Optimal design of a novel crash box with functional gradient negative Poisson’s ratio structure

Crashworthiness and anti-vibration performance play critical roles in the performance of passenger cars. Aiming at enhancing the crash resistance and vibration resistance of vehicles thus providing good protection for passengers and drivers, a novel crash box with three-dimensional double arrow type negative Poisson’s ratio structure with functional gradient filling inner core (FGNPR crash box) is introduced in this paper and its performance is studied in detail through the comparison with the conventional crash box and the crash box filled with the uniform gradient negative Poisson’s ratio structure (NPR crash box) in crashworthiness and vibration resistance. Furthermore, range analysis is used to screen out the design variables that have little influence on the evaluation indexes and eliminate them. Based on these, neighborhood cultivation genetic algorithm (NCGA) and non-dominated sorting genetic algorithm-ii (NSGA-II) are selected as the optimization algorithms to carry out optimization design respectively and a comparison is made between the two suboptimal results screened out based on the normal boundary intersection (NBI) method to determine the overall optimal solution. Results show that the optimized FGNPR crash box has better crashworthiness and vibration resistance over the other crash boxes and its performance is further verified based on the peak acceleration of B-pillar in full vehicle crash condition. This paper provides some theoretical reference support for the development and exploration of automobile crash box systems.

Proximal CA3 is the primary locus of age-related pattern separation deficits in rats

Age-related deficits in pattern separation have been postulated to bias the output of hippocampal memory processing toward pattern completion, which can cause deficits in accurate memory retrieval. While the CA3 region of the hippocampus is often conceptualized as a homogeneous network involved in pattern completion, growing evidence demonstrates a functional gradient in CA3 along the transverse axis, with proximal CA3 supporting pattern separation and distal CA3 supporting pattern completion. We examined the neural representations along the CA3 transverse axis in young (Y), aged memory-unimpaired (AU), and aged memory-impaired (AI) rats when different changes were made to the environment. When the environmental similarity was high (e.g., altered cues or altered environment shapes in the same room), Y and AU rats showed more orthogonalized representations in proximal CA3 than in distal CA3, consistent with prior studies showing a functional dissociation along the transverse axis of CA3. In contrast, AI rats showed less orthogonalization in proximal CA3 than Y and AU rats but showed more normal (i.e., generalized) representations in distal CA3, with little evidence of a functional gradient. When the environmental similarity was low (e.g., recordings were done in different rooms), representations in proximal and distal CA3 remapped in all rats, showing that AI rats are able to dissociate representations when inputs show greater dissimilarity. These results provide evidence that the aged-related bias towards pattern completion is due to the loss in AI rats of the normal transition from pattern separation to pattern completion along the CA3 transverse axis and, furthermore, that proximal CA3 is the primary locus of this age-related dysfunction in neural coding.