Long-term variations of water quality in a reservoir in China

To study the spatial and temporal trends of water quality in the Yuqiao Reservoir (Ji County, Tianjin) in China, water quality data for ten physical and chemical parameters from three monitoring stations (S1, S2 and S3) was collected from 1989 to 2007 and from an other three stations (S4, S5 and S6) during the period of 1999-2007. A one-way ANOVA was employed to evaluate the spatial variation of water quality for each station. The results showed that there were statistically significant spatial differences for most water quality parameters except temperature and dissolved oxygen in the entire reservoir, and the concentrations of most parameters were higher in the uppermost part of the reservoir. The temporal trend study was conducted using the Seasonal-Kendall's test. The results revealed improving trends of water quality from 1989 to 2007, including a reduction of total phosphorous, temperature and biochemical oxygen demand and an increase of dissolved oxygen. High N:P ratios, ranging from 52.61 to 78.75, indicated that the reservoir was a phosphorous-limited environment. This study suggests long-term spatial and temporal variations of water quality in the Yuqiao Reservoir, which could be informative for water quality managers and scientists.     

基于Nios Ⅱ的多功能数码相框

介绍了基于Nios Ⅱ的多功能数码相框的实现。系统基于Nios Ⅱ处理器,设计用户自定义模块,构建了灵活性高、可重配置的SoPC系统。设计自定义模块控制LCM显示;采用流水线方式设计JPEG解码自定义模块以提高解码效率;根据SD协议设计SD卡控制器扩展SD卡。实现了FAT16文件系统,便于对SD卡进行文件管理及多平台上的数据交换,并使用μC/OS-Ⅱ操作系统简化软件设计复杂度、提高系统稳定性。最终实现可播放音频并能显示、缩放、旋转图像且带有图像切换特效的多功能数码相框。     

Automatic cage generation by improved OBBs for mesh deformation

In cage-based deformation, the most tedious task is to construct the coarse cage bounding a model. Currently, the coarse cage is constructed mainly by hand, and the construction usually takes several hours, even longer. Therefore, it is important to develop a convenient method to generate the coarse cage bounding a model. In this paper, we devise a method to construct the coarse cage automatically using the improved OBB tree, while allowing the users to modify the cage easily. Firstly, the OBB tree bounding the model is generated, where we propose an improved OBB slicing rule to make the generated OBBs close to the model it contains. Secondly, the OBBs are adjusted and merged into a whole entity by the boolean union operation. Finally, the outer surface of the entity is extracted as the coarse cage. Empirical results demonstrate the effectiveness and efficiency of the automatic coarse cage-generation method.     

Pareto-optimal coordination of multiple robots with safety guarantees

This paper investigates the coordination of multiple robots with pre-specified paths, considering motion safety and minimizing the traveling time. A method to estimate possible collision point along the local paths of the robots is proposed. The repulsive potential energy is computed based on the distances between the robots and the potential collision points. This repulsive potential energy is used as the cost map of the probabilistic roadmap (PRM), which is constructed in the coordination space for multiple robots taking into account both motion time cost and safety cost. We propose a search method on the PRM to obtain the Pareto-optimal coordination solution for multiple robots. Both simulation and experimental results are presented to demonstrate the effectiveness of the algorithms.     

Track following servo control for rotary piezoelectric motor based primary actuation in hard disk drives

In this paper, we show the tracking performance of a rotary piezoelectric motor based hard disk drive actuator. The actuator is built and modeled for positioning servo in disk drive systems. The Piezo motor replaces the voice-coil-motor based primary actuation. Simulation and experimental results for its servo system proves that it can help to achieve track density of more than 1000?KTPI.     

Laguerre超群上的Hardy-Littlewood-Sobolev不等式

利用Laguerre超群K上的广义次拉普拉斯算子L定义K上的Riesz位势,并证明它是Lp(1p+∞)有界和弱(1,1)有界的,即证明K上的Hardy-Littlewood-Sobolev不等式.它为进一步分析K上的偏微分方程问题提供了一个有利的工具.     

一种与材料状态相关的砂土剪胀性理论模型

结合密砂和中密砂的相变点的概念,提出了以相变状态为参考状态的状态参量表达式,并将此状态参数引入剪胀比的计算公式.在修正剑桥模型的基础上,提出了新的塑性势函数和硬化参数表达式以消除应力路径的影响.在增量塑性理论的基础上,建立了一种适合于密砂和中密砂的与材料状态相关的剪胀性理论模型.     

循环流化床灰对聚羧酸减水剂竞争吸附的影响研究

为研究循环流化床灰对聚羧酸减水剂竞争吸附的影响,通过在Ⅱ级粉煤灰中掺加无水硫酸纳、二水硫酸钙和氧化铁的方式来改变粉煤灰中三氧化硫和氧化铁含量,使其化学成分接近循环流化床灰,利用成分单因素分析的方法,测试减水剂水泥浆体的净浆流动度、zeta电位和混凝土性能.研究结果表明循环流化床灰中的三氧化硫和氧化铁对聚羧酸减水剂的吸附有明显负面影响,当可溶性硫酸盐掺量达到胶凝材料的3%、氧化铁掺量达到6%时,相应浆体均失去流动性.Zeta电位试验表明随着无水硫酸钠和氧化铁掺量的增大,Zeta电位绝对值越小,粒子间相互斥力越弱,分散性越差,分散体系就越不稳定.混凝土性能试验表明无水硫酸钠和氧化铁的掺入使得混凝土的流动性和抗压强度均变小,坍落度由220 mm降至125 mm,强度降低幅度最高达45%.