Interaction Problems Research Articles

A generalized scalar auxiliary variable approach for the Navier–Stokes-[formula omitted]/Navier–Stokes-[formula omitted] equations based on the grad-div stabilization

In this article, based on the grad-div stabilization, we propose a generalized scalar auxiliary variable approach for solving a fluid–fluid interaction problem governed by the Navier–Stokes-ω/Navier–Stokes-ω equations. We adopt the backward Euler scheme and mixed finite element approximation for temporal-spatial discretization, and explicit treatment for the interface terms and nonlinear terms. The proposed scheme is almost unconditionally stable and requires solving only the linear equation with constant coefficient at each time step. It can also penalize for lack of mass conservation and improve the accuracy. Finally, a series of numerical experiments are carried out to illustrate the stability and effectiveness of the proposed scheme.

Religious and Educational Activities of the Tatars in the Turgai Region at the Second Half of the 19th – Beginning of the 20th Centuries

In the article the author for the first time analyzes legislative, religious and educational activities of Tatars in the Turgai region on the basis of archival, periodic, statistical sources. This ethnic minority activity is interesting from the point of view of studying the problem of interaction between the empire, the mobile diaspora and the local population in the context of the frontier modernization process. The aim of the study is to identify the main results of religious and educational activity of the Tatar population in the region. The author comes to the conclusion that the main directions of religious-educational work were missionary activities of Tatars in Kazakh auls, construction of mosques, functioning of mektebs and madrasas, theaters, libraries, public Muslim organizations, attempts to publish books, brochures and newspapers. Many of these initiatives were strongly opposed by the empire. The result of the activities of the Tatar population was not only the maintenance of ethno-cultural diversity, but also a versatile influence on the Kazakhs manifested in the religious, cultural, political sphere and in the formation of a multi-ethnic (Tatar-Kazakh) Muslim socio-cultural space of the empire, which became part of the global Islamic network community. The Tatars spread the ideas of Jadidism and became competitors of the Russians in familiarizing the local population with European culture and pedagogy. The article is intended for specialists in the field of history of Kazakhstan, Islam, Tatars, national policy of the Russian Empire.

Identifying interaction boundary of inverter-based generation in assessing system strength of power grids using relative electrical distance concept

The increasing use of inverter-based generation (IBG) in power grids raises concern about system strength. This is partly due to the inherent interactions among multiple IBGs in close proximity to one another. This paper proposes an approach to identifying the existential boundary of interaction in a network using the relative electrical distance (RED) concept. The mathematical formulation of the RED concept to address the interaction problem among the IBGs involved utilising the power system network’s admittance matrix to capture its structural characteristics. An interaction matrix derived from the RED values of all IBG pairs was then developed to identify the interacting IBG groups. The proposed approach was demonstrated using the IEEE 39-bus system and a practical 72-bus Nigerian power grid. Results showed that RED values effectively group interacting IBGs, with values closer to 0 signifying higher interaction levels, values closer to 1 indicating lower interaction, and a value of 1 denoting no interaction. Time-domain simulations confirmed the accuracy of the approach, demonstrating that the effect of control interaction propagates proportionally to neighbouring IBGs based on RED values. However, fault currents can influence the impact of control interactions. This approach, which requires less computational effort, provides a quick identification tool for potential areas of concern based on the degree of interaction, enhancing the reliability of power grids with high IBG penetration.

“You should have addressed it directly”: the ideals and ideologies of managing interaction problems in healthcare work

PurposeAn “open communication culture” in the workplace is considered a key contributor to high-quality interaction and providing means to address problems at work. We study how the ideals of “open communication” operate in healthcare.Design/methodology/approachWe use discourse analysis to investigate the audio-recorded data from 14 workshop team discussions in older people services.FindingsWe found four imperatives concerning the interactional conduct of their colleagues in problematic situations that nursing professionals prefer: (1) Engage in direct communication and avoid making assumptions, (2) Address problems immediately, (3) Deal directly with the person involved in the matter and (4) Summon the courage to speak up. Through these imperatives, the nursing professionals invoke and draw upon the “open communication” discourse. Although these ideals were acknowledged as difficult to realize in practice and as leading to experiences of frustration, the need to comply with them was constructed as beyond doubt.Practical implicationsWorkplace communication should be enhanced at a communal level, allowing those with less power to express their perspectives on shaping shared ideals of workplace interaction.Originality/valueThe expectation that an individual will simply “speak up” when they experience mistreatment by a colleague might be too much if the individual is already in a precarious position.

Design of railway simulation training system based on WebGL

Abstract In order to solve the problems of poor interaction with students and insufficient practicality in the previous railway freight station operation training, this article developed a training system based on WebGL technology that can interact with students and truly display the operation situation of the freight yard. This system is based on the Unity3D engine and WebGL technology. It imports 3D models to build large map scenes, and introduces functions such as cargo bundling and map roaming. The complete designed system is published to the Web through WebGL technology. After experimental analysis, the parking lot training system has solved the problems of poor practicality, little interaction, low efficiency, and narrow coverage in previous teaching. It has promoted the standardization and standardization of training students’ future work, and has effectively improved the professionalism of parking lot managers.

Time domain characterization of nonstationary low-Mach number aeroacoustic sources using principal component analysis.

This paper presents the use of principal component analysis (PCA) for time domain microphone array denoising to characterize an impulsive aeroacoustic source, which is illustrated with the aeroacoustic emission caused by a vortex ring/edge interaction. Prior studies have used signal processing approaches that required assumptions about the source directivity or user intervention at low signal-to-noise ratio (SNR) conditions. In this context, PCA, a matrix decomposition tool which identifies the most common features across an ensemble of observations, provides a data-driven (hands-off) approach to signal processing. For microphone array time series, particular attention is paid to the temporal alignment of the signals to facilitate PCA. A time domain approach is necessary when sources are impulsive and nonstationary. Two such signal arrangements are discussed in this work. Results from this method are in good agreement with theory, validated by prior results using an ensemble averaging approach requiring user support. Furthermore, the results of this method are improved when compared to the ensemble averaging approach without user intervention. A SNR limit is identified where PCA becomes less effective for the vortex/edge interaction problem. This SNR limit is intended to aid in the design of similar future experiments.

Series solution and its extension for the nonlinear flow response of soft hair beds

In nature and engineering applications, flexible fiber beds covering biological surfaces can play a role in reducing resistance. These fibers deform under the action of fluids, and this deformation affects the fluid flow state, forming a complex fluid–solid interaction phenomenon. To quantitatively analyze these issues, the physical model is simplified. We focus on the deformation of a soft hair bed caused by Stokes flow. Additionally, we study the deformation of a single hair under Stokes flow in greater detail. The deformation problem of an elastic single fiber in a channel caused by Stokes flow can be described by a nonlinear integral equation. We have obtained a new series solution, which has been compared with the previous perturbation method to verify the accuracy and effectiveness of the series solution. Meanwhile, we have further provided an extended form of flexible fiber deformation through experimental fitting. This fluid–solid interaction problem involves multiple fields and is very important in many natural and engineering systems. The research in this paper can not only help us better understand complex phenomena in nature but also delve into the interaction mechanism between fluids and solids, providing a theoretical basis for future scientific research and engineering applications.

Interaction leads to symmetry breaking in an array of cantilever plates in oscillatory cross flow

By using a computational model based on the immersed-boundary framework, a new mode of symmetry breaking is discovered in a fluid–structure interaction problem featuring an array of cantilever plates in a cross flow whose strength and direction varies sinusoidally with time. Specifically, within the physical parameters considered in this study, the motion of a single plate remains symmetric, whereas a system containing multiple plates can move asymmetrically so that the symmetry-breaking instability comes from fluid-dynamic interactions among individual plates. Further examination suggests that vortices shed from the free ends of the plates play an important role. Indeed, symmetry breaking occurs only when these vortices are sufficiently strong and when the distance between plates lies within certain range. If the distance is too small, a vortex shed from one plate can only stay in the gap between this plate and its neighboring plate for a short time so that it does not have the chance to interact extensively with the neighbor. On the other hand, if the distance is too large it is also difficult for this vortex to interact with the neighbor since it has to travel a long distance to reach there while the background flow keeps changing its direction. In either case, the system does not display asymmetric behavior.

Interaction of public administration and mass media in the context of digitalisation: problem statement

The article considers the current topic of interaction between public administration and mass media in the context of digitalisation. Digitalisation is defined as a glob -al trend changing socio-political reality. The concepts of “mass media” and “mass communication” are analysed in detail, and the features of their cooperation while expanding digital audience are revealed. In the realities of the 21st century, when digita lisation has a significant impact, the state transforms its functions, starting to actively interact with society and citizens, creating equal relations in the updated political system. An important link that unites information is mass media which closely cooperates with state authorities and the entire management system. Through the media, government agencies coordinate the efforts of various social groups and organisations without coercion, defining the main directions and strategies of socio-political initiatives and actions. The article highlights the use of the mass media as a political tool and a way to organise a dialogue between the state and civil society. It also analyses the influence of the mass media as the fourth branch of government. The author concludes that it is necessary to comprehensively study the problem of interaction between public administration and mass media for more effective functioning of both institutions. This means that in the context of digitalisation, there is a need to consider changes in the media sphere and develop new approaches to media policy, given modern challenges and trends.

PSYCHOLOGICAL ANALYSIS OF PEDAGOGICAL SITUATIONS OF DIFFICULT INTERACTION

Background. The relevance is due to the role of the educational environment in the formation of a culture of relationships and the need to reduce negative excesses in society. This can be ensured, among other things, during the prevention and constructive resolution of pedagogical situations of difficult interaction in the teacher-student system. Within the framework of the work, a theoretical analysis of studies of pedagogical situations of difficult interaction implemented in pedagogical communication is carried out. An empirical study was conducted aimed at identifying their manifestations and causes in the educational process of the school. Purpose. Identification of the specifics and causes of pedagogical situations of difficult interaction of subjects of the educational process in the teacher-student system. Materials and methods. The research methods included: a theoretical analysis of the results of research on the problem of difficult interaction; a written survey of 40 students – future teachers and teachers-psychologists to identify the causes and manifestations of pedagogical situations of difficult interaction in the teacher-student system. Results. The situation of difficult interaction is presented as a pre-conflict situation when the subject experiences a real (or imaginary) threat to meet his needs and expectations, has difficulty making an optimal decision about his actions, or makes a decision that turns the pre-conflict situation into a destructive conflict with negative consequences for himself and other participants in the interaction. As the survey showed, the initiators of such situations at school are both students and teachers themselves. It is necessary to increase the psychological and legal competence of the subjects of the educational process in the direction of creating conditions for the harmonization of relations and productive interaction. The presented results of theoretical and empirical research can serve as a basis for the development of a comprehensive program for the prevention and constructive resolution of pedagogical situations of difficult interaction implemented in the teacher-student system.

Monolithic finite element modeling of compressible fluid‐structure‐electrostatics interactions in MEMS devices

AbstractThis work presents a monolithic finite element strategy for the accurate solution of strongly‐coupled fluid‐structure‐electrostatics interaction problems involving a compressible fluid. The complete set of equations for a compressible fluid is employed within the framework of the arbitrary Lagrangian–Eulerian (ALE) fluid formulation on the reference configuration. The proposed numerical approach incorporates geometric nonlinearities of both the structural and fluid domains, and can thus be used for investigating dynamic pull‐in phenomena and squeeze film damping in high aspect‐ratio micro‐electro‐mechanical systems (MEMS) structures immersed in a compressible fluid. Through various illustrative examples, we demonstrate the significant influence of fluid compressibility on the dynamics of MEMS devices subjected to constrained geometry and/or high‐frequency electrostatic actuation. Moreover, we compare the proposed formulation with the nonlinear compressible Reynolds equation and highlight that, particularly at low pressures and high fluid viscosity, the Reynolds equation fails to provide a reliable approximation to the complete set of equations utilized in our proposed formulation.

Participation of the Prosecutor’s Office in the Protection of Socio-economic Rights of Citizens in Bankruptcy Cases: the Problem of Procedural Interaction with Arbitration Courts

The analysis of the legal basis for the participation of the prosecutor’s office in court proceedings in order to protect the most important socio-economic rights of citizens, such as labor and housing rights, in bankruptcy cases. The research focuses on the Russian and Chinese practice of procedural interaction between the prosecutor’s office and the courts in bankruptcy cases. Based on a comparative legal analysis, the author assesses the trend towards increasing the activity of the Russian prosecutor’s office to participate in arbitration proceedings as promising, but requiring regulatory legalization in order to increase the effectiveness of protecting the socio-economic rights of citizens. In order to effectively ensure legality in the field of bankruptcy, it is necessary to legislate the participation of the prosecutor in part 5 of Article 52 of the Arbitration Procedural Code of the Russian Federation for cases when bankruptcy arbitration cases affect not only housing, but also the labor rights of citizens.

SPH simulations of complex 3D fluid–solid interactions with an improved single-layer particle boundary technique preventing boundary penetration

The smoothed particle hydrodynamics (SPH) method has been widely used to simulate fluid–solid interaction (FSI) problems. The solid boundary treatment under complex geometric configurations has always been a hot topic in the SPH numerical simulation. An improved single-layer particle technique combined with an effective anti-penetration boundary improvement algorithm is proposed in this paper, which allows for multi-resolution single-layer particle distribution and effectively prevents particle penetration under complex geometric configurations. Four engineering problems are simulated with the improved technique: dam-break flows with a rectangular prism, water entry of a revolution body, oscillations of a floating body, and gearbox operation. The simulation results of four engineering problems are in good agreement with the reference results, which demonstrates that the improved single-layer particle boundary technique proposed in this paper can accurately simulate the FSI problem of complex geometric configurations.

A poroelastic [formula omitted]-SPH model for modeling biofilm deformation and sloughing in microfluidic channels

We present a poroelastic fluid–structure interaction δ-SPH model for simulating biofilm deformation and sloughing in microfluidic channels. Based on the mixture theory, this model accurately handles large deformations of solid structures and simultaneously simulates seepage flow within the porous biofilm and external flow. A key advantage of the model is its reliance on the solid phase material properties rather than the averaged properties of the biofilm, enabling the modeling of changes in porosity and biofilm material properties induced by loads. Model verification is achieved through two benchmark problems, followed by application to biofilm deformation and sloughing studies. The Young’s modulus of biofilms is a key parameter of interest in many studies. Calibration of the biofilm’s solid material elasticity modulus by using the presented model yields a value of 200 Pa, aligning with previous reports in literature. Additionally, the model is capable of simulating the sloughing process by evaluating local von Mises equivalent stress, reproducing different detachment patterns corresponding to various material strengths. This δ-SPH model offers an efficient numerical tool for biofilm analysis and is extendable to simulate other fluid–structure interaction problems involving porous media with large deformations, such as soil, debris flow, and biological tissues.

Whistleblowing – an extension of working life democracy? The case of Norway

Working life relations are in a continuous state of change. So are the institutions of working life democracy. In Norway, three well-established components of working life democracy have been in place since the 1960s and 1970s, developing along different institutional tracks: collective bargaining at the national level, employee representation on the boards, and employee participation in protection of health and safety in the work environment. From 2007, legal protection of whistleblowing was included in the Working Environment Act (WEA), anchored in specific institutional arrangements. Before the turn of the century, a common assumption was that whistleblowing mainly targets irregular, even criminal, dispositions of the enterprise. After the inclusion in the WEA, data from Norway from the years 2016 to 2022 demonstrate that to a large extent, psycho-social problems have become the object of whistleblowing. However, institutional specificities limit the handling of social interaction problems by the traditional work environment arrangements. Against the background of its separate institutions for the handling of grievances, it is argued that whistleblowing, along with freedom of expression, are parts of a fourth track of democratization. Even though the institutional setup of whistleblowing has been revised twice since 2007, the findings indicate that additional revisions are still desirable.

Navigating speed–accuracy trade-offs for multi-physics simulations

AbstractThis paper introduces a novel approach aimed at addressing persistent challenges inherent in conventional multiphysics modeling methodologies. Existing techniques, such as numerical modeling and analytical calculations, often suffer from time-consuming and computationally intensive processes, leading to inefficiencies, particularly in intricate simulations. The proposed methodology employs regression machine learning algorithms as a black-box solution to anticipate errors and execution times in multiphysics simulations. Diverging from conventional methods, this approach streamlines the exploration of simulation options, providing discernible choices for balancing speed and precision. The efficacy of the methodology is exemplified through successful applications to heat transfer and fluid–structure interaction problems, illustrating its adaptability across diverse scenarios. Notably, the approach upholds the integrity of physics equations and simulation convergence while markedly reducing the trial-and-error efforts and computational burdens associated with traditional methodologies. In summary, the proposed approach emerges as an innovative and promising solution to augment the accuracy, efficiency, and dependability of multiphysics simulations.

A low‐rank method for parameter‐dependent fluid‐structure interaction discretizations with hyperelasticity

AbstractFluid‐structure interaction models are used to study how a material interacts with different fluids at different Reynolds numbers. Examining the same model not only for different fluids but also for different solids allows to optimize the choice of materials for construction even better. A possible answer to this demand is parameter‐dependent discretization. Furthermore, low‐rank techniques can reduce the complexity needed to compute approximations to parameter‐dependent fluid‐structure interaction discretizations. Low‐rank methods have been applied to parameter‐dependent linear fluid‐structure interaction discretizations. The linearity of the operators involved allows to translate the resulting equations to a single matrix equation. The solution is approximated by a low‐rank method. In this paper, we propose a new method that extends this framework to nonlinear parameter‐dependent fluid‐structure interaction problems by means of the Newton iteration. The parameter set is split into disjoint subsets. On each subset, the Newton approximation of the problem related to the median parameter is computed and serves as initial guess for one Newton step on the whole subset. This Newton step yields a matrix equation whose solution can be approximated by a low‐rank method. The resulting method requires a smaller number of Newton steps if compared with a direct approach that applies the Newton iteration to the separate problems consecutively. In the experiments considered, the proposed method allows to compute a low‐rank approximation up to twenty times faster than by the direct approach.

A formulation for fluid–structure interaction problems with immersed flexible solids: Application to splitters subjected to flow past cylinders with different cross-sections

In the finite element method framework, a fluid–structure formulation is developed by coupling an Eulerian fixed-mesh fluid approach with a Lagrangian deforming-mesh description for a flexible solid. The coupled formulation is solved using a staggered scheme during time. For the fluid solution stage, the solid walls are considered as a time-variable internal boundary. The velocity and pressure fields are obtained by solving the weak form of the fluid dynamic equations in which the solid velocity is imposed on the internal boundary via a penalization term. For the solid solution stage, the displacement field is obtained by solving the discrete solid dynamic equations which consider traction forces computed by integrating pressures and viscous stresses on the nodes belonging to the solid walls. This novel technique is firstly applied to analyze a flexible splitter under the shedding of a flow past square cylinder due to this problem is considered as a benchmark in the literature. The present solutions agree with those computed using body-fitted techniques, thus validating the proposal. Secondly, flexible splitter motions under the shedding of flow past cylinders with different cross-sections and splitter lengths are comprehensively studied. Overall, the computed results confirmed that the hydrodynamic coefficients on the cylinders were reduced because of the presence of the splitter.

Optimized scheduling of integrated community energy stations based on improved NSGA-III algorithm

To cope with the problem of building and using a large number of fast electric vehicle stations (FEVS), adding FEVS to the integrated community energy system (ICES) provides new ideas for solving the problems of interaction with the grid, overall system stability, revenue benefits, and environmental pollution. To this end, this paper designs an ICES model with FEVS (ICES-FEVS). This model considers economy, stability, and sustainability to achieve all-around consideration. To further solve the complex multi-objective problem, the multi-objective improvement strategy NSGA-III algorithm (IS-NSGA-III), combined with fuzzy comprehensive evaluation (FCE), is used to solve the model. In the solution phase, the advantages of the IS-NSGA-III algorithm are first verified by the benchmark function, and the validity of the ICES-FEVS model is verified by comparing different models. In the optimization results, daily revenue was increased by 6.3 %, daily battery life loss was increased by 26.03 %, and pollution emissions were reduced by 46.9 %. The analysis of the results shows that introducing Electric Vehicle (EV) fast charging stations in an integrated community energy system ensures economic improvement, sustainable development, and more favorable regulation of the energy storage system. The simulation results show that compared with other algorithms, the HV metrics of IS-NSGA-III are lower by about 6.8 %, Spread metrics are better by about 1.35 %, and the proposed IS-NSGA-III is better in terms of convergence and distributivity.

Dynamic modelling and experimental validation of a dynamic track stabiliser vehicle–track spatially coupling dynamics system

A dynamic track stabiliser vehicle is an unconventional vehicle for maintaining the quality of ballasted tracks, and its dynamic performance has a significant impact on its working efficiency. For the first time, this paper proposes a comprehensive dynamic track stabiliser vehicle–track coupled vertical and lateral multi-body dynamics model based on classical vehicle–track coupling dynamics theory. In this model, detailed attention is given to the vertical, lateral, roll, yaw, and pitch motions of the components, including the vehicle body, bogies, wheelsets and stabilisers. The Shen–Hedrick–Elkins theory is employed to describe non-linear wheel–rail contact relationships between the bogie wheelsets and the rails, and three various methodologies are adopted to address complicated wheel–rail interaction problems between the stabiliser wheelsets and the rails. This comprehensive multi-body dynamics model enables a detailed investigation of the dynamic performance of the system under complex excitations, such as the lateral excitation of the stabilisers and vertical downward pressure exerted by hydraulic cylinders, especially the dynamic response of the stabilisers in the vibration environment of the complete vehicle. The dynamics model was fully validated by comparing its results with time- and frequency-domain data obtained from field tests. The results indicate that the model is capable of being used for analysis of the dynamic performance of dynamic track stabiliser vehicles.