ABSTRACT
The ongoing COVID19 pandemic is having detrimental effects on the mental and emotional well-being of many adults and children. It is relevant therefore to explore the combination of personal strengths and attributes that can help an individual develop resilience to such stress. Little is known about how psychological strength assets such as social connectedness, grit, hope, life meaning, and life satisfaction are inter-related, and if certain factors play a central role. This study involved a sample of 1,405 school-aged children in Hong Kong (50% female) from seven schools that participated in an online survey of psychological strengths. Data were analyzed by constructing a psychological network that found strength factors are inter-connected, and that 'school connectedness' and 'agency thinking' are central to the network. The information gained can be of value in any schools that are planning to provide strength-based interventions to help students maintain their psychological well-being during and after the COVID-19 pandemic.
ABSTRACT
Replacing existing inert binders with energetic ones in composite explosives is a novel way to improve the explosive performance, on the proviso that energetic binders are capable of releasing chemical energy rapidly in the detonation environment. Known to be a promising candidate, the reaction mechanism of glycidyl azide polymer (GAP) at typical detonation temperatures higher than 3000 K has been theoretically studied in this work at the atomistic level. By analyzing and tracking the cleavage of characteristic chemical bonds, it was found that at the detonation temperature, GAP was able to release a large amount of energy and small molecule products at a speed comparable to commonly used explosives in the early reaction stage, which was mainly attributed to the decomposition of azide groups into N2 and the main chain breakage into small fragments. Moreover, N2 generation was found to be accelerated by H atom transfer at an earlier reaction step. The dissociation energy of the main chain was lowered with structure deformation so as to facilitate the fragmentation of the GAP chain. Based on this analytical study of reaction kinetics, GAP was found to have higher reactivity at the detonation temperature than at lower temperatures. The small molecules' yield rate is of the same order of magnitude as an explosive detonation reaction, indicating that GAP has the potential to improve the performance of composite explosives. Our study reveals the chemical decomposition mechanism of a typical energetic binder, which would aid in the future design and synthesis of energetic binders so as to achieve both sensitivity-reducing and energy-enhancing performance goals simultaneously.
