Search

The mechanical and dielectric properties of transformer insulating paper are key factors that require close attention to ensure optimal operation. In this study, a novel approach of enhancing properties by nanocellulose modification was proposed. To investigate the effect of doping, insulating paper with different doping mass fractions of cellulose nanocrystals (CNCs) was prepared, and multiple properties of the sample were characterized. By applying a doping concentration gradient, the non-monotonic trend in performance with doping levels was revealed, and the impact of doping concentration on the data variability was investigated. The effects of CNC doping on the surface pore size of the samples were analyzed by SEM (scanning electron microscopy) and a mercury intrusion method, and the regularity of CNC dispersion uniformity with doping concentration was investigated. The Brunauer, Emmett, and Teller model was employed to fit the water vapor adsorption isotherm data, providing an analysis of the impact of doping on hydrogen bond connections and the moisture adsorption properties. Tensile strength and Young's modulus were measured and analyzed using the Page model and the Halpin–Kardos model. The tensile strength of the 6 wt. % CNC-modified paper was increased by 6.91%. 10 wt. % CNC-modified paper had a Young's modulus increase of 11.98%. 3 wt. % CNC-modified paper has a 28.53% increase in the AC breakdown field strength and an 8.72% increase in the DC breakdown field strength. The influence of CNC on the dielectric properties of the insulating paper was discussed using the Havriliak–Negami (H–N) model. The results indicate that the introduction of CNC can effectively enhance the comprehensive performance of oil-immersed insulating paper. [ABSTRACT FROM AUTHOR]

This work describes a novel technique for the measurement of inorganic arsenic in water by generating arsine gas and detecting the conductivity of moving protons, H+ (aqueous or aq), produced by the reaction: Ag+ (aq) + AsH3 (gas, g) → AgAsH2 (solid, s) + H+ (aq). The detection is based on an electrochemical gradient of protons in a confined porous substrate (filter paper) and measures the change in the conductance due to the higher mobility of H+ compared to other ions. The conductance was measured with a pair of silver electrodes attached to opposite sides of the substrate with a bipolar pulse conductance technique. The method is established in theory and in practice. The theoretical equation for conductance change shows that a constant increase in conductance is directly proportional to the As(total) concentration. The method is validated with a standard reference material and applied to the measurement of the groundwater sample. [ABSTRACT FROM AUTHOR]

The cellulose fibers that form washi are longer than those of regular paper made from wood pulp. Hence, the mechanical properties of washi can be higher than those of conventional paper. This study evaluated the magnetic, magnetostrictive, and tensile properties of negative magnetostrictive cobalt ferrite (CoFe2O4) particle dispersed handmade washi (washi−CoFe2O4). The CoFe2O4 additives magnetized the washi, which displayed negative magnetostriction with the fiber direction perpendicular to the magnetic field and in the parallel fiber direction. Concerning the mechanical properties, the washi−CoFe2O4 displayed an elongation of up to 77% after yielding. [ABSTRACT FROM AUTHOR]

To develop special insulating paper is of great significance to promote the service life of transformers. Using molecular simulation to guide the development of special insulating paper can greatly reduce the trial-and-error rate and waste of resources in traditional experiments. The effect of different types of polysilsesquioxane (POSS) on cellulose insulating paper was investigated by using molecular simulation. This paper investigated the thermal stability and mechanical properties and electrical characteristics of caged POSS, semi-caged POSS, and ladder-like POSS doped cellulose insulating paper. The results show that POSS with all types can enhance the performance of cellulose insulating paper, and ladder-like POSS possess the best modification effect. The glass transition temperature was increased by 58 K, and the bulk modulus, shear modulus, and elastic modulus of cellulose insulating paper doped with ladder-like POSS can improve up to 27.07%, 45.67%, and 41.28%, respectively. Meanwhile, the dielectric properties of ladder-like POSS modified insulating paper are also significantly improved. The findings of this paper propose a method for the preparation of ladder-like POSS modified insulating paper, which provides theoretical guidance for the experimental preparation of special insulating paper. [ABSTRACT FROM AUTHOR]

Magnetometers have received considerable attention in recent years. Magnetic components offer an alternative methodology to improve the sensitivity. Due to their exceedingly small structural dimensions, metasurfaces exhibit significant competitiveness in field modulation. A magnetic field concentration phenomenon of spheres at the nanoscale is presented in this paper. The sensitivity of a magnetometer is, therefore, improved through the enhanced static or quasistatic magnetic field by the nanosphere concentrator. Magnetic field redistribution due to the assistance of nanospheres is discussed in this paper using the finite element method. The numerical method is verified with classical analytical equations with a single sphere. The simulation results show that the magnetic field concentrates in the near field behind the nanosphere along the direction of the magnetic flux density. The radius, material or permeability exactly, and distribution are critical parameters to the concentration strength. The magnetic gain of a single nanosphere with typical positive permeability of the typical soft magnetic material reaches 3, and thus, the field along the magnetic flux direction concentrates. Furthermore, the amplification factor is more prominent with the nanosphere arrays compared to a single sphere with the same scale of size, and amplification improves with the sphere numbers and distributions in the array arrangement, which provides a novel approach for the designing of the magnetic flux concentrator being monolithically integrated with the magnetometer probe. Our simulation results provide a new degree of freedom by using nanoscale structures to manipulate magnetic fields. [ABSTRACT FROM AUTHOR]

In recent years, there has been significant development in acoustic waveguides through the introduction of topological phase correlation concepts in acoustics. Many studies have shown the properties of acoustic unidirectional transmission. This paper presents a new ring-shaped acoustic topological insulator that is multi-band, unlike previous structures. The structure improves internal space utilization with the same dimensions, reducing acoustic wave conduction frequency in air environments. Additionally, the introduction of a multistage ring-shaped resonant cavity enables the conduction of acoustic waves in multiple frequency bands. This paper employs the rotational scattering mechanism to invert the topological phase of the lattice. This allows for the construction of two crystals with opposite phases, which can be used to create a topological channel for the transmission of acoustic waves. At the topological interface, the acoustic transmission losses within the four bands are small. Furthermore, this paper verifies by simulation that the defects have little effect on acoustic transmission. The paper's research offers potential for multiband acoustic control. [ABSTRACT FROM AUTHOR]

In this paper, we present a methodology of laser ablation simulation including electronic entropy effects. Ablation by ultrashort laser pulses is suitable for micromachining because of its small thermal damage. To further enhance its effectiveness, it is crucial to explore both theoretically and experimentally the desirable conditions for processing. The density functional theory calculations predict that hot electrons make crystalline lattice thermodynamically unstable at electronic temperature roughly above 20 000 K due to the electronic entropy-driven mechanism. In our simulations, equations combining hydrodynamic equations and the two-temperature model are modeled and are numerically solved, where the electronic entropy effects are included as the electronic temperature-dependent latent heat, boiling point, and melting point. For metal targets, Al and Cu, the calculated ablation rates for 100 fs laser pulses agree with the experimental one at laser fluences up to 10 J/cm 2. The heat-affected zone (HAZ) is numerically evaluated from the thickness of the molten layer. Short pulses produce a high ablation rate and small HAZ because of the suppression of diffusion of the deposited pulse energy. Electronic entropy effects make a clear difference between 100 fs and 10 ps pulses. The calculation method presented in this paper serves as a useful tool for exploring nonequilibrium between electrons and ions in the equation of states for metals such as Al and Cu. [ABSTRACT FROM AUTHOR]

Organic/inorganic thermoelectric hybrids demonstrate great potential for wearable applications. However, their scalability is hindered by an inferior power factor (S 2 σ). Nowadays, achieving deep optimization of S 2 σ necessitates a strategy to decouple the Seebeck coefficient (S) and electrical conductivity (σ). In this work, we propose a strategy to break the coupling between S and σ by constructing a Schottky interface that exhibits an energy-filtering effect. We validate the feasibility of this approach using a PANI/TiN–TiO2/carbon paper. The results demonstrate a 1.16-fold increase in σ and a 1.08-fold increase in S in PANI/TiN–TiO2/carbon paper achieved through the construction of a Schottky-type TiN/TiO2 interface. The separation of hole/electron at the TiN/TiO2 interface serves as the scattering center for ionized impurity scattering and facilitates the transport pathway for charge carriers. These factors are crucial in determining the simultaneous optimization of S and σ , respectively. Additionally, the energy-filtering effect of the TiN/TiO2 interface plays a positive role in the ionized impurity scattering mechanism by selectively filtering out low-energy carriers. This further strengthens decoupling of the thermoelectric properties. The 14.9% PANI/11.2% TiN–14.5% TiO2/59.44% carbon paper displays the highest S 2 σ and achieves a high ZT value of 223.6 μVm−1 K−2 and 0.31 at 300 K, highlighting the advantages of PANI-based thermoelectric hybrids. This work provides valuable guidance for the design of thermoelectric hybrids incorporating multi-interface morphology. [ABSTRACT FROM AUTHOR]

A Conductor on Round Core (CORC) cable wound with a high-temperature superconductor is an important cable concept for high-current density applications. It is widely used in large power systems because of its advantages of good flexibility and high engineering current density. However, the complex design structure of CORC cable makes it very difficult to understand its electromagnetic properties (such as AC loss). In particular, the different winding directions of each layer in multi-layer cable have a great influence on its electromagnetic characteristics. In this paper, the H-method is used to solve the electromagnetism and mechanics equations. The influence of the winding direction of CORC cable on its electromagnetic field distribution characteristics, AC loss, and mechanical variation under the action of external magnetic field is investigated. The AC loss study of single-layer cable reveals that when the applied magnetic field is increased from 0.01 to 0.02 and 0.03 T, the AC loss peak of the cable increases by 107 and 103 orders of magnitude, respectively, indicating that the effect of low applied magnetic field on the AC loss of the cable is more significant. For multi-layer cables, cables with opposite winding directions have a greater depth of current density penetration than cables with the same winding direction. In addition, the mechanical variations of multi-layer cables with different winding orientations are explored. The results show that the Mises stress in the cable with the same winding direction is about 32% higher than that of the cable with the opposite winding direction, which indicates that the method of winding the cable in the opposite direction between adjacent layers of tape can avoid excessive mechanical stress. [ABSTRACT FROM AUTHOR]

This paper presents BubbleID, a sophisticated deep learning architecture designed to comprehensively identify both static and dynamic attributes of bubbles within sequences of boiling images. By amalgamating segmentation powered by Mask R-CNN with SORT-based tracking techniques, the framework is capable of analyzing each bubble's location, dimensions, interface shape, and velocity over its lifetime and capturing dynamic events such as bubble departure. BubbleID is trained and tested on boiling images across diverse heater surfaces and operational settings. This paper also offers a comparative analysis of bubble interface dynamics prior to and post-critical heat flux conditions. [ABSTRACT FROM AUTHOR]

As a promising preclinical imaging technique, optical molecular tomography (OMT) shows great potential in early detection and diagnosis of tumor diseases. However, its widespread application has been hindered by the limitations of traditional reconstruction methods, specifically the accuracy of optical transmission models and the ill-posed nature of inverse reconstruction. The development of deep learning has offered novel solutions for OMT, enabling efficient reduction of the ill-posed nature in reconstruction. The existing deep learning approaches employ conventional neural networks and objective functions, which retains significant scope for enhancing the accuracy of image reconstruction. In this paper, we propose a source distribution correlation enabled self-attention residual network (DCeSR network) to address the need for accurate OMT reconstruction. The DCeSR network leverages a residual learning strategy and a self-attention mechanism to effectively integrate the deep and shallow features, subsequently extracting highly informative surface measurements to accurately predict the three-dimensional distribution of light sources within tissues. The efficacy of the DCeSR network was validated through training and testing with two distinct numerical simulated datasets, each encompassing both single and dual source configurations. Both qualitative and quantitative analyses demonstrate the superior performance of the DCeSR network in achieving accurate OMT reconstructions. [ABSTRACT FROM AUTHOR]

Lamb wave resonators (LWRs) based on lithium niobate on insulator (LNOI) substrates operating in an A1 mode at frequencies above 5 GHz typically exhibit high electromechanical coupling coefficients (K2) ranging from 20% to 30%. This makes them promising candidates to replace current bulk acoustic wave technology in next-generation broadband RF filters. However, the K2 of conventional LWRs still struggles to meet application requirements for bandwidths exceeding 1 GHz, such as WiFi-6E. This paper presents an analytical optimization approach for rapid and comprehensive scanning of the full 3D Euler space to find the maximum effective K2 of LWR devices. Such a full scan is difficult to achieve by the conventional time-consuming finite element method (FEM). The K2 results for a selected subset of Euler angles obtained through this analytical approach align with FEM simulation results. The optimized results show that LWRs on LNOI can achieve the highest K2 of 59.92% at Euler angles of (0, −151°, −60°), providing bandwidths exceeding 1 GHz at 5 GHz. To validate this optimization approach, LWRs with various orientations were fabricated on both 41° YX-cut and Z-cut LNOI wafers, with measured K2 values at different Euler angles agreeing well with both analytical and FEM results. The proposed K2 optimization method serves as a valuable guideline for selecting substrate cuts and device orientations in the design of ultra-broadband filters for next-generation telecommunications. [ABSTRACT FROM AUTHOR]

This paper unveils a pioneering ultra-wideband metasurface, achieving both optical transparency and significantly reduced scattering, surpassing current stealth material limitations. A novel dual-layer meta-atom, expertly balanced for polarization conversion and absorption, is meticulously fine-tuned through equivalent circuit analysis and a sophisticated genetic algorithm, targeting a broad operational bandwidth. By ingeniously arranging these meta-atoms alongside their mirrored twins, we facilitate an efficient redistribution of scattered cross-polarized energy, leading to substantial reductions in radar detectability. Simulation validations and experimental results affirm a marked improvement in stealth performance, characterized by a co-polarized RCS reduction in excess of 10 dB across the extensive 3.7–25.9 GHz band. This groundbreaking metasurface offers a versatile solution for wideband electromagnetic control in aerospace, telecommunications, and stealth applications, pushing the boundaries of stealth technology. [ABSTRACT FROM AUTHOR]

Drop impact onto wettability-patterned surfaces is of great significance in industries. Self-propulsion, self-splitting, and directional rebounding can be realized when drops impact on such surfaces. This paper established a diffuse interface/phase field model to delve into drop impact onto wettability-patterned surfaces, with two typical surfaces considered, one having a step change in the contact angle and the other having a smooth change in it. The diffuse interface model used the phase field to track the liquid–gas interface, was discretized on a half-staggered grid, and was run in a parallel manner. The model was validated first against an impact onto a uniform surface and then against an impact onto a hydrophilic surface coated with a superhydrophobic strip. A mesh independence study was conducted for the phase field modeling. Grid independence was achieved while the phase field mobility was kept fixed in meshes of varied resolutions. The major findings are as follows. The spreading of a spherical drop on gradient wettability surfaces resembles that of an ellipsoidal drop on a uniform surface, and axis-switching was observed. On the other hand, directional rebounding on multi-region wettability surfaces is enhanced with increased wettability contrast. [ABSTRACT FROM AUTHOR]

Many plasma systems and technologies, such as Hall thrusters for spacecraft propulsion, exhibit complex underlying physics that affect the global operation. When characterizing such systems in an experiment, obtaining full spatiotemporal maps of the involved state variables can be, thus, highly informative. However, this goal is not practically realizable because of various experimental limitations, e.g., finite spatial resolution of the diagnostics and geometrical accessibility constraints. Therefore, having the capability to reconstruct the full high-dimensional states of plasma systems from low-dimensional time-history measurements is greatly desirable. Compressed sensing is a signal processing technique that can answer this crucial need. However, existing compressed sensing approaches have several limitations that restrict their effectiveness for complex physical systems like plasma technologies. These include the need for abundant sensor measurements and a principled sensor placement. In this paper, we demonstrate the capabilities of Shallow Recurrent Decoder (SHRED) architecture for compressed sensing. We show in several plasma test cases that SHRED can robustly infer full high-dimensional spatiotemporal state vectors of these systems (i.e., all macroscopic plasma properties) from minimal system information. This minimal information can consist of three finite time-history measurements of either local values of a plasma property or the global plasma properties (spatially averaged or performance parameters). An application of SHRED's inference capability in the numerical plasma simulation context is "super-resolution" enhancement. We will discuss this application by presenting how SHRED can effectively establish mappings between a low-resolution and a high-resolution simulation, recovering detailed spatial plasma features that are below the simulation's grid size. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel contour search algorithm (CSA) for image processing. Its efficacy is evaluated through a comparative analysis with established techniques such as Canny Edge and Snakes: Active contour models, utilizing infrared thermography (IRT) images. Based on the new CSA, we investigate the influence of different pulse shapes on the IRT post-processing methodology, particularly focusing on the thermal shock response spectrum (TSRS), using two different heat sources: xenon flash lamps and a laser. Moreover, this allows for a more precise quantitative comparison of the TSRS with existing IRT post-processing techniques, including pulse phase thermography and thermal signal reconstruction, concerning the detection of defects in composite materials, particularly in carbon fiber-reinforced polymer. A quantitative comparison was performed using the Tanimoto criterion and signal-to-noise ratio. A more detailed analysis is conducted to identify inherent limitations and potential benefits of the new TSRS methodology. We further investigate and experimentally confirm our previous finding on the qualitative correlation between the one-dimensional thermal N-layer model and test data from the TSRS optimization process for defect determination. This correlation can eliminate the time-consuming optimization step, making TSRS a more attractive alternative to common IRT methods and enhancing the quantitative description of defects. [ABSTRACT FROM AUTHOR]

The magnetic performance of NdFeB permanent magnets rapidly decreases as their operation temperature increases. This limits the power output of electric motors as their internal temperature quickly increases with the power demand. This is particularly problematic for applications where high peak power is required for a short period of time, for example during automobile highway acceleration or during an airplane lift-off. With the advances in additive manufacturing, one can envision to fabricate more complex motor geometries and magnetic structures, without additional costs, allowing for enhanced functionalities such as better thermal management. In this context, this paper investigates the feasibility of using phase changing materials (PCMs) to mitigate the temperature rise in permanent magnets (PMs) fabricated by additive manufacturing. The potential of PCM and its relevance was validated by modeling the thermal response of an electric motor during a representative electric vehicle driving scenario. It was found that segmented magnets with embedded phase changing materials would allow to efficiently control temperature rise. To validate the simulation results, PM test pieces with and without embedded PCMs were fabricated using cold spray additive manufacturing and tested using a custom laser thermal cycling setup. [ABSTRACT FROM AUTHOR]

In this paper, we developed a theoretical model for the photothermal deflection technique in order to investigate the electronic parameters of three-layer semiconductor structures. This model is based on the resolution of thermal and photogenerated carrier diffusion-wave equations in different media. Theoretical results show that the amplitude and phase of the photothermal deflection signal is very sensitive to the nonradiative recombination parameters. The theoretical model is applied to one layer of InAs quantum dots (QDs) inserted in GaAs matrix InAs/GaAs QDs in order to investigate the QD density effects on nonradiative recombination parameters in InAs through fitting the theoretical photothermal beam deflection signal to the experimental data. It was found that the minority carrier lifetime and the electronic diffusivity decrease as functions of increasing InAs QD density. This result is also related to the decrease in the mobility from 21.58 to 4.17 (±12.9%) cm2/V s and the minority carrier diffusion length from 0.62 (±5.8%) to 0.14 (±10%) μm, respectively. Furthermore, both interface recombination velocities S 2 / 3 of GaAs/InAs (QDs) and S 1 / 2 of InAs (QDs)/GaAs increase from 477.7 (±6.2%) to 806.5 (±4%) cm/s and from 75 (±7.8%) to 148.1 (±5.5%) cm/s, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical study of the thermal conductivity of Si–Ge nanograin mixtures using a multiscale computational methodology based on solving the Boltzmann transport equation for phonons with first-principles techniques. A size-dependent correction factor is developed to account for the spatial dependence of the phonon distribution function on nanograin size, with parameters derived from the phonon properties of infinite Si and Ge crystals. This approach makes it possible to accurately calculate the thermal conductivity within a single nanograin, using force constants obtained from first-principles calculations. Thermal energy transport by phonons across grain boundaries is modeled by accounting for phonon transmission by two-phonon processes, weighting specular, and diffuse transmission for each phonon mode as a function of the root-mean-square roughness of the boundary relative to the phonon wavelength. The boundary thermal conductance model, previously validated against experimental data, is implemented using first-principles techniques. This approach excludes specular transmission for phonon modes with specific symmetries while ensuring conservation of the total number of modes in each symmetry class. The study examines the influence of grain size, nanograin mixture composition, temperature, and boundary asperities on the thermal conductivity of nanograin mixtures. [ABSTRACT FROM AUTHOR]

Impedance spectroscopy is vital for material characterization and assessing electrochemical device performance. It provides real-time analysis of dynamic processes such as electrode kinetics, electrons, holes or ion transport, and interfacial or defect driven phenomena. However, the technique is sensitive to experimental conditions, introducing potential variability in results. The intricate interplay of transient effects within the realm of spectral impedance analyses introduces a layer of complexity that may impede straightforward interpretations. This demands a nuanced approach for refining analytical methodologies and ensuring the fidelity of impedance characterization once the dynamic contributions of transient ingredients cannot be disentangled from the underlying steady-state characteristics. In our study, we experimentally identify that the transient effects in a memristor device are most pronounced near an optimal frequency related to intrinsic relaxation times, with these effects diminishing as the frequency varies beyond or below this range. While inherent systematic errors impose a practical limit (accuracy floor) on achievable measurement accuracy, this paper offers qualitative and quantitative insights into how specific procedures affect this limit and how to reduce it in orders of magnitude. Only by effectively addressing these errors, we can push beyond this constraint. [ABSTRACT FROM AUTHOR]

Acoustic metasurfaces are widely used for noise attenuation due to their outstanding acoustic performance and subwavelength characteristics. The paper introduces a topology-optimized inverse design approach for broadband sound-absorbing metasurfaces, aiming to achieve efficient sound absorption performance across a wide frequency spectrum. By integrating genetic algorithms with the finite element method and driven by objectives such as the absorption frequency range and absorption coefficient, we can transcend the limitations of manual design and fully exploit the design potential of structures. Furthermore, the study investigates the sound absorption mechanism and thermal-viscous dissipation through finite element simulations and experimental validations. The research findings reveal that the proposed broadband sound-absorbing metasurfaces demonstrate excellent sound absorption capabilities across the designated frequency range, boasting an average sound absorption coefficient exceeding 85%. These findings offer fresh perspectives and methodologies for advancing the research and practical application of broadband sound-absorbing metasurfaces. [ABSTRACT FROM AUTHOR]

This paper studies innovative microwave resonators, utilizing special dispersive materials whose relative permittivity is inversely proportional to the frequency square. The "dispersive material" refers not only to natural or synthesized materials but also to equivalent materials achieved through advanced dispersion management techniques. The new resonator theory and analysis of the electromagnetic properties and eigenmode frequency of these new resonators are presented comprehensively and validated through a combination of analytical and numerical simulations using commercially available electromagnetic simulation software (CST Studio Suite). Detailed deduction and demonstration of wideband resonance characteristic, unloaded quality factor (Q), and new formulas are given. Several new types of resonators are introduced including rectangular waveguide cavity resonators and dielectric resonators. This inverse-square property of the special dispersive material provides the new resonators with wideband resonance characteristics. Besides, other dispersive materials whose relative permittivity is inversely proportional to the frequency by the power of n are also demonstrated to be useful for bandwidth enhancement. Moreover, the theory behind these dispersive materials and their equivalent approaches for achieving similar material characteristics through various techniques of dispersion management are also discussed in detail. Compared with the traditional resonator, the new resonator breaks the bandwidth limitation and offers the potential to a variety of new microwave devices and antennas such as bandwidth enhancement, stable radiation patterns, and other merits. This could make it useful for a variety of applications including 6G communication, broadband radar systems, and ultrahigh-speed data transfer. [ABSTRACT FROM AUTHOR]

The document discusses the integration of machine learning (ML) into thermal transport research, highlighting its transformative impact on understanding and controlling heat transfer processes. It features 31 papers categorizing ML applications into machine learning potentials, predicting thermal properties, design and optimization, data analysis, and tutorials. ML has enabled accurate simulations, precise property predictions, innovative system designs, and efficient data analysis in thermal transport research, showcasing the potential for further advancements in the field. Despite challenges like model transferability, data scarcity, and interpretability, the document emphasizes the promising future of ML in advancing thermal science and engineering. [Extracted from the article]

Nanotechnology's impact on semiconductor industry advancement, particularly through the engineering of nanostructures like nanowires, opens new possibilities for material functionality due to the tunable physical properties of nanostructures compared to bulk materials. This paper presents a comprehensive study on group IV semiconductors and their binaries across four polytypes: 2H, 3C, 4H, and 6H, focusing on their optoelectronic application potential. Deep understanding of these polytypes is particularly relevant for nanowire-based technologies. Through first principles modeling, we examine the structural and electronic properties of these materials, emphasizing their band structure, stability, and the feasibility for light-emitting applications. We use a generalized Ising model to discuss materials stability and tendency for polytypism. We also determine relative band edge positions and employ a six-band k⋅p model for a detailed understanding of the materials' electronic properties. Due to the comprehensive nature of this study, we provide insight on the chemical trends present in all of the studied properties. Our theoretical predictions align well with the existing experimental data, suggesting new avenues for nanostructure-based device development. The discussion extends to the implications of these findings for the fabrication of optoelectronic devices with the studied IV–IV materials, highlighting the challenges and opportunities for future research in nanowire synthesis and their applications. [ABSTRACT FROM AUTHOR]

Refractory high-entropy alloys (RHEAs) have attracted increasing interest due to their excellent mechanical properties under extreme conditions. However, the lattice thermal conductivity is still not well studied. In this paper, we calculate the lattice thermal conductivity of the NbMoTaW RHEA using the equilibrium molecular dynamics method with a machine learning-based interatomic potential. We find that with increasing Mo concentration, the lattice thermal conductivity increased from 1.72 to 2.16 W/mK, an increase of 25.6%. The underlying mechanism is explained by the phonon density of states and phonon mode participation. Increasing the Mo concentration can induce a blueshift in both the low-frequency and high-frequency phonons. Moreover, we find that at the frequency corresponding to the phonon density of states peak, the NbMo1.5TaW RHEA has the largest mode participation rate, which is the main reason for the anomalous lattice thermal conductivity. In addition, we investigate the effect of temperature on the lattice thermal conductivity and the results show that anharmonicity has a dominant effect. Finally, the effect of compressive strain on the lattice thermal conductivity is explored. Our work discloses that the phonon density of states associated with phonon mode participation plays critical roles in the thermal conductivity of the RHEA, rather than the previously recognized conformational entropy. This contributes to the understanding of the thermal behavior of RHEA and provides an effective route to tune its thermal conductivity. [ABSTRACT FROM AUTHOR]

Noncontact transportation and separation techniques using airborne ultrasound are attractive for use in industrial fields in which micrometer- to millimeter-sized objects can be levitated, rotated, and transported in the air using acoustic standing-wave and traveling-wave fields. This paper discusses a method to rotate a small object in the air without physical contact using ultrasound. The experimental system comprises a vibrating disk with four bolt-clamped Langevin-type ultrasound transducers and two semicircular reflectors. The flexural vibration of the disk generates an acoustic standing wave between them, and a small object can be levitated at the nodal position. An acoustic traveling wave was generated in the horizontal direction in an asymmetric acoustic field by inclining one of the two reflectors, which induced rotation of the object in the clockwise or counterclockwise direction. The acoustic intensity in the circumferential direction acting on the object was then calculated, and the directions of rotation predicted by the calculations corresponded with the experimental results. Higher input currents produced higher rotation speeds; the rotation speed reached a maximum value of 6.8 ± 0.9 rps at an input current of 1.1 App. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically and numerically demonstrate a tunable and polarization-dependent electromagnetically induced transparency analogy based on graphene terahertz metasurfaces. The unit cell of the metasurface consists of three-layer graphene strips embedded in a silicon grating. The dynamic adjustment of the transparent window can be achieved by changing the coupling distance between the graphene layers and the polarization direction of the incident lights. The operation mechanism behind the phenomenon can be attributed to the near-field interaction and electromagnetic coupling of modes in graphene strips. Furthermore, the full wave electromagnetic simulations obtained by the finite-difference time-domain method agree well with the theoretical fitting results based on the three-harmonic oscillator model. In addition, by changing the Fermi levels, it can not only realize the outstanding slow-light effects with a maximum group index of 3750 but also obtain the four-frequency asynchronous optical switch function in terahertz regions. Therefore, our proposed metamaterial device may have potential applications in image switching, optical switches, slow-light device, optical communication, and optical storage. [ABSTRACT FROM AUTHOR]

The thermomechanical behavior of materials is known to be sensitive to preexisting defects in their microstructure. In this paper, non-equilibrium molecular dynamics simulations have been used to investigate the effects of the microvoid size on the plastic deformation in single-crystal iron shock-compressed along the [ 001 ] crystallographic direction. The higher the microvoid radius, the faster the kinetics of dislocations. Thus, as the microvoid radius increases, the plastic activity evolves from a regime where the deformation is dominated by twin activities to a regime where both twin and dislocation activities play an essential role and then to a regime where the deformation is dominated by dislocation slip. Furthermore, in both defect-free and defective initial crystal states, the elastic precursor wave is observed to decay with propagation distance, resulting in a constitutive functional dependence of the yielding pressure, σ E , on the plastic deformation rate, ε ˙ p. In the regime where both deformation twinning and dislocation slip play important roles, the constitutive behavior is consistent with the original Swegle–Grady model and is in overall agreement with experimental data and thermomechanical simulations. [ABSTRACT FROM AUTHOR]

Nanoparticles play an important role in the properties of metallic glasses (MGs) due to their diversified structures; however, their structure–property relationship is unclear. In this paper, three ex situ metallic glass matrix composites were assembled by three kinds of nanoparticles and Cu50Co50 MG obtained by rapid cooling, and their structural evolution under uniaxial compression is investigated by molecular dynamic simulation. It is found that the activated atoms always preferentially accumulate in the amorphous region near the embedded nanoparticles (ENPs). ENPs hinder the propagation of shear bands and lead to strain-hardening behavior. The fractal structures convert the HCP and tDh atoms into atoms of other structures to improve the anti-deformation ability, and the parallel-twin structure improves the anti-deformation ability through the mutual conversion of the FCC and HCP atoms. These findings provide a new idea for improving the mechanical properties of MGs. The change in the ENP structure provides theoretical support for the design of composite materials with specific requirements for structural evolution. [ABSTRACT FROM AUTHOR]

In this paper, we report on the electrical impedance measurement of human endothelial cellular networks and show the existence of emergent power law behavior in its admittance. In particular, we find that the admittance scales with the frequency ω as ωα, with the exponent that varies with the degree of the disruption caused by the inflammation in the endothelial cellular network. We demonstrate that the power law of the measured electrical admittance can be understood by a simple percolation model of a large R–C (resistor–capacitor) network, which allows us to relate quantitatively and the intensity of inflammation. Our results suggest that the electrical properties of heterogeneous biomaterials, like living tissues, behave as a complex microstructural network. [ABSTRACT FROM AUTHOR]

Owing to charge free property, magnon is highly promising to achieve dissipationless transport without Joule heating and, thus, potentially applicable to energy efficient devices. In this paper, using the non-equilibrium Green's function, we present the bulk-boundary correspondence for magnonic Kagome lattices by studying the edge magnons transport. With staggered exchange interaction and Dzyaloshinskii–Moriya interaction in the Kagome lattices, one can observe valley contrasting magnon Hall effect, which endows magnon transport with the valley degree of freedom and adds a new dimension to regulate magnon excitation. In particular, we demonstrate that the valley splitting in the Kagome lattice enables a tunable single edge chiral transport. Thermal rectification is a direction-dependent asymmetric heat transfer phenomenon; here, we report the tunable thermal rectification by asymmetric nonlinear effect, and it is, indeed, regulated by the Dzyaloshinskii–Moriya interaction direction (D → − D) and the exchange of J 1 and J 2 (J 1 ↔ J 2). Moreover, we show that the topological edge state mainly localizes around edges and leaks into the bulk with oscillatory decay. These give full play to spin and valley degrees of freedom and provide various avenues for information encoding and manipulation based on valley related magnonic flux. [ABSTRACT FROM AUTHOR]

Due to the high conductivity and low permeability of giant magnetostrictive materials (GMMs), eddy currents and temperature rise caused by these materials are unavoidable. These factors will significantly impact the output efficiency and reliability of giant magnetostrictive transducers (GMTs). It is essential to conduct precise evaluations of the output characteristics in various temperature settings to effectively design and optimize the transducer. However, to reduce the eddy current loss of GMMs, a radial slit is introduced. The intricate geometry also contributes to the complexity of analysis. According to the practical engineering requirements, this paper initially established a testing system for GMM characteristic and analyzed the mechanism between material temperature and output characteristics. Second, improvements have been made to the equivalent circuit method. Research has been conducted on the influence of temperature and eddy currents on the electrical and mechanical equivalent circuits, leading to the creation of a comprehensive equivalent circuit model for GMTs. Finally, a testing platform has been set up to assess the temperature-output characteristics of the transducer. The impedance and displacement characteristics of a GMT were examined to validate the proposed model. The test results demonstrated that within the 20 – 100 °C range, the discrepancy between the model and the measured impedance is under 1%, and the displacement amplitude error is less than 5%, thus confirming the precision of the proposed model. [ABSTRACT FROM AUTHOR]

The dynamic response and damage fracture of brittle materials under explosive cutting have always been important research issues in the fields of military, aerospace, and other engineering fields. In this paper, a linear shaped charge cutting model for explosive cutting of brittle materials is proposed. This model suggests that explosive cutting is caused by the combined effects of jet penetration, spallation, and impact fracture. Theoretical calculation models for jet penetration, spallation, and impact fracture were constructed, and the concept of impact strength was introduced to establish dynamic mechanical performance parameters for brittle materials. A calculation program for explosive cutting of brittle materials was developed using the Python language, which can calculate the jet penetration depth, spallation thickness, and impact fracture thickness by inputting parameters such as the size and mechanical properties of the linear shaped charge and target plate, and determine whether the target plate can be successfully cut. Subsequently, a series of explosion cutting experiments and numerical simulations for brittle target plates were conducted to verify the accuracy of the calculation program. The results indicate a high degree of consistency between simulation, experimentation, and program calculation results. This work can provide guidance and promotion for the design and application of explosive energy harvesting cutters. [ABSTRACT FROM AUTHOR]

Fluorographene, a fluorinated graphene-derivative, is expected to feature both high thermal conductivity and electrical insulation simultaneously, making it an emerging material for thermal management in electronic devices. In this paper, we investigated the lattice thermal conductivity and phonon transport properties of monolayer fluorographene using first-principles calculation. The solution of the fully linearized phonon Boltzmann transport equation gives the lattice thermal conductivity of monolayer fluorographene as 145.2 W m−1 K−1 at 300 K, which is about 20 times smaller than that of monolayer graphene. We systematically compared the phonon transport properties of all phonon modes in graphene and fluorographene in terms of phonon polarization. The significantly reduced thermal conductivity of fluorographene can be attributed to the lowering of both the lifetime of the flexural acoustic phonons and the group velocities of all acoustic phonons. We concluded that the broken in-plane mirror symmetry and the weaker in-plane chemical bonds induced by fluorination led to the suppression of the lattice thermal conductivity of fluorographene. Finally, we investigated the anomalously large contribution of optical phonons to the thermal transport process in fluorographene, where the large group velocities of selected optical phonons were derived from the in-plane acoustic modes of graphene. Our work provides a new approach to studying the influence of chemical functionalization on the phonon structure and exploring graphene-derived thermal management materials. [ABSTRACT FROM AUTHOR]

Molecular quantum-dot cellular automata (QCA) may provide high speed, low-power, classical information processing in the post-CMOS era. The readout of molecular QCA bits is challenging because the molecules may be much smaller than transistors and even single-electron transistors. This paper builds on a recent proposal for the spectroscopic readout of bits from asymmetric QCA molecules. Here, we propose circuits for fanning out a bit onto a large QCA circuit to increase the spectroscopic signal-to-noise ratio. As the number of molecules in a fanout circuit grows, the internal bias of each asymmetric cell accumulates, and the circuit may become stuck, tolerating only a very small internal bias. We also propose the use of an applied electric field to compensate for a candidate molecule's internal bias, thereby restoring switchability, even when the internal bias is significant. [ABSTRACT FROM AUTHOR]

This paper studies full-scale gas neutron tube modeling, including the following processes: gas discharge combustion in a Penning ion source, particle motion in an ion optical system, and modeling the in-target processes, such as sputtering, diffusion, thermal desorption of hydrogen isotopes, and nuclear reactions. Plasma modeling in quadrupole electric and axial magnetic fields was based on the electrostatic particle-in-cell method with molecular kinetic processes. The TechX Vsim software package was used. The neutron tube element sputtering by ions was simulated using SRIM/TRIM software based on Monte–Carlo methods. The OpenFOAM, as an open integrated platform for numerical simulation in continuum mechanics, was used to calculate the hydrogen thermal desorption activated by ion irradiation. The time-dependent neutron yield modeling was performed using the Geant4 software based on Monte–Carlo methods with CHIPS-TPT VNIIA-developed library. In addition, an experimental study of a gas neutron tube with a Penning ion source was conducted here as well. Details are given on the experiment and measurement technique used in this study. The operating characteristics for the gas neutron tube, including amplitude-time characteristics of current flashes (discharge and extraction currents), were determined. The neutron flux dependencies on the discharge current at various accelerating voltages were also obtained. Finally, a comparison between the experimental and calculated results is presented. [ABSTRACT FROM AUTHOR]

Ultrashort pulse (USP) lasers provide a novel approach to microwave production for remote applications. In this scheme, the plasma produced in the interaction of a USP with a material surface at a distance serves as a localized source of radio frequency (RF) radiation. Ultrashort pulses allow for the long-range projection of high-intensity light (∼1013 W/cm2), through the phenomenon of laser filamentation, thereby enabling the efficient generation of transient plasmas on remote material surfaces. In this paper, the mechanism of RF production in the laser–matter interaction is discussed and experimental characterization of the RF emission in a variety of target geometries is presented. Both transient dipole radiation and resonance absorption are discussed as theoretical mechanisms of RF generation. Furthermore, spectral composition of the RF emission, angular distribution of the emission, and dependence of the RF on laser focusing conditions are all characterized for a number of target materials in the single to tens of GHz range, using microwave horn antennas in conjunction with heterodyning electronics. [ABSTRACT FROM AUTHOR]

Vanadium dioxide ( VO 2) as a typically strongly correlated material has an attractive near-room-temperature metal–insulator transition (MIT). This transition shifted between metallic rutile and insulating monoclinic phases can be reversed by external thermal stimulation, accompanied by alterations in the lattice structure and electronic energy band structure, which bring about drastic changes in optical, electrical, thermal, and mechanical properties. Based on these unique characteristics, the VO 2 -integrated element can be utilized in the versatile transduction that converts indirect measurable factors into detectable physical quantities, representing a leap forward in sensing technology and facilitating the development of advanced systems toward an unprecedented level of sensitivity and responsiveness. In this perspective, we review the multifunctional advantages of VO 2 , driven by its thermally induced MIT, which transforms its crystal and electronic structures, leading to changes in optical, electrical, thermal, and mechanical properties. Our paper highlights that VO 2 can serve as a high-performance transduction element, leveraging its attractive properties to facilitate the conversion of various variations into measurable signals, thereby enabling diverse advanced applications. To maximize the advantages of VO 2 , we identify the key challenges and opportunities related to this material, offering guidance and recommendations for future research directions. [ABSTRACT FROM AUTHOR]

There is no consensus among researchers regarding how phase transitions occur in antiferroelectric (AFE) epitaxial heterostructures, in particular, in heterostructures based on model AFE lead zirconate. The questions about the number of phase transitions in such films and by what mechanism they occur remain controversial. This paper presents a look at the phase transition scenario in two types of epitaxial heterostructures: PbZrO 3 /Ba[La–Sn]O 3 /MgO (001) thin films with thicknesses from 25 to 1000 nm and PbZrO 3 /SrRuO 3 /SrTiO 3 (001) thin film 100 nm thick using the diffuse x-ray scattering in the grazing incidence setup. We register the characteristic butterfly-shaped diffuse scattering (DS) intensity distribution in the H K pseudocubic planes, which corresponds to the anisotropic ferroelectric soft mode. No incommensurate soft mode was observed in the cuts of reciprocal space parallel to the film surface by diffuse scattering. We reproduce the shape of DS distribution at different temperatures by the model based on the dielectric stiffness and the electric polarization correlation tensor in the cubic approximation. Such modeling allows not only to characterize the DS parameters from the challengingly low signal-to-background data set, but also to extract experimentally the sensitivity of the materials with respect to inhomogeneous polarization. While the observed temperature evolution of DS is consistent with the dielectric measurements, the correlation between the DS and the phase transition sequence observed by superstructure reflections is yet to be understood better. [ABSTRACT FROM AUTHOR]

This paper presents the design of a single-phase solid phononic crystal (PnC) structure featuring a regular hexagonal perforation pattern. The structure manifests three negative refraction bands, encompassing one for transverse waves and two for longitudinal waves, thereby enabling simultaneous control of shear and longitudinal waves. Due to the high symmetry of the triangular lattice, the equal frequency curves corresponding to the negative refraction band approach circular shapes, suggesting a nearly isotropic negative refraction effect. This negative refraction effect is achieved through specific mass resonance modes closely related to the porous structure designed in this paper. Initially, we analyze the band structure of the PnC, followed by designing the PnC plate structure to achieve negative refraction control for transverse waves at a frequency of 32.4 kHz, with a negative refraction index of −1. Additionally, negative refraction control for longitudinal waves is attained at frequencies of 44 and 64.54 kHz. Subsequently, we scrutinize the influence of various conditions on negative refraction, including different structural parameters, incident angles, and operating frequencies, while verifying the robustness of the designed phonon crystal structure. Leveraging the negative refraction characteristics of the structure, we construct an elastic wave lens to achieve perfect imaging of shear and longitudinal waves. Finally, employing finite element simulation and analyzing focusing imaging characteristics with different source positions, we validate that the results closely align with theoretical expectations. The solid PnC structure designed in this study holds significant potential for applications in the fields of elastic wave imaging. [ABSTRACT FROM AUTHOR]

The time-modulated active medium with linear independent frequency conversion method has been demonstrated to enable wave orientation and reconstruction. However, due to the symmetric scattering field, this technique requires intricate microcircuit designs. To overcome this limitation, this paper proposes a tunable piezoelectric metasurface based on acoustic black holes (ABHs) to redirect flexural wave reflections. The system can convert an incident flexural wave into a reflected wave of any direction and frequency. This is accomplished through the linear time modulation of the sensing signal, which breaks the constraints of Snell's law inherent in traditional designs and is insensitive to the incident amplitude. The coupling of the ABH damping system with a linear independent frequency conversion mechanism allows for the conversion of an incident flexural wave into a reflected wave in any direction and frequency while also eliminating the influence of second harmonic reflection on the wave field and simplifying the time modulation circuit. In addition, this paper demonstrates arbitrary angle reflection, focusing, beam splitting, and frequency conversion of the incident wave. By improving the flexibility of elastic wave manipulation, this paper introduces a new approach for active control of elastic waves and provides a design method that can be employed in a variety of applications ranging from vibration protection of engineering structures to vibration sensing and evaluation. [ABSTRACT FROM AUTHOR]

In this work, in-plane thermal conductivity measurement was carried out on graphene-based papers. Graphene-based papers were fabricated using various processing techniques such as chemical vapor deposition (CVD), hot pressing of graphene slurry, and evaporation induced self-assembly. The prepared materials were characterized using scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. In-plane thermal conductivity measurement was performed via a steady state thin film thermal conductivity apparatus. The in-plane thermal conductivity measurements show that the CVD based sample has the highest thermal conductivity. COMSOL Multiphysics was used to simulate the in-plane thermal conductivity of graphene-based papers. [ABSTRACT FROM AUTHOR]

Cellulose insulating paper is widely used in the power industry for its good electrical insulating properties. Moisture sharply increases its conductivity, which directly leads to the weakening of insulation performance and greatly increases the risk of subsequent electric field distortion and insulation breakdown. This paper focuses on the microscopic mechanism of moisture changing the characteristics of charge transport in cellulose insulation and attempts to reveal the related conductivity mechanism. To achieve this purpose, microscopic and macroscopic perspectives are integrated and several simulation and experimental methods are utilized comprehensively. The molecular dynamics simulation results showed that most water molecules in damped cellulose were individually and uniformly adsorbed on the hydroxyl groups by hydrogen bond, and the quantum chemistry computation results showed that the lowest unoccupied molecular orbital more appeared on the water molecule and the corresponding density of state increased. Then, experimentally, it was confirmed that the trap energy level decreased by the thermally stimulated current method. On this basis, the promotion effect of moisture on charge transport is predicted and verified by polarization and depolarization current methods. As the moisture content increased, more charge carriers escaped from the trap by hopping and participated in long-range continuous charge motion. Therefore, after dampness, the current of cellulose insulating paper increased exponentially with the increase in electric field strength, which was consistent with the hopping conductivity mechanism. [ABSTRACT FROM AUTHOR]

In this paper, a Zr–5W alloy was fabricated via casting. In order to obtain the mechanical properties of the material, quasi-static compression tests at room temperature and split Hopkinson pressure bar tests at various temperatures were carried out. The x-ray diffraction result showed that the main components of the alloy were αZr and W2Zr, where αZr is the matrix and W2Zr is the reinforcement. The metallographic characterization results showed that there were two main forms of W2Zr in the material, namely, large particle boundary and small diffuse submicrometer precipitates. The reinforcements of both distributions have the effect of increasing the strength of the material, but the small submicrometer W2Zr precipitates would cause microcrack nucleation during the late plastic deformation stage, resulting in damage softening. In order to make theoretical calculations of the mechanical properties of materials, the Johnson–Cook (JC) constitutive model and Zerilli–Armstrong (ZAM) constitutive model of the material were obtained. It was found that the JC constitutive model had poor consistency in describing material properties. Although the consistency of the ZAM constitutive model was higher than that of the JC constitutive model, it still had obvious shortcomings. Combined with the deformation mechanism of the alloy, a modified constitutive relation was established by adding damage softening terms based on the hexagonal close-packed metal constitutive model inferred by the kinetics of heat-activated dislocations. The relative error results of all working conditions show that the correlation consistency of the improved constitutive model in this paper is significantly better than that of JC constitutive and ZAM constitutive. [ABSTRACT FROM AUTHOR]

The study of insulation degradation processes is crucial for the reliable operation of power equipment and electronic devices. The phase field method has been widely used in recent years to simulate the degradation process of insulation materials. However, the effect of space charge was ignored. In this paper, a novel phase field method based on the bipolar carrier transfer model is suggested. This model can simulate degradation under different temperatures and DC or combined AC/DC voltage. The cases under AC and combined AC/DC voltage at different temperatures are simulated by COMSOL. Methods to ensure model convergence are proposed. The results show that the field strength distribution under a combined AC/DC field is more uniform, especially for negative polarity. For the same voltage form, temperature and breakdown time show an exponential relationship. The results are consistent with those of previous experimental studies, proving the usability of the model. In addition, the processes of initiation, growth, and breakdown stage of the dielectric degradation process, as well as the stagnation period, are explored theoretically. The stagnation time at low temperatures under combined AC/negative DC voltage is long. The research in this paper is useful for insulation optimization design, condition assessment, and longevity prediction. [ABSTRACT FROM AUTHOR]

Alternating current (ac) losses in conductor-on-rounded-core (CORC) cables of YBCO high-temperature superconducting (HTS) tapes are a significant challenge in HTS power applications. This study employs two finite element analysis (FEA) models to investigate the contributions from different ac loss components and provide approaches for reducing ac losses in cables. An FEA model based on the T-A formulation treats the cross section of thin superconducting layers as 1D lines and, therefore, only can predict the ac loss generated by the perpendicular magnetic field. In contrast, the model based on H-formulation can be performed on the actual 2D rectangular cross section HTS tapes to provide the total ac losses generated by magnetic fluxes penetrating from both the edges and surfaces of HTS tapes, although this model requires more computing time and memory. The 1D and 2D simulation models were validated by cross comparing the results from both models and by comparing sub-section and full cross section models. Subsequently, two models relate cable design and operational parameters to the surface and edge losses of a two-layer CORC cable by considering the (1) relative contributions of edge and surface losses to the overall ac losses; (2) effect of the current distribution between inner and outer HTS layers on ac losses; (3) impact of the tape alignment on ac losses in each HTS layer; (4) influence of the thickness of HTS layers on ac losses; (5) effect of size and number of inter-tape gaps on ac losses; and (6) contribution frequency on the ac losses. The research results given in this paper are therefore not only valuable to suggest strategies for reducing ac loss in multi-layer cables but also for developing more accurate and effective methods to calculate ac loss in CORC HTS cables. [ABSTRACT FROM AUTHOR]

Magnetic Johnson noise is an important consideration for many applications involving precision magnetometry, and its significance will only increase in the future with improvements in measurement sensitivity. The fluctuation–dissipation theorem can be utilized to derive analytic expressions for magnetic Johnson noise in certain situations, but when used in conjunction with finite element analysis tools, the combined approach is particularly powerful as it provides a practical means to calculate the magnetic Johnson noise arising from conductors of arbitrary geometry and permeability. In this paper, we demonstrate this method to be one of the most comprehensive approaches presently available to calculate thermal magnetic noise. In particular, its applicability is shown to not be limited to cases where the noise is evaluated at a point in space but also can be expanded to include cases where the magnetic field detector has a more general shape, such as a finite-size loop, a gradiometer, or a detector that consists of a polarized atomic species trapped in a volume. Furthermore, some physics insights gained through studies made using this method are discussed. [ABSTRACT FROM AUTHOR]

Recently developed ductile inorganic semiconductors have opened a new avenue toward potential applications such as flexible electronics. Significant studies have been conducted based on different atomic models to understand the deformation mechanism using first-principle calculations; however, the comparative study on these atomic models remains unexplored. In this paper, taking Ag2S as an example, we simulated the slipping process using bulk, slab, and tilt-cell models. Systematic supercell tests were performed to investigate the convergence of the slip/cleavage energy based on the three atomic models. It was found that a reasonably large supercell is required to converge the slip/cleavage energy, and the ratio between minimum cleavage and maximum slip energy converges to a comparable value among different atomic models, where the tilt-cell and slab models show slightly higher energy ratio values compared with the bulk model. However, the comparison of different exchange-correlation functionals and van der Waals corrections indicates that the calculations of slip and cleavage energies are sensitive to the choice of calculation methods, highlighting the importance of using the same method for comparing slip and cleavage energies of different materials. This work provides insights into understanding different atomic models of ductility mechanisms in ductile inorganic semiconductors. [ABSTRACT FROM AUTHOR]

The fully discrete dislocation equation can be rationally derived from the spectrum model. In this paper, the previous spectrum model is reinterpreted to cover the global feature of the spectrum. Instead of the local behavior around the origin of the Brilouin zone, the global spectrum model focuses the maximum at the boundary of the Brillouin as well as the slope at the origin of the Brilouin zone. The strength of the point-contact interaction that effectively describes the discreteness effect becomes larger because the whole lattice effect is included in the global spectrum model. The validness and signification of the new model are illustrated by a solvable lattice dynamical model of the cubic lattice. [ABSTRACT FROM AUTHOR]

This paper presents an improved two-dimensional logistic map. Relative to the original logistic map, the improved chaos map has better performance, e.g., larger chaotic range, higher complexity, and boosting sequence. Based on these good performances, a novel encipherment strategy is designed according to the hybrid coding of DNA and S-box algorithm. During the design of the algorithm, the primary operations include chaotic stream generation, permutation, and diffusion. The chaotic streams are constructed from the improved two-dimensional logistic map. The diffusion stage is achieved by the spatiotemporal chaos algorithm. The security test reflects that the design algorithm can effectively defend against external attacks. [ABSTRACT FROM AUTHOR]