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Long-term Correlations and Extreme Wind Speed Estimations

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Advances in Atmospheric Sciences 2019年第10期36卷 1121-1128页

作者： Lei LIU fei hu State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric University of Chinese Academy of Sciences Beijing 100049 China

In this paper, we use fluctuation analysis to study statistical correlations in wind speed time series. Each time series used here was recorded hourly over 40 years. The fluctuation functions of wind speed time series were found to scale with a universal exponent approximating to 0.7, which means that the wind speed time series are long-term correlated. In the classical method of extreme estimations, data are commonly assumed to be independent (without correlations). This assumption will lead to an overestimation if data are long-term correlated. We thus propose a simple method to improve extreme wind speed estimations based on correlation analysis. In our method, extreme wind speeds are obtained by simply scaling the mean return period in the classical method. The scaling ratio is an analytic function of the scaling exponent in the fluctuation analysis.

关键词： extreme wind speed fluctuation analysis generalized Pareto distribution long-term correlation

The Payouts Choice for Deposit Insurance System

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Journal of Systems Science & Complexity 2019年第5期32卷 1404-1425页

作者： CHANG Yiming ZHAO Shangmei hu fei School of Economics and Management Beihang UniversityBeijing 100191China Institute of Market and Price National Development and Reform CommissionBeijing 100038China.

Entropy balancing is introduced to assess the deposit insurance design characteristics in this paper. Applying an extensive duration data including 141 countries from 1960 to 2015, the authors employ the entropy balancing method to simulate the data structure under the implicit deposit insurance system. Then the paper adopts an endogenous treatment effects model and a Heckman two-step selection model to examine payouts choice of the deposit insurance. It is found that entropy balancing can calibrate unit weights and reweight treatment and control groups by a maximum entropy ***, a possibly given conditions will be satisfied and information concerning sample moments will be integrated. The results show clearly that different payouts choice and the corresponding coverage setting can effectively reduce the moral hazards that may result from the introduction of a deposit insurance scheme. When the Payouts is Per Depositor Account or Per Depositor, the banks’ moral hazard is higher. However, the payment method of Per Depositor Per Institution can effectively restrain the banks’ risk-taking activities.

关键词： Deposit insurance entropy balancing payouts choice treatment effects

Optimal production lot size with process deterioration under an extended inspection policy

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Journal of Systems Engineering and Electronics 2009年第4期20卷 768-776页

作者： hu fei Xu Genqi Ma Lixia Dept. of Mathematics Tianjin Univ. Tianjin 300072 P. R. China

A mathematical model to determine the optimal production lot size for a deteriorating production system under an extended product inspection policy is developed. The last-K product inspection policy is considered so that the nonconforming items can be reduced, under which the last K products in a production lot are inspected and the nonconforming items from those inspected are reworked. Consider that the products produced towards the end of a production lot are more likely to be nonconforming, is proposed an extended product inspection policy for a deteriorating production system. That is, in a production lot, product inspections are performed among the middle K1 items and after inspections, all of the last K2 products are directly reworked without inspections. Our objective here is the joint optimization of the production lot size and the corresponding extended inspection policy such that the expected total cost per unit time is minimized. Since there is no closed form expression for our optimal policy, the existence for the optimal production inspection policy and an upper bound for the optimal lot size are obtained. Furthermore, an efficient solution procedure is provided to search for the optimal policy. Finally, numerical examples are given to illustrate the proposed model and indicate that the expected total cost per unit time of our product inspection model is less than that of the last-K inspection policy.

关键词： production lot size product inspection policy deteriorating production system economic manufacturing quantity.

EBSD parameter assessment and constitutive models of crept HR3C austenitic steel

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Journal of Iron and Steel Research International 2023年第4期30卷 772-781页

作者： Jie Zhang Zheng-fei hu Zhen Zhang Shanghai Key Laboratory for R&D and Application of Metallic Functional Materials School of Materials Science and EngineeringTongji UniversityShanghai 201804China School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing 211167JiangsuChina

Creep damage and evolution of HR3C steel at 650℃ were investigated using electron backscatter diffraction(EBSD),and EBSD-based parameter assessments were *** analyses show that the grain size is almost unchanged and no obvious texture formed after creep at different creep *** lowest proportion of low Σ coincidence site lattice grain boundaries under 150 MPa implies that the primary twin structures are preserved under the low stress level,while some twin structures evolved into general grain boundaries at the high creep *** main damage features of microcracks and cavities can be seen along the grain boundaries:the former emerged at higher stress levels,while the latter appeared at the lower stress level,and both were shown under medium *** contrast shows that the most severe creep damage is present at 170 *** implies that the creep mechanism differs distinctly under different stress levels,and the transition point is around 170 *** average misorientation is better to describe the local plastic deformation related to the strain distribution while grain reference orientation deviation describes the inhomogeneous strain *** lifetime prediction models including the isothermal method,Larson-Miller parameter method and Monkman–Grant relation were evaluated by the experimental data and literature data,and they are valid for predicting creep behavior.

关键词： Austenitic heat-resistant steel Creep damage Electron backscatter diffraction Creep constitutive model Creep lifetime prediction

Symplectic system based analytical solution for bending of rectangular orthotropic plates on Winkler elastic foundation

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Acta Mechanica Sinica 2011年第6期27卷 929-937页

作者： Wei-An Yao Xiao-fei hu Feng Xiao State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology 116024 Dalian China Department of Computer Science Dalian Medical University 116044 Dalian China

This paper analyses the bending of rectangular orthotropic plates on a Winkler elastic *** definition of symplectic inner product and symplectic space formed by generalized displacements establish dual variables and dual equations in the symplectic *** operator matrix of the equation set is proven to be a Hamilton operator *** of variables and eigenfunction expansion creates a basis for analyzing the bending of rectangular orthotropic plates on Winkler elastic foundation and obtaining solutions for plates having any boundary *** is discussion of symplectic eigenvalue problems of orthotropic plates under two typical boundary conditions,with opposite sides simply supported and opposite sides *** equations of eigenvalues and symplectic eigenvectors in analytical form *** solutions using two examples are presented to show the use of the new methods described in this *** verify the accuracy and convergence,a fully simply supported plate that is fully and simply supported under uniformly distributed load is used to compare the classical Navier method,the Levy method and the new *** show that the new technique has good accuracy and better convergence speed than other methods,especially in relation to internal forces.A fully clamped rectangular plate on Winkler foundation is solved to validate application of the new methods,with solutions compared to those produced by the Galerkin method.

关键词： Orthotropic plate Symplectic space Winklerelastic foundation Analytical solution

Higher-order electroelastic modelling of piezoelectric cylindrical nanoshell on elastic matrix

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Defence Technology（防务技术） 2022年第5期18卷 781-796页

作者： Xiao-ping huang Peng-fei hu Mohammad Arefi College of Mechanical and Electrical Engineering Nanning UniversityNanning530000GuangxiChina School of Materials Science and Engineering Luoyang Institute of TechnologyLuoyang471023HenanChina Department of Solid Mechanics Faculty of Mechanical EngineeringUniversity of KashanKashan87317-51167Iran

This paper develops electro-elastic relations of functionally graded cylindrical nanoshell integrated with intelligent layers subjected to multi-physics loads resting on elastic *** piezoelectric layers are actuated with external applied *** nanocore is assumed in-homogeneous in which the material properties are changed continuously and gradually along radial ***-order shear deformation theory is used for the description of kinematic relations and electric potential distribution is assumed as combination of a linear function along thickness direction to show applied voltage and a longitudinal ***-elastic size-dependent constitutive relations are developed based on nonlocal elasticity theory and generalized Hooke’s *** principle of virtual work is used to derive governing equations in terms of four functions along the axial and the radial directions and longitudinal electric potential *** numerical results including radial and longitudinal displacements are presented in terms of basic input parameters of the integrated cylindrical nanoshell such as initial electric potential,small scale parameter,length to radius ratio and two parameters of *** is concluded that both displacements are increased with an increase in small-scale parameter and a decrease in applied electric potential.

关键词： Higher-order shear deformation theory Electro-elastic bending Functionally graded materials Size-dependent analysis Nonlocal parameter Cylindrical nano shell

A new family of covariate-adjusted response adaptive designs and their properties

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Applied Mathematics(A Journal of Chinese Universities) 2009年第1期24卷 1-13页

作者： ZHANG Li-Xin hu fei-fang Institute of Statist. and Dept. of Math. Zhejiang Univ. Hongzhou 310027 China Dept. of Statist. Univ. of Virginia Charlottesville VA 22904-4135 USA

It is often important to incorporate covariate information in the design of clinical trials. In literature there are many designs of using stratification and covariate-adaptive randomization to balance certain known covariate. Recently, some covariate-adjusted response-adaptive （CARA） designs have been proposed and their asymptotic properties have been studied （Ann. Statist. 2007）. However, these CARA designs usually have high variabilities. In this paper, a new family of covariate-adjusted response-adaptive （CARA） designs is presented. It is shown that the new designs have less variables and therefore are more efficient.

关键词： adaptive design covariate efficiency asymptotic variability

Variability of turbulence dispersion characteristics during heavy haze process: A case study in Beijing

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Journal of Environmental Sciences 2023年第2期124卷 440-450页

作者： Lei Liu Yu Shi Zhe Zhang fei hu LAPC Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100049China

The turbulent standard deviations and the turbulent third-order and fourth-order moments are the key turbulence dispersion parameters in Lagrangian dispersion ***,the characteristics of these parameters under heavy haze conditions in urban areas have not been fully investigated,and the commonly used similarity relations of these parameters in modelswere based on observations in highly flat and sparsely populated *** this paper,the vertical profiles of these parameters and their local similarity relations under heavy haze conditions in the wintertime of Beijing have been analyzed by using data collected at a 325-m meteorological *** heavy haze process has been divided into three stages:transport stage(TS),cumulative stage(CS),and dispersion stage(DS).Results show that the turbulent dispersion parameters behave differently during three *** the TS and DS,the maxima appear in the profiles of the turbulent standard deviations above the urban canopy;in the CS,the turbulent standard deviation are almost constant with *** analysis of the third and fourth order moments shows that the wind velocities above the urban canopy in the TS deviate from the Gaussian distribution more significantly than those in the CS and *** local similarity relations of the turbulent dispersion parameters in the TS,especially for the longitudinal wind components,are normally different from those in the CS and ***,different from the common assumptions in Lagrangian models,the turbulence dispersion in horizontal directions is anisotropic and should be parameterized by multiple similarity relations under heavy haze conditions.

关键词： Heavy haze Turbulence dispersion Local similarity Lagrangian model

Emphasizing Essential Words for Sentiment Classification Based onRecurrent Neural Networks

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Journal of Computer Science & Technology 2017年第4期32卷 785-795页

作者： fei hu Li Li Zi-Li Zhang Jing-Yuan Wang Xiao-fei Xu College of Computer and Information Science Southwest University Chongqing 400715 China Network Centre Chongqing University of Education Chongqing 400065 China

With the explosion of online communication and publication, texts become obtainable via forums, chat messages, blogs, book reviews and movie reviews. Usually, these texts are much short and noisy without sufficient statistical signals and enough information for a good semantic analysis. Traditional natural language processing methods such as Bow-of-Word (BOW) based probabilistic latent semantic models fail to achieve high performance due to the short text environment. Recent researches have focused on the correlations between words, i.e., term dependencies, which could be helpful for mining latent semantics hidden in short texts and help people to understand them. Long short-term memory (LSTM) network can capture term dependencies and is able to remember the information for long periods of time. LSTM has been widely used and has obtained promising results in variants of problems of understanding latent semantics of texts. At the same time, by analyzing the texts, we find that a number of keywords contribute greatly to the semantics of the texts. In this paper, we establish a keyword vocabulary and propose an LSTM-based model that is sensitive to the words in the vocabulary; hence, the keywords leverage the semantics of the full document. The proposed model is evaluated in a short-text sentiment analysis task on two datasets: IMDB and SemEval-2016, respectively. Experimental results demonstrate that our model outperforms the baseline LSTM by 1%similar to 2% in terms of accuracy and is effective with significant performance enhancement over several non-recurrent neural network latent semantic models (especially in dealing with short texts). We also incorporate the idea into a variant of LSTM named the gated recurrent unit (GRU) model and achieve good performance, which proves that our method is general enough to improve different deep learning models.

关键词： short text understanding long short-term memory (LSTM) gated recurrent unit (GRU) sentiment classification deep learning