球形弹丸超高速撞击铝靶的分子动力学模拟

基于开源分子动力学程序LAMMPS建立球形铝弹丸超高速撞击铝靶的计算模型,模拟弹丸以10 km/s的速度超高速撞击单层靶、双层靶和半无限厚靶;获得了超高速碰撞靶板的物理过程及靶板损伤特性,与超高速碰撞宏观现象相似;厚靶成坑坑深与宏观经验公式计算结果基本一致。模拟结果初步表明,分子动力学方法可以对弹丸超高速碰撞薄靶和半无限厚靶进行模拟,为揭示碰撞过程中的微观机理提供了一种新的研究方法。     

基于Unity3D的月面复杂地形场景构建及模拟驾驶系统

为了验证未来月面复杂地形操控技术方案,基于Unity3D物理引擎对月表模型、月球物理环境以及月面光照环境进行了模拟,设计并开发了一套用于模拟月球自主进行着陆点选址以及在线航天器着陆轨迹规划的系统。该模拟系统的工作过程包含了：基于面阵雷达与立体相机信息融合的局部月表重建、基于3D重建结果的月表地形着陆代价的快速评估与自动着陆选址,以及使登陆器能够到达选址目标的最优燃料消耗着陆运动规划,实现了月球着陆器短距离自主选址着陆的模拟系统构建,同时也从仿真的角度初步验证了“地形重建-地形评估-自主选址-软着陆”这一自主着陆过程的可行性。     

Local controllability and stabilization of spacecraft attitude by two single-gimbal control moment gyros

The attitude control problem of a spacecraft underactuated by two single-gimbal control moment gyros （SGCMGs） is investigated. Small-time local controllability （STLC） of the attitude dynamics of the spacecraft-SGCMGs system is analyzed via nonlinear controllability theory. The conditions that guarantee STLC of the spacecraft attitude by two non-coaxial SGCMGs are obtained with the momentum of the SGCMGs as inputs, implying that the spacecraft attitude is STLC when the total angular momentum of the whole system is zero. Moreover, our results indi- cate that under the zero-momentum restriction, full attitude stabilization is possible for a spacecraft using two non-coaxial SGCMGs. For the case of two coaxial SGCMGs, the STLC property of the spacecraft cannot be determined. In this case, an improvement to the previous full attitude stabilizing control law, which requires zero-momentum presumption, is proposed to account for the singu- larity of SGCMGs and enhance the steady state performance. Numerical simulation results demonstrate the effectiveness and advantages of the new control law.     

复合材料压力容器在航天领域的应用研究

综述了复合材料压力容器在航天领域的最新应用进展,列举了国外空间系统应用的几个典型实例,从金属内衬、纤维材料及树脂基体方面给出了比较重要的技术信息.论述了低温复合材料压力容器的研发与应用趋势,金属内衬和缠绕纤维在低温环境下的性能表现优异及低温环境下树脂基体的选择.探讨了复合材料压力容器无损检测方法的研究现状及展望.未来复合材料压力容器无损检测技术将向着高效实时、精确定位、定量分析及由局部缺陷检测向整体缺陷检测的方向发展.     

固体运载火箭发射轨道一种快速生成方法

通过采用牛顿迭代法快速优化发射方位角,克服了发射方位角初值偏差过大的缺陷,极大缩短了优化时间。通过采用基于特征参数网格化的程序角优化设计技术,建立了程序角设计参数数据库,在机动发射的情况下能够快速进行参数插值,避免了大量优化计算过程,有力地支持了机动发射情况下发射轨道的快速生成。最后通过仿真证明设计算法的有效性和正确性。     

Analysis on the Bonding Failure Mechanism of High Modulus Carbon Fiber Composites

In order to explore the bonding failure mechanism of high modulus carbon fiber composite materials, the tensile experiment and finite element numerical simulation for single-lap and bevel-lap joints of unidirectional laminates are carried out, and the stress distributions, the failure modes, and the damage contours are analyzed. The analysis shows that the main reason for the failure of the single-lap joint is that the stress concentration of the ply adjacent to the adhesive layer is serious owing to the modulus difference, and the stress cannot be effectively transmitted along the thickness direction of the laminate. When the tensile stress of the ply exceeds its ultimate strength in the loading process, the surface fiber will fail. Compared with the single-lap joint, the bevel-lap joint optimizes the stress transfer path along the thickness direction, allows each layer of the laminate to share the load, avoids the stress concentration of the surface layer, and improves the bearing capacity of the bevel-lap joint. The improved bearing capacity of the bevel-lap joint is twice as much as that of the single-lap joint. The research in this paper provides a new idea for the subsequent study of mechanical properties of adhesively bonded composite materials.     

基于DSP的中断冲突避免机制的研究与实现*

针对基于DSP芯片TMS320C6701的嵌入式软件系统设计过程中常见的中断冲突问题,提出相应的解决方法和简单有效的避免机制。通过将周期性中断改为主循环查询模式、将DSP系统计时由定时器中断改为FPGA同步计时等方式,使系统中多个中断设计简化为一个中断,避免中断间的冲突。针对中断和主程序间的访问冲突,通过在主程序中关中断等方式,避免共享资源访问冲突。针对DSP系统和外部总线的访问冲突,通过约定接口的通信协议,避免时序冲突。通过静态分析和动态长周期测试验证,方法有效避免了中断冲突,实现简单;针对不同冲突机制,措施灵活。设计已应用于星载相关设备,也可推广至其他嵌入式软件系统使用。     

飞机起落架系统建模与教学实验平台研究

基于MATLAB/Simulink平台,建立了某大型商用飞机的起落架模型。系统建立了起落架的减震支柱、轮胎侧向力、收放等模型,在此基础上能够实时模拟收放、前起落架转向、主起落架刹车等过程。结合验证数据进行比较证明,仿真结果合理,模型正确。将起落架模型集成到整个飞行实时仿真系统中进行实时仿真,可用于起落架相关的课程教学与研究中。     

Quantitative Analysis of Relationship Between Pore Structure and Compressive Strength of Foamed Concrete

The effect of dry density,water-cement ratio,the addition of fly ash,and sand content on the porosity and pore distribution of foamed concrete is investigated.Digital microscopy and Image J software are employed to examine the landscape of pores with different sizes.Based on the Balshin empirical formula,a mathematical model is established to quantitatively predict the relationship between the pore structures and the compressive strength of foamed concrete.The results well demonstrate that there is a significant correlation between the modified formula and empirical parameters.     

辐射加热对返回舱气动热环境影响的数值研究

基于高超声速再入飞行器气动热环境预测分析的需要,建立了高温非平衡气体辐射加热对飞行器热环境影响的计算分析手段。采用数值求解化学非平衡N-S方程的方法,对返回舱绕流流场进行模拟,获得高温空气组分质量分数和温度等流场参数分布。基于辐射传输方程,考虑高温气体组分的主要辐射机制,计算分析高温流场气体辐射加热对返回舱热环境的影响。分析表明,在同一飞行弹道条件下,返回舱大底半径尺寸对气动加热的影响较大,在再入热环境严酷区,辐射加热对物面总热流的贡献达30!;产生辐射加热效应的主要机制是高温流场中O和N原子产生连续谱和线状谱以及N2的第一正带系;物面催化效应对辐射加热影响不大。