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On Coexistence with COVID-19:Estimations and Perspectives

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China CDC weekly 2021年第50期3卷 1057-1061页

作者： yuan Zhang Chong You Xin Gai xiaohua Zhou School of Mathematical Sciences Peking UniversityBeijingChina Center for Statistical Sciences Peking UniversityBeijingChina Beijing International Center for Mathematical Research Peking UniversityBeijingChina Department of Biostatistics School of Public HealthPeking UniversityBeijingChina.

Given the harsh reality faced by the global effort to contain coronavirus disease 2019(COVID-19)and the virtual impossibility of its worldwide eradication in the foreseeable future,global human coexistence with fast mutating severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)may have to occur,for the time being,irrespective of the wishes and aspirations of our people.Therefore,for China,the risk associated with small to medium scale outbreaks induced by imported cases and the corresponding need to continuously and promptly suppress domestic infections would persist for a certain period of time.

关键词： acute respiratory prompt

Determining the Covertness of COVID-19-Wuhan,China,2020

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China CDC weekly 2021年第8期3卷 170-173,I0001-I0006页

作者： Chong You Xin Gai yuan Zhang xiaohua Zhou Beijing International Center for Mathematical Research Peking UniversityBeijingChina Department of Biostatistics School of Public HealthPeking UniversityBeijingChina School of Mathematical Sciences Peking UniversityBeijingChina Center for Statistical Sciences Peking UniversityBeijingChina.

Introduction:The coronavirus disease 2019(COVID-19)pandemic has been going on for over a year and has reemerged in several regions.Therefore,understanding the covertness of COVID-19 is critical to more precisely estimating the pandemic size,especially the population of hidden carriers(those with very mild or no symptoms).Methods:A stochastic dynamic model was proposed to capture the transmission mechanism of COVID-19 and to depict the covertness of COVID-19.The proposed model captured unique features of COVID-19,changes in the diagnosis criteria,and escalating containment measures.Results:The model estimated that,for the epidemic in Wuhan,79.8%(76.7%-82.7%)of the spread was caused by hidden carriers.The overall lab-confirmation rate in Wuhan up until March 8,2020 was 0.17(0.15-0.19).The diagnostic rate among patients with significant symptoms went up to 0.82 on March 8,2020 from 0.43 on January 1,2020 with escalating containment measures and nationwide medical supports.The probability of resurgence could be as high as 0.72 if containment measures were lifted after zero new reported(lab-confirmed or clinically confirmed)cases in a consecutive period of 14 days.This probability went down to 0.18 and 0.01 for measures lifted after 30 and 60 days,respectively.Discussion:Consistent with the cases detected in Wuhan in mid-May,2020,this study suggests that much of the COVID-19 pandemic is underreported and highly covert,which suggests that strict measures must be enforced continuously to contain the spread of the pandemic.

关键词： diagnosis measures Wuhan

Sharp bounds for spectral radius of nonnegative weakly irreducible tensors

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Frontiers of Mathematics in China 2019年第5期14卷 989-1015页

作者： Lihua YOU xiaohua HUANG Xiying yuan School of Mathematical Sciences South China Normal UniversityGuangzhou 510631China Department of Mathematics Shanghai UniversityShanghai 200444China

We obtain the sharp upper and lower bounds for the spectral radius of a nonnegative weakly irreducible tensor.By using the technique of the representation associate matrix of a tensor and the associate directed graph of the matrix,the equality cases of the bounds are completely characterized by graph theory methods.Applying these bounds to a nonnegative irreducible matrix or a connected graph(digraph),we can improve the results of L.H.You,Y.J.Shu,and P.Z.yuan[Linear Multilinear Algebra,2017,65(1):113-128],and obtain some new or known results.Applying these bounds to a uniform hypergraph,we obtain some new results and improve some known results of X.Y.yuan,M.Zhang,and M.Lu[Linear Algebra Appl.,2015,484:540-549].Finally,we give a characterization of a strongly connected/c-uniform directed hypergraph,and obtain some new results by applying these bounds to a uniform directed hypergraph.

关键词： Nonnegative weakly irreducible tensors uniform(directed)hypergraph spectral radius bound

Detection of decomposition products of SF6/air gas mixture by electron attachment mass spectrometry

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High Voltage 2022年第3期7卷 536-544页

作者： Huan yuan Xiaonan Wang Aijun Yang Dingxin Liu xiaohua Wang Mingzhe Rong State Key Laboratory of Electrical Insulation and Power Equipment Xi'an Jiaotong UniversityXi'anChina

Sulphur hexafluoride(SF_(6))is widely used in gas insulation,and its decomposition products can be used to diagnose potential insulation failures.Quick and accurate detection of decomposition products can help to understand equipment-operating conditions in time.In this study,the decomposition products of SF_(6)/air gas mixtures under different pulsed discharge voltages were studied.It was found that the main products were SOF_(2),SO_(2)F_(2),SO_(2),CF_(4)and SOF_(4),and the yields of SOF_(2),SO_(2)F_(2),SO_(2)and SOF_(4)increased with the number of discharge pulse.The productive rate of SOF_(2),SO_(2)and SOF_(4)were positively correlated with the discharge voltage,and when the discharge voltage increased from 5 to 15 kV,their yields after 50,000 discharges increased by 49%,120%and 1100%,respectively.The productive rate of SOF_(2)and SO_(2)were positively correlated with the proportion of air in the gas mixtures while that of SOF_(4)was opposite.When the proportion of air increases from 0%to 90%,their yields after 50,000 discharges became 270%,3169%and 10%of the originals,respectively.In addition,the productive rate of SO_(2)F_(2)was not affected by discharge voltage and the proportion of air in the gas mixtures.SO_(2)F_(2),SOF_(2),SOF_(4)and SO_(2)can be used as the basis for judging the discharge failures and the discharge degree of power equipment.

关键词： insulation decomposition SF6

Progress of studies in China from July 2010 to May 2015 on the influence of the Kuroshio on neighboring Chinese seas and the Ryukyu Current

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Acta Oceanologica Sinica 2015年第12期34卷 1-10页

作者： yuan Yaochu ZHU xiaohua ZHOU Feng State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of Oceanography State Oceanic Administration

The influence of the Kuroshio on neighboring Chinese seas and the Ryukyu Current is a very important subject of interest in physical oceanography. To deeply explain the research progress made by Chinese scientists from July2010 to May 2015, the following three aspects are reviewed in this paper. The first concerns the Kuroshio intrusion into the South China Sea（SCS） and its circulation around the Luzon Strait. There are two very important points to be explained： the seasonal and inter-annual variation of the Kuroshio intrusion and the mechanisms of the Kuroshio intrusion and the influence of the Kuroshio on currents in the Luzon Strait and circulation in the northern SCS. The second concerns the variability of the Kuroshio and its interaction with the East China Sea（ECS）. There are following four interesting topics to be explained： an overview of studies on the Kuroshio in the ECS; the Kuroshio intrusion into the ECS, water exchange, and dynamic impacts; the downstream increase of nutrient transport by the Kuroshio; and the application of satellite remote sensing on terrestrial material transport by the Kuroshio intrusion into the ECS. Third, the interaction between the Ryukyu Current and Kuroshio in the ECS are also discussed. Finally, the main results are summarized and areas of further study are simply discussed.

关键词： Kuroshio intrusion circulation South China Sea East China Sea currents in Luzon Strait Ryukyu Current

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Research on vibration energy harvesting technology of power equipment based on alternating magnet array

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High Voltage 2024年第2期9卷 336-345页

作者： Pinlei Lv Chengyu Fan Aijun Yang Huan yuan Jifeng Chu Mingzhe Rong xiaohua Wang State Key Laboratory of Electrical Insulation and Power Equipment Xi'an Jiaotong UniversityXi'anChina State Grid Sichuan Electric Power Research Institute ChengduChina

Vibration with a frequency of 100 Hz is widely distributed in the power equipment,and it can provide a new way to supply energy for sensors by vibration energy harvesting.The vibration energy harvesting method based on electromagnetic induction principle was studied through the arrayed structure of magnets and coils.Static magnetic field models were established for four magnet array structures and it was found that the alternating magnet array has the largest magnetic flux and magnetic flux gradient.Based on the alternating magnet array,prototypes of energy harvester with vertical and parallel movement mode were proposed.Through structural parameter optimisation analysis,two different energy harvesters were fabricated and it was found that the energy harvester with a parallel movement mode has better output performances.The energy harvester could provide output voltage/current and power of 8.35 V/17.39 mA and 15.13 mW(matched resistance is 200Ω)at an acceleration of 5 m⋅s^(-2).The 100 mF capacitor could be charged to 2.72 V within 300 s,and the final voltage of the capacitor is greater than 3 V,which could sustainably drive commercial wireless temperature/humidity sensors.

关键词： power energy alternating

Microstructure and mechanical properties of Ti_(3)(Al,Ga)C_(2)/Al_(2)O_(3) composites prepared by in situ reactive hot pressing

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Journal of Advanced Ceramics 2020年第6期9卷 782-790页

作者： yuan FANG xiaohua LIU Yuxia FENG Jianfeng ZHU Wei JIANG School of Material Science and Engineering Shaanxi Key Laboratory of Green Preparation and Functionalization for Inorganic MaterialsShaanxi University of Science and TechnologyXi’an 710021China

In this study,Ti_(3)(Al,Ga)C_(2)/Al_(2)O_(3) composites were successfully synthesized by in situ hot pressing at 1350℃ for 2 h using Ti,Al,TiC,and Ga_(2)O_(3) as raw materials.X-ray diffraction and scanning electron microscopy were used for characterizing the phase identities and microstructures of the sintered composites.The dependence of the Vickers hardness and flexural strength on the Al_(2)O_(3) content was found to be in single-peak type.Ti_(3)(Al_(0.6),Ga_(0.4))C_(2)/10.3vol% Al_(2)O_(3) composite exhibited significantly improved mechanical properties.Vickers hardness and flexural strength of the composite reached 6.58 GPa and 527.11 MPa,which were 40% and 74% higher than those of Ti_(3)AlC_(2),respectively.Formation of solid solution and incorporation of second phase of Al_(2)O_(3) resulted in the opposite influence on the fracture toughness.Finally,the hardening and strengthening mechanisms were discussed in detail.

关键词： Ti_(3)AlC_(2) solid solution ceramic composites microstructure mechanical properties

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An Improved Algorithm for Blind Carrier Frequency Estimation with Burst MPSK Transmissions

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Wuhan University Journal of Natural Sciences 2013年第1期18卷 55-58页

作者： YUAN xiaohua ZHENG Hui ZHAO Zhengyu ZHOU Chen National Key Laboratory of Blind Signals Processing School of Electronic Information Wuhan University

This paper presents an improved non-data-aided algo- rithm for carrier frequency estimation for burst M-ary PSK signals when modulation order M and training symbols are unknown. Unlike data-aided estimation, a phase clustering algorithm is used first to estimate M and modulated information is removed by a vari- able interval linear phase unwrapping. Then, a high-order correlation algorithm with proper correction is present, which reduces the probability of phase ambiguity and promotes anti-noise capability of the estimation. Simulations are given to analyze the unbiased esti- mation range, and the asymptotic performance and symbol number are needed to compare with the former algorithms. The new algo- rithm has a large estimation range close to the theoretical maximum value for non-data-aided estimation and has a better performance than earlier non-data-aided techniques for large frequency offset, low signal-to-noise ratio, and limited symbol numbers.

关键词： burst MPSK signal automatic modulation recognition non-data-aided carrier frequency offset linear phase unwrapping high-order correlation

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Adipose-derived stem cell/FGF19-loaded microfluidic hydrogel microspheres for synergistic restoration of critical ischemic limb

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Bioactive Materials 2023年第9期27卷 394-408页

作者： Ruihan Wang Fangqian Wang Shan Lu Bin Gao yuanqing Kan Tong yuan Yisheng Xu Chen yuan Daqiao Guo Weiguo Fu xiaohua Yu Yi Si Department of Vascular Surgery Zhongshan Hospital Fudan UniversityShanghai200032PR China Institute of Vascular Surgery Fudan UniversityShanghai200032PR China National Clinical Research Center for Interventional Medicine Shanghai200032PR China Department of Orthopedics The Second Affiliated Hospital of Zhejiang University School of MedicineHangzhou310009ZhejiangPR China Key Laboratory of Motor System Disease Research and Precision Therapy of Zhejiang Province Hangzhou310000ZhejiangPR China State Key Laboratory of Chemical Engineering East China University of Science and TechnologyShanghai200237China

The efficacy of stem cell therapy is substantially compromised due to low cell survival rate and poor local retention post-delivery. These issues drastically limit the application of stem cells for ischemic limb therapy, which requires effective blood perfusion and skeletal muscle regeneration. Herein, based on microfluidic technology, an integrated stem cell and cytokine co-delivery system designed for functional ischemic limb salvage was constructed by first incorporating the myogenic cytokine, fibroblast growth factor 19 (FGF19), into microspheres composed of methacrylate gelatin (GelMA). Then adipose-derived stem cells (ADSCs) were highly absorbed into the porous structure of the microspheres, overcoming the insufficient loading efficiency and activities by conventional encapsulation strategy. The fabricated ADSCs/FGF19@μsphere system demonstrated a uniform size of about 180 μm and a highly porous structure with pore sizes between 20 and 40 μm. The resultant system allowed high doses of ADSCs to be precisely engrafted in the lesion and to survive, and achieved sustained FGF19 release in the ischemic region to facilitate myoblast recruitment and differentiation and myofibrils growth. Furthermore, the combination of ADSCs and FGF19 exhibited a positive synergistic effect which substantially improved the therapeutic benefit of angiogenesis and myogenesis, both in vitro and in vivo. In summary, a stem cell and cytokine co-delivery system with the properties of easy preparation and minimal invasiveness was designed to ensure highly efficient cell delivery, sustained cytokine release, and ultimately realizes effective treatment of ischemic limb regeneration.

关键词： Microfluidic technology Stem cell Cytokine Porous microspheres Ischemic limb salvage