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1.
In this paper we study the infiltration of DNAPL in a porous medium containing a single low-permeable lens. Our aim is to
determine whether or not DNAPL infiltrates into the lens. A key role is played by the capillary pressure: DNAPL cannot infiltrate
into the lens unless the capillary pressure exceeds the entry pressure of the lens. In the model this is reflected by an interface
condition, the extended capillary pressure condition. To derive analytical approximations we first consider a steady-state
DNAPL plume in a homogeneous medium. This results in an estimate of the DNAPL plume width as a function of depth, and an asymptotic
solution for small saturations. Assuming that the extent of the lens is much larger than the width of the unperturbed DNAPL
plume in the homogeneous medium, we derive an explicit criterion for DNAPL infiltration into the lens in terms of a critical
inflow rate. A numerical algorithm is presented in which the extended capillary pressure condition is incorporated. The numerical
and analytical results show good qualitative agreement.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
柱撑蛭石吸附去除废水中重金属离子的实验研究 总被引:2,自引:0,他引:2
分别利用有机柱化剂十二烷基磺酸钠(SDS)和无机柱化剂聚羟基铝(HA)对蛭石进行柱撑制得十二烷基磺酸钠柱撑蛭石(SDS-V erm icu lite)和聚羟基铝柱撑蛭石(HA-V erm icu lite),并通过XRD、红外光谱、ZETA电位等表征手段对柱撑蛭石进行表征,同时针对柱撑蛭石对Cu2 ,Cd2 ,C r3 3种重金属离子的吸附进行研究,结果表明:吸附去除率受反应时间、重金属离子的初始浓度、pH值等因素的影响,经柱撑后的蛭石对重金属离子吸附的吸附性能比蛭石原矿要强。柱撑蛭石吸附3种重金属离子的动力学吸附过程可用E lov icb方程和双常数方程进行较好的拟合。 相似文献
3.
M. Henze W. Pietsch F. Haberl G. Sala M. Hernanz D. Hatzidimitriou A. Rau D.H. Hartmann J. Greiner M. Orio H. Stiele M.J. Freyberg 《Astronomische Nachrichten》2010,331(2):193-196
Classical novae (CNe) have recently been reported to represent the major class of supersoft X‐ray sources (SSSs) in the central area of our neighbouring galaxy M 31. This paper presents a review of results from recent X‐ray observations of M 31 with XMM‐Newton and Chandra. We carried out a dedicated optical and X‐ray monitoring program of CNe and SSSs in the central area ofM 31. We discovered the first SSSs in M 31 globular clusters (GCs) and their connection to the very first discovered CN in a M 31 GC. This result may have an impact on the CN rate in GCs. Furthermore, in our optical and X‐ray monitoring data we discovered the CN M3 1N 2007‐11a, which shows a very short SSS phase of 29–52 days. Short SSS states (durations ≤ 100 days) of CNe indicate massive white dwarfs (WDs) that are candidate progenitors of supernovae type Ia. In the case of M31N 2007‐11a, the optical and X‐ray light curves suggest a binary containing a WD with MWD > 1.0 M⊙. Finally, we present the discovery of the SSS counterpart of the CN M31N 2006‐04a. The X‐ray light curve of M31N 2006‐04a shows short‐time variability, which might indicate an orbital period of about 2 hours (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
4.
5.
基于葵花8卫星的上海市夏季对流初生预报研究 总被引:2,自引:0,他引:2
参考Mecikalski et al(2010a;2010b)提出的基于GOES系列卫星的对流初生预报方法,针对上海市夏季对流天气特征建立了基于高时空分辨率的静止气象卫星数据的上海市对流初生判识及预报方法。利用该方法对上海市的一次对流初生个例进行了分析,并对2016年7-8月的12次对流初生事件进行了预报试验,结果表明:方法提取的各个指标能够很好地体现对流初生过程中云团的发展变化特征并能剔除掉成熟对流云团边缘像元的干扰;在12次对流初生事件中,成功地预报了其中的11次,预报时间较对流初生时间平均提前了约30 min,但是对于局地弱对流过程该方法仍有一定的缺陷。 相似文献
6.
W. A. Mulder 《Computational Geosciences》1997,1(1):85-108
Simulation of wave propagation for seismic purposes is usually restricted to a small portion of the earth. Artificial boundary
conditions are required where the subsurface model is truncated. Absorbing boundaries should ensure that waves hitting the
artificial boundaries are not reflected. The vast amount of literature on the subject suggests that “good” conditions have
not been found, and only “reasonable” solutions exist. A cursory overview of existing and a few new ideas is presented that
may guide the construction of suitable boundary conditions. Because the intended application of the boundary conditions was
a high-order finite-difference code that runs on a parallel computer, we have restricted our attention to local boundary conditions.
A fundamental problem in the design of accurate local boundary conditions is pointed out: accuracy is required to keep the
amount of reflected energy small, but at the same time allows for growing low-frequency modes. We have settled for Higdon’s
boundary conditions. Higdon proposes to include some damping to suppress the growing low-frequency modes. We show that third-order
conditions provide acceptable results for the simple scalar wave equation and the acoustic equation. In the elastic case,
an additional low-frequency growing mode may occur. This mode can be suppressed by using a dissipative boundary scheme and
by increasing the amount of damping. The increase in damping results in an increase in the amount of reflected energy, which
is larger than in the scalar case. Numerical experiments exhibit a reasonable performance, although some improvement would
be useful, particularly in the anisotropic elastic case.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
H.?Liu W. A.?Caldwell L. R.?Benedetti W.?Panero R.?JeanlozEmail author 《Physics and Chemistry of Minerals》2003,30(9):582-588
The high-pressure behavior of 06g7j5b3x8tf9p4/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-Fe2O3 has been studied under static compression up to 60 GPa, using a laser-heated diamond anvil cell. Synchrotron-based angular-dispersive X-ray diffraction shows that the sample remains in the corundum structure up to 50 GPa, but with the appearance of coexisting diffraction lines from a high-pressure phase at pressures above 45 GPa. A least-squares fit of low-pressure phase data to an Eulerian finite-strain equation of state yields linear incompressibilities of K
a
0=749.5 (± 18.4) GPa and K
c
0= 455.7 (± 21.4) GPa, differing by a factor of 1.6 along the two directions. The enhanced compressibility of the c axis may lead to breaking of vertex- or edge-sharing bonds between octahedra, inducing the high-pressure phase transformation at 50 GPa. Analysis of linear compressibilities suggests that the high-pressure phase above 50 GPa is of the Rh2O3 (II) structure. Continuous laser heating reveals a new structural phase transformation of 06g7j5b3x8tf9p4/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-Fe2O3 at 22 GPa, to an orthorhombic structure with a=7.305(3) Å, b=7.850(3) Å, and c=12.877(14) Å, different from the Rh2O3 (II) structure. 相似文献
8.
In recent years, the data collecting and processing of magnetotelluric sounding (MT) have progressed greatly. How to improve the quality of field surveyed data and obtain the high quality parameters such as apparent resistivity and phase is the most important link during the overall flow. It is closely related to the signal-to-noise ratio of magnetic sensors, the resolution of data collecting units and relevant processing methods as well. Produced by Germany Metronix Measurement Instruments and Electronics Ltd., the new type multi-channel geophysical measurement system GMS-06 was already adopted and used by domeslic units such as Institute of Geology and Geophysics of Chinese Academy of Sciences and Tongji University. Based on the brief introduction of GMS-06, this paper will give the comparisons and analyses of the synchronous surveyed MT data by GMS-06, MMS-03 MT system which was also produced by Metronix and V5-2000 MT system produced by Canada Phoenix Geophysics Ltd.. Then the preliminary processing and interpretation results of the long period MT data observed by GMS-06 in the area of Shanghai and Zhejiang are also discussed in the paper. 相似文献
9.
Joanna M. Rankin Geoffrey A. E. Wright 《Monthly notices of the Royal Astronomical Society》2007,379(2):507-517
We present a detailed study of the single pulses of the bright radio pulsar B0834+06, and offer evidence that the dominant periodic modulation in this pulsar's emission governs the occurrence of nulls. The nulls of B0834+06 constitute approximately 9 per cent of the total pulses and we demonstrate that they do not occur at random in the pulse sequence. On the contrary, they are found to occur preferentially close to the minimum of the pulsar's emission cycle, whose period jitters around a central value of P 3 ≈ 2.17 rotation periods. It is likely that the intrinsic duration of the nulls averages about 0.2 times the pulsar rotation period. Surprisingly, the clearly distinct population of nulls and partial nulls of B0834+06 exhibit a two-peak profile slightly broader than that of the normal emission. This is in contrast to the profile of extremely weak normal pulses, which is narrower than the overall profile. A flow/counterflow model for the pulsar's two components can reproduce the essential observed features of the emission in its dominant mode, with nulls occurring at the point where the minima of the two systems are aligned. This suggests that the observed nulling rate is determined by the chance positioning of our sightline with respect to the system. If the flow is interpreted as part of a circulating carousel, a fit yields a best estimate of 14 'sparks'. 相似文献
10.
Astrid Holstad 《Computational Geosciences》2000,4(2):103-139
We formulate mathematical and numerical models for multispecies, multi-phase and non-isothermal reactive fluid flow in porous
media focusing on the chemical reactions and the transport of solutes. Mass conservation and stability in the time integration
are emphasized. We use cell-centered finite volume differencing in space and an implicit Runge-Kutta method in time. Assuming
two space dimensions, we introduce flux approximation for arbitrarily shaped convex quadrilaterals. On equidistant and variable
sized rectangular grids we choose limited κ=
related schemes to approximate the advective flux and the central difference scheme for the diffusive flux. On non-rectangular
grids we recommend the VF9 scheme for the estimation of the diffusive flux. Our model exists as a code.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献