The role of calcium in blended fly ash geopolymers

In this research effort, the role of calcium in geopolymers was investigated through a series of syntheses where a high-calcium fly ash was blended with a low-calcium fly ash. Increased calcium content led to accelerated set-up times, increased compressive strength, and increased product formation. Powder X-ray diffraction results showed the majority of that product to be geopolymer framework with only minor contributions from calcium silicate phases. Thermal analysis confirmed the absence of a calcium silicate hydrate phase. Analysis of fly ash dissolution showed that calcium aided in aluminosilicate dissolution and therefore the geopolymerization reaction. While aiding in this reaction, calcium became incorporated into the pore structure of the geopolymer as a counter-balancing cation, according to ion exchange experiments. Thus, geopolymer synthesis with increased calcium content through the use of a high-calcium fly ash under these experimental conditions produced a quick-setting, strong, calcium incorporated geopolymer material.     

Tensile behaviour of patch-repaired CFRP laminates

The present study examines the tensile behaviour of composite structures repaired by bonding external patches. Various patches of different stacking sequences placed on both sides of the parent plate were considered. Damage development and the failure process of the repaired plates were analyzed and a parent plate fracture model has been proposed. Optimised patch repairs were calculated by finite element modelling. It was found that high stress concentration along the longitudinal edges of circular patches and/or at the transverse edges of the hole leads to early damage initiation in the parent plate. However, the position of damage initiation and the process of damage progression depend particularly on the properties of repair patches. In order to optimise patch repairs, finite element modelling was used and it was founded possible to attain over 90% of the strength of an unnotched specimen. The optimised patch design can be characterised by an optimal strength ratio R^*, which should be minimized when selecting repair parameters.     

Pressure dependence of morphology and phase composition of SiC films deposited by microwave plasma chemical vapor deposition on cemented carbide substrates

SiC films were deposited on cemented carbide substrates by employing microwave plasma chemical vapor deposition method using tetramethylsilane (Si(CH₃)₄) diluted in H₂ as the precursor. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and scratching technique were used to characterize morphology, composition, phases present and adhesion of the films. Experimental results show that the deposition pressure has great influence on morphologies and phase composition of the films. In sequence, SiC films with a cauliflower-like microstructure, granular films with terrace-featured SiC particles coexisting with Co₂Si compound and clusters of nanometer SiC nanoplatelets appear as a function of the deposition pressure. In terms of plasma density and substrate temperature, this sequential appearance of microstructures of SiC films was explained. Adhesion tests showed that among the three types of films studied, the films with the terrace-featured SiC particles have relatively higher adhesion. Such knowledge will be of importance when the SiC films are used as interlayer between diamond films and cemented carbide substrates.     

May the force be with you [electrostatics applications]

Although commonly viewed as a serious hazard, static electricity can transform the effectiveness of many industrial processes. Here, the author reports on some of the latest developments in harnessing electrostatic forces     

Oxidative degradation of diethyl phthalate by photochemically-enhanced Fenton reaction

A kinetic investigation into the photo-degradation of aqueous diethyl phthalate by Fenton reagent was conducted in this study. The obtained results showed the enhancement of diethyl phthalate (DEP) decomposition by UV irradiation with the Fenton reaction. It was found that H2O2 concentration, Fe2+ concentration, and aqueous pH value were the three main factors that could significantly influence the degradation rates of DEP. The highest degradation percentage (75.8%) of DEP was observed within 120 min at pH 3 in the UV/H2O2/Fe2+ system, with original H2O2 and Fe2+ concentrations of 5.00 x 10(-4) and 1.67 x 10(-4)mol L(-1), respectively. The present study provides an effective approach to the treatment of wastewater containing DEP.     

Leadership and the spatial factor in small groups.

The present study extends the hypothesis that "persons tend to interact more in group discussion with persons sitting opposite them than they do with their neighbors." This effect seems to be manifested most strongly in groups with no designated leader. "It will tend to disappear in groups where group direction is shared about equally by the members and the designated leader, and it will be reversed in situations where the designated leader gives very strong direction." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

SP3-coupled global variance reduction method based on RMC code

A global variance reduction(GVR)method based on the SPN method is proposed.First,the global multi-group cross-sections are obtained by Monte Carlo(MC)global homogenization.Then,the SP3 equation is solved to obtain the global flux distribution.Finally,the global weight windows are approximated by the global flux distribution,and the GVR simulation is performed.This GVR method is implemented as an automatic process in the RMC code.The SP3-coupled GVR method was tested on a modified version of C5G7 benchmark with a thick-ened water shield.The results show that the SP3-coupled GVR method can improve the efficiency of MC criticality calculation.     

胶束电动毛细管色谱法分析3种交链孢毒素主成分含量

目的 建立胶束电动毛细管色谱法(micellar electrokinetic chromatographic, MEKC)测定3种交链孢毒素[交链孢酚(alternariol, AOH)、交链孢酚单甲醚(alternariol monomethyl ether, AME)和交链孢菌酮酸(tenuazonic acid, TeA)]主成分含量的新分析方法。方法 以未涂层熔融石英毛细管柱(50μm×30 cm, 20 cm, i.d.)为分离柱,分别以3种分离缓冲溶液[40 mmol/L Na_2B_4O_7-120 mmol/L十二烷基硫酸钠(sodium dodecyl sulfate, SDS)(含体积分数为5%的乙腈)、30mmol/LNa_2B_4O_7-40mmol/LSDS(含体积分数为30%的异丙醇)和60mmol/L Na_2B_4O_7-180 mmol/L脱氧胆酸钠]及2种样品缓冲溶液[8 mmol/L硼砂(含体积分数为57%的甲醇用于AOH和TeA)、8mmol/L硼砂(含体积分数为57%的异丙醇用于AME)]分析AOH、AME和TeA的主成分含量。结果 AOH、AME、TeA的方法精密度分别为0.05%、0.01%和0.21%(n=5),检出限分别为5、15和0.5 mg/L。主成分含量分别为99.94%、99.78%和97.28%,且与高效液相色谱法(high performance liquid chromatography, HPLC)的结果无显著差异(α=0.05)。结论 MEKC法可作为HPLC法测定3种交链孢毒素主成分含量方法的互补方法 ,能够满足3种交链孢菌毒素主成分含量分析的要求。