Designing Fully Distributed Consensus Protocols for Linear Multi-agent Systems with Directed Graphs

This paper addresses the distributed consensus protocol design problem for multi-agent systems with general linear dynamics and directed communication graphs. Existing works usually design consensus protocols using the smallest real part of the nonzero eigenvalues of the Laplacian matrix associated with the communication graph, which however is global information. In this paper, based on only the agent dynamics and the relative states of neighboring agents, a distributed adaptive consensus protocol is designed to achieve leader-follower consensus for any communication graph containing a directed spanning tree with the leader as the root node. The proposed adaptive protocol is independent of any global information of the communication graph and thereby is fully distributed. Extensions to the case with multiple leaders are further studied.Comment: 16 page, 3 figures. To appear in IEEE Transactions on Automatic Contro

A Novel Dynamic Event-triggered Mechanism for Dynamic Average Consensus

This paper studies a challenging issue introduced in a recent survey, namely designing a distributed event-based scheme to solve the dynamic average consensus (DAC) problem. First, a robust adaptive distributed event-based DAC algorithm is designed without imposing specific initialization criteria to perform estimation task under intermittent communication. Second, a novel adaptive distributed dynamic event-triggered mechanism is proposed to determine the triggering time when neighboring agents broadcast information to each other. Compared to the existing event-triggered mechanisms, the novelty of the proposed dynamic event-triggered mechanism lies in that it guarantees the existence of a positive and uniform minimum inter-event interval without sacrificing any accuracy of the estimation, which is much more practical than only ensuring the exclusion of the Zeno behavior or the boundedness of the estimation error. Third, a composite adaptive law is developed to update the adaptive gain employed in the distributed event-based DAC algorithm and dynamic event-triggered mechanism. Using the composite adaptive update law, the distributed event-based solution proposed in our work is implemented without requiring any global information. Finally, numerical simulations are provided to illustrate the effectiveness of the theoretical results.Comment: 9 pages, 8 figure

Distributed Adaptive Attitude Synchronization of Multiple Spacecraft

This paper addresses the distributed attitude synchronization problem of multiple spacecraft with unknown inertia matrices. Two distributed adaptive controllers are proposed for the cases with and without a virtual leader to which a time-varying reference attitude is assigned. The first controller achieves attitude synchronization for a group of spacecraft with a leaderless communication topology having a directed spanning tree. The second controller guarantees that all spacecraft track the reference attitude if the virtual leader has a directed path to all other spacecraft. Simulation examples are presented to illustrate the effectiveness of the results.Comment: 13 pages, 11 figures. To appear in SCIENCE CHINA Technological Science

“COMFORTABLE FOSSILIZATION” CHINESE EFL LEARNER’S ACQUISITION AND USE OF FORMULAIC SEQUENCES IN L2 WRITING

The present study set out to investigate the knowledge and use of formulaic sequences in Chinese EFL learner‟s L2 writing. Adopting Alison Wray‟s definition (Wray, 2000, p.465), formulaic sequence was operationalized as “idioms, collocations and sentence frames (including connectives)”. Authentic samples written by 16 advanced EFL writers in China were collected and analyzed with a view to probing into their knowledge and use of formulaic sequences. The results indicated that a strong influence of these EFL learners‟ native language (L1) affected their knowledge and use of formulaic sequences in L2 writing. The study argues that such over-reliance on these incorrect formulaic sequences is likely to become what Skehan and Foster (2001) have called “comfortable fossilization”. Implications of these results for EFL writing instructions are discussed

<b>A new perspective on foreign language aptitude research: building and supporting a case for "working memory as language aptitude"</b><br>

The present paper proposes and argues a case for incorporating the working memory (WM) construct as a component of foreign language aptitude. As such, it first briefly reviews previous research on foreign language aptitude, which lays the ground for the proposal. Then, by drawing on recent research from both the fields of cognitive psychology and second language acquisition, the paper will summarize the key representative theoretical models, major claims and empirical evidence supporting the role of WM in different aspects of L2 learning, such as listening, reading, speaking, writing and interpreting, thus rendering the proposal a feasible blueprint for future research on foreign language aptitude

Short-term and working memory capacity and the language device: Chunking and parsing complexity

Many general linguistic theories and language processing frameworks have assumed that language processing is largely a chunking procedure and that it is underpinned and constrained by our memory limitations. Despite this general consensus, the distinction between short-term memory (STM) and working memory (WM) limitations as they relate to language processing has remained elusive. To resolve this issue, we propose an integrated memory- and chunking-based metric of parsing complexity, in which STM limitations of 7±2 (Miller, 1956a) are relevant to the Momentary Chunk Number (MCN), while WM limitations of 4±1 (Cowan, 2001) are relevant to the Mean Momentary Chunk Number (MMCN). Examples of concrete calculations of our new metric are presented vis-à-vis Liu’s MDD metric and Hawkins’ IC-to-word Ratio metric. Related methodology issues are also discussed. We conclude the paper by echoing some recently repeated calls (O'Grady, 2012 &amp; 2017; Gómez-Rodríguez et al., 2019; Wen, 2019) to include STM and WM limitations as part and parcel of the language device (LD; cf. Chomsky, 1957) in that their impacts are ubiquitous and permeating in all essential linguistic domains ranging from phonology to grammar, discourse comprehension and production. (PDF) Short-term and working memory capacity and the language device: Chunking and parsing complexity. Available from: https://www.researchgate.net/publication/340490956_Short-term_and_working_memory_capacity_and_the_language_device_Chunking_and_parsing_complexity [accessed May 31 2021]