Power-law Theory Research Articles

Effect of concentration and electrical charge of maltodextrin, and packing factor on electrospinning processing

The power law ηrel ∼ Ca of maltodextrins with higher entanglement concentrations (Ce) of dextrose equivalent (DE) 4, 10, and 18 exhibits an unusually high exponent a, ranging from 10.34 to 14.38 in congested solutions where particles occupy significant space. This contrasts with the dilute exponents (a ∼2) typically observed in polymer–solvent systems. To address this issue, several viscosity factors were evaluated using the Einstein–Roscoe and Mooney equations, which demonstrated viscosity dependence due to volume fraction (ϕ) > 0.35, shape, crowding factor (k) packing factor (1/k∼0.5) and centered cubic cell (CC), particularly for larger chain sizes (>20 glucoses) in DE-4. Chain electrical charges significantly stiffen the chain and increase its length beyond the theoretically predicted Kuhn persistent length (Lp), which seems to be responsible for the exponential increase in viscosity. Normalizing the viscosity/charge data revealed a log–log plot consistent with the exponent a of the general power law theory. In addition to concentration, electrospinning processing is influenced by strong particle–particle charge interactions, (ϕ), packing factor (1/k), CC, and chain sizes. The Maxwell model demonstrated poor interaction for DE-4 (modulus ∼286 Pa at maximum ϕ due to loose packing of CC, in contrast to DE-18, which exhibited a modulus of 994 Pa for a solution with maximum ϕ> 0.5 and a congested solution of 52% w/v, packing factor of 0.68, and high particle–particle interaction of the body-centered cubic (BCC) cell, favoring electrospun fiber formation. The packing factor, ϕ, and cell type, are highly sensitive and have potential applications in food systems, 3D bioprinting, among many other scientific domains.

Extreme Space Weather Impacts on GNSS Timing Signals for Electricity Grid Management

AbstractExtreme space weather events can have serious impacts on critical infrastructure, including Global Navigation Satellite Systems (GNSS). The use of GNSS, particularly as sources of accurate timing signals, is becoming more widespread, with one example being the measurement of electricity grid frequency and phase information to aid grid management and stability. Understanding the likelihood of extreme space weather impacts on GNSS timing signals is therefore becoming vital to maintain national electricity grid resilience. This study determines critical intensity thresholds above which the complete failure of a GNSS based timing system may occur. Solar radio bursts are identified as a simple example to investigate in more detail. The probability of occurrence of an extreme space weather event with an intensity equal to or greater than the critical intensity is estimated. Both a power law and extreme value theory were used to evaluate recurrence probabilities based on historical event frequencies. The probability was estimated to be between 3%–12% per decade to cause the complete failure of any GNSS‐based timing system.

Antisolvent crystallization kinetics of different substances in solvent–antisolvent systems

Published experimental data of metastable zone width (MSZW) for the crystallization of four different solutes from their saturated solutions, determined as the maximum antisolvent content Δxmax, by addition of selected antisolvents as a function of feeding rate RA using theoretical equations based on power law (PL) and classical nucleation theory (CNT) are analyzed and trends of variations of the parameters of the equations and relationship between the parameters of the two approaches are discussed. With Δxmax taken in mole fraction of the antisolvent, from the analysis of the Δxmax(RA) data for the different investigated systems the following conclusions may be drawn:(1)The values of the parameters of the linear dependence of ln(Δxmax) on lnRA of the PL-based approach and those of the parameters of the linear dependence of (Δxmax)−2 on lnRA of the CNT-based approach are mutually related.(2)The preexponential factor A of the CNT, associated with the frequency of attachment of solute molecules with, and their detachment from, the growing three-dimensional nuclei, and their solute–solution interfacial energy γeff mainly depend on the product fa2, where f is the number of molecules or ions of solute per m3 in its saturated solution and a2 is the dimensionless solvent–antisolvent interaction parameter. The sequence of variation of γeff is opposite to that of the preexponential factor A.(3)The observed trend of variation of the nucleation constant K calculated from the analysis of antisolvent content Δxmax taken in mole fraction is similar to that of the A for different systems. However, A ≫ K and the ratio A/K ≈ 106.(4)The values of γeff obtained from the MSZW data of the investigated compounds are low and suggest the occurrence of their crystallization by heterogeneous nucleation.

Nonzero spatial curvature in symmetric teleparallel cosmology

We consider the symmetric teleparallel fQ-gravity in Friedmann–Lemaître–Robertson–Walker cosmology with nonzero spatial curvature. For a nonlinear fQ model there exist always the limit of General Relativity with or without the cosmological constant term. The de Sitter solution is always provided by the theory and for the specific models fAQ≃Qαα−1,fBQ≃Q+f1Qαα−1 and fCQ≃Q+f1QlnQ it was found to be the unique attractor. Consequently small deviations from STGR can solve the flatness problem and lead to a de Sitter expansion without introduce a cosmological constant term. This result is different from that given by the power-law theories for the other two scalar of the trinity of General Relativity. What makes the nonlinear symmetric teleparallel theory to stand out are the new degree of freedom provided by the connection defined in the non-coincidence frame which describes the nonzero spatial curvature.

Hierarchical Zinc Stannate Nanoneedle-Based Sensitive Detection of Formaldehyde

Perovskite-type ternary metal oxides have persisted as an area of research toward developing interesting nanostructures and their subsequent application. The paper presents a nanodimensional needle-like hierarchical structure of zinc stannate (ZnSnO3) material for the sensitive detection of formaldehyde. The nanomaterial was successfully synthesized through a simple and low-cost hydrothermal process. The morphology and structural properties were validated through various material characterization techniques. The nanoneedles were formed with a definite shape having an average thickness and a length of 20 and 450 nm, respectively, along with high crystallinity. Additionally, the evolution process of the grown nanostructure was discussed considering the involved chemical reactions. The gas-sensing behavior was investigated, where the maximum response was found toward formaldehyde with admirable sensitivity, fast kinetics, complete reversibility, and good selectivity and reproducibility. The limit of detection was found to be 717 ppb using the power law theory of semiconducting gas sensors. The sensing mechanism was explained using adsorption theory and the corresponding electron depletion layer modulation. The reported results indicate the potential influence of the prepared ZnSnO3 nanoneedles toward efficient integration in various electrochemical applications.

Spatial disparity of urban performance from a scaling perspective: a study of industrial features associated with economy, infrastructure, and innovation

ABSTRACT The power-law scaling theory has been widely applied in urban studies. Industrial development is tied to cities. However, current research on scaling pace development of industrial features in cities, and industrial features’ association with urban indicators in cities are limited. This study develops power-law scaling regression and robust geographical detector-based spatial models to (i) identify spatial disparities of urban performance from a scaling perspective and (ii) explore the spatial association between industrial scaling features and other urban features. The developed models are implemented in three essential industries, including mining, manufacturing, and utility supply and waste services, in Australia. This study investigates urban scaling features in 101 Australian significant urban areas (SUAs) and assesses the spatial association between industrial features and indicators from the perspectives of the economy, infrastructure design, and innovation. This study has general results on Australian urban scaling development and specific spatial association results on industrial scaling features. In general, the study validates the consistency of the scaling development among Australian cities with the power-law theory and the similarity of scaling disparity features among top-populated cities. In specific, the urban innovation indicator and the income level are predominantly and positively associated factors with industrial companies and employees, indicating that the innovation growth and economic development in Australian cities would stimulate the performance of industrial companies and the employment scale. The synergy between urban innovation and industrial company performance is especially significant in major capital cities. The developed spatial models have a broad potential to address spatial and scaling characteristics of industrial features.

Enhanced electrical and magnetic functionality of Ni-Zn-co-doped CoFe2O4 rGO nanocomposites.

Enhancement in electrical and magnetic functionalities of rGO CoFe2O4 and Co0.7Zn0.3Fe1.7Ni0.3O4 nanocomposites was identified compared to their spinel-type metal oxides. Moreover, changes in morphology that occurred during the formation of the composites were fabricated via a simple in situ hydrothermal route. Electron microscopic investigations confirmed that the microspheres of the metal oxides were constructed by porous nanolamellae comprising nanoparticles interconnected to form highly stable porous microspheres. Conversely, in rGO-CoFe2O4 and rGO-Co0.7Zn0.3Fe1.7Ni0.3O4 composites, distorted spinel-type metal oxide spheres on rGO sheets were observed. Frequency-dependent conductivity increased with an increase in temperature, obeying Jonscher's power law and Koop's phenomenological theory. The resistance of ferrites decreased from ∼1.4 MΩ to 30 KΩ for their respective rGO-based nanocomposites. The hysteresis curves of all the compounds showed them to be isotropic, soft ferrimagnetic in nature. Furthermore, a 30-50% enhancement in the values of magnetic parameters of the ferrites occurred when they were interfaced with rGO sheets. This enhancement was probably due to the interfacial interaction of rGO with ferrites. Such enhancement may afford an advancement in the potential applications of these nanocomposites.

Structural, electrical and gas sensing functionality of fabricated Co1-xZnxFe2-xNixO4 (x= 0.0,0.3) nanoparticles

This article reports for the first time the structural, electrical, and gas sensing functionality of novel composition of spinel-type porous Co0.7Zn0.3Fe1.7Ni0.3O4 microspheres fabricated through a simple hydrothermal route. The structural, morphological, and elemental properties of the materials are characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) along with selected area electron diffraction pattern. XRD and XPS data reveal a pure phase spinel-type cubic crystal formation. Electron microscopic investigations confirm that the microspheres are devloped by the porous nano-lamellae made up of nanoparticles that are interconnected in a manner to form highly stable porous microspheres. AC impedance spectroscopy is utilized to analyse the electrical conductivity at different temperatures which disclose extrinsic semiconductor behaviour. The DC conductivity derived activation energy of the sample is found to be 0.76 eV. The frequency dependent conductivity of the compound obeyed Jonscher's power law and Koop's phenomenological theory. The sensing properties of the Zn and Ni doped ferrite were investigated for different gases and it demonstrates the promising sensing behaviour towards butane gas.

Modeling Rheological Behavior of Beef based on Time-Dependent Deformation and Packaging

Modeling of food deformation behavior is vital for structural characterization. This research was undertaken to study the rheological properties of beef by developing mathematical models for different packaging and temperature conditions. The rheological properties of the beef sample, packaged in a polyethylene (LD and HD) and aluminum foil (A foil), were determined experimentally at -20oC and 5oC for 0‒ 60 days. Power law, Herschel-Bulkley and Tiu-Boger theories, formulated for a period-dependent deformation, were used to constitute the models. Results show that the deformation index varies in the range of 1< n< 3, indicating a nonNewtonian shear thickening behavior. Also, a better estimation of the deformation consistency, k was obtained using the Tiu-Boger theory for the A. Foil at 5oC and Herschel-Bulkley theory for the LD at -20oC. The models are significant with MSE <5% and R2 > 85%, suggesting their suitability for industrial scale-up prediction.

Asset Price Bubble under Behaviroral Finance Theory: Based on Log-Periodic Power Law Model

The asset price bubble problem is not only the most concerned topic in the financial circle, but also one of the most important research topics in the financial circle. In history, every time asset prices skyrocketed, bubbles were accumulated, and every asset price crash resulted in a massive shrinking of wealth, bankruptcy of enterprises, and economic recession. This paper is based on the theory of investor behavioral bias in behavioral finance theory, and is based on the log-periodic power law (LPPL) theory of iron ore futures, apple futures, coke futures and stock market indices that is widely used in Chinese financial markets. The market index and bitcoin price are empirically analyzed through the process of bubble accumulation, and the stock market index of China's stock market and the index of China's capital market are predicted and analyzed based on LPPL theory.

Experimental and Numerical Studies of Ignition Delay Time and Laminar Flame Speed of JP-10 at Elevated Temperature Conditions

In this work, the laminar flame speeds of JP-10/air mixtures and ignition delay time of JP-10/O2/Ar mixtures have been studied over a wide range of experimental conditions using a premixed Bunsen flame and a shock tube. Laminar flame speed measurements of the JP-10/air mixture were measured at T = 360–453 K, φ = 0.7–1.3 and p = 1 atm. The ignition delay times of JP-10 with fuel mole fraction of 0.2% JP-10/2.8% O2/97% Ar were measured with a heated shock tube behind the reflected shock wave at 1183–1478 K and pressure of 3.4 atm. Numerical calculation and sensitivity analysis of the laminar flame speed and ignition delay time of JP-10 were performed by using published detailed and skeletal kinetic mechanisms. The comparison of experimental and numerical results showed that all models tend to overestimate the laminar flame speed under the studied conditions, especially under lower temperature conditions (360–423 K). A temperature dependency empirical correlation of laminar flame speed was then proposed by power law theory. The sensitivity analysis identified three important reactions [H+O2 = O+OH, C5H5+H (+M) = C5H6(+M), C3H3+C2H2 = C5H5] that determined the laminar flame speed and ignition delay time.

F(T) cosmology with nonzero curvature

We investigate exact and analytic solutions in [Formula: see text] gravity within the context of a Friedmann–Lemaître–Robertson–Walker background space with nonzero spatial curvature. For the power-law theory [Formula: see text] we find that the field equations admit an exact solution with a linear scalar factor for negative and positive spatial curvature. That Milne-like solution is asymptotic behavior for the scale factor near the initial singularity for the model [Formula: see text]. The analytic solution for that specific theory is presented in terms of Painlevé series for [Formula: see text]. Moreover, from the value of the resonances of the Painlevé series we conclude that the Milne-like solution is always unstable while for large values of the independent parameter, the field equations provide an expanding universe with a de Sitter expansion of a positive cosmological constant. Finally, the presence of the cosmological term [Formula: see text] in the studied [Formula: see text] model plays no role in the general behavior of the cosmological solution and the universe immerge in a de Sitter expansion either when the cosmological constant term [Formula: see text] in the [Formula: see text] model vanishes.

Thermomechanical Buckling Analysis of the E&P-FGM Beams Integrated by Nanocomposite Supports Immersed in a Hygrothermal Environment.

Due to the widespread use of sandwich structures in many industries and the importance of understanding their mechanical behavior, this paper studies the thermomechanical buckling behavior of sandwich beams with a functionally graded material (FGM) middle layer and two composite external layers. Both composite skins are made of Poly(methyl methacrylate) (PMMA) reinforced by carbon-nano-tubes (CNTs). The properties of the FGM core are predicted through an exponential-law and power-law theory (E&P), whereas an Eshelby–Mori–Tanaka (EMT) formulation is applied to capture the mechanical properties of the external layers. Moreover, different high-order displacement fields are combined with a virtual displacement approach to derive the governing equations of the problem, here solved analytically based on a Navier-type approximation. A parametric study is performed to check for the impact of different core materials and CNT concentrations inside the PMMA on the overall response of beams resting on a Pasternak substrate and subjected to a hygrothermal loading. This means that the sensitivity analysis accounts for different displacement fields, hygrothermal environments, and FGM theories, as a novel aspect of the present work. Our results could be replicated in a computational sense, and could be useful for design purposes in aerospace industries to increase the tolerance of target productions, such as aircraft bodies.

Fundamental investigation of the gas permeation mechanism of facilitated transport membranes with Co(salen)-containing ionic liquid as O2 carriers

Metal-containing ionic liquids (MCILs) composed of a cobalt(II)–salen complex and ionic liquid-based axial ligands (ligand ILs) can chemically absorb O2 and act as O2 carriers in facilitated transport membranes. O2 and N2 permeation tests using supported MCIL membranes with various MCILs revealed that the effective diffusion coefficients of N2 and O2–MCIL complexes did not follow to the trend expected by power law theories against viscosity (e.g. the Stokes–Einstein equation), because the MCILs are not in normal liquid state due to the strong intermolecular interaction, but instead showed a tendency predicted by the free volume theory. This means the MCILs behave as a solid rather than a liquid, and N2, O2, and the O2–MCIL complexes would diffuse through the free volume of the MCILs. The solubility selectivity and the diffusion selectivity of the supported MCIL membrane decreased and increased, respectively, with the increase on MCIL molecular wight (free volume). Thus, there was trade-off relationship between the solution selectivity and the diffusion selectivity. It was suggested that the most important criteria for designing MCILs for highly selective O2 permeation in supported MCIL membranes is the use of an O2-absorbable metal complex without the strong intermolecular interaction.

Size-dependent vibration in two-directional functionally graded porous nanobeams under hygro-thermo-mechanical loading

In this study, vibrational behavior of a two-directional functionally graded (2D-FG) porous nanobeam is investigated under hygro-thermo-mechanical loading, based on the Euler-Bernoulli beam theory for various boundary conditions. The properties of the 2D-FG nanobeam are assumed to be in the form of power-law theory. Furthermore, using Eringen’s nonlocal elasticity theory, Hamilton’s principle is utilized to derive the governing equation. Subsequently, the governing equation is converted to an ordinary differential equation using the Galerkin method. The obtained equation is then solved through the Ritz averaging technique for simply-simply supported (S-S), clamped-simply supported (C-S), and clamped-clamped (C-C) boundary conditions to achieve the frequency response of the 2D-FG nanobeam. To validate the obtained equation and the solution procedure, the obtained numerical results are compared with those of a well-known reference in the literature, under similar boundary conditions, material properties, and the values of porosity index and nonlocal parameter, through which the good agreement between the results is demonstrated. Finally, influences of various parameters including moisture (hygro-)effect, porosity, thermal change, nonlocal parameters, and power-law indices in the x - and z -directions are examined for various boundary conditions.

Turbulent Transport of Spray Droplets in the Vicinity of Moving Surface Waves

AbstractA common technique for estimating the sea surface generation functions of spray and aerosols is the so-called flux–profile method, where fixed-height concentration measurements are used to infer fluxes at the surface by assuming a form of the concentration profile. At its simplest, this method assumes a balance between spray emission and deposition, and under these conditions the concentration profile follows a power-law shape. It is the purpose of this work to evaluate the influence of waves on this power-law theory, as well as investigate its applicability over a range of droplet sizes. Large-eddy simulations combined with Lagrangian droplet tracking are used to resolve the turbulent transport of spray droplets over moving, monochromatic waves at the lower surface. The wave age and the droplet diameter are varied, and it is found that droplets are highly influenced both by their inertia (i.e., their inability to travel exactly with fluid streamlines) and the wave-induced turbulence. Deviations of the vertical concentration profiles from the power-law theory are found at all wave ages and for large droplets. The dynamics of droplets within the wave boundary layer alter their net vertical fluxes, and as a result, estimates of surface emission based on the flux–profile method can yield significant errors. In practice, the resulting implication is that the flux–profile method may unsuitable for large droplets, and the combined effect of inertia and wave-induced turbulence is responsible for the continued spread in their surface source estimates.

Cosmography and the redshift drift in Palatini f({{mathcal {R}}}) theories

We present an application to cosmological models in f({{mathcal {R}}}) theories within the Palatini formalism of a method that combines cosmography and the explicit form of the field equations in the calculation of the redshift drift. The method yields a sequence of constraint equations which lead to limits on the parameter space of a given f({{mathcal {R}}})-model. Two particular families of f(mathcal{R})-cosmologies capable of describing the current dynamics of the universe are explored here: (i) power law theories of the type f({{mathcal {R}}})={{mathcal {R}}}-beta /{{mathcal {R}}}^n, and (ii) theories of the form f({{mathcal {R}}})={{mathcal {R}}}+alpha ln {{{mathcal {R}}}} -beta . The constraints on (n,beta ) and (alpha ,beta ), respectively, limit the values to intervals that are narrower than the ones previously obtained. As a byproduct, we show that when applied to General Relativity, the method yields values of the kinematic parameters with much smaller errors that those obtained directly from observations.

Design of passive launch and on-orbit vibration isolation system for control moment gyroscopes

This paper proposes a robust design of a passive nonlinear viscous damping system, which is capable of not only isolating disturbances induced by control moment gyroscopes (CMGs) but also reducing the launch loads transmitted to CMGs. A novel and robust design of viscous damper is developed in the current work, which can provide high damping for launch dynamic loading and low damping for on-orbit micro-vibration loading. In order to understand the nonlinear damping mechanisms of such a viscous damper, a theoretical analysis based on power-law fluid theory is given in this paper. The nonlinear effect and performance of the isolation system are demonstrated by launch environment tests and micro-vibration tests. The test results indicate that the isolation system guarantees the dynamic safety of CMGs under the launch environment and the micro-vibration isolation efficiency of CMGs on orbit.

Novel viscoelastic model for predicting the synthetic polymer’s viscoelastic behavior in porous media using direct extensional rheological measurements

High molecular weight, flexible polymers used for heavy oil recovery exhibits viscoelasticity that causes the thickening of apparent viscosity which could not be predicted by the conventional shear thinning rheological models. Unified apparent viscosity model (UVM) developed at UT-Austin based on the postulation that the apparent viscosity of polymer solutions is the sum of shear and elongational viscosity accounts for the viscoelastic thickening in the extensional part through relaxation time, maximum elongational viscosity and strain hardening index. Although UVM addresses the other limitation of the previous viscoelastic models, its dependence on the core flood data to predict maximum elongational viscosity and strain hardening index limits its commercial independent usage for preliminary screening.These limitations are addressed in our novel viscoelastic model named as Azad Trivedi Viscoelastic Model (AT-VEM), which could predict the apparent viscosity in the shear thickening region using the extensional parameters measured by capillary breakup extensional rheometer (CaBER) through the combination of Upper Convected Maxwell (UCM), finite extensible nonlinear elasticity (FENE) and power law theories. CaBER set up uses a step-strain to stretch the drop of polymeric liquid placed between the two plates and monitor its midpoint diameter during filament drainage. The relaxation time is determined by fitting the filament diameter from the region representing the balance between the elastic stress and surface tension into UCM. As per FENE theory, fluid relaxes at the rate two-third of its strain rate and the extensional viscosity around the critical Deborah number of 0.66 corresponds to the maximum elastic limit and would be the maximum elongational viscosity. Filament during drainage gets strained and the corresponding increment in extensional viscosity is fitted with power law to determine the strain hardening index.A series of core flood data (performed using partially hydrolyzed polyacrylamide (HPAM) polymers) from the UT-Austin that validated the UVM model was used extensively. Other reported literature data were also used. Extensional rheology was performed on those polymers at the similar conditions to determine the relaxation time, maximum elongational viscosity, and strain hardening index. These parameters along with the shear parameters were used to match the reported apparent viscosity. All the experiments fairly match well with the average downscaling power factor of 0.35 to the maximum elongational viscosity and subtrahend of 1.2 to the strain hardening index. Downscaling and subtrahend factor is essential to scale down the pure elongation in the extensional bulk field to the combination of shear and elongation experienced in the porous media.AT-VEM can be incorporated into commercial numerical simulators for predicting the injectivity and recovery due to viscoelastic thickening independently and thereby assist in quick screening polymers for oil recovery applications.

The elusive linkage between CEO pay and performance

ObjetivoDiscutimos o trabalho de Aguinis et al. (2018). Acreditamos que as suas hipóteses são provavelmente verdadeiras, mas a sua metodologia apresenta deficiências e os dados apresentados não suportam as conclusões.Design/metodologiaAnalisamos e comentamos o trabalho de Aguinis et al. (2018).ResultadosOs dados não demonstram adequadamente a existência de uma distribuição de poder-lei porque suas análises não consideram as condições externas que afetam o resultado da empresa e os autores fazem uso impróprio das variáveis dependentes. As análises não mostram que as recompensas dos CEOs seguem uma distribuição da lei do poder porque não tomam em consideração as mudanças no nível ou na composição da remuneração sobre o tempo. As análises não mostram falta de sobreposição entre as duas distribuições, porque não têm em conta a forma como os CEOs são pagos pelos resultados e porque utilizam a retribuição média calculada sobre a antiguidade do CEO.Limitações/implicaçõesUma análise mais convincente da hipótese proposta requer o uso do desempenho total dos acionistas como uma variável de resultados organizacionais e um número muito mais específico de variáveis de controle.Implicações práticasOs autores incentivam os profissionais a pensar mais em termos de uma distribuição da lei de potência quando se define o salário do CEO. Suas análises indicam que os profissionais já pensam em termos dessa distribuição e distribuem as recompensas de forma proporcional a ela. Além do mais, os resultados derivados da teoria da lei de poder podem ser erroneamente usados como uma desculpa para pagar menos para o CEO médio.Implicações sociaisAgregamos uma outra perspectiva no pagamento ao CEO.Originalidade/valorNossa perspectiva é apoiada pelo nosso pesquisa e experiência de consultoria em projetos de remuneração para CEOs.