Ultrasonic Wave Propagation Studies in Anisotropic Plates with built-In Material Degratdation

Anomalies of several kind are often found unavoidable during the manufacturing process of 0fiber reinforced composite parts. Several ultrasonic wave propagation and feature based signal analysis techniques can be found for characterizing these defects. Such methods are currently established on a problem to problem basis. Hence, the NDE methods are unable to keep up with the rapidly progressing materials technology and there is a need for a quick turnaround generalized method for anomaly modeling and experimental simulation to physically study the anomaly influence process on the ultrasonic signal. This paper addresses issues regarding the emerging new methods of ultrasonics oblique incidence techniques for the non-destructive evaluation of anisotropic plates. In this paper, efforts on theoretical modeling of imperfect composite structures, with in-built anomalies, have been attempted. Some of the common types of anomalies which can be considered, includes micro and macro porosity, fiber fraction changes, fiber mis-orientation, improper lay-up, interfacial weakness, improper curing, et

Effect of construction joints on the splitting tensile strength of concrete

AbstractThe purpose of this study is to experimentally correlate the compressive strength (f′c) of concrete to the splitting tensile strength (T) for plain concrete in the existence of a construction joint, and formulate an empirical equation relating T to f′c. Both the American Concrete Institute code (ACI 318-08 (ACI Committee 318, 2008)) and the American Society for Testing and Materials (ASTM (ASTM Standard C496, 2002; ASTM Standard C192/C192M, 2002; ASTM Standard C39/C39M, 2005; ASTM Standard C617, 2002)) provide the testing methods and standards, as well as the applicable theoretical and experimental formulas for the correlation between T to f′c for concrete specimens, which are monolithic, indicating that the specimens lack any construction joints. Providing a useful reduction factor in the splitting tensile strength of concrete due the existence of a construction joint is essential. It is a well known fact that construction joints are used in every concrete structure, which indicates that engineers would definitely benefit from an equation that could relate the splitting tensile strength of concrete in function of its compressive strength.The results suggest that the reduction in the splitting tensile strength in the presence of a construction joint is not as much as most engineers tend to believe. Due to that belief, most engineers tend to overdesign for steel reinforcement at those joints to compensate for this reduction. The objective of the study is to better the understanding of the effects of a construction joint on the splitting tensile strength. Thus provide an empirical equation to assist engineers in their design calculations, therefore reducing the amount of steel reinforcement at the construction joints. Thus also leading to cost saving on projects

An Application of Finite Element Analysis to Wood Drying

Because of the nonhomogeneous and nonlinear properties of wood, exact solutions for heat and mass transfer are difficult to obtain by current methods of analysis. This work presents a numerical solution for the analysis of drying wood using the finite element method. A nonlinear model was established on a two-dimensional finite element grid structure that considers local density variation. Through the finite element method of analysis of unsteady-state heat and moisture transfer in wood, the dynamic profiles of temperature and moisture content were determined at a series of drying times. The resulting numerical solutions match well with experimental results and with published results. The results will help to extend understanding of wood-water and temperature relations. In future studies, these data can be incorporated into drying stress analysis to analyze checking or warping

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

An Updated Review on the Effect of CFRP on Flexural Performance of Reinforced Concrete Beams

Abstract This detailed review looks at how carbon fiber-reinforced polymer (CFRP) may be used to improve the flexural capacity of reinforced concrete (RC) beams. It investigates the history, characteristics, and research trends of FRP composites, assesses various flexural strengthening methods utilizing FRP, and addresses the predictive power of finite-element (FE) modeling. The assessment highlights the importance of enhanced design codes, failure mode mitigation, and improved predictive modeling methodologies. It emphasizes the advantages of improving FRP reinforcement levels to meet code expectations and covers issues, such as FRP laminate delamination and debonding. The findings highlight the need of balancing load capacity and structural ductility, as well as the importance of material behavior and failure processes in accurate prediction. Overall, this review offers valuable insights for future research and engineering practice to optimize flexural strengthening with CFRP in RC beams

Ultrasonic Wave Propagation Studies in Anisotropic Plates with built-In Material Degratdation

Anomalies of several kind are often found unavoidable during the manufacturing process of 0fiber reinforced composite parts. Several ultrasonic wave propagation and feature based signal analysis techniques can be found for characterizing these defects. Such methods are currently established on a problem to problem basis. Hence, the NDE methods are unable to keep up with the rapidly progressing materials technology and there is a need for a quick turnaround generalized method for anomaly modeling and experimental simulation to physically study the anomaly influence process on the ultrasonic signal. This paper addresses issues regarding the emerging new methods of ultrasonics oblique incidence techniques for the non-destructive evaluation of anisotropic plates. In this paper, efforts on theoretical modeling of imperfect composite structures, with in-built anomalies, have been attempted. Some of the common types of anomalies which can be considered, includes micro and macro porosity, fiber fraction changes, fiber mis-orientation, improper lay-up, interfacial weakness, improper curing, etc</p

The effect of concrete vertical construction joints on the modulus of rupture

The purpose of this study is to experimentally correlate the compressive strength (f′c) of concrete to the modulus of rupture (fr) for plain concrete beams with a vertical construction joint placed at their center. The ACI code provides a formula for the correlation of fr to f′c, but with the provision that the concrete specimen is monolithic (no joints). It is well known that no concrete structure is built without the use of construction joints, whether planned or un-planned, an engineer would definitely benefit from an equation that could relate the modulus of rupture of concrete as a function of its compressive strength. A better understanding of the effects of construction joints on the modulus of rupture will assist engineers in making rational decisions on how to deal with vertical construction joints, which in turn will lead to ultimate cost savings on large-scale projects. In this study, seven different concrete mix designs were used. From each concrete mix, six plain concrete beams were poured, half of which were monolithic and the other half with a vertical construction joint at the beam center. Four cylinders per design mix were casted for the purpose of obtaining the mix compressive strength. The experimental results indicate that for monolithic beams, the ACI Code always underestimates the modulus of rupture, whereas in the presence of a vertical construction joint, the conducted experiments yield a significant loss in the modulus of rupture of concrete that varies between 24% and 83%. Thus, there is a clear justification for providing dowels at construction joints in order to assure continuity in strength over joints in plain concrete

The effect of construction joints on the flexural bending capacity of singly reinforced beams

The main purpose of conducting this study is to determine the difference in the bending capacity between a singly reinforced monolithic beam and a singly reinforced beam with a construction joint at the beam center, for a range of different compressive strength (f’c) of concrete. Testing was conducted according to applicable ASTM standards. During humongous construction projects, it is very rare to build a concrete structure without instigating the use of construction joints, whether by design or by de facto forces. On site, the construction supervisor would contemplate whether one could relate the bending capacity of the concrete beam with the use of accidently imposed construction joint. Thus it is very essential to determine the effect the construction joint has on the flexural bending capacity of the concrete. Provided are charts to account for the loss in the bending capacity of singly reinforced beam in the existence of a construction joint for a specific concrete compressive strength

Sustainable masonry blocks: Olive wood waste as substitute for fine aggregates

Due to the high level of pollution generated from the burning of wood waste and the scarcity of natural resources like sand that is causing a change in the eco-system, a greater need to find alternative and innovative solutions is warranted. Thus, this study explores the effect of olive wood waste (OWW) as a replacement for sand in mortar mixes as utilized in concrete masonry blocks. OWW replacement ratios of 25, 50, and 100 % were explored. Properties that were examined included the flexural strength, the compressive strength, and the heat of hydration. The compressive strength and flexural strength were analyzed at 3, 7, 14, 28, and 40 days, while the flowability was measured immediately following the fresh mixing process, and the heat of hydration was measured for 48 h after casting. The results indicated that 25 and 50 % of standard sand replacement by OWW yielded a flexural strength that exceeded the reference mix, while reducing the heat of hydration, and maintaining an acceptable compressive strength for non-structural applications such as sidewalks, borders, ditches, filler blocks, and masonry blocks