This study investigated the physicochemical properties,enzyme activities,volatile flavor components,microbial communities,and sensory evaluation of high-temperature Daqu(HTD)during the maturation process,and a standar...This study investigated the physicochemical properties,enzyme activities,volatile flavor components,microbial communities,and sensory evaluation of high-temperature Daqu(HTD)during the maturation process,and a standard system was established for comprehensive quality evaluation of HTD.There were obvious changes in the physicochemical properties,enzyme activities,and volatile flavor components at different storage periods,which affected the sensory evaluation of HTD to a certain extent.The results of high-throughput sequencing revealed significant microbial diversity,and showed that the bacterial community changed significantly more than did the fungal community.During the storage process,the dominant bacterial genera were Kroppenstedtia and Thermoascus.The correlation between dominant microorganisms and quality indicators highlighted their role in HTD quality.Lactococcus,Candida,Pichia,Paecilomyces,and protease activity played a crucial role in the formation of isovaleraldehyde.Acidic protease activity had the greatest impact on the microbial community.Moisture promoted isobutyric acid generation.Furthermore,the comprehensive quality evaluation standard system was established by the entropy weight method combined with multi-factor fuzzy mathematics.Consequently,this study provides innovative insights for comprehensive quality evaluation of HTD during storage and establishes a groundwork for scientific and rational storage of HTD and quality control of sauce-flavor Baijiu.展开更多
Shock wave caused by a sudden release of high-energy,such as explosion and blast,usually affects a significant range of areas.The utilization of a uniform fine mesh to capture sharp shock wave and to obtain precise re...Shock wave caused by a sudden release of high-energy,such as explosion and blast,usually affects a significant range of areas.The utilization of a uniform fine mesh to capture sharp shock wave and to obtain precise results is inefficient in terms of computational resource.This is particularly evident when large-scale fluid field simulations are conducted with significant differences in computational domain size.In this work,a variable-domain-size adaptive mesh enlargement(vAME)method is developed based on the proposed adaptive mesh enlargement(AME)method for modeling multi-explosives explosion problems.The vAME method reduces the division of numerous empty areas or unnecessary computational domains by adaptively suspending enlargement operation in one or two directions,rather than in all directions as in AME method.A series of numerical tests via AME and vAME with varying nonintegral enlargement ratios and different mesh numbers are simulated to verify the efficiency and order of accuracy.An estimate of speedup ratio is analyzed for further efficiency comparison.Several large-scale near-ground explosion experiments with single/multiple explosives are performed to analyze the shock wave superposition formed by the incident wave,reflected wave,and Mach wave.Additionally,the vAME method is employed to validate the accuracy,as well as to investigate the performance of the fluid field and shock wave propagation,considering explosive quantities ranging from 1 to 5 while maintaining a constant total mass.The results show a satisfactory correlation between the overpressure versus time curves for experiments and numerical simulations.The vAME method yields a competitive efficiency,increasing the computational speed to 3.0 and approximately 120,000 times in comparison to AME and the fully fine mesh method,respectively.It indicates that the vAME method reduces the computational cost with minimal impact on the results for such large-scale high-energy release problems with significant differences in computational domain size.展开更多
In this paper,a new technique is introduced to construct higher-order iterative methods for solving nonlinear systems.The order of convergence of some iterative methods can be improved by three at the cost of introduc...In this paper,a new technique is introduced to construct higher-order iterative methods for solving nonlinear systems.The order of convergence of some iterative methods can be improved by three at the cost of introducing only one additional evaluation of the function in each step.Furthermore,some new efficient methods with a higher-order of convergence are obtained by using only a single matrix inversion in each iteration.Analyses of convergence properties and computational efficiency of these new methods are made and testified by several numerical problems.By comparison,the new schemes are more efficient than the corresponding existing ones,particularly for large problem sizes.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
Long-term responses of floating structures pose a great concern in their design phase. Existing approaches for addressing long-term extreme responses are extremely cumbersome for adoption. This work aims to develop an...Long-term responses of floating structures pose a great concern in their design phase. Existing approaches for addressing long-term extreme responses are extremely cumbersome for adoption. This work aims to develop an approach for the long-term extreme-response analysis of floating structures. A modified gradient-based retrieval algorithm in conjunction with the inverse first-order reliability method(IFORM) is proposed to enable the use of convolution models in long-term extreme analysis of structures with an analytical formula of response amplitude operator(RAO). The proposed algorithm ensures convergence stability and iteration accuracy and exhibits a higher computational efficiency than the traditional backtracking method. However, when the RAO of general offshore structures cannot be analytically expressed, the convolutional integration method fails to function properly. A numerical discretization approach is further proposed for offshore structures in the case when the analytical expression of the RAO is not feasible. Through iterative discretization of environmental contours(ECs) and RAOs, a detailed procedure is proposed to calculate the long-term response extremes of offshore structures. The validity and accuracy of the proposed approach are tested using a floating offshore wind turbine as a numerical example. The long-term extreme heave responses of various return periods are calculated via the IFORM in conjunction with a numerical discretization approach. The environmental data corresponding to N-year structural responses are located inside the ECs, which indicates that the selection of design points directly along the ECs yields conservative design results.展开更多
To study the influence of silicon(Si)on 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20),NC/CL-20 composite explosives and Si/NC/CL-20 composite explosives were prepared by the electrostatic spraying ...To study the influence of silicon(Si)on 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20),NC/CL-20 composite explosives and Si/NC/CL-20 composite explosives were prepared by the electrostatic spraying method.The morphology,structure and thermal decomposition properties of the samples were analyzed using scanning electron microscopy(SEM),X-ray energy spectroscopy(EDS),infrared spectroscopy(FT-IR),and simultaneous thermal analyzer(TG-DSC).Additionally,the combustion process of the samples was tested using a high-speed camera.The results show that the addition of nano-Si contributes to the formation of composite explosives with regular morphology and smaller particle size.The Si/NC/CL-20 composite explosive has better and more uniform sphericity,with an average particle size of 73.4 nm,compared to the NC/CL-20 composite explosive.The Si/NC/CL-20 composite explosive which produced by the electrostatic spraying method,achieves physically uniform distribution of the components including NC,CL-20,Si.The addition of Si promotes the thermal decomposition of CL-20.In comparison to the NC/CL-20 composite explosive,the activation energy of the Si/NC/CL-20 composite explosive decreases by 16.78 kJ/mol,and the self-accelerated decomposition temperature and the critical temperature of thermal explosion decreases by 3.12 K and 2.61 K,respectively.Furthermore,Si/NC/CL-20 composite explosive has shorter ignition delay time and faster combustion rate compared to the NC/CL-20 composite explosive,which shows that Si can improve the combustion performance of CL-20.展开更多
Without knowing the emittance value, it is difficult to optimize ion beam optics for minimum beam loss during transmission, especially considering the very high emittance values of electron cyclotron resonance(ECR) io...Without knowing the emittance value, it is difficult to optimize ion beam optics for minimum beam loss during transmission, especially considering the very high emittance values of electron cyclotron resonance(ECR) ion sources.With this in mind, to measure the emittance of the ion beams produced by the mVINIS ECR, which is part of the FAMA facility at the Vin?a Institute of Nuclear Sciences, we have developed a pepper-pot scintillator screen system combined with a CMOS camera. The application, developed on the Lab VIEW platform, allows us to control the camera's main attribute settings, such as the shutter speed and the gain, record the images in the region of interest, and process and filter the images in real time. To analyze the data from the obtained image, we have developed an algorithm called measurement and analysis of ion beam luminosity(MAIBL) to reconstruct the four-dimensional(4D) beam profile and calculate the root mean square(RMS) emittance. Before measuring emittance, we performed a simulated experiment using the pepper-pot simulation(PPS) program. An exported file(PPS) gives a numerically generated raw image(mock image) of a beam with a predefined emittance value after it has passed through a pepper-pot mask. By analyzing data from mock images instead of the image obtained by the camera and putting it into the MAIBL algorithm, we can compare the calculated emittance with PPS's initial emittance value. In this paper, we present our computational tools and explain the method for verifying the correctness of the calculated emittance values.展开更多
To enhance the computational efficiency of spatio-temporally discretized phase-field models,we present a high-speed solver specifically designed for the Poisson equations,a component frequently used in the numerical c...To enhance the computational efficiency of spatio-temporally discretized phase-field models,we present a high-speed solver specifically designed for the Poisson equations,a component frequently used in the numerical computation of such models.This efficient solver employs algorithms based on discrete cosine transformations(DCT)or discrete sine transformations(DST)and is not restricted by any spatio-temporal schemes.Our proposed methodology is appropriate for a variety of phase-field models and is especially efficient when combined with flow field systems.Meanwhile,this study has conducted an extensive numerical comparison and found that employing DCT and DST techniques not only yields results comparable to those obtained via the Multigrid(MG)method,a conventional approach used in the resolution of the Poisson equations,but also enhances computational efficiency by over 90%.展开更多
The diffuse-interface immersed boundary method(IBM)possesses excellent capabilities for simulating flows around complex geometries and moving boundaries.In this method,the flow field is solved on a fixed Cartesian mes...The diffuse-interface immersed boundary method(IBM)possesses excellent capabilities for simulating flows around complex geometries and moving boundaries.In this method,the flow field is solved on a fixed Cartesian mesh,while the solid boundary is discretized into a series of Lagrangian points immersed in the flow field.The boundary condition is implemented by introducing a force term into the momentum equation,and the interaction between the immersed boundary and the fluid domain is achieved via an interpolation process.Over the past decades,the diffuse-interface IBM has gained popularity and spawned many variants,effectively handling a wide range of flow problems from isothermal to thermal flows,from laminar to turbulent flows,and from complex geometries to fluidstructure interaction scenarios.This paper first outlines the basic principles of the diffuse-interface IBM,then highlights recent advancements achieved by the authors’research group,and finally shows the method’s excellent numerical performance and wide applicability through several case studies involving complex moving boundary problems.展开更多
Currently,the cranes used at sea do not have enough flexibility,efficiency,and safety.Thus,this study proposed a floating multirobot coordinated towing system to meet the demands for offshore towing.Because of the fle...Currently,the cranes used at sea do not have enough flexibility,efficiency,and safety.Thus,this study proposed a floating multirobot coordinated towing system to meet the demands for offshore towing.Because of the flexibility of rope-driven robots,the one-way pulling characteristics of the rope,and the floating characteristics of the base,towing robots are easily overturned.First,the spatial configuration of the towing system was established according to the towing task,and the kinematic model of the towing system was established using the coordinate transformation.Then,the dynamic model of the towing system was established according to the rigid-body dynamics and hydrodynamic theory.Finally,the stability of the towing system was analyzed using the stability cone method.The simulation experiments provide a reference for the practical application of the floating multirobot coordinated towing system,which can improve the stability of towing systems by changing the configuration of the towing robot.展开更多
In this paper,a linear optimization method(LOM)for the design of terahertz circuits is presented,aimed at enhancing the simulation efficacy and reducing the time of the circuit design workflow.This method enables the ...In this paper,a linear optimization method(LOM)for the design of terahertz circuits is presented,aimed at enhancing the simulation efficacy and reducing the time of the circuit design workflow.This method enables the rapid determination of optimal embedding impedance for diodes across a specific bandwidth to achieve maximum efficiency through harmonic balance simulations.By optimizing the linear matching circuit with the optimal embedding impedance,the method effectively segregates the simulation of the linear segments from the nonlinear segments in the frequency multiplier circuit,substantially improving the speed of simulations.The design of on-chip linear matching circuits adopts a modular circuit design strategy,incorporating fixed load resistors to simplify the matching challenge.Utilizing this approach,a 340 GHz frequency doubler was developed and measured.The results demonstrate that,across a bandwidth of 330 GHz to 342 GHz,the efficiency of the doubler remains above 10%,with an input power ranging from 98 mW to 141mW and an output power exceeding 13 mW.Notably,at an input power of 141 mW,a peak output power of 21.8 mW was achieved at 334 GHz,corresponding to an efficiency of 15.8%.展开更多
A Wentzel-Kramers-Brillouin(WKB)method is introduced for obtaining a uniform asymptotic solution for underwater sound propagation at very low frequencies in deep ocean.The method utilizes a mode sum and employs the re...A Wentzel-Kramers-Brillouin(WKB)method is introduced for obtaining a uniform asymptotic solution for underwater sound propagation at very low frequencies in deep ocean.The method utilizes a mode sum and employs the reference functions method to describe the solution to the depth-separated wave equation approximately using parabolic cylinder functions.The conditions for the validity of this approximation are also discussed.Furthermore,a formula that incorporates waveguide effects for the modal group velocity is derived,revealing that boundary effects at very low frequencies can have a significant impact on the propagation characteristics of even low-order normal modes.The present method not only offers improved accuracy compared to the classical WKB approximation and the uniform asymptotic approximation based on Airy functions,but also provides a wider range of depth applicability.Additionally,this method exhibits strong agreement with numerical methods and offers valuable physical insights.Finally,the method is applied to the study of very-low-frequency sound propagation in the South China Sea,leading to sound transmission loss predictions that closely align with experimental observations.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
Solid-state batteries(SSBs) with high safety are promising for the energy fields,but the development has long been limited by machinability and interfacial problems.Hence,self-supporting,flexible Nano LLZO CSEs are pr...Solid-state batteries(SSBs) with high safety are promising for the energy fields,but the development has long been limited by machinability and interfacial problems.Hence,self-supporting,flexible Nano LLZO CSEs are prepared with a solvent-free method at 25℃.The 99.8 wt% contents of Nano LLZO particles enable the Nano LLZO CSEs to maintain good thermal stability while exhibiting a wide electrochemical window of 5.0 V and a high Li~+ transfer number of 0.8.The mean modulus reaches 4376 MPa.Benefiting from the interfacial modulation,the Li|Li symmetric batteries based on the Nano LLZO CSEs show benign stability with lithium at the current densities of 0.1 mA cm^(-2),0.2 mA cm^(-2),and 0.5 mA cm^(-2).In addition,the Li|LiFePO_(4)(LFP) SSBs achieve favorable cycling performance:the specific capacity reaches128.1 mAh g^(-1) at 0.5 C rate,with a capacity retention of about 80% after 600 cycles.In the further tests of the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811) cathodes with higher energy density,the Nano LLZO CSEs also demonstrate good compatibility:the specific capacities of NCM811-based SSBs reach 177.9 mAh g^(-1) at 0.5 C rate,while the capacity retention is over 96% after 150 cycles.Furthermore,the Li|LFP soft-pack SSBs verify the safety characteristics and the potential for application,which have a desirable prospect.展开更多
An optical emission spectroscopy(OES)method with a non-invasive measurement capability,without inducing disturbance to the discharge,represents an effective method for material monitoring.However,when the OES method i...An optical emission spectroscopy(OES)method with a non-invasive measurement capability,without inducing disturbance to the discharge,represents an effective method for material monitoring.However,when the OES method is employed to monitor the trace erosion product within the ceramic channel of a Hall thruster,it becomes challenging to distinguish between signal and noise.In this study,we propose a model filtering method based on the signal characteristics of the Hall thruster plume spectrometer.This method integrates the slit imaging and spectral resolution features of the spectrometer.Employing this method,we extract the spectral signals of the erosion product and working gas from the Hall thruster under different operating conditions.The results indicate that our new method performs comparably to the traditional method without model filtering when extracting atom signals from strong xenon working gas.However,for trace amounts of the erosion product,our approach significantly enhances the signal-to-noise ratio(SNR),enabling the identification of extremely weak spectral signals even under low mass flow rate and low-voltage conditions.We obtain boron atom concentration of 3.91×10^(-3) kg/m^(3) at a mass flow rate of 4×10^(-7) kg/s and voltage of 200 V while monitoring a wider range of thruster operating conditions.The new method proposed in this study is suitable for monitoring other low-concentration elements,making it valuable for materials processing,environmental monitoring and space propulsion applications.展开更多
The glutenite reservoir is strongly heterogeneous due to the random distribution of gravels, making it challenging to perform hydraulic fracturing effectively. To solve this issue, it is essential to study interaction...The glutenite reservoir is strongly heterogeneous due to the random distribution of gravels, making it challenging to perform hydraulic fracturing effectively. To solve this issue, it is essential to study interaction behavior between hydraulic fractures(HFs) and gravels. A coupled hydro-mechanical model is proposed for HF propagation in glutenite using a grain-based discrete element method. This paper first investigates the dynamic evolution of HFs in glutenite, then analyzes the influences of various factors such as horizontal stress difference(Δσ), minimum horizontal stress(σh), gravel content(Vg), gravel size(dg), and stiffness ratio of gravel to matrix(Rs) on HF propagation geometries. Results show that penetrating the gravel is the primary HF-gravel interaction behavior, which follows sequential and staggered initiation modes. Bypassing the gravel is the secondary behavior, which obeys the sequential initiation mode and occurs when the orientation of the gravel boundary is inclined to the maximum horizontal stress(σH). An offset along the gravel boundary is usually formed while penetrating gravels, and the offsets may cause fracture widths to decrease by 37.8%-84.4%. Even if stress dominates the direction of HF propagation, HFs still tend to deflect within gravels. The deviation angle from σH decreases with rising Δσand increases with the increase of dgand Rs. Additionally, intra-gravel shear HFs(IGS-HFs) are prone to be generated in coarse-grained glutenite under high Δσ, while more gravel-bypassing shear HFs(GBSHFs) tend to be created in argillaceous glutenite with high Rsthan in sandy glutenite with low Rs. The findings above prompt the emergence of a novel HF propagation pattern in glutenite, which helps to understand the real HF geometries and to provide theoretical guidance for treatments in the field.展开更多
This study aimed to model and identify the most productive cutting methods of tree plantations by comparing a forward felling technique(C)with sideways techniques outside(A and D)or inside cutting edge(B and E).Drone ...This study aimed to model and identify the most productive cutting methods of tree plantations by comparing a forward felling technique(C)with sideways techniques outside(A and D)or inside cutting edge(B and E).Drone video material of each tree was analyzed by comparing time distribution of work phases.The relation between this input data and harvester production data was analyzed by regression models.A quadratic model predicted productiv-ity precisely(R^(2)=0.95)and explained the effective-hour productivity in cutting cycle with dummy variables of har-vesting conditions.The productivity was explained by tree size and cutting cycle time,while effects of operator and harvester were eliminated by statistical analysis.In loblolly pine(Pinus taeda L.)plantations on flat terrain,cutting method B was 4.8 m3/E0h(effective working hour)more productive than method A,and 6.7 m^(3)/E0h than method C.In Sydney blue gum(Eucalyptus saligna Sm.)plantations,cutting method E was 1.8 m^(3)/E0h more productive than cut-ting method D on sloping terrain.Of the time-cycle vari-ables,time consumption of the“moving of tree”changed significantly between the cutting methods,of which the ones that used the sideways felling technique inside cutting edge were most efficient.This quadratic modeling structure can be recommended for precise studies in similar harvesting conditions.展开更多
To investigate the residual stress distribution and its influence on machining deformation in 6061-T651 aluminum alloy plates,this paper uses the crack compliance method to study the residual stress characteristics of...To investigate the residual stress distribution and its influence on machining deformation in 6061-T651 aluminum alloy plates,this paper uses the crack compliance method to study the residual stress characteristics of 6061-T651 aluminum alloy plates with a thickness of 75 mm produced by two domestic manufacturers in China.The results indicate that both types of plates exhibit highly consistent and symmetrical M-shaped residual stress profile along the thickness direction,manifested as surface layer compression and core tension.The strain energy density across all specimens ranges from 1.27 kJ/m^(3)to 1.43 kJ/m^(3).Machining deformation simulations of an aerospace component incorporating these measured stresses showed minimal final deformation difference between the material sources,with a maximum deviation of only 0.009 mm across specimens.These findings provide critical data for material selection and deformation control in aerospace manufacturing.展开更多
A meshless particle method based on the smoothed particle hydrodynamics(SPH)method is first proposed for the numerical prediction of physical phenomena of nonlinear solitary wave propagation and complex phenomena aris...A meshless particle method based on the smoothed particle hydrodynamics(SPH)method is first proposed for the numerical prediction of physical phenomena of nonlinear solitary wave propagation and complex phenomena arising from the inelastic interactions of solitary waves.The method is a fully discrete implicit scheme.This method does not rely on a grid,avoids the need to solve for derivatives of kernel functions,and makes the calculation more convenient.Additionally,the unique solvability of the proposed implicit scheme is proved.To verify the effectiveness and flexibility of the proposed method,we apply it to solving various time fractional nonlinear Schrödinger equations(TF-NLSE)on both regular and irregular domains.This mainly includes general or coupled TF-NLSE with or without analytical solutions.Moreover,the proposed method is compared with the existing methods.Through examples,it has been verified that this method can effectively predict complex propagation phenomena generated by the collision of nonlinear solitary waves,such as the collapse phenomenon of solitary waves with increasing fractional-order parameters.Research results indicate that this method provides a new and effective meshless method for predicting the propagation of nonlinear solitary waves,which can better simulate TF-NLSE in complex domains.展开更多
文摘This study investigated the physicochemical properties,enzyme activities,volatile flavor components,microbial communities,and sensory evaluation of high-temperature Daqu(HTD)during the maturation process,and a standard system was established for comprehensive quality evaluation of HTD.There were obvious changes in the physicochemical properties,enzyme activities,and volatile flavor components at different storage periods,which affected the sensory evaluation of HTD to a certain extent.The results of high-throughput sequencing revealed significant microbial diversity,and showed that the bacterial community changed significantly more than did the fungal community.During the storage process,the dominant bacterial genera were Kroppenstedtia and Thermoascus.The correlation between dominant microorganisms and quality indicators highlighted their role in HTD quality.Lactococcus,Candida,Pichia,Paecilomyces,and protease activity played a crucial role in the formation of isovaleraldehyde.Acidic protease activity had the greatest impact on the microbial community.Moisture promoted isobutyric acid generation.Furthermore,the comprehensive quality evaluation standard system was established by the entropy weight method combined with multi-factor fuzzy mathematics.Consequently,this study provides innovative insights for comprehensive quality evaluation of HTD during storage and establishes a groundwork for scientific and rational storage of HTD and quality control of sauce-flavor Baijiu.
基金supported by the National Natural Science Foundation of China(Grant Nos.12302435 and 12221002)。
文摘Shock wave caused by a sudden release of high-energy,such as explosion and blast,usually affects a significant range of areas.The utilization of a uniform fine mesh to capture sharp shock wave and to obtain precise results is inefficient in terms of computational resource.This is particularly evident when large-scale fluid field simulations are conducted with significant differences in computational domain size.In this work,a variable-domain-size adaptive mesh enlargement(vAME)method is developed based on the proposed adaptive mesh enlargement(AME)method for modeling multi-explosives explosion problems.The vAME method reduces the division of numerous empty areas or unnecessary computational domains by adaptively suspending enlargement operation in one or two directions,rather than in all directions as in AME method.A series of numerical tests via AME and vAME with varying nonintegral enlargement ratios and different mesh numbers are simulated to verify the efficiency and order of accuracy.An estimate of speedup ratio is analyzed for further efficiency comparison.Several large-scale near-ground explosion experiments with single/multiple explosives are performed to analyze the shock wave superposition formed by the incident wave,reflected wave,and Mach wave.Additionally,the vAME method is employed to validate the accuracy,as well as to investigate the performance of the fluid field and shock wave propagation,considering explosive quantities ranging from 1 to 5 while maintaining a constant total mass.The results show a satisfactory correlation between the overpressure versus time curves for experiments and numerical simulations.The vAME method yields a competitive efficiency,increasing the computational speed to 3.0 and approximately 120,000 times in comparison to AME and the fully fine mesh method,respectively.It indicates that the vAME method reduces the computational cost with minimal impact on the results for such large-scale high-energy release problems with significant differences in computational domain size.
基金Supported by the National Natural Science Foundation of China(12061048)NSF of Jiangxi Province(20232BAB201026,20232BAB201018)。
文摘In this paper,a new technique is introduced to construct higher-order iterative methods for solving nonlinear systems.The order of convergence of some iterative methods can be improved by three at the cost of introducing only one additional evaluation of the function in each step.Furthermore,some new efficient methods with a higher-order of convergence are obtained by using only a single matrix inversion in each iteration.Analyses of convergence properties and computational efficiency of these new methods are made and testified by several numerical problems.By comparison,the new schemes are more efficient than the corresponding existing ones,particularly for large problem sizes.
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.
基金Supported by the National Natural Science Foundation of China (Grant Nos.52088102 and 51879287)National Key Research and Development Program of China (Grant No.2022YFB2602301)。
文摘Long-term responses of floating structures pose a great concern in their design phase. Existing approaches for addressing long-term extreme responses are extremely cumbersome for adoption. This work aims to develop an approach for the long-term extreme-response analysis of floating structures. A modified gradient-based retrieval algorithm in conjunction with the inverse first-order reliability method(IFORM) is proposed to enable the use of convolution models in long-term extreme analysis of structures with an analytical formula of response amplitude operator(RAO). The proposed algorithm ensures convergence stability and iteration accuracy and exhibits a higher computational efficiency than the traditional backtracking method. However, when the RAO of general offshore structures cannot be analytically expressed, the convolutional integration method fails to function properly. A numerical discretization approach is further proposed for offshore structures in the case when the analytical expression of the RAO is not feasible. Through iterative discretization of environmental contours(ECs) and RAOs, a detailed procedure is proposed to calculate the long-term response extremes of offshore structures. The validity and accuracy of the proposed approach are tested using a floating offshore wind turbine as a numerical example. The long-term extreme heave responses of various return periods are calculated via the IFORM in conjunction with a numerical discretization approach. The environmental data corresponding to N-year structural responses are located inside the ECs, which indicates that the selection of design points directly along the ECs yields conservative design results.
基金National Natural Science Foundation of China(No.22275150)。
文摘To study the influence of silicon(Si)on 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20),NC/CL-20 composite explosives and Si/NC/CL-20 composite explosives were prepared by the electrostatic spraying method.The morphology,structure and thermal decomposition properties of the samples were analyzed using scanning electron microscopy(SEM),X-ray energy spectroscopy(EDS),infrared spectroscopy(FT-IR),and simultaneous thermal analyzer(TG-DSC).Additionally,the combustion process of the samples was tested using a high-speed camera.The results show that the addition of nano-Si contributes to the formation of composite explosives with regular morphology and smaller particle size.The Si/NC/CL-20 composite explosive has better and more uniform sphericity,with an average particle size of 73.4 nm,compared to the NC/CL-20 composite explosive.The Si/NC/CL-20 composite explosive which produced by the electrostatic spraying method,achieves physically uniform distribution of the components including NC,CL-20,Si.The addition of Si promotes the thermal decomposition of CL-20.In comparison to the NC/CL-20 composite explosive,the activation energy of the Si/NC/CL-20 composite explosive decreases by 16.78 kJ/mol,and the self-accelerated decomposition temperature and the critical temperature of thermal explosion decreases by 3.12 K and 2.61 K,respectively.Furthermore,Si/NC/CL-20 composite explosive has shorter ignition delay time and faster combustion rate compared to the NC/CL-20 composite explosive,which shows that Si can improve the combustion performance of CL-20.
基金funded by the Ministry of Education, Science and Technological Development of the Republic of Serbia via the FAMA project (research topic “Physics and chemistry with ion beams”)。
文摘Without knowing the emittance value, it is difficult to optimize ion beam optics for minimum beam loss during transmission, especially considering the very high emittance values of electron cyclotron resonance(ECR) ion sources.With this in mind, to measure the emittance of the ion beams produced by the mVINIS ECR, which is part of the FAMA facility at the Vin?a Institute of Nuclear Sciences, we have developed a pepper-pot scintillator screen system combined with a CMOS camera. The application, developed on the Lab VIEW platform, allows us to control the camera's main attribute settings, such as the shutter speed and the gain, record the images in the region of interest, and process and filter the images in real time. To analyze the data from the obtained image, we have developed an algorithm called measurement and analysis of ion beam luminosity(MAIBL) to reconstruct the four-dimensional(4D) beam profile and calculate the root mean square(RMS) emittance. Before measuring emittance, we performed a simulated experiment using the pepper-pot simulation(PPS) program. An exported file(PPS) gives a numerically generated raw image(mock image) of a beam with a predefined emittance value after it has passed through a pepper-pot mask. By analyzing data from mock images instead of the image obtained by the camera and putting it into the MAIBL algorithm, we can compare the calculated emittance with PPS's initial emittance value. In this paper, we present our computational tools and explain the method for verifying the correctness of the calculated emittance values.
基金Supported by Shanxi Province Natural Science Research(202203021212249)Special/Youth Foundation of Taiyuan University of Technology(2022QN101)+3 种基金National Natural Science Foundation of China(12301556)Research Project Supported by Shanxi Scholarship Council of China(2021-029)International Cooperation Base and Platform Project of Shanxi Province(202104041101019)Basic Research Plan of Shanxi Province(202203021211129)。
文摘To enhance the computational efficiency of spatio-temporally discretized phase-field models,we present a high-speed solver specifically designed for the Poisson equations,a component frequently used in the numerical computation of such models.This efficient solver employs algorithms based on discrete cosine transformations(DCT)or discrete sine transformations(DST)and is not restricted by any spatio-temporal schemes.Our proposed methodology is appropriate for a variety of phase-field models and is especially efficient when combined with flow field systems.Meanwhile,this study has conducted an extensive numerical comparison and found that employing DCT and DST techniques not only yields results comparable to those obtained via the Multigrid(MG)method,a conventional approach used in the resolution of the Poisson equations,but also enhances computational efficiency by over 90%.
基金partially supported by the National Natural Science Foundation of China(Nos.92271103,12202191)。
文摘The diffuse-interface immersed boundary method(IBM)possesses excellent capabilities for simulating flows around complex geometries and moving boundaries.In this method,the flow field is solved on a fixed Cartesian mesh,while the solid boundary is discretized into a series of Lagrangian points immersed in the flow field.The boundary condition is implemented by introducing a force term into the momentum equation,and the interaction between the immersed boundary and the fluid domain is achieved via an interpolation process.Over the past decades,the diffuse-interface IBM has gained popularity and spawned many variants,effectively handling a wide range of flow problems from isothermal to thermal flows,from laminar to turbulent flows,and from complex geometries to fluidstructure interaction scenarios.This paper first outlines the basic principles of the diffuse-interface IBM,then highlights recent advancements achieved by the authors’research group,and finally shows the method’s excellent numerical performance and wide applicability through several case studies involving complex moving boundary problems.
基金Supported by the National Natural Science Foundation of China under Grant No.51965032the Natural Science Foundation of Gansu Province of China under Grant No.22JR5RA319+2 种基金the Excellent Doctoral Student Foundation of Gansu Province of China under Grant No.23JRRA842the Sichuan Province Engineering Technology Research Center of General Aircraft Maintenance under Grant No.GAMRC2023YB05the Key Research and Development Project of Lanzhou Jiaotong University under Grant No.LZJTUZDYF2302.
文摘Currently,the cranes used at sea do not have enough flexibility,efficiency,and safety.Thus,this study proposed a floating multirobot coordinated towing system to meet the demands for offshore towing.Because of the flexibility of rope-driven robots,the one-way pulling characteristics of the rope,and the floating characteristics of the base,towing robots are easily overturned.First,the spatial configuration of the towing system was established according to the towing task,and the kinematic model of the towing system was established using the coordinate transformation.Then,the dynamic model of the towing system was established according to the rigid-body dynamics and hydrodynamic theory.Finally,the stability of the towing system was analyzed using the stability cone method.The simulation experiments provide a reference for the practical application of the floating multirobot coordinated towing system,which can improve the stability of towing systems by changing the configuration of the towing robot.
基金Supported by the Beijing Municipal Science&Technology Commission(Z211100004421012),the Key Reaserch and Development Pro⁃gram of China(2022YFF0605902)。
文摘In this paper,a linear optimization method(LOM)for the design of terahertz circuits is presented,aimed at enhancing the simulation efficacy and reducing the time of the circuit design workflow.This method enables the rapid determination of optimal embedding impedance for diodes across a specific bandwidth to achieve maximum efficiency through harmonic balance simulations.By optimizing the linear matching circuit with the optimal embedding impedance,the method effectively segregates the simulation of the linear segments from the nonlinear segments in the frequency multiplier circuit,substantially improving the speed of simulations.The design of on-chip linear matching circuits adopts a modular circuit design strategy,incorporating fixed load resistors to simplify the matching challenge.Utilizing this approach,a 340 GHz frequency doubler was developed and measured.The results demonstrate that,across a bandwidth of 330 GHz to 342 GHz,the efficiency of the doubler remains above 10%,with an input power ranging from 98 mW to 141mW and an output power exceeding 13 mW.Notably,at an input power of 141 mW,a peak output power of 21.8 mW was achieved at 334 GHz,corresponding to an efficiency of 15.8%.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12174048 and 12204128)。
文摘A Wentzel-Kramers-Brillouin(WKB)method is introduced for obtaining a uniform asymptotic solution for underwater sound propagation at very low frequencies in deep ocean.The method utilizes a mode sum and employs the reference functions method to describe the solution to the depth-separated wave equation approximately using parabolic cylinder functions.The conditions for the validity of this approximation are also discussed.Furthermore,a formula that incorporates waveguide effects for the modal group velocity is derived,revealing that boundary effects at very low frequencies can have a significant impact on the propagation characteristics of even low-order normal modes.The present method not only offers improved accuracy compared to the classical WKB approximation and the uniform asymptotic approximation based on Airy functions,but also provides a wider range of depth applicability.Additionally,this method exhibits strong agreement with numerical methods and offers valuable physical insights.Finally,the method is applied to the study of very-low-frequency sound propagation in the South China Sea,leading to sound transmission loss predictions that closely align with experimental observations.
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supported by Science and Technology Project of China Southern Power Grid (SZKJXM20230049/090000KC23010038)。
文摘Solid-state batteries(SSBs) with high safety are promising for the energy fields,but the development has long been limited by machinability and interfacial problems.Hence,self-supporting,flexible Nano LLZO CSEs are prepared with a solvent-free method at 25℃.The 99.8 wt% contents of Nano LLZO particles enable the Nano LLZO CSEs to maintain good thermal stability while exhibiting a wide electrochemical window of 5.0 V and a high Li~+ transfer number of 0.8.The mean modulus reaches 4376 MPa.Benefiting from the interfacial modulation,the Li|Li symmetric batteries based on the Nano LLZO CSEs show benign stability with lithium at the current densities of 0.1 mA cm^(-2),0.2 mA cm^(-2),and 0.5 mA cm^(-2).In addition,the Li|LiFePO_(4)(LFP) SSBs achieve favorable cycling performance:the specific capacity reaches128.1 mAh g^(-1) at 0.5 C rate,with a capacity retention of about 80% after 600 cycles.In the further tests of the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811) cathodes with higher energy density,the Nano LLZO CSEs also demonstrate good compatibility:the specific capacities of NCM811-based SSBs reach 177.9 mAh g^(-1) at 0.5 C rate,while the capacity retention is over 96% after 150 cycles.Furthermore,the Li|LFP soft-pack SSBs verify the safety characteristics and the potential for application,which have a desirable prospect.
基金financially supported by National Natural Science Foundation of China(No.U22B2094)。
文摘An optical emission spectroscopy(OES)method with a non-invasive measurement capability,without inducing disturbance to the discharge,represents an effective method for material monitoring.However,when the OES method is employed to monitor the trace erosion product within the ceramic channel of a Hall thruster,it becomes challenging to distinguish between signal and noise.In this study,we propose a model filtering method based on the signal characteristics of the Hall thruster plume spectrometer.This method integrates the slit imaging and spectral resolution features of the spectrometer.Employing this method,we extract the spectral signals of the erosion product and working gas from the Hall thruster under different operating conditions.The results indicate that our new method performs comparably to the traditional method without model filtering when extracting atom signals from strong xenon working gas.However,for trace amounts of the erosion product,our approach significantly enhances the signal-to-noise ratio(SNR),enabling the identification of extremely weak spectral signals even under low mass flow rate and low-voltage conditions.We obtain boron atom concentration of 3.91×10^(-3) kg/m^(3) at a mass flow rate of 4×10^(-7) kg/s and voltage of 200 V while monitoring a wider range of thruster operating conditions.The new method proposed in this study is suitable for monitoring other low-concentration elements,making it valuable for materials processing,environmental monitoring and space propulsion applications.
基金supported by the National Natural Science Foundation of China(Grant No.52304003)the Natural Science Foundation of Sichuan Province(Grant No.2024NSFSC0961)the Postdoctoral Fellowship Program of CPSF(Grant No.GZB20230090).
文摘The glutenite reservoir is strongly heterogeneous due to the random distribution of gravels, making it challenging to perform hydraulic fracturing effectively. To solve this issue, it is essential to study interaction behavior between hydraulic fractures(HFs) and gravels. A coupled hydro-mechanical model is proposed for HF propagation in glutenite using a grain-based discrete element method. This paper first investigates the dynamic evolution of HFs in glutenite, then analyzes the influences of various factors such as horizontal stress difference(Δσ), minimum horizontal stress(σh), gravel content(Vg), gravel size(dg), and stiffness ratio of gravel to matrix(Rs) on HF propagation geometries. Results show that penetrating the gravel is the primary HF-gravel interaction behavior, which follows sequential and staggered initiation modes. Bypassing the gravel is the secondary behavior, which obeys the sequential initiation mode and occurs when the orientation of the gravel boundary is inclined to the maximum horizontal stress(σH). An offset along the gravel boundary is usually formed while penetrating gravels, and the offsets may cause fracture widths to decrease by 37.8%-84.4%. Even if stress dominates the direction of HF propagation, HFs still tend to deflect within gravels. The deviation angle from σH decreases with rising Δσand increases with the increase of dgand Rs. Additionally, intra-gravel shear HFs(IGS-HFs) are prone to be generated in coarse-grained glutenite under high Δσ, while more gravel-bypassing shear HFs(GBSHFs) tend to be created in argillaceous glutenite with high Rsthan in sandy glutenite with low Rs. The findings above prompt the emergence of a novel HF propagation pattern in glutenite, which helps to understand the real HF geometries and to provide theoretical guidance for treatments in the field.
文摘This study aimed to model and identify the most productive cutting methods of tree plantations by comparing a forward felling technique(C)with sideways techniques outside(A and D)or inside cutting edge(B and E).Drone video material of each tree was analyzed by comparing time distribution of work phases.The relation between this input data and harvester production data was analyzed by regression models.A quadratic model predicted productiv-ity precisely(R^(2)=0.95)and explained the effective-hour productivity in cutting cycle with dummy variables of har-vesting conditions.The productivity was explained by tree size and cutting cycle time,while effects of operator and harvester were eliminated by statistical analysis.In loblolly pine(Pinus taeda L.)plantations on flat terrain,cutting method B was 4.8 m3/E0h(effective working hour)more productive than method A,and 6.7 m^(3)/E0h than method C.In Sydney blue gum(Eucalyptus saligna Sm.)plantations,cutting method E was 1.8 m^(3)/E0h more productive than cut-ting method D on sloping terrain.Of the time-cycle vari-ables,time consumption of the“moving of tree”changed significantly between the cutting methods,of which the ones that used the sideways felling technique inside cutting edge were most efficient.This quadratic modeling structure can be recommended for precise studies in similar harvesting conditions.
基金supported in part by the National Natural Science Foundation of China(Nos.61201048,61107063)the National Science and Technology Major Project(No.2017-VI-001-0094).
文摘To investigate the residual stress distribution and its influence on machining deformation in 6061-T651 aluminum alloy plates,this paper uses the crack compliance method to study the residual stress characteristics of 6061-T651 aluminum alloy plates with a thickness of 75 mm produced by two domestic manufacturers in China.The results indicate that both types of plates exhibit highly consistent and symmetrical M-shaped residual stress profile along the thickness direction,manifested as surface layer compression and core tension.The strain energy density across all specimens ranges from 1.27 kJ/m^(3)to 1.43 kJ/m^(3).Machining deformation simulations of an aerospace component incorporating these measured stresses showed minimal final deformation difference between the material sources,with a maximum deviation of only 0.009 mm across specimens.These findings provide critical data for material selection and deformation control in aerospace manufacturing.
基金supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region,China(Grant No.2024D01C44).
文摘A meshless particle method based on the smoothed particle hydrodynamics(SPH)method is first proposed for the numerical prediction of physical phenomena of nonlinear solitary wave propagation and complex phenomena arising from the inelastic interactions of solitary waves.The method is a fully discrete implicit scheme.This method does not rely on a grid,avoids the need to solve for derivatives of kernel functions,and makes the calculation more convenient.Additionally,the unique solvability of the proposed implicit scheme is proved.To verify the effectiveness and flexibility of the proposed method,we apply it to solving various time fractional nonlinear Schrödinger equations(TF-NLSE)on both regular and irregular domains.This mainly includes general or coupled TF-NLSE with or without analytical solutions.Moreover,the proposed method is compared with the existing methods.Through examples,it has been verified that this method can effectively predict complex propagation phenomena generated by the collision of nonlinear solitary waves,such as the collapse phenomenon of solitary waves with increasing fractional-order parameters.Research results indicate that this method provides a new and effective meshless method for predicting the propagation of nonlinear solitary waves,which can better simulate TF-NLSE in complex domains.
