A model-based method for the computation of fingerprints'' orientation field

As a global feature of fingerprints, the orientation field is very important for automatic fingerprint recognition. Many algorithms have been proposed for orientation field estimation, but their results are unsatisfactory, especially for poor quality fingerprint images. In this paper, a model-based method for the computation of orientation field is proposed. First a combination model is established for the representation of the orientation field by conidering its smoothness except for several singular points, in which a polynomial model is used to describe the orientation field globally and a point-charge model is taken to improve the accuracy locally at each singular point. When the coarse field is computed by using the gradient-based algorithm, a further result can be gained by using the model for a weighted approximation. Due to the global approximation, this model-based orientation field estimation algorithm has a robust performance on different fingerprint images. A further experiment shows that the performance of a whole fingerprint recognition system can be improved by applying this algorithm instead of previous orientation estimation methods.     

Complex images for electrostatic field computation in multilayeredmedia

A rapidly convergent algorithm to find the spatial simulated images of a point charge in multilayered media is presented. The simulated images turn out to be complex; i.e. they have complex amplitudes and are located at complex positions. Surprisingly, these complex images give the static field in multilayered media very accurately (errors ~0.1%). The examples of two- and three-layered media are examined, together with the available exact image solutions of singly or doubly infinite series     

Hybrid treatment for electromagnetic field computation in multipleregions

The numerical solution of complex electromagnetic problems via heterogeneous solution methods is proposed. This hybrid method is capable of analysing a system of multiple physically-unconnected regions by employing the principle of equivalent sources. The case of multiple sources in the presence of scattering objects is discussed and the results are compared with other available data     

Application of on-surface MEI method on wire antennas

The formulas of the on-surface measured equation of invariance (OSMEI) for wire antennas are derived. The unknowns of each node on the antenna surface are expressed by the vector potential function and surface current density. The unknowns in the vicinity of each node are coupled in a linear equation and the coefficients of the linear equation are determined by the measured equation of invariance (MEI) method. The final impedance matrix obtained by the OSMEI is a highly sparse matrix. It demonstrates that the currents on thin wire antennas may also be solved by a differential equation-based formulation in addition to the conventional integral equations     

Interactive computation of coverage regions for wirelesscommunication in multifloored indoor environments

For indoor wireless communication systems, radio frequency (RF) transceivers need to be placed strategically to achieve optimum communication coverage at the lowest cost. Unfortunately, the coverage region for a transceiver depends heavily on the type of building and on the placement of walls within the building. Traditionally, therefore, transceiver locations have been selected by human experts who rely on experience and heuristics to obtain the optimum (or near-optimum) placement. This paper describes an interactive software system that can be used to assist in transceiver placement. It is intended to be easy to use by individuals who are not experts at wireless communication system design. After the user has selected transceiver locations within a graphical floor plan, the system interprets the floor plan and uses simple path loss models to estimate coverage regions for each transceiver. These regions are highlighted, enabling the user to assess the total coverage. This paper describes the methodology used to compute the coverage regions for multifloored buildings and discusses the effect of interference sources. The resulting system is expected to be useful in the specification of indoor wireless systems     

New computation method for characteristic modes

To compute the characteristic modes of a perfectly conducting object a new weighted eigenvalue equation is derived, using the magnetic-field integral equation. The method of moments is used to solve this eigenvalue equation, and a number of bodies of revolution are examined. The results are presented and compared with those of previous methods.     

基于单多普勒激光雷达的机场风场预报方法

基于机场上空的低空小尺度天气系统风场结构以及单多普勒激光雷达测风原理,对已有变分同化方法和涡度-散度风场反演方法进行改进,利用变分同化方法对由单多普勒激光雷达所测的径向风速进行同化,预报它在未来时序时的估计值,再利用改进的涡度-散度方法对预报的径向风速进行反演,实现对三维风场的反演,从而成功实现对风场的预报.最后,通过对机场上空的天气结构仿真,分析了这种方法对径向风速实现的三维风场的预报的优缺点及其误差.     

EMC methodology for numerical electric field computation insideenclosure with aperture

A proposed methodology for simulating and calculating the electric field inside enclosures is introduced which is less time-consuming and does not require the entire environments of the enclosure to be simulated     

Acceleration of on-surface MEI method by new metrons and FMM for 2-D conducting scattering

A new kind of metron is proposed and rapid integration provided by fast multipole methods (FMM) is implemented to dramatically reduce the CPU time of finding the MEI coefficients in the on-surface measured equation of invariance (OSMEI) method. The numerical example of the scattering of a large conducting elliptical cylinder shows that the computation speed is at least one order of magnitude faster than that of the original OSMEI, where sinusoidal metrons are used, and about 25% faster than that of the FMM, where the iteration method is used.     

Interpolated histogram method for area optimised median computation

The article describes an area efficient algorithm for real-time approximate median computation on VLSI platforms. The improvement in performance and area optimisation are achieved through linear interpolation within a reduced number of histogram bins. In order to reduce the hardware utilisation further, an approximation technique for interpolation is also proposed. This approach extends the utility of the histogram method to data sets having a large dynamic range. The performance of the proposed algorithm in terms of mean squared error (MSE) and resource utilisation is provided and compared to that of the existing algorithms. This comparison indicates that more than 60% optimisation in resources is achieved with marginal compromise in the accuracy of the median. The proposed algorithm finds applications in the areas of image processing, time series analysis and median absolute deviation (MAD) computation.     

飞行器参数辨识的一种演化计算方法

将混合遗传算法应用于飞行器气动参数辨识。该方法结合了遗传算法的全局寻优能力和极大似然法的局部寻优能力,使得混合遗传算法不受极大似然法初值选取的影响,同时也解决了遗传算法收敛速度慢和收敛精度较低的问题。在混合遗传算法寻优过程中,仅对最优个体和变异后的个体执行局部寻优操作,从而使得混合遗传算法的计算量维持在一个适当的水平。最后,一个飞行器纵向模型气动参数的辨识仿真表明：混合遗传算法的收敛性和精度都远高于没有采用局部寻优策略的遗传算法。     

Capacitance extraction for electrostatic multiconductor problems byon-surface MEI

In this paper, on-surface measured equation of invariance (OSMEI) method is implemented for capacitance extraction of electrostatic multiconductor interconnect problems. OSMEI uses the same mesh as that in method of moments (MoM), but generates highly sparse matrices rather than a full matrix. In comparison with “standard” MEI which contains a few finite difference (FD) or finite element (FE) mesh layers, the number of unknowns and the computation memory can be saved. For each OSMEI equation in the multiconductor interconnects, a given node on a given conductor is forced into coupling with the few adjacent nodes on conductor itself and the few sampled nodes on other conductors. Thus, the system sparse matrices can be generated. The convergent behavior of the capacitance with the number of the nodes in the OSMEI equations has been widely investigated, Numerical examples of the capacitance extraction for two-dimensional (2-D) and three-dimensional (3-D) multiconductor interconnects show that the computing errors are within 24%. The OSMEI method may become a powerful technique for the more complex interconnect problems     

Matching of equivalent field regions

In aperture problems, integral equations for equivalent currents are often found by enforcing matching of equivalent fields. The enforcement is made in the aperture surface region adjoining the two volumes on each side of the aperture. In the case of an aperture in a planar perfectly conducting screen, having the same homogeneous medium on both sides and an impressed current on one side, an alternative procedure is relevant. We make use of the fact that in the aperture the tangential component of the magnetic field due to the induced currents in the screen is zero. The use of such a procedure shows that equivalent currents can be found by a consideration of only one of the two volumes into which the aperture plane divides the space. Furthermore, from a consideration of an automatic matching at the aperture, additional information about tangential as well as normal field components is obtained. We compare the two procedures in this tutorial article.     

A rigorous method for computation of ferrite toroidal phaseshifters

Coupled-wave theory is used to calculate the performance of twin-toroidal phase shifters. Computation results show that this method is effective, rather simple, and easy to handle. In comparison with the single-toroid phase shifter, the twin-toroidal model's phase shift is considerably larger and its production is simpler. The wires carrying magnetizing currents are located in the weak microwave electric field area. Hence, their influence on the performance of the phase shifter is negligible; this also facilitates production. The loss factors of these two kinds of toroid phase shifters are about the same. Experimental results are in good agreement with theoretical analysis. On this basis, it is concluded that coupled-wave theory is a powerful method for treating electromagnetic problems of waveguides loaded with magnetized ferrites     

A fast computation method for time scale signal denoising

This paper presents a novel and fast scheme for signal denoising in the wavelet domain. It exploits the time scale structure of the wavelet coefficients by modeling them as superposition of simple atoms, whose spreading in the time scale plane formally is the solution of a couple of differential equations. In this paper, we will show how the numerical solution of such equations can be avoided leading to a speed up of the scale linking computation. This result is achieved through a suitable projection space of the wavelet local extrema, requiring just least squares and filtering operations. Intensive experimental results show the competitive performances of the proposed approach in terms of signal to noise ratio (SNR), visual quality and computing time.     

Improved method for computation of potentials in a realistic headshape model

The lead field analysis (LFA) algorithm, a new computational technique for the calculation of potentials on the surface of a realistic head shaped volume conductor model based on the boundary element method and the reciprocity theorem, is presented. The new algorithm, in comparison to the standard boundary element method, offers improved computational efficiency and lower storage requirements. It also yields more accurate surface potential results in the face of varying dipole source locations for a head shape boundary element model with a given number of nodes. Additionally, the algorithm results in quasi-analytic expressions of the derivatives of the surface potential with respect to the location of the sources, allowing the use of optimization techniques with better convergence properties. A set of simulations demonstrating the increased robustness of the LFA algorithm in the face of varying dipole source parameters is also described     

Diffraction field computation from arbitrarily distributed data points in space

Computation of the diffraction field from a given set of arbitrarily distributed data points in space is an important signal processing problem arising in digital holographic 3D displays. The field arising from such distributed data points has to be solved simultaneously by considering all mutual couplings to get correct results. In our approach, the discrete form of the plane wave decomposition is used to calculate the diffraction field. Two approaches, based on matrix inversion and on projections on to convex sets (POCS), are studied. Both approaches are able to obtain the desired field when the number of given data points is larger than the number of data points on a transverse cross-section of the space. The POCS-based algorithm outperforms the matrix-inversion-based algorithm when the number of known data points is large.     

General computation method of outage time for digital radio links

A method to compute outage time during clear air conditions on any radio path for various types of digital modulation is proposed. The performance of digital systems depends on combined effects of in-band amplitude dispersion (IBAD) in the channel bandwidth, and of carrier to noise ratio (CNR). Outage time is then computed for a given period using the statistical dependence of IBAD and CNR in the propagation mechanisms occurring on the path and using the formal relation of IBAD with CNR characterising the digital equipment in service.<>     

Stationary phase method for far-field computation of defocused reflector antennas

Computation of the far field of a defocused reflector antenna using the stationary phase method is described. The positions of the stationary phase points are determined, to eliminate one of the two numerical integrations of the radiation integral. Examples of scan patterns and computational time saving are presented.     

Improved computation method for radio systems single-tone spuriousprohibited frequencies list

For reliability purposes, a realistic computation method that presents, for each desired receiver channel, a list of single-tone spurious (STS) prohibited frequencies is useful. A previously developed STS computation method is significantly improved by applying the results of comparing the former computer-based prohibited values with the measured values based on two UHF receiver engineering models. The new approach incorporates a correction factor for the nonlinear amplitude-dependent effects from the receiver frequency converter stages. A more realistic STS prohibited list that includes accurate values for the system receiver rejection ratio is obtained. It helps to improve radio interference immunity from the initial stages of radio system design and to optimize the frequency allocation management policy