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Before a wide range of enhanced oil recovery (EOR) techniques were implemented for an oilfield, the EOR potential and economic evaluation of the techniques should be evaluated in advance for each reservoir to determine which EOR technique was proper. In an oilfield developed with fluvial delta reservoirs, the complicated distribution of scattered small reservoirs in vertical and horizontal directions brought trouble for evaluation work. A rapid and reliable evaluation model for EOR techniques applicability was necessary to deal with the evaluation simulation for many small reservoirs of an oilfield. Combining fraction theory model with auxiliary equations, which describe the effect of formation heterogeneity and mechanism of different EOR technique on fractional flow rate, an evaluation analysis method for EOR techniques applicability of gas flooding, foam flooding and surfactant flooding was proposed. In the gas flooding model, the minimum miscible pressure of impure gas was introduced, and the relative permeability was modified by the minimum miscible factor. In the foam flooding model, changes in the mobility ratio and chemical adsorption were considered and a reduction factor of mobility ratio was introduced. In the surfactant flooding model, calculation formulas of viscosity and interfacial tension as well as the relative permeability were introduced. Finally, the model was simulated for a low permeability reservoir, and the simulation results were compared with that from Eclipse software. The similar results, little calculation time and feasibility of predicting optimal injection parameter had shown the reliability of the rapid evaluation model.

Bilayer graphene (BLG) is intriguing for its unique properties and potential applications in electronics, photonics, and mechanics. However, the chemical vapor deposition synthesis of large-area high-quality bilayer graphene on Cu is suffering from a low growth rate and limited bilayer coverage. Herein, we demonstrate the fast synthesis of meter-sized bilayer graphene film on commercial polycrystalline Cu foils by introducing trace CO2 during high-temperature growth. Continuous bilayer graphene with a high ratio of AB-stacking structure can be obtained within 20 min, which exhibits enhanced mechanical strength, uniform transmittance, and low sheet resistance in large area. Moreover, 96 and 100% AB-stacking structures were achieved in bilayer graphene grown on single-crystal Cu(111) foil and ultraflat single-crystal Cu(111)/sapphire substrates, respectively. The AB-stacking bilayer graphene exhibits tunable bandgap and performs well in photodetection. This work provides important insights into the growth mechanism and the mass production of large-area high-quality BLG on Cu.

Bangladesh-China relations have strengthened over recent decades due to financial, military, trade, and political ties. Relations between Bangladesh and China were originally established in 1976. Progressive leaders of the two countries have pledged to advance China-Bangladesh bilateral trade relations. The strengthening of China-Bangladesh relations and the promotion of trade relations and financial participation are the main interests of these two countries which help in the development of the people. Approved social events, correspondence, and concerted efforts and cooperation at the level of advanced government authorities were agreed upon. To develop Bangladesh-China bilateral trade relations, the administration empowered to redesign investments in the main assembly, the Joint Monetary and Exchange Board of Trustees, and the Joint Horticulture Council, including machinery and other Content. The various gatherings are trying to increase compensation, speculation, cultivation, transportation, and infrastructure development, depending on the basic bilateral trade between the two countries. The Belt and Road Initiative has contributed to the development of bilateral trade relations between the two countries. "Sister Cities" alliances have been established. This paper aims to analyze and explore current bilateral trade relations and trade agreements, investment, agriculture, transport, and infrastructure development. An exploration of bilateral relations between Bangladesh and China. This article attempts to reveal the current pattern of bilateral relations between Bangladesh and China. This research paper is based on a literature review and related data and analyzed in consultation with recent bilateral trade relations scholarship.

Although single-particle cryogenic electron microscopy (cryo-EM) has been applied extensively for elucidating many crucial biological mechanisms at the molecular level, this technique still faces critical challenges, the major one of which is to prepare the high-quality cryo-EM specimen. Aiming to achieve a more reproducible and efficient cryo-EM specimen preparation, novel supporting films including graphene-based two-dimensional materials have been explored in recent years. Here we report a robust and simple method to fabricate EM grids coated with single- or few-layer reduced graphene oxide (RGO) membrane in large batch for high-resolution cryo-EM structural determination. The RGO membrane has decreased interlayer space and enhanced electrical conductivity in comparison to regular graphene oxide (GO) membrane. Moreover, we found that the RGO supporting film exhibited nice particle-absorption ability, thus avoiding the air–water interface problem. More importantly, we found that the RGO supporting film is particularly useful in cryo-EM reconstruction of sub-100-kDa biomolecules at near-atomic resolution, as exemplified by the study of RBD-ACE2 complex and other small protein molecules. We envision that the RGO membranes can be used as a robust graphene-based supporting film in cryo-EM specimen preparation.

Additional file 2. Table S1. Predictive accuracy comparison of the variables for the onset of HCC in Changzhou cohort. Table S2. Predictive accuracy comparison of score model for the onset of HCC in patients with different AJCC TNM stages. Table S3. Baseline characteristics of patients in Wuxi cohort.

Additional file 1. Figure S1. The Venn diagram indicated intersection of the serum markers associated with HCC onset (Green, serum markers identified by ROC analysis with AUC > 0.55; blue, serum markers screened by univariate logistic regression analysis with p < 0.25). Figure S2. Kaplan–Meier analysis for overall survival between high risk group and low risk group. A In Changzhou cohort. B In Wuxi cohort.

Deflagration fracturing technique also named high energy gas fracturing (HEGF) technique was applied for creating several radial fractures nearby the wellbore to improve the conductivity. Because of the good applicability for different reservoirs, deflagration fracturing technique was also tried in a screen completed well. However, the theoretical literatures about deflagration fracturing were mainly focused on the open-hole completed or perforated well. A simulation on the dynamic variation of gas pressure in screen completed well was required to avoid destroying the tool because of the structural difference between the screen pipe and casing tube. A model describing the deflagration fracturing process in screen completed well was built. Except for the traditional equations for a perforated well, an equation for the propellant burning, that for the displacement of pressurized liquid column with downhole pipe string operating, and that for the fluid flow through the screen pipe was introduced. Then, a numerical simulation was carried out to validate. Compared with the real production-increasing ratio, the simulated accuracy approached 90%. The calculated maximum pressure was 50.3 MPa when a simulation was done with the given parameters, in accordance with the safety command of screen completed well. The maximum gas pressure had decreased with the increase of hole density and size of the screen pipe. A suggestion for operating pipe during deflagration fracturing was given. Operation with a downhole pipe string of large size and large wall thickness was beneficial for the safety during fracturing process.

In the field of fixed wing aircraft, many morphing technologies have been applied to the wing, such as adaptive airfoil, variable span aircraft, variable swept angle aircraft, etc., but few are aimed at the tail. The traditional fixed wing tail includes horizontal and vertical tail. Inspired by the bird tail, this paper will introduce a new bionic tail. The tail has a novel control mode, which has multiple control variables. Compared with the traditional fixed wing tail, it adds the area control and rotation control around the longitudinal symmetry axis, so it can control the pitch and yaw of the aircraft at the same time. When the area of the tail changes, the maneuverability and stability of the aircraft can be changed, and the aerodynamic efficiency of the aircraft can also be improved. The aircraft with morphing ability is often difficult to establish accurate mathematical model, because the model has a strong nonlinear, model-based control method is difficult to deal with the strong nonlinear aircraft. In recent years, with the rapid development of artificial intelligence technology, learning based control methods are also brilliant, in which the deep reinforcement learning algorithm can be a good solution to the control object which is difficult to establish model. In this paper, the model-free control algorithm PPO is used to control the tail, and the traditional PID is used to control the aileron and throttle. After training in simulation, the tail shows excellent attitude control ability., PDF, 8 pages with 10 figures, IEEE Robotics and Automation Letters and ICRA (under review)

Most of the current magnetic-driven micro-nano robots have achieved post-maintenance functions. The tools for preventive maintenance are becoming richer and the challenges are diminishing. The future development of medical nanobots is bound to move towards predictive maintenance. To that end, Andrew Conrad told the WSJD online global technology conference that Google is designing nanobots that can enter the human circulatory system for early diagnosis of disease. It is believed that magnetically driven micro-nano robots with predictive maintenance direction will be available soon.

Four gramineous energy plants, Miscanthus sacchariflorus, M. floridulus, Phragmites australis, and Arundo donax were grown on copper tailings in the field for four years. Their phytoremediation potential was examined in terms of their effects on the fractions of heavy metals and soil enzyme activities. Results showed that plantation of these four gramineous plants has improved the proportion of organic material (OM)-binding fraction of heavy metals in copper tailings as a whole, and reduced the proportion of exchangeable and residual fractions. In particular, M. sacchariflorus growth improved significantly the proportion of the OM-binding fractions of Cu (1.73 times), Cd (1.71 times), Zn (1.18 times), and Pb (3.14 times) (P < 0.05) and reduced markedly the residual fractions of Cu (64.45%), Cd (82.38%), Zn (61.43%), and Pb (73.41%) (P < 0.05). Except for A. donax, the growth of other three energy plants improved the activity of phosphatase, urease and dehydrogenase in copper tailings to some extent. In particular, the activity of soil phosphatase and urease in planted tailings differed significantly from that of control (P < 0.05). The effect of M. sacchariflorus growth on soil enzyme was the highest, followed by P. australis, M. floridulus, and A. donax. The content of each heavy metal fraction in soil was correlated with soil enzyme activities, especially the content of OM-binding fraction, which correlated significantly with the activities of phosphatase, urease and dehydrogenase in soil. According to the effects of four gramineous plants growth on activity of soil enzymes and fractions of heavy metals, M. sacchariflorus had the optimal effects for phytoremediation. Therefore, M. sacchariflorus was a candidate plant with great potential for the revegetation of heavy metal tailings.

This paper proposed a physical model of electron trapping/detrapping in electrically stressed oxide. The new model is based on both inelastic multi-phonon trap-assisted tunneling and thermal emission, and the capture effect of oxide bulk traps is considered as well. The dynamic procedure of traps capture and emission of electrons are established. Finally, the filling state of all the oxide traps at any stress and any time can be obtained accurately and effectively which is very useful for the modeling of the endurance and data retention characteristics of floating gate nonvolatile memories.

The thermal protection characteristics of metallic honeycomb core panel structures in high-temperature environments are important parameters for the structure design of thermal protection for high-speed aircraft. A self-developed transient aerodynamic thermal simulation system for high-speed aircraft is used to test the thermal protection performance of metallic honeycomb core panels in a dynamic high-temperature environment at temperatures up to 950°C. The heat transfer characteristics of metallic honeycomb core panels in transient and steady states and the heat shield effects at various temperatures are determined. By considering the internal radiation of honeycomb core panels as well as the heat transfer between a metal structure and air within a honeycomb core cavity, three-dimensional finite element models are established for numerical simulations and computations of the thermal protection properties of metallic honeycomb core panels. The experimental results agree well with the numerical simulations...

Hierarchical Beta zeolite with mesoporous/microporous structure was synthesized by employing a bifunctionalized amphiphilic surfactant. N 2 adsorption–desorption isotherms indicated the presence of hierarchical mesopores in this sample. Transmission electron microscopy images confirmed the co-presence of ordered micropores and hierarchical mesopores. This sample exhibited excellent hydrothermal stability. In addition, the prepared hierarchically structured Beta zeolite showed greatly enhanced catalytic activity as compared with conventional counterpart for probe reaction involving large molecules due to the highly mesoporous structure, in which diffusion constraints of reactant molecules are the main concern. Such hierarchical micro/mesostructure Beta zeolite combined good hydrothermal stability and high activities may find potential applications in catalysis and adsorption involving bulky molecules.

In many Radio Frequency Identification (RFID) applications, the reader recognizes the tags within its scope repeatedly. For these applications, some algorithms such as the adaptive query splitting algorithm (AQS) and the novel semi-blocking AQS (SBA) were proposed. In these algorithms, a staying tag retransmits its ID to the reader to be identified, even though the ID of the tag is stored in the reader’s memory. When the length of tag ID is long, the reader consumes a long time to identify the staying tags. To overcome this deficiency, we propose a slot allocated blocking anti-collision algorithm (SABA). In SABA, the reader assigns a unique slot to each tag in its range by using a slot allocation mechanism. Based on the allocated slot, each staying tag only replies a short data to the reader in the identification process. As a result, the amount of data transmitted by the staying tags is reduced greatly and the identification rate of the reader is improved effectively. The identification rate and the data amount transmitted by tags of SABA are analyzed theoretically and verified by various simulations. The simulation and analysis results show that the performance of SABA is superior to the existing algorithms significantly.

Nowadays, Internet of Things (IOT) are used more and more widely, and showed continued hot situation. IOT is a strategic emerging industry in China. To meet the modern industrial society, the development of global economic integration of the general direction, it is a Chinese future development trend in higher engineering education to establish high-quality, distinctive engineering colleges. In order to cultivate a group of international engineering education background, and innovative Chinese characteristics of IOT engineering personnel, the French engineers education modes are studied in this paper. And its status are compared with Chinese IOT education. This paper discusses the existing IOT teaching situation in China from three aspects: the team learning, cooperating with the French engineer school and the deep-level school-enterprise cooperation teaching methods. The paper contributes to the systematization and diversification of the talented personnel training plan of our excellent engineers.

The carrier leakage is one of the major factor that limits the performance of the UHF RFID reader. Compared to conventional method which uses vector modulator, this paper presents a passive carrier suppression method achieving low noise. Through experiments, the implemented carrier suppression circuit exhibits 40dB with transmission power of 28dBm; As a result, the sensitivity of reader improved 14dB when the BER of 10 -5 . The proposed method is successfully applied to the design of the UHF RFID reader.

It is shown by a prototype experiment that the deformation of a support structure leads to relative deflection of the optical axes of a multiwaveband imaging system and then inconsistency of the fields of view of the subsystems. To solve this issue, a topology optimization method with the objective of minimizing the deflection angles of the optical axes is proposed. The method consists of the establishment of a deflection angle equation, the construction of an objective function, and the achievement of optimization using commercial software. Then, a new optimization structure is extracted from the topology optimization model. The comparative analysis between the original structure and the optimization structure shows that the deflection angles of the optical axes after topology optimization decrease greatly, which proves the effectiveness of the proposed method.

Thermal decomposition reactions of hexaamminecobalt(III) chloride in the presence of anion salts KY (Y = Cl − , Br − , I − , CN − , SCN − , OH − ) are investigated, mainly by gas chromatographic, infrared spectroscopic and X-ray diffraction methods. Kinetic parameters are calculated. The deammine activation energy is found to vary with the different anions (Y), increasing in the order OH − − − − , Br − − . Possible mechanisms and factors affecting the results are discussed.

According to the grouping teaching characteristics to students from overseas, “Face the World, Application Oriented” is taken as the main idea. In order to solve problems during the study of microcomputer principle and interface technology, we propose to re-integrate the teaching content, make abstract content figurative, use new teaching tools and methods.Practice shows that the methods is effective, enhances students' interests, strengthens the theoretical foundation of students.

Hierarchically structured ZSM-5 zeolites were synthesized by employing only one dual-porogenic surfactant, and the hydrothermal crystallization of hierarchical structured zeolites were investigated under rotating and static synthesis conditions. X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption–desorption isotherms, 27Al magic-angle spinning nuclear magnetic resonance (27Al MAS NMR) and thermogravimetric analysis (TGA) were used to characterize the structural and textural features of the resultant zeolite products. By tuning the synthesis conditions from rotating to static, the morphology of the as-obtained hierarchical structure ZSM-5 zeolites changed from silk-like to nanoparticles with a disordered arrangement. Furthermore, the obtained zeolites under static conditions showed a higher BET surface area and lower total pore volume than those of zeolites synthesized under rotating conditions. In addition, quantum chemical calculation results show that the inner ammonium groups may have greater contribution in directing the zeolite structure than tailed ammonium groups. More importantly, the hierarchical structured ZSM-5 zeolites synthesized under static conditions exhibited a higher benzyl alcohol conversion rate and lower ester selectivity compared to those of the samples prepared under rotating conditions. Consideration of the effects of synthesis conditions may be useful for modulating the textural and catalytic properties of hierarchical zeolites.

Hierarchical zeolites have emerged as an important class of materials for applications in adsorption, separation and catalysis. Herein, hierarchical zeolite Y was hydrothermally synthesized using an organosilane surfactant, which was added into the conventional synthesis composition for crystalline microporous aluminosilicates as mesopore-generating agent. X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) (with KBr and pyridine), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), 27Al magic-angle spinning nuclear magnetic resonance (27Al MAS NMR) and N2 adsorption–desorption isotherms were used to characterize structural and textural features of the hierarchical zeolite Y. In addition, the molecular properties of the organosilane surfactant were investigated by density functional theory calculation. The hierarchical zeolite Y with mesoporous characteristics and the microporous crystalline structure of zeolites exhibited high catalytic activity and resistance to deactivation in the aldol condensation of benzaldehyde with n-butyl alcohol, as compared with conventional zeolite Y. This phenomenon could be attributed to improved mass transport ability of guest species through the interconnected micropore-to-mesopore networks. Such a hierarchical zeolite Y, that combines the advantages of two different pore structures, may find potential applications as advanced materials in various fields such as adsorption, separation and catalysis.