Stability Of System Research Articles

Credit risk and Tunisian bank stability in the Covid-19 wave

<p style="text-align:justify"><span style="font-size:16px"><span style="font-family:Times New Roman,Times,serif"><span dir="ltr" lang="EN-US"><span style="color:black">Banks are at the core of economic functioning in various countries and are the cause of their development in various fields. In a changing environment, they must deal with certain risks and maintain financial stability as the ultimate objective. The primary objective of this study is to examine the correlation between credit risk and bank stability within the Tunisian banking sector, with a specific focus on understanding the moderating impact of the COVID-19 pandemic. To achieve this, we employ several econometric techniques, including panel unit root and cointegration tests, panel Vector Error Correction Model (VECM), Fully Modified Ordinary Least Squares (FMOLS), and Dynamic Ordinary Least Squares (DOLS). Our empirical analysis relies on a panel dataset that encompasses a comprehensive sample of 8 Tunisian banks over 2000-2020. The results of our analysis unveil a significant negative relationship between credit risk and bank stability, indicating that higher levels of credit risk exert a detrimental effect on the overall stability of Tunisian banks. Furthermore, our study highlights that this adverse impact is further exacerbated during the COVID-19 pandemic, suggesting that the pandemic acts as a moderator. The findings of this study hold substantial implications for policymakers, regulators, and bank managers in Tunisia. They emphasize the critical importance of implementing robust risk management practices to mitigate credit risk and bolster bank stability. Additionally, the research underscores the need to consider the unique challenges introduced by external shocks, such as the COVID-19 pandemic, when assessing the overall stability of the banking system.</span></span></span></span></p>

Comparative Analysis of Single Stage and Dual Stage PV Based Generation System for Pollution Reduction in Asian Nations

The growing need for sustainable and clean energy solutions has elevated photovoltaic (PV) systems to the forefront of competitive options. In order to evaluate the performance and viability of single-stage and dual-stage single-phase PV voltage source inverter systems within the context of renewable energy, this study undertakes a thorough comparative analysis. MATLAB Simulink has been used to run the simulations, and the results produced show that the selected configurations are robust and closely match theoretical expectations. The study explores the subtle distinctions, benefits, and drawbacks that come with single- and dual-stage systems. By extensively evaluating the consequences on system stability, grid synchronisation, and power quality, useful insights emerge. The simplicity and efficiency of the single-stage system are demonstrated by the direct connectivity between the PV MPPT output and the inverter. In contrast, the dual-stage system addresses the issue of low PV output voltage by incorporating a boost converter with an MPPT algorithm, albeit at the expense of more parts and complexity. The research described here adds a great deal to the current discussion on PV system optimization. The study notably clarifies methods for improving dependability and efficiency in applications involving renewable energy. With the increasing worldwide trend towards sustainable energy, it is critical to comprehend the subtle dynamics of various PV setups. In addition to offering a comprehensive grasp of the complexities involved in single- and dual-stage single-phase PV voltage source inverter systems, this research paves the way for future developments in the planning and execution of effective renewable energy solutions especially for Asian nations that still rely on coal-based power plants. Increased contribution of solar based electricity generation will lead to a significant drop in pollution contributed by the ash and gases released by thermal power plants that employ fossil fuels. The ultimate goal of this study is to provide information to stakeholders in the renewable energy industry so that they may make more informed decisions and create PV systems that are both sustainable for the environment and efficient for the utility.

The role of conflict in the formation and maintenance of variant sex chromosome systems in mammals.

The XX/XY sex chromosome system is deeply conserved in therian mammals, as is the role of Sry in testis determination, giving the impression of stasis relative to other taxa. However, the long tradition of cytogenetic studies in mammals documents sex chromosome karyotypes that break this norm in myriad ways, ranging from fusions between sex chromosomes and autosomes to Y chromosome loss. Evolutionary conflict, in the form of sexual antagonism or meiotic drive, is the primary predicted driver of sex chromosome transformation and turnover. Yet conflict-based hypotheses are less considered in mammals, perhaps because of the perceived stability of the sex chromosome system. To address this gap, we catalogue and characterize all described sex chromosome variants in mammals, test for family-specific rates of accumulation, and consider the role of conflict between the sexes or within the genome in the evolution of these systems. We identify 152 species with sex chromosomes that differ from the ancestral state and find evidence for different rates of ancestral to derived transitions among families. Sex chromosome-autosome fusions account for 80% of all variants whereas documented sex chromosome fissions are limited to three species. We propose that meiotic drive and drive suppression provide viable explanations for the evolution of many of these variant systems, particularly those involving autosomal fusions. We highlight taxa particularly worthy of further study and provide experimental predictions for testing the role of conflict and its alternatives in generating observed sex chromosome diversity.

Stability Assessment of the High-Speed Flywheel with AMBs on a Rotating Platform

With the continuous improvement of the performance and capabilities of spacecrafts, the application of active magnetic bearings (AMBs) has become a major focus in current research. The AMBs-flywheel system is not only responsible for attitude control but also provides the required energy during shadow periods. In magnetically suspended single gimbal control moment gyroscope (SGCMG), self-excited vibration caused by high-speed rotor rotation significantly affects the stability of the AMB system. The research focus lies in magnetically supporting the flywheel at high speeds with low power consumption to explore gyroscopic mechanics at ultra-high speeds and assess the corresponding stability. This study presents an assessment of the stability performance of a high-speed flywheel equipped on a single gimbal with an angular momentum of 75 Nm. To achieve ultra-high-speed operation under low driving power, a high-precise dynamic balance was performed followed by a novel unbalance control strategy of a radial and axial automatic balancing algorithm to suppress effectively synchronous vibrations due to nutation and precession. Corresponding experiments including static stable suspension experiments as well as low-speed, high-speed, and series-based stability assessments were conducted. Stable suspension at any speed ranging from 0 to 30,000 r/min was successfully implemented. The stability performance of the high-speed flywheel on a rotating platform at different gimbal speeds was verified, with a maximum speed reaching 31,200 r/min. The entire output torque process within the range of 30,000 r/min was revealed.

High‐Resolution Printing‐Based Vertical Interconnects for Flexible Hybrid Electronics

AbstractFlexible hybrid electronics (FHE) is an emerging area that combines printed electronics and ultra‐thin chip (UTC) technology to deliver high performance needed in applications such as wearables, robotics, and internet‐of‐things etc. The integration of UTCs on flexible substrates and the access to devices on them requires high resolution interconnects, which is a challenging task as thermal and mechanical mismatches do not allow conventional bonding methods to work. To address this challenge, the resource‐efficient, area‐efficient, and low‐cost printing routes for obtaining vertical interconnection accesses (VIAs) are demonstrated here. It is demonstrated how high‐resolution printers (electrohydrodynamic and extrusion‐based direct‐ink writing printers) can be used for patterning of high‐resolution, freeform, vertical conductive structures. To access the transistors on UTCs, the VIAs, obtained using conventional photolithography and plasma etching steps, are filled with conductive silver nanoparticle‐based ink/paste using high‐resolution printers. Comprehensive studies are performed to compare and benchmark in terms of: i) the printing speed and throughput of the printers, ii) the electrical performance of vertically connected transistors in UTCs, and iii) the electrical performance stability of FHE system (interconnects and UTCs) under mechanical bending conditions. This in‐depth study shows the potential use of printing technologies for development of high‐density 3D integrated FHE systems.

Complexity analysis of technology spillover supply chain with dual business objectives

ABSTRACT Based on the existence of technology spillover effect of manufacturers, considering the manufacturer's commercial goals of profit and market share, a dynamic price game model of technology spillover supply chain with dual commercial goals is established. Based on game theory and nonlinear dynamics theory, the equilibrium point and local stability of the system are analyzed. In addition, the effects of price adjustment rate, balance coefficient of business objectives, and technology spillover on model complexity, the change of manufacturer price and profit were analyzed through numerical simulation. The results show that the price adjustment rate, the balance coefficient of business objectives, and the technology spillover have an impact on the stability and complexity of the manufacturer's price competition model. Rationally controlling the price adjustment rate, and enhancing technological spillovers are beneficial to the healthy development of manufacturers and the healthy competition among manufacturers, maintaining the stability of product market prices, and effectively avoiding market chaos. Moreover, when considering market share, manufacturers can expand the system stability domain.

Virtual Inertia Control for Power Electronics-Integrated Power Systems: Challenges and Prospects

In modern power systems, conventional energy production units are being replaced by clean and environmentally friendly renewable energy resources (RESs). Integrating RESs into power systems presents numerous challenges, notably the need for enhanced grid stability and reliability. RES-dominated power systems fail to meet sufficient demand due to insufficient inertia responses. To address this issue, various virtual inertia emulation techniques are proposed to bolster power system stability amidst the increased integration of renewable energy sources into the grid. This review article explores state-of-the-art virtual inertia support strategies tailored to accommodate the increased penetration of RESs. Beginning with an overview of this study, it explores the existing virtual inertia techniques and investigates the various methodologies, including control algorithms, parameters, configurations, key contributions, sources, controllers, and simulation platforms. The promising virtual inertia control strategies are categorised based on the techniques used in their control algorithms and their applications. Furthermore, this review explains evolving research trends and identifies promising avenues for future investigations. Emphasis is placed on addressing key challenges such as dynamic response characteristics, scalability, and interoperability with conventional grid assets. The initial database search reveals 1529 publications. Finally, 106 articles were selected for this study, adding 6 articles manually for the review analysis. By synthesising current knowledge and outlining prospective research directions, this review aims to facilitate the current state of research paths concerning virtual inertia control techniques, along with the categorisation and analysis of these approaches, and showcases a comprehensive understanding of the research domain, which is essential for the sustainable integration of renewable energy into modern power systems via power electronic interface.

A novel approach to the FPIBSC strategy for an electric power steering system

The electric power steering system is used to improve comfort and steering feel for the user. In this article, we propose to use an integrated nonlinear control strategy for the electric steering system, which is described based on a complicated dynamic model. This work provides two new contributions. First, this control algorithm combines backstepping and proportional–integral (PI) techniques with parameters adjusted by a fuzzy algorithm, so it is called Fuzzy proportional–integral backstepping control (FPIBSC). The output of the PI algorithm is the input of the backstepping technique, while system stability is evaluated based on the Lyapunov function with virtual control variables. Second, road reaction torque is calculated based on a spatial dynamic model, which considers the influence of many other factors. Numerical simulation methods are used to evaluate the performance of the system. According to research findings, the value of the steering motor angle (controlled object) continuously tracks the desired value with negligible error. Under some specific conditions, the error between signals can be reduced to zero. In addition, other outputs that are obtained from the FPIBSC algorithm also tend to follow the reference signal with high accuracy. The phase difference phenomenon only occurs when using the conventional backstepping algorithm instead of FPIBSC. The assisted torque increases as speed decreases or the driver torque increases. In general, the system’s stability is always guaranteed under many different simulation conditions.

Models of quality costs by A. Feigenbaum, J. Juran, F. Crosby in the concept of the development of quality economics

Aim. Consider the specifics and features of quality cost models by A. Feigenbaum, J. Juran, F. Crosby in the context of increasing the efficiency of cost management.Objectives. Describe Joseph M. Juran's model (Juran's Spiral); classify quality costs by J. Juran — A. Feigenbaum; describe the classification of costs by F. Crosby.Methods. This work uses general scientific research methods: deduction, induction, generalization, comparative analysis, synthesis (unification), study and theoretical analysis.Results. In the modern economy, product quality plays a critical role, influencing the competitiveness and stability of the country's economic system, which makes quality management not just a formality, but a strategic necessity. Active implementation and development of quality systems is considered by enterprises as a means to improve reputation, increase market share and strengthen customer loyalty, and such systems help reduce costs by preventing defects and optimizing processes.Conclusions. An analysis of quality cost models was carried out as one of the key methods in increasing the economic efficiency of the organization. In modern quality management practice, special attention is paid not only to the identification and assessment of quality costs, but also to their role in the process of making managerial and technical decisions. This is especially true when planning the production activities of an enterprise. Quality cost analysis is becoming an important tool to help management formulate economically sound decisions.

Fuzzy sliding mode control with adaptive exponential reaching law for inverters in the photovoltaic microgrid

Photovoltaic inverters are widely utilized in microgrid systems working as the key equipment for converting solar energy into usable electricity. This paper presents a fuzzy sliding mode control (FSMC) method for the photovoltaic inverter in a microgrid. The inverter module uses voltage control to achieve stable AC output voltage. Moreover, to deal with system uncertainty and non-linearity in the photovoltaic inverter, a fuzzy controller was designed to realize real-time adaptation of the gains of the constant term and the reaching term in the sliding mode control law, which serves as a compensating controller for traditional sliding mode control. The gains of the exponential reaching law can be adjusted according to the system state instead of fixed gains, which can effectively reduce the chattering phenomenon and improve the robustness of the photovoltaic microgrid. Finally, the Lyapunov stability theory was used to ensure the stability of the entire control system, achieving a high-performance independent power supply for loads in a microgrid. Simulation results show that the designed control system is more robust to load disturbances and has superior dynamic performance.

Reinforcement learning-based secure synchronization for two-time-scale complex dynamical networks with malicious attacks

This paper studies the secure synchronization problem for two-time-scale complex dynamical networks with unknown dynamics information and malicious attacks. The challenge is that under complex dynamic networks with unknown dynamic information, all system matrices are unknown. To ameliorate this conundrum, we design a reinforcement learning algorithm, conjoined with a full-order processing of singularly perturbed parameters, with the express objective of securing the stability of the synchronization error system within a context devoid of adversarial intrusions. Second, in order to reduce the impact of malicious attacks, a switching function is developed based on feedback gain. Besides, it is proved that the proposed distributed controllers can still guarantee the convergence of the synchronization error system under malicious attacks. Finally, two numerical examples are given to illustrate the applicability and effectiveness of the proposed algorithm.

Acoustic Characterization of Integrated Circuits During Operation

Abstract Power electronics are widely serving as core components of propulsion systems in electric vertical takeoff and landing (VTOL) aircraft. Nevertheless, affected by the Paschen effect, the breakdown voltage of these electronics during flight is significantly lower than that on the ground, which could deteriorate system stability, or even cause aircraft faults or crashes, increasing safety risks for the public. As such, condition monitoring of power electronics has become critical for the safe operation of eVTOL. To achieve non-intrusive monitoring, acoustic emissions (AE) sensors have gained traction with their prominent resistance to electromagnetic interference and high temperatures. However, existing studies yield conflicting results regarding whether an increase in loading voltage impacts the internal mechanical stress of electronics. To address this issue, we present this work to probe the existence and the pattern of a relationship between load voltage and stress wave, since the change of mechanical stress could generate acoustic waves that can be acquired by AE sensors. In this study, an AE sensor was applied onto an oscillator placed upon an epoxy substrate to characterize the acoustic waves emitted from the device under various input loads. In the experiment, we observed a unique AE signal pattern characterized by two distinct components that consistently intersect at a specific frequency. The time required to establish such intersections progressively lengthens as the load voltage increases. Through time-domain and frequency-domain analyses of the unique AE signals under different load voltages, it was discovered that certain features of the unique AE signals have an approximately linear relationship with the load voltage.

The effects of various distributed generating types on the smart grid have been demonstrated using transient stability study and steady state voltage analysis

Renewable energy and smart grid technologies are crucial in the modern era due to climate change and the need for secure energy sources. To address concerns regarding energy security, efficiency and aging energy infrastructure, it is necessary to move away from centralized power generation and embrace decentralized distributed generation and smart grid technologies. This transformation will meet the increasing demand for electricity, improve the quality of service, and reduce pollution. However, there are technical challenges to overcome, such as maintaining system stability when incorporating distributed generation into the smart grid. This research focuses on evaluating the impact of distributed generation on the smart grid, especially the system stability after integrating distributed generation. System stability was evaluated and confirmed using Dig-SILENT Power Factory V 13.2 software, which simulates connection issues and failures.

Active suspension hierarchical control with parameter uncertainty and external disturbance of electro-hydraulic actuators

In order to improve the ride comfort and handling stability of the electro-hydraulic active suspension system, a hierarchical control strategy is proposed. For the active suspension system with body mass uncertainty and safety constraints, an enhanced constraint adaptive backstepping controller is designed to generate the target force of body vertical motion. When dealing with constraints, nonlinear filters are introduced, backstepping technology and quadratic Lyapunov function are used to combine the control target and domain constraints, and the vertical displacement of the body and the suspension deflection control index are synthesized into a single controlled variable, so that the control variable converging to zero meets the suspension dynamic displacement limit. The ride comfort and safety of the active suspension system are improved. Secondly, stability analysis is conducted on the zero dynamic error system to ensure that all safety performance indicators are bounded. The effects of external disturbances, parameter uncertainties and modelling errors on the force tracking accuracy of asymmetric cylinder electrohydraulic systems are addressed. A backstepping dynamic surface control method based on a nonlinear perturbation observer is proposed, which estimates the composite perturbation terms such as modelling error and external perturbation, and uses the estimated value of the nonlinear observer to design a feedforward compensating control term to offset the effect of the composite perturbation on the system performance. In addition, the dynamic surface control method is used to calculate the derivative of the target force input, which avoids the derivative explosion phenomenon and reduces the computational complexity of the system. Simulation test results show that this method reduces the computational complexity of the system and improves the control performance. And under random and bumpy road conditions, the root-mean-square value of sprung mass acceleration performance index is reduced by 48.354 % and 72.677 % compared with passive suspension, which improves the ride comfort of the vehicle.

Combining finite-time control and prescribed tracking performance for uncertain PMSM driven steer-by-wire system with unknown disturbance

To solve the uncertainties in permanent magnet synchronous motor (PMSM) driven steer-by-wire (SbW) system, a prescribed-performance-control (PPC) based finite-time fuzzy controller is proposed. Specifically, the dynamics of SbW system driven by PMSM is analyzed, and combine PPC technology to transform the tracking error coordinates. Then, the velocity signal is obtained from the sigmoid function-based tracking differentiator by using the position signal. To solve the problem of mismatched disturbance, fuzzy logic system (FLS) are used as a universal approximator to estimate the lumped nonlinear friction and other unknown functions, the boundary of lumped disturbance is estimated by the designed adaptive updating law. By fusing the designed virtual controller and the intermediate control law, the controller needs no precise parameters of system, under which the effect of uncertainty of control gain can be compensated completely. Finally, rigorous theoretical analysis based on the Lyapunov stability theory is provided to demonstrate the finite-time stability of the closed-loop system under consideration. Simulation and experiment results are presented to show the effectiveness of the developed control approach, and some comparisons are given to show the rapid and accurate position tracking control performance.

Use of analytical hierarchy process for selecting and prioritizing islanding detection methods in power grids

One of the problems that are associated to power systems is islanding condition, which must be rapidly and properly detected to prevent any negative consequences on the system's protection, stability, and security. This paper offers a thorough overview of several islanding detection strategies, which are divided into two categories: classic approaches, including local and remote approaches, and modern techniques, including techniques based on signal processing and computational intelligence. Additionally, each approach is compared and assessed based on several factors, including implementation costs, non-detected zones, declining power quality, and response times using the analytical hierarchy process (AHP). The multi-criteria decision-making analysis shows that the overall weight of passive methods (24.7%), active methods (7.8%), hybrid methods (5.6%), remote methods (14.5%), signal processing-based methods (26.6%), and computational intelligent-based methods (20.8%) based on the comparison of all criteria together. Thus, it can be seen from the total weight that hybrid approaches are the least suitable to be chosen, while signal processing-based methods are the most appropriate islanding detection method to be selected and implemented in power system with respect to the aforementioned factors. Using Expert Choice software, the proposed hierarchy model is studied and examined.

Speed control of PM brushless DC motor using sensorless hybrid controller

In most industrial processes, rising productivity necessitates increased demand on electrical motors in order to minimize costs and improve drive system efficiency. The sensorless technique is preferred. Brushless DC (BLDC) motors compete with a wide range of different motor types in the motion control industry. The nonlinearity of BLDC motor characteristics is challenging to manage with a traditional proportional integral derivative (PID) controller. The PID controller's fuzzy logic allowed it to tune itself while operating online. Hybrid approaches outperform stand-alone algorithms because they can overcome their weaknesses without losing their advantage. The purpose of this study is to present a fuzzy PI+D controller that is simulated over a wide range of reference speeds, loads, and parameter variations. This paper presents a model of a sensorless BLDC motor with a speed controller. The responses of the rotor speed, electromagnetic torque, stator back electromotive force (EMF), and stator currents are effectively monitored. The findings from the simulation indicate that the hybrid controller presented in this study exhibits resilience to rapid load torque and parameter fluctuation. Furthermore, it demonstrates superior dynamic performance and exhibits notable enhancements in speed tracking and system stability. The performance of the system is enhanced through the utilization of the proposed hybrid intelligent controller.

Exploring the Effectiveness of Nurses' Usage of a Wound-Photography System.

As a result of rapid advancements in health information technology, uploading health-related information and records onto an electronic health record system has become a common practice. Photographs of patients' wounds have been uploaded electronically, but widespread acceptance by nurses has been prevented owing to issues such as file size and equipment. This research explores the attitude and satisfaction toward using an electronic health record for uploading wound photos. Through the integration of the Technology Acceptance Model, Information System Success Model, and other study results, this research aims to explore the impact of the following variables: system quality, information quality, perceived usefulness, perceived ease of use, user attitude, user satisfaction, and net benefits. We also tested nurses' understanding regarding the process of taking photographs and explored the photograph quality and the photography uploading rates. The results revealed that users were satisfied with the wound-photography system, but some believed that the system stability, processing time, and image resolution should be improved. In addition, more than 80% of the nurses correctly answered photo-taking questions, the study photos reached 70% of the quality standards, and the average uploading rate was 74%. The results could serve as guidelines for system design in the future.

Distributed Optimal Attitude Synchronization Control of Multiple QUAVs via Adaptive Dynamic Programming.

This article proposes a distributed optimal attitude synchronization control strategy for multiple quadrotor unmanned aerial vehicles (QUAVs) through the adaptive dynamic programming (ADP) algorithm. The attitude systems of QUAVs are modeled as affine nominal systems subject to parameter uncertainties and external disturbances. Considering attitude constraints in complex flying environments, a one-to-one mapping technique is utilized to transform the constrained systems into equivalent unconstrained systems. An improved nonquadratic cost function is constructed for each QUAV, which reflects the requirements of robustness and the constraints of control input simultaneously. To overcome the issue that the persistence of excitation (PE) condition is difficult to meet, a novel tuning rule of critic neural network (NN) weights is developed via the concurrent learning (CL) technique. In terms of the Lyapunov stability theorem, the stability of the closed-loop system and the convergence of critic NN weights are proved. Finally, simulation results on multiple QUAVs show the effectiveness of the proposed control strategy.

Research on Power Angle Characteristics of One-Machine Infinite-Bus Power Systems of Mixed Gauss and Poisson Stochastic Excitation

Background: A high percentage of renewable energy and a high percentage of power electronic devices are connected to the power system, which leads to the diversification and complexity of stochastic excitation, and the traditional single-excitation stochastic model is no longer applicable. Objective: The study aimed to solve the problem that the high proportion of renewable energy and the high proportion of power electronic equipment are connected to the power system, which leads to the diversification and complexity of stochastic excitation and makes the traditional stochastic model of single excitation no longer applicable. Methods: Firstly, stochastic differential equations for power systems have been modelled with mixed Gaussian white noise and Poisson white noise excitation. Secondly, the Milstein-Euler predictor-corrector method has been developed to solve the stochastic differential equation model of the power system. Finally, the influence of Gauss white noise and Poisson white noise on the power system stability under different excitation intensities has been analyzed. The rationality and correctness of the model have been verified by the simulation of a one-machine infinitebus (OMIB) system. Results: The stochastic differential equation model of a power system with Gauss white noise and Poisson white noise excitation has been established and its angle stability has been analyzed. Increasing the Gaussian white noise and Poisson white noise excitation intensity can lead to an increase in the fluctuation of the power angle curve, as well as an increase in the standard deviation and expected value of the power angle mean curve, which may decrease the stability of the power system. Conclusion: This study provides a reference for stochastic power systems modeling and efficient simulation, and has important application value for power system stability assessment and safety evaluation as well as related patent applications.