Multidimensional Strain Research Articles

Complex High‐Cyclic Loading in an Accumulation Model for Sand

ABSTRACTExperimental evidence indicates that multidimensional cyclic loading of soils causes larger accumulation of deformations than equivalent one‐dimensional loading. The response of sand to high‐cyclic loading with 10,000 cycles and up to four‐dimensional stress paths (i.e., four independent oscillating components) is examined in 120 triaxial and hollow cylinder tests in this work to extend these findings. With increasing number of oscillating stress components, the accumulation of permanent strains tends to increase. It is demonstrated that the definition of the multidimensional strain amplitude incorporated in the high‐cycle accumulation (HCA) model can account for this. The validation of the HCA model for complex cyclic loading is complemented by the simulation of model tests on monopile foundations of offshore wind turbines subjected to multidirectional cyclic loading, for which the consideration of spatially variable cyclic loading with nonconstant load amplitudes in the HCA model is discussed. For this purpose, an extension of the HCA model considering multiple strain amplitudes is presented.

Myocardial injury and clinical outcome in octogenarians after non-ST-elevation myocardial infarction.

The aim of this study was to analyze age-associated myocardial injury and clinical outcome after non-ST-elevation myocardial infarction (NSTEMI). This prospective, multicenter study consists of 440 patients with NSTEMI enrolled at 7 centers. All patients were treated with primary percutaneous coronary intervention and underwent cardiac magnetic resonance (CMR) imaging 1-10 days after study inclusion. CMR parameters of myocardial injury and clinical outcome were evaluated by creating 2 subgroups: <80 years vs. ≥80 years. The clinical endpoint was the 1-year incidence of major adverse cardiac events (MACE) consisting of death, re-infarction and new congestive heart failure. Elderly patients ≥80 years accounted for 13.9% of the study population and showed a divergent cardiovascular risk profile compared to the subgroup of patients <80 years. CMR imaging did not reveal significant differences regarding infarct size, microvascular obstruction, left ventricular ejection fraction or multidimensional strain analysis between the study groups. At 1-year follow-up, MACE rate was significantly increased in patients ≥80 years compared to patients aged <80 years (19.7% vs. 9.6%; p = 0.019). In a multiple stepwise logistic regression model, the number of diseased vessels, aldosterone antagonist use and left ventricular global longitudinal strain were identified as independent predictors for MACE in all patients, while there was no independent predictive value of age regarding 1-year clinical outcome. This prospective, multicenter analysis shows that structural and functional myocardial damage is similar in younger and older patients with NSTEMI. Furthermore, in this heterogeneous but also clinically representative cohort with reduced sample size, age was not independently associated with 1-year clinical outcome, despite an increased event rate in patients ≥80 years.

Magnetically induced anisotropic conductive hydrogels for multidimensional strain sensing and magnetothermal physiotherapy

Magnetically induced anisotropic conductive hydrogels for multidimensional strain sensing and magnetothermal physiotherapy

Piezo-gated flexible transistors: A path to energy-efficient multi-functional piezotronic devices

Developing smart sensors and advanced electronics for the need of the internet of things prevails yet under the constraint of energy efficiency. Therefore, the development of multi-functional devices toward low power is the research spotlight. Due to the low energy consumption, semiconductor-based piezo-gated devices hold great promises. Herein, a flexible multi-dimensional strain sensor by growing two ZnO thin film-based terminals on both sides of a mica substrate is developed. This Multidimensional Piezo-Gated Flexible Transistor (M-PGFT) device successfully detects the positive (upward) bending, negative (downward) bending, and compressive load. Where the gauge factor (GF) of the Top/Bottom terminals under positive and negative bending strains are −3.44/+9.78 and +5.44/−4.03, respectively, and +94.93/+74.70 for compressive load is obtained. Notably, the GF of both ZnO terminals is asymmetric under two bending types of loads, whereas symmetric under compressive load. This unique behavior made this smart multi-dimensional strain sensor to distinguish between different types of strains. Furthermore, the same device can be implemented as a piezo-gated three-valued logic device, demonstrating standard ternary inversion and standard ternary NAND operations. This study presents a unique and simple design to fabricate flexible multi-functional piezo-gated devices for multi-dimensional strain sensing and three-valued logic operation at low power.

Highly Aligned Cellulose/Polypyrrole Composite Nanofibers via Electrospinning and In Situ Polymerization for Anisotropic Flexible Strain Sensor.

Flexible strain sensors have recently attracted great attention due to their promising applications in human motion detection, healthcare monitoring, human-machine interfaces, and so forth. However, traditional uniaxial strain sensors can only detect strain in a single direction. Herein, an anisotropic flexible strain sensor is fabricated based on conductive and highly aligned cellulose composite nanofibers, via facile electrospinning cellulose acetate, deacetylation, and in situ polymerization of pyrrole, to detect complex multidimensional strains. Benefiting from the unique well-ordered structure of conductive composite nanofibers, the obtained strain sensor shows extraordinary anisotropic sensing performance with a sensitivity of 0.73 and 0.01 for the tensile applied perpendicular and parallel to the nanofiber alignment, respectively. The sensor also exhibits outstanding durability (2000 cycles) due to the strong hydrogen bonding between cellulose nanofibers and polypyrrole. Moreover, the flexible strain sensors exhibit promising potentials for application in motion detection, as demonstrated by the detection of various joint movements in the human body.

MuST: An interpretable multidimensional strain theory model for corporate misreporting prediction

Corporate misreporting has become a serious problem in both e-commerce and offline economies. Developing models to predict corporate misreporting involves challenges related to (1) the lack of interpretability in the past literature, (2) corporate fraud prevention, (3) the heterogeneity in both the corporate ability and complexity of regulatory requirements, and (4) the sparsity of misreporting observations. This study proposes a novel multidimensional strain theory (MuST) model to address these challenges. Inspired by strain theory, we quantify the incentive to misreport as the gap between corporate abilities and the complexity of regulatory requirements. Experiments show that our model achieves high accuracy in identifying various types of corporate misreporting indicated by comment letters from regulators. Furthermore, the interpretability and application analyses show that latent corporate abilities learned from the MuST model effectively reflect inherent corporate risks and can further be applied to the classified supervision of e-commerce companies. Our paper contributes to the emerging literature on misreporting prediction and provides a precise and interpretable prediction model for e-commerce supervision.

Laser-Patterned Hierarchical Aligned Micro-/Nanowire Network for Highly Sensitive Multidimensional Strain Sensor.

Flexible multidirectional strain sensors capable of simultaneously detecting strain amplitudes and directions have attracted tremendous interest. Herein, we propose a flexible multidirectional strain sensor based on a newly designed single-layer hierarchical aligned micro-/nanowire (HAMN) network. The HAMN network is efficiently fabricated using a one-step femtosecond laser patterning technology based on a modulated line-shaped beam. The anisotropic performance is attributed to the significantly different morphological changes caused by an inhomogeneous strain redistribution among the HAMN network. The fabricated strain sensor exhibits high sensitivity (gauge factor of 65 under 2.5% strain and 462 under larger strains), low response/recovery time (140 and 322 ms), and good stability (over 1000 cycles). Moreover, this single-layer strain sensor with high selectivity (gauge factor differences of ∼73 between orthogonal strains) is capable of distinguishing multidimensional strains and exhibits decoupled responses under low strains (<1%). Therefore, the strain sensors enable the precise monitoring of subtle movements, including radial pulses and wrist bending, and the rectification of pen-holding posture. Benefitting from these remarkable performances, the HAMN-based strain sensors show potential applications, including healthcare and complex human motion monitoring.

‘Hot cities’ and rapid growth; experiences and responses of urban planning departments

AbstractIt is presumed that rapidly growing ‘hot cities’ adapt their planning and operations to meet their evolving population's needs. These presumptions inspired the development of the following mixed‐method, convergent parallel study. Data from urban planning officials across nine rapidly growing ‘hot cities’ were collected through pre‐interview surveys and qualitative key‐informant interviews. Thematic analysis was used to identify salient issues regarding awareness and perception of rapid population growth and the resulting response from their departments. Results indicate two main themes; Multidimensional Strain and Mitigation Strategies describe city experiences with rapid population growth effects and response. Across cities, urban planners expressed similar experiences of stress on land usage, housing, transportation, programing, and service delivery. Similar response patterns included evaluation and innovation of growth management strategies, enhanced collaboration, and equity considerations. This snapshot of rapid population growth repercussions and current city mitigation strategies may have future implications for public health and urban planning administrators in practice. Results shared also indicate how population data use and sharing can support Mitigation Strategies and impact community health.

Right ventricular volume-strain loops using 3D echocardiography-derived mesh models: proof-of-concept application on patients undergoing different types of open-heart surgery.

Right ventricular (RV) function can be quantified by right heart catheterization-derived pressure-volume loops. While this technique is invasive, echocardiography-based volume-strain loops (VSLs) potentially reflect a non-invasive alternative. In this study, an approach to generate VSLs from volume and multidimensional strain data of 3D echocardiography-derived RV mesh models is evaluated with regard to feasibility and reproducibility. In a retrospective cohort study design, 3D intraoperative transesophageal echocardiograms of twenty-three patients undergoing aortic valve surgery (AVS) and eighteen patients undergoing off-pump coronary artery bypass (OPCAB) grafting were available prior to sternotomy and after sternal closure. RV meshes were generated using 3D speckle-tracking. Custom-made software quantified the meshes' volumes, global longitudinal (RV-GLS) and global circumferential strain (RV-GCS) for VSL generation. Linear regression of systolic VSLs yielded slopes, intercepts and systolic areas. Polynomial regression of two orders was used to analyze systolic-diastolic coupling at 10% increments of the RV end-diastolic volume (RVEDV). Reproducibility was analyzed by fourfold double-measurements of four datasets. VSL calculation was feasible from all included 3D datasets. RV-GLS remained unaltered, but RV-GCS worsened in AVS [abs. diff. (∆) 3.9%, P<0.01] and OPCAB patients (∆4.5%, P<0.001). While RV-GCS systolic areas were markedly reduced at the end of AVS (∆268mL%, P<0.01) and OPCAB (∆185mL%, P<0.001), RV-GCS slopes did not change. Systolic-diastolic uncoupling was not observed, but in trend, decreased diastolic RV-GCS after AVS (P=0.06) and increased diastolic RV-GCS after OPCAB (P=0.06) were observed. Intraclass correlation coefficients (0.84-0.98) and coefficients of variation (6.4-11.8%) indicated good reproducibility. RV VSL generation using 3D echocardiography-derived mesh models is feasible. Longitudinal and circumferential strain vectors yield intrinsically different VSL indices. In future investigations, VSLs of multidimensional strains could provide further insight into periprocedural changes of RV mechanics.

Anisotropic Printed Resistor with Linear Sensitivity Based on Nano–Microfiller‐Filled Polymer Composite

Abstract3D printing electronics provides great potential to build structural objects with multiple functionalities, with the assistance of shape design and the shear force on the filler orientation. In the study, nano–microanisotropic sensors with oriented fillers assure its linear sensitive properties, where the sensors are 3D‐printed based upon the carbon fiber (CF)‐ and multiwalled carbon nanotube (MCNT)‐filled polydimethylsiloxane (PDMS). The synergistic effect of CF and MCNT modifies the printability, mechanical properties, and sensitivity of printed sensors. The introduction of anticatalyst and catalyst guarantee the printable mixtures with a stable printability in a long term (&gt;15 days). Assisted by the shear flow, the fillers own the orientation ration of 78.53%, which further contribute to the linear sensing behaviors under the tensile strain of 0–20% and compressive stress of 0–20 kPa. Frequency‐domain signals and visual demonstration on the cyclic stretch test reveal that the double peak is originated from the hysteresis of the strain to applied stress. Anisotropic electromechanical behaviors of the resistors will inspire to quantitatively analyze multidimensional strains in practical applications. The fingerprint inspired resistors with multiple sensing signals further demonstrate the convenience of the printing process on the design of wearable electronics.

Study on the Relationship between Cardiomyocyte Apoptosis and Left Ventricular Function in Spontaneously Hypertensive Rats

At present, hypertension is a relatively common cardiovascular disease. It not only affects the normal operation of target organs such as the heart and kidneys, but also causes cardiovascular and cerebrovascular diseases, which can lead to death. The apoptosis of cardiomyocytes is widespread in the cardiovascular system and is closely related to vascular diseases. Therefore, the purpose of this article is to explore the relationship between changes in left ventricular function, myocardial multidimensional strain and interstitial fibrosis in spontaneously hypertensive rats (SHR) during cardiomyocyte apoptosis. Whether the research is consistent in terms of order, as the age of hypertensive rats increases, whether there is a close connection between myocardial cell apoptosis and the structure and function of the left heart. The method in this article is to use the method of experimental comparison to randomly group 60 experimental mice and observe the changes of various indicators of rats of different ages, from 12 weeks to 84 weeks. The observations include left ventricular mass index (LVMI), left ventricular ejection fraction (LVEF), left ventricular short axis shortening rate (FS), LVEDP, LV+dp/dtmax, LV-dp/dtmax. At the same time, using the TUNEL labeling method, the left ventricular myocardial tissue was sliced, and the apoptosis index of subendocardial and subepicardial myocardial cells was calculated. Then 3 groups were randomly selected from the experimental group, and Western blotting was used to quantitatively detect apoptosis-related the expression of the proteins Bcl-2, Bax, and Fas were compared between the groups. After analysis and determination, it can be found that the apoptosis index of cardiomyocytes is positively correlated with LVMI, CVF, and PVCA (r is 0.83, 0.89, 0.72, respectively, p=0.00). Corresponding conclusions are drawn from the comparison of data. As hypertensive rats grow older, the apoptotic index of cardiomyocytes will continue to increase, and when the myocardial hypertrophy is severe to heart failure, the apoptotic index of cardiomyocytes will increase significantly. This shows that the increase in cardiomyocyte apoptosis is closely related to left heart remodeling, the development of myocardial fibrosis and overall cardiac dysfunction.

Flexible and Anisotropic Strain Sensors with the Asymmetrical Cross-Conducting Network for Versatile Bio-Mechanical Signal Recognition.

Flexible strain sensors with high performance are actively and widely investigated for wearable electronic devices. However, the conventional sensors often suffer from a lack of detection of complex multidimensional strain, which severely limits their wide applications. To overcome this critical challenge, we propose a pattern design by screen printing to construct an asymmetrical cross-conductive network in the piezoresistive strain sensor, which can enhance the response to external stimuli in different directions. The unique network endows the prepared sensors with the excellent ability of instantaneous detection and accurate identification of multidimensional strains. Moreover, the sensor also demonstrates high sensitivity, fast response, an ultra-wide sensing range, and excellent stability and durability. Benefiting from the outstanding comprehensive performance of the prepared sensor, a full range of human actions (wink, smile, swallowing, and joint bending) and subtle bio-signals (pulse and breathing) are easily and accurately monitored. A wireless wearable device assembled by the sensor shows great potential applications in practical real-time physiological monitoring and intelligent mobile diagnosis for humans. This work provides an innovative and effective strategy for manufacturing flexible and multifunctional strain sensors to fully satisfy versatile applications of new-generation wearable electronic devices.

Research on a multidimensional strain energy estimation method for welding spots based on performance optimization

Research on a multidimensional strain energy estimation method for welding spots based on performance optimization

M13 Bacteriophage-Assisted Morphological Engineering of Crack-Based Sensors for Highly Sensitive and Wide Linear Range Strain Sensing.

Despite their extraordinary mechanosensitivities, most channel-like crack-based strain sensors are limited by their poor levels of stretchability and linearity. This work presents a simple yet efficient way of modulating the cracking structure of thin metal films on elastomers to facilitate the development of high-performance wearable strain sensors. A net-shaped crack structure based on a thin platinum (Pt) film can be produced by coating an elastomer surface with M13 bacteriophages (phages) and consequently engineering the surface strain upon stretching. This process produces a Pt-on-phage (PoP) strain sensor that simultaneously exhibits high levels of stretchability (24%), sensitivity (maximum gauge factor ≈ 845.6 for 20-24%), and linearity (R2 ≈ 0.988 up to 20%). In addition, the sensor performance can be further modulated by either changing the phage coating volume or adding a silver nanowire coating to the PoP sensor film. The balanced strain-sensing performance, combined with fast response times and high levels of mechanical flexibility and operational stability, enables the devices to detect a wide range of human motions in real time after being attached to various body parts. Furthermore, PoP-based strain sensors can be usefully extended to detect more complex multidimensional strains through further strain engineering on a cross-patterned PoP film.

Utilization and Appropriateness of Transthoracic Echocardiography in Response to the COVID-19 Pandemic

Utilization and Appropriateness of Transthoracic Echocardiography in Response to the COVID-19 Pandemic

Human skin-inspired integrated multidimensional sensors based on highly anisotropic structures

A novel multidimensional strain sensor mimicking human skin is developed. In-plane and pressure subsensors are integrated into a sensor with exceptional sensitivity and selectivity capable of detecting stimuli from 3D directions.

4934Biventricular global and regional strain measured by cardiovascular magnetic resonance based tissue tracking

Abstract Background CMR based tissue tracking (CMR-TT), considered as a novel modality, provides additional insight into left and right ventricular (LV/RV) mechanical function and deformation. The vendor-specific reference values of global and regional strains for volunteers without history of cardiovascular disease are necessary as an important step in clinical routine to help detect early abnormality. Purpose To determine the reference value of LV/RV multi-dimensional global and segmental strains and diagnostic specificity of global longitudinal peak strain (GLS). Biventricular global and segmental radial, circumferential and longitudinal systolic peak strains (GRS, GCS, GLS and SRS, SCS, SLS) of 150 healthy adults in three age subgroups (G20–40, G41–60 and G61–80) were derived by post-hoc imaging software in standard steady-state free precession cine images acquired at 1.5T. LV strains were calculated with three-dimensional (3D) CMR-TT in the modified AHA 16-segment model via a short-axis stack and long axis 2-, 3-, 4-chamber cine images, and RV strains were generated with 2D CMR-TT via 4-chamber cine images. Results The reference values of LV global peak strains resulted as 44.4±13.0% for GRS, −17.0±2.7% for GCS, and −15.4±2.3% for GLS, respectively. RV-GLS was measured as −24.9±5.1%. Global and segmental strains might differ between males and females. Females showed significant age-associated difference of LV global peak strains (P&lt;0.05) as the opposite of males (Figure 1). Females also presented higher magnitude of LV global peak strains than males in the eldest group G61–80 (P&lt;0.05). Unlike LV, no age-associated difference of RV-GLS was detected in both gender groups. However, females showed less negative RV-GLS than males in G20–40 and more negative RV-GLS than males older than 40 years old (P&lt;0.05). The local discrepancy of biventricular SRS, SCS and SLS was observed. It seemed that LV mid-cavity played a more essential role on LV shortening (more negative SCS and SLS) than wall thickening (smaller SRS) compared with base and apex. RV basal and mid SLS, derived from segment 1–4, was more negative than apical SLS derived from segment 5–6. The specificity of LV- and RV-GLS cut-off value (mean value+1.96*standard deviation) generated from the vendor-, age- and gender-specific reference value in evaluating heart contractile function reached 97.3% and 94.7%, respectively. Conclusions Considering the vendor-, gender- and age-associated difference of biventricular global strains, specific reference values need to be established to facilitate the wide application of strain in clinical routine. Meanwhile, segmental strains are also fundamental for detecting local abnormality of myocardial deformation.

The relationship between left ventricular myocardial strain and different stages of cardiac dysfunction in spontaneously hypertensive rats evaluated by two-dimensional strain echocardiography

Objective To investigate the relationship between multi-dimensional myocardial strain and global cardiac function in different stages of cardiac dysfunction in spontaneously hypertensive rats (SHR) by two-dimensional strain echocardiography. Methods According to cardiac function measurements, SHR of 28 to 102 weeks were divided into 3 groups: Normal group[Group A, normal left ventricular ejection fraction(LVEF) and left ventricular end-diastolic pressure(LVEDP), n=13], diastolic dysfunction group (Group B, normal LVEF but increased LVEDP, n=24), and systolic dysfunction group (Group C, decreased LVEF and increased LVEDP, n=17), with WKY rats at similar weeks of age as controls (group a, n=7; group b, n=12; and group c, n=16). Morphological parameters of left ventricular were measured by echocardiography. Using EchoPac workstation, systolic peak longitudinal strain, circumferential and radial strain were calculated at the left ventricular middle levels. Extracellular collagen content was observed histologically. Results Left atrial dimension increased in group B and larger in group C, and dilated left ventricular and thickened wall were only found in group C. Systolic peak longitudinal strain of group B was significantly lower than group A and group a(all P 0.05). Collagen content in endocardial and mid-layer myocardium increased in group B and C, and increased epicardial collagen occurred in group C. Systolic peak longitudinal strain, circumferential and radial strain were correlated positively with LVEF(r=0.65, 0.80, 0.80, all P<0.01). Conclusions In SHR, systolic peak longitudinal strain obtained by echocardiography is decreased in the period of diastolic dysfunction, while the damage of systolic peak circumferential and radial strain leads to the systolic dysfunction. Key words: Echocardiography; Spontaneously hypertensive rat; Strain; Cardiac dysfunction

New Evaluation Procedure for Multi-Dimensional Mechanical Strains and Tangent Moduli of Breast Implants: IDEAL IMPLANT® Structured Breast Implant Compared to Silicone Gel Implants.

The IDEAL IMPLANT® Structured Breast Implant is a dual lumen saline-filled implant with capsular contracture and deflation/rupture rates much lower than single-lumen silicone gel-filled implants. To better understand the implant’s mechanical properties and to provide a potential explanation for these eight-year clinical results, a novel approach to compressive load testing was employed. Multi-dimensional strains and tangent moduli, metrics describing the shape stability of the total implant, were derived from the experimental load and platen spacing data. The IDEAL IMPLANT was found to have projection, diametric, and areal strains that were generally less than silicone gel implants, and tangent moduli that were generally greater than silicone gel implants. Despite having a relatively inviscid saline fill, the IDEAL IMPLANT was found to be more shape stable compared to gel implants, which implies potentially less interaction with the capsule wall when the implant is subjected to compressive loads. Under compressive loads, the shape stability of a higher cross-link density, cohesive gel implant was unexpectedly found to be similar to or the same as a gel implant. In localized diametric compression testing, the IDEAL IMPLANT was found to have a palpability similar to a gel implant, but softer than a cohesive gel implant.

Piezoresistivity of polymer-matrix carbon fiber filament in plane stress state

In this work, the relation between 2D- and 3D-strain based piezoresistive gauge factors for carbon fiber filament in plane stress states is developed theoretically. For measuring the gauge factors, carbon fiber filaments are attached to the base specimen surface at different angles. Their resistance response to multidimensional strain field is investigated by four-point bending tests. Piezoresistive models of carbon fiber filament in plane stress states are created using the test results. In the test setup, carbon fiber filaments are placed both on the tension side and the compression side. Both the models show that the piezoresistive response of carbon fiber filament is dominated by the longitudinal strain. Based on the inequality in the sensitivities to tensile strain and compressive strain, the piezoresistive models are modified further. The modified piezoresistive models reveal the following 3D-strain based gauge factors: 1.82 for longitudinal tensile strain, 1.64 for longitudinal compressive strain, 0.10 for transverse tensile strain, and −0.25 for transverse compressive strain. The 2D-strain based gauge factors depend not only on the polarity of the longitudinal strain and transverse strain, but also on the polarity of the strain in the thickness direction. The piezoresistive models are verified experimentally.