高职《电机检修实训》课程教学的创新与实践     

何磊  李伟祥  何翠 《大众科技》2013,(2):107-108

文章结合广西电力职业技术学院教学改革的实践,总结了《电机检修实训》课程教学的创新与实践,提出了项目化的模块式教学方法,为本课程的教学改革和建设提供了一种新的借鉴。  相似文献   

异步电机的节能使用     

潘知意  陈名利 《大众科技》2013,(1):63-64

电机的耗电量约占全国总发电量40％左右,电机的节能使用对国民经济意义重大。为达到节能的目的,在设计环节,我们在电机结构、额定电压、容量、效率方面进行合理的选择;在使用环节,我们从技术和管理角度实施,通过电压的稳定、负荷率的提高、空转时间的降低、功率因数的提高、变频技术的应用等,可达到使电机节能运行的目的。  相似文献   

Strapping rowers to their sliding seat improves performance during the start of ergometer rowing     

A.J. “Knoek” van Soest  Mathijs Hofmijster 《Journal of sports sciences》2013,31(3):283-289

Abstract

Rowers sit on a seat that slides relative to the boat/ergometer. If a rower lifts him or herself from this sliding seat at any time, the seat will move away from under them and the rowing action is disrupted. From a mechanical perspective, it is clear that the need for the rower to remain in contact with the sliding seat at all times imposes position-dependent constraints on the forces exerted at the oar handle and the footstretcher. Here we investigate if the mechanical power output during rowing, which is strongly related to these forces, might be improved if the contact with the sliding seat was of no concern to the rower. In particular, we examine if elimination of these constraints by strapping the rower to the sliding seat leads to an increase in performance during the start on a standard rowing ergometer. Eleven well-trained female rowers performed 5-stroke starts in normal and strapped conditions. Handle force, vertical seat force, footstretcher force, and handle kinematics were recorded, from which mechanical power and work output were calculated. Most of the relevant mechanical variables differed significantly between the normal and strapped conditions. Most importantly, mechanical power output (averaged over the 5-stroke start) in the strapped condition was 12% higher than in the normal condition. We conclude that strapping a rower's pelvis to the sliding seat allows more vigorous execution of the stroke phases, resulting in a substantial improvement in performance during the start of ergometer rowing.  相似文献   

Participation in sports in childhood and adolescence and physical activity in adulthood: A systematic review     

Mariana Biagi Batista  Catiana Leila Possamai Romanzini  Cynthia Correa Lopes Barbosa  Gabriela Blasquez Shigaki  Marcelo Romanzini  Enio Ricardo Vaz Ronque 《Journal of sports sciences》2013,31(19):2253-2262

ABSTRACT

The aim of this study was to systematically review the literature to verify the association between participation in sports (PS) in childhood and adolescence and physical activity (PA) in adulthood. A systematic search was conducted in the following databases: Medline (PUBMED), Web of Science, Scopus, and SPORTDiscus, LILACS and SciELO. All steps of the process followed the recommendations of the PRISMA FlowDiagram. After all the steps of the process, 29 articles were included for analysis. In general, only three of the studies analyzed found no relation between PS in childhood and adolescence and PA in adulthood. However, a positive relationship was found to be weak in only 7% of the studies, a moderate relation in 62% of the studies, and a strong relation in 21%. It was found that higher weekly frequencies of PS; persistence of at least three years of PS and, finally, the highest level of practice and/or competition reached were related to higher levels of PA in adulthood. Thus, it can be concluded that there is a positive association considered moderate to strong between PS in childhood and adolescence and PA in adulthood.  相似文献   

Precision of Knowledge of Results: Consideration of the Accuracy Requirements Imposed by the Task     

T. Gilmour Reeve  Lanie A. Dornier  Daniel J. Weeks 《Research quarterly for exercise and sport》2013,84(3):284-290

Abstract

To investigate whether spatial assimilation effects are due to premovement control processes or postinitiation feedback processes, surface EMG recordings were made from two agonists and one antagonist during both single and dual movements involving the upper limb(s). In the single condition, subjects (N=7) made 25 Short (20°) and 25 Long (60°) reversal movements using levers in the sagittal plane, in 195 ms to reversal. In the dual condition, both Short and Long movements were performed simultaneously for 75 trials, the last 25 of which were without knowledge of results. Subjects overshot the Short target in the dual condition, showing spatial assimilation effects. Overshooting was associated with increased peak EMG in the initial (premovement) agonist burst, supporting the notion that spatial assimilation effects are modulated via premovement control processes.  相似文献   

Distribution of Practice in Motor Skill Acquisition: Different Effects for Discrete and Continuous Tasks     

Timothy D. Lee  Elizabeth D. Genovese 《Research quarterly for exercise and sport》2013,84(1):59-65

Abstract

Research on the benefits of distributed practice for the acquisition and retention of motor skills has a long history. The majority of this research has involved skill acquisition of continuous tasks. However, there is some evidence to suggest that distribution of practice effects are quite different for discrete tasks than for continuous tasks. In the present study, we used a single task, formed discrete and continuous versions of the task, and examined how acquisition and retention were affected by the length of inter-trial interval. The basic task was a movement timing task that involved either one timing estimate per trial (the “discrete” version) or twenty successive estimates per trial (the “continuous” version). Separate groups of subjects learned one version of the task under either distributed (25 s inter-trial intervals) or massed (0.5 s inter-trial intervals) practice conditions. Both massed and distributed retention trials were performed on the same version of the task according to a double transfer design. The results confirmed the apparent disparity: Acquisition and retention were facilitated by distributed practice on the continuous task, but by massed practice on the discrete task. These results were discussed in terms of the role of the inter-trial interval in discrete and continuous tasks.  相似文献   

The Relationship Between Motor Skill Proficiency and Body Mass Index in Preschool Children     

Samuel W. Logan  Kristin Scrabis-Fletcher  Christopher Modlesky  Nancy Getchell 《Research quarterly for exercise and sport》2013,84(3):442-448

Abstract

The purpose of this study was to examine the relationship between motor proficiency and body mass index (BMI) in preschool children. Thirty-eight children ages 4–6 years had their BMI calculated and were assessed using the Movement Assessment Battery for Children-2 (MABC-2; Henderson, Sugden, & Barnett, 2007). These data were analyzed in two ways. The correlation between BMI and MABC-2 percentile ranks was calculated. Next, the groups were subdivided based on BMI status (high, M = 85.5; medium, M = 49.8; low, M = 10.8), and compared using t tests to determine if differences existed in MABC-2 percentile ranks. No significant relationship existed between MABC-2 and BMI percentile ranks (r = -.237). However, significant differences in MABC-2 percentile ranks existed between high and low (p = .042), and high and medium (p = .043) groups. These results suggest that preschool children classified as overweight or obese may have lower motor proficiency than their normal weight and under weight peers. This study indicates there is a direct relationship between motor proficiency and BMI in the preschool population.  相似文献   

Self-Controlled Amount of Practice Benefits Learning of a Motor Skill     

Phillip G. Post  Jeffrey T. Fairbrother  Joao A.C. Barros 《Research quarterly for exercise and sport》2013,84(3):474-481

Abstract

Self-control over factors involving task-related information (e.g., feedback) can enhance motor learning. It is unknown if these benefits extend to manipulations that do not directly affect such information. The purpose of this study was to determine if self-control over the amount of practice would also facilitate learning. Participants learned to throw a dart using their nonpreferred hand. The self-control (SC) group decided when to stop practice. The yoked group completed the same number of trials as their SC counterparts. Results revealed the SC group was more accurate during transfer and in recalling the number of trials completed. These findings indicate that self-control benefits extend to factors that do not directly alter task-related information.  相似文献   

On the role of imagery modalities on motor learning     

Lucette Toussaint  Yannick Blandin 《Journal of sports sciences》2013,31(5):497-504

Abstract

In the present study, we examine specifically how the sensory conditions available during physical practice of a task might influence the subsequent use of motor imagery. First, as a pre-test, participants had to physically reproduce knee joint positions with or without vision. Second, they practised motor imagery (15 and 150 trials) with visual, kinaesthetic or visuo-kinaesthetic imagery. A control group with no imagery was included. Post-tests were then performed 10 min and 24 h after each imagery session in a sensory condition similar to that used in the pre-test. Results showed that efficient motor imagery instructions have to take account of the sensory information available during physical experience of the task: kinaesthetic or visuo-kinaesthetic imagery in a no-vision condition, and visual imagery or, to a lesser extent, visuo-kinaesthetic imagery in a vision condition. Discussion focuses on the role of sensory motor memory on motor prediction to simulate a specific movement, and on the similarities between physical and mental practice in the development of sensory-specific movement representation.  相似文献   

Effect of target change during the simple attack in fencing     

Marcos Gutiérrez-Dávila  Matteo Caletti  Raquel Antonio  Enrique Navarro 《Journal of sports sciences》2013,31(10):1100-1107

Abstract

The aim of this study was to test the effect that changing targets during a simple long lunge attack in fencing exerts on the temporal parameters of the reaction response, the execution speed, and the precision and the coordination of the movement pattern. Thirty fencers with more than 10 years of experience participated in this study. Two force platforms were used to record the horizontal components of the reaction forces and thereby to determine the beginning of the movement. A three-dimensional (3D) system recorded the spatial positions of the 9 markers situated on the fencer plus the epee, while a moving target was projected on a screen, enabling the control of the target change. The results indicated that when a target change is provoked the reaction time (RT), movement time (MT), and the time used in the acceleration phase of the centre of mass (CM) increases significantly with respect to the attack executed with a straight thrust. The speed and horizontal distance reached by the CM at the end of the acceleration phase (V_X(CM) and S_X(CM), respectively) significantly decreased, while the errors increased. However, the temporal sequence of the movement pattern did not appreciably change.  相似文献