Browsing by Subject "Nonlinearity"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Open Access Comparison of geometric and drive-induced nonlinearities in doubly clamped, thermoelastic nanoelectromechanical systems(TÜBİTAK, 2019-06) Hanay, Mehmet SelimThe performance of resonant sensors based on nanoelectromechanical systems depends critically on the maximum amplitude of oscillation reached in the linear regime. The maximum linear amplitude is determined by nonlinear mechanisms that can originate from the material, geometric and transduction mechanism related factors. Here we compare the two competing effects, the geometric and drive-induced nonlinearities, for a commonly used device family, the thermoelastically driven, doubly clamped beams. We find that the geometric nonlinearity dominates for most of the device designs used in the literature, however the drive-induced nonlinearity becomes the determining factor for thicker beams with small electrode lengths.Item Open Access Designing an efficient wide bandwidth single cell CMUT for airborne applications using nonlinear effects(IEEE, 2013) Unlugedik, Aslı; Atalar, Abdullah; Köymeni, HayrettinIn this work, we propose a new approach to obtain wider bandwidth for an airborne capacitive micromachined ultrasonic transducer (CMUT) cell without sacrificing sensitivity. This is done through employing the stiffening effect created by the atmospheric pressure. We use an equivalent lumped element circuit to model both electrical and mechanical properties of an airborne CMUT cell. We determine the lowest achievable mechanical quality factor of the cell in the elastically linear region. By extending the analysis to elastically nonlinear region, a significantly lower mechanical quality factor is obtained. © 2013 IEEE.Item Open Access Exploiting linearity of modular multiplication(Springer, 2020) Yıldırım, Hamdi MuratThe XOR Open image in new window and the addition ⊞⊞ operations have been widely used as building blocks for many cryptographic primitives. These operations and the multiplication ⊙⊙ operation are successively used in the design of IDEA and the MESH block ciphers. This work presents several interesting algebraic properties of the multiplication operation. By fixing one operand, we obtain vector valued function ggZggZ on Zn2Z2n, associated with ⊙⊙. In this paper we show that the nonlinearity of ggZggZ remains the same under some transformations of Z and moreover we give an upper bound for the nonlinearity of ggZggZ when Z is a power of 2. Under weak-key assumptions, we furthermore present a list of new linear relations for 1-round IDEA cipher, some of directly derived and others algorithmically generated using these relations and known ones. We extend the largest linear weak key class for IDEA cipher with size 223223 to derive such a class with sizes 224224. Under the independent key subblocks (subkeys) and weak-key assumptions we derive many linear relations for IDEA cipher using linear relations for 1-round IDEA cipher.Item Open Access Silicon based dielectrics : growth, characterization, and applications in integrated optics(Bilkent University, 2005) Ay, FeridunIn recent years, growing attention has been paid to silicon based dielectrics, such as silicon oxynitrides, silicon nitrides, and semiconductor doped silicon oxides, all combined under the name silica on silicon technology. This attention has been motivated mainly due to their excellent optical properties such as well controlled refractive index and high transparency over a wide range of wavelength. In accordance with the main goal of this study that relied on the utilization of silicon based dielectrics and their optimization for applications in integrated optics, an emphasis was given to optimize the compositional and optical properties of these materials. A detailed quantitative compositional analysis using Fourier transform infrared spectroscopy resulted in identification of the germanosilicate dielectrics as the most promising candidates for use in integrated optics. The first reported systematic study of propagation losses for different-index planar waveguides by using prism coupling method was correlated with the compositional analysis. This study had an important outcome for planar waveguides fabricated with germanosilicate core layers resulting in the lowest propagation loss values reported so far for as deposited CVD-grown films at λ=1.55 µm, eliminating the need for costly and cumbersome annealing process. An improvement of the prism coupling technique led to a new approach for elasto-optic characterization of thin polymer films. This completely new method allows one to determine the optical anisotropy and out-of-plane mechanical properties and to correlate both in order to obtain the elasto-optical properties of thin polymer films, for the first time. Of interest as potential electro-optic material, we have concentrated on thermally poled germanosilicate films deposited on fused-silica substrates by PECVD. As a result of an optimization study, we demonstrated a record peak nonlinear coefficient of ∼1.6 pm/V, approximately twice as strong as the highest reliable value reported in a thermally poled fused silica glass. Finally, we have demonstrated several applications of this technology in the field of integrated optics. Since optical waveguides constitute the building blocks of many integrated optical devices, we had first concentrated on design and optimization of waveguides employing germanosilicates as the core layers. The final step of our work concentrated on design and implementation of microring resonator devices based on germanosilicate layers.