Dispersion Terms Research Articles

A general tight-binding based energy decomposition analysis scheme for intermolecular interactions in large molecules.

In this work, a general tight-binding based energy decomposition analysis (EDA) scheme for intermolecular interactions is proposed. Different from the earlier version [Xu et al., J. Chem. Phys. 154, 194106 (2021)], the current tight-binding based density functional theory (DFTB)-EDA is capable of performing interaction analysis with all the self-consistent charge (SCC) type DFTB methods, including SCC-DFTB2/3 and GFN1/2-xTB, despite their different formulas and parameterization schemes. In DFTB-EDA, the total interaction energy is divided into frozen, polarization, and dispersion terms. The performance of DFTB-EDA with SCC-DFTB2/3 and GFN1/2-xTB for various interaction systems is discussed and assessed.

Relationship between microstructure and strain-hardening behaviour of 3D printed engineered cementitious composites

The tensile behaviour of engineered cementitious composites (ECC) is highly dependent on their microstructure characteristics. To date, the strain-hardening behaviour of printed ECC in relation to its microstructure is not yet fully understood. This study presents a systematic investigation on the macroscopic mechanical properties of normal and printed ECC with various polyethylene (PE) fibre lengths (6 and 12 mm) in relation to their microstructural features in terms of pore structure characteristics, fibre orientation and fibre dispersion through a series of mechanical tests and X-ray computed tomography (CT) and backscattered electron (BSE) image acquisition, processing and analysis. Results indicate that it is desirable to use block specimens for mould-casting fabrication as contrast to printed ECC samples. The printed ECC containing 1.5 vol% 6 mm and 0.5 vol% 12 mm PE fibres by extrusion-based 3D printing exhibits unique tensile ductility of over 5% and average crack width of less than 100 μm. Regarding pore structure, normal ECC has a higher probability of large pores (over 1 mm3) than printed ECC, which would increase the risk of damage localization and lead to a significant variation in tensile properties. Besides, normal ECC with thickness of 30 mm and printed ECC possess a similar fist cracking strength as indicated by similar pore size and fracture toughness. Compared to normal ECC, printed ECC has a more uniform dispersion of PE fibres, the orientation of which is more perpendicular to the loading direction, resulting in a higher average tensile strength and strain capacity than normal ECC.

Implementation of symmetry-adapted perturbation theory based on density functional theory and using hybrid exchange-correlation kernels for dispersion terms.

We report the implementation of a symmetry-adapted perturbation theory algorithm based on a density functional theory [SAPT(DFT)] description of monomers. The implementation adopts a density-fitting treatment of hybrid exchange-correlation kernels to enable the description of monomers with hybrid functionals, as in the algorithm by Bukowski, Podeszwa, and Szalewicz [Chem. Phys. Lett. 414, 111 (2005)]. We have improved the algorithm by increasing numerical stability with QR factorization and optimized the computation of the exchange-correlation kernel with its 2-index density-fitted representation. The algorithm scales as O(N5) formally and is usable for systems with up to ∼3000 basis functions, as demonstrated for the C60-buckycatcher complex with the aug-cc-pVDZ basis set. The hybrid-kernel-based SAPT(DFT) algorithm is shown to be as accurate as SAPT(DFT) implementations based on local effective exact exchange potentials obtained from the local Hartree-Fock (LHF) method while avoiding the lower-scaling [O(N4)] but iterative and sometimes hard-to-converge LHF process. The hybrid-kernel algorithm outperforms Hartree-Fock-based SAPT (SAPT0) for the S66 test set, and its accuracy is comparable to the many-body perturbation theory based SAPT2+ approach, which scales as O(N7), although SAPT2+ exhibits a more narrow distribution of errors.

Investigation of through-thickness microstructural evolution and mechanical properties variation in friction stir alloyed Al-Fe alloy system

The present study investigates the through-thickness microstructural evolution, particle dispersion, and mechanical properties of the Al-Fe alloy system fabricated via friction stir alloying (FSA). The EDS and TEM analysis confirm Al13Fe4 as the main reaction product of the Al-Fe alloy system in the present study. However, the inhomogeneity in the distribution of Fe and Al13Fe4 IMC particles was observed across the thickness of the fabricated alloy. The middle section (starts at 2 mm and ends at 4 mm from the FSA surface) of the alloy was identified as the best region in terms of particle dispersion, fine grain size (~3.6 µm), and improved mechanical properties. The average microhardness in the stir zone (SZ) of the middle region was increased by ~62% as compared to the base metal (BM). The middle section also shows the maximum ultimate tensile strength (UTS) of ~134 MPa which is ~30% and ~38% higher than the UTS of the top and bottom sections, respectively. A detailed discussion is provided on the correlation of mechanical properties with various factors such as Fe particle dispersion, material flow, IMC morphology, and involved reaction mechanisms.

FORMULATION AND EVALUATION OF SEA GRAPE (Caulerpa racemose) EXTRACT AS HAND CREAM AND ITS ANTIOXIDANT ACTIVITY TEST

Caulerpa racemosa (C. racemosa) is a seaweed containing folic acid, thiamine, ascorbic acid, and phenol as secondary metabolites that function as antioxidants. This study aims to formulate a hand moisturizing cream containing C. racemosa extract and evaluate the quality of the cream preparation. The manufacture of hand cream from C. racemosa extract was carried out in several stages, namely C. racemosa extraction, antioxidant testing, formulation of cream preparations, and evaluation. Evaluation of hand cream preparations of C. racemosa extract included organoleptic tests, homogeneity, pH measurement, viscosity, spreadability, and adhesion. The yield of C. racemosa from the extract was 33%. The IC50 of the C. racemosa extract was 159.8 ppm. The results of the organoleptic test of hand cream preparations showed physical characteristics in terms of pH, viscosity, homogeneity, dispersibility, and adhesion following the requirements of cosmetic preparations from the Directorate General of BPOM.

Perturbation of dispersive optical solitons with Schrödinger–Hirota equation with Kerr law and spatio-temporal dispersion

Objective:The principal purpose of this paper is to examine the perturbed Schrödinger–Hirota equation with the effect of spatio-temporal dispersion and Kerr law nonlinearity which governs the propagation of dispersive pulses in optical fibers by proposing and using a direct algebraic form of the enhanced modified extended tanh expansion method for the first time. Our aim is not only restricted to obtaining different and more soliton solutions by proposed method for the first time in this study, but also includes examining the effect of the coefficients of self-steepening and nonlinear dispersion terms to the soliton propagation in the investigated problem. Methodology:Utilizing a traveling wave transformation, the perturbed Schrödinger–Hirota equation with the effect of spatio-temporal dispersion and Kerr law nonlinearity can be transformed into an nonlinear ordinary differential equation (NODE). Then, the NODE is convert into a set of algebraic equations by taking account into the Riccati differential equation. Solving the set of algebraic equations, we acquire the analytical soliton solutions of the perturbed Schrödinger–Hirota equation with the effect of spatio-temporal dispersion and Kerr law nonlinearity. In the proposed method, the modified extended tanh function method is enhanced by presenting more solutions of Riccati differential equations with the direct algebraic form, is utilized. Results:The more solutions have been established to the literature with new significant physical properties of the perturbed Schrödinger–Hirota equation with the effect of spatio-temporal dispersion and Kerr law nonlinearity. We indicated that the presented method are effective, easily computable, and reliable in solving such nonlinear problems. Moreover, we demonstrate the dynamical behaviors and physical significance of some soliton solutions at appropriate values of parameters. Originality:A variety of soliton solutions to the perturbed Schrödinger–Hirota equation with Kerr law non-linearity by the direct algebraic form of enhanced modified extended tanh expansion method have been acquired. These solutions are dark–bright, trigonometric, hyperbolic, periodic, and singular soliton solutions. 3D, contour and 2D plots of some obtained solutions have been demonstrated to interpret the physical meaning of the equation. For some parameter values in the equation, the behavior of soliton solutions has been examined. The constraint conditions are established to confirm the existence of valid solutions. The obtained results can be effective in interpreting the physical meaning of this nonlinear system. We have seen that the proposed direct algebraic form of the enhanced modified extended tanh expansion method is a powerful mathematical technique which can be utilized to acquire the analytical solutions to different complex nonlinear mathematical models.

Microwave-Assisted Rapid Synthesis of Luminescent Tryptophan-Stabilized Silver Nanoclusters for Ultra-Sensitive Detection of Fe(III), and Their Application in a Test Strip.

A new preparation method for extreme fluorescent green emission tryptophan-stabilized silver nanoclusters (Tryp-AgNCs) is presented in this scientific research. The produced silver nanoclusters are dependent on tryptophan amino acid which contributes to normal growth in infants and the sublimation and recovery of human protein, muscles, and enzymes. Herein, we have introduced a green method by using microwave-assisted rapid synthesis. The subsequent silver nanoclusters (AgNCs) have excitation/emission peaks at 408/498 nm and display a considerable selectivity to Fe(III) ions. The tryptophan amino acid molecule was used in the synthesis process as a reducing and stabilizing agent. The Tryp-AgNCs’ properties were investigated in terms of morphology, dispersity, and modification of the synthesized particles using different advanced instruments. The luminescent nanoclusters traced the Fe(III) ions by the luminescence-quenching mechanism of the Tryp-AgNCs luminescence. Therefore, the extreme selectivity of the prepared nanoclusters was exhibited to the Fe(III) ions, permitting the sensitive tracing of ferric ions in the lab and in the real environmental samples. The limit of detection for Fe(III) ions based on Tryp-AgNCs was calculated to be 16.99 nM. The Tryp-AgNCs can be efficiently applied to a paper test strip method. The synthesized nanoclusters were used efficiently to detect the Fe(III) ions in the environmental samples. Moreover, we examined the reactivity of Tryp-AgNCs on various human tumor cell lines. The results show that the Tryp-AgNCs exhibited their activity versus the cancer cells in a dose-dependent routine for the perceived performance versus the greatest-used cancer cell lines.

Experimental study on dispersion characteristics and CH4 recovery efficiency of CO2, N2 and their mixtures for enhancing gas recovery

Dispersion is considered as an important indicator to reflect the contamination of produced gas during CO2 enhanced gas recovery (EGR). Reducing dispersion while obtaining a high CH4 recovery is the primary goal of EGR research. In this work, the effects of core permeability and different types of displacing fluids on dispersion and CH4 recovery efficiency were investigated. The CO2 dispersion and the recovery efficiency were compared in the pressure range from gaseous to supercritical state, it was found that the CO2 dispersion coefficient is anomalously large near the critical point. The results reveal that the implementation of EGR at supercritical conditions is most favorable in terms of less CO2 dispersion and higher CH4 recovery. Higher permeability of porous media has a weakening effect on dispersion and increases the CH4 recovery efficiency. In vertical upward displacement experiments, CO2 has a smaller dispersion coefficient and higher CH4 recovery efficiency compared to N2. However, in the horizontal displacement experiments, the gravity effect on CO2 was more pronounced in the high permeability cores, resulting in greater dispersion and lower recovery efficiency. Moreover, it was found that the CH4 recovery efficiency provided by the displacing fluids with high CO2 concentration becomes larger as the injection flow rate increases, while the displacing fluids with high N2 concentration gradually decreases after reaching the maximum recovery efficiency as the injection flow rate increases.

Investigations of chemical sensing properties of Al24N24, B24N24, and B24P24 nanoclusters toward carbamazepine: A DFT study

By employing density functional theory (DFT) calculations, the adsorption properties of carbamazepine (CBZ) molecules on the Al24N24, B24N24, and B24P24 nanoclusters were investigated for its detection. All calculations were executed at the B3LYP level of theory and 6-311G (d, p) basis set employing an empirical dispersion term (B3LYP-D) to consider dispersion interactions. The CBZ molecules were adsorbed on the Al24N24, B24N24, and B24P24 nanoclusters with adsorption energies of −38.02, −16.96, and −16.00 kcal mol−1 in their most stable configuration, respectively. After the interaction of nanoclusters with CBZ, significant changes of −12.9%, –33.3%, and −7.7% in their electrical conductivity (σ) took place, respectively. These results indicate the higher sensitivity of the B24N24 nanocluster for its detection. Furthermore, the required time for CBZ desorption from B24N24 was about 0.03 s, demonstrating its short recovery time based on transition theory calculations. The possibility of CBZ detection in the liquid solution was investigated for the selected adsorption configurations. It was shown that they are stable in this phase, and the values of adsorption energies have not changed noteworthy. UV–vis spectroscopy results demonstrated that the B24N24 nanocluster's spectrum exhibits a more significant shift to the higher wavelength (lower energies) region. These results show that it is possible to utilize the B24N24 for the detection of CBZ.

Quantum model for supercontinuum generation process

A quantum theory is established for the propagation of electromagnetic waves in highly nonlinear dispersive optical fibers. By applying the method recently presented dispersion terms and retarded response of the medium are included for the propagation of light in a fiber in this work. A coupled stochastic generalized nonlinear Schrödinger equation (GNLSE) is obtained via the coherent positive-P representation to describe the supercontinuum generation process. This coupled quantum-stochastic equation is applied to obtain the linearized fluctuation equation for studying quantum noise and the fluctuation in the vicinity of the formed solitons in the supercontinuum generation process in the region of anomalous dispersion. Also, these equations can be used to study the soliton self-frequency shift quantum mechanically. Finally, we simulate the obtained coupled stochastic generalized nonlinear Schrödinger in the mean case and compare our simulation results with experimental results.

New impressive representations for the soliton behaviors arising from the (2+1)-Boussinesq equation

In the present work, we will detect unpredicted conducts “which weren't realized before” to the soliton solutions of the (2+1)-Boussinesq equation by using three distinct algorithms. The proposed equation is the famous nonlinear one which distinguishes the waves of coastal and ocean engineering that involve the nonlinearity and dispersion terms. Moreover, it is a developed form of the standard Boussinesq equation which describes the solution interaction mechanism of shallow-water waves that involve many waves and shallow water influences refraction, diffraction, shoaling and weak nonlinearity properties arising in fluid dynamics. It also plays principal role in many physics branches, such as propagation of long waves in shallow water, vibrations in a nonlinear string and ion sound waves in plasma and one-dimensional nonlinear lattice waves. The three algorithms that will select for this purpose are the (G′G) -expansion method, the extended direct algebraic method (EDAM) and the extended simple equation method (ESEM). These three distinct manners are applied in the same time and parallel. We will show comparison between our new soliton solution behaviours with that constructed before.

Closed form solutions for the generalized0fifth-order KDV equation by using the modified exp-function method

• The new approach of modified exp-function method has been effectively executed. • Find exact soliton solutions to the non-linear partial differential equation. • We have applied successfully modified exponential function method to the generalized fifth- order KDV equation. We investigate solitary wave solutions of the generalized fifth-order Korteweg–de Vries equation, which includes additional terms such as cubic nonlinearity and fifth order linear dispersion, as well as two nonlinear dispersive terms, in addition to the traditional quadratic nonlinearity and third-order dispersion. The projected modified exponential function approach is used to find exact solitary wave solutions to this equation, and the dependence of their amplitude, width, and speed on the parameters of the governing equation is investigated. Depending on the equation parameters, the resultant solution can represent either an embedded or regular soliton. Hyperbolic, trigonometric, and rational function solutions are obtained as a result. The symbolic computation software Maple verifies the accuracy of all obtained solutions. Finally, 3D, 2D, and contour plots of some of the derived solutions are shown to demonstrate the model's physical look. Many scientific and oceanographic applications involving ocean gravity waves and other associated phenomena require our acquired conclusions in this work concerning our examined equation.

Study Regarding the Evaluation of Prediction Models for Determining the Concrete Compressive Strength Using Non-Destructive Testing (NDT) Data: Validation Stage

In the evaluation of an existing reinforced concrete structure, a fundamental issue is determining the concrete compressive strength as accurately as possible. This process can be conducted by using destructive and non-destructive methods. The destructive method presumes a limited number of cores extracted from the concrete structure. A higher number of cores would affect the structural safety and is time and resource consuming. Therefore, the conclusions drawn using exclusively this method can also generate errors in correctly estimating the load bearing capacity of a structure, thus leading to the possibility of implementing deficient measures in order to ensure a structural safety. Data obtained via non-destructive methods are more comprehensive. Due to their non-destructive nature, there are no limitations regarding the number of elements investigated and are fast in delivering results. One of the main concerns of researchers in this field is developing a direct relationship between the measured indicators through non-destructive testing (NDT) methods and concrete compressive strength. Over the years different equations with different mathematical structure (linear, polynomial, power, exponential and logarithmic) were developed with the main purpose of delivering fast and accurate results concerning concrete compressive strength by the means of NDT. The aim of this paper is to validate some of the most important prediction models using an original set of data. The database consists in a number of 96 concrete cores that were subjected to Ultrasonic Pulse Velocity (UPV) and Schmidt Rebound Hammer (SRH) testing. The accuracy of the results was determined by using two statistical parameters the mean absolute error (MAE) and mean absolute percentage error (MAPE). The proposed equations have been analyzed in terms of prediction and dispersion of values. It was noticed that some of the formulations predict values that are higher than the ones obtained destructively, others provide a larger dissipation of values, while some equations deliver a compact distribution of results with higher rate in terms of accuracy. This study proposes a data validation of some of the most popular empirical equations, used for the estimation of the concrete compressive strength, elaborated through the years, using a new set of data.

INTERFEROMETRIC SAR DEFORMATION MONITORING USING PASSIVE REFLECTORS AND ASCENDING AND DESCENDING PASSES

Abstract. The article concerns the estimation of land deformation in an area of copper mining using the Persistent Scatterer Interferometry (PSI) technique and C-band data coming from the Sentinel-1 satellite. The aim of the work is a comparison of two different PSI approaches exploiting passive corner reflectors deployed pairwise, oriented towards the satellites in ascending and descending orbits. The comparison was done in the line of sight geometry. In addition, a validation was carried out using GNSS measurements. The results achieved using the two PSI approaches are consistent and mutually coherent. They are also congruent with observations from GNSS stations. These results proves that the method proposed to identify pixels on multi-looked images is correct. In addition, the intermediary results on the corner reflectors shows that their responses, in terms of dispersion of amplitude and the coherence, is slightly different. This needs to be further studied.

Quintic-Septic Nonlinear Schrödinger Equation with a Third-Order Dispersion Term

In the present study, the quintic-septic nonlinear modulation of a longitudinal wave propagating to contribute the dispersive and higher-order nonlinear effects in a generalized cubically nonlinear elastic medium is considered. In recent work, for the modulation of a longitudinal wave, a cubic nonlinear Schrödinger equation with a third-order dispersive term is obtained by using a multi-scale expansion of quasi-monochromatic wave solutions. The third- quintic-septic longitudinal wave, by choosing specific values of material constants and wave number for which some coefficients of nonlinear terms are disappeared. In this case, a new perturbation expansion is needed to balance nonlinear effects with dispersive effects. As a result, a quintic-septic nonlinear Schrödinger equation with a third-order dispersion term is obtained as a new model that balances quintic-septic nonlinearity with a third-order dispersion term.

Numerical Simulation for One-Dimensional (1D) Wave Propagation by Solving the Shallow Water Equations using the Preissmann Implicit Scheme

This research simulated one-dimensional wave propagation by solving the shallow water equations using the Preissman implicit numerical scheme due to its ability to maintain simplicity and stability at a larger time step value. This numerical model was fundamentally developed to satisfy the shallow water condition, where the water depth or horizontal-length scale is much smaller than the free-surface disturbance wavelength or vertical-length scale, and to comprehensively test the accuracy of the model. Consequently, three different types of waves were considered and these include (1) tidal, (2) roll, and (3) solitary. In the first case, the model was proven to be robust and accurate due to its relatively-small errors for both water-surface elevation and velocity indicating that the Preismann scheme is suitable for longwave simulations. In the second case, it was fairly accurate in capturing the periodic permanent roll waves despite showing a higher water-surface elevation than the one observed and this discrepancy is due to the neglect of the turbulent Reynold stress in the model. Meanwhile, the last case showed remarkable discrepancies in the water-surface elevation because the dispersion effect is quite significant during the wave propagation. This indicates that the Preismann scheme underestimated the wave crest along with time when the dispersion term was neglected. All simulations were performed using the tridiagonal matrix algorithm, thereby eliminating the need for iterations for the solution of the Preismann scheme. The findings of this study are beneficial to the next generation of the Preissmann-scheme models which can be designed to include turbulence and dispersion terms.

Quasiclassical Trajectory Study of the Si + SH Reaction on an Accurate Double Many-Body Expansion Potential Energy Surface

An accurate potential energy surface (PES) for the HSiS system based on MRCI+Q calculations extrapolated to the complete basis set limit is presented. Modeled with the double many-body expansion (DMBE) method, the PES provides an accurate description of the long-range interactions, including electrostatic and dispersion terms decaying as R-4, R-5, R-6, R-8, R-10 that are predicted from dipole moments, quadrupole moments, and dipolar polarizabilities, which are also calculated at the MRCI+Q level. The novel PES is then used in quasiclassical trajectory calculations to predict the rate coefficients of the Si + SH → SiS + H reaction, which has been shown to be a major source of the SiS in certain regions of the interstellar medium. An account of the zero-point energy leakage based on various nonactive models is also given. It is shown that the reaction is dominated by long-range forces, with the mechanism Si + SH → SiSH → SSiH → SiS + H being the most important one for all temperatures studied. Although SSiH corresponds to the global minimum of the PES, the contribution from the direct reaction Si + SH → SSiH → SiS + H is less than 0.5% for temperatures higher than 500 K. The rovibrational distributions of the products are calculated using the momentum Gaussian binning method and show that as the temperature is increased the average vibrational quantum number decreases while the rotational distribution spreads up to larger values.

Asymptotic stability of small ground states for NLS under random perturbations

We consider the cubic Schrödinger (NLS) equation on the Euclidean space perturbed by a short-range potential V . The presence of a negative simple eigenvalue for -\Delta+V gives rise to a curve of small and localized nonlinear ground states that yield some time-periodic solutions known to be asymptotically stable in the energy space. We study the persistence of these coherent states under rough perturbations. We shall construct a large measure set of small scaling-supercritical solutions below the energy space that display some asymptotic stability behaviors. The main difficulty is the need to handle the interactions of localized and dispersive terms in the modulation equations. To do so, we use a critical-weighted strategy to combine probabilistic nonlinear estimates in critical spaces based on U^p , V^q (controlling higher-order terms) with some local energy decay estimates (controlling lower-order terms). We also revisit in the perturbed setting the analysis of Bényi, Oh, and Pocovnicu (2015) on the probabilistic global well-posedness and scattering for small supercritical initial data. We use a distorted Fourier transform and semiclassical functional calculus to generalize probabilistic and bilinear Strichartz estimates.

Detailed analysis for chirped pulses to cubic-quintic nonlinear non-paraxial pulse propagation model

This paper's main focus is on chirped pulses (CP) for a cubic-quintic nonlinear non-paraxial pulse propagation (CQ-NNP-PP) model. Chirped solitons are a relatively new single wave phenomena. The exact CPs generate from the derivative nonlinear Schrödinger equations (NLSE). Chirp is a signal with a changing frequency over time. CPs are used in spread spectrum communications as well as some sonar and radar devices. The propagation of CPs in fibre optics is getting popular due to a wide range of applications in amplification and pulse compression. In an NLSE, the dispersion management (DM) term can influence the velocity of chirp-free nonautonomous soliton but has no effect on its shape. When there is no gain, the classical optical soliton can be expressed with a variable dispersion term and nonlinearity. DM can impact the shape and motion of non autonomous solitons for CPs. We obtain hyperbolic and periodic solutions, as well as a class of solitary wave (SW) solutions such as bright, dark, singular and bell soliton solutions. The governing model will be analyzed with the aid of Jacobian elliptic functions (JEF). We also show accomplished results in 3D and 2D structures.

A characteristic expanded mixed finite element numerical method for incompressible miscible displacement problem involving dispersion term

A characteristic expanded mixed finite element method is presented for miscible displacement problem involving dispersion term. Two-grid algorithm is used to linearize the nonlinear coupling equations. The error estimations of the two-grid solution is conduced in detail by L q $L^q$ error estimates of characteristic expanded mixed finite element methods. Numerical experiment shows that this algorithm is more efficient when the dispersion term D ( u ) $\bm {D}(\bm {u})$ is very small.