Effect of polycarboxylate-type superplasticizer on the paste fluidity based on the water film thickness of flocs

The excess water film theory and the properties of flocs are integrated to examine the effect of the polycarboxylate-type superplasticizer on the paste fluidity.The theory states that excess water can surround the flocs rather than the particles and that the cell consists of a floc and a superficial water film.Experiments on limestone powder pastes were conducted to verify the theory.The superplasticizer dosage(sp%)and the water–powder ratio by volume(Vw/Vp)were systematically varied.A sedimentation balance method was used to measure the size distribution of the flocs in the limestone powder pastes.The water film thickness(WFT)of flocs was then calculated and shown to determine the paste fluidity.Based on this WFT of flocs,the effect of the sp on the paste fluidity was determined and then compared with the effect of water.     

Consecutively spin-assembled layered nanoarchitectures of poly(sodium 4-styrene sulfonate) and poly(allylamine hydrochloride)

The recently established spin-coating electrostatic self-assembly (SCESA) technique has been shown to facilitate not only the rapid fabrication of polyelectrolyte multilayer assemblies, but also allow each layer to be easily controlled on a monomolecular scale by minimizing the film thickness across a substrate surface. In this paper, the influence of polyelectrolyte concentration on the amount and thickness of spin-deposited polymer films has been examined for a multilayer system of poly(allyamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS), when the washing steps employed for removing weakly bound polyelectrolytes on a resultant film on a substrate are excluded from the standard fabrication procedure of the SCESA method. The thickness of the spin-deposited PAH/PSS bilayer increased linearly for the PSS concentrations in the range from 1 to 10 mM with PAH constant at 1 mM, which demonstrates the uniform deposition of each layer material onto the thin film. The thickness of PAH/PSS bilayers increased from 1.43 ± 0.06 to 3.37 ± 0.08 nm as the PSS concentration increased from 1 to 10 mM, while the PAH concentration was kept constant at 1 mM. The multilayer films were found to be stable in a good solvent (H₂O) for at least 30 h, without any noticeable loss of the adsorbed layer component of the polyelectrolyte. This improvement to the SCESA method (exclusion of washing steps) provides a convenient way to create multilayer heterostructures with the thickness of each layer being easily adjusted.     

一种新的三相AC／DC PWM整流器控制策略

为了实现交流输入和整功率因数,提出了一种基于自适应B样条(BS)神经网络的三相PWM整流器控制策略;建立了在线训练BS神经网络的控制规律;提出了神经网络在线学习的新算法;运用空间矢量建模获得整流器的开关常数;使整个控制策略能够适合实时控制和自适应场合．利用DSP技术实现了整个控制策略．同时通过计算机仿真和现场实验证明了这个控制策略不仅具有稳定性好,而且具有响应快和整功率因数等优点．     

采用数字校正、PWM反馈技术的硅微加速度计

本文提出了基于数字信号处理器TMS320F2810的数字控制、PWM静电力反馈硅微加速度计方案.介绍了该方案的基本工作原理,建立了相应的闭环系统数学模型,并在s域设计了系统校正环节.文章还提出了数字校正环节的设计方法,并分析了其对系统动态特性的影响.该方案可以实现硅微加速度计的数字闭环控制,并可以实现加速度计的PWM数字信号输出.     

硬质合金添加陶瓷颗粒3Y-PSZ的实验研究

为研究3Y—PSZ颗粒在外力作用下t→m相变增韧增强金属陶瓷材料的可行性，采用热等静压真空烧结工艺制备不同含量3Y—PSZ的WC-20％Co硬质合金。试验结果表明：3Y—PSZ在WC-20％Co基体中呈球形，均匀分布在Co相和WC相中，添加了3Y—PSZ的WC-20％Co的硬质合金抗弯强度和冲击韧性明显提高，耐磨性能有明显改善。     

Catalytic Activity of Ceria-Zirconia Nanostructured Materials Prepared via Reversed Microemulsion Method

CeO2-ZrO2mixed oxides have a number of i mpor-tant catalytic applications[1].They are extensively em-ployed in current automotive three-way catalysts(TWCs)as the oxygen storage promoters,i.e.materi-als that regulate the oxygen partial pressure throughtheC…     

单质铝水解机理研究(Ⅲ)——单质铝水解结晶过程研究

为了了解单质铝在水解过程中产物物相的变化规律,对单质铝水解过程进行了全过程监测,在反应的不同时段取样并对其进行XRD、SEM分析。以XRD分析结果为依据,对单质铝水解结晶过程中产物物相的变化进行了深入研究,彻底弄清了水解产物的生成顺序。以SEM分析为依据,对影响水解产物形貌、粒度及粒度分布的因素进行了研究。分析认为,团聚、二次成核、搅拌等因素对结晶过程中水解产物的形貌、粒度有显著影响。     

大型机电设备故障诊断装置的实现

为了解决大型机电设备电控系统故障诊断的难题，分析了采用分布式控制方式和模块化结构设计出的一种便携式电控系统故障诊断装置的硬件，介绍了利用多媒体技术的专家系统，该装置成功地解决了大型机电设备电控系统故障排除的难题，并且也可作为其它大型机电设备电控系统进行故障诊断的参考。     

两种标准信号之间的函数变换

用函数变换的方法解决两种标准信号之间的转换，进而阐述了数学在解决实际问题中的应用。     

On the Role of the Law of Large Numbers in the Theory of Randomness

Problems of Information Transmission - In the first part of this article, we answer Kolmogorov's question (stated in 1963 in [1]) about exact conditions for the existence of random generators....