Theory Techniques Research Articles

Safe self-adjusting trajectory tracking control method for air cushion vehicle

ABSTRACT The safety of autonomous driving systems is a critical factor in the operation of high-speed air cushion vehicle (ACV). This paper presents a safety-guaranteed trajectory tracking controller for ACV. A safe self-adjusting speed guidance law is developed based on the finite-time auxiliary system. It can autonomously regulate tracking errors in accordance with the vehicle’s motion states and control inputs. Building on this framework, a trajectory tracking controller is developed utilising Lyapunov stability theory and finite-time control techniques to ensure safe operation. The stability of the proposed controller is rigorously proven. Simulation results demonstrate that the controller effectively mitigates tracking errors, ensuring that key motion parameters – such as speed, turn rate and drift angle – remain within predefined safety limits. Moreover, the control signals generated by the controller are shown to be compatible with the physical limitations of the vehicle’s actuators during trajectory tracking.

A Review of Experiment Methods, Simulation Approaches and Wake Characteristics of Floating Offshore Wind Turbines

With the urgent demand for net-zero emissions, renewable energy is taking the lead and wind power is becoming increasingly important. Among the most promising sources, offshore wind energy located in deep water has gained significant attention. This review focuses on the experimental methods, simulation approaches, and wake characteristics of floating offshore wind turbines (FOWTs). The hydrodynamics and aerodynamics of FOWTs are not isolated and they interact with each other. Under the environmental load and mooring force, the floating platform has six degrees of freedom motions, which bring the changes in the relative wind speed to the turbine rotor, and furthermore, to the turbine aerodynamics. Then, the platform’s movements lead to a complex FOWT wake evolution, including wake recovery acceleration, velocity deficit fluctuations, wake deformation and wake meandering. In scale FOWT tests, it is challenging to simultaneously satisfy Reynolds number and Froude number similarity, resulting in gaps between scale model experiments and field measurements. Recently, progress has been made in scale model experiments; furthermore, a “Hardware in the loop” technique has been developed as an effective solution to the above contradiction. In numerical simulations, the coupling of hydrodynamics and aerodynamics is the concern and a typical numerical simulation of multi-body and multi-physical coupling is reviewed in this paper. Furthermore, recent advancements have been made in the analysis of wake characteristics, such as the application of instability theory and modal decomposition techniques in the study of FOWT wake evolution. These studies have revealed the formation of vortex rings and leapfrogging behavior in adjacent helical vortices, which deepens the understanding of the FOWT wake. Overall, this paper provides a comprehensive review of recent research on FOWT wake dynamics.

Synthesis, Photophysical Properties and Systematic Evaluation of New Class Fluorescein Based Derivative with Organic Solvents: Spectroscopic and Density Functional Theory Methods for Optoelectronic Applications.

In this report the photophysical property of newly synthesized fluorescein based derivative 2-(5-((2,4-dichlorophenyl)diazenyl)-6-hydroxy-3-oxo-3H-xanthen-9-yl)benzoic acid has studied by spectroscopic and theoretical that is by Density Functional Theory technique. The structural and functional group of the synthesized molecule was confirmed by nuclear magnetic resonance and fourier transform infrared spectroscopy technique, and from the result so far obtained has been confirmed that molecule has a stable structure and confirmed the presence the functional groups present in the sample. The optical properties of the molecule are studied using the spectroscopic technique and it has revealed the solute-solvent interaction behaviour of the molecule and it has been observed that the bathochromic shift was of about 5nm, from the fluorescence measurement it has revealed that the emission has been observed at green region and from the power spectra it has been confirmed the same. The DFT study has been derived for the synthesized molecule the optimized structure, electrostatic potential maps, theoretical energy band gap and HOMO and LUMO visualizations are derived from the Gaussian 09W software and it has been found that the bandgap energy is found to be 2.607eV for benzene solvent and 3.081eV in methanol solvent, the electrophilic and nucleophilic sites exhibited at the substitution group of the molecule. The outcomes of the study clearly endorse the synthesized fluorescein derivative suitable for photonic/optoelectronic applications.

On the reducibility of X q − 1 in the monoid ring F p [ X ; 〈 2 , 3 〉 ]

Using techniques of algebraic and analytic number theory, we resolve a question on monoid rings posed by Kulosman et al. under the assumption of the Generalized Riemann Hypothesis (GRH). Specifically, we show that under an appropriate GRH, for any (rational) prime p the set E ( p ) = { q prime | X q − 1 factors in F p [ X ; M ] } , where M = 〈 2 , 3 〉 = N 0 ∖ { 1 } , contains a subset with positive natural density. In particular E ( p ) ≠ ∅ . This proves that M is not a so-called “Matsuda monoid” of any positive type. For p = 2 , 3 this was observed by Kulosman, who provided factorizations of X 7 − 1 and X 11 − 1 in F 2 [ X ; M ] and F 3 [ X ; M ] , respectively. Our results explain and reproduce both of these factorizations, as well.

Design of a Finite-Time Bounded Tracking Controller for Time-Delay Fractional-Order Systems Based on Output Feedback

This paper focuses on a class of fractional-order systems with state delays and studies the design problem of the finite-time bounded tracking controller. The error system method in preview control theory is first used. By taking fractional-order derivatives of the state equations and error signals, a fractional-order error system is constructed. This transforms the tracking problem of the original system into an input–output finite=time stability problem of the error system. Based on the output equation of the original system and the error signal, an output equation for the error system is constructed, and a memory-based output feedback controller is designed by means of this equation. Using the input–output finite-time stability theory and linear matrix inequality (LMI) techniques, the output feedback gain matrix of the error system is derived by constructing a fractional-order Lyapunov–Krasovskii function. Then, a fractional-order integral of the input to the error system is performed to derive a finite-time bounded tracking controller for the original system. Finally, numerical simulations demonstrate the effectiveness of the proposed method.

When Resources Become Stressors: Dynamics of the Stress Process in the Flint Water Crisis.

Disasters create and intensify stress for communities, with many factors contributing to how that stress results in mental health outcomes. Guided by the stress process model, this article presents findings from a qualitative investigation of the meaning of stress among community leaders in the context of the water crisis in Flint, Michigan. Semi-structured interviews were conducted with six community leaders in Flint and analyzed using grounded theory techniques. Secondary stressors such as necessary changes to everyday routines, being discredited by government officials, and perceptions of a lack of government action and accountability were perceived to impact the community's mental health, with potentially more influence than the impact of the primary stressor of contaminated water. Findings indicate that both stressors and coping resources evolve with profound intrapersonal impact, such that proposed social coping resources become stressors when they do not meet individual or community needs or expectations.

Leader-following privacy-preserving consensus control of nonlinear multi-agent systems: a state decomposition approach

This paper focuses on a nonlinear multi-agent system (MAS) in the presence of unknown dynamics and eavesdroppers. An output consensus control strategy is proposed based on an extended state observer, which achieves leader-following privacy-preserving consensus in a backstepping framework. Different from existing distributed average consensus approaches that require each follower to exchange and expose state information to its neighbours, our strategy avoids the requirement for communication during information interaction by decomposing each follower's state information into two sub-states. The status information is leaked, thereby achieving privacy preservation. Furthermore, for this class of MAS with unknown dynamics, we use an extended state observer to estimate the unknown dynamics and design an auxiliary system. The auxiliary variables generated by this auxiliary system combined with the back-stepping method can effectively compensate for dynamics. By combining graph theory knowledge and techniques such as Lyapunov functions, it is proven that the output-consensus tracking error of an MAS is ultimately bounded. Finally, the effectiveness of the control strategy is verified via an example.

Computational study on adsorption and separation of H2/CH4/CO2 in double-walled metal-dipyrazole frameworks

The density functional theory (DFT) and molecular simulation techniques were employed to comprehensively study the structural characteristics and adsorption and separation properties of H2/CH4/CO2 in six novel double-walled dipyrazole metal-organic frameworks (MOFs), BUT-53 to BUT-58 (BUT: Beijing University of Technology). The six new MOFs were characterized using numerical Monte Carlo methods, based on crystal structures optimized through DFT calculations. The results reveal that six MOFs exhibit large specific surface area (1068 – 1780 cm2·g-1), high porosity (0.27 – 0.44 cm3·g-1), and suitable pore size (4.34 – 8.15Å), which are advantageous for gas adsorption and separation. Grand canonical Monte Carlo (GCMC) simulation was implemented to study gas adsorption and separation properties at both 77 and 298K. The simulation results demonstrate that BUT-57 possesses the highest storage capacity for pure component gas, while BUT-53 owns the best separation properties for binary mixture gases. Meanwhile, we propose an approach to enhance the selectivity for CO2 by augmenting the availability of nitrogen sites in porous MOFs, thereby offering some insights for related experimental investigations.

Explainable post hoc portfolio management financial policy of a Deep Reinforcement Learning agent.

Financial portfolio management investment policies computed quantitatively by modern portfolio theory techniques like the Markowitz model rely on a set of assumptions that are not supported by data in high volatility markets such as the technological sector or cryptocurrencies. Hence, quantitative researchers are looking for alternative models to tackle this problem. Concretely, portfolio management (PM) is a problem that has been successfully addressed recently by Deep Reinforcement Learning (DRL) approaches. In particular, DRL algorithms train an agent by estimating the distribution of the expected reward of every action performed by an agent given any financial state in a simulator, also called gymnasium. However, these methods rely on Deep Neural Networks model to represent such a distribution, that although they are universal approximator models, capable of representing this distribution over time, they cannot explain its behaviour, given by a set of parameters that are not interpretable. Critically, financial investors policies require predictions to be interpretable, to assess whether they follow a reasonable behaviour, so DRL agents are not suited to follow a particular policy or explain their actions. In this work, driven by the motivation of making DRL explainable, we developed a novel Explainable DRL (XDRL) approach for PM, integrating the Proximal Policy Optimization (PPO) DRL algorithm with the model agnostic explainable machine learning techniques of feature importance, SHAP and LIME to enhance transparency in prediction time. By executing our methodology, we can interpret in prediction time the actions of the agent to assess whether they follow the requisites of an investment policy or to assess the risk of following the agent's suggestions. We empirically illustrate it by successfully identifying key features influencing investment decisions, which demonstrate the ability to explain the agent actions in prediction time. We propose the first explainable post hoc PM financial policy of a DRL agent.

Exploring Number Theory and Its Applications in Quantum Computing

This paper discusses the deep connection between Number Theory, Cryptography, and Quantum Computing techniques in an endeavor to understand their application in developing new cryptographic techniques, optimization problems, and computational complexity. Like modular arithmetic, which uses prime factorization, in most quantum algorithms like Shor’s and Grover's algorithms, number theory is one of the significant paradigms. This work gives a detailed analysis of some mathematical derivation, theore,m and proof of these algorithms to their practical use as well as computational efficiency. Discussed issues include scaling, correction of errors, and unsolved concerns applying number theory; all discussed from the perspective of existing quantum architecture. Addressing this new research directions of the field, the paper also presents further developments in quantum cryptography, topological quantum computing, and the algorithmic area. In highlighting both theoretical and computational challenges, this work has shown that the synergy between number theory and quantum computing has the opportunity to revolutionize cryptography and optimization and to lay the groundwork for future quantum advancements

The adjustment disorder is not a wastebasket diagnosis: a grounded theory study of psychiatrists’ and psychologists’ clinical reasoning

ABSTRACT Background: the aim of this study is to understand the diagnostic process undertaken by psychiatrists and psychologists regarding adjustment disorder (AD) in their clinical practice and how they differentiate it from major depressive episode (MDE). Methods: A hermeneutic study using grounded theory techniques was carried out. Semi-structured interviews were conducted with twelve psychiatrists and eight psychologists in Colombia, and transcribed verbatim. Initial line-by-line coding was performed, followed by focused and axial coding to construct categories explaining the professionals’ reasoning process. Results: The clinical reasoning of professionals regarding AD was understood through four major categories. (1) Difficulty in addressing the experience of stressful events, as there is a risk of pathologizing and medicalizing them. (2) Mental health diagnoses are necessary but not apodictic. (3) The diagnostic category of AD allows for the description of a fluctuating depressive and anxious syndrome occurring in reaction to a stressful event, whose abnormality criteria are based on intersubjective knowledge of the patient's life history and consequential reasoning regarding the need for professional support. (4) The AD label could potentially protect against overdiagnosis of MDE and overuse of antidepressants. Many clinicians in their practice thus subordinate the diagnosis of MDE to ensuring it is not AD, contrary to what is outlined in diagnostic manuals. Conclusion: This study allowed us to understand the clinical reasoning of psychiatrists and psychologists about AD as a diagnosis that inherently indicates the need to work on coping and intervene in the stressor and should be considered as a diagnostic possibility in the same hierarchy as MDE in reactive syndromes, rather than a residual category.

Attitude Control and Trajectory Tracking of a Shipboard Quadrotor Unmanned Aerial Vehicle Based on Self-Improvement Algorithm

With the rapid development of Industry 4.0 and urbanisation around the world, computer control technology and electromechanical systems, the development of UAVs around the world has entered a period of rapid development. As UAVs enter the rapid development stage, higher requirements are placed on the precise control rate during UAV missions. Multi-rotor UAVs have been used on ships in large scale due to their easy-to-manoeuvre characteristics. However, shipboard UAVs are affected by many factors during flight, such as crosswinds, gusts and wave effects at sea. Therefore, it is necessary to optimise the robustness and safety of the control process of shipborne UAVs through self-immunity algorithms. In the research process of UAV, modern control theory has developed very rapidly, but it is difficult to be applied in practice, and there is a certain gap. The reason for this is that advanced control theory techniques require an accurate mathematical model of the controlled object.In this study, the position and attitude equations of motion of the quadrotor UAV are firstly obtained according to the rigid body mechanics, the UAV dynamics model is deduced, and for the UAV attitude control and trajectory tracking requirements, the inner loop adopts the self-immobilisation control and the outer loop adopts the PID control, and the relevant control structure is designed. Through relevant Simulink simulation and comparison with the effect of traditional PID control, the optimisation effect of the self-immunity algorithm on the control of shipborne quadrotor UAV is verified.

Dribbling emotions and anxiety in women’s football: a scoping review

Background and Study Aim. Fear of failure, choking under pressure, financial disparities in income, and concerns related to body image and social pressure may intensify on-field challenges. These factors make the competitive environment particularly demanding for female soccer players. The aim of the current review is to map the available evidence on anxiety in women's football over the past decade and to identify interventions designed to manage anxiety among female soccer players. Material and Methods. A scoping review was conducted following the PRISMA-ScR guidelines. An extensive search was carried out across four major databases for publications dated between 2014 and 2024. Two independent reviewers screened titles and abstracts, followed by full-text screening and data extraction. Any disagreements were resolved by a third researcher. The findings were tabulated and synthesized in a narrative format. The study was pre-registered on the Open Science Framework. Results. The search yielded 2885 unique records. A total of 21 texts were reviewed in full, and the final sample included 14 studies. Some of the records included mentioned modifications to psychosocial interventions, such as Virtual Reality (VR) relaxation sessions, pre-exercise sporting massage, and psychological training programs (including psycho-neuromuscular theory and visualization techniques). These interventions led to a reduction in anxiety, though their effectiveness varied significantly across different approaches. Our results suggest that research on women's football may disproportionately focus on psychological interventions for managing anxiety. This highlights the need for broader investigations into other factors that influence athletes' performance and well-being. Conclusions. This scoping review helps clarify the current landscape of anxiety research in women's soccer. It highlights both promising interventions and gaps in the research over the past decade. Although the body of evidence on anxiety interventions is small, it suggests that psychological interventions may be effective in reducing anxiety among female soccer players.

Determining the optimal oxidation temperature of non-isothermal liquid fuels injections using modeling based on statistical droplet distribution

Single-hole injections of liquid hydrocarbon fuels (isooctane and dodecane) under high turbulence have been investigated using direct numerical simulation based on the statistical model considering the droplets’ atomization, distribution, and combustion. The study objects are the heat and mass transfer processes during atomization and combustion of liquid fuels injections within the combustion chambers of thermal engines. The temperature and carbon dioxide concentration distributions of the fuel-air mixture, the distributions of the droplets, their velocities, and the Sauter mean radius within the isooctane and dodecane oxidation in the engine’s combustion space were obtained. An investigation of the oxidizer’s initial temperature influence on the droplets’ atomization and combustion processes showed that the optimal temperature for both fuels is 900 K. The obtained modeling results were confirmed in good agreement with theoretical and experimental data. Thanks to the integrated use of approaches from statistical theory, numerical algorithms and 3D computer modeling techniques, the results obtained are distinguished by high accuracy, efficiency in reducing computational resources, scientific novelty in the type of droplet atomization and suitability for practical application for technological solutions not only for single-hole, but also for multi-hole injections of liquid fuels and studying the jet-to-jet interaction phenomena. The obtained research results can be applied in miscellaneous internal combustion engines development with different atomization types, which will allow us to contemporaneously settle the concerns of streamlining the combustion process, improving the completeness of fuel combustion and reducing emissions of harmful substances

PROPERTIES OF SOLUTIONS IN THE DUBINS CAR CONTROL PROBLEM

TThis paper addresses the time-optimal control problem of the Dubins car, which is closely related to the problem of constructing the shortest curve with bounded curvature between two points in a plane. This connection allows researchers to apply both geometric methods and control theory techniques during their investigations. It is established that the time-optimal control for the Dubins car is a piecewise constant function with no more than two switchings. This characteristic enables the categorization of all such controls into several types, facilitating the examination of the solutions to the control problem for each type individually. The paper derives explicit formulas for determining the switching times of the control signal. In each case, necessary and sufficient conditions for the existence of solutions are obtained. For certain control types, the uniqueness of optimal solutions is established. Additionally, the dependence of the movement time on the initial and terminal conditions is studied.

Interventions for improving treatment adherence in young people with inflammatory bowel disease (IBD): A systematic review of behaviour change theory and behaviour change techniques.

Treatment adherence is important but challenging for young people with inflammatory bowel disease (IBD). Behavioural interventions may support adherence, leading to improved condition management. This review aimed to evaluate interventions designed to improve treatment adherence in young people (aged 13-18) with IBD and identify their use of behaviour change theory and behaviour change techniques (BCTs). Five databases (PsycInfo, Embase, MEDLINE, Web of Science and Scopus) were searched to identify eligible articles published between 1980 and 2022. Articles were critically appraised using the Mixed Methods Appraisal Tool. Findings were synthesised narratively. Seven articles reporting seven oral medication adherence interventions were included. Study designs included five randomised controlled trials and two single-arm clinical trials. Eleven BCTs were identified across seven articles. No article discussed how an intervention was informed by behaviour change theory. Interventions that included additional family members and/or offered tailored adherence support generally had greater effects, as did interventions including education and goal setting components. Reporting of intervention content was poor, limiting our ability to make concrete recommendations regarding intervention effectiveness, use of behaviour change theory and BCTs. Further research is needed to understand how theory-driven behaviour change interventions can improve treatment adherence in young people with IBD.

Design and analysis of diisobutoxybenzodithiophene based donor for application in organic solar cell: DFT and TD-DFT Study

The newly designed chromophores (BT1-BT7) of the highly unsaturated donor-acceptor (D-A) were theoretically analyzed and recommended for applications in organic solar cells (OSCs). Conjugated A-groups have been replaced in the reference (BTR) during its design. The structural and optoelectronic properties of designed molecules were calculated using density functional theory (DFT) and Time-dependent DFT (TD-DFT) techniques. The frontier molecular orbitals (FMO) study revealed that BT7 has the lowest energy gap of 2.01 eV, which has significantly less than BTR (2.34 eV), and a significant amount of charge transfer (CT) between HOMO and LUMO has been observed. Out of all the newly designed chromophores in chloroform, the highest absorption spectra were found in the visible region with a bathochromic shift up to 768 nm. The dipole moment values of all the new chromophores (BT1-BT7) were significantly higher than the BTR (5.46 D), which resulted in good solvation. ESP analysis revealed electron distribution on various parts of the molecules by colored maps that are found to be effective for better ICT. The electron transition density resulting from light absorption at different chemical sites was shown using TDM plots. The electron and hole reorganization energy (RE) values were proved as highly efficient in promoting charge mobility and hindered charge recombination for new compounds. By scaling our designed donor to the recognized acceptor Y6, which has demonstrated the creation of OSCs, the open circuit voltage of each molecule was ascertained. The designed molecules exhibited higher open circuit voltages than the reference, indicating improved and fine-tuned optoelectronic properties that would aid in the development of solar cell devices in the future.

Axion Mass and the Ground State of Deconfining SU(2) Yang–Mills Thermodynamics

For the deconfinement phase of an SU(2) Yang–Mills theory, we compute the axion mass mA by appealing to the Veneziano–Witten formula. The topological susceptibility χ arises (i) from a precisely computable thermal ground-state contribution due to a center of a relevant (anti)caloron, and (ii) from contributions due to free thermal quasi-particles in the effective theory. Both (i) and (ii) are derived by using standard Euclidean thermal field theory techniques. While contribution (i) is positive and ∝T4, contribution (ii) is negative, as demanded by reflection positivity, but negligible compared to contribution (i). As a consequence, practically from the critical temperature Tc onward, a real-valued axion mass mA(T)=23πT2MP emerges when the Peccei–Quinn scale is assumed to be the Planck mass MP, independently of the Yang–Mills scale that the axion associates with. We discuss why our results deviate from those found in the dilute instanton gas and interacting instanton liquid approximations, and from results obtained in lattice simulations. Assuming the universe is dark sector to be based on such ultralight axion species, which are nonrelativistic for T≪MP, we investigate the cosmological conditions for their global Bose condensation as the very early universe cooled to temperatures of the order of 109eV.

Rayleigh waves in thermoelastic medium based on a novel nonlocal three-phase-lag diffusion model with double porosity

PurposeThis paper is concerned with the study of the propagation of Rayleigh waves in a homogeneous isotropic, generalized thermoelastic medium with mass diffusion and double porosity structure using the theoretical framework of three-phase-lag model of thermoelasticity.Design/methodology/approachUsing Eringen’s nonlocal elasticity theory and normal mode analysis technique, this paper solves the problem. The medium is subjected to isothermal, thermally insulated stress-free, and chemical potential boundary conditions.FindingsThe frequency equation of Rayleigh waves for isothermal and thermally insulated surfaces is derived. Propagation speed, attenuation coefficient, penetration depth and specific loss of the Rayleigh waves are computed numerically. The impact of nonlocal, void and diffusion parameters on different physical characteristics of Rayleigh waves like propagation speed, attenuation coefficient, penetration depth and specific loss with respect to wave number for isothermal and thermally insulated surfaces is depicted graphically.Originality/valueSome limiting and particular cases are also deduced from the present investigation and compared with the existing literature. During Rayleigh wave propagation, the path of the surface particle is found to be elliptical. This study can be extended to fields like earthquake engineering, geophysics and the degradation of old building materials.

Airport Flight-Gate Allocation Assignment Using Local Antimagic Vertex Coloring

The management of aviation gate assignments may significantly affect the overall productivity of an airport. This work presents a novel approach to enhancing gate assignment algorithms. The methodology used in this study incorporates graph theory and other intricate techniques, with specific focus on the concept of local antimagic vertex coloring. This study presents a comprehensive methodology for identifying optimal gate locations, which incorporates several factors such as aircraft characteristics, passenger capacity, and resource availability. Based on the results of this study, the incorporation of local antimagic vertex coloring exhibits the capacity to significantly enhance the operational effectiveness of airports via the reduction of passenger line wait times and alleviation of traffic congestion challenges. The aforementioned result was derived by using comprehensive models of the physical cosmos and conducting a meticulous analysis of empirical facts. This novel concept has the capacity to enhance the efficacy of airport gate allocation, resulting in heightened levels of customer contentment and reduced operational costs. The implementation of this procedure will facilitate the preservation of the efficiency of the operational networks for air transportation.