Use Of Multilayer Structures Research Articles

Discriminative feature selection using signed Laplacian restricted Boltzmann machine for speed and generalization improvement of high dimensional data classification

Deep classifiers require lots of computations due to the use of multi-layer structure and processing of bulk input samples. Selecting effective features that have the same accuracy as full features, has recently been considered. Using feature selection, less calculation is needed to update the weights and consequently the speed of the training/testing process is increased. In this research, a new deep feature selection method called Discriminative Deep Feature Selection using Signed Laplacian Restricted Boltzmann Machine (DDFS-SLRBM) is proposed. In the approach, full training samples are fed into a SLRBM model. In the updates, the weight matrix is recomputed using the neighborhood matrix of similar and dissimilar classes which results in the discriminative property of the approach. Then, selected features are identified based on the minimum reconstruction error criterion. The efficiency of the proposed algorithm is demonstrated by performing different experiments on MNIST, GISETTE and Protein datasets. The experiments show that the proposed method is able to improve the classification accuracy and the generalizability of the approach while reducing the processing time. Also, the proposed approach shows scalability on the type of the problem, number of original features, number of samples and the number of final selected features.

An Optimization Framework for the Design of High-Speed PCB VIAs

Signal integrity represents a key issue in all modern electronic systems, which are strongly dominated by the extreme component density usually employed on PCBs and the associated increase in the interconnection density. The use of multi-layer structures with microstrips connected by various types of Vertical Interconnect Accesses (VIAs) calls for design strategies that reduce the impedance mismatch and signal attenuation. The paper proposes a thorough analysis of the effects associated with the VIA geometry and presents a parametric evaluation of them. The obtained results represent the starting point for a possible design procedure that manages the geometric aspects of differential VIAs, aiming to optimize their electrical performance while reducing their occupation of PCB area. The optimization technique considers a differential VIA as a four-port circuit whose characteristics are evaluated with suitable Figures of Merit (FoMs), thus striving for an optimal design obtained with closed-loop iterations. The analysis is performed in both the time (TDR: Time-Domain Reflectometry) and frequency domains (S and Z parameters), thus allowing a dramatic reduction in the number of cases to be analyzed. The procedure is thoroughly described and validated using simulation results.

Two-layer logic elements for classic cryogenic computers

In this paper, for the first time, two-layer logic elements "NOT", "AND", "OR" and "NOR" were manufactured, in which the heating element of a nanowire in one layer is located in the place where the heated element of another superconductive nanowire is located in a nearest NbN layer. The film thickness of NbN (5-7 nm) was used to form of superconducting nanowires in different layers, and the thickness of Al2O3 (25 nm) was used as an interlayer dielectric. The paper shows the design of logic elements, and also demonstrates their operation in pulse mode. The use of multilayer structures without galvanic coupling between nanowires allows the design of multi-level logic devices. Keywords: NbN thin superconducting films, contactless switching of the superconductor state, cryoelectronic devices, integrated cryogenic resistors, logic elements "NOT"/"AND"/"OR"/"NOR", cryogenic computers.

Emission enhancement and color modulation of Tm(Ho)/Yb codoped Gd2(MoO4)3 thin films via the use of multilayered structure

The multilayered structure thin films (Gd2(MoO4)3:Ho(Tm)/Yb@Gd2(MoO4)3:Yb)) were prepared through sol–gel and spin-coating method, while the average thinness was nearly 140 nm. We investigated the up-conversion luminescence of Gd2(MoO4)3:Ho(Tm)/Yb@Gd2(MoO4)3:Yb thin films. The results show that the double-layer structured thin films are able to increase the emission intensity. The fluorescence enhancement factors of the luminescence from Gd2(MoO4)3:Ho/Yb@Gd2(MoO4)3:Yb thin films, located at 540 and 662 nm, reach 7.5 and 4.3, respectively. And the enhancement factors of emissions located at 450, 475 and 650 nm (Gd2(MoO4)3:Tm/Yb@Gd2(MoO4)3:Yb)) reach 9, 2 and 2, respectively. The considerable enhancement is due to the suppression of surface quenching and energy harvesting via the Yb ions in the outer shell. In addition, the emission color of thin films can be modulated from yellow to blue via tuning the number of Gd2(MoO4)3:Ho/Yb and Gd2(MoO4)3:Tm/Yb layers, which provides a feasible strategy to tune the up-conversion emission color.

Transition between gap waveguides for use in multilayer structures at millimeter-wave frequencies

This is the peer reviewed version of the following article: Carrera-Suarez, F., Navarro-Mendez, D., Baquero-Escudero, M. and Sanchez-Escuderos, D. (2016), Transition between gap waveguides for use in multilayer structures at millimeter-wave frequencies. Microw. Opt. Technol. Lett., 58: 102–106., which has been published in final form at http://dx.doi.org/10.1002/mop.29507. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

Influence of layer type and order on barrier properties of multilayer PECVD barrier coatings

Due to their macromolecular structure, plastics are limited in their scope of application whenever high barrier functionality against oxygen and water vapour permeation is required. One solution is the deposition of thin silicon oxide coatings in plasma-enhanced chemical vapour deposition (PECVD) processes. A way to improve performance of barrier coatings is the use of multilayer structures built from dyad layers, which combine an inorganic barrier layer and an organic intermediate layer. In order to investigate the influence of type and number of dyads on the barrier performance of coated 23 µm PET films, different dyad setups are chosen. The setups include SiOCH interlayers and SiOx-barrier layers deposited using the precursor hexamethyldisiloxane (HMDSO). A single reactor setup driven in pulsed microwave plasma (MW) mode as well as capacitively coupled plasma (CCP) mode is chosen. In this paper the effects of a variation in intermediate layer recipe and stacking order using dyad setups on the oxygen barrier properties of multilayer coatings are discussed with regard to the chemical structure, morphology and activation energy of the permeation process.Changes in surface nano-morphology of intermediate layers have a strong impact on the barrier properties of subsequent glass-like coatings. Even a complete failure of the barrier is observed. Therefore, when depositing multilayer barrier coatings, stacking order has to be considered.

Ion beam analysis of ancient Egyptian wall paintings

Polychromatic decorations of ancient Egyptians tombs and temples have a long tradition over three millennia but are hard to identify because many pigments have been subjected to severe chemical reactions, which have entirely changed their original colours. Optical microscopy, PIXE and microbeam-PIXE have been used for determination of the nature of pigments, their chronology, and identification of domestic and imported materials. Paint flakes from various archeological sites in Egypt were analyzed: we report the results of the analysis of samples which were collected at the Mortuary Temple of Ramesses III (Habu Town), and the tombs of Tuthmosis III (Valley of the Kings) and Sennefer (Valley of the Noblemen). The paint is composed of grains of sizes typically ranging from 50 μm to 300 μm embedded in binding material and has great non-uniformity of pigment depth and lateral distributions and discontinuity of the paint layers. Qualitative analysis using broad beam PIXE has been performed to allow determination of the average composition of both support and pigments. Microbeam-PIXE has been used for mapping of selected grains. Goethite FeO(OH) (yellow), orpiment As 2S 3 (green), and the two blues: Egyptian Blue CaCuSi 4O 10 and Green Frit CaCuSiO 3 (mixed with the red haematite Fe 2O 3) were identified, and interesting details of the painting technique of ancient masters, like blending of pigments and the use of multilayer structures, were revealed.

Nano-lamination in amorphous carbon for tailored coating in micro-dry stamping of AISI-304 stainless steel sheets

Nano-lamination is a new way to make full use of multi-layered structure for coating instead of the mono-layered coating system. Different from the conventional nano-lamination approach, where two different kinds of material system are deposited in layers, the amorphous carbon layer, a-C:H, is alternatively deposited with graphite-like cluster layer, resulting in an amorphous carbon base nano-laminated coating. In this nano-lamination, the pulse bias voltage and the pulse duration time are programmed to control the bi-layer thickness and number of laminates. Furthermore, the mechanical properties are also controllable by varying the bi-layer thickness and sub-layer ratio. In this paper, the effect of number of layers and bi-layer thickness on the mechanical properties is investigated by the nano-indentation technique. Higher hardness and Young's modulus is attained with reduction of bi-layer thickness. The scratching test of this nano-laminated coating is made to demonstrate that it has sufficient scratch load above 100 N. Furthermore, a dry micro stamping test is performed to prove that this nano-laminated coating has sufficient wear-toughness enough to make dry stamping in 10,000 times in practice even if it has nearly the same Young's modulus and hardness as the mono-layered coating. No delamination or break-away occurs on the ironed surface of coated tools while severe delamination is observed in the conventional mono-layered coating.

Functional barriers in PET recycled bottles. Part II. Diffusion of pollutants during processing

AbstractRecycled plastics may be polluted by various chemicals available to consumers. When such materials are used to manufacture packaging materials intended to be in direct contact with food, these pollutants may migrate into food. The use of multilayer structures with a virgin polymer layer as a functional barrier may prevent such migration. This work deals with the possible diffusion of pollutants into and through the virgin layer during processing at high temperatures. A test is designed to measure diffusion coefficients in elastomeric and glassy polymers, in their molten state; 2.5‐dimethoxyacetophenone was used as a surrogate pollutant, and its concentration profiles are monitored by UV microscopy. Based on diffusion coefficients and on activation energies, glassy polymers appear to be much better barriers than polyolefins, even in their molten state. We then focus on poly(ethylene terephthalate) (PET) bottle preforms, processed by injection molding. In a first approach, a worst case situation was simulated by numerical analysis, using both overestimated diffusion coefficient values and very low values of activation energy. It appears that migration into foodstuffs through functional barriers can only be observed with unrealistic high diffusion coefficients and low activation energies. These results were confirmed by experimental determination of the concentration gradients of model pollutants in multilayer structures. It appears that little diffusion occurs, despite at a very high temperature. The effects of temperature and thickness of the functional barrier are discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2859–2870, 2004

Use of multilayer structures, periodically etched, to implement compact diffractive optical devices

Periodic multilayer structures, periodically etched, can be used to implement a large variety of diffractive optical devices, as these structures can combine the principle of diffraction by periodic structures, guiding properties and high reflection coefficients. In this paper, using a rigorous coupled-wave method we developed elsewhere, we model and size several devices which can operate as polarizing mirrors, narrowband transmission filters and blazed binary diffractive elements. We show the first experimental realizations we have carried out using Si/Si3N4 stacks obtained by PECVD and a focused ion beam etching.

Adhesion between semi-crystalline polymers: grafted PE/EVOH copolymer

Amongst modern polymeric materials, the use of multi-layer structures is becoming popular. This study deals specifically with a five-layer system composed of two outer strata of high-density polyethylene (HDPE) with an inner layer of an ethylene/vinyl alcohol copolymer (EVOH). The further two layers consist of an “adhesive” between the HDPE and EVOH phases: a grafted polyethylene (PE *). We study here the adhesion between EVOH and PE * by means of peel tests. Rate- and temperature-dependent behaviour is described by time–temperature superposition. High values of peel energy are partly attributable to considerable dissipation during elasto-plastic deformation of the peel arm, yet the intrinsic, local adhesion energy is also large. The latter can be partially explained using the Dugdale model, but a second mechanism related to shear would also seem important.

Magnetism in thin films

In the last decade enormous effort has been made in research and investment to study magnetic properties of thin films because of their obvious practical applications. Coincidentally, it happens that theory has made enormous progress. Ab initio calculations and microscopic theories allow us for the first time in the history of magnetism to study and manipulate the magnetism on an atomic scale. In contrast to bulk magnetic materials, ultrathin films allow us to manipulate magnetism via the thickness and, by use of artificial structure growth, to produce structures which do not appear in nature. Here we discuss the fundamental magnetic observables, i.e. magnetization, Curie temperature, magnetic moment per atom, susceptibility and magnetic anisotropy, for idealized prototype thin films like Fe, Co, Ni on metal substrates such as Cu, W, Re. Finally, we present studies on trilayers, i.e. magnetic thin films separated by a spacer, like Cu. These trilayers present prototypes of interlayer coupling relevant for practical use of multilayer structures.

Use of multilayer structures and composite materials for reconstructing the runner pits of turbine-generator units

Use of multilayer structures and composite materials for reconstructing the runner pits of turbine-generator units

Multilayers: A Research Tool for Mechanical Property and Alloy Phase Stability Investigations

The magic of multilayer structures — comprised of a regular repeating pattern of alternating layers that vary in thickness from less than 1 nm to more than several micrometers — is present today in nearly every facet of materials science.A technological gamut of issues has been approached through the use of multilayer structures. Material systems have been routinely investigated, ranging from simple binary through complex quaternary and including nearly every element of the periodic table. Applications include thin-film semiconductor devices in the form of strained-layer superlattices; protective coatings for improved surface hardness and wear resistance of conventional alloys (tribology); and reflective and transmissive x-ray optical devices. Multilayer structures have also provided an experimental means to investigate the interdiffusion and stability of alloy phases; the relationship between the presence, lack, or variations of crystallinity with magnetism (and most recently superconductivity); and the role of interfaces in adhesion and elastic/plastic behavior.

A process simulation model for multilayer structures involving polycrystalline silicon

The increasing complexity of VLSI fabrication often requires the use of multilayer structures above the silicon substrate. Electrical and metallurgical properties of multilayer structures have an important effect on circuit performance and reliability. Although process simulation models are available and widely used for computer-aided process design, none of the existing process simulation programs have the capability for modeling multilayer structures. A new model with such capability has been developed and this paper presents the physics as well as the results of simulation supported by experimental data. The model can simulate many desirable properties of multilayer structures involving polycrystalline silicon, such as grain growth, resistivity and oxidation rate of the polysilicon layer, the impurity redistribution across multilayers after high-temperature thermal processing, impurity segregation both at grain boundaries and at interfaces, and the interdependent phenomena of dopant-dependent oxidation/diffusion.