Circuit Impedance Research Articles

Nano carbon powder‐multiwalled carbon nanotubes/poly(vinylidene fluoride) percolating composites with low‐percolation binary functional phases and negative permittivity

AbstractPolymer percolating composites with negative permittivity via the construction of percolating structures are of great interest in electromagnetism. In this study, nano carbon powder‐multiwalled carbon nanotubes/poly(vinylidene fluoride) (CP‐MWCNTs/PVDF) composites comprising binary functional phases CP‐MWCNTs were fabricated using hot‐pressing method. The composites achieved both low percolation threshold and tunable negative permittivity properties across the entire frequency range of testing. Percolation phenomenon was observed as functional phases content reaching 5 wt%, which was reflected as the establishment of percolation network and the occurrence of electrical percolation, resulting in a shift toward metal‐like conduction mechanism. Additionally, the notably low percolation threshold can be ascribed to the synergistic effect between the binary functional phases. The plasma oscillation of free electrons within conductive percolation network plays a crucial role in achieving negative permittivity, a phenomenon that can be elucidated using the Drude model from the free electron theory. Furthermore, analyses of the impedance and equivalent circuit illuminate the connection between percolation phenomenon and dielectric behavior. These findings further reveal the influence of functional phases' morphology and composition on percolation behavior and negative permittivity properties, while expanding the application of polymer‐based percolating composites in electromagnetic devices.Highlights Tunable negative permittivity related to plasma oscillation is achieved. Binary functional phases exhibit a low percolation threshold. Synergistic effect of functional phases leads to low percolation threshold.

Improving Anti-Corrosion Property of Aluminium Alloy by Fabrication MAO Coating via Mixing Titanium Potassium Oxalate into Electrolyte.

Titanium potassium oxalate had been mixed into the electrolyte to improve the anti-corrosion property of the micro arc oxidation coating on the surface of the aluminium alloy. The surface and cross-section of the coating at different titanium potassium oxalate concentrations had been observed by scanning electron microscopy, showing that when the titanium potassium oxalate concentration was 10 g/L, the coating compactness was better. Additionally, the element content of the coating had been studied by the energy dispersive spectrometer, and results proved that the coating consisted of Al, O, Ti, Si, and P. The Ti increased with the increase in titanium potassium oxalate concentration. The X-ray diffractometer had been employed to analyze the crystalline structure of the coating. Then, it was found that after the micro arc oxidation, an alumina oxide coating was prepared on the surface of the aluminium alloy, and the Al2O3 and TiO2 characteristic peak was observed. Furthermore, the electrochemical workstation was used to test the anti-corrosion of the coating. It was proved that when the titanium potassium oxalate concentration was 10 g/L, the open circuit voltage, corrosion current, corrosion potential, and impedance of the coating were improved, and the anti-corrosion property of the aluminium alloy had been strengthened.

A novel design method for dual-band Wilkinson power dividers with different power split ratios on each band based on extended pi-shaped microstrip line

This paper proposes a novel method for designing a dual-band Wilkinson power divider with different power split ratios on each band. The circuit is designed based on the proposed dual-band matching impedance circuit, with input and output impedances varying according to the working band. The isolation resistor of the circuit is calculated using exact building formulas to ensure output matching and isolation conditions between output ports at two operating bands. A design procedure with analytical design equations is described in the paper. To validate the proposed design method, a dual-band Wilkinson power divider operating at 1 and 2.2 GHz with power split ratios on each band are 1:1 and 2:1, respectively was designed, simulated, fabricated, and tested. The agreement between simulated and measured results has validated the proposed design concept.

Advanced titanium implants: combating corrosion and infection with cutting-edge coatings

Abstract The presented research investigates the corrosion behavior of commercially pure titanium (cp-Ti) and amorphous calcium phosphate–chitosan (ACP@ChOL) coatings enriched with selenium on titanium in simulated body fluid (SBF). Using potentiodynamic polarization techniques, it was sought to derive essential corrosion parameters – corrosion potential, corrosion current density, breakdown potential, and passivation current. This study pioneers a comparative analysis of the corrosion stability of both samples. SEM/EDS analysis of surfaces pre- and postpotentiodynamic measurements offered insights into morphology and elemental composition. The aim was to elucidate the corrosion mechanism by integrating these techniques. Additionally, spontaneous corrosion behavior over 7 days, monitoring changes in open circuit potential, polarization resistance, and impedance were investigated. Furthermore, the antimicrobial efficacy of ACP@ChOL enriched with Se on titanium was assessed against Escherichia coli, Staphylococcus aureus, and Candida albicans, as well as in vitro release of Se. The presented study extends understanding, offering a unique perspective on the corrosion behavior and antimicrobial attributes of ACP@ChOL coatings enriched with Se on titanium. This composite material exhibits promise for medical applications, presenting an innovative avenue for addressing corrosion concerns and potentially reducing antibiotic reliance.

The Influence of Impedance on the Efficacy of Radiofrequency Ablation for Benign Thyroid Nodules.

Radiofrequency ablation (RFA) uses the heat generated by a high-frequency alternating electric current, and according to Ohm's and Joule's law, the delivered current is inversely proportional to the circuit impedance. The primary objective of this study was to investigate whether tissue impedance during radiofrequency ablation (RFA) for benign thyroid nodules is related to the degree of volume reduction. This observational study included consecutive patients treated with RFA for benign thyroid nodules from February 2020 to August 2023. Technical effectiveness was defined as a volume reduction percentage (VRP) >75% at 6 months after the treatment. Multivariate logistic regression analyses were performed to identify the potential role of clinical factors and changes in tissue impedance on technique effectiveness. Totally 72 patients were included with 73 benign thyroid nodules. Maximal impedance peaks reached <18 times, and mean procedural impedance ≤300 Ω were significantly associated with a volume decrease of >75% at bivariate analysis. These cutoff points were exploratory, as no existing literature suggests these variables are related to the degree of volume reduction. After adjusting for age, volume, and composition, significant associations were found for mean electrical impedance in the multivariate analysis (OR = 4.86 [confidence interval [CI] 1.29-18.26], p = 0.019). The energy adjusted by volume (delivered energy) was not associated with a VRP >75% (p = 0.7746). This study suggests that a mean procedural impedance </= 300 Ω is related to the effectiveness of RFA as measured by VRP. Additional prospective and randomized studies are needed to compare electrical parameters with VRP. 3 Laryngoscope, 134:5231-5238, 2024.

High Performance of Anion Exchange Membrane Fuel Cells By Introducing Hydrophobic Carbon Nanotube Diffusion Layer

In recent years, anion exchange membrane fuel cells have garnered significant attention due to their ability to utilize low platinum group metal catalysts, thereby reducing manufacturing costs. In contrast to proton exchange membrane fuel cells, anion exchange membrane fuel cells have a distinctive operational characteristic where they produce water at the anode electrode while consuming water on the cathode electrode. The primary challenge hindering their advancement is managing water, specifically addressing the uneven distribution of water between the anode and cathode. As one of the crucial components of the fuel cell, the gas diffusion layer conducts electrons from the catalytic layer to the bipolar plate, transports reaction gases to the catalytic layer for electrochemical reactions, and removes excess water and waste heat generated on the anode electrode. Carbon nanotubes have high specific surface area, superior electrical conductivity, excellent mechanical properties, and inherent hydrophobicity due to their high degree of graphitization, and are considered to be promising materials for optimizing mass transport within gas diffusion layers. Abundant carbon nanotubes are synthesized in situ on carbon fibers to create a three-dimensional network structure, which not only provides more attachment sites for catalytic particles but also facilitates the electron flow path by interlacing carbon nanotubes within the catalytic layer.In this work, the iron-cobalt catalyst was uniformly sprayed onto the gas diffusion substrate through ultrasonic spraying technology. The carbon source atmosphere was ionized and deposited under plasma radio frequency to synthesize abundant carbon nanotubes in the radial direction of the carbon fibers. Contact angle measurements revealed that the carbon nanotube-modified gas diffusion layer exhibited an approximate contact angle of 145°, which was significantly greater than that of the commercial gas diffusion media. Experimental research results indicated that, under various lower relative humidity conditions, when the cathode and anode inlet flow rates were set at 0.3 L/min and 0.5 L/min, respectively, the peak power generated by the membrane electrode assembled with the carbon nanotube-modified gas diffusion layer reached 988.9 mW/cm². This represents a substantial 27.1% increase compared to the performance achieved using the commercial gas diffusion layer. Upon further increasing the cathode and anode inlet flow rates to 0.6 L/min and 1 L/min, respectively, and operating under different higher relative humidity conditions, the membrane electrode assembled with the carbon nanotube-modified gas diffusion layer exhibited a peak power of 1031.7 mW/cm². In stark contrast, the commercial gas diffusion layer achieved only 760.6 mW/cm² under similar conditions. Through equivalent circuit and electrochemical impedance test analysis, it can be seen that the carbon nanotube-modified gas diffusion layer can effectively improve concentration polarization loss and ohmic polarization loss.

Interface Characterization of Fusion Bonded Composites Made from Laser-Pretreated Steel and Glass Fiber-Reinforced Thermoplastics Using Electrochemical Impedance Spectroscopy

Material-hybrid designs made of metal and plastic are becoming increasingly important in the automotive and aerospace industries. They place new demands on joining technology in particular. One promising process is the fusion bonding of metals and fiber-reinforced thermoplastics. In this process, the thermoplastic matrix material of the fiber-reinforced composite component is melted and a direct adhesive bond is created with the metallic joining partner. This joining technology has already been extensively studied in the past. In particular, the interface between the joining partners has been identified as a critical factor for the long-term quality of the joint. The interface can be altered by influences during production, such as e-coat process or the effects of harsh environmental conditions during operation like corrosion and thermomechanical loads. Determining the extent of these influences on the interface condition and thus the quality of the joint is difficult, but it is essential to support the use of the joining method in safety-critical areas. Previous investigations of this joining method have mostly been carried out destructively using tensile shear tests and non-destructively using fiber optic and piezo ceramic sensors, but all approaches have only shown limited significance with regard to the metal-plastic interface in detail. Electrochemical impedance spectroscopy (EIS) as a very sensitive measurement method could represent an almost non-destructive and at the same time very sensitive alternative which is currently not reported for this use case in the literature. In previous internal investigations, we found that EIS can be used to measure layer thicknesses of up to 3.5 mm, contrary to the usual use of this test method for characterizing the properties of thin coatings, corrosion behavior and battery performance. In fusion bonding applications, typical material thicknesses of thermoplastics above the interface are around 1.5 mm and are thus well above the usual layer thicknesses of approx. 20 µm to 100 µm for typical EIS applications.This study aims to examine how EIS can be used advantageously for the interface characterization of fusion bonded specimens and up to which extent the EIS can provide a statement about the metal-plastic interface. In this study, a joint of a laser-pretreated steel and a glass fiber-reinforced PA6 is investigated. We measured specimens directly after production, after a treatment similar to an automotive e-coat process and after certain intervals of a salt spray test. Using the Kramers-Kronig transformation, the EIS data was validated and qualitatively analyzed with Nyquist and Bode diagrams, the impedance at 0.1 Hz, the maximum impedance and equivalent circuits. Tensile shear and edge shear test serve as destructive reference tests to determine strength parameters of the joints and evaluate the respective fracture patterns. This opens up the possibility to correlate the results of EIS and destructive measurements. In summary, EIS is suitable for characterizing the metal-plastic interface, even with polymer thicknesses of 1.5 mm, which are comparatively high for EIS. Due to the very low phase angle and the resulting low dielectricity of the glass fiber-reinforced thermoplastic, changes in the impedance data are directly related to the interface condition. The measured impedance spectra could be differentiated with Nyquist and Bode diagrams, the impedance at 0.1 Hz and the maximum impedance.

Impact of Impedances and Solar Inverter Grid Controls in Electric Distribution Line with Grid Voltage and Frequency Instability

The penetration of solar energy into centralized electric grids has increased significantly during the last decade. Although the electricity from photovoltaics (PVs) can deliver clean and cost-effective energy, the intermittent nature of the sunlight can lead to challenges with electric grid stability. Smart inverter-based resources (IBRs) can be used to mitigate the impact of such high penetration of renewable energy, as well as to support grid reliability by improving the voltage and frequency stability with embedded control functions such as Volt-VAR, Volt–Watt, and Frequency–Watt. In this work, the results of an extensive experimental study of possible interactions between the unstable grid and two residential-scale inverters from different brands under different active and reactive power controls are presented. Two impedance circuits were installed between Power Hardware-in-the-loop (P-HIL) equipment to represent the impedance in an electric distribution line. Grid voltage and frequency were varied between extreme values outside of the normal range to test the response of the two inverters operating under different controls. The key findings highlighted that different inverters that have met the same requirements of IEEE 1547-2018 responded to grid instabilities differently. Therefore, commissioning tests to ensure inverter performance are crucial. In addition to the grid control, the residential PV installed capacity and physical distances between PV homes and the substation, which impacted the distribution wiring impedance which we characterized by the ratio of the reactive to real impedance (X/R), should be considered when assigning the grid-supporting control setpoints to smart inverters. A higher X/R of 3.5 allowed for more effective control to alleviate both voltage and frequency stability. The elimination of deadband in an aggressive Volt-VAR control also enhanced the ability to control voltage during extreme fluctuation. The analysis of sudden spikes in the grid responses to a large frequency drop showed that a shallow slope of 1.5 kW/Hz in the droop control resulted in a &gt;65% lower sudden reactive power overshoot amplitude than a steeper slope of 2.8 kW/Hz.

Modeling of Static Stress Identification Using Electromechanical Impedance of Embedded Piezoelectric Plate.

Working stress is an important indicator reflecting the health status of structures. Passive-monitoring technology using the piezoelectric effect can effectively monitor the dynamic stress of structures. However, under static loads, the charge generated by the piezoelectric devices can only be preserved when the external circuit impedance is infinitely large, which means passive-monitoring techniques are unable to monitor static and quasi-static stress caused by slow-changing actions. In current studies, experimental observations have shown that the impedance characteristics of piezoelectric devices are affected by external static loads, yet the underlying mechanisms remain inadequately explained. This is because the impedance characteristics of piezoelectric devices are actually dynamic characteristics under alternating voltage. Most existing impedance analysis models are based on linear elastic dynamics. Within this framework, the impact of static stress on dynamic characteristics, including impedance characteristics, cannot be addressed. Accounting for static stress in impedance modeling is a challenging problem. In this study, the static stress applied on an embedded piezoelectric plate is abstracted as the initial stress of the piezoelectric plate. Based on nonlinear elastic dynamic governing equations, using the displacement method, an impedance analysis model of an embedded piezoelectric plate considering initial stress is established and verified through a fundamental experiment and a finite element analysis. Based on this, the explicit analytical relation between initial stress and impedance characterizations is provided, the mechanism of the effect of initial stress on the impedance characterizations is revealed, and procedures to identify static stress using impedance characterizations is proposed. Moreover, the sensitivities of the impedance characterizations in response to the initial stress are thoroughly discussed. This study mainly provides a theoretical basis for monitoring static stress using the electromechanical impedance of an embedded piezoelectric plate. And the results of the present study can help with the performance prediction and design optimization of piezoelectric-based static stress sensors.

An adaptive distance protection scheme considering fault resistance, injected current, and structural changes in the power system

AbstractFaults in power systems occur for various reasons, such as aging or natural disasters. Detecting, locating, and promptly clearing these faults is crucial for maintaining the safety and reliability of transmission lines (TLs). Distance relays (DRs), which protect TLs, detect faults, estimate their location, and send the required commands. However, these relays may experience mis‐detection due to manipulated impedance arising from both internal and external factors. These factors include measurement device errors, network topology changes, the presence of fault resistance (FR), and injected currents from remote line terminals. To address this challenge, an innovative adaptive protection scheme that considers FR, changes in network topology, and injected current from the opposite end of the line is proposed. By estimating the equivalent circuit impedances (ECIs) of the network connected to the terminal of the TL, this protection scheme utilizes impedance estimation techniques at the line terminals and offline network information. Simulation studies (tested on the IEEE 39‐bus standard network) show that the proposed scheme accurately estimates fault location (FL) and FR with high precision. The simulation results demonstrate its effectiveness in improving the performance of conventional distance protection relays in both the first and second protection zones ( and ).

Appraisal of partial anomalous pulmonary venous drainage through a lumped-parameter mathematical model: a new pathophysiological proof of concept.

Haemodynamic determinants of the ratio between pulmonary and systemic flow (Qp/Qs) in partial anomalous pulmonary venous return (PAPVR) are still not fully understood. Indeed, among patients with the same number of lung segments draining anomalously, a great variability is observed in terms of right ventricular overload. The aim of this study was to test the hypothesis that the anatomic site of drainage, affecting the total circuit impedance, independently influences the magnitude of shunt estimated by Qp/Qs. A zero-dimensional lumped parameter mathematical model was developed and validated on a sample of patients. We developed a zero-dimensional lumped parameter model, using time-varying elastances for heart chambers, RLC Windkessel circuits for the systemic and pulmonary circulations. Patients were categorized into vena cava (VC) type (including left drainage to anomalous vein) and right atrium (RA) type. The mathematical model is a system of ordinary differential equations that are numerically solved by means of the ode15s solver in the MATLAB environment. The model showed an increase of Qp/Qs with the increase of the number of anomalous veins. With the same number of anomalous veins, Qp/Qs was lower in patients with anomalous drainage to the VC as compared with RA. The validation sample consisted of 49 patients (27, 55% females). As predicted by the model, patients with PAPVR with VC type displayed a lower invasive and cardiac magnetic resonance Qp/Qs as compared with drainage to RA: 1.4 (1.2-1.7) and 1.45 (1.25-1.6) versus 2 (1.75-2.1) and 1.9 (1.6-2), P < 0.05. After stratifying for number of lung territories, a lower Qp/Qs was measured in patients with VC PAPVR as compared with RA. In patients with PAPVR, the site of anomalous drainage modulates the Qp/Qs. According to the model, this effect is mediated by the post-capillary impedance of the circuit and significantly decreases with the increase of pulmonary vascular resistances.

Tunable flexural waves by piezoelectric metasurface with shunt circuits

Elastic metasurfaces have been rapidly developed for effective modulation of elastic wave propagation. Among them, utilizing the electromechanical coupling effect of piezoelectric materials provides a promising way to design tunable and multifunctional elastic metasurfaces, but piezoelectric metasurfaces still face big challenges in theoretical guidance and experiments. In this paper, a tunable piezoelectric metasurface is proposed for achieving modulation of flexural wave in broad working frequency range. Based on the developed electromechanical coupling model, the piezoelectric patch with shunt resistor–inductor circuit is analyzed, and the functional unit of metasurface with only two piezoelectric patches is designed for modulating the flexural wave in thin plate. By using Antoniou’s circuit and considering the effect of impedance in circuit, the arbitral phase shift of functional unit is experimentally achieved by adjustable shunt circuits to verify the turnability in a full 2π range. Further, the piezoelectric metasurface by assembling functional units can realize multiple functions, like tunable anomalous refraction and wave focusing, by adjusting shunt circuits.

Temperature-dependent dielectric measurements of polypyrrole/zinc cobalt oxide nanocomposites by impedance spectroscopy

This study characterizes the conduction mechanism in Zinc Cobalt oxide/Polypyrrole nanocomposites (ZCO/PPy NCs) concerning temperature (303–453 K) and frequency (100 Hz–1 MHz). To obtain the ZCO/PPy nanocomposites for the experiments, we used the in-situ chemical polymerization technique to disseminate varying weight percentages of ZCO nanoparticles (ZCO NPs) in the PPy matrix. The total electrical conductivity graph consists of a step-like feature of a plateau and dispersive regimes. The dispersive zone, which follows Jonscher's power law, correlates to AC conductivity, whereas the plateau region, which corresponds to DC conductivity, is thermally activated. The extracted DC conductivity values are of the order of 10‐4 S/m at 303 K. The conduction mechanism in ZCO/PPy nanocomposites is depicted by the Non-Overlapping Large Polaron Tunneling (NSPT) model. The dielectric studies confirm the non-Debye-like relaxation in PPy and ZCO/PPy NCs. In addition, the complex impedance and equivalent circuit analysis showed maximum contribution from grain and grain boundaries. The grain and grain boundary resistances are of the order of 103 Ω, depicting the electrical homogeneity in the PPy and ZCO/PPy nanocomposites.

Design of interline hybrid continuous trans-impedance turns ratio controlled tuning power filter: New approach to suppress harmonics in energy system

Harmonic distortion (HRD) is a major issue in power and energy systems due to its effect on output, power factor and performance of entire system. Interline hybrid continuous network impedance (IL-hCONTI) tuned filter is proposed to suppress the harmonic distortion in a inter tied i.e. integrated energy system. In a proposed method, effective transformer impedance i.e. trans-impedance is utilized rather than using entire grid impedance power system. Transformer impedance control (Tf-ZPC) in the power network under testing is possess the reactive voltage drop at point of common coupling (PoC). Transformer impedance is proportional to the turns ratio and the concern voltage change and it is imposed by the proposed tuned filter. Tuned filter is designed with the Tf-ZPC along with filter circuit impedance to control the harmonic currents and PoC voltage profile. Proposed hybrid filter design utilizes the both instantaneous capacitor voltage and inductive capacitor filter (LCF) voltage component to suppress harmonic component. Hence improved power factor of energy system is assured using proposed technique. Proposed IL-hCONTI tuned filter is tested over a strong grid conditions, as well as weak grid conditions for linear, non-linear loading.

Source characterization of a ducted source using acoustic free velocity

A common method to characterize linear time invariant ducted acoustic sources is the electroacoustic analogy. The sources are typically defined by their internal source strength and source impedance. Various methods have emerged to determine the source characteristics, broadly categorized into direct and indirect methods. Direct methods involve using a secondary source with significantly higher amplitude to measure source impedance, but those methods are unable to determine source strength. Indirect methods vary acoustic loads to obtain both source strength and source impedance, but accuracy depends on appropriate load combinations. In this research, we propose an inverse method to determine the acoustic source strength from the measured acoustic transfer function and the operational acoustic pressure. This approach yields the “acoustic free velocity,” corresponding to a volume velocity source that characterizes the original sound source. Subsequently, the source impedance is obtained using the acoustic free velocity in conjunction with the load impedance and acoustic pressure in the acoustic circuit. The method is demonstrated using a compressor driver source attached to an impedance tube. Validation of the measured source strength and source impedance is conducted using a two-load method. Prediction of muffler insertion loss shows good correlation with experimental measurements.

Solidifying Transmission Reduction of Piezoelectric Metamaterial Beam Through Synthetic Impedance Circuits With Parasitic Resistance Compensation

Solidifying Transmission Reduction of Piezoelectric Metamaterial Beam Through Synthetic Impedance Circuits With Parasitic Resistance Compensation

Frequency tunable non-invasive microwave blood glucose sensor based on negative impedance circuit

Abstract This article proposes a frequency adjustable non-invasive blood glucose microwave sensor based on negative impedance circuit. Firstly, this article establishes a skin-blood-skin human tissue model for the detection of non-invasive microwave sensors. Compared to traditional passive microwave blood glucose sensors, this design uses a negative impedance compensation circuit (NIC), greatly increasing microwave penetration and improving its detection sensitivity. In addition, this design achieves the goal of adjustable operating frequency by adding an additional dielectric layer at the detection end. This function is of great significance for microwave non-invasive blood glucose sensors. On the one hand, it can adjust to the optimal operating frequency band according to the characteristics of blood glucose changes; On the other hand, it is possible to measure changes in blood glucose concentration at multiple frequency points, thereby increasing the accuracy of detection. The relevant results show that adjusting the frequency band can reach 1–4 GHz, and the specific method of frequency adjustment is provided in the article; Meanwhile, four initial frequency points were selected in the article, at which the results show that the sensitivity reaches 1.356 × 10−3, 3.142 × 10−3, 2.071 × 10−3, 1.903 × 10−3. The above results demonstrate the superiority of our design, and blood glucose sensors based on this principle are expected to break through the limitations of current blood glucose sensors.

Bandwidth Extension of the Doherty Power Amplifier Using the Impedance Distribution and Control Circuit for the Post-Matching Network

Owing to the high impedance transformation ratio, the Doherty power amplifier (DPA) with a large output power back-off generally has bandwidth limitations. This study proposes an asymmetric DPA with an impedance distribution and control circuit (IDCC) at the post-matching network to improve the bandwidth. The IDCC, based on a resonance circuit and a series transmission line, distributes and controls the load impedance according to the frequency so that the bandwidth of the DPA can be extended. To verify the proposed IDCC, an asymmetric DPA was designed using GaN HEMT with a power capacity of 6 W and 10 W for the carrier and peaking amplifiers, respectively. The implemented DPA was evaluated for the broad frequency band between 3.3 GHz and 3.8 GHz using a 5G new radio (NR) signal with a bandwidth of 100 MHz and a peak-to-average power ratio of 7.8 dB. A drain efficiency between 43.2% and 50.7% and an adjacent channel leakage power ratio between –23.4 dBc and –27.3 dBc were achieved at an average power level that ranged between 33.5 dBm and 34.3 dBm.

Multifrequency Circuit Impedance Measurements may Improve Durable Ablation Lesion Assessment: Differentiating Cellular Destruction From Tissue Heating

Multifrequency Circuit Impedance Measurements may Improve Durable Ablation Lesion Assessment: Differentiating Cellular Destruction From Tissue Heating

Source characterization of a ducted source using acoustic free velocity

A common method to characterize linear time invariant ducted acoustic sources is the electro-acoustic analogy. The sources are typically defined by their internal source strength and source impedance. Various methods have emerged to determine the source characteristics, broadly categorized into direct and indirect methods. Direct methods involve using a secondary source with significantly higher amplitude to measure source impedance but cannot determine source strength. Indirect methods vary acoustic loads to obtain both source strength and source impedance, accuracy depends on appropriate load combinations. In this research, we propose an inverse method to determine the acoustic source strength from the measured acoustic transfer function and the operational acoustic pressure. This approach yields what we term as the "acoustic free velocity," corresponding to a plane monopole source that characterizes the original sound source. Subsequently, the source impedance is obtained using the acoustic free velocity in conjunction with the load impedance and acoustic pressure in the acoustic circuit. The method is demonstrated using a compressor driver source attached to a 1 3/8" impedance tube. Validation of the measured source strength and source impedance is conducted using a two-load method. Additionally, prediction of muffler insertion loss shows a good correlation with experimental measurements, affirming the efficacy of the proposed methodology.