Dissimilar Layers Research Articles

An Efficient Monitoring of Real Time Traffic Clearance for an Emergency Service Vehicle Using IOT

In this paper, a real time emergency vehicle tracking through architecture of instinctive emergency recognition system with high-intensity digital camera it is located in a national high way traffic signal. In a recent survey, there are thousands of people losing their lives due to the delay in the emergency services. Resent survey say that more than 4000 heart attack victims can be saved each year if the delay could be minimized and in the present scenario the number of deaths is in lakhs and this number can be effectively reduced by providing timely and accurate emergency service all the way through avoiding the unnecessary time delay near traffic jams during an emergency situation (Tagne et al. in IEEE Trans Intell Transp Syst 17(3):796–809, 2015). This method clarifies the modeling and working of different units of the emergency vehicle identification system such that optimized emergency vehicle tracking algorithm, with the traffic supervision unit. In this article confer the basic components and their function such that internet of things and their dissimilar layers of protocol, raspberry pi and its architecture, with interfacing sensors such as Siren sound detect (REES-52), the Wireless sensor (NRF905se). It is direct and the most efficient route that is asphalt construct to the central server checks for the location of the vehicle and change the traffic signal. When the emergency vehicle is approaching the traffic lights. The system generate in sequence regarding the traffic emergency situations such as ambulance and siren sound (Emergency Services Review: A comparative review of international ambulance service best practice. http://www.aace.org.uk. Accessed 28 July 2017, 2017). The processed information can be used to divert the live traffic as desirable to avoid the problems related to real time road traffic (Sundar et al. in Sens J IEEE 15(2):1109–1113, 2015).

Transient response of dissimilar piezoelectric layers with multiple interacting interface cracks

In this study, we examine the dynamic behavior of two bonded dissimilar piezoelectric layers containing multiple interfacial cracks subjected to electro-mechanical impact loading. The problem was formulated through Fourier transformation into singular integral equations in which the unknown variables are the jumps of displacement and electric potential across the crack surface in the Laplace transform domain. The resulting integral equations together with the corresponding single-valued conditions are solved numerically for the densities of electro-elastic dislocations on a crack surface. The dynamic field intensity factors and dynamic energy release rate (DERR) history are obtained for both permeable and impermeable crack. The stress field is also obtained for the interface crack under impact loads. The results show that the field intensity factors at the crack tips and dynamic energy release rate depend on the interfacial crack geometry, electromechanical coupling and the electric boundary conditions on the crack surface.

Above 14% efficiency earth-abundant selenium solar cells by introducing gold nanoparticles and Titanium sub-layer

In this paper, a new Selenium (Se) solar cell design based on inserting dissimilar ultrathin metallic layers (MLs), (Au and Ti), is proposed. Analytical models of the proposed design are developed, where the analytical results are in agreement with the experimental data. In addition, the role of the introduced ultrathin MLs in enhancing the light-scattering in the Se solar cell structure is also demonstrated. Moreover, the impact of the Mg mole fraction of the ZnMgO buffer layer on the device performance is investigated. It is revealed that the proposed structure give rise to optical micro-cavity effects which leads to improve the absorbance and reduce the reflection. Genetic Algorithm (GA) technique is used to boost up the solar cell efficiency by selecting both the appropriate position of the ultrathin MLs and the suitable Mg mole fraction of the ZnMgO layer. It is concluded that the optimized design with Ti MLs pinpoint a new path toward achieving superior power efficiency of 13.2%, where improved Isc of 21 mA/cm2 and enhanced Voc of 1 V are recorded. Moreover, the impact of the metallic nanoparticles (MNPs) introduced in the ZnMgO buffer layer on the device performance is also investigated, where an improved power efficiency value of 14.7% is recorded. This makes the optimized designs potential alternative top cells for developing high-efficiency tandem photovoltaic devices at a reasonable cost.

Heterointerface effects in the electrointercalation of van der Waals heterostructures.

Molecular-scale manipulation of electronic and ionic charge accumulation in materials is the backbone of electrochemical energy storage1-4. Layered van der Waals (vdW) crystals are a diverse family of materials into which mobile ions can electrochemically intercalate into the interlamellar gaps of the host atomic lattice5,6. The structural diversity of such materials enables the interfacial properties of composites to be optimized to improve ion intercalation for energy storage and electronic devices7-12. However, the ability of heterolayers to modify intercalation reactions, and their role at the atomic level, are yet to be elucidated. Here we demonstrate the electrointercalation of lithium at the level of individual atomic interfaces of dissimilar vdW layers. Electrochemical devices based on vdW heterostructures 13 of stacked hexagonal boron nitride, graphene and molybdenum dichalcogenide (MoX2; X = S, Se) layers are constructed. We use transmission electron microscopy, in situ magnetoresistance and optical spectroscopy techniques, as well as low-temperature quantum magneto-oscillation measurements and ab initio calculations, to resolve the intermediate stages of lithium intercalation at heterointerfaces. The formation of vdW heterointerfaces between graphene and MoX2 results in a more than tenfold greater accumulation of charge in MoX2 when compared to MoX2/MoX2 homointerfaces, while enforcing a more negative intercalation potential than that of bulk MoX2 by at least 0.5 V. Beyond energy storage, our combined experimental and computational methodology for manipulating and characterizing the electrochemical behaviour of layered systems opens new pathways to control the charge density in two-dimensional electronic and optoelectronic devices.

Effect of lattice stacking orientation and local thickness variation on the mechanical behavior of few layer graphene oxide

Investigation of few layer 2D materials is fundamentally important to bridge the gap between monolayer and bulk properties, and practically meaningful for applications as reinforcement nanofillers and layered electronic devices. Few layer introduces differences from intrinsic properties of monolayers due to the complexity of structural heterogeneities, such as lattice stacking orientation and local thickness variation. In this work, few layer graphene oxide (GO) with different structural heterogeneities were studied using atomic force microscopy-based deflection measurements and transmission electron microscopy (TEM). Direct TEM evidence of fracture surfaces and molecular dynamics (MD) simulations revealed decoupled and dissimilar layer crack patterns for misaligned bilayer. In contrast, aligned bilayer GO generally fractured with a larger portion of common cracks shared by both layers, indicating stronger interlayer interaction. MD results also revealed insignificant effect of lattice alignment on the strength and toughness of GO bilayers. Scaling up even to ∼5 layers and above revealed significant local thickness heterogeneity and consequently a ∼60% reduction of the normalized fracture force and toughness. MD simulations on partially intercalated few layer GO revealed anisotropic and heterogeneous stress distributions, as well as stress concentration near the inner edges, which may account for the significant reduction of strength and toughness.

Finite element investigation on mode I crack tip characteristics in residually stressed glare

PurposeBehavior of mode I crack tip in fiber metal laminate (FML) differs from that in homogeneous or plain specimen made of metal used in the laminate due to the load transfer effect in the laminate caused by property mismatch between dissimilar material layers. The purpose of this paper is to present a finite element investigation on the characteristics of crack tip in monotonically loaded and residually stressed FML.Design/methodology/approachCrack tip characteristics are assessed by: the sizes of various zones that form at the tip; and crack tip energy release rates. The same are found by modeling two types of Glare laminates under monotonic tension with different crack orientations in SSY regime – Type I and Type II. Residual stresses are externally introduced in the models. Delaminations are modeled by cohesive elements. Crack tip zone sizes are measured from finite element solutions. Values of J integrals are computed over cyclic paths near the crack tips. Identically cracked and loaded plain aluminum alloy specimens are also modeled for comparison.FindingsThe sizes of crack tip zones in Glare laminates are found to be different than those in plain specimens. Process zone is observed to form at crack tip in Type I laminate whereas it does not develop in Type II laminate, the reverse being true in plain specimens. Values of J integrals near crack tips are also found to deviate from those in plain specimens, higher in Type I laminate due to crack tip stress amplification and lower in Type II laminate due to stress reduction. Crack orientation decides the amplification or shielding effect in the laminate.Research limitations/implicationsThere is scope for validating the numerical results reported in the paper by theoretical models.Practical implicationsThe method to quantify crack tip shielding and amplification is presented that shall be useful in checking the structural integrity/safety of the laminate during actual service conditions.Originality/valueShielding and amplification effects are explicitly described and illustrated in the paper. Suitability of using J integrals over paths crossing non-homogeneous and property mismatched material layers is tested. Use of cohesive zone method that is readily applicable in finite element procedures and is relatively simple, fast and reasonably accurate is also demonstrated.

Material Selection for Interfacial Bond Layer in Electronic Packaging

In electronic packaging, typically two or more thin dissimilar plates or layers are bonded together by an extremely thin adhesive bond layer. Electronic assemblies are usually operated under high power conditions which predictably produces a high temperature environment in the electronic devices. Therefore, thermal mismatch shear and peeling stress inevitably arise at the interfaces of the bonded dissimilar materials due to differences in Coefficient of Thermal Expansion (CTE) typically during the high temperature change in the bond process. As a result, delamination failure may occur during manufacturing, machining, and field use. As such, these thermo-mechanical stresses play a very significant role in the design and reliability of the electronic packaging assembly. Consequently, critical investigations of interfacial stresses under variable load conditions in composite structure can result in a better design of electronic packaging with higher reliability and minimize or eliminate the risk of functional failure. In order to formulize bond material selection, analytical studies are carried out in order to study the influence of bond layer parameters on interfacial thermal stresses of a given package. These parameters include Coefficient of thermal expansion (CTE), poison’s ratio, temperature, thickness, and stiffness (compliant and stiff) of the bond layer. From the study, stiffness and bond layer thickness are identified as the key parameters influencing interfacial shearing and peeling stresses. The other parameters namely CTE, poisons ratio has shown insignificant influence on interfacial stresses due to the very thin section of bond layer compared to the top and bottom layers. The results also show that the interfacial stresses increases proportionally with the increase of temperature in the layers. Therefore, it is very important that the temperature is maintained as low as possible during the chip manufacturing and operating stages. Since only two parameters namely stiffness and bond layer thickness are identified as the key parameters, the interface thermal mismatch stresses can be reduced or eliminated by controlling these two parameters only. Therefore the identification of suitable bond layer parameters selection with reasonable accuracy is possible even without performing optimization process. Finally, this paper proposes a Metal Matrix Composite (MMC) bond material selection approach using rule of mixture material design. The outcome of this research can be seen in the forms of practical and beneficial tools for interfacial stress evaluation and physical design and fabrication of layered assemblies. The Engineers can utilize this research outcome in conjunction with guidelines for electronic packaging under variable thermal properties of layered composites.

Transient fracture of a piezoelectric-piezomagnetic sandwich structure: anti-plane case

In this article, we investigate the transient fracture behavior of piezoelectric (PE)–piezomagnetic (PM) sandwich structures under combined anti-plane shear mechanical and in-plane electrical impacts. A PM layer with an eccentric crack is sandwiched between two dissimilar PE layers. The Laplace and Fourier transforms are employed to reduce the mixed boundary valued problem to a standard Cauchy singular integral equation of the first kind in the Laplace transform domain. Then the Cauchy singular integral equation is solved by the Gauss–Chebyshev collocation method. By utilizing the numerical Laplace inversion, the dynamic stress intensity factors (DSIFs) are obtained in the time domain. Numerical results are presented to show the effects of the material combinations, crack location, structure geometries and electromechanical coupled loads on DSIFs. The findings of the present paper may be useful for the design and fracture prediction of layered PE–PM structures.

Graphdiyne-WS2 2D-Nanohybrid electrocatalysts for high-performance hydrogen evolution reaction

Layered two-dimension (2D) materials have attracted substantial interest as alternative catalysts for hydrogen evolution reaction (HER). However, there exists a significant challenge in that is the only limited density of active sites concentrated at the layer edges. Herein, for the first time, graphdiyne (GD), a new generation of 2D carbon allotrope developed from the graphene family, is found to be an effective stabilizer and also a reducing agent when it is used to form a layered 2D-nanohybrid (GD-WS2 2D-NH) with WS2 owing to its highly conjugated electronic structure and low reduction potential. Further study shows that the layered GD-WS2 2D-NH synthesized with abundant active edges. Such defect-rich structure with large surface area renders ultrahigh catalytic activity and durability for HER in acidic media. Furthermore, owing to the built-in electric field formed among dissimilar layers (GD and WS2), the enhanced charge transfer leads to high activity of the basal plane sites that were inactive for the HER. As a result, the GD-WS2 2D-NH catalyst presents a reduced HER onset potential as small as 140 mV and a superior Tafel slope as low as 54 mV per decade, making the GD-WS2 2D-NH a promising stable catalyst for the HER reaction.

Thermomechanical Extended Layerwise Method for laminated composite plates with multiple delaminations and transverse cracks

A Thermomechanical Extended Layerwise Method (TELM) is developed for the laminated composite plates with multiple delaminations and transverse cracks. The discontinuity of displacements and temperature induced by multiple delaminations is simulated by strong discontinuous function while the discontinuity of strain and temperature gradient between dissimilar layers is modeled by a weak discontinuous function. Transverse cracks are modeled using classical Extended Finite Element Method (XFEM). The coupled thermomechanical variational principle is employed to derive the Euler equations and the discrete forms. Since the displacement and temperature fields are solved simultaneously, a fully coupled time integration method is developed based on the Newmark integration algorithm and Crank-Nicolson scheme. The strain energy release rate for multiple delamination fronts and stress intensity factors for transverse cracks are calculated by the Virtual Crack Closure Technique and the Interaction Integral Method, respectively. The proposed method is applied to the steady-state thermomechanical problems, elastic and thermomechanical dynamic problems for isotropic and composite plates with transverse cracks and multiple delaminations.

Interaction of Three Interfacial Cracks between an Orthotropic Half-Plane Bonded to a Dissimilar Orthotropic Layer with Punch

Abstract This article deals with the interactions between a central crack and a pair of outer cracks situated at the interface of an orthotropic elastic half-plane bonded to a dissimilar orthotropic layer with a punch. The problem is reduced to the solution of three simultaneous singular integral equations that are finally solved using Jacobi polynomials. The phenomena of crack shielding and crack amplification have been depicted through graphs for different particular cases.

Anti-plane interface cracks between two dissimilar orthotropic layers

The problem of an anti-plane crack situated in the interface between two bonded dissimilar orthotropic layers is considered. Fourier transforms are used to reduce the problem to a system of singular integral equations with simple Cauchy kernel. The integral equations are solved numerically by converting to a system of linear algebraic equations and by using a collocation technique. The equations are solved for various crack length, material combinations, and external loads. The numerical results given in the paper include the stress intensity factors of several interfacial cracks

The Influence of Structural Parameter on the Properties of PCF

By analyzing the structure and properties of photonic crystal fiber (PCF), a method for calculating cladding-effective-index was proposed. Then, the influence of changing the diameters of fiber core and cladding air holes and the interval of cladding air holes on the single mode property, dispersion, attenuation characteristics and nonlinearity was analyzed. Single mode transmission was able to be achieved based on the designed PCF in large band width. Anomalous dispersion and the movement of zero dispersion point to the direction of short wavelength were both realized within short wavelength range. Furthermore, the changes of structure parameters in dissimilar layers led to different changes of the properties of PCF.

Manufacturing of Al–Al2O3–Mg multilayered nanocomposites by accumulative roll bonding process and study of its microstructure, tensile, and bending properties

Accumulative roll bonding is used for producing multilayered composites, with exciting mechanical properties, via the creation of bonding between dissimilar metallic layers. In this study for the first time, Al–Mg multilayered composites reinforced with nano-Al2O3 particles were produced by the accumulative roll bonding process at different temperatures. However, there was a problem regarding the adhesion of the nanoceramic particles with each other and with the sheet metals. To avoid these disadvantageous effects of the Al2O3 particle addition and to create better adhesion at interfaces, Al and different percentages of Al2O3 powders were ball milled and Al/Al2O3 composite powders were produced. Afterward, the composite powder was added between Al and Mg sheets and they were rolled to 50% reduction in thickness in each cycle. The process was continued up to four cycles at different temperatures. The microstructural evaluation and mechanical properties of aluminum/nanoalumina/magnesium composites showed that 300℃ is suitable temperature for accumulative roll bonding of Al and Mg sheets with nano-Al2O3 particles. Accumulative roll bonded composites with Al/5 wt% Al2O3 composite powder showed higher tensile strength while the maximum bending strength was related to the composites containing Al/10 wt% Al2O3. Fracture surfaces of the nanocomposites revealed a brittle fracture at higher cycles.

Finite Element Analysis of Plastic Instability Phenomenon in Cold Rolling of Clad Sheets

Clad sheets with stacked dissimilar metal layers are used in various industries. Layers often deform non-uniformly during cold rolling in manufacturing processes. Criteria for onset of this plastic instability has not been fully understood. In this study, one-pass cold rolling of three-layered sheet having hard inner layer and soft outer layers has been analyzed by the elastic-plastic finite element method. As a result, periodical necking of the inner layer is reproduced successfully. It is found that higher difference in flow stresses between layers and lower work hardening result in the periodical necking.

Elimination of pores in Ag–Sn TLP bonds by the introduction of dissimilar intermetallic phases

Low-temperature transient liquid phase (TLP) bonding is a very promising technology for achieving die attachment in high-temperature power devices. However, the Ag–Sn TLP-bonded joint has high sensitivity to shrinkage pores, which will lead to the deterioration of mechanical, thermal, and electrical properties. In this study, we have proposed two novel methods to solve the problem of pores in Ag–Sn TLP bonding through the introduction of second phases. The first method is replacing Ag substrate on one side with Cu substrate to create dual layers of dissimilar intermetallic compounds (IMCs). Consequently, the dual layers of Cu6Sn5 (or Cu3Sn) and Ag3Sn IMCs emerge on the cross-sections of bonded joint, resulting in the effective elimination of pores, which can be attributed to the change of the microstructure and the interface migration between two dissimilar IMC layers (e.g., Cu6Sn5/Ag3Sn). The second method is coating a thin Cu film on the Ag substrate to introduce Cu–Sn IMC particles. As a result, a great number of Cu6Sn5 particles disperse in the middle of the Ag3Sn layer, filling the micropores efficiently, such that a significant decrease in shrinkage pores is achieved. Both methods have been experimentally verified to improve the mechanical properties, and they have high potential to be implemented in other TLP systems.

MgO/Cu2O Superlattices: Growth of Epitaxial Two-Dimensional Nanostructures

Alternated stacking of dissimilar layers can produce novel superlattice materials with multiple functionalities. The majority of such work reported in literature on epitaxial superlattices has been on alternating layers with the same space group (SG) and crystal structure (CS), whereas superlattices with the same CS but different SG have not been studied as much. We have grown superlattices with two well-known oxide materials, viz. cuprite (Cu2O, CS = cubic and SG = Pn $$ \bar{3} $$ m) and magnesium oxide (MgO, CS = cubic, SG = Fm $$ \bar{3} $$ m). An MgO buffer layer grown near 650°C at the film–substrate interface was found to be essential to achieving reasonable long-range atomic order. Grazing-angle x-ray diffraction, x-ray reflectivity, and electron diffraction analyses as well as transmission electron microscopy were used to investigate the interface abruptness, smoothness, and general crystallinity of the individual layers. Interdiffusion between MgO and Cu2O near interfacial regions places a limit of 250°C on the growth temperature for fabrication of superlattices with reasonably sharp interfaces.

Role of metal layer in improving the UV-photodetector performance of TiO2/Metal/TiO2/Si structure

In this paper, a new metallic thin film engineering aspect is proposed to achieve superior absorption for TiO2/Metal/TiO2 on Silicon substrate UV-based photodetectors (PDs). The overall device optical performance comparison with three dissimilar metallic layers (Au, Ti, and Ag) is performed numerically using accurate solutions of Maxwell׳s equations. A comprehensive study of the device optical parameters such as the integral absorption, reflection, and rejection ratio is carried out, in order to reveal the device optical performance for UV optical interconnects and environment monitoring applications. We find that the optical performance are considerably improved as compared to the conventional design, where the proposed design offers superior integral absorption and lower total reflection with an acceptable rejection ratio in comparison with those provided by the conventional one. These improvements suggest the opportunity for optimizing the proposed design using particle swarm optimization (PSO) approach for achieving higher optical performance, where excellent capability is recorded in enhancing the device optical behavior. The obtained results make the proposed device very efficient for compatible CMOS modern technology.

Effect of Poisson’s ratio mismatch on brittle interfacial cracking between two dissimilar elastic layers

Previous work by the authors (Harvey et al., 2015) on brittle interfacial cracking between two dissimilar elastic layers is extended to accommodate Poisson’s ratio mismatch in addition to the existing capability for elastic modulus mismatch. Under crack tip bending moments and axial forces, it is now possible to use a completely analytical 2D elasticity-based theory to calculate the complex stress intensity factor (SIF) and the crack extension size-dependent energy release rates (ERRs). To achieve this, it is noted that for a given geometry and loading condition, the total ERR and bimaterial mismatch coefficient are the two main factors affecting the partitions of ERR. Based on this, equivalent material properties are derived for each layer, namely, an equivalent elastic modulus and an equivalent Poisson’s ratio, such that both the total ERR and the bimaterial mismatch coefficient are maintained in an alternative equivalent case. Cases for which no analytical solution for the SIFs and ERRs currently exist can therefore be ‘transformed’ into cases for which the analytical solution does exist. The approach is verified against results from 2D finite element method simulations in which excellent agreement is observed for cases of plane stress and plane strain with a variety of loading conditions.

Omnidirectional broadband THz filter based on a one-dimensional Thue–Morse quasiperiodic structure containing graphene nanolayers

The transmission properties of a one-dimensional graphene-based Thue–Morse quasiperiodic structure in which graphene nanolayers are embedded between dissimilar adjacent dielectric layers have been investigated. From the numerical results performed by transfer matrix method, it is found that the structure possesses an omnidirectional photonic bandgap called a graphene-induced photonic bandgap (GIPBG) due to the existence of the graphene nanolayers, in addition to the structural Bragg gaps. To design an omnidirectional broadband THz filter, the effects of many parameters such as the scale length and relative permittivity of the layers on the properties of GIPBG are discussed. Our findings show that the frequency range of the omnidirectional GIPBG increases as the scaling decreases. In contrast to Bragg gaps, the width of such an omnidirectional bandgap is notably enhanced by reducing the contrast of the layers’ permittivity and reaches a maximum value when the constituent layers have the same relative permittivity. Our investigations also reveal that in the case of a uniform material, the lowest permittivity of the dielectric material would result in the widest omnidirectional GIPBG. Moreover, the possibility of external control of the omnidirectional bandwidth using a gate voltage is shown. Finally, the application of the structure as a polarizing beam splitter has been shown.