Modeling the Formation of Fluid Banks During Counter-Current Flow in Porous Media

Fluid banks sometimes form during gravity-driven counter-current flow in certain natural reservoir processes. Prediction of flow performance in such systems depends on our understanding of the bank-formation process. Traditional modeling methods using a single capillary pressure curve based on a final saturation distribution have successfully simulated counter-current flow without fluid banks. However, it has been difficult to simulate counter-current flow with fluid banks. In this paper, we describe the successful saturation-history-dependent modeling of counter-current flow experiments that result in fluid banks. The method used to simulate the experiments takes into account hysteresis in capillary pressure and relative permeabilities. Each spatial element in the model follows a distinct trajectory on the capillary pressure versus saturation map, which consists of the capillary hysteresis loop and the associated capillary pressure scanning curves. The new modeling method successfully captured the formation of the fluid banks observed in the experiments, including their development with time. Results show that bank formation is favored where the p_c-versus-saturation slope is low. Experiments documented in the literature that exhibited formation of fluid banks were also successfully simulated.     

银行间债券市场的外部效率:基于商业银行的视角

以参与我国银行间债券市场的商业银行为研究对象,运用面板数据模型检验银行间债券市场的外部效率对于商业银行经营绩效的影响.实证结果表明:我国银行间债券市场的发展对于商业银行的盈利能力和流动性管理水平均有较强的外部正效率,而对于商业银行传统盈利模式和风险管理则具有负面影响.建议商业银行应利用银行间债券市场的外部正效率提高其资产负债管理水平,通过提升自身经营管理水平来降低银行间债券市场外部负效率对自身的影响;此外监管当局还应该降低小型金融机构进入银行间债券市场的门槛,以发挥该市场外部正效率对化解区域金融风险的作用.     

基于竞合关系的合同制造商融资策略研究

考虑由竞争合同制造商和原始设备生产商(OEM)组成的竞合供应链,竞争合同制造商在上游是OEM的合作者,在下游市场上是OEM的竞争者。当合同制造商因资金约束而不能进行生产运营时,一个通常做法是向银行贷款或者OEM融资;为了更好地探讨竞合供应链的融资决策,考虑了批发价格分别为外生变量和内生变量两种不同的情况下,以OEM为Stackelberg领导者的博弈,这与实际情况很接近。分析结果表明,当批发价格分别为外生变量时,合同制造商融资方式的选择主要受融资利率的影响;当批发价格为内生变量时,合同制造商融资方式的选择主要受自身自有资金量的影响。研究揭示了竞合供应链的融资决策过程,阐明了合同制造商的融资方式选择与自身的自有资金量和融资利率的关系。最后用数值算例对上述结论进行了验证说明。     

Geometric Analysis and Symbol Calculus: Fourier Transform Magnetic Resonance Imaging and Wavelets

Due to its unequalled advantages, the magnetic resonance imaging (MRI) modality has truly revolutionized the diagnosis and evaluation of pathology. Because many morphological anatomic details that may not be visualized by other high tech imaging methods can now be readily shown by diagnostic MRI, it has already become the standard modality by which all other clinical imaging techniques are measured. The unique quantum physical basis of the MRI modality combined with the imaging capabilities of current computer technology has made this imaging modality a target of interdisciplinary interest for clinicians, physicists, biologists, engineers, and mathematicians. Due to the fact that MRI scanners perform corticomorphic processing, this modality is by far more complex than all the other high tech clinical imaging techniques. The purpose of this paper is to outline a phase coherent wavelet approach to Fourier transform MRI. It is based on distributional harmonic analysis on the Heisenberg nilpotent Lie group G and the associated symplectically invariant symbol calculus of pseudodifferential operators. The contour and contrast resolution of MRI scans which is controlled by symplectic filter bank processing gives the noninvasive MRI modality superiority over X-ray computed tomography (CT) in soft tissue differentiation.     

Is the rigid-body assumption reasonable?: Insights into the effects of dynamics on the electrostatic analysis of barnase-barstar

Electrostatically-driven association of proteins is important to many biological functions, and understanding which amino acid residues contribute to these interactions is crucial to protein design. Theoretical calculations that are used to elucidate the role of electrostatics in association are typically based on a single experimentally determined protein structure, while an underlying rigid-body assumption is adopted. The goal of this study was to investigate the role of conformational fluctuations on electrostatic interaction energies, as applied to the electrostatic analysis of barnase-barstar. For our calculations, we apply theoretical alanine-scan mutagenesis to introduce charge perturbations by replacing every ionizable residue with alanine, one at a time. Electrostatic clustering and free energy calculations based on the Poisson-Boltzmann method are used to evaluate the effects of each perturbation. Molecular dynamics simulations are performed for the barnase-barstar parent complex and seven experimental alanine mutations from the literature, in order to introduce relaxation before and after mutation. We discuss the effects of dynamics, in the form of pre- and post-mutation relaxation, on electrostatic clustering and free energies of association in light of experimental data. We also examine the utility of nine electrostatic similarity methods for clustering of barnase alanine-scan mutants. Our calculations suggest that the rigid-body assumption is reasonable for electrostatic calculations of barnase-barstar.     

不良贷款约束下我国上市商业银行全要素生产率时序演变及其驱动因素研究——基于非期望产出的Malmquist-luenberger和Tobit模型

基于我国上市商业银行2007~2013年面板数据,构建包括不良贷款约束条件下我国上市商业银行投入产出指标体系,采用基于非期望产出的M-L生产率指数方法对我国上市商业银行全要素生产率跨期动态变化进行实证测度,并应用Tobit回归分析方法对影响我国上市商业银行全要素生产率的因素进行实证分析,实证结果显示:我国上市商业银行全要素生产率平均增长率为2.4%,上市城市商业银行全要素生产率高于股份制上市商业银行,而股份制商业银行高于国有商业银行,其主要来源与规模效率提升;此外,银行规模和存贷比对商业银行技术效率提升产生显著的正向驱动影响;而银行集中度对其产生显著的负向驱动影响;资产收益率和所有权结构对其影响不显著。     

产需不确定下面向资金约束供应商的供应链融资策略研究

以包含一个供应商和一个分销商的供应链为研究对象,其中分销商面临市场需求不确定性,供应商存在资金约束且面临产出不确定性。 提出期望利率的概念,研究银行贷款期望利率一定的情况下,供应链银行融资最优策略。 构建了供应链预付款融资机制,在此基础上研究预付款模式下供应链的融资与生产订购的最优策略,并讨论了预付款期望利率的可行范围。 研究表明,预付款融资模式下,分销商愿意以低于银行贷款利率的期望利率向供应商提供预付款; 存在预付款期望利率可行区间,实现预付款协调模式下供应链系统的帕累托改进。     

Development and application of an ultratrace method for speciation of organotin compounds in cryogenically archived and homogenized biological materials

An accurate, ultra-sensitive and robust method for speciation of mono, di, and tributyltin (MBT, DBT, and TBT) by speciated isotope-dilution gas chromatography-inductively coupled plasma-mass spectrometry (SID-GC-ICPMS) has been developed for quantification of butyltin concentrations in cryogenic biological materials maintained in an uninterrupted cryo-chain from storage conditions through homogenization and bottling. The method significantly reduces the detection limits, to the low pg g(-1) level (as Sn), and was validated by using the European reference material (ERM) CE477, mussel tissue, produced by the Institute for Reference Materials and Measurements. It was applied to three different cryogenic biological materials-a fresh-frozen mussel tissue (SRM 1974b) together with complex materials, a protein-rich material (whale liver control material, QC03LH03), and a lipid-rich material (whale blubber, SRM 1945) containing up to 72% lipids. The commutability between frozen and freeze-dried materials with regard to spike equilibration/interaction, extraction efficiency, and the absence of detectable transformations was carefully investigated by applying complementary methods and by varying extraction conditions and spiking strategies. The inter-method results enabled assignment of reference concentrations of butyltins in cryogenic SRMs and control materials for the first time. The reference concentrations of MBT, DBT, and TBT in SRM 1974b were 0.92 +/- 0.06, 2.7 +/- 0.4, and 6.58 +/- 0.19 ng g(-1) as Sn (wet-mass), respectively; in SRM 1945 they were 0.38 +/- 0.06, 1.19 +/- 0.26, and 3.55 +/- 0.44 ng g(-1), respectively, as Sn (wet-mass). In QC03LH03, DBT and TBT concentrations were 30.0 +/- 2.7 and 2.26 +/- 0.38 ng g(-1) as Sn (wet-mass). The concentration range of butyltins in these materials is one to three orders of magnitude lower than in ERM CE477. This study demonstrated that cryogenically processed and stored biological materials are a promising alternative to conventional freeze-dried materials for organotin speciation analysis, because these are, at present, the best conditions for minimizing degradation of thermolabile species and for long-term archival. Finally, the potential of the analytical method was illustrated by analysis of polar bear (Ursus maritimus) and beluga whale (Delphinapterus leuca) liver samples that had been collected in the Arctic and archived at the Marine Environmental Specimen Bank. Significant concentrations of butyltin compounds were found in the samples and provide the first evidence of the presence of this class of contaminant in the Arctic marine ecosystem. Figure Eye catch image.     

河型发育过程的二维数值模拟研究

改进已有二维平面水沙模型,进一步考虑河床粗化、弯道二次流及河床结构对泥沙输运的影响;并针对河湾形态对崩岸的影响提出新的非粘性土崩岸模拟方法,使其能模拟边滩的形成。利用改进后模型分别对Yen弯道水槽泥沙冲淤试验及Friendkin室内弯曲小河塑造试验进行模拟;模拟结果与试验观测资料吻合较好,表明考虑弯道对泥沙输运及河岸崩塌影响的模型能够更准确反映天然河流演化过程,为研究河型演化机理及各控制因素变化规律提供新手段。