Computational study of ultra-wideband wave propagation into the human chest

2011 ◽  
Vol 5 (5) ◽  
pp. 559 ◽  
Author(s):  
A. Khaleghi ◽  
I. Balasingham ◽  
R. Chávez-Santiago
Keyword(s):  
Wave Propagation ◽  
Computational Study ◽  
Ultra Wideband

PROPAGATION CHARACTERIZATION OF IMPLANTABLE ANTENNA AT UWB FREQUENCY – A REVIEW

2015 ◽  
Vol 77 (7) ◽  
Author(s):  
Maisarah Abu ◽  
Najmiah Radiah Mohamad ◽  
Adib Othman ◽  
Nor Azlan Mohd Aris ◽  
Indra Devi S. ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Radio Wave ◽  
Human Body ◽  
Wireless Body Area Network ◽  
Data Rate ◽  
Healthcare Management ◽  
Implantable Device ◽  
Radio Wave Propagation ◽  
Ultra Wideband ◽  
Area Network

A technology of wireless body area network (WBAN) was invented in order to enhance the quality of healthcare management as well as to determine faster disease prevention. However, to obtain the real-time data of images and videos from inside the human body, an implantable device is required. Currently, the Medical Implant Communication System (MICS) is used, but, this system has limited data rate which is a narrow-band of 402 – 405 MHz. Thus, this study on Ultra Wideband (UWB) for implanted device is conducted as UWB offers a wide transmission bandwidth as well as high data rate. Knowledge of radio wave propagation behaviour inside human body is needed to perform the implantation. Past researches related to this topic are limited and those conducted focused only on the human torso. This paper aims to provide a better understanding on the characteristics of radio wave propagation inside the human body by using an implantable device at UWB frequency. It is also hoped that this study could be used as reference for future research on this subject.

Acoustic Non-Reciprocity in Lattices With Nonlinearity, Internal Hierarchy, and Asymmetry: Computational Study

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Matthew D. Fronk ◽  
Sameh Tawfick ◽  
Chiara Daraio ◽  
Shuangbao Li ◽  
Alexander Vakakis ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Linear Time ◽  
Lattice Structure ◽  
Computational Study ◽  
Unit Cell ◽  
Linear Time Invariant ◽  
Scale Unit ◽  
Unit Cells ◽  
Linear Time Invariant Systems ◽  
System Properties

Reciprocity is a property of linear, time-invariant systems whereby the energy transmission from a source to a receiver is unchanged after exchanging the source and receiver. Nonreciprocity violates this property and can be introduced to systems if time-reversal symmetry and/or parity symmetry is lost. While many studies have induced nonreciprocity by active means, i.e., odd-symmetric external biases or time variation of system properties, considerably less attention has been given to acoustical structures that passively break reciprocity. This study presents a lattice structure with strong stiffness nonlinearities, internal scale hierarchy, and asymmetry that breaks acoustic reciprocity. Macroscopically, the structure exhibits periodicity yet asymmetry exists in its unit cell design. A theoretical study, supported by experimental validation, of a two-scale unit cell has revealed that reciprocity is broken locally, i.e., within a single unit cell of the lattice. In this work, global breaking of reciprocity in the entire lattice structure is theoretically analyzed by studying wave propagation in the periodic arrangement of unit cells. Under both narrowband and broadband excitation, the structure exhibits highly asymmetrical wave propagation, and hence a global breaking of acoustic reciprocity. Interpreting the numerical results for varying impulse amplitude, as well as varying harmonic forcing amplitude and frequency/wavenumber, provides strong evidence that transient resonant capture is the driving force behind the global breaking of reciprocity in the periodic structure. In a companion work, some of the theoretical results presented herein are experimentally validated with a lattice composed of two-scale unit cells under impulsive excitation.

Computational study of detonation wave propagation in narrow channels

2013 ◽  
Vol 25 (3) ◽  
pp. 036101 ◽  
Author(s):  
Ashwin Chinnayya ◽  
Abdellah Hadjadj ◽  
Davy Ngomo
Keyword(s):  
Wave Propagation ◽  
Detonation Wave ◽  
Computational Study ◽  
Narrow Channels ◽  
Detonation Wave Propagation

scholarly journals Επίδοση ασύρματων επίγειων και στρατοσφαιρικών δικτύων εξαιρετικά υψηλών συχνοτήτων

2012 ◽  
Author(s):  
Ευαγγελία Γεωργιάδου
Keyword(s):  
Wave Propagation ◽  
Propagation Model ◽  
Wireless Access ◽  
Ultra Wideband ◽  
Millimetre Wave ◽  
Millimetre Wave Propagation ◽  
Method Of Auxiliary Sources ◽  
Fixed Wireless Access ◽  
Fixed Wireless ◽  
Wave Propagation Model

Η παρούσα διδακτορική διατριβή μελετά προβλήματα διάδοσης σε συχνότητες της Ka, της V και της EHF (30-300GHz) ζώνης, μοντελοποιώντας το ασύρματο κανάλι και τις ατμοσφαιρικές επιδράσεις. Εκτιμά τη σπουδαιότητα και το μέγεθος των συνδυασμένων επιπτώσεων διαφορετικών μετεωρολογικών παραγόντων στη λειτουργία των συστημάτων και εξετάζει τεχνικές άμβλυνσης διαλείψεων υπό συνθήκες βροχής. Τα τηλεπικοινωνιακά συστήματα με τα οποία ασχολείται είναι αφενός επίγεια συστήματα σταθερής ασύρματης πρόσβασης FWA (Fixed Wireless Access), αφετέρου επίγεια συστήματα πολύ ευρείας ζώνης UWB (Ultra-WideBand) που κάνουν χρήση εξαιρετικά στενών παλμών για τη μετάδοση της πληροφορίας, καθώς και ευρυζωνικά στρατοσφαιρικά δίκτυα σταθερών επικοινωνιών που υλοποιούνται μέσω εναέριων σταθμών HAPS (High Altitude Platform Stations). Πιο αναλυτικά, στο πρώτο κομμάτι της διατριβής προτείνεται ένα νέο εμπειρικό μοντέλο υπολογισμού της πιθανότητας υπέρβασης μιας στάθμης απόσβεσης βροχής σε επίγειες ζεύξεις οπτικής επαφής δικτύων σταθερής ασύρματης πρόσβασης, η καινοτομία του οποίου έγκειται στη θεώρηση Pruppacher-Pitter για το σχήμα των βροχοσταγόνων. Η ανάλυση ξεκινά με εφαρμογή της μεθόδου των βοηθητικών πηγών MAS (Method of Auxiliary Sources) στο πρόβλημα σκέδασης επίπεδου ηλεκτρομαγνητικού κύματος από σταγόνα βροχής και τα αποτελέσματα του μοντέλου συγκρίνονται με πειραματικά δεδομένα επίγειων ζεύξεων. Στη συνέχεια μελετώνται προβλήματα διάδοσης παλμών UWB σε εξωτερικό χώρο, επιχειρώντας συνδυασμένες εκφράσεις για την επίδραση τόσο των αερίων της ατμόσφαιρας μέσω του μοντέλου διάδοσης χιλιοστομετρικών κυμάτων MPM (Millimetre-wave Propagation Model) όσο και της συνεισφοράς της βροχής για σταγόνες Pruppacher-Pitter. Εκτιμάται η παλμική διαταραχή και η σπουδαιότητα της ενσωμάτωσης του παράγοντα βροχής στο μοντέλο καθαρού ουρανού. Τέλος εξετάζεται η επίδοση σχημάτων διπλής διαφορικής λήψης θέσης σε στρατοσφαιρικά δίκτυα. Η καινοτομία του προτεινόμενου μοντέλου εστιάζεται στην αποτίμηση της ολικής απόσβεσης που προκαλείται από τη δράση πολλαπλών πηγών ταυτόχρονης ατμοσφαιρικής εξασθένησης, υιοθετώντας παράλληλα το μοντέλο των συνεκτικών βροχοπυρήνων για την περιγραφή της βροχής. Εφαρμογή της μεθόδου σε ποικίλες τοπολογίες οδηγεί σε πολύτιμα συμπεράσματα για τη βέλτιστη σχετική τοποθέτηση του εναλλακτικού δέκτη στην περιοχή κάλυψης της στρατοσφαιρικής πλατφόρμας.

scholarly journals A Computational Study of the Effects of Tachycardia-Induced Remodeling on Calcium Wave Propagation in Rabbit Atrial Myocytes

2021 ◽  
Vol 12 ◽  
Author(s):  
Márcia R. Vagos ◽  
Hermenegild Arevalo ◽  
Jordi Heijman ◽  
Ulrich Schotten ◽  
Joakim Sundnes
Keyword(s):  
Wave Propagation ◽  
Computational Study ◽  
Experimental Studies ◽  
Wave Pattern ◽  
Calcium Handling ◽  
Calcium Wave ◽  
Atrial Myocytes ◽  
Open Probability ◽  
Rapid Pacing ◽  
The Individual

In atrial cardiomyocytes without a well-developed T-tubule system, calcium diffuses from the periphery toward the center creating a centripetal wave pattern. During atrial fibrillation, rapid activation of atrial myocytes induces complex remodeling in diffusion properties that result in failure of calcium to propagate in a fully regenerative manner toward the center; a phenomenon termed “calcium silencing.” This has been observed in rabbit atrial myocytes after exposure to prolonged rapid pacing. Although experimental studies have pointed to possible mechanisms underlying calcium silencing, their individual effects and relative importance remain largely unknown. In this study we used computational modeling of the rabbit atrial cardiomyocyte to query the individual and combined effects of the proposed mechanisms leading to calcium silencing and abnormal calcium wave propagation. We employed a population of models obtained from a newly developed model of the rabbit atrial myocyte with spatial representation of intracellular calcium handling. We selected parameters in the model that represent experimentally observed cellular remodeling which have been implicated in calcium silencing, and scaled their values in the population to match experimental observations. In particular, we changed the maximum conductances of ICaL, INCX, and INaK, RyR open probability, RyR density, Serca2a density, and calcium buffering strength. We incorporated remodeling in a population of 16 models by independently varying parameters that reproduce experimentally observed cellular remodeling, and quantified the resulting alterations in calcium dynamics and wave propagation patterns. The results show a strong effect of ICaL in driving calcium silencing, with INCX, INaK, and RyR density also resulting in calcium silencing in some models. Calcium alternans was observed in some models where INCX and Serca2a density had been changed. Simultaneously incorporating changes in all remodeled parameters resulted in calcium silencing in all models, indicating the predominant role of decreasing ICaL in the population phenotype.

scholarly journals Computational study of wave propagation in materials with microstructure effect

2011 ◽  
Author(s):  
Αλέξιος Παπαχαραλαμπόπουλος
Keyword(s):  
Wave Propagation ◽  
Acoustic Waves ◽  
Lamb Waves ◽  
Computational Study ◽  
Interstitial Tissue ◽  
Isotropic Composite ◽  
Relaxation Functions ◽  
The Matrix ◽  
Microstructure Effect ◽  
Non Destructive

Fractures are common at human bones. So, a callus is formed and the procedureof osteogenesis is initiated. Medical doctors need to have a tool that allowsthem to evaluate the healing procedure without taking X-ray photos every week.Such a variety of tools can be provided by non-destructive inspection techniques.But rst, one has to create a model for predicting phenomena such as size-eectsand in particular dispersive acoustic waves propagation.Before this thesis, there has been made an attempt by (Vavva, 2009), topredict modal wave propagation with Mindlin's Form-II. Herein, for the rsttime there are presented dynamic solutions of this theory.To begin with, the bone is considered to be a dampless homogeneous (ortho)isotropic composite material, with interstitial tissue being the matrix andthe osteons being the bres. So, Mindlin's theory can be applied in this case.Next, a fundamental solution is obtained for Mindlin's Form-II of his gradientelasticity theory. In conjunction to an existing integral representation, there canbe obtained solutions using the Boundary Element Method. With the help of aconsidered Representative Volume Element, simulations have been conducted andresults are presented for the cases of P, S and Rayleigh waves, as well as guidedwaves in plates. The dispersion diagrams as given by Wigner-Ville representationsare compared to the theoretical ones. What is more, the validity and accuracy ofthe BEM code have been checked using analytical solutions of one-dimensionalproblems.Furthermore, relaxation functions from viscoelastic theories are consideredand are taken into account using the correspondence principle. So, both viscoelasticand gradient-visco-elastic models have been considered and the resultsof various cases (P, S, Rayleigh and Lamb waves) have been compared to theabove.Finally, since the present thesis has to do with information extracted fromdispersive wave propagation, some studies have been made and measures havebeen proposed for velocities and dispersion.All in all, this has been a work dealing with the fact that micro-structureaects the macro-behavior of a material concerning waves propagation and, inthe framework of Mindlin's Form-II, there have been extracted several conclusionsconcerning bone-like materials.

Sign in / Sign up

Export Citation Format

Share Document