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A combined experimental and DEM investigation of grain interlocking in sheared granular assemblies

Particuology 2024年第7期90卷 436-451页

作者： Rui Lu Qiang Luo Tengfei Wang David P.Connolly tao xie() School of Civil Engineering Southwest Jiaotong UniversityChengdu 610031China Key Laboratory of High-Speed Railway Engineering(Southwest Jiaotong University) Ministry of EducationChengdu 610031China School of Civil Engineering University of LeedsLeeds LS29JTUK Department of Civil Engineering McMaster UniversityHamiltonONCanada

Compacted granular material,integral to geotechnical engineering,undergoes translation,rotation,and interlocking when subject to shear displacements or external *** present study focuses on the interlocking of heterogeneous granular materials,a complex behavior influenced by gradation,compaction,and varying particle geometry,and has consequently received limited attention in existing *** address this research gap,we conducted an analysis on the effect of grain interlocking on the shear resistance of granular assemblies,using a combination of laboratory testing and the discrete element method(DEM).Initially,large-scale direct shear tests were conducted on gravel−sand mixes with varying degrees of compaction and normal *** of the mixes also underwent subsequent shear reversal to explore the differences in grain interlocking between the two shearing processes on the shear *** analyzing the laboratory results,a mesoscopic scale investigation was performed by replicating the test using discrete element *** facilitate this,granular particle geometries were measured using 3D laser scanning based on the physical lab ***,based on these scans,discrete element R-block and ball models were utilized to construct both the coarse and fine particles within the *** vibro-compaction was employed to regulate the degree of *** results indicate that an increase in vertical pressure,coupled with a zero dilatancy angle,results in a rising stress ratio,indicative of grain *** interlocking exhibits a positive correlation with both the coarse content and the degree of compaction,and varies depending on the shear *** interlocking progresses,the shear band,induced by particle movement,expands and is associated with reduced particle rotation near the shear *** study further reveals a consistent positive correlation between interlocking and the principal orientation angle of strong normal c

关键词： Granular material Interlocking Shear resistance Direct shear Discrete element method Vibro-compaction

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Catalyst-free and Reprocessable Aromatic Polydithiourethanes

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Chinese Journal of Polymer Science 2024年第10期42卷 1435-1441页

作者： Bo Yang Hai-Jun Feng Tian-Tian Ni Xiao-Rui Zhou tao xie() Ning Zheng State Key Laboratory of Chemical Engineering College of Chemical and Biological Engineering Zhejiang University Department of Colorectal Surgery and Oncology Key Laboratory of Cancer Prevention and Intervention Ministry of Education The Second Affiliated HospitalZhejiang University School of Medicine

The incorporation of dynamic covalent bonds into thermosets facilitates the reprocessing of polymer networks, thereby meeting the sustainable requirements for polymer recycling. However, the mechanical properties of many materials often decline significantly upon reprocessing due to side reactions caused by harsh processing conditions. In this work, we find that the aromatic dithiocarbamate bond can undergo dissociation under mild conditions without the need for a catalyst, enabling the efficient reprocessing of the corresponding *** a consequence, the mechanical properties of the polydithiourethane can be largely preserved after reprocessing. The discovery of this dynamic chemistry is anticipated to broaden the potential for material design in dynamic covalent polymer networks.

关键词： Dynamic covalent bond Polydithiourethane Reprocessing

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Special Issue: Dynamic Polymer Networks

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Chinese Journal of Polymer Science 2024年第10期42卷 1401-1402页

作者： Jun-Qi Sun ZhiBo Li tao xie()

The ease of processing and light weight have made polymeric materials uniquely suited for numerous general applications. Increasingly, realization of their switchable chain configuration/mobility and molecular design versatility has pushed polymers into new territories that require materials to dynamically alter their states during their lifespan. These so-called dynamic polymers can self-heal when damaged and undergo highly controllable shapemorphing or other changes (e.g., optical properties) when desired. They open up a variety of new applications such as sensors, soft robotics, and medical devices. Most com-

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Highly efficient photo-thermal synergistic catalysis of CO_(2)methanation over La_(1-x)Ce_(x)NiO_(3)perovskite-catalyst

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Nano Research 2024年第9期17卷 7945-7956页

作者： Ting Li Zhen-Yu Zhang De-Cun Luo Bo-Yu Xu Rong-Jiang Zhang Ji-Long Yao Dan Li tao xie() Institute of Industrial Catalysis School of Chemical Engineering and TechnologyXi’an Jiaotong UniversityXi’an 710049China

Solar-driven photo-thermal catalytic CO_(2)methanation reaction is a promising technology to alleviate the problems posed by greenhouse gases ***,designing advanced photo-thermal catalysts remains a research challenge for CO_(2)methanation *** this work,a series of ABO3(A=lanthanide,B=transition metal)perovskite catalysts with Ce-substituted LaNiO3(La_(1-x)Ce_(x)NiO_(3),x=0,0.2,0.5,0.8,1)were synthesized for CO_(2)*** La_(0.2)Ce_(0.8)NiO_(3) exhibited the highest CH_(4) formation rate of 258.9 mmol·g^(-1)·hcat-1,CO_(2)conversion of 55.4%and 97.2%CH_(4) selectivity at 300℃with the light intensity of 2.9 W·cm^(-2).Then the catalysts were thoroughly analyzed by physicochemical structure and optical properties *** partial substitution of the A-site provided more active sites for the adsorption and activation of CO_(2)/H_(2).The sources of the active sites were considered to be the oxygen vacancies(O_(v))created by lattice distortions due to different species of ions(La^(3+),Ce^(4+),Ce^(3+))and exsolved Ni0 by H_(2)*** catalysts have excellent light absorption absorbance and low electron-hole(e^(-)/h^(+))recombination rate,which greatly contribute to the excellent performance in photo-thermal synergistic catalysis(PTC)CO_(2)*** results of in situ irradiated electron paramagnetic resonance spectrometer(ISI-EPR)and ISI-X-ray photoelectron spectroscopy(XPS)indicated that the aggregation of unpaired electrons near the defects and Ni metal(from La and Ce ions to Ov and Ni0)accelerated adsorption and activation of CO_(2)/H_(2).At last,the catalyst properties and structure were correlated with the proposed reaction mechanism from the in situ diffuse reflection infrared Fourier transform spectrum(DRIFTS)*** in situ precipitation of the B-site enhanced the dispersion of Ni,while its enriched photoelectrons upon illumination further promote hydrogen *** H^(*)spillover accelerated t

关键词： photo-thermal catalysis CO_(2)methanation perovskite A-site substitution in situ diffuse reflection infrared Fourier transform spectrum(DRIFTS)

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Reconfigurable and orthogonal stiffness-structure patterning of dynamically crosslinked amphigels

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SmartMat 2024年第2期5卷 145-155页

作者： Chen Yang Weizhong Zheng Chujun Ni Ye Li Di Chen tao xie() Qian Zhao State Key Laboratory of Chemical Engineering College of Chemical and Biological EngineeringZhejiang UniversityHangzhouChina Ningbo Innovation Center Zhejiang UniversityNingboChina School of Chemical Engineering East China University of Science and TechnologyShanghaiChina

Patterning diversified properties and surface structure of polymer materials are of great importance toward their potential in biology,optics,and ***,achieving both the patternability of stiffness and microstructure in a reconfigurable manner remains ***,we prepare amphigels crosslinked by dynamic disulfide bonds,which can be reversibly swollen by immiscible water or liquid *** the paraffingel form,the materials exhibited a high modulus of 130 MPa due to densified hydrogen *** swollen by water,the modulus fell over two orders of magnitude owing to the destruction of the hydrogen *** regionalized swelling of the solvents,well-controlled and rewritable soft/stiff mechanical patterns can be *** the other hand,the dynamic exchange of the disulfide crosslinking enables mechanophoto patterning to fabricate sophisticated macrogeometries and *** reconfigurable stiffness-structure patterning can be manipulated orthogonally,which will create more application opportunities beyond conventional hydrogels and organogels.

关键词： amphigels dynamic crosslinking hydrogels organogels surface patterning

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区域国别研究:从服务国家战略需求到建构自主知识体系

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清华大学学报（哲学社会科学版） 2024年第3期39卷 36-46,242页

作者：谢韬北京外国语大学国际关系学院北京100081

无论西方还是中国,服务国家战略需求是区域国别研究兴起的原动力。把区域国别研究作为一个独立的一级学科则无疑是中国的一大创举,也是我国区域国别研究历史上的一个里程碑,为其飞速发展注入了强劲动力。然而在为区域国别研究面临的重... 详细信息

无论西方还是中国,服务国家战略需求是区域国别研究兴起的原动力。把区域国别研究作为一个独立的一级学科则无疑是中国的一大创举,也是我国区域国别研究历史上的一个里程碑,为其飞速发展注入了强劲动力。然而在为区域国别研究面临的重大机遇而庆祝时,我们还必须清醒地认识到,这个新兴学科面临诸多重要挑战,尤其是咨政服务与学术研究之间的张力、高等教育国际化程度不够、理论创新越来越难,等等。在我国的政治和学术体制下,区域国别学能否繁荣发展,关键在于政府这个指挥棒。只要相关政府部门继续支持区域国别研究,并通过各种措施引导研究者从事基础性、创新性研究,那么构建中国自主的区域国别学知识体系将指日可待。

关键词：区域国别学政策咨询学术研究高等教育国际化理论创新

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Ultratough Yet Dynamic Crystalline Poly(thiourethane)Network Directly from Low Viscosity Precursors

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CCS Chemistry 2024年第3期6卷 682-692页

作者： Haijun Feng Yi Sheng Guancong Chen Binjie Jin Zizheng Fang Bo Yang Xiaorui Zhou Wenxuan Wu tao xie() Ning Zheng State Key Laboratory of Chemical Engineering College of Chemical and Biological EngineeringZhejiang UniversityHangzhou 310058 Department of Colorectal Surgery and Oncology Key Laboratory of Cancer Prevention and InterventionMinistry of EducationThe Second Affiliated HospitalZhejiang University School of MedicineHangzhou 310027

Thermosets based on direct curing of multifunctional monomers offer processing flexibility that thermoplastics cannot ***,this type of thermoset is typically amorphous since it is difficult to meet the stringent requirement of long-range molecular regularity for ***,we report here a crystallizable poly(thiourethane)thermoset synthesized directly from the curing of low-viscosity liquid precursors that does not employ any *** crystalline nature results in superior toughness,comparable to commercial high-density polyethylene,in sharp contrast to the brittleness of the typical,rigid,glassy thermoset *** that,the network polymer exhibits shape-memory behavior in which the crystalline transition is utilized for temporary shape fixing/recovery whereas the dynamic thiourethane bonds can be activated for bond exchange as a mechanism for complex shape *** with these combined features represent attractive options for demanding engineering applications due to their high performance and multifunctinality.

关键词： thermosets crystalline polymer thiourethane thermadapt

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Structural transition,electric transport,and electronic structures in the compressed trilayer nickelate La4Ni3O10

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Science China(Physics,Mechanics & Astronomy) 2024年第11期Mechanics & Astronomy) .卷 13-19页

作者： Jingyuan Li Cui-Qun Chen Chaoxin Huang Yifeng Han Mengwu Huo Xing Huang Peiyue Ma Zhengyang Qiu Junfeng Chen Xunwu Hu Lan Chen tao xie() Bing Shen Hualei Sun Dao-Xin Yao Meng Wang Center for Neutron Science and Technology Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices School of Physics Sun Yat-sen University Center for Materials of the Universe School of Molecular Sciences Arizona State University School of Sciences Sun Yat-sen University

Atomic structure and electronic band structure are fundamental properties for understanding the mechanism of superconductivity. Motivated by the discovery of pressure-induced high-temperature superconductivity at 80 K in the bilayer Ruddlesden-Popper nickelate La3Ni2O7, the atomic structure and electronic band structure of the trilayer nickelate La4Ni3O10under pressure up to 44.3 GPa are investigated. A structural transition from the monoclinic P21/a space group to the tetragonal I4/mmm around 12.6-13.4 GPa is identified, accompanied by a drop of resistance below 7 K. Density functional theory calculations suggest that the bonding state of Ni 3dz2orbital rises and crosses the Fermi level at high pressures, which may give rise to possible superconductivity observed in resistance under pressure in La4Ni3O10. The trilayer nickelate La4Ni3O10shows some similarities with the bilayer La3Ni2O7and has unique properties, providing a new platform to investigate the underlying mechanism of superconductivity in nickelates.

关键词： La4Ni3O10 high pressure synchrotron X-ray diffraction structural transition DFT calculations

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一种变工况下海流发电机叶片附着物检测方法

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电机与控制学报 2024年第5期28卷 101-110,118页

作者：谢涛王天真汤天浩徐玉洁上海海事大学物流工程学院上海201306 上海电源学会上海200086

针对流速变化使得变工况下海流发电机叶片附着物故障特征模糊、鉴别性差的问题,提出一种基于自适应频率正比采样(APFS)的叶片附着物检测方法。首先,采集不同工况下海流发电机电流信号,通过希尔伯特变换提取出定子电流信号的瞬时频率;然... 详细信息

针对流速变化使得变工况下海流发电机叶片附着物故障特征模糊、鉴别性差的问题,提出一种基于自适应频率正比采样(APFS)的叶片附着物检测方法。首先,采集不同工况下海流发电机电流信号,通过希尔伯特变换提取出定子电流信号的瞬时频率;然后,利用瞬时频率与采样频率比值变步长采样瞬时频率序列,将非稳定瞬时转动频率转变为稳定值;最后,利用排列熵设置采样迭代停止阈值,将重采样后的瞬时频率序列作为故障特征划分为样本矩阵,建立主成分分析检测模型以实现附着物检测。基于0.23 kW海流发电样机的实验平台被搭建用于验证所提方法的有效性,实验结果表明,所提算法在对抗流速变化下引起的海流发电机变工况问题中,误报率低至0.25%,具备较高检测精度和鲁棒性。

关键词：海流发电机故障检测叶片附着物希尔伯特变换自适应频率正比采样主元成分分析

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基于强化学习与种群博弈的近距空战决策

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航空学报 2024年第12期45卷 169-184页

作者：王宝来高显忠谢涛侯中喜国防科技大学计算机学院长沙410073 国防科技大学空天科学学院长沙410073

随着人工智能与无人机(UAV)技术的发展,近距空战智能决策得到了世界各国的广泛关注。针对传统强化学习在解决近距空战智能决策问题时存在过拟合与策略循环等问题,提出了一种基于种群博弈的空战智能决策模型训练范式。通过构建由多个无... 详细信息

随着人工智能与无人机(UAV)技术的发展,近距空战智能决策得到了世界各国的广泛关注。针对传统强化学习在解决近距空战智能决策问题时存在过拟合与策略循环等问题,提出了一种基于种群博弈的空战智能决策模型训练范式。通过构建由多个无人机智能体组成的种群,并为每个智能体赋予不同奖励权重系数,实现了无人机智能体多样化的风险偏好。种群中不同风险偏好的智能体模型相互进行对抗训练,能够有效避免过拟合和策略循环问题。在训练过程中,每个无人机智能体根据与不同对手策略的对抗结果自适应地优化奖励权重系数。在数值仿真实验中,种群博弈训练中的智能体5与智能体3分别以88%和85%的胜率击败了专家系统对抗训练和自博弈训练得到的智能决策模型,算法性能得到有效验证。此外,通过进一步实验表明了种群博弈训练范式中权重系数动态调整的必要性,并在异构机型上验证了所提训练范式的通用性。

关键词：近距空战智能决策强化学习种群博弈 SAC算法

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