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Wavefronts of a Nonlocal State-dependent Time Delay Model

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Acta Mathematica Sinica,English Series 2020年第1期36卷 77-92页

作者： rui Jun XIE Rong yuan Zhi Hui YANG School of Statistics and Applied Mathematics Anhui University of Finance and EconomicsBengbu 233030P.R.China School of Mathematical Sciences Beijing Normal UniversityBeijing 100875P.R.China

This paper is concerned with the travelling wavefronts of a nonlocal dispersal cooperation model with harvesting and state-dependent delay,which is assumed to be an increasing function of the population density with lower and upper ***,state-dependent delay is introduced into a nonlocal reaction-diffusion *** conditions of Schauder's fixed point theorem are proved by constructing a reasonable set of functionsΓ(see Section 2)and a pair of upper-lower solutions,so the existence of traveling wavefronts is *** present study is continuation of a previous work that highlights the Laplacian diffusion.

关键词： Nonlocality state-dependent delay cooperation traveling wavefronts

An overview of healthcare monitoring by flexible electronics

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Science China(Physics,Mechanics & Astronomy) 2018年第9期61卷 1-18页

作者： JianQiao Hu rui Li yuan Liu Ye Wang Su State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering Mechanics and International Research Center for Computational Mechanics Dalian University of Technology Dalian 116024 China Applied Mechanics Laboratory School of Aerospace Engineering Tsinghua University Beijing 100084 China School of Engineering Science University of Chinese Academy of Sciences Beijing 100049 China State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan 430074 China

Flexible electronics integrated with stretchable/bendable structures and various microsensors that monitor the temperature,pressure, sweat, bioelectricity, body hydration, etc., have a wide range of applications in the human healthcare sector. The science underlying this technology draws from many research areas, such as information technology, materials science, and structural mechanics, to efficiently and accurately monitor technology for various signals. In this paper, we make a classification and comb to the designs, materials, structures and functions of numerous flexible electronics for signal monitoring in the human healthcare sector. Some perspectives in this field are discussed in the concluding remarks.

关键词： flexible electronics stretchable electronics signal monitoring human healthcare

Nonlinearity analysis of piezoelectric micromachined ultrasonic transducers based on couple stress theory

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Acta Mechanica Sinica 2012年第1期28卷 104-111页

作者： Xin Kang fu-Jun Yang Xiao-yuan He Department of Applied Mechanics Nanjing University of Science and Technology210094 NanjingChina Department of Mechanical and Aeronautical Engineering University of CaliforniaDavis95616US Institute of Engineering Mechanics Southeast University210096 NanjingChina

This paper studies the static deformation behavior of a piezoelectric micromachined ultrasonic transducer （PMUT） actuated by a strong external electric field. The transducer membrane consists of a piezoelectric layer, a passive layer and two electrode layers. The nonlinearities of the piezoelectric layer caused by electrostriction under a strong electric field are analyzed. Because the thickness of the transducer membrane is on the microscale, the size dependence of the deformation behavior is evaluated using the couple stress theory. The results show that the optimal ratio of the top electrode diameter and the membrane diameter is around 0.674. It is also found that this optimal value does not depend on any other parameters if the thicknesses of the two electrodes are negligible compared with those of the piezo- electric and passive layers. In addition, the nonlinearities of the piezoelectric layer will become stronger along with the increase of the electric field, which means that softening of the membrane stiffness occurs when a strong external electric field is applied. Meanwhile, the optimal thickness ratio for the passive layer and the piezoelectric layer is not equal to 1.0 which is usually adopted by previous researchers. Because there exists size dependence of membrane deforma-tion, the optimal value of this thickness ratio needs to be greater than 1.0 on the microscale.

关键词： Piezoelectric micromachined ultrasonic trans- ducer (PMUT) Couple stress theory Static deformation - Nonlinearity analysis

Cosmological twinlike models with multi scalar fields

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Science China(Physics,Mechanics & Astronomy) 2018年第9期61卷 31-36页

作者： yuan Zhong Chun E fu Yu Xiao Liu School of Science Xi'an Jiaotong University Institute of Theoretical Physics Lanzhou University

In this study, we consider cosmological models driven by several canonical or noncanonical scalar fields, and we show the manner in which twinlike models for a canonical model can be constructed from noncanonical ones using the superpotential method. We conclude that it is possible to construct twinlike models for multifield cosmological models, even with a nonzero spatial *** work extends the discussions of [D. Bazeia, and J. D. Dantas, Phys. Rev. D 85, 067303(2012)] to cases with multi scalar fields and with non-vanished spatial curvature, by using a different superpotential method.

关键词： cosmological twinlike models superpotential method noncanonical scalar field

Progressive prediction method for failure data with small sample size

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航空动力学报 2011年第9期26卷 2049-2053页

作者： WANG Zhi-hua fu Hui-min LIU Cheng-rui Research Center of Small Sample Technology Beijing University of Aeronautics and Astronautics Beijing 100191 China Science and Technology on Space Intelligent Control Laboratory Beijing Institute of Control Engineering Beijing 100191 China

The small sample prediction problem which commonly exists in reliability analysis was discussed with the progressive prediction method in this *** modeling and estimation procedure,as well as the forecast and confidence limits formula of the progressive auto regressive(PAR) method were discussed in great *** model not only inherits the simple linear features of auto regressive(AR) model,but also has applicability for nonlinear *** application was illustrated for predicting the future fatigue failure for Tantalum electrolytic *** results of PAR model were compared with auto regressive moving average(ARMA) model,and it can be seen that the PAR method can be considered good and shows a promise for future applications.

关键词： failure data forecast system reliability small sample progressive prediction nonlinear system

A trust-aware random walk model for return propensity estimation and consumer anomaly scoring in online shopping

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Science China(Information Sciences) 2019年第5期62卷 75-91页

作者： Xiaolin LI yuan ZHUANG Yanjie fu Xiangdong HE School of Business Nanjing University Department of Computer Science Missouri University of Science and Technology Network and Information Center Nanjing University

In online shopping, most of consumers will not clear their return reasons when submitting return requests(e.g., select the option "other reasons"). Prior literature mostly investigates into the return event at the transaction level, and the underlying force of returns remains untracked. To deal with this problem, we propose a machine learning algorithm named as trust-aware random walk model(TARW). In the proposed model, four patterns of consumers can be identified in terms of return forces:(i) selfish consumers,(ii) honest consumers,(iii) fraud consumers, and(iv) irrelevant consumers. To profile consumers’ return patterns, we capture consumers’ similarities in order preferences and return tendencies separately. Based on consumers’ similarities, we obtain a return pattern trust network by introducing the trust network and collaborative filtering algorithms. Subsequently, we develop two important applications based on the trust network:(i)estimating consumers’ return propensities for product types;(ii) scoring the anomaly for consumers’ returns for one product. Finally, we conduct extensive experiments with the real-world data to validate the model’s effectiveness in predicting and tracing consumers’ returns. With the proposed model, we can help retailers improve the conversion rates of selfish consumers, retain honest consumers, and block fraud consumers.

关键词： machine learning return abuse random walk collaborative filtering return pattern

A Universal Blown Film Apparatus for in Situ X-ray Measurements

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Chinese Journal of Polymer Science 2017年第12期35卷 1508-1516页

作者： rui Zhang 纪又新 Qian-lei Zhang Jian-zhu Ju Ali Sarmad Li-fu Li Hao-yuan Zhao 李良彬 National Synchrotron Radiation Lab and College of Nuclear Science and Technology Chinese Academy of Sciences Key Laboratory of Soft Matter Chemistry University of Science and Technology of China

A setup of blown film machine combined with in situ synchrotron radiation X-ray diffraction measurements and infrared temperature testing is reported to study the structure evolution of polymers during film blowing. Two homemade auto-lifters are constructed and placed under the blown machine at each end of the beamline platform which move up and down with a speed of 0.05 mm/s bearing the 200 kg weight machine. Therefore, structure development and temperature changes as a function of position on the film bubble can be obtained. The blown film machine is customized to be conveniently installed with precise servo motors and can adjust the processing parameters in a wide range. Meanwhile, the air ring has been redesigned in order to track the structure information of the film bubble immediately after the melt being extruded out from the die exit. Polyethylene（PE） is selected as a model system to verify the feasibility of the apparatus and the in situ experimental techniques. Combining structure information provided by the WAXD and SAXS and the actual temperature obtained from the infrared probe, a full roadmap of structure development during film blowing is constructed and it is helpful to explore the molecular mechanism of structure evolution behind the film blowing processing, which is expected to lead to a better understanding of the physics in polymer processing.

关键词： Blown film machine Synchrotron radiation X-ray diffraction In situ measurement Structure evolution

THE SYNTHESIS OF Ag-POLYPYRROLE NANOCOMPOSITE COATED LATEX PARTICLES AND THEIR APPLICATION AS A FLUORESCENT QUENCHING AGENT

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Chinese Journal of Polymer Science 2013年第3期31卷 434-443页

作者： Jiang-ru Zhang 邱藤 Hong-fu yuan 李效玉 College of Materials Science and Engineering State of Key Laboratory of Organic-Inorganic Composites Key Laboratory of Carbon Fiber and functional Polymers Ministry of EducationBeijing University of Chemical Technology

Submicron-sized Ag-polypyrrole/poly（styrene-co-methacrylic acid）（Ag-PPy/P（St-co-MAA）） composite particles were fabricated via a redox reaction between pyrrole and AgNO3 in the presence of P（St-co-MAA） soap-free latex. The products are characterized by transmission electron microscopy （TEM）, electron diffraction spectra （EDS）, Raman spectra, thermogravimetric analysis （TGA） and scanning electron microscopy （SEM）. The results showed that Ag-PPy nanocomposites were in situ deposited onto the surface of P（St-co-MAA） latex particles tailored by carboxylic-acid groups. The nanocomposites of Ag-PPy distributed on the surface of polymer particles transformed from discretely dots to continuously coating as the reaction temperature increased from 15℃ to 60℃. Strawberry-like composite particles were obtained at the reaction temperature of 60℃. The TGA characterization confirmed that the Ag-PPy nanocomposites loading onto the P（St-co-MAA） particles were systematically controlled over a range of 6 wt%-42 wt% by changing the reaction temperatures. The fluorescence quenching effect of the Ag-PPy/P（St-co-MAA） composite particles was explored on Rhodamine B as a model molecule with the Stern-Volmer quenching constant Ksv of 5.9 × 104 （g/mL）-1. It is suggested that the fluorescence quenching effect is caused by the resonance energy transfer mechanism.

关键词： Nanocomposite-coated latex particles PPy Ag nanoparticles Synthesis Fluorescence quenching.

Observation and analysis of atmospheric volatile organic compounds in a typical petrochemical area in Yangtze River Delta, China

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Journal of Environmental Sciences 2018年第9期30卷 233-248页

作者： Yunchen Zhang rui Li Hongbo fu Dong Zhou Jianmin Chen Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention Department of Environmental Science & Engineering Fudan University Shanghai 200433 China Shanghai Institute of Pollution Control and Ecological Security Shanghai 200092 China Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET) Nanjing University of Information Science and Technology Nanjing 210044 China

Volatile organic compounds （VOCs） are a kind of important precursors for ozone photochemical formation. In this study, VOCs were measured from November 5th, 2013 to January 6th, 2014 at the Second Jinshan Industrial Area, Shanghai, China. The results showed that the measured VOCs were dominated by alkanes （41.8%）, followed by aromatics （20.1%）, alkenes （17.9%）, and halo-hydrocarbons （12.5%）. The daily trend of the VOC concentration showed a bimodal feature due to the rush-hour traffic in the morning and at nightfall. Based on the VOC concentration, a receptor model of Positive Matrix Factorization （PMF） coupled with the information related to VOC sources was applied to identify the major VOC emissions. The result showed five major VOC sources： solvent use and industrial processes were responsible for about 30% of the ambient VOCs, followed by rubber chemical industrial emissions （23%）, refinery and petrochemical industrial emissions （21%）, fuel evaporations （13%） and vehicular emissions （13%）. The contribution of generalized industrial emissions was about 74% and significantly higher than that made by vehicle exhaust. Using a propylene-equivalent method, alkenes displayed the highest concentra-tion, followed by aromatics and alkanes. Based on a maximum incremental reactivity （MIR） method, the average hourly ozone formation potential （OFP） of VOCs is 220.49 ppbv. The most significant source for ozone chemical formation was identified to be rubber chemical industrial emissions, following one by vehicular emission. The data shown herein may provide useful information to develop effective VOC pollution control strategies in industrialized area.

关键词： VOCs PMF Emission sources Photochemical reactivity MIR OFP