Terahertz Spoof Surface Plasmon Polariton Waveguides: A Comprehensive Model with Experimental Verification

Spoof surface plasmon polariton waveguides are perfect candidates to enable novel, miniaturized terahertz integrated systems, which will expedite the next-generation ultra-wideband communications, high-resolution imaging and spectroscopy applications. In this paper, we introduce, for the first time, a model for the effective dielectric constant, which is the most fundamental design parameter, of the terahertz spoof surface plasmon polariton waveguides. To verify the proposed model, we design, fabricate and measure several waveguides with different physical parameters for 0.25 to 0.3THz band. The measurement results show very good agreement with the simulations, having an average and a maximum error of 2.6% and 8.8%, respectively, achieving 10-to-30 times better accuracy than the previous approaches presented in the literature. To the best of our knowledge, this is the first-time investigation of the effective dielectric constant of the tera hertz spoof surface plasmon polariton waveguides, enabling accurate design of any passive component for the terahertz band.Turkish Academy of Sciences (TUBA GEBIP 2015

Biologic features and fishing of the Gediz river basin

Batı Anadolu'da 17.500 km2lik bir alan kaplayan Gediz Akarsuyu Havzası; doğuda, İçbatı Anadolu'daki Mura t Dağından başlar ve orta mecralarda beraberinde birçok tali kollan da alarak, batıda Foça'nın güneyinde Ege Denizi'nde son bulur (Şekil 1). Havza içindeki mevcut akarsu, doğal göl ve baraj gölleri zengin biyolojik özelliklere sahiptir. Bu özelliğinden dolayı da önemli bir balık üretim potansiyeline sahiptir. Bu potansiyelin tamamı bugün çeşitli sebeplerden dolayı değerlendirilememektedir. Diğer taraftan, yapılacak olan baraj golleriyle bu potansiyeli bir kat daha arttırmak mümkündür

Evaluation of Plasticity Models Using Uniaxial Tensile Test

In this study, it is aimed to evaluate plasticity model prediction performance for plastic behavior of materials using a uniaxial tensile test. For this purpose, von Mises, Hill-48, Hill-93, Barlat-89 and Hu -2003 plasticity models are studied, and DC04, DP780, 6000 series aluminum alloy are used as materials. Tensile tests are performed with three directions (rolling, diagonal, transverse), and mechanical properties of materials are obtained. In addition, anisotropy coefficients of materials are calculated by uniaxial tensile tests. Validation of plasticity models is performed using obtained material parameters. Yield locus and yield stresses-anisotropy coefficients depends on directions are used in evaluation of plasticity models. As a result of this study, Hu-2003 showed the best modeling performance for all materials

A Reflectarray Antenna Using Hexagonal Lattice With Enhanced Beam Steering Capability

This paper presents a novel reflectarray antenna with enhanced beam steering capability. The reflectarray antenna is based on the hexagonal distribution of the unit cells on the antenna surface. The hexagonal topology changes the angle between the principal axes of the unit cell distribution, preventing the formation of the grating lobe, and improving the beam steering capability of the reflectarray antenna. To verify the proposed idea, two different sets of reflectarray antennas, which includes square and hexagonal lattice topologies with inter-element spacings of 0.52 lambda and 0.6 lambda, have been designed, fabricated, and measured at 8.23 GHz. The measurements of the all fabricated reflectarray antennas are in very good agreement with the simulations, and the comparison of the square and hexagonal topologies show that the beam steering capability can be improved by 50% for 0.6 lambda inter-element spacing by using a hexagonal topology. This improvement shows that a simple modification in the array configuration can be a viable solution for satellite and 5G communication applications that require increased beam steering capability