Improved evidence for the existence of an intermediate phase during hydration of tricalcium silicate

Tricalcium silicate (Ca₃SiO₅) with a very small particle size of approximately 50 nm has been prepared and hydrated for a very short time (5 min) by two different modes in a paste experiment, using a water/solid-ratio of 1.20, and by hydration as a suspension employing a water/solid-ratio of 4000. A phase containing uncondensed silicate monomers close to hydrogen atoms (either hydroxyl groups or water molecules) was formed in both experiments. This phase is distinct from anhydrous tricalcium silicate and from the calcium-silicate-hydrate (C-S-H) phase, commonly identified as the hydration product of tricalcium silicate. In the paste experiment, approximately 79% of silicon atoms were present in the hydrated phase containing silicate monomers as determined from ²⁹Si{¹H} CP/MAS NMR. This result is used to show that the hydrated silicate monomers are part of a separate phase and that they cannot be attributed to a hydroxylated surface of tricalcium silicate after contact with water. The phase containing hydrated silicate monomers is metastable with respect to the C-S-H phase since it transforms into the latter in a half saturated calcium hydroxide solution. These data is used to emphasize that the hydration of tricalcium silicate proceeds in two consecutive steps. In the first reaction, an intermediate phase containing hydrated silicate monomers is formed which is subsequently transformed into C-S-H as the final hydration product in the second step. The introduction of an intermediate phase in calculations of the early hydration of tricalcium silicate can explain the presence of the induction period. It is shown that heterogeneous nucleation on appropriate crystal surfaces is able to reduce the length of the induction period and thus to accelerate the reaction of tricalcium silicate with water.     

集装箱喷漆废水处理工艺试验研究

在实验室对集装箱喷漆废水处理工艺及主要参数进行了研究。结果表明，采用SBR生化降解-物化混凝处理喷漆废水在技术上完全可行。采用SBR法处理喷漆废水时，喷漆废水与生活污水按6：4左右的比例混合．使进水COD控制在1400—1600mg／L。在此条件下，经过24h的生物好氧处理，能将出水的COD降至150mg／L以下。之后．再投加混凝剂[V（聚铝）：V（聚丙烯酰胺）=2：1]进行混凝处理，可进一步将出水COD降到80mg／L以下，达到国家二级排放标准。     

Residence time distribution and modeling of the liquid phase in an impinging stream reactor

Based on some experimental investigations of liquid phase residence time distribution (RTD) in an impinging stream reactor, a two-dimensional plug-flow dispersion model for predicting the liquid phase RTD in the reactor was proposed. The calculation results of the model can be in good agreement with the experimental RTD under different operating conditions. The axial liquid dispersion coefficient increases monotonously with the increasing liquid flux, but is almost independent of gas flux. As the liquid flux and the gas flux increase, the liquid dispersion coefficient of center-to-wall decreases. The axial liquid dispersion coefficient is much larger than that of center-to-wall, which indicates that the liquid RTD is dominated mainly by axial liquid dispersion in the impinging stream reactor.     

原油分离建模中的要点分析

Aspen Plus作为一种有效的模拟计算工具在装置筹建和改造中得到了广泛地应用,Aspen Plus在已建成装置实际生产中的应用受到原油性质、操作强度的影响,建立一个和实际过程完全吻合的模型比较困难.以常减压原油分离过程为例,阐述实际建模过程涉及的要点,提供的诸多方法可用于其他油品的分离计算.     

Mathematical modeling of the dispersed phase dynamics

A vector equation of motion in the Lagrangian frame of reference is rearranged into a set of two scalar equations to determine the relative-velocity magnitude of a particle and its direction. The resulting system, written in terms of the Lamé coefficients, is solved jointly with continuum equations of motion in the Eulerian frame of reference. The method is exemplified by the flow of a heterogeneous mixture between permeable parallel walls and the flow of a heterogeneous non-Newtonian fluid over the surface of a sedimentation centrifuge rotor.Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 2, 2005, pp. 206–215.Original Russian Text Copyright © 2005 by Kholpanov, Ibyatov.     

锌精矿沸腾焙烧两个关键工艺参数的选取

锌精矿的沸腾焙烧 ,无论是氧化焙烧还是酸化焙烧 ,其工艺参数的选取对锌焙砂质量有着相当大的影响 ,并且该工艺参数与硫铁矿沸腾焙烧相比有着较大的差别。重点介绍了锌精矿沸腾焙烧两个关键参数———焙烧温度和空气过剩系数对锌焙砂质量的影响 ,以及如何正确选取这两个参数     

Mathematical modeling and the estimation of parameters for the melt viscosity of polyamides

Capillary rheometry data of a range of commercial polyamide engineering materials was obtained from a mould-flow analysis material database, from which melt viscosity data was obtained at different temperatures, which made comparison of the viscosities difficult. In an attempt to make a reasonable comparison between the melt viscosities of the various polyamide materials at different temperatures, it was necessary to obtain the mathematical functions which describe the relationships between: (i) the melt viscosity and the shear rate, (ii) the melt viscosity and temperature and (iii) the melt viscosity and the combined effect of the shear rate and temperature of each of the polyamides studied. Therefore, melt viscosity was modelled as a function of shear rate at the three temperatures (275°C, 295°C and 315°C), at which the viscosities were determined. The function obtained represented smoothed versions of the experimental data, eliminating the experimental noise and enabling the generation of melt viscosity data at the six different shear rates of the original data. It was established that the melt viscosity as a function of shear rate at constant temperature, in the shear rate range 500-700 s m 1 , is incorrectly described by the Ostwald-de-Waele's model, \eta_{\rm T}={\rm f}({\dot \gamma})={\rm K}({\dot \gamma})^{({\rm n}-1)} , while the melt viscosity of the polyamides studied, as a function of temperature, is correctly described by the model \eta_{\dot \gamma}={\rm g}{(\rm T)}={\rm Pe}^{\left (\rm {QT/R}\right )} . But the response-surface melt viscosity is effectively described as a function of both shear rate and temperature by the model: \eta=\vert {\dot \gamma}\vert^{(\rm n-1)}{\rm Ae}^{(\rm ET/R)} . The parameters A, E and n are highly interrelated as they all influence the average melt viscosity. All are temperature sensitive and also, to some degree, shear sensitive.     

Some parameters of spinning poly-p-phenylene terephthalamide fibres through an air gap

The spinneret draw ratio for jets of LC solutions of PPTA (range of 1 to 10) is a basic parameter in spinning of high-strength fibres through an air gap. The strength of the fibres is a function of the conditions of intense spinneret drawing of the jets of LC solutions of PPTA and the spinning speed. Most of the sulfuric acid (solvent) passes into the spinning bath as a result of brief contact of the jet of LC PPTA solution and fibres with it during spinning. Translated from Khimicheskie Volokna, No. 2, pp. 12–14, March–April, 1998.     

汽车涂装锆盐前处理的关键工艺参数优化

研究了汽车涂装前处理锆化槽液中不同Zr2+质量浓度、pH、浸渍时间和温度对冷轧板和镀锌板电泳后耐腐蚀性能的影响.通过中性盐雾试验衡量板材的防腐性能,利用SEM表征锆化膜的表面形态.结果表明:当槽液温度为20℃,Zr2+质量浓度为1.1 g/L,pH=4.5,处理时间为90 s时,所得的锆化膜结构致密,无裂纹,均匀性好,耐酸/碱性1级,电泳后盐雾试验至960 h时的平均腐蚀宽度符合车身用板材的要求.     

六氟丙烯气相氧化合成六氟丙酮的催化剂

综述了六氟丙烯气相氧化合成六氟丙酮催化荆的研究进展,主要讨论了催化剂的制备方法、种类、结构和性质等对六氟丙烯氧化反应的影响,并对活性组分的形成过程和催化机理进行了论述.指出六氟丙烯气相氧化反应存在的问题是六氟丙烯转化率和六氟丙酮选择性均较低,且催化剂稳定性差.提出开发能够降低气相氧化反应活化能的新型催化剂及能够保持活性组分稳定性的助剂是今后六氟丙烯氧化催化剂的研究重点.     

Improved predictions of alarm and safety system performance through process and operator response‐time modeling

Dynamic risk analysis (DRA) has been used widely to analyze the performance of alarm and safety interlock systems of manufacturing processes. Because the most critical alarm and safety interlock systems are rarely activated, little or no data from these systems are often available to apply purely‐statistical DRA methods. Moskowitz et al. (2015)¹ introduced a repeated‐simulation, process‐model‐based technique for constructing informed prior distributions, generating low‐variance posterior distributions for Bayesian analysis,¹ and making alarm‐performance predictions. This article presents a method of quantifying process model quality, which impacts prior and posterior distributions used in Bayesian Analysis. The method uses higher‐frequency alarm and process data to select the most relevant constitutive equations and assumptions. New data‐based probabilistic models that describe important special‐cause event occurrences and operators’ response‐times are proposed and validated with industrial plant data. These models can be used to improve estimates of failure probabilities for alarm and safety interlock systems. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3461–3472, 2016     

Mathematical modeling and optimization of gas transport through carbon molecular sieve membrane and determining the model parameters using genetic algorithm

Permeation of N₂, CH₄, O₂ and CO₂ molecules through a carbon molecular sieve (CMS) was studied over a wide range of pressures using the transport mechanism. For proper utilization of carbon molecular sieve membrane in gas separation processes, prediction of behavior and recognition of proper gas transport mechanism as well as finding effective permeation parameters are necessary. A mathematical model of the gas transfer through a CMS membrane was developed using genetic algorithm (GA). Numerous types of mechanisms have been proposed so far for gas transport through capillaries, namely: Knudsen, slip and viscous flow. Moreover, surface flow usually occurs in parallel with other transport mechanisms such as Knudsen or viscous flow. The experimental data of gas permeation in CMS membranes and an appropriate genetic algorithm-based optimization method were used to establish the transport parameters. A GA, an optimization procedure based on the theory of evolution, was compared with non-linear regression for the ability of these two algorithms to fit the coefficients of Poultry growth models. It was found that GA approach could be more capable to define the parameters of permeation equation than non-linear regression. The model in most cases showed a good agreement between the predicted and measured values of the permeability.     

重溶沉淀相消除07MnCrMoVR钢球罐再热裂纹的实践

用加热到Ac3重溶沉淀相,并以压缩空气冷却的方法成功消除了07MnCrMoVR钢球罐焊接接头的再热裂纹,满足了07MnCrMoVR钢要求的力学性能.     

Bayesian calibration of thermodynamic parameters for geochemical speciation modeling of cementitious materials

Chemical equilibrium modeling of cementitious materials requires aqueous–solid equilibrium constants of the controlling mineral phases (K_sp) and the available concentrations of primary components. Inherent randomness of the input and model parameters, experimental measurement error, the assumptions and approximations required for numerical simulation, and inadequate knowledge of the chemical process contribute to uncertainty in model prediction. A numerical simulation framework is developed in this paper to assess uncertainty in K_sp values used in geochemical speciation models. A Bayesian statistical method is used in combination with an efficient, adaptive Metropolis sampling technique to develop probability density functions for K_sp values. One set of leaching experimental observations is used for calibration and another set is used for comparison to evaluate the applicability of the approach. The estimated probability distributions of K_sp values can be used in Monte Carlo simulation to assess uncertainty in the behavior of aqueous–solid partitioning of constituents in cement-based materials.     

Determination of unblended chain dynamic parameters of a polar discontinuous phase in an immiscible polymer blend

A method is described by which the relaxation characteristics of a polar polymer in an included phase of an immiscible polymeric blend can be determined from those of the composite. The necessary prerequisite is that the relaxation regions of the matrix and of the dispersed phase do not overlap. First, the dynamic relaxation data of the composite is fitted to the Havriliak-Negami function using a multi-response fitting method. Next, the relaxation function for the included phase is determined using composite mixing equations and the data for the pure matrix. This method is demonstrated for dielectric data on a polypropylene/polyurethane (PP/PUR) composite containing 20 wt% polar additive. The resulting unblended relaxation function parameters of PUR are discussed and compared to other unblended PUR literature data. Blending PUR with PP did not change the shape of the relaxation process, did shift the maximum frequency by about half a decade, and significantly reduced the limiting values of the dielectric constants.     

Influence of rheological properties on the sagging of polypropylene and abs sheet for thermoforming applications

The isothermal sagging resistance of different grades of conventional and a high melt strength (HMS) PP has been correlated with the rheological characteristics of the polymers, such as dynamic shear properties, melt strength, and zero shear viscosity. A thermoforming grade of acrylonitrile‐butadiene‐styrene (ABS) was used as a reference material. At 190°C, ABS had the highest viscosity and elastic modulus in the frequency range measured, showing that this polymer is highly elastic. HMS PP had a greater shear thinning behavior than conventional PP because of its broader molecular weight distribution. The tan δ of the polymers showed that conventional PP had a higher tendency to flow than HMS PP and ABS when heated above 172°C. This was confirmed with sagging experiments performed in an air circulating oven, where the rate of sagging decreased as the melt strength and the zero shear viscosity of the polymer increased.     

人才是企业发展之本──介绍上海振华造漆厂两位技术人员

本文重点介绍了上海振华造漆厂吴锐娟和曹民忠两位技术人员平凡的工作事迹，从侧面反映了该厂领导对技术人员的重视和信赖。     

The effect of long chain branching on the processability of polypropylene in thermoforming

Linear polypropylene was modified by reaction with peroxydicarbonates in a twin screw extruder to obtain varied degrees of long chain branching. The melt strength and the elasticity of the modified polymers were found to increase with the modification. The processability in foaming and thermoforming processes improved with branching and showed an optimum, beyond which higher degrees of long chain branching appeared not to help any further. The branched PP samples showed distinct strain hardening in the elongational viscosity, which was absent from the original linear melts. Melt strength, elasticity and strain hardening increased with the increase of the number of long chain branches on the main chain. The effect of molecular weight and molecular weight distribution of the precursor on the improvement of the processability of the polymer was examined. Polym. Eng. Sci. 44:973–982, 2004. © 2004 Society of Plastics Engineers.     

Bayesian analysis for determination and uncertainty assessment of strength and crack growth parameters of brittle materials

To determine the strength and the crack growth parameters of brittle materials, the common approach is to first evaluate the strength and then the crack growth parameters. When the parameters are needed for different temperatures, the procedure is repeated for each temperature of interest. Since the number of test specimens is generally small, the separated analysis of strength and crack growth parameters for each tested temperature leads to large parameters uncertainty. In order to improve the accuracy of the parameters, we propose a Bayesian method that allows to combine all strength and lifetime data obtained at different temperatures and determine the distribution of all material parameters in a single analysis. The results obtained from the analysis of measured skutterudite data show that in comparison to the standard approach the presented method significantly reduces the material parameters uncertainty and therefore is well adapted for a reduced number of samples.