隐身技术在飞机上的应用

根据隐身技术的工作波段，把飞机隐身技术为雷达波隐身，红外隐身，激光隐身等文章结合国内外隐身飞机的应用，对这三种技术进行了讨论，对其中应用最早和最广和雷达波隐身技术作了较为详细的讨论，最后阐述了隐身技术的发展方向。     

ICCD型与CCD型弱光哈特曼-夏克波前传感器的性能分析与对比

哈特曼－夏克（Ｈａｒｔｍａｎｎ－Ｓｈａｃｋ）波前传感器由于其光能利用率高、结构简单、通道容量大等突出优点,是目前自适应光学系统波前传感器的主流形式。本文深入分析和比较了目前普遍采用的ＩＣＣＤ型和ＣＣＤ型这两种主要类型的弱光哈特曼－夏克波前传感器的特点和波前相位探测精度,导出了定量分析数学模型,给出了实验结果。此研究结果对弱光哈特曼－夏克波前传感器的技术方案选定和工程设计有指导意义。     

泡沫塑料快速富集—石墨炉原子吸收法测定化探样品中的痕量金

用射频消融成功地阻断３４例病人的房室旁道，基中Ｗ－Ｐ－Ｗ综合征２４例，陷匿性房室旁道１０例。射频消融术后５４．１７％的Ｗ－Ｐ－Ｗ综合征病人有Ｔ波改变，其Ｔ波改变的特点主要与术前心电图波方向有关，百与射频电能对心肌的损伤无关。     

惠更斯原理的修正

本文对惠更斯原理作出修正，定义一种取向垂直于波阵面的时空偶极子，用它们取代惠更斯原理中波阵面上的点光源，它们只发出向前传播的波，不产生向后传播的波，这就克服了惠更斯原理不加说明地舍弃了子波的向后传播部分的困难。     

反铁磁自旋波对高温超导体的电阻特性的影响

针对含铜氧化物超导体，本引用一个传导电子与局域电子间的自旋耦合来描述Ｃｕ－Ｏ平面上巡游空穴与铜离子上的局域空穴之间的相互作用。采用自旋波近似，使该自旋耦合表现为巡游载流子与自旋波之间的相互作用，其形式与电－声相互作用类似，据此可得到因自旋波对载流子的散射引起的电阻与温度的依赖关系，其性质与电－声散射电阻相同。同时还引入具有自旋波子吸收或发射的层间遂穿散射过程，讨论了垂直方向上的电阻。所得结果与实     

^11B快中子非弹性散射的理论计算

本文采用直接作用模型和扭曲波玻恩近似理论，计算了＾１１Ｂ的２．１４ＭｅＶ激发态在入射中子能量为７．５４－２０．０ＭｅＶ的非弹性散射的积分截面和角分布，计算结果与评价的实验值进行了比较，符合较好。对实验上所缺乏的数据作出了理论预期值。     

近垂直传播电子回旋寻常波的传播和吸收特性的解析研究

对近垂直入射的电子回旋寻常波的传播和吸收，用相对论等离子体色散关系进行了分区分析，获得了共振层附近内区O－模与X－模的耦合的准确表达式，该结果与非相对论近似下的结论有重大差别，获得了波衰减因子的解析表达式，波的衰减因子由两部分组成：O－模的相对论衰减及与O－模耦的X－模的衰减。     

光频支格波对晶格热容的贡献

讨论晶格的光频支格波对晶格热容的贡献，得到了这部分的热容的表达式。在低温极限情况下,光频支格波对晶格热容的贡献很小，可以忽略，只有频率较低的声频支格波对晶格热容有重要贡献；在高温情况下，复式 和中光频支格波对晶格热容有重要贡献，高温情况下的结果与杜隆－珀蒂定律给出的经典数值一致，该定律在高温时与实际实验符合得很好。     

远震P波群信号的自适应时-频分析

简要叙述了地震事件临测研究的历史和现状，结合远震信号的地震学特点，对远震Ｐ波群信号进行了自适应时－频分析。实验结果表明，特定台站－区域对爆炸远震Ｐ波群的时－频分布具有极强的相似性。     

激光跟踪装置

激光跟踪装置ＰａｖｅＰｅｎｎｙ是激光跟踪吊舱的别名，起初用于Ａ－１０近距离支援攻击机，后来也用于Ａ－７Ｄ、Ｆ－１６等其它飞机。目标指示由地面或其它飞机的空中前进控制员完成，即ＰａｖｅＰｅｎｎｙ吊舱的作用是捕获和跟踪所指示的这些目标，并把输出传输到驾驶...     

Stratospheric ozone descent into the troposphere: Case studies

Summary The penetration of stratospheric air into the troposphere, revealed by high ozone concentrations measured both by an aircraft (Electra) and at a mountain station (Mt. Cimone) during a lee cyclogenesis event (April 24–25, 1982), is investigated. A detailed analysis of the meteorological fields and the application of the isentropic-trajectory method allowed us to reveal the dynamical processes responsible for the ozone transport into the troposphere. We show that the two episodes of high ozone concentrations have to be attributed to the evolution of two distinct upper vortexes, only one of which was associated with surface lee cyclone development. Paper presented at the 1° Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 19–22, 1984, Rome.     

A measurement model for general noise reaction in response to aircraft noise

In this paper a measurement model for general noise reaction (GNR) in response to aircraft noise is developed to assess the performance of aircraft noise annoyance and a direct measure of general reaction as indicators of this concept. For this purpose GNR is conceptualized as a superordinate latent construct underlying particular manifestations. This conceptualization is empirically tested through estimation of a second-order factor model. Data from a community survey at Frankfurt Airport are used for this purpose (N=2206). The data fit the hypothesized factor structure well and support the conceptualization of GNR as a superordinate construct. It is concluded that noise annoyance and a direct measure of general reaction to noise capture a large part of the negative feelings and emotions in response to aircraft noise but are unable to capture all relevant variance. The paper concludes with recommendations for the valid measurement of community reaction and several directions for further research.     

沙丘粗糙面的二次极化电磁散射

研究了新月形沙丘粗糙面的二次极化电磁散射. 结合射线追踪理论, 由一次散射面元的反射场照射到二次散射面元, 采用基尔霍夫近似推导了二次散射面元的二次极化散射场. 计算结果表明二次极化散射结果在特定的角度和类型范围内有显著影响. 在电磁波射向背风坡时可以发现其同极化散射截面在入射角较大时大于其他入射方向的结果, 入射角在休止角附近时的交叉极化散射截面出现峰值, 以及前后狭长沙丘之间的二次极化散射特别突出. 本文结果可用于反演分析沙漠地区的风场信息. 关键词： 新月形沙丘 二次极化散射 射线追踪 休止角     

Fan beam and double crosshole Lamb wave tomography for mapping flaws in aging aircraft structures

As the worldwide aviation fleet continues to age, methods for accurately predicting the presence of structural flaws-such as hidden corrosion and disbonds-that compromise airworthiness become increasingly necessary. Ultrasonic guided waves, Lamb waves, allow large sections of aircraft structures to be rapidly inspected. However, extracting quantitative information from Lamb wave data has always involved highly trained personnel with a detailed knowledge of mechanical waveguide physics. The work summarized here focuses on a variety of different tomographic reconstruction techniques to graphically represent the Lamb wave data in quantitative maps that can be easily interpreted by technicians. Because the velocity of Lamb waves depends on thickness, for example, the traveltimes of the fundamental Lamb modes can be converted into a thickness map of the inspection region. This article describes two potentially practical implementations of Lamb wave tomographic imaging techniques that can be optimized for in-the-field testing of large-area aircraft structures. Laboratory measurements discussed here demonstrate that Lamb wave tomography using either a ring of transducers with fan beam reconstructions, or a square array of transducers with algebraic reconstruction tomography, is appropriate for detecting flaws in multilayer aircraft materials. The speed and fidelity of the reconstruction algorithms as well as practical considerations for person-portable array-based systems are discussed in this article.     

Numerical predictions and experiments for optimizing hidden corrosion detection in aircraft structures using Lamb modes

To increase the sensitivity of Lamb waves to hidden corrosion in aircraft structures, a preliminary step is to understand the phenomena governing this interaction. A hybrid model combining a finite element approach and a modal decomposition method is used to investigate the interaction of Lamb modes with corrosion pits. The finite element mesh is used to describe the region surrounding the corrosion pits while the modal decomposition method permits to determine the waves reflected and transmitted by the damaged area. Simulations make easier the interpretation of some parts of the measured waveform corresponding to superposition of waves diffracted by the corroded area. Numerical results permit to extract significant information from the transmitted waveform and thus to optimize the signal processing for the detection of corrosion at an early stage. Now, we are able to detect corrosion pits down to 80-μm depth distributed randomly on a square centimeter of an aluminum plate. Moreover, thickness variations present on aircraft structures can be discriminated from a slightly corroded area. Finally, using this experimental setup, aircraft structures have been tested.     

Rise and flow of volcanic clouds observed from the ground and from satellites

Typical patterns of volcanic clouds from Mt. Sakurajima are discussed with photographs and satellite images. Volcanic clouds are classified into three types, i.e., eruption cloud, steady flow as a plume, and sequential puffs, according to the variation of the ejection activity with time. While the rise of eruption clouds depends on the strength of the eruption, the vertical shapes of the plumes are sensitive to the velocity of the cross winds around and above the summit of the volcanic mountain. Very strong winds cause blowing down and bouncing up of the plume along the mountain lee wave. Various patterns of horizontal dispersion are observed from the ground and from satellites; typical ones are linear advection, fan- and belt-type spreads, and flat stagnation. These patterns are essentially determined by the wind shear within the vertical thickness of the volcanic cloud.     

电磁波在非均匀磁化的等离子体鞘套中传输特性研究

采用流场模拟软件模拟了十一组分RAM-II飞行器表面等离子体鞘套的分布,提取了四个典型飞行高度、飞行状态下的等离子体鞘套的分布信息.然后根据RAM-II飞行器等离子体鞘套数据,利用计算色散介质的Z变换FDTD方法主要计算了电磁波在四个不同高度处等离子体鞘套中的功率反射系数和功率透射系数.此外,根据目前可以做出的磁场强度的大小,对四个不同高度下的非均匀等离子体鞘套层按距飞行器表面的距离进行相应的非均匀磁化.由于左旋极化波和右旋极化波在磁化等离子体中的传输特性不同,最后对比了左旋极化波、右旋极化波在非磁化和磁化情况下的传输特性,对飞行器导航通信磁窗天线的设计给出建议.     

Hidden corrosion detection in aircraft aluminum structures using laser ultrasonics and wavelet transform signal analysis

Preliminary results of hidden corrosion detection in aircraft aluminum structures using a noncontact laser based ultrasonic technique are presented. A short laser pulse focused to a line spot is used as a broadband source of ultrasonic guided waves in an aluminum 2024 sample cut from an aircraft structure and prepared with artificially corroded circular areas on its back surface. The out of plane surface displacements produced by the propagating ultrasonic waves were detected with a heterodyne Mach-Zehnder interferometer. Time-frequency analysis of the signals using a continuous wavelet transform allowed the identification of the generated Lamb modes by comparison with the calculated dispersion curves. The presence of back surface corrosion was detected by noting the loss of the S(1) mode near its cutoff frequency. This method is applicable to fast scanning inspection techniques and it is particularly suited for early corrosion detection.     

Modelling of Internal and Surface Waves of the Real Ocean in the Large Thermostratified Experimental Tank at the Institute of Applied Physics of the Russian Academy of Sciences

We discuss the results of studies of surface-wave transformation by nonuniform flows, performed in the tank of the Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), and the results of modelling of the influence of iceberg motion on regular background internal waves in the subsurface pycnocline.Transformation of surface waves in the flow field past an immersed sphere is studied both experimentally and theoretically. It is shown that even fairly weak nonuniform flows can cause noticeable changes in the surface-wave field. The sizes of the spatial region in which the characteristics of the surface waves are changed exceed considerably the sizes of the nonuniform-flow region. It is found that the nonlinearity of surface waves leads to an increase in the variability of the surface-wave amplitude in a broad frequency range. The proposed theoretical model describes well the main experimentally observed features of the transformation of nonlinear surface waves in the nonuniform-flow field.It is proved experimentally that background internal waves with frequencies close to those of internal waves in an iceberg wake lead to a considerable transformation of the field of lee waves. The parameters of the resulting wave system are independent of characteristic horizontal sizes of the iceberg model and the length of the internal wave. The total wave system is stationary in the entire velocity range of the model in the case of counterpropagation of background waves. In the case of copropagation of background waves, the nature of the wave system depends on the ratio between the towing velocity and the phase velocity of background waves. In particular, the wave system in the wake can have both a pronounced nonstationary nature and a typical stationary phase pattern.     

Estimation of electron concentration in plasma and plasma frequency in the vicinity of a hypersonic aircraft that moves in atmosphere and analysis of propagation frequencies of electromagnetic waves in such plasma

Electron concentration in plasma and plasma frequency are estimated for the plasma that is formed in the vicinity of a hypersonic aircraft that moves in atmosphere. The frequencies of electromagnetic waves that may propagate in plasma emerging in the vicinity of the aircraft are determined. Formulas that make it possible to analytically (rather than graphically) calculate electron concentration in plasma at altitudes of 30, 60, and 90 km are derived for two speeds. Several specific features of variations in the electron concentration in plasma depending on the above altitudes and speeds are presented. Quasi-periodic variations in the plasma concentration can be obtained using an increase and decrease in the speed of aircraft.