The synthesis of low crystallinity polyacetylene from the precursor polymer polybenzvalene

The synthesis and properties of the conductive polymer precursor polybenzvalene (PBV) and its conversion to polyacetylene (PA) are presented. PBV was synthesized by ring-opening metathesis polymerization (ROMP) of benzvalene (BV) with non-Lewis acidic tungsten alkylidene catalysts. Treatment of PBV with solutions of HgCl₂, HgBr₂, ZnI₂ and AgBF₄ results in a CC bond rearrangement, and produces polyacetylene PA. The PA films produced with HgCl₂ displayed the highest conductivities and the best mechanical properties. The PA produced was of low crystallinity and upon treatment with I₂ exhibited conductivities of 1 Ω⁻¹cm⁻¹. Oriented PA was produced by stretching the PBV and converting it to PA. With I₂ doping, the oriented PA (l/l₀=6) displayed a conductivity of 49 Ω⁻¹cm⁻¹.     

Comparison of geometries and electronic structures of polyacetylene,polyborole, polycyclopentadiene,polypyrrole, polyfuran,polysilole, polyphosphole,polythiophene, polyselenophene and polytellurophene

Geometries of monomers through hexamers of cylopentadiene, pyrrole, furan, silole, phosphole, thiophene, selenophene and tellurophene, and monomers through nonamers of borole were optimized employing density functional theory with a slightly modified B3P86 hybrid functional. Bandgaps and bandwidths were obtained by extrapolating the appropriate energy levels of trimers through hexamers (hexamers through nonamers for borole) to infinity. Bandgaps increase with increasing π-donor strengths of the heteroatom. In general, second period heteroatoms lead to larger bandgaps than their higher period analogs. Polyborole is predicted to have a very small or no energy gap between the occupied and the unoccupied π-levels. Due to its electron deficient nature polyborole differs significantly from the other polymers. It has a quinoid structure and a large electron affinity. The bandgaps of heterocycles with weak donors (CH₂, SiH₂ and PH) are close to that of polyacetylene. For polyphosphole this is due to the pyramidal geometry at the phosphorous which prevents interaction of the phosphorus lone pair with the π-system. The bandgap of polypyrrole is the largest of all polymers studied. This can be attributed to the large π-donor strength of nitrogen. Polythiophene has the third largest bandgap. The valence bandwidths differ considerably for the various polymers since the avoided crossing between the flat HOMO — 1 band and the wide HOMO band occurs at different positions. The widths of the wide HOMO bands are similar for all systems studied. All of the polymers studied have strongly delecalized π-systems.     

化学镀铜新工艺及其在电子工业中的应用

介绍了一种国内最新的化学镀铜工艺的原理、镀液的成分、配方和操作条件等,叙述了该工艺镀铜层的组成、表面形态及其在电子工业中的应用。     

Ferromagnetism in a new type of organic polymer based on benzene rings bridged by carbons

A new organic polymer with a three-dimensional network of carbons is proposed as a prototype organic ferromagnet. It is composed of benzene rings bridged by carbon atoms. The ground and the excited states of π electrons of this polymer are studied within the Hubbard model combined with the mean-field theory, and it turns out that this polymer becomes a ferromagnet (a ferrimagnet). The one-electron energy band and the spin density at each carbon as well as the magnon spectrum are calculated.     

A new strategy to design eutectic high-entropy alloys using mixing enthalpy

Although eutectic high entropy alloys (EHEAs) display homogeneously fine microstructure, excellent castability and promising industrial application potential, how to design eutectic compositions in high entropy alloys (HEAs) remains to be challenging. Here, a novel strategy, specifically, through calculation of mixing enthalpy, was used to locate eutectic compositions in HEAs. As a proof of this concept, a series of EHEAs were located and prepared following the mixing enthalpy method. Using this new strategy, eutectic compositions can be designed conveniently, once one can classify elements into two different groups. This new alloy design strategy can be readily adapted to locate new EHEAs.     

Study on the electronic structures of REBaCuO superconductors and their relation to superconductivity

Electronic structures of REBaCuO(RE=La,Pr,Nd,Sm,Gd,Dy,Ho and Er) systems were calculated by means of SCF-Xα-SW methods.Results show that there is an inner-orbit coupling for these oxide superconductor systems.The inner-ordit coupling was resulted from the interaction of two electronic orbits of RE 5p and O 2s,since they have similar energy state levels and relatively larger orbital electronic clouds.Compared with experimental facts,it is also found that the overlap in space between the two orbits has a similar tendency to Tc and the number of enrolling electrons has a close relation to Jc,therefore,the influence of inner-ordit coupling on superconductivity could not be overlooked.     

一种新型滤芯检测机器人控制系统的设计

讨论了一种新型滤芯检测机器人控制系统的设计，控制系统硬件用高精度步进电机加工驱动器，其他控制功能在上层软件中实现，滤芯检测机器人的末端速度采用了双梯形升降速规律，很好利用了电机的工作频率特性，控制系统软件基于Windows98操作系统平台，用VC6.0开发，为保证其实时性，控制软件采取了多线程实时优先级的策略。整套控制系统具有硬件成本低，系统操作方便的特点，在一定检测精度下是一种理想的选择。     

一种新型行程可控压力机设计

为解决目前机械曲柄压力机公称压力行程较小,压力行程不可调以及液压机在中厚板冲压、拉深时行程次数较低等问题,通过比较分析曲柄压力机与液压机的特点,结合机械多杆压力机与液压机的优点,经过多次机械运动仿真分析、液压传动仿真分析,以及尺寸优化计算,设计了一种新型行程可控压力机。该机空行程和压力行程均可控,且压力行程可根据工艺需求,在一定范围内可调节,此外该机行程次数高,滑块总行程量大,装模高度调节量大,通用性较广。     

The scaling of strength in the design of high-power MEMS structures

The prediction of the strength of complicated structures based on material test data is important for high-power density microelectromechanical systems. Probalistic analysis is used to predict the strength of pressure-tested microfabricated silicon structures from simpler test specimens. The predictions are found to be non-conservative. This is probably due to interactions between the etching process and the structural geometry, which changes the flaw distribution between the two statistical populations. In both cases secondary smoothing etches recover the strength.     

复合型柔性腕的新型结构设计

文章主要致力于大位移误差补偿问题,对复合柔性腕的开发以及设计进行了有关结构方案的研究.针对柔性腕的特殊使用要求,在传统RCC(Remote Center Compliance远中心柔顺结构)的基础上,对普通的RCC进行了结构创新,开发设计了复合柔顺手腕.     

A new approach to optimal design of multi-stage metal forming processes with micro genetic algorithms

This paper describes a new method for design optimization of process variables in multi-stage metal forming processes. The selected forming processes are multi-pass cold wire drawing, multi-pass cold drawing of a tubular profile and cold forging of an automotive outer race preform. An adaptive micro genetic algorithm (μGA) scheme has been implemented for minimizing a wide variety of objective-cost functions relevant to the respective processes. The chosen design variables are die geometry, area reduction ratios and the total number of forming stages. Significant improvements in the simulated product quality and reduction in the number of passes has been observed as a result of the micro genetic algorithms-based optimization process.     

Geometric and electronic structures of isothianaphthene and thieno[3,4-C]thiophene: A theoretical investigation

We present a theoretical (MNDO-SCF-MO and VEH) investigation of the geometry and electronic properties of isothianaphthene (benzo[c]-thiophene) and another thiophene derivative, thieno[3,4-c]thiophene. Our goal is to understand better, at the molecular level, the reasons for a small band-gap in polyisothianaphthene and possibly to guide the organic synthesis towards other interesting polymeric materials. Compared to the parent thiophene molecule, isothianaphthene and thieno[3,4-c]thiophene possess significantly lower ionization potentials and present a strongly conjugated path along their periphery.     

一种曲轴精密校直液压机的液压系统设计

介绍一种曲轴精密校直液压机的液压系统设计,采用比例伺服系统,满足了精密校直液压机的重复定位精度要求,保证了压机的校直精度。     

圆钢立椭孔型的新设计

为解决圆钢轧制时圆弧槽底的立椭孔型稳定性差问题,将槽底圆弧段改为直线段。经生产实践证明,新孔型不仅轧制稳定性提高。而且取得产品质量和生产率提高的良好效果。     

A new time-frequency detection method of stray current field interference on metal structures

A new detection method has been presented of stray current field interference on underground metal structures. The method employs short time Fourier transformation (STFT). This method of analysis allows determination of signal spectral power density changes (e.g., structure potential) in the function of time. In the paper results have been presented of total time-frequency analysis of a pipeline potential in a stray current field generated by a tram traction. The presented results have unequivocally shown that the described method allows accurate identification of the stray current source and determination if it interacts with the underground metal structure.     

Application of detonation coatings to design a new metal cutting tool

This paper presents the results of a research and development study of a new metal-working tool using detonation spray hard alloy coating. The influence of a heat-insulating sublayer on thermal flows occurring at flow drilling has been studied. New design and technology to manufacture punches for plastic drilling with heat-insulating ceramic sublayer aimed at decreasing a parasitic thermal flow through the tool to the lathe’s spindle have been developed. In addition, a new design and manufacturing technology for replaceable cutting plates for lathe working involving the use of detonation spray hard alloy coating have been created. The proposed application of the new tool allows reduction of its conversion cost and improving of performance characteristics.