Formation of textures and microstructures in asymmetrically cold rolled and subsequently annealed aluminum alloy 1100 sheets

The formation of textures and microstructures in asymmetrically cold rolled and subsequently annealed AA 1100 sheets was investigated. The asymmetrical rolling procedure in this experiment was performed in a rolling mill with different roll velocities (roll velocity ratio of 1.5/1.0). In order to enhance the shear deformation, asymmetrical rolling was performed by a large reduction per pass and without lubrication. Asymmetrical rolling led to the formation of strong shear textures. The evolution of asymmetrically cold rolled textures was analyzed by FEM simulations. After recrystallization annealing, pronounced {111}//ND orientations prevailed in all thickness layers. Intensified shear deformations by asymmetrical rolling also led to the formation of ultra-fine grains after recrystallization annealing.     

Two-dimensional scattering center extraction based on multiple elastic modules network

The concept of scattering centers on a target is commonly used for radar signature modeling and data compression, as well as target recognition. In particular, two-dimensional (2-D) scattering centers are useful features in automatic target recognition, which uses a synthetic aperture radar system, because they are directly related to physical scattering mechanisms and also have small dimensionality. We propose a new technique for estimating 2-D scattering centers using radar data in the frequency-aspect domain. The technique first estimates one-dimensional scattering centers at several aspects, and the multiple elastic modules network optimization is exploited to find 2-D locations and amplitudes of the target's scattering centers. Experimental results illustrate that the proposed method is efficient not only for estimating 2-D scattering centers on the target but also in computation.     

Electromagnetic scattering from eccentric multilayered dielectricbodies of revolution-numerical solution

In this paper, a numerical method for the scattering problem of multilayered dielectric bodies of revolution is introduced. Since the scatterer may be eccentrically layered, and since the rotation axis of each layer may be different from each other, conventional methods for bodies of revolution are not applicable to the scattering problem of this type. Thus, an iterative method is introduced in this paper. The electromagnetic problem of each layer is solved separately to take advantage of the rotational symmetry of each layer. This boundary value problem is solved from the outermost layer to the innermost layer, and this procedure is repeated until the desired degree of accuracy is obtained. The validity of this method is shown from numerical results. A mode-matching solution for a multilayered dielectric sphere is given to provide data which verify the accuracy of the method introduced in this paper     

Prediction of beam tilting effects using an enhanced ray launchingmodel in the urban area

This paper presents an effective propagation area method that enhances the computation efficiency of the existing ray launching model. Using the effective propagation area method, the effective propagation region to be considered can be constructed from a given geographical database, and buildings that have a substantial effect on the total received power can be considered in a very efficient manner. In order to verify the predicted accuracy of the proposed model, the received power has been predicted for the real microcellular environment and compared with the published measurement. It is observed from the prediction results that the proposed model shows considerable improvement in computation speed and good agreement with the measurements. In addition, the effect of beam tilting on the path loss in an urban area is analyzed using the proposed model. It has been observed that beam downtilting can effectively confine the signal to the desirable home cell with reduced transmitting power, narrow half-power beam width (HPBW), and suitable fixed antenna height     

On the uncertainty in the current waveform measurement of an ESDgenerator

The uncertainty in the current waveform measurement of an electrostatic discharge (ESD) generator is evaluated. The measurands are the current amplitude and the rise time of the output current waveform of the ESD generator. An intuitively simple model is proposed to evaluate the uncertainty in the current amplitude measurement. Type A and Type B evaluations for all contributions to the measurement uncertainty are performed to obtain the combined standard uncertainty. The evaluated expanded uncertainty (95.5% confidence level) of the current amplitude and the rise time at ESD voltages of 2, 4, 6, and 8 kV are within the specification of IEC 61000-4-2. The results show that the uncertainty in the current amplitude measurement stems from the voltage reading of the measuring equipment, the difference between the displayed and the actual voltages of the discharge tip of the ESD generator, and the inaccuracy of the delta time measurement of an oscilloscope, whereas the uncertainty in the rise time measurement mainly originates from the measuring equipment     

Efficient radar target classification using adaptive jointtime-frequency processing

This paper presents a new target recognition scheme via adaptive Gaussian representation, which uses adaptive joint time-frequency processing techniques. The feature extraction stage of the proposed scheme utilizes the geometrical moments of the adaptivity spectrogram. For this purpose, we have derived exact and closed form expressions of geometrical moments of the adaptive spectrogram in the time, frequency, and joint time-frequency domains. Features obtained by this method can provide substantial savings of computational resources, preserving as much essential information for classifying targets as possible. Next, a principal component analysis is used to further reduce the dimension of feature space, and the resulting feature vectors are passed to the classifier stage based on the multilayer perceptron neural network. To demonstrate the performance of the proposed scheme, various thin-wire targets are identified. The results show that the proposed technique has a significant potential for use in target recognition     

Natural frequency-based neural network approach to radar target recognition

Time domain response-based neural networks and frequency domain response-based neural networks have been proposed for radar target recognition. We propose a natural frequency-based neural network for radar target recognition. Our scheme takes advantage of an aspect angle independence of a natural frequency. It is shown from experimental results that a natural frequency based-neural network using the first natural frequency pair is superior to a time domain response-based neural network in the case of a single aspect angle and that a natural frequency based-neural network using the first natural frequency pair or the first two natural frequency pairs is superior to a time domain response-based neural network in the case of a multiple aspect angle.     

Efficient radar target recognition using the MUSIC algorithm andinvariant features

An efficient technique is developed to recognize target type using one-dimensional range profiles. The proposed technique utilizes the Multiple Signal Classification algorithm to generate superresolved range profiles. Their central moments are calculated to provide translation-invariant and level-invariant feature vectors. Next, the computed central moments are mapped into values between zero and unity, followed by a principal component analysis to eliminate the redundancy of feature vectors. The obtained features are classified based on the Bayes classifier, which is one of the statistical classifiers. Recognition results using five different aircraft models measured at compact range are presented to assess the effectiveness of the proposed technique, and they are compared with those of the conventional range profiles obtained by inverse fast Fourier transform     

Wiregrid modelling scheme for curvature varying surface

A new wiregrid modelling scheme for a curvature varying scatterer is proposed. A conducting elliptic cylinder is modelled by wires with radii of different sizes depending on the radius of curvature on the surface. The size of each wire is generated from the model equation suggested in the study. Numerical results show that this new wiregrid model can be applied to enhance the accuracy of solutions for a curvature varying scatterer     

High-frequency analysis of EM scattering from a conducting spherecoated with a composite material

The asymptotic high-frequency solution for the scattered field produced by a plane wave incident on a perfectly conducting sphere coated with a thin composite material is considered. In the shadow region, the high-frequency scattered field is entirely associated with the usual creeping-wave diffraction. In the lit region, the scattered field can be expressed as a sum of geometrical optics (GO) and creeping-wave diffraction terms. The field in the caustic regions, where the ray solution fails, is excluded. The appropriate formula for each term is derived, and the result is presented in a form suitable for computation. Numerical results for the bistatic scattering patterns of the coated sphere show excellent agreement with the rigorous eigenfunction solutions