A novel method for synthesis of substituted u-oxo-bis[tetraphenyl porphyrinatoiron] compotmds （[TRPPFe]20） based on the reaction among free base porphyrins （TRPPH2）, FeSO4·7H2O and H2O in one pot was proposed...A novel method for synthesis of substituted u-oxo-bis[tetraphenyl porphyrinatoiron] compotmds （[TRPPFe]20） based on the reaction among free base porphyrins （TRPPH2）, FeSO4·7H2O and H2O in one pot was proposed and investigated. Four kinds of [TRPPFe]2O were synthesized by this novel synthetic method, and their structures were characterized by elemental analysis, infrared spectra and UV-vis spectroscopy. The reaction conditions, including the effect of different iron salts on the formation of [TRPPFe]2O, the reaction time between FeSO4-7H2O and TRPPH2, the molar ratio of FeSO4-7H2O/TRPPH2 as well as the volume ratio of H2O/DMF, were investigated. The [TRPPFe]2O yield of 93% 98% could be obtained under the following optimal conditions： the reaction time of FeSOn-7H2O with TRPPH2 was about 10 h, the molar ratio of FeSOn-7H2O/TRPPH2 about 5 ： 1, and the volume ratio of H2O/DMF exceeded 2 ： 1. Further research indicated that only TRPPFeCI were formed once FeSOn-7H2O was replaced by FeCl2-4H2O, the reason of which might be that halogen ions in iron salts interfered the formation of [TRPPFe]2O, suggesting that halogen ions should be avoided in this novel synthetic method.展开更多
The highly-dispersed iron element decorated Ni foam was prepared by simple immersion in a ferric nitrate solution at room temperature without using acid etching, and characterized by X-ray powder diffraction(XRD), sca...The highly-dispersed iron element decorated Ni foam was prepared by simple immersion in a ferric nitrate solution at room temperature without using acid etching, and characterized by X-ray powder diffraction(XRD), scanning electron microscopy(SEM), EDAX spectrum(EDAX mapping) and Raman spectroscopy. The EDAX spectrum illustrated that iron element was highly-dispersed over the entire surface of nickel foam, and the Raman spectroscopy revealed that both Ni-O and Fe-O bonds were formed on the surface of the as-prepared electrode. Moreover, the iron element decorated Ni foam electrode can be used as non-enzymatic glucose sensor and it exhibits not only an ultra-wide linear concentration range of 1-18 mmol/L with an outstanding sensitivity of 1.0388 m A·mmol/(L·cm2), but also an excellent ability of stability and selectivity. Therefore, this work presents a simple yet effective approach to successfully modify Ni foam as non-enzymatic glucose sensor.展开更多
A mild, one-pot procedure for the synthesis of vinyl ethers in good yields from 2-hydroxyalkyl phenyl selenides with primary or secondary organic halides has been developed.
Three new multi-step one-pot processes for high-yielding cyclohexanecarbonitrile synthesis starting from cyclohexanone were developed for industrial application. In contrast to the current synthetic process, all of th...Three new multi-step one-pot processes for high-yielding cyclohexanecarbonitrile synthesis starting from cyclohexanone were developed for industrial application. In contrast to the current synthetic process, all of the processes described were designed to proceed completely in methanol as a uniform solvent and the key oxidation step can be realized either as stoichiometric or catalytic. Atom efficiency of processes is relatively advanced with high regioselectivity, reaction by-products are either from environmental pool—carbon dioxide and nitrogen—or they can be reused—sodium chloride. Solvent—methanol—and other auxiliaries—cyclohexane, copper catalyst—can be reused after recycling as well. EcoScale for all three designed processes was evaluated and compared with current synthesis described in the past. Green chemistry metrics, including newly introduced evaluative tool—Sustainability Index of the Synthesis (SIS), were applied to evaluate design of described one-pot syntheses.展开更多
Nitrogen oxide(NO_(x))is one of the most critical contaminants in the air,and the control of NO_(x)emission from diesel vehicles is very important.Cu-based small-pore zeolites have already been applied for NO_(x)abate...Nitrogen oxide(NO_(x))is one of the most critical contaminants in the air,and the control of NO_(x)emission from diesel vehicles is very important.Cu-based small-pore zeolites have already been applied for NO_(x)abatement on diesel vehicles.Among the small-pore zeolites,Cu-SSZ-50 catalysts with good NH_(3)-SCR catalytic activity were believed to have potential for application.In this study,a one-pot synthesis method for Cu-SSZ-50 catalysts was developed for the first time,using the co-templates of Cu-TEPA and 2,6-dimethyl-N-methylpyridinium hydroxide.In this synthesis method,Cu-SSZ-50 with various Cu contents can be obtained by adjusting the amount of Cu-TEPA without the need for a further after-treatment process.The addition of Cu-TEPA affected the framework atoms and Cu species,and a lower Si/Al ratio and more SCR active Cu species were obtained.The synthesized catalyst with a Cu/Al ratio of 0.40 exhibited over 90%NO_(x)conversion between 200℃and 450℃for the selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR).Meanwhile,over 80%NO_(x)conversion could be obtained from 250℃to 450℃after hydrothermal aging at 750℃for 16 h.In addition,both L-H and E-R mechanisms were proven to exist for the one-pot-synthesized Cu-SSZ-50 by in situ DRIFTS experiments.The simple synthesis procedure,excellent catalytic activity and hydrothermal stability brighten the prospects for the application of Cu-SSZ-50.展开更多
The separation-of-variable(SOV)methods,such as the improved SOV method,the variational SOV method,and the extended SOV method,have been proposed by the present authors and coworkers to obtain the closed-form analytica...The separation-of-variable(SOV)methods,such as the improved SOV method,the variational SOV method,and the extended SOV method,have been proposed by the present authors and coworkers to obtain the closed-form analytical solutions for free vibration and eigenbuckling of rectangular plates and circular cylindrical shells.By taking the free vibration of rectangular thin plates as an example,this work presents the theoretical framework of the SOV methods in an instructive way,and the bisection–based solution procedures for a group of nonlinear eigenvalue equations.Besides,the explicit equations of nodal lines of the SOV methods are presented,and the relations of nodal line patterns and frequency orders are investigated.It is concluded that the highly accurate SOV methods have the same accuracy for all frequencies,the mode shapes about repeated frequencies can also be precisely captured,and the SOV methods do not have the problem of missing roots as well.展开更多
This study aims to develop a chloride diffusion simulation method that considers the hydration microstructure and pore solution properties during the hydration of tricalcium silicate(C3S).The method combines the hydra...This study aims to develop a chloride diffusion simulation method that considers the hydration microstructure and pore solution properties during the hydration of tricalcium silicate(C3S).The method combines the hydration simulation,thermodynamic calculation,and finite element analysis to examine the effects of pore solution,including effect of electrochemical potential,effect of chemical activity,and effect of mechanical interactions between ions,on the chloride effective diffusion coefficient of hydrated C3S paste.The results indicate that the effect of electrochemical potential on chloride diffusion becomes stronger with increasing hydration age due to the increase in the content of hydrated calcium silicate;as the hydration age increases,the effect of chemical activity on chloride diffusion weakens when the number of diffusible elements decreases;the effect of mechanical interactions between ions on chloride diffusion decreases with the increase of hydration age.展开更多
To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fract...To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fractures,this study considered the combined impact of geological-engineering factors on conductivity.Using reservoir production parameters and the discrete elementmethod,multispherical proppants were constructed.Additionally,a 3D fracture model,based on the specified conditions of the L block,employed coupled(Computational Fluid Dynamics)CFD-DEM(Discrete ElementMethod)for joint simulations to quantitatively analyze the transport and placement patterns of multispherical proppants in intersecting fractures.Results indicate that turbulent kinetic energy is an intrinsic factor affecting proppant transport.Moreover,the efficiency of placement and migration distance of low-sphericity quartz sand constructed by the DEM in the main fracture are significantly reduced compared to spherical ceramic proppants,with a 27.7%decrease in the volume fraction of the fracture surface,subsequently affecting the placement concentration and damaging fracture conductivity.Compared to small-angle fractures,controlling artificial and natural fractures to expand at angles of 45°to 60°increases the effective support length by approximately 20.6%.During hydraulic fracturing of gas wells,ensuring the fracture support area and post-closure conductivity can be achieved by controlling the sphericity of proppants and adjusting the perforation direction to control the direction of artificial fractures.展开更多
In the independent electro-hydrogen system(IEHS)with hybrid energy storage(HESS),achieving optimal scheduling is crucial.Still,it presents a challenge due to the significant deviations in values ofmultiple optimizatio...In the independent electro-hydrogen system(IEHS)with hybrid energy storage(HESS),achieving optimal scheduling is crucial.Still,it presents a challenge due to the significant deviations in values ofmultiple optimization objective functions caused by their physical dimensions.These deviations seriously affect the scheduling process.A novel standardization fusion method has been established to address this issue by analyzing the variation process of each objective function’s values.The optimal scheduling results of IEHS with HESS indicate that the economy and overall energy loss can be improved 2–3 times under different optimization methods.The proposed method better balances all optimization objective functions and reduces the impact of their dimensionality.When the cost of BESS decreases by approximately 30%,its participation deepens by about 1 time.Moreover,if the price of the electrolyzer is less than 15¥/kWh or if the cost of the fuel cell drops below 4¥/kWh,their participation will increase substantially.This study aims to provide a more reasonable approach to solving multi-objective optimization problems.展开更多
Understanding the wind power potential of a site is essential for designing an optimal wind power conditioning system. The Weibull distribution and wind speed extrapolation methods are powerful mathematical tools for ...Understanding the wind power potential of a site is essential for designing an optimal wind power conditioning system. The Weibull distribution and wind speed extrapolation methods are powerful mathematical tools for efficiently predicting the frequency distribution of wind speeds at a site. Hourly wind speed and direction data were collected from the National Aeronautics and Space Administration (NASA) website for the period 2013 to 2023. MATLAB software was used to calculate the distribution parameters using the graphical method and to plot the corresponding curves, while WRPLOTView software was used to construct the wind rose. The average wind speed obtained is 3.33 m/s and can reach up to 5.71 m/s at a height of 100 meters. The wind energy is estimated to be 1315.30 kWh/m2 at a height of 100 meters. The wind rose indicates the prevailing winds (ranging from 3.60 m/s to 5.70 m/s) in the northeast-east direction.展开更多
Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the structure.Therefore,it is particularly significant to identify the structural modal parameters accordi...Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the structure.Therefore,it is particularly significant to identify the structural modal parameters according to the monitoring data information in the structural health monitoring(SHM)system,so as to provide a scientific basis for structural damage identification and dynamic model modification.In view of this,this paper reviews methods for identifying structural modal parameters under environmental excitation and briefly describes how to identify structural damages based on the derived modal parameters.The paper primarily introduces data-driven modal parameter recognition methods(e.g.,time-domain,frequency-domain,and time-frequency-domain methods,etc.),briefly describes damage identification methods based on the variations of modal parameters(e.g.,natural frequency,modal shapes,and curvature modal shapes,etc.)and modal validation methods(e.g.,Stability Diagram and Modal Assurance Criterion,etc.).The current status of the application of artificial intelligence(AI)methods in the direction of modal parameter recognition and damage identification is further discussed.Based on the pre-vious analysis,the main development trends of structural modal parameter recognition and damage identification methods are given to provide scientific references for the optimized design and functional upgrading of SHM systems.展开更多
The prediction of the fracture plane orientation in fatigue is a scientific topic and remains relevant for every type of material. However, in this work, we compared the orientation of the fracture plane obtained expe...The prediction of the fracture plane orientation in fatigue is a scientific topic and remains relevant for every type of material. However, in this work, we compared the orientation of the fracture plane obtained experimentally through tests on specimens under multiaxial loading with that calculated by the variance method. In the statistical approach criteria, several methods have been developed but we have presented only one method, namely the variance method using the equivalent stress. She assumes that the fracture plane orientation is the one on which the variance of the equivalent stress is maximum. Three types of equivalent stress are defined for this method [1]: normal stress, shear stress and combined normal and shear stress. The results obtained were compared with experimental results for multiaxial cyclic stress states, and it emerges that the variance method for the case of combined loading is conservative as it gives a better prediction of the fracture plane.展开更多
To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based sim...To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based simulation(NNS)method with higher accuracy and better efficiency was proposed.The NNS method consisted of three main steps.First,the parameters of blast loads,including the peak pressures and impulses of cylindrical charges with different aspect ratios(L/D)at different stand-off distances and incident angles were obtained by two-dimensional numerical simulations.Subsequently,incident shape factors of cylindrical charges with arbitrary aspect ratios were predicted by a neural network.Finally,reflected shape factors were derived and implemented into the subroutine of the ABAQUS code to modify the CONWEP model,including modifications of impulse and overpressure.The reliability of the proposed NNS method was verified by related experimental results.Remarkable accuracy improvement was acquired by the proposed NNS method compared with the unmodified CONWEP model.Moreover,huge efficiency superiority was obtained by the proposed NNS method compared with the CEL method.The proposed NNS method showed good accuracy when the scaled distance was greater than 0.2 m/kg^(1/3).It should be noted that there is no need to generate a new dataset again since the blast loads satisfy the similarity law,and the proposed NNS method can be directly used to simulate the blast loads generated by different cylindrical charges.The proposed NNS method with high efficiency and accuracy can be used as an effective method to analyze the dynamic response of structures under blast loads,and it has significant application prospects in designing protective structures.展开更多
Fractional-order time-delay differential equations can describe many complex physical phenomena with memory or delay effects, which are widely used in the fields of cell biology, control systems, signal processing, et...Fractional-order time-delay differential equations can describe many complex physical phenomena with memory or delay effects, which are widely used in the fields of cell biology, control systems, signal processing, etc. Therefore, it is of great significance to study fractional-order time-delay differential equations. In this paper, we discuss a finite volume element method for a class of fractional-order neutral time-delay differential equations. By introducing an intermediate variable, the fourth-order problem is transformed into a system of equations consisting of two second-order partial differential equations. The L1 formula is used to approximate the time fractional order derivative terms, and the finite volume element method is used in space. A fully discrete format of the equations is established, and we prove the existence, uniqueness, convergence and stability of the solution. Finally, the validity of the format is verified by numerical examples.展开更多
Bearing is an indispensable key component in mechanical equipment,and its working state is directly related to the stability and safety of the whole equipment.In recent years,with the rapid development of artificial i...Bearing is an indispensable key component in mechanical equipment,and its working state is directly related to the stability and safety of the whole equipment.In recent years,with the rapid development of artificial intelligence technology,especially the breakthrough of deep learning technology,it provides a new idea for bearing fault diagnosis.Deep learning can automatically learn features from a large amount of data,has a strong nonlinear modeling ability,and can effectively solve the problems existing in traditional methods.Aiming at the key problems in bearing fault diagnosis,this paper studies the fault diagnosis method based on deep learning,which not only provides a new solution for bearing fault diagnosis but also provides a reference for the application of deep learning in other mechanical fault diagnosis fields.展开更多
Accurate acquisition and prediction of acoustic parameters of seabed sediments are crucial in marine sound propagation research.While the relationship between sound velocity and physical properties of sediment has bee...Accurate acquisition and prediction of acoustic parameters of seabed sediments are crucial in marine sound propagation research.While the relationship between sound velocity and physical properties of sediment has been extensively studied,there is still no consensus on the correlation between acoustic attenuation coefficient and sediment physical properties.Predicting the acoustic attenuation coefficient remains a challenging issue in sedimentary acoustic research.In this study,we propose a prediction method for the acoustic attenuation coefficient using machine learning algorithms,specifically the random forest(RF),support vector machine(SVR),and convolutional neural network(CNN)algorithms.We utilized the acoustic attenuation coefficient and sediment particle size data from 52 stations as training parameters,with the particle size parameters as the input feature matrix,and measured acoustic attenuation as the training label to validate the attenuation prediction model.Our results indicate that the error of the attenuation prediction model is small.Among the three models,the RF model exhibited the lowest prediction error,with a mean squared error of 0.8232,mean absolute error of 0.6613,and root mean squared error of 0.9073.Additionally,when we applied the models to predict the data collected at different times in the same region,we found that the models developed in this study also demonstrated a certain level of reliability in real prediction scenarios.Our approach demonstrates that constructing a sediment acoustic characteristics model based on machine learning is feasible to a certain extent and offers a novel perspective for studying sediment acoustic properties.展开更多
In this article, a finite volume element algorithm is presented and discussed for the numerical solutions of a time-fractional nonlinear fourth-order diffusion equation with time delay. By choosing the second-order sp...In this article, a finite volume element algorithm is presented and discussed for the numerical solutions of a time-fractional nonlinear fourth-order diffusion equation with time delay. By choosing the second-order spatial derivative of the original unknown as an additional variable, the fourth-order problem is transformed into a second-order system. Then the fully discrete finite volume element scheme is formulated by using L1approximation for temporal Caputo derivative and finite volume element method in spatial direction. The unique solvability and stable result of the proposed scheme are proved. A priori estimate of L2-norm with optimal order of convergence O(h2+τ2−α)where τand hare time step length and space mesh parameter, respectively, is obtained. The efficiency of the scheme is supported by some numerical experiments.展开更多
As a key sector in advancing China’s“carbon neutrality”goal,the machinery manufacturing industry has achieved remarkable development in recent years.Against this backdrop,the scientific and objective evaluation of ...As a key sector in advancing China’s“carbon neutrality”goal,the machinery manufacturing industry has achieved remarkable development in recent years.Against this backdrop,the scientific and objective evaluation of the financial performance of machinery manufacturing enterprises has become a pressing issue in financial research.This topic is not only crucial for optimizing enterprise management and improving operational efficiency but also essential for enhancing overall industry performance and promoting sustainable development.This paper first introduces the concept of financial performance,followed by an analysis of related financial performance evaluation theories.It then focuses on the application of the entropy method in evaluating the financial performance of machinery manufacturing enterprises,detailing its analytical steps.Finally,a financial performance evaluation index system is constructed based on four dimensions:profitability,solvency,operational efficiency,and growth potential.展开更多
BACKGROUND Gastric ulcer perforation is a critical condition that can lead to significant morbidity and mortality if not promptly addressed.It is often the result of chronic peptic ulcer disease,which is characterized...BACKGROUND Gastric ulcer perforation is a critical condition that can lead to significant morbidity and mortality if not promptly addressed.It is often the result of chronic peptic ulcer disease,which is characterized by a breach in the gastric wall due to ulceration.Surgical intervention is essential for managing this life-threatening complication.However,the optimal surgical technique remains debatable among clinicians.Various methods have been employed,including simple closure,omental patch repair,and partial gastrectomy,each with distinct advantages and disadvantages.Understanding the comparative efficacy and postoperative outcomes of these techniques is crucial for improving patient care and surgical decision-making.This study addresses the need for a comprehensive analysis in this area.AIM To compare the efficacy and postoperative complications of different surgical methods for the treatment of gastric ulcer perforation.METHODS A retrospective analysis was conducted on 120 patients who underwent surgery for gastric ulcer perforation between September 2020 and June 2023.The patients were divided into three groups based on the surgical method:Simple closure,omental patch repair,and partial gastrectomy.The primary outcomes were the operative success rate and incidence of postoperative complications.Secondary outcomes included the length of hospital stay,recovery time,and long-term quality of life.RESULTS The operative success rates for simple closure,omental patch repair,and partial gastrectomy were 92.5%,95%,and 97.5%,respectively.Postoperative complications occurred in 20%,15%,and 17.5%of patients in each group,respectively.The partial gastrectomy group showed a significantly longer operative time(P<0.001)but the lowest rate of ulcer recurrence(2.5%,P<0.05).The omental patch repair group demonstrated the shortest hospital stay(mean 7.2 days,P<0.05)and fastest recovery time.CONCLUSION While all three surgical methods showed high success rates,omental patch repair demonstrated the best overall outcomes,with a balance of high efficacy,low complication rates,and shorter recovery time.However,the choice of the surgical method should be tailored to individual patient factors and the surgeon’s expertise.展开更多
基金Supported by the National Natural Science Foundation of China （20776003, 20576005） and the Key Project of Natural Science Foundation of Beijing （2061001）.
文摘A novel method for synthesis of substituted u-oxo-bis[tetraphenyl porphyrinatoiron] compotmds （[TRPPFe]20） based on the reaction among free base porphyrins （TRPPH2）, FeSO4·7H2O and H2O in one pot was proposed and investigated. Four kinds of [TRPPFe]2O were synthesized by this novel synthetic method, and their structures were characterized by elemental analysis, infrared spectra and UV-vis spectroscopy. The reaction conditions, including the effect of different iron salts on the formation of [TRPPFe]2O, the reaction time between FeSO4-7H2O and TRPPH2, the molar ratio of FeSO4-7H2O/TRPPH2 as well as the volume ratio of H2O/DMF, were investigated. The [TRPPFe]2O yield of 93% 98% could be obtained under the following optimal conditions： the reaction time of FeSOn-7H2O with TRPPH2 was about 10 h, the molar ratio of FeSOn-7H2O/TRPPH2 about 5 ： 1, and the volume ratio of H2O/DMF exceeded 2 ： 1. Further research indicated that only TRPPFeCI were formed once FeSOn-7H2O was replaced by FeCl2-4H2O, the reason of which might be that halogen ions in iron salts interfered the formation of [TRPPFe]2O, suggesting that halogen ions should be avoided in this novel synthetic method.
基金Project(2019zzts684)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The highly-dispersed iron element decorated Ni foam was prepared by simple immersion in a ferric nitrate solution at room temperature without using acid etching, and characterized by X-ray powder diffraction(XRD), scanning electron microscopy(SEM), EDAX spectrum(EDAX mapping) and Raman spectroscopy. The EDAX spectrum illustrated that iron element was highly-dispersed over the entire surface of nickel foam, and the Raman spectroscopy revealed that both Ni-O and Fe-O bonds were formed on the surface of the as-prepared electrode. Moreover, the iron element decorated Ni foam electrode can be used as non-enzymatic glucose sensor and it exhibits not only an ultra-wide linear concentration range of 1-18 mmol/L with an outstanding sensitivity of 1.0388 m A·mmol/(L·cm2), but also an excellent ability of stability and selectivity. Therefore, this work presents a simple yet effective approach to successfully modify Ni foam as non-enzymatic glucose sensor.
基金the Natural Science Foundation of Jiangxi Province(No.0420017)for financial support
文摘A mild, one-pot procedure for the synthesis of vinyl ethers in good yields from 2-hydroxyalkyl phenyl selenides with primary or secondary organic halides has been developed.
文摘Three new multi-step one-pot processes for high-yielding cyclohexanecarbonitrile synthesis starting from cyclohexanone were developed for industrial application. In contrast to the current synthetic process, all of the processes described were designed to proceed completely in methanol as a uniform solvent and the key oxidation step can be realized either as stoichiometric or catalytic. Atom efficiency of processes is relatively advanced with high regioselectivity, reaction by-products are either from environmental pool—carbon dioxide and nitrogen—or they can be reused—sodium chloride. Solvent—methanol—and other auxiliaries—cyclohexane, copper catalyst—can be reused after recycling as well. EcoScale for all three designed processes was evaluated and compared with current synthesis described in the past. Green chemistry metrics, including newly introduced evaluative tool—Sustainability Index of the Synthesis (SIS), were applied to evaluate design of described one-pot syntheses.
基金financially supported by the National Natural Science Foundation of China(Nos.52200136,52225004 and 51978640)the Science and Technology Innovation“2025”major program in Ningbo(No.2020Z103)。
文摘Nitrogen oxide(NO_(x))is one of the most critical contaminants in the air,and the control of NO_(x)emission from diesel vehicles is very important.Cu-based small-pore zeolites have already been applied for NO_(x)abatement on diesel vehicles.Among the small-pore zeolites,Cu-SSZ-50 catalysts with good NH_(3)-SCR catalytic activity were believed to have potential for application.In this study,a one-pot synthesis method for Cu-SSZ-50 catalysts was developed for the first time,using the co-templates of Cu-TEPA and 2,6-dimethyl-N-methylpyridinium hydroxide.In this synthesis method,Cu-SSZ-50 with various Cu contents can be obtained by adjusting the amount of Cu-TEPA without the need for a further after-treatment process.The addition of Cu-TEPA affected the framework atoms and Cu species,and a lower Si/Al ratio and more SCR active Cu species were obtained.The synthesized catalyst with a Cu/Al ratio of 0.40 exhibited over 90%NO_(x)conversion between 200℃and 450℃for the selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR).Meanwhile,over 80%NO_(x)conversion could be obtained from 250℃to 450℃after hydrothermal aging at 750℃for 16 h.In addition,both L-H and E-R mechanisms were proven to exist for the one-pot-synthesized Cu-SSZ-50 by in situ DRIFTS experiments.The simple synthesis procedure,excellent catalytic activity and hydrothermal stability brighten the prospects for the application of Cu-SSZ-50.
基金supported by the National Natural Science Foundation of China(12172023).
文摘The separation-of-variable(SOV)methods,such as the improved SOV method,the variational SOV method,and the extended SOV method,have been proposed by the present authors and coworkers to obtain the closed-form analytical solutions for free vibration and eigenbuckling of rectangular plates and circular cylindrical shells.By taking the free vibration of rectangular thin plates as an example,this work presents the theoretical framework of the SOV methods in an instructive way,and the bisection–based solution procedures for a group of nonlinear eigenvalue equations.Besides,the explicit equations of nodal lines of the SOV methods are presented,and the relations of nodal line patterns and frequency orders are investigated.It is concluded that the highly accurate SOV methods have the same accuracy for all frequencies,the mode shapes about repeated frequencies can also be precisely captured,and the SOV methods do not have the problem of missing roots as well.
基金Funded by the Natural Science Foundation of Jiangsu Province(No.BK20241529)China Postdoctoral Science Foundation(No.2024M750736)。
文摘This study aims to develop a chloride diffusion simulation method that considers the hydration microstructure and pore solution properties during the hydration of tricalcium silicate(C3S).The method combines the hydration simulation,thermodynamic calculation,and finite element analysis to examine the effects of pore solution,including effect of electrochemical potential,effect of chemical activity,and effect of mechanical interactions between ions,on the chloride effective diffusion coefficient of hydrated C3S paste.The results indicate that the effect of electrochemical potential on chloride diffusion becomes stronger with increasing hydration age due to the increase in the content of hydrated calcium silicate;as the hydration age increases,the effect of chemical activity on chloride diffusion weakens when the number of diffusible elements decreases;the effect of mechanical interactions between ions on chloride diffusion decreases with the increase of hydration age.
基金funded by the project of the Major Scientific and Technological Projects of CNOOC in the 14th Five-Year Plan(No.KJGG2022-0701)the CNOOC Research Institute(No.2020PFS-03).
文摘To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fractures,this study considered the combined impact of geological-engineering factors on conductivity.Using reservoir production parameters and the discrete elementmethod,multispherical proppants were constructed.Additionally,a 3D fracture model,based on the specified conditions of the L block,employed coupled(Computational Fluid Dynamics)CFD-DEM(Discrete ElementMethod)for joint simulations to quantitatively analyze the transport and placement patterns of multispherical proppants in intersecting fractures.Results indicate that turbulent kinetic energy is an intrinsic factor affecting proppant transport.Moreover,the efficiency of placement and migration distance of low-sphericity quartz sand constructed by the DEM in the main fracture are significantly reduced compared to spherical ceramic proppants,with a 27.7%decrease in the volume fraction of the fracture surface,subsequently affecting the placement concentration and damaging fracture conductivity.Compared to small-angle fractures,controlling artificial and natural fractures to expand at angles of 45°to 60°increases the effective support length by approximately 20.6%.During hydraulic fracturing of gas wells,ensuring the fracture support area and post-closure conductivity can be achieved by controlling the sphericity of proppants and adjusting the perforation direction to control the direction of artificial fractures.
基金sponsored by R&D Program of Beijing Municipal Education Commission(KM202410009013).
文摘In the independent electro-hydrogen system(IEHS)with hybrid energy storage(HESS),achieving optimal scheduling is crucial.Still,it presents a challenge due to the significant deviations in values ofmultiple optimization objective functions caused by their physical dimensions.These deviations seriously affect the scheduling process.A novel standardization fusion method has been established to address this issue by analyzing the variation process of each objective function’s values.The optimal scheduling results of IEHS with HESS indicate that the economy and overall energy loss can be improved 2–3 times under different optimization methods.The proposed method better balances all optimization objective functions and reduces the impact of their dimensionality.When the cost of BESS decreases by approximately 30%,its participation deepens by about 1 time.Moreover,if the price of the electrolyzer is less than 15¥/kWh or if the cost of the fuel cell drops below 4¥/kWh,their participation will increase substantially.This study aims to provide a more reasonable approach to solving multi-objective optimization problems.
文摘Understanding the wind power potential of a site is essential for designing an optimal wind power conditioning system. The Weibull distribution and wind speed extrapolation methods are powerful mathematical tools for efficiently predicting the frequency distribution of wind speeds at a site. Hourly wind speed and direction data were collected from the National Aeronautics and Space Administration (NASA) website for the period 2013 to 2023. MATLAB software was used to calculate the distribution parameters using the graphical method and to plot the corresponding curves, while WRPLOTView software was used to construct the wind rose. The average wind speed obtained is 3.33 m/s and can reach up to 5.71 m/s at a height of 100 meters. The wind energy is estimated to be 1315.30 kWh/m2 at a height of 100 meters. The wind rose indicates the prevailing winds (ranging from 3.60 m/s to 5.70 m/s) in the northeast-east direction.
基金supported by the Innovation Foundation of Provincial Education Department of Gansu(2024B-005)the Gansu Province National Science Foundation(22YF7GA182)the Fundamental Research Funds for the Central Universities(No.lzujbky2022-kb01)。
文摘Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the structure.Therefore,it is particularly significant to identify the structural modal parameters according to the monitoring data information in the structural health monitoring(SHM)system,so as to provide a scientific basis for structural damage identification and dynamic model modification.In view of this,this paper reviews methods for identifying structural modal parameters under environmental excitation and briefly describes how to identify structural damages based on the derived modal parameters.The paper primarily introduces data-driven modal parameter recognition methods(e.g.,time-domain,frequency-domain,and time-frequency-domain methods,etc.),briefly describes damage identification methods based on the variations of modal parameters(e.g.,natural frequency,modal shapes,and curvature modal shapes,etc.)and modal validation methods(e.g.,Stability Diagram and Modal Assurance Criterion,etc.).The current status of the application of artificial intelligence(AI)methods in the direction of modal parameter recognition and damage identification is further discussed.Based on the pre-vious analysis,the main development trends of structural modal parameter recognition and damage identification methods are given to provide scientific references for the optimized design and functional upgrading of SHM systems.
文摘The prediction of the fracture plane orientation in fatigue is a scientific topic and remains relevant for every type of material. However, in this work, we compared the orientation of the fracture plane obtained experimentally through tests on specimens under multiaxial loading with that calculated by the variance method. In the statistical approach criteria, several methods have been developed but we have presented only one method, namely the variance method using the equivalent stress. She assumes that the fracture plane orientation is the one on which the variance of the equivalent stress is maximum. Three types of equivalent stress are defined for this method [1]: normal stress, shear stress and combined normal and shear stress. The results obtained were compared with experimental results for multiaxial cyclic stress states, and it emerges that the variance method for the case of combined loading is conservative as it gives a better prediction of the fracture plane.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52271317 and 52071149)the Fundamental Research Funds for the Central Universities(HUST:2019kfy XJJS007)。
文摘To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based simulation(NNS)method with higher accuracy and better efficiency was proposed.The NNS method consisted of three main steps.First,the parameters of blast loads,including the peak pressures and impulses of cylindrical charges with different aspect ratios(L/D)at different stand-off distances and incident angles were obtained by two-dimensional numerical simulations.Subsequently,incident shape factors of cylindrical charges with arbitrary aspect ratios were predicted by a neural network.Finally,reflected shape factors were derived and implemented into the subroutine of the ABAQUS code to modify the CONWEP model,including modifications of impulse and overpressure.The reliability of the proposed NNS method was verified by related experimental results.Remarkable accuracy improvement was acquired by the proposed NNS method compared with the unmodified CONWEP model.Moreover,huge efficiency superiority was obtained by the proposed NNS method compared with the CEL method.The proposed NNS method showed good accuracy when the scaled distance was greater than 0.2 m/kg^(1/3).It should be noted that there is no need to generate a new dataset again since the blast loads satisfy the similarity law,and the proposed NNS method can be directly used to simulate the blast loads generated by different cylindrical charges.The proposed NNS method with high efficiency and accuracy can be used as an effective method to analyze the dynamic response of structures under blast loads,and it has significant application prospects in designing protective structures.
文摘Fractional-order time-delay differential equations can describe many complex physical phenomena with memory or delay effects, which are widely used in the fields of cell biology, control systems, signal processing, etc. Therefore, it is of great significance to study fractional-order time-delay differential equations. In this paper, we discuss a finite volume element method for a class of fractional-order neutral time-delay differential equations. By introducing an intermediate variable, the fourth-order problem is transformed into a system of equations consisting of two second-order partial differential equations. The L1 formula is used to approximate the time fractional order derivative terms, and the finite volume element method is used in space. A fully discrete format of the equations is established, and we prove the existence, uniqueness, convergence and stability of the solution. Finally, the validity of the format is verified by numerical examples.
文摘Bearing is an indispensable key component in mechanical equipment,and its working state is directly related to the stability and safety of the whole equipment.In recent years,with the rapid development of artificial intelligence technology,especially the breakthrough of deep learning technology,it provides a new idea for bearing fault diagnosis.Deep learning can automatically learn features from a large amount of data,has a strong nonlinear modeling ability,and can effectively solve the problems existing in traditional methods.Aiming at the key problems in bearing fault diagnosis,this paper studies the fault diagnosis method based on deep learning,which not only provides a new solution for bearing fault diagnosis but also provides a reference for the application of deep learning in other mechanical fault diagnosis fields.
基金funded by the Basic Scientific Fund for National Public Research Institutes of China(No.2022 S01)the National Natural Science Foundation of China(Nos.42176191,42049902,and U22A2012)+5 种基金the Shandong Provincial Natural Science Foundation,China(No.ZR2022YQ40)the National Key R&D Program of China(No.2021YFF0501202)the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.SML2023 SP232)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(No.241gqb006)Data acquisition and sample collections were supported by the National Natural Science Foundation of China Open Research Cruise(Cruise No.NORC2021-02+NORC2021301)funded by the Shiptime Sharing Project of the National Natural Science Foundation of China。
文摘Accurate acquisition and prediction of acoustic parameters of seabed sediments are crucial in marine sound propagation research.While the relationship between sound velocity and physical properties of sediment has been extensively studied,there is still no consensus on the correlation between acoustic attenuation coefficient and sediment physical properties.Predicting the acoustic attenuation coefficient remains a challenging issue in sedimentary acoustic research.In this study,we propose a prediction method for the acoustic attenuation coefficient using machine learning algorithms,specifically the random forest(RF),support vector machine(SVR),and convolutional neural network(CNN)algorithms.We utilized the acoustic attenuation coefficient and sediment particle size data from 52 stations as training parameters,with the particle size parameters as the input feature matrix,and measured acoustic attenuation as the training label to validate the attenuation prediction model.Our results indicate that the error of the attenuation prediction model is small.Among the three models,the RF model exhibited the lowest prediction error,with a mean squared error of 0.8232,mean absolute error of 0.6613,and root mean squared error of 0.9073.Additionally,when we applied the models to predict the data collected at different times in the same region,we found that the models developed in this study also demonstrated a certain level of reliability in real prediction scenarios.Our approach demonstrates that constructing a sediment acoustic characteristics model based on machine learning is feasible to a certain extent and offers a novel perspective for studying sediment acoustic properties.
文摘In this article, a finite volume element algorithm is presented and discussed for the numerical solutions of a time-fractional nonlinear fourth-order diffusion equation with time delay. By choosing the second-order spatial derivative of the original unknown as an additional variable, the fourth-order problem is transformed into a second-order system. Then the fully discrete finite volume element scheme is formulated by using L1approximation for temporal Caputo derivative and finite volume element method in spatial direction. The unique solvability and stable result of the proposed scheme are proved. A priori estimate of L2-norm with optimal order of convergence O(h2+τ2−α)where τand hare time step length and space mesh parameter, respectively, is obtained. The efficiency of the scheme is supported by some numerical experiments.
文摘As a key sector in advancing China’s“carbon neutrality”goal,the machinery manufacturing industry has achieved remarkable development in recent years.Against this backdrop,the scientific and objective evaluation of the financial performance of machinery manufacturing enterprises has become a pressing issue in financial research.This topic is not only crucial for optimizing enterprise management and improving operational efficiency but also essential for enhancing overall industry performance and promoting sustainable development.This paper first introduces the concept of financial performance,followed by an analysis of related financial performance evaluation theories.It then focuses on the application of the entropy method in evaluating the financial performance of machinery manufacturing enterprises,detailing its analytical steps.Finally,a financial performance evaluation index system is constructed based on four dimensions:profitability,solvency,operational efficiency,and growth potential.
文摘BACKGROUND Gastric ulcer perforation is a critical condition that can lead to significant morbidity and mortality if not promptly addressed.It is often the result of chronic peptic ulcer disease,which is characterized by a breach in the gastric wall due to ulceration.Surgical intervention is essential for managing this life-threatening complication.However,the optimal surgical technique remains debatable among clinicians.Various methods have been employed,including simple closure,omental patch repair,and partial gastrectomy,each with distinct advantages and disadvantages.Understanding the comparative efficacy and postoperative outcomes of these techniques is crucial for improving patient care and surgical decision-making.This study addresses the need for a comprehensive analysis in this area.AIM To compare the efficacy and postoperative complications of different surgical methods for the treatment of gastric ulcer perforation.METHODS A retrospective analysis was conducted on 120 patients who underwent surgery for gastric ulcer perforation between September 2020 and June 2023.The patients were divided into three groups based on the surgical method:Simple closure,omental patch repair,and partial gastrectomy.The primary outcomes were the operative success rate and incidence of postoperative complications.Secondary outcomes included the length of hospital stay,recovery time,and long-term quality of life.RESULTS The operative success rates for simple closure,omental patch repair,and partial gastrectomy were 92.5%,95%,and 97.5%,respectively.Postoperative complications occurred in 20%,15%,and 17.5%of patients in each group,respectively.The partial gastrectomy group showed a significantly longer operative time(P<0.001)but the lowest rate of ulcer recurrence(2.5%,P<0.05).The omental patch repair group demonstrated the shortest hospital stay(mean 7.2 days,P<0.05)and fastest recovery time.CONCLUSION While all three surgical methods showed high success rates,omental patch repair demonstrated the best overall outcomes,with a balance of high efficacy,low complication rates,and shorter recovery time.However,the choice of the surgical method should be tailored to individual patient factors and the surgeon’s expertise.
