Three-layer Structures Research Articles

Investigation of the regimes of mixing of superconducting tunneling structures

The regimes of operation of a superconductor–insulator–superconductor tunnel junction based on three-layer structures Nb/AlOx/Nb and Nb/AlN/NbN as a harmonic mixer (for frequencies of the order of 600 and 20 GHz, respectively) and a frequency up-converter (in the frequency range from 0.1 to 5.0 GHz) have been investigated experimentally. The quasiparticle and Josephson mixing regimes have been compared. It has been shown that, in some practical applications, such as the use of the superconductor–insulator–superconductor junction as a cryogenic harmonic phase detector, the Josephson mixing regime is more preferable, because it can provide a higher signal and a greater signal-to-noise ratio as compared to the quasiparticle mixing regime. It has also been demonstrated that the Josephson mixing regime is promising for the use in signal multiplexing systems for superconducting detectors.

A three-dimensional ultra-broadband metamaterial absorber in terahertz region

In this paper, we proposed a three-dimensional metamaterial absorber with ultra-broadband in terahertz region. Compared with other three-layer structures, our structure is only composed of graphite film and a metal plate. The simulated results show that the metamaterial absorber can achieve an ultra-broadband absorption more than 90 % from 3 to 9 THz for either transverse electric or magnetic polarization wave at normal incidence. In addition, the absorption properties based on the oblique incidence and different polarization angles are also observed. A good absorption bandwidth can be kept when the incidence angle is up to 60°. Moreover, the absorber is polarization-insensitive with the polarization angle increase. Finally, the power loss density and surface current distributions at distinct resonance point are analyzed, which can demonstrate that the graphite plays an important role for the absorption of electromagnetic waves. We believe that the design idea of the three-dimensional metamaterial absorber maybe can extend to microwave, infrared or optical region.

Oxidation Behavior of ZrB2–SiC Composites at 1650 °C

The oxidation behavior of ZrB2–SiC composites in air was studied at 1650 °C. Diffusion-controlled oxidation kinetics were found for the composites studied. A parabolic rate constant of 1.2 × 10−8 g2 cm−4 s−1 was measured for ZrB2–10 % SiC composite. A transition in the oxidation kinetics was observed for ZrB2–30 % SiC composite with the initial parabolic rate constant being 1.3 × 10−8 g2 cm−4 s−1. After exposure for 60 min, the parabolic rate constant was found to be 0.3 × 10−8 g2 cm−4 s−1. A single ZrO2-rich oxide layer was found in the oxide scale structure of ZrB2–10 % SiC composite. On the other hand, three-layer oxide structures, namely SiO2-rich top layer, followed by ZrO2-rich oxide scale and SiC-depleted layer, were found for ZrB2–30 % SiC composite. The outer layer in the oxide scale structure of ZrB2–SiC composite was tapered with enhanced oxidation at the corners of the sample. Vortex formation during the viscous flow of B2O3–SiO2–ZrO2 liquid near the corners on the surface was proposed as the root cause for enhanced oxidation at the corners of the sample.

Natural transition in natural convection boundary layers

The ‘natural transition’ of a natural convection boundary layer adjacent to an isothermally heated vertical surface is investigated by means of three-dimensional direct numerical simulation (DNS). In order to trigger ‘natural transition’ numerically, spatially and temporally random perturbations are introduced into the upstream boundary layer. The propagation of the random perturbations in the streamwise direction is observed. It is found that there exist two competing wavenumbers of spanwise vortical structures, one large and the other small. The large wavenumber dominates in the upstream boundary layer, whereas the small wavenumber dominates in the downstream boundary layer. The streamwise evolution of the mean (time-averaged) streamwise vorticity observed at planes perpendicular to the heated surface in general reveals two- and three-layer longitudinal roll structures. Nonlinear processes in a transitioning natural convection boundary layer are also analysed using Bicoherence method. The transition route and mechanism are discussed based on the power spectra and Bicoherence spectra of the temperature time series obtained in the boundary layer. A spectrum filling process during the ‘natural transition’ to turbulence is also observed, which is qualitatively similar to that observed in Blasius boundary layers.

Slab waveguide sensor utilizing left-handed material core and substrate layers

Propagation of transverse electric (TE) polarized light in two three-layer slab waveguide structures comprising left-handed materials (LHMs) is studied for sensing applications. The LHM layer occupies the core layer in the first structure and the substrate layer in the second structure. The sensitivity of the effective refractive index of the guided mode to any change in the index of an analyte medium located in the cladding region is derived and studied. The optimal structure parameters corresponding to the highest sensitivity are found. The results reveal that the sensitivity of the second structure with LHM substrate is much higher than that of the first with LHM core layer. The sensitivity can reach up to 70% for the LHM substrate structure for some waveguide configurations whereas it can reach up to 45.5% for the LHM core structure. The sensitivities of the two structures are found to be significantly high when compared to those of the conventional three-layer slab waveguide structure comprising dielectric media.

Nanoliposome is a Promising Carrier of Protein and Peptide Biomolecule for the Treatment of Cancer.

Nano-liposomes are the newly developed delivery systems for cancer therapy that are finding a position particularly suitable as peptide and protein carriers. These are three-layered self-assembled structures with nanoparticulate carrier systems. The overall pharmacological properties of commonly used protein and peptide in cancer therapy can be improved by the incorporation of protein and peptide into the nano-liposome. The surface modifications can be made liposomes to make compatible with targeting ligands has made these nanocarriers for targeted delivery. This review discusses the method of preparation and characterization of liposome based protein peptide delivery for the treatment of cancer. This review also explores latest work intended for targeted treatment of cancer by nano-liposomal protein and peptide delivery system. This type of delivery is targeting protein and peptide to tumor site by avoiding the reticuloendothelial system. Methods of nano-liposome delivery containing protein and peptide are also highlighted.

Three-Layered Polyelectrolyte Structures as Inkjet Receptive Coatings: Part 2. Interaction With Pigment-based Inks

Three-Layered Polyelectrolyte Structures as Inkjet Receptive Coatings: Part 2. Interaction With Pigment-based Inks

Three-Layered Polyelectrolyte Structures as Inkjet Receptive Coatings: Part 1. Interaction with Dye-based Ink

Three-Layered Polyelectrolyte Structures as Inkjet Receptive Coatings: Part 1. Interaction with Dye-based Ink

Coupled effect of strain rate and solvent on dynamic mechanical behaviors of separators in lithium ion batteries

Mechanical properties of separators have a great impact on the electrochemical performance of lithium ion battery, such as capacity, charge/discharge behavior, charging cycles and among others. In the present study, two typical widely commercialized separators, Celgard 2400 and Celgard 2340, are the investigation objects with single layer and three-layer structures respectively. Firstly, to investigate material anisotropy and strain rate effects, tensile tests conducted on MTS and Instron at various strain rates from 0.01 to 50s−1 are carried out with samples prepared at three different directions: transverse direction (TD, 0°), machine direction (MD, 90°) and 45°. The failure strain decreases while failure stress increases with the strain rate for materials in all three directions. Material anisotropy is observed within the porous structure with nanofiber reinforced in the polymer matrix. Secondly, the environmental solvent effect is also examined: dimethyl carbonate (DMC) solution has a negative effect on the mechanical property of the separator while water may exert a positive effect. Furthermore, DMA Q800 is employed to study the viscoelasticity of separators at various temperatures and frequencies. A simple viscoelastic model based on Kelvin–Voigt model is proposed for the two types of separators. This research may serve as a solid step towards the comprehensive understanding of LIB separator and shed light on the future research of unveiling physical relation between mechanical properties and electrochemical performance of LIB.

爆炸、冲击防护材料复合结构研究进展

本文从材料组成结构及其对性能影响的规律出发，总结了国内外大量关于抗爆炸、冲击材料复合结构的设计和研究，系统介绍了由水泥混凝土、金属、有机材料等基体材料组成的复合结构的设计方法、特点和及其防护效果，重点介绍两层材料组合结构和三层材料组合结构；期望能够为有抗爆炸、抗冲击要求的各类国防工程、人防工程，以及民用和工业建筑进行防护材料和结构的研制提供参考。 Based on material composition structure and its effects on impact performance, the literature of anti-explosion and impact composite structure design and research is summarized. The design, technical feature and efficiency of composition structure based on cement concrete, metal and organic materials respectively are summarized, especially introducing the two-layer and three-layer structures. The paper may provide a technical reference for all kinds of studies and designs about the anti-explosion and anti-impact structure of national defense engineering, civil air defense engineering, as well as civil and industrial buildings.

Goos-Hänchen shift at the reflection of light from the complex structures composed of superconducting and dielectric layers

The Goos-Hänchen effect of light reflected from sandwich (three-layered) structures composed of a superconducting YBa2Cu3O7 film and two different dielectric films is investigated theoretically. It has been shown that optical anisotropy of YBa2Cu3O7 film, as well as its positions in the three-layer specimen, strongly effects on the lateral shift values. We have shown that, for all positions of the superconducting film in the three-layered structure, variation of temperature makes possible to control the values of the lateral shift of TE-polarized light at the incidence angles close to pseudo-Brewster angles, whereas for TM-polarized light the lateral shift is only significant at grazing incidence.

Origin of interfacial perpendicular magnetic anisotropy in MgO/CoFe/metallic capping layer structures.

Spin-transfer-torque magnetic random access memory (STT-MRAM) attracts extensive attentions due to its non-volatility, high density and low power consumption. The core device in STT-MRAM is CoFeB/MgO-based magnetic tunnel junction (MTJ), which possesses a high tunnel magnetoresistance ratio as well as a large value of perpendicular magnetic anisotropy (PMA). It has been experimentally proven that a capping layer coating on CoFeB layer is essential to obtain a strong PMA. However, the physical mechanism of such effect remains unclear. In this paper, we investigate the origin of the PMA in MgO/CoFe/metallic capping layer structures by using a first-principles computation scheme. The trend of PMA variation with different capping materials agrees well with experimental results. We find that interfacial PMA in the three-layer structures comes from both the MgO/CoFe and CoFe/capping layer interfaces, which can be analyzed separately. Furthermore, the PMAs in the CoFe/capping layer interfaces are analyzed through resolving the magnetic anisotropy energy by layer and orbital. The variation of PMA with different capping materials is attributed to the different hybridizations of both d and p orbitals via spin-orbit coupling. This work can significantly benefit the research and development of nanoscale STT-MRAM.

Tunable graphene metasurfaces by discontinuous Pancharatnam–Berry phase shift

Metal–dielectric–graphene three-layer structures are proposed to improve the interaction of graphene micro- and nanostructures with incident waves, as the upper graphene cut-wire layer introduces a discontinuous Pancharatnam–Berry phase profile. A semi-analytical method based on the Jones calculus is conducted to investigate the conversion efficiency of cross-polarized light on this graphene metasurface for circularly polarized wave incidence, which predicts that the physical constraint (25%) of cross-coupling conversion efficiency for individual graphene layers can be overcome. Numerical simulations confirm the conclusion and demonstrate an efficiency as high as 60%. Based on this mechanism, high-efficiency anomalous reflection surfaces and flat focal mirrors are designed with the tunability of reflection angles and one order of magnitude improved focusing intensity. This method paves the way to engineering high-efficiency graphene metasurfaces for tunable electromagnetic wave manipulation.

Monte Carlo simulation of multilayer magnetic structures and calculation of the magnetoresistance coefficient

The Monte Carlo study of three-layer and spin-valve magnetic structures with giant magnetoresistance effects has been performed with the application of the Heisenberg anisotropic model to the description of the magnetic properties of thin ferromagnetic films. The dependences of the magnetic characteristics on the temperature and external magnetic field have been obtained for the ferromagnetic and antiferromagnetic configurations of these structures. A Monte Carlo method for determining the magnetoresistance coefficient has been developed. The magnetoresistance coefficient has been calculated for three-layer and spin-valve magnetic structures at various thicknesses of ferromagnetic films. It has been shown that the calculated temperature dependence of the magnetoresistance coefficient is in good agreement with experimental data obtained for the Fe(001)/Cr(001) multilayer structure and the CFAS/Ag/CFAS/IrMn spin valve based on the Co2FeAl0.5Si0.5 (CFAS) Heusler alloy.

Tolerance modelling of vibrations of periodic three-layered plates with inert core

In this note a free vibration analysis of periodic three-layered sandwich structures is performed. Basing on the Kirchhoff’s thin plate theory simplified equations of motion are derived, which are characterised by highly-oscillating, periodic and non-continuous coefficients. In order to obtain a system of equations with constant coefficients, the tolerance averaging technique is used. An application of the proposed tolerance model to analyse free vibration frequencies of a three-layered plate strip is shown – for both lower order frequencies related to its macrostructure and higher order frequencies related to its microstructure. Some comparisons of results of lower frequencies, obtained in the tolerance, the asymptotic and the known homogenised models are presented. Moreover, a certain verification of the proposed model is performed using the Ritz method. It can be observed that the tolerance model can be successfully applied to analyse vibration problems of vast variety of periodic three-layered plates and can significantly improve the optimisation process of such structures.

Characterization and Thermodynamics of Al2O3-MnO-SiO2 (-MnS) Inclusion Formation in Carbon Steel Billet

A method to extract inclusion particles from solid steel by electrolysis with organic electrolyte solution was introduced; meanwhile, thermodynamics of inclusion formation was calculated using FactSage software. The results showed that there were two kinds of inclusions in the billet, i. e. Al2 O3-MnO-SiO2-MnS (AMS-MnS) and A12O3-MnO-SiO2 (AMS). Most of AMS-MnS inclusion particles, with diameter of 10 – 30 µm, showed three-layer structures: SiO2-rich core with a small quantity of Mn, intermediate AMS layer, and MnS outer layer containing small quantities of Al and O. Most AMS inclusion particles were 50 – 90 µm and exhibited homogeneous composition. Thermodynamic results indicated that SiO2-rich core could form firstly by Si reacting with O in molten steel at temperatures above 1923 K during Si-Fe alloy addition, and then, the SiO2-rich core could react with Mn and Al to form liquid AMS enveloping the SiO2-rich core at 1823 – 1873 K. MnS began to precipitate from AMS when temperature reached 1728 K. Liquid AMS could form by coupled reaction among Si, Mn, Al and O in molten steel.

Solitary superconductivity in a ferromagnet–superconductor heterostructure

A ferromagnet (F)–superconductor (S) (F1F2S) three-layer heterostructure has been studied using Usadel equations with allowance for the pair electron–electron interaction in ferromagnetic layers. The appearance of regions with solitary superconductivity on the phase diagram has been predicted for the antiparallel configuration of the magnetization in F layers. Conditions for the possible experimental observation of solitary superconductivity in FFS three-layer structures, as well as for the detection of the electron–electron interaction in ferromagnets, have been discussed.

ANALYSIS OF ELECTROPHYSICAL CHARACTERISTICS OF GROUNDS IN THE VICINITY ELECTRICAL SUBSTATION OF UKRAINE

Purpose. Definition of the direction for further research to improve accuracy of the calculation of rated parameters of ground grids based on the analysis of statistical databases of electro-physical characteristics of the soil. Methodology . To solve this problem we compiled the statistical base of soil of Ukraine in the location of electrical substation, we performed the statistical analysis for the number of layers of geoelectric structure, and electrical characteristics. In the experiments implemented the comparing of accuracy calculation of the most typical three-layer soil in the Ukraine, by the new three-layer model of ground grids and the equivalent two-layer model, which used previously. Results . On the results of analysis the ranges of the electrical resistivity and statistical distribution for electro-physical characteristics of the soil are determined. The resulting distributions allow to develop criteria for instruments, installations and means of interpretation during the sounding of soil, as well as the requirements for mathematical models of ground grids. It was found that the most typical for places of locations the electrical substations in Ukraine are three-layer geoelectric structures. In the paper the statistical distribution for three-layer soil by type (Q, K, H, A) are described. The results of numerical experiments show that the use of methods to simplify of the multilayers soil does not allow the calculation of grounding grids with high accuracy. In the work recommendations for applicability the method equivalenting depending on the type of geoelectric structure are developed. Originality . For the first time, we obtained the statistical distribution of stratification of the soil in the location of power plant in Ukraine, determined the accuracy of the method to simplify a multi-layer soil in determining the rated parameters of grounding grids. In the paper the necessity to develop a mathematical model of the grounding device located in the three-layer soil is shown, as well as a new installation of soil sounding, which allows to increase the depth of sounding and new means of interpreting the results of sounding Wenner installing a four-layers geoelectric structure. Practical value The resulting recommendations for the applicability of equivalenting of multilayer soil, as well as research in specific work areas would help to reduce costs on materials and labours during the modernization and upgrade of grounding devices, moreover it will increase the electrical safety and reliable operation of electrical substation.

Complete tunneling through three-layered periodic structures with metamaterial in far-infrared region

We study the tunneling modes in three different periodic structures with epsilon-negative (ENG) and mu-negative (MNG) materials defined by Lorentz type model in far-infrared region, including (ENG–MNG)N, (ENG–MNG–ENG)N and (MNG–ENG–MNG)N. Transfer matrix method is used to analyze these periodic structures, and the influences of the incident angle, the period number, thickness of every layer and their ratio on the transmittance spectra are discussed based on simulation results. Simulation results show the periodic structure with unit of (MNG–ENG–MNG) is a better choice for stable band-pass tunneling modes.

Application of three-coordinate copper(I) complexes with halide ligands in organic light-emitting diodes that exhibit delayed fluorescence.

A series of three-coordinate copper(I) complexes (L(Me))CuX [X = Cl (1), Br (2), I (3)], (L(Et))CuBr (4), and (L(iPr))CuBr (5) [L(Me) = 1,2-bis[bis(2-methylphenyl)phosphino]benzene, L(Et) = 1,2-bis[bis(2-ethylphenyl)phosphino]benzene, and L(iPr) = 1,2-bis[bis(2-isopropylphenyl)phosphino]benzene] exhibit efficient blue-green emission in the solid state at ambient temperature with peak wavelengths between 473 and 517 nm. The emission quantum yields were 0.38-0.95. The emission lifetimes were measured in the temperature range of 77-295 K using a nanosecond laser technique. The temperature dependence of the emission lifetimes was explained using a model with two excited states: a singlet and a triplet state. The small energy gaps (<830 cm(-1)) between the two states suggest that efficient emission from 1-5 was thermally activated delayed fluorescence (TADF). Alkyl substituents at ortho positions of peripheral phenyl groups were found to have little effect on the electronic excited states. Because the origin of the emission of complexes 2, 4, and 5 was thought to be a (σ + Br)→π* transition, photoluminescence characteristics of these complexes were dominated by the diphosphine ligands. Complexes 2, 4, and 5 had similar emission properties. Complexes 1-5 had efficient green TADF in amorphous films at 293 K with maximum emission wavelengths of 508-520 nm and quantum yields of 0.61-0.71. Organic light-emitting devices that contained complexes 1-5 and exhibited TADF exhibit bright green luminescence with current efficiencies of 55.6-69.4 cd A(-1) and maximum external quantum efficiencies of 18.6-22.5%.