一种S波段基于注入锁定技术高效的MOSFET大功率微波源

本文提出了一种利用不平衡耦合谐振器的反馈电路,实现高效率的S波段基于注入锁定技术高效的MOSFET振荡器,在2.45GHz可以获得203 W的输出功率和54.18%的漏极效率,其注入信号为输出信号的1/1000,锁定带宽为2.0MHz。相对于传统的大功率微波源,基于注入锁定技术高效的MOSFET振荡器,工作电压低,相位和频率可控性有明显优势,更有利于实现微波化学实验中的均匀加热以及精确的温度控制。     

继电器延迟时间测量电路的研究与设计

由于继电器触点开关“吸合”“释放”时要产生延时参数。此延时给自动控制带来麻烦。本文论述了继电器触点“开”“关”延迟理论。设计了一种简单可靠的延时测试电路。用此电路对市场上两种继电器抽检测试结果,均符合继电器技术条件要求。论文从理论上计算了它的延迟时间,并与测试结果进行了分析。本电路可应用于对继电器有延时要求的设计师和工厂检验人员制作检测装置或设备使用。     

Nucleation undercooling,solidification structures and magnetic properties of Nd_9Fe_(85–x)Ti_4C_2B_x (x=10–15) magnetic alloys

Nd_9Fe_(85–x)Ti_4C_2B_x(x=10–15) magnetic alloys were investigated by differential thermal analysis and X-ray diffraction analysis. The results showed that with the B content increasing from 10 at.% to 15 at.%, the liquidus temperatures TL of the alloys decreased from 1498.5 to 1472.5 K; the solidus temperatures TS of them increased from 1353.2 to 1358.3 K; and the nucleation undercooling of the alloy melts cooled at the rate of 40 K/min decreased from 122.8 to 95.9 K, resulting in the solidification structures consisting of Nd_2Fe_(14)B, Fe_3B, α-Fe, Nd1.1Fe4B4 and TiC nanocrystallines. Furthermore, the Nd_9Fe_(85–x)Ti_4C_2B_x(x=11, 13, 15) bulk alloys in sheet form with the thickness of 0.7 mm were prepared by copper mold suction casting and their solidification characteristics and solidification structures under sub-rapidly cooling rate were investigated. The results showed that partially amorphous structures were obtained in the as-cast bulk alloys and the amount of amorphous decreased with the increase of the B content. By annealing the as-cast bulk alloys at 923 K for 10 min, the nanocomposite microstructures composed with Nd_2Fe_(14)B, Fe_3B and α-Fe nanocrystallines, which showed a single-phase hard magnetic behavior and enhanced magnetic properties, were achieved.     

Nd_9Fe_(72)Ti_4C_2B_(13)合金过热熔体的过冷度及其对非晶形成能力和磁性能的影响

采用差热分析法研究了Nd_9Fe_(72)Ti_4C_2B_(13)永磁合金形核过冷度ΔT~-与其熔体过热度ΔT~+的关系。在此基础上,通过对不同熔体过热度的薄带进行微观结构分析、热分析和磁性能测试,研究了熔体过热度对合金的非晶形成能力、组织演化和磁性能的影响。结果表明,合金的过冷度拐点对应的临界过热度为67K。在8~67K的过热度范围内,ΔT~-随ΔT~+的提高而急剧增大了58K;而在67~146K的过热度范围内,ΔT~-随ΔT~+而变化的幅度不大,其间的平均过冷度达到了181K。ΔT~+为60K的快淬薄带的微观组织由Nd_2Fe_(14)B、Fe_3B、α-Fe、Nd_2Fe_(23)B_3相的纳米晶和少量非晶组成。随着ΔT~+从60K提高至130K,快淬薄带中的Nd_2Fe_(23)B_3、α-Fe和Fe_3B纳米晶逐步消失,而非晶含量逐步增大,最终得到完全非晶。ΔT~+为60K的薄带退火组织中存在有损于磁性的亚稳相Nd_2Fe_(23)B_3,其磁性能低下;而ΔT~+分别为90,110和130K的薄带退火组织均由Nd_2Fe_(14)B、Fe_3B、和α-Fe纳米晶组成,它们的磁性能较ΔT~+为60K的薄带的大幅提高。其中,ΔT~+为90K的退火薄带的磁性能取得了最大值,其最佳值为H_(ci)=521.57kA/m,B_r=0.75T,(BH)_(max)=66.31kJ/m~3,M_r/M_s=0.67。     

边条翼夹板结构强度设计

利用解析与有限元方法分别对3种结构形式的导弹边条翼夹板进行了强度对比分析.分析得出了这3种形式夹板的受力特点以及承载能力的强弱.在此基础上,进一步采用有限元方法对不同形式夹板两两组合运用时的力学性能进行了数值仿真对比,给出了各组夹板的应力分布规律,推荐了较优的组合方案.最后对夹板厚度进行了优化设计.文中研究可为夹板结构设计提供参考依据.     

桥式起重机箱形梁的结构优化设计研究

桥式起重机是起重机械的一种类型,它的性能很大程度上取决于其箱形梁结构.在对箱形梁进行全面的受力分析的基础上,建立了桥式起重机主梁结构的优化数学模型,并采用有限元软件Patran/Nastran和MMA算法程序对其进行了结构优化.最终,得到了满意的结果.