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Alireza Karimi Reza Razaghi Mahdi Navidbakhsh Toshihiro Sera Susumu Kudo 《Sports Engineering》2016,19(2):105-115
Although it might be believed that the eye only comprised a very small area of the face, its injury due to the ball impacts in different sports seems to be severe enough to entice many researchers to determine the level of injury and then attempt to minimize it. Sports-related eye injuries, especially tennis, pose a substantial and preventable problem to the eye due to the high speed of the tennis ball (69 m/s). This is why many ophthalmologists provide a wide range of information for their patients regarding the risks of eye injuries in tennis to prevent the injury to well over 100,000 eyes each year. However, so far although there are some general information regarding the injury to the human eye components due to the tennis ball impact, the details of the stresses and deformations have not been well determined. Therefore, the goal of this study was to determine the stresses and deformations of the eye components, including cornea, aqueous body, iris, ciliary body, lens, vitreous body, retina, sclera, optic nerve, extra and intraconal fats, and muscles, attributable to the tennis ball impact via a Lagrangian–Eulerian computational coupling model. Magnetic resonance imaging was employed to establish a finite element model of the human eye according to a normal human eye. The numerical results revealed the highest amount of stress in the iris (19.2 MPa), whereas the lowest one was observed in the vitreous body (1.77 Pa). The cornea also experienced the stress of 8.27 MPa which might be high enough to invoke rupture in this delicate material. In addition, the results exhibited a decreasing and increasing of the radius of curvature for the cornea and lens, respectively. Finally, the collision of the tennis ball to the eye triggered the resultant displacement of 0.045 µm in the optic nerve which may imply a non-significant injury to that. The findings of this study may have implications not only for understating the values of stresses and deformations in the human eye components but also for helping the ophthalmologists to have a more precise diagnosis about the injury position in the eye due to the tennis ball impact. 相似文献
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Studies of social networks highlight the importance of network structure or structural properties of a given network and its impact on performance outcome. One of the important properties of this network structure is referred to as social capital, which is the network of contacts and the associated values attached to these networks of contacts. This study provides empirical evidence of the influence of social capital and performance within the context of academic collaboration (coauthorship) and suggests that the collaborative process involves social capital embedded within relationships and network structures among direct coauthors. Association between scholars' social capital and their citation-based performance measures is examined. To overcome the limitations of traditional social network metrics for measuring the influence of scholars' social capital within coauthorship networks, the traditional social network metrics is extended by proposing two new measures, of which one is non-weighted (the power–diversity index) and the other (power–tie–diversity index) is weighted by the number of collaboration instances. The Spearman's correlation rank test is used to examine the association between scholars' social capital measures and their citation-based performance. Results suggest that research performance of authors is positively correlated with their social capital measures. The power–diversity index and power–tie–diversity index serve as indicators of power and influence of an individual's ability to control communication and information. 相似文献
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This article adds to the existing literature on nonformal learning in education in general and the role played by written feedback in providing the space for such learning in particular. The study was conducted in an English as a Foreign Language context in which the participating students received written feedback on their English writings. Employing qualitative interviews and stimulated recall methodology, we explored interstudent interactions, cross-cultural understanding, and initiation into communities of practice, and categorized these as reactive and deliberative types of nonformal learning. Drawing upon Eraut's typology of nonformal learning, we would argue that formative written feedback provided on students' writings could lead to nonformal learning because it encourages them to act upon it. 相似文献
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In order to acquire the numerous advantages of electronic commerce, issue of evaluating electronic commerce adoption has its own importance. For this purpose, based on the scientific research and literature reviews, technical, organizational and inter-organizational are identified as the three dimensions for evaluating electronic commerce adoption of the companies. Thereafter, expert viewpoints were put forward about criteria and indicators in each of the above-mentioned dimensions. On the basis of identified indicators and criteria, a framework was developed for evaluating the electronic commerce adoption in Iranian companies. Furthermore in this research, the framework is tested in 27 Iranian companies. The result indicates that there is a significant positive relationship between degree of electronic commerce adoption and stages of electronic commerce development in the companies. Based on the findings and test of the framework, it will present necessary guidelines for evaluating electronic commerce adoption. 相似文献
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Alireza Karimi Reza Razaghi Seyed Mohammadali Rahmati Toshihiro Sera Susumu Kudo 《Sports Engineering》2018,21(4):359-365
Eye injuries from blunt forces and penetrating objects can cause morbidity, disability, and blindness. Most of these injuries are preventable not only by understanding the detail of injury, but also by portraying the role of the ball’s characteristics. Basketball can induce severe forms of injuries to the eye. This study was aimed at performing a numerical analysis through the fluid–structure interaction on ocular trauma. Balls with different diameters, elastic moduli, and pressures were shot to the eye. Injury in terms of the stresses and deformations in each component of the eye was computed at ~?0.72 mm deformation in the apex of the cornea. By increasing the diameter of the ball from 20 to 26 cm the stress in the eye components, excluding the aqueous body, vitreous body, and extraconal fat, increased. Stresses of 2.68 and 3.19 MPa were observed in the cornea under the ball diameters of 20 and 26 cm, respectively. Conversely, the elastic modulus and pressure of the ball in the defined range showed no considerable role on the stress in the eye components. The results revealed the importance of the ball size compared to the elastic modulus and pressure in the stress accumulation as a result of ocular trauma. 相似文献
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软件的修改管理问题是信息系统开发中的一个重要问题,该问题也是软件工业中所面临的十分重要的挑战。因此,现代的软件修改管理工具,或着称为配置控制工具,必须能对影响软件开发中的各种修改进行有效的管理。本文就此问题进行了探讨。 相似文献
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We examined how subjective assessments of recollection guide decision making. Subjective recollection was dissociated from accuracy during a forced-choice recognition task. Distracters were either similar to targets (match condition) or to other studied, but untested items (nonmatch condition). We assessed 223 participants (112 males) across three experiments (137 White, 37 Asian-American, 7 African-American, 4 American-Indian, 32 mixed race, 6 undisclosed). In Experiment 1, 6- to 10-year-olds and adults (N = 119) were less accurate (d = 0.70), but more likely to claim subjective recollection and make memory selections in anticipation of a reward in the nonmatch condition (ds = 0.64–0.70). This pattern was eliminated in 6- to 7-year-olds when we limited the number of selections (Experiment 2, N = 52), but was replicated when we required the selections to be counted (Experiment 3, N = 52), underscoring the effects of decision complexity on children’s self-reflections. 相似文献