Influence of Pressure and Temperature on the Strength Properties of a Laminate Produced by the RTM Method

This paper discusses the effect of pressure on the content of microvoids and defects inside laminates fabricated under different pressures, by vacuum methods. Two basic vacuum methods resin transfer molding (RTM) and vacuum bag method were used in this paper. A glass mat with an alignment angle of (0□/90□) and a mass of 450 g/cm2 was used to produce the laminate, and a polymer resin was used as the matrix. Special attention was paid to the technological parameters of both processes. A mathematical analysis of the most important parameters which include flow rate, permeability, and gelation temperature has been carried out. In addition, the resin temperature is used to reduce the viscosity of the resin to facilitate its flow through the reinforcement, and in the final stage of production to control the chemical reactions occurring in the mold. The pressure is chosen so that the resin flow is continuous. The synchronization of these two parameters and the measurement of the time in which they occur are called the “cure cycle”. In the final step of the study, the composite was subjected to a static tensile test, using specimens of two different dimensions (scale effect) to evaluate the effect of microvoids and microcracks created by the processes on the strength of the material.

Generation of elliptical isolated attosecond pulse from oriented $\textrm{H}_{2}^{+}$ in a linearly polarized laser field

We investigate the ellipticity of the high-order harmonic generation from the oriented $\textrm{H}_{2}^{+}$ exposed to a linearly polarized laser field by numerically solving the two dimensional time-dependent Schr$\ddot{\textrm{o}}$dinger equation (2D TDSE). Numerical simulations show that the harmonic ellipticity is remarkably sensitive to the alignment angle. The harmonic spectrum is highly elliptically polarized at a specific alignment angle $\theta = 30^\circ $, which is insensitive to the variation of the laser parameters. The position of the harmonic intensity minima indicates the high ellipticity, which can be attributed to the two-center interference effect. The high ellipticity can be explained by the phase difference of the harmonics. The results that we obtain facilitates the synthesis of a highly elliptical isolated attosecond pulses with duration down to 65 as, which can be served as a powerful tool to explore the ultrafast dynamics of molecules and study chiral light-matter interaction.

Characterisation of the opening behavior of multilayer films with cohesive failure mechanism by in situ peel tests in the ESEM

In this work, peel tests inside the chamber of an ESEM ( in situ peel tests) are described with heat-sealed test specimens of packaging systems made of multilayer films that simulate different flexible packaging types, according to the packaging line used. The in situ peel tests provided evidence to describe the influence of three different main aspects of the packaging process in relation to the opening behavior of the sealing packages. The investigated aspects are the peel angle, the alignment angle between the orientation of the multilayer films and the seal, and the bulge formation as a consequence of inadequate sealing parameters. In situ peel tests enabled the differentiation between peel angle and local (micro) peel angle, which results from the overall stiffness of the multilayer structure film. Alignment angles of 90° and 45° were found to produce similar opening forces. Images showing the formation of various new local micro fissures on new planes during the in situ peel test explained how the opening force can be dramatically increased during the tearing of two sealed multilayer films.

Towards planning of osteotomy around the knee with quantitative inclusion of the adduction moment: a biomechanical approach

Purpose Despite practised for decades, the planning of osteotomy around the knee, commonly using the Mikulicz-Line, is only empirically based, clinical outcome inconsistent and the target angle still controversial. A better target than the angle of frontal-plane static leg alignment might be the external frontal-plane lever arm (EFL) of the knee adduction moment. Hypothetically assessable from frontal-plane-radiograph skeleton dimensions, it might depend on the leg-alignment angle, the hip-centre-to-hip-centre distance, the femur- and tibia-length. Methods The target EFL to achieve a medial compartment force ratio of 50% during level-walking was identified by relating in-vivo-measurement data of knee-internal loads from nine subjects with instrumented prostheses to the same subjects’ EFLs computed from frontal-plane skeleton dimensions. Adduction moments derived from these calculated EFLs were compared to the subjects’ adduction moments measured during gait analysis. Results Highly significant relationships (0.88 ≤ R2 ≤ 0.90) were found for both the peak adduction moment measured during gait analysis and the medial compartment force ratio measured in vivo to EFL calculated from frontal-plane skeleton dimensions. Both correlations exceed the respective correlations with the leg alignment angle, EFL even predicts the adduction moment’s first peak. The guideline EFL for planning osteotomy was identified to 0.349 times the epicondyle distance, hence deducing formulas for individualized target angles and Mikulicz-Line positions based on full-leg radiograph skeleton dimensions. Applied to realistic skeleton geometries, widespread results explain the inconsistency regarding correction recommendations, whereas results for average geometries exactly meet the most-consented “Fujisawa-Point”. Conclusion Osteotomy outcome might be improved by planning re-alignment based on the provided formulas exploiting full-leg-radiograph skeleton dimensions.

CHARACTERIZING DRIVER TAKE-OVER ACCURACY: EFFECT OF AGE, SEX, STARTLE, AND SECONDARY TASK

The Acoustic Startling Pre-stimulus (ASPS, i.e. a loud sound preceding a physical perturbation was previously found to accelerate take-over actions in adults but not teens in autonomous vehicle scenarios. It is not clear if the ASPS also influences the accuracy of the take-over response across ages and sexes. Therefore the aims of this study are: to characterize take-over accuracy across age/experience and sex and to examine the effect of the ASPS and a secondary task on steering wheel alignment in autonomous vehicle take-over scenarios. Fourteen adult (7 males and 13 teenage (6 males drivers volunteered for this study. Participants were instructed to align a marker on the steering wheel with a marker on a lateral post as fast as they could, when a sled perturbation started. Two of the conditions included the ASPS. Two of the conditions involved mobile texting while the sled started moving. The angle between the steering wheel and the lateral post was used to quantify overshooting, undershooting, or correct alignment during steering. Results showed that adult female subjects reached correct alignment slightly more frequently than any other group, while male adult drivers decreased their alignment error after the first trial. Both female and male adult drivers had a reduced alignment angle when the first trial had an ASPS compared to when the first trial had no ASPS while teen drivers performed similarly with ASPS or without. This study showed that take-over accuracy and steering control are influenced by sex, age/experience, and a startle-based warning.

Reoperations are few and confined to the most valgus phenotypes 4 years after unrestricted calipered kinematically aligned TKA

Purpose The present study determined the postoperative phenotypes after unrestricted calipered kinematically aligned (KA) total knee arthroplasty (TKA), whether any phenotypes were associated with reoperation, implant revision, and lower outcome scores at 4 years, and whether the proportion of TKAs within each phenotype was comparable to those of the nonarthritic contralateral limb. Methods From 1117 consecutive primary TKAs treated by one surgeon with unrestricted calipered KA, an observer identified all patients (N = 198) that otherwise had normal paired femora and tibiae on a long-leg CT scanogram. In both legs, the distal femur–mechanical axis angle (FMA), proximal tibia–mechanical axis angle (TMA), and the hip–knee–ankle angle (HKA) were measured. Each alignment angle was assigned to one of Hirschmann’s five FMA, five TMA, and seven HKA phenotype categories. Results Three TKAs (1.5%) underwent reoperation for anterior knee pain or patellofemoral instability in the subgroup of patients with the more valgus phenotypes. There were no implant revisions for component loosening, wear, or tibiofemoral instability. The median Forgotten Joint Score (FJS) was similar between phenotypes. The median Oxford Knee Score (OKS) was similar between the TMA and HKA phenotypes and greatest in the most varus FMA phenotype. The phenotype proportions after calipered KA TKA were comparable to the contralateral leg. Conclusion Unrestricted calipered KA’s restoration of the wide range of phenotypes did not result in implant revision or poor FJS and OKS scores at a mean follow-up of 4 years. The few reoperated patients had a more valgus setting of the prosthetic trochlea than recommended for mechanical alignment. Designing a femoral component specifically for KA that restores patellofemoral kinematics with all phenotypes, especially the more valgus ones, is a strategy for reducing reoperation risk. Level of evidence Therapeutic, Level III

Development of new 9-ball test protocols for assessing expertise in cue sports

Background This study aimed to develop new test protocols for evaluating 9-ball expertise levels in cue sports players. Methods Thirty-one male 9-ball players at different playing levels were recruited (recreational group, n = 8; university team, n = 15; national team, n = 8). A 15-ball test was administered to indicate overall performance by counting the number of balls potted. Five skill tests (power control, cue alignment, angle, back spin, and top spin) were conducted to evaluate specific techniques by calculating error distances from pre-set targets using 2D video analysis. Results Intra-class correlation analyses revealed excellent intra-rater and inter-rater reliability in four out of five skill tests (ICC > 0.95). Significant between-group differences were found in 15-ball test performance (p < 0.001) and absolute error distances in the angle (p < 0.001), back spin (p = 0.006), and top spin tests (p = 0.045), with the recreational group performing worst while the national team performing best. Greater inter-trial variability was observed in recreational players than the more skilled players (p < 0.005). Conclusions In conclusion, the 9-ball test protocols were reliable and could successfully discriminate between different playing levels. Coaches and researchers may employ these protocols to identify errors, monitor training, and rank players.

Effects of Different Prosthetic Instrumentations on Tibial Bone Resection in Total Knee Arthroplasty

Objective For total knee arthroplasty (TKA) tibial bone resection, various manufacturers provide cutting blocks with fixed angles. But the accuracy of these angles is uncertain. Our aim was to assess the accuracy of the obtained posterior tibial slope (PTS) with a fixed angle cutting block.Methods 247 TKAs in 213 patients were reviewed. We included 104 Legion Prosthesis, 76 U2 Knee Prosthesis, 46 NexGen LPS-Flex Prosthesis, and 21 Vanguard Knee System products. Preoperative and postoperative PTS were measured via expanded lateral tibia radiographs. The tibial component coronal alignment angle (TCCA) was measured on postoperative standing full-length anteroposterior radiographs, and the tibia length was measured on preoperative standing full-length radiographs. Results For postoperative PTS, the Legion group had significantly smaller slopes than the U2 Knee group and Vanguard group. However, there was no significant difference between the Legion and NexGen groups, and no significant difference among the NexGen, U2 Knee, and Vanguard groups. One sample t-test indicated that only the NexGen group showed no statistical difference from the 7° PTS and 90° TCCA it aimed to provide. Multiple linear regression showed that the different tibial lengths and preoperative PTS had statistically significant effect on postoperative PTS. However, there were weak correlations between the tibial length and PTS, and between preoperative and postoperative PTS.Conclusion For TKA, using conventional tibial bone resection technology with different tibial cutting instrumentations provided by various manufacturers can obtain safe PTS. However, the PTS is not completely consistent with the angle of the cutting block.