Multilayer Solution Research Articles

A multilayer innovative solution to improve the adhesion of nanocrystalline diamond coatings

Nano-crystalline diamond (NCD) films grown under negative biased substrates by chemical vapor deposition (CVD) are widely used as surface overlay coating onto cermet WC-Co cutting tools to get better performances. To improve the diamond adhesion to the cermet substrate, suitable multi-layer systems have been added. They are composed of a cobalt diffusion barrier close to the substrate (single and sequenced nitrides layers) coated with a nucleation extra layer to improve the nucleus density of diamond during CVD processing. For all systems, before and after diamond deposition, transmission electron microscopy (TEM) has been performed for a better understanding of the diffusion phenomena occurring at the interfaces and to evaluate the presence of graphitic species at the interface with the diamond. Innovative multilayer system dedicated to the regulation of cobalt diffusion coated with a bilayer system optimized for the carbon diffusion control, is shown as an efficient solution to significantly reduce the graphite layer formation at the interface with the diamond down to 10nm thick and to increase the adhesion of NCD diamond layer as scratch-tests confirm.

A joint multi-layer planning algorithm for IP over flexible optical networks

We consider the multi-layer network planning problem for IP over flexible optical networks, which consists of three subproblems at two layers: the Routing problem at the IP-layer (IPR), the routing, modulation level (RML), and the spectrum allocation (SA) problems at the optical layer. The input includes the IP end-to-end traffic matrix, the modular model of the IP/MPLS routers, and the feasible transmission configurations of the flexible optical transponders. Demands are served for their requested rates by selecting the IP/MPLS routers modules to be used, the routes in the IP (virtual) topology, and the corresponding paths and spectrum slots in the underlying optical topology, together with the optical transponders' configurations. The proposed algorithm follows a multi-cost approach that solves jointly the IPR, the RML, and the SA problems. It serves demands one-by-one, reusing existing equipment and favoring the deployment of new equipment that could also be reused by subsequent connections, aiming to minimize the total network cost. The problem definition is generic and the proposed algorithm is applicable to both fixed- and flex-grid optical networks. We evaluate the performance gains that can be obtained by the proposed joint multi-layer network planning solution, as opposed to a sequential planning solution that separately plans the IP and optical layers. We also compare a flexible network, using flex-grid optical switches and flexible optical transponders, to a mixed line rate (MLR) network, using fixed-grid or flex-grid optical switches but fixed optical transponders.

A Cluster‐Based Opportunistic Multicast in Multi‐hop Wireless Networks

Multicast has become increasingly important in multi-hop wireless networks for such applications which deliver shared media and data to multiple receivers. However, the existing multicast protocols for wireless network have large control overhead, and cannot adequately take the advantage of broadcast communication mode in multicast structure for sharing the forwarding path. This paper proposes a Cluster-based opportunistic multicast (COM) algorithm, which constructs multicast tree structure based on clusters by utilizing a stability greedy algorithm to achieve the minimum total Cluster-based expected transmission count (CETX). In this multicast tree structure, the edge is created between the kernel sets respectively belonging to two clusters for improving the forwarding efficiency and the stability of this structure. In the process of data distribution, our multi-layer solution combines multicast and opportunistic routing to improve the efficiency of transmission. Simulation results show that COM scheme can achieve the less total number of sending packets, and higher stability than other topology-based solutions and opportunistic multicast.

A multilayer ice-flow model generalising the shallow shelf approximation

AbstractA new hybrid model for the dynamics of glaciers, ice sheets and ice shelves is introduced. In this ‘multilayer’ model the domain of ice consists of a pile of thin layers, which can spread out, contract and slide over each other such that the two most relevant types of stresses are accounted for: membrane and vertical shear. Assuming the horizontal velocity field to be vertically piecewise constant in each layer, the model is derived from local depth integrations of the hydrostatic approximation of the Stokes equations. These integrations give rise to interlayer tractions, which can be redefined at zeroth order in the interlayer surface slope by keeping the vertical shear stress components. Furthermore, if the layers are chosen such that they are aligned with the streamlines, then second-order accurate interlayer tractions can replace zeroth-order ones. The final model consists of a tridiagonal system of two-dimensional nonlinear elliptic equations, the size of this system being equal to the number of layers. When running the model for prognostic flowline ISMIP-HOM benchmark experiments, the multilayer solutions show good agreement with the higher-order solutions if no severe depression occurs in the bedrock. As an alternative to three-dimensional models, the multilayer approach offers to glacier and ice sheet modellers a way of upgrading the commonly used shallow shelf approximation model into a mechanically complete but mathematically two-dimensional model.

The strength of sintered and adhesively bonded zirconia/veneer-ceramic bilayers

ObjectivesRecently all-ceramic restorative systems have been introduced that use CAD/CAM technology to fabricate both the Y-TZP core and veneer-ceramic layers. The aim was to identify whether the CAD/CAM approach resulted in more favourable stressing patterns in the veneer-ceramic when compared with a conventionally sintered Y-TZP core/veneer-ceramic. MethodsNominally identical Vita VM9 veneer-ceramic disc-shaped specimens (0.7mm thickness, 12mm diameter) were fabricated. 20 specimens received a surface coating of resin-cement (Panavia 21); 20 specimens were bonded with the resin-cement to fully sintered Y-TZP (YZ Vita Inceram Vita) discs (0.27mm thickness, 12mm diameter). A final series of 20 Y-TZP core/veneer-ceramic specimens were manufactured using a conventional sintering route. Biaxial flexure strength was determined in a ball-on-ring configuration and stress at the fracture origin calculated using multilayer closed-form analytical solutions. Fractography was undertaken using scanning electron microscopy. The experimental test was simulated using Finite Element Analysis. Group mean BFS were compared using a one-way ANOVA and post hoc Tukey tests at a 95% significance level. ResultsResin cement application resulted in significant strengthening of the veneer-ceramic and further significant strengthening of the veneer-ceramic (p<0.01) occurred following bonding to the Y-TZP core. The BFS calculated at the failure origin for conventionally sintered specimens was significantly reduced when compared with the adhesively bonded Y-TZP/veneer-ceramic. ConclusionsUnder the test conditions employed adhesive cementation between CAD/CAM produced Y-TZP/veneer-ceramic layers appears to offer the potential to induce more favourable stress states within the veneer-ceramic when compared with conventional sintered manufacturing routes. Clinical significanceThe current investigation suggests that the stressing patterns that arise in all-ceramic restorations fabricated using CAD/CAM for both the core and veneer-ceramic layers differ from those that occur in conventionally sintered bilayer restorations. Further work is required to ascertain whether such differences will translate into improved clinical outcomes.

Analytical model of well leakage pressure perturbations in a closed aquifer system

Deep saline aquifers are commonly used for disposal and storage of various surface fluids. The target injection zone must be hydraulically isolated from overlying zones in order to ensure containment of the injected fluids. Improperly plugged nonoperational abandoned wells that penetrate the injection zone are the main potential leakage pathways. Leakage through such wells may cause an observable pressure signal in a zone overlying the injection zone; such a signal can be used to detect the leakage. In this paper we develop an analytical model to evaluate the pressure change induced by leakage through a well in a multilayer system. Unlike previous analytical models on the topic, our model uses a closed system, which may significantly affect the strength and behavior of the pressure signal induced by leakage. The analytical model is first presented for a two-layer system centered at the leaky well location. We evaluate the leakage-induced pressure change using the Laplace transform of Duhamel’s superposition integral, yielding the solution in the Laplace domain. We then derive a late-time asymptotic solution using the final value theorem, which suggests that the leakage rate becomes constant after sufficient time. We then obtain the multilayer solution by extending the two-layer solution and presenting it in matrix form in the Laplace domain. We apply the solution to three examples. In the first example, we apply the analytical model to a two-layer system, investigating its behavior and comparing the results with a numerical solution. In order to demonstrate behavior and potential applications of the multilayer analytical model, we present two multilayer examples: one with identical layers and another, replicating a CO2 storage site, with dissimilar layers. The leakage-induced pressure change does not necessarily decrease as the distance increases from the injection zone toward the surface.

Multidepth Pumping Tests in Deep Aquifers

Multidepth pumping tests (MDPTs), in which different sections of a screen are pumped in sequence, are not being used by hydrogeologists, despite the capability of such tests to resolve uncertainties in the estimation of aquifer characteristics. MDPTs can be used to discern the effects of partial penetration and vertical anisotropy. This article demonstrates the use of MDPTs for a deep and vertically anisotropic aquifer, based on a real and unique series of pumping tests conducted in the Indus Basin. Traditional single-layer methods, which incorporate partial penetration and vertical scaling, were employed to evaluate these tests. However, the drawdowns of the 19 piezometers at different depths for which times series data were available could not be matched, presumably because of the layered structure of the aquifer. Numerical (MODFLOW) and multilayer analytical (Hemker and Maas 1987; Hemker 1999) approaches were used to assess the benefits of using MDPTs in the analysis of deep layered and anisotropic aquifers. The multilayer analytical solution results are consistent with the measured and numerically computed drawdowns. The original step-drawdown data were used to verify the model independently. The results of statistical analyses indicate that the parameters for a three-layer system are uniquely estimated. A sensitivity analysis showed that aquifer depths greater than 900 m do not affect the drawdown. The multilayer analytical solution was implemented in MATLAB and can be found in the online version of this article. This multilayer analytical approach was implemented in MLU by Hemker and Randall (2013) for up to 40 layers. The results of this study will be useful in groundwater management, exploration, and optimal well depth estimation for the Indus Basin aquifer and other vertically heterogeneous aquifers.

Efficient filtering processes for machine-to-machine data based on automation modules and data-agnostic algorithms

Machine-to-machine (M2M) platforms are evolving as large-scale multi-layer solutions that unify the access and the control of all devices that are being equipped with the capability to perform automated tasks and to report data based on connectivity to a backend system. As the integration of more and more devices in such platforms results in the need to handle big M2M data, M2M platforms need to automate their configuration and include appropriate data filtering frameworks and algorithms. Otherwise, the collected raw data can become expensive, unmanageable, and of low quality. This paper presents how data filtering processes can be automated as part of an M2M self-configuration framework and describes a solution that enables the seamless adjustment of domain-specific filtering thresholds in domain-agnostic platforms, based on quality-of-information calculations and M2M-specific data categorisation. An evaluation from the facilities-monitoring domain shows that our approach was the only one to achieve, for example, forwarding less than 25% of the monitored data maintaining at the same time a coverage ratio bigger than 50% for all considered applications. Further, a projection of this evaluation to a Smart City scale indicates that such gains can make database queries up to many seconds faster.

High efficiency solution processed inverted white organic light emitting diodes with a cross-linkable amino-functionalized polyfluorene as a cathode interlayer

Highly efficient inverted white organic light emitting diodes (IWOLEDs) were achieved by a simple solution processing technique, in which cross-linkable amino-functionalized polyfluorene poly[9,9-bis(6′-(N,N-diethylamino)hexyl)-fluorene-alt-9,9-bis(3-ethyl(oxetane-3-ethyoxy)-hexyl)-fluorene] (PFN-OX) served as electron injection/transporting layer (EIL) deposited onto indium tin oxide (ITO) directly without n-type inorganic metal oxides (MOs). The light emitting layer consisted of a (poly(N-vinylcarbazole) (PVK)/1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]phenylene (OXD-7) blend as host and phosphorescent iridium complexes as guests. Our results demonstrated that ITO could serve as cathode and inject electrons into the phosphorescent system directly and efficiently by using PFN-OX as single EIL. As a result, a high performance IWOLED device with Commission Internationale de L'Eclairage (CIE) coordinate of (0.35, 0.45), colour rendering index (CRI) of 70, maximum luminous efficiency (LE) of 18.1 cd A−1 and maximum power efficiency (PE) of 6.6 lm W−1 was achieved. This result provides an easy way of fabricating multilayer solution processed high efficiency IWOLEDs.

Multi-layer optimization with backpressure and genetic algorithms for multi-hop wireless networks

This paper presents an efficient scheme to optimize multiple layers in multi-hop wireless networks with throughput objectives. Considering channel sensing and power control at the physical layer, a non-convex throughput optimization problem is formulated for resource allocation and a genetic algorithm is designed to allow distributed implementation. To address link and network layers, a localized back-pressure algorithm is designed to make routing, scheduling, and frequency band assignments along with physical-layer considerations. Our multi-layer scheme is extended to cognitive radio networks with different user classes and evaluate our analytical solution via simulations. Hardware-in-the-loop emulation test results obtained with real radio transmissions over emulated channels are presented to verify the performance of our distributed multi-layer optimization solution for multi-hop wireless networks. Finally, a security system is considered, where links have their security levels and data flows require certain security levels on each of its links. This problem is addressed by formulating additional constraints to the optimization problem.

Multilayer Control for Packet-Optical Networks [Invited

This paper describes a novel multilayer (ML) path computation element (PCE) architecture based on a hybrid approach. Such a method operates in all network life cycles, optimizing both the design and the operative phases. The hybrid PCE is based on combined non-real-time and real-time operation and is able to integrate control and management functions. This architecture results in a reduction of overprovisioning during network design while guaranteeing availability of traffic by using control-plane-driven dynamic recovery schemes. It introduces advanced control functionality into the network, providing an easy-to-integrate solution. To fully exploit the control plane capabilities, a new architecture of colorless, directionless, and contentionless reconfigurable optical add/drop multiplexers and its related cost model are also presented. The solution has been assessed by simulations on the Spanish backbone network of Telefonica. The simulation analysis demonstrates the good performance of the proposed ML solution. The reduction of overprovisioning allows a capital expenditure saving of up to 46% with respect to a single-layer approach without any effect on the level of survivability of the traffic, thanks to new ML recovery schemes.

An equivalent solution for the electromagnetic scattering of multilayer particle

This paper reports on a new solution to the scattering properties of a small multilayer particle. The procedure is based on a prescription which uses the equivalent dielectric constant to represent the integrated permittivity of the multilayer particle, and then directly get the particle's scattering properties with the classical Mie code. By means of comparisons of the proposed method and the multilayer Mie solutions, it is evident that the model presented in this paper is accurate and more simple.

Study of the one dimensional and transient bioheat transfer equation: Multi-layer solution development and applications

In this work we derive an analytical solution given by Bessel series to the transient and one-dimensional (1D) bioheat transfer equation in a multi-layer region with spatially dependent heat sources. Each region represents an independent biological tissue characterized by temperature-invariant physiological parameters and a linearly temperature dependent metabolic heat generation. Moreover, 1D Cartesian, cylindrical or spherical coordinates are used to define the geometry and temperature boundary conditions of first, second and third kinds are assumed at the inner and outer surfaces. We present two examples of clinical applications for the developed solution. In the first one, we investigate two different heat source terms to simulate the heating in a tumor and its surrounding tissue, induced during a magnetic fluid hyperthermia technique used for cancer treatment. To obtain an accurate analytical solution, we determine the error associated with the truncated Bessel series that defines the transient solution. In the second application, we explore the potential of this model to study the effect of different environmental conditions in a multi-layered human head model (brain, bone and scalp). The convective heat transfer effect of a large blood vessel located inside the brain is also investigated. The results are further compared with a numerical solution obtained by the Finite Element Method and computed with COMSOL Multiphysics v4.1©.

Asymptotical construction of a Reissner-like model for multilayer functionally graded magneto-electro-elastic plates

A magneto-electro-elastic Reissner–Mindlin model is developed for heterogeneous multilayer laminates made of functionally graded magneto-electro-elastic material using the variational asymptotical method. This model is applicable to laminates without prescribed electric and magnetic potential though the thickness. Taking advantage of the smallness of the plate thickness, we asymptotically decouple the original 3D magneto-electro-elastic problem into a 1D through-the-thickness analysis and a 2D plate analysis, and both are fully-coupled magneto-electro-elastic analyses. Interface continuity conditions are explicitly derived and solved to obtain the multilayer solutions. Various examples have been used to demonstrate the accuracy and application of this model.

Hyperbolic vortices with large magnetic flux

There has been some recent interest in the study of non-abelian BPS monopoles in the limit of large magnetic charge. Most investigations have used a magnetic bag approximation, in which spherical symmetry is assumed within an abelian description. In particular, this approach has been used to suggest the existence of two types of magnetic bag, with differing distributions of the zeros of the Higgs field, together with multi-layer structures, containing several magnetic bags. This paper is concerned with the analogous situation of abelian BPS vortices in the hyperbolic plane, in the limit of large magnetic flux. This system has the advantage that explicit exact solutions can be obtained and compared with a magnetic bag approximation. Exact BPS vortex solutions are presented that are analogous to the two types of magnetic bags predicted for BPS monopoles and it is shown that these structures can be combined to produce exact multi-layer solutions.

Thin smart multilayer microwave absorber based on hybrid structure of polymer and carbon nanotubes

We present a thin and flexible multilayer solution for effective absorption of electromagnetic waves from 8 to 40 GHz and probably higher. Submillimetric conductive and dielectric layers based on polymer and carbon nanotubes are successively stacked. A smart gradient-periodic arrangement results in a very high absorption index despite overall millimetric thickness of the system.

Partial-mixed special finite element for the analysis of multilayer composites and FGM

A partial-mixed special finite element (FE) is proposed for the static analysis of multilayer composite and functionally graded material plates. Using the Hamiltonian formalism, the three-dimensional elasticity equations are first reformulated so that a partial-mixed variational formulation, retaining as primary variables the translational displacements augmented with the transverse stresses only, is obtained; this allows, in particular, a straightforward fulfilment of the multilayer interfaces continuity conditions. After an only in-plane FE discretisation, the static problem is then reduced, for a single layer, to a Hamiltonian eigenvalue problem that is solved analytically, through the layer thickness, using the symplectic formalism; the multilayer solution is finally reached via the state-space method and the propagator matrix concept. The performance, in convergence and accuracy, of the proposed approach, applied to representative examples, is shown to be very satisfactory.

Hamiltonian partial mixed finite element-state space symplectic semi-analytical approach for the piezoelectric smart composites and FGM analysis

A partial mixed finite element (FE)–state space method (SSM) semi-analytical approach is presented for the static analysis of piezoelectric smart laminate composite and functionally graded material (FGM) plates. Hence, using the Hamiltonian formalism, the three-dimensional piezoelectricity equations are first worked so that a partial mixed variational formulation, which retains the translational displacements, electric potential, transverse stresses, and transverse electric displacement as primary variables, is obtained; this allows, in particular, straightforward fulfillment of the electromechanical continuity constraints at the laminate interfaces. After an in-plane FE discretization only, the problem is first reduced, for a single layer, to a Hamiltonian eigenvalue problem that is solved using the symplectic approach; then, the multilayer solution is reached via the SSM propagator matrix. The proposed methodology is finally applied to the static analysis of piezoelectric-cross-ply hybrid laminated composite and FGM plates. In a comparison with open literature, available tabulated results show good agreements, thus validating the proposed approach.

Inverse kinematics of a 6 DoF human upper limb using ANFIS and ANN for anticipatory actuation in ADL-based physical Neurorehabilitation

ObjectiveThis research is focused in the creation and validation of a solution to the inverse kinematics problem for a 6 degrees of freedom human upper limb. This system is intended to work within a real-time dysfunctional motion prediction system that allows anticipatory actuation in physical Neurorehabilitation under the assisted-as-needed paradigm. For this purpose, a multilayer perceptron-based and an ANFIS-based solution to the inverse kinematics problem are evaluated. Materials and methodsBoth the multilayer perceptron-based and the ANFIS-based inverse kinematics methods have been trained with three-dimensional Cartesian positions corresponding to the end-effector of healthy human upper limbs that execute two different activities of the daily life: ‘serving water from a jar’ and ‘picking up a bottle’. Validation of the proposed methodologies has been performed by a 10 fold cross-validation procedure. ResultsOnce trained, the systems are able to map 3D positions of the end-effector to the corresponding healthy biomechanical configurations. A high mean correlation coefficient and a low root mean squared error have been found for both the multilayer perceptron and ANFIS-based methods. ConclusionsThe obtained results indicate that both systems effectively solve the inverse kinematics problem, but, due to its low computational load, crucial in real-time applications, along with its high performance, a multilayer perceptron-based solution, consisting in 3 input neurons, 1 hidden layer with 3 neurons and 6 output neurons has been considered the most appropriated for the target application.

Partial-mixed special finite element for the analysis of multilayer composites and FGM

A partial-mixed special finite element (FE) is proposed for the static analysis of multilayer composite and functionally graded material plates. Using the Hamiltonian formalism, the three-dimensional elasticity equations are first reformulated so that a partial-mixed variational formulation, retaining as primary variables the translational displacements augmented with the transverse stresses only, is obtained; this allows, in particular, a straightforward fulfilment of the multilayer interfaces continuity conditions. After an only in-plane FE discretisation, the static problem is then reduced, for a single layer, to a Hamiltonian eigenvalue problem that is solved analytically, through the layer thickness, using the symplectic formalism; the multilayer solution is finally reached via the state-space method and the propagator matrix concept. The performance, in convergence and accuracy, of the proposed approach, applied to representative examples, is shown to be very satisfactory.