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Non-salient region erasure for time series augmentation

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Frontiers of Computer Science 2022年第6期16卷 203-205页

作者： Pin LIU Xiaohui GUO Bin SHI Rui WANG Tianyu WO Xudong LIU State Key Lab of Software Development Environment(SKLSDE) Beihang UniversityBeijing100191China Beijing Advanced Innovation Center for Big Data and Brain Computing(BDBC) Beijing100191China Hangzhou Innovation Institute Beihang UniversityHangzhou310052China School of Computer Science and Technology Xi’an Jiaotong UniversityXi’an710049China

1 Introduction Time seriesaugmentationis an essential approachto solvethe overfitting problem on the time series classification(TSC)task[1,2].Although existing approaches perform better in mitigating this problem,none of them focus on protecting saliency regions on time *** key informative shapelets contained in these regions are the core basis for distinguishing categories(e.g.,upward spikes in ECG and high amplitude in Sensor).

关键词： Sensor series series

series expansion feasibility of singular integral in method of moments

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Journal of Systems Engineering and Electronics 2014年第3期25卷 386-392页

作者： Jinzu Ji Peilin Huang School of Aeronautic Science and Engineering Beihang University

When calculating electromagnetic scattering using method of moments （MoM）, integral of the singular term has a significant influence on the results. This paper transforms the singular surface integral to the contour integral. The integrand is expanded to Taylor series and the integral results in a closed form. The cut-off error is analyzed to show that the series converges fast and only about 2 terms can agree wel with the accurate result. The comparison of the perfect electric conductive （PEC） sphere＇s bi-static radar cross section （RCS） using MoM and the accurate method validates the feasibility in manipulating the singularity. The error due to the facet size and the cut-off terms of the series are analyzed in examples.

关键词： method of moments (MoM) singular term series cut-off error radar cross section (RCS).

A series Piezoelectric Quartz Crystal Response Kinetics for *** Growth in the Presence of Cu(Ⅱ)

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Journal of Central South University 2000年第1期12卷 15-19页

作者： CHAI Li yuan 1,2 ,WEI Wan zhi 2,YAO Shou zhuo 2(1. Department of Metallurgical Science and Engineering, Central South University of Technology, Changsha 410083, China 2. College of Chemistry and Chemical Engineering, Hunan University, Changsha Department of Metallurgical Science and Engineering Central South University of Technology Changsha China College of Chemistry and Chemical Engineering Hunan University Changsha China

The kinetics on the growth of *** in the presence of Cu(Ⅱ) was studied using of series piezoelectric quartz crystal (SPQC). Arsenic ion inhibits the growth of *** , which is consistent with the previous results by other measuring methods. This further demonstrates that the SPQC can monitor the chemical activity of *** growth. Cupric ion accelerates the growth of *** . The mechanism was discussed, i. e., copper promotes the protein enzyme of *** , rusticyanin, to form over the range of cupric ion concentration studied. The reaction order of cupric ion in accelerating the bacterial growth is 0.067. The growth of *** is dependent on temperature, the apparent reaction activation energy decreases from 25.56 kJ/mol to 18.32 kJ/mol because of the addition of 10 mg/L Cu(Ⅱ) to the bacterial growth solution of pH 2.0 at initial inoculum of 10%.

关键词： series piezoelectric quartz crystal T.ferrooxidans growth kinetics sigmoid curve cupric ion

Analysis on the capacity degradation mechanism of a series lithium-ion power battery pack based on inconsistency of capacity

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Chinese Physics B 2013年第8期22卷 746-755页

作者：王震坡刘鹏王丽芳 National Engineering Laboratory for Electric Vehicles Beijing Institute of Technology Key Laboratory of Power Electronics and Electric Drive Institute of Electrical Engineering Chinese Academy of Sciences

The lithium-ion battery has been widely used as an energy source. Charge rate, discharge rate, and operating tem- perature are very important factors for the capacity degradations of power batteries and battery packs. Firstly, in this paper we make use of an accelerated life test and a statistical analysis method to establish the capacity accelerated degradation model under three constant stress parameters according to the degradation data, which are charge rate, discharge rate, and operating temperature, and then we propose a capacity degradation model according to the current residual capacity of a Li-ion cell under dynamic stress parameters. Secondly, we analyze the charge and discharge process of a series power battery pack and interpret the correlation between the capacity degradations of the battery pack and its charge/discharge rate. According to this cycling condition, we establish a capacity degradation model of a series power battery pack under inconsistent capacity of cells, and analyze the degradation mechanism with capacity variance and operating temperature difference. The comparative analysis of test results shows that the inconsistent operating temperatures of cells in the series power battery pack are the main cause of its degradation; when the difference between inconsistent temperatures is narrowed by 5 ℃, the cycle life can be improved by more than 50%. Therefore, it effectively improves the cycle life of the series battery pack to reasonably assemble the batteries according to their capacities and to narrow the differences in operating temperature among cells.

关键词： lithium-ion battery pack series capacity degradation dynamic stress

Anomalous crystal structure of γ" phase in the Mg-RE-Zn(Ag) series alloys:Causality clarified by ab initio study

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Journal of Materials Science & Technology 2020年第1期36卷 167-175页

作者： Junyuan Bai Xueyong Pang Xiangying Meng Hongbo Xie Hucheng Pan Yuping Ren Min Jiang Gaowu Qin Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Materials Science and EngineeringNortheastern UniversityShenyang 110819China Research Center for Metallic Wires Northeastern UniversityShenyang 110819China

The crystal structure of the single-unit-cell thickness γ " phase,as a key strengthening phase in Mg-REZn(Ag) series alloys,has been extensively studied,and several structural models have been proposed in the past two ***,these reported models,and even the lattice constants at the same proposed structure,are scattered severely,which has led to considerable confusion and not available for further mechanical property simulation and prediction of Mg alloys containing this *** this study,by using first-principles calculations,the crystal structure of y" phase is clarified,resolving the discrepancies among different experiments,and its intrinsic mechanical properties have also been studied for the first *** is verified that the γ " phase contains quasi-five atomic layers,instead of the previously reported tri-layer,and surprisingly,its crystal structure has many variants,which would change with the alloy ***,with the help of the simulated selected area electron diffraction(SAED) patterns,it is found that the atoms in the central layer remain partially ordered distribution,and this ordered extent primarily depends on the atomic ratio of RE:Zn(Ag) and the solute content in an *** is,the ordered extent increases with decreasing the atomic ratio of RE:Zn(Ag) and/or increasing solute content of alloy,and vice *** and Zn dissolved in the γ" phase would produce almost opposed mechanical anisotropy for the γ " phase under the identical crystal structure,and the addition of Ag shows more efficient on increasing the shear modulus of γ" phase.

关键词： First-principles γ"phase Mg-RE-based series alloys Crystal structure Mechanical-properties

Position Control of a series Elastic Actuator Based on Global Sliding Mode Controller Design

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IEEE/CAA Journal of Automatica Sinica 2019年第3期6卷 850-858页

作者： Wei Yin Lei Sun Meng Wang Jingtai Liu IEEE the Institute of Robotics and Automatic Information System Nankai University and also with Tianjin Key Laboratory of Intelligent Robotics

A series elastic actuator(SEA) is a powerful device in the area of human-machine integration, but it still suffers from difficult position control issues. Therefore, in this paper,an efficient approach is proposed to solve this problem. The approach design is divided into two steps: feedback linearization(FL) and global sliding mode(GSM) controller design. The bounded analysis is presented and global asymptotic convergence is analytically proven. Simulation and experiment results illustrate the effectiveness of the proposed scheme.

关键词： Feedback linearization (FL) global sliding mode (GSM) position control series elastic actuator (SEA)

Fast correlation coefficient estimation algorithm for HBase-based massive time series data

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Frontiers of Computer Science 2019年第4期13卷 864-878页

作者： Wen LIU Tuqian ZHANG Yanming SHEN Peng WANG Department of Electrical and Information Engineering Xinjiang Institute of Engineering Urumqi 830091 China School of Computer Science and Technology Dalian University of Technology Dalian 116024 China School of Computer Science Fudan University Shanghai 201203 China

In recent years, the rapid development of Internet of Things and sensor networks makes the time series data experiencing explosive growth. OpenTSDB and other emerging systems begin to use Hadoop, HBase to store massive time series data, and how to use these platforms to query and mine time series data has become a current research hotspor. As a typical time series distance measurement method, correlation coefficient is widely used in various applications. However, it requires a large amount of I/O and network transmission to compute the correlation coefficient of long time sequence on HBase in real time, and therefore cannot be applied to interactive query. To address this problem, in this paper, we present two methods to estimate the correlation coefficients of two sequences on HBase. We first propose a fast estimation algorithm for the upper and lower bounds of correlation coefficient, named as DCE. In order to further reduce the cost of I/O, we extend the DCE algorithm, and propose the ADCE algorithm, which can estimate the correlation coefficient quickly with an iterative manner. Experiments show that the algorithms proposed in this paper can quickly calculate the correlation coefficient of the long time series.

关键词： time series HBase correlation coefficient fast estimation

Residuals-Based Deep Least Square Support Vector Machine with Redundancy Test Based Model Selection to Predict Time series

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Tsinghua Science and Technology 2019年第6期24卷 706-715页

作者： Yanhua Yu Jie Li the School of Computer Beijing University of Posts and Telecommunications

In this paper, we propose a novel Residuals-Based Deep Least Squares Support Vector Machine(RBDLSSVM). In the RBD-LSSVM, multiple LSSVMs are sequentially connected. The second LSSVM uses the fitting residuals of the first LSSVM as input time series, and the third LSSVM trains the residuals of the second, and so on. The original time series is the input of the first LSSVM. Additionally, to obtain the best hyper-parameters for the RBD-LSSVM, we propose a model validation method based on redundancy test using Omni-Directional Correlation Function(ODCF). This method is based on the fact when a model is appropriate for a given time series, there should be no information or correlation in the residuals. We propose the use of ODCF as a statistic to detect nonlinear correlation between two random variables. Thus, we can select hyper-parameters without encountering overfitting,which cannot be avoided by only cross validation using the validation set. We conducted experiments on two time series: annual sunspot number series and monthly Total Column Ozone(TCO) series in New Delhi. Analysis of the prediction results and comparisons with recent and past studies demonstrate the promising performance of the proposed RBD-LSSVM approach with redundancy test based model selection method for modeling and predicting nonlinear time series.

关键词： time series prediction information redundancy residuals-based deep Least Squares Support Vector Machine (LSSVM) Omni-Directional Correlation Function (ODCF)

Goodness-of-fit tests for vector autoregressive models in time series

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Science China Mathematics 2010年第7期53卷 187-202页

作者： WU JianHong 1,& ZHU LiXing 21 College of Statistics and Mathematics,Zhejiang Gongshang University,Hangzhou 310018,China 2 Department of Mathematics,Hong Kong Baptist University,Hong Kong,China College of Statistics and Mathematics Zhejiang Gongshang University Hangzhou China Department of Mathematics Hong Kong Baptist University Hong Kong China

The paper proposes and studies some diagnostic tools for checking the goodness-of-fit of general parametric vector autoregressive models in time series. The resulted tests are asymptotically chi-squared under the null hypothesis and can detect the alternatives converging to the null at a parametric rate. The tests involve weight functions,which provides us with the flexibility to choose scores for enhancing power performance,especially under directional alternatives. When the alternatives are not directional,we construct asymptotically distribution-free maximin tests for a large class of alternatives. A possibility to construct score-based omnibus tests is discussed when the alternative is saturated. The power performance is also investigated. In addition,when the sample size is small,a nonparametric Monte Carlo test approach for dependent data is proposed to improve the performance of the tests. The algorithm is easy to implement. Simulation studies and real applications are carried out for illustration.

关键词： goodness-of-fit test maximin test nonparametric Monte Carlo test score type test time series vector autoregressive model