基于非线性器件特征的辐射源识别

为提高雷达辐射源的正确识别率以满足航空电子对抗需求,提出基于非线性器件特征的辐射源识别方法.在非线性失真分析的基础上,通过谱再生现象的观测,对非线性器件的功率级数系数进行了估计,由于不同的雷达系统设计和随机组装,因此这种特征对每一辐射源是唯一的.仿真结果表明,该特征提取方法在低信噪比环境下可以获得高的辐射源识别率,证实...     

某型高级教练机尾旋特性预测研究

首先,利用各种判据分析了某型高级教练机的失速偏离特性和尾旋敏感性,建立了尾旋运动的动力学模型;其次,分析比较了两种尾旋运动的分解方法,并在此基础上建立了气动力数学模型;最后,对某型高级教练机尾旋时间历程进行了数值仿真,结果表明,基于Kalviste运动分解并结合大迎角静态、旋转天平及强迫振荡试验数据,可以较准确地预测飞...     

高职高专院校学报对科研工作的积极影响

在我国高职高专教育事业蓬勃发展的同时,高职高专教育教学研究室院校学报已成长为一支生力军。高职高专院校学报既是各高职院校学术交流的宣传交流窗口,又是广大教师展示科研成果与技术创新成果的有效平台。学报的论文发表与交流,既可以提高教师的业务水平,又可以进一步提升学校教学、科研的整体水平,使学校形成一个良好的学术氛围,对推动高职高专教育的发展起到良好的促进作用。虽然高职高专院校学报起步晚,底子薄,经验少,但是依据自身的优势和地方特点,坚持特色办刊的理念,多数学报已经成为了独树一帜的学术交流平台。     

基于SVM的航空发动机油样光谱诊断界限值制定

运用支持向量机(SVM)估计航空发动机油样光谱数据的概率密度函数,根据光谱数据的概率分布求出航空发动机光谱诊断各金属元素的质量分数、质量分数梯度及质量分数比例的正常、警告、以及异常界限值.利用实际的航空发动机光谱数据进行了研究,并与传统的基于正态分布假设下所确定的界限值进行了比较分析.结果表明,实际的航空发动机光谱数据...     

火花型合成射流激励器流动特性及其激励参数数值研究

利用能量方程中的源项模拟电火花能量的输入,数值模拟了火花型合成射流激励器的流场,获得了激励器的能量蓄积、喷射和吸入过程.结果表明:电火花瞬间能量的输入产生了腔体内的高温、高压环境,从而诱发合成射流的形成;在周期性激励下,合成射流在3个周期后稳定,喷口处的速度呈现非正弦的周期性变化,射流喷射过程时间极短,吸入外界环境气体...     

一种基于谱方法的三维热声不稳定模型

研究流体的流动参数,包括热源热释放的周向不均匀分布对热声不稳定现象的影响,将欧拉方程进行线化处理之后,对轴向和径向方向进行基于切比雪夫多项式的谱离散,周向方向则进行基于傅里叶多项式的谱离散,建立了一种三维热声不稳定数值模型.通过对圆柱管道共振频率以及声场的求解,进行了一系列算例的验证,证实了该方法的可靠性,并且通过热释...     

Research on influence of typical microstructure characteristics of Ni base single crystal on creep rupture and deformation analysis of turbo blade

Considering the influence of typical microstructure characteristics on creep performance,a series of UM-F single crystal alloys which had similar element components but different microstructures were used to analyze the relationship between creep life and microstructure characteristics of Ni base single crystal.Three main factors were proposed:misfit,volume fraction of precipitate and maximum matrix channel width.The Microstate parameter Ymicro was established to estimate the deformation state of the materials.The linear relationship between the initial value of microstate parameter Y0 and creep life under a certain temperature/load was affirmed.By analyzing the high temperature region of turbo blade using the material parameters of DD 3,the creep deformation and the life prediction of the critical points of blade were obtained and the result closed to the test.     

Tracking characteristics of tracer particles for PIV measurements in supersonic flows

The tracking characteristics of tracer particles for particle image velocimetry (PIV) mea-surements in supersonic flows were investigated. The experimental tests were conducted at Mach number 4 in Multi-Mach Wind Tunnel (MMWT) of Shanghai Jiao Tong University. The motion of tracer particles carried by the supersonic flow across shockwaves was theoretically modelled, and then their aerodynamic characteristics with compressibility and rarefaction effects were evalu-ated. According to the proposed selection criterion of tracer particles, the PIV measured results clearly identified that the shockwave amplitude is in good agreement with theory and Schlieren visu-alizations. For the tracer particles in nanoscales, their effective aerodynamic sizes in the diagnostic zone can be faithfully estimated to characterize the tracking capability and dispersity performance based on their relaxation motion across oblique shockwaves. On the other hand, the seeding system enabled the tracer particles well-controlled and repeatable dispersity against the storage and humidity.     

Observation of Transition Region Fine Structures with Soho/Sumer

We present a preliminary analysis of two quiet Sun transition region areas observed with the SOHO/SUMER spectrometer, using lines from oxygen, nitrogen and silicon. The average quiet Sun physical parameters are studied as a function of line intensity. Systematic variations of line position and width with increasing intensity are found. A large number of small-scale active points have been observed, and preliminary analysis of the physical properties and dynamics of these active features is presented. A jet-like structure, found in an active point, is also investigated and its velocity along the line of sight determined. This revised version was published online in June 2006 with corrections to the Cover Date.     

空化对流体管路瞬态特性影响分析

空化（或称气穴）是流体系统中常见的现象，它显著地影响着流体管路的瞬态特性。考虑气体在液体工作介质中溶解和析出以及液体介质自身气化，建立相应的流体属性模型，计算不同压力下流体的等效密度及体积模量；同时以一维管道瞬变流理论为基础，考虑流体系统中的空化及气泡溃灭，采用有限差分法计算流体管路锤击过程中的压力脉动。求得的结果与真实物理现象较为接近，能够为流体系统的设计提供依据和参考。