Destructive Interaction Research Articles

Types of organization of communicative management space in the context of the implementation of national projects: regional cross-section

. This article continues a series of studies on the organization of communicative space in the management of regions. The effectiveness of the implementation of certain management decisions may depend on many factors, including a qualitatively built dialogue between interested parties of social management representing the interests of various categories of citizens. The article presents the results of a search study on the identification of types of the communicative management space’ organization in the context of the implementation of national projects in regions with different levels of socio-cultural modernization. The main task was to determine the levels of constructive (balanced) and destructive (inconsistent) interaction between the subjects of three levels – managerial, resource and basic. With the help of secondary conceptualization of data from a mass survey of the population and mass expert surveys conducted in 12 regions of Russian Federation, it was possible to identify typical signs of organized communication between particular subjects in each of the studied areas by analyzing the opinion of experts. The validity of this group of respondents is confirmed by the presence of experience in management practice, education and professional competence. The authors studied the relations between the subjects of management (regional authorities, local self-government, business communities, public organizations, scientific organizations and the population) in each region. There were constructed the types of the communicative management space’ organization of the region by assessing the similarities and differences of communication connections: 1) balanced constructive, 2) with elements of mismatch, 3) inconsistent (unbalanced, destructive). During the analysis, it was revealed that assessment of the interaction of management subjects is related to the assessment of the management style in the region, the agreement with the managerial style of the regional authorities among representatives of the expert community is associated with an assessment of the nature of the constructiveness of relations between regional authorities and the population.

Low-NA two-photon lithography patterning of metal/dielectric tapered optical fibers for depth-selective, volumetric optical neural interfaces.

Optical neural implants allow neuroscientists to access deep brain regions, enabling to decipher complex patterns of neural activity. In this field, the use of optical fibers is rapidly increasing, and the ability to generate high-quality metal patterns on their non-planar surface would further extend their application. Here, we propose to use alternating metal shielding and dielectric confinement to engineer the mode-division properties of tapered optical fiber neural implants. This is accomplished through an unconventional application of two-photon lithography (TPL), which employs a low-numerical aperture objective to pattern extensive waveguide sections at both low and high curvature radii. The low-NA TPL is used to polymerize a mask of photoresist, while the rest of the taper undergoes wet metal etching. This implies no direct destructive interaction between the laser beam and the metal to be removed, preserving the optical properties of the dielectric waveguide and of the metal coating. The advantages provided by the presented fabrication method, combined with the intrinsic modal properties of the dielectric waveguide, enable the engineering of the light guiding mechanisms, achieving depth-selective light delivery with a high extinction ratio. The device's light emission and collection properties were investigated in quasi-transparent media and highly scattering brain slices, finding that our proposed method facilitates 360° symmetric light collection around the dielectric-confined section with depth resolution. This opens a perspective for the realization of optical neural implants that can interface the implant axis all-around, with low-NA TPL that can also be applied on other types of non-planar surfaces.

Covenantal Pluralism’s Enabling Conditions in South African Context: The Example of Multi-Faith Schools

The religious freedom provisions within the South African Constitution strive to protect the rights of every citizen, irrespective of their religious beliefs, while fostering a diverse and inclusive society. However, one inevitable outcome of diversity is the potential for tension and conflict among various religious communities. This paper explores the potential for covenantal pluralism in South Africa, specifically focusing on multi-faith schools. It underscores the importance of religious literacy as a critical educational objective within the realm of religious education in public schools, as outlined in the Policy on Religion and Education in South Africa. Additionally, the paper suggests transformative and African mediation as effective conflict resolution strategies for managing conflicts in schools. These approaches focus on redefining the relationship between opposing parties, often transitioning from negative and destructive interactions to positive and constructive ones.

Molecular dynamics simulation of nanocellulose and cement matrix composites

The interfacial properties of nanocellulose and cement matrix are the key factors affecting the mechanical properties of composite materials. However, it is challenging to study the interface combination through conventional experiments and microscopic characterization techniques. Molecular dynamics simulation (MD), as a nanoscale analytical method, can be used to calculate and analyze the strength, deformation, destruction and interfacial interaction of materials on the atomic scale. Since the existing methods of C-S-H modeling and fiber pull-out from the matrix in molecular dynamics simulations were not suitable for cellulose/C-S-H composite models. In this paper, a molecular dynamics simulation method for nanocellulose cement matrix composites was proposed. Based on the embedded composite model, the tensile stress-strain, interfacial interaction energy, hydrogen bond, and interface failure mode were studied when cellulose was pulled out of the matrix. The results showed that adding cellulose could improve the local ductility and tensile strength of cement matrix materials. The interfacial interaction energy between cellulose and C-S-H was approximately −1.09 J/m2, which was much higher than that between carbon nanotubes and C-S-H. Cellulose would adsorb hydrogen and oxygen atoms on H2O, OH− and silica tetrahedron in C-S-H. In the pull-out simulation of cellulose in C-S-H, C-S-H on the surface of cellulose would be destroyed and attached to the cellulose surface and moved along with it, indicating that cellulose could play a good bridging role in the matrix. The simulation results revealed the action mechanism of cellulose in cement matrix materials.

Structure-dependent destructive adsorption of organophosphate flame retardants on lipid membranes

The widespread use of organophosphate flame retardants (OPFRs), a serious type of pervasive environmental contaminants, has led to a global concern regarding their diverse toxicities to living beings. Using a combination of experimental and theoretical approaches, we systematically studied the adsorption, accumulation, and influence of a series of OPFRs on the lipid membranes of bacteria and cells. Our results revealed that OPFRs can aggregate in lipid membranes, leading to the destruction of membrane integrity. During this process, the molecular structure of the OPFRs is a dominant factor that significantly influences the strength of their interaction with the lipid membrane, resulting in varying degrees of biotoxicity. Triphenyl phosphate (TPHP), owing to its large molecular size and strong hydrophobicity, causes severe membrane disruption through the formation of nanoclusters. The corresponding severe toxicity originates from the phase transitions of the lipid membranes. In contrast, smaller OPFRs such as triethyl phosphate (TEP) and tris(2-chloroethyl) phosphate (TCEP) have weaker hydrophobicity and induce minimal membrane disturbance and ineffective damage. In vivo, gavage of TPHP induced more severe barrier damage and inflammatory infiltration in mice than TEP or TCEP, confirming the higher toxicity of TPHP. Overall, our study elucidates the structure-dependent adsorption of OPFRs onto lipid membranes, highlighting their destructive interactions with membranes as the origin of OPFR toxicity.

Hydrodynamic performance of multi-chamber oscillating water columns in a caisson array

A theoretical model based on the linear potential flow theory and eigenfunction expansion-matching method is developed to analyze the interaction between water waves and multi-chamber oscillating water columns (OWCs) embedded in a caisson array. The semi-analytical solution consists of the diffraction and radiation components of periodic OWCs. The velocity singularity at the tip of the OWC chamber walls is resolved by implementing a Chebyshev polynomial expansion. The unknown expansion coefficients are determined by the continuity equations of velocity and pressure at the interface of subdomains. The semi-analytical solution is verified using the Haskind relation and the conservation law of wave energy flux. It is found that multi-chamber OWCs have higher hydrodynamic efficiency over a broader frequency bandwidth than traditional single- and dual-chamber OWCs. The maximum hydrodynamic efficiency η increases with increasing of chamber number (J), from 0.5 (J = 1) to nearly 1.0 (J = 8 and 12). It is also found that a larger incident wave angle leads to a narrower frequency bandwidth for energy capturing. Increasing the incident wave angle from π/3 to 5π/12 results in a decrease of the first cutoff frequency kc from 2.41 to 2.02, and therefore results in the energy capture bandwidth narrowing accordingly. Both constructive and destructive hydrodynamic interactions between caissons array and OWCs are observed over the tested frequency range. Interestingly, when configuration of the OWC chambers is reversed, the transmission coefficient remains unchanged.

Spinning and corkscrewing of oceanic macroplankton revealed through in situ imaging.

Helical motion is prevalent in nature and has been shown to confer stability and efficiency in microorganisms. However, the mechanics of helical locomotion in larger organisms (>1 centimeter) remain unknown. In the open ocean, we observed the chain forming salp, Iasis cylindrica, swimming in helices. Three-dimensional imaging showed that helicity derives from torque production by zooids oriented at an oblique orientation relative to the chain axis. Colonies can spin both clockwise and counterclockwise and longer chains (>10 zooids) transition from spinning around a linear axis to a helical swimming path. Propulsive jets are non-interacting and directed at a small angle relative to the axis of motion, thus maximizing thrust while minimizing destructive interactions. Our integrated approach reveals the biomechanical advantages of distributed propulsion and macroscale helical movement.

Dynamics of seaweed-inspired piezoelectric plates for energy harvesting from oscillatory cross flow

Inspired by the vibrations of aquatic plants such as seaweed in the unsteady flow fields generated by free-surface waves, we investigate a novel device based on piezoelectric plates to harvest energy from oscillatory cross flows. Towards this end, numerical studies are conducted using a flow-structure-electric interaction model to understand the underlying physical mechanisms involved in the dynamics and energy harvesting performance of one or a pair of piezoelectric plates in an oscillatory cross flow. In a single-plate configuration, both periodic and irregular responses have been observed depending on parameters such as normalized plate stiffness and Keulegan–Carpenter number. Large power harvesting is achieved with the excitation of natural modes. Besides, when the time scale of the motion and the intrinsic time scale of the circuit are close to each other the power extraction is enhanced. In a two-plate configuration with tandem formation, the hydrodynamic interaction between the two plates can induce irregularity in the response. In terms of energy harvesting, two counteracting mechanisms have been identified, shielding and energy recovery. The shielding effect reduces plate motion and energy harvesting, whereas with the energy recovery effect one plate is able to recovery energy from the wake of another for performance enhancement. The competition between these mechanisms leads to constructive or destructive interactions between the two plates. These results suggest that for better performance the system should be excited at its natural period, which should be close to the intrinsic time scale of the circuit. Moreover, using a pair of plates in a tandem formation can further improve the energy harvesting capacity when conditions for constructive interaction are satisfied.

Investigation on the turbulent structures in combined wave-current boundary layers

The problem of turbulent vortices and vortex dynamics under the influence of ocean waves is a subject of continuing research in the field of wave-current interaction. Thus, this study investigates the evolution of turbulence structures and vortex interactions in combined wave-current boundary layers, where water waves propagate with currents. Experiments were performed in two glass-walled laboratory channels with water depths of 160 and 400 mm. A two-dimensional two-component (2D2C) Particle Image Velocimetry (PIV) system was used to measure the velocities. Periodic variations in turbulence are observed for combined wave-current flows. Pairs of counter-rotating vortices are identified in the outer region when the combined flow is reversed, leading to destructive vortex interactions. This process leads to a reduction in the turbulent kinetic energy (TKE) and TKE production and dissipation during the passage of the wave trough. A conceptual model of hairpin vortices in combined wave-current flows is proposed in this study. The results of this study provide novel insights into the hydrodynamics of combined wave-current flows.

Negative speaks louder than positive: Negative implicit partner evaluations forecast destructive daily interactions and relationship decline

Romantic relationships are affectively complex. Any given interaction consists of both rewarding and aversive features. Recent work has shown that implicit partner evaluations (IPEs)—evaluations spontaneously triggered when one thinks about one’s partner—are also affectively complex. Does such complexity in IPEs help individuals navigate rewarding and aversive aspects inherent in interactions? The present work examined the proposition that negative IPEs uniquely forecast aversive daily relationship behaviors, whereas positive IPEs uniquely forecast rewarding daily relationship behaviors. Individuals self-identified as in a heterosexual romantic relationship completed measures to assess their implicit and explicit partner evaluations at two time points, spanning a three-month period, as well as a daily diary component. Time-1 negative IPEs forecasted perceiving and enacting negative behaviors during a 14-day daily diary, which, in turn, predicted deterioration in explicit partner and relationship evaluations 3-months later. The predictive ability of negative IPEs remained even after statistically controlling for positive IPEs and explicit evaluations. Positive IPEs were weak and inconsistent predictors of outcomes. The findings shine a spotlight on the differential functions of positive and negative IPEs, the importance of assessing negative IPEs independently from positive IPEs, and the role of negative IPEs in predicting destructive relationship experiences.

Combined Effects of Chemical Reaction and Radiation on MHD Squeezing Flow of Casson Fluid

The impacts of chemical reaction on the magnetohydrodynamic (MHD) squeezing Casson fluid flow through a porous medium under the slip condition with viscous dissipation the presence of radiation parameter have been discussed. The flow is produced when two plates are compressed together in close proximity to one another. Using similarity variables may successfully convert partial differential equations (PDEs) to ordinary differential equations (ODEs). The shooting technique was used to perform the numerical analysis, which entailed solving the competent governing equations with dominating parameters for a thin liquid layer. This was done to determine the results of the study. It is essential to evaluate the numerical results in light of previously conducted research to validate the current answers. According to the results, an increase in the distance between the two plates leads to a rise in the velocity and the wall shear stress. The gas's velocity, temperature, and concentration all drop due to an increase in the Hartmann and Casson parameters. Both the temperature and the rate of heat transfer rise in direct proportion to the amount of viscous dissipation. In addition, it has been shown that the rate of mass transfer rises during destructive chemical interactions, but during constructive chemical reactions, the contrary occurs, which results in adverse effects.

Acoustic far field of a propeller working in the wake of a hydrofoil

The Ffowcs-Williams & Hawkings (FWH) acoustic analogy is adopted to reconstruct the acoustic far field of a system consisting of an upstream hydrofoil and a downstream propeller, considering the former at incidence angles of 0°, 10°, and 20°. Also comparisons against the same propeller working in isolated conditions are reported. Fluid dynamic data from earlier high-fidelity, Large-Eddy Simulations (LES) on a grid consisting of 1.7 × 109 points are utilized. The analysis demonstrates that, with some exceptions at the smallest frequencies, the acoustic far field is dominated by the loading sound coming from the propeller, achieving its highest values of acoustic pressure in the upstream and downstream directions. In contrast, the lowest values occur on the propeller plane, whose minima are aligned with the spanwise direction of the hydrofoil. A strong dependence on the incidence angle of the hydrofoil is found, although decreasing toward higher frequencies. Interestingly, while at the shaft and at the blade frequencies the acoustic pressure coming from the hydrofoil-propeller system is always higher than that from the open-water propeller working alone, as expected, at higher harmonics of the blade frequency this is not the case. This may be due to phenomena of destructive interactions across the acoustic sources on the surface of the propeller or the result of a shift of the acoustic signature toward even higher frequencies, beyond the range covered by the database available to the present study.

Finite Froude and Rossby numbers counter-rotating vortex pairs

We investigate the nonlinear evolution of pairs of three-dimensional, equal-sized and opposite-signed vortices at finite Froude and Rossby numbers. The two vortices may be offset in the vertical direction. The initial conditions stem from relative equilibria obtained numerically in the quasi-geostrophic regime, for vanishing Froude and Rossby numbers. We first address the linear stability of the quasi-geostrophic opposite-signed pairs of vortices, and show that for all vertical offsets, the vortices are sensitive to an instability when close enough together. In the nonlinear regime, the instability may lead to the partial destruction of the vortices. We then address the nonlinear interaction of the vortices for various values of the Rossby number. We show that as the Rossby number increases, destructive interactions, where the vortices break into pieces, may occur for a larger separation between the vortices, compared to the quasi-geostrophic case. We also show that for well-separated vortices, the interaction is non-destructive, and ageostrophic effects lead to the deviation of the trajectory of the pair of vortices, as the anticyclonic vortex dominates the interaction. Finally, we show that the flow remains remarkably close to a balanced state, emitting only waves containing negligible energy, even when the interaction leads to the destruction of the vortices.

Numerical study of the unsteady blade root aerodynamics of a 2 MW wind turbine equipped with vortex generators

Abstract. In order to design vortex generators for modern multi-megawatt wind turbines accurately, the 3D behaviour of the boundary layer has to be considered. Due to the rotation of the blade, the lift-enhancing rotational augmentation has a considerable impact, especially in the inner blade sections. To investigate the interaction of vortex generators and rotational augmentation, high-fidelity computational flow simulations by means of unsteady Reynolds-averaged Navier–Stokes methods are presented for a rotating blade of a generic 2 MW horizontal-axis wind turbine. The inner blade section is analysed with and without vortex generators for two different pitch settings, including one causing largely separated flow. Two ways of placing the vortex generators on the blade with different radial starting positions are investigated in order to find out if the coexistence of the two lift-enhancement methods (i.e. rotational augmentation and vortex generators) is beneficial. All simulations are performed with the flow solver FLOWer, and the vortex generators are modelled by the introduction of source terms into the computational domain through a so-called BAY (Bender–Anderson–Yagle)-type model. For the case without vortex generators, it is found that the strength of rotational augmentation largely depends on the effective angles of attack (i.e. the pitch setting). For the case with lower effective angles of attack, rotational augmentation is a cyclic phenomenon, whereas for the case with higher effective angles of attack, it generates large loads in the inner root section due to a constant centrifugal pumping mechanism in time. The results from the cases with vortex generators display a rather destructive interaction of vortex generators and rotational augmentation on the torque. For low effective angles of attack and thus attached flow conditions, vortex generators exhibit slight losses compared to the case without vortex generators, as they inhibit spanwise flow through rotational augmentation. For high effective angles of attack, the vortex generators placed over 30 % of the blade produce an increase of 3.28 % in torque compared to the case without vortex generators and high centrifugal pumping.

Heterogeneous WEC array optimization using the Hidden Genes Genetic Algorithm

Wave Energy Converters (WEC) are deployed in arrays to improve the overall quality of the delivered power to the grid and reduce the cost of power production by minimizing the cost of design, deployments, mooring, maintenance, and other associated costs. WEC arrays often contain devices of identical dimensions and modes of operation. The devices are deployed in close proximity, usually having destructive inter-device hydrodynamic interactions. However, in this work, we explore optimizing the number of devices in the array and concurrently, the dimensions of the individual devices (heterogeneous) to achieve better performance compared to an array of identical devices (homogeneous) with comparable overall submerged volume. A techno-economic objective function is formulated to measure the performance of the array while accounting for the volume of material used by the arrays. The power from the array is computed using a time-domain array dynamic model and an optimal constrained control. The hydrodynamic coefficients are computed using a semi-analytical method to enable computationally efficient optimization. The Hidden Gene Genetic Algorithm (HGGA) formulation is used in this optimization problem. During the optimization, tags are assigned to genes to determine whether they are active or hidden. An active gene simulates an active WEC device in the heterogeneous array, while the hidden gene results in a reduction in the total number of devices in the array compared with the homogeneous array. The volume of the heterogeneous array is constrained to be close to that of the homogeneous array. These hidden tags do not exclude the associated devices from the optimization process; these devices keep evolving with the active devices as they might become active in subsequent generations. Heterogeneous arrays were found to perform better than homogeneous arrays.

Power capture analysis of a five-unit oscillating water column array integrated into a breakwater in terms of flow field visualization

Oceanic waves possess immense untapped potential as a renewable energy resource, presenting a remarkable opportunity for energy extraction. To unleash the full extent of wave power within a given region and generate substantial quantities of electricity for widespread distribution, it is plausible to envision the deployment of wave farms—expansive arrays comprising wave energy converters. This study investigates the performance of an oscillating water column (OWC) array system integrated into a straight breakwater for wave power extraction. The array consists of five identical rectangular-shaped OWC units with a circular-curve bottom profile, arranged in a linear configuration. Computational Fluid Dynamics simulations are conducted to analyze the power capture of the array system and understand the operational dynamics compared to individual OWC device. Flow field visualization is employed to gain insights into the array effects and the influence of the transverse spacing between the interior units. The array configuration reveals that the OWC units positioned at the lateral sides exhibit the highest performance, while the central chamber achieves the lowest performance. However, none of the units within the array surpass the wave power extraction of an individual OWC device. The array effect introduces interference, significantly influencing the velocity field distribution of the water flow and contributing to disparities in wave power extraction between the individual device and the closely-adjacent array configuration. The study also emphasizes the role of transverse spacing between the interior units in the array. Within a certain range of transverse spacing, increasing the spacing enhances the power capture by mitigating destructive interactions involved in the inflow and outflow processes between adjacent chambers. However, when the transverse spacing becomes sufficiently large, the behavior of each unit within the array resembles that of an individual OWC device, and the constructive interaction effects between units become negligible, thereby weakening wave power extraction.

Focusing of jet from synthetic jet array using non-linear phase delay

In the present investigation, a novel focusing technique is proposed and demonstrated to enhance the strength of a synthetic jet array (SJ array). Here, for the same geometric and operating parameters, focusing of the SJ array is achieved by providing a non-linear phase delay (∅) between the actuators. An open-source software, OpenFOAM, is used to study the influence of the Strouhal number (St=0.028, 0.086, and 0.13) and ∅ s (range: 0°−180°) on the focusing behavior of the SJ array for fixed Reynolds number Re=300. Irrespective of ∅s, due to strong suction effect, focusing is not achieved for the SJ array operated at low St=0.028. However, maximum focusing is achieved for intermediate St=0.086 and ∅=90°, which shows an increment of ∼52% in the time-averaged streamwise velocity (Vavg) measured at y=20d compared to ∅=0°. Similarly, the Vavg is enhanced by ∼37% for high St=0.13 with ∅=120°. Also, the variation of Vavg along the jet centerline shows a decrease in the slope of the decay profiles due to focusing. Most importantly, the temporal evolution of the pumping power shows that no additional energy is required for enhancing the strength of SJ array. The proper orthogonal decomposition analysis illustrates that maximum focusing (St=0.086 and ∅=90°) conserves ∼ 43% of total kinetic energy, which was lost due to destructive interaction between the vortices in the case of ∅=0°. Hence, for effective implementation in flow control, electronic cooling, and other applications, it is recommended to focus the SJ array by operating it at intermediate St with a moderate non-linear phase delay (∅=60° and 90°).

Effects of medium viscoelasticity on bubble collapse strength of interacting polydisperse bubbles

Due to its physical and/or chemical effects, acoustic cavitation plays a crucial role in various emerging applications ranging from advanced materials to biomedicine. The cavitation bubbles usually undergo oscillatory dynamics and violent collapse within a viscoelastic medium, which are closely related to the cavitation-associated effects. However, the role of medium viscoelasticity on the cavitation dynamics has received little attention, especially for the bubble collapse strength during multi-bubble cavitation with the complex interactions between size polydisperse bubbles. In this study, modified Gilmore equations accounting for inter-bubble interactions were coupled with the Zener viscoelastic model to simulate the dynamics of multi-bubble cavitation in viscoelastic media. Results showed that the cavitation dynamics (e.g., acoustic resonant response, nonlinear oscillation behavior and bubble collapse strength) of differently-sized bubbles depend differently on the medium viscoelasticity and each bubble is affected by its neighboring bubbles to a different degree. More specifically, increasing medium viscosity drastically dampens the bubble dynamics and weakens the bubble collapse strength, while medium elasticity mainly affects the bubble resonance at which the bubble collapse strength is maximum. Differently-sized bubbles can achieve resonances and even subharmonic resonances at high driving acoustic pressures as the elasticity changes to certain values, and the resonance frequency of each bubble increases with the elasticity increasing. For the interactions between the size polydisperse bubbles, it indicated that the largest bubble generally has a dominant effect on the dynamics of smaller ones while in turn it is almost unaffected, exhibiting a pattern of destructive and constructive interactions. This study provides a valuable insight into the acoustic cavitation dynamics of multiple interacting polydisperse bubbles in viscoelastic media, which may offer a potential of controlling the medium viscoelasticity to appropriately manipulate the dynamics of multi-bubble cavitation for achieving proper cavitation effects according to the desired application.

Drag reduction by flapping a pair of flexible filaments behind a cylinder

The hydrodynamic mechanism of drag reduction by flapping a pair of flexible filaments behind a cylinder was explored using the penalty immersed boundary method. The effects of the phase difference between two filaments, the attachment height, and the flapping amplitude on drag reduction were examined. The flapping filaments weaken the vortex shedding via the destructive interaction between the vortices with the opposite signal. The clapping (out-of-phase) flexible filaments experience a lower friction drag and reduce a form drag of the cylinder, showing a better drag reduction than the snaking (in-phase) flexible filaments and the clapping rigid filaments. A minimum drag is obtained at an appropriate attachment height and flapping amplitude that avoid collision of the filaments and weaken the shear-layer–filaments interaction. The effectiveness ratio of the clapping filaments is higher than that of the snaking filaments. Energy saving can be achieved by avoiding the shear layer–filament interaction at a low flapping amplitude, whereas the filaments can further reduce the drag with greater energy consumption at an appropriate flapping amplitude. In addition, the total drag decreases with increasing Reynolds number, accompanied by a transition of the wake pattern from the 2S mode to the P + S mode.

Hybrid Self-Organizing Networks: Evolution, Standardization Trends, and a 6G Architecture Vision

Self-organizing networks (SONs) need to be endowed with self-coordination capabilities to manage the complex relations between their internal components and to avoid their destructive interactions. Existing communication technologies commonly implement responsive self-coordination mechanisms that can be very slow in dynamic situations. The sixth generation (6G) networks, being in their early stages of research and standardization activities, open new opportunities to opt for a design-driven approach when developing self-coordination capabilities. This can be achieved through the use of hybrid SON designs. A hybrid architecture combines the centralized and distributed management and control. In this article, we review the history of SONs, including the inherent self-coordination feature. We then delve into the concept of hybrid SONs (H-SONs), and we summarize the challenges, opportunities, and future trends for H-SON development. We provide a comprehensive collection of standardization activities and recommendations, discussing the key contributions and potential work to continue the evolution and push for a wide adoption of the H-SON paradigm. More importantly, as a key 6G architectural feature we propose that H-SONs should be loosely coupled networks. Loose coupling refers to the weak interaction of different layers and weak interaction between users in the same layer, that is, the various feedback loops must be almost isolated from each other to improve the stability and to avoid chaotic situations. We finally conclude the article with the key hints about the future landscape and the key drivers of 6G H-SONs.