Simple Layered Structure Research Articles

Investigation of the structural and magnetic properties of the GdCoC compound featuring excellent cryogenic magnetocaloric performance

Magnetic refrigeration (MR) based on the magnetocaloric effect (MCE) has been recognized as an environmentally benign and energy-efficient cooling technology. Exploring suitable magnetocaloric materials is a crucial prerequisite for practical MR applications. We have herein provided a systematic investigation of the crystal structure, microstructure, electronic structure, magnetic phase transition, critical behavior, and MCE of the GdCoC compound featuring excellent cryogenic magnetocaloric performance by means of experimental determination and theoretical calculation. The GdCoC compound is crystallized in a simple layered tetragonal crystal structure with a P42/mmc space group and undergoes two successive ferromagnetic (FM) transitions along with a low-temperature weak antiferromagnetic (AFM) transition under low magnetic fields. Density functional theory calculations confirms the FM coupling of the Gd and Co intra-sublattice interactions, whereas AFM coupling for their inter-sublattice interaction. The magnetic transitions are merged in to one under high magnetic fields which has been confirmed to be second-order type and its critical behavior can be understood in the framework of tri-critical mean-field model, whereas the low-temperature weak AFM transition is belonging to the first-order type. The excellent magnetocaloric performance of the GdCoC compound was identified by the parameters of magnetic entropy change, adiabatic temperature change, temperature-averaged entropy change, relative cooling power, and refrigerant capacity, which are superior to most of the well-known magnetocaloric materials with similar working temperatures, making it attractive for practical cryogenic MR applications.

Isostructural behaviour in ammonium and potassium salt forms of sulfonated azo dyes.

The structures of five ammonium salt forms of monosulfonated azo dyes, derivatives of 4-(2-phenyldiazen-1-yl)benzenesulfonate, with the general formula [NH4][O3S(C6H4)NN(C6H3)RR']·XH2O [R = OH, NH2 or N(C2H4OH)2; R' = H or OH] are presented. All form simple layered structures with alternating hydrophobic (organic) and hydrophilic (cation, solvent and polar groups) layers. To assess for isostructural behaviour of the ammonium cation with M+ ions, the packing of these structures is compared with literature examples. To aid this comparison, the corresponding structures of four potassium salt forms of the monosulfonated azo dyes are also presented herein. Of the five ammonium salts it is found that three have isostructural equivalents. In two cases this equivalent is a potassium salt form and in one case it is a rubidium salt form. The isostructurality of ion packing and of unit-cell symmetry and dimensions tolerates cases where the ammonium ions form somewhat different interaction types with coformer species than do the potassium or rubidium ions. No sodium salt forms are found to be isostructural with any ammonium equivalent. However, similarities in the anion packing within a single hydrophobic layer are found for a group that consists of the ammonium and rubidium salt forms of one azo anion species and the sodium and silver salt forms of a different azo species.

Tunable multiband THz perfect absorber due to the strong coupling of distributed Bragg reflector cavity mode and Tamm plasma polaritons modes based on MoS2 and graphene

In this work, we propose a multiband terahertz perfect absorber by combining a distributed Bragg reflector (DBR) cavity with molybdenum disulfide (MoS2) and graphene. The absorption peak comes from the strong coupling of the DBR cavity mode and the two Tamm plasma polaritons (TPPs) modes. Our numerical simulations demonstrate that the degree of coupling in this hybrid system is tunable by adjusting the structural parameters, thereby allowing for control over the position and intensity of the absorption peaks. Furthermore, utilizing the tunable Fermi energy level of graphene and controlled variation of the molybdenum disulfide carrier concentration enables active switching between absorption-free, dual-band, and triple-band absorption. Additionally, the high absorption efficiency in a wide angular range and sensitivity make this device highly versatile. The coupled harmonic oscillator model is used to explain the strong coupling phenomena of the system. This simple layered structure provides a hybrid coupling system with a controlled number of bands suitable for potential active terahertz optoelectronic devices.

ON OBTAINING INITIAL APPROXIMATION FOR FULL WAVE INVERSION PROBLEM USING CONVOLUTIONAL NEURAL NETWORK

The paper considers the problem of choosing the initial approximation when using gradient optimization methods for solving the inverse problem of restoring the distribution of velocities in a heterogeneous continuous medium. A system of acoustic equations is used to describe the behavior of the medium, and a finite-difference scheme is used to solve the direct problem. L-BFGS-B is used as a gradient optimization method. Adjoint state method is used to calculate the gradient of the error functional with respect to the medium parameters. The initial approximation for the gradient method is obtained using a convolutional neural network. The network is trained to predict the distribution of velocities in the medium from the wave response from it. The paper shows that a neural network trained on responses from simple layered structures can be successfully used to solve the inverse problem for a complex Marmousi model.

Economical preparation and characterization of dual-ion conducting fuel cell

The composites consisted of oxygen ion conductive (La0.75Sr0.2Ba0.05)0.175Ce0.825O1.891 (LSBC) and proton conductive BaZr0.1Ce0.7Y0.2O3-δ (BZCY) prepared by solid state reaction and impregnation are sintered to form composite and phase gradient membranes, respectively. The conductivity of (100-x)LSBC-xBZCY composite membranes exhibit non-ohmic in air and semiconductive diode behavior in Ar/5%H2 higher than 500 °C. The elemental concentration gradient of Ba, Ce and O at grain boundaries of LSBC/BZCY corresponds to the inter-diffusion and Schottky barrier formation. The Schottky barrier of dual phase boundary (DPB) may be beneficial for dual-ion conduction. The microstructures of sintered and polished (100-x)LSBC-xBZCY surface exhibit convex hard LSBC and concave soft BZCY. The percolated 70LSBC-30BZCY of the composite membrane obtains the power density of 20.51 mW/cm2. The phase gradient membrane of BZCY impregnated LSBC presents the higher power density of 40.6 mW/cm2 (700 °C). The new two-phase composite and phase gradient membranes generate more simple and compact layer structure than sandwiched solid oxide fuel cell. Such two-phase dual-ion membranes provided by our economical process can be considered to develop new single membrane fuel cells possibly.

Observations and improvements on the impact-echo method used for blast furnace hearth refractory measurement

ABSTRACT The refractory thickness of the blast furnace hearth is a critical parameter for the safe operation of a blast furnace. A replacement of the refractory comes with high costs and, therefore, unnecessary repairs should be avoided. A promising method to estimate the refractory thickness is the impact-echo method. For the interpretation of impact-echo, often, the peaks in the spectrum of the measured signal are associated with the echo from an interface. In this paper, it is shown that this method should be used with care when applied to multi-layered structures. An alternative approach is presented for the calculation of the thickness of multi-layered structures. This method solves the wave equation based on transmission line theory. The formula is checked against 2D finite element analysis and for simple layered structures, good agreement is found. Three cases are simulated using finite element models. Both the impact-echo method and the proposed method overestimate the refractory thickness.

A Case Study on Integrated Modeling of Spatial Information of a Complex Geological Body

Abstract To ensure the safety of project construction and reduce development costs, it is necessary to obtain a reasonable design before project initiation and to analyze and study geological information from multiple perspectives to achieve intuitive and effective project planning. Therefore, it is proposed to integrate above- and underground information to realize integrated spatial information expression. Generally, geological body model construction is based on drilling data, but most geological bodies are not simple layered structures, and complex geological phenomena usually occur, such as faults, lenses, and fissures. It is difficult to construct a high-quality geological body model with only limited drilling data. To fully consider existing geological information in complex geological areas with limited geological data information available, profile maps are considered in the modeling process. This article focuses on the geological model construction of a primary school in Shuicheng County, Guizhou Province, using the GoCAD platform. The Structure and Stratigraphy Workflow is applied in three-dimensional geological body structure model establishment, the stratum rock mass is outlined, and the complex geological structure (karst cave) is embedded into the geological surface. The model can be sliced at any angle to accomplish integrated spatial information expression of above- and underground building information combined with the same platform’s geological body to obtain engineering information and analyze future construction problems.

Two branchial pathological conditions, nuclear hypertrophy and abnormal epithelial proliferation, in Mya arenaria from northwest Russian coasts.

Histopathological analysis of soft-shell clams Mya arenaria collected from 2 northwest Russian locations disclosed high prevalence of 2 pathological gill conditions. One involved the occurrence of more or less extended gill areas in which the branchial filaments showed hyperchromatic (basophilic) epithelium with some hypertrophied nuclei, which were considered presumptive signs of viral infection. Another pathological condition involved abnormal proliferation of the branchial epithelium, which lost the main differential features of the normal branchial epithelium (ciliated and simple cell layer structure), becoming non-ciliated, pseudostratified or stratified hyperchromatic epithelium with abundant mitotic figures and frequent apoptotic cells. The most complex cases involved loss of the normal branchial filament architecture, which was replaced with tumour-like growths consisting of branching, convoluted epithelial projections with a connective stroma. Images suggesting migration (invasion) of cells from the abnormally proliferating epithelium to the subjacent connective tissue, which would involve malignancy, were observed in one individual. The occurrence of both pathological conditions in clams from both locations and their co-occurrence in one clam suggest the possibility of a common, possibly viral, aetiology. Furthermore, the high prevalence of the abnormal proliferative disorder in non-polluted areas suggests an infectious aetiology. Additional studies are needed to assess a viral aetiology for the nuclear hypertrophy and/or the abnormal epithelial proliferation as well as the malignancy of the latter condition.

Noise immune state of charge estimation of li-ion battery via the extreme learning machine with mixture generalized maximum correntropy criterion

The state of charge (SOC) plays a crucial role in battery management system, which directly reflects the usage of the battery. Recently the extreme learning machine (ELM) model as a data-driven method has been utilized to estimate SOC due to its simple single hidden layer structure and fast learning performance. The battery management system, however, may usually work in complex working conditions, which means that the non-Gaussian complex noise (or outliers) interference problem may exist in some measurement data for model training. So the performance of the classical ELM with mean square error (MSE) criterion may be degraded under this case. This work considers Non-Gaussian noise interference issue, the MSE in ELM is substituted by mixture generalized maximum correntropy criterion (MGMCC), and a novel robust ELM model is developed to improve the SOC estimation capability which mainly relies on the stable and robust nonlinear similarity characteristics of the MGMCC. A data set from a Panasonic 18,650 battery cell is used to verify the robustness of the proposed model, the experiment results demonstrate that it can achieve better estimation performance in terms of different evaluation metrics compared with the traditional methods.

Spin orbit torque switching in an antiferromagnet through Néel reorientation in a rare-earth ferrite

We suggest coherent switching of canted antiferromagnetic (AFM) spins using spin-orbit torque (SOT) in small magnet. The magnetic system of orthoferrite features biaxial easy anisotropy and the Dzyaloshinskii Moriya interaction, which is perpendicular to the easy axes and therefore creates weak magnetization (m). A damping-like component of the SOT induces N\'eel reorientation along one of the easy axes and then exerts torque on m, leading to tilting of the N\'eel order l. The torque on the magnetization becomes stronger due to coupling with the induced Oersted field or the field-like component of the SOT, enhancing the tilting of l. Therefore, l is found to experience deterministic switching after the SOT is turned off. Based upon both numerical and analytical analysis of the coherent switching, XOR logic gates are also found to be implemented in a single magnetic layer. In addition, we investigate how magnetic parameters affect the critical reorientation angle and current density in a simple layered structure of platinum and a canted AFM. Our findings are expected to provide an alternative spin-switching mechanism for ultrafast applications such as spin logic and electronic devices.

A method for capacity estimation of lithium-ion batteries based on adaptive time-shifting broad learning system

Accurate capacity estimation of lithium-ion batteries can improve the safety and reliability of equipment. Deep learning provides a new approach for capacity estimation. However, it is still difficult to adapt to the changes in different stages of capacity degradation due to many and complex parameters in deep structure network and the time-invariant model parameters. Considering that Broad Learning System is a neural network independent of deep structure, which has a simple single hidden layer structure and fewer parameters, this paper proposes an Adaptive Time-shifting Broad Learning System (ATBLS) capacity estimation model. For input layer, the input data of each time step is combined with the output of previous time step to get a new input, so as to provide local information to hidden unit of the network and provide guidance for local parameters. For hidden layer, the hidden unit of each time step is weighted-fused with the hidden unit of previous time step to update the parameters, so as to reflect the long-term dynamics of sequence. The experiment are conducted on three different data sets. And the effectiveness of ATBLS is verified by comparing with other methods.

Intelligent light-driven flexible solar thermoelectric system

Solar thermoelectric generation (STEG) is an excellent and environmentally-friendly way to convert thermal energy into electricity by utilizing Seebeck effect of thermoelectric material. However, how to overcome the rigidity and large output fluctuation of traditional STEG is the key to realize its large-scale application in self-powered devices. Herein, a smart light-driven flexible STEG system was designed and constructed through simple layered structure of VO2 flexible film and carbon nanotube (CNT) thermoelectric modules. Based on the optical control characteristics of VO2 flexible film due to the thermal crystal phase transformation, and the light capture, photo-thermal-electric conversion capabilities of CNT flexible film, the smart light-driven flexible STEG system exhibits good flexibility, light-thermal-electrical conversion and stable voltage output. In the above system, CNT, polyvinylidene fluoride (PVDF) as raw material and polyethyleneimine (PEI) as electron donor, p- and n-type flexible thermoelectric films and modules were constructed; VO2 ultrafinepowder was dispersed in polyvinylpyrrolidone(PVP), and the optical control VO2 flexible film was obtained by simple spin coating on the flexible substrate. The system is so flexible that can be folded or bended to different shapes to adapt to different application environments. Furthermore, the intelligent light-driven flexible STEG system can obtainrelatively stable voltage to prevent the damage of equipment caused by large voltage fluctuation and has great application potential in civil micro-self-powered devices.

Multithermally invisible cloaks and sensors with complex shapes

Multithermal metamaterials are more practical to control thermal energy because there are three basic modes of thermal transport in nature. However, existing theories for multithermotics, such as the transformation theory and effective medium theory, are limited to complicated parameters or regular shapes. To solve the problem, we apply the thermal uniqueness theorem together with the heat flux conservation to design multithermal metamaterials including invisible cloaks and sensors. Multithermotics refers to the combination of conduction and radiation, which are described by the Fourier law and the Rosseland diffusion approximation, respectively. The present scheme can simplify parameters despite complex shapes, which only requires simple layered structures. We further perform finite-element simulations with different shapes to confirm the desired effects. These results provide guidance for multithermal management such as considering the combination of other basic modes of thermal transport.

Calculation and Analysis of the Structure and Viscosity of B2O3-Regulated CaO-Al2O3-Based Mold Fluxes

The high content of aluminum in the steel reacts with the CaO-Si2O-based mold fluxes, resulting in deterioration of the mold slag physical and chemical properties, which cannot be applied to the continuous casting molten slag casting process of high-Mn high-Al steel Herein, the thermodynamic and structural properties of low-reactivity CaO-Al2O3-based mold fluxes were investigated. The thermodynamic properties were studied based on the first principles of quantum mechanics. The results show that the formation of stable structures of B-O and O-B-O in the mold fluxes was beneficial to reduce the probability of structural interconnection, degree of polymerization, and viscosity of the molten slag. The increase in the ratio of CaO/Al2O3 = 0.88–2 led to an increase in the O2− concentration. O2− entered the [AlO4] structure to form a stable structure of [AlO6] and [AlO5], wherein [AlO6] was more stable than [AlO5], reducing the degree of polymerization of the network structure. When cosolvent content B2O3 = 2%–10%, a simple layered structure of [BO3] was formed, and the particle migration resistance, break temperature, and viscous activation energy of the mold fluxes were reduced, while the corrected optical basicity of mold fluxes was gradually increased.

Ballistic Behavior of Oblique Ceramic Composite Structure against Long-Rod Tungsten Projectiles

Oblique ceramic armor structure composed of an oblique part and a backing part was designed to resist the ballistic impact of long rod penetrators. The front part consisted of an oblique silicon carbide ceramic and a triangular titanium alloy prism. The backing part contained layered silicon carbide and armor steel designed to absorb the residual energy of penetrators. The structure’s response to penetration was examined experimentally by considering different impact locations on oblique targets. Numerical simulations of the experiments were performed to reproduce the penetration and failure processes that occurred in the armor modules. In addition, a simple layer structure with the identical line-of-sight thickness of each material used in the oblique impact was simulated under a normal impact. The rod and target performances with the oblique impact and normal impact were compared and analyzed in detail. The results showed that the oblique structure had a better ballistic performance as a result of an extra short dwell period before penetrating the ceramic in comparison with the normal layer case. The ability of the oblique targets to defeat long rod projectiles differed with the impact location on the ceramic. The present study paves the way for ceramic armor obliquity applications.

Investigation of the localized surface plasmon resonance of Ag@SiO2 core-shell nanocubes and its application in high-performance blue organic light-emitting diodes

A blue organic light-emitting diode (OLED) with silica-coated silver nanocubes (Ag@SiO2 NCs) inserted at the hole transporting layer/emission layer interface is reported. The localized surface plasmon resonance (LSPR) properties of the Ag@SiO2 NCs were characterized by the measured absorption spectra, stable-stated and transient photoluminescence, and calculated dipole radiation power. The results suggest that the Ag NCs significantly improved the radiation intensity of the nearby excitons due to their sharp corners and edges, but had less impact on the radiation rate of the excitons. The exciton recombination zone in the blue OLED was confirmed by a group of devices with an ultra-thin yellow emission layer located at different places, which helped to figure out the distribution of the excitons around the Ag@SiO2 NCs and deeply understand the coupling between the excitons and the Ag@SiO2 NCs. In our blue OLED, an appropriate distance between the Ag NCs and the excitons was realized by the SiO2 coating layer and the exciton distribution, which greatly improved the energy transfer between the excitons and the Ag NCs. In addition, the LSPR enhanced electric field around the Ag@SiO2 NCs improved the carrier injection at the hole transporting layer/emission layer interface and increased the current density of the blue OLED. Finally, the blue OLED with a simple triple layer structure achieved a high current efficiency of 51.1 cd A−1.

Evidence of anisotropic Majorana bound states in 2M-WS2

Searching for Majorana bound states has become an important topic because of its potential applications in topological quantum computing. 2M-phase WS2, a newly synthesized superconductor, not only presents the highest superconducting transition temperature (Tc = 8.8 K) among the intrinsic transition metal dichalcogenides but also is predicted to be a promising candidate as a topological superconductor. Using scanning tunnelling microscopy, we observe a U-shaped superconducting gap in 2M-WS2. Probable Majorana bound states are observed in magnetic vortices, which manifest as a non-split zero-energy state coexisting with the ordinary Caroli–de Gennes–Matricon bound states. Such non-split bound states in 2M-WS2 show highly spatial anisotropy, originating from the anisotropy of the superconducting order parameter and Fermi velocity. Due to its simple layered structure and substitution-free lattice, 2M-WS2 can be a building block to construct novel heterostructures and provides an ideal platform for the study of Majorana bound states. Potential Majorana bound states are seen in the vortex cores of a transition metal dichalcogenide. The properties of the superconductor mean that the bound states are highly anisotropic, and can appear at higher temperatures than other materials.

Strong longitudinal coupling of Tamm plasmon polaritons in graphene/DBR/Ag hybrid structure

In this paper, strong longitudinal coupling of the Tamm plasmon polaritons (TPPs) is investigated in a graphene/DBR/Ag slab hybrid system. It is found that TPPs can be excited at both the top graphene and the bottom silver slab interface, which can strongly interact with each other in this coupled structure. Numerical simulation results demonstrate that the vertical Tamm plasmon coupling can be either tuned by adjusting the geometric parameters or actively controlled by the Fermi energy in graphene sheet as well as the incident angle of light, allowing for strong light-matter interaction with a tunable dual-band perfect absorption. Moreover, the coupling strength of the hybrid modes exhibits a large tuning range, from a large Rabi splitting to an extremely narrow induced transparency in this coupled regime. Coupled mode theory has been employed to explain the strong coupling phenomenon. The controllable TPP coupling with an ultrahigh dual-band absorption capability offered by this simple layered structure opens new avenues for developing a broad range of graphene-based active optoelectronic and polaritonic devices.

Investigation of near-surface structures using seismic refraction and multi-channel analysis of surface waves methods—a case study of the University of Lagos main campus

The need to use locations which are hitherto swamps or recreation centers to construct more building facilities that range from medium to huge structures within the University main campus informed the decision to embark on this study. Structures within the subsurface layers were investigated by analyzing the distribution pattern of some geophysical properties such as compressional wave (P-wave) velocity, shear wave (S-wave) velocity, and Poisson ratio. The near-surface layers were identified from the first break picks of P-waves velocities. Moreover, the dispersive capability of the surface wave produced S-wave velocity information that identified different geological structures based on the orientations of the lithological layer’s rigidity. The P-wave velocities reveal three-layer structures of thicknesses between 3.0 m to 6.0 m and 2.0 m to 5.0 m for Layer 1 and Layer 2 respectively. These layers are in three categories of “Complex”, “Mild,” and “Simple” based on the distribution pattern of shear velocities. Poisson ratio analysis shows two categories of Topsoil/Lateritic layer of less than 2.0 m (thin) and between 2.0 m and 4.5 m (thick). Areas identified as “Complex” structure with thick Topsoil will require comprehensive foundation design than other areas especially when erecting huge building. Whereas, locations around the New Halls (NHs) may require simple foundation plan for building development compared to other areas since it is characterized by thin Topsoil and simple layer structure. The study will assist construction engineers with prior information of the structures of subsurface layers which thereby reduce time and cost of building development within the University campus.

Characterisation of seismic site effects influenced by near-surface structures using 3D waveform modelling

Seismic waves propagating from source to surface can be significantly affected by vertical and lateral heterogeneities of the near-surface geology. These modified waves can lead to local amplification or attenuation effects of the wave amplitude at the surface. In the assessment of seismic events and the evaluation of possible impacts on infrastructures, the analysis of such site effects is an important issue. In this study, the amplification behaviour of typical near-surface structures in Northern Germany is investigated depending on various parameters to assemble a catalogue of typical structures in the area, which can be used to quickly assess the impact of induced seismic events at the surface. The effect of incoming seismic waves on simple model structures as layer, channel and lens geometries is analysed using 3D waveform simulations with dominant signal frequencies between 1 and 10 Hz based on the spectral element method. The dimensions of the modelled structures range from tens of metres to a few hundred metres. The parameter study shows the dependency of the resulting amplitude at the surface on the impedance contrast, geometrical features and the dominant signal frequency, which are quantified as amplification (attenuation) factors. Simple layer structures reveal low amplification values ranging from 1 to 3.5 and smooth amplification curves, which become more complex for channel and lens type structures while the maximum amplification increases by a factor of two. Focusing and interference effects could be observed depending on the structure type itself as well on the edge shape of the structure. Furthermore, the results of the simple model simulations are used in combination with additional borehole, geological and geophysical data to generate a first large-scale model of the area of the natural gas fields in Northern Germany. Waveform simulations of the large-scale model illustrate the influence of near-surface structures on wave propagation and allow to calculate the amplification behaviour at the surface. These (regional) model simulations can be essential for the reliable assessment of site effects and minimising uncertainties in the interpolation of the ground velocity distribution.