Research on Feature Extraction of Remnant Particles of Aerospace Relays

The existence of remnant particles, which significantly reduce the reliability of relays, is a serious problem for aerospace relays. The traditional method for detecting remnant particles—particle impact noise detection (PIND)—can be used merely to detect the existence of the particle; it is not able to provide any information about the particles’ material. However, information on the material of the particles is very helpful for analyzing the causes of remnants. By analyzing the output acoustic signals from a PIND tester, this paper proposes three feature extraction methods: unit energy average pulse durative time, shape parameter of signal power spectral density (PSD), and pulse linear predictive coding coefficient sequence. These methods allow identified remnants to be classified into four categories based on their material. Furthermore, we prove the validity of this new method by processing PIND signals from actual tests.     

Interactive Multi-objective Optimization Design for the Pylon Structure of an Airplane

The pylon structure of an airplane is very complex, and its high-fidelity analysis is quite time-consuming. If posterior preference optimization algorithm is used to solve this problem, the huge time consumption will be unacceptable in engineering practice due to the large amount of evaluation needed for the algorithm. So, a new interactive optimization algorithm-interactive multi-objective particle swarm optimization （IMOPSO） is presented. IMOPSO is efficient, simple and operable. The decision-maker can expediently determine the accurate preference in IMOPSO. IMOPSO is used to perform the pylon structure optimization design of an airplane, and a satisfactory design is achieved after only 12 generations of IMOPSO evolutions. Compared with original design, the maximum displacement of the satisfactory design is reduced, and the mass of the satisfactory design is decreased for 22%.     

基于图象处理的QR码识别

随着智能手机技术的发展和二维码技术的推广,QR码的手机识别技术的应用越来越广泛.根据QR条码图像符号的特殊性,针对QR码识别过程中手机图像采集的实际情况,应用并改进多种图像处理的方法,用C语言实现了对QR条码的译码,取得了良好的效果.     

改进的图像相关匹配算法

将遗传算法用于低对比度小目标图像相关匹配跟踪,提出了改进的快速图像相关匹配算法。结合图像匹配本身的特点,采用新的编码方式克服了二进制编码的缺点。采用NPROD匹配准则在同样的匹配效果条件下,提高了匹配精度,该算法在计算速度上较原始算法提高了至少12倍以上,同时该算法还具有每帧图像匹配计算时间基本恒定的优点,便于在实际系统中采用。实验结果表明该方法可以有效地跟踪低对比度小目标。     

基于加权模糊C均值聚类的图像分割算法

模糊C均值(FCM)算法用于灰度图像分割是一种非监督模糊聚类后再标定的过程,适合灰度图像中存在着模糊和不确定性的特点。但是这种算法存在着本质上的缺陷,就是仅利用了图像的灰度信息,而没有考虑像素的空间信息,使得其对于实际的含有噪声的图像分割效果不理想。因此,提出了一种新的加权模糊C均值聚类算法,实践证明,该方法可以有效地、实时地把目标从背景中分割出来,并具有较强的鲁棒性。     

Unsteady flow phenomena associated with leading-edge vortices

This paper presents selected results from extensive experimental investigations on turbulent flow fields and unsteady surface pressures caused by leading-edge vortices, in particular, for vortex breakdown flow. Such turbulent flows may cause severe dynamic aeroelastic problems like wing and/or fin buffeting on fighter-type aircraft. The wind tunnel models used include a generic delta wing as well as a detailed aircraft configuration of canard-delta wing type. The turbulent flow structures are analyzed by root-mean-square and spectral distributions of velocity and pressure fluctuations. Downstream of bursting local maxima of velocity fluctuations occur in a limited radial range around the vortex center. The corresponding spectra exhibit significant peaks indicating that turbulent kinetic energy is channeled into a narrow band. These quasi-periodic velocity oscillations arise from a helical mode instability of the breakdown flow. Due to vortex bursting there is a characteristic increase in surface pressure fluctuations with increasing angle of attack, especially when the burst location moves closer to the apex. The pressure fluctuations also show dominant frequencies corresponding to those of the velocity fluctuations. Using the measured flow field data, scaling parameters are derived for design purposes. It is shown that a frequency parameter based on the local semi-span and the sinus of angle of attack can be used to estimate the frequencies of dynamic loads evoked by vortex bursting.     

Remnants of compact binary mergers

We investigate the long-term evolution and observability of remnants originating from the merger of compact binary systems and discuss the differences to supernova remnants. Compact binary mergers expel much smaller amounts of mass at much higher velocities, as compared to supernovae, which will affect the dynamical evolution of their remnants. The ejecta of mergers consist of very neutron rich nuclei. Some of these neutron rich nuclei will produce observational signatures in form of gamma ray lines during their decay. The composition of the ejecta might even give interesting constraints about the internal structure of the neutron star. We further discuss the possibility that merger remnants appear as recently discovered ‘dark accelerators’ which are extended TeV sources which lack emission in other bands.     

Longitudinal distribution of thermospheric densities and ionization rates in the upper atmosphere of Mars at mid-latitude using MGS ACC data

The Accelerometer Experiment (ACC) onboard Mars Global Surveyor (MGS) measured 1600 density profiles in the upper atmosphere of Mars during aerobraking. These measurements reveal large-scale and small-scale structure in the thermosphere of Mars. Here, the measurements of mass density for 115 orbits (#P0670–P0789) from November 1 to 30, 1998, under spring equinox and medium solar activity conditions (average F_10.7 ∼ 137) during phase 2 of the aerobraking in the thermosphere of Mars at different altitudes and longitudes are presented for northern mid-latitude (17–42°N) in the dayside atmosphere using ACC onboard MGS. From these mass densities, the neutral densities of different gases are derived from their mixing ratios. Using these neutral densities, the longitudinal distribution of photoionization rates and photoelectron impact ionization rates are calculated at wavelength range 1–102.57 nm due to EUV and soft X-ray radiation under photochemical controlled region using Analytical Yield Spectrum approach (AYS). These conditions are appropriate for MGS Phase 2 aerobraking period from which the accelerometer data is used. Under the photochemical equilibrium condition, the electron density near the peak varies as the square root of the total peak ionization rate. Using this fact, an attempt is being made to estimate the mean primary and secondary peak electron density by averaging the longitudinal variations of total peak ionization rates in the northern mid-latitude (17–42°N) ionosphere of Mars, as there is no radio science measurement at this latitude region by MGS.     

可视化技术在分析新型蓄冷材料——笼型化合物(Clathrate)溶解过程中的应用(一)

混浊液内部的流动 ,由于微粒子之间的相互作用以及因浊度高不易进行内部观察 ,所以无论是分析还是可视化实验都相当困难 ,存在着许多未弄清的问题。通过采用折射率匹配 (Refractive IndexMatching)技术 ,使透明的微粒子与透明的溶媒的折射率近乎相同 ,做成一种透明的“混浊液” ,从而使混入其中的示踪粒子的运动轨迹能被摄像机捕捉到 ,并以微粒子的沉降和温度的干涉所引起的流动现象为焦点 ,利用图像速度测量法来处理分析所拍摄到的可视化图像 ,成功地获得了定量的混浊液内部的速度场 ,为进一步揭示混浊液内部自然对流的流动机理提供了实验依据。     

The Effects of Transverse Magnetic Field and Density Variations on the Particle Energy Spectra in a Reconnecting 3D Current Sheet

Electron and proton acceleration by a super-Dreicer electric field is further investigated in a non-neutral reconnecting current sheet (RCS) with a variable plasma density. The tangential B _z and transverse magnetic field components B _x are assumed to vary with the distances x and z from the X nullpoint linearly and exponentially, respectively; the longitudinal component (a ‘guiding field’) is accepted constant. Particles are found to gain a bulk of their energy in a thin region close to the X nullpoint where the RCS density increases with z exponentially with the index λ and the tangential magnetic field B _x also increases with z exponentially with the index α. For the RCS with a constant density (λ = 0), the variations of the tangential magnetic field lead to particle power-law energy spectra with the spectral indices γ₁ being dependent on the exponent α as: for protons and for electrons in a strong guiding field (β > 10⁻²) and for electrons in a moderate or weak guiding field (β > 10⁻⁴). For the RCS with an exponential density increase in the vicinity of the X nullpoint (λ≥ 0) there is a further increase of the resulting spectral indices γ that depends on the density exponent index λ as for protons and for electrons in weaker guiding fields and as for electrons in stronger guiding fields. These dependencies can explain a wide variety (1.5–10) of particle spectral indices observed in solar flares by the variations of a magnetic field topology and physical conditions in a reconnecting region. This can be used as a diagnostic tool for the investigation of the RCS dynamics from the accelerated particle spectra found from hard X-ray and microwave emission.