Ring‐opening polymerization of lactones initiated by diphenylzinc–coinitiator systems

Diphenylzinc, alone or in combination with water and butanone as coinitiators, was used as a polymerization initiator system for a variety of lactones at varying temperatures. The resulting data indicate that the course of the polymerization is greatly influenced by the lactone structure, as well as by the molar ratio of coinitiator to diphenylzinc. When used alone, diphenylzinc exhibited high activity as an initiator in δ‐valerolactone polymerizations, although it was less efficient when used in the β‐butyrolactone and the β‐propiolactone polymerizations. Activity in the polymerization of β‐lactones was increased by adding small amounts of butanone or water. It was also observed that the diphenylzinc–butanone combination was more effective than the diphenylzinc–water mixture in the polymerizations of β‐butyrolactone and β‐propiolactone. Copyright © 2003 Society of Chemical Industry     

地面油管漏失定量测试方法探讨

对油管漏失进行定量测试的方法确定具体漏失位置。方法运用双频道回声探仪探测动液面的原理和工作方法，根据油管漏失形成的死油坏在测试曲线上出现特殊波位置判断油管漏失位置。结果：经过７０多井次的现场试验，该方法具有较高的准确性和可靠性。结论：利用特殊波可以有效监测油管漏失，并具有推广使用价值。     

Magnetization and rotation of MTG HTSC ring in magnetic field

The magnetization of a melt-texture growth (MTG) HTSC ring has been studied. It is shown that the magnetic field inside the ring is larger than the external field under a certain range of external magnetic fields. We have also investigated the magnetic field dependence of the response of a detective coil near a rotating superconducting ring. The responses of the MTG sample are different for different cooling methods.     

冷轧带肋钢筋直径与拉丝机卷筒直径的匹配

采用被动式工艺生产冷轧带肋钢筋须经过减径、成型两台轧机连续轧制．要求钢材的秒流量相等，否则将造成断线停产或线材在拉丝机卷筒上打滑，致使卷筒严重磨损．用双层卷筒拉丝机提供动力生产冷轧带肋钢筋时，线材直径与卷筒直径的匹配是在一个小的调整范围，通过轧机拉力控制在一定范围变化，可保证成品尺寸符合公差要求而不产生打滑，从而避免了卷筒严重磨损．     

环锭细纱机减少成纱毛羽的对策

通过对环锭细纱机成纱毛羽的成因分析 ,提出减少成纱毛羽的措施。     

Ring‐opening polymerization of D,L‐lactide by rare earth 2,6‐dimethylaryloxide

Ring‐opening polymerization of D,L ‐lactide (LA) has been successfully carried out by using rare earth 2,6‐dimethylaryloxide (Ln(ODMP)₃) as single component catalyst or initiator for the first time. The effects of different rare earth elements, solvents, monomers and catalyst concentration as well as polymerization temperature and time on the polymerization were investigated. The results show that La(ODMP)₃ exhibits higher activity to prepare poly(D,L ‐lactide) (PLA) with a viscosity molecular weight of 4.5 × 10⁴ g mol^?1 and the conversion of 97 % at 100 °C in 45 min. The catalytic activity of Ln(ODMP)₃ has following sequence: La > Nd > Sm > Gd > Er > Y. A kinetic study has indicated that the polymerization is first order with respect to both monomer and catalyst concentration. The apparent activation energy of the polymerization of LA with La(ODMP)₃ is 69.6 kJ mol^?1. The analyses of polymer ends indicate that the LA polymerization proceeds according to ‘coordination–insertion’ mechanism with selective cleavage of the acyl–oxygen bond of the monomer. Copyright © 2004 Society of Chemical Industry     

Note on ‘Construction of Double Sampling s‐Control Charts for Agile Manufacturing’

He and Grigoryan (Quality and Reliability Engineering International 2002; 18 :343–355) formulated the design of a double‐sampling (DS) s control chart as an optimization problem and solved it with a genetic algorithm. They concluded that the DS s control charts can be a more economically preferable alternative in detecting small shifts than traditional s control charts. We explain that, since they only considered the average sample size when the process is in control, their conclusion is questionable. Copyright © 2006 John Wiley & Sons, Ltd.     

国产螺旋槽密封在进口压缩机上的应用

介绍了国产螺旋槽密封在进口压缩机上的应用，分析了原进口机械-浮环组合密封的失效原因，叙述了改造后国产浮环螺旋槽组合密封的结构和特点。     

Determination of shear strength values according to EN 408

This paper presents the results of 382 shear tests carried out according to EN 408. The test pieces consisted of spruce (Picea abies) and varied in density and ring width orientation (radial, tangential and at an angle of 45° to the steel plates). In addition pieces containing pith and knots were tested. The paper discusses problems observed when using this test configuration and shows that the test results do not support the characteristic shear strength values as given in EN 338. Moreover, the test results do not support the relationship between characteristic shear strength and characteristic bending strength as given in EN 384.

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Résumé Cet article présente les résultats de 382 essais de cisaillement menés conformément à EN 408. Les éprouvettes d’essai sont en épicéa (Picea abies) et présentent une variabilité en termes de masse volumique et d’orientation des cernes d’accroissement (radiale, tangentielle, à un angle de 45° par rapport aux plaques métalliques). Des éprouvettes supplémentaires contenant du cœur et des nœuds ont également été testées. L’article évoque les problèmes qui ont été mis en évidence lors de l’utilisation de ce dispositif expérimental et montre que les résultats expérimentaux ne sont pas en accord avec les valeurs caractéristiques de résistance au cisaillement données dans EN 338. De plus, ces résultats ne confirment pas la relation entre résistance caractéristique au cisaillement et résistance caractéristique à la flexion telle que stipulée dans EN 384.

     

连轧机用人字轮齿轴断裂失效分析

用宏观断口分析、化学检验、力学性能测定、低倍检查、金相组织及夹杂物评定鉴别、受力分析及强度寿命定量估算的方法，对人字轮被动齿轴端断裂失效原因进行分析，并提出改进措施。