基于CS5463的双流制机车电度表设计

设计一种基于CS5463的双流制机车电度表。介绍了双流制电度表的技术性能、总体结构以及程序设计方法,通过对电能计量模块、中央处理模块、双路供电设备以及GPRS与RS485通信模块进行设计,实现机车交流与直流的显示、与TAX2机车监控装置通信以及远程无线抄表功能。采用型式试验、例行试验对新研制的双流制机车电度表进行测试,试验结果表明,该电度表具有制造成本低、数据处理能力强、安全保障度高、测量精度高、抗干扰能力强等优点。     

Mechanism for clogging of microchannels by small particles with liquid cohesion

We numerically investigate the effect of liquid cohesion on the clogging of microchannels induced by small wet particles. The computer simulation is performed by the discrete element method (DEM) with cohesive contact models in presence of pendular liquid bridges, which is embedded into the computational fluid dynamics (CFD). We find that liquid cohesion significantly promotes particle deposition and agglomerate growth. A clogging phase diagram, in the form of Weber number and Stokes number, is constructed to quantify the clogging-nonclogging transition. The competition between particle–particle and particle–fluid interactions is quantitatively discussed in terms of particle velocity and slip velocity. Strong cohesion can address a greater slip velocity or drag between particles and fluid, which depresses the resuspension of deposited particles and results in clogging. Finally, we compare our results with clogging induced by van der Waals adhesion of small dry particles and find that the competence of liquid cohesion is more prominent.     

Prestructured MXene fillers with uniform channels to enhance CO2 selective permeation in mixed matrix membranes

The packing pattern of two-dimensional (2D) sheet-like fillers in membranes is relatively random, leading to the unfavorable permeability from tortuous diffusion pathway. A new strategy that using prestructured materials with uniform channels as fillers was proposed. In this work, Ti₃AlC₂ is etched to prepare multilayered MXene (m-MXene), the channels aggregate as a whole unit, ensure the impossibility of ineffective packing compared with traditional individual sheets, largely facilitating the selective permeation. Then, the m-MXene/Poly (amide-6-b-ethylene oxide) (Pebax) MMMs are synthesized. SEM images demonstrate the accordion shaped structure of filler, which is the multi-channels laminates. Furthermore, the results of gas permeation test exhibit enhanced performance of m-MXene/Pebax MMMs. MMM with 0.5 wt.% m-MXene behaved best, CO₂ permeability of 86.22 Barrer as well as CO₂/N₂ selectivity of 104.85, transcending the Robeson upper bound (2008). Having distinct enhancement for CO₂ separation, the m-MXene/Pebax MMMs in this work offer prospective practical applications.     

High-efficiency ammonium polyphosphate intumescent encapsulated polypropylene flame retardant

The flame retardant polypropylene containing the micro-envelope core-shell structure flame retardant, which encapsulated ammonium polyphosphate into melamine-formaldehyde resin and sodium silicate through in situ polymerization was prepared with polyamide 6, added as a carbon-forming agent. The composition of ammonium polyphosphate, encapsulated ammonium polyphosphate with melamine-formaldehyde resin and the micro-envelope core-shell structure flame retardant were characterized. The fire safety and thermal stability were investigated and showed an improvement including limiting oxygen index, thermogravimetric analysis, vertical burning tests, and microscale combustion calorimeter. The burned compounds were also studied to confirm the burning mechanism. The results showed the flame retardant performance had been greatly improved, while polyamide 6 had better char-forming effect. Besides, the water solubility of flame retardants and their influence on the mechanical properties of polypropylene were also investigated. The results on the effects of additives demonstrated a high efficiency flame retardant to polypropylene. A core-shell flame retardant that sodium silicate and melamine-formaldehyde resin-coated ammonium polyphosphate had been constructed. The effect of the built flame retardant system on the combustion performance of polypropylene was studied from the mechanism and performance. The LOI of the most flame retardant polypropylene reached 28.6%, and UL-94 reached the V-0 level.     

Effect of different surface treatments on polypropylene composites reinforced with yerba mate fibers: Physical,mechanical, chemical,and morphological properties

This study presents the preparation of post-consumer polypropylene (r-PP) composites filled with 30 wt% yerba mate (YM) stick particles. To improve the fiber–matrix adhesion, three surface treatments were performed: alkaline treatment with sodium hydroxide (NaOH) and use of 3-aminopropyltriethoxysilane (APTS) and maleic anhydride graft polypropylene copolymer (PP-g-MA) as coupling agents. Mechanical properties including tensile, flexural, and impact resistance were determined, and chemical (Fourier transform infrared spectroscopy [FTIR]), physical (water absorption), and morphological analyses were performed. The main findings show that the treatments were efficient in improving the mechanical properties of the composites, with emphasis on the r-PP/YM30/APTS and r-PP/YM30/PP-g-MA composites, which proved to be superior in tensile, flexion and impact strength and absorption of water compared to the untreated composite. The morphological analysis showed a better interaction between the fiber and the polymeric matrix for the composites with YM/APTS and YM/PP-g-MA, which corroborates the results of tensile and flexural strength, as well as with the spectra of FTIR in which the chemical modification of the fibers is observed. However, the results show that these treatments are promising in obtaining composites with recycled matrix with better properties.     

计及直流微电网扰动抑制的残差动态分散补偿控制策略

针对直流微电网电能质量问题与环流问题,提出一种计及直流微电网扰动抑制的残差动态分散补偿控制策略.此策略在直流下垂控制的基础上,首先分析直流微电网扰动问题及并联状态下的环流问题;其次建立Buck型与Boost型多DC-DC变换器并联的状态空间模型,推导基于残差的变换器动态分散补偿结构,该结构直接在电压环输出端进行补偿,通过扰动抵消计算补偿控制器Q*(s).采用小信号稳定性分析方法证明本文补偿结构的稳定性;最后基于RTDS搭建数字物理实验平台,以相同与不同类型变换器并联为例进行实验验证.该结构能够加快分布式电源及公共负荷投切时直流母线电压动态响应速度,有效地抑制了环流影响和交流侧不平衡情况引起的直流母线电压二倍工频扰动,维持了电压的一致性,保证了母线电压的稳定,有助于实现分布式电源的"即插即用"技术.     

基于柔性变电站的双向DC/AC变换器关键控制技术综述

基于交直流混合配电技术的柔性变电站是未来配电网发展的一大趋势,柔性变电站因其具备中/低压、交/直流多端接口、具有潮流柔性管控、多形态能源接入、故障限流和隔离等多种功能而受到广泛关注.双向DC/AC变换器是柔性变电站的重要组成部分,可实现低压交直流端口间能量的双向流动.为使双向DC/AC变换器在柔性变电站环境中安全可靠运行,研究双向DC/AC变换器控制策略成为迫切的需求.以张北交直流配电网及柔性变电站示范工程为实例,根据双向DC/AC变换器不同控制目标,从谐波补偿、不平衡电压抑制、多机并联等关键控制技术进行综述,并对基于柔性变电站双向DC/AC变换器控制技术的发展趋势进行探讨,为建设柔性变电站工程提供参考.     

反向工程中测量点云配准的新方法

在光学非接触三维测量中，复杂对象的重构需要多组测量数据的配准。为了获得好的配准结果，提出一种新的配准方法——直接误差分析配准方法。该方法基于一种新型的双目CCD光栅投影测量系统进行测量和分析。实验结果表明该测量方法的配准误差大约0．2mm左右．从而证实该方法的可行性。     

钻杆环缝数控自动焊机

研制的钻杆环缝数控自动机焊为全自动的数控焊机。用于钻杆与两端法兰的内外共4条环缝的焊接。工件的上料、定位、夹紧、内外焊枪的到位、内外焊枪的焊接、自动排列焊道各层各道的焊接工艺参数的改变等均能自动进行。不同管径和不同壁厚采用的各种焊接参数都可在人机界面上预置。采用富氩混合气体保护焊工艺方法，焊缝美观，性能优良，几乎没有飞溅。经大量的生产实践证明该钻杆环缝数控自动焊机焊接质量好，生产效率高。     

三峡引水压力钢管的自动化焊接

在三峡工程建设中,引水压力钢管焊接是一项庞大的工程,为新技术的应用推广创造了难得的机遇,也向焊接工作者提出了巨大的挑战.结合水电四局水工机械总厂三峡分厂在三峡压力钢管自动焊接施工中的突破性实践,对目前各种常用焊接工艺方法进行了对比,对脉冲MAG自动焊的工艺、性能和经济效益进行了简要分析.