Linked influence of pH and cations on fatty-acid monolayer integrity related to high-quality Langmuir-Blodgett films

This study shows the connection between the morphological structure of transferred films and the chemical composition of the monolayer before transfer. The stability of a behenic acid monolayer depends on the linked influence of the type of cation and of the pH value in the aqueous subphase. The stability of the monolayer is assessed by the expansion of the solid-packed state and by the relaxation time. Its integrity is characterized by the number of crystal defects which appear in transferred Langmuir-Blodgett (LB) films as seen through Nomarski microscope observations. Both stability and integrity are greatly improved when Cd²⁺ or Mn²⁺are added to the subphase at pH 5.75 and 6 respectively. In these conditions, the transfer is very efficient and the LB films thus obtained are of very high quality. The pH values of the subphase at which the molecules of behenic acid are transformed into bivalent salts differ significantly according to the nature of the cation involved. Comparing infrared spectra of the LB films, it appeared that the relative amount of acid/salt found in the monolayer was practically the same with a subphase containing either Cd²⁺ at pH 5.75 or Mn²⁺ at pH 6. This suggests that the ratio of acidic and salt forms would be a key parameter for obtaining high-quality LB films.     

图形电镀铜的常见缺陷及故障排除

本文主要阐述印制电路板生产中图形电镀铜常见缺陷及成因,查找影响其品质的因素和工序并结合相关生产制定相应的预防措施,有效提高产品质量。     

BYJ型防喷脱接器的设计与应用

本文介绍了BYJ型防喷脱接器的结构和工作原理。它既有抽油杆与大泵活塞脱接功能,又能实现不压井作业施工,是大型抽油泵理想的配套工具。现场应用表明,该防喷脱接器对接成功率较高,并实现了大泵井不压井施工。     

Graph‐Theory Approach to Eigenvalue Problem of Large Space Structures

The dynamic analysis and control system design of large space structures involve the solution of the large‐dimensional generalized matrix eigenvalue problem. The computational effort involved is proportional to the third power of the dimension of the matrices involved. To minimize the computational time a graph‐theory approach to reduce a matrix to lower‐ordered submatrices is proposed. The matrix‐reduction algorithm uses the Boolean matrices corresponding to the original numerical matrices and, thus, the computational effort to reduce the original matrix is nominal. The computational savings directly depend upon the number of submatrices into which the original matrix is reduced. A free‐free square plate is considered as an example to illustrate the technique. In this example a matrix of 16th order is reduced to three scalars corresponding to three rigid‐body modes, and three matrices of order three and one matrix of order four.     

大型储罐的罐壁设计

根据十万立方米浮顶油罐罐壁板应力测试的实测结果，运用应力分析程序，对罐壁板应力分布情况进行了分析和比较，通过调整罐壁板的厚度，使新设计储罐的罐壁板应力分布更加均匀、合理。     

Relaxation phenomena caused by equilibration of point defects

Relaxation phenomena due to equilibration of point defects in metals are reviewed. The relaxation effect in specific heat observed in tungsten and platinum confirms that in both cases the nonlinear increase in the high-temperature specific heat has to be attributed to point-defect formation. Relaxation phenomena observed by measurements of electrical resistivity and positron annihilation are also considered. The comparison of the data seems to be favorable for the conclusion that all the phenomena are of one origin.     

Effect of Forming Pressure on the Internal Structure of Alumina Green Bodies Examined with Immersion Liquid Technique

Green bodies prepared by compaction of alumina granules were made transparent by an immersion liquid technique, and the internal structure was characterized with an optical microscope to study the effect of forming pressure on the internal structure. Clear images obtained by the technique provide more detailed information than other existing methods for structures ranging from one to tens of micrometers. Intergranular pores were present between unfractured granules. Their sizes and concentration tended to decrease with increasing forming pressure. However, pores were clearly present even in the green body prepared at 600 MPa. A rod- and needlelike feature was also found and was concluded to correspond to a high-density region. The significance of large pores and high-density regions on processing as well as the details of the technique is discussed.     

新一代高强韧性WDL系列钢综合性能及应用

本文着重介绍武汉钢铁公司近年来研制开发的第二代高强度低合金钢—高强韧性WDL系列钢的综合性能及应用情况。该钢具有优异的焊接性能和低温韧性,板厚≤50mm钢板焊前不预热或稍加预热而不产生焊接裂纹,是制造大型压力容器（特别是低温和常温球罐）、水电站压力钢管和水轮机蜗壳、高寒地区使用的大型工程机械、大跨度桥梁及海上采油平台等装备的理想用材。     

厚膜混合集成电路常见工艺缺陷及其消除方法

除设计和材料外，工艺和操作对厚膜混合集成电路的质量和性能也有较大的影响。分析了厚膜混合集成电路生产过程中一些常见的工艺缺陷，如线条变形、起泡、阻值不稳、元件受损、锡珠等的产生原因，并提出了相应的消除方法。