基于UPSD32xx的串口-以太网转换器设计

本文详细地说明了基于UPSD32xx控制器与RTL8019AS芯片实现串口和以太网互连的过程,并在此基础上研究了转换器参数配置的几种方法,使得我们可以根据实际需要选择最佳的配置方法来完成我们各种通信参数的设置工作,从而满足大众化的需求。     

Is academic tracking related to gains in learning competence? Using propensity score matching and differential item change functioning analysis for better understanding of tracking implications

This study analyzes gains in cognitive components of learning competence with respect to cohorts based on ability tracking in a Czech longitudinal study. Propensity score matching is used to form parallelized samples of academic and non-academic track students and to eliminate the effect of selective school intake. We applied regression models on the total scores to test for the overall track effect. Furthermore, we analyze scores and gains on the subscores and check for differential item functioning in Grade 6 and in change to Grade 9. While after 3 years, no significant difference between the two tracks was apparent in the total learning competence score, we did, however, find significant differences in some subscores and in the functioning of some items. We argue that item-level analysis is important for deeper understanding of the tracking implications and may provide the basis for more precise evidence-based decisions regarding the tracking policy.     

单片机以太网嵌入式系统的实现方法

随着INTERNET在中国的普及,针对INTERNET的各种技术也随之产生.目前,以太网协议已经广泛地应用在各种计算机网络,如办公局域网、工业控制网络、因特网等场合.基于以太网协议的各种设备也不断出现.本文介绍了用8位单片机采用以太网协议通过因特网传输数据的技术.     

因特网AS级拓扑测量和分析的进展

测量和分析因特网AS级拓扑是研究因特网宏观特征和选路行为的基本手段。概述了两种测量AS级拓扑的方法,即从包含BGP选路信息的数据中发现AS级拓扑和从traceroute测量数据生成AS级拓扑;对比了不同测量数据的涵义和完整性;综述了多种分析因特网拓扑特性的测度;讨论了AS商业关系及相关选路行为的研究现状;给出了当前面临的技术挑战。     

Mass Transfer of MTBE in Groundwater During Air Sparging

A one-dimensional column is set up to study the mass transfer during air sparging process for methyl tertiary butyl ether(MTBE) removal in saturated soil and groundwater, with the condition of different airflow and soil penetrability. It is shown that the removal rate of MTBE can reach 80%, 90% and 95% when airflow is 0.05 m3/h, 0.085 m3/h and 0.10 m3/h, respectively. Increasing airflow will help to increase the removal rate of dissolved MTBE, but eventually a threshold removal rate is reached, above which further increasing air injection rates does not increase the removal rate. Fine sand allows the injected air to travel in bubble form, while coarse sand and medium sand allow the injected air to travel in the form of discrete channels; the greater the soil grain size is, the more extensive the channel net work forms, which in turn leads to higher removal rate. A tailing effect of lingering residual contaminant concentrations occur within the fine sand. About 20% of MTBE cannot be removed.     

遗传算法在双深式自动化立体仓库货位分配中的应用

双深式自动化立体仓库是一种新兴的高效仓储系统,相比传统的自动化立体仓库,它可以有效降低运营成本和减少用地面积,但其结构的特殊性却给货位优化提出了更高的要求。为了提高货位优化的效率,采用两级库位编码的方式对双深式立库的货位分配进行研究,建立了关于货架稳定性和出库效率两个方面的多目标优化数学模型,然后利用遗传算法进行求解,最后在MATLAB仿真软件中进行仿真实验。实验结果表明,遗传算法可以很好地实现双深式立库的货位优化,极大提高了双深式立库的工作效率。     

运动与脂联素的研究进展

脂联素(Acrp30)是一种新的由脂肪细胞特异分泌的蛋白,具有调节糖脂代谢、抗炎症反应、抗动脉粥样硬化等多种效应.综述了Acrp30与AS、肥胖、糖尿病、及心血管疾病密切相关以及运动对Acrp30含量变化的影响的研究进展.     

一种用于双负载重力货架自动存取系统的排序方法(英文)

重力货架自动存取系统的双提取操作排序问题等价于在一组提取货物中进行两两配对以生成最小执行成本的双提取操作序列,因此双提取操作排序问题被建模为一个匹配问题.提出一个基于匈牙利方法的启发式方法 RSHM来生成具有最小总行驶时间的双提取命令.为了保证生成可行的双提取操作序列,对称标记法被引入RSHM;为了打破对称标记法引起的无限循环,RSHM被设计成一个递归过程.仿真实验对双负载装卸设备的成本效益和RSHM的性能进行了评价和分析.仿真实验结果显示:与单负载设备相比,采用双负载装卸设备可以节省超过40%的提取操作总行驶时间;与贪婪规则相比,RSHM能够减少5%~10%的总行驶时间.     

嵌入式以太网通讯模块的设计

提出了一种基于单片机的嵌入式以太网通讯模块的设计方案,搭建了系统的硬件平台,实现了嵌入式简化TCP/IP协议栈,系统运行稳定、可靠.该解决方案为现代工业控制、智能建筑等领域的数据传输和采集提供了一个可移植的应用平台.     

基于Flash CS4中AS3多媒体演示动画的设计与实现

多媒体演示动画是Flash动画有广阔前景的一个应用领域。本文阐述了多媒体演示动画完整的设计与实现过程,并详细介绍了如何利用AS3实现影片的跳转、音乐的添加等制作过程中常用的功能。