Preparation of a Novel Coal Gangue-Polyacrylamide Hybrid Flocculant and Its Flocculation Performance

A novel flocculant based on hybrid coal gangue-polyacrylamide (HCGPAM) has been prepared by using modified coal gangue and polyacrylamide. Factors related to the preparation such as reaction time, temp...     

毛细管气相色谱法分析工业丙烯腈中噁唑的含量

采用毛细管色谱柱,确立了工业丙烯腈中微量噁唑的最佳分离条件。以丁酮为内标,通过大量的试验,确定了噁唑的相对质量校正因子,建立了定量分析工业丙烯腈中微量噁唑的气相色谱法。方法精密度、准确度及重复性良好。     

Model-Free Predictive Control for a Kind of High Order Nonlinear Systems

一类高阶非线性系统的无模型预测控制

田野 苏佰丽

（曲阜师范大学 工学院,山东 日照 276826）

摘要：

针对一类模型未知的高阶离散非线性系统,提出一种无模型预测控制算法。首先,利用改进的投影算法来逼近被控非线性系统,给出一个估计模型。然后,基于估计模型,通过求解有限时域滚动优化二次函数,设计预测控制器,得到控制器的显式解析解。同时保证了闭环系统的稳定性。仿真结果表明,该控制策略具有良好的稳定性和鲁棒性,且与无模型滑模控制相比,该控制策略具有更快的收敛速度和更稳定的动态特性。

关键词：非线性系统;紧格式动态线性化;模型预测控制;无模型控制;改进的投影算法

     

Ti掺杂对NaAlH4储氢性能的影响

采用基于密度泛函理论(DFT)的平面波赝势(PW-PP)方法,分别计算纯净以及掺杂Ti的NaAlH4和Na3AlH6的晶格结构参数、能量变化和电子态密度(DOS),分析比较Ti掺杂对NaAlH4和Na3AlH6储氢性能的影响。结果表明:Ti掺杂后的晶格结构比原纯净的NaAlH4和Na3AlH6稳定,且脱氢所需能量减少。Ti替代Na后,Ti吸引周围的H原子,使Al-H键变弱;Ti替代Al,Ti-H键比原Al-H键明显减弱,使掺杂后脱氢所需能量降低。通过对比分析Ti掺杂对NaAlH4和Na3AlH6结构和态密度的影响,得出Ti的催化作用主要发生在脱氢反应的第一步。     

自动寻找中心宏程序开发

开发自动寻找工件x和y方向中心宏程序,通过自动记录4处碰刀点x和y的坐标值,根据4点定中心法则计算出工件中心,并自动对G54坐标赋值。省略了已往对刀中手工记录、计算和输入坐标值的3个过程,节约了辅助加工时间,并避免了在3个过程中可能发生的错误,提高了生产效率和对刀准确率。     

低压供气式射流器的性能研究

设计加工了一套供气式射流曝气器清水充氧性能测试装置,并利用该装置对新型的低压供气式射流曝气器进行清水充氧性能研究。清水试验表明：低压供气式射流曝气器氧利用率达16．34％;理论动力效率达2．65～3．05kgO2／kWh。优于其它形式的曝气设备,能有效降低能耗。     

氧化淀粉和聚乙烯醇混合液在高档双胶纸上的应用

纸张的表面强度是决定印刷品质量的重要因素之一。印刷表面强度是指纸张在印刷过程中受到油墨剥离张力作用时所具有的抗掉粉、掉毛、起泡以及撕裂的性能,用纸张的拉毛速度来表示,单位是m／s。     

沂、沭河流域临沂市境内水环境现状及对策

由于经济的高速发展,地表污、废水的排放,沂、沭河流域临沂市境内的地表水遭受到污染;临沂城区地下水的超采,改变了地下水的动力条件,引起地面塌陷,而且有进一步加强的趋势;临沂城区地表污、废水向地下渗透,使地下水受到污染;较低的山区植被覆盖率,导致大量的水土流失,河流产生淤积.为此提出了加强环境执法力度、加强生态环境保护、改善枯水期河流水质、加强水资源管理、合理开采地下水及减少农业面源污染等防治环境恶化的措施.     

The role of cooperatives in food safety management of fresh produce chains: Case studies in four strawberry cooperatives

Recent outbreaks with fresh produce have raised questions regarding management of quality and safety in the complex supply chains, where cooperatives play a central role. The overall objective of this article was to investigate the role of cooperatives in food quality and safety management in the fresh produce chain, focussing on the food safety management systems implemented on the farms. More specifically, we raise the question how a more market-like or a more hierarchy-like governance of transactions via cooperatives affect the quality and safety management system of the members. The research employed case studies in four cooperatives in Belgium and the Netherlands, each with different size and per cent of contractual sales. Data was collected with a diagnostic tool for assessment of food safety management systems (FSMS) on the farms, and semi-structured interviews with the quality assurance managers of the cooperative firms. Twenty-eight strawberry farms were assessed with the diagnostic tool, seven per each cooperative. Cooperatives play a double role in managing quality and safety in the food supply chain. They are responsible for the supply chain management, including tactical decisions about coordination of quality and safety requirements between customers, cooperative firms and their farmers. At the same time, they are selling the products of their members and make strategic decisions about the governance of transactions in the supply chain, which ultimately may have an impact on the supply chain management and the FSMS on the farms. Farmers in cooperatives with more hierarchical relationships showed better operation of control activities (score 3), and advanced assurance activities at score 4 (advanced level), more science-based, adapted and tested for their effectiveness. This was associated with more effort put in supply chain management by the cooperative to support collaboration and coordination in the chain. However, the largest cooperative had moderate scores for several key control functions, suggesting that large cooperatives with complex business functions may suffer from lower commitment of members, leading to lower FSMS performance at farms.     

厚薄承台界定的新方法和梁式模型法的修正

大量的试验与研究结果均表明,梁式模型法适用于多桩薄承台设计,对于厚承台并不适用。通过对国内外桩基承台试验数据统计,确定空间桁架方法和梁式模型方法应用于承台的界限,也即如何定义"薄"承台和"厚"承台;并且通过对试验数据的数学统计,考虑承台底层纵筋对抗剪和抗冲切的有利作用,对梁式模型法的冲切和剪切公式进行了修正。