Cooperative global optimal preview tracking control of linear multi-agent systems: an internal model approach

© 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This paper investigates the cooperative global optimal preview tracking problem of linear multi-agent systems under the assumption that the output of a leader is a previewable periodic signal and the topology graph contains a directed spanning tree. First, a type of distributed internal model is introduced, and the cooperative preview tracking problem is converted to a global optimal regulation problem of an augmented system. Second, an optimal controller, which can guarantee the asymptotic stability of the augmented system, is obtained by means of the standard linear quadratic optimal preview control theory. Third, on the basis of proving the existence conditions of the controller, sufficient conditions are given for the original problem to be solvable, meanwhile a cooperative global optimal controller with error integral and preview compensation is derived. Finally, the validity of theoretical results is demonstrated by a numerical simulation

Composition design and physical properties prediction of mold flux for continuous casting of high Mn–HIGH Al steel

The deterioration of CaO-SiO2 based mold flux caused by the reaction of steel -slag interface is a bottleneck restricting the high Mn-Al steel continuous casting production efficiently. Therefore, the development of low-reactivity mold flux has become a research hotspot. In this paper, the scheme of high Al2O3 and low SiO2 was adopted to suppress or reduce the occurrence of steel-slag reaction. Drawing binary phase diagram of mold flux based on the CaO–Al2O3 composition, the influence of different solvents on the melting characteristics of the mold flux were investigated and the reasonable mass ratio of CaO/Al2O3and the content of SiO2, SrO, MgO, Na2O and B2O3 were determined. According to the viscosity and the melting temperature model calculation, the physical property is beneficial for the composition design of low-reactivity mold flux

Composition design and physical properties prediction of mold flux for continuous casting of high Mn–HIGH Al steel

The deterioration of CaO-SiO2 based mold flux caused by the reaction of steel -slag interface is a bottleneck restricting the high Mn-Al steel continuous casting production efficiently. Therefore, the development of low-reactivity mold flux has become a research hotspot. In this paper, the scheme of high Al2O3 and low SiO2 was adopted to suppress or reduce the occurrence of steel-slag reaction. Drawing binary phase diagram of mold flux based on the CaO–Al2O3 composition, the influence of different solvents on the melting characteristics of the mold flux were investigated and the reasonable mass ratio of CaO/Al2O3and the content of SiO2, SrO, MgO, Na2O and B2O3 were determined. According to the viscosity and the melting temperature model calculation, the physical property is beneficial for the composition design of low-reactivity mold flux

A novel route to phase formation of cobalt oxyhydrates using KMnO4 as an oxidizing agent

We have first succeefully synthesized the sodium cobalt oxyhydrate superconductors using KMnO4 as a de-intercalating and oxidizing agent. It is a novel route to form the superconductive phase of NaxCoO2.yH2O without resorting to the commonly used Br2/CH3CN solution. The role of the KMnO4 is to de-intercalate the Na+ from the parent compound Na0.7CoO2 and oxidize the Co ion as a result. The higher molar ratio of KMnO4 relative to the sodium content tends to remove more Na+ from the parent compound and results in a slight expansion of the c-axis in the unit cell. The superconducting transition temperature is 4.6-3.8 K for samples treated by the aqueous KMnO4 solution with the molar ratio of KMnO4 relative to the sodium content in the range of 0.3 and 2.29.Comment: 10 pages, 3 figure

A digital grayscale generation equipment for image display standardization

The standardization of grayscale display is essentially significant for image signal communication, transmission, and terminal reading. The key step of this standardization is establishing a traceable equipment of grayscale. As a relative value, grayscale is transferred to two different absolute values to satisfy different traceability methods, including optical density for hardcopy image and luminance for softcopy. For luminance, a generation equipment is designed to build the relationship between luminance and grayscale. In this work, novel equipment is established using digital light processing (DLP) by time-frequency modulation, and the corresponding uncertainty is analyzed. The experiment result shows that this digital equipment builds the relationship between grayscale and luminance in the range of 0.16-4000 cd/m2. It enables traceable measurement of grayscale to luminance on this equipment with high accuracy and can provide a standardized reference for the display of grayscale images in the fields of medicine, remote sensing, non-destructive testing, etc.</jats:p

Biological advances in Bergenia genus plant

Bergenia, a genus belonging to Saxifragaceae family, is one of the most important medicinal plants, has high application values for human. Currently, wild Bergenia is becoming lacking, due to destruction of ecological environment and excessive excavation; furthermore, the study on it is not deep enough,many related important problems have not been resolved. To protect and utilize more effectively the elite germplasm resource, this study introduced its germplasm situation and reviewed its application values in medicine, horticulture, food and cosmetic and summarized its research advances in biochemistry, cytology and molecular biology. This review can provide an important reference for further study in Bergenia.Key words: Bergenia, species, application, biological advance

Dynamics of vibro-impact drilling with linear and nonlinear rock models

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordThis paper presents a comprehensive numerical study of a higher order drifting oscillator that has been used to model vibro-impact drilling dynamics in previous publications by our research group [1,2,3,4,5,6,7,8,9]. We focus on the study of the bit-rock interactions, for which both linear and nonlinear models of the drilled medium are considered. Our investigation employed a numerical approach based on direct numerical integration via a newly developed MATLAB-based computational tool, ABESPOL (Chong et al., 2017) [10], and based on path-following methods implemented via a software package for continuation and bifurcation analysis, COCO (Continuation Core) (Dankowicz and Schilder, 2013) [11]. The analysis considered the excitation frequency, amplitude of excitation and the static force as the main control parameters, while the rate of penetration (ROP) was chosen as the main system output so as to assess the performance of the system when linear and nonlinear bit-rock impact models are used. Furthermore, our numerical investigation reveals a rich system dynamics, owing to the presence of codimension-one bifurcations of limit cycles that influence the system behaviour dramatically, as well as multistability phenomenon and chaotic motion.This paper is supported by National Key Basic Research Program of China (973 Program) (Grant No. 2015CB251206), and the National Natural Science Foundation of China （No. 51775038

An Overview of Systematic Reviews of Acupuncture for Dysphagia Post-acute Stroke: a protocol

Introduction The results of previous systematic reviews (SRs) and meta-analyses on acupuncture for post-acute stroke dysphagia have provided conflicting evidence. This systematic review of overviews will aim to summarize and evaluate the quality of the existing SRs and meta-analyses with the aim of identifying whether acupuncture could provide a therapeutic option to treat patients with dysphagia post-acute stroke. Methods A systematic search of seven electronic databases (Pubmed, EMBASE, Cochrane library, CNKI, Wanfang, SinoMed and VIP) will be performed according to a predefined search strategy for SRs and meta-analyses of randomized controlled trials (RCTs) and quasi-RCTs on acupuncture for dysphagia post-acute stroke. Two authors will independently select SRs and meta-analyses and collect appropriate data. The reporting quality of included SRs and meta-analyses will be assessed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The revised Assessment of Multiple Systematic Reviews (AMSTAR 2) will be used to assess the quality of the SRs and meta-analyses. If necessary, GRADE will be used to rate the quality of evidence. Results This overview will identify current SRs and meta-analyses of RCTs or quasi-RCTs of acupuncture treatment for dysphagia post-acute stroke. Discussion The current evidence will be evaluated to help answer the question - is acupuncture a potentially effective treatment for dysphagia after stroke

Towards Impartial Multi-task Learning

Multi-task learning (MTL) has been widely used in representation learning. However, naively training all tasks simultaneously may lead to the partial training issue, where specific tasks are trained more adequately than others. In this paper, we propose to learn multiple tasks impartially. Specifically, for the task-shared parameters, we optimize the scaling factors via a closed-form solution, such that the aggregated gradient (sum of raw gradients weighted by the scaling factors) has equal projections onto individual tasks. For the task-specific parameters, we dynamically weigh the task losses so that all of them are kept at a comparable scale. Further, we find the above gradient balance and loss balance are complementary and thus propose a hybrid balance method to further improve the performance. Our impartial multi-task learning (IMTL) can be end-to-end trained without any heuristic hyper-parameter tuning, and is general to be applied on all kinds of losses without any distribution assumption. Moreover, our IMTL can converge to similar results even when the task losses are designed to have different scales, and thus it is scale-invariant. We extensively evaluate our IMTL on the standard MTL benchmarks including Cityscapes, NYUv2 and CelebA. It outperforms existing loss weighting methods under the same experimental settings