Time-dependent interaction of granules with magnetic flux tubes     

P. Venkatakrishnan  S. S. Hasan 《Journal of Astrophysics and Astronomy》1981,2(2):133-139

The time-dependent interaction of the granulation velocity field with a magnetic flux tube is investigated here. It is seen that when a magnetic field line is displaced normal to itself so as to simulate thebuffeting action of granules, a flow of gas is initiated along the field. By choosing a lateral velocity field which is consistent with observations of granules, it is found that the resulting gas motion is a downward flow with a velocity compatible with the observed downflow in isolated photospheric flux tubes. It is therefore proposed that the observed photospheric downflow is a manifestation of the interaction of granules with flux tubes.  相似文献   

Kinematic solar dynamo models with a deep meridional flow     

G. A. Guerrero  J. D. Muñoz 《Monthly notices of the Royal Astronomical Society》2004,350(1):317-322

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Thermo-economic Investigation of an Enhanced Geothermal System Organic Rankine Cycle and Combined Heating and Power System     

WANG Lingbao  BU Xianbiao  LI Huashan 《《地质学报》英文版》2021,95(6):1958-1966

As a potentially viable renewable energy, Enhanced Geothermal Systems (EGSs) extract heat from hot dry rock (HDR) reservoirs to produce electricity and heat, which promotes the progress towards carbon peaking and carbon neutralization. The main challenge for EGSs is to reduce the investment cost. In the present study, thermo-economic investigations of EGS projects are conducted. The effects of geofluid mass flow rate, wellhead temperature and loss rate on the thermo-economic performance of the EGS organic Rankine cycle (ORC) are studied. A performance comparison between EGS-ORC and the EGS combined heating and power system (CHP) is presented. Considering the CO2 emission reduction benefits, the influence of carbon emission trading price on the levelized cost of energy (LCOE) is also presented. It is indicated that the geofluid mass flow rate is a critical parameter in dictating the success of a project. Under the assumed typical working conditions, the LCOE of EGS-ORC and EGS-CHP systems are 24.72 and 16.1 cents/kWh, respectively. Compared with the EGS-ORC system, the LCOE of the EGS-CHP system is reduced by 35%. EGS-CHP systems have the potential to be economically viable in the future. With carbon emission trading prices of 12.76 USD/ton, the LCOE can be reduced by approximately 8.5%.  相似文献   

High-redshift QSOs in the FIRST survey     

C.R. Benn  M. Vigotti  M. Pedani  J. Holt  K.-H. Mack  R. Curran  S.F. Sánchez 《Monthly notices of the Royal Astronomical Society》2002,329(1):221-226

In a pilot search for high-redshift radio quasi-stellar objects (QSOs), we have obtained spectra of 55 FIRST sources     with very red     starlike optical identifications. 10 of the candidates are QSOs with redshifts     (four were previously known), six with     . The remaining 45 candidates comprise: one     broad-absorption-line (BAL) QSO; three low-redshift galaxies with narrow emission lines; 18 probable radio galaxies; and 23 M stars (mainly misidentifications). The success rate (high-redshift QSOs / spectroscopically-observed candidates) for this search is 1/2 for     , and 1/9 for     . With an effective search area of 4030 deg², the surface density of high-redshift     QSOs discovered with this technique is 0.0015 deg⁻².  相似文献   

色球和日冕的MHD加热机制     

王华宁 《天文学进展》1996,(3)

扼要地介绍了色球和日冕加热问题的研究历史。随着空间太阳观测技术的进步，人们认识到色球和日冕加热机制主要与MHD过程有关。因此，在本文中着重介绍四种MHD色球和日冕加热机制：（1）阿尔芬波；（2）MHD湍动；（3）场向电流；（4）磁重联。由于这四种加热机制的有效性都需要通过高分辨率观测来判定，所以空间太阳观测对于研究色球和日冕加热问题具有重大意义。  相似文献   

太阳大气磁精细结构的射电探讨     

傅其骏 《天文学进展》1997,15(3):198-217

太阳大气磁场的研究对于太阳大气物理及太阳活动研究是十分重要的。目前探测光球以外的日够以球，过渡区磁场的几乎唯一办法，是在紧密联系其他频说段取得的信息基础上使用射电观测。根据在微波，米波段有关辐射机制和传播过程，介绍了推导磁场讯息的基本射电方法。  相似文献   

Control of emission rates     

Y.N. Skiba  D. Parra-Guevara 《Atmósfera》2013,26(3):379-400

The advection-diffusion equation is used for describing the dispersion of pollutants in a limited area. Methods for preventing dangerous levels of pollutants in ecologically important zones are suggested. The methods are based on the control of emission rates of sources and use the direct and adjoint estimates of the average pollution concentration in the zones. While the direct estimates use solutions of the pollution transport problem and permit to study the ecological situation in the whole domain, the adjoint estimates allow getting information only in the selected zones of the domain. The adjoint estimates are obtained with solutions to the adjoint problem and depend explicitly on the positions of the sources and their emission rates, and on the initial distribution of pollutants in the region. In each such estimate, the adjoint problem solution serves as the influence function that shows the quantitative contribution of every source into the pollution of the corresponding zone. This makes the adjoint estimates very efficient tools in the study of the model response to changes in emission rates and initial conditions, as well as in the development of control strategies. Both non-optimal (sufficient) and optimal control strategies are suggested. Each strategy consists in reducing the emission rates of sources, and defines maximum allowable intensity (in case of optimal control), or sufficient intensity (in case of sufficient control) of each source to avoid violations of hygiene standards. Such criteria are designed taking into account dynamic conditions in the atmosphere or ocean (sea), that is, the processes of propagation, dispersion and transformation of pollutants, as well as the number of sources to control, their locations and the sanitary norms. The control methods developed are illustrated with simple examples using two-dimensional dispersion models. However, these methods can also be applied to three-dimensional models. As an example, in the last part of the article, a three-dimensional model of dispersion is considered. In addition, to expand the scope of application of the methods of control of the intensity of sources, the optimal control strategies are applied to a source that emits a chemical substance to clean aquatic systems contaminated with biofilms (remediation) or oil (bioremediation).  相似文献   

粘滑过程中的多点错动   总被引：3，自引：2，他引：1       下载免费PDF全文

李普春  刘力强  郭玲莉  刘培洵 《地震地质》2013,35(1):125-137

在实验室利用分布式多通道瞬态信号采集系统,从近场条件下研究了岩石粘滑过程中沿断层的声发射信号的初动到时和初动方向空间分布,并结合瞬态高频应变记录系统观测沿断层的应变分布特征,对粘滑过程中的震源错动行为进行了研究。实验在双轴伺服加载系统上进行。分析表明,一次突发应力降对应的瞬时震源滑动过程是由多次更短暂的微小错动组成的,每次短小错动都产生自己的声发射事件,并依次对应不同的应变值快速改变。而每一次的微小错动也可能不止一个位错点,而是对应空间上多个启动点,从振动波初动信号的空间分布形式与沿断层应变场不均匀分布中可以找到证据。近场条件下观测到的粘滑过程多点错动现象对于理解震源过程的复杂性,解释现场地震震源不确定性与震源机制解的高矛盾比现象提供了可能的依据。  相似文献   

基于逾渗模型的盐岩损伤与破坏研究     

孙中秋  谢凌志  刘建锋 《岩土力学》2014,299(2):441-448

逾渗是一种分形模型,利用声发射点定位盐岩内部破坏网格来建立逾渗模型,可以分析三轴压缩条件下盐岩逾渗特征以及损伤演变发展。研究发现,各试样逾渗模型团簇(cluster)数与最大团簇占有率关系曲线斜率在70%应力峰值后基本相等,利用最大团簇沿试样轴向的延伸来描述裂缝的扩展规律,并通过最大团簇在轴向的延伸终点得到了各试样逾渗的临界破坏比率,它对于研究渗透陡增点非常重要。提出利用逾渗关联长度(关联长度?代表处于同一团簇中的两个点的平均距离)确定试样损伤起始点,并通过计算逾渗模型破坏比率得到损伤变量,它和基于AE振铃计数以及AE能量计算得到的损伤变量结果相近。研究结果表明,逾渗可以形象地表述岩石内部破裂过程和损伤情况,为研究岩石破坏失效及裂缝衍生发展提供了新的思路。  相似文献   

湿地土壤气体排放对水位变化响应的持续性动态特征          下载免费PDF全文

吕海波 《干旱区地理》2022,45(3):860-866

为探索湿地水位变化与土壤气体排放之间的关系,对黄河中游芦苇湿地进行了半注水和满注水样地处理后的动态监测,对比了7 d水位变化过程中土壤气体排放差异。结果表明：注水造成了土壤CO₂排放速率的显著差异;随土壤温度上升,H₂O、CO₂、H₂S排放速率都有上升趋势（满注水样地的H₂O除外）;半注水和满注水造成的影响,H₂O排放速率表现为趋同-异步-消失的特征,在注水前期（63.73 h）半注水和满注水差异基本一致,后期差异较大,直至125.64 h后注水的影响才消失,总体分别造成H₂O排放总量76.3%和31.3%的增加;CO₂排放速率表现为异步-趋同的特征,注水初期环境的改变造成CO₂排放的一致减少,37.69~68.66 h二者出现明显差异,68.66~125.64 h水位虽然恢复,但差异仍然存在,注水分别造成CO₂排放总量50.1%和43.2%的减少;H₂S排放速率表现为无变化-异步-无变化的特征,总体造成H₂S排放总量42.3%和32.3%的增加。研究追踪了水位上升后土壤H₂O、CO₂和H₂S排放速率变化的动态过程,其影响具有异步性和持续性的特点,CO₂排放速率表现出较长的响应周期。研究结果对于河流湿地生态功能研究具有重要意义,湿地土壤气体排放对水位变化的响应滞后意味着对湿地生态功能的重要影响,其波动过程需要更长时段的精准研究。  相似文献