Search Results (45)

Fractional-order four-wing (FO 4-wing) systems are of significant importance due to their complex dynamics and wide-ranging applications in secure communications, encryption, and nonlinear circuit design, making their control and stabilization a critical area of study. In this research, a novel model-free finite-time flexible sliding mode control (FTF-SMC) strategy is developed for the stabilization of a particular category of hyperchaotic FO 4-wing systems, which are subject to unknown uncertainties and input saturation constraints. The proposed approach leverages fractional-order Lyapunov stability theory to design a flexible sliding mode controller capable of effectively addressing the chaotic dynamics of FO 4-wing systems and ensuring finite-time convergence. Initially, a dynamic sliding surface is formulated to accommodate system variations. Following this, a robust model-free control law is designed to counteract uncertainties and input saturation effects. The finite-time stability of both the sliding surface and the control scheme is rigorously proven. The control strategy eliminates the need for explicit system models by exploiting the norm-bounded characteristics of chaotic system states. To optimize the parameters of the model-free FTF-SMC, a deep reinforcement learning framework based on the adaptive dynamic programming (ADP) algorithm is employed. The ADP agent utilizes two neural networks (NNs)—action NN and critic NN—aiming to obtain the optimal policy by maximizing a predefined reward function. This ensures that the sliding motion satisfies the reachability condition within a finite time frame. The effectiveness of the proposed methodology is validated through comprehensive simulations, numerical case studies, and comparative analyses. Full article

In time-sensitive aerial missions such as urban surveillance, emergency response, and adversarial airspace operations, achieving rapid and reliable formation control of multi-UAV systems is crucial. This paper addresses the challenge of ensuring robust and efficient formation control under stringent time constraints. The proposed singularity-free prescribed-time formation (PTF) control scheme guarantees task completion within a user-defined time, independent of initial conditions and control parameters. Unlike existing scaling-based prescribed-time methods plagued by unbounded gains and fixed-time strategies with non-tunable convergence bounds, the proposed scheme uses fixed-time stability theory and systematic parameter tuning to avoid singularity issues while ensuring robustness and predictable convergence. The method also accommodates directed communication topologies and unknown external disturbances, allowing follower UAVs to track a dynamic leader and maintain the desired geometric formation. Finally, some simulation results demonstrate the effectiveness of the proposed control strategy, showcasing its superiority over existing methods and validating its potential for practical applications. Full article

Rural public cultural spaces serve as vital venues for information exchange, interpersonal interaction, and cultural and leisure activities in rural communities. Since the Rural Revitalization Strategy was proposed in 2017, the planning and provision of rural public cultural spaces have attracted increasing attention in China. However, many such spaces remain underutilized, accompanied by low levels of user satisfaction among villagers. A key reason for this is the mismatch between standardized spatial configurations and villagers’ dynamic functional needs. Drawing on Hertzberger’s theory of spatial polyvalence, this study proposes a framework to evaluate spatial flexibility in rural public cultural spaces. The framework introduces quantitative indicators and computational methods across two dimensions: “competence”, referring to a space’s potential to accommodate multiple functions, and “performance”, reflecting the efficiency of functional transformation during actual use. Employing the proposed method, this study conducts a case analysis of the Xiangyang Village Neighborhood Center in Shanghai to evaluate its spatial characteristics and actual usage. The evaluation reveals two key issues at the overall level: (1) many residual spaces remain undesigned and lack strategies to support spontaneous use; (2) the spatial layout shows rigid public–private divisions, with little adaptability. At the room level, spaces such as the elevator, hairdressing room, party secretary’s office, and health center are functionally rigid and underutilized. Drawing on exemplary cases, this study proposes several key strategies such as (1) optimizing and innovatively activating residual spaces, (2) integrating multifunctional programs, and (3) improving spatial inclusiveness. Full article

In China, educators are encouraged by administrators to assume instructional and language strategies to align with their students’ needs so as to enhance classroom communicative effectiveness, with students’ perceptions of teachers’ behavior being a salient factor in this process. This study, based on communication accommodation theory, examines how students’ perceptions of teachers’ behaviors influence reports of positive classroom outcomes. Using structural equation modeling, we analyzed responses from a sample of 422 university students in Shanghai. The results showed that the students’ perceptions of teachers’ communication accommodation behaviors, such as verbal and nonverbal tactics, teaching content, and emotional support behaviors, significantly and positively impacted students’ learning effectiveness, teacher credibility, and communication satisfaction. Furthermore, teacher credibility partially mediated the relationship between perceptions of accommodation and learner effectiveness. The findings offer practical insights for educators by suggesting that strategic adaptions of communication accommodations behaviors can promote students’ learning outcomes. Full article

Frequency-modulated continuous wave (FMCW) and orthogonal frequency-division multiplexing (OFDM) technologies play significant roles in millimeter-wave radar and communication. Their combinations, however, are understudied in the literature. This paper introduces a novel OFDM-FMCW dual-functional radar-communications (DFRC) system that takes advantage of the merits of both technologies. Specifically, we introduce a baseband modulation to the traditional FMCW radar system architecture. This integration combines the advantages of both waveforms, enhancing the diversity of radar transmission waveforms without compromising high-resolution distance detection and enjoying the communication capabilities of OFDM in the meantime. We establish the system and signal models for the proposed DFRC and develop holistic methods for both sensing and communications to accommodate the integration. For radar, we develop an efficient radar sensing scheme, with the impacts of adding OFDM also being analyzed. A communication scheme is also proposed, utilizing the undersampling theory to recover the OFDM baseband signals modulated by FMCW. The theoretical model of the communication receive signal is analyzed, and a coarse estimation combined with a fine estimation method for Carrier Frequency Offset (CFO) estimation is proposed. System simulations validate the feasibility of radar detection and communication demodulation. Full article

This study assesses the informational usefulness of several uncertainty metrics in predicting the monetary policy and actual economic activity of Tunisia. We use a Bayesian time-varying vector autoregressive (VAR) model to identify uncertainty shocks sequentially. We complement the analysis with the use of local projections (LPs), a recently flexible and simple method that accommodates the effect of an exogenous intervention on policy outcomes. The findings suggest that shocks to global and spillover uncertainty are important in elucidating the dynamics of industrial production and consumer prices. The impulse response functions (IRFs) show that the central bank does not follow a linear-rule-based monetary strategy. The irreversibility theory, or the “precautionary” behavior, is tested in a vector error correction model (VECM). The money market rate impacts industrial production and consumer prices differently during high versus low uncertainty, depending on the uncertainty variable and the horizon (short versus long run). The effects can be insignificant or significantly dampened during high uncertainty, indicating that conventional monetary policy may be ineffective or less influential. The “wait and see” strategy adopted by economic agents implies that they do not take timely actions until additional pieces of information arrive. While this could not be the sole explanation of our findings, it conveys the importance of dealing with uncertainty in decision-making and highlights the necessity of a clear and credible communication strategy. Importantly, the central bank should complement interest rates with the use of unconventional monetary policy instruments for better flexibility. Our work provides a comprehensive and clear picture of the Tunisian economy and a focal guide for the central bank’s future practices to achieve macroeconomic objectives. Full article

In Hungary, the monastic orders were dissolved in 1950 during the harshest communist dictatorship. A total of 11,538 people were affected by the ban. The consequences of the dissolution of the monastic orders not only affected the people who were directly involved but also practically the whole society. The orders had an important role on the education, society and culture of the country, and their banning for ideological reasons had enormous consequences. The question is how dissolved monks and nuns managed to integrate into a society where they were marginalized. Through the life story of a nun, named Speravia (1914–2009), I present the behavioral patterns which helped to survive the persecution of religion during communism and then in socialism. I found that she maintained her religious identity through change and resilient means. Identity maintenance in modern society is a dynamic process in which there is room for change through constant adaptation to the environment. Her obedience was transformed into accommodation to the political system by making deals with the system. This behavior can be called resilience. Resilient behavior is characterized by both resistance and accommodation. To do this, she had to be active and have the support of her environment. In this study, I used the principles of Grounded Theory, which is a specific content analysis method. I analyzed the interview using the Grounded Theory approach, at least some of its techniques. I coded some parts of the interview line by line and other parts only as units of thought. Then, I aggregated the codes and I formulated categories. After this process, I compared the meanings of the categories and it became clear to me that my interviewee’s behavior could be understood as resilient. This is why I emphasized the role of resilience in identity maintenance in the title of the study. My conclusion is that while Sperávia flexibly adapted to the new political system, she could also preserve her identity as a nun. I call this survival strategy religious resilience. Full article

This paper evaluates the socioecological classroom in the context of a whole-school approach to inclusive education, which has evolved beyond the traditional classroom setting. Inclusive education calls for a paradigm shift to accommodate learners previously marginalised, with the classroom transforming into an ecosystem. The socioecological paradigm steers away from the notion that psychological and physiological elements are the main causes of disability. The importance of addressing multiple layers of influence is emphasised to create a supportive and inclusive learning environment. First, Bronfenbrenner’s Ecological Systems Theory, which emphatically explains how a learner’s development is influenced by the systems in the environment that surrounds them, and then Foucault’s Theory of Power and Knowledge, in which power and knowledge are interconnected and inseparable, with power being exercised through the creation and control of knowledge, guided this study. A qualitative approach was adopted, and semi-structured interviews, focus group discussions and non-participant observation were used to collect data. Phenomenological analysis was used to analyse the data from these data-collecting instruments. It was found that learners with disabilities need support at home, with imbalances being found in the power–knowledge relations between teachers and parents, and teachers occupying a superior position regarding academic knowledge. Some teachers still believe in the Medical-Deficit Model. A strengths-based approach should rather be adopted. Strategies for enhancing community–school collaboration that balances teacher–parent power dynamics should be explored. Full article

The Gaussian signaling strategy with power control for the Gaussian Z-interference channel with weak interference is reviewed in this paper. In particular, we study the various communication strategies that may arise at various points of the capacity region and identify the locations of the phase transitions between the various strategies. The Gaussian Z-interference channel with weak interference is known to have two critical points in its capacity region, where the slope of the region shows a sudden change. They occur at the points of the unconditional maximum rate for one of the users and the maximum rate that can be accommodated by the other user. In this paper, we discuss additional critical points (locations of phase transitions) in the achievable region of this channel. These turn out to be second-order phase transitions, i.e., we do not observe a discontinuous slope in the achievable rate region, but there is a discontinuity in the second derivative of the rate contour of the achievable region. This review paper is mainly based on some of our ITA (Information Theory and Applications Workshop, UCSD, San Diego, CA, USA) papers since 2011. Full article

This article investigates the resilient-based consensus analysis of fractional-order nonlinear leader-following systems with distributed and input lags. To enhance the practicality of the controller design, an incorporation of a disturbance term is proposed. Our modeling framework provides a more precise and flexible approach that considers the memory and heredity aspects of agent dynamics through the utilization of fractional calculus. Furthermore, the leader and follower equations of the system incorporate nonlinear functions to explore the resulting changes. The leader-following system is expressed by a weighted graph, which can be either undirected or directed. Analyzed using algebraic graph theory and the fractional-order Razumikhin technique, the case of leader-following consensus is presented algebraically. To increase robustness in multi-agent systems, input and distributive delays are used to accommodate communication delays and replicate real-time varying environments. This study lays the groundwork for developing control methods that are more robust and flexible in complex networked systems. It does so by advancing our understanding and practical application of fractional-order multi-agent systems. Additionally, experiments were conducted to show the effectiveness of the design in achieving consensus within the system. Full article

The assessment of suitability is the cornerstone for the development of ecotourism in nature reserves. This paper adopts the Delphi method to invite 30 experts to score and screen a series of indicators and then calculates the weight of each indicator through the hierarchical analysis method (AHP) to establish a comprehensive evaluation index system for the suitability of ecotourism development. The AHP method includes four constraints layers (tourism resources, socio-economic environment, ecological conditions, and tourism market), in addition to eleven element layers and thirty-eight indicators. It establishes overarching criteria for evaluating ecotourism suitability. Our research focuses on Dinghushan, Xilin Gol Grassland, Hongze Lake Wetland, and Jiuzhai valley, and the results are as follows: (1) Ecotourism suitability evaluation level is divided into five levels, level I (0 ≤ S < 30) ecotourism development suitability is the lowest, meaning an area is extremely unsuitable for ecotourism development. Level V (90 ≤ S < 100) has a very high ecotourism value, meaning an area is highly suitable for ecotourism development. (2) Jiuzhai valley scored the highest ecotourism suitability evaluation score of 87.63, and Xilingol Grassland scored the lowest score of 81.27. However, the composite scores of all the nature reserves were above 80, placing them at Suitability Level IV, and thereby indicating a high suitability for ecotourism development. (3) Divergences in ecotourism suitability emerge among various nature reserve types, with grassland and meadow reserves exhibiting lower suitability levels. Addressing this, a robust management and monitoring system is imperative, alongside intensified efforts in ecological restoration, vegetation protection, community engagement, education, awareness, and increased policy support and tourism capital investment. (4) The results of the expert questionnaire showed that the maximum weight of the indicators affecting the evaluation of the suitability of ecotourism was the satisfaction of tourists (0.120), and the minimum weight was the accommodation facilities (0.002), which illustrated the important role of tourists in the ecotourism development carried out in the nature reserve. (5) Through empirical analysis of numerous cases, the study validates the practicality and effectiveness of the index system and provides scientific guidelines for the suitability of existing nature reserves for further ecotourism development. This contributes to the research theory on the suitability evaluation of ecotourism development and serves as a valuable reference for the future ecotourism development of diverse nature reserves. Full article

This study focuses on sustainable development in urban planning and develops a 21st century sustainable neighborhood. For empirical neighborhood design, urban design was conducted on a specific 5.2 ha site in Le Rheu Commune, France. Targeting a site with the attributes of ecologically based sustainable urban planning, this study derived a neighborhood design model using sustainable development strategy methods from environmental, economic, and social perspectives. Consequently, an infrastructure-based design was created, integrating and accommodating the infrastructure and various urban amenities necessary for the neighborhood. Additionally, infrastructure within the neighborhood was proposed as a design element for technology-based sustainable urban planning. This is a novel, empirical study based on urban planning theory. This theory-based empirical research model contributes to urban planning theory and the knowledge of urban planners and architects. Future studies should conduct urban planning research that combines sustainable neighborhood planning based on ecological infrastructure, as attempted in Le Rheu Commune, with the IoT, such as smart home care. Full article

Accurate thermal infrared (TIR) fast-forward models are critical for weather forecasting via numerical weather prediction (NWP) satellite radiance assimilation and operational environmental data record (EDR) retrieval algorithms. The thermodynamic and compositional data about the surface and lower troposphere are derived from semi-transparent TIR window bands (i.e., surface-sensitive channels) that can span into the far-infrared (FIR) region under dry polar conditions. To model the satellite observed radiance within these bands, an accurate a priori emissivity is necessary for the surface in question, usually provided in the form of a physical or empirical model. To address the needs of hyperspectral TIR satellite radiance assimilation, this paper discusses the research, development, and preliminary validation of a physically based snow/ice emissivity model designed for practical implementation within operational fast-forward models such as the U.S. National Oceanic and Atmospheric Administration (NOAA) Community Radiative Transfer Model (CRTM). To accommodate the range of snow grain sizes, a hybrid modeling approach is adopted, combining a layer scattering model based on the Mie theory (viz., the Wiscombe–Warren 1980 snow albedo model, its complete derivation provided in the Appendices) with a specular facet model. The Mie-scattering model is valid for the smallest snow grain sizes typical of fresh snow and frost, whereas the specular facet model is better suited for the larger sizes and welded snow surfaces typical of aged snow. Comparisons of the model against the previously published spectral emissivity measurements show reasonable agreement across zenith observing angles and snow grain sizes, and preliminary observing system experiments (OSEs) have revealed notable improvements in snow/ice surface window channel calculations versus hyperspectral TIR satellite observations within the NOAA NWP radiance assimilation system. Full article

This article focuses on methods for designing heuristic models within the paradigm of systems theory and in the disciplinary context of intercultural communication. The main question arises from the striking observation that common language is insufficient to develop knowledge about human communication, especially when many factors of complexity (such as ambiguity, paradoxes, or uncertainty) are involved in the composition of an abstract research object. This epistemological, theoretical, and methodological problem is one of the main challenges to the scientificity of anthropological theories and concepts on culture. Moreover, these questions lie at the heart of research on intercultural communication. Authors and theorists in the complexity sciences have already stressed the need, in such cases, to think in terms of models or semiotic representations, since these tools of thought can mediate much more effectively than unformalized language between the heterogeneous set of perceptions arising from the field of experience, on the one hand, and the philosophical principles that organize speculative thought, on the other. This sets the scene for a reflection on the need to master the theory of heuristic models when it comes to developing scientific knowledge in the field of intercultural communication. In this essay, my first aim is to make explicit the conditions likely to ensure the heuristic value of a model, while my second aim is to clarify the operational function and required level of abstraction of certain terms, such as heading, concept, category, model, and system that are among the most commonly used by academics in their descriptive accounts or explanatory hypotheses. To achieve this second objective, I propose to create cognitive meta-categories to identify the three (nominal, cardinal, or ordinal) roles of words in the reference grids that we use to classify our ideas and to specify how to use these meta-categories in the construction of our heuristic models. Alongside the theoretical presentation, examples of application are provided, almost all of which are drawn from my own research into the increased cultural vigilance of the majority population in Québec since the reasonable accommodation crisis in this French-speaking province of Canada. The typology I propose will perhaps help to avoid the confusion regularly committed by authors who attribute only cosmetic functions to words that nevertheless have a highly heuristic value and who forget to consider the logical leaps of their theoretical thinking in the construction of heuristic models. Full article

Intergenerational integration has given rise to a novel aging paradigm known as all-age communities, which is garnering international attention. In China, the aging population and the implementation of the three-child policy have resulted in increased demand for retirement and childcare services among residents in older neighborhoods. Consequently, there is a pressing need to retrofit these older neighborhoods to accommodate all-age living arrangements given the high demand they generate. Therefore, this study undertakes research interviews with residents and constructs an exploratory theoretical model rooted in established theory. To assess the significance of our model, we employ Smart PLS 3.0 based on 297 empirical data points. Our findings indicate that anxiety has a significant negative effect on payment behavior; objective perception, willingness to pay, and government assistance exert significant positive effects on payment behavior. By comprehensively analyzing the mechanisms underlying residents’ payment behavior, this study provides valuable insights for the government for promoting the aging process within communities and formulating effective transformation policies. Full article