无机/有机复合圆弧风挡抗鸟撞能力数值分析

利用非线性动力响应有限元分析程序(DYNA3D),对无机/有机复合圆弧风挡的设计方案的抗鸟撞能力进行了数值模拟分析.根据数值分析得到的应力、应变和位移等结果,采用3.5mmGlass+2.5mmPU+10PMMA结构的风挡可抵抗550km/h的鸟撞击.分析结果的可靠性得到后来试验结果的证实.     

直XX型机桨叶折叠角度符合性计算

本文简要介绍了直XX型机旋翼折叠的工作原理,重点介绍了桨叶折叠角度的计算方法。之后就安装后折叠角度不符合设计要求进行分析,并提出了具体解决方案。     

多分量测力仪的研究

主要介绍了多分量测力仪及其校准的概念以及发展和应用现状,"九五"期间研制完成的单体式、组合式多分量测力仪的技术指标和结构设计等内容.     

工况压力对分层火焰系统中压力振荡的影响

为了研究工况压力对分层火焰系统中压力振荡频率的影响,通过实验方法测量了不同工况压力下分层火焰燃烧系统中的压力振荡特性,通过基于火焰响应模型的理论分析方法研究了压力振荡频率变化的原因。实验测试结果表明,当进口压力降低从2.6MPa降低至1.4MPa时,压力振荡频率具有规律性的减小约4%;而相对振荡幅值保持在0.2～0.3范围内,没有明显的规律。火焰响应模型的计算结果显示,雾化过程对火焰的响应特性影响最大。     

气体状态方程对正十二烷射流燃烧的影响

选取正十二烷作为航空煤油的替代燃料,应用大涡数值模拟方法和详细化学反应动力学相结合的方法对该燃料在超临界环境下的射流燃烧进行计算,研究其射流、燃烧及排放特性。重点考察了气体状态方程对射流形态、贯穿距、温度、混合分数等的影响。结果表明:理想气体和真实气体状态方程对仿真得到的射流贯穿距和宏观形态影响不大,而真实气体状态方程可以更好地反映在超临界环境下的液体燃料射流内部特征,如混合分数、温度;燃烧方面,仿真的点火延迟与实验存在10%的误差,火焰浮起长度、火焰形态、碳烟等均得到很好的预测,NOx与OH分布与温度场具有高度一致性。     

Interplanetary Physics in Mainland China

During the past two years (2016-2018), great achievements have been made in the Chinese research of interplanetary physics, with nearly 100 papers published in the academic journals. The achievements are including but not limited to the following topics:solar corona; solar wind and turbulence; filament/prominence and jets; solar flare; radio bursts; particle acceleration at coronal shocks; magnetic flux ropes; instability; instrument; Coronal Mass Ejections (CMEs) and their interplanetary counterparts; Magnetohydrodynamic (MHD) numerical modeling; solar energetic particles and cosmic rays. The progress further improves our understanding of the eruptions of solar activities, their evolutions and propagations in the heliosphere, and final geoeffects on our Earth. These results were achieved by the Chinese solar and space scientists independently or via international collaborations. This paper will give a brief review of these achievements.      

Numerical evaluation of acoustic characteristics and their damping of a thrust chamber using a constant-volume bomb model

In order to numerically evaluate the acoustic characteristics of liquid rocket engine thrust chambers by means of a computational fluid dynamics method, a mathematical model of an artificial constant-volume bomb is proposed in this paper. A localized pressure pulse with a very high amplitude can be imposed on specified regions in a combustion chamber, the numerical procedure of which is described. Pressure oscillations actuated by the released constant-volume bomb can then be analyzed via Fast Fourier Transformation (FFT), and their modes can be identified according to the theoretical acoustic eigenfrequencies of the thrust chamber. The damping performances of the corresponding acoustic modes are evaluated by the half-power bandwidth method. The predicted acoustic characteristics and their damping for a special engine combustor agree well with the experimental data, validating the mathematical model and its numerical procedures. A small-thrust liquid rocket engine chamber is then analyzed by the present model. The First Longitudinal (1L) acoustic mode can be excited easily and is hard to be damped. The axial position of the central constant-volume bomb has little influence on the amplitude and damping capacity of the First Radial (1R) and 1L acoustic modes. Tangential acoustic modes can only be triggered by an off-centered constant-volume bomb, among which the First Tangential (1T) mode is the strongest and regarded as the most harmful one. The amplitude of the 1L acoustic mode is smaller, but its damping factor is larger, as a constant-volume bomb is imposed approaching the injector face. These results are contributed to evaluate the acoustic characteristics and their damping of the combustion chamber.     

2005年8月24日强磁暴事件对高层大气密度的扰动

对2005年8月24日发生的突发型强磁暴(Kp峰值达到9)事件,利用星载大气密度探测器在轨实时的连续探测数据进行了处理和分析.结果表明,此次强磁暴事件期间,引起560 km高度附近大气密度剧烈扰动,并存在着两种响应过程.一种是跟随地磁扰动程度变化的全球性大气密度涨落变化,响应时间滞后6h左右, 最大涨落变化比为2.5;另一种为磁暴峰期出现在高纬地区的大气密度突发性跃增,增变比高达5.5.后者存在着区域上的不对称性及时间上的突发性和增幅的差异.此次强磁暴峰期还同时出现了南北半球高纬地区的大气密度跃增双峰.同时还表明这种增变峰可能存在着由高纬向低纬地区迅速推移的现象,在中纬地区推移速度可达15°/h(纬度)左右.      

一种基于序贯最小优化改进的支持向量机空间有形小目标识别方法

提出了一种基于序贯最小优化改进的支持向量机空间有形小目标识别方法。首先陈述了空间有形目标识别的意义并分析了其特点,进而提出了一种基于预分类的两级分类识别策略。在此基础上重点针对空间有形小目标识别所具有的小样本学习问题的本质和特点,采用基于序贯最小优化(Sequential Minimal Optimization :SMO)改进的支持向量机解决训练问题,从而提高了训练的效率和精度。最后,通过10类空间有形小目标共1360个成像尺度不大于30×30像素的仿真样本进行仿真检验,结果表明本文所提出的识别方法的正确率达到了98%(训练样本数454,测试样本数906),完全可以满足实际应用需要,而且具有良好的实时性。     

550～600 km高度上热层大气密度的中长期变化

选用了2005年8月20日至2006年7月28日高度550～600 km附近的热层大气密度探测数据,对表征太阳活动的F10.7值和表征地磁活动强度的Ap指数进行了相关特性的统计.分析结果表明,在无明显地磁扰动时热层大气密度日平均值的涨落呈现27日和准半年的周期性变化,但在地磁扰动期间这种变化的周期性会被削弱,且大气密度的周日变化幅度与F10.7值呈正相关关系.