To automatically detect oil tanks in polarimetric synthetic aperture radar（SAR） images, a coastal oil tank detection method is proposed based on recognition of T-shaped harbor. First of all, the T-shaped harbor is d...To automatically detect oil tanks in polarimetric synthetic aperture radar（SAR） images, a coastal oil tank detection method is proposed based on recognition of T-shaped harbor. First of all, the T-shaped harbor is detected to locate the region of interest（ROI） of oil tanks. Then all suspicious targets in the ROI are extracted by the segmentation of strong scattering targets and the classifier of H/α. The template targets are selected from the suspicious targets by the combination of a proposed circular degree parameter and the similarity parameter（SP） of the polarimetric coherency matrix. Finally, oil tanks are detected according to the statistics of the similarity parameter between each suspicious target and template targets in ROI. Polarimetric SAR data acquired by RADARSAT-2 over Berkeley and Singapore areas are used for testing. Experiment results show that most of the targets are correctly detected and the overall detection rate is close to 80%.The false rate is effectively reduced by the proposed algorithm compared with the method without T-shaped harbor recognition.展开更多
In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to ...In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to obtain the maximal positive definite solution of nonlinear matrix equation X+A^(*)X|^(-α)A=Q with the case 0<α≤1.Based on this method,a new iterative algorithm is developed,and its convergence proof is given.Finally,two numerical examples are provided to show the effectiveness of the proposed method.展开更多
In this paper,a novel method for investigating the particle-crushing behavior of breeding particles in a fusion blanket is proposed.The fractal theory and Weibull distribution are combined to establish a theoretical m...In this paper,a novel method for investigating the particle-crushing behavior of breeding particles in a fusion blanket is proposed.The fractal theory and Weibull distribution are combined to establish a theoretical model,and its validity was verified using a simple impact test.A crushable discrete element method(DEM)framework is built based on the previously established theoretical model.The tensile strength,which considers the fractal theory,size effect,and Weibull variation,was assigned to each generated particle.The assigned strength is then used for crush detection by comparing it with its maximum tensile stress.Mass conservation is ensured by inserting a series of sub-particles whose total mass was equal to the quality loss.Based on the crushable DEM framework,a numerical simulation of the crushing behavior of a pebble bed with hollow cylindrical geometry under a uniaxial compression test was performed.The results of this investigation showed that the particle withstands the external load by contact and sliding at the beginning of the compression process,and the results confirmed that crushing can be considered an important method of resisting the increasing external load.A relatively regular particle arrangement aids in resisting the load and reduces the occurrence of particle crushing.However,a limit exists to the promotion of resistance.When the strain increases beyond this limit,the distribution of the crushing position tends to be isotropic over the entire pebble bed.The theoretical model and crushable DEM framework provide a new method for exploring the pebble bed in a fusion reactor,considering particle crushing.展开更多
Effective partitioning is crucial for enabling parallel restoration of power systems after blackouts.This paper proposes a novel partitioning method based on deep reinforcement learning.First,the partitioning decision...Effective partitioning is crucial for enabling parallel restoration of power systems after blackouts.This paper proposes a novel partitioning method based on deep reinforcement learning.First,the partitioning decision process is formulated as a Markov decision process(MDP)model to maximize the modularity.Corresponding key partitioning constraints on parallel restoration are considered.Second,based on the partitioning objective and constraints,the reward function of the partitioning MDP model is set by adopting a relative deviation normalization scheme to reduce mutual interference between the reward and penalty in the reward function.The soft bonus scaling mechanism is introduced to mitigate overestimation caused by abrupt jumps in the reward.Then,the deep Q network method is applied to solve the partitioning MDP model and generate partitioning schemes.Two experience replay buffers are employed to speed up the training process of the method.Finally,case studies on the IEEE 39-bus test system demonstrate that the proposed method can generate a high-modularity partitioning result that meets all key partitioning constraints,thereby improving the parallelism and reliability of the restoration process.Moreover,simulation results demonstrate that an appropriate discount factor is crucial for ensuring both the convergence speed and the stability of the partitioning training.展开更多
The application of nitrogen fertilizers in agricultural fields can lead to the release of nitrogen-containing gases(NCGs),such as NO_(x),NH_(3) and N_(2)O,which can significantly impact regional atmospheric environmen...The application of nitrogen fertilizers in agricultural fields can lead to the release of nitrogen-containing gases(NCGs),such as NO_(x),NH_(3) and N_(2)O,which can significantly impact regional atmospheric environment and con-tribute to global climate change.However,there remain considerable research gaps in the accurate measurement of NCGs emissions from agricultural fields,hindering the development of effective emission reduction strategies.We improved an open-top dynamic chambers(OTDCs)system and evaluated the performance by comparing the measured and given fluxes of the NCGs.The results showed that the measured fluxes of NO,N_(2)O and NH_(3)were 1%,2%and 7%lower than the given fluxes,respectively.For the determination of NH_(3) concentration,we employed a stripping coil-ion chromatograph(SC-IC)analytical technique,which demonstrated an absorption efficiency for atmospheric NH_(3) exceeding 96.1%across sampling durations of 6 to 60 min.In the summer maize season,we utilized the OTDCs system to measure the exchange fluxes of NO,NH_(3),and N_(2)O from the soil in the North China Plain.Substantial emissions of NO,NH_(3) and N_(2)O were recorded following fertilization,with peaks of 107,309,1239 ng N/(m^(2)·s),respectively.Notably,significant NCGs emissions were observed following sus-tained heavy rainfall one month after fertilization,particularly with NH_(3) peak being 4.5 times higher than that observed immediately after fertilization.Our results demonstrate that the OTDCs system accurately reflects the emission characteristics of soil NCGs and meets the requirements for long-term and continuous flux observation.展开更多
Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The t...Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.展开更多
At present,there is currently a lack of unified standard methods for the determination of antimony content in groundwater in China.The precision and trueness of related detection technologies have not yet been systema...At present,there is currently a lack of unified standard methods for the determination of antimony content in groundwater in China.The precision and trueness of related detection technologies have not yet been systematically and quantitatively evaluated,which limits the effective implementation of environmental monitoring.In response to this key technical gap,this study aimed to establish a standardized method for determining antimony in groundwater using Hydride Generation–Atomic Fluorescence Spectrometry(HG-AFS).Ten laboratories participated in inter-laboratory collaborative tests,and the statistical analysis of the test data was carried out in strict accordance with the technical specifications of GB/T 6379.2—2004 and GB/T 6379.4—2006.The consistency and outliers of the data were tested by Mandel's h and k statistics,the Grubbs test and the Cochran test,and the outliers were removed to optimize the data,thereby significantly improving the reliability and accuracy.Based on the optimized data,parameters such as the repeatability limit(r),reproducibility limit(R),and method bias value(δ)were determined,and the trueness of the method was statistically evaluated.At the same time,precision-function relationships were established,and all results met the requirements.The results show that the lower the antimony content,the lower the repeatability limit(r)and reproducibility limit(R),indicating that the measurement error mainly originates from the detection limit of the method and instrument sensitivity.Therefore,improving the instrument sensitivity and reducing the detection limit are the keys to controlling the analytical error and improving precision.This study provides reliable data support and a solid technical foundation for the establishment and evaluation of standardized methods for the determination of antimony content in groundwater.展开更多
In order to study influences of geometric parameters on the T-shaped components local loading process, a new mathematical model considering the fillet radius and draft angle was established by using the slab method. T...In order to study influences of geometric parameters on the T-shaped components local loading process, a new mathematical model considering the fillet radius and draft angle was established by using the slab method. The results obtained by the mathematical model agree with the data form experiment and numerical simulation, and the results are closer to the experimental and simulation results. The influence of draft angle may be neglected under the forming conditions used. The influence of fillet radius is notable, especially in the case that the ratio of fillet radius to rib width is less than 0.75.展开更多
This study examines the design provisions of the Chinese GB 50011-2010 code for seismic design of buildings for the special boundary elements of T-shaped reinforced concrete walls and proposes an improved design metho...This study examines the design provisions of the Chinese GB 50011-2010 code for seismic design of buildings for the special boundary elements of T-shaped reinforced concrete walls and proposes an improved design method. Comparison of the design provisions of the GB 50011-2010 code and those of the American code ACI 318-14 indicates a possible deficiency in the T-shaped wall design provisions in GB 50011-2010. A case study of a typical T-shaped wall designed in accordance with GB 50011-2010 also indicates the insufficient extent of the boundary element at the non-flange end and overly conservative design of the flange end boundary element. Improved designs for special boundary elements ofT-shaped walls are developed using a displacement-based method. The proposed design formulas produce a longer boundary element at the non-flange end and a shorter boundary element at the flange end, relative to those of the GB 50011-2010 provisions. Extensive numerical analysis indicates that T-shaped walls designed using the proposed formulas develop inelastic drift of 0.01 for both cases of the flange in compression and in tension.展开更多
A self-aligned InP/GalnAs single heterojunction bipolar transistor（HBT） is investigated using a novel T-shaped emitter. A U-shaped emitter layout,selective wet etching,laterally etched undercut, and an air-bridge ar...A self-aligned InP/GalnAs single heterojunction bipolar transistor（HBT） is investigated using a novel T-shaped emitter. A U-shaped emitter layout,selective wet etching,laterally etched undercut, and an air-bridge are applied in this process. The device, which has a 2μm×12μm U-shaped emitter area,demonstrates a common-emitter DC current gain of 170,an offset voltage of 0.2V,a knee voltage of 0.5V, and an open-base breakdown voltage of over 2V. The HBT exhibits good microwave performance with a current gain cutoff frequency of 85GHz and a maximum oscillation frequency of 72GHz, These results indicate that these InP/InGaAs SHBTs are suitable for low-voltage,low-power,and high-frequency applications.展开更多
Spur dike is one of the river training structures. This work presented a numerical simulation of flow field and three-dimensional velocity around a T-shaped spur dike located in bend using SSIIM model. The main object...Spur dike is one of the river training structures. This work presented a numerical simulation of flow field and three-dimensional velocity around a T-shaped spur dike located in bend using SSIIM model. The main objective of this work is to investigate the three-dimensional velocities and streamlines at transverse and longitudinal sections and plan views around the T-shaped spur dike in different submergence ratios(0, 5%, 15%, 25% and 50%). It is concluded that by increasing the submergence ratio from 5% to 50%, the maximum of scour is reduced; the maximum of longitudinal velocity increases by 7.7% and occurs at the water surface in spur dike axis. Near the bed, the maximum of vertical velocity occurs at the end of spur wing. By analyzing the streamlines at transverse sections, the followings were deduced for different submergence ratios: different dimensions and different positions of vortices around the spur dike.展开更多
An analytical procedure is presented to evaluate the fluid sloshing characteristics in a two-dimensional(2D)rectangular container with a bottom-mounted T-shaped baffle.The fluid region is divided into several sub-doma...An analytical procedure is presented to evaluate the fluid sloshing characteristics in a two-dimensional(2D)rectangular container with a bottom-mounted T-shaped baffle.The fluid region is divided into several sub-domains with hypothetical interfaces and the velocities and pressures of the fluid on adjacent interfaces should be identical.The separation of variables in conjunction with the superposition principle is employed to formulate the velocity potential of each sub-domain.The Fourier series expansion is used to derive the eigenvalue equation by substituting the velocity potential solutions into the free surface conditions and the continuity conditions on adjacent interfaces.Under the horizontal base excitation,the total velocity potential of fluid is decomposed of the impulsive and perturbed velocity potentials.The orthogonality of the sloshing modes is demonstrated by implementing Gauss formula.The dynamic response equation is established by incorporating the total velocity potential solution into the surface wave equation.Excellent agreements are achieved between the present results and those from the reported literature and finite element code.Numerical results are exhibited to reveal the effect of the baffle parameters and excitation frequency on sloshing characteristics and responses of liquid.展开更多
The present work establishes an analytical model for computing the temperature distribution, fin efficiency and optimum design parameters of a constructal T-shaped porous fin operating in fully wet condition. For more...The present work establishes an analytical model for computing the temperature distribution, fin efficiency and optimum design parameters of a constructal T-shaped porous fin operating in fully wet condition. For more practical results, this study considers a cubic polynomial relationship between the humidity ratio of saturated air and the corresponding fin surface temperature. The temperature distribution has been determined by solving the highly non-linear governing equations using a semi-analytical transformation technique called Differential Transform Method. A comparison of the results with that of a numerical model shows that this transformation method is a very efficient and convenient tool for solution of non-linear problems. The effects of various geometric, thermo-physical and psychometric parameters on the temperature distribution, fin efficiency and optimum design condition have been investigated. Also, a comparison has been presented between solid and porous fins and the results point out that by selecting an appropriate value of porosity, the heat transfer rate can be increased than the corresponding solid fin.展开更多
A novel A1GaN/GaN high electron mobility transistor （HEMT） with a source-connected T-shaped field-plate （ST-FP HEMT） is proposed for the first time in this paper. The source-connected T-shaped field-plate （ST-FP...A novel A1GaN/GaN high electron mobility transistor （HEMT） with a source-connected T-shaped field-plate （ST-FP HEMT） is proposed for the first time in this paper. The source-connected T-shaped field-plate （ST-FP） is composed of a source-connected field-plate （S-FP） and a trench metal. The physical intrinsic mechanisms of the ST-FP to improve the breakdown voltage and the FP efficiency and to modulate the distributions of channel electric field and potential are studied in detail by means of two-dimensional numerical simulations with Silvaco-ATLAS. A comparison to the HEMT and the HEMT with an S-FP （S-FP HEMT） shows that the ST-FP HEMT could achieve a broader and more uniform channel electric field distribution with the help of a trench metal, which could increase the breakdown voltage and the FP efficiency remarkably. In addition, the relationship between the structure of the ST-FP, the channel electric field, the breakdown voltage as well as the FP efficiency in ST-FP HEMT is analyzed. These results could open up a new effective method to fabricate high voltage power devices for the power electronic applications.展开更多
In this study, nonlinear static and dynamic responses of a microcantilever with a T-shaped tip mass excited by electrostatic actuations are investigated. The electrostatic force is generated by applying an electric vo...In this study, nonlinear static and dynamic responses of a microcantilever with a T-shaped tip mass excited by electrostatic actuations are investigated. The electrostatic force is generated by applying an electric voltage between the horizontal part of T-shaped tip mass and an opposite electrode plate. The cantilever microbeam is modeled as an Euler-Bernoulli beam. The T-shaped tip mass is assumed to be a rigid body and the nonlinear effect of electrostatic force is considered. An equation of motion and its associated boundary conditions are derived by the aid of combining the Hamilton principle and Newton’s method. An exact solution is obtained for static deflection and mode shape of vibration around the static position. The differential equation of nonlinear vibration around the static position is discretized using the Galerkin method. The system mode shapes are used as its related comparison functions. The discretized equations are solved by the perturbation theory in the neighborhood of primary and subharmonic resonances. In addition, effects of mass inertia, mass moment of inertia as well as rotation of the T-shaped mass, which were ignored in previous works, are considered in the analysis. It is shown that by increasing the length of the horizontal part of the T-shaped mass, the amount of static deflection increases, natural frequency decreases and nonlinear shift of the resonance frequency increases. It is concluded that attaching an electrode plate with a T-shaped configuration to the end of the cantilever microbeam results in a configuration with larger pull-in voltage and smaller nonlinear shift of the resonance frequency compared to the configuration in which the electrode plate is directly attached to it.展开更多
A novel vertical InN/InGaN heterojunction tunnel FET with hetero T-shaped gate as well as polarization-doped source and drain region(InN-Hetero-TG-TFET)is proposed and investigated by Silvaco-Atlas simulations for the...A novel vertical InN/InGaN heterojunction tunnel FET with hetero T-shaped gate as well as polarization-doped source and drain region(InN-Hetero-TG-TFET)is proposed and investigated by Silvaco-Atlas simulations for the first time.Compared with the conventional physical doping TFET devices,the proposed device can realize the P-type source and N-type drain region by means of the polarization effect near the top InN/InGaN and bottom InGaN/InN heterojunctions respectively,which could provide an effective solution of random dopant fluctuation(RDF)and the related problems about the high thermal budget and expensive annealing techniques due to ion-implantation physical doping.Besides,due to the hetero T-shaped gate,the improvement of the on-state performance can be achieved in the proposed device.The simulations of the device proposed here in this work show ION of 4.45×10^(-5)A/μm,ION/IOFF ratio of 10^(13),and SS_(avg)of 7.5 mV/dec in InN-Hetero-TG-TFET,which are better than the counterparts of the device with a homo T-shaped gate(InN-Homo-TG-TFET)and our reported lateral polarization-induced InN-based TFET(PI-InN-TFET).These results can provide useful reference for further developing the TFETs without physical doping process in low power electronics applications.展开更多
The study of the dynamic disaster mechanism of coal and gas outburst two-phase flow is crucial for improving disaster reduction and rescue ability of coal mine outburst accidents.An outburst test in a T-shaped roadway...The study of the dynamic disaster mechanism of coal and gas outburst two-phase flow is crucial for improving disaster reduction and rescue ability of coal mine outburst accidents.An outburst test in a T-shaped roadway was conducted using a self-developed large-scale outburst dynamic disaster test system.We investigated the release characteristics of main energy sources in coal seam,and obtained the dynamic characteristics of outburst two-phase flow in a roadway.Additionally,we established a formation model for outburst impact flow and a model for its flow in a bifurcated structure.The results indicate that the outburst process exhibits pulse characteristics,and the rapid destruction process of coal seam and the blocking state of gas flow are the main causes of the pulse phenomenon.The outburst energy is released in stages,and the elastic potential energy is released in the vertical direction before the horizontal direction.In a straight roadway,the impact force oscillates along the roadway.With an increase in the solid–gas ratio,the two-phase flow impact force gradually increases,and the disaster range extends from the middle of the roadway to the coal seam.In the area near the coal seam,the disaster caused by the two-phase flow impact is characterized by intermittent recovery.In a bifurcated roadway,the effect of impact airflow on impact dynamic disaster is much higher than that of two-phase flow,and the impact force tends to weaken with increasing solid-gas ratio.The impact force is asymmetrically distributed;it is higher on the left of the bifurcated roadway.With an increase in the solid-gas ratio,the static pressure rapidly decreases,and the bifurcated structure accelerates the attenuation of static pressure.Moreover,secondary acceleration is observed when the shock wave moves along the T-shaped roadway,indicating that the bifurcated structure increases the shock wave velocity.展开更多
The transport of liquid plugs in microchannels is very important for many applications such as in medical treatments in airways and in extraction of oil from porous rocks.A plug of wetting and non-wetting liquids driv...The transport of liquid plugs in microchannels is very important for many applications such as in medical treatments in airways and in extraction of oil from porous rocks.A plug of wetting and non-wetting liquids driven by a constant pressure difference through a T-shaped microchannel is studied numerically with lattice Boltzmann(LB) method.A two-phase flow LB model based on field mediators is built.Three typical flow patterns(blocking,rupture and splitting flow) of plug flow are obtained with different driving pressures.It is found that it becomes difficult for a plug with short initial plug length to leave the microchannel;the flow pattern of plug transport varies with the contact angle,especially from wetting to nonwetting;with the increase of interfacial tension,the front interface of plug moves faster;the front and rear interfaces of the plug with small viscosity ratio move faster in the microchannel than those of the plug with large viscosity ratio.The study is helpful to provide theoretical data for the design and scale-up of liquid-liquid reactors and separators.展开更多
The study of pedestrian evacuation in channels with different structures is important among optimizing through efficiency,avoiding accidents and designing passageway.It is of significant reference to set up a specific...The study of pedestrian evacuation in channels with different structures is important among optimizing through efficiency,avoiding accidents and designing passageway.It is of significant reference to set up a specific model on account of the real traffic system and design an appropriate controller to apply on it.This paper establishes a macroscopic model for T-shaped channel with a number of controlled entrances basing on the law of mass conservation.Then,with the method of cascade,a kind of sliding mode controller is designed to achieve the control target of avoiding the blocking and maximizing the pedestrian flow of the whole model,the stability of the system is proved by the Lyapunov stability theory,and the boundary layer method is applied to restrain the chattering of the controller.Finally,simulation results show the efficiency of the sliding mode controller and the improvement brought by the boundary layer method.展开更多
The general solution of stresses is derived for a T-shaped junction of two thin plates with an adhesion crack. The plates are orthotropic. A shear force is applied on the crack surface. The analysis is based on the su...The general solution of stresses is derived for a T-shaped junction of two thin plates with an adhesion crack. The plates are orthotropic. A shear force is applied on the crack surface. The analysis is based on the supposition that the stresses in each plate can be approximated by a plane stress condition. The results obtained are verified by numerical calculation of FEM.展开更多
基金supported by the National Key R&D Program of China(2017YFB0502700)the National Natural Science Foundation of China(61490693+3 种基金61771043)the High-Resolution Earth Observation Systems(41-Y20A14-9001-15/1630-Y20A12-9004-15/1630-Y20A10-9001-15/16)
文摘To automatically detect oil tanks in polarimetric synthetic aperture radar（SAR） images, a coastal oil tank detection method is proposed based on recognition of T-shaped harbor. First of all, the T-shaped harbor is detected to locate the region of interest（ROI） of oil tanks. Then all suspicious targets in the ROI are extracted by the segmentation of strong scattering targets and the classifier of H/α. The template targets are selected from the suspicious targets by the combination of a proposed circular degree parameter and the similarity parameter（SP） of the polarimetric coherency matrix. Finally, oil tanks are detected according to the statistics of the similarity parameter between each suspicious target and template targets in ROI. Polarimetric SAR data acquired by RADARSAT-2 over Berkeley and Singapore areas are used for testing. Experiment results show that most of the targets are correctly detected and the overall detection rate is close to 80%.The false rate is effectively reduced by the proposed algorithm compared with the method without T-shaped harbor recognition.
基金Supported in part by Natural Science Foundation of Guangxi(2023GXNSFAA026246)in part by the Central Government's Guide to Local Science and Technology Development Fund(GuikeZY23055044)in part by the National Natural Science Foundation of China(62363003)。
文摘In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to obtain the maximal positive definite solution of nonlinear matrix equation X+A^(*)X|^(-α)A=Q with the case 0<α≤1.Based on this method,a new iterative algorithm is developed,and its convergence proof is given.Finally,two numerical examples are provided to show the effectiveness of the proposed method.
基金supported by Anhui Provincial Natural Science Foundation(2408085QA030)Natural Science Research Project of Anhui Educational Committee,China(2022AH050825)+3 种基金Medical Special Cultivation Project of Anhui University of Science and Technology(YZ2023H2C008)the Excellent Research and Innovation Team of Anhui Province,China(2022AH010052)the Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology,China(2021yjrc51)Collaborative Innovation Program of Hefei Science Center,CAS,China(2019HSC-CIP006).
文摘In this paper,a novel method for investigating the particle-crushing behavior of breeding particles in a fusion blanket is proposed.The fractal theory and Weibull distribution are combined to establish a theoretical model,and its validity was verified using a simple impact test.A crushable discrete element method(DEM)framework is built based on the previously established theoretical model.The tensile strength,which considers the fractal theory,size effect,and Weibull variation,was assigned to each generated particle.The assigned strength is then used for crush detection by comparing it with its maximum tensile stress.Mass conservation is ensured by inserting a series of sub-particles whose total mass was equal to the quality loss.Based on the crushable DEM framework,a numerical simulation of the crushing behavior of a pebble bed with hollow cylindrical geometry under a uniaxial compression test was performed.The results of this investigation showed that the particle withstands the external load by contact and sliding at the beginning of the compression process,and the results confirmed that crushing can be considered an important method of resisting the increasing external load.A relatively regular particle arrangement aids in resisting the load and reduces the occurrence of particle crushing.However,a limit exists to the promotion of resistance.When the strain increases beyond this limit,the distribution of the crushing position tends to be isotropic over the entire pebble bed.The theoretical model and crushable DEM framework provide a new method for exploring the pebble bed in a fusion reactor,considering particle crushing.
基金funded by the Beijing Engineering Research Center of Electric Rail Transportation.
文摘Effective partitioning is crucial for enabling parallel restoration of power systems after blackouts.This paper proposes a novel partitioning method based on deep reinforcement learning.First,the partitioning decision process is formulated as a Markov decision process(MDP)model to maximize the modularity.Corresponding key partitioning constraints on parallel restoration are considered.Second,based on the partitioning objective and constraints,the reward function of the partitioning MDP model is set by adopting a relative deviation normalization scheme to reduce mutual interference between the reward and penalty in the reward function.The soft bonus scaling mechanism is introduced to mitigate overestimation caused by abrupt jumps in the reward.Then,the deep Q network method is applied to solve the partitioning MDP model and generate partitioning schemes.Two experience replay buffers are employed to speed up the training process of the method.Finally,case studies on the IEEE 39-bus test system demonstrate that the proposed method can generate a high-modularity partitioning result that meets all key partitioning constraints,thereby improving the parallelism and reliability of the restoration process.Moreover,simulation results demonstrate that an appropriate discount factor is crucial for ensuring both the convergence speed and the stability of the partitioning training.
基金supported by the National Key Research and Develop-ment Program(No.2022YFC3701103)the National Natural Science Foundation of China(Nos.42130714 and 41931287).
文摘The application of nitrogen fertilizers in agricultural fields can lead to the release of nitrogen-containing gases(NCGs),such as NO_(x),NH_(3) and N_(2)O,which can significantly impact regional atmospheric environment and con-tribute to global climate change.However,there remain considerable research gaps in the accurate measurement of NCGs emissions from agricultural fields,hindering the development of effective emission reduction strategies.We improved an open-top dynamic chambers(OTDCs)system and evaluated the performance by comparing the measured and given fluxes of the NCGs.The results showed that the measured fluxes of NO,N_(2)O and NH_(3)were 1%,2%and 7%lower than the given fluxes,respectively.For the determination of NH_(3) concentration,we employed a stripping coil-ion chromatograph(SC-IC)analytical technique,which demonstrated an absorption efficiency for atmospheric NH_(3) exceeding 96.1%across sampling durations of 6 to 60 min.In the summer maize season,we utilized the OTDCs system to measure the exchange fluxes of NO,NH_(3),and N_(2)O from the soil in the North China Plain.Substantial emissions of NO,NH_(3) and N_(2)O were recorded following fertilization,with peaks of 107,309,1239 ng N/(m^(2)·s),respectively.Notably,significant NCGs emissions were observed following sus-tained heavy rainfall one month after fertilization,particularly with NH_(3) peak being 4.5 times higher than that observed immediately after fertilization.Our results demonstrate that the OTDCs system accurately reflects the emission characteristics of soil NCGs and meets the requirements for long-term and continuous flux observation.
基金Supported by the National Natural Science Foundation of China under Grant No.51975138the High-Tech Ship Scientific Research Project from the Ministry of Industry and Information Technology under Grant No.CJ05N20the National Defense Basic Research Project under Grant No.JCKY2023604C006.
文摘Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.
基金supported by the National Natural Science Foundation of China(Project No.42307555).
文摘At present,there is currently a lack of unified standard methods for the determination of antimony content in groundwater in China.The precision and trueness of related detection technologies have not yet been systematically and quantitatively evaluated,which limits the effective implementation of environmental monitoring.In response to this key technical gap,this study aimed to establish a standardized method for determining antimony in groundwater using Hydride Generation–Atomic Fluorescence Spectrometry(HG-AFS).Ten laboratories participated in inter-laboratory collaborative tests,and the statistical analysis of the test data was carried out in strict accordance with the technical specifications of GB/T 6379.2—2004 and GB/T 6379.4—2006.The consistency and outliers of the data were tested by Mandel's h and k statistics,the Grubbs test and the Cochran test,and the outliers were removed to optimize the data,thereby significantly improving the reliability and accuracy.Based on the optimized data,parameters such as the repeatability limit(r),reproducibility limit(R),and method bias value(δ)were determined,and the trueness of the method was statistically evaluated.At the same time,precision-function relationships were established,and all results met the requirements.The results show that the lower the antimony content,the lower the repeatability limit(r)and reproducibility limit(R),indicating that the measurement error mainly originates from the detection limit of the method and instrument sensitivity.Therefore,improving the instrument sensitivity and reducing the detection limit are the keys to controlling the analytical error and improving precision.This study provides reliable data support and a solid technical foundation for the establishment and evaluation of standardized methods for the determination of antimony content in groundwater.
基金Project (50935007) supported by the National Natural Science Foundation for Key Program of ChinaProject (2010CB731701) supported by the National Basic Research Program of ChinaProject (50905145) supported by the National Natural Science Foundation of China
文摘In order to study influences of geometric parameters on the T-shaped components local loading process, a new mathematical model considering the fillet radius and draft angle was established by using the slab method. The results obtained by the mathematical model agree with the data form experiment and numerical simulation, and the results are closer to the experimental and simulation results. The influence of draft angle may be neglected under the forming conditions used. The influence of fillet radius is notable, especially in the case that the ratio of fillet radius to rib width is less than 0.75.
基金International Science&Technology Cooperation Program of China under Grant No.2014DFA70950Tsinghua University Initiative Scientific Research Program under Grant No.2012THZ02-1National Natural Science Foundation of China under Grant No.91315301
文摘This study examines the design provisions of the Chinese GB 50011-2010 code for seismic design of buildings for the special boundary elements of T-shaped reinforced concrete walls and proposes an improved design method. Comparison of the design provisions of the GB 50011-2010 code and those of the American code ACI 318-14 indicates a possible deficiency in the T-shaped wall design provisions in GB 50011-2010. A case study of a typical T-shaped wall designed in accordance with GB 50011-2010 also indicates the insufficient extent of the boundary element at the non-flange end and overly conservative design of the flange end boundary element. Improved designs for special boundary elements ofT-shaped walls are developed using a displacement-based method. The proposed design formulas produce a longer boundary element at the non-flange end and a shorter boundary element at the flange end, relative to those of the GB 50011-2010 provisions. Extensive numerical analysis indicates that T-shaped walls designed using the proposed formulas develop inelastic drift of 0.01 for both cases of the flange in compression and in tension.
文摘A self-aligned InP/GalnAs single heterojunction bipolar transistor（HBT） is investigated using a novel T-shaped emitter. A U-shaped emitter layout,selective wet etching,laterally etched undercut, and an air-bridge are applied in this process. The device, which has a 2μm×12μm U-shaped emitter area,demonstrates a common-emitter DC current gain of 170,an offset voltage of 0.2V,a knee voltage of 0.5V, and an open-base breakdown voltage of over 2V. The HBT exhibits good microwave performance with a current gain cutoff frequency of 85GHz and a maximum oscillation frequency of 72GHz, These results indicate that these InP/InGaAs SHBTs are suitable for low-voltage,low-power,and high-frequency applications.
文摘Spur dike is one of the river training structures. This work presented a numerical simulation of flow field and three-dimensional velocity around a T-shaped spur dike located in bend using SSIIM model. The main objective of this work is to investigate the three-dimensional velocities and streamlines at transverse and longitudinal sections and plan views around the T-shaped spur dike in different submergence ratios(0, 5%, 15%, 25% and 50%). It is concluded that by increasing the submergence ratio from 5% to 50%, the maximum of scour is reduced; the maximum of longitudinal velocity increases by 7.7% and occurs at the water surface in spur dike axis. Near the bed, the maximum of vertical velocity occurs at the end of spur wing. By analyzing the streamlines at transverse sections, the followings were deduced for different submergence ratios: different dimensions and different positions of vortices around the spur dike.
基金The study was financially supported by the National Natural Science Foundation of China(Grant No.51978336)the Science and Technology Project of Water Resources Department of Jiangsu Province(Grant No.2021022).
文摘An analytical procedure is presented to evaluate the fluid sloshing characteristics in a two-dimensional(2D)rectangular container with a bottom-mounted T-shaped baffle.The fluid region is divided into several sub-domains with hypothetical interfaces and the velocities and pressures of the fluid on adjacent interfaces should be identical.The separation of variables in conjunction with the superposition principle is employed to formulate the velocity potential of each sub-domain.The Fourier series expansion is used to derive the eigenvalue equation by substituting the velocity potential solutions into the free surface conditions and the continuity conditions on adjacent interfaces.Under the horizontal base excitation,the total velocity potential of fluid is decomposed of the impulsive and perturbed velocity potentials.The orthogonality of the sloshing modes is demonstrated by implementing Gauss formula.The dynamic response equation is established by incorporating the total velocity potential solution into the surface wave equation.Excellent agreements are achieved between the present results and those from the reported literature and finite element code.Numerical results are exhibited to reveal the effect of the baffle parameters and excitation frequency on sloshing characteristics and responses of liquid.
文摘The present work establishes an analytical model for computing the temperature distribution, fin efficiency and optimum design parameters of a constructal T-shaped porous fin operating in fully wet condition. For more practical results, this study considers a cubic polynomial relationship between the humidity ratio of saturated air and the corresponding fin surface temperature. The temperature distribution has been determined by solving the highly non-linear governing equations using a semi-analytical transformation technique called Differential Transform Method. A comparison of the results with that of a numerical model shows that this transformation method is a very efficient and convenient tool for solution of non-linear problems. The effects of various geometric, thermo-physical and psychometric parameters on the temperature distribution, fin efficiency and optimum design condition have been investigated. Also, a comparison has been presented between solid and porous fins and the results point out that by selecting an appropriate value of porosity, the heat transfer rate can be increased than the corresponding solid fin.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61574112,61334002,61306017,61474091,and 61574110)the Natural Science Basic Research Plan in Shaanxi Province,China(Grant No.605119425012)
文摘A novel A1GaN/GaN high electron mobility transistor （HEMT） with a source-connected T-shaped field-plate （ST-FP HEMT） is proposed for the first time in this paper. The source-connected T-shaped field-plate （ST-FP） is composed of a source-connected field-plate （S-FP） and a trench metal. The physical intrinsic mechanisms of the ST-FP to improve the breakdown voltage and the FP efficiency and to modulate the distributions of channel electric field and potential are studied in detail by means of two-dimensional numerical simulations with Silvaco-ATLAS. A comparison to the HEMT and the HEMT with an S-FP （S-FP HEMT） shows that the ST-FP HEMT could achieve a broader and more uniform channel electric field distribution with the help of a trench metal, which could increase the breakdown voltage and the FP efficiency remarkably. In addition, the relationship between the structure of the ST-FP, the channel electric field, the breakdown voltage as well as the FP efficiency in ST-FP HEMT is analyzed. These results could open up a new effective method to fabricate high voltage power devices for the power electronic applications.
文摘In this study, nonlinear static and dynamic responses of a microcantilever with a T-shaped tip mass excited by electrostatic actuations are investigated. The electrostatic force is generated by applying an electric voltage between the horizontal part of T-shaped tip mass and an opposite electrode plate. The cantilever microbeam is modeled as an Euler-Bernoulli beam. The T-shaped tip mass is assumed to be a rigid body and the nonlinear effect of electrostatic force is considered. An equation of motion and its associated boundary conditions are derived by the aid of combining the Hamilton principle and Newton’s method. An exact solution is obtained for static deflection and mode shape of vibration around the static position. The differential equation of nonlinear vibration around the static position is discretized using the Galerkin method. The system mode shapes are used as its related comparison functions. The discretized equations are solved by the perturbation theory in the neighborhood of primary and subharmonic resonances. In addition, effects of mass inertia, mass moment of inertia as well as rotation of the T-shaped mass, which were ignored in previous works, are considered in the analysis. It is shown that by increasing the length of the horizontal part of the T-shaped mass, the amount of static deflection increases, natural frequency decreases and nonlinear shift of the resonance frequency increases. It is concluded that attaching an electrode plate with a T-shaped configuration to the end of the cantilever microbeam results in a configuration with larger pull-in voltage and smaller nonlinear shift of the resonance frequency compared to the configuration in which the electrode plate is directly attached to it.
基金the Key Research and Development Program of Shaanxi Province,China(Grant No.2020ZDLGY03-05)the National Natural Science Foundation of China(Grant No.61574112).
文摘A novel vertical InN/InGaN heterojunction tunnel FET with hetero T-shaped gate as well as polarization-doped source and drain region(InN-Hetero-TG-TFET)is proposed and investigated by Silvaco-Atlas simulations for the first time.Compared with the conventional physical doping TFET devices,the proposed device can realize the P-type source and N-type drain region by means of the polarization effect near the top InN/InGaN and bottom InGaN/InN heterojunctions respectively,which could provide an effective solution of random dopant fluctuation(RDF)and the related problems about the high thermal budget and expensive annealing techniques due to ion-implantation physical doping.Besides,due to the hetero T-shaped gate,the improvement of the on-state performance can be achieved in the proposed device.The simulations of the device proposed here in this work show ION of 4.45×10^(-5)A/μm,ION/IOFF ratio of 10^(13),and SS_(avg)of 7.5 mV/dec in InN-Hetero-TG-TFET,which are better than the counterparts of the device with a homo T-shaped gate(InN-Homo-TG-TFET)and our reported lateral polarization-induced InN-based TFET(PI-InN-TFET).These results can provide useful reference for further developing the TFETs without physical doping process in low power electronics applications.
基金This work was supported by the National Natural Science Foundation of China(Nos.51874055,52074047,and 52064016).
文摘The study of the dynamic disaster mechanism of coal and gas outburst two-phase flow is crucial for improving disaster reduction and rescue ability of coal mine outburst accidents.An outburst test in a T-shaped roadway was conducted using a self-developed large-scale outburst dynamic disaster test system.We investigated the release characteristics of main energy sources in coal seam,and obtained the dynamic characteristics of outburst two-phase flow in a roadway.Additionally,we established a formation model for outburst impact flow and a model for its flow in a bifurcated structure.The results indicate that the outburst process exhibits pulse characteristics,and the rapid destruction process of coal seam and the blocking state of gas flow are the main causes of the pulse phenomenon.The outburst energy is released in stages,and the elastic potential energy is released in the vertical direction before the horizontal direction.In a straight roadway,the impact force oscillates along the roadway.With an increase in the solid–gas ratio,the two-phase flow impact force gradually increases,and the disaster range extends from the middle of the roadway to the coal seam.In the area near the coal seam,the disaster caused by the two-phase flow impact is characterized by intermittent recovery.In a bifurcated roadway,the effect of impact airflow on impact dynamic disaster is much higher than that of two-phase flow,and the impact force tends to weaken with increasing solid-gas ratio.The impact force is asymmetrically distributed;it is higher on the left of the bifurcated roadway.With an increase in the solid-gas ratio,the static pressure rapidly decreases,and the bifurcated structure accelerates the attenuation of static pressure.Moreover,secondary acceleration is observed when the shock wave moves along the T-shaped roadway,indicating that the bifurcated structure increases the shock wave velocity.
基金Supported by the National Basic Research Program of China（2012CB224806）the National Natural Science Foundation of China（20990224,21276256）+1 种基金the National Natural Science Fund for Distinguished Young Scholars（21025627）the National High Technology Research and Development Program of China（2012AA03A606）
文摘The transport of liquid plugs in microchannels is very important for many applications such as in medical treatments in airways and in extraction of oil from porous rocks.A plug of wetting and non-wetting liquids driven by a constant pressure difference through a T-shaped microchannel is studied numerically with lattice Boltzmann(LB) method.A two-phase flow LB model based on field mediators is built.Three typical flow patterns(blocking,rupture and splitting flow) of plug flow are obtained with different driving pressures.It is found that it becomes difficult for a plug with short initial plug length to leave the microchannel;the flow pattern of plug transport varies with the contact angle,especially from wetting to nonwetting;with the increase of interfacial tension,the front interface of plug moves faster;the front and rear interfaces of the plug with small viscosity ratio move faster in the microchannel than those of the plug with large viscosity ratio.The study is helpful to provide theoretical data for the design and scale-up of liquid-liquid reactors and separators.
基金the National Natural Science Founda-tion of China(No.61374133)the Natural Science Foun-dation of Jiangsu Province(No.BK20191286)the Fundamental Research Funds for the Central Universi-ties(No.30920021139)。
文摘The study of pedestrian evacuation in channels with different structures is important among optimizing through efficiency,avoiding accidents and designing passageway.It is of significant reference to set up a specific model on account of the real traffic system and design an appropriate controller to apply on it.This paper establishes a macroscopic model for T-shaped channel with a number of controlled entrances basing on the law of mass conservation.Then,with the method of cascade,a kind of sliding mode controller is designed to achieve the control target of avoiding the blocking and maximizing the pedestrian flow of the whole model,the stability of the system is proved by the Lyapunov stability theory,and the boundary layer method is applied to restrain the chattering of the controller.Finally,simulation results show the efficiency of the sliding mode controller and the improvement brought by the boundary layer method.
文摘The general solution of stresses is derived for a T-shaped junction of two thin plates with an adhesion crack. The plates are orthotropic. A shear force is applied on the crack surface. The analysis is based on the supposition that the stresses in each plate can be approximated by a plane stress condition. The results obtained are verified by numerical calculation of FEM.
