Experimental Study on the Pore Structure Fractals and Seepage Characteristics of a Coal Sample Around a Borehole in Coal Seam Water Infusion

In this study, a two-dimensional fully coupled computational model is developed for simulation of proppant settlement in hydro-fractures with the use of the extended finite element framework. The porous domain is governed by the well-known \((\mathbf{u}-p)\) formulation, which consists of the momentum balance equation of the bulk, in conjunction with the momentum balance and continuity equations of the pore fluid. The hydro-fracture inflow is modeled as a 1D flow on the basis of the Darcy law, in which fracture permeability is incorporated by means of the cubic law. Contact constraints are elaborated to eliminate the overlap of fracture edges and the leak-off flow. Proppant settlement is conducted on the basis of Stokes’ law for particle terminal velocity, in which the effects of fracture walls, concentration, viscosity and bridging are incorporated into the model. A fixed-point algorithm is introduced to achieve the optimum combination for the proppant injection. Using the extended finite element method, the strong discontinuity in the displacement field due to crack body, as well as the weak discontinuity in the pressure field due to leakage, is included in the model with the use of the Heaviside and modified level set enrichment functions, respectively. The robustness and versatility of the proposed numerical algorithm in determining the optimum proppant injection is examined through several numerical simulations.     

高应变率下多孔未极化PZT95/5铁电陶瓷的非线性力学行为

采用添加造孔剂的方法制备了4种不同孔隙率的未极化PZT95/5铁电陶瓷。采用基于超高速相机与数字图像相关性方法的试样全场应变测量技术以及分离式霍普金森压杆（SHPB）技术，对多孔未极化PZT95/5铁电陶瓷进行高应变率单轴压缩实验研究。全场应变测量结果显示:轴向应变仅在试样中部分布较均匀，将该区域的平均应变作为应力-应变关系中的试样应变测量值较为合理，而由SHPB原理计算的试样应变值明显偏大，需要摒弃或修正传统的SHPB数据处理方法。通过波形整形技术实现了恒应变率加载，弱化了径向惯性效应的影响，揭示出多孔未极化PZT95/5铁电陶瓷的压缩强度具有显著的应变率效应。通过分析试样轴向应变和径向应变随着加载应力的变化，阐明多孔未极化PZT95/5铁电陶瓷的非线性变形行为的物理机制是畴变和相变共同作用，并发现畴变临界应力和相变临界应力都随着应变率升高而增大。保持加载应变率不变，讨论了孔隙率对多孔未极化PZT95/5铁电陶瓷动态力学行为的影响，发现随着孔隙率的升高，动态压缩强度呈非线性衰减，而畴变临界应力和相变临界应力则基本呈线性衰减。     

Nine components pharmacokinetic study of rat plasma after oral administration raw and prepared Semen Cassiae in normal and acute liver injury rats

In China, Semen Cassiae has long been used to protect liver, brighten eyes, and relieve constipation. Prepared Semen Cassiae is produced from raw Semen Cassiae by processing, the two forms of Semen Cassiae have different clinical applications. Pathological state is an important factor affecting the efficacy of drugs, the pharmacokinetic behavior of drugs could be significantly changed when people or animal were under different pathological state. To clarify the effect of processing mechanism and pathological state for pharmacokinetic behavior, the pharmacokinetics of nine components of raw and prepared Semen Cassiae under normal and acute liver injury rats were examined. The results showed that the bimodal phenomenon appeared on the plasma concentration‐time profiles of obtusin, emodin, chrysophanol, aloe emodin and rhein. The T_max of aurantio‐obtusin, obtusin, chrysoobtusin, emodin, chrysophanol, aloe emodin, physcion in normal groups administrated prepared Semen Cassiae were shorter than those administrated raw Semen Cassiae. For the AUC_0–t, aurantio‐obtusin, obtusin, chrysoobtusin, chrysophanol, aloe emodin and physcione in model groups administrated prepared Semen Cassiae were significantly higher than other groups, unlike above components, rhein had poor absorption in model groups. The study would be useful for further studies on pharmacokinetics and clinical application of raw and prepared Semen Cassiae.     

Porous ZnO/Co3O4/N‐doped carbon nanocages synthesized via pyrolysis of complex metal–organic framework (MOF) hybrids as an advanced lithium‐ion battery anode

Metal oxides have a large storage capacity when employed as anode materials for lithium‐ion batteries (LIBs). However, they often suffer from poor capacity retention due to their low electrical conductivity and huge volume variation during the charge–discharge process. To overcome these limitations, fabrication of metal oxides/carbon hybrids with hollow structures can be expected to further improve their electrochemical properties. Herein, ZnO‐Co₃O₄ nanocomposites embedded in N‐doped carbon (ZnO‐Co₃O₄@N‐C) nanocages with hollow dodecahedral shapes have been prepared successfully by the simple carbonizing and oxidizing of metal–organic frameworks (MOFs). Benefiting from the advantages of the structural features, i.e. the conductive N‐doped carbon coating, the porous structure of the nanocages and the synergistic effects of different components, the as‐prepared ZnO‐Co₃O₄@N‐C not only avoids particle aggregation and nanostructure cracking but also facilitates the transport of ions and electrons. As a result, the resultant ZnO‐Co₃O₄@N‐C shows a discharge capacity of 2373 mAh g^?1 at the first cycle and exhibits a retention capacity of 1305 mAh g^?1 even after 300 cycles at 0.1 A g^?1. In addition, a reversible capacity of 948 mAh g^?1 is obtained at a current density of 2 A g^?1, which delivers an excellent high‐rate cycle ability.     

Energy band modulation of GaAs/Al0.26Ga0.74As quantum well in 3D self-assembled nanomembranes

In this study, we investigate the modulation of energy band in 3D self-assembled nanomembranes containing GaAs/Al_0.26Ga_0.74As quantum wells (QWs). Photoluminescence (PL) characterizations demonstrate that the self-assembled structures have different optical transition properties and the modulation of the energy band is thus realized. Detailed spectral analyses disclose that the small strain change in structures with different curvatures cannot cause remarkable change in energy bands in Al_0.26Ga_0.74As layer. On the other hand, the optical transitions of GaAs QW layer is influenced by the strain evolution in term of light emission intensity. We also find the first order Stark effect in rolled-up nanomembrane with diameter of 150 μm, which is closely connected with the coupling effect between the deformation potential and the piezoelectric potential. Our work may pave a way for the fabrication of high performance rolled-QW infrared photo-detectors.     

Multistrain edge‐based compartmental model on networks

Multistrain diseases, which are infected through individual contacts, pose severe public health threat nowadays. In this paper, we build competitive and mutative two‐strain edge‐based compartmental models using probability generation function (PGF) and pair approximation (PA). Both of them are ordinary differential equations. Their basic reproduction numbers and final size formulas are explicitly derived. We show that the formula gives a unique positive final epidemic size when the reproduction number is larger than unity. We further consider competitive and mutative multistrain diseases spreading models and compute their basic reproduction numbers. We perform numerical simulations that show some dynamical properties of the competitive and mutative two‐strain models.     

Cations Controlling the Chiral Assembly of Luminescent Atomically Precise Copper(I) Clusters

Chiral assembly and asymmetric synthesis are critically important for the generation of chiral metal clusters with chiroptical activities. Here, a racemic mixture of [K(CH₃OH)₂(18‐crown‐6)]⁺[Cu₅(S^tBu)₆]^? ( 1?CH₃OH ) in the chiral space group was prepared, in which the chiral red‐emissive anionic [Cu₅(S^tBu)₆]^? cluster was arranged along a twofold screw axis. Interestingly, the release of the coordinated CH₃OH of the cationic units turned the chiral 1?CH₃OH crystal into a mesomeric crystal [K(18‐crown‐6)]⁺[Cu₅(S^tBu)₆]^? ( 1 ), which has a centrosymmetric space group, by adding symmetry elements of glide and mirror planes through both disordered [Cu₅(S^tBu)₆]^? units. The switchable chiral/achiral rearrangement of [Cu₅(S^tBu)₆]^? clusters along with the capture/release of CH₃OH were concomitant with an intense increase/decrease in luminescence. We also used cationic chiral amino alcohols to induce the chiral assembly of a pair of enantiomers, [d /l ‐valinol(18‐crown‐6)]⁺[Cu₅(S^tBu)₆]^? ( d /l ‐Cu_5V ), which display impressive circularly polarized luminescence (CPL) in contrast to the CPL‐silent racemic mixture of 1?CH₃OH and mesomeric 1 .     

Magnetic solid‐phase extraction based on carbon nanosphere@Fe3O4 for enantioselective determination of eight triazole fungicides in water samples

In this work, a carbon nanosphere decorated by Fe₃O₄ nanoparticles was prepared, characterized and used as the magnetic adsorbent. Eight commonly used chiral triazole fungicides, including penconazole, uniconazole, paclobutrazol, triazolone, tebuconazole, hexaconazole, triticonazole and epoxiconazole were extracted from two environmental water samples (river water and lake water) by magnetic solid‐phase extraction, followed by the enantiomeric analysis on a Chiralpark IC column coupled with a triple quadrupole mass spectrometry to evaluate their possible stereoselective degradation occurring in the water samples. The possible factors affecting the extraction performance, such as amount of used adsorbents, pH and ionic strength of water solution, types and volumes of desorption solvents were systematically investigated. Under the optimum conditions, extraction yields of eight triazole fungicides were above 80% and the concentration factors were as high as 1000. Method detection and quantification limits for the enantiomers of eight triazole fungicides were in the range of 0.56–6.95 ng/L. Satisfactory accuracy (relative recovery 77.8–93.5%), good intraday precision (RSD 4.3–9.8%) and interday precision (RSD 3.1–7.9%) were also obtained. The developed method provided the simplicity of operation, rapidity and high enrichment factor, which can be used to monitor and evaluate the behavior of the individual enantiomer of chiral triazole fungicides.     

Carbon nanotube@ZIF–derived Fe-N-doped carbon electrocatalysts for oxygen reduction and evolution reactions

Journal of Solid State Electrochemistry - Iron-nitrogen co-doped hierarchical porous carbon (Fe-N-HPC) was synthesized through the carbonization of carbon nanotube@ZIF composite. It was found that...