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We present dynamic density functional theory (DDFT) incorporating general inhomogeneous, incompressible, time-dependent background flows and inertia, describing externally driven passive colloidal systems out of equilibrium. We start by considering the underlying nonequilibrium Langevin dynamics, including the effect of the local velocity of the surrounding liquid bath, to obtain the nonlinear, nonlocal partial differential equations governing the evolution of the (coarse-grained) density and velocity fields describing the dynamics of colloids. In addition, we show both with heuristic arguments, and by numerical solution, that our equations and solutions agree with existing DDFTs in the overdamped (high friction) limit. We provide numerical solutions that model the flow of hard spheres, in both unbounded and confined domains, and compare with previously derived DDFTs with and without the background flow. [ABSTRACT FROM AUTHOR]

Under unsteady operating conditions in turbomachinery, the performance is unable to respond rapidly enough to follow characteristic curves for the steady condition. To design a reliable turbomachinery under unexpected unsteady conditions, we evaluated the dynamic transfer matrix of a three-dimensional centrifugal impeller. The working fluid is incompressible air. To make the current results more applicable in a broader sense such as pumps, all parameters and results were normalized. The experimental results showed a more significant negative slope in the unsteady performance curve compared to that in the steady performance curve. This was mainly caused by the phase delay of the pressure rise to the pulsating flowrate. We clarified the changes in gain and phase delay under unsteady conditions by conducting numerical simulations. The numerical results showed that the unsteady pressure rise was primarily generated by inertia and power terms in the unsteady energy conservation equation. The power term was predominantly influenced by the angular momentum flowrate difference and the change rate of angular momentum. Each term was quantitatively evaluated, and its contribution to the unsteady pressure rise was discussed. Within the range of frequencies tested in this study, the transfer matrix for the three-dimensional centrifugal impeller could be effectively approximated through a first-order lag approximation considering a series-connected derivative system. We believe that our findings can be extended to centrifugal pumps when disregarding the compressibility effects such as cavitation. [ABSTRACT FROM AUTHOR]

We show the existence of a weak solution for a system of partial differential equations describing the motion of a flexible solid inside a fluid: A nonlinear, viscoelastic, n-dimensional bulk solid governed by a PDE including inertia is interacting with an incompressible fluid governed by the (n-dimensional) Navier-Stokes equation for n ≥ 2. The result is the first allowing for large bulk deformations in the regime of long time existence for fluid-structure interactions. The existence is achieved by introducing a novel variational scheme involving two time-scales that allows us to extend the method of minimizing movements to hyperbolic problems involving nonconvex and degenerate energies. [ABSTRACT FROM AUTHOR]

The advent of distributed generation has brought with it a plethora of challenges for the nascent power systems that are being deployed on a large scale. Firstly, the majority of power electronic converters connected to the grid are in current source mode, which results in a lack of inertia and an inability to provide effective inertia or achieve damping support during fluctuations in grid frequency. Secondly, the issue of power quality, caused by the presence of harmonics, is becoming increasingly severe. This is particularly problematic in microgrids or systems with high line impedance, where harmonics can be amplified, thereby further compromising the stability of the power system. To address the deficiency in system inertia, numerous scholars are currently utilizing grid-forming (GFM) technology to achieve virtual inertia. In order to address the issue of system harmonics, it is possible to install active power filter (APF) devices at the point of common coupling (PCC), which serve to mitigate the effects of harmonics. This paper puts forth a proposal for the implementation of an APF with virtual inertia, based on PR + RC composite control. This composite control mechanism serves to enhance the harmonic suppression capabilities of the APF. The introduction of a frequency droop enables the capacitor voltage amplitude to be adjusted during fluctuations in system frequency, thereby achieving virtual inertia and providing active support for system frequency. The experimental results demonstrate that this strategy not only reduces the total harmonic distortion (THD) by 13% in comparison to PI control, indicating excellent harmonic suppression performance, but also allows the system to be inert, achieving positive results in suppressing frequency fluctuations during transients. [ABSTRACT FROM AUTHOR]

The overall motion performance of mechatronic machines depends heavily on proper knowledge of the machine's characteristics, among which the inertia. Moreover, the inertia of most multi-body mechanisms, for example, reciprocating slider-crank mechanisms, varies as a function of the machine position, thereby challenging optimal control. Nevertheless, the inertia's variation is sometimes not known accurately enough or changes over time due to, e.g. a production process or premature wear, forcing an online control/correction of the inertia profile. Therefore, earlier, the author developed a new computational-friendly online method based on a frequency-specific magnitude response to estimate the machine's position-dependent load side inertia, assuming good knowledge of all other machine properties. Yet, to guarantee accuracy, the maximum machine speed during estimation had to be strongly reduced, resulting in an undesirable longer motion time. Therefore, in this work, the failure mechanism of the earlier proposed estimator is analysed and overcome by intelligently separating estimation and motion signals. As a result, the estimator is no longer limited by the machine's motion speed but rather by a maximum in the inertia variation per signal excitation period and, thus, time. Moreover, given this limiting variation, a guideline was established to evaluate the new method's estimation quality. Finally, both in simulation and on a physical machine, by taking advantage of the newly proposed method, the minimal required estimation time is reduced significantly (up to 50% on the machine) without diminishing the estimation accuracy. [ABSTRACT FROM AUTHOR]

In this work, we discuss size-dependent and microinertia effects on the static and dynamic performances of a microscale model based on the microinertia-based modified couple stress theory, a non-classical continuum theory capable of capturing the behavior of size dependence and frequency dispersion characteristics. In the framework of the variational statement, a microscale structure model is developed and the governing equations of equilibrium as well as all boundary conditions for statics and dynamics are reformulated. The developed theory is imposed to tackle microstructure-dependent Timoshenko beam model in two distinct scale parameters: the material length scale parameter is utilized to determine the size dependence and the microinertia length scale parameter is employed to describe the higher-order microrotation relation. The generally valid closed-form analytic expressions are obtained and suitable for various formats of boundaries and mechanical loads. As case studies, the predicted trends agree with those observed within the framework of the modified couple stress theory. Results indicate that the material microlength scale parameter strengthens the static deformations, while the microinertia length scale parameter weakens the dynamic frequencies. In addition, boundary conditions are also an important aspect in statics and dynamics as well as the mechanical response predicted by non-classical continuum theories. [ABSTRACT FROM AUTHOR]

Atmospheric gravity waves have conventionally been studied and characterized using temperature and wind data from radiosondes. In this study we outline and adapt several previously established wave-detection methods for use with solely high-resolution position and velocity measurements from student-constructed GPS units. We consider both vertical and horizontal profiles, utilizing Fourier, hodograph, and polarization analyses, which primarily target low-frequency inertia gravity waves. Using eleven balloon flights over central Montana and New Mexico conducted during 2021–2023 summers by the Balloon Outreach Research Exploration and Landscape Imaging Systems (BOREALIS) program, we show the validity of our procedures in successfully locating inertia gravity waves and finding wave parameters consistent with those of existing studies. A total of eleven waves were found in seven of the flights, with the same wave likely showing up more than once in two flights. The detected waves generally had intrinsic frequencies of one to two times the Coriolis frequency, spanned vertical wavelengths between one and two kilometers, and had periods of between 10 and 15 h. [ABSTRACT FROM AUTHOR]

In recent years, the innovative design of metamaterials and the study of bandgap characteristics have become the focus of research. The flexible setting of small added mass in locally resonant metamaterials can effectively regulate bandgap characteristics and wave transmission. In this paper, a novel tunable piezoelectric metamaterial beam on periodic elastic foundation is proposed for realizing the wider bandgap region and the stronger attenuation capability. Based on Timoshenko beam theory, wave equation of the metamaterial beam considering the piezoelectric and the inertial amplification effects is obtained from the transfer matrix method, and the calculational results are compared to that of numerical simulation. The results show that periodic elastic foundation can improve the overall stiffness of the structure, and the bending wave attenuation frequency domain will broaden with the increase of the elastic foundation stiffness. The metamaterial beam exhibits the strong wave attenuation in the bandgap induced by external negative capacitance shunt circuit, and the wave transmission loss is improved about 20 dB than the short circuit case. The coupling effects between the local resonance and the inertial amplification mechanism can cause the coupled bandgaps, which expand the original bandgap range by at least 25%. In addition, the coupled bandgaps boundary can be extended to lower frequencies by adjusting the angle of rigid rod and the additional mass separately, resulting in broadband wave attenuation. This work will provide valuable ideas for the design of advanced smart materials and structures in the field of vibration and noise reduction. • A novel tunable piezoelectric metamaterial beam on periodic foundation is proposed. • Bandgaps with tunability and strong attenuation are realized by the external shunt circuit. • Bandgap coupling effects are achieved by combining piezoelectric shunt technique and inertial amplification mechanism. • Significant parameters of the inertia amplication structure can effectively control wave propagation and transmission. [ABSTRACT FROM AUTHOR]

This work proposes a penalty 20‐node hexahedral element for size‐dependent electromechanical analysis based on the consistent couple stress theory. The nodal rotation degrees of freedom (DOFs) are used to approximate the mechanical rotation, meeting the C1 requirement in a weak sense by using the penalty function method, and to effectively enhance the standard isoparametric interpolation for determining the displacement test function. The normalized stress functions that satisfy the relevant equilibrium equation and strain compatibility equation a priori are employed to formulate the stress trial function. Since the element has only three displacement, three rotation and the electric potential DOFs per node, it has relatively simple formulation and can be readily incorporated into the existing finite element program. Several benchmarks are examined and the results demonstrate that the new element has good numerical accuracy and captures the size dependence effectively. In addition, the influence of the micro‐inertia on electromechanical dynamic responses of flexoelectric solids at small scale are analyzed using the proposed element. It is shown that the nature frequency decreases with the increase of micro‐inertia and in general, the influences are more obvious on higher order modes. [ABSTRACT FROM AUTHOR]

The Challenge to stabilize the grid frequency increases with the increment of renewable energy resources. System inertia/frequency control is a significant concern for maintaining system stability with a fast response time during the load transition. This manuscript proposes surface-mounted permanent magnet synchronous generator (SPMSG) based wind energy conversion system (WECS) with a frequency support DC-link controlling loop and a converter protective DC-link voltage-controller frequency support system. To achieve power exchange, the frequency control system (FCS) for the SPMSG-based wind turbine supports the grid-side virtual inertia. The DC-link voltage is disturbed during the load transition to maintain the frequency, while the electrolytic capacitor requires extra care regarding the DC bus voltage. This manuscript incorporates the FCS system with a supercapacitor and dynamic voltage limiter to avoid additional care of the DC bus voltage. A detailed analysis of system frequency with the additional load increment, normal connected load decrement, and various fault scenarios has been done. The proposed system is compared with the existing virtual inertia support (VIS). The simulation results show that the proposed frequency control system-based VIS efficiently limits the frequency deviations & DC-link voltage. The results are verified in the OPAL-RT 4510 real-time simulator environment to ensure the efficacy of the proposed system. [ABSTRACT FROM AUTHOR]

This paper aims to highlight the idea of re-reading Albanian literature and re-dimensioning it into an authentic literary system, unaffected by the extra-literary interventions from which it suffered in the period of socialist realism. Albanian literature needs not only the return of literature banned for political and ideological views, but also the fair re-reading of works that were not banned from circulation, but were misinterpreted, according to the political aspects of the time. Among other things, this is where Migjen's work comes into play. It demands to be read and interpreted according to the most advanced literary thought, in a time of complete freedom. Can we deconstruct the official literary thought that has dominated for several decades and whose inertia still continues? What are the ways to do this? These are the main questions that will guide us while working with this paper. [ABSTRACT FROM AUTHOR]

Islanded microgrids with low-inertia distributed energy resources (DERs) are prone to frequency fluctuations. With the increasing integration of DERs in microgrids, the complexity of control and stability has also increased. Moreover, the integration of DERs into microgrids may result in a power imbalance between energy supply and demand during sudden changes in load or energy generation. This can cause frequency variations in the microgrid, which could have disastrous consequences such as equipment damage or even blackouts. This paper proposes a control strategy to ensure the efficient operation of an islanded hybrid microgrid consisting of a PV generator, battery energy storage system (BESS), and emergency diesel generator. According to Energy Exchange Model proposed in this paper, the hybrid system presented operates independently without being connected to the electrical grid, where the PV system and BESS act as the main energy sources, while the emergency diesel generator provides active power backup with voltage and frequency regulation. The novel in this paper is also that DER aids in frequency regulation during active power transients by delivering and absorbing active power in accordance with the inverter's suggested P droop control strategy. In this way inverter droop control decreases system frequency nadir emulating so called "synthetic inertia". To design both the islanded hybrid system and the proposed control strategy, the MATLAB/Simulink environment is utilized. Based on the results, it can be concluded that the analyzed microgrid system is capable of maintaining stability and operating efficiently in a range of operating conditions. [ABSTRACT FROM AUTHOR]

A gradient-type theory with flexomagnetic/flexoelectric and micro-inertia effects is used to study Love wave propagation in the layered magneto-electro-elastic structures. Two waveguide structures are considered: flexo-piezoelectric layer deposited on the piezomagnetic half-space and flexo-piezomagnetic layer resting on the piezoelectric half-space. The dispersion equations are numerically investigated for the magneto-electrically open and short circuit conditions. It is concluded that the profile of dispersion curves depends on the material composition of the waveguide structure, the guiding layer thickness, and the relative values of flexomagnetic/flexoelectric coefficients and the micro-inertia length-scale parameter. The obtained results are helpful for mathematical modeling of new small-sized acoustic devices. [ABSTRACT FROM AUTHOR]

Plasma waves with helical wavefront are studied theoretically from the quantum mechanical viewpoint and are shown to produce a spinning motion of a charged macroparticle in a complex plasma. The electrostatic helical perturbations are described by the wave function for a Laguerre–Gaussian beam mode with the radial/angular mode numbers n/ l. The interaction and the transfer of angular momentum from the wave to a particle are analyzed by the method of second quantization with the help of the Feynman diagram. Laguerre function, instead of the Born approximation, is introduced to describe plasma waves with helical wavefront. A pair of dust particles in a complex plasma exchange a quasiparticle (virtual plasmon) resulting in the acquisition of angular momentum, which makes a dust particle spin in motion with rotational frequency Ω ϕ . The resonance condition ω − k v z − l Ω ϕ = 0 and the conservation of angular momentum I d Ω ϕ = l ℏ determine the rotational frequency, where ω and k are frequency and axial wave number of the helical wave, and v z and I d are axial velocity and the moment of inertia of a dust particle. [ABSTRACT FROM AUTHOR]

In a recent paper [Hassager, J. Rheol. 64, 545–550 (2020)], Hassager performed an analysis of the start up of stress-controlled oscillatory flow based on the general theory of linear viscoelasticity. The analysis provided a theoretical basis for exploring the establishment of a steady strain offset that is inherent to stress controlled oscillatory rheometric protocols. However, the analysis neglected the impact of instrument inertia on the establishment of the steady periodic response. The inclusion of the inertia term in the framework is important since it (i) gives rise to inertio-elastic ringing and (ii) introduces an additional phase shift in the periodic part of the response. Herein, we modify the expressions to include an appropriate inertial contribution and demonstrate that the presence of the additional terms can have a substantial impact on the time scale required to attain the steady state periodic response. The analysis is then applied to an aqueous solution of wormlike micelles. [ABSTRACT FROM AUTHOR]

Wheelchair ergometers are widely used in research, clinical practice, and sports environments. The majority of wheelchair ergometers are roller systems that allow for wheelchair propulsion in the personal wheelchair on one or two (instrumented) rollers. Oftentimes these systems are only statically calibrated. However, wheelchair propulsion is dynamic by nature, requiring a dynamic validation process. The aim of the current project was to present a low-cost portable system for the dynamic metrological verification of wheelchair roller ergometers, based on an instrumented reference wheel. The tangential force on the roller is determined, along with its uncertainty, from the reference wheel properties, and compared with the force measured by the ergometer. Uncertainty of this reference wheel system was found to be lower than the one of the ergometer used, indicating that this novel approach can be used for the metrological verification of ergometers. [ABSTRACT FROM AUTHOR]

Dynamic investigation of vehicle collisions with stationary obstacles in most cases concerns solutions to complex tasks related to identification of occupant position in the vehicle. The focus of the study is on how forces of inertia change their magnitude and direction during car motion. This requires specific analysis done by dividing vehicle trajectory into separate stages according to certain indicators, such as free motion, impact process, postimpact residual motion. Particular attention has been paid to the impact itself, in which the forces of inertia are the most intense, and their magnitude and direction change abruptly. Solution to Cauchy problem has been found, in which initial kinematic parameters of the crash process are considered, satisfying the kinematic values at rest position. Dynamic analysis of the impact phase of a vehicle-fixed barrier collision has been performed by the finite element method using the software product Abaqus/Explicit. [ABSTRACT FROM AUTHOR]

The increasing use of renewable energy sources in place of conventional generation units is leading to a reduction in onshore inertia and to the development of offshore wind park grids connected by multiple high-voltage direct current (HVDC) connections to the onshore alternating current (AC) grid. For AC-side meshed offshore grids with voltage-source converter (VSC) and diode rectifier unit (DRU) HVDC connections towards onshore grids, this study focuses on the energetic feasibility of synthetic inertia (SI) and primary control reserve (PCR) contributions triggered locally at the onshore converters of both connection types. To this end, the obstacles preventing contributions for VSC HVDC connections and the mechanisms allowing contributions for DRU HVDC connections are identified first. Based on these findings, the article proposes an enhancement of the offshore HVDC converter controls that is continuously active and allows locally triggered onshore contributions at all onshore HVDC converters of both connection types without using communication and requiring only minimal system knowledge. Additional simulations confirm that, although the enhancement is continuously active, the operational performance of the offshore HVDC converter controls for normal offshore grid operation and its robustness against offshore AC-side faults are not affected. [ABSTRACT FROM AUTHOR]

This paper proposes an approach for thermal analysis of articulated systems subject to boundary and motion constraints (BMC). The solution framework is designed to capture large temperature fluctuations, significant change in geometry due to reference configuration and deformations, and geometric nonlinearity due to articulated mechanical systems (AMS) large displacements and spinning motion. Thermal-expansion displacements, which do not contribute to rigid-body translations, are determined from thermal stretch of position-gradient vectors using a new sweeping matrix technique designed to eliminate dependence on translational rigid-body modes. A new quadratic thermal-energy kinetic form is defined and used to formulate a dynamic force vector that accounts for thermal transient and inertia effects. Nodal thermal displacements are used in formulating AMS differential/algebraic equations (DAEs), and consequently, thermal stresses due to BMC equations are automatically accounted for based on integration of thermal analysis and Lagrange-D'Alembert principle, which is the foundation of computational multibody system (MBS) algorithms. The approach used in this study for large-displacement constrained and unconstrained thermal expansions is based on multiplicative decomposition of position-gradient matrix, instead of strain additive decomposition, for solution of thermo-elasticity problems. Four configurations are used to define continuum geometry and displacements: straight configuration, reference configuration, thermal-expansion configuration, and current configuration. The proposed approach allows applying thermal loads during constrained large displacements, does not impose restrictions on the choice of thermal coefficients, captures reference-configuration geometry and change in inertia forces due to temperature fluctuations, accounts for thermal displacement in formulating AMS nonlinear constraint equations, and allows for integration with MBS algorithms for the study of a wide range of thermo-elasticity problems. [ABSTRACT FROM AUTHOR]

In this research, an efficient thermal-stress coupling design method for a Chiplet-based system with a coaxial through silicon via (CTSV) array is developed by combining the support vector machine (SVM) model and particle swarm optimization algorithm with linear decreasing inertia weight (PSO-LDIW). The complex and irregular relationship between the structural parameters and critical indexes is analyzed by finite element simulation. According to the simulation data, the SVM model is adopted to characterize the relationship between structural parameters and critical indexes of the CTSV array. Based on the desired critical indexes of the CTSV array, the multi-objective evaluation function is established. Afterwards, the structural parameters of the CTSV array are optimized through the PSO-LDIW algorithm. Finally, the effectiveness of the developed method is verified by the finite element simulation. The simulated peak temperature, peak stress of the Chiplet-based system, and peak stress of the copper column (306.16 K, 28.48 MPa, and 25.76 MPa) well agree with the desired targets (310 K, 30 MPa, and 25 MPa). Therefore, the developed thermal-stress coupling design method can effectively design CTSV arrays for manufacturing high-performance interconnect structures applied in Chiplet-based systems. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An analysis of the influence of inertia forces and ponderomotive forces on the destabilization of the flow of viscous fluids in the hydrodynamic initial section is given. Cases of flow of viscous, anomalously viscous and electrically conductive liquids are considered; the degree of influence of mass forces on the destabilization of the flow is estimated. As applied to the flow in the hydrodynamic initial section, the degree of influence of inertia forces from convective acceleration and forces with a magnetic nature can be different. Inertia forces stimulate the accelerated movement of the fluid, and in the case of forces with a magnetic nature, ponderomotive forces contribute to deceleration, which is confirmed by the results of studies of the velocity field. Recommendations are given for calculating the length of the hydrodynamic initial section in the presence of mass forces with different nature. [ABSTRACT FROM AUTHOR]

With a simple structure and control method, the piezo-inertia actuator is a preferred embodiment in the field of microprecision industry. However, most of the previously reported actuators are unable to achieve a high speed, high resolution, and low deviation between positive and reverse velocities at the same time. To achieve a high speed, high resolution, and low deviation, in this paper we present a compact piezo-inertia actuator with a double rocker-type flexure hinge mechanism. The structure and operating principle are discussed in detail. To study the load capacity, voltage characteristics, and frequency characteristics of the actuator, we made a prototype and conducted a series of experiment. The results indicate good linearity in both positive and negative output displacements. The maximum positive and negative velocities are about 10.63 mm/s and 10.12 mm/s, respectively, and the corresponding speed deviation is 4.9%. The positive and negative positioning resolutions are 42.5 nm and 52.5 nm, respectively. In addition, the maximum output force is 220 g. These results show that the designed actuator has a minor speed deviation and good output characteristics. [ABSTRACT FROM AUTHOR]

System kinetic inertia is declining due to the rapid replacement of synchronous generators (SG) by renewable power generations (RPG). To maintain grid inertia, this paper proposes a generic synthetic inertia (GSI) scheme for RPGs, enabling inertial response by a supercapacitor (SC) bank integrated with a voltage source inverter (VSI) DC link via a DC/DC converter. A GSI control loop is developed for the DC/DC converter controller to vary the SC voltage along with the grid frequency for power exchange following the SG swing equation. The GSI scheme realizes plug‐and‐play advantage without modifying the RPG original system. Small‐signal stability analysis is carried out to optimize the GSI controller parameters. The performance of the GSI scheme is evaluated using a modified IEEE 39‐bus test system. [ABSTRACT FROM AUTHOR]

An analytical and numerical Fourier transform based approach is presented to investigate the space-time dependence for the longitudinal velocity resulting from the longitudinal impact force excitation of viscoelastic rods with lateral inertia. A one-dimensional dissipative Rayleigh-Love wave equation including material memory, dissipation, and/or transverse effects due to Poisson coupling is developed from a generic model of the time dependent stress strain relationship for the rod material. A Gaussian signal with a suitable time scale is used to represent the hammer impact forces. Fourier transform, standing wave, and modal methods are utilized to develop analytical solutions for the longitudinal velocity resulting from the impact excitation of semi-infinite and finite length free-free elastic rods with no transverse effects to provide a baseline and segue to analogous results for viscoelastic rods with transverse effects. Numerical results from an FFT approach are presented to illustrate the effects of material losses and transverse effects on attenuation and dispersion in viscoelastic rods using the Kelvin-Voigt model for the constitutive equation of the rods. [ABSTRACT FROM AUTHOR]

With the large-scale centralized penetration of renewable energy represented by wind turbine and photovoltaic power generation, the equivalent inertia and synchronous torque of traditional power grids have decreased, which is worsening the frequency dynamics and threatening the stability and reliability of power grids. Virtual synchronous generators (VSGs) are a type of grid-friendly inverter in microgrids (MGs) that mimic rotational synchronous generators (SGs) to maintain system stability with the increasing penetration of power electronic converters. In this paper, the stability analysis method of one type of VSG, synchronverter, is investigated based on internal voltage dynamics. The torque components affecting the stability mechanism of synchronizing, inertia, and damping torque is introduced, which offers a physical insight into transient stability and dynamic performance. Insufficiency in either damping or synchronizing torque would increase the unstable possibility. The characterization method of stability mechanisms can be illustrated by the phasor diagram of synchronverter internal voltage. Some cases under different disturbances which change the pattern of synchronizing and damping torque and in turn influence the internal voltage dynamics of synchronverters, are also discussed. In addition, an auxiliary correction control loop is proposed and added in the synchronverter control loop to enhance the robustness of the synchronverter against disturbances. The tunable coefficient of the correction loop is analyzed based on the internal voltage method. Simulation results verify the validity of the internal voltage stability method in synchronverters. [ABSTRACT FROM AUTHOR]

We examine if Saturn's moon Tethys may be an ocean world by assuming that spatial variations in tidal heating are responsible for thickness or temperature variations in an isostatic ice shell, which manifests as surface topography. Because patterns of tidal heating depend on average ice shell thickness and whether the shell overlies a rigid or liquid layer, we can use Tethys' long‐wavelength topography to infer its interior structure. We test a wide range of assumed parameters to hone in on the characteristics of Tethys that produce self‐consistent and physically plausible interior models. To verify our technique, we apply it to Enceladus and recover the signature of a sub‐surface global ocean with an appropriately thick ice shell and moment of inertia. Our best‐fit Tethys models require Pratt isostasy and obliquity tides, with a normalized moment of inertia 0.340–0.345 and an average surface heat flux 1–2 mW m−2. The best‐fit basal heat flux distribution indicates that Tethys does not have an ocean. The total power inferred (4–8 GW) to produce Tethys' shape from tidal heating indicates either a highly dissipative interior or an obliquity higher than previously estimated. The topography may also be a relic of a warmer past when the obliquity was higher. Plain Language Summary: Oceans have been discovered beneath the surfaces of many icy moons, the most famous among them being Europa and Enceladus. We examine if Tethys, a moon of Saturn's, may also have a sub‐surface ocean. We cannot answer this question using the techniques employed at other worlds, as those required close flybys of spacecraft. However, the movement of Tethys within Saturn's gravity field causes tidal heating in Tethys' interior. The exact spatial distribution of tidal heating can indicate if there is a liquid or rigid layer beneath Tethys' ice shell, as well as how thick this ice shell is. This tidal heating can be inferred from the large scale topography (essentially, the shape) of Tethys. We iterate through assumed values for a series of parameters to find a scenario that best explains Tethys' interior, finding that it does not have an interior ocean. However, the amount of tidal heating we infer indicates that Tethys should have a higher tilt relative to its orbit than is currently predicted. Given how long heat takes to conduct through ice, we may be seeing the effect of a high tilt from a billion years ago. Key Points: We can infer patterns of tidal heating from long wavelength topography of an icy satelliteThe tidal heating pattern can indicate a moon's internal structureTethys has no sub‐surface ocean, but could have had a larger obliquity in the past [ABSTRACT FROM AUTHOR]

From technical and economical viewpoints, an all‐dc offshore wind farm (OWF) with a high‐voltage direct‐current (HVDC) connection, which is also known as HVDC‐connected all‐dc OWF, is the future trend for offshore wind energy applications. However, due to the decoupling effect of power converters, all‐dc OWF cannot directly provide short‐term frequency support for the onshore ac gird, that is, primary frequency response and inertia support. To address this issue, this paper presents a distributed model predictive control (DMPC) scheme for all‐dc OWF. By directly suppressing the voltage deviation and the rate of change of voltage of the offshore dc collection network, this scheme indirectly decreases the frequency deviation and the rate of change of frequency (RoCoF) of the onshore ac grid. Meanwhile, the scheme ensures the stability of wind turbines in all‐dc OWF during the frequency events. Considering a large number of wind turbines in the OWF, the corresponding optimization problem is solved in a distributed way using the alternating direction method of multipliers (ADMM), thus reducing the computational burden. Simulations including the performance comparison with droop control validate the effectiveness of this scheme. [ABSTRACT FROM AUTHOR]

Copyright of Latin-American Journal of Physics Education is the property of Latin-American Physics Education Network and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As a diffusionless phase transformation, martensite evolves at the speed close to sound, with its kinetics and morphology dominated by the mechanical energy. However, the mechanism of martensitic phase transformation with the consideration of inertia is rarely investigated. This paper presents a multiphase-field model, where the transformation strain in martensite performs as the mechanical wave source, and in return the kinetic energy contributes to the driving force for phase transformation. As a result, the mechanical fields, i.e., the stress and the velocity, are derived according to the increment of the transformation strain. The propagation direction of the mechanical wave is corrected by considering the growth of the martensitic nucleus. With the 1D and 2D analysis, as well as the comparison against 2D static case, the mechanism of martensitic phase transformation is investigated, and the advantage of mechanical model accounting for inertia effects is illustrated. [Display omitted] • A multiphase-field model including dynamic mechanics is proposed. • The transformation strain in martensite acts as a mechanical wave source. • The kinetic energy contributes to the driving force. • The mechanism of martensitic phase transformation is investigated in 1D and 2D cases. • The multiphase-field model with dynamic mechanics is more accurate than static. [ABSTRACT FROM AUTHOR]

Nano-scale wave dispersion beyond the First Brillouin Zone is often observed as descending branches and inflection points when plotting frequency or phase velocity against the wave number. Modeling this with discrete chain models is hampered by their restricted resolution. A continuum model equipped with higher-order inertia gradients is here developed as a suitable and versatile alternative. This model can be derived from discrete chain models, thereby providing a lower-scale motivation for the higher-order gradient terms. The derived gradient model is without free parameters, as the material constants are calculated a priori by minimising the error with respect to the discrete chain response. Unlike asymptotic approximations that provide a best fit for vanishing wave numbers, the error is here minimised over the entire range of reduced wave numbers 0 to 1, which leads to a much improved accuracy beyond the First Brillouin Zone. The new gradient model has been validated against (i) phonon dispersion curves measured through neutron scattering experiments in bismuth, aluminum, and nickel and (ii) Molecular Dynamics (MD) flexural wave propagation simulations of carbon nanotubes. The model captures all qualitative aspects of the experimental and MD dispersion curves without requiring a bespoke curve fitting procedure. With the exception of one set of MD results, the accuracy of the gradient model is very good. [ABSTRACT FROM AUTHOR]

Interfacial reactions and underlying atomic mechanisms between Ta contacts (space group I m 3 ¯ m) and thermoelectric Bi2Te3 (space group R 3 ¯ m) are studied experimentally and theoretically. A Ta/Bi2Te3 mixture is found to be inert up to the melting point of Bi2Te3 (∼589 °C) based on calorimetry and interfacial composition analyses. This can be understood using density functional theory. Bi and Te adatoms hop across a close-packed Ta(110) surface in the <111>, <110>, and <100> directions with the highest dwelling time on equilibrium (fourfold hollow) sites, but they do not exchange with Ta surface atoms. To identify the electronic structure fingerprint of Ta(110) inertness, the adsorption energies and electron density distributions are calculated for the Bi2Te3 constituting atoms and possible dopants (15 elements) stemming from C, N, and O groups. C, N, O, and S strongly adsorb to Ta(110), exhibiting enhanced reactivity. We propose that these four species can initiate exchange diffusion with Ta due to ionic interactions between Ta and the adsorbates. Our results imply that elements with a high electronegativity should be avoided in Bi2Te3 doping because interfacial interactions may occur, degrading its stability and transport properties. [ABSTRACT FROM AUTHOR]

Interfacial reactions and underlying atomic mechanisms between Ta contacts (space group I m 3 ¯ m) and thermoelectric Bi2Te3 (space group R 3 ¯ m) are studied experimentally and theoretically. A Ta/Bi2Te3 mixture is found to be inert up to the melting point of Bi2Te3 (∼589 °C) based on calorimetry and interfacial composition analyses. This can be understood using density functional theory. Bi and Te adatoms hop across a close-packed Ta(110) surface in the <111>, <110>, and <100> directions with the highest dwelling time on equilibrium (fourfold hollow) sites, but they do not exchange with Ta surface atoms. To identify the electronic structure fingerprint of Ta(110) inertness, the adsorption energies and electron density distributions are calculated for the Bi2Te3 constituting atoms and possible dopants (15 elements) stemming from C, N, and O groups. C, N, O, and S strongly adsorb to Ta(110), exhibiting enhanced reactivity. We propose that these four species can initiate exchange diffusion with Ta due to ionic interactions between Ta and the adsorbates. Our results imply that elements with a high electronegativity should be avoided in Bi2Te3 doping because interfacial interactions may occur, degrading its stability and transport properties. [ABSTRACT FROM AUTHOR]

This paper defines an agile power system as a system in which the physical structure can change due to the connection/disconnection of subsystems, such as microgrids. These systems pose serious difficulties in their operations and control. Some of these challenges are reviewed. One operational issue is the energy balancing or the load frequency control problem when microgrids with a low inertia are connected to the main grid. The paper identifies the need for new rules of operation. Furthermore, in this paper, decentralized and data-driven voltage control designs are proposed, compared and illustrated on a microgrid. They take into consideration the structure and the usage of the large amount of data provided by the proliferation of sensors. [ABSTRACT FROM AUTHOR]

Study of the heat transfer performance of twisted tubes have been limited to forced convective conditions (inertia-dominated flow) without studying the effect of different isothermal wall temperature (buoyancy force). Therefore, this work investigated the flow and heat transfer behavior of a twisted square tube of a varying pitch length at different mixed convective regimes. The model continuity, momentum, and energy equations were solved using the finite volume technique. The numerical model setup was validated using experimental results and a satisfactory result was achieved. The result shows that the twisted square tube performs better than the smooth tube subjected to the same conditions. The heat transfer rate and drag coefficient increase with decreasing twist pitch length. In addition, the result shows that increment of buoyancy force, while inertia force is kept constant leads to a high reduction of drag as compared to increasing inertia force, while buoyancy force is kept constant. Overall, a 15% increase (at Ri=1) is obtained in the drag coefficient and a 13% increase (at Ri=0.5) is obtained in the heat transfer rate in the 100 mm twist pitch length as compared to the 600 mm twist pitch length. [ABSTRACT FROM AUTHOR]

The Indian Regional Navigation Satellite System provides accurate positioning service to the users within and around India, extending up to 1500 km. However, when a receiver encounters a Continuous Wave Interference, its positioning accuracy degrades, or sometimes it even fails to work. Wavelet Packet Transform (WPT) is the most widely used technique for anti-jamming in Global Navigation Satellite System receivers. But the conventional method suffers from threshold drifting and employs inflexible thresholding functions. So, to address these issues, an efficient approach using Improved Particle Swarm Optimization based Parametric Wavelet Packet Thresholding (IPSO-PWPT) is proposed. Firstly, a new parameter adaptive thresholding function is constructed. Then, a new form of inertia weight is presented to enhance the performance of PSO. Later, IPSO is used to optimize the key parameters of WPT. Finally, the implementation of the IPSO-PWPT anti-jamming algorithm is discussed. The performance of the proposed technique is evaluated for various performance metrics in four jamming environments. The evaluation results manifest the proposed method's efficacy compared to the conventional WPT in terms of anti-jamming capability. Also, the results show the ability of the new thresholding function to process various signals effectively. Furthermore, the findings reveal that the improved PSO outperforms the variants of PSO. [ABSTRACT FROM AUTHOR]

The origin of Saturn’s ~26.7° obliquity and ~100-million-year-old rings is unknown. The observed rapid outward migration of Saturn’s largest satellite, Titan, could have raised Saturn’s obliquity through a spin-orbit precession resonance with Neptune. We use Cassini data to refine estimates of Saturn’s moment of inertia, finding that it is just outside the range required for the resonance. We propose that Saturn previously had an additional satellite, which we name Chrysalis, that caused Saturn’s obliquity to increase through the Neptune resonance. Destabilization of Chrysalis’s orbit ~100 million years ago can then explain the proximity of the system to the resonance and the formation of the rings through a grazing encounter with Saturn. [ABSTRACT FROM AUTHOR]

Virtual synchronous generator (VSG)-based control approaches for AC machine drivers have attracted much attention in recent years. The contradiction between the strong motor loading capacity and the small DC voltage fluctuation is disregarded in previous studies. A larger virtual inertia is required to raise the torque gain and drive the motor with heavier loads, thus resulting in greater DC voltage variations. A systematic method is proposed for the optimal design of the virtual inertia for VSG-based motor starting systems to achieve the maximal motor loading capacity and the low DC voltage fluctuation in this paper. Firstly, the relationship between the virtual inertia and the loading capacity is revealed on the basis of the closed-loop analysis. Considering the DC voltage variation, the constraint on the maximal value of the virtual inertia is proposed from the energy-balance perspective despite the unknown contribution of the DC capacitors to the virtual inertia. To fully exploit the energy storage capacity of the DC capacitors and raise the upper limit of the virtual inertia under the same permitted DC voltage variation, a modified DC voltage reference is introduced. Extensive simulation and experimental results are presented to validate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

This study determines the inertial characteristics of bodies with probabilistic algorithms of the Monte Carlo type. To determine the mechanical moments of inertia in the case of three-dimensional bodies, the bodies are decomposed into simple bodies for which the moments of inertia are calculated, which are added to Steiner's relations. If the bodies have complex shapes to determine the moments of mechanical inertia, numerical or probabilistic algorithms can be used. This paper presents the main stages in the use of probabilistic algorithms for calculating moments of inertia and finally a program in MATLAB that allows determining the moments of inertia for bodies. [ABSTRACT FROM AUTHOR]

At the ground floor halls with an opening or more, the forces that are transmitted through the pillars due to gravitational loads (snow, and her weight) have high values. The gravitational difference that is transmitted to the pillars increases the greater the opening between the pillars is. In this Article we analyse the pillars of halls that are articulated recessed, because they have the advantage that the joints do not transmit bending moments. In the case of halls with large openings or halls rehabilitated or strengthened, to increase the critical load of loss of stability can increase the moment of inertia of the pillars from the recessed to the articulated end. In this Article, a parametric numerical study is presented, which establishes the critical load at a pillar with a variable section, depending on the length of the area where the moment of inertia of the slat has been increased. [ABSTRACT FROM AUTHOR]

In this paper, the design issue of effective damping of electromechanical swings in a medium voltage network with distributed generation by the use of a PSS2A type power system stabiliser is described. This stabiliser was installed in the generating unit with the highest rated power. Time constants of correction blocks, as well as the main gain, were determined by analyzing a single-machine system, generating unit - infinite bus. The time constants were calculated on the basis of the frequency-phase transfer functions both of the electromagnetic moment to the voltage regulator reference voltage and of the generator voltage to the voltage regulator reference voltage, under the assumption of an infinite and real value of the generating unit inertia time constant for various initial generator loads. The main stabiliser gain was calculated by analyzing the position, on the complex plane, of eigenvalues of the state matrix of the single-machine system, linearised around a steady operating point, at the changed value of this gain. [ABSTRACT FROM AUTHOR]

The paper presents a dynamic control approach using impedance control to reduce inertia factors acting on a Mecanum Wheeled Vehicle (MWV) on cornering roads. Inertia in a mobile vehicle is one of the issues that affect the safety and energy efficiencies of the vehicle, especially when maneuvering on cornering and confined paths. With reference to the problem statements in the dynamics analyses, velocity-based impedance control was proposed where the derived interaction translational forces on the vehicle that consider friction and touching forces on vehicle-terrain are controlled through the velocities of the vehicle. This study emphasized shaping the axial velocities input of the MWV for both longitudinal and latitude motions to control the sensitivity of the vehicle during cornering periods. The verification was done through several simulations on the proposed velocity-based impedance control on the MWV plant. The results show that the different forces on MWV axial motion were capable of reducing inertia via velocity input during the cornering period of maneuvering by increasing the stiffness and damping ratio of the controller at about 2 and 9 for stiffness x-axis and y-axis, respectively, and 15 and 10 for damping ration of the x-axis and y-axis respectively. Moreover, with the proposed controller, inertia on MWV can be controlled on the slippery road such as asphalt roads. This scenario has influenced the overall kinetic energy of the vehicle down to about 26%, thus, able to control the overdriven occurred on cornering road. [ABSTRACT FROM AUTHOR]

To reduce the horizontal vibration of a high-speed elevator car caused by the excitation of a guide rail more effectively, a differential magnetic suspension active guide shoe based on the principle of the differential magnetic suspension actuator is designed. Then the dynamic model of the active vibration damping system of the elevator car is established and an LQR controller is designed to reduce the horizontal vibration of the car. To search the weighting coefficient matrix of the LQR controller more efficiently, an algorithm named Jumping inertia Weight Particle Swarm Optimization (JWPSO) algorithm is proposed, and the frequently used fitness function verifies the optimization effect of the JWPSO algorithm. The weighting coefficient matrix of the LQR controller is optimized using the JWPSO algorithm. Finally, the impact of the JWPSO algorithm-optimized LQR controller is verified by MATLAB. The simulation result shows that the designed active vibration controller can effectively attenuate the horizontal vibration of the elevator car, and the control effect is significantly better than the LQR controller optimized by the GA algorithm and the H1 controller optimized by LMI. This paper provided a new method for horizontal vibration reduction of the high-speed elevator car. [ABSTRACT FROM AUTHOR]

The article integrates three theory fragments of organizational ecology using symbolic logic. It takes an earlier model that aligned inertia theory with Red Queen competition theory as a departure point and extends this model with temporal niche theory effects. The conflicting predictions between earlier and new theory phases are reconciled by applying the knowledge-updating feature of non-monotonic logic. The results indicate a rationale for discriminating between qualitative and quantitative aspects of environmental change, and also for telling apart ways of organizational adaptation based on effectiveness and efficiency. [ABSTRACT FROM AUTHOR]