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1
Gubert, Serge. "« DU VENTRE DE LA ROYAUTÉ AUX JARDINS DE LA PAPAUTÉ » : ENTRE ISLAM ET CHRÉTIENTÉ, LE LEXIQUE ET LA MÉTAPHORE DU CORPS". Arabica 49, nr 3 (2002): 267–98. http://dx.doi.org/10.1163/157005802760253243.
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AbstractÀ partir d'un exemple historique, celui de la dynastie mérinide (13ème-15ème siècle), cet article envisage la convergence entre lexique religieux et métaphores du corps tirées de la médecine humorale, au profit d'une énonciation discursive et visuelle de la souveraineté. Après l'examen de la métaphore du « ventre de pestilence » (Ibn Haldūn, Muqaddima), la deuxième partie opère une relecture du corps de la royauté mérinide (lexique emblématique, récit de fondation, cérémonial). Cette étude est enrichie grâce aux travaux réalisés sur le corps des rois, de l'empereur et du pape dans la sphère chrétienne. Il existerait une trajectoire historique commune aux deux rives, une matrice de la culture politique du corps étayée auprès des sciences arabes. Paradoxe, cette trajectoire est aujourd'hui mieux connue pour l'Occident chrétien, et appelle de nouvelles recherches dans le domaine arabo-islamique pour mieux cerner, dans le temps, une convergence du théologique et du corporel qui pourrait être celle du spirituel (imāma) et du temporel (mulk).
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SAIDI, IMEN, i NAHLA TOUATI. "APPRENTISSAGE DE COMMANDE POUR LE SUIVI DE TRAJECTOIRE D'UN PENDULE INVERSÉ À ROUE D'INERTIE NON LINÉAIRE". REVUE ROUMAINE DES SCIENCES TECHNIQUES — SÉRIE ÉLECTROTECHNIQUE ET ÉNERGÉTIQUE 68, nr 4 (23.12.2023): 424–30. http://dx.doi.org/10.59277/rrst-ee.2023.4.17.
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Cet article propose le contrôle d'apprentissage itératif pour les systèmes sous-actionnés non linéaires. Pour améliorer la vitesse de convergence du contrôle d'apprentissage itératif pour de tels systèmes et réduire la fluctuation de l'erreur du système, un algorithme de contrôle d'apprentissage itératif en boucle fermée de type D à gain variable exponentiel a été choisi. L'analyse de simulation MATLAB a ensuite été réalisée sur un système sous-actionné, non linéaire et instable, à savoir le pendule inversé à roue d'inertie. Les résultats de la simulation montrent que l'algorithme est efficace. De bonnes performances de suivi ont été obtenues. Le système converge vers des cycles limites stables après quelques itérations, garantissant des erreurs fluides et une vitesse de convergence satisfaisante.
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Rzezuchowski, Tadeusz. "Strong convergence of selections implied by weak". Bulletin of the Australian Mathematical Society 39, nr 2 (kwiecień 1989): 201–14. http://dx.doi.org/10.1017/s0004972700002677.
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In some situations weak convergence in L1, implies strong convergence. Let P, L: T → C∘(ℝd) be measurable multifunctions (C∘(ℝd) being the set of closed, convex subsets of ℝd) the values L(t) affine sets and W(t) = P(t) ∩ L(t) extremal faces of P(t). Let pk be integrable selections of P, the projection of pk,(t) on L(t) and pk(t) on W(t). We prove that if converges weakly to zero then pk − k converges to zero in measure. We give also some extensions of this theorem. As applications to differential inclusions we investigate convergence of derivatives of convergent sequences of solutions and we describe solutions which are in some sense isolated. Finally we discuss what can be said about control functions u when the corresponding trajectories of ẋ = f(t, x, u) are convergent to some trajectory.
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Purchase, Sharon, Christina Kum i Doina Olaru. "An analysis of technical and commercialization paths for an innovation trajectory". Journal of Business & Industrial Marketing 32, nr 6 (3.07.2017): 848–63. http://dx.doi.org/10.1108/jbim-06-2015-0111.
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Purpose The purpose of this study is to investigate sequences of event and the resulting innovation paths and trajectories followed by a university spin-off organization. Design/methodology/approach A single longitudinal case study methodology was applied to analyze innovation events and paths along the trajectory. Narrative methods were used to analyze actor perceptions on innovation processes/events. Findings The study categorizes events and paths in two categories, technical and commercialization, and finds that lock-in events matter for convergence of an innovation trajectory. The results indicate that understanding critical events may assist timely interventions in the innovation paths, thus potentially avoiding disruptions of the development of an innovation trajectory. The temporal processes reveal contrasting convergence–divergence patterns in the trajectory, depending on the types of events that occur. Research limitations/implications Using a single case data may limit the applicability of the findings, which calls for future research. Practical implications Industries could monitor the technical and commercialization paths as a strategy to reduce “vulnerability” of the innovation trajectory and possible negative impacts. Knowledge about the role of the CEO is key for a university spin-off organization. Originality/value This study presents a new typology of events and paths, identifies and characterizes lock-in events and shows the relatively fragile dexterity between convergent and divergent paths along an innovation trajectory.
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Talbot, Aurélien. "La traductique en débat : émergence et usages d’un néologisme". Équivalences 50, nr 1 (2023): 19–41. http://dx.doi.org/10.3406/equiv.2023.1607.
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Le néologisme «traductique » apparaît et commence à circuler dans la deuxième moitié des années 1980. Le concept qu’il désigne fait alors l’objet de débats en écho à ceux ayant accompagné l’apparition du néologisme «traductologie » . Nous cherchons ainsi à dégager deux visages de la traductique en revenant brièvement sur la diffusion de ce néologisme qu’Antoine Berman aurait été «le premier à défendre activement » (Collectif 1988) avant qu’il ne soit repris dans une toute autre optique de recherche et développement (L’Homme 1988 ; 1999). Nous observons ensuite comment la ligne de partage entre traductique et traductologie semble renforcer la distinction ancienne entre traduction littéraire et spécialisée alors que la traductique contribue par ailleurs à faire émerger une préoccupation transversale aux différents genres de traduction comme en témoignent les recherches d’Elmar Tophoven. Face à cette contradiction, nous montrons, enfin, que la trajectoire du néologisme «traductique » est traversée par la question du point de bascule entre une convergence redoutée et une convergence heureuse entre traduction et informatique, son apparition ayant permis de rappeler le caractère «d’emblée technique » de la traduction tout en soulignant les risques liés à son «devenir industriel » (Stiegler 1987).
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Cui, Hong, i Chongwen Yu. "A Mathematical Model for Self-Twist Yarn Spinning Process". Research Journal of Textile and Apparel 18, nr 1 (1.02.2014): 1–5. http://dx.doi.org/10.1108/rjta-18-01-2014-b001.
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A mathematical model is established for self-twist spinning process by applying laws of fluid mechanics (i.e. mass conservation and momentum conservation). The motion curve of the convergent point was determined and the convergence point was decided by densities and velocities of two fed-in strands and the resultant self-twist yarn, independent of their mechanical properties. The experimental verification proves that the motion trajectory of the convergence point reaches a better agreement with the theoretical trajectory. The results provide general way to study the self-twist yarn spinning process and optimize the process parameters.
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Zhironkin, Sergey A., Vladimir V. Guzyr i Magerram A. Gasanov. "Economic convergence in the methodology of structural shifts". Vestnik Tomskogo gosudarstvennogo universiteta. Ekonomika, nr 58 (2022): 24–41. http://dx.doi.org/10.17223/19988648/58/2.
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Throughout the entire period of market transformations, the trend towards the distance of the Russian economy from technologically advanced countries has persisted, in terms of both the dynamics of the main macroeconomic indicators and structural proportions. This is due to the high sensitivity of the Russian economy to external shocks, including technological ones, as well as a number of successive negative structural shifts. At the same time, the commonality of endogenous processes, which affect the structure of factors of production and distribution of national income, in the economies of advanced and catching up countries is not fully associated with economic convergence. The studies are dominated by exogenous sources of convergence - sociopolitical, cultural. Therefore, the study of the role and place of structural shifts in the system of economic convergence is a methodological approach that allows one to come close to the theoretical foundations for stabilizing macroeconomic dynamics, reducing the susceptibility of the national economy to external shocks, and entering a long-term growth trajectory above world rates. In this article, the authors consider the problem of launching convergent structural shifts - the basis for the transition of the Russian economy from economic divergence to convergence with advanced countries, which was the basis for the aim of this study. Within the framework of this article, a methodology for analyzing structural shifts in their mutual influence on technological, structural and economic convergence is presented. The authors give a typology of convergent and divergent structural shifts that bring the national economy closer or further away from technologically advanced market systems. Such a typology of structural shifts implies the endogenous nature of economic convergence, due to a change in the proportions of accumulation and consumption, the involvement of production factors in the creation of national income and its distribution, contrary to the prevailing exogenous approach to the study of economic convergence. Based on the presented typology, the article highlights the factors of structural convergence -neo-industrial and fundamental investment, associated with a priority increase in funding for fundamental research, the creation of new innovation and investment partnerships between the state and business, and the modernization of basic industries based on convergent technologies. The authors show that these factors should be institutionalized in a system of convergence-oriented structural policy, which is a key condition for the transition of the Russian economy from structural divergence to convergence, with access to a sustainable growth trajectory and a reduction in exposure to external shocks.
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Gan, Wenyang, Tianxing Xia i Zhenzhong Chu. "A Prognosis Technique Based on Improved GWO-NMPC to Improve the Trajectory Tracking Control System Reliability of Unmanned Underwater Vehicles". Electronics 12, nr 4 (12.02.2023): 921. http://dx.doi.org/10.3390/electronics12040921.
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The dynamics model of the unmanned underwater vehicle (UUV) system is highly nonlinear, multi-degree-of-freedom, strongly coupled, and time-varying. Its motion control has been a complex problem due to the unknown information about and the uncertainty of the working environment. To improve the performance and reliability of UUV trajectory tracking control, a trajectory tracking method based on nonlinear model predictive control is designed, and an improved gray wolf optimization (IGWO) is proposed for the optimization of nonlinear model predictive control. The convergence factor of IGWO is designed as a nonlinear attenuation function, and the memory function is added to the position update equation to enhance the effect of trajectory tracking control. Through the simulation in the ROS environment, the influence of the convergence factor on the convergence rate of trajectory tracking error and tracking control performance is obtained. By comparing the tracking effects of several groups of reference trajectories, it is shown that the proposed method is universally applicable and effective to the trajectory tracking control of UUV. Compared with traditional gray wolf optimization (GWO), SQP, and other optimization algorithms, the reliability of the proposed method for UUV trajectory tracking control is demonstrated.
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Ning, Tan, Zhang Yun-Jun, Ouyang Qi i Geng Zhi. "Dynamical Convergence Trajectory in Networks". Chinese Physics Letters 22, nr 9 (25.08.2005): 2447–50. http://dx.doi.org/10.1088/0256-307x/22/9/085.
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Le Bas, Christian. "Anticipations, compétence économique et régimes technologiques". Économie appliquée 50, nr 2 (1997): 37–61. http://dx.doi.org/10.3406/ecoap.1997.1631.
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Cet article traite des anticipations faites par les firmes industrielles concernant les technologies. Deux approches sont retenues dans la littérature : la première considère que sous certaines conditions les anticipations technologiques peuvent être contre-productives, une seconde retient un schéma où les «prévisions» quant aux innovations sont autoréalisatrices. Nous montrons ensuite pourquoi les anticipations des agents sont cruciales dans une approche évolutionniste. On considère un schéma simple d’accumulation technologique de type kaldorien dans lequel les anticipations concernant le taux de progrès technique sont adaptatives. On montre que la trajectoire de croissance équilibrée est unique mais que les propriétés de convergence vers le point fixe sont différentes selon les régimes technologiques identifiés par Winter : on converge de façon monotone en régime routinier, par fluctuations en régime entrepreneurial. Ce résultat dépend de la façon dont la compétence économique fonctionne dans les deux régimes.
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Kim, Maksim, Olesya Glushchenko i Catherine Puck. "Convergent Journalism: The Main Vectors of Development and Prospects". Theoretical and Practical Issues of Journalism 12, nr 3 (30.09.2023): 399–417. http://dx.doi.org/10.17150/2308-6203.2023.12(3).399-417.
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Today, convergence is called both the business strategy for the development of media holdings, and the tactics of convergence of different media to promote services, and the merging of competencies in the training and professional activities of various media professionals, and the adaptation of public text to the realities of the latest technological revolution in the digital world, etc. The classical understanding of convergence as a mechanical merger is being revised. The generalized results of convergence in the media are new formats of information transmission and organizational and managerial structures optimized for this, hybrid content-genre forms, functional transformation of the media and much more. Convergence appears to be an evolutionary process that unfolds at different speeds across a variety of vectors in the instrumental-technological, organizational-managerial and text-centric spheres. With a large assumption, it is possible to construct a universal periodization of media convergence with an indication of the time range for each stage, since different media follow their own trajectory in convergent evolution. The authors propose to count the start of evolutionary processes in each area and, according to the configuration of new features and specific results of evolution, predict a development model with promising tracks for a particular media. Using structural and comparative analysis, the authors study in detail the approaches to the interpretation of the concept of "convergence", comprehend its true nature, and also explore the instrumental-technological, organizational-managerial and text-centric spheres of media convergence. This makes it possible to predict promising directions of convergent evolution in each area. Special attention is paid to the analysis of new selective features of journalistic text in the digital environment, the vector of their development is determined. The authors deal with the problems of professional training of journalists, analyzes changes in the professional skills of specialists for convergent journalism.
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Qian, Dongjin, Haiqing Liu, Shengli Wang, Shuo Zhang i Jingyi Shi. "Research on Path Planning for Unmanned Surface Vessels Based on AIS Data". Journal of Physics: Conference Series 2694, nr 1 (1.01.2024): 012051. http://dx.doi.org/10.1088/1742-6596/2694/1/012051.
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Abstract To address the issues of poor endpoint convergence and suboptimal path quality in global path planning for unmanned surface vessels (USVs), this paper proposes an endpoint-convergence oriented improved genetic algorithm based on AIS data. Firstly, utilizing a genetic algorithm with an endpoint-convergence objective function, a set of paths with strong endpoint convergence is selected. Secondly, to overcome the limitations of a single optimization algorithm, a multi-objective path planning approach is employed using a genetic algorithm, thereby improving the distance and trajectory smoothness in global path planning for unmanned ships. Finally, the planned paths are evaluated by comparing them with the real paths from AIS data. The simulation results demonstrate that the proposed method outperforms other traditional algorithms in terms of average path turn count and turn angle, reducing them by an average of 35.41% and 35.72%, respectively. Moreover, the proposed method exhibits the smallest error compared to the real trajectories, with an average reduction of 18.26%. These results validate the effectiveness and rationality of the proposed approach in improving path quality, reducing path turn count, and achieving better alignment with actual trajectories.
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Deng, Jiao-Jiao, Hsiao-Dong Chiang i Tian-Qi Zhao. "Newton Method and Trajectory-Based Method for Solving Power Flow Problems: Nonlinear Studies". International Journal of Bifurcation and Chaos 25, nr 06 (15.06.2015): 1530018. http://dx.doi.org/10.1142/s0218127415300189.
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This paper analyzes the convergence properties and convergence region of a class of trajectory-based power flow methods. The convergence region of the trajectory-based method is a connected set and possesses the near-by property. The convergence region of Newton method and trajectory-based method in solving power flow problems are numerically investigated. Since the convergence region of trajectory-based method corresponds to the stability region of the nonlinear dynamic system, the stability regions of two dynamic systems are computed. The numerical results indicate that the stability region of the dynamic system possesses better geometry features than the convergence region of Newton method. These properties make the trajectory-based power flow method robust, especially on heavy loading conditions.
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Cecchin, Alekos. "Finite state N-agent and mean field control problems". ESAIM: Control, Optimisation and Calculus of Variations 27 (2021): 31. http://dx.doi.org/10.1051/cocv/2021032.
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We examine mean field control problems on a finite state space, in continuous time and over a finite time horizon. We characterize the value function of the mean field control problem as the unique viscosity solution of a Hamilton-Jacobi-Bellman equation in the simplex. In absence of any convexity assumption, we exploit this characterization to prove convergence, as N grows, of the value functions of the centralized N-agent optimal control problem to the limit mean field control problem value function, with a convergence rate of order [see formula in PDF]. Then, assuming convexity, we show that the limit value function is smooth and establish propagation of chaos, i.e. convergence of the N-agent optimal trajectories to the unique limiting optimal trajectory, with an explicit rate.
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Andrews, Justine. "Conveyance and Convergence: Visual Culture in Medieval Cyprus". Medieval Encounters 18, nr 4-5 (2012): 413–46. http://dx.doi.org/10.1163/15700674-12342114.
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Abstract While the trajectory of transmission of art in the Mediterranean has often been understood as West to East, here I will consider the transmission of artistic sources to Cyprus from both the West and East. These trajectories open a dialogue regarding the question of how the many sources that underpin Cypriot medieval art converged on the island. Focusing on commissions of the Lusignan dynasty, as well as other powerful communities such as the Orthodox Greeks and the Genoese, this paper shows that the social and political identity of these groups was constantly in flux; the artistic styles they used to express themselves changed according to their shifts in status. Thus, their use of artistic and architectural styles was strategic and both reflected and shaped the family’s changing political and economic position in the Mediterranean.
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Cvetkovic, Bosko, i Mihailo Lazarevic. "Fractional-order iterative learning control for robotic Arm-PD2Dα type". Filomat 35, nr 1 (2021): 1–10. http://dx.doi.org/10.2298/fil2101001c.
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In this paper, a new open-loop PD2D? type a fractional order iterative learning control (ILC) is studied for joint space trajectory tracking control of a linearized uncertain robotic arm. The robust convergent analysis of the tracking errors has been done in time domain where it is theoretically proven that the boundednesses of the tracking error are guaranteed in the presence of model uncertainty. The convergence of the proposed open-loop ILC law is proven mathematically using Gronwall integral inequality for a linearized robotic system and sufficient conditions for convergence and robustness are obtained.
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Xia, Youshen, i Gang Feng. "On Convergence Conditions of an Extended Projection Neural Network". Neural Computation 17, nr 3 (1.03.2005): 515–25. http://dx.doi.org/10.1162/0899766053019926.
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The output trajectory convergence of an extended projection neural network was developed under the positive definiteness condition of the Jacobian matrix of nonlinear mapping. This note offers several new convergence results. The state trajectory convergence and the output trajectory convergence of the extended projection neural network are obtained under the positive semidefiniteness condition of the Jacobian matrix. Comparison and illustrative examples demonstrate applied significance of these new results.
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Liang, Chengbin, i JinRong Wang. "Analysis of iterative learning control for an oscillating control system with two delays". Transactions of the Institute of Measurement and Control 40, nr 6 (1.02.2017): 1757–65. http://dx.doi.org/10.1177/0142331217690581.
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In order to track the desired reference trajectory from an oscillating control system with two delays in a finite time interval, we design iterative learning control updating laws to generate a sequence of input control functions such that the error between the output and the desired reference trajectories tends to zero via a suitable norm in the sense of uniform convergence. Here, we adopt a delayed matrix function to characterize the output state, which can be easily solved in the simulation. As a result, convergence analysis results are given. Finally, simulation results are provided to illustrate the effectiveness of the proposed controllers.
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González-García, Josué, Alfonso Gómez-Espinosa, Luis Govinda García-Valdovinos, Tomás Salgado-Jiménez, Enrique Cuan-Urquizo i Jesús Arturo Escobedo Cabello. "Experimental Validation of a Model-Free High-Order Sliding Mode Controller with Finite-Time Convergence for Trajectory Tracking of Autonomous Underwater Vehicles". Sensors 22, nr 2 (9.01.2022): 488. http://dx.doi.org/10.3390/s22020488.
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Several control strategies have been proposed for the trajectory tracking problem of Autonomous Underwater Vehicles (AUV). Most of them are model-based, hence, detailed knowledge of the parameters of the robot is needed. Few works consider a finite-time convergence in their controllers, which offers strong robustness and fast convergence compared with asymptotic or exponential solutions. Those finite-time controllers do not permit the users to predefine the convergence time, which can be useful for a more efficient use of the robot’s energy. This paper presents the experimental validation of a model-free high-order Sliding Mode Controller (SMC) with finite-time convergence in a predefined time. The convergence time is introduced by the simple change of a time-base parameter. The aim is to validate the controller so it can be implemented for cooperative missions where the communication is limited or null. Results showed that the proposed controller can drive the robot to the desired depth and heading trajectories in the predefined time for all the cases, reducing the error by up to 75% and 41% when compared with a PID and the same SMC with asymptotic convergence. The energy consumption was reduced 35% and 50% when compared with those same controllers.
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Driessen, Brian J., i Alexandre L. Robin. "A globally convergent tracking controller for the X4 flyer rotor craft for reference trajectories with positive thrust". Robotica 22, nr 4 (sierpień 2004): 375–88. http://dx.doi.org/10.1017/s0263574704000165.
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In this paper we present a globally convergent and ultimately exponentially convergent tracking controller for an X4 Flyer rotor craft. The desired or reference trajectory is restricted in one way: its scalar thrust must be uni signed and bounded away from zero. The proposed controller is a two phase one. Phase I converges the attitude (orientation) error and thrust error to zero globally and ultimately exponentially. Phase II is a position tracking and relative yaw angle tracking controller, which is not globally convergent by itself. By carefully postponing a switch from Phase I to Phase II, we are able to assure that Phase II will ultimately drive the position error and relative yaw angle error to zero exponentially. In problem-statement/theorem/proof format, we define the system, the control objective, the proposed controller, and a rigorous proof that the controller maintains boundedness of all closed loop signals and provides global convergence of the tracking error to zero and also ultimately exponential convergence of the tracking error to zero.
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Yessenbekova, U. M., A. A. Mamankul, A. A. Syzdykova i B. Kutym. "Media convergence in social communication and cyberculture". BULLETIN of L.N. Gumilyov Eurasian National University. Journalism Series 144, nr 3 (2023): 87–102. http://dx.doi.org/10.32523/2616-7174-2023-144-3-87-102.
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The article is devoted to a theoretical study of the role of media convergence in the formation of social communication and cyber culture. Comprehensive analysis showed that the convergence of mass media has become a defining factor in the interaction between people and the media. During the discussion of various aspects of media convergence and its place in public relations, connections with traditional culture, scientific conclusions were drawn. The study found how media convergence contributes to the development of cyberculture. People actively interact through social networks, forums, blogs and other online platforms, forming their own digital communities and groups. In the virtual space, they share their knowledge, interests and new ideas, thus creating modern forms of cyberculture. The authors showed that media convergence, driven by such active connections, increases the accessibility and convenience of information and entertainment.The final results of the article confirm that media convergence is an important determining factor in the formation of social communication and cyber culture. The influence of convergence on the relationship between people and the trajectory of the development of the information society as a whole is assessed.The findings of the study show that the study of convergent trends in the mass media helps to predict the development of the state and society, to develop strategies that direct social communication and virtual culture in a direction that is useful for society
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An, Zhenzhou, Xiaoyan Wang i Xinling Shi. "A Study on the Convergence of Family Particle Swarm Optimization". Mathematical Problems in Engineering 2017 (2017): 1–14. http://dx.doi.org/10.1155/2017/6129865.
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The sociological concept of family has been introduced in the particle swarm optimization (PSO) and the family PSO (FPSO) has been proposed, in which the particle swarm consisted of different families, each family consisted of different members, and there were different constraint relationships between family members. To further study the sensitivity of FPSO to the control parameters, this paper proposed a special model of FPSO and analyzed the convergence of FPSO theoretically. This model offered a new view to research the particle trajectory and divided the position sequence of particle into the even and odd subsequences. By mathematical analysis, the condition of two subsequences convergence was obtained and the related convergent theories and corollaries were proved. Simulations for benchmark functions showed that the convergence behavior of model and experimental results provided a valuable guideline for selecting control parameters.
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Mireles, Caridad, Alejandro Lozano, Mariana Ballesteros, David Cruz-Ortiz i Ivan Salgado. "Asymmetric Constrained Control of a Cervical Orthotic Device Based on Barrier Sliding Modes". Applied Sciences 12, nr 20 (13.10.2022): 10286. http://dx.doi.org/10.3390/app122010286.
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This work proposes a robust sliding mode controller to enforce the tracking trajectory of a cervical orthotic device subjected to asymmetric box constraints. The convergence analysis employs an asymmetric barrier Lyapunov function (ABLF), whose argument is a restricted sliding surface. The stability analysis demonstrates the finite-time convergence of the states towards the sliding surface and, therefore, the exponential stability of the system trajectories. The controller ensures the fulfillment of the restrictions imposed on the sliding surface and consequently over the states. Numerical simulations exhibit the performance of the proposed controller ensuring restricted movements for flexion and extension of a virtual orthotic cervical device. The restricted movements obey asymmetric constraints according to the therapies proposed by medical specialists.
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Marden, Albert, i Kurt Strebel. "Asymptotic convergence of trajectories of quadratic differentials". Annales Academiae Scientiarum Fennicae. Series A. I. Mathematica 10 (1985): 365–76. http://dx.doi.org/10.5186/aasfm.1985.1040.
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Lyman, Edward, i Daniel M. Zuckerman. "Ensemble-Based Convergence Analysis of Biomolecular Trajectories". Biophysical Journal 91, nr 1 (lipiec 2006): 164–72. http://dx.doi.org/10.1529/biophysj.106.082941.
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Kejak, Michal, Stephan Seiter i David Vávra. "Accession trajectories and convergence: endogenous growth perspective". Structural Change and Economic Dynamics 15, nr 1 (marzec 2004): 13–46. http://dx.doi.org/10.1016/j.strueco.2003.07.003.
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ALQUDSI, Yunes Sh, Ayman H. KASSEM i Gamal M. El-BAYOUMI. "A Robust Hybrid Control for Autonomous Flying Robots in an Uncertain and Disturbed Environment". INCAS BULLETIN 13, nr 2 (4.06.2021): 187–204. http://dx.doi.org/10.13111/2066-8201.2021.13.2.17.
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With the aim of efficiently achieving complex trajectory tracking missions in the presence of model uncertainties and exogenous disturbances, this paper proposes a robust hybrid control for the orientation and position of flying robots by adopting insights from sliding mode, geometric tracking, and nonlinear feedback control strategies. Various retrofits are implemented to the composite control scheme in order to tackle the system uncertainties, eliminate the chattering effects, and enhance the trajectory tracking performance. The convergence and stability analysis demonstrated the asymptotic stability of the proposed control algorithm. To reveal the promising performance of the developed control schemes, a qualitative comparative analysis of different proposed control approaches is performed. The comparative analysis examines highly maneuverable trajectories for various tracking scenarios in the presence of uncertain disturbances. The simulation results demonstrated the versatility, robustness, and convergence of the developed control laws that allow autonomous flying robots to effectively perform agile maneuvers.
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Gindis, David, Jeroen Veldman i Hugh Willmott. "Convergent and divergent trajectories of corporate governance". Competition & Change 24, nr 5 (22.07.2020): 399–407. http://dx.doi.org/10.1177/1024529420944017.
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This Special Issue revisits the classic question of comparative corporate governance research, namely whether national corporate governance systems are converging. More specifically, it focuses on several ‘convergence vectors’ which comprise the political, legal, economic and social arrangements that influence or drive the international trajectories of governance systems towards a common denominator. Taken together, the contributors to this Special Issue invite us to think critically about the functional explanations commonly mobilized in favour of convergence and consider instead the convergence debate from a broader and more interdisciplinary point of view.
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Zhu, Wenxing, Lihui Wang, Yuan Ren i Yong Li. "Trajectory Tracking of UAVs Using Sigmoid Tracking Differentiator and Variable Gain Finite-Time Extended State Observer". Drones 6, nr 11 (12.11.2022): 350. http://dx.doi.org/10.3390/drones6110350.
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The problem of quadrotor attitude and position control is considered in the presence of generally lumped disturbances: external disturbances and model uncertainty. The improved active disturbance rejection controller (ADRC) for quadrotor trajectory tracking is proposed for compensating the lumped disturbances. Firstly, the improved sigmoid tracking differentiator (ISTD), combining improved Sigmoid function and sliding mode terminal attractor is proposed, which can accelerate the global convergence rate and effectively reduce the chattering. Secondly, a novel variable gain finite-time extended state observer (VGFESO) approach is proposed to effectively estimate the lumped disturbances, while the observation errors are convergent to zero in finite time. Then, a super-twisting sliding model controller (STWSMC) is utilized for tracking control of the desired position and attitude. Finally, the convergence of VGFESO and the closed-loop stability of the control system are proved. The results show that the convergence time of the proposed control scheme is the shortest, and the integral absolute error of improved ADRC is reduced from 2.64 to 0.91. The anti-disturbance capability of the proposed controller is fully illustrated when compared with ADRC and robust adaptive nonsingular fast terminal sliding-mode controller (RANFTSMC).
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Boţ, Radu Ioan, i Dang-Khoa Nguyen. "Improved convergence rates and trajectory convergence for primal-dual dynamical systems with vanishing damping". Journal of Differential Equations 303 (grudzień 2021): 369–406. http://dx.doi.org/10.1016/j.jde.2021.09.021.
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Eshmetova, S. D., i O. N. Khakimov. "On dynamics of infinite dimensional Volterra QSOs". UZBEK MATHEMATICAL JOURNAL 68, nr 2 (30.08.2024): 69–75. http://dx.doi.org/10.29229/uzmj.2024-2-8.
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In this paper, we investigate the behavior of infinite-dimensional Volterra quadratic stochastic operators corresponding to the negative upper triangular skew-symmetric matrix. It is proved that the trajectory of such operators cannot consist of convergent subsequences. This property immediately implies non-ergodicity of the operator. Moreover, it is shown that the operator's dynamics with respect to pointwise convergence are regular.
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HACKLIN, FREDRIK, VICENTE RAURICH i CHRISTIAN MARXT. "IMPLICATIONS OF TECHNOLOGICAL CONVERGENCE ON INNOVATION TRAJECTORIES: THE CASE OF ICT INDUSTRY". International Journal of Innovation and Technology Management 02, nr 03 (wrzesień 2005): 313–30. http://dx.doi.org/10.1142/s0219877005000526.
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Current innovation management literature and research statically differentiates between incremental and disruptive innovation, as far as the trajectory development is concerned. Incremental innovation is generally comprehended as an improvement of technology performance or product feature enhancement, whereas disruptive innovation is defined based on technologies previously new to the world, combined with their effects on markets. The authors of this research present how a convergence of several well-known, incrementally developing technologies can result in innovations with highly disruptive character in terms of innovation trajectories. Paradoxically, in disruptive situations, operative actions must be taken before strategic planning can be made, as the industrial and economic environment can be regarded as extremely uncertain. In this context, however, we argue that this special case caused by the convergence of technologies can serve to understand certain areas of emerging industrial disruptions and hence support the strategic planning and technology management of a firm acting in this area. The case of information and communication technology (ICT) industry is used to highlight this convergence phenomenon as a special case of emerging disruptive innovation. Based on this example, the process of innovations transforming from incremental towards disruptive due to convergence will be examined, and entrepreneurial recommendations for sustaining the competitive advantage and supporting value creation will be derived.
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Becerra, Héctor M., J. Armando Colunga i Jose Guadalupe Romero. "Simultaneous convergence of position and orientation of wheeled mobile robots using trajectory planning and robust controllers". International Journal of Advanced Robotic Systems 15, nr 1 (1.01.2018): 172988141875457. http://dx.doi.org/10.1177/1729881418754574.
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This article is devoted to the design of robust position-tracking controllers for a perturbed wheeled mobile robot. We address the final objective of pose-regulation in a predefined time, which means that the robot position and orientation must reach desired final values simultaneously in a user-defined time. To do so, we propose the robust tracking of adequate trajectories for position coordinates, enforcing that the robot’s heading evolves tangent to the position trajectory and consequently the robot reaches a desired orientation. The robust tracking is achieved by a proportional–integral action or by a super-twisting sliding mode control. The main contribution of this article is a kinematic control approach for pose-regulation of wheeled mobile robots in which the orientation angle is not directly controlled in the closed-loop, which simplifies the structure of the control system with respect to existing approaches. An offline trajectory planning method based on parabolic and cubic curves is proposed and integrated with robust controllers to achieve good accuracy in the final values of position and orientation. The novelty in the trajectory planning is the generation of a set of candidate trajectories and the selection of one of them that favors the correction of the robot’s final orientation. Realistic simulations and experiments using a real robot show the good performance of the proposed scheme even in the presence of strong disturbances.
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Xu, Huiyan, Guoqing Zhai i Xiaofan Li. "Precipitation Efficiency and Water Budget of Typhoon Fitow (2013): A Particle Trajectory Study". Journal of Hydrometeorology 18, nr 9 (15.08.2017): 2331–54. http://dx.doi.org/10.1175/jhm-d-16-0273.1.
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Abstract In this study, the WRF Model is used to simulate the torrential rainfall of Typhoon Fitow (2013) over coastal areas of east China during its landfall. Data from the innermost model domain are used to trace trajectories of particles in three major 24-h accumulated rainfall centers using the Lagrangian flexible particle dispersion model (FLEXPART). Surface rainfall budgets and cloud microphysical budgets as well as precipitation efficiency are analyzed along the particles’ trajectories. The rainfall centers with high precipitation efficiency are associated with water vapor convergence, condensation, accretion of cloud water by raindrops, and raindrop loss/convergence. The raindrop loss/convergence over rainfall centers is supported by the raindrop gain/divergence over the areas adjacent to rainfall centers. Precipitation efficiency is mainly determined by hydrometeor loss/convergence. Hydrometeor loss/convergence corresponds to the hydrometeor flux convergence, which may be related to the increased vertical advection of hydrometeors in response to the upward motions and upward decrease of hydrometeors, whereas hydrometeor gain/divergence corresponds to the reduction in hydrometeor flux convergence, which may be associated with the decreased horizontal advection of hydrometeors in response to the zonal decrease in hydrometeors and easterly winds and the meridional increase in hydrometeors and southerly winds. The water vapor convergence and associated condensation do not show consistent relationships with orographic lifting all the time.
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Zhang, Junzi, Jongho Kim, Brendan O'Donoghue i Stephen Boyd. "Sample Efficient Reinforcement Learning with REINFORCE". Proceedings of the AAAI Conference on Artificial Intelligence 35, nr 12 (18.05.2021): 10887–95. http://dx.doi.org/10.1609/aaai.v35i12.17300.
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Policy gradient methods are among the most effective methods for large-scale reinforcement learning, and their empirical success has prompted several works that develop the foundation of their global convergence theory. However, prior works have either required exact gradients or state-action visitation measure based mini-batch stochastic gradients with a diverging batch size, which limit their applicability in practical scenarios. In this paper, we consider classical policy gradient methods that compute an approximate gradient with a single trajectory or a fixed size mini-batch of trajectories under soft-max parametrization and log-barrier regularization, along with the widely-used REINFORCE gradient estimation procedure. By controlling the number of "bad" episodes and resorting to the classical doubling trick, we establish an anytime sub-linear high probability regret bound as well as almost sure global convergence of the average regret with an asymptotically sub-linear rate. These provide the first set of global convergence and sample efficiency results for the well-known REINFORCE algorithm and contribute to a better understanding of its performance in practice.
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Liu, Zhen, Fei-Yan Qi, Dong-Ming Xu, Xin Zhou i Peng Shi. "Genomic and functional evidence reveals molecular insights into the origin of echolocation in whales". Science Advances 4, nr 10 (październik 2018): eaat8821. http://dx.doi.org/10.1126/sciadv.aat8821.
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Echolocation allows toothed whales to adapt to underwater habitats where vision is ineffective. Because echolocation requires the ability to detect exceptional high-frequency sounds, fossils related to the auditory system can help to pinpoint the origin of echolocation in whales. However, because of conflicting interpretations of archaeocete fossils, when and how whales evolved the high-frequency hearing correlated with echolocation remain unclear. We address these questions at the molecular level by systematically investigating the convergent evolution of 7206 orthologs across 16 mammals and find that convergent genes between the last common ancestor of all whales (LCAW) and echolocating bats are not significantly enriched in functional categories related to hearing, and that convergence in hearing-related proteins between them is not stronger than that between nonecholocating mammalian lineages and echolocating bats. However, these results contrast with those of parallel analyses between the LCA of toothed whales (LCATW) and echolocating bats. Furthermore, we reconstruct the ancestral genes for the hearing proteinprestinfor the LCAW and LCATW; we show that the LCAWprestinexhibits the same function as that of nonecholocating mammals, but the LCATWprestinshows functional convergence with that of extant echolocating mammals. Mutagenesis shows that functional convergence of prestin is driven by convergent changes in the prestins S392A and L497M in the LCATW and echolocating bats. Our results provide genomic and functional evidence supporting the origin of high-frequency hearing in the LCAW, not the LCATW, and reveal molecular insights into the origin and evolutionary trajectories of echolocation in whales.
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KARABACAK, ÖZKAN, i PETER ASHWIN. "On statistical attractors and the convergence of time averages". Mathematical Proceedings of the Cambridge Philosophical Society 150, nr 2 (12.01.2011): 353–65. http://dx.doi.org/10.1017/s0305004110000642.
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AbstractThere are various notions of attractor in the literature, including measure (Milnor) attractors and statistical (Ilyashenko) attractors. In this paper we relate the notion of statistical attractor to that of the essential ω-limit set and prove some elementary results about these. In addition, we consider the convergence of time averages along trajectories. Ergodicity implies the convergence of time averages along almost all trajectories for all continuous observables. For non-ergodic systems, time averages may not exist even for almost all trajectories. However, averages of some observables may converge; we characterize conditions on observables that ensure convergence of time averages even in non-ergodic systems.
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Papageorgiou, Nikolaos S. "Trajectories of set valued integrals". Bulletin of the Australian Mathematical Society 31, nr 3 (czerwiec 1985): 389–411. http://dx.doi.org/10.1017/s0004972700009357.
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The purpose of this paper is to study the trajectory multifunction Φ(·) determined by the indefinite set valued integral of a measurable Banach space valued multifunction F(·), that is for all t ∈ [0, T], , where the set valued integral is interpreted in the sense of Aumann. We study the topological and algebraic properties of SΦ equaling the set of selectors of Φ(·) whose primitive is an integrable selector of F(·). We also determine several useful properties that Φ(·) possesses and finally we present some convergence and stability results using the Kuratowski-Mosco convergence of sets.
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Xu, Liu, Wei Min Li, Lin Zhang i An Tang Zhang. "The Applications of Improved Genetic Algorithm on Hypersonic Vehicle Trajectory Optimization". Advanced Materials Research 466-467 (luty 2012): 1095–99. http://dx.doi.org/10.4028/www.scientific.net/amr.466-467.1095.
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The Optimal trajectory design for hypersonic cruise missile is an optimal control problem with strict terminal constraints and variable final time. The classical algorithms always encounter the problems of high sensitivity to initial guess and local convergence in solving this problem. Aiming at these problems, genetic algorithm (GA) which is of good global convergence is applied to designing the optimal trajectory for hypersonic cruise missile. In order to improve the convergence rate of GA and overcome its premature problems, this text introduces a predatory search (PS) strategy to speed the convergence of genetic algorithms, robust and closer to the optimal solution. This text compares the original genetic algorithm (GA) and improved genetic algorithm by the emulate experiments, and the results show that the PSGA is a more effective method to design the Optimal trajectory for hypersonic cruise missile than the original genetic algorithm.
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Rincón, Alejandro, Gloria Yaneth Florez i Gerard Olivar. "Convergence Assessment of the Trajectories of a Bioreaction System by Using Asymmetric Truncated Vertex Functions". Symmetry 12, nr 4 (2.04.2020): 513. http://dx.doi.org/10.3390/sym12040513.
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In several open and closed-loop systems, the trajectories converge to a region instead of an equilibrium point. Identifying the convergence region and proving the asymptotic convergence upon arbitrarily large initial values of the state variables are regarded as important issues. In this work, the convergence of the trajectories of a biological process is determined and proved via truncated functions and Barbalat’s Lemma, while a simple and systematic procedure is provided. The state variables of the process asymptotically converge to a compact set instead of an equilibrium point, with asymmetrical bounds of the compact sets. This convergence is rigorously proved by using asymmetric forms with vertex truncation for each state variable and the Barbalat’s lemma. This includes the definition of the truncated V i functions and the arrangement of its time derivative in terms of truncated functions. The proposed truncated function is different from the common one as it accounts for the model nonlinearities and the asymmetry of the vanishment region. The convergence analysis is valid for arbitrarily large initial values of the state variables, and arbitrarily large size of the convergence regions. The positive invariant nature of the convergence regions is proved. Simulations confirm the findings.
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Zhao, Bocheng, Mingying Huo, Ze Yu, Naiming Qi i Jianfeng Wang. "Model-Reference Reinforcement Learning for Safe Aerial Recovery of Unmanned Aerial Vehicles". Aerospace 11, nr 1 (27.12.2023): 27. http://dx.doi.org/10.3390/aerospace11010027.
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In this study, we propose an aerial rendezvous method to facilitate the recovery of unmanned aerial vehicles (UAVs) using carrier aircrafts, which is an important capability for the future use of UAVs. The main contribution of this study is the development of a promising method for online generation of feasible rendezvous trajectories for UAVs. First, the wake vortex of a carrier aircraft is analyzed using the finite element method, and a method for establishing a safety constraint model is proposed. Subsequently, a model-reference reinforcementearning algorithm is proposed based on the potential function method, which can ensure the convergence and stability of training. A combined reward function is designed to solve the UAV trajectory generation problem under non-convex constraints. The simulation results show that, compared with the traditional artificial potential field method under different working conditions, the success rate of this method under non-convex constraints is close to 100%, with high accuracy, convergence, and stability, and has greater application potential in the aerial recovery scenario, providing a solution to the trajectory generation problem of UAVs under non-convex constraints.
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Ling, Guo, Du Weiwei, Yang Jiancheng, Wang Liping, Wan Ping i Liu Ling. "A Thermal Load Forecasting Algorithm Based on Trajectory Tracking". Mathematical Problems in Engineering 2020 (16.11.2020): 1–12. http://dx.doi.org/10.1155/2020/5919238.
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The heating load forecast provides a basis for saving heating energy. Considering the nonstationary, nonlinear, and large time-delay characteristics of thermal load, this paper introduces the trajectory tracking stability theory into the field of load forecasting and proposes a heuristic correction that can ensure the convergence of forecast errors and does not depend on the system prediction model algorithm. The Lyapunov method is used to derive an error convergence criterion that has nothing to do with the prediction model, and a heuristic correction algorithm is designed for the predicted value with error divergence trend to ensure the error convergence of the load forecast sequence.
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Trofimov, Ivan D. "Factor price convergence in OECD economies: the case of three profit rates indicators". Estudos Econômicos (São Paulo) 53, nr 3 (wrzesień 2023): 607–38. http://dx.doi.org/10.1590/1980-53575335idt.
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Abstract This paper examines profit rate (rates of return to capital) convergence in OECD economies in the periods of 1960-2016 and relevant sub-periods. It also performs comparison of profit rates convergence in selected developed and developing economies, using the data for 1973-2003 period. Economy-wide, productive economy and manufacturing rates are estimated and three convergence concepts are considered (beta, sigma, and stochastic convergence). We use a combination of cross-sectional and univariate time series models and density distribution analysis. For each profit rate measure, a strong evidence of beta convergence is provided. In contrast, sigma convergence is indicated only in the case of productive economy profit rate; while in other cases, sigma divergence or the absence of either convergence or divergence are likely. Stochastic convergence is present in a smaller number of economies and is confined to productive economy and manufacturing. The comparison of convergence dynamics in developed versus developing economies confirmed beta convergence in both groups and for their aggregate, but did not establish sigma convergence, given the significant diversity of economies and their different economic trajectories.
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Bigras, Pascal, Maarouf Saad i Jules O'shea. "Convergence Analysis of an Inverse Flexible Manipulator Model Algorithm". Journal of Vibration and Control 9, nr 10 (październik 2003): 1141–58. http://dx.doi.org/10.1177/107754603030705.
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In this paper we present a convergence analysis of an iterative method to obtain the inverse model in the virtual joint space of a class of flexible manipulators. Virtual joints are defined so as to be related kinematically to the workspace. Thus, when the desired trajectory can be transformed from the workspace to the virtual joint space, the inverse model in the virtual joint space can be used to obtain a trajectory tip-tracking controller. Because the robot model in the virtual joint space is a non-minimum phase system, its inverse is unstable. The inverse method is then based on a causal-anticausal integration approach used in an iterative manner. The convergence analysis of this inverse algorithm is based on the contraction-mapping theorem and provides a very simple way to expand the desired trajectory to ensure its convergence. Finally, the inverse algorithm and its convergence analysis are validated by simulating a controller, based on the inverse model, that drives a two-link manipulator made up of one rigid and one flexible link. The simulation results demonstrate the good performance of the inverse algorithm and its convergence analysis presented here.
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Wang, JinRong, Michal Fečkan i Shengda Liu. "Convergence characteristics of PD-type and PDDα-type iterative learning control for impulsive differential systems with unknown initial states". Journal of Vibration and Control 24, nr 16 (26.05.2017): 3726–43. http://dx.doi.org/10.1177/1077546317710159.
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An important issue in the area of multi-operation systems is the observation of a discontinuous trajectory. In order to track a discontinuous output trajectory, we choose impulsive differential systems to generate a series of local continuous state trajectories, which become a set of output trajectories via the action of the output functions. Concerning impulsive differential control systems, we design proportional–derivative (PD-type) and proportional plus one order derivative and fractional order derivative (PDD α-type) iterative learning control laws with initial state learning. In particular, the PDD α-type law is more flexible due to the impact of a certain fractional order factor α. Thereafter, we give the associated convergence characteristics by establishing sufficient conditions on open-loop and closed-loop iterative learning schemes in the sense of λ-norm under mild assumptions. Finally, several numerical examples, including an application to robotic fish, are given to illustrate our results.
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Pan, Huihui, i Guangming Zhang. "Adaptive Fast Nonsingular Fixed-Time Tracking Control for Robot Manipulators". Complexity 2021 (8.05.2021): 1–16. http://dx.doi.org/10.1155/2021/6629993.
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This paper studies the fixed-time trajectory tracking control problem of robot manipulators in the presence of uncertain dynamics and external disturbances. First, a novel nonsingular fixed-time sliding mode surface is presented, which can ensure that the convergence time of the suggested surface is bounded regardless of the initial states. Subsequently, a novel fast nonsingular fixed-time sliding mode control (NFNFSMC) is developed so that the closed-loop system is fixed-time convergent to the equilibrium. By applying the proposed NFNFSMC method and the adaptive technique, a novel adaptive nonsingular fixed-time control scheme is proposed, which can guarantee fast fixed-time convergence of the tracking errors to small regions around the origin. With the proposed control method, the lumped disturbance is compensated by the adaptive technique, whose prior information about the upper bound is not needed. The fixed-time stability of the trajectory tracking control under the proposed controller is proved by the Lyapunov stability theory. Finally, corresponding simulations are given to illustrate the validity and superiority of the proposed control approach.
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ROMANOV, A. V. "Ergodic properties of discrete dynamical systems and enveloping semigroups". Ergodic Theory and Dynamical Systems 36, nr 1 (4.08.2014): 198–214. http://dx.doi.org/10.1017/etds.2014.62.
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For a continuous semicascade on a metrizable compact set ${\rm\Omega}$, we consider the weak$^{\ast }$ convergence of generalized operator ergodic means in $\text{End}\,C^{\ast }({\rm\Omega})$. We discuss conditions under which: every ergodic net contains a convergent sequence; all ergodic nets converge; all ergodic sequences converge. We study the relationships between the convergence of ergodic means and the properties of transitivity of the proximality relation on ${\rm\Omega}$, minimality of supports of ergodic measures, and uniqueness of minimal sets in the closure of trajectories of a semicascade. These problems are solved in terms of three associated algebraic-topological objects: the Ellis semigroup $E$, the Köhler operator semigroup ${\rm\Gamma}\subset \text{End}\,C^{\ast }({\rm\Omega})$, and the semigroup $G=\overline{\text{co}}\,{\rm\Gamma}$. The main results are stated for semicascades with metrizable $E$ and for tame semicascades.
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Zheng, Jingjing, Abuduwaili Abulikemu, Yan Wang, Meini Kong i Yiwei Liu. "Convection Initiation Associated with the Merger of an Immature Sea-Breeze Front and a Gust Front in Bohai Bay Region, North China: A Case Study". Atmosphere 13, nr 5 (6.05.2022): 750. http://dx.doi.org/10.3390/atmos13050750.
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The mechanism for convection initiation (CI) associated with the merger of an immature sea-breeze front (SBF) and gust front (GF) that occurred in North China on 31 July 2010 was investigated based on both observations and Weather Research and Forecasting (WRF) model simulation. The results show that many CIs occurred continuously in the merging area, and eventually resulted in an intense mesoscale convective system (MCS). The WRF simulation captured the general features of the SBF, GF, their merger processes and associated CIs, as well as the resulting MCS. Quantitative Lagrangian vertical momentum budgets, in which the vertical acceleration was decomposed into dynamic and buoyant components, were conducted along the backward trajectories of air parcels within a convective cell initiated in the merger processes. It was found that both of the dynamic and buoyant accelerations played important roles for the CI. The buoyant acceleration was dominated by the warming due to the latent heat release within the convective cell. Further decomposition of the dynamic acceleration showed the vertical twisting and extension contributed significantly to the dynamic acceleration, while the horizontal curvature was rather small. The vertical twisting was generated due to the vertical shear of horizontal wind, while the extension indicated convergences owing to a mid-level blocking convergence effect and squeezing, and (or) merging of the convergent leading edges of both fronts during their merger processes. The weak convergent leading edge of the immature SBF played an important role for the formation of the convergences.
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Umoh, Edwin A., i Ogechukwu N. Iloanusi. "Synchronized Dynamics of Hyperchaotic Flows via an Improved Finite-Time Adaptive Controller Design". International Journal of Engineering Research in Africa 48 (maj 2020): 49–62. http://dx.doi.org/10.4028/www.scientific.net/jera.48.49.
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We proposed a performance-improved finite-time adaptive synchronizing controllers and parameter update laws for coupling the dynamics of identical 4D hyperchaotic flows. The four-dimensional hyperchaotic flows consists of 12 terms and 11 system parameters and possessed very rich dynamics and larger parameter space. The performance of the proposed finite-time adaptive synchronizing controller was enhanced by the introduction of scalar quantities known as global controller strength coefficients and parameter update strength coefficients respectively, into the algebraically-derived control and parameter update structures, in order to constrained overshoots of the trajectories of the coupled systems and accelerate their rate of uniform convergence in finite time. Numerical simulation results obtained confirmed that the uniform asymptotic convergence rate of the coupling trajectories was faster, while the parameter update laws give a stable identification of the unknown system parameters in a global synchronizing time. A comparative analysis of the convergence time of the proposed adaptive controllers with recently published works indicated that the proposed controller has faster rates of uniform convergence of system trajectories.
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Liu, Lili, Yixin Lu, Bufan Yang, Longyue Yang, Jianyong Zhao, Yue Chen i Longhai Li. "Research on a Multi-Strategy Improved Sand Cat Swarm Optimization Algorithm for Three-Dimensional UAV Trajectory Path Planning". World Electric Vehicle Journal 15, nr 6 (31.05.2024): 244. http://dx.doi.org/10.3390/wevj15060244.
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In response to the issues of premature convergence, lack of population diversity, and poor convergence accuracy in the traditional Sand Cat Swarm Optimization (SCSO) algorithm, a Multi-Strategy Improved SCSO (MISCSO) algorithm is proposed. Firstly, multiple population strategies are used to avoid premature convergence and falling into local optima traps. Secondly, a distribution estimation learning strategy is introduced to represent the relationships between individuals, using probability models to improve algorithm performance. Next, the diversity of candidate solutions in the elite pool is utilized to expand the search space and enhance the algorithm’s ability to avoid local solutions. Lastly, a Cauchy disturbance strategy is adopted to accelerate the convergence speed of the algorithm, thereby improving the search efficiency and convergence accuracy. The experimental results of CEC2017 tests show that the improved algorithm balances convergence speed and global search capabilities effectively. Finally, the algorithm is applied to actual drone path planning and compared with six other intelligent algorithms, demonstrating the practicality and effectiveness of the improved algorithm.