The aim of this paper is to show the effectiveness of the finite element method (FEM) to study the properties of different kinds of photonic crystal fibers (PCFs), presenting…
Abstract
Purpose
The aim of this paper is to show the effectiveness of the finite element method (FEM) to study the properties of different kinds of photonic crystal fibers (PCFs), presenting results which highlight the FEM flexibility, exploited according to the particular PCF feature under investigation.
Design/methodology/approach
The FEM has been applied to a new emerging class of optical fibers, the so‐called PCFs, also known as microstructured or holey fibers.
Findings
It has been shown how to design and customize the PCF cross‐section to achieve desired values of dispersion, confinement loss, nonlinear or amplification properties. Reported examples prove the FEM ability to deal with complex geometries, arbitrary refractive index steps and distribution, and to be integrated with other approaches for a better and accurate analysis of the considered fiber.
Research limitations/implications
Limitation in the FEM use can be given by the required computation effort in terms of memory occupancy and time, even if computational power of modern workstations can attenuate this aspect.
Practical implications
The FEM can be a very powerful tool to investigate and design actual structures to be used in several fields, as telecom, sensing, fiber lasers, spectroscopy.
Originality/value
The novelty of the paper is given by the exploitation of the FEM feature to design a new emerging class of optical fibers, considering all numerical aspects given by the unusual characteristics of the domain and problem under investigation.
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Ugo d'Elia, Giuseppe Pelosi, Stefano Selleri and Ruggero Taddei
A design procedure for multi-layer absorbers based on carbon nanotubes (CNT) frequency selective surfaces (FSS) sheets is here developed. The paper aims to discuss there issues…
Abstract
Purpose
A design procedure for multi-layer absorbers based on carbon nanotubes (CNT) frequency selective surfaces (FSS) sheets is here developed. The paper aims to discuss there issues.
Design/methodology/approach
Single layer FSS are first analyzed via finite element (FE). Then equivalent sheets admittances are extracted in a transmission line model. Neural networks (NNs) interpolation over this data and subsequent multi-objective genetic algorithm (GA) based optimizations are then performed to design multiple layers absorbing structures. Designs are finally validated via full wave FEM simulations.
Findings
In this paper, some absorbing structures made of three or four FSS sheets with total thicknesses around 6 mm are synthesized.
Research limitations/implications
NNs' accuracy used in the equivalent model can be refined with further training.
Practical implications
Low profile absorbing materials are of relevant industrial interest both for radar cloaking and anechoic chambers.
Originality/value
The transmission line model combined with NNs and GA optimization is capable of speeding up the design procedure with respect to a conventional full-wave FEM approach.
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Giacomo Guarnieri, Giuseppe Pelosi, Lorenzo Rossi and Stefano Selleri
The paper's aim is to devise a fast method for microwave waveguide filter permittivity tolerance analysis.
Abstract
Purpose
The paper's aim is to devise a fast method for microwave waveguide filter permittivity tolerance analysis.
Design/methodology/approach
A 2D finite elements (FEs) formulation is combined via a Schur complement‐based domain decomposition (DD) technique to reduce the tolerance affected part of the analysis to a smaller domain.
Findings
The paper shows how to combine FEs and DD in an efficient way for material parameters tolerance analyses in microwave waveguide filters, showing speedup results.
Research limitations/implications
The formulation here presented is 2D but can be easily extended to 3D.
Originality/value
The application of DD to solve numerically large problem is well‐known, the idea and organization of the algorithm to allow iteration on parameter values on a single sub‐domain is here proposed.
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Majid Monajjemi and Fatemeh Mollaamin
Recently, powerful instruments for biomedical engineering research studies, including disease modeling, drug designing and nano-drug delivering, have been extremely investigated…
Abstract
Purpose
Recently, powerful instruments for biomedical engineering research studies, including disease modeling, drug designing and nano-drug delivering, have been extremely investigated by researchers. Particularly, investigation in various microfluidics techniques and novel biomedical approaches for microfluidic-based substrate have progressed in recent years, and therefore, various cell culture platforms have been manufactured for these types of approaches. These microinstruments, known as tissue chip platforms, mimic in vivo living tissue and exhibit more physiologically similar vitro models of human tissues. Using lab-on-a-chip technologies in vitro cell culturing quickly caused in optimized systems of tissues compared to static culture. These chipsets prepare cell culture media to mimic physiological reactions and behaviors.
Design/methodology/approach
The authors used the application of lab chip instruments as a versatile tool for point of health-care (PHC) applications, and the authors applied a current progress in various platforms toward biochip DNA sensors as an alternative to the general bio electrochemical sensors. Basically, optical sensing is related to the intercalation between glass surfaces containing biomolecules with fluorescence and, subsequently, its reflected light that arises from the characteristics of the chemical agents. Recently, various techniques using optical fiber have progressed significantly, and researchers apply highlighted remarks and future perspectives of these kinds of platforms for PHC applications.
Findings
The authors assembled several microfluidic chips through cell culture and immune-fluorescent, as well as using microscopy measurement and image analysis for RNA sequencing. By this work, several chip assemblies were fabricated, and the application of the fluidic routing mechanism enables us to provide chip-to-chip communication with a variety of tissue-on-a-chip. By lab-on-a-chip techniques, the authors exhibited that coating the cell membrane via poly-dopamine and collagen was the best cell membrane coating due to the monolayer growth and differentiation of the cell types during the differentiation period. The authors found the artificial membrane, through coating with Collagen-A, has improved the growth of mouse podocytes cells-5 compared with the fibronectin-coated membrane.
Originality/value
The authors could distinguish the differences across the patient cohort when they used a collagen-coated microfluidic chip. For instance, von Willebrand factor, a blood glycoprotein that promotes hemostasis, can be identified and measured through these type-coated microfluidic chips.
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Tarek Sallam and Ahmed M. Attiya
The purpose of this paper is to build a neural network (NN) inverse model for the multi-band unequal-power Wilkinson power divider (WPD). Because closed-form expressions of the…
Abstract
Purpose
The purpose of this paper is to build a neural network (NN) inverse model for the multi-band unequal-power Wilkinson power divider (WPD). Because closed-form expressions of the inverse input–output relationship do not exist, the NN becomes an appropriate choice, because it can be trained to learn from the data in inverse modeling. The design parameters of WPD are the characteristic impedances, lengths of the transmission line sections and the isolation resistors. The design equations used to train the NN inverse model are based on the even–odd mode analysis.
Design/methodology/approach
An inverse model of a multi-band unequal WPD using NNs is presented. In inverse modeling of a microwave component, the inputs to the model are the required electrical parameters such as reflection coefficients, and the outputs of the model are the geometrical or the physical parameters.
Findings
For verification purposes, a quad-band WPD and a penta-band WPD are designed. The results of the full-wave simulations verify the validity of the design procedure. The resulting NN model outperforms traditional time-consuming optimization procedures in terms of computation time with acceptable accuracy. The designed WPDs using NN are implemented by microstrip lines and verified by using full-wave analysis based on high-frequency structure simulator (HFSS). The results of the microstrip WPDs have good agreements with the corresponding results obtained by using ideal transmission line sections.
Originality/value
The associated time-consuming procedure and computational burden in realizing WPD through optimization are major disadvantages; needless to mention the substantial increase in optimization time because of the multi-band design. NNs are one of the best candidates in addressing the abovementioned challenges, owing to their ability to process the interrelation between electrical and geometrical/physical characteristics of the WPD in a superfast manner.
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Vadim V. Yakovlev, Ethan K. Murphy and E. Eugene Eves
To outline different versions of a novel method for accurate and efficient determining the dielectric properties of arbitrarily shaped materials.
Abstract
Purpose
To outline different versions of a novel method for accurate and efficient determining the dielectric properties of arbitrarily shaped materials.
Design/methodology/approach
Complex permittivity is found using an artificial neural network procedure designed to control a 3D FDTD computation of S‐parameters and to process their measurements. Network architectures are based on multilayer perceptron and radial basis function nets. The one‐port solution deals with the simulated and measured frequency responses of the reflection coefficient while the two‐port approach exploits the real and imaginary parts of the reflection and transmission coefficients at the frequency of interest.
Findings
High accuracy of permittivity reconstruction is demonstrated by numerical and experimental testing for dielectric samples of different configuration.
Research limitations/implications
Dielectric constant and the loss factor of the studied material should be within the ranges of corresponding parameters associated with the database used for the network training. The computer model must be highly adequate to the employed experimental fixture.
Practical implications
The method is cavity‐independent and applicable to the sample/fixture of arbitrary configuration provided that the geometry is adequately represented in the model. The two‐port version is capable of handling frequency‐dependent media parameters. For materials which can take some predefined form computational cost of the method is very insignificant.
Originality/value
A full‐wave 3D FDTD modeling tool and the controlling neural network procedure involved in the proposed approach allow for much flexibility in practical implementation of the method.
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Keywords
Abstract
Graphical abstarct
Purpose
This paper aims to improve the refractive index sensor performance for analytes with large refractive index by adopting the technology of microstructured fiber (MF) and surface plasmon resonance (SPR).
Design/methodology/approach
The structure adopts an MF with a hexagonal lattice cladding structure composed of all-circular air holes, and three defect regions are introduced. The liquid analyte that needs to be tested is filled in the defect area. The surface plasmon polarition mode is generated and coupled with the core mode, thus forming a refractive index sensing channel. When the resonance conditions are satisfied, the resonance wavelength will be changed with the refractive index of the liquid analyte. All parameters that may affect the performance of the sensor are numerical simulated, and the structure is optimized through a large number of calculations.
Findings
The results demonstrate that the maximum dynamic sensitivity (SR) can reach to 24,260 nm/RIU, and the average sensitivity (SR-AV) can reach to 18,046 nm/RIU when the refractive index range is from 1.42 to 1.47. Besides, the sensitivity linearity (R2) is approximately 0.965, and its resolution is 4.1 × 10–6 RIU. The comparison with some literature results shown that the proposed sensor has certain advantages over the sensors reported in these literatures.
Originality/value
This work proposed an SPR-based refractive index sensor with a simple MF structure. It has a certain reference significance for the design and optimization of SPR-based MF sensors. Moreover, owing to its simple structure, high refractive index sensitivity and linear sensing performance, this sensor will play an important role in the detection of high refractive index liquid analytes.
Details
Keywords
Pankaj Mandpe, Bala Prabhakar, Hunny Gupta and Pravin Shende
The present study aims to summarize different non-invasive techniques for continuous glucose monitoring (CGM) in diabetic patients using glucose-oxidase biosensors. In diabetic…
Abstract
Purpose
The present study aims to summarize different non-invasive techniques for continuous glucose monitoring (CGM) in diabetic patients using glucose-oxidase biosensors. In diabetic patients, the self-monitoring of blood glucose (BG) levels through minimally invasive techniques provides a quick method of measuring their BG concentration, unlike conventional laboratory measurements. The drawbacks of minimally invasive techniques include physical pain, anxiety and reduced patient compliance. To overcome these limitations, researchers shifted their attention towards the development of a pain-free and non-invasive glucose monitoring system, which showed encouraging results.
Design/methodology/approach
This study reviews the development of minimally and non-invasive method for continuous glucose level monitoring in diabetic or hyperglycemic patients. Specifically, glucose monitoring using non-invasive techniques, such as spectroscopy-based methods, polarimetry, fluorescence, electromagnetic variations, transdermal extraction-based methods and using body fluids, has been discussed. The various strategies adopted for improving the overall specificity and performance of biosensors are discussed.
Findings
In conclusion, the technology of glucose oxidase-based biosensors for glucose level monitoring is becoming a strong competitor, probably because of high specificity and selectivity, low cost and increased patient compliance. Many industries currently working in this field include Google, Novartis and Microsoft, which demonstrates the significance and strong market potential of self-monitored glucose-oxidase-based biosensors in the near future.
Originality/value
This review paper summarizes comprehensive strategies for continuous glucose monitoring (CGM) in diabetic patients using non-invasive glucose-oxidase biosensors. Non-invasive techniques received significant research interest because of high sensitivity and better patient compliance, unlike invasive ones. Although the results from these innovative devices require frequent calibration against direct BG data, they might be a preferable candidate for future CGM. However, the challenges associated with designing accurate level sensors to biomonitor BG data easily and painlessly needs to be addressed.
Contact with other researchers working in the field of surreal numbers, and in particular of their application to computation, and to physics, is sought. An outline research paper…
Abstract
Contact with other researchers working in the field of surreal numbers, and in particular of their application to computation, and to physics, is sought. An outline research paper on surreal models of arithmetic is presented as an invitation to workers in cybernetics and systems to participate in the study. The extension to Turing computability provided by the surreal models of arithmetic is provably, without any loss of mathematical generality, polynomially complex so that Psurreal = NP surreal. It is shown that these models could have widespread practical application in safety‐critical systems, and that they demonstrably determine régimes for computation in a minimum number of ways.