探析农村生源大学生返乡就业问题

农村生源大学生是国家建设与发展的宝贵人力资源,建设社会主义新农村,加快建设小康社会都需要他们的智慧和才干.农村生源大学生毕业返乡就业应以科学技术为依托,以科技人员为纽带,以服务三农为出发点,政府通过运用利益机制引导一批农业科技综合素质较高的人才,尤其是农村生源地的专业技术人才大学毕业后返回农村,为农民提供包括示范、培训...     

The relative age effect has no influence on match outcome in youth soccer

PurposeIn age-restricted youth sport, the over-selection of athletes born in the first quarter of the year and under-selection of athletes born in the last quarter of the year has been called the relative age effect (RAE). Its existence in youth sports like soccer is well established. Why it occurs has not been identified, however, one thought is that older players, generally taller and heavier, are thought to improve the team's chances of winning. To test this assumption, birth dates and match outcome were correlated to see if teams with the oldest mean age had a systematic advantage against teams with younger mean ages.MethodsPlayer birth dates and team records (n = 5943 players on 371 teams; both genders; U11–U16) were obtained from the North Carolina Youth Soccer Association for the highest level of statewide youth competition.ResultsThe presence of an RAE was demonstrated with significant oversampling from players born in the 1st vs. the 4th quarter (overall: 29.6% vs. 20.9% respectively, p < 0.0001). Mean team age was regressed on match outcomes (winning %, points/match, points/goal, and goals for, against, and goal difference), but there was no evidence of any systematic influence of mean team age and match outcomes, except possibly in U11 males.ConclusionSelecting players based on physical maturity (and subsequently, on age) does not appear to have any systematic influence on match outcome or season record in youth soccer suggesting that the selection process should be focused on player ability and not on physical maturation.     

类书和《幼学琼林》

文章对类书的体例、内容和作用进行了说明，并简介了几本主要的类书。文章认为《幼学琼林》这本微型的类书，对于阅读一般古籍，特别对阅读唐宋以来的著作，现在仍有一定的价值。     

斜井淹井工作面帷幕注浆

斜井在开凿过程中，遇导水断层，或穿越强含水层时突水淹井，如条件允许应首选在工作面进行堵水注浆。     

Modelling the flight of a soccer ball in a direct free kick

This study involved a theoretical and an experimental investigation of the direct free kick in soccer. Our aim was to develop a mathematical model of the ball's flight incorporating aerodynamic lift and drag forces to explore this important 'set-play'. Trajectories derived from the model have been compared with those obtained from detailed video analysis of experimental kicks. Representative values for the drag and lift coefficients have been obtained, together with the implied orientation of the ball's spin axis in flight. The drag coefficient varied from 0.25 to 0.30 and the lift coefficient from 0.23 to 0.29. These values, used with a simple model of a defensive wall, have enabled free kicks to be simulated under realistic conditions, typical of match-play. The results reveal how carefully attackers must engineer the dynamics of a successful kick. For a central free kick some 18.3 m (20 yards) from goal with a conventional wall, and initial speed of 25 m·s^?1, the ball's initial elevation must be constrained between 16.5° and 17.5° and the ball kicked with almost perfect sidespin.     

Footedness in world soccer: an analysis of France '98

Most football players and coaches agree that players are capable of learning to use both feet with equal frequency and efficiency – that is, become 'two-footed'. There is also some consensus that two-footed play is associated with skill in individual players. If these assumptions are true, then the world's elite football players should be substantially less 'one-footed' than the rest of the population. To examine this issue, we quantified the pattern of foot use in a sample of 236 players from 16 teams in the 1998 World Cup (France '98). Our findings indicate that World Cup players are as right-footed as the general population (~79%). The remaining players were largely leftfooted and as biased towards the use of their preferred foot as their right-footed counterparts. Very few players used each foot with equal frequency. Remarkably, both left- and right-footed players were as skilled, on average, with their non-preferred foot as they were with their preferred foot, on the rare occasions when they used it. Therefore, it is unlikely that infrequent use of one foot compared to the other foot can be accounted for by skill differences between the feet. Players were most asymmetrical for set pieces; nevertheless, first touches, passes, dribbles and tackles were rarely performed with the non-preferred foot as well. Our results support a biological model of foot preference and performance, as well as demonstrating the usefulness of soccer for studies of lateral asymmetries.     

面向知识评价的规范文档建设方法

学术论文是主要的知识载体之一,通过对评价要素和角度的分析,提出知识评价对学术论文数据的著录要求;对比资源组织工作,提出面向知识评价的规范文档的独特性;介绍中国科技信息研究所在此方面的实践探索,给出规范文档建设的实例;最后预测规范文档的建设和应用前景。     

A systematic review of the technology-based assessment of visual perception and exploration behaviour in association football

To visually perceive opportunities for action, athletes rely on the movements of their eyes, head and body to explore their surrounding environment. To date, the specific types of technology and their efficacy for assessing the exploration behaviours of association footballers have not been systematically reviewed. This review aimed to synthesise the visual perception and exploration behaviours of footballers according to the task constraints, action requirements of the experimental task, and level of expertise of the athlete, in the context of the technology used to quantify the visual perception and exploration behaviours of footballers. A systematic search for papers that included keywords related to football, technology, and visual perception was conducted. All 38 included articles utilised eye-movement registration technology to quantify visual perception and exploration behaviour. The experimental domain appears to influence the visual perception behaviour of footballers, however no studies investigated exploration behaviours of footballers in open-play situations. Studies rarely utilised representative stimulus presentation or action requirements. To fully understand the visual perception requirements of athletes, it is recommended that future research seek to validate alternate technologies that are capable of investigating the eye, head and body movements associated with the exploration behaviours of footballers during representative open-play situations.     

Movement pattern and physiological response in recreational small-sided football – effect of number of players with a fixed pitch size

Recreational soccer is an effective health-promoting activity, but it is unclear how different game formats influence internal and external load. Thus, to be able to advise how to maximise the outcome of recreational football, we examined movement pattern and physiological response in 11 untrained men (32.6 ± 6.7 yrs, 23.3 ± 4.9 fat%, 43.4 ± 5.3 ml·min^?1·kg^?1) during three football sessions comprising 4 × 12 min of 3v3, 5v5 or 7v7 with a constant pitch size of 20 × 40 m. Movement pattern, heart rate (HR), blood lactate and RPE were measured during and after the 12-min periods. Greater (P < 0.05) total distance and high-speed distance was covered during 3v3 than 5v5 (14 and 30%) and 7v7 (15 and 75%). Mean HR was higher in 3v3 (85.7 ± 5.7%HRmax) and 5v5 (84.2 ± 5.1%HRmax) than in 7v7 (80.7 ± 4.6%HRmax, P < 0.05) and percentage time >90%HR was higher in 3v3 (43 ± 18%, P < 0.05) than in 5v5 (28 ± 21%) and 7v7 (18 ± 14%). Blood lactate was higher in 3v3 (7.4 ± 2.7 mmol·l^?1) than in 7v7 (4.5 ± 2.2 mmol·l^?1, P < 0.001) but not in 5v5 (6.1 ± 2.1 mmol·l^?1, P = 0.061). RPE was higher in 3v3 (6.7 ± 2.3, P < 0.01) than in 5v5 (5.2 ± 2.2) and 7v7 (4.3 ± 2.3). In conclusion, higher external and internal load was found with fewer players, when the pitch size is fixed.     

Long-term effects of the 11+ warm-up injury prevention programme on physical performance in adolescent male football players: a cluster-randomised controlled trial

This study examined the long-term effects of the 11+ on physical performance in adolescent male football (soccer) players. Eighty-two 14- to 16-year-old male football players (11+ = 42 players, control = 40 players) participated. Teams were randomised to control (CON) and intervention (INT) groups. INT applied the 11+ injury prevention programme for 30 weeks at least twice a week as a warm-up. CON performed their standard warm-up. Motor performance tests were conducted 1 week prior and 1 week after the competition season. We used magnitude-based inferences and linear mixed-effects models to analyse performance test results. INT showed superior results compared to CON in the vertical jump height 7.5% (95%-CI 4.4%, 10.7%), the Bosco 15-s-jump test 7.2% (95%-CI 2.2%, 12.4%), and the Illinois agility test ?2.6% (95%-CI ?4.1%, ?1.1%). Possibly beneficial effects in favour of INT were found in the 9.1 m sprint test ?3.1% (95%-CI ?6.1%, 0.1%). Possibly harmful effects (i.e. in favour of CON) were observed in the dribbling test 2.8% (95%-CI ?0.8%, 6.4%). The 11+ warm-up programme can improve different performance measures in football players. Coaches might implement additional dribbling drills next to the 11+ to achieve improvements observed in dribbling ability when using a regular warm-up programme.