磁阀式可控电抗器的损耗计算与分析

磁阀式可控电抗器(Magnetic-valve controllable reactor, MCR)具有直流偏磁、绕组电流谐波大和磁路中磁通密度不同的特点,这些特点不仅导致其损耗计算方法与电力变压器不同,而且使准确计算MCR的铁芯和绕组损耗比较困难。本文将铁芯分区与J-A动态逆模型相结合,提出MCR铁芯损耗的计算方法;考虑漏磁和谐波的影响,分析推导得到MCR的绕组损耗系数的计算方法和表达式。最后,通过实例的仿真和实验,验证了提出的铁芯损耗计算方法和绕组损耗系数的正确可靠性。     

Calculation of the Characteristics of Salient‐Pole Synchronous Machines Assisted by Permanent Magnets on the Basis of the Operating Principle

In this study we investigate a method for accurately calculating the characteristics of salient‐pole synchronous machines assisted by permanent magnets. First, the operating principle of the machines is investigated by using both finite element analysis and a simple magnetic circuit. Then, a theoretical representation of the assist effect on the permanent magnets is derived based on the magnetic circuit. Finally, the measured and calculated results are compared in order to confirm the validity of the proposed calculation method. We show that the load characteristics of the proposed machine can be accurately estimated from the no‐load and short‐circuit characteristics of the conventional machine without permanent magnets, and the size and magnetization of the inserted permanent magnets.     

Influence of the rigidity of the steroid core in the structure of chiral dopants on the temperature dependence of cholesteric short pitch

New chiral compounds of the steroid type, namely, 3-alkanoyl- and 3-alkyl derivatives of 16-arylidene estrone, were synthesized and exhibited high helical twisting power (HTP) in nematic liquid crystals E63 and LC-1289. The peculiarities of the molecular structure of chiral compounds (CCs) and their high degree of chirality were discussed. Quite small concentrations of chiral compounds in both nematic solvents were needed to obtain a short-pitch cholesteric helical macrostructure with the selective light reflection in the visible range of the spectrum. The insignificant temperature dependence of the maximum wavelength of the selective light reflection obtained on the whole cholesteric range for all studied liquid crystalline (LC) systems could be related to relatively rigid molecular structure of the chiral compounds. The cholesteric LC mixtures comprising 3-alkanoyl- and 3-alkyl derivatives of 16-arylidene estrone were characterized by the phase stability and the stability of reflective characteristics in time that makes it possible to consider this series of dopants as appropriate for development of bistable cholesteric reflective LC displays.     

Preparation and Applications of Chiral Polymeric Particles

Chiral polymeric particles (CPPs) have been gathering increasing interest as typical functional polymeric particles in recent decades. This article presents a review on the preparation and applications of CPPs. The methods for preparing CPPs are classified into two major groups: The first one is the direct polymerization of monomers and the other is the post-treatment of preformed polymers. CPPs have been explored as a unique type of chiral materials in various fields like asymmetric catalysis, enantioselective release, enantioselective crystallization, and enantioseparation. This review article is expected to accelerate the progress of scientific research dealing with CPPs and their applications in chirality-related fields.     

SC15/182F分体式电驱梭车的研制及应用

梭车是短壁机械化开采技术的重要运输设备。简要介绍了现有梭车的现状及应用局限,详细阐述了分体梭车的主要设计思路,重点介绍了薄壁分体式机架的结构特征,阐述了分体梭车在模块化卷电缆装置、四象限变频驱动等方面的技术升级,并介绍了分体梭车在国内矿区的应用情况。     

Piecewise constant strain kinematic model of externally loaded concentric tube robots

This paper presents a piecewise constant strain kinematic model for concentric tube robots (CTR) in externally loaded conditions. It discretizes the pre-curved tubes comprising the robot into a finite number of pieces and involves external effects as a set of wrench vectors exerted along the robot backbone. Constant strain lets us describe the pieces with helices in which shear deformation and elongation are neglected. The resulting piecewise helix is the simplest curve that can catch the torsion of tubes that play a crucial role in kinematic behavior. This approximation transforms the conventional boundary value problem (BVP) of CTRs models into a set of nonlinear equations that drastically decreases the model resolution time. The present method uses a Lyapunov function and torsional Jacobian to ensure the distal torsion constraint consistently and, as a result, the solution’s convergence. The paper’s primary purpose is to present a fast, numerically stable, and relatively accurate kinematic model not reliant on measurement data. Experimental results on a two-tube prototype and provided for different tip loading conditions reveal maintaining a balance between adequate accuracy and reasonable running time, about 7 ms for five pieces per section, for real-time applications in the presence of external load.     

创新式三工位钢丝圈包布机的研究与设计

截止目前,在市面上常见的对轮胎用钢丝圈进行包布缠绕的设备一般都是采用一台包布机对应一个钢丝圈进行包布缠绕,当需要同时进行多个钢丝圈缠绕时则需要多台包布机,且由于单个包布机之间需要保留一定的安全距离,使得整体所需的工厂占地面积较大;此外,通常情况下是一个操作员操作一台包布机,如果需要多台包布机同时工作则需要多个操作员进行操作,这样会导致生产人力成本上升,且人工操作生产效率较低。     

Experimental and computational analysis of the coolant distribution considering the viscosity of the cutting fluid during machining with helical deep hole drills

An experimental analysis regarding the distribution of the cutting fluid is very difficult due to the inaccessibility of the contact zone within the bore hole. Therefore, suitable simulation models are necessary to evaluate new tool designs and optimize drilling processes. In this paper the coolant distribution during helical deep hole drilling is analyzed with high-speed microscopy. Micro particles are added to the cutting fluid circuit by a developed high-pressure mixing vessel. After the evaluation of suitable particle size, particle concentration and coolant pressure, a computational fluid dynamics (CFD) simulation is validated with the experimental results. The comparison shows a very good model quality with a marginal difference for the flow velocity of 1.57% between simulation and experiment. The simulation considers the kinematic viscosity of the fluid. The results show that the fluid velocity in the chip flutes is low compared to the fluid velocity at the exit of the coolant channels of the tool and drops even further between the guide chamfers. The flow velocity and the flow pressure directly at the cutting edge decrease to such an extent that the fluid cannot generate a sufficient cooling or lubrication. With the CFD simulation a deeper understanding of the behavior and interactions of the cutting fluid is achieved. Based on these results further research activities to improve the coolant supply can be carried out with great potential to evaluate new tool geometries and optimize the machining process.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00383-w     

大型PVC空心缠绕管用于瓦斯管试验研究

大口径PVC缠绕管是近2 a新开发研制并发展成熟起来的塑料应用技术,有自己独特的加工成型工艺。其应用范围广,通过原料配方的改进,可用于煤矿瓦斯抽放。这种产品充分发挥了PVC材料自身的优良特性,有着良好的阻燃及抗静电性能,满足煤矿安全要求,是代替金属、玻璃钢以及其他材料抽放管道的理想产品。     

用无溶剂漆代替有溶剂漆浸渍电机绕组

通过无溶剂漆与有溶剂漆各项性能的对比分析,认为用无溶剂漆代替有溶剂漆浸渍电机的绕组可提高电机绕组浸化质量,并改善劳动条件和工作环境。