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Though the bumper of a vehicle plays a major role in protecting the vehicle body against damage in low speed impacts, many bumpers, particularly in large vehicles, are too stiff for pedestrian protection. In designing a bumper for an automobile, pedestrian protection is as important as bumper energy absorption in low speed collisions. To prevent lower extremity injuries in car-pedestrian collisions, it is important to determine the loadings that car front structures impart on the lower extremities and the mechanisms by which injury is caused by these loadings. The present work was focused on gaining more insight into the injury mechanisms leading to both ligament damage and bone fracture during bumper-pedestrian collisions. The European Enhanced Vehicle-safety Committee （EEVC） legform impactor model was introduced and validated against EEVCAVG17 criteria. The collision mechanism between a bumper and this legform impactor was investigated numerically using LS-DYNA software. To identify the effect of the bumper beam material on leg injuries, four analyses were performed on bumpers that had the same assembly but were made from different materials. 相似文献
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Virtual reality (VR) platforms act as a potentially transformative tool in learning and teaching. The aim of this study was to examine pre-service teachers’ (PST) perceptions about VR, inclusive of their beliefs about its capacity to be used as a teaching and learning tool. A case-study, conducted at an urban university in Australia involved a sample of n = 41. Participants’ positive perceptions of VR in their teaching relate to its potential to engage learners, the immersive potential of the platform and the scope of VR to offer students experiences they might otherwise not have with other learning tools. Concerns expressed by PSTs include their relatively low self-efficacy to use VR in their teaching, monitoring-related matters, financial cost and implementing the technology in a safe and supportive way. There was a significant difference in PSTs’ amount of self-efficacy to teach using VR when compared to their overall confidence to use digital technologies. PSTs typically had greater awareness of the immersive and engagement potential of VR and less awareness about its potential to foster and promote collaborative learning. This paper contributes to an emerging discourse regarding the possible applications of VR in educational environments and particularly in relation teacher-educator contexts. 相似文献
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Ever-increasing hardware capabilities and computation powers have enabled acquisition and analysis of big scientific data at the nanoscale routine, though much of the data acquired often turn out to be redundant, noisy and/or irrelevant to the problems of interest, and it remains nontrivial to draw clear mechanistic insights from pure data analytics. In this work, we use scanning probe microscopy (SPM) as an example to demonstrate deep data methodology for nanosciences, transitioning from brute-force analytics such as data mining, correlation analysis and unsupervised classification to informed and/or targeted causative data analytics built on sound physical understanding. Three key ingredients of such deep data analytics are presented. A sequential excitation scanning probe microscopy (SE-SPM) technique is first developed to acquire high-quality, efficient and physically relevant data, which can be easily implemented on any standard atomic force microscope (AFM). Brute-force physical analysis is then carried out using a simple harmonic oscillator (SHO) model, enabling us to derive intrinsic electromechanical coupling of interest. Finally, principal component analysis (PCA) is carried out, which not only speeds up the analysis by four orders of magnitude, but also allows a clear physical interpretation of its modes in combination with SHO analysis. A rough piezoelectric material has been probed using such a strategy, enabling us to map its intrinsic electromechanical properties at the nanoscale with high fidelity, where conventional methods fail. The SE in combination with deep data methodology can be easily adapted for other SPM techniques to probe a wide range of functional phenomena at the nanoscale. 相似文献
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Martina Rinaldi Yasmen Nasr Ghada Atef Fabiano Bini Tiwana Varrecchia Carmela Conte 《European Journal of Sport Science》2018,18(6):796-805
The aims of this study were: (i) to determine kinematic, kinetic, and electromyographic characteristics of Junzuki karate punch in professional karate athletes; (ii) to identify biomechanical parameters that correlate with punch force and lead to a higher punching performance; (iii) to verify the presence of muscle co-activation in the upper limb, trunk, and lower limb muscles. Data were collected from nine experienced karatekas from the Accademia Italiana Karate e Arti Marziali during the execution of the specific punch. Mean punch forces (181.2?N) delivered to the target, the range of motion of both right and left knees (1.13 and 0.82?rad) and right elbow (1.49?rad) joints, and the angles at impact (knee: 0.81 and 0.91?rad; elbow: 1.19?rad) in the sagittal plane were computed. Furthermore, the trunk rotational angular acceleration (63.1?rad?s?2), force related to the lower limbs (550.2 and 425.1?N), and co-activation index for the upper limb (36.1% and 34.7%), trunk (24.5% and 16%), and lower limbs (16.0% and 16.1%) muscles were evaluated bilaterally. Significant positive correlations were found between the punch force and both right and left knee flexion at the instant of impact and right and left leg force. Significant negative correlation was found between the punch force and maximum trunk angular acceleration. Significant differences (p?=?.03) in the co-activation index among the upper limb, trunk, and lower limbs muscles highlighted a rostro-caudal gradient on both body sides. This research could be of use to performers and coaches when considering training preparations. 相似文献
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