On the role of cubic nonlinearity in localization of longitudinal strain waves

2006 ◽  
Author(s):  
A. V. Porubov
Keyword(s):  
Longitudinal Strain ◽  
Cubic Nonlinearity ◽  
Strain Waves

Measurement of Impact Strains by a Carbon-Strip Extensometer

1940 ◽  
Vol 7 (1) ◽  
pp. A24-A28
Author(s):  
R. Fanning ◽  
W. V. Bassett
Keyword(s):  
High Speed ◽  
Longitudinal Strain ◽  
Sufficient Accuracy ◽  
Time Curve ◽  
Resistance Strain Gage ◽  
Strain Waves ◽  
Yield Information ◽  
Well Yield ◽  
Impact Problems ◽  
Actual Stress

Abstract This paper describes a method of experimentally ascertaining the actual stress-time curve in a mechanical part subjected to an impact blow. The apparatus consists of a resistance strain gage in conjunction with a high-speed recording oscillograph, the combination being sufficiently rapid in response to record strain variations occurring within a few microseconds. Consequently, the strains during impact are recorded with sufficient accuracy for detailed analysis. Longitudinal strain waves in long bars striking end to end have been subjected to theoretical analysis and have served as a subject for testing of the apparatus. The theory is reviewed in this paper, and computed results based thereon are compared with experimental data. The agreement is shown to be satisfactory, the form being as predicted and the magnitude within a few per cent of the computed value. The strain waves and reflections occurring in this simple case are surprisingly complex. An investigation of other impact problems by this method, such as the correlation of standard impact tests of materials, might well yield information of considerable value.

Supplementary role of left ventricular global longitudinal strain for predicting sudden cardiac death in hypertrophic cardiomyopathy

2021 ◽  
Author(s):  
Hyun-Jung Lee ◽  
Hyung-Kwan Kim ◽  
Sang Chol Lee ◽  
Jihoon Kim ◽  
Jun-Bean Park ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Sudden Cardiac Death ◽  
Risk Score ◽  
Primary Endpoint ◽  
Cardiac Death ◽  
Longitudinal Strain ◽  
Global Longitudinal Strain ◽  
Left Ventricular ◽  
C Statistic

Abstract Aims We investigated the prognostic role of left ventricular global longitudinal strain (LV-GLS) and its incremental value to established risk models for predicting sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM). Methods and results LV-GLS was measured with vendor-independent software at a core laboratory in a cohort of 835 patients with HCM (aged 56.3 ± 12.2 years) followed-up for a median of 6.4 years. The primary endpoint was SCD events, including appropriate defibrillator therapy, within 5 years after the initial evaluation. The secondary endpoint was a composite of SCD events, heart failure admission, heart transplantation, and all-cause mortality. Twenty (2.4%) and 85 (10.2%) patients experienced the primary and secondary endpoints, respectively. Lower absolute LV-GLS quartiles, especially those worse than the median (−15.0%), were associated with progressively higher SCD event rates (P = 0.004). LV-GLS was associated with an increased risk for the primary endpoint, independent of the LV ejection fraction, apical aneurysm, and 2014 European Society of Cardiology (ESC) risk score [adjusted hazard ratio (aHR) 1.14, 95% confidence interval (CI) 1.02–1.28] or 2011 American College of Cardiology/American Heart Association (ACC/AHA) risk factors (aHR 1.18, 95% CI 1.05–1.32). LV-GLS was also associated with a higher risk for the composite secondary endpoint (aHR 1.06, 95% CI 1.01–1.12). The addition of LV-GLS enhanced the performance of the ESC risk score (C-statistic 0.756 vs. 0.842, P = 0.007) and the 2011 ACC/AHA risk factor strategy (C-statistic 0.743 vs. 0.814, P = 0.007) for predicting SCD. Conclusion LV-GLS is an important prognosticator in patients with HCM and provides additional information to established risk stratification strategies for predicting SCD.

Waterhammer in Non-Rigid Pipes: Precursor Waves and Mechanical Damping

1977 ◽  
Vol 19 (6) ◽  
pp. 237-242 ◽  
Author(s):  
D. J. Williams
Keyword(s):  
Elastic Strain ◽  
Longitudinal Strain ◽  
Viscous Damping ◽  
Flexural Waves ◽  
Strain Waves ◽  
Fluid Theory ◽  
Mechanical Damping ◽  
Theory And Experiment

When a pipe can move, waterhammer effects are altered by the existence of precursor waves, i.e. longitudinal elastic strain waves in the pipe walls, modified by the presence of the fluid. Theory and experiment show that precursor waves cannot be ignored, if the effect of longitudinal strain is to be considered; conventional waterhammer theory is thus unsatisfactory. Flexural waves may also occur. It was found experimentally that pipe motion caused mechanical damping of the waterhammer–greater than the viscous damping. Viscoelastic piping also gave rise to strong mechanical damping, even without pipe motion.

Role of anomalous self-steepening in controlling self-accelerating Airy pulses in nonlinear metamaterials

2016 ◽  
Vol 25 (01) ◽  
pp. 1650010 ◽  
Author(s):  
Jinggui Zhang ◽  
Yuanjiang Xiang ◽  
Yongfan Li ◽  
Dajun Lei ◽  
Lifu Zhang
Keyword(s):  
Pulse Propagation ◽  
Dynamical Behavior ◽  
The Self ◽  
Cubic Nonlinearity ◽  
Great Flexibility ◽  
Ultrashort Pulse Propagation ◽  
Nonlinear Metamaterials ◽  
Opposite Situation ◽  
Positive Index

The additional dispersive magnetic permeability in metamaterials (MMs) described by the Drude model is able to generate the anomalous self-steepening (SS) effect which can be positive, negative even zero. This provides more great flexibility for us to control ultrashort pulse propagation, when compared with the corresponding case in naturally positive-index materials (PIMs). In this paper, we theoretically investigate the self-accelerating control of Airy pulse through such anomalous SS effect in MMs with a cubic nonlinearity. The emphasis is given to the counterintuitive dynamical behavior different from those in PIMs. It is shown that positive SS in MMs acts to promote the self-acceleration of such pulse and the corresponding spectral features exhibits a broad redshifted behaviors, as it does in PIMs; while the negative SS gives rise to the appearance of the opposite situation. That is to say, the self-acceleration of Airy pulse will be delayed through broadening the spectrum toward blue side. Meanwhile, the effect of the specific truncation coefficient imposed on Airy pulses in MMs also be discussed under the roles of positive and negative SS, respectively. Our findings show that the SS effect in MMs can provide a more powerful tool in controlling the self-accelerating of Airy pulse when compared with the corresponding case in PIMs.

scholarly journals Strain Echocardiography Is a Promising Tool for the Prognostic Assessment of Sarcoidosis

Life ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1065
Author(s):  
Paolo Cameli ◽  
Maria Concetta Pastore ◽  
Giulia Elena Mandoli ◽  
Mariangela Vigna ◽  
Giuseppe De Carli ◽  
...  
Keyword(s):  
Longitudinal Strain ◽  
Pulmonary Function Tests ◽  
Global Longitudinal Strain ◽  
Left Ventricular ◽  
Cardiac Events ◽  
Prognostic Assessment ◽  
Promising Tool ◽  
Adverse Cardiac Events

Sarcoidosis is a systemic chronic granulomatous disease with significant morbidity and mortality. Although basic transthoracic echocardiography (TTE) is not recommended for the assessment of sarcoidosis, speckle tracking echocardiography (STE) has emerged as more sensitive for the early detection of cardiac sarcoidosis and its outcome. The aim of the study was to assess the utility of left atrial and left ventricular longitudinal STE for the prediction of major adverse cardiac events (MACE) and sarcoidosis relapses. We enrolled 172 consecutive patients with sarcoidosis who underwent TTE and pulmonary function tests (PFTs). All patients were followed for a sarcoidosis relapse and MACE. During a median follow-up of 2217 days, 8 deaths, 23 MACE and 36 sarcoidosis relapses were observed. LV global longitudinal strain (GLS) was significantly lower in patients with MACE (p = 0.025). LV-GLS < 17.13% (absolute value) was identified as a fair predictor of MACE. Concerning the sarcoidosis control, TTE revealed a reduction of the LV ejection fraction (p = 0.0432), tricuspid annular plane systolic excursion (p = 0.0272) and global peak atrial longitudinal strain (PALS, p = 0.0012) in patients with relapses. PALS < 28.5% was the best predictor of a sarcoidosis relapse. Our results highlight a potential role of LV-GLS and PALS as prognostic markers in sarcoidosis, supporting the use of STE in the clinical management of these patients.

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