Impact of Rock Heterogeneity on Interactions of Microbial-Enhanced Oil Recovery Processes

Residual oil saturation reduction and microbial plugging are two crucial factors in microbial-enhanced oil recovery (MEOR) processes. In our previous study, the residual saturation was defined as a nonlinear function of the trapping number, and an explicit relation between the residual oil saturation and the trapping number was incorporated into a fully coupled biological (B) and hydrological (H) finite element model. In this study, the BH model is extended to consider the impact of rock heterogeneity on microbial-enhanced oil recovery phenomena. Numerical simulations of core flooding experiments are performed to demonstrate the influences of different parameters controlling the onset of oil mobilization. X-ray CT core scans are used to construct numerical porosity-permeability distributions for input to the simulations. Results show clear fine-scale fingering processing, and that trapping phenomena have significant effects on residual oil saturation and oil recovery in heterogeneous porous media. Water contents and bacterial distributions for heterogeneous porous media are compared with those for homogenous porous media. The evolution of the trapping number distribution is directly simulated and visualized. It is shown that the oil recovery efficiency of EOR/MEOR will be lower in heterogeneous media than in homogeneous media, largely due to the difficulty in supplying surfactant to unswept low-permeability zones. However, MEOR also provides efficient plugging along high-permeability zones which acts to increase sweep efficiency in heterogeneous media. Thus, MEOR may potentially be more suited for highly heterogeneous media than conventional EOR.     

光电跟踪系统的共轴跟踪控制技术研究

为了提高光电跟踪系统的跟踪精度,对其粗跟踪环节的共轴跟踪控制技术进行了研究。介绍了共轴跟踪控制的基本原理,分析了常用非线性卡尔曼滤波算法,并仿真比较了无迹卡尔曼滤波(UKF)和容积卡尔曼滤波(CKF)的位置和速度的预测精度。在此基础上综合UKF和CKF的优点,设计了对延迟的合成位置信号进行处理的双并联滤波器,实现了光电跟踪系统的共轴跟踪控制。利用实测数据仿真实验表明,光电跟踪系统的跟踪精度明显提高。     

THE VALUE DISTRIBUTION AND UNIQUENESS OF ONE CERTAIN TYPE OF DIFFERENTIAL-DIFFERENCE POLYNOMIALS

In this article, we investigate the distribution of the zeros and uniqueness of differential-difference polynomials G(z) =(fn(fm(z)- 1)dΠj=1f(z + cj)vj)(k)- α(z),H(z) =(fn(f(z)- 1)mdΠj=1f(z + cj)vj)(k)- α(z),where f is transcendental entire function of finite order, cj(j = 1, 2, ···, d), n, m, d, and vj(j = 1, 2, ···, d) are integers, and obtain some theorems, which extended and improved many previous results.     

逐差法弥补了算术平均法处理数据的不足

本阐述了逐差法弥补算术平均法处理数据的不足，指出逐差法配合作图法组织教学更直观更形象，用逐差法能获得近似最佳直线方程。     

胆囊癌中PTEN基因异常表达及甲基化的研究

目的 探讨胆囊癌的发生、发展及转移与PTEN 基因异常表达及其基因启动子区异常甲基化的关系。方法 选取胆囊癌标本44 例（胆囊癌组）和胆囊炎标本20 例（对照组）,通过免疫组织化学染色、Western-blot、甲基化特异性PCR法分析两组患者胆囊组织中PTEN 基因表达及启动子区甲基化差异。结果 与对照组相比,胆囊癌组中PTEN 基因表达阳性率明显下降（P＜0.01）,而启动子区甲基化阳性率显著增高（P＜0.01）;胆囊癌组中有淋巴结转移者PTEN 基因表达阳性率较无淋巴结转移者降低（P＜0.05）,而启动子区甲基化阳性率增高（P＜0.05）;胆囊癌分期增高,PTEN 基因表达阳性率降低（P＜0.05）,而启动子区甲基化阳性率增高（P＜0.05）。结论 PTEN 基因低表达是胆囊癌的发生、发展及转移的重要原因之一,其低表达与启动子区过度甲基化有关。     

Covalent Organic Frameworks: Chemical Approaches to Designer Structures and Built‐In Functions

A new approach has been developed to design organic polymers using topology diagrams. This strategy enables covalent integration of organic units into ordered topologies and creates a new polymer form, that is, covalent organic frameworks. This is a breakthrough in chemistry because it sets a molecular platform for synthesizing polymers with predesignable primary and high‐order structures, which has been a central aim for over a century but unattainable with traditional design principles. This new field has its own features that are distinct from conventional polymers. This Review summarizes the fundamentals as well as major progress by focusing on the chemistry used to design structures, including the principles, synthetic strategies, and control methods. We scrutinize built‐in functions that are specific to the structures by revealing various interplays and mechanisms involved in the expression of function. We propose major fundamental issues to be addressed in chemistry as well as future directions from physics, materials, and application perspectives.     

Topology‐Templated Synthesis of Crystalline Porous Covalent Organic Frameworks

A strategy is presented for the synthesis of crystalline porous covalent organic frameworks via topology‐templated polymerization. The template is based on imine‐linked frameworks and their (001) facets seed the C=C bond formation reaction to constitute 2D sp² carbon‐conjugated frameworks. This strategy is applicable to templates with different topologies, enables designed synthesis of frameworks that cannot be prepared via direct polymerization, and creates a series of sp² carbon frameworks with tetragonal, hexagonal, and kagome topologies. The sp² carbon frameworks are highly luminescent even in the solid state and exhibit topology‐dependent π transmission and exciton migration; these key fundamental π functions are unique to sp² carbon‐conjugated frameworks and cannot be accessible by imine‐linked frameworks, amorphous analogues, and 1D conjugated polymers. These results demonstrate an unprecedented strategy for structural and functional designs of covalent organic frameworks.     

Topology-Templated Synthesis of Crystalline Porous Covalent Organic Frameworks

A strategy is presented for the synthesis of crystalline porous covalent organic frameworks via topology-templated polymerization. The template is based on imine-linked frameworks and their (001) facets seed the C=C bond formation reaction to constitute 2D sp² carbon-conjugated frameworks. This strategy is applicable to templates with different topologies, enables designed synthesis of frameworks that cannot be prepared via direct polymerization, and creates a series of sp² carbon frameworks with tetragonal, hexagonal, and kagome topologies. The sp² carbon frameworks are highly luminescent even in the solid state and exhibit topology-dependent π transmission and exciton migration; these key fundamental π functions are unique to sp² carbon-conjugated frameworks and cannot be accessible by imine-linked frameworks, amorphous analogues, and 1D conjugated polymers. These results demonstrate an unprecedented strategy for structural and functional designs of covalent organic frameworks.