The cathode-active materials, Li1＋yMxMn2-xO4 （M = Al, Co, Ni, Zn, y = 0.02, x = 0.02） powder, were synthesized by sol-gel method using LiOH, Mn（NO3）2 as the starting materials, citric acid as a carrier and Al（NO...The cathode-active materials, Li1＋yMxMn2-xO4 （M = Al, Co, Ni, Zn, y = 0.02, x = 0.02） powder, were synthesized by sol-gel method using LiOH, Mn（NO3）2 as the starting materials, citric acid as a carrier and Al（NO3）3·9H2O or Co（NO3）2·6H2O or Ni（NO3）2·6H2O or Zn（NO3）2·6H2O as dopants. The influence of different doping elements on the structural properties of the as-prepared samples was investigated by X-ray diffraction （XRD）, infrared （IR） spectroscopy and scanning electron microscopy （SEM）. X-ray diffraction patterns of the prepared samples were identified as the spinel structure with space group Fd3m. The grain size increases gradually as the sintering temperature rises and corresponding activation energies for the grain growth have been estimated using Arrhenius’ empirical relation.展开更多
Ink-jet printing of ceramic thick films is one of low cost on-site ceramic pattern fabrication methods.It is necessary to investigate the rheological behaviour of ceramic inks and drying behaviour of droplets.Two kind...Ink-jet printing of ceramic thick films is one of low cost on-site ceramic pattern fabrication methods.It is necessary to investigate the rheological behaviour of ceramic inks and drying behaviour of droplets.Two kinds of BaTiO3 ceramic inks were prepared by mechanical mixing and sol-gel methods,respectively.The effect of preparation parameters,such as quantity of polyacrylic acid(PAA)and solid content,on physicochemical and rheologic properties of the ceramic inks was investigated.The results show that they satisfy the requirements of continuous ink-jet printing.The appearances of printed dots and single printed layers were observed by SEM.The SEM images indicate that dots printed with mixing method ink are in ring shape,and dots printed with sol-gel method ink are in pancake shape,so the printed layer surface with the latter ink is smoother.The causes of these phenomena were discussed.展开更多
The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X...The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.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
Silica glasses doped with Eu3＋ ions prepared by sol-gel methods were investigated. The X-ray diffraction （XRD） was used to verify the nature of the studied systems. Excitation and emission spectra of Eu3＋ ions in ...Silica glasses doped with Eu3＋ ions prepared by sol-gel methods were investigated. The X-ray diffraction （XRD） was used to verify the nature of the studied systems. Excitation and emission spectra of Eu3＋ ions in sol-gel glass materials were detected. Red-to-orange luminescence intensity ratios R/O related to integrated intensities of 5D0→TF2 to 5D0→7TF1 transitions and luminescence lifetimes for 5D0 state of Eu3＋ ions were determined. The results indicated that spectroscopic parameters for Eu3＋ ions strongly de- pended on reagents and their relative ratios used for sol-gel glass preparation.展开更多
The capability of sol-gel and conventional precipitation techniques for the synthesis of nanocrystalline γ-alumina was investigated. These catalysts were used for vapor-phase dehydration of methanol to dimethyl ether...The capability of sol-gel and conventional precipitation techniques for the synthesis of nanocrystalline γ-alumina was investigated. These catalysts were used for vapor-phase dehydration of methanol to dimethyl ether in a fixed-bed reactor under the same operating conditions （T = 300 ？C, P = 1 bar, LHSV = 2.8, 11.7, 26.1 h？1） and characterized by means of N2 adsorption-desorption, NH3-TPD, XRD, TGA and SEM techniques. According to the experimental results, the catalysts prepared using sol-gel method in non-aqueous medium showed better performance compared with those prepared by other methods.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 focused on the comparison of the Pechini and sugar-based combustion synthesis methods to produce nano-zirconia. Zirconium hydroxide was utilized as metal precursor and citric acid, sucrose, and fructose wer...This study focused on the comparison of the Pechini and sugar-based combustion synthesis methods to produce nano-zirconia. Zirconium hydroxide was utilized as metal precursor and citric acid, sucrose, and fructose were used as chelating agents, followed by calcination at 500, 600, and 700°C in air, respectively. Characterization was conducted by thermal analysis, specific surface area measurement, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning and transmission electron microscopy. When sucrose and citric acid were used as chelating agents during synthesis, mixtures of monoclinic and tetragonal phases were formed after calcination at 600 and 700°C. In the fructose samples, the tetragonal structure was the unique characterized phase. The tetragonal parameters in the fructose samples were determined using the diffraction data and the lattice parameter ratio was proven to increase with the temperature increase. Compared with the citrate and sucrose samples, the largest specific surface area(27 m2·g-1) and smallest particle size(39.1 nm) were obtained for the fructose sample after calcination at 700°C. The study revealed the formation of single-phase stabilized tetragonal zirconia using fructose as chelating agent after calcination at 500°C, and the presence and formation mechanism of stabilized tetragonal phase were also discussed on the basis of the X-ray and electron diffraction studies.展开更多
Soil improvement is one of the most important issues in geotechnical engineering practice.The wide application of traditional improvement techniques(cement/chemical materials)are limited due to damage ecological en-vi...Soil improvement is one of the most important issues in geotechnical engineering practice.The wide application of traditional improvement techniques(cement/chemical materials)are limited due to damage ecological en-vironment and intensify carbon emissions.However,the use of microbially induced calcium carbonate pre-cipitation(MICP)to obtain bio-cement is a novel technique with the potential to induce soil stability,providing a low-carbon,environment-friendly,and sustainable integrated solution for some geotechnical engineering pro-blems in the environment.This paper presents a comprehensive review of the latest progress in soil improvement based on the MICP strategy.It systematically summarizes and overviews the mineralization mechanism,influ-encing factors,improved methods,engineering characteristics,and current field application status of the MICP.Additionally,it also explores the limitations and correspondingly proposes prospective applications via the MICP approach for soil improvement.This review indicates that the utilization of different environmental calcium-based wastes in MICP and combination of materials and MICP are conducive to meeting engineering and market demand.Furthermore,we recommend and encourage global collaborative study and practice with a view to commercializing MICP technique in the future.The current review purports to provide insights for engineers and interdisciplinary researchers,and guidance for future engineering applications.展开更多
In order to solve the problem of the variable coefficient ordinary differen-tial equation on the bounded domain,the Lagrange interpolation method is used to approximate the exact solution of the equation,and the error...In order to solve the problem of the variable coefficient ordinary differen-tial equation on the bounded domain,the Lagrange interpolation method is used to approximate the exact solution of the equation,and the error between the numerical solution and the exact solution is obtained,and then compared with the error formed by the difference method,it is concluded that the Lagrange interpolation method is more effective in solving the variable coefficient ordinary differential equation.展开更多
Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.Howev...Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.However,the widened hydraulic excitation frequency may satisfy the blade resonance due to the time variation in the velocity and angle of attack of the ocean current,even resulting in blade fatigue and destructively interfering with grid stability.A key parameter that determines the resonance amplitude of the blade is the hydrodynamic damping ratio(HDR).However,HDR is difficult to obtain due to the complex fluid-structure interaction(FSI).Therefore,a literature review was conducted on the hydrodynamic damping characteristics of blade-like structures.The experimental and simulation methods used to identify and obtain the HDR quantitatively were described,placing emphasis on the experimental processes and simulation setups.Moreover,the accuracy and efficiency of different simulation methods were compared,and the modal work approach was recommended.The effects of key typical parameters,including flow velocity,angle of attack,gap,rotational speed,and cavitation,on the HDR were then summarized,and the suggestions on operating conditions were presented from the perspective of increasing the HDR.Subsequently,considering multiple flow parameters,several theoretical derivations and semi-empirical prediction formulas for HDR were introduced,and the accuracy and application were discussed.Based on the shortcomings of the existing research,the direction of future research was finally determined.The current work offers a clear understanding of the HDR of blade-like structures,which could improve the evaluation accuracy of flow-induced vibration in the design stage.展开更多
Unmanned aerial vehicles(UAVs)have become crucial tools in moving target tracking due to their agility and ability to operate in complex,dynamic environments.UAVs must meet several requirements to achieve stable track...Unmanned aerial vehicles(UAVs)have become crucial tools in moving target tracking due to their agility and ability to operate in complex,dynamic environments.UAVs must meet several requirements to achieve stable tracking,including maintaining continuous target visibility amidst occlusions,ensuring flight safety,and achieving smooth trajectory planning.This paper reviews the latest advancements in UAV-based target tracking,highlighting information prediction,tracking strategies,and swarm cooperation.To address challenges including target visibility and occlusion,real-time prediction and tracking in dynamic environments,flight safety and coordination,resource management and energy efficiency,the paper identifies future research directions aimed at improving the performance,reliability,and scalability of UAV tracking system.展开更多
The element-free Galerkin(EFG)method,which constructs shape functions via moving least squares(MLS)approximation,represents a fundamental and widely studied meshless method in numerical computation.Although it achieve...The element-free Galerkin(EFG)method,which constructs shape functions via moving least squares(MLS)approximation,represents a fundamental and widely studied meshless method in numerical computation.Although it achieves high computational accuracy,the shape functions are more complex than those in the conventional finite element method(FEM),resulting in great computational requirements.Therefore,improving the computational efficiency of the EFG method represents an important research direction.This paper systematically reviews significant contributions fromdomestic and international scholars in advancing the EFGmethod.Including the improved element-free Galerkin(IEFG)method,various interpolating EFG methods,four distinct complex variable EFG methods,and a series of dimension splitting meshless methods.In the numerical examples,the effectiveness and efficiency of the three methods are validated by analyzing the solutions of the IEFG method for 3D steadystate anisotropic heat conduction,3D elastoplasticity,and large deformation problems,as well as the performance of two-dimensional splitting meshless methods in solving the 3D Helmholtz equation.展开更多
RNAs have important biological functions and the functions of RNAs are generally coupled to their structures, especiallytheir secondary structures. In this work, we have made a comprehensive evaluation of the performa...RNAs have important biological functions and the functions of RNAs are generally coupled to their structures, especiallytheir secondary structures. In this work, we have made a comprehensive evaluation of the performances of existingtop RNA secondary structure prediction methods, including five deep-learning (DL) based methods and five minimum freeenergy (MFE) based methods. First, we made a brief overview of these RNA secondary structure prediction methods.Afterwards, we built two rigorous test datasets consisting of RNAs with non-redundant sequences and comprehensivelyexamined the performances of the RNA secondary structure prediction methods through classifying the RNAs into differentlength ranges and different types. Our examination shows that the DL-based methods generally perform better thanthe MFE-based methods for RNAs with long lengths and complex structures, while the MFE-based methods can achievegood performance for small RNAs and some specialized MFE-based methods can achieve good prediction accuracy forpseudoknots. Finally, we provided some insights and perspectives in modeling RNA secondary structures.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
In this research study,magnesium-aluminum(Mg-Al)bimetallic oxide powders are synthesized via the sol-gel auto combustion method using diethanolamine(DEA)as the fuel.In order to subsequently determine the influence of ...In this research study,magnesium-aluminum(Mg-Al)bimetallic oxide powders are synthesized via the sol-gel auto combustion method using diethanolamine(DEA)as the fuel.In order to subsequently determine the influence of calcination temperatures upon the structure,chemical bonding,morphology,optical properties,and fluorescence properties of the as-synthesized and calcined Mg-Al bimetallic oxide powders,the researcher employed X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),transmission electron microscopy(TEM),UV–visible diffuse reflectance spectroscopy(UV-DRS),and photoluminescence spectroscopy(PL),respectively.It was apparent on the basis of the XRD and FT-IR analyses that those powders undergoing calcination at temperatures of 500℃,700℃,and 900℃contained the major phase magnesium aluminate(Mg Al_(2)O_(4))spinel with trace magnesium oxide(Mg O)and hydrotalcite(Mg_(6)Al_(2)(CO_(3))(OH)_(16)).When the calcination temperature rose to 1100℃,this resulted in a single phase MgAl_(2)O_(4)while MgO and(Mg_(6)Al_(2)(CO_(3))(OH)_(16))were no longer observed.UV-DRS analysis revealed that in optimized conditions,calcination resulted in better sample absorption and reflection levels when compared to the ultraviolet,visible,and infrared spectra observed in the case of the as-synthesized sample.The bandgap energy(E_(g))for calcined samples was in the range of 2.65 e V to 5.85 e V,in contrast to the value of 4.10 e V for the as-synthesized sample.Analysis of photoluminescence showed that for the as-synthesized samples and those calcined at low temperatures,visible light was emitted only in the violet,blue,and green regions with low intensity,while for samples calcined at higher temperatures,the emissions showed greater intensity and extended to the yellow and orange regions.Multiple defect centers were found in the bandgap which can explain these findings.展开更多
Purpose–For the commonly used concrete mix for railway tunnel linings,concrete model specimens were made,and springback and core drilling tests were conducted at different ages.The springback strength was measured to...Purpose–For the commonly used concrete mix for railway tunnel linings,concrete model specimens were made,and springback and core drilling tests were conducted at different ages.The springback strength was measured to the compressive strength of the core sample with a diameter of 100mm and a height-to-diameter ratio of 1:1.By comparing the measured strength values,the relationship between the measured values under different strength measurement methods was analyzed.Design/methodology/approach–A comparative test of the core drilling method and the rebound method was conducted on the side walls of tunnel linings in some under-construction railways to study the feasibility of the rebound method in engineering quality supervision and inspection.Findings–Tests showed that the rebound strength was positively correlated with the core drill strength.The core drill test strength was significantly higher than the rebound test strength,and the strength still increased after 56 days of age.The rebound method is suitable for the general survey of concrete strength during the construction process and is not suitable for direct supervision and inspection.Originality/value–By studying the correlation of test strength of tunnel lining concrete using two methods,the differences in test results of different methods are proposed to provide a reference for the test and evaluation of tunnel lining strength in railway engineering.展开更多
As pivotal supporting technologies for smart manufacturing and digital engineering,model-based and data-driven methods have been widely applied in many industrial fields,such as product design,process monitoring,and s...As pivotal supporting technologies for smart manufacturing and digital engineering,model-based and data-driven methods have been widely applied in many industrial fields,such as product design,process monitoring,and smart maintenance.While promising,both methods have issues that need to be addressed.For example,model-based methods are limited by low computational accuracy and a high computational burden,and data-driven methods always suffer from poor interpretability and redundant features.To address these issues,the concept of data-model fusion(DMF)emerges as a promising solution.DMF involves integrating model-based methods with data-driven methods by incorporating big data into model-based methods or embedding relevant domain knowledge into data-driven methods.Despite growing efforts in the field of DMF,a unanimous definition of DMF remains elusive,and a general framework of DMF has been rarely discussed.This paper aims to address this gap by providing a thorough overview and categorization of both data-driven methods and model-based methods.Subsequently,this paper also presents the definition and categorization of DMF and discusses the general framework of DMF.Moreover,the primary seven applications of DMF are reviewed within the context of smart manufacturing and digital engineering.Finally,this paper directs the future directions of DMF.展开更多
In this research work,sol-gel technique was employed to prepare the strontium based spinel ferrite nanoparticles(SrFe_(2)O_(4))with different ratios of terbium(Tb).Different characterization techniques were used to in...In this research work,sol-gel technique was employed to prepare the strontium based spinel ferrite nanoparticles(SrFe_(2)O_(4))with different ratios of terbium(Tb).Different characterization techniques were used to investigate the structural,morphological,dielectric and magnetic properties of the prepared samples.X-ray diffraction(XRD)result suggests that face-centered cube spinel nanocrystalline structure is formed.Crystallite size of the SrFe_(2)O_(4)decreases with rising of Tb ratio.The morphology,shape and size of the SrFe_(2)O_(4)were examined by scanning electron microscopy(SEM)analysis and results reveal inhomogeneous distributions of the nanostructures with high agglomeration.The electrical resistivity of the SrFe_(2)O_(4)increases with rising of Tb ratio,which is confirmed from the cyclic voltammetry.It is observed that dielectric constant of all the samples decreases with the increasing frequency range.It is determined that the dielectric constants of the spinel ferrites are frequency dependent and decrease with increasing the frequency of applied electric field.The magnetic behavior of SrFe_(2)O_(4)with different ratios of Tb was studied and it is found that the saturation magnetization values of samples decrease with increase in the substitution of Tb^(3+)at octahedral sites for Fe^(3+).This decrease in the values of M_(s) is also attributed to spin at surface of nanoparticles.展开更多
Ferromagnetic Fe3O4 nanoparticles were synthesized using water as the solvent through the sol-gel method, which was selected for its cost-effectiveness, simplicity, and eco-friendly nature. The synthesized nanoparticl...Ferromagnetic Fe3O4 nanoparticles were synthesized using water as the solvent through the sol-gel method, which was selected for its cost-effectiveness, simplicity, and eco-friendly nature. The synthesized nanoparticles were characterized using a variety of techniques, including Fourier Transform Infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and Vibrating Sample Magnetometer (VSM). These characterizations confirmed the successful formation of Fe3O4 nanoparticles. The FTIR spectra identified characteristic peaks corresponding to the functional groups present, and XRD analysis, using Scherer’s equation, determined an average crystalline size of 1.2 nm for the Fe3O4 nanoparticles. TGA results demonstrated the thermal stability of the nanoparticles, SEM imaging revealed distinct honeycomb-like structures for the nanoparticles synthesized with water as the solvent, while the VSM analysis was used to determine the magnetic behavior of the nanoparticles.展开更多
基金This work was supported by the National Natural Science Foundation of China (60671010)Natural Science Foundation of Shandong Province (Y2006B29)
文摘The cathode-active materials, Li1＋yMxMn2-xO4 （M = Al, Co, Ni, Zn, y = 0.02, x = 0.02） powder, were synthesized by sol-gel method using LiOH, Mn（NO3）2 as the starting materials, citric acid as a carrier and Al（NO3）3·9H2O or Co（NO3）2·6H2O or Ni（NO3）2·6H2O or Zn（NO3）2·6H2O as dopants. The influence of different doping elements on the structural properties of the as-prepared samples was investigated by X-ray diffraction （XRD）, infrared （IR） spectroscopy and scanning electron microscopy （SEM）. X-ray diffraction patterns of the prepared samples were identified as the spinel structure with space group Fd3m. The grain size increases gradually as the sintering temperature rises and corresponding activation energies for the grain growth have been estimated using Arrhenius’ empirical relation.
基金Project(106151)supported by the Major Program of the Ministry of Education of ChinaProject(59842001)supported by the National Natural Science Foundation of China
文摘Ink-jet printing of ceramic thick films is one of low cost on-site ceramic pattern fabrication methods.It is necessary to investigate the rheological behaviour of ceramic inks and drying behaviour of droplets.Two kinds of BaTiO3 ceramic inks were prepared by mechanical mixing and sol-gel methods,respectively.The effect of preparation parameters,such as quantity of polyacrylic acid(PAA)and solid content,on physicochemical and rheologic properties of the ceramic inks was investigated.The results show that they satisfy the requirements of continuous ink-jet printing.The appearances of printed dots and single printed layers were observed by SEM.The SEM images indicate that dots printed with mixing method ink are in ring shape,and dots printed with sol-gel method ink are in pancake shape,so the printed layer surface with the latter ink is smoother.The causes of these phenomena were discussed.
基金financially supported by (i) Suranaree University of Technology,(ii) Thailand Science Research and Innovation,and (iii) National Science,Research and Innovation Fund(project codes 90464 and 160363)。
文摘The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.
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Silica glasses doped with Eu3＋ ions prepared by sol-gel methods were investigated. The X-ray diffraction （XRD） was used to verify the nature of the studied systems. Excitation and emission spectra of Eu3＋ ions in sol-gel glass materials were detected. Red-to-orange luminescence intensity ratios R/O related to integrated intensities of 5D0→TF2 to 5D0→7TF1 transitions and luminescence lifetimes for 5D0 state of Eu3＋ ions were determined. The results indicated that spectroscopic parameters for Eu3＋ ions strongly de- pended on reagents and their relative ratios used for sol-gel glass preparation.
基金supported by Iranian Nanotechnology Initiative Council
文摘The capability of sol-gel and conventional precipitation techniques for the synthesis of nanocrystalline γ-alumina was investigated. These catalysts were used for vapor-phase dehydration of methanol to dimethyl ether in a fixed-bed reactor under the same operating conditions （T = 300 ？C, P = 1 bar, LHSV = 2.8, 11.7, 26.1 h？1） and characterized by means of N2 adsorption-desorption, NH3-TPD, XRD, TGA and SEM techniques. According to the experimental results, the catalysts prepared using sol-gel method in non-aqueous medium showed better performance compared with those prepared by other methods.
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.
文摘This study focused on the comparison of the Pechini and sugar-based combustion synthesis methods to produce nano-zirconia. Zirconium hydroxide was utilized as metal precursor and citric acid, sucrose, and fructose were used as chelating agents, followed by calcination at 500, 600, and 700°C in air, respectively. Characterization was conducted by thermal analysis, specific surface area measurement, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning and transmission electron microscopy. When sucrose and citric acid were used as chelating agents during synthesis, mixtures of monoclinic and tetragonal phases were formed after calcination at 600 and 700°C. In the fructose samples, the tetragonal structure was the unique characterized phase. The tetragonal parameters in the fructose samples were determined using the diffraction data and the lattice parameter ratio was proven to increase with the temperature increase. Compared with the citrate and sucrose samples, the largest specific surface area(27 m2·g-1) and smallest particle size(39.1 nm) were obtained for the fructose sample after calcination at 700°C. The study revealed the formation of single-phase stabilized tetragonal zirconia using fructose as chelating agent after calcination at 500°C, and the presence and formation mechanism of stabilized tetragonal phase were also discussed on the basis of the X-ray and electron diffraction studies.
基金funded by the National Natural Science Foundation of China(No.41962016)the Natural Science Foundation of NingXia(Nos.2023AAC02023,2023A1218,and 2021AAC02006).
文摘Soil improvement is one of the most important issues in geotechnical engineering practice.The wide application of traditional improvement techniques(cement/chemical materials)are limited due to damage ecological en-vironment and intensify carbon emissions.However,the use of microbially induced calcium carbonate pre-cipitation(MICP)to obtain bio-cement is a novel technique with the potential to induce soil stability,providing a low-carbon,environment-friendly,and sustainable integrated solution for some geotechnical engineering pro-blems in the environment.This paper presents a comprehensive review of the latest progress in soil improvement based on the MICP strategy.It systematically summarizes and overviews the mineralization mechanism,influ-encing factors,improved methods,engineering characteristics,and current field application status of the MICP.Additionally,it also explores the limitations and correspondingly proposes prospective applications via the MICP approach for soil improvement.This review indicates that the utilization of different environmental calcium-based wastes in MICP and combination of materials and MICP are conducive to meeting engineering and market demand.Furthermore,we recommend and encourage global collaborative study and practice with a view to commercializing MICP technique in the future.The current review purports to provide insights for engineers and interdisciplinary researchers,and guidance for future engineering applications.
文摘In order to solve the problem of the variable coefficient ordinary differen-tial equation on the bounded domain,the Lagrange interpolation method is used to approximate the exact solution of the equation,and the error between the numerical solution and the exact solution is obtained,and then compared with the error formed by the difference method,it is concluded that the Lagrange interpolation method is more effective in solving the variable coefficient ordinary differential equation.
基金Supported by the National Natural Science Foundation of China(Nos.52222904 and 52309117)China Postdoctoral Science Foundation(Nos.2022TQ0168 and 2023M731895).
文摘Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.However,the widened hydraulic excitation frequency may satisfy the blade resonance due to the time variation in the velocity and angle of attack of the ocean current,even resulting in blade fatigue and destructively interfering with grid stability.A key parameter that determines the resonance amplitude of the blade is the hydrodynamic damping ratio(HDR).However,HDR is difficult to obtain due to the complex fluid-structure interaction(FSI).Therefore,a literature review was conducted on the hydrodynamic damping characteristics of blade-like structures.The experimental and simulation methods used to identify and obtain the HDR quantitatively were described,placing emphasis on the experimental processes and simulation setups.Moreover,the accuracy and efficiency of different simulation methods were compared,and the modal work approach was recommended.The effects of key typical parameters,including flow velocity,angle of attack,gap,rotational speed,and cavitation,on the HDR were then summarized,and the suggestions on operating conditions were presented from the perspective of increasing the HDR.Subsequently,considering multiple flow parameters,several theoretical derivations and semi-empirical prediction formulas for HDR were introduced,and the accuracy and application were discussed.Based on the shortcomings of the existing research,the direction of future research was finally determined.The current work offers a clear understanding of the HDR of blade-like structures,which could improve the evaluation accuracy of flow-induced vibration in the design stage.
基金financial support provided by the Natural Science Foundation of Hunan Province of China(Grant No.2021JJ10045)the Open Research Subject of State Key Laboratory of Intelligent Game(Grant No.ZBKF-24-01)+1 种基金the Postdoctoral Fellowship Program of CPSF(Grant No.GZB20240989)the China Postdoctoral Science Foundation(Grant No.2024M754304)。
文摘Unmanned aerial vehicles(UAVs)have become crucial tools in moving target tracking due to their agility and ability to operate in complex,dynamic environments.UAVs must meet several requirements to achieve stable tracking,including maintaining continuous target visibility amidst occlusions,ensuring flight safety,and achieving smooth trajectory planning.This paper reviews the latest advancements in UAV-based target tracking,highlighting information prediction,tracking strategies,and swarm cooperation.To address challenges including target visibility and occlusion,real-time prediction and tracking in dynamic environments,flight safety and coordination,resource management and energy efficiency,the paper identifies future research directions aimed at improving the performance,reliability,and scalability of UAV tracking system.
基金supported by the National Natural Science Foundation of China(Grant No.12271341).
文摘The element-free Galerkin(EFG)method,which constructs shape functions via moving least squares(MLS)approximation,represents a fundamental and widely studied meshless method in numerical computation.Although it achieves high computational accuracy,the shape functions are more complex than those in the conventional finite element method(FEM),resulting in great computational requirements.Therefore,improving the computational efficiency of the EFG method represents an important research direction.This paper systematically reviews significant contributions fromdomestic and international scholars in advancing the EFGmethod.Including the improved element-free Galerkin(IEFG)method,various interpolating EFG methods,four distinct complex variable EFG methods,and a series of dimension splitting meshless methods.In the numerical examples,the effectiveness and efficiency of the three methods are validated by analyzing the solutions of the IEFG method for 3D steadystate anisotropic heat conduction,3D elastoplasticity,and large deformation problems,as well as the performance of two-dimensional splitting meshless methods in solving the 3D Helmholtz equation.
基金supported by grants from the National Science Foundation of China(Grant Nos.12375038 and 12075171 to ZJT,and 12205223 to YLT).
文摘RNAs have important biological functions and the functions of RNAs are generally coupled to their structures, especiallytheir secondary structures. In this work, we have made a comprehensive evaluation of the performances of existingtop RNA secondary structure prediction methods, including five deep-learning (DL) based methods and five minimum freeenergy (MFE) based methods. First, we made a brief overview of these RNA secondary structure prediction methods.Afterwards, we built two rigorous test datasets consisting of RNAs with non-redundant sequences and comprehensivelyexamined the performances of the RNA secondary structure prediction methods through classifying the RNAs into differentlength ranges and different types. Our examination shows that the DL-based methods generally perform better thanthe MFE-based methods for RNAs with long lengths and complex structures, while the MFE-based methods can achievegood performance for small RNAs and some specialized MFE-based methods can achieve good prediction accuracy forpseudoknots. Finally, we provided some insights and perspectives in modeling RNA secondary structures.
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financial supported from the Thailand Research Fund,Office of the Higher Education Commission(Grant number MRG6280220)。
文摘In this research study,magnesium-aluminum(Mg-Al)bimetallic oxide powders are synthesized via the sol-gel auto combustion method using diethanolamine(DEA)as the fuel.In order to subsequently determine the influence of calcination temperatures upon the structure,chemical bonding,morphology,optical properties,and fluorescence properties of the as-synthesized and calcined Mg-Al bimetallic oxide powders,the researcher employed X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),transmission electron microscopy(TEM),UV–visible diffuse reflectance spectroscopy(UV-DRS),and photoluminescence spectroscopy(PL),respectively.It was apparent on the basis of the XRD and FT-IR analyses that those powders undergoing calcination at temperatures of 500℃,700℃,and 900℃contained the major phase magnesium aluminate(Mg Al_(2)O_(4))spinel with trace magnesium oxide(Mg O)and hydrotalcite(Mg_(6)Al_(2)(CO_(3))(OH)_(16)).When the calcination temperature rose to 1100℃,this resulted in a single phase MgAl_(2)O_(4)while MgO and(Mg_(6)Al_(2)(CO_(3))(OH)_(16))were no longer observed.UV-DRS analysis revealed that in optimized conditions,calcination resulted in better sample absorption and reflection levels when compared to the ultraviolet,visible,and infrared spectra observed in the case of the as-synthesized sample.The bandgap energy(E_(g))for calcined samples was in the range of 2.65 e V to 5.85 e V,in contrast to the value of 4.10 e V for the as-synthesized sample.Analysis of photoluminescence showed that for the as-synthesized samples and those calcined at low temperatures,visible light was emitted only in the violet,blue,and green regions with low intensity,while for samples calcined at higher temperatures,the emissions showed greater intensity and extended to the yellow and orange regions.Multiple defect centers were found in the bandgap which can explain these findings.
文摘Purpose–For the commonly used concrete mix for railway tunnel linings,concrete model specimens were made,and springback and core drilling tests were conducted at different ages.The springback strength was measured to the compressive strength of the core sample with a diameter of 100mm and a height-to-diameter ratio of 1:1.By comparing the measured strength values,the relationship between the measured values under different strength measurement methods was analyzed.Design/methodology/approach–A comparative test of the core drilling method and the rebound method was conducted on the side walls of tunnel linings in some under-construction railways to study the feasibility of the rebound method in engineering quality supervision and inspection.Findings–Tests showed that the rebound strength was positively correlated with the core drill strength.The core drill test strength was significantly higher than the rebound test strength,and the strength still increased after 56 days of age.The rebound method is suitable for the general survey of concrete strength during the construction process and is not suitable for direct supervision and inspection.Originality/value–By studying the correlation of test strength of tunnel lining concrete using two methods,the differences in test results of different methods are proposed to provide a reference for the test and evaluation of tunnel lining strength in railway engineering.
基金supported in part by the National Natural Science Foundation of China(NSFC)under Grants(52275471 and 52120105008)the Beijing Outstanding Young Scientist Program,and the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘As pivotal supporting technologies for smart manufacturing and digital engineering,model-based and data-driven methods have been widely applied in many industrial fields,such as product design,process monitoring,and smart maintenance.While promising,both methods have issues that need to be addressed.For example,model-based methods are limited by low computational accuracy and a high computational burden,and data-driven methods always suffer from poor interpretability and redundant features.To address these issues,the concept of data-model fusion(DMF)emerges as a promising solution.DMF involves integrating model-based methods with data-driven methods by incorporating big data into model-based methods or embedding relevant domain knowledge into data-driven methods.Despite growing efforts in the field of DMF,a unanimous definition of DMF remains elusive,and a general framework of DMF has been rarely discussed.This paper aims to address this gap by providing a thorough overview and categorization of both data-driven methods and model-based methods.Subsequently,this paper also presents the definition and categorization of DMF and discusses the general framework of DMF.Moreover,the primary seven applications of DMF are reviewed within the context of smart manufacturing and digital engineering.Finally,this paper directs the future directions of DMF.
基金the Deanship of Scientific Research at King Khalid University for funding this work through Large Groups Project under(RGP.2/111/44)。
文摘In this research work,sol-gel technique was employed to prepare the strontium based spinel ferrite nanoparticles(SrFe_(2)O_(4))with different ratios of terbium(Tb).Different characterization techniques were used to investigate the structural,morphological,dielectric and magnetic properties of the prepared samples.X-ray diffraction(XRD)result suggests that face-centered cube spinel nanocrystalline structure is formed.Crystallite size of the SrFe_(2)O_(4)decreases with rising of Tb ratio.The morphology,shape and size of the SrFe_(2)O_(4)were examined by scanning electron microscopy(SEM)analysis and results reveal inhomogeneous distributions of the nanostructures with high agglomeration.The electrical resistivity of the SrFe_(2)O_(4)increases with rising of Tb ratio,which is confirmed from the cyclic voltammetry.It is observed that dielectric constant of all the samples decreases with the increasing frequency range.It is determined that the dielectric constants of the spinel ferrites are frequency dependent and decrease with increasing the frequency of applied electric field.The magnetic behavior of SrFe_(2)O_(4)with different ratios of Tb was studied and it is found that the saturation magnetization values of samples decrease with increase in the substitution of Tb^(3+)at octahedral sites for Fe^(3+).This decrease in the values of M_(s) is also attributed to spin at surface of nanoparticles.
文摘Ferromagnetic Fe3O4 nanoparticles were synthesized using water as the solvent through the sol-gel method, which was selected for its cost-effectiveness, simplicity, and eco-friendly nature. The synthesized nanoparticles were characterized using a variety of techniques, including Fourier Transform Infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and Vibrating Sample Magnetometer (VSM). These characterizations confirmed the successful formation of Fe3O4 nanoparticles. The FTIR spectra identified characteristic peaks corresponding to the functional groups present, and XRD analysis, using Scherer’s equation, determined an average crystalline size of 1.2 nm for the Fe3O4 nanoparticles. TGA results demonstrated the thermal stability of the nanoparticles, SEM imaging revealed distinct honeycomb-like structures for the nanoparticles synthesized with water as the solvent, while the VSM analysis was used to determine the magnetic behavior of the nanoparticles.
