Layers Of Different Materials Research Articles

Generation of Hard Bremsstrahlung at the Grazing Incidence of 18-MeV Electrons of a Betatron Beam on the Surface of Тa Foil 13 µm Thick

The properties of the hard bremsstrahlung generated at the grazing incidence of 18-MeV electrons on the surface of a thin tantalum foil 13 μm thick and 2.5 mm long are studied using a facility based on the B‑18 betatron. The foil is placed in a goniometer inside the betatron chamber to obtain the orientation dependence of the generated radiation. A strong dependence of the angular distributions of hard bremsstrahlung on the orientation of a thin target is revealed, which is not observed at the normal incidence of electrons on its surface. Using the generated radiation, magnified images of the Duplex IQI reference and an object, consisting of thin layers of different materials, are obtained. The contribution of the absorption and edge phase contrasts to the formation of images of the wire structures of the reference and the planar interfaces in the complex object is studied. High-quality images of the objects are shown to be obtained due to the small horizontal size of the radiation source, which amounts to 13 μm for radiation emitted along the target and increases with growth in the angle of radiation emission.

Boundary element method for nonadhesive and adhesive contacts of a coated elastic half-space

We present a new formulation of the boundary element method for simulating the nonadhesive and adhesive contact between an indenter of arbitrary shape and an elastic half-space coated with an elastic layer of different material. We use the Fast Fourier Transform-based formulation of boundary element method, while the fundamental solution is determined directly in the Fourier space. Numerical tests are validated by comparison with available asymptotic analytical solutions for axisymmetric flat and spherical indenter shapes.

Impact on the Production of Cold After Addition of a Second Layer of Material to a Generator of a Refrigerating Machine Operating with Magnetocaloric Effect

Work is being done today to overcome the problems generated by conventional refrigeration (compression / expansion of a refrigerant) by following two parallel paths. In the first, we seek to maintain conventional technology and find new refrigerants less polluting. The second is to achieve a technological breakthrough and find new ways to achieve energy efficient systems while having a low environmental impact. This is the case of magnetic refrigeration which is the subject of this communication. Magnetic refrigeration is based on the magneto-caloric effect (MCE); an intrinsic property of certain magnetic materials that results in a change of their thermal state (hot/cold) during the variation of their magnetic state (magnetized/demagnetized) induced by an external magnetic field. The (MCE) decreases rapidly as the temperature of the material moves away from its transition temperature. To overcome this problem, it would be possible to use a combination of layers of different materials each having a transition temperature adapted to the local temperature, which would keep a sufficient EMC throughout the regenerator. But the question is how to stratify and place these materials along magnetic generator and what is the portion of each material in order to have better cold production. This present investigation serves to determine the best combination of two materials among six materials respectively having the Curie temperature (transition temperature) 270, 275, 280, 282, 285 and 290 [K °] and which are united on the common formula LaFe13 -xyCoxSiy. Our mathematical model is based on the laws of classical conservations, to take into account the porous structure of the generator (stacking of spheres) we use the model of (Darcy-Brikman-Forchheimer). To overcome the non-linearity of the mathematical model as well as the strong dependence between the dynamic field and the thermal field, the Simpler algorithm is used. At the end of this investigation we manage to draw the three essential points: 1-The material (layer) with the lower Curie temperature should be placed on the cold side of the refrigerating machine. 2-The combination (20%, 80%) is the most qualified to have the best cold-production. 3- The combination (80%, 20%) is the most disqualified and gives the lowest production.

Modeling of Multilayered Media Green’s Functions With Rough Interfaces

Horizontally stratified media are commonly used to represent naturally occurring and man-made structures, such as soils, roads, and pavements, when probed by ground-penetrating radar (GPR). Electromagnetic (EM) wave scattering from such multilayered media is dependent on the roughness of the interfaces. In this paper, we developed a closed-form asymptotic EM model considering random rough layers based on the scalar Kirchhoff-tangent plane approximation (SKA) model that we combined with planar multilayered media Green’s functions. In order to validate our extended SKA model, we conducted simulations using a numerical EM solver based on the finite-difference time-domain (FDTD) method. We modeled a medium with three layers—a base layer of perfect electric conductor (PEC) overlaid by two layers of different materials with rough interfaces. The reflections at the first and at the second interface were both well reproduced by the SKA model for each roughness condition. For the reflection at the PEC surface, the extended SKA model slightly overestimated the reflection, and this overestimation increased with the roughness amplitude. Good agreement was also obtained between the FDTD simulation input values and the inverted root mean square (rms) height estimates of the top interface, while the inverted rms heights of the second interface were slightly overestimated. The accuracy and the performances of our asymptotic forward model demonstrate the promising perspectives for simulating rough multilayered media and, hence, for the full waveform inversion of GPR data to noninvasively characterize soils and materials.

Ocular drug delivery system: Approaches to improve ocular bioavailability

Ocular drug delivery system (ODDS) is one of the most challenging tasks faced by pharmaceutical researchers. For a prolonged duration the major barriers in ocular medication are the ability to maintain a therapeutic level of the drug at the site of action. The ophthalmic preparations are available as buffered, sterile and isotonic solution. For the ocular delivery of drugs, several types of dosage forms are prepared and marketed. As drops are easier to administer so the most prescribed dosage form is the eye drop solution. For prolonged therapeutic action ointment, suspensions and gelled systems are also used. Frequent dosing in case of eye drop is the main issue for this system. The new drug delivery systems for this type of delivery is ocuserts, which are designed to eliminate the frequent administration of the drug by releasing the drug at predetermined and predictable rates. For this system the bioerodible implantable elements having multiple layers of different materials with different concentrations of materials are used and this generally include controlled, delayed and or sustained released formulation. The elements generally include an inner layer, or core, including a therapeutic agent, and one or more outer layers made of polymeric materials and this system is also able to prolong the residence time.

Slope-based segmentation of articular cartilage using polarization-sensitive optical coherence tomography phase retardation image.

.A segmentation method based on phase retardation measurements from polarization-sensitive optical coherence tomography (PS-OCT) is developed to differentiate the structural zones of articular cartilage. The organization of collagen matrix in articular cartilage varies over the different structural zones, generating different tissue birefringence. Analyzing the slope of the accumulated phase retardation at different depths can detect the variation in tissue birefringence and be used to segment the structural zones. The method is validated on phantoms composed of layers of different materials. Articular cartilage samples from adult swine are segmented with the method. The characteristics in each segmented zone are also examined by histology and high-resolution second-harmonic generation imaging, showing distinctive properties that match with the anatomical structure of articular cartilage. The segmentation algorithm is also applied on PS-OCT images acquired at multiple illumination angles, where the angular dependence of tissue birefringence in the deep zone is detected. This method offers a noninvasive imaging approach to differentiating the structural zones of articular cartilage, as well as a quantification approach based on the phase retardation measurements of PS-OCT. This method has great potential in studying depth-related progression of cartilage degeneration.

Freestanding Functional Structures by Aerosol‐Jet Printing for Stretchable Electronics and Sensing Applications

AbstractModern electronic devices, particularly those intended for wearable or human health monitoring applications, require high levels of flexibility and stretchability. Hence devices, as well as interconnects, need to be capable of retaining functionality even when being mechanically deformed. Most approaches towards achieving this rely on printing or transferring structures onto elastomeric substrates that can withstand stretching. However, the processing involved can often be cumbersome, and the structures themselves tend to suffer from poor fatigue and/or are limited by the mechanical properties of the underlying substrate. Here, we have developed a novel aerosol jet printing technique capable of building fully freestanding functional structures layer by layer, which are robust and reliable upon thousands of stretching cycles. The process involves printing a combination of layers of different materials with the desired functionality, onto a substrate coated with a sacrificial film that is subsequently dissolved to release the printed structure. Using this method, we demonstrate freestanding conductive wires that can be used as stretchable interconnects/electrodes, and that also function as strain‐sensors. Additionally, we show that a freestanding capacitive structure functions as a robust, stretchable humidity sensor, paving the way for the development of other multilayer, multifunctional stretchable devices and sensors.

Ocular Drug Delivery System: A Novel Approach

Ocular drug delivery is one of the most challenging tasks faced by Pharmaceutical researchers. The ophthalmic preparations are available as sterile, buffered, isotonic solution. Several types of dosage forms are applied as the delivery system for the ocular delivery of drugs. The most prescribed dosage form is the eye drop solution as drops are easier to administer. Characteristics of ophthalmic preparations should be non-irritating to the ocular tissue, homogenous, relatively non-greasy, should not cause blurred vision. Prolonged drug release can be achieved using ophthalmic inserts, solid devices placed in the eye, but the inserts must then be removed when they are no longer needed. Ocuserts are the new drug delivery systems which are designed in such a way that they release the drug at predetermined and predictable rates thus eliminating the frequent administration of the drug. The systems generally include controlled, delayed and or sustained release bio-erodible implantable elements having multiple layers of different materials and/or different concentrations of materials. The elements generally include an inner layer, or core, including a therapeutic agent, and one or more outer layers made of polymeric materials.

Simulation and Analysis of Methylammonium Lead Iodide (CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub>) Perovskite Solar Cell with Au Contact Using SCAPS 1D Simulator

Hybrid organic-inorganic perovskite solar cells have attracted the attention of researchers and scientists throughout the world. From 2009, when actual research work began on photovoltaic perovskite applications, a lab power conversion efficiency above 23.3% have been achieved. Whereas, silicon solar cells have only achieved power conversion efficiencies around 17.5% in both residential and commercial applications. A typical perovskite solar cell consists of 6 main layers of different materials: a glass layer, a thin layer of fluorine-doped tin oxide substrate (FTO), an electron transport layer of TiO2, a perovskite active layer known as methylammonium lead iodide (CH3NH3PbI3), a hole transport layer of Spiro-Ometad, and a gold (Au) electrode. This paper summarizes the research that focused on the selective use of the perovskite solar cell’s composite materials, specifically, the Spiro-Ometad layer, the methylammonium lead iodide layer (CH3NH3PbI3), and the TiO2 layer with a variation of the thickness of the perovskite layer. Initial simulation results show a power conversion efficiency of 20.34% when using a gold (Au) electrode. Further research is needed, in which new technology for device fabrication will create homogeneous thin-film layers that will be tested for increased efficiency.

Experimental assessment of the lumped lithium–ion battery model

In this study, an axisymmetric computational lumped model is used to investigate the thermal and electrical behavior of a cylindrical Lithium-ion (Li–ion) battery during various discharging processes at 0-20-50°C operating temperatures. A typical cylindrical Li–ion cell consists ofmultiple spiral layers, on the other hand, the model employs the lumped battery interface approach in COMSOL Multiphysics to reduce the computational effort. In the lumped approach, layers of different materials are approximated as a uniform material with effective properties. Among other parameters, the Open Circuit Voltage (OCV) as a function of the State of Charge (SOC) is determined experimentally andused as input to the model. The model is then used to analyze the effects of the correlations of various parameters on the transient electrical and thermal responses of the battery and validated by comparing predicted results with experimental data.

KOMPARASI KEKUATAN TEKUK PADA KOMPOSIT LAMINA DENGAN MATRIK DUA JENIS KAYU DAN REINFORCEMENT BAMBU

Natural materials are environmentally friendly materials that can be made as components of matrix and reinforcement. Wood is part of the stem or branches and twigs of hardened plant due to lignification. Bamboo is a type of grass plants belonging to the order Graminae, familia Bambuseae, rooted fibers, the trunk-shaped cylinder with a diameter that varies from base to tip, hollow, hard. The composite is a composite of two or more materials that are integrated macroscopically and form a new properties. The composite type used in the laminate composite consists of two different layers of material and combined together, using adhesive, the manufacturing process using the hand lay up method. Matrix used balsa and mahoni wood, for reinforcement used type of bamboo apus molded basket woven. Bending test, using ASTM D7264 / D7264M-07 standard. The results of the experiment by testing each test, using 3 test specimens, then taken the average value. For balsa wood matrix, with plain woven reinforcement, buckling strength with value 35.60 ± 2.30 MPa, for balsa wood matrix, with basket woven reinforcement, buckling strength with value 32.64 ± 4.20 MPa. For mahoni matrix, with plain woven reinforcement, buckling strength of 55.15 ± 4.89 MPa, for mahoni matrix, with basket woven reinforcement, buckling strength of 77.15 ± 4.88 MPa. From these data shows that by using mahoni matrix the buckling strength is greater than using balsa wood matrix, either using plain or basket woven.

A new numerical scheme for using the two-energy equation model for turbulent buoyant flow in a composite enclosure

Walls made of layers of different materials and sizes, including empty spaces, can be used for modulating energy transfer across such composite structures. By changing layer thicknesses and by using distinct porous and solid materials, the overall cavity Nusselt number can be modified in regard to its traditional behavior found in cavities fully fitted with porous materials or with no obstructions. Numerical simulations of transport equations for such composite systems poses an additional difficulty if one considers the different layers, appropriate interface conditions between them and the need to use one single computational domain for simplicity. Motivated by such engineering application and numerical need, this work presents the analysis about natural convection in a two-dimensional horizontal composite square cavity, using laminar and k-ε turbulence models. Both the one energy equation (1EEM) and two energy equation (2EEM) closures are applied. The composite square cavity is equally divided and formed by three distinct regions. Non-dimensional temperatures are proposed such that the entire computational domain is handled in a single numerical scheme. It was found that the fluid begins to permeate the porous medium for values of Ra greater than 106. Nusselt number values show that for the range of Ra analyzed there are no significant variation between the laminar/turbulent and 1EEM/2EEM model solution. When comparing the effects of Ra, thermal conductivity ratio and Da on Nu, results indicate that has a greater influence in controlling heat transfer rates across the composite cavity.

Multilayer test masses to enhance the collapse noise

Recently, a non-thermal excess noise, compatible with the theoretical prediction provided by collapse models, was measured in a millikelvin nanomechanical cantilever experiment [Vinante et al., Phys. Rev. Lett. 119, 110401 (2017)]. We propose a feasible implementation of the cantilever experiment able to probe such a noise. The proposed modification, completely within the grasp of current technology and readily implementable also in other type of mechanical non-interferometric experiments, consists in substituting the homogeneous test mass with one composed of different layers of different materials. This will enhance the action of a possible collapse noise above that given by standard noise sources.

Design of micro-transformer in monolithic technology for high-frequency flyback-type converters

The work presented in this article concerns the design of micro-transformer in monolithic technology for high frequencies comprised of planar-type coil and a magnetic circuit made of several layers of materials. This micro-transformer will be integrated into a micro-converter of type flyback. The Mohan method for determining the geometric parameters and the use of S-parameters for the calculation of technological parameters was chosen. The electrical model in π perfectly summarizes the various parasitic effects generated by stacking layers of different materials constituting the micro-transformer. The study of electromagnetic effects allowed us to show the role of ferrite, which is used to confine the magnetic field lines and minimize disruption of the neighbor ship. To validate dimensioning of the geometrical and technological parameters, we have simulated with the help of the software PSIM 6.0, the equivalent electrical circuit of the converter containing the electrical circuit of the dimensioned planar micro-transformer.

Nano-Engineering of 2D Materials for Supercapacitors

Exfoliation/restacking of 2D materials has recently been considered for the preparation of nanostructured electrode materials for supercapacitors. This approach consists in rebuilding new electrode materials from exfoliated layers of 2D materials either by restacking layers of different materials, by wrapping 3D materials with exfoliated layers, after chemical/morphological modification of those layers... with the aim of taking advantages of synergistic effects from distinct but complementary intrinsic behaviors together with the specific morphology of the resulting material. This can be, for example, to associate a 2D conductive material with a 2D pseudocapacitive material, eventually resulting in a more powerful nanocomposite electrode material [1]. This can also be about associating Faradaic layered double hydroxides (LDHs), for energy density, to more stable and powerful pseudocapacitive MnO2 [2], or opening a new macro/meso -porosity in Mxene layers for enhanced diffusion of electrolytic moieties in the reconstructed material. This paper will present our most recent results gained while exploring these various approaches.

Selective Laser-Assisted Synthesis of Tubular van der Waals Heterostructures of Single-Layered PbI2 within Carbon Nanotubes Exhibiting Carrier Photogeneration.

The electronic and optical properties of two-dimensional layered materials allow the miniaturization of nanoelectronic and optoelectronic devices in a competitive manner. Even larger opportunities arise when two or more layers of different materials are combined. Here, we report on an ultrafast energy efficient strategy, using laser irradiation, which allows bulk synthesis of crystalline single-layered lead iodide in the cavities of carbon nanotubes by forming cylindrical van der Waals heterostructures. In contrast to the filling of van der Waals solids into carbon nanotubes by conventional thermal annealing, which favors the formation of inorganic nanowires, the present strategy is highly selective toward the growth of monolayers forming lead iodide nanotubes. The irradiated bulk material bearing the nanotubes reveals a decrease of the resistivity as well as a significant increase in the current flow upon illumination. Both effects are attributed to the presence of single-walled lead iodide nanotubes in the cavities of carbon nanotubes, which dominate the properties of the whole matrix. The present study brings in a simple, ultrafast and energy efficient strategy for the tailored synthesis of rolled-up single-layers of lead iodide (i.e., single-walled PbI2 nanotubes), which we believe could be expanded to other two-dimensional (2D) van der Waals solids. In fact, initial tests with ZnI2 already reveal the formation of single-walled ZnI2 nanotubes, thus proving the versatility of the approach.

Humidity-responsive Bilayer Actuators Comprised of Porous and Nonporous Poly(acrylic acid)/Poly(allylamine hydrochloride) Films

Bilayer humidity-responsive actuators are generally composed of actuating and supporting layers of different materials with largely different wettability. Such kinds of bilayer actuators suffer from low adhesive force between the two layers during usage. This study demonstrates the preparation of humidity-responsive bilayer actuators that have the same materials in the actuating and supporting layers to avoid the adhesive issue. The bilayer actuators consist of a porous poly(acrylic acid) (PAA)/poly(allylamine hydrochloride) (PAH) layer and a nonporous PAA/PAH layer that are fabricated by exponentially layer-by-layer assembly method. At a high/low relative humidity (RH), the nonporous PAA/PAH layer can efficiently expand/shrink by absorbing/desorbing water while the volume expansion/shrinkage of the porous PAA/PAH layer in an environment with changed humidity is significantly suppressed by the micrometer-sized pores. The largely different expansion/shrinkage of the nonporous and porous PAA/PAH layers when subjected to humidity changes enables rapid and reversible rolling/unrolling motions of the bilayer actuator. The bilayer actuator shows a faster rolling speed and a larger bending curvature when subjected to a larger humidity increase.

Characterization of Fe–C–Cr Based Hardfacing Alloys

Hardfacing is one of the adaptable methods that can build up the hard and wear resistant surface layer of different materials on the surface of substrate material. It helps them withstand wear, as well as prevent corrosion and high temperature oxidation. In the present investigation three different types of Fe–C–Cr based hardfacing electrodes with varying chemical compositions were deposited on ASTM A36 steel substrate by using manual metal arc welding (MMAW) process. ASTM A36 steel was selected as a base material after consulting with Pressure and Process Boilers, Saharanpur (India), which is a leading manufacturer of boilers. ASTM A36 steel is mostly used by this company for the production of induced draft fans. MMAW process with direct current constant current type power source was used to deposit the hardfaced layers of uniform quality. Straight polarity was used for MMAW process so that more of the arc heat should be concentrated on the electrode. The hardfaced samples were characterized using various characterization techniques and the results of the same were also outlined in the present investigation.

Passive thermal behaviour of buildings: Performance of external multi-layered walls and influence of internal walls

In contemporary architecture, the opaque building envelope is usually realised by multi-layered walls; that is, a sequence of homogeneous layers of different materials. The layer sequence and distribution affect the wall behaviour in terms of its overall thermal inertia, or heat storage capability; hence, analysis of the thermal performance of a multi-layered wall becomes very important under dynamic heat transfer conditions, as usually occurs during summer.In this study, the authors employ analytical models based on the heat transfer matrix method, with the aim of predicting the dynamic thermal behaviour of external and internal building walls. Although numerous studies have been devoted to investigating the dynamic thermal behaviour of walls, the approach followed and results obtained by the authors are original and have significant implications that are of practical interest. By using the analytical models, the effects of continuous variations in the positioning and thickness distribution of the insulation material on the dynamic thermal performance (dynamic thermal transmittance, decrement factor and time lag) are demonstrated with reference to different constructive solutions (from a light-weight wall with a surface mass of 85 kg/m2 to a massive wall with a surface mass of 294 kg/m2). Moreover, a simplified correlation is proposed, which allows for correction of the dynamic thermal transmittance and time lag of external walls to take consider the effect of the internal walls (partition walls and slabs) on the dynamic thermal behaviour of a room. The results presented in the paper can be used during the building envelope design stage as a guideline for the improvement of the dynamic thermal performance of multi-layered walls. Furthermore, the insight provided into the building envelope thermal behaviour could prove useful for understanding how to maximise the effectiveness of possible retrofit interventions.

Non-equilibrium thermodynamic approach to spin pumping and spin Hall torque effects

This paper introduces a non-equilibrium thermodynamic approach to describe vector magnetization in the presence of a magnetic moment current. The Larmor term present in the theory describes in this case how the magnetization dynamics can be a source of magnetic moment currents and vice versa. The model discussed here is applied to describe the reciprocity between spin pumping and spin Hall torque effects found in bilayers composed of a metal with a large spin Hall effect (e.g. platinum, Pt) and a ferromagnetic insulator (e.g. yttrium iron garnet, YIG). The result is that the two effects are related to the transport of the magnetic moment between layers of different materials. In particular, for thin YIG the two effects are related each other by two parameters: the diffusion length of Pt, lPt, and the conductance of Pt, , where is a time constant. Both parameters can be determined by comparison with experiments.