Active Thermal Shearography and Infrared Thermography Applied to NDT of Reinforced Concrete Structure by Glued CFRP

International audienceThis research paper presents the study of thermography and shearography to evaluate CFRP reinforcement of concrete structures. The study explores the strengths and weaknesses of both non-destructive-testing (NDT) methods. It will be shown that by coupling the methods, the detection is more reliable and the defect evaluation more thorough as both the thermal and thermo mechanical properties are tested. Once the core theoretical concept regarding both methods is presented, the viability is demonstrated in the experimentation part of this study. With the experimental results confirming the feasibility of the coupling of both methods, the numerical model conceived allow to better conduct analysis that are not otherwise possible with the experimental results

Comparison between SPT and PT for defect characterization of CFRP plates glued on concrete or wood structures using optical active infrared thermography

International audienceThe objectives of the study summarized hereafter are to compare square pulse and pulsed thermography fordefect detection and characterization of CFRP plates used as structural reinforcement in Civil Engineering applications.Image processing and an inverse method coupled with thermal quadrupoles model are also studied

Square Heating Applied to Shearography and Active Infrared Thermography Measurements Coupling: From Feasibility Test in Laboratory to Numerical Study of Pultruded CFRP Plates Glued on Concrete Specimen

International audienceThis paper investigates thermography and shearography couplings, using feasibility trials and numerical simulations, for non-destructive control evaluations of bonding of carbon fiber-reinforced polymer plates glued over concrete structures. Those are well-known methods in non-destructive testing (NDT) applied to civil engineering, but in this context, they are seen as paired because they use the same excitation source: square-pulsed optical heating. Furthermore, because both methods are based on different properties, the detection of defects is optimised regardless of its nature or type. The combination of the methods allows the measurement of a thermal as well as a thermomechanical response from the structure at the same time. A quick review of those methods and their respective advantage and inconvenient is mentioned. An in-depth study of the interpretation of the thermal and mechanical responses is carried out in relation to the thermal excitation. Then, the thought process behind the conception of the finite element model and its limitation is discussed. The experimental setup, used for feasibility testing, is described as well as a thorough analysis of the experimental and simulated results. Finally, the pairing of both methods is discussed regarding the evaluation of the bond quality, as well as the similitude of the sample and its numerical model

Square pulse heating infrared thermography and shearography applied simultaneously on CFRP tissue bonded to reinforced concrete

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Non Destructive Testing by active infrared thermography coupled with shearography under same optical heat excitation

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Coronary angiographic significance of left anterior fascicular block during acute myocardial infarction

The clinical and angiographic significance of isolated left anterior fascicular block occurring during the early stage of acute myocardial infarction was studied in 141 consecutive patients who underwent cardiac catheterization before hospital discharge. Left anterior fascicular block occurred in 15 of the 62 patients with an anterior wall infarction and in 13 of the 79 with an inferior infarction. None of the clinical characteristics differed among patients with or without left anterior fascicular block. The number of coronary vessels with significant stenosis, the Friesinger and the Gensini scores for severity of stenosis and the ejection fraction were also similar in the two groups. Patients with left anterior fascicular block had more severe narrowing of the coronary artery supplying the infarct zone (88 ± 21 versus 70 ± 35%, p < 0.001) and tended to have less developed collateral circulation (collateral score 0.7 ± 0.8 versus 1 ± 0.8, p = 0.10). A significant stenosis of the left anterior descending coronary artery was found as frequently in patients with as in those without left anterior fascicular block (64 versus 65%); 29% of the patients with inferior wall infarction and left anterior fascicular block had left anterior descending coronary artery stenosis compared with 47% of the patients without this conduction disturbance (no significant difference). When the infarction was located anteriorly, a significant stenosis of the proximal segment of the left anterior descending coronary artery was present in 47% of the patients with and in 45% of the patients without left anterior fascicular block.In this study, the occurrence of left anterior fascicular block during the course of an acute myocardial infarction was not an indication of left anterior descending coronary artery involvement or of more extensive coronary disease. Other pathophysiologic mechanisms, such as a dual blood supply to the anterior fascicle of the left bundle branch or a longitudinal dissociation of conduction in the His bundle, could be involved in the etiology of left anterior fascicular block

Comparison of clinical variables and variables derived from a limited predischarge exercise test as predictors of early and late mortality after myocardial infarction

An exercise test limited to 5 METS or 70% of agepredicted maximal heart rate was performed 1 day before hospital discharge by 225 survivors of acute myocardial infarction, all of whom were subsequently followed up for at least 5 years. The mortality rate was 11.1% during the first year, but averaged only 2.9% per year from the second to fifth year. Over the entire follow-up period, the five variables that predicted mortality by multivariate analysis were QRS score, an exercise-induced ST segment shift, previous infarction, failure to achieve target heart rate or work load and ventricular arrhythmia during the exercise test. Because mortality differed markedly before and after 1 year, Cox regression analyses were performed separately for both of these periods.The factors that were predictive of mortality during the first year were an exercise-induced ST shift (p < 0.0001, relative risk 7.8), failure to increase systolic blood pressure by 10 mm Hg or more during exercise (p = 0.0039, relative risk 4.3) and angina in hospital 48 hours or longer after admission (p = 0.0046, relative risk 3.4). None of these three variables was predictive of mortality after 1 year. Previous infarction (p = 0.0007), QRS score (p = 0.0042) and ventricular arrhythmia during the exercise test (p = 0.016) were predictive of mortality after the first year.Thus, clinical and exercise test variables are complementary predictors of mortality after myocardial infarction. An abnormal ST segment response during an early limited exercise test and angina in the hospital are common strong predictors of mortality to 1 year, but not thereafter. Late mortality correlates with markers of poor left ventricular function

Robust Principal Component Thermography for Defect Detection in Composites

Pulsed Thermography (PT) data are usually affected by noise and as such most of the research effort in the last few years has been directed towards the development of advanced signal processing methods to improve defect detection. Among the numerous techniques that havebeen proposed, principal component thermography (PCT)—based on principal component analysis (PCA)—is one of the most effective in terms of defect contrast enhancement and data compression. However, it is well-known that PCA can be significantly affected in the presence of corrupted data (e.g., noise and outliers). Robust PCA (RPCA) has been recently proposed as an alternative statistical method that handles noisy data more properly by decomposing the input data into a low-rank matrix and a sparse matrix. We propose to process PT data by RPCA instead of PCA in order to improve defect detectability. The performance of the resulting approach, Robust Principal Component Thermography (RPCT)—based on RPCA, was evaluated with respect to PCT—based on PCA, using a CFRP sample containing artificially produced defects. We compared results quantitatively based on two metrics, Contrast-to-Noise Ratio (CNR), for defect detection capabilities, and the Jaccard similarity coefficient, for defect segmentation potential. CNR results were on average 40% higher for RPCT than for PCT, and the Jaccard index was slightly higher for RPCT (0.7395) than for PCT (0.7010). In terms of computational time, however, PCT was 11.5 times faster than RPCT. Further investigations are needed to assess RPCT performance on a wider range of materials and to optimize computational time.LDCOM

The evolution of mean arterial pressure in critically ill patients on vasopressors before and during a trial comparing a specific mean arterial pressure target to usual care

Abstract Background In randomized clinical controlled trials, the choice of usual care as the comparator may be associated with better clinician uptake of the study protocol and lead to more generalizable results. However, if care processes evolve to resemble the intervention during the course of a trial, differences between the intervention group and usual care control group may narrow. We evaluated the effect on mean arterial pressure of an unblinded trial comparing a lower mean arterial pressure target to reduce vasopressor exposure, vs. a clinician-selected mean arterial pressure target, in critically ill patients at least 65 years old. Methods For this multicenter observational study using data collected both prospectively and retrospectively, patients were recruited from five of the seven trial sites. We compared the mean arterial pressure of patients receiving vasopressors, who met or would have met trial eligibility criteria, from two periods: [1] at least 1 month before the trial started, and [2] during the trial period and randomized to usual care, or not enrolled in the trial. Results We included 200 patients treated before and 229 after trial initiation. There were no differences in age (mean 74.5 vs. 75.2 years; p = 0.28), baseline Acute Physiology and Chronic Health Evaluation II score (median 26 vs. 26; p = 0.47) or history of chronic hypertension (n = 126 [63.0%] vs. n = 153 [66.8%]; p = 0.41). Mean of the mean arterial pressure was similar between the two periods (72.5 vs. 72.4 mmHg; p = 0.76). Conclusions The initiation of a trial of a prescribed lower mean arterial pressure target, compared to a usual clinician-selected target, was not associated with a change in mean arterial pressure, reflecting stability in the net effect of usual clinician practices over time. Comparing prior and concurrent control groups may alleviate concerns regarding drift in usual practices over the course of a trial or permit quantification of any change