Automatic Monitoring Alarm Method of Dammed Lake Based on Hybrid Segmentation Algorithm.

Mountainous regions are prone to dammed lake disasters due to their rough topography, scant vegetation, and high summer rainfall. By measuring water level variation, monitoring systems can detect dammed lake events when mudslides block rivers or boost water level. Therefore, an automatic monitoring alarm method based on a hybrid segmentation algorithm is proposed. The algorithm uses the k-means clustering algorithm to segment the picture scene in the RGB color space and the region growing algorithm on the image green channel to select the river target from the segmented scene. The pixel water level variation is used to trigger an alarm for the dammed lake event after the water level has been retrieved. In the Yarlung Tsangpo River basin of the Tibet Autonomous Region of China, the proposed automatic lake monitoring system was installed. We pick up data from April to November 2021, during which the river experienced low, high, and low water levels. Unlike conventional region growing algorithms, the algorithm does not rely on engineering knowledge to pick seed point parameters. Using our method, the accuracy rate is 89.29% and the miss rate is 11.76%, which is 29.12% higher and 17.65% lower than the traditional region growing algorithm, respectively. The monitoring results indicate that the proposed method is a highly adaptable and accurate unmanned dammed lake monitoring system.

Phase-field modeling of the coupled domain structure and dielectric breakdown evolution in a ferroelectric single crystal.

The study of domain switching and dielectric breakdown behavior of ferroelectrics together with their relations is crucial for understanding the essence of ferroelectric physics and exploring their applications. In this work, a phase-field method is developed to reveal the coupled domain structure and dielectric breakdown evolution in a ferroelectric single crystal (FSC) by employing the Ginzburg-Landau kinetic equation and Griffith type energy criterion. Results show that the domain switching mobility, symbolizing the speed of polarization evolution, has a significant influence on ferroelectric properties, namely coercive field, dielectric breakdown strength (DBS), discharge energy density (DED), and energy storage efficiency (ESE). It is found that FSC with the higher domain switching mobility always displays a lower coercive field and smaller remanent electric displacement (or polarization) together with a higher DBS, accounting for a higher DED and ESE. Such findings can provide effective guidance in understanding and designing high-DBS and high-energy-density ferroelectrics. In addition, the defect concentration has a significant influence on the DBS and the pattern of breakdown paths.

Study on Adsorption Characteristics and Water Retention Properties of Attapulgite-Sodium Polyacrylate and Polyacrylamide to Trace Metal Cadmium Ion.

The adsorption mechanism of superabsorbent polymer (SAP) can provide theoretical guidance for their practical applications in different environments. However, there has been limited research on the mechanism of attapulgite-sodium polyacrylate. This research aimed to compare the Cd(II) adsorption characteristics and water retention properties of organic-inorganic composite SAP (attapulgite-sodium polyacrylate, OSAP) and organic SAP (polyacrylamide, JSAP). Batch experiments were used to investigate the kinetics of Cd(II) adsorption, as well as the thermodynamic properties and factors influencing these properties. The results show that the Cd(II) adsorption capacity was directly proportional to the pH value. The maximum adsorption capacities of OSAP and JSAP were of 770 and 345 mg·g-1. The Cd(II) adsorption for OSAP and JSAP conformed to the Langmuir and the quasi-second-order kinetic model. This indicates that chemical adsorption is the primary mechanism. The adsorption process was endothermic (ΔH0 > 0) and spontaneous (ΔG0 < 0). The water adsorption ratios of OSAP and SAP were 474.8 and 152.6 in pure water. The ratio decreases with the increase in Cd(II) concentration. OSAP and JSAP retained 67.23% and 38.37% of the initial water adsorption after six iterations of water adsorption. Hence, OSAP is more suitable than JSAP for agricultural and environmental ecological restoration in arid and semi-arid regions.

A Three-Dimensional Inversion Method for Small-Scale Magnetic Objects Based on Normalized Magnetic Source Strength.

The exploration of some dangerous or important small-scale magnetic objects requires accurate three-dimensional inversion results. In this paper, a three-dimensional inversion method for small-scale magnetic objects is proposed. Normalized magnetic source strength, which is weakly sensitive to the magnetization direction, is used for inversion, which avoids the influence of the remanence of magnetic objects. The planted inversion method is improved to make the inversion results more similar to the real results; normalized magnetic source strength is used to estimate the center position of the magnetic objects, which provides a priori information for the inversion; the weighting function is added in the inversion process to improve the inversion accuracy. The simulation and experimental results show that the method is not affected by the remanence, and effectively reduces the interference of non-target field sources. The obtained inversion results have higher accuracy.

A Small Target Localization Method Based on the Magnetic Gradient Tensor.

Currently, many small target localization methods based on a magnetic gradient tensor have problems, such as complex solution processes, poor stability, and multiple solutions. This paper proposes an optimization method based on the Euler deconvolution localization method to solve these problems. In a simulation, the Euler deconvolution method, an improved method of the Euler deconvolution method and our proposed method are analyzed under noise conditions. These three methods are evaluated in the field with complex magnetic interference in an experiment. The simulations show that the accuracy of the proposed method is higher than that of the improved Euler deconvolution method and is slightly lower for noisy conditions. The experimental results show that the proposed method is more precise and accurate than the Euler deconvolution and enhanced methods.

Effects of Nanofibers Orientation and Aspect Ratio on Dielectric Properties of Nanocomposites: A Phase-Field Simulation.

Polymer-based dielectrics with high energy storage density are attracting increasing attention due to their wide applications in pulsed-discharge and power conditioning electronic fields. Despite some numerical simulation about effects of horizontally arranged and vertically arranged fibers on dielectric properties of composites already studied, the influence mechanism of the specific orientation and aspect ratio still remains to be studied. In this work, the effects of orientation angles and aspect ratios of nanofiber fillers on breakdown behavior and dielectric properties of composites are theoretically analyzed by the finite element and phase-field method. The results show that the more inclined the nanofiber fillers is, the higher the nominal breakdown strength is, which benefits from the obstruction of the conductive channels by the nanofibers. However, the dielectric constant shows the opposite law, which is the result of the decreased polarization along the electric field direction of the nanofiber fillers. Besides this, by modulating the distribution of local electric field, a higher aspect ratio of nanofiber fillers helps to achieve a much higher breakdown strength with a slight sacrifice of dielectric constant. The present work provides a comprehensive and quantitative understanding of the orientation and aspect ratio of nanofiber fillers on the dielectric and breakdown properties of composites, providing important guidance on optimizing the energy storage performance.

Multiphase Engineered BNT-Based Ceramics with Simultaneous High Polarization and Superior Breakdown Strength for Energy Storage Applications.

Dielectric ceramics are crucial for high-temperature, pulse-power energy storage applications. However, the mutual restriction between the polarization and breakdown strength has been a significant challenge. Here, multiphase engineering controlled by the two-step sintering heating rate is adopted to simultaneously obtain a high polarization and breakdown strength in 0.8(0.95Bi0.5Na0.5TiO3-0.05SrZrO3)-0.2NaNbO3 (BNTSZNN) ceramic systems. The coexistence of tetragonal (T) and rhombohedral (R) phases benefits the temperature stability of BNTSZNN ceramics. Increasing the heating rate during sintering reduces the diffusion of SrZrO3 and NaNbO3 into Bi0.5Na0.5TiO3, which results in a high proportion of the R phase and a finer grain size. The overall polarization is enhanced by increasing the proportion of the high-polarization R phase, which is demonstrated using a first-principles method. Meanwhile, the finer grain size enhances the breakdown strength. Following this design philosophy, an ultrahigh Wdis of 5.55 J/cm3 and η above 85% is achieved in BNTSZNN ceramics as prepared with a fast heating rate of 60 °C/min given a simultaneously high polarization of 43 µC/cm2 and high breakdown strength of 350 kV/cm. Variations in the discharge energy density from room temperature to 160 °C are less than 10%. Additionally, such BNTSZNN ceramics exhibit an ultrafast discharge speed with τ0.9 at approximately 60 ns, which shows great potential in pulse-power system applications.