Evaluation of the lift-off robustness of eddy current imaging techniques

The development of lift-off invariant strategies is one of the main goals in Eddy Current Non-Destructive Testing research. In the present work, from the analysis of amplitude and phase signals of magnetic field sensors under Multi-Frequency Eddy Current excitation, two imaging procedures are analyzed and compared with respect to their ability to retrieve reliable results even in presence of huge changes of lift-off. A figure of merit based on the Signal to Noise Ratio evaluated on the 2D reconstructed images allows the comparison of the different strategies in terms of the quality of the image to show the defect. The numerical and the experimental tests realized show that the imaging procedure relying on the analysis of the phase-lag is quite insensitive to changes in the lift-off with respect to that based on the amplitude analysis. In detail the former guarantees good results even when the probe lift-off is randomly changed during the test with variations up to 3 mm, while the latter is able to tolerate only lift-off fluctuation lower than 1 mm.     

液氮传导冷却型高温超导电流引线研制

80 A和200 A液氮传导冷却型高温超导(HTS)电流引线由铜引线段、中间过渡段和高温超导段组成,HTS热端采用液氮传导冷却,HTS冷端采用液氦传导冷却。铜引线段工作在室温到中间温度(~80 K),高温超导段工作温区6—80 K。介绍该传导冷却型电流引线的结构设计和低温性能测试。实验结果表明,中间过渡段温度~78 K,高温超导热端温度77 K;80 A、200 A电流引线液氦下稳态测试电流分别为100 A和250 A。     

现代有轨电车杂散电流危害的监控防护分析

对现代有轨电车杂散电流危害做出分析,并详细介绍了杂散电流系统的防护和监测系统的应用。     

The influence of nitrogen doping on reduced graphene oxide as highly cyclable Li-ion battery anode with enhanced performance

A straightforward, one-step route has been established to fabricate reduced- (rGO) and nitrogen-doped reduced graphene oxide (NrGO) with remarkable lithium-ion storage properties. The graphene oxide (GO) was synthesized as starting material by improved Hummers’ method. Thereafter, thermally annealing GO with NH₃ at elevated temperature to synthesize NrGO was yielded a more open structure with nitrogen sites suitable for enhanced Li intercalation. NrGO exhibited a reversible capacity of 240 mAhg^?1 at 10 Ag^-1 after 500 cycles with 90% capacity retention, which is the best result achieved among graphene oxide-based anodes at this current density. In contrast to rGO, NrGO cells exhibited a gradually increasing capacity profile, reaching up to 114% of the initial capacity at 0.1, 2, and 10 Ag^-1 current densities. Results showed that high occupancy of pyridinic N within NrGO enhanced battery performance and cell kinetics upon cycling which offers long-time operability at high current density.     

An innovating application of PEM fuel cell: Current source controlled by hydrogen supply

Fuel cells are complex systems which can be considered as low voltage electrical source. Preliminary investigations led with a single proton exchange membrane fuel cell, either short-circuited or hybridized by discharged supercapacitors, could evidence the behavior as a current source, in which the current is directly controlled by the hydrogen flow rate. This operation mode imposes the fuel cell voltage to be far below the threshold recommended by the fuel cell manufacturer. The paper deals with this unusual application of fuel cell and its benefits such as the high quality current, free of oscillations that might be upgraded for superconducting coil supply. To investigate this operation mode an appropriate single fuel cell model is established and then validated by means of a test bench equipped with a proton exchange membrane single fuel cell.     

TIG焊接电流对C24S铝锂合金接头组织和性能的影响

采用四种不同的焊接电流对C24S铝锂合金进行TIG焊试验,并研究了焊缝的成形及接头的微观组织和力学性能。结果表明,当焊接电流55 A时,焊接热输入量不足,导致焊缝未焊透;当焊接电流60 A时,焊缝成形良好,接头的组织细小,抗拉强度达到母材强度的65%;当焊接电流继续增加时,焊缝的宽度明显增大,焊缝区强化相会大量溶解,晶粒明显粗化,同时Li元素的蒸发及热影响区的显著软化严重降低了接头的力学性能。     

天车电子称的维修与改进

分析唐钢第一钢轧厂天车称重系统使用过程中故障产生的原因,提出故障处理方法和改造建议。     

Discharge characteristic of nanosecond-pulse DBD in atmospheric air using magnetic compression pulsed power generator

Dielectric barrier discharge driven by repetitive nanosecond pulses can offer highly efficient non-thermal plasma at atmospheric pressure and is widely used for plasma applications. In this paper, the discharge is generated using a compact pulsed power generator based on one-stage magnetic compression. The output pulse can be up to 30 kV with a rise time of about 40 ns and a full width at half maximum of 70 ns. The electrical characteristics of the discharge parameters are studied by the measurement of voltage and current waveforms. The effects of applied voltage amplitude, voltage polarity, pulse repetition frequency, and barrier dielectric on discharge characteristics are investigated, respectively. The experimental results show that the discharge current, discharge power and electron density increase with the increase of the applied voltage, and the pulse repetition frequency has a slight effect on the electrical parameters. Moreover, the discharge current is influenced by the dielectric barrier, but it is not varied with the polarity of applied pulses.     

现代导弹导引头发展综述

介绍了导弹导引头的功能及组成,综述了现代导弹导引头的发展与现状,通过举例说明了当代国外一些典型先进导引头的主要战技指标,最后评述了导弹导引头的发展趋势。