Field Curves Research Articles

Noise Elimination for Wide Field Electromagnetic Data via Improved Dung Beetle Optimized Gated Recurrent Unit

Noise profoundly affects the quality of electromagnetic data, and selecting the appropriate hyperparameters for machine learning models poses a significant challenge. Consequently, the current machine learning denoising techniques fall short in delivering precise processing of Wide Field Electromagnetic Method (WFEM) data. To eliminate the noise, this paper presents an electromagnetic data denoising approach based on the improved dung beetle optimized (IDBO) gated recurrent unit (GRU) and its application. Firstly, Spatial Pyramid Matching (SPM) chaotic mapping, variable spiral strategy, Levy flight mechanism, and adaptive T-distribution variation perturbation strategy were utilized to enhance the DBO algorithm. Subsequently, the mean square error is employed as the fitness of the IDBO algorithm to achieve the hyperparameter optimization of the GRU algorithm. Finally, the IDBO-GRU method is applied to the denoising processing of WFEM data. Experiments demonstrate that the optimization capacity of the IDBO algorithm is conspicuously superior to other intelligent optimization algorithms, and the IDBO-GRU algorithm surpasses the probabilistic neural network (PNN) and the GRU algorithm in the denoising accuracy of WFEM data. Moreover, the time domain of the processed WFEM data is more in line with periodic signal characteristics, its overall data quality is significantly enhanced, and the electric field curve is more stable. Therefore, the IDBO-GRU is more adept at processing the time domain sequence, and the application results also validate that the proposed method can offer technical support for electromagnetic inversion interpretation.

Advances in Cryptographic Algorithms: The Mathematics behind Secure Communication

This research discusses the mathematical aspects and evolution of cryptographic algorithms and underlines the importance of these principles for current digital communication protection. Cryptography uses algorithms from mathematical areas like modular arithmetic, finite field and elliptic curve to ensure that data being transferred is coded and decoded. Consequently, the contexts of symmetric algorithms such as AES or asymptotic systems like RSA and ECC are analyzed with reference to their mathematical components and usage. It also assesses the time complexity, security in general, and weak points of these algorithms using the backdrop of current and future risks such as those posed by quantum computing. Quantum technologies produce great difficulties for original cryptographic systems, which leads to the need to create quantum-secure ones. The project discusses selected post-quantum cryptographic techniques like lattice based, code based, and hash based cryptographic technique and evaluates if these can provide security in post-quantum world. Furthermore, the importance of cryptographic algorithm used in various sectors like business finance, healthcare units, blockchain technology, and other security-based sectors are discussed including how it has revolutionized the field of secured communication systems. Consequently, the results highlighted the role of mathematical creativity in enhancing cryptographic defense, repairing the flaws, and preparing for the subsequent technology change. In this light, this project enriches the comprehension of the dynamics of utilizing cryptography in securing digital systems from theoretical research to implementation.

A Comprehensive Study of Ferroelectric Properties of Fluorite-Structured Hf1-XZrxO2 Thin Films Grown on Mo Electrode with Various Thicknesses and Compositions

Since ferroelectricity in Si-doped HfO2 was first reported in 2011,[1] HfO2-based thin films have attracted significant attention as an emerging material for ferroelectric devices due to their advantages such as scalability and compatibility with Complementary Metal-Oxide-Semiconductor (CMOS) processes. Generally, TiN has been used as electrode material in semiconductor processes. However, other electrode materials such as W and Mo have attracted increasing interest for HfO2-based ferroelectric thin films due to their higher remanent polarization (Pr) than the TiN electrode.[2 ,3 ] Recently, it has been reported that Mo electrodes can be easily oxidized even at low temperatures such as atomic layer deposition (ALD) processes, and the formed MoOx layer can sufficiently act as the oxygen supplier, resulting in the larger orthorhombic phase fraction and higher remanent polarization compared with TiN electrodes.[3] Nevertheless, the effect of the film thickness and composition on the ferroelectric properties of HZO thin films grown on Mo electrodes is yet to be elucidated. Therefore, in this study, the electrical, physical, and chemical properties of HZO films with various thicknesses (6 – 11 nm) and Zr/(Hf+Zr) ratios (0.5 – 0.7) are examined.In the case of the HZO films grown on the TiN electrode, when the film thickness decreases or the Zr/(Hf+Zr) ratio increases, the switchable polarization (2Pr) decreases with a distortion of polarization-electric field (P-E) curves owing to the increased fraction of the antiferroelectric tetragonal phase. However, 2Pr as high as 57.5 µC/cm2 on the Mo electrode could be achieved even in the 7.6 nm-thick Hf0.4Zr0. 6O2 thin film with a little distortion of the P-E curve. The highest 2Pr of 68.3 µC/cm2 was observed in the 10.9 nm thick Hf0.4Zr0. 6O2 film, which is 31.3 % higher than the highest 2Pr (52.0 µC/cm2) of the HZO thin film on TiN reported so far.[ 4] Additionally, in the (Grazing Incidence X-ray Diffraction) results of all samples, it can be observed that the m-phase which deteriorates the Pr values is sufficiently suppressed. These results are consistent with the tendency of previously reported results.[3] Therefore, It is believed that the Mo electrode would induce a higher orthorhombic phase fraction in HZO thin films compared to the TiN electrode resulting in higher 2Pr values. This enables ferroelectricity to be achievable within a wider range of film thicknesses and Zr/(Hf+Zr) ratios.

Negative differential resistance and resistive switching behavior in broad-spectrum electroluminescent devices based on Si3N4/Si thin films deposited by E-beam

This work focuses on the study of the electro-optical properties of Si3N4/Si multilayer (ML) structures deposited by electron beam evaporation and thermally annealed to induce the silicon nanocrystals (Si-ncs) formation. The increase in band gap and the changes of photoluminescence spectra indicate a phase change of the material after thermal annealing (TA). However, the TA favored the diffusion of Si from Si-layers throughout Si3N4 layers losing the ML structure. This Si diffusion produced the formation of Si-nanopyramids at the ML/Si substrate interface as well as Si-ncs, as corroborated by transmission electron microscopy. Current density vs. electric field (E) curves showed the presence of a negative differential resistance (NDR) which is related to the annihilation of preferential conductive filaments (CFs) created by the Si-nanopyramids with Si-ncs. As the E exceeds −1 MV/cm, a resistive switching (RS) from a high resistance to low resistance state (LRS) was observed, where the ON/OFF ratio increases as the area of the devices decreases. In addition, a broad-spectrum electroluminescence (EL, white light) was obtained during the RS phenomenon reaching optical powers up to 3 nW. Once the LRS is reached, the E required to obtain EL reduces up to 28.7 %, thus improving the devices performance.

Magnetization Plateaus by the Field-Induced Partitioning of Spin Lattices

To search for a conceptual picture describing the magnetization plateau phenomenon, we surveyed the crystal structures and the spin lattices of those magnets exhibiting plateaus in their magnetization vs. magnetic field curves by probing the three questions: (a) why only certain magnets exhibit magnetization plateaus, (b) why there occur several different types of magnetization plateaus, and (c) what controls the widths of magnetization plateaus. We show that the answers to these questions lie in how the magnets under field absorb Zeeman energy, hence changing their magnetic structures. The magnetic structure of a magnet insulator is commonly described in terms of its spin lattice, which requires the determination of the spin exchanges’ nonnegligible strengths between the magnetic ions. Our work strongly suggests that a magnet under the magnetic field partitions its spin lattice into antiferromagnetic (AFM) or ferrimagnetic fragments by breaking its weak magnetic bonds. Our supposition of the field-induced partitioning of spin lattices into magnetic fragments is supported by the anisotropic magnetization plateaus of Ising magnets and by the highly anisotropic width of the 1/3-magnetization plateau in azurite. The answers to the three questions (a)–(c) emerge naturally by analyzing how these fragments are formed under the magnetic field.

Effect of salinity-clay variation on the transient magnetic field in the Quaternary aquifer, theoretically and practically

This study focuses on understanding the physical foundations of the transient electromagnetic method, such as the transition from a simple basic principle to a more complex principle, starting from the Biot-Savart law until the current concept. It calculates the steady and transient magnetic fields around any electrical wire system. Accordingly, this law will be used to determine the magnetic field around the square loop configuration, which matches the magnetic field arising from the circular loop configuration. The square loop equation was derived and extended to include changes in the half-space, which allows us to understand how the electromagnetic waves travel in the subsurface and the farthest point, that can record the TEM response from the TEM loop, according to the loop size and loop current. Accordingly, the deduced equations were applied to predict the transient magnetic field curves of the Quaternary aquifer in three different water zones along the Nile delta, depending on the values of resistivity and chargeability caused by the variations in salinity and clay contents. The calculated transient magnetic curves were then compared with other measured field curves to confirm the validity of the derived equations. Therefore, these curves are expected to be used as guide curves for the transient magnetic field response in this aquifer. Also, these curves are important in estimating the hydro-geophysical characteristics of the main groundwater aquifer in the selected area and in other areas with the same geologic and hydrogeologic settings. Also, a common model is presented for any delta environment in the world in measured and calculated data.

Tunnel magnetoresistive sensors with non-hysteretic resistance–magnetic field curves using noncollinear interlayer exchange coupling through RuFe spacers

Tunnel magnetoresistive sensors with non-hysteretic resistance–magnetic field curves using noncollinear interlayer exchange coupling through RuFe spacers

High-quality Extragalactic Legacy-field Monitoring (HELM) with DECam: Project Overview and First Data Release

High-quality Extragalactic Legacy-field Monitoring (HELM) is a long-term observing program that photometrically monitors several well-studied extragalactic legacy fields with the Dark Energy Camera (DECam) imager on the CTIO 4 m Blanco telescope. Since 2019 February, HELM has been monitoring regions within COSMOS, XMM-LSS, CDF-S, S-CVZ, ELAIS-S1, and SDSS Stripe 82 with few-day cadences in the (u)gri(z) bands, over a collective sky area of ∼38 deg2. The main science goal of HELM is to provide high-quality optical light curves for a large sample of active galactic nuclei (AGNs), and to build decades-long time baselines when combining past and future optical light curves in these legacy fields. These optical images and light curves will facilitate the measurements of AGN reverberation mapping lags, as well as studies of AGN variability and its dependencies on accretion properties. In addition, the time-resolved and coadded DECam photometry will enable a broad range of science applications from galaxy evolution to time-domain science. We describe the design and implementation of the program and present the first data release that includes source catalogs and the first ∼3.5 yr of light curves during 2019A–2022A.

Sol-gel fabrication of transparent ferroelectric (K,Na)NbO3/La0.06Ba0.94SnO3 heterostructure

Lead-free K0.5Na0.5NbO3 (KNN) ferroelectric film and transparent La0.06Ba0.94SnO3 (LBSO) bottom electrode are fabricated on (001)-oriented SrTiO3 (STO) substrate by sol-gel. The characterization results confirm an epitaxial relationship between the films and the substrate, as well as a uniform structure and good crystallization quality of the films. The optical measurement shows that the film heterostructure exhibit a high transmittance with a maximum transmittance of ∼80 %. The polarization-electric field (P-E) curves demonstrate that the twice remanent polarization value of the ∼500 nm thick KNN film reaches up to 28 μC/cm2 under an electric field of 800 kV/cm, and the effective piezoelectric strain constant (d33∗) is measured as 24.8 p.m./V. The dielectric properties of the film are displayed, and the leakage behavior can be divided into three stages of Ohmic conduction, Schottky emission and Poole-Frenkel emission with increasing the applied electric field. This study indicates that transparent lead-free ferroelectric KNN heterostructures can be prepared using a cost-effective sol-gel method and shows promise for future applications.

Constructing superparaelectric state for NaNbO3-based ceramics electrostatic supercapacitors

A crucial prerequisite for developing high-performance energy storage devices for high pulsed power systems is the urgent necessity to acquire dielectric ceramics with high recoverable energy density (Wrec) and ultrahigh energy efficiency (η), particularly through an environmentally friendly lead-free approach. Here, superparaelectric state with ultra-small nanodomains in NaNbO3-based ceramics is successfully induced by implementing a superparaelectric modulation strategy. This innovation not only reduces the curvature value of the polarization–electric field (P-E) curve, but also produces negligible remanent polarization (Pr) and a linear-like P-E curve, obtaining outstanding efficiency (η) of 92.2 % and high energy storage density (Wrec) of 7.05 J/cm3. This achievement not only opens new avenues for enhancing the energy storage performance of dielectric ceramics but also heralds extensive applications of this material in high-pulse power electronic devices.

Homogeneous Projective Coordinates for the Bondi–Metzner–Sachs Group

This paper studies the Bondi–Metzner–Sachs group in homogeneous projective coordinates because it is then possible to write all transformations of such a group in a manifestly linear way. The 2-sphere metric, the Bondi–Metzner–Sachs metric, asymptotic Killing vectors, generators of supertranslations as well as boosts and rotations of Minkowski spacetime are all re-expressed in homogeneous projective coordinates. Lastly, the integral curves of vector fields which generate supertranslations are evaluated in detail. This work paves the way for more advanced applications of the geometry of asymptotically flat spacetime in projective coordinates by virtue of the tools provided from complex analysis in several variables and projective geometry.

Direct Field Curve Fitting Method to Determine Hardening Soil Parameter for Geotechnical Projects

Abstract In a wide archipelago country like Indonesia, transporting soil samples for laboratory tests are quite a bit of challenge in terms of cost and time as those need to be transported for weeks to nearest big cities. In-situ tests and correlation methods can be used as an alternative solution for preliminary or detailed design beside having on site laboratory. Correlating in-situ test results to hardening soil parameter (e.g. E 50) is common but it is not clear how those should be adjusted for Plaxis input. Two deep excavation projects and a lateral pile load test are used to see the performance of direct field curve fitting method utilizing SPT correlation to HS parameter. From the analysis, using E 50=4000N for clay soils and E 50=2800N for sand soils as upper bound parameters produce the best results with lesser discrepancy with the field measurements compared to calculations with lower bound parameters. For the deep excavation cases (Case 1 and Case 2), calculated lateral displacement results using upper bound parameters overestimates inclinometers measurement for less than 1.5 cm for both cases. For the case of lateral pile load test (Case 3), calculation using upper bound parameters succeed to capture a high detail of unloading-reloading curves similar to the actual measurement. This method can be used as a technique to design geotechnical projects and it proposes a framework for future research regarding a new possibility to establish various E 50 correlations.

Investigations of energy storage and thermal stability properties in eco-friendly B-site substituted Na0.5Bi0.5TiO3

In this work, (Mg1/3Nb2/3)4+ cationic substitution in lead-free polycrystalline Na0.5Bi0.5TiO3 (NBT) has been adopted to synthesize by the conventional solid-state reaction method. The cationic substitution was introduced into NBT through compositional modification, which significantly restricted grain growth and promoted a ferroelectric to relaxor ferroelectric phase transition. The substitution of (Mg1/3Nb2/3)4+ influenced the crystal structure, ferroelectric, dielectric properties, and micromorphology, which had been investigated systematically. The enhancement of relaxor nature is found with this substitution and further verified by dielectric curve, polarization (P) - electric field (E) hysteresis loop, and current (I)- electric field (E) curve. The recoverable energy density was determined to be 1.09 J/cm3 and 1.24 J/cm3 at 101 kV/cm and 114 kV/cm in the 10 mol% and 20 mol% of (Mg1/3Nb2/3)4+ substituted systems, respectively. Furthermore, over the 35 ˚C to 490 ˚C temperature range, the 30 mol% (Mg1/3Nb2/3)4+ substituted composition showed superior thermal stability in the permittivity. Therefore, this study concluded that these cationic substituted NBT compositions are appropriate materials for applications involving higher-temperature and energy storage in electronic devices.

Role of grain interface on dielectric and multiferroic properties of 0-3 type (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 nanocomposites

The (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 (0-3 type particulate) nanocomposites with x = 0.00, 0.02, 0.04, 0.06, 0.08, and 1.00 were prepared by the solid-state method. Cobalt ferrite crystallized into cubic crystal symmetry with an Fd3̄m space group. Strontium-substituted barium titanate crystallized into a tetragonal crystal structure with a P4mm space group. Field emission scanning electron microscopy and transmission electron microscopy techniques show the distribution of different sizes of particle. Polarization vs electric field curves show the highest maximum polarization (Pm) of 10.26 μC/cm2, remnant magnetization (Pr) of 11.70 μC/cm2, and coercivity (Ec) of 19.95 kV/cm for x = 0.04 composition at 35 kV/cm. However, it is smaller than the Ba0.8Sr0.2TiO3 phase (Pm = 16.86 μC/cm2, Pr = 13.20 μC/cm2, and EC = 10.80 kV/cm). The highest dielectric constant of around 9800 was found for x = 0.04 composition, with a very small dielectric loss factor of about 0.02, i.e., less than even 2%. This is ∼10 times compared to that of Ba0.8Sr0.2TiO3 (BSTO), which has been explained by considering interaction at the interface of CoFe2O4 (CFO) and BSTO, leakage current, and variation of the lattice parameter of BSTO in (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 nanocomposite. The magnetic hysteresis loops show squeezing near the origin. The magnetic parameters like coercivity, remnant magnetization, and saturation magnetization increased with the increase in the CoFe2O4 weight fraction. Magnetic interaction between surfaces of magnetic CFO and non-magnetic BSTO is evident from the ΔH vs M plots, and it also evidences the magnetism at the surface of BSTO due to uncompensated spins.

Magnetization switching by electric field in ZnFe2O4/ZnO heterostructure

We have fabricated the ZnFe2O4/ZnO (ZFO/ZnO) heterostructure on a silicon substrate by pulsed laser deposition technique and studied the magnetization switching by the electric field in the ZFO/ZnO heterostructure using an indigenously developed optical cantilever beam magnetometer setup. The magnetization (M) vs electric field (E) curve reveals that the magnetization of the ZFO film has been switched by an electric field applied along the thickness of the ZnO film. The saturation magnetization is found to be 28.77 MA/m from the M–E curve. The emergence of electric field-driven magnetization switching in the ZFO/ZnO heterostructure is attributed to the strain-mediated magnetoelectric coupling between the electric polarization of the ZnO film and the magnetization of the ZFO film as evidenced by the butterfly-type hysteresis behavior of magnetization with the applied electric field. However, the realization of electric field-controlled magnetization switching in the ZFO/ZnO heterostructure is regarded as a potential aspect for the fabrication of energy-efficient spintronic devices such as magnetoelectric random access memory cells, highly sensitive magnetic field sensors, magneto-logic devices, and neuromorphic devices.

Magnetic, Optical, Electrical and Antimicrobial Properties of MnCuZnFe2O4 Nanoparticles

AbstractThe Mn0.92Cu0.08‐yZnyFe2O4 (y=0.02, 0.04, 0.06 and 0.08) nanoparticles (MCZF NPs) were synthesized via the hydrothermal process at low operating temperature. The MCZF system generated a cubic spinel structure as seen by the X‐ray diffraction patterns. The average crystallite size was observed to be increasing from 25 to 30 nm. The broad (γ1) and narrow (γ2) absorption bands were seen in FTIR spectra and the cation distributions at tetrahedral (A) and octahedral (B) sites, respectively, was indicated. The surface morphology was analyzed using electron microscopy. Clarification was provided for the dependence of the optical bandgap shift (Eg~1.96–2.15 eV) on the concentration of substituent. The superparamagnetic nature of MCZF can be advantageous for biomedical applications and it was demonstrated by the magnetization versus applied magnetic field (M−H) loops. Small values of remanence magnetization (Mr) and coercivity (Hc) were found using magnetization versus magnetic field (M−H) curves at y=0.02, 0.04, 0.06, and 0.08. This proved that MCZF NPs exhibited the superparamagnetic behavior. The cation distribution at two sublattices was also estimated using a two‐sublattice model. The greatest zone of inhibition in an antibacterial study of MCZF (produced by the green method) was 10.8 mm for Pseudomonosa aeruginosa and 9.4 mm for Staphylococcus aureus.

Anomaly Identification for Photovoltaic Power Stations Using a Dual Classification System and Gramian Angular Field Visualization

With the increasing scale of photovoltaic (PV) power stations, timely anomaly detection through analyzing the PV output power curve is crucial. However, overlooking the impact of external factors on the expected power output would lead to inaccurate identification of PV station anomalies. This study focuses on the discrepancy between measured and expected PV power generation values, using a dual classification system. The system leverages two-dimensional Gramian angular field (GAF) data and curve features extracted from one-dimensional time series, along with attention weights from a CNN network. This approach effectively classifies anomalies, including normal operation, aging pollution, and arc faults, achieving an overall classification accuracy of 95.83%.

Hysteresis-free reversible magnetocaloric effect and critical behavior of Ni39.56Fe7.27Co2.97Mn40.65Sn9.55 full heusler alloy

Utilizing the magnetocaloric effect (MCE), magnetic refrigeration technology offers an advantage over traditional gas-based refrigerators, which produce harmful gases. Herein, we study the MCE and critical magnetic behavior of Fe and Co substituted Ni39.56Fe7.27Co2.97Mn40.65Sn9.55 Heusler alloy near the paramagnetic (PM) to ferromagnetic (FM) transition temperature. With Fm3̅m space group, the present sample crystallizes in cubic L21 structure. Arrott plots and hysteresis-free continuous phase transition confirm a second-order transition from FM to PM. Again, this second-order transition is verified by collapsing scaled entropy curves for various fields into a single universal curve. The critical exponent values obtained using several analytical techniques, like the Kouvel-Fisher method, modified Arrott plot, and critical isotherm, correspond to the mean-field theory universality class having long-range ordering. The above findings suggest our sample to be a suitable magnetic refrigerant by overcoming the difficulty of obtaining a reversible and high value of magnetic entropy change along with substantial relative cooling power across the second-order phase transition.

Construction and implementation of a poplar spectral library based on phenological stages for land cover classification using high-resolution satellite images

ABSTRACT As valued members of forest ecosystems, fast-growing tree species are of great importance for protecting natural forests, fulfilling the demand for raw wood material, and preserving biodiversity and ecosystem services. In this regard, multi-temporal monitoring and evaluation of poplar planted areas are essential for decision makers and planners to keep the inventory maps of planted areas up-to-date and track the temporal changes accurately. Using a spectral library, available spectral knowledge can be incorporated into inventory mapping and image classification processes. In this study, in situ spectral measurements of five Populus (four clones and one species) planted sites in Türkiye were collected at three phenological stages (early, mid, and late vegetation) and a novel spectral library was created after completing strict processing stages. Analysis of the spectral reflectances of the Populus species revealed that their spectral properties in the visible region are similar, whereas the discrimination in the near-infrared and shortwave infrared (SWIR) regions was noticeably higher. Two types of applications were conducted to effectively use the spectral library. First, the spectral library was used to validate the poplar class labels of the sites visited during the field campaign. The effectiveness of Worldview-3 imagery with eight SWIR bands was evaluated by pairwise comparison of the spectral curves of the sample fields with those of the spectral library. Second, the spectral library facilitated the extraction of poplar samples from Sentinel-2 imagery in an unvisited region, and a supervised classification process was conducted using the random forest algorithm. The results revealed that the Populus species (Samsun and I-214) could be delineated with high accuracy (>70%) using 10-band Sentinel-2 imagery, and object-based classification outperformed pixel-based classification by approximately 5% for the poplar types. The developed spectral library stands as a valuable asset for studies focused on identifying and classifying Populus species using high-resolution imagery.

Observations and Variability of Near-Surface Atmospheric Electric Fields across Multiple Stations

The near-surface atmospheric electrostatic field plays a pivotal role in comprehending the global atmospheric circuit model and its influence on climate change. Prior to delving into the intricate interplay between solar activities, geological activities, and atmospheric electric field, a comprehensive examination of the diurnal fair atmospheric electric field’s baseline curve within a specific region is essential. Based on the atmospheric electric field network monitoring in Yunnan Province in the year 2022, this study systematically investigated the distribution of the atmospheric electric field under both fair-weather and disturbed weather conditions at a quadrilateral array encompassing Chuxiong Station, Mouding Station, Lufeng Station, and Dali Station. The primary focus was on elucidating the variations in the daily variation curves of fair atmospheric electric fields and conducting a comparative analysis with the Carnegie curves. The possible reasons for the differences among them are also discussed in this study, but more observational evidence is required to confirm the specific causes in the future.