2,312 publications from this institution
This paper applies bifurcation analysis to the well-known van der Pol oscillator to obtain approximations of its periodic solutions in the nearly sinusoidal regime. A frequency domain method based on harmonic balance approximations is used for small values of the bifurcation parameter. Moreover, a comparison with some other frequency domain approaches is also given. Finally, a total harmonic distortion is computed using the information provided by the frequency domain approach.
In retrieval-augmented generation (RAG) question answering systems, generating citations for large language model (LLM) outputs enhances verifiability and helps users identify potential hallucinations. However, we observe two problems in the citations produced by existing attribution methods. First, the citations are typically provided at the sentence or even paragraph level. Long sentences or paragraphs may include a substantial amount of irrelevant content. Second, sentence-level citations may omit information that is essential for verifying the output, forcing users to read the surrounding context. In this paper, we propose generating sub-sentence citations that are both concise and sufficient, thereby reducing the effort required by users to confirm the correctness of the generated output. To this end, we first develop annotation guidelines for such citations and construct a corresponding dataset. Then, we propose an attribution framework for generating citations that adhere to our standards. This framework leverages LLMs to automatically generate fine-tuning data for our task and employs a credit model to filter out low-quality examples. Our experiments on the constructed dataset demonstrate that the propose approach can generate high-quality and more readable citations.
We investigate the flocking problem of multiple nonlinear dynamical mobile agents with a virtual leader in a dynamic proximity network. We assume that only a fraction of agents in the network are informed and propose a connectivity-preserving flocking algorithm. Under the assumption that the initial network is connected, we introduce local adaptation strategies for both the weights on the velocity navigational feedback and the coupling strengths that enable all agents to track the virtual leader, without requiring the knowledge of the agent dynamics. The resulting flocking algorithm works even for the case where only one agent is informed.
In this article, a linear quadratic (LQ) scheme is proposed for bumpless transfer between two tracking controllers. The controllers have integral actions which are used to eliminate the steady-state tracking errors. A compensator is designed using the LQ technique to minimise the differences between two sets of signals, the differences between two control signals as well as the differences between the two input signals which drive the two controllers. Under such circumstances, complete information of the system is taken into account and utilised for achieving satisfactory control. It is shown that the ideal bumpless transfer is achievable with the proposed control scheme. Moreover, the results are extended to discrete-time systems. Finally, simulation results are given to demonstrate the effectiveness of the proposed control scheme.
A constructive theorem is established for generalized synchronization (GS) related to C1 diffeomorphic transformations of unidirectionally coupled dynamical arrays. The theorem provides some interpretations about the underlying mechanism of various GS phenomena in nature. As a direct application of the theorem, a chaos-based secure Internet communication scheme is proposed. Moreover, a cellular neural network (CNN) of Chen's chaotic circuits with GS property is designed and studied. Numerical simulation shows that this Chen's CNN has high security and is fast and reliable for secure Internet communications.
This article introduces the new notion of complex networks,especially the representative models of random-graph networks,small-world networks and scale-free networks as well as related basic concepts and modeling parameters.It also briefly summarizes their applications to biological systems and neural networks, epidemic spreading and immunization over networks,transportation systems,social and economic networks, wireless communication and sensor networks.And finally it reviews the problems of distributed control,stability and consensus analysis in their applications to swarming,flocking and synchronization.
This paper investigates branched $α$-flows on branched weighted triangulated closed surfaces with Euler characteristic \(χ\leq 0\), focusing on establishing their connections with topological-combinatorial structures and geometric structures. In Euclidean (\(\mathbb{E}^2\)) and hyperbolic (\(\mathbb{H}^2\)) geometries, we define branched $α$-curvatures and corresponding branched $α$-flows. By introducing branched $α$-potentials, we prove the existence and uniqueness of constant branched $α$-metrics through topological-combinatorial structures, thus avoiding reliance on flow convergence. Key results include: 1. Exponential convergence of branched $α$-flows to constant branched $α$-metrics in both geometries. 2. Strict convexity of branched $α$-potentials, ensuring unique critical points that correspond to constant curvatures. 3. Extension to prescribing curvature problems under the relaxed precondition $χ(M)\in \mathbb{Z}$ via alternative $α$-flows, establishing admissibility conditions for prescribed curvatures and their exponential convergence to target metrics. These findings bridge discrete circle packing metrics with smooth geometric invariants, providing a unified framework for studying curvature flows on surfaces with branch structures.
No abstract is provided for this article.
A closed-form solution for the stable region of the control gains in the Proportional Integral control Active Queue Management scheme is presented. It is demonstrated that the specified region is in a generalised form of an existing result on integral control AQM. Using this closed-form solution, it is further shown that, for a stable network, its stability is preserved despite the increase in the number of connections, decrease in the round-trip time, and decrease in the link capacity.
No abstract is provided for this article.
A novel method is presented for controlling the amplitudes and stability of orbits generated from Neimark–Sacker bifurcations in discrete-time systems. The technique is rooted in the frequency-domain approach for the study of bifurcations in maps.
In this paper, we introduce the concepts of the large deviations theorem of weaker types, i.e., type I, type I', type II, type II', type III, and type III', and present a systematic study of the ergodic and chaotic properties of dynamical systems satisfying the large eviations theorem of various types. Some characteristics of the ergodic measure are obtained and then applied to prove that every dynamical system satisfying the large deviations theorem of type I' is ergodic, which is equivalent to the large deviations theorem of type II' in this regard, and that every uniquely ergodic dynamical system restricted on its support satisfies the large deviations theorem. Moreover, we prove that every dynamical system satisfying the large deviations theorem of type III is an $E$-system. Finally, we show that a dynamical system satisfying the central limit theorem, introduced in [Y. Niu, Y. Wang, Statist. Probab. Lett., {\bf 80} (2010), 1180--1184], does not exist.
This chapter focuses on leader-follower consensus of nonlinear multi-agent systems in homogenous networks and heterogenous networks via distributed impulsive control, respectively. Leader-follower consensus problem in homogenous networks is studied in Sect. 2. Then in Sect. 3, a network-based leader-following consensus problem is considered, and distributed delayed impulsive protocols are designed for nonlinear multi-agent systems. Finally, bounded leader-follower consensus problem is well investigated in heterogenous networks in Sect. 4. How to obtain a tight error bound, to optimize the error bound, and to design the impulse intervals and coupling strength within a prescribed error bound are addressed.
