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A search for metal-poor stars pre-enriched by pair-instability supernovae I. A pilot study for target selection from Sloan Digital Sky Survey

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Research in Astronomy and Astrophysics 2012年第12期12卷 1637-1648页

作者： Jing ren Norbert Christlieb gang Zhao School of Space Science and Physics Shandong University at Weihai Weihai 264209 China Zentrum ftir Astronomie der Universitat Heidelberg Landessternwarte Konigstuhl 12 D-69117Heidelberg Germany Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

We report on a pilot study on identifying metal-poor stars pre-enriched by Pair-Instability Supernovae（PISNe）.Very massive,first generation（Population Ⅲ） stars（140 M⊙≤M≤260 M⊙）end their lives as PISNe,which have been predicted by theories,but no relics of PISNe have been observed *** the distinct characteristics of the yields of PISNe,as predicted by theoretical calculations,are a strong odd-even effect,and a strong overabundance of Ca with respect to iron and the solar *** use the latter characteristic to identify metal-poor stars in the Galactic halo that have been pre-enriched by PISNe,by comparing metallicites derived from strong, co-added Fe lines detected in low-resolution（i.e.,R=λ/△λ～2000）spectra of the Sloan Digital Sky Survey（SDSS）,with metallicities determined by the SDSS Stellar Parameters Pipeline（SSPP）.The latter are based on the strength of the CaⅡ K line and assumptions on the Ca/Fe abundance *** are selected as candidates if their metallicity derived from Fe lines is significantly lower than the SSPP *** a sample of 12 300 stars for which SDSS spectroscopy is available,we have identified 18 candidate *** resolution and signal-to-noise ratio spectra of these candidates are being obtained with the Very Large Telescope of the European Southern Observatory and the XSHOOTER spectrograph,to determine their abundance patterns,and to verify our selection *** plan to apply our method to the database of several million stellar spectra to be acquired with the Guo Shou Jing Telescope （LAMOST）in the next five years.

关键词： stars:PopulationⅡ PopulationⅢ-stars:supernovae(PISNe)-stars: abundance-stars:chemically peculiar-method:data analysis-techniques:spec- troscopic-instrumentation:spectrographs

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First-principles Calculations of Strengthening Compounds in Magnesium Alloy： A General Review

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Journal of Materials Science & Technology 2016年第12期32卷 1222-1231页

作者： Yong Liu Hui ren Wen-cheng Hu De-Jiang Li Xiao-Oin Zeng Ke-gang Wang Jian Lu Key Laboratory of Near Net Forming of Jiangxi Province. Nanchang University Nanchang 330031 China National Engineering Research Center of Light Alloys Net Forming Shanghai Jiao Tong University Shanghai 200240 China State Key Laboratories of Metal Matrix Composite Shanghai Jiao Tong University Shanghai 200240 China Mechanical and Aerospace Engineering Department Florida Institute of Technology Melbourne FL 32901 USA Department of Mechanical and Biomedical Engineering City University of Hong Kong Kowloon Hong Kong China Centre for Advanced Structural Materials City University of Hong Kong Shenzhen Research Institute 8 Yuexing 1st Road Shenzhen Hi-Tech Industrial Park Nanshon District Shenzhen China

First-principles computation methods play an important role in developing and designing new magnesium *** this article,we present an overview of the first-principles modeling techniques used in recent years to simulate ideal models of the structure of strengthening compounds in Mg *** typical Mg compounds,structural stability,mechanical properties,electronic structure and thermodynamic properties have been ***,the elastic anisotropies of these compounds are examined,which is highly correlated with the possibility of inducing ***,some heterogeneous nucleation interfaces investigated by first-principles method are *** of the theoretical results are compared with available experimental *** hope to illustrate that the first-principles computation can help to accelerate the design of new Mg-based materials and the development of materials genome *** problems and future directions in this research field are considered.

关键词： Magnesium alloy Strengthening compounds First-principles calculation Mechanical properties Thermodynamic properties

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A Prelude Staircase to a Type V Intermittency in Two—Dimensional Discontinuous Maps

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Communications in Theoretical Physics 2003年第6期39卷 657-662页

作者： WANGXU-Ming ZHAOJin-gang HEDa-ren SchoolofPhysicsandElectricInformation NingxiaUniversityYinchuan750021China ComplexScienceCenter yangzhouUniversityYangzhou225002China

A sequence of periodic attractors has been observed in a two-dimensional discontinuous map, which canbe considered as a model of impact oscillator. The so-called 'transfer number', which is defined as the mean numberof transfer from non-impact state to impact state per iteration, is locked onto a lot of rational values to form a curveconsisting of many steps. Our numerical investigation confirms that every step is confined by conditions created by thecollision between the periodic orbit and the discontinuous boundary of the system. After the last collision the systemshows a chaotic motion with intermittent characteristics. Therefore the staircase can be addressed as a 'prelude staircaseto type V intermittency'. The similar phenomenon has also been observed in a model of electric circuit. These resultsof our study suggest that this kind of staircases is common in two (or even higher) dimensional discontinuous maps.

关键词： two-dimensional map type V intermittency prelude staircase

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Model and application of bidirectional pedestrian flows at signalized crosswalks

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Chinese Physics B 2018年第7期27卷 606-618页

作者： Tao Zhang gang ren Zhi-gang Yu Yang Yang Jiangsu Key Laboratory of Urban ITS Southeast UniversityNanjing 210096China

This research of bidirectional pedestrian flows at signalized crosswalks is divided into two parts： model and applica- tion. In the model part, a mixed survey including the questionnaire investigation and tracking investigation is conducted to gain the basic data about walking tendentiousness of a pedestrian crossing. Then, the forward, right-hand, outstripping, and influential coefficients are outlined to quantize walking tendentiousness of pedestrian crossing and estimate transition probabilities of pedestrians. At last, an improved cellular automation model is proposed to describe walking tendentious- ness and crossing behaviors of pedestrians. In the application part, channelization research of bidirectional pedestrian flows is presented for real signalized crosswalk. In this process, the effects of right-side-walking and conformity behaviors on the efficiency of pedestrian crossing are thoroughly analyzed based on simulations and experiments to obtain a final channelization method to raise the efficiency of a pedestrian crossing at the crosswalk.

关键词： pedestrian flows right-side-walking behavior conformity behavior simulation

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苗草专用型大麦品种鉴定及全基因组关联分析

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作物学报 2025年第1期51卷 91-102页

作者：马敏虎常华瑜陈朝燕仁增刘廷辉邢国芳郭刚刚山西农业大学农学院/杂粮种质创新与分子育种山西省重点实验室山西晋中030801 中国农业科学院作物科学研究所/农业农村部粮食作物基因资源评价利用重点实验室/农作物基因资源与基因改良国家重大科学工程北京100081 甘孜藏族自治州农业科学研究所四川甘孜626000

苗草工厂为实现草食动物的饲草周年供应提供了新的解决方案。针对苗草生产的品种需求,本研究对124份中国大麦育成品种(系)与种质开展了苗草转化率鉴定和生物量调控位点发掘。结果显示,大麦种子萌动后,水培条件下苗草生物量呈指数增长趋... 详细信息

苗草工厂为实现草食动物的饲草周年供应提供了新的解决方案。针对苗草生产的品种需求,本研究对124份中国大麦育成品种(系)与种质开展了苗草转化率鉴定和生物量调控位点发掘。结果显示,大麦种子萌动后,水培条件下苗草生物量呈指数增长趋势并在7 d后进入平台期。在植物工厂条件下,鉴定出冬青16、扎青6号等10个高苗草转化率品种且分析发现苗草生物量与籽粒千粒重呈一定的负相关。进一步通过全基因组关联分析,共鉴定到12个苗草生物量相关QTL位点,从中预测出8个调控苗草生物量的候选基因。本研究不仅为大麦苗草工厂化生产筛选出高转化率品种,同时也为苗草专用型大麦品种的遗传改良奠定了基础。

关键词：大麦苗草生物量调控位点全基因组关联分析

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Effect of Manufacturing Errors on Static Characteristics of Externally Pressurized Spherical Air Bearings

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Chinese Journal of Mechanical Engineering 2009年第6期22卷 896-902页

作者： ren Di WANG Zuwen YANG Qingjun BAO gang School of Mechanical and Electrical Engineering Harbin Institute of Technology Harbin 150001 China Transportation and Logistics Engineering College Dalian Maritime University Dalian 116026 China

Externally pressurized spherical air bearings are the key component of the three-axis air bearing table, and the manufacturing errors of the bearing affects the performance of the air bearing table. However, the manufacturing errors are unavoidable, and the pursuit to enhance the manufacturing accuracy will increase the cost greatly. In order to provide some theoretical guideline for the tolerance choice in the design of the externally pressurized spherical air bearings with inherent compensation, the effects of several manufacturing errors on the static characteristics of the air bearing are studied. Due to the complex geometry of the computational domain, an unstructured meshing technology is used for mesh generation. A finite-volume method is adopted to discretize the three-dimensional steady-state compressible Navier-Stokes equations. A modified SIMPLE algorithm which is suitable for compressible flows is applied to solve the discretized governing equations. The effects of the dimension error and the roundness error of the ball head and the ball socket on the static characteristics are investigated. The investigation result shows that the positive dimension error and the oblate spheroid-type roundness error of the ball head as well as the negative dimension error and the prolate spheroid-type roundness error of the ball socket can improve the bearing capacity and static stiffness of the air bearings by reducing the mass flow. The calculation method proposed in this paper fits well for the general principle, which can be extended to the characteristics analysis of other air bearings.

关键词： externally pressurized spherical air bearings manufacturing errors bearing capacity static stiffness mass flow

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Is Yang-Mills theory unitary in fractional spacetime dimensions?

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Science China(Physics,Mechanics & Astronomy) 2024年第7期67卷 59-64页

作者： Qingjun Jin Ke ren gang Yang Rui Yu Graduate School of China Academy of Engineering Physics Beijing 100193China School of Physics and Astronomy Sun Yat-Sen UniversityZhuhai 519082China CAS Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesHangzhou 310024China International Centre for Theoretical Physics Asia-Pacific Hangzhou 310024China School of Physical Science and Technology Inner Mongolia UniversityHohhot 010021China Beijing Computational Science Research Center Beijing 100193China

We present concrete evidence that Yang-Mills theory exhibits non-unitarity in non-integer spacetime *** violation of unitarity stems from evanescent operators that,while vanishing in four dimensions,are non-zero in general d *** demonstrate that these evanescent operators lead to the emergence of both negative-norm states and complex anomalous dimensions.

关键词： gauge field theories field theories in dimensions other than four renormalization

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Secure DHCPv6 Mechanism for DHCPv6 Security and Privacy Protection

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Tsinghua Science and Technology 2018年第1期23卷 13-21页

作者： Lishan Li gang ren Ying Liu Jianping Wu Institute for Network Sciences and Cyberspace Tsinghua University Beijing 100084 China

With the rapid developmen of the Internet, the exhaustion of IPv4 address limited the development of the Internet for years. IPv6, as the core technology of the next generation Internet, has since been rapidly deployed around the world. As the widely deployed address configuration protocol, DHCPv6 is responsible for allocating globally unique IPv6 addresses to clients, which is the basis for all the network services. However, the initial design of the DHCPv6 protocol gave little consideration to the privacy and security issues, which has led to a proliferation of privacy and security accidents breaches in its real deployment. In this paper, to fundamentally solve a range of possible security and privacy issues, we propose a secure DHCPv6 mechanism, which adds authentication and encryption mechanisms into the original DHCPv6 protocol. Compared with other proposed security mechanisms for the DHCPv6, our method can achieve all-around protection for the DHCPv6 protocol with minimal change to the current protocol, easier deployment, and low computing cost.

关键词： DHCPv6 security privacy IETF authentication encryption

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RISP： An RPKI-Based Inter-AS Source Protection Mechanism

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Tsinghua Science and Technology 2018年第1期23卷 1-12页

作者： Yihao Jia Ying Liu gang ren Lin He Institute for Network Sciences and Cyberspace Tsinghua University Beijing 100084 China

IP source address spoofing is regarded as one of the most prevalent components when launching an anonymous invasion, especially a Distributed Denial-of-Service （DDoS） attack. Although Source Address Validations （SAVs） at the access network level are standardized by the Internet Engineering Task Force （iETF）, SAV at the inter-Autonomous System （AS） level still remains an important issue. To prevent routing hijacking, the IETF is constructing a Resource Public Key Infrastructure （RPKI） as a united trust anchor to secure interdomain routing, in this study, we creatively use the RPKI to support inter-AS SAV and propose an RPKI-based Inter-AS Source Protection （RISP） mechanism. According to the trust basis provided by the RPKI, RISP offers ASes a more credible source-oriented protection for the IP addresses they own and remains independent of the RPKI. Based on the experiments with real Internet topology, RISP not only provides better incentives, but also improves efficacy and economizes bandwidth with a modest resource consumption.

关键词： IP spoofing source address validation inter-AS RPKI DDoS

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InAlAs/InGaAs Quantum Well Infrared Photodetectors with 3-5μm Band Grown by Gas Source Molecular Beam Epitaxy

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Chinese Physics Letters 1997年第6期14卷 443-445页

作者： ZHANG Yong-gang LI Ai-zhen CHEN Jian-xin ren Yao-cheng State Key Laboratory of FUnctional Materials for Informatics Shanghai Institute of MetallurgyChinese Academy of SciencesShanghai 200050

The relationship between well width and subband energy as well as response wavelength of the InAlAs/InGaAs multi-quantum well structures have been calculated for the design of the devices by using Kronig-Penney *** using gas source molecular beam epitaxy grown InAlAs/InGaAs quantum well infrared photodetector(QWIP)materials have been used to fabricate QWIP devices with 3-5μm band.Ⅰ-Ⅴ characteristics and response spectra of the devices have been *** show that the devices have peak response at 4.0μm with full width of half maximum of about 29.5meV.

关键词： InAlAs/InGaAs Epitaxy Infrared

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