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Numerical study on influence of protrusion heights on Reynolds stress and viscous stress variations in turbulent vortical structures

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Chinese Journal of Aeronautics 2024年第9期37卷 59-71页

作者： Zhiping LI Long HE Jingsai ZHOU Yueren ZUO Yao YIN Peng ZHANG bo meng Research Institute of Aero-Engine Beihang UniversityBeijing 100191China School of Energy and Power Engineering Beihang UniversityBejing 100191China Institute of Acoustics Chinese Academy of SciencesBeijing 100190China College of Aeronautical Engineering Civil Aviation University of ChinaTianjin 300300China AECC Hunan Aviation Powerplant Research Institute Zhuzhou 412002China

Analysing the infuence mechanism of the riblet protrusion height on turbulent drag components is more beneficial in organising the vortical structure over the riblet ***,the Large Eddy Simulation(LES)is used to investigate the vortex structure over the rib-let surface with different protrusion ***,the variations of Reynolds stress and viscous shear stress in a turbulent channel are *** a result,the drag reduction rate increases from 3.4%when the riblets are completely submerged in the turbulent boundary layer to 7.9%when the protrusion height is *** analysis shows that the protrusion height affects the streamwise vortices and the normal diffusivity of spanwise and normal vortices,thus driving the variation of Reynolds *** with the smooth surface,the vorticity strength and the number of streamwise vortices are weakened near the wall but increase in the logarithmic layer with increased protrusion ***,the normal diffusivity of spanwise vorticity decreases with the increase of protrusion height,and the normal diffusivity of normal vorticity is the smallest when the protrusion height is ***,the protrusion height affects the velocity gradient of the riblet tip and riblet valley,thus driving the variation of viscous shear *** the increase of protrusion height,the velocity gradient of the riblet tip increases dramatically but decreases in the riblet valley.

关键词： Riblet Dragreduction Protrusion height Vortical structure Vortexdiffusivity Reynolds stress Viscous stress

Risk Assessment of Deep-Water Horizontal X-Tree Installation

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China Ocean Engineering 2024年第2期38卷 210-220页

作者： meng Wen-bo FU Guang-ming HUANG Yi LIU Shu-jie HUANG Liang GAOYong-hai CNOOC China Limited Zhanjiang BranchZhanjiang 524057China Key Laboratory of Unconventional Oil and Gas Development Ministry of Education(China University of Petroleum(East China))Qingdao 266580China

Due to the high potential risk and many influencing factors of subsea horizontal X-tree installation,to guarantee the successful completion of sea trials of domestic subsea horizontal X-trees,this paper established a modular risk evaluation model based on a fuzzy fault ***,through the analysis of the main process oftree down and combining the Offshore&Onshore Reliability Data(OREDA)failure statistics and the operation procedure and the data provided by the job,the fault tree model of risk analysis of the tree down installation was ***,by introducing the natural language of expert comprehensive evaluation and combining fuzzy principles,quantitative analysis was carried out,and the fuzzy number was used to calculate the failure probability of a basic event and the occurrence probability of a top ***,through a sensitivity analysis of basic events,the basic events of top events significantly affected were determined,and risk control and prevention measures for the corresponding high-risk factors were proposed for subsea horizontal X-tree down installation.

关键词： subsea horizontal X-tree risk assessment fuzzy fault tree modular risk evaluation model

How Does Economic Policy Uncertainty Impact a Country's Position in Global Value Chains?

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China & World Economy 2024年第5期32卷 28-52页

作者： Jiaxuan Zhang Hongsheng Zhang Xuhang Shen bo meng Institute of Economics School of Social SciencesTsinghua UniversityChina China Academy of Digital Trade Zhejiang UniversityChina HSBC Business School Peking UniversityChina Institute of Developing Economies Japan External Trade OrganizationJapan Collaborative Innovation Center for Emissions Trading System Co-constructed by the Province and Ministry Hubei University of EconomicsChina

Economic globalization in the 21st century has been characterized by the rise and spread of global value chains(GVCs).It faces significant challenges due to increasing domestic and international policy uncertainty in the context of emerging mega risks like geopolitical tensions and climate *** paper begins by constructing a theoretical model for an open economy to study how risk-averse firms make decisions regarding the sourcing of intermediate inputs in an uncertain *** model solution proposes that firms will source fewer intermediate inputs from countries with more economic *** increase in domestic and foreign uncertainty will have opposite impacts on a country's position in *** this sense,we argue that a country tends to move downstream along GVCs if its own economic policies become more uncertain,and it tends to move upstream with an increase in the uncertainty of its trading partner *** regression analyses,based on data including the World Input-Output Database,World Development Indicators,the UN Comtrade database,and the Economic Policy Uncertainty Index,provide empirical support for this model-based *** findings highlight that a nation must consider foreign economic policy uncertainty and maintain domestic policy stability to participate in GVCs.

关键词： economic policy uncertainty global value chain GVC participation GVC position

Continuous-wave operation of 1550 nm low-threshold triple-lattice photonic-crystal surface-emitting lasers

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Light(Science & Applications) 2024年第3期13卷 446-453页

作者： Ziye Wang Xia Liu Pinyao Wang Huanyu Lu bo meng Wei Zhang Lijie Wang Yanjing Wang Cunzhu Tong State Key Laboratory of Luminescence and Applications Changchun Institute of OpticsFine Mechanics and PhysicsChinese Academy of SciencesChangchun 130033China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Central Research Institute Planning Dept 2012 LabsHuawei Technologies Company Ltd.Shenzhen 518129China

Benefitting from narrow beam divergence,photonic crystal surface-emitting lasers are expected to play an essential role in the ever-growing fields of optical communication and light detection and *** operating with 1.55μm wavelengths have attracted particular attention due to their minimum fiber loss and high eye-safe ***,high interband absorption significantly decreases their performance at this 1.55μm ***,stronger optical feedback is needed to reduce their threshold and thus improve the output *** this goal,photonic-crystal resonators with deep holes and high dielectric contrast are often ***,the relevant techniques for high-contrast photonic crystals inevitably complicate fabrication and reduce the final *** this paper,we demonstrate the first continuous-wave operation of 1.55μm photonic-crystal surface-emitting lasers by using a‘triple-lattice photonic-crystal resonator’,which superimposes three lattice point groups to increase the strength of in-plane optical *** this geometry,the in-plane 180°coupling can be enhanced threefold compared to the normal single-lattice *** theoretical and experimental investigations demonstrate the much lower threshold current density of this structure compared to‘single-lattice’and‘double-lattice’photonic-crystal resonators,verifying our design *** findings provide a new strategy for photonic crystal laser miniaturization,which is crucial for realizing their use in future high-speed applications.

关键词： resonator crystal lattice

Multi-distortion suppression for neutron radiographic images based on generative adversarial network

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Nuclear Science and Techniques 2024年第4期35卷 176-188页

作者： Cheng-bo meng Wang-Wei Zhu Zhen Zhang Zi-Tong Wang Chen-Yi Zhao Shuang Qiao Tian Zhang School of Physics Northeast Normal UniversityChangchun 130024China

Neutron radiography is a crucial nondestructive testing technology widely used in the aerospace,military,and nuclear ***,because of the physical limitations of neutron sources and collimators,the resulting neutron radiographic images inevitably exhibit multiple distortions,including noise,geometric unsharpness,and white ***,these distortions are particularly significant in compact neutron radiography systems with low neutron ***,in this study,we devised a multi-distortion suppression network that employs a modified generative adversarial network to improve the quality of degraded neutron radiographic *** neutron radiographic image datasets with various types and levels of distortion were built for the first time as multi-distortion suppression ***,the coordinate attention mechanism was incorporated into the backbone network to augment the capability of the proposed network to learn the abstract relationship between ideally clear and degraded *** experiments were performed;the results show that the proposed method can effectively suppress multiple distortions in real neutron radiographic images and achieve state-of-theart perceptual visual quality,thus demonstrating its application potential in neutron radiography.

关键词： Neutron radiography Multi-distortion suppression Generative adversarial network Coordinate attention mechanism

SARS-CoV-2 and innate immunity:the good,the bad,and the"goldilocks"

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Cellular & Molecular Immunology 2024年第2期21卷 171-183页

作者： Benjamin L.Sievers Mark T.K.Cheng Kata Csiba bo meng Ravindra K.Gupta Department of Medicine University of CambridgeCambridgeUK Cambridge Institute of Therapeutic Immunology&Infectious Disease(CITID) Department of MedicineUniversity of CambridgeCambridgeUk

An ancient conflict between hosts and pathogens has driven the innate and adaptive arms of *** about this interplay can not only help us identify biological mechanisms but also reveal pathogen vulnerabilities that can be leveraged *** humoral response to SARS-CoV-2 infection has been the focus of intense research,and the role of the innate immune system has received significantly less ***,we review current knowledge of the innate immune response to SARS-CoV-2 infection and the various means SARS-CoV-2 employs to evade innate defense *** also consider the role of innate immunity in SARS-CoV-2 vaccines and in the phenomenon of long COVID.

关键词： SARS-CoV-2 Innate immune response Interferon Cytokines Inflammation Antiviral targets

Feasibility Analysis of IMA Configuration Design Tool

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International Journal of Plant Engineering and Management 2024年第1期29卷 1-13页

作者： FENG Guangding meng bo XIANG Yangkui PLA Unit 32382 Wuhan 430000China

With the widespread application of integrated modular aviation(IMA)electronic systems,the requirements of IMA characteristic analysis and configuration generation have also improved significantly."Configuration and design system based on AADL models(real-time,reliability,interactive complexity,and schedulability)analysis of the AADL model"mainly get through key characteristic analysis for optimization,combined with input of component parameter information and constraint information,assist designers in generating system configuration information,and form a comprehensive modular avionics system resource configuration strategy generation ***,the tool can generate configuration plans for avionics system software and hardware physical architecture *** analysis of the avionics system model mainly involves designers inputting the existing system model architecture for multi characteristic analysis,it can realize the multi-character analysis based on software intensive system architecture models for software dense ***-complexity and schedulability analysis,and according to characteristic constraint analysis、system model assessment parameters and system architecture constraint parameters to generate configuration scheme information that meets the *** system can meet domestic and foreign software-intensive systems and meet its quality requirements.

关键词： integrated modular aviation(IMA) multi-character analysis constraint analysis configuration generation

Shear mechanical properties and fracturing responses of layered rough jointed rock-like materials

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International Journal of Minerals,Metallurgy and Materials 2024年第11期31卷 2417-2434页

作者： Xinxin Nie Qian Yin Manchao He Qi Wang Hongwen Jing bowen Zheng bo meng Tianci Deng Zheng Jiang Jiangyu Wu State Key Laboratory for Geomechanics&Deep Underground Engineering China University of Mining and TechnologyXuzhou 221116China State Key Laboratory for Geomechanics&Deep Underground Engineering China University of Mining and Technology(Beijing)Beijing 100083China Key Laboratory of Shale Gas and Geoengineering Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Department of Materials University of OxfordOxford OX13PHUK

This study aims to investigate mechanical properties and failure mechanisms of layered rock with rough joint surfaces under direct shear *** layered samples with dimensions of 100 mm×100 mm×100 mm were casted using rock-like materials,with anisotropic angle(α)and joint roughness coefficient(JRC)ranging from 15°to 75°and 2-20,*** direct shear tests were conducted under the application of initial normal stress(σ_(n)) ranging from 1-4 *** test results indicate significant differences in mechanical properties,acoustic emission(AE)responses,maximum principal strain fields,and ultimate failure modes of layered samples under different test *** peak stress increases with the increasingαand achieves a maximum value atα=60°or 75°.As σ_(n) increases,the peak stress shows an increasing trend,with correlation coefficients R² ranging from 0.918 to 0.995 for the linear least squares *** JRC increases from 2-4 to 18-20,the cohesion increases by 86.32%whenα=15°,while the cohesion decreases by 27.93%whenα=75°.The differences in roughness characteristics of shear failure surface induced byαresult in anisotropic post-peak AE responses,which is characterized by active AE signals whenαis small and quiet AE signals for a largeα.For a given JRC=6-8 andσ_(n)=1 MPa,asαincreases,the accumulative AE counts increase by 224.31%(αincreased from 15°to 60°),and then decrease by 14.68%(αincreased from 60°to 75°).The shear failure surface is formed along the weak interlayer whenα=15°and penetrates the layered matrix whenα=60°.Whenα=15°,as σ_(n) increases,the adjacent weak interlayer induces a change in the direction of tensile cracks propagation,resulting in a stepped pattern of cracks *** increase in JRC intensifies roughness characteristics of shear failure surface for a smallα,however,it is not pronounced for a largeα.The findings will contribute to a better understanding of the mechanical responses and failure mechanisms of the layered roc

关键词： layered samples anisotropic angle joint roughness coefficient mechanical properties acoustic emission response fracturing evolution failure modes

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改进YOLOv7的交通标志识别模型

中国图象图形学报 2024年第9期29卷 2737-2752页

作者：孟勃史伟大东北电力大学计算机学院吉林132012 东北电力大学机器人视觉与虚拟现实实验室吉林132012 东北电力大学电力机器人实验室吉林132012

目的随着自动驾驶和辅助驾驶的快速发展,交通标志识别研究变得越来越重要。但是现阶段交通标志识别算法对交通标志识别的精度较低,尤其在面对目标背景较为复杂、光照不足和小目标交通标志的场景时,更加容易出现错检和漏检情况。针对以... 详细信息

目的随着自动驾驶和辅助驾驶的快速发展,交通标志识别研究变得越来越重要。但是现阶段交通标志识别算法对交通标志识别的精度较低,尤其在面对目标背景较为复杂、光照不足和小目标交通标志的场景时,更加容易出现错检和漏检情况。针对以上问题,提出了一种改进YOLOv7(you only look once version 7)的交通标志识别模型。方法首先,采用空间金字塔池化快速跨级部分连接(spatial pyramid pooling fast cross stage partial concat,SPPFCSPC)方法,替换YOLOv7算法使用的空间金字塔池化跨级部分连接(spatial pyramid pooling cross stage partial concat,SPPCSPC)方法,提高算法的特征提取能力。其次,采用加权双向特征金字塔网络(bi-directional feature pyra⁃mid network,BiFPN),增强算法的多尺度特征融合能力。接着,采用一种新的框间距离度量的归一化Wasserstein距离(normalized Wasserstein distance,NWD)方法,解决传统的IoU(intersection over union)度量对小目标交通标志检测过于敏感的问题。最后,使用特征内容的感知重组(content-aware reassembly of feature,CARAFE)算子,通过输入的特征,自适应生成上采样内核,有效地增加模型的感受域,更好地利用目标周边的信息,减少交通标志错检和漏检情况。结果实验结果表明,在减少算法参数量的基础上,改进算法在TT100K交通标志数据集上的mAP@0.5和mAP@0.5∶0.9值分别达到了92.50%和72.21%,较原始的YOLOv7算法分别提高了3.24%和1.83%。同时,在具有小目标特性的CCTSDB交通标志数据集和整理的国外交通标志数据集上验证了模型改进的有效性。结论通过实验验证和主客观评价,证明了本文改进算法的可行性,能够有效地对多种环境下的小目标交通标志进行识别,并在降低算法参数量的前提下,进一步提高了YOLOv7算法对交通标志识别的平均精度。

关键词：交通标志识别空间金字塔池化快速跨级部分连接(SPPFCSPC) 加权双向特征金字塔网络(BiFPN) 归一化Wasserstein距离(NWD) 特征内容的感知重组(CARAFE) 小目标