Design and simulation of the electromagnetic heating of a biological tissue

2017 ◽  
Vol 36 (2) ◽  
pp. 408-416 ◽  
Author(s):  
Mykola Ostroushko ◽  
André Buchau ◽  
Wolfgang Rucker
Keyword(s):  
Immune Response ◽  
Time Domain ◽  
Thermal Ablation ◽  
Power Transmission ◽  
Heating System ◽  
Content Type ◽  
Ablation Therapy ◽  
Electromagnetic Heating ◽  
The Time Domain ◽  
Inductive Power Transmission

Purpose The purpose of this paper is to present the design and the numerical calculation of the electromagnetic heating system for the ablation therapy. Hence, the heating of the tumor cells must be processed very carefully to achieve a localized coagulative necrosis and to avoid too high temperatures inside the tissue. Design/methodology/approach The non-invasive method of the ablation therapy is implemented due to the inductive power transmission between the generator and implant. The ferromagnetic implant has a small size and can be placed intravenously into tumor cells. High-frequency driving currents are necessary to obtain high induced eddy currents within the ferromagnetic implant. Findings Finite element analysis has been used for the design and numerical calculation of the electromagnetic heating system. The electromagnetic analysis is done in the time domain due to the nonlinearity of the ferromagnetic implant. Magnetic fields are computed based on a magnetic vector potential formulation. The thermal analysis is done in the time domain as well. The temperature computation in biological tissue is based on a heat balance equation. Research limitations/implications This paper is focused on the design and simulation of the inductive system for the ablation therapy. Practical implications The designed system can be practically implemented. It can be used for the clinical study of the immune response by the thermal ablation therapy. Originality/value The common method of thermal ablation is combined with an inductive power transmission. It enables a repetitive application of this method to study the immune response.

On a mixed time integration procedure for non-linear structural dynamics

2015 ◽  
Vol 32 (2) ◽  
pp. 329-369 ◽  
Author(s):  
Mário Rui Tiago Arruda ◽  
Dragos Ionut Moldovan
Keyword(s):  
Time Domain ◽  
Equations Of Motion ◽  
Time Integration ◽  
Linear Analysis ◽  
Integration Scheme ◽  
Decomposition Technique ◽  
Modal Decomposition ◽  
Content Type ◽  
Non Linear ◽  
The Time Domain

Purpose – The purpose of this paper is to report the implementation of an alternative time integration procedure for the dynamic non-linear analysis of structures. Design/methodology/approach – The time integration algorithm discussed in this work corresponds to a spectral decomposition technique implemented in the time domain. As in the case of the modal decomposition in space, the numerical efficiency of the resulting integration scheme depends on the possibility of uncoupling the equations of motion. This is achieved by solving an eigenvalue problem in the time domain that only depends on the approximation basis being implemented. Complete sets of orthogonal Legendre polynomials are used to define the time approximation basis required by the model. Findings – A classical example with known analytical solution is presented to validate the model, in linear and non-linear analysis. The efficiency of the numerical technique is assessed. Comparisons are made with the classical Newmark method applied to the solution of both linear and non-linear dynamics. The mixed time integration technique presents some interesting features making very attractive its application to the analysis of non-linear dynamic systems. It corresponds in essence to a modal decomposition technique implemented in the time domain. As in the case of the modal decomposition in space, the numerical efficiency of the resulting integration scheme depends on the possibility of uncoupling the equations of motion. Originality/value – One of the main advantages of this technique is the possibility of considering relatively large time step increments which enhances the computational efficiency of the numerical procedure. Due to its characteristics, this method is well suited to parallel processing, one of the features that have to be conveniently explored in the near future.

The discrete Fourier transformation for seasonality and anomaly detection of an application to rare data

2020 ◽  
Vol 54 (2) ◽  
pp. 121-132
Author(s):  
Aryana Collins Jackson ◽  
Seán Lacey
Keyword(s):  
Time Domain ◽  
Fourier Transformation ◽  
Binary Data ◽  
Low Frequency ◽  
Discrete Fourier Transformation ◽  
Cycle Number ◽  
Content Type ◽  
Hard Drive ◽  
Period Detection ◽  
The Time Domain

PurposeThe discrete Fourier transformation (DFT) has been proven to be a successful method for determining whether a discrete time series is seasonal and, if so, for detecting the period. This paper deals exclusively with rare data, in which instances occur periodically at a low frequency.Design/methodology/approachData based on real-world situations is simulated for analysis.FindingsCycle number detection is done with spectral analysis, period detection is completed using DFT coefficients and signal shifts in the time domain are found using the convolution theorem. Additionally, a new method for detecting anomalies in binary, rare data is presented: the sum of distances. Using this method, expected events which have not occurred and unexpected events which have occurred at various sampling frequencies can be detected. Anomalies which are not considered outliers to be found.Research limitations/implicationsAliasing can contribute to extra frequencies which point to extra periods in the time domain. This can be reduced or removed with techniques such as windowing. In future work, this will be explored.Practical implicationsApplications include determining seasonality and thus investigating the underlying causes of hard drive failure, power outages and other undesired events. This work will also lend itself well to finding patterns among missing desired events, such as a scheduled hard drive backup or an employee's regular login to a server.Originality/valueThis paper has shown how seasonality and anomalies are successfully detected in seasonal, discrete, rare and binary data. Previously, the DFT has only been used for non-rare data.

Reducing Fatigue Loading due to Pressure Shift in Discrete Fluid Power Force Systems

2016 ◽  
Author(s):  
Anders Hedegaard Hansen ◽  
Henrik C. Pedersen
Keyword(s):  
Time Domain ◽  
Power Transmission ◽  
Fatigue Loading ◽  
Current Paper ◽  
Fluid Power ◽  
Pressure Oscillations ◽  
Force System ◽  
Force Systems ◽  
The Time Domain ◽  
Pressure Overshoot

Discrete Fluid Power Force Systems is one of the topologies gaining focus in the pursuit of lowering energy losses in fluid power transmission systems. The cylinder based Fluid Power Force System considered in this article is constructed with a multi-chamber cylinder, a number of constant pressure lines and a valve manifold. The valve manifold is used to control the connections between the cylinder chambers and the pressure lines and hereby the resulting force form the cylinder. The valve manifold is equipped with fast on/off valves. However, shifting between pressure lines may yield pressure oscillations in the cylinder chamber, especially for systems with long connections between the cylinder and the valve manifold. Hose pressure oscillations will induce oscillations in the produced piston force. Hence, pressure oscillations may increase the fatigue loading on systems employing a discrete fluid power force system. The current paper investigates the correlation between pressure oscillations in the cylinder chambers and valve flow in the manifold. Furthermore, the correlation between the pressure shifting time and the pressure overshoot is investigated. The study therefore focus on how to shape the valve flow in the manifold to reduce the added fatigue loads. A simple transmission line model is developed for the analysis. Two inputs are given in the Laplace domain and the time domain solution of the cylinder pressure to the given inputs are derived through inverse Laplace transformation. Based on the time domain solutions the pressure overshoot for various pressure shifting times is investigated. With the two input functions defined by the pressure shifting time, T, the main results of the current paper show the correlation between the minimum shifting time and the pressure overshoot in a given cylinder chamber with a given line connection.

The link between financial stress index and economic activity: prominent Granger causalities across frequencies in Luxembourg

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Pejman Bahramian ◽  
Andisheh Saliminezhad ◽  
Şule Aker
Keyword(s):  
Granger Causality ◽  
Time Domain ◽  
Economic Activity ◽  
Financial Stress ◽  
Financial Sector ◽  
Stress Index ◽  
Content Type ◽  
Financial Stress Index ◽  
The Time Domain ◽  
The Relationship

PurposeIn spite of the certain risk imposed by financial stress on the real economy, the relationship between financial stress and economic activity is complicated and underresearched, meaning that important gaps still remain in the authors’ understanding of this critical relationship. Therefore, the current study aims to answer the significant question regarding whether a stressful financial sector has predictive power on the real sector and vice versa. Hence, the study examines the causal interrelationship between financial stress index (FSI) and economic activity in Luxembourg as a sample country.Design/methodology/approachIn this study, accompanying the time domain Granger causality framework of Hacker and Hatemi-J (2012), the authors utilize the spectral causality technique of Breitung and Candelon (2006), which is based on the study of Geweke (1982) and Hosoya (1991). This method enables the researcher to measure the degree of a particular variation in time series. Moreover, it allows considering the nonlinearities and causality cycles. The authors further apply the recent method of Farné and Montanari (2018) that is a bootstrap framework on Granger-causality spectra, which allows for disambiguation in causalities.FindingsThe time-domain approach finds evidence of bidirectional causation between the variables. However, the spectral causality results indicate the causal linkages between the series are only valid under the medium-run frequency. This study’s findings emphasize covering the frequency causality to deliver a more comprehensive picture of the interrelationship between the variables.Originality/valueThere are many studies in this area that examine the nexus between financial stress and economic activity. However, the authors believe this paper is the first study in the context of Luxemburg. The authors focus on this country since its financial sector is designated as the most important pillar for the economy. Thus, a careful and reliable examination of the relationship between the financial sector and economic activity is likely to be of considerable interest to policymakers and researchers in this field.

Analysis of damping performance of frame structure with viscoelastic dampers

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Min Zhang ◽  
Huaying Pang
Keyword(s):  
Seismic Response ◽  
Time Domain ◽  
Seismic Effect ◽  
Frame Structure ◽  
Content Type ◽  
Vibration Equation ◽  
Viscoelastic Dampers ◽  
Inverse Transform ◽  
Time Coefficient ◽  
The Time Domain

Purpose The purpose of this paper is to equip damping performance of frame structure with viscoelastic dampers connected to supports is studied, the influence of the damper supports and the damping parameters on the damping performance of the structure is analyzed, the practical economical arrangement of viscoelastic dampers on each floor is researched and the calculation method of the seismic effect of the damping structure is presented. Design/methodology/approach In this paper, Fourier transform is applied to the vibration equation of the structure equipped with viscoelastic dampers, the frequency domain solution of the vibration equation is solved and the time-domain solution of the equation is obtained by Fourier inverse transform, from which effects of the support coefficient and the relaxing time coefficient on the seismic response of the structure are analyzed. Findings The seismic effect of each floor and the bottom shear force of each vibration mode of a structure are analyzed, which indicates that the relaxing time coefficient of the damper should be controlled reasonably. Originality/value In this paper, the vibration equation is solved in the frequency domain for frame structure equipped with viscoelastic dampers. The time-domain solution of the equation is obtained by Fourier inverse transform, from which the seismic response of frame structure equipped with viscoelastic damper connected to supports is studied.

Time domain finite element method for metamaterial-based low frequency near field systems

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Zhi Gong ◽  
Shiyou Yang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Frequency Domain ◽  
Time Domain ◽  
Near Field ◽  
Low Frequency ◽  
Electromagnetic Properties ◽  
Content Type ◽  
The Time Domain ◽  
Element Method

Purpose The purpose of this work is to develop a computational paradigm for performance analysis of low-frequency electromagnetic devices containing both magnetic metamaterials (MTMs) and natural media. Design/methodology/approach A time domain finite element method (TDFEM) is proposed. The electromagnetic properties of the MTMs are modeled by a nonstandard Lorentz model. The time domain governing equation is derived by converting the one from the frequency domain into the time domain based on the Laplace transform and convolution. The backward difference is used for the temporal discretization. An auxiliary variable is introduced to derive the recursive formula. Findings The numerical results show good agreements between the time domain solutions and the frequency domain solutions. The error convergence trajectory of the proposed TDFEM conforms to the first-order accuracy. Originality/value To the best knowledge of the authors, the presented work is the first one focusing on TDFEMs for low-frequency near fields computations of MTMs. Consequently, the proposed TDFEM greatly benefits the future explorations and performance evaluations of MTM-based near field devices and systems in low-frequency electrical and electronic engineering.

A Novel Transient Directional Unit Based on Adaptive Median Filtering

2012 ◽  
Vol 433-440 ◽  
pp. 4500-4505
Author(s):  
Ren Wang He ◽  
Yi Bo Yang
Keyword(s):  
Transmission Lines ◽  
Time Domain ◽  
Traveling Wave ◽  
High Speed ◽  
Power Transmission ◽  
Median Filtering ◽  
Power Transmission Lines ◽  
Short Period ◽  
Transient Energy ◽  
The Time Domain

A new transient directional unit for extra high voltage(EHV) power transmission lines is proposed, which identifies fault direction by means of comparing the time-domain transient energy of the forward traveling-wave with that of the backward one in the very short period of time after fault occurs. The unit algorithm is designed with the technology of adaptive median filtering, which is first employed to process the forward and backward traveling-waves, and then calculates the time-domain transient energy ratio of the forward traveling-wave to the back one, by which the fault direction is discriminated. Numerous ATP-EMTP simulation tests show that this proposed directional unit not only operates reliably, sensitively and ultra-high-speed, but also endure the influences of various factors, including different fault types, fault locations, transition resistances or fault inception angles. It will be worthy of application greatly.

Apodisation in the time domain

1992 ◽  
Vol 2 (4) ◽  
pp. 615-620
Author(s):  
G. W. Series
Keyword(s):  
Time Domain ◽  
The Time Domain

JOINT INTERPRETATION OF AIRBORNE ELECTROMAGNETIC DATA IN THE TIME DOMAIN AND FREQUENCY DOMAIN

2018 ◽  
Vol 12 (7-8) ◽  
pp. 76-83
Author(s):  
E. V. KARSHAKOV ◽  
J. MOILANEN
Keyword(s):  
Fourier Transform ◽  
Frequency Domain ◽  
Time Domain ◽  
Frequency Interval ◽  
Single Spectrum ◽  
Simultaneous Inversion ◽  
Homogeneous Half Space ◽  
Time Domain Data ◽  
The Time Domain

Тhe advantage of combine processing of frequency domain and time domain data provided by the EQUATOR system is discussed. The heliborne complex has a towed transmitter, and, raised above it on the same cable a towed receiver. The excitation signal contains both pulsed and harmonic components. In fact, there are two independent transmitters operate in the system: one of them is a normal pulsed domain transmitter, with a half-sinusoidal pulse and a small "cut" on the falling edge, and the other one is a classical frequency domain transmitter at several specially selected frequencies. The received signal is first processed to a direct Fourier transform with high Q-factor detection at all significant frequencies. After that, in the spectral region, operations of converting the spectra of two sounding signals to a single spectrum of an ideal transmitter are performed. Than we do an inverse Fourier transform and return to the time domain. The detection of spectral components is done at a frequency band of several Hz, the receiver has the ability to perfectly suppress all sorts of extra-band noise. The detection bandwidth is several dozen times less the frequency interval between the harmonics, it turns out thatto achieve the same measurement quality of ground response without using out-of-band suppression you need several dozen times higher moment of airborne transmitting system. The data obtained from the model of a homogeneous half-space, a two-layered model, and a model of a horizontally layered medium is considered. A time-domain data makes it easier to detect a conductor in a relative insulator at greater depths. The data in the frequency domain gives more detailed information about subsurface. These conclusions are illustrated by the example of processing the survey data of the Republic of Rwanda in 2017. The simultaneous inversion of data in frequency domain and time domain can significantly improve the quality of interpretation.

Sign in / Sign up

Export Citation Format

Share Document