To accurately control the full-span erection of continuous steel box girder bridges with complex cross-sections and long cantilevers, both the augmented finite element method(A-FEM) and the degenerated plate elements ...To accurately control the full-span erection of continuous steel box girder bridges with complex cross-sections and long cantilevers, both the augmented finite element method(A-FEM) and the degenerated plate elements are adopted in this paper. The entire construction process is simulated by the A-FEM with the mesh-separation-based approximation technique, while the degenerated plate elements are constructed based on 3D isoparametric elements, making it suitable for analysis of a thin-walled structure. This method significantly improves computational efficiency by avoiding numerous degrees of freedom(DoFs) when analyzing complex structures. With characteristics of the full-span erection technology, the end-face angle of adjacent girder segments, the preset distance of girder segments from the design position, and the temperature difference are selected as control parameters, and they are calculated through the structural response of each construction stage. Engineering practice shows that the calculation accuracy of A-FEM is verified by field-measured results. It can be applied rapidly and effectively to evaluate the matching state of girder segments and the stress state of bearings as well as the thermal effect during full-span erection.展开更多
In this paper, the interaction parameters in the subregular solution model, λ1 and λ2, are regarded as a linear function of temperature, T. Therefore, the molar excess Gibbs energy of A-B binary system may be reexpr...In this paper, the interaction parameters in the subregular solution model, λ1 and λ2, are regarded as a linear function of temperature, T. Therefore, the molar excess Gibbs energy of A-B binary system may be reexpressed as follows:Gm^E=xAxB[(λ11+λ12T)+(λ21+λ22T)xB]The calculation of the model parameters, λ11, λ12, λ21and λ22, was carried out numerically from the phase diagrams for 11 alkali metal-alkali halide or alkali earth metal-halide systems. In addition, artificial neural network trained by known data has been used to predict the values of these model parameters. The predicted results are in good agreement with the .calculated ones. The applicability of the subregular solution model to the alkali metal-alkali halide or alkali earth metal-halide systems were tested by comparing the available experimental composition along the boundary of miscibility gap with the calculated ones which were obtained by using genetic algorithm. The good agreement between the calculated and experimental results across the entire liquidus is valid evidence in support of the model.展开更多
Parameter calculation and result storage, as two necessary steps in phase-field simulation play an important role in ensuring the accuracy of simulation results. A strategy of parameter calculation and result storage ...Parameter calculation and result storage, as two necessary steps in phase-field simulation play an important role in ensuring the accuracy of simulation results. A strategy of parameter calculation and result storage is presented for phase-field simulation in α-Mg dendrite growth of Mg-5-wt% Zn alloy under isothermal solidification. Based on the phase diagram and empirical formulas, key parameters of the phase-field model, such as equilibrium partition coefficient k, liquidus slope m, solutal diffusion coefficient in liquid Dl, and solutal diffusion coefficient in solid Ds, can be obtained.Both structured grid method and structured point method can be used to store simulation results, but using the latter method will reduce about 60% storage space and 37.5% storage time compared with the former. Finally, convergent simulation results of α-Mg dendrite growth are obtained and they are in good agreement with the experimental results about optical micrograph, which verify the accuracy of parameters and stability of storage method.展开更多
By integrating advanced digital technologies such as cloud computing and the Internet of Things in sensor measurement,information communication,and other fields,the digital DC distribution network can efficiently and ...By integrating advanced digital technologies such as cloud computing and the Internet of Things in sensor measurement,information communication,and other fields,the digital DC distribution network can efficiently and reliably access DistributedGenerator(DG)and Energy Storage Systems(ESS),exhibiting significant advantages in terms of controllability and meeting requirements of Plug-and-Play(PnP)operations.However,during device plug-in and-out processes,improper systemparametersmay lead to small-signal stability issues.Therefore,before executing PnP operations,conducting stability analysis and adjusting parameters swiftly is crucial.This study introduces a four-stage strategy for parameter optimization to enhance systemstability efficiently.In the first stage,state-of-the-art technologies in measurement and communication are utilized to correct model parameters.Then,a novel indicator is adopted to identify the key parameters that influence stability in the second stage.Moreover,in the third stage,a local-parameter-tuning strategy,which leverages rapid parameter boundary calculations as a more efficient alternative to plotting root loci,is used to tune the selected parameters.Considering that the local-parameter-tuning strategy may fail due to some operating parameters being limited in adjustment,a multiparameter-tuning strategy based on the particle swarm optimization(PSO)is proposed to comprehensively adjust the dominant parameters to improve the stability margin of the system.Lastly,system stability is reassessed in the fourth stage.The proposed parameter-optimization strategy’s effectiveness has been validated through eigenvalue analysis and nonlinear time-domain simulations.展开更多
In the context of the global“Carbon Peaking and Carbon Neutrality”initiative,the injection of carbon dioxide(CO_(2))into depleted gas reservoirs represents a dual-purpose strategy—facilitating long-term carbon sequ...In the context of the global“Carbon Peaking and Carbon Neutrality”initiative,the injection of carbon dioxide(CO_(2))into depleted gas reservoirs represents a dual-purpose strategy—facilitating long-term carbon sequestration while enhancing hydrocarbon recovery.However,variations in injection parameters at the wellhead can exert pronounced effects on the temperature and pressure conditions at the bottomof the well.These variations,in turn,influence the geomechanical behavior of reservoir rocks and the displacement efficiency of CO_(2) within the formation.Precise prediction of downhole thermodynamic conditions is therefore essential for optimizing injection performance and ensuring reservoir stability.To address this need,the present study develops a robust coupled model to simulate the behavior of CO_(2) within the wellbore,incorporating momentum conservation,mass continuity,and steady-state heat transfer equations.Validation against field-measured data confirms the model’s reliability and applicability under realworld operating conditions.Parametric analysis reveals the complex influence of injection conditions on bottom-hole states.Injection pressure primarily affects downhole pressure,exerting minimal influence on temperature.In contrast,low injection temperatures and elevated flow rates lead to reduced bottom-hole temperatures and heightened pressures.Owing to the interplay of convective and conductive heat transfer mechanisms,the relationship between injection rate and bottom-hole temperature exhibits nonlinearity.Notably,injection scenarios characterized by low temperature,high pressure,and high velocity promote a deeper penetration of the CO_(2) critical phase transition point within the tubing.Among the parameters examined,injection temperature emerges as the dominant factor affecting the depth of CO_(2)’s phase transformation,followed by injection rate,with pressure exerting the least influence.A strong correlation is observed between injection rate and the depth of the critical phase transition,offering a practical framework for tailoring injection strategies to enhance both CO_(2) storage capacity and recovery efficiency.展开更多
As an important component of oil-immersed transformers,the bushing's internal insu-lation ageing and dampness after the long-term operation can cause changes in the in-ternal electric and temperature fields,seriou...As an important component of oil-immersed transformers,the bushing's internal insu-lation ageing and dampness after the long-term operation can cause changes in the in-ternal electric and temperature fields,seriously threatening its safe operation.This paper tested the power frequency permittivity and direct current conductivity of aged and damp oil-paper insulation samples at different testing temperatures,and constructed a dynamic dielectric parameter calculation model.Meanwhile,a simulation model was established based on the actual structure of the 252 kV/1250 A bushing which is mainly used for the oil-immersed high-voltage bushings of 110 kV and above.The electric-magnetic-thermal multi-physical fields were used for simulation analysis.The influence of ageing/moisture(different degrees of dampness in the upper and lower regions)on the electric field distribution in the bushing was obtained.During the initial to steady-state process,the electric field distribution at the zero and end shield shows a reversal phenomenon.When the capacitor core has different degrees of dampness in the upper and lower regions,the impedance distribution of the capacitor core is non-uniform.This phenomenon will lead to an increase in the radial electric field gradient at the end shield of the capacitor core,which is prone to the risk of slip-flashing discharge.In summary,this paper adopts the field-induced dynamic parameters method to analyse the changes of multi-physical fields in the bushing.This can provide theoretical guidance for optimising the bushing structure and on-site maintenance.展开更多
The effect zones of layer face for RCC （rolled control concrete） dam have gradual change characteristics. Based on the analysis thought of complex material, a model was built to analyze above principle of RCC dam by...The effect zones of layer face for RCC （rolled control concrete） dam have gradual change characteristics. Based on the analysis thought of complex material, a model was built to analyze above principle of RCC dam by use of series-wound and shunt-wound connection. Some methods were proposed to determine the instantaneous Young＇s modulus, delayed Young＇s modulus and viscosity coefficient of effect zones of layer face. Above models and methods were used to mine the principle of gradual change of key calculation parameters which can response the characteristics of effect zones. The principle of gradual change was described. A model was established to analyze the threedimensional viscoelastic problem of RCC dam. Above programs were developed. The examples show that the proposed models and methods to determine the key calculation parameters of effect zones can reflect the status of RCC dam accurately.展开更多
A deep foundation pit constructed for an underground transportation hub was excavated near the Yangtze River. Among the strata, there are two confined aquifers, between which lies an aquiclude that is partially missin...A deep foundation pit constructed for an underground transportation hub was excavated near the Yangtze River. Among the strata, there are two confined aquifers, between which lies an aquiclude that is partially missing. To guarantee the safety of pit excavation, the piezometric head of the upper confined aquifer, where the pit bottom is located, should be 1 m below the pit bottom, while that of the lower confined aquifer should be dewatered down to a safe water level to avoid uplift problem. The Yangtze River levee is notably close to the pit, and its deformation caused by dewatering should be controlled. A pumping test was performed to obtain the hydraulic conductivity of the upper confined aquifer. The average value of the hydraulic conductivity obtained from analytical calculation is 20.45 m/d, which is larger than the values from numerical simulation（horizontal hydraulic conductivity K_H = 16 m/d and vertical hydraulic conductivity K_V = S m/d）. The difference between K_H and K_V indicates the anisotropy of the aquifer. Two dewatering schemes were designed for the construction and simulated by the numerical models for comparison purposes. The results show that though the first scheme could meet the dewatering requirements, the largest accumulated settlement and differential settlement would be94.64 mm and 3.3‰, respectively, greatly exceeding the limited values. Meanwhile, the second scheme,in which the bottoms of the waterproof curtains in ramp B and the river side of ramp A are installed at a deeper elevation of-28 m above sea level, and 27 recharge wells are set along the levee, can control the deformation of the levee significantly.展开更多
Estimating the intention of space objects plays an important role in air-craft design,aviation safety,military and otherfields,and is an important refer-ence basis for air situation analysis and command decision-making...Estimating the intention of space objects plays an important role in air-craft design,aviation safety,military and otherfields,and is an important refer-ence basis for air situation analysis and command decision-making.This paper studies an intention estimation method based on fuzzy theory,combining prob-ability to calculate the intention between two objects.This method takes a space object as the origin of coordinates,observes the target’s distance,speed,relative heading angle,altitude difference,steering trend and etc.,then introduces the spe-cific calculation methods of these parameters.Through calculation,values are input into the fuzzy inference model,andfinally the action intention of the target is obtained through the fuzzy rule table and historical weighted probability.Ver-ified by simulation experiment,the target intention inferred by this method is roughly the same as the actual behavior of the target,which proves that the meth-od for identifying the target intention is effective.展开更多
This paper calculates the parameters of image position and orientation,proposes a mathematical model and adopts a new method with three steps of transformations based on parallel ray projection.Every step of the model...This paper calculates the parameters of image position and orientation,proposes a mathematical model and adopts a new method with three steps of transformations based on parallel ray projection.Every step of the model is strict,and the map function of each transformation is the first order polynomials and other simple function.The final calculation of the parameters is for the linear equations with good status.As a result,the problem of the relativity of image parameter calculation is solved completely.Some experiments are carried out.展开更多
Nineteen preschisanartane-type schinortriterpenoids(SNTs),among which eleven ones were previously undescribed,were isolated from two Schisandra species,S.sphaerandra and S.rubriflora.Their structures were determined u...Nineteen preschisanartane-type schinortriterpenoids(SNTs),among which eleven ones were previously undescribed,were isolated from two Schisandra species,S.sphaerandra and S.rubriflora.Their structures were determined using 1 D and 2 D NMR spectroscopic analyses,NMR data comparison,quantum chemical calculation of NMR parameters,electronic circular dichroism(ECD),X-ray single crystal diffraction,and chemical derivation.Furthermore,structural re-examination of a few previously reported preschisanartane-type SNTs led to the structural revision of preschisanartanin J.Besides,it is suggested that the reported structures of arisanlactone D and schilancidilactone W should be re-checked.Finally,a few isolated SNTs were found to possess neurite outgrowthpromoting activities,and protective activities against neural injuries.展开更多
Uncertainties in modern assessments of the impact of long-term climatic variations on the characteristics of groundwater discharge and groundwater resources are considered.The authors show that when assessing groundwa...Uncertainties in modern assessments of the impact of long-term climatic variations on the characteristics of groundwater discharge and groundwater resources are considered.The authors show that when assessing groundwater resources and especially forecasting groundwater resources,the main calculated hydrogeological parameters are insufficiently reliable and estimates of possible changes of main meteorological characteristics should be considered.Therefore,it is currently almost impossible to forecast the impacts of climate change on groundwater resources and regime for the coming decades.A scenario-based approach is the most promising for studying the potential effects of climate change on groundwater.展开更多
With the development of aviation industry,civil aviation has become an indispensable part.Our team will take all the structural dimensions,loads and material parameters in the wing beam structure as the specific value...With the development of aviation industry,civil aviation has become an indispensable part.Our team will take all the structural dimensions,loads and material parameters in the wing beam structure as the specific values determined during the structural design to conduct deflection analysis on the wing beam structure of A380 passenger plane.According to the deflection and parameters analyzed,the stress distribution and maximum stress position on the wing beam can be known.Through the analysis of the wing parameters,the finite element analysis of the wing beam,the mesh sensitivity analysis,and the analysis of the wing tip deflection,the relevant safety factors of the aircraft are obtained.The results show that the wing of airbus A380 is more reliable and safer through the calculation of deflection,stress and safety factor.展开更多
In order to reveal the reasons for the differences in initial water production characteristics of gas wells in different regions of the East China Sea Basin and to screen favorable targets for low-permeability reservo...In order to reveal the reasons for the differences in initial water production characteristics of gas wells in different regions of the East China Sea Basin and to screen favorable targets for low-permeability reservoir reconstruction,a calculation method of initial production wateregas ratios at different gas column heights was established by combining gas-water two-phase capillary pressure with J function definition,power function relative permeability model and fractional flow equation.Then based on the experimental data of standard capillary pressure and standard relative permeability in the gas province of the East China Sea,an evaluation chart on initial production wateregas ratio of the East China Sea at different gas column heights was calculated and established.Finally,the evaluation chart was validated by using the data of the tested or commissioned gas wells in the gas reservoirs of the East China Sea,and the physical property conditions suitable for reservoir reconstruction of low-permeability gas reservoirs in the East China Sea were determined according to the evaluation chart.The following research results were obtained.First,the evaluation chart established in this paper reflects that the correlation between the parameters is similar to the actual production law and matches well with the actual data,which verifies the correctness and reliability of the chart establishment method and the key parameter calculation method.Second,with the production wateregas ratio less than 1 m3/104 m3 as the screening condition,for the permeability of the low-permeability gas reservoirs(with gas column height of about 50 m)in the west sub-sag,the central uplift belt and the periphery suitable for reservoir reconstruction shall be greater than 0.65 mD,and that of the large low-permeability gas reservoirs(with a gas column height of more than 100 m)in the north of central uplift belt shall be greater than 0.26 mD.Third,there is no gasewater contact in gas reservoirs under the hydrocarbon accumulation conditions of in-situ reservoirs,so the method and the evaluation chart proposed in this paper are not applicable.It is concluded that the method of establishing the initial water production evaluation chart and the method of calculating the key parameters proposed in this paper can provide meaningful reference for the development and evaluation of other gas fields in China.展开更多
This article aims to discuss the design process of the CAD system dedicated for sport bike frame structure, introducing in detail its design concept and the scheme of implementation. Based on the different usages of s...This article aims to discuss the design process of the CAD system dedicated for sport bike frame structure, introducing in detail its design concept and the scheme of implementation. Based on the different usages of sport bikes and the requirements on the system made out by Beijing Hanglun Sport Apparatus Company Limited. Structural analysis on two types of bikes frames is carried out. The system defines the basic design parameters and analyses the constraint conditions.Then calculating formulas with constraint conditions are derived. The system solves equations with Visual C++ program, realizes input of the original data and output of the results through interactive system. With AutoCAD14.0 as the platform, the system uses VC++ and ObjectARX to realize auto output of bike frame graphics. The system has been put into use. Practice has affirmed that the system抯 convenience, applicability and reliability all have reached the expected goal.展开更多
In some control strategies of the direct-rive permanent magnet generator(DDPMG),the mathematics model is excessively simplified and some complex nonlinear characteristics,such as core saturation and cross-saturation,a...In some control strategies of the direct-rive permanent magnet generator(DDPMG),the mathematics model is excessively simplified and some complex nonlinear characteristics,such as core saturation and cross-saturation,are generally neglected.To solve this problem,this paper utilizes the frozen element permeability method to compute the armature self-and mutual-inductance,permanent magnet d-and q-axis flux varying with d-axis and q-axis current,then an improved model is presented in which the core saturation and cross-saturation between d-axis and q-axis are considered effectively.Based on this model,the method for computing the performance of the generators is also proposed.Taking a 1.5-MW DDPMG as an example,the time-stepping finite element method(T-S FEM) is adopted to analyze the performance with no-load and loaded conditions,the results show a good agreement with the ones obtained by the improved model.Compared with the simplified model,it is demonstrated that the presented model has the high efficiency and reliability and can provide a good reference for optimization design of DDPMG and other PM motors.展开更多
Computational fluid dynamics(CFD)methods are being increasingly used for predicting airflow fields around buildings,but personal computers can still take tens of hours to create a single design using traditional compu...Computational fluid dynamics(CFD)methods are being increasingly used for predicting airflow fields around buildings,but personal computers can still take tens of hours to create a single design using traditional computing models.Considering both accuracy and efficiency,this study compared the performances of the conventional algorithm PIMPLE,fast fluid dynamics(FFD),semi-Lagrangian PISO(SLPISO),and implicit fast fluid dynamics(IFFD)in OpenFOAM for simulating wind flow around buildings.The effects of calculation parameters,including grid resolution,discrete-time step,and calculation time for these methods are analyzed.The results of the simulations are compared with wind tunnel tests.It is found that IFFD and FFD have the fastest calculation speeds,but also have the largest discrepancies with test data.The PIMPLE algorithm has the highest accuracy,but with the slowest calculation speed.The calculation speeds of the FFD,SLPISO,and IFFD models are 6.3,3 and 13.3 times faster than the PIMPLE model,respectively.The calculation accuracy and speed of the SLPISO model are in between those of the IFFD,FFD and PIMPLE models.An appropriate algorithm for a project may be chosen based on the requirements of the project.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.51578496 and 51878603)the Zhejiang Provincial Natural Science Foundation of China(No.LZ16E080001)。
文摘To accurately control the full-span erection of continuous steel box girder bridges with complex cross-sections and long cantilevers, both the augmented finite element method(A-FEM) and the degenerated plate elements are adopted in this paper. The entire construction process is simulated by the A-FEM with the mesh-separation-based approximation technique, while the degenerated plate elements are constructed based on 3D isoparametric elements, making it suitable for analysis of a thin-walled structure. This method significantly improves computational efficiency by avoiding numerous degrees of freedom(DoFs) when analyzing complex structures. With characteristics of the full-span erection technology, the end-face angle of adjacent girder segments, the preset distance of girder segments from the design position, and the temperature difference are selected as control parameters, and they are calculated through the structural response of each construction stage. Engineering practice shows that the calculation accuracy of A-FEM is verified by field-measured results. It can be applied rapidly and effectively to evaluate the matching state of girder segments and the stress state of bearings as well as the thermal effect during full-span erection.
文摘In this paper, the interaction parameters in the subregular solution model, λ1 and λ2, are regarded as a linear function of temperature, T. Therefore, the molar excess Gibbs energy of A-B binary system may be reexpressed as follows:Gm^E=xAxB[(λ11+λ12T)+(λ21+λ22T)xB]The calculation of the model parameters, λ11, λ12, λ21and λ22, was carried out numerically from the phase diagrams for 11 alkali metal-alkali halide or alkali earth metal-halide systems. In addition, artificial neural network trained by known data has been used to predict the values of these model parameters. The predicted results are in good agreement with the .calculated ones. The applicability of the subregular solution model to the alkali metal-alkali halide or alkali earth metal-halide systems were tested by comparing the available experimental composition along the boundary of miscibility gap with the calculated ones which were obtained by using genetic algorithm. The good agreement between the calculated and experimental results across the entire liquidus is valid evidence in support of the model.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 52074246, 52275390, 52205429, and 52201146)the National Defense Basic Scientific Research Program of China (Grant Nos. JCKY2020408B002 and WDZC2022-12)+1 种基金the Science and Technology Major Project of Shanxi Province, China (Grant Nos. 20191102008 and 20191102007)the Guiding Local Science and Technology Development Projects by the Central Government, China (Grant Nos. YDZJSX2022A025 and YDZJSX2021A027)。
文摘Parameter calculation and result storage, as two necessary steps in phase-field simulation play an important role in ensuring the accuracy of simulation results. A strategy of parameter calculation and result storage is presented for phase-field simulation in α-Mg dendrite growth of Mg-5-wt% Zn alloy under isothermal solidification. Based on the phase diagram and empirical formulas, key parameters of the phase-field model, such as equilibrium partition coefficient k, liquidus slope m, solutal diffusion coefficient in liquid Dl, and solutal diffusion coefficient in solid Ds, can be obtained.Both structured grid method and structured point method can be used to store simulation results, but using the latter method will reduce about 60% storage space and 37.5% storage time compared with the former. Finally, convergent simulation results of α-Mg dendrite growth are obtained and they are in good agreement with the experimental results about optical micrograph, which verify the accuracy of parameters and stability of storage method.
基金supported by State Grid Information and Telecommunication Group Scientific and Technological Innovation Project“Research on Power Digital Space Technology System and Key Technologies”(Program No.SGIT0000XMJS2310456).
文摘By integrating advanced digital technologies such as cloud computing and the Internet of Things in sensor measurement,information communication,and other fields,the digital DC distribution network can efficiently and reliably access DistributedGenerator(DG)and Energy Storage Systems(ESS),exhibiting significant advantages in terms of controllability and meeting requirements of Plug-and-Play(PnP)operations.However,during device plug-in and-out processes,improper systemparametersmay lead to small-signal stability issues.Therefore,before executing PnP operations,conducting stability analysis and adjusting parameters swiftly is crucial.This study introduces a four-stage strategy for parameter optimization to enhance systemstability efficiently.In the first stage,state-of-the-art technologies in measurement and communication are utilized to correct model parameters.Then,a novel indicator is adopted to identify the key parameters that influence stability in the second stage.Moreover,in the third stage,a local-parameter-tuning strategy,which leverages rapid parameter boundary calculations as a more efficient alternative to plotting root loci,is used to tune the selected parameters.Considering that the local-parameter-tuning strategy may fail due to some operating parameters being limited in adjustment,a multiparameter-tuning strategy based on the particle swarm optimization(PSO)is proposed to comprehensively adjust the dominant parameters to improve the stability margin of the system.Lastly,system stability is reassessed in the fourth stage.The proposed parameter-optimization strategy’s effectiveness has been validated through eigenvalue analysis and nonlinear time-domain simulations.
基金supported by the National Natural Science Foundation of China(Nos.52304046,52204051,52174033 and U23B20156).
文摘In the context of the global“Carbon Peaking and Carbon Neutrality”initiative,the injection of carbon dioxide(CO_(2))into depleted gas reservoirs represents a dual-purpose strategy—facilitating long-term carbon sequestration while enhancing hydrocarbon recovery.However,variations in injection parameters at the wellhead can exert pronounced effects on the temperature and pressure conditions at the bottomof the well.These variations,in turn,influence the geomechanical behavior of reservoir rocks and the displacement efficiency of CO_(2) within the formation.Precise prediction of downhole thermodynamic conditions is therefore essential for optimizing injection performance and ensuring reservoir stability.To address this need,the present study develops a robust coupled model to simulate the behavior of CO_(2) within the wellbore,incorporating momentum conservation,mass continuity,and steady-state heat transfer equations.Validation against field-measured data confirms the model’s reliability and applicability under realworld operating conditions.Parametric analysis reveals the complex influence of injection conditions on bottom-hole states.Injection pressure primarily affects downhole pressure,exerting minimal influence on temperature.In contrast,low injection temperatures and elevated flow rates lead to reduced bottom-hole temperatures and heightened pressures.Owing to the interplay of convective and conductive heat transfer mechanisms,the relationship between injection rate and bottom-hole temperature exhibits nonlinearity.Notably,injection scenarios characterized by low temperature,high pressure,and high velocity promote a deeper penetration of the CO_(2) critical phase transition point within the tubing.Among the parameters examined,injection temperature emerges as the dominant factor affecting the depth of CO_(2)’s phase transformation,followed by injection rate,with pressure exerting the least influence.A strong correlation is observed between injection rate and the depth of the critical phase transition,offering a practical framework for tailoring injection strategies to enhance both CO_(2) storage capacity and recovery efficiency.
基金National Natural Science Foundation of China,Grant/Award Number:52307164Heilongjiang Provincial Natural Science Foundation of China,Grant/Award Number:YQ2024E044。
文摘As an important component of oil-immersed transformers,the bushing's internal insu-lation ageing and dampness after the long-term operation can cause changes in the in-ternal electric and temperature fields,seriously threatening its safe operation.This paper tested the power frequency permittivity and direct current conductivity of aged and damp oil-paper insulation samples at different testing temperatures,and constructed a dynamic dielectric parameter calculation model.Meanwhile,a simulation model was established based on the actual structure of the 252 kV/1250 A bushing which is mainly used for the oil-immersed high-voltage bushings of 110 kV and above.The electric-magnetic-thermal multi-physical fields were used for simulation analysis.The influence of ageing/moisture(different degrees of dampness in the upper and lower regions)on the electric field distribution in the bushing was obtained.During the initial to steady-state process,the electric field distribution at the zero and end shield shows a reversal phenomenon.When the capacitor core has different degrees of dampness in the upper and lower regions,the impedance distribution of the capacitor core is non-uniform.This phenomenon will lead to an increase in the radial electric field gradient at the end shield of the capacitor core,which is prone to the risk of slip-flashing discharge.In summary,this paper adopts the field-induced dynamic parameters method to analyse the changes of multi-physical fields in the bushing.This can provide theoretical guidance for optimising the bushing structure and on-site maintenance.
基金Project supported by the National Natural Science Foundation of China (Nos.50579010, 50539010)the National Basic Research Program of China (973 Program) (No.2002CB412707)the National Basic Research Program of Ministry of Water Resources, China (No.CT200612)
文摘The effect zones of layer face for RCC （rolled control concrete） dam have gradual change characteristics. Based on the analysis thought of complex material, a model was built to analyze above principle of RCC dam by use of series-wound and shunt-wound connection. Some methods were proposed to determine the instantaneous Young＇s modulus, delayed Young＇s modulus and viscosity coefficient of effect zones of layer face. Above models and methods were used to mine the principle of gradual change of key calculation parameters which can response the characteristics of effect zones. The principle of gradual change was described. A model was established to analyze the threedimensional viscoelastic problem of RCC dam. Above programs were developed. The examples show that the proposed models and methods to determine the key calculation parameters of effect zones can reflect the status of RCC dam accurately.
基金financially supported by the doctoral fund of the Ministry of Education of Chinathe Nature Science Foundation of Jiangsu Province, China (Grant Nos. 20130091110020 and BE2015675)
文摘A deep foundation pit constructed for an underground transportation hub was excavated near the Yangtze River. Among the strata, there are two confined aquifers, between which lies an aquiclude that is partially missing. To guarantee the safety of pit excavation, the piezometric head of the upper confined aquifer, where the pit bottom is located, should be 1 m below the pit bottom, while that of the lower confined aquifer should be dewatered down to a safe water level to avoid uplift problem. The Yangtze River levee is notably close to the pit, and its deformation caused by dewatering should be controlled. A pumping test was performed to obtain the hydraulic conductivity of the upper confined aquifer. The average value of the hydraulic conductivity obtained from analytical calculation is 20.45 m/d, which is larger than the values from numerical simulation（horizontal hydraulic conductivity K_H = 16 m/d and vertical hydraulic conductivity K_V = S m/d）. The difference between K_H and K_V indicates the anisotropy of the aquifer. Two dewatering schemes were designed for the construction and simulated by the numerical models for comparison purposes. The results show that though the first scheme could meet the dewatering requirements, the largest accumulated settlement and differential settlement would be94.64 mm and 3.3‰, respectively, greatly exceeding the limited values. Meanwhile, the second scheme,in which the bottoms of the waterproof curtains in ramp B and the river side of ramp A are installed at a deeper elevation of-28 m above sea level, and 27 recharge wells are set along the levee, can control the deformation of the levee significantly.
基金supported by the National Key R&D Program of China,Grant No.2018YFA0306703 and J2019-V-0001-0092.
文摘Estimating the intention of space objects plays an important role in air-craft design,aviation safety,military and otherfields,and is an important refer-ence basis for air situation analysis and command decision-making.This paper studies an intention estimation method based on fuzzy theory,combining prob-ability to calculate the intention between two objects.This method takes a space object as the origin of coordinates,observes the target’s distance,speed,relative heading angle,altitude difference,steering trend and etc.,then introduces the spe-cific calculation methods of these parameters.Through calculation,values are input into the fuzzy inference model,andfinally the action intention of the target is obtained through the fuzzy rule table and historical weighted probability.Ver-ified by simulation experiment,the target intention inferred by this method is roughly the same as the actual behavior of the target,which proves that the meth-od for identifying the target intention is effective.
文摘This paper calculates the parameters of image position and orientation,proposes a mathematical model and adopts a new method with three steps of transformations based on parallel ray projection.Every step of the model is strict,and the map function of each transformation is the first order polynomials and other simple function.The final calculation of the parameters is for the linear equations with good status.As a result,the problem of the relativity of image parameter calculation is solved completely.Some experiments are carried out.
基金supported by the National Natural Science Foundation of China(No.81903520)the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(No.2019QZKK0502)
文摘Nineteen preschisanartane-type schinortriterpenoids(SNTs),among which eleven ones were previously undescribed,were isolated from two Schisandra species,S.sphaerandra and S.rubriflora.Their structures were determined using 1 D and 2 D NMR spectroscopic analyses,NMR data comparison,quantum chemical calculation of NMR parameters,electronic circular dichroism(ECD),X-ray single crystal diffraction,and chemical derivation.Furthermore,structural re-examination of a few previously reported preschisanartane-type SNTs led to the structural revision of preschisanartanin J.Besides,it is suggested that the reported structures of arisanlactone D and schilancidilactone W should be re-checked.Finally,a few isolated SNTs were found to possess neurite outgrowthpromoting activities,and protective activities against neural injuries.
基金Russian Scientific Foundation for financial support of the investigations by the project#14-17-00791.
文摘Uncertainties in modern assessments of the impact of long-term climatic variations on the characteristics of groundwater discharge and groundwater resources are considered.The authors show that when assessing groundwater resources and especially forecasting groundwater resources,the main calculated hydrogeological parameters are insufficiently reliable and estimates of possible changes of main meteorological characteristics should be considered.Therefore,it is currently almost impossible to forecast the impacts of climate change on groundwater resources and regime for the coming decades.A scenario-based approach is the most promising for studying the potential effects of climate change on groundwater.
基金This paper was supported by Educational Reform Project of Zijin College,Nanjing University of Science and Technology(No.20200101002)。
文摘With the development of aviation industry,civil aviation has become an indispensable part.Our team will take all the structural dimensions,loads and material parameters in the wing beam structure as the specific values determined during the structural design to conduct deflection analysis on the wing beam structure of A380 passenger plane.According to the deflection and parameters analyzed,the stress distribution and maximum stress position on the wing beam can be known.Through the analysis of the wing parameters,the finite element analysis of the wing beam,the mesh sensitivity analysis,and the analysis of the wing tip deflection,the relevant safety factors of the aircraft are obtained.The results show that the wing of airbus A380 is more reliable and safer through the calculation of deflection,stress and safety factor.
基金supported by the National Major Science and Technology Project“Key technologies for effective development of large,very thick and heterogeneous gas reservoirs in the East China Sea”(No.:2016ZX05027-004)Joint Science and Technology Research Project with CNOOC China Limited“Key issues research on reserves producing of typical gas fields in the East China Sea”(No.:YXKY-2017-ZY-13).
文摘In order to reveal the reasons for the differences in initial water production characteristics of gas wells in different regions of the East China Sea Basin and to screen favorable targets for low-permeability reservoir reconstruction,a calculation method of initial production wateregas ratios at different gas column heights was established by combining gas-water two-phase capillary pressure with J function definition,power function relative permeability model and fractional flow equation.Then based on the experimental data of standard capillary pressure and standard relative permeability in the gas province of the East China Sea,an evaluation chart on initial production wateregas ratio of the East China Sea at different gas column heights was calculated and established.Finally,the evaluation chart was validated by using the data of the tested or commissioned gas wells in the gas reservoirs of the East China Sea,and the physical property conditions suitable for reservoir reconstruction of low-permeability gas reservoirs in the East China Sea were determined according to the evaluation chart.The following research results were obtained.First,the evaluation chart established in this paper reflects that the correlation between the parameters is similar to the actual production law and matches well with the actual data,which verifies the correctness and reliability of the chart establishment method and the key parameter calculation method.Second,with the production wateregas ratio less than 1 m3/104 m3 as the screening condition,for the permeability of the low-permeability gas reservoirs(with gas column height of about 50 m)in the west sub-sag,the central uplift belt and the periphery suitable for reservoir reconstruction shall be greater than 0.65 mD,and that of the large low-permeability gas reservoirs(with a gas column height of more than 100 m)in the north of central uplift belt shall be greater than 0.26 mD.Third,there is no gasewater contact in gas reservoirs under the hydrocarbon accumulation conditions of in-situ reservoirs,so the method and the evaluation chart proposed in this paper are not applicable.It is concluded that the method of establishing the initial water production evaluation chart and the method of calculating the key parameters proposed in this paper can provide meaningful reference for the development and evaluation of other gas fields in China.
文摘This article aims to discuss the design process of the CAD system dedicated for sport bike frame structure, introducing in detail its design concept and the scheme of implementation. Based on the different usages of sport bikes and the requirements on the system made out by Beijing Hanglun Sport Apparatus Company Limited. Structural analysis on two types of bikes frames is carried out. The system defines the basic design parameters and analyses the constraint conditions.Then calculating formulas with constraint conditions are derived. The system solves equations with Visual C++ program, realizes input of the original data and output of the results through interactive system. With AutoCAD14.0 as the platform, the system uses VC++ and ObjectARX to realize auto output of bike frame graphics. The system has been put into use. Practice has affirmed that the system抯 convenience, applicability and reliability all have reached the expected goal.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50977028,51077048)
文摘In some control strategies of the direct-rive permanent magnet generator(DDPMG),the mathematics model is excessively simplified and some complex nonlinear characteristics,such as core saturation and cross-saturation,are generally neglected.To solve this problem,this paper utilizes the frozen element permeability method to compute the armature self-and mutual-inductance,permanent magnet d-and q-axis flux varying with d-axis and q-axis current,then an improved model is presented in which the core saturation and cross-saturation between d-axis and q-axis are considered effectively.Based on this model,the method for computing the performance of the generators is also proposed.Taking a 1.5-MW DDPMG as an example,the time-stepping finite element method(T-S FEM) is adopted to analyze the performance with no-load and loaded conditions,the results show a good agreement with the ones obtained by the improved model.Compared with the simplified model,it is demonstrated that the presented model has the high efficiency and reliability and can provide a good reference for optimization design of DDPMG and other PM motors.
基金supported by the National Key R&D Project“Research on key technologies for environmental protection and energy saving of industrial buildings with high pollution emission”(No.2018YFC0705300)the National Natural Science Foundation of China Youth Fund Project“Fast reverse identification of indoor multiple gaseous pollutant sources”(No.51708084)+1 种基金the joint research project of the Wind Engineering Research Center,Tokyo Polytechnic University(MEXT(Japan)Promotion of Distinctive Joint Research Center Program grant number:JPMXP0619217840,JURC grant number:192013).
文摘Computational fluid dynamics(CFD)methods are being increasingly used for predicting airflow fields around buildings,but personal computers can still take tens of hours to create a single design using traditional computing models.Considering both accuracy and efficiency,this study compared the performances of the conventional algorithm PIMPLE,fast fluid dynamics(FFD),semi-Lagrangian PISO(SLPISO),and implicit fast fluid dynamics(IFFD)in OpenFOAM for simulating wind flow around buildings.The effects of calculation parameters,including grid resolution,discrete-time step,and calculation time for these methods are analyzed.The results of the simulations are compared with wind tunnel tests.It is found that IFFD and FFD have the fastest calculation speeds,but also have the largest discrepancies with test data.The PIMPLE algorithm has the highest accuracy,but with the slowest calculation speed.The calculation speeds of the FFD,SLPISO,and IFFD models are 6.3,3 and 13.3 times faster than the PIMPLE model,respectively.The calculation accuracy and speed of the SLPISO model are in between those of the IFFD,FFD and PIMPLE models.An appropriate algorithm for a project may be chosen based on the requirements of the project.
