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We aim to explore how the COVID-19 crisis has initiated entrepreneurship amongst micro-scale businesses in the notably vulnerable street food industry. We highlight Malaysian street food vendors’ remarkable resilience as they evolved from informal enterprises into innovative entrepreneurs during the pandemic. This involves comprehending the pandemic’s impact and the coping strategies these businesses adopt to endure, evolve and thrive.

We carried out a semi-structured interview with 20 street food vendors in Kuala Lumpur, Malaysia. By using a qualitative approach and integrating theories on appraisal, resource management and self-regulated activities, this paper explores vendors’ experiences on their journey towards becoming entrepreneurs regardless of limited resources.

Despite the disruption, COVID-19 offers a crucial wake-up call even for micro-scale businesses. We discover the capability of street food vendors to outlast crisis through transformation into individuals with an entrepreneurial mindset. They adapted by diversifying their offerings and implementing new strategies like digital marketing and e-commerce. We also emphasise the contribution of family members in providing psychosocial support and navigating business challenges as an advantage of employing a highly self-efficacious individual within the group. This transformation not only ensures the survival of micro-scale enterprises but also underscores their potential to thrive and innovate, even in the face of adversity.

This paper extends the existing literature on street vending by integrating the appraisal theory of emotion, resource-based view theory and self-efficacy theory to explore how street food vendors with limited resources have managed to transform the informal business nature into an entrepreneurial environment under the pressure of a crisis.

This study aims to validate the linear flow theory with computational fluid dynamics (CFD) simulations and to propose a novel shape for the airfoil that will improve supersonic aerodynamic performance compared to the National Advisory Committee for Aeronautics (NACA) 64a210 airfoil.

To design the new airfoil shape, this study uses a convex optimization approach to obtain a global optimal shape for an airfoil. First, modeling is conducted using linear flow theory, and then numerical verification is done by CFD simulations using ANSYS Fluent. The optimization process ensures that the new airfoil maintains the same cross-sectional area and thickness as the NACA 64a210 airfoil. This study found that an efficient way to obtain the ideal airfoil shape is by using linear flow theory, and the numerical simulations supported the assumptions inherent in the linear flow theory.

This study’s findings show notable improvements (from 4% to 200%) in the aerodynamic performance of the airfoil, especially in the supersonic range, which points to the suggested airfoil as a potential option for several fighter aircraft. Under various supersonic conditions, the optimized airfoil exhibits improved lift-over-drag ratios, leading to improved flight performance and lower fuel consumption.

This study was conducted mainly for supersonic flow, whereas the subsonic flow is tested for a Mach number of 0.7. This study would be extended for both subsonic and supersonic flights.

Convex optimization and linear flow theory are combined in this work to create an airfoil that performs better in supersonic conditions than the NACA 64a210. By closely matching the CFD results, the linear flow theory's robustness is confirmed. This means that the initial design phase no longer requires extensive CFD simulations, and the linear flow theory can be used quickly and efficiently to obtain optimal airfoil shapes.

The proposed airfoil can be used in different fighter aircraft to enhance performance and reduce fuel consumption. Thus, lower carbon emission is expected.

The unique aspect of this work is how convex optimization and linear flow theory were combined to create an airfoil that performs better in supersonic conditions than the NACA 64a210. Comprehensive CFD simulations were used for validation, highlighting the optimization approach's strength and usefulness in aerospace engineering.