医疗电子设备的传导EMI噪声机理分析与处理

本文针对医疗电子设备的电磁兼容问题,分析了其传导EMI噪声的生成机理,包括瞬态电流、接地不良、串扰和电容耦合4种情况. 本文还根据4种传导EMI噪声生成机理提出了相应的噪声处理方法,包括电源去耦、设计滤波器、采用铁氧体磁环、屏蔽等,并通过两个工程实例验证了其有效性与实用性.     

高能球磨法制备MgB2材料的研究进展

MgB₂超导体临界温度为39 K,具有价格低廉和临界转变温度相对较高等优点,具有工程应用前景,然而其大尺度应用还依赖于超导性能的改善。经过系统的研究发现高能球磨和元素掺杂是提高MgB₂磁场下J_c性能最有效的方法。本文介绍了采用高能球磨法制备MgB₂的研究现状,采用高能球磨能有效细化晶粒,有利于提高超导芯丝的致密度,强化MgB₂晶粒的连接性,同时晶粒细化形成的更多晶界能形成钉扎中心,进一步提高线/带材在高磁场下的临界电流密度。我们还介绍了通过分步反应法和高能球磨在常压条件下合成MgB₂,高能球磨法可以减少MgB₂长线中的孔洞并提高粉体密度。     

Novel Fe‐based complex oxide catalysts for hydroxylation of phenol

Novel catalysts for the hydroxylation of phenol, Fe–Si–O, Fe–Mg–O and Fe–Mg–Si–O complex oxides, have been synthesized by a coprecipitation method. X‐ray diffraction studies show that MgFe₂O₄ crystallites with spinel structure are formed in Fe–Mg–Si–O and Fe–Mg–O complex oxides and the crystallite size of the metal oxide or complex oxide is reduced after addition of Si. In the hydroxylation of phenol with hydrogen peroxide, Fe‐based complex oxides exhibit high activities after a short induction period. The phenol conversion is improved when silicon is introduced into the Fe‐based complex oxides, and formation of MgFe₂O₄ crystals with spinel structure in the catalysts increases the diphenol selectivity. The addition of a little acetic acid to the reaction liquid can shorten the induction period effectively. Under the same reaction conditions, phenol conversion and diphenol selectivity over the Fe–Mg–Si–O catalyst are close to those over TS‐1, and furthermore, the reaction time is more than ten times shorter as compared to TS‐1. The reaction mechanism of the hydroxylation of phenol on the catalysts has been studied, and a free‐radical mechanism initiated by the formation of phenoxy free radicals is suggested. This revised version was published online in August 2006 with corrections to the Cover Date.     

赤天化合成塔上层催化剂的装卸及还原

介绍改造型Ｋｅｌｌｏｇｇ合成塔上层催化剂的装卸及还原操作,为全塔催化剂的卸出作了有益的尝试。     

Study on corrosion electrochemical behavior of several different coating systems by EIS

Corrosion electrochemical behavior of chlorinated rubber top coating (single-layer), inorganic zinc-rich primer/chlorinated rubber top coating (double-layers) and inorganic zinc-rich primer/epoxy middle paste/chlorinated rubber top coating (tri-layers) in 3.5 wt% NaCl solution was studied by electrochemical impedance spectroscopy (EIS). A series of impedance spectra of the three coating systems during immersion were measured; and their protective properties were compared according to the spectra. The experimental results showed that, the protective properties of the double-layers coating system were even worse than that of the single-layer coating system; and the tri-layers coating system had the best protective properties in the three coating systems; epoxy middle paste had played a very important role for protective properties of the composite coating system.     

In vitro hydrolytic degradation of poly(para-dioxanone) with high molecular weight

The in vitro hydrolytic degradation of high molecular weight poly (para-dioxanone) was studied by examining the changes of weight retention, water absorption, pH value, tensile strength, break elongation, thermal properties, and morphology of high molecular weight PPDO in phosphate buffered saline (PBS) (pH 7.44) at 37°C for 8 weeks. During the degradation, all samples’ weight retention decreased and water absorption increased significantly, whereas hydrolysis rate of PPDO bars varied with molecular weight. Compared with lower molecular weight samples, higher molecular weight PPDO samples exhibited higher hydrolysis rate. The samples’ glass transition temperature (Tg) decreased notably, while the degrees of crystallinity (Dc) increased. The samples almost totally lost their tensile strengths and breaking elongation after 4 weeks of degradation. The results suggested that the stability of PPDO in vitro hydrolytic degradation increased with the increase of molecular weight.     

涂层硬质合金结构及材料的研究进展

涂层硬质合金具有高硬度和优良的耐磨性,延长了其制品的使用寿命.本文主要从材料学角度,综述了涂层结构类型、涂层材料及结构、涂层基体等方面国内外涂层硬质合金的研究进展,联系具体涂镀技术和工艺,对比和讨论了不同类型涂层的物理性能、机械性能和切削性能,并对涂层硬质合金行业的发展进行了展望.     

单片机在自吸式烧嘴梭式窑控制系统中的应用

自吸式烧嘴液化气梭式窑投资少、使用灵活、烧成成本较低,已广泛应用于日用瓷、艺术瓷等生产中.但自吸式烧嘴液化气梭式套难以实现自动控制,靠手工操作很难保证烧成质量.本文自行开发了成本低的单片机,并改装了烧嘴、排烟闸板的传动装置,对自吸式烧嘴液化气梭式窑进行了温度与气氛控制的实验.经过工况实验证明,用单片机实现液化气梭式窑的自动控制是可行的,并取得了较好的控制效果.     

浅谈陶瓷装饰中的色彩运用

简述了陶瓷装饰中色彩与中国画的色彩关系,并强调了色彩在陶瓷创作中的具体运用:处理好色与墨的关系.以及色彩的客观与主观关系.     

Effect of Interfacial Bonds on the Morphology of InAs QDs Grown on GaAs (311) B and (100) Substrates

The morphology and transition thickness (t _c) for InAs quantum dots (QDs) grown on GaAs (311) B and (100) substrates were investigated. The morphology varies with the composition of buffer layer and substrate orientation. And t _c decreased when the thin InGaAs was used as a buffer layer instead of the GaAs layer on (311) B substrates. For InAs/(In)GaAs QDs grown on high miller index surfaces, both the morphology and t _c can be influenced by the interfacial bonds configuration. This indicates that buffer layer design with appropriate interfacial bonds provides an approach to adjust the morphologies of QDs grown on high miller surfaces.