Relative permeabilities of a near critical binary fluid

Relative permeabilities were measured at very low interfacial tensions (IFT) for two-phase mixtures of methanol and hexane flowing through Clashach sandstone. These two components pass from a two- to a single-phase system as the temperature is increased above the critical solution temperature (CST). The interfacial tension between the coexisting phases approaches zero as the solution reaches miscibility. The phase behaviour of methanol and hexane mixtures has been well characterised allowing the calculation of relative permeabilities, saturations and capillary numbers. Flow data are reported for four different temperatures in the two-phase region (i.e., four values of IFT and capillary number). The capillary desaturation curve (CDC) for the strongly wetting methanol rich phase is also presented. In addition to the novel technique presented for measurement of relative permeability, the results indicate that relative permeabilities approach straight line functions very near the critical point. Furthermore, desaturation of the wetting phase was found to be dependent on the capillary number which, in turn, depends on the location of the mixture on the fluid phase diagram and the proximity to the critical temperature.     

Numerical Homogenization of the Absolute Permeability Using the Conformal-Nodal and Mixed-Hybrid Finite Element Method

The modeling of hydrocarbon reservoirs and of aquifer-aquitard systems can be separated into two activities: geological modeling and fluid flow modeling. The geological model focuses on the geometry and the dimensions of the subsurface layers and faults, and on its rock types. The fluid flow model focuses on quantities like pressure, flux and dissipation, which are related to each other by rock parameters like permeability, storage coefficient, porosity and capillary pressure. The absolute permeability, which is the relevant parameter for steady single-phase flow of a fluid with constant viscosity and density, is studied here. When trying to match the geological model with the fluid flow model, it generally turns out that the spatial scale of the fluid flow model is built from units that are at least a hundred times larger in volume than the units of the geological model. To counter this mismatch in scales, the fine-scale permeabilities of the geological data model have to be upscaled' to coarse-scale permeabilities that relate the spatially averaged pressure, flux and dissipation to each other. The upscaled permeabilities may be considered as complicated averages, which are derived from the spatially averaged flow quantities in such a way that the continuity equation, Darcy's law and the dissipation equation remain valid on the coarse scale. In this paper the theory of upscaling will be presented from a physical point of view aiming at understanding, rather than mathematical rigorousness. Under the simplifying assumption of spatial periodicity of the fine-scale permeability distributions, homogenization theory can be applied. However, even then the spatial distribution of the permeability is generally so intricate that exact solutions of the homogenized permeability cannot be found. Therefore, numerical approximation methods have to be applied. To be able to estimate the approximation error, two numerical methods have been developed: one based on the conventional nodal finite element method (CN-FEM) and the other based on the mixed-hybrid finite element method (MH-FEM). CN-FEM gives an upper bound for the sum of the diagonal components of the homogenized mobility matrix, while MH-FEM gives a lower bound. Three numerical examples are presented.     

Nuclear magnetic resonance imaging of miscible fingering in porous media

Nuclear Magnetic Resonance Imaging (MRI) can noninvasively map the spatial distribution of Nuclear Magnetic Resonance (NMR)-sensitive nuclei. This can be utilized to investigate the transport of fluids (and solute molecules) in three-dimensional model systems. In this study, MRI was applied to the buoyancy-driven transport of aqueous solutions, across an unstable interface in a three-dimensional box model in the limit of a small Péclet number (Pe<0.4). It is demonstrated that MRI is capable of distinguishing between convective transport (fingering) and molecular diffusion and is able to quantify these processes. The results indicate that for homogeneous porous media, the total fluid volume displaced through the interface and the amplitude of the fastest growing finger are linearly correlated with time. These linear relations yielded mean and maximal displacement velocities which are related by a constant dimensionless value (2.4±0.1). The mean displacement velocity (U) allows us to calculate the media permeability which was consistent between experiments (1.4±0.1×10^–7cm²).U is linearly correlated with the initial density gradient, as predicted by theory. An extrapolation of the density gradient to zero velocity enables an approximate determination of the critical density gradient for the onset of instability in our system (0.9±0.3×10^–3 g/cm³), a value consistent with the value predicted by a calculation based upon the modified Rayleigh number. These results suggest that MRI can be used to study complex fluid patterns in three-dimensional box models, offering a greater flexibility for the simulation of natural conditions than conventional experimental modelling methods.     

Novel sulfonated poly (ether ether ketone)/silica coated carbon nanotubes high‐performance composite membranes for direct methanol fuel cell

The major risk of using carbon nanotubes (CNTs) to modify proton exchange membranes (PEMs) in fuel cells is possible short‐circuiting due to the excellent electrical conductivity of CNTs. In this article, silica‐coated CNTs (SiO₂@CNTs) were successfully prepared by a simple sol–gel process and then used as a new additive in the preparation of sulfonated poly (ether ether ketone) (SPEEK)‐based composite membranes. The insulated and hydrophilic silica coated on the surface of CNTs not only eliminated the risk of short‐circuiting, but also enhanced the interfacial interaction between CNTs and SPEEK, and hence promoted the homogeneous dispersion of CNTs in the SPEEK matrix. Moreover, compared to the methanol permeability of the pure SPEEK membrane (3.42 × 10^?7 cm² s^?1), the SPEEK/SiO₂@CNT composite membrane with a SiO₂@CNT loading of 5 wt% exhibits almost one order of magnitude decrease of methanol crossover, while the proton conductivity still remained above 10^?2 S cm^?1 at room temperature. The obtained results expose the possibility of SPEEK/SiO₂@CNT membranes to be served as high‐performance PEMs in direct methanol fuel cells. Copyright © 2015 John Wiley & Sons, Ltd.     

Development of a Sensitive Bioluminogenic Probe for Imaging Highly Reactive Oxygen Species in Living Rats

A sensitive bioluminogenic probe for highly reactive oxygen species (hROS), SO₃H‐APL, was developed based on the concept of dual control of bioluminescence emission by means of bioluminescent enzyme‐induced electron transfer (BioLeT) and modulation of cell‐membrane permeability. This probe enables non‐invasive visualization of physiologically relevant amounts of hROS generated deep inside the body of living rats for the first time. It is expected to serve as a practical analytical tool for investigating a wide range of biological functions of hROS in vivo. The design concept should be applicable to other in vivo bioluminogenic probes.     

Gold(III)–pyrrolidinedithiocarbamato Derivatives as Antineoplastic Agents

Transition metals offer many possibilities in developing potent chemotherapeutic agents. They are endowed with a variety of oxidation states, allowing for the selection of their coordination numbers and geometries via the choice of proper ligands, leading to the tuning of their final biological properties. We report here on the synthesis, physico-chemical characterization, and solution behavior of two gold(III) pyrrolidinedithiocarbamates (PDT), namely [Au^IIIBr₂(PDT)] and [Au^IIICl₂(PDT)]. We found that the bromide derivative was more effective than the chloride one in inducing cell death for several cancer cell lines. [Au^IIIBr₂(PDT)] elicited oxidative stress with effects on the permeability transition pore, a mitochondrial channel whose opening leads to cell death. More efficient antineoplastic strategies are required for the widespread burden that is cancer. In line with this, our results indicate that [Au^IIIBr₂(PDT)] is a promising antineoplastic agent that targets cellular components with crucial functions for the survival of tumor cells.     

Laplace方程有孔椭圆区域边值问题的解析解

本文利用相似流动替换方法 ,解决了中心有圆孔的椭园形区域上 Laplace方程第一类边值问题 ;采用分区域解法 ,给出了中心有椭园孔的椭园形区域上 Laplace方程第一类边值问题的解析通解 .这一结果在许多工程领域有重要应用 ,本文给出了油藏工程实例     

具有混合边界透水条件的多孔饱和半空间上刚性圆板的垂直振动

用积分变换和积分方程研究多孔饱和半空间上刚性圆板的垂直振动问题。首先应用逐次解耦方法求解多孔饱和固体的动力基本方程－Ｂｉｏｔ波动方程。然后考虑混合边界透水条件（半空间表面与圆板的接触面是不透水的,而其余表面是透水的）,建立子多孔饱和半空间上刚性圆板垂直振动的对偶积分方程,并化对偶积分方程为第二类Ｆｒｄｄｈｏｌｍ积分方程。     

冲击载荷下饱和砂土渗流和破坏的实验研究

对饱和破土在冲击载荷下发现的变形和流动效应进行了落锤模拟实验研究,发现砂土骨架出现纵向排水通道和横向断裂等现象,对可能影响这些现象的主要因素进行了对比的实验,对上述实验现象进行了初步的解释．     

激光差拍波等离子体加速装置中约束磁场的计算研究

 通过对等离子体发生器建立三维模型,计算得到磁场在该装置中的分布情况。所得结果与实际测量基本一致 ,从而说明所建模型的合理性。通过调节一些参数,对该模型进一步搞清了导致等离子体发生器中真实磁场较实验设计要求偏低的主要原因,并提出了相应的改进方案。