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171.
Jinho Kim Hee Il Kim Hyung Mok Lee 《Monthly notices of the Royal Astronomical Society》2009,399(1):229-238
We obtain equilibrium solutions for rotating compact stars, including special relativistic effects. The gravity is assumed to be Newtonian, but we use the active mass density, which takes into account all energies such as the motion of the fluid, internal energy and pressure energy in addition to the rest-mass energy, in computing the gravitational potential using Poisson's equation. Such a treatment could be applicable to neutron stars with relativistic motions or a relativistic equation of state. We applied Hachisu's self-consistent field (SCF) method to find spheroidal as well as toroidal sequences of equilibrium solutions. Our solutions show better agreement with general relativistic solutions than the Newtonian relativistic hydrodynamic approach, which does not take into account the active mass. Physical quantities such as the peak density and equatorial radii in our solutions agree with the general relativistic ones to within 5 per cent. Therefore our approach can be used as a simple alternative to the fully relativistic one when a large number of model calculations is necessary, as it requires much fewer computational resources. 相似文献
172.
Chemical Characteristics of Carbonaceous Aerosols During Dust Storms over Xi'an in China 总被引:1,自引:0,他引:1
Characterization of carbonaceous aerosols including CC (carbonate carbon), OC (organic carbon), and EC (elemental carbon) were investigated at Xi'an, China, near Asian dust source regions in spring 2002. OC varied between 8.2 and 63.7μgm^- 3, while EC ranged between 2.4 and 17.2 μ m^-3 during the observation period. OC variations followed a similar pattern to EC and the correlation coefficient between OC and EC is 0.89 (n=31). The average percentage of total carbon (TC, sum of CC, OC, and EC) in PM2.5 during dust storm (DS) events was 13.6%, which is lower than that during non-dust storm (NDS) periods (22.7%). CC, OC, and EC accounted for 12.9%, 70.7%, and 16.4% of TC during DS events, respectively. The average ratio of OC/EC was 5.0 in DS events and 3.3 in NDS periods. The OC-EC correlation (R^2=0.76, n=6) was good in DS events, while it was stronger (R^2=0.90, n=25) in NDS periods. The percentage of watersoluble OC (WSOC) in TC accounted for 15.7%, and varied between 13.3% and 22.3% during DS events. The distribution of eight carbon fractions indicated that local emissions such as motor vehicle exhaust were the dominant contributors to carbonaceous particles. During DS events, soil dust dominated the chemical composition, contributing 69% to the PM2.5 mass, followed by organic matter (12.8%), sulfate (4%), EC (2.2%), and chloride (1.6%). Consequently, CC was mainly entrained by Asian dust. However, even in the atmosphere near Asian dust source regions, OC and EC in atmospheric dust were controlled by local emission rather titan the transport of Asian dust. 相似文献
173.
A heavy rainfall case related to Mesoscale Convective Systems (MCSs) over
the Korean Peninsula was selected to investigate the impact of radar data
assimilation on a heavy rainfall forecast. The Weather Research and
Forecasting (WRF) three-dimensional variational (3DVAR) data assimilation
system with tuning of the length scale of the background error covariance
and observation error parameters was used to assimilate radar radial
velocity and reflectivity data. The radar data used in the assimilation
experiments were preprocessed using quality-control procedures and
interpolated/thinned into Cartesian coordinates by the SPRINT/CEDRIC
packages. Sensitivity experiments were carried out in order to determine the
optimal values of the assimilation window length and the update frequency
used for the rapid update cycle and incremental analysis update experiments.
The assimilation of radar data has a positive influence on the heavy
rainfall forecast. Quantitative features of the heavy rainfall case, such as
the maximum rainfall amount and Root Mean Squared Differences (RMSDs) of
zonal/meridional wind components, were improved by tuning of the length
scale and observation error parameters. Qualitative features of the case,
such as the maximum rainfall position and time series of hourly rainfall,
were enhanced by an incremental analysis update technique. The positive
effects of the radar data assimilation and the tuning of the length scale
and observation error parameters were clearly shown by the 3DVAR increment. 相似文献
174.
175.
LEE J. ARNOLD RICHARD G. ROBERTS 《Boreas: An International Journal of Quaternary Research》2011,40(3):389-416
Arnold, L. J. & Roberts, R. G. 2011: Paper I – Optically stimulated luminescence (OSL) dating of perennially frozen deposits in north?central Siberia: OSL characteristics of quartz grains and methodological considerations regarding their suitability for dating. Boreas, Vol. 40, pp. 389–416. 10.1111/j.1502‐3885.2011.00209.x. ISSN 0300?9483. Optically stimulated luminescence (OSL) dating of coarse‐grained quartz is increasingly being used as the main chronological tool in late Quaternary palaeoenvironmental reconstructions of Siberia. However, relatively little information has been published on the suitability of OSL dating for the various types of perennially frozen sediments found in this region. Here we provide a systematic examination of the quartz luminescence characteristics of 21 perennially frozen samples from the Taimyr Peninsula and adjacent coastal lowlands of north‐central Siberia, and discuss their implications for the reliability of single‐grain and multi‐grain OSL chronologies in such contexts. The results of this study suggest that the quartz luminescence characteristics of these samples are, in principle, favourable for OSL dating but, in practice, require that a series of validation checks are made of the chosen experimental conditions. If these tests are satisfied, then reliable OSL chronologies should be obtained for sedimentary deposits in this region. Importantly, however, the single‐grain and multi‐grain aliquot equivalent dose (De) distribution characteristics for our samples reveal that there are advantages in targeting certain types of depositional settings for OSL dating studies of Siberian sediments. We also show that samples from the same depositional settings, and even from the same sites, do not necessarily display similar De distribution characteristics. The latter complication favours the use of single‐grain analysis to unravel the bleaching and burial histories of young (mid‐ to late Holocene) sediments in these Arctic environments. 相似文献
176.
LEE J. ARNOLD RICHARD G. ROBERTS ROSS D. E. MACPHEE JAMES S. HAILE FIONA BROCK PER MÖLLER DUANE G. FROESE ALEXEI N. TIKHONOV ALLAN R. CHIVAS M. THOMAS P. GILBERT ESKE WILLERSLEV 《Boreas: An International Journal of Quaternary Research》2011,40(3):417-445
Arnold, L. J., Roberts, R. G., MacPhee, R. D. E., Haile, J. S., Brock, F., Möller, P., Froese, D. G., Tikhonov, A. N., Chivas, A. R., Gilbert, M. T. P. & Willerslev, E. 2010: Paper II – Dirt, dates and DNA: OSL and radiocarbon chronologies of perennially frozen sediments in Siberia, and their implications for sedimentary ancient DNA studies. Boreas, Vol. 40, pp. 417–445. 10.1111/j.1502‐3885.2010.00181.x. ISSN 0300‐9483 The sedimentary ancient DNA (sedaDNA) technique offers a potentially invaluable means of investigating species evolution and extinction dynamics in high‐latitude environments. An implicit assumption of the sedaDNA approach is that the extracted DNA is autochthonous with the host deposit and that it has not been physically transported from older source deposits or reworked within the sedimentary profile by postdepositional mixing. In this paper we investigate whether these fundamental conditions are upheld at seven perennially frozen wetland sites across the Taimyr Peninsula and coastal lowlands of north‐central Siberia. Optically stimulated luminescence (OSL) and radiocarbon (14C) dating are used to constrain the ages of both the inorganic and organic fractions of perennially frozen deposits from which sedaDNA of extinct and extant species have been recovered. OSL and 14C age/depth profiles, as well as single‐grain equivalent dose (De) distribution characteristics, are used to assess the stratigraphic integrity of these sedaDNA sequences by (i) identifying the presence of primary or reworked organic and inorganic material, and (ii) examining the types of depositional and postdepositional processes that have affected specific sedimentary facies. The results of this study demonstrate that even though DNA preservation and stratigraphic integrity are commonly superior in perennially frozen settings, this does not, in itself, guarantee the suitability of the sedaDNA approach. The combined OSL and 14C chronologies reveal that certain perennially frozen sites may be poorly suited for sedaDNA analysis, and that careful site selection is paramount to ensuring the accuracy of any sedaDNA study – particularly for ‘latest appearance date’ estimates of extinct taxa. 相似文献
177.
178.
安徽铜陵地区中酸性侵入岩及其岩石包体中的矿物包裹体研究 总被引:14,自引:2,他引:14
铜陵地区是长江中、下游铁、铜、硫、金成矿带的重要组成部分。笔者对铜陵地区中酸性侵入岩及其岩石包体中的包裹体进行了较系统的岩相学、显微测温和激光拉曼光谱研究。通过岩相学观察发现了 3类包裹体 ,即晶质熔融包裹体、流体熔融包裹体和流体包裹体。显微测温资料表明 ,本区的岩浆流体成矿演化可分为 3个阶段 :岩浆阶段 ( >12 5 0~ 90 0℃± )、过渡岩浆阶段 ( 90 0~ 75 0℃± )和岩浆期后热液阶段 ( <75 0℃ )。部分熔浆的温度之高 (可达 12 5 0℃ ) ,表明其可能是底侵幔源岩浆同熔下地壳形成的。在老庙基岩体、小铜官山岩体、鸡冠石岩体和小陶家岩体中产有晶质熔融包裹体、流体熔融包裹体和流体包裹体这 3种包裹体 ,表明相应的岩浆流体演化具有连续性、继承性和阶段性 ,其对应的成矿溶液以岩浆热液为主 ;与此不同的是 ,在鸡冠山岩体和白芒山岩体中仅产有晶质熔融包裹体和流体包裹体两种类型的包裹体 ,表明相应的岩浆流体演化不具连续性 ,其对应的成矿溶液以天水热液为主。此外 ,在小铜官山岩体和鸡冠石岩体的中酸性侵入岩中 ,发现了不混溶包裹体 ,其可能是在压力释放条件下形成的。 相似文献
179.
桂北新元古代两类过铝花岗岩的地球化学研究 总被引:24,自引:3,他引:24
广西北部新元古代花岗岩类岩石包括黑云母花岗闪长岩和黑云母花岗岩。地球化学特征表明,黑云母花岗闪长岩与含堇青石的过铝花岗岩(CPG)相当,而黑云母花岗岩则类似于白云母二长花岗岩(MPG)。黑云母花岗岩类是成熟地宙岩石部分熔融作用的产物,而黑云母花岗闪长岩类的形成与地幔柱起源的镁铁质岩浆和地壳起源的过铝质黑云母花岗岩浆之间的混合作用有关。这两类新元古代过铝花岗岩的形成与碰撞造山导致地壳加厚的挤压性构造无关,而与导致Rodinia超大陆裂解的地幔柱上升诱发岩石圈伸展的张性构造相联系。 相似文献
180.