From arithmetical thought to algebraic thought: The role of the “variable”

The introduction of the concept of the variable represents a critical point in the arithmetic–algebraic transition. This concept is complex because it is used with different meanings in different situations. Its management depends on the particular way of using it in problem-solving. The aim of this paper was to analyse whether the notion of “unknown” interferes with the interpretation of the variable “in functional relation” and the kinds of languages used by the students in problem-solving. We also wanted to study the concept of the variable in the process of translation from algebraic language into natural language. We present two experimental studies. In the first one, we administered a questionnaire to 111 students aged 16–19 years. Drawing on the conclusions of this research we carried out the second study with two pairs of students aged 16–17 years.

我国高校科研管理中人本理念的思考

科学研究是高校的三大职能之一,而一所高校的科研实力很大程度上取决于该校科研管理能力的高低。随着经济文化的全球化．高等教育管理与世界接轨的要求促使了高校科研管理部门加快了对科研管理的改革和创新,其中以人为本的管理理念逐渐受到管理者们的重视。笔者认为对科研人员进行有效激励、沟通服务,并重视对其引导是科研人本管理的核心内容,本文将对这三方面问题进行思考．对人本理念的应用和科研管理能力提高问的关系提出一点见解。     

Anticipated IT infrastructure and supply chain integration capabilities for RFID and their associated deployment outcomes

This study looks at the perceived ability of components of IT infrastructure integration and supply chain process integration to predict specific radio frequency identification (RFID) system deployment outcomes—exploration, exploitation, operational efficiency, and market knowledge creation. Data for this pilot research study was collected using a survey questionnaire administered online to members of the Council of Supply Chain Management Professionals (CSCMP). It was hypothesized that data consistency and cross-functional application integration, both elements constituting IT infrastructure integration, and information flow integration, physical flow integration, and financial flow integration, all elements constituting supply chain process integration would be positively associated with and predict the four RFID system outcomes. Multiple regression results show partial support for all four proposed hypotheses. Cross-functional application integration and financial flow integration predicted exploration, while data consistency and physical flow integration predicted exploitation. Data consistency and cross-functional application integration, on the other hand, predicted both operational efficiency and market knowledge creation. Supply chain managers planning to deploy RFID systems are alerted to the criticality of these IT infrastructure issues as they brace for a likely widespread implementation of RFID in supply chains they participate in.     

基于中频采样的星载合成孔径雷达的数据处理

研究了基于中频采样的星载合成孔径雷达(synthetic aperture RADAR, SAR)数据处理技术及其FPGA实现. 常规星载SAR系统对模拟解调后的视频数据进行采样,然后对数据进行压缩和格式化处理并下传. 采用中频采样技术实现星载SAR数据的正交解调和处理,对数字正交解调算法和合成孔径雷达BAQ压缩算法进行分析,完成FPGA的硬件设计和仿真. 结果表明,基于FPGA实现星载SAR中频采样的数据处理方法可行. 与传统模拟方法相比,中频采样系统性能和可靠性都有提高,是未来星载SAR数据处理的发展趋势.     

一种EPC Gen2 RFID标签时钟校准方法

设计了一种对Gen2 RFID标签的振荡器频率进行校准的方法. 该方法设计了时钟校准命令; 并给出了读写器使用时钟校准命令对标签时钟频率进行逐次逼近的校准过程. 验证结果表明,带有8位校准寄存器的电路可以把时钟偏差从50%校准到0.4%以内.     

g指数在共词分析主题词选取中的应用研究

为了克服共词分析中主题词选取主观性强的缺陷,借鉴g指数的思想,提出一种基于g指数的主题词选取方法——词频g指数。以图书情报学为例,对词频g指数进行了实证分析,并与齐普夫第二定律的选词结果进行比较,得出其选词结果很好的满足二八定律。同时对主题词进行聚类分析得到良好的结果,为共词分析的准确性提供了理论依据。     

关键词词频变化视角下我国“科学数据”领域研究主题演化分析

本文利用CNKI数据库通过词频分析法结合共词分析法对2005-2016年我国"科学数据"领域的研究主题进行演化分析。选取2005-2016年"科学数据"领域发表于北大中文核心期刊和CSSCI来源期刊的547篇期刊论文作为数据来源,通过对数似然值结合相对变化率判断关键词词频的相对增长、平稳和下降趋势,识别不同研究时段"科学数据"领域的核心词、突变词和新生词,并结合共词分析法揭示"科学数据"领域相关文献研究主题的动态演化趋势。研究结果表明：2005-2016年我国"科学数据"领域的相关研究从以技术层面的研究主题为主逐渐过渡到管理层面、服务层面和政策层面的研究主题,图书情报领域已逐渐成为我国"科学数据"相关研究的主要学科领域。     

期刊单元下参考文献与论文被引频次间的关系——以Web of Science凝聚态物理学科为例

【目的】 探究参考文献各指标与论文被引频次之间的关系,为撰写高被引论文、科学评价计量学指标等提供参考。【方法】 以2013年Web of Science中凝聚态物理学科下的12种期刊共计8847篇论文为样本数据,利用负二项回归模型测度了参考文献的4类指标与论文被引频次之间的关系。【结果】 在控制期刊影响因子的前提下,12种期刊的代表时间维度的普赖斯指数都与论文被引频次之间存在显著的正相关关系;在大多数期刊中,参考文献的数量和表征跨学科性的香农指数也对论文的被引频次有显著正影响;而表征论文质量的篇均参考文献被引频次中值与论文被引频次之间的相关关系不明确。【结论】 参考文献的一些指标可能影响论文的被引频次,结合实证结果,对科研工作者合理利用参考文献产出高质量论文提出相应建议。     

Step-to-step spatiotemporal variables and ground reaction forces of intra-individual fastest sprinting in a single session

We aimed to investigate the step-to-step spatiotemporal variables and ground reaction forces during the acceleration phase for characterising intra-individual fastest sprinting within a single session. Step-to-step spatiotemporal variables and ground reaction forces produced by 15 male athletes were measured over a 50-m distance during repeated (three to five) 60-m sprints using a long force platform system. Differences in measured variables between the fastest and slowest trials were examined at each step until the 22nd step using a magnitude-based inferences approach. There were possibly–most likely higher running speed and step frequency (2nd to 22nd steps) and shorter support time (all steps) in the fastest trial than in the slowest trial. Moreover, for the fastest trial there were likely–very likely greater mean propulsive force during the initial four steps and possibly–very likely larger mean net anterior–posterior force until the 17th step. The current results demonstrate that better sprinting performance within a single session is probably achieved by 1) a high step frequency (except the initial step) with short support time at all steps, 2) exerting a greater mean propulsive force during initial acceleration, and 3) producing a greater mean net anterior–posterior force during initial and middle acceleration.