Increase In Radius Research Articles

Simulation of threshold displacement energy in Fe-Cr-Al alloys using molecular dynamics

The threshold displacement energy of Fe and Fe-Cr-Al alloys and the influence factors were investigated using molecular dynamic simulations. The mechanism of defect recombination was discussed, as was the evaluation of the recombination radius for Fe and Fe-Cr-Al. The simulation results show that Fe and Fe-Cr-Al have big differences in threshold displacement energies and directional dependencies at low temperatures, but the differences become less pronounced at high temperatures. The cause might be that the replacement collision sequence can effectively separate an interstitial from a vacancy in Fe-Cr-Al and greatly reduce threshold displacement energy at low temperatures. In addition, the energy transfer efficiency of primary knock-on Al atoms is low due to the difference in atomic mass, and the recombination effect for Cr is hindered by the formation of Fe-Cr 〈110〉 dumbbell. However, the effect of solute atoms on threshold displacement energy is insignificant at high temperatures, due to the increase in the recombination radius and a reduction in the effect of the aforementioned factors.

Calculation of Mechanical Properties, Electronic Structure and Optical Properties of CsPbX3 (X = F, Cl, Br, I).

We utilized a first-principle density functional theory for a comprehensive analysis of CsPbX3 (X = F, Cl, Br, I) to explore its physical and chemical properties, including its mechanical behavior, electronic structure and optical properties. Calculations show that all four materials have good stability, modulus of elasticity, hardness and wear resistance. Additionally, CsPbX3 demonstrates a vertical electron leap and serves as a semiconductor material with direct band gaps of 3.600 eV, 3.111 eV, 2.538 eV and 2.085 eV. In examining its optical properties, we observed that the real and imaginary components of the dielectric function exhibit peaks within the low-energy range. Furthermore, the dielectric function gradually decreases as the photon energy increases. The absorption spectrum reveals that the CsPbX3 material exhibits the highest UV light absorption, and as X changes (with the increase in atomic radius within the halogen group of elements), the light absorption undergoes a red shift, becoming stronger and enhancing light utilization. These properties underscore the material's potential for application in microelectronic and optoelectronic device production. Moreover, they provide a theoretical reference for future investigations into CsPbX3 materials.

Impact of Climate Change on Maximum Sustained Wind Radius and its Associated Storm Surge Estimation along the Coast of Bangladesh

This research is a basic study on cyclones. The changing behaviour of storm surge in the Bay of Bengal due to the impact of climatic changes has been analyzed in this study. Certain characteristics of cyclones, such as the maximum sustained wind radius, have been analyzed, and their effect due to climatic change has been determined. The correlation between the maximum sustained wind radius and surge height was observed for this purpose. To accurately determine surge height, the vertically integrated shallow water wave model equation was employed, and it was solved using the semi-implicit finite difference method through the Arakawa-C grid. The surge model was performed by increasing and decreasing its wind radius by 10% to 20%, based on changes in the maximum sustained wind radius due to the effects of climate change. A strong conclusion was reached from the obtained results, indicating a significant effect of the maximum sustained wind radius on storm surge. But if it increases, there is a visible change in storm in some area of the coast of Bangladesh. For example, 1% increase in wind radius, the surge height increases by 0.032m, where the storm strikes. In some areas far away from where the storm hits the rising rate of the surge height is much lower. Finally, it may be stated that the surge height is affected by the maximum sustained wind radius and that it is altered by climatic impacts.

Modeling car and heavy commercial vehicle crashes on two-lane rural highways using the Poisson-Tweedie regression approach

This article develops vehicle type–based crash-prediction models for cars and heavy commercial vehicles (HCVs) as a function of the curve geometry and vehicle-based design consistency criteria under heterogeneous traffic conditions on two-lane, two-way rural highways, specifically in hilly terrains. A National Highway (NH-953) connecting Netrang and Rajpipla in India was selected. There are 38 curves in the study section, each having a different curve geometry. Speed data were collected using the radar gun for cars and HCVs. The geometric design consistency was evaluated using Criterion I (the difference between operating and design speeds). The results show that 53% of the curves for cars have good consistency, compared to 32% and 29% of the curves for HCVs, which have fair and poor consistency, respectively. The Poisson-Tweedie regression technique, which provides a unified framework to model over-dispersed, under-dispersed, zero-inflated, count-data, and multiple-response variables, was used to develop the crash prediction models. The results revealed that crashes (cars and HCVs) decrease as the curve radius, deflection angle, and length increase. Similarly, as the tangent length increases, the difference between operating and design speeds increases, making inconsistent highway alignment, resulting in increased chances of crashes. The results of the present study can help highway authorities to evaluate highway alignment consistency and develop corresponding proactive strategies to improve highway safety.

Morphology of Star-forming Clumps in Ram-pressure Stripped Galaxies as Seen by HST

We characterize the morphological properties of a statistically relevant sample of Hα and UV young star-forming clumps and optical complexes, observed with the Hubble Space Telescope in six galaxies of the GASP sample undergoing ram pressure stripping. The catalogs comprise 2406 (323 in the tails) Hα clumps, 3750 (899) UV clumps, and 424 tail optical complexes. About 15%–20% of the clumps and 50% of the complexes are resolved in size. We find that more than half of the complexes contain no Hα clumps, while most of them contain at least one UV clump. The clump number and size increase with the complex size, while the median complex filling factor is larger for UV clumps (0.27) than that for Hα clumps (0.10) and does not correlate with almost any morphological property. This suggests that the clumps' number and size grow with the complex keeping the filling factor constant. When studying the position of the clumps inside their complexes, Hα clumps, and UV clumps to a lesser extent, show a displacement from the complex center of 0.1–1 kpc, and in ∼60% of the cases, they are displaced away from the galactic disk. This is in accordance with the fireball configuration, already observed in the tails of stripped galaxies. Finally, the filling factor and the clump radius increase with the distance from the galactic disk, suggesting that the reciprocal displacement of the different stellar generations increases as a consequence of the velocity gradient caused by ram pressure.

New experiments and theory on ferrofluid cylinder in an azimuthal magnetic field

We conducted experiments to study the stability of a ferrofluid cylinder in an azimuthal magnetic field. The ferrofluid cylinder is formed on a current-carrying wire for creating the azimuthal magnetic field and is surrounded by a non-magnetic fluid of the same density to neglect the gravitational effect. Experiments were performed for different wire and cylinder radii. Data were analyzed to extract the growth rate and the wavelength of the perturbation characterizing the ferrofluid cylinder. The influence of the wire radius on the cylinder stability is used to respond to an issue, recently raised, in relation to the growth rate data obtained by the first experimental work. The results of the experiments confirm the theoretical predictions, namely, a decrease in the growth rate when the ratio between the wire radius and the ferrofluid cylinder radius increases. However, the isothermal theory overpredicts the growth rate observed in this experiment and sources of this discrepancy are explored. In particular, a theoretical model considering a thermocapillary effect is developed and it is shown that this non-isothermal theory can explain the observed discrepancy.

Shadow, quasinormal modes, greybody bounds, and Hawking sparsity of loop quantum gravity motivated non-rotating black hole

We consider loop quantum gravity (LQG) motivated 4D polymerized black hole and study shadow, quasinormal modes, and Hawking radiation. We obtain analytical expressions of photonsphere radius and shadow radius and study their qualitative and quantitative nature of variation with respect to the LQG parameter α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}. We also show shadows of the black hole for various values of α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}. Our study reveals that both radii increase with an increase in the parameter value. We, then, study quasinormal modes for scalar and electromagnetic perturbations using the 6th order WKB method. Our study reveals that the LQG parameter impacts quasinormal modes. We observe that the oscillation of gravitational wave (GW) and decay rate decrease as α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} increases. At the same time, the error associated with the 6th order WKB method increases with an increase in α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}. The ringdown waveform for electromagnetic and scalar perturbations is shown. We also study greybody bounds, power spectrum, and sparsity of Hawking radiation. Greybody bounds for electromagnetic perturbations do not depend on α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}. For scalar perturbation, greybody bounds increase as the LQG parameter increases, but the variation with α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} is very small. The peak of the power spectrum as well as total power emitted decrease as we increase the value of α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}. Also, the sparsity of Hawking radiation gets significantly impacted by quantum correction. Finally, we obtain the area spectrum of the black hole. It is found to be significantly different than that for the Schwarzschild black hole.

Rydberg-Rydberg interaction strengths and dipole blockade radii in the presence of Förster resonances.

Achieving a substantial blockade radius is crucial for developing scalable and efficient quantum communication and computation. In this theoretical study, we present the enhancement of the Rydberg blockade radius by utilizing Förster resonance. This phenomenon occurs when the energy difference between two initial Rydberg states closely matches that between the corresponding final Rydberg states, giving rise to a resonant energy transfer process. We employ quantum defect theory to numerically calculate the 87Rb-87Rb Rydberg atomic pair, enabling us to accurately estimate the van der Waals interaction. Our investigation reveals that when the principal quantum numbers of two Rydberg states differ only slightly, the Förster transition is rarely able to achieve a large blockade radius. However, in cases where the principal quantum numbers differ significantly, we substantially improve the Rydberg blockade radius. Most notably, we identify transition channels exhibiting an extensive blockade radius, surpassing 50 μm. This significant increase in the blockade radius enables larger-scale quantum operations and advances quantum technologies, with broad implications for achieving long-range quantum entanglement and robust quantum processes.

Axial Compression Performance Test and Bearing Capacity Calculation of RC Square Column Strengthened by FRP Textile Grid-reinforced ECC

In order to investigate the strengthening effect of FRP textile grid reinforced ECC composite (abbreviated: TRE) restrained RC columns, this study conducted experimental and theoretical studies on the axial compression performance of TRE strengthened RC square columns with RC square columns as the research object. The effects of the chamfer radius of the original column, the type of FRP grid and the number of layers of the grid on the axial compression performance of the TRE-strengthened RC square column were considered. The axial compression tests showed that the strengthened layer exhibited excellent crack control, the reinforced column cracked as a whole without breaking when it was damaged, and the strengthened layer adhered well to the core concrete. Compared with unstrengthened specimens, the compressive strength, ductility and deformation capacity of the RC square column under TRE restraint were significantly higher. The increase of chamfer radius of square column makes the TRE restraint effect better. Increasing the number of grid layers can significantly improve the ultimate bearing capacity and ductility of the strengthened specimens. The effects of TRE strengthening methods with different FRP grids differed, with the same number of grid layers, the ultimate bearing capacity of the specimens strengthened with CFRP grid reinforced ECC was higher, and the cracking load of the specimens strengthened with BFRP grid reinforced ECC was higher. A model for calculating the ultimate bearing capacity of the TRE-constrained RC square column was established, and the validity of the model was verified by comparing the results of this test.

Effect of different counterions on the self-assembly structures and properties of imidazole based ionic liquids surfactant: A molecular dynamics study

Self-assembly of ionic liquids (ILs) in solution has attracted wide attention due to their potential applications in various fields. The nature of counterions, especially aromatic counterions, will significantly affect the aggregation and morphological properties of ILs surfactants. In this paper, molecular dynamics (MD) simulations are applied to study the influence of three organic and inorganic counterions (phenolate (PO−), benzoate (BZ−), and Cl−) on the micellar structure of imidazolium (C14mim+) based ILs surfactant in aqueous solutions. Three micelles all possess prolate shape. The PO−, BZ−, and Cl− ions hardly affect the orientation and length of hydrophobic chains in micellar interior. Hydration numbers and average radial density distributions analyses show that interactions between micelles and water molecules are different in studied micelles. Surrounding water molecules penetrate into the deepest region in [C14mim][Cl] micelle. However, adsorbed Cl− ions are mainly located on micellar surface, not penetrating into micellar interior. Due to the intrinsic hydrophobicity of organic ions, both PO− and BZ− ions enter into deeper positions in micelles. Unlike Cl− ions, there exist π-interactions between adsorbed PO− and BZ− ions themselves. One interesting finding is that adsorbed PO− and BZ− ions can make micelle radius (Rg) increase but make solvent accessible surface area (SASA) decrease. Conversely, adsorbed Cl− ions make both Rg and SASA increase. Three MD models for different C14mim+ based micelles are proposed.

The Influence of Traditional Ethnic Villages on Forest Structure Based on PLS-SEM: A Case Study of Miao Inhabited Area

The activity characteristics of the village and its symbiotic relationship with the environment play an important role in the sustainable development of the surrounding environment. Miao villages have a long history. In the process of long-term interaction with the surrounding natural environment, Miao villages have formed a unique forest culture, which has an important impact on the distribution of the surrounding forests and plays a crucial role in local forest management. In this study, we took the Miao villages of China that are distributed in Qiandongnan Miao and Dong Autonomous Prefecture of China as an example and constructed a research framework to study the interaction between the natural environment and human activities around the Miao villages and its impact on forest change based on partial least squares structural equation modeling (PLS-SEM) and geographically weighted regression modeling (GWR) methods. The validity and reliability evaluations showed that the PLS-SEM model was reasonable. The results showed that the Miao villages were randomly distributed within 0–2 km and clustered in the 8–10 km buffer zone. The temporal variation of the forest landscape around the Miao villages was small, and the spatial heterogeneity was obvious. Within the 0~2 km buffer zone, the proportion of closed-canopy forest was the largest, and with the increase in the buffer zone radius, the proportion of closed-canopy forest gradually decreased, the open-canopy forest gradually grew, and the proportion of shrubbery and other forests showed an upward trend first and then a downward trend. Temporally, the four forest landscapes did not change much, with closed and open forests sliding, and shrubbery and other forests increasing. Regarding the drivers of forest structure change, topographic factors and landscape patterns had a positive effect on forest structure, while human activities had a negative effect. The influence of topography on human activities in the Miao villages weakened the direct positive effect of topography on forests and promoted the positive effect of the landscape pattern on forests. There were significant spatial differences in the GWR regression coefficients of the effects of different factors on forest structure in 2020, with a pivotal negative correlation between NDVI and night-time light data. In addition, the higher the elevation, the more unfavorable the distribution of open-canopy forests and the better the distribution of closed-canopy forests. The higher the slope, the higher the NDVI but the more unfavorable the distribution of closed-canopy forests. In general, the impacts of Miao villages on forest structure are highly complex and interactive, with both direct and indirect effects. Different factors interact to affect the structure of the forest. The study on the effect of Miao villages on forests is helpful for more targeted forest protection and the formulation of laws and regulations, so as to find a balance between human activities and forest management, in order to maintain the ecological balance of local areas. This study introduced the PLS-SEM model to investigate the impacts of Miao villages on forest structure, which effectively enhanced our understanding of the drivers and impacts of forest change and provides theoretical support and a basis for forest protection and management.

Assessing the impact of aneurysm morphology on the risk of internal carotid artery aneurysm rupture: A statistical and computational analysis of endovascular coiling

Computational modeling and investigation have become increasingly useful in assessing the hemodynamic and structural factors that contribute to aneurysm rupture, particularly when conventional clinical tools are inadequate. To this end, we conduct a study of a realistic internal carotid artery (ICA) under various working conditions using computational fluid dynamics. We analyze nine specific real ICA geometries in terms of coiling porosity and blood hematocrit, using a response surface model to evaluate 25 runs across selected geometrical parameters and treatment factors. The computational domain is created using computed tomography data from an actual patient, and we apply proposed boundary conditions to solve three-dimensional transient Navier–Stokes equations. By analyzing these cases, we try to understand how the sac section area, mean radius of the parent vessel, hematocrit, and coiling porosity interact and affect the risk of ICA rupture. We conduct an extensive study of the effects of sac section area and mean radius of the parent vessel on blood hemodynamics, examining several factors and comparing them at the peak systolic time instant, including wall shear stress (WSS), oscillatory shear index (OSI), pressure distributions, and velocity. Our results show that a 12% increase in the mean radius of the parent vessel reduced the maximum OSI value by approximately 50%, while a 120% increase in the sac section area decreases WSS on the aneurysm wall by up to 300%. These findings demonstrate the potential of computational modeling to provide valuable insight into the complex factors that influence aneurysm rupture, especially in cases where traditional clinical tools may be insufficient.

Optical Intelligent Reflecting Surface for Cascaded FSO-VLC Communication System

For optical wireless communication, laser-based free-space optical communication (FSO) has high energy utilization efficiency and speed, but is easily blocked and cannot support multiple users. Visible light communication (VLC) based on light-emitting diode (LED) can support multiple mobile users, but has low energy efficiency in long-distance communication. Aiming at the above problems, this paper proposes an OIRS-assisted cascaded FSO-VLC system. In this system, we adopt a FSO link with OIRSs at the front end. Multiple OIRSs are utilized to screen the optimal channel, thereby improving the flexibility and robustness of the system. The VLC link is used in the back end to support multi-user mobile communication. By jointly considering atmospheric turbulence, pointing error, OIRS's physical model and VLC geometric model, the closed-form solutions of the system's precise outage probability, asymptotic outage probability and BER have been derived. It is shown through numerical results that the derivation results are accurate. We can observe that both the increase of VLC source's coverage radius in VLC link and the decrease of pointing error in FSO link can effectively improve the system performance. Based on theoretical analysis and simulation results, the effect of each parameter and system design have been discussed.

Induced delamination in REBCO coated-conductor tape by a scratch line and bending

The aim of this work is to study delamination promotion of the coated conductor (CC) tape under the influences of the scratches on the Ag surface when bending. For this purpose, the microstructural and superconducting properties of the CC tape bent in helical fashion with different former diameters were analyzed. Such CC tape that exhibits visible damage along its length in the form of “scratch line” caused on the final product was used. The CC tape was bent at a constant lay angle of 45° with a superconducting layer positioned inward to the former core experiencing compression. Transport current measurements in liquid nitrogen were performed to study superconducting properties of the CC tape.The results showed that delamination of the REBCO (Rare-Earth Barium Copper Oxide) layer started to form exclusively on the scratch location at tube diameter of 7 mm (corresponding to strain ε = −0.71 %) while the rest of the REBCO surface started to delaminate at tube diameter of 5 mm (ε = −0.99 %). As the superconducting properties of the CC tape are related with the REBCO delamination, the critical current degraded when first signs of REBCO delamination appeared as expected. Thus, it was observed that the scratches induce REBCO delamination during the bending process resulting in increase of critical bending radius.

Enhancement of the technology of caved ore drawing from the ore deposit footwall “triangle”

In mining iron ore, over 60% of underground mines at Kryvyi Rih iron ore basin apply a system with the bulk caving of ore and overlying rocks. However, when the deposit dip is 45-60 degrees, application of this mining system leads to losses of about 30-40% of the footwall ore. Available methods of the loss reduction result in an increase in production costs or a decrease in the iron content in the mined ore mass. After analyzing the mechanism of forming the figure of drawing, it is proposed to change its parameters without significant costs due to the use of an inclined plane and an overcompacted ore layer. The presented study enables stating that with an increase in the inclined plane angle from 45 to 75 degrees the draw crater radius increases from 2 to 7.5 m, and a decrease in the factor of first loosening of ore leads to an increase in the radius of the crater to 10 m. Thus, for the first time it is proved that a decrease in the first loosening factor leads to the increased semi-minor axis of the ellipsoid of drawing and the width of the active drawing area, which will reduce losses of caved ore when drawing it from the stoping block in the footwall area. It is established that in order to minimize losses and dilution of ore when using level mining systems, the drawpoint should be located in the block sill at a distance ensuring formation of the 20 to 25 m high ellipsoid of drawing. In case of an overcompacted 22 m thick ore layer, it is possible to significantly reduce ore losses from 14 to 10% and ore dilution from 16 to 9%, thereby enhancing ore mass extraction indices without additional costs.

Three-dimensional numerical study on the effect of radius of the equal-area mixing chamber on auxiliary entraining of the two-stage ejector

In this study, for the two-stage ejector under three inlet conditions of air-conditioning, refrigerating and freezing, a three-dimensional simulation is used to study the impact of the mixing chamber radius of the first and second stage on the minimum pressure in the ejector without auxiliary entraining first, and then, the impact of real auxiliary entraining effects on ejector performance for two-stage ejector with varied equal-area mixing chamber radius is evaluated accordingly. Results show that: (1) as the second stage equal-area mixing chamber radius (Ram2) increases, the minimum first stage ejector pressure (Pmin1) decreases and the minimum second stage ejector pressure (Pmin2) increases; (2) with the increase of radius of the first-stage equal-area mixing chamber (Ram1) , the decreasing effect of Pmin1 and the increasing effect of Pmin2 are both weakened as Ram2 increases from 3.0 mm to 4.6 mm; (3) the minimum pressures of the two-stage have a great influence on the auxiliary entraining effect.

Study on flame propagation and inherent instability of hydrogen/ammonia/air mixture

To improve the safety and reliability of hydrogen energy, this paper studied the flame propagation and instability characteristics of hydrogen/ammonia/air mixture under different hydrogen contents, equivalence ratios and initial pressures. The results show that three typical phenomena are observed in the premixed hydrogen/ammonia/air flame propagation process under different experimental conditions. In a stable flame, the roughness of the flame surface does not increase, while during unstable flame expansion, the cracking of the flame surface splits and increases. In addition, under the condition of low equivalence ratio and hydrogen content, significant flame uplift is observed. With the increase in hydrogen content, the flame thickness and critical instability radius of the hydrogen/ammonia/air mixture decrease monotonously. The increase of hydrogen content mainly strengthens the hydrodynamic instability, leading to the weakening of flame stability. With the increase of the equivalence ratio, the Markstein length and the critical instability radius increase monotonically. The minimum value of flame thickness appears at the equivalence ratio of 1.0. The Lewis number is always less than 1 for poor combustion and greater than 1 for rich combustion. An increase in the hydrogen content only moves the Lewis number further away from 1. In rich burn, the thermal-diffusion is beneficial to flame stability, and the flame thickness increases with the increasing equivalence ratio. Under the combined effect of thermal-diffusion and hydrodynamic instability, the overall stability of the hydrogen/ammonia/air flame gradually increases with the increasing equivalence ratio. With the increase of initial pressure, the flame thickness decreases gradually. The critical instability radius and Markstein length both decrease rapidly with the increase of initial pressure.

Intercorrelations of structural-magnetic properties of La0.7A0.3MnO3 (A=Ba, Sr, Pb) manganites and the energy harvesting applications of their flexible nanocomposite films

Ferromagnetic La0.7Ba0.3MnO3 (LBMO), La0.7Sr0.3MnO3 (LSMO) and La0.7Pb0.3MnO3 (LPMO) nanoparticles (NPs) were prepared by sol-gel auto-combustion method. Microstructural analysis of these NPs was done using electron microscopy. The variation of crystallite size and the corresponding lattice strain of the prepared NPs were analyzed with Williamson-Hall plot. Elemental composition and oxidation states of the prepared NPs were analyzed with x-ray photoelectron spectroscopy. Comparative studies on the variation of ∠Mn-O-Mn bond angle and the Mn-O bond length with the increase of mean radius of A-site ion are reported which in turn alter the structural and magnetic properties of LBMO, LSMO and LPMO NPs. Further, 0.5 vol% (0–3) LBMO/P(VDF-TrFE), LSMO/P(VDF-TrFE) and LPMO/P(VDF-TrFE) flexible nanocomposite films were prepared by solution casting method and these were used to show direct magnetoelectric effect-based energy harvesting from magnetic noise generated from cooling/exhaust fan and electric cable wire carrying current at 50 Hz.

A three‐dimensional two‐hemisphere model for unmanned aerial vehicle multiple‐input multiple‐output channels

AbstractThe application of unmanned aerial vehicles (UAVs) has recently attracted considerable interest in various areas. A three‐dimensional multiple‐input multiple‐output concentric two‐hemisphere model is proposed to characterize the scattering environment around a vehicle in an urban UAV‐to‐vehicle communication scenario. Multipath components of the model consisted of line‐of‐sight and single‐bounced components. This study focused on the key parameters that determine the scatterer distribution. A time‐variant process was used to analyze the nonstationarity of the proposed model. Vital statistical properties, such as the space–time–frequency correlation function, Doppler power spectral density, level‐crossing rate, average fade duration, and channel capacity, were derived and analyzed. The results indicated that with an increase in the maximum scatter radius, the time correlation and level‐crossing rate decreased, the frequency correlation function had a faster downward trend, and average fade duration increased. In addition, with the increase of concentration parameter, the time correlation, space correlation, and level‐crossing rate increased, average fade duration decreased, and Doppler power spectral density became flatter. The proposed model was compared with current geometry‐based stochastic models (GBSMs) and showed good consistency. In addition, we verified the nonstationarity in the temporal and spatial domains of the proposed model. These conclusions can be used as references in the design of more reasonable communication systems.

A Numerical Simulation Study on DC Positive Corona Discharge Characteristics at the Conductor’s Tip Defect

For investigating the relationship between the surface corona discharge of a DC wire and other influencing factors, a hybrid numerical model based on a fluid-chemical reaction was proposed to simulate the discharge process at the tip defect of the wire. Under different defect geometries and gas pressures achieved via simulation, the microscopic process of the reaction and movement of electrons and heavy particles during a positive corona discharge was studied, and characteristic parameters such as corona inception voltage and discharge current were analyzed. Furthermore, through the corona cage test, for a specific electrode configuration, corona inception voltages under different pressures were compared and verified, which showed that the model was reasonable. The results showed that the maximum electron density of the streamer head was about 1 × 1020 m−3, the rise time of the pulse current was about 10 ns, and the decay time was about 300–500 ns. The corona inception voltage decreased with an increase in the tip height and decreases in the tip curvature radius, conductor radius, and background air pressure; the amplitude of the pulse current increased with increases in the wire radius and curvature radius of the defect tip and decreases in tip height and background air pressure. The experimental results are consistent with the simulation results, which verifies the reasonability of the model.