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Optimal lay-up of hybrid composite beams, plates and shells using cellular genetic algorithm
Rajasekaran, S.,Nalinaa, K.,Greeshma, S.,Poornima, N.S.,Kumar, V. Vinoop Techno-Press 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.16 No.5
Laminated composite structures find wide range of applications in many branches of technology. They are much suited for weight sensitive structures (like aircraft) where thinner and lighter members made of advanced fiber reinforced composite materials are used. The orientations of fiber direction in layers and number of layers and the thickness of the layers as well as material of composites play a major role in determining the strength and stiffness. Thus the basic design problem is to determine the optimum stacking sequence in terms of laminate thickness, material and fiber orientation. In this paper, a new optimization technique called Cellular Automata (CA) has been combined with Genetic Algorithm (GA) to develop a different search and optimization algorithm, known as Cellular Genetic Algorithm (CGA), which considers the laminate thickness, angle of fiber orientation and the fiber material as discrete variables. This CGA has been successfully applied to obtain the optimal fiber orientation, thickness and material lay-up for multi-layered composite hybrid beams plates and shells subjected to static buckling and dynamic constraints.
Razzack Aminah Abdul,Hassan Syed Adeel,Pasya Sai Kumar Reddy,Erasani Greeshma,Kumar Sham,Rocha-Castellanos Dario Missael,Lopez-Mendez Alfonso,Razzack Sarah Abdul 대한감염학회 2021 Infection and Chemotherapy Vol.53 No.3
Background: The World Health Organization guidelines did not make a recommendation on use of remdesivir based on disease severity. Little is known regarding effectiveness of remdesivir in critically ill coronavirus disease 2019 (COVID-19) patients. This has led to a state of dilemma for doctors leaving them skeptical of whether they should continue to recommend the drug or not. Materials and Methods: A systematic search adhering to preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines was conducted from inception until February 20, 2020. Electronic bibliographic databases (PubMed, Cochrane database, Scopus, Embase) were included. Using dichotomous data for select values, the unadjusted odds ratios (ORs) were calculated applying Mantel Haenszel (M-H) using random-effects model. The primary outcome of interest was all-cause mortality in ventilated and nonventilated patients. Results: The Remdesivir arm was associated with similar rates of 28-day all-cause mortality (OR: 0.93, 95% confidence interval [CI]: 0.80 - 1.08; P = 0.33). Remdesivir was not found to be favorable for ventilated patients. Non ventilated COVID-19 patients showed a significant lower in-hospital mortality rate as compared with patients requiring mechanical ventilatory support (OR: 6.86, 95% CI: 5.39 - 268.74; P <0.0001). Conclusion: Non-ventilated patients were associated with significant lower all-cause mortality rates. Prudent use of remdesivir is recommended in critically ill COVID-19 patients.
Prabhat Ranjan Prem,Vignesh Kumar Ramamurthy,Vaibhav Vinod Ingle,Darssni Ravichandran,Greeshma Giridhar 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.6
The study investigated the behavior of plain and fibered Ultra-High Performance Concrete (UHPC) beams under varying loading conditions using integrated analysis of the flexure and acoustic emission tests. The loading rate of testing is -0.25 -2 mm/min. It is observed that on increasing loading rate, flexural strength increases, and toughness decreases. The acoustic emission testing revealed that higher loading rates accelerate crack propagation. Fiber effect and matrix cracking are identified as significant contributors to the release of acoustic emission energy, with fiber rupture/failure and matrix cracking showing rate-dependent behavior. Crack classification analysis indicated that the rise angle (RA) value decreased under quasistatic loading. The average frequency (AF) value increased with the loading rate, but this trend reversed under rate-dependent conditions. K-means analysis identified distinct clusters of crack types with unique frequency and duration characteristics at different loading rates. Furthermore, the historic index and signal strength decreased with increasing loading rate after peak capacity, while the severity index increased in the post-peak zone, indicating more severe damage. The sudden rise in the historic index and cumulative signal strength indicates the possibility of several occurrences, such as the emergence of a significant crack, shifts in cracking modes, abrupt failure, or notable fiber debonding/pull-out. Moreover, there is a distinct rise in the number of AE knees corresponding to the increase in loading rate. The crack mapping from acoustic emission testing aligned with observed failure patterns, validating its use in structural health monitoring.