螺纹量规的数字化检测方法

螺纹量规是判定螺纹紧固件合格与否的重要量具,其几何参数的精确测量具有重要意义。利用螺纹综合测量仪完成了螺纹量规的数字化测量试验,分析得出该方法的测量结果准确,精度可靠。同时对螺纹综合测量仪测量中径的不确定度进行了评定,为螺纹量规的测量质量提供了参考依据。     

Physicochemical,textural and volatile characteristics of fermented milk co-cultured with Streptococcus thermophilus,Bifidobacterium animalis or Lactobacillus plantarum

Fermented milks were prepared with various culture combinations of Lactobacillus plantarum or Bifidobacterium animalis with Streptococcus thermophilus, and the impact of microbes combinations on acidification, proteolysis, lipolysis, texture, volatiles and sensory quality of fermented milk was investigated during 21-day storage at 4 °C. The results showed that products from the co-cultures displayed higher titratable acidity, more peptides, higher proteolytic activity and lipolysis capacity compared with that from the pure strains of S. thermophilus. When L. plantarum and B. animalis combined in a ratio of 2:1 with S. thermophilus, the products maintained relatively more viable cell counts of the 3 strains, strong proteolysis ability and lipolysis capacity during the storage. Milk fermented by co-cultures of the 3 strains exhibited higher cohesiveness, more volatiles and better sensory quality compared with these fermented by S. thermophilus only or in co-cultures with either B. animalis or L. plantarum based on principal component analysis.     

Modeling the final sintering stage of doped ceramics: mutual interaction between grain growth and densification

Applying the thermodynamic extremal principle, a model for grain growth and densification in the final stage of sintering of doped ceramics was derived, with segregation-dependent interfacial energies and mobilities (or diffusivities). The model demonstrated an interdependence between the driving forces of grain growth and densification during sintering evolution, observed because the surface energy contributes positively to the driving force of grain growth while the GB energy negatively to the driving force of densification. The model was tested in alumina as a host system, and calculations demonstrate that dopants with more negative GB (or surface) segregation enthalpy or which cause lower GB diffusion coefficient can induce higher relative densities at a given grain size. Comparatively studying yttria- and lanthana-doped alumina, the lanthana doping showed significantly enhanced sintering attributed to the larger La³⁺ radius causing a more negative GB segregation energy. This present model is expected to help dopant designing to improve control over sintering.     

植物浸取剂原地浸出离子型稀土矿中试模拟

分别以“散样重装”和保持矿体原样的离子型稀土矿为原料，开展植物浸取剂浸出稀土的小试和“原地浸出”中试模拟试验。探讨了试验动力学，探索了植物浸取剂浓度和用量对浸出的影响，并它的渗透性和浸取性能与硫酸铵为浸出剂时的进行了对比。结果表明，植物浸取剂浸出稀土过程的动力学符合“收缩未反应核模型”；128.2 kg浓度为2%植物浸取剂浸出451 kg稀土矿是合适的；保持矿体原样的稀土矿渗透性较差，植物浸取剂的水平平均渗透速度、垂直平均渗透速度、浸出率分别为0.141 cm/min、0.213 cm/min、94.40%，均好于硫酸铵的。     

Influence of Negative Pressure Gradient on Pressure Distribution and Gas-Solid Flow Pattern of Solid Feed Systems

A series of experiments on a solid feed system was performed to investigate the effect of negative pressure gradient on the gas-solid flow pattern and hydrodynamic characteristics.Based on the non-fluidized gas-solid two phase flow and particulate mechanics in the standpipe,a method for predicting the pressure of the air passing through the recycle chamber and the pressure drop through the loop seal slit in these systems is also presented.The predicted pressure profile along the negative pressure gradient from the proposed model exhibits a good agreement with the experimental data.The experimental data show that the gas flow in the standpipe is always upward in the negative pressure gradients,while the direction ofthe superficial gas velocity through the recycle chamber of the loop seal does not affect the pressure drop in standpipe.It increases with an increasing negative pressure gradient.     

风电机组传动链典型故障特征提取方法

为解决风电机组传动链易发生故障的问题,文章阐述了风电机组齿轮箱特征频率的计算方法和基于振动信号分析的故障特征提取方法。结合实际情况,以行星级齿轮磨损、中间轴小齿轮崩齿、高速轴齿轮崩齿和发电机轴承电腐蚀等典型故障为例,通过齿轮箱特征频率和传动链典型故障振动信号基本特征分析,可较好地完成故障识别。结果表明,采用经典信号处理方法能对上述典型故障进行特征提取,验证了经典方法对单一、明显故障特征提取的有效性,为深入开展传动链故障特征提取方法研究奠定了基础,为风电机组故障检修维护提供了技术支撑。     

Strengthening mechanisms in magnesium alloys containing ternary Ⅰ,W and LPSO phases

This study was aimed at identifying underlying strengthening mechanisms and predicting the yield strength of as-extruded Mg-Zn-Y alloys with varying amounts of yttrium(Y) element. The addition of Y resulted in the formation of ternary I(Mg_3 YZn_6), W(Mg_3 Y_2 Zn_3) and LPSO(Mg_(12) YZn) phases which subsequently reinforced alloys ZM31 + 0.3 Y, ZM31 + 3.2 Y and ZM31 + 6 Y, where the value denoted the amount of Y element(in wt%). Yield strength of the alloys was determined via uniaxial compression testing, and grain size and second-phase particles were characterized using OM and SEM. In-situ high-temperature XRD was performed to determine the coefficient of thermal expansion(CTE), which was derived to be 1.38 × 10~(-5 K~(-1) and 2.35 × 10~(-5) K~(-1) for W and LPSO phases, respectively. The individual strengthening effects in each material were quantified for the first time, including grain refinement, Orowan looping, thermal mismatch, dislocation density, load-bearing, and particle shearing contributions. Grain refinement was one of the major strengthening mechanisms and it was present in all the alloys studied,irrespective of the second-phase particles. Orowan looping and CTE mismatch were the predominant strengthening mechanisms in the ZM31 + 0.3 Y and ZM31 + 3.2 Y alloys containing I and W phases, respectively, while load-bearing and second-phase shearing were the salient mechanisms contributing largely to the superior yield strength of the LPSO-reinforced ZM31 + 6 Y alloy.