混凝土冻融劣化后动态单轴抗压特性试验研究

为研究混凝土冻融循环后的动态力学性能,利用10 MN动静三轴仪对不同冻融劣化程度的混凝土在不同加载速率下进行单轴压缩试验,同时采集声发射数据分析试验过程中能量释放及损伤演化规律。最后,选用Weibull-Lognormal损伤本构模型,对试验数据进行拟合分析,并分析不同工况混凝土的损伤随应变的发展规律。研究结果表明:①相同冻融劣化程度时,随应变速率增加,峰值应力增大,峰值应变减小;冻融劣化程度会影响峰值应力的率敏感性;②在应变速率相同时,随冻融循环次数增加,峰值应力随之减小,峰值应变随之增大。③混凝土冻融劣化后应力应变关系峰前服从Weibull统计分布,峰后服从Lognormal统计分布。④在相同应变速率下,随着冻融循环次数的增加,混凝土的累计塑性应变整体呈增大趋势。     

基于层面参数等效的碾压混凝土坝渗流场与应力场耦合分析

受施工、龄期、环境及服役期大坝承受的反复静动荷载等多因素影响,坝体和层面出现不同程度的劣化损伤,碾压层本体及层面物理参数呈渐变特性。针对碾压层内力学参数渐变的特性,提出了相应物理参数的等效算法,且给出了耦合性态参数间的数学转换关系,分析坝体应力场与渗流场相互影响机理,据此建立了考虑层内参数渐变的碾压混凝土坝渗流场与应力场耦合分析模型,并编制了相应的有限元分析程序。工程实例分析表明,耦合作用致使大坝的渗流场发生改变,坝体的应力较未耦合时普遍偏大,坝踵处的应力集中显著;渗流场与应力场耦合作用激励下的不利因素可为大坝的设计、施工及安全运行提供参考。     

PEO/Na-MMT粉体与聚氯乙烯复合材料的制备及性能研究

通过溶胶凝胶法,制备了聚氧乙烯(PEO)和钠基蒙脱土的复合粉体PMMT,经XRD和透射电镜分析,蒙脱土在聚氯乙烯中基体进行了纳米级的分散;通过对材料力学性能、毛细管流变和TGA测试表明,PMMT对聚氯乙烯具有增韧和增强的效果,同时使PVC的流变性和热稳定性也有一定的提高。     

循环水冷却塔的改造

分析了循环水冷却塔存在的问题,重点论述了冷却塔的改造及其经济效益。     

Phase holdup and liquid dispersion in gas-liquid-solid circulating fluidized beds

Axial and radial profiles of gas and solids holdups have been studied in agas-liquid-solid circulating fluidized bed at 140mm i.d..Experimental results indicate that the axialand radial profiles of gas and solids holdups are more uniform than those in a conventionalfluidized bed.Axial and radial liquid dispersion coefficients in the gas-liquid-solid circulating fluidizedbed are investigated for the first time.It is found that axial and radial liquid dispersioncoefficients increases with increaes in gas velocity and solids holdup.The liquid velocity has littleinfluence on the axial liquid dispersion coefficient,but would adversely affect the redial liquiddispersion coefficient.It can be concluded that the gas-liquid-solid circulating fluidized bed hasadvantages such as better interphase contact and lower liquid dispersion along the axial directionover the expanded bed.     

Event-driven observer-based output feedback control for linear systems

This paper concerns the problem of event-driven observer-based output feedback control of linear systems. Contrary to normal sampled-data control systems, where the controller is updated periodically, in event-driven systems, it is updated only when an “event” happens, and a typical event is defined as some error signals exceeding a given threshold. Both continuous- and discrete-time event detector cases are considered. It is shown that even with the significantly reduced sampling frequency, the global uniform ultimate boundedness of the event-driven closed-loop systems can also be guaranteed. A numerical example is finally used to illustrate the effectiveness and advantages of the proposed approaches.     

Observability of linear systems with commensurate delays and unknown inputs

This paper investigates the observability analysis for linear time systems whose outputs are affected by unknown inputs. Three different definitions of observability are proposed. By introducing the Smith form and comparing the invariant factors, a sufficient condition is deduced for each proposed observability definition. Three examples are given for the purpose of highlighting the effectiveness of the proposed approach.     

甲基二氯硅烷的化学反应及其综合利用

简述了甲基二氯硅烷的硅氢化反应、热缩合反应、水解反应和醇解反应，及其重要反应产物甲基氯丙基二氯硅烷、甲基乙烯基二氯硅烷、甲基三氟丙基二氯硅烷、甲基苯基二氯硅烷、甲基含氢环体和含氢硅油的制备和应用。     

碘掺杂的聚二茂铁基席夫碱的合成与性能研究

利用二茂铁甲醛与对、间、邻苯二胺在中性条件下缩合,得到了3种小分子二茂铁基席夫碱,利用Friedel-Crafts反应合成了一类新型的导电聚二茂铁基席夫碱,然后用碘对其进行掺杂,得到了系列电荷转移配合物.聚合物的电导率经碘掺杂后可提高几个数量级,同时均有紫外吸收功能;其中碘掺杂聚对二茂铁基席夫碱配合物的电导率最高,达3.17×10-4S/cm,而碘掺杂聚邻二茂铁基席夫碱配合物的磁增重另外2种配合物的2～3倍.     

纳米钛酸钡的制备及表征

以硝酸钡与偏钛酸为原料,用共沉淀法制备了钛酸钡纳米粉体。研究了沉淀温度、洗涤条件及煅烧温度对钛酸钡纯度、粒径和晶形的影响。结果表明,在0℃下制得沉淀产物,并以先水洗后醇洗的方式去除杂质和水分,在800℃下煅烧2h,可得到粒径约为60nm的钛酸钡,粒径均匀,团聚较小。