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Driving factors behind multiple populations

Science China(Physics,Mechanics & Astronomy) 2024年第5期67卷 172-181页

作者： Ruoyun Huang Baitian Tang Chengyuan Li doug Geisler Mario Mateo Ying-Yi Song Holger Baumgardt Julio A.Carballo-Bello Yue Wang Jundan Nie Bruno Dias JoséG.Fernández-Trincado School of Physics and Astronomy Sun Yat-sen UniversityZhuhai 519082China CSST Science Center for the Guangdong-Hong Kong-Macao Greater Bay Area Zhuhai 519082China Departamento de Astronomía Universidad de ConcepcionConcepcionChile Instituto de Investigación Multidisciplinario en Ciencia y Tecnología Universidad de La SerenaLa SerenaChile Departamento de Astronomía Facultad de CienciasUniversidad de La SerenaChile Department of Astronomy University of MichiganAnn Arbor 48109USA David A.Dunlap Department of Astronomy&Astrophysics University of TorontoToronto ON M5S 3H4Canada Dunlap Institute for Astronomy&Astrophysics University of TorontoToronto ON M5S 3H4Canada School of Mathematics and Physics The University of QueenslandSt.Lucia QLD 4072Australia Instituto de Alta Investigación Universidad de TarapacáAricaChile CAS Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Instituto de Astrofísica Departamento de Ciencias FísicasFacultad de Ciencias ExactasUniversidad Andres BelloSantiagoChile Instituto de Astronomía Universidad Católica del NorteAntofagastaChile

Star clusters were historically considered simple stellar populations,with all stars sharing the same age and initial chemical ***,the presence of chemical anomalies in globular clusters(GCs),called multiple stellar populations(MPs),has challenged star formation theories in dense *** studies show that mass,metallicity,and age are likely controlling parameters for the manifestation of *** the limit between clusters with/without MPs in physical parameter space is crucial to reveal the driving mechanism behind their *** this study,we look for MP signals in Whiting 1,which is traditionally considered a young *** the Magellan telescope,we obtained low-resolution spectra withinλλ=3850-5500?for eight giants of Whiting *** measured the C and N abundances from the CN and CH spectral indices.C and N abundances have variations comparable with their measurement errors(~0.1 dex),suggesting that MPs are absent from Whiting *** these findings with literature studies,we propose a limit in the metallicity *** compactness index parameter space,which relatively clearly separates star clusters with/without MPs(GCs/open clusters).This limit is physically *** a larger scale,the galactic environment determines cluster compactness and metallicity,leading to metal-rich,diffuse,old clusters formed ex *** proposed limit also impacts our understanding of the formation of the Sagittarius dwarf galaxy:star clusters formed after the first starburst(age≤8-10 Gyr).These clusters are simple stellar populations because the enriched galactic environment is no longer suitable for MP formation.

关键词： stellar galactic galaxy

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COADJOINT ORBITS FOR THE CENTRAL EXTENSION OF Diff^+(S^1) AND THEIR REPRESENTATIVES

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Acta Mathematica Scientia 2004年第2期24卷 185-205页

作者：戴佳玲 doug pickrell Department of Mathematics the University of ArizonaTucsonAZ85721USA

According to Kirillov's idea, the irreducible unitary representations of a Lie group G roughly correspond to the coadjoint orbits (?).In the forward direction one applies the methods of geometric quantization to produce a representation, and in the reverse direction one computes a transform of the character of a representation, to obtain a coadjoint orbit. The method of orbits in the representations of Lie groups suggests the detailed study of coadjoint orbits of a Lie group G in the space (?)~* dual to the Lie algebra (?) of G. In this paper, two primary goals are achieved: one is to completely classify the smooth coadjoint orbits of Virasoro group for nonzero central charge c; the other is to find representatives for coadjoint orbits. These questions have been considered previously by Segal, Kirillov, and Witten, but their results are not quite complete. To accomplish this, the authors start by describing the coadjoint action of D-the Lie group of all orientation preserving diffeomorphisms on the circle S^1, and its central extension (?), then the authors will give a complete classification of smooth coadjoint orbits. In fact, they can be parameterized by a subspace Of conjugacy classes of (?)(1,1). Finally, the authors will show how to find representatives f coadjoint orbits by analyzing the vector fields stabilizing the orbits, and describe the amazing connection between the characteristic (trace) of conjugacy classes of (?)(1, 1) and that of vector fields stabilizing orbits.

关键词： Coadjoint representations coadjoint orbits stabilizers vector fields representatives

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Development of a spring analogue approach for the study of pillars and shafts

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International Journal of Mining Science and Technology 2018年第2期28卷 267-274页

作者： Amichai Mitelman Davide Elmo doug Stead NBK Institute of Mining Engineering University of British Columbia Department of Earth Sciences Simon Fraser University

In civil and mining operations that involve ground excavation and support, the loads are distributed between the ground and support depending on their relative stiffness. This paper presents the development of conceptual single-degree-of-freedom models, which are used to derive equations for estimating displacements and stresses for ground-support interaction problems encountered in pillars in room-andpillar mining(natural support system), and liners for circular vertical shafts(artificial support systems).For pillar assessment, mine-pillar interaction curves can be constructed using a double spring ***, the effectiveness of different support systems can be evaluated depending on their effect upon the mine-pillar system. For shaft design, an initial estimation of the required lining strength and thickness can be readily made based on a double ring analogue. For both problems, the results from the proposed approach compare well with those obtained by finite element numerical simulations.

关键词： Room and pillar Shafts Ground-support interaction Spring analogue Rockbolts

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A 360-Degree Panoramic Image Inpainting Network Using a Cube Map

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Computers, Materials & Continua 2021年第1期66卷 213-228页

作者： Seo Woo Han doug Young Suh Department of Electronic Engineering Kyung Hee UniversityYoungin17104South Korea

Inpainting has been continuously studied in the field of computer *** artificial intelligence technology developed,deep learning technology was introduced in inpainting research,helping to improve ***,the input target of an inpainting algorithm using deep learning has been studied from a single image to a ***,deep learning-based inpainting technology for panoramic images has not been actively *** propose a 360-degree panoramic image inpainting method using generative adversarial networks(GANs).The proposed network inputs a 360-degree equirectangular format panoramic image converts it into a cube map format,which has relatively little distortion and uses it as a training *** the cube map format is used,the correlation of the six sides of the cube map should be ***,all faces of the cube map are used as input for the whole discriminative network,and each face of the cube map is used as input for the slice discriminative network to determine the authenticity of the generated *** proposed network performed qualitatively better than existing single-image inpainting algorithms and baseline algorithms.

关键词： Panoramic image image inpainting cube map generative adversarial networks

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New approaches to quantify progressive damage and associated dynamic rock mass blockiness

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第2期15卷 285-295页

作者： Ladan Karimi Sharif Davide Elmo doug Stead NBK Institute of Mining Engineering The University of British ColumbiaVancouverCanada Department of Earth Science Simon Fraser UniversityBurnabyCanada

In the past decade, numerical modelling has been increasingly used for simulating the mechanical behaviour of naturally fractured rock masses. In this paper, we introduce new algorithms for spatial and temporal analyses of newly generated fractures and blocks using an integrated discrete fracture network (DFN)-finite-discrete element method (FDEM) (DFN-FDEM) modelling approach. A fracture line calculator and analysis technique (i.e. discrete element method (DEM) fracture analysis, DEMFA) calculates the geometrical aspects of induced fractures using a dilation criterion. The resultant two-dimensional (2D) blocks are then identified and characterised using a graph structure. Block tracking trees allow track of newly generated blocks across timesteps and to analyse progressive breakage of these blocks into smaller blocks. Fracture statistics (number and total length of initial and induced fractures) are then related to the block forming processes to investigate damage evolution. The combination of various proposed methodologies together across various stages of modelling processes provides new insights to investigate the dependency of structure's resistance on the initial fracture configuration.

关键词： Numerical modelling Spatial analysis Temporal analysis Discrete fracture network(DFN) Finite-discrete element method(FDEM)modelling Block calculations Graph structure

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Structure-Based Deadlock Checking of Asynchronous Circuits

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Journal of Computer Science & Technology 2011年第6期26卷 1031-1040页

作者：任洪广王志英 doug Edwards School of Computer National University of Defense Technology CCF ACM IEEE School of Computer Science University of Manchester

It is important to verify the absence of deadlocks in asynchronous circuits. Much previous work relies on a reachability analysis of the circuits＇ states, with the use of binary decision diagrams （BDDs） or Petri nets to model the behaviors of circuits. This paper presents an alternative approach focusing on the structural properties of well-formed asynchronous circuits that will never suffer deadlocks. A class of data-driven asynchronous pipelines is targeted in this paper, which can be viewed as a network of basic components connected by handshake channels. The sufficient and necessary conditions for a component network consisting of Steer, Merge, Fork and Join are given. The slack elasticity of the channels is analyzed in order to introduce pipelining. As an application, a deadlock checking method is implemented in a syntax-directed asynchronous design tool Team The proposed method shows a great runtime advantage when compared against previous Petri net based verification tools.

关键词： asynchronous pipeline data-driven deadlock verification

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Influence of vitamin D on liver fibrosis in chronic hepatitis C: A systematic review and meta-analysis of the pooled clinical trials data

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World Journal of Hepatology 2017年第5期9卷 278-287页

作者： Alia S Dadabhai Behnam Saberi Katie lobner Russell T Shinohara Gerard E Mullin Division of Gastroenterology and Hepatology the Johns Hopkins University School of Medicine Department of Biostatistics and Epide-miology Perelman School of Medicine University of Pennsylvania

AIM To investigate the relationship between vitamin D and liver fibrosis in hepatitis C-monoinfected or hepatitis C virus(HCV)-human immunodeficiency virus(HIV) coinfected patients. METHODS Pertinent studies were located by a library literature search in PubM ed/Embase/Cochrane/Scopus/LILACS by two individual reviewers. Inclusion criteria:(1) studies with patients with HCV or co-infected HCV/HIV;(2) studies with patients ≥ 18 years old;(3) studies that evaluated liver fibrosis stage, only based on liver biopsy; and(4) studies that reported serum or plasma 25(OH)D levels. Studies that included pediatric patients, other etiologies of liver disease, or did not use liver biopsy for fibrosis evaluation, or studies with inadequate data were excluded. Estimated measures of association reported in the literature, as well as corresponding measures of uncertainty, were recorded and corresponding odds ratios with 95%CI were included in a meta-analysis. RESULTS The pooled data of this systematic review showed that 9 of the 12 studies correlated advanced liver disease defined as a Metavir value of F3/4 with 25(OH) D level insufficiency. The meta-analysis indicated a significant association across *** Low vitamin D status is common in chronic Hepatitis C patients and is associated with advanced liver fibrosis.

关键词： Vitamin D Liver fibrosis Hepatitis C virus Chronic hepatitis C

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Variations in net litter nutrient input associated with tree species influence on soil nutrient contents in a subtropical evergreen broad-leaved forest

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Chinese Science Bulletin 2014年第1期59卷 46-53页

作者： Lu Qiao doug Allen Schaefer Xiaoming Zou Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical Garden Chinese Academy of Sciences University of Chinese Academy of Sciences Department of Environmental Studies University of Puerto Rico

The influence of tree species on soils has received much attention,but we know little about either the pattern and underlying mechanisms of net nutrient and carbon inputs under canopy for various tree species or the effects of net nutrient input on soil nutrient *** address these issues,we selected three tree species with distinct leaf sizes and arranged litter traps around the target individuals to test what affected net nutrient and carbon inputs under canopy of target individuals,and how net nutrient inputs influenced soil nutrient *** results showed that net litter manganese(Mn)and lignin inputs were significantly different among these tree species,as well as soil exchangeable potassium(K),available iron(Fe)and available *** results also revealed that the species with the smallest sized leaves may stimulate more net Mn and lignin inputs than the species with the largest sized *** the same time,net nutrient inputs correlated with soil available Fe,while the ratio of lignin to nitrogen of net litter correlated with total phosphorus *** results demonstrated that litter production may be the main factor deciding net nutrient and carbon inputs under different tree species’canopy,which significantly differentiated soil iron’s availability.

关键词：土壤养分含量亚热带常绿阔叶林树种枯落物输入营养养分投入木质素

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Efficient Computation Offloading in Mobile Cloud Computing for Video Streaming Over 5G

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Computers, Materials & Continua 2019年第8期61卷 439-463页

作者： Bokyun Jo MdJalil Piran Daeho Lee doug Young Suh DEE Kyung Hee UniversityYongin17104South Korea DCSE Sejong UniversitySeoul05006South Korea

In this paper,we investigate video quality enhancement using computation offloading to the mobile cloud computing(MCC)*** objective is to reduce the computational complexity required to covert a low-resolution video to high-resolution video while minimizing computation at the mobile client and additional communication *** do so,we propose an energy-efficient computation offloading framework for video streaming services in a MCC over the fifth generation(5G)cellular *** the proposed framework,the mobile client offloads the computational burden for the video enhancement to the cloud,which renders the side information needed to enhance video without requiring much computation by the *** cloud detects edges from the upsampled ultra-high-resolution video(UHD)and then compresses and transmits them as side information with the original low-resolution video(e.g.,full HD).Finally,the mobile client decodes the received content and integrates the SI and original content,which produces a high-quality *** our extensive simulation experiments,we observed that the amount of computation needed to construct a UHD video in the client is 50%-60% lower than that required to decode UHD video compressed by legacy video encoding ***,the bandwidth required to transmit a full HD video and its side information is around 70% lower than that required for a normal UHD *** subjective quality of the enhanced UHD is similar to that of the original UHD video even though the client pays lower communication costs with reduced computing power.

关键词： 5G video streaming cloud computation offloading energy efficiency upsampling MOS

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Characterizing the influence of stress-induced microcracks on the laboratory strength and fracture development in brittle rocks using a finite-discrete element method-micro discrete fracture network FDEM-μDFN approach

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第6期7卷 609-625页

作者： Pooya Hamdi doug Stead Davide Elmo Simon Fraser University 8888 University Drive NBK Institute of Mining Engineering University of British Columbia

Heterogeneity is an inherent component of rock and may be present in different forms including mineralheterogeneity, geometrical heterogeneity, weak grain boundaries and micro-defects. Microcracks areusually observed in crystalline rocks in two forms： natural and stress-induced; the amount of stressinducedmicrocracking increases with depth and in-situ stress. Laboratory results indicate that thephysical properties of rocks such as strength, deformability, P-wave velocity and permeability areinfluenced by increase in microcrack intensity. In this study, the finite-discrete element method （FDEM）is used to model microcrack heterogeneity by introducing into a model sample sets of microcracks usingthe proposed micro discrete fracture network （mDFN） approach. The characteristics of the microcracksrequired to create mDFN models are obtained through image analyses of thin sections of Lac du Bonnetgranite adopted from published literature. A suite of two-dimensional laboratory tests including uniaxial,triaxial compression and Brazilian tests is simulated and the results are compared with laboratory *** FDEM-mDFN models indicate that micro-heterogeneity has a profound influence on both the mechanicalbehavior and resultant fracture pattern. An increase in the microcrack intensity leads to areduction in the strength of the sample and changes the character of the rock strength envelope. Spallingand axial splitting dominate the failure mode at low confinement while shear failure is the dominantfailure mode at high confinement. Numerical results from simulated compression tests show thatmicrocracking reduces the cohesive component of strength alone, and the frictional strength componentremains unaffected. Results from simulated Brazilian tests show that the tensile strength is influenced bythe presence of microcracks, with a reduction in tensile strength as microcrack intensity increases. Theimportance of microcrack heterogeneity in reproducing a bi-linear or S-shape failure

关键词： Finite-discrete element method(FDEM) Micro discrete fracture network(μDFN) Brittle fracture

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