Thermodynamic investigation of phase equilibria on the (W,Mo)C-(Co,Ni) cemented carbides

The C-Co-Mo-W and C-Mo-Ni-W quaternary systems have been critically evaluated by means of the CALPHAD approach, in which the Co-Mo-W system was readjusted to ensure the model consistency. The thermodynamic models of Gibbs energies for individual phases in the ternary and quaternary systems are described, including substitutional solution model, sublattice model and linear compound model. The modeling covers the whole temperature and composition ranges, and a set of self-consistent thermodynamic parameters for the C-Co-Mo-W and C-Mo-Ni-W quaternary systems is obtained. According to the comprehensive comparisons between the reported and calculated phase diagram data, the reliable equilibria information is satisfactorily accounted for by the modeling. Based on the present work together with the previously reported assessments of binary, ternary and quaternary sub-systems, a thermodynamic database for the C-Co-Mo-Ni-W quinary system is constructed and applied to calculate the sintering region phase equilibria of the (W,Mo)C-(Co,Ni) cemented carbides.     

以天青石矿为原料生产高纯硫酸锶工艺研究

针对青海天青石矿的特点以及高纯硫酸锶的市场特性、生产关键技术与配套工艺的关键性问题，提出具有针对性、先进性并可实现产业化的生产高纯硫酸锶的工艺方案。重点提出了以碳还原法加工天青石矿制取高纯硫酸锶的工艺路线。通过单因素实验确定了最佳工艺条件：煅烧温度为1 200 ℃，天青石精矿和煤粉的质量比为5∶1，硫化锶浸取温度为90 ℃，氢氧化锶溶液和稀硫酸的质量比为1∶1.1。在此条件下，高纯硫酸锶的平均收率为95.53%。实验制备的硫酸锶产品为白色，纯度为99.3%，各项指标达到化学纯的要求。     

Deformation analysis of geosynthetic-encased stone column using cavity expansion models with emphasis on boundary condition

This paper presents a modified theoretical model to predict the deformation of geosynthetic-encased stone column (GESC) and surrounding soil, using cylindrical cavity expansion model (CEM). The model was distinguished for single GESC and GESC in groups with emphasis on the different boundary conditions. The displacement boundary of CEM was used for GESC in groups, and the stress boundary of CEM was adopted for single GESC. The plasticity development of the soil obeying the Mohr-Coulomb yielding criterion was considered. The stress and settlement of the GESC were analyzed by radial stress and vertical stress equilibrium. This method has been verified via comparison with test data and numerical simulation results. The influences of applied loading, geosynthetic encasement stiffness, and soil stiffness on the mechanical performance of the GESC and the surrounding soil have also been investigated. The proposed theoretical approaches are suitable for predicting the deformation of the GESC, and the surrounding soil. The proposed method in unit cell analysis was more reasonable for GESC in groups.     

Transport Map sampling with PGD model reduction for fast dynamical Bayesian data assimilation

The motivation of this work is to address real-time sequential inference of parameters with a full Bayesian formulation. First, the proper generalized decomposition (PGD) is used to reduce the computational evaluation of the posterior density in the online phase. Second, Transport Map sampling is used to build a deterministic coupling between a reference measure and the posterior measure. The determination of the transport maps involves the solution of a minimization problem. As the PGD model is quasi-analytical and under a variable separation form, the use of gradient and Hessian information speeds up the minimization algorithm. Eventually, uncertainty quantification on outputs of interest of the model can be easily performed due to the global feature of the PGD solution over all coordinate domains. Numerical examples highlight the performance of the method.     

Formation and O2/CO2 combustion characteristics of real-environment coal char in high-temperature oxy-fuel conditions

Oxygen-fuel combustion is a promising technology for CO₂ emission reduction. The high-temperature entrained flow reactor and high-temperature drop tube furnace were used to analyses the formation and O₂/CO₂ combustion characteristics of real-environment coal char in high-temperature oxy-fuel conditions. It proposed “inflection point standard” of high-temperature flame method for the preparation of real-environmental oxy-fuel coal char according to the flame method. The results show that the ratios of C=O/C-O and C=O/C_ar increase in the coal char compared with the raw coals. The trend of C=O/C_ar in oxy-fuel condition is opposite to that in the inert atmosphere, due to the effect of high-concentration CO₂. To achieve the burnout rate similar to air combustion for coal char, with the increase of coal rank, the O₂ concentration should be enhanced. The optimal O₂ concentration for the oxy-fuel combustion of JC anthracite is 30%, while that of other low-rank coals could be lower than 30%. The combustion characteristic of JC anthracite is with the highest sensitivity to temperature and O₂ concentration.     

CO2 capture using mesocellular siliceous foam (MCF)-supported CaO

CaO is a promising material as an alternative CO₂ capture material which can be used at high temperature. However, CaO sinters to form large particles under long-term high temperature conditions, resulting in a rapid decrease of its surface area and the capacity of CO₂ capture. Incorporating CaO into inert materials is a promising strategy to enhance the performance of CO₂ capture. This work investigated a novel composite material called mesocellular siliceous foam (MCF)-supported CaO to enhance the stability and capacity of CaO-based materials for CO₂ capture. The crystal structure, surface morphology and porosity property of the developed composite materials were investigated. Thermogravimetric measurements were carried out to study the cyclic CO₂ capture performance of the MCF-supported CaO composites. The results showed that a part of CaO reacted with the silica wall, and the formation of Ca₂SiO₄ within the MCF framework limited the presence of CaO in the mesopores, thus inhibited the sintering of CaO. The sample of MCF-3CaO exhibited a better performance of CO₂ capture and long-term stability, compared with the materials prepared with lower CaO loading. This work contributes to the development of high temperature CO₂ capture adsorbents, which can be applied for decarbonizing major industrials e.g. power plant.     

Microscale investigation into mechanical behaviors of heat-bonded nonwoven geotextile using DEM

Heat-bonded nonwoven geotextiles (HBNGs) made from synthetic fibers are widely used in engineering practices. One of the challenges on the way is to link the properties of fibers and the fabric's microstructure to the deformation and failure mechanisms of HBNGs. In this study, a random distribution geometry method was developed to reproduce the complex fibrous structure of HBNG. A piecewise linear model was adopted to reproduce the nonlinear stress-strain relationships of single fibers. The present method has been successfully applied in the simulation of uniaxial and biaxial tensile tests and puncture test. The orientation distribution of fibers and the mechanical behaviors (e.g., deformation, strain localization, force-strain relationship) of HBNG specimen were reasonably simulated. Specifically, the hourglass shape during uniaxial tensile test, the axisymmetric deformation pattern during biaxial tensile test and the trumpet shape during puncture test were all well reproduced. The present method provides an applicable tool to study the complicated mechanical behaviors of HBNG and is also helpful to obtain a better understanding of its deformation and failure mechanisms.     

Evaluation of adult and offspring thiamine deficiency in salmonine species from Lake Ontario

Thiamine Deficiency Complex (TDC) is an ongoing problem impacting salmonine health in various waterbodies, including Lake Ontario. The prevalence of TDC has been variable and explanations for differences are limited. In the current study, thiamine concentrations were measured in eggs, liver tissue, and muscle tissue sampled from brown trout (Salmo trutta), Chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), lake trout (Salvelinus namaycush), and steelhead trout (O. mykiss) that were collected from Lake Ontario and its surrounding tributaries. The occurrence of TDC was measured for each species based on TDC-induced offspring mortality rates under laboratory conditions. TDC-induced offspring mortality was observed for all species except brown trout. For affected species, egg free thiamine (Th) was consistently low compared to lake trout collected from Lake Superior that are considered thiamine replete. In addition, species with the lowest percentages of Th in their eggs were the most susceptible to TDC, suggesting that limited thiamine reserves in the form of Th may cause TDC-induced offspring mortality. Lastly, our results show that egg thiamine concentrations have yearly variation and increased for all species throughout the study. Reasons for such variation are undetermined; but, if egg thiamine concentrations continue to increase, the impacts of TDC on these salmonine species may lessen. Future monitoring is needed for determining if thiamine concentrations are increasing and the potential impacts that may have on the entire Lake Ontario fishery.     

密集颗粒流动的连续性方法应用研究

颗粒流动广泛存在于自然现象和工程应用中，无论是山体坍塌还是工程上球床模块式高温气冷堆和中国科学院近代物理研究所提出的新型流态固体颗粒靶概念。本文基于适用于处理大变形问题的物质点法（MPM），采用μ(I)流变模型，实现了用连续性方法模拟密集颗粒流动的计算框架，并模拟了颗粒坍塌实验和漏斗流动现象，数值模拟结果与实验结果、DEM计算结果均吻合较好。本文采用的连续性本构和MPM能有效模拟密集颗粒流动。可在本文探究的连续性方法模拟密集颗粒流动的框架基础上，完善边界条件和本构模型，为用连续性方法处理大量颗粒的工程问题提供借鉴。     

二醋酸纤维素薄膜剂量计的制备和性能研究

为了改善醋酸纤维素薄膜剂量计在γ辐射剂量测定中稳定性欠佳的问题，拓展其辐射测量应用范围，采用离子液体均相乙酰化纤维素方法制得的二醋酸纤维素（CDA）粉末为原料，优化CDA薄膜制备工艺，研究其γ辐射变色性能及稳定性，制备适用于γ辐射剂量测量且性能优良的CDA薄膜剂量计。基于CDA的辐射变色机理，该薄膜剂量计在270 nm的单位厚度吸光度与吸收剂量存在良好的线性关系，剂量率、CDA的取代度和辐照气氛对薄膜的工作曲线影响较小。CDA薄膜剂量计的剂量检测量程为50~400 kGy，扩展不确定度为8.8%（K=2），辐照后24 h内吸光度测试稳定，具有良好的辐照稳定性，基本满足工业上对于辐射剂量计的使用要求，有望应用于γ辐射剂量的测量。