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141.
142.
为系统研究锂基润滑脂的流变性能,以12-羟基硬脂酸锂皂为稠化剂和聚-α烯烃(PAO)油为基础油制备了锂基润滑脂。考察了稠化剂含量、基础油黏度和温度对锂基润滑脂的触变性、储存模量、损耗模量、表观黏度和应变幅度等流变参数的影响,并对其影响机理进行了探讨。实验表明:锂基润滑脂是屈服性假塑性流体,在很小应变范围内以可恢复的弹性变形为主导,达到其屈服应力后,具有明显的剪切变稀现象;达到其流动点后,表现出黏性流体性质。 相似文献
143.
在有源干扰条件下,雷达网部署直接影响着防区内指挥信息系统的预警监测能力。由于防区内由分散于不同位置,且重要度不同的责任区组成的,那么实现全方位全纵深的预警能力,将是雷达网部署的重要方面。根据覆盖系数和重叠系数为主要优化目标,基于NSGA-Ⅱ算法进行多目标优化。首先定义了覆盖系数和全局重叠系数两个指标,尤其是全局重叠系数打破了以往重叠系数的概念,从全局出发引导雷达网优化部署;同时,提出基于NSGA-Ⅱ的多目标优化部署算法,采用诱导跳跃、基因到位、诱导交叉等候选解生成方式,保持种群多样性,提高算法收敛性。实验表明,部署优化算法耗时较低,不同干扰源部署态势使网络节点部署产生较大差异,多样的候选解生成方法明显提高了算法的收敛速度。 相似文献
144.
片上网络逐渐成为片上众核中非常有前景的互连方式.基于目录的cache一致性协议的维护需要片上互连网络高效的支持多播.在借鉴单播的网络吞吐率模型基础上,建立了面向多播的网络吞吐率模型和体系结构级的能量模型.相对于传统的多播路由算法,负载平衡维序路由算法(BDoR)和最小路径维序路由算法(MPDoR)通过平衡X和Y两个方向... 相似文献
145.
机动管线水底穿越江河,裸管铺设在河床上,由于水流的作用,通常需要施加压载才能保持稳定.针对机动管线在水底的受力情况,研究管线受力的影响因素,探讨管线能够保持稳定的临界流速,并以DN150管线为例进行计算,得到管线需要施加压载稳管的临界流速;提出采用机动管线配备的管子和器材,以管线充水作为压载的稳管方法,并进行了理论分析... 相似文献
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提升无人机的自主控制能力可有效提高无人机在复杂对抗环境下的作战性能。系统工程是指导复杂系统研制的有效手段,采用系统的思维方法,关注系统的整体效能优化实现。系统工程覆盖复杂工程型号生命周期的全流程活动,包括概念论证、工程开发、生产制造、使用服役、综合保障以及系统退出等过程,能够为系统开发中各工程技术的应用,跨专业工程合作以及项目管理建立切实的技术路径。无人机外部应用背景环境与内部体系结构相互交联,是一个典型的“系统之系统”(System of Systems)。无人机自主控制系统是跨域、跨平台的复杂“系统之系统”。本文从系统复杂性出发,介绍了无人机系统组成、自主控制系统以及无人机自主能力等级,以期为无人机自主控制技术的发展提供参考和借鉴。 相似文献
148.
Su-wei Wang Xiu-duo Song Zong-kai Wu Lei Xiao Guang-pu Zhang Yu-bing Hu Ga-zi Hao Wei Jiang Feng-qi Zhao 《防务技术》2021,17(6):1954-1966
The frequent occurrence of safety accidents during the calendering process is caused by the flammable and explosive properties of composite modified double-base (CMDB) propellant. Optimization of process parameters with the aid of fluid simulation technology could effectively ensure the safety of the calendering process. To improve the accuracy of the simulation results, material parameters and model structure were corrected based on actual conditions, and adaptive grid technology was applied in the local mesh refinement. In addition, the rheological behavior, motion trajectories and heat transfer mechanisms of CMDB propellant slurry were studied with different gaps, rotational rates and temperatures of two rollers. The results indicated that the refined mesh could significantly improve the contour clarity of boundaries and simulate the characteristics of CMDB propellant slurry reflux movement caused by the convergent flow near the outlet. Compared with the gap, the increased rotational rate of roller could promote the reflux movement and intensify the shear flow of slurry inside the flow region by viscous shear dragging. Meanwhile, under the synergistic effect of contact heat transfer as well as convective heat exchange, heat accumulated near the outlet and diffused along the reflux movement, which led to the countercurrent heat dissipation behavior of CMDB propellant slurry. The plasticizing mechanism of slurry and the safety of calendering under different conditions were explored, which provided theoretical guidance and reference data for the optimization of calendering process conditions. Based on the simulation results, the safety of the CMDB propellant calendering process could be significantly improved with a few tests conducted during a short research and development cycle. 相似文献
149.
Projectiles made of reactive structure materials(RSM)can damage the target with not only kinetic but also chemical energy,but the enhanced damage potential of RSM may become compromised if extreme loading condition disintegrates the projectile before the target is reached.In this work,a ductile coating of Ni was introduced to a tungsten-zirconium(W-Zr)alloy,a typical brittle RSM,to preserve the damage potential of the projectile.Detonation driving tests were carried out with X-ray photography and gun-powder deflagration driving tests were carried out with high-speed photography for the coated and uncoated RSM samples,respectively.The craters on the witness target were analyzed by scanning electron microscopy and X-ray diffraction.The Ni coating was found to effectively preserve the damage potential of the W-Zr alloy under extreme loading conditions,whereas the uncoated sample fractured and ignited before impacting the target in both detonation and deflagration driving.The crack propa-gation between the reactively brittle core and the ductile coating was analyzed based on the crack arrest theory to mechanistically demonstrate how the coating improves the structural integrity and preserves the damage potential of the projectile.Specifically,the Ni coating envelops the W-Zr core until the coated sphere penetrates the target,and the coating is then eroded and worn to release the reactive core for the projectile to damage the target more intensively. 相似文献
150.