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The pairwise velocity difference of over 2000 BHB stars in the Milky Way halo

Research in Astronomy and Astrophysics 2009年第11期9卷 1230-1240页

作者： xiang-xiang xue Hans-Walter Rix Gang Zhao National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Max-Planck-Institute for Astronomy Konigstuhl 17 D-69117 Heidelberg Germany Graduate University of Chinese Academy of Sciences Beijing 100049 China

Models of hierarchical galaxy formation predict that the extended stellar halos of galaxies like our Milky Way show a great deal of sub-structure, arising from disrupted satellites. Spatial sub-structure is directly observed, and has been quantified, in the Milky Way＇s stellar halo. Phase-space conservation implies that there should be sub-structure in position-velocity space. Here, we aim to quantify such position-velocity sub-structure, using a state-of-the art data set having over 2000 blue horizontal branch （BHB） stars with photometry and spectroscopy from SDSS. For stars in dynamically cold streams （＂young＂ streams）, we expect that pairs of objects that are physically close also have similar velocities. Therefore, we apply the well-established ＂pairwise velocity difference＂（PVD） statistic （｜ △Vlos ｜）（△r）, where we expect （｜ △Vlos ｜） to drop for small separations At. We calculate the PVD for the SDSS BHB sample and find 〈｜ △Vlos ｜〉（△r） ≈ const., i.e. no such signal. By making mock-observations of the simulations by Bullock ＆ Johnston and applying the same statistic, we show that for individual, dynamically young streams, or assemblages of such streams, （｜ △Vlos ｜） drops for small distance separations At, as qualitatively expected. However, for a realistic complete set of halo streams, the pair-wise velocity difference shows no signal, as the simulated halos are dominated by ＂dynamically old＂ phase-mixed streams. Our findings imply that the sparse sampling and the sample sizes in SDSS DR6 are still insufficient to use the position-velocity sub-structure for a stringent quantitative data-model comparison. Therefore, alternate statistics must be explored and much more densely sampled surveys, dedicated to the structure of the Milky Way, such as LAMOST, are needed.

关键词： cosmology dark matter-- galaxies individual (Milky Way) -- galaxy halo -- stars horizontal-branch- stars kinematics

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Optimizing hemicelluloses pre-extraction in eucalyptus kraft pulping:A pathway towards enhancing pulp mill biorefineries

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Chinese Journal of Chemical Engineering 2024年第6期70卷 162-172页

作者： Yuhan Wang Danqi xue Jingjing Zhuo Zhouyang xiang State Key Laboratory of Pulp and Paper Engineering South China University of TechnologyGuangzhou 510640China

A critical pathway towards enhancing pulp mill biorefineries is to integrate the extraction and utilization of hemicelluloses into the pulping ***,an industrial pre-extraction strategy for hemicelluloses targeting eucalyptus kraft pulping process was *** solution or pulping white liquor was used to pre-extract hemicelluloses before the actual pulping *** response surface methodology(RSM)technique was applied to investigate the most suitable conditions to maximize the yield of these hemicelluloses while simultaneously minimizing the damage to pulp yields and ***(105 to 155℃),alkali concentration(3%to 8%),sulfidity(20%to 30%)and retention time(19 to 221 min)were combined to evaluate their effects on hemicellulose yields and chemical *** optimal pre-extraction conditions identified in this work(5.75%NaOH concentration,25%sulfidity at 135℃for 60 min)successfully allowed recovering 4.8%of hemicelluloses(based on the wood dry mass)and limited damages to pulp yields and *** cellulose content in pulp can even be increased by about 10%.Hemicellulose emulsification properties were also evaluated,which were comparable to synthetic *** study provides an industrial pathway to effectively separate and utilize wood hemicelluloses from the pulping process,which has the potential to improve the economy and material utilization of pulp and paper mills.

关键词： Hemicelluloses Xylan Pre-extraction Kraft pulping Emulsifying Response surface methodology(RSM)

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The mass of the Galactic dark matter halo from-9000 LAMOST DR5 K giants

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Research in Astronomy and Astrophysics 2018年第9期18卷 89-100页

作者： Meng Zhai xiang-xiang xue Lan Zhang Cheng-Dong Li Gang Zhao Cheng-Qun Yang National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China

We constrain the mass of the Milky Way＇s dark matter halo, based on the kinematics of 9627 K giants at Galactocentric distances ranging over 5 kpc 〈 r 〈 120 kpc drawn from LAMOST *** substructure in this sample has been identified and removed carefully to enable construction of the underlying line-of-sight velocity dispersion at different radii from the Galactic center. We interpret the radial profile of the line-of-sight velocity dispersion using a spherical Jeans equation under the assumptions of anisotropy/isotropy and that radial velocity dispersion is approximately equal to line-ofsight velocity dispersion σ_r（r）≈σ_（los）（r）. If we assume that the dark matter halo follows an NFW profile and the stellar halo is isotropic（β = 0）, then σlos（r） can be directly used to estimate the virial mass of the Galactic dark matter halo, M_（vir） = 1.08_（-0.14）^（＋0.17） ×10^（12） M⊙, and concentration parameter c = 18.5＋-2.***.3.6 In case that the stellar halo is anisotropic, we cannot avoid differentiation of sparse velocity dispersions according to the Jeans equation, which may cause overestimation of the mass. We use an isotropic case to test and find that d ln（σ_（los）~2 （r））/d ln r overestimates the virial mass by 15% but within 1-σ error. We use d ln（σ2 los（r））/d ln r to fit the NFW profile and get M_（vir） = 1.11_（-0.20）^（＋0.24） ×10^（12） M⊙and c = 13.8-2.2＋3.0 in case of β = 0.3.

关键词： dark matter - Galaxy halo - stars kinematics and dynamics

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Exploring multiple phases and first-order phase transitions in Kármán Vortex Street

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Science China(Physics,Mechanics & Astronomy) 2024年第11期67卷 47-54页

作者： Xu Li Xing xiang Tingting xue Limin Wang Xiaosong Chen School of Systems Science and Institute of Nonequilibrium Systems Beijing Normal UniversityBeijing 100875China State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy ofSciencesBeijing 100190China School of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China

Kármán Vortex Street, a fascinating phenomenon of fluid dynamics, has intrigued the scientific community for a long time. Many researchers have dedicated their efforts to unraveling the essence of this intriguing flow pattern. Here, we apply the lattice Boltzmann method with curved boundary conditions to simulate flows around a circular cylinder and study the emergence of Kármán Vortex Street using the eigen microstate approach, which can identify phase transition and its order-parameter. At low Reynolds number, there is only one dominant eigen microstate W_(1) of laminar flow. At Re_(c)^(1)= 53.6, there is a phase transition with the emergence of an eigen microstate pair W^(2,3) of pressure and velocity fields. Further at Re_(c)^(2)= 56, there is another phase transition with the emergence of two eigen microstate pairs W^(4,5) and W^(6,7). Using the renormalization group theory of eigen microstate,both phase transitions are determined to be first-order. The two-dimensional energy spectrum of eigen microstate for W^(1), W^(2,3) after Re_(c)^(1), W^(4-7) after Re_(c)^(2) exhibit-5/3 power-law behavior of Kolnogorov's K41 theory. These results reveal the complexity and provide an analysis of the Kármán Vortex Street from the perspective of phase transitions.

关键词： Kármán Vortex Street first-order phase transition eigen microstate approach renormalization group theory of eigen microstate

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Toward a fundamental understanding of the heterogeneous multiphysics behaviors of silicon monoxide/graphite composite anodes

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Carbon Energy 2024年第1期6卷 142-158页

作者： xiang Gao Suli Li Jiachen xue Dianyang Hu Jun Xu Department of Mechanical Engineering and Engineering Science University of North Carolina at CharlotteCharlotteNorth CarolinaUSA Vehicle Energy and Safety Laboratory(VESL) Battery ComplexityAutonomous Vehicleand Electrification(BATT CAVE)Research CenterUniversity of North Carolina at CharlotteCharlotteNorth CarolinaUSA Zhuhai CosMX Battery Co.Ltd. ZhuhaiGuangdongChina School of Data Science University of North Carolina at CharlotteCharlotteNorth CarolinaUSA

Silicon monoxide(SiO)(silicon[Si]mixed with silicon dioxide[SiO_(2)])/graphite(Gr)composite material is one of the most commercially promising anode materials for the next generation of high-energy-density lithium-ion *** major bottleneck for SiO/Gr composite anode is the poor cyclability arising from the stress/strain behaviors due to the mismatch between two heterogenous materials during the lithiation/delithiation *** date,a meticulous and quantitative understanding of the highly nonlinear coupling behaviors of such materials is still ***,an electro–chemo–mechanics-coupled detailed model containing particle geometries is *** underlying mechanism of the regulation between SiO and Gr components during electrochemical cycling is quantitatively *** discover that increasing the SiO weight percentage(wt%)reduces the utilization efficiency of the active materials at the same 1C rate charging and enhances the hindering effects of stress-driven flux on *** addition,the mechanical constraint demonstrates a balanced effect on the overall performance of cells and the local behaviors of *** study provides new insights into the fundamental interactions between SiO and Gr materials and advances the investigation methodology for the design and evaluation of next-generation high-energydensity batteries.

关键词： interactions lithium-ion batteries mechanical constraint multiphysics modeling Si-based anode

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Intensified warming suppressed the snowmelt in the Tibetan Plateau

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Advances in Climate Change Research 2024年第3期15卷 452-463页

作者： xiang LI Peng CUI xue-Qin ZHANG Fang ZHANG Key Lab of Land Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources ResearchBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China China‒Pakistan Joint Research Center on Earth Sciences Chinese Academy of Sciences and Higher Education CommissionIslamabad 45320Pakistan

Understanding how hydrological factors interrelate is crucial when examining the impact of climate warming on ***,these connections are often overlooked,leading to an unclear relationship between temperature and *** study investigates the complex interplay between temperature and snowmelt in the Tibetan Plateau from 1961 to 2020,focusing on how extreme high-temperature events affect the frequency of extreme *** a structural equation model,we detected three temperature-related factors that predominantly influenced snowmelt and extreme *** annual average temperature was found to have a significant indirect impact on snowmelt,mediated by changes in snowfall,snow depth and snow *** contrast,high-temperature days(daily maximum temperatures exceeding the 90th percentile)and heat waves(at least three consecutive high-temperature days)negatively affected extreme snowmelt directly or *** direct effect of increasing extreme temperature events was associated with an earlier onset of high-temperature periods,which accelerated snowmelt and shortened the duration of extreme snowmelt ***,the reduction in snow cover owing to warming emerged as a main factor suppressing snowmelt and extreme snowmelt *** also revealed spatiotemporal variations in the temperature‒snowmelt relationship that highly depended on changes in snowmelt *** study elucidated why warming suppresses snowmelt and extreme snowmelt events in the Tibetan Plateau,highlighting the mediating roles of snow-related and phenological *** findings will provide scientific support for climate simulation and water management policymaking in alpine regions worldwide.

关键词： Climate change Extreme temperature Snowmelt Structural equation model Tibetan Plateau

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Learning a Mixture of Conditional Gating Blocks for Visual Question Answering

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Journal of Computer Science & Technology 2024年第4期39卷 912-928页

作者： Qiang Sun Yan-Wei Fu xiang-Yang xue School of Statistics and Information Shanghai University of International Business and EconomicsShanghai 201620China Academy for Engineering and Technology Fudan UniversityShanghai 200433China School of Data Science Fudan UniversityShanghai 200433China School of Computer Science Fudan UniversityShanghai 200433China

As a Turing test in multimedia,visual question answering(VQA)aims to answer the textual question with a given ***,the“dynamic”property of neural networks has been explored as one of the most promising ways of improving the adaptability,interpretability,and capacity of the neural network ***,despite the prevalence of dynamic convolutional neural networks,it is relatively less touched and very nontrivial to exploit dynamics in the transformers of the VQA tasks through all the stages in an end-to-end ***,due to the large computation cost of transformers,researchers are inclined to only apply transformers on the extracted high-level visual features for downstream vision and language *** this end,we introduce a question-guided dynamic layer to the transformer as it can effectively increase the model capacity and require fewer transformer layers for the VQA *** particular,we name the dynamics in the Transformer as Conditional Multi-Head Self-Attention block(cMHSA).Furthermore,our questionguided cMHSA is compatible with conditional ResNeXt block(cResNeXt).Thus a novel model mixture of conditional gating blocks(McG)is proposed for VQA,which keeps the best of the Transformer,convolutional neural network(CNN),and dynamic *** pure conditional gating CNN model and the conditional gating Transformer model can be viewed as special examples of *** quantitatively and qualitatively evaluate McG on the CLEVR and VQA-Abstract *** experiments show that McG has achieved the state-of-the-art performance on these benchmark datasets.

关键词： visual question answering Transformer dynamic network

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Oxidation behavior of low-grade vanadiferous titanomagnetite concentrate with high titanium

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Journal of Iron and Steel Research International 2024年第2期31卷 329-341页

作者： Jin-sheng Liu Zhen-xing Xing Gong-jin Cheng xue-yong Ding xiang-xin xue School of Metallurgy Northeastern UniversityShenyang110819LiaoningChina Liaoning Key Laboratory of Recycling Science for Metallurgical Resources Shenyang110819LiaoningChina Innovation Research Institute of Vanadium and Titanium Resource Industry Technology Northeastern UniversityShenyang110819LiaoningChina

In order to clarify the oxidation mechanisms and make better use of the low-grade vanadiferous titanomagnetite concentrate with high titanium(LVTC),the oxidation behavior of LVTC was *** results showed that oxidation degree was achieved within 90 min when temperature was not lower than 700°C,and the main phases of the oxidized LVTC consisted of Fe9TiO15,Fe2O3,CaSiTiO5 and a small amount of *** temperature is favorable to the formation of *** surface of LVTC gradually becomes rough,with fine particles of needle-like and granular shape appearing on the surface,which finally turn from laminar to creamy,spread out,and are interspersed with many tiny *** phase oxidation paths in LVTC were as follows:(1)Fe2.75Ti0.25O4→Fe9TiO15+Fe2O3;(2)Fe2.75Ti0.25O4→Fe2O3+FeTiO3→Fe2TiO5;(3)FeTiO3→Fe2O3+Fe2Ti3O9→*** is predominantly mesoporous whether oxidized or not,with the pores mainly distributed in the range of 2–40 nm,and the specific surface area of LVTC decreases significantly with increasing temperature.

关键词： Low-grade vanadiferous titanomagnetite concentrate Oxidation degree Phase transformation Micromorphology Oxidation path Pore structure

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Characteristic Study of Self-Powered Sensors Based on Native Protein Composite Film

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Energy & Environmental Materials 2024年第1期7卷 222-228页

作者： Jiehui xue Huijing xiang Yanrong Zhang Jun Yang Xia Cao Zhonglin Wang Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of SciencesBeijing 101400China School of Resources Environment and MaterialsSchool of PhysicsScience and TechnologyCenter on Nanoenergy ResearchGuangxi UniversityNanning 530004China Center for Green Innovation School of Mathematics and PhysicsUniversity of Science and Technology BeijingBeijing 100083China Research Centre of Information Technology Shenzhen Institute of Information TechnologyShenzhen 518172China School of Chemistry and Biological Engineering University of Science and Technology BeijingBeijing 100083China School of Materials Science and Engineering Georgia Institute of TechnologyAtlanta GA 30332-0245USA

Flexible electronic sensors composed of flexible film and conductive materials play an increasingly important role in wearable and internet information *** has received more and more attention and made some progress over the ***,it is still a great challenge to prepare biocompatible and highly transparent conductive *** white is a pure natural protein-rich *** cellulose has a good compatibility and high transparency,which is an ideal material for flexible ***,we overcome the problem of poor mechanical flexibility and electrical conductivity of protein,and develop a high transparency and good flexibility hydroxypropylmethyl cellulose/egg white protein composite membrane-based triboelectric nanogenerator('X'-TENG).The experimental results show that the flexible pressure sensor based on'X'-TENG has a high sensitivity,fast response speed,and low detection *** can even be used as a touch/pressure sensing artificial electronic *** can also be made into an intelligent waffle keyboard for recording and tracking users of the *** strategy may provide a new way to easily build flexible electronic sensors and move toward practical applications.

关键词： flexible sensors intelligent sensing natural protein-rich material triboelectric nanogenerators

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Influence of pressure disturbance wave on dynamic response characteristics of liquid film seal for multiphase pump

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Petroleum Science 2024年第3期21卷 2048-2065页

作者： Qing-Ping Li Jin-Ya Zhang Jia-xiang Zhang Yong-xue Zhang CNOOC Research Institute Company Limited Beijing100028China State Key Laboratory of Natural Gas Hydrate Beijing100028China College of Mechanical and Transportation Engineering China University of PetroleumBeijing2249China

Slug flow or high GVF(Gas Volume Fraction)conditions can cause pressure disturbance waves and alternating loads at the boundary of mechanical seals for multiphase pumps,endangering the safety of multiphase pump *** mechanical seal model is simplified by using periodic boundary conditions and numerical calculations are carried out based on the Zwart-Gerber-Belamri cavitation ***(User Define Function)programs such as structural dynamics equations,alternating load equations,and pressure disturbance equations are embedded in numerical calculations,and the dynamic response characteristics of mechanical seal are studied using layered dynamic mesh *** results show that when the pressure disturbance occurs at the inlet,as the amplitude and period of the disturbance increase,the film thickness gradually *** the fundamental reason for the hysteresis of the film thickness change is that the pressure in the high-pressure area cannot be restored in a timely *** maximum value of leakage and the minimum value of axial velocity are independent of the disturbance period and determined by the disturbance *** mutual interference between enhanced waves does not have a significant impact on the film thickness,while the front wave in the attenuated wave has a promoting effect on the subsequent film thickness changes,and the fluctuation of the liquid film cavitation rate and axial velocity under the attenuated wave condition deviates from the initial *** with pressure disturbance conditions,alternating load conditions have a more significant impact on film thickness and *** actual operation,it is necessary to avoid alternating load conditions in multiphase pump mechanical seals.

关键词： Multiphase pump Liquid film seal Pressure disturbance wave Dynamic response characteristics

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