Experimental Deductions Research Articles

Challenges in non-destructive X-ray CT testing of riveted joints in the automotive industry

Despite recent advancements, contemporary laboratory-based industrial computed tomography (CT) technology has not yet achieved the status of an efficient and economically viable in situ non-destructive method for examining riveted joints that are commonly used in the automotive industry. 2D X-ray or 3D CT systems can only reliably assess a rivet joint’s condition in rare, and favorable circumstances. Moreover, a comprehensive analysis to identify the obstacles preventing CT from efficiently capturing high-resolution, and contrast-rich scans of riveted joints in general is lacking. This work delves into the challenges and limitations of the technology that prevent operators from reaching the desired precision required for rigorous quality control. The study specifically addresses questions concerning in situ reachability and positioning of the sample structure, radiodensity and beam hardening, the relationship between spot size and power, and economic feasibility—all within the context of analyzing riveted joints in the automotive industry. Additionally, we provide an abstracted overview of the current industrial X-ray tube market, which informs our discussion on these specific aspects. Through a combination of experimental findings, analytical insights, and deductions, we shed light on the persistent difficulties in achieving resolutions comparable to macro-sectioning and microscopy, which are currently considered the gold standard in examining riveted joints. Our investigation further explores the potential of a photon-counting detector paired with a conventional, laboratory-based X-ray source. Furthermore, we investigate the use of a synchrotron beamline as an X-ray source in conjunction with a custom-designed detector optimized for such beam geometries. This detector employs scintillators coupled with optical magnification, functioning similarly to an X-ray microscope. Our findings and data collection conclusively reveal that commercially available CT systems still fail to meet the requirements for efficient testing, underscoring the urgent need for further research and development to enable widespread implementation.

Adsorption of synthetic dyed wastewater using activated carbon from rice husk

The purpose of this study was to remove dyes from synthetic dyed wastewater using activated carbon derived from rice husk. The initial dye concentration was 45 mg/L. The batch adsorption worked best in an acidic medium of pH 2, adsorbent dosage of 13 g/L and agitation speed of 100 rpm with maximum dye removal of 80% after 10 min. The maximum adsorption capacity of the absorbent was found to be 2.0 mg/g with a final dye concentration of 10.8 mg/L. The adsorption was found to be a non-spontaneous, endothermic chemisorption process with less disorder which best fitted the Temkin model and followed pseudo-second order. For column adsorption, the highest qo corresponds to 12.8 mg/g and the maximum dye removal was above 99.5%. Some of the experimental deductions were confirmed by gas-phase computations [B3LYP/6-31G(d)].

Prismatic Slip in Magnesium

Magnesium is the lowest-density structural metal but has low ductility that limits applications. The low ductility is related to the hexagonally close-packed crystal structure where activation of nonbasal slip is required for general plasticity. Here, our recent neural network potential (NNP) for Mg, trained using Kohn–Sham density functional theory (DFT), is used to examine slip of ⟨a⟩ dislocations on the prismatic plane. The generalized stacking fault surface energies (GSFEs) for basal and prismatic slip are computed and agree better with Kohn–Sham density functional theory (KS-DFT) than orbital-free density functional theory (OF-DFT) and modified embedded atom method (MEAM), which predict spurious minima. Consistent with the generalized stacking fault energy (GSFE), direct simulations of the prismatic ⟨a⟩ screw dislocation show it is unstable to dissociate into the ⟨a⟩ basal screw dislocation; this is mostly consistent with OF-DFT while MEAM predicts stability. Prismatic slip is thus achieved by a double-cross-slip process of the stable basal dislocations driven by a resolved shear stress on the orthogonal prismatic plane; this is consistent with the process deduced from experiments. The Nudged Elastic Band method is used with the NNP to examine the atomistic path and the stress-dependent enthalpy barrier for this mechanism; this requires many tens of thousands of atoms. The basal-prismatic cross-slip occurs in increments of c/2 via basal constriction, cross-slip on the prism plane, cross-slip back onto the basal plane, and lateral motion of the created jogs to extend the new basal dislocation. Comparisons with experimental deductions show some agreement and some notable disagreement. Resolution of the differences points toward further large-scale studies that require the accuracy and efficiency of KS-DFT-trained NNP, an approach that is also naturally extendable to the important domain of Mg alloys.

Comparative study on the transversal/lengthwise thermal failure propagation and heating position effect of lithium-ion batteries

Because of the multi-layer structure and the diversified connection modes of most battery modules, systematically investigating the thermal failure propagation principles and mechanisms of lithium-ion batteries is critical to provide early warnings and protection for thermal runaway. In this work, a series of experimental studies and mathematical deductions were conducted to investigate the propagation behavior of thermal failures within two types of cells under various heating modes, and their heat transfer mechanisms were analyzed. In general, the thermal runaway phenomenon in Li (Ni1/3Co1/3Mn1/3) O2 cells is more severe than that in LiCoO2 cells. For different heating modes, lengthwise thermal failure propagation is more unlikely to occur in comparison with transversal thermal failure propagation; however, the former involves a more violent combustion. For different heating positions, heating near the positive pole results in the most violent phenomena. Additionally, a higher Tmax of 185.6 °C was obtained via middle heating in comparison with that obtained via heating on the poles. The temperature rising rate also varied, taking 1619, 1578, and 1699 s for the temperature to rise from 20 °C to 168.9 °C, 185.6 °C, and 173.4 °C through bottom, middle, and top heating, respectively. These phenomena were consequently ascribed to the different heat transfer rates along different directions inside the cells, including transversal/lengthwise propagation, and positive-pole-directional/negative-pole-directional propagation. These encouraging results may raise concerns about developing more precise and suitable surveillance and control measures to further enhance the thermal safety performance of cells/modules from both external and internal perspectives.

Host Feasibility Investigation to Improve Robustness in Hybrid DWT+SVD Based Image Watermarking Schemes

Today, we face different approaches to enhance the robustness of image watermarking schemes. Some of them can be implemented, but others in spite of spending money, energy, and time for programming purpose would fail because of not having a strong feasibility study plan before implementation. In this paper, we try to show a rational feasibility study before implementation of an image watermarking scheme. We develop our feasibility study by proposing three types of theoretical, mathematical, and experimental deductions. Based on the theoretical deduction, it is concluded that the “S” coefficients in the second level of Singular Value Decomposition (SVD) offer high robustness to embed watermarks. To prove this, a mathematical deduction composed of two parts is presented and the same results were achieved. Finally, for experimental deduction, 60 different host images in both normal and medical images from various sizes of 256⁎256 to 1024⁎1024 were imposed to 9 common geometric and signal processing attacks and the resistances of “S” coefficients against the attacks in the first and second levels of SVD were compared. Experimental result shows significant enhancement in stability and robustness of the “S” coefficients in the second level of SVD in comparison to the first level. Consequently all theoretical, mathematical, and experimental deductions confirmed domination of the “S” coefficients in the second level of SVD than the first level. In this paper, we do not show any specific implementation for the watermarking scheme. Instead, we investigate the potential performance gains from the singular values (S), of the second level of SVD and Discrete Wavelet Transform (DWT), and prove their superiority in comparison to conventional SVD+DWT watermarking schemes.

Physico-chemical properties of aqueous drug solutions: From the basic thermodynamics to the advanced experimental and simulation results

The physical chemical properties of aqueous solutions of model compounds are illustrated in relation to hydration and solubility issues by using three perspectives: thermodynamic, spectroscopic and molecular dynamics simulations. The thermodynamic survey of the fundamental backgrounds of concentration dependence and experimental solubility results show some peculiar behavior of aqueous solutions with several types of similar solutes. Secondly, the use of a variety of experimental spectroscopic devices, operating under different experimental conditions of dimension and frequency, has produced a large amount of structural and dynamic data on aqueous solutions showing the richness of the information produced, depending on where and how the experiment is carried out. Finally, the use of molecular dynamics computational work is presented to highlight how the different types of solute functional groups and surface topologies organize adjacent water molecules differently. The highly valuable contribution of computer simulation studies in providing molecular explanations for experimental deductions, either of a thermodynamic or spectroscopic nature, is shown to have changed the current knowledge of many aqueous solution processes. While this paper is intended to provide a collective view on the latest literature results, still the presentation aims at a tutorial explanation of the potentials of the three methodologies in the field of aqueous solutions of pharmaceutical molecules.

Ab initio investigation of the AlN:Er system

In the present study an ab initio investigation on the AlN:Er system for concentrations of Er ranging from 0.78 to 12.5% is presented. The crystallographic localisation of the rare earth atoms in the wurtzite lattice is determined, elucidating previously published experimental deductions, and the existence of a solid solution in the AlN:Er system in this range is confirmed. Er incorporation in the tetrahedral and octahedral insertion sites is shown to be thermodynamically metastable and is found to induce shallow states in the bandgaps. The effect of Er concentration on the lattice constants and bandgaps and bandstructures of the ErxAl1−xN ternary compound is presented. Finally, in accordance with experimental specifications, Er incorporation in the AlNO system is also examined.

Theoretical studies of structure and dynamics of molten salts: the LiF-ThF4 system.

LiF-ThF4 molten salt (MS) is the fuel for advanced MS reactors. Knowledge of the microscopic MS structure and dynamics is required for an understanding of the macroscopic physical and chemical properties of the MS phases. We have performed molecular dynamics simulations on LiF-ThF4 MS at different molar percentages (LiF/ThF4 = 20.0 to 0.5) and temperatures (1100 to 1400 K). Experimental deductions and recent theoretical results on the coordination structures and transport properties of the MS are well reproduced. The density of states of the [ThF8](4-) species and the character of the Th-F bonding are investigated. The interplay between the microscopic structures and the dynamical properties is elucidated. Corresponding to the smaller effective radius of Zr, the activation barrier of the M(4+)-F(-) dissociation and the lifetime of the first coordination shell of M(4+) are both smaller for M = Th than for M = Zr in the respective LiF-MF4 systems. The shorter Zr-F bond is stronger than the longer Th-F bond, while the coordination number of the predominant [ZrF7](3-) species is smaller than that of the dominant [ThF8](4-) species. An approximate formula is proposed for the lifetime of F(-) ions in the first solvation shell of molten MFn (M = Y, Zr, Th) in terms of the radial distribution function.

On structure and bonding of lanthanoid trifluorides LnF3 (Ln = La to Lu)

The trends in the series of lanthanoid (lanthanide) trifluoride molecules LnF3 (Ln = La to Lu) are governed by the valence-active Ln(4f,5d,5p,6s) shells. The series is investigated by quasi-relativistic density functional theory at both the scalar and spin-orbit-coupled levels. Integrating many of the previous experimental and theoretical deductions, we obtain the following comprehensive picture: (1) The comparatively small Ln-F bond length contraction of 14 pm from La to Lu is rather smooth but weakly modulated by spin-orbit coupling. (2) From La to Lu the floppy structure becomes more quasi-planar. (3) The heterolytic LnF bond energies (⅓LnF3→⅓Ln(3+) + F(-)) at the spin-orbit averaged level increase smoothly from 15.3 to 16.3 eV for La to Lu, only the 'divalent' lanthanoids Eu and Yb are outliers with 0.2 eV higher bond energies. (4) The homolytic LnF bond energies (⅓LnF3→⅓Ln + F) however show an overall W-shaped double-periodicity with maxima for LaF3, GdF3 and LuF3, decreasing from La to Eu and from Gd to Yb, the large individual variations being caused by different spin-orbit coupling and Coulomb interaction effects in Ln(0) and LnF3. (5) The Ln-F interaction is basically ionic (increasing with decreasing ionic radii) with some dative Ln(3+)← F(-) bonding. (6) The latter is of the Ln(5d)-F(2p) type with a rather constant bond order from La to Lu, with small Ln(5p) and very small Ln(4f) semi-core contributions decreasing from La to Lu. All these trends are rationalized.

Quantitative Visualization of Molecular Transport through Porous Membranes: Enhanced Resolution and Contrast Using Intermittent Contact-Scanning Electrochemical Microscopy

The use of intermittent contact-scanning electrochemical microscopy (IC-SECM) in diffusion-limited amperometric mode to visualize and quantify mass transport through multiporous membranes is described using dentin as a model example. The IC mode of SECM employs the damping of a vertically modulated ultramicroelectrode (UME) to achieve positioning close to the receptor side of a membrane. In this way the UME can detect electroactive species close to the pore exit. A key aspect of IC-SECM is that in addition to the direct current (dc) from the diffusion-limited detection of the analyte, an alternating current (ac) also develops due to the motion of the probe. It demonstrates that this ac signal enhances the spatial resolution of SECM detection and allows the hydrodynamic flow of species to be detected from individual closely spaced pores. The experimental deductions are supported by three-dimensional finite element modeling which allows IC-SECM current maps to be analyzed to reveal transport rates through individual pores. The method described should be widely applicable to multiporous membrane transport.

On a new semi‐empirical electrotopological index for QSRR models

AbstractA new semi‐empirical electrotopological index, ISET, for quantitative structure–retention relationships (QSRR) models was developed based on the refinement of the previously published semi‐empirical topological index, IET. We demonstrate that the values of Ci fragments that were firstly attributed from the experimental chromatographic retention and theoretical deductions have an excellent relationship with the net atomic charge of the carbon atoms. Thus, the values attributed to the vertices in the hydrogen‐suppressed graph of carbon atoms (Ci) are calculated from the correlation of the net atomic charge in each carbon atom, which is obtained from quantum chemical semi‐empirical calculations, and the Ci fragments for primary, secondary, tertiary and quaternary carbon atoms (1.0, 0.9, 0.8 and 0.7, respectively) obtained from the experimental values. This shows that IET encoded this quantum physical reality and that it is possible to calculate a new ISET (the semi‐empirical electrotopological index) through the net atomic charge values obtained from a Mulliken population analysis using the semi‐empirical AM1 method and their correlation with the values attributed to the different types of carbon atoms. This demonstrates that the ISET encodes information on the charge distribution of the solute on which dispersive and electrostatic interactions between the solute (alkanes and alkenes) and the stationary phase strongly depend. Thus, this new method can be considered as an initial step towards forthcoming QSRR/QSAR studies. Copyright © 2008 John Wiley & Sons, Ltd.

Interaction of methanol with amorphous solid water

The interaction of methanol (MeOH) with amorphous solid water (ASW) composed of D2O molecules, prepared at 125 K on a polycrystalline Ag substrate, was studied with metastable-impact-electron spectroscopy, reflection-absorption infrared spectroscopy, and temperature-programmed desorption mass spectroscopy. In connection with the experiments, classical molecular dynamics (MD) simulations have been performed on a single CH3OH molecule adsorbed at the ice surface (T=190 K), providing further insights into the binding and adsorption properties of the molecule at the ice surface. Consistently with the experimental deductions and previous studies, MeOH is found to adsorb with the hydroxyl group pointing toward dangling bonds of the ice surface, the CH3 group being oriented upwards, slightly tilted with respect to the surface normal. It forms the toplayer up to the onset of the simultaneous desorption of D2O and MeOH. At low coverage the adsorption is dominated by the formation of two strong hydrogen bonds as evidenced by the MD results. During the buildup of the first methanol layer on top of an ASW film the MeOH-MeOH interaction via hydrogen-bond formation becomes of importance as well. The interaction of D2O with solid methanol films and the codeposition of MeOH and D2O were also investigated experimentally; these experiments showed that D2O molecules supplied to a solid methanol film become embedded into the film.

Multidimensional systems: Flow in electromagnetic fields and some fundamental implications

AbstractFor an electromagnetic (EM) field, local properties such as field velocity, rest field, and rest energy density are introduced. These are physically justified and mathematically defined by starting from what are the only assumptions on which this paper rests: the strict validity of Maxwell's equations and their inherent relativistic transformation rules. A variety of additional properties are presented that confirm the judiciousness of the chosen definitions. Based on these, flow equations of an EM field are derived, which offer remarkable analogies with equations of fluid dynamics and thus suggest attempting some mechanistic interpretation. Doing this by strictly adhering to the details of classical theories, however, is found to lead to incompatibilities, but a consistent interpretation is feasible in the context of some alternative relativistic results that have been presented in recent years and have originally been suggested by basic issues concerning passivity and losslessness in one‐ and multidimensional nonlinear Kirchhoff circuits and related areas of digital signal processing. In the light of these findings, available experimental evidence and original theoretical deductions are reassessed and shown not to contradict the present results. Potential models for electrons (rotating EM field) and photons (localized planar field that offers a natural solution to the wave‐particle duality) are obtained as rigorous solutions of Maxwell's equations, and possible consequences are discussed. Copyright © 2007 John Wiley & Sons, Ltd.

X‐ray diffraction study of the single‐crystal elastic moduli of ε‐Fe up to 30 GPa

Room temperature investigations of the single‐crystal elastic moduli and anisotropy of the ε phase of iron are performed up to 30.3 GPa using the radial X‐ray diffraction technique. The accuracy of the calculated elastic moduli has improved compared to previous measurements using similar techniques because of an increase in accuracy of the measurement, confinement of the sample to limit the effect of plasticity, and better calibration of the stress conditions. The aggregate shear modulus that we obtain is in good agreement with a variety of other experimental deductions but differs from first‐principles calculations. The effects of the calibration of stress and micromechanical model on the deduction of elastic moduli and elastic anisotropy are discussed in detail. The anisotropy we obtain has the same order of magnitude as first‐principles calculations but the direction is reversed, with a weaker amplitude that previous measurements.

Nanoindentation study of the superlattice hardening effect at TiC(110)/NbC(110) interfaces

We present an atomistic calculation using the embedded atom method in order to investigate nanoindentation in superlattices based on carbide materials. The purpose is to conduct a nanoindentation simulation study in order to evaluate the hardness of TiC and the one of TiC∕NbC. Results clearly show that this calculated quantity increases considerably from the carbide alone to the carbide in sandwich with another one like NbC. This mainly highlights the possibility to increase the hardness of carbide materials and confirms theoretically the previous experimental deductions.

The microwave and infrared spectroscopy of benzaldehyde: conflict between theory and experimental deductions.

Recently, it has been proposed that ab initio calculations cannot accurately treat molecules comprised of a benzene ring with a pi-conjugated substituent, for example, benzaldehyde. Theoretical predictions of the benzaldehyde barrier to internal rotation are typically a factor of 2 too high in comparison to the experimental values of 4.67 (infared) and 4.90 (microwave) kcal mol(-1). However, both experiments use Pitzer's 1946 model to compute the reduced moment of inertia and employ the experimentally observed torsional frequency to deduce benzaldehyde's rotational barrier. When Pitzer's model is applied to a system with a nonconjugated functional group, such as phenol, the model and theoretical values are in close agreement. Therefore, we conclude the model may not account for conjugation between the substituent and the pi-system of benzene. The experimental values of the benzaldehyde rotational barrier are therefore misleading. The true rotational barrier lies closer to the theoretically extrapolated limit of 7.7 kcal mol(-1), based on coupled cluster theory.

Three dimensional pharmacophore modeling of human CYP17 inhibitors. Potential agents for prostate cancer therapy.

We report here a molecular modeling investigation of steroidal and nonsteroidal inhibitors of human cytochrome P450 17alpha-hydroxylase-17,20-lyase (CYP17). Using the pharmacophore perception technique, we have generated common-feature pharmacophore model(s) to explain the putative binding requirements for two classes of human CYP17 inhibitors. Common chemical features in the steroid and nonsteroid human CYP17 enzyme inhibitors, as deduced by the Catalyst/HipHop program, are one to two hydrogen bond acceptors (HBAs) and three hydrophobic groups. For azole-steroidal ligands, the 3beta-OH group of ring A and the N-3 of the azole ring attached to ring D at C-17 act as hydrogen bond acceptors. A model that permits hydrogen bond interaction between the azole functionality on ring D and the enzyme is consistent with experimental deductions for type II CYP17 inhibitors where a sixth ligating atom interacts with Fe(II) of heme. In general, pharmacophore models derived for steroid and nonsteroidal compounds bear striking similarities to all azole sites mapping the HBA functionality and to three hydrophobic features describing the hydrophobic interactions between the ligands and the enzyme. Using the pharmacophore model derived for azole-steroidal inhibitors as a 3D search query against several 3D multiconformational Catalyst formatted databases, we identified several steroidal compounds with potential inhibition of this enzyme. Biological testing of some of these compounds show low to high inhibitory potency against the human CYP17 enzyme. This shows the potential of our pharmacophore model in identifying new and potent CYP17 inhibitors. Further refinement of the model is in progress with a view to identifying and optimizing new leads.

The enhancement factor and the characterization of amorphous carbon field emitters

We report on the results of a combined experimental and computational investigation on the properties of amorphous carbon nano-tips grown by carbon contamination in a scanning electron microscope and used as electron field emitters. We have calculated the strength of the electric field at the emitter surface F tip and the dimensionless enhancement factor γ (=F tip /F m ) for various geometries and sizes by means of the finite element method. By using F tip, experimental data and results from the Fowler–Nordheim plot, we have found consistent values of the work function, the surface emitting area and the current density J. The values of F tip and J are in reasonable agreement with other experimental deductions.

Mechanism of the C2H5+O2 reaction

The geometries, energies, and vibrational frequencies of the reactants, transition states, intermediates, and products of the reaction of ethyl radical with the oxygen molecule have been examined using density functional theory (DFT). Rather different theoretical predictions are obtained from the BLYP, B3LYP, and BHLYP methods. Comparisons with experimental deductions and high-level coupled cluster results suggest that the B3LYP method is superior for the C2H5+O2 problem. Using the B3LYP method with a triple-zeta plus double-polarization plus f function (TZ2Pf) basis set, a transition state between the ethylperoxy radical and products is discovered which lies 3.3 kcal mol−1 below reactants. This transition-state energy is consistent with the observed high yields of ethylene in the high-temperature reaction and is in good agreement with the height of the barrier estimated via modeling of the experimental kinetic data. However, this transition state (TS1) corresponds not to the internal proton transfer leading to the hydroperoxyethyl radical C2H4OOH but to the concerted elimination of ethylene. For the reverse reactionC2H4+HO2→C2H4OOH, the TZ2Pf UB3LYP classical barrier is 11.2 kcal mol−1.

Effective Valence Bond Model Study on Conjugated Hydrocarbons Containing Four-Membered Rings

By employing the Lanczos method, the effective valence bond model (EVB) is exactly solved for a series of conjugated hydrocarbons with four-membered rings. Several indices calculated from the EVB ground-state energies and wave functions are applied to interrelate with bond lengths, stabilities, and reactivities of these systems. Our results agree well with related experimental observations and deductions of molecular orbital theory. The failure of the classical valence bond theory in these systems is also exposed.