Numerous Experimental Techniques Research Articles

Study on the association driving force of low temperature coal tar asphaltenes

The aggregation of petroleum asphaltenes has been studied for decades by numerous experimental techniques, however, few studies had been performed on the special supramolecular structure of coal tar asphaltenes. In this paper, the methylation, alkylation experiments and molecular dynamics simulation were used to study the π-π interaction and hydrogen bond between coal tar asphaltenes. The results showed that the inter aromatic layer distance (Me) of asphaltenes, methylated and alkylated asphaltenes were 3.74, 2.12 and 1.73 respectively, and the average number of aromatic sheets (dm) was increased compared with asphaltenes. Asphaltenes existed in the form of aggregates in the toluene, as the concentration increased, the particle size also increased significantly, moreover, the particle size and the Me of alkylated asphaltenes are significantly less than asphaltenes, indicating that the π-π interaction was the main driving force for asphaltene association. Meanwhile, molecular simulation results showed the π-π interaction energy of asphaltenes dimers was -165.269 kcal·mol−1, which was much larger than the hydrogen bond energy -5.807 kcal·mol−1. In addition, the asphaltenes dimer layer spacing in quinoline, toluene and ethanol were 3.836 Å, 2.57 Å, and 4.783 Å respectively, which were all larger than the interlayer spacing of asphaltenes dimer 1.99 Å, and the asphaltenes dimer had a better disaggregates effect in quinolone.

Simulated Study and Surface Passivation of Lithium Fluoride-Based Electron Contact for High-Efficiency Silicon Heterojunction Solar Cells

Numerical simulation and experimental techniques were used to investigate lithium fluoride (LiFx) films as an electron extraction layer for the application of silicon heterojunction (SHJ) solar cells, with a focus on the paths toward excellent surface passivation and superior efficiency. The presence of a 7 nm thick hydrogenated intrinsic amorphous silicon (a-Si:H(i)) passivation layer along with thermally evaporated 4 nm thick LiFx resulted in outstanding passivation properties and suppresses the recombination of carriers. As a result, minority carrier lifetime (τ eff) as well as implied open-circuit voltage (iVoc) reached up 933 μs and iVoc of 734 mV, accordingly at 120 °C annealing temperature. A detailed simulated study was performed for the complete LiFx based SHJ solar cells to achieve superior efficiency. Optimized performance of SHJ solar cells using a LiFx layer thickness of 4 nm with energy bandgap (Eg) of 10.9 eV and the work function of 3.9 eV was shown as: Voc = 745.7 mV, Jsc = 38.21 mA cm−2, FF = 82.17%, and η = 23.41%. Generally, our work offers an improved understanding of the passivation layer, electron extraction layer, and their combined effects on SHJ solar cells via simulation.

Characterization of Woven Composite Material Properties by Using an Inverse Technique Based on Vibration Tests

A mixed numerical-experimental technique based on vibration tests is modified and applied to determine the elastic material properties of woven composites. This non-destructive technique consists of physical experiments, numerical modelling and material identification procedure. For the purpose of characterization, two carbon fiber panels were prepared by manual layout technology. An evaluation of the accuracy of woven composite elastic properties is executed comparing the numerical and experimentally obtained resonant frequencies.

Static and dynamic response of a carbon composite full-scale hydrofoil manufactured using automated fibre placement

Experimental demonstration and performance evaluation on a shape-adaptive carbon composite full-scale hydrofoil manufactured using automated fibre placement (AFP) are presented in this paper. The experimental responses of the hydrofoil are validated with the finite element analysis (FEA) tools. The static performance of the hydrofoil was investigated using quasi-static cantilever load, whereas the dynamic response was studied using experimental modal analysis (EMA) to assess the structural quality of the manufactured hydrofoil. The variation between predicted and experimental modal and bending stiffness was found to be within 20%. Structural strains were also monitored using a network of distributed fibre optic sensors on the surface as well as embedded in conjunction with a network of strain gauges. The outcomes from this work demonstrates a framework of numerical analysis and experimental validation techniques using multiple sensors, which will pave the way towards further demonstrating the structural adequacy and performance of such hydrofoil, made of automated techniques and embedded with optical fibre sensor systems.

Surface modification and improvements of wicking properties and dyeability of grey jute-cotton blended fabrics using low-pressure glow discharge air plasma

Herein, we reported the improvements of wicking properties and dyeability of the jute-cotton blended (40:60) fabrics due to the effect of low-pressure glow discharge (LPGD) air plasma under selected exposure times. The microscopic features, functional groups, wettability, contact angles, wetting area, wicking rates, and reflectance values of the jute-cotton blended fabrics were analyzed using numerous experimental techniques. The scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques were used to investigate the morphological and compositional modifications of plasma-treated jute blended cotton fabrics. The compositional analysis confirmed various functional groups such as –OH, C–O, and COO− on the surface of jute blended cotton fabrics. The average pore radii and diffusion coefficient were calculated by using the modified Lucas-Washburn equation. The plasma-treated fabrics were shown to have an average pore radius of 0.93, 1.46, 2.26, and 4.8 μm under treatment time of 5,10,15, and 20 min. Nearly 50% reduction of contact angle was observed after a plasma treatment time of 20 min. The absorption to scattered ratio, K/S (determined using Kubel-Munk model) of the colored fabrics with 5 min pre-treated plasma was 6.47, although it was raised up to 8.51 after 20 min of pre-treatment. A reactive dye, Bezaktiv Red S–3B, was used for the dyeability test, and our findings showed that the dyeability and the wettability of the fabric were substantially enhanced with the treatment time of LPGD air plasma. Among the samples, only 10 min plasma pre-treated colored fabric exhibited a color difference of less than one compared to the standard one.

Peroxiredoxins wear many hats: Factors that fashion their peroxide sensing personalities

Peroxiredoxins (Prdxs) sense and assess peroxide levels, and signal through protein interactions. Understanding the role of the multiple structural and post-translational modification (PTM) layers that tunes the peroxiredoxin specificities is still a challenge. In this review, we give a tabulated overview on what is known about human and bacterial peroxiredoxins with a focus on structure, PTMs, and protein-protein interactions. Armed with numerous cellular and atomic level experimental techniques, we look at the future and ask ourselves what is still needed to give us a clearer view on the cellular operating power of Prdxs in both stress and non-stress conditions.

A Robust Finite Element-based Filter for Digital Image and Volume Correlation Displacement Data

Digital Image and Volume Correlation (DIC and DVC) are non-contact measurement techniques that are used during mechanical testing for quantitative mapping of full-field displacements. The relatively high noise floor of DIC and DVC, which is exasperated when differentiated to obtain strain fields, often requires some form of filtering. Techniques such as median filters or least-squares fitting perform poorly over high displacement gradients, such as the strain localisation near a crack tip, discontinuities across crack flanks or large pores. As such, filtering does not always effectively remove outliers in the displacement field. This work proposes a robust finite element-based filter that detects and replaces outliers in the displacement data using a finite element method-based approximation. A method is formulated for surface (2D and Stereo DIC) and volumetric (DVC) measurements. Its validity is demonstrated using analytical and experimental displacement data around cracks, obtained from surface and full volume measurements. It is shown that the displacement data can be filtered in such a way that outliers are identified and replaced. Moreover, data can be smoothed whilst maintaining the nature of the underlying displacement field such as steep displacement gradients or discontinuities. The method can be used as a post-processing tool for DIC and DVC data and will support the use of the finite element method as an experimental–numerical technique.

Measurement of mixed-mode fracture characteristics of an epoxy-based adhesive using a hybrid digital image correlation (DIC) and finite elements (FE) approach

The present work seeks to investigate the semi-circular beam (SCB) geometry for studying mixed-mode (mode-I and -II) fracture of a rubber-toughened epoxy-based adhesive material. A hybrid experimental-numerical technique involving digital image correlation technique and finite element modeling is formulated for extracting the J-integral values and stress intensity factors (SIF). Experiments are conducted to compare the results extracted using the hybrid approach with those from regression analysis of measured crack tip displacements. Critical stress intensity factors are extracted for a range of mode mixities. Based on a curve fit of the test data, the mode I and mode II critical stress intensity factors are estimated to be 1.19 MPa/√m and 1.46 MPa/√m, respectively. The specimen geometry, loading configuration and experimental setup are critically assessed to identify and understand effects and outcomes associated with friction at the supports and unintended support asymmetry on stress intensity factors. Several different techniques are also discussed for mapping measured displacement data onto the finite element model for reliably extracting the fracture parameters. Recommendations are made regarding best practices for using this geometry and the associated hybrid technique for extracting fracture parameters.

Nanoparticle and Bioparticle Deposition Kinetics: Quartz Microbalance Measurements.

Controlled deposition of nanoparticles and bioparticles is necessary for their separation and purification by chromatography, filtration, food emulsion and foam stabilization, etc. Compared to numerous experimental techniques used to quantify bioparticle deposition kinetics, the quartz crystal microbalance (QCM) method is advantageous because it enables real time measurements under different transport conditions with high precision. Because of its versatility and the deceptive simplicity of measurements, this technique is used in a plethora of investigations involving nanoparticles, macroions, proteins, viruses, bacteria and cells. However, in contrast to the robustness of the measurements, theoretical interpretations of QCM measurements for a particle-like load is complicated because the primary signals (the oscillation frequency and the band width shifts) depend on the force exerted on the sensor rather than on the particle mass. Therefore, it is postulated that a proper interpretation of the QCM data requires a reliable theoretical framework furnishing reference results for well-defined systems. Providing such results is a primary motivation of this work where the kinetics of particle deposition under diffusion and flow conditions is discussed. Expressions for calculating the deposition rates and the maximum coverage are presented. Theoretical results describing the QCM response to a heterogeneous load are discussed, which enables a quantitative interpretation of experimental data obtained for nanoparticles and bioparticles comprising viruses and protein molecules.

Experimental Validation of the Noncoding Potential for lncRNAs.

In recent years, long noncoding RNAs (lncRNAs) have been increasingly recognized as critical regulators of a broad spectrum of cellular processes. Recent advancements in proteomic technologies have uncovered that an abundance of noncoding genes, including lncRNAs, have been misannotated and in reality encode proteins. This revelation underscores the need to accurately determine the coding potential of lncRNAs prior to assessment of their functional mechanisms. Here, we detail numerous experimental techniques useful in the determination of lncRNA coding potential. Several of these methods are doubly useful in that they may also be employed in studying the function of a lncRNA, be it via an RNA, protein, or both.

Damage and failure mechanisms of ductile metals in biaxial experiments with non‐proportional loading paths

AbstractThe paper deals with an experimental series and corresponding numerical simulations of the biaxial X0‐specimen to study the loading path dependence of ductile damage and fracture under non‐proportional loading. Experimentally the specimen surfaces have been monitored by digital image correlation (DIC). The experimental–numerical technique applied to the non‐proportional biaxial experiments provides new insights of the stress and load‐history dependent damage and fracture processes.

Characteristics and Behavior of Different Catalysts Used for Water Decontamination in Photooxidation and Ozonation Processes

The objective of this study was to summarize the results obtained in a wide research project carried out for more than 15 years on the catalytic activity of different catalysts (activated carbon, metal–carbon xerogels/aerogels, iron-doped silica xerogels, ruthenium metal complexes, reduced graphene oxide-metal oxide composites, and zeolites) in the photooxidation (by using UV or solar radiation) and ozonation of water pollutants, including herbicides, naphthalenesulfonic acids, sodium para-chlorobenzoate, nitroimidazoles, tetracyclines, parabens, sulfamethazine, sodium diatrizoate, cytarabine, and surfactants. All catalysts were synthesized and then texturally, chemically, and electronically characterized using numerous experimental techniques, including N2 and CO2 adsorption, mercury porosimetry, thermogravimetric analysis, X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, diffuse reflectance UV–vis spectroscopy, photoluminescence analysis, and transmission electron microscopy. The behavior of these materials as photocatalysts and ozonation catalysts was related to their characteristics, and the catalytic mechanisms in these advanced oxidation processes were explored. Investigations were conducted into the effects on pollutant degradation, total organic carbon reduction, and water toxicity of operational variables and the presence of different chemical species in ultrapure, surface, ground, and wastewaters. Finally, a review is provided of the most recent and relevant published studies on photocatalysis and catalyzed ozonation in water treatments using similar catalysts to those examined in our project.

Finite Element Model Calibration of Sandwich Structure Based on Mixed Numerical Experimental Technique

This paper presents the implementation of the mixed numerical experimental technique for the finite element (FE) model calibration of a sandwich structure by using modal data. Model calibration is conducted by minimizing the difference between the numerical and experimental dynamic parameters. In this study, instead of the direct minimisation of the response discrepancy, the experiment design and the response surface method is employed to solve the inverse (calibration) problem. Numerical eigenfrequencies are obtained by performing FE calculations in sample points derived by Latin Hypercube experiment design where each sample point represents a unique engineering constant configuration in the FE model of the sandwich panel. Using the information on the dynamic responses of the panel in the sample points, response functions describing the relationship between the engineering constants and the calculated eigenfrequencies are obtained by means of response surface method. Genetic algorithm is employed to solve the minimisation of the response discrepancy where the response functions instead of FE calculations are used to obtain the numerical modal frequencies. The verification results show that proposed method is capable to calibrate a numerical model with a good prediction accuracy and small uncertainties.

Analysis of strain and disordering kinetics based on combined RBS-channeling and X-ray diffraction atomic-scale modelling

Ion beams delivered by particle accelerators are routinely used to emulate harsh, radiative environments and they also constitute the foundations of the modern microelectronics industry. To characterize irradiated materials, numerous experimental and computational techniques can be implemented, but it is extremely difficult to effectively intertwine them, and to compare the associated data. In the present work, we present an integrated, experimental and computational approach that uses a same set of molecular dynamics simulations to generate signals of Rutherford backscattering spectrometry in channelling condition and X-ray diffraction, with UO2 as a test-case material. From these signals, parameters to monitor the damage level are computed, compared and confronted with experimental data. Although the evolution of the strain and disordering kinetics obtained by simulations differ on an absolute scale from those obtained experimentally (a discrepancy inherent to the method used to generate the atomic-scale data), a very good relative agreement is obtained, which demonstrates the validity of the approach, hence providing a new tool for the fine study of irradiation effects in materials.

An Integrated Experimental and Computational Approach for the Investigation of Irradiation Effects in Materials

Ion beams delivered by particle accelerators are routinely used to emulate harsh, radiative environments and they also constitute the foundations of the modern microelectronics industry. To characterize irradiated materials, numerous experimental and computational techniques can be implemented, but it is extremely diffcult to effectively intertwine them, and to compare the associated data. In the present work, we present an integrated, experimental and computational approach that uses a same set of molecular dynamics simulations to generate signals of Rutherford backscattering spectrometry in channelling condition andX-ray diffraction, with UO2 as a test-case material. From these signals, parameters to monitor the damage level are computed, compared and confronted with experimental data. The good agreement that comes out demonstrates the validity of the approach, hence providing a new tool for the fine study of irradiation effects in materials.

Numerical Modelling and Experimental Testing of the Hydrodynamic Characteristics for an Open-Frame Remotely Operated Vehicle

The remotely operated vehicles (ROVs) are important to provide the technology support for both the traditional offshore structures and rapidly-growing renewable energy facilities during their full-lifecycles, such as site survey, installation, inspection, maintenance and repair. Regarding the motion and performance of a ROV, the understanding of its hydrodynamic properties is essential when exposing to the disturbances of wave and current. In this study, a numerical model is proposed within the frame of an open-source platform OpenFOAM. The hydrodynamics of the adopted ROV (BlueRov2) in its four principal degrees of freedoms (DOFs) is numerically simulated by a Reynolds-Averaged Navier-Stokes (RANS) solver. Meanwhile, an experimental test is carried out by using a novel technique on measuring the hydrodynamic forces and moments. To validate the numerical prediction methodologies, a set of systematic simulations of the ROV subjected to the disturbances caused by various flow conditions are performed. Comparing to the model test measurement, the numerical model proved to be reliable in offering a good estimation of the hydrodynamic parameters. This also indicates that the presented numerical methodologies and experimental techniques can be applied to other types of open-frame ROVs in quantifying the hydrodynamic parameters, capturing the physics of the fluid-structure interaction (FSI) and feature of the turbulent vorticity which are all essential for the effective control of the ROVs under the nonlinear flow disturbances.

Sustainability, transfer and containment properties of concrete subject to delayed ettringite formation (DEF)

This work used numerous experimental techniques to evaluate the physicochemical and mechanical modifications of concrete damaged by swelling due to internal sulfate attack. The first objective was to determine property sensitive to DEF (delayed ettringite formation) and able to detect it before apparent cracking. The second objective was to quantify the evolution of the properties that impact the containment property and the sustainability of concrete after expansion and damage. It was found that gas permeability, electrical resistivity and static moduli results were the most promising techniques to detect DEF during the latency period. The loss of containment appears for damage lower than 20%.

Vortex dynamics and acoustic sources in the wake of finned cylinders during resonance excitation

The flow–sound interaction mechanism and its effect on the vortex dynamics in the wake of circular finned cylinders are experimentally investigated using phase-locked particle image velocimetry at Reynolds numbers between 7 × 104 and 9.5 × 104. In addition, a hybrid experimental–numerical technique using the theory of vortex sound is employed to quantify the acoustic sources and sinks in the vicinity of finned cylinders with different fin-to-root diameter ratios, Df/Dr = 1.5, 2.0, and 2.5. The results show that changing the diameter ratio of the fins induces fundamental changes in the wake structure and the vortex shedding process downstream of the cylinder. Finned cylinders induce stronger vortex cores with a shorter formation length compared to their equivalent bare cylinders. Moreover, the flow topology over the spanwise direction shows that acoustic resonance results in uniform cylindrical vortex cores with less three-dimensional distortion, which demonstrates that the flow field becomes highly two-dimensional during resonance excitation. Quantification of the energy transfer between the flow and the sound fields reveals an enhancement in the acoustic energy production closer to the cylinder with a significant dependence on its fin-to-root diameter ratio.

Application of Raman Spectroscopy to Ancient Materials: Models and Results from Archaeometric Analyses

Numerous experimental techniques of analysis find applications in many branches of the archaeometry. Among them, Raman spectroscopy carved out a niche in the field of diagnostic and conservation of cultural heritage. The exceptional ability to predict and discover the structural properties of materials set for Raman spectroscopy, an exclusive role among the analytic techniques, is further boosted when it is coupled with mathematical or statistical models able to deepen the studied phenomena. In this work, we present a review of recent studies where pairing Raman spectroscopy and mathematical models allowed achieving important results in the case of potteries, porcelains, ancient and modern paper, ancient jewelry, and pigment degradation. The potentialities of this approach are evidenced and analyzed in detail.

Analysis of Wave Patterns Under the Region of Macro-Fiber Composite Transducer to Improve the Analytical Modelling for Directivity Calculation in Isotropic Medium

Analytical modelling is an efficient approach to estimate the directivity of a transducer generating guided waves in the research field of ultrasonic non-destructive testing of the large and complex structures due to its short processing time as compared to the numerical modelling and experimental techniques. The wave patterns or the amplitude variations along the region of ultrasonic transducer itself depend on its behavior, excitation frequency, and the type of propagating wave mode. Depending on the wave-pattern of a propagating wave mode, the appropriate value of the amplitude correction factor must be multiplied to the amplitudes of the excitation signal for the accurate evaluation of directivity pattern of the ultrasonic transducers generating guided waves in analytical modelling. The objective of this work is to analyse the wave patterns under the region of macro-fiber composite (MFC) transducer to improve the accuracy of a previously developed analytical model for the prediction of directivity patterns. Firstly, the amplitude correction factor based on the wave patterns under the region of P1-type MFC (MFC-2814) transducer at two different frequencies (80 kHz, 3 periods and 220 kHz, 3 period) glued on 2 mm Al alloy plate has been estimated analytically in the case of an asymmetric (A0) guided Lamb wave. The validation of analytically estimated amplitude correction factor is performed by a proposed experimental method that allows analyzing the behaviour of MFC transducer under its region by gluing MFC on bottom surface and scanning the receiver on the top surface of the sample. Later on, the estimated amplitude correction factor is included in the previously developed 2D analytical model for the improvement in the directivity patterns of the A0 mode. The modified analytical model shows a significant improvement in the directivity pattern of the A0 wave mode in comparison to the results obtained by the previous model without considering the proper wave patterns. The results reveal that errors between the directivity estimated by the present modified 2D analytical model and experimental investigation are reduced by more than 58% in comparison to the previously developed analytical model.