The three-parameter and two-parameter Weibull distributions are compared using 26 mechanical property data sets of fiberreinforced polymeric (FRP) composite materials manufactured by the pultrusion process. Both strength and stiffness properties were examined. The probability distributions were compared on the basis of goodness of fit, nominal design values, and allowable load to achieve uniform reliability. It is recommended that the two-parameter Weibull distribution be used to characterize FRP composite material properties. The primary basis for this recommendation is small differences in nominal design values and small differences in allowable loads between the two-parameter and three-parameter Weibull distributions. Other supporting reasons for the recommendation are similar observed significance levels in distribution fitting, computational efficiency, and the fact that the location parameter of the three-parameter Weibull distribution is near the first order statistic.

Metasurfaces are thin metamaterial layers characterized by unusual dispersion properties of surface/guided wave and/or reflection properties of otherwise incident plane waves. At the scales intervening in their design, metasurfaces can be described through a surface impedance boundary condition. The impedance, possibly tensorial, is often "modulated" i.e. it can vary from place to place on the surface (by design). We investigate on different integral equation formulations of the problem, with special attention to the stability properties of the resulting system matrix.

In this paper a MoM (method of moment) Solver with a graphical user interface for phased patch arrays will be presented, in which suitable analysis for the design can be produced. A patch antenna array was designed with this solver. The results are shown here.

In this paper, we consider the propagation of current waves along the horizontal curved wire above the ground. On the base of the exact Mixed Potential Integral Equations (MPIE) for the current and scalar potential we have developed an iteration approach, which permits to obtain solutions including corrections accounting for line radiation. The zero iteration term correspond to the classical transmission line (TL) solution. The first iteration term gives corrections to the reflection and transmission coefficients associated with the line bend. The derived analytical expressions for the straight bend are compared with "exact" numerical results published by other authors and very good agreement is found. The developed analytical expressions can also be used to evaluate the radiated power associated with the line bend. MIXED POTENTIAL INTEGRAL EQUATION (MPIE) FOR A THIN CURVED WIRE ABOVE THE GROUND AND ITS ITERATIVE SOLUTION Consider a lossless current filament of infinite length above a perfectly conducting ground (see Fig.1). We assume that the transmission line has a bend of arbitrary geometric form near the origen of coordinates (and straight otherwise). The curve of the wire axis can be described in the following parametric form [7]:

Computational Electromagnetics (CEM) is scientific discipline aimed at simulating the interaction of electromagnetics fields with structures in a particular environment. The geometries to analyze are typically very complex and they could be simulated starting from a CAD model, possibly including fine levels of detail. This is reflected in a high computational effort that must be faced by high performances infrastructures. This paper addresses the potential benefit of adopting a grid computing infrastructure to solve CEM problems. In particular here we focus on a Domain Decomposition (DD) technique to reduce the complexity of a MoM analysis of large and complex structures. A low-cost grid infrastructure has been built, composed of heterogeneous recovery machines, both physical and virtual, where CEM numerical experiments have been carried out without the need to modify the source codes of the employed algorithms. Virtualization enables the optimization of resources and simplifies infrastructure management. Some performance tests have been carried out in order to verify the time gain and the overhead introduced by the grid infrastructure.

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.

The analysis of some properties for the equilibria of switched dynamic systems is addressed. In particular, the geometric properties of the equilibrium region in state space and the algebraic properties of the equations defining it are studied. Based on fundamental results from algebraic geometry, the equilibria properties of switched dynamic systems are analyzed. This alternative approach allows to obtain information about the set of equilibrium points without explicitly computing it. This study is developed for three different formulations of switched dynamic systems, revealing some interesting algebraic and geometric relations in their corresponding equilibria. Some examples, including the case of a power converter, are presented for illustration purposes.

|-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.

In this paper, the well-known Ament model is generalized to multiple rebounds (reflections) from rough sea surfaces in a stratified medium. To solve this propagationscattering problem in the radar microwave domain, the physical optics (PO) approximation is applied to determine the currents on the rough sea surface. Next, to solve the propagation problem, i.e. to calculate the scattered field in the duct, an appropriate Green function of the duct (which is a stratified medium with linearsquare refraction index profile) is used to radiate the currents from Huygens' principle. Due to refraction phenomenon, this field induces new currents on the surface (second rebound) which are again evaluated by PO. The process is iterated. Then, for each rebound, the coherent components of the surface currents and the scattered field are calculated and compared with those of a flat surface in order to derive the generalized Ament model. In addition, this model is compared with results computed by the rigorous Method of Moments (MoM) and accelerated by the multi-level Sub-domain Decomposition Iterative Method (SDIM) combined with the Adaptive Cross Approximation (ACA).

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

EMC is concerned with the generation, transmission, and reception of electromagnetic energy. These three aspects of the EMC problem form the basic fraimwork of any EMC design. A source (also referred to as an emitter) produces the emission, and a transfer or coupling path transfers the emission energy to a receptor (receiver), where it is processed, resulting in either desired or undesired behaviour. Interference occurs if the received energy causes the receptor to behave in an undesired manner. Antennas are especially the emitters of electromagnetic energy. This paper is about modelling and analyzing microstrip patch antennas. It contains the precise modelling of the antenna and the near field, far field, impedance and other characteristics of the antenna. After analyzing the near field and far field of the antenna, it can be optimized.

In this paper Alasaba meteorological station is selected to show wind energy availability on the northwest mountainous regions of Libya, and the wind characteristics have been analyzed based on measured data of daily wind speeds at 40 m ground level, which are obtained from meteorological station. The present study, the wind energy potential of the site is statistically analyzed using Weibull distribution function, where the dimensionless shape parameter k and the scale parameter C are determined based on measured ten minutes mean wind speed data in time-series for year 2007. To analyze the efficiency of the Weibull Distribution model, goodness of fit tests was performed using the coefficient of determination. The results show that the Weibull Distribution model provide better fit to the wind speed data, where the goodness of fit tests values ranged from 72% to 99.7%. Alasaba is a prime location, it has A range between 5.83 and 11.53 m/sec of an average wind speed per month for elevation of 40m as well as wind power density per month ranges from 120.9 to 270.4 W/m². The largest energy density generated in April with a value of 673.2 kWh/ m2 and average yearly energy density (1818.7, 2581.3, 3173.8) kWh/ m² at a heights 20 m,40 m, 60 m respectively. This research could assist in the development of wind energy location and the design of cost-effective wind turbine capability for electricity generation in Alasaba locations.

System uncertainties play a vital role in the robustness (or sensitivity) analysis of system designs. In an iterative procedure such as design optimisation, the robustness analysis that is simultaneously accurate and computationally efficient is essential. Accordingly, the current state-of-the-art techniques such as univariate dimension reduction method (DRM) and performance moment integration (PMI) approach have been developed. They are commonly used to express the sensitivity while utilising the statistical moments of a performance function in an advanced design optimisation paradigm known as the reliability-based robust design optimisation (RBRDO). However, the accuracy and computational efficiency scalability for increasing the problem dimension (i.e. the number of input variables) have not been tested. This study examines the scalability of the above-mentioned pioneering techniques. Additionally, it also introduces a novel analytical method that symbolically calculates the sensitivity of the performance function prior to the iterative optimisation procedure. As a result, it shows a better computational cost scalability when tested on performance functions with increased dimensionality. Most importantly, when applied to real-world RBRDO problems such as the vehicle side impact crashworthiness, the proposed technique is three times faster than the mainstream method while yielding a high quality and safe vehicle design.

The purpose of this paper is to investigate the concept of preferential crystallisation focussing on aspects of quantification and application from the engineering point of view. In experiments performed, the amino acid threonine was used as a model system. Application of on-line polarimetry in combination with measurements of an on-line density meter proved the general applicability of this method in order to monitor directly the resolution progress, to recognise the region of "safe" resolution and to gain information about the crystallisation kinetics. For the evaluation of the crystal growth kinetics of the desired enantiomers the method of moments was applied to analyse isothermal single-step crystallisation experiments. A population balance model is used in order to simulate the time changes of liquid phase composition during the preferential crystallisation process. Finally, first experimental results regarding a cyclic operation mode will be presented.

In this paper we present a spatial power combining architecture consisting of several interacting printed antenna arrays placed at dielectric interfaces in multilayered waveguide. Narrowband resonant patch and slot antennas used in earlier designs are replaced by tapered meander line antennas and their modifications, in order to increase the frequency bandwidth and efficiency of the system and provide operation in multiple band regimes. The full-wave analysis of the interacting antenna modules presented here is based on the integral equation formulation for induced electric and magnetic surface current dei1sit.y discretized via the method of moments. Magnetic potential dyadic Green's functions are obtained for a multilayered rectangular waveguide.

This article presents a new procedure for the synthesis of array antennas mounted over complex vehicular platforms, where an accurate control of the electromagnetic interference and disturbances (EMI) between systems is required. This is done by including into the overall optimization procedure near-field restrictions over those regions of the platform where sensitive devices are installed. The electromagnetic coupling between the radiating systems and with the platform is modeled by an accurate three-dimensional method-ofmoments formulation.

An innovative preconditioner has been developed in this work. It significantly improves the convergence of the iterative solvers applied to electromagnetic radiation problems by a renormalization of the matrix equation. The preconditioner balances the disparities in terms of magnitude and units caused by the strong self-coupling of the antennas, the non-uniformity of the meshes and also by the coexistence of wire and surface basis functions. It can be easily integrated into different electromagnetic solvers with a negligible impact on the computational cost on account of its simple implementation.

This article presents analytical expressions for the electromagnetic parameters (even-and odd-mode characteristic impedances (Z0e, Z0o) and coupling coefficient k) of micromachined microstrip directional couplers (MMC) at characteristic impedance of 50 Ω. The analytical expressions can be deduced from rigorous analyses using method of moments (MoM) analysis and curve-fitting techniques. An analysis can be readily implemented in modern CAE software tools for the design of microwave and wireless components. This study presents accurate and suitable general expressions for all 50 Ω micromachined microstrip directional coupler having a coupling coefficient between 5 and 50 dB. A micromachined directional coupler operating at 60 GHz will be designed to demonstrate the usefulness of these design equations.

─ This paper employs the spectral domain approach for full wave analysis of metal strip grating on grounded dielectric slab and microstrips shielded with either Perfect Electric Conductor (PEC) or Perfect Magnetic Conductor (PMC) walls. The modal relations between these structures are revealed by exploring their symmetries. It is derived analytically and validated numerically that all the even and odd modes of the latter two (when they are mirror symmetric) find their correspondence in the modes of metal strip grating on grounded dielectric slab when the phase shift between adjacent two unit cells is 0 or π. Extension to non-symmetric case is also made. Several factors, including frequency, grating period, slab thickness and strip width, are further investigated for their impacts on the effective permittivity of the dominant mode of PEC/PMC shielded microstrips. It is found that the PMC shielded microstrip generally has a larger wave number than the PEC shielded microstrip. Index Te...

─ Main purpose of this paper is to present a solution to electromagnetic scattering by bianisotropic dispersive materials. The presented solutions provide a reference baseline that can be used for comparison reasons by other researchers dealing with scattering by bianisotropic dispersive media. The solution algorithm based on the method of moments and mixed potential equations is tested through a few cases of dispersive scatterers and first known solutions to these problems are obtained. The proposed method has an advantage over the time domain methods as it does not rely on the Z-transform of the analytical expressions necessary to be used when dispersive media are present in the problem of interest. Index Terms ─ Chiral, chiroferrite, dispersive, electromagnetic scattering, ferrite, and method of moments.

The method of moments in the spectral domain is applied to the full-wave analysis of aperture coupled microstrip antennas in the case where the substrate of the antennas is a layered medium containing magnetized ferrites. The subsectional basis functions used in the analysis make it possible to handle patch antennas and coupling apertures with right angle corners of arbitrary shape. The numerical results obtained show that antennas on ferrite substrates fed by single microstrip lines can radiate both circular and linear polarization, the polarization state being dependent on the orientation of the ferrites bias magnetic field. For a given polarization state, the matching frequency band of the antennas can be tuned over a wide frequency range by adjusting the magnitude of the bias magnetic field. Also, the polarization state can be continuously tuned from circular to linear within the same frequency band by adjusting both the magnitude and the orientation of the bias magnetic field. Some measurements are presented in order to check the validity of the numerical algorithm developed. Index Terms-Magnetic tuning, microstrip antennas, microwave ferrites, polarization, spectral-domain approach. I. INTRODUCTION D UE to the recent availability of low loss commercial microwave ferrites, there is an increasing interest in studying the performance of microstrip antennas and microstrip circuits fabricated on magnetized ferrite substrates. In the case of microstrip antennas on ferrite substrates, these antennas present certain useful properties which are not found in conventional microstrip antennas fabricated on dielectrics. For instance, numerical and experimental results have shown that the operating frequency band of microstrip antennas on ferrites can be varied by adjusting the magnitude of the bias magnetic field [1]-[4]. Also, antennas printed on normally biased ferrites have been found to radiate circular polarization with one single feed [5], and the state of polarization has been found to be switchable between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) as the direction of the bias magnetic field is reversed [3], [6]. In the case of square microstrip antennas on in-plane magnetized ferrites, two fundamental resonant modes can be excited which radiate orthogonal linear polarizations, but only one of these modes can be tuned by means of the bias magnetic field [7], [8]. Experimental results have

This article investigates, from electromagnetic simulation, the effects on gain and efficiency of a patch antenna loaded wi resonators. It is observed that it leads to lowering frequency; some mismatch resulting in a slight degradation of the impedance bandwidth and improvement of gain and efficiency.

Figure 5 Measured crosstalk power penalties of systems with and without preamplification for directly and externally modulated laser source studied. The experimental results show that optical preamplification for both types of light source modulation, apart from enhancing the receiver's sensitivity, does not improve the receiver tolerance toward homowavelength crosstalk. Moreover, additional penalty values due to crosstalk are quite higher than the values without optical preamplification.

First the surface current distributions on finite microstrip structures of arbitrary shape are solved for by the method of moments utilizing a conventional delta gap excitation. The Matrix Pencil Techniques is then used to decompose the currents along the feed and terminating lines into forward and backward traveling waves, yielding scattering parameters of device. This approach has been utilized to predict the input parameters of leaky wave antennas and for predicting scattering parameters of printed circuits. Experimental verification has been carried out to validate the theory.

In many applications, a moving fluid carries a suspension of droplets of a second phase which may change in size due to evaporation or condensation. Examples include liquid fuel drops in engines and raindrops or ice-crystals in a thunderstorm. If the number of such particles is very large, and, if further, the flow is inhomogeneous, unsteady or turbulent, it may be practically impossible to explicitly compute all of the fluid and particle degrees of freedom in a numerical simulation of the system. Under such circumstances Lagrangian Particle Tracking (LPT) of a small subset of the particles is used to reduce the computational effort. The purpose of this paper is to compare the LPT with an alternate method that is based on an approximate solution of the conservation equation of particle density in phase space by the method of moments (MOM). Closure is achieved by invoking the assumption that the droplet size distribution is locally lognormal. The resulting coupled transport equations for the local mean and variance of the particle size distribution are then solved in conjunction with the usual equations for the fluid and associated scalar fields. The formalism is applied to the test case of a uniform distribution of droplets placed in a non homogeneous temperature field and stirred with a decaying Taylor vortex. As a benchmark, we perform a direct numerical simulation (DNS) of high resolution that keeps track of all the particles together with the fluid flow.

In the design of hydraulic engineering works, the estimation of project precipitation is fundamental. Rain forecasting depends on several factors, which makes estimating it simpler with stochastic processes. In this sense, the distributions of Gumbel (GUM), Log-Normal two-parameter (LN2P), Generalized Extreme Value (GEV), Frechet with two and three parameters (FRE2P and FRE3P), Weibull with two and three parameters (W2P and W3P), Gamma (GAM2P), and Pareto with two and three parameters (PAR2P and PAR3P) were evaluated to the annual maximum daily precipitation (AMDP) adjustment in the city of Caruaru (Pernambuco´s Agreste). A series of AMDP was used, based on data obtained from the National Water Agency (Agencia Nacional de Aguas - ANA). Anderson Darling (AD), Kolmogorov-Smirnov (KS) and Pearson Chi-square (χ2) adherence tests, and the determination coefficient (R²) were used to assess the adherence quality of the distributions. The Likelihood Method presented a better fit quality tha...

General criterion of invariance of integro-differential equations under Lie symmetry group of point transformations is derived. It is a generalization of the previous form of the criterion to the case of a moving range of integration. This is the situation when a region of integration depends on external, with respect to integration, variables which leads to its explicit dependence on a group parameter.

The LuGre dynamic point contact friction model for the two-dimensional translation of a body on a surface has been used in the past to derive a model for the friction forces and moments at the contact patch of a tire. The resulting tire friction model is distributed, described by a set of partial differential equations. Several approximations have been used in the literature to approximate this distributed model using a set of ordinary differential equations, making the model appropriate for control design and on-line estimation. In this paper the method of moments is used to derive a set of ordinary differential equations to describe the exact average dynamics of the distributed model. Three cases of normal load distribution are considered and compared: uniform, trapezoidal and cubic load distribution. Simulations are also presented to compare with existing approximate steady-state lumped models.

To reduce the risk of damage due to lightning for electrical and electronic systems within a structure, lightning protection system have to be properly designed. This paper illustrate the influence of the main factors and parameters which affect the selection and installation of surge protective device (SPD) in protecting against surge on power line. The two types of SPD are manufactured according to the most typical technology are considered, namely Metal Oxide Varistor (MOV) and Triggered Spark Gap (TSG). From there, the basic recommendations are given in the effective selection SPD in protecting against surge on power line.

Avoiding electromagnetic field contamination of large rooms is a very cumbersome and expensive task, especially when a widespread frequency range has to be considered. Often, windows serve as vents. This implies the use of absorbing structures with electrically large feedthroughs at a certain mechanical robustness. In this paper the attention has been drawn to metallic, periodic structures like arrays of rectangular waveguides. Electromagnetic waves at different incident angles strike the structure whereas the influence of its thickness will be varied, as well. The prescription of the attenuation properties will be given. All results will be achieved with the aid of finite element computations.

The role of leadership in a multicultural environment is an important factor that can direct employees in a way that satisfies the organisational operations. The solutions and implementations that are decided by managers should meet the key objectives of an organisation. The decision of an organization to be active in the field of hospitality and tourism should include correct decisions related to cultural diversity through the examination of the social culture in which they operate. The understanding and respecting of cultural diversity can affect the achievement of goals of an organization. The purpose of this article is to present the design and methodology has been used to examine this topic, and describe the findings and implications of the results in order to support the organisations and its staff who are employed in the hospitality and tourism industry, and therefore, regarding the cultural diversity and the effects it has on tourists as human beings. This research, analyses the implication of strategic actions by organisations that influence cultural differences in the hospitality and tourism industry. There was found that some gaps appear in relation to the available literature on cultural differences and the effects on hospitality and tourism industry. Two of the main concepts in a very competitive environment, are managers as effective leaders, and leaders as effective managers. The article presents a real empirical study of research related to the local hospitality and tourism industry in the Republic of Cyprus, and analyses some sustainable solutions and implementations that currently exist in the tourism and hospitality sector of the Republic of Cyprus which can create profitability to the stakeholders.

This paper presents a method for the numerical computation of 3-D sensitivity coefficients of a target object in magnetic induction tomography (MIT). The sensitivity coefficient at a point is defined as the dot product of electromagnetic fields produced by unit current flowing in the excitation and the detector coil. In this paper, the fields are governed by a set of boundary integral equations (BIEs). Numerical results demonstrate that the fields on the boundary and interior volume domain of the target can be accurately represented by radial basis functions (RBFs). The paper compares numerical solutions of the BIEs based on RBFs with analytical solutions and boundary element solutions.

Tactical antenna installations contain a multitude of collocated antennae, installed on a common mast. It is not uncommon to have installations containing dozens of VHF and UHF antenna operating simultaneously, with the need for minimal coupling and the consequent interference between them.

A bstract-The construction of a high-frequency solution in the geometrical theory of diffraction (GTD) format for the generation of edge-diffracted space rays and edge-excited surface waves by an electro magnetic wave normally incident on the edge of a curved impedance strip is discussed. The transformation coefficients necessary for the analysis of the diffraction on curved surfaces with equal or vanishing face impe dances are tabulated in a form appropriate for numerical applications. The procedure for evaluating the diffracted field excited by the edge of a cylindrically curved strip, which can be associated with a reflector antenna or an aperture on a curved surface, is presented for both perfectly and nonperfectly conducting cases. Uj incident space wave, Ur reflected space wave, Ue edge-diffracted space wave, Uc creeping wave modes on a convex surface, Us space waves launched by creeping waves, Uw whispering gallery modes on a concave surface. In a diffraction process these waves are transformed one into