Asymmetric explosions of thermonuclear supernovae     

C. R. Ghezzi  E. M. de Gouveia Dal Pino  J. E. Horvath 《Monthly notices of the Royal Astronomical Society》2004,348(2):451-457

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EFFECT OF ANTHROPOGENIC CO_2 ON THE pH AND THE SATURATION STATES OF CALCITE AND ARAGONITE OF SEAWATER     

陈镇东  王树伦 《中国海洋湖沼学报》1997,(2)

unODUcrIONIntereStinthecarboncycehasinamsedbouseoftheobservedincreaseinatmosphericCO,leveIsduetothebumingoffossilfuelandthedearingofforestsre-sultinginlargedhaticandbiogeochdrica1consequenas(ChenandDrake,l986).Experi-mentalstudisofp1antShaveshownresponsesoftypically2O%-4O%highergroWthunderdoubledCo,conditions.Ontheotherhand,theeffedofelevatalCO=conditionsinincreasinggroWth,knownastheCO,fertilimtioneffed,isnotbe1ievedtobetwortantintheoasns(Schimeletal.,1995).Althoughithasbeensuggestedt…  相似文献   

Measuring the Fundamental Parameters of Hot Hydrogen－Rich White Dwarfs     

M.A.Barstow 《中国天文和天体物理学报》2003,3(4):287-310

This review considers the observations of hot, hydrogen-rich white dwarf stars, with particular reference to measurements of temperature, surface gravity and composition. Spectroscopic data from a variety of wavelength ranges are required for this work and, in particular, the important contributions from optical, ultraviolet and extreme ultraviolet studies are discussed. Using the values of Tefr and log g determined for an individual white dwarf, estimates of mass and radius might be derived from the theoretical mass-radius relation. The issue of the accuracy of the theoretical mass-radius calculations and the prospects for making empirical tests using observational data are outlined.  相似文献   

Non-dissipative tidal synchronization in accreting binary white dwarf systems     

Étienne Racine  E. Sterl Phinney  Phil Arras 《Monthly notices of the Royal Astronomical Society》2007,380(1):381-398

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X-ray emissions from two-temperature accretion flows within a dipole magnetic funnel     

Curtis J. Saxton  Kinwah Wu  João B. G. Canalle  Mark Cropper  Gavin Ramsay 《Monthly notices of the Royal Astronomical Society》2007,379(2):779-790

We investigate the hydrodynamics of accretion channelled by a dipolar magnetic field (funnel flows). We consider situations in which the electrons and ions in the flow cannot maintain thermal equilibrium [two-temperature (2T) effects] due to strong radiative loss, and determine the effects on the keV X-ray properties of the systems. We apply this model to investigate the accretion shocks of white dwarfs in magnetic cataclysmic variables (mCVs). We have found that the incorporation of 2T effects could harden the keV X-rays. Also, the dipolar model yields harder X-ray spectra than the standard planar model if white dwarf is sufficiently massive  (≳1 M_⊙)  . When fitting observed keV X-ray spectra of mCVs, the inclusion of 2T hydrodynamics and a dipolar accretion geometry lowers estimates for white dwarf masses when compared with masses inferred from models excluding these effects. We find mass reductions ≲9 per cent in the most massive cases.  相似文献   

Ionization structure in accretion shocks with a composite cooling function     

Kinwah Wu  Mark Cropper  Gavin Ramsay 《Monthly notices of the Royal Astronomical Society》2001,327(1):208-216

We have investigated the ionization structure of the post-shock regions of magnetic cataclysmic variables, using an analytic density and temperature structure model in which effects caused by bremsstrahlung and cyclotron cooling are considered. We find that in the majority of the shock-heated region where H- and He-like lines of the heavy elements are emitted, the collisional-ionization and corona-condition approximations are justified. We have calculated the line emissivity and ionization profiles for iron as a function of height within the post-shock flow. For low-mass white dwarfs, line emission takes place near the shock. For high-mass white dwarfs, most of the line emission takes place in regions well below the shock and hence it is less sensitive to the shock temperature. Thus, the line ratios are useful to determine the white dwarf masses for the low-mass white dwarfs, but the method is less reliable when the white dwarfs are massive. Line spectra can, however, be used to map the hydrodynamic structure of the post-shock accretion flow.  相似文献   

Magnetized fragmented mass transfer in cataclysmic variables: AE Aquarii, a trial case     

P. J. Meintjes 《Monthly notices of the Royal Astronomical Society》2004,352(2):416-426

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Magnetic field evolution in accreting white dwarfs   总被引：1，自引：0，他引：1  

Andrew Cumming † 《Monthly notices of the Royal Astronomical Society》2002,333(3):589-602

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珠三角城市经济升级与社会升级的耦合协调关系及其影响因素     

蔡勃伟  邢祖哥  周进  黄耿志 《热带地理》2022,42(8):1228-1240

采用熵值法综合比较了2006―2019年珠三角经济升级和社会升级的现状,运用改进的耦合协调度模型定量衡量其经济升级和社会升级的耦合度、耦合协调度变化,并分析影响经济和社会升级耦合协调度的因素,结果表明：1）2006―2019年珠三角经济升级和社会升级过程总体上呈现波动上升的趋势,全球金融危机和珠三角的产业结构转型是影响2个系统升级过程的重要因素;2）2006―2019年珠三角2个系统的整体耦合度呈现“U”型演变的态势,由高水平耦合阶段降至磨合阶段再恢复至高水平耦合阶段;3）2006―2019年珠三角9市2个系统耦合协调度总体呈现上升趋势,经济升级系统和社会升级系统之间的协调性逐渐增强;4）人力资本、消费需求、外商投资和政府治理对珠三角经济升级和社会升级的耦合协调度有正向影响,而环境污染则起负面影响作用。  相似文献   

基于体制转换的乡村转型时空格局及演变机理——以甘肃省榆中县为例     

石育中  赵琳林  赵雪雁  兰海霞 《地理科学进展》2022,41(12):2311-2326

乡村转型是乡村振兴的关键,也是“三农”转型的重要抓手。论文以黄土高原沟壑区甘肃省榆中县为例,从人口转型、土地转型和产业转型3个维度构建乡村转型指标体系,基于2002—2018年统计数据、农户调研数据、遥感数据等多源数据,运用熵值法、层次分析法、乡村转型度模型和空间分析方法,从县域和农户视角,量化与分析榆中县乡村转型及其时空演变格局,刻画农户生计转型路径;在此基础上,引入体制转换理论阐释乡村转型过程机理,并运用逐步回归分析方法识别驱动乡村转型的关键因素。结果表明：① 2002—2018年榆中县乡村转型度、产业转型度和人口转型度明显上升,而土地转型度稳中有降,乡村转型度和产业转型差异明显且变化较大,在中部川区最为突出。② 乡村转型、人口转型、产业转型均呈现“中部川区较高速和高速转型、北部山区低速转型、南部山区由低速转型向较高速过渡转型的空间格局”,并伴有逐级式和跨级式的变化特点,土地转型空间分布较为分散;乡村转型、人口转型、产业转型和土地转型的热点区主要集聚在中部川区,冷点区主要集聚于北部山区。③ 农户生计表现出多路径转型特征,北部山区为综合型生计转型路径,中部川区和南部山区为兼农型生计转型路径。④ 中部川区实现乡村体制转换,南部山区乡村发展明显升级转型,但未形成新的乡村体制,而北部山区乡村转型不够显著。⑤ 固定资产投资是决定榆中县乡村转型的关键因素。研究结果可为乡村转型提供新的研究视角,也为黄土高原沟壑区乡村振兴与乡村高质量发展提供理论依据。  相似文献