Peak Strain Values Research Articles

Influence of fiber shapes on the compressive behaviors of ultra-high performance concrete containing coarse aggregate

The addition of coarse aggregate in ultra-high performance concrete (UHPC-CA) has the potential to reduce autogenous shrinkage and improve mechanical properties. However, it also affects the fiber distribution and crack propagation, thereby compressive relationship of UHPC. This study investigated the effects of different fiber shapes on the compressive behaviors of UHPC-CA. Three fiber shapes (straight fiber, hooked fiber, and hybrid fiber) and six coarse aggregate content (0 - 1200 kg/m3) are the main variables. The test results have indicated that the addition of coarse aggregate in UHPC rendered wider main cracks. Hybrid fiber was preferred over the hooked-end and straight fibers to optimize ductility in UHPC-CA. An increase in compressive strength of up to 17.7% and elastic modulus of UHPC of up to 23.7% after moderate addition of coarse aggregate contents, The fiber shape affected peak strain and ultimate strain values for UHPC-CA. Their peak and ultimate strains were improved by 12.8% - 15.3% and 38.2%-127.4% with the inclusion of 2% hooked and hybrid fibers. Based on the experimental data and relevant equations, a proper rational equation from the existing literature is used to generate the complete compressive stress-strain curves of UHPC-CA with different fiber shapes. In summary, this study establishes that hybrid fiber shapes significantly enhance the compressive properties of UHPC-CA. The high elastic modulus and ductility of the UHPC-CA with hybrid fiber are particularly promising for blast and impact applications.

Utilizing echocardiography and unsupervised machine learning for heart failure risk identification

BackgroundGlobal longitudinal strain (GLS) is recognized as a powerful predictor of heart failure (HF). However, the entire strain curve may entail important prognostic information regarding HF risk that might be undiscovered by only focusing on the peak strain value. ObjectiveThe hypothesis of the present study was, that analysis of the entire strain curve using unsupervised machine learning (uML) would reveal novel ventricular deformation patterns capable of predicting incident HF independently of GLS. MethodsLongitudinal strain curves from 3710 subjects from the general population without prevalent HF were analyzed using uML. ResultsMean age was 56 years and 43 % were male. During a median follow-up of 5.3 years, 92 subjects (2.5 %) developed HF. The uML algorithm generated a hierarchical clustering tree (HCT) resulting in 10 different clusters. Generally, the strain curves displayed reduced early diastolic strain to peak-strain ratio with an increasing incidence rate of HF. In multivariable Cox regressions, cluster 9 was significantly associated with increased risk of HF when compared to cluster 2–5, and 7–8 [For cluster 3: HR 8.95, 95 %CI: 2.08;38.48, P = 0.003] even though the subjects of cluster 9 were younger, displayed healthier clinical baseline characteristics, and only had slightly reduced GLS. The mean strain curve of cluster 9 displayed an early systolic lengthening followed by a late and reduced contraction specifically related to the basal lateral segment. ConclusionThe unsupervised machine learning algorithm identified unknown strain patterns beyond GLS presumably related to increased risk of HF.

Assessment by finite element analysis modelling of tissue strains associated with the use of two different nasogastric tube securement devices.

Nasogastric tube use can lead to pressure injury. Some nasogastric tube securement devices (NG-SD) include hard plastic components. In the current study, we assessed the differences in strain profiles for two NG-SD, one with hard segments and one without hard segments, using finite element analysis (FEA) to measure strain and deformation occurring at the nasogastric tube-tissue interface. FEA in silico models of devices were based on device mechanical test data and clinically relevant placements. Peak strain values were determined by modelling different scenarios using Abaqus software whereby the tubing is moved during wear. The modelling showed peak strains ranging from 52% to 434% for the two NG-SD depending on the tubing placement and device type. Peak strain was always higher for the hard plastic device. Tissue strain energy was a minimum of 133.8 mJ for the NG-SD with no hard parts and a maximum of 311.6 mJ for the NG-SD with hard parts. This study provided evidence through in silico modelling that NG-SD without hard components may impart less strain and stress to tissues which may provide an option for tube securement that is less likely to cause medical device-related pressure injury.

Fractional viscoelastic constitutive modelling of real-time strain response for asphalt pavement composites subjected to simulating wheel loadings

ABSTRACT This paper proposed a replacement of the Kelvin–Voigt model with fractional basic elements, and the model constructed with this method was used to describe the viscoelastic strain response of asphalt pavement materials under the simulated wheel loading. Similarities between Abel element and Kelvin–Voigt model were explored, and strain response analytical solutions of Burgers and 1S1A1D models under intermittent have sine loading were derived. Then, different intermittent loading tests of asphalt binder and mixture were carried out. The results showed that both the Abel element and the Kelvin–Voigt model could represent the delayed viscoelastic behaviours accurately, and the strain response represented by them could be fully recovered during the unloading stage. Furthermore, parameters of the Abel element and Kelvin–Voigt model showed a high degree of correlation, and the 1S1A1D model exhibited the best effects for asphalt binders, particularly during the unloading period, with correlation coefficients mostly above 0.999. Moreover, when expressing the strain response of asphalt mixture under simulated wheel loading, the 1S1A1D model outperformed the Burgers model in terms of peak strain value, residual strain and changing trends. This study demonstrated that the fractional constitutive model was advantageous in representing the strain response of asphalt pavement composites.

The Role of Galectin-3 Levels for Predicting Paroxysmal Atrial Fibrillation in Patients with Embolic Stroke of Undetermined Source.

Background/Objectives: Paroxysmal atrial fibrillation (PAF) is an important cause that is thought main potential factor in Embolic stroke of undetermined source (ESUS). Extended Holter ECG is an expensive and time-consuming examination. It needs another tools for predicting PAF in ESUS patients. In this study, serum galectin-3 levels, ECG parameters (PR interval, P wave time and P wave peak time) LA volume index, LA global peak strain and atrial electromechanical conduction time values were investigated for predicting PAF. Methods: 150 patients with ESUS and 30 volunteers for the control group were recruited to study. 48-72 h Holter ECG monitoring was used for detecting PAF. Patients were divided into two groups (ESUS + PAF and ESUS-PAF) according to the development of PAF in Holter ECG monitoring. Results: 30 patients with ESUS whose Holter ECG monitoring showed PAF, were recruited to the ESUS + PAF group. Other 120 patients with ESUS were recruited to the ESUS-PAF group. PA lateral, PA septum, and PA tricuspid were higher in the ESUS + PAF group (p < 0.001 for all). Serum galectin-3 levels were significantly higher in ESUS + PAF than in ESUS-PAF and control groups (479.0 pg/mL ± 435.8 pg/mL, 297.8 pg/mL ± 280.3 pg/mL, and 125.4 ± 87.0 pg/mL, p < 0.001, respectively). Serum galectin-3 levels were significantly correlated with LAVI, PA lateral, and global peak LA strain (r = 0.246, p = 0.001, p = 0.158, p = 0.035, r = -0.176, p = 0.018, respectively). Conclusion: Serum galectin-3 levels is found higher in ESUS patients which developed PAF and Serum galectin-3 levels are associated LA adverse remodeling in patients with ESUS.

In vivo measurement of strain in the periodontal space of pig (Sus scrofa) incisors using in-fiber Bragg sensors.

The incisor teeth in pigs, Sus scrofa, function in association with a disc-shaped snout to explore the environment for potential food. Understanding how mechanical loading applied to the tooth deforms the periodontal ligament (PDL) is important to determining the role of periodontal mechanoreceptors during food exploration and feeding. The objective of this study was to use fiber Bragg (FBG) sensors to measure strain in vivo within the PDL space of pig incisors. The central mandibular incisors of pigs underwent spring loaded lingual tipping during FBG strain recording within the labial periodontal space. FBG sensors were placed within the periodontal space of the central mandibular incisors of ~2-3-month-old farm pigs. The magnitude and orientation of spring loads are expected to mimic incisor contact with food. During incisor tipping with load calibrated springs, FBG strains in vitro (N = 6) and in vivo (N = 6) recorded at comparable load levels overlapped in range (-10-20 με). Linear regressions between peak FBG strains, that is, the highest recorded strain value, and baseline strains, that is, strain without applied spring load, were significant across all in vivo experiments (peak strain at 200 g vs. baseline, p = .04; peak strain at 2000 g vs. baseline p = .03; peak strain at 2000 g vs. 200 g, p = .004). These linear relationships indicate that on a per experiment basis, the maximum measured strain at different spring loads showed predictable differences. A Friedman test of the absolute value of peak strain confirmed the significant increase in strain between baseline, 200 g, and 2000 g spring activation (p = .02). Mainly compressive strains were recorded in the labial PDL space and increases in spring load applied in vivo generated increases in FBG strain measurements. These results demonstrate the capacity for FBG sensors to be used in vivo to assess transmission of occlusal loads through the periodontium. PDL strain is associated with mechanoreceptor stimulation and is expected to affect the functional morphology of the incisors. The overall low levels of strain observed may correspond with the robust functional morphology of pig incisors and the tendency for pigs to encounter diverse foods and substrates during food exploration.

Predictive value of left ventricular global longitudinal peak strain for the prognosis of septic patients

To investigate the predictive value of left ventricular global longitudinal peak strain (GLPS) for the prognosis of septic patients. A prospective cohort study was conducted. Patients diagnosed with sepsis and admitted to the intensive care unit (ICU) of the First Affiliated Hospital, Sun Yat-sen University from December 2018 to November 2019 were enrolled. The patient characteristics, cardiac ultrasound parameters [left ventricular ejection fraction (LVEF), right ventricular ejection fraction (RVEF), four-dimensional ejection fraction (4DEF), GLPS] and cardiac biomarkers [N-terminal pro-brain natriuretic peptide (NT-proBNP), cardiac troponin T (cTnT)] within 24 hours of ICU admission, organ support therapies, severity of illness, and prognostic indicators were documented. The differences in clinical parameters between patients with varying outcomes during ICU hospitalization were assessed. Pearson correlation analysis was employed to explore the correlation between GLPS and other cardiac systolic parameters, as well as the associations between various cardiac systolic parameters and sequential organ failure assessment (SOFA) score. Receiver operator characteristic curve (ROC curve) was drawn to analyze the predictive capacity of cardiac ultrasound parameters and cardiac biomarkers for death during ICU hospitalization in septic patients. A total of 50 septic patients were enrolled, with 40 surviving and 10 dying during ICU hospitalization, resulting in a mortality of 20.0%. All patients in the death group were male. Compared with the survival group, the patients in the death group were older, had a higher prevalence of diabetes mellitus, and received continuous renal replacement therapy (CRRT) more frequently, additionally, they exhibited more severe illness and had longer length of ICU stay. The levels of GLPS and cTnT in the death group were significantly elevated as compared with the survival group [GLPS: -7.1% (-8.5%, -7.0%) vs. -12.1% (-15.5%, -10.4%), cTnT (μg/L): 0.07 (0.05, 0.08) vs. 0.03 (0.02, 0.13), both P < 0.05]. However, no statistically significant difference was found in other cardiac ultrasound parameters or cardiac biomarkers between the two groups. Pearson correlation analysis revealed a negative correlation between GLPS and LVEF (r = -0.377, P = 0.014) and 4DEF (r = -0.697, P = 0.000), while no correlation was found with RVEF (r = -0.451, P = 0.069). GLPS demonstrated a positive correlation with SOFA score (r = 0.306, P = 0.033), while LVEF (r = 0.112, P = 0.481), RVEF (r = -0.134, P = 0.595), and 4DEF (r = -0.251, P = 0.259) showed no significant correlation with SOFA score. ROC curve analysis indicated that the area under the ROC curve (AUC) of GLPS for predicting death during ICU hospitalization in septic patients was higher than other cardiac systolic parameters, including LVEF, RVEF, and 4DEF, as well as cardiac biomarkers NT-proBNP and cTnT (0.737 vs. 0.628, 0.556, 0.659, 0.580 and 0.724). With an optimal cut-off value of -14.9% for GLPS, the sensitivity and negative predictive value reached to 100%. GLPS < -14.9% within 24 hours of ICU admission in septic patients indicated a reduced risk of death risk during ICU hospitalization, while also correlating with the severity of organ dysfunction in this patient population.

Evaluation of Left Ventricular Function in Patients With Severe Aortic Stenosis Utilizing Automated Cardiac Motion Quantitation Techniques

ObjectiveThe objective of this study is to explore the patterns of alteration in left ventricular systolic function among patients with severe aortic stenosis (SAS) through the application of automatic myocardial motion quantification (aCMQ) techniques. Furthermore, we seek to ascertain dependable quantitative markers for the assessment of impaired left ventricular function in patients with SAS and an ejection fraction (EF) ≥ 60%. MethodsSeventy patients who underwent echocardiography and received a diagnosis of severe aortic stenosis (SAS) in the hospital from November 2021 to August 2022 were selected for the SAS group and categorized into three subgroups based on ejection fraction (EF)—SAS group with EF ≥ 60%, SAS group with EF ranging from 50% to 59%, and SAS group with EF < 50%. Concurrently, 30 healthy individuals were recruited at the hospital during the same timeframe to serve as the control group. Participants from both groups underwent standard transthoracic echocardiography to assess conventional echocardiographic parameters. Dynamic images were examined using automatic myocardial motion quantification (aCMQ) software to derive longitudinal peak strain (LPS) parameters, which were then subjected to statistical analysis. ResultsIn comparison to the control group participants, the measurements of ascending aorta diameter (AoD), left atrium diameter (LAD), interventricular septal end diastolic thickness (IVSd), left ventricular posterior wall end diastolic thickness (LVPWd), peak systolic velocity (Vmax), and mean pressure gradient (MPG) were significantly higher in the SAS groups (p < 0.05). When compared to participants in the SAS group with an EF ≥ 60%, the values of IVSd, LVPWd, Vmax, and MPG in the SAS group with EF ranging from 50% to 59% were significantly elevated (p < 0.05). Similarly, left ventricular end-diastolic diameter (LVEDD), the ratio of early diastolic mitral inflow velocity to early diastolic mitral annular velocity (E/e'), and the ratio of early to late diastolic mitral inflow velocities (E/A) in the SAS group with EF < 50% were significantly elevated (p < 0.05). The absolute values of longitudinal peak strain (LPS) in the SAS groups were significantly lower in comparison to those in the control group (p < 0.05). Furthermore, all measurements of left ventricular global longitudinal systolic peak strain (GLPS) showed a positive correlation with MPG, a moderate negative correlation with aortic valve area index (AVAI), and a moderate positive correlation with E/A. ConclusionsPatients with SAS and an EF < 50% exhibited the most profound impairment in left ventricular myocardial function. Utilizing the aCMQ technique enables the precise and quantitative evaluation of the severity of impaired left ventricular systolic function in patients within the SAS group with an EF ≥ 60%.

Investigation of Head Kinematics and Brain Strain Response During Soccer Heading Using a Custom-Fit Instrumented Mouthguard

Association football, also known as soccer in some regions, is unique in encouraging its participants to intentionally use their head to gain a competitive advantage, including scoring a goal. Repetitive head impacts are now being increasingly linked to an inflated risk of developing long-term neurodegenerative disease. This study investigated the effect of heading passes from different distances, using head acceleration data and finite element modelling to estimate brain injury risk. Seven university-level participants wore a custom-fitted instrumented mouthguard to capture linear and angular acceleration-time data. They performed 10 headers within a laboratory environment, from a combination of short, medium, and long passes. Kinematic data was then used to calculate peak linear acceleration, peak angular velocity, and peak angular acceleration as well as two brain injury metrics: head injury criterion and rotational injury criterion. Six degrees of freedom acceleration-time data were also inputted into a widely accepted finite element brain model to estimate strain-response using mean peak strain and cumulative strain damage measure values. Five headers were considered to have a 25% concussion risk. Mean peak linear acceleration equalled 26 ± 7.9 g, mean peak angular velocity 7.20 ± 2.18 rad/s, mean peak angular acceleration 1730 ± 611 rad/s2, and 95th percentile mean peak strain 0.0962 ± 0.252. Some of these data were similar to brain injury metrics reported from American football, which supports the need for further investigation into soccer heading.

Two-dimensional Speckle Tracking Imaging in Cardiotoxicity Caused by Treatment of Breast Carcinoma with Anthracyclines.

Objective: This research was conducted to investigate the monitoring values of routine echocardiography (ECG) and two-dimensional speckle tracking imaging (2D-STI) in cardiotoxicity caused by the treatment of breast carcinoma with anthracyclines (ANTH). Methods: 100 patients with breast carcinoma were selected and enrolled into normal group (n=53 cases) and abnormal group (47 cases) according to whether ECG was abnormal. Routine ECG and 2D-STI were employed for the detection, ECG- and 2D-STI-related parameters were compared, receiver operating characteristic (ROC) curves were drawn, and the clinical application values of monitoring methods for two groups were assessed. Results: Before chemotherapy, no remarkable statistical difference was detected in routine ECG and 2D-STI parameters between normal and abnormal groups (P>0.05). After 6 cycles, E/V value of abnormal group was inferior to that of normal group ((0.93±0.16) vs (1.33±0.23). Besides, longitudinal peak strain (SRI) values of rear wall, front spacer, and rear spacer in abnormal group were inferior to those in normal group (P<0.05). Routine ECG combined with 2D-STI had the best predictive effect followed by 2D-STI and routine ECG. Conclusion: To sum up, 2D-STI was a new method for assessing myocardial lesions and possessed significant early clinical monitoring values in cardiotoxicity caused by chemotherapy after the treatment of breast carcinoma with ANTH. It had higher clinical application values than routine ECG.

Whipping motion of airplane composite fan blades due to bird strike

Composite fan blades made of CFRP have been developed and investigated to reduce the weight of aircraft engines. Aircraft fan blades are subjected to high-speed impact by foreign objects, such as bird strikes. Because CFRP has lower impact resistance than metal materials, it is necessary to focus on possible failure not only at the impact point but also at the tip and trailing edge of the fan blade. This paper developed a finite element analysis model of fan blade geometry and investigated the dynamic deformation that may induce peripheral fracture when a bird strike occurs on a composite fan blade. Natural vibration analysis and transient response analysis were performed to analyze the vibration behavior at the fan blade periphery. The natural vibration analysis showed that the vibration modes in the out-of-plane direction of the blade are of low order. In the transient response analysis, when a group of particles defined by the equation of state and the SPH method collided, a sudden deformation in the periphery, called a whipping motion, was observed immediately after the impact. The spanwise strain has a peak value at the trailing edge of the fan blade, while the chordwise strain has a peak value at the leading edge of the fan blade. Furthermore, the transient response analysis with the fan blades rotating showed an increase in the peak strain value. A comparison of the impact loads and displacements immediately below the impact indicated that the centrifugal force increased the geometric stiffness, which increased the reaction force due to the fan blade, increasing the peak value.

Reduced right ventricular outflow tract strain at cardiac magnetic resonance correlates with low-voltage areas at unipolar electroanatomic mapping in patients with brugada syndrome

Abstract Background Brugada Syndrome (BrS) was initially described as a channelopathy without underlying structural substrate, but pathological and electroanatomic abnormalities of the right ventricular outflow tract (RVOT), are increasingly recognized, suggesting a possible role of electroanatomic mapping (EAM) in risk stratification of these patients. New echocardiographic and cardiac magnetic resonance (CMR) tools are able to identify subtle structural and functional myocardial abnormalities associated with an increased arrhythmic risk. Purpose We aimed to assess the presence of structural and functional abnormalities of RVOT by CMR-derived RV and RVOT feature tracking in BrS patients. We also sought to evaluate the relationship between RVOT functional abnormalities and the presence and extension of RVOT abnormal voltage areas at EAM. Methods we retrospectively enrolled BrS patients submitted to CMR comprehensive of RVOT sequences and bipolar and unipolar endocardial EAM. Abnormal voltage areas were defined by the presence of signal amplitude &amp;lt;4mV at unipolar mapping and signal amplitude &amp;lt;1.5mV at bipolar mapping. We included a control group of 15 healthy volunteers submitted to CMR including RVOT sequences. Results We studied 16 patients, 12/16 males, mean age 42±9 years. In all cases CMR showed normal left and right ventricular ejection fraction (LVEF 57±4%, RVEF 56±6%). RVOT peak strain values were significantly impaired in BrS patients compared to controls (-17.9±8.6% vs -26.4±9.5%, p=0.011), while RV-GLS did not differ between the two groups (-22.2±4.0% vs 24.6±2.5%, p=0.061). EAM showed the presence of pathological voltages at both unipolar and bipolar mapping in 12 patients, abnormal unipolar and normal bipolar maps in 1 case and both unipolar and bipolar normal maps in 3 patients. Median extent of abnormal voltage areas was 5.3 cm2 [IQ 1-4 = 0.6-9.3 cm2] at unipolar and 4.1 cm2 [IQ 1-4 = 0.7-7.5 cm2] at bipolar map. RVOT peak strain showed a significant correlation with abnormal voltage areas at unipolar EAM (r=0.546, r2=0.525, p=0.029). Patients with both unipolar and bipolar normal maps (n=3) had normal RVOT strain values compared to controls (-25.7±3.9 vs -26.4±9.5%, p=0.90). Conclusions In patients with BrS, RVOT peak strain is significantly reduced compared to controls and is associated with abnormal voltage areas at endocardial unipolar EAM. Noninvasive evaluation of BrS patients with CMR-derived RVOT feature tracking may help to identify patients requiring invasive evaluation with EAM. Prospective studies evaluating the prognostic role of RVOT strain and EAM in BrS patients are needed.

Right and left ventricular cardiac magnetic resonance imaging derived peak systolic strain is abnormal in children with myocarditis.

Cardiac Magnetic resonance (CMR) derived left ventricular longitudinal and circumferential strain is known to be abnormal in myocarditis. CMR strain is a useful additional tool that can identify subclinical myocardial involvement and may help with longitudinal follow-up. Right ventricular strain derived by CMR in children has not been studied. We sought to evaluate CMR derived biventricular strain in children with acute myocarditis. Children with acute myocarditis who underwent CMR between2016-2022 at our center were reviewed, this group included subjects with COVID-19 myocarditis. Children with no evidence of myocarditis served as controls Those with congenital heart disease and technically limited images for CMR strain analysis were excluded from final analysis. Biventricular longitudinal, circumferential, and radial peak systolic strains were derived using circle cvi42®. Data between cases and controls were compared using an independent sample t-test. One-way ANOVA with post hoc analysis was used to compare COVID-19, non-COVID myocarditis and controls. 38 myocarditis and 14 controls met inclusion criteria (mean age14.4 ± 3 years). All CMR derived peak strain values except for RV longitudinal strain were abnormal in myocarditis group. One-way ANOVA revealed that there was a statistically significant difference with abnormal RV and LV strain in COVID-19 myocarditis when compared to non-COVID-19 myocarditis and controls. CMR derived right and left ventricular peak systolic strain using traditionally acquired cine images were abnormal in children with acute myocarditis. All strain measurements were significantly abnormal in children with COVID-19 even when compared to non-COVID myocarditis.

Directional rock blasting using shaped charges using combined charge liners with different shapes

AbstractThe shape of a charge liner used in shaped charges with a combined liner will greatly influence the blasting effect. In this study, we examined how combined charge liners with different shapes affected directional rock blasting, and we assessed the influence mechanism. The numerical simulation results showed that among the three shaped charge liners, liners with arc and triangular shapes performed significantly better than the flat‐top liner, and the triangular liner was slightly superior to the arc‐shaped liner. Model testing indicated that principal cracks in the arc‐shaped and triangular liners developed along the combined energy‐gathering direction, while the principal cracks of the flat‐top liner deviated 32° from the axis. Therefore, the directional cracking effect of arc‐shaped and triangular liners was superior to the flat‐top liner. According to the peak strain values on the liners, the peak strain in the combined energy‐gathering direction was greater than that in the slot and nonenergy‐gathering directions, and the order of the peak strain of the three liners followed arc‐shaped liner &gt; triangular liner &gt; flat‐top liner. The directional blasting effect of the triangular liner was slightly better than the arc‐shaped liner. In conclusion, the findings of this study suggested that the best directional rock‐blasting effect was achieved when the shape of the combined charge liner was triangular.

Dynamic response and progressive damage modes of fault-crossing tunnels simulated using similar materials

Tunnels are widely constructed because they can effectively withstand seismic loads and avoid tunnel collapse in high-intensity seismic zones. However, in the case of fault-crossing tunnel, the fault crossing tunnel will be seriously damaged in seismic activities because the tunnel lining follows the deformation of surrounding rock. Therefore, the researches of the dynamic response and failure modes of fault-crossing tunnel are highly significant. In this study, quartz sand, cement and detergent were used to simulate similar materials of surrounding rock. A gypsum-based materials have been selected as similar materials for tunnels. The shaking table model tests were conducted on fault-crossing tunnel and conventional tunnel based on the Xianglushan Tunnel. The dynamic response characteristics of the fault-crossing tunnel were analyzed, and draw the conclusions: The acceleration amplification coefficients of the two sets of tests exceeded 1. The acceleration dynamic response of the fault-crossing tunnel was greater than the conventional tunnel, and the acceleration dynamic response at the fault was greater than the monitoring surface on both sides, rendering the acceleration dynamic response at the fault abrupt. Compared to other cross sections, tunnel lining structures at faults had the strongest dynamic response. The maximum peak strain value of the fault-crossing tunnel was magnified 4.4 times, and the bending moment value was magnified 2.3 times, relative to those of the conventional tunnel. The fault markedly increased the strain peak and bending moment values, causing cracks and damage even at a small peak acceleration value, weakening the seismic capacity of the tunnel. The lining at the fault was dominated by longitudinal cracks, and dislocation occurred. The degree of destruction and development of tunnel at faults was greater than that of other cross sections. The research results and conclusions could provide a reference to prevent the destruction of fault-crossing tunnel in an earthquake.

A Morphologically Individualized Deep Learning Brain Injury Model.

The brain injury modeling community has recommended improving model subject specificity and simulation efficiency. Here, we extend an instantaneous (< 1 sec) convolutional neural network (CNN) brain model based on the anisotropic Worcester Head Injury Model (WHIM) V1.0 to account for strain differences due to individual morphological variations. Linear scaling factors relative to the generic WHIM along the three anatomical axes are used as additional CNN inputs. To generate training samples, the WHIM is randomly scaled to pair with augmented head impacts randomly generated from real-world data for simulation. An estimation of voxelized peak maximum principal strain of the whole-brain is said to be successful when the linear regression slope and Pearson's correlation coefficient relative to directly simulated do not deviate from 1.0 (when identical) by more than 0.1. Despite a modest training dataset (N = 1363 vs. ∼5.7 k previously), the individualized CNN achieves a success rate of 86.2% in cross-validation for scaled model responses, and 92.1% for independent generic model testing for impacts considered as complete capture of kinematic events. Using 11 scaled subject-specific models (with scaling factors determined from pre-established regression models based on head dimensions and sex and age information, and notably, without neuroimages), the morphologically individualized CNN remains accurate for impacts that also yield successful estimations for the generic WHIM. The individualized CNN instantly estimates subject-specific and spatially detailed peak strains of the entire brain and thus, supersedes others that report a scalar peak strain value incapable of informing the location of occurrence. This tool could be especially useful for youths and females due to their anticipated greater morphological differences relative to the generic model, even without the need for individual neuroimages. It has potential for a wide range of applications for injury mitigation purposes and the design of head protective gears. The voxelized strains also allow for convenient data sharing and promote collaboration among research groups.

Experimental Analysis of the Mechanical Response of Masonry Columns Partially Confined with PBO FRCM (Fabric Reinforced Cementitious Mortar) Composites.

An experimental investigation on partially PBO (short of Polyparaphenylenebenzobisthiazole) FRCM (Fiber Reinforced Cementitious Mortar) confined clay brick masonry columns has been conducted. Ten small-scale specimens measuring 445 mm high with a square cross-section of the 250 mm side have been tested under monotonic axial loading until collapse. Two columns were unconfined, while the remaining ones were confined with single-layer PBO FRCM jackets varying the geometric configuration along their height. The vertical spacing ratio sf'/sf, being sf' and sf the center-to-center and the net spacings between two consecutive jackets, respectively, was considered as the key parameter of the confinement configuration. The failure modes, stress-strain curves and peak axial stress and strain values are reported. The experimental results have been compared to the predictions of models found in the Italian guidelines CNR DT 215/2018 and the American ACI 549-R20 standards. The main aspects analyzed involved (i) the evaluation of the effectiveness of partial confinement on the mechanical response of columns, (ii) the definition of the mechanical and geometrical parameters that influence the structural response of partially confined columns, and (iii) the development of appropriate analytical models for the prediction of the resisting capacity of masonry columns partially confined with PBO FRCM.

The novel left atrial appendage strain parameters are associated with thrombosis risk in patients with non-valvular atrial fibrillation.

We sought to explore a novel left atrial appendage (LAA) strain parameter which could represent the cumulative adverse impact of chronic Atrial fibrillation (AF) on the LAA function, and the relationship between the LAA strain parameter and thrombosis risk in patients with non-valvular AF. We enrolled 268 patients with non-valvular AF and 58 sinus rhythm subjects who underwent transesophageal echocardiography in the study. LAA longitudinal strain amplitude (LAA LSA) was defined as the sum of the value of the maximum positive peak strain (LAA PLS) and the absolute value of the minimum negative peak strain (LAA NLS). Dense spontaneous echo contrast (SEC) was defined as grade 3 or 4 SEC. Compared to sinus rhythm group, the global LAA strain parameters were significantly lower in paroxysmal AF (n = 148), and the lowest of them were found in persistent AF (n = 120), which suggested that the global LAA strain parameters could evaluate LAA function in sinus rhythm, paroxysmal AF and persistent AF. Compared with patients in AF without SEC/thrombus (n = 113), the regional and global LAA strain parameters were significantly depressed in AF with SEC/thrombus (n = 155). Multivariate logistic regression analyses showed that LAA global LSA (OR 0.768; 95% CI:0.569, 0.970; p = 0.027) was an independent predicter of the SEC/thrombus. Compared with patients in AF without dense SEC or thrombus (n = 210), the regional and global LAA strain parameters were significantly impaired in the patients with dense SEC/thrombus(n = 58). LAA global LSA (AUC 0.884) had the best predictable accuracy for dense SEC or thrombus, and outperformed LAA PLS, LAA NLS, CHA2DS2-VASc score and conventional LAA functional parameters that have been used in the evaluation blood flow stasis in LAA. LAA LSA showed excellent interobserver and intra-observer agreement beyond LAA PLS and LAA NLS. The novel LAA strain parameters, which were feasible and reproducible parameters for evaluation LAA mechanic function, had good predictive accuracy for blood flow stasis in LAA beyond conventional LAA functional parameters.

Nano filler incorporated epoxy based natural hybrid fiber confinement of concrete systems: Effect of fiber layers and nano filler addition

The utilization of environment friendly materials in the construction industry is essential for sustainable development. For the purpose of strengthening and retrofitting concrete structures, fiber reinforced polymer (FRP) composites have been predominantly used. In the area of structural strengthening, as an alternative to synthetic fiber reinforced composites, the application of natural fiber reinforced composites is of immense interest. This study discusses the mechanical properties of externally strengthened concrete cylinders using a natural hybrid fiber system with two layers of sisal fiber sheets followed by 1 to 3 layers of basalt fiber sheets. In addition, the effect of multi walled carbon nanotubes (MWCNT) incorporation in the epoxy matrix from 0.5 to 1.5 wt%, on the various properties are analyzed. The inclusion of MWCNT in the epoxy matrix improved the overall performance of the FRP significantly. The results show that there is substantial improvement in mechanical properties up to 1 wt% MWCNT content in composites, beyond which it is reduced due to agglomeration of nanofiller. The MWCNT incorporated epoxy based five layered hybrid sisal basalt FRP confined specimens showed an improvement of 114% and 427% in peak strength and strain values under axial compressive strength tests. Moreover, the axial compressive behavior, stress–strain response, energy absorption and ductility characteristics of the confined column specimens were evaluated. The major focus of the study is to assess the influence of basalt FRP layers on the ultimate load carrying capacity and performance of hybrid sisal basalt FRP (HSBFRP) confined specimens. Statistical analysis of variance (ANOVA) was carried out and revealed that the number of FRP layers and addition of MWCNT in epoxy significantly affect the overall performance. The addition of basalt fiber layers in hybrid sisal basalt FRP systems is found to improve the load carrying capacity and energy absorption characteristics of confined specimens. Therefore, HSBFRP confinement can be used in areas where moderate strength and greater ductility is commanded.

Effect of Stress Levels and Temperatures on Creep Compliance of Asphalt Binders

Abstract: Mostly, the laboratories in Pakistan use DSR (Dynamic Shear Rheometer) Test AASHTO T 315 for quality control purposes but it was designed for unmodified asphalt binders, and it gives inadequate results of modified binders. On the other hand, AASHTO T 350 called as multiple stress creep recovery (MSCR) test gives better result for modified binders. MSCR grades of mostly modified binders with additives, nano composites, viscous fluids is determined in this research paper. The effect of these modified as well as unmodified binders on the Creep Compliance factor is also evaluated. To characterize Creep Compliance factor along with Stress Sensitivity and Traffic Loading this test is now used. For evaluating the Stress Sensitivity of modified binders there is development of new factor called as JNR Slope instead of JNR Difference. Jnr Slope gives vast representation of asphalt binders and there is no congestion left between them. The binders which fail in JNR Difference might get satisfactory results from JNR Slope Which gives better results than the conventional way of testing. For determining the rutting behavior of modified as well as unmodified asphalt binders there is usage of peak strain factor at stress level of 100 Pascal, and 3200Pascal relatively. The values of JNR at the stress levels 25 Pascal to 25600 Pascal gives almost linear variation between modified as well as unmodified binders. This research paper is developed to determine Peak strain values, Creep Compliance factors, Stress Sensitivity Factors, And MSCR grading according to the Traffic Loading.