Preparation and properties of nanosize MnZn ferrite from δ-FeOOH

Ferrous ion was transformed into feroxyhyte (δ-FeOOH) by oxidation. Then, manganese sulfate and zinc sulfate in some ratio were added to the feroxyhyte solution. The co-precipitation was boiling reflux conditions sometime under constant stirring. The nanosize MnZn ferrite powder was formed. The mechanism of preparation of the nanosize MnZn ferrite was discussed, and the formation of feroxyhyte which was playing a key role during the process was mentioned. The properties of powder was tested by means of X-ray diffraction, transmission electron microscopy and vibrating sample magnetometer. The results show that the samples of spherical particles about 20 nm, which have characteristics of ferrimagnetism, has larger saturation magnetization, but the remanent magnetization and coercivity are comparatively smaller. The spinel MnZn ferrite nanosize powder was successfully prepared from δ-FeOOH at low temperature, with low-carbon steel and peroxide as main material.     

Random-effects regression analysis of correlated grouped-time survival data

Random-effects regression modelling is proposed for analysis of correlated grouped-time survival data. Two analysis approaches are considered. The first treats survival time as an ordinal outcome, which is either right-censored or not. The second approach treats survival time as a set of dichotomous indicators of whether the event occurred for time periods up to the period of the event or censor. For either approach both proportional hazards and proportional odds versions of the random-effects model are developed, while partial proportional hazards and odds generalizations are described for the latter approach. For estimation, a full-information maximum marginal likelihood solution is implemented using numerical quadrature to integrate over the distribution of multiple random effects. The quadrature solution allows some flexibility in the choice of distributions for the random effects; both normal and rectangular distributions are considered in this article. An analysis of a dataset where students are clustered within schools is used to illustrate features of random-effects analysis of clustered grouped-time survival data.     

世界化纤发展趋势

对纤维的需求不断增长，天然纤维缺口将愈来愈大，均为化纤发展带来了机遇。化纤工业竞争激烈，主要趋势为扩大规模提高效率。无人化、环保化也是一种趋势。同时也发展了一些与下游名牌产品联系在一起的小型专业厂．高技术、高性能纤维发展较快．在技术方面，认为纤维超细化、废弃物回收重新纺制纤维，注意环保，设备增容、高效化，高性能纤维开发等是主要趋势．     

下河沉积型瓷石的工艺特性与开发应用的探讨

本文论述了新近在江西下河发现的沉积型瓷石的地质特点、矿石特征、精泥性能、成瓷工艺及其开发应用前景。     

结焦抑制剂N-360在乙烷炉上的应用

中国石化扬子石油化工股份有限公司烯烃厂1号乙烯装置两台乙烷炉运行周期一直偏低,辐射段炉管使用寿命较短,并影响急冷油减粘系统的稳定运行。应用结焦抑制剂N-360后,乙烷炉运行周期与辐射段炉管使用寿命大幅延长,并且能耗下降、产品收率提高。     

近十年常温干法精脱硫专利技术发展动态

收集了近十年来国内的常温干法精脱硫专利，并分类列举出各种脱硫剂的物化性质和几种常温精脱硫工艺，重点阐述了该技术的优缺点及其未来发展方向。     

羟基烷基磺酸镀液电镀Sn—Pb合金的研究

我国自行研制生产的羟基烷基磺酸电镀Sn-Pb合金镀液已经在部分厂家投产使用.生产实践证明,该镀液能获得不同铅含量的、可焊性优良且镀层结晶细致而光亮的Sn-Pb合金镀层.本研究重点测定了该镀液的电化学性能,如阴极电流效率、分散能力及深镀能力.并对添加剂的作用进行了研究探讨.     

氧化铝上吸附平衡与动力学的分形特性

在实验测定氧化铝吸附氮气的平衡和动力学过程的基础上 ,由平衡数据得到分形维数 ,对动力学结果分别用欧氏几何和分形几何的动力学模型进行处理 ,比较两种方法得到的扩散系数之间的差别。结果表明 :粉状氧化铝的分形维数为 2 .12 ;采用分形动力学模型得到的扩散系数同欧氏几何扩散模型的结果不一样 ,扩散系数不随浓度的变化而改变 ;而欧氏几何扩散模型中的扩散系数随浓度变化发生改变 ,且变化符合Darken关系     

农药工业的发展趋势与专利状况

通过我国农药工业与国外的差距的分析,笔者认为我国农药企业要走集团化的道路,由仿制为主转向刨制,并调整产品结构。文中还介绍了有关农药的专利知识及国外新农药的创制情况。     

Dynamic output feedback control of a flexible air-breathing hypersonic vehicle via T–S fuzzy approach

By utilising Takagi–Sugeno (T–S) fuzzy set approach, this paper addresses the robust H_∞ dynamic output feedback control for the non-linear longitudinal model of flexible air-breathing hypersonic vehicles (FAHVs). The flight control of FAHVs is highly challenging due to the unique dynamic characteristics, and the intricate couplings between the engine and fight dynamics and external disturbance. Because of the dynamics’ enormous complexity, currently, only the longitudinal dynamics models of FAHVs have been used for controller design. In this work, T–S fuzzy modelling technique is utilised to approach the non-linear dynamics of FAHVs, then a fuzzy model is developed for the output tracking problem of FAHVs. The fuzzy model contains parameter uncertainties and disturbance, which can approach the non-linear dynamics of FAHVs more exactly. The flexible models of FAHVs are difficult to measure because of the complex dynamics and the strong couplings, thus a full-order dynamic output feedback controller is designed for the fuzzy model. A robust H_∞ controller is designed for the obtained closed-loop system. By utilising the Lyapunov functional approach, sufficient solvability conditions for such controllers are established in terms of linear matrix inequalities. Finally, the effectiveness of the proposed T–S fuzzy dynamic output feedback control method is demonstrated by numerical simulations.