finite difference time domain implementation of surface impedance boundary conditions surface impedance boundary conditions can be utilized to avoid using small cells made necessary by shorter wavelengths in conducting media throughout the solution volume the standard approach is to approximate the surface impedance over a very small bandwidth by its value at the center frequency and then use that result in the boundary condition in this paper two implementations of the surface impedance boundary condition are presented one implementation is a constant surface impedance boundary condition and the other is a dispersive surface impedance boundary condition that is applicable over a very large frequency bandwidth and over a large range of conductivities frequency domain results are presented in one dimension for two conductivity values and are compared with exact results scattering width results from an infinite square cylinder are presented as a two dimensional demonstration

on the controllability properties of circulant networks this paper examines the controllability of a group of first order agents adopting a weighted consensus type coordination protocol over a circulant network specifically it is shown that a circulant network with laplacian eigenvalues of maximum algebraic multiplicity q is controllable from q nodes our approach leverages on the cauchy binet formula which in conjunction with the popov belevitch hautus test leads to new insights on structural aspects of network controllability

fdtd calculation of radiation patterns impedance and gain for a monopole antenna on a conducting box the ability of the finite difference time domain fdtd method to calculate radiation patterns input impedance and gain for a monopole antenna on a conducting box is demonstrated results are given for the bare box and with the box coated with a dielectric layer radiation patterns are compared with measurements and with the method of moments for the bare box radiation patterns for the dielectric covered box and all impedance and gain results are compared with measurements only good agreement is obtained in all cases the fdtd approach includes a dielectric covering quite easily while this would be quite difficult for a method of moments approach the fdtd method requires similar computer time as the method of moments for a single frequency result but produces wide bandwidth impedance and gain results with much less computer time

electromagnetic scattering from 3 d curved dielectric bodies using time domain integral equations a boundary integral equation bie approach is developed to calculate transient scattering from dielectric bodies the treatment is directly in terms of the e and h fields rather than magnetic and electric currents it employs curvilinear quadratic modeling which allows accurate representation of arbitrarily shaped curved bodies the treatment is isoparametric with the same quadratic representation of the spatial field variation and with the temporal variation modeled by similar quadratic elements integration employs high order gaussian quadrature with special treatment of the singular and hypersingular integrals that arise the treatment is implicit requiring the solution of a sparse matrix equation at each timestep this adds only trivially to the cost at each timestep and by freeing the timestep from the constraint that it be smaller than the smallest nodal spacing can greatly reduce the number of timesteps that must be employed additionally it produces stable results without resort to the averaging processes proposed elsewhere example calculations of scattering from a sphere a cube and an almond are presented and compared with earlier published transient results and with results from a frequency domain treatment good agreement and improved accuracy is found

a bayesian variable selection approach for analyzing designed experiments with complex aliasing experiments using designs with complex aliasing patterns are often performed for example twolevel nongeometric plackett burman designs multilevel and mixed level fractional factorial designs two level fractional factorial designs with hard to control factors and supersaturated designs hamada and wu proposed an iterative guided stepwise regression strategy for analyzing the data from such designs that allows entertainment of interactions their strategy provides a restricted search in a rather large model space however this article provides an efficient methodology based on a bayesian variable selection algorithm for searching the model space more thoroughly we show how the use of hierarchical priors provides a flexible and powerful way to focus the search on a reasonable class of models the proposed methodology is demonstrated with four examples three of which come from actual industrial experiments

some risks in the construction and analysis of supersaturated designs a designed experiment in which the number of factors is at least as large as the number of runs is referred to as a supersaturated ss design recently these designs have received increased attention construction of such designs and analysis of data from them have been discussed by several authors our objective in this article is to examine these designs and methods for their analysis an important finding for practitioners is that the correlation structure inherent in ss designs can obscure real effects or promote nonreal effects whatever analysis method is used this problem can occur although all subsets regression is preferable to stepwise regression hence one should be cautious with the use of ss designs

screening strategies in the presence of interactions product and process improvement can involve a large number of factors that must be varied simultaneously understanding how factors interact is a key step in identifying those factors that have a substantial impact on the response this article gives the first comprehensive assessment and comparison of screening strategies for interactions using two level supersaturated designs group screening and a variety of data analysis methods including shrinkage regression and bayesian methods we develop novel methodology to allow application of bayesian methods in two stage group screening insights on using the strategies are provided through a variety of simulation scenarios and open issues are discussed supplementary materials are available online

fdtd model of electrically thick frequency dispersive coatings on metals and semiconductors based on surface impedance boundary conditions a new finite difference time domain fdtd model for conductors coated with electrically thick frequency dispersive coatings is developed the model is based on first order impedance boundary conditions as the most important original feature of the model the frequency dependence of the material parameters of the coating is very general dispersive coatings of lorentz debye or drude type with multiple pole pairs and a fixed electrical conductivity can be modeled with the proposed technique another new property of the model is the use of rational approximation in a way that enables accurate approximation of the impedance function in a wide range corresponding to several thickness resonances of the coating the conductor losses in the metal backing that are neglected in many earlier models are accounted for in the proposed model the model is formulated for planar interfaces in the general three dimensional situation for the yee algorithm and verified against analytical reference results with numerical examples in one dimensional and two dimensional problems

construction of e s 2 optimal supersaturated designs booth and cox proposed the e s 2 criterion for constructing two level supersaturated designs nguyen technometrics 38 1996 69 73 and tang and wu canad j statist 25 1997 191 201 independently derived a lower bound for e s 2 this lower bound can be achieved only when m is a multiple of n 1 where m is the number of factors and n is the run size we present a method that uses difference families to construct designs that satisfy this lower bound we also derive better lower bounds for the case where the nguyen tang wu bound is not achievable our bounds cover more cases than a bound recently obtained by butler mead eskridge and gilmour j r stat soc ser b stat methodol 63 2001 621 632 new e s 2 optimal designs are obtained by using a computer to search for designs that achieve the improved bounds

fresnel s formulas in time domain a time spatial representation of fresnel s formulas is obtained that permits description of the interaction of complex electromagnetic signals with a flat interface between dielectric media to be made in the time domain this description is made by means of integral equations and includes the case when the boundary is nonstationary for example if it is created at some instant in time the solutions of these equations give the transmitted and reflected signals by virtue of resolvent integral operators that take into account the structure of the field polarization these three dimensional 3 d operators are derived for the case when the medium in one of the two half spaces changes its permittivity and acquires a conductivity the weight factors in the kernels of these operators are simply the analogues of fresnel s formulae the oblique incidence of a plane monochromatic wave on the flat boundary of the medium whose permittivity changes abruptly in time is also considered it is shown that the transient accompanies the transformed field in contrast to the case of the normal incidence when the transformed field only consists of the monochromatic secondary waves

multilevel surface decomposition algorithm for rapid evaluation of transient near field to far field transforms a fast multilevel algorithm with reduced memory requirements for the evaluation of transient near field to far field transforms is presented the computational scheme is based on a hierarchical decomposition of an arbitrary shaped enclosing surface over which the near fields of an antenna or a scatterer are given for surface subdomains at the highest decomposition level the angular temporal far field patterns are calculated directly from the known near fields over a sparse angular grid of directions and a short temporal duration the multilevel computation comprises angular and temporal interpolations thus increasing angular resolution and temporal duration of radiation patterns while aggregating the subdomain contributions between successive decomposition levels these steps are repeated until obtaining the transient far field response of the whole enclosing surface the computational complexity of the proposed algorithm is substantially lower than that of the direct evaluation reduction in memory requirements is obtained by formulating the algorithm as a marching on in time windowed scheme this approach allows for embedding of the accelerated transforms within existing near field modeling tools

on the use of the geometric mean in fdtd near to far field transformations near to far field transformations require the tangential electric and magnetic fields over a surface which we call the integration boundary however the staggered nature of the finite difference time domain grid is problematic in that the electric and magnetic fields are not collocated in either space or time for harmonic transformations i e ones which rely upon a fourier transform of the time domain near fields one can account for the temporal offset with a simple phase correction in the frequency domain to account for spatial offsets previously an arithmetic mean of the time domain fields to either side of the integration boundary has been used here we show that superior results are obtained by instead using a geometric mean of the harmonic fields to either side of the integration boundary

some hidden projection properties of orthogonal arrays with strength three summary it is shown that a two level orthogonal array with strength three whose run size is not a multiple of 16 has the hidden projection property that in its projection on to any five factors all the main effects and two factor interactions are estimable if the higher order interactions are negligible the result applies to the fold over of any strength two orthogonal array whose run size is not a multiple of 8 this extends diamond s 1995 result on the fold over of the 12 run plackett burman design some connections with search designs are also presented

a parallel finite volume runge kutta algorithm for electromagnetic scattering a 3d explicit finite volume algorithm has been developed to simulate scattering from complex geometries on parallel computers using structured body conformal curvilinear grids most simulations for practical 3d geometries require a large number of grid points for adequate spatial resolution making them suitable to parallel computation the simulations have been carried out using a multi block zonal approach in the message passing paradigm on the sp 2 each zone is placed on a separate processor and inter processor communication is carried out using the message passing library interface mpl mpi integration of maxwell s equations is performed using the four stage runge kutta time integration method on a dual grid this method of integrating on a staggered grid gives enhanced dissipative and dispersive characteristics a scattered field formulation has been used and the liao boundary condition is used at the outer nonreflecting boundary the far zone transformation has also been implemented efficiently using specialized mpl functions to evaluate the far zone scattering results results show extremely good comparisons for scattering from the sphere and the ogive with the exact solution and standard fdtd type algorithms comparisons for nonaxisymmetric targets like the nasa almond with experimental data has also been found to be extremely good

a finite difference time domain near zone to far zone transformation electromagnetic scattering an efficient time domain near zone to far zone transformation for fdtd finite difference time domain computations is presented the approach is to keep a running accumulation of the far zone time domain vector potentials due to the tangential electric and magnetic fields on a closed surface surrounding the scatterer at each time step at the end of the computation these vector potentials are converted to time domain far zone fields many far zone bistatic directions can be included efficiently during one fdtd computational run frequency domain results can be obtained via fast fourier transform wideband results for scattering from a perfectly conducting plate were obtained from a single fdtd computation transformed to the frequency domain and compared with moment method results this approach is significantly more efficient than computing many fdtd results using sinusoidally varying excitation if a wide frequency band is of interest coupled with recent advances in computing fdtd results for frequency dependent materials wideband results for far zone scattering from targets including frequency dependent materials can be obtained efficiently

narrow waisted gaussian beam discretization for short pulse radiation from one dimensional large apertures we develop a gabor based gaussian beam gb algorithm for representing two dimensional 2 d radiation from finite aperture distributions with short pulse excitation in the time domain td the work extends previous results using 2 d frequency domain fd narrow waisted gaussian beams the fd algorithm evolves from the rigorous kirchhoff integration over the aperture distribution which is then parameterized via the discrete gabor basis and evaluated asymptotically for high frequencies to furnish the gb propagators to the observer the td results are obtained by fourier inversion from the fd and yield pulsed beams pb we describe the resulting td algorithm for several aperture distributions ranging from simple linearly phased linear delay to arbitrary time delay profiles the latter accommodate the important case of focusing td aperture fields for modulated pulses with gaussian envelopes we compute accurate closed form analytic solutions which have been calibrated against numerical reference data our results confirm that the previously established utility of the gabor based narrow waisted fd gb algorithm for radiation from distributed apertures remains intact in the td

signal processing techniques to reduce the sinusoidal steady state error in the fdtd method techniques to improve the accuracy of the finite difference time domain fdtd solutions employing sinusoidal excitations are developed the fdtd computational domain is considered as a sampled system and analyzed with respect to the aliasing error using the nyquist sampling theorem after a careful examination of how the high frequency components in the excitation cause sinusoidal steady state errors in the fdtd solutions the use of smoothing windows and digital low pass filters is suggested to reduce the error the reduction in the error is demonstrated for various cases

near and far field calculations in fdtd simulations using kirchhoff surface integral representation kirchhoff s surface integral representation ksir is used to calculate the near and far fields from the finite difference time domain fdtd simulation the ksir is very simple to implement and its distinct advantage is that the calculation of any of the six field components depends on the value of the same field component over a closed surface this avoids interpolation errors when using the popular yee scheme for fdtd in addition to its efficiency and simplicity of implementation the ksir leads to highly accurate near fields that reduce absorbing boundary condition abc errors

a new 3 d conformal pec fdtd scheme with user defined geometric precision and derived stability criterion a new conformal finite difference time domain cfdtd updating scheme for metallic surfaces nonaligned in the grid is presented in this paper in contrast to existing conformal models the new model can be formulated with the original yee fdtd update equation therefore the proposed scheme can be easily added in standard fdtd codes even if the codes are already parallelized or hardware accelerated in addition based on the commonly used conventional stability criterion a derivation of the stability is presented and based on the conformal geometric information a time step reduction formula is presented the time step reduction is used as a user defined parameter to tradeoff speed versus accuracy the achievable geometric precision is optimized to a given time step therefore even with the conventional time step no reduction the presented scheme profits from the conformal discretization to show the performance and the robustness of the proposed scheme canonical validations and two real world applications were investigated a broadband low profile circular antenna was successfully simulated showing the benefit of the conformal fdtd method compared to the conventional scheme furthermore a cad based mobile phone was conformally discretized and successfully simulated showing that the proposed scheme is highly suited for the simulation of advanced engineering problems

nearly orthogonal arrays with mixed levels and small runs in running a factorial experiment it may be desirable to use an orthogonal array with different mixed numbers of factor levels because of the orthogonality requirement such arrays may have a large run size by slightly sacrificing the orthogonality requirement we can obtain nearly orthogonal arrays with economic run size some general methods for constructing such arrays are given for 12 18 20 and 24 runs many orthogonal arrays and nearly orthogonal arrays with mixed levels are constructed and tabulated effects of near orthogonality on estimation efficiency and analysis are studied

integral representations of bivariate complex geometric mean and their applications abstract in the paper the authors survey integral representations including the levy khintchine representations and applications of some bivariate means including the logarithmic mean the identric mean stolarsky s mean the harmonic mean the weighted geometric means and their reciprocals and the toader qi mean and the multivariate weighted geometric means and their reciprocals derive integral representations of bivariate complex geometric mean and its reciprocal and apply these newly derived integral representations to establish integral representations of heronian mean of power 2 and its reciprocal

columnwise pairwise algorithms with applications to the construction of supersaturated designs motivated by the construction of supersaturated designs we develop a class of algorithms called columnwise pairwise exchange algorithms they differ from the k exchange algorithms in two respects 1 they exchange columns instead of rows of the design matrix and 2 they employ a pairwise adjustment in the search for a better column the proposed algorithms perform very well in the construction of supersaturated designs both for a single criterion and for multiple criteria they are also applicable to the construction of designs that are not supersaturated

k circulant supersaturated designs a class of supersaturated designs called k circulant designs is explored these designs are constructed from cyclic generators by cycling k elements at a time the class of designs includes many es2 optimal designs some of which are already known and some of which are more efficient than known designs for model estimation under factor sparsity generators for the most efficient designs are listed and projection properties of some of the designs are explored we also illustrate that some k circulant supersaturated designs can be augmented with interaction columns to produce efficient designs for a larger number of factors or for estimating interactions

electromagnetic transmission through multiple circular apertures in a thick conducting plane the boundary value problem of electromagnetic wave scattering from multiple circular apertures in a thick conducting plane is rigorously solved the eigenfunction expansion integral transform and superposition principle are utilized to represent the scattered field in the discrete and continuous modes the boundary conditions are enforced to obtain a set of simultaneous equations for the discrete modal coefficients the transmission coefficient is represented in a fast convergent series computation is performed to illustrate the behavior of transmission and coupling through multiple circular apertures in terms of the aperture geometry

a new class of supersaturated designs supersaturated designs are useful in situations in which the number of active factors is very small compared to the total number of factors being considered in this article a new class of supersaturated designs is constructed using half fractions of hadamard matrices when a hadamard matrix of order n is used such a design can investigate up to n 2 factors in n 2 runs results are given for n 60 extension to larger n is straightforward these designs are superior to other existing supersaturated designs and are easy to construct an example with real data is used to illustrate the ideas

time domain fields exterior to a two dimensional fdtd space a transformation algorithm for the near zone and far zone fields exterior to a two dimensional 2 d finite difference time domain fdtd field lattice has been developed entirely in the time domain the fields are found from a surface integration of the convolution of the time derivative of equivalent currents and charges along a contour that encloses the scatterer or radiator of interest the kernel of the convolution integral has a square root singularity for which an efficient numerical integration rule is presented using this technique a very accurate solution is obtained however convolution integrals are computationally expensive with or without singularities as an alternative a rapidly convergent approximate series expansion for the convolution integral is presented which can be used both in the near and far zone results using the new 2 d transform are compared with analytical expressions for the fields generated by a modulated gaussian pulse for te and tm line sources in addition the 2 d transform solution for the near zone fields scattered from an open ended cavity for a te incident modulated gaussian pulse plane wave is compared against a full grid fdtd solution for accuracy and efficiency the 2 d transform far zone fields are compared against an alternative technique which uses a double fourier transform to perform the convolution in the frequency domain

finite difference time domain calculation of transients in antennas with nonlinear loads transient currents for an antenna with a nonlinear load are calculated using finite difference time domain fdtd methods the fdtd electric field across the nonlinear load which determines the voltage across the load is calculated by solving a nonlinear equation at each time step this allows the time step to be at the courant limit and is more efficient than reducing the time step size in all the fdtd cells to maintain stability in just the cell containing the nonlinear load the stability of this approach relative to a simpler approach of approximating the diode as a variable resistor is demonstrated as a validation of the method the transient current in a long dipole antenna with a nonlinear load excited by a pulsed plane wave is computed and compared with calculated results obtained by another method the approach given here extends the applicability of the fdtd method to problems involving radiation and scattering from antennas including nonlinear loads

time domain extrapolation to the far field based on fdtd calculations a scheme to extrapolate scattered fields calculated by the finite difference time domain fdtd method to the far zone is developed it could replace the usual extrapolation scheme for a single frequency in that it yields a spectrum with only one incident pulse the method comprises the following steps 1 using an incident pulse 2 performing an fdtd calculation and using the currently calculated data on s to extrapolate to the far field and 3 fourier transforming the far field time response to obtain the frequency domain response the approach seems to be more convenient in time domain calculations and more in agreement with the spirit of fdtd

full wave analysis and wide band design of probe fed multilayered cylindrical rectangular microstrip antennas the input impedance and radiation pattern of the probe fed multilayered cylindrical rectangular microstrip antennas pmcmsa are analyzed by using a novel approach which combines the conformal finite difference time domain fdtd and gedney s unsplit version of the perfectly matched layer absorbing boundary condition method and the green s functions in cylindrically stratified media the near fields of such antennas and the current distributions on the patches are obtained by the conformal fdtd method numerically and then the modified spectral domain green s functions in arbitrary cylindrically stratified media are used to determine the radiation pattern the effect of the small radius of the probe on the performance of antennas is investigated through the thin wire algorithm in cylindrical coordinates a simple design scheme of the probe fed cylindrically stacked antennas is also proposed for increasing the impedance bandwidth

the reciprocal of the geometric mean of many positive numbers is a stieltjes transform in the paper by the cauchy integral formula in the theory of complex functions an integral representation for the reciprocal of the geometric mean of many positive numbers is established as a result the reciprocal of the geometric mean of many positive numbers is verified to be a stieltjes transform and consequently a logarithmically completely monotonic function

a complete monotonicity property of the gamma function abstract a logarithmically completely monotonic function is completely monotonic the function 1 ln x 1 x ln x 1 is strictly completely monotonic on 0 the function x 1 x x is strictly logarithmically completely monotonic on 0

a general criterion for factorial designs under model uncertainty motivated by two industrial experiments in which rather extreme prior knowledge was used to choose the design we show that the qb criterion which aims to improve the estimation in as many models as possible by incorporating experimenters prior knowledge along with an approximation to the as criterion is more general and has a better statistical interpretation than many standard criteria the generalization and application of the criterion to different types of designs are presented the relationships between qb and other criteria for different situations are explored it is shown that the e s2 criterion is a special case of qb and several aberration type criteria are limiting cases of our criterion so that qb provides a bridge between alphabetic optimality and aberration the two case studies illustrate the potential benefits of the qb criterion r programs for calculating qb are available online as supplemental materials

generating systematic supersaturated designs practitioners are routinely faced with distinguishing between factors that have real effects and those whose apparent effects are due to random error when there are many factors the usual advice given is to run so called main effect designs resolution iii designs in the orthogonal case that require at least k 1 runs for investigating k factors this may be wasteful however if the goal is only to detect those active factors this is particularly true when the number of factors is large in such situations a supersaturated design can often save considerable cost a supersaturated design is a fraction of a factorial design composed of n observations where n k 1 when such a design is used the abandonment of orthogonality is inevitable this article examines the maximum number of factors that can be accommodated when the degree of the nonorthogonality is specified furthermore interesting properties of systematic supersaturated designs are revealed for example such a design may be adequate

projective properties of certain orthogonal arrays summary a question of importance in factor screening is when a two level orthogonal design for a multifactor experiment can be projected into lower dimension typically p 2 or 3 new results relate to the projectivity p of saturated designs in which n 1 factors are tested in n runs it is shown that a design obtained by doubling an n x n orthogonal array is always of projectivity p 2 a twolevel cyclic design is either a factorial array and hence has p 2 or it has p 3 a two level orthogonal design with 4m runs m odd has p 3 in particular these results allow the designs derived by plackett burman 1946 to be categorised in terms of these projective properties

an rwg basis function based near to far field transformation for 2 d triangular grid finite difference time domain method a near to far field transformation ntft based on the rao wilton glisson rwg basis function is proposed for a 2 d triangular grid fdtd method the surface equivalence theorem is applied and the equivalent current density j sub z in the tm sub z case or m sub z in the te sub z case on the radiation contour is interpolated by using rwg basis functions the interpolation is valid for the ntft in either the time or frequency domain formulations for the interpolation scheme and the ntft are presented for the tm sub z case the scattering by an infinite dielectric circular cylinder due to an electric line source is simulated by using the triangular grid fdtd as well as the proposed ntft numerical results in both the time domain and frequency domain are demonstrated and verified by comparison with analytical solutions

a two dimensional time domain near zone to far zone transformation a 2d version of a time domain transformation useful for extrapolating 3d near zone finite difference time domain fdtd results to the far zone is outlined while the 3d transformation produced a physically observable far zone time domain field this is not convenient for the 2d case however a representative 2d far zone time domain result can be obtained directly this result can then be transformed to the frequency domain using a fast fourier transform corrected with a simple multiplicative factor and used for example to calculate the complex wideband scattering width of a target if an actual time domain far zone result is required it can be obtained by inverse fourier transform of the final frequency domain result

a two stage bayesian model selection strategy for supersaturated designs in early stages of experimentation one often has many candidate factors of which only few have significant influence on the response supersaturated designs can offer important advantages however standard regression techniques of fitting a prediction line using all candidate variables fail to analyze data from such designs stepwise regression may be used but has drawbacks as reported in the literature a two stage bayesian model selection strategy able to keep all possible models under consideration while providing a level of robustness akin to bayesian analyses incorporating noninformative priors is proposed the strategy is demonstrated on a well known dataset and compared to competing methods via simulation

far field time domain calculation from aperture radiators using the fdtd method it is often desirable to determine the far field radiation pattern from an aperture in a metal plate the use of time domain methods like the finite difference time domain fdtd method is problematic because of the necessity of modeling the entire space of interest this is often circumvented by using the equivalence principle to determine the far field by equivalent currents generated in the near field however these transformations are often mathematically complex this paper presents an extremely simple formulation for calculating the time domain fields from some types of aperture radiators by using wavelet analysis the pertinent parameters can be compressed and stored to be used later to resynthesize the radiated fields

projection properties of plackett and burman designs the projection properties of the 2 r q p fractional factorials are well known and have been used effectively in a number of published examples of experimental investigations the plackett and burman designs also have interesting projective properties knowledge of which allows the experimenter to follow up an initial plackett and burman design with runs that increase the initial resolution for the factors that appear to matter and thus permit efficient separation of effects of interest projections of designs into 2 5 dimensions are discussed and the 12 run case is given in detail a numerical example illustrates the practical uses of these projections

a general method of constructing e s2 optimal supersaturated designs there has been much recent interest in supersaturated designs and their application in factor screening experiments supersaturated designs have mainly been constructed by using the e s 2 optimality criterion originally proposed by booth and cox in 1962 however until now e s 2 optimal designs have only been established with certainty for n experimental runs when the number of factors m is a multiple of n 1 and in adjacent cases where m q n 1 r r 2 q an integer a method of constructing e s 2 optimal designs is presented which allows a reasonably complete solution to be found for various numbers of runs n including n 8 12 16 20 24 32 40 48 64

construction of optimal multi level supersaturated designs author s xu hongquan wu cfj abstract a supersaturated design is a design whose run size is not large enough for estimating all the main effects the goodness of multi level supersaturated designs can be judged by the generalized minimum aberration criterion proposed by xu and wu 2001 optimal supersaturated designs are shown to have a periodic property and general methods for constructing optimal multilevel supersaturated designs are proposed inspired by the addelman kempthorne construction of orthogonal arrays optimal multi level supersaturated designs are given in an explicit form columns are labeled with linear or quadratic polynomials and rows are points over a finite field additive characters are used to study the properties of resulting designs some small optimal supersaturated designs of 3 4 and 5 levels are listed with their properties

a spatial high order hexahedral discontinuous galerkin method to solve maxwell s equations in time domain in this paper we present a non dissipative spatial high order discontinuous galerkin method to solve the maxwell equations in the time domain the non intuitive choice of the space of approximation and the basis functions induce an important gain for mass stiffness and jump matrices in terms of memory this spatial approximation combined with a leapfrog scheme in time leads also to a fast explicit and accurate method a study of the dispersive error is carried out and a stability condition for the proposed scheme is established some comparisons with other schemes are presented to validate the new scheme and to point out its advantages finally in order to improve the efficiency of the method in terms of cpu time on general unstructured meshes a strategy of local time stepping is proposed

construction of supersaturated designs through partially aliased interactions summary an n x n hadamard matrix can be used to construct a saturated 2 n 1 design with n runs furthermore if an interaction column for two of the columns of the matrix is not fully aliased with any column of the matrix this interaction column can be used as a supplementary column for studying an additional factor for some small hadamard matrices studied by plackett burman 1946 the number of such interaction columns is very large thus allowing the construction of supersaturated designs whose number of factors far exceeds the number of runs a general method of construction along these lines is proposed the efficiency of the constructed designs is studied by using three criteria

near to far field transformation by a time domain spherical multipole analysis the contribution deals with a new time domain near to far field nff transformation which is particularly suited for the finite difference time domain fdtd method the far field is derived from the tangential field components on a surface enclosing the scatterer by employing a time domain spherical multipole representation the necessary time domain convolution is performed as on the fly in parallel with the fdtd time stepping algorithm the efficiency of the method is improved by incorporating a temporal linear interpolation of the near field data with the once obtained multipole amplitudes an analytic series representation of the time domain far field is achieved which allows a physical interpretability of the result moreover this expansion serves as an ideal basis for a systematic and efficient post processing the proposed technique may also be useful for other numerical and for asymptotic methods

fdtd calculation of wide band antenna gain and efficiency absolute gain and radiation efficiency are calculated using the finite difference time domain fdtd method the method described utilizes pulsed excitation so that wideband results are available from a single fdtd computation the approach is demonstrated for a simple wire antenna geometry and is validated by comparison with results obtained using the method of moments

detection of interactions in experiments on large numbers of factors one of the main advantages of factorial experiments is the information that they can offer on interactions when there are many factors to be studied some or all of this information is often sacrificed to keep the size of an experiment economically feasible two strategies for group screening are presented for a large number of factors over two stages of experimentation with particular emphasis on the detection of interactions one approach estimates only main effects at the first stage classical group screening whereas the other new method interaction group screening estimates both main effects and key two factor interactions at the first stage three criteria are used to guide the choice of screening technique and also the size of the groups of factors for study in the first stage experiment the criteria seek to minimize the expected total number of observations in the experiment the probability that the size of the experiment exceeds a prespecified target and the proportion of active individual factorial effects which are not detected to implement these criteria results are derived on the relationship between the grouped and individual factorial effects and the probability distributions of the numbers of grouped factors whose main effects or interactions are declared active at the first stage examples are used to illustrate the methodology and some issues and open questions for the practical implementation of the results are discussed