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Forming limits under multi-index constraints in NC bending of aluminum alloy thin-walled tubes with large diameters

Science China(Technological Sciences) 2010年第2期53卷 326-342页

作者： YAN Jing, YANG He, ZHAN Mei & LI Heng College of Materials Science and Engineering, State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China 1. College of Materials Science and Engineering State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi’an 710072 China

With increasing diameters of aluminum alloy thin-walled tubes (AATTs), the tube forming limits, i.e. the minimum bending factors, and their predictions under multi-index constraints including wrinkling, thinning and flattening have been being a key problem to be urgently solved for improving tube forming potential in numerical control (NC) bending processes of AATTs with large diameters. Thus in this paper, a search algorithm of the forming limits is put forward based on a 3D elastic-plastic finite element (FE) model and a wrinkling energy prediction model for the bending processes under axial compression loading (ACL) or not. This algorithm enables to be considered the effects of process parameter combinations including die, friction parameters on the multi-indices. Based on this algorithm, the forming limits of the different size tubes are obtained, and the roles of the process parameter combinations in enabling the limit bending processes are also revealed. The followings are found: the first, within the appropriate ranges of friction and clearances between the different dies and the tubes enabling the bending processes with smaller bending factors, the ACL enables the tube limit bending processes after a decrease of the mandrel ball thickness and diameters; then, without considering the effects of the tube geometry sizes on the tube constitutive equations, the forming limits will be decided by the limit thinning values for the tubes with diameters smaller than 80 mm, while the wrinkling for the tubes with diameters no less than 80 mm. The forming limits obtained from this algorithm are smaller than the analytical results, and reduced by 57.39%; the last, the roles of the process parameter combinations in enabling the limit bending processes are verified by experimental results.

关键词： forming limit NC tube bending aluminum alloy thin-walled tubes with large diameters multi-index constraints finite element method

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The 20-nm Skyrmion Generated at Room Temperature by Spin-Orbit Torques

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Chinese Physics Letters 2022年第1期39卷 40-45页

作者： Jiahao Liu Zidong Wang Teng Xu Hengan Zhou Le Zhao Soong-Guen Je Mi-Young Im Liang Fang Wanjun Jiang State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics Tsinghua UniversityBeijing 100084China Frontier Science Center for Quantum Information Tsinghua UniversityBeijing 100084China Institute for Quantum Information&State Key Laboratory of High Performance Computing College of ComputerNational University of Defense TechnologyChangsha 410073China Center for X-ray Optics Lawrence Berkeley National LaboratoryCyclotron RoadBerkeleyCA 94720USA Department of Physics Chonnam National UniversityGwangju61186Republic of Korea

The discovery of magnetic skyrmions provides a promising pathway for developing functional spintronic memory and logic devices. Towards the future high-density memory application, nanoscale skyrmions with miniaturized diameters, ideally down to 20 nm are required. Using x-ray magnetic circular dichroism transmission microscopy,nanoscale skyrmions are observed in the [Pt/Co/Ir]15 multilayer at room temperature. In particular, small skyrmions with minimum diameters approaching 20 nm could be generated by the current-induced spin-orbit torques. Through implementing material specific parameters, the dynamic process of skyrmion generation is further investigated by performing micromagnetic simulations. According to the simulation results, we find that both the tube-like Neel-type skyrmions and the bobber-like Neel-type skyrmions can be electrically generated. In particular, the size of the bobber-like Neel-type skyrmions can be effectively reduced by the spin-orbit torques,which leads to the formation of 20 nm Neel-type skyrmions. Our findings could be important for understanding the formation dynamics of nanoscale Neel-type spin textures, skyrmions and bobber in particular, which could also be useful for promoting nanoscale skyrmionic memories and logic devices.

关键词： temperature diameters approaching

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Advanced machine learning decision policies for diameter control of carbon nanotubes

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npj Computational Materials 2021年第1期7卷 1454-1462页

作者： Rahul Rao Jennifer Carpena-Núñez Pavel Nikolaev Michael A.Susner Kristofer G.Reyes Benji Maruyama Materials and Manufacturing Directorate Air Force Research LaboratoryWPAFBDaytonOH 45433USA UES Inc.DaytonOH 45423USA Department of Materials Design and Innovation University at BuffaloBuffaloNY 14260USA

The diameters of single-walled carbon nanotubes(SWCNTs)are directly related to their electronic properties,making diameter control highly desirable for a number of *** we utilized a machine learning planner based on the Expected Improvement decision policy that mapped regions where growth was feasible *** feasible and further optimized synthesis conditions to selectively grow SWCNTs within a narrow diameter *** maximized two ranges corresponding to Raman radial breathing mode frequencies around 265 and 225 cm^(−1)(SWCNT diameters around 0.92 and 1.06 nm,respectively),and our planner found optimal synthesis conditions within a hundred *** post-growth characterization showed high selectivity in the optimized growth experiments compared to the unoptimized growth ***,our planner revealed significantly different synthesis conditions for maximizing the two diameter ranges in spite of their relative *** study shows the promise for machine learning-driven diameter optimization and paves the way towards chirality-controlled SWCNT growth.

关键词： synthesis carbon diameters

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Electronic Localization Length of Carbon Nanotubes with Different Chiral Symmetries

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Chinese Physics Letters 2001年第8期18卷 1105-1107页

作者： YANG Hua-Tong DONG Jin-Ming XING Ding-Yu Department of Physics and National Laboratory of Solid State Microstructures Nanjing UniversityNanjing 210093

The electronic localization lengthsλof metallic carbon nanotubes with different chiral symmetries have been calculated by one parameter scaling *** is found thatλis independent of the nanotube chirality,but depends linearly on their *** dependence ofλon the disorder strength W has also been studied,and a power-law relation betweenλand W is also found to be independent of the tube *** numerical results are in good agreement with recent experimental observations and other theoretical result for only the“armchair”nanotubes.

关键词： diameters scaling Carbon

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Flow Characteristics of Deionized Water in Microtubes Absorbing Fluoro-Alkyl Silanes

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Chinese Physics Letters 2011年第10期28卷 150-153页

作者： QU Chao SONG Fu-Quan Department of Physics Zhejiang Normal University Jinhua 321004

In order to find the drag reduction mechanism of surface wettability,some experiments are carried out to research the flow of deionized water through *** flow rate of liquid through microtubes adsorbing Fluoro–Alkyl silanes(FAS)or not are *** inner diameters of the microtubes are 100µm,75µm and 50µm,*** relations of shear rate and slip velocity,and shear rate and slip length are *** inner surface wettability of the microtubes changes from hydrophilic at a contact angle of 23°to weak hydrophobic at a contact angle of 107°by adsorbing *** results indicate that the flow rate in microtubes adsorbing FAS is larger than those without FAS,the efficiency of drag reduction if about 13%,the slip velocity near the wall is proportional to the shear rate and the slip length remains invariant for different shear rates in microtubes with different diameters.

关键词： diameters inner flow

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Dust-Induced Regulation of Thermal Radiation in Water Droplets

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Chinese Physics Letters 2023年第5期40卷 52-57页

作者：张传新李天骄须留钧黄吉平 Department of Physics State Key Laboratory of Surface Physicsand Key Laboratory of Micro and Nano Photonic Structures(MOE)Fudan UniversityShanghai 200438China MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing 210094China Graduate School of China Academy of Engineering Physics Beijing 100193China

Accurate and fast prediction of thermal radiation properties of materials is crucial for their potential ***,some models assume that the media are made up of pure water droplets,which do not account for the increasing deviations caused by volcanic eruptions,pollution,and human activities that exacerbate dust *** distinct radiation properties of water and dust particles make it challenging to determine the thermal radiation properties of water droplets containing dust *** address this issue,we investigate the influence of dust particles on light transmission and energy distribution in water droplets using the multiple sphere T-matrix *** considering different droplet and dust diameters,volume fractions,and position distributions,we analyze how extinction regulation is achieved in dust-containing water *** results reveal the significant role of dust particles in the thermal radiation effect and provide insights into the electromagnetic properties of colloidal ***,the dust-induced reestablishment of energy balance raises concerns about environmental management and climate *** research highlights the importance of accounting for dust particles in atmospheric models and their potential impact on radiative balance.

关键词： thermal diameters extinction

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Integrating planar photonics for multi-beam generation and atomic clock packaging on chip

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Light(Science & Applications) 2023年第4期12卷 691-701页

作者： Chad Ropp Wenqi Zhu Alexander Yulaev Daron Westly Gregory Simelgor Akash Rakholia William Lunden Dan Sheredy Martin MBoyd Scott Papp Amit Agrawal Vladimir Aksyuk Physical Measurement Laboratory National Institute of Standards and TechnologyGaithersburgMD 20899USA Department of Chemistry and Biochemistry University of MarylandCollege ParkMD 20742USA Vector Atomic Inc.PleasantonCA 94588USA Physical Measurement Laboratory National Institute of Standards and TechnologyBoulderCO 80305USA

The commercialization of atomic technologies requires replacing laboratory-scale laser setups with compact and manufacturable optical *** arrangements of free-space beams can be generated on chip through a combination of integrated photonics and metasurface *** this work,we combine these two technologies using flip-chip bonding and demonstrate an integrated optical architecture for realizing a compact strontium atomic *** planar design includes twelve beams in two co-aligned magneto-optical *** beams are directed above the chip to intersect at a central location with diameters as large as 1 *** design also includes two co-propagating beams at lattice and clock *** beams emit collinearly and vertically to probe the center of the magneto-optical trap,where they will have diameters of≈100μ*** these devices we demonstrate that our integrated photonic platform is scalable to an arbitrary number of beams,each with different wavelengths,geometries,and polarizations.

关键词： planar diameters atomic

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Packing Effect of Excluded Volume on Hard-Sphere Colloids

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Chinese Physics Letters 2001年第7期18卷 950-952页

作者： XIAO Chang-Ming JIN Guo-Jun Ma Yu-Qiang National Laboratory of Solid State Microstructures Nanjing UniversityNanjing 210093

We apply the principle of maximum entropy to consider the excluded volume effect on the phase separation of binary mixtures consisting of hard spheres with two different *** show that a critical volume fraction of hard spheres exists locating the packing of large *** particular,through numerical calculation,we have found that the critical volume fraction becomes lower when the ratioα=σ1/σ2 of large-to-small sphere diameters increases,but becomes higher when the ratio of the large sphere volume fraction to the total volume fraction of large and small spheres increases.

关键词： diameters spheres locating

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Computational design of bimetallic core-shell nanoparticles for hot-carrier photocatalysis

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npj Computational Materials 2018年第1期4卷 389-395页

作者： Luigi Ranno Stefano Dal Forno Johannes Lischner Department of Materials Imperial College LondonLondon SW72AZUK Department of Physics Imperial College LondonLondon SW72AZUK Department of Physics and Department of Materials and the Thomas Young Centre for Theory and Simulation of MaterialsImperial College LondonLondon SW72AZUK

Computational design can accelerate the discovery of new materials with tailored properties,but applying this approach to plasmonic nanoparticles with diameters larger than a few nanometers is challenging as atomistic first-principles calculations are not feasible for such *** this paper,we employ a recently developed material-specific approach that combines effective mass theory for electrons with a quasistatic description of the localized surface plasmon to identify promising bimetallic core-shell nanoparticles for hot-electron ***,we calculate hot-carrier generation rates of 100 different core-shell nanoparticles and find that systems with an alkali-metal core and a transition-metal shell exhibit high figures of merit for water splitting and are stable in aqueous *** analysis reveals that the high efficiency of these systems is related to their electronic structure,which features a two-dimensional electron gas in the *** calculations further demonstrate that hotcarrier properties are highly tunable and depend sensitively on core and shell *** design rules resulting from our work can guide experimental progress towards improved solar energy conversion devices.

关键词： applying alkali diameters

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Rapid Unconscious Acquisition of Conditioned Fear with Low-Spatial-Frequency but Emotionally Neutral Stimuli

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Research 2024年第1期2023卷 753-762页

作者： Yujie Chen Si Chen Zhongju Sun Xilei Zhang Xiangyong Yuan Liang Wang Yi Jiang State Key Laboratory of Brain and Cognitive Sciences CAS Center for Excellence in Brain Science and Intelligence TechnologyInstitute of PsychologyChinese Academy of SciencesBeijing 100101China Department of Psychology University of Chinese Academy of SciencesBeijing 100049China Chinese Institute for Brain Research Beijing 102206China CAS Key Laboratory of Mental Health Institute of PsychologyChinese Academy of SciencesBeijing 100101China

It has long been proposed that emotionally“prepared”(i.e.,fear-related)stimuli are privileged in the unconscious acquisition of conditioned ***,as fear processing is suggested to highly depend on the coarse,low-spatial-frequency(LSF)components of the fear-related stimuli,it is plausible that LSF may play a unique role in the unconscious fear conditioning even with emotionally neutral ***,we provided empirical evidence that,following classical fear conditioning,an invisible,emotionally neutral conditioned stimulus(CS+)with LSF,but not with high spatial frequency(HSF),can rapidly elicit stronger skin conductance responses(SCRs)and larger pupil diameters than its CS−*** comparison,consciously perceived emotionally neutral CS+with LSF and HSF elicited comparable *** together,these results support that the unconscious fear conditioning does not necessarily entail emotionally prepared stimuli but prioritizes LSF information processing and highlight the crucial distinctions between the unconscious and the conscious fear *** findings not only coincide with the postulation that a rapid,spatial-frequency-dependent subcortical route is engaged in unconscious fear processing but also suggest the existence of multiple routes for conscious fear processing.

关键词： neutral necessarily diameters

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