Inter-comparative study of quantitative methods of industrial clinker

Impurities from the raw materials, the grinding and the homogenization of the raw materials, the kiln instability and the complexity of the cooling step, all these factors make it difficult to obtain a perfect evaluation of the mineralogical composition of Portland clinker. We studied the limitations of the most commonly used quantitative methods and recommend some procedures to obtain reliable and reproducible results of quantitative analyses. Different clinker samples (provided by the Bizerte Cement Company (Tunisia)) were subjected to an elemental analysis by X-ray fluorescence and the mineralogical composition was determined by the Bogue calculation and by X-ray powder diffraction combined with the Rietveld method (Different softwares were used: XPert High Score Plus version 2.0 and TOPAS version 4.2). We then compared the results obtained by the Rietveld method and the Bogue calculation to the specific peak areas of each phase. The content of each phase, determined by the Rietveld method, varied proportionally to the change in peak area; a significant difference in these results was found by using the elementary Bogue calculation.     

一种基于并联机构的航天器姿态模拟装置的设计开发

航天器发射升空前进行地面测试和试验是航天器研制过程中的重要环节。文中针对一种基于并联机构的姿态模拟装置的设计开发,从位置分析、速度分析和虚拟样机的建造和仿真分析等方面对3UPS-PU并联机构进行研究,完成姿态模拟装置的设计,为航天器装配、试验和测试设备的设计提供一种新的思路。     

Microstructural characterization of Cu/Al composites and effect of cooling rate at the Cu/Al interfacial region

Cu/Al composites are of vital importance in industrial applications because of their numerous advantages. The influence of bond-ing temperature and cooling rate on the microstructure and morphology of ...     

一种能量均衡的无线传感器网络分簇算法*

为了延长网络的生存时间,提出了一种能量均衡的无线传感器网络分簇算法（EBCA）,该算法优先选择剩余能量较多的节点作为簇首,以平衡节点的能量消耗。仿真实验结果表明：无论同构网还是异构网,该算法都能显著地推迟网络第一个节点的死亡时间,其性能明显优于LEACH算法。     

Air impingement and intermittent drying: Application to apple and to mango

An original drying process combining air impingement and intermittent drying was studied on apple slices and mango cubes. The influence of four operating parameters (air velocity, drying/tempering periods, upper height, and air temperature) on the drying time and on the drying rate was evaluated. Continuous and intermittent drying were compared. The intermittency α = 1/7 (τ_on = 10 seconds and τ_off = 60 seconds) gave the best results. A time savings of 54% for apple and 67% for mango was reached. In continuous drying, a time savings of 4620 seconds was observed by increasing the air velocity from 6 to 40 m s^?1 for apple. Air temperatures of 328 K for apple and of 328 K or 338 K for mango were determined as optimum to prevent case‐hardening. Experimental results were fitted with the analytical solution of Fick's second law and the modified Page equation (average values R² = 0.985 and 0.961, for apple and mango, respectively). For both products, the apparent moisture diffusivity D_app, the drying constant k, the drying coefficient n, and the activation energy E_a, were identified. Activation energies calculated from the analytical solution were 30.3 and 36.8 kJ mol^?1 and were 25.4 and 30.0 kJ mol^?1 using the modified Page equation for apple and mango, respectively. Mango has an increased temperature sensitivity and thus will need less energy for drying than apple.     

一个具有物理意义的再结晶动力学模型的建立及验证

采用位错理论推导出了一个具有晶界迁移能、再结晶平均晶粒尺寸以及位错密度等材料物理参数再结晶动力学模型。用该模型验证了无间隙原子钢经不同形变量在630℃退火的再结晶过程。结果表明，该模型能很好地描述无间隙原子钢等温退火再结晶过程。     

Inhibition of pure iron by new synthesized tripyrazole derivatives in HCl solution

Inhibitory effect of some new synthesized tripyrazole compounds on corrosion of pure iron in 1 M HCl solution has been studied using weight-loss measurements and various electrochemical techniques polarization and impedance spectroscopy methods. The inhibiting action is more pronounced with N,N,N-tris[(3,5-dimethyl-1H-pyrazol-1-yl)methyl] amine (P1), and its inhibition efficiency increases with its concentration and attains the maximum value of 94% at the 2.5 × 10⁻⁴ M. The effect of temperature on the corrosion behaviour of iron was studied in the range from 298 to 353 K with and without P1 at 2.5 × 10⁻⁴ M. We note a good agreement between gravimetric and electrochemical methods potentiodynamic polarization and impedance spectroscopy (EIS). Polarization measurements show also that the compound acts mixed inhibitor. The catholic curves indicate that the reduction of proton at the pure iron surface happens within a pure activating mechanism. EIS measurements show the increase of the transfer resistance with the inhibitor concentration. The presence of the N,N,N-tris[(3,5-dimethyl-1H-pyrazol-1-yl)methyl] amine increases the inhibition efficiency and not caused a drastic change in its adsorption mechanism. The adsorption of P1 on the surface of iron in 1 M HCl obeys a Langmuir isotherm adsorption.     

Relation between impurities and oxide-scale growth mechanisms on Ni-34Cr and Ni-20Cr alloys. II. Influence of sulphur

The oxidation of presulphidized Ni-Cr alloys has been studied by taking into account the influence of the two distinct oxidation mechanisms described in part I of this article. Sulphur enters the Cr₂O₃ scale (in Ni-34Cr alloys) mainly as S^2– species, which at high temperatures increases the V_Cr content, and hence the oxidation kinetics. Sulphur is randomly distributed in the scale, except at the inner oxide-alloy interface, where intergranular microsulphides are analyzed in the oxide-scale zone. In the case of NiO, NiCr₂O₄, Cr₂O₃ oxide multilayers (in a Ni-20Cr alloy), sulphur in the S^2– state is distributed in the oxide layers or at Si-precipitate interfaces. Such a distribution leads to crack formation, especially during cooling.     

2004年起中国将启用新的金属废料分类目录及报关方法

在交流条件硅酸钠溶液中利用微等离子体氧化技术合成了陶瓷涂层。通过XRD，EPMA分析了所得陶瓷涂层在不同层面上的相组成、微观结构及元素分布。由陶瓷涂层截面的背散射图看出陶瓷涂层较致密、与基体结合强度高。XRD分析结果显示，陶瓷涂层的最外层由莫来石及γ-Al2O3相组成，随着向陶瓷涂层内部的移动，莫来石的含量逐渐减少，α-Al2O3，γ-A12O3相的含量逐渐提高，而且陶瓷涂层的颜色由白色逐渐变为黑色。硅元素在陶瓷涂层的外侧及陶瓷涂层与基体的交界处陶瓷涂层一侧含量较多，在陶瓷涂层中间含量少。而陶瓷涂层的硬度变化也出现了中间高，两侧低的分布情况。     

异形件的滚压成形工艺设计及滚压线的调试

该文对异形件的几处滚压工艺忌区诸如半径过大 ,不能使材料达到屈服成形状态 ;翻转 1 80°的成形 ;弯边太短 ,难以成形 ;重叠弯曲 ,材料易位移 ,难以控制等现象进行了讨论 ,提出了对滚压忌区的解决方法和设计要领 ,指出了在模具设计制造中应注意的事项 ,对提高滚制精度有一定的参考价值