Stability Problem Research Articles

Frequency stabilization of interconnected diverse power systems with integration of renewable energies and energy storage systems

Recent improvements in renewable energy sources (RESs) and their extensive use in the power industry have created significant issues for their operation, security, and management. Due to the ongoing reduction of power system inertia, maintaining operational frequency at its nominal value and minimizing tie-line power variations constitute essential variables for these improvements. A novel improved frequency stabilization approach based on modified fractional order tilt controller is presented for interconnected diverse power systems with integration of sea wave energy, photovoltaic, wind, energy storage system and biodiesel generator. The fractional order tilt integral double derivative (FOTIDD2) is a novel controller that is developed to address the frequency stabilization problems of a hybrid power structure that is integrated with sources of clean energy and devices for storing energy. A recent optimization algorithm inspired by human behavior called mother optimization algorithm (MOA) is applied to adjust the coefficient of the proposed cascaded controller. The FOTIDD2 controller was compared with other control methods in terms of its transient performance, in order to determine its effectiveness. Further, the mother optimization algorithm results are compared with those of sine cosine algorithm (SCA), fox optimization algorithm (FOA), and grey wolf optimization (GWO). FOTIDD2 controller was found to be more effective than PID controller in respect of reducing overshoot (Osh) by 79.31%, 83.78% and 67.99%, improving time settlement by 33.22%, 29.87%, and 22.45% and reducing undershoot (Ush) by 79.13%, 89.34%, and 86.90% for the (∆F1), (∆F2), and (∆Ptie), respectively.

Static output feedback control for positive 2D discrete systems in Roesser model

Abstract This paper investigates the output stabilization problem for multi-input multi-output positive 2D systems described by a linear discrete-time Roesser system. This kind of systems have the property that the horizontal and vertical states take non-negative values whenever the initial boundaries are non-negative. Conditions for the existence of desired static output feedback controllers guaranteeing the resultant closed-loop system to be positive and asymptotically stable are obtained. Also, the synthesis of static output feedback controllers, including the requirement of positivity of the controllers, is solved. These results are then extended to the case of uncertain plants. All of the proposed conditions are expressed in terms of Linear Programming, which can be easily verified by using standard numerical software. Finally, several numerical examples are included to illustrate the validity and the effectiveness of the developed results.

Stability Analysis of Matrices and Single-Parameter Matrix Families on Special Regions

This paper proposes an efficient method for determining the D-stability of matrices using Kelley’s cutting-plane method. The study examines the D-stability of matrices in symmetric regions of the complex plane, defined by quadratic matrix inequalities (QMI) and polynomial functions. Using Kelley’s cutting-plane method, we present an iterative algorithm for determining the D-stability of a given matrix. Further, the robustness of single-parameter matrix families is analyzed, and a method is proposed for considering their D-stability. Through examples, we indicate the possible applicability of the proposed approach in addressing stability problems in linear systems.

Surface Cladding Engineering via Oxygen Sulfur Distribution for Stable Electrocatalytic Oxygen Production

AbstractInevitable leaching and corrosion under anodic oxidative environment greatly restrict the lifespan of most catalysts with excellent primitive activity for oxygen production. Here, based on Fick’ s Law, we present a surface cladding strategy to mitigate Ni dissolution and stabilize lattice oxygen triggering by directional flow of interfacial electrons and strong electronic interactions via constructing elaborately cladding‐type NiO/NiS heterostructure with controlled surface thickness. Multiple in situ characterization technologies indicated that this strategy can effectively prevent the irreversible Ni ions leaching and inhibit lattice oxygen from participating in anodic reaction. Combined with density functional theory calculations, we reveal that the stable interfacial O−Ni−S arrangement can facilitate the accumulation of electrons on surficial NiO side and weaken its Ni−O covalency. This would suppress the overoxidation of Ni and simultaneously fixing the lattice oxygen, thus enabling catalysts with boosted corrosion resistance without sacrificing its activity. Consequently, this cladding‐type NiO/NiS heterostructure exhibits excellent performance with a low overpotential of 256 mV after 500 h. Based on Fick's law, this work demonstrates the positive effect of surface modification through precisely adjusting of the oxygen‐sulfur exchange process, which has paved an innovative and effective way to solve the instability problem of anodic oxidation.

Exponential stability of positive implicit dynamic equations with constant coefficients

In this paper, the problem of positivity and stability for linear time-invariant implicit dynamic equations is generally studied. We provide necessary and sufficient conditions for positivity of these equations. This characterization can be considered as a unification and generalization for some previous results. On the other hand, we study the exponential stability of positive implicit dynamic equations. Previously, this issue was not completely addressed. By using Krein–Rutman theorem, we show that a positive implicit dynamic equation on a time scale is uniformly exponentially stable if and only if the characteristic polynomial of the matrix pair defining the equation has all its coefficients of the same sign.

A size-switchable microsphere loaded with salmon calcitonin as two-weekly dosing for osteoporosis therapy

Osteoporosis is a disease with an increased incidence of fractures due to decreased bone mass and destruction of the microstructure of bone tissue. Salmon calcitonin (sCT), as a peptide, possesses the ability to inhibit osteoclast activity and thus regulate bone metabolism in clinical. However, short half-life and unstable physicochemical properties leading to rapid degradation of sCT have severely limited its clinical application. In this study, a size-switchable microsphere was developed to solve the problem of frequent administration and poor stability of sCT. sCT was encapsulated into Egg PC to form anhydrous reverse micelles (ARM) and then ARM was encapsulated into microspheres (MS@ARM). The degradable composite microspheres were utilized to provide a drug reservoir for sustained release of ARM encapsulated with sCT to reduce the frequency of drug administration, while the released ARM encapsulated with sCT entered the blood circulation to further protect sCT. In vitro release experiments demonstrated that the microspheres could sustain the release of sCT for at least 16 days. The microspheres MS@ARM showed the advanced therapeutic effect on the mouse model of glucocorticoid-induced osteoporosis (GIOP) at a low dosing frequency. The size-switchable microsphere is expected to be a new strategy for delivering sCT for osteoporosis treatment.

A Review on Secure Outsourcing and Privacy-Preserving Traffic Monitoring in Fog-Enabled VANETs

New possibilities for fog-based vehicle monitoring have emerged with the expansion of fog computing, but present privacy concerns provide a significant barrier that limits the extent to which vehicles can participate. Because of its potential to improve road network security and vehicle productivity, the field of Vehicle-based Ad hoc Networks (VANETs) is gaining prominence. The security problems with VANETs, such as data confidentiality and message access control are still need better solutions to provide better Quality of Service (QoS). The effectiveness of VANET networks is diminished due to their instability problem. Vehicles continually add requests to the Road Side Unit (RSU) queue whenever they want specific information. For ever-evolving networks like VANETs, better routing is a continual process. Fundamental problems arise in large-scale systems when centralized procedures are used to assign jobs to the nodes along a route. The present centralized system for computing and safety has many needs, including the protection of data storage, user authentication, access control, system availability across multiple network connections, and the provision of a real-time data flow overview. Distributed problem solving and work sharing between multiple agents can improve the system's scalability. This paper provides a brief survey on the secured outsourcing and privacy preservation-based traffic monitoring model with routing and task scheduling models in Fog-enabled VANETS. This survey presents the limitations of the traditional models that help the researchers design new solutions for secure outsourcing in VANETs.

Organic Electrolyte Additives for Aqueous Zinc Ion Batteries:Progress and Outlook.

Aqueous zinc ion batteries (AZIBs) are considered one of the most prospective new-generation electrochemical energy storage devices with the advantages of high specific capacity, good safety, and high economic efficiency. Nevertheless, the enduring problems of low Coulombic efficiency (CE) and inadequate cycling stability of zinc anodes, originating from dendrites, hydrogen precipitation and passivation, are closely tied to their thermodynamic instability in aqueous electrolytes, which significantly shortens the cycle life of the battery. Electrolyte additives can solve the above difficulties and are important for the advancement of affordable and reliable AZIBs. Organic electrolyte additives have attracted widespread attention due to their unique properties, however, there is a lack of systematic discussion on the performance and mechanism of action of organic electrolyte additives. In this review, a comprehensive overview of the application of organic electrolyte additives in AZIBs is presented. The role of organic electrolyte additives in stabilizing zinc anodes is described and evaluated. Finally, further potential directions and prospects for improving and directing organic electrolyte additives for AZIBs are presented.

Optimal Control Allocation for 2D Reaction‐Diffusion Equations With Multiple Locally Distributed Inputs

ABSTRACTIn this article, the problem of stabilization of a 2D unstable parabolic equation with multiple distributed inputs is addressed using a spectral decomposition approach. Furthermore the underlying redundancy of the actuation arrangement is exploited and actively used by introducing a suitable control allocation architecture. In particular, two optimal allocation policies have been considered: gradient descent and linear quadratic allocation. A simulation study supports and illustrates the theoretical findings.

On-line and real-time controller tuning architecture based on Youla–Kucera controller parameterization

This paper presents an on-line and real-time controller tuning architecture based on Youla–Kucera controller parameterization. First, a coarse controller is designed to satisfy nominal performance of closed-loop system. Second, Youla parameter is used to construct an on-line and real-time fine tuning mechanism including a group of controller candidates under arbitrary switching strategy. The mechanism can adjust the control performance on-line to achieve the balance between dynamic and steady-state performance without resulting in any closed-loop stability problems.

Resolving subgrid-scale structures for multiphase flows using a filament moment-of-fluid method

Multiphase flows are present in many industrial and engineering applications as well as in some physical phenomena. Capturing the interface between the phases for complex flows is challenging and requires an accurate method, especially to resolve fine-scale structures. The moment-of-fluid (MOF) method improves drastically the accuracy of interface reconstruction compared to previous geometrical methods. Instead of refining the mesh to capture increased levels of detail, the MOF method, which uses zeroth and first moments as well as a conglomeration algorithm, enables subgrid structures such as filaments to be captured at a small extra cost. Coupled to a finite volume Navier–Stokes solver, the MOF method has been tested on a fixed grid and validated using well-known benchmark problems such as dam break flows, the Rayleigh–Taylor and Kelvin–Helmholtz instability problems, and a rising bubble. The ability of the novel filament MOF method to capture the filamentary structures that eventually form for the Rayleigh–Taylor instability and rising bubble problems is assessed. Good agreement has been found with other numerical results and experimental measurements available in the literature.

Three-dimensional intelligent monitoring and early warning technology for tailings ponds based on spatiotemporal fusion of multisource big data.

To solve the difficult problems of tailings dam instability and environmental pollution, multisource information perception, prediction and early warning technology for tailings dams are investigated. Taking a tailings pond in China as an example, a three-dimensional visualization intelligent management platform based on the spatiotemporal fusion of multisource big data is established to realize intelligent real-time monitoring, prediction and early warning of tailings dams. A monitoring system for air-space-ground integration was developed via high-resolution optical image recording, unmanned aerial vehicles (UAVs), radar, video surveillance and displacement sensors. This approach can realize pollution monitoring and efficient identification of high-risk areas. In addition, a machine learning algorithm is used to mine spatiotemporal data in detail. The Alibaba cloud platform was adopted to develop a data integration framework. Multisensor spatiotemporal data from tailings dams and multisource monitoring data from the environment were integrated. The integrated management of tailings dam environmental monitoring, pollution and stability assessment is realized. A stability prediction model for tailings dams based on multisource data is proposed. The temporal and spatial information of various forms of data is analysed from multiple levels and perspectives. Rapid prediction of the disaster situation and stability of tailings ponds is realized. Moreover, a tailings pollution assessment model based on a neural network is integrated with multisource information to establish a multifactor environmental pollution neural network assessment model and a multilevel warning platform. This work can provide technical support for intelligent monitoring and early warning systems for tailings ponds.

The study of phycocyanin-quercetin complex on color stability under light condition

In this study, phycocyanin (PC) -quercetin (PC) complex (PC-QR) was prepared, and the effect of QR on the structure and storage stability of PC was evaluated. UV and fluorescence results showed that the weak interaction between PC and QR promoted the change of PC spatial conformation and tryptophan (Trp) microenvironment. Circular dichroism (CD) and Fourier transform infrared (FTIR) analysis showed that QR caused changes in the secondary structure of PC by partially unwinding the α-helix. From the zeta potential and particle size, the appropriate concentration of QR can promote PC polymerization. When the molar ratio of yellow QR to PC was 1:80, the binding of blue PC was induced to form a stable green PC-QR. The stability of the complex was better than that of PC after 7 days of storage under light conditions. This study proposes a new method to obtain natural colorants with better stability and wider color range by forming PC-QR. This method solves the problems of instability and limited color range of PC and QR as natural nutritional pigments, and expands their potential applications in food, cosmetics and pharmaceutical industries.

The impact of religious diversity on the Kurdish identity within a geopolitical framework

Importance. The Kurds are currently dispersed across four countries (Turkey, Syria, Iran, and Iraq), which are quite negative towards them, trying to suppress expression of their identity. Historiographically, the Kurdish issue is usually perceived as another obstacle to regional stability in the Middle East, but the uniqueness of their position forces us to look at the situation from a different perspective. The aim of the study is to prove that the experience of asymmetric interaction of Kurds with various social actors can be extrapolated to address the problem of long-term stability in the Middle East and the resolution of other conflicts.Materials and Methods. The research is based on the principles of historicism and objectivity; chronological and structural methods and comparative analysis are used.Results and Discussion. The novelty of the study is that it allows us to consider the religious heterogeneity of the Kurds as a possible positive factor that can be used to build a new Kurdish identity. The peculiarities of the situation of the Kurds in different territories, including in a religious context, are also analyzed. The trends in ethnic relations in the territories of four nearby countries (Syria, Iraq, Iran, and Turkey) are determined.Conclusion. The eclectic nature of Kurdistan’s religious composition has greatly influenced Kurdish political identity, and despite external divisive factors, the diverse Kurdish population is united due to its culture of tolerance, which stems from its long history of diverse religious traditions. At the same time, it complicates their interactions with the neighbouring states that are intolerant of dissent and other faiths.

Effect of surface morphology on the deformation mechanism of Cu nanocrystal under cyclic loading at different temperatures: Molecular dynamics simulations

Micro-electromechanical systems (MEMS) are often subject to mechanical vibration or temperature, the fatigue reliability of small metal parts is a potential problem for long-term operational stability. Since the MEMS packaging is performed at a high temperature of about 600 K. Therefore, in this paper, the deformation mechanisms of copper nano-single crystals with different surface morphologies under cyclic loading were investigated by molecular dynamics calculations at room temperature (300 K) and high temperature (600 K) to provide a theoretical basis for the design of copper nanomaterials. The results show that the plastic deformation modes of the models with different surface morphologies during cyclic loading are mainly Shockley partial dislocations slipping along {111}. In contrast, the fatigue damage modes are extrusion intrusion induced by high shear strain. Compared with the surface containing a pore, the damage caused by the circular and sharp recesses through the surface is more serious. The causes of stress concentration during deformation are mainly the entanglement of Shockley partial dislocations and the generation of Lomer-Corell lock fixed dislocations. The locations of these stress concentrations will produce pores in the subsequent deformation. In addition, since periodic interfaces do not cause particularly pronounced stress concentrations and shear strain concentrations on the surface compared to other models with defects, and the resulting shear strain concentration bands are split by shear strain bands in the other direction, extrusion intrusion is prevented. Therefore, at room temperature, the model with a one-dimensional sinusoidal surface has the strongest resistance to fatigue damage, while at high temperatures, the model with a two-dimensional sinusoidal surface has the optimal resistance to fatigue damage. This provides a basis for the design of NEMS/MEMS working at high temperatures.

Ultrahigh thermal stability and piezoelectricity of lead-free KNN-based texture piezoceramics

The contradiction between high piezoelectricity and uniquely poor temperature stability generated by polymorphic phase boundary is a huge obstacle to high-performance (K, Na)NbO3 -based ceramics entering the application market as Pb-based substitutes. We possess the phase boundary by mimicking Pb(Zr, Ti)O3’s morphotropic phase boundary structure via the synergistic optimization of diffusion phase boundary and crystal orientation in 0.94(Na0.56K0.44)NbO3−0.03Bi0.5Na0.5ZrO3−0.03(Bi0.5K0.5)HfO3 textured ceramics. As a result, a prominent comprehensive performance is obtained, including giant d33 of 550 ± 30 pC/N and ultrahigh temperature stability (d33 change rate less than 1.2% within 25-150 °C), representing a significant breakthrough in lead-free piezoceramics, even surpassing the Pb-based piezoelectric ceramics. Within the same temperature range, the d33 change rate of the commercial Pb(Zr, Ti)O3−5 ceramics is only about 10%, and more importantly, its d33 (~ 350 pC/N) is much lower than that of the (K, Na)NbO3-based ceramics in this work. This study demonstrates a strategy for constructing the phase boundary with MPB feature, settling the problem of temperature instability in (K, Na)NbO3-based ceramics.

Microenvironment Manipulation Strategies for Acidic CO2 Electrolysis

AbstractThe electrochemical reduction of CO2 (CO2RR) has gained significant attention due to its potential to reduce carbon emissions and produce valuable fuels and chemicals. CO2RR is typically carried out in neutral or alkaline conditions, while challenges such as the carbon crossover and salt precipitate can hinder the practical application. Conducting CO2RR in acidic media presents a promising method to address these issues, although it faces the problem of low efficiency and poor catalysis stability. Regulating the interface/surface microenvironment near the catalysts is crucial to minimize the competitive hydrogen evolution reaction and enhance CO2RR activity and long‐term stability. This review outlines recent advancements in acidic CO2RR, emphasizing various microenvironment engineering strategies for optimizing the CO2RR kinetics including electrolyte composition manipulation, catalyst design, electrode modification and cell configuration optimization. Additionally, the review addresses challenges into developing practical and cost‐effective CO2RR systems.

An Updated Review Summarizing the Anticancer Potential of Poly(Lactic-co-Glycolic Acid) (PLGA) Based Curcumin, Epigallocatechin Gallate, and Resveratrol Nanocarriers.

The utilization of nanoformulations derived from natural products for the treatment of many human diseases, including cancer, is a rapidly developing field. Conventional therapies used for cancer treatment have limited efficacy and a greater number of adverse effects. Hence, it is imperative to develop innovative anticancer drugs with superior effectiveness. Among the diverse array of natural anticancer compounds, resveratrol, curcumin, and epigallocatechin gallate (EGCG) have gained considerable attention in recent years. Despite their strong anticancer properties, medicinally significant phytochemicals such as resveratrol, curcumin, and EGCG have certain disadvantages, such as limited solubility in water, stability, and bioavailability problems. Encapsulating these phytochemicals in poly(lactic-co-glycolic acid) (PLGA), a polymer that is nontoxic, biodegradable, and biocompatible, is an effective method for delivering medication to the tumor location. In addition, PLGA nanoparticles can be modified with targeting molecules to specifically target cancer cells, thereby improving the effectiveness of phytochemicals in fighting tumors. Combining plant-based medicine (phytotherapy) with nanotechnology in a clinical environment has the potential to enhance the effectiveness of drugs and improve the overall health outcomes of patients. Therefore, it is crucial to have a comprehensive understanding of the different aspects and recent advancements in using PLGA-based nanocarriers for delivering anticancer phytochemicals. This review addresses the most recent advancements in PLGA-based delivery systems for resveratrol, EGCG, and curcumin, emphasizing the possibility of resolving issues related to the therapeutic efficacy and bioavailability of these compounds.

Local Stability Analysis of a Composite Corrugated Steel Plate Pipe-Arch in Soil

The straight part of the corrugated steel plate (CSP) pipe-arch structure in soil may cause local buckling instability due to insufficient load-bearing capacity. Recently, composite CSP pipe-arch has been widely utilized to enhance structural stability, and their stability needs to be thoroughly investigated. This paper studies the local buckling stability problem of the straight part of composite CSP pipe-arch in soil by simplifying the soil support and introducing the inter-layer bonding effect. Based on elastic stability theory, a theoretical mechanical model of composite CSP pipe-arch was proposed. The Rayleigh–Ritz method and the semi-combined composite structure stiffness approximation were used to derive the critical buckling conditions for the straight part of the composite CSP pipe-arch. Through numerical calculation and influencing factors analysis, it is concluded that the critical buckling load of the straight part of the composite CSP pipe-arch structure is affected by the elastic modulus, thickness, Poisson’s ratio, rotational restraint stiffness and side length of the straight part of the material. In particular, it is found that as the inter-layer bonding coefficient increases, the critical buckling load is improved, while the critical buckling wave number is mainly influenced by the width of the straight part, elastic modulus, and inter-layer bonding coefficient. Additionally, we discussed the coupling effect of several key parameters on the stability of the structure. The results of this study offer theoretical foundations and guidance for the application of composite CSP pipe-arch in soil engineering, such as culverts, tunnels, and pipeline transportation.

Synergistic Reduction and Oxidation Resistant Interface Modifier for High‐Voltage and High‐Loading Solid‐State Lithium Batteries

AbstractSolid‐state batteries (SSBs) with high‐voltage cathodes and Li‐anodes offer promising energy density and safety for next‐generation batteries. However, poor contact and electrochemical instability of solid electrolyte interfaces hinder their long‐term performance. Traditional rigid solidification interlayers possess restricted capability to address these issues. Herein, a composite buffer interlayer (CBI) with localized high‐concentration electrolytes (LHCEs) in a flexible polymer scaffold, tackling contact and stability problems and ensuring a perfect interface is developed. The extended electrochemical window provides it with synergistic antioxidation and antireduction capabilities, making it compatible with high‐voltage cathodes and Li anodes, while an in situ formed LiF‐Li3N rich inorganic interface ensures uniform lithium deposition and prevents dendrite formation. This CBI enables lithium symmetric cells to achieve a super high critical current density of 7.2 mA cm−2. Most impressively, coupled with a high‐voltage LiNi0.83Co0.12Mn0.05O2 cathode (NCM83), the full cell achieves 94.1% capacity retention after 125 cycles (coulombic efficiency >99.8%) at a mass loading of 14.6 mg cm−2 and a high voltage of 4.45 V. Additionally, a pouch cell with 17.2 mg cm−2 NCM83 achieves an initial discharge capacity of 3.82 mAh cm−2 an superior cycling stability (75 cycles, 89% capacity retention), showcasing the practical potential of LHCE‐CBI enabled SSBs.