Simulation Method and Feature Analysis of Shutdown Pressure Evolution During Multi-Cluster Fracturing Stimulation

Multistage multi-cluster hydraulic fracturing has enabled the economic exploitation of shale reservoirs,but the interpretation of hydraulic fracture parameters is challenging.The pressure signals after pump shutdown are influenced by hydraulic fractures,which can reflect the geometric features of hydraulic fracture.The shutdown pressure can be used to interpret the hydraulic fracture parameters in a real-time and cost-effective manner.In this paper,a mathematical model for shutdown pressure evolution is developed considering the effects of wellbore friction,perforation friction and fluid loss in fractures.An efficient numerical simulation method is established by using the method of characteristics.Based on this method,the impacts of fracture half-length,fracture height,opened cluster and perforation number,and filtration coefficient on the evolution of shutdown pressure are analyzed.The results indicate that a larger fracture half-length may hasten the decay of shutdown pressure,while a larger fracture height can slow down the decay of shutdown pressure.A smaller number of opened clusters and perforations can significantly increase the perforation friction and decrease the overall level of shutdown pressure.A larger filtration coefficient may accelerate the fluid filtration in the fracture and hasten the drop of the shutdown pressure.The simulation method of shutdown pressure,as well as the analysis results,has important implications for the interpretation of hydraulic fracture parameters.

Vote-Based Feature Selection Method for Stratigraphic Recognition in Tunnelling Process of Shield Machine

Shield machines are currently the main tool for underground tunnel construction. Due to the complexity and variability of the underground construction environment, it is necessary to accurately identify the ground in real-time during the tunnel construction process to match and adjust the tunnel parameters according to the geological conditions to ensure construction safety. Compared with the traditional method of stratum identifcation based on staged drilling sampling, the real-time stratum identifcation method based on construction data has the advantages of low cost and high precision. Due to the huge amount of sensor data of the ultra-large diameter mud-water balance shield machine, in order to balance the identifcation time and recognition accuracy of the formation, it is necessary to screen the multivariate data features collected by hundreds of sensors. In response to this problem, this paper proposes a voting-based feature extraction method (VFS), which integrates multiple feature extraction algorithms FSM, and the frequency of each feature in all feature extraction algorithms is the basis for voting. At the same time, in order to verify the wide applicability of the method, several commonly used classifcation models are used to train and test the obtained efective feature data, and the model accuracy and recognition time are used as evaluation indicators, and the classifcation with the best combination with VFS is obtained. The experimental results of shield machine data of 6 diferent geological structures show that the average accuracy of 13 features obtained by VFS combined with diferent classifcation algorithms is 91%;among them, the random forest model takes less time and has the highest recognition accuracy, reaching 93%, showing best compatibility with VFS. Therefore, the VFS algorithm proposed in this paper has high reliability and wide applicability for stratum identifcation in the process of tunnel construction, and can be matched with a variety of classifer algorithms. By combining 13 features selected from shield machine data features with random forest, the identifcation of the construction stratum environment of shield tunnels can be well realized, and further theoretical guidance for underground engineering construction can be provided.

Methods to Evaluate and Measure Power of Pneumatic System and Their Applications

Pneumatic system has been widely used throughout industry, and it consumes more than billions kW h of electricity one year all over the world. So as to improve the efficiency of pneumatic system, its power evaluation as well as measurement methods should be proposed, and their applicability should be validated. In this paper, firstly, power evaluation and measurement methods of pneumatic system were introduced for the first time. Secondly, based on the proposed methods, power distributions in pneumatic system was analyzed. Thirdly, through the analysis on pneumatic efficiencies of typical compressors and pneumatic components, the applicability of the proposed methods were validated. It can be concluded that, first of all, the proposed methods to evaluation and measurement the power of pneumatic system were efficient. Furthermore, the pneumatic power efficiencies of pneumatic system in the air production and cleaning procedure are respectively about 35%–75% and 85%–90%. Moreover, the pneumatic power efficiencies of pneumatic system in the transmission and consumption procedures are about 70%–85% and 10%–35%. And the total pneumatic power efficiency of pneumatic system is about 2%–20%, which varies largely with the system configuration. This paper provides a method to analyze and measure the power of pneumatic system, lay a foundation for the optimization and energy-saving design of pneumatic system.

Gas Leakage Detection and Pressure Difference Identification by Asymmetric Differential Pressure Method

Currently,the measurement methods for pneumatic system leakage include bubbling,ultrasonic,and pressure detection methods.These methods are sensitive to high-precision sensors,long detection times,and stable external environments.The traditional differential pressure method involves severe differential pressure fluctuations caused by environmental pressure fluctuations or electromagnetic noise interference of sensors,leading to inaccurate detection.In this paper,a differential pressure fitting method for an asymmetric differential pressure cylinder is proposed.It overcomes the limitation of the detection efficiency caused by the asynchronous temperature recovery of the two chambers in the asymmetric differential pressure method and uses the differential pressure substitution equation to replace the differential calculation of the differential pressure.The improved differential pressure method proposes an innovation based on the detection principle and calculation method.Additionally,the influence of the parameters in the differential pressure substitution equation on the leakage calculation results was simulated,and the specific physical significance of the parameters of the differential pressure substitution equation was explained.The experiments verified the fitting effect and proved the accuracy of this method.Compared with the traditional differential pressure method,the maximum leakage deviation of inhibition was 0.5 L/min.Therefore,this method can be used to detect leaks in air tanks.

The soybean PLATZ transcription factor GmPLATZ17 suppresses drought tolerance by interfering with stress-associated gene regulation of GmDREB5

Plant AT-rich sequence and zinc binding(PLATZ)transcription factors are a class of plant specific zincdependent DNA-binding proteins that function in abiotic stress response and plant development.In this study,31 GmPLATZ genes were identified in soybean.GmPLATZ17 was down-regulated by drought and exogenous abscisic acid.Transgenic Arabidopsis and soybean hairy roots overexpressing GmPLATZ17 showed drought sensitivity and inhibition of stress-associated gene transcription.In contrast,suppressed expression of GmPLATZ17 led to increased drought tolerance in transgenic soybean hairy roots.The GmPLATZ17 protein was verified to interact physically with the GmDREB5 transcription factor,and overexpression of GmDREB5 increased drought tolerance in soybean hairy roots.Interaction of GmPLATZ17 with GmDREB5 was shown to interfere with the DRE-binding activity of GmDREB5,suppressing downstream stress-associated gene expression.These results show that GmPLATZ17 inhibits drought tolerance by interacting with GmDREB5.This study sheds light on PLATZ transcription factors and the function of GmPLATZ17 in regulating drought sensitivity.

Phosphine-free synthesis of FeTe2 nanoparticles and self-assembly into tree-like nanoarchitectures

Manipulating the self-assembly of transition metal telluride nanocrystals(NCs) creates opportunities for exploring new properties and device applications. Iron ditelluride(FeTe2) has recently emerged as a new class of magnetic semiconductor with three-dimensional(3D) magnetic ordering and narrow band gap structure, yet the self-assembly of FeTe2 NCs has not been achieved. Herein, the tree-like FeTe2 nanoarchitectures with orthorhombic crystal structure have been successfully synthesized by hot-injection solvent thermal approach using phosphine-free Te precursor. The morphology, size, and crystal structure have been investigated using transmission electron microscopy(TEM), high-resolution TEM(HRTEM),and powder x-ray diffraction(XRD). We study the formation process of tree-like FeTe2 NCs according to trace the change of the sample morphology with the reaction time. It was found that the FeTe2 nanoparticles show oriented aggregation and self-assembly behavior with the increase of reaction time, which is attributed to size-dependent magnetism properties of the samples. The magnetic interaction is thought to be the driving force of nanoparticle self-organization.

Dimensionless Study on Secretion Clearance of a Pressure Controlled Mechanical Ventilation System with Double Lungs

A pressure controlled mechanical ventilator with an automatic secretion clearance function can improve secretion clearance safely and efficiently.Studies on secretion clearance by pressure controlled systems show that these are suited for clinical applications.However,these studies are based on a single lung electric model and neglect the coupling between the two lungs.The research methods applied are too complex for the analysis of a multi-parameter system.In order to understand the functioning of the human respiratory system,this paper develops a dimensionless mathematical model of doublelung mechanical ventilation system with a secretion clearance function.An experiment is designed to verify the mathematical model through comparison of dimensionless experimental data and dimensionless simulation data.Finally,the coupling between the two lungs is studied,and an orthogonal experiment designed to identify the impact of each parameter on the system.

Research on the Pressure Regulator Effect on a Pneumatic Vibration Isolation System

The pneumatic vibration isolator(PVI)plays an increasingly important role in precision manufacturing.In this paper,aiming to detect the performance of the pressure regulator in the PVI system,a PVI testing system with a pressure regulator is designed and developed.Firstly,the structure of the pneumatic spring is presented and analyzed,and the nonlinear stiffness is obtained based on the ideal gas model and material mechanics.Then,according to the working principle and continuity equations of ideal airflow,a dynamic model of the PVI system with a pressure regulator is established.Through the simulation analysis,the vibration isolation performance is improved with the efficient and precise pressure regulator.The average values of both the vibration velocity and transmission rate decrease when the vibration is set to 4,10,20 and 40 Hz,respectively.The experiments demonstrate the reliability and effectiveness of the pressure regulator.This achievement will become an important basis for future research concerning precision manufacturing.

Modeling and Simulation of an Invasive Mild Hypothermic Blood Cooling System

Nowadays,mild hypothermia is widely used in the fields of post-cardiac arrest resuscitation,stroke,cerebral hemorrhage,large-scale cerebral infarction,and craniocerebral injury.In this paper,a locally mixed sub-low temperature device is designed,and the cold and hot water mixing experiment is used to simulate the human blood transfer process.To set a foundation for the optimization of the heat transfer system,the static characteristics are analyzed by building the mathematic model and setting up the experimental station.In addition,the affection of several key structure parameters is researched.Through experimental and simulation studies,it can be concluded that,firstly,the mathematical model proved to be effective.Secondly,the results of simulation experiments show that 14.52℃ refrigeration can reduce the original temperature of 33.42℃ to 32.02℃,and the temperature of refrigerated blood rises to 18.64℃,and the average error is about 0.3℃.Thirdly,as the thermal conductivity of the vascular sheath increases,the efficiency of the heat exchange system also increases significantly.Finally,as the input cold blood flow rate increases,the mass increases and the temperature of the mixed blood temperature decreases.It provides a research basis for subsequent research on local fixed-point sub-low temperature control technology.

Interlayer environment engineered MXene: Pre-intercalated Zn^(2+)ions as intercalants renders the modulated Li storage

The intercalation of foreign species into MXene, as an approach of tuning the interlayer environment, is employed to improve electrochemical ion storage behaviors. Herein, to understand the effect of confined ions by the MXene layers on the performance of electrochemical energy storage, Zn^(2+) ions were employed to intercalate into MXene via an electrochemical technique. Zn^(2+) ions induced a shrink of the adjacent MXene layers. Meaningfully, a higher capacity of lithium ion storage was obtained after Zn^(2+) preintercalation. In order to explore the roles of the intercalated Zn^(2+) ions, the structural evolution, and the electronic migration among Zn, Ti and the surface termination were investigated to trace the origination of the higher Li^(+) storage capacity. The pre-intercalated Zn^(2+) ions lost electrons, meanwhile Ti of MXene obtained electrons. Moreover, a low-F surface functional groups was achieved. Contrary to the first shrink, after 200 cycles, a larger interlayer distance was monitored, this can accelerate the ion transport and offer a larger expansile space for lithium storage. This may offer a guidance to understand the roles of the confined ion by two-dimensional(2D) layered materials.

Information Theoretic Weighted Fuzzy Clustering Ensemble

In order to improve performance and robustness of clustering,it is proposed to generate and aggregate a number of primary clusters via clustering ensemble technique.Fuzzy clustering ensemble approaches attempt to improve the performance of fuzzy clustering tasks.However,in these approaches,cluster(or clustering)reliability has not paid much attention to.Ignoring cluster(or clustering)reliability makes these approaches weak in dealing with low-quality base clustering methods.In this paper,we have utilized cluster unreliability estimation and local weighting strategy to propose a new fuzzy clustering ensemble method which has introduced Reliability Based weighted co-association matrix Fuzzy C-Means(RBFCM),Reliability Based Graph Partitioning(RBGP)and Reliability Based Hyper Clustering(RBHC)as three new fuzzy clustering consensus functions.Our fuzzy clustering ensemble approach works based on fuzzy cluster unreliability estimation.Cluster unreliability is estimated according to an entropic criterion using the cluster labels in the entire ensemble.To do so,the new metric is dened to estimate the fuzzy cluster unreliability;then,the reliability value of any cluster is determined using a Reliability Driven Cluster Indicator(RDCI).The time complexities of RBHC and RBGP are linearly proportional with thnumber of data objects.Performance and robustness of the proposed method are experimentally evaluated for some benchmark datasets.The experimental results demonstrate efciency and suitability of the proposed method.

Correlation Between ASI and Yield and Drought Resistance of Maize Inbred

Maize is the main grain crop and important forage crop in China. The correlation between ASI and yield of maize inbred lines and whether ASI and the ASI extension time(Dct) of maize inbred lines could be used as a direct indicator of drought resistance of maize inbred lines were explored. The results showed that the goodness of fit of ASI and Dct with DI were 0.478 and 0.829, respectively, and the ASI had an extremely significant negative correlation with yield per plant. ASI and Dct could be used as a parameter to evaluate drought resistance of maize inbred lines, but Dct was more effective than ASI in determining drought resistance index(DI) of maize inbred lines.

A method for satellite time series anomaly detection based on fast-DTW and improved-KNN

In satellite anomaly detection,there are some problems such as unbalanced sample distribution,fewer fault samples,and unobvious anomaly characteristics.These problems cause the extisted anomaly detection methods are difficult to train accurate classification model,and the accuracy of anomaly detection is hard to improve.At the same time,the monitoring data of satellite has high dimension and is difficult to extract effective features.Based on the DTW over-sampling method,this paper realizes the over-sampling of fault samples in satellite time series,and constructs a distributed and balanced time series data set.The Fast-DTW method is applied to calculate the distance between different time series,which can improve the speed of similarity calculation.KNN(K-Nearest Neighbor)method is applied for classification and the best classification result is obtained by search the optimal hyper-parameters k.The results show that the proposed method has high anomaly detection accuracy and consumes short calculation time.

杂Diels-Alder环加成反应级联RAFT聚合

Diels-Alder(DA)反应温度可逆、无需催化剂、高效快速且无有害产物,成为构建可自愈和可回收的动态共价弹性体网络的有利选择。然而传统的DA反应(比如呋喃和马来酰亚胺)存在反应时间长、反应温度高和模块化差等问题。近年来研究发现,具有高反应性的二烯可与特异性的RAFT试剂发生HDA反应(含杂原子硫的Diels-Alder环加成反应),实现HDA反应与RAFT聚合的高效级联,降低DA反应温度及反应时间的同时,又将RAFT聚合对于聚合物分子量以及分子量分布的精确可控性结合到DA反应中,在制备高分子量嵌段及接枝聚合物、表面修饰等方面有广泛的应用潜力。本文综述了近十五年来HDA-RAFT级联反应的研究与应用,探讨了目前仍存在的一些问题和解决方法,并对未来这一领域的发展进行了展望。

Multi-ion intercalated Ti_(3)C_(2)T_(x)MXene and the mutual modulation within interlayer

Intercalation of ions between the adjacent MXene layers can change the interlayer environment and influence the electrochemical ion storage capacity.In order to understand the effect of multi-ions confined by the MXene layers on the performance of electrochemical energy storage,Co^(2+),Mn^(2+)and Ni^(2+)intercalated into Ti_(3)C_(2)T_(x)MXene which already pre-intercalated Al3+are obtained by spontaneous static action.Based on the monitor of(002)crystal orientation,intercalated multi-ions can regulate and control the interlayer environment of MXenes via stress,which induces lattice shrinkage occurring in the c axis.Limited by ion storage mechanism-performance,the multi-ion occupies the interspace of MXene and affects the electrochemical performance.This work would offer guidance to understand the relationship among the multi-ion and MXene by two-dimensional(2D)layered materials.

Recent advances in the development of perovskite@metal-organicframeworks composites

Metal-organic frameworks(MOFs)have received considerable attention because of their advantages of adjustable structure,high porosity,and rich active centers.Meanwhile,perovskite has attracted research interest due to its unique highemission quantum yield and excellent optoelectronic properties.However,the instability of perovskites under certain conditions hinders their more comprehensive development.A novel strategy encapsulates perovskite in the pores of MOFs to protect it from external interference and increase the active centers,thus improving the performance of perovskite@MOF composites.In this review,the latest research progress in the synthesis strategy,function,and application of perovskite@MOF composites is systematically summarized.Additionally,the challenges of further developing perovskite@MOF composites are discussed.Hopefully,this review provides creative inspiration to advance future studies on perovskite@MOF composites in this emerging field.

Application of dynamic recrystallization model in AZ12 magnesium alloy rolling process

To deeply understand the dynamic recrystallization behavior of as-cast AZ12 magnesium alloy in deformation process,the uniaxial hot compression experiments were implemented through systematic isothermal compression experiments.The true strain of thermal compression experiments was set to 50%with temperatures of 200,250,300,350,400℃and the strain rates of 0.001,0.01,0.1,1 s^(-1).The Dynamic Recrystallization(DRX)kinetic model of AZ12 magnesium alloy was established and the accuracy of this model was verified.The model is used to predict the volume fraction of the sheet obtained by rolling through different rolling passes under the condition of consistent total reduction(50%).And the predicted results are in good agreement with the experimental results.

Spatial distribution of charcoal in topsoil and its potential determinants on the Tibetan Plateau

As an important proxy for investigating past fire activities,charcoal is often used to explore the characteristics of fire distribution and its relationships with vegetation,climate,and human activities.Research into the spatial distribution and environmental determinants for charcoal,however,is still limited.In this study,we identified and counted charcoal from topsoil samples covering the Tibetan Plateau using the pollen methodology,and investigated its relationships with vegetation net primary production(NPP),elevation,climate(precipitation,mean temperature of the coldest month and warmest month)and human population by boosted regression trees(BRT).Results reveal that the concentration of microscopic charcoal,macroscopic charcoal,and total charcoal all increase from south-west to north-east,which is consistent with the trend that the population density on the Tibetan Plateau is high in the east and low in the west,suggesting that an increase in human activity is likely to promote the occurrence of fire.The BRT modeling reveals that NPP,elevation,and mean temperature of the coldest month are important factors for total charcoal concentration on the Tibetan Plateau,and the frequency and intensity of fires further increase with increasing vegetation biomass,decreasing elevation,and decreasing mean temperature of the coldest month.The spatial variation characteristics of charcoal from topsoil on the Tibetan Plateau not only reflect well the spatial fire situation in the region,but also have a good indicative significance for vegetation,climate,and human activities.

Bilineage embryo-like structure from EPS cells can produce live mice with tetraploid trophectoderm

Self-organized blastoids from extended pluripotent stem(EPs)cells possess enormous potential for investigating postimplantation embryo development and related diseases.However,the limited ability of postimplantation development of Eps-blastoids hinders its further application.In this study,single-cell transcriptomic analysis indicated that the“trophectoderm(TE)-like structure”of EPSblastoids was primarily composed of primitive endoderm(PrE)-related cells instead of TE-related cells.We further identified PrE-like cells in EPS cell culture that contribute to the blastoid formation with TE-like structure.Inhibition of PrE cell differentiation by inhibiting MEK signaling or knockout of Gata6 in EPS cells markedly suppressed EPS-blastoid formation.Furthermore,we demonstrated that blastocyst-like structures reconstituted by combining the EPs-derived bilineage embryo-like structure(BLEs)with either tetraploid embryos or tetraploid TE cells could implant normally and develop into live fetuses.In summary,our study reveals that TE improvement is critical for constructing a functional embryo using stem cells in vitro.