AC Current Research Articles

3D numerical simulation of magnetization loss in multifilamentary MgB2wires at 20 K

Abstract High-power density all-superconducting rotating machines have potential for application in electrical aircraft motors.
However, superconductors in the armature windings of such rotating machines carry AC currents under AC/rotating magnetic fields, resulting in AC losses For. reducing AC loss, low-cost, round magnesium diboride (MgB2) wires are one promising material due to their multifilamentary structure, fine filament size and tight twist. To date, previous 3D AC loss simulations have focused on MgB2 wires with a magnetic matrix operating at low frequency and 4.2 K, which are not relevant to aviation applications. In this work, 3D simulations of magnetization loss at 20 K of twisted 2-filament and 54-filament wires with a non-magnetic matrix are carried out using the finite element method, based on the H-formulation, with AC field amplitudes from 0.1 T to 2 T and frequencies up to 200 Hz. The measured Jc(B, 20 K) and n(B, 20 K) data of a non magnetic MgB- 2 wiremanufactured by Hyper Tech Research is assumed as input parameters. For the 2-filament wire, the operational frequency,the twist pitch, the filament size, the matrix resistivity, and inter-filament gap have been varied to systematically study their impacts on magnetization loss and its loss components (hysteresis loss, coupling loss and eddy currents). The simulation results show that the 2-filament wire with a 5 mm twist pitch and a higher resistivity matrix operated at 50 Hz has the lowest magnetization loss through decoupling the filaments. Furthermore, a lower coupling loss at 200 Hz for field amplitudes exceeding 1 T is observed, this is because critical coupling frequency fc shifts to small values with increasing field amplitudes. For the 54-filament MgB2 wire, the magnetization loss of a 5 mm twist pitch and a higher resistivity matrix wire operated at 50 Hz is estimated. The simulations show that the hysteresis loss of the 54-filament wire can be well predicted by the analytical hysteresis loss equation for a cylindrical superconductor multiplied by 54 (the number of filaments) because the filaments are in an uncoupled state. Good agreement is also observed between the simulated coupling loss and the analytical coupling loss equation from Wilson book for a circular-arranged multifilamentary superconducting wire.

Numerical study of the synergetic current drive by lower hybrid waves and loop voltage

Abstract Thanks to the tail of fast electrons generated by the lower hybrid (LH) waves, the plasma conductivity changes significantly with respect to the ohmic heating status (Fisch 1985 Phys. Fluids 28 245). In this paper, the synergy effects of lower hybrid current drive (LHCD) in the presence of a DC electric field (namely, the loop voltage V loop ≠ 0) on the EAST tokamak are studied numerically using the ray tracing and Fokker–Planck tools of C3PO/LUKE. In addition to the normal case of a positive loop voltage with an asymmetric power spectrum (namely, co-current LHCD), the synergy effects of negative loop voltage with an asymmetric power spectrum (namely, counter LHCD), and positive/negative loop voltage with a symmetric power spectrum are also investigated, which are previously rarely reported. It is found that the total plasma conductivity can be increased by a factor of 1.68–2.18 (depending on the value of V loop) when a 1.1 MW LH power at 2.45 GHz with a symmetric power spectrum is injected. Furthermore, unlike the asymmetric power spectrum, the direction of the sum of the pure LH current (I lh0) and the synergetic current (I ad) resulting from the variation in plasma conductivity is always in line with the ohmic current (I oh) for a symmetric power spectrum, which is favorable for AC tokamak operation. These simulated results are helpful for LHCD applications, especially in current ramp-up and AC operation.

The electromagnetic field of a circular parallel plate capacitor excited by an AC current and AC voltage supply

Abstract This study investigates the electromagnetic field (EMF) distribution of an ideal circular parallel plate capacitor excited by a time-harmonic power source. Considering the lead wire and capacitor as a charged whole, we formulate the boundary value problems of the Helmholtz equation for the EMF in the lead wire space and capacitor space, respectively. First, we solve for the EMF generated by the total current in the lead wire space of an AC current. Following this, we solve for the EMF boundary value problem of a capacitor filled with linear, uniform, isotropic, and non-magnetic lossy dielectric under an AC current excitation, using the continuity of the total current as a basis. Second, the EMF distributions in the capacitor space and the lead wire space under an AC voltage excitation are provided, following the principles of the generalized Helmholtz theorem. Third, the EMF distribution is discussed when the electromagnetic ‘standing-wave phenomenon’ occurs in the ideal dielectric capacitor, and identify the ‘resonance phenomenon’ and the ‘current-stopping phenomenon’ of the capacitor's EMF when excited by an AC current and AC voltage, respectively. We also present the corresponding ‘resonance frequency’ and ‘current-stopping frequency’. Finally, we explore the quasi-stable solution of the capacitor's EMF under low-frequency condition and the static solutions of the electric and magnetic fields under DC excitation and static voltage excitation. Our findings suggest that the existing formula for the capacitor's EMF approximates our analytical solution under quasi-stable condition.

Development of an operational trap for collection, killing, and preservation of triatomines (Hemiptera: Reduviidae): the kissing bug kill trap.

Surveillance of triatomines or kissing bugs (Hemiptera: Reduviidae: Triatominae), the insect vectors of Trypanosoma cruzi, a Chagas disease agent, is hindered by the lack of an effective trap. To develop a kissing bug trap, we made iterative improvements over 3 years on a basic design resulting in 7 trap prototypes deployed across field sites in Texas, United States and Northern Mexico, yielding the capture of 325 triatomines of 4 species (Triatoma gerstaeckeri [Stål], T. sanguisuga [LeConte], T. neotomae [Neiva], and T. rubida [Uhler]). We began in 2019 with vertical transparent tarpaulin panel traps illuminated with artificial light powered by AC current, which were successful in autonomous trapping of flying triatomines, but were expensive, labor-intensive, and fragile. In 2020, we switched to white LED lights powered by a solar cell. We tested a scaled-down version of the vertical panel traps, a commercial cross-vane trap, and a multiple-funnel trap. The multiple-funnel traps captured 2.6× more kissing bugs per trap-day than cross-vane traps and approached the performance of the vertical panel traps in number of triatomines captured, number of triatomines per trap-day and triatomines per arthropod bycatch. Multiple-funnel traps required the least labor, were more durable, and had the highest triatomines per day per cost. Propylene glycol in the collection cups effectively preserved captured triatomines allowing for molecular detection of T. cruzi. The trapping experiments established dispersal patterns for the captured species. We conclude that multiple-funnel traps with solar-powered LED lights should be considered for adoption as surveillance and potentially mass-trapping management tools for triatomines.

Research on the Development of LDO Chip Technology

Abstract. Whether portable electronic devices are powered by rectified AC mains or by batteries, the power supply voltage will vary over a large range during operation. In order to ensure a stable power supply voltage, almost all electronic devices must be powered by a voltage regulator. In order to meet the requirements of precision electronic equipment, a linear regulator should be added to the input end of the power supply to ensure a constant power supply voltage and achieve active noise filtering. LDO can help achieve this function. This article first introduces the basic concepts of low-dropout linear regulators and sorts out the advantages of low-dropout linear regulators. Secondly, the parameters that need to be studied for LDO are sorted out, which are also the direction for breakthroughs in LDO research. The third part introduces some basic structures of LDO, including the design of LDO structure without external capacitors, the design of bandgap reference LDO structure, and the design of high PRSS structure. Finally, the application of LDO is roughly summarized, as well as the trends and challenges of LDO development.

Isostructural Oxamate Complexes with Visible Luminescence (Eu3+) and Field-Induced Single-Molecule Magnet (Nd3+).

The search for new metal-organic compounds as candidates for quantum information processing technologies is in the spotlight. Several metal ions and organic linkers have been used to obtain such compounds. Herein, we describe the synthesis, crystal structures, and cryomagnetic properties of two air-stable isostructural neodymium(III) and europium(III) one-dimensional (1D) coordination polymers of formula [Nd(Hmpa)3(DMSO)2]n (1) and [Eu(Hmpa)3(DMSO)2]n (2) [Hmpa=N-(4-methylphenyl)oxamate, and DMSO=dimethylsulfoxide]. These complexes were prepared by reacting n-Bu4N(Hmpa) proligand [n-Bu4N+=tetra-n-butylammonium] and the correspondent LnCl3 ⋅ 6H2O salt (Ln=Nd or Eu) in the open air and mild conditions. The crystal structures of 1 and 2 reveal the Ln3+ ion surrounded by two DMSO molecules and three oxamate ligands, one of them connecting to adjacent mononuclear entities through carboxylate bridges featuring a homometallic chain, while the other two establishing double N-H ⋅ ⋅ ⋅ O hydrogen bonds among adjacent polymers to give a resultant supramolecular 2D network. Cryomagnetic measurements in the static (dc) and dynamic current (ac) regimes reveal that 1 behaves as a field-induced single-molecule magnet below 8.8 K. A photoluminescence study shows that Hmpa ligands efficiently sensitize the luminescence of Eu3+ complex in the visible region in the solid state at room temperature.

Dynamic stability analysis of the aircraft electrical power system in the more electric aircraft concept

This paper presents the modelling and analysis process of the electrical power management system on board an electrified aircraft conforming to the More/All Electric Aircraft concept. The main objective of the study is to assess the stability of the Electric Power Distribution System under different operational conditions, including the aspect of constant power loads. The paper describes the structure of the system, in which the key role is played by a synchronous generator and a three-phase rectifier converting alternating current AC into direct current DC. To solve the problem, modeling methods in the Matlab/Simulink environment were used, which enabled the analysis of the dynamic properties of the system and the assessment of stability under various types of loads. The obtained test results show that the presence of constant power loads can lead to instability in the EPDS system, manifested by voltage and current oscillations exceeding the standards specified in the MIL-STD-704E standard. The paper also provides tools for predicting system stability without the need to conduct full stability tests, which is important for the design of modern aviation power systems. The final section of the work presents the research results obtained and the resulting significant insights and practical conclusions.

Investigation of slow magnetic relaxation in a series of 1D polymeric cyclobutane-1,1-dicarboxylates based on LnIIIVIV2 units (LnIII = Tb, Dy, Ho, Er, Tm, Yb): rare examples of VIV-4f single-molecule magnets.

The reactions of VOSO4·3H2O with Na2(cbdc) (cbdc2- - dianion of cyclobutane-1,1-dicarboxylic acid) and lanthanide(III) nitrates taken in a molar ratio of 1 : 2 : 1 were found to yield a series of isostructural heterometallic compounds [NaLn(VO)2(cbdc)4(H2O)10]n (1Ln, Ln = Tb, Dy, Ho, Er, Tm, Yb). These compounds are constructed from trinuclear anionic units [Ln(VO)2(cbdc)4(H2O)8]- ({LnV2}-) linked by Na+ ions into 1D polymeric chains. The crystal structures of 1Dy and 1Er were determined by single-crystal X-ray diffraction (XRD), and their isostructurality with 1Tb, 1Ho, 1Tm, and 1Yb was proved by powder X-ray diffraction (PXRD). According to alternating current (ac) magnetic susceptibility measurements, 1Dy, 1Er, and 1Yb exhibited field-induced slow relaxation of magnetization. Compound 1Er is the first representative of ErIII-VIV single-molecule magnets. Measuring the temperature dependences of the phase memory time (Tm) for 1Dy and 1Yb using pulsed EPR spectroscopy allowed us to observe the phenomenon of phase relaxation enhancement (PRE) at temperatures below 30 K. In future, this phenomenon may contribute to the evaluation of relaxation times of the lanthanide ions.

Critical current density and AC magnetic susceptibility of high-quality FeTe0.5Se0.5 superconducting tapes

Iron telluride-selenium superconducting materials, known for their non-toxicity, ease of preparation, simple structure, and high upper critical fields, have attracted much research interest in practical application. In this work, we conducted electrical transport measurements, magneto-optical imaging, and AC magnetic susceptibility measurements on FeTe0.5Se0.5 superconducting long tapes fabricated via reel-to-reel pulsed laser deposition. Our transport measurements revealed a high critical current density that remains relatively stable even with increasing external magnetic fields, reaching over 1 × 105 A/cm2 at 8 K and 9 T. The calculated pinning force density indicates that normal point pinning is the primary mechanism in these tapes. The magneto-optical images demonstrated that the tapes show homogeneous superconductivity and uniform distribution of critical current density. The AC magnetic susceptibility measurements also confirmed their strong flux pinning nature of withstanding high magnetic field. Based on these characteristics, FeTe0.5Se0.5 superconducting tapes show promising prospects for applications under high magnetic field.

Advanced Anti-icing and Deicing Strategies for Overhead Power Transmission Lines Based on Giant Magnetocaloric Effect of La0.7Ca0.254Sr0.046MnO3.

Perovskite manganates (AMnO3) exhibit diverse structural, thermal, electrical, and magnetic properties. Their strong magnetocaloric effect (MCE) near the Curie temperature (TC) makes them ideal for magnetic-thermal anti-icing and deicing in power transmission lines. Below TC, ferromagnetic AMnO3 produces heat through multiple mechanisms, with the changing magnetic field induced by the strong AC current, causing heat through magnetic hysteresis and eddy currents, alongside the direct MCE. Above TC, no heating is generated, as MCE is unfavorable, thus preventing additional energy loss at elevated temperatures. In this work, La0.7Ca0.254Sr0.046MnO3 with TC close to 0 °C were synthesized by solid-state reaction. It is found that particle size >10 μm is beneficial for a large MCE, based on the results of particle size dependence of MCE. The resulting maximum magnetic entropy change at 277 K is 7.69 J·kg-1·K-1, and an adiabatic temperature change of 3.87 K at 277 K is achieved under 5 T. The prototype cable is fabricated using a well-established wire drawing process. A climate-simulation chamber is employed for the anti-icing and deicing experiments. The prototype cables demonstrated a strong capability for deicing and anti-icing. This simple and cost-effective prototype cable shows significant potential for mitigating the icing problem of overhead high-voltage power transmission lines.

Miniaturized device to measure urease activity in the soil interstitial fluid using wenner method

This paper presents a microdevice developed to measure the electrical conductivity of a liquid or a saturated porous medium using Wenner method. It is developed in the context of biocementation as soil improvement technique, which is used in Civil Engineering applications to produce calcium carbonate through bacterial or enzymatic activity, replacing the use of other binder materials such as cement or resins, and therefore reducing carbon footprint. The microdevice was used to measure urease activity in the soil interstitial fluid, to investigate if bacterial activity could be affected by the presence of the particles and tortuosity from pore geometry. Such analysis is important to understand biocementation mechanism inside the soil and helps to improve the design of such treatment solutions. The device is basically a squared reservoir printed in polypropylene using a 3D printing machine, incorporating stainless steel electrodes in its base. The electrical resistivity was computed adopting Wenner method, by connecting 4 PCB electrodes to a signal generator and an oscilloscope for measuring the voltage when a AC current of 1 mA was applied. Both square and sinusoidal waves with 5 kHz frequency were selected among other frequencies. The measurements were adjusted during the calibration of the microdevice, done using standard salt solutions with known electrical conductivity measured using an electrical conductivity probe. For the bacterial activity measurements, the bacterial and urea solutions were added to a uniform-graded size quarzitic sand (average diameter 0.3 mm) placed inside the microdevice and covering completely the electrodes. Bacterial activity was not affected by the presence of the sand, which confirms that this treatment is effective for this type of soils.

Electromagnetic and thermal performance study on a canted stack of REBCO tapes

Abstract Due to the critical current limitation of a single REBCO tape, stacking methods are generally employed to increase the current carrying capacity in practical high-temperature superconducting (HTS) applications. However, the overall critical current is strongly dependent on the self-magnetic field, which is influenced by the geometrical arrangement of conductors in the stack. Due to the brittle ceramic property, REBCO tapes are conventionally bent along the thickness side of the tape. However, the difference in bending radii of the outer and inner tape surfaces in the stack may lead to fracture deformation, thereby limiting the stacking number of REBCO tapes. To balance the stacking number with the bending issue, canted stack is proposed as a variant of normal stack for REBCO tapes. As a potential HTS intermediate component, it is imperative to conduct a comprehensive study on electromagnetic and thermal performance of canted stack. The unique geometrical arrangement of canted stack introduces new factors that affect critical current and transport AC loss. This paper concludes the special influencing factors of canted stack, including canted angle, stacking number, tape width, and spatial structure. The metal interleaving method is introduced for spatial distribution changing and thermal stability. Furthermore, orthogonal analysis is performed to elucidate the comprehensive correlation among these multiple factors. This study provides insights into the overall critical current and transport AC loss for different combinations of canted stack and establishes a predicting function for critical current to support the structural design of canted stack. Based on the specific case study, the improvement effect of canted stack is confirmed by both experiments and simulations.

Triple-Decker Hexaazamacrocyclic Lanthanide(III) Complexes: Structure, Magnetic Properties, and Temperature-Dependent Luminescence.

The reaction of fluoride anions with mononuclear rare-earth(III) complexes of the hexaazamacrocycle derived from 2,6-diformylpyridine and ethylenediamine affords trinuclear coordination compounds [Ln3L3(μ2-F)4(NO3)2](NO3)3. The X-ray crystal structures of these complexes show triplex cationic complexes where the three roughly parallel macrocyclic lanthanide(III) units are linked by bis-μ2-F bridges. The detailed analysis of the photophysical properties of the [Eu3L3(μ2-F)4(NO3)2](NO3)3·2H2O and [Tb3L3(μ2-F)4(NO3)2](NO3)3·3H2O complexes reveals different temperature dependence of luminescence intensity and luminescence decay time of the Eu(III) and Tb(III) derivatives. The spectra of mixed species of average composition [Eu1.5Tb1.5L3(μ2-F)4(NO3)2](NO3)3·3H2O are in accordance with the ratiometric luminescent thermometer behavior. Measurements of the direct-current (dc) magnetic susceptibility of the [Dy3L3(μ2-F)4(NO3)2](NO3)3·2H2O complex indicate possible ferromagnetic interactions between the Dy(III) ions. Alternating current (ac) susceptibility measurements of this complex indicate single-molecule magnet behavior in zero dc field with magnetic relaxation dominated by Orbach mechanism and an effective energy barrier Ueff = 12.3 cm-1 (17.7 K) with a pre-exponential relaxation time, τ0 of 7.3 × 10-6 s. A similar reaction of mononuclear macrocyclic complexes with a higher number of fluoride equivalents results in polymeric {[Ln3L3(μ2-F)5](NO3)4}n complexes. The X-ray crystal structure of the Nd(III) derivative of this type shows trinuclear units that are additionally linked by single fluoride bridges to form a linear coordination polymer.

Efficient power factor correction in single phase AC–DC boost converter for retrofitted electric bicycle battery charging: A finite element analysis approach

This research paper describes modifying a conventional bicycle into an electric bike by retrofitting it with a single-phase boost power factor correction (PFC) rectifier for low power battery chargers. The proposed work was designed and developed in a single stage, as opposed to the traditional two-stage chargers used to charge E-bicycle, to provide the desired outcomes of enhanced efficiency, good power quality, and dependability due to the charger's lower cost. Additionally, the proposed converter uses a single switch, which reduces not necessary body diode conduction and circulating current and enhances the PFC device's thermal management. Additionally, this research makes use of the diode bridge rectifier (DBR) arrangement, which offers low current stress and is suitable for electric bicycles. The converter operates at a low cost with reduced magnetics (DCM) by operating the charger in discontinuous conduction mode at such low voltage levels. It also accomplishes intrinsic power factor at the ac mains by employing a simple control method to maintain the battery in high power density constant current (CC) and constant voltage (CV) states. A thorough state space investigation is carried out in combination with modeling and testing to ensure that the electric bicycle charger operates effectively. Consequently, low power chargers are a good fit for the proposed single stage front-end converter, and a 250 W hardware prototype is used to verify the findings.

Finite Element Analysis in The Investigation of Methods to Model AC Resistance in A Coated Conductor

In our electricity dependent and rapidly automated society, the manipulation and usage of electricity to transmit energy is of significant prevalence. In particular, the application of current in high frequency transformers, inductors and motor generators presents a unique efficiency problem: The loss of energy through the spiking of effective resistance intrinsically related to the skin and proximity effects of an AC current. By the usage of Finite Element Analysis (FEA) in the simulative investigation of various variables on AC resistance, this paper seeks to provide insights into how coated conductors might offer advantages over the standard conductor in certain conditions, thus guiding future design and application in high-efficiency electronics. The papers findings reveal that adding a layer of coating with a lower conductivity than the core material could offer reduced energy losses up to the point when the skin depth matches the coating’s thickness. Moreover, the study explored the influence of the coating’s conductivity, suggesting that an increased conductivity of the coating material could further minimize copper losses, albeit with the trade-off of potentially higher costs. The study concludes with a Taylor Series approximation of the relationship between AC resistance and frequency using simulative data.

Short-Term forecasting of floating photovoltaic power generation using machine learning models

Floating photovoltaic (FPV) power generation requires accurate short-term forecasting to optimize operational efficiency and enhance grid integration. This study investigates the application of machine learning models for predicting FPV power generation using data from the Universiti Malaysia Pahang Al-Sultan Abdullah (UMPSA) solar installation, which has a capacity of 157.20 kWp. Data were collected at 15-minute intervals from January 15 to January 21, 2024, encompassing nine input features such as ambient temperature, transient horizontal irradiation, daily horizontal irradiation, AC voltages, and AC currents for phases A, B, and C, with the total active power in kW as the target variable. The dataset was divided into a training set (first five days) and a testing set (remaining two days), and five machine learning models—Neural Networks (NN), Random Forest (RF), Extreme Learning Machine (ELM), Support Vector Regression (SVR), and Long Short-Term Memory (LSTM)—were employed. The results indicate that the Neural Networks model consistently outperforms the other machine learning algorithms in terms of predictive accuracy. These findings underscore the efficacy of machine learning techniques in forecasting FPV power generation, which has significant implications for enhancing the operational efficiency and grid integration of floating solar installations.

Wattmeter based on tunnel-effect magnetoresistance sensor.

This work shows how the tunnel-effect based magnetoresistance (TMR) technology can be used as a competitive sensing method in electrical current and power processors. The sensor is arranged in a Wheatstone bridge topology, and each magnetoresistance was composed of a series connection of 360 magnetic tunnel junction elements with the following structure (thickness in nm): 100 SiO2/5 Ta/15 Ru/5 Ta/15 Ru/5 Ta/5 Ru/20 IrMn/2 CoFe30/0.85 Ru/2.6 CoFe40B20/1.2 MgO/2 CoFe40B20/0.21 Ta/4 NiFe/0.20 Ru/6 IrMn/2 Ru/5 Ta/10 Ru. First, the electrical and thermal characteristics of the sensor were evaluated by analyzing its response to DC current sweeps at various temperatures, controlled using a climatic chamber. Nominal values of current sensitivity S (0.324 mV/A), bridge output offset voltage Vo,s,o (-37.1 mV), bridge input resistance Rinp,bridge (0.958 kΩ), and their thermal behavior were obtained (0.0036 mV/A°C, 0.079 mV/°C, and -0.31 Ω/°C). Second, an instrumentation system is introduced to characterize the sensor, measuring its sensitivity to AC line currents from the mains up to 10Arms. Finally, an electronic wattmeter was developed showing the relevant quantities of its design. The circuit is able to interface a TMR Wheatstone bridge to an analog processor. Power and current measurements were obtained from a 150Vrms AC mains 1.5 kW load with resistive and capacitive components, achieving less than 1% deviation over the expected values. The circuit shown can be used to interface these signals to more complex smart digital engines with active or reactive energy processing capabilities, while providing inherent high voltage isolation, thanks to its TMR measurement technology.

Power factor preregulation in power supplies using modified single stage non-isolated interleaved Sepic converter with minimal part count

This paper pontificates on design and realization of low-cost single phase single stage modified interleaved Sepic (MILS) converter for power supplies. On contrary to the classical Sepic power converters, the introduced active power factor correction (APFC) converter involves simple idea of paralleling that enables low input and output ripples with minimal device count. The interleaving conceptualization also lessens current stresses and static losses. Also, this modified power processing converter reveals natural power factor correction (PFC) and zero current switching (ZCS) features by discontinuous conduction mode (DCM) operation. Furthermore, the practical corroboration of the proposed converter is built and tested for 250 W hardware model to affirm benefits with 92 % efficiency and their relevant outcomes are reported in this scope. Finally, the power quality (PQ) attributes like, input power factor (PF), total harmonic distortion (THD) over input current under stable and transient cases are disclosed to prove bettered PQ limits at the AC mains as prescribed by various IEEE-519 and IEC 61,000–3-2 standards.

A Study on the Problem of AC Corrosion of Power Umbilical Cables Caused by Electromagnetic Induction Phenomena

During the normal laying and operation of a three-core umbilical cable, AC current can easily lead to AC electrochemical corrosion on the outer surface of the steel tube. To explore the electrochemical corrosion mechanism and the factors affecting the three-core umbilical cable, this paper optimizes the internal induced potential calculation method for three-core umbilical cables. It analyzes the changes in the characteristics of the induced potential and explores the variations in the density of induced current under different conditions. The research results show that by optimizing the calculation method for the induction potential of the umbilical cable’s steel pipe, for the electromagnetic significance of the smallest repeating unit, the induction potential on the steel pipe’s surface exhibited a cyclic change. The peak part of the induction potential is most likely to experience electrochemical corrosion. Additionally, reducing the radius of the outer insulation aperture of the steel pipe and improving the conductivity of seawater will increase the density of the induced current in the insulation aperture, thereby increasing the risk of electrochemical corrosion. As the cable pitch and AC frequency increase, the current density in the steel pipe pores will also rise.

Exploring the structural characteristics and electrical conductivity of MnTiO3 across ferroelectric and paraelectric phases

In this study, we present the ceramic's structural, dielectric, and impedance characteristics obtained through the solid-state reaction method synthesis. Initial structural analysis was conducted utilizing X-ray diffraction at room temperature. The XRD results show that MnTiO3 exhibits rhombohedral symmetry. SEM images of MnTiO3 show the presence of both cubic and large agglomerated grains. This demonstrates the effectiveness of the dielectric HN model in controlling the mechanism. The alternating current (ac) conductivity, when examined in relation to frequency, displays a remarkable adherence to the Johnscher's power law. The change in electrical modulus and the width at half maximum (FWHM) of the curve indicate that the as-prepared sample exhibits a non-Debye relaxation mechanism. Both the temperature data and the frequency dependence of the impedance were used to analyze the electrical conductivity of the sample, which showed a negative temperature coefficient resistance (NTCR).