Command-filtered-based neuroadaptive control for multi-input multi-output saturated nonstrict-feedback nonlinear systems with prescribed tracking performance

In this article, the prescribed performance control strategy is extended to multi-input multi-output nonstrict-feedback nonlinear systems with asymmetric input saturation, and not only each element in tracking error vector converges to a prescribed small region within preassigned finite time, but also the converging mode during the preset time is prespecifiable and controllable explicitly. By blending the barrier function with novel speed function, a prescribed performance controller using command-filtered-based vector-backstepping design framework is proposed to steer the tracking error vector for the first time, where the boundedness of filter errors is guaranteed by sufficiently small time constant and an error compensator is constructed to handle the effects of filter errors. To attenuate the adverse effects resulted from nondifferentiable input saturation, hyperbolic tangent function is utilized to estimate asymmetric saturation function such that the control input is designed as a new state variable with initial value of zero in augmented system. Nussbaum function is employed to overcome singularity problem caused by the differentiation of hyperbolic tangent function. At each step of backstepping design, the universal approximation property of neural network and the command filter system are utilized to approximate uncertain dynamics and to solve algebraic loop obstacle due to nonstrict-feedback structure, respectively. Moreover, only one parameter needs to be updated online to cope with the lumped uncertain dynamics by virtual parameter technology, rendering a control strategy with low complexity computation. The validity of the presented controller is verified by theoretical analysis and two-link robotic system.     

Microwave hybrid fast sintering of red clay ceramics

This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X-ray fluorescence, loss on ignition (LOI), X-ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre-sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X-ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C.     

抗高血压药丁酸氯维地平的合成研究

以2,3-二氯苯甲醛和乙酰乙酸叔丁酯为原料,经Knoevenage反应、水解、缩合后与β-氨基巴豆酸甲酯环合得丁酸氯维地平。对反应物配比、催化剂、反应时间和温度等因素进行了研究,总收率达51.34%(以2,3-二氯苯甲醛计),其结构经IR、1H NMR和MS确证。     

木脂素的生物合成及其微生物法生产的研究进展

木脂素是一类分布于植物中的次级代谢产物,由两分子苯丙素衍生物聚合而成。木脂素具有抗细菌、抗病毒和抗真菌活性,被广泛用于药物和食品中。目前,木脂素的生产主要依赖于植物提取。植物生长周期长、木脂素含量低等问题,限制了木脂素的商业应用。随着木脂素合成路径和关键酶的不断解析,木脂素的生物催化合成过程受到了越来越多的关注。本文总结了典型木脂素的生物活性、生物合成路径和微生物法生产的研究进展,可以为深入研究木脂素的微生物合成提供参考。     

基于改进胶囊网络的运维知识库故障分类方法

针对传统运维知识库不具备图像故障现象识别能力,无法处理非结构化数据的问题,基于深度学习的故障分类网络,提出改进胶囊网络特征提取结构的Caps-DRFN算法,实现机电设备运维图像自动分类。首先,针对运维图像存在的多噪声问题,引入深度残差收缩网络(deep residual shrinkage networks, DRSN)提高模型在含噪声数据上的特征提取效果。然后,针对实际拍摄的运维图像多尺度问题,结合FPN(feature pyramid networks)算法,实现图像多尺度特征融合提高模型分类准确率。最后,利用胶囊结构构建向量神经元,通过动态路由的特征传递方式,得到分类结构数字胶囊,实现机电设备故障分类。实验结果表明,相较于传统胶囊网络算法,提出的基于特征融合的Caps-DRFN算法准确率提高了15%且有着更强的鲁棒性。     

耐张线夹和接续管压接质量的在线检测

在架空输电线路中,时常出现掉线等现象而引发线路事故,严重影响输电线路的运行安全。经事后处理分析多为耐张线夹和接续管因压接操作不符合相关规程而致,不仅如此,还会产生过热等不正常运行的现象。为杜绝上述事故与现象的发生,文中对压接型金具内部压接状态的检测方法进行了研究,提出射线检测方法可直观、无损的判别压接质量;研制的检测装置适用于施工压接中的检验,更可在空中直接对耐张线夹及接续管的内部压接状态进行非破坏性检验,并已在工程的线路上进行了应用。实现了架空输电线路中耐张线夹和接续管内部压接质量在线检测,在电力系统内杜绝因此类问题引发事故起到了关键的作用。     

低铬X70管线钢组织及其抗CO2

为了明确Cr的质量分数高低对埋地用输油输气管线钢性能的影响,设计了4种Cr的质量分数的X70管线钢,研究了不同Cr的质量分数下管线钢组织及其力学性能,并采用高温高压反应釜进行了实验钢的CO₂腐蚀试验.结果表明：钢中加入0.1%~0.8%的Cr后,其组织均由针状铁素体和准多边形铁素体构成,Cr元素均呈现明显的沿晶界分布状态;随着Cr的质量分数的增加,钢板强度随之升高,晶界中Cr分布密度随之增大,Cr（OH）₃在腐蚀产物膜中的富集量增加,促使钢板的平均腐蚀速率降低;同时由于Cr（OH）₃可以有效阻碍阴离子穿透腐蚀产物膜,因而大大减少了Cl-的催化作用导致的点蚀,使得钢板点蚀速率明显降低.     

Characterization of the Ion Beam Current Density of the RF Ion Source with Flat and Convex Extraction Systems

Silicon - The characterization of ion beam current density distribution and beam uniformity is crucial for improving broad-beam ion source technologies. The design of the broad ion beam extraction...     

壳牌煤气化工艺技术中水汽管道的设计特点分析

水汽系统是壳牌粉煤气化技术的核心之一。介绍了壳牌煤气化技术中水汽系统的工艺流程,并结合实际工程经验,探讨了以气化炉、合成气冷却器、中压蒸汽汽包、中压循环水泵为核心的水汽系统的设备布置;提出了水汽系统进水主管、进水支管、回水主管、回水支管、汽包进出口管道、循环水泵进出口管道等主要管道的设计要点,并对水汽系统管道的支吊架设置特点进行了分析与研究。     

GLP与矿用材料实验室建设和管理

介绍了GLP(Good Laboratory practice)和SOP(Standard Operating Procedures)的发展过程与实际意义,并将SOP作为管理理念引入材料实验室建设与管理。探讨了材料实验室SOP建设的意义、特点、范围和内容。指出SOP建设与实施可以保障实验室安全、高效运行,保证研究工作质量和研究资料可比性、完整性与准确性。