Frequency-dependent Parameters Research Articles

A Fault Location Method Based on Electromagnetic Transient Convolution Considering Frequency-Dependent Parameters and Lossy Ground

A Fault Location Method Based on Electromagnetic Transient Convolution Considering Frequency-Dependent Parameters and Lossy Ground

Ultralow-content Co decoration on Ti3C2Tx MXene induced electromagnetic characteristic modulation for efficient microwave absorption

Ti3C2Tx MXene has been regarded as a promising candidate for advanced microwave absorption materials. However, the microwave absorbing performance of Ti3C2Tx MXene is suppressed by the single dielectric loss mechanism and impedance mismatch because of the high conductivity. To effectuate a good absorption capability of Ti3C2Tx MXene, this paper constructs a heterostructured Co/Ti3C2Tx hybrid by atomic layer depositing magnetic Co nanoparticles on Ti3C2Tx nanosheets. The microstructures, magnetism, and microwave absorption behaviors of the Co/Ti3C2Tx hybrids are investigated systematically. The results show that the frequency-dependent electromagnetic parameters of the Ti3C2Tx Mxene become tunable by controlling the content of Co decorations, which are conducive to both magnetic loss and impedance matching. The Co/Ti3C2Tx hybrid with ultralow Co decoration content (only 1.52 wt.%) achieves the minimum reflect loss of -54.32 dB at a thin matched thickness of 1.29 mm, and the corresponding effective absorption bandwidth with reflection loss below -10 dB reaches 4.29 GHz. The atomic layer deposited magnetic metal nanostructures provides an effective strategy for preparing MXene-based hybrids which not only have high absorption efficiency but also significantly reduce the use of magnetic metals.

Determination of elastic loss of piezoelectric materials by impedance curve fitting using intelligent algorithms

Understanding the loss parameters of piezoelectric materials is crucial for designing effective piezoelectric sensors. Traditional elastic loss parameter measurement techniques mainly rely on three methods: 3 dB bandwidth, impedance fitting, and ultrasonic attenuation. However, the elastic losses obtained through these methods are constant and frequency-independent, which does not align with the actual vibration characteristics of piezoelectric materials. Therefore, there is a need for a fast, accurate, and frequency-dependent method to obtain the elastic loss of piezoelectric materials. This paper introduces an approach that utilizes intelligent algorithms for fitting impedance curve to calculate elastic loss parameters. A frequency-dependent second-order energy loss model for piezoelectric materials is established. Then, a genetic algorithm is introduced to obtain the optimal elastic loss parameters. The results demonstrate a high consistency between theoretical and experimental impedances, with an error less than 5%. The elastic loss parameters obtained through intelligent algorithm-based impedance curve fitting match well with stress experiment results, with an error less than 6%. This method provides a rapid, accurate, and cost-effective way to obtain frequency-dependent second-order elastic loss parameters for piezoelectric materials.

2-D Sn wave attenuation tomography beneath the Eastern Himalaya

SUMMARY The Arunachal and Bhutan Himalaya, which are tectonically distinct from other regions of the Himalaya, have a structure that is quite intricate. The eastern Himalayan segment is a component of the region where the Indian and Eurasian plates collided 50 Myr. The Indian Plate goes beneath the Eurasian Plate in the north, and in the eastern part of the region, the Indian Plate subducts under the Burmese Plate. Here, we studied the seismic attenuation of the uppermost mantle by measuring the quality factor of the Sn wave (SnQ) to understand the dynamics of the lithospheric mantle and the cause of the seismic anomalies found in this area. The upper mantle Q structure has significant lateral differences in Arunachal and the Bhutan Himalaya. Arunachal Himalaya’s central region is characterized by a very low $Q\, (\le 150)$. The successive low-high-low SnQ values in eastern Arunachal Himalaya near Siang region have been observed. The western Arunachal region, close to the Bhutan border, exhibits a contrast in Q values. We notice that low Q values (≤200) predominate in the central to eastern Bhutan Himalaya. The western part of Bhutan Himalaya exhibits relatively high $Q\, (\ge 200)$ values, mostly near Paro and Thimpu. Interestingly, a clear boundary between low and high Q has been observed near Kakthang thrust (KT) in the Bhutan Himalaya. We found significant lateral variation of frequency dependent parameter (η) across the study region. They range from 0.25 to 0.75, with low values (≤0.5) found mostly in the central Bhutan Himalaya and in a few isolated areas of the Arunachal Himalaya. Low Q and a relatively higher $\eta \, (\ge 0.5)$ might suggest that the scattering attenuation is the controlling mechanism for Sn wave attenuation in the upper mantle beneath Arunachal Himalaya. On the contrary, dominant low Q values across the central segment of the Bhutan Himalaya, along with a low to moderate body wave velocity and dominating low η values, subsequently corroborate that intrinsic attenuation is the dominant factor in the upper mantle of the central Bhutan Himalaya.

Abstract 7378: Using game theory to investigate the therapeutic potential of disrupting tumor-microenvironment interactions

Abstract Cancer is a complex disease involving the interplay of several types of malignant and nonmalignant cells. The growth of tumors and surrounding stromal cells can be modeled as an ecosystem, where populations of cancerous and healthy cells interact and compete for resources. In this work, we have explored the application of game theoretic models of cancer to the design of novel anticancer therapies. Notably, a game theoretic-model of tumor-stromal interactions can capture the impact of interactions between cell types and can be used to investigate frequency-dependent parameters describing the impact of drug action during the initiation and growth of metastatic cancers. Previous studies using game theoretic models to describe cancer have focused on explaining progression patterns of specific tumors with known tumor-stromal interactions. This study takes a more general approach to cancer growth dynamics, modeling cancer as a simple game between healthy and cancer cells. This simplified model is used to make general predictions about cancer progression and the efficacy of treatment strategies. Our work suggests that disruption of beneficial interactions between healthy and cancer cells may be a viable treatment strategy for small tumors and preventing metastasis by ensuring that the healthy cell strategy is evolutionarily stable. The efficacy of treatment strategies that disrupt cancer cell cooperation or tumor-stromal dynamics changes as the cancer cell frequency changes. Our work suggests that drugs that target tumor-stromal cell interactions would need to be combined with other types of treatments to be effective against large tumors. Although based on a simplistic model of cancer initiation and progression, the framework derived here can be extended to the real-world design of experimental anticancer therapeutics, and fundamental analyses of this nature can be of practical utility in setting strategy for Target Product Profile design. Citation Format: Debra Van Egeren, Andrew Chen, Madison Stoddard, Lin Yuan, Arijit Chakravarty. Using game theory to investigate the therapeutic potential of disrupting tumor-microenvironment interactions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7378.

Modeling, identification, and high-speed compensation study of dynamic hysteresis nonlinearity for piezoelectric actuator

Hysteresis nonlinearity widely exists in the piezoelectric actuator (PEA), and the hysteresis nonlinearity has strong dynamic characteristics that lead to deterioration of tracking performance. To decrease the positioning error caused by hysteresis nonlinearity, a generalized Bouc-Wen (GBW) hysteresis model and its compensation method are proposed in this paper. First, based on the Bouc-Wen hysteresis model, two asymmetric terms and a second-order IIR filter are applied to describe the asymmetric hysteresis and high-frequency phase lag characteristics of PEA. Then, the model parameters with strong relevance to frequency variation are modified as frequency-dependent parameters. Meanwhile, based on the particle swarm optimization (PSO) algorithm, a novel parameter identification algorithm is designed for identifying the parameters of GBW hysteresis model. Then, an inverse feedforward controller is constructed based on the GBW hysteresis model, and a composite compensation control algorithm combining PID controller and repetitive controller is developed to reduce the unmodeled dynamics errors and unknown external disturbances. Finally, the comparison experiment results show that the accuracy and performance of the GBW model proposed in this paper are much better than the classical Bouc-Wen (CBW) model and the enhanced Bouc-Wen (EBW) model, and the developed compensation controller has excellent control performance and robustness.

Frequency-dependent physical parameters, the voltage-dependent profile of surface traps, and their lifetime of Au/(ZnCdS-GO:PVP)/n-Si structures by using the conductance method

In this study, frequency-dependent physical parameters, voltage-dependent of surface traps/states, and their lifetime of the Au/(ZnCdS-GO:PVP)/n-Si (MPS) type structures were investigated by using conductance measurements (Y = 1/Z = G + jωC) both in wide range frequency (3 kHz-3 MHz) and voltage (from − 4.00 V to 1.50 V). Firstly, basic physical parameters such as density of doping donor atoms (ND), diffusion potential (VD), Fermi-energy (EF), barrier height ΦB(C-V), depletion-layer thickness (WD), and maximum electric field (Em) were calculated from these measurements for each frequency. These values were found as 1.69 × 1016 cm−3, 0.444 eV, 0.193 eV, 0.606 eV, 1.31 × 10−5 cm, 7.66 × 104 V/cm for 10 kHz, and 1.42 × 1016 cm−3, 0.461 eV, 0.198 eV, 0.628 eV, 1.46 × 10−5 cm, 7.80 × 104 V/cm for 3 MHz, respectively. While ND decreases with increasing frequency, the other parameters increase. The density of surface states (Nss) and their lifetimes (τ) were also obtained from conductance techniques. While the Nss were changed between 2.78 × 1012 at 0.40 V and 2.61 × 1012 eV-1cm−2 at 1.3 V, and the Nss-V curve shows two distinctive peaks which correspond to 0.5 V (2.87 × 1012 eV−1cm−2) and 1.2 V (2.68 × 1012 eV−1cm−2), respectively. The values of τ were changed between 105 µs (at 0.4 V) and 15.3 µs (at 1.3 V) and decreased with increasing voltage as exponentially. These lower values of Nss were attributed to the used (ZnCdS-GO:PVP) interlayer.

Filter Approximations for Random Vibroacoustics of Rigid Porous Media

Abstract An approximate efficient stochastic dynamics technique is developed for determining response statistics of linear systems with frequency-dependent parameters, which are used for modeling wave propagation through rigid porous media subject to stochastic excitation. This is done in conjunction with a filter approximation of the system frequency response function. The technique exhibits the following advantages compared to alternative solution treatments in the literature. First, relying on an input–output relationship in the frequency domain, the response power spectrum matrix is integrated analytically for determining the stationary response covariance matrix, at zero computational cost. Second, the proposed filter approximation facilitates a state-variable formulation of the governing stochastic differential equations in the time domain. This yields a coupled system of deterministic differential equations to be solved numerically for the response covariance matrix. Thus, the nonstationary (transient) response covariance can be computed in the time domain at a relatively low computational cost. Various numerical examples are considered for demonstrating the accuracy and computational efficiency of the herein developed technique. Comparisons with pertinent Monte Carlo simulation (MCS) data are included as well.

Temperature Effect on Fluorescence Intensity and Dipole Moment Using Thermochromic Shift Method of 7DA3MHBI-2HChromen-2-one Laser Dye in Highly Viscous Glycerol Solvent.

The steady-state method is used to study the effect of temperature on the fluorescence characteristics of 7-(diethylamino)-3-(1-methyl-1H-benzo[d]imidazol-2-yl)-2H-chromen-2-one (7DA3MHBI-2HChromen-2-one) laser dye in glycerol solvent for the temperature range 293-343K. Absorption and emission characteristics are affected by varying temperatures due to induced thermal effects. Transition probabilities mechanism of non-radiative and radiative are studied and frequency dependent parameters are estimated. Dipole moments in the ground and excited state are estimated using the thermochromic shift method over general solvatochromic methods.

Quantitative prediction of the fracture scale based on frequency-dependent S-wave splitting

The development of natural fractures has a significant impact on underground reservoirs and leads to seismic anisotropy. Furthermore, the scale of natural fractures directly affects oil and gas preservation, hydraulic fracture construction, and the production development of shale reservoirs. The S-wave anisotropy is a frequency-dependent parameter and the change in S-wave anisotropy with frequency is a function of the fracture scale. We develop an innovative method for predicting the fracture scale quantitatively using frequency-dependent S-wave anisotropy. The quantitative relationship between different fracture scales and the frequency-dependent response of the S-wave splitting (SWS) anisotropy can be obtained using a dynamic rock-physics model. The frequency-dependent S-wave anisotropy is calculated via SWS analysis in the frequency domain, after which this quantitative relationship and the calculated frequency-dependent response are used to establish an objective function for the inversion of the fracture scale at different depths using the least-squares algorithm. We synthesize data under ideal conditions, test our method, apply our method to field data, and find that the quantitative prediction method of the fracture scale yielded reasonable prediction results. The S-wave anisotropy is calculated based on the SWS analysis from the horizontal components of the upgoing wavefields of the field vertical seismic profile. We compare the fracture scale calculated from logging data using our method, and the results obtained indicate that this method can successfully predict the fracture scale quantitatively.

Co-evaluation of power system frequency performance and operational reliability considering the frequency regulation capability of wind power

With the increasing proportion of renewable energy, the power system inertia decreases, and the operation uncertainty rises. It brings concerns about the system frequency and operational reliability. However, the impacts of the power system frequency performance on the reliability parameters of generation units have not been fully investigated. This paper studies the frequency performance and the operational reliability co-evaluation for power systems considering wind turbines. Firstly, a power system frequency regulation model is established considering the regulation capability of wind turbines. Then, the cluster of equivalent wind turbines is incorporated into the frequency regulation architecture of thermal power units, which accelerates the analysis of frequency performance. Then, the frequency performance of the power system with the participation of wind turbines under the operation uncertainty and the unit random faults is quantitatively analyzed. A frequency-dependent generator reliability parameter model is derived. Next, a multi-time scale co-evaluation framework is proposed to realize the co-evaluation of frequency performance and operational reliability. Case studies are carried out on the modified IEEE RTS-79 system and a provincial power system. Results show that compared with the existing research, the proposed method can obtain the frequency performance and reliability results efficiently.

High frequency modeling of dry type detuned reactor for transient studies: Simulation and experimental analyses

Dry-type detuned reactor (DDR) is a key component for power quality management. Improper design of DDR may result in insulation failure during power system transient events. This can be avoided by developing a proper DDR high frequency model that can accurately capture the behavior of the reactor during transients and provide better insight into its performance under various operating conditions. One of the main challenges of proper DDR modeling is the shape of the leakage flux, which is strongly dependent on the shielding effect of the foil conductors and hence affecting the winding frequency response at high frequencies. This paper proposes a high-frequency lumped equivalent circuit model for DDR with frequency-dependent parameters. The frequency-dependent inductances and resistances are calculated using anisotropic equivalent complex permeability to represent the damping effects in the core and winding. A combined analytical-finite element modelling approach is employed to calculate the winding capacitances. The accuracy of the proposed model is verified by comparing its frequency response with the experimental results obtained from a laboratory prototype. Furthermore, the impulse voltage distribution within the windings is obtained through simulation and measurement analyses to attest the robustness of the proposed model. The proposed model is expected to aid in the proper design and optimization of DDR to improve its insulation withstand capability and enhance its performance during transient events within power grids.

Frequency Dependence of Parameters of an Inductive RF Discharge Placed in a Weak Magnetic Field

Frequency Dependence of Parameters of an Inductive RF Discharge Placed in a Weak Magnetic Field

Evaluation of synthesized new cellulose derivatives to make diodes and investigation of electrical and photoelectrical characteristics of these diodes

Firstly, two new cellulose derivatives (CelB33′44′TD and Cel44′OA) were synthesized, which were confirmed by FTIR and 13C CP-MAS NMR spectra. These derivatives were then used in the construction of new diodes (Au/CelB33′44′TD/p-Si and Au/Cel44′OA/p-Si). Later, the atomic force microscope (AFM) images of the interface layers were taken, and the current–voltage (I–V) graphs of the diodes were determined both in the dark and under different illumination intensities (DIIs). Using the Bethe's thermionic emission (TE) theory the ideality factors and barrier heights of the diodes, using the Cheung & Cheung functions the ideality factors, series resistances and barrier heights of the diodes, and using the Norde function the barrier heights and series resistances of the diodes were calculated. Finally, the capacitance–voltage (C–V) and conductance–voltage (G–V) graphs of the diodes at different frequencies (DFs) were examined and some frequency-dependent electrical parameters of the diodes were calculated using the 1/C2–V plots.

Frequency response of dielectric relaxation modes in a room temperature antiferroelectric phase liquid crystalline mixture

Thermodynamic, optical, and electrical characterization of a newly formulated mixture of chiral mesogenic molecules has been carried out. The material exhibits different mesophases like paraelectric smectic (SmA*), ferroelectric chiral smectic (SmC*) with synclinic structure, and wide temperature range antiferroelectric chiral smectic (SmCa*) with anticlinic structure. These studies show that at room temperature, the SmCa* phase is present in a wide temperature range of ∼128 °C (from −35.0 °C to 92.6 °C) followed by the SmC* phase (from 92.6 °C to 110.8 °C) as well as SmA* phase (from 110.8 °C to 113.9 °C). Besides the wide temperature range, the SmCa* phase has also been optimized for high helical pitch length, which is useful for helix unwound cells through surface stabilization for application. Frequency-dependent dielectric parameters have been determined for the material in the frequency range of 1 Hz to 40 MHz. The dielectric spectroscopy shows six different relaxation modes in various phases due to the collective and individual molecular behavior. The SmA* phase exhibits soft mode relaxation associated with variations in the amplitude of the tilt angle. The identified soft mode is significantly temperature-dependent. Using the Curie-Weiss law, the transition temperature for the paraelectric SmA* phase to the ferroelectric SmC* phase (Tc) is found to be 111.4 °C. Two relaxation modes in the SmC* phase have been identified Goldstone mode and a domain mode. These modes have extremely high dielectric strength resulting in high permittivity in comparison with other modes. Three modes of relaxation have been detected in the antiferroelectric SmCa* phase. Different characteristic parameters of these modes are strongly temperature-dependent. This study signifies that the present room-temperature antiferroelectric liquid crystals may be a potential candidate for display applications.

Algorithms for fast calculation of energization overvoltage of hybrid overhead line-cable transmission lines based on full frequency-dependent parameters

Algorithms for fast calculation of energization overvoltage of hybrid overhead line-cable transmission lines based on full frequency-dependent parameters

Passive Lumped Model With Frequency-Dependent Parameters for Multiconductor DC Cables

Passive Lumped Model With Frequency-Dependent Parameters for Multiconductor DC Cables

Characterizing the channel dependence of vegetation effects on microwave emissions from soils

ABSTRACT The two vegetation transfer parameters of (Vegetation Optical Depth,VOD) and (Omega) could vary significantly across microwave channels in terms of frequencies, polarizations, and incidence angles, and their channel-dependent characteristics have not yet been fully investigated. In this study, we investigate the channel dependence of vegetation effects on microwave emissions from soils using a higher-order vegetation radiative transfer model of Tor Vergata. Corn was selected as the subject of investigation, and a corn growth model was developed utilizing field data collected from the multifrequency and multi-angular ground-based microwave radiation experiment from the Soil Moisture Experiment in the Luan River (SMELR). Upon compilation of the simulation dataset of microwave emissions of the corn field, the effective scattering albedo across different channels were calculated using the Tor Vergata model. Results show that vertical polarization of the vegetation optical depth is more affected by incidence angle changes, while horizontal polarization exhibits lower variations in vegetation optical depth due to incidence angle adjustments. The channel dependence of vegetation optical depth can be described as the polarization dependence parameter () and the frequency dependence parameter (). These two parameters enable the calculation of vegetation optical depth at any channel under three adjacent frequencies (L-band, C-band and X-band). The effective scattering albedo of vegetation does not vary significantly with vegetation height or angle. It primarily depends on frequency and polarization, showing an overall increasing trend with increasing frequency. The effective scattering albedo with vertical polarization is slightly higher than that with horizontal polarization at higher frequencies, while both are lower in the L-band. This investigation is helpful for understanding the vegetation effects on microwave emissions from soils, ultimately advancing the accuracy of large-scale soil moisture retrieval in vegetated areas.

Correlated Electronic Structure of La_{3}Ni_{2}O_{7} under Pressure.

Recently, superconductivity with a T_{c} up to 78K has been reported in bulk samples of the bilayer nickelate La_{3}Ni_{2}O_{7} at pressures above 14GPa. Important theoretical tasks are the formulation of relevant low-energy models and the clarification of the normal state properties. Here, we study the correlated electronic structure of the high-pressure phase in a four-orbital low-energy subspace using different many-body approaches: GW, dynamical mean field theory (DMFT), extended DMFT (EDMFT) and GW+EDMFT, with realistic frequency-dependent interaction parameters. The nonlocal correlation and screening effects captured by GW+EDMFT result in an instability toward the formation of charge stripes, with the 3d_{z^{2}} as the main active orbital. We also comment on the potential relevance of the rare-earth self-doping pocket, since hole doping suppresses the ordering tendency.

Nondestructive evaluation of aircraft stealth coating by Terahertz-time domain spectroscopy: experimental and numerical investigation

ABSTRACT Particle-reinforced polymer matrix composites (PMCs) are often used as radar-absorbing materials (RAM) in aircraft stealth applications. The thickness evaluation of such multilayered coatings with micrometre-level thickness is highly challenging from single-side access. In this study, we used Terahertz Time-domain Spectroscopy (THz-TDS) in the transmission mode to extract the refractive index of the dielectric coatings for measuring the thickness using the time-of-flight method. A numerical study based on the Finite Element method (FEM) has also been developed to validate the transmission experiments. A frequency-dependent complex dielectric parameters must be considered for coatings with high absorption in the THz regime. This was addressed by performing the finite element simulations in a frequency domain. The thickness of each layer of a multi-layered coating is estimated by carrying out the experiments in reflection mode. Since the interface echoes were overlapping, a deconvolution algorithm and frequency thresholding were employed to reconstruct the signals reflected from the different interfaces. Using this technique, the thickness of each layer of coating is estimated accurately in a single measurement, which was challenging to measure using other conventional non-destructive testing (NDT) methods.