采用固–液混合法制备出不同锇（Os）含量（原子数分数）的亚微米级钨锇混合粉体，通过微波烧结获得了孔道结构均匀的钨锇混合基扩散型阴极。电子发射测试结果表明，元素Os的加入使浸渍型钨基阴极的发射性能有明显提高。对比不同锇含量的混合基阴极，发现W-25Os阴极（Os原子数分数为25%）具有相对较低的逸出功和较高的发射电流密度，其在1100℃时脉冲发射电流密度为42.86 A·cm -2 ，斜率为1.40，发射电流密度是同等工作条件下传统钡钨阴极的1.7倍，达到了覆膜M型阴极的电子发射水平。W-25Os混合基阴极的有效逸出功最低为1.93 eV，有利于活性自由钡（Ba）的生成，表层元素摩尔比Ba:（W+Os）为0.83:1.00，比传统钡钨阴极中Ba:W（约为0.50:1.00）摩尔比有了明显提高。

锇靶是制备M型阴极常用的一类靶材,须具有纯度高、致密度高、晶粒细小等特性,然而,传统工艺烧结因烧结温度较高获得的靶材晶粒较粗大,对阴极覆膜沉积不利.本研究对锇粉模压成圆饼压坯,之后采用微波烧结压坯.微波烧结锇压坯过程中以碳化硅、氧化锆作为辅助加热材料,氧化铝作为保温材料,升温速率在20～30 min/℃之间.结果 表明,当随着压强从100增加到300MPa,微波烧结1500℃保温60 min后,样品相对密度从80.61％快速增加到93.44％.当压强继续增加到400MPa时,相对密度随着压强的增长变缓达到94.25％.当压强从400增加到500MPa,烧结后样品的相对密度增长不明显,并有裂纹出现.锇烧结体的相对密度和直径收缩率随着保温时间的延长先快速增加,然后缓慢增加,最后增加趋于平缓.在微波烧结1500℃下,随着保温时间的延长直径收缩率从11.67％快速增加到14.99％,然后缓慢增加到15.56％,相对密度从87.97％快速增加到93.78％,然后缓慢增加到94.25％,而孔隙的数量和尺寸随着保温时间的延长而减小,最终呈球形,晶粒尺寸在1 μm左右.

Os sintered body was prepared by microwave sintering process. The influences of the green compact pressure and the microwave sintering parameters (heating rate, sintering temperature, and holding time) on the microstructure and relative density of Os sintered bodies were investigated. The densification mechanism of Os microwave sintering was analyzed. The results show that, the average grain size of Os after microwave sintering at 1350 ℃ is about 0.22 μm, which is close to the average particle size of the Os powders. With the increase of the sintering temperature to 1500 ℃, the grain size grows to 0.76 μm. The relative density of the Os sintered body increases rapidly at first and then slowly after prolonging the holding time sintered at 1500 ℃. After microwave sintering at 1500 ℃ for 60 min, the relative density of the Os sintered body is 94.3%, and the average particle size is less than 1 μm. The sintering kinetics analysis shows that the densification process of Os is the result of the combined action of volume diffusion and grain boundary diffusion. With the increase of the sintering temperature, the diffusion mechanism gradually transfers from grain boundary diffusion to volume diffusion.

介绍一种应用于毫米波制导体制半实物仿真系统中3 mm收发变频组件的设计方案.主要对组件中核心器件:中频放大器、谐波混频器、3 mm前端低噪放、自动增益控制(AGC)等模块进行了选型分析和研究.此外,文中对3 mm射频前端加载圆极化器以适应抗干扰、高分辨雷达体制仿真的要求提出了可行方案.最终,该组件放置在有雷达导引头参与的闭环仿真实验中进行检验和测试,结论表明该组件应用在毫米波制导仿真系统回路中具有幅相稳定性高、动态范围大、信噪比高、频谱性能好等特点.

To study emission property and microstructure of Re doped cathode,the Sol-Gel combined with a two-step hydrogen reduction method was adopted to fabricate R5S5( 5% Sc2O3+ 5% Re2O7) codoped tungsten powder. The rare-earth doped matrix cathodes were prepared by the pressing,sintering,impregnating and ultra-sonic watering. Microstructure and emission property of cathodes were investigated by modern analysis techniques, such as SEM and UHV electron emission surveyor. The emission properties of R5S5 cathodes were excellent,i. e.,the current density Jdivreaching 30. 14 A / cm2at850 ℃b. The local electric fields around the nanoparticles on the cathode surface increased,resulting in the improvement of emission property of the cathode.

In order to improve data management of the hardware in loop simulation system,and simplify the complexity in database operation,the application of SQLite database in the simulation system was introduced.According to the hard real time requirement,5 optimization principles were proposed to improve the SQLite's performance.The test and experiment show that the SQLite database could be a good substitute for commercial DBMS,and can meet the simulation system's data storage and management requirement.

In order to clearly define function requirements,visually describe the system architecture and static/dynamic structures during the RF control software design,the unified modeling language(UML)was used,and the software was implemented based on the UML models.The fact proves that the UML method can greatly deepen developers' understanding of the requirements,architecture and modules facilitate the division of the large-scale software,shorten the software development cycle.

In order to predict characteristics of high-thrust rocket launching noise,a sub-scale solid engine was chosen for experiment.The wavelet transform and FFT methods were used in processing experimental noise data,the following results can be found out: the low-frequency and high-amplitude shock components are found in the engine's working time,and their amplitude and frequency are very different from classic jet broadband noise;The filtered noise spectrum is typical turbulent broadband noise spectrum,and the sound efficiency of jet noise is 0.51%,which is in good agreement with empirical data of rocket launching,so it can be concluded that shock noise is not a part of jet noise.

In order to weaken the impact and ablation effect on the launcher by motor jet,an experimental study was developed on flow field of solid rocket motor plume injected by water.The films of flow fields were photographed and compared fewer than two conditions of no-water-injected and water-injected by two non-contact measuring devices of high-speed photography and infrared thermograph.The flow pattern and temperature distribution under two conditions were compared,analyzed and researched.It is concluded that the heat impact and ablation effect can be weakened,and the length and area of potential core has been reduced by water injection.

In order to decrease the temperature of flow field of engine plume impinging jet,and weaken the impact and ablation effect on the launcher,an experimental study was developed on flow field of high temperature supersonic impinging jet injected by water.The films of flow field were photographed and compared under two conditions of no-water-injected and water-injected by two non-contact measuring devices of high-speed photography and infrared thermograph,and the temperature of impinging region on bottom plate was measured by thermocouples.Two-phase impinging flow structure and temperature distribution under condition of water-injected were detailedly analyzed and researched,and then compared with condition of no-water-injected.It is concluded that the length and area of potential core have been reduced,the temperature of head face can be decreased,and the thermal impact and ablation effect can be weakened by water injection.