Double polarization hysteresis and dramatic influence of small compositional variations on the electrical properties in Bi4Ti3O12 ceramics

This work reports the existence of double polarization hysteresis (P–E) loop in Aurivillius-phase ferroelectric Bi₄Ti₃O₁₂ (BiT) and reveals dramatic influence of small compositional variations on the electrical properties of it. The double polarization hysteresis is a characteristic of the interaction of defects with domain walls. This characteristic becomes more pronounced in Bi-deficient and Mg-doped BiT due to an increase in oxygen vacancy concentration at the lattices. Normal and saturated P–E loop is recalled by Nb donor doping, and associated composition Bi₄Ti_2.97Nb_0.03O_12.015 (BiT-0.03Nb) shows high remnant polarization (P_r = 12.5 μC/cm²) and large field-induced strain (S₃₃ = 5.6 × 10^?4). In addition, this doping results in bulk conductivity (σ_b) of BiT decreasing dramatically and associated activity energy (E_a) increasing significantly. In contrast, high oxide ion conductivity is induced with Mg²⁺ acceptor doping, and at 600 °C the optimum composition has ionic conductivity of ?0.65 × 10^?2 S cm^?1 in the bulk.     

Preparation of fused silica membrane with high performance for high temperature gas filtration by sealing and spray coating

In order to improve the gas permeability and thermal shock resistance of the ceramic membranes applied in high temperature gas-solid separation techniques, fused silica and graphite particles were used as the primary raw material and pore-former agent, and the spray coating based-on PVA sealing was applied to prepare the separation membrane. These approaches remarkably decreases filtration resistance by increasing support permeability and reducing the intrusion of ceramic membrane forming particles into the support as well as the thickness of the membrane. The fabricated membrane had an average pore diameter of 9.85?μm and a gas permeability value of 8.2?×?10⁴?m³/(m² h bar), its dust removal efficiency reached 98.6%.     

Study on the long-term behaviour of glass fibre in the tensile stress field

Glass fibre is a random network structure composed of [SiO₄] tetrahedra. The structure contains a large number of defects, which act as crack initiation points. Under tensile stress, cracks undergo crack initiation, stable propagation, failure propagation, and fracture, and the stress that begins after unstable propagation is called the critical fracture stress. When the stress is less than the critical value, the crack is subject to the force of chemical bonds during the crack propagation process, and crack arrest occurs. When the stress is greater than the critical value, the glass fibre will undergo destructive fracture. In this paper, long-term tensile tests were carried out on glass fibre and a glass fibre composite under different constant tensile stress conditions. The fracture times of the glass fibre and glass fibre composite under different tensile stresses were obtained, the critical fracture stress of glass fibre was inferred, and the fracture mechanism was explained.     

鲁固特高压直流黄河大跨越导线与地线选择

鲁固特高压直流,是继±660 kV银东线、±800 kV昭沂直流后的第3条外电入鲁直流输电通道,在山东境内跨越黄河,主跨越档距超过1 300 m,最高铁塔高度接近140 m,设计阶段需按照大跨越设计。结合工程实际,重点介绍黄河大跨越的导线与地线选择,包括选择原则、导线材质的确定、载流量计算、电气特性、机械特性、经济特性的计算,给出了导、地线的选型意见,可为后续工程的黄河大跨越提供设计参考。     

OPM3要素对项目组合管理能力影响的SD建模与仿真

根据组织项目管理成熟度模型（OPM3），确定影响项目组合管理能力的OPM3要素，分析OPM3要素与项目组合管理能力的因果关系，构建系统动力学模型，仿真模拟OPM3要素对项目组合管理能力的影响。仿真结果表明：OPM3要素与项目组合管理能力正相关；OPM3要素对项目组合管理能力的影响在短期内并不显著；在OPM3要素中，对项目组合管理能力影响较为显著的是战略执行与规划、组织领导能力和信息分析。     

Fully transient analytical solution for degradable organic contaminant transport through GMB/GCL/AL composite liners

In this study, analytical solution for degradable organic contaminant transport through a composite liner consisting of a geomembrane (GMB) layer, a geosynthetic clay liner (GCL) and an attenuation layer (AL) is derived by the separation of variables method. The transient contaminant transport in the whole composite liner can be well described avoiding some weird phenomena in existing analytical solutions. The results of parametric study show that GCL has significant effect on improving the barrier efficiency especially for scenarios with high leachate head. The biodegradation and adsorption in GCL have significant influence on the contaminant transport through the composite liner when the half-life of contaminant in GCL is less than 5 years. Otherwise, the effect can be neglected.     

Extraction optimisation,antioxidant activity and inhibition on α-amylase and pancreatic lipase of polyphenols from the seeds of Syzygium cumini

The objectives of this study were to determine the optimal extraction conditions of polyphenols from Syzygium cumini seeds by response surface methodology and investigate their antioxidant activity and inhibition on α-amylase and pancreatic lipase. As results, the optimal extraction conditions in the ultrasonic extraction process which maximised total polyphenols content, minimised the IC₅₀ values of α-amylase and pancreatic lipase were determined as follows: extraction time 60 min, ethanol concentration 63% and solvent/solid ratio 44 mL g⁻¹. The main phenolic compounds in partially purified fraction of Syzygium cumini seeds were catechin, epicatechin, kaempferol, gallic, 5-caffeoylquinic, caffeic and ferulic acids. In addition, the partially purified fraction inhibited 87.66 ± 5.55 and 86.61 ± 3.15% of α-amylase and pancreatic lipase, respectively. The results suggested that Syzygium cumini seeds could be explored as a natural antioxidant and could be used as a source of highly antidiabetic and anti-obesity bioactive compounds.     

水泥砂浆基体中玄武岩纤维的拔出试验研究

纤维与水泥砂浆间界面粘结性能是影响纤维混凝土宏观力学性能的重要因素.通过一系列单根玄武岩纤维拔出试验,考虑了三种不同纤维埋置深度(6 mm、9 mm、12 mm)和三种不同水灰比的水泥砂浆基体(0.40、0.49、0.65)两个因素的影响,得到了玄武岩纤维从水泥砂浆基体被拔出时的荷载位移曲线,确定了埋置深度为12 mm时界面粘结最强.最后通过宏观力学性能试验研究了12 mm长度下玄武岩纤维的掺量对混凝土宏观力学性能的影响.     

Reaction synthesis of spark plasma sintered MoSi2-B4C coatings for oxidation protection of Nb alloy

MoSi₂-B₄C coatings with different B₄C contents were prepared on Nb alloy by spark plasma sintering (SPS) process. Powder mixtures of Mo, Si and B₄C were used as the coating starting materials. Besides MoSi₂ and B₄C phases, small amounts of SiC and MoB are also found in the coatings because of the reactions of Mo, Si and B₄C powders during sintering. Compared with single MoSi₂ coating, the MoSi₂-B₄C coatings show better oxidation resistance at 1450?℃, and dense B₂O₃-SiO₂ oxide scales form after 100?h oxidation. The B₄C or MoB in the MoSi₂-B₄C coatings can serve as the B donor for the formation of B₂O₃. A slight degradation in the microstructure of the MoSi₂-B₄C coatings after oxidation is observed, which can be attributed to the presence of an NbB layer in the inter-diffusion zone of the coatings that retards the inward diffusion of Si from the coating into the substrate alloy. The microstructure development and oxidation behavior of the MoSi₂-B₄C coatings have been discussed.