空化水射流热效应影响煤体渗透率试验研究   总被引：1，自引：0，他引：1  

卢义玉  丁红  葛兆龙 《岩土力学》2014,35(5):1247-1254

对空化水射流空泡溃灭瞬间和空化噪声声场作用产生的热效应进行了分析,得到了热效应作用下的煤体渗透率表达式,并开展了不同空化条件(泵压、空化腔围压)下的煤体温度和瓦斯渗流试验。结果表明:空化腔围压一定时,温度随泵压的增大而升高;而泵压一定时,温度随空化腔围压的增大而减小。当热应力大于平均有效应力时,煤体热膨胀出现微变形,产生的张应力使裂隙变宽、数量增多;热效应使得游离瓦斯内能增加,分子自由程大大缩短,同时吸附瓦斯解吸使得煤基质发生收缩效应,导致微孔隙及微裂隙结构产生膨胀变形,从而影响煤体渗透率。试验得到渗透率随温度升高呈指数规律增大,与理论得到的渗透率表达式描述的规律相符。  相似文献   

明渠水流自掺气发展区水气结构分析          下载免费PDF全文

卫望汝  邓军  田忠  张法星 《水科学进展》2014,25(5):704-712

为研究明渠水流自掺气发展区内水气结构特征,采用针式掺气流速仪对自掺气发展区内气泡尺寸与数量进行了试验研究,比较了气泡尺寸与数量随自掺气发展的变化规律,结果显示,同一水流断面上,随着掺气浓度的减小,气泡弦长尺寸分布范围与弦长平均值逐渐减小,掺气区内小尺寸气泡在数量上占有较大的比例,而大尺寸气泡则在含气量上占有较大的比例,分析认为从水面附近高掺气浓度区至自掺气区域底缘低掺气浓度区,明渠自掺气水流水气结构发展过程为“水面变形为主—水面变形与个体空气泡共存—个体空气泡”,为进一步研究明渠自掺气形成机理提供了一定的参考。  相似文献   

The resolved red giant branches of E/S0 galaxies     

Regina E. Schulte-Ladbeck  Igor O. Drozdovsky  Michèle Belfort  Ulrich Hopp 《Astrophysics and Space Science》2003,284(2):909-912

Formation paradigms for massive galaxies have long centered around two antipodal hypotheses – the monolithic-collapse and the accretion/merger scenarios. Empirical data on the stellar contents of galaxy halos is crucial in order to develop galaxy formation and assembly scenarios which have their root in observations, rather than in numerical simulations. The Hubble Space Telescope (HST) has enabled us to study directly individual stars in the nearby E/S0 galaxies Cen A, NGC 3115, NGC 5102, and NGC 404. We here present and discuss HST single-star photometry in V and I bands. Using color-magnitude diagrams and stellar luminosity functions, we gauge the galaxies' stellar contents. This can be done at more than one position in the halo, but data with deeper limiting magnitudes are desired to quantify the variation of metallicity with galactocentric radius. We here compare the color distributions of red giant stars with stellar isochrones, and we intercompare the galaxies' halo populations, noting that their total absolute V magnitudes cover the range from about –21.5 to –17.5. In the future, we plan to model the stellar metallicity distributions with the aim to constrain chemical enrichment scenarios, a step towards unravelling the evolutionary history of elliptical and lenticular galaxies. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

The next generation stellar population synthesis library     

Reynier Peletier 《Astrophysics and Space Science》2003,284(2):957-960

Most of the analysis of absorption lines in galaxies is done in the Lick system, defined in the 1970's and 1980's by Faber, Burstein and collaborators. Working in this system is difficult, since it is based on low resolution spectra taken with a non-linear detector without flux-calibration. Due to intrinsic errors in the published indices the Lick system limits the accuracy with which one can analyse galaxy spectra. In the last 2 years we have observed a new stellar library to replace the Lick system. It consists of 1100 stars, covering a wide range in metallicity, abundance ratio, temperature and gravity, observed at a resolution of 2.0Å (9 for Lick) from 3500–7500Å, and calibrated in flux. With this library galaxy spectra can be analysed much more accurately than before, and in much more detail. Most important, the library now makes it possible to study absorption lines of galaxies at intermediate and high redshift, something which was impossible with the Lick system. With this library it will be possible for the first time to synthesise full Spectral energy distributions of galaxies in the optical based fully on observational spectra.  相似文献   

Kinematics and stellar populations of 17 dwarf early-type galaxies     

Daniel Thomas  Ralf Bender  Ulrich Hopp  Claudia Maraston  Laura Greggio 《Astrophysics and Space Science》2003,284(2):599-602

We present kinematics and stellar population properties of 17 dwarf early-type galaxies in the luminosity range -14 ≥ M _B ≥ -19. Our sample fills the gap between the intensively studied giant elliptical and Local Group dwarf spheroidal galaxies. The dwarf ellipticals of the present sample have constant velocity dispersion profiles within their effective radii and do not show significant rotation, hence are clearly anisotropic. The dwarf lenticulars, instead, rotate faster and are, at least partially, supported by rotation. From optical Lick absorption indices, we derive metallicities and element abundances. Combining our sample with literature data of the Local Group dwarf spheroidals and giant ellipticals, we find a surprisingly tight linear correlation between metallicity and luminosity over a wide range: -8 ≥ M _B ≥ -22. The α/Fe ratios of our dwarf ellipticals are significantly lower than the ones of giant elliptical galaxies, which is in agreement with spectroscopy of individual stars in Local Group dwarf spheroidals. Our results suggest the existence of a clear kinematic and stellar population dichotomy between dwarf and giant elliptical galaxies. This result is important for theories of galaxy formation, because it implies that present-day dwarf ellipticals are not the fossiled building blocks of giant ellipticals. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

The search for the origin of the Local Bubble redivivus     

B. Fuchs  D. Breitschwerdt  M. A. de Avillez  C. Dettbarn  C. Flynn 《Monthly notices of the Royal Astronomical Society》2006,373(3):993-1003

We present a new unbiased search and analysis of all B stars in the solar neighbourhood (within a volume of 400 pc diameter) using the Arivel data base to track down the remains of the OB associations, which hosted the supernovae (SNe) responsible for the Local Bubble (LB) in the interstellar gas. We find after careful dereddening and by comparison with theoretical isochrones, that besides the Upper Scorpius the Upper Centaurus Lupus and Lower Centaurus Crux subgroups are the youngest stellar associations in the solar neighbourhood with ages of 20–30 Myr, in agreement with previous work. In search for the 'smoking gun' of the origin of the LB, we have traced the paths of the associations back into the past and found that they entered the present bubble region 10–15 Myr ago. We argue that the LB began to form then and estimate that 14–20 SNe have gone off since. It is shown that the implied energy input is sufficient to excavate a bubble of the presently observed size.  相似文献   

火山"熔岩流气泡古高度计"及其在云南腾冲火山区的应用   总被引：6，自引：5，他引：1  

郭正府  张茂亮  成智慧  刘嘉麒  张丽红  李晓惠 《岩石学报》2011,27(10):2863-2872

通过对火山熔岩流及其气泡特征的研究能够确定熔岩流喷发时的古高度,本文将这一方法称为火山“熔岩流气泡古高度计”.“熔岩流气泡古高度计”是在实地测量熔岩流厚度和实验室对熔岩流顶底气泡体积精确测定的基础上,利用流体力学原理和气体状态方程,通过计算古大气压强,最终获得火山喷发时的古高度.由于火山岩是开展同位素测年的理想材料,并且利用熔岩流计算古高度所需的参数(熔岩流厚度和气泡体积)不受古气候等因素(温度、降雨量等)影响,因此,这一方法以其可靠的年龄和独立的计算参数明显区别于其它古高度计.“熔岩流气泡古高度计”核心技术包括:(1)熔岩流的挑选与厚度测量;(2)熔岩流底部和顶部气泡体积的计算.中等规模、具简单冷凝历史,并且厚度稳定的偏基性熔岩流,是开展古高度计算的理想对象.熔岩流气泡体积的测试手段包括注胶、岩石抛光-扫描、体视学转换和三维CT扫描4种方法.“熔岩流气泡古高度计”最终计算结果误差为400m左右.本文利用“熔岩流气泡古高度计”计算了腾冲火山区熔岩流的古高度,研究结果显示:“熔岩流气泡古高度计”计算的黑空山熔岩流高程与目前的实际高程相吻合.开展“熔岩流气泡古高度计”研究的前提是研究区必须出露保存完好的熔岩流.我国青藏高原的隆升历史一直是国际学术界争论的热点课题,那里出露大面积熔岩流.可以预见,“熔岩流气泡古高度计”将会逐渐成为研究青藏高原隆升历史的有效手段之一.  相似文献   

Resistance among wild invertebrate populations to recurrent estuarine acidification   总被引：1，自引：0，他引：1  

Valter Amaral  Henrique N. Cabral  Melanie J. Bishop 《Estuarine, Coastal and Shelf Science》2011

Acid sulphate soils (ASS), which occur on floodplains worldwide, pose a significant threat to estuarine ecosystems. In laboratory and field experiments, naïve calcifying organisms that are exposed for even short periods (1–2 mo) to runoff from ASS suffer 80% mortality and slowed growth. Based on these observations we expected that sampling of wild oyster, gastropod and crab populations at sites close to and away from drains discharging ASS runoff would reveal more depauperate populations, of sparser and smaller-sized individuals at the more acidified sites. Sampling within three estuaries of New South Wales, Australia, confirmed that the oyster Saccostrea glomerata and gastropods (primarily Bembicium auratum) were less abundant at ASS-affected than reference sites. Nevertheless, crab abundances did not differ between the acidified and reference sites and impacts to bivalves and gastropods were far smaller than predicted. Although at ASS-affected sites gastropod populations were dominated by smaller individuals than at reference sites, oyster populations were skewed towards larger individuals. Even at ASS-affected sites, oyster and gastropod abundances were within the range encountered in estuaries that are not influenced by ASS runoff. Behaviour, long-term physiological acclimation or genetic selection may be responsible for differences in the responses of wild and naïve macroinvertebrates to acidification. Alternatively, wild populations may exhibit some recovery between the rainfall events that transport ASS runoff into estuaries, despite the persistently lower pH near outflow drains. Irrespective, this study suggests that at the population level, calcifying organisms display a certain degree of natural resistance to recurrent disturbance from ASS runoff.  相似文献   

Research on experiment and calculation of foam bursting device   总被引：1，自引：0，他引：1  

Hazaea Mohammed  Youhong SUN  Ould El HousseinYarbana  Longxiang XU  Al-Aswar Fahmi 《世界地质(英文版)》2007,10(1)

This research presents experimental data on mechanical foam bursting device, based on the high speed of air fluid impinging insidethe foam bursting device, foam bubbles disrupted as a consequence of pressures changed very quickly as shear force and their impact forces. Experimental data on foam-bursting capacity have been presented. Designed device can provide effective foam bursting on collapse foam.  相似文献   

Estimating the mean time between meals in the field from stomach content data and gastric evacuation functions of whiting (Merlangius merlangus L.) feeding on sandeel (Ammodytes marinus Raitt)     

Temming  A.; Mergardt  N. 《ICES Journal of Marine Science》2002,59(4):782-793

  相似文献