非均质油藏特高含水开发期空气泡沫驱实验研究

孤岛油田在经历水驱、聚合物驱和聚驱后水驱等多轮开采后,地下剩余油高度分散,采出液含水高,开采难度加大。如何提高聚驱后油藏的采收率对于提高油田的整体开发效益尤为重要。基于“边调边驱”原则,室内开展了空气泡沫驱提高采收率方法研究。模拟了正韵律高含水油藏地质模型(由高、中、低渗并联岩心管组成)。通过对不同发泡剂质量分数、不同气液比下泡沫体系阻力因子的测定,得到最佳条件为发泡剂质量分数0.5％`和最佳气液体积比1∶1。经室内高、低采出程度下空气泡沫体系的封堵性和调驱性能实验,结果表明,优化空气泡沫的段塞组合,可大大提高不同采出程度下油藏的采收率。第一轮水驱后岩心为15.37％的低采出程度条件下,空气泡沫调驱采收率可提高22.02％;岩心采出程度高达45.53％的条件下,第二轮带有纯空气段塞的泡沫驱采收率可提高9.35％。     

基于节点服务能力的自适应P2P模型

P2P网络的节点在处理能力、存储能力、网络带宽、兴趣域等特性上存在着明显的异构性,在早期的研究中,这种异构性往往被忽略或者仅仅简单、单一地被考虑。综合利用节点的这些异构性,提出基于节点服务能力的自适应P2P模型。模型中,节点通过服务能力自主选择邻居进行聚类,根据网络的需求和动态变化自适应地调整聚类的规模和节点间的连接。仿真实验结果表明,该模型减少了网络拓扑失配和freerider现象,有效地提高了网络的搜索效率。     

基于模型参考的异构多智能体平均一致性

针对参数未知的异构线性多智能体系统，在无向或平衡有向网络下提出一种固定输出平均一致性协议，使得每个智能体的输出达到它们初始输出的平均值。首先，网络中每个智能体都被建模成阶数不同且相关度为1或2的未知线性系统，并根据自身及其邻居节点的输出更新其状态；其次，基于模型参考控制方法，对不同相关度的智能体定义相对应的模型；最后，提出一致性协议使每个智能体的输出收敛至其参考模型的输出，即达到固定输出平均一致。仿真实验利用了一个说明性的例子验证了所提协议的有效性和收敛性。     

苏里格气田苏53区块合理井网井距研究

苏53区块是典型的低压、低渗、低丰度、非均值性强的岩性气藏,应用经济极限及合理采气速度方法计算了该区块的技术合理井网井距,并结合数值模拟研究及现场试验结果确定该区块气藏的合理井距。建议开发方案:储量丰度高于1.3×108m3/km2区域采用600m×800m近似菱形不规则井网一次成形,集中建产;而储量丰度低于1.3×108m3/km2区域先采用600m×1 200m近似菱形不规则井网控制。     

特低渗透率储层水驱油规律实验研究

为研究特低渗透率储层水驱油规律,文中选取鄂尔多斯盆地3个井区的57块岩心进行水驱油实验分析,并研究了特低渗透率条件下水驱油效率与渗透率大小、注入倍数、注水压力等参数的关系。岩心主要为特低渗透率岩心,渗透率大小为研究区长4+5储层、长6储层和长8储层渗透率范围。实验结果表明:驱油效率随着渗透率增加而提高,而且在渗透率低值阶段,驱油效率提高更快;随着注水倍数的增加,驱油效率提高,直到含水100%为止,但含水越高,增加幅度越小;在同样的水驱速度下,渗透率越大,驱油效率越高,如果水驱速度不同,采收率会产生波动,但存在一个最佳驱油速度,且渗透率越大,最佳驱油速度变大;随着注水压力增加,无水期驱油效率总体呈下降趋势,但含水期驱油效率随着注水压力增加而逐渐提高,当达到一个最佳注水压力后,驱油效率又呈下降趋势;层内非均质性越强,驱油效率越低。     

Complex Conformational Dynamics of the Heart Failure-Associated Pre-miRNA-377 Hairpin Revealed by Single-Molecule Optical Tweezers

Pre-miRNA-377 is a hairpin-shaped regulatory RNA associated with heart failure. Here, we use single-molecule optical tweezers to unzip pre-miRNA-377 and study its stability and dynamics. We show that magnesium ions have a strong stabilizing effect, and that sodium ions stabilize the hairpin more than potassium ions. The hairpin unfolds in a single step, regardless of buffer composition. Interestingly, hairpin folding occurs either in a single step (type 1) or through the formation of intermediates, in multiple steps (type 2) or gradually (type 3). Type 3 occurs only in the presence of both sodium and magnesium, while type 1 and 2 take place in all buffers, with type 1 being the most prevalent. By reducing the size of the native hairpin loop from fourteen to four nucleotides, we demonstrate that the folding heterogeneity originates from the large size of the hairpin loop. Further, while efficient pre-miRNA-377 binders are lacking, we demonstrate that the recently developed C2 ligand displays bimodal activity: it enhances the mechanical stability of the pre-miRNA-377 hairpin and perturbs its folding. The knowledge regarding pre-miRNA stability and dynamics that we provide is important in understanding its regulatory function and how it can be modulated to achieve a therapeutic effect, e.g., in heart failure treatment.     

A novel free boundary algorithm for the solution of cell population balance models

There exists an abundance of experimental evidence in a variety of systems, showing that cell populations are heterogeneous systems in the sense that properties such as size, shape, DNA and RNA content are unevenly distributed amongst the cells of the population. The quantitative understanding of heterogeneity is of great significance, since neglecting its effect can lead to false predictions. Cell population balance models are used to address the implications of heterogeneity and can accurately capture the dynamics of heterogeneous cell populations. They are first-order partial-integral differential equations and due to the complexity of formulation, analytical solutions are hard to obtain in the majority of cases. Despite the recent progress, the efficient solution of cell population balance models remains a challenging task. One of the main challenges stems from the fact that the boundaries of the intracellular state space are typically not known a priori and using fixed-boundary algorithms leads to inaccuracies and increased computational time demands. Motivated by this challenge, we formulated a free boundary finite element algorithm, capable of solving cell population balance equations more efficiently than the traditional fixed-boundary algorithms. The implementation of the algorithm is accommodated, in the finite element based software package COMSOL Multiphysics. We demonstrate the efficiency of this algorithm using the lac operon gene regulatory network as our model system and perform transient and asymptotic behavior analysis. In the latter case, the pseudo-arc-length continuation algorithm is incorporated, in order to investigate the existence of a bistability region, also observed at the single-cell level. Our analysis, revealed the existence of a region of bistability when cell heterogeneity is taken into account; however, its extend shrinks comparing to homogeneous cell populations. The free boundary algorithm can be easily extended for problems of higher dimensionality and we present results for a two-dimensional cell population balance model, which can exhibit an oscillatory behavior. It is shown that oscillations do not persist when the intracellular content is unevenly distributed amongst the daughter cells.     

一种新的基于非结构化P2P网络的语义覆盖网络

在经典的语义覆盖网络中,所有节点都处于对等地位,没有考虑节点间共享资源数量及相对位置的差异,这使网络中节点分组信息的维护与资源搜索成本较高。丈中分析了节点间共享资源数量及相对位置的差异对语义覆盖网络中节点分组信息的维护与资源搜索代价的影响,并在此基础上提出了一种新的基于非结构化P2P网络的语义覆盖网络。该结构利用P2P网络的拓扑匹配与区分索引技术有效减少了经典语义覆盖网络中节点分组信息的维护及资源搜索代价,提升了网络的整体性能。     

锂离子电池介尺度电化学反应非均匀性

锂离子电池是重要的一类能量存储与转化装置。本文从化工角度上出发,将电池视为一类“特殊的”化工反应器,其中也存在着“三传一反”：电子传输、离子传输、热量传递和电化学反应。电极是这些传递与反应过程发生的主要场所;在不同空间与时间尺度上,电极中的传递与反应过程具有不均匀性,进而导致电池材料的利用与失效的差异。本文进一步讨论了研究电极反应不均匀性的必要性,并从准二维电极模拟计算与多尺度表征分析技术两个角度,对不均匀电极反应过程的传质、传热过程、电化学反应过程、电极结构演变规律、电极失效机制等方面的研究进行综述,对未来高性能、长寿命和具备快充性能的电池开发具有一定的指导意义。     

一种高温酸性α-淀粉酶基因的高效表达和表达产物分析

一种高温酸性α-淀粉酶基因经密码子优化后在巴斯德毕赤酵母中得到了高效表达,表达的重组α-淀粉酶rBD5063具有α-淀粉酶的活性,表达量达到60mg／L。对rBD5063进行了纯化并对多组分的表达产物进行了研究。rBD5063作用最适pH值为5．0,在pH3．5～10．0范围内酶活性保留50％以上,最适温度在105～110℃之间,在90℃下酶活性半衰期约30min。低浓度Ca^2＋对激活rBD5063活性和维持稳定性是必需的,高浓度对活性会产生轻微抑制作用,Mg^2＋、SDS和Trition X-100都能够部分抑制rBD5063活性,Cu^2＋和EDTA严重抑制rBD5063活性。表达产物水解可溶性淀粉主要产物是单糖和低聚寡糖。表达产物包括分子量分别是62、56、44kD的3种活性组分,在通常情况下主要以大分子量活性多聚体的形式存在。重组α-淀粉酶rBD5063不存在N-连接的糖基化,但是存在O-连接的糖基化现象,O-连接对rBD5063的热稳定性和最适温度没有显著影响。