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Foam diversion acidizing can effectively solve the problem of acid distribution with severe heterogeneity between and within layers. Based on the foam diversion principle, the gas trap theory, and volume conservation principle, the foam slug diversion acidizing model was established and solved considering the change of bottomhole temperature and deviation factor of foam. The simulation results show that the change of temperature has a great influence on the diversion effect at the initial stage of injection, but a small influence at the middle and late stage. The effect of temperature on the highly permeable layer is greater than that of temperature on the low permeability layer. The deviation factor of foam is mainly controlled by temperature at the initial stage, and by pressure at the middle and late stage, and the whole process shows a downward trend, which has little influence on the diversion effect. The quasi-skin factor of gas trap is the most important parameter that influences the effect of foam diversion. The water saturation of the low permeability layer rises faster than that of the high permeability layer, and the effect of diversion is obvious. The research results have a strong guiding significance for foam diversion acidizing.

The woven glass fiber reinforced composites (GFRP) subjected to high-speed impact is investigated to identify the hygrothermal aging effect on the impact resistance. Both the hygrothermal aged and unaged glass/epoxy laminates are subjected to different impact velocities, which is confirmed as a sensitive factor for the failure modes and mechanisms. The results show the hygrothermal aging effect decreases the ballistic limit by 14.9%, but the influence on ballistic performance is limited within the impact velocity closed to the ballistic limit. The failure modes and energy dissipation mechanisms are confirmed to be slightly influenced by the hygrothermal aging effect. The hygrothermal aging effect induced localization of structural deformation and degradation of mechanical properties are the main reasons for the composite undergoing the same failure modes at smaller impact velocities. Based on the energy absorption mechanisms, analytical expressions predict the ballistic limit and energy absorption to reasonable accuracy, the underestimated total energy absorption results in a relatively poor agreement between the measured and predicted energy absorption efficiency.

Abnormal tendons are rarely ever repaired to the natural structure and morphology of normal tendons. To better guide the repair and regeneration of injured tendons through a tissue engineering method, it is necessary to have insights into the internal morphology, organization, and composition of natural tendons. This review summarized recent researches on the structure and function of the extracellular matrix (ECM) components of tendons and highlight the application of multiple detection methodologies concerning the structure of ECMs. In addition, we look forward to the future of multi-dimensional biomaterial design methods and the potential of structural repair for tendon ECM components. In addition, focus is placed on the macro to micro detection methods for tendons, and current techniques for evaluating the extracellular matrix of tendons at the micro level are introduced in detail. Finally, emphasis is given to future extracellular matrix detection methods, as well as to how future efforts could concentrate on fabricating the biomimetic tendons., Graphical abstract Image 1, Highlights • Summarize recent research on the structure and function of the extracellular matrix (ECM) components of tendons. • Comments on current research methods concerning the structure of ECMs. • Perspective on the future of multi-dimensional detection techniques and structural repair of tendon ECM components.

Evaluating the correlation between hypoxia inducible factor 1 (HIF-1) and nitric oxide (NO) generated under hypoxia is of great significance. In this work, we developed a fluorescent probe for the monitor of HIF-1 activity influenced by NO under hypoxia in hepatoma cells with dual-targeting for hepatocyte and lipid droplet (LD). The probe shows excellent selectivity to NO and high sensitivity with 6000-fold fluorescence enhancement. Live cell imaging experiments revealed the probe's capability of imaging exogenous and endogenous NO with specific in LDs of HepG2 cells. For cells under hypoxia, HIF-1 induced LD level is observed to correlate with NO level. This work provides the in-situ visualization of NO-dependent HIF-1 upregulation through LD accumulation.

The development of poly(3,4-ethylenedioxythiophene) (PEDOT) with high specific capacitance is the key to pursuing high-performance supercapacitors, and the electrochemical properties of PEDOT are closely related to the oxidation degree and conjugated chain length of its molecular chain. In this work, the influences of various oxidants (FeCl3, Fe(Tos)3 and MoCl5) on the molecular chain structure and capacitive properties of PEDOT via vapor phase polymerization were systematically investigated. Fe(Tos)3 can significantly improve the degree of oxidation and the length of the conjugated chain of PEDOT compared to FeCl3 and MoCl5, enhancing the conductivity and providing more active sites for Faraday reaction. Therefore, the PEDOT/P(Fe(Tos)3) electrode displays a considerable conductivity of 73 S cm-1, high areal capacitance (419 mF cm-2) and excellent electrochemical stability under the different bent state. Moreover, the conjugated structure strengthens the interaction between PEDOT chains, achieving good cycle stability. Therefore, Fe(Tos)3 is an ideal oxidant for obtaining high-performance PEDOT electrode materials.

Development of highly efficient and long stable hydrodesulfurization (HDS) catalysts still is a great challenge for the refining industry. In this work, a series of intermetallic noble metal silicides supported by carbon nanotubes catalysts (Pt2Si/CNTs, RhxSi/CNTs, and RuSi/CNTs) have been developed by chemical vapor deposition successfully, using dichlorodimethylsilane as Si source. These materials were used as efficient catalysts for the deep HDS of dibenzothiophenes (4,6-DMDBT and DBT) and performed high selectivity to the direct desulfurization pathway. The sequence of HDS activity over noble metal silicides catalysts is in keeping with the sequence of HDS activity of the corresponding metal catalysts, which is Pt2Si/CNTs > RhxSi/CNTs >> RuSi/CNTs. In addition, the Pt2Si/CNTs performed an excellent stability in 100 h stability testing for HDS of 4,6-DMDBT. Therefore, this sulfur-tolerant noble metal silicides could be as promising catalysts for the ultra-deep HDS of fossil-fuel.

The two-dimensional principal component analysis (2DPCA) has been one of the basic methods of developing artificial intelligent algorithms. To increase the feasibility, we propose a new general ridge regression model for 2DPCA and variations, with extracting low dimensional features under two projection subspaces. A new relaxed 2DPCA under the quaternion framework is proposed to utilize the label (if known) and color information to compute the essential features of generalization ability with optimization algorithms. The 2DPCA-based approaches for face recognition are also improved by weighting each principle component a scatter measure, which increases efficiently the rate of face recognition. In numerical experiments on well-known standard databases, the R2DPCA approach has high generalization ability and achieves a higher recognition rate than the state-of-the-art 2DPCA-like methods, and has better performance than the basic deep learning methods such as CNNs, DBNs, and DNNs in the small-sample case.

Bearings are one of the most important components in modern industry. Rolling contact fatigue (RCF) initiating from surface and subsurface is the major failure mode. In this paper, a typical high speed thrust angular contact ball bearing was selected, and the machined surface quality and near-surface microstructure of the race-way and rolling ball were systematically characterized by using of a probe surface profiler, white light interferometer, optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) combined with focused ion beam (FIB). Two kinds of precursor, probably resulting in pitting or spalling during the following rolling contact, were detected. One is the defects on the surface of either the race-way or the rolling ball, such as heavy machining marks, scratches and slag-hole. The other is nano-crystalline layer due to machining, in the outermost layer around the surface of race-way. The results may well lay foundation for our further research on RCF with the real part of such typical rolling bearings.

Tendon/ligament-to-bone healing poses a formidable clinical challenge due to the complex structure, composition, cell population and mechanics of the interface. With rapid advances in tissue engineering, a variety of strategies including advanced biomaterials, bioactive growth factors and multiple stem cell lineages have been developed to facilitate the healing of this tissue interface. Given the important role of structure-function relationship, the review begins with a brief description of enthesis structure and composition. Next, the biomimetic biomaterials including decellularized extracellular matrix scaffolds and synthetic-/natural-origin scaffolds are critically examined. Then, the key roles of the combination, concentration and location of various growth factors in biomimetic application are emphasized. After that, the various stem cell sources and culture systems are described. At last, we discuss unmet needs and existing challenges in the ideal strategies for tendon/ligament-to-bone regeneration and highlight emerging strategies in the field., Graphical abstract Image 1, Highlights • The interface tissue engineering for enthesis regeneration is promising. • The biomimetic scaffolds are examined. • The key issues in the biomimetic application of growth factors are emphasized. • The various stem cell sources and culture systems are described. • The challenges and emerging strategies for enthesis regeneration are presented.

Achieving nanometric surface on single-crystal silicon is important for semiconductor and optoelectronics industries. In recent years, thermal assisted machining (hot machining) raises as an effective technique for high-quality surface fabrication of single-crystal silicon. However, the formation mechanism of the subsurface damage at elevated cutting temperatures is still unclear. In this paper, molecular dynamics simulation and cutting experiments were conducted to study the subsurface damage evolution in single-crystal silicon at elevated cutting temperatures. The cutting mechanism and behavior of the amorphous phase were investigated. The results indicate that with an increase of the cutting temperature, the subsurface damage can be greatly suppressed and the cutting mechanism can be distinct with ordinary cutting. Furthermore, the lubricant effect of the amorphous layer and the recrystallization process are determined as two important reasons for suppression of the subsurface damage at high cutting temperature. The lubricant effect reduces the deformation of the crystal substrate and decreases the frictional coefficient during cutting. While the recrystallization mainly occurs before the compressive stress decrease to zero, which causes point-like subsurface damage and thinner amorphous layer on the machined surface.

Multifunctional nanodevices have shown great promise as robust tools in cancer theranostics. Carbon nanohorns (CNHs) of large specific surface area, low toxicity and unique physicochemical properties are among one of ideal platforms to fabricate the nanodevices. Herein, we develop a water-dispersible carbon nanohorn−polyglycerol−gold (CNH-PG-Au) nanohybrid through surface engineering of CNHs, which is further loaded with chemotherapeutic drug doxorubicin (DOX) to afford DOX@CNH-PG-Au nanodevice. Benefiting from the excellent hydrophilicity of PG, as-prepared multifunctional DOX@CNH-PG-Au possesses good aqueous dispersibility and colloidal stability enabling biomedical applications. DOX@CNH-PG-Au nanoparticles are taken up by 4T1 mouse breast cancer cells and mainly disperse in the lysosomes, where the mild acidic condition promotes the release of DOX. DOX@CNH-PG-Au induces more cell apoptosis under X-ray irradiation than DOX@CNH-PG of the same DOX concentrations, which is attributed to increased DNA damage by synergistic effect of DNA intercalation of DOX and radiosensitization of Au nanoparticles. Upon intravenous administration, DOX@CNH-PG-Au nanoparticles steadily accumulate in 4T1 tumor through enhanced permeability and retention (EPR) effect, and the tumor can be clearly observed by photoacoustic imaging. In vivo tumor treatment using DOX@CNH-PG-Au together with X-ray irradiation effectively inhibits tumor growth through radiochemotherapy. Our work demonstrates the great potential of DOX@CNH-PG-Au nanodevice in cancer theranostics.

In the numerous low-permeability reservoirs, knowing the real productivity of the reservoir became one of the most important steps in its exploitation. However, the value of permeability interpreted by a conventional well-test method is far lower than logging, which further leads to an inaccurate skin factor. This skin factor cannot match the real production situation and will mislead engineer to do an inappropriate development strategy of the oilfield. In order to solve this problem, key parameters affecting the skin factor need to be found. Based on the real core experiment and digital core experiment results, stress sensitivity and threshold pressure gradient are verified to be the most influential factors in the production of low-permeability reservoirs. On that basis, instead of a constant skin factor, a well-test interpretation mathematical model is established by defining and using a time-varying skin factor. The time-varying skin factor changes with the change of stress sensitivity and threshold pressure gradient. In this model, the Laplace transform is used to solve the Laplace space solution, and the Stehfest numerical inversion is used to calculate the real space solution. Then, the double logarithmic chart of dimensionless borehole wall pressure and pressure derivative changing with dimensionless time is drawn. The influences of parameters in expressions including stress sensitivity, threshold pressure, and variable skin factor on pressure and pressure derivative and productivity are analyzed, respectively. At last, the method is applied to the well-test interpretation of low-permeability oil fields in the eastern South China Sea. The interpretation results turn out to be reasonable and can truly reflect the situation of low-permeability reservoirs, which can give guidance to the rational development of low-permeability reservoirs.

Li-rich layered oxides (LLOs) are promising cathode materials for Li-ion batteries owing to their high capacities (>250 mAh g-1), however, they suffered from severe capacity and voltage fading caused by irreversible oxygen loss and phase changes. Herein, the structural stability of single crystalline and polycrystalline Li1.14Ni0.32Mn0.44Co0.04O2 was compared in detail. It was found that the stability of oxidized oxygen ions on the near surface was improved in single crystals, which retarded oxygen loss from surface and surficial phase changes, possibly owing to the facet regulating and low surface curvature. In addition, the formation-migration of Mn3+, one of the crucial factors that caused capacity fading of LLOs, can be mitigated by increasing Ni3+ ratio. Under the synergistic effect of low oxygen defects on the near surface and high Ni3+ ratio, stable cycling performances and higher thermal stability were obtained.

Graphene(Gr) reinforced copper matrix composites(Gr/Cu) were prepared by powder metallurgy process, and the effects of graphene content on microstructure and properties of the composites were investigated. The microstructure, density, hardness and electrical conductivity of the composites were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), density measurement, hardness tester and conductivity meter. The results show that the interface bonding of the composite is good, there is no crack and no obvious interface reaction; there are a lot of dislocations and twins in Cu matrix. With the increase of graphene content, the density, heat capacity and thermal conductivity of the composites decrease, but the hardness increases first and then decreases.

In nanometric cutting, the dominant material removal mechanism can be greatly different with macroscopic cutting process. In this work, molecular dynamics (MD) simulation was carried out to investigate the cutting features of single-crystal silicon. The effect of the tool rake angle and the workpiece crystal orientation on the transition of the material removal mechanism was studied. Theoretical analysis and cutting experiments were conducted to verify the simulation results. The results indicate that with a decrease of the tool rake angle, the material removal mechanism could transform from shear to extrusion and finally no material would be removed. In this process, the position of the stagnation region increases rapidly when the dominant material removal mechanism becomes extrusion and would reache to the uncut surface when no material is removed. The shear to extrusion transition is greatly influenced by the tool rake angle and workpiece crystal orientation while the dominant factor that affect the transition from extrusion to no removal is the position of the stagnation region and frictional force on tool rake face. Furthermore, based on the simulation results and theoretical analysis, when the tool rake angle is decreased, the shear stress plays an important role in the formation of the subsurface damage.

Due to the extensive use of xylooligosaccharides (XOS) as functional food ingredients, many inferior goods and even adulterants are generally found in the market, which may pose a health hazard to certain populations. Chromatography method such as high-performance liquid chromatography (HPLC) and high-performance thin-layer chromatography (HPTLC) is traditionally applied for the quality analysis of XOS. However, it is time consuming due to the prolonged separation and pre- or post- derivatization procedure. In this study, a fast saccharide mapping method based on matrix-assisted laser desorption/time-of-flight mass spectrometry (MALDI-TOF-MS) was developed for the quality consistency analysis of 22 batches of XOS collected from different manufacturers in China. The time needed for saccharides analysis using MALDI-MS was less than 30 min for one plate, at least 6 times faster than that by the traditional HPTLC chromatography method. In addition, MALDI-MS possessed higher resolution for XOS with DP4-DP7 based on the difference of m/z, which is hardly separated using HPTLC. The results showed that XOS were present only in samples XY01-XY11, samples XY12-XY14 only consisted of hex oligosaccharides, and samples XY15-XY22 were free of oligosaccharides. These indicate that the quality consistency of XOS products in the China market was poor, which should be carefully investigated., Highlights • Fast saccharide mapping method was developed based on MADLI-TOF-MS. • Quality consistency of commercial xylooligosaccharides collected in China was evaluated. • Glycosidic linkage analysis was also used for identification of xylooligosaccharides. • Fifty percent of commercial xylooligosaccharides are mislabeled.

Inhomogeneous structures have significant impact on the drag. In this work, direct numerical simulations of flows past fluidized spheres are performed to investigate the effect of inhomogeneities on the drag at low Reynolds numbers. The inhomogeneities are quantified using various sub-grid quantities including a newly defined quantity named the solid drift flux, which is a measure of the correlation between the gas volume fraction and the particle phase velocity. Following the methodology of Rubinstein et al. (2017), a new drag model that depends simultaneously on the solid drift flux and the scalar variance of solid volume fraction is then developed. Given that these two sub-grid quantities are readily available in Eulerian-Lagrangian (EL) simulations, the developed model can be directly used in EL simulations without any additional closures for sub-grid quantities. An a priori analysis demonstrates that this model achieves satisfactory performance in predicting the drag in inhomogeneous structures.

Phase change materials (PCMs) play a critical role in heat-related managements, however, are usually insulating and insensitive to temperature gradient which are not capable of providing sustainable thermal energy and restrict the real applications. Herein, a novel electric/photo to thermal response reduced graphene@N-doped porous carbon (RGO@PC) supporting scaffold is developed for encapsulating lauric acid (LA). Three-dimensional reduced graphene provides continuous pathways for electron transfer which ensures a rapid electro- and photo-to thermal response. Furthermore, N-doped porous carbon provides electron to the π-conjugated system and reduces the electric conductivity of the composite. Moreover, the interfacial interaction between N-doped porous carbon and RGO was enhanced which prevents convective heat dissipation between RGO@PC and surrounding air. Owing to these structural and compositional features, LA/RGO@PC possess an ultra-low operational voltage of 0.5 V, and a rapid photo-driven thermal response within 4 min which show great potential for manipulating urban heating systems.

Air pollution in China, caused by the country’s extensive economic growth model, threatens the health of residents, especially of low-income groups. The impact and influence mechanism of this pollution on physical health has not been investigated adequately at different income levels. We examine the impact of fine particulate matter on health using panel data for the period 2010–2016 from approximately 100,000 respondents surveyed by China Family Panel Studies. In analysis, we use the hierarchical regression model according to household income per capita. We also examine the effect of residents’ human and physical capital on the relationship between air pollution and health. Our research shows that air pollution has an adverse effect on physical health. However, the significance of this effect is income-based: the effect on low-income groups is significant, while that on high-income groups is not. We also find that air pollution causes both direct and indirect impacts on residents’ health. Indirect impacts entail reductions in human and physical capital; however, this impact is less than the direct one. Therefore, the Chinese government should implement high environmental standards and strict regulations to control air pollution. It should also invest more in low-income areas to improve accessibility of healthcare services.

Hardened steel is an important material related to the development of modern industry branches. In order to satisfy the adhesion strength as well as the corrosion and wear resistance under extreme conditions, the modification of the wettability of hardened steel has become an important scientific topic. As micro/nano-structured surfaces play an essential role to induce advanced functional surfaces with wettability control, this contribution aims at presenting the feasibility of micro/nano sculpturing of hardened steels by elliptical vibration diamond cutting. The influence of the fabricated micro/nano structures on the resulting wettability is discussed and related to the contact line density as well as asperity heights. In this regard, it has been verified that a pitch value of 12 μm and structural height of 500 nm are the preferred structural parameters to increase the hydrophobicity of the textured steel specimens.

A modern power system is characterized by a stochastic variation of the loads and an increasing penetration of renewable energy generation, which results in large uncertainties in its states. These uncertainties bring formidable challenges to the power system planning and operation process. To address these challenges, we propose a cost-effective, iterative response-surface-based approach for the chance-constrained AC optimal power-flow problem that aims to ensure the secure operation of the power systems considering dependent uncertainties. Starting from a stochastic-sampling-based framework, we first utilize the copula theory to simulate the dependence among multivariate uncertain inputs. Then, to reduce the prohibitive computational time required in the traditional Monte-Carlo method, we propose, instead of using the original complicated power-system model, to rely on a polynomial-chaos-based response surface. This response surface allows us to efficiently evaluate the time-consuming power-system model at arbitrary distributed sampled values with a negligible computational cost. This further enables us to efficiently conduct an online stochastic testing for the system states that not only screens out the statistical active constraints, but also assists in a better design of the tightened bounds without using any Gaussian or symmetric assumption. Finally, an iterative procedure is executed to fine-tune the optimal solution that better satisfies a predefined probability. The simulations conducted in multiple test systems demonstrate the excellent performance of the proposed method.

Intelligent reflecting surface (IRS) consisting of massive passive elements is a promising technology to save the hardware cost and energy consumption, but with a challenging channel estimation of IRS transmission links. In this letter, a low-complexity channel estimation method is first proposed for IRS-enhanced multi-user massive multiple-input and multiple-output systems, which can attain the separate channel state information (CSI) of the cascaded link. The acquisition of the separate CSI contributes to the flexibility of channel estimations for the multi-user case with user mobility. The proposed channel estimation consists of direction-of-arrival and path gain estimations, which are implemented by using the limited radio frequency chains and pilots, respectively. Besides, the computational complexity is analyzed for the proposed and existing methods for comparison. Numerical results show that the proposed method can achieve accurate channel estimation with a low complexity.

Propylene dimerization is an attractive way to branch out the bulk chemicals to high-value-added fine chemicals. Based on the coordinatively unsaturated surface sites of nickel and solid acid sites for boosting highly selective dimerization of propylene, a series of NiSO₄/Nb₂O₅ catalysts were synthesized by tuning the synergistic effect through adjusting the calcination temperatures. Under the conditions of 70 °C, 2.5 MPa, and LHSV = 3 h–¹ in a fixed-bed reactor, the NiSO₄/Nb₂O₅-400 catalyst exhibits the highest propylene conversion of ca. 89% with 75% selectivity to C6 products (mainly including 4-methyl-2-pentene and 3-hexene). A possible Cossee–Arlman pathway has been proposed for the dimerization of propylene. In the long-term stability testing, an induction period has been observed, which may be attributed to the coordination of propylene molecules to unsaturated Ni²⁺ cations generating some active nickel species. Subsequently, the NiSO₄/Nb₂O₅-400 catalyst presents a stability up to 30 h. The interesting results inspired us to modulate the interaction of metal (salt) and acid sites to strengthen the selective dimerization of low-carbon olefins.

Single-molecule imaging is challenging but highly beneficial for investigating intermolecular interactions at the molecular level1–6. Van der Waals interactions at the sub-nanometre scale strongly influence various molecular behaviours under confinement conditions7–11. Inspired by the traditional compass12, here we use a para-xylene molecule as a rotating pointer to detect the host–guest van der Waals interactions in the straight channel of the MFI-type zeolite framework. We use integrated differential phase contrast scanning transmission electron microscopy13–15 to achieve real-space imaging of a single para-xylene molecule in each channel. A good correlation between the orientation of the single-molecule pointer and the atomic structure of the channel is established by combining the results of calculations and imaging studies. The orientations of para-xylene help us to identify changes in the van der Waals interactions, which are related to the channel geometry in both spatial and temporal dimensions. This work not only provides a visible and sensitive means to investigate host–guest van der Waals interactions in porous materials at the molecular level, but also encourages the further study of other single-molecule behaviours using electron microscopy techniques. The orientation of a rotating para-xylene molecule in the nanochannel of a zeolite framework can be visualised by electron microscopy to determine the host–guest van der Waals interaction inside the channel.

The coarse-grained discrete element method (CGDEM) is promising for its ability to reduce computational cost. However, compared with discrete element method (DEM), CGDEM often overpredicts the gran...

In this brief, the output feedback based finite-time attitude containment control problem for multiple spacecrafts is investigated. A novel finite-time command filtered backstepping containment control scheme is proposed for attitude systems with unmeasurable states, inertia uncertainties, external disturbances and input saturations, which can not only guarantee the containment control errors converge to the sufficient small neighborhood of the origin in finite-time, but also overcome the computation complexity problem in traditional backstepping. The simulation results show the effectiveness of the proposed control scheme.

The micro-structures of catalyst materials basically affect their macro-architectures and catalytic performances. Atomically resolving the micro-structures of zeolite catalysts, which have been widely used in the methanol conversion, will bring us a deeper insight into their structure-property correlations. However, it is still challenging for the atomic imaging of silicoaluminophosphate zeolites by electron microscopy due to the limits of their electron beam sensitivity. Here, we achieve the real-space imaging of the atomic lattices in SAPO-34 and SAPO-18 zeolites, including the Al–O–P atoms and bonds, by the integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM). The spatial distribution of SAPO-34 and SAPO-18 domains in SAPO-34/18 intergrowths can be clearly resolved. By changing the Si contents and templates in feed, we obtain two SAPO-34/18 catalysts, hierarchical and sandwich catalysts, with highly-mixed and separated SAPO-34 and SAPO-18 lattices respectively. The reduced diffusion distances of inside products greatly improve the catalytic performances of two catalysts in methanol conversion. Based on the observed distributions of lattices and elements in these catalysts, we can have a preliminary understanding on the correlation between the synthesis conditions and structures of SAPO-34/18 intergrowth catalysts to further modify their performances based on unique architectures., The micro-structures of zeolite catalysts affect their macroarchitectures and catalytic performances. Here, the different SAPO-34/18 intergrowth catalysts are atomically resolved, and the correlation between synthesis conditions and zeolite structures is revealed to further enhance their performances in methanol conversion.

In underground coal mines, the methane distribution under actual conditions has a certain concentration gradient due to various factors such as air leakage and lower air velocity in local areas. In...

Understanding pore growth is of great significance to investigating reservoir performance in shale-gas systems. However, different from the marine shale reservoir, the lacustrine shale reservoir is commonly rich in clay minerals, resulting in a complicated and poorly understood pore system. We have investigated the impact of coexisting clay mineral and organic matter on pore growth in the Lower Jurassic Da’anzhai Shale in the Northeast Sichuan Basin, West China, through performing total organic carbon (TOC) analysis, X-ray diffraction, field-emission scanning electron microscopy, focused ion beam-scanning electron microscopy (FIB-SEM), [Formula: see text] and [Formula: see text] adsorption experiment, and high-pressure mercury intrusion porosimetry. Our results indicate that the Da’anzhai Shale is dominated by clay-mineral-hosted pores, which are commonly filled or partly filled by pyrobitumen. Controlled by organic maceral, organic pores are poorly and heterogeneously developed in pyrobitumen, and minor or even no organic pores grow in vitrinite. Mesopore and macropore are popular in the Da’anzhai Shale reservoir with complex shapes, e.g., slit- or plate-like shapes combined with “ink-bottle” shapes, confirming a pore system dominated by clay-mineral-hosted pores. The weak positive correlation between the clay mineral content and the meso/macropore volume confirms that the clay mineral is a positive contributor to the storage space, and the weak negative correlation between the TOC and the mesopore volume suggests that infilling of pyrobitumen decreases the pore volume significantly. Similar correlations occur between specific surface area and clay mineral/TOC. FIB-SEM observation confirms that the pore system, e.g., the pore size, pore shape, and pore volume, is controlled by the coexisting clay mineral and pyrobitumen filling in a later stage. The calculated plane porosity of the initial inorganic pore and the unfilled inorganic pore in the Da’anzhai Shale is in the range of 3.66%–10.95% and 0.79%–1.46%, respectively, suggesting that 76.66% of inorganic pores is inactive due to pyrobitumen filling. All of this evidence suggests that pore growth in the Da’anzhai Shale is positively contributed by clay minerals, but it is negatively contributed by pyrobitumen filling. Further discussion suggests that pyrobitumen infilling between clay minerals in the Da’anzhai lacustrine shale can decrease the original pore volume significantly, which work together to govern the pore system in shale reservoirs.

Silicon has attracted significant attention as a promising anode material owing to its highest theoretical capacity. However, the commercialization of Si faces numerous challenges because of the huge volumetric effect and side reaction with LiPF6. SiOx, a derivative of Si, has received wide interest for its smaller volume change rate compared with that of Si. However, the side reaction with electrolytes has been ignored and seldom studied. In this work, we studied the side reactivity of Si and SiOx electrodes with a LiPF6-based electrolyte. The negative Gibbs free energy change (−ΔG) of SiOx is approximately 20% that of Si, while the reaction activation energy (Ea) of SiOx is nearly 2 times higher than that of Si, indicating that the much higher energy barrier of SiOx could indeed prevent the side reaction. The carbon coating on SiOx could further improve the resistance to this side reaction. These results indicate another important mechanism why SiOx is a more stable and a better cyclic anode material than Si for Li-ion batteries.

Lithium metal batteries are regarded as promising alternatives to lithium ion batteries due to their high specific capacity. However, lithium dendrite growth during cycling causes safety problem and rapid capacity loss. Here, we report a composite Li anode composed (LYF) of metallic Li and trace amounts (1–2 wt%) of two-dimensional YFδ. The lithiophilic nature of YFδ enables its homogeneous dispersion in metallic lithium. The LYF electrode exhibits lower resistance, higher chemical and mechanical stability, and longer cycle life compared to bare Li electrode due to uniform Li stripping and plating with YFδ incorporation, which was confirmed by in-situ optical microscope observation. X-ray photoelectron spectroscopy reveals that LiF can in-situ form on the LYF electrode with reactions between Li and YFδ during cycling. The spontaneous reactions are clarified by density functional theory calculations. A quasi-solid-state cell with LYF anode, LiFePO4 cathode and cathode-supported solid electrolyte layer has been constructed with a soft interface constructed between Li anode and solid electrolyte by in-situ thermal polymerization. The cell shows a high initial discharge capacity of 147 mAh g−1 at 0.5 C at 60 °C and sustains a stable cycling over 50 cycles with the in-situ formed LiF-rich layer and soft interface.

The strain rate effect of ordinary concrete is researched through the particle discrete element method. A random construction method of three-dimensional aggregate is used, and the numerical sample consistent with the experimental specimen is constructed using particle flow code. Moreover, the simulation method that can properly reflect the strain rate effect with the parallel bond model is proposed. The meso-parameters are calibrated by triaxial compression test. Based on the proposed simulation method and calibrated meso-parameters, the numerical tests of direct tension, uniaxial compression, and cyclic loading under strain rates from 10−5 s−1 to 10−1 s−1 are carried out. The results show that the strain rate effect of concrete can be simulated with particle flow code by assuming that the micromechanical properties of materials vary with the strain rate, and the strength and failure characteristics of numerical samples under different strain rates are described well by the proposed method. In addition, the different mechanical responses of the samples to the strain rate in the compression test and the tensile test are obtained, and the changes of mechanical parameters and damage degree with strain rates in the cyclic loading test are also successfully simulated. This study can provide a feasible numerical method for the follow-up research of dynamic mechanical behavior of concrete and offer theoretical guidance for the stability assessment of concrete engineering.

As fossil fuels are constantly depleted, valorization of lignocellulosic biomass into valuable aromatic compounds is of great significance but exceedingly challenging. In this work, the structure and catalytic performance of various Rh/Nb₂O₅ catalysts were studied in detail via the catalytic hydrodeoxygenation of a representative lignin monophenol compound 2-methoxy-4-propylphenol. The best catalytic performance was obtained over Rh/Nb₂O₅-400 (Nb₂O₅ calcined at 400 °C) with an exceptional 98% yield of propylbenzene under 0.5 MPa H₂, which was mainly due to the cooperation between highly dispersed Rh metals and NbOₓ species, in which Rh was responsible for dissociation of H₂ and NbOₓ for breaking of C–O bonds at the metal–support interface. Besides, the lignin oil obtained in depolymerization of raw pine wood was directly used as the substrate in the catalytic hydrodeoxygenation reaction over the Rh/Nb₂O₅-400 catalyst under 0.5 MPa H₂. Encouragingly, the liquid products were identified and found that lignin oil was completely converted into C₆–C₁₀ hydrocarbons (>99% selectivity) with an 80.1 mol % yield of aromatics. The results achieved in this work highlighted that high-value utilization of lignocellulosic biomass feedstocks to produce aromatic chemicals and liquid fuels could be achieved over Rh/Nb₂O₅ under a low hydrogen pressure.

Recently, with the high requirement of electromagnetic interference (EMI) shielding materials, micro- or nano-fibrillated cellulose reinforced Ti3C2Tx nanosheets (transition-metal carbides/carbonitrides, MXene) composites have attracted wide attention due to their complementary functional properties. Nevertheless, it is still challenging to overcome a trade-off between EMI shielding performance and mechanical enhancement with the addition of reinforcing fillers. Herein, modified bacterial cellulose nanofiber (BCNF), with well-tuned micro structure, is employed as the unique reinforcing unit to self-assembly with MXene. The mechanical and electrical properties of different cellulose-derived composites were further compared to get insights into the effect of the fiber configuration on reinforcing properties. Particularly, the optimized MXene/BCNF sample simultaneously exhibited high tensile strength (252.2 MPa), excellent folding endurance (> 10,000 times), and high electrical conductivity (443.5 S cm−1). With striking shielding effectiveness (19,652 dB cm2 g−1), the sample effectively interferes with emitted electromagnetic waves, and is therefore a promising candidate for wearable devices and human electronic equipment.

Conventional methods for monitoring pavement healthy states have the disadvantages of low efficiency and being time-consuming and destructive. Current studies indicate that traditional machine lear...

Micron-sized single crystal particles could be used to intensify structural changes between bulk and surface area during the charge-discharge process owing to their long-range order. In this study, the effects of Mn3+ formation-migration and oxygen loss on the structure change from the bulk side to the near surface in single crystalline Li1.2Mn0.54Ni0.13Co0.13O2 were decoupled by regulating the voltage windows of 2-4.5, 3-4.8, and 2-4.8 V because Mn3+ formation-migration and oxygen loss mainly occurred below 3 V and beyond 4.5 V, respectively. It is found that oxygen vacancies and phase transformation can be retarded by suppressing the formation-migration of Mn3+. Finally, we also conducted an important insight that boron ion doping in tetrahedral site could be used to suppress Mn3+ migration from octahedral site to tetrahedral site and disrupt the synergistic effect of Mn3+ migration and oxygen loss.

As the symbol of gemini surfactants, the spacer group connects two surfactant monomers and plays an important role in the self-assembling of gemini surfactants. Recent attention has been paid to the effects of spacer nature and length in aqueous systems. In this study, the aggregation behaviours of quaternary ammonium gemini surfactants 12-s-12 with different spacer length (s = 2, 3, 4, 5, 6, 8, 10, 12) have been investigated in the protic ionic liquid EAN. The micellization behaviour was characterized by surface tension measurement. With the help of small-angle X-ray scattering (SAXS), the size and shape of aggregates were verified. The spacer length effect could be reflected by the changes in the micellization and phase behaviours of 12-s-12/EAN systems. The critical packing parameter of gemini molecules would decrease monotonically with the spacer length, which is supported by SAXS results. Due to the charge screening effect of EAN, the aggregation behaviours of 12-s-12 would be mainly influenced by spacer length. Our results would be the important supplement to the spacer length effect of gemini surfactants in the nonaqueous systems. With the increase of spacer chain length, the reverse hexagonal lyotropic liquid crystal phase would transform into the micellar phase.

In high geostress areas, rocks tend to experience plastic deformation processes and show ductility. Therefore, the study of the mechanical properties of rocks, especially the post-peak behavior, is crucial for underground geotechnical engineering. For this reason, the macroscopic mechanical property of marble is studied by using the PFC/PBM numerical method. An improved numerical marble sample with random properties is used by setting different contact strengths following a bimodal Weibull distribution. Thereafter, on the basis of an improved boundary servo mechanism, the brittle–ductile transition appearing in laboratory tests on marble is successfully realized by the discrete approach, and a servo velocity threshold function of axial loading speed and confining pressure is obtained. Furthermore, the marble model and servo method are applied in the excavation of typical underground caverns. The effects of constrained velocity and geostress level on the surrounding rock failure model of the cavern are described and analyzed. In addition, mechanism of the excavation failure under high geostress is discussed.

Bacterial resistance has become a serious global health issue over the past decades due to the misuse and abuse of antibiotics. The development of effective antibacterial drugs with a new antibacterial mechanism is thus very critical. At present, there are many reports on the antibacterial properties and mechanisms of two-dimensional materials. Currently, the modification of g-C3N4 materials, as widely used two-dimensional materials, has become a key step in extending their potential applications in the field of antimicrobial therapy. In the present work, we prepared sulfur-doped g-C3N4 nanosheets (SCNNSs), which have good water dispersibility and sharp tips. The electrostatic interaction of SCNNSs with Tetrastigma hemsleyanum Diels & Gilg's polysaccharide-3 (THDG-3) provides a new strategy that can improve the killing efficiency of SCNNSs. In addition, THDG-3 can rapidly inhibit bacterial proliferation in the early stage of administration. Combined with the antibacterial activity of the SCNNSs, TPS/SCNNSs can inhibit bacteria for a long time. Scanning electron microscopy (SEM) observation of Escherichia coli (E. coli) after administration of the materials revealed that the bacterial cells were ruptured and their intracellular contents were completely separated from the cell membrane. Therefore, we speculate that the bactericidal mechanism of the TPS/SCNNSs probably involves cell membrane damage. In summary, TPS/SCNNSs achieve fast, long-term, dual-function bacteriostatic properties.

This paper presents a research on the kinetics and gas release laws of the cooperative spontaneous combustion of coal-polyurethane binary system by means of thermogravimetric analysis and spontaneous combustion simulation experiments. The coal-polyurethane binary system is more prone than individual samples to combustion. The polyurethane mass fraction has a great influence on the cooperative spontaneous combustion process. As the polyurethane mass fraction rises, the activation energies of oxygen absorption stage and pyrolysis stage decrease. The combustion residues of coal-polyurethane binary system scorches into lumps and the surfaces of the particles become rougher. During spontaneous combustion, the initial release temperatures of the four gases CO2, CO, C2H6 and C2H4 drop as the polyurethane mass fraction increases. The gas release amount of them increases with increasing polyurethane mass fraction. And the amount of CH4 decreases as the polyurethane mass fraction increases. The CO/CO2 ratio with temperature for different polyurethane mass fraction have the same trends. The results of this study have implications concerning polyurethane materials application and fire protection in coal mine.

The controllable synthesis and customized design of micro/nanomotors represents a highly desired paradigm in the field of intelligent nanovehicles. Exploiting asymmetrical structures and geometry-dependent propulsion are the two main strategies for achieving light-driven micro/nanomotors. However, inherent crystal-structure differences in a single colloidal motor have rarely been explored. Here, we propose the first surface-heterojunction-induced propulsion methodology for cuprous oxide (Cu2O) nanomotors, by tailoring the crystal morphology of a Cu2O crystalloid from a sphere into a truncated octahedron and preserving the controllable-index crystal facets of {100} and {111} in a single colloid. Due to the high crystallinity and distinct activity of the exposed crystal facets, a surface heterojunction between the {100} and {111} facets is formed to enhance electron-hole separation, as confirmed by density functional theory (DFT) calculations, thus endowing the truncated octahedral Cu2O nanomotors with autonomous and vigorous movement in biocompatible fuels under visible light. These Cu2O nanomotors can reach a propulsion speed in water of over two times faster than that of polycrystalline spherical motors with low crystallinity. The efficient Cu2O nanomotors offer a promising guideline not only for the synthesis of novel light-driven motors with desired structures, but also for potential applications in biocompatible environments.

Advanced communication technologies (e.g., 5G) probably elicit a complete change of network and its applications. For example, a growing number of services begin shifting from central clouds to vast mobile devices, as the hybrid use of cloud and fog computing technologies can provide enhanced quality of service and efficient utilization of resources. However, to design such complex hybrid cloud-fog (HCF) systems, it remains a challenge to implement time-consuming modeling and inefficient evaluation in its early design stage based on the conventional simulation or practical experimentation. Therefore, how to reduce design cost and improve development efficiency becomes a crucial issue in the process of designing large-scale HCF systems. To address the issue, this paper proposes a novel modeling framework for large-scale HCF systems based on a high-level formal language, i.e. performance evaluation process algebra (PEPA). Toward the key components of an HCF system, the proposed framework includes three crucial model prototypes: compositional architecture model , abstract communication model and scheduling model . Moreover, the scheduling model is designed with a novel smart scheduling scheme that integrates two atomic scheduling algorithms and a decision module to make an efficient algorithm selection. The smart scheduling algorithm can well adapt the HCF systems by yielding stable and fast response to end-users, particularly under dynamical system conditions. Finally, the framework is the first research achieving the full potential of formal methods to implement industry-level modeling and evaluation.

The increasing penetration of renewable energy resources in power systems, represented as random processes, converts the traditional deterministic economic dispatch problem into a stochastic one. To estimate the uncertainty in the stochastic economic dispatch (SED) problem for the purpose of forecasting, the conventional Monte-Carlo (MC) method is prohibitively time-consuming for practical applications. To overcome this problem, we propose a novel Gaussian-process-emulator (GPE)-based approach to quantify the uncertainty in SED considering wind power penetration. Facing high-dimensional real-world data representing the correlated uncertainties from wind generation, a manifold-learning-based Isomap algorithm is proposed to efficiently represent the low-dimensional hidden probabilistic structure of the data. In this low-dimensional latent space, with Latin hypercube sampling (LHS) as the computer experimental design, a GPE is used, for the first time, to serve as a nonparametric, surrogate model for the original complicated SED model. This reduced-order representative allows us to evaluate the economic dispatch solver at sampled values with a negligible computational cost while maintaining a desirable accuracy. Simulation results conducted on the IEEE 118-bus test system reveal the impressive performance of the proposed method.

Oxidative stress has been proven to play a critical role in the pathogenesis of neuronal injury. As a novel adipocytokine, omentin is produced by visceral adipose with insulin sensitizing effects and has been revealed to possess anti-inflammatory effects. However, the possible effect of omentin on oxidative stress remains unknown. The present study aimed to detect the potential protective effect of omentin against hydrogen peroxide (H

The solar rotation causes the solar Doppler difference bias, which leads to the decline of the velocity measurement accuracy. Modeling and compensation are an effective solution. The limited model with specific geometric direction, where the solar rotation axis is perpendicular to the plane through the Sun, the Earth and Mars, was established. However, in fact, the geometric relationship among the Sun, Mars and the spacecraft is not fully in line with the hypothesis of the model due to the spacecraft orbital angle and the solar rotation axis drift. Thus, this model is not consistent with the fact. In order to solve this problem, a universal solar Doppler difference bias model, which provides the expression with arbitrary rotation axis, is established in this paper. In this method, for any point at the solar surface, four variables including the direction of the solar rotation linear velocity at this point, the distance from this point to the rotation axis, the vector from this point to Mars, and the vector from this point to the spacecraft are calculated. Based on these four variables, the solar Doppler difference bias corresponding to this point is obtained. The theoretical analysis and simulation results demonstrate that the solar Doppler difference bias model with the actual rotation axis is different from that with one of the specific rotation axes. Therefore, it is indispensable to build the proposed model for compensation. Besides, the direction of the solar rotation axis, the spacecraft-Mars-Sun angle and the spacecraft-to-Mars distance are important impact factors for the proposed model.

Obtaining a molecular-level understanding of hydrogen production from alcohols with model catalysts is critical for improving industrial catalytic hydrogen production processes. In this work, hydro...

Mechanical damage and resultant permeability evolution during compaction of highly porous reservoir rocks have strong implications on the extraction of mineral and energy resources. Laboratory Experiments can be performed to quantify this effect; however, the effect of size on these processes and the information they provide need to be evaluated before any conclusion can be drawn. As part of this study, conventional triaxial compression tests under different confining pressures were carried out on large samples (30 mm diameter and 60 mm length). These experiments were compared to the same setup for small samples with 12.7 mm diameter and 25.4 mm length which allowed monitoring of the pore structure changes through the use of an X-ray transparent triaxial cell at constant confining pressure. Both scales showed a similar mechanical response. The large-scale experiments were used to investigate the transition from brittle to ductile deformation, and the small-scale experiments allowed detailed investigation of the microstructural changes affecting the permeability evolution. The permeabilities of the specimens were continually measured during the triaxial loading at both scales. At defined increasing axial strain levels, the small sample was imaged using X-ray computed tomography (XRCT) and internal structural changes were mapped. A series of digital rock analysis techniques and Pore Network Modelling allowed accurate analysis of the evolution of the microstructure and its effect on permeability evolution using Pore Network Models. An XRCT-based, microstructurally enriched, continuum model successfully describes the permeability evolution measured during triaxial testing. Self-organized criticality of the propagating front of compaction was also shown by R2 values > 0.95 for a double Pareto fractal scaling law. Both approaches, as well as the macroscale experiments, confirmed a phase change in permeability at ~ 5% axial strain which provided a solid basis for microstructurally enriched assessment of the dynamic permeability.

Functional micro/nano structures are promising for enhancing the performance of CaF2-based devices. However, it is still a challenge to precisely manufacture CaF2 micro/nano structures due to their brittleness. In the present work, we demonstrated the machinability of ductile-mode diamond cutting of CaF2 and the ability to sculpture sophisticated micro/nano structures on CaF2 by applying elliptical vibration cutting. Firstly, the nanoindentation of CaF2 reveals the crystal orientation-dependent interaction between dislocation slip and crack propagation, thus obtaining the optimal crystal orientation for plasticity. Subsequently, the grooving tests were conducted along the crystal orientation of (111) [ 1 ‾ 2 1 ‾ ] . With elliptical vibration cutting, the critical depth of cut from ductile-to-brittle transition is increased by 42 times as compared with ordinary cutting. Furthermore, considering the instantaneous uncut chip thickness in each vibration cycle, the influence of vibration amplitude on the ductile machinability of CaF2 is discussed in detail. Finally, based on these fundamental results, ultra-precision hexagonal microlenses were successfully sculptured on CaF2 by applying the amplitude-controlled sculpturing method in elliptical vibration cutting.

A modern power system is characterized by an increasing penetration of wind power, which results in large uncertainties in its states. These uncertainties must be quantified properly; otherwise, the system security may be threatened. Facing this challenge, we propose a cost-effective, data-driven approach to assessing a power system's load margin probabilistically. Using actual wind data, a kernel density estimator is applied to infer the nonparametric wind speed distributions, which are further merged into the framework of a vine copula. The latter enables us to simulate complex multivariate and highly dependent model inputs with a variety of bivariate copulae that precisely represent the tail dependence in the correlated samples. Furthermore, to reduce the prohibitive computational time of traditional Monte-Carlo simulations that process a large amount of samples, we propose to use a nonparametric, Gaussian-process-emulator-based reduced-order model to replace the original complicated continuation power-flow model through a Bayesian-learning framework. To accelerate the convergence rate of this Bayesian algorithm, a truncated polynomial chaos surrogate, which serves as a highly efficient, parametric Bayesian prior, is developed. This emulator allows us to execute the time-consuming continuation power-flow solver at the sampled values with a negligible computational cost. Results of simulations that are performed on several test systems reveal the impressive performance of the proposed method in the probabilistic load-margin assessment.

Summary Ideal heterogeneous metal hydrogenation catalysts are featured by simultaneously high activity, selectivity, and stability. Herein, we report a general yet powerful strategy to design and fabricate dual-active-sites Co@C core-shell nanoparticle for boosting selective hydrogenation of various N-heteroarenes. It can break the limitation of scaling relation on traditional metal surfaces, and thus afford unprecedentedly high selectivity, activity, and stability. Combining kinetics analysis and DFT calculations with multiple techniques directly unveil that the critical porous carbon shell with a pore size of 0.53 nm not only allows H2 diffusion to Co sites for activation and blocks accessibility of N-heteroarenes but also catalyzes hydrogenation of N-heteroarenes via hydrogen spillover from Co sites. In addition, the presence of surface/subsurface carbon at the Co sites shows high anti-sulfur poisoning and anti-oxidant capability. This work is valuable for guiding the design and manipulation of cost-effective and robust hydrogenation catalysts.