Stability Analysis Research Articles

Analysis and Improvement of Transient Voltage Stability for Grid-Forming Converters

Analysis and Improvement of Transient Voltage Stability for Grid-Forming Converters

Stability and Intervehicle Distance Analysis of Vehicular Platoons: Highlighting the Impact of Bidirectional Communication Topologies

Stability and Intervehicle Distance Analysis of Vehicular Platoons: Highlighting the Impact of Bidirectional Communication Topologies

Stability Analyses of Shallow Rectangular Tunnels in Anisotropic and Nonhomogeneous Soils Using a Kinematic Approach

Stability Analyses of Shallow Rectangular Tunnels in Anisotropic and Nonhomogeneous Soils Using a Kinematic Approach

Impedance-Based Stability Analysis of Power System Wideband Oscillations: A Bridge between s Domain and Frequency Domain

Impedance-Based Stability Analysis of Power System Wideband Oscillations: A Bridge between <i>s</i> Domain and Frequency Domain

Stability Analysis of Multi-Bus Power Electronics Defined Power Systems Using Phase Information of Nodal Admittance Matrix

Stability Analysis of Multi-Bus Power Electronics Defined Power Systems Using Phase Information of Nodal Admittance Matrix

Passivity-Based Stability Analysis of DC Microgrids Using Physically Decoupled Model

Passivity-Based Stability Analysis of DC Microgrids Using Physically Decoupled Model

Single-network based adaptive dynamic programming optimal control for robotic manipulator with joint limitation under input saturation

Single-network based adaptive dynamic programming optimal control for robotic manipulator with joint limitation under input saturation

Time-varying equivalent circuit for dynamically modulated dielectric slabs and its implications for stability analysis

Equivalent circuits (ECs) have played an instrumental role in analyzing and modeling distributed electromagnetic structures for many decades, owing to their intrinsic simplicity and the valuable intuition and physical insights they provide. Here, we envision what we believe to be a novel class of ECs featuring linear time-varying (LTV) circuit elements to harness the power of EC analysis for studying LTV structures, particularly LTV dielectric slabs. Our time-varying equivalent circuit (TVEC)—consisting of infinitely many time-varying LC resonators interconnected in either series or parallel—is rigorously derived and exact, with closed-form expressions for the circuit elements. Its convenient form, enabled by a judicious use of Mittag-Leffler expansion, simplifies the analysis of LTV slabs experiencing various resonant and harmonic phenomena. We demonstrate this point by applying our TVEC to the problem of parametric instability in linear time-periodic slabs. Despite its immense importance, instability has been largely neglected in the literature on periodically modulated structures, mainly due to the inherent complexity of problems involving partial differential equations with time-periodic coefficients. Time-periodic circuits, on the other hand, enjoy an abundance of mathematical tools and methods in the form of the theory of Hill’s equation. We utilize this rich theory to investigate the nature of parametric instability in linear time-periodic slabs. Numerical results are then presented to verify these findings. Our TVEC is simple, applicable to any form of temporal modulation (not just periodic), and potentially extensible to other geometries, making it likely to have a significant impact on a multitude of hotly researched LTV topics.

Stability Analysis of Steel Columns with Fixed-Free Ends under Axial Compression: Uniform and Non-Uniform Square Hollow Sections

Stability Analysis of Steel Columns with Fixed-Free Ends under Axial Compression: Uniform and Non-Uniform Square Hollow Sections

RMS error analysis of spatial uniformity and energy stability of laser beam in second harmonic generation

RMS error analysis of spatial uniformity and energy stability of laser beam in second harmonic generation

Microscopic deformation mechanism and characteristics of carbonaceous slate during the creep process

Carbonaceous slate exhibits a significant creep deformation that seriously affects the construction and operation of underground projects. To investigate the microstructural changes characteristics and reveal the microscopic deformation mechanism of the carbonaceous slate during the creep process, multiple methods were performed, including the triaxial creep test, SEM and MIP. The following conclusions were drawn: The rock samples underwent three stages during the creep test: microporosity closure at a low-stress level, material densification at an intermediate stress level, and microcracks emerging and expanding to failure at the high stress. The creep deformation was particularly significant in the first and third processes. The lamellar particles are compressed or bent under stress in parallel and vertical directions, showing the anisotropic properties of deformation. The deformation of the rock sample is related to the angle between the bedding and the orientation of major principal stress, and the effect of the anisotropy decreases with the increased stress level. The sprouting and expansion of microfractures occur at high-stress levels, showing pressure dissolution of mineral particles, migration of very fine particles, and cement damage between lamellar particles. Finally, the horizontal samples formed a combined rupture surface composed of the laminar surface and the fracture surface intersecting it, showing brittle damage, while the vertical samples formed a fracture surface parallel to the laminar surface, showing a ductile damage pattern. Those results could provide the basis for a further understanding of the mechanical properties of carbonaceous slate and the improvement of its creep model and parameters. It was significant for the stability analysis and deformation prediction of engineering structures using numerical simulation.

Efficient photocatalytic activity and selective adsorption of UiO-67 (Zr)/g-C3N4 composite toward a mixture of parabens

In this study, UiO-67 (Zr)/g-C3N4 composites (U67N) were synthesized at wt.% ratios of 05:95, 15:85, and 30:70 using the solvothermal method at 80 °C for 24 h followed by calcination at 350 °C. The composites were characterized using UV–Vis diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy–energy-dispersive X-ray spectroscopy, transmission electron microscopy, and nitrogen physisorption analysis. In addition, thermal stability analysis of UiO-67 was conducted using thermogravimetric analysis.The photocatalytic performance of the composites was assessed during the degradation and mineralization of a mixture of methylparaben (MeP) and propylparaben (PrP) under simulated sunlight. The adsorption process of U67N 15:85 was characterized through kinetic studies and adsorption capacity experiments, which were modeled using pseudo-first-order and pseudo-second-order kinetics and Langmuir and Freundlich isotherms, respectively.The influence of pH levels 3, 5, and 7 on the photocatalytic degradation of the mixture was investigated, revealing enhanced degradation and mineralization at pH 3. The U67N composite exhibited dual capability in removing contaminants through adsorption and photocatalytic processes. Among the prepared composites, U67N 15:85 demonstrated the highest photocatalytic activity, achieving removal efficiencies of 96.8% for MeP, 92.5% for PrP, and 45.7% for total organic carbon in 300 kJ/m2 accumulated energy (3 h of reaction time). The detoxification of the effluent was confirmed through acute toxicity evaluation using the Vibrio fischeri method.The oxidation mechanism of the heterojunction formed between UiO-67 (Zr) and g-C3N4 was proposed based on PL analysis, photoelectrochemistry studies (including photocurrent response, Nyquist, and Mott–Schottky analyses), and scavenger assays.

Structural Stability and Mechanical Analysis of PVC Pipe Jacking under Axial Force

Structural Stability and Mechanical Analysis of PVC Pipe Jacking under Axial Force

Optimization of cold-formed steel beam cross-sections for pallet rack storage systems

This paper aims to obtain optimized cold-formed beam cross-sections for industrial pallet rack storage systems. The optimal sections were obtained by applying fitness functions aimed at reducing cross-sectional area and/or displacement and solving them using the Genetic Algorithm. These functions imposed a behavioral constraint so that all optimized solutions had the same resistant bending moment. The calculation of the characteristic resistant bending moment was carried out according to the direct strength method, with load factors defined by the elastic stability analysis with CUFSM, in an analysis routine implemented on the MATLAB platform. Four parameterized sections were studied, verifying the optimum set of height, width and stiffening elements that met the objectives defined by functions, assuming reference values of a rectangular hollow section. Manufacturing constraints were also taken into account. The results show that it is possible to manufacture cold-formed beams that consume less material and/or have a better moment of inertia in relation to the reference section, without compromising the strength of the structural element.

Inspection of a Time-Delayed Excited Damping Duffing Oscillator

This paper examines a time delay in position and velocity to minimize the nonlinear vibration of an excited Duffing oscillator (DO). This model is highly beneficial for capturing the nonlinear characteristics of many different applications in engineering. To achieve an estimated uniform solution to the problem under consideration, a modified homotopy perturbation method (HPM) is utilized. This adaptation produces a more accurate precise approximation with a numerical solution (NS). This is obtained by employing Mathematica software 12 (MS) in comparison with the analytical solution (AS). The comparison signifies a good match between the two methodologies. The comparison is made with the aid of the NS. Consequently, the work allows for a qualitative assessment of the results of a representative analytical approximation approach. A promising stability analysis for the unforced system is performed. The time history of the accomplished results is illustrated in light of a diverse range of physical frequency and time-delay aspects. The outcomes are theoretically discussed and numerically explained with a set of graphs. The nonlinear structured prototype is examined via the multiple-scale procedure. It investigates how various controlling limits affect the organization of vibration performances. As a key assumption, according to cubic nonlinearity, two significant examples of resonance, sub-harmonic and super-harmonic, are explored. The obtained modulation equations, in these situations, are quantitatively investigated with regard to the influence of the applied backgrounds.

Gas‐sensing properties of polyaniline‐based nanocomposites for d‐limonene detection

AbstractThis paper introduces a novel wearable flexible gas sensor designed specifically for the detection of d‐limonene. The sensor utilizes materials recognized for their high efficiency‐to‐cost ratio, notably polyaniline (PANI) combined with carboxylated multiwalled carbon nanotubes (MWCNT) and graphene oxide (GO) as sensing layers. The study conducts a comprehensive analysis of the nanocomposite layers, examining their functional groups, morphology, topography, thickness, crystallinity, thermal behavior, surface area, as well as the size and volume of their pores. This examination showed distinctions among the nanocomposite layers. PANI/GO exhibited larger pore size and thickness, while PANI/MWCNT_COOH demonstrated a higher surface area. The analysis of thermal stability demonstrated that the film employing the DBSA dopant exhibited the lowest stability. Morphological characterizations showed a globular structure for PANI, tubular characteristics for PANI/MWCNT_COOH, and a flat nature for PANI/GO. When detecting d‐limonene, nanocomposite films doped with HCl demonstrated notably superior response levels. The gas sensors exhibited high sensitivity (&gt;2.24 mV/ppm), a narrow range for the limit of detection (0.12–0.52 ppm), and excellent reversibility, stability, and selectivity. These findings suggest the possibility of broadening the application of gas sensors to monitor additional volatile compounds, with a particular emphasis on the online monitoring of agricultural products.

Wpływ ograniczenia naprężenia na stabilność masy skalnej

A huge number of factors controls rock mass failure, but it is mainly influenced by the state of stress and in particular on the bearing capacity and failure mechanism of the massif. The evaluation of rock mass strength in confined and unconfined compression, as well as its tension strength, are key issues to understand rock mass behaviour prior to failure. A connection between the laboratory analyses of the rock mass and the practical use of the obtained data is presented in the current work. The strength properties, confinement effect and failure mechanisms are successfully studied in volcanic rock specimens from an underground mine. In order to estimate the confinement effect on rock mass strength properties, different confined compression stresses on rock specimens are applied. In addition, the crack initiation and propagation in rock samples are observed and rock mass failure mechanisms are studied. The obtained data is used for stability analyses of an underground openings through determination of the safety factor. The obtained results of the safety factors underlined the influence of the confining stress on the rock mass. The tendency of increasing values of the shear safety factor and decreasing values of the tensile safety factor as confinement increases is found. This is an important observation that would allowed more accurate predictions of the stable and unstable zones of the underground openings to be carried out, and thus the stability of the rock mass to be improved.

Stability analysis of plasma waves driven by runaway electrons in tokamak hot plasmas

The local stability analysis of plasma waves driven by runaway electrons (REs) has been performed considering hot plasma Maxwellian background, with electron and ion temperatures of the order of 1 keV. It is shown that hot plasma waves, namely electron plasma waves (EPWs) and ion Bernstein waves (IBWs) can be driven unstable by RE at their coalescence frequency via Cherenkov resonance by RE with energy distribution peaked at about 8 MeV. A skew-normal distribution is used as a model of the RE energy distribution. The EPW and IBW couples of waves occur between any successive ion-cyclotron harmonics frequencies nf ci, above the lower hybrid resonance. At their confluence, the perpendicular group velocity vanishes and significant RF emissions are expected. The frequency gap between two successive confluences is ∼f ci. Groups of RF line emissions, separated by almost constant frequency gap ∼f ci/2 are detected during various quiescent runaway plasma discharges in the FTU tokamak. The analysis of a specific discharge suggests that the frequencies of the line emissions observed and the frequencies occurring at the EPW-IBW confluences are in reasonable agreement. A possible explanation of the line emissions with ∼f ci/2 gap in terms of nonlinear mode coupling is proposed.

Constraining Variable Generalized Chaplygin Gas model in Matter Creation Cosmology

Abstract We explore the variable generalized Chaplygin gas (VGCG) model in the theory of matter creation cosmology within the framework of a spatially homogeneous and isotropic flat Friedmann - Lema\^{i}tre - Robertson - Walker space-time. Matter creation cosmology is based on reinterpretation of energy-momentum tensor in Einstein's field equations. This creation corresponds to an irreversible energy flow from the gravitational field to the created matter constituents. The variable Chaplygin gas (VCG) is also studied as a particular solution. We use the Markov Chain Monte Carlo method to constrain the free parameters of three models, namely, $\Lambda$CDM, VGCG and VCG models with and without matter creation from the latest observational data from baryon acoustic oscillations, cosmic chronometer, type Ia supernovae (Pantheon) including gamma-ray burst, quasars, and the local measurement of $H_0$ from R21 data. Two different combinations of dataset provide a fairly tight constraint on the parameters of the $\Lambda$CDM, VGCG and VCG models. The present values of various cosmological parameters are obtained which give very close to $\Lambda$CDM model. Furthermore, we perform the stability analysis, Bayesian evidence analysis and information criteria analysis for these models through studying the sound speed, Bayes factor, and AIC and BIC selection criterion. The values of sound speed for VGCG and VCG models shows that both the models are stable. According to AIC, it is observed that VGCG and VCG models with matter creation are supported considerably less by current observations whereas BIC shows that these models are not favoured by observational data.

A fractional-order multiple-model type-2 fuzzy control for interconnected power systems incorporating renewable energies and demand response

Frequency regulation in Multi-region Interconnected Power Systems (MIPS), incorporating wind turbine systems, energy storage units, and demand response, is a challenging control problem. The problem involves maintaining grid stability, integrating variable renewable energy sources, enhancing grid resilience, optimizing energy storage and demand response capabilities, and ensuring regulatory compliance. Effective frequency regulation is a key problem for reliable and sustainable power system operation. In this paper, complex and uncertain dynamics in various components of a MIPS are modeled using multiple first-order dynamic fractional-order Type-2 Fuzzy Logic Systems (T2-FLSs). The models are evaluated, and the best possible dynamic model is chosen. With the best possible model, an optimal controller is designed. The stability and optimality analysis are presented through a Linear Matrix Inequality (LMI) approach. The adaptive laws of T2-FLSs are derived such that some LMI-based conditions are satisfied. The designed controller does not depend on the dynamics of MIPS. The uncertainties of time-varying load, wind energy, and solar power are modeled using T2-FLSs. The suggested LMI technique presents adaptation laws for T2-FLSs to ensure stability in the presage of natural disturbances and errors. The designed scheme is validated by applying to a practical 39-bus IEEE test system that includes the wind farms, demand response, and energy storage systems. The simulation results under various conditions verify the usefulness of the suggested controller. The comparisons with conventional controllers demonstrate that the suggested approach is more effective under uncertainties and natural perturbations.