Double-layer System Research Articles

Theoretical Analysis of Tunable Multimode Coupling in a Grating-Assisted Double-Layer Graphene Plasmonic System

A double-layer graphene hybrid system is proposed to investigate the multimode coupling at far-infrared frequencies. With the assistance of metallic grating, the upper- and lower-layer graphene sur...

Observer based adaptive double-layer fuzzy control for nonlinear systems with prescribed performance and unknown control direction

This paper investigates an observer based adaptive double-layer fuzzy control design problem for strict feedback nonlinear systems with prescribed performance and unknown control direction. To this end, a class of T-S fuzzy systems with unknown fuzzy rules are considered, and an adaptive interval type-2 (IT2) fuzzy controller is proposed for these systems. By using the presented control scheme, the unknown functions of the system can be ultimately approximated by the double-layer fuzzy logic systems (FLSs) which contain the first-layer type-1 FLSs and the second-layer IT2 FLSs. A state observer is applied to handle the unmeasurable states, and the Nussbaum gain method is employed to cope with the unknown control direction. In order to guarantee the prescribed performance of the output tracking error, a tracking error transformation method is utilized, and an improved robust adaptive control scheme is proposed based on the backstepping technique. Then, the stability of the closed-loop system and the achievability of the prescribed tracking performance are proved. Finally, simulation results illustrate the efficacy of the proposed control method.

Space charge accumulation in double-layer dielectric systems—measurement methods and quantum chemical calculations

A new perception of interface charge accumulation in HVDC cable joints was inspired by novel measurement methods of PEA and Q(t) and quantum chemical calculations.

Electro-Optically Active Polyaniline-Polypyrrole Double Layer Polymer Semiconducting Composite

Optically active polyanilines have been synthesized in the presence of chiral camphorsulfonic acid (CSA) by electrochemical polymerization in water medium. Polyaniline forms various electronic states such as emeraldine base, emeraldine salt, and pernigraniline. As prepared polyaniline in the presence of (+)-CSA is called as emeraldine salt. In this case, (+)-CSA shows two functions as 1) electro-dopant and 2) chiral inducer for the polyaniline, producing radical cation (polarons) and diction (bipolarons) as charge carriers and one-handed helically twist for the main chain. In the present research, we succeeded to obtain double layer conductive polymer film consisting of polyaniline and polypyrrole with electrochemical method. Fig. 1 shows the structure of the double layer polymer film. The optical activity of the polymer film was examined with optical rotatory dispersion (ORD). The double layer supports strength of the polymer film form. Electrical conductivity of the polymer film is ca. 0.25 S/cm evaluated with four-probe method. We carried out synthesis of a single layer polyaniline with (+)-CSA with potentiostat with three electrode system, Pt counter electrode saturated calomel electrode (SCE) as reference, and the polymer as working electrode. Fig.2 shows the results. Five scans afford to produce green polymer film deposited on the indium-tin oxide (ITO) coated grass electrode. The polymer shows redox activity conformed with cyclic voltammetry (CV). Increase of scan rate provides increase of current density in the electrochemical measurement because of increase of diffusion of ionic species in the electrolyte solution. The single layer polyaniline film displays electrochemical driven change in optical rotation evaluated with in-situ ORD/CV. The double layer polymer film was synthesized as followed. First, electrochemical polymerization of aniline as a monomer was carried out in concentrated optically active (+)-CSA with two electrode system. An application of electric filed (3.0 V) between electrodes in the electrolyte solution was carried out. The electrochemical polymerization reaction is rapidly progressed for formation of polymer thin film onto the anode side. Continuously, pyrrole as another kind of monomer was added to the electrolyte solution. The sequential electrochemical polymerization process affords to yield polypyrrole layer deposited onto the polyaniline layer. ORD measurement revealed that the double layer polymer film thus obtained is optically active. The bottom layer of polyaniline can be formed helical structure due to combination with optically active (+)-CSA. The top layer of polypyrrole may also form helical structure with aid of (+)-CSA as chiral doping agent. Chemical structure of the double layer polymer (composite) is examined with Fourie transform infrared optical absorption spectroscopy measurements. This result indicates that the polymer composite consists of polyaniline, polypyrrole, and CSA. The composite shows intense and wide range optical absorptions from invisible to infrared range due to delocalized charge carriers along the main-chain. The advantages of double conductive polymer film are redox activity, tunable optical activity, and color coordination. Top layer of polypyrrole is black in color with no polish and good redox character, and polyaniline as the bottom layer displays electro-optical activity. This paper reports convenient method for preparation of double layer system with electrochemical method. Further variation can be expected using different type of monomers for construction of multi-layer conductive polymer composite. This concept can be a first example as an electro-optically active conducting polymer composite. Figure 1

Modelling sound absorption of tunable double layer woven fabrics

The woven fabric is known to have micro structures inherently so that it can be employed as sound absorber with the same absorption mechanism as the micro-perforated panel (MPP) when it is backed up by an air cavity. In the context of multi-layer system, having high flow resistance at all layers do not guarantee high sound absorption coefficients are achieved apart from narrow absorption bandwidth issue in the MPP. These have been extensively discussed in fibrous porous materials, but it is lacking for the woven fabrics, particularly on the analysis of the relationship of flow resistance for each layer to the sound absorption bandwidth. In this paper, a double-layer system of woven fabric is considered. Two cases are studied: a system with identical flow resistance and one with non-identical flow resistance. The Johnson-Champoux-Allard (JCA) formulation and the transfer matrix method are used to develop the prediction model. It is revealed that for a system with identical flow resistances, high flow resistance produces low amplitude of absorption coefficient, but with relatively wide frequency bandwidth. Lower flow resistance can improve the absorption amplitude, but with a dip in between two absorption peaks which degrades the half absorption bandwidth. This can be solved by having the combination of non-identical resistance between the layers. The selection of flow resistances together with the ratio of the air cavity depths can be used in tuning the performance of the double-layer woven fabric absorber. The experimental data show good agreement with the predictions.

Characteristics of Oceanic Warm Cloud Layers within Multilevel Cloud Systems Derived by Satellite Measurements

Low-level warm clouds are a major component in multilayered cloud systems and they are generally hidden from the top-down view of satellites with passive measurements. This study conducts an investigation on oceanic warm clouds embedded in multilayered structures by using spaceborne radar data with fine vertical resolution. The occurrences of warm cloud overlapping and the geometric features of several kinds of warm cloud layers are examined. It is found that there are three main types of cloud systems that involve warm cloud layers, including warm single layer clouds, cold-warm double layer clouds, and warm-warm double layer clouds. The two types of double layer clouds account for 23% and in the double layer occurrences warm-warm double layer subsets contribute about 13%. The global distribution patterns of these three types differ from each other. Single-layer warm clouds and the lower warm clouds in the cold-warm double layer system they have nearly identical geometric parameters, while the upper and lower layer warm clouds in the warm-warm double layer system are distinct from the previous two forms of warm cloud layers. In contrast to the independence of the two cloud layers in cold-warm double layer system, the two kinds of warm cloud layers in the warm-warm double layer system may be coupled. The distance between the two layers in the warm-warm double layer system is weakly dependent on cloud thickness. Given the upper and lower cloud layer with moderate thickness of around 1 km, the cloudless gap reaches its maximum when exceeding 600 m. The cloudless gap decreases in thickness as the two cloud layers become even thinner or thicker.

Helicoidal excitonic phase in an electron-hole double-layer system

We propose helicoidal excitonic phase in a Coulomb-coupled two-dimensional electron-hole double layer (EHDL) system with relativistic spin-orbit interaction. Previously, it was demonstrated that layered InAs/AlSb/GaInSb heterostructure is an ideal experimental platform for searching excitonic condensate phases, while its electron layer has non-negligible Rashba interaction. We clarify that due to the Rashba term, the spin-triplet (spin-1) exciton field in the EHDL system forms a helicoidal structure and the helicoid plane can be controlled by an in-plane Zeeman field. We show that due to small but finite Dirac term in the heavy hole layer the helicoidal structure of the excitonic field under the in-plane field results in a helicoidal {\it magnetic} order in the electron layer. Based on linearization analyses, we further calculate momentum-energy dispersions of low-energy Goldstone modes in the helicoidal excitonic phase. We discuss possible experimental probes of the excitonic phase in the EHDL system.

Role of Graphene Surface Ripples and Thermal Vibrations in Molecular Dynamics of C60

Nanocars are artificial molecular machines with chassis, axles, and wheels designed for nanoscale transport at materials’ surfaces. Understanding the dependence of surface dynamics of nanocars on the substrate’s physicochemical properties is critical to the design of the transport properties of such man-made nanoscale devices. Among the multitude of potential substrates for the nanotransporters, graphene exhibits intrinsic ripples on its surface, which may affect the surface dynamics of nanocars. In this work, we report our molecular dynamics study of motion of C60, a popular nanocar wheel, on the graphitic substrates with systematically controllable surface ripples. We find that surface ripples increase the amplitude of fullerene fluctuation in the direction normal to surface, which leads to decrease of the desorption temperature from 650 K on a double-layer graphite system with less ripples to 550 K on single-layer graphene with more ripples. The surface diffusion of C60 follows the rare hops mechanism ...

Acoustic Absorption Analysis and Modeling of Asphalt Mixtures

Abstract Highway traffic noise is a major environmental issue all over the world. This is particularly annoying to residents who live nearby major transportation corridors. Noise pollution adversely affects the quality of their life. It also causes sleep disturbance and anxiety. The most commonly used noise abatement technique is the use of noise barrier walls, which is costly and not always effective. Reducing the tire–pavement noise at the source is a viable alternative to cut down the noise level. This study examined the use of an impedance tube to measure the acoustic absorption of asphalt mixtures in the laboratory. The effect of various parameters on the acoustic absorption was investigated including aggregate gradation, aggregate type, binder type, percent air voids, and specimen thickness. In addition, factors that could affect the acoustical performance of asphalt mixtures after pavement construction were also investigated including air void structure, surface texture, temperature, and surface conditions. Percent air voids and layer thickness were found to have a significant influence on the acoustic absorption of asphalt mixtures. An analytical model was proposed to estimate the acoustic absorption coefficient of asphalt mixtures during the design stage. A good correlation was found between predicted and measured absorption coefficients in the laboratory. In addition, a double-layer system of asphalt mixtures was found to be effective in providing improved acoustical performance that overcomes the issues associated with the use of open-graded friction course as a wearing surface.

Plasmon modes in graphene — GaAs heterostructures at finite temperature

This paper is to investigate the dispersion relation and decay rate of plasmon modes in a double layer system made of monolayer graphene (MLG) and infinite GaAs quantum well at finite temperature within the generalized random-phase-approximation and taking into account the 2DEG layer-thickness and the inhomogeneity of the background dielectric. Calculations demonstrate that when the quantum well width increases, the acoustic (AC) plasmon frequency decreases dramatically, but the optical (OP) one seems unchanged. In addition, the results also illustrate that the temperature and separated distance affect significantly both AC and OP plasmon modes of the system. Finally, the dielectric of the background acts strongly on the OP plasmon curve while carrier density in two layers and exchange-correlation effects only lead to remarkable changes for the acoustic one.

Stability analysis and performance comparison of large-scale hyperbolic steel cooling towers with different latticed shell systems

The cooling tower is a very important building for the thermal power plant. The large steel cooling tower is proposed to overcome the serious challenges that arise from modern cooling towers being higher, larger, and more complex. In this study, for the large-scale hyperbolic steel cooling tower, seven different latticed shell systems with different grid forms, including five double-layer systems and two single-layer systems, were designed and studied in detail. For different heights, grid sizes, and shell thicknesses, numerous parametric analyses (792 models) of the structures were performed. The static behaviors—including the steel quantity, peak displacement, and peak stress—of the seven structural systems were obtained and compared. The variation laws of the steel quantity and peak displacement with respect to the parameters were presented, and the reasonable range of the parameters for the steel cooling tower with different heights were obtained. The results show that the optimal structural system is different for the steel cooling towers with different heights. Additionally, based on the nonlinear stability analysis, a reasonable strengthening scheme was proposed for the single-layer system with poor stability. The results will be of great help for further research on large steel cooling towers and provide guidance for actual engineering design of the structures.

Intelligent vibration detection and control system of agricultural machinery engine

Vibration of agricultural machinery not only affects the quality and effect of the operation, but also reduces the service life of machinery. A vibration detection and control system based on intelligent sensor nodes was developed to detect and control the frame vibration caused by high-power engine in agricultural machinery. Each intelligent detection node can work independently or networking as Internet of Things system. The effect of the vibration isolation system can be assessed by installing the test nodes at the measuring points of the two-stage vibration isolation system. In this paper, intelligent sensor nodes were used to reduce the vibration of an agricultural machinery engine. According to the optimized stiffness of the double-layer vibration isolation system, a test platform system is designed. The intelligent sensor nodes were used to assess the vibration spectrum characteristics of engine under various working conditions, and acceleration values of upper and lower measuring points of stage 1 and stage 2 isolators. The relationship between acceleration transfer rate and engine speed was analyzed before and after double-layer vibration isolation was used, and the vibration isolation effect of double-layer vibration isolation system is verified. The results show that the double-layer vibration isolation system can play a significant role in changing the stiffness of the whole system and avoiding the occurrence of coupling resonance. The transmission rate of vibration acceleration decreases from 0.94 to 0.54 at the engine speed of 2700 r/min, with a decrease of 42.3%. The results show that the proposed intelligent detection node is able to detect the engine vibration in agricultural machinery, and the proposed double-layer vibration isolation system can effectively reduce the engine vibration.

Reconstruction of three-dimensional anisotropic media based on analysis of morphological completeness

The physical properties of porous media can be more effectively observed and understood when analyzing three-dimensional (3D) structures. The use of computer-based mathematical modeling methods has been proven effective for reconstructing 3D structures of porous media from two-dimensional (2D) images. However, reconstructing a heterogeneous 3D structure from a single 2D image is currently challenging for computer-based mathematical modeling methods. Focusing on the reconstruction of heterogeneous 3D structures from a single anisotropic training image (TI), this paper first introduces a morphological completeness analysis method, which presents a completely new approach to reconstruction in which only two sections are controlled. Then, to enhance the constraint on the simulation points in this new approach to reconstruction, a double-layer and multi-grid system (DLMGS) is proposed. The updated pattern density function simulation, based on the DLMGS, is then taken as the specific reconstruction algorithm in this work. Finally, our reconstruction method is tested using a core image, and the performance of the reconstruction result is assessed using multiple functions. Detailed experiments show that our method can successfully reconstruct a heterogeneous 3D structure from a single anisotropic image, which reduces the required dimensionality of input data for 3D reconstruction and extends the applicable scope.

DLMPCS‐based improved yaw stability control strategy for DDEV

The yaw stability of distributed drive electric vehicle (DDEV) can be guaranteed by the active steering and torque distribution systems. Conventional yaw stability control strategy mainly focuses on the study of yaw moment, while the tyre lateral saturation and excessive longitudinal skid problems are difficult to be solved efficiently. This may lead to the unstable yaw phenomenon of the vehicle such as the sideslip or tail flick. To improve the yaw stability of DDEV under the tyre lateral saturation and excessive longitudinal skid situations, a double-layer model predictive control system (DLMPCS) is presented in this work. The proposed DLMPCS consists of an anti-saturation yaw stability controller (AYSC) and an anti-slip torque distribution controller (ATDC). The AYSC is designed to guarantee the vehicle yaw stability under the tyre lateral saturation situation, through the active steering and yaw moment. The ATDC is designed to realise the torque distribution and keep the longitudinal slip ratio within the stable zone; then, the vehicle can be prevented from the excessive skid phenomenon. The simulation results confirm the improved yaw performance of the DLMPCS for DDEV under different situations.

Bearing capacity of strip footing resting on fibre-reinforced pond ash overlying soft clay

The use of the industrial hazardous waste like pond ash to strengthen the soft clay (weak soil) is also helpful in solving the land requirement problem for its deposition. In the present study, the results of an investigation carried out on double-layer soil system have been presented. The model tests have been conducted with a strip footing resting on soil system which contains unreinforced and randomly distributed fibre-reinforced pond ash (RDFP) layer over soft clay. The effect of the pond ash layer thickness (i.e. 0.5B, 1.0B and 1.5B) compacted at optimum moisture content, the fibre length (6 mm, 12 mm and 18 mm) and the percentage of fibres in RDFP layer, i.e. 0.5%, 0.75% and 1.0% have been studied. The results have indicated that the provision of compacted pond ash layer and the addition of fibres into pond ash significantly influence the ultimate bearing capacity. The results in the form of bearing pressure ratio (BPR) have shown that the improvement with 1.5B thickness of RDFP and 1% of fibre inclusions is maximum. The validation of results has also been done using a finite element tool PLAXIS 3D.

A theoretical study of collective plasmonic excitations in double-layer silicene at finite temperature

We explore the temperature-dependent plasmonic modes of an n-doped double-layer silicene system which is composed of two spatially separated single layers of silicene with a distance large enough to prevent interlayer electron tunneling. By applying an externally applied electric field, we numerically obtain the poles of the loss function within the so-called random phase approximation to investigate the effects of temperature and geometry on the plasmon branches in three different regimes: topological insulator, valley-spin polarized metal, and band insulator. Also, we present the finite-temperature numerical results along with the zero-temperature analytical ones to support a discussion of the distinct effects of the external electric field and temperature on plasmon dispersion. Our results show that at zero temperature both the acoustic and optical modes decrease when the applied electric field is increased and experience a discontinuity at the valley-spin polarized metal phase as the system transitions from a topological insulator to a band insulator. At finite temperature, the optical plasmons are damped around this discontinuity, and the acoustic modes may exhibit a continuous transition. Moreover, while the optical branch of plasmons changes non-monotonically and noticeably with temperature, the acoustic branch dispersion displays a negligible growth with temperature for all phases of silicene. Furthermore, our finite-temperature results indicate that the dependency of two plasmonic branches on the interlayer separation is not affected by temperature at long wavelengths; the acoustic mode energy varies slightly with an increase in the interlayer distance, whereas the optical mode remains unchanged.

Anderson-Bogoliubov and Carlson-Goldman modes in counterflow superconductors: Case study of a double monolayer graphene

The impact of electron-hole pairing on the spectrum of plasma excitations in double layer systems is investigated. The theory is developed with reference to a double monolayer graphene. Taking into account the coupling of scalar potential oscillations with oscillations of the order parameter $\Delta$, we show that the spectrum of antisymmetric (acoustic) plasma excitations contains two modes: a weakly damped mode below the gap $2\Delta$ and a strongly damped mode above the gap. The lower mode can be interpreted as an analog of the Carlson-Goldman mode. This mode has an acoustic dispersion relation at small wave vectors and it saturates at the level $2\Delta$ at large wave vectors. Its velocity is larger than the velocity of the Anderson-Bogoliubov mode $v_{AB}=v_F$/$\sqrt{2}$, and it can be smaller than the Fermi velocity $v_F$. The damping rate of this mode strongly increases under increase of temperature. Out-of-phase oscillations of two order parameters in two spin subsystems are also considered. This part of the spectrum contains two more modes. One of them is interpreted as an analog of the Anderson-Bogoliubov (phase) mode and the other, as an analog of the Schmid (amplitude) mode. With minor modifications the theory can be extended to describe collective modes in a double bilayer graphene as well.

Finite-time control for double-layer Peltier system based on finite-time observer

The Peltier is a refrigeration device and usually used in the form of single layer. Sometimes single-layer Peltier may not have sufficient refrigerating capacity with deeper application. To this end, a double-layer Peltier system is proposed in this article. With the increasing layers, the nonlinearity of the system is enhanced and the multiple variables are coupled, bringing about control difficulty. To solve these control problems and promote the disturbance rejection performance, a composite controller is presented, consisting of feedback regulation based on finite-time control and feed-forward compensation based on finite-time disturbance observer. Then, finite-time Lyapunov stability analysis is shown to prove that this control scheme can converge to the equilibrium point in finite time. Last but not least, simulation and experiment are conducted to verify that the proposed strategy has not only a rapid convergence performance but also a prominent disturbance rejection property.

A quantitatively controllable mesoscopic reliability model of an interdependent public transit network considering congestion, time-delay interaction and self-organization effects

This paper establishes a multi-parameter controlling cascading failures (CFs) model for measuring interdependent public transit network (PTN) reliability under mesoscopic perspective. First, we abstract the weighted PTN and geospatial PTN into a double-layered passenger flow system that considers the influences of the transportation infrastructure and the interaction between the passenger flow transited via the public transit mode and that transited via all other urban traffic modes. Second, for embedding the congestion, time-delay interaction and self-organization effects in the CFs model of an interdependent PTN, we propose the failure load dynamic redistribution (FLDR) considering the congestion effect in each sub-network, define the interaction way (another FLDR form) considering time-delay effect between two sub-networks and establish the CFs judging method considering the self-organization effect in the interdependent PTN. Furthermore, the multi-perspective measurement indicator system (i.e., (i) the global and local perspectives and (ii) the aggregated and discretized perspectives) is defined to provide a full viewing perspective for better understanding and capturing the CFs process. Finally, through a simulation analysis of Jinan’s PTN, the adaptability of the proposed CFs model is verified, and the significant nonlinearity is found, i.e., there is a threshold value of the station load tolerance parameter $$\lambda _C$$ , making the cascading survivability of interdependent PTN significantly increase, when the actual station load tolerance parameter is larger than $$\lambda _C$$ ; moreover, increasing the control parameter of the connected edge transit capacity (parameter $$\theta $$ ) can speed up the process of finding this $$\lambda _C$$ of an interdependent PTN. This nonlinearity provides the simulation evidence of the CFs controllability in the interdependent PTN.

Vibration Transmission and Isolation in the Cutting Process of Machine Tools

Background: Machining is an important method for manufacturing parts. It is characterized by high cutting speed with a considerable influence of high-frequency vibration. Various relevant papers and patents have studied vibration transmission and isolation in the machining process. Objective: To investigate vibration transmission and isolation in the machining process, and simplify the cutting process of a machine tool. Methods: Firstly single-layer and double-layer vibration isolation models are established, the substructure matrix analysis method is adopted and the vibration power flow transmission characteristics of double-layer vibration isolation system under complex excitation are analyzed. Secondly, the optimal control strategy based on the minimum power flow inputted into the base is proposed. Then the control effect of the active actuator under different installation modes is analysed and compared. Results: It has been proved that low-frequency coupling is characterized by the rigid mode of the workpiece or the grinding wheel when cutting, whereas high-frequency coupling exhibits the dynamic characteristics of the machine tool bed. A good vibration isolation effect can be achieved for three types of installation modes in a double-layer vibration isolation system, and only the actuators installed between the vibration source and the middle mass exhibit the best control effect. Conclusion: The vibration isolation model has been established and the optimal installation mode of the actuator in the double-layer vibration isolation system has been found. And the paper provides a reference for the study of vibration transmission, control of machine tools and the elimination of grinding chatter.