Electric Frequency Research Articles

A novel perspective of addressing the hydraulic dynamic imbalance in district heating network: The application of nonlinear programming

Hydraulic balance within the heating system's pipeline network is essential for efficient operation. Hydraulic imbalances can result in increased energy consumption and heat loss. Accordingly, a new dynamic hydraulic model has been developed, leveraging the topological structure of the network. This model incorporates the nonlinear constraints associated with flow coupling between electric valves and variable frequency pumps, with the objective of minimizing energy used in pump operation. It determines the optimal pump frequency and valve settings for operational adjustments. The model's predictive accuracy was validated using real operational data from a campus heating system. Additionally, it calculates the campus's ideal load and evaluates the potential for energy savings. Three adjustment strategies were established based on different temporal scales: hourly, day-and-night, and daily. Findings indicate that the optimized system offers substantial energy savings, particularly the hourly adjustment, which reduces pump energy consumption by 38.2 % and total system flow by 9.0 %. The day-and-night variable frequency was the next most effective, reducing pump energy consumption by 32.8 %, and total system flow by 7.6 %. The daily variable frequency strategy showed the least energy savings, with pump energy consumption by 25.0 %, and total system flow by 5.5 %. This dynamic hydraulic regulation optimization model serves as a valuable tool for developing intelligent heating systems.

Advanced ENF Region Classification Using UniTS-SinSpec: A Novel Approach Integrating Sinusoidal Activation Function and Spectral Attention

The electric network frequency (ENF), often referred to as the industrial heartbeat, plays a crucial role in the power system. In recent years, it has found applications in multimedia evidence identification for court proceedings and audio–visual temporal source identification. This paper introduces an ENF region classification model named UniTS-SinSpec within the UniTS framework. The model integrates the sinusoidal activation function and spectral attention mechanism while also redesigning the model framework. Training is conducted using a public dataset on the open science framework (OSF) platform, with final experimental results demonstrating that, after parameter optimization, the UniTS-SinSpec model achieves an average validation accuracy of 97.47%, surpassing current state-of-the-art and baseline models. Accurate classification can significantly aid in ENF temporal source identification. Future research will focus on expanding dataset coverage and diversity to verify the model’s generality and robustness across different regions, time spans, and data sources. Additionally, it aims to explore the extensive application potential of ENF region classification in preventing crimes such as telecommunications fraud, terrorism, and child pornography.

"Seeing" ENF From Neuromorphic Events: Modeling and Robust Estimation.

Most artificial lights exhibit subtle fluctuations in intensity and frequency in response to the influence of the grid's alternating current, providing the potential to estimate the Electric Network Frequency (ENF) from conventional frame-based videos. Nevertheless, the performance of Video-based ENF (V-ENF) estimation largely relies on the imaging quality and thus may suffer from significant interference caused by non-ideal sampling, scene diversity, motion interference, and extreme lighting conditions. In this paper, we show that the ENF can be extracted without the above limitations from a new modality provided by the so-called event camera, a neuromorphic sensor that encodes the light intensity variations and asynchronously emits events with extremely high temporal resolution and high dynamic range. Specifically, we formulate and validate the physical mechanism for the ENF captured in events and then propose a simple yet robust Event-based ENF (E-ENF) estimation method through mode filtering and harmonic enhancement. To validate the effectiveness, we build the first Event-Video ENF Dataset (EV-ENFD) and its extension EV-ENFD+ with diverse scenarios, including static, dynamic, and extreme lighting scenes. Comprehensive experiments have been conducted on our proposed datasets, showcasing that our proposed E-ENF significantly outperforms the V-ENF in extracting accurate ENF traces, especially in challenging environments.

An in-phase filter-based flux observation strategy for sensorless control of PMSMs

Due to the complexity of determining the initial rotor flux and detecting errors, conventional rotor flux observation methods are easily affected by direct current (DC) components and harmonics. To address this issue, this paper proposes an in-phase filter (IPF)-based rotor flux observation strategy for sensorless control of permanent magnet synchronous machines (PMSMs). The core components of the IPF consist of a double second-order generalized integrator (DSOGI) and a phase angle compensation transfer function (PACTF). The DSOGI provides a accurate electrical angular frequency, while the PACTF implements a phase correction to the vq′ signals. By employing IPF structure, accurate observations for rotor flux, electronic speed, and rotor position are achieved, which can be effectively used in the sensorless control of PMSMs, eliminating the need for magnitude and phase compensations. Finally, the proposed observation strategy is applied to an experimental bench of a PMSM, and its effectiveness is illustrated by experimental results. From experimental results, it can be concluded that the IPF is significantly better than the LPF, and 5% more accurate than the observer based on cascade second-order generalized integral(CSOGI) overall.

Modulating droplet electrohydrodynamics via the interplay of extensional flow and an alternating current electric field

Electric fields can be used to exert controlled time-varying forces on a droplet under progressive stretching in an extensional flow, allowing for its precise manipulation in various industrial and scientific applications, including microfluidics, materials science, and biological studies. However, the interaction between the combined extensional flow field and electric field may trigger a complex electrohydrodynamic response, as determined primarily by the capillary and viscous forces and the convection of surface charge. Here, we theoretically and computationally analyze the deformation and breakup of a droplet subjected to an alternating current (AC) electric field and uniaxial extensional flow. Our asymptotic theory, applicable in the small-deformation limit, quantifies the contributions of each applied field to the shape oscillations. Numerical simulations are employed to explore the dynamical evolution of the droplet in the nonlinear regime of variation in the capillary number. Our theoretical and numerical results are in excellent agreement, demonstrating that an AC electric field can significantly alter transient deformation depending on its magnitude and frequency. We identify the threshold frequency, dependent on the ratios of electrical properties, which can induce periodic oblate-prolate shape transitions. The interaction between viscous and electric stresses driving these transients is discussed. Contrary to intuition, strong electric fields greatly suppress shape oscillations, leading instead to large continuous elongations that eventually result in an end-pinching breakup mode, forming elongated bulbous-ended droplets. The breakup state, characterized by droplet length and shape at the onset of breakup, is determined by the field parameters and the physical properties of the fluids. Notably, the breakup state length and total breakup time have a non-monotonic relationship with the applied electric field frequency. The insights gained into the physics of oscillatory stable deformation and non-oscillatory unstable deformation offer new means of droplet manipulation in droplet-based micro-mechano-electrical systems that remained unexplored thus far.

Interaction of pans and groundwater: A case study in the Khakhea- Bray Transboundary aquifer portion in South Africa

Understanding the groundwater-surface water interaction is important for the sustainable management of water resources and ecology. Most of the studies on groundwater-surface interactions are confined to aquifer-river and aquifer-lake interactions. The interactions of water pans and groundwater have not received much attention. The study aims to provide insights into the interaction of the pans and groundwater at a case study in the Khakhea-Bray dolomite Transboundary Aquifer (TBA) shared by Botswana and South Africa. The study uses field observations, geology, hydrogeophysics, and stable isotopes complimentary tools. Complimentary tools provide several evidence to corroborate the findings. The hydrogeophysics taps into the recently developed Telluric Electric Frequency Selection Method (TEFSM). Groundwater discharge zones/springs were delineated at the geological contact of the boundary of the Khakhea-Bray dolomite transboundary aquifer and the granite of the Kalahari group. 4 of the 33 research pans are in the groundwater discharge zone and are classified as groundwater dependent. The findings highlight the benefits of complimentary approaches to corroborate the findings on groundwater-surface water interactions. The TEFSM hydrogeophysics can be able to delineate groundwater discharge zones, aquifer boundaries, and the mapping of TBAs. More studies are recommended to test the TEFSM hydrogeophysical approach to study groundwater-surface water in different hydrological environments.

High voltage pulsed electric field: A novel method for killing parasitic eggs on the surface of raisins

Aiming to address the issue of stored grain pests easily breeding during the process of dried fruits in Xinjiang, this study proposes a method and a device for killing raisin parasitic eggs based on a high-voltage pulsed electric field. A one-way test and a Box-Behnken central combination test were conducted to investigate the effects of high-voltage pulsed electric field strength and frequency on the unhatched rate and larval survival rate of Plodia interpunctella eggs on raisin surfaces. The experimental results were qualitatively and quantitatively analyzed using biooptical microscope observation and incubation at constant temperature and humidity post-treatment. The findings revealed that with an output voltage of 22.8 kV, the delivery speed of 0.024 m/s, and the electric field frequency of 3.8 Hz, the unhatched rate of the eggs was 68.14 % while the survival rate of the larvae was 20.36 %. These results can provide new insights for both theoretical development and system implementation regarding the use of high voltage pulsed electric fields for eliminating raisin surface eggs, as well as providing valuable academic references for field crop diseases and pests control strategies.

Interpretable machine learning for understanding compositional and testing condition effects on refractive index, density, dielectric constant, and loss tangent of inorganic melts and glasses

Artificial intelligence (AI) and machine learning (ML) have enabled property-targeted design of glasses. Several machine learning models and open-source tools in the literature allow researchers to predict the optical, physical, mechanical, and electrical properties of glasses as a function of their chemical compositions. However, these properties also depend on testing conditions. In this paper, we train machine learning models by considering composition and wavelength, temperature, and frequency to predict the refractive index, density, and the two electrical properties, i.e., dielectric constant and loss tangent of glasses, respectively. The predictions of trained models are explained using SHAP analysis, revealing that testing conditions, such as wavelength and temperature, interact majorly with network formers while predicting refractive index and density. In the case of electrical properties, network formers and frequency have the highest interactions, followed by network modifiers and intermediates, and hence govern predictions of dielectric constant and loss tangent. Overall, AI/ML models that can predict the properties of glasses as a function of their composition and testing conditions, coupled with SHAP plots, provide a practical tool to develop a range of glasses for application under varying conditions.

System Design, Modelling, Energy Analysis, and Industrial Applications of Ohmic Heating Technology

AbstractThe food and drink industry is gradually gaining sustainability pressure due to the high carbon emissions rate and limited availability of traditional energy supplies. Thus, it is essential to consider energy efficiency and decarbonisation of the ever-expanding food and drink industry. Ohmic heating technology is a highly energy-efficient and quick method of electrically heating food products. It uses the resistance of the food material to convert electrical energy into heat. However, the heating rate of ohmic heating depends on several process variables, such as electrical conductivity, voltage gradient, and voltage frequency. Therefore, it is important to study and understand the effects of these process variables to optimise the modelling and control of ohmic heating systems to obtain desirable output from food products. Hence, this study presents a review of the effects of process parameters on nutritional and organoleptic qualities, product yields, and energy efficiency of ohmic heating, along with its various industrial applications. The technology shows promising advancements in colour and nutritional quality, increasing energy efficiency, shorter processing times, and higher product yields compared to conventional heating processes.

Uptake of substances into living mammalian cells by microwave induced perturbation of the plasma membrane

Delivering foreign molecules and genetic material into cells is a crucial process in life sciences and biotechnology, resulting in great interest in effective cell transfection methods. Importantly, physical transfection methods allow delivery of molecules of different chemical composition and are, thus, very flexible. Here, we investigated the influence of microwave radiation on the transfection and survival of mammalian cells. We made use of an optimized microwave-poration device and analyzed its performance (frequency and electric field strength) in comparison with simulations. We, then, tested the effect of microwave irradiation on cells and found that 18 GHz had the least impact on cell survival, viability, cell division and genotoxicity while 10 GHz drastically impacted cell physiology. Using live-cell fluorescence microscopy and image analysis, we tested the uptake of small chemical substances, which was most efficient at 18 GHz and correlated with electric field strength and frequency. Finally, we were able to obtain cellular uptake of molecules of very different chemical composition and sizes up to whole immunoglobulin antibodies. In conclusion, microwave-induced poration enables the uptake of widely different substances directly into mammalian cells growing as adherent cultures and with low physiological impact.

Electrokinetic particle trapping in microfluidic wells using conductive nanofiber mats.

The frequency dependence of electrokinetic particle trapping using large-area (>mm2) conductive carbon nanofiber (CNF) mat electrodes is investigated. The fibers provide nanoscale geometric features for the generation of high electric field gradients, which is necessary for particle trapping via dielectrophoresis (DEP). A device was fabricated with an array of microfluidic wells for repeated experiments; each well included a CNF mat electrode opposing an aluminum electrode. Fluorescent microspheres (1µm) were trapped at various electric field frequencies between 30kHz and 1MHz. Digital images of each well were analyzed to quantify particle trapping. DEP trapping by the CNF mats was greater at all tested frequencies than that of the control of no applied field, and the greatest trapping was observed at a frequency of 600kHz, where electrothermal flow is more significantly weakened than DEP. Theoretical analysis and measured impedance spectra indicate that this result was due to a combination of the frequency dependence of DEP and capacitive behavior of the well-based device.

Synchronously coupled magnetic field weakening the dynamic deformation response of salt-containing droplet to an electric field

Combining a magnetic field with an electric field offers a promising approach for enhancing oil–water separation, yet its underlying mechanisms are not fully understood. We systematically investigated the dynamic deformation of salt-containing water droplet suspended in oil under an electric–magnetic coupling field. Integrating high-speed camera experiments with molecular dynamics simulations, we found that the dynamic response amplitude of droplet is reduced compared to a single electric field. Our analysis suggests that ions deflect under electric–magnetic coupling, affecting ion enrichment and water molecule polarization, thereby weakening droplet tip charge and induced electric forces, which suppresses droplet deformation. Increasing the electric capillary number and ion concentration enhances suppression, whereas improving the electric field frequency to 500 Hz almost eliminates this suppression effect. Notably, the degree of droplet deformation inhibition remains consistent across different viscosity ratios. These research findings offer insights for designing dehydrators to intensify oil–water separation.

Catalytic activity of chitinase encapsulated with alginate and its application in a biosensor for postharvest fungal detection

This research aimed to preserve the chitinase catalytic activity using alginate and zinc oxide nanoparticles (ZnO-NPs), to evaluate its thermal stability at 37 ºC, 50 ºC, and 70 ºC and its ability to detect Rhizopus stolonifer, Colletotrichum fragariae, and Alternaria alternata in a capacitive transducer-based biosensor. The ZnO-NPs measured less than 100 nm. The phosphate buffer-citric acid was a better solvent than water. Al+ZnONPs Ch showed the highest thermal stability at 37 ºC and 50 ºC (2 IU) for 45 d. Conversely, the free enzyme lost its activity from day 1–28 at 37 ºC (3.3 IU-2.8 IU), and alginate-encapsulated chitinase (AlCh) had the lowest activity at 50 ºC during 45 d (1.3 IU). Chitinase, alginate, and the ZnO-NPs were confirmed for FTIR spectra. The Al+ZnONPs Ch had the best response in the biosensor, observing a decrease in electrical frequency when the concentration of the tested fungi increased (106 spores mL−1 =100–250 kHz and 104 spores mL−1 = 400 kHz). In conclusion, at 37 ºC and 50 ºC, the chitinase had a stable catalytic activity compared to the remaining treatments, and it could be used to detect fungi in a biosensor at concentrations from 103 to 106 spores mL−1.

Bandgap Calculation and Experimental Analysis of Piezoelectric Phononic Crystals Based on Partial Differential Equations.

Focusing on the bending wave characteristic of plate-shell structures, this paper derives the complex band curve of piezoelectric phononic crystal based on the equilibrium differential equation in the plane stress state using COMSOL PDE 6.2. To ascertain the computational model's accuracy, the computed complex band curve is then cross-validated against real band curves obtained through coupling simulations. Utilizing this model, this paper investigates the impact of structural and electrical parameters on the bandgap range and the attenuation coefficient in the bandgap. Results indicate that the larger surface areas of the piezoelectric sheet correspond to lower center bands in the bandgap, while increased thickness widens the attenuation coefficient range with increased peak values. Furthermore, the influence of inductance on the bandgap conforms to the variation law of the electrical LC resonance frequency, and increased resistance widens the attenuation coefficient range albeit with decreased peak values. The incorporation of negative capacitance significantly expands the low-frequency bandgap range. Visualized through vibration transfer simulations, the vibration-damping ability of the piezoelectric phononic crystal is demonstrated. Experimentally, this paper finds that two propagation modes of bending waves (symmetric and anti-symmetric) result in variable voltage amplitudes, and the average vibration of the system decreases by 4-5 dB within the range of 1710-1990 Hz. The comparison between experimental and model-generated data confirms the accuracy of the attenuation coefficient calculation model. This convergence between experimental and computational results emphasizes the validity and usefulness of the proposed model, and this paper provides theoretical support for the application of piezoelectric phononic crystals in the field of plate-shell vibration reduction.

The Impact of Electrical Muscle Stimulation Frequency on Lower Limb Strength and Muscular Endurance During Squats

The Impact of Electrical Muscle Stimulation Frequency on Lower Limb Strength and Muscular Endurance During Squats

Flow Analysis of Centrifugal Compressor using ANSYS

Abstract: The aerodynamic and structural designs of the impeller are vital to the functioning of the entire compressor stage in centrifugal compressors. In contrast to previous years, there has been a greater demand for industrial centrifugal compressors to operate with greater efficiency and operational range. Although the efficiency of low-pressure-ratio centrifugal compressors has nearly achieved its maximum, intermediate and high-pressure ratio machines still lag behind the state-of-the-art in terms of efficiency. Maintaining maximum efficiency while extending the working range is a challenging task in centrifugal compressor design. Furthermore, a single design must be usable globally due to product globalisation, even in the face of technological disparities and variances in electricity frequency of up to 10 percent in some nations. Often operating at different rotational speeds, centrifugal compressors add another layer of complexity to the impeller structural design. A full-3D impeller design that is optimised for both structural integrity and aerodynamic performance is shown in this study .For air conditioning systems of the future, centrifugal compressor performance must be improved. This research focusses on systematic numerical simulation, a computationally efficient method of optimising centrifugal compressor performance. ANSYS simulations are used in conjunction with a thorough literature review on the aerodynamic behaviour of materials used in centrifugal compressors. For the purpose of performing flow simulations under subsonic circumstances with suitable boundary conditions and grid independence checks, geometric modelling was completed using CATIAV5R22 and imported into ANSYS. Tests were conducted using various aluminium materials and mass flow rates, and enhanced efficiency findings were confirmed by comparison with experimental data. Materials Processing and Characterisations is in charge of peer review.

Frequency response sensitivity to crack for piezoelectric FGM beam subjected to moving load

Since functionally graded material (FGM) is increasingly used in high-tech engineering, free and forced vibrations of FGM structures become an important issue. This report addresses the analysis of frequency response sensitivity to crack for piezoelectric FGM beams subjected to moving load. First, a frequency domain model of a cracked FGM beam with a piezoelectric layer is conducted to derive an explicit expression of the electrical charge produced in the piezoelectric layer under the moving load. It was shown in the previous works of the authors that the electrical charge is a reliable representation of the beam frequency response to moving load and can be efficiently employed as a measured diagnostic signal for structural health monitoring. Then, a damage indicator acknowledged as a spectral damage index (SDI) calculated from the electrical frequency response is introduced and used for sensitivity analysis of the response to crack. Under the sensitivity analysis the effect also of FGM and moving load parameters on the sensitivity is examined and illustrated by numerical results.

Operation strategy and capacity configuration of digital renewable energy power station with energy storage

As the utilization of renewable energy sources continues to expand, energy storage systems assume a crucial role in enabling the effective integration and utilization of renewable energy. This underscores their fundamental significance in mitigating the inherent intermittency and variability associated with renewable energy sources. This study focuses on the involvement of photovoltaic (PV) plants in medium and long-term transactions. It also explores the participation of battery energy storage system (BESS) in electricity trading and frequency regulation ancillary services. The objective is to establish a strategic research model for maximizing the benefits of PV plant and the BESS in the energy arbitrage and frequency regulation markets. Sensitivity analysis was conducted to assess the impact of variations in both the rated power and maximum continuous energy storage duration of the BESS. Base on the NSGA-II algorithm and TOPSIS algorithm, an optimization model for energy storage capacity configuration is developed. The optimal capacity configuration and maximum continuous energy storage duration are determined through computational analysis, yielding values of 30.8 MW and 4.521 h, respectively. At this configuration, the daily average revenue is 2.362 × 105 yuan, the initial investment cost is 1.45 × 109 yuan, and the payback period is 4.562 years.

Flexural–torsional modal interaction in MEMS actuators initiated by minuscule asymmetry

AbstractAn efficient actuation technique for electrostatic MEMS actuators exploiting electro-mechanical-mechanical modal interactions is proposed. The flexural–torsional equations of motion are established, and we manifest that the initiation of a 2:1 autoparametric modal interaction between in-plane bending and torsional modes of the actuator that is supposed to be symmetrical with respect to its axis of rotation is contingent upon the presence of a quadratic stiffness term, which arises from the existence of non-zero first moments of area of the actual cross-section in prismatic microbeams. In order to efficiently reduce the AC voltage value required to reach the activation of the 2:1 mechanical modal interaction, the electrical resonant frequency is syntonized to half of the natural frequency of the in-plane bending mode. The results indicate that the amplitude of the in-plane motion saturates upon the initiation of an energy exchange between the bending and torsional motions. Through suitable tuning of the AC frequency, the amplitude of the in-plane motion is minimized, while the amplitude of the torsional motion, the indirectly excited mode, is maximized. Our results demonstrate that the actuator's torsional motion, when subjected to a 1:2:1 electro-flexural–torsional modal interactions, is triggered by applying a maximum voltage of 10 V, resulting in about 20 degrees rotational angle. Furthermore, prolific frequency combs are generated as a result of secondary Hopf bifurcations along the large-amplitude response branches, inducing quasi-periodicity in the MEMS dynamics.

New Regime of Inertial Alfvén Wave Turbulence in the Auroral Ionosphere.

We investigate a new regime of inertial Alfvén wave turbulence observed in the very low beta plasma of the auroral ionosphere using electric and magnetic field measurements by the TRICE-2 sounding rocket. Combining the observed features of the electric and magnetic field frequency spectra with the linear properties of inertial Alfvén waves, we deduce the path of the anisotropic turbulent cascade through wave vector space. We find a critically balanced cascade through the magnetohydrodynamic scales of the inertial range down to the perpendicular scale of the plasma skin depth, followed by a parallel cascade to the ion inertial length. We infer damping of the cascade by a combination of proton cyclotron damping and electron Landau damping.