无抑制剂生产取向硅钢的最新进展

概述了无抑制剂生产取向硅钢所关注的问题（如：需要板坯高温加热、最终高温退火时间长、能耗高、氧化铁皮生成量大）;探讨了无抑制剂生产的原理、应具备的条件及控制方法。研究表明,应控制氧化物和氮化析出物的晶粒大小及数量。     

无汞锌粉生产过程的质量控制

讨论了无汞锌粉生产过程(含合金化、雾化、筛分等)中影响产品质量的因素及相应的控制手段;指出,通过加强对合金化、雾化和筛分过程的有限控制,减少各流程的污染,能生产出高质量的无汞锌粉。同时指出,析气量检测是测试锌粉质量好坏的一种重要手段,但析气量检测结果仅能作为锌粉生产厂家的参考依据。     

无刷双馈电机智能控制策略综述

简要分析了无刷双馈电机结构与数学模型。在此基础上,介绍了无刷双馈电机的三种智能控制策略:模糊自适应PID控制、模糊神经网络控制、专家自适应PID控制。最后展望了无刷双馈电机控制策略的发展趋势。     

无轴承开关磁阻电机的功率变换器研究

无轴承开关磁阻电机结构简单、运行效率高、容错能力强,具有良好的高温和高速适应性。介绍了无轴承开关磁阻电机的悬浮原理和系统构成,简要分析了其控制策略。根据其控制特点,设计了主绕组和悬浮绕组功率电路拓扑结构,通过实验样机验证了功率电路的可靠性。     

无卤低烟阻燃控制电缆的研制

阐述了无卤低烟阻燃控制电缆的结构设计、主要性能及关键工序要点。     

无模型自适应控制技术

介绍了无模型自适应控制的概念、系统的结构及优点，通过液位控制的实例说明了它的应用步骤。     

无位置传感器无刷直流电机控制的简易方法

介绍了Micro Linear公司生产的ML4428无刷直流电机无传感器PWM智能控制器的内部结构,它是无位置传感器无刷直流电动机控制的简易方法,该控制器内部的反电势电路、起动及换向逻辑电路、限流比较器和保护电路简化了无位置传感器无刷直流电动机的控制,做到单独控制的正反向运行,起动时无反转,采用PWM控制或最小噪声的线性控制,可获得最高效率。     

采用dsPIC30F6010的无刷直流电动机控制系统设计

在全面分析研究了无位置传感器无刷直流电动机运行方式的基础上，阐述了无刷直流电动机的控制原理以及反电势过零检测、控制系统的硬件及软件实现方法，并且为了在较宽的范围内提高无刷直流电动机的调速性能，系统采用高性能dsPIC30F6010数字信号控制器作为微控制器，实现数字转速开环控制。     

无刷电动机简述

在现代的生产、生活中,无刷电动机由于其调速性能的优越性,得到了越来越广泛的应用.本文简述了无刷电动机的工作原理及组成,重点阐述了无刷电动机的调速作用.     

无粘结预应力混凝土工程施工阶段质量控制分析

通过工程实践,解决了无粘结预应力砼在施工过程中的具体问题。论述了无粘结预应力混凝土工程施工的质量控制方法和要点,提出建议和施工方案,以供施工及设计人员参考。     

放电等离子烧结纳米晶NdFeB合金的组织特征和磁性能

通过对快淬NdFeB粉末进行放电等离子烧结(SPS),制备出各向同性NdFeB永磁材料,研究了烧结工艺对磁体组织形貌和性能的影响.结果表明,SPS烧结产生的颗粒放电导致粉末边界区域晶粒长大,形成了边界粗晶区,而粉末内部仍保持了快淬粉末的细晶结构.烧结温度和压力对晶粒尺寸有较大的影响,从而影响烧结磁体的磁性能.较低的烧结温度和高的烧结压力既可以获得高致密磁体,也可以有效减小粗晶区的尺寸,从而提高材料综合磁性能.     

微量硼对20 MnVB 与25 MnTiB 钢淬透性的影响

本研究工作采用硼自射线照像技术,使用了 SSNTD(CAB)[固体核径迹探测器(为醋酸纤维)]检测 B 放射性同位素的重新分布.由此研究了 ppm 数量级的 B 对合金淬透性的贡献.研究时发现在高温臭氏体化过程中硼偏聚消失,含硼合金在淬火过程中产生的硼在晶界的偏聚为一非平衡热力学过程.奥氏体化后,偏聚程度随淬火温度的升高而增加,在晶界附近出现贫硼区,是晶界非平衡偏聚之突出特征.研究结果表明:微量硼对提高合金的淬透性是有利的.     

Synthesis of nanosized (1 − x)BiScO3 − xPbTiO3 ferroelectric ceramic powders

Nanosized (1???x)BiScO₃???xPbTiO₃ ferroelectric ceramic powders was obtained by the metal citrate sol–gel method. The decomposition process of the polymer was studied by using infrared spectral absorption and X-ray diffraction. Perovskite phase can be obtained at the calcining temperature as low as 450 °C and the average grain sizes of powders were calculated by XRD method. The influence of the grain size by pH value of the solution is explained. The calcining temperature is proved to be the foremost factor to determine the grain size which grew from 12 to 23 nm when calcined at different temperatures. The holding time can also affect the grain size. The sintering temperature can be reduced by 100 °C using nano powders than using traditionally prepared large grain powders.     

三菱350 MW机组滑参数停机分析

滑参数停机能快速降低缸温,有利于尽快对汽轮机本体进行检修.阐述了三河发电有限责任公司在停机过程中,汽轮机与锅炉紧密配合,将汽轮机胀差和高、中压缸温差等参数控制在合理范围内的整个过程.分析了机组滑停过程中的不足和问题,针对滑参数停机过程需要注意的问题提出了合理化建议.     

低温烧结Ni0．24Cu0．21Zn0．55Fe2O4铁氧体的工艺条件

采用了固相反应法制备了Ni0.24Cu0.21Zn0.55Fe2O4铁氧体材料,研究了制备工艺(预烧温度、烧结温度、升温速度、保温时间)及助熔剂Bi2O3对材料显微结构和电磁性能的影响.结果表明,预烧温度、烧结温度、升温速度、保温时间和助熔剂Bi2O3对NiCuZn铁氧体材料的晶粒尺寸、晶粒分布均匀度、品质因数、起始磁导率和介电常数等影响显著.通过制备工艺参数的优化,确定出适当的工艺条件:预烧温度875℃,烧结温度900℃,升温速度2℃/min,保温时间2h.利用上述工艺制得的材料,不仅具有良好的电磁性能,而且实现了低温烧结.     

AC and DC conductivity studies in pulsed laser ablated (Ba,Sr)TiO3 thin films

Abstract

A comparison of the ac conductivity of laser ablated (Ba, Sr)TiO₃ thin films was made for films grown at different substrate temperatures. The ac conductivity was studied as a function of frequency and ambient temperature ranging from room temperature to 460°C. Conductivity results from ac and dc measurements were compared in their an respective Arrhenius plots revealing interesting coincidences. The value of the activation energies computed from the Arrhenius plot of à _ac with 1000/T ranged from 0.97 to 1.3 eV in the high temperature region to 0.36 to 0.54 eV in the low temperature region for different samples. The activation energies obtained from pure dc measurement for fields greater than 100 kV/cm across the samples were in the range of 1.06 to 1.32 eV for different samples. The similarity in results suggests a common origin in the de conduction process in the concerned temperature range and was attributed to ionic conduction resulting from oxygen vacancy motion which has been observed to be significant at high temperatures and high fields. For high temperature grown samples the value of activation energy computed from the Arrhenius plots was comparatively less than those grown at lower substrate temperatures. The difference was attributed to the microstructure and the effect of grain boundaries on the motion of oxygen vacancies leading to the conduction process.     

Varistor behavior of Mn doped ZnO ceramics prepared from nanosized precursors

Polycrystalline ZnO doped with MnO, from 2 to 15?mol%, was prepared from nanosized precursors. The effect of Mn doping and sintering temperature on phase evolution, microstructure and V-I characteristics were investigated. SEM images showed that the great merit of using nanoparticles is that the samples with high microstructural uniformity and lower grain size can be achieved. Varistor behavior was observed in all specimens, even in the undoped ceramics due to the oxidation process of zinc interstitial defects at grain boundaries. The electric field versus current density (E-J) curves indicated that the breakdown field E_b increased and the nonlinear coefficient ?? decreased with the increase in doping level. 2?mol% Mn doped ceramic sintered at 1100?°C exhibited the highest nonlinear coefficient, ???=?40. The stability test under DC stress was performed for the undoped ZnO ceramics. ZnO varistor sintered at 1300?°C showed not only high nonlinearity, but also high stability under DC stress.     

Modeling of transport properties of interfacially controlled electroceramics: Application to n-conducting barium titanate

Grain boundary regions in n-conducting barium titanate (BaTiO₃) are re-oxidized during the cooling process after sintering the ceramics in air. The kinetics of this re-oxidation process is determined by rapid transport of oxygen along the grain boundaries and slow (rate-determining) diffusion of cation vacancies from the grain boundaries into the grains until the diffusion process is frozen-in. Based on numerical calculations of frozen-in diffusion profiles of cation vacancies at grain boundary regions for various cooling rates, a modified Schottky-barrier model is introduced in order to calculate the grain boundary resistivity as a function of temperature from the Curie-point up to 900°C. A change of the activation energy at approximately 500°C is predicted owing to an enrichment of holes in the space charge layers at elevated temperatures. The modeling results are compared with experimental data for BaTiO₃-based positive temperature coefficient resistors (PTCRs).     

对核电发电机转子铜排的晶粒均匀加工工艺探讨

研究了1100MW级核电发电机转子用两种类型铜排的加工工艺对晶粒度尺寸、均匀性的影响。通过对核电转子铜排的软态、硬态试样以及在不同加工温度下的材料金相分析,摸索了成品试样截面不同位置的晶粒度差异。最终摸索出能获得较均匀晶粒度的加工工艺。