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GLOBAL INSTABILITY OF MULTI-DIMENSIONAL PLANE SHOCKS FOR ISOTHERMAL FLOW

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Acta Mathematica Scientia 2022年第3期42卷 887-902页

作者： Ning-An lai wei XIANG Yi ZHOU College of Mathematics and Computer Science Zhejiang Normal UniversityJinhua 321004China Department of MathematicsLishui UniversityLishui 323000China Department of Mathematics City University of Hong KongKowloonHong Kong 999077China School of Mathematical Sciences Fudan UniversityShanghai 200433China

In this paper,we are concerned with the long time behavior of the piecewise smooth solutions to the generalized Riemann problem governed by the compressible isothermal Euler equations in two and three dimensions.A non-existence result is established for the fan-shaped wave structure solution,including two shocks and one contact discontinuity which is a perturbation of plane ***,unlike in the one-dimensional case,the multi-dimensional plane shocks are not stable ***,a sharp lifespan estimate is established which is the same as the lifespan estimate for the nonlinear wave equations in both two and three space dimensions.

关键词： Blow-up global solution instability shock contact disctinuity Euler equations isothermal generalized Riemann problem nonlinear wave equations

Design and hovering control of a twin rotor tail-sitter UAV

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Science China(Information Sciences) 2019年第9期62卷 185-187页

作者： Wufan WANG Jihong ZHU Minchi kuang Xiaming YUAN Yunfei TANG Yaqing lai Lyujie CHEN Yunjie YANG Department of Computer Science and Technology Tsinghua University

The tail-sitter unmanned aerial vehicles (UAVs)combine the vertical takeoff and landing (VTOL)capabilities of rotary-wing UAVs and the efficient long-distance flight capability of fixed-wing *** compared with other hybrid aircraft configurations such as tilt-rotor [1] and tilt-wing [2]UAVs, the tail-sitter UAV possesses the simplest configuration and requires no extra mechanisms for performing the VTOL maneuver. This brings several benefits including high payload and low susceptibility to malfunctions.

关键词： Design and hovering control of a twin rotor tail-sitter UAV pro

Understanding Fatigue Failure in Binary Rubber Blends: Role of Crack Initiation and Propagation

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Chemical Research in Chinese Universities 2024年第6期40卷 987-993页

作者： PAN Lijia WANG Yuge wei lai SUN Zhaoyan Xinjiang Laboratory of Phase Transitions and Microstructures in Condensed Matters College of Physical Science and TechnologyYili Normal UniversityYining 835000P.R.China State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022P.R.China University of Science and Technology of China Hefei 230026P.R.China

Under cyclic loading conditions,the breakdown of rubber products is mainly caused by the formation and spread of *** study focuses on understanding how cracks initiate and grow during the fatigue failure of blended *** prepared composite materials by blending bio-mimetic rubber (BMR);butadiene rubber (BR) in different mass ratios and evaluated their resistance to crack initiation and *** results indicate a clear trend: as the BR content increases,crack initiation in blended rubber is inhibited,while crack propagation is *** shift leads to a change in the primary factor influencing fatigue fracture from crack initiation to crack ***,we observed that the fatigue life of the rubber blend initially increases and then decreases as the BMR content rises,indicating a critical threshold when the mass ratio of BMR to BR is *** closely examining the materials using a scanning electron microscope (SEM);image analysis,we confirmed that before the threshold,crack initiation is the dominant factor in fatigue failure,while after the threshold,crack propagation takes *** study provides valuable insights into the mechanisms behind fatigue failure in rubber blends,contributing to a better understanding of this important material behavior.

关键词： Blended rubber Fatigue failure Crack initiation Crack propagation Fracture microstructure

Optimal Strategy for Aircraft Pursuit-evasion Games via Self-play Iteration

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Machine Intelligence Research 2024年第3期21卷 585-596页

作者： Xin Wang Qing-lai wei Tao Li Jie Zhang State Key Laboratory of Management and Control for Complex Systems Institute of AutomationChinese Academy of SciencesBeijing100190China School of Artificial Intelligence University of Chinese Academy of SciencesBeijing100049China Institute of Systems Engineering Macao University of Science and TechnologyMacao999078China

In this paper,the pursuit-evasion game with state and control constraints is solved to achieve the Nash equilibrium of both the pursuer and the evader with an iterative self-play *** the condition where the Hamiltonian formed by means of Pontryagin’s maximum principle has the unique solution,it can be proven that the iterative control law converges to the Nash equilibrium ***,the strong nonlinearity of the ordinary differential equations formulated by Pontryagin’s maximum principle makes the control policy difficult to figured *** the system dynamics employed in this manuscript contains a high dimensional state vector with *** practical applications,such as the control of aircraft,the provided overload is ***,in this paper,we consider the optimal strategy of pursuit-evasion games with constant constraint on the control,while some state vectors are restricted by the function of the *** address the challenges,the optimal control problems are transformed into nonlinear programming problems through the direct collocation ***,two numerical cases of the aircraft pursuit-evasion scenario are given to demonstrate the effectiveness of the presented method to obtain the optimal control of both the pursuer and the evader.

关键词： Differential games pursuit-evasion games nonlinear control optimal control Nash equilibrium solution

Physical characterization of meloxicam-β-cyclodextrin inclusion complex pellets prepared by a fluid-bed coating method

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Particuology 2009年第1期7卷 1-8页

作者： Yi Lu Xingwang Zhang Jie lai Zongning Yin wei Wu School of Pharmacy Fudan University Shanghai China West China School of Pharmacy Sichuan University Chengdu china

Meloxicam-β-cyclodextrin （ME-β-CD） inclusion complex was prepared by a fluid-bed coating technique upon solvent removal and simultaneous depositing onto the surface of nonpareil pellets and using PVP K30 as a binding agent to facilitate good coating. The resultant pellets were spherical and intact in shape with good flowability and friability. SEM analysis showed that the pellets were smooth and had a tightly coated inclusion complex layer. In vitro dissolution of the inclusion complex pellets in pH 7.4 phosphate buffer was dramatically enhanced at an ME/CD ratio of 1/1. DSC and powder X-ray diffractometry proved the absence of crystallinity in the ME/CD inclusion complexes. Moreover, Fourier transform-infrared spectrometry together with Raman spectrometry indicated that the thiazole ring of ME was possibly included in the cavity of β-CD.

关键词： Meloxicam Inclusion complex β-Cyclodextrin Fluid-bed Pellets Dissolution Characterization

Migration and accumulation characteristics of natural gas hydrates in the uplifts and their slope zones in the Qiongdongnan Basin,China

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China Geology 2022年第2期5卷 234-250页

作者： Yu-lin He Jin-qiang Liang Zeng-gui kuang wei Deng Jin-feng Ren Hong-fei lai Miao-miao Meng wei Zhang Southern Marine Science and Engineering Guangdong Laboratory Guangzhou 511458China Guangzhou Marine Geological Survey China Geological SurveyMinistry of Natural ResourcesGuangzhou 510075China National Engineering Research Center of Gas Hydrate Exploration and Development Guangzhou 511458China

Various factors controlling the accumulation of natural gas hydrates(NGHs)form various enrichment and accumulation modes through organic *** study mainly analyzes the geological and geophysical characteristics of the NGHs occurrence in the uplifts and their slope zones within the deep-water area in the Qiongdongnan(QDN)Basin(also referred to as the study area).Furthermore,it investigates the dominant governing factors and models of NGHs migration and accumulation in the study *** results are as follows.(1)The uplifts and their slope zones in the study area lie in the dominant pressure-relief direction of fluids in central hydrocarbon-rich sags in the area,which provide sufficient gas sources for the NGHs accumulation and enrichment through pathways such as gas chimneys and faults.(2)The top and flanks of gas chimneys below the bottom simulating reflectors(BSRs)show high-amplitude seismic reflections and pronounced transverse charging of free gas,indicating the occurrence of a large amount of gas accumulation at the heights of the uplifts.(3)Chimneys,faults,and high-porosity and high-permeability strata,which connect the gas hydrate temperature-pressure stability zones(GHSZs)with thermogenic gas and biogenic gas,form the main hydrate migration system.(4)The reservoir system in the study area comprises sedimentary interlayers consisting of mass transport deposits(MTDs)and *** addition,the reservoir system has developed fissure-and pore-filling types of hydrates in the *** above well-matched controlling factors of hydrate accumulation enable the uplifts and their slope zones in the study area to become the favorable targets of NGHs exploration.

关键词： Gas chimney Overpressure Migration characteristics of gas hydrates Accumulation characteristics of gas hydrates Oil and gas exploration engineering NGHs exploration trial engineering Uplifts and slope zones Qiongdongnan Basin China

Wet spinning of PVA composite fibers with a large fraction of multi-walled carbon nanotubes

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Progress in Natural Science:Materials International 2015年第5期25卷 445-452页

作者： Dengpan lai Yizhe wei Liming Zou Yongjing Xu Hongwei Lu State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and Engineering Donghua University

PVA composites fibers with a large fraction of multi-walled carbon nanotubes modified by both covalent and non-covalent functionalization were produced by a wet-spinning *** XQ-1 tensile tester,thermogravimetric analysis,scanning electron microscopy,differential scanning calorimetry,and wide-angle X-ray diffraction were used to characterize the properties of PVA/MWNT composite *** TGA results suggested that MWNTs content in composite fibers were ranged from 5.3 wt%to 27.6 wt%.The mechanical properties of PVA/MWNT composite fibers were obviously superior to pure PVA *** Young's modulus of composite fibers enhanced with increasing the content of MWNTs,and it rised gradually from 6.7 GPa for the pure PVA fiber to 12.8 GPa for the composite fibers with 27.6 wt%***,the tensile strength increased gradually from 0.39 GPa for the pure PVA fiber to 0.74 GPa for the composite fibers with 14.4 wt%***,the tensile strength of the composite fibers decreased as the MWNTs content up to 27.6 wt%.SEM results indicated that the MWNTs homogeneously dispersed in the composite fibers,however some agglomerates also existed when the content of MWNTs reached27.6 wt%.DSC results proved strong interfacial interaction between MWNTs and PVA chain,which benefited composite fibers in the efficient *** characterization showed that the orientation of PVA molecules declined from 94.1%to 90.9%with the increasing of MWNTs *** good dispersibility of MWNTs throughout PVA matrix and efficient stress-transfer between MWNTs and PVA matrix may contributed to significant enhancement in the mechanical properties.

关键词： Multi-walled carbon nanotubes(MWNTs) Poly(vinyl alcohol)(PVA) Wet-spinning Composite fibers

THR-βAgonist for Nonalcoholic Steatohepatitis Treatment:Challenges of a Promising Drug

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Journal of Clinical and Translational Hepatology 2024年第8期12卷 755-757页

作者： Feng Xue lai wei School of Clinical Medicine Tsinghua UniversityBeijingChina Hepatopancreatobiliary Center Beijing Tsinghua Changgung HospitalTsinghua UniversityBeijingChina

*** incidence of nonalcoholic steatohepatitis(NASH)is ***,a thyroid hormone receptorβTHR-βagonist,has demonstrated a good safety profile in published phase 2 and phase 3 studies,meeting the *** and Drug Administration(FDA)-required histological endpoint for ***,on March 14,2024,resmetirom became the first drug to receive FDA approval for the treatment of NASH patients with fibrosis,marking a significant milestone in the field of ***,there are still some challenges in the clinical application of resmetirom.

关键词： THR hepatitis histological

Effects of binder components and PVA modifier on bonding performance of phosphate binder for sand core-making

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China Foundry 2023年第2期20卷 134-138页

作者： wei-hua Liu Xin Jia lai Song Ying-min Li School of Materials Science and Engineering Shenyang University of TechnologyShenyang 110870China

A type of heat-curing phosphate binder was proposed,and orthogonal experiments based on the tensile strength of sand samples determined that the optimal composition of the binder was phosphoric acid:water:aluminum hydroxide:magnesium oxide:boric acid=300:70:60:9:*** 10%polyvinyl alcohol(PVA)solution during the sand mixture process can significantly improve the 24 h tensile strength of sand *** adding 30 g phosphate binder and 8 g 10%PVA solution,the initial tensile strength of the sample is 0.76 MPa,the room temperature tensile strength is 2.29 MPa,and the 24 h tensile strength is 1.73 *** heat-curing modified phosphate sand mold has high tensile strength and low gas generation,which can meet general casting production requirements.

关键词： phosphate binder heat curing modifier tensile strength