Nonsymbolic and symbolic magnitude comparison skills as longitudinal predictors of mathematical achievement

What developmental roles do nonsymbolic (e.g., dot arrays) and symbolic (i.e., Arabic numerals) magnitude comparison skills play in children's mathematics? We assessed a large sample in kindergarten, grade 1 and 2 on two well-known nonsymbolic and symbolic magnitude comparison measures. We also assessed children's initial IQ and developing Working Memory (WM) capacities. Results demonstrated that symbolic and nonsymbolic comparison had different developmental trajectories; the first underwent larger developmental improvements. Both skills were longitudinal predictors of children's future mathematical achievement above and beyond IQ and WM. Nonsymbolic comparison was moderately predictive only in kindergarten. Symbolic comparison, however, was a robust and consistent predictor of future mathematics across all three years. It was a stronger predictor compared to nonsymbolic, and its predictive power at the early stages was even comparable to that of IQ. Furthermore, the present results raise several methodological implications regarding the role of different types of magnitude comparison measures.     

基于网络的大学英语考试系统设计与开发

随着计算机技术和网络技术的发展,计算机辅助考试（CAT）从单机走向网络化.为了适应未来新的考试模式,设计了＂基于网络的大学英语考试系统＂.该系统采用三层结构的C/S和B/S混合模式,选择delphi编程语言,使用SQL Server 2000数据库作为系统开发工具.本文分析了系统功能模块的组成,研究了试题抽取技术,同时提出了翻译题阅卷策略.     

伽玛分布的优良特性及其在风险管理中的应用

研究了伽玛分布的优良特性以及平移伽玛近似,以便在风险管理中更好的运用它们.     

Indexing the bit-code and distance for fast KNN search in high-dimensional spaces

Various index structures have recently been proposed to facilitate high-dimensional KNN queries, among which the techniques of approximate vector presentation and one-dimensional (1D) transformation can break the curse of dimensionality. Based on the two techniques above, a novel high-dimensional index is proposed, called Bit-code and Distance based index (BD). BD is based on a special partitioning strategy which is optimized for high-dimensional data. By the definitions of bit code and transformation function, a high-dimensional vector can be first approximately represented and then transformed into a 1D vector, the key managed by a B -tree. A new KNN search algorithm is also proposed that exploits the bit code and distance to prune the search space more effectively. Results of extensive experiments using both synthetic and real data demonstrated that BD out- performs the existing index structures for KNN search in high-dimensional spaces.     

露天矿生产的车辆安排

旨在解决露天矿实际生产中运输车辆的统筹分配问题,根据线性规划原则的思想,建立方程、不等式,分析有关决策变量,确定车辆具体安排,从而实现最优.     

基于广义Logistic赤潮模型的变结构控制

基于广义Logistic种群生长模型,建立一个浮游动植物相互作用模型,利用微分方程稳定性理论分析其平衡点的性态,得到模型由稳定到周期解的阈值.设计变结构控制器,抑制赤潮周期性爆发.最后,通过仿真模拟,验证结论的正确性.     

利用Monte Carlo方法与渐进展开式近似计算ln2

本文从三方面讨论ln2的近似值的计算问题,首先从槡2的近似值出发通过构造函数估计ln2的近似值,其次利用Monte Carlo方法编写SAS程序近似计算ln2,最后利用ln2的一些渐进展开式近似计算ln2,所得结果有利于估计ln2近似计算中的误差和扩散学习思维。     

Use of permutation prefixes for efficient and scalable approximate similarity search

We present the Permutation Prefix Index (this work is a revised and extended version of Esuli (2009b), presented at the 2009 LSDS-IR Workshop, held in Boston) (PP-Index), an index data structure that supports efficient approximate similarity search.     

岳阳月田话的概数助词“把”

概数助词"把"是月田话中的一个高频词,文章试从"把"对数量词的选择,"把"的句法分布和语法意义等方面进行分析,并通过与其他方言的比较来展示其独特之处。     

与近似凸集有关的一个集合

给出了与近似凸集有关的一个集合的一些性质及它的闭包的证明,并由此给出近似凸函数的类似性质。