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Kinematic analysis of flexible bipedal robotic systems

Applied Mathematics and Mechanics(English Edition) 2024年第5期45卷 795-818页

作者： r.FAZEL A.M.SHAFEI S.r.NEKOO Department of Mechanical Engineering Shahid Bahonar University of KermanKerman ***Iran Departamento de Ingenieria de Sistemas y Automatica Escuela Técnica Superior de IngenieriaUniversidad de SevillaSeville 41092Spain

In spite of its intrinsic complexities,the passive gait of bipedal robots on a sloping ramp is a subject of interest for numerous *** distinguishes the present research from similar works is the consideration of flexibility in the constituent links of this type of robotic *** is not a far-fetched assumption because in the transient(impact)phase,due to the impulsive forces which are applied to the system,the likelihood of exciting the vibration modes increases ***,the human leg bones that are involved in walking are supported by viscoelastic muscles and ***,for achieving more exact results,it is essential to model the robot links with viscoelastic *** this end,the gibbs-Appell formulation and Newton's kinematic impact law are used to derive the most general form of the system's dynamic equations in the swing and transient phases of *** most important issue in the passive walking motion of bipedal robots is the determination of the initial robot configuration with which the system could accomplish a periodic and stable gait solely under the effect of gravitational *** extremely unstable nature of the system studied in this paper and the vibrations caused by the impulsive forces induced by the impact of robot feet with the inclined surface are some of the very serious challenges encountered for achieving the above-mentioned *** overcome such challenges,an innovative method that uses a combination of the linearized equations of motion in the swing phase and the algebraic motion equations in the transition phase is presented in this paper to obtain an eigenvalue *** solving this problem,the suitable initial conditions that are necessary for the passive gait of this bipedal robot on a sloping surface are *** effects of the characteristic parameters of elastic links including the modulus of elasticity and the Kelvin-Voigt coefficient on the walking stability of this type of

关键词： bipedal robot flexible link swing phase transient phase eigenvalue problem Kelvin-Voigt coefficient

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The magnetosheath at high spectral resolution

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Earth and Planetary Physics 2024年第1期8卷 234-246页

作者： K.D.Küntz D.Koutroumpa W.r.Dunn A.Foster F.S.Porter D.g.Sibeck B.Walsh The Henry A.rowland Department of Physics and Astronomy Johns Hopkins University3701 San Martin DriveBaltimoreMD21218USA NASA goddard Space Flight Center 8800 Greenbelt RoadGreenbeltMD 20771USA LATMOS-OVSQ CNRSUVSQ Paris-SaclaySorbonne Université11 Boulevard d’Alembert78280GuyancourtFrance Department of Physics and Astronomy University College LondonLondonUK The Centre for Planetary Science at UCL/Birkbeck Gower StreetLondon WC1E 6BTUK Center for Astrophysics Harvard University&Smithsonian Institution60 Garden StreetCambridgeMA 02138USA Center for Space Physics Boston University110 Cummington MallBostonMAUSA

While we eagerly anticipate SMILE’s(Solar wind Magnetosphere Ionosphere Link Explorer)unprecedented X-ray observations of the Earth’s magnetosheath and the initiation of a new era of magnetospheric research,it seems appropriate to look ahead to the abilities of the next generation of astrophysics *** these,the Line Emission Mapper(LEM),a large aperture micro-calorimeter based mission,is currently planned to be able to observe the magnetosheath at high spectral resolution(~2 eV).With a field of view of~30′,LEM will allow higher spatial resolution and higher cadence measurement of the motion of a very small portion of the magnetopause over relatively short periods of time(multiple hours),complementing SMILE’s global ***’s strength is its spectral *** will be able to measure the abundance of a broad range of elements and ionization states,many of which are inaccessible to current in situ instruments,and will be able to separate the emission from the magnetosheath from the emission from the cosmic X-ray background using the difference in their relative velocities.

关键词： magnetosheath charge exchange solar wind abundances

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Holographic dark energy in non-conserved gravity theory

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Communications in Theoretical Physics 2024年第4期76卷 126-133页

作者： H r Fazlollahi Institute of gravitation and Cosmology Peoples Friendship University of Russia(RUDN University)6 Miklukho-Maklaya StMoscow117198Russia

recently, reconsidering the rastall idea T_(μ;νν)^(v)=α_(,μ) through relativistic thermodynamics gives a new form for the scalar field α which led us to construct modern modified theory of gravity debugged ‘non-conserved gravity theory’ Fazlollahi 2023 Euro. Phys. J. C 83 923. This theory unlike other modified theories of gravity cannot directly explain the current acceleration expansion in the absence of the cosmological constant and or existence of other forms of dark energy. Hence, in this study we have reinvestigated holographic dark energy Ρ_(X)~H^(2) in the non-conserved theory of gravity. In this context, the density and pressure of dark energy depend on the non-conserved term and density of the dust matter field. As shown, due to non-conservation effects on large-scale structures, unlike the original holographic model, our model onsets an acceleration epoch for the current Universe satisfies observations. Moreover, the interaction and viscous scenarios are studied for this model.

关键词： non-conserved gravity covariant form of thermodynamics holographic dark energy

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Electrochemical realization of 3D Interconnected MoS_(3)/PPy Nanowire Frameworks as Sulfur-Equivalent Cathode Materials for Li-S Batteries

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Energy & Environmental Materials 2024年第2期7卷 9-17页

作者： Hongtao Yu Andreas Siebert Shilin Mei raul garcia-Diez roberto Félix Ting Quan Yaolin Xu Johannes Frisch regan g.Wilks Marcus Bär Chun Pei Yan Lu Department for Electrochemical Energy Storage Helmholtz-Zentrum Berlin für Materialien und Energie GmbH(HZB)Hahn-Meitner Platz 114109 BerlinGermany guangdong Province Key Laboratory of Durability for Marine Civil Engineering School of Civil EngineeringShenzhen UniversityShenzhenGuangdong 518060China Department of Interface Design HZBAlbert-Einstein-Str.1512489 BerlinGermany Energy Materials In-Situ Laboratory Berlin(EMIL) Albert-Einstein-Str.1512489 BerlinGermany Helmholtz-Institute Erlangen-Nürnberg for renewable Energy(HI ErN) Albert-Einstein-Str.1512489 BerlinGermany Department of Chemistry and Pharmacy Friedrich-Alexander-Universität Erlangen-NürnbergEgerlandstr.391058Erlangen Germany Institute of Chemistry University of Potsdam14467Potsdam Germany

The development of freestanding and binder-free electrode is an effective approach to perform the inherent capacity of active materials and promote the mechanism study by minimizing the interference from ***,we construct a freestanding cathode composed of MoS_(3)/PPy nanowires(NWs)deposited on porous nickel foam(NF)(MoS_(3)/PPy/NF)through electrochemical methods,which can work efficiently as sulfur-equivalent cathode material for Li-S *** structural stability of the MoS_(3)/PPy/NF cathode is greatly enhanced due to its significant tolerance to the volume expansion of MoS_(3)during the lithiation process,which we ascribe to the flexible 3D framework of PPy NWs,leading to superior cycling performance compared to the bulk-MoS_(3)/NF *** the interference of binder and carbon additives,the evolution of the chemical and electronic structure of Mo and S species during the discharge/charge was studied by X-ray absorption near-edge spectroscopy(XANES).The formation of lithium polysulfides was excluded as the driving cathode reaction mechanism,suggesting the great potential of MoS_(3)as a promising sulfur-equivalent cathode material to evade the shuttle effect for Li-S *** present study successfully demonstrates the importance of structural design of freestanding electrode enhancing the cycling performances and revealing the corresponding mechanisms.

关键词： 3D-Network electrochemical lithium-sulfur battery MoS_(3) PPy

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Nanozyme catalysis in a crowded environment:The impact of diffusion and surface shielding

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Nano research 2024年第7期17卷 5795-5800页

作者： Vasily g.Panferov Juewen Liu Department of Chemistry Waterloo Institute for NanotechnologyWaterlooOntario N2L 3G1Canada

Nanozymes are widely used in various applications as nanosized catalysts for replacing *** accurate estimation of the catalytic activity of nanozymes in real conditions is *** this article,for the first time,we systematically studied the effect of macromolecular molecules co-existing in the real system on the oxidoreductase(peroxidase,oxidase,and catalase)-mimicking nanozymes made of a gold nanoparticle core and a platinum shell,Prussian Blue,Mn_(2)O_(3) and CoO *** were made with horseradish *** distinguished two main mechanisms of the negative impact of macromolecules on nanozyme catalysis—slowed diffusion and surface shielding of *** the first mechanism is typical for enzymes,the second one is specific only for *** the mechanisms is essential for developing approaches to reduce the unavoidable impact of macromolecules for various analytical and biomedical applications.

关键词： molecular crowding biosensors nanoparticles

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LKB1 depletion-mediated epithelial-mesenchymal transition induces fibroblast activation in lung fibrosis

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genes & Diseases 2024年第3期11卷 417-426页

作者： Zijian Xu Elizabeth r.Davies Liudi Yao Yilu Zhou Juanjuan Li Aiman Alzetani Ben g.Marshall David Hancock Tim Wallis Julian Downward rob M.Ewing Donna E.Davies Mark g.Jones Yihua Wang Biological Sciences Faculty of Environmental and Life SciencesUniversity of SouthamptonSouthampton SO171BJUK clinical and Experimental Sciences Faculty of MedicineUniversity of SouthamptonSouthampton SO166YDUK Institute for Life Sciences University of SouthamptonSouthampton SO171BJUK NIHr Southampton Biomedical research Centre University Hospital SouthamptonSouthampton SO166YDUK University Hospital Southampton Southampton SO166YDUK Oncogene Biology The Francis Crick InstituteLondon NW11ATUK

The factors that determine fibrosis progression or normal tissue repair are largely *** previously demonstrated that autophagy inhibition-mediated epithelial-mesenchymal transition(EMT)in human alveolar epithelial type Il(ATIl)cells augments local myofibroblast differentiation in pulmonary fibrosis by paracrine ***,we report that liver kinase B1(LKB1)inactivation in ATIl cells inhibits autophagy and induces EMT as a *** IPF lungs,this is caused by the down-regulation of CAB39L,a key subunit within the LKB1 complex.3D co-cultures of ATIl cells and MrC5 lung fibroblasts coupled with rNA sequencing(rNA-seq)confirmed that paracrine signaling between LKB1-depleted ATIl cells and fibroblasts augmented myofibroblast ***,these data suggest that reduced autophagy caused by LKB1 inhibition can induce EMT in ATIl cells and contribute to fibrosis via aberrant epithelial-fibroblast crosstalk.

关键词： CAB39L Crosstalk EMT LKB1 Pulmonary fibrosis

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Magnesium oxide(MgO)nanoadsorbents in wastewater treatment:A comprehensive review

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Journal of Magnesium and Alloys 2024年第5期12卷 1709-1773页

作者： H.C.S.Perera V.gurunanthanan Anoop Singh M.M.M.g.P.g.Mantilaka g.Das Sandeep Arya Department of Physics Khalifa UniversityAbu Dhabi12788United Arab Emirates Postgraduate Institute of Science University of PeradeniyaPeradeniyaSri Lanka Department of Humanities and Sciences Guru Nanak Institutions Technical CampusIbrahimpatnamHyderabad501506India Centre for global Health research Saveetha Medical College and HospitalsSaveetha Institute of Medical and Technical SciencesChennai602105Tamil NaduIndia Department of Physics University of JammuJammu and Kashmir180006India

Wastewater contamination by heavy metals and synthetic dyes presents a significant environmental challenge,necessitating effective and sustainable separation *** review article provides a detailed examination of magnesium oxide(MgO)nanoparticles as an innovative nanoadsorbent for wastewater treatment,with a specific focus on heavy metal and dye *** review comprehensively explores various aspects of MgO nanoparticles,including their structural characteristics and synthesis *** article delves into the morphology and crystallographic arrangement of MgO nanoparticles,offering insights into their structural *** the complexity of adsorption processes,the review identifies and analyzes parameters influencing the adsorption efficiency of MgO nanoparticles,such as temperature,pH,contact time,initial concentration,and co-existing *** interplay between these parameters and the adsorption capability of MgO nanoparticles emphasizes the importance of optimizing operational ***,the review assesses various synthesis methods for MgO nanoparticles,including sol-gel,hydrothermal,precipitation,green synthesis,solvothermal,and template-assisted *** discusses the advantages,limitations,and resulting nanoparticle characteristics of each method,enabling readers to grasp the implications of synthesis processes on adsorption *** comprehensive review consolidates current insights into the effectiveness of MgO nanoparticles as a potent nanoadsorbent for removing heavy metals and dyes from wastewater covering a wide spectrum of aspects related to MgO ***,there is a need to investigate the use of MgO in the treatment of actual wastewater or river water,in order to leverage its cost-effectiveness and high efficiency for practical water treatment applications in real-time.

关键词： MgO nanoparticles Nanoadsorbent Wastewater treatment Heavy metals Dye separation Adsorption Synthesis methods

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Quantitative Mapping of Transient Thermodynamic States in Ultrafast Laser Nanostructuring of Quartz

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Ultrafast Science 2024年第2期4卷 9-18页

作者： H.D.Nguyen A.Tsaturyan S.Sao Joao r.Dwivedi A.Melkonyan C.D’Amico E.Kachan J.P.Colombier g.Kermouche r.Stoian Laboratoire Hubert Curien UMR 5516 CNRSUniversite Jean Monnet42000 Saint EtienneFrance Laboratoire george Friedel UMR 5307 CNRSEcole des Mines de Saint Etienne42000 Saint EtienneFrance

Understanding material structural reaction to light is of utmost importance to advance processing resolution in ultrafast laser volume structuring into the *** thermodynamic pathways are required to quench energy transport in the most rapid manner and to confine the process to nanometer lengths,bypassing optical *** material dynamics under confinement,with in situ access to transient local temperature and density parameters,thus becomes key in understanding the *** report in situ reconstruction of thermodynamic states over the entire matter relaxation path in bulkα-quartz irradiated by ultrafast nondiffractive laser beams using time-resolved qualitative and quantitative optical phase *** dynamics indicate rapid spatially confined crystalline-to-amorphous transition to a hot dense fused silica *** exceeds 20%and the matrix temperature rises to more than 2,000 K in the first *** structural state relaxes in hundreds of *** dispersion and time design of the optical beam to picosecond durations increases the spatial confinement and triggers an extreme nanostructuring process based on nanocavitation that occurs within the amorphizing material,where the low-viscosity phase lowers the mechanical requirements for the *** feature scales of less than a tenth of the optical wavelength are obtained in the *** allows for structural and morphological nanoscale material features under 3D confinement that can engineer optical materials.

关键词： Quartz hundreds qualitative

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Analysis of the discrete contact characteristics based on the greenwood-Williamson model and the localization principle

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Friction 2024年第5期12卷 1042-1056页

作者： Anastasiya A.YAKOVENKO Irina g.gOrYACHEVA Ishlinsky Institute for Problems in Mechanics rAS Moscow119526Russia

The contact of a rigid body with nominally flat rough surface and an elastic half-space is *** solve the contact problem,the greenwood-Williamson statistical model and the localization principle are *** developed contact model allows us to investigate the surface approach and the real contact area with taking into account the asperities *** is shown that the mutual influence of asperities changes not only contact characteristics at the macroscale,but also the contact pressure distribution at the *** follows from the results,the inclusion in the contact model of the effect of the mutual influence of asperities is especially significant for studying the real contact area,as well as the contact characteristics at high applied *** results calculated according to the proposed approach are in a good agreement with the experimentally observed effects,i.e.,the real contact area saturation and the additional compliance exhaustion.

关键词： surface roughness elasticity greenwood-Williamson model localization principle asperity interaction

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Numerical simulation of three dimensional concrete printing based on a unified fluid and solid mechanics formulation

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Frontiers of Structural and Civil Engineering 2024年第4期18卷 491-515页

作者： Janis rEINOLD Koussay DAADOUCH günther MESCHKE Institute for Structural Mechanics Ruhr University BochumBochum 44801Germany

Deformation control constitutes one of the main technological challenges in three dimensional(3D)concrete printing,and it presents a challenge that must be addressed to achieve a precise and reliable construction ***-based information of the expected deformations and stresses is required to optimize the construction process in association with the specific properties of the concrete *** this work,a novel thermodynamically consistent finite strain constitutive model for fresh and early-age 3D-printable concrete is *** model is then used to simulate the 3D concrete printing process to assess layer shapes,deformations,forces acting on substrate layers and prognoses of possible structural collapse during the layer-by-layer *** constitutive formulation is based on a multiplicative split of the deformation gradient into elastic,aging and viscoplastic parts,in combination with a hyperelastic potential and considering evolving material properties to account for structural buildup or *** advantage of this model is the stress-update-scheme,which is similar to that of small strain plasticity and therefore enables an efficient integration with existing material *** constitutive model uses the particle finite element method,which serves as the simulation framework,allowing for modeling of the evolving free surfaces during the extrusion *** analyses of three printed layers are used to create deformation plots,which can then be used to control the deformations during 3D concrete *** study offers further investigations,on the structural level,focusing on the potential structural collapse of a 3D printed concrete *** capability of the proposed model to simulate 3D concrete printing processes across the scales—from a few printed layers to the scale of the whole printed structure—in a unified fashion with one constitutive formulation,is demonstrated.

关键词： particle finite element method 3D concrete printing multiplicative split additive manufacturing elastoviscoplasticity

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