Simulation research on the protection performance of fall protection net at the end of truck escape ramp

Introduction: Although the fall protection net installed at the end of the truck escape ramp has a protective effect on trucks and drivers, but lacks sufficient theoretical basis and verification method. Objectives: The primary objective of this paper was to design a fall protection net that meets the regulations and research its protection performance. Methods: The finite-element method was used to design the overall size, material, mesh length, mesh type, shape, and supporting structure of the fall protection net installed at the end of truck escape ramp, then dummy and truck models were used to impact the fall protection net to verify the rationality of the design. After the design completed, the truck model was used to impact the fall protection net twice to research the cumulative protection performance. Results: A fall protection net with a width of 6000 mm, a span of 6000 mm, a depth of 5196 mm, a mesh length of 150 mm, a mesh type of diamond mesh, a shape of 60-degree V-shaped, a supporting structure of steel pipe supporting has a better effect on energy absorption and protection. Within the two consecutive impacts, the residual plastic deformation and stress of the fall protection net generated in the first impact severely affect the protection performance in the second impact. Conclusion: It is feasible to use the finite-element method to design and research the fall prevention net installed at the end of the truck escape ramp, and the fall protection net can indeed protect the trucks and drivers, and it should be inspected and maintained after impact to ensure the protective performance in subsequent use.

Ultrasound evaluation of anterior transvaginal mesh for pelvic organ prolapse: correlation to 5-year clinical outcomes

Introduction and hypothesis Vaginal prolapse mesh may effectively restore vaginal anatomy. The aim of this study was to investigate how the in vivo mesh position correlates to clinical outcomes. Methods Seventy-one women operated on using Uphold mesh for apical pelvic organ prolapse (POP-Q, C ≥ stage II) were examined 5 years after surgery by introital-perineal 2D ultrasound in a midsagittal plane at rest and Valsalva. The horizontal line and pubis symphysis were considered the reference for all measures. Ultrasound measures were statistically compared to clinical outcomes: POP-Q, Pelvic Floor Distress Inventory (PFDI-20) and subscales [Pelvic Organ Distress Inventory (PODI-6), and Urinary Distress Inventory (UDI-6)] and the VAS scale for pain. Results Original mesh length was preserved by 86% and correlated to improved pain as estimated by VAS scale (r 0.321). Valsalva was associated with a lowering of the superior and inferior mesh margins by 7.3 and 6.1 mm, respectively (p < 0.001) but a reduction of total mesh length by only 1 mm (30.2 ± 5.2 to 29.2 ± 4.7 mm, p < 0.001). Mobility of the anterior vaginal wall (bladder neck and midurethra) at Valsalva was parallel to downward movement of the mesh inferior margin (r 0.346 and 0.314) but inversely correlated to total UDI-6 (r − 0.254 and − 0.263). Mobility of the midurethra was inversely correlated to bladder emptying (PFDI-20 Question 19, r − 0.245). Conclusions Five years after surgery, preserved original length of the mesh with apical support was correlated to improved anatomical and patient-reported outcomes. Mesh support to the vaginal apex was associated with improved bladder emptying and total urinary distress outcomes but not stress urinary incontinence.

Research on the Impact of Honeycomb Sandwich Plates at Natural Frequency Changed with Geometric Parameters

In this paper, in order to find the impact of sandwich plates at natural frequency changed with its geometric and physical parameters, we deduced free vibration equation derived sandwich panels. We took the hexagonal honeycomb sandwich plates as example, and derived natural frequencies for each for use in the modeling and modal analysis, and then discussed the effect of skin thickness, core spacing and core height on the natural frequency of honeycomb sandwich plates. The result shows that the honeycomb sandwich plates have great rigidity, and compared to other parameters, the change of core height has a greater impact on the natural frequencies of honeycomb sandwich plates. When the surface thickness of quadrilateral honeycomb sandwich plates becomes thicker, its natural frequency increases with increasing length of core grid. When sandwich mesh length reaches a certain level, the natural frequency increased firstly and then decreased. When the sandwich mesh length is longer enough, the frequency decreased with the increase in the length. When the core height increased, the natural frequency increased. When the quadrilateral mesh becomes longer, its natural frequency appears to decline after the initial increase. The influence of geometric parameters on hexagonal honeycomb sandwich plates is same as on quadrilateral honeycomb and other soft sandwich plates. Later experiments confirmed some of above conclusions.

Optimal High-Order Method of Moment combined with NURBS for the scattering by a 2D cylinder.

This paper deals with the High-Order Method of Moments (HO-MoM) combined with Non-Uniform Rational Basis Splines (NURBS) segments to evaluate the scattering by a 2D cylinder. The authors mainly focus upon the influence of the different parameters (polynomial basis, order, mesh length, curvature, polarization,...) and try to determine if a optimal choice exists or not for the convergence speed.

On the Interaction of a Weak-R Type Ionization Front and a Contact Discontinuity

A numerical solution is given to the problem of a weak R type ionization front approaching a contact discontinuity across which the density increases. During the interaction it is found that there are three possible configurations produced; the weak-R type ionization front becomes (a) weak-R type but slower for ρ1/ρ0 < 1.15, (b) strong-D type for 1.15 < ρ1/ρ0 < 3.4 or (c) weak-D type for ρ1/ρ0 > 3.4, where the original ionization front travels through a region of initial density go and across the contact discontinuity the density becomes ρ1. A fine spacial mesh length is chosen so that the structures of the resulting ionization fronts and shock waves may be identified clearly at any time.