图书流通数据分析的H类指数遴选及应用——以西北农林科技大学图书馆为例     

净玲娣  王立宏  王芹  李雅 《图书情报工作》2020,64(9):65-72

[目的/意义] 优化藏书采访工作和流通管理，实现对藏书采访、藏书总量和结构等状况适时监测、评估、调控等的标准化管理。[方法/过程] 通过对H类指数中的H指数、A指数和G指数相关性、变异性和适应性分析，遴选适用于图书流通数据分析的A指数，并根据帕累托定律采用A指数对西北农林科技大学图书馆2014-2018年的前20%的图书流通数据分别进行统计分析。[结果/结论] 研究结果表明：平均A指数对中图法一级类目与读者性别、读者专业、读者年级以及图书出版社、图书出版年、单位等数据统计分析具有较理想的表现，能够更全面、准确地遴选核心读者群、核心出版者和核心出版年；同时发现，布拉德福定律不仅能够应用于期刊管理，而且能够应用于藏书管理。本文研究能够为探索H类指数分析高校图书馆藏书流通数据提供参考依据。  相似文献   

游泳运动中静态阻力的数值模拟     

王新峰  王连泽  阎卫星 《北京体育大学学报》2005,28(2):206-207

针对前人对游泳运动中静态阻力的研究都是根据试验测量来进行的,引入一种新的分析方法--计算流体力学法,通过该方法,先建立人体简化几何模型,然后计算不同来流速度条件下处于水平俯卧状态下人体模型所受到的阻力,即静态阻力,同时计算静态阻力系数,并与前人的实验结果做对比分析.  相似文献   

基于主成分分析法的科技期刊评价方法   总被引：6，自引：1，他引：5  

张弘  赵惠祥  刘燕萍  陶文文 《编辑学报》2008,20(1):87-90

针对目前科技期刊评价方法中存在的指标之间相关性问题和指标权重选取问题,提出了基于主成分分析的科技期刊评价方法.该评价方法通过相关系数矩阵的特征向量将评价指标线性变化成彼此独立的主成分,根据主成分累计贡献值确定主成分的取用维数,由主成分方差确定权重.其优点是:可以消除由于指标间的相关性带来的偏差,降低计算维数,从而降低指标选择的难度,提高评价结果的可信度;此外,可以消除人为确定指标权重引起的弊病,使评价结果更具客观性和准确性.  相似文献   

影响雪与滑板摩擦系数的几种因数的研究     

白质明  杨海亮 《实验室研究与探索》2006,25(11):1360-1362

介绍了雪与滑板的测量系统和利用单片机对数据采集系统。为了提高实验精度,对光电门进行了改进,大大缩短了电平跳变时间,同时对雪与滑板之间的摩擦系数作了比较系统的实验研究。实验结果为制作雪的模型材料提供了基本依据。  相似文献   

4周下肢间歇负压干预对优秀赛艇运动员心率变异性和儿茶酚胺的影响     

董徽徽  高炳宏 《上海体育学院学报》2020,(4):78-83

目的探讨下肢间歇负压干预对赛艇运动员心率变异性(HRV)相关指标和儿茶酚胺的影响。方法将国家赛艇队的14名运动员分为试验组和对照组,试验组运动员每周用间歇负压干预5 d,持续4周,对照组无其他干预方式。试验期间均对2组运动员进行HRV相关指标和儿茶酚胺的测试。结果试验前2组运动员各指标均无统计学差异。开始干预后2组的变化如下:①在时域指标中,试验组正常窦性R-R间期标准差(SDNN)在第3周时高于对照组(P<0.05)。②在频域指标中,试验组高频(HF)值在第2周和第3周时高于对照组(P<0.05),而其高频与低频比(LF/HF)在第1、3和4周时低于对照组(P<0.05)。③2组儿茶酚胺组内、组间比较均无统计学差异,但试验组儿茶酚胺下降程度比对照组高。结论4周的间歇负压干预对运动员自主神经系统功能的恢复有明显促进作用,对儿茶酚胺的分泌也具有抑制趋势;这有利于降低运动员心脏负荷,促进运动后的生理恢复。  相似文献   

Comparing the magnitude and direction of asymmetry during the squat,countermovement and drop jump tests in elite youth female soccer players     

Chris Bishop  Lucas A. Pereira  Valter P. Reis  Paul Read  Anthony N. Turner  Irineu Loturco 《Journal of sports sciences》2020,38(11-12):1296-1303

ABSTRACT

The aims of the present study were to provide an in-depth comparison of inter-limb asymmetry and determine how consistently asymmetry favours the same limb during different vertical jump tests. Eighteen elite female under-17 soccer players conducted unilateral squat jumps (SJ), countermovement jumps (CMJ) and drop jumps (DJ) on a portable force platform, with jump height, peak force, concentric impulse and peak power as common metrics across tests. For the magnitude of asymmetry, concentric impulse was significantly greater during the SJ test compared to CMJ (p = 0.019) and DJ (p = 0.003). No other significant differences in magnitude were present. For the direction of asymmetry, Kappa coefficients revealed fair to substantial levels of agreement between the SJ and CMJ (Kappa = 0.35 to 0.61) tests, but only slight to fair levels of agreement between the SJ and DJ (Kappa = ?0.26 to 0.18) and CMJ and DJ (Kappa = ?0.13 to 0.26) tests. These results highlight that the mean asymmetry value may be a poor indicator of true variability of between-limb differences in healthy athletes. The direction of asymmetry may provide a useful monitoring tool for practitioners in healthy athletes, when no obvious between-limb deficit exists.  相似文献   

The application of inertial measurement units and functional principal component analysis to evaluate movement in the forward 3½ pike somersault springboard dive     

Cherie Walker  John Warmenhoven  Peter J. Sinclair 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(2):146-162

Based on technological and analytical advances, the capability to more accurately and finitely examine biomechanical and skill characteristics of movement has improved. The purpose of this study was to use Inertial Measurement Units (IMUs) and Functional Principal Components Analysis (fPCA) to examine the role of movement variability (assessed via angular velocity), on 2 divers (1 international level; 1 national) performing the forward 3½ pike somersault dive. Analysis of angular velocity curves during ive-flight identified 5 fPCs, accounting for 96.5% of movement variability. The national diver’s scatter plots and standard deviation of fPC scores illustrated larger magnitudes of angular velocity variability across dive flight. For fPC1 and fPC3, magnitudes of SD variability were 282.6 and 201.5, respectively. The international diver illustrated more consistent angular velocity profiles, with clustering of fPCs scores (e.g., fPC1 & 3 = SD’s of 75.2 & 68.0). To account for lower variability in the international diver, the ability to better coordinate movement sequences and functionally utilise feedback in response to initiation of the somersault position is highlighted. Overall, findings highlight how both IMUs and fPCA can more holistically and finitely examine the biomechanical and skill characteristics of movement sequences with the capability to inform athlete development.  相似文献   

比较文学教学的四个关键词     

吴家荣 《安徽教育学院学报》2011,29(1):116-118

比较文学作为一门学科,内容丰富、学理性强。如何使学生真正了解比较文学学科的价值、意义,使他们正确运用比较文学原理、方法,深入开展文学研究,四个关键词至关重要,即：比较;影响;可比性;变异性。学生只有充分了解关键词的含义,切实掌握了关键词的运用,比较文学的教学才能收到事半功倍的成效。  相似文献   

Components of Variance of Scales With a Bifactor Subscale Structure From Two Calculations of α     

David Andrich 《Educational Measurement》2016,35(4):25-30

Since Cronbach's (1951) elaboration of α from its introduction by Guttman (1945), this coefficient has become ubiquitous in characterizing assessment instruments in education, psychology, and other social sciences. Also ubiquitous are caveats on the calculation and interpretation of this coefficient. This article summarizes a recent contribution (Andrich, 2015) on the use of coefficient α which complements these many caveats. It shows that in the presence of a simple bifactor structure of a scale where unique components of variance are homogeneous in magnitude, three components of variance and the common latent common correlation among the subscales can be calculated from the ratio of two calculations of α, one at the level of the items, the other at the level of the subscales. It was suggested that these two ready calculations and their interpretation, and the reporting of all four indices in the analysis of scales with a subscale structure, would reduce the misinterpretation of this coefficient. An illustrative example of the application of the calculations is also shown.  相似文献   

运算放大器工作状态的判断及分析     

吴恒玉  唐民丽 《孝感职业技术学院学报》2006,9(1):91-92

在电子技术教学中,分析运算放大器系统时,应根据运算放大器系统的反馈情况,判断它的工作状态;分析工作状态时,要充分考虑运放系统是处于线性区还是饱和区。线性区可按虚短或虚地原则处理,饱和时不能按虚短原则处理,应用“虚短”和“虚地”时应注意“虚短”是“虚地”的特殊形式。  相似文献