Search

A particle-free surface coupled model has been developed using the Eulerian–Eulerian approach for revealing the gas–steel–slag multiphase flow in the vacuum chamber of a 210-ton RH degasser. The particle submodel preferred to predict the gas–steel and gas–slag interpenetrating phenomena, while the free surface submodel focused on tracking the steel–slag interface flow. The mesh sensitivity analysis has been investigated, and the coupled model was validated by the measured values. Using this coupled model, some previously unknown problems about multiphase flow in the vacuum chamber were revealed, such as the effect of the free surface fluctuation, variation of the liquid level, and slag flow behavior.

Mixture cure models have been developed as an effective tool to analyze failure time data with a cure fraction. Used in conjunction with the logistic regression model, this model allows covariate-adjusted inference of an exposure effect on the cured probability and on the hazard of failure for the uncured subjects. However, the covariate-adjusted inference for the overall exposure effect is not directly provided. In this paper, we describe a Cox proportional hazards cure model to analyze interval-censored survival data in the presence of a cured fraction and then apply a post-estimation approach by using model-predicted estimates difference to assess the overall exposure effect on the restricted mean survival time scale. For baseline hazard/survival function estimation, simple parametric models as fractional polynomials or restricted cubic splines are utilized to approximate the baseline logarithm cumulative hazard function, or alternatively, the full likelihood is specified through a piecewise linear approximation for the cumulative baseline hazard function. Simulation studies were conducted to demonstrate the unbiasedness of both estimation methods for the overall exposure effect estimates over various baseline hazard distribution shapes. The methods are applied to analyze the interval-censored relapse time data from a smoking cessation study.

We summarize extensions to the analysis of restricted mean survival time (RMST) in the context of time-to-event outcomes. The RMST estimate and its inference are based on the classical Kaplan-Meier curves. When covariate effects are considered, an adjusted RMST (ARMST) estimate can be derived analogously based on adjusted Kaplan-Meier curves. The adjusted Kaplan-Meier Estimator (AKME) was developed to reduce confounding by the method of inverse probability of treatment weighting. We will show how the ARMST method combines the concepts of the RMST and AKME to make inferences. Two regression based methods to adjust for potential covariate effect on the RMST estimates will be compared with the ARMST approach. Simulation studies are performed to compare the different methods with and without covariate adjustments. In addition, we will summarize the extension of RMST and ARMST to the setting with competing risks. The restricted mean time lost (RMTL) and adjusted RMTL (ARMTL) are estimates of interest from cumulative incidence curves. A phase 3 oncology clinical trial example is provided to demonstrate the applications of these methods.

Path planning for wheeled mobile robots on partially known uneven terrain is an open challenge since robot motions can be strongly influenced by terrain with incomplete environmental information such as locally detected obstacles and impassable terrain areas. This paper proposes a hierarchical path planning approach for a wheeled robot to move in a partially known uneven terrain. We first model the partially known uneven terrain environment respecting the terrain features, including the slope, step, and unevenness. Second, facilitated by the terrain model, we use A⋆ algorithm to plan a global path for the robot based on the partially known map. Finally, the Q-learning method is employed for local path planning to avoid locally detected obstacles in close range as well as impassable terrain areas when the robot tracks the global path. The simulation and experimental results show that the designed path planning approach provides satisfying paths that avoid locally detected obstacles and impassable areas in a partially known uneven terrain compared with the classical A⋆ algorithm and the artificial potential field method.

The application of artificial intelligence has realized the transformation of people's production and lifestyle, and also promoted the progress of physical education and comprehensive health quality. The application of artificial intelligence in the current physical education movement is increasing. By utilizing its advanced method of virtual simulation technology, the purpose of this paper is to realize the interventional research on the physical education movement and comprehensive health quality in the environment of artificial intelligence. This paper proposes to use the virtual simulation technology and Kinect algorithm in artificial intelligence to design the virtual sports simulation teaching mode. The functional module design part where the Kinect algorithm helps the teaching of virtual sports simulation experiments, which is helpful to analyze and solve the objective system imbalance and ecological imbalance in online physical education teaching. By using the principles and rules of the Mean Shift image segmentation algorithm for reference, the investigation and research on the comprehensive health quality of students are carried out, so as to realize the ecologicalization of the virtual sports school. In the investigation and research on the comprehensive quality of students, the results show that the overall quality of these students who has reached the level of qualified or unqualified is accounting for about 30% of the total number. It is worth noting that in terms of scientific and cultural quality, only 43.34% of all students have excellent grades. It can be seen that the important training goal of current school research is how to use reasonable and effective methods and strategies to improve students' scientific and cultural level, and improve students' other comprehensive scores at the same time.

The present paper deals with the investigation of dynamic responses of a rotating pre-deformed blade in four cases of resonance, including two subharmonic resonances and two combination resonances. The dimensionless gas excitation amplitude is assumed to share the same order with the dimensionless vibration displacement. Four cases of resonance are confirmed by examining the secular terms. The theoretical analysis framework is established for each resonance case based on the method of multiple scales. The original dynamic system is integrated numerically by the Runge–Kutta method. The frequency components and phases obtained from fast Fourier transform of the numerical response are used to verify the theoretical results. For the purpose of contrast, modulation equations are also integrated numerically. In all four resonance cases, the theoretical results agree well with the numerical simulation. Parameter studies are conducted to clarify the effects of system parameters on the perturbation curves. Various results are obtained for the rotating blade. A quasi-saturation phenomenon occurs in both combination resonances of summed type and difference type, and the corresponding limit value of the second-mode response can be reduced by decreasing the external detuning parameter. The quasi-saturation phenomenon of rotating blade only appears with high gas pressure. The subharmonic resonance of second mode and the combination resonance of summed type are hard to excite in practice compared with the other two cases.

To build models based on conventional logistic regression (LR) and machine learning (ML) algorithms combining clinical, morphological, and hemodynamic information to predict individual rupture status of unruptured intracranial aneurysms (UIAs), afterwards tested in internal and external validation datasets.Patients with intracranial aneurysms diagnosed by computed tomography angiography and confirmed by invasive cerebral angiograph or clipping surgery were included. The prediction models were developed based on clinical, aneurysm morphological, and hemodynamic parameters by conventional LR and ML methods.The training, internal validation, and external validation cohorts were composed of 807 patients, 200 patients, and 108 patients, respectively. The area under curves (AUCs) of conventional LR models 1 (clinical), 2 (clinical and aneurysm morphological), and 3 (clinical, aneurysm morphological and hemodynamic characteristics) were 0.608, 0.765, and 0.886, respectively (all p 0.05). The AUCs of ML models using random forest (RF), multilayer perceptron (MLP), and support vector machine (SVM) were 0.871, 0.851, and 0.863, respectively. There were no difference among AUCs of conventional LR, RF, and SVM (all p 0.05/6), while the AUC of MLP was lower than that of conventional LR (p = 0.0055).Hemodynamic parameters play an important role in the prediction performance of the models. ML methods cannot outperform conventional LR in prediction models for rupture status of UIAs integrating clinical, aneurysm morphological, and hemodynamic parameters.• The addition of hemodynamic parameters can improve prediction performance for rupture status of unruptured intracranial aneurysms. • Machine learning algorithms cannot outperform conventional logistic regression in prediction models for rupture status integrating clinical, aneurysm morphological, and hemodynamic parameters. • Models integrating clinical, aneurysm morphological, and hemodynamic parameters may help choose the optimal management.

In this paper, the gauge points setting is introduced in the SPH simulation to analyze the debris cloud structure generated by the hypervelocity impact of disk projectile on thin plate. Compared with the experiments, more detailed information of the debris cloud structure can be classified from the numerical simulation. However, due to the solitary dispersion and overlap display of the particles in the SPH simulation, accurate comparison between numerical and experimental results is difficult to be performed. To track the velocity and spatial distribution of the particles in the debris cloud induced from disk and plate, gauge points are locally set in the single-layer profile in the SPH model. By analyzing the gauge points’ spatial coordinate and velocity, the location and velocity of characteristic points in the debris cloud are determined. The boundary of debris cloud is achieved, as well as the fragments distribution outside the main structure of debris cloud.

A particle-free surface coupled (PFC) model was developed using the Eulerian–Eulerian approach to predict fluid flow behavior in a gas-stirred ladle. The relative parameters of the model have been optimized, and the model was validated against measured values. The present model can simultaneously predict the bubble trajectories, free surface fluctuations, and the formation of slag open-eye in a wide range of gas flow rates.

This research is focused on the effects of nonlinear terms on the dynamical behavior of graphene reinforced laminated composite plates. Firstly, the governing equations of the graphene reinforced composite thin plate subjected to transverse excitations are derived by using the Hamilton's principle and the von Karman deformation theory. Then numerical method is applied to investigate the nonlinear behaviors of graphene reinforced composite plates. Bifurcation diagram, waveform and phase portrait are demonstrated to analyze the nonlinear dynamics of the graphene reinforced laminated composite plates. Furthermore, the effects of nonlinear terms on the dynamical behavior are discussed in detail, where both the stronger and weaker nonlinear characteristics of lower modes of the plate are presented. Moreover, some interesting phenomena are obtained in numerical simulation.

Importance Moyamoya disease (MMD), a progressive vasculopathy leading to narrowing and ultimate occlusion of the intracranial internal carotid arteries, is a cause of childhood stroke. The cause of MMD is poorly understood, but genetic factors play a role. Several familial forms of MMD have been identified, but the cause of most cases remains elusive, especially among non-East Asian individuals. Objective To assess whether ultrarare de novo and rare, damaging transmitted variants with large effect sizes are associated with MMD risk. Design, setting, and participants A genetic association study was conducted using whole-exome sequencing case-parent MMD trios in a small discovery cohort collected over 3.5 years (2016-2019); data were analyzed in 2020. Medical records from US hospitals spanning a range of 1 month to 1.5 years were reviewed for phenotyping. Exomes from a larger validation cohort were analyzed to identify additional rare, large-effect variants in the top candidate gene. Participants included patients with MMD and, when available, their parents. All participants who met criteria and were presented with the option to join the study agreed to do so; none were excluded. Twenty-four probands (22 trios and 2 singletons) composed the discovery cohort, and 84 probands (29 trios and 55 singletons) composed the validation cohort. Main outcomes and measures Gene variants were identified and filtered using stringent criteria. Enrichment and case-control tests assessed gene-level variant burden. In silico modeling estimated the probability of variant association with protein structure. Integrative genomics assessed expression patterns of MMD risk genes derived from single-cell RNA sequencing data of human and mouse brain tissue. Results Of the 24 patients in the discovery cohort, 14 (58.3%) were men and 18 (75.0%) were of European ancestry. Three of 24 discovery cohort probands contained 2 do novo (1-tailed Poisson P = 1.1 × 10-6) and 1 rare, transmitted damaging variant (12.5% of cases) in DIAPH1 (mammalian diaphanous-1), a key regulator of actin remodeling in vascular cells and platelets. Four additional ultrarare damaging heterozygous DIAPH1 variants (3 unphased) were identified in 3 other patients in an 84-proband validation cohort (73.8% female, 77.4% European). All 6 patients were non-East Asian. Compound heterozygous variants were identified in ena/vasodilator-stimulated phosphoproteinlike protein EVL, a mammalian diaphanous-1 interactor that regulates actin polymerization. DIAPH1 and EVL mutant probands had severe, bilateral MMD associated with transfusion-dependent thrombocytopenia. DIAPH1 and other MMD risk genes are enriched in mural cells of midgestational human brain. The DIAPH1 coexpression network converges in vascular cell actin cytoskeleton regulatory pathways. Conclusions and relevance These findings provide the largest collection to date of non-East Asian individuals with sporadic MMD harboring pathogenic variants in the same gene. The results suggest that DIAPH1 is a novel MMD risk gene and impaired vascular cell actin remodeling in MMD pathogenesis, with diagnostic and therapeutic ramifications.

As a novel kind of cold roller steel, Cr8 alloy steel has the characteristics of high hardness, high wear resistance and good toughness, which can effectively prolong the service life of the roller that is an important part of the steel rolling mill. How to accurately define the constitutive model parameters of metal materials is the major problem, because it seriously affects the accuracy of numerical simulation results of the roller hot forming process. In the study of Cr8 alloy steel’s thermal deformation behavior of the present paper, the high temperature compression test was done on a Gleebel-1500D thermal/force simulation testing machine. A novel method of parameter identification was proposed based on inverse optimization. The Hansel–Spittel constitutive model was established by using the inverse optimization method. To carry out the verification on the accuracy of the established constitutive model, the predicted flow-stress of constitutive model was made a contrast to the experimental flow-stress, and the standard statistical parameters were also applied to further evaluation. The results showed a relatively high prediction accuracy of the Hansel–Spittel constitutive model based on the inverse optimization algorithm. Meanwhile, to obtain optimal parameters of Cr8 alloy steel in the thermal processing, 3D thermal processing maps concerning strain-rate, strain and temperature were built based on the dynamic material model. According to the 3D processing map, the most adequate thermal processing parameters of Cr8 alloy steel were obtianed as follows: strain 0.2–0.4, strain-rate 0.05–0.005 s−1, temperature 1100–1150 °C.

Background To minimize the rate of in vitro fertilization (IVF)- associated multiple-embryo gestation, significant efforts have been made. Previous studies related to machine learning in IVF mainly focused on selecting the top-quality embryos to improve outcomes, however, in patients with sub-optimal prognosis or with medium- or inferior-quality embryos, the selection between SET and DET could be perplexing. Methods This was an application study including 9211 patients with 10,076 embryos treated during 2016 to 2018, in Tongji Hospital, Wuhan, China. A hierarchical model was established using the machine learning system XGBoost, to learn embryo implantation potential and the impact of double embryos transfer (DET) simultaneously. The performance of the model was evaluated with the AUC of the ROC curve. Multiple regression analyses were also conducted on the 19 selected features to demonstrate the differences between feature importance for prediction and statistical relationship with outcomes. Results For a single embryo transfer (SET) pregnancy, the following variables remained significant: age, attempts at IVF, estradiol level on hCG day, and endometrial thickness. For DET pregnancy, age, attempts at IVF, endometrial thickness, and the newly added P1 + P2 remained significant. For DET twin risk, age, attempts at IVF, 2PN/ MII, and P1 × P2 remained significant. The algorithm was repeated 30 times, and averaged AUC of 0.7945, 0.8385, and 0.7229 were achieved for SET pregnancy, DET pregnancy, and DET twin risk, respectively. The trend of predictive and observed rates both in pregnancy and twin risk was basically identical. XGBoost outperformed the other two algorithms: logistic regression and classification and regression tree. Conclusion Artificial intelligence based on determinant-weighting analysis could offer an individualized embryo selection strategy for any given patient, and predict clinical pregnancy rate and twin risk, therefore optimizing clinical outcomes.

Objective To discuss the study design and data analysis for three-phase interrupted time series (ITS) studies to evaluate the impact of health policy, systems, or environmental interventions. Simulation methods are used to conduct power and sample size calculation for these studies. Methods We consider the design and analysis of three-phase ITS studies using a study funded by National Institutes of Health as an exemplar. The design and analysis of both one-arm and two-arm three-phase ITS studies are introduced. Results A simulation-based approach, with ready-to-use computer programs, was developed to determine the power for two types of three-phase ITS studies. Simulations were conducted to estimate the power of segmented autoregressive (AR) error models when autocorrelation ranged from -0.9 to 0.9 with various effect sizes. The power increased as the sample size or the effect size increased. The power to detect the same effect sizes varied largely, depending on testing level change, trend changes, or both. Conclusion This article provides a convenient tool for investigators to generate sample sizes to ensure sufficient statistical power when three-phase ITS study design is implemented.

Muzhailing Highway Extra-long Tunnel in Lanzhou, Gansu Province, China, belongs to the soft rock tunnel in the extremely high geostress area. During the construction process, large deformation of the soft rock occurred frequently. Taking the no. 2 inclined shaft of Muzhailing tunnel as the research object, an NPR (negative Poisson’s ratio) constant resistance and large deformation anchor cable support system based on high prestress force, constant resistance, and releasing surrounding rock pressure was proposed. The characteristics of the surrounding rock under the steel arch support and NPR anchor cable support were compared and analyzed by using 3DEC software. A series of field tests were conducted in the no. 2 inclined shaft, and the rock strength, displacement of the surrounding rock, deep displacement of the surrounding rock, internal force of steel arch, and axial force of anchor cable were measured to study the application effect of the NPR anchor cable support system in tunnel engineering. Moreover, the 3DEC numerical simulation results were compared with the field test results. The research results show that the application of NPR constant resistance and large deformation anchor cable support system in tunnel engineering has achieved good results, and it plays a significant role in controlling the large deformation of the tunnel surrounding rock.

Rotational malalignment between the femoral and tibial components in total knee arthroplasty (TKA) can affect clinical outcomes, but there is no consensus on how to best determine tibia tray orientation. The posterolateral corner-locked (PLCL) technique may be a new method. This study aims to assess the applicability of this technique in a Chinese population. Forty normal Chinese volunteers were recruited and underwent computed tomography (CT) of the lower limbs. Knee model reconstructions and simulated standard tibial osteotomy were conducted digitally. The transepicondylar axis (TEA), the Akagi line, and the line connecting the medial third of the tibial tubercle with the midpoint of the posterior cruciate ligament (PCL) were projected to the tibial cross-section and marked. The PLCL technique was applied using either symmetrical or asymmetrical tibial tray templates, and the anteroposterior (AP) axis of the tibial tray was marked. The angles between the TEA and these lines were calculated, and the statistical differences were analyzed. The angle between the TEA and the Akagi line and between the TEA and the line connecting the medial third of the tibial tubercle with the midpoint of the PCL were 96.90 ± 5.57 and 107.31 ± 5.95 degrees, respectively. The angles between the TEA and the AP axis of the symmetrical and the asymmetrical design tibial trays were 94.01 ± 4.21 and 96.65 ± 4.70 degrees, respectively. Except for the Akagi line and AP axis of the asymmetrical tibial tray, statistical differences were found between all lines (p

An earth-air heat exchanger (EAHE) system is an effective energy-saving technique for heating and cooling a space by using Earth’s subsurface heat. The EAHE system has been widely applied in residential and public buildings, but feasibility research is still needed because of the regional restrictions and influencing factors that may be involved. In this paper, a 1:20 scale model is created to study the influence parameters on the thermal performance of the EAHE due to the limitations of field test. By dimensionless analysis of the momentum and heat conduction equations, the key similarity numbers Re and Fo and the similar scales are proposed. The experimental data were compared with other studies and achieved good agreement. The original soil temperatures at different depths in Xi'an are calculated by MATLAB software. On this basis, a preliminary design scheme for the EAHE system of a memorial is proposed and analyzed by numerical simulation.

A numerical model based on the one-dimensional unsteady flow theory was established to simulate the large pulsation of the reciprocating compressor. The simulation model was consisting of the single straight pipeline system, the straight pipe +volume chamber pipeline system and the straight pipe + reducer pipeline system. The models were solved by using the two steps method and the method of characteristics. To validate the simulation model, the experiment to measure the pressure pulsation was done in different exhaust pressures, different rotate speeds and different pipeline systems. The waveforms of the simulation results and the experimental results were in good agreement and all of the relative errors of the pressure unevenness were below 10%. The simulation results were consistent with the experiment results. The model established in this paper was accurate.

A computational fluid dynamics numerical simulation of a spatial wind field under a complex terrain was conducted, and a prediction model of wind characteristics was proposed based on the correlation of simulation results. A large eddy simulation turbulent model was employed to simulate the behavior of the turbulent flow of the spatial wind field by using OpenFOAM 4.0. Then, the prediction model of the spatial wind field was established according to the “triangle edge angle relationship” for the mean wind velocity and spatial correlation analysis for the fluctuating wind velocity. The predicted model was further validated by simulation velocity time histories, reaching good agreement with the simulated results, which indicated that the predicted model had a higher precision. Finally, the proposed model was utilized to predict natural wind field characteristics, and they were compared with field measurement data acquired from ultrasonic anemometers. A comparison of the fluctuating wind velocity time histories, mean wind speeds, and fluctuating wind velocity spectra indicated that the predicted model was practical.

Shenmu Gas Field is a multilayer tight sandstone gas reservoir with low vertical well production. The task of gas field productivity construction is heavy. It is an effective way to increase the production of a single well by excavating local superior areas and implementing horizontal well development. Therefore, it is necessary to evaluate the adaptability and establish the reservoir limits of horizontal well in Shenmu Gas Field. Systematically study the superposition mode and development scale of reservoir sand bodies, and use the reserve concentration to divide the multi-layer gas reservoirs into three types, and they are single-layer, double-layer and multi-layer, respectively. The numerical simulation method is used to compare the development effects of horizontal wells and vertical wells, to determine the reserves concentration limits and reserves physical property limits of horizontal well development. The selection criteria for geological targets suitable for horizontal well is established. The research shows that ① A large-scale composite effective reservoir is formed in the local area of the Taiyuan Formation and Shan2 Formation in Shenmu Gas Field, with a length of 1600–3200 m and a width of 800–2000 m, and it has the geological conditions for horizontal well development; ② the reserve concentration in the main development zone of the horizontal well should be over 75%, and it should have a continuous effective thickness of 5.0 m, The permeability ratio between the primary and the secondary layer should be between 0.8 and 3.9; ③ the Shenmu Gas Field is generally not suitable for large-scale horizontal well overall development, but is suitable for centralized development in local single-layer advantageous areas. The research result can provide technical support for the horizontal wells of similar gas reservoirs at home and abroad, and are of great significance for the efficient development of gas fields.

Gob-side entry retaining is a common method in underground coal mining. Conventional gob-side entry retaining (CGER) always causes stress concentration and large deformation around roadways under the condition of thick and hard sandstone roofs. Thus, an innovative method of no pillar gob-side entry retaining (NPGER) in longwall mining is proposed in this paper. First, a physical model was established to explore the mechanism of the new method. The modeling results indicate that the progressive caving of the strata in the middle of the stope is consistent with CGER. The major difference between NPGER and CGER is that CGER collapsed with a structure of a long arm beam, but NPGER collapsed with a structure of a short arm beam near the roadway. In the end, a new roadway with a gangue rib was formed when the immediate roof and main roof slipped along the pre-cutting plane. Subsequently, the numerical simulation software Universal Distinct Element Code (UDEC) was adopted to establish the numerical model of the 8501 working face in Tangshangou coal mine. The NPGER process is simulated. The evolution of the roof structure and stress characteristics were clearly demonstrated. The results showed that the roof structure noticeably changed from a long beam to a short beam after roof fracturing. The retained roadway was under low stress conditions, and the stress was transferred to the deep rock. In the end, the NPGER method was applied in the field, and the results showed that the retained roadway could meet the requirements of the next working face, which may provide guidance for longwall mining with thick and hard roofs.

Reducing the transient grounding impedance of the grounding device is an important measure for lightning protection. However, due to the inductive reactance of the grounding electrode, the transient grounding impedance is usually very high. This paper analyzes the parameters that affect the inductive reactance of the grounding electrode, and studies the influence of the electrode radius on the inductive reactance. Considering the cost and the effective current leakage length of the grounding electrode, a method of reducing the transient grounding impedance is proposed. That is using a piece of grounding electrode with large radius near the current injection point of the grounding device, and then gradually reducing the radius along electrode. The effectiveness of the method is verified by numerical simulation, and the optimal arrangement is analyzed. It can be seen that the method can greatly increase the effective current leakage length of the grounding electrode and reduce the transient grounding impedance of the grounding device.

The interaction of a plane shock wave in air with concave profiles has been used in the past to understand the nature of shock wave focusing. The current study examines the complex two-dimensional flow field resulting from the interaction of a plane shock wave entering a symmetrical cavity with a curved end wall. The development of reflection patterns of the incident shock wave at the profile wall and the process of gas dynamic focus are of particular interest. In this study, numerical and experimental studies are performed to understand the ignition behavior in a stoichiometric methane-oxygen-argon mixture due to shock wave reflection from a variety of shapes, including planar, 60° and 90° conical and hemispherical reflectors. The numerical simulation reveals the complex two-dimensional flow field when the shock wave collides head-on with different reflectors and the propagation behavior of the reflected waves in the process of focusing. The instantaneous maximum temperature and pressure as a function of shock wave intensity in four reflectors are given and analyzed. The experimental results show that two ignition modes, namely, weak ignition and strong ignition, occur in those reflectors when the incident shock wave velocity (Vi) is greater than a critical value, and the separatrix between the weak and strong ignition for each reflector is demonstrated to be highly dependent on Vi. The critical values of Vi for the 60° conical, 90° conical and hemispherical reflectors are 740, 775 and 780 m/s, respectively. The ignition delay time (tign) of the combustible mixture under shock wave focusing for various reflectors is provided. The results show that in the weak ignition mode, tign is shorter in the hemispherical reflector than in the others, and therefore, its Pign (the maximum pressure after ignition) is higher. However, the result is completely opposite in the strong ignition mode, which is mainly because the ignition temperature of hot spots in the hemispherical reflectors is much lower than those in the conical reflectors. This study provides new simulation and experimental evidence of the ignition behavior in various reflectors, supporting the effect of enhancing shock wave focusing on the ignition performance.

Productivity prediction is one of the important issues for the economic and effective development of gas hydrate deposit. Therefore, this paper proposes a method to establish productivity prediction for the Class III gas hydrate developed by depressurization and horizontal wells. The method are divided into four steps, including numerical simulation, production performance analysis, revision of formulas and quantitative calculation of key factors. The prediction method is based on inflow performance relationship (IPR) of gas hydrate. Considering the shape of IPR curves, Fetkovich’s formula and Vogel’s formula are selected as the basic formulas respectively for the increasing part and decreasing part of gas hydrate production. To revise Fetkovich’s formula, the deposit pressure is replaced by comprehensive deposit pressure, which is determined by energy coefficient B0. Through the analysis and evaluation of influencing factors, B0 is described by a equation related to gas hydrate saturation. To revise the Vogel’s formula, the lowest production pressure is set as the four phase point pressure, leading to the change of production pressure difference and maximum gas production rate. The key coefficient C is calculated by a equation related to gas hydrate saturation and well spacing. Compared with simulation results, the results of proposed formulas show good accuracy in the prediction of production rate of gas hydrate. The results of test point predicted by revised Fetkovich’s formula almost coincide with simulation results. The average error between results of revised Vogel’s formula and simulation results is 4.24%. So the proposed method can be applied to predict the productivity of gas hydrate for its good accuracy, fast speed and simple calculation.

Coal contains a large number of fractures, whose characteristics are difficult to describe in detail, while their spatial distribution patterns may follow some macroscopic statistical laws. In this paper, several fracture geometric parameters (FGPs) were used to describe a fracture, and the coal seam was represented by a two-dimensional stochastic fracture network (SFN) which was generated and processed through a series of methods in MATLAB. Then, the processed SFN image was able to be imported into COMSOL Multiphysics and converted to a computational domain through the image function. In this way, the influences of different FGPs and their distribution patterns on the permeability of the coal seam were studied, and a finite element model to investigate gas flow properties in the coal seam was carried out. The results show that the permeability of the coal seam increased with the rising of fracture density, length, aperture, and with the decrease of the angle between the fracture orientation and the gas pressure gradient. It has also been found that large-sized fractures have a more significant contribution to coal reservoir permeability. Additionally, a numerical simulation of CBM extraction was carried out to show the potential of the proposed approach in the application of tackling practical engineering problems. According to the results, not only the connectivity of fractures but also variations of gas pressure and velocity can be displayed explicitly, which is consistent well with the actual situation.

International audience; The injection and atomization of gasoline fuels are critical to the performance of gasoline direct injection engines. Due to the complex nature of the primary breakup of the liquid jet in the near field, high-level details are often difficult to measure in experiments. In the present study, detailed numerical simulations are performed to investigate the primary breakup of a gasoline surrogate jet under non-evaporative "Spray G" operating conditions. The Spray G injector and operating conditions, developed by the Engine Combustion Network (ECN), represent the early phase of spray-guided gasoline injection. To focus the computational resources on resolving the primary breakup, simplifications have been made on the injector geometry. The effect of the internal flow on the primary breakup is modeled by specifying a nonzero injection angle at the inlet. The nonzero injection angle results in an increase of the jet penetration speed and also a deflection of the liquid jet. A parametric study on the injection angle is performed, and the numerical results are compared to the experimental data to identify the injection angle that best represents the Spray G conditions. The nonzero injection angle introduces an azimuthally non-uniform velocity in the liquid jet, which in turn influences the instability development on the jet surfaces and also the deformation and breakup of the jet head. The asymmetric primary breakup dynamics eventually lead to an azimuthal variation of droplet size distributions. The number of droplets varies significantly with the azimuthal angle, but interestingly, the probability density functions (PDF) of droplet size for different azimuthal angles collapse to a self-similar profile. The self-similar PDF is fitted with both lognormal and gamma distribution functions. Analysis has also been conducted to estimate the percentage and statistics of the tiny droplets that are under resolved in the present simulation. The PDF of the azimuthal angle is also presented, which is also shown to exhibit a self-similar form that varies little over time. The PDF of the azimuthal angle is well represented by a hyperbolic tangent function. Finally, a model is developed to predict the droplet number as a function of droplet diameter, azimuthal angle where a droplet is located, and time.

Latent membrane protein 1 (LMP1) is a gene product of the Epstein-Barr virus (EBV), a widely spread virus present in 90-95% of the world's population. EBV can lead to several malignancies, in which LMP1 was shown to play a key role. LMP1 is active only in the oligomeric form and its fifth transmembrane domain (TMD-5) is critical for the oligomerization, with D150 identified as a key residue for LMP1 activation. Here we propose an NMR-based approach to treat the complex oligomerization equilibria with slow conformational exchange. Using this method we investigate the TMD-5 in DPC micelles. We show that the pKa of D150 equals 7.4. Uncharged form of TMD-5 associates into dimers and trimers, deprotonation of D150 induces the high-order oligomerization of the protein and enhances dramatically its trimerization. Pentamidine interacts mainly with the charged TMD-5, destroying the oligomers and stabilizing the monomer and trimer. Using computer simulations we investigate the structural basis of TMD-5/pentamidine interaction. Our data suggest that D150 is likely charged in the full-length LMP1 under native conditions.

As high mine-cooling costs have become a restriction for deep mining, a new cooling method has been proposed. In the area of filling mining, the CPB (cemented paste backfill) was given the cooling function by mixing it with phase change material (PCM). In deep mines, the PCM (e.g., ice particles) absorb heat and change phases to cool the surrounding environment. A deep-mine-cooling mode based on the new CPB and upward sublevel filling method was designed, and the characteristics of the phase change were analyzed by numerical simulation. From the simulation results of the cooling period, this cooling method was effective during the whole stopes mining period. The CLS (cold load and storage) CPB mass concentration and the PCM initial proportion are the important factors controlling the cooling effect. It is concluded that the phase change duration decreased with the increasing mass concentration, while it increased with the increasing initial proportion of ice to water. Note that the thickness of CLS-functional CPB should be as small as possible to ensure the cold release rate. This study provides a theoretical foundation of heat transfer for the design and implementation of deep-mine cooling by applying CLS-functional CPB.

The allowed injection pressure algorithm has been used with overburden pressure. Casing damage is still serious because of the difference in water injection and injection, the influence of formation dip, fault and mudstone immersion. After the casing damage happened at the second member of Nenjiang Formation of the injecting well, the allowed pressure is the reduction pressure from the drill hole depth to the second member of Nenjiang Formation. Whether the pressure reduction is reasonable or not requires in-depth study. The geological structure of the test block is complex. After several wells and layers are developed, it is a casing damage-prone area. As the research area, the reasonable water injection pressure was determined. Based on the numerical simulation calculation, the calculation method of the injection pressure limit of the injection well was determined with the influence of the dip angle, fault and mudstone immersion. Through the statistical analysis of the actual situation of production, theoretical research was carried out to understand the influence of the change of water injection and injection pressure on the casing damage. The calculation method of the limit pressure after the immersion of the oil shale in the second member of Nenjiang Formation was determined. The result show the new calculation method of the allowable injection pressure in the polymer flooding.

The deformation characteristics of the rock mass in the intersection between the Muzhailing highway tunnel and the inclined shaft is a complicated three-dimensional problem. Under the influence of high geostress, large deformation hazards may occur in the surrounding rock. Taking this as the research background, this paper analyzes the deformation mechanism of surrounding rock before and after prestressed anchor cable support through numerical simulation. Then, through theoretical analysis, a new tunnel support method using high prestressed constant resistance and large deformation anchor cable was proposed. The field monitoring results show that the constant resistance and large deformation anchor cable support can well control the deformation of surrounding rock, and the maximum deformation is within 300 mm. At the same time, the constant resistance anchor cable can always maintain a high prestress, which makes the stress of the surrounding rock uniform, and reduces the risk of damage to the steel arch due to local pressure. Moreover, the support method limits the expansion of the plastic zone and improves the overall stability of the surrounding rock.

The shock wave generated by a severe gas explosion accident can damage the main fan, and the toxic and harmful gases in the well cannot be discharged in time, leading to the expansion of disaster accidents. Therefore, it is meaningful to study impact loads of main fan blades in gas explosion. In this paper, a full-scale three-dimensional numerical simulation model has been established based on No. 2 Yangchangwan Coal Mine in China. The propagation of shock wave in shaft and air tunnel and the dynamic process of main fan blade subjected to shock load when gas explosion of different volume occurs in heading face have been simulated. The overpressure on the blade at different times, the overpressure distribution on the blade, and the relationship between the overpressure and the explosion intensity have been obtained. The results showed that the time when the explosion shock wave reached, each blade of the wind turbine was basically the same, and the time when each blade reached, the maximum overpressure was basically the same. With the increase of gas explosion volume, occurrence time of overpressure and maximum overpressure time on the fan blade were shortened, and the time interval between them was also shortened. There is a little difference in the overpressure of each blade. Fan blade directly above the hub was subject to the highest overpressure, and fan blade directly below the hub was subject to the lowest overpressure. The overpressure of the maximum overpressure blade was 5.44% to 6.77% higher than that of the minimum overpressure blade. The distribution of overpressure on each fan blade was uneven, and the overpressures on blade edges were the lowest. The overpressure on the fan blades showed a corrugated distribution along the radial direction. There was 12.06% to 15.40% difference between the maximum and minimum overpressure section on the fan blade.

In order to accurately grasp the characteristics and influencing factors of gas explosion in heading face, the mathematical model of gas explosion was determined. According to the actual size of a heading face of a coal mine, a 3D geometric model with a length of 100 m was established, and the effects of ignition energy and gas explosion equivalent on the gas explosion characteristics of the heading face were analyzed. The results show the following. (1) The mathematical models for numerical simulation of gas explosion can accurately simulate the gas explosion and its propagation process. The time-space step size has a great influence on the simulation results. The grid spacing for numerical simulation of mine gas explosion is determined to be 0.1 m and the time step length is determined to be 0.001 s. (2) The ignition energy has a limited effect on gas explosion characteristics. It only has a certain influence on the gas explosion process, but has little influence on the overpressure of shock wave. The larger the ignition energy is, the faster the explosion reaction speed is, and the maximum overpressure increases slightly. When the ignition energy increases to a certain value, the time of peak shock wave and the maximum overpressure both tend to be stable. The ignition energy has little effect on gas explosion characteristics when an explosion accident occurs underground with a large amount of gas accumulation. (3) The gas explosion equivalent has a great influence on the overpressure of gas explosion shock wave. The higher the explosion equivalent is, the greater the pressure is, and the peak value of the shock wave overpressure increases with the explosion equivalent as a power function. The research results have important guiding significance for the research and development of new technology for prevention and control of gas explosion.

In this paper, the numerical simulation of flow and leakage characteristics in two straight-through composite structures of oblique smooth labyrinth and honeycomb are carried out separately. Through which, the effect of honeycomb on leakage characteristics of labyrinth seal was studied. The results show that honeycomb has a great influence on the flow and leakage characteristics of labyrinth structure, which depends on the pressure ratio. The leakage characteristics of the labyrinth structure with honeycomb is better than the one with the smooth, which happens at high pressure ratio.

The in-depth understanding of the gas&ndash, solid flow and reaction behaviors, and their coupling characteristics during the chemical looping combustion (CLC) process has the guiding significance for the operation and optimization of a chemical looping combustor. A three-dimensional numerical model is applied to investigate the char-fueled CLC characteristics in a fuel reactor for efficient CO2 separation and capture. Simulations are carried out in a bubbling fluidized bed fuel reactor with a height of 2.0 m and a diameter of 0.22 m. The initial bed height is 1.1 m, and hence the height&ndash, diameter ratio of the slumped bed is five. The oxygen carrier is prepared with 14 wt% of CuO on 86 wt% of inert Al2O3. In the process of mathematical modeling, a Eulerian-Eulerian two-fluid model is adopted for both of the gas and solid phases. Gas turbulence is modeled on the basis of a k&ndash, &epsilon, turbulent model. The reaction kinetics parameters are addressed based upon previous experimental investigations from literature. During the simulation, the gas&ndash, solid flow patterns, composition distributions, and reaction characteristics are obtained. Moreover, the effects of solids inventory and fluidizing number on the reaction performance are elucidated in-depth. The results have shown that the reaction rates have close relationship with the flow patterns and the distributions of gas concentrations. Compared to the steam-char gasification over sand, the application of char-fueled CLC can effectively promote the conversion of gasification products. In addition, higher CO2 concentration at the outlet can be achieved by increasing the initial solids inventory or decreasing the fluidizing number. Some calculated values are verified by the previous data, indicating that the current three-dimensional models are reasonable to study the process mechanism of char-fueled CLC.

The issue of exponential synchronization of stochastic time-delayed memristor-based neural networks via distributed impulsive control is considered. Based on the characteristics of memristor, the corresponding drive and response stochastic memristor-based neural networks with distributed impulsive control input are established. Then the synchronization error system is gained by using the concept of synchronization and stochastic differential inclusion theory. Through the generalized impulsive delay differential inequality technique, the criteria to guarantee that the error system is exponentially mean square stable, namely that the drive and response systems achieve the exponential synchronization is acquired. At last, the numerical simulation verifies the effectiveness of the obtained theoretical results.

RNA-sequencing (RNA-seq) can generate millions of reads to provide clues for analyzing novel or abnormal alternative splicing (AS) events in cells. However, current methods for exploring AS events are still far from being satisfactory. Here, we present Comprehensive AS Hunting (CASH), which constructs comprehensive splice sites including known and novel AS sites in cells, and identifies differentially AS events between cells. We illuminated the versatility of CASH on RNA-seq data from a wide range of species and also on simulated in silico data, validated the advantages of CASH over other AS predictors and exhibited novel differentially AS events. Moreover, we used CASH to identify SRSF10-regulated AS events and investigated the evolution of SRSF10-regulated splicing. The results showed that SRSF10-regulated splicing events are highly evolvable from chickens, mice to humans. However, SRSF10-regulated splicing model was observed to be immutable, in which SRSF10 binding to cassette exon promotes exon inclusion while binding to downstream exon induces exon skipping. Altogether, CASH can significantly improve the detection of AS events and facilitate the study of AS regulation and function in cells; the SRSF10 data first demonstrate a flexibility of SRSF10 with their regulated splicing events but an immutability of SRSF10-regulated splicing model to produce opposite AS outcomes in vertebrates.

Three-dimension path planning of uninhabited combat aerial vehicle (UCAV) is a complicated optimal problem, which mainly focused on optimizing the flight route considering the different types of constrains under complex combating environment. A novel predator-prey pigeon-inspired optimization (PPPIO) is proposed to solve the UCAV three-dimension path planning problem in dynamic environment. Pigeon-inspired optimization (PIO) is a new bio-inspired optimization algorithm. In this algorithm, map and compass operator model and landmark operator model are used to search the best result of a function. The prey-predator concept is adopted to improve global best properties and enhance the convergence speed. The characteristics of the optimal path are presented in the form of a cost function. The comparative simulation results show that our proposed PPPIO algorithm is more efficient than the basic PIO, particle swarm optimization (PSO), and different evolution (DE) in solving UCAV three-dimensional path planning problems.

Ethylene (C 2 H 4 ) is a hydrocarbon fuel and widely used in chemical industry, however, ethylene is highly flammable and therefore presents a serious fire and explosion hazard. This work is initiated by addressing the hazard assessment of ethylene mixtures in different scale channels ( d = 5 mm, 10 mm and 20 mm) from the aspect of flame acceleration (FA) and deflagration-to-detonation transition (DDT) by using large eddy simulation (LES) method coupled with the artificially thickened flame (ATF) approach. The fifth order local characteristics based weighted essentially non-oscillatory (WENO) conservative finite difference scheme is employed to solve the governing equations. The numerical results confirm that flame velocity increase rapidly at the beginning stage in three channels, and the flame acceleration rate is slower in the subsequent stage, afterwards, the flame velocity has an abrupt increase, and the onset of detonation occurs. Due to the fact that wall effect is significant in the narrow channel (e.g.,5 mm), especially in the ignition stage of the flame, flames have different shapes in wider channels (10 mm and 20 mm) and narrow channel (5 mm). Both the pressure and temperature profiles confirm DDT run-up distances are 0.251 m, 0.203 m and 0.161 m in 20 mm, 10 mm and 5 mm channels, respectively, which indicates that a shorter run-up distance is required in narrower channel. The cellular detonation structures for the ethylene-air mixture in different channels indicate that multi-headed detonation structures can be found in 20 mm channel, as the channel width decreases to 10 mm, detonation has a single-headed spinning structure, as the width is further reduced to 5 mm, only large longitudinal oscillation of the pressure can be observed.

In order to ensure that the ultra-high voltage SF 6 circuit breaker has good breaking performance, the two nozzle structures respectively using one expansion angle and two expansion angles are designed. The flow field distribution during the breaker breaking process is obtained by numerical simulation, and the influence of the two kinds of expansion angle design structures on the breaking performance are compared and analyzed. The several different design structures of one expansion angle are also researched, and the recommended interrupter structure is verified by short-circuit breaking test. The results of simulation and test show that, compared with the two expansion angle structure, the interrupter using one expansion angle structure has better breaking performance, which is of great significance to the design of ultra-high voltage SF6 circuit breaker nozzle.

Frequency hopping communication and spread spectrum communication are the common means of anti-jamming, and these means have their own limitations. In the case of unpredictable jamming, reinforcement learning algorithm can provide good guidance for communication frequency. Firstly, this paper introduces the framework of communication system and the jamming modes commonly used in communication. Then the basic principle of Q-Learning algorithm is briefly introduced. Meanwhile, the meanings of the parameters in the algorithm are explained. In the part of numerical simulation, different jamming modes are used to test the performance of the algorithm. It proves that Q-Learning algorithm has good memory in sweeping, sinusoidal and Gaussian random jamming. It can provide better policy for communication frequency in real time.

Summary In this paper, we propose a new method for the inversion of large fixed-loop transient electromagnetic (TEM) data. The unstructured tetrahedral grids with flexibility to delineate the rugged topography are adopted to discretize the inverse model. The transmitting source is divided into short electric dipoles to simulate its practical shape, size and attitude. In the numerical simulation, we adopt the edge-based finite-element method (FEM) to discretize the governing equation in space, and the unconditionally stable second-order of Backward Euler (BE) scheme to discretize the time. The final forward modelling equation is solved for all time channels iteratively from an initial field. Since the full-channel forward modelling matrix is asymmetric, we use a backward recursive method to solve the adjoint forward problem to compute the Jacobian matrix. Considering the limited power of personal computational devices, we apply the limited-memory BFGS optimization method to accomplish our three-dimensional (3D) inversions. The inversion algorithm is tested firstly on a synthetic example. The inversion results show that the proposed inversion scheme can well invert TEM data with sharp topography. We further test our inversion code on a field survey data and obtained results that agree well with the geology and other geophysical information.

Sideflash is a kind of lightning striking on the side wall of tall buildings. This unexpected thunder stroke often leads to big property losses and endangers lives of people. However, the origin and development mechanism of this lightning stroke are still not clear. To simulate the sideflash, a 3-D numerical model of negative cloud-to-ground lightning is built which is composed of two parts: the thundercloud model and the stepped leader model. The thundercloud model is based on the 3-D dynamics and electrification coupled model. And the stepped leader model is based on the Dielectric Breakdown Model (DBM). The Poisson's Equation solved by the Successive Over-Relaxation method is employed to refresh the spatial electric potential field. Finally, some buildings with different heights are set on the ground. In the numerical simulation, some sideflashes are observed. Based on the comparison experiments, the origin of these phenomena is discussed.

This paper focuses on the nonlinear aeroelastic system identification method based on an artificial neural network (ANN) that uses time-delay and feedback elements. A typical two-dimensional wing section with control surface is modelled to illustrate the proposed identification algorithm. The response of the system, which applies a sine-chirp input signal on the control surface, is computed by time-marching-integration. A time-delay recurrent neural network (TDRNN) is employed and trained to predict the pitch angle of the system. The chirp and sine excitation signals are used to verify the identified system. Estimation results of the trained neural network are compared with numerical simulation values. Two types of structural nonlinearity are studied, cubic-spring and friction. The results indicate that the TDRNN can approach the nonlinear aeroelastic system exactly.

The primary resonances of a pre-deformed rotating beam model including the quadratic and cubic nonlinearities are investigated in the presence of the 3:1 internal resonance. The steady state responses of the beam are analyzed in two cases of the primary resonance with the method of multiple scales. The original dynamic equation is integrated numerically in two frequency sweep directions. The theoretical results are consistent with those obtained in the numerical simulation. The contributions of quadratic nonlinearities and cubic nonlinearities to the primary resonances behavior of the rotating beam are clarified. The frequency response curves are discussed by considering different model parameters such as the thermal gradient, the rotating speed, the damping coefficient and the gas pressure. The stability regions of coupled mode solutions are compared between the models with different nonlinearities in the case of the primary resonance of the second mode. A series of interesting findings are presented.

Due to the finite expanding order in an actual numerical simulation, the finite-difference time-domain method based on weighted Laguerre polynomials (Laguerre-FDTD) often has a large error near $t=0$ . In this communication, a new temporal basis is proposed to solve this problem, which is composed of three weighted Laguerre polynomials in adjacent orders. Based on this new temporal basis, the matrix equation for three-dimensional (3-D) FDTD method is derived in which the accumulation term is eliminated. By introducing a perturbation term and an iterative procedure to the matrix equation, an efficient 3-D FDTD method is obtained. To verify the accuracy and efficiency of the proposed FDTD method, two structures are calculated as examples. Numerical results show that the solution of the proposed method has no error at $t=0$ and the efficiency of the proposed method is superior to the conventional FDTD method, the alternating direction implicit (ADI) FDTD method, and the original efficient Laguerre-FDTD method using a single Laguerre polynomial at a comparable accuracy.

At present, the flame retardant system was adopted by Cnooc offshore oil engineering (Qingdao) co, LTD (COOEC) workshop ton class jacket platform, whose heat resistance temperature is no more than 80°C. The part of flame retardant area is burned by excessively high temperature and excessive on-site repair work at COOEC workshop due to reserved area of flame retardant is not accurate. In this paper the welding simulation software SYSWELD was used to analyze the temperature distribution of weld joint of typical assembly at workshop. The process parameters, material and model input parameters were adjusted by the field data feedbacks to obtain the optimized welding temperature distribution. The results show that the temperature distribution simulated by the SYSWELD was similar to the field actual measurements. The results of the temperature distribution of the weld joint give the accurate reserved area of flame retardant.

This paper focuses on the semiglobal stabilization for a class of nonlinear systems with nonstrict feedback form. Based on a generalized scaling technique, an adaptive control algorithm with dynamic high gain is developed for a class of nonstrict feedback nonlinear systems. It can be proved that, under some appropriate design parameters, all signals of the resulting closed-loop system are bounded semiglobally, and the system state will be convergent to origin exponentially. Finally, a numerical simulation is provided to confirm the effectiveness of the proposed method.

In this paper, the effect of pre-existing discrete fracture network (DFN) connectivity on hydraulic fracturing is numerically investigated in a rock mass subjected to in-situ stress. The simulation results show that DFN connectivity has a significant influence on the hydraulic fracture (HF) & DFN interaction and hydraulic fracturing effectiveness, which can be characterized by the total interaction area, stimulated DFN length, stimulated HF length, leak-off ratio, and stimulated total length. In addition, even at the same fluid injection rate, simulation models exhibit different responses that are strongly affected by the DFN connectivity. At a low injection rate, total interaction area decreases with increasing DFN connectivity; at a high injection rate, total interaction area increases with the increase of DFN connectivity. However, for any injection rate, the stimulated DFN length increases and stimulated HF length decreases with the increase of connectivity. Generally, this work shows that the DFN connectivity plays a crucial role in the interaction between hydraulic fractures, the pre-existing natural fractures and hydraulic fracturing effectiveness; in return, these three factors affect treating pressure, created microseismicity and corresponding stimulated volume. This work strongly relates to the production technology and the evaluation of hydraulic fracturing effectiveness. It is helpful for the optimization of hydraulic fracturing simulations in naturally fractured formations.

Grounding is the fundamental measure of lightning protection for power systems, industries, and buildings, and the lightning impulse behavior of grounding electrodes plays a very important role. How to correctly consider the lightning impulse characteristics of grounding electrodes is the fundament in lightning protection design. This paper summarized the progress in lightning impulse characteristics of grounding electrodes with soil ionization, including the images of soil ionization, the residual resistivity of ionized soil, the critical breakdown electrical field, the impulse breakdown delay characteristics of soil, and the impulse breakdown mechanism of soil. Finally, the numerical simulation methods for lightning impulse characteristics of grounding electrodes are classified, and some key performances of grounding electrodes under lightning impulse were presented.