The effect of fly ash and limestone fillers on the viscosity and compressive strength of self-compacting repair mortars

Today, self-compacting mortars are preferred for repair purposes due to the application easiness and mechanical advantages. However, for self-compactability, the paste phase must meet some certain criteria at fresh state. The cement as well as the ingredients of the paste, powders with cementitious, pozzolanic or inert nature and plasticizing chemical admixtures should be carefully chosen in order to obtain a suitable paste composition to enrich the granular skeleton of the mix. The physical properties of powders (shape, surface morphology, fineness, particle size distribution, particle packing) and physico-chemical (time-dependent hydration reactions, zeta potentials) interactions between cement powder and plasticizer should be taken into consideration. All these parameters affect the performance of fresh paste in different manners. There is no universally accepted agreement on the effect of these factors due to the complexity of combined action; thus, it is hard to make a generalization.This study deals with the selection of amount and type of powders from the viewpoint of fresh state rheology and mechanical performance. The influence of powder materials on self-compactability, viscosity and strength were compared with a properly designed set of test methods (the mini-slump, V-funnel tests, viscosity measurements and compressive strength tests). It may be advised that, for each cement-powder-plasticizer mixture, a series of test methods can be used to determine the optimum content and type of materials for a specified workability.     

Liquefaction of municipal waste plastics in VGO over acidic and non-acidic catalysts

Co-processing of municipal waste plastics (MWP) with vacuum gas oil (VGO) over HZSM-5, DHC-8 (commercial silica-alumina catalyst) and cobalt loaded active carbon catalyst has been comparatively studied. Co-processing experiments were carried out under hydrogen atmosphere at temperatures between 425 and 450 °C. The composition, sulphur and chlorine amount of liquid products were determined. The product distribution and the composition of liquids were changed depending upon the temperature and the catalyst type. As expected temperature led to increase in cracking activity of catalysts. DHC-8 and HZSM-5 showed substantially different activities in co-processing due to the difference in their acidity. HZSM-5 gave highest gas yield at all temperatures and highest liquid yield (38.3) at low temperature. Although Co-AC was a neutral catalyst, it showed the cracking activity as well as HZSM-5 and more than DHC-8. No chlorine compound was observed in liquid products. The sulphur amount in liquid products varied with the catalyst type. Although HZSM-5 showed good cracking activity at low temperatures, it gave the liquid product containing highest sulphur amount. By considering both the quantity and quality of liquid fuel obtained from co-processing, it may be concluded that Co-AC gave the best result in the co-processing of the MWP/VGO blend. To observe the effect of metal type loaded on active carbon on catalyst activity, a series of co-processing experiments was also carried out.     

Sensitivity Analyses and Sensitivity Coefficients of Standardized Daily ASCE-Penman-Monteith Equation

The sensitivity of the standardized ASCE grass-reference Penman-Monteith evapotranspiration (ASCE-PM ETo) equation to climate variables in different regions has not yet been studied. Sensitivity analyses for the standardized daily form of the ASCE-PM equation were conducted on wind speed at 2?m height (U2), maximum and minimum air temperatures (Tmax and Tmin), vapor pressure deficit (VPD), and solar radiation (Rs) in the following regions of the United States: semiarid (Scottsbluff, Nebraska, and Bushland, Texas), a Mediterranean-type climate (Santa Barbara, California), coastal humid (Fort Pierce, Florida), inland humid and semihumid (Rockport, Missouri, and Clay Center, Nebraska), and an island (Twitchell Island, California). The sensitivity coefficients were derived for each variable on a daily basis. In general, ETo was most sensitive to VPD at all locations, while sensitivity of ETo to the same variable showed significant variation from one location to another and at the same location within the year. After VPD, ETo was most sensitive to U2 in semiarid regions (Scottsbluff, Clay Center, and Bushland) during the summer months. The Rs was the dominant driving force of ETo at humid locations (Fort Pierce and Rockport) during the summer months. At Santa Barbara, the sensitivity of ETo to U2 was minimal during the summer months. At Bushland, Scottsbluff, and Twitchell Island, ETo was more sensitive to Tmax than Rs in summer months, whereas it was equally sensitive to Tmax and Rs at Clay Center. The ETo was not sensitive to Tmin at any of the locations. The change in ETo was linearly related to change in climate variables (with r2 ≥ 0.96 in most cases), with the exception of Tmin, at all sites. Increase in ETo with respect to increase in climate variable changed considerably by month. On an annual average, a 1°C increase in Tmax resulted in 0.11, 0.06, 0.16, 0.07, 0.11, 0.08, and 0.10?mm increases in ETo at Scottsbluff, Santa Barbara, Bushland, Fort Pierce, Twitchell Island, Rockport, and Clay Center. A 1?m?s?1 increase in U2 resulted in 0.42, 0.18, 0.37, 0.28, 0.31, 0.20, and 0.26?mm increases in ETo at the same locations. A unit increase in Tmax resulted in the largest increase in ETo at Bushland, and a unit increase in Rs caused the largest increases in ETo at Fort Pierce. A 1?MJ?m?2?d?1 increase in Rs resulted in 0.05, 0.08, 0.06, 0.11, 0.05, 0.06, and 0.06?mm increases in ETo at the same locations. A 0.4?kPa increase in VPD resulted in 1.13, 0.54, 1.29, 0.57, 1.04, 1.10, and 1.22?mm increases in ETo at the same locations. The U2 had the most effect on ETo at Scottsbluff and Bushland, the two locations where dry and strong winds are common during the growing season. The sensitivity coefficient for Rs was higher during the summer months and lower during the winter months, and the opposite was observed for VPD (except for Twitchell Island). The decrease of the sensitivity coefficients for Rs corresponding to an increase in the sensitivity coefficient for VPD is due to a decrease in the energy term in favor of the increase in significance of the aerodynamic term of the standardized ASCE-PM equation in summer versus winter months. Because the ASCE-PM and the Food and Agriculture Organization paper number 56 Penman-Monteith (FAO56-PM) equations are identical when applied on a daily time step, the results of the sensitivity analyses and sensitivity coefficients of this study should be directly applicable to the FAO56-PM equation.     

Stochastic modeling and simulation of photopolymerization process

In this study, the effect of photoinitiator concentration on the gelation time of different resins were studied in the absence of oxygen in the reaction volume by using passive microrheology technique. Four different monomers which are ethoxylated pentaerythritol tetraacrylate (SR494), trimethylolpropane triacrylate (SR351), triethylene glycol diacrylate (SR272), and 2(2‐ethoxyetoxy) ethyl acrylate (SR256) were used in these experiments. Resins were prepared from these four different monomers by mixing them with various amount of 2,2‐dimethoxy 1,2‐diphenylethanone photoinitiator molecule with high absorption coefficient at the frequency of UV light used in these experiment. The simulations of the results obtained from microrheology experiments were carried out with the new model based on the stochastic Monte Carlo approach in order to account for the inherently random and discrete nature of the photopolymerization reactions. The model captures the nonlinear decrease of gelation time with increasing photoinitator concentration and number of acrylate fragments on each monomer. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Removal of lead (II) and nickel (II) ions from aqueous solution using activated carbon prepared from rapeseed oil cake by Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> activation

In this study, rapeseed oil cake as a precursor was used to prepare activated carbons by chemical activation with sodium carbonate (Na₂CO₃) at 600 and 800 °C. The activated carbon with the highest surface area of 850 m² g^?1 was produced at 800 °C. The prepared activated carbons were mainly microporous. The activated carbon having the highest surface area was used as an adsorbent for the removal of lead (II) and nickel (II) ions from aqueous solutions. The effects of pH, contact time, and initial ion concentration on the adsorption capacity of the activated carbon were investigated. The kinetic data of adsorption process were studied using pseudo-first-order, pseudo-second-order kinetic models and intraparticle diffusion model. The experimental data were well adapted to the pseudo-second-order model for both tested ions. The adsorption data for both ions were well correlated with Langmuir isotherm. The maximum monolayer adsorption capacities of the activated carbon for the removal of lead (II) and nickel (II) ions were determined as 129.87 and 133.33 mg g^?1, respectively.     

基于相控外差干涉技术的纳米定位方法的研究

针对工业领域和计量界对定位精度要求的提高,提出了一种基于迈克尔逊干涉仪反向特性的定位控制方法。该方法采用相位锁定控制和外差干涉技术来完成位置测量和控制。在严格控制实验环境条件下,得到了步距值为5 nm的双向步进位移。步距值的不确定度为8×10-9 nm,位移重复性误差小于1 nm。该定位方法的测量尺寸可直接溯源至长度标准,并且采用光电步进相移法可克服压电陶瓷的非线性和蠕变的机械缺陷。该方法在系统环境控制条件下适用于毫米行程位移,可应用于纳米计量和超精密加工等领域。     

The effects of moderately oxidised dietary oil with or without vitamin E supplementation on performance, nutrient digestibility, some blood traits, lipid peroxidation and antioxidant defence of male broilers

BACKGROUND: The experiment was conducted to determine the effects of dietary supplementation of oxidised oil with or without vitamin E on performance, nutrient digestibility, some blood traits, lipid peroxidation and antioxidant defence system of male broilers. RESULTS: The supplementation of oxidised oil with or without vitamin E to the grower diets did not significantly affect performance, the pH and viscosity values of excreta and nutrient digestibilities in male broilers. Oxidised oil supplementation slightly increased plasma triglyceride and cholesterol concentrations but did not alter plasma glucose concentration. Although malondialdehyde (MDA) and nitric oxide concentrations tended to be higher in the oxidised oil group, these increases were not significant. Birds fed the diet containing oxidised oil had significantly lower superoxide dismutase (SOD) activity. However, no differences were observed in glutathione peroxidase (GSH‐Px) activity and uric acid concentrations of broilers fed oxidised oil as compared to the control group. Dietary vitamin E supplementation decreased MDA concentration whereas increasing SOD activity, suggesting that vitamin E supplementation reduced susceptibility to lipid peroxidation. CONCLUSION: The results showed that a milder oxidative stress occurred by supplementation of moderately oxidised oil to the diet of broilers and vitamin E supplementation had been helpful in alleviating lipid peroxidation. Copyright © 2011 Society of Chemical Industry