Search Results (25)

This paper presents an analytical exploration of how diverse dynamical systems, arising from different scientific domains, can be reformulated (under specific approximations and assumptions) into a common set of equations formally equivalent to the Lorenz system originally derived to model atmospheric convection. Unlike previous studies that focus on analyzing or applying the Lorenz equations, our objective is to show how these equations emerge from distinct models, emphasizing the underlying structural and dynamical similarities. The mathematical steps involved in these reformulations are included. The systems examined include Lorenz’s original atmospheric convection model, the chaotic water wheel, the Maxwell–Bloch equations for lasers, mechanical gyrostat, solar dynamo model, mesoscale reaction dynamics, an interest rate economic model, and a socioeconomic control system. This work includes a discussion of the unifying features that lead to similar qualitative behaviors across seemingly unrelated systems. By highlighting the Lorenz system as a paradigmatic limit of a broad class of nonlinear models, we underscore its relevance as a unifying framework in the study of complex dynamics. Full article

Food delivery apps (FDAs) have emerged as transformative tools in the digital age, reshaping consumer behavior and urban mobility through their convenience and accessibility. This study explores the factors influencing the adoption of FDAs among university students in a secondary city in Thailand, framed within the broader context of smart mobility. This study employs an extended Unified Theory of Acceptance and Use of Technology (UTAUT) framework, incorporating key constructs including performance expectancy, effort expectancy, social influence, facilitating conditions, and environmental concerns. Data were collected from 396 students at Mahasarakham University through a structured questionnaire and analyzed using structural equation modeling. The results reveal that effort expectancy, social influence, and environmental concerns significantly impact behavioral intention, while behavioral intention and facilitating conditions drive actual usage behavior. Environmental concerns emerged as a critical determinant, reflecting the growing alignment between consumer preferences and sustainability goals. The findings underscore the role of FDAs as key enablers of smart mobility, optimizing urban logistics, reducing transportation inefficiencies, and supporting sustainable city systems. By integrating environmental concerns into the UTAUT model, this study contributes to understanding technology adoption dynamics in secondary cities. Practical implications include promoting eco-friendly practices, enhancing digital infrastructure, and leveraging FDAs to foster sustainable and inclusive mobility ecosystems. Full article

This paper explores the concept of “bioharmonism” as a model for addressing sustainability and the Sustainable Development Goals (SDGs) by integrating the principles of biological balance and life harmony at various levels of nature and society. The purpose of this paper is to propose an integrative paradigm that rationally organizes the component concepts of different approaches and nuances developed over time in an attempt to find a path forward regarding contemporary societal changes. Thus, along the lines of transdisciplinary and holistic approaches, a connection is made between natural sciences, specifically life sciences, and social sciences, to understand in this way the evolution of human society. Specifically, the objective of this conceptual viewpoint is related to sustainability, resilience, and planetary health, indicating the need to analyze planetary bioharmony and transfer the model to the structure and functionality of human society. This is achieved by describing the pillars of this complex endeavor in a unified and coherent approach to highlight the bioharmonization process. This paper analyzes the definition and role of societal bioharmonism, then the methodological argumentation based on specific notions, principles, and laws, and finally, describes the application lines of the pillars of bioharmonism, using as a case study the provision of food for the human population. Solutions are highlighted that can conceptually contribute to the evolution of contemporary society, considering the convergence of anthroposystems with ecosystems, based on the interconnection of the current Biological Revolution with the performances offered by the Information Era. These solutions aim at societal bioharmonization, supported complementarily by its specific conceptual pillars, which, through integration and emergence, lead to a dynamic systemic balance. This, in turn, lays the foundation for reintegrating the environment and biodiversity into the economic equation, the citizen into the social equation, and science into the political equation. Full article

The shift to sustainable energy requires a thorough understanding of the elements affecting policy adoption, especially regarding political and economic dynamics. Current approaches, such as the technology acceptance model (TAM), theory of planned behavior (TPB), and unified theory of acceptance and use of technology (UTAUT), mainly emphasize individual behavioral aspects, often neglecting macro-level implications. This research uses the hybrid model for energy policy adoption (HMEPA) to bridge this gap, including economic and political factors with behavioral theories to evaluate energy policy acceptability. We propose that social impact, attitudes toward the policy, and financial and political considerations substantially affect stakeholders’ acceptance intentions. We gathered 421 valid answers from people in Taiwan using a questionnaire survey and analyzed the data using structural equation modeling (SEM). The findings demonstrate that whereas effort expectation and enabling circumstances have little impact, social influence and attitude are the most significant determinants of policy adoption intention. Moreover, political variables influence attitudes and social dynamics, while economic policy impacts performance expectations, perceived behavioral control, and enabling circumstances. These results underscore the need to synchronize policy plans with political and economic realities. Policymakers may use these findings to formulate stakeholder-oriented policies that promote sustainable energy transitions. Full article

This paper reviews the heat transfer mechanism and structural failure model of carbon fiber-reinforced polymers (CFRP) under the action of external flames. It introduces the extensive application of CFRP in aviation and the associated fire safety challenges, emphasizing the importance of studying its heat transfer and failure mechanisms. The paper elaborates on the heat transfer model of CFRP in fire, including the formulation of energy equations, the variation in physical property parameters (such as density, thermal conductivity, and specific heat capacity), and the determination of boundary conditions, providing a theoretical basis for simulating the material’s dynamic response to fire. Furthermore, the thermal damage model of CFRP in fire is analyzed, discussing key damage mechanisms, such as porosity formation, stratified damage, decomposition, and carbon formation, and evaluating their impact on the material’s mechanical properties. The paper compares the accuracy and limitations of different models in predicting fire response, identifies the shortcomings of current research, and suggests future development directions. Finally, the importance of developing a unified model that can comprehensively consider multiple damage mechanisms is emphasized. This includes improving the predictive ability of thermal models in complex fire scenarios and enhancing the application of mechanical models under complex loading conditions, thereby providing theoretical support for the safe application of CFRP in aviation and other fields with high safety requirements. Full article

Social networks have become a significant part of people’s daily lives, particularly in the purchasing process. In this context, digital influencers have played an essential role in shaping consumers’ opinions. In this sense, studying the role of social networks and influencers in the online product purchase decision process was considered pertinent. We selected two technology adoption models to fulfill this purpose: the Technology Acceptance Model (TAM) and the Unified Theory of Acceptance and Use of Technology (UTAUT). We conducted an exploratory study using a quantitative approach, with data being collected through a questionnaire distributed online. The statistical analysis of the empirical model employed a partial least squares structural equation modeling (PLS-SEM) technique. Analyzing the 135 responses allowed us to conclude that social networks are relevant in consumers’ purchase decision process. This research highlights the importance of the credibility of influencers, emotional connections with audiences, and the dynamics of the media in shaping consumer behavior. It highlights the strong influence of digital influencers on purchasing decisions and makes a methodological contribution with a rigorous empirical model. This study also suggests avenues for future research in order to deepen the understanding of influencer and social media marketing strategies. Full article

This paper presents the parallelization of two widely used implicit numerical solvers for the solution of partial differential equations on structured meshes, namely, the ADI (Alternating-Direction Implicit) solver for tridiagonal linear systems and the SIP (Strongly Implicit Procedure) solver for the penta-diagonal systems. Both solvers were parallelized using CUDA (Computer Unified Device Architecture) Fortran on GPGPUs (General-Purpose Graphics Processing Units). The parallel ADI solver (P-ADI) is based on the Parallel Cyclic Reduction (PCR) algorithm, while the parallel SIP solver (P-SIP) uses the wave front method (WF) following a diagonal line calculation strategy. To map the solution schemes onto the hierarchical block-threads framework of the CUDA on the GPU, the P-ADI solver adopted two mapping methods, one block thread with iterations (OBM-it) and multi-block threads (MBMs), while the P-SIP solver also used two mappings, one conventional mapping using effective WF lines (WF-e) with matrix coefficients and solution variables defined on original computational mesh, and a newly proposed mapping using all WF mesh (WF-all), on which matrix coefficients and solution variables are defined. Both the P-ADI and the P-SIP have been integrated into a two-dimensional (2D) hydrodynamic model, the CCHE2D (Center of Computational Hydroscience and Engineering) model, developed by the National Center for Computational Hydroscience and Engineering at the University of Mississippi. This study for the first time compared these two parallel solvers and their efficiency using examples and applications in complex geometries, which can provide valuable guidance for future uses of these two parallel implicit solvers in computational fluids dynamics (CFD). Both parallel solvers demonstrated higher efficiency than their serial counterparts on the CPU (Central Processing Unit): 3.73~4.98 speedup ratio for flow simulations, and 2.166~3.648 speedup ratio for sediment transport simulations. In general, the P-ADI solver is faster than but not as stable as the P-SIP solver; and for the P-SIP solver, the newly developed mapping method WF-all significantly improved the conventional mapping method WF-e. Full article

Against a backdrop of globalization, dynamic shifts in consumer demand, and climate change impact, the intricacies of agri-food supply chains have become increasingly convoluted, necessitating innovative measures to guarantee agri-food security and authenticity. Blockchain technology emerges as a promising solution, offering transparency, immutability, traceability, and efficiency in the overall supply chain. This study aims to investigate determinants impacting both the intention to use and the actual usage of blockchain-driven agri-food supply chain platforms. To achieve this, an expanded and adapted conceptual model rooted in the Unified Theory of Acceptance and Use of Technology (UTAUT) was formulated and empirically examined through Partial Least Squares Structural Equation Modeling using data from 175 respondents from agri-food companies across eight European countries. Agri-Food Supply Chain Partner Preparedness (FSCPP) emerged as the pivotal factor with the highest degree of influence on the intention to use blockchain-driven supply chain platforms. Additionally, the results from this study offer support for the significant influence of Performance Expectancy (PE), Effort Expectancy (EE), and Perceived Trust (PT) on usage intention, while also revealing the positive impact of Organizational Blockchain Readiness (OBR) on expected Usage Behavior (UB). This study provides significant insights into blockchain adoption within agri-food supply chains, contributing to the existing literature through an extended UTAUT framework. Full article

In the context of China’s rural revitalization and expanding digital economy, this study aims to elucidate how digital financial inclusion technologies can better allocate financial resources across newly evolved agricultural entities—such as family farms, farmers’ cooperatives, and agricultural enterprises. By employing structural equation modeling (SEM) based on the Unified Theory of Acceptance and Use of Technology (UTAUT), we identify key determinants affecting farmers’ credit availability. Our results emphasize the overwhelming role of Digital Financial Inclusion Technology Applications (DAs) in a wide range of financial variables, particularly credit availability (CA). Notably, performance expectation did not exert a significant impact on credit availability, while variables like effort expectation, facilitating conditions, and especially social influence were significant contributors. As for social impacts, social influence emerged as a multifaceted enabler, encouraging collective support within farmer communities and thereby facilitating credit accessibility. In conclusion, our study reinforces the critical influence of DAs in molding the financial landscape and recommends targeted interventions that leverage these technologies and social dynamics to boost financial inclusion and drive rural prosperity. Full article

This study examines the mechanism of nonlinear supratransmission (NST), which involves the transfer of disturbance to discrete media at frequencies not supported by the structure. We considered a model crystal with A3B stoichiometry. The investigation was carried out using atomistic modeling through molecular dynamics. The interatomic interaction was determined by a potential obtained through the embedded atom method, which approximates the properties of the Pt₃Al crystal. The effect of NST is an important property of many discrete structures. Its existence requires the discreteness and nonlinearity of the medium, as well as the presence of a forbidden zone in its spectrum. This work focuses on the differences in the NST effect due to the anisotropy of crystallographic directions. Three planes along which the disturbance caused by NST propagated were considered: (100), (110), and (111). It was found that the intensity of the disturbance along the (100) plane is an order of magnitude lower than for more densely packed directions. Differences in the shape of solitary waves depending on the propagation direction were shown. Moreover, all waves can be described by a single equation, being a solution of the discrete variational equations of macroscopic and microscopic displacements, with different parameters, emphasizing the unified nature of the waves and the contribution of crystal anisotropy to their properties. Studying the NST phenomenon is essential due to numerous applications of the latter, such as implications in information transmission and signal processing. Understanding how disturbances propagate in discrete media could lead to advancements in communication technologies, data storage, and signal amplification where the earlier mentioned ability to describe it with analytical equations is of particular importance. Full article

Structures with inhomogeneous materials, non-uniform cross-sections, non-uniform supports, and subject to non-uniform loads are increasingly common in aerospace applications. This paper presents a simple and unified numerical dynamics model for all beams with arbitrarily axially varying cross-sections, materials, foundations, loads, and general boundary conditions. These spatially varying properties are all approximated by high-order Chebyshev expansions, and discretized by Gauss–Lobatto sampling. The discrete governing equation of non-uniform axially functionally graded beams resting on variable Winkler–Pasternak foundations subjected to non-uniformly distributed loads is derived based on the Euler–Bernoulli beam theory. A projection matrix method is employed to simultaneously assemble spectral elements and impose general boundary conditions. Numerical experiments are performed to validate the proposed method, considering different inhomogeneous materials, boundary conditions, foundations, cross-sections, and loads. The results are compared with those reported in the literature and obtained by the finite element method, and excellent agreement is observed. The convergence, accuracy, and efficiency of the proposed method are demonstrated. Full article

The platform economy has emerged as a transformative force in various industries, reshaping consumer behavior and the way businesses operate in the digital age. Understanding the factors that influence the adoption of these platforms is essential for their continued development and widespread use. This study examines the determinants of economic platform adoption in Tunisia by extending the widely used unified theory of acceptance and use of technology 2 (UTAUT2) model with a privacy calculus model. By applying the partial least squares structural equation modeling (PLS-SEM) technique, the research provides significant insight. The results highlight the critical influence of factors such as performance expectancy, habit formation, trust in technology, perceived risk, privacy concerns, and price value on users’ behavioral intentions and actual usage of the platforms. These findings provide a deeper understanding of the dynamics surrounding the adoption of the platform economy in developing countries and offer valuable insight for stakeholders. By leveraging this knowledge, stakeholders can foster an inclusive digital ecosystem, drive economic growth, and create an environment conducive to the widespread adoption and use of the platform economy in developing countries. Full article

This paper elaborates on the modeling and control of an Unmanned Aerial Vehicle (UAV) for delivery purposes, thereby integrating computer-aided design, multibody dynamic modeling, and motion control analysis in a unified framework. The UAV system designed in this study and utilized for item delivery has a quadcopter structure composed of four arms connected to a central trunk. In this investigation, the proposed design of the delivery drone is systematically modeled employing the multibody approach, while SIMSCAPE MULTIBODY is the software used for performing the dynamic analysis and for devising the final design of the control system. To this end, starting from the CAD model designed using SOLIDWORKS, the control system of the quadcopter is developed by performing dynamic simulations in the MATLAB/SIMULINK environment. Additionally, another fundamental contribution of this paper is the analytical derivation of the nonlinear set of algebraic constraint equations peculiar to the present multibody system, which characterizes the kinematics of the delivery drone and describes the relative angular velocity imposed between two rigid bodies as nonholonomic constraints. Furthermore, as discussed in detail in this paper, the choice of the propulsion system and the design of the individual components heavily depends on the structural and functional needs of the UAV under study. On the other hand, the control system devised in this work is based on cascaded Proportional-Integral-Derivative (PID) controllers, which are suitable for achieving different maneuvers that are fundamental for the motion control of the delivery drone. Therefore, the final performance of the UAV system is a consequence of the regulation of the feedback parameters that characterize the PID controllers. In this respect, the paper presents the refining of the parameters characterizing the PID controllers by using both an internal MATLAB tool, which automatically tunes the controller gains of single-input single-output systems, and by observing the resulting transient behavior of the UAV system, which is obtained through extensive dynamical simulations. The set of numerical results found in this investigation demonstrates the high performance of the dynamical behavior of the UAV system designed in this work. Full article

In this paper, a parallel mechanism with two rotational degrees of freedom is proposed. It could rotate freely and continuously around the two coordinate axes at the fixed origin of the coordinate frame. The structure of the mechanism is a second-order over constraint parallel structure and the moving platform and base platform are connected by five kinematic chains. The motion characteristics of this structure are analyzed by reciprocal screw equation. Then, the kinematics and dynamics modelling are carried out systematically in a unified way. The kinematics of the mechanism is established by means of screws, the displacements and accelerations of each joint and any point on a link could be calculated by the kinematic screw equation directly. The analysis of acceleration and its mathematical expression in screw form are given, and the acceleration matrix could be applied into the dynamic analysis based on the Newton–Euler equation. All the constraint forces and torques could be obtained by a single set of Newton–Euler equations. Full article

The rheological behavior of gel propellants is crucial for their practical applications, especially in the rocket engine and ramjet fields. The thixotropic characteristics of gel propellants are an important component of their rheological properties and have a notable impact on their flow and injection process. However, most gel propellants contain rich, dynamic cross-linked network structures, which impart complex non-Newtonian fluid properties, and it is difficult to establish a unified mathematical model. In view of this, this study addresses the thixotropy of a prepared RP-3 kerosene gel and determines the mathematical model and model parameters describing its thixotropy. Experiments show that the kerosene gel exhibits shear-thinning properties as well as thixotropy. To describe the microstructural changes in the gel, three thixotropic constitutive models are introduced to analyze the rheological data, and the constitutive equation parameters are optimized. The three models are all structural dynamic models, which can be used to describe microstructural changes within the material. In addition, the fitting of the constitutive equation is a multiparameter optimization problem, and an appropriate optimization method must be used for parameter fitting. Therefore, the Bayesian optimization method combined with Gaussian process regression and the upper confidence bound (UCB) acquisition function is used in the multiparameter fitting of the constitutive models. Both experiments and numerical results show that the thixotropic model, which introduces a pre-factor with shear strain and assumes that the breakdown of the gel structure is related to energy dissipation rather than the shear rate, has a better fitting effect and prediction ability with regard to the gel. Combined with transient experiments at different shear rates, the model parameters of the constitutive law can be determined quickly by applying the Bayesian optimization method. Full article