Towards a new standard model for black hole accretion     

Zdenka Kuncic  Geoffrey V. Bicknell 《Astrophysics and Space Science》2007,311(1-3):127-135

We briefly review recent developments in black hole accretion disk theory, emphasizing the vital role played by magnetohydrodynamic (MHD) stresses in transporting angular momentum. The apparent universality of accretion-related outflow phenomena is a strong indicator that large-scale MHD torques facilitate vertical transport of angular momentum. This leads to an enhanced overall rate of angular momentum transport and allows accretion of matter to proceed at an interesting rate. Furthermore, we argue that when vertical transport is important, the radial structure of the accretion disk is modified at small radii and this affects the disk emission spectrum. We present a simple model demonstrating how energetic, magnetically-driven outflows modify the emergent disk emission spectrum with respect to that predicted by standard accretion disk theory. A comparison of the predicted spectra against observations of quasar spectral energy distributions suggests that mass accretion rates inferred using the standard disk model may be severely underestimated.  相似文献   

GPS和GLONASS系统下RAIM空洞预报     

任锴  杨力 《全球定位系统》2009,34(4):25-28,36

接收机自主完好性监测（RAIM）是卫星导航系统完好性监测的方法之一。一定时空条件下的RAIM可用性，可以通过RAIM空洞直观的反映出来，可以为飞行提供预警；利用不同期GPS、GLONASS实际星座，仿真分析了单星座以及GPS／GLONASS组合星座RAIM可用性，绘制了RAIM空洞图，具有一定的参考价值。  相似文献   

Evidence of the Link between Broad Emission Line Regions and Accretion Disks in Active Galactic Nuclei     

Yun Xu    Xin-Wu Cao Shanghai Astronomical Observatory  Chinese Academy of Sciences  Shanghai  Graduate School of Chinese Academy of Sciences  Beijing 《中国天文和天体物理学报》2007,7(1):63-70

1 INTRODUCTION Most bright active galactic nuclei (AGNs) exhibit broad emission lines, with full width at half maximum (FWHM ≥ 103 km s?1) (Peterson et al. 1999). Some type 1 AGNs could have very broad emission lines (FWHM≥ 20 000 km s?1). Type 2 AGNs s…  相似文献   

加蓬G4-188区块钻井技术实践认识     

石强 《海洋地质译丛》2008,(1):82-87

加蓬G4-188区块是一个新的海外勘探区块,在钻井过程中遇到了井壁垮塌、气侵、井斜控制困难等诸多难题,影响了钻井施工的速度。针对这些难题,实施了解决G4-188区块钻井施工难点的各项技术措施,为G4-188区块后续钻井施工提供了有益的技术支持。  相似文献   

Nautilus矿业公司SMS勘探中采用的取样技术与装备   总被引：1，自引：0，他引：1  

戴瑜  刘少军  李流军  胡小舟 《海洋技术学报》2008,27(2):12-17

海底大块状硫化物(SMS)富含铜、锌、铅等金属,特别是富含贵金属金、银,引起了国际采矿业的浓厚兴趣。近年来,以澳大利亚Nautilus矿业公司为先驱代表的国际大型资源开发商和投资商已介入海底多金属硫化物的商业化开采。文中介绍了Nautilus公司在巴布亚新几内亚专属经济区针对海底块状硫化物矿床开展的一系列以商业开采为目的的勘探取样活动,详细介绍了勘探中所采用的基本方法与技术,并重点对其地质调查中所应用的拖网挖掘取样、ROV海底表面取样、大洋钻探船岩芯取样和专门开发的ROV岩芯钻探取样的装备、取样结果及作业效率进行了较为系统全面地介绍。  相似文献   

春晓气田泥岩垮塌测井数据校正及应用     

谢月芳  陈敏 《海洋地质译丛》2009,(4):73-76

由于存在部分泥岩井眼垮塌，东海春晓气田测井曲线砂泥岩阻抗部分叠置。针对这一现象，采用未垮塌段泥岩伽马与密度拟合关系校正垮塌段泥岩密度，声波时差经本区伽德那公式拟合后求取。通过泥岩垮塌测井数据校正前后对比、直方交会、岩石物理、正演及反演效果分析，认为校正后的测井数据比较真实地反映垮塌段扩径泥岩地层特征，储层与围岩波阻抗差异明显，为储层反演、砂体空间展布分析提供了有力依据。  相似文献   

钻井柱状图可视化查询系统的设计与实现   总被引：1，自引：1，他引：0  

李继园  刘展  孟令奎 《地理空间信息》2009,7(5):75-78

钻井柱状图是石油行业勘探开发最常用的一种图件。为了开发出灵活通用的钻井柱状图制作软件，为可视化分析提供良好基础，提出了“两库四类三层”系统设计方案，应用COM思想和模板定制技术，采用C#．net语言从底层进行了软件实现，所开发的软件模块具备一定的独立性和较好的通用性。  相似文献   

Advances in understanding of the mechanism for generation of earthquake thermal precursors detected by satellites     

Arun K. Saraf  Vineeta Rawat  Swapnamita Choudhury  Sudipta Dasgupta  Josodhir Das 《International Journal of Applied Earth Observation and Geoinformation》2009

Stresses building up during an earthquake preparation phase also manifest themselves in the form of a so called increased land surface temperature (LST) leading to a thermal precursor prior to the earthquake event. This phenomenon has now been validated by our observations of short-term thermal anomalies detected by infrared satellite sensors for several recent past earthquakes around the world. The rise in infrared radiance temperature was seen to vary between 5 and 12 °C for different earthquakes. We discuss in this paper different explanations for the generation of such anomalies that have been offered. Emission of gases due to the opening and closure of micropores upon induced stresses and also the participation of ground water have been propounded as a possible cause for generation of thermal anomalies. Seismo-ionosphere coupling, by which gases like radon move to the earth–atmosphere interface and cause air ionization thus bringing about a change in air temperature, relative humidity, etc., has been put forth by some workers. A mechanism of low frequency electromagnetic emission was tested and experimented by scientists with rock masses in stressed conditions as those that exist at tectonic locations. The workers proposed the positive hole pair theory, which received support from several scientific groups. Positive holes (sites of electron deficiency) are activated in stressed rocks from pre-existing yet dormant positive hole pairs (PHPs) and their recombination at rock–air interface leads to a LST rise. A combination of remote sensing detection of rock mechanics behavior with a perception of chemistry and geophysics has been applied to propose the remote sensing rock mechanics theory. Remote sensing detections of such anomalies confirm so far proposed lab theories for such a hotly debated field as earthquake precursor study by providing unbiased observations with consistency in time and space distribution.  相似文献   

莆田近岸海域海带烂孔病起因的初步研究   总被引：1，自引：0，他引：1       下载免费PDF全文

张丽 《应用海洋学学报》2019,38(3):433-439

2019年3月莆田近岸海域海带尾部烂孔后逐渐向根部蔓延,孔洞相连后海带脱落,时空规律为先南后北逐渐发病,共涉及养殖面积约7 km2,给莆田近岸海带养殖带来了较大的损失。初步研究分析了海带大规模烂孔的原因,主要结果如下:海区温度异常升高,盐度持续较低,连续阴天光照不足,环境变化超出了细胞生理承受能力从而造成海带烂孔。此次诊断,对渔业生产及海洋环境监测结果在渔业上的应用均具有一定的现实意义。  相似文献   

A new model for the periodic outbursts of the BL Lac object OJ287     

Weizhao Shi  Xiang Liu  Huagang Song 《Astrophysics and Space Science》2007,310(1-2):59-63

Recent observations provide strong evidence for the BL Lac object OJ287 exhibiting a 11.6±0.5 yr periodicity with a double-peaked maxima in its optical flux variations. Several models have been proposed for the optical behavior. The 2005 November outburst in OJ287 gives us a surprising result since calculation based on the periodicity was predicting such an outburst in late 2006. Here we suggest a new model, it can not only explain the optical quasi-periodic behavior, but also the radio flares behavior which is and simultaneous with the optical flares. We propose that OJ287 is a binary pair of super-massive black holes, both of them creating a jet. The quasi-periodic double peaks would be due to the relativistic beaming effect on the emission coming from the double helix jets. We used “core flares” to explain the large lags between light curves at different frequencies, and the assumption of two jets appear to be merged with each other partly in the radio frequency emitting regions provides a viable interpretation that we can see only a broad maximum which contains two radio flares that we cannot distinguish.  相似文献