Consolidation considering increasing soil column radius for dredged slurries improved by vacuum preloading method

Soil column is often investigated in the improvement of dredged slurries. Different from the smear zone, the soil column forms gradually and has extremely low permeability. This study presents an analytical solution for soil consolidation considering the increasing radius of the soil column and time-dependent discharge capacity. Based on the solution, the influence of the radius' increase on the consolidation behavior is found significant when the soil column has low permeability and large final radius, and the increase of formation time can lead to the increase of consolidation speed and final consolidation degree.     

Influence of Se and Te substitutions at Tl-site of Tl(Ba,Sr)CaCu2O7 superconductor on the AC susceptibility and electrical properties

The Sr and Ba bearing Tl-1212 phase, Tl(Ba,Sr)CaCu₂O₇ is an interesting superconductor. The Sr only bearing TlSr₂CaCu₂O₇ is not easily prepared in the superconducting form. The Ba only bearing TlBa₂CaCu₂O₇ on the other hand does not show improvement in the transition temperature with elemental substitution. In this work the influence of multivalent Se (non-metal) and Te (metalloid) substitutions at the Tl-site of Tl_1-xM_x(Ba,Sr)CaCu₂O₇ (M = Se or Te) superconductors for x = 0–0.6 was studied. The samples were prepared via the conventional solid-state reaction method. XRD patterns showed a single Tl-1212 phase for x = 0 and 0.1 Se substituted samples. The critical current density at the peak temperature, T_p of the imaginary (χ”) part of the AC susceptibility (χ = χ’ +χ”), J_c-inter(T_p) for all samples was between 15 and 21 A cm⁻². The highest superconducting transition temperature was shown by the x = 0.3 Se-substituted sample (T_c-onset = 104 K, T_c-zero = 89 K, T_cχ’ = 104 K and T_p = 80 K). Te suppressed the superconductivity of Tl-1212 phase. The order of highest transition temperatures are as follows: Tl_1-xTe_x(Ba,Sr)CaCu₂O₇<Tl(Ba,Sr)CaCu₂O₇<Tl_1-xSe_x(Ba,Sr)CaCu₂O₇. This work showed that Se was better than Te in improving the transition temperature and flux pinning of the Tl-1212 phase. The roles of ionic radius of Se and Te on the superconductivity of Tl(Ba,Sr)CaCu₂O₇ are discussed in this paper.     

滚齿工艺对齿根粗糙度的影响

针对国内外风电和工业齿轮箱轻量化的设计趋势,较低的安全系数对齿轮齿根弯曲强度提出了更为严格的要求。研究表明,在材料技术和齿形设计难以再优化的情况下,滚齿加工的粗糙度,尤其是齿根部位的粗糙度对齿轮弯曲强度的影响尤为敏感。针对滚齿工艺过程,从滚齿加工参数、刀具前刀面粗糙度和刀具刃口圆角三方面进行分析,验证其对齿根粗糙度的影响。     

组合轮径差对地铁车辆动力学性能的影响

为了研究各种轮径差组合形式对地铁车辆动力学性能的影响,基于车辆系统动力学和赫兹非线性接触理论,建立地铁动车非线性动力学模型,分析各种轮径差组合工况下地铁车辆的临界速度、平稳性、安全性和磨耗功率及其变化规律。结果表明:在多种轮径差组合工况下,轮径差增大会使地铁车辆的临界速度有较大幅度降低,会使地铁车辆的横向平稳性和磨耗功率明显增大;轮径差对地铁车辆的垂向平稳性、轮轴横向力、轮轨垂向力、脱轨系数和轮重减载率影响较小;通过左、右曲线时,轮径差对磨耗功率增幅的影响存在差异,但变化规律一致。     

采煤工作面煤层注水参数试验研究

通过在6198采煤工作面现场施工煤层注水钻孔采取煤样,实验室试验注水钻孔水压力分布、煤样含水率变化,得到了工作面煤层注水影响半径等技术参数,为采煤工作面煤层注水提供了一定的参考依据。     

Macromolecular motions and hydrodynamic radius variation in dilute solutions under shear action

Understanding the dynamics of single polymer chains and rheological mechanism in dilute polymer solutions under shear stress is essential for fields such as the petroleum and food industries, biomedical materials and drug delivery. Here we present an experimental method for measuring the viscosity of polymer solutions and studying the variation of single polymer chain conformation and the mechanism of molecular motions according to the relationship between the intrinsic viscosity, [η], and the shear rate. Of striking interest is that we find that [η] changing with the shear rate presents three stages which may explain the nature of the viscoelastic performance of polymer solutions and the isolated molecular motions. The significance of these results is the finding of the polymer chain deformation to match the pore throat which has enormous potential implications in drug delivery, genetics and biomedicine © 2014 Society of Chemical Industry.     

Elemental substitution at Tl-site of TlSr2CaCu2O7 superconductor: A review

This review is on the effects of elemental substitutions at the Tl-site of TlSr₂CaCu₂O₇ (Tl-1212) superconductor. The objective of this paper was to determine the elements that enhance or suppress the superconducting transition temperature, T_c of (Tl_1-xM_x)Sr₂CaCu₂O₇ phase. The elements included in this review were M = Pb, Bi, Cr, V, Re, Zr, In, Er, Gd, Na, K, Rb and Se. The relations between transition temperature and the ionic radius, coordination number, valence state and optimization of the hole concentration of the selected elements were studied. The preparation methods, sintering temperature, Tl-1212 phase and structural stability were also discussed. All alkali metals (K, Na and Rb) suppressed the transition temperature of the Tl-1212 phase. The transition temperature generally decreased linearly with ionic radius except for Cr which showed the highest T_c although its ionic radius is smaller.     

Effect of ionic radius on colossal permittivity properties of (A,Ta) co-doped TiO2 (A= alkaline-earth ions) ceramics

(A, B) co-doped TiO₂ ceramics attract great interests due to the excellent dielectric properties. In this work, the (A, Ta) co-doped TiO₂ ceramics were prepared by a solid state reaction process. The effect of the acceptors ionic radius on the structure and properties of TiO₂ ceramics was investigated. According to XRD analysis, the main phase is rutile TiO₂ for all samples. Due to the larger ionic radius, it is hard to replace Ti site in TiO₆ octahedron. As a result, the content of the secondary phase increased with increasing ionic radius. The dielectric properties were significantly enhanced by co-doping of alkaline-earth ions and tantalum ions, and the best dielectric constant obtained at 3% (Sr, Ta) co-doped compositions, where ε’ = 2.1 × 10⁵, tanδ = 0.21. Meanwhile, the XPS analysis suggested that the concentration of the defect dipoles exhibit a maximum in Sr-doped TiO₂ ceramics. The larger ionic radius of the acceptors leads to the more stability of the defect structure. However, for Ba ions, the replacement concentration decreased due to the excessive ionic radius, which in turn reduces the defect concentration. This work is meaningful for the further investigations on TiO₂-based colossal permittivity materials.     

非均质煤层瓦斯分布特征及钻孔抽采瓦斯运移规律研究

为了提高煤矿瓦斯抽采率，节约瓦斯抽采时间，分析了非均质煤层瓦斯分布特征及钻孔抽采瓦斯运移规律，采用透气性系数研究了非均质煤层瓦斯压力分布特点；分析了非均质煤层单钻孔瓦斯压力分布、原始瓦斯压力、原始透气性系数对有效抽采半径的影响。研究对指导现场瓦斯抽采以及促进煤矿安全生产具有重要意义。     

A molecular model for ion dehydration in confined water

Although ion dehydration in confined water is ubiquitous in many important processes concerning ion adsorption, transport and separation, and so forth, few theoretical models have been developed to unravel the mechanism of dehydration in confined space. Herein, a molecular model is proposed by weighing the molecular orientation of surrounding water within the first hydration shell, and then this model is applied to predict the hydration numbers and hydrated radii of simple ions with the help of molecular density functional theory. The predictions are rationalized not only with parallel simulations but also with relevant experimental measurements. We find that the ion hydration in confined water is depressed owing to the confinement, and thus the multilayer hydration shell is disturbed, which results in the decline of hydration number and hydrated radius, favoring the ion dehydration. This work provides an insightful route toward the quantitative understanding and prediction of ion dehydration in confined water.