Single-layer Configuration Research Articles

Investigation of heave response of the deepwater octagonal FDPSO using various heave plate configurations

Heave plates can be employed to control undesirable heave motion amplitudes of the deepwater octagonal Floating, Drilling, Production, Storage, and Offloading (FDPSO) platform. Numerical simulations and model tests were applied to analyze and investigate the hydrodynamic response and the feasibility of the heave plate configurations. The diameter and the depth below the free surface of a single-layer heave plate, as well as the spacing of two-layer heave plates, were considered as the primary variables when studying the effect of heave plates on FDPSO hydrodynamics. The analysis results indicate that the heave plate diameter significantly affects the heave hydrodynamics, and heave performance could be improved with an increased diameter. In addition, increasing the depth below the free surface of a single-layer heave plate does not effectively suppress the heave motion within the range of draft depths tested. The target FDPSO obtained better heave characteristics with increased spacing between the two-layer heave plates. Furthermore, the global performances of the octagonal FDPSO with these typical heave plate configurations were comparatively analyzed. The results indicate that from a hydrodynamic point of view, the single-layer heave plate configuration has an advantage over the two-layer heave plate configuration.

Numerical and experimental evaluation and optimization of ceramic foam as solar absorber – Single-layer vs multi-layer configurations

This work targets the numerical and experimental evaluation of ceramic foam as solar absorber material for solar thermal power generation. Two different 1-D model types with local thermal non-equilibrium (LTNE) have been developed independently at CENER and Fraunhofer-IKTS. The modeling of radiation propagation inside the foam is considered via two approaches. One approach is based on a discrete-ordinate solution of the radiation transport equation; the other imposes the solar flux defining an exponential attenuation, as derived from Bouguer’s law, and considering thermal radiation transport according to Rosseland’s diffusion approximation.Both models have been successfully checked for consistency against experimental data obtained at a 4 kW solar simulator. Then, the models have been run applying automatic scripts, performing a large number of parameter variations, optimizing for the absorber thermal efficiency. It is important to note that single, double and triple layer absorber configurations have been studied, since previous works found that a decreasing porosity in direction of flow can enhance absorber performance.The parametric optimization studies have shown that the porosity of the foam is strongly related to the obtained thermal efficiency. The higher the porosity of the foam, the higher is also the absorber thermal efficiency. A broad plateau-like efficiency maximum can be observed for cell densities between 30 and 50 PPI (pores per inch). When applying a multi-layer configuration, no significant correlation can be observed between efficiency and the properties of the second or third layer. Only the parameters of the first layer seem to determine the thermal performance. This leads to the conclusion that an optimized single-layer configuration is the absorber of choice. If necessary, a second layer could be applied to satisfy mechanical stability aspects.

A 60 GHz Horizontally Polarized Magnetoelectric Dipole Antenna Array With 2-D Multibeam Endfire Radiation

A novel substrate integrated waveguide (SIW) fed horizontally polarized endfire magnetoelectric (ME) dipole antenna composed of an open-ended SIW with broad walls vertical to substrates and a pair of electric dipoles realized by four metallic patches is proposed. Simple configuration and excellent performance including an impedance bandwidth of 46.5%, stable gain of around 6 dBi, and symmetrical cardioid radiation patterns with low backward radiation and low cross polarizations are achieved. An SIW 90° twist integrated in three-layered substrate is implemented in order to connect the ME-dipole antenna conveniently to the SIW beam-forming network with broad walls parallel to substrates. A $4 \times 4$ SIW Butler matrix with a three-layered zigzag topology is then designed, which enables a size reduction of 45% for the matrix compared with conventional single-layered configuration but not affecting its operating characteristics. By employing a $2 \times 4$ ME-dipole array with 90° twists, two-folded Butler matrices and four SIW 3 dB E-plane couplers, a multibeam endfire array that can radiate eight beams scanning in two dimensions is designed at the 60 GHz band. The fabricated prototype verifies that a wide impedance bandwidth of 22.1%, gain varying from 10 to 13 dBi and stable radiation beams can be obtained. Due to good performance and the compact structure with low fabrication costs, the proposed design would be attractive for future millimeter-wave wireless applications including 5G communications and the WiGig system.

A numerical analysis of a magnetocaloric refrigerator with a 16-layer regenerator

A numerical analysis was conducted to study a room temperature magnetocaloric refrigerator with a 16-layer parallel plates active magnetic regenerator (AMR). Sixteen layers of LaFeMnSiH having different Curie temperatures were employed as magnetocaloric material (MCM) in the regenerator. Measured properties data was used. A transient one dimensional (1D) model was employed, in which a unique numerical method was developed to significantly accelerate the simulation speed of the multi-layer AMR system. As a result, the computation speed of a multi-layer AMR case was very close to the single-layer configuration. The performance of the 16-layer AMR system in different frequencies and utilizations has been investigated using this model. To optimize the layer length distribution of the 16-layer MCMs in the regenerator, a set of 137 simulations with different MCM distributions based on the Design of Experiments (DoE) method was conducted and the results were analyzed. The results show that the 16-layer AMR system can operate up to 84% of Carnot cycle COP at a temperature span of 41 K, which cannot be obtained using an AMR with fewer layers. The DoE results indicate that for a 16-layer AMR system, the uniform distribution is very close to the optimized design.

Effect of different mini-volume colloid centrifugation configurations on flow cytometrically sorted sperm recovery efficiency and quality using a computer-assisted semen analyzer.

Straws of sex-sorted sperm are usually packaged at a low concentration (e.g., ~2.1×106 sperm/ml) and cost significantly more than unsorted conventional semen from the same sire. In order to maximize the efficiency of using sex-sorted sperm under in vitro fertilization conditions, the selection of an appropriate sperm separation technique is essential. In this study, the effect of using different silane-coated silica colloid dilutions and layering configurations during centrifugation of sex-sorted sperm was examined over an extended period of incubation time. Sperm recovery and viability after centrifugation using the colloid separation technique were measured along with several sperm motility parameters using CASA. For this purpose, frozen and thawed sex-sorted sperm samples were centrifuged using mini-volume single-layer (40%, 60% and 80%) and mini-volume two-layer (45%/90%, 40%/80% and 30%/60%) separation configurations using PureSperm® . A single layer of 40% PureSperm® recovered significantly more sex-sorted sperm (78.07%±2.28%) followed by a single layer of 80% PureSperm® (68.43%±2.33%). The lowest sperm recovery was obtained using a two-layer PureSperm® dilution of 45%/90% (47.57%±2.33%). Single-layer centrifugation recovered more sorted sperm (68.67%±1.74%) than two layer (53.74%±1.74%) (p<.0001). A single layer of 80% PureSperm® exhibited the highest sorted sperm viability (72.01%±2.90%) after centrifugation (p<.05). The mini-volume single layer of 80% PureSperm® was determined to be an effective alternative to a two-layer centrifugation configuration for sex-sorted sperm selection. In addition, single-layer colloid dilution of 80% performed either as well as or significantly outperformed the other treatments, as well as the control, with regard to motility (MOT) for all time periods of analysis.

Modification of the contact surfaces for improving the puncture resistance of laminar structures

Uncovering energy absorption and surface effects of various penetrating velocities on laminar structures is essential for designing protective structures. In this study, both quasi-static and dynamic penetration tests were systematical conducted on the front surfaces of metal sheets coated with a graphene oxide (GO) solution and other media. The addition of a GO fluid film to the front impact surface aided in increasing the penetration strength, improving the failure extension and dissipating additional energy under a wide-range of indentation velocity, from 3.33 × 10−5 m/s to 4.42 m/s. The coated -surfaces improved the specific energy dissipation by approximately 15~40% relative to the dry-contact configuration for both single-layer and double-layer configurations, and specific energy dissipations of double-layer configurations were 20~30% higher than those of the single-layer configurations. This treatment provides a facile strategy in changing the contact state for improving the failure load and dissipate additional energy.

Note: Mechanical in situ exfoliation of van der Waals materials.

Exfoliation, namely, the peeling of layered materials down to a single unit-cell thin foil, opens promising avenues to fabricate novel electronic materials. New properties and original functionalities emerge in the single and few layer configurations of a number of layered compounds, in particular in transition metal dichalcogenides. However, many of these thin exfoliated materials are very sensitive to ambient conditions impeding the exploration of this new and fascinating parameter space. Here we describe a method of mechanical exfoliation in ultra-high vacuum (UHV). This technique is easily adaptable to any UHV system and allows preparing and studying air sensitive nanoflakes in situ. We present the basic design and proof-of-concept scanning tunneling microscopy imaging of VSe2 nanoflakes.

Giant edge spin accumulation in a symmetric quantum well with two subbands

We have studied the edge spin accumulation due to an electric current in a high mobility two-dimensional electron gas formed in a symmetric well with two subbands. This study is strongly motivated by the recent experiment of Hernandez et al. (Phys. Rev. B, 88 (2013) 161305(R)) who demonstrated the spin accumulation near the edges of a symmetric bilayer GaAs structure in contrast to no effect in a single-layer configuration. The intrinsic mechanism of the spin-orbit (SO) interaction we consider arises from the coupling between two subband states of opposite parities. We obtain a parametrically large magnitude of the edge spin density for a two-subband well as compared to the usual single-subband structure. We show that the presence of a gap in the system, i.e., the energy separation Δ between the two subband bottoms, changes drastically the picture of the edge spin accumulation. The gap value governs the effective strength of the inter-subband SO interaction which provides a controllable crossover from the regime of weak spin accumulation to the regime of the strong one by varying the Fermi energy (electron density) and/or Δ. We estimate that by changing the gap Δ from zero up to 1–2 K, the magnitude of the effect changes by three orders of magnitude. This opens up the possibility for the design of new spintronic devices.

Multi-layer PCM solidification in a finned triplex tube considering natural convection

Efficient latent heat storage systems represent an important opportunity to improve the thermal performance and operational capability of industrial systems (e.g. solar thermal). In this paper, numerical study is performed to evaluate the heat transfer and solidification features, phase change period and temperature distribution of double-layer Phase Changing Materials (PCM) in a finned triplex tube. A two-dimensional finite volume numerical technique is used to solve the governing equations considering conduction and convection heat transfer mechanisms at a fixed Rayleigh number of 106. After comparing the results for single and double layer configurations, possible arrangements of two different PCMs are discussed in terms of different thicknesses of each PCM, fin sizes and different heat transfer fluid temperatures. Results are illustrated as the form of temperature, liquid fraction, stream function and velocity magnitude contours and their changes over the freezing time. Variation of liquid fraction values, average and minimum temperatures of layers in a double-layer PCM are reported for better insight into the heat transfer features of the latent heat thermal energy storage system to enable uniform discharging designs and balance the phase changing rate within the whole annulus.

A Novel Surface-Wave-Based High-Impedance Surface Multibeam Antenna With Full Azimuth Coverage

This paper presents a novel surface-wave (SW)-based high-impedance surface (HIS) multibeam antenna with 360° scanning capability in azimuth. The proposed antenna consists of four rotationally symmetric beamforming networks (BFNs) and a microstrip patch array-based HIS. Regarding to the BFN, it is formed by a planar offset parabolic reflector fed by multiple substrate integrated waveguides. Through proper design, the proposed BFN can efficiently launch guided SWs with TM0 mode. With the perturbation of the HIS structure, the bounded SWs can be transformed to $m=-1$ space harmonic mode leaky-wave radiation. Combining the feature of the leaky-wave radiation in the elevation plane and the manipulation of the propagation direction of the SWs by switching the feeding ports, beam scanning in the azimuth direction with a tilted elevation angle can be realized. As the HIS is shared by the four BFNs, the size of the antenna can be reduced and a broadened antenna scanning range is achieved. In this paper, a prototype of the proposed antenna with 28 feeding ports, 7 in each BFN, is numerically analyzed and experimentally demonstrated. The proposed antenna features low-cost, low-profile, and single layer configuration.

Current Rectification through Vertical Heterojunctions between Two Single-Layer Dichalcogenides (WSe2|MoS2 pn-Junctions).

We form junctions between two single layers of p-type WSe2 and n-type MoS2 in both sequences. The WSe2|MoS2 and MoS2|WSe2 junctions of ultimate thickness limit exhibit current rectification when characterized vertically with a scanning tunneling microscope (STM) tip. The direction of rectification in the pn-junction is opposite to that of the np-junction, confirming occurrence of the rectification to be due to the junctions themselves. From scanning tunneling spectroscopy (STS) and correspondingly the density of states (DOS), we locate the conduction and valence band edges (CB and VB, respectively) of the materials inferring their single-layer and 2H phase configuration. Band edges of the semiconductors form a type-II band alignment resulting in current rectification. In junctions of WSe2 and MoS2 with single layers having a partial overlap, we map band edges along different points on individual semiconductors and the overlapped region (junction). The results have provided experimental evidence of current rectification through van der Waals vertical heterojunctions between two single layers.

Gain Enhancement in Circular Microstrip Antenna via Linear Superposition of Higher Zeros

This letter presents a single-layer high-gain circular-microstrip antenna configuration. Broadside high gain is attributed to the linear superposition of the radiated fields by TM 12 and TM 14 modes. At first, it is shown by the theory of linear summation of modes that the high E-plane sidelobes in the radiation pattern of the TM 14 mode can be suppressed by adding the contribution of TM 12 mode. This is further confirmed by the simulations and measurements. Next, a simple single-layer circular-microstrip antenna configuration with a measured peak gain of 15 dBi and sidelobe level of -11 dB is presented.

Simulation and Measurement of the Current Density Distribution in Lithium-Ion Batteries by a Multi-Tab Cell Approach

A single-layered NMC/graphite pouch cell is investigated by means of differential local potential measurements during various operation scenarios. 44 tabs in total allow for a highly resolved potential measurement along the electrodes whilst the single layer configuration guarantees the absence of superimposed thermal gradients. By applying a multi-dimensional model framework to this cell, the current density and SOC distribution are analyzed quantitatively. The study is performed for four C-rates (0.1C, 0.5C, 1C, 2C) at three temperatures (5°C, 25°C, 40°C). The maximum potential drop as well the corresponding SOC deviation are characterized. The results indicate that cell inhomogeneity is positively coupled to temperature, i.e. the lower the temperature, the more uniform the electrodes will be utilized.

Silicon carbide based surface plasmon resonance waveguide sensor with a bimetallic layer for improved sensitivity

In this letter, silicon carbide (SiC) waveguide based surface plasmon resonance optical sensor with an Ag-Au bilayer metal configuration was studied. The wide bandgap energy of SiC allows the sensor to operate in visible and near-infrared range. The spectrum of resonant wavelength with refractive index shows improved sensitivity and sensing resolution in the Au-Ag bilayer configuration than in the single Au layer configuration. A sensitivity of 2581nm/RIU (refractive index unit) indicated by the shift of resonant wavelength with refractive index was observed from a refractive index range of n=1.34–1.36, showing that the sensor is desirable for sensing in a series of biological analytes interesting to research, such as Hepatitis B virus (HBV), glucose, etc.

Sandwich-structured polymer nanocomposites with high energy density and great charge–discharge efficiency at elevated temperatures

The demand for a new generation of high-temperature dielectric materials toward capacitive energy storage has been driven by the rise of high-power applications such as electric vehicles, aircraft, and pulsed power systems where the power electronics are exposed to elevated temperatures. Polymer dielectrics are characterized by being lightweight, and their scalability, mechanical flexibility, high dielectric strength, and great reliability, but they are limited to relatively low operating temperatures. The existing polymer nanocomposite-based dielectrics with a limited energy density at high temperatures also present a major barrier to achieving significant reductions in size and weight of energy devices. Here we report the sandwich structures as an efficient route to high-temperature dielectric polymer nanocomposites that simultaneously possess high dielectric constant and low dielectric loss. In contrast to the conventional single-layer configuration, the rationally designed sandwich-structured polymer nanocomposites are capable of integrating the complementary properties of spatially organized multicomponents in a synergistic fashion to raise dielectric constant, and subsequently greatly improve discharged energy densities while retaining low loss and high charge-discharge efficiency at elevated temperatures. At 150 °C and 200 MV m(-1), an operating condition toward electric vehicle applications, the sandwich-structured polymer nanocomposites outperform the state-of-the-art polymer-based dielectrics in terms of energy density, power density, charge-discharge efficiency, and cyclability. The excellent dielectric and capacitive properties of the polymer nanocomposites may pave a way for widespread applications in modern electronics and power modules where harsh operating conditions are present.

Modeling and experimental analysis of polypropylene honeycomb multi-layer sandwich composites under four-point bending

The behavior of a simple and innovative multi-layer sandwich panels having a polypropylene honeycomb core has been investigated carefully, theoretically and experimentally. A four-point bending test was performed to detect the mechanical characteristics of the multi-layer core. The experimental results emphasize a better rigidity of the multi-layer structure compared to the weakness displayed by the single-layer configuration. In fact, a small increase in the final weight of the component leads to a significant increase of the mechanical properties. In the second part of this study, analytical and numerical homogenization approaches were developed to compute the effective properties of the single polypropylene honeycomb core. The numerical model complies with the experimental protocol, and the simulation conducted is aiming to reproduce a typical four-point bending test on a polypropylene honeycomb multi-layer sandwich panel. Both numerical and experimental results are presented in details and a good correlation between them is highlighted.

Mechanical properties and tribological behavior at micro and macro-scale of WC/WCN/W hierarchical multilayer coatings

It is known that a hierarchical configuration helps to improve adhesion to the substrate and reduce the effects that generate a sharp change in a conventional multilayer coating, like interface stresses. We present a study of the mechanical properties and tribological behavior at the micro and macro scale of WC/WCN/W multilayer coatings deposited by magnetron sputtering, combining soft and hard layers with a hierarchical architecture. Variations in the number of layers and thicknesses, as well as the distribution within the coating are determinant to obtain the adequate mechanical properties in order to reduce the wear rate. It was found that the coating with high hierarchical configuration presented lower wear rates, in comparison to single layer and low hierarchical configuration coatings.

SPR based fiber-optic sensor with enhanced electric field intensity and figure of merit using different single and bimetallic configurations

We present numerical simulations of electric field intensity, sensitivity and figure of merit (FOM) for different single and bimetallic configured surface plasmon resonance (SPR) fiber optic sensors. The metals considered are gold (Au), silver (Ag), copper (Cu) and aluminum (Al). The overall performance of the sensor is evaluated in terms of electric field intensity, sensitivity, FOM, chemical stability and the cost of fabrication of the sensor. More specifically, in terms of the sensing parameters, Al and Cu bimetallic configuration is found to be much better than the single and the other bimetallic configured sensors. The bimetallic configuration of Al and Cu for fiber optic SPR sensor is also evaluated experimentally. Additionally, the film adhesion capability of both the materials gets improved when used in bimetallic combination which further improves the chemical stability of the sensor; this is a serious problem with Al and Cu in their single layer configuration. The combinations which possess gold as outer layer are more chemically stable but found to be weaker in terms of sensing parameters and cost of fabrication as gold is highly expensive.

Vertically Stacked Multilayer Photonics on Bulk Silicon Toward Three-Dimensional Integration

Vertically stacked hydrogenated amorphous silicon (a-Si:H) and aluminum nitride (AlN) photonic circuits are fabricated on bulk silicon using complementary metal-oxide semiconductor back-end-of-line-compatible technology. The 0.5 μm × 0.22 μm a-Si:H and 1 μm × 0.4 μm AlN channel waveguides exhibit relatively low propagation losses of ∼3.8 and ∼1.4 dB/cm at 1550-nm telecom wavelengths, respectively, thus enabling the realization of various high-performance photonic devices on these two layers, such as multimode interference power splitters, waveguide ring resonators, arrayed-waveguide gratings, etc. In particular, the a-Si:H layer is suitable for ultra-compact thermo-optic (TO) devices because of its large refractive index of ∼3.5 and large TO coefficient (TOC) of ∼2.60 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1 </sup> , whereas the AlN layer is suitable for large-size temperature-insensitive devices because of its relatively small refractive index of ∼2.0 and small TOC of ∼3.56 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−5</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1 </sup> . A cascade directional coupler structure is proposed for connection between these two layers, which provides coupling efficiency of ∼ –1.0 dB, as estimated from numerical simulations. The feasibility of stacking different photonic layers on bulk Si paves the way to realize complex 3-D photonic circuits on chip which are not possible in the conventional single-layer configuration.

Transparent and Flexible Thin Film Electroluminescent Devices Using HiTUS Deposition and Laser Processing Fabrication

Highly transparent thin film electroluminescent structures offering excellent switch on characteristics, high luminance and large break-down voltages have been deposited onto glass and flexible polymeric materials with no substrate heating using high target utilization sputtering. Deposition of ZnS:Mn as the active light emitting layer and Y2O3, Al2O3, Ta2O5, and HfO2 as dielectric materials arranged in single and multiple layer configurations were investigated. Devices incorporating Al2O3, HfO2 quadruple layers demonstrate the highest attainable luminance at low threshold voltage. Single pulse excimer laser irradiation of the phosphor layer prior to deposition of the top dielectric layer enhanced the luminance of the devices. The devices fabricated on glass and polymeric substrates exhibited a maximum luminance of 500 and 450 cdm $^{-2}$ when driven at $270~{\mathrm{ V}}_{\mathrm{ RMS}} $ and $220~{\mathrm{ V}}_{\mathrm{ RMS}} $ , respectively, with a 1.0 kHz sine wave.