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Extraction of a crack opening from a continuous approach using regularized damage models
Frédéric Dufour,Gilles Pijaudier-Cabot,Marta Choinska,Antonio Huerta 사단법인 한국계산역학회 2008 Computers and Concrete, An International Journal Vol.5 No.4
Crack opening governs many transfer properties that play a pivotal role in durability analyses. Instead of trying to combine continuum and discrete models in computational analyses, it would be attractive to derive from the continuum approach an estimate of crack opening, without considering the explicit description of a discontinuous displacement field in the computational model. This is the prime objective of this contribution. The derivation is based on the comparison between two continuous variables: the distribution if the effective non local strain that controls damage and an analytical distribution of the effective non local variable that derives from a strong discontinuity analysis. Close to complete failure, these distributions should be very close to each other. Their comparison provides two quantities: the displacement jump across the crack [U] and the distance between the two profiles. This distance is an error indicator defining how close the damage distribution is from that corresponding to a crack surrounded by a fracture process zone. It may subsequently serve in continuous/discrete models in order to define the threshold below which the continuum approach is close enough to the discrete one in order to switch descriptions. The estimation of the crack opening is illustrated on a one-dimensional example and the error between the profiles issued from discontinuous and FE analyses is found to be of a few percents close to complete failure.
( Miguel Angel Zavala Gonzales ),( Amyra Ali Azamar Jacome ),( Arturo Meixueiro Daza ),( Antonio Ramos De La Medina ),( Job Reyes Huerta J ),( Federico Roesch Dietlen ),( Jose Maria Remes Troche ) 대한소화기기능성질환·운동학회 2014 Journal of Neurogastroenterology and Motility (JNM Vol.20 No.4
Background/Aims Different non-invasive diagnostics strategies have been used to assess patients with gastroesophageal reflux. Gastroesophageal reflux disease (GERD) questionnaire (GerdQ) is a 6-item, easy to use questionnaire that was developed primarily as a diagnostic tool for GERD in primary care. Our aim was to validate and assess diagnostic utility of GerdQ questionnaire in Mexican patients in the primary care setting. Methods The study was performed in 3 phases: (1) a questionnaire translation and comprehension study (n = 20), (2) are a reproducibility and validation study (50 patients and 50 controls) and (3) a study to assess the clinical utility in 252 subjects with GERD symptoms. Diagnostic accuracy was calculated using endoscopy and/or pH-metry as the gold standard. Results Internal consistency measured by the Cronbach``s a coefficient was 0.81 for patients and 0.90 for healthy controls, with a mixed coefficient of 0.93. Reproducibility for GerdQ was very good and its discriminating validity was 88%. Most of the patients with erosive reflux and non-erosive reflux with abnormal pH-metry had scores > 8, meanwhile most of the patients with functional heartburn and hypersensitive esophagus had < 8. Sensitivity, specificity and positive predictive value of GerdQ compared to the gold standard were 72%, 72% and 87%, respectively.Conclusions In Mexico, the GerdQ questionnaire Spanish validated version is useful for GERD diagnosis in the primary care setting. (J Neurogastroenterol Motil 2014;20:475-482)