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Microwave-induced thermoacoustic imaging (TAI) is a hybrid imaging technique that combines electromagnetic radiation and ultrasonic waves to achieve high imaging contrast and submillimeter spatial resolution. These characteristics make TAI a good candidate to detect material anomalies that change the material electric properties without a noticeable variation in material density. Conventional pulsed TAI systems work by sending a single short pulse to the imaged target and then detecting the generated pressure signal; therefore, a very high peak power microwave pulse or data averaging is needed to produce images with a high signal-to-noise ratio (SNR). In this paper, we propose to enhance the SNR of pulsed TAI systems by using non-coherent pulse compression. In this approach, a predefined pulse coded signal is used to illuminate the imaged sample and the received pressure signal is cross correlated with a template that is related to the power profile of the excitation signal. The proposed approach can be easily deployed to pulsed TAI systems without the need for major system modifications to the RF source because it only requires a timing circuit to control the triggering time of the RF pulses. In this paper, we demonstrate experimentally that the proposed approach highly improves the SNR of TAI signals and images and can be used to reduce the acquisition time by lowering the number of data averaging or reduce the required peak power from RF sources. [ABSTRACT FROM AUTHOR]

Graphene is a highly promising material in the field of spin electronics. Recent experiments on electron spin resonance have observed a reduction in the g-factor of graphene. In our previous paper [J. Phys. Soc. Jpn. 88, 094707 (2019)], we demonstrated that one of sources for this reduction is the diamagnetic property of graphene. However, the diamagnetic property by itself does not fully account for the magnitude of the reduction observed in the experiments. In this paper, we focus on the Rashba effect, which is caused by the work function existing near the surface of graphene. The Rashba effect tilts the spin magnetic moment to the in-plane direction of the graphene sheet, potentially reducing the g-factor. We evaluate this reduction using a simple model system incorporating the Rashba and spin Zeeman effects. We then demonstrate that the resultant g-factor is in close agreement with that observed in the prior experiments, indicating that the Rashba effect is able to account for the remaining reduction in the g-factor of graphene. [ABSTRACT FROM AUTHOR]

The article discusses the highlights of the 11th International Surface X-ray and Neutron Scattering (SXNS-11) Conference that took place at the Northwestern University (NU) campus in Evanston, Illinois from July 13-17, 2010. The conference, which was hosted by the NU Materials Research Science and Engineering Center, has gathered 164 delegates from 16 countries. Information on papers presented at the conference are presented.

Magnetic fields emitted by wireless power transfer systems are of high importance with respect to human safety and health. Aluminum and ferrite are used in the system to reduce the fields and are termed as passive shielding. In this paper, the influence of these materials on the space profile has been investigated with the help of simulations on Comsol for the four possible geometries--no shielding, ferrite, aluminum, and full shielding. As the reflected impedance varies for the four geometries, the primary current is varied accordingly to maintain constant power transfer to the secondary side. Surrounding magnetic field plots in the vertical direction show that maxima's of the two coils for the no shielding geometry are centered at the respective coils and for the remaining three are displaced closer to each other. This closeness would lead to more effective addition of the two coil fields and an increase in the resultant field from space point of view. This closeness varies with distance in the horizontal direction and vertical gap between the coils and is explained in the paper. This paper provides a better understanding of effect of the passive shielding materials on the space nature of magnetic fields for wireless power transfer for vehicle applications. [ABSTRACT FROM AUTHOR]

A preface to the Special Topic section of selected papers for the 20th International Symposium on Integrated Ferroelectrics is presented.

The stacking orders that may be generated by mirroring a layer of Cr X 3 (X = I, Br, Cl) through its Cr atomic layer in heterostructures are easy to be ignored so that the influence of these stacking orders has not yet been well explored. In this paper, we have constructed all eight stable highly symmetric stacking orders that maintain translational symmetry in a Cr I 3 / α - In 2 S e 3 heterostructure and systematically studied the dependence of the structure, magnetism, electronic structure on stacking orders, and ferroelectric polarization directions by using the first principles method, especially that the system energy and magnetism have certain differences between normal and mirror stacking orders. The regulation of system energy and interlayer distance, magnetism, and band structure can be, respectively, explained by the different stacking relationships of atomic layers in different stacking orders, the different influences of different deformations of a Cr I 3 atomic structure on a magnetic exchange interaction in different stacking orders, and the different band alignments corresponding to different vacuum energy levels at different interfaces of α - In 2 S e 3. Our work will have a certain reference value for understanding the material properties and practical applications of such ferromagnetic/ferroelectric heterostructures. [ABSTRACT FROM AUTHOR]

The velocity and density of a jet resulting from the reflection of a shock wave on a surface with geometric defects (the micro-jetting process) can be an important component of jet fragmentation models. While several models in the literature allow for the calculation of jet velocity, the density is generally ignored. In this paper, we present a semi-analytical method for determining both the velocity and density of a jet from a triangular defect. This model is an extension to micro-jetting specificities of the model usually used for shaped charges. Based on the physics of two-dimensional shocks, it allows a good restitution of the jet velocity and density from classical molecular dynamics simulations. It also provides a good agreement with the literature data, both experimental and numerical. [ABSTRACT FROM AUTHOR]

The enhancement of plasma generation in atmospheric pressure dielectric barrier discharge (DBD) is gaining increasing interest for various plasma applications. In this paper, the effect of surface charges moving with the rotating dielectric plate on improving the generation of streamer channels is investigated by a statistical analysis of electrical measurements, optical diagnostics, and numerical simulation in a needle-plate DBD device with a rotating dielectric plate. Results suggest that rotating the dielectric plate can improve the spatiotemporal distribution of streamer channels by inducing a bending of the streamer channels and an increase in the number of discharges. Statistical results show that the number of current pulse and discharge energy are increased by 20% and 47%, respectively, at the rotating speed of 160 rps (revolution per second). Based on the interaction between the applied electric field and the electric field induced by surface charges, a formula is proposed to govern the effect of rotating the dielectric plate on the discharge energy and streamer bending. To further understand the mechanism of the influence of rotating the dielectric plate on plasma properties, a 2D fluid model is implemented, and the reduced electric field and streamer propagation are analyzed. Results show that the effective transfer and reuse of surface charges play an important role in the enhancement of plasma generation. [ABSTRACT FROM AUTHOR]

Over the last 30 years, various dielectric resonator antennas (DRAs) have been developed for application in portable wireless communications and millimeter wave systems. However, current methods to feed the antennas suffer from radiation leakage and high losses. In this paper, we propose using a topological photonic crystal (TPC) as an effective feeding method, which can effectively suppress the reflecting loss at the feeder/DRA interface. As a demonstration, we numerically design a DRA with a TPC feeder, operating in a high-order resonant mode at 1.5 THz. Simulation results show that the antenna has a return loss as low as 44 dB, an impedance bandwidth of 3.9%, a maximum gain of 7.4 dBi, and 3dB angular widths of 58 degrees. Over 99% radiation efficiency can be achieved at the operating THz band. The proposed all-dielectric antenna can be suitably used for integrated photonic chips, biomedical applications, and 6G. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigate the transmission properties of a structure composed of a topological one-dimensional photonic crystal (1D PhC) heterostructure and a conventional 1D PhC containing indium-antimonide (InSb) as a defect layer using the transfer matrix method. The phenomenon of Fano resonance can be achieved by coupling the defect mode with the topological edge state mode, which is supported by the topological PhC. The numerical results show that a narrow Fano resonance is observed in the transmission spectrum of the structure in the presence of the external magnetic field applied to the InSb defect layer. The optical properties of the InSb defect layer, and, therefore, the Fano resonance, can be dynamically controlled by changing the applied external magnetic field. The results obtained with the proposed structure reveal that the magnetic field has the greatest influence on controlling the optical properties of the Fano resonance. These findings could be beneficial for optical devices such as optical filters, sensors, and optical switches. [ABSTRACT FROM AUTHOR]

Edge kinetics in 2D structures has been a key to understanding the growth. In this paper, the effect of hydrogen passivation on the growth of hexagonal boron nitride (h-BN) was studied. Without hydrogen, the filling process of the gap on bare edges of h-BN is difficult because of the formation of dimers that distorts the edge. With hydrogen passivation, such difficulty can be largely reduced. In addition, hydrogen passivation can reduce the edge bending to the substrate. In summary, the amount of hydrogen passivation during the growth is the long-ignored parameter and can be the key to a good crystal quality. [ABSTRACT FROM AUTHOR]

Nanostructures incorporating copper oxide (CuO), a narrow bandgap p-type semiconductor, are well suited for applications such as gas/biosensors, field emission devices, and photodetectors. However, the use of CuO nanocomponents in these applications is currently limited by the availability of fabrication and in situ processing techniques. In this paper, we show that the electrical and mechanical properties of CuO nanowire (NW) networks can be adjusted through sequential processing with nanosecond laser radiation. This new two-stage process involves selective breakage/cleaving of CuO NWs with an initial set of laser pulses, followed by irradiation with a second set of laser pulses applied in an optimized orientation to tailor bonding and junction formation between pairs and bundles of previously separated CuO NWs. We find that stage one processing introduces a high concentration of oxygen vacancies in NWs leading to the nucleation of dislocations and high strain. This localized strain is responsible for the breaking of individual NWs, while the high oxygen vacancy concentration modifies the electrical conductivity within each NW. The second stage involves re-orientation of the laser beam, followed by additional laser irradiation of the NW network. This has been found to result in the bonding of NWs and the creation of junctions in regions where CuO NWs are in contact. Laser-induced heating under these conditions produces melting in the contact areas between NWs and is accompanied by the reduction of CuO to form Cu2O as verified via XPS and Raman analysis. XRD and TEM observations demonstrate that plastic deformation within CuO NWs dominates in stage one laser processing. The enhancement of electrical conductivity observed, following stage two processing, is attributed due to an increase in the concentration of laser-induced oxygen vacancies as well as the formation of localized bridging and junction sites in the overall NW network. [ABSTRACT FROM AUTHOR]

In this paper, a double-layer acoustic metasurface (DAM) composed of a fixed lower acoustic metasurface (LAM) and a rotatable upper acoustic metasurface (UAM) is proposed for the generation of mode-reconfigurable acoustic orbital angular momentum (OAM). The UAM and LAM are divided into multiple sections, in which the hybrid structures combining cascaded Helmholtz resonators and a straight pipe are adopted to achieve specific phase compensation. By rotating the UAM, the incident acoustic plane wave can be efficiently converted into the vortex acoustic waves of reconfigurable topological charges ranging from −5 to +5 with distinguishable purity. Furthermore, the influences of the parameters on the purity of the generated topological charges have been investigated and discussed, such as the distance between LAM and UAM, rotatable angle error, and operating frequency. With the capability of reconfigurable OAM modes, the proposed DAM can be used to efficiently increase capacity or to conveniently switch between different channels in underwater vortex acoustic communications. [ABSTRACT FROM AUTHOR]

Quantum identity authentication (QIA) ensures that entities of quantum communication will not be impersonated by attackers. As an auxiliary protocol, an ideal QIA protocol cannot take up too many quantum resources and needs to be embedded in the original protocol to enhance security. In this paper, we propose a flexible ternary quantum homomorphic encryption (QHE) protocol using qubit rotation and indicate that the QHE framework can be used to design QIA protocols. The ternary QIA protocol based on QHE can be embedded in the original protocol because both protocols use the same quantum resources. The proposed protocol uses different vouchers from previous protocols, allowing it to prevent various types of attacks and performs well in terms of communication efficiency. The QHE framework can benefit other quantum cryptographic fields. [ABSTRACT FROM AUTHOR]

Photochromic diarylethene is known to exhibit reversible photoisomerization under irradiation with ultraviolet (UV) and visible light. Besides reversible optical properties upon light irradiation, a variety of discontinuous morphological changes of the crystals are reported in the literature, such as sudden crystal bending, cracking, and photosalient effects, which are caused simply by UV and visible light irradiation. These morphological phenomena with discontinuities are micro-scale changes caused by photoisomerization of molecules at the nanoscale and lead to the realization of important functions for optical devices. However, the theoretical models behind these phenomena are not well understood. In this paper, we construct a mathematical model that can treat diverse phenomena in a unified model by using swallow-tail catastrophe, a higher-order catastrophe than cusp catastrophe, from the seven elementary catastrophes that can describe discontinuities in the phenomena. By introducing hyperbolic operating curves in the model, the intrinsic properties of the photochromic crystals are represented. The induced morphogenesis, such as bending, cracking, and photosalient effects, are systematically classified by the proposed catastrophe model, which even implies the possibility of unexplored operating conditions of the crystals and explains known phenomena. The proposed catastrophe-theory-based modeling provides a foundation for understanding and discovering the versatile morphogenesis in photochromic crystals. Furthermore, the proposed approach provides a basis for understanding and discovering various morphological changes in photochromic crystals and similar systems. [ABSTRACT FROM AUTHOR]

ZnO varistors are widely employed for overvoltage protections and surge absorptions due to their excellent nonlinear current–voltage characteristics originating from double Schottky barriers (DSBs). In most cases, they are operating under moderate ac voltages, while calculating the transient current responses of DSBs remains a challenge, impeding the development of condition assessments. In this paper, a transient conducting model for the DSB is proposed by quantifying the charge trapping processes of the interface states. The DSB is found to quickly reach a quasi-steady state, where the interfacial charge stabilizes with only small modulations at a relatively high level above the dc equilibrium value, even though the applied ac voltage varies in time and polarity. This is the result of efficient charge trapping and slow de-trapping by grain boundary interface states. For charge compensation under the time-varying voltage, the width of the two depletion regions of the DSB shows periodic changes. The proposed model is validated by a satisfying agreement between experimentally measured current responses and simulation results of ZnO varistors. The findings of this study provide a perspective on investigating the time-varying conducting systems and open avenues for condition assessments of nonlinear conducting devices. [ABSTRACT FROM AUTHOR]

The main aim of the present paper is to clarify the influence of the SF6 fraction in the SF6/N2 mixture on the breakdown voltage. For this, the two-dimensional axisymmetric fluid model coupled with the comprehensive mechanism of plasma chemical reactions is used. In addition, the influence of various parameters such as the voltage rise time and the SF6 fraction in the mixture is analyzed. It is observed that depending on the voltage rise time an admixture of only 1% of SF6 to N2 results in an increase in the breakdown voltage by 7%–43%. The sensitivity of breakdown voltage decreases with decreasing voltage rise time and is caused by the electron attachment time scale becoming comparable to the breakdown time. The results of simulations confirm that the increase in the SF6 fraction in the mixture leads to an increase in the breakdown voltage. This is explained by the influence of the SF6 fraction on the electron attachment rate coefficients rather than on the ionization reactions. [ABSTRACT FROM AUTHOR]

Controlling the flow of light is fundamental for on-chip optical signal processing. In this paper, we investigate how to realize high contrast, high unidirectional transmission rate, and reconfigurable nonreciprocal light transmission, based on a nonlinear nanocavity asymmetrically side-coupled with a specially designed slow-light waveguide. We analytically and numerically demonstrate that the unusual multiple threshold pump power points for trigging the photon transitions between bistable states, as well as the sensitivity of the dynamic interactions to the relative delay time between the signal light and pump pulse, play crucial roles in this optical diode system. Based on these findings, a high contrast (over 22 dB) and high unidirectional transmission rate (over 70%) optical diode is achieved. More importantly, the conducting direction of the optical diode can be controllably reversed, without the need of changing the signal's wavelength or power as usually done. This approach is promising in the fields of optical information processing and quantum computing. [ABSTRACT FROM AUTHOR]

Additive manufactured (AM) foams in the context of high-power laser–matter interaction have emerged as a topic of significant interest. Printed foam targets provide a highly controlled environment for laser interaction and permit a high degree of versatility in terms of average density, spatial structure, and materials. These features are of great value to a variety of applications, including inertial confinement fusion and generation of intense x-rays and gamma rays. This paper describes an approach to the design and fabrication of AM foams for laser–plasma interaction experiments, including the selection of cellular structure, optimization of mechanical properties using a finite element approach, and foam printing on dielectric and conducting substrates. [ABSTRACT FROM AUTHOR]

Magnetocaloric refrigeration has remained a promising alternative to conventional refrigeration for the last few decades. The delay in reaching the market is significantly based on materials' related issues, such as hysteresis/reversibility, mechanical stability, or formability. This perspective paper shows the current trends in magnetocaloric materials research, highlighting the families of alloys and compounds that are gaining attention in the recent years. It also includes an overview of novel approaches that can be used to analyze these properties that could improve the applicability of magnetocaloric materials. [ABSTRACT FROM AUTHOR]

In this paper, novel nonlocal reformulations of the conventional continuum-based models for modeling the thermoelastic behavior of cubic crystals based on a recently developed lattice particle method are presented. Like molecular dynamics simulation, the lattice particle method decomposes the grain domain into discrete material particles that are regularly packed according to the underlying atomic lattice. Nonlocal interactions are introduced between material particles and top-down approaches are used to relate model parameters to the material physical constants. Three equivalency assumptions are used in the top-down approach, namely, energy equivalency for the mechanical model, heat transfer rate equivalency for the thermal model, and thermal strain equivalency for the thermal-mechanical coupling model. Different from coordinates transformation used in the conventional continuum-based models, lattice rotation is adopted in the lattice particle method to equivalently represent the material anisotropy while explicitly capturing the crystallographic orientation. Two most common Bravais cubic lattices are studied, i.e., the body-centered cubic lattice and the face-center cubic lattice. The validity and prediction accuracy of the developed models are established by comparing the predicted displacements and temperature results with solutions of conventional continuum theories using the finite element method. [ABSTRACT FROM AUTHOR]

Nucleate boiling is a phenomenon of significant importance in a broad range of industries. Increasing boiling performance parameters could lead to more efficient power plants and better electronics thermal management. However, difficulties associated with studying this extremely complex phenomenon have prevented a meaningful progress in the area of boiling heat transfer enhancement. In this paper, we implement a laser-based controlled bubble generation technique to enable accurate phenomenological studies of the boiling process. We present details of the transient focused-laser heating mechanism used to nucleate a microscale vapor embryo on the boiling surface. We present high-speed optical imaging data showing how this vapor embryo grows into a bubble using electrically applied background heat flux. Unlike the currently available artificial bubble generation approaches, which either generate unphysical bubbles or are extremely difficult to implement, we show that the laser-nucleated controlled single bubble demonstrates bubble ebullition characteristics closely representative of naturally occurring bubbles in nucleate pool boiling. [ABSTRACT FROM AUTHOR]

In this paper, a transmissive reconfigurable polarization converter (RPC) based on an active metasurface is proposed, which can regulate the ideal plane wave and the spherical wave as a cladding of the horn antenna. The metasurface unit is composed of a single-layer F4B dielectric substrate and two double-cross metal strips with a p–i–n diode on the top and seven vertical metal strips on the bottom. One RPC prototype with 15 × 15 units has been fabricated and measured when it regulates an ideal plane wave. By controlling the states of diodes, the RPC can realize the linear-to-circular polarization conversion (LCPC) or the linear polarization maintaining (LPM) function from 2.5 to 3.64 GHz. Furthermore, the RPC is used as the cladding of a horn antenna for high integration in practical applications. The measured results show that this RPC-antenna system can still achieve LCPC or LPM function from 3.1 to 4.5 GHz. It is worth mentioning that the 3 dB axial ratio beam width of RPC can cover from −65° to 65° in LCPC. The proposal has advantages of a wideband, simple biasing network, and easy fabrication and integration, which can be widely applied in modern wireless communication systems. [ABSTRACT FROM AUTHOR]

Muography is a rapidly developing and non-destructive tomographic technology that uses cosmic ray muons. Due to the natural presence and deeper penetration of cosmic ray muons, scientists have performed various pioneer studies in fields, such as customs security, the internal imaging of volcanoes, scientific archaeology, and others. With unique advantages, muography has gained increasing attention from archaeologists as a novel and innovative tool to investigate large-scale archaeological sites. This approach may be especially helpful for identifying endangered cultural relics and monuments. In the work, we employ a compact, rugged, and portable muon imaging system, CORMIS (COsmic Ray Muon Imaging System), deployed at up to six measurement locations to perform a case study of three-dimensional muography in Xi'an city, China. Cultural cities, such as Xi'an, have long histories and could benefit from innovative techniques used to investigate, conserve, and protect large historical sites. In this paper, we present in detail a high resolution survey on a rampart of a Xi'an defensive wall in demand of urgent protection. The survey data are carefully processed with advanced statistical methods newly introduced in muography, and the results indicate density anomalies inside the rampart with unprecedented levels of precision. The density anomalies are potential safety hazards and need to be eliminated as soon as possible. The successful implementation of this survey significantly encourages more engagement on the tangible application of high-precision 3D muography in archaeological investigations and protection projects around the world. [ABSTRACT FROM AUTHOR]

Machine learning potentials (MLPs) developed from extensive datasets constructed from density functional theory calculations have become increasingly appealing to many researchers. This paper presents a framework of polynomial-based MLPs, called polynomial MLPs. The systematic development of accurate and computationally efficient polynomial MLPs for many elemental and binary alloy systems and their predictive powers for various properties are also demonstrated. Consequently, many polynomial MLPs are available in a repository website [A. Seko, Polynomial Machine Learning Potential Repository at Kyoto University, https://sekocha.github.io]. The repository will help many scientists perform accurate and efficient large-scale atomistic simulations and crystal structure searches. [ABSTRACT FROM AUTHOR]

Due to the difficulty of forming a low Schottky barrier at the interface of a metal/SiC contact, preparing Ohmic contacts is still a key technical problem in developing SiC devices. In this paper, the effects of MoS2 intercalation on the interface properties of metal/SiC (Al, Ag, Ti, Au, and Mg) systems were investigated by first-principles calculation. The calculations show that all the metal/SiC contacts exhibit p-type Schottky contacts with strong Fermi level pinning (FLP) at the interfaces. After inserting a layer of MoS2, the Schottky barrier heights are significantly reduced. All the metal/MoS2/SiC systems are tuned to be n-type Ohmic contacts. By calculating and analyzing electron localization functions, projected band structure, partial density of states, and planar-averaged charge density difference, the Ohmic contact formation mechanism may be due to the saturation of dangling bonds of the SiC surface, the reduction in metal-induced gap states, the formation of interface dipole layer, and the shift of FLP position to the interface of metal/MoS2. [ABSTRACT FROM AUTHOR]

In the last decades, numerical simulation has become a precious tool to assist the design and study of electron sources based on regular arrays of field emitters. Simulations of field emitter arrays (FEAs) require 3D treatment to account for the interactions between neighbor emitters. Therefore, modeling the thermal evolution of FEAs involves high computational resources due to the multi-physics approach and time dependency. The present paper proposes an algorithm which gives a fast prediction of the self-heating of a large array of N axisymmetric field emitters. It consists in finding for each emitter the equivalent 2D axisymmetric situation yielding the same electron current at 300 K as in the 3D array. The 3D modeling is thus efficiently split into N simulations in 2D, with a significant computation time reduction by at least one order of magnitude. The proof of concept uses 3 × 3 arrays of ideal emitters. Our results show a correct prediction, within a few percent, of the array thermo-field current and maximum temperature—two quantities of high interest for thermal failure and breakdown voltage considerations. The algorithm paves the way for including thermal effects in future optimization studies of realistic FEAs. [ABSTRACT FROM AUTHOR]

Boron carbide (B 4 C) has been well studied both theoretically and experimentally in its bulk form due to its exceptional hardness and use as a high-temperature thermoelectric. However, the properties of its two-dimensional nanosheets are not well established. In this paper, using van der Waals-corrected density-functional theory simulations, we show that bulk B 4 C can be cleaved along different directions to form B 4 C nanosheets with low formation energies. We find that there is minimal dependence of formation energies on cleavage planes and surface terminations, even though the bulk is not van der Waals layered. This anomalous stability of B 4 C nanosheets is found to be a result of surface reconstructions that are unique to B-rich systems. While the density of states of the bulk B 4 C indicate that it is a semiconductor, the B 4 C nanosheets are found to be predominantly metallic. We attribute this metallic behavior to a redistribution of charges on the surface bonds of the films. The Seebeck coefficients of the B 4 C films remain comparable to those of the bulk and are nearly constant as a function of temperature. Our results provide guidance for experimental synthesis efforts and future application of B 4 C nanosheets in nanoelectronic and thermoelectric applications. [ABSTRACT FROM AUTHOR]

The shear strength of materials under shock-loading conditions has long been recognized as being of the utmost importance, as this can be related to deformation mechanisms and ballistic performance. As such, a number of experimental techniques have been developed to study this component of shock loading, and in this paper, we concentrate on the embedded lateral stress gauge. We acknowledge that as the requirements of the target assembly necessitate that the target be sectioned, the gauge glued in place, and the target reassembled, it is possible that the gauge response is dominated by its local environment. As a consequence, we have, therefore, asked three questions—can the gauge be placed in a known stress condition and measure the correct lateral stress and shear strengths; do the results from the lateral stress gauge agree with other non-invasive techniques; and finally, if we do trust the results from lateral gauges, can they be placed in context with other known shock-induced materials responses. In all three cases, we believe that the answer is yes, and we present evidence for all three situations. [ABSTRACT FROM AUTHOR]

In this paper, the nanolamination of a ZrO2 insulator by Al2O3 for metal insulator metal capacitor applications has been studied. The insulating layers (ZrO2 and Al2O3) were deposited by atomic layer deposition and the electrodes were made of TiN. Different configurations of ZrO2 and Al2O3 alternations were studied, including 1 to 16 Al2O3 inclusions in the ZrO2 layer. X-ray diffraction of the insulator configurations showed that with four or more Al2O3 inclusions, the structure loses its crystalline orientation and becomes amorphous. Electrical characterizations have been conducted to study the capacitance, breakdown field, and leakage current for every insulator configuration. The capacitance density significantly decreases as the number of Al2O3 layers increases, except when an amorphous transition occurs; at this point, a local maximum of 17 nF/mm2 was found. A 19% increase of the breakdown field of samples with two or more Al2O3 inclusions has been correlated with an increase of leakage current explained by the emergence of the Fowler–Nordeim conduction mechanism at electrical fields higher than 4 MV/cm. [ABSTRACT FROM AUTHOR]

For a diverse range of semiconductor devices, the charge carrier lifetime is an essential characteristic. However, the carrier lifetime is difficult to control, as it is usually determined by a variety of recombination processes. For indirect bandgap materials, it is well known that effective carrier lifetimes can be improved by passivating the surface, effectively extinguishing surface-related recombination processes. However, for some applications, such as photomodulators for sub-infrared radiation, it is beneficial to tailor lifetimes to specific values, in this particular case trading off between photo-efficiency and switching speed. In this paper, we design a new type of silicon-based metamaterial with a tunable electron–hole lifetime. By periodically patterning a dielectric surface passivation layer, we create a metamaterial whereby the filling fraction of passivated relative to unpassivated areas dictates the effective charge carrier lifetime. We demonstrate tunable lifetimes between 200 μs and 8 ms in a 670 μm thick Si wafer, though in principle our approach allows one to generate any lifetime between the fully passivated and unpassivated limits of a bulk semiconductor. Finally, we investigate the application of these metamaterials as photomodulators, finding switching times that depend upon both the photoexcitation intensity, wafer thickness, and the carrier lifetime. [ABSTRACT FROM AUTHOR]

Two-dimensional molybdenum disulfide (2D MoS2) has great application prospects in the field of optoelectronic devices. Defect engineering is an effective way to regulate the electronic and optical properties of 2D MoS2. However, defect controlling on 2D materials remains a major challenge. Fluorine, as the most electronegative element, may cause many interesting phenomena after doping in 2D materials. So far, there have been no reports on the effect of fluoride ion (F− ion) irradiation on 2D material properties. In this paper, the monolayer MoS2 (ML-MoS2) synthesized by the chemical vapor deposition method was taken as the research object, and defects with controllable densities were produced by 30 keV F− ion irradiation, in which the defects were dominated by S vacancies. Based on Raman, photoluminescence, and x-ray photoelectron spectroscopy, it is shown that the ion irradiation-induced defects significantly affect the optoelectronic properties of MoS2. We also observed the p-doping of ML-MoS2, which is attributed to the introduction of F− ions and the electron transfer from MoS2 to O2 at defect adsorption sites. This study reveals that 2D materials could be effectively doped or compensated using irradiation technology, potentially fabricating novel 2D electrical devices through defect engineering. [ABSTRACT FROM AUTHOR]

Irradiation creep is known to be an important process for structural materials in nuclear environments, potentially leading to creep failure at temperatures where thermal creep is generally negligible. While there is a great deal of data for irradiation creep in steels and zirconium alloys in light water reactor conditions, much less is known for first wall materials under fusion energy conditions. Lacking suitable fusion neutron sources for detailed experimentation, modeling, and simulation can help bridge the dose-rate and spectral-effects gap and produce quantifiable expectations for creep deformation of first wall materials under standard fusion conditions. In this paper, we develop a comprehensive model for irradiation creep created from merging a crystal plasticity representation of the dislocation microstructure and a defect evolution simulator that accounts for the entire cluster dimensionality space. Both approaches are linked by way of a climb velocity that captures dislocation-biased defect absorption and a dislocation strengthening term that reflects the accumulation of defect clusters in the system. We carry out our study in Fe under first wall fusion reactor conditions, characterized by a fusion neutron spectrum with average recoil energies of 20 keV and a damage dose rate of ≈ 3 × 10 − 7 dpa/s at temperatures between 300 and 800 K. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of pulse compression capability in hybrid and gyromagnetic non-linear transmission lines (NLTLs). The corresponding theoretical analysis in the hybrid NLTLs is derived and discussed in detail with the generation and sharpening aspects of leading and trailing pulse edges. The parameters responsible for pulse sharpening are examined and their corresponding pulse compression capability is modelled by providing the output waveform while varying these parameters. A holistic overview and mathematical development of gyromagnetic NLTLs are also conducted, which are modeled and validated through an equivalent lumped element model. Important parameters such as saturation magnetization, gyromagnetic NLTL sections, and damping parameter are elaborated and their influences on pulse sharpening and compression capability are studied. Validation of the theoretical and parametric analysis is performed by an experimental demonstration. The results achieved from hybrid and gyromagnetic NLTLs are briefly summarized, and their corresponding advantages and disadvantages are highlighted. This research is set to provide a fresh and successful debut for investigating gyromagnetic and hybrid NLTLs and their inherent effects on pulse compression for future ultrafast electronic systems and interconnects. [ABSTRACT FROM AUTHOR]

Nanocomposite permanent magnets are considered as a strong candidate for the next generation of high-performance permanent magnet materials due to their ultra-high theoretical magnetic energy product. In this paper, a nanocomposite theoretical model based on the shape anisotropy of the soft phase (Fe65Co35) is constructed to guide the improvement of coercivity, the lack of which has become a critical problem in improving the performance of Nd-Fe-B nanocomposites further. The results of micromagnetic simulation show that adding a shape anisotropic soft phase to nanocomposites can effectively improve coercivity, delay nucleation during the magnetization reversal process, and help obtain a demagnetization curve with high squareness. When the length size of the soft phase ds ≤ 21 nm and the aspect ratio of the soft phase I = 5 for the Nd2Fe14B/Fe65Co35 nanocomposites, almost square demagnetization curves can be obtained, particularly when ds = 21 nm, the size of the soft phase is 21 × 21 × 105 nm3, the content of the soft phase is 42.1 vol. %, and the Nd2Fe14B/Fe65Co35 nanocomposite achieves a maximum magnetic energy product of 94.4 MGOe. In addition, the results also show that, compared with the cubic nanocomposite model (I = 1), the larger size of the soft phase can be accommodated into the nanocomposites by the addition of shape anisotropy, on the premise of ensuring the soft–hard coupling effect. Our design provides a new strategy and approach for preparing high-performance nanocomposite permanent magnets. [ABSTRACT FROM AUTHOR]

Charge accumulation on the surface of insulation dielectric used in high voltage DC equipment is one of the important causes of surface flashover. Surface charge accumulation is closely related to surface trap characteristics. In this paper, the surface trap energy level distribution of polyimide (PI) was calculated and analyzed by the corona charging method and surface potential decay method. Besides, electron and hole trap characteristics were studied by changing the polarity and amplitude of the charging voltage. Furthermore, the influence of surface charge polarity and quantity on the flashover voltage was researched. Experimental results indicate that the energy level of traps corresponding to the maximum trapped charge density ranges around 0.94 eV. In addition, the energy level of the hole trap is slightly higher than that of the electron trap. The maximum charge density captured by the electron trap and hole trap is about 1.17 × 1021 and 1.03 × 1021 eV−1 m−3, respectively. The polarity of the surface charge can influence the conductivity characteristics of PI, the surface heterocharge reduces the volume conductivity by about 80% while the surface homocharge improves the volume conductivity of PI by about 6.4 times. Besides, both negative and positive surface charges can improve surface conductivity. The polarity of surface charge influences the flashover characteristics of PI, the flashover voltage increases by about 37.8% with the increase of homocharge density and decreases by about 23.8% with the increase of heterocharge density, which is related to the change of electric field near the cathode caused by surface charge accumulation. [ABSTRACT FROM AUTHOR]

In this paper, the unidirectional transmission of surface water waves is experimentally observed by connecting the mode-selective channel and the spatial symmetry-breaking channel. The proposed mode-selective channel contains a symmetry structure but only allows the propagation of anti-symmetric modes in a specific frequency band, while the antisymmetric modes can be excited in the channel with spatial symmetry-breaking. Therefore, the surface water waves can only propagate through the channel when the fundamental plane wave mode is excited at the entrance of the spatial symmetry-breaking channel, but not vice versa. The results of theoretical and numerical analyses indicate that the evanescent wave mode caused by non-Bragg resonances is responsible for the emergence of the antisymmetric mode transmission. The non-Bragg evanescent wave mode, generated by the resonance between the fundamental and higher-order modes, widens the unidirectional transmission band of surface water waves. Limited by the small structure, the experimental observed unidirectional transmission has a wave extinction ratio of 20.49 dB. The simulations closer to the ocean situation show that the bandwidth can reach 0.18 Hz, and the extinction ratio is 46.09 dB. The realization of surface water wave transmission not only enriches our knowledge on ubiquitous wave phenomenon, but also benefits applications in ocean engineering, such as coastal protection, ocean wave control, green energy collection, and reef maintenance. [ABSTRACT FROM AUTHOR]

Conventional strategies for materials design have long been used by leveraging primary bonding, such as covalent, ionic, and metallic bonds, between constituent atoms. However, bond energy required to break primary bonds is high. Therefore, high temperatures and enormous energy consumption are often required in processing and manufacturing such materials. On the contrary, intermolecular bonds (hydrogen bonds, van der Waals forces, electrostatic interactions, imine bonds, etc.) formed between different molecules and functional groups are relatively weaker than primary bonds. They, thus, require less energy to break and reform. Moreover, intermolecular bonds can form at considerably longer bond lengths between two groups with no constraint on a specific bond angle between them, a feature that primary bonds lack. These features motivate unconventional strategies for the material design by tuning the intermolecular bonding between constituent atoms or groups to achieve superior physical properties. This paper reviews recent development in such strategies that utilize intermolecular bonding and analyzes how such design strategies lead to enhanced thermal stability and mechanical properties of the resulting materials. The applications of the materials designed and fabricated by tuning the intermolecular bonding are also summarized, along with major challenges that remain and future perspectives that call for further attention to maximize the potential of programming material properties by tuning intermolecular bonding. [ABSTRACT FROM AUTHOR]

The recent decade brought many advances to plasmonics, but high power density plasmonic antennas designed to behave as heaters or operate in high temperature environments are still facing material stability challenges preventing their ultimate use. Gold has been the optimal choice among plasmonic materials but experiences morphology changes at temperature that result in device efficiency reduction and failure. Bulk titanium nitride has been explored as a solution but has deal-breaking tradeoffs in device quality factor. In this paper, we explore via proof-of-concept the use of a metal–ceramic composite structure to determine whether a bulk Au nanorod can provide strong plasmonic resonances while coated with an ultrathin conformal layer of titanium nitride or silica to provide morphological stability and sufficient plasmonic activity without excessive resonance quality degradation. We show SEM-level morphological stability for temperatures up to 500 °C with coatings below 4 nm. Computer modeling suggests the ultrathin titanium nitride has detrimental effects on the strong plasmonic resonances of a Au nanorod. We then looked into other possible coatings for solutions to stabilize high power density plasmonic antennas including plasmonic oxides, metal adhesion layers, and silica, the latter appearing to be the best option while lowering the overall peak electric field intensity, the silica increases the electric field intensity at its boundary. [ABSTRACT FROM AUTHOR]

Hollow cathode plasma discharges are a fundamental part of a large variety of applications in industry, academia, and space. From surface processing and coatings deposition to plasma–surface interaction research and electric propulsion, advances in hollow cathode modeling and performance are critically important to the progress and evolution of these and other areas of technology. This paper describes perspectives on the progress that has been made in recent years in the capabilities and modeling of hollow cathodes used in plasma discharges. While many of the developments have been driven by the demanding requirements of electric propulsion applications, the information provided applies to all thermionic hollow cathodes and their applications. In the paper, we describe the status of 2D global simulations of hollow cathode plasmas, hollow cathode plume instabilities, and the development of higher current cathodes and low-current heaterless cathode technologies. Advances in our understanding and technology in these areas and some of the challenges that still need to be addressed and solved are discussed. [ABSTRACT FROM AUTHOR]

Non-uniform deformation of the dielectric subjected to external forces can induce the electrical response, i.e., flexoelectricity. The crumpling of a thin dielectric film can induce considerable strain gradients (i.e., non-uniform deformation), and due to flexoelectricity, considerable polarization occurs. In this paper, to improve the flexoelectric response when the dielectric film undergoes crumpling deformation, we investigate the crumpling problem of the three-layer laminated film whose edge layers have the same thickness. A theoretical model for the crumpling problem of the laminated film is developed. The induced flexoelectric effect associated with it is analyzed. The results indicate that the laminated films with reduced Young's modulus in the edge layers can effectively improve the flexoelectric response of the film subjected to crumpling deformation. The optimal size of the laminated film appears around three times of magnitude higher than that of the homogeneous film. At the same time, the flexoelectric energy efficiency of the laminated film is one order higher than that of the homogeneous film. Therefore, the laminated film is more justifiable on practical application. This work can provide a theoretical basis for the design of miniature energy-capture devices with high energy conversion efficiency. [ABSTRACT FROM AUTHOR]

An improved plane wave expansion (PWE) method is developed based on the governing equations of a lattice unit cell, providing support for calculating the band structures of a locally resonant (LR) plate with multiple arrays of multiple degree-of-freedom resonators. The extended plane wave expansion (EPWE) method is correspondingly presented to obtain the complex band structures of the LR plate. Then the bandgap properties of LR plate systems with single/multiple arrays of single/multiple degree-of-freedom resonators are analyzed, which present a good agreement with the results calculated by the classical theory or finite element method. Compared with the classical theory, the improved PWE and EPWE methods have excellent efficiency and broad applicability for LR plate systems with complex attachments. Furthermore, when the damping of resonators is taken into account, the merging of the multiple bandgaps can be observed using the EPWE method adopted in this paper, which gives a useful tool to analyze the band structures of an LR plate with merged bandgaps for broadband vibration suppression. [ABSTRACT FROM AUTHOR]

Gaseous detectors are widely used in high energy physics and are an attractive choice in tracking systems for cosmic muon imaging, also called muography. Such detectors offer high resolution and high efficiency at a reasonable cost for large sizes; however, one of the drawbacks is that the gaseous detection medium must be prevented from contamination by outside air or internal outgassing. Standard systems work with a constant gas flow, leading to regular maintenance in the form of gas cylinder changes, which can be an issue for remote field applications. In this paper, we discuss the practical possibilities to reduce the gas consumption of an outdoor gaseous tracker, where particularly the gas density change from daily temperature cycling limits the input flow. Such a "breathing" effect can be circumvented by a well designed buffer volume, which must prevent external air contamination. A realistic multi-wire proportional chamber tracking test system with 0.9 m 2 area and a total volume of 160 l has been operated for 36 days with a flow of 3 l/day, confirming the buffer volume; in this case, a 50 m long and 10 l volume low diffusion tube ensures the sufficient gas quality. The key effects governing the gas flow dynamics, including diffusion and gas volume change, have been studied quantitatively, leading to practical design prescriptions. [ABSTRACT FROM AUTHOR]

Harnessing detachment of an aqueous droplet via electrowetting on a flat surface has been of considerable interest for potential practical applications, ranging from self-cleaning to novel optical and digital microfluidic devices, due to the wettability of the droplet on a solid substrate enhanced by applying an electric voltage between the droplet and the insulated substrate. However, a quantitative understanding of the detachment process and an accurate prediction on the thresholds of applied voltage for droplet detachment on curved surfaces are still lacking. In this paper, based on energy conservation, we derive a critical condition theoretically for electrowetting-induced droplet detachment from a hydrophobic curved surface. Furthermore, phase diagrams are constructed in terms of droplet volume, viscosity, the Ohnesorge number, friction coefficient at contact line, surface curvature, surface wettability, and electrowetting number. The deduced critical condition offers a general and quantitative prediction on when the detachment occurs, a criterion enabling us to gain more insights into how to accurately manipulate the electrowetting-induced detachment of an aqueous droplet on a curved surface. The results obtained in this paper also imply that the detachable regimes of the phase diagrams can be enlarged through increasing droplet volume and surface curvature and reducing liquid viscosity, friction coefficient, the Ohnesorge number, and wettability of substrates. [ABSTRACT FROM AUTHOR]

Using the transfer matrix method, the absorption, reflection, and nonreciprocity of the cylindrical photonic crystals (CPCs) consisting of graphene and two layers of ordinary medium cascaded by a periodic sequence and a Rudin–Shapiro quasiperiodic sequence are investigated under a large incidence angle of electromagnetic wave. By comparing the cascade of two periodic structures and the case of a single periodic structure, it is concluded that the structure proposed in this paper has better nonreciprocal phenomena and wider relative absorption bandwidth at a large incidence angle, reaching 162.2%, which is also much higher than the general planar photonic crystals. The absorption performance of this structure in TE and TM modes is compared at different angles and it is found that TM mode has a wider absorption bandwidth and has an ideal bandwidth in a large range of incident angle from 20° to 80°. Meanwhile, the optimum parameters of chemical potential and medium thickness are discussed, which can meet the requirements of large absorption bandwidth and significant nonreciprocity at a large incident angle. The CPCs embedded in graphene adopted in this paper are structures that have never been studied before. The electrical conductivity of graphene can be adjusted by the chemical potential, which can more conveniently realize many optical phenomena and provide reference and application values for optical sensing, optical filtering, and optical detection. [ABSTRACT FROM AUTHOR]

Nanosecond plasmas in liquids are being used for water treatment, electrolysis, or biomedical applications. The exact nature of these very dynamic plasmas and, most importantly, their ignition physics are strongly debated. The ignition itself may be explained by two competing hypotheses: ignition in water may occur (i) via field effects at the tip of the electrode followed by tunneling of electrons in between water molecules causing field ionization or (ii) via gaseous processes of electron multiplication in nanovoids that are created from liquid ruptures due to the strong electric field gradients. Both hypotheses are supported by theory, but experimental data are very sparse due to the difficulty in monitoring the very fast processes in space and time. In this paper, we analyze nanosecond plasmas in water that are created by applying a positive and a negative polarity to a sharp tungsten electrode. The main diagnostics are fast camera measurements and fast emission spectroscopy. It is shown that plasma ignition is dominated by field effects at the electrode–liquid interface either as field ionization for positive polarity or as field emission for negative polarity. This leads to a hot tungsten surface at a temperature of 7000 K for positive polarity, whereas the surface temperature is much lower for negative polarity. At ignition, the electron density reaches 4 × 10 25 m − 3 for the positive and 2 × 10 25 m − 3 for the negative polarity. At the same time, the emission of the H α light for the positive polarity is four times higher than that for the negative polarity. During plasma propagation, the electron densities are almost identical of the order of 1– 2 × 10 25 m − 3 followed by a decay after the end of the pulse over 15 ns. It is concluded that plasma propagation is governed by field effects in a low density region that is created either by nanovoids or by density fluctuations in supercritical water surrounding the electrode that is created by the pressure and temperature at the moment of plasma ignition. [ABSTRACT FROM AUTHOR]

This paper utilizes a coupled chemomechanical model that integrates chemical reactions, diffusion, and mechanical deformation to describe the high-temperature interfacial reactions and stress evolution within an enamel coating/Ni-based super-alloy system. Through finite element simulation, we conduct a comprehensive analysis of multiple reactions and processes at the interface. Experimental characterization of the concentration distribution of various elements is employed to verify the accuracy of the proposed chemomechanical model. Additionally, the simulation reveals that the interface region experiences compressive circumferential stress, which can potentially lead to interfacial failure due to buckling. On the other hand, the enamel coating undergoes tensile circumferential stress, resulting in the formation of vertical surface cracks. These findings hold practical implications for the development of advanced coatings with enhanced durability and performance. Future research can further optimize coating design and enhance the reliability of high-temperature applications based on these results. [ABSTRACT FROM AUTHOR]

Quantum random number generators (QRNGs) produce random numbers based on the intrinsic probabilistic nature of quantum mechanics, making them true random number generators. In this paper, we design and fabricate an embedded QRNG that produces random numbers based on fluctuations of spontaneous emission and absorption in a light-emitting diode. To achieve a robust and reliable QRNG, we compare some usual post-processing methods and select the finite impulse response method for a real-time device. This device could pass the National Institute of Standards and Technology tests, the generation rate is 1 Mbit/s, and the randomness of the output data is invariant in time. [ABSTRACT FROM AUTHOR]

This paper introduces a versatile design method for reconfigurable metasurfaces based on the Pancharatnam–Berry phase theory. Unlike traditional reconfigurable metasurfaces that require designing independent surfaces for specific applications, leading to a significant time investment for designers to learn and create, this study proposes a foundational, invariant metasurface. By selectively metallizing holes or inserting metal cylinders, it achieves nine available functionalities. Regardless of the chosen operating function, the metasurface demonstrates high efficiency at 8.2 GHz, with amplitude loss less than 1 dB. Additionally, when operating in phase modulation mode, the design provides a 360 ° phase adjustment range and a 30 ° phase step. A prototype containing 31 × 31 units (425.6 × 425.6 mm 2) has been fabricated and tested under function 7 (TM and RHCP transmission phase modulation). Measurement results confirm the metasurface's capability for polarization conversion and phase modulation at the frequency of 8.2 GHz. [ABSTRACT FROM AUTHOR]