Stability Of System Research Articles

Financial security of Arab countries: analysis of some aspects

Issues of ensuring the financial security of the country have always played an important role not only in times of crises but also in conditions of relatively stable functioning of the economy and financial system. Financial security, along with food and energy security, is part of national economic security and plays a leading role at the macro and micro economic levels. It is especially necessary to note the rapid development of digitalization processes which directly affect the stability of the financial system and its security. The financial systems of Arab countries, being included in the global financial system, are directly or indirectly exposed to almost all possible risks that arise and evolve in the global financial markets and in the global economy. Ensuring financial security in the countries of the Middle East and North Africa region is one of the top priorities for the leadership of these countries. These tasks boil down to, among other things, reducing sovereign risk ensuring unity in regulatory approaches to ensuring cross–border transactions, transparency in trade finance transactions taking into account the imposition of sanctions against some countries, and ensuring cybersecurity in the context of digitalization of financial processes remains an important aspect. This article examined and analyzed some of the aspects of the financial security of Arab countries including taking into account the inclusion of innovative processes in world practice, and there are also presented the problems of the countries of the Middle East and North Africa region which contribute to an increase in the likelihood of imbalance in processes to ensure the financial security of the region generally.

Nonlinear disturbance observer-based geometric attitude fault-tolerant control of quadrotors

This paper is concerned with nonlinear disturbance observer (DO)-based geometric attitude fault-tolerant control (FTC) problem of quadrotor unmanned aerial vehicles (UAVs) subject to system uncertainties, exogenous disturbances, and actuator faults. A disturbance observer-based control (DOBC) framework is devised to tackle the difficulties caused by system uncertainties and external disturbances. The FTC is proposed to cope with the occurrence of actuator faults which can be modelled as a constant loss of effectiveness. The proposed design scheme can provide an effective way to analyse the stability of the closed-loop system, which can ensure the asymptotical convergence of the error. The other method considers actuator failures as part of the lumped disturbance, and the attitude tracking problem of quadrotors concerning the lumped disturbance is solved by the DO-based control method, which can ensure the exponential convergence of the error. The numerical simulations are performed to illustrate the effectiveness of the design techniques.

Financial security of Arab countries: analysis of some aspects

Issues of ensuring the financial security of the country have always played an important role not only in times of crises but also in conditions of relatively stable functioning of the economy and financial system. Financial security, along with food and energy security, is part of national economic security and plays a leading role at the macro and micro economic levels. It is especially necessary to note the rapid development of digitalization processes which directly affect the stability of the financial system and its security. The financial systems of Arab countries, being included in the global financial system, are directly or indirectly exposed to almost all possible risks that arise and evolve in the global financial markets and in the global economy. Ensuring financial security in the countries of the Middle East and North Africa region is one of the top priorities for the leadership of these countries. These tasks boil down to, among other things, reducing sovereign risk ensuring unity in regulatory approaches to ensuring cross–border transactions, transparency in trade finance transactions taking into account the imposition of sanctions against some countries, and ensuring cybersecurity in the context of digitalization of financial processes remains an important aspect. This article examined and analyzed some of the aspects of the financial security of Arab countries including taking into account the inclusion of innovative processes in world practice, and there are also presented the problems of the countries of the Middle East and North Africa region which contribute to an increase in the likelihood of imbalance in processes to ensure the financial security of the region generally.

High‐rate Dissolution Mechanism of Ti‐48Al‐2Cr‐2Nb Alloy in Electrochemical Machining from a Nonlinear Dynamic PeWen Yuan Lirspective

The high‐rate dissolution process of Ti‐48Al‐2Cr‐2Nb alloy in electrochemical machining exhibits strong nonlinear dynamic characteristics, but the quantitative relationship between these nonlinear characteristics and surface topography, as well as the electro‐dissolution mechanism, is unknown. Therefore, the fractal and recursive features of dissolution behavior was investigated, and the dissolved surface topography was quantitatively characterized. Additionally, an electro‐dissolution mechanism model in electrochemical machining process was presented. Applying a moderate extraction potential of 8 V instead of 11 V can enhance the stability of the electrochemical system, resulting in a smoother and uniform surface. At 11 V, the saturation correlation dimension, surface roughness, and integral area of lacunarity initially decrease before increasing with higher electrolytic pressure, while laminarity (𝐿𝐴𝑀) and determinism (𝐷𝐸𝑇) show an initial increase followed by a decrease. These five characteristic parameters reach their optimal values at an electrolyte pressure of 0.4 MPa, indicating that achieving a stable and deterministic electrochemical system is crucial for obtaining a uniform smooth surface. These nonlinear dynamic characteristic parameters can be considered as in‐situ monitoring parameters for surface quality in ECM. The anodic dissolution process comprises three stages: initial passive film dissolution and breakdown, rapid dissolving with surface coarsening, and stable dissolving with polishing.This article is protected by copyright. All rights reserved.

Monetary Policy Challenges and Strategies in the Globalization: An Analysis of the Federal Reserve's Approach to the Trilemma

This study explores the Federal Reserve's (Fed's) approach to the financial trilemma in the era of globalization, emphasizing the trade-offs between monetary policy autonomy, exchange rate flexibility, and open capital markets. It delves into the challenges posed by increased global financial integration and the effectiveness of traditional and innovative monetary tools. The paper advocates for the adoption of a macroprudential policy framework to enhance financial system stability without compromising policy objectives. The findings highlight the Fed's strategic use of macroprudential measures alongside conventional tools to navigate the trilemma, illustrating the importance of flexibility and innovation in central banking practices amidst global financial complexities.

Automatic Power Factor Controller

Automatic Power Factor Controllers (APFCs) play a crucial role in modern electrical systems by ensuring efficient electrical power and improving power quality. This paper presents a comprehensive overview of the Design, implementation, and performance analysis of an APFC system. The proposed APFC system employs advanced control techniques to regulate the power factor of the electrical load, thereby minimizing reactive power consumption and optimizing overall system efficiency. The design process encompasses the selection of suitable power electronics converters, control algorithms, and sensing techniques tailored to the requirements of an application. The results demonstrate significant improvements in power quality, energy utilization, and system stability, thereby highlighting the practical relevance and applicability of the developed APFC technology.

Effect of Plate Configuration in the Primary Stability of Osteotomies and Biological Reconstructions of Femoral Defects: Finite-Element Study

Background/objective: Osteosynthesis is an alternative treatment for stabilizing femur-bone traumas. The initial stability of the fixation systems is one of the biomechanical parameters affecting implant failure and bone union, especially in surgeries of intercalary reconstructions after the removal of bone tumors. This study aimed to investigate the initial biomechanical effect of using one or two osteosynthesis plate configurations for femoral fixation and the effect of fastening the allograft to the osteosynthesis plate in the case of femoral allograft reconstructions. Methods: Three finite-element models of a femur with three different fixation conditions for a transverse osteotomy in the middle of the diaphysis, i.e., using one and two osteosynthesis plates and an intercalary allograft, were constructed. An eight-hole compression plate and a six-hole second plate were used to simulate osteosynthesis plates. The plate screws were tightened previously to the loading, and the tightening sequences simulate the bolt-tightening procedure in a surgical environment. The models were imported into the ADINA System for nonlinear analysis, using compression loads applied over the femur head. Results: Models with the dual fixation systems had the most outstanding compression stiffness. The femur head movement in the dual plate system was 24.8% smaller than in the single plate system. A statistical analysis of a region of interest (VOI) placed in the femur diaphysis showed that the biomechanical effect of using the dual plate system is smaller in the osteotomy region than at the femur head, e.g., a displacement average decrease of only 5% between the two systems, while the maximum value decreases by 26.8%. The allograft fixation to the second osteosynthesis plate leads to an improvement in the system stability. Conclusions: The results presented in this work show that including the bolt analysis in the femoral diaphysis osteotomy fixation will allow for capturing the nonlinear behavior of the osteotomy region more realistically. The stability of the intercalary reconstruction of the femoral diaphysis was higher when the allograft was fastened to the second osteosynthesis plate.

An improved adaptive position tracking strategy for automatic shift actuator with uncertain parameters

Realizing precise and fast position control of the gear is a challenging issue because of its nonlinearity, parameter uncertainty and external disturbance. Therefore, this paper researches the clutch position control considering the influence because of the factor on the system performance. By virtue of the traditional adaptive control method, an improved strategy based on finite time theory is proposed to further improve the convergence rate as well as the position tracking precision. First, a model of electromechanical clutch actuator system is established by theoretical analysis. Then, an enhanced adaptive controller is designed using finite time idea by introducing power function in the virtual control. And parameter update rate is adopted in the control action. Next, the stability of the control system is proved theoretically. Finally, Matlab simulations and experimental bench test are carried out to exhibit the effectiveness of the presented method. The results show that the satisfactory performance has been achieved with accurate position tracking and fast convergence speed.

Enhanced anaerobic digestion of landfill leachate based on a novel redox mediator: Synergistic mechanism of enhancing extracellular electron transfer

The presence of recalcitrant compounds and toxic substances in landfill leachate results in low anaerobic digestion (AD) efficiency and poor methane production performance. Strengthening the extracellular electron transfer of microorganisms represents an effective approach to promote the AD of landfill leachate. In this study, a novel redox mediator (FeNC-RM) was synthesized through the combination of metal and non-metal doping, intensifying the stable operation of the landfill leachate AD system. Through characterization techniques including X-ray photoelectron spectroscopy and X-ray diffraction, it was observed that FeNC-RM possesses a larger specific surface area, abundant functional groups, and exceptional electrochemical performance. By adding FeNC-RM, the stability and efficiency of the medium-temperature AD system in the treatment of landfill leachate were improved: Obtained a high removal of chemical oxygen demand which was increased by 30 % compared to the control group and enhanced the specific methanogenic activity by 57.5 % compared to the control group. The electron transport system (ETS) activities of the experimental groups with the addition of RMs were all significantly higher than those of the control group, and the ETS activity of the sludge from the FeNC-RM group was 79.6 % higher than that of the control group. Through a comprehensive analysis of the underlying mechanism, it was determined that three aspects synergistically facilitated electron transfer: FeNC-RM, endowed with electrochemical capabilities, assumed a pivotal role in establishing a conduit for electron transport, thus promoting the synthesis of extracellular humic substances and augmenting electron transport activity. Furthermore, the microbial community was optimized by FeNC-RM, thereby fostering a co-nutritional mechanism between hydrolytic acidification bacteria and methanogens, establishing a direct interspecific electron transport pathway. In this study, an “endogenous + exogenous” electron transport model based on the enhanced extracellular electron transport pathway facilitated by FeNC-RM was proposed. This study offered valuable contributions to the advancement of anaerobic treatment technology for landfill leachate.

Study of cabbage antioxidant system response on early infection stage of Xanthomonas campestris pv. campestris

Black rot, caused by Xanthomonas campestris pv. campestris (Xcc) significantly affects the production of cabbage and other cruciferous vegetables. Plant antioxidant system plays an important role in pathogen invasion and is one of the main mechanisms underlying resistance to biological stress. Therefore, it is important to study the resistance mechanisms of the cabbage antioxidant system during the early stages of Xcc. In this study, 108 CFU/mL (OD600 = 0.1) Xcc race1 was inoculated on “zhonggan 11” cabbage using the spraying method. The effects of Xcc infection on the antioxidant system before and after Xcc inoculation (0, 1, 3, and 5 d) were studied by physiological indexes determination, transcriptome and metabolome analyses. We concluded that early Xcc infection can destroy the balance of the active oxygen metabolism system, increase the generation of free radicals, and decrease the scavenging ability, leading to membrane lipid peroxidation, resulting in the destruction of the biofilm system and metabolic disorders. In response to Xcc infection, cabbage clears a series of reactive oxygen species (ROS) produced during Xcc infection via various antioxidant pathways. The activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) increased after Xcc infection, and the ROS scavenging rate increased. The biosynthesis of non-obligate antioxidants, such as ascorbic acid (AsA) and glutathione (GSH), is also enhanced after Xcc infection. Moreover, the alkaloid and vitamin contents increased significantly after Xcc infection. We concluded that cabbage could resist Xcc invasion by maintaining the stability of the cell membrane system and improving the biosynthesis of antioxidant substances and enzymes after infection by Xcc. Our results provide theoretical basis and data support for subsequent research on the cruciferous vegetables resistance mechanism and breeding to Xcc.

Robust vibration control for a flexible cable gantry crane system subject to boundary disturbance

This paper addresses the robust vibration control problem for a gantry crane system which is governed by a partial differential equation. The control objectives are to transport the cargo from the initial position to the desired position and suppress the vibration of the cable and payload in the presence of boundary disturbance. To achieve the objectives, a sliding-mode controller is proposed by repressing the boundary disturbance. By using the operator semigroup theory, the well-posedness of the closed-loop system is guaranteed. The asymptotic stability of the closed-loop system is proven by using the extended LaSalle’s invariance principle. Both numerical simulations and experiments are provided to illustrate the effectiveness of the proposed boundary control method.

Light energy utilization and microbial catalysis for enhanced biohydrogen: Ternary coupling system of triethanolamine-mediated Fe@C-Rhodobacter sphaeroides

This study investigated the mediating effect of Triethanolamine on Fe@C-Rhodobacter sphaeroides hybrid photosynthetic system to achieve efficient biohydrogen production. The biocompatible Fe@C generates excited electrons upon exposure to light, releasing ferrum for nitrogenase synthesis, and regulating the pH of the fermentation environment. Triethanolamine was introduced to optimize the electron transfer chain, thereby improving system stability, prolonging electron lifespan, and facilitating ferrum corrosion. This, in turn, stimulated the lactic acid synthetic metabolic pathway of Rhodobacter sphaeroides, resulting in increased reducing power in the biohybrid system. The ternary coupling system was analyzed through the regulation of concentration, initial pH, and light intensity. The system achieved the highest total H2 production of 5410.9 mL/L, 1.29 times higher than the control (2360.5 mL/L). This research provides a valuable strategy for constructing ferrum-carbon-based composite-cellular biohybrid systems for photo-fermentation H2 production.

Research on Maximum Power Control of Direct-Drive Wave Power Generation Device Based on BP Neural Network PID Method

Ocean wave energy is a new type of clean energy. To improve the power generation and wave energy conversion efficiency of the direct-drive wave power generation system, by addressing the issue of large output errors and poor system stability commonly associated with the currently used PID (proportional, integral, and derivative) control methods, this paper proposes a maximum power control method based on BP (back propagation) neural network PID control. Combined with Kalman filtering, this method not only achieves maximum power tracking but also reduces output ripple and tracking error, thereby enhancing the system’s control quality. This study uses a permanent magnet linear generator as the power generation device, establishes a system dynamics model, and predicts the main frequency of irregular waves through the Fast Fourier Transform method. It designs a desired current tracking curve that meets the maximum power strategy. On this basis, a comparative analysis of the control accuracy and stability of three control methods is conducted. The simulation results show that the BP neural network PID control method improves power generation and exhibits better accuracy and stability.

Optimized fuzzy type 1 Mamdani controller to enhance transient stability of AC-power system

Optimized fuzzy type 1 Mamdani controller to enhance transient stability of AC-power system

First Principles Evaluation of Phase Stability in the In-Sn Binary System

AbstractThe In-Sn binary alloy system exhibits several unusual features that challenge crystallographic and thermodynamic expectations. We combine first principles total energy calculation with simple thermodynamic modeling to address two key points. First, we evaluate energies along the Bain path to interpret the discontinuous transition between the phases α-In (Pearson type tI2) and β-In3Sn (also Pearson type tI2) that are identical in symmetry. Second, we demonstrate that the solid solution phases β-In3Sn and γ-InSn4 (Pearson type hP1) exist at high temperatures only, and they exhibit eutectoid decompositions at low temperatures.

Optimal Frequency determination for Wind-Hydro hybrid unit using Telegrapher’s Method for Low frequency transmission lines

This study addresses the optimal load flow problem for low-frequency transmission lines connected to wind farms and pumped storage Hydropower (PSH). The losses in LF-HVac system and the voltage stability index heavily dependent on the operating frequency. Therefore, an optimal load flow (OLF) method must be incorporated to determine the proper solutions for these systems. This system analyses the load flow solutions in which newton Raphson with STATCOM requires large vector calculations with variables. So, to reduce the mathematical calculation a two-port equivalent model for transmission lines based on solutions to Telegrapher’s method has been proposed. The proposed OLF method is tested with other algorithms and implemented in IEEE 39-BUS system. The results obtained indicate that the LF method with the proposed metaheuristic algorithm gives optimal frequency for low-frequency HVac systems while maintaining the stability of system.

Outlier-resistant non-fragile observer-based fuzzy boundary control for interconnected nonlinear PDE systems

This paper investigates an observer-based boundary controller design for interconnected nonlinear partial differential equation (PDE) systems. First, the Takagi–Sugeno (T–S) fuzzy model is adopted to accurately describe the target systems. Then, boundary measurements are employed to reduce the number of sensors. Next, considering the phenomenon of abnormal interference that may lead to measurement outliers and observer parameters’ uncertainties, an outlier-resistant non-fragile observer expressed by a saturation function is designed to guarantee the desired control objectives. Moreover, the boundary control approach is employed to trade-off the cost of system design and system performance. Furthermore, utilizing the membership function-dependent Lyapunov functions and free-weight matrixes, sufficient conditions ensuring the closed-loop systems’ exponential stability are obtained while decreasing the conservativeness of the system stability analysis. Finally, the proposed method’s feasibility and effectiveness are validated by an example.

Experimental Study of Vibration Isolation Using Electromagnetic Damping

This study presents an experimental investigation focused on the reduction of vibrations using electromagnetic damping techniques. The objective is to explore the effectiveness of electromagnetic damping in mitigating undesirable vibrations and enhancing system stability. A single-degree vertically constrained spring-mass system, two pairs of electromagnets, Lab VIEW software, an accelerometer, DAQ card were used for the experimentation. SWG 17 and SWG19 coil electromagnets were used in different conditions of energization to evaluate the effectiveness of the electromagnetic damping system. The parameters such as excitation frequency, vibration amplitude, and electromagnetic damping force are systematically varied and their effects on vibration isolation are analysed. The results demonstrate that the electromagnetic damping system effectively isolates base induced vibrations across a range of frequencies and amplitudes. The experimental data reveal  that at lower frequencies, upto 6Hz the amplitude of RMS acceleration was same as that of the system without energizing the electromagnet and at higher frequencies, above 10 Hz, all 2V,4V and 6V of energized electromagnets in the SDVC system  showed negligible  variation in the  RMS amplitude of acceleration. A substantial isolation of top plate was observed at higher frequencies of base excitation.
  
  

Effects of throughflow and gravity modulation on triple-diffusive convection in a sparsely packed porous medium

This article investigates the impact of four different gravity modulations on triple-diffusive convection in a porous layer with throughflow. The study conducts a weakly nonlinear stability analysis. Additionally, cubic Ginzburg–Landau equation is derived to observe the effects of throughflow, gravity modulation, and concentration. The solution of Ginzburg–Landau equation is used to calculate heat transfer and mass transport in terms of the Nusselt and Sherwood numbers, respectively. Furthermore, the mean Nusselt and Sherwood numbers are calculated. The study investigates the influence of Lewis numbers, solutal Rayleigh numbers, and Peclet numbers on the stability and instability of the system graphically for the four types of gravity modulations. The results show that the Sawtooth modulation destabilizes the system, while the square waveform modulation stabilizes it. The mean Nusselt number decreases with both the first Lewis number Le 1 and the second Lewis number Le 2, as well as the mean Sherwood number, which decreases with the first solutal Rayleigh number Rs 1 and the second solutal Rayleigh number Rs 2. This indicates system stability. Furthermore, it is noted that the heat and mass transport for triangular modulation fall between those of sawtooth modulation and square modulation.

Mittag‐Leffler stability of neural networks with Caputo–Hadamard fractional derivative

In this paper, a Hopfield‐type neural network system with Caputo–Hadamard fractional derivative is discussed. The importance of the existence of the equilibrium point in the analysis of artificial neural networks is well known. Another important investigation is the stability properties. So, the stability of a neural network system is dealt with in the present paper. First, a theorem that asserts the existence and uniqueness of the equilibrium point of the system is proven. Later, the conditions that ensure the Mittag‐Leffler stability of the equilibrium point is obtained by using the Lyapunov's direct method. In addition, an example is given with numerical simulations to show the effectiveness of our theoretical results.