Calculation Of Transfer Function Research Articles

A generalized analysis of high‐order N‐path filters

AbstractIn N‐path filter analysis, assumptions are used to simplify their analysis to avoid the complexity of the calculations. These assumptions limit the number of examinable circuits. This paper analyzes a general system including an arbitrary number of N‐path filters to generalize the analysis. In the proposed method, due to the calculation of harmonic transfer functions for each independent capacitor in each time interval, it is possible to examine N‐path filters in the presence of common capacitors between multiple branches, leakage resistors, and branches with asymmetric switching. The absence of discontinuous jumps during the switching moments and switching operation in a non‐overlapping fashion with a specified periodicity are the only assumptions of the proposed method. As a result, more LPTV (linear periodically time‐varying) systems can be analyzed using the calculations provided. After presenting the method, we show the proposed method's ability by analyzing a recently published impedance‐transforming N‐path filter and examining its details.

Cerebral Autoregulation Assessment Using the Near Infrared Spectroscopy 'NIRS-Only' High Frequency Methodology in Critically Ill Patients: A Prospective Cross-Sectional Study.

Impairments in cerebral autoregulation (CA) are related to poor clinical outcome. Near infrared spectroscopy (NIRS) is a non-invasive technique applied to estimate CA. Our general purpose was to study the clinical feasibility of a previously published ‘NIRS-only’ CA methodology in a critically ill intensive care unit (ICU) population and determine its relationship with clinical outcome. Bilateral NIRS measurements were performed for 1–2 h. Data segments of ten-minutes were used to calculate transfer function analyses (TFA) CA estimates between high frequency oxyhemoglobin (oxyHb) and deoxyhemoglobin (deoxyHb) signals. The phase shift was corrected for serial time shifts. Criteria were defined to select TFA phase plot segments (segments) with ‘high-pass filter’ characteristics. In 54 patients, 490 out of 729 segments were automatically selected (67%). In 34 primary neurology patients the median (q1–q3) low frequency (LF) phase shift was higher in 19 survivors compared to 15 non-survivors (13° (6.3–35) versus 0.83° (−2.8–13), p = 0.0167). CA estimation using the NIRS-only methodology seems feasible in an ICU population using segment selection for more robust and consistent CA estimations. The ‘NIRS-only’ methodology needs further validation, but has the advantage of being non-invasive without the need for arterial blood pressure monitoring.

DOE-ANOVA for Identifying the Effect of Extreme Sea-States over the Structural Dynamic Parameters of a Floating Structure

Sea extreme events affect the integrity and operation of the offshore structures, then, it is important to analyze wind-waves-currents loads over the structural dynamics. Traditional offshore designing identifies structural parameters with certain limitations: physical modeling involves using shaking tables in dry conditions; numerical simulations have not sufficiently considered the effects of combined extreme waves-wind-current loads over the structure and the significance of the near and far hydrodynamic field over the structure. The non-linear interactions in the near hydrodynamic field generate viscous damping that modifies the dynamic structural parameters of the offshore structures. The traditional determination of structural parameters considers the hydrodynamic forces computed from wave records, omitting fluid-structure interactions that could generate unexpected damped periods and amplification peaks. This study applied physical modeling to determine floating structural parameters, considering combined loads and the effect of far and near hydrodynamic field in the fluid-structure interaction. The calculated transfer functions in the near hydrodynamic field revealed the highest amplification of the structural accelerations, and the transfer functions in the far field did not evidence structural resonance. Finally, this study recommends measuring the near hydrodynamic field and applying DOE-ANOVA for offshore designing to assess the viscous damping that may provoke dangerous structural amplifications.

Simulation of a double-circuit subordinated coordinate regulation system of the active po wer factor corrector for the electric locomotive auxiliary electric drive

Introduction. The object of this study is an auxiliary frequency-controlled electric drive of an AC locomotive, or more specifically, the structure and parameters of the system for regulating the coordinates of the active power factor corrector, which is a part of the electric drive and a unit that ensures the energy efficiency of the electric drive as well as its electromagnetic compatibility with other equipment on board the electric locomotive and the power network. The purpose of the study is to substantiate the structure of the system for regulating the coordinates of an active power factor corrector, the choice of types of regulators and the calculation of their parameters.Materials and methods. The author has chosen as the research method the calculation of transfer functions of regulators of the subordinated regulation system, followed by computer simulation of the processes in electrical circuits using the OrCAD computer-aided design system.Results. The author made a conclusion about the expediency of using a two-circuit system of subordinated coordinate regulation containing a voltage control circuit and a current control circuit. The researcher presented and analytically compares the results of modelling of a two-circuit coordinate regulation system for the active power factor corrector for various types of regulators. The models with an aperiodic current regulator and a proportional-integral voltage regulator showed the best results.Discussion and conclusion. The obtained data serve as the basis for further improvement of the active power factor corrector operation by improving and optimising the settings, structure and algorithms of the control system, which, with the selected hardware components of the power unit, will enable it to perform its functions with a high degree of reliability in the entire range of disturbing and controlling actions on board of an electric locomotive.

Performance evaluation of a micro-CT system for laboratory animal imaging with iterative reconstruction capabilities.

In recent years, there has been a rapid proliferation in micro-computed tomography (micro-CT) systems becoming more available for routine preclinical research, with applications in many areas, including bone, lung, cancer, and cardiac imaging. Micro-CT provides the means to non-invasively acquire detailed anatomical information, but high-resolution imaging comes at the cost of longer scan times and higher doses, which is not desirable given the potential risks related to x-ray radiation. To achieve dose reduction and higher throughputs without compromising image quality, fewer projections can be acquired. This is where iterative reconstruction methods can have the potential to reduce noise since these algorithms can better handle sparse projection data, compared to filtered backprojection PURPOSE: We evaluate the performance characteristics of a compact benchtop micro-CT scanner that provides iterative reconstruction capabilities with GPU-based acceleration. We thereby investigate the potential benefit of iterative reconstruction for dose reduction. Based on a series of phantom experiments, the benchtop micro-CT system was characterized in terms of image uniformity, noise, low contrast detectability, linearity, and spatial resolution. Whole-body images of a plasticized ex vivo mouse phantom were also acquired. Different acquisition protocols (general-purpose versus high-resolution, including low dose scans) and different reconstruction strategies (analytic versus iterative algorithms: FDK, ISRA, ISRA-TV) were compared. Signal uniformity was maintained across the radial and axial field-of-view (no cupping effect) with an average difference in Hounsfield units (HU) between peripheral and central regions below 50. For low contrast detectability, regions with at least ∆HU of 40 to surrounding material could be discriminated (for rods of 2.5mm diameter). A high linear correlation (R2 =0.997) was found between measured CT values and iodine concentrations (0-40mg/ml). Modulation transfer function (MTF) calculations on a wire phantom evaluated a resolution of 10.2 lp/mm at 10% MTF that was consistent with the 8.3% MTF measured on the 50µm bars (10 lp/mm) of a bar-pattern phantom. Noteworthy changes in signal-to-noise and contrast-to-noise values were found for different acquisition and reconstruction protocols. Our results further showed the potential of iterative reconstruction to deliver images with less noise and artefacts. In summary, the micro-CT system that was evaluated in the present work was shown to provide a good combination of performance characteristics between image uniformity, low contrast detectability, and resolution in short scan times. With the iterative reconstruction capabilities of this micro-CT system in mind (ISRA and ISRA-TV), the adoption of such algorithms by GPU-based acceleration enables the integration of noise reduction methods which here demonstrated potential for high-quality imaging at reduced doses.

RAD_IQ: A free software for characterization of digital X-ray imaging devices based on the novel IEC 62220-1-1:2015 International Standard

Characterization of digital X-ray imaging devices is very important because it can be used to measure and compare the performance of detectors used in Diagnostic Radiology. This characterization is usually made through the calculation of Modulation Transfer Function (MTF), Noise Power Spectrum (NPS) and Detective Quantum Efficiency (DQE). These parameters, especially the DQE, are very important because they quantify the effect of spatial resolution, contrast and noise on Radiographic image quality (IQ). The IEC 62220-1-1:2015 International Standard provides comprehensive guidelines how to capture and analyze X-ray images to characterize digital X-ray detectors. A novel, fast and free MATLAB-based software was developed, named RAD_IQ, to calculate the Signal Transfer Property (STP), perform Noise Component Analysis (NCA), and calculate the parameters MTF, NPS & DQE of X-ray detectors based on the novel IEC 62220-1-1:2015 International Standard for General Radiography and IEC 62220-1-1:2007 for Digital Mammography. Our results were validated against well-established software products used for quantitative image analysis of digital X-ray detectors. The calculated parameters were within 5% difference compared to available software products. The conclusion of our study was that RAD_IQ can be easily used from Medical Physicists, Biomedical Engineers and researchers without any programming experience to characterize the performance of digital X-ray detectors used in Diagnostic Radiology.

Electronically Tunable Third Order Feed Forward CM Band Pass Filter for Q = 10

A new electronically tunable current-mode third order filter is proposed in this paper. OP-AMP is used as an active building block. With current input the filter can realize band pass responses in current mode. The filter circuit realizes calculated transfer function. The other attractive features of the filter are a) Employment of minimum active and passive elements b) Responses are electronically tunable c) Low active and passive sensitivities d) Suitable for high frequency operation e) Ideal for integrated circuit implementation.

Method for Prediction of Extreme Wave Loads Based on Ship Operability Analysis Using Hindcast Wave Database

The method for the prediction of extreme vertical wave bending moments on a passenger ship based on the hindcast database along the shipping route is presented. Operability analysis is performed to identify sea states when the ship is not able to normally operate and which are likely to be avoided. Closed-form expressions are used for the calculation of transfer functions of ship motions and loads. Multiple operability criteria are used and compared to the corresponding limiting values. The most probable extreme wave bending moments for the short-term sea states at discrete locations along the shipping route are calculated, and annual maximum extreme values are determined. Gumbel probability distribution is then fitted to the annual extreme values, and wave bending moments corresponding to a return period of 20 years are determined for discrete locations. The system reliability approach is used to calculate combined extreme vertical wave bending moment along the shipping route. The method is employed on the example of a passenger ship sailing across the Adriatic Sea (Split, Croatia, to Ancona, Italy). The contribution of the study is the method for the extreme values of wave loads using the hindcast wave database and accounting for ship operational restrictions.

Surface manifestation of stochastically excited internal gravity waves

ABSTRACT Recent photometric observations of massive stars show ubiquitous low-frequency ‘red noise’ variability, which has been interpreted as internal gravity waves (IGWs). Simulations of IGWs generated by convection show smooth surface wave spectra, qualitatively matching the observed red noise. Theoretical calculations using linear wave theory by Shiode et al. and Lecoanet et al. predict IGWs should manifest at the surface as regularly spaced peaks associated with standing g modes. In light of the apparent discrepancy between these theories and simulations/observations, we test the theories with simplified 2D numerical simulations of wave generation by convection. The simulations agree with the transfer function calculations presented in Lecoanet et al., demonstrating that the transfer function correctly models linear wave propagation. However, there are differences between our simulations and the g-mode amplitude predictions of Shiode et al. This is because that work did not take into account the finite width of the g-mode peaks; after correcting for this finite width, we again find good agreement between theory and simulations. This paper verifies the theoretical approach of Lecoanet et al. and strengthens their conclusion that IGWs generated by core convection do not have a surface manifestation consistent with observed low-frequency variability of massive stars.

Gap resonance from linear to quartic wave excitation and the structure of nonlinear transfer functions

Resonant response of water waves in a narrow gap, with the interaction of multiple highly resonant modes, is an interesting hydrodynamic phenomenon with practical applications. Gap resonances between two identical fixed rectangular boxes are experimentally investigated for unidirectional waves with broadside incidence. We show that gap resonances can be driven through both linear wave excitation and nonlinear processes, i.e. frequency doubling, tripling and quadrupling – apparently new observations. It is striking that the time histories of the gap resonances excited through different nonlinear interactions are remarkably similar to each other. It seems likely that the nonlinear sum-frequency transfer functions for gap resonances depend strongly on the output frequency sum of the interacting linear components, but only weakly on the frequency difference. In terms of their structure in multiple frequency space (at second order the bi-frequency plane for two components), these transfer functions must then have a near-flat form in the direction(s) perpendicular to the leading diagonal. This is supported by our potential flow calculations of the quadratic transfer functions (QTFs). It is therefore convenient to approximate the QTF matrix as ‘flat’ in the direction perpendicular to the leading diagonal. This approximation is justified through experimental data that includes viscous damping. It is too complex, if not impossible, to calculate the full cubic or quartic transfer functions as direct evidence. However, the experimental analysis does provide some support for the near-flat structure being applicable to transfer functions above second order. The flat form approximation greatly reduces lengthy calculations of the high-order transfer functions.

Three-dimensional transfer function of optical microscopes in reflection mode.

Three-dimensional (3D) transfer functions build the basis for a comprehensive characterization of optical imaging systems in the spatial frequency domain. Utilizing the projection-slice theorem, the 2D modulation transfer function of an incoherent imaging system can be derived from a 3D transfer function by integration with respect to the axial spatial frequency. For a diffraction limited microscope with homogeneous incoherent pupil illumination, the modulation transfer function equals the 2D autocorrelation function of a circular disc. However, until now to the best of our knowledge no 3D transfer function has been published, which exactly leads to the 2D modulation transfer function of a diffraction limited microscope in reflection mode. In this article, we derive a formula, which after integration with respect to the axial spatial frequency coordinate perfectly fits to the diffraction limited 2D modulation transfer function. The inverse three-dimensional Fourier transform of the 3D transfer function results in a complex-valued 3D point spread function, from which the depth of field, the lateral resolution and, in addition, the corresponding 3D point spread function of both, a conventional and an interference microscope, can beobtained.

Iliski, a software for robust calculation of transfer functions.

Understanding the relationships between biological processes is paramount to unravel pathophysiological mechanisms. These relationships can be modeled with Transfer Functions (TFs), with no need of a priori hypotheses as to the shape of the transfer function. Here we present Iliski, a software dedicated to TFs computation between two signals. It includes different pre-treatment routines and TF computation processes: deconvolution, deterministic and non-deterministic optimization algorithms that are adapted to disparate datasets. We apply Iliski to data on neurovascular coupling, an ensemble of cellular mechanisms that link neuronal activity to local changes of blood flow, highlighting the software benefits and caveats in the computation and evaluation of TFs. We also propose a workflow that will help users to choose the best computation according to the dataset. Iliski is available under the open-source license CC BY 4.0 on GitHub (https://github.com/alike-aydin/Iliski) and can be used on the most common operating systems, either within the MATLAB environment, or as a standalone application.

Functional scheme of the transformer-rectifier unit of the centrifugal oil cleaning installation

Annotation. Problem. The reduction of reliability, economical and mass-dimensional indicators is one of available ways for centrifugal cleaning transformer olives installations, which based on electric drives with icreased frequency. In addition to the development and calculation of the power scheme of the installation, the issue of developing an calculation power supply system from the industrial power system is relevant. In this case, the task of developing and researching a voltage and frequency converter, which is an intermediate link between the industrial power system and the centrifugal oil cleaning installation and provides the specified parameters of electricity, requires the solution of additional partial problems. Goal. The goal is to develop and study the functional scheme of the transformer-rectifier unit with an automated output voltage control system for the installation of centrifugal cleaning of transformer oil. Methodology. Analytical methods of research, methods of the theory of electric machines and electric drives, and also methods of calculation of transfer functions of elements of the automated control systems and their dynamic characteristics are used. Results. The structural scheme of the transformer-rectifier unit with the automated control system of the output voltage of the installation for cleaning transformer oil on the basis of the electric drive of the increased frequency is developed. Calculations of transfer functions of elements of the offered automated control system of the transformer-rectifier unit are executed and its dynamic characteristics are investigated. Originality. The scheme of the transformer-rectifier unit for installation of centrifugal cleaning of transformer oil with the electric drive of the increased frequency is developed and investigated. Practical value. The introduction of centrifugal transformer oil cleaning units with a high-frequency electric drive will increase the reliability, economy and weight of such units. The calculations allow us to draw conclusions about the compliance of the proposed scheme of the transformer-rectifier unit with an automated voltage control system for reliability and dynamic characteristics of the requirements for the secondary power supply of the centrifugal oil cleaning installation.

A RANS approach for transfer function plot based on discrete fourier transform

ABSTRACT Besides the other hydrodynamic phenomena, the ship design process includes also the accurate prediction of the motions in waves. In this paper, a Discrete Fourier Transform (DFT) based method is presented for calculations of ship motion transfer functions (TFs) by using Reynolds Averaged Navier Stokes (RANS) approach. The DTMB 5512 hull form is selected for the proof of the accuracy of the proposed method at the Froude number of 0.41 and head waves. Instead of sending regular waves separately to the model ship in a virtual towing tank, a wave energy spectrum is defined and the created long-crested irregular wave system is sent to the model ship. With the aid of the DFT technique, irregular vertical ship motions in the time domain are transformed into the frequency domain. With the proposed RANS method, it is reported that CPU time spent for CFD analyses are significantly dropped compared to traditional RANS TFs calculation processes.

Quaternion domain Laplace transform of the pulse vector

The Laplace transform (LT) is widely used in radio engineering for signal and circuit analysis. The PL greatly facilitates the solution of differential equations, the calculation of transfer functions, the finding of impulse responses, etc. Multiple-Input Multiple-Output (MIMO) systems are becoming more common today. With input influences on such systems, at the output signals are obtained, the elements of which are closely related to each other, and changes in some influencing elements of the input vector change the values of others. Such changes are usually associated with the preservation of the vector norm during transformation. Obviously, this completely changes the shape of the output response and, accordingly, its spectrum. To calculate such changes, it is possible to use the usual PL of real signals and the corresponding theorems. However, this approach requires a significant investment of time and computational resources. If you change the amplitude, shape, time shift of at least one pulse, you will have to repeat all the calculations again. Quaternion transformations, including the Laplace transform, have been studied in many works. However, these studies are often of a general theoretical nature or are used only to obtain the Fractional Quaternion Laplace Transform of 2D images. To calculate the LT of the impulse vector when using the MIMO scheme, it is proposed to use hypercomplex numbers, in the particular case, quaternions. Quaternion is a hypercomplex number with one scalar and three imaginary numbers i, j, k. To get rid of operations with imaginary numbers, the quaternion is represented as an orthogonal 4×4 matrix. The matrix, in turn, is decomposed into 4 basis matrices. Moreover, operations with matrices correspond to operations with imaginary units and the quaternion as a whole. It is shown that the quaternionic Laplace transform (QLT) of the vector is represented as a one-dimensional integral from 0 to ∞ of the vector. In this case, the matrix exponent in the power of the quaternion frequency matrix S = Eσ + 1/√3(I + J + K)ω is used as the transformation kernel, where E, I, J, K are basis matrices. The main properties of the QLT are considered. It is shown that in terms of the notation form, the properties of the QLT correspond to the properties of the LT of real functions, taking into account the non-commutativity of matrix multiplication. Therefore, to calculate the QLT, it is possible to use the well-known expressions for the LT of real pulses with the replacement of the complex frequency s by the matrix of quaternion frequencies S. Expressions for the QLT are obtained for the pulse vectors, which are often used to solve radio engineering problems. It is shown that for σ = 0 these expressions correspond to the quaternionic Fourier transform of the vector pulses. In general, vector pulses can have different delays, amplitudes and shapes. Expressions are obtained for finding the QLT of such vectors.

Assessment of Uncertainty Depending on Various Conditions in Modulation Transfer Function Calculation Using the Edge Method.

In medical X-ray imaging, to perform optimal operations, it is essential for the user to understand whether a required image quality level which depends on a diagnostic task can be achieved with the imaging system used. This study focuses on the effects of noise on the modulation transfer function (MTF) using the edge method, the most widely used to evaluate the task dependence property. The purpose is to verify the uncertainty of the MTF value at each spatial frequency and examine the conditions under which the accuracy is ensured. By using a Monte Carlo simulation, edge images with various contrast-to-noise ratio (CNR) are acquired. MTFs are then calculated with different edge spread function (ESF) lengths. The uncertainties for each spatial frequency are estimated based on the independent MTF calculations obtained from the five edge data. The uncertainty of the MTF is inversely proportional to the CNR. In the frequency range up to the Nyquist frequency, the uncertainty in five calculations is <0.01 when the CNR is more than 60. In addition, it is observed that the uncertainty increases as the ESF length increases. This relationship depends on the frequency range, but it is proportional to the 0.3–0.5 power of the ESF length. The results in which the uncertainty is most likely to be large in the MTF calculation are clearly shown. Therefore, it is expected to provide an important barometer and useful insights for a proper image quality measurement.

Acceleration of the Multi-Level Fast Multipole Algorithm Using K-Means Clustering

The multilevel fast multipole algorithm (MLFMA) using K-means clustering to accelerate electromagnetic scattering analysis for large complex targets is presented. By replacing the regular cube grouping with the K-means clustering, the addition theorem is more accurately approximated. The convergence rate of an iterative solver is thus improved significantly. However, irregular centroid locations as a result of the K-means clustering increase the amount of explicit transfer function calculations, compared with the regular cubes. In the MLFMA, a multilevel hierarchical structure is applied to the finite multipole method (FMM) to reduce transfer function calculations. Therefore, the MLFMA is suitable for applying K-means clustering. Simulation results with both canonical and realistic targets show an improvement in the computation time of the proposed algorithm.

Surface finishing by laser re-melting applied to robotized laser metal deposition

Low surface quality of as-deposited laser metal deposition (LMD) parts is one of the main drawbacks of this additive manufacturing technology that prevents direct use without the implementation of costly and time consuming post-processes. An in-process surface finishing operation without the need of auxiliary equipment is highly appealing to overcome such issues. For this reason, laser re-melting performed with the same laser equipment used for the deposition process is a promising technology capable of redistributing the deposited material onto a smoother surface. Combined with a robotic manipulation system used for both the LMD and laser re-melting phases, complex geometries can potentially be produced in near net-shape conditions. An important issue concerning development of this process development regards the use of standardized roughness and waviness parameters, which can fail to address the texture specific to the LMD process. Indeed, the laser re-melting process can produce new texture formation under non-optimal conditions. Hence, an analysis of the surface topography in the frequency domain along with the standard surface roughness and waviness parameters would be more appropriate. In this work, laser re-melting is applied to AISI 316L thin walled structures right after the deposition process. An experimental campaign aimed at finding the process parameters and re-melting strategy capable of improving the surface quality was carried out. Areal surface profile measurements were used for characterizing the effect of the process parameters. The surface power spectrum on the S-F surface was calculated to point out the presence of periodical components in the surface structure and a transfer function calculation was performed to define the surface quality improvement in the frequency domain compared to the LMD as-deposited surface. The acquired surface areal data was assessed at two different spatial frequency regions corresponding to the S-L and L-F surfaces. The arithmetic average of the filtered surface areal data was used to calculate Sa, SF and Sa, LF analogously to the average roughness and waviness parameters of linear measurements respectively. Results showed, in the optimized conditions, a reduction of up to 79% in Sa, SF corresponding to the roughness related frequency range. On the other hand, the Sa, LF parameter corresponding to the waviness realted frequency range was reduced up to 58% due to the low effectiveness of laser re-melting in reducing the amplitude of the lowest frequency components. The overall improvement in terms of process capability was evaluated as mean ± 3 times the sample standard deviation values (µ±3σ). The average surface roughness Sa, SF could be reduced from 10.35±0.42 µm to 1.92±0.11 µm and average surface waviness Sa, LF from 9.57±0.48 µm to 4.04±0.20 µm.

Seismic Microzoning Method with using procedures by spectrum ratio H/V

Seismic Microzoning Method (SMM) proposed in the article, may be used in engineering seismology for measuring intensity of seismic waves taking into account soil properties of city areas, building plots etc. This Method is based on procedures of spectrum ratio HVSR (Horizontal to Vertical Spectral Ratio-an analogue of quasi-transition function. Nogoshi &amp; Igarashi, (1971). It was later sufficiently completed and transformed by Y. Nakamura, and obtained maximal distribution as «H/V Nakamura's ratio», and proved oneself to be good at the studies of both resonant properties of soils and dynamic characteristics of different construxtional objects. The authors of this article proposed one more application of the procedure for seismic microzoning aimed at increase of efficiency of these studies and accuracy and stability of determination of accretion of seismic intensity on the studied soils during elastic actions produced for instance by earthquakes of native or anthropogenic nature. In the area of exploration a record of micro-fluctuations is conducted with the help of three-component seismic sensors installed on the soils with different engineering-geological conditions. The obtained seismogram is subdivided into a lot of small fragments with minimum noises. The spectrum of each fragment is calculated. Then spectra of horizontal components X and Y, and vertical component Z are calculated for every small fragment. Resulting spectra of horizontals components H and spectra of vertical component V are found. After calculation of transfer function H/V, maximum of gain factor by cross-cut vibrations on the exploration area [(H/V)max]i and on the weighted average (calibration) area [(H/V)max]0 are determined. Then the increase of seismic intensity is calculated: As a result of using the novel Seismic Microzoning Method productivity of labour, accuracy and stability of calculation of ΔI is increased.

Numerical calculation of the radiofrequency transfer function of cochlear implants for assessing deposited power in MRI

The medical imaging of patients with a cochlear implant inside a Magnetic Resonance Imaging (MRI) scanner carries the risk of power deposition in the tissues at the tip of the implant lead, which may result in their heating. In order to assess this risk, ISO/TS 10 974 () describes a methodology (Tier 3 approach) whereby a radiofrequency electrical model for the implant lead in the form of a transfer function is constructed. The construction of the transfer function takes place by assuming that a homogenous medium surrounds the implant, whereas, in reality, implants can traverse various tissues of different electrical properties. The results show that the use of a High Permittivity Medium (HPM) overestimates the Tier 3 calculated deposited power by almost 6 dB, whereas a Low Permittivity Medium (LPM) underestimates it by 9 dB, compared to the in vivo power deposition in three virtual human models, obtained following the Tier 4 approach of ISO/TS 10 974(). Since the Tier 3 approach requires less computational resources compared to Tier 4, we suggest its modification with the use of two media (mixed media approach), where implant is immersed. By carefully choosing the media electrical properties, it is possible to calculate power deposition values at the lead tip that differ less than 1 dB from the in vivo ones.