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The joint Laplace transforms for killed diffusion occupation times

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Applied Mathematics(A Journal of Chinese Universities) 2024年第3期39卷 398-415页

作者： LI Ying-qiu CHEN ye School of Mathematics and Statistics Changsha University of Science and TechnologyChangsha 410114China College of Mathematics and Computational Science Hunan University of Arts and ScienceChangde 415000China

The approach of Li and Zhou(2014)is adopted to find the Laplace transform of occupation time over interval(0,a)and joint occupation times over semi-infinite intervals(-∞,a)and(b,∞)for a time-homogeneous diffusion pr... 详细信息

关键词： time-homogeneous diffusion process occupation time joint occupation time Laplace transform Brownian motion with drift

Effects of microenvironment and biological behavior on the paracrine function of stem cells

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Genes & Diseases 2024年第1期11卷 135-147页

作者： Zhixin Xue Yunjun Liao ye Li The Department of Plastic and Cosmetic Surgery Nanfang HospitalSouthern Medical UniversityGuangzhouGuangdong 510515China

Mesenchymal stem cells(MSCs),the most well-studied cell type in the field of stem cell therapy,have multi-lineage differentiation and self-renewal ***-based thera-pies have been used to treat diverse diseases because of their ability to potently repair tissue and locally restore *** increasing body of evidence demonstrates that paracrine func-tion is central to the effects of MsC-based *** factors,cytokines,chemokines,extracellular matrix components,and extracellular vehicles all contribute to the beneficial ef-fects of MSCs on tissue regeneration and *** paracrine substances secreted by MSCs change depending on the tissue microenvironment and biological *** this review,we discuss the bioactive substances secreted by MsCs depending on the microenvironment and biological behavior and their regulatory mechanisms,which explain their potential to treat human diseases,to provide new ideas for further research and clinical cell-free therapy.

关键词： Bioactive behavior Mesenchymal stem cells Microenvironment Paracrine Secretome

Noninvasive beam diagnosis based on the TM_(010)mode

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Nuclear Science and Techniques 2024年第7期35卷 115-125页

作者： Chuang-ye Song Wen-Hui Huang Department of Engineering Physics Tsinghua University BeijingBeijing100084China of Education Beijing100084China

A resonant cavity based on the TM_(010)mode is an effective tool for noninvasive beam characterization. This technique has the advantages of a high signal-to-noise ratio, compact structure, and is related to multiple parameters compared with other beam monitors. In this study, high-precision measurements of the bunch charge, arrival time, bunch length, and energy parameters based on the TM_(010)mode are discussed. A cavity beam arrival time monitor(BAM) utilizing a phase cavity has been widely used in many facilities. Regarding bunch-length measurements, the influence of the beam energy, beam offset,and longitudinal spectrum on the TM_(010)mode are carefully considered to reduce errors, and the theoretical resolution of two cavities with different frequencies is analyzed. Owing to the dependence of the beam velocity of the beam loss factor, this method can also be used for the detection low beam energy using two cavities with the same frequency but different cavity lengths. A set of three cavities with different lengths and frequencies of 1.902 and 11.424 GHz is presented for measuring the four aforementioned parameters.

关键词： TM_(010)mode Noninvasive diagnosis Beam length Low energy

Buckling optimization of curvilinear fiber-reinforced composite structures using a parametric level set method

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Frontiers of Mechanical Engineering 2024年第1期19卷 149-160页

作者： ye TIAN Tielin SHI Qi XIA State Key Laboratory of Intelligent Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China

Owing to their excellent performance and large design space,curvilinear fiber-reinforced composite structures have gained considerable attention in engineering fields such as aerospace and *** addition to the stiffness and strength of such structures,their stability also needs to be taken into account in the *** study proposes a level-set-based optimization framework for maximizing the buckling load of curvilinear fiber-reinforced composite *** the proposed method,the contours of the level set function are used to represent fiber *** a composite laminate with a certain number of layers,one level set function is defined by radial basis functions and expansion coefficients for each ***,the fiber angle at an arbitrary point is the tangent orientation of the contour through this *** the finite element of buckling,the stiffness and geometry matrices of an element are related to the fiber angle at the element *** study considers the parallelism constraint for fiber *** the sensitivity calculation of the objective and constraint functions,the method of moving asymptotes is utilized to iteratively update all the expansion coefficients regarded as design *** numerical examples under different boundary conditions are given to validate the proposed *** show that the optimized curved fiber paths tend to be parallel and equidistant regardless of whether the composite laminates contain holes or ***,the buckling resistance of the final design is significantly improved.

关键词： buckling optimization curvilinear fiber composite structure level set method manufacturing constraint

Explaining the dynamics of the sub-relativistic electron third belt in the Earth's radiation belts by using medium Earth orbit satellite observations

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Earth and Planetary Physics 2024年第5期8卷 762-775页

作者： JiaLi Chen Hong Zou YuGuang ye Institute of Space Physics and Applied Technology Peking University

The Earth's electron radiation belts typically exhibit a two-belt structure. However, observations from the Van Allen Probes revealed the existence of a three-belt structure. This structure consists of an inner belt, a slot region, a remnant belt, a “second slot,” and a new outer belt(or the “third belt”). The formation of the structure involves both the partial loss of the original outer belts and the formation of the third belts. These processes are likely associated with radial diffusion induced by ultra-low-frequency(ULF) waves. In this study, we mainly analyzed electron flux data from medium Earth orbit(MEO) navigation satellites M17–M19 to supplement the observational evidence for the sub-relativistic electron(～100–500 keV) three-belt structure. Evidence of substorm injections and ULF waves during the three-belt event was identified, suggesting they played significant roles in the formation and evolution of the third *** injections may introduce new electron populations to the third belt, whereas ULF waves may influence the evolution of the third belt through radial diffusion. Toward the end of the three-belt event, the compression of the magnetosphere by shocks may lead to the dropout of the third belt because of the magnetopause shadowing effect and outward radial diffusion, ultimately disrupting the three-belt structure. This study provides more evidence for the presence of a sub-relativistic electron three-belt structure and offers an analysis of the evolutionary mechanisms of the third belt, which may contribute to a comprehensive understanding of the electron three-belt structure in the radiation belts.

关键词： third belt sub-relativistic electrons three-belt structure radiation belts magnetic storms and substorms wave–particle interactions

Apatite Fission-Track Thermochronology in the Tamusu Area,Bayingobi Basin,NW China,and its Geological Significance

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Acta Geologica Sinica(English Edition) 2024年第3期98卷 585-601页

作者： TONG Qinlong QIN Mingkuan ye Fawang CNNC Beijing Research Institute of Uranium Geology National Key Laboratory of Remote Sensing Information and Image Analysis TechnologyBeijing 100029China

The Bayingobi basin is located in the middle of Central Asia Orogenic Belt,at the intersection of Paleo-Asian Ocean and Tethys Ocean,as well as the junction of multiple tectonic *** unique tectonic setting underpins the basin's intricate history of tectonic *** unravel the multifaceted tectono-thermal evolution within the southwestern region of the basin and to elucidate the implications of sandstone-hosted uranium mineralization,granitic and clastic rock samples were collected from the Zongnai *** and Yingejing depression,and apatite fission track(AFT)dating and thermal history simulation analysis were *** dating findings reveal that the apparent ages of all samples fall within the range of 244 Ma to 112 *** particular,the bedrock of the Zongnai *** Jurassic detrital apatite fission tracks have undergone complete annealing,capturing the uplift-cooling ***,the AFT ages of Cretaceous detrital rocks are either equivalent to or notably exceed the age of sedimentary strata,signifying the cooling age of the provenance.A comprehensive examination of AFT ages and palaeocurrent direction analyses suggests that the Cretaceous source in the Tamusu area predominantly originated from the central and southern sectors of the Zongnai ***,at a certain juncture during the Late Early Cretaceous,the Cretaceous provenance expanded to include the northern part of the Zongnai *** on the results of thermal history simulations and previous studies,it is considered that the Tamusu area has undergone four distinct tectonic uplift events since the Late *** first is the Late Permian to Early Triassic(260-240 Ma),which is associated with the closure of the Paleo-Asian Ocean and the accretionary orogeny within the Alxa *** second uplift event took place in the Early Jurassic(190-175 Ma)and corresponded to intraplate orogeny following the closure of the Paleo-Asian *** third uplift event is the Lat

关键词： apatite fission-track tectono-thermal history sandstone-hosted uranium deposit Bayingobi basin Central Asian Orogenic Belt

Simplified design of nonlinear damper parameters and seismic responses for long-span cable-stayed bridges with nonlinear viscous dampers

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Frontiers of Structural and Civil Engineering 2024年第7期18卷 1103-1116页

作者： Huihui LI Lifen. LI Rui HU Meng ye College of Civil and Transportation Engineering Shenzhen UniversityShenzhen 518060China Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering Shenzhen UniversityShenzhen 518060China College of Civil Engineering Hunan UniversityChangsha 410082China

Viscous dampers are widely used as passive energy dissipation devices for long-span cable-stayed bridges for mitigation of seismic load-induced ***,complicated finite element(FE)modeling,together with repetitive and computationally intensive nonlinear time-history analyses(NTHAs)are generally required in conventional design *** streamline the preliminary design process,this paper developed a simplified longitudinal double degree of freedom model(DDFM)for single and symmetric twin-tower cable-stayed *** on the proposed simplified longitudinal DDFM,the analytical equations for the relevant mass-and stiffness-related parameters and longitudinal natural frequencies of the structure were derived by using analytical and energy *** of the relationship between the nonlinear viscous damper parameters and the equivalent damping ratio was achieved through the equivalent linearization ***,the analytical equations of longitudinal seismic responses for long-span cable-stayed bridges with nonlinear viscous dampers were *** on the developed simplified DDFM and suggested analytical equations,this paper proposed a simplified calculation framework to achieve a simplified design method of nonlinear viscous damper ***,the effectiveness and applicability of the developed simplified longitudinal DDFM and the proposed calculation framework were further validated through numerical analysis of a practical cable-stayed ***,the results indicated the following.1)For the obtained fundamental period and longitudinal stiffness,the differences between results of the simplified longitudinal DDFM and numerical analysis were only 2.05%and 1.5%,respectively.2)Relative calculation errors of the longitudinal girder-end displacement and bending moment of the bottom tower section of the bridge obtained from the simplified longitudinal DDFM were limited to less than 25%.3)The equivalent damping ratio of nonline

关键词： cable-stayed bridges viscous dampers simplified analytical model equivalent damping ratio seismic mitigation

3D coarse-grained DPM simulation of the MIP reaction-regeneration loop

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Particuology 2024年第6期89卷 57-66页

作者： Yanhao ye Shuai Zhang Ji Xu Wei Ge State Key Laboratory of Mesoscience and Engineering(formerly State Key Laboratory of Multiphase Complex Systems) Institute of Process EngineeringChinese Academy of SciencesBeijing100190China School of Chemical Engineering University of Chinese Academy of SciencesBeijing100049China

The reactor-regenerator loop is the core facility of the maximizing iso-paraffin(MIP)*** the discrete particle method(DPM)simulation can provide detailed information at the particle scale,it has been unable to simulate such a complex loop system due to limitations of coarse-grained(CG)models,computing software,and *** this study,a newly proposed soft-shell CG-DPM model with a CG ratio of up to 800 is used to simulate a 3.5 Mt/a industrial-scale MIP reactor-regenerator *** solid fraction distribution obtained is found to agree well with in-situ *** properties including the distribution of solid fraction,gas and solid velocity,standard derivation of solid fraction with time,temporal distribution of the flow field,and particle residence time distribution are measured in the simulation,which are meaningful to better design and operate such systems in the future.

关键词： Discrete particle method Coarse-grain Maximizing iso-paraffins Full-loop Reaction-regeneration system

Rotor cross-tilt optimization for yaw control improvement of multi-rotor eVTOL aircraft

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Chinese Journal of Aeronautics 2024年第3期37卷 153-167页

作者： Xufei YAN ye YUAN Yanqin ZHAO Renliang CHEN Zhejiang Lab Hangzhou 311100China Department of Aerospace Engineering Swansea UniversitySwanseaWales SA28PPUK National Key Laboratory of Rotorcraft Aeromechanics Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Manned multi-rotor electric Vertical Takeoff and Landing(eVTOL)aircraft is prone to actuator saturation due to its weak yaw control *** address this inherent problem,a rotor cross-tilt configuration is applied in this paper,with an optimization method proposed to improve the overall control efficiency of the ***,a flight dynamics model of a 500-kg manned multi-rotor eVTOL aircraft is *** accuracy of the co-axial rotor model is verified using a single arm test bench,and the accuracy of the flight dynamics model is verified by the flight test ***,an optimization method is designed based on the flight dynamics model to calculate an optimal rotor cross-tilt mounting angle,which not only improves the yaw control efficiency,but also basically maintains the efficiency of other control *** ideal rotor cross-tilt mounting angle for the prototype is determined by comprehensively considering the optimal results with different payloads,forward flight speeds,and rotor mounting angle ***,the feasibility of the rotor cross-tilt mounting angle is proved by analyzing the control derivatives of the flight dynamics model,the test data of a ground three Degree-of-Freedom(3DOF)platform,and the actual flight data of the *** results show that a fixed rotor cross-tilt mounting angle can achieve ideal yaw control effectiveness,improving yaw angle tracking and hold ability,increasing endurance time,and achieving good yaw control performance with different payloads and forward speeds.

关键词： Multi-rotor eVTOL Control efficiency Flight dynamics model Cross-tilt optimization Endurance time