The role of varied metal protrusions on the conductor surfaces in corona discharge subjected to DC high voltages

Conductor corona performance is significant in the evaluation of electromagnetic environment for high voltage power transmission lines. The influence of artificial contaminated conductors on corona discharge was studied and turned out to be complicated. The ionized field strength on the corona cage was measured by field mill. Meanwhile, photos of corona plumes were photographed and grayed to quantitate the corona discharge intensity. Subsequently, a calculation model for equivalent electric field strength coefficient was established to evaluate the discharge intensity of conductors in coaxial cylindrical electrode. It could be found the computational results achieved an agreement with the observed experimental phenomena. By means of simulation results, a reasonable explanation was given to the finding that the closer the distance between the two protrusions was, the lower the corona discharge intensity and higher corona inception voltage of the conductors would be. In summary, the distributions of corona sources played an important role in the corona discharge and this work would provide an important reference for the evaluation of corona effects on the surface of contaminated conductors.     

基于Modelica语言的压水堆稳压器建模及其仿真

稳压器是压水堆核电站的重要设备之一。使用面向对象的建模工具Modelica/Open Modelica仿真软件对稳压器进行新模型的开发,并将模型仿真结果与希平港核电站减负荷试验结果进行比较,验证新建模型的有效性,可为核电站其它系统设备的建模仿真的应用提供参考。Modelica语言对象导向的特性为核电站系统设备全生命周期的模型开发实现继承和延伸管理。     

超重力法制备纳米Y型酞菁氧钛

采用超重力旋转填充床制备了纳米 Y 型酞菁氧钛(Y-TiOPc),并与烧瓶中的研究结果进行了比较。结果表明,在旋转填充床中可以得到粒径为55 nm 左右的 Y-TiOPc,其饱和电位为-538 V,半衰曝光量为0.452 lux·s,在波长200～450 nm 和550～850 nm 内具有良好的吸收,相对于传统方法制备的 Y-TiOPc 具有明显的光导性能优势,可以满足办公室自动化的应用需要。     

Surface-initiated nitroxide-mediated radical polymerization of 2-(dimethylamino)ethyl acrylate on polymeric microspheres

2-(Dimethylamino)ethyl acrylate (DMAEA) was grafted from the surface of alkoxyamine-functionalized crosslinked poly(styrene-co-chloromethylstyrene) microspheres by nitroxide-mediated radical polymerization (NMRP). Latex particles (∼60 nm diameter) bearing chloromethyl groups were synthesized by emulsion polymerization. N-tert-butyl-N-(1-diethyl phosphono-2,2-dimethylpropyl)nitroxide (SG1) was then immobilized on the particle surface. Microspheres grafted with the homopolymer pDMAEA, as well as block copolymers poly(styrene-b-DMAEA) and poly(butyl acrylate-b-DMAEA) were prepared by surface-initiated NMRP in N,N-dimethylformamide at 112 °C, with the addition of free SG1 to ensure that control is maintained. Particle size increases with number average molecular weight (M_n) of untethered polymers. The polymerizations exhibit linear first order kinetic plots and slight curvature of evolution of M_n with conversion. The functional microspheres were analyzed by infrared spectroscopy, transmission electron microscopy and thermal analysis, as well as their dispersibility in water; the results support the formation of surface-grafted pDMAEA on the microspheres.     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/montmorillonite nanocomposites

The melt intercalation method was employed to prepare poly(butylene terephthalate) (PBT)/montmorillonite (MMT) nanocomposites, and the microstructures were characterized with X‐ray diffraction and transmission electron microscopy. Then, the nonisothermal crystallization behavior of the nanocomposites was studied with differential scanning calorimetry (DSC). The DSC results showed that the exothermic peaks for the nanocomposites distinctly shifted to lower temperatures at various cooling rates in comparison with that for pure PBT, and with increasing MMT content, the peak crystallization temperature of the PBT/MMT hybrids declined gradually. The nonisothermal crystallization kinetics were analyzed by the Avrami, Jeziorny, Ozawa, and Mo methods on the basis of the DSC data. The results revealed that very small amounts of clay (1 wt %) could accelerate the crystallization process, whereas higher clay loadings reduced the rate of crystallization. In addition, the activation energy for the transport of the macromolecular segments to the growing surface was determined by the Kissinger method. The results clearly indicated that the hybrids with small amounts of clay presented lower activation energy than PBT, whereas those with higher clay loadings showed higher activation energy. The MMT content and the crystallization conditions as well as the nature of the matrix itself affected the crystallization behavior of the hybrids. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3257–3265, 2006     

An EXAFS study on oxidic and sulfided K-MoO3/γ-Al2O3 catalysts

By analyzing the extended X-ray absorption fine structure (EXAFS) of the Mo K-absorption edge, structural information for both oxidic and sulfided K-MoO₃/-Al₂O₃ catalysts with different potassium content was obtained. The oxidic samples show two backscatterer peaks in the radial distribution function (RDF), which correspond to the Mo-O coordinations in the nearest Mo-O shell. The nearest oxygen atoms are present with large configurational disorder. The RDF for the K/Mo = 0 sample is significantly different from that for crystalline MoO₃ and ammonium heptamolybdate. The RDFs for potassium promoted samples are, in some extent, similar to that for ammonium heptamolybdate. The sample with K/Mo = 0.8 and that with K/Mo=1.5 do not show obvious difference in their local Mo-O structures. The EXAFS results support the earlier conclusions from Raman spectroscopy studies on identical samples [7]. When the samples are sulfided, a rearrangement of the local neighbors around Mo atoms takes place, to form small MoS₂-like crystallites. The Mo-S and Mo-Mo coordination distances on these catalysts are the same as those in crystalline MoS₂, but the coordination numbers are significantly lower than in MoS₂. The EXAFS results indicate that Mo species on the K/Mo=0 catalyst mainly consist of Mo-S-Mo units (the basic building units of MoS₂), which are highly dispersed and show a higher level of disorder than in MoS₂. With the modification by the potassium promoter, Mo species are significantly aggregated and their local neighbors are more similar to those in MoS₂, but the Mo species still exist in a state of high dispersion.     

高强韧性液压支柱无缝钢管的研制开发

目前国内开采煤炭用液压支柱及矿用支架普遍采用27SiMn无缝钢管,随着煤炭工业的发展以及煤炭生产对安全性的更高要求,该钢种无缝钢管管体在大生产中热处理后的力学性能已达不到高强度高韧性的要求。通过优化钢管的化学成分,研究生产工艺路线及冶炼工艺、热处理工艺,成功开发出高强韧性液压支柱用无缝钢管并投入批量生产。使用结果表明,该产品的强韧性、焊接性能等满足用户要求。     

热型连铸过程液／固界面位置对过程参数变化的响应

热型连铸过程的实时控制涉及到过程液/固界面位置对控制参数(冷却距离和牵引速度)的响应.根据热型连铸过程的凝固传热特性,建立了热型连铸过程的物理、数学模型,获得了OCC过程中液/固界面位置对不同的冷却距离和牵引速度变化量的响应函数.通过数值模拟,考察了冷却距离和牵引速度变化时液/固界面位置的响应过程,并明确了在OCC过程的闭环控制过程中,冷却距离和牵引速度两控制量调整的先后顺序.     

纳米SiO_2与POE协同增韧增强PP三元复合材料的制备及性能研究

利用熔融共混挤出方法制备了聚烯烃热塑性弹性体乙烯-辛烯共聚物(POE)/纳米二氧化硅(nano-SiO2)协同增韧增强聚丙烯(PP)三元复合材料(PP/POE/nano-SiO2)。通过冲击实验、拉伸实验、熔融结晶分析和热失重实验研究了POE与nano-SiO2的协同作用、nano-SiO2的含量对复合材料力学性能、熔融结晶行为和热学性能的影响。研究结果表明,POE与nano-SiO2的协同增韧明显优于POE单独对PP的增韧,nano-SiO2还体现出明显的增强作用。当nano-SiO2的质量分数为2%时,复合材料的室温冲击强度达最大值,其较PP/POE提高了72.6%,而在-35℃下较PP/POE的提高了200%。当nanoSiO2的质量分数为4%时,复合材料的室温拉伸强度达最大值,其较PP/POE增大了38.9%。熔融结晶分析表明,添加nano-SiO2导致复合材料的结晶度增大。热学性能分析表明,nano-SiO2的加入使PP/POE/nano-SiO2三元复合材料的热稳定性提高。     

Structure Stability and Microwave Dielectric Properties of (1 − x) Ba(Mg1/2W1/2) O3 + xBa(Y2/3W1/3)O3 Ceramics

The structure stabilities of double perovskite ceramics‐ (1 ? x) Ba(Mg_1/2W_1/2)O₃ + xBa(Y_2/3W_1/3)O₃ (0.01 ≤ x ≤ 0.4) have been studied by X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), and Raman spectrometry in this study. The microwave dielectric properties of the ceramics were studied with a network analyzer at the frequency of about 8–11 GHz. The results showed that all the compounds exhibited face‐centered cubic perovskite structure. Part of Y³⁺ and W⁶⁺ cations occupied 4a‐site and the remaining Y³⁺ and Mg²⁺ distributed over 4b‐site, respectively, and kept the B‐site ratio 1:1 ordered. Local ordering of Y³⁺/Mg²⁺ on 4b‐site and Y³⁺/W⁶⁺ cations on 4a‐site within the short‐range scale could be observed with increasing Y‐doping content. The decomposition of the double perovskite compound at high temperature was successfully suppressed by doping with Y on B‐site. However, Ba₂Y_0.667WO₆ impurity phase appeared when x > 0.1. The optimized dielectric permittivity increased with the increase in Y doping. The optimized Q × f value was remarkably improved with small amount of Y doping (x ≤ 0.02) and reached a maximum value of about 160 000 GHz at x = 0.02 composition. Further increasing in Y doping led to the decrease in Q × f value. All compositions exhibited negative τ_f values. The absolute value of τ_f decreased with increasing Y‐doping content. Excellent combined microwave dielectric properties with ε_r = 20, Q × f = 160 000 GHz, and τ_f = ?21 ppm/°C could be obtained for x = 0.02 composition.