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At present, the proportion of tight oil in non-renewable hydrogen energy is increasing. According to an initial exploration and attemptable practice on the exploration of tight oil, it is found that the cost can be controlled effectively and positive effects are achieved. But this technique cannot make sure the proppants filled uniformly in the long fracture. Several researches on the proppants migration experiment devices and factors influencing on proppant setting are reviewed and a new set of experimental device to simulate the laws of proppants setting in long fracture is developed. This device can simulate the main factors influencing proppants setting performance. It analyzes several factors such as wall filtration, construction displacement, sand concentration, proppant size and density, viscosity of fracturing fluid is used to rank the influencing degree of every factor. Considering the effects of mutual interference between proppants, width of fracture, rough fracture surface and fracture surface filtration during the proppants setting progress, the mathematical model of proppant setting is modified by adding sand concentration correction factor, wall effect correction factor and filtration correction factor. The experimental data verify the accuracy of the settlement model is established using the data getting from experiment.

Polymers of intrinsic microporosity (PIMs) have numerous advantages such as good thermal stability (Tg > 300 °C) and mechanical stability (tensile strength at break > 60 MPa) as well as excellent electrical insulation performance and chemical/electrochemical stability. Herein, a macroporous membrane made up of a polymer of intrinsic microporosity (PIM-1) was fabricated and used as a separator of a rechargeable Li-ion battery for the first time. The PIM-1-based separator showed good thermal resistance with Tg > 300 °C, high electrolyte uptake, and excellent Li-ion conductivity.

Although mixed matrix membranes (MMM) possess remarkably improved gas separation performance compared to traditional polymeric membranes, membrane stability including CO2 plasticization and aging is still a serious issue due to the existence of interfacial defects. In this work, we report an efficient and less destructive route to cross-link the MOFs/polyimide (PI) MMM, where amine group-functionalized MOF (NH2-UiO-66) nanoparticles are thermally cross-linked with a carboxylic acid-functionalized PI (COOH-PI) matrix to form an amide bond at the interface at 150 °C under vacuum condition. Such a chemical cross-linking strategy conducted at a relatively mild condition improves membrane stability greatly while ensuring that the membrane structure is not destroyed. The resulting cross-linked MMM achieves enhanced mechanical strength with higher Young's modulus than a pristine polymer membrane. The CO2 antiplasticization pressure of the MMM after cross-linking is enhanced by 200% from ∼10 to >30 bar and the CO2 permeability of MMM only drops slightly from 995 to 735 Barrer after 450 days. At the same time, the separation performance of H2/CH4 gas pair surpasses the 2008 upper bound and that of CO2/CH4 gas pair nearly approaches the 2008 upper bound. The cross-linking strategy used herein provides a feasible and effective route for improving membrane stability and membrane performance in the MMM system for gas separation.

We describe a facile synthesis of Mn 3 O 4 nanoplates (NPs)-anchored graphene microspheres (GSs) and their applications as electrode materials for supercapacitors. The use of GSs as substrate significantly improve the electrochemical performance of Mn 3 O 4 , which can be attributed to unique spherical structure of graphene and excellent stability and anti-reunion of Mn 3 O 4 NPs. The success of this synthesis depends on the in situ reduction of Mn cations by carbon from GSs under hydrothermal conditions. The resultant Mn 3 O 4 NPs with an average thickness of 37 nm were uniformly distributed on the surface of GSs. Material characterizations, including XRD, Raman, FTIR and XPS, have been performed to confirm their shape, composition and structure. As a positive material, the as-prepared Mn 3 O 4 NPs/GSs composites exhibited excellent electrochemical property in a three-electrode system. In particular, their specific capacitance reached as high as 317 F g −1 at a scan rate of 10 mV s −1 , and a remarkable stability (about 100% retention of its initial capacitance) was achieve after 4000 galvanostatic charge-discharge cycles at the current density of 2 A g −1 . Therefore, Mn 3 O 4 NPs/GSs can have been used as an electrode material for supercapacitors.

Development of high-tapped-density graphene-based materials with satisfactory Brunauer–Emmett–Teller (BET) surface area can be beneficial to the optimization of the volumetric performance of supercapacitors for practical use. Herein, we report a simple and scalable route for the synthesis of high-tapped-density N-doped graphene (HNG). The success of this work relies on the use of polyethyleneimine (PEI) to react with graphene oxide under ambient conditions to realize fast cross-linking and thus rapid sedimentation, followed by thermal treatment of the precipitates. The resultant HNG exhibits a good balance between the tapped density and BET surface area, where the tapped density can be tuned in the range of 0.90–1.20 g cm −3 and the BET surface area is maintained in the range of 457.0–119.6 m 2 g −1 . The interaction between PEI and graphene oxide successfully prevents restacking of the graphene layers during thermal treatment while allowing maximal volume shrinkage. When applied as an electrode material in supercapacitors, the HNG exhibits a volumetric capacitance up to 547.8 F cm −3 at a scan rate of 10 mV s −1 and 317.3 F cm −3 at a current density 0.2 A g −1 , and it shows no apparent decrease in the specific capacitance after 5000 cycles at 2 A g −1 . The results demonstrate the feasibility of the new strategy for designing high-tapped-density graphene-based materials for supercapacitors.

Two new Co(II)-containing coordination polymers, {[Co1.5(2,4′-Hbpt)(btec)0.5(H2btec)0.5(H2O)]·(H2O)}n (1) and [Co2(3,4′-Hbpt)2(btc)(ac)(H2O)]n (2), have been successfully synthesized with different polycarboxylates (H4btec = 1,2,4,5-benzenetetra-carboxylic acid, H3btc = 1,3,5-benzenetri-carboxylic acid, ac = acetic acid) and pyridine-based triazoles (2,4′-Hbpt = 1H-3-(2-pyridyl)-5-(4′-pyridyl)-1,2,4-triazole, 3,4′-Hbpt = 1H-3-(3-pyridyl)-5-(4′-pyridyl)-1,2,4-triazole). Compound 1 displays a 3D 2-nodal (4, 6)-connectivity topology network, whereas 2 features a self-interpenetrating 2D layer structure. Magnetic studies demonstrate spin-canting like weak ferromagnet and antiferromagnetism behaviors are observed in 1 and 2, respectively.

We propose an active meta-lens that can dynamically switch the coaxial focus on three statuses with the external optical pump. The meta-lens composes of two concentric sets of complementary split-ring resonator (CSRR) arrays, which function at different focal lengths, atop the silicon on sapphire substrate. With specifically structured phase distribution, the meta-lens can form completely separated double foci simultaneously. Through illuminating the internal or external CSRR arrays individually with patterned optical pump, the meta-lens switches to single focus at different points. The proposed design provides a new avenue for developing terahertz multifunctional devices applied in microscope imaging and tomography.

Radial well technology in combination with hydraulic fracturing technology has gained encouraging achievements as a new method of increasing production in oil fields. Compared with conventional perforation fracturing, radial well fracturing has an obvious advantage in breaking through polluted borehole areas, and it is superior to horizontal well fracturing because of the shorter construction period, less consumption of fracturing fluid and lower damage to the reservoir. Currently, in China, the study on the position of fracture starting point and fracture propagation of radial well is still at the preliminary stage and the fracture initiation pressure and position of fracture starting point remain unclear. Consequently, it's difficult to design radial well completion parameters (length of radial well, diameter of radial well and fracturing truck units) precisely and implement the technology more efficiently. Based on fluid-solid coupling effect and the maximum tensile-stress criterion, this paper follows the concept of dynamic analysis and analyzes the influence rule of the length, diameter and azimuth of radial well, horizontal in-situ stress and natural fracture on fracture initiation pressure and fracture starting point under the stress of strike-slip fault by using ABAQUS to simulate and study local stress accumulation situation caused by drilling vertical well section, radial well section and fracturing section through finite element method. The result shows that initiation pressure and distance between well and fracture starting point increases as the length, diameter and azimuth of radial well section rise. Azimuth is most influenced, followed by length, and lastly diameter of radial well section. When the horizontal in-situ stress ratio (σH:σh) is decreased from 1.9 to 1.1, if the azimuth is 0°, the initiation pressure increases by 41.35%; if the azimuth is 90°, the initiation pressure declines 0.8%. However, the positions of these two fracture starting point remain unchanged. The permeability increases by four orders of magnitudes and the fracture initiation pressure goes up 34.5%, with no influence on the fracture starting point. When there existed natural fractures in the reservoir, the intersection between fracture section and radial well section firstly shows fracturing. Besides, the fracture initiation pressure and the hydrostatic fluid column pressure in vertical wellbore are equivalent. Reduced length and diameter of radial well section as well as reservoir permeability and properly increased azimuth of radial well are conducive to fracture at the toe end of the radial well section. On the contrary, fracture at shaft linings of vertical well section is easily occurred. The research result can be used to predict the direction of fracture propagation to some extent and is favorable for designing parameters of radial well completion and fracturing operation.

In this work, ultrasmall metal-organic frameworks (MOFs) nanoparticles, UIO-66-NH2 nanoparticles were synthesized and embedded in an ultrathin polyamide (PA) active layer via the interfacial polymerization reaction on a polydopamine-wrapped single-walled carbon nanotube film. A thin-film nanocomposite nanofiltration (TFN NF) membrane with a PA/UIO-66-NH2 active layer as thin as 20 ± 3 nm was thus fabricated. The loading mass of the nanoparticles in the TFN NF membrane could be tuned by controlling the nanoparticles concentration in aqueous phase. Benefiting from the ultrathin thickness of active layer and the high loading mass of the MOFs nanoparticles, water permeability up to 46 L m−2 h−1 bar−1 along with a Na2SO4 rejection of 97.1% was achieved, which is 53% increase of the TFC NF membrane without the addition of UIO-66-NH2 nanoparticles. Our membrane owns the thinnest active layer in the category of TFN NF membranes reported so far and exhibits outstanding desalination performance.

With the rapid development of the Internet of things and other advanced sensing technologies, the demand for real-time fault diagnosis of bearings is increasing a lot. In order to improve the real-time and numerical stability of on-line fault diagnosis of bearings, an online diagnosis method based on feature fusion is proposed in this paper. The method uses Kernel Principal Component Analysis (KPCA) to fuse feature combinations extracted by Empirical Mode Decomposition(EMD) and Wavelet Packet Transform(WPT), and uses the online extreme learning machine to construct the online diagnosis model. The whole process can be divided into offline stage and online stage: in off-line stage, combining EMD and WPT features under different fault status, the kernel feature vectors are obtained by KPCA, and then the initial online extreme learning machine model is constructed; In online stage, EMD and WPT are firstly used to extract features for sequentially arrived raw signals, and according to the feature's weights which are obtained in offline stage, the new features are reduced directly and the online extreme learning machine model is updated adaptively. The experimental results on the IMS bearing data set show that the method can make full use of the complementary characteristics of different information, and effectively improve the accuracy and stability of online diagnosis without increasing the reaction time.