wave

2020 ◽  
Author(s):  
Diana De Padova ◽  
Michele Mossa
Keyword(s):  
Flow Field ◽  
Surf Zone ◽  
Laser Doppler Anemometry ◽  
Single Point ◽  
Measurement Techniques ◽  
Experimental Studies ◽  
Outer Region ◽  
Breaking Wave ◽  
Measured Velocity ◽  
Spatial Gradients

Turbulence and undertow currents play an important role in surf-zone mixing and transport processes; therefore, their study is fundamental for the understanding of nearshore dynamics and the related planning and management of coastal engineering activities. Pioneering studies qualitatively described the features of breakers in the outer region of the surf zone. More detailed information on the velocity field under spilling and plunging breakers can be found in experimental works, where single-point measurement techniques, such as Hot Wire Anemometry and Laser Doppler Anemometry (LDA), were used to provide maps of the flow field in a time-averaged or ensemble-averaged sense. Moreover, the advent of non-intrusive measuring techniques, such as Particle Image Velocimetry (PIV) provided accurate and detailed instantaneous spatial maps of the flow field. However, by correlating spatial gradients of the measured velocity components, the instantaneous vorticity maps could be deduced. Moreover, the difficulties of measuring velocity due to the existence of air bubbles entrained by the plunging jet have hindered many experimental studies on wave breaking encouraging the development of numerical model as useful tool to assisting in the interpretation and even the discovery of new phenomena. Therefore, the development of an WCSPH method using the RANS equations coupled with a two-equation k–ε model for turbulent stresses has been employed to study of the turbulence and vorticity distributions in in the breaking region observing that these two aspects greatly influence many coastal processes, such as undertow currents, sediment transport and action on maritime structures.

A Coupled Tube-Tissue Model for Frequency Calculation of Arterial Tubes With Tissue

2003 ◽  
Author(s):  
Xiaoming Zhang ◽  
Mostafa Fatemi ◽  
James F. Greenleaf
Keyword(s):  
Vibration Analysis ◽  
Tissue Characterization ◽  
Experimental Studies ◽  
Radiation Force ◽  
Imaging Method ◽  
Large Artery ◽  
Rubber Tube ◽  
Tissue Model ◽  
Frequency Calculation

Vibro-acoustography is a new noncontact imaging method based on the radiation force of ultrasound. We extend this new technique for tissue characterization of arterial vessels by vibration techniques. In this paper a theoretical model for vibration analysis of arterial vessel with tissue is developed. Experimental studies were carried out on a silicone rubber tube embedded in a cylindrical gelatin phantom of larger radius, which simulates a large artery and the tissue body. The fundamental mode is well excited by the radiation force of ultrasound. The fundamental frequency was measured 81.8 Hz for a tube-phantom structure that is quite close to our theoretical prediction of 83.3 Hz.

scholarly journals Phase Optimization for Multipoint Haptic Feedback Based on Ultrasound Array

2021 ◽  
Author(s):  
Zhili Long ◽  
Shuyuan Ye ◽  
Zhao Peng ◽  
Yuyang Yuan ◽  
Zhouhua Li
Keyword(s):  
Optimization Model ◽  
Acoustic Pressure ◽  
Haptic Feedback ◽  
Low Cost ◽  
Single Point ◽  
Electrical Circuit ◽  
Ultrasound Transducer ◽  
Field Programmable ◽  
Phase Optimization ◽  
Phase Solution

Ultrasound based haptic feedback is a potential technology for human-computer interaction (HCI) with the advantages of low cost, low power consumption and controlled force. In this paper, the phase optimization for multipoint haptic feedback based on ultrasound array is investigated and the corresponding experimental verification is provided. A mathematical model of acoustic pressure is established for the ultrasound array and then a phase optimization model for an ultrasound transducer is constructed. We propose a pseudo-inverse (PINV) algorithm to accurately determine the phase contribution of each transducer in the ultrasound array. By controlling the phase difference of the ultrasound array, the multipoint focusing forces are formed leading to various shapes such as geometries and letters that can be visualized. Because the unconstrained PINV solution results in unequal amplitudes for each transducer, a weighted amplitude iterative optimization is deployed to further optimize the phase solution, by which the uniform amplitude distributions of each transducer are obtained. For the purpose of experimental verifications, a platform of ultrasound haptic feedback consisting of a Field Programmable Gate Array (FPGA), an electrical circuit and an ultrasound transducer array is prototyped. The haptic performances of single point, multiple points and dynamic trajectory were verified by controlling the ultrasound force exerted on the liquid surface. The experimental results demonstrate that the proposed phase optimization model and theoretical results are effective and feasible, and the acoustic pressure distribution is consistent with the simulation results.

Interface Properties Due to Microslip From Vibration Measurement

1999 ◽  
Vol 123 (1) ◽  
pp. 230-233 ◽  
Author(s):  
H. A. Sherif ◽  
T. M. Abu Omar
Keyword(s):  
Contact Stiffness ◽  
Single Point ◽  
Peak Frequency ◽  
Vibration Measurement ◽  
Interface Properties ◽  
Flat Surfaces ◽  
Dry Contact ◽  
Impulse Excitation ◽  
Interface Parameters ◽  
Two Degree Of Freedom

A method of measuring contact stiffness and friction damping at interacting plane surfaces of a mechanical system comprised of two sub-structures in dry contact is presented. The method is based on the measurement of displacement ratio of the contacting sub-structures as a function of frequency due to light impulse excitation at a single point on any of the two sub-structures. The theoretical analysis depends on a very simple model of a two-degree-of-freedom system with elastic coupling. The effects of applied normal loads, and contact configuration on the interface parameters are shown. The theoretical and experimental analyses show that the interface properties for the flat-on-flat surfaces of the two contacting sub-structures can be determined from the measured peak amplitude and peak frequency of the microslip in the frequency domain.

Plane Maps with Denominator. Part II: Noninvertible Maps with Simple Focal Points

2003 ◽  
Vol 13 (08) ◽  
pp. 2253-2277 ◽  
Author(s):  
Gian-Italo Bischi ◽  
Laura Gardini ◽  
Christian Mira
Keyword(s):  
Focal Point ◽  
Single Point ◽  
Focal Points ◽  
Previous Part ◽  
Noninvertible Maps ◽  
Set Of Points

This paper is the second part of an earlier work devoted to the properties specific to maps of the plane characterized by the presence of a vanishing denominator, which gives rise to the generation of new types of singularities, called set of nondefinition, focal points and prefocal curves. A prefocal curve is a set of points which are mapped (or "focalized") into a single point, called focal point, by the inverse map when it is invertible, or by at least one of the inverses when it is noninvertible. In the case of noninvertible maps, the previous text dealt with the simplest geometrical situation, which is nongeneric. To be more precise this situation occurs when several focal points are associated with a given prefocal curve. The present paper defines the generic case for which only one focal point is associated with a given prefocal curve. This is due to the fact that only one inverse of the map has the property of focalization, but with properties different from those of invertible maps. Then the noninvertible maps of the previous Part I appear as resulting from a bifurcation leading to the merging of two prefocal curves, without merging of two focal points.

scholarly journals Full-Field Vibration Measurement Using Camera Through Shearlet System

2018 ◽  
Vol 217 ◽  
pp. 01002
Author(s):  
C.A. Wee ◽  
M. Z. Ngali
Keyword(s):  
Promising Result ◽  
Single Point ◽  
Laser Doppler Vibrometer ◽  
Field Capacity ◽  
Vibration Signal ◽  
Vibration Measurement ◽  
Single Frequency ◽  
Mode Shapes ◽  
Circular Membrane ◽  
Full Field

Traditionally, vibration measurement is done using an accelerometer or Laser Doppler Vibrometer, which is an intrusive and single point measurement respectively. This paper demonstrated vibration signal extracted from a perceptually invisible vibrating object using only a camera non-intrusively at full-field capacity. the camera that is capable to capture 1000 frames-per-second video was used to capture the motion of the vibrating object. Each frame of the video was decomposed using complex shearlet transform and the extracted signal was compared to an accelerometer. Shearlet decomposed each frame of the video into complex coefficients which were later used to recover the motion between two consecutive frames. Phase information that were used to retrieve the vibration signal were weighted to decrease unwanted noise. Resonant frequencies of a simply supported beam at 104.0 Hz, 209.5 Hz and 396.0Hz were successfully recovered. Single frequency extraction from an excited loud-speaker at specific frequencies were also conducted and showed a clear peak-to-valley frequency spectrum recovery. the potential of using camera as a full-field displacement measurement where each pixel acting as a vibrometer was explored. Full-field test to recover the mode shape of a circular membrane showed promising result with eight mode shapes successfully retrieved. the experiments proved that each individual pixel was able to retrieve motion at subpixel level that is at 0.00001 pixel scale.

scholarly journals Increasing the Reliability of Flood Embankments with Neural Imaging Method

2018 ◽  
Vol 8 (9) ◽  
pp. 1457 ◽  
Author(s):  
Grzegorz Kłosowski ◽  
Tomasz Rymarczyk ◽  
Arkadiusz Gola
Keyword(s):  
Neural Networks ◽  
Internal Structure ◽  
Single Point ◽  
Tomographic Reconstruction ◽  
Imaging Method ◽  
Neural Imaging ◽  
Non Invasive ◽  
Innovative System ◽  
High Resolution Images ◽  
Resolution Problem

This paper presents an innovative system of many artificial neural networks that enables the tomographic reconstruction of the internal structure of a flood embankment. An advantage of the proposed method is that it allows us to obtain high-resolution images, which essentially contributes to early, precise and reliable prediction of operational hazards. The method consists in training a cluster of separate neural networks, each of which generates a single point of the output image. The simultaneous and parallel application of the set of neural networks led to effective reconstruction of the internal structure of a deposition site for floatation tailings. Results obtained from the study allow us to solve the low resolution problem that usually occurs with non-invasive imaging methods. This effect was possible thanks to the design of a new intelligent image reconstruction system.

scholarly journals The Visual Measurement of Velocity Profile Distribution in Silt Carrying Flow by Using Ultrasound PIV and Iterative Multi-Grid Deformation Technique

2021 ◽  
Vol 11 (15) ◽  
pp. 6952
Author(s):  
Xianjian Zou ◽  
Wenbin Hu ◽  
Huan Song ◽  
Bingrui Chen
Keyword(s):  
Velocity Profile ◽  
Flow Velocity ◽  
Measurement Technique ◽  
Imaging System ◽  
Single Point ◽  
Interrogation Window ◽  
Measured Velocity ◽  
Visual Measurement ◽  
Grid Deformation ◽  
Profile Distribution

Flow velocity in silt carrying flow is one key parameter to many river engineering problems. A visual measurement technique of velocity profile distribution in silt carrying flow is provided using a portable ultrasound imaging system and an improved iterative multi-grid deformation algorithm. A convex array probe in the system is used to obtain a series of ultrasonic images at different times. Window offset and an iterative computing scheme for reducing interrogation window size in the algorithm improve the accuracy and efficiency of flow velocity measurement in regions with velocity gradients. Results show that the measured profile velocities can be more acceptable after being compared with time-averaged stream-wise velocities of profiles at ten positions in the same silt carrying flow and subsequently verified by comparing the point-by-point standard value. The measured velocity is more in agreement with the theoretical value, with the minimum root mean square error in the ultrasound beam sweep effect calculated by using optimal interrogation size parameters. The system is a feasible alternative to the single-point measurement technique in silt carrying flow. The iterative multi-grid deformation algorithm can analyze velocity profile distribution with gradients simultaneously, which can help the real-time measurement of multiple spatial velocity distribution and turbulence.

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