Layer Solution Research Articles

Improved techniques for the solution of several circular dielectric and hollow layers in a straight rectangular waveguide

The first objective of this research is to develop two effective techniques for solving inhomogeneous problems in a rectangular waveguide with several circular dielectric and hollow layers. The cross section consists of a four-layer periodic circular structure with alternating dielectric and hollow layers. We assume that the dielectric profile is different in each circular dielectric layer. The first technique enables the calculation of the dielectric profile and the elements of the matrices of circular dielectric layers by using the image method. The second alternative technique improves the first technique by using the ω ε function as well as the image method. The second objective is to examine the influence of this discontinuous cross section on the output field. The contribution of the proposed techniques is important to improve the mode model method especially in the case of a large number of circular dielectric and hollow layers in the cross section. The application is useful for an inhomogeneous cross section with several circular dielectric and hollow layers in millimeter regime.

Impregnated layer solution combustion synthesized CaO-based composite pellets with enhanced CO2 sorption property

The impregnated layer solution combustion synthesis (SCS) technique was employed to synthesize CaO-based sorbents supported by inert stabilizers so as to improve the cyclic CO2 uptake stability. Four different inert stabilizers were evaluated for their impact on the cyclic CO2 uptake stability of sorbents. It found that the Mg-based inert stabilizer significantly outperforms the other three in improving cyclic CO2 sorption capabilities of sorbents synthesized by the impregnated layer SCS method. Moreover, MgO-supported sorbent pellets were prepared via graphite hydrophobic layer-assisted casting, with the magnesia load within the pellets being regulated between 15 and 45 wt %. It is the addition of MgO stabilizer that significantly improves the performance of CaO-based sorbents, with the improvements being notably more pronounced at higher MgO loads. The calcium-based sorbent pellets containing 45 wt % MgO show extremely stable CO2 sorption performance; after 17 cycles, the carbonation conversion rate is 73.6%, about three times the rate of pellets without MgO loading. The uniform dispersion of MgO inert stabilizer inside pellets improves high-temperature sintering resistance and, concurrently, enhances the mechanical property. Furthermore, the use of waste cigarette butts as impregnated layer templates, rather than other organic additives, will significantly reduce the cost of synthesizing MgO-supported CaO-based sorbents.Graphical

Bearing capacity of strip footings in unsaturated soils reinforced with layered geogrid sheets using upper bound method

A frequently overlooked aspect in previous research on bearing capacity of reinforced foundations is the prevalent unsaturated properties of soils. This paper provides an analytical framework for evaluating the bearing capacity of strip footings with single-layer and double-layer reinforcement in unsaturated soils. Four classical nonlinear expressions are used to determine the additional cohesion induced by matric suction. Solutions for the reinforcement layer undergoing tensile failure and sliding failure are provided separately. In the former case, where the bearing capacity depends on the reinforcement's tensile strength, the Prandtl mechanism is employed. In the latter case, where the bearing capacity is influenced by the characteristics of the reinforcement-soil interface, a multi-block mechanism is adopted. Additionally, sliding failure exhibits different mechanisms depending on the reinforcement's embedded depth. By comparing the results of different failure mechanisms, accurate upper bound solutions for bearing capacity are obtained. In the case of sliding failure, the optimal reinforcement depths that maximize the bearing capacity are identified for both single-layer and double-layer reinforcement. To facilitate engineering use, the optimum depths and corresponding bearing capacity factors are given in tabular form. The effectiveness of the framework is demonstrated through comparisons with previous theories, experiments, and finite element simulation results.

Existence and stability of boundary spike layer solutions of an attractive chemotaxis model with singular sensitivity and nonlinear consumption rate of chemical stimuli

This paper is devoted to the study of the existence and stability of non-trivial steady state solutions to the following coupled system of PDEs on the half-line R+=(0,∞): ut=uxx−χ[u(lnw)x]x,wt=ɛwxx−uγwm, which is a model of chemotaxis of Keller–Segel type. When u is subject to the no-flux boundary condition, w equals a positive value at the origin, and assuming the functions vanish at the far field, a unique steady state (U,W) is constructed under suitable restrictions on the system parameters, which is capable of describing fundamental phenomena in chemotaxis, such as spatial aggregation. Moreover, the steady state is shown to be nonlinearly asymptotically stable if (u0−U) carries zero mass, w0(x) matches W(x) at the far field, and the initial perturbation is sufficiently small in weighted Sobolev spaces.

Influence of spanwise wall vibration on non-modal perturbations subject to freestream vortical disturbances in hypersonic boundary layers

In this paper, we study the effect of lateral wall vibrations on the excitation and evolution of non-modal perturbations in hypersonic boundary layers subject to low-frequency freestream vortical disturbances (FSVDs). A novel, high-efficiency numerical approach, combining the harmonic weakly nonlinear Navier–Stokes and nonlinear parabolised stability equation approaches, is developed, which is sufficient to accommodate both the rapid distortion of the perturbation in the leading-edge vicinity and the nonlinear development of finite-amplitude high-order harmonics in the downstream region. The boundary-layer response to low-frequency FSVDs shows a longitudinal streaky structure, for which the temperature perturbation shows much greater magnitude than the streamwise velocity perturbation. The lateral vibration induces a Stokes layer solution for the spanwise velocity perturbation, which interacts with the FSVD-induced perturbations and leads to a suppression of the non-modal perturbation and an enhancement of the downstream modal perturbation. The new perturbations excited by the FSVD–vibration interaction strengthen as the vibration intensifies, and they could become comparable with the FSVD-induced perturbations in downstream locations at a high vibration intensity, indicating a remarkable modification of the streaky structure and its instability property. Secondary instability (SI) analyses based on the streaky base flow indicate that the vibration could enhance or suppress the SI modes, depending on their initial phases over the vibration period. Overall, the average effect is that the low-frequency and high-frequency SI modes are stabilised and destabilised by the vibration, respectively. Since the high-frequency SI modes undergo higher amplifications, the subsequent bypass transition is likely to be promoted by relatively strong vibrations.

Spatially averaged, vegetated, oscillatory boundary and shear layers

Oscillatory boundary layers over flat and rippled seabeds are well described in the literature. However, the presence of protruding vegetation stems has received no theoretical or experimental attention. The present work establishes an analytical constant viscosity model akin to the Stokes oscillatory boundary layer solution and a nonlinear varying-viscosity numerical model with a turbulence closure. The two models are used to describe the importance of vegetation and free stream velocity characteristics on spatially averaged oscillatory boundary layers: their friction factors, thickness and phase leads over the free-stream velocity. The models are periodic in time and resolve boundary and shear layers over the vertical, contrary to past efforts applying two-layer models. The models are extended to investigate the importance of finite wavelengths with steady streaming stresses and their associated mean velocity profile. Steady streaming is quantified both for the near-bottom streaming within the canopy and for the streaming in the shear layer above the canopy. Finally, akin to theoretical and experimental works on mean flows over unvegetated and flat seabeds due to oscillatory and nonlinear free-stream velocities, the numerical model investigates varying degree of nonlinearity for velocity- and acceleration-skewed velocity signals, and it is identified that the presence of vegetation stems gives rise to an additional contribution to the horizontal momentum balance which is not present for unvegetated conditions. Finally, it is discussed how the presence of a free surface, contrary to purely oscillatory conditions, alters the horizontal momentum balance within and above the canopy.

Enhancing Indoor Photovoltaic Performance of Inverted Type Organic Solar Cell by Controlling Photoactive Layer Solution Concentration

With the development of various low-power indoor electronic devices, indoor photovoltaics, particularly organic solar cells (OSCs) have attracted a lot of interest in recent years. Increasing the light absorption and suppressing the leakage current are pivotal to improve the indoor photovoltaic performance of OSCs. In this study, the carbon quantum dots (CQDs)-incorporated photoactive layer solution concentration was varied to improve the photovoltaic performance under 1-sun and indoor white LED illumination. The photoactive layer was composed of (6,6)-phenyl-C61-butyric acid methyl ester) (PCBM) as the acceptor and poly(3-hexylthiophene) (P3HT) as the donor. The ZnO electron transport layer was deposited on fluorine-doped tin oxide (FTO)-coated glass substrates using a spin coating technique. The photoactive layers with different solution concentrations were spin coated on top of the ZnO layer. For device completion, silver anode was thermally evaporated. It is interesting to find that the optimum solution concentration obtained under white LED illumination is larger than that under 1-sun illumination. The maximum power conversion efficiency (PCE) of 0.95% was obtained under 1-sun illumination for device with the solution concentration of 36 mg/mL, whereas, under white LED illumination, the highest PCE of 3.59% was obtained for the device with solution concentration of 48 mg/mL.The discrepancy is ascribed to the higher light absorption of thicker photoactive layer and less significant charge recombination loss under weak light intensity. This study highlights the importance of using different optimization strategies to improve the photovoltaic performance of OSCs for outdoor and indoor applications.

Single transition layer in mass-conserving reaction-diffusion systems with bistable nonlinearity

Abstract Mass-conserving reaction-diffusion systems with bistable nonlinearity are useful models for studying cell polarity formation, which is a key process in cell division and differentiation. We rigorously show the existence and stability of stationary solutions with a single internal transition layer in such reaction-diffusion systems under general assumptions by the singular perturbation theory. Moreover, we present a meaningful model for understanding the existence of an unstable transition layer solution; our numerical simulations show that the unstable solution is a separatrix of the dynamics of the model.

GDEMM2024: Global Digital Elevation Merged Model 2024 for surface, bedrock, ice thickness, and land-type masks

Various research topics in geosciences such as gravity modelling, terrain correction and ocean circulation, require high resolution and accuracy global elevations for land topography, bathymetry, and ice thickness that refer to a consistent vertical datum. Unfortunately, most of the existing DEMs do not provide such solutions for Earth relief layers with the same resolution globally. To overcome this deficiency, we merged various DEMs published in the recent years and compiled an up-to-date global solution. We provide 30 arcsecond grid suite for relief layers and land-type masks which have been substantially improved w.r.t. the grids in literature. The quality of the merged surface elevation is assessed against the GNSS heights at about globally distributed 22000 stations. The merged surface model shows a reduction in standard deviation of a factor of three compared to other commonly used DEMs. Other evaluations are performed over land-ice and oceans which supports the advancement of GDEMM2024. The improvements are due to the accuracy and coverage of the original input data, updated land-type masks and merging methodology.

Mobility–Multihoming Duality

In modern Internet-based communication, especially mobile systems, a mobile node (MN) will commonly have more than one possibility for Internet Protocol (IP) connectivity. For example, an MN such as a smartphone may be associated with an IEEE 802.11 network at a site while also connected to a cellular base station for 5G. In such a scenario, the smartphone might only be able to utilise the IEEE 802.11 network, not making use of the cellular connectivity simultaneously. Currently, IP does not allow applications and devices to easily utilise multiple IP connectivity opportunities—multihoming for the MN—without implementing special mechanisms to manage them. We demonstrate how the use of the Identifier Locator Network Protocol (ILNP), realised as an extension to IPv6, can enable mobility with multihoming using a duality mechanism that treats mobility and multihoming as the same logical concept. We present a network layer solution that does not require any modification to transport protocols, can be implemented using existing application programming interfaces (APIs), and can work for any application. We have evaluated our approach using an implementation in Linux and a testbed. The testbed consisted of commercial equipment to demonstrate that our approach can be used over existing network infrastructure requiring only normal unicast routing for IPv6.

The asymptotic solution of the elasticity theory problem for a radially inhomogeneous cylinder

The elasticity theory problem for a radially inhomogeneous cylinder of small thickness, whose elastic moduli are arbitrary continuous functions depending on the radius of the cylinder, is considered. It is assumed that the side surface of the cylinder is stress-free, and the boundary conditions that keep the cylinder in equilibrium are given at its seats. Asymptotic solutions are constructed by the asymptotic integration method. It is shown that the asymptotic solution consists of the sum of the penetrating solution, simple boundary effect and boundary layer solutions. The character of the stress-strain state corresponding to the penetrating solution, simple boundary effect and boundary layer solutions is determined. Asymptotic formulas are obtained for displacements and stresses, which allow to calculate the stress-strain state of a cylinder.The problem of torsion of a radially inhomogeneous cylinder is studied, with its lateral surface free from stress and the boundary conditions keeping it in equilibrium at its seats. By applying the asymptotic integration method, it is determined that the asymptotic solution for the torsion problem consists of the sum of the penetrating solution and boundary layer solutions.Numerical analysis is performed and the effect of material inhomogeneity on the stress-strain state of the cylinder is evaluated.

EHD Instabilities in Two Layers of Insulating and Conducting Immiscible Liquids Subjected to Unipolar Charge Injection

In this paper, the instability of two layers of insulating and conducting immiscible liquids separated by a deformable interface and subjected to unipolar injection is examined. Taking into account the slight deformation of the interface between the two liquids, a system of equations and boundary conditions is derived at marginal state. Non zero numerical solutions for both layers exist only for eigenvalues of the instability parameter T, which depends on the following parameters: injection level C, Bond number Bo, a new non-dimensional parameter P proportional to interfacial tension and the ratio of the layers’ thickness and of liquids viscosity. The variations in the instability criterion Tc, corresponding to the smallest eigenvalue, are examined in detail as a function of the main characteristic parameters C, P and the Bond number. We find that for some values of P, two instability mechanisms convective and interfacial ones can take place. When the strength of interfacial tension or the liquid thickness ratio is very low, the critical number tends to a value corresponding to interfacial instability. The influence of injection-induced convection in the insulating layer and the effect of interfacial deformation on interfacial instability are also discussed.

Trust Computation Model for IoT devices using Soft Computing and Machine Learning Techniques for Health Care Applications

The calculation of trust for online web services is of utmost importance due to the security risks associated with network devices. various cloud platforms offer diverse services for communicating with various IoT devices and generating predictions based on the collected data. Occasionally, data may be compromised by either internal or external groups through low-impact hacking techniques. Investigating assaults and ensuring the elimination of connections can be a laborious task in a sensitive setting. Despite some progress, there are still many unresolved security issues that provide barriers to addressing security problems. This article seeks to conduct a comprehensive examination of existing security solutions for the lowest layer of the Internet of Things (IoT) and promote the development of more inventive IoT designs for those who invest in them. This paper proposes a system for calculating trust in IoT devices using both supervised and unsupervised machine learning algorithms for non-invasive health care applications. Both strategies were assessed based on trust computation weights and compared with their respective machine learning algorithms. The K-means clustering technique is employed for one strategy, while the SVM algorithm is used for the other approach. The aim of this successful implementation is to identify and eradicate a minor threat that occurs during the trusted execution process. An experimental analysis was conducted using NS2 2.35 in combination with an open-source Java platform. At first, a total of 100 nodes are created in the simulation environment. These nodes are then assessed using a clustering method to determine if they are trustworthy or untrustworthy, resulting in the generation of labels. The experimental research demonstrated the superior efficacy of attack detection in comparison to traditional methods of attack detection.

RSTC: Residual Swin Transformer Cascade to approximate Taylor expansion for image denoising

Traditional denoising methods establish mathematical models by employing different priors, which can achieve preferable results but they are usually time-consuming and their outputs are not adaptive on regularization parameters. While the success of end-to-end deep learning denoising strategies depends on a large amount of data and lacks a theoretical interpretability. In order to address the above problems, this paper proposes a novel image denoising method, namely Residual Swin Transformer Cascade (RSTC), based on Taylor expansion. The key procedures of our RSTC are specified as follows: Firstly, we discuss the relationship between image denoising model and Taylor expansion, as well as its adjacent derivative parts. Secondly, we use a lightweight deformable convolutional neural network to estimate the basic layer of Taylor expansion and a residual network where swin transformer block is selected as a backbone for pursuing the solution of the derivative layer. Finally, the results of the two networks contribute to the approximation solution of Taylor expansion. In the experiments, we firstly test and discuss the selection of network parameters to verify its effectiveness. Then, we compare it with existing advanced methods in terms of visualization and quantification, and the results show that our method has a powerful generalization ability and performs better than state-of-the-art denoising methods on performance improvement and structure preservation.

The effect of vertical temperature gradient on the equivalent depth in thin atmospheric layers

AbstractThe equivalent depth of an atmospheric layer is of importance in determining the phase speed of gravity waves and characterizing wave phenomena. The value of the equivalent depth can be obtained from the eigenvalues of the vertical structure equation (the vertical part of the primitive equations) where the mean temperature profile is a coefficient. Both numerical solutions of the vertical structure equation and analytical considerations are employed to calculate the equivalent depth, , as a function of the atmospheric layer's thickness, . Our solutions for layers of thickness 100 2000 m show that for baroclinic modes, can be over two orders of magnitudes smaller than . Analytic expressions are derived for in layers of uniform temperature and numerical solutions are derived for layers in which the temperature changes linearly with height. A comparison between the two cases shows that a slight temperature gradient (of say 0.65 K across a 100 m layer) decreases by a factor of 3 (but can reach a factor of 10 for larger gradients) compared with its value in a layer of uniform temperature, while a change of 10 K in the layer's uniform temperature hardly changes . The baroclinic mode exists in all combinations of boundary conditions top and bottom while the barotropic mode only exists when the vertical velocity vanishes at both boundaries of the layer.

Influence of upwelling mantle magmas on cratonic crust implied from Vp/Vs beneath South America platform

SUMMARY The crust of the South American platform recorded imprints of dynamic processes related with the opening of the Central and South Atlantic but has not been well measured. Crustal structure can be retrieved from teleseismic receiver functions using H–κ stacking, but nearly parallel stripes of high stacking values existing in stacking images for seismic stations in sedimentary area cause difficulties in identifying solutions. We show that some seemingly spurious stripes that do not point to any layer solution are helpful in the identification of the solution position. With the aid of the auxiliary stripes, we retrieved thicknesses and Vp/Vs of sedimentary and crystalline crust for 65 permanent stations of the Brazilian Seismographic Network and six new portable seismic stations in Brazil and Uruguay. The resulted sedimentary thickness and Vp/Vs exhibit a good correlation with the Phanerozoic sediments in the South American basins. The crust of Paraná–Etendeka Large Igneous Province (LIP) had been expected to be more mafic since it had ever been penetrated by mantle magma in the Cretaceous related to the south Atlantic opening. However, we found very low Vp/Vs (1.67) in the crystalline crust beneath the LIP, implying a more felsic crust and that no significant mafic intruding/underplating has occurred in the region. The more felsic crust may be formed in a special evolution early than the magmatic event, or during the magmatic event by releasing crustal volatiles. The resulted sedimentary thickness and Vp/Vs ratios exhibit a good correlation with the Phanerozoic sediments in the South American basins, which implies that Triassic–Jurassic and Cretaceous magmatism did not cause significant metamorphism in sediments formed before the magmatic events.

Energy Efficient AODV routing protocols for FANETs

All system units in flying UAV like transmitter, receiver equipment, control unit, information processing unit and payloads are powered by in build power sources. UAVs equipped with the limited on-board energy capability restrict the flying time, which will significantly affect the performance of a FANETs. Optimizing the energy consumption among nodes is one of the important research challenges. Optimization techniques for energy usage can be implemented at different OSI layer level. In our study we focused on OSI networks layers solution for performance improvements based on energy efficient routing techniques in flying ad hoc network environments. Routing algorithm that is used in MANETs applications can be optimized and used in FANETS as in both networks majority of the operational characteristics similar. But Few characteristics in FANETs like distance coverage, node mobility velocity, capacity and types of power supply used differentiate from other mobiles networks (VANETs,MANETs). During first phase of our work we evaluated the performance of classical routing protocols AODV, DSR, DSDV in FANETs using energy metrics. Result in first phase revel that AODV performance is superior to other protocols in FANETs. In second phase we designed EEAODV protocols which use energy metrics in addition to hop count for path optimization. Finally details performance comparison study between EEAODV and AODV performed, the result shows that EEAODV performance is much better that AODV. For our performance evaluation we used NS-3 simulator and random waypoint mobility models.

Interface strengthening mechanism of TZM/Q235 joint by ultrasonic-assisted electron beam welding with high entropy alloy interlayer

The high-strength joints of TZM/CoCrFeNiMo0.2/Q235 were realized by ultrasonic-assisted electron beam welding. The effects of ultrasonic vibration on the microstructure evolution and mechanical properties of the reaction layers were analyzed. A reaction layer with a thickness of >10 μm was observed at the TZM side region. The reaction layer was characterized by columnar Fe2Mo phases growing perpendicular to the fusion line and FCC solid solutions with different grain orientations. Under the action of ultrasonic vibration, the eutectic structure of Fe2Mo phases and FCC solid solutions was evenly distributed in the reaction layer, and the grain orientation of the FCC solid solutions in the reaction layer changed to be the same as that in the fusion zone. Compared with the joint without ultrasonic vibration, the difference of nanoindentation hardness between the Fe2Mo phases and FCC solid solutions and the residual stress inside the reaction layer of the welding joint with an ultrasonic power of 80 W were significantly reduced. The maximum tensile strength of the joints was 318.4 ± 26 MPa, which was 18.9% higher than that of the joint without ultrasonic vibration.

MXene-based novel nanocomposites doped SnO2 for boosting the performance of perovskite solar cells

Since being first published in 2018, the use of two-dimensional MXene in solar cells has attracted significant interest. This study presents, for the first time, the synthesis of an efficient hybrid electrocatalyst in the form of a nanocomposite (MXene/CoS)-SnO2 designed to function as a high-performance electron transfer layer (ETL). The study can be divided into three distinct parts. The first part involves the synthesis of single-layer Ti3C2Tx MXene nanosheets, followed by the preparation of a CoS solution. Subsequently, in the second part, the fabrication of MXene/CoS heterostructure nanocomposites is carried out, and a comprehensive characterization is conducted to evaluate the physical, structural, and optical properties. In the third part, the attention is on the crucial characterizations of the novel nanocomposite-electron transport layer (ETL) solution, significantly contributing to the evolution of perovskite solar cells. Upon optimising the composition, an exceptional power conversion efficiency of more than 17.69% is attained from 13.81% of the control devices with fill factor (FF), short-circuit current density (Jsc), and open-circuit voltage (Voc) were 66.51%, 20.74 mA/cm2, and 1.282 V. Therefore, this PCE is 21.93% higher than the control device. The groundbreaking MXene/CoS (2 mg mL−1) strategy reported in this research represents a promising and innovative avenue for the realization of highly efficient perovskite solar cells.

Sensitivity of a Process for Heating Thin Metal Film Described by the Dual-Phase Lag Equation with Temperature-Dependent Thermophysical Parameters to Perturbations of Lag Times

In the paper, an equation with two delay times (dual-phase lag Equation (DPLE)) in a version that takes into account the dependence of thermophysical parameters (volumetric specific heat and thermal conductivity) on temperature is considered. In particular, an analysis of the sensitivity of transient temperature field in relation to disturbances in delay times (the relaxation and thermalization times) is performed. The sensitivity model concerns the process of heating an ultrathin metal layer with a laser beam. First, the equation with two delay times in the case of temperature-dependent thermophysical parameters is presented. Next, the sensitivity equations with respect to delay times are derived using the direct method. The algorithms for solving the basic and sensitivity tasks are also briefly presented. At the stage of computations, an authorial program based on the implicit scheme of a finite-difference method is developed. In the final part of the paper, examples of numerical solutions (for layers made from gold and nickel) are presented. The research conducted here shows that disturbances in the temperature field are clearly visible and depend, on the one hand, on the thermophysical parameters of the material, and on the other hand, on the intensity of heating with an external heat source.