Properties Of Different Layers Research Articles

Simulation of Tsunami Effect by Seismic Wave Propagation in Hypoplastic Medium at Vicinity of Free Boundary

A theoretical study of seismic waves propagation in a soil layer with a free surface has a great importance for a prediction in engineering decisions. Wave packets are radiated from an earthquake source and transfer energy. A transformation and a selection of wave packets occur in a process of wave propagating that why waves which arrive in a layer have a length considerably greater than a variation scale of heterogeneity in a medium in a layer near free surface. In the case, when the properties of different layers affect a relatively small degree on a behavior of the waves, an approximation of effective medium gives a fairly good solution. A model of a hypoplastic medium is used for a describing of some effects, which are observed in the time of seismic wave propagation. The model of hypoplastic medium allows describing many effects which are observed in granular soils. We consider a successive application of effective medium and ray methods in order to receive of approximate analytical solutions wishing to describe shear wave propagation in stratified layer, which lies on a half-space.

Electrical properties and back contact study of CZTS/ZnS heterojunction

In the present work, we have studied the effect of metal back contact nature on the electrical properties of CZTS/ZnS based heterojunction prepared by spray pyrolysis. Three different back contact metals (Al, Au and Ag) were tested as alternative of the commonly used Molybdenum. Structural and optical properties of different layers are characterized. The electrical devices characterization were achieved by (I–V) at ambient and at different temperatures and capacitance-conductance vs frequency (C-G–f) measurements. The realized structures exhibit a rectifying behavior. The ideality factor of all devices were found to be large, it is found equal to 5.9 when using Au contact and equal to 10.5 and 11.4 in heterojunction prepared with Ag and Al back contact respectively. The anomalous ideality factor is due to the Schottky contact between Al, Ag and CZTS and to the presence of density of defect at the interface CZTS/ZnS. The latter was estimated from conductance measurement as a function of frequency and found equal to 1010cm−2eV−1. From this study we inferred that Au contact can be an alternative of Mo as back contact of CZTS based solar cell.

Global multi-layer network of human mobility

ABSTRACTRecent availability of geo-localized data capturing individual human activity together with the statistical data on international migration opened up unprecedented opportunities for a study on global mobility. In this paper, we consider it from the perspective of a multi-layer complex network, built using a combination of three datasets: Twitter, Flickr and official migration data. Those datasets provide different, but equally important insights on the global mobility – while the first two highlight short-term visits of people from one country to another, the last one – migration – shows the long-term mobility perspective, when people relocate for good. The main purpose of the paper is to emphasize importance of this multi-layer approach capturing both aspects of human mobility at the same time. On the one hand, we show that although the general properties of different layers of the global mobility network are similar, there are important quantitative differences among them. On the other hand, we demonstrate that consideration of mobility from a multi-layer perspective can reveal important global spatial patterns in a way more consistent with those observed in other available relevant sources of international connections, in comparison to the spatial structure inferred from each network layer taken separately.

Parameter sensitive analysis of flexible pavement

This paper describes the usefulness of FEM for exploring the parameter sensitive analysis. Using 2D axisymmetric analysis, the critical performance parameters are examined by varying the thickness and material properties of different layers of flexible pavement. Hypothetical pavement sections are also analyzed with a view to check the sensitivity of horizontal axisymmetric extent and refinement of mesh. The developed computer program after validation is used to calculate the horizontal tensile strain at the bottom of the bituminous layer (BL) and the vertical compressive strain at the top of the subgrade. These computed strains are incorporated in the fatigue and rutting criteria recommended in Indian Road Congress (IRC: 37-2012) to estimate the pavement life for various hypothetical conditions. Tensile strain at the bottom of BL and compressive strain on top of the subgrade decreases with an increase in the thickness of BL, which results in increase of fatigue and rutting lives. An increase in thickness of the base layer and the increase in its elastic modulus reduces the damage due to rutting, while it has less effect on damage due to fatigue. Such type of analysis proves beneficial for designing a pavement, keeping equilibrium between fatigue and rutting lives.

(Invited) New Benzoxazine Resins Coated on Anodized Aluminium Alloys: Electrochemical Behaviour of Efficient Corrosion Protection Systems

Aluminum alloys are widely used in aircraft applications, especially series 2xxx (Cu) and 7xxx (Ti). Those alloys offer improved mechanical properties compared to pure aluminum, but are strongly sensitive to corrosion. Chromic anodizing combined with chromate containing epoxy primer was used as an efficient system to prevent corrosion. Nevertheless, due to health and environmental issues, this treatment is going to be forbidden. Alternative solutions have to be developed to reach aircraft standards considering health and environmental concerns. This work aims at proposing an alternative protective system, consisting in an oxide layer obtained from sulfotartaric anodizing (TSA) and coated with benzoxazine organic layers. Benzoxazine resins offer high chemical resistance and low shrinkage and so are very good candidates for coating applications. Investigated layers have been prepared on both bare and clad Al-2024 T3 substrates. The morphology and the thickness of coating systems were determined using Field Emission Gun Scanning Electron Microscopy (FEG-SEM). Electrochemical Impedance Spectroscopy (EIS) was used to characterize the electrochemical behaviour of obtained systems and separated layers in order to emphasize synergetic effects. The AC/DC/AC electrochemical tests were carried out to evaluate the cathodic disbonding sensitivity of these new coating systems. The results were fitted by Equivalent electrical circuits to model the electrochemical properties of different layers and the evolution of their properties over immersion time in an aggressive saline solution and during AC/DC/AC cycles. The results confirmed the strong potential of such systems for future corrosion protection applications.

Mechanistic modeling of the dielectric impedance of layered membrane architectures

Electrochemical impedance spectroscopy (EIS) is frequently used to investigate properties of layered membrane systems in aqueous electrolyte solutions. However, attributing features of the underlying plots to chemical or structural characteristics of the system is difficult, as it usually requires the assumption of structural elements of an analogous equivalent electrical circuit. Furthermore, some parameters are not easily accessible in experimental studies, making the analysis of EIS subject to interpretation rather than rigorous understanding. We address these difficulties by conducting direct numerical simulations of layered structures composed of electrolyte solutions, ion exchange membranes and membrane modification layers, using our EnPEn framework. By changing the parameters of the model, it is possible to isolate features of impedance spectra as they relate to chemical and structural properties of different layers and interfaces. For the first time, we show the general influence of the thickness and charge density of surface modification layers on the complex impedance of such layered membrane architectures in multi-ionic mixtures. The results can be used to characterize and understand impedance spectra gained by experiments. This is important in increasingly complex systems with multiple layers and complex multi-ionic electrolyte solutions. Understanding the influence of design parameters on the performance of a membrane is important for a wide range of applications, such as ion selective electrodes, desalination and deionization. The dynamic EnPEn framework closes the gap between experimental EIS and the uncertainty introduced by assuming equivalent circuits.

Fabrication of Nanosized Lanthanum Zirconate Powder and Deposition of Thermal Barrier Coating by Plasma Spray Process

The present manuscript discusses our findings on fabrication of nanosized lanthanum zirconate powder for thermal barrier coating application and its coating by plasma spray on nickel-based superalloy substrate. Single-phase La2Zr2O7 coating of thickness of the order of 45 µm on the Ni-Cr-Al bond coat coated Ni-based superalloy substrate was deposited by plasma spray process. The layers at the interface did not show spallation and inter diffusion was very less. The microstructure, interface, porosity, and mechanical properties of different layers are investigated. The lanthanum zirconate hardness and modulus were 10.5 and 277 GPa, respectively. The load depth curve for lanthanum zirconate showed good elastic recovery around 74%.

Thermal wave imaging of microelectronics

Thermal waves can reveal thermal properties of different layers forming a multilayer structure. If the thickness of each layer is known, specific ranges of thermal wave frequencies can be implemented to study the thermal response of a specific number of layers and eventually extract the thermal properties of individual layers. As a first approach this idea can be simplified by means of the thermal penetration depth parameter, δ. The thermal penetration depth is defined as, δ=k/πCf, where k and C are respectively the thermal conductivity and volumetric heat capacity of the material carrying the thermal wave and f is the frequency of the thermal wave. From this expression it can be seen how it is possible to constrain the material thermal response to a desired depth by controlling the frequency. Thus, using high enough frequencies, the top layer properties would be measured first. Decreasing the thermal wave frequency by an appropriate amount would include the next layer in the thermal response. Since the properties of the first layer are now known, it would be possible to extract the properties of the current layer. The measurement would continue in a similar fashion for the remaining layers. Frequency domain thermoreflectance (FDTR) can be used to generate thermal waves. In this technique, a periodically modulated continuous wave laser (red pump beam) provides the periodic heat flux input into the material while a second laser (green probe beam) monitors the surface temperature through a proportional change of the surface reflectivity. The measured value is the phase lag (degrees) between the incoming thermal wave and the surface temperature response. In this study, an FDTR system was used in conjunction with a piezo stage to obtain thermal images of two different multilayer structures. The first one consisted of a CPU chip formed mainly by layers of SiO2 and Cu. The second case consisted of a TFT LCD screen from a mobile device. Regarding the CPU chip, the low frequency thermal wave travelled well past the second layer of Cu wires and provided thermal information about the bottom layers of the chip. In contrast, the high frequency wave could not penetrate through the second layer, which resulted in a more sensitive response upon the Cu wires close to the surface. A similar phenomenon occurred with the LCD screen. In this case the top layer was a glass layer used to sandwich the liquid crystal and the second layer is composed of the ITO electrodes that provide the electric field. It can be observed how the high frequency wave did not penetrate through the top glass layer providing no thermal information about the bottom layer as opposed to the low frequency wave, which clearly shows the ITO electrodes. The estimated thermal penetration depths displayed on top of each image were calculated using the equation provided before with known thermal properties of SiO2, Cu and ITO.

Three-Layer Al/Al–B4C Composite Material Prepared by Casting and Hot Rolling

Casting and hot rolling are proposed to verify a semi-continuous casting and hot rolling process to produce a three-layer Al/Al–B 4 C metal-cermet composite. The outer layer is pure Al, the inner layer is Al matrix composite reinforced with B 4 C particles (the mass fraction of Al and B 4 C are 62.36 and 37.64%, respectively). The results show that the reinforced particles are distributed in the inner layer homogeneously, and both layers are sintered together with no pores or flaws. The clad ratios of the composites of 26, 5, 3, and 1 mm are 50.28, 54.67, 61.23, and 57.46%, respectively. The Vickers hardness varies from 46 HV for the outer pure aluminum layer to 158 HV for the inner composite layer in 3 mm specimen, indicating totally different properties in different layers.

Electrical conductivity of PEMFC under loading

Conducting an experimental investigation, we show that the electrical conductivity σ (Sm−1) of the gas diffusion layer (GDL) and bipolar plates in stainless steel foam (SSF), as the heart of a Proton Exchange Membrane Fuel Cell (PEMFC), depends in fact strongly on mechanical compression arising in an operating system. Thus, this mechanical compression significantly affects the current density and σ; while it is not so far introduced in modelling and performance analysis. By mean of a developed metrology for this purpose and using Van der Pauw method, we studied, upon applied mechanical loads by varying the compression p, the electrical properties of different layers of a carbon cloth for GDL, of SSF, and, as in operating fuel cell, of the combination GDL + SSF in a sandwich form. A strong dependency is observed for each of these materials and their combination up to saturation for high enough p which is seen then to reduce the electrical resistance; while the number of layers has no influence. The obtained results are analysed in term of rate of increase of σ with an interesting conclusion for their application.

Observed Phenomena during the Development of an Adhesion Test for Coated Medical Devices

Devices used in the field of medical technology require high biocompatibility. Medical devices that are made from stainless steel have good biocompatible properties, but polymer coatings can radically improve it. One of the most important quality of the coating is adhesion, and this was our rationale for developing a polymer adhesion testing protocol. In our research, two biocompatible polymers were compared, polyurethane (PUR) and poly-(DL-lactic-co-glycolic acid) (PDLG). Surface-treated stainless steel sheets were used as carrier for polymer layers. The adhesive properties of different layers were compared. Adhesion of the coatings was characterised by concentration of coating solution and surface roughness of the carriers, and some phenomena were observed.

A thermo-elasto-plastic model for a fiber-metal laminated beam with interfacial damage

In this paper, a thermo-elasto-plastic model for the fiber-metal laminated (FML) beams is established and the mechanic characterization of a FML beam with interfacial damage under thermal environment is investigated. The elasto-plastic behavior of the FML beam is modeled by a macromechanical orthotropic plasticity theory, where the composite layers in the FML are assumed to be linearly elastic and the aluminum layers are taken as orthotropic elasto-plastic. Additionally, the thermal stresses in the FML beam are studied by introducing heat conduction equation. Considering the mismatch in properties of different layers, the interfacial damage is investigated based on cohesive zone model and shear-lag model, and the evolution of the interfacial damage is addressed as well. The incremental thermo-elasto-plastic governing equations for the FML beams are solved by finite difference method and iteration method. In the numerical simulations, the temperature variation, the elasto-plastic deformation and the interfacial damage evolution of the elasto-plastic FML beam are discussed in detail. The results show that mode II interfacial damage occurs at 1/4 and 3/4 length of the beam and mode I damage is most likely to happen at the center.

Quantitative elasticity measurement of urinary bladder wall using laser-induced surface acoustic waves

The maintenance of urinary bladder elasticity is essential to its functions, including the storage and voiding phases of the micturition cycle. The bladder stiffness can be changed by various pathophysiological conditions. Quantitative measurement of bladder elasticity is an essential step toward understanding various urinary bladder disease processes and improving patient care. As a nondestructive, and noncontact method, laser-induced surface acoustic waves (SAWs) can accurately characterize the elastic properties of different layers of organs such as the urinary bladder. This initial investigation evaluates the feasibility of a noncontact, all-optical method of generating and measuring the elasticity of the urinary bladder. Quantitative elasticity measurements of ex vivo porcine urinary bladder were made using the laser-induced SAW technique. A pulsed laser was used to excite SAWs that propagated on the bladder wall surface. A dedicated phase-sensitive optical coherence tomography (PhS-OCT) system remotely recorded the SAWs, from which the elasticity properties of different layers of the bladder were estimated. During the experiments, series of measurements were performed under five precisely controlled bladder volumes using water to estimate changes in the elasticity in relation to various urinary bladder contents. The results, validated by optical coherence elastography, show that the laser-induced SAW technique combined with PhS-OCT can be a feasible method of quantitative estimation of biomechanical properties.

Microstructure and Mechanical Properties of Al-Li Alloy 2397-T87 Rolled Plate

The microstructure, tensile property and fracture toughness of Al-Li alloy 2397-T87 rolled plate were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, tensile and plane-strain fracture toughness tests. The results show that a pronounced texture variation through the plate thickness was found. Near the surface, Goss texture dominated. While in the center of the plate, typical β fiber texture and a scattering of cube texture were observed. And the subsurface layer exhibited a very weak texture. From the center to the subsurface, the fraction of β fiber texture and cube texture decreased. In contrast, the fraction of shear type texture reaching the maximum in subsurface layer increased. The tensile properties in different layers along the thickness direction were inhomogeneous. The strengths near the surface were lower than those in the center. And the through-thickness strength properties variation in the rolling direction was more remarkable than that in the long transverse direction. In the same thickness layer, the fracture toughness and the strengths were anisotropic. The strengths in the rolling direction were higher than those in the long transverse direction and the short transverse direction, and the strengths in the short transverse direction were the lowest. The fracture toughness in L-T orientation was the highest, followed by that in T-L orientation, and the fracture toughness in S-L orientation was the lowest.

Flux Pinning in YBCO Single Crystal Grown on Y2O3 Layer

In this study, single-crystal Y123 samples were grown by a cold top-seeding method by using Nd123 seed, and the effect of Y2O3 buffer layer was investigated. The upper critical magnetic field and coherence length were established as 110 T and 17.3 Ǻ, respectively. The dependence of the effective activation energy U of the flux pinning on the magnetic field and temperature of the sample were determined using the Arrhenius activation energy law from the resistivity curves. It was found that the deduced value of the activation energy for a Y123 sample is in good agreement with the corresponding values in YBCO samples. The maximum activation energy value was approximately 0.9 eV in the zero magnetic field. In order to examine the homogeneity of the pinning properties of different layers, rectangular specimens were cut from the sample. AC susceptibility measurement was performed, and it was found that the shifting of the peak temperature (Tp) with an AC magnetic field is small, indicating good pinning properties. The normalized pinning force density versus the reduced field was examined at different temperatures to determine the pinning mechanism. It was found that normal core-type pinning was effective, and in low fields, pinning was only due to Y211 particles.

Study on Loading Rate-Dependent Property of Different Layers in Articular Cartilage Based on ABAQUS

A new biomechanical model of articular cartilage was developed using ABAQUS to investigate the mechanical properties of different layers under different loading rates. It is found that the compressive strain of superficial layer is the largest, the compressive strain of deep layer is the smallest and the compressive strain of middle layer is between the superficial and deep layer under constant loading rate. The compressive strains of different layers increase with increasing loading rates. At the beginning of loading, fluid flows mainly in the superficial layer and flows into the middle and deep layer with the increasing time and the position of the maximum flow moves downward. Void ratio also increases with the loading time.

Development of adhesion test for coated medical device

High biocompatibility is a basic requirement in medical technology. Polymer coatings can radically improve medical device biocompatibility, especially for surfaces like stainless steel. Adhesion is an important quality in a coating, and this was our rationale for developing a polymer adhesion testing protocol. We compared two biocompatible polymers, polyurethane (PUR) and poly-(DL-lactic-co-glycolic acid) (PDLG). Polymer layers were created on surface-treated stainless steel. The properties of different layers were compared. Adhesion of the coatings was characterised by concentration of coating solution, rate of the contacted surface and surface roughness of the carriers. PUR showed better adhesion under our test conditions. DOI: 10.17489/biohun/2013/1/32

Real-time Estimation of Elastic Properties of Formation Rocks Based on Drilling Data by Using an Artificial Neural Network

Understanding the mechanical properties of formations has its importance in the drilling, production, and management phases of reservoirs. In petroleum engineering, measurements through wire-line logs, which run in the boreholes after the drilling phase, are of the most common methods to estimate mechanical properties of different layers. Elastic rock mechanic measurements from logs are dynamic values and need to be upscaled and calibrated to fit the corresponding pseudo-static measurements that are obtained from cores in the laboratory. As a practical approach to having a continuous profile of these static parameters and surmount the arduousness that confronts by using core samples and laboratory tests, many researchers tried to deploy predictive methods and empirical correlations. However, it will be a great advantage to have a real-time estimation of these static parameters while drilling based on bit and formation rock interaction. Artificial neural networks are powerful tools for estimation of complex functions subjected to availability of large enough data sets that present samples of actual behavior of the function. In this study, artificial neural networks were implemented to estimate in situ rock mechanical properties, including Unconfined Compressive Strength, Young's Modulus of Elasticity, and the ratio of these parameters known as Modulus Ratio, by using operational drilling parameters as inputs. Required data were gathered from drilling reports, logging operations, and core samples from nine wells placed in Ahwaz Oilfield located in south-west Iran. The trained networks showed satisfactory low errors in the testing process and sketched the capability of artificial neural networks in estimation of complex functions. The accuracy of the presented model was then compared with the results of calibrated regional correlations and modified Warren's equation. These correlations are used in the candidate wells to estimate Unconfined Compressive Strength and Young's Modulus of Elasticity. It was observed that the new artificial neural network approach is a competent and accurate method for real-time calculation of static elastic properties of formation rocks. The results of this work could be used for drilling optimization, reducing stability problems, and lithologic boundary detection while drilling.

Neural dynamics and information representation in microcircuits of motor cortex

The brain has to analyze and respond to external events that can change rapidly from time to time, suggesting that information processing by the brain may be essentially dynamic rather than static. The dynamical features of neural computation are of significant importance in motor cortex that governs the process of movement generation and learning. In this paper, we discuss these features based primarily on our recent findings on neural dynamics and information coding in the microcircuit of rat motor cortex. In fact, cortical neurons show a variety of dynamical behavior from rhythmic activity in various frequency bands to highly irregular spike firing. Of particular interest are the similarity and dissimilarity of the neuronal response properties in different layers of motor cortex. By conducting electrophysiological recordings in slice preparation, we report the phase response curves (PRCs) of neurons in different cortical layers to demonstrate their layer-dependent synchronization properties. We then study how motor cortex recruits task-related neurons in different layers for voluntary arm movements by simultaneous juxtacellular and multiunit recordings from behaving rats. The results suggest an interesting difference in the spectrum of functional activity between the superficial and deep layers. Furthermore, the task-related activities recorded from various layers exhibited power law distributions of inter-spike intervals (ISIs), in contrast to a general belief that ISIs obey Poisson or Gamma distributions in cortical neurons. We present a theoretical argument that this power law of in vivo neurons may represent the maximization of the entropy of firing rate with limited energy consumption of spike generation. Though further studies are required to fully clarify the functional implications of this coding principle, it may shed new light on information representations by neurons and circuits in motor cortex.

Land Subsidence in Central Calcutta

In this paper, two approaches have been mentioned to calculate subsidence. One is based on the linear theory (considering elastic property of the material) and the other on the logarithmic theory. In the linear theory, coefficient of volume compressibility (denoted as m v ) indicates the nature of soil towards compression, and in the logarithmic theory, compression index (denoted as C c ) indicates the same. The top 30 m of the subsurface soil stratification in Calcutta generally indicates softer clayey soil in the first 15 m having higher m v values and relatively stiffer clayey soil between 15 m and 30 m having lower mv values. Further below, the compressibility of the layers diminishes due to increasing overburden pressure also. In the analysis section for subsidence in two localities in Central Calcutta, firstly, data of soil characteristics and properties in different layers and change in piezometric level or depth of water table from 1956 to 2000 are represented. Based on these data, intergranular pressures for different layers are calculated, and finally total subsidence in the said time span is estimated using the linear theory. This comes out to be 0.4932 m (average) for Central Calcutta region from 1956 to 2000, and hence, estimated average subsidence rate is 11.208 mm/year.