Buried small objects detected by UWB GPR

A ground penetrating radar (GPR) using short-pulse is developed to detect small and shallow metal objects buried underground. A bistatic mode in which the GPR system uses separate transmitting and receiving antennas is applied. A modified fat dipole antenna is developed for the transmitting and receiving antennas. The prototype of the system is tested in the real environment and 2D visualization of raw data is achieved. We show that the developed system has a good ability to detect underground metal objects, and even small targets of several centimeters.     

翼-身组合体绕流的Euler方程数值模拟

用代数方法生成翼-身组合体H-O型网格,并用有限体积法研制出翼-身组合体绕流三维Euler方程计算程序。该方法的特点是改进了机身与机翼表面网格点分布,机翼后缘有后掠时也能保证后缘与网格线一致。程序除能按常规提供横流截面展向压强分布外,还能提供弦向压强分布。对NASA TND-712的翼-身组合体模型的计算结果与实验符合很好。     

Calculation of an unsteady jet flow around the plate cascade

In the framework of the general theory for unsteady weakly disturbed fluid flows with free boundaries, a problem is solved to calculate a jet flow around the cascade of plates executing the harmonic oscillations. We developed a program that enables us for the first time to carry out systematic calculations of flow characteristics depending on arbitrary values of determining parameters.     

Fast data association using multidimensional assignment withclustering

We present a fast data association technique based on clustering and multidimensional assignment algorithms for multisensor-multitarget tracking Assignment-based methods have been shown to be very effective for data association. Multidimensional assignment for data association is an NP-hard problem and various near-optimal modifications with (pseudo-)polynomial complexity have been proposed. In multidimensional assignment, candidate assignment tree building consumes about 95% of the time. We present the development of a fast data association algorithm, which partitions the problem into smaller sub-problems. A clustering approach, which attempts to group measurements before forming the candidate tree, is developed for various target-sensor configurations. Simulation results show significant computational savings over the standard multidimensional assignment approach without clustering     

Dynamic Targets in CRRs Part II: Experiments and SAR Correspondence

Expressions describing the correspondence between moving-target artifacts for synthetic-aperture radar (SAR) and compact radar range (CRR) emulations are developed. Experimental results are then presented to verify the accuracy of these equations and to characterize the capacity of CRRs to emulate translating, vibrating, and rotating targets. We show that phase-compensation techniques can be applied to CRR data, providing a suitable test bed for SAR phase-compensation techniques.     

A technique for numerical modeling of liquid film disintegration in the pneumatic injector of aircraft engines

A technique for calculating the two-phase flows in the pneumatic injector of the aircraft engine is developed based on solving the model problem, namely, on verification of the two-phase flow model by means of solving the problem of liquid column disintegration under the effect of an incident airflow. We determine the turbulence models that satisfactorily describe the biphase flow processes.     

Extension of a Two-Step Calibration Methodology to Include Nonorthogonal Sensor Axes

We present an extension of the nonlinear two-step estimation algorithm originally developed for the calibration of solid-state strapdown magnetometers. We expand the algorithm to include nonorthogonality within a sensor set for both two- and three-axis sensors. Nonorthogonality can result from manufacturing issues, installation geometry, and in the case of magnetometers, from soft iron bias errors. Simulation studies for both two- and three-axis sensors show convergence of the improved algorithm to the true values, even in the presence of realistic measurement noise. Finally the algorithm is experimentally validated on a low-cost solid-state three-axis magnetometer set, which shows definite improvement postcalibration. We note that the algorithm is general and can be applied to any two- or three-axis sensor set (such as accelerometers) with an error model consisting of scale, offset, and nonorthogonality errors.     

Emulating Dynamic Target in Compact Radar Ranges. Part I: Theory

Analytical expressions are developed that describe the artifacts encountered when translating, rotating, and vibrating point sources are imaged by compact radar ranges (CRRs) emulating airborne synthetic-aperture radar (SAR). The approach starts with coherent-aperture imaging basics and develops a general solution for imaging using the Born approximation. We show that moving-target artifacts on CRRs are similar to the artifacts encountered with SAR moving targets, suggesting that CRRs may be suitable for such emulations.     

The finite element analysis of shells of revolution with a branching meridian

We present an algorithm for calculating the shells of revolution with the branching meridian using the triangular finite elements, the rigidity matrices of which are formed based on the vector method of displacement interpolation [1]. The correct kinematic and static conditions of shell conjugation on the line of their coupling have been developed. The shell structure consisting of a cylinder and adjacent shells is calculated under various conditions of support.     

某机种复合材料构件的模态分析

 <正> 对某机种碳纤维复合材料垂尾加强肋、座舱盖、垂尾蒙皮等构件进行模态分析试验,所采用的试验方法如图1所示。     

Pickup Ion Acceleration at the Termination Shock and in the Heliosheath

We discuss pickup ion acceleration and transport near the solar wind termination shock from the perspective of their spectral, spatial, and pitch-angle distributions. Our study is performed in the framework of a recently developed anisotropic transport model based on a Legendre polynomial expansion technique. Voyager 1 LECP angular distributions of 1 MeV protons, represented in the form of an expansion in spherical harmonics in the frame aligned with the measured interplanetary magnetic field, are used as benchmarks for our theory. We find the observed distributions consistent with our model predictions for particle acceleration and reflection at a highly oblique shock wave. It is shown that first-order (field aligned) anisotropy is a measure of shock obliquity while the second-order (transverse) anisotropy reflects the energy dependence of the particle scattering mean free path. We also discuss the role of enhanced scattering and momentum diffusion on the spectral properties of energetic charged particles.     

Interplanetary Coronal Mass Ejections Observed in the Heliosphere: 1. Review of Theory

With the recent advancements in interplanetary coronal mass ejection (ICME) imaging it is necessary to understand how heliospheric images may be interpreted, particularly at large elongation angles. Of crucial importance is how the current methods used for coronal mass ejection measurement in coronagraph images must be changed to account for the large elongations involved in the heliosphere. In this review of theory we build up a picture of ICME appearance and evolution at large elongations in terms of how it would appear to an observer near 1 AU from the Sun. We begin by revisiting the basics of Thomson scattering describing how ICMEs are detected, in this we attempt to clarify a number of common misconceptions. We then build up from a single electron to an integrated line of sight, consider the ICME as a collection of lines of sight and describe how a map of ICME appearance may be developed based on its appearance relative to each line of sight. Finally, we discuss how the topology of the ICME affects its observed geometry and kinematic properties, particularly at large elongations. This review is the first of a three-part series of papers, where a review of theory is presented here and a model is developed and used in subsequent papers.     

Aircraft system for measuring the angular deflections of control surfaces

We consider the aircraft system hardware and software to measure the angular deflections of control surfaces. The experimental studies of a photoelectric transducer for converting the control surface angular deflections into digital codes are performed. The mathematical models are obtained to describe a dependence of measuring errors on the coordinates of emitter arrangement. The optimal emitter arrangement is determined using the mathematical models and a pilot model of the aircraft system proposed has been developed.     

广义Stokes问题的区域分裂解法及其事后误差估算

本文的主要目的在于将Ｌａｇｒａｎｇｅ乘子技术应用于广义Ｓｔｏｋｅｓ问题的非匹配网格上的区域分裂解法中;这种方法非常适用于有限元空间近似。Ｌａｇｒａｎｇｅ乘子是在分段常数函数的空间中近似的。同时,基于求解当地问题,我们还构造了离散近似的事后误差估算器,并基于此对网格进行了自适应处理。数值实验的结果验证了本文所发展的方法。     

Obstacle detection by recognizing binary expansion patterns

A technique is described for obstacle detection, based on the expansion of the image-plane projection of a textured object, as its distance from the sensor decreases. Information is conveyed by vectors whose components represent first-order temporal and spatial derivatives of the image intensity, which are related to the time to collision through the local divergence. Such vectors may be characterized as patterns corresponding to “safe” or “dangerous” situations. We show that the essential information is conveyed by single-bit vector components, representing the signs of the relevant derivatives. We use two recently developed, high capacity classifiers, employing neural learning techniques, to recognize the imminence of collision from such patterns     

基于InTouch的工业锅炉监控系统

基于局域网环境,利用InTouch、VB、SQLServer等多种工具开发了工业锅炉监控系统。介绍了系统的功能及设计和实现方案。讨论和展示了InTouch和VB之间的互补优势,利用InTouch完成工作场景界面的设计,VB完成局域网上数据通信和数据库维护的设计,可迅速有效地完成应用开发过程。本文所述方法,对局域网环境下SCA DA系统的开发具有普遍的指导意义。     

Visual analysis in a deployable antenna experiment [satellite antenna]

To establish a large deployable antenna, monitoring and collimation are essential for reliable and precise deployment. We have developed an analysis method to detect shifts in several images, in which the combination of cross-correlations between images and approximations at subpixel precision enables us to detect shifts in images with a precision of up to 0.01 pixels. The LDREX mission; which was a preliminary experiment for a large deployable antenna, ETS-VIII, was performed in December 2000. During this experiment, anomalies occurred in the antenna, and deployment was aborted. To understand the cause of the anomalies, we used our visual analysis method. Using this analysis, we detected vibrating features in the antenna, which were useful for explaining the anomalies. We outline our visual analysis method and discuss its application in monitoring the deployable antenna.