Numerical Characterization Research Articles

Building efficient photoelectric properties with Si/Graphene/ZnO interface structure

We perform a numerical evaluation and test characterization on adjusting the bonding of the Si/ZnO interface to improve the photoelectric properties of the Si/ZnO heterojunction. We used Graphene as a buffer layer to perform density functional calculations to investigate the interfacial characteristic and photoelectric characteristic of Si/ZnO and Si/Graphene/ZnO. The results show that the Si–O covalent bond is formed in Si/ZnO interlamination; the Si/Graphene/ZnO interlamination's interaction is Van der Waals force. We detected some interesting phenomena that due to the insertion of Graphene, the valence band of the Si/Graphene/ZnO structure moves to the conduction band, the conductivity of the system is improved, the dominant proportion of Si/Graphene/ZnO in visible light utilization is 74.50 % higher than that of Si/ZnO. It implies a detailed understanding for manipulating the photoelectric properties with Si/Graphene/ZnO structure for getting high effecint photoelectric conversion in solar cell applications. The presence of O atoms at the layer interface also affects the conductivity of heterojunctions. It is proved experimentally that the introduction of Graphene makes ZnO grow better on Si substrate, and improves the photoelectric performance of heterostructures.

Numerical simulation and characterization of high-power gallium nitride based Junctionless Accumulation Mode Nanowire FET (GaN-JAM-NWFET) for small signal high frequency terahertz applications

This paper presents numerical simulation and characterization of high-power Gallium Nitride Junctionless Accumulation Mode Nanowire FET (GaN-JAM-NWFET) which has improved analog performance and is suitable for high-frequency applications. In GaN-JAM-NWFET, GaN and Aluminium Oxide (Al2O3) replace Silicon (Si) and Silicon Oxide (SiO2), respectively. Because of the larger bandgap and strong breakdown field, GaN based devices can handle higher voltages and powers with good carrier transport qualities, which permit a higher driving current than Si devices. Moreover, GaN-JAM-NWFET has a better performance than GaN based Junctionless (JL) NWFET due to the benefit of JAM structure over JL device, having increased carrier mobility in the lightly doped channel. These cumulative benefits of GaN with JAM manifest improvement in drain current, output conductance, subthreshold swing, transconductance, gate capacitance, cut-off frequency, Frequency Transconductance Product (FTP), Gain Frequency Product (GFP), Gain Transconductance Frequency Product (GTFP), intrinsic gain, Unilateral Power Gain (UPG) and Maximum Transducer Power Gain (MTPG) in proposed GaN-JAM-NWFET among GaN-JL-NWFET, Si based JAM NWFET, and Si-JL NWFET devices. The S-parameters such as transmission coefficients (S12 & S21) and reflection coefficients (S11 & S22) also confirm the proposed GaN-JAM-NWFET has better small signal performance than other devices.

Focal-plane wavefront sensing with photonic lanterns II: numerical characterization and optimization

We present numerical characterizations of the wavefront sensing performance for few-mode photonic lantern wavefront sensors (PLWFSs). These characterizations include calculations of the throughput, control space, sensor linearity, and an estimate of the maximum linear reconstruction range for standard and hybrid lanterns with between 3 and 19 ports, at λ=1550nm. We additionally consider the impact of beam-shaping optics and a charge-1 vortex mask placed in the pupil plane. The former is motivated by the application of PLs to high-resolution spectroscopy, which could enable efficient injection into the spectrometer along with simultaneous focal-plane wavefront sensing; similarly, the latter is motivated by the application of PLs to vortex fiber nulling (VFN), which can simultaneously enable wavefront sensing and the nulling of on-axis starlight. Overall, we find that the PLWFS setups tested in this work exhibit good linearity out to ∼0.25−0.5 radians of RMS wavefront error (WFE). Meanwhile, we estimate the maximum amount of WFE that can be handled by these sensors to be around ∼1−2 radians RMS before the sensor response becomes degenerate. In the future, we expect these limits can be pushed further by increasing the number of degrees of freedom, either by adopting higher mode-count lanterns, dispersing lantern outputs, or separating polarizations. Finally, we consider optimization strategies for the design of the PLWFS, which involve both modification of the lantern itself and the use of pre- and post-lantern optics like phase masks and interferometric beam recombiners.

Porosity-permeability tensor relationship of closely and randomly packed fibrous biomaterials and biological tissues: Application to the brain white matter

The constitutive model for the porosity-permeability relationship is a powerful tool to estimate and design the transport properties of porous materials, which has attracted significant attention for the advancement of novel materials. However, in comparison with other materials, biomaterials, especially natural and artificial tissues, have more complex microstructures e.g. high anisotropy, high randomness of cell/fibre dimensions/position and very low porosity. Consequently, a reliable microstructure-permeability relationship of fibrous biomaterials has proven elusive. To fill this gap, we start a mathematical derivation from the fundamental brain white matter (WM) formed by nerve fibres. This is augmented by a numerical characterisation and experimental validations to obtain an anisotropic permeability tensor of the brain WM as a function of the tissue porosity. A versatile microstructure generation software (MicroFiM) for fibrous biomaterial with complex microstructure and low porosity was built accordingly and made freely accessible here. Moreover, we propose an anisotropic poro-hyperelastic model enhanced by the newly defined porosity-permeability tensor relationship which precisely captures the tissues macro-scale permeability changes due to the microstructural deformation in an infusion scenario. The constitutive model, theories and protocols established in this study will both provide improved design strategies to tailor the transport properties of fibrous biomaterials and enable the non-invasive characterisation of the transport properties of biological tissues. This will lead to the provision of better patient-specific medical treatments, such as drug delivery. Statement of significanceDue to the microstructural complexity, a reliable microstructure-permeability relationship of fibrous biomaterials has proven elusive, which hinders our way of tuning the fluid transport property of the biomaterials by directly programming their microstructure. The same problem hinders non-invasive characterisations of fluid transport properties in biological tissues, which can significantly improve the efficiency of treatments e.g. drug delivery, directly from the tissues accessible microstructural information, e.g. porosity. Here, we developed a validated mathematical formulation to link the random microstructure to a fibrous material’s macroscale permeability tensor. This will advance our capability to design complex biomaterials and make it possible to non-invasively characterise the permeability of living tissues for precise treatment planning. The newly established theory and protocol can be easily adapted to various types of fibrous biomaterials.

Significance of plasma-surface interactions in the etch behavior of low-k materials

Low-k materials are an integral component in the advancement of semiconductor device performance by reducing parasitic capacitance and enabling faster device switching for a given thickness compared to traditional dielectric materials such as SiO2. With the advances in logic scaling, low-k materials are increasingly more prominent in the structures of advanced devices. For example, low-k materials are essential as the spacer material to provide both etch selectivity between dielectric materials and electrical isolation in field effect transistors. Consequently, the integration of low-k materials requires that the etch behavior of these materials be well understood so that the device structures can be reliably and reproducibly fabricated. In this study, the authors used a high-density plasma reactor with benchmark CF4- and NF3-based process chemistries to etch low-k materials including SiCN, SiOCN, and SiBCN in addition to Si, SiO2, and SiN reference materials. Numerous characterization techniques were utilized to understand the relationships between the plasma conditions, the evolution of the surface chemistry of the materials, and the resulting etch behavior. These techniques consisted of optical emission spectroscopy, spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and attenuated total reflection Fourier transform infrared spectroscopy. The etch behavior of low-k materials under a given etch process is vital for establishing the etch selectivities in multilayer structures that are required to yield complex device geometries. For example, a directly proportional correlation was observed between the etch rate and intrinsic nitrogen concentration of the low-k materials. Potential mechanisms for the observed etch behaviors were explored using modeling and found that the intrinsic nitrogen composition in the low-k materials can result in energetically favorable reactions that result in the weakening and volatilization of the Si–N bond. Identifying the underlying mechanisms for the etch behaviors of low-k materials will provide key guidance into the development of etch processes that integrate these materials in current and future device structures.

Self-powered retractable reel sensor for crack monitoring and warning in civil infrastructures

Crack occurrence and propagation are among the critical factors that affect the performance and lifespan of civil infrastructure such as bridges, buildings, etc. Therefore, numerous crack detection and characterization techniques have been developed over the past decades. In this study, we proposed the self-powered with the merits of cost-affordable, high resolution, and wide monitoring range to monitor small cracks in infrastructure. The self-powered retractable reel sensor includes two triboelectric nanogenerator (TENG) sensing units for low and high speed fracture monitoring, respectively. By using the principle of retractable reel structure, the linear motion of the crack is converted into the rotation of the TENG. Through peak extraction and pulse counting, the testing of crack velocity and displacement was realized simultaneously. A real resolution of 0.222 mm are achieved through the structural design and electrical performance characterization. With the help of the LabVIEW platform and multi-channel data acquisition program, its application in crack monitoring and early warning is successfully demonstrated. This work presents a novel self-powered sensor for crack monitoring and early warning, such a strategy is potentially available for distributed sensor construction towards structural health monitoring (SHM) of the infrastructure.

Tuning Confined States and Valley G‐Factors by Quantum Dot Design in Bilayer Graphene

Electrostatically confined quantum dots in bilayer graphene have shown potential as building blocks for quantum technologies. To operate the dots, e.g., as qubits, a precise understanding and control of the confined states and their properties is required. Herein, a large‐scale numerical characterization of confined quantum states in bilayer graphene dots is performed over an extensive range of gate‐tunable parameters such as the dot size, depth, shape, and the bilayer graphene gap. The dot states’ orbital degeneracy, wave function distribution, and valley g‐factor are established and the parametric dependencies to achieve different regimes are provided. It is found that the dot states are highly susceptible to gate‐dependent confinement and material parameters, enabling efficient tuning of confined states and valley g‐factor modulation by quantum dot design.

Fenugreek seeds extract mediated nickel oxide nanoparticles and their potential biomedical applications

The biogenic nanoparticle synthesis is much interest in the field of modern science and technology because of their excellent inhibition of potential pathogens. A quick, dependable, and efficient way to create very stable metal nanoparticles is by Phytosynthesis. Hence, Fenugreek seeds extract-mediated nickel oxide nanoparticles (NF) are synthesized by an eco-friendly, greener approach. Numerous characterization methods, including X-ray diffraction (XRD), Fourier transform infrared (FT-IR), ultraviolet visible (UV–Vis), photoluminescence (PL), scanning electron microscope (SEM), transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy (EDX), were used to confirm the as-prepared nanoparticles. Powder X-ray diffraction (PXRD) and selected area electron diffraction (SAED) show the prepared NiO NPs crystallinity. The FT-IR spectrum ensures the vibrational modes present in the prepared compound. The formation of NiO NPs is confirmed from the ultraviolet–visible (UV–Vis) spectrum analysis with the surface plasmon resonance (SPR) band at 320 nm. The morphological behavior is shown by the field emission-scanning electron microscope (FE-SEM) and high-resolution transmission electron microscope (HR-TEM). This prepared Fenugreek seeds extract assisted NiO NPs were examined with different biomedical studies such as anti-diabetic, anti-oxidant, and anti-inflammatory. The green approach to NiO NPs shows 82.21 % anti-diabetic, 79.82 % anti-oxidant, and 94.54 % anti-inflammatory and anti-bacterial activities. Moreover, it can act as an excellent inhibitor with the potential to cure various diseases like diabetes, oxidative stress, and inflammation.

Steady and Unsteady Numerical Characterization of the Secondary Flow Structures of a Highly Loaded Low-Pressure Compressor Stage

This paper presents the numerical characterization of a highly loaded compressor by means of 3D unsteady RANS simulations. The focus is on critical flow structures and their evolution at different operating points of the machine. First, the numerical setup and mesh quality are presented to support the reliability of the provided results. The comparison against experiments is then described for this purpose. Later, a full description of the unsteady behavior of the machine is provided, giving special attention to the two regions where the most critical features are expected: the rotor hub wall and the casing. Rotor–stator interactions are then investigated and the role of the inlet guide vane (IGV) is finally discussed. Results are analyzed at design and near-stall conditions, with a focus on the behavior close to the stability limit at 100% speed.

Experimental and numerical characterization of timing jitter for short electron beams in a linear photo-injector

In modern particle accelerators involving short (few hundreds of fs or less) photon and particle beams, a crucial requirement is the arrival timing jitter and its modeling, taking into account different noise sources. This paper considers the arrival timing jitter of an electron beam measured at the SPARC_LAB photo-injector test facility (INFN-LNF, Frascati) and studies how the different jitter sources impact on the beam arrival time, considering three velocity bunching machine working points (WPs). This study includes the development of a first order mathematical model that describes the jitter contributions, the PIC code simulations for the machine WP description and experimental data acquired in a dedicated run at SPARC_LAB to benchmark both the proposed model and simulations.

Simplified approach for modeling standard PVB at large deformations and long-term loading

Recently, the numerical simulation of the residual load-bearing capacity of laminated glass (LG) is an often discussed but not sufficiently solved problem in structural glass design yet. According to CEN/TS 19100:2021 (2021a), and CEN/TS 19100:2021 (2021b), the design in the Post Fracture Limit State (PFLS) is possible experimentally and numerically. Experimental verification requires large-scale component tests, which are often costly and time-consuming. The resource-saving numerical approach is to be preferred. However, at the moment, there is no sound numerical model capable of representing the complex load-bearing mechanisms of broken laminated glass (LG) in civil engineering practice. These mechanisms are the finite-strain response of the interlayer, the contact between glass fragments or shards themselves, and the bond between glass and interlayer. Delamination governs the latter one mainly. This work focuses on the experimental, mechanical, and numerical characterization of the finite-strain behavior of polymeric laminated glass interlayers at long load durations by the example of standard single-layer Polyvinylbutyral (PVB). Based on that, it introduces an approach enabling the simplified numerical simulation of LSG interlayers. The considerations rely on experiments and thermodynamic considerations.

Bio-engineered sensing of Atrazine by green CdS quantum dots: Evidence from electrochemical studies and DFT simulations

The present investigation reports a comprehensible and responsive strategy for identifying atrazine in several conditions using an extensive electrochemical method. CdS Quantum dots were synthesized via a greener approach, and their formation was endorsed by numerous characterization techniques such as FTIR, SEM, Raman, UV–Vis, and XRD. Owing to the splendid electrocatalytic behavior, Green CdS quantum dots (QDs) of crystallite size ∼2 nm was opted as the sensor material and were, therefore, incorporated on the bare carbon paste electrode's surface. The developed sensor demonstrated an impressive outcome for atrazine sensing accompanied by superior selectivity and sensitivity. The lower detection limit (LLOD) of 0.53 μM was attained using the developed sensor in a linear concentration range of 10–100 μM. Furthermore, the practical pertinence of the developed sensor was examined on distilled water, wastewater, and fresh liquid milk, resulting in a tremendous retrieval of atrazine (91.33–99.8%).

Experimental and numerical characterisation of two-phase flow in NETmix reactors

NETmix has been shown to be an efficient mixing technology for miscible fluids, promoting large heat and mass transfer rates. This work intends to assess NETmix for multiphase mixing, which is particularly relevant to evaluate the NETmix’s ability to couple mixing and heat transfer. The first step is to build fundamental knowledge regarding two-phase flow in these devices. A 2D CFD two-phase model was implemented based on the Euler‑Euler approach with the Volume of Fluid (VOF) method using the NETmix Unit Block (NUB). The two phases are liquids with equal density and viscosity, enabling the study of the impact of the interfacial tension and contact angle on the flow dynamics and drop formation. Mass transfer was assessed from the flow shear at the interface of the two phases. The CFD model was experimentally validated using a water-cyclohexane system. The NETmix technology promotes high flow dynamics and large interfacial area generation between the two phases. The successive split and recombining of flow contribute to an intense fluid renewal around the two phases’ interface, enhancing the mass transfer rate. NETmix shows potential for multiphase applications, particularly between two immiscible liquid phases, with a four-fold increase of the interfacial area of immiscible fluids.

Simulations of idealised 3D atmospheric flows on terrestrial planets using LFRic-Atmosphere

Abstract. We demonstrate that LFRic-Atmosphere, a model built using the Met Office's GungHo dynamical core, is able to reproduce idealised large-scale atmospheric circulation patterns specified by several widely used benchmark recipes. This is motivated by the rapid rate of exoplanet discovery and the ever-growing need for numerical modelling and characterisation of their atmospheres. Here we present LFRic-Atmosphere's results for the idealised tests imitating circulation regimes commonly used in the exoplanet modelling community. The benchmarks include three analytic forcing cases: the standard Held–Suarez test, the Menou–Rauscher Earth-like test, and the Merlis–Schneider tidally locked Earth test. Qualitatively, LFRic-Atmosphere agrees well with other numerical models and shows excellent conservation properties in terms of total mass, angular momentum, and kinetic energy. We then use LFRic-Atmosphere with a more realistic representation of physical processes (radiation, subgrid-scale mixing, convection, clouds) by configuring it for the four TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI) scenarios. This is the first application of LFRic-Atmosphere to a possible climate of a confirmed terrestrial exoplanet. LFRic-Atmosphere reproduces the THAI scenarios within the spread of the existing models across a range of key climatic variables. Our work shows that LFRic-Atmosphere performs well in the seven benchmark tests for terrestrial atmospheres, justifying its use in future exoplanet climate studies.

Experimental and numerical fatigue damage characterization in multidirectional thermoplastic glass/polypropylene laminates based on in-situ damage observations

Quantifying microscopic damage mechanisms in opaque composite laminates with multiple off-axis plies throughout fatigue experiments is challenging. However, if successful, important relations can be revealed between actual evolving damages and their contribution to the mechanical laminate response. This study characterizes the evolution of matrix cracking in ±45 and 90 embedded off-axis plies together with effects of delamination and relates them to the global mechanical property reductions in Glass/Polypropylene laminates. [0/45/0/-45]s and [0/45/90/-45]s laminates are tested under tension-tension fatigue over 500 000 cycles at three different stress levels. In-situ edge damage detection by optical measurements are performed as well as the validation of damages by detailed post-mortem microscopy. Moreover, through-the-width sectioning is applied to reveal the damages inside the laminate after testing. Additionally, the effects of different fabrication histories on damage progression are assessed. Influences of 45-ply thickness and different ply neighbouring orientations on the damage behaviour are discussed with their contribution to the normalized stiffness degradation and Poisson's ratio evolution. Moreover, experimental results are compared with a modelling approach by which the effects of damages in multiple plies can be considered, showing very good accordance.

Investigation of optical and structural properties of copper oxide nanoparticles synthesized via green method using Bougainvillea leaves extract

This study presents an innovative approach for synthesizing copper oxide nanoparticles (CuO-NPs) using an aqueous extract derived from Bougainvillea leaves as a reducing and capping agent. The synthesized CuO-NPs underwent numerous characterization using various techniques, including Fourier transform infrared spectroscopy (FT-IR), UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD analysis confirmed the well-crystalline and monoclinic structure of the CuO-NPs, with lattice constants a = 4.6667, b = 3.4070, and c = 5.1376. SEM and TEM analysis revealed predominantly spherical shapes of the CuO-NPs, with sizes ranging from 7 to 22 nm and an average size of 15 nm. Combining the results from FT-IR, XRD, and TEM, it was evident that the synthesized CuO-NPs were highly pure. UV-Vis analysis yielded valuable insights into the optical properties of the CuO-NPs. Notably, an absorbance peak at 318 nm was observed. Moreover, the energy bandgap of the CuO-NPs was determined to be 2.74 eV. Additionally, various optical properties were quantified and interpreted based on the UV-Vis analysis including the absorption coefficient (α), skin depth (penetration depth) (δ), optical density (Dopt), extinction (attenuation) coefficient (k), optical conductivity (σopt), and the optical dielectric constant (ε). The comprehensive investigation of the optical and structural properties of the prepared CuO-NPs enhances understanding of their behavior when interacting with light and paves the way for their utilization in a vast range of practical applications.

Synthesis and electrochemical properties of CuS/C-dots microflower for high-performance supercapacitor

Transition metal sulfides have recently captured the utmost attention as an energy storage device owing to their excellent electrochemical activity and conductivity. The amalgamation of carbonaceous materials along with transition metal sulfides was found to do wonders in the field of supercapacitors by amplifying the surface area, conductivity, capacitance, and stability of the active electrode material. In the present work microflower like CuS and CuS/C-dots composite was synthesized via the facile hydrothermal method. Numerous characterization techniques like XRD, SEM, TEM, XPS, and EDS were used to study the properties of the as-prepared samples. The CuS/C-dots composite as an active anode material exhibited an outstanding electrochemical performance with a superior specific capacitance of 2642 Fg−1 at a current density of 2 Ag−1. Furthermore, CuS/C-dots composite material displayed excellent capacitance retention of 58 % after 2000 cycles at a current density of 10 Ag−1. The superior charge transfer kinetics, unique structure, and conductivity of CuS/C-dots composite make it a remarkable material for electrochemical energy storage devices.

A Novel Exoskeleton Design and Numerical Characterization for Human Gait Assistance

This paper addressed attention to the design of a new lower limb exoskeleton that can be used for human gait assistance as based on kinematic considerations. The designed leg exoskeleton had on its own structure a combination of three mechanism types, namely a Chebyshev mechanism, a pantograph, and a Stephenson six-bar mechanism. The design core focused on inserting the Stephenson six-bar bar mechanism in order to obtain an imposed motion at the ankle joint level. Numerical simulations of the designed lower limb exoskeleton have been developed and the obtained results demonstrate the engineering feasibility of the proposed prototype, with a characterization of satisfactory operation performance.

Nuclear Phenotype and Karyotype Analysis in two Varieties of Lathyrus Sativus L.

Lathyrus sativus known as grass pea belongs to the family of Fabaceae commonly grown for human consumption and livestock feed throughout the world. This study based on the morphological features of the basic chromosome numbers and numerical characterization of the karyotypes using total chromosome length (TCL), arm ratio and total fraction frequency. Outcome of BARI Khesari-2 is more effective than BARI Khesari-3 on the basis of mitotic index, nuclear volume and interphase chromosome volume. Whereas, mitotic index directly relevant to cell division; when MI high than cell division rate will be high. The two varieties (BARI Khesari-2 and BARI Khesari-3) were found to possess 2n = 14 chromosomes. Karyotype analysis is an essential tool for studying the genetic constitution of any organism. In this investigation, we found the karyotype formula of BARI Khesari-2 is 7L 4m + 2sm + 1st and BARI Khesari-3 is 7L 2m +3sm + 2st. Chromosome morphology showed a variation in the chromosome length, chromosome structure and centromere position of the accessions. Presence of sub-terminal chromosome in both varieties shows asymmetric karyotype which indicates advanceness. The variation in L. sativus may be regarded as having evolution and adaptive significance. J. Bio-Sci. 30(2): 59-65, 2022

Analytical and numerical characterisation of terminal velocities of Tenebrio molitor larvae in a new, asymmetrical zigzag based separation system

Abstract Separation of Tenebrio molitor larvae from unwanted residues, like frass, feed or exuviae is a key process step for an industrial scale plant. One method to separate larvae from residues is using a zigzag air classifier. For designing and for an efficient operation of a zigzag air classifier, the terminal velocity is a key parameter to separate larvae from different residues with a high separation sensitivity. In this work, the terminal velocities of different larvae sizes are evaluated analytically, numerically and experimentally. For this, the sizes of 3 week to 12 week old larvae were used to calculate and simulate the terminal velocity. To validate the results, an experiment was carried out and compared with the analytical and numerical data. For this, a model for T. molitor larvae was designed to calculate the surface and volume of a larva to produce equivalent spheres with the same physical properties as a real larva. The results are showing similar curves with terminal velocities from 5 m/s for young larvae (3 weeks old) to 12 m/s for older larvae (12 weeks old). The deviations between each method are 1 m/s for smaller larvae and 1.5 m/s for bigger larvae. In further experiments and simulations, approaches with calculation methods for non-spherical particles are necessary to achieve results closer to reality due to the cylindrical shape of T. molitor larvae.