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Cumulative activation in social networks

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Science China(Information Sciences) 2019年第5期62卷 108-128页

作者： Xiaohan SHAN wei CHEN qiang LI Xiaoming SUN Jialin ZHANG Department of Computer Science and Technology Tsinghua University Microsoft CAS Key Lab of Network Data Science and Technology Institute of Computing TechnologyChinese Academy of Sciences University of Chinese Academy of Sciences

Most studies on influence maximization focus on one-shot propagation, i.e., the influence is propagated from seed users only once following a probabilistic diffusion model and users’ activation are determined via single cascade. In reality it is often the case that a user needs to be cumulatively impacted by receiving enough pieces of information propagated to her before she makes the final purchase decision. In this paper we model such cumulative activation as the following process: first multiple pieces of information are propagated independently in the social network following the classical independent cascade model, then the user will be activated(and adopt the product) if the cumulative pieces of information she received reaches her cumulative activation threshold. Two optimization problems are investigated under this framework: seed minimization with cumulative activation(SM-CA), which asks how to select a seed set with minimum size such that the number of cumulatively active nodes reaches a given requirement η; influence maximization with cumulative activation(IM-CA), which asks how to choose a seed set with fixed budget to maximize the number of cumulatively active nodes. For SM-CA problem, we design a greedy algorithm that yields a bicriteria O(ln n)-approximation when η = n, where n is the number of nodes in the network. For both SM-CA problem with η < n and IM-CA problem, we prove strong inapproximability results. Despite the hardness results, we propose two efficient heuristic algorithms for SM-CA and IM-CA respectively based on the reverse reachable set approach. Experimental results on different real-world social networks show that our algorithms significantly outperform baseline algorithms.

关键词： social networks cumulative activation influence maximization seed minimization

Study of lithium storage properties of the Sn-Ni alloys prepared by magnetic sputtering technology

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Acta Metallurgica Sinica(English Letters) 2010年第5期23卷 363-369页

作者： Xianhua HOU Shejun HU wei PENG Zhiwen ZHANG qiang RU School of Physics and Telecommunication Engineering South China Normal University Guangzhou 510006 China

Nano-level Sn-Ni alloy thin-film electrode materials prepared by magnetic sputtering technology are characterized with X-ray diffraction （XRD）, atom force microscopy （AFM） and scanning electron microscopy （SEM）. The charge/discharge and cyclic voltammograms （CV） of the films electrodes are tested by the battery testing system of high precision. The results indicate that the materials prepared by direct current （DC） and radio frequency （RF） methods differ greatly in their performance. Ni3Sn2 alloy phase constitutes the main components prepared by DC method, the particles on the surface are tiny and show steady cycling performance, the deficiency is that they have low initial efficiency and small discharge capacity of 72% and 108 mA·h/g, respectively. Contrary to the former, Ni3Sn4 alloy phase constitutes the main com- ponents prepared by RF method, the particles on the surface appear comparatively larger, their discharge capacity did not decline in the first 15 times, keeping above 500 mA·h/g, but began to decline after 15 times.

关键词： Lithium ion battery Sn-Ni alloy Electrochemical property

Height prediction of water-flowing fracture zone with a geneticalgorithm support-vector-machine method

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International Journal of Coal Science & Technology 2020年第4期7卷 740-751页

作者： Enke Hou qiang Wen Zhenni Ye wei Chen Jiangbo wei Xi'an University of Science and Technology Xi'an 710054China

Prediction of the height of a water-flowing fracture zone(WFFZ)is the foundation for evaluating water bursting conditions on roof *** taking the Binchang mining area as the study area and conducting an in-depth study of the influence of coal seam thickness,burial depth,working face length,and roof category on the height of a WFFZ,we proposed that the proportion of hard rock in different roof ranges should be used to characterise the influence of roof category on WFFZ *** on data of WFFZ height and its influence index obtained from field observations,a prediction model is established for WFFZ height using a combination of a genetic algorithm and a support-vector *** reliability and superiority of the prediction model were verified by a comparative study and an engineering *** results show that the main factors affecting WFFZ height in the study area are coal seam thickness,burial depth,working face length,and roof *** with multiple-linear-regression and back-propagation neural-network approaches,the height-prediction model of the WFFZ based on a genetic-algorithm support-vector-machine method has higher training and prediction accuracy and is more suitable for WFFZ prediction in the mining area.

关键词： Water-flowing fracture zone Roof category Proportion of hard rock Genetic algorithm Support-vector machine

Fluorite Ce_(0.8)Sm_(0.2)O_(2-δ) porous layer coating to enhance the oxygen permeation behavior of a BaCo_(0.7)Fe_(0.2)Nb_(0.1)O_(3-δ) mixed conductor

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International Journal of Minerals,Metallurgy and Materials 2016年第6期23卷 698-703页

作者： Tai-he Wang wei-jia Song Rong Li qiang Zhen Nano-Science and Technology Research Center Shanghai University Materials Science and Engineering College Shanghai University

Fluorite Ce0.8Sm0.2O2-δ（SDC） nanopowder with a crystallite size of 15 nm was synthesized by a co-precipitation method. An SDC porous layer was coated onto a BaCo0.7Fe0.2Nb0.1O3-δ（BCFN） mixed conductor to improve its oxygen transport behavior. The results show that the SDC-coated BCFN membrane exhibits a remarkably higher oxygen permeation flux（JO2） than the uncoated BCFN in the partial oxidation of coke oven gas（COG）. The maximum JO2 value of the SDC-coated BCFN is 18.28 mL ·min^-1·cm^-2 under a COG/air flux of 177 mL ·min^-1/353 mL ·min^-1 at 875℃ when the thickness of the BCFN membrane is 1 mm; this JO2 value is 23% higher than that of the uncoated BCFN membrane. This enhancement is likely because of the higher oxygen ionic conductivity of SDC, which supplies oxygen vacancies and accelerates oxygen exchange on the membrane/coating layer/gas three-phase boundary.

关键词： chemical stability surface coating oxygen permeable membrane coke oven gas

Maximal admissible mode decision delay in terminal guidance

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Chinese Journal of Aeronautics 2019年第8期32卷 1959-1966页

作者： Shengwen XIANG Tiancheng LI wei CHEN Hongqi FAN qiang FU National Key Laboratory of Science and Technology on ATR College of Electronic ScienceNational University of Defense TechnologyChangsha 410073China School of Science University of SalamancaSalamanca 37008Spain Aviation Key Laboratory of Science and Technology on Airborne Guided Weapons China Airborne Missile AcademyLuoyang 471009China

Mode decision-maker is a critical component in the logic-based Integrated Estimation and Guidance(IEG) system. For the best possible estimation and guidance performance, the mode decision delay of the mode decision-maker should be limited to a range as small as possible. This paper presents a numerical method for computing the maximal admissible mode decision delay that varies with time-to-go. Particular attention has been paid to highly maneuvering target interception in terminal guidance. The results of this research offer useful guidelines for the design of the mode decision-maker in IEG systems.

关键词： Highly maneuvering target interception Integrated Estimation and Guidance Maximal admissible mode decision delay Mode decision-maker Numerical methods

Palladium-catalyzed direct construction of oxazoline-containing polycyclic scaffolds via tandem addition/cyclization of nitriles and arylboronic acids

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Organic Chemistry Frontiers 2022年第1期9卷 123-128页

作者： Shu-qiang Cui Na Cheng Qian-Qian Ma Zhong-Lin wei wei-wei Liao Department of Organic Chemistry College of ChemistryJilin UniversityChangchun 130012P.R.China State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032P R China

An efficient construction of oxazoline-containing polycyclic scaffolds is presented through a Pd-catalyzed addition/cyclization of(hetero)arene tethered O-acyl cyanohydrin units and arylboronic *** oxazoline-containing polycyclic compounds can be prepared in good to high yields under mild reaction *** method can be extended to prepare multi-substituted polycyclic heterocyclic compounds via a Pd-catalyzed addition/cyclization/arylation tandem sequence using arylboronic acid and different heteroarene scaffolds such as thiophene,pyrrole and furan analogues.

关键词： conditions boron catalyzed

On-surface stereoconvergent synthesis, dimerization and hybridization of organocopper complexes

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Science China Chemistry 2019年第1期62卷 126-132页

作者： Chi Zhang qiang Sun Huihui Kong Chunxue Yuan wei Xu Interdisciplinary Materials Research Center College of Materials Science and Engineering Tongji University

Despite the vital role of stereoconvergent synthesis in modern chemistry, the on-surface stereoconvergent synthesis of organometallic complexes involving transformation among several stereoisomers to one specific form has been few reported. By combination of high-resolution scanning tunneling microscopy(STM) imaging/manipulation and density functional theory(DFT) calculations, we have displayed the stereoconvergent synthesis of organocopper complexes via the Cu-alkene interaction and further dimerization into H-shaped motifs, in which two cis-forms and one trans-form are involved, and the specific adsorption configuration of one cis-form is revealed to be the key for such a synthesis. Furthermore, the generality of the dimerization of organocopper complexes has also been verified by codeposition of two similar molecular precursors, and the hybridized K-shaped motifs(made up of two kinds of organocopper complexes) have been successfully achieved. These findings may provide atomic-scale insights into the synthesis of specific stereoisomers in the fields of pharmaceuticals, biochemistry and organometallic chemistry.

关键词： scanning tunneling microscopy density functional theory surface chemistry organometallic complex stereoconvergent synthesis

A computational method for the load spectra of large-scale structures with a data-driven learning algorithm

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Science China(Technological Sciences) 2023年第1期66卷 141-154页

作者： CHEN XianJia YUAN Zheng LI qiang SUN ShouGuang wei YuJie The State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBejing 100190China School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBejing 100044China School of Enginering Sciences University of Chinese Academy of SciencesBeijing 100049China

For complex engineering systems, such as trains, planes, and offshore oil platforms, load spectra are cornerstone of their safety designs and fault diagnoses. We demonstrate in this study that well-orchestrated machine learning modeling, in combination with limited experimental data, can effectively reproduce the high-fidelity, history-dependent load spectra in critical sites of complex engineering systems, such as high-speed trains. To meet the need for in-service monitoring, we propose a segmentation and randomization strategy for long-duration historical data processing to improve the accuracy of our data-driven model for longterm load-time history prediction. Results showed the existence of an optimal length of subsequence, which is associated with the characteristic dissipation time of the dynamic system. Moreover, the data-driven model exhibits an excellent generalization capability to accurately predict the load spectra for different levels of passenger-dedicated lines. In brief, we pave the way, from data preprocessing, hyperparameter selection, to learning strategy, on how to capture the nonlinear responses of such a dynamic system, which may then provide a unifying framework that could enable the synergy of computation and in-field experiments to save orders of magnitude of expenses for the load spectrum monitoring of complex engineering structures in service and prevent catastrophic fatigue and fracture in those solids.

关键词： load spectrum computational mechanics deep learning data-driven modeling gated recurrent unit neural network

Imitation Learning Based Real-time Decision-making of Microgrid Economic Dispatch Under Multiple Uncertainties

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Journal of Modern Power Systems and Clean Energy 2024年第4期12卷 1183-1193页

作者： wei Dong Fan Zhang Meng Li Xiaolun Fang qiang Yang School of Automation Hangzhou Dianzi UniversityHangzhou 310018China College of Electrical Engineering Zhejiang UniversityHangzhou 310027China

The intermittency of renewable energy generation,variability of load demand,and stochasticity of market price bring about direct challenges to optimal energy management of *** cope with these different forms of operation uncertainties,an imitation learning based real-time decision-mak-ing solution for microgrid economic dispatch is *** this solution,the optimal dispatch trajectories obtained by solving the optimal problem using historical deterministic operation patterns are demonstrated as the expert samples for imitation *** improve the generalization performance of imitation learning and the expressive ability of uncertain variables,a hybrid model combining the unsupervised and supervised learning is *** denoising autoencoder based unsupervised learning model is adopted to enhance the feature extraction of operation ***,the long short-term memory network based supervised learning model is used to efficiently characterize the mapping between the input space composed of the extracted operation patterns and system state variables and the output space composed of the optimal dispatch *** numerical simulation results demonstrate that under various operation uncertainties,the operation cost achieved by the proposed solution is close to the minimum theoretical *** with the traditional model predictive control method and basic clone imitation learning method,the operation cost of the proposed solution is reduced by 6.3% and 2.8%,respectively,overa test period of three months.

关键词： Energy management imitation learning datadriven decision economic dispatch