Stability Problem Research Articles

Numerical study on efficiency and robustness of wave energy converter-power take-off system for compressed air energy storage

The unpredictable fluctuations of wave lead to an imbalance between energy supply and demand. This article proposes a wave-driven compressed air energy storage system, which uses wave mechanical energy instead of electrical energy as the direct driving force for the compressors. Compressed air energy storage solves the problem of stability of wave energy output by accumulating and storing wave energy and then releasing it in a centralized manner. Due to the significant change in load damping compared to the generator, the damping force of the power take-off with compressed air energy storage load is analyzed. And a robust strategy with adjustable buoy draft and load compressor number is proposed, and the highest capture width ratio of 26.71 % and wave energy to compressed air energy conversion efficiency of 13.00 % are achieved under regular wave conditions. Surface seawater is used for heat supplementation in the expansion phase, and a closed-loop system is designed to avoid the damage of low-temperature condensation, the round-trip efficiency of the system is 11.26 %. This research provides a potential power generation path for wave energy and surface seawater heat. And it may beneficial to provide stable and relatively cheap power supply for coastal and offshore users.

Face stability assessment of a longitudinally inclined tunnel considering pore water pressure

AbstractThe face stability analysis of a longitudinally inclined shield tunnel using an analytical approach in water‐rich areas is still a research gap. To solve this face stability problem, a numerical simulation based on the FLAC3D is first conducted to calculate the seepage field behind the inclined tunnel face. An improved rotational failure mechanism is developed to make it possible to investigate the face stability of inclined tunnels using analytical approaches. In the framework of the kinematic approach of limit analysis, the limit support pressures and corresponding failure surfaces of the inclined tunnel face are determined to analyze the face stability issue. The interpolation tool (griddata) in MATLAB is adopted to involve the obtained numerical values of pore water pressures into the analysis of the stability issue. The analytical solutions obtained from the proposed method are validated by comparisons with existing results from published literatures and numerical results. For a quick estimation of the inclined tunnel face stability in water‐rich areas, a series of design charts are then presented for various soil strength parameters, water tables, and inclined angles. Finally, an application of the proposed method to a practical tunneling case is provided, which further illustrates the effectiveness of the proposed method.

Nitrogen-phosphorus co-doped carbon layer-confined cobalt phosphide-anchored nickel molybdate heterojunctions for efficient electrocatalytic overall water splitting

Aiming at the problems of low catalytic activity and poor stability of nickel molybdate-based catalysts. Herein, we successfully prepared nitrogen and phosphorus co-doped carbon (NPC) layer-confined cobalt phosphide (CoP)-anchored nano-cuboid nickel molybdate (NNM) catalysts (NNM-CoP@NPC/NF) on nickel foam (NF) by hydrothermal and phosphating methods. The strong interaction between CoP and NNM is verified by experimental characterization and theoretical calculation, which improves the electronic structure of NNM and reduces the orbital energy of the central anti-bond, thus optimizing the adsorption and desorption of reaction intermediates/products. NiOOH and MoO42− formed by reforming the catalyst under the action of NPC-confined layer maintain catalytic activity and stability in cooperation with CoP and NPC, respectively. Accordingly, in the assembled two-electrode system NNM-CoP@NPC/NF, the cell voltage of only 1.51 V is needed to drive a current density of 10 mA cm−2. More importantly, the current density remained at 100 mA cm−2 for 100 h under the voltage of 1.66 V with almost no attenuation. This strategy of constructing interface regulation and confinement provides a new insight for improving the activity and stability of water splitting in alkaline media.

Trajectory planning and tracking of dynamic lane change for autonomous buses considering vehicle stability in dynamic traffic scenarios

Trajectory planning and tracking of lane change are critical technologies for autonomous buses. Characteristics of the buses susceptible to stability problems resulting from the high height, large passenger capacity and long lengths, coupling the dynamic traffic with the dynamic changes in the states of adjacent vehicles and road adhesion coefficient, put forward great challenges in lane change for autonomous buses (ABs). To cope with the foregoing challenges, a framework is proposed to achieve the trajectory planning and tracking of dynamic lane change for ABs. For trajectory planning approach, the trajectory planning and replanning is optimized in the safe range of longitudinal length of the lane-changing trajectory to obtain the real-time reference trajectory, combining consideration of vehicle yaw, roll stability and lane-changing efficiency. The minimum longitudinal length of lane-changing trajectory determined by the yaw stability and roll stability of ABs, combined with the maximum length formed by the adjacent vehicles with dynamic states, form the real-time safe range for lane-changing trajectory planning. For trajectory tracking approach, a tracking approach using model predictive control based on multipoint preview is proposed to achieve the real-time planned trajectory tracking considering buses stability. The effectiveness of the proposed strategy is evaluated by simulating an experimentally validated Trucksim model in different dynamic traffic scenarios to demonstrate the capability of the strategy in trajectory planning and tracking, and guaranteeing vehicle stability for dynamic lane change of ABs.

Distributed formation containment control for multi-agent systems via dynamic event-triggering communication mechanism

This paper focuses on resolving the distributed formation containment control issue in general multi-agent systems (MASs) possessing multiple leader agents subject to limited communication resources. The unnecessary data transmissions among agents in MASs are reduced by utilizing a unique dynamic event-triggering communication mechanism (DETCM), which can build communication time sequences for each agent automatically. Based on the sampled states of agents at event-triggering instants, a novel distributed formation containment control protocol is proposed. By mathematical analysis, the formation containment control problem is turned into the problem of stability in a reduced-order system. The global formation containment of the MASs is finally achieved through the application of Lyapunov-Krasovskii functionals and general inequalities. Moreover, a valid example is also given to support the validity and effectiveness of the findings.

High-speed 3D printing temperature system with optimized PlD parameters based on improved ant lion optimization algorithm

An Ant Lion Optimization algorithm based on elite Opposition-based learning and Cosine factors (OCALO) is proposed to address the problem of poor response and stability during heating process in high-speed 3D printing temperature system.The generation of the initial solution in OCALO algorithm is enhanced by the introduction of a new Tent-Logistic-Cotangent composite chaotic mapping, which guarantees the diversity of population. The PID parameters are optimized using the improved algorithm. Compared with two existing classical algorithms and three improved ALO algorithms, the proposed algorithm improves the convergence speed, global search ability and the ability to jump out of the local optimal solution. The outcomes of simulation and experimentation demonstrate that the algorithm improves the transient and steady-state performance of temperature control with better accuracy and robustness. It takes at least 123 s faster than other controllers to reach stability and is more than two times stronger than other PID controllers, making it better suited to high-speed 3D printing temperature systems.

Memory‐based event‐triggered control for networked control system under cyber‐attacks

AbstractThis article focuses on the problem of stability for a class of linear networked control systems (NCSs) subjected to network communication delays and random deception attacks. A new memory event‐triggered mechanism (METM) is proposed to reduce the unnecessary transmitted data through the communication channel and then enhance the network resources. In this context, a new memory stochastic state feedback controller is proposed to stabilize the closed‐loop networked control system. A new randomly occurring deception attacks model is employed to deal with the security problem of NCSs. Sufficient stability conditions are derived based on a suitable Lyapunov‐Krasovskii functional (LKF). The designed methodology is proposed in terms of linear matrix inequality to synthesize both event‐triggered parameters and controller gains, and to reduce the conservatism of the system some integral lemma are exploited to bind the time derivative of the LKF. Finally, two numerical examples are presented to illustrate the effectiveness of the proposed method which provides a maximal upper bound value of the network‐induced delay and less transmitted packet regarding the maximal value delay obtained in other works, so less conservatism results are obtained, compared to previous ones in the literature.

A Generalized Load Model Considering the Fault Ride-Through Capability of Distributed PV Generation System

Considering the voltage stability problem brought by large-scale distributed PV access to the distribution network, this paper proposes a generalized load model that considers the fault ride-through capability of distributed PV. Firstly, the detailed model of the distribution network is established, and the detailed model is calibrated based on the measured data, the simulation errors are below 1%. And then establish a generalized load model considering distributed PV high and low voltage traversal ability. The sensitivity analysis results are used to rank the parameters to be identified, and the parameters with higher sensitivity are identified. The parameters are obtained from the detailed model and measured data, and four sets of parameters are identified and simulated under different PV penetration rates and fault conditions. The calculated fitting errors are less than 1%. The results show that the generalized load gray box model of the distribution network with distributed PV high and low voltage ride-through capability can reflect the dynamic characteristics of the distribution network well.

Parameter-dependent conditions for H ∞ stabilisation of polynomial parameter-varying system with delay

This paper considers the problems of achieving exponential stability and H ∞ stabilisation for polynomial parameter-varying system with time-varying delay. Unlike some existing linear parameter-varying results that treat system parameters as time invariant factors, this paper makes full use of the nonlinearity and time-varying characteristics of system through introducing a novel delay-and-parameter-dependent Lyapunov function. The main conclusions are discussed in three cases (system without input, system with disturbance input, system with disturbance input and control input). And the H ∞ stabilisation problem is solved by constructing a controller which is inserted with system parameters and their derivatives. The structures of Lyapunov function and controller lead to that the derived criteria for exponential stabilisation are expressed by state-and-parameter-dependent linear matrix inequalities, which are efficiently solved by sum-of-squares program. The effectiveness and superiority are verified through two numerical examples.

Thermal buckling of variable stiffness composite laminates using high order plate finite elements

This paper proposes a study on the thermal buckling of Variable Angle Tow (VAT) composite plates using high-order theories. Here, the governing equations are derived via the principle of virtual work. Under the assumption of linear pre-buckling, the stability problem is reduced to a linear eigenvalue analysis considering proportional geometric stiffness. In contrast, a constant thermal load is assumed to be known along the plate thickness, and the uncoupled thermo-mechanical formulation is used, where the thermal effects are described as external loads. The plate is discretized using the Finite Element Method (FEM) and high-order theories are developed using the Carrera Unified Formulation (CUF). Using the CUF, the equations are expressed as an invariant of the plate theory approximation order. Therefore, Equivalent Single Layer (ESL) and Layer-Wise (LW) models can be easily implemented. Several geometries and lamination cases are considered for verification purposes, including different side-to-thickness ratios and fiber orientations, which result in various anisotropy effects. In addition, the effect of changing constraints and materials is evaluated. Particular attention is paid to the effect of the structural theory approximation on the evaluation of the thermal buckling load. It is shown that the correct evaluation is highly dependent on the edge-to-thickness ratio and on the anisotropy given by both the fiber orientation and the material properties. As a final remark, sensitivity analysis and best fiber angle solutions are discussed to highlight the importance of the LW modeling approach.

Adaptive Internal Model Backstepping Control for a Class of Second-Order Electromagnetic Micromirror with Output Performance Constraints and Anomaly Control.

This paper investigates the asymptotic tracking problem for a class of second-order electromagnetic micromirror model with output performance constraints and anomaly control, which is subject to model parameter uncertainties and external disturbances. Specifically, this paper formulates the trajectory tracking control problem of an electromagnetic micromirror as a closed-loop control trajectory tracking problem based on the general solution framework of output regulation. Moreover, the extended internal model is introduced to reformulate the closed-loop control problem into a state stabilization problem of the augmented system. Based on the augmented system, an internal model backstepping controller is proposed by integrating the barrier Lyapunov Functions (BLF) and the Nussbaum gain function with the backstepping structure.This controller not only satisfies the output performance constraints of the micromirror, but also maintains the control performance in anomalous control situations. The final performance simulation demonstrates the efficacy of the proposed controller.

Ensuring grid resilience: Voltage stability analysis and contingency ranking in electric power systems

Modern-day power systems are highly stressed and operate close to the stability limit. The bus voltage variation in power systems generally infringes on the researcher's mind about voltage stability. The main focus of this manuscript is the voltage stability problem and voltage security assessment rather than the angle stability problem. Voltage security can be determined by running a full-load AC load flow with contingency analysis. In real-time analysis, running thousands of contingencies in online mode is quite a cumbersome task, so here in this manuscript, we have proposed a functional link-based ANN for voltage security assessment and then predicted the weakest voltage control area by the entropy concept along with the placement of FACTS devices according to the voltage control area weakness factor and contingencies ranking. The novel technique is then tested with IEEE-14 Bus and IEEE-30 Bus systems with voltage stability performance indicators.

Some new results about the stability radius of infinite-dimensional systems perturbed stochastically and deterministically

This paper presents two significant contributions: First, we examine linear infinite-dimensional systems perturbed in deterministic and stochastic ways. The stability radius method is used to solve the robust stability. Bounds on the perturbations are obtained, guaranteeing that the troubled system is stable. The outcomes are determined via a Lyapunov equation. Secondly, we study the robust stabilisation problem. We investigate the maximisation of the stability radius when the input operator is unbounded in the general case. Also, we establish the conditions under which suboptimal controllers exist. An infinite-dimensional Riccati equation describes the supreme achievable stability radius.

Extracellular vesicles the delivery of drugs through genetic engineering

Researchers from a variety of disciplines are investigating the use of extracellular vesicles (EVs) as delivery vehicles for pharmaceutical solutions. In order to make the most of the therapeutic potential of EVs, various loading strategies have been devised. Despite the widespread application of exogenous methods, endogenous approaches are becoming increasingly preferred instead. Medicinal macro molecules such as proteins and nucleic acids can be loaded with relative ease using this technology that manipulates parental cells through genetic engineering. We examine the most effective ways for EV loading and demonstrate why endogenous is superior. Extracellular vesicles (EVs), which are able to transport pharmaceuticals, have the potential to tackle the problems of biologic therapeutic stability and off-target undesirable effects. In addition, we investigate the most recent findings and applications of this innovative method in order to shed light on the numerous potential therapeutic possibilities in the field of EV-based treatments. The possibility of endogenous loading of EVs with big biological medicines has been brought to light by recent research. In order to optimize the loading of biologic drugs in extracellular vesicles (EVs), researchers have been able to apply cargo selection and loading pathway molecules thanks to advancements in EV biogenesis. It has been established that endogenous EV loading is successful in preclinical in vivo trials, which demonstrates its promise in a variety of therapeutic situations.

Application of new technologies to enhance the stability of high embankment slopes

This study aims to investigate the stability problems of high road embankment slopes in the Republic of Moldova, revealing shortcomings of classical methods. The authors propose a solution by using the RG system, equipped with specialized vibration drilling equipment from "RTG RAMMTECHNIC Gmbh". The method provides for the creation of piles in deep boreholes using the vibrating d, filling the cavities with soil, with subsequent compaction of soil in stages. Experimental field and laboratory research has demonstrated the effectiveness of this method. The results showed significant improvements in soil properties: increased density, strength, and deformation characteristics. The proposed technology offers advantages such as: increased load-bearing capacity of the soil-pile massif, practically complete elimination of dynamic effects on the ground and structures located in close proximity to the construction site, reduced manual labor costs, and a decrease in the overall cost of the construction work. The study aimed the application of this method in Moldova's road construction, highlighting its potential to counteract slope deformations caused by the action of various factors of any nature. The authors suggest the need for further research for refine the methodology, assess economic feasibility, and perform stress-strain analysis using the Finite Element Method. The study was concluded by outlining plans for future research on embankment slopes stabilized by soil piles using the RG installation.

Study of Slope Stability of the Mining Wall in an Open-Pit Coal Mine by the Paste Cut-and-Backfill Method

According to this study’s findings, slope stability problems in open-pit coal mines can be avoided, and mine wall collapse can be effectively mitigated by the use of cut-and-backfill mining techniques. The main research results are as follows: (1) The stope and waste rock’s geotechnical, physical, and mechanical characteristics were gathered and examined; the geotechnical and mechanical characteristics found in this study largely satisfy the criteria for slope stability analysis. (2) Cemented paste backfill (CPB) materials were made of mine waste rock and fly ash at a desired ratio, mixed with cement as a bond material, and were tested in the laboratory, using a combination of cement percentages of 6%, 8%, and 10% for the cement content and 25%, 30%, 35%, and 40% for the fly ash content, to determine the ideal mix for artificial ground support in underground mines, taking into account both economic and performance factors. (3) By using this model, the changes in CPB strength were investigated under various factors influencing the cement ratio, and limit equilibrium modeling was used with the FLAC-Slope 8.1 program with different cement paste backfill ratio to calculate the factor of safety for each cement percentage after 1 day, 3 days, 7 days, and 28 days of curing time (CT) to obtain the optimum compressive strength and shear straight of cemented paste backfill with high paste fill shear strength on the slope. (4) The research results are of great significance for the safety of important facilities in open-pit mines and provide a basis for the design and safety implementation of open-pit slope engineering.

Local exponential stabilisation of the delayed Fisher's equation

Exponential stabilisation is undoubtedly an essential property to study for any control system. This property is often difficult to establish for nonlinear distributed systems and even more difficult if the state of such a system is subject to a time-delay. In this context, this paper is devoted to the study of the well-posedness and exponential stabilisation problems for the one-dimensional delayed Fisher's partial differential equation (PDE) posed in a bounded interval, with homogeneous Dirichlet condition at the left boundary and controlled at the right boundary by Dirichlet condition. Based on the infinite dimensional backstepping method for the linear and undelayed corresponding case, a feedback law is built. Under this feedback, we prove that the closed-loop system is well-posed in L 2 ( 0 , 1 ) and locally exponentially stable in the topology of the L 2 ( 0 , 1 ) -norm by the use of semigroup theory relating to differential difference equations and Lyapunov–Razumikhin analysis, respectively. A numerical example that reflects the effectiveness of the proposed approach is given.

Consensus control and initialization region optimization for leader‐following multi‐agent systems under time‐varying communication delay and consecutive packet dropouts

AbstractThis article is to investigate the consensus control and initialization region optimization for leader‐following multi‐agent systems with time‐varying communication delay and nonidentical consecutive packet dropouts. By combining the Bernoulli distribution model of the data loss and the Hadamard product, the control protocols affected by both communication delay and packet dropouts are utilized to formulate the consensus problem into the mean‐square stability problem of the augmented error systems. Resorting to the Lyapunov function methodology and a structure separation method, a sufficient condition to ensure the consensus is built in the form of linear matrix inequality. Relying on the given Lyapunov function and set‐membership analysis, an optimization procedure is proposed to simultaneously ensure the consensus and enlarge the estimated ellipsoid of initial conditions. The validity of the provided method is illustrated through a comparative simulation.

Ensuring information security and stability: The application of blockchain in naming system

In recent years, network information security and stability problems have emerged one after another, and people's personal privacy and property security are being threatened. A large part of these problems are caused by two major characteristics of traditional DNSinsecurity and instability. Therefore, this article aims to explore a new internet naming system the Blockchain Naming Systemto address the current issues of internet information security and stabilityespecially the problems caused by the traditional DNS system. This article adopts scientific research methods such as literature survey, comparative research, experimental exploration, analogy research, and model building. By analyzing the current situation, studying the feasibility of the blockchain naming system, and comparing its advantages and disadvantages with the traditional DNS system, it is not difficult to conclude that this new blockchain naming system has huge potential. It can not only ensure stability and security but also contribute to other fields.

Phase engineering boosting heterogeneous interface effect in RuO2/MnO2 catalysts for acidic oxygen evolution reaction

Oxygen evolution reaction (OER) of ruthenium dioxide (RuO2) in acidic media usually faces the problem of poor stability caused by excessive oxidation and dissolution. To address this issue, the present work prepares heterojunction catalysts by introducing RuO2 into manganese dioxide (MnO2) with different crystal types. The obtained RuO2/MnO2-γ exhibited excellent acid OER activity (η = 220 mV at 10 mA·cm−2) and could operate stably for 80 h. Mainly because the Ru-O-Mn bonds generated at the RuO2/MnO2-γ heterointerface fine-tune the charge environment of RuO2. The formation of this particular interface can enable MnO2-γ to produce more reactive oxygen defects, which promotes the transfer of electrons. At the same time, it can also minimize the peroxidation reaction and structural collapse of RuO2 under acidic conditions, thereby suppressing the Lattice Oxygen Mechanism (LOM) to improve stability. Density functional theory (DFT) results show that RuO2/MnO2-γ lowers the energy barrier for the *O to *OOH conversion. This research findings provides a new perspective for elucidating the role of the regulated electronic environment arising from heterogeneous interfaces.