排序方式: 共有74条查询结果,搜索用时 15 毫秒
51.
Carlos Humberto Almeida Ricardo Duarte Anna Volossovitch António Paulo Ferreira 《Journal of sports sciences》2016,34(14):1355-1362
ABSTRACTThis study aimed to examine the scoring mode (line goal, double goal or central goal) and age-related effects on the defensive performance of youth soccer players during 4v4 small-sided games (SSGs). Altogether, 16 male players from 2 age groups (U13, n = 8, mean age: 12.61 ± 0.65 years; U15, n = 8, 14.86 ± 0.47 years) were selected as participants. In six independent sessions, participants performed the three SSGs each during 10-min periods. Teams’ defensive performance was analysed at every instant ball possession was regained through the variables: ball-recovery type, ball-recovery sector, configuration of play and defence state. Multinomial logistic regression analysis used in this study revealed the following significant main effects of scoring mode and age: (1) line goal (vs. central goal) increased the odds of regaining possession through tackle and in the defensive midfield sector, and decreased the odds of successful interceptions; (2) double goal (vs. central goal) decreased the odds of regaining possession through turnover won and with elongated playing shapes; (3) the probability of regaining possession through interception significantly decreased with age. Moreover, as youth players move forward in age groups, teams tend to structurally evolve from elongated playing shapes to flattened shapes and, at a behavioural level, from defending in depth to more risky flattened configurations. Overall, by manipulating the scoring mode in SSGs, coaches can promote functional and coadaptive behaviours between teams not only in terms of configurations of play, but also on the pitch locations that teams explore to regain possession. 相似文献
52.
Definitions of bullying: a comparison of terms used,and age and gender differences,in a fourteen-country international comparison 总被引:2,自引:0,他引:2
Smith PK Cowie H Olafsson RF Liefooghe AP Almeida A Araki H del Barrio C Costabile A Dekleva B Houndoumadi A Kim K Olafsson RP Ortega R Pain J Pateraki L Schafer M Singer M Smorti A Toda Y Tomasson H Wenxin Z 《Child development》2002,73(4):1119-1133
The study of school bullying has recently assumed an international dimension, but is faced with difficulties in finding terms in different languages to correspond to the English word bullying. To investigate the meanings given to various terms, a set of 25 stick-figure cartoons was devised, covering a range of social situations between peers. These cartoons were shown to samples of 8- and 14-year-old pupils (N = 1,245; n = 604 at 8 years, n = 641 at 14 years) in schools in 14 different countries, who judged whether various native terms cognate to bullying, applied to them. Terms from 10 Indo-European languages and three Asian languages were sampled. Multidimensional scaling showed that 8-year-olds primarily discriminated nonaggressive and aggressive cartoon situations; however, 14-year-olds discriminated fighting from physical bullying, and also discriminated verbal bullying and social exclusion. Gender differences were less appreciable than age differences. Based on the 14-year-old data, profiles of 67 words were then constructed across the five major cartoon clusters. The main types of terms used fell into six groups: bullying (of all kinds), verbal plus physical bullying, solely verbal bullying, social exclusion, solely physical aggression, and mainly physical aggression. The findings are discussed in relation to developmental trends in how children understand bullying, the inferences that can be made from cross-national studies, and the design of such studies. 相似文献
53.
Michael F. Almeida Carolliny M. Silva Rodrigo S. Chaves Nathan C. R. Lima Renato S. Almeida Karla P. Melo 《Journal of sports sciences》2018,36(12):1363-1370
Moderate physical exercise acts at molecular and behavioural levels, such as interfering in neuroplasticity, cell death, neurogenesis, cognition and motor functions. Therefore, the aim of this study is to analyse the cellular effects of moderate treadmill running upon substantia nigra during early neurodegeneration. Aged male Lewis rats (9-month-old) were exposed to rotenone 1mg/kg/day (8 weeks) and 6 weeks of moderate treadmill running, beginning 4 weeks after rotenone exposure. Substantia nigra was extracted and submitted to proteasome and antioxidant enzymes activities, hydrogen peroxide levels and Western blot to evaluate tyrosine hydroxylase (TH), alpha-synuclein, Tom-20, PINK1, TrkB, SLP1, CRMP-2, Rab-27b, LC3II and Beclin-1 level. It was demonstrated that moderate treadmill running, practiced during early neurodegeneration, prevented the increase of alpha-synuclein and maintained the levels of TH unaltered in substantia nigra of aged rats. Physical exercise also stimulated autophagy and prevented impairment of mitophagy, but decreased proteasome activity in rotenone-exposed aged rats. Physical activity also prevented H2O2 increase during early neurodegeneration, although the involved mechanism remains to be elucidated. TrkB levels and its anterograde trafficking seem not to be influenced by moderate treadmill running. In conclusion, moderate physical training could prevent early neurodegeneration in substantia nigra through the improvement of autophagy and mitophagy. 相似文献
54.
Jediael Machín Almeida Alexander G. Loukianov José M. Cañedo Castañeda Jorge Rivera Dominguez 《Journal of The Franklin Institute》2018,355(7):3221-3248
Using a nonlinear complete order model of a synchronous motor, a robust second order sliding mode observer based control scheme is proposed. For that, a generalized super-twisting 3rd order observer is proposed for nonlinear systems. Based on the proposed observer scheme, a robust rotor flux observer is designed, then, a stator current observer is proposed using a classical super-twisting algorithm for extracting information of the rotor speed by means of the equivalent control method. The control design for the output tracking of a desired reference signal for the rotor speed is carried out with a classical super-twisting sliding mode algorithm and adaptive backstepping techniques. Due to the number of inputs, the flux in the excitation winding, and the direct component of the stator currents are also regulated. Numeric simulations predict a good performance of the closed-loop synchronous motor with parameter variations. 相似文献
55.
Our aim was to analyse the impact of the characteristics of words used in spelling programmes and the nature of instructional
guidelines on the evolution from grapho-perceptive writing to phonetic writing in preschool children. The participants were
50 5-year-old children, divided in five equivalent groups in intelligence, phonological skills and spelling. All the children
knew the vowels and the consonants B, D, P, R, T, V, F, M and C, but didn’t use them on spelling. Their spelling was evaluated
in a pre and post-test with 36 words beginning with the consonants known. In-between they underwent a writing programme designed
to lead them to use the letters P and T to represent the initial phonemes of words. The groups differed on the kind of words
used on training (words whose initial syllable matches the name of the initial letter—Exp. G1 and Exp. G2—versus words whose
initial syllable is similar to the sound of the initial letter—Exp. G3 and Exp. G4). They also differed on the instruction
used in order to lead them to think about the relations between the initial phoneme of words and the initial consonant (instructions
designed to make the children think about letter names—Exp. G1 and Exp. G3—versus instructions designed to make the children
think about letter sounds—Exp. G2 and Exp. G4). The 5th was a control group. All the children evolved to syllabic phonetisations
spellings. There are no differences between groups at the number of total phonetisations but we found some differences between
groups at the quality of the phonetisations. 相似文献
56.
Self-concept, self-esteem and academic achievement: strategies for maintaining self-esteem in students experiencing academic failure 总被引:2,自引:0,他引:2
Francisco Peixoto Leandro S. Almeida 《European Journal of Psychology of Education - EJPE》2010,25(2):157-175
Previous research into the relationship between self-esteem and academic achievement shows that despite differences in academic
self-evaluation, students’ global self-representations do not differ as a result of their grades at school. In this study,
we will analyse the strategies that underachievers used to maintain their self-esteem at an acceptable level. The participants
were 955 adolescents in the 7th, 9th and 11th grades at four secondary schools in Lisbon. Three hundred fifty-two of these
students had retaken a year at least once in their school careers, whilst 603 had never done so. We collected the data using
both a self-concept scale and a scale for evaluating attitudes towards school. Results show that self-esteem is maintained
through positive self-representations in non-academic facets of self-concept and/or by devaluing school-related competences.
They also show that younger students are less likely to maintain self-esteem by devaluing the school experience. 相似文献
57.
Ricardo Primi Maria Eugénia Ferrão Leandro S. Almeida 《Learning and individual differences》2010,20(5):446-451
The association between fluid intelligence and inter-individual differences was investigated using multilevel growth curve modeling applied to data measuring intra-individual improvement on math achievement tests. A sample of 166 students (88 boys and 78 girls), ranging in age from 11 to 14 (M = 12.3, SD = 0.64), was tested. These individuals took four math achievement tests, which were vertically equated via Item Response Theory, at the beginning and end of the seventh and eighth grade. The cognitive abilities studied were Numerical Reasoning, Abstract Reasoning, Verbal Reasoning, and Spatial Reasoning (as measured by the Differential Reasoning Test). The general cognitive factor was significantly associated with the parameters of initial level (intercept) and rate of change (slope). A high level of intelligence was associated with higher initial scores, as well as a steeper rise in math scores across the two years. 相似文献
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60.
Startup size and the mechanisms of external learning: increasing opportunity and decreasing ability?
An important area of investigation in the field of entrepreneurship examines how people and organizations exploit technological opportunities. Prior research suggests that alliances, the mobility of experts, and the informal mechanisms associated with geographic co-location can present firms with useful opportunities to source technological knowledge. This paper uses insights from strategic management and organizational theory to suggest that organizational size may have an important impact on the extent of external learning, since it differentially affects the likelihood of learning via formal and informal mechanisms.Examining a cross-section of semiconductor startups, we find that external learning increases with startup size. With regard to the specific mechanisms of learning, we find that firms learn from alliances regardless of their size. For the informal mechanisms of mobility and geographic co-location, however, learning decreases with firm size. These results suggest that as startups grow, they may have increasing opportunities to access and exploit external knowledge, but their motivation (and hence ability) to learn from more informal sources may decrease. 相似文献