The fatigue of concrete structures will gradually appear after being subjected to alternating loads for a long time,and the accidents caused by fatigue failure of bridge structures also appear from time to time.Aiming...The fatigue of concrete structures will gradually appear after being subjected to alternating loads for a long time,and the accidents caused by fatigue failure of bridge structures also appear from time to time.Aiming at the problem of degradation of long-span continuous rigid frame bridges due to fatigue and environmental effects,this paper suggests a method to analyze the fatigue degradation mechanism of this type of bridge,which combines long-term in-site monitoring data collected by the health monitoring system(HMS)and fatigue theory.In the paper,the authors mainly carry out the research work in the following aspects:First of all,a long-span continuous rigid frame bridge installed with HMS is used as an example,and a large amount of health monitoring data have been acquired,which can provide efficient information for fatigue in terms of equivalent stress range and cumulative number of stress cycles;next,for calculating the cumulative fatigue damage of the bridge structure,fatigue stress spectrum got by rain flow counting method,S-N curves and damage criteria are used for fatigue damage analysis.Moreover,it was considered a linear accumulation damage through the Palmgren-Miner rule for the counting of stress cycles.The health monitoring data are adopted to obtain fatigue stress data and the rain flow counting method is used to count the amplitude varying fatigue stress.The proposed fatigue reliability approach in the paper can estimate the fatigue damage degree and its evolution law of bridge structures well,and also can help bridge engineers do the assessment of future service duration.展开更多
Several methods for analysis of dissolved total phosphorus in seawater were reviewed. Discussions were focused on UV irradiation and persulphate oxidation methods which are the most popular dissolved organic phosphoru...Several methods for analysis of dissolved total phosphorus in seawater were reviewed. Discussions were focused on UV irradiation and persulphate oxidation methods which are the most popular dissolved organic phosphorus determination methods presently. The compounds used for the phosphorus recovery test were categorized into three groups according to their chemical structure. It was found that low power UV irradiation can decompose P-O-C or P-C bonds efficiently but may be inefficient for P-O-P bonds. Heating-bath in acid condition is useful for decomposing P-O-P bonds. Using the continuous flow analysis system (Auto-analyzer Ⅱ), UV digestion and heating-bath, series experiments were carried out based on the above analysis. Eleven model compounds were employed for the phosphorus recovery test and the factors influencing the decomposition efficiency of dissolved compounds containing phosphorus were clarified. Finally,the optimal design for determination of dissolved total phosphorus in seawater based on the routine continuous flow analysis system was presented. For the organic mono-phosphate, the recovery is more than 90% and a recovery of 33%～51% was obtained for inorganic or organic polyphosphates. Up to now, this is the highest decomposition efficiency for dissolved phosphorus based on the continuous flow analysis system.展开更多
The uncertainty of nuclide libraries in the analysis of the gamma spectra of low-and intermediate-level radioactive waste(LILW)using existing methods produces unstable results.To address this problem,a novel spectral ...The uncertainty of nuclide libraries in the analysis of the gamma spectra of low-and intermediate-level radioactive waste(LILW)using existing methods produces unstable results.To address this problem,a novel spectral analysis method is proposed in this study.In this method,overlapping peaks are located using a continuous wavelet transform.An improved quadratic convolution method is proposed to calculate the widths of the peaks and establish a fourth-order filter model to estimate the Compton edge baseline with the overlapping peaks.Combined with the adaptive sensitive nonlinear iterative peak,this method can effectively subtracts the background.Finally,a function describing the peak shape as a filter is used to deconvolve the energy spectrum to achieve accurate qualitative and quantitative analyses of the nuclide without the aid of a nuclide library.Gamma spectrum acquisition experiments for standard point sources of Cs-137 and Eu-152,a segmented gamma scanning experiment for a 200 L standard drum,and a Monte Carlo simulation experiment for triple overlapping peaks using the closest energy of three typical LILW nuclides(Sb-125,Sb-124,and Cs-134)are conducted.The results of the experiments indicate that(1)the novel method and gamma vision(GV)with an accurate nuclide library have the same spectral analysis capability,and the peak area calculation error is less than 4%;(2)compared with the GV,the analysis results of the novel method are more stable;(3)the novel method can be applied to the activity measurement of LILW,and the error of the activity reconstruction at the equivalent radius is 2.4%;and(4)The proposed novel method can quantitatively analyze all nuclides in LILW without a nuclide library.This novel method can improve the accuracy and precision of LILW measurements,provide key technical support for the reasonable disposal of LILW,and ensure the safety of humans and the environment.展开更多
With the structure of two air gaps and two rotors,the electromagnetic continuously variable transmission(EMCVT) is a novel power-split continuously variable transmission(CVT).There are two kinds of power flowing throu...With the structure of two air gaps and two rotors,the electromagnetic continuously variable transmission(EMCVT) is a novel power-split continuously variable transmission(CVT).There are two kinds of power flowing through the EMCVT,one is mechanical power and the other is electric power. In the mean time,there are three power ports in the EMCVT,one is the outer rotor named mechanical power port and the other two are the inner rotor and the stator named electric power ports.The mechanical power port is connected to the driving wheels through the fmal gear and the electric ports are connected to the batteries through the transducers.The two kinds of power are coupled on the outer rotor of the EMCVT.The EMCVT can be equipped on the conventional vehicle being regarded as the CVT and it also can be equipped on the hybrid electric vehicle(HEV) as the multi-energy sources assembly.The power flows of these two kinds of applications are analysed.The back electromotive force(EMF) equations are illatively studied and so the dynamic mathematic model is theorized.In order to certify the feasibility of the above theories,three simulations are carried out in allusion to the above two kinds of mentioned applications of the EMCVT and a five speed automatic transmission(AT) vehicle.The simulation results illustrate that the efficiency of the EMCVT vehicles is higher than that of the AT vehicle owed to the optimized operation area of the engine.Hence the fuel consumption of the EMCVT vehicles is knock-down.展开更多
Machine learning(ML)-based prediction models for mapping hazard(e.g.,landslide and debris flow)susceptibility have been widely developed in recent research.However,in some specific areas,ML models have limited applica...Machine learning(ML)-based prediction models for mapping hazard(e.g.,landslide and debris flow)susceptibility have been widely developed in recent research.However,in some specific areas,ML models have limited application because of the uncertainties in identifying negative samples.The Parlung Tsangpo Basin exemplifies a region prone to recurrent glacial debris flows(GDFs)and is characterized by a prominent landform featuring deep gullies.Considering the limitations of the ML model,we developed and compared two combined statistical models(FA-WE and FA-IC)based on factor analysis(FA),weight of evidence(WE),and the information content(IC)method.The final GDF susceptibility maps were generated by selecting 8 most important static factors and considering the influence of precipitation.The results show that the FA-IC model has the best performance.The areas with a very high susceptibility to GDFs are primarily located in the narrow valley section upstream,on both sides of the valley in the middle and downstream of the Parlung Tsangpo River,and in the narrow valley section of each tributary.These areas encompass 86 gullies and are characterized as"narrow and steep".展开更多
The present paper investigates the magnetohydrodynamic(MHD) flow of a viscous fluid towards a nonlinear porous shrinking sheet.The governing equations are simplified by similarity transformations.The reduced problem i...The present paper investigates the magnetohydrodynamic(MHD) flow of a viscous fluid towards a nonlinear porous shrinking sheet.The governing equations are simplified by similarity transformations.The reduced problem is then solved by the homotopy analysis method.The pertinent parameters appearing in the problem are discussed graphically and presented in tables.It is found that the shrinking solutions exist in the presence of MHD.It is also observed from the tables that the solutions for f(0) with different values of parameters are convergent.展开更多
In this paper,we first establish a new fractional magnetohydrodynamic(MHD)coupled flow and heat transfer model for a generalized second-grade fluid.This coupled model consists of a fractional momentum equation and a h...In this paper,we first establish a new fractional magnetohydrodynamic(MHD)coupled flow and heat transfer model for a generalized second-grade fluid.This coupled model consists of a fractional momentum equation and a heat conduction equation with a generalized form of Fourier law.The second-order fractional backward difference formula is applied to the temporal discretization and the Legendre spectral method is used for the spatial discretization.The fully discrete scheme is proved to be stable and convergent with an accuracy of O(τ^(2)+N-r),whereτis the time step-size and N is the polynomial degree.To reduce the memory requirements and computational cost,a fast method is developed,which is based on a globally uniform approximation of the trapezoidal rule for integrals on the real line.The strict convergence of the numerical scheme with this fast method is proved.We present the results of several numerical experiments to verify the effectiveness of the proposed method.Finally,we simulate the unsteady fractional MHD flow and heat transfer of the generalized second-grade fluid through a porous medium.The effects of the relevant parameters on the velocity and temperature are presented and analyzed in detail.展开更多
Computational simulations and high-temperature measurements of velocities near the surface of a mold were carried out by using the rod deflection method to study the effects of various operating parameters on the flow...Computational simulations and high-temperature measurements of velocities near the surface of a mold were carried out by using the rod deflection method to study the effects of various operating parameters on the flow field in slab continuous casting(CC)molds with narrow widths for the production of automobile exposed panels.Reasonable agreement between the calculated results and measured subsurface velocities of liquid steel was obtained under different operating parameters of the CC process.The simulation results reveal that the flow field in the horizontal plane located 50 mm from the meniscus can be used as the characteristic flow field to optimize the flow field of molten steel in the mold.Increases in casting speed can increase the subsurface velocity of molten steel and shift the position of the vortex core downward in the downward circulation zone.The flow field of liquid steel in a 1040 mm-wide slab CC mold can be improved by an Ar gas flow rate of 7 L·min^−1 and casting speed of 1.7 m·min^−1.Under the present experimental conditions,the double-roll flow pattern is generally stable at a submerged entry nozzle immersion depth of 170 mm.展开更多
In this paper, a new unsteady aerodynamic design method is presented based on the Navier-Stokes equations and a continuous adjoint approach. A basic framework of time-accurate unsteady airfoil optimization which adopt...In this paper, a new unsteady aerodynamic design method is presented based on the Navier-Stokes equations and a continuous adjoint approach. A basic framework of time-accurate unsteady airfoil optimization which adopts time-averaged aerodynamic coefficients as objective functions is presented. The time-accurate continuous adjoint equation and its boundary conditions are derived. The flow field and the adjoint equation are simulated numerically by the finite volume method(FVM). Feasibility and accuracy of the approach are perfectly validated by the design optimization results of the plunging NACA0012 airfoil.展开更多
In this paper, the asymmetric laminar flow in a porous channel with expanding or contracting walls is investigated. The governing equations are reduced to ordinary ones by using suitable similar transformations. Homot...In this paper, the asymmetric laminar flow in a porous channel with expanding or contracting walls is investigated. The governing equations are reduced to ordinary ones by using suitable similar transformations. Homotopy analysis method (HAM) is employed to obtain the expres- sions for velocity fields. Graphs are sketched for values of parameters and associated dynamic characteristics, especially the expansion ratio, are analyzed in detail.展开更多
Submerged horizontal plate can be considered as a new concept breakwater.In order to reveal the wave elimination mechanism of this type breakwater,boundary element method is utilized to investigate the velocity field ...Submerged horizontal plate can be considered as a new concept breakwater.In order to reveal the wave elimination mechanism of this type breakwater,boundary element method is utilized to investigate the velocity field around plate carefully.The flow field analysis shows that the interaction between incident wave and reverse flow caused by submerged plate will lead to the formation of wave elimination area around both sides of the plate.The velocity magnitude of flow field has been reduced and this is the main reason of wave elimination.展开更多
The effects of axisymmetric flow of a Powell-Eyring fluid over an impermeable radially stretching surface are presented. Characteristics of the heat transfer process are analyzed with a more realistic condition named ...The effects of axisymmetric flow of a Powell-Eyring fluid over an impermeable radially stretching surface are presented. Characteristics of the heat transfer process are analyzed with a more realistic condition named the convective boundary condition.Governing equations for the flow problem are derived by the boundary layer approximations. The modeled highly coupled partial differential system is converted into a system of ordinary differential equations with acceptable similarity transformations. The convergent series solutions for the resulting system are constructed and analyzed. Optimal values are obtained and presented in a numerical form using an optimal homotopy analysis method(OHAM). The rheological characteristics of different parameters of the velocity and temperature profiles are presented graphically. Tabular variations of the skin friction coefficient and the Nusselt number are also calculated. It is observed that the temperature distribution shows opposite behavior for Prandtl and Biot numbers. Furthermore,the rate of heating/cooling is higher for both the Prandtl and Biot numbers.展开更多
Based on linearized 2-D Navier-Stokes equation,a Laplace transform-boundary element couplingmethod for viscous fluid-structure impact analysis is proposed.Under assumption of incompressibility for thefluid,the corresp...Based on linearized 2-D Navier-Stokes equation,a Laplace transform-boundary element couplingmethod for viscous fluid-structure impact analysis is proposed.Under assumption of incompressibility for thefluid,the corresponding equivalent boundary integral equation in terms of the potential function and streamfunction is first established by Lamb’s transform in the Laplace transform domain.It enables us to solve im-pact water problems in frequency domain by the boundary element method,in which the effect of viscous flowon the dynamic response can be taken into account.Then a complete solution of the problem under consider-ation in time domain is obtained by means of Durbin’s formulas for the numerical inversion of the Laplacetransform.Finally,a practical example is given to confirm the validity of the present method.展开更多
A coupled thermo-mechanical model containing metal flow and temperature field for calculating temperature variation has been developed on fourteen-pass hot continu-ous rolling of round rod for Inconel 718 alloy using ...A coupled thermo-mechanical model containing metal flow and temperature field for calculating temperature variation has been developed on fourteen-pass hot continu-ous rolling of round rod for Inconel 718 alloy using 3D elastic-plastic finite element method(FEM).The temperature of characteristic analysis points in the intermedi-ate cross-section of the workpiece has been simulated at initial temperature ranging from 960 to 1000 °C and initial velocity in range of 0.15-0.55 m·s-1.Based on fi-nite element analysis and microstructural observation in cylindrical hot compression experiments,the appropriate hot continuous rolling technologies have been designed for rod products with different diameters.For a real rolling practice,the simulated surface temperature was examined and is in good agreement with the measured one.展开更多
The mega debris flow occurred on August 13 th 2010 in Qingping town,China(hereafter called '8.13' Debris Flow) have done great damage to the local habitants as well as to the re-construction projects in the qu...The mega debris flow occurred on August 13 th 2010 in Qingping town,China(hereafter called '8.13' Debris Flow) have done great damage to the local habitants as well as to the re-construction projects in the quake-hit areas,and the channel-fill deposit problem caused by the debris flow was the most destructive.Moreover,it is of high possibility that an even severe deposit problem would reappear and result in worse consequences.In order to maximize risk reduction of this problem,relevant departments of the government established a series of emergency river restoration schemes,for which the numerical analysis is an important procedure to evaluate and determine the optimized one.This study presents a numerical analysis by applying a twodimensional debris flow model combined with a relevant water-sediment model to simulate the deposit during the progress of the debris flow,and to calculate and analyze the river flow field under both the present condition and different restoration conditions.The results show that the debris flow model,which takes the confluence of the Wenjia Gully to the main river into account,could simulate the deposit process quite well.In the reproduced debris flow from the simulation of the '8.13' Debris Flow,the original river flow path has switched to a relatively lower place just along the right bank with a high speed of near 7m.s-1 after being blocked by the deposit,which is highly hazardous.To prevent this hazard,a recommended scheme is derived through inter-comparison of different restoration conditions.It shows that the recommended scheme is able to reduce the water level and as well to regulate the flow path.Based on the given conditions of the mainstream and the tributary confluence for the simulated '8.13' Debris Flow,when encountering a debris flow with deposit volume less than 0.5 million m3,the river channel can endure a 20-year return flood;however,when the deposit volume increases to 2 million m3,the flood capacity of the river will be greatly impacted and the scheme becomes invalid.The recommended scheme supported by the present study has been applied to the emergency river restoration after this mega-debris flow.展开更多
Power flow analysis is a numerical way of study of behavior of flow of electric power in an interconnected system. In order to meet the growing demands of electrical energy in an optimum way, there is a need to upgrad...Power flow analysis is a numerical way of study of behavior of flow of electric power in an interconnected system. In order to meet the growing demands of electrical energy in an optimum way, there is a need to upgrade existing systems or to install new systems. Therefore, planning of new installations and determination of best operating conditions of existing systems need power flow analysis. In this way, cost/benefit ratio for both suppliers and customers is maintained. This research involves the design and power flow analysis of IEEE-14 bus system. Newton Raphson method is applied for better efficiency and reduced computational time. Simulation analysis is conducted in ETAP software because of its excessive used in real life systems.展开更多
The continuation power flow method combined with the Jacobi-Davidson method is presented to trace the critical eigenvalues for power system small signal stability analysis. The continuation power flow based on a predi...The continuation power flow method combined with the Jacobi-Davidson method is presented to trace the critical eigenvalues for power system small signal stability analysis. The continuation power flow based on a predictor- corrector technique is applied to evaluate a continuum of steady state power flow solutions as system parameters change;meanwhile, the critical eigenvalues are found by the Jacobi-Davidson method, and thereby the trajectories of the critical eigenvalues, Hopf bifurcation and saddle node bifurcation points can also be found by the proposed method. The numerical simulations are studied in the IEEE 30-bus test system.展开更多
The control rod drive mechanism(CRDM)is an essential part of the control and safety protection system of pressurized water reactors.Current CRDM simulations are mostly performed collectively using a single method,igno...The control rod drive mechanism(CRDM)is an essential part of the control and safety protection system of pressurized water reactors.Current CRDM simulations are mostly performed collectively using a single method,ignoring the influence of multiple motion units and the differences in various features among them,which strongly affect the efficiency and accuracy of the simulations.In this study,we constructed a flow field fusion simulation method based on model features by combining key motion unit analysis and various simulation methods and then applied the method to the CRDM simulation process.CRDM performs motion unit decomposition through the structural hierarchy of function-movement-action method,and the key meta-actions are identified as the nodes in the flow field simulation.We established a fused feature-based multimethod simulation process and processed the simulation methods and data according to the features of the fluid domain space and the structural complexity to obtain the fusion simulation results.Compared to traditional simulation methods and real measurements,the simulation method provides advantages in terms of simulation efficiency and accuracy.展开更多
Complex energy and environment system, especially nuclear fuel cycle system recently raised socialconcerns about the issues of economic competitiveness, environmental effect and nuclear proliferation. Only underthe co...Complex energy and environment system, especially nuclear fuel cycle system recently raised socialconcerns about the issues of economic competitiveness, environmental effect and nuclear proliferation. Only underthe condition that those conflicting issues are gotten a consensus between stakeholders with different knowledgebackground, can nuclear power industry be continuingly developed. In this paper, a new analysis platform has beendeveloped to help stakeholders to recognize and analyze various socio-technical issues in the nuclear fuel cycle systembased on the functional modeling method named Multilevel Flow Models (MFM) according to the cognition theoryof human being. Its character is that MFM models define a set of mass, energy and information flow structures onmultiple levels of abstraction to describe the functional structure of a process system and its graphical symbol representationand the means-end and part-whole hierarchical flow structure to make the represented process easy to beunderstood. Based upon this methodology, a micro-process and a macro-process of nuclear fuel cycle system wereselected to be simulated and some analysis processes such as economics analysis, environmental analysis and energybalance analysis related to those flows were also integrated to help stakeholders to understand the process of decision-making with the introduction of some new functions for the improved Multilevel Flow Models Studio, and finallythe simple simulation such as spent fuel management process simulation and money flow of nuclear fuel cycleand its levelised cost analysis will be represented as feasible examples.展开更多
An iteration method similar to the thin-wing-expansion method for the compressible flow has been proposed to solve the boundary layer flow past a flat plate. Using such an iteration, the first step of which is Oseen’...An iteration method similar to the thin-wing-expansion method for the compressible flow has been proposed to solve the boundary layer flow past a flat plate. Using such an iteration, the first step of which is Oseen’s approximation, the boundary layer past a flat plate is studied. As proceeding from the first approximation to the second and third approximations, it is realized that our solution approaches to a well known Howarth’s bench mark one gradually. Hence, it is concluded that the usefulness of the present method has been confirmed.展开更多
文摘The fatigue of concrete structures will gradually appear after being subjected to alternating loads for a long time,and the accidents caused by fatigue failure of bridge structures also appear from time to time.Aiming at the problem of degradation of long-span continuous rigid frame bridges due to fatigue and environmental effects,this paper suggests a method to analyze the fatigue degradation mechanism of this type of bridge,which combines long-term in-site monitoring data collected by the health monitoring system(HMS)and fatigue theory.In the paper,the authors mainly carry out the research work in the following aspects:First of all,a long-span continuous rigid frame bridge installed with HMS is used as an example,and a large amount of health monitoring data have been acquired,which can provide efficient information for fatigue in terms of equivalent stress range and cumulative number of stress cycles;next,for calculating the cumulative fatigue damage of the bridge structure,fatigue stress spectrum got by rain flow counting method,S-N curves and damage criteria are used for fatigue damage analysis.Moreover,it was considered a linear accumulation damage through the Palmgren-Miner rule for the counting of stress cycles.The health monitoring data are adopted to obtain fatigue stress data and the rain flow counting method is used to count the amplitude varying fatigue stress.The proposed fatigue reliability approach in the paper can estimate the fatigue damage degree and its evolution law of bridge structures well,and also can help bridge engineers do the assessment of future service duration.
基金The research was supported by the National Basic Research Program(“973”Program)of China under contract No.2002CB412405the Key Science and Technology Plan of the Ministry of Education of China under contract No.[2000]156-00079the Joint Sino-German Project under contract No.03F0189A.
文摘Several methods for analysis of dissolved total phosphorus in seawater were reviewed. Discussions were focused on UV irradiation and persulphate oxidation methods which are the most popular dissolved organic phosphorus determination methods presently. The compounds used for the phosphorus recovery test were categorized into three groups according to their chemical structure. It was found that low power UV irradiation can decompose P-O-C or P-C bonds efficiently but may be inefficient for P-O-P bonds. Heating-bath in acid condition is useful for decomposing P-O-P bonds. Using the continuous flow analysis system (Auto-analyzer Ⅱ), UV digestion and heating-bath, series experiments were carried out based on the above analysis. Eleven model compounds were employed for the phosphorus recovery test and the factors influencing the decomposition efficiency of dissolved compounds containing phosphorus were clarified. Finally,the optimal design for determination of dissolved total phosphorus in seawater based on the routine continuous flow analysis system was presented. For the organic mono-phosphate, the recovery is more than 90% and a recovery of 33%～51% was obtained for inorganic or organic polyphosphates. Up to now, this is the highest decomposition efficiency for dissolved phosphorus based on the continuous flow analysis system.
基金supported by the National Natural Science Foundation of China(Nos.12205190,11805121)the Science and Technology Commission of Shanghai Municipality(No.21ZR1435400).
文摘The uncertainty of nuclide libraries in the analysis of the gamma spectra of low-and intermediate-level radioactive waste(LILW)using existing methods produces unstable results.To address this problem,a novel spectral analysis method is proposed in this study.In this method,overlapping peaks are located using a continuous wavelet transform.An improved quadratic convolution method is proposed to calculate the widths of the peaks and establish a fourth-order filter model to estimate the Compton edge baseline with the overlapping peaks.Combined with the adaptive sensitive nonlinear iterative peak,this method can effectively subtracts the background.Finally,a function describing the peak shape as a filter is used to deconvolve the energy spectrum to achieve accurate qualitative and quantitative analyses of the nuclide without the aid of a nuclide library.Gamma spectrum acquisition experiments for standard point sources of Cs-137 and Eu-152,a segmented gamma scanning experiment for a 200 L standard drum,and a Monte Carlo simulation experiment for triple overlapping peaks using the closest energy of three typical LILW nuclides(Sb-125,Sb-124,and Cs-134)are conducted.The results of the experiments indicate that(1)the novel method and gamma vision(GV)with an accurate nuclide library have the same spectral analysis capability,and the peak area calculation error is less than 4%;(2)compared with the GV,the analysis results of the novel method are more stable;(3)the novel method can be applied to the activity measurement of LILW,and the error of the activity reconstruction at the equivalent radius is 2.4%;and(4)The proposed novel method can quantitatively analyze all nuclides in LILW without a nuclide library.This novel method can improve the accuracy and precision of LILW measurements,provide key technical support for the reasonable disposal of LILW,and ensure the safety of humans and the environment.
基金supported by National Natural Science Foundation of China(No.50605020)Guangdong Provincial Science and Technology Project of China(No.2006A10501001).
文摘With the structure of two air gaps and two rotors,the electromagnetic continuously variable transmission(EMCVT) is a novel power-split continuously variable transmission(CVT).There are two kinds of power flowing through the EMCVT,one is mechanical power and the other is electric power. In the mean time,there are three power ports in the EMCVT,one is the outer rotor named mechanical power port and the other two are the inner rotor and the stator named electric power ports.The mechanical power port is connected to the driving wheels through the fmal gear and the electric ports are connected to the batteries through the transducers.The two kinds of power are coupled on the outer rotor of the EMCVT.The EMCVT can be equipped on the conventional vehicle being regarded as the CVT and it also can be equipped on the hybrid electric vehicle(HEV) as the multi-energy sources assembly.The power flows of these two kinds of applications are analysed.The back electromotive force(EMF) equations are illatively studied and so the dynamic mathematic model is theorized.In order to certify the feasibility of the above theories,three simulations are carried out in allusion to the above two kinds of mentioned applications of the EMCVT and a five speed automatic transmission(AT) vehicle.The simulation results illustrate that the efficiency of the EMCVT vehicles is higher than that of the AT vehicle owed to the optimized operation area of the engine.Hence the fuel consumption of the EMCVT vehicles is knock-down.
基金funded by the National Natural Science Foundation of China(Grant Nos.42377170).
文摘Machine learning(ML)-based prediction models for mapping hazard(e.g.,landslide and debris flow)susceptibility have been widely developed in recent research.However,in some specific areas,ML models have limited application because of the uncertainties in identifying negative samples.The Parlung Tsangpo Basin exemplifies a region prone to recurrent glacial debris flows(GDFs)and is characterized by a prominent landform featuring deep gullies.Considering the limitations of the ML model,we developed and compared two combined statistical models(FA-WE and FA-IC)based on factor analysis(FA),weight of evidence(WE),and the information content(IC)method.The final GDF susceptibility maps were generated by selecting 8 most important static factors and considering the influence of precipitation.The results show that the FA-IC model has the best performance.The areas with a very high susceptibility to GDFs are primarily located in the narrow valley section upstream,on both sides of the valley in the middle and downstream of the Parlung Tsangpo River,and in the narrow valley section of each tributary.These areas encompass 86 gullies and are characterized as"narrow and steep".
文摘The present paper investigates the magnetohydrodynamic(MHD) flow of a viscous fluid towards a nonlinear porous shrinking sheet.The governing equations are simplified by similarity transformations.The reduced problem is then solved by the homotopy analysis method.The pertinent parameters appearing in the problem are discussed graphically and presented in tables.It is found that the shrinking solutions exist in the presence of MHD.It is also observed from the tables that the solutions for f(0) with different values of parameters are convergent.
基金supported by the Project of the National Key R&D Program(Grant No.2021YFA1000202)National Natural Science Foundation of China(Grant Nos.12120101001,12001326 and 12171283)+2 种基金Natural Science Foundation of Shandong Province(Grant Nos.ZR2021ZD03,ZR2020QA032 and ZR2019ZD42)China Postdoctoral Science Foundation(Grant Nos.BX20190191 and 2020M672038)the Startup Fund from Shandong University(Grant No.11140082063130)。
文摘In this paper,we first establish a new fractional magnetohydrodynamic(MHD)coupled flow and heat transfer model for a generalized second-grade fluid.This coupled model consists of a fractional momentum equation and a heat conduction equation with a generalized form of Fourier law.The second-order fractional backward difference formula is applied to the temporal discretization and the Legendre spectral method is used for the spatial discretization.The fully discrete scheme is proved to be stable and convergent with an accuracy of O(τ^(2)+N-r),whereτis the time step-size and N is the polynomial degree.To reduce the memory requirements and computational cost,a fast method is developed,which is based on a globally uniform approximation of the trapezoidal rule for integrals on the real line.The strict convergence of the numerical scheme with this fast method is proved.We present the results of several numerical experiments to verify the effectiveness of the proposed method.Finally,we simulate the unsteady fractional MHD flow and heat transfer of the generalized second-grade fluid through a porous medium.The effects of the relevant parameters on the velocity and temperature are presented and analyzed in detail.
基金This work was financially supported by the Hunan Valin Lianyuan Iron&Steel Co.,Ltd.,China(No.18H00582).The authors are grateful to Hunan Valin Lianyuan Iron&Steel Co.,Ltd.,China for their assistance with the industrial measurement of velocities near the mold surface.
文摘Computational simulations and high-temperature measurements of velocities near the surface of a mold were carried out by using the rod deflection method to study the effects of various operating parameters on the flow field in slab continuous casting(CC)molds with narrow widths for the production of automobile exposed panels.Reasonable agreement between the calculated results and measured subsurface velocities of liquid steel was obtained under different operating parameters of the CC process.The simulation results reveal that the flow field in the horizontal plane located 50 mm from the meniscus can be used as the characteristic flow field to optimize the flow field of molten steel in the mold.Increases in casting speed can increase the subsurface velocity of molten steel and shift the position of the vortex core downward in the downward circulation zone.The flow field of liquid steel in a 1040 mm-wide slab CC mold can be improved by an Ar gas flow rate of 7 L·min^−1 and casting speed of 1.7 m·min^−1.Under the present experimental conditions,the double-roll flow pattern is generally stable at a submerged entry nozzle immersion depth of 170 mm.
基金supported by the Shanghai Municipal Natural Science Foundation(No.13ZR1415700)
文摘In this paper, a new unsteady aerodynamic design method is presented based on the Navier-Stokes equations and a continuous adjoint approach. A basic framework of time-accurate unsteady airfoil optimization which adopts time-averaged aerodynamic coefficients as objective functions is presented. The time-accurate continuous adjoint equation and its boundary conditions are derived. The flow field and the adjoint equation are simulated numerically by the finite volume method(FVM). Feasibility and accuracy of the approach are perfectly validated by the design optimization results of the plunging NACA0012 airfoil.
基金supported by the National Natural Science Foundations of China (50936003, 50905013)The Open Project of State Key Lab. for Adv. Matals and Materials (2009Z-02)Research Foundation of Engineering Research Institute of USTB
文摘In this paper, the asymmetric laminar flow in a porous channel with expanding or contracting walls is investigated. The governing equations are reduced to ordinary ones by using suitable similar transformations. Homotopy analysis method (HAM) is employed to obtain the expres- sions for velocity fields. Graphs are sketched for values of parameters and associated dynamic characteristics, especially the expansion ratio, are analyzed in detail.
基金supported by the Fundamental Research Funds for the Dalian University of Technology(Grant No.DUT10LK43)the National Key Basic Research Program of China(Grant No.2013CB036101)
文摘Submerged horizontal plate can be considered as a new concept breakwater.In order to reveal the wave elimination mechanism of this type breakwater,boundary element method is utilized to investigate the velocity field around plate carefully.The flow field analysis shows that the interaction between incident wave and reverse flow caused by submerged plate will lead to the formation of wave elimination area around both sides of the plate.The velocity magnitude of flow field has been reduced and this is the main reason of wave elimination.
文摘The effects of axisymmetric flow of a Powell-Eyring fluid over an impermeable radially stretching surface are presented. Characteristics of the heat transfer process are analyzed with a more realistic condition named the convective boundary condition.Governing equations for the flow problem are derived by the boundary layer approximations. The modeled highly coupled partial differential system is converted into a system of ordinary differential equations with acceptable similarity transformations. The convergent series solutions for the resulting system are constructed and analyzed. Optimal values are obtained and presented in a numerical form using an optimal homotopy analysis method(OHAM). The rheological characteristics of different parameters of the velocity and temperature profiles are presented graphically. Tabular variations of the skin friction coefficient and the Nusselt number are also calculated. It is observed that the temperature distribution shows opposite behavior for Prandtl and Biot numbers. Furthermore,the rate of heating/cooling is higher for both the Prandtl and Biot numbers.
基金the National Defence Foundation of Science & Technology of China (No.J14.8.1.JW0515)
文摘Based on linearized 2-D Navier-Stokes equation,a Laplace transform-boundary element couplingmethod for viscous fluid-structure impact analysis is proposed.Under assumption of incompressibility for thefluid,the corresponding equivalent boundary integral equation in terms of the potential function and streamfunction is first established by Lamb’s transform in the Laplace transform domain.It enables us to solve im-pact water problems in frequency domain by the boundary element method,in which the effect of viscous flowon the dynamic response can be taken into account.Then a complete solution of the problem under consider-ation in time domain is obtained by means of Durbin’s formulas for the numerical inversion of the Laplacetransform.Finally,a practical example is given to confirm the validity of the present method.
基金the financial supports from the National Natural Science Foundation of China (Key Program,Grant No.50634030)the Program for New Century Excellent Talents in University (Grant No.NCET-06-0285)
文摘A coupled thermo-mechanical model containing metal flow and temperature field for calculating temperature variation has been developed on fourteen-pass hot continu-ous rolling of round rod for Inconel 718 alloy using 3D elastic-plastic finite element method(FEM).The temperature of characteristic analysis points in the intermedi-ate cross-section of the workpiece has been simulated at initial temperature ranging from 960 to 1000 °C and initial velocity in range of 0.15-0.55 m·s-1.Based on fi-nite element analysis and microstructural observation in cylindrical hot compression experiments,the appropriate hot continuous rolling technologies have been designed for rod products with different diameters.For a real rolling practice,the simulated surface temperature was examined and is in good agreement with the measured one.
基金supported by the National Basic Research Program of China ("973" Project) (Grant No. 2011CB409903)the National Natural Science Foundation of China (Grant No. 50739002)
文摘The mega debris flow occurred on August 13 th 2010 in Qingping town,China(hereafter called '8.13' Debris Flow) have done great damage to the local habitants as well as to the re-construction projects in the quake-hit areas,and the channel-fill deposit problem caused by the debris flow was the most destructive.Moreover,it is of high possibility that an even severe deposit problem would reappear and result in worse consequences.In order to maximize risk reduction of this problem,relevant departments of the government established a series of emergency river restoration schemes,for which the numerical analysis is an important procedure to evaluate and determine the optimized one.This study presents a numerical analysis by applying a twodimensional debris flow model combined with a relevant water-sediment model to simulate the deposit during the progress of the debris flow,and to calculate and analyze the river flow field under both the present condition and different restoration conditions.The results show that the debris flow model,which takes the confluence of the Wenjia Gully to the main river into account,could simulate the deposit process quite well.In the reproduced debris flow from the simulation of the '8.13' Debris Flow,the original river flow path has switched to a relatively lower place just along the right bank with a high speed of near 7m.s-1 after being blocked by the deposit,which is highly hazardous.To prevent this hazard,a recommended scheme is derived through inter-comparison of different restoration conditions.It shows that the recommended scheme is able to reduce the water level and as well to regulate the flow path.Based on the given conditions of the mainstream and the tributary confluence for the simulated '8.13' Debris Flow,when encountering a debris flow with deposit volume less than 0.5 million m3,the river channel can endure a 20-year return flood;however,when the deposit volume increases to 2 million m3,the flood capacity of the river will be greatly impacted and the scheme becomes invalid.The recommended scheme supported by the present study has been applied to the emergency river restoration after this mega-debris flow.
文摘Power flow analysis is a numerical way of study of behavior of flow of electric power in an interconnected system. In order to meet the growing demands of electrical energy in an optimum way, there is a need to upgrade existing systems or to install new systems. Therefore, planning of new installations and determination of best operating conditions of existing systems need power flow analysis. In this way, cost/benefit ratio for both suppliers and customers is maintained. This research involves the design and power flow analysis of IEEE-14 bus system. Newton Raphson method is applied for better efficiency and reduced computational time. Simulation analysis is conducted in ETAP software because of its excessive used in real life systems.
文摘The continuation power flow method combined with the Jacobi-Davidson method is presented to trace the critical eigenvalues for power system small signal stability analysis. The continuation power flow based on a predictor- corrector technique is applied to evaluate a continuum of steady state power flow solutions as system parameters change;meanwhile, the critical eigenvalues are found by the Jacobi-Davidson method, and thereby the trajectories of the critical eigenvalues, Hopf bifurcation and saddle node bifurcation points can also be found by the proposed method. The numerical simulations are studied in the IEEE 30-bus test system.
基金supported by the National Natural Science Foundation of China (No. 52075350)the Special City School Strategic Cooperation Project of Sichuan University and Zigong (No.2021CDZG-3)
文摘The control rod drive mechanism(CRDM)is an essential part of the control and safety protection system of pressurized water reactors.Current CRDM simulations are mostly performed collectively using a single method,ignoring the influence of multiple motion units and the differences in various features among them,which strongly affect the efficiency and accuracy of the simulations.In this study,we constructed a flow field fusion simulation method based on model features by combining key motion unit analysis and various simulation methods and then applied the method to the CRDM simulation process.CRDM performs motion unit decomposition through the structural hierarchy of function-movement-action method,and the key meta-actions are identified as the nodes in the flow field simulation.We established a fused feature-based multimethod simulation process and processed the simulation methods and data according to the features of the fluid domain space and the structural complexity to obtain the fusion simulation results.Compared to traditional simulation methods and real measurements,the simulation method provides advantages in terms of simulation efficiency and accuracy.
文摘Complex energy and environment system, especially nuclear fuel cycle system recently raised socialconcerns about the issues of economic competitiveness, environmental effect and nuclear proliferation. Only underthe condition that those conflicting issues are gotten a consensus between stakeholders with different knowledgebackground, can nuclear power industry be continuingly developed. In this paper, a new analysis platform has beendeveloped to help stakeholders to recognize and analyze various socio-technical issues in the nuclear fuel cycle systembased on the functional modeling method named Multilevel Flow Models (MFM) according to the cognition theoryof human being. Its character is that MFM models define a set of mass, energy and information flow structures onmultiple levels of abstraction to describe the functional structure of a process system and its graphical symbol representationand the means-end and part-whole hierarchical flow structure to make the represented process easy to beunderstood. Based upon this methodology, a micro-process and a macro-process of nuclear fuel cycle system wereselected to be simulated and some analysis processes such as economics analysis, environmental analysis and energybalance analysis related to those flows were also integrated to help stakeholders to understand the process of decision-making with the introduction of some new functions for the improved Multilevel Flow Models Studio, and finallythe simple simulation such as spent fuel management process simulation and money flow of nuclear fuel cycleand its levelised cost analysis will be represented as feasible examples.
文摘An iteration method similar to the thin-wing-expansion method for the compressible flow has been proposed to solve the boundary layer flow past a flat plate. Using such an iteration, the first step of which is Oseen’s approximation, the boundary layer past a flat plate is studied. As proceeding from the first approximation to the second and third approximations, it is realized that our solution approaches to a well known Howarth’s bench mark one gradually. Hence, it is concluded that the usefulness of the present method has been confirmed.
