Circumferential Shear Research Articles

Study on the characteristics of cavitation and COD removal of an addendum rotational hydrodynamic cavitation reactors

AbstractThis paper presented an addendum rotational hydrodynamic cavitation reactors (ARHCR) that enabled circumferential shear cavitation, axial cavitation, and the Venturi effect, thus increasing cavitation efficiency. The experiments on hydroxyl (·OH) release and chemical oxygen demand (COD) removal demonstrate the feasibility of cavitation performance characterization and COD removal rate. The findings indicate that the COD removal rate can reach a maximum value of 28% or 30% with an increase in flow rate or rotating speed, respectively. Specifically, the maximum values were achieved at a rotation speed of 2,500 rpm or a flow rate of 1.0 m3·h−1. Based on the mechanism of the addendum cavitation, the wedge angles, and the crucial structural parameters, were examined for optimizing cavitation performance. The results revealed that the cavitation number and cavitation bubble were significantly influenced by wedge angles, as well as the efficiency of cavitation energy. The mechanical shear of fluid was enhanced by wedge angles, resulting in constant compression and release of fluid with increased kinetic energy. This led to stronger effects on bulge blocks, and the formation of vortexes that rebounded constantly, resulting in lower pressure areas and expanded regions of cavitation. Among the wedge angles tested, the wedge angle of 15° exhibited the highest cavitation bubbles with a maximum value of 46%. This was 31% higher than the grooves‐type cavitator reported. Furthermore, the cavitation performance was extremely improved with a wedge angle of 15°, as corresponding with the maximum efficiency of cavitation energy. These explorations provide references for the removal of COD in industrial and agricultural wastewater, as well as the development of novel reactors for wastewater treatment.

Local carotid stiffness, hemodynamic forces and blood viscosity in patients with cerebral lacunar infarctions.

The carotid stiffness is an important factor in the pathogenesis of cerebrovascular small vessel disease. Our study aimed to evaluate the relation of the local arterial stiffness of the common carotid artery (CCA) to the hemodynamic forces and blood viscosity in patients with cerebral lacunar infarctions (LI). Twenty-two patients with chronic LI and 15 age-matched controls were examined. An ultrasound examination of the CCA intima-media thickness (IMT), the parameters of local CCA stiffness: distensibility (DC) and compliance coefficients (CC), α and β stiffness indices and pulse wave velocity (PWV) was performed. The local hemodynamic forces were calculated: circumferential wall tension (CWT) and wall shear stress (WSS). Whole blood viscosity (WBV) and shear stresses at shear rates of 0.277 s-1 to 94.5 s-1 were measured in patients and controls. Higher values of IMT, a significant decrease of DC and CC and an increase of α and β stiffness indices and PWV in the LI patients compared to the controls were obtained. A parallel significant increase in CWT and a decrease in WSS was found. An increase in WBV and a significant increase in shear stresses were detected. In the LI patients, the increased stiffness indices were associated with an increase in age, cholesterol and WBV at higher shear rates in the left CCA. In the controls, the IMT and stiffness indices correlated significantly with the hemodynamic factors and WBV in both CCAs, while the stiffness indices correlated with the hemodynamic forces in the left CCA. The results of the present study demonstrate different associations of the local carotid stiffness indices with the hemodynamic forces and WBV in patients with LI and controls.

Development of a Meander-Coil-Type Dual Magnetic Group Circumferential Magnetostrictive Guided Wave Transducer for Detecting Small Defects Hidden behind Support Structures.

In order to solve the problem that small defects hidden behind pipeline support parts are difficult to detect effectively in small spaces, such as offshore oil platforms, a meander-coil-type dual magnetic group circumferential magnetostrictive guided wave transducer is developed in this paper. The transducer, which consists of a coil, two sets of permanent magnets, and a magnetostrictive patch, can excite a high-frequency circumferential shear horizontal (CSH) guided wave. The energy conversion efficiency of the MPT is optimized through magnetic field simulation and experiment, and the amplitude of the defect signal is enhanced 1.9 times. The experimental results show that the MPT developed in this paper can effectively excite and receive CSH2 mode guided waves with a center frequency of 1.6 MHz. Compared with the traditional PPM EMAT transducer, the excitation energy of the transducer is significantly enhanced, and the defects of the 2 mm round hole at the back of the support can be effectively detected.

Enlarged Curvature, Torsion and Torque in Helical Conformations and the Stability and Growth of α-Peptide under the Isochoric and Isobaric Conditions: Variatonal Optimization

The torsional deformation behavior of an elastic bar with a circular cross-section was investigated by applying invariant dyadic analysis, where the small finite displacement functions advocated by Saint-Venant (1855) were fully employed. It was found that the previously overlooked circumferential shear force field generated by pure torsion on the side walls of a bar produces an unusual torque term induced by the skew-symmetric part of the deformation tensor and exhibits quadratic length dependence along the z-axis of the bar. The adaptation of this torque term for a helical conformation of α-peptides creates moments acting on the circular cross-sections and is directed along the surface normal of circular cross-sections, which coincides with the tangent vector of the helix. The projection of this torque along the z-axis of the helix varies quadratically with the azimuthal angle. The radial component of the unusual torque, which also lies along the principal normal vector of the helix, starts to perform a precession motion by tracking a spiral orbit around the z-axis, whereas its apex angle decreases asymptotically with the azimuthal angle and finally reaches a finite value depending on the height of the helix along the z-axis. The ordinary torque terms, which are also deduced from the self- and anti-self-conjugate parts of the deformation tensor, have magnitudes half that of the full torque term reported in the literature. The present results were applied to the helical conformation of α-peptides designated by {3.611} to show that the mechanical stability of strained open-ended helical conformations can be successfully achieved by spontaneous readjustments of the surface and bulk Helmholtz free energies under isothermal isochoric conditions. It has been demonstrated that the main contribution to the mechanical stability of α-peptide 3.611 cannot come alone from the electrostatic dipole-dipole interaction potential of the anti-align excess dipole pairs but also from the surface Helmholtz free energy, which is characterized by a binding free energy of -15.5 eV/molecule (-32.56 Kcal/mole) for an alpha-peptide composed of 11 amino acid residues with a critical arc length of approximately 10 nm, assuming that the shear modulus is G = 1GPa and the surface Helmholtz specific free energy density is fs = 800 erg/cm2. This result was in excellent agreement with the experimental observations of the AH-1 conformation of (Glu)n Cys at pH 8. The present theory indicates that only two excess permanent anti-align dipole pairs for one α-Helical peptide molecule is requirement to stabilize the whole secondary structure of the protein that is exposed to heavy torsional deformation during the folding processes which amounts to 7.75 eV/molecule stored electrostatic energy compared to the interfacial Helmholtz free energy of -23.25 eV/molecule, which is exposed to hydrophobic environments.

Effect of β nucleating agent and rotational shear on morphology and mechanical properties of polypropylene pipes

AbstractHerein, we report a new method of introducing circumferential shear to polypropylene (PP) pipes via a self‐designed rotational shear system (RSS) with the addition of a β‐nucleating agent (TMB‐5). The prepared PP pipes exhibited remarkable enhancement in toughening and tensile strength over conventional PP pipes incorporating 0.025 wt% of the nucleating agent into the sheared sample increased the elongation at break to 243.30%. At 0.05 wt% nucleating agent content, an optimal tensile strength of 40.98 MPa was attained compared to 33.62 MPa for unsheared PP, and the elongation at break also reached 108.09%. In creep tests, the PP pipes prepared with nucleating agents and shear rotation exhibited a minimum displacement of 2.1 mm and the lowest creep rate of 3.23 × 10−5 mm/s. In addition, the samples also showed a high resistance to crack growth compared to conventional PP pipes with a crack initiation time of 24 h and a crack growth rate of 0.08 mm/s.Highlights Reinforced and toughened PP pipes were prepared using a rotational shear system. The shish‐kebab structure and β‐crystals exhibited a synergistic effect. Both short‐term and long‐term mechanical properties were studied.

Research on circumferential joint shear damage characteristics of segments with positioning tenon through distributed fiber optic-based sensing technique

Positioning tenons have been used in more and more subway projects to improve segment assembly performance and to limit the occurrence of common problems between segments. The joints are the weak parts of the segment connection and are often damaged during construction. However, there are limited studies on the joints of segments with positioning tenons, and their damage characteristics have yet to be investigated. In this study, circumferential joint shear damage in segments with positioning tenons is studied and the evolution of the distributed damage is monitored by distributed fiber optics. First of all, the shear performance of segments with positioning tenons is investigated under different axial forces. Particularly, the damage distribution and development of segments subjected to the extrusion of the positioning tenons are analyzed through the strain signals and the macroscopic cracks during the shearing process. Furthermore, the changes in the strain signals of the distributed fiber before shear failure are analyzed. Based on the above study, the failure patterns of the inner surfaces and circumferential joint surfaces of segments with grooves are revealed. The interaction between the positioning tenons and the segments is analyzed, and the damage characteristics of the tenons are obtained. Finally, the main crack shear coefficient is proposed to evaluate the residual shear performance of segments when the macroscopic main crack occurs on the inner surface. This study aims to reveal the interaction between positioning tenons and segments and to promote the application of positioning tenons in subways. Further, it lays the foundation for optimizing the flexible joints of segments in subways and contributes to the safe construction of subway tunnels.

TRIPTANS: HOPE FOR THE BEST, PREPARE FOR THE WORST

Abstract The estimated prevalence of headaches in the population is 66%. According to recent guidelines, basic analgesics, nonsteroidal anti–inflammatory drugs (NSAIDs), or acetaminophen are frequently used as first–line treatment for mild migraine attacks. A triptan is added when analgesic–resistant attacks occur. So these drugs are used as a second–line medication for mild migraines and a first–line medication for moderate to severe headaches. A correlation between spontaneous coronary artery dissection (SCAD) and triptans has already been reported in the literature. If myocardial infarction is more common in patients with cardiovascular risk factors, SCAD seems more frequent in young and smoker females. What is interesting is the speculation of the pathophysiological mechanisms of SCAD after triptans use. A possible option may consist in the fact that the dissection of the anterior descending artery is due to circumferential shear stress caused by these drugs, combined with smoking habits and estrogen deprivation. These latters influence the immune system and the circulating progenitor cells, which are reduced and less active to replace senescent endothelial cells. That is why an intimal flap is formed so that the blood would enter the media and the dissection would be perpetuated. The suspension of the drug is necessary to prevent the vasoconstriction of the vessel from exacerbating the wall stress caused by smoke and sexual hormones deficiency.

Generation of bidirectional shear horizontal guided waves by size optimization of face-shear piezoelectric transducers

Generating directional guided waves helps to avoid unwanted reflections while providing location information for defects. Bidirectional waves focus wave beams in two opposite directions, which can be applied for generating circumferential zero-order shear horizontal (SH0) waves for large-diameter pipe inspection. In this paper, a novel method for generating bidirectional SH0 waves through size optimization using face-shear (d24) lead zirconate titanate (PZT) transducer is proposed. A theoretical model is established based on the shear-lag model and the Huygens principle, which describes the generation and propagation of SH0 waves in thin plate by bonded d24 PZT transducer. The theoretical model is validated by multi-physics finite element (FE) simulation results in terms of SH0 displacement wavefield. Based on the theoretical model, the performance of bidirectional SH0 wave generation is studied. The maximum bidirectional ratio that can be achieved by d24 PZT within a size range (1–25 mm) under a five-cycle sinusoid tone-burst excitation at a center frequency range (50–300 kHz) is studied. Results show that over 20 dB effect can be achieved at the PZT with a specific aspect ratio. Laboratory experiments are conducted using d24 PZT transducers at 50–300 kHz to validate the effect of bidirectional wave generation in practical detection scenarios. Experimental results show effects of over 20 dB within a certain frequency range can be achieved when using a PZT with a large aspect ratio, which agree well with the theoretical predictions.

Electromagnetic Acoustic Detection of Pipe Defects Hidden above T-Type Support Structures with Circumferential Shear Horizontal Guided Wave.

When pipe defects are generated above the T-type support structure location, it is difficult to distinguish the reflection signals caused by the weld bead at the support structure from the reflection echoes of pipe defects. Therefore, in order to effectively detect pipe defects, a waveform subtraction method with a circumferential shear horizontal (CSH) guided wave is proposed, which is generated by an electromagnetic acoustic transducer (EMAT). First, a CSH0 guided wave mode with a center frequency of 500 kHz is selected to establish a three-dimensional model with and without pipe defects above the support structure. Following this, the influence of different widths of support structures on the echo signal is compared. Moreover, simulation and experimental results are used to compare the influence of different welding qualities on the detection results. Finally, the waveform subtraction method is used to process the simulation and experimental signals, and the influence of pipe defects with different lengths and depths is discussed. The results show that the non-through crack defect of 5 mm × 1 mm (length × depth) can be detected. The results show that this method can effectively detect the cracks by eliminating the influence of the weld echo, which provides a new concept for the detection of the defect above the support structure.

Analytical determination and numerical validation of the shear factor in annular sector cross sections

In the present study, the shear factor of an annular sector cross section, including the thickness effect, has been analytically determined for the first time. The shear factors depend on the angle of the sector and on the mean radius to thickness ratio. Two approaches were used to determine circumferential and radial shear stresses. The limits of validity of the approach were established, based on the similarity of the shear factors determined from both approaches. The results obtained from the present analytical approach were compared with the results of another analytical approach developed for thin sections. To check the suitability of analytically determined shear factors, unidirectional composite cantilever beams have been analysed by the finite element method, for different cross sections and cantilever lengths. With the material properties and displacement at the cantilever tip known, shear factors were determined and compared with those obtained from the analytical approach. The script used to calculate the shear factors is included as an appendix.

Dynamic engraving characteristics of nylon belt under different charge conditions

Abstract In the present study, a 105 mm short tube gun system was designed to conduct the firing experiments under low charge conditions, which could precisely obtain the projectile displacement data and projectile base pressure data during the engraving process. Besides, a 3-dimensional dynamic engraving FEM-SPH model was established by coupling the internal ballistic process to much authentic investigate the engraving characteristics of the projectile, which were verified and compared through the experiment. On this premise, the influence mechanism and engraving features of the nylon belt were numerically calculated under higher charge conditions. The comparison between the experimental recovery belt and the numerical calculation results shows that the damage to the front of the nylon belt is axial compression wear, while the damage to the back of the nylon belt is circumferential shear wear. The direction of force exerted by the slope chamber and the projectile body on the belt was inconsistent, causing a bulge in the middle of the nylon belt. The more rapid the average boosting rate, the stronger the instantaneous impact on the nylon belt, the larger the stress and the strain damage on the nylon belt, the higher the pressure at the end of the engraving process and the greater the maximum engraving resistance. When the average boosting rate increased from 2.7 MPa⋅ms−1 to 33.0 MPa⋅ms−1, the engraving time was shortened by 73.9%, while the maximum engraving resistance increased by 78.2%.

Correlation of four-dimensional ultrasound strain analysis with computed tomography angiography wall stress simulations in abdominal aortic aneurysms

ObjectiveBiomechanical modeling of infrarenal aortic aneurysms seeks to predict ruptures in advance, thereby reducing aneurysm-related deaths. As individual methods focusing on strain and stress analysis lack adequate discretization power, this study aims to explore multifactorial characterization for progressive aneurysmal degeneration. The study’s objective is to compare stress- and strain-related parameters in infrarenal aortic aneurysms. MethodsTwenty-two patients with abdominal aortic aneurysms (AAAs) (mean maximum diameter, 53.2 ± 7.2 mm) were included in the exploratory study, examined by computed tomography angiography (CTA) and three-dimensional real-time speckle tracking ultrasound (4D-US). The conformity of aneurysm anatomy in 4D-US and CTA was determined with the mean point-to-point distance (MPPD). CTA was employed for each AAA to characterize stress-related indices using the semi-automated A4-clinics RE software. Five segmentations from one 4D-US examination were fused into one averaged model for strain analysis using MATLAB and the Abaqus solver. ResultsThe mean MPPD between the adjacent points of the 4D-US and CTA-derived geometry was 1.8 ± 0.4 mm. The interclass correlation coefficients for all raters and all measurements for the maximum AAA diameter in 2D, 4D ultrasound, and CTA indicate moderate to good reliability (interclass correlation coefficient1 0.69 with 95% confidence interval [CI], 0.49-0.84; P < .001). The peak wall stress (PWS) correlates fairly with the maximum AAA diameter in 2D-US (r = 0.54; P < .01) and 4D-US (r = 0.53; P < .05) and moderately strongly with the maximum exterior AAA diameter (r = 0.63; P < .01). The peak wall rupture risk index shows a strong correlation with the PWS (ρ > 0.9; P < .001) and is influenced by anatomical parameters with equal strength. Isolated observation of the intraluminal thrombus does not provide significant information in the determination of PWS. The maximum AAA diameter in 2D-US shows a fair negative correlation with the mean circumferential, longitudinal and in-plane shear strain (ρ = −0.46; r = −0.45; ρ = −0.47; P < .05 for all). The circumferential strain ratio as an indicator of wall motion heterogeneity increases with the aneurysm diameter (r = 0.47; P < .05). The direct comparison of wall strain and wall stress indices shows no quantitative correlation. ConclusionsThe strain and stress analyses provide independent biomechanical information of AAAs. At the current stage of development, the two methods are considered complementary and may optimize a more patient-specific rupture risk prediction in the future.

The circumferential force on a cylindrical rotating detonation engine

Rotating detonation engines (RDEs) utilize single or multiple detonation waves continuously traveling at velocities ranging from 1 to 3 km/s. These waves induce a strong swirl near the inlet surface, generating circumferential shear stress on the surface of the combustion chamber. This stress works as torque in the axial direction. This characteristic is promising for turbine applications. However, for long-term operation, such applications require reduction in the thermal damage risk. While annular RDEs, which have an inner wall surface, involve the thermally independent center body, cylindrical RDEs have no center body and more suitable. On the other hand, the contact surface exposed to the swirling flow is smaller. This study evaluated the differences in combustion mode and circumferential phenomena between annular and cylindrical RDEs through the measurement of thrust and torque. The results showed that the torque generated by the cylindrical RDE was as large (around 0.1 Nm) as that generated by the annular RDE under mass flow rate of approximately 0.05 kg/s. This was due to the stronger swirl derived from the 16 % faster detonation waves. In addition, the presence of strong detonation combustion around the outer wall of the cylindrical RDE was indicated through the control surface method. When a fuel‒oxidizer was supplied to the strong detonation combustion region, the detonation waves reached velocities around the Chapman–Jouguet value, with the maximum torque in this study being 0.127 Nm. From these results, the effect of the propagation mode of detonation waves on the circumferential flow and force was evaluated. The results indicated that the increase of detonation wave velocity enhanced the circumferential flow and force. The tendency to increase became large as the number of the detonation waves increased.

Circumferential shear for an incompressible non-Green elastic cylindrical annulus

The circumferential shear of a nonlinear isotropic incompressible elastic annulus is studied using the neo-Hookean, Ogden constitutive relations in addition to a new constitutive relation for the Hencky strain in terms of the Cauchy stress. The predictions of the three constitutive relations to the specific boundary value problem are delineated. In view of the predictions being quite distinct between the new constitutive relation studied and that for the Ogden constitutive relation, it would be worthwhile to carry out an experiment to determine the efficacy of the models.

Texture adjustment approach of magnesium alloys via variable strain path calculated by an integrated finite element-viscoplastic self-consistent model

An integrated calculated approach based on weakly coupled finite element (FEM)-viscoplastic self-consistent (VPSC) model was established to simulate the texture evolution during the variable strain path extrusion process of magnesium alloys. The spiral die extrusion (SDE) process with additional circumferential shear deformation was applied to investigate the effect of path control on texture adjustment and verify the accuracy of the model. The results indicated that the additional spiral shear resulting from the overall inclined flow path effectively reduced the intensity of the {0002}//ED fiber texture by suppressing basal slip activation in the core area, while the local shear deformation along the spiral equal channel strain path led to the formation of an inclined {0002}//ND plane texture on the side. Using the modified Hall–Petch relationship, the correlation between texture and yield strength was quantified. Specifically, the weakening of the texture effectively suppressed {10–12} tensile twinning, which compensated for the deficiency of compressive yield strength without significantly sacrificing tensile yield strength, and thus improved the tension-compression asymmetry. Furthermore, the strongly inclined {0002}//ND plane texture inhibited the widespread activation of basal slip during tensile yielding, thereby enhancing the yield strength.

On the identification of the ultra-structural organization of elastic fibers and their effects on the integrity of annulus fibrosus

Due to the complicated structure of the elastic fiber network in annulus fibrosus, existing in-silico studies either simplified or just overlooked its distribution pattern. Nonetheless, experimental and simulation results have proven that elastic fibers are of great importance to maintaining the structural integrity of annulus fibrosus and therefore to ensuring the load-bearing ability of intervertebral discs. Such needs call for a fine model. This work aims at developing a biphasic annulus fibrosus model by incorporating the accurate distribution pattern of collagen and elastic fibers. Both the structural parameters and intrinsic mechanical parameters were successfully identified using single lamella and inter-lamella microscopy anatomy and micromechanical testing data. The proposed model was then used to implement finite element simulations on various anterior and posterolateral multi-lamellae annulus fibrosus specimens. In general, simulation results agree well with available experimental and simulation data. On this basis, the effects of elastic fibers on the integrity of annulus fibrosus were further investigated. It was found that elastic fibers significantly influence the free swelling, radial stretching and circumferential shear performances of annulus fibrosus. Nonetheless, no significant effects were found for the circumferential stretching capability. The proposed biphasic model considers for the first time the distribution characteristics of elastic fibers at two scales, including both the principal orientations of all fiber families and the detailed distribution pattern within each family. Better understandings on the functions of collagen and elastic fibers can therefore be realized. To further enhance its prediction capability, the current model can be extended in the future by taking the fiber–matrix interaction as well as progressive damages into consideration.

Circumferential SH wave in piezo-reinforced composite structure with imperfect interface bonding

The present study fundamentally focuses on analyzing the limitations and transference of circumferential shear horizontal (CSH) waves in a four-layered compounded cylinder. The geometrical structure consists of cylinders of infinite length composed of self-reinforced (SR), fibre-reinforced (FR), piezo-magnetic (PM), and piezo-electric(PE) materials. In order to make the structure sensitive to the application pertaining to sensors and actuators, the PM and PE cylinders have been categorically placed in the outer part of the geometry. Whereas in order to provide stiffness and stability to the structure, the inner part consists of SR and FR materials. The common boundary between each of the cylinders has been essentially considered as imperfectly bounded. At the interface of PE and PM media, mechanical, electrical, magnetic, and inter-coupled types of imperfections have been exhibited. The closed-form of dispersion relation has been deduced for two contrast cases i.e. electrically open magnetically short (EOMS) and electrically short and magnetically open (ESMO) circuit conditions. Dispersion curves have been plotted to illustrate the salient features of parameters like normalized imperfect interface parameters, initial stresses, and radii of the concentric cylinders. The comparative effect of each one of these parameters on the phase velocity of the wave has been enlisted and marked individually. Every graph has been presented with two successive modes for a comprehensive understanding. This theoretical study may be implemented to improvise the performance of surface acoustic wave (SAW) sensors, actuators, and Piezo-cables in the form of Piezo-polymer sensors consisting of piezo-electric quartz, piezo-composite concentric cylinders, and coaxial piezo-cables.

Fluid dynamics by 4D flow CMR in Marfan and Loeys-Dietz patients before and after valve sparing aortic root replacement

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III (Spain), Sociedad Española de Cardiología Introduction Patients with Marfan or Loeys-Dietz syndrome present abnormal aortic flow patterns in the arch and the proximal descending aorta that may contribute to aortic dilation (1,2). Valve sparing aortic root replacement, which is effective in reducing the risk of aortic dissection in case of severe dilation, may also normalize flow patterns beyond the replaced aorta and potentially slow its progressive aortic dilation. Purpose To assess aortic flow dynamics in these patients with Marfan or Loeys-Dietz by 4D flow cardiovascular magnetic resonance (CMR) before and after valve sparing aortic root replacement (David surgery), and to compare the results with those of healthy volunteers (HV). Methods Patients with Marfan or Loeys-Dietz syndrome underwent two non-contrast enhanced 4D flow CMR, one before and another after undergoing David surgery. Healthy volunteers matched for age, sex and BSA were also included for comparison. Maximum velocity, in-plane rotational flow (IRF), systolic flow reversal ratio (SFRR) and wall shear stress (WSS) magnitude and its axial and circumferential components were obtained at 24 planes covering the thoracic aorta from the sinotubular junction to the descending aorta at the diaphragmatic level (3–5). Results Sixteen patients and 21 healthy volunteers were included. Demographic and clinical data is presented in Table. The mean time between the CMR prior and posterior to surgery was 15 months. Compared to HV, patients with CTD before intervention presented lower maximum velocity at the proximal ascending aorta (Figure 1A), lower IRF and circumferential WSS at the arch and the proximal descending aorta (Figure 1B and F), lower magnitude and axial WSS at the proximal ascending and descending aorta (Figure 1E and D), and increased SFRR at the proximal descending aorta (Figure 1C). The intervention completely restored maximum velocity and partially-restored physiological helical flow and circumferential WSS, but barely improved axial WSS and SFRR. Conclusion Valve sparing aortic root replacement in patients with Marfan or Loeys-Dietz syndrome partially restore to physiological level both in-plane rotational flow and circumferential wall shear stress in the descending aorta.

Research on Crossing-Pipe Support Structure Defect Detection of EMAT-Excited CSH Wave

A circumferential shear horizontal (CSH) guide wave-detection method using a periodic permanent magnet electromagnetic acoustic transducer (PPM EMAT) was proposed to solve the defect detection located at the inside of the pipe welded by supporting structures. Firstly, a low-frequency CSH0 mode was selected to establish a three-dimensional equivalent model for the defect detection to cross the pipe support, and the ability of the CSH0 guided wave to propagate through the support and weld structure was analyzed. Then, an experiment was used for the further exploration of the influence of different sizes and types of defects on detection after using the support, as well as the ability of detection mechanism to cross different pipe structures. The results show that both the experiment and the simulation received a good detection signal at 3 mm crack defects, which proves that the method can detect the defects by crossing the welded supporting structure. At the same time, the support structure shows a greater impact on the detection of small defects than the welded structure. The research in this paper can provide ideas for guide wave detection across the support structure in the future.

Three-Dimensional Ultrasound Elastography Detects Age-Related Increase in Anterior Peripapillary Sclera and Optic Nerve Head Compression During IOP Elevation.

High-frequency ultrasound elastography offers a tool to resolve the complex and heterogeneous deformation through the full thickness of the optic nerve head (ONH) and peripapillary sclera (PPS). Using this tool, we quantified the three-dimensional deformation of the ONH and PPS in human donor eyes and evaluated age-associated changes. The ONH and PPS in 15 human donor globes were imaged with a 50-MHz ultrasound probe while increasing intraocular pressure (IOP) from 15 to 30 mmHg. Tissue displacements were obtained using correlation-based ultrasound speckle tracking. Three-dimensional spherical strains (radial, circumferential, meridional, and respective shear strains) were calculated for the ONH and PPS volumes segmented from three-dimensional ultrasound images. Age-related trends of different strains in each region of interest were explored. The dominant form of IOP-induced deformation in the ONH and PPS was radial compression. High-magnitude localized out-of-plane shear strains were also observed in both regions. Most strains were concentrated in the anterior one-half of the ONH and PPS. The magnitude of radial and volumetric strains increased with age in the anterior ONH and anterior PPS, indicating greater radial compression and volume loss during IOP elevation in older age. The age-associated increase of radial compression, the predominant form of IOP-induced deformation in anterior ONH and PPS, may underlie age-associated glaucoma risk. High-frequency ultrasound elastography offers a useful tool to quantify all types of deformation comprehensively in all regions of ONH and PPS, which may improve our understanding of the biomechanical factors contributing to glaucoma risk.