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Egecan Ozcakar; Osman Sayginer; Gullu Kiziltas
In: 2021 International Applied Computational Electromagnetics Society Symposium (ACES), pp. 1-4, 2021, ISSN: 1054-4887.
Breast cancer is a very common and serious condition that affects many women and needs early intervention to minimize the impact on health. Differentiation of the cancerous tissue from the healthy tissue can be carried out using electromagnetic waves by utilizing the different responses due to varying electromagnetic material characteristics. The specific absorption rate is a measurement of the absorbed electromagnetic energy in a volume which can be very useful in the detection of cancerous tissue. In this work, we focus on the design of an antenna that is distinctive in its geometric properties as it is bendable in two axes (both x and y) and hence can fit onto a half-spherical array. An antenna array that consists of antennas of size 18mm x 18mm x 2 mm is designed to be conformal to a bra's shape. A three-layered 3D breast model of different tissue types and a tumor medium is used to investigate the specific absorption rate through simulations.
Osman Sayginer; Erica Iacob; Stefano Varas; Anna Szczurek; Maurizio Ferrari; Anna Lukowiak; Giancarlo C Righini; Oreste S Bursi; Alessandro Chiasera
In: Optical Materials, vol. 115, pp. 111023, 2021, ISSN: 0925-3467.
We introduce an easily implementable optomechanical device for pressure and vibration sensing using a multilayer structure on a flexible substrate. We present the design, fabrication and evaluation steps for a proof-of-concept device as well as optical glass components. The design steps include optical, mechanical, and optomechanical correlation simulations using the transfer matrix method, finite element analysis, geometric optics and analytical calculations. The fabrication part focuses on the deposition of multilayers on polymeric flexible substrates using the radio frequency sputtering technique. To investigate the quality of the glass coatings on polymeric substrates, atomic force microscopy and optical microscopy are also performed. Optical measurements reveal that, even after bending, there are no differences between multilayer samples deposited on the polymeric and SiO2 substrates. The performance assessment of the proof-of-concept device shows that the sensor resonance frequency is around 515 Hz and the sensor static response is capable of sensing from 50 Pa to 235 Pa.
Hao Chen; Alessandro Chiasera; Stefano Varas; Osman Sayginer; Cristina Armellini; Giorgio Speranza; Raffaella Suriano; Maurizio Ferrari; Silvia Maria Pietralunga
In: Optical Materials: X, vol. 12, pp. 100093, 2021, ISSN: 2590-1478.
Tungsten oxide WO3-x is a transition metal oxide and a wide bandgap semiconductor, with a wide range of possible optical and photonic applications. In dependence on the fabrication techniques different stoichiometric ratios (x) and crystalline phases are obtained, which end up with an overall polymorph and extremely versatile material, characterized by tailorable dielectric properties. In particular, WO3-x thin film deposition by Radio-Frequency (RF) sputtering techniques provides a precise control of thickness, composition and nanostructure. In this work we introduce and discuss a specific process of deposition, that is magnetron RF-sputtering as a suitable way to grow WO3-x thin films with selected properties. Possibility of integrating WO3-x thin film on to one-dimensional (1D) photonic crystal structures is also explored. Films are transparent in the near and short-wavelength infrared optical spectral range. Their quality is assessed by morphological, structural and compositional characterizations. Dielectric properties are characterized by optical spectroscopy and ellipsometry, the latter also evaluates the degree of optical anisotropy of thin films in their crystalline phase. An 1D photonics bandgap structure is designed, formed by a SiO2–TiO2 multilayer and capped with a 450 nm-thick transparent WO3-x film, so that surface confinement and local enhancement of the optical field at 1416 nm in the topmost WO3-x layer is obtained.
Osman Sayginer; Rocco di Filippo; Aurelien Lecoq; Alessandra Marino; Oreste S Bursi
In: Experimental Techniques, 2020, ISSN: 1747-1567.
In order to shed light on the seismic response of complex industrial plants, advanced finite element models should take into account both multicomponents and relevant coupling effects. These models are usually computationally expensive and rely on significant computational resources. Moreover, the relationships between seismic action, system response and relevant damage levels are often characterized by a high level of nonlinearity, which requires a solid background of experimental data. Vulnerability and reliability analyses both depend on the adoption of a significant number of seismic waveforms that are generally not available when seismic risk evaluation is strictly site-specific. In addition, detection of most vulnerable components, i.e., pipe bends and welding points, is an important step to prevent leakage events. In order to handle these issues, a methodology based on a stochastic seismic ground motion model, hybrid simulation and acoustic emission is presented in this paper. The seismic model is able to generate synthetic ground motions coherent with site-specific analysis. In greater detail, the system is composed of a steel slender tank, i.e., the numerical substructure, and a piping network connected through a bolted flange joint, i.e., the physical substructure. Moreover, to monitor the seismic performance of the pipeline and harness the use of sensor technology, acoustic emission sensors are placed through the pipeline. Thus, real-time acoustic emission signals of the system under study are acquired using acoustic emission sensors. Moreover, in addition to seismic events, also a severe monotonic loading is exerted on the physical substructure. As a result, deformation levels of each critical component were investigated; and the processing of acoustic emission signals provided a more in-depth view of the damage of the analysed components.
Osman Sayginer; Alessandro Chiasera; Stefano Varas; Anna Lukowiak; Maurizio Ferrari; Oreste S Bursi
International Society for Optics and Photonics SPIE, vol. 11357, 2020.
Multilayer structures are commonly used components in optics and photonics due to their unique properties to manipulate the spectral response of light. Multilayer-driven components for sensing purposes can bring some advantages such as high sensitivity, fast signal response, electromagnetic interference immunity, and low power consumption. Thus, a mechanically coupled optical system can be the right candidate for force and vibration detection. In this work, we propose and demonstrate an optomechanical sensing system for pressure and vibration detection using two multilayer structures, a circular membrane, a light source, and a photodiode. The design of this proposed system consists of two parts, which are optical design and mechanical design. In the optical design, we modeled the optical response of the multilayer structures in the visible spectra using the Transfer Matrix Method. The mechanical response, on the other hand, is calculated using finite element simulations via the COMSOL Multiphysics software. The multilayer structures are fabricated by RF-Sputtering technique and then integrated through a 3D printed mechanical housing. The sensor characteristics (sensitivity and resonance frequency) are experimentally investigated by a static loading test and a transient response analysis. Results are shown that the sensor frequency around 510 Hz and the sensitivity of the sensor about 50 Pa.
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