This paper deals with the development of a cyclic plasticity model suitable for predicting the strain range dependent behavior of austenitic steels. The proposed cyclic plasticity model uses the virtual back-stress variable corresponding to a cyclically stable material under strain control. This new internal variable is defined by means of a memory surface introduced in the stress space. The linear isotropic hardening rule is also superposed. First, the proposed model was validated on experimental data published for the SS304 material (Kang et al. Constitutive modeling of strain range dependent cyclic hardening. Int J Plast 19 (2003) 1801–1819). Subsequently, the proposed cyclic plasticity model was applied to own experimental data from uniaxial tests realized on 08Ch18N10T at room temperature. The new cyclic plasticity model can be calibrated by the relatively simple fitting procedure that is described in the paper. A comparison between the results of a numerical simulation and the results of real experiments demonstrates the robustness of the proposed approach.

Hybrid nanofluid boundary layer flow past a stretching surface with zero mass flux boundary condition is explored in this article. The main aim of this article is to analyze the electromagnetohydrodynamic role in a hybrid nanofluid containing silver and molybdenum disulfide nanoparticles. The self-similar solution is

Introduction: Pneumothorax (PTX) and/or pneumomediastinum (PMD) are rare complications of Coronavirus Disease-2019 (COVID-19) and are linked to high mortality. Incidence rates vary between 0.56-2.01% in the reported literature. With clinical examination being hampered in the current pandemic setting, there is a delay in the diagnosis. There is a need to identify and establish potential predictive factors, that may aid in identifying patients with a high-risk of developing PTX and/or PMD. Aim: To identify potential risk factors and thus, explore their association with PTX and/or PMD among patients with COVID-19. Materials and Methods: A retrospective case-control study was conducted at MS Ramaiah Medical College and Hospital, Bangalore, South India over a six-month period. A total of 130 patients diagnosed with COVID-19 were recruited in a 1:3 ratio as cases and controls respectively. Cases were patients, diagnosed radiologically with PTX and/or PMD, and controls were, matched individuals without PTX and/or PMD. Patient’s clinical and laboratory parameters (complete blood count, renal and liver function tests, serum levels of inflammatory markers such as C-reactive protein (CRP), lactate dehydrogenase (LDH), and D-Dimer were tested for potential association with PTX and/or PMD. Student’s t-test, Chi-square test, multivariate and univariate logistic regression analysis were performed. Results: During the study period, there was a total of 3,251 COVID-19 admissions at the centre with 976 patients requiring Intensive Care Unit (ICU) admission. The overall incidence of PTX and/or PMD during the study period was (31/3251) 0.95%. The previous history of COVID-19, non vaccination with COVID-19 vaccine, cough as a predominant symptom, high values of baseline CRP, total bilirubin, Aspartate Transaminase (AST), and total leukocyte counts had a positive association. In-hospital mortality (54.8% vs 33.30%) and mortality 28 days (35.7% vs 7.6%) following discharge, were higher among those with PTX and/or PMD. Conclusion: Patients with a history of previous infection with COVID-19, non vaccination /incomplete-vaccination with COVID-19 vaccines, and patients with increasing total leukocyte counts and AST levels, high baseline total serum bilirubin were at increased risk of a detrimental clinical course and may indicate, the possibility of development of PTX and/or PMD in COVID-19 disease.

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We present a mathematical model that describes thermo-mechanical deformations and thermal gradients on the unsteady burning of a heterogeneous solid propellant. A scaling study shows that the deformations in solid at combustion timescales can be treated as quasi-static. The resulting thermo-mechanical formulation is formulated on a Cartesian grid and makes use of a weak form of Chorin-type projection method to deal with large difference in shear modulus of constituent materials. A one-dimensional verification study is carried out by comparing numerical simulations with those of an analytical model. In addition, convergence studies for a two-dimensional propellant sandwich configuration are presented for the stress, velocity, and reference map components. Finally, simulations are carried out for a two-dimensional random propellant pack and the time-averaged burn rate and strains are reported.