百兆瓦级反向开关晶体管脉冲功率组件及其水下脉冲放电研究

基于反向开关晶体管的工作原理,设计了水下脉冲放电系统.根据负载击穿特性,首次提出不使用磁开关阻断主电压的设计思路,这提高了主电流上升率.确定了实验参数,并进行了放电实验.实验过程可见,在击穿过程中,负载相当于一阻值很小的电阻,且击穿过程有一个时间延迟.在12kV主电压和4kV预充电压下,负载击穿时间约为25μs;反向开关晶体管预充电流峰值为397A,脉宽为3μs;主电流峰值为6.5kA,脉宽为5μs,di/dt为3.2kA/μs.     

稀土硼铬共渗工艺及渗层性能的研究

研究了４５钢、Ｔ１０钢固体粉末法稀土硼铬共渗工艺及渗层的耐磨性、耐蚀性和高温抗氧化性能。发现ＲＥ－Ｂ－Ｃｒ共渗速度低于ＲＥ－Ｂ共渗，但稀土对硼铬共渗有明显的催渗作用，其最佳浓度为３％；ＲＥ－Ｂ－Ｃｒ共渗层具有较高的表面硬度和较小的硬度梯度，和渗硼层相比，耐磨性和耐蚀性分别提高３倍，抗７００℃氧化性提高１０倍左右。     

Cu<Subscript>3</Subscript>Mo<Subscript>2</Subscript>O<Subscript>9</Subscript>: An Ultralow-Firing Microwave Dielectric Ceramic with Good Temperature Stability and Chemical Compatibility with Aluminum

An ultralow-firing microwave dielectric ceramic Cu₃Mo₂O₉ with orthorhombic structure has been fabricated via a solid-state reaction method. X-ray diffraction analysis, Rietveld refinement, Raman spectroscopy, energy-dispersive spectrometry, and scanning electron microscopy were employed to explore the phase purity, crystal structure, and microstructure. Pure and dense Cu₃Mo₂O₉ ceramics could be obtained in the sintering temperature range from 580°C to 680°C. The sample sintered at 660°C for 4 h exhibited the highest relative density (～ 97.2%) and best microwave dielectric properties with ε _r = 7.2, Q × f = 19,300 GHz, and τ _f = ? 7.8 ppm/°C. Chemical compatibility with aluminum electrodes was also confirmed. All the results suggest that Cu₃Mo₂O₉ ceramic is a promising candidate for use in ultralow-temperature cofired ceramic applications.     

高温钢管漏磁检测的仿真与试验研究

高温钢管的快速无损检测对于保证管体质量、降低后续加工成本具有重要的意义;研制了漏磁检测系统和具有多种冷却方式的检测探头,研究了高温钢管实施漏磁检测的信号特性,证实管体温度在居里点以下时开展漏磁检测是可行的;试验和仿真结果表明,普通探头在15～780℃下检测时,探头受温度影响大,在室温和650℃时信号分别为2.12V和2.27V;高温探头采用风冷和水冷的方式,大大改善了探头的温度特性,信号在100～650℃范围内变化较小;铁磁性材料在居里点附近饱和磁化强度迅速下降,缺陷信号也随之减小,揭示了漏磁检测的适用温度范围。     

A permanent magnetic perturbation testing sensor

A new PMP (permanent magnetic perturbation) testing sensor for NDT (nondestructive testing) was proposed for the first time based on the analysis of magnetic perturbation mechanism and PMP principle. Afterwards, the proposed PMP sensor was developed and its relevant structural parameter for design was analyzed by experiments. The comparisons among PMP, MFL (magnetic flux leakage) and ECT (eddy-current testing) sensor were carried out, which suggest that PMP is a new method. Finally, some practical engineering application cases of PMP sensor were presented, which further indicate that the proposed PMP sensor is of great practical value and the potential of wide industrial applications as a supplement of conventional NDT methods.     

下坂地水电站1＃机组启动试运行综述

新疆下坂地水电站1 #机组启动试运行是对枢纽水工建筑、金属结构、机电设备的设汁、施工、制造、安装调试、检查、试验、验收等成果的综合考核.依据《水轮发电机组安装技术规范》( GB/T8564-2003)、《水轮发电机组启动试验规程》(DL/T507-2002)、设计和厂家有关图纸、技术文件、合同文件及其他应遵循的国家和行业规程规范,结合现场设备实际对下坂地1#机组启动试运行予以综述,其电气主接线如图1所示.     

BaTiO_3 : Ce 桥式互泵浦相位共轭

在ＢａＴｉＯ３：Ｃｅ光折变晶体中实现了桥式互泵浦相位共轭．它和以往所有的互泵浦相位共轭镜不同之处在于这种晶体的ａ面入射光能产生强的自泵浦相位共轭,这使桥式互泵浦相位共轭产生的条件极为苛刻．然而本文通过选择最佳实验条件,使这种共轭光的的透射率高达４０％．也从理论上对ＢａＴｉＯ３：Ｃｅ桥式互泵浦相位共轭的形式作了分析和讨论．     

Nature-Inspired Interconnected Macro/Meso/Micro-Porous MXene Electrode

The geometric multiplication development of MXene has promoted it to become a star material in numerous applications including, but not limited to, energy storage. It is found that pore structure modulation engineering can improve the inherent properties of MXene, in turn significantly enhancing its electrochemical performance. However, most of the current works have focused on exploring the structure-effective relationships of the single-scale pore structure regulation of MXene. Inspired by Murray's law from nature where a highly graded structure of the organisms is discovered and used to achieve effective diffusion and maximize mass transfer, a hierarchically interconnected porous MXene electrode across micro-meso-macroporous is constructed. This MXene-based electrode provides large amounts of active sites while greatly shortening the ion diffusion channel. Finally, the zinc ion microcapacitor based on this MXene electrode exhibits an ultrahigh area-specific capacitance up to 410 mF cm⁻² and an energy density up to 103 µWh cm⁻² at a power density of 2100 µW cm⁻². The areal energy density outperforms the currently reported zinc ion microcapacitors. This study supports an effective strategy for electrode materials (including but not limited to MXene) to achieve ultra-short ion diffusion channels and maximum transport efficiency for next-generation high-performance energy storage.     

Investigation of ultra‐wideband Bowtie antennas for phased array feed application

In this article, two new ultra‐wideband (UWB) dual‐polarized Bowtie antennas are investigated as the elements for a phased array feed for reflectors. In addition to its UWB impedance matching characteristic, the Bowtie antennas have stable large beam‐width and a low cross‐polar level over a wide frequency band with a compact size, which is an essence for phased array applications. The simulated and measured results state a low ohmic loss, good impedance matching (S₁₁ below ?15 dB) and good radiation performance, with a simple structure for easy manufacturing. The proposed antennas can be good candidates for phased array feed (PAF) in FAST and the SKA (square kilometer array) pathfinder PHAROS2 projects, and massive MIMO antennas in wireless communication systems.