体育数学模型的理论与方法     

李建良  蒋勇  刘昌源 《体育科学》1992,(2)

本文从体育问题与数学模型、体育数学模型的建立过程和方法、体育现象和数学模型的类别以及体育数学模型与计算机应用四个方面,概要介绍了体育数学模型的理论与方法。  相似文献   

Effects of power variation on cycle performance during simulated hilly time-trials     

Marc S. Wells 《European Journal of Sport Science》2016,16(8):912-918

It has previously been shown that cyclists are unable to maintain a constant power output during cycle time-trials on hilly courses. The purpose of the present study is therefore to quantify these effects of power variation using a mathematical model of cycling performance. A hypothetical cyclist (body mass: 70?kg, bicycle mass: 10?kg) was studied using a mathematical model of cycling, which included the effects of acceleration. Performance was modelled over three hypothetical 40-km courses, comprising repeated 2.5-km sections of uphill and downhill with gradients of 1%, 3%, and 6%, respectively. Amplitude (5–15%) and distance (0.31–20.00?km) of variation were modelled over a range of mean power outputs (200–600?W) and compared to sustaining a constant power. Power variation was typically detrimental to performance; these effects were augmented as the amplitude of variation and severity of gradient increased. Varying power every 1.25?km was most detrimental to performance; at a mean power of 200?W, performance was impaired by 43.90?s (±15% variation, 6% gradient). However at the steepest gradients, the effect of power variation was relatively independent of the distance of variation. In contrast, varying power in parallel with changes in gradient improved performance by 188.89?s (±15% variation, 6% gradient) at 200?W. The present data demonstrate that during hilly time-trials, power variation that does not occur in parallel with changes in gradient is detrimental to performance, especially at steeper gradients. These adverse effects are substantially larger than those previously observed during flat, windless time-trials.  相似文献   

应用管理系统在局域网中的总体设计     

齐继平  李衍珩 《大连大学学报》1994,(4)

随着计算机关系型数据库语言的丰富与完善,特别是FOXBASE最新一代的数据库管理系统软件的出现,以及各种管理系统开发工具软件的使用,使得在开发一个计算机系统时,最感困难和复杂的已不再是具体程序的编写,而是整个系统的规划。大连市委组织部开发的《大连市组织工作信息管理网络系统》即是整个系统的规划在局域网络中的总体设计的想法和思路。  相似文献   

Explaining the substantial inter-domain and over-time correlations in student achievement: the importance of stable student attributes     

Gary N. Marks 《Educational Research and Evaluation》2016,22(1-2):45-64

Multi-domain and longitudinal studies of student achievement routinely find moderate to strong correlations across achievement domains and even stronger within-domain correlations over time. The purpose of this study is to examine the sources of these patterns analysing student achievement in 5 domains across Years 3, 5 and 7. The analysis is of longitudinal population data of over 22,000 students and utilizes fixed-effects models to incorporate stable general and domain-specific latent factors. These latent factors correspond to a general cognitive-ability-like factor and specific aptitudes in particular, or types of, subject areas. The preferred model incorporates both general and domain-specific latent factors with stronger effects for the general factor, although the domain-specific factors are particularly strong for spelling and numeracy. When taking into account general and domain-specific latent factors, the effects of student’s socioeconomic status (SES) and school SES are trivial.  相似文献   

水墨写意画造型特点分析     

王西军 《周口师范学院学报》2007,24(3):154-156

中国画的造型方式有别于其他画种,既不追求绝对的写实,又不主张脱离真实物象的过分夸张变形,而是力求在尊重客观对象的基础上,对形象进行适当的处理,使所表现的形象更加符合画家的主观意图,更加生动,更具表现力。“意象造型”是水墨写意画所采用的基本造型手段,也是中国画造型的显著特征。  相似文献   

Do digital natives differ by computer self-efficacy and experience? An empirical study     

Timothy Teo 《Interactive Learning Environments》2016,24(7):1725-1739

This study serves to validate a Chinese translation of the Digital Native Assessment Scale (C-DNAS) and assess if significant differences exist between a sample of students and teachers from a culture different than the one used in the development of the DNAS. Participants were 402 university students from one province in Mainland China. Results of the confirmatory factor analysis revealed that the C-DNAS possessed a stable factorial structure and was a valid measure among Chinese-speaking participants in Mainland China. Tests of measurement invariance revealed score equivalence among the students for each of the four factors of the C-DNAS: grew up with technology; comfortable with multitasking; reliant on graphics for communication; and thrive on instant gratifications and rewards, by computer self-efficacy and experience. Finally, tests of latent mean differences revealed significant differences in each of the four factors by computer experience but not by computer self-efficacy. Implications for research are discussed.  相似文献   

A framework for the application of distributed broadband multimedia communication services in education and training     

CONSTANTINE A. Papandreou  DIONISIS X. Adamopoulos 《Education and Information Technologies》1997,2(3):207-218

This paper examines the influence of multimedia communication services in education and training. After a brief introduction in multimedia communication systems and an analysis of the learning process, a framework for the application of distributed, broadband multimedia communication services in education and training is proposed. Its main elements, which are a set of requirements, a generic layered model and a list of important related matters, are then discussed in considerable detail. Finally, the application of the proposed framework in the field of telecommunications training is suggested  相似文献   

Experimental and FEM Study of Coated and Uncoated Tools Used for Dry Milling of Compacted Graphite Cast Iron     

陈明  姜立  郭国强  安庆龙 《天津大学学报(英文版)》2011,17(4):235-241

Compacted graphite cast iron (CGI) has been the material for high-power diesel engines recently, but its increased strength causes poor machinability. In this study, coated and uncoated carbide tools were used in dry milling experiment and FEM simulation to study the machinability of CGI and wear behaviour of tools. The experimental and FEM simulation results show that coated tool has great advantage in dry milling of CGI. SEM and EDS analysis of tool wear indicate the wear morphology and wear mechanism. Adhesive wear is the main mechanism to cause un-coated tool wear, while abrasive wear and delamination wear are the main mechanism to cause coated tool wear. Stress and temperature distribution in FEM simulation help to understand the wear mechanism including the reason for coating peeled off.  相似文献   

Expectancy value interactions and academic achievement: Differential relationships with achievement measures     

《Contemporary educational psychology》2019

Motivation predicts academic achievement beyond cognitive ability. Expectancy value theory (Eccles et al., 1983) is a widely accepted and powerful approach explaining academic achievement as well as educational choices and attainment. Recently, attention to the multiplicative term of expectancy and value beliefs has increased. Trautwein et al. (2012) reported a detrimental effect of high task value when expectancy beliefs were low. We aimed to replicate and extend their study by using a large, representative sample of students attending upper secondary school in the German federal state Schleswig-Holstein (N = 3367). Following Trautwein et al. (2012), we applied latent interaction modelling to test whether the predictive value of expectancy value interactions differs for grades, final examinations, and standardized test scores as measures of achievement in two domains. We took the multi-dimensional structure of task value into consideration, analyzing the four components (attainment, intrinsic value, utility and cost) separately. Both a verbal and a non-verbal domain (English as a foreign language and mathematics) were investigated. Overall, the results supported those of Trautwein et al. (2012). However, our findings suggested measure- and domain-specific differences when using expectancy value beliefs and their interactions to predict academic achievement. Interaction terms predicted final examination results in both English and mathematics. Further, interaction effects were significant for grades in English but not mathematics. In general, effect sizes of multiplicative terms were small, especially in contrast to expectancy beliefs. Findings are discussed regarding the practical and conceptual importance of the multiplicative term in expectancy value theory applied in an educational setting.  相似文献   

Differences in the utilisation of active power in squat and countermovement jumps     

Damián Ferraro  Gabriel Fábrica 《European Journal of Sport Science》2017,17(6):673-680

The aim of this article was to understand how active power is used in squat and countermovement jumps. A simple empirical model comprising a mass, a spring, an active element and a damper, together with an optimisation principle, was used to identify the mechanical factors that maximise performance of jumps without countermovement (squat jumps, SJ) and with countermovement (CMJ). Twelve amateur volleyball players performed SJ from two initial positions and CMJ with two degrees of counterbalancing, while kinematic data were collected (jump height, push-off duration and position of the centre of mass). The model adjusted well to real data of SJ through all the impulse phase, and slightly less adequately at the end of this phase for CMJ. Nevertheless, it provides a satisfactory explanation for the generation and utilisation of active power for both type of jumps. On average, the estimated power of the active elements, the spring, and the damper were greater in the SJ. Based upon the result obtained with this model, we suggest that active power is best evaluated with SJ. The reason for this is that, during this kind of jump, the elements associated with the damper consume much of the energy produced by the active elements. The participation of the elements that consume the energy generated by the active elements is less in CMJ than in SJ, allowing for a better utilisation of this energy. In this way it is possible to achieve a better performance in CMJ with less active power.  相似文献