Behavior Of System Research Articles

Fluidized bed reactor for 4-chlorophenol photodegradation via solar and visible radiation using ZnO/g-C3N4/carbon xerogel as a photocatalyst

This study investigates the feasibility of employing a fluidized bed reactor for the degradation of 4-chlorophenol (4CP), considering multiple operational parameters (type of radiation, fresh inlet flow rate and recycle flow rate). The selection of the ZnO/g-C3N4/carbon xerogel as photocatalyst, a choice motivated by the improved charge transfer and increased catalyst activity under visible radiation provided by the presence of carbon xerogel and g-C3N4, was previously determined through tests conducted in a jacketed batch reactor under visible radiation, in which the ternary material efficiency was compared to their constituting counterpart materials. The semiconductors constituting the unary, binary, and ternary materials were chosen based on considerations of availability, sustainability, and abundance in nature. The use of the proposed fluidized bed reactor brings advantages in scalability, distribution of irradiated light and overall costs when compared to commonly used batch reactors, whereas the investigation of the flow parameters involved in such process is of great importance to understand and optimize the efficiency of the pollutant degradation process. Regarding the ternary photocatalyst, X-ray diffractometry (XRD) revealed the presence of zinc oxide's hexagonal crystalline structure. Moreover, additional characterization using Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive spectroscopy (EDS) confirmed the presence not only of ZnO but also of carbon xerogel and g-C3N4 in the composite. From the photodegradation experiments, it was determined that the optimal fresh inlet flow rate to achieve the best degradation, as well as the recycle flow rate for this purpose, were 0.07 and 25 L h−1, respectively. Mathematical simulations described that the model that best fits the system's behavior considers the specific reaction rate as dependent on the concentration of the catalyst in the medium.

Hydrogen Production using PEM Electrolyzer

Abstract: This paper presents a simulation study of alkaline electrolysis for H2 production using Aspen Plus. The simulation model incorporates reactor, separators, mixer, and heat exchanger units to accurately represent the AWE process. The model is designed to evaluate the performance of an AWE system under different operating conditions and aims to achieve a reference H2 production rate of 0.179663 kg/hr. The simulation results demonstrate that the AWE system can successfully produce H2 at the specified rate. The model provides a detailed analysis of the system's behavior and H2 production rate, under varying operating conditions. The findings of this study provide valuable insights into optimizing the design and operation of AWE systems for large-scale H2 production

Human control of AI systems: from supervision to teaming

AbstractThis article reviews two main approaches to human control of AI systems: supervisory human control and human–machine teaming. It explores how each approach defines and guides the operational interplay between human behaviour and system behaviour to ensure that AI systems are effective throughout their deployment. Specifically, the article looks at how the two approaches differ in their conceptual and practical adequacy regarding the control of AI systems based on foundation models––i.e., models trained on vast datasets, exhibiting general capabilities, and producing non-deterministic behaviour. The article focuses on examples from the defence and security domain to highlight practical challenges in terms of human control of automation in general, and AI in particular, and concludes by arguing that approaches to human control are better served by an understanding of control as the product of collaborative agency in a multi-agent system rather than of exclusive human supervision.

High-precision two- and three- dimensional atom localization in a microwave and radio-frequency driven Δ∇ system

We introduce a new approach for precise and high-resolution two-dimensional (2D) and three-dimensional (3D) atom localization in a four-level Δ∇ atomic system driven by microwave (M) and radio frequency (R) fields. In the proposed work, additional microwave and radio-frequency fields are utilized for an efficient control of the localization precision. Due to the spatially varying atom-field interaction, the probe susceptibility become position dependent and therefore, one can directly ascertain the position probability distribution of an atom by analyzing the probe spectra. The phase-sensitive property of the atomic system plays a significant role in substantially reducing the uncertainty associated with atom position measurements. We have studied the system behavior through the analysis of dressed states, which forms the basis for its physical interpretation. The increase in precision for measuring the atom’s position is a result of interference between one-photon excitation and the phase-dependent three-photon excitation arising from the closed interacting contour within the laser-driven atomic system, as demonstrated through both numerical calculations and qualitative analyses. The findings indicate that precise sub-wavelength atom localization can be attained by appropriately adjusting the system parameters. Also, the optimal adjustment of these parameters can lead to 100% probability of locating the atom at a particular position within 2D and 3D subspaces.

Dynamic behaviours of rack vehicle-track system considering rack flexibility under gear-rack mesh impact

ABSTRACT There are complex and large gradients for the rack vehicle running on the large mountain slope line. Under such a circumstance, the driving gear-rack interactions will be more intensified and could induce the larger tooth bending stress of the rack. At present, the dynamics modelling of the rack in the existing literature is generally treated as a rigid body or an infinite beam model, however, which is inconsistent with reality. To accurately simulate the vibration characteristics and bending stress of the rack structure, it is necessary to establish a detailed dynamic model considering the flexibility of the rack structure. In this study, the free beam and rod models are, respectively, used to describe the vertical and longitudinal flexibilities of the rack with the finite length. Then, the proposed rack dynamics model is introduced into a rack vehicle-track coupled system, and the developed dynamics model is validated by comparing the results from the simulation with the tested data. Finally, the vibration and bending stress features of the driving gear-rack engagement are analysed under different mounting deviations. The simulated results can give theoretical references for the design and structure optimization of the rack track structure.

A Step-by-Step Methodology for Obtaining the Reliability of Building Microgrids Using Fault TreeAnalysis

This paper introduces an improved methodology designed to address a practical deficit of existing methodologies by incorporating circuit-level analysis in the assessment of building microgrid reliability. The scientific problem at hand involves devising a systematic approach that integrates circuit modeling, Probability Density Function (PDF) selection, formulation of reliability functions, and Fault Tree Analysis (FTA) tailored specifically for the distinctive features of building microgrids. This method entails analyzing inter-component relationships to gain comprehensive insights into system behavior. By harnessing the circuit models and theoretical framework proposed herein, precise estimations of microgrid failure rates can be attained. To complement this approach, we propose a thorough investigation utilizing reliability curves and importance measures, providing valuable insights into individual device failure probabilities over time. Such time-based analysis plays a crucial role in proactively identifying potential failures and facilitating efficient maintenance planning for microgrid devices. We demonstrate the application of this methodology to the University of Antioquia (UdeA) Microgrid, a low-voltage system comprising critical components such as solar panels, microinverters, inverters/chargers, batteries, and charge controllers.

Symmetry and complexity: A Lie symmetry method tobifurcation, chaos, multistability and soliton solutions of thenonlinear generalized advection-diffusion-reaction equation

Abstract This paper deals into the complexities of nonlinear dynamics within the nonlinear generalized advection-
diffusion-reaction equation, which describes intricate transport phenomena involving advection, diffusion,
and reaction processes occurring simultaneously. Through the utilization of the Lie symmetry approach,
we thoroughly examine this proposed model, transforming the partial differential equation into an ordinary
differential equation using similarity reduction techniques to facilitate a more comprehensive analysis. Ex-
act solutions for this transformed equation are derived employing the extended simplest equation method
and the new extended direct algebraic method. To enhance understanding, contour plots along with 2D
and 3D visualizations of solutions are employed. Additionally, we explore bifurcation and chaotic be-
haviours through a qualitative analysis of the model. Phase portraits are meticulously scrutinized across
various parameter values, offering insights into system behavior. Introduction of an external periodic
strength allows us to utilize various tools including time series, 3D, and 2D phase patterns to discern
chaotic and quasi-periodic behaviors. Furthermore, a multistability analysis is conducted to examine the
impacts of diverse initial conditions. These findings underscore the efficacy and practicality of the pro-
posed methodologies in evaluating soliton solutions and elucidating phase dynamics across a spectrum of
nonlinear models, offering novel perspectives on intricate physical phenomena.

Self acceleration from spectral geometry in dissipative quantum-walk dynamics

The dynamic behavior of a physical system often originates from its spectral properties. In open systems, where the effective non-Hermitian description enables a wealth of spectral structures in the complex plane, the concomitant dynamics are significantly enriched, whereas the identification and comprehension of the underlying connections are challenging. Here we experimentally demonstrate the correspondence between the transient self-acceleration of local excitations and the non-Hermitian spectral topology using lossy photonic quantum walks. Focusing first on one-dimensional quantum walks, we show that the measured short-time acceleration of the wave function is proportional to the area enclosed by the eigenspectrum. We then reveal a similar correspondence in two-dimension quantum walks, where the self-acceleration is proportional to the volume enclosed by the eigenspectrum in the complex parameter space. In both dimensions, the transient self-acceleration crosses over to a long-time behavior dominated by a constant flow at the drift velocity. Our results unveil the universal correspondence between spectral topology and transient dynamics, and offer a sensitive probe for phenomena in non-Hermitian systems that originate from spectral geometry.

Electrical Power Systems Reinforcement through Overall Contingency Index Analysis and Improvement

This paper analyzes the behavior of an electrical power system when N-1 contingencies occur in the transmission stage, which can be produced by incorrect operation of the protection relays, phenomena of natural origin, or increased loadability, which affect the operation and reliability of the electrical system. The operation output of a transmission line results in the variation of the nominal values of the electrical parameters involved because they disturb the stability of the generation, transmission systems, and the supply of electrical energy to the loads, such as voltages and angles of the nodes and the active and reactive power of the system. The proposed methodology was based on analyzing the different electrical parameters of the power system, quantifying the contingency index in a state of regular operation, and comparing it to operation in contingency N-1, with which the most severe contingency was determined and, therefore, achieved; identifying contingencies that can cause system collapses; improving the contingency index from 23.08555 to 22.9276624 for the L16–19 contingency and to 22.9795235 for the L21–22 contingency, which are the most severe contingencies determined with the proposed methodology. To test the proposed methodology, the IEEE 39 bus-bar test system was considered, and the elements that should be implemented to avoid the vulnerability of the power system to N-1 contingencies were determined.

Investigation of Nerve Fiber Network in THz Spectrum Range

The behavior of the nerve fiber system of the spinal cord of animals in the THz wavelength range (0.1-3 THz) was experimentally studied using a time domain spectrometer. Terahertz wave transmittance of nerve tissue is investigated, when DC voltage is applied to the sample. It has been shown that when a constant voltage is applied along the nerve fibers (also in the absence of voltage), no noticeable changes occur in the transmitted THz wave, regardless of the orientation of the sample relative to the THz E-field vector. Significant changes in the electrodynamic properties of the sample were observed when the nerve fibers were parallel to the THz E-field vector and the applied voltage was perpendicular to the nerve fibers, particularly, resonant absorption was observed at frequencies of 0.6 THz and 2 THz.

Optimization and comparative analysis of an AISD suspension system with inerter element for enhanced ride and handling

This paper presents a comprehensive study on the modeling and optimization of an advanced suspension system, known as the Air Springs Inerter-Spring-Damper (AISD) system, incorporating an inerter element. A linear quarter car model is utilized to analyze the vibrational behavior of the AISD system when subjected to harmonic road disturbances. The steady-state response of the system is investigated by deriving the root mean square (RMS) values of the absolute relative displacement and acceleration of the sprung mass. To optimize the quarter car model, a criterion based on minimizing the absolute acceleration RMS while considering the relative displacement RMS is employed to calculate the inerter coefficient. The performance of the AISD suspension system is compared to that of both conventional quarter car systems and traditional air quarter car systems, with a focus on ride comfort and handling. The results demonstrate that the proposed AISD system outperforms the other two suspension systems, exhibiting a significant improvement in ride quality. Specifically, the AISD system achieves a 45% enhancement over the air suspension and an 82% improvement over the classic suspension system.

On the behavior of auxetic inserts: a numerical analysis to derive design guidelines

Abstract Auxetics are a class of materials and metamaterials with a negative Poisson’s ratio (ν) and have gained tremendous popularity over the last three decades. Many studies have focused on characterizing designs that allow obtaining a negative ν. However, some open issues remain concerning understanding the auxetic behavior in operational conditions. Studies have been centered on analyzing the response of specific auxetic topologies instead of treating auxeticity as a property to be analyzed in a well-defined structural context. This study aims to contribute to the investigation of auxetic materials with a structural application, focusing on maximizing performance. The field of application of auxetics for designing inserts was selected and a model of a nail-cavity system was created to determine the effects of different design choices on the system behavior by exploring relationships between selected parameters and the auxetic insert behavior. The exploration combines finite element modeling analyses with their surrogate models generated by supervised learning algorithms. This approach allows for exploring the system’s behavior in detail, thus demonstrating the potential effectiveness of auxetics when used for such applications. A list of design guidelines is elaborated to support the exploitation of auxetics in nail-cavity systems.

Deciphering the U-Pb dates of sedimentary phosphates: A complex example from the Upper Cretaceous-Lower Paleogene series in northwestern Morocco

Uranium‑lead geochronology rapidly generates dates of rock deposition/formation with reasonable precision and accuracy using laser ablation inductively coupled plasma mass spectrometry, which is needed for bracketing stratigraphy. However, previous radiometric U-Pb dating of biogenic (i.e., bones and teeth) and sedimentary phosphate minerals have had limited success, probably because of the nanometric to micrometric crystallites that generate open system behavior. Sediment lithification inhibiting trace element exchange between minerals and porewaters and thus forcing phosphorus-rich crystallites to adopt a closed system behavior has been suggested for interpreting U-Pb dating of carbonate fluorapatite (CFA). Despite these insights, what remains lacking is extensive U-Pb CFA dating at the regional scale to test whether several processes influence the timing of U-Pb system closure by inhibiting U and Pb exchanges. Here, we report U-Pb CFA dating from four sampling sites in northwestern Morocco to understand better the meaning of U-Pb dates in CFA. The Upper Cretaceous-Lower Paleogene phosphate series yields anomalously low 207Pb/206Pb initial ratios and young dates ranging from 37.3 ± 2.4 Ma to 22.7 ± 0.7 Ma, which does not agree with the terrestrial lead model composition for Paleogene ages and the known biostratigraphic ages, respectively. We argue that ancient radiogenic Pb from leached polymetallic mineralizations of the regional environment have been incorporated into CFA and that a 25 to 40 Ma-long widespread resetting of the U-Pb system has affected the northwestern Moroccan phosphates. Neither CFA-hosted CO32− concentrations nor rare earth element and yttrium contents indicate post-depositional modifications of the chemical nature of phosphate-bearing rocks. Burial diagenesis promoting sediment lithification is one of the mechanisms that have triggered final closure of the U-Pb system of CFA minerals and, interestingly, the sedimentation rate was probably not a controlling factor. Unexpectedly, U-Pb dates of ∼23 Ma from three stratigraphic levels separated by several million years seem to be concomitant with the regional emersion and generalized continentalization of northwestern Morocco, allowing CFA to behave as a closed system. We conclude that the laser ablation inductively coupled mass spectrometry U-Pb dating of biogenic and sedimentary CFA minerals must be carefully employed to date the timing of fossilization or sediment deposition.

Testing dynamic correlations and nonlinearity in bivariate time series through information measures and surrogate data analysis

The increasing availability of time series data depicting the evolution of physical system properties has prompted the development of methods focused on extracting insights into the system behavior over time, discerning whether it stems from deterministic or stochastic dynamical systems. Surrogate data testing plays a crucial role in this process by facilitating robust statistical assessments. This ensures that the observed results are not mere occurrences by chance, but genuinely reflect the inherent characteristics of the underlying system. The initial process involves formulating a null hypothesis, which is tested using surrogate data in cases where assumptions about the underlying distributions are absent. A discriminating statistic is then computed for both the original data and each surrogate data set. Significantly deviating values between the original data and the surrogate data ensemble lead to the rejection of the null hypothesis. In this work, we present various surrogate methods designed to assess specific statistical properties in random processes. Specifically, we introduce methods for evaluating the presence of autodependencies and nonlinear dynamics within individual processes, using Information Storage as a discriminating statistic. Additionally, methods are introduced for detecting coupling and nonlinearities in bivariate processes, employing the Mutual Information Rate for this purpose. The surrogate methods introduced are first tested through simulations involving univariate and bivariate processes exhibiting both linear and nonlinear dynamics. Then, they are applied to physiological time series of Heart Period (RR intervals) and respiratory flow (RESP) variability measured during spontaneous and paced breathing. Simulations demonstrated that the proposed methods effectively identify essential dynamical features of stochastic systems. The real data application showed that paced breathing, at low breathing rate, increases the predictability of the individual dynamics of RR and RESP and dampens nonlinearity in their coupled dynamics.

Power-exponential and fixed-time consensus of conformable fractional-order quantum cellular neural networks via event-triggered control

Quantum neural networks (QNNs) are considered to be superior to classical ANNs in machine learning, memory capacity, information processing, and quantum system simulation. However, In a practical and complex system, the dynamic behavior of an open quantum system could not be accurately described by an integer-ordered Schrödinger equation. In this paper, the conformable time-fractional-order Schrödinger equation is proposed, and accordingly, the model of conformable fractional-order quantum cellular neural networks (CFOQCNNs) is established and derived from the as-proposed equation. The properties of the conformable fractional-order derivative are studied and several new inequalities regarding the power-exponential and fixed-time convergence of conformable fractional-order systems are obtained. To save the communication resource, we introduce the event-triggered mechanism to construct the controllers and then the power-exponential and fixed-time synchronizations of the master-slave systems derived from the above CFOQCNNs are studied. We also prove the absence of Zeno behaviors regarding the event-triggered strategies. According to the numerical simulation, the dynamic behavior of the CFOQCNNs is discussed and the dissipativity of the CFOQCNNs is briefly revealed. Then the synchronization behaviors of the master and slave CFOQCNNs under power-exponential and fixed-time event-triggered control are demonstrated, where the effectiveness of the event-triggered control strategy is verified. Control behaviors with different fractional orders are also presented. We also discuss the hybrid of power-exponential control and fixed-time control and illustrate the advantages of the hybrid strategy. In the last, we conclude our studies, analyze the drawbacks of this work, and briefly introduce our future research.

Input-to-state stability of impulsive switched systems under mode-dependent event-triggered impulsive control

This paper aims to investigate input-to-state stability (ISS) of nonlinear impulsive switched systems under mode-dependent event-triggered impulsive control (MDETIC) method. A novel mode-dependent event-triggered mechanism (MDETM) is devised, where triggering impulsive instants are determined by some predesigned event conditions. Different from existing MDETM, there are two types of impulsive behavior involved, including the impulsive behavior of system itself and event-triggered one. The novel MDETM not only reduces communication cost and energy consumption but also excludes “Zeno behavior.” Then, the ISS criteria of the closed-loop system are established based on MDETIC strategy, admissible edge-dependent average dwell time (AED-ADT), and admissible edge-dependent average impulsive interval (AED-AII) methods. Finally, two examples are given to verify the effectiveness of the main results.

Finite element analysis of the thermal and thermo-mechanical coupling problems in the dry friction clutches using functionally graded material

Abstract The friction clutch is an important machine part in the torque transmission system, where it is responsible for gently transmitting the power from the engine to the gearbox and damping the tensional vibration. At the beginning of the engagement between the clutch’s elements, a large amount of heat is released due to frictional sliding between the elements of the clutch system, generating very high temperatures. In this work, the two- and three-dimensional finite element models were developed from scratch to explore the clutch disk’s temperature and contact pressure behaviors using an alternative frictional material such as functionally graded material (FGM). The two assumptions for the thermal loads were considered: uniform wear and uniform pressure assumptions. The thermal–structural problem for the new frictional material was solved numerically and then presented as the temperature distributions and the contact pressure at any instant of sliding time. Also, a comparison was made between the clutch system behaviors when using FGM with different frictional materials. The results showed that the FGM has superior results to the other available frictional materials.

Relationship between learners’ L2 Motivational Self System and parental investment behavior in learners’ English learning

Students’ motivation and learning behavior are significantly impacted by parents’ participation and investment. It has been demonstrated that parental investment behavior could exert a direct effect on students’ L2 Motivational Self System (L2MSS) mediated by parental investment belief. Nevertheless, the relationship between components of parental investment behavior and students’ language learning motivation remains a topic necessitating further scholarly investigation. In response to this gap, we conducted a quantitative study involving a survey of 900 high school students to explore the relationship between students’ English learning motivation, as conceptualized by the L2 Motivational Self System and parental investment behavior based on a four-component model. The findings in this study indicated that high school students exhibited moderate levels of L2MSS and relatively low levels of parental investment behavior. Moreover, students’ L2MSS was found to have a significant positive correlation with the global parental investment behavior, with parental emotional investment behavior emerging as a positive predictor of high school students’ L2MSS. These results underscore the importance of parental provision of sufficient economic, relationship, knowledge, and emotional support in cultivating a nurturing and supportive familial context conducive to the development of students’ positive future selves.

Optimizing functionally graded tibial components for total knee replacements: a finite element analysis and multi-objective optimization study

The optimal design of complex engineering systems requires tracing precise mathematical modeling of the system’s behavior as a function of a set of design variables to achieve the desired design. Despite the success of current tibial components of knee implants, the limited lifespan remains the main concern of these complex systems. The mismatch between the properties of engineered biomaterials and those of biological materials leads to inadequate bonding with bone and the stress-shielding effect. Exploiting a functionally graded material for the stem of the tibial component of knee implants is attractive because the properties can be designed to vary in a certain pattern, meeting the desired requirements at different regions of the knee joint system. Therefore, in this study, a Ti6Al4V/Hydroxyapatite functionally graded stem with a laminated structure underwent simulation-based multi-objective design optimization for a tibial component of the knee implant. Employing finite element analysis and response surface methodology, three material design variables (stem’s central diameter, gradient factor, and number of layers) were optimized for seven objective functions related to stress-shielding and micro-motion (including Maximum stress on the cancellous bone, maximum and mean stresses on predefined paths, the standard deviation of mean stress on paths, maximum and mean micro-motions at the bone-implant interface and the standard deviation of mean micro-motion). Then, the optimized functionally graded stem with 6 layers, a central diameter of 5.59 mm, and a gradient factor of 1.31, was compared with a Ti6Al4V stem for various responses. In stress analysis, the optimal stem demonstrated a 1.92% improvement in cancellous bone stress while it had no considerable influence on the maximum, mean, and standard deviation of stresses on paths. In micro-motion analysis, the maximum, mean, and standard deviation of mean micro-motion at the interface were enhanced by 24.31%, 39.53%, and 19.77%, respectively.

A novel approach to runway overrun risk assessment using FRAM and flight data monitoring

Abstract Runway overruns (ROs) are the result of an aircraft rolling beyond the end of a runway, which is one of the accident’s types that most frequently occurs on aviation. The risk of an RO arises from the synergistic effect among its precursors, such as unstable approaches, long touchdowns and inadequate use of deceleration devices. To analyse this complex socio-technical system, the current work proposes a customised functional resonance analysis method, called FRAM-FDM, as traditional techniques of risk and safety assessment do not identify the interactions and couplings between the various functional aspects of the system itself, especially regarding human and organisational components. Basically, FRAM-FDM is the coupling of a traditional FRAM with flight data monitoring (FDM) techniques, used here to quantify the variabilities of the flight crew performance while executing the required activity (i.e. the landing). In this proposal, these variabilities (i.e. the FRAM functions aspects) are aggregated by the addend of a logistic regression, resulting in a model to evaluate the flare operations and the brake application profile effect on the remaining distance to the end of the runway, used as a reference to classify the landing as acceptable or not. The present application of the FRAM-FDM assesses the operational risk of a sample fleet in overrunning the runway during landing, highlighting the brake pedal application profile as the most relevant contributor. The model improves the knowledge about the system behaviour, being useful to direct flight crew training.