Nonlinear Distribution Research Articles

Free vibration response of rotating pretwisted porous exponential and sigmoid functionally graded conical shells in thermal environment

A finite element method is used to analyze the free vibration of rotating functionally graded (FG) porous conical shell in thermal environment. Exponential and sigmoid laws are used for grading the FG conical shell in the presence of even and uneven porosity distributions. The one-dimensional Fourier heat conduction equation is used to calculate the nonlinear temperature distribution across the thickness of the shell. The parametric studies reveal that the porosity volume fraction has a significant impact on natural frequency. Centrifugal stiffening, which manifests as a geometrical stiffness matrix, causes rotational speed to enhance the natural frequency of the FG shell.

What we learn from nexus between greener growth andenergy‐relatedemissions: Sustainability perspective evidence in context of financial globalization

With gradually increasing global climate issues, the Energy Protection Agency (EPA) emphasizes emission reduction measures at the national and international levels. Financial globalization and green innovation are considered a solution to the low‐income problem through internalization and specialization of markets and bring technological progress and innovation through open market access. The developed nations have been using financial globalization as the main driver of economic progress. This study examines the effects of financial globalization and green innovation on energy‐related greenhouse gas emissions for G7 countries. Unlike the literature that considered carbon and overall greenhouse gas emissions, this study is novel as it specifically focuses on energy‐related emissions in developed economies. The authors use the panel data of G7 economies from 1990 to 2020. To estimate the individual effects of each explanatory variable on emissions despite the nonlinear data distribution, this study uses the novel method of moment quantile regression (MMQR) approach. The results suggested that financial globalization, income, eco‐innovation, financial risk and human capital significantly influence greenhouse gas emissions in G7 countries, where economic growth and human capital are the leading drivers of energy‐related emissions. However, green technology, financial globalization and financial risk significantly help improve the environmental quality of the region. The results suggested fruitful implications, including increased participation in global economic activities, investment in green innovation, human capital and efficient financial risk management to attain sustainable development.

Design and analysis of ultra-low moment noise flexure pivot in space gravitational wave detectors

To control the pointing accuracy of the telescope in the space gravitational wave detector at the nano-radian level, it is essential to design a flexure pivot with extremely low rotational moment nonlinearity during rotation. This study derives the theoretical equation of the nonlinear rotational moment of flexure pivot based on the beam bending strain energy equation and completes the design of ultra-low moment noise flexure pivot by integrating the structural form of conventional cross-spring flexure pivot. The nonlinear moment noise distribution in the frequency domain of three kinds of flexure pivots is then compared regarding TianQin’s circular high orbits. Then the relevant finite element simulation analysis will be performed for the flexure pivot structures, respectively, to ensure the accuracy of its rotational stiffness model and verify the correctness of nonlinear moment theory optimization through physical experiments. The results show that the optimized flexure pivot can effectively reduce the nonlinearity, and basically meet the nonlinear moment requirements in space gravitational wave detection.

Effects of heat treatment on the microstructure and flexural mechanical properties of carbon fiber reinforced composite cured by electron beam

Carbon fiber (CF)-reinforced composite materials are attracting attention in the automobile and aerospace industries based on their light weight and excellent mechanical properties. Electron beam curing technology is replacing the thermal curing process and can improve productivity by shortening the curing time of CF-reinforced composite materials to minutes. However, the electron beam-cured CF-reinforced composite materials have weak flexural strength. We have found that the deterioration of flexural strength of electron beam-cured CF-reinforced composites can be solved by heat treatment in a vacuum bag prior to the electron beam curing process. Through heat treatment under vacuum, the viscosity of the matrix resin was lowered, and voids between the laminated surfaces of the CF prepregs could be removed. Through this approach, the flexural strength of the electron beam cured composite material reached 1.6 GPa, which was approximately 65% improved compared to the non-heat treated material. In addition, the energy distribution transmitted when the composite material is irradiated with an electron beam was simulated using the Geant4 code. It was confirmed that the nonlinear distribution of energy transmitted to the inside of the specimen according to the electron beam energy should be carefully considered in the design of the product shape and when setting the electron beam irradiation conditions.

Temperature-Dependent Vibration Characteristics of Porous FG Material Plates Utilizing FSDT

This study focuses on the vibration characteristics of the functionally graded materials (FGMs) porous plate. The plate is to be supported on different boundary constraints with linearly varying thicknesses. Existence of different porosity (void) pattern, within the materials, are taken into consideration using the power (P-FGM) and sigmoidal (S-FGM) gradation laws. The current methodology was developed utilizing the FSDT (first-order shear deformation theory) under thermal environmental conditions. Variations of temperature like as uniform, linearly varying, and nonlinear distribution patterns were examined by including temperature-dependent and independent material properties. The equations of motion including all the effects are derived from Hamilton’s principle and, subsequently solved using the Galerkin’s Vlasov method for various plate boundary conditions. Finally, the analytical outcomes are verified numerically, with the existing works. Furthermore, the study demonstrates that the fundamental frequency of porous FGM tapered plate is very close to the result obtained by the other researchers. Moreover, a detailed examination has been carried out to reveal the effect of various factors such as volume exponent index ([Formula: see text], side-to-thickness ratio ([Formula: see text]/[Formula: see text], and temperature effect ([Formula: see text]. In addition to this, some new benchmark results are obtained for free vibration analysis of tapered plates under a thermal environment.

Numerical elastic fracture analysis of SENT test specimen subjected to non-linear loading

Crack characterization of any component depends on specimen type and geometry, material properties, and loading pattern. The geometrical and material property dependency of crack description is well established in literature, but loading pattern influence is limited to classical Mode-I, II and III types. Here, an effort is made to relate the crack stress state for different load pattens and crack length to specimen width, (a/W) using 2D and 3D linear elastic fracture analysis. The crack stress state is characterized by KI and T-stress in the present analysis using ABAQUS software. The non-uniform load patterns were defined by a non-linear stress distribution term σ (x). The stress distributions applied on the crack faces and were classified as constant, linear, parabolic, and cubic. The a/W varied as 0.2, 0.4, 0.6, and 0.8 to account the in-plane dimension effect on crack driving parameters. The 3D normalized KI and T-stress magnitudes were directly proportional to a/W. The normalized KI magnitudes decreased in the stress distribution order of constant, linear, parabolic and cubic. 3D normalized KI and T-stress values represented the real stress state of the crack. To ease the complex computational simulations, simple equations were proposed to estimate the normalized KI and T-stress for the different load patterns and a/W. To avoid the conservatism in component design, an attempt is made to represent the real load patterns through constraint inclusiveness in the 3D fracture analysis.

Stress-strain state of composite multi-layer stay rope considering breakages in reinforcing elements and nonlinear distribution of mechanical properties

Purpose. Formulation of an algorithm for considering the influence of continuity breakages in fiber reinforcing elements on stay rope strength. Methods. Construction and analytical solution of a mathematical model of interaction for parallel fiber reinforcingelements connected through elastic material, in a case of continuity breakage of individual elements in reinforcement. Findings. A static strength calculation algorithm for a multi-layer stay rope with breakages in one cross-section of reinforcing elements is developed. It is established that a continuity breakage of an arbitrary element of a stay rope reinforcement leads to a significant change in internal loads of only the adjacent reinforcing elements and is practically independent of a nonlinear deformation character of cable components. Greater loads on reinforcing elements occur in a case of breakage of a corner reinforcing element, and the smallest loads – in a case of breakage of a central one.It is established that a number of rows of reinforcing elements in a stay rope and location of a damaged reinforcing element do not significantly affect displacement of cable end and do not affect distribution of loads among reinforcing elements in a damaged cross-section. Displacements depend on a ratio of shear modulus of elastic material and Young's modulus of reinforcing elements; the ratio is varied along cable length. It is established that a reinforcing element location with discontinuity does not significantly affect the character of relative growth of stay rope deformations in a case of nonlinear character of elastic shell deformation. Deformation nonlinearity of cable components does not affect redistribution of forces in stay rope with damaged reinforcing elements. Maximum relative displacements of reinforcing elements and the resulting maximum shear angles of material located between reinforcing elements are smaller than a value of the assumed nonlinearity coefficient. Characters of displacements of reinforcing elements are qualitatively similar. Scientific novelty. An analytical algorithm is developed for calculating a stress-strain state of a multilayer stay rope considering its design, nonlinearly of mechanical properties of its components distributed along the cable with damage to an arbitrary group of reinforcing elements in one cross-section. Practical significance. The developed algorithm allows considering a nonlinear deformation character of stay rope components on its stress state in a case of breakages in an arbitrary number of reinforcing elements arbitrarily located in a stay rope with a continuity breakage in one cross-section. The algorithm can be applied to determine a stress-stress state of a stay rope with breakage in a cross-section infinitely distant from rope ends. The algorithm allows considering the influence of breakages in reinforcing elements on rope strength, which increases rope reliability in a structure.

Effect of combined (radial-axial-angular direction) misalignment on sliding wear of spur gears: A comprehensive study

This study explores accelerated gear failures due to misalignment-induced geometric stress concentration. A mathematical model is derived to assess misalignment effects on sliding wear of driver gears using MATLAB. The model's accuracy is validated against literature and experiments. A parametric study investigates the impact of design parameters on wear in combined misaligned gear pairs. Findings show that increasing radial misalignment raises pressure and sliding wear in the single-tooth contact zone, while axial misalignment decreases the contact zone, resulting in increased wear throughout the mesh cycle. Angular misalignment reduces the contact zone, leading to non-linear wear distribution along the tooth flank. Combined misalignment has the most severe effects, causing higher contact pressure, non-linear wear distribution, and increased wear in transition zones.

Parameters identification of closely spaced modes with the covariance-drivern stochastic subspace and damping ratio dispersion method

Electromechanical equipment with quasi-symmetric and partially symmetrical structures is widespread in the industry, which not only makes the dynamic characteristics of the system more complex but also leads to severe closely spaced modes. The existence of closely spaced modes can lead to more confusion, because severe closely spaced modes have similar frequency eigenvalues and some singular eigenvalues are prone to generate spurious modes in matrix computations. In this paper, the covariance-drivern stochastic subspace and damping ratio dispersion (SSI-COV-DRD) method is proposed, which in comparison with previous methods, identification process directly is performed in the stochastic subspace by solving the system matrix of the time domain signal to overcome modal aliasing of the frequency-based method. Firstly, a Toeplitz matrix is constructed with a time series signal and then the system modal parameters are gained from the system matrix after performing singular value decomposition (SVD) to the Toeplitz matrix. Subsequently, the poles of the continuous model order are classified by a hierarchical clustering algorithm to obtain stabilization diagram and the real physical modes are automatically extracted from the stabilization diagram according to the choice criteria. Finally, the damping ratio dispersion index is calculated to express the nonlinear distribution characteristic of the damping ratio. Numerical examples for the five-order free vibration simulation signals with noise-free and noise indicate that the proposed method can simultaneously identify the modal frequency and damping ratio with high accuracy in severe closely spaced modes, especially for the repeated frequency modes. Since the bolt connection rotor of the aero-engine usually produces severe closely spaced modes in vibration due to the structural symmetry, the frequency and damping ratio are extracted and the damping ratio dispersion index is calculated from different bolt loosening states, which is helpful for the bolt loosening detection of aviation safety assurance and maintenance.

Asymmetries in multi-target monetary policy rule and the role of uncertainty: Evidence from China

Have monetary policies asymmetrically responded to targets besides output and inflation? Multiple targets have been found to exist for monetary authority, and uncertainty is having a growing impact on monetary policy in China. Using the nonlinear autoregressive distribution lag (NARDL) model and data from China from 2001Q1–2022Q3, we build a multi-target monetary policy rule with uncertainty and verify the monetary authority’s asymmetric reactions to the exchange rate, housing price, and uncertainty. Specifically, the Monetary authority of China responds more to a decline than increase in the output gap, and responds more to an increase than decrease in the inflation gap, exchange rate gap, housing price gap, and uncertainty. This practice supports the view of expanding the targets of the Taylor rule, while also providing innovative ideas for asymmetric monetary policy responses for countries with an economic structure or population density comparable to China.

Transverse energy loss slope in meandering channels

Limited research has been conducted on transverse energy loss in meandering channels. Previous studies made assumptions regarding a linear vertical profile of transverse velocity and rectangular cross sections with horizontal transverse beds, neglecting the effects of nonlinear transverse velocity profiles and transverse bed slopes that contribute to topographic steering. In this study, a novel expression for the transverse energy loss slope is derived analytically. This expression incorporates a nonlinear vertical distribution for transverse velocity and considers non-rectangular cross sections, thereby improving the computation of roughness coefficients in curved channels. A topographic steering number is introduced, which indicates the presence of topographic steering when it exceeds unity. The developed equation rectifies the previous underestimation of sinuosity in natural rivers when compared to existing equations. Additionally, an expression for superelevation is derived, accounting for channel roughness and transverse bed slope, unlike previous equations. The study reveals that roughness can significantly affect the height difference between outer and inner banks. Under higher roughness conditions, the height difference can exceed predictions from existing formulas by up to 50%. This emphasizes the importance of considering roughness effects in accurately estimating superelevation. The developed equations are validated through comparisons with available field, laboratory, and numerical data.

Thermoelastic free vibration of rotating tapered porous functionally graded conical shell based on non-polynomial higher-order shear deformation theory

This study uses a non-polynomial higher-order shear deformation theory to calculate the fundamental frequency of a rotating cantilevered porous functionally graded (FG) conical shell with variable thickness. Eight noded isoparametric shell elements having seven degrees of freedom per node are used to discretize the shell. Utilizing a simple power law, the temperature-dependent material characteristics of the FG conical shell are determined. The one-dimensional Fourier heat conduction equation is used to obtain the nonlinear temperature distribution. Lagrange’s equation is used to derive the dynamic equation of motion. Finally, a parametric study is presented.

Temperature and COVID-19 Incidence: An Ecologic Study

Background: According to the hypothesis, COVID-19 is less prevalent in regions with warm climates. Contradictory results have led us to investigate the correlation between temperature and the cumulative COVID-19 incidence rate. Methods: We obtained COVID-19 data from CRONALAB, COVID-DASHBOARD, and MCMC databases of Fars Province, Iran, linked the data and finalized daily COVID-19 cases. The daily data on the temperature was gotten from meteorological stations’ reports from March 21, 2020, to March 21, 2021, for each county of Fars Province, Southern Iran. The daily weighted cumulative incidence rate of COVID-19 cases was calculated for all counties, separately. Initially, for uniform data visualization, the average air temperature data were transformed into ranked percentiles. Then, to visually assess the study hypothesis, the distribution of COVID-19 cumulative incidence was visualized on percentiles of temperature. Given the non-linear distribution of the data, we performed exploratory analyses using the generalized additive models and locally weighted (polynomial) regressions to choose the best response function. Then, the generalized linear models were used to parametrically build the model. Results: The generalized additive models showed a small decreasing, near horizontal, linear pattern for COVID-19 incidence rate as the function of temperature (pseudo R2: 0.001, deviance explained: 0.13%, coefficient: -0.02). The GLMs showed head-to-head results (deviance explained: 0.13%, coefficient: -0.02], supported by similar Akaike information criteria (AICs) (34945). However, according to the locally weighted regressions model’s curve, lower COVID-19 incidence rates were recorded on days when the temperatures ranged from 60 to 80 percentiles, equal to 20°C to 25°C in a cold climate and 25°C to 35°C in a warm climate. This is while the rates increased at lower and upper temperatures. Conclusion: Daily COVID-19 incidence rate cannot be explained as a function of daily temperature in Southern parts of Iran. Higher rates of disease transmission out of the range of 20°C to 25°C for cold temperatures and 25°C to 35°C for warm climates might be linked to people’s indoor gatherings, coupled with insufficient ventilation.

Marangoni instability of an evaporating binary mixture droplet

Evaporation of a binary mixture droplet (BMD) is a common natural phenomenon and widely applied in many industrial fields. For the case of a sessile BMD being the only contact-line pinning throughout an entire evaporation, a theoretical model describing the evaporating dynamics is established when considering the comprehensive effect of evaporative cooling, the thermal Marangoni effect, the solutal Marangoni effect, the convection effect, and the Stefan flow. The dynamics of a binary ethanol–water droplet on a heated substrate is simulated using a cylindrical coordinate system. The reasons for Marangoni instability-driven flow (MIF) are discussed, and the influence of initial ethanol concentration and substrate heating temperature are examined. An evaporating BMD first forms a MIF at the contact line and quickly affects the whole droplet. Under the influence of the Marangoni instability, the BMD presents a complex internal flow structure with multiple-vortex and nonlinear temperature and ethanol concentration distributions. The positive feedback induced by vortices and the nonlinear distribution of concentration and temperature promotes the development of a MIF. At low initial ethanol concentrations, the MIF loses its driving force and turns into a stable counterclockwise single-vortex flow as ethanol evaporates completely. However, at high initial ethanol concentrations, the MIF exists in the entire evaporation. Increasing ethanol concentration and substrate heating temperature can delay the appearance of the MIF; ethanol concentration affects the MIF duration time, and heating temperature alters the MIF intensity. To enhance flow intensity and mass transfer of BMDs, the temperature difference should first be increased, followed by increased ethanol concentration.

Integrating discoverability and prominence in video-on-demand consumption choices. A qualitative user study in Belgium

As video-on-demand services have taken a central position in audiovisual distribution in European markets, over-the-top viewing has become increasingly popular. This shift has heavily impacted consumption patterns and exposure diversity, as they are reshaped by non-linear distribution and technological affordances. This article aims to integrate debates on discoverability and prominence within wider research on video-on-demand consumption. It does so by widening the existing focus on the strategies deployed by video-on-demand services to capture users’ contexts and actions in the consumption decision-making process. The framework is based on exploratory qualitative research conducted in Belgium through a diary study and in-depth interviews and can contribute to future audience research on video-on-demand consumption choices. We find that users discover and choose audiovisual content to consume on demand through a combination of formal and informal factors. These are grouped into four thematic categories, namely technological affordances, perceived offering, external ‘nudges’, and process.

Nonlinear active distribution network optimization for improving the renewable energy power quality and economic efficiency: a multi-objective bald eagle search algorithm

Nonlinear active distribution network optimization for improving the renewable energy power quality and economic efficiency: a multi-objective bald eagle search algorithm

Improved history matching of channelized reservoirs using a novel deep learning-based parametrization method

Most of the geological parametrization techniques used in history matching of sub-surface formations including the deep learning-based methods could not capture the non-linear and non-Gaussian dependencies and were limited to facies realizations. This paper proposes a novel method for parametrization of permeability realizations using ConvLSTM layers to build a Variational Autoencoder, named ConvLSTM-VAE, for the first time in this study. Since geological layers of the reservoir models are deposited during different periods, reservoir properties have a spatial distribution along the third dimension that can be regarded as a temporal distribution. To evaluate the proposed method, its parametrization results were compared with those of 3D convolutional VAE (3DCNN-VAE), which was recently used in the literature. Quantitative and visual results showed that the proposed method was far better than the 3DCNN-VAE, where the train, validation, and test losses obtained by the ConvLSTM-VAE was 0.3663, 0.3695, and 0.3710, and by the 3DCNN-VAE was 0.3980, 0.4086, 0.4095, respectively. In addition, history matching with parametrized realizations by the ConvLSTM-VAE could preserve the geologic realism in the conditioned realizations with significantly low data mismatch errors in the historical and prediction phases; however, history matching with 3DCNN-VAE parametrization and without any parametrization could not preserve the geologic realism. Finally, this paper can guide reservoir engineers to select a proper parametrization method for highly channelized, 3D, complex reservoirs with non-linear and non-Gaussian distribution of the uncertain parameters.

Theoretical background of electron tunneling in electrochemical double layer

The electron tunneling or overflow in the electrochemical double layer has been mentioned in many previous reports, but its detailed influence mechanism is often neglected. In this work, we combined quantum chemistry and electrochemical double layer theory mathematically to investigate the reason for the nonlinear distribution of potential. By analyzing the electron transfer theory, we determined the condition and criterion for electron tunneling. We derived a formula for the relation between diffusion layer potential and electrode potential and compared it with the traditional model. The resulting curve exhibits a widened, sloped platform near the zero potential point. In addition, we analyzed the effects of the electrochemical double layer on input system signals using signal simulation. These results provide a foundation for further research in this area.

Spatial modeling and analysis based on spatial information of the ship encounters for intelligent navigation safety

The analysis of dangerous navigation situations is crucial for the advancement of intelligent shipping technology. In this study, we propose a spatial modeling and analysis method in the space domain of ship encounters based on a geographic information system spatial information platform and analysis technology. The proposed method employs various parameters, such as the approaching rate of a ship, the relative orientation, the encounter danger, the relative spatial position, and the power coefficient of the exponential mathematical curve to establish a dynamic spatial–temporal model of ship encounters. This allows for the spatial modeling and analysis of the spatial characteristics and distributions of encounter-danger surface sources. The proposed method enables in-depth analysis of potential nonlinear spatial characteristics and distribution patterns of ship-encounter danger during navigation and provides spatial analysis results, including encounter-safety features and spatial–temporal attribute information for safe ship navigation. This can greatly improve the spatial analysis and perception ability of ships encountering dangerous situations, thereby effectively reducing the spatial ambiguity of encountering danger. This study performs case analysis and comparative verification using two types of encounter scenarios, and the results reveal the accuracy and superiority of the proposed method.

Non-linear heat and mass transfer in packed spherical horticultural produce: Heterogeneity and irreversibility

Heterogeneous distribution of heat generation from respiration reaction inside produce as well as irreversibility from different sources are still not analyzed especially for non-linear phenomena with different external operating conditions and internal produce properties. In this study, a numerical model of coupled heat and mass transfer with reaction kinetics of respiration is developed for packed spherical postharvest produce. We then analyze the distribution and irreversibility of respiration heat inside them under different inlet velocity, gas diffusivities and reaction rate of aerobic and anaerobic respiration. The result shows that non-linear distribution of respiration heat is identified as the transition of dominated mechanisms from convective mass transfer and diffusion of O2 resulting in local peaks between produce surface and center to convective cooling and thermal conduction leading to peak convergence with decreasing values near produce center. Increasing inflow air velocity causes reduced heterogeneity of respiration heat and earlier transition with shorter duration. Furthermore, in response to different gas diffusivity and respiration rate, non-linear variations of distribution characteristics for respiration heat are obtained by coupling effects of heat and mass transfer with complex reaction kinetics. While airflow and heat transfer processes are the main irreversibility sources, non-linear variations of entropy generation for mass transfer and respiration reaction are also obtained under external and internal influence.