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Numerical Analysis of Perforation during Hydraulic Fracture Initiation Based on Continuous-Discontinuous Element Method

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Computer Modeling in Engineering & Sciences 2024年第8期140卷 2103-2129页

作者： Rui zhang Lixiang Wang Jing Li Chun Feng yiming zhang School of Civil and Transportation Engineering Hebei University of TechnologyTianjin300401China Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of MechanicsChinese Academy of SciencesBeijing100190China School of Civil Engineering and Architecture Zhejiang Sci-Tech UniversityHangzhou310018China Jinyun Institute Zhejiang Sci-Tech UniversityLishui321400China

Perforation is a pivotal technique employed to establish main flow channels within the reservoir formation at the outset of hydraulic fracturing *** perforation designs is critical for augmenting the efficacy of hydraulic fracturing and boosting oil or gas *** this study,we employ a hybrid finite-discrete element method,known as the continuous–discontinuous element method(CDEM),to simulate the initiation of post-perforation hydraulic fractures and to derive enhanced design *** model incorporates the four most prevalent perforation geometries,as delineated in an engineering technical ***-world perforations deviate from the ideal cylindrical shape,exhibiting variable cross-sectional profiles that typically manifest as an initial constriction followed by an expansion,a feature consistent across all four perforation *** simulations take into account variations in perforation hole geometries,cross-sectional diameters,and perforation *** findings show that perforations generated by the 39g DP3 HMX perforating bullet yield the lowest breakdown pressure,which inversely correlates with increases in sectional diameter and perforation ***,this study reveals the relationship between breakdown pressure and fracture degree,providing valuable insights for engineers and designers to refine perforation strategies.

关键词： Hydraulic fracturing real perforation shape breakdown pressure perforation layout design CDEM

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Prediction of the Pore-Pressure Built-Up and Temperature of Fire-Loaded Concrete with Pix2Pix

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Computers, Materials & Continua 2024年第5期79卷 2907-2922页

作者： Xueya Wang yiming zhang Qi Liu Huanran Wang Mechanics and Materials Science Research Center Ningbo UniversityNingbo315211China Jinyun Institute Zhejiang Sci-Tech UniversityLishui321400China School of Civil Engineering and Architecture Zhejiang Sci-Tech UniversityHangzhou310018China School of Computer Science Nanjing University of Information Science and TechnologyNanjing210044China

Concrete subjected to fire loads is susceptible to explosive spalling, which can lead to the exposure of reinforcingsteel bars to the fire, substantially jeopardizing the structural safety and stability. The spalling of fire-loaded concreteis closely related to the evolution of pore pressure and temperature. Conventional analytical methods involve theresolution of complex, strongly coupled multifield equations, necessitating significant computational efforts. Torapidly and accurately obtain the distributions of pore-pressure and temperature, the Pix2Pix model is adoptedin this work, which is celebrated for its capabilities in image generation. The open-source dataset used hereinfeatures RGB images we generated using a sophisticated coupled model, while the grayscale images encapsulate the15 principal variables influencing spalling. After conducting a series of tests with different layers configurations,activation functions and loss functions, the Pix2Pix model suitable for assessing the spalling risk of fire-loadedconcrete has been meticulously designed and trained. The applicability and reliability of the Pix2Pix model inconcrete parameter prediction are verified by comparing its outcomes with those derived fromthe strong couplingTHC model. Notably, for the practical engineering applications, our findings indicate that utilizing monochromeimages as the initial target for analysis yields more dependable results. This work not only offers valuable insightsfor civil engineers specializing in concrete structures but also establishes a robust methodological approach forresearchers seeking to create similar predictive models.

关键词： Fire loaded concrete spalling risk pore pressure generative adversarial network(GAN) Pix2Pix

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Grapevine-like high entropy oxide composites boost high-performance lithium sulfur batteries as bifunctional interlayers

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Green Energy & Environment 2024年第3期9卷 565-572页

作者： Huarong Fan Yubing Si yiming zhang Fulong Zhu Xin Wang Yongzhu Fu College of Chemistry and Center of Green Catalysis Zhengzhou UniversityZhengzhou450001China School of Materials and Energy University of Electronic Science and Technology of ChinaChengdu611731China

Lithium-sulfur batteries(LSBs)with high energy densities have been demonstrated the potential for energy-intensive demand ***,their commercial applicability is hampered by hysteretic electrode reaction kinetics and the shuttle effect of lithium polysulfides(LiPSs).In this work,an interlayer consisting of high-entropy metal oxide(Cu_(0.7)Fe_(0.6)Mn_(0.4)Ni_(0.6)Sn_(0.5))O_(4) grown on carbon nanofibers(HEO/CNFs)is designed for *** CNFs with highly porous networks provide transport pathways for Li^(+) and e^(-),as well as a physical sieve effect to limit LiPSs *** particular,the grapevine-like HEO nanoparticles generate metal-sulfur bonds with LiPSs,efficiently anchoring active *** unique structure and function of the interlayer enable the LSBs with superior electrochemical performance,i.e.,the high specific capacity of 1381 mAh g^(-1) at 0.1 C and 561 mAh g^(-1) at 6 *** work presents a facile strategy for exploiting high-performance LSBs.

关键词： Electrospun carbon nanofibers Grapevine-like morphology Hierarchical physical sieve effect High-entropy induced chemisorption Lithium-sulfur battery

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Investigations of the mechanical response of dummy HTPB propellant grain under ultrahigh acceleration overload conditions using onboard flight-test measurements

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Defence Technology（防务技术） 2024年第2期32卷 473-484页

作者： yiming zhang Ningfei Wang Weihua Ma Ran Wang Long Bai Yi Wu School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China Beijing System Design Institute of Electro-mechanic Engineering Beijing 100854China Xi'an Changfeng Research Institute of Mechanism and Electricity Xi'an 710065China

In this paper,to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process,specifically designed projectile flight tests with an onboard measurement system were *** projectiles containing dummy HTPB propellant grains were successfully recovered after the flight tests with an ultrahigh acceleration overload value of 8100 *** onboard-measured time-resolved axial displacement,contact stress and overload values were successfully obtained and *** compression tests of the dummy HTPB propellant used in the gunlaunched tests were carried out at low and intermediate strain rates to characterize the propellant's dynamic properties.A linear viscoelastic constitutive model was employed and applied in finite-element simulations of the projectile-launching *** the launch process,the dummy propellant grain exhibited large deformation due to the high acceleration overload,possibly leading to friction between the motor case and propellant *** calculated contact stress showed good agreement with the experimental results,though discrepancies in the overall displacement of the dummy propellant grain were *** dynamic mechanical response process of the dummy propellant grain was analysed in *** results can be used to estimate the structural integrity of the analysed dummy propellant grain during the gun-launch process.

关键词： Gun-launched flight test Dummy HTPB propellant Onboard measurements Utrahigh overload Mechanical response

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Influences of mechanized tillage and sowing modes on soil physical properties, soybean yield and economic benefits in mollisols region of Northeast China

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INTERNATIONAL JOURNAL OF AGRICULTURAL AND BIOLOGICAL ENGINEERING 2024年第3期17卷 130-139页

作者： Chen, Haitao Sun, Jian zhang, yiming Qiao, Jinyou Northeast Agr Univ Coll Engn Harbin 150030 Peoples R China Heilongjiang Prov Technol Innovat Ctr Mechanizat & Harbin 150030 Peoples R China East Univ Heilongjiang Coll Mech & Elect Engn Harbin 150066 Peoples R China

Appropriate mechanized straw returning and tillage sowing techniques were effective means to optimize soil physical properties and enhance agricultural productivity, as well as important measures for the conservation and restoration of mollisols region in Northeast China. Under the condition of full-scale maize straw returning, four mechanized tillage and sowing modes were set, including plough tillage and sowing (PTS), combined tillage and sowing (CTS), no-tillage and sowing (NTS), and no-tillage and sowing with straw mulching (NTSM). In 2020 and 2021, the study investigated the effects of different mechanized tillage and sowing modes on soil physical properties, soybean yield and economic benefits. The results showed that during the pod-setting and pod-filling period of soybean, the NTS and NTSM treatments exhibited better effects on deep soil insulation and shallow soil moisture retention, the soil physical structure of PTS and CTS treatments were relatively ideal. Compared with PTS and CTS treatments, NTS and NTSM treatments significantly increased soil gravimetric water content (SWC) by 2.35% to 7.98% in the 5-15 cm soil layer and increased soil temperature (ST) by 3.94% to 10.42% in the 25-35 cm soil layer (p0.05), p >0.05), the soybean yield of NTSM treatment in 2021 significantly increased by 7.30% and 5.84% over PTS and CTS treatments, respectively. And the average annual profit per unit area of NTSM treatment increased by 12.84%, 12.41% and 8.57% compared with PTS, CTS a

关键词： mechanized tillage and sowing modes full-scale straw returning soil physical properties soybean yield economic benefits mollisols conservation WATER-USE EFFICIENCY ORGANIC-CARBON LOESS PLATEAU WINTER-WHEAT COVER CROPS L. TEMPERATURE MANAGEMENT STORAGE GROWTH

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Neural stem cell-derived exosomes promote mitochondrial biogenesis and restore abnormal protein distribution in a mouse model of Alzheimer's disease

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Neural Regeneration Research 2024年第7期19卷 1593-1601页

作者： Bo Li Yujie Chen Yan Zhou Xuanran Feng Guojun Gu Shuang Han Nianhao Cheng Yawen Sun yiming zhang Jiahui Cheng Qi zhang Wei zhang Jianhui Liu Department of Radiology Renji HospitalSchool of MedicineShanghai Jiao Tong UniversityShanghaiChina Morphology and Spatial Multi-Omics Technology Platform Shanghai Institute of Nutrition and HealthChinese Academy of SciencesShanghaiChina Department of Anesthesiology Tongji HospitalSchool of MedicineTongji UniversityShanghaiChina Department of Blood Transfusion Huashan HospitalFudan UniversityShanghaiChina

Mitochondrial dysfunction is a hallmark of Alzheimer’s *** previously showed that neural stem cell-derived extracellular vesicles improved mitochondrial function in the cortex of AP P/PS1 *** Alzheimer’s disease affects the entire brain,further research is needed to elucidate alterations in mitochondrial metabolism in the brain as a ***,we investigated the expression of several important mitochondrial biogenesis-related cytokines in multiple brain regions after treatment with neural stem cell-derived exosomes and used a combination of whole brain clearing,immunostaining,and lightsheet imaging to clarify their spatial ***,to clarify whether the sirtuin 1(SIRT1)-related pathway plays a regulatory role in neural stem cell-de rived exosomes interfering with mitochondrial functional changes,we generated a novel nervous system-SIRT1 conditional knoc kout AP P/PS1mouse *** findings demonstrate that neural stem cell-de rived exosomes significantly increase SIRT1 levels,enhance the production of mitochondrial biogenesis-related fa ctors,and inhibit astrocyte activation,but do not suppress amyloid-β***,neural stem cell-derived exosomes may be a useful therapeutic strategy for Alzheimer’s disease that activates the SIRT1-PGC1αsignaling pathway and increases NRF1 and COXIV synthesis to improve mitochondrial *** addition,we showed that the spatial distribution of mitochondrial biogenesis-related factors is disrupted in Alzheimer’s disease,and that neural stem cell-derived exosome treatment can reverse this effect,indicating that neural stem cell-derived exosomes promote mitochondrial biogenesis.

关键词： Alzheimer’s disease mitochondrial biogenesis neural stem cell-derived exosome SIRT1-PGC1α regional brain distribution whole brain clearing and imaging

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Tungsten oxide-anchored Ru clusters with electron-rich and anti-corrosive microenvironments for efficient and robust seawater splitting

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SusMat 2024年第1期4卷 106-115页

作者： yiming zhang Weiqiong Zheng Huijuan Wu Ran Zhu Yinghan Wang Mao Wang Tian Ma Chong Cheng Zhiyuan Zeng Shuang Li College of Polymer Science and Engineering State Key Laboratory of Polymer Materials EngineeringSichuan UniversityChengduChina Department of Chemical and Biomolecular Engineering National University of SingaporeSingaporeSingapore Department of Materials Science and Engineering and State Key Laboratory of Marine PollutionCity University of Hong KongKowloonHong KongChina Shenzhen Research Institute City University of Hong KongShenzhenChina

Ruthenium(Ru)has been recognized as a prospective candidate to substitute platinum catalysts in water-splitting-based hydrogen ***,minimizing the Ru contents,optimizing the water dissociation energy of Ru sites,and enhancing the long-term stability are extremely required,but still face a great ***,we report on creating tungsten oxide-anchored Ru clusters(Ru-WO_(x))with electron-rich and anti-corrosive microenvironments for efficient and robust seawater *** from the abundant oxygen vacancy structure in tungsten oxide support,the Ru-WO_(x)exhibits strong Ru-O and Ru-W bonds at the *** study elucidates that the strong Ru-O bonds in Ru-WO_(x)may accelerate the water dissociation kinetics,and the Ru-W bonds will lead to the strong metal-support interaction and electrons transfer fromWto *** optimal Ru-WO_(x)catalysts exhibit a low overpotential of 29 and 218mVat the current density of 10 mA cm^(−2) in alkaline and seawater media,*** outstanding long-term stability discloses that the Ru-WO_(x)catalysts own efficient corrosion resistance in seawater *** believe that thiswork offers new insights into the essential roles of electron-rich and anti-corrosivemicroenvironments in Ru-based catalysts and provide a new pathway to design efficient and robust cathodes for seawater splitting.

关键词： hydrogen production microenvironment modulation noble metal catalysts seawater splitting tungsten oxide

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考虑智能网联车辆影响的八车道高速公路施工区可变限速控制方法

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东南大学学报（自然科学版） 2024年第2期54卷 353-359页

作者：过秀成肖哲张一鸣张叶平许鹏宇东南大学交通学院南京211189 江苏省规划设计集团有限公司交通规划与工程设计院南京210019

为提升车联网环境下高速公路施工区交通运行效率及安全水平,提出了一种基于强化学习的可变限速控制方法.选取智能驾驶模型和真车试验模型,分别对传统人工车辆和智能网联车辆的跟驰行为进行建模,构建了以瓶颈下游路段交通流量为效率指标... 详细信息

为提升车联网环境下高速公路施工区交通运行效率及安全水平,提出了一种基于强化学习的可变限速控制方法.选取智能驾驶模型和真车试验模型,分别对传统人工车辆和智能网联车辆的跟驰行为进行建模,构建了以瓶颈下游路段交通流量为效率指标、瓶颈路段速度标准差为安全指标的复合奖励值,利用深度确定性策略梯度算法,分车道动态求解最佳限速值.仿真结果表明,所提可变限速控制方法在不同智能网联车辆渗漏率条件下均能有效提升交通流运行效率和安全水平,且在智能网联车辆渗漏率较低时,提升效果更加显著.当智能网联车辆渗漏率为1.0时,瓶颈下游路段交通流量提升10.1%,瓶颈路段速度标准差均值下降68.9%;当智能网联车辆渗漏率为0时,瓶颈下游路段交通流量提升20.7%,瓶颈路段速度标准差均值下降78.1%.智能网联车辆的引入能够提升至多52.0%的瓶颈下游路段交通流量.

关键词：可变限速控制深度确定性策略梯度算法八车道高速公路施工区智能网联车辆协同自适应巡航控制

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双机器人协作轴孔装配力柔顺控制技术研究

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机械工程学报 2024年第3期60卷 20-33页

作者：王战玺张益铭张邦海罗子彦史梦格西北工业大学机电学院西安710072 南京电子技术研究所南京210012

轴孔精密装配是加工制造业中常见的装配形式,其完成过程同时存在位置约束和力约束关系,因此采用工业机器人实现轴孔自动装配一直是具有挑战性的热点问题。首先分析了轴孔装配过程插孔阶段的典型的单点接触和双点接触受力模型,并针对不... 详细信息

轴孔精密装配是加工制造业中常见的装配形式,其完成过程同时存在位置约束和力约束关系,因此采用工业机器人实现轴孔自动装配一直是具有挑战性的热点问题。首先分析了轴孔装配过程插孔阶段的典型的单点接触和双点接触受力模型,并针对不同的接触状态提出了机器人整体力调控策略;其次在基于位置的阻抗模型基础上,建立对环境位置和刚度具有自适应效果的力柔顺控制模型,通过仿真验证了控制模型可以消除力跟踪过程的系统稳态误差;然后建立了主从式双机器人协作轴孔装配模型,并进行轴孔装配仿真实验,在不同的机器人位置和姿态误差下验证双机器人协作装配的力位控制效果;最后搭建主从式双机器人装配实验平台,验证自适应力柔顺控制模型和主从式协作模型的可行性。

关键词：轴孔装配力柔顺控制阻抗控制主从式协作

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可信执行环境:现状与展望

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计算机研究与发展 2024年第1期61卷 243-260页

作者：张锋巍周雷张一鸣任明德邓韵杰南方科技大学斯发基斯可信自主系统研究院广东深圳518055 南方科技大学计算机科学与工程系广东深圳518055

当前在云服务、移动社交网络下用户普遍追求隐私保护、安全计算,从而推动了隐私计算、机密计算等领域的快速发展.可信执行环境(trusted execution environment,TEE)作为机密计算服务中重要的技术基础已经广泛部署到各类计算平台中.目前,... 详细信息

当前在云服务、移动社交网络下用户普遍追求隐私保护、安全计算,从而推动了隐私计算、机密计算等领域的快速发展.可信执行环境(trusted execution environment,TEE)作为机密计算服务中重要的技术基础已经广泛部署到各类计算平台中.目前,以Intel,Arm等为代表的设备制造商采用软硬件隔离机制,推出了多类实用TEE技术并不断迭代更新,从功能上更加方便设备管理者、普通用户使用安全服务.研究人员则根据不同的系统架构和应用需求,优化TEE模型,扩大可信应用领域并提升其工作效率.全面分析主流系统架构(包括x86、Arm、RISC-V、异构计算单元)中TEE技术发展路线、技术特点包括基础硬件设施设计、软件接口定义、安全边界等,挖掘TEE技术可行的应用场景.同时,分析各类TEE技术面临的挑战,探讨TEE技术局限性以及自身面临的安全风险如侧信道攻击等.在此基础上,从安全性、功能性等方面总结各类TEE技术优缺点,并提出TEE技术未来的发展思路.

关键词：可信执行环境操作系统架构内存隔离处理器模式安全性验证

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