Alessandro Mauro, Mario R. Romano, Vito Romano and P. Nithiarasu
The purpose of this paper is to compare the fluid dynamic performance of two Aqueous Humor (AH) ocular drainage devices, the SOLX® Gold Micro Shunt (GMS) and the novel Silicon…
Abstract
Purpose
The purpose of this paper is to compare the fluid dynamic performance of two Aqueous Humor (AH) ocular drainage devices, the SOLX® Gold Micro Shunt (GMS) and the novel Silicon Shunt Device (SSD), implanted by surgeons in human eyes to reduce the IntraOcular Pressure towards physiological values, by draining the AH from the Anterior Chamber to the Suprachoroidal Space, to cure eyes with glaucoma.
Design/methodology/approach
The generalized porous medium model is solved to simulate the AH flow through the two ocular drainage devices and the surrounding porous tissues of the eye.
Findings
In the GMS, probable stagnation regions have been found, due to the very small AH velocity values inside the device and to the surrounding tissues, creating possible blockage and malfunction of the device. The simple microtubular geometry of the novel SSD allows to have a regular AH flow and to choose shunts with different diameters and/or with the presence of radial holes, based on patient needs, with consequent reduction of post-operative complications.
Research limitations/implications
The present model will be further developed taking into account the insertion of the present drainage devices inside the anterior section of the eye. The present results show the comparative fluid dynamic performance of the two shunts considered, and can be useful for surgeons to choose the adequate shunt, based on the required AH flow rate for a specific patient.
Practical implications
The present numerical approach, employing the generalized porous medium model, represents a useful tool to study the fluid dynamics of ocular drainage devices and to design these shunts, to reduce post-operative complications.
Originality/value
The generalized porous medium model is here applied for the first time to simulate the interaction of ocular drainage devices with the surrounding porous tissues of the eye.
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Mauro Feliziani, Alessandro Salvini, Alessandro Toscano and Lucio Vegni
Concettina Buccella, Valerio De Santis, Mauro Feliziani and Piero Tognolatti
The paper aims to propose a three‐dimensional (3D) finite element analysis to evaluate the electrical performances of a FBAR (thin‐film bulk acoustic resonator) resonator.
Abstract
Purpose
The paper aims to propose a three‐dimensional (3D) finite element analysis to evaluate the electrical performances of a FBAR (thin‐film bulk acoustic resonator) resonator.
Design/methodology/approach
The piezoelectric theory that uses an equivalent circuit is able to evaluate the thickness‐extensional vibration modes in simple 1D configuration but it is not adequate to predict spurious modes with lateral wave vector. Therefore, a fully 3D finite element analysis has been carried out to evaluate the characteristics of a real FBAR prototype that has been fabricated in a research center.
Findings
The measured characteristics of the FBAR prototype are compared with simulations obtained by the 3D finite element analysis. The agreement between experimental and numerical results confirms the accuracy of the proposed technique.
Originality/value
The paper proposes a 3‐D numerical approach to design and analyze the electrical characteristics of a real FBAR which has been fabricated following the guidelines obtained by the proposed numerical design.
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Valerio De Santis, Mauro Feliziani and Francescaromana Maradei
The aim of the paper is to apply a numerical dosimetry procedure to a biological tissue with an embedded discrete vascularisation in order to evaluate the temperature increase…
Abstract
Purpose
The aim of the paper is to apply a numerical dosimetry procedure to a biological tissue with an embedded discrete vascularisation in order to evaluate the temperature increase produced by radio‐frequency (RF) exposure.
Design/methodology/approach
The blood temperature inside thin vessels is analysed by a 1D finite difference procedure to solve the convection‐dominated heat problem. The tissue temperature inside the remaining 3D domain governed by the heat diffusion equation is calculated by the finite element method. Then, the two separate numerical methods are coupled by an iterative time domain procedure.
Findings
The main advantage of the proposed hybrid method is found to be the considerable reduction of the number of unknowns respect to other traditional numerical techniques.
Research limitations/implications
In this paper, only the numerical model of the new hybrid procedure has been proposed. In future work realistic biological regions will be examined and the proposed model will be improved by considering the artery/vein coupled structure.
Originality/value
The originality of the proposed method regards the solution of the bio‐heat equation by means of a new hybrid finite element/finite difference procedure. This procedure is applied inside a vascularized region considering a discrete blood vessel structure.
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Sebastian Emanuel Lauro, Filiberto Bilotti, Alessandro Toscano and Lucio Vegni
To devise a parametric study using a new application of the boundary element method (BEM) and to propose an efficient approach for speeding up the computation time of the BEM…
Abstract
Purpose
To devise a parametric study using a new application of the boundary element method (BEM) and to propose an efficient approach for speeding up the computation time of the BEM based on neural networks (NNs).
Design/methodology/approach
A 3D finite elements formulation is combined with radial basis function NNs to speeding up the computation time.
Findings
The paper shows how to estimate the role of thin slabs filled with unconventional media in order to increase the coupling values when placed between two metallic strips in a coupled microstrip line layout or to improve the shielding properties when used as absorber.
Research limitations/implications
The numerical results here presented are not bianisotropic but can be easily extended to take into account bianisotropic media.
Originality/value
The formulation is one of the only with the potential for investigating unconventional bianisotropic media like Chiral materials which are seen as one possible route to achieving double negative media.
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F. Frezza, L. Pajewski, S. Paulotto, C. Ponti and G. Schettini
The purpose of this paper is to investigate the role of electromagnetic band‐gap (EBG) materials in the enhancement of antennas' directivity.
Abstract
Purpose
The purpose of this paper is to investigate the role of electromagnetic band‐gap (EBG) materials in the enhancement of antennas' directivity.
Design/methodology/approach
An analysis of a woodpile EBG material is performed, which points out its band properties. Woodpile cavities are then considered, obtained by interrupting the periodicity of the crystal. A woodpile cavity is then superimposed to a double‐slot antenna, resulting in a compound radiating device. The behavior of the EBG and of the radiating structure are simulated through Ansoft HFSS V11.
Findings
The woodpile EBG, when used as a cavity, acts as a spatial filter for the radiation coming from the antenna. The directivity of the new radiator is considerably increased, since now the illumination covers an area larger than the antenna.
Originality/value
Using new materials to obtain high‐directivity and compact radiators.
Details
Keywords
S. Coco, A. Laudani, F. Riganti Fulginei and A. Salvini
The aim of this work is to show how evolutionary computation can improve the quality of 3D‐FE mesh that is a crucial task for field evaluations using 3‐D FEM analysis.
Abstract
Purpose
The aim of this work is to show how evolutionary computation can improve the quality of 3D‐FE mesh that is a crucial task for field evaluations using 3‐D FEM analysis.
Design/methodology/approach
The evolutionary approach used for optimizing 3D mesh generation is based on the bacterial chemotaxis algorithm (BCA). The objective function corresponds to the virtual bacterium best habitat, and the motion rules followed by each virtual bacterium are inspired to the natural behaviour of bacteria in real habitat.
Findings
The obtained results show that the present approach returns good accuracy performances with low‐computational costs.
Practical implications
The procedure is robust and converges for all the practical cases examined for validation.
Originality/value
The adoption of a correct optimization algorithm is fundamental to obtain good performances in terms of robustness of the results and the low‐computational costs. In this sense, the BCA is a valid instrument for improving the quality of 3D‐FE mesh.
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Salvatore Coco, Antonino Laudani and Giuseppe Pollicino
The paper's aim is to focus on the utilization of the GRID distributed computing environment in order to reduce simulation time for parameter studies of travelling wave tube (TWT…
Abstract
Purpose
The paper's aim is to focus on the utilization of the GRID distributed computing environment in order to reduce simulation time for parameter studies of travelling wave tube (TWT) electron guns and helix slow‐wave structures.
Design/methodology/approach
Two TWT finite‐element analysis modules were adapted to be run on the GRID, for this purpose scripts were written to submit a collection of independent jobs (the parameter study) to the GRID and collect the results.
Findings
A 25‐job electron gun parameter study runs on the GRID in 30‐40 min instead of 7 h locally. A 16‐job slow‐wave structure parameter study runs in 1 h on the GRID instead of 8 h locally. Turnaround time on the GRID was limited by priority levels presently set by GRID management for the various jobs submitted.
Practical implications
The procedures guarantee a remarkable reduction of the computing time.
Originality/value
For heavy‐computational cost tasks such as the above finite element electromagnetic calculations, the effective use of a heterogeneous, distributed, computing platform (the GRID computing platform) is very advantageous. The paper shows the development of new generation collaborative tools.
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Carlos Alberto Ferreira Fernandes
The aim of this paper is to develop simulation tools for the analysis of modified structures of distributed feedback (DFB) laser diodes adequate for single longitudinal mode (SLM…
Abstract
Purpose
The aim of this paper is to develop simulation tools for the analysis of modified structures of distributed feedback (DFB) laser diodes adequate for single longitudinal mode (SLM) operation.
Design/methodology/approach
The paper uses matricial techniques: the transfer matrix method (TMM). When compared to the eigenvalue approach, the matricial techniques are more general and flexible and hence are especially adequate to deal with the analysis and structural design of DFB laser diodes. In this work, the author makes a general description of the TMM, enhancing its importance with some applications by considering the threshold and above‐threshold analysis of a modified DFB laser structure.
Findings
The increasing demands on laser performance, mainly in the area of optical communication systems, have lead to the fabrication of more‐and‐more complex structures. In viewing the development of the associated technology, the importance of the simulation tools revealed of crucial importance.
Originality/value
The simulation model used in this work has been described in other works of the author. In the present analysis a general description of the TMM was implemented, summarizing the results of previous studies for the threshold and above‐threshold regimes of modified DFB laser structures specially designed to show SLM operation.
Details
Keywords
B. Vahidi, B. Hemmatian and S.H. Hosseinian
To find an easy and accurate method for evaluating the Pollaczek's integral in earth‐return path impedance calculation.
Abstract
Purpose
To find an easy and accurate method for evaluating the Pollaczek's integral in earth‐return path impedance calculation.
Design/methodology/approach
The Monte Carlo method of evaluating the Pollaczek's integral is introduced.
Findings
The Monte Carlo method is easy and accurate method for this computation.
Research limitations/implications
Using proposed method in cases of earth stratification.
Practical implications
The proposed method can be used in power system transient software.
Originality/value
The proposed method introduces a computation method for calculation of Pollaczek's integral which is valuable for power engineers.