Search Results (71)

I analyze the nonlinear Hamiltonian equations of motion for a one-dimensional chain of transverse magnetic nano-islands, seeking solutions for different types of static domain walls (DWs) connecting uniform static states. The system of elongated magnetic islands oriented transverse (y-direction) to the chain direction (x-direction) experiences an applied magnetic field transverse to the chain. The macro-spin model includes dipole interactions between islands, their uniaxial and easy-plane anisotropies, and Oersted energy of the applied field. DWs can form most easily between pairs of degenerate uniform states, described by their local magnetizations as oblique, y-parallel, and y-alternating. The DWs between oblique states are well described with scalar ${\phi }^4$ theory. General DW structures are found via a numerical energy relaxation scheme. At some anisotropy and field parameters, nearest-neighbor dipole interactions drive antiferromagnetic order inside the DW itself. Full article

This study examines the grammaticalization of visual perception verbs in Hlai, a Kra–Dai language spoken on Hainan Island. Based on original fieldwork data, the paper identifies two core verbs of visual perception, zo³³ and laai⁵⁵, which differ systematically in their semantic profiles and diachronic developments. While both verbs encode basic visual perception, zo³³ exhibits a broader range of activity-oriented meanings (e.g., ‘watch’, ‘read’, ‘visit’, ‘judge’) and has developed a tentative marker function. In contrast, laai⁵⁵ patterns as an experience-type perception verb and has undergone a distinct grammaticalization pathway, developing into a conditional conjunction meaning ‘if’ and, in combination with negation, an ‘otherwise’ marker. Adopting a typological framework of perception verbs and a model of semantic extension, this study demonstrates that the two verbs diverge not only in aspectual type (activity vs. experience) but also in their susceptibility to functional reanalysis. A comparative analysis with Mandarin and Hainan Min suggests that the tentative use of zo³³ is plausibly contact-induced, whereas the conditional development of laai⁵⁵ lacks a clear parallel in the contact languages and is more likely to represent a language-internal innovation. The findings contribute to the documentation of Hlai and to cross-linguistic discussions of perception verbs, semantic change, and the typology of conditional marking. Full article

As renewable energy integration accelerates, the displacement of synchronous generators by inverter-based resources (IBRs) necessitates advanced grid-forming (GFM) control strategies to maintain system stability. While techniques such as Droop control, Virtual Synchronous Generator (VSG), and Dispatchable Virtual Oscillator Control (dVOC) are well-established, their comparative performance under coordinated cyber-physical stress remains underexplored. This paper presents a comprehensive Controller Hardware-in-the-Loop (CHIL) assessment of these three GFM strategies within a networked microgrid environment. Utilizing a co-simulation framework that integrates an OPAL-RT real-time simulator with the EXata CPS network emulator, we evaluate the dynamic resilience of each controller under islanded, parallel, and fault-induced reconfiguration scenarios. Experimental results demonstrate that the VSG strategy offers superior transient performance, characterized by faster settling times and enhanced fault-ride-through capabilities compared to the Droop and dVOC strategies. Furthermore, recognizing the vulnerability of connected microgrids to cyber threats, this study investigates the impact of False Data Injection (FDI) attacks on the control layer. To address this, a model-reference resilience layer is proposed and validated on a TI C2000 DSP. The results confirm that this protection mechanism effectively detects and mitigates attacks on control references and feedback measurements, ensuring stable operation despite cyber-physical disturbances. Full article

Optimizing the furniture layout of middle school laboratories is crucial for improving the emergency safety, operational efficiency, and resilience of teaching buildings. This study used AnyLogic software to model and simulate pedestrian evacuation behavior in a typical middle school laboratory layout. In a standardized laboratory (90.75 m²), we constructed a behavior-oriented multi-agent evacuation model. The model incorporated key student parameters, including shoulder width (312–416 mm), walking speed (1.5–2.5 m/s), and reaction time (10–15 s). To ensure comparability between different layouts, the number of evacuees was fixed at 48. Evacuation performance was evaluated based on total evacuation time, spatial density, and detour distance. The results showed that the hybrid layout achieved the shortest evacuation time (28.0 s), which was 10.3% shorter than the island layout (31.2 s) and 34.7% shorter than the parallel layout (42.9 s). The hybrid layout also had a shorter average detour distance (9.78 m) and the lowest path variability (coefficient of variation CV = 0.33), indicating a more balanced evacuation load and a smaller bottleneck effect. Overall, these findings provide evidence-based recommendations for improving laboratory safety, space utilization, and behavioral adaptability, and provide a quantitative reference for updating educational building codes, school laboratory construction standards, and guidelines for laboratory furniture and safety facility configuration. Full article

The paper examines the phenomenon of urban envelopes, a conceptual parallel to building envelopes, which is considered an emerging theme in studies of the built environment. The term ‘envelope’ refers to various physical and non-physical occurrences in the built environment that delimit, enclose, or demarcate spatial configurations. In the first part of the paper, six distinct types of urban envelopes are identified: physical, programmatic, technological, ecological, environmental, and representational. These are defined based on a systematic literature review to clarify their form, role, and meaning in the context of contemporary cities. All six urban envelope types are formalised using ontology-building methods in Protégé and visualised through WebVOWL, producing domain-agnostic RDF/OWL models that support semantic interoperability. The results provide a concise definition of urban envelopes, which are becoming increasingly relevant in their non-physical representations, such as spaces of control (surveillance of public urban spaces), dynamic environmental and ecological phenomena (pollution, heat islands, and more), temporal or dynamic definitions of space use, and many others in the context of contemporary smart city development. The analysis of possible alignment with existing smart city-related ontologies is presented. By providing the methodology for linking urbanistic principles with data-driven smart city frameworks, the paper provides a unified methodological foundation for incorporating such emerging spatial phenomena into formal urban models. Full article

The rapid increase in global data generation has intensified the demand for magnetic storage systems with substantially higher areal density. Double-layer bit-patterned media recording (DLBPMR), which integrates the benefits of bit-patterned media recording (BPMR) and double-layer magnetic recording (DLMR), provides a promising pathway by combining nanoscale patterned islands with multilayer recording structures. However, severe two-dimensional intersymbol interference (ISI) within each layer, together with interlayer interference (ILI) between stacked layers, continues to present significant challenges for reliable data detection. To address these issues, this work investigates and advances the structure of DLMR to improve signal separation and recovery. In particular, we emphasize that detection plays a crucial role in mitigating both ISI and ILI. Accordingly, we propose a maximum a posteriori (MAP) detection scheme derived for a newly developed generalized two-layer partial-response (PR) model that accurately characterizes intra-layer ISI and cross-layer interference coupling. A parallel detection architecture is designed and employed for the upper and lower layers of the DLMR system, enabling the exchange of extrinsic information and enhancing MAP detection performance. Simulation results demonstrate that the proposed PR modeling and MAP-based detection framework achieves significant bit error rate (BER) improvements over existing detection methods, highlighting its strong potential for next-generation ultra-high-density DLBPMR systems. Full article

Amid accelerating climate change, intensifying urban heat island effects, and rising public demand for livable, walkable streets, there is an urgent practical need for interpretable and actionable evidence on streetscape quality. Yet, research on streetscape quality has often relied on single data sources and linear models, limiting insight into multidimensional perception; evidence from temperate monsoon cities remains scarce. Using Tianjin’s main urban area as a case study, we integrate street-view imagery with remote sensing imagery to characterize satellite-derived environmental indicators at the point scale and examine the following five perceptual outcomes: comfort, aesthetics, perceived greenness, summer heat perception, and willingness to linger. We develop a three-step interpretable assessment, as follows: Elastic Net logistic regression to establish directional and magnitude baselines; Generalized Additive Models with a logistic link to recover nonlinear patterns and threshold bands with Benjamini–Hochberg false discovery rate control and binned probability calibration; and Shapley additive explanations to provide parallel validation and global and local explanations. The results show that the Green View Index is consistently and positively associated with all five outcomes, whereas Spatial Balance is negative across the observed range. Sky View Factor and the Building Visibility Index display heterogeneous forms, including monotonic, U-shaped, and inverted-U patterns across outcomes; Normalized Difference Vegetation Index and Land Surface Temperature are likewise predominantly nonlinear with peak sensitivity in the midrange. In total, 54 of 55 smoothing terms remain significant after Benjamini–Hochberg false discovery rate correction. The summer heat perception outcome is highly imbalanced: 94.2% of samples are labeled positive. Overall calibration is good. On a standardized scale, we delineate optimal and risk intervals for key indicators and demonstrate the complementary explanatory value of street-view imagery and remote sensing imagery for people-centered perceptions. In Tianjin, a temperate monsoon megacity, the framework provides reproducible, actionable, design-relevant evidence to inform streetscape optimization and offers a template that can be adapted to other cities, subject to local calibration. Full article

This work proposes an intelligent strategy for the coordinated management of active and reactive power in Battery Energy Storage Systems (BESSs) within AC microgrids operating under both grid-connected (GCM) and islanded (IM) modes to minimize daily operational costs. The problem is formulated as a mixed-variable optimization model that explicitly leverages the control capabilities of BESS power converters. To solve it, a Parallel Particle Swarm Optimization (PPSO) algorithm is employed, coupled with a Successive Approximation (SA) power flow solver. The proposed approach was benchmarked against parallel implementations of the Crow Search Algorithm (PCSA) and the JAYA algorithm (PJAYA), both in parallel, using a realistic 33-node AC microgrid test system based on real demand and photovoltaic generation profiles from Medellín, Colombia. The strategy was evaluated under both deterministic conditions (average daily profiles) and stochastic scenarios (100 daily profiles with uncertainty). The proposed framework is evaluated on a 33-bus AC microgrid that operates in both grid-connected and islanded modes, with a battery energy storage system dispatched at both active and reactive power levels subject to network, state-of-charge, and power-rating constraints. Three population-based optimization algorithms are used to coordinate BESS schedules, and their performance is compared based on daily operating cost, BESS cycling, and voltage profile quality. Quantitatively, the PPSO strategy achieved cost reductions of 2.39% in GCM and 1.62% in IM under deterministic conditions, with a standard deviation of only 0.0200% in GCM and 0.2962% in IM. In stochastic scenarios with 100 uncertainty profiles, PPSO maintained its robustness, reaching average reductions of 2.77% in GCM and 1.53% in IM. PPSO exhibited consistent robustness and efficient performance, reaching the highest average cost reductions with low variability and short execution times in both operating modes. These findings indicate that the method is well-suited for real-time implementation and contributes to improving economic outcomes and operational reliability in grid-connected and islanded microgrid configurations. The case study results show that the different strategies yield distinct trade-offs between economic performance and computational effort, while all solutions satisfy the technical limits of the microgrid. Full article

With increasing penetration of renewable energy sources, virtual synchronous generator (VSG) control is playing an increasingly vital role in islanded microgrids’ frequency stabilization. However, frequency stability becomes a critical challenge when multiple VSGs operate in parallel within an islanded microgrid. This paper conducts in-depth research on frequency stability control in islanded microgrids with multi-VSGs. The prevailing frequency modeling approaches and underlying mechanisms of frequency instability are analyzed. Furthermore, both conventional and emerging machine learning-based frequency stability control strategies are comprehensively surveyed. Finally, potential research directions are outlined to facilitate future advancements. Full article

To address the power sharing dissymmetry in islanded microgrids with multiple parallel inverters caused by asymmetrical line impedance distribution and internal parameter mismatches, this paper proposes an adaptive virtual complex impedance control strategy based on line impedance identification for symmetry restoration. The strategy incorporates model predictive control (MPC) into the current inner loop and a two-degree-of-freedom (2-DOF) control into the voltage outer loop of inverters. By establishing a real-time impedance identification mechanism and generating adaptive virtual impedance, the system achieves symmetrical power sharing under asymmetrical grid conditions. Firstly, the voltage-current dual-loop design eliminates the impact of internal impedance dissymmetry and enhances disturbance rejection capabilities. Secondly, the adaptive virtual complex impedance actively compensates for line impedance mismatches among units, thereby resolving power unbalance and restoring operational symmetry. Simulation results validate the strategy’s effectiveness in enabling balanced power sharing and symmetrical operation of distributed inverters. Full article

Coastal reclamation reshapes both soils and vegetation, yet their coupled trajectories remain poorly understood. Here we investigated soil–vegetation co-evolution across a 15-year chronosequence on Hengsha Island in the Yangtze River estuary. The reclaimed soils were formed primarily from dredged estuarine silt and clay slurry deposited during hydraulic filling. Four representative sites were studied, spanning 3 (Y3), 7 (Y7), 10 (Y10), and 15 (Y15) years since reclamation. Soil physicochemical properties (pH, electrical conductivity, salinity, nitrogen, phosphorus, potassium) were measured, while vegetation cover was quantified using NDVI and fractional vegetation cover (FVC) derived from satellite data. Soil conditions improved markedly with reclamation age: pH, conductivity, and salinity declined, whereas nitrogen, phosphorus, and potassium accumulated significantly (p < 0.001). Vegetation shifted from salt-tolerant pioneers (e.g., Suaeda salsa, Phragmites australis) to mixed communities and cultivated rice fields (Oryza sativa), reflecting progressive improvements in soil quality. Vegetation cover increased in parallel, with NDVI rising from 0.12 ± 0.05 (Y3) to 0.35 ± 0.09 (Y15), reflecting a shift from salt-tolerant pioneers to structurally complex communities. Mantel tests revealed strong positive associations of NDVI with organic matter, nitrogen, and phosphorus, and negative associations with pH, conductivity, and salinity. Structural equation modeling identified organic matter and nitrogen enrichment, along with declining pH and dissolved salts, as dominant drivers of vegetation recovery. These results highlight a co-evolutionary process in which soil improvement and vegetation succession reinforce one another, offering insights for ecological restoration and sustainable management in coastal reclamation landscapes. Full article

Photovoltaic (PV) inverters are key elements in modern distributed generation systems. One of the critical requirements for their reliable operation is islanding detection, as defined by IEEE 1547.1-2020 and PN-EN 62116 standards. This study investigates the performance of 28 commercially available, low-voltage, prosumer-dedicated PV inverters under unintentional islanding conditions, analyzing detection time, voltage amplitude, frequency deviations, and rate of change of frequency (ROCOF). Experimental results confirm that while most units comply with the 2 s disconnection limit, significant variability in reaction times was observed, with some units exceeding standard thresholds. Moreover, deviations in voltage and frequency indicate that in many cases, power quality standards were not maintained, potentially leading to safety and stability concerns. In the second stage of tests, a parallel operation of inverters was examined, revealing additional disturbances, such as voltage swells and beat phenomena caused by phase-locked loop (PLL) desynchronization. A simplified theoretical model confirmed the possibility of resonance and oscillatory interactions between parallel inverters during islanding. These findings highlight the need for improved coordination and control strategies for distributed generation based on inverters, particularly in microgrid applications. Full article

This paper presents an optimization-based scheduling strategy for battery energy storage systems (BESS) in alternating current microgrids, considering both grid-connected and islanded operation. The study addresses two independent objectives: minimizing energy losses in the distribution network and reducing carbon dioxide emissions from dispatchable power sources. The problem is formulated using a full AC power flow model that simultaneously manages active and reactive power flows in BESS located in the microgrid, while enforcing detailed operational constraints for network components, generation units, and storage systems. To solve it, a parallel implementation of the Particle Swarm Optimization (PPSO) algorithm is applied. The PPSO is integrated into the objective functions and evaluated through a 24-h scheduling horizon, incorporating a strict penalty scheme to guarantee compliance with technical and operational limits. The proposed method generates coordinated charging and discharging plans for multiple BESS units, ensuring voltage stability, current limits, and optimal reactive power support in both operating modes. Tests are conducted on a 33-node benchmark microgrid that represents the power demand and generation from Medellín, Colombia. This is compared with two methodologies reported in the literature: Parallel Crow Search and Parallel JAYA optimizer. The results demonstrate that the strategy produces robust schedules across objectives, identifies the most critical network elements for monitoring, and maintains safe operation without compromising performance. This framework offers a practical and adaptable tool for microgrid energy management, capable of aligning technical reliability with environmental goals in diverse operational scenarios. Full article

Rapid urbanization has led to substantial changes in land use, resulting in challenges related to the urban microclimate across multiple scales. Given the strong relationship between urban morphology and microclimatic conditions, designing appropriate urban fabric models plays a key role in supporting sustainable urban development. The spatial form and geometry of buildings influence external environmental conditions and affect the performance of urban architecture. This study investigates how morphological and geometric characteristics of urban form influence microclimate, using a case study approach. Data were obtained through a literature review and existing urban development plans. ENVI-met software was used to simulate microclimatic variables, which were treated as dependent factors. In parallel, morphological components—treated as independent variables—were analyzed using GIS Pro software. Findings reveal that the configuration of urban fabric has a notable impact on microclimate. Specifically, higher building density is associated with greater heat accumulation around structures. Urban areas with fragmented and highly granular layouts tend to trap more heat, thereby intensifying the urban heat island effect. Conversely, when buildings are spaced apart, increased wind flow helps reduce temperatures in central urban zones of urban development in District 9, Mashhad, Iran. The results also emphasize the importance of vegetation placement. While greenery can mitigate heat in ventilated areas, dense vegetation in wind-restricted zones may raise ambient temperatures. Overall, the study offers a simulation-based understanding of how urban form influences microclimate. These insights can assist urban planners and designers in creating environments that promote more favorable local climatic conditions. Full article

Interfaces between two fluids exhibit an excess free-energy cost per unit area that is manifested as surface tension. This equilibrium property generally depends on temperature, which enables the phenomenon of thermocapillary flow, wherein application of a temperature gradient having a component parallel to the surface generates a net in-plane effective body force on the fluid and thereby causes flow. Here, we study the thermocapillary flow in fluid smectic liquid crystal films freely suspended in air and stabilized in thickness by the smectic layering. If such films are a single layer (~3 nm) or a few layers thick, they have the largest surface to volume ratio of any fluid preparation, making them particularly interesting in the context of thermocapillary flow, which is two-dimensional (2D) in the film plane. Five-layer thick films in the form of spherical bubbles were subjected to a north–south temperature gradient field along a polar axis, with flow fields mapped using inclusions on the film surface as tracers, where the inclusions were “islands”, small circular stacks of extra layers. These experiments were carried out on the International Space Station to avoid interference from thermal convention of the air. The flow field as a function of latitude on the bubble can be successfully modeled using Navier–Stokes hydrodynamics, modified to include permeative flow out of the background fluid into the islands. Full article