Properties of eigen-solutions in parallel plate waveguides partially loaded with Lorentz type Double Negative Materials (DNG), modelled by lossless/lossy, identical/non-identical electric, magnetic parameters are presented. Modal cut-off phenomena associated with surface waves, transitions between evanescent/propagating, forward/backward waves and their dependence on frequency, filling factor and dispersive material parameters are investigated. Novel conditions are given for the existence of surface waves and for the emergence of complex eigenvalues in the absence of losses, and supported with numerical results of exact frequency domain analysis.

Reflections from boundaries of the FDTD computational domain lead to inaccurate, even unstable codes when dealing with problems involving double negative (DNG) materials. Here, an efficient and simple algorithm is presented for terminating FDTD in DNG medium which is based on first and second order Mur's absorbing boundary conditions (ABC). FDTD update equations for Mur's ABC formulations are obtained from frequency domain one-way wave equations using piecewise linear recursive convolution (PLRC) method. Numerical examples are given both for 1D and 2D scenarios to demonstrate the validity and stability of the proposed Mur formulations, and its advantages over uniaxial perfectly matched layer (UPML) in reducing computational time and memory requirements.

A novel approach utilizing one-dimensional (1D) wave equation based finite difference time domain (FDTD) formulations for Lorentz-type Epsilon-Negative (ENG) medium is developed. To demonstrate the validity and accuracy of the formulation, reflection of a plane wave normally incident at free spaceENG interface is compared with the analytical solution. Moreover, propagation characteristics of Lorentz-type ENG medium is investigated using the FDTD formulations both for wave equation and Maxwell's curl equations in 1D case. Comparisons of memory and computational time requirements of both formulations are given. (c) 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:304-310, 2016.

An extremely rapid, versatile prototyping methodology is developed for waveguide filters with periodic dielectric loading which enables direct dimensional synthesis of the unit cell starting from given design objectives. A prototype filter has been designed using a low dielectric constant material and built for the purposes of testing the feasibility of the proposed approach. Our numerical results are compared with an independent commercial software package and also with experimental measurements. Simulation results are also presented for a filter loaded high dielectric constant material. In both cases the results are in excellent agreement with the theory and demonstrate the validity and the applicability of the proposed method.

Kismen dielektrik yuklu dalga kilavuzlari cok sayida mikrodalga cihazinda kullanilmaktadir. Kismen dielektrik yuklu dikdortgen dalga kilavuzlari ile malzemelerin karmasik dielektrik gecirgenliklerinin ve dielektrik yuklu metalik dalga kilavuzlarinda propagasyon karakteristiklerinin belirlenmesi bircok muhendislik uygulamasinda onemlidir. Bu calisma bahsedilen her iki alandaki mevcut literature katki yapilmasini amaclamaktadir. Dielektrik yuklu metalik dalga kilavuzlari icin yansima iletim olcmeleri ile malzemelerin karmasik dielektrik gecirgenliklerinin belirlenmesi amaciyla yapilmis olan calismalar nispeten basit durumlari icermektedirler. Bu calismada, dikdortgen dalga kilavuzu icerisine yerlestirilen sutun seklindeki dielektrigin gecirgenliginin belirlenmesi ters sacilma problemi olarak formule edildi ve literaturdeki sinirlamalar ortadan kaldirildi. Oldukca esnek ve genel tipteki problemleri icerecek sekilde, dogru ve sayisal olarak verimli bir algoritma verildi. Ayni zamanda bu calismada, kayipsiz periyodik yapilardaki birim hucrenin Genellestirilmis Sacilma Matrisi icin bir sakinim iliskisi ortaya konuldu. Bu sakinim iliskisi, tek Floquet modlu bolge icerisinde yer alan iletim/durdurma band gecis frekanslarini dogru olarak kestiren yeni bir yontem saglamaktadir. Bu yontem iletim durdurma band bolgeleri verilen/olculen periyodik yapiyi kullanarak belirli topolojiler icin birim hucre boyutlarinin belirlenmesi ters problemine uygulanabilir niteliktedir. Anahtar Kelimeler: Karmasik dielektrik gecirgenlik, periyodik yuklu dalga kilavuzu.

Dunya uzerinde secilen herhangi iki nokta arasindaki yer dalgasi yayilim problemi, yirminci yuzyilin basindan bu yana ilgi odagi olmasina karsin, henuz sayisal olarak hesaplanabilen analitik tam cozum ya da genel olarak uygulanabilecek uc boyutlu sayisal cozum bulunamamistir. Bu calismada, problemin cozumu icin kullanilmakta olan isin – mod cozumu gibi yaklasik analitik ve Fourier donusumu yardimi ile parabolik denklem cozumune dayanan yari analitik –sayisal teknikler gecerlilik bolgeleri ile birlikte ayrintili olarak incelenmistir. Daha sonra, yer dalgasi yayilim probleminin cozumu icin zamanda sonlu farklar teknigine dayanan, saf sayisal yeni bir yontem onerilmis ve bahsedilen diger teknikler ile elde edilen sonuclarla karsilastirilmistir. Anahtar Kelimeler: Yer dalgasi yayilimi, Zamanda sonlu farklar, isin – mod cozumu, parabolic denklem, TDWP.

Dogrusal fazli/sirayla uyarilan periyodik dipol dizilerinin frekans ve zaman domeni yanitlari, Floquet dalga ve eleman-eleman toplama gosterilimleri kullanilarak incelenmistir. Her bir dipolun katkisinin ayri ayri hesaplanip toplanmasi ile bulunan eleman-eleman toplama yonteminin yakinsaklik ozelliklerini iyilestiren bir formulasyon gelistirilmistir. Periyodiklik ozellikleri kullanilarak, dizinin toplam isinim alani icin Floquet dalgalari ve sonsuz periyodik bir dizinin sonlandirilmasinin etkilerini karakterize eden uc kirinim bilesenlerini iceren alternatif bir formulasyon elde edilebilir ve biri digerine gore kaydirilmis ve uygun sekilde agirlastirilmis iki yari-sonsuz cizgisel periyodik dizinin farkini alarak sonlu cizgisel diziler modellenebilir. Yukarida deginilen yaklasim literaturde incelenmistir, bu calismada onerilen ve yapay aciklik yaklasimi adi verilen yontemde ise, Lz kadar kaydirilmis dizinin bir P(x,y,z) gozlem noktasinda olusturacagi alan, diziyi kaydirmak yerine gozlem noktasini zit yonde kaydirarak, orijinal kaydirilmamis dizinin bir P’(x,y,z-Lz) sanal gozlem noktasinda olusturacagi alan bulunarak hesaplanmaktadir. Onerilen bu yapay aciklik yaklasimi, cizgisel dipol dizilerinin superpozisyonu alinarak elde edilebilen her turlu duzlemsel ve uc boyutlu dipol dizisinin etkin bicimde modellenmesinde de kullanilmistir. Isinim yapan, yapmayan ve kirinan dalga bilesenleri cinsinden ifade edilen Floquet dalga gosteriliminin etkinligini gostermek icin sayisal ornekler verilmis ve bu sonuclar eleman-eleman toplama yontemi ile karsilastirilip dogrulanmistir. Dipollerin genis bantli kaynak fonksiyonlariyla suruldugu durumda karsilasilan konvolusyon integrallerinin hesaplanmasi icin kaynak fonksiyonuna genlik ve sureleri adaptif bicimde belirlenen parca parca surekli bir dizi dikdortgen darbe ile yaklasiklik yapilmasina dayanan analitik bir yontem gelistirilmistir. Anahtar Kelimeler: Green fonksiyonu, Floquet dalgalar, faz farkli anten dizileri, periyodik diziler.

Basics of reliability analysis are reviewed, and elements of topological reliability models are introduced. The effectiveness of preventive maintenance in improving system service-life performance, and that of redundancy in improving system-availability performance, are discussed.

Floquet wave and element-by-element summation representations are implemented to investigate the radiation from a periodic, rectangular array of linearly phased/sequentially pulsed dipoles in the frequency- and time-domains. A synthetic aperture type formulation for Floquet wave representation and an asymptotic formulation for the element-by-element summation representation are developed. Numerical results are presented to demonstrate the efficiency of the Floquet wave representation in terms of radiating, non-radiating and diffracted wave constituents and then validated via comparison with direct summation over the contributions of individual dipole radiations.

Radiation from large arrays of finite one- and two-dimensional periodic, linearly phased, electric current dipoles is investigated. The classical element-by-element summation representation is modified to speed up the convergence. A synthetic aperture type approach is applied in the Floquet domain for modeling finite arrays. Numerical results for the radiated field are presented both in frequency and also in time domains.

Some new results are presented on the properties of generalized scattering matrix representations for metallic waveguides with axially periodic dielectric loadings.A unified framework is given for describing the frequency dependence and for identifying the emergence of propagating, nonpropagating, and complex Floquet modes in single mode, as well as multimode, regions.Two new conservation relations are formulated for the general;zed scattering matrix of the unit cell in lossless periodic structures. One of these relations provides a convenient means for checking the correctness of the values of calculated matrix elements, while the other relation yields accurate estimates for the stopband-passband transition frequencies located within single Floquet-mode regions.

In this study, full wave solutions are presented for a photonic crystal fiber structure with cylindrical air holes of circular cross-section in a honeycomb type periodic arrangement on silica substrate, and a low index core region obtained by introducing an extra air hole. Numerical results are presented for the variations of the band structure and modal fields which are obtained via plane wave and localized basis function expansion techniques, respectively.

In this study, coupling between two cores in a specific photonic crystal fiber (PCF) structure is investigated via Localized Basis Function (LBF) method. The PCF structure considered here consists of an unbounded periodic cladding and two high index core regions. In the LBF method, a guided mode localized in the core regions and periodic variation of the refractive index in the transverse domain are decomposed by using Hermite-Gaussian type Localized Basis Functions and Fourier type expansions. Simulation results are presented which demonstrate that the coupling between two cores in the PCF structure can be obtained in accurate and numerically efficient manner utilizing the LBF approach proposed in this work.

Burst switching appears to be the most promising technique for meeting transperancy and bandwidth-on-demand requirements in wavelength division multiplexed, ultra high capacity, backbone optical networks. Modeling and simulation of such networks present challenges which are rather difficult, and in extreme cases impossible to meet using analytical or discrete event approaches. This is due to the absence of sufficiently accurate models for the former, and due to the required exessively large computational resources for the latter approach. In this paper a different modeling approach is presented, which under the assumptions of stationarity of distributions allows for implementation of Monte Carlo sampling for calculating overall burst loss probability performance of JIT protocol in optical burst switched networks. Simulation results are presented for NSFNet and Pan-European Network, which demonstrate the applicability of the proposed approach.

In this study, full wave solutions are presented for a specific photonic crystal fiber (PCF) structure via the localized basis function (LBF) method. The PCF structure consists of an unbounded periodic cladding and a high index core region. In the LBF method, a guided mode localized in the core region and the transverse refractive index of the PCF structure are decomposed by using Hermite-Gaussian basis functions and periodic functions. Numerical results are presented to demonstrate the variation of the modal fields in the PCF

Determination of the complex permittivity of materials via transmission/reflection measurement in rectangular waveguides is formulated as an inverse scattering problem. The presented approach is directly applicable to measurements performed with various sample sizes and orientations. The predicted results are compared with measurements and good agreement is obtained.