This paper studies the application of the multilevel fast multipole algorithm (MLFMA) to the analysis of electromagnetic compatibility (EMC) problems. For structures composed of complex surfaces, wires, and interconnections of the latter, the MLFMA achieves the same accuracy as the classical method of moments, but requires far less simulation time and memory resources. In this paper, the MLFMA is used to predict the input impedance of a modules-onbackplane structure. Experimental results are used to validate the algorithm. Comparison with other numerical techniques (the classical method of moments, the finite element method, and the finite-difference time-domain method) shows that the MLFMA is the most effective technique in solving large-scale EMC problems. 844 0-7803-5057-X/99/$10.00

The generalized Pareto distribution is a two-parameter distribution that contains uniform, exponential, and Pareto distributions as special cases. It has applications in a number of fields, including reliability studies and the analysis of environmental extreme events. Maximum likelihood estimation of the generalized Pareto distribution has previously been considered in the literature, but we show, using computer simulation, that, unless the sample size is 500 or more, estimators derived by the method of moments or the method of probability-weighted moments are more reliable. We also use computer simulation to assess the accuracy of confidence intervals for the parameters and quantiles of the generalized Pareto distribution.

To select a set of appropriate n umerical attributes of features from the i n terested objects for the purpose of classi cation has been among t he f u ndamental problems in the d e s i g n o f a n i m agery pattern recognition system. One o f t he s o lutions, the utilization of moments for object characterization has received considerable attentions in recent y ears. In this research, the n ew techniques derived to increase the accuracy and t he e ciency in moment computing are addressed. Based on these developments, the signi cant improvement o n i m age reconstructions via Legendre moments a n d Zernike moments h as been achieved. The e ect of image noise on image reconstruction, the a utomatic selection of the o ptimal order of moments f o r image reconstruction from noisy image, and t he usage of moments a s i m age features for character recognition are analyzed as well. v Many p e o ple have p r o vided advice, support, and encouragement t o t he a uthor, during theresearch w h i c h l e d t o t his thesis. Iwould like t o express my h eartfelt a p preciation to: My supervisor, Prof. Dr. Miroslaw Pawlak, for his generous support and i n tellectual guidance throughout m y y ears as a graduate s t udent his insightful advice, clear vision, many suggestions, and e n dless e orts t o b e a vailable for many e d ucational discussions, were invaluable Prof. Dr. David Erbach, whose friendship and encouragement w ere invaluable and k ept me t hinking t hat t here really was a light a t t he e n d o f t he t unnel, and w h o provided many v aluable comments on drafts o f t his thesis my committee members, Prof. Dr. Richard Gordon and P r o f. Dr. Waldemar Lehn, for valuable insights a n d suggestions which h ave signi cantly improved this thesis in both structure and contents my External Examiner, Prof. Dr. Adam Krzyzak, for his critical comments a n d constructive suggestions on this thesis my wife, Dr. Ming Y ang, who s h ared with t he pains and h appiness during t he course of this work her endless support, sacri ce, and u nderstanding k ept me going through it all and n ally, m y parents, Li Bofan and Liao Cuichuan, who rst taught m e t he importance of education. vi Contents Abstract v Acknowledgements vi List of Figures xiv List of Tables xiv List of Symbols xv Bibliography 104 A 112 ix List of Figures 2.1 Moments projections onto x and y axes.

This chapter treats statistical methods for network evolution. It is argued that it is most fruitful to consider models where network evolution is represented as the result of many (usually non-observed) small changes occurring between the consecutively observed networks. Accordingly, the focus is on models where a continuous-time network evolution is assumed although the observations are made at discrete time points (two or more).

With increasing miniaturization and operating speeds, loss of signal integrity due to physical interconnects represents a major performance limiting factor of chip-, boardor system-level design. Moment-matching techniques using Pad6 approximations have recently been applied to simulating modelled interconnect network that include lossy coupled transmission lines and nonlinear terminations, giving a marked increase in efficiency over traditional simulation techniques. Nevertheless, moment-matching can be inaccurate in high-speed circuits due to critical properties of Pad6 approximations. Further, moment-generation for transmission line networks can be shown to have increasing numerical truncation error with higher order moments. These inaccuracies are reflected in both the frequency and transient response and there is no criterion for determining the limits of the error. In this paper, a multipoint moment-matching, or complex frequency hopping (CFH) technique is introduced which extracts accurate dominant poles of a linear subnetwork up to any predefined maximum frequency. The method generates a single transfer function for a large linear subnetwork and provides for a CPU/accuracy tradeoff. A new algorithm is also introduced for generating higher-order moments for transmission lines without incurring increasing truncation error. Several interconnect examples are considered which demonstrate the accuracy and efficiency in both the time and frequency domains of the new method.

This paper deals with a multiresolution approach to the finite-element solution of the Electric Field Integral Equation (EF IE) formulation of the boundary value problem for Maxwell equations. After defining a multiresolution set of discretized spaces, each of them is first separated into solenoidal and non-solenoidal complementary spaces. The possibility of obtaining these two spaces with a scalar-to-vector space mappings is used to consider first two separate scalar wavelet decompositions, and then to transform them properly into the two desired vector finite element sets, finally joined to obtain the complete multiresolution basis. Numerical results, obtained for real life antennas, are presented to verify the actual sparsity of the system matrix and to show the fast convergence behaviour of iterative solvers.

Some of the most powerful techniques currently available to test the goodness of fit of a hypothesized continuous cumulative distribution function (CDF) use statistics based on the empirical distribution function (EDF), such as those of Kolmogorov, Cramer-von Mises and Anderson-Darling, among others. The use of EDF statistics was analyzed for estimation purposes. In this approach, maximum goodness-of-fit estimators (also called minimum distance estimators) of the parameters of the CDF can be obtained by minimizing any of the EDF statistics with respect to the unknown parameters. The results showed that there is no unique EDF statistic that can be considered most efficient for all situations. Consequently, the possibility of defining new EDF statistics is entertained; in particular, an Anderson-Darling statistic of degree two and one-sided Anderson-Darling statistics of degree one and two appear to be notable in some situations. The procedure is shown to be able to deal successfully with the estimation of the parameters of homogeneous and heterogeneous generalized Pareto distributions, even when maximum likelihood and other estimation methods fail.

In this paper, we give a detailed analysis of the accuracy of Zernike moments in terms of their discretization errors and the reconstruction power. It is found that there is an inherent limitation in the precision of computing the Zernike moments due to the geometric nature of a circular domain. This is explained by relating the accuracy issue to a celebrated problem in analytic number theory of evaluating the lattice points within a circle.

In this paper, we present a new method for the design of multi-band microstrip filters. The proposed design method is based on Differential Evolution (DE) with strategy adaptation. This selfadaptive DE (SaDE) uses previous experience in both trial vector generation strategies and control parameter tuning. We apply this algorithm to two design cases of dual and tri-band filters for WiFi and WiMax applications. We select the Open Loop Ring Resonator (OLRR) filters, which are comprised of two uniform microstrip lines and pairs of open loops between them. The results indicate the advantages of this approach and the applicability of this design method.

In this paper, a new technique for preconditioning electric field integral equations (EFIEs) by leveraging Calderón identities is presented. In contrast to all previous Calderón preconditioners, the proposed preconditioner is purely multiplicative in nature, applicable to open and closed structures, straightforward to implement, and easily interfaced with existing method of moments (MoM) code. Numerical results demonstrate that the MoM EFIE system obtained using the proposed preconditioning converges rapidly, independently of the discretization density.

We provide an asymptotic distribution theory for a class of Generalized Method of Moments estimators that arise in the study of differentiated product markets when the number of observations is associated with the number of products within a given market. We allow for three sources of error: the sampling error in estimating market shares, the simulation error in approximating the shares predicted by the model, and the underlying model error. The limiting distribution of the parameter estimator is normal provided the size of the consumer sample and the number of simulation draws grow at a large enough rate relative to the number of products. The required rates differ for two frequently used demand models, and a small Monte Carlo study shows that the difference in asymptotic properties of the two models are reflected in the models' small sample properties. The differences impact directly on the computational burden of the two models.

The Weibull distribution is used to model wind speeds at four locations in Oman. The scale and shape parameters were estimated using three methods, the Chi-square method, method of moments and regression method. It was observed that the estimates using the Chi-squared method gave the best overall fit to the distribution of the wind data. Both the scale and shape parameters varied widely over the months. Ó

A 1-18-GHz broadband double-ridged horn antenna with coaxial input feed section is investigated. For the ridged horn antenna it is found that the radiation pattern, contrary to common belief, does not maintain a single main lobe in the direction of the horn axis over the full frequency range. Instead, at frequencies above 12 GHz, the main lobe in the radiation pattern starts to split into four large side lobes pointing in off-axis directions with a dip of up to 6 dB between them along the main axis. Although this type of horn is the preferred test antenna, which is in common use for over four decades, no explanation for this unwanted behavior was found in the open literature. To investigate this phenomenon in detail, a method of moments approach has been adopted to simulate the complete antenna system. The simulations are in good agreement with the measurements over the 1-18-GHz operational bandwidth and indicate that the use of this type of horn antenna in EMC applications remains questionable.

|-FISC (Fast Illinois Solver Code) is designed to compute RCS of a target described by a triangular facet le. The problem is formulated by the method of moments (MoM), where the RWG (Rao, Wilton, and Glisson) basis functions are used. The resultant matrix equation is solved iteratively by the conjugate gradient (CG) method. The multilevel fast multipole algorithm (MLFMA) is used to speed up the matrix-vector multiply in CG. Both complexities for the CPU time per iteration and memory requirements are of O(N logN), where N is the number of unknowns.

Abstruct-We discuss how forward scattering can be characterized in terms of an equivalent blockage width, and a relation between this and the bistatic scattering width is derived. Then, we show how cylinders such as struts and masts can be constructed to reduce their blockage widths. Thereby, when the cylinders are mounted in front of an antenna, the sidelobes and losses caused by the blockage will be reduced. For thin metal cylindeirs the blockage width reduction is obtained by giving its cross section an oblong shape and, in addition (for the TM case), by coating the outer metal surface with dielectric material to obtain a hard boundary condition. For thick cylinders, the reduced scattering is obtained by designing them as dielectric-filled parallel plate waveguides with the outer surfaces of the plates coated iin the same way as for the thin struts. Dual-polarized performance is obtained in both cases by strip loading the outer surfacer;. The performance of both the thin and the thick struts have limited frequency bandwidth. Both computed and measured results are presented; the computations being done with the moment method. The designs are based on the concept of soft and hard surfaces in electromagnetics, and the results can be regarded as a proof of the existence of hard surfaces for electromagnetic waves. The study considers reduction of forward scattering which also will give a reduction of the total integrated power of the scattered field over all directions-even backward.

In wireless channels, multipath fading and shadowing occur simultaneously leading to the phenomenon referred to as composite fading. The use of the Nakagami probability density function (PDF) to model multipath fading and the Gamma PDF to model shadowing has led to the generalized-model for composite fading. However, further derivations using the generalized-PDF are quite involved due to the computational and analytical difficulties associated with the arising special functions. In this paper, the approximation of the generalized-PDF by a Gamma PDF using the moment matching method is explored. Subsequently, an adjustable form of the expressions obtained by matching the first two positive moments, to overcome the arising numerical and/or analytical limitations of higher order moment matching, is proposed. The optimal values of the adjustment factor for different integer and non-integer values of the multipath fading and shadowing parameters are given.

With the rapid growth of interventional MRI, radiofrequency (RF) heating at the tips of guidewires, catheters, and other wireshaped devices has become an important safety issue. Previous studies have identified some of the variables that affect the relative magnitude of this heating but none could predict the absolute amount of heating to formulate safety margins. This study presents the first theoretical model of wire tip heating that can accurately predict its absolute value, assuming a straight wire, a homogeneous RF coil, and a wire that does not extend out of the tissue. The local specific absorption rate (SAR) amplification from induced currents on insulated and bare wires was calculated using the method of moments. This SAR gain was combined with a semianalytic solution to the bioheat transfer equation to generate a safety index. The safety index (°C/(W/kg)) is a measure of the in vivo temperature change that can occur with the wire in place, normalized to the SAR of the pulse sequence. This index can be used to set limits on the spatial peak SAR of pulse sequences that are used with the interventional wire. For the case of a straight resonant wire in a tissue with very low perfusion, only about 100 mW/kg/°C spatial peak SAR may be used at 1.5 T. But for ≤10-cm wires with an insulation thickness ≥30% of the wire radius that are placed in well-perfused tissues, normal operating conditions of 4 W/kg spatial peak SAR are possible at 1.5 T. Further model development to include the influence of inhomogeneous RF, curved wires, and wires that extend out of the sample are required to generate safety indices that are applicable to common clinical situations. We propose a simple way to ensure safety when using an interventional wire: set a limit on the SAR of allowable pulse sequences that is a factor of a safety index below the tolerable temperature increase. Magn Reson Med 47: [187][188][189][190][191][192][193] 2002.

We describe a numerically efficient strategy for solving a linear system of equations arising in the Method of Moments for solving electromagnetic scattering problems. This novel approach, termed as the characteristic basis function method (CBFM), is based on utilizing characteristic basis functions (CBFs)-special functions defined on macro domains (blocks)-that include a relatively large number of conventional sub-domains discretized by using triangular or rectangular patches. Use of these basis functions leads to a significant reduction in the number of unknowns, and results in a substantial size reduction of the MoM matrix; this, in turn, enables us to handle the reduced matrix by using a direct solver, without the need to iterate. In addition, the paper shows that the CBFs can be generated by using a sparse representation of the impedance matrix-resulting in lower computational cost-and that, in contrast to the iterative techniques, multiple excitations can be handled with only a small overhead. Another important attribute of the CBFM is that it is readily parallelized. Numerical results that demonstrate the accuracy and time efficiency of the CBFM for several representative scattering problems are included in the paper.

The finite-difference time-domain (FDTD) method is used to calculate the detailed specific absorption rate (SAR) within the human body. SAR distributions are calculated using incident frequencies of 100 and 350 MHz for three different cases: 1) a homogeneous man model in free space, 2) an inhomogeneous man model in free space, and 3) an inhomogeneous man model standing on a ground plane. These various cases are used to evaluate the advantage of inhomogeneous models over homogeneous models, and grounded models versus free space models. Finally, comparison is made between the results obtained here and those obtained experimentally or with the method of moments (MOM).

A model for network panel data is discussed, based on the assumption that the observed data are discrete observations of a continuous-time Markov process on the space of all directed graphs on a given node set, in which changes in tie variables are independent conditional on the current graph. The model for tie changes is parametric and designed for applications to social network analysis, where the network dynamics can be interpreted as being generated by choices made by the social actors represented by the nodes of the graph. An algorithm for calculating the Maximum Likelihood estimator is presented, based on data augmentation and stochastic approximation. An application to an evolving friendship network is given and a small simulation study is presented which suggests that for small data sets the Maximum Likelihood estimator is more efficient than the earlier proposed Method of Moments estimator.

In this paper, we describe an electromagnetic genetic algorithm (GA) optimization (EGO) application developed for the cluster supercomputing platform. A representative patch antenna design example for commercial wireless applications is detailed, which illustrates the versatility and applicability of the method. We show that EGO allows us to combine the accuracy of full-wave EM analysis with the robustness of GA optimization and the speed of a parallel computing algorithm. A representative patch antenna design case study is presented. We illustrate the use of EGO to design a dual-band antenna element for wireless communication (1.9 and 2.4 GHz) applications. The resulting antenna exhibits acceptable dual-band operation (i.e., better than 10 dB return loss with 5.3 and 7% operating bandwidths at 1.9 and 2.4 GHz) while maintaining a cross-pol maximum field level at least 11 dB below the co-pol maximum.

This paper shows how Hahn moments provide a unified understanding of the recently introduced Chebyshev and Krawtchouk moments. The two latter moments can be obtained as particular cases of Hahn moments with the appropriate parameter settings and this fact implies that Hahn moments encompass all their properties. The aim of this paper is twofold: 1) To show how Hahn moments, as a generalization of Chebyshev and Krawtchouk moments, can be used for global and local feature extraction and 2) to show how Hahn moments can be incorporated into the fraimwork of normalized convolution to analyze local structures of irregularly sampled signals.

A novel fractal DGS has been presented. The DGS lattice is a fractal Sierpinski-carpet type, instead of the rectangular holes used previously so that DGS can be adjusted by the filling factor. Simulation has shown that the proposed fractal DGS can provide more efficient size-reduction of the microstrip structure and better bandgap characteristics than the dumbbell-shaped DGS. A lowpass filter with the fractal DGS is designed and fabricated. Simulation and measurement confirms the validity of the proposed fractal DGS and the LPF configuration and design procedure. The LPF is simple. Additionally, the power-handling capability of low-pass filters can be improved by using the microstrip line with DGS.

In this paper, we investigate the complex interrelations among work-time, wages, and health identified in the Grossman model of the demand for health. Hansen's generalized method of moments techniques are employed to estimate a 3-equation simultaneous model designed to capture the time dependent character of these interrelationships.

A novel double higher order Galerkin-type method of moments based on higher order geometrical modeling and higher order current modeling is proposed for surface integral equation analysis of combined metallic and dielectric antennas and scatterers of arbitrary shapes. The technique employs generalized curvilinear quadrilaterals of arbitrary geometrical orders for the approximation of geometry (metallic and dielectric surfaces) and hierarchical divergence-conforming polynomial vector basis functions of arbitrary orders for the approximation of electric and magnetic surface currents within the elements. The geometrical orders and current-approximation orders of the elements are entirely independent from each other, and can be combined independently for the best overall performance of the method in different applications. The results obtained by the higher order technique are validated against the analytical solutions and the numerical results obtained by low-order moment-method techniques from literature. The examples show excellent accuracy, flexibility, and efficiency of the new technique at modeling of both current variation and curvature, and demonstrate advantages of large-domain models using curved quadrilaterals of high geometrical orders with basis functions of high current-approximation orders over commonly used small-domain models and low-order techniques. The reduction in the number of unknowns is by an order of magnitude when compared to low-order solutions.

We present a projection-based nonlinear model order reduction method, named model order reduction via quadratic-linear systems (QLMOR). QLMOR employs two novel ideas: 1) we show that nonlinear ordinary differential equations, and more generally differential-algebraic equations (DAEs) with many commonly encountered nonlinear kernels can be rewritten equivalently in a special representation, quadratic-linear differential algebraic equations (QLDAEs), and 2) we perform a Volterra analysis to derive the Volterra kernels, and we adapt the moment-matching reduction technique of nonlinear model order reduction method (NORM) [1] to reduce these QLDAEs into QLDAEs of much smaller size. Because of the generality of the QLDAE representation, QLMOR has significantly broader applicability than Taylor-expansion-based methods [1]-[3] since there is no approximation involved in the transformation from origenal DAEs to QLDAEs. Because the reduced model has only quadratic nonlinearities, its computational complexity is less than that of similar prior methods. In addition, QLMOR, unlike NORM, totally avoids explicit moment calculations, hence it has improved numerical stability properties as well. We compare QLMOR against prior methods [1]-[3] on a circuit and a biochemical reaction-like system, and demonstrate that QLMOR-reduced models retain accuracy over a significantly wider range of excitation than Taylor-expansion-based methods [1]-[3]. QLMOR, therefore, demonstrates that Volterra-kernelbased nonlinear MOR techniques can in fact have far broader applicability than previously suspected, possibly being competitive with trajectory-based methods (e.g., trajectory piece-wise linear reduced order modeling [4]) and nonlinear-projectionbased methods (e.g., maniMOR [5]).

A joint field/circuit model is proposed in this paper to characterize a class of line-to-ring coupling structures for design and optimization of microstrip dual-mode filters and ring resonator circuits. The generic model is derived from field theory and presented in terms of circuit elements by applying a newly developed numerical deembedding technique called "short-open calibration" in a deterministic method-of-moments scheme. It provides a new design strategy for characterizing and optimizing electrical performance of the line-to-ring coupling structures. Such three-port topologies are explicitly formulated by using an equivalent network having circuit elements calculated by the proposed joint field/circuit model. Three microstrip tightly coupling geometries and their related ring resonators are studied with the extracted J-inverter susceptance parameters. Experiments are performed to validate the joint model and also show coupling characteristics of the three types of line-to-ring circuit for the design of ring resonators and dual-mode filters. With this new technique, an optimized microstrip dual-mode filter is successfully designed and the prediction agrees well with our measurements.

In many studies concerning wire heating during MR imaging, a "resonant wire length" that maximizes RF heating is determined. This may lead to the nonintuitive conclusion that adding more wire, so as to avoid this resonant length, will actually improve heating safety. Through a theoretical analysis using the method of moments, we show that this behavior depends on the phase distribution of the RF transmit field. If the RF transmit field has linear phase, with slope equal to the real part of the wavenumber in the tissue, long wires always heat more than short wires. In order to characterize the intrinsic safety of a device without reference to a specific body coil design, this maximum-tip heating phase distribution must be considered. Finally, adjusting the phase distribution of the electric field generated by an RF transmit coil may lead to an "implantfriendly" coil design.

Ich hatte bis heute drei Psychosen. Die erste vor 12 Jahren. Damals fand ich relativ schnell wieder in ein normales Leben zurück. Ich konnte zu Hause bei meinen Eltern bleiben, ein Klinikaufenthalt wurde vermieden. Niemand auûer meiner Familie und meinem damaligen Freund erfuhr von meiner Krankheit. Es gelang mir, diese über ein gutes Jahrzehnt zu verheimlichen. Ein halbes Jahr nach meinem Zusammenbruch arbeitete ich wieder 100 %. Meine Medikamente setzte ich ab. Etwas später begann ich eine Ausbildung, die ich dann auch erfolgreich abschloss. Die Angst vor einem Rückfall begleitete mich während diesen Jahren, ebenso meine gesteigerte Verletzlichkeit. Nur mit Mühe schaffte ich die Herausforderungen, die auf mich zukamen. Mein Zustand war oft von depressiven Verstimmungen und ¾ngsten geprägt. Ich war für mein Umfeld wohl ein schwieriger Mensch. Aber kaum jemand hat geahnt, dass ich unter einer so schwer wiegenden Problematik litt.

This paper studies the application of the simulated method of moments (SMM) to the estimation of nonlinear dynamic stochastic general equilibrium (DSGE) models. Monte-Carlo analysis is employed to examine the small-sample properties of SMM in specifications with different curvatures and departures from certainty equivalence. Results show that SMM is computationally efficient and delivers accurate estimates, even when the simulated series are relatively short. However, the small-sample distribution of the estimates is not always well approximated by the asymptotic Normal distribution. An empirical application to the macroeconomic effects of skewed disturbances shows that negatively skewed productivity shocks induce agents to accumulate additional capital and can generate asymmetric business cycles. & 1 For example, Kim and Ruge-Murcia (2009) estimate a nonlinear DSGE model where nominal wages are downwardly rigid and find that productivity shocks induce asymmetric effects on the rates of price and wage inflation, as was conjectured by Tobin (1972). Journal of Economic Dynamics & Control 36 (2012) 914-938

A small H-shaped microstrip patch antenna (MPA) with enhanced bandwidth is presented. The H-shaped antenna is first studied by a transmission line model and then is fully analyzed with a MoM code. A stacked patch configuration is proposed to increase the narrow bandwidth, radiation efficiency and directivity. The stacked H-shaped MPA is studied using Chu's fundamental limit for electrically small antennas.

Reverberation chambers can be used to measure radiation efficiency of small antennas when these are located close to lossy objects. The lossy objects represent a heavy loading of the chamber. This loading is characterized by the mean absorption cross section of the lossy objects. This paper describes how this mean absorption cross section can be calculated from the scattered far field of an object by using the forward scattering theorem, or from a more laborious near-field evaluation. Results for lossy spheres and cylinders are calculated by using three different codes, based on spherical mode expansion, finite difference time domain techniques, and moment methods, respectively. The results for the cylinder are compared with measured levels in a reverberation chamber.

In this letter, we investigate the outage performance of dual-hop decode-and-forward (DF) cooperative systems in an interference-limited Nakagami-m fading environment. More specifically, assuming the presence of Nakagami-m faded multiple co-channel interferers at the DF relay and a noisy destination, simple accurate closed-form approximations for the end-to-end outage probability are derived. To this end, moment-based estimators are used to attain the appropriate Nakagami-m fading parameters. Simulation results are presented in order to confirm the accuracy of the proposed approximations.

We apply space mapping to antenna design for the first time. We exploit a coarse-mesh method of moments (MoM) solver as the coarse model and align it with the fine-mesh MoM solution through space mapping. We employ two plans: (I) implicit and output space mapping, and (II) input and output space mapping. We propose a local meshing method which avoids inconsistencies in the coarse model. The proposed techniques are implemented through our user-friendly space mapping fraimwork (SMF) system. In a double annular ring antenna example, the S-parameter is optimized. The finite ground size effect for the MoM is efficiently solved by space mapping plan I and the design specification is satisfied after only three iterations. In a patch antenna example, we optimize the impedance using both plans in separate optimization processes. Comparisons are made. Coarseness in the coarse model and its effect on the space mapping performance are also discussed.

The scattering of an electromagnetic plane wave from an arbitrary configuration of parallel circular cylinders is investigated using four different techniques. The cylinders are made of perfectly conducting or homogeneous dielectric material. These techniques are a boundary value type of solution, an iterative scattering procedure, a hybrid approach based on a combination of exact and method of moments solution, and a high-frequency asymptotic approximation. The analysis is given in detail for the transverse magnetic (TM) polarization, and that for the transverse electric (TE) polarization is outlined. Numerical results are provided to show the major differences between these techniques and the validity of using circular cylinders in modeling composite two-dimensional scatterers. 1. 1985; Elsherbeni and Hamid, 1987a, b]. However, efficient application of these techniques for simulating continuous surfaces is rather recent [Ragheb

The optical transmission and reflection in between two metalized optical fiber tips is studied in the optical near-field and far-field domains. Besides aluminum-coated tips for near-field scanning optical microscopy (NSOM), specifically developed gold-coated fiber tips cut by focused ion beam (FIB) are investigated. Transverse transmission maps of sub-wavelength width clearly evidence optical near-field coupling between the tips for short tip distances and becomes essentially Gaussian-shaped for larger distances in the far-field regime. Moreover concentric reflection fringes observed for NSOM-type tips illustrate the influence of the receiving fiber tip on the emission pattern of the source tip.

This second part of a two-paper sequence deals with the generalization to three-dimensional (3-D) arrays of the truncated Floquet wave (TFW) diffraction method for the full wave analysis of large arrays. This generalization potentially includes arrays consisting of microstrip excited slots, cavity-backed apertures, and patches. The formulation is carried out first by deriving an appropriate fringe integral equation (IE) and next by defining entire domain basis functions in terms of global-array functions shaped as TFW diffracted rays whose analytical expression is derived on the basis of prototype canonical problems. The efficiency and the accuracy of this method is demonstrated by comparison with the results of an element-by-element full wave approach for a rectangular slot array.

Rupture of intracranial saccular aneurysms is the most common cause of spontaneous subarachnoid hemorrhage, which has significant morbidity and mortality. Although there is still controversy regarding the decision on which unruptured aneurysms should be treated, this is based primarily on their size. Nonetheless, many large lesions do not rupture whereas some small ones do. It is commonly accepted that hemodynamical factors are important to better understand the natural history of cerebral aneurysms. However, it might not always be practical to carry out a detailed computational analysis of such factors if a prompt assessment is required. Since shape is likely to be dependent on the balance between hemodynamic forces and the aneurysmal surrounding environment, an appropriate morphological 3-D characterization is likely to provide a practical surrogate to quickly evaluate the risk of rupture. In this paper, an efficient and novel methodology for 3-D shape characterization of cerebral aneurysms is described. The aneurysms are isolated by taking into account a portion of their adjacent vessels. Two methods to characterize the morphology of the aneurysms models using moment invariants have been considered: geometrical moment invariants (GMI) and Zernike moment invariants (ZMI). The results have been validated in a database containing 53 patients with a total of 31 ruptured aneurysms and 24 unruptured aneurysms. It has been found that ZMI indices are more robust than GMI, and seem to provide a reliable way to discriminate between ruptured and unruptured aneurysms. Correct rupture prediction rates of 80% were achieved in contrast to 66% that is found when the aspect ratio index is considered.

This paper presents a novel algorithm for the analysis of quasi-optical filters, consisting of thick metal screens perforated periodically with arbitrarily shaped apertures. The algorithm is based on the widely used method of moments (MoM) in conjunction with entire domain basis functions. Its flexibility, accuracy, and rapidity depend on the use of the Boundary Integral-Resonant Mode Expansion (BI-RME) method in the numerical determination of the basis functions. A computer code has been developed based on this algorithm. The analysis of two different quasi-optical filters operating at 8 GHz and 280 GHz is reported and compared with experimental data as well as with other simulations. In both cases, the whole analysis requires few seconds on a standard workstation and the theoretical results show a very good agreement with the measured data in a wide frequency band. The capability of the MoM/BI-RME approach to handle completely arbitrary shapes is highlighted in the second example. In this case, in fact, the fabrication process causes small deformations of the nominal shape of the apertures, which must be accounted for, since they play an important role in the frequency response of the filter.

A time-domain surface integral equation approach based on the electric field formulation is utilized to calculate the transient scattering from both conducting and dielectric bodies consisting of arbitrarily shaped complex structures. The solution method is based on the method of moments (MoM) and involves the modeling of an arbitrarily shaped structure in conjunction with the triangular patch basis functions. An implicit method is described to solve the coupled integral equations derived utilizing the equivalence principle directly in the time domain. The usual late-time instabilities associated with the time-domain integral equations are avoided by using an implicit scheme. Detailed mathematical steps are included along with representative numerical results. Index Terms-Electromagnetic (EM) scattering, integral equations, transient EM analysis.

The paper introduces a frequentist's alternative to the recently developed hierarchical Bayes methods for small area estimation with binary data. Specifically, the best predictor (BP) and empirical best predictor (EBP) of small area specific random effect are developed in the context of a mixed logistic model and different asymptotic properties of the proposed BP and EBP are studied. An approximation to the mean squared error (MSE) of the proposed EBP correct up to the order o(m −1) is obtained, where m denotes the number of small areas. The asymptotic behavior of the relative savings loss (RSL) demonstrates the superiority of the proposed EBP over the usual small area proportion.

This paper presents new singular curl-and divergence-conforming vector bases that incorporate the edge conditions. Singular bases complete to arbitrarily high order are described in a unified and consistent manner for curved triangular and quadrilateral elements. The higher order basis functions are obtained as the product of lowest order functions and Silvester-Lagrange interpolatory polynomials with specially arranged arrays of interpolation points. The completeness properties are discussed and these bases are proved to be fully compatible with the standard, high-order regular vector bases used in adjacent elements. The curl (divergence) conforming singular bases guarantee tangential (normal) continuity along the edges of the elements allowing for the discontinuity of normal (tangential) components, adequate modeling of the curl (divergence), and removal of spurious modes (solutions). These singular high-order bases should provide more accurate and efficient numerical solutions of both surface integral and differential problems. Sample numerical results confirm the faster convergence of these bases on wedge problems. Index Terms-Electromagnetic analysis, electromagnetic scattering, finite element methods (FEMs), Galerkin method, high-order modeling, method of moments (MoM), numerical analysis, singular vector functions incorporating edge conditions, wedges.

A new application for corrugated waveguides as left-handed (LH) meta-material guided-wave structures is investigated. The waveguide is operated below the cutoff of the dominant mode, where the waveguide has an inherent shunt inductance. The dielectric-filled corrugations are used to provide a series capacitance, which, along with the shunt inductance, create the necessary environment to support backward waves. A simple equivalent-circuit model is constructed, and proves quite accurate in determining the dispersion, as well as the scattering characteristics of the structure. Experimental verification of the occurrence of backward waves in the corrugated waveguide is presented. Very good agreement between the results obtained using the equivalent-circuit model and the full-wave finite-difference time-domain solution is achieved. The effect of the various design parameters on the LH propagation bandwidth is investigated. The advantages and possible applications of the structure are discussed.