Variation Of Layer Thickness Research Articles

Numerical Simulation for Flow and Heat Transfer of a Nanofluid Over Lubricated Stretchable Surface

The lubricants mostly used in industry have non-Newtonian properties and adhere to a variety of constitutive connections. The power law lubricant, which follows the Ostwald model and is widely used in engineering lubrication, is one of them. In this study the flow analysis of nanofluid in the vicinity of a stagnation point over a lubricated stretching surface has been investigated. The lubrication is provided by a thin layer of variable thickness of power-law fluid. Impact of thermophoresis and Brownian motion is also investigated. To acquire the dimensionless governing equations utilized an appropriate transformation. A newly developed powerful numerical procedure known as Legendre wavelet spectral collocation method (LWSCM) has been employed to acquire the similar solution. A comparison in the special cases between the published and present results substantiate the obtained solutions. Addition of the lubrication enhances the fluid velocity and reduces the temperature of the nanofluid at the stretchable surface.

Dopant Selective Photoelectrochemical Etching of SiC

Single crystalline 4H-SiC is a wide-gap semiconductor with optical properties that are poised to enable new applications in MEMS and quantum devices. A number of key hurdles remain with respect to the micro and nano-fabrication of SiC to prepare precise photonic structures with nanometer-scale precision. These challenges include development of a fast, scalable etching process for SiC capable of producing a sub-nanometer roughness semiconductor surface while simultaneously reducing the total thickness variation across a wafer. Our investigation into UV photoelectrochemical processing of SiC reveals high dopant-type selectivity and the advantage of multiple etch stops to reduce layer thickness variation. We demonstrate dopant-type selectivities >20:1 using a single step and a >100x reduction in surface variation by combining two etch stops. Moreover, the etch rate is fast (>4 μm h−1) and the etched surface is smooth (∼1 nm RMS). These results demonstrate a scalable path to the fabrication of precise nanoscale SiC structures and electronic devices that will enable the next generation of MEMS and photonic quantum devices.

Study on the Effects of Protective Layer on the Electron and Hole Transmission of Cadmium Sulfide (CdS) Photocatalyst Based on a Simple Quantum Mechanical Model

Cadmium Sulfide (CdS) is a photocatalyst material with a low energy band gap, which exhibits a potential application for the visible light spectrum. However, the serious photo-corrosion of CdS inhibits its wide applications. To prevent photo-corrosion, one can coat the CdS surface coated with an insulating material. The addition of this insulating layer will produce a barrier potential on the surface of the CdS thereby blocking the transmission of electrons and holes. If the thickness of this protective layer is thin enough the electron and hole can be transmitted by the quantum tunneling effect. Using a simple quantum mechanical model, the phenomena of electron and hole transmission through potential barriers due to the presence of a protective layer on the CdS surface can be analyzed. Based on this model, the effects of variations in thickness and type of protective layer on the performance of CdS photocatalyst materials are studied by calculating the transmission coefficient and injection efficiency values. The protective coatings used in this study were Aluminum Oxide (Al2O3), Hafnium Dioxide (HfO2), and Silicon Dioxide (SiO2). The results show that transmission decreases as the thickness of the protective increases. Among the three types of protective coatings used, HfO2 material has the potential to be used because it has the best injection efficiency value.

The frost restraining effect of solar air collector applied to air source heat pump

The air source heat pump has been demonstrated to be an efficient clean space heating technology, but the frosting on the exterior surface of the evaporator will largely decrease its performance. In this paper, the triangular solar air collector is adopted for evaporator frost restraint of the air source heat pump, and the dynamic heat transfer model of the triangular solar air collector and quasi-steady-state frosting model of the evaporator were established and coupled. The effect of frost layer thickness variation on evaporator air flow is considered based on the resistance factor to improve the applicability of the model. The heat flux and water vapor diffusion flux at different frost time and frost thickness were calculated, and the frosting characteristics of the air source heat pump with the triangular solar air collector and the conventional air source heat pump were compared on varying working conditions and typical daily meteorological parameters. Results show that triangular solar air collector can effectively restrain the frosting of the air source heat pump, and when the solar irradiance is 500 W/m2, the triangular solar air collector can reduce the frost thickness by more than 15 %. The triangular solar air collector increases the total heat flux by 101.4 W/m2 under frosting conditions, which reduces half of the defrosting times and increases the heat exchange of the evaporator by 36.6 % during a typical day, indicating that triangular solar air collector significantly improved the energy efficiency of air source heat pump on frosting condition.

МОДЕЛИРОВАНИЕ ТЕМПЕРАТУРНОГО РАСПРЕДЕЛЕНИЯ НА ПЕРЕДНЕЙ ПОВЕРХНОСТИ ТОКАРНОГО РЕЗЦА С УЧЁТОМ ГЕОМЕТРИЧЕСКИХ ПАРАМЕТРОВ ЗОНЫ ВТОРИЧНЫХ ПЛАСТИЧЕСКИХ ДЕФОРМАЦИЙ

The study objective: modeling of the temperature distribution along the front surface of the lathe cutter for a given moment of the cutting system evolution.
 The problem to which the paper is devoted. To evaluate the influence of the geometric parameters of the secondary plastic zone of on the characteristics of the temperature distribution for the front surface of the lathe cutter. 
 Research methods. Geometric parameters of the plastically deformed layer are defined by digital modeling of contact processes by the finite element method. Some initial data for computer modeling and subsequent verification of its results are carried out on the basis of a full-scale experiment with longitudinal turning of a work piece made of stainless steel 12X18H9T with a T15K6 solid-alloy plate.
 The novelty of the work. Prediction of the temperature on the cutter front surface for a given moment of the cutting system evolution based on a scientific approach of using hydrodynamic analogies to the evaluation of deformation processes in the machined material and combined data of a full-scale and digital experiment. 
 The study results. By means of a digital experiment, the boundaries of the secondary plastic zone in the chip are determined, then a temperature distribution curve is made on the cutter front surface in two variants: for variable and for a constant average thickness of the deformed layer. It is found that the average value of the contact temperature in both cases differs slightly and agrees well with the results of the full-scale experiment. The difference between the maximum temperature values is significant: with a variable layer thickness, the calculated temperature is 11% lower than for the variant with a constant value of this parameter. 
 Conclusions: to calculate the average temperature in the secondary plastic zone, the average value of the deformed layer thickness can be used. In the case of solving problems related to determining the maximum temperature in the cutting zone, it is advisable to take into account the change in the thickness of the plastically deformed layer in the chip along the cutter front surface.

Optimasi Parameter Produk 3D Printing Terhadap Kekuatan Bending Dengan Menggunakan Filamen Nylon

3D Printing or additive manufacturing is a new technology for the industry. The machine has created an object for 3D layer by layer that makes a product with accurate dimensions and certain patterns, as the technology developed, the manufacturing industry began to develop products using additive material methods known as rapid prototyping or layer manufacturing, one of which was the use of 3D printer technology. This research was conducted on a 3D Printing FDM model Ender 3 Pro with dimensions 220 mm x 220 mm x 250 mm and using a nozzle with a 0,4 mm diameter. The material for this research is Nylon 6 with a diameter of 1,75 mm with variations in Layer Thickness (0,21 mm 0,24mm 0,27 mm), Infill Pattern (Rectilinear, Grid, Wiggle), Z-Orientation (0°,15°,30°) which will be determined in Ultimaker Cura 4.4.0 software and Taguchi Method in software minitab19.1. resulting in OA L9 with 3 times replication printed sample. The results obtained after testing the highest bending stress values are found in the 9th specimen which is 16,7 MPa average with 0,27 Layer Thickness, Wiggle Infill Pattern, and 15° Z-Orientation. While the lowest bending stress values are found in the 4th specimen which is 12,7 MPa average with 0,24mm Layer Thickness, Rectilinear Infill Pattern, and 15° Z-Orientation.

Enhance the Properties of BiI3‐Based Resistive Switching Devices via Mixing Ag and Au Electrodes

AbstractThe correlation between the electrodes and the properties of the BiI3 device is systematically investigated. The X‐ray and UV photoemission spectroscopies are carried out to study the chemical state and electronic structure of the metal/BiI3 interfaces formed by the in‐situ deposition of BiI3 on the metal. This revealed the upward diffusion of Ag and the self‐formation of a conductive filament; the latter is further confirmed via tunneling electron microscopy. By coating the Au substrate with Ag layers of various thicknesses as a buffer layer, the morphology, surface roughness, chemical states, and quantity of the filament in the BiI3 layer can be manipulated. The device with the structure of Au/10 nm Ag/BiI3/Au demonstrated an ultrahigh on/off ratio of 109, good retention of 104 s, and multistate data storage. This study provides not only a fundamental insight into the interaction of BiI3 with metal, which will be helpful to design resistive switching devices and optoelectronics based on BiI3 material, but also a facile method to control the quantity of conductive filament in the BiI3 layer.

Impact of Platinum Loading and Layer Thickness on Cathode Catalyst Degradation in PEM Fuel Cells

In this work we investigate the effect of platinum loading and layer thickness on cathode catalyst degradation by a comprehensive in situ and STEM-EDS characterization. To decouple the effect of the platinum loading and layer thickness from each other, the experiments were categorized in two sets, each with cathode loadings varying between 0.1 and 0.4 mgPt cm−2: (i) Samples with a constant Pt/C ratio and thus varying layer thickness, and (ii) samples with varying Pt/C ratios, achieved by dilution with bare carbon, to maintain a constant layer thickness at different platinum loadings. Every MEA was subjected to an accelerated stress test, where the cell was operated for 45,000 cycles between 0.6 and 0.95 V. Regardless of the Pt/C ratio, a higher relative loss in electrochemically active surface area was measured for lower Pt loadings. STEM-EDS measurements showed that Pt was mainly lost close to the cathode—membrane interface by the concentration driven Pt2+ ion flux into the membrane. The size of this Pt-depletion zone has shown to be independent on the overall Pt loading and layer thickness, hence causing higher relative Pt loss in low thickness electrodes, as the depletion zone accounts for a larger fraction of the catalyst layer.

Analysis of the ionic and dielectric properties of perovskites by impedance spectroscopy

For understanding the operation of perovskite solar cells and light-emitting diodes, knowledge of the dielectric properties is indispensable. The dielectric properties of perovskites are frequency dependent due to the presence of moving ions, which complicates the interpretation of impedance spectra. Using Au/CsPbI2Br/Au capacitors with varied layer thickness as a model system, we demonstrate that in the dark, an extended Maxwell circuit consistently describes the impedance data. From the thickness dependence of the resistivities, both the electronic and ionic conductivities are obtained, whereas the combination of electronic and ionic capacitances with the characteristic frequencies for space-charge formation determines the ion diffusion coefficient and ion density. At low frequencies, a slow transient process with a fixed time constant of ∼0.1 s occurs, governed by the electronic conductivity, being independent of illumination strength and sample thickness. As a possible mechanism, we propose the spatial reorganization of ions within the ion accumulation layer at the electrode/perovskite interface.

Plane problems of multiple interactions of rigid punches and bodies with complex multilayer coatings

The article deals with the most general formulation of the problem of the interaction of a system of rigid punches and a viscoelastic aging foundation covered by several different nonuniform thin layers of variable thickness. It is shown that the mathematical model of such a problem is a system of mixed integral equations with additional integral conditions. On the basis of a special approach described in present article, an analytical solution is obtained in series for various versions of the problem statement. It is indicated that the obtained solution representation is effective even in the case when the properties of the coating layers and the shape of the contacting surfaces are described by complex functions.

Study on Controlling Residual Stress in Thick Copper Film for Heat Sink Using Graphene

Nowadays, high-density electronic devices and component mounting have gained popularity. Because of the heat generated from these devices, efficiency of the electronic parts is significantly lowered and life time of these devices is considerably shortened. Therefore, it is very important to efficiently dissipate the heat generated from the device to extend product. In this study, a copper thick film was deposited using a sputtering technique using plasma. In addition, graphene, a two-dimensional nanomaterial, was inserted in the form of a sandwich structure between the deposited copper (Cu) layers of various thicknesses. Through this, a study was conducted to control the residual stress of thick copper foil deposited by sputtering. In this study, the residual stress was measured according to the location where graphene was inserted, the treatment method, and the transfer area. As a result, the highest residual stress reduction effect was observed when the transfer area of graphene was about 70%. Reduction of residual stress was observed by inserting graphene into the deposited copper thick film of various thicknesses. In addition, by increasing the number of layers of graphene inserted, changes in residual stress were observed.

Synergistic effects of the use of metakaolin, sand and water on the properties of cementitious composites for 3D printing

3D concrete printing (3DCP) is a construction technique based on the deposition of successive layers of a cementitious composite without the need for conventional formwork. For the technique to be applied it is necessary that the cementitious composite used allows the passage in continuous flow in a 3D printing nozzle (extrusion capacity) and presents low deformation of the printed layers (buildability). In this perspective, the aim of this study was to understand the influence of Metakaolin (MK), sand and water incorporation on the extrusion capabilities and buildability of cementitious composites for 3D printing. The analysis was designed in a simplex lattice mixture statistical experimental planning. Extrusion ability was evaluated using an experimental flow rate by extruder mill and slump flow. Buildability was analyzed by the maximum number of printed layers, shape retention index, layer thickness variation, and squareness deviation in printed blocks. The squeeze flow test was carried out as a parameter for both printing properties. The water/binder ratio was the most determinant variable in extrusion capacity for its responsibility to fluidize the mixture. Increasing the sand content improves buildability but reduces the application time. On the other hand, MK presented the advantage of controlling viscosity and maintaining good fluidity over time, due to a slower setting. There was a significant interaction between sand and MK in the packing of grains, increasing the properties related to extrusion. It was possible to print with a 30% MK content by adjusting the water. The yield stress was directly related to the flow rate, validating the experimental methodology created. Thus, it was possible to understand the effect of each component, as well as their interactions.

Manipulating the Micromagnetic Structure of Multiphase CoPt Thin Films by Varying Layer Thicknesses

The magnetic properties and micromagnetic structure of [Co/Pt]10 multilayer magnetic films formed by independent variation of the Co and Pt layer thicknesses have been studied. The possibility of the film magnetization parameters manipulation was shown. It is found that the micromagnetic structure of the layers is significantly modified with a change in the thickness of the layers which correlates with the magnetization data. In particular, magnetic force microscopy revealed a system of magnetic skyrmions for a number of structures. The skyrmion density was found to be dependent on the growth conditions which in turn correlates with the shape of the magnetic hysteresis loop. Changing the thickness of the Co and Pt layers makes it possible to control the density of skyrmions in the range from 0.2 to 10.5 mkm-2. Keywords: micromagnetic structure, skyrmions, CoPt films, electron beam evaporation.

Investigation of persistent photoconductance and related electron mobility in thin IGZO layers with the PDL Hall technique

Indium gallium zinc oxide (IGZO) is a popular material to fabricate thin-film transistors (TFT). The light induced long-term conductance change in the thin IGZO layers (known as persistent photoconductance, PPC) is a significant phenomenon that should be deeply understood and controlled. We used the Parallel dipole line (PDL) AC Hall measurement technique to study the light induced change of the conductance and mobility of charge carriers in IGZO layers and its relaxation in dark. In the PDL systems rotating permanent magnets are applied to realize the AC Hall measurement at large magnetic field with harmonic modulation in a very compact design. Several samples with varying layer thickness, composition, and passivation conditions were prepared to investigate the PPC phenomenon. The magnitude and relaxation of PPC show a very strong dependence on IGZO preparation conditions. In some samples over tenfold conductance increase was observed at room temperature. Relaxations times varied from a few hours up to a few days. An interesting observation was that the mobility (in the range of 1 cm2/Vs-8.9 cm2/Vs) also increases with the conductance as the result of illumination.

DC pulsed plasma magnetron sputtering of CdO/Cu/CdO multilayers thin films for self-cleaning and optoelectronic applications

In this study, CdO/Cu/CdO multilayers thin films were organized on glass substrates with different Cu intermetallic layer thickness engaging DC plasma magnetron sputtering. The optoelectronic properties and structural characteristics of the multilayers at various Cu intermetallic layer thicknesses which were varied from 4 to 16 nm were explored. The calculated band gap was reduced from 2.66 eV to 2.48 eV as the Cu intermetallic layer thickness increased from 4 to 16 nm. The refractive index and coefficient of extinction of CdO/Cu/CdO multilayers increased with increasing the Cu intermetallic layer thickness. The resistivity is reduced from 1.8 × 10−2 Ω cm for CdO single layer to reach a value of 2.7 × 10−4 Ω cm for CdO/Cu (16 nm)/CdO multilayer. Further, the sheet resistance is decreased from 1000 to 13.8 Ω/sq. with the variation in Cu intermetallic layer thickness from 0 to 16 nm. CdO/Cu (4 nm)/CdO multilayer film recorded the best figure of merit (2.3 × 10−4 Ω−1). After sunlight illumination for the multilayers, the surface wettability was improved and the contact angle recorded lowest value of nearly 24° for CdO/Cu (8 nm)/CdO and CdO/Cu (12 nm)/CdO.

Study on the Seismic Effect of the Pebble Soil Site in the Zhongwei Basin

Based on a large amount of drilling and geophysical exploration work in the Zhongwei Basin, and combined with the collected borehole data of a seismic safety assessment, this paper summarizes and builds 16 typical pebble soil layer calculation models. The effects of the thickness of the pebble layer, the thickness of the overlying silty clay, the top interface of the pebble layer on the peak acceleration and the response spectrum of the site seismic response were analyzed using the equivalent linearization method of the one-dimensional soil layer seismic response. The analysis results showed that the variation in pebble layer thickness had no obvious effect on the peak acceleration of the ground surface under different inputs; the influence of the pebble layer thickness on the ground acceleration response spectrum was primarily concentrated in the middle/high-frequency band of 0.2–0.6 s. Within this range, the acceleration response spectrum of the site with a 30 m pebble layer thickness was small, and the response spectrum curve showed a “trough” shape with a certain “weak isolation” effect. Under the same pebble layer thickness, the upper ground surface peak acceleration with a silty clay layer thickness increased with the increase in the central basin pebble soil field, where a short cycle of the seismic wave amplification effect was more obvious. The response spectrum peak period points were within 0.1–0.2 s and were influenced by the action of rare earthquakes. Moreover, the response spectrum curve showed a more obvious phenomenon of “twin peaks”, and the second peak point appeared in the period of 0.5–0.7 s. With the increase in the input intensity, the PGA amplification ratio of the pebble-top interface was significantly smaller than that of the site surface; under different intensities of input, the acceleration response spectrum of the pebble-top interface showed a “trough” phenomenon that was lower than the bedrock input at approximately 0.1 s. Under the action of rare ground motion, the acceleration response spectrum curve of the pebble-top interface showed a “double peak” phenomenon, and within 0.24–0.4 s, the spectrum value was lower than the bedrock input, showing an obvious shock absorption and isolation effect. Under the action of an earthquake, the energy of the pebble-top interface was concentrated in the low-frequency range of 1.1–2.2 Hz, and the amplification effect was obvious. In the range of 8–10 Hz, the amplitude was lower than the bedrock input, and the seismic isolation effect was obvious.

Studying the effect of space radiation induced defects in multijunction solar cell using APSYS simulation software and comparison with the experimental data

In this paper, the state-of-the-art triple junction solar cell with three sub cells and two tunnel diodes is modeled using two dimensional (2D) APSYS finite element analysis software tool. The effect of electron radiation at 1 MeV and 10 MeV energies for different fluences are investigated by introducing different trap levels, trap states and trap concentrations in InGaP top and InGaAs middle sub cells. Two different structures are modeled by varying layer thickness of base and emitter of both top and middle sub cells to understand its effect on the electrical parameters and efficiency of the solar cell. The main indicative parameters - trap concentration and carrier lifetime is affected by the radiation resulting in alteration of electrical performance of solar cells. The radiation induced defects cause permanent damage to the solar cell structure and degrades the electrical performance of solar cells until its end of life (EOL). In this work, APSYS software tool is used to model radiation induced traps with different trap concentrations, generated the electrical parameters and compared with the experimental results. The results obtained from simulation are in good agreement with the experimental data. Probable traps, trap concentrations and carrier lifetime for different electron radiation energies and fluences were extracted by simulation, which can prove to be difficult to perform experimentally as only a few methods like deep level trap spectroscopy and deep level optical spectroscopy exist for deep level trap studies. This study can therefore save valuable R&D time and cost..

Numerical Study of CiS Solar Cell with CuInSe2‐Undoped Layer

Herein, a CuInSe2 thin film solar cell with an intrinsic thin layer (HIT) is modeled and simulated using SCAPS. The HIT is deposited between a thin CdS window layer of reduced thickness of 20 nm to minimize cadmium toxicity and an absorbing layer of variable thickness. The aim is to study the influence of the thickness of absorber and HIT layer, level doping and defect densities of CuInSe2 layer, and high work function (between 5 and 5.6 eV) effect on performance parameters of the solar cell. In general, a significant increase in efficiency is observed. The HIT and the absorber thicknesses are optimized to be 0.3 and 0.5 μm, respectively. A conversion efficiency of 24.2%, a V oc of 0.78 V, J sc of 45.4 mA cm−2, and an FF of 68.3% are obtained for the proposed AZO/ZnO/CdS/CuInSe2/Mo/glass. These simulation results encourage using intrinsic thin layers in CIS solar cell structure.

Assessment of visual function and the neuroretina in subjects diagnosed with colour blindness

AbstractPurpose: To assess whether the existence of colour vision deficiency or colour blindness involves impairment of visual acuity, contrast sensitivity and colour vision and results in variations in retinal nerve fibre layer (RNFL) thickness, macular area, retinal ganglion cell complex and retinal layers that contain photoreceptors (bastons and cones) versus subjects with normal colour vision within the same age and gender distribution.Methods: Cross‐sectional and observational study including 50 eyes of subjects with colour blindness and 50 eyes of control subjects. Visual function (visual acuity, contrast sensitivity and colour vision) and neuroretinal structure were assessed in all subjects using optical coherence tomography (OCT).Results: Significant thinning of the retinal nerve fibre layer, ganglion cell layer and retina were observed in the colour blindness group. Significant thinning was also recorded in layers that involve photoreceptor nuclei (between the outer limiting layer and the Bruch membrane and between the outer plexiform layer and the outer limiting membrane).Conclusions: Significantly reduced thicknesses in the RNFL and several retinal layers (ganglion cell and photoreceptor layers) were found, demonstrating that colour blindness is associated with thinning in retinal and RNFL thickness, and in the retinal layers that involve photoreceptor nuclei. OCT study with retinal segmentation therefore seems to be a marker of colour blindness of utility in clinical practice in the case of doubt regarding diagnosis. This analysis could be useful in evaluating the effectiveness of potential therapies such as gene treatment.

Systematic Control of the Interlayer Exchange Coupling in Perpendicularly Magnetized Synthetic Antiferromagnets

Controlling the interlayer exchange coupling in synthetic antiferromagnets (SAFs) is crucial for realizing spintronic phenomena and devices. Here researchers investigate such control in Pt/Co/Ru/Fe${}_{0.55}$Tb${}_{0.45}$ by tuning the thicknesses of various layers. Complementary measurements using three techniques show that SAFs with different magnetization-reversal characteristics may be clearly resolved. The results suggest that the interlayer exchange coupling may be tuned effectively in this manner, which could be quite useful for designing SAF-based magnetic memory or sensing devices.