Dynamical Theory Research Articles

Canonical Transformations and Poisson Theory for Dynamics with Non-Standard Lagrangians

Canonical Transformations and Poisson Theory for Dynamics with Non-Standard Lagrangians

Influence of guide vane opening on channel vortex and pressure pulsation in Francis turbine runners

In order to investigate the impact of guide vane opening on channel vortex and pressure pulsation within the runner of a Francis turbine, this research examines the cavitation phenomenon, channel vortex phenomenon, and flow field characteristics of a power station's turbine in China. The investigation is conducted using computational fluid dynamics theory. Furthermore, the analysis focuses on the influence of changes in guide vane opening on the flow state within the turbine runner. The findings indicate that the occurrence of rotor cavitation is severe when the opening is small, and increasing the opening reduces the cavitation capacity of the rotor. The presence of a lobe vortex phenomenon is mainly observed within a small range of guide vane openings, and altering the opening modifies both the range of influence and flow characteristics of the lobe vortex. In the middle range of guide vane openings, vortex pressure pulsation dominates within the rotor, with the highest amplitude of pressure pulsation occurring at a 60% opening. In the large opening range, pressure pulsation mainly occurs in the lobe frequency pressure pulsation of the rotor within the lobe-less area. The amplitude of blade frequency is typically small, indicating good hydraulic stability of the unit. These study results elucidate the interval of stable operating conditions for the unit and offer valuable insights for maintaining its stable operation.

Study on the coupling calculation method for the launch dynamics of a self-propelled artillery multibody system considering engraving process

The launch dynamics theory for multibody systems emerges as an innovative and efficacious approach for the study of launch dynamics, capable of addressing the challenges of complex modeling, diminished computational efficiency, and imprecise analyses of system dynamic responses found in the dynamics research of intricate multi-rigid-flexible body systems, such as self-propelled artillery. This advancement aims to enhance the firing accuracy and launch safety of self-propelled artillery. Recognizing the shortfall of overlooking the band engraving process in existing theories, this study introduces a novel coupling calculation methodology for the launch dynamics of a self-propelled artillery multibody system. This method leverages the ABAQUS subroutine interface VUAMP to compute the dynamic response of the projectile and barrel during the launch process of large-caliber self-propelled artillery. Additionally, it examines the changes in projectile resistance and band deformation in relation to projectile motion throughout the band engraving process. Comparative analysis of the computational outcomes with experimental data evidences that the proposed method offers a more precise depiction of the launch process of self-propelled artillery, thereby enhancing the accuracy of launch dynamics calculations for self-propelled artillery.

Experimental and theoretical fluid dynamics of spherical Savonius turbines operated in pipe flows

The performance of Savonius turbines driven by flow in a pipe is experimentally investigated. The turbine is manufactured to have a spherical outline based on the pipe cross section at a small clearance. The torque and power of the turbine are obtained from the time derivative of the rotational speed measured using a high-speed camera and an equation of rotational motion. We find that the idling tip-speed ratio of the turbine exceeds 5, which is much greater than that of a turbine operating in an open free stream. This proves the dominance of pulsatile flow through the gap between two hemispherical blades in torque generation. Widely varying the gap (i.e., the overlap ratio OR of the Savonius turbine) reveals that a turbine with OR = 30 % has the highest power coefficient. The output efficiency exceeds 50 % for a tip-speed ratio of approximately 3. These experimental results are supported by fluid dynamics theory and computational fluid dynamics simulation, which clarify the driving mechanism of the turbine in a pipeline.

Molecular modeling of CO2 affecting competitive adsorption within anthracite coal

This study aimed to investigate the adsorption properties of CO2, CH4, and N2 on anthracite. A molecular structural model of anthracite (C208H162O12N4) was established. Simulations were performed for the adsorption properties of single-component and multi-component gases at various temperatures, pressures, and gas ratios. The grand canonical ensemble Monte Carlo approach based on molecular mechanics and dynamics theories was used to perform the simulations. The results showed that the isotherms for the adsorption of single-component CO2, CH4, and N2 followed the Langmuir formula, and the CO2 adsorption isotherm growth gradient was negatively correlated with pressure but positively correlated with temperature. When the CO2 injection in the gas mixture was increased from 1 to 3% for the multi-component gas adsorption, the proportion of CO2 adsorption rose from 1/3 to 2/3, indicating that CO2 has a competing-adsorption advantage. The CO2 adsorption decreased faster with increasing temperature, indicating that the sensitivity of CO2 to temperature is stronger than that of CH4 and N2. The adsorbent potential energies of CO2, CH4, and N2 diminished with rising temperature in the following order: CO2 < CH4 < N2.

Role of Knowledge Management Practices in Enhancing Innovation and Competitiveness in the Ethiopian Leather Industry

Purpose: The aim of the study was to investigate the role of knowledge management practices in enhancing innovation and competitiveness in the Ethiopian leather industry.&#x0D; Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries.&#x0D; Findings: The role of knowledge management practices in enhancing innovation and competitiveness in the Ethiopian leather industry is significant. Through effective knowledge management strategies, such as knowledge sharing, transfer, and utilization, firms can capitalize on their intellectual capital to foster innovation and improve competitiveness. By leveraging existing knowledge assets and creating a culture of continuous learning and innovation, Ethiopian leather companies can position themselves for sustained growth and success in both domestic and international markets.&#x0D; Unique Contribution to Theory, Practice and Policy: Resource-based view (RBV) theory, dynamic capabilities theory &amp; social capital theory may be used to anchor future studies on the role of knowledge management practices in enhancing innovation and competitiveness in the Ethiopian leather industry. Organizations within the Ethiopian leather industry should invest in capacity-building programs to enhance employees' knowledge management capabilities. Government policies should be formulated to support knowledge management initiatives and innovation in the Ethiopian leather industry.

Orbital-Selective Mott Transition Effects and Nontrivial Topology of Iron Chalcogenide.

The iron-based superconductor FeSe_{1-x}Te_{x} has recently gained significant attention as a host of two distinct physical phenomena: (i)Majorana zero modes that can serve as potential topologically protected qubits, and (ii)a realization of the orbital-selective Mott transition. In this Letter, we connect these two phenomena and provide new insights into the interplay between strong electronic correlations and nontrivial topology in FeSe_{1-x}Te_{x}. Using linearized quasiparticle self-consistent GW plus dynamical mean-field theory, we show that the topologically protected Dirac surface state has substantial Fe(d_{xy}) character. The proximity to the orbital-selective Mott transition plays a dual role: it facilitates the appearance of the topological surface state by bringing the Dirac cone close to the chemical potential but destroys the Z_{2} topological superconductivity when the system is too close to the orbital-selective Mott phase. We derive a reduced effective Hamiltonian that describes the topological band. Its parameters capture all the chemical trends found in the first principles calculation. Our findings provide a framework for further study of the interplay between strong electronic correlations and nontrivial topology in other iron-based superconductors.

A Systematic Review of Second Language Acquisition from the Perspective of Complex Dynamic System Theory

From the Complex Dynamic Systems Theory (CDST) point of view, second language development has unpredictable and non-linear patterns that vary from learner to learner. Keeping track of such dynamic development requires longitudinal studies with sufficient data points. The present systematic literature review attempts to present an overview on the previously conducted longitudinal studies that have investigated the development of second language subsystems from the CDST perspective. Starting from 1884 publications, the systematic searching strategy led to 45 articles which were examined in order to highlight the state of the art. The observations of the reviewed studies are conclusively supportive of the CDST principles in second language development. The synthesis of the findings of the papers will be presented and, finally, a multitude of suggestions for further research will be provided which can help future studies clarify the existing gaps that exist in the literature.

A study on the arch mechanism of pedestrian evacuation and congestion alleviation strategies at building exits

The pedestrian flow capacity of building exits has always been a focus of research in evacuation field. This paper focuses on the congestion mechanism of pedestrian flow at exit bottlenecks through simulation and crowd experiments, and tries to propose strategies to alleviate evacuation congestion. Firstly, pedestrian flow evacuation experiments were conducted by setting up scenarios with exits in the middle and corners, and corresponding exit structure models were established using Massmotion software to analyze the congestion mechanisms of pedestrian flow at the exits through simulations coupled with the social force model. Secondly, the severity of congestion in the exit structure was quantified using the example of the middle exit. The width range of the pedestrian evacuation trajectory within 1 m before the exit was defined as the average chord length of the arch structure, and the area enclosed by the semicircular arch with this chord length was defined as the area with a relatively high instantaneous density of pedestrian flow. The results indicate that corner exits are more conducive to evacuation as they reduce the expected velocity of pedestrians near the center of congested areas. Both building width and the inflow rate of pedestrian flow, along with the number of pedestrians, demonstrate significant effects on the average chord length of the arch. The research results can be used to further supplement and improve the dynamic theory of pedestrian flow evacuation in buildings and provide a scientific reference for crowd congestion control at building exits.

Theory of interlayer exciton dynamics in two-dimensional transition metal dichalcogenide heterolayers under the influence of strain reconstruction and disorder

Theory of interlayer exciton dynamics in two-dimensional transition metal dichalcogenide heterolayers under the influence of strain reconstruction and disorder

Identification of Wind Load Exerted on the Jacket Wind Turbines from Optimally Placed Strain Gauges Using C-Optimal Design and Mathematical Model Reduction

Wind turbine towers experience complex dynamic loads during actual operation, and these loads are difficult to accurately predict in advance, which may lead to inaccurate structural fatigue and strength assessment during the structural design phase, thereby posing safety risks to the wind turbine tower. However, online monitoring of wind loads has become possible with the development of load identification technology. Therefore, an identification method for wind load exerted on wind turbine towers was developed in this study to estimate the wind loads using structural strain, which can be used for online monitoring of wind loads. The wind loads exerted on the wind turbine tower were simplified into six equivalent concentrated forces on the topside of the tower, and the initial mathematical model for wind load identification was established based on dynamic load identification theory in the frequency domain, in which many candidate sensor locations and directions were considered. Then, the initial mathematical model was expressed as a linear system of equations. A numerical example was used to verify the accuracy and stability of the initial mathematical model for the wind load identification, and the identification results indicate that the initial mathematical model combined with the Moore–Penrose inverse algorithm can provide stable and accurate reconstruction results. However, the initial mathematical model uses too many sensors, which is not conducive to engineering applications. Therefore, D-optimal and C-optimal design methods were used to reduce the dimension of the initial mathematical model and determine the location and direction of strain gauges. The C-optimal design method adopts a direct optimisation search strategy, while the D-optimal design method adopts an indirect optimisation search strategy. Then, four numerical examples of wind load identification show that dimensionality reduction of the mathematical model leads to high accuracy, in which the C-optimal design algorithm provides more robust identification results. Moreover, the fatigue damage calculated based on the load identification wind loads closely approximates that derived from finite element simulation wind load, with a relative error within 6%. Therefore, the load identification method developed in this study offers a pragmatic solution for the accurate acquisition of the actual wind load of a wind turbine tower.

Perseveration on suicidal thoughts and images in daily life: An examination of the cognitive model of suicide through a dynamic systems lens

According to the cognitive model of suicide, interactions between hopelessness and attentional biases toward suicidal information create a narrowed attentional focus on suicide as a viable solution, particularly in the presence of life stress, leading to increased suicide risk. This study used a dynamic systems approach to examine the short-term temporal patterns between stress, hopelessness, suicide-specific rumination, and suicidal intent. Adults (N = 237; M = 27.12 years; 62% cisgender women; 87% White/European American) with elevated suicidal ideation completed ecological momentary assessments six times a day for 14 days. A multilevel model approach informed by dynamic systems theory was used to simultaneously assess stable and dynamic temporal processes underlying perceived stress, hopelessness, suicide-specific rumination, and suicidal intent. Each variable demonstrated temporal stability. In support of the cognitive model of suicide, we observed (1) a reciprocal relationship between stress and hopelessness such that stress and hopelessness amplified each other (early-stage processes), and (2) reinforcing loops such that hopelessness, suicide-specific rumination, and suicidal intent amplified each other (later-stage processes). A dynamic systems modeling approach underscored the negative impact of a perpetuating cycle of suicide-specific rumination, deepening hopelessness, and escalating suicidal intent on increasing suicide risk, which may be targets for intervention.

What explain capital structure determinants choices of Shariah firms?

This study aims to discover key capital structure determinants for the entire Shariah firms operating in dissimilar contexts. Moreover, it also estimates the adjustment speed for these firms to maintain targeted capital structures at all times. For this purpose, 321 Shariah firms that are operational in Saudi Arabia, Pakistan, the UAE, and Indonesia are nominated. The empirical analysis is conducted using 11 years, i.e., 2011-2021, of balanced Panel Data. The debt-to-asset and debt-to-equity ratios are used as variables of interest, whereas the asset tangibility ratio, current ratio, return on equity, size, non-debt-tax shield, inflation, and gross domestic product are used as explanatory variables. The robust estimator, i.e., Generalized Method of Moments (GMM), is executed to perform the analysis. The results show that the most important factors for Shariah-tagged firms are inflation, the gross domestic product, the asset ratio, the return on equity, the non-debt tax shield, and the lagged dependent variables. The important role of asset tangibility, lagged variables, and the presence of adjustment speed postulate that Shariah-tagged firms are following the provided guidelines of Dynamic Trade-Off theory to preserve capital structure. The findings are a new contribution to the limited empirical inquiries of Shariah firms’ capital structure and a fresh addition to Islamic Finance literature. Besides, the outcomes are also helpful for policymakers and assist them in developing an optimal model of capital structure for Shariah-tagged firms that decreases overall capital costs and enhances these firms’ market value.

Dynamical theory of topological defects II: universal aspects of defect motion

We study the dynamics of topological defects in continuum theories governed by a free energy minimization principle, building on our recently developed framework (Romano et al 2023 J. Stat. Mech. 083211). We show how the equation of motion of point defects, domain walls, disclination lines and any other singularity can be understood with one unifying mathematical framework. For disclination lines, this also allows us to study the interplay between the internal line tension and the interaction with other lines. This interplay is non-trivial, allowing defect loops to expand, instead of contracting, due to external interaction. We also use this framework to obtain an analytical description of two long-lasting problems in point defect motion, namely the scale dependence of the defect mobility and the role of elastic anisotropy in the motion of defects in liquid crystals. For the former, we show that the effective defect mobility is strongly problem-dependent, but it can be computed with high accuracy for a pair of annihilating defects. For the latter, we show that at the first order in perturbation theory, anisotropy causes a non-radial force, making the trajectory of annihilating defects deviate from a straight line. At higher orders, it also induces a correction in the mobility, which becomes non-isotropic for the +1/2 defect. We argue that, due to its generality, our method can help to shed light on the motion of singularities in many different systems, including driven and active non-equilibrium theories.

Even imprudent risk lovers may engage in precautionary saving

AbstractRecent developments in dynamic consumption theory have shown that risk-loving agents, much like their risk-averse analogues, can exhibit downside risk aversion (prudence) and thus demand precautionary savings. I complement this finding by showing that risk-seeking preferences also magnify the role of natural borrowing limits in shaping consumers’ behavior, causing risk lovers to increase savings against income uncertainty in cases where risk averters would not: even imprudent risk lovers may engage in precautionary saving.

Confined grotthuss proton-conduction along polyoxometalate chains inside carbon nanotubes for high-rate charge storage

Redox-active materials with excellent rate capability and cycling performance are in highly demand for electrochemical energy storage and conversion applications. Here, we unveil the confined proton-conduction behavior of one-dimensional polyoxometalate chains inside single-walled carbon nanotubes (SWNTs). The polyoxometalate molecules including phosphomolybdic acid {HPMo} and phosphotungstic acid {HPW} are encapsulated within SWNTs via host–guest recognition, driven by the electron transfer from nanotubes to polyoxometalates. Impressively, the redox hybrids of polyoxometalate@SWNTs deliver abnormal rate performance in acidic solution with capacity retentions over 73 % at high sweep rate of 1000 mV s−1, relative to the capacity at 10 mV s−1. This value is comparable to that of the pure SWNTs, typically known as double-layer capacitive materials. Electrochemical analyses reveal the Grotthuss proton-conduction mechanism of {HPMo} in SWNTs with a low activation energy of 0.11 eV. Therefore, the {HPMo}@SWNT hybrid demonstrates quasi diffusion-free characteristic with dominant capacitive contribution over 60 % at different sweep rates. Molecular dynamic simulations and density functional theory calculations evidence the strong burst-like transport of protons in the {HPMo}@SWNT hybrid. This process is dynamically favored in the continuous and long-range hydrogen-bond network along polyoxometalate chains with bound/free water molecules inside SWNTs. The superiority of nanoconfined Grotthuss mechanism may engender an exciting avenue for developing high-performance energy storage materials.

Adequacy of the dynamical mean field theory for low density and Dirac materials

Adequacy of the dynamical mean field theory for low density and Dirac materials

Bifurcations, chaotic behavior, and optical solutions for the complex Ginzburg–Landau equation

This research focuses on investigating an extended version of the Ginzburg–Landau (GL) equation that describes the motion of particles in a plasma. The other applications of this model can be found in optics, and other related fields. As part of our approach, we seek to discover some new wave solutions to the model, and then use the Galilean transformation in order to determine the model’s dynamical properties. After that, we use planar dynamical system theory to perform an in-depth bifurcation analysis, which gives us valuable insight into the system. By conducting thorough mathematical and bifurcation analyses, we identify the fundamental dynamics and critical points that regulate the system’s behavior. Moreover we explore the chaotic nature of the system, uncovering potential chaotic tendencies and their consequences. Further, we obtain several categories of optical solutions of the complex GL equation by utilizing new logarithmic transformations, offering valuable insight into its behavior and potential applications in optics. Our analytical technique yields closed-form solutions expressing elementary functions. In order to ensure the reliability of our findings, we rigorously validate the obtained solutions by substituting them back into the original model. Our research helps us better understand this equation’s characteristics and its relevance across a wide range of disciplines.

The influence of digitalization on SMEs’ OFDI in emerging countries

The role of digitalization has been understudied in the literature on small and medium-sized enterprises’ (SMEs) outward foreign direct investment (OFDI) in emerging countries. Building on the internalization and dynamic capabilities theories, this paper examines how digitalization facilitates OFDI by SMEs in emerging countries. Using a dataset of 562 Chinese SMEs from 2011 to 2020, we find that SMEs’ digitalization has a positive impact on their OFDI levels, measured using both the number of overseas subsidiaries and the number of host countries. This effect is mediated by a firm’s dynamic capability and moderated by top managers’ international experience and industry competitive intensity. This paper contributes to the literature by revealing the mechanisms by which digitalization affects SMEs’ OFDI and the boundary conditions that may moderate this relationship.

MATHEMATICAL THEORY OF THE INCLINED PLANE

The laws of mutual transformation of statistical and dynamic effects on an inclined plane are shown, a mathematical justification is given for obtaining a gain from the action or the possibility of saving the main useful action and facilitating the actions of Gravity. All the above statements are carried out using the basic elements of the theories of dynamics, statics and trigonometric calculations. The influence of the geometric dimensions of the inclined plane on the transformation of actions is estimated. The mechanism of statistical and dynamic equilibrium of actions on an inclined plane is substantiated through mathematical expressions of the conservation law and the relationship between the components of the vector.