Theoretical design of new bridge-ring insensitive high energy compounds by selected normal Diels-Alder reactions between NH2-substituted oxazoles and NO2/NF2/NHNO2-substituted ethylenes/acetylenes

In this work, NH₂-substituted oxazoles and NO₂/NF₂/NHNO₂-substituted ethylenes/acetylenes were designed and used as dienes and dienophiles, respectively, in order to develop new bridge-ring insensitive high energy compounds through the Diels-Alder reaction between them. The reaction type, reaction feasibility and performance of reaction products were investigated in detail theoretically. The results showed that dienes most possibly react with dienophiles through the HOMO-diene controlled normal Diels-Alder reaction at relatively low energy barrier. Tetranitroethylene could react with the designed dienes much more easily than other dienophiles, and was employed to further design 29 new bridge-ring energetic compounds. Due to high heat of formation, density and oxygen balance, all designed bridge-ring energetic compounds have outstanding detonation performance, 16 of them have higher energy than HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocine) and 2 others even possess comparative energy with the representative of high energy compounds CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane). The predicted average h₅₀ value of these bridge-ring energetic compounds is 83 cm, showing their low impact sensitivity. The NH₂ groups could obviously impel the proceeding of Diels-Alder reactions, but would slightly decrease the energy and sensitivity performance. In all, the new designed bridge-ring compounds have both high energy and low sensitivity, and may be produced through Diels-Alder reactions at relatively low energy barrier. This paper may be helpful for the theoretical design and experiment synthesis of new advanced insensitive high energy compounds.     

Supercritical carbon dioxide as a new working medium for pneumatic launch: A theoretical study

Compared with the conventionally gaseous or liquid working media, the specific internal energy of supercritical carbon dioxide (SCD) is higher at the same temperature and pressure, and the critical temperature of carbon dioxide is close to room temperature, making SCD a potential new working medium for pneumatic launch. To analyze the feasibility of this conception, an analytical model of a pneumatic catapult is established on basis of the conservations of mass and energy. The model consists of a high-pressure chamber and a low-pressure chamber connected by multiple valves, and there is a movable piston in the low-pressure chamber that can push an aircraft to accelerate. The effects of the launch readiness state of SCD in the high-pressure chamber, the initial volume of the low-pressure chamber and the valve control on the movement of the aircraft are analyzed. It is found that there is a restrictive relation between the temperature and pressure of the launch readiness state of SCD, i.e., there is a maximum allowable launch readiness pressure when the launch readiness temperature is fixed. If this restrictive relation is not satisfied, the working medium in the low-pressure chamber will drop to its triple point within a few milliseconds, leading to a launch failure. Owing to this restrictive relation, there is an optimal launch readiness state of SCD with the highest working capacity for any allowable launch readiness temperature. The pressure of the low-pressure chamber will decrease significantly as the initial volume increases, leading to a decreased acceleration of the aircraft. The ac-celeration can be controlled below a critical value by a designed sequential blasting technique of multiple valves. The calculated results show that a 500 kg aircraft can be accelerated from 0 to 58 m/s in 0.9 s with 36 kg of carbon dioxide. This research provides a new technique for the controllable cold launch of an aircraft.     

Performance study of jute-epoxy composites/sandwiches under normal ballistic impact

This study is undertaken to explore the use of natural fiber Jute-epoxy (JE), Jute-epoxy-rubber (JRE) sandwich composite for ballistic energy absorption. Energy absorbed and residual velocities for these composites are evaluated analytically and through Finite Element Analysis (FEA). FE analysis of JE plates is carried out for different thicknesses (3, 5, 10 and 15 mm). JE plates and JRE sandwiches having the same thickness (15 mm) are fabricated and tested to measure residual velocity and energy absorbed. The analytical results are found to agree well with the results of FE analysis with a maximum error of 9%. The study on JE composite plate reveals that thickness influences the energy absorption. Experimental and FE analysis study showed that JRE sandwiches have better energy absorption than JE plates. Energy absorption of a JRE sandwich is about 71% greater than JE plates. Damages obtained from FEA and testing are in good agreement. SEM analysis confirms composites failed by fiber rupture and fragmentation.     

分析仿真联邦多次运行机制研究

为提高运行效率和降低操作强度,提出了分析仿真联邦运行控制框架,以及重新创建联邦、成员一次加入联邦、成员多次加入联邦3种多次运行机制,并分析了各自的优缺点。采用成员多次加入联邦方法构建了分析仿真联邦多次运行控制原型系统,验证了该机制的合理性和可行性。研究成果适用于不同类型和层次的分析仿真联邦。     

H-PRF方式地面情报雷达杂波抑制性能分析

针对提高地面情报雷达杂波抑制性能的问题,在阐述PD体制信号处理的基础上,主要结合与传统的L-PRF方式对比,对应用H-PRF方式PD体制信号处理的改善因子进行了分析论证.     

高频雷达多波束最优天线方向图综合

在高频雷达中 ,多个部分重叠的波束被用来形成对预定空域的覆盖 ,而射频干扰和期望信号的空间结构之间的差异以及接收天线阵列的空间多样性则被用来抑制干扰以提高高频雷达的整体工作性能。然而如何在实时地形成多波束的同时有效地抑制射频干扰仍然是高频雷达一个急待解决的问题。基于最优天线方向图综合方法 ,通过主瓣形状保持和干扰抑制之间的合理折衷进一步提出了多波束形成算法。仿真结果表明该算法可以快速、灵活地形成多个波束来覆盖预定的空域 ,同时最大限度地抑制射频干扰 ,从而极大地提高了高频雷达的工作性能     

基于HLA仿真的装备采办体系需求论证研究

在简单介绍基于仿真的采办和高层体系结构基本概念的基础上 ,针对我军装备采办的特点和要求 ,以陆军装备自行高炮为例 ,提出了应用高层体系结构仿真技术加强装备论证研究中体系需求的技术方法