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71.
72.
The field hockey hit is an important but poorly understood stroke. In this study, we investigated the planarity of the stickface motion during the downswing to better characterize the kinematics and to assess the suitability of planar pendulum models for simulating the hit. Thirteen experienced female field hockey players were filmed executing hits with a single approach step, and the kinematics of the centre of the stickface were measured. A method was developed for identifying how far back from impact the stickface motion was planar. Orthogonal regression was used to fit least-squares planes to the stickface path during sections of the downswing of varying length, with each section ending at impact. A section was considered planar if the root mean square residual between the stickface path and the fitted plane was less than 0.25% of the distance travelled by the stickface during that period. On average, the stickface motion was planar for the last 83 ± 12% of its downswing path, with the length of the planar section ranging from 1.85 m to 2.70 m. The suitability of a planar model for the stickface motion was supported, but further investigation of the stick and arm kinematics is warranted. 相似文献
73.
Silva DA Benedetti TR Ferrari EP Meurer ST Antes DL Silva AM Santos DA Matias CN Sardinha LB Vieira F Petroski EL 《Journal of sports sciences》2012,30(5):479-484
The objective of this study was to describe the anthropometric profiles of elite older triathletes participating in the 2009 Ironman Brazil and to compare their somatotype, anthropometric and body composition characteristics with those of elite young triathletes and older non-athletes. The sample consisted of 64 males, divided into three groups: (1) older triathletes (n = 17), (2) young triathletes (n = 24), and (3) older non-athletes (n = 23). Somatotype was analysed according to the Carter and Heath ( 1990 ) method. Body mass index, sum of four skinfolds, percentage body fat, body fat mass, and fat-free mass were also estimated. Older non-athletes had higher endomorphy, sum of four skinfolds, fat percentage, and body fat mass than the athletes. Older athletes who participated in the Ironman and elite young triathletes had higher fat-free mass than older non-athletes. Older triathletes and older non-athletes were considered mainly endomorphic mesomorphs and young triathletes mainly ectomorphic mesomorphs. The findings that characterize the anthropometric profile of athletes in this sports modality could be used as a reference. 相似文献
74.
Recommender systems play an important role in reducing the negative impact of information overload on those websites where users have the possibility of voting for their preferences on items. The most normal technique for dealing with the recommendation mechanism is to use collaborative filtering, in which it is essential to discover the most similar users to whom you desire to make recommendations. The hypothesis of this paper is that the results obtained by applying traditional similarities measures can be improved by taking contextual information, drawn from the entire body of users, and using it to calculate the singularity which exists, for each item, in the votes cast by each pair of users that you wish to compare. As such, the greater the measure of singularity result between the votes cast by two given users, the greater the impact this will have on the similarity. The results, tested on the Movielens, Netflix and FilmAffinity databases, corroborate the excellent behaviour of the singularity measure proposed. 相似文献
75.
This paper proposes a new sliding mode observer for fault reconstruction, applicable for a class of linear parameter varying (LPV) systems. Observer schemes for actuator and sensor fault reconstruction are presented. For the actuator fault reconstruction scheme, a virtual system comprising the system matrix and a fixed input distribution matrix is used for the design of the observer. The fixed input distribution matrix is instrumental in simplifying the synthesis procedure to create the observer gains to ensure a stable closed-loop reduced order sliding motion. The ‘output error injection signals’ from the observer are used as the basis for reconstructing the fault signals. For the sensor fault observer design, augmenting the LPV system with a filtered version of the faulty measurements allows the sensor fault reconstruction problem to be posed as an actuator fault reconstruction scenario. Simulation tests based on a high-fidelity nonlinear model of a transport aircraft have been used to demonstrate the proposed actuator and sensor FDI schemes. The simulation results show their efficacy. 相似文献
76.
Amparo Núñez Andrés Felipe Buill Pozuelo Joaquín Regot Marimón Andrés de Mesa Gisbert 《Journal of Cultural Heritage》2012,13(1):103-106
Different techniques and tools currently exist to generate three-dimensional models of small elements, buildings and cities. Apart from being easier to interpret than two-dimensional drawings, these models facilitate data necessary for reconstruction projects, preservation or rehabilitation of the architectural or archaeological heritage. Traditional surveying only enables us to obtain discrete information of the characteristic lines that define each surface, edge, slope change etc. whereas work with massive capture techniques allows us to obtain continuous points of the surfaces. Photogrammetry or laser scanning combined with conventional photography provides information of the building in addition to its geometry. We carried out a review of the different techniques showing the advantages and disadvantages of each technique as well as the information that can be obtained by applying these techniques to the survey of the great Gate of Antioch in the town of Aleppo, declared a World Heritage Site by UNESCO in 1986, in Syria. 相似文献
77.
The study examined the role of sign language and fingerspelling in the development of the reading and writing skills of deaf children and youth. Twenty-six deaf participants (13 children, 13 adolescents), whose first language was Chilean Sign Language (CHSL), were examined. Their dactylic abilities were evaluated with tasks involving the reading and writing of dactylic and orthographic codes. The study included three experiments: (a) the identification of Chilean signs and fingerspelled words, (b) the matching of fingerspelled words with commercial logos, and (c) the decoding of fingerspelled words and the mapping of these words onto the writing system. The results provide convergent evidence that the use of fingerspelling and sign language is related to orthographic skills. It is concluded that fingerspelling can facilitate the internal representation of words and serve as a supporting mechanism for reading acquisition. 相似文献
78.
In this paper a generalisation of the h-index and g-index is given on the basis of non-negative real-valued functionals defined on subspaces of the vector space generated by the ordered samples. Several Hirsch-type measures are defined and their basic properties are analysed. Empirical properties are illustrated using examples from the micro- and meso-level. Among these measures, the h-index proved the most, the arithmetic and geometric g-indices, the least robust measures. The μ-index and the harmonic g-index provide more balanced results and are still robust enough. 相似文献
79.
80.
As in many other parts of the world, ‘academic literacy’ has emerged as both a concern and a contested concept in South African universities. In this article we focus specifically on academic reading, which we argue is a relatively underemphasized aspect of academic literacy. This article is the product of reflections on academic reading during and subsequent to the development and presentation of a postgraduate module presented at Stellenbosch University. It briefly explores the literature on academic literacy; develops the Bourdieusian perspective on academic reading that we used to develop the module; and concludes with a discussion of the module. Our intention was to make ‘reading as social practice’ more visible to students. Bourdieu's concepts of ‘competence’, ‘habitus’ and ‘field’ set the scene for a discussion of the role of reading in different disciples and more generally within the social sciences and humanities. 相似文献