Study and Application Progress of Virtual Water

虚拟水是解决水资源短缺和粮食安全问题的新途径,是目前国际新兴的研究热点。文中系统地阐述了虚拟水的概念和内涵,归纳总结了关于产品的虚拟水含量的计算方法,包括基于不同产品类型区别计算的方法和产品生产树的方法。并且介绍了虚拟水的应用情况,还对今后的研究方向进行了探讨。Virtual water,a new research topic,is considered as an innovative solution to solve the problem of water scarcity and food security.This study expounded the concept and connotation of virtual water,and also summarized the methodologies to calculate virtual water,in terms of the methods based on distinguishing calculation of different product and the methods of production tree.Furthermore,the application of virtual water,as well as its further study directions was introduced.国家自然科学基金(40701178);福建省自然科学基金(2009J01190);中央高校基本科研业务费项目(厦门大学教师类基础创新科研基金)(2011121008

Water-quality impact assessment on open-sea reclamation planning——A case study of Fujian Province,China

基于开阔海域围填海的特殊性,已有的水质影响评价定量方法较难直接应用。本文通过水动力因子分析确定污染物扩散条件,根据水质现状、围填面积和规划利用方式确定水质压力。基于上述污染物扩散条件和水质压力参数,以水质影响程度等级作为评价结果,设计了半定量评价矩阵对福建省湾外围填海规划的10个围填区进行了水质影响评价。评价结果表明:其中有1个围填区水质影响程度较大,其余围填区水质影响程度均在中等以下。此外,水质影响程度评价结果可同时为湾外围填海规划决策者提供相应的决策依据。案例应用表明:该半定量方法可以推广应用于决策型的、影响机制复杂、不确定性较强的人类活动的水质影响评价。The marine reclamation is one of the major kinds of coastal projects,which may cause the negative impacts on water quality.Due to the particularity of reclamation in open-sea,the existing quantitative methods of water-quality impact assessment are inapplicable.In this study,an assessing matrix based on the pollutant diffusion condition and water quality pressure was developed to predict the water-quality impacts of 10 reclamation blocks in the planning of reclamation outside bays in Fujian Province.In which,the diffusing condition of pollutants is determined by the hydrodynamic analysis,and the pressure on water quality is determined by the analyzing current water quality,reclamation areas and their functions.The application of this semi-quantitative matrix,the results showed that the water quality impact of one reclamation area is comparative high,while others have lower impacts.These results of different impact degrees of water quality provided a supporting tool for the environmental management decision-making.The successful application in the case study also reveals that the semi-quantitative water-quality impact assessment methodology can be applied to those with the complicated impact mechanism,highly uncertain and decision-supportive anthropogenic impacts.国家海洋公益项目(200905005-06);2011年度“厦门大学基础创新科研基金”(中央高校基本科研业务费专项资金)项目(2011121008

Optimization of medium components for inulinase production of a strain using Taguchi method

鉴定一株从菊芋根际土壤中分离出的产外切型菊粉酶活力较高的菌株C-56。通过16S r DNA序列分析构建系统发育树,初步确定菌株的分类地位,利用单因素实验和田口方法优化培养基配方。实验发现菌株C-56属于伯克霍尔德氏菌属(Burkholderia),单因素实验确定菌株产酶的最佳碳源、氮源、无机盐分别为菊粉、酵母膏、MgSO_4&middot;7H_2O。应用田口方法优化菌株的培养基,统计学分析发现菊粉对菌株产酶的影响最大,最佳培养基配方为菊粉50 g/L,酵母浸粉20 g/L,Mg SO_4&middot;7H_2O 6 g/L,p H6.0。在最佳条件下获得的菊粉酶活力为(29.34&plusmn;1.95)U/m L,比初始菊粉酶酶活力(6.25&plusmn;0.84)U/m L提高了3.69倍。</p

基于神经网络-牛顿混合算法的盾构机掘进位姿求解研究

为了解决盾构机推进系统运动学建模及正解求解困难等问题，采用简化等效模型法，构建了盾构机推进系统简化模型，将n-SPS的盾构并联推进系统简化为4-SPS的等效并联推进机构，并构建其运动学模型。根据建立的等效机构运动学模型，采用神经网络-牛顿混合算法求解盾构掘进位姿；利用神经网络的解域搜索功能，对初值进行预测并把预测结果代入牛顿迭代法进行计算求解，分析比较了单一神经网络预测值与BP神经网络-牛顿迭代混合算法计算结果的优劣性。研究发现，盾构机推进系统等效模型的建立可以大大简化运动学建模复杂度，而且利用混合算法求解运动学正解的求解精度更高，可以提高盾构机掘进位姿控制精度，从而提高掘进隧洞质量

机床主轴轴承摩擦生热特性分析

为研究圆柱滚子轴承摩擦生热特性，构建了一种考虑了主轴-轴承装配过盈量、离心力以及配合表面粗糙度的拟静力学分析模型。应用局部法计算得到轴承各部件间的摩擦生热量，通过实例分析了不同工况条件以及润滑参数对摩擦生热的影响。结果表明，轴承转速及外载荷对摩擦生热量有较大影响，转速越高，摩擦生热量增长越明显；润滑油动力黏度或油气比例系数的增大，均使得轴承摩擦生热量出现增长的趋势

弹流润滑状态下机床主轴轴承刚度特性分析

圆柱滚子轴承的刚度特性会对机床动态性能产生较大影响。在双列圆柱滚子轴承力学分析的基础上，综合赫兹接触与润滑油膜对轴承刚度的影响，分析了不同工况以及润滑参数下的轴承刚度变化特性。分析结果表明，弹流润滑产生的润滑油膜会使轴承综合刚度下降；随着外载荷的增大，赫兹刚度与油膜刚度均有所提升，轴承综合刚度提高；提升轴承预紧量有利于提高轴承综合刚度；随着转速的提升，轴承综合刚度呈下降趋势；润滑油动力黏度以及黏压系数的增大均使得轴承综合刚度下降

China Survey Report on High Schools' Online Learning Status During the Pandemic

Highlights We examined the results of a large-scale national survey of online secondary education in China. The online survey of 33,194 high school students and 5,667 teachers has provided comprehensive and representative data regarding the quality of online education and its implementation during the pandemic. Questionnaire surveys administered to students and teachers in different grades and comparative analysis of different cohorts revealed group heterogeneity of the online learning effect. The findings have elucidated the emergency teaching situation in China during the pandemic, yielding targeted suggestions for school education following the resumption of classes

基于齐次变换矩阵的盾构机掘进位姿建模与求解研究

为了更加精确快速地求解盾构机在掘进过程中的姿态变化，采用基于空间齐次变换矩阵元素的位姿正解求解方法建立盾构机位姿正解解算模型，并利用牛顿拉夫逊算法对得到的以齐次变换矩阵元素为未知量的非线性方程组进行逐次迭代求解，得到齐次变换矩阵各元素数值解；然后，根据齐次变换矩阵各元素与位姿映射关系求解对应位姿。并根据各个液压缸杆长约束条件建立位姿反解数学模型，在Matlab中对位姿正反解进行求解，并分析比较正反解结果的吻合度。结果表明，其误差在0.018%左右，在误差允许范围内，证明了所建立的盾构掘进位姿正反解数学模型的正确性