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Exploring the mechanical behavior and microstructure of compacted loess subjected to dry-wet cycles and chemical contamination

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第9期16卷 3673-3695页

作者： Yongpeng nie Wankui Ni Xiangfei lü Wenxin Tuo College of Geological Engineering and Geomatics Chang'an UniversityXi'an710054China Department of Civil Engineering Nagoya Institute of TechnologyNagoya466-8555Japan School of Water and Environment Chang'an UniversityXi'an710054China

Due to climatic factors and rapid urbanization,the soil in the loess Plateau,China,experiences the coupled effects of dry-wet cycles and chemical *** the mechanical behavior and corresponding microstructural evolution of contaminated loess subjected to dry-wet cycles is essential to elucidate the soil degradation ***,direct shear and consolidation tests were performed to investigate the variations in mechanical properties of compacted loess contaminated with acetic acid,sodium hydroxide,and sodium sulfate during dry-wet *** mechanical response mechanisms were investigated using zeta potential,mineral chemical composition,and scanning electron microscopy(SEM)*** results indicate that the mechanical deterioration of sodium hydroxidecontaminated loess during dry-wet cycles decreases with increasing contaminant concentration,which is mainly attributed to the thickening of the electrical double layer(EDl)by Nat and the precipitation of calcite,as well as the formation of colloidal flocs induced by Oh,thus inhibiting the development of large pores during the dry-wet *** contrast,the attenuation of mechanical properties of both acetic acid-and sodium sulfate-contaminated loess becomes more severe with increasing contaminant concentration,with the latter being more particularly *** is primarily due to the reduction of the EDl thickness and the erosion of cement in the acidic environment,which facilitates the connectivity of pores during dry-wet ***,the salt expansion generated by the drying process of saline loess further intensifies the structural ***,the mechanical performance of compacted loess is sensitive to both pollutant type and concentration,exhibiting different response patterns in the dry-wet cycling condition.

关键词： Contaminated loess Dry-wet cycles Compressibility Shear strength Microstructural evolution

Simulation and evaluation study of atmospheric aerosol nonsphericity as a function of particle size

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Particuology 2024年第7期90卷 281-291页

作者： Qianjun Mao Xin nie School of Urban Construction Wuhan University of Science and TechnologyWuhan430065China College of New Energy and Materials Northeast Petroleum UniversityDaqing163318China

Aerosol nonsphericity causes great uncertainty in radiative forcing assessments and climate *** considerable studies have attempted to quantify this uncertainty,the relationship between aerosol nonsphericity and particle size is usually not considered,thus reducing the accuracy of the *** this study,a coupled inversion algorithm combining an improved stochastic particle swarm optimization algorithm and angular light scattering is used for the nonparametric estimation of aerosol nonsphericity variation with particle size,and the optimal sample selection method is employed to screen the *** on the verification of inversion accuracy,the variation of aerosol aspect ratio with particle size based on the ellipsoidal model in global regions has been obtained from Aerosol Robotic Network(AERONET)data,and the effect of nonsphericity on radiative forcing and dry deposition has been *** results show that the aspect ratio increases with particle size in all regions,with the maximum ranging from 1.4 to 1.8 in the desert,reflecting the differences in aerosol composition at different particle *** radiation calculations,considering aerosol nonsphericity makes the aerosol cooling effect weaker and surface radiative fluxes increase,but hardly changes the aerosol absorption,with maximum differences of 9.22%and 22.12%at the bottom and top of the atmosphere,***,the differences in radiative forcing between aspect ratios as a function of particle size and not varying with particle size are not significant,averaging less than 2%.Besides,the aspect ratio not varying with particle size underestimates the deposition velocity of small particles and overestimates that of large particles compared to that as a function of particle size,with maximum differences of 7%and 4%,respectively.

关键词： Aerosol nonsphericity Inversion Aspect ratio Radiative forcing Dry deposition velocity

Comprehensive insights:unraveling the mechanisms of gut commensals in glucose metabolism regulation

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Science China(life Sciences) 2024年第2期67卷 414-417页

作者： Zhipeng li Qixing nie Shao-Ping nie State Key laboratory of Food Science and Resources China-Canada Joint Lab of Food Science and Technology(Nanchang)Key Laboratory of Bioactive Polysaccharides of Jiangxi ProvinceNanchang UniversityNanchang 330047China

The prevalence of type 2 diabetes(T2D)has escalated to a global epidemic,garnering widespread *** research utilizing germ-free(GF)mice,antibiotic treatments,and fecal microbiota transplantation approaches has established the critical role of gut microbiota in modulating glucose *** microbiota interacts with diets and the mucosal immune system,influencing intestinal permeability and the penetration of microbial products.

关键词： metabolism utilizing insight

Recent advances in small-scale hydrogel-based robots for adaptive biomedical applications

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Nano Research 2024年第2期17卷 649-662页

作者： Mingzhe nie Qilong Zhao Xuemin Du Institute of Biomedical&health Engineering Shenzhen Institute of Advanced Technology(SIAT)Chinese Academy of Sciences(CAS)Shenzhen 518055China

Small-scale robots,ranging in size from micrometers to centimeters,have gained significant attention in the biomedical ***,conventional small-scale robots made of rigid materials encounter challenges in adapting themselves to the soft tissues and complicated environments of human *** to the rigid counterpart,small-scale hydrogel-based robots hold great promises due to their tissue-like low modulus,outstanding biocompatibility and accessible stimuli-responsive *** attributes offer small-scale hydrogel-based robots with multimodal locomotion and reinforced functions,further enhancing the adaptability in manipulation and tasks execution for various biomedical *** this review,we present recent advances in small-scale hydrogel-based *** first summarize the design principles of small-scale hydrogel-based robots including materials,fabrication techniques and manipulation strategies,then highlighting their upgraded functions and adaptive biomedical ***,we discuss existing challenges and future perspectives for small-scale hydrogel-based robots.

关键词： small-scale robot hydrogel locomotion multi-function adaptability

Collectively induced transparency and absorption in waveguide quantum electrodynamics with Bragg atom arrays

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Communications in Theoretical Physics 2024年第8期76卷 19-28页

作者： haolei Cheng Wei nie Center for Joint Quantum Studies and Department of Physics School of ScienceTianjin UniversityTianjin 300350China Tianjin Key laboratory of low Dimensional Materials Physics and Preparing Technology Tianjin UniversityTianjin 300350China

Collective quantum states, such as subradiant and superradiant states, are useful for controlling optical responses in many-body quantum systems. In this work, we study novel collective quantum phenomena in waveguide-coupled Bragg atom arrays with inhomogeneous *** atoms without free-space dissipation, collectively induced transparency is produced by destructive quantum interference between subradiant and superradiant states. In a large Bragg atom array, multi-frequency photon transparency can be obtained by considering atoms with different frequencies. Interestingly, we find collectively induced absorption(CIA) by studying the influence of free-space dissipation on photon transport. Tunable atomic frequencies nontrivially modify decay rates of subradiant states. When the decay rate of a subradiant state equals to the free-space dissipation, photon absorption can reach a limit at a certain frequency. In other words, photon absorption is enhanced with low free-space dissipation, distinct from previous photon detection schemes. We also show multi-frequency CIA by properly adjusting atomic frequencies. Our work presents a way to manipulate collective quantum states and exotic optical properties in waveguide quantum electrodynamics(QED) systems.

关键词： waveguide quantum electrodynamics collective quantum states photon absorption Bragg atom array

Matched Volterra reduced-order model for an airfoil undergoing periodic translation

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Chinese Journal of Aeronautics 2024年第1期37卷 19-23页

作者： lianrui nie Ziniu WU Department of Engineering Mechanics Tsinghua UniversityBeijing 100084China

This paper is devoted to application of the Reduced-Order Model(ROM)based on Volterra series to prediction of lift and drag forces due to airfoil periodic translation in transonic flow *** there is large amplitude oscillation of the relative Mach number,as appeared in helicopter rotor movement in forward flight,the conventional Volterra ROM is found to be *** cover such applications,a matched Volterra ROM,inspired from previous multistep nonlinear indicial response method based on Duhamel integration,is thus considered,in which the step motions are defined inside a number of equal intervals with both positive and negative step motions to match the airfoil forward and backward movement,and the kernel functions are constructed independently at each *** shows that,at least for the translation movement considered,this matched Volterra ROM greatly improves the accuracy of ***,the matched Volterra ROM,with the total number of step motions and thus the computational cost close to those of the conventional Volterra ROM method,has the additional advantage that the same set of kernels can match various translation motions with different starting conditions so the kernels can be predesigned without knowing the specific motion of airfoil.

关键词： Airfoil periodic translation lift and drag Reduced-order model Transonic flow Unsteady flow

A variable structure passivity control method for elastic joint robots based on cascaded high-order state estimation

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Science China(Technological Sciences) 2024年第2期67卷 395-407页

作者： ZhANG JieXin nie PingYun ZhANG Bo State Key laboratory of Mechanical System and Vibration School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai200240China

Passivity-based controllers are widely used to facilitate physical interaction between humans and elastic joint robots,as they enhance the stability of the interaction ***,the joint position tracking performance can be limited by the structures of these controllers when the system is faced with uncertainties and rough high-order system state measurements(such as joint accelerations and jerks).This study presents a variable structure passivity(VSP)control method for joint position tracking of elastic joint robots,which combines the advantages of passive control and variable structure *** method ensures the tracking error converges in a finite time,even when the system faces *** method also preserves the passivity of the ***,a cascaded observer,called ChOSSO,is also proposed to accurately estimate high-order system states,relying only on position and velocity *** observer allows independent implementation of disturbance compensation in the acceleration and jerk estimation *** particular,the observer has an enhanced ability to handle fast time-varying disturbances in physical human-robot *** effectiveness of the proposed method is verified through simulations and experiments on a lower limb rehabilitation robot equipped with elastic joints.

关键词： motion control elastic joint robot finite-time convergence high-order system state estimation physical human-robot interaction

Fabrication of micro-nano patterned materials mimicking the topological structure of extracellular matrix for biomedical applications

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Nano Research 2024年第5期17卷 4244-4258页

作者： Yifeng nie Dong han Xiang li CAS Center for Excellence in Nanoscience National Center for Nanoscience and TechnologyBeijing 100190China School of Future Technology University of Chinese Academy of SciencesBeijing 100049China

With the advent of tissue engineering and biomedicine,the creation of extracellular matrix(ECM)biomaterials for in vitro applications has become a prominent and promising *** ECM materials provide physical,biochemical,and mechanical properties that guide cellular behaviors,such as proliferation,differentiation,migration,and *** micro-and nano-patterned materials have a unique surface topology and low energy replication process that directly affect cellular biological behaviors at the interface,the fabrication of micro-nano pattern biomaterials and the regulation of surface physical and chemical properties are of great significance in the fields of cell regulation,tissue engineering,and regenerative ***,we provide a comprehensive review of the progress in the fabrication and application of patterned materials based on the coupling of mechanical action at the micro-and nano-meter scale,including photolithography,micro-contact printing,electron beam lithography,electrospinning,and 3D printing ***,a summary of the fabrication process,underlying principles,as well as the advantages and disadvantages of various technologies are *** also discuss the influence of material properties on the fabrication of micro-and nano-patterns.

关键词： micro/nano hybrid materials patterning fabrication techniques extracellular matrix substrate-cell interaction biomedical engineering

Recent advances in high charge density triboelectric nanogenerators

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International Journal of Extreme Manufacturing 2024年第4期6卷 1-19页

作者： Xin Cui Jiaheng nie Yan Zhang School of Physics University of Electronic Science and Technology of ChinaChengdu 611731People's Republic of China School of Cybersecurity Chengdu University of Information TechnologyChengdu 610225People's Republic of China Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of SciencesBeijing 100083People's Republic of China School of Nanoscience and Technology University of Chinese Academy of SciencesBeijing 100049People's Republic of China

Triboelectric materials with high charge density are the building-block for the commercial application of triboelectric nanogenerators(TENGs).Unstable dynamic processes influence the change of the charge density on the surface and inside of triboelectric *** charge density of triboelectric materials depends on the surface and the internal charge transfer *** focus of this review is on recent advances in high charge density triboelectric materials and advances in the fabrication of *** summarize the existing strategies for achieving high charge density in triboelectric materials as well as their fundamental *** then review current optimization methods for regulating dynamic charge transfer processes to increase the output charge density:first,increasing charge injection and limiting charge dissipation to achieve a high average surface charge density,and second,regulating the internal charge transfer process and storing charge in triboelectric materials to increase the output charge ***,we present the challenges and prospects in developing high-performance triboelectric materials.

关键词： triboelectric nanogenerator charge density charge transfer charge store