Dynamical Theory Research Articles

Closing in on possible scenarios for infinite-layer nickelates: Comparison of dynamical mean-field theory with angular-resolved photoemission spectroscopy

Conflicting theoretical scenarios for infinite-layer nickelate superconductors have been hotly debated, particularly regarding whether only a single Ni-3dx2−y2 band is relevant at low energies besides electron pockets or whether multiorbital physics including Ni-3dz2 is instead essential. The first scenario has emerged from density-functional theory plus dynamical mean-field theory (DFT + DMFT) calculations. Comparing the previous DFT + DMFT spectra to recent angular-resolved photoemission spectroscopy (ARPES) experiments, we find excellent agreement for both the Fermi surface and the strongly renormalized quasiparticle bands, supporting the first scenario. Our key findings further suggest that the “waterfalls” observed in ARPES might emerge from the quasiparticle-to-Hubbard-band crossover, and that additional spectral weight close to the A pocket likely originates from the Ni-3dxy orbital. Published by the American Physical Society 2024

Application of the Finite Element Method for Analyzing the Vibration Characteristics of a Spindle System and Fault Diagnosis

The performance of a spindle will gradually decline, the vibration intensity will increase, and the temperature rise will become abnormal with the accumulation of service time. Consequently, the accuracy of the machining product will not meet its production requirements. Studies on the variation characteristics of the spindle unit have clarified the reasons for its abnormal vibration and temperature rise, in principle, to help enterprises conduct preventive maintenance before any serious failure occurs and improve production efficiency. Based on the Timoshenko beam model and rotor dynamics theory, this study uses the finite element method (FEM) to analyze the vibration characteristics of the spindle rotor system. Moreover, it thoroughly analyzes the influence of the spindle bearing heat on the stiffness of the spindle system and identifies the resonance conditions of the spindle rotor within the power frequency range. This research has identified that when the vibration frequency of the spindle operates at a speed of 12,000 r/min, if its vibration frequency is lower than 200 Hz, it will be affected by abnormal vibrations during startup, which will weaken the health status of the spindle and reduce its service life. Similarly, when the working speed of the spindle is 30,000 r/min, if its vibration frequency is lower than 50 Hz, abnormal vibration will occur during startup and operation, thereby reducing its service life.

On Some Dynamics in Conceptual Spaces

AbstractIn this text, we consider Gärdenfors’ conceptual spaces that are separable Hilbert spaces. In particular, the results we obtained apply to finite-dimensional Euclidean spaces. Our main contribution can be formulated as a combination of the theory of opinion dynamics with the theory of conceptual spaces. This combination, in turn, leads us to propose a new model for the time evolution of conceptual spaces. To achieve this goal, we propose some extension of the multidimensional opinion dynamics model of Parsegov, Proskurnikov, Tempo and Friedkin to opinions with values in Hilbert spaces.

ICT Growth and the Fintech Boom: A Mismatched Capability Perspective from Nigeria

This article draws on both, dynamic capability theory and reviews of contemporary market research studies to assess the sustainability of Nigeria’s burgeoning fintech sector. It highlights the need for targeted education and training schemes to address a skills-driven, dynamic capability mismatch between larger and micro-enterprise employers in Nigeria’s organizational landscape. The talent pool of qualified candidates is limited, competition is intense, and the fintech boom has led to substantial emigration of the young and digitally skilled. Although unevenly distributed government efforts are evident, micro-employers have yet to benefit from these interventions.

Strategic Technological Innovations Influencing Competitive Advantage Among Micro and Small Enterprises in Nairobi County, Kenya

Purpose: The ability of businesses to integrate information technology in their operations has been found to be an integral driver to their success. Through information technology, firms can utilize technological innovations to strengthen the uniqueness of their products in the market thus enhancing their competitive advantage. However, with limited evidence in the local context especially among the micro and small enterprises which continue to face a continuous decline, it warrants the study to assess how strategic technological innovations have been embraced among the small and micro enterprises and the role the innovations have played in enhancing the competitive advantage of the enterprises. Specifically, the study will examine the influence of enterprise’s IT Capabilities on competitive advantage among Micro and Small Enterprises (MSEs); determine the influence of Technological resources on competitive advantage among Micro and Small Enterprises (MSEs); explore the influence of adopted new technologies on competitive advantage among Micro and Small Enterprises; and establish the influence of Technological Processes and Products (TPP) on competitive advantage among Micro and Small Enterprises (MSEs) in Nairobi County, Kenya. The objectives will be anchored on dynamic capabilities theory, Schumpeter theory of innovation, technology acceptance model and diffusion theory of innovation. Methodology: Using a descriptive research approach, the study will collect and analyse both qualitative and quantitative data. This data was obtained from 386 micro and medium enterprises in Nairobi Central Business District, drawn from a population of 11,245 MSEs registered by the Nairobi City County in the CBD. A questionnaire was the main instrument of data collection, which was pilot-tested for validity and reliability. The collected data was analyzed using descriptive and inferential statistics. Findings: The findings were presented using frequency tables and graphs. In conclusion, the findings emphasize the critical role of technology in driving market expansion, customer engagement, and operational efficiency. The study highlights the importance of strategic support and intervention to address technological adoption challenges. By encouraging technological development and integration, policymakers and other stakeholders can assist MSEs in improving their operations, boosting the economy of Nairobi County. Investing in technological education and infrastructure is essential for MSEs to optimally benefit from TPP in the contemporary digital economy. Unique Contribution to theory, policy and practice: Training and development on how MSEs can use the platforms effectively, online marketing and selling needs to be promoted to help MSEs build their capacities. Therefore, when equipped with the appropriate knowledge and tools, the policymakers can help the MSEs to adopt e-commerce and increase their market access and productivity.

Protracted Kondo coherence with dilute carrier density in cerium based nickel pnictides

Nozières' exhaustion theory argues that the temperature for coherently screening of all local moments in Kondo lattice could be much lower than the temperature of single moment screening in case of insufficient conduction electrons. Experiments indicate that cerium based nickel pnictides CeNi2−δAs2(δ≈0.28) is an ideal material to exam such protracted Kondo screening. Using density functional theory plus dynamical mean-field theory, we found CeNi2As2 presents a transition from the local moment states to the coherent Kondo screening states under compression, accompanied by topological changes of the Fermi surface. Similar phase transition could be driven by chemical pressure via the isovalence As→P substitution. The derived coherent Kondo temperature Tcoh is much lower than the single-impurity Kondo temperature TK due to the diluted Ni-3d conduction electrons, indicating the protraction of Kondo screening in crystal. In contrast to structurally analogous layered iron pnictides, the electronic structures of the present systems show strong three-dimensionality.

Strategic Collaborations and Performance of Oil Marketing Firms in Kenya

Purpose: Little attention has been paid to the effect of strategic collaboration on performance of oil marketing firms in Kenya. As a result, it is vital to investigate the effect of strategic collaboration on performance of oil marketing firms in Kenya. The study's particular aim was to investigate the impact of strategic alliances, mergers and acquisitions, franchising, and joint ventures on performance of oil marketing firms in Kenya. Four theoretical reviews are included in this research paper: Resource Based Theory, Transaction Cost Theory, Trust Theory and Dynamic Capability Theory. Methodology: Using descriptive research approaches, this study evaluated the data and offered findings. Over a certain time period, data was collected from oil marketing firms in Kenya. The research relied on primary data gathered via structured questionnaires as well as secondary data. The study's target population was Kenya's oil marketing firms in Kenya. The study also used stratified random sampling. The study's data was collected using Google forms and sent through email. The questionnaire data was sorted, classified, and analyzed using Statistical Packages for Social Sciences (SPSS). Findings: finding demonstrate that savvy partnerships among Kenyan oil marketers improve performance. Businesses appreciate shared storage, cooperative networks, and specialized service sharing for increasing operational efficiency and competitiveness. Statistical analysis reveals that these partnerships influence company performance, accounting for 81.5% of the variance, with a strong correlation coefficient (R = 0.903) and a substantial ANOVA F-value. Unique contribution to theory, Policy and Publication: To obtain additional information and draw meaningful conclusions about the variables of interest, descriptive studies was conducted where survey was used to provide a snapshot of the population. Tables was used to display the data. This study will be useful to academics and researchers in finance and economics.

Large-Scale Group Decision Making with Dual Feedback from Community Residents Based on the Organizational Invisible Field

In China, communities function as grassroots self-governing bodies, and the enhancement of public participation in community governance has remained a central focus of study. This paper applies the Large-Scale Group Decision-Making (LSGDM) method to the process of community self-governance and proposes a dual feedback group consensus decision-making model that takes into account the unique social relations among residents. Firstly, the concept of the Organizational Invisible Field—formed in communities by intangible social capital such as positional power and interpersonal relationships within the organization—is introduced. The definition of Invisible Field Force is utilized to measure the influence of these forms of capital on social relationships. Subsequently, drawing on field dynamic theory, the process by which residents’ preferences within the organization are shaped by the action of Invisible Field Force is explored. Secondly, acknowledging that invisible relationships can be affected by dynamic interactions during the decision-making process, the Invisible Field Force change model is constructed. Building on this, a dual feedback consensus coordination mechanism—encompassing both in-organization members and all residents—is designed. Finally, the validity and utility of the model are verified through case studies and sensitivity analyses.

Invariant solutions, lie symmetry analysis, bifurcations and nonlinear dynamics of the Kraenkel-Manna-Merle system with and without damping effect

This work investigates the Kraenkel-Manna-Merle (KMM) system, which models the nonlinear propagation of short waves in saturated ferromagnetic materials subjected to an external magnetic field, despite the absence of electrical conductivity. The study aims to explore and derive new solitary wave solutions for this system using two distinct methodological approaches. In the first approach, the KMM system is transformed into a system of nonlinear ordinary differential equations (ODEs) via Lie group transformation. The resulting ODEs are then solved analytically using a similarity invariant approach, leading to the discovery of various types of solitary wave solutions, including bright, dark, and exponential solitons. The second approach involves applying wave and Galilean transformations to reduce the KMM system to a system of two ODEs, both with and without damping effects. This reduced system is further analyzed to investigate its bifurcation behavior, sensitivity to initial conditions, and chaotic dynamics. The analysis reveals the presence of strange multi-scroll chaotic dynamics in the presence of damping and off-boosting dynamics without damping. In addition to these approaches, the study also applies the planar dynamical theory to obtain further new soliton solutions of the KMM system. These solitons include bright, kink, dark, and periodic solutions, each of which has been visualized through 3D and 2D graphs. The results of this research provide new insights into the dynamics of the KMM system, with potential applications in magnetic data storage, magnonic devices, material science, and spintronics.

Harvesting strategies in ecological systems: Evaluating their efficiency in infection dominance

In population biology, the interplay between prey and predators in the presence of infection can give rise to complex dynamics. On the flip side, implementing harvesting is an infection control measure. In the present work, we use the dynamical system theory to discuss the dynamics of the harvested prey–predator system in the presence of infection in prey species. Detailed mathematical and numerical evaluations have been presented to discuss the susceptible‐free state, infection‐free state, predator‐free state, species coexistence, stability, and occurrence of various bifurcations (saddle‐node, transcritical, and Hopf bifurcation). The study reveals the impact of harvesting parameters on the dynamics. Interestingly, we observe that an infection‐free state could be achieved by varying the harvesting parameter under all three harvesting schemes (linear, quadratic, and nonlinear). Moreover, with the help of reproduction number, we claim that linear harvesting is more effective in controlling the infection than quadratic and nonlinear harvesting provided the half‐saturation constant for nonlinear harvesting is greater than a threshold value ; otherwise, nonlinear harvesting is more effective. Also, the system can support more susceptible prey in the presence of harvesting. The present theoretical study suggests different threshold values of implemented harvesting to control the disease.

Analysis of the Vertical Dynamic Response of SDCM Piles in Coastal Areas

The stiffened deep cement mixing (SDCM) pile, as a new type of rigid–flexible composite pile, significantly enhances the vertical bearing capacity of traditional precast piles, thus holding broad application prospects in the substructure construction of nearshore bridges and marine energy structures. This paper investigates the vertical dynamic response of SDCM piles through theoretical derivation and parameter analysis. Firstly, based on elastic dynamics theory and the three-phase porous media model, vertical vibration control equations for both SDCM piles and fractional-order viscoelastic unsaturated soils are established. Secondly, theoretical derivations yield exact analytical solutions for the surrounding dynamic impedance, top dynamic stiffness, and dynamic damping of the SDCM pile. Finally, through numerical examples and parameter studies, the impact mechanisms of physical parameters in the SDCM pile–unsaturated soil dynamic coupling system on the top dynamic stiffness and dynamic damping of the SDCM pile are analyzed. The research results presented in this paper indicate that reducing the radius of the rigid core pile while increasing the thickness of the exterior pile has a positive effect on enhancing its vibration resistance. Additionally, increasing the length of SDCM piles contributes to improved vibration performance. However, an increase in the elastic modulus of the cement–soil exterior pile is detrimental to the vibration resistance of the rigid composite pile. On the other hand, an increase in the elastic modulus of the concrete core pile only enhances its ability to resist vibration under low-frequency load excitation. Furthermore, enlarging the soil saturation, decreasing the intrinsic permeability, and enlarging the soil relaxation shear modulus have a significant positive impact on improving the vibration resistance of SDCM piles. In contrast, changes in porosity have a negligible effect on the ability to resist vertical vibrations of SDCM piles.

Enhancing Organizational Performance: Can Innovative Millennial Entrepreneurship and Business Continuity Take on A Mediating Role?

Facing business challenges requires creative ideas that can push into the realm of innovation. Innovation, which is widely held by the millennial generation, is advantageous for companies because this generation is good at developing ideas. However, the phenomenon is that 67% of creative media businesses in 2021 declined in revenue. In connection with these main obstacles, the purpose of this study is to identify constructs that can mediate the role of Relational Capital (RC) in organizational performance (OP). To address the research objective, this study concentrates on the creative media industry, utilizing a sample of 163 respondents. The data were analyzed using Structural Equation Modeling (SEM) through the AMOS software. The results reveal that RC does not have a significant impact on OP.This research examines the role of Innovative Millennial Entrepreneurship (IME) and Business Continuity (BC) in mediating RC to OP. This study empirically proved that RC has no significant effect on OP, but IME and BC can increase RC to OP, with a total effect of 1.487 for IME and 0.509 for BC. Based on this result, it is empirically proven that IME and BC fully mediate the role of RC in CP. This is a contribution to the theoretical domain of dynamic capacity theory.

THE WHY AND WHAT OF AI DEPLOYMENT AND INNOVATION IN COMPANIES — RESULTS AND LEARNINGS FROM A SYSTEMATIC LITERATURE RESEARCH ENLIGHTENED BY THE CAPABILITY THEORY

Despite soaring interest in Artificial Intelligence (AI), only one-tenth of companies have reported tangible business results. We conducted a Systematic Literature Research on peer-reviewed reports to establish an updated status and baseline of AI deployment for research and companies. We analysed selected peer-reviewed articles for deployment objectives, approaches, results, and learnings. This research confirms that AI is still at the early stages of deployment and innovation in companies. Deploying AI successfully represents a management — rather than a technology — challenge. It requires more cognisance, innovation, learning, and effort than generally thought. Through the results and a novel conceptual framework, this research increases the knowledge and emphasises the importance of the pre-deployment from theoretical and practical viewpoints. The Sensing stage of the Dynamic Capability theory aligns well with the developed pre-deployment concept. We propose several research topics to increase the knowledge and theoretical understanding of deploying AI cognisably for business and stakeholder benefits.

Two-Band Electronic Reconstruction Induced via Correlation and CDW Order Effects

The emergence of a charge density wave (CDW) in transition-metal dichalcogenides opens up a route to charge order, followed by superconductivity at low temperatures. A key question here concerns how many particle electron–electron interations govern the low-energy electronic structure in the normal and CDW states. Using dynamical mean-field theory, we explore the many-body properties of an extended, two-band Hubbard model applicable to 2H-TaSe2. We reveal the electronic structure reconstruction in the normal and CDW states driven by two-band dynamical correlations. Our results demonstrate a remarkable renormalization of the Ta-5d bands crossing the Fermi level, showing a continuous reduction in the CDW gap up to an incomplete gapping, followed by a CDW to a CDW–Mott phase transition pertinent to strongly correlated transition-metal dichalcogenides.

Fate of the Mollow triplet in strongly coupled atomic arrays

Subwavelength arrays of quantum two-level emitters have emerged as an interesting platform displaying prominent collective effects that can be harnessed for applications. Here, we study such arrays under strong coherent driving, realizing an open quantum many-body problem in a strongly nonlinear regime. For this we introduce an approach to this problem in terms of a dynamical mean-field theory, paving the way for further studies. We show that the spectrum of scattered light, characterized by the famous Mollow triplet for a single atom, develops a characteristic line shape with flat sidebands determined by dipolar interactions and relevant for experiments. Remarkably, this is to some extent independent of the specific geometry, but is sensitive to the ordered arrangement of the atoms. This line shape therefore characterizes atomic arrays and distinguishes them from disordered ensembles and noninteracting emitters. Published by the American Physical Society 2024

A dynamical optimal control theory and cost-effectiveness analyses of the HBV and HIV/AIDS co-infection model

Studies have shown that the co-infection of Human Immunodeficiency Virus (HIV) and Hepatitis B Virus (HBV) poses a major threat to the public health due to their combined negative impacts on health and increased risk of complications. Even though, some scholars formulated and analyzed the HBV and HIV co-infection model they did not consider the compartment that contains protected individuals against both HBV and HIV infections. They incorporated the optimal control theory and cost-effectiveness analysis simultaneously. With this in mind, we are motivated to formulate and analyze the HBV and HIV co-infection model, considering the protected group and incorporating optimal control theory and cost-effectiveness. In this study, we have theoretically computed all of the models disease-free equilibrium points, all the models effective reproduction numbers and unique endemic equilibrium points. The two sub-models disease-free equilibrium points are locally as well as globally asymptotically stable whenever their associated effective reproduction numbers are less than one. We reformulated the optimal control problem by incorporating five time-dependent control measures and conducted its theoretical analysis by utilizing the Pontryagin's maximum principle. Using the fourth order Runge–Kutta numerical method and MATLAB ODE45, we performed the numerical simulations with various combinations of control efforts to verify the theoretical results and investigate the impacts of the suggested protection and treatment control strategies for both the HBV and HIV diseases. Also, we carried out a cost-effectiveness analysis of the proposed control strategies. Eventually, we compared our model results with other researcher similar model results whenever cost-effectiveness analysis is not carried out the findings of this particular study suggest that implementing each of the proposed control strategies simultaneously has a high potential to reduce and control the spread of HBV and HIV co-infections in the community. According to the cost-effectiveness analysis, implementing the HBV treatment and the HIV and HBV co-infection treatment measures has a high potential effect on reducing and controlling the HBV and HIV co-infection transmission problem in the community.

Posttraumatic Growth: The Role of Health and Financial Difficulties During a Pandemic.

Trauma can have a range of effects on individuals over time, including the potential for positive changes in favorable outcomes commonly referred to as posttraumatic growth. The posttraumatic growth literature has been criticized for various methodological limitations and has largely neglected the exploration of factors that may strengthen or weaken posttraumatic growth trajectories. The present study contributes to this literature by investigating trajectories of five dimensions of posttraumatic growth during the COVID-19 pandemic and the moderating effects of health and financial difficulties on these trajectories. Longitudinal data were collected monthly between July 2020 and December 2022 from a sample of employed adults in Germany, involving N = 1678 participants over 30 time points (Nobservations = 29,552). Results suggest that certain dimensions of posttraumatic growth showed significant increases (i.e., relationships) or decreases (i.e., spirituality and possibilities) over time and that trajectories of three dimensions (i.e., relationships, appreciation, and strength) demonstrated distinctive patterns of interaction with health and financial difficulties. Findings are discussed in the context of the pandemic as well as dynamic theories of personality and identity, with implications for advancing posttraumatic growth theory and research.

Nutation-orbit resonances: The origin of the chaotic rotation of Hyperion and the barrel instability

While numerous planetary and asteroid satellites show evidence for non-trivial rotation states, none are as emblematic as Hyperion, which has long been held as the most striking example of chaotic spin-orbit evolution in the Solar System. Nevertheless, an analytically tractable theory of the full 3D spin-orbit dynamics of Hyperion has not been developed. We derive the Hamiltonian for a spinning axisymmetric satellite in the gravitational potential of a planet without assuming planar or principal axis rotation and without averaging over the spin period. Using this model, we demonstrate the emergence of resonances between the nutation and orbital frequencies that act as the primary drivers of the spin dynamics. This analysis reveals that, contrary to long-held belief, Hyperion is not tumbling chaotically. Instead, it lies near or in a nutation-orbit resonance that is first-order in eccentricity, allowing it to rotate quasi-regularly. The most reliable observations are consistent with either nonchaotic motion or chaos that is orders of magnitude smaller than originally claimed. A separate phenomenon, the so-called barrel instability, is shown to be related to a different set of nutation-orbit resonances that generalize the planar spin-orbit resonances. Finally, we show that changes in spin states over long timescales are best understood by considering chaotic diffusion of quasi-conserved quantities.

On the Existence of Extreme Coherent Distributions with No Atoms

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Dynamic wheel-rail interaction of a train crossing a turnout under traction/braking behaviour and research on rail wear of the turnout

In order to study the dynamic behaviour of a vehicle passing through turnouts under traction and braking conditions, as well as its influence on the wear of turnout rails, a high-speed vehicle-turnout rigid-flexible coupling dynamic model is established based on the coupling dynamic theory of vehicle and turnout, using China’s No. 18 high-speed turnout and CRH380 high-speed EMU as prototypes. The model is used to analyse wheel-rail creep characteristics, wheel-rail contact mechanics, and wheel-rail wear under traction and braking conditions. The results indicate that when a high-speed train passes through a turnout under traction or braking conditions, the longitudinal creepage of the wheel-rail will change due to the rotative speed difference generated by traction or braking. Furthermore, due to the existence of the lead curve, the longitudinal creep rate of the wheel-rail becomes even more complex when passing through the turnout in the diverging route. The calculations reveal that the traction behaviour of the train leads to a significant increase in wear at the front of the switch rail and nose rail, while the wear number of the switch rail in the heel of the frog after 6m increases significantly under braking conditions. The different impact characteristics of vehicle traction and braking conditions on turnout rail wear obtained in this study can provide guidance for optimizing and grinding the profiles of turnout rails at the throat of railway stations.