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There are increasingly high performance requirements of energy-absorbing systems in aerospace, defense and military, transportation and other fields, especially in the field of emergency protection where the study of self-locking characteristics is of great significance. In this paper, an energy absorption system is designed by snap-fit thin-walled tubes, which can be edited, easy to assemble quickly and spatial omnidirectional self-locking, and the spatial self-locking characteristic of the system was verified by numerical simulation under the uniform/concentrated impact loadings. The results show that the energy-absorbing system can withstand the uniform/concentrated impact loadings in all directions in space. Furthermore, the good comprehensive performance of the loading condition in direction 3 (α = 90 deg, β = 0 deg) was verified by the quantitative analysis of the complex proportional assessment (COPRAS) method and the qualitative analysis of Radar Diagram method. [ABSTRACT FROM AUTHOR]

Both the distribution and orientation of anisotropic materials have great effects on the performance of civil and mechanical structures. Taking the maximum structural stiffness as the design objective, a concurrent method for determining the optimal distribution and orientation of orthotropic materials is proposed in this article. The method for determining material orientation theoretically overcomes the 'repeated global minimum' phenomenon, which often occurs in strain-based and stress-based methods, when the material is shear 'strong'. Then, the concurrent optimization methodology for material distribution and orientation is developed by introducing an independent discrete topology variable and continuous material orientation angle. The optimized designs of material distribution and orientation are obtained concurrently by the gradient-based bi-directional evolutionary structural optimization method and the proposed material orientation optimization method. Numerical two- and three-dimensional examples are presented to demonstrate the effectiveness of the proposed concurrent optimization algorithm. [ABSTRACT FROM AUTHOR]

Thin-walled structures have been widely used as energy absorbers due to their significant advantages on crashworthiness and light weight. Relatively few studies have been reported about thin-walled structures with variable diameter along the longitudinal direction in a nonlinear manner. In this paper, a new functionally graded thin-walled structure with variable diameter (functionally graded tapered tube, FGTT) is introduced; and its crashworthiness is comprehensively discussed in terms of specific energy absorption (SEA) and initial peak crushing force (IPCF). The results show that FGTT is of great advantages on energy absorption over the conventionally straight/tapered circular tubes under the same weight. Then, a parametric study is carried out to investigate the effects of wall thickness, gradient variations of section and diameter range between top and bottom diameters on the crashworthiness of FGTTs. Finally, the multiobjective non-dominated sorting genetic algorithm (NSGA-II) is used to further optimise the FGTTs for maximising SEA and minimising IPCF. The optimal FGTTs are found to have superior crashworthiness and great potential for energy absorber. [ABSTRACT FROM PUBLISHER]

Aims: To establish a simple criterion for determining a failed His-bundle pacing (HBP). This criterion states that if stimulus to QRS end interval is longer than His-bundle potential to QRS end interval ('S-QRSend > H-QRSend') then a failed HBP can be determined., Methods and Results: We performed retrospective analysis on 737 pacing tests around His-bundle in 241 patients and prospective analysis on 400 tests in 123 patients. A successful HBP is defined as that whole His-bundle is captured with or without capture of adjacent ventricular myocardium, otherwise, a failed HBP was considered. The output criteria and effective refractory period criteria were used as the gold standards for determining a successful HBP. The gold standards are that if decreasing the pacing output or pacing cycle length to a certain level results in duration or morphology changes of QRS, then a successful HBP is ascertained. In retrospective analysis of patients with normal His-Purkinje conduction, a failed HBP was determined in 31% (154/492) of pacing tests according to 'S-QRSend > H-QRSend'; all of them were validated by the gold standards (specificity = 100%). In prospective study, a failed HBP was confirmed according to the simple criterion with 100% accuracy in 33% (79/241) pacing tests. This simple criterion was also suitable for patients with His-Purkinje conduction disease although cases with 'S-QRSend > H-QRSend' rarely occurred., Conclusion: A failed HBP can be easily and reliably determined solely by 'S-QRSend > H-QRSend' in more than 30% pacing tests., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2020. For permissions, please email: journals.permissions@oup.com.)