化学类论文中溶液组成的规范表达     

马英霞  李学良 《编辑学报》2008,20(1):38-40

采用GB3102.8-1993中规定的量名称和量符号是规范溶液组成表达的依据和基础.该标准中列出的相关量名称和量符号可划分为"浓度"类、"分数"类和"比"类.进一步分析指出:对由SI基本量"物质的量"导出的导出量,必须遵守使用单位"摩尔"应指明物质的基本单元的使用规则;组合单位中词头的选用应符合有关词头的使用规则;量纲一的量的量值表达则需遵守相关规则.据此,就目前化学类论文中有关溶液组成的几个常见问题进行简析.  相似文献   

访问国内外学术网站数据流量费的解决办法     

常晓群  宁劲 《大学图书情报学刊》2005,23(5):43-44

教学科研需要检索和下载国内外学术站点的学术文献,我国现阶段网络通讯的收费政策与读者需要支付网络流量费是一对矛盾.文章通过分析学术网站访问需求与支付流量费的实际,介绍中国科学技术大学图书馆与网络中心解决流量费问题的方法和实践,以及取得的效果.  相似文献   

Effects of pairs of problems and examples on task performance and different types of cognitive load     

《Learning and Instruction》2014

In two studies, we investigated whether a recently developed psychometric instrument can differentiate intrinsic, extraneous, and germane cognitive load. Study I revealed a similar three-factor solution for language learning (n = 108) and a statistics lecture (n = 174), and statistics exam scores correlated negatively with the factors assumed to represent intrinsic and extraneous cognitive load during the lecture. In Study II, university freshmen who studied applications of Bayes' theorem in example–example (n = 18) or example–problem (n = 18) condition demonstrated better posttest performance than their peers who studied the applications in problem–example (n = 18) or problem–problem (n = 20) condition, and a slightly modified version of the aforementioned psychometric instrument could help researchers to differentiate intrinsic and extraneous cognitive load. The findings provide support for a recent reconceptualization of germane cognitive load as referring to the actual working memory resources devoted to dealing with intrinsic cognitive load.  相似文献   

Effects of tapering on physical match activities in professional soccer players     

Mohamed Saifeddin Fessi  Nidhal Zarrouk  Valter Di Salvo  Cristoforo Filetti  Alan R. Barker 《Journal of sports sciences》2016,34(24):2189-2194

ABSTRACT

This study aimed to examine: (i) the effect of decreasing training load (TL) during taper weeks on physical match activities in professional soccer players, and (ii) to disclose the relationship between weekly TL and physical match activities. Rating of perceived exertion was collected after each training session and match to quantify the TL in 19 professional players over 17 standard and 7 taper weeks during the season. Physical match activities were quantified by a computerised match analysis system and compared between standard training and taper weeks. Compared to standard weeks, the duration and frequency of training sessions during the taper weeks decreased (?21.7% and ?18.8%, respectively; P < 0.01) with no change in intensity (?4.8%; P = 0.09). Consequently, the weekly TL decreased during the taper weeks (?25.5%; P < 0.01). Increases in distance covered by intense running (+15.1%; P < 0.05), high-intensity running (HIR) (+15.7%; P < 0.01), number of sprints (+17.8%; P < 0.05) and number of high-speed runs (+15.7%; P < 0.05) were observed during the seven matches played after the taper weeks. High relationships were observed between TL and HIR distance covered, number of HIR and number of sprints (r = ?0.53; r = ?0.55; r = ?0.65, respectively; P < 0.01). Decreasing TL during taper weeks by reducing training duration and frequency but maintaining intensity was associated with an increase in physical activities during matches. However, it needs to be determined whether tapering or other match factors led to the changes in match activity.  相似文献   

Force–velocity property of leg muscles in individuals of different level of physical fitness     

Ivan Cuk  Dragan Mirkov  Aleksandar Nedeljkovic  Milos Kukolj  Dusan Ugarkovic 《Sports biomechanics / International Society of Biomechanics in Sports》2016,15(2):207-219

The present study explored the method of testing muscle mechanical properties through the linear force–velocity (F–V) relationships obtained from loaded vertical jumps. Specifically, we hypothesised that the F–V relationship parameters depicting the force, power, and velocity of the tested muscles will differ among individuals of different physical fitness. Strength trained, physically active, and sedentary male participants (N = 10 + 10 + 10; age 20–29 years) were tested on maximum countermovement and squat jumps where manipulation of external loads provided a range of F and V data. The observed F–V relationships of the tested leg muscles were approximately linear and mainly strong (median correlation coefficients ranged from 0.77 to 0.92; all p < 0.05), independently of either the tested group or the jump type. The maximum power revealed higher values in the strength trained than in the physically active and sedentary participants. This difference originated from the differences in F-intercepts, rather than from the V-intercepts. We conclude that the observed parameters could be sensitive enough to detect the differences among both the individuals of different physical fitness and various jump types. The present findings support using loaded vertical jumps and, possibly, other maximum performance multi-joint movements for the assessment of mechanical properties of active muscles.  相似文献   

Determining optimal cadence for an individual road cyclist from field data     

Robert Reed  Simon Adrian Jobson  Louis Passfield 《European Journal of Sport Science》2016,16(8):903-911

The cadence that maximises power output developed at the crank by an individual cyclist is conventionally determined using a laboratory test. The purpose of this study was two-fold: (i) to show that such a cadence, which we call the optimal cadence, can be determined using power output, heart-rate, and cadence measured in the field and (ii) to describe methodology to do so. For an individual cyclist's sessions, power output is related to cadence and the elicited heart-rate using a non-linear regression model. Optimal cadences are found for two riders (83 and 70 revolutions per minute, respectively); these cadences are similar to the riders’ preferred cadences (82–92?rpm and 65–75?rpm). Power output reduces by approximately 6% for cadences 20?rpm above or below optimum. Our methodology can be used by a rider to determine an optimal cadence without laboratory testing intervention: the rider will need to collect power output, heart-rate, and cadence measurements from training and racing sessions over an extended period (>6 months); ride at a range of cadences within those sessions; and calculate his/her optimal cadence using the methodology described or a software tool that implements it.  相似文献   

Effects of load mass carried in a backpack upon respiratory muscle fatigue     

Mark Faghy  Sam Blacker  Peter I. Brown 《European Journal of Sport Science》2016,16(8):1032-1038

Purpose: The purpose of this study was to investigate whether loads carried in a backpack, with a load mass ranging from 0 to 20?kg, causes respiratory muscle fatigue. Methods: Eight males performed four randomised load carriage (LC) trials comprising 60?min walking at 6.5?km?h^?1 wearing a backpack of either 0 (LC₀), 10 (LC₁₀), 15 (LC₁₅) or 20?kg (LC₂₀). Inspiratory (P_Imax) and expiratory (P_Emax) mouth pressures were assessed prior to and immediately following each trial. Pulmonary gas exchange, heart rate (HR), blood lactate and glucose concentration and perceptual responses were recorded during the first and final 60?s of each trial. Results: Group mean P_Imax and P_Emax were unchanged following 60-min load carriage in all conditions (p?>?.05). There was an increase over time in pulmonary gas exchange, HR and perceptions of effort relative to baseline measures during each trial (p?p?>?.05). Conclusions: These findings indicate that sub-maximal walking with no load or carrying 10, 15 or 20?kg in a backpack for up to 60?min does not cause respiratory muscle fatigue despite causing an increase in physiological, metabolic and perceptual parameters.  相似文献   

矿井多风机风压优化计算机调节系统设计     

王国臣  刘宪文 《鸡西大学学报》2001,(3)

经过对多风机通风网络分析,利用现有的VNETPC模拟程序,建立了多风机风压优化计算机调节系统.该系统允许计算机自动调整多风机风压,直到各用风地点获得最佳可接受的风量分配为止.  相似文献   

一种高速网络下分布式入侵检测体系结构的设计与实现     

李浪  李仁发  李肯立  许琼方 《衡阳师范学院学报》2006,27(3):73-77

随着网络速度不断提高和规模的快速扩展,对入侵检测系统的模型、结构和实现技术提出了新的需求。在深入分析和讨论现有入侵检测模型和技术优缺点的基础上,针对高速网络的特点,本文提出了一种层次可变的树状分布式入侵检测体系结构。该结构可以根据网络规模的变化动态地进行配置,各节点的增加和删除采取注册和注销的方式,而且树状结构中的每一个独立节点都可视为一个完整的入侵检测系统。利用动态负载均衡与基于协议分析的多模式匹配技术对其进行实现。  相似文献   

用常量仪器进行半微量化学分析实验的研究     

李春香  王晨 《鸡西大学学报》2002,2(2):74-75

本从培养学生技能、降低实验开支、减少环境污染的角度出发，围绕常量仪器进行半微量化学分析实验进行研究。  相似文献