Circumferential Deformation Research Articles

Inclination information-aided circumferential deformation reconstruction error correction method for CFRP belt integrated with optical fiber sensor

In view of the problem that the distributed optical fiber-based deformation reconstruction method can produce serious accumulated errors, this paper developed a smart fiber optic sensor belt that employs a carbon-fiber composite material as the matrix and strain-sensing fiber optics as the sensing element and is based on the key-point dip angle information acquired by a high-precision tilt sensor. The method of in situ correction for the cumulative error of circumferential deformation was investigated, and the particle swarm optimization algorithm was adopted to perform in situ correction for the reconstructed circumferential deformation field of the sensor belt to reduce the cumulative measurement error of the circumferential deformation field. Simulations and indoor tests were systematically performed. After the correction, the errors of the simulation and indoor tests were reduced from 210.83 and 235.82 mm to 2.17 and 4.04 mm, respectively, which verified the effectiveness and accuracy of the aforementioned method.

The left ventricular strain-volume loop in a healthy Dutch population: age- and sex related differences

Abstract Introduction By combining left ventricular (LV) global longitudinal strain (GLS) with LV volume during the cardiac cycle, LV strain-volume loops can be generated. LV SV-loop derived parameters provide new insights into the interaction between cardiac contraction and volume in a variety of cardiac diseases (1,2) and may even have prognostic value. (3,4) Reference values for healthy individuals with attention to sex- and age-related differences have not been established yet. Therefore, the aim of this study is to provide reference ranges in a healthy adult population and investigate potential sex- and age-related differences of LV SV-loop characteristics. Methods In 125 healthy volunteers aged 18-72 years, apical 2-, 3- and 4-chamber views were acquired to measure GLS. Custom software was used to combine strain and volume data to construct SV-loops. Different parameters were derived: (i)linear slope of systolic strain-volume relation (S-Slope); (ii) early linear slope of systolic strain-volume relation (ES-Slope); (iii) early linear slope of diastolic strain-volume relation (ED-Slope); and (iv) uncoupling between systolic and diastolic strain-volume relation (UNCOUP). Results For the systolic strain-volume relation higher values were observed in females as compared with males with S-Slope values of 0.19 [0.17-0.22] %/mL m-² and 0.13 [0.11-0.15] %/mL m-² respectively. ED-Slope was higher in females as compared with males with values of 0.18 [0.09-0.28] %/mL m-² and 0.12 [0.06-0.18] %/mL m-² respectively. Relative coupling of the systolic and diastolic strain-volume relation was observed with a mean value of 0.34 ± 1.1. UNCOUP was correlated with age with a value for r of 0.4. Conclusion Higher values for the systolic and early-diastolic strain-volume relation in females can be reflective of different cardiomechanics as LV contraction is not only comprised of longitudinal but also circumferential and radial deformation. In line with current literature our custom software found relative coupling of the systolic and diastolic strain-volume relation in our cohort of healthy subjects. Towards older age relative uncoupling of the systolic and diastolic strain-volume relation was found.Figure 1.Strain-volume loop

3D bi-directional auxetic square metastructure with programmable thermal expansion and Poisson's ratio

Multifunctional integration research on metastructures has become the current development trend and hotspot, especially satellite platforms and hypersonic aircraft in the aerospace field. A 3D bi-directional auxetic square metastructure (BASM) with the programmable coefficient of thermal expansion (CTE) and Poisson's ratio (PR) is designed through the combination of re-entrant hexagonal structures and bi-material triangles. Specimens in the form of the 1*2 array are designed and fabricated through 3D printing. The correctness of the results of finite element analysis (FEA) of the BASM is verified by uniaxial compression experiments. Additionally, FEA is adopted to investigate the effective mechanical properties of the BASM with the form of the 2*3 array, and deformation mechanisms are further explored. Results indicate that the CTE, PR, and stiffness of the BASM depend on material combinations and geometric parameters. Under thermal and mechanical loads, the BASM achieves bi-directional regulation of the CTE and PR, encompassing both axial and circumferential deformations. Notably, the deformation mechanisms and critical conditions of the BASM are explored under the thermo-mechanical load. A novel strategy for programming the PR of the BASM is proposed in addition to changing the geometric parameters and the material combinations.

Continuous and synchronous calibration process of ovality and straightness for longitudinally submerged arc welding pipes with three rollers.

A new process of continuous and synchronous calibration process of ovality and straightness for LSAW (Longitudinally Submerged Arc Welding, LSAW) pipes with three rollers is proposed. Specifically, the process is introduced from three aspects: roller-shape, loading parameters and axial and circumferential deformation paths. The process is verified by numerical simulation and physical experiments. Further, the stress-strain in the Sections Ⅱ and Ⅳ is analyzed. The relationship between the process parameters and the residual ovality and residual straightness by experiments is discussed. The calibration scheme of LSAW pipes is put forward by using the control variable method. The results show that the shear stress is the principal stress direction in the Sections Ⅱ and Ⅳ. The residual ovality and residual straightness decrease with the increase of the radial reduction and times of reciprocating bending. The reciprocating bending process can eliminate the difference of the initial curvature, make the curvature of each section tend to be uniform. After calibration, the residual straightness is less than 0.2% and the residual ovality is less than 1%, demonstrating a good feasibility of this process.

Perinatal Cardiac Functional Adaptation in Hypoplastic Left Heart Syndrome: A Longitudinal Analysis

The perinatal transition is characterized by acute changes in cardiac loading. Compared with normal newborn combined cardiac output (CCO), single right ventricular (RV) output of neonates with hypoplastic left heart syndrome (HLHS) is markedly greater. The aim of this study was to examine the mechanisms of cardiac adaptation that facilitate this perinatal transition from late fetal to early neonatal life in HLHS. Prospectively recruited pregnancies complicated by fetal HLHS (n=35) and healthy control subjects (Ctrl; n=17) underwent serial echocardiography in late gestation (38±1weeks) and 6, 24, and 48hours after birth. Cardiac function was assessed using conventional, Doppler tissue, and speckle-tracking echocardiography. Term fetuses with HLHS had RV output comparable with Ctrl CCO via higher stroke volume. Compared with both left ventricular and RV indices of Ctrl, they exhibited globular and dilated right ventricles with reduced relative wall thickness (0.40±0.08 vs 0.49±0.10, P<.01), increased Tei index' (HLHS vs Ctrl left ventricle/Ctrl right ventricle: sphericity index, 0.9±0.25 vs 0.5±0.10/0.6±0.11; RV area index, 28±6 vs 15±3/17±5cm2/m2; Tei index', 0.65±0.11 vs 0.43±0.07/0.45±0.09; P<.0001 for all). Neonates with HLHS generated elevated RV cardiac output compared with Ctrl CCO via higher heart rate and stroke volume, with further RV dilatation, increased longitudinal systolic strain at 48hours (-17±4% vs -14±3%/14±5%) with reduced circumferential and rotational myocardial deformation and altered diastolic function. Neonates with HLHS also demonstrated right atrial enlargement with increased longitudinal strain: 6hours (33±12% vs 26±6%), 24hours (37±15% vs 26± 13%), and 48hours (38±11% vs 24±13%) (P<.0001). Term fetuses with HLHS exhibit altered RV geometry and RV systolic and diastolic functional parameters. After birth, further alterations in these cardiac parameters likely reflect adaptation to acutely altered RV loading from increasing cardiac output and pulmonary artery flow demands.

A novel 3D Z-shape design of compression-twist coupling metamaterial

Compression-twist coupling (CTC) metamaterials are the type of mechanical metamaterials which can convert the axial deformation into circumferential deformation. In order to design CTC metamaterials, connecting two lattice layers with chiral oblique rods is an effective method, and the unit cell is a cube with 2D Z-shape structure on the lateral side. In this study, a new 3D spatial Z-shape CTC structure is firstly proposed by rotating the upper layer with different angles in the traditional 3D Z-shape structure. Then, the torsion angles are analyzed with changes of unit cell geometries by theoretical method, finite element simulation and experiments. Finally, by extending the new 3D Z-shape structures, the typical pyramid frustum and oblique-rod-enhanced structures are designed and their mechanical behaviors are studied.

Effect of rapid cooling, frozen storage, and thawing on the passive viscoelastic properties and structure of the rat aorta

Biological tissues decay over time after harvesting, which alters their biomechanical properties. This poses logistical challenges for studies investigating passive arterial biomechanics as tissues need to be characterized shortly after excision. Freezing and cryopreservation methods can help alleviate the need for biomechanical testing of fresh tissue in human ex vivo studies. However, these methods tend to eliminate or reduce arterial cell functionality and affect passive biomechanics. Furthermore, their impact on dynamic arterial biomechanics remains unknown despite arterial viscoelastic properties being an integral component contributing to arterial stiffness under in vivo loading conditions. The present study aims to investigate the impact of rapid cooling and subsequent storage at −80 °C on the passive viscoelastic properties of arterial tissue and aid in ascertaining whether this is a suitable method to delay tissue analysis for studies investigating passive arterial biomechanics. Control and frozen abdominal rat aorta segments were quasi-statically and dynamically tested using a biaxial testing set-up. The results were modeled using a constituent-based quasi-linear viscoelastic modeling framework, yielding directional stiffness parameters, individual constituent biomechanical contributions, and a quantification of viscoelastic stiffening under dynamic pressurization conditions. Frozen samples displayed significantly decreased wall thickness, viscoelastic dissipation, viscoelastic stiffening, and significantly decreased circumferential deformation with changes in luminal pressure. Furthermore, frozen samples displayed significantly increased circumferential stiffness, pulse wave velocity, and collagen load bearing. Consequently, these changes should be considered when utilizing this tissue preservation method to delay biomechanical characterization of rat aortic tissue.

Intelligent circumferential deformation prediction of structures in PCCP-E with a large diameter under internal water overpressure based on prototype experiments and Inception-ResNet-LSTM

Prestressed Concrete Cylinder Pipe (PCCP) is extensively employed in long-distance water transmission projects, owing to its notable pressure-bearing capacity and durability. Nonetheless, the operation under overpressure conditions poses a risk of structural damage and functional failure to PCCP during its service life. Consequently, accurate prediction of the deformation characteristics of overpressure operation with the structural deformation data under standard water pressure is of great importance for ensuring the safety and reliability of the project. However, it is a challenge to obtain spatiotemporal features for traditional algorithms. As a consequence, a novel deep learning model, i.e. Inception-ResNet-LSTM, is put forward to forecast PCCP deformation. It integrates the Inception, ResNet, and Long Short-Term Memory (LSTM). Based on the prototype experiments, the monitoring was undertaken on the deformations of the inner and outer concrete layers, the steel cylinders, and the prestressed steel wire under internal water pressures of 0 MPa, 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa, 1.0 MPa, and 1.15 MPa. In the case study, the deformation data of different structures are input into Inception-ResNet-LSTM to establish a model. For all the structures, the R2 (coefficient of determination) of the Inception-ResNet-LSTM model exceeds 0.97. Based on the results, it is demonstrated that the model has captured the spatiotemporal features from the monitoring data. In comparison to models based on DL and ML algorithms, Inception-ResNet-LSTM demonstrates superior performance, exhibiting heightened accuracy and enhanced generalization capabilities. It provides a new method for PCCP deformation estimation under overpressure.

Deep cardiac phenotyping by cardiovascular magnetic resonance reveals subclinical focal and diffuse myocardial injury in patients with psoriasis (PSOR-COR study).

Psoriasis vulgaris (PV) is a chronic inflammatory disorder frequently associated with cardiovascular disease (CVD). This study aims to provide a prospective tissue characterization in patients with PV without major CVD using cardiovascular magnetic resonance (CMR). Patients with PV underwent laboratory assessment, a 12-lead and 24-h ECG, and a CMR exam at a 1.5-T scanner. Scan protocol included assessment of left (LV) and right (RV) ventricular function and strain analysis, native and post-contrast T1 mapping, T2 mapping and late gadolinium enhancement (LGE). In total, 60 PV patients (median(IQR) age in years: 50.0 (36.0-60.8); 34 men (56.7%)) were recruited and compared to 40 healthy volunteers (age in years: 49.5 (37.3-57.8); 21 men (53.0%)). No differences were found regarding LV and RV function (p = 0.78 and p = 0.75). Global radial and circumferential strains were lower in patients (p < 0.001 and p < 0.001, respectively). PV had higher global T1 times (1001 (982-1026) ms vs. 991 (968-1005) ms; p = 0.01) and lower global T2 times (48 (47-49) ms vs. 50 (48-51) ms; p < 0.001); however, all values were within local reference ranges. Focal non-ischemic fibrosis was observed in 17 (28.3%) PV patients. Deep cardiac phenotyping by CMR revealed subclinical myocardial injury in patients with PV without major CVD, despite preserved LV and RV function. Diffuse and focal fibrosis might be the first detectable signs of adverse tissue remodeling leading to reduced circumferential and radial myocardial deformation. In the background of local and systemic immunomodulatory therapy, no signs of myocardial inflammation were detected. The exact impact of immunomodulatory therapies on the myocardium needs to be addressed in future studies. ISRCTN71534700.

Stress analysis under centrifugal load of the multiple corrugated diaphragm coupling based on rotating shell thin film model

Centrifugal force is one of the factors that cannot be ignored in high-speed shaft systems. The multiple corrugated diaphragm (MCD) Coupling is suitable for high-power and high-speed situations; hence, it is crucial to investigate the stress and deformation of the wave disc under centrifugal load. This paper first uses the rotating shell thin film model to derive the circumferential stress and deformation displacement of the MCD under centrifugal load. Then, the finite element method is used to verify the results obtained from the analytical solution. The results show the feasibility of using the rotating shell thin film model for centrifugal load analysis of the MCD, providing a new approach for the theoretical analysis of the MCD.

Dynamic compressive properties of 2D-aligned steel fiber reinforced cement-based composites

Dynamic compression may happen in some protective cement-based composite structures. Cement-based composites are compressed at loading direction when subjected to dynamic compression, however expansion occurs in the direction perpendicular to the loading. As a quasi-brittle material, the expansion of the cement-based composites may result in the disintegration and hence the failure of the material. Incorporating steel fibers is a valid solution of reinforce the composites to resist dynamic compression. Usually, steel fibers are randomly dispersed throughout the composites. Actually, steel fibers with the same direction of the dynamic loading are ineffective. Only steel fibers perpendicular to the orientation of the dynamic compression load can they effectively restrict the expansion of the composites and enhance its dynamic compressive properties. So, cylindrical specimens using two-dimensionally aligned steel fiber reinforced cement-based composites (2D-SFRC) were prepared and tested. In specimens all steel fibers are perpendicular to the dynamic compression load, which limits the circumferential expansion and deformation of the specimens when subjected to dynamic compression and significantly enhances its performance resisting dynamic compression. When preparing 2D-SFRC specimens, the magnetic field was used to align steel fibers to achieve the two-dimensionally aligned steel fiber in specimens. Then, 2D-SFRC specimens were tested for their dynamic compressive properties. The results indicate that the dynamic compressive strength and toughness of 2D-SFRC specimens are significantly increased compared with unidirectional and random steel fiber distribution specimens. By analyzing the stress distribution and tensile force of steel fibers, the reinforcing mechanism of two-dimensionally aligned steel fibers was revealed. The two-dimensional alignment of steel fibers increased the number and the tensile force of fibers, which effectively restrained the circumferential expansion of the cylinder specimens.

Characterization of Potting Epoxy Resins Performance Parameters Based on a Viscoelastic Constitutive Model.

To describe the evolution of residual stresses in epoxy resin during the curing process, a more detailed characterization of its viscoelastic properties is necessary. In this study, we have devised a simplified apparatus for assessing the viscoelastic properties of epoxy resin. This apparatus employs a confining cylinder to restrict the circumferential and radial deformations of the material. Following the application of load by the testing machine, the epoxy resin sample gradually reduces the gap between its surface and the inner wall of the confining cylinder, ultimately achieving full contact and establishing a continuous interface. By recording the circumferential stress-strain on the outer surface of the confining cylinder, we can deduce the variations in material bulk and shear moduli with time. This characterization spans eight temperature points surrounding the glass transition temperature, revealing the bulk and shear relaxation moduli of the epoxy resin. Throughout the experiments, the epoxy resin's viscoelastic response demonstrated a pronounced time-temperature dependency. Below the glass transition temperature, the stress relaxation response progressively accelerated with increasing temperature, while beyond the glass transition temperature, the stress relaxation time underwent a substantial reduction. By applying the time-temperature superposition principle, it is possible to construct the relaxation master curves for the bulk and shear moduli of the epoxy resin. By fitting the data, we can obtain expressions for the constitutive model describing the viscoelastic behavior of the epoxy resin. In order to validate the reliability of the test results, a uniaxial tensile relaxation test was conducted on the epoxy resin casting body. The results show good agreement between the obtained uniaxial relaxation modulus curves and those derived from the bulk and shear relaxation modulus equations, confirming the validity of both the device design and the testing methodology.

Echocardiographic evaluation of myocardial structural and functional changes in patients with stage 5 chronic kidney disease before and after kidney transplantation

Introduction. Chronic kidney disease, stage 5, leads to structural remodeling of the myocardium, and heart failure. Kidney transplantation promotes normalization of structural and functional parameters of the myocardium through reverse remodeling with an improvement of its systolic function.Aim. To evaluate structural and functional changes of the myocardium in patients before and after kidney transplantation, using echocardiography.Material and methods. A retrospective cross-sectional study included 111 individuals of whom 36 patients underwent evaluation for kidney transplant waiting list placement program (Group I), and 51 patients received kidney transplants from deceased donors (Group II). Group III consisted of 24 individuals without kidney pathology. All patients underwent transthoracic two-dimensional echocardiography using the Phillips Epiq 7 device to determine the structural and functional parameters of the heart, including the use of speckle-tracking technique to assess longitudinal and circumferential myocardial deformation of the left ventricle.Results. There were no statistically significant differences in transthoracic echocardiography results between patients in Group I and Group II. When compared to the parameters of patients in Group III, statistically significant differences were found in the following parameters: volume and volume index of the left atrium, end-diastolic volume index, left ventricular mass index, interventricular septum thickness and posterior wall thickness of the left ventricle, as well as diastolic function parameters (E/A). Patients in Group I and Group II had significantly higher values of left atrium diameter: 32 (26.0;38.0) mmHg and 31.0 (27.3;40.0) mmHg, respectively, (p1-2=0.949), while in Group III this parameter value was 22.5 (20.8;25.3) mmHg (p1-3&lt;0.001, p2-3&lt;0.001). Correlation analysis revealed statistically significant correlations between left ventricular mass index and global circumferential strain (r=0.41, p=0.0027), as well as between E/e' ratio and left ventricular mass index (r=0.323, p=0.00197). It was found that after 3 months post kidney transplantation, there was a decrease in the left atrium diameter, volume, and volume index. The values of left atrium diameter immediately after kidney transplantation and after 3 months were 40 (32.5;45) mmHg and 35 (25.5;41.0) mmHg (p=0.049); those of the left atrium volume were 62.5 (50.0;77.3) and 51.5 (47.5;64.5) ml (p=0.03); and those of the left atrium volume index were 33.4 (29.3;40.2) and 28.3 (25.5;33.6) ml/m2 (p=0.01) respectively.Conclusions. Patients with chronic kidney disease stage 5 have a high incidence of functional and structural abnormalities of the left heart chambers; left ventricular mass index positively correlates with E/e' and global circumferential strain. At 3 months after kidney transplantation, there was a slight positive trend manifested in the form of a decrease in left atrium diameter and a decrease in left ventricle volume. Further dynamic study of this group of patients in the long term after kidney transplantation is planned.

Innovative local shear forming method for enhanced formability of tubular parts with high stiffened ribs

Large-sized thin-walled tubular parts with high stiffened ribs are key lightweight structural components used in transportation. To address the challenges of integral forming, a novel local shear forming (LSF) technique that combines the advantages of spinning and shear forging (SFG) is proposed. Finite element (FE) simulations and experimental work have revealed the distinct deformation mechanisms of local shear forming in contrast to those of conventional shear forging or spinning. During local shear forming, the surface material of the billet undergoes sequentially axial upsetting deformation, primary shear deformation, reverse shear deformation, circumferential tensile deformation and radial displacement to form the rib. Gradient plastic deformation is observed through the thickness of the formed wall rather than near the wall surface. The effects of local loading include reduction of the secondary shear deformation zone, reduction of circumferential constraint in the loading zone, material circumferential transfer, and expansion-shrinkage deformation of the billet. The former two decrease the rib thickness and promote radial transfer of the material. The latter two result in a significant strengthening of the formed rib and wall. Moreover, tearing and buckling are suppressed, which enhances the relative wedge thickness up to 50 % of the wall thickness of the billet. The aspect ratio of the formed rib can be as high as 3 for the high strength 2A12 alloy and 6 for the highly ductile 1A30 alloy. Shear deformation in the rib promotes recrystallization in the subsequent T6 heat treatment and refines the microstructure. Corrosion resistance is not degraded though microstructural change. Local shear forming shows good potential for forming tubular parts with an external rib structure.

Investigations of stress and strain state of aluminum alloys during a hot extrusion and patterns of structure and feature formation

This paper investigates the stress and strain state as well as formation processes of structure and features of aluminum alloys during the hot extrusion. It has been shown that during the hot extrusion the ring layers of an extruded element experience not only longitudinal and transverse deformations, but also a slip. The slip increases from inner layers to the surface layer. The tensile principal stresses and the sum of slip deformations also increase. It has been also demonstrated that at the exit of the pressing part the tensile principal stresses have different directions, forming an angle with extruder axis, which also increases towards the surface. In conclusion, it has been stated that the main radial and circumferential deformations act as restraining deformations.

Plastic and damage energy dissipation characteristics and damage evolution of Beishan granite under triaxial cyclic loading

The damage and failure of rock under triaxial stress is an irreversible process of energy dissipation, which mainly includes plastic energy dissipation and damage energy dissipation. However, it is difficult and rare to separate plastic energy dissipation and damage energy dissipation and to conduct relevant research on this basis. In this work, a loading control method with a combination of load (0.5 kN/s) and circumferential deformation (0.01 mm/min) was used, and triaxial cyclic loading and unloading tests under five different confining pressures were performed on granite from the Beishan site area of China's high-level radioactive waste repository. The results indicate that the angle between the main fracture surface and the longitudinal axis increases with the increase of confining pressure. According to the characteristics of the stress–strain curve and energy dissipation, the test process can be divided into five stages: the initial compaction and elastic stage, the stable crack growth stage, the unstable crack growth stage, the postpeak unstable fracture stage and the residual stress stage. Importantly, a separate determination method of plastic energy dissipation and damage energy dissipation was proposed, and the evolution characteristics of plastic energy dissipation and damage energy dissipation were revealed. The ratio of plastic energy dissipation to input energy decreases slightly in the initial compaction and elastic stage, stabilizes at a low level in the stable and unstable crack growth stages, increases significantly in the postpeak unstable fracture stage and remains at a high level in the residual stress stage. Meanwhile, the ratio of damage energy dissipation to input energy increases slightly before the unstable crack growth stage, increases abruptly at the end of the unstable crack growth stage and the initial part of the postpeak unstable fracture stage, then declines rapidly, and finally remains at a low level. Furthermore, the qualitative and quantitative research results of damage evolution show that the plastic shear strain and damage variable established by damage energy dissipation can qualitatively and quantitatively describe the damage evolution of Beishan granite respectively. Finally, the verification results of Beishan granite and two other rock types show that the separation method for calculating plastic energy dissipation and damage energy dissipation proposed in this work has good adaptability, and the qualitative damage development analysis based on plastic shear strain can be verified and supplemented with the quantitative damage development analysis based on energy theory.

Left ventricular speckle tracking echocardiography in predicting of fibrosis in children after correction of anomalous origin of the left coronary artery from the pulmonary artery in the late postoperative period

The aim of our study is a comprehensive echo assessment of the LV function using the speckle tracking technique in children with abnormal origin of the left coronary artery from the pulmonary artery in the late postoperative period аnd a comparative analysis segmental longitudinal and circumferential LV deformation with cardiac magnetic resonance late enhancement of myocardium. Methods. The search is a prospective observational study. We examined and analyzed 25 children with AOLCA from PA in late postoperative period. Obtained morphofunctional LV and RV echo parameters were compared with LV ejection fraction and dimensions, the grade of mitral insufficiency and age at the time of operation. CMR was performed in 15 patients (60%; n = 15/25) using Avanto 1.5T. The average age of children at the time of the study was 8.8 ± 3.5 years.Results. 1) Reduce of LV segmental longitudinal deformation is unique in each patient’s case. The largest number of segments with reduced longitudinal deformation was detected in the 2d (anteroseptal basal); in 4th (inferior basal); 5th (inferolateral basal), 6th (anterolateral basal), 11th (inferolateral middle) segments of LV myocardium. 2) There is no relationship between LV global longitudinal and circumferential deformation in children in the late postoperative period after correction of AOLCA from PA and initial LV morphological and functional echo data (at the time of defect correction). 3) Segmental LV longitudinal deformation Area Under the Curve is 0.64 (0.56–0.72) with “cut-off” 9.5% with a sensitivity of 92% and a specificity of 85% and circumferential segmental deformity Area Under the Curve is 0.48 (0.40–0.56) in the predicting of fibrosis according to CMR data.

The effect of varying stress intervals on fatigue of rock salt

The surrounding rock of underground energy storage salt caverns is subjected to periodic loading with stress intervals during actual operation. To study the fatigue behavior of rock salt with such stress intervals, one conventional fatigue test and three fatigue tests with multi-step varying stress intervals (MVSIs) were conducted. The results show that the circumferential deformation first decreases and eventually becomes similar to the axial deformation in fatigue tests with MVSIs, as the interval duration increases. Both the dissipated energy and the spacing between the loading and unloading curves of a single cycle first decreased, then remained constant, and finally increased sharply as the stress interval increased. When the stress intervals corresponded to the elastic phase of loading (between 20% and 40% of the uniaxial compressive strength), the rock salt was subjected to the minimum damage. Based on the Bauschinger effect and dislocation internal friction theory, the micromechanism of rock salt fatigue was further explained.

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.

Tele-ultrasound in community with limited resources: The association of hypertension on reduced carotid artery circumferential strain

Introduction: Stroke is one of the leading causes of death worldwide, in majority triggered by modifiable risk factors such as hypertension. AIM: to assess relations between hypertension and carotid arteries radial and circumferential deformation, assessing a population of participants after a first ischemic stroke and healthy controls. Methods: Retrospective study, from 2016 to 2017, with a sample of the PAI project control group, an urban population of the São Francisco Valley in the Northeast of Brazil, 105 people between 40-80 years-old, including patients after a first episode of ischemic stroke in the absence of known cardiovascular disease; and a control group of healthy volunteers, matched by age, sex, and presence of hypertension. Asynchronous analysis was performed by tele-ultrasonography of carotid artery ultrasound with images acquisition of EKG-synchronized videos in cross-section of the common carotid artery bilaterally and then strain values were acquired by Speckle Tracking technique, computing the mean circumferential and radial peaks of both carotids. Univariate and multivariable analyses assessed the association between carotid strain and hypertension. Results: 84 participants had analyzable images (29 patients after a first episode of stroke). The mean age was 60.5 + 11.6 years, 46.5% were women, 70.2% had hypertension. Radial deformation was lower but non-significant in participants with hypertension compared to those without hypertension (-3.13% vs. -3.35%, respectively, p = 0.54). There was significantly less circumferential deformation among participants who had hypertension compared to those without hypertension (4.16% vs. 5.3%, respectively, p = 0.003). Hypertension maintained association with lower circumferential strain in multivariate analysis (coef = -1.13; p = 0.019). Conclusion: hypertension was independently associated with the decrease in the carotid artery circumferential deformation. Tele-ultrasound associated with carotid strain analysis shows promising results for the evaluation of subclinical changes in carotid arteries in populations with limited resources in remote regions such as the Northeast of Brazil.