Completion and stimulation trends in North American unconventional plays and resulting impact on well productivity

过去十年,非常规油气勘探开发在全球范围内大幅扩张。水平钻井和多级水力压裂技术也在不断地发展和创新,使得超长水平井成为可能。同时,因为压裂强度不断增加,作业者可以最大限度地提高储层接触面积和对储层的改造体积 （SRV）。然而,完井优化方面的挑战仍然存在,作业者持续不断地尝试和试验各种完井与增产参数组合,以确保非常规油气藏开发的经济可行性。优选最佳的完井与增产参数组合是一项非常关键的任务,应结合油气田的具体储层特征进行优化。本文总结了2014—2020年间北美9个主要非常规油气藏的压裂增产趋势,包括Marcellus, Haynesville, Barnett, Utica, Bone Spring, Bakken, Wolfcamp Midland, Eagle Ford, Scoop/Stack。分析了各油气田几个关键的完井和增产参数的整体趋势,同时还评估了单个参数（如水平段压裂长度、支撑剂强度、段间距等）对井产能的影响。然后对比分析相应的初始井产量（90 天平均初始产量）,评估各个参数对产能的影响,从而确定每个完井参数的最佳范围,以实现产能最优化。     

Structure and Optical Behavior of Nanocomposite Hybrid Films of Well Monodispersed ZnO Nanoparticles into Poly （vinylpyrrolidone）

We fabricated an inorganic-polymeric photoluminescent thin film based on ZnO nanoparticles, which were grown directly in the poly（vinylpyrrolidone） （PVP） matrix. The microstructure, composition, thermal stability, and the temperature-dependent photoluminescence of the thin film were investigated. X-ray diffraction （XRD） and transmission electron microscopy （TEM） results indicated that all the ZnO nanoparticles with a polycrys talline hexagonal wurzite structure were well separated from each other and were dispersed in the polymeric matrix homogeneously and randomly. Raman spectrum （Raman） showed a typical resonant multi-phonon process within the hybrid thin film. The shifts of infrared bands for PVP in the hybrid film should be attributed to strong coulombic interaction between ZnO and polymeric matrix. The stability of the hybrid film and the effect of the perturbation of ZnO on the stability were determined by means of the thermogravimetric analysis （TG） and differential thermal analysis （DTA）. The ultraviolet-visible adsorption （UV-vis） showed distinct excitonic features. The photoluminescent spectrum （PL） of the ZnO nanoparticles modified by PVP molecules showed markedly enhanced ultraviolet emission and significantly reduced green emission, which was due to the Perfect surface passivation of ZnO nanoparticles. Temperature dependent photoluminescent spectrum studies suggested that the ultraviolet emission was associated with bound exciton recombination.     

A recursive field-normalized bibliometric performance indicator: an application to the field of library and information science

Two commonly used ideas in the development of citation-based research performance indicators are the idea of normalizing citation counts based on a field classification scheme and the idea of recursive citation weighing (like in PageRank-inspired indicators). We combine these two ideas in a single indicator, referred to as the recursive mean normalized citation score indicator, and we study the validity of this indicator. Our empirical analysis shows that the proposed indicator is highly sensitive to the field classification scheme that is used. The indicator also has a strong tendency to reinforce biases caused by the classification scheme. Based on these observations, we advise against the use of indicators in which the idea of normalization based on a field classification scheme and the idea of recursive citation weighing are combined.     

Mathematical Model for Electroslag Remelting Process

 A mathematical model, including electromagnetic field equation, fluid flow equation, and temperature field equation, was established for the simulation of the electroslag remelting process. The distribution of temperature field was obtained by solving this model. The relationship between the local solidification time and the interdendritic spacing during the ingot solidification process was established, which has been regarded as a criterion for the evaluation of the quality of crystallization. For a crucible of 950 mm in diameter, the local solidification time is more than 1 h at the center of the ingot with the longest interdendritic spacing, whereas it is the shortest at the edge of the ingot according to the calculated results. The model can be used to understand the ESR process and to predict the ingot quality.     

Fractal Study on Raceway Boundary

  The raceway has been studied extensively both theoretically and experimentally. The raceway boundary is coarse and fragmentary, but all of previous studies are based on Euclidean geometry, which regards the dimension of raceway as an integer. The fractal method of calculating raceway size, which describes boundary with extremely irregular or fragmentary characteristic, is brought forward in physical model. The fractal theory is used to calculate the fractal dimension of raceway boundary and the precise surface area of ellipsoidal raceway boundary. The result shows that the surface area based on fractal is larger than that based on Euclidean. And the surface area increases with the rise of blowing rate.     

Study on grain refinement of interstitial-free steel during continuous frictional angular extrusion

To explore the application of severe plastic deformation for grain refinement in steel production,a new method called continuous frictional angular extrusion (CFAE) was applied to refine the grain of interstitial-free steel.The deformation was carried out at room temperature and individual sheet specimens were processed in different number of passes.An overall grain size of 200nm was achieved after 8 passes and the proportion of high-angle boundaries to the total boundaries was more than 60%.Through the characterization of high resolution EBSD,X-ray diffraction (XRD) and hardness testing,this paper discussed the evolution of microstructures and textures during deformation and explored the development direction of the method.     

Metal-Organic Framework Nanocarriers for Drug Delivery in Biomedical Applications

Investigation of metal–organic frameworks(MOFs)for biomedical applications has attracted much attention in recent years.MOFs are regarded as a promising class of nanocarriers for drug delivery owing to well-defined structure,ultrahigh surface area and porosity,tunable pore size,and easy chemical functionalization.In this review,the unique properties of MOFs and their advantages as nanocarriers for drug delivery in biomedical applications were discussed in the first section.Then,state-ofthe-art strategies to functionalize MOFs with therapeutic agents were summarized,including surface adsorption,pore encapsulation,covalent binding,and functional molecules as building blocks.In the third section,the most recent biological applications of MOFs for intracellular delivery of drugs,proteins,and nucleic acids,especially aptamers,were presented.Finally,challenges and prospects were comprehensively discussed to provide context for future development of MOFs as efficient drug delivery systems.     

Tiered clustering-based management architecture in mega-satellite networks

Hybrid orbital networking and the proliferation of satellites raise explosive management complexity in mega-satellite networks(MSNs) and prompt the management architecture to the hierarchy. In this regard, we propose a tiered clustering-based management architecture(TCMA) to realize the high-efficient and low-cost management performance. Specifically, based on the constrained satellite coverage, we derive an expression of the mapping relationship between the required control overhead of the cont...     

Edge Caching in Blockchain Empowered 6G

The sixth generation(6G)of wireless cellular networks is expected to incorporate the latest developments in network infrastructure and emerging advances in technology.In the age of 6G,edge caching technology will evolve towards intelligence,dynamics,and security.However,the security problems of edge caching,including data tampering and eavesdropping,are seldomly considered in most literatures.In this paper,we consider the two-hop edge caching where the blockchain and physical layer security technologies are adopted to prevent data from being tampered with and eavesdropped.We design blockchain-based framework to guarantee the reliability of important data such as the frequency of contents and jointly optimize content caching probability and redundancy rate to maximize the secure transmission probability.Extensive simulation shows that our optimization scheme can significantly improve the secure transmission probability of edge cache network,whether facing the threat of independent eavesdropping or joint eavesdropping.     

Power Allocation for NOMA in D2D Relay Communications

Non-orthogonal multiple access(NOMA)is considered as one of the key technologies for the fifth generation(5G)wireless communications.The integration of NOMA and device-to-device(D2D)communications has recently attracted wide attention.In this paper,a relaying D2D communications assisted with cooperative relaying systems using NOMA(DRC-NOMA)is considered.We analyze the ergodic sum-rate for the proposed system and then derive the closed-form expressions.In addition,an optimal power allocation strategy maximizing the ergodic sum-rate is proposed based on these analysis results.Numerical results show the good agreement between the results of analysis and Monte Carlo method.The proposed DRC-NOMA has a great improvement of the ergodic sum-rate in the small regime of average channel gain of D2D pair.