Surface and chemical diffusion effects of nanowire electrodes in lithium-ion batteries

Science China Technological Sciences - Nanostructured electrodes with surface effect show a distinct advantage in prolonging the lifetime of lithium-ion (Li-ion) battery. In order to characterize...     

高职建筑结构课程教学与研究

根据高职水利类建筑结构的课程体系及特征,结合高等职业教育的特点,改革教学办法和手段,探讨培养学生实践能力和应用能力,提高学生创新素质,促进学生全面发展的教学模式.     

前视红外图像质量评价指标研究

实时图像质量严重影响景象匹配性能,但目前尚无通用可行的评价标准来衡量其质量,而且不同匹配算法对各种图像特征的敏感性有差异,需要根据算法对图像质量评价问题展开分类研究。文中首先给出了图像质量评价的工作方式,然后从成像质量和目标凸显程度两个方面进行指标分析,提出了包括信噪比、模糊度、目标局部凸显程度和全局凸显程度在内的指标体系。实验表明,各指标与匹配性能之间具有单调一致关系。     

A Decomposition Route for Synthesis of Al2O3 Crystal and its Applications as Thermal Conductivity Filler

Platelike α‐Al₂O₃ powder was obtained at 850°C by thermal decomposition of ammonium aluminum carbonate hydroxide precursor, which was treated by hydrofluoric acid. The results showed the decomposition of the as‐prepared precursors experienced via three steps, adsorption of physical water, dehydration of crystalline water, and decomposition of the precursor, and the activation energies of the above three steps were calculated using the Coats–Redfern method. Meanwhile, the intermediate of (NH₄)₃AlF₆ obtained played an important role in decreasing activation energy of the decomposition and phase transformation. Moreover, the thermal conductivity of the epoxy resin filled with platelike alumina was improved obviously.     

A New Ferroelectric Phase of YMnO3 Induced by Oxygen‐Vacancy Ordering

Manganese oxides are good candidates of strongly correlated electron materials due to the uniqueness of electronic structure of manganese and the mobility of oxygen among lattice sites under external impacts. Here, we used electron beam as the excitation source to explore the structural evolution of YMnO₃ and identified a new phase under the radiation of electron beam in the transmission electron microscope. Analyses of the electron energy‐loss spectra reveal that this phase originates from ordered oxygen vacancy. We applied the first principles calculation to pick out the optimized stable structure with a lower polarization, and verified its correctness by electron diffraction and image simulations. Analyses of density of states indicate that weak Y–O covalence is favorable for the existence of ferroelectricity, supporting the electrostatic nature of ferroelectricity in the YMnO₃.     

混合溶剂芳脂比与特定温度下密度的关系

为提高生产效率、降低生产成本、快速判断混合溶剂芳脂比,研究了混合溶剂芳脂比与特定温度下密度的关系。实验结果表明,混合溶剂的芳脂比与其特定温度下的密度之间存在明显线性关系,且该线性关系对生产具有指导意义。     

Tuning of dielectric and ferroelectric properties in single phase BiFeO3 ceramics with controlled Fe/Fe ratio

Single phase multiferroic BiFeO₃ (BFO) ceramics were synthesized with controllable amount of Fe²⁺ and oxygen vacancies in a very wide concentration range. Double ferroelectric hysteresis loops are observed in fresh BFO ceramics at room temperature without any aging processes. Detailed study shows that this is due to the defect dipoles which have preferential orientations antiparallel to the direction of spontaneous polarization, providing a driving force for domain back-switching. The dielectric constant of BFO could be enormously enhanced by 100 times by increasing the Fe²⁺ content, employing a polaronic relaxation process.     

锅炉点火系统故障分析与处理

我厂有两台循环流化床锅炉,各有一套独立的自动点火系统。两套点火系统均使用天然气作为燃料,自投用以来经历了无数次的点火,其过程中也出现了许多问题,本文将对其中的典型故障进行分析和探讨。     

基于催化剂防护及SNG品质的甲烷化工艺设计

描述了甲烷化过程中发生的主要反应,指出多级循环绝热固定床是适合完全甲烷化的成熟工艺。着重分析了甲烷化催化剂4种失活模式:高温烧结、硫中毒、析碳及羰基镍形成带来的活性流失,指出有效的应对措施是:循环气稀释进气CO反应浓度、进一步深度脱硫、保持高温水汽比及开停车过程N2置换。基于煤基合成气甲烷化过程中所有耗氢反应物质的量的配比平衡,推导了进气组分配比模数公式,提出了以平衡模值为基点建立模数调节区间的方法,端点模值对应SNG最低的质量保证值。实例证明以此方法可得到预期的SNG组分,并验证了所得SNG是一种优质清洁的替代性天然气。     

Refractory Ceramic Fiber and the Products GB/T 3003-2006

正GB/T 3003-20061 Scope This standard specifies the terms,definitions,classifications,brands,technical requirements,test methods,quality appraisal procedure,packing,marking,transportation,storage and quality certificate of