COMPARATIVE STUDY FOR WAVE SPEED ESTIMATION AT A SINGLE AND TWO MEASUREMENT POINTS

2021 ◽  
pp. 2150048
Author(s):  
ASMA AYADI ◽  
WASSILA SAHTOUT ◽  
OLIVIER BALEDENT
Keyword(s):  
Regression Models ◽  
Wave Speed ◽  
Single Point ◽  
Area Formula ◽  
Reflected Waves ◽  
Cepstral Analysis ◽  
Contrast Magnetic Resonance ◽  
Local Wave ◽  
Blood Flow Velocities ◽  
Total Agreement

Local wave speed is a prognostic detector that allows the analysis of cardiovascular function. Objectives: This study compared wave speed ([Formula: see text] measurements at single-point and two-point techniques. Material and methods: [Formula: see text] were determined from the cepstral analysis of the blood flow velocities, which identified the arrivals times of reflected waves. The blood velocities waveforms were measured by using phase-contrast magnetic resonance (PCMR) for 20 subjects on young and old healthy subjects.  Local wave speed was estimated through the arrivals time of reflections waves ([Formula: see text] and the distance separating the measurement site to reflection area ([Formula: see text] or the distance separating the two measurement sites. Results: Our obtained results were in total agreement with reference values reported in the literature. Moreover, the detected results show that there is a high correlation ([Formula: see text]) between the two methods. Conclusion: The analysis of the wave speed variations with advancing age is also achieved out through different regression models.

A New Noninvasive Method for Determining the Local (True) Wave Speed: Application to Internal Carotid Artery

2018 ◽  
Vol 13 (02) ◽  
pp. 61-73
Author(s):  
Asma Ayadi ◽  
Wassila Sahtout ◽  
Olivier Baledent
Keyword(s):  
Carotid Artery ◽  
Wave Speed ◽  
Internal Carotid ◽  
Test Analysis ◽  
Cepstral Analysis ◽  
Wall Stiffness ◽  
Significant Difference ◽  
Contrast Magnetic Resonance ◽  
Local Wave ◽  
Young Subjects

Local wave speed plays an interesting role in investigating cardiovascular diseases and arterial wall stiffness. The aim of this study was to implement a novel method based on cepstral analysis for noninvasive determination of local wave speed in the carotid artery. To show the precision of the proposed method, we specially focused on the effect of age. In addition, we intended to compare the obtained results to those obtained by the foot-to-foot method. Our method consists in measuring the instantaneous blood velocity in the internal carotid by using phase-contrast magnetic resonance imaging in 20 healthy subjects distributed as follows: 10 young subjects aged between 22 and 41 years, and 10 old subjects aged between 50 and 86 years. The cepstral analysis was used to determine the arrival time of the reflection wave and the wave speed in the carotid artery. A statistical test analysis was conducted in order to establish the relation between the wave speed and the age in the sample under investigation. Our main finding was that there was a high significant difference between the two groups forming the studied sample ([Formula: see text]). In terms of the internal carotid arterial branch, our experimental results were in total agreement with reference values by the invasive method reported in the literature. Moreover, the wave speed detected using our method correlated with that detected using foot-to-foot analysis ([Formula: see text], [Formula: see text]). We can conclude that the new technique described in this paper offers a promising, convenient and efficient method to measure wave speed noninvasively.

Windkesselness of coronary arteries hampers assessment of human coronary wave speed by single-point technique

2008 ◽  
Vol 295 (2) ◽  
pp. H482-H490 ◽  
Author(s):  
Christina Kolyva ◽  
Jos A. E. Spaan ◽  
Jan J. Piek ◽  
Maria Siebes
Keyword(s):  
Coronary Arteries ◽  
Wave Speed ◽  
Single Point ◽  
Coronary Vessels ◽  
Distal Segment ◽  
Doppler Velocity ◽  
Healthy Human ◽  
Catheterization Laboratory ◽  
Before And After ◽  
Local Wave

A novel single-point technique to calculate local arterial wave speed ( SPc) has recently been presented and applied in healthy human coronary arteries at baseline flow. We investigated its applicability for conditions commonly encountered in the catheterization laboratory. Intracoronary pressure (Pd) and Doppler velocity ( U) were recorded in 29 patients at rest and during adenosine-induced hyperemia in a distal segment of a normal reference vessel and downstream of a single stenosis before and after revascularization. Conduit vessel tone was minimized with nitroglycerin. Microvascular resistance (MR) and SPc were calculated from Pd and U. In the reference vessel, SPc decreased from 21.5 m/s (SD 8.0) to 10.5 m/s (SD 4.1) after microvascular dilation ( P < 0.0001). SPc was substantially higher in the presence of a proximal stenosis and decreased from 34.4 m/s (SD 18.2) at rest to 27.5 m/s (SD 13.4) during hyperemia ( P < 0.0001), with a concomitant reduction in Pd by 20 mmHg and MR by 55.4%. The stent placement further reduced hyperemic MR by 26% and increased Pd by 26 mmHg but paradoxically decreased SPc to 13.1 m/s (SD 7.7) ( P < 0.0001). Changes in SPc correlated strongly with changes in MR ( P < 0.001) but were inversely related to changes in Pd ( P < 0.01). In conclusion, the single-point method yielded erroneous predictions of changes in coronary wave speed induced by a proximal stenosis and distal vasodilation and is therefore not appropriate for estimating local wave speed in coronary vessels. Our findings are well described by a lumped reservoir model reflecting the “windkesselness” of the coronary arteries.

Experimental evaluation of local wave speed in the presence of reflected waves

2014 ◽  
Vol 47 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Alessandra Borlotti ◽  
Ye Li ◽  
Kim H. Parker ◽  
Ashraf W. Khir
Keyword(s):  
Experimental Evaluation ◽  
Wave Speed ◽  
Reflected Waves ◽  
Local Wave

Parameter optimization and texture evolution in single point incremental sheet forming process

2019 ◽  
Vol 234 (1-2) ◽  
pp. 126-139 ◽  
Author(s):  
Shamik Basak ◽  
K Sajun Prasad ◽  
Amarjeet Mehto ◽  
Joy Bagchi ◽  
Y Shiva Ganesh ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Process Parameters ◽  
Regression Models ◽  
Incremental Forming ◽  
Single Point ◽  
Sheet Forming ◽  
Incremental Sheet Forming ◽  
Single Point Incremental Forming ◽  
Input Process ◽  
Truncated Cone

Prototyping through incremental sheet forming is emerging as a latest trend in the manufacturing industries for fabricating personalized components according to customer requirement. In this study, a laboratory scale single-point incremental forming test setup was designed and fabricated to deform AA6061 sheet metal plastically. In addition, response surface methodology with Box–Behnken design technique was used to establish different regression models correlating input process parameters with mechanical responses such as angle of failure, part depth per unit time and surface roughness. Correspondingly, the regression models were implemented to optimize the input process parameters, and the predicted responses were successfully validated at the optimal conditions. It was observed that the predicted absolute error for angle of failure, part depth per unit time and surface roughness responses was approximately 0.9%, 4.4% and 6.3%, respectively, for the optimum parametric combination. Furthermore, the post-deformation responses from an optimized single point incremental forming truncated cone were correlated with microstructural evolution. It was observed that the peak hardness and highest areal surface roughness of 158 ± 9 HV and 1.943 μm, respectively, were found near to the pole of single-point incremental forming truncated cone, and the highest major plastic strain at this region was 0.80. During incremental forming, a significant increase in microhardness occurred due to grain refinement, whereas a substantial increase in the Brass and S texture component was responsible for the increase in the surface roughness.

Arterial waves in humans during peripheral vascular surgery

2001 ◽  
Vol 101 (6) ◽  
pp. 749-757 ◽  
Author(s):  
Ashraf W. KHIR ◽  
Michael Y. HENEIN ◽  
Tat KOH ◽  
Saroj K. DAS ◽  
Kim H. PARKER ◽  
...  
Keyword(s):  
Vascular Surgery ◽  
Wave Speed ◽  
Lv Function ◽  
Peripheral Vascular ◽  
Reflected Waves ◽  
Peripheral Vascular Surgery ◽  
Aortic Clamping ◽  
Compression Waves ◽  
Reflected Wave ◽  
Catheter Tip

The purpose of this study was to investigate the effect of aortic clamping on arterial waves during peripheral vascular surgery. We measured pressure and velocity simultaneously in the ascending aorta, in ten patients (70±5 years) with aortic-iliac disease intra-operatively. Pressure was measured using a catheter tip manometer, and velocity was measured using Doppler ultrasound. Data were collected before aortic clamping, during aortic clamping and after unclamping. Hydraulic work in the aortic root was calculated from the measured data, the reflected waves were determined by wave-intensity analysis and wave speed was determined by the PU-loop (pressure-velocity-loop) method; a new technique based on the ‘water-hammer’ equation. The wave speed is approx. 32% (P < 0.05) higher during clamping than before clamping. Although the peak intensity of the reflected wave does not alter with clamping, it arrives 30ms (P < 0.05) earlier and its duration is 25% (P < 0.05) longer than before clamping. During clamping, left ventricule (LV) hydraulic systolic work and the energy carried by the reflected wave increased by 27% (P < 0.05) and 20% (P < 0.05) respectively, compared with before clamping. The higher wave speed during clamping explains the earlier arrival of the reflected waves suggesting an increase in the afterload, since the LV has to overcome earlier reflected compression waves. The longer duration of the reflected wave during clamping is associated with an increase in the total energy carried by the wave, which causes an increase in hydraulic work. Increased hydraulic work during clamping may increase LV oxygen consumption, provoke myocardial ischaemia and hence contribute to the intra-operative impairment of LV function known in patients with peripheral vascular disease.

scholarly journals Reconstructing the wave speed and the source

2021 ◽  
Author(s):  
Amin Boumenir ◽  
Vu Kim Tuan
Keyword(s):  
Inverse Problem ◽  
Wave Equation ◽  
Wave Speed ◽  
Simple Procedure ◽  
Single Point ◽  
Spectral Estimation ◽  
New Method ◽  
Estimation Techniques ◽  
Nodal Lines

We are concerned with the inverse problem of recovering the unknown wave speed and also the source in a multidimensional wave equation. We show that the wave speed coefficient can be reconstructed from the observations of the solution taken at a single point. For the source, we may need a sequence of observation points due to the presence of multiple spectrum and nodal lines. This new method, based on spectral estimation techniques, leads to a simple procedure that delivers both uniqueness and reconstruction of the coefficients at the same time.

scholarly journals The Pyramid – Resonator of waves

2021 ◽  
Author(s):  
Junaid Aziz
Keyword(s):  
Energy Transport ◽  
Golden Ratio ◽  
Single Point ◽  
Fibonacci Number ◽  
Sine Wave ◽  
Curved Surface ◽  
Reflected Waves ◽  
Great Pyramid ◽  
The Law ◽  
The Waves

The Great Pyramid of Giza has fascinated us all as it encodes enormous amount of numerical coincidences such as dimensional precision, movement of our planet, speed of light, the golden ratio of Pi & Phi, etc.Studies have reasoned that the great pyramid of Giza has expressed the key ratio of an AC voltage sine wave as well as the ratios of Fibonacci number in developing the pyramidal design. Therefore in this study, the pyramid structure is considered as a resonator of waves where reflection of waves is an obvious phenomenon. The waves entering the pyramidal resonator will be reflected inward as they reflect from a curved surface according to the law of reflection. Since, a reflecting wave involves the energy-transport process, it determines our main objective to review and internalize the energy caused by reflection of the waves which occurs inside the pyramidal resonator. It is assumed that there is a strength point of such energy due to a higher volume of reflected waves to a single point. According to the law of reflection, when reflection occurs through a curved surface, it focuses incoming parallel waves to a convergence spot. This project is subjected to study the pyramid as a resonator of waves and aims to detect, observationally, the strength point of energy assumed to be caused by maximum number of reflected waves.

Sign in / Sign up

Export Citation Format

Share Document