Relative Impedance Research Articles

Potential program invariant representation of diffusion-adsorption related voltammograms and impedance spectra

A theory is presented by which voltammograms, and dynamic electrochemical impedance spectroscopy (dEIS) measurements of diffusion-hindered adsorption processes can be analyzed. By the proposed procedure, from a set of voltammograms, taken at varied scan-rates, parameters of the kinetics and isotherm of the adsorption can be calculated. These are scan-rate independent functions of potential. The theory also comprises the analysis of the high frequency impedance spectra of the same system, which have been measured during dynamic conditions, i.e., during potential scans. The properties of the analysis are illustrated by transformation of simulated cyclic voltammograms. The presented theory is a synthesis of previous ones on diffusion-controlled charge transfer and on adsorption. The theory supports the determination of rate coefficients as a function of electrode potential from fast dEIS measurements.

High-Gain and Wideband Circularly Polarized Endfire Leaky-Wave Antenna Array Based on the Complementary Dipole

A circularly polarized (CP) endfire leaky-wave antenna (LWA) array with the merits of high-gain and broad operation band is proposed in this communication. This array configuration is composed of double-row antenna cells arranged linearly, which derives from the performance of the complementary dipole (loop and electric dipole). By introducing the coupling loop and the electric dipole along both side of a metallic parallel strip line (PSL), the effective radiation is generated from this structure due to the periodic perturbation. Based on the intrinsic 90° phase differences of the complementary dipole, CP performance is easily achieved by turning the antenna unit size reasonably. Similar to the yagi antenna, this linearly antenna array achieves an endfire radiation. A fabricated prototype has verified the design concept, which shows that the proposed antenna has a relative impedance bandwidth of 51.1%, 3dB axial ratio (AR) bandwidth of 25%, and the gain of 1.1-13.59dBi within the operation band.

Terahertz Selective Active Electromagnetic Absorption Film Based on Single-layer Graphene

In this paper, a terahertz selective active electromagnetic frequency absorption film based on single-layer graphene is proposed. The film can achieve electromagnetic wave absorption rate higher than 0.9 at 2.4-4 THz and 7-8.6 THz in the THz band. And, through parameter inversion analysis of the relative impedance, it is found that the relative impedance of the film in the strong absorption part matches the free space impedance, which is consistent with the classical theory. The absorption mechanism of the high absorption of the film is also studied by analyzing the electric field distribution and the pattern changed simulation of graphene. The film has good stability at different incident angles and shows strong polarization incoherence. The characteristics of the film can be tuned by tuning the physical parameters, graphene Fermi energy and relaxation time. Interestingly, under some parameters, the film will change the original absorption mode. This paper introduces five absorption modes: double bandwidth absorption mode, two different single bandwidth absorption mode and two different double peak and bandwidth absorption mode. To sum up, the film has strong application value in aerospace, military, medical and other fields.

Modified combination of triple split ring resonator based triple band single negative metamaterial for satellite applications

This paper investigates a modified combination of triple split ring resonator (SRR) based triple band single negative metamaterial for satellite applications. The proposed unit cell structure has a triple split ring resonator i.e. square, circular and rhombus shape. The lower plane completely encloses the FR-4 substrate with a thickness of 1.6 mm, on top of which the metallic resonating structure with thickness of 0.035 mm is attached. The structure provides quad band resonances of transmission coefficient (S21) at 2.02 (S-band), 6.77 (C-band), and 13.22 (Ku-band) GHz with magnitude of -27.8, -23.2, and -27.2 dB, respectively and also offers the wider bandwidth. The plot of relative permittivity, permeability, refractive index and impedance is used to explain the metamaterial behavior. Additionally, a plot of the electromagnetic field and surface current analysis for a separate frequency that belongs to the S, C, and Ku band makes the unit cell structure to help illustrate the metamaterial behavior. The effective medium ratio (EMR) of the structure is 14.85, demonstrating its compactness. The performance of the structure is validated through the simulation result using CST Microwave Studio and HFSS simulator. The suggested structure will be a possible option for satellite communication (S, C and Ku-band) because of wider bandwidth and excellent EMR.

Estimation of Relative Acoustic Impedance Perturbation from Reverse Time Migration Using a Modified Inverse Scattering Imaging Condition

Reverse Time Migration (RTM) is a preferred depth migration method for imaging complex structures. It solves the complete wave equation and can model all types of complex wave propagation with no dip limitation. Reverse time migration using the inverse scattering imaging condition produces structural images with an amplitude approximate to the reflectivity, which is a composite effect of the impedance and velocity changes in the acoustic media with variable velocity and density. In this study, we present a modified inverse scattering imaging condition to separate the effect of the impedance and velocity perturbations from the reflectivity. The proposed imaging condition is designed to predict the relative impedance perturbation by selecting near-angle reflections during common-shot RTM. We validate our approach on synthetic models and show that the proposed method can estimate reliable impedance perturbation.

Polynomial analysis as a new way of describing dynamic impedance spectra – Differential and relative impedance spectra

Model measurements of an equivalent electrical system were carried out using the technique of Dynamic Electrochemical Impedance Spectroscopy. The measurement took the form of potentiodynamic changes imposed on the tested system. Using the possibility of continuous impedance measurements, an attempt was made to develop an original and innovative method of analyzing impedance spectrograms, which is termed polynomial analysis. As a result of this approach, it is possible to generate two novel impedance spectra from the primary impedance spectrogram. The innovation lies in the use of simple polynomials to describe a set of spectra, and then performing differential and division operations, which result in differential- and relative-impedance spectra. Among other things, differential spectra have the ability to track the rate of change in impedance as a function of an independent variable. By contrast, relative impedance spectra eliminate surface influence, which opens the way to the direct comparison of physicochemical processes and more.

Tunable and switchable terahertz absorber based on photoconductive silicon and vanadium dioxide

In this paper, a tunable and switchable absorber based on photoconductive silicon (Si) and vanadium dioxide (VO2) is proposed. The designed absorber can achieve tunable bifunctional single-/dual-band absorption and switchable perfect absorption, by optically pumped silicon and temperature controlled VO2 individually or simultaneously. The absorption mechanism is explained by relative impedance theory. Moreover, a multiple interference model based on quasi-Fabry-Pérot cavity resonance is established to further reveal the principle of absorption, and the theoretical result is in good agreement with the numerical ones. Influence of structural parameters, polarization and angle of incident wave on absorption performances are systematically studied. The flexible tunable characteristics and polarization insensitivity of the designed absorber for multi-dimensional operation has potential applications in dynamic terahertz (THz) devices.

Application of artificial neural network and seismic attributes to predict the distribution of Late Oligocene sandstones in the Cuu Long basin

Artificial neural network (ANN) has been widely applied in oil and gas exploration and production. This study presents the results of predicting the distribution of Late Oligocene sandstones in the Cuu Long basin based on the application of ANN and seismic attributes. These results have great significance, helping to orient the oil and gas prospection and exploration of the Cuu Long basin and other exploration objects on the continental shelf of Vietnam. The authors used unsupervised neural networks (UNN) and UNN methods constantly associated with the principal component analysis (PCA) to divide seismic facies. Seismic attributes such as Root mean square (RMS), Frequency, Envelope, Relative Acoustic Impedance (RAI), Phase, Sweetness, Amplitude, and t-Attenuation were analyzed and selected as input for the ANN training and testing process. These attributes can reflect changes in lithology, and sedimentary facies, from which will have a better view of the distribution of reservoirs in the study area. From 4 to 10 classes of seismic facies have been tested using each method to improve the results. Comparing the results of seismic facies classification by the UNN method and by UNN combined with PCA, it can be seen that the UNN combined with PCA will help reduce noise in seismic data better than UNN only. The research results have identified the distribution of Late Oligocene potential sandstones in the study area in the Cuu Long basin, which are mainly concentrated on the slopes of a large lake, with the direction of sediment transport from the West and Northwest.

Broadband Dual-Polarized Antenna With Stable Radiation Patterns for Base Station Applications

A broadband differentially fed slant ±45° dual-polarized stacked patch antenna is presented to cover 2.3–5 GHz for base station applications. In this letter, both semicircular and sector loaded slotlines are employed to generate three resonant frequencies. A slotted ring is utilized to generate a new resonant frequency, and could make the radiation patterns stable at high frequencies. To verify antenna performances, the proposed design is fabricated. From measurement, it is seen that its relative impedance bandwidth achieves 75.9% (2.28–5.07 GHz), and its port isolation reaches more than 35 dB. Moreover, in the whole band, the gain variation is smaller than 0.8 dB. Therefore, the proposed design could provide great candidate for LTE/5G base station applications.

Vocal Tract Resonance Detection at Low Frequencies: Improving Physical and Transducer Configurations

Broadband excitation introduced at the speaker's lips and the evaluation of its corresponding relative acoustic impedance spectrum allow for fast, accurate and non-invasive estimations of vocal tract resonances during speech and singing. However, due to radiation impedance interactions at the lips at low frequencies, it is challenging to make reliable measurements of resonances lower than 500 Hz due to poor signal to noise ratios, limiting investigations of the first vocal tract resonance using such a method. In this paper, various physical configurations which may optimize the acoustic coupling between transducers and the vocal tract are investigated and the practical arrangement which yields the optimal vocal tract resonance detection sensitivity at low frequencies is identified. To support the investigation, two quantitative analysis methods are proposed to facilitate comparison of the sensitivity and quality of resonances identified. Accordingly, the optimal configuration identified has better acoustic coupling and low-frequency response compared with existing arrangements and is shown to reliably detect resonances down to 350 Hz (and possibly lower), thereby allowing the first resonance of a wide range of vowel articulations to be estimated with confidence.

Wideband high gain SIW horn antenna loaded with half Maxwell fish‐eye fabricated by 3‐D‐printing

AbstractThis letter presents a wideband high gain substrate integrated waveguide horn antenna (SIWHA) loaded with half Maxwell fish‐eye (HMFE) fabricated by 3‐D‐Printing. The impedance bandwidth of the SIWHA is narrow, mainly caused by the discontinuity between the substrate with the air. By introducing the HMFE and a match layer between the SIWHA with HMFE, the impedance continuity can be realized, which can not only improve the impedance bandwidth but also enhance the antenna gain. Experimental results show that the proposed antenna can achieve more than 6 dBi gain and 60.9% relative impedance bandwidth with reflection coefficients lower than −10 dB.

Seismic Attributes Analysis as a Precursor for Hydrocarbon Indication: A Case Study of Onshore Fuba field, Niger Delta, Nigeria

Seismic attributes analysis as a precursor for hydrocarbon indication in onshore Fuba Field, Niger Delta, Nigeria using Well-logs and 3D Seismic data are here presented. Well-to-seismic ties, faults and horizon mapping, time-surface generation, depth conversion and seismic attributes generation were carried out using Petrel software. The structural interpretation of seismic data reveal highly synthetic and antithetic faults which are in line with faults trends identified in the Niger Delta. Of the 36 interpreted faults, only synthetic and antithetic faults are regional, running from the top to bottom across the field. These faults play significant roles in trap formation at the upper, middle and lower sections of the field. Three distinct horizons were mapped. Reservoir M is found at a shallower depth from 10937 to 10997 ft, reservoir N is found at a depth ranging from 11213 to 11241 ft while reservoir O is found at a deeper depth ranging from 11681 to 11871 ft respectively. Analysis of the relevant seismic attributes such as variance edge, root mean square, maximum amplitude and relative acoustic impedance were applied to the seismic data. The variance values ranges from 0.0 to 1.0. The Variance edge analysis was used to delineate the prominent and subtle faults in the area. The RMS amplitude values ranges from 9,000 to 13,000 in the reservoirs. The root mean square amplitude and maximum amplitude analysis reveal bright spot anomaly. These amplitude anomalies served as direct hydrocarbon indicators (DHIs), unravelling the presence and possible hydrocarbon prospective zones. The relative acoustic impedance analysis was used for delineating lithology variation in the seismic sections. Results from this study have shown that away from the currently producing zone of the field, additional leads and prospects exist, which could be further evaluated for hydrocarbon production.

On using the corpses of large mammals as model objects for studying the postmortem period

Is to justify using the corpses of large mammals as model objects for studying the postmortem period. Similarities in processes occurring postmortem in human and swine corpses (decomposition stages and the structure of dominant necrophilic organisms inhabiting the corpse), as well as similar changes of relative impedance parameters for the cartilaginous tissue and musculoskeletal flap of swine and human corpses have been established. The results obtained allow recommending the swine corpse as an adequate human corpse model both for scientific studies and for solving specific scientific and practical issues arising in the practice of forensic examination when determining the prescription of death coming and the postmortem period conditions.

Dynamically changeable terahertz metamaterial absorbers with intelligent switch and high sensitivity and wide and narrow band perfect absorption.

In this work, we theoretically designed a dynamically changeable terahertz metamaterial absorber with intelligent switch and high sensitivity, wide band and narrow band perfect absorption based on the combination of Dirac semimetal (BDS) and vanadium dioxide (VO2). It features two methods for absorption adjustment: altering the Fermi energy level of BDS to modify the resonant frequency of the absorption peaks and utilizing the phase change of VO2 to regulate the absorption rate of the peaks. In addition, its rotational symmetric design ensures strong polarization-insensitivity. The simulation results demonstrate the presence of two narrowband absorption peaks and one mini-broadband absorption peak within the frequency range of 6.0-9.5 THz, all with absorption rates exceeding 90%. We provide an explanation of the absorption mechanism of the device, employing the relative impedance theory and localized surface plasmon resonance to analyze its electric field distribution. We also defined the refractive index sensitivity (S), which is SI = 378 GHz per RIU and SIII = 204 GHz per RIU. Our device possesses high sensitivity and two methods of adjusting absorption modes, which endow it with advantages in the fields of metamaterial absorbers, intelligent switch, and optical sensors.

Novel Approach for the Monitoring of Single Phase-to-Ground Fault Associated with Power Arc

This paper presents a general theoretical overview of a novel approach for the monitoring of the single phase-to-ground fault associated with power arc. Although several existing fault protection methods have been employed in order to resolve the power arcing faults associated with the single phase-to-ground faults, still ongoing research is trying to develop efficient methods that could help to suppress completely these dangerous power arcs from the systems. The operation of the protective relays and fuse systems is quite often questionable during recurrent failures in detecting the electric arcs as expected, especially during these arcs earlier events of formation. The most relevant reason causing these traditional faults protective switchgears seldom failures, limitations and drawbacks include essentially the varying amounts of resistance associated with these previously mentioned power arcs. Subsequently, the electric arcs related impedance and that of the power system tend to limit the arcing fault currents and voltages quantities at very low rates. Hence preventing the existing fault protective devices and switchgears to detect these arcs hazards, as long as the arcing fault related currents and voltages quantities are kept for a relatively long period of time below the nominal setting values of both the relays and the fuses systems. Subsequently, the entire power distribution system experiences the devastating effects of theses dangerous parasitic electric arcs hazards. However, in order to overcome the limitations, the disadvantages and the drawbacks of the above mentioned conventional fault protective devices, this paper divorces completely with the traditional practices in order to propose a radio measurement method.

Invulnerability of the Urban Agglomeration Integrated Passenger Transport Network under Emergency Events.

Urgent natural environmental events, such as floods, power failures, and epidemics, result in disruptions to the traffic system and heavy disturbances in public requirements. In order to strengthen the ability of the transport network to handle urgent natural environmental issues, this paper simulates the disruption situation of traffic stations in the urban agglomeration by attacking nodes, and evaluates the ability of the transport network to resist disruptions (i.e., invulnerability). Firstly, the model of the urban agglomeration integrated passenger transport network is established based on complex network theory. The highway network, railway network, and coupling network are combined into a multi-layer network space structure, and the edge weight is calibrated by travel time and cost. Secondly, the invulnerability simulation process including multiple attack modes under random and deliberate attack strategies is sorted out. By improving the traditional network efficiency indicator, the network impedance efficiency indicator is proposed to measure network performance, and the network relative impedance efficiency indicator is used to evaluate network invulnerability and identify key nodes. Finally, Chengdu-Chongqing urban agglomeration is taken as a case study. The results show that the network does not collapse quickly and it shows certain invulnerability and robustness under continuous random attacks. Network performance and invulnerability are not necessarily positively correlated. The failure of individual nodes that are small in scale but act as transit hubs may significantly degrade the network performance. The identified key nodes have significance for guiding the construction, maintenance, and optimization of the urban agglomeration passenger transport network, which is conducive to promoting public safety.

Design of planar wideband surface‐wave excited substrate integrated waveguide horn antenna loaded with metamaterials

AbstractIn this paper, a wideband planar substrate integrated waveguide (SIW) horn antenna based on surface wave excitation through loading metamaterials is designed. Strong coupling effect is realized between the employed bilayer metamaterial unit with the top layer as a π‐shaped‐slotted patch while the bottom layer as the complementary cross‐shaped‐slotted patch. The equivalent permittivity of the extended substrate in front of the planar horn aperture can be effectively reduced to unity and impedance mismatching for conventional planar SIW horn antenna can be reduced in a wide bandwidth. Results indicate that the working frequency of the antenna is 12.3–15.8 GHz with the relative impedance bandwidth of 24.6%.

Investigation of relationship between tau PET SUVR and an indicator of post‐translational modification of tau in human blood plasma using electrochemical assay

AbstractBackgroundHuman tau protein is a well‐known biomarker to predict and diagnose the progress of Alzheimer’s disease [1]. The tau protein undergoes various post‐translational modificiation (PTM) of tau such as phosphorylation, O‐glycosylation, nitration, and glycation. Recently, abnormal phosphorylation of tau protein is observed in AD patients, while the level of O‐GlcNAcylation on tau protein is relatively elevated in brains of normal controls [2]. Reference: [1] L.M. Ittner et al. Nature Reviews Neuroscience, 12 (2011) 67. [2] C. Alquezar et al. Frontiers in Neurology, 11 (2021) 595532:Method(Figure 1) To investigate tau protein in human blood plasma and its PTM, a novel type of electrochemical sensor demonstrated and obtained Taumeter, an indicator as relative impedance changes of phosphorylated tau and O‐glycosylated tau, using secondary antibodies Finally, the as‐obtained Taumeter and PET SUVR were investigated for a relationship.ResultWe investigated the clinical relationship between Taumeters for AT8 and AT270 and tau PET SUVR, respectively, obtained from human blood plasma from normal control (NC, n=9), mild cognitive impairment (MCI, n=14), and Alzheimer’s disease (AD, n=13). In the case of AT8, it was observed that average Taumeters in MCI and AD were 2.86 and 4.73 times higher than those in NC (p=0.078 between NC and AD) (Figure 2a). In the case of AT270, average Taumeters in MCI and AD were 1.84 and 4.24 times higher than those in NC (p=0.057 between NC and AD) (Figure 2b). In further study, Taumeters for AT8 and AT270 correlated with tau PET SUVR (r=0.151, p=0.384 and r=0.575, p<0.001) (Figure 2c‐d).ConclusionIn this study, we investigated Taumeter reflecting PTM of tau proteins using secondary antibodies (O‐GlcNAc antibody, AT8, and AT270) in human blood and tau PET scan to investigate the relationship of Taumeter and tau PET SUVR in NC, MCI, and AD. As a result, it can be carefully implied that Taumeter has the relationship with the progress of AD.

Inclusion of seismic attributes in reservoir ensemble coverage analysis

There is a lack of quality-control (QC) methods to ensure measured seismic data are within the span of modeled seismic data in the context of ensemble-based seismic history matching of reservoir models. The dimensionality of seismic data makes it difficult to visualize the data and further compare them to the large number of ensembles in an efficient manner. Two attributes called coverage and importance are introduced to incorporate the key elements of reviewing an ensemble. The coverage attribute delineates where the set of models replicates the measured data, and the importance attribute identifies where it is important to fit the data above the noise threshold. The two attributes are then combined to highlight in which spatial area our reservoir model ensemble appropriately models the data and where a significant discrepancy exists between our ensemble of models and the measured data. The attributes are closely connected to noise, as coverage always must be analyzed in terms of the noise level. Although noise may not be explicitly corrected for, the methodology corrects the attributes for the noise assessed. The method is applied on two data examples from field seismic data: a 4D absolute difference amplitude map and a 4D relative impedance difference cube. The first example shows how changing the oil-water contact of the ensemble can improve the coverage without any history matching, and the second shows how it is more difficult to get a good coverage using 3D seismic attributes rather than using 2D maps of seismic data. The proposed QC attributes provide tools to better manage coverage of seismic data in the ensemble.

3D MODEL DESİGNED FOR FOOT OF HORİZON I OF MAYKOP İN NAFTALAN FİELD APPLYİNG SEİSMİC ATTRİBUTE ANALYSİS

The paper is devoted to design of 3D model of the study area by use of attribute analysis of 3D seismic data applied to study the geology of Naftalan oil field in more detail. The field is located in Naftalan-North Naftalan area of Ganja Oil and Gas Province, Yevlakh-Aghjabadi depression. The paper expounds the data on Naftalan field considered an ancient brachianticline type of field in Azerbaijan. The history of study of the field using geological and geophysical techniques has been briefly given. Geological evaluation of the cube derived by processing of 3D seismic data acquired in Naftalan area in 2012 made it possible to outline a confidently traced interval reflecting the foot of Horizon I of Maykop. Through selection of areas featured by variation of wavefield characteristics, we have calculated several attributes in this interval and analyzed the acquired results gaining more accurate seismic data and confident tracing of seismic horizons. To avoid repetition, some poorly informative attributes or attributes providing similar results have not been applied in further studies. Our study aims to define attributes (RMS amplitude (Root mean square), Variance/Edge method, Relative Acoustic Impedance) that are more effective for outlining disjunctive dislocations of various amplitude and can be applied for 3D model design of the geology of study area. Processing results of all 3D data have been given in form of cubes of seismic attributes. Further analysis of these attribute cubes enables us to study the geological setting of the foot of Horizon I of Maykop and select the most effective attributes. As a result, the 3D model of the study area for seismic horizon reflecting the foot of Horizon I of Maykop has been designed. Keywords: attribute analysis, 3D seismic survey, Naftalan, seismic horizon, Maykop deposits, dislocations.