Natural gas hydrate(NGH)has a bright future as a clean energy source with huge reserves.Coring is one of the most direct methods for NGH exploration and research.Preserving the in-situ properties of the core as much a...Natural gas hydrate(NGH)has a bright future as a clean energy source with huge reserves.Coring is one of the most direct methods for NGH exploration and research.Preserving the in-situ properties of the core as much as possible during the coring process is crucial for the assessment of NGH resources.However,most existing NGH coring techniques cannot preserve the in-situ temperature of NGH,leading to distortion of the physical properties of the obtained core,which makes it difficult to effectively guide NGH exploration and development.To overcome this limitation,this study introduces an innovative active temperature-preserved coring method for NGH utilizing phase change materials(PCM).An active temperature-preserved corer(ATPC)is designed and developed,and an indoor experimental system is established to investigate the heat transfer during the coring process.Based on the experimental results under different environment temperatures,a heat transfer model for the entire ATPC coring process has been established.The indoor experimental results are consistent with the theoretical predictions of the heat transfer model,confirming its validity.This model has reconstructed the temperature changes of the NGH core during the coring process,demonstrating that compared to the traditional coring method with only passive temperature-preserved measures,ATPC can effectively reduce the core temperature by more than 5.25℃.With ATPC,at environment temperatures of 15,20,25,and 30℃,the duration of low-temperature state for the NGH core is 53.85,32.87,20.32,and 11.83 min,respectively.These findings provide new perspectives on temperature-preserving core sampling in NGH and provide technical support for exploration and development in NGH.展开更多
With Beijing Huilongguan Sports and Cultural Park as the research object,this study was conducted to investigate public service satisfaction in the park by the Importance-Performance Analysis(IPA)method.A questionnair...With Beijing Huilongguan Sports and Cultural Park as the research object,this study was conducted to investigate public service satisfaction in the park by the Importance-Performance Analysis(IPA)method.A questionnaire covering six dimensions,including public transportation,sanitation and environment,and supporting facility construction,was designed.A total of 208 valid samples were collected,and SPSS was employed for reliability and validity tests as well as IPA analysis.The findings were as follows:①Visitors were generally quite satisfied with the overall public services in Huilongguan Sports and Cultural Park.②The highest satisfaction levels were observed in sanitation and environment services and the sports and cultural atmosphere,while lower satisfaction was noted for supporting facility construction and public information services.③The advantage enhancement zone includes sanitation and environment services and sports and cultural atmosphere;and the continuous maintenance zone includes public transportation services and security management amd maintenance;the subsequent opportunity zone includes supporting facility construction and public information services;and there are no dimensions in the urgent improvement zone.The study recommends strengthening the service connotations from three aspects:enhancing facilities with sports as the core,optimizing services with a people-centered approach,and upgrading the information platform through technological efficiency.Additionally,a multi-stakeholder collaborative mechanism involving the government in coordinating policy resources,the operator in improving implementation efficiency,and the public participating in supervision and evaluation is proposed to drive the enhancement of public service quality at Huilongguan Sports and Cultural Park.展开更多
The application of multi-material topology optimization affords greater design flexibility compared to traditional single-material methods.However,density-based topology optimization methods encounter three unique cha...The application of multi-material topology optimization affords greater design flexibility compared to traditional single-material methods.However,density-based topology optimization methods encounter three unique challenges when inertial loads become dominant:non-monotonous behavior of the objective function,possible unconstrained characterization of the optimal solution,and parasitic effects.Herein,an improved Guide-Weight approach is introduced,which effectively addresses the structural topology optimization problem when subjected to inertial loads.Smooth and fast convergence of the compliance is achieved by the approach,while also maintaining the effectiveness of the volume constraints.The rational approximation of material properties model and smooth design are utilized to guarantee clear boundaries of the final structure,facilitating its seamless integration into manufacturing processes.The framework provided by the alternating active-phase algorithm is employed to decompose the multi-material topological problem under inertial loading into a set of sub-problems.The optimization of multi-material under inertial loads is accomplished through the effective resolution of these sub-problems using the improved Guide-Weight method.The effectiveness of the proposed approach is demonstrated through numerical examples involving two-phase and multi-phase materials.展开更多
In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to ...In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to obtain the maximal positive definite solution of nonlinear matrix equation X+A^(*)X|^(-α)A=Q with the case 0<α≤1.Based on this method,a new iterative algorithm is developed,and its convergence proof is given.Finally,two numerical examples are provided to show the effectiveness of the proposed method.展开更多
In this paper,a novel method for investigating the particle-crushing behavior of breeding particles in a fusion blanket is proposed.The fractal theory and Weibull distribution are combined to establish a theoretical m...In this paper,a novel method for investigating the particle-crushing behavior of breeding particles in a fusion blanket is proposed.The fractal theory and Weibull distribution are combined to establish a theoretical model,and its validity was verified using a simple impact test.A crushable discrete element method(DEM)framework is built based on the previously established theoretical model.The tensile strength,which considers the fractal theory,size effect,and Weibull variation,was assigned to each generated particle.The assigned strength is then used for crush detection by comparing it with its maximum tensile stress.Mass conservation is ensured by inserting a series of sub-particles whose total mass was equal to the quality loss.Based on the crushable DEM framework,a numerical simulation of the crushing behavior of a pebble bed with hollow cylindrical geometry under a uniaxial compression test was performed.The results of this investigation showed that the particle withstands the external load by contact and sliding at the beginning of the compression process,and the results confirmed that crushing can be considered an important method of resisting the increasing external load.A relatively regular particle arrangement aids in resisting the load and reduces the occurrence of particle crushing.However,a limit exists to the promotion of resistance.When the strain increases beyond this limit,the distribution of the crushing position tends to be isotropic over the entire pebble bed.The theoretical model and crushable DEM framework provide a new method for exploring the pebble bed in a fusion reactor,considering particle crushing.展开更多
Effective partitioning is crucial for enabling parallel restoration of power systems after blackouts.This paper proposes a novel partitioning method based on deep reinforcement learning.First,the partitioning decision...Effective partitioning is crucial for enabling parallel restoration of power systems after blackouts.This paper proposes a novel partitioning method based on deep reinforcement learning.First,the partitioning decision process is formulated as a Markov decision process(MDP)model to maximize the modularity.Corresponding key partitioning constraints on parallel restoration are considered.Second,based on the partitioning objective and constraints,the reward function of the partitioning MDP model is set by adopting a relative deviation normalization scheme to reduce mutual interference between the reward and penalty in the reward function.The soft bonus scaling mechanism is introduced to mitigate overestimation caused by abrupt jumps in the reward.Then,the deep Q network method is applied to solve the partitioning MDP model and generate partitioning schemes.Two experience replay buffers are employed to speed up the training process of the method.Finally,case studies on the IEEE 39-bus test system demonstrate that the proposed method can generate a high-modularity partitioning result that meets all key partitioning constraints,thereby improving the parallelism and reliability of the restoration process.Moreover,simulation results demonstrate that an appropriate discount factor is crucial for ensuring both the convergence speed and the stability of the partitioning training.展开更多
The application of nitrogen fertilizers in agricultural fields can lead to the release of nitrogen-containing gases(NCGs),such as NO_(x),NH_(3) and N_(2)O,which can significantly impact regional atmospheric environmen...The application of nitrogen fertilizers in agricultural fields can lead to the release of nitrogen-containing gases(NCGs),such as NO_(x),NH_(3) and N_(2)O,which can significantly impact regional atmospheric environment and con-tribute to global climate change.However,there remain considerable research gaps in the accurate measurement of NCGs emissions from agricultural fields,hindering the development of effective emission reduction strategies.We improved an open-top dynamic chambers(OTDCs)system and evaluated the performance by comparing the measured and given fluxes of the NCGs.The results showed that the measured fluxes of NO,N_(2)O and NH_(3)were 1%,2%and 7%lower than the given fluxes,respectively.For the determination of NH_(3) concentration,we employed a stripping coil-ion chromatograph(SC-IC)analytical technique,which demonstrated an absorption efficiency for atmospheric NH_(3) exceeding 96.1%across sampling durations of 6 to 60 min.In the summer maize season,we utilized the OTDCs system to measure the exchange fluxes of NO,NH_(3),and N_(2)O from the soil in the North China Plain.Substantial emissions of NO,NH_(3) and N_(2)O were recorded following fertilization,with peaks of 107,309,1239 ng N/(m^(2)·s),respectively.Notably,significant NCGs emissions were observed following sus-tained heavy rainfall one month after fertilization,particularly with NH_(3) peak being 4.5 times higher than that observed immediately after fertilization.Our results demonstrate that the OTDCs system accurately reflects the emission characteristics of soil NCGs and meets the requirements for long-term and continuous flux observation.展开更多
Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The t...Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.展开更多
At present,there is currently a lack of unified standard methods for the determination of antimony content in groundwater in China.The precision and trueness of related detection technologies have not yet been systema...At present,there is currently a lack of unified standard methods for the determination of antimony content in groundwater in China.The precision and trueness of related detection technologies have not yet been systematically and quantitatively evaluated,which limits the effective implementation of environmental monitoring.In response to this key technical gap,this study aimed to establish a standardized method for determining antimony in groundwater using Hydride Generation–Atomic Fluorescence Spectrometry(HG-AFS).Ten laboratories participated in inter-laboratory collaborative tests,and the statistical analysis of the test data was carried out in strict accordance with the technical specifications of GB/T 6379.2—2004 and GB/T 6379.4—2006.The consistency and outliers of the data were tested by Mandel's h and k statistics,the Grubbs test and the Cochran test,and the outliers were removed to optimize the data,thereby significantly improving the reliability and accuracy.Based on the optimized data,parameters such as the repeatability limit(r),reproducibility limit(R),and method bias value(δ)were determined,and the trueness of the method was statistically evaluated.At the same time,precision-function relationships were established,and all results met the requirements.The results show that the lower the antimony content,the lower the repeatability limit(r)and reproducibility limit(R),indicating that the measurement error mainly originates from the detection limit of the method and instrument sensitivity.Therefore,improving the instrument sensitivity and reducing the detection limit are the keys to controlling the analytical error and improving precision.This study provides reliable data support and a solid technical foundation for the establishment and evaluation of standardized methods for the determination of antimony content in groundwater.展开更多
By utilizing phase field method combined with analysis on free energy and interatomic potentials, pre-precipitation phase formation and transformation process of Ni0.75Al0.05Fe0.2 alloy in early precipitation stage du...By utilizing phase field method combined with analysis on free energy and interatomic potentials, pre-precipitation phase formation and transformation process of Ni0.75Al0.05Fe0.2 alloy in early precipitation stage during the ageing process under 1 000 K were studied. And free energy, microstructures, compositions and volume fractions of pre-precipitation phase and equilibrium phase were analyzed. The simulation results indicate that nonstoichiometric Llo pre-precipitation phase formed first, and then would gradually transform into L12 equilibrium phase. It is discovered that the phase transformation process was closely related to free energy and interatomic potentials. Additionally, it is revealed that free energy of Llo pre-precipitation phase was higher and interatomic potential was smaller than that of L12 equilibrium phase. Therefore, it is concluded that Llo phase was unstable, and phase transformation would occur to L12 which was more stable.展开更多
Deployment of buoy systems is one of the most important procedures for the operation of buoy system. In the present study, a single-point mooring buoy system which contains surface buoy, cable segments with components...Deployment of buoy systems is one of the most important procedures for the operation of buoy system. In the present study, a single-point mooring buoy system which contains surface buoy, cable segments with components, anchor and so on is modeled by applying multi-body dynamics method. The motion equations are developed in discrete node description and fully Cartesian coordinates. Then numerical method is used to solve the ordinary differential equations and dynamics simulations are achieved while anchor is casting from board. The trajectories and velocities of different nodes without current and with current in buoy system are obtained. The transient tension force of each part of the cable is analyzed in the process of deployment. Numerical results indicate that the transient payload increases to a peak value when the anchor is touching the seabed and the maximum tension force will vary with different floating configuration. This work is helpful for design and deployment planning of buoy system.展开更多
Single-point incremental forming （SPIF） is an innovational sheet metal forming method without dedicated dies, which belongs to rapid prototyping technology. In generalizing the SPIF of sheet metal, the deformation a...Single-point incremental forming （SPIF） is an innovational sheet metal forming method without dedicated dies, which belongs to rapid prototyping technology. In generalizing the SPIF of sheet metal, the deformation analysis on forming process becomes an important and useful method for the planning of shell products, the choice of material, the design of the forming process and the planning of the forming tool. Using solid brick elements, the finite element method（FEM） model of truncated pyramid was established. Based on the theory of anisotropy and assumed strain formulation, the SPIF processes with different parameters were simulated. The resulted comparison between the simulations and the experiments shows that the FEM model is feasible and effective. Then, according to the simulated forming process, the deformation pattern of SPIF can be summarized as the combination of plane-stretching deformation and bending deformation. And the study about the process parameters＇ impact on deformation shows that the process parameter of interlayer spacing is a dominant factor on the deformation. Decreasing interlayer spacing, the strain of one step decreases and the formability of blank will be improved. With bigger interlayer spacing, the plastic deformation zone increases and the forming force will be bigger.展开更多
Large-scale slope destabilization could be aggravated due to swift urbanization and ever-rising demands of geoengineering projects such as dams,tunnels,bridges and widening roads.National Highway-58 connects Delhi to ...Large-scale slope destabilization could be aggravated due to swift urbanization and ever-rising demands of geoengineering projects such as dams,tunnels,bridges and widening roads.National Highway-58 connects Delhi to Badrinath in India,which passes through complex geomorphological and geological terrain and often encounters cut slopes susceptible to slope failures.In the present investigation,a detailed geotechnical appraisal is conducted along the road cut slopes from Rishikesh to Devprayag in the Himalayas.Twenty vulnerable road cut slopes were demarcated for detailed slope stability analysis using Phase2D finite element modeling simulator.Nonlinear generalized Hoek-Brown(GHB)criterion was adopted for stability analyses.Out of 20 slopes,five slopes(S6,S7,S18,S19 and S20)are unstable with factor of safety(FoS)less than or equal to 1,and thus needs immediate attention.The FoS values of four slopes(S2,S9,S13 and S17)lie between 1 and 1.3,i.e.marginally stable,and slopes S1,S3,S4,S5,S8,S10,Sll,S12,S14,S15 and S16 are stable.Mohr-Coulomb(MC)criterion was also adopted to compare the slope stability analysis with GHB criterion.The FoS calculated from GHB criterion is close to that using MC criterion for lower values of FoS whereas for higher values,the difference is marked.For the jointed rock in the Himalayan region,the nonlinear GHB criterion gives better results as compared to MC criterion and matches with the prevailing field conditions.Accordingly,some suggestions are proposed to strengthen the stability of cut slopes.展开更多
This article presents a multiobjective approach to the design of the controller for the swing-up and handstand control of a general cart-double-pendulum system （CDPS）. The designed controller, which is based on the ...This article presents a multiobjective approach to the design of the controller for the swing-up and handstand control of a general cart-double-pendulum system （CDPS）. The designed controller, which is based on the human-simulated intelligent control （HSIC） method, builds up different control modes to monitor and control the CDPS during four kinetic phases consisting of an initial oscillation phase, a swing-up phase, a posture adjustment phase, and a balance control phase. For the approach, the original method of inequalities-based （MoI） multiobjective genetic algorithm （MMGA） is extended and applied to the case study which uses a set of performance indices that includes the cart displacement over the rail boundary, the number of swings, the settling time, the overshoot of the total energy, and the control effort. The simulation results show good responses of the CDPS with the controllers obtained by the proposed approach.展开更多
All-inorganic perovskites CsPbX_(3)(X=Cl,Br,I)have attracted worldwide interest due to their excellent lumi-nescent performances.Meanwhile,Cs_(4)PbBr_(6) have been studied because they can enhance the luminescent effi...All-inorganic perovskites CsPbX_(3)(X=Cl,Br,I)have attracted worldwide interest due to their excellent lumi-nescent performances.Meanwhile,Cs_(4)PbBr_(6) have been studied because they can enhance the luminescent efficiency and stability of CsPbBr_(3).Herein,we introduced a microfluidic method based on room-temperature supersat-urated recrystallization to synthesize blue-emitting CsPbBr_(3)nanocrystals(NCs)and green-emitting CsPbBr_(3)/Cs_(4)PbBr_(6)NCs.The ultrasmall CsPbBr_(3)NCs emitted at a deep blue wavelength of 461 nm with the full width at half maximum(FWHM)of 15 nm.transmission electron microscopy(TEM)results demonstrated that ultrasmall CsPbBr_(3)NCs with the average particle size of 3.8 nm were synthesized and the CsPbBr_(3)NCs were crystallized as monoclinic structure.展开更多
The influence of wind on the pointing accuracy of large aperture radio telescopes is becoming increasingly serious, especially at high observing frequency. Obtaining the wind field characteristics efficiently is very ...The influence of wind on the pointing accuracy of large aperture radio telescopes is becoming increasingly serious, especially at high observing frequency. Obtaining the wind field characteristics efficiently is very important to reduce the wind disturbance on antenna structure. In this paper, an error evaluation of numerical simulation method is established based on the measured data of single point wind tower, and the wind field characteristics are obtained from the evaluated numerical simulation results combined with the measured data for the 110 m aperture Qi Tai radio Telescope(QTT) site. According to the simulation results, compared with the measured data, the root mean square error(RMSE) of wind speed is less than 1 m s^-1, and the minimum wind speed RMSE is 0.2 m s^-1. An analysis of the wind field characteristics of the QTT site suggests that the active wind resistance design of the antenna periphery should focus on the SSW(south-south-west) direction.展开更多
Line profile analysis of X-ray and neutron diffraction patterns is a powerful tool for determining the microstructure of crystalline materials. The Convolutional-Multiple-Whole-Profile (CMWP) procedure is based on phy...Line profile analysis of X-ray and neutron diffraction patterns is a powerful tool for determining the microstructure of crystalline materials. The Convolutional-Multiple-Whole-Profile (CMWP) procedure is based on physical profile functions for dislocations, domain size, stacking faults and twin boundaries. Order dependence, strain anisotropy, hkl dependent broadening of planar defects and peak shape are used to separate the effect of different lattice defect types. The Marquardt-Levenberg (ML) numerical optimiza-tion procedure has been used successfully to determine crystal defect types and densities. However, in more complex cases like hexagonal materials or multiple phases the ML procedure alone reveals uncer-tainties. In a new approach the ML and a Monte-Carlo statistical method are combined in an alternative manner. The new CMWP procedure eliminates uncertainties and provides globally optimized parameters.展开更多
This paper investigates the phenomenon of three-pulse photon echo in thick rare-earth ions doped crystal whose thickness is far larger than 0.002 cm which is adopted in previous works.The influence of thickness on the...This paper investigates the phenomenon of three-pulse photon echo in thick rare-earth ions doped crystal whose thickness is far larger than 0.002 cm which is adopted in previous works.The influence of thickness on the three-pulse photon echo＇s amplitude and efficiency is analyzed with the Maxwell-Bloch equations solved by finite-difference timedomain method.We demonstrate that the amplitude of three-pulse echo will increase with the increasing of thickness and the optimum thickness to generate three-pulse photon echo is 0.3 cm for Tm^（3＋）：YAG when the attenuation of the input pulse is taken into account.Meanwhile,we find the expression 0.09 exp（α＇L）,which is previously employed to describe the relationship between echo＇s efficiency and thickness,should be modified as 1.3 · 0.09 exp（2.4 ·α＇L） with the propagation of echo considered.展开更多
A new algorithm called homotopy iteration method based on the homotopy function is studied and improved. By the improved homotopy iteration method, Polynomial systems with high Order and deficient can be solved fast a...A new algorithm called homotopy iteration method based on the homotopy function is studied and improved. By the improved homotopy iteration method, Polynomial systems with high Order and deficient can be solved fast and efficiently comparing to the original homotopy iteration method. Numerical examples for the ninepoint path synthesis of four-bar linkages show the advantages and efficiency of the improved homotopy iteration method.展开更多
Pulse-width sequences are identified as the determining factor for common-mode(CM)voltage,which together with CM path generate CM current.This paper introduces a series of pulse-width modulation(PWM)methods,which are ...Pulse-width sequences are identified as the determining factor for common-mode(CM)voltage,which together with CM path generate CM current.This paper introduces a series of pulse-width modulation(PWM)methods,which are focusing on reducing CM noise of three-phase inverters as motor controller.Firstly,theoretic analysis and PWM reduction methods of CM voltage for general three-phase two-level inverters are introduced.Analysis results indicate that the realization of CM noise reduction should take switching frequency and loop impedance into consideration together to avoid CM resonant phenomenon.The regular three-phase two-level inverter is incapable of eliminating CM voltage because of the limitation of topology.Then,optimal PWM methods applied to for advanced topologies can be utilized to eliminate the CM voltage theoretically.Two typical typologies presented in this paper are three-level inverters and paralleled inverters.Three-level inverters can achieve zero-CM output voltage by selecting zero-CM voltage vectors at the expense of power quality.However,for paralleled inverters,zero-CM PWM method is able to achieve zero CM voltage output,as well as the improved output current harmonics and voltage balancing.展开更多
基金financially supported by Shenzhen Science and Technology Program(Nos.JSGG20220831105002005 and KJZD20231025152759002)the National Natural Science Foundation of China(Nos.52274133 and 523B2101).
文摘Natural gas hydrate(NGH)has a bright future as a clean energy source with huge reserves.Coring is one of the most direct methods for NGH exploration and research.Preserving the in-situ properties of the core as much as possible during the coring process is crucial for the assessment of NGH resources.However,most existing NGH coring techniques cannot preserve the in-situ temperature of NGH,leading to distortion of the physical properties of the obtained core,which makes it difficult to effectively guide NGH exploration and development.To overcome this limitation,this study introduces an innovative active temperature-preserved coring method for NGH utilizing phase change materials(PCM).An active temperature-preserved corer(ATPC)is designed and developed,and an indoor experimental system is established to investigate the heat transfer during the coring process.Based on the experimental results under different environment temperatures,a heat transfer model for the entire ATPC coring process has been established.The indoor experimental results are consistent with the theoretical predictions of the heat transfer model,confirming its validity.This model has reconstructed the temperature changes of the NGH core during the coring process,demonstrating that compared to the traditional coring method with only passive temperature-preserved measures,ATPC can effectively reduce the core temperature by more than 5.25℃.With ATPC,at environment temperatures of 15,20,25,and 30℃,the duration of low-temperature state for the NGH core is 53.85,32.87,20.32,and 11.83 min,respectively.These findings provide new perspectives on temperature-preserving core sampling in NGH and provide technical support for exploration and development in NGH.
基金Sponsored by The Youth Project of National Social Science Foundation of China(21CTY007)Special Fund for Basic Scientific Research Business Expenses of Central Universities(2024DAWH008).
文摘With Beijing Huilongguan Sports and Cultural Park as the research object,this study was conducted to investigate public service satisfaction in the park by the Importance-Performance Analysis(IPA)method.A questionnaire covering six dimensions,including public transportation,sanitation and environment,and supporting facility construction,was designed.A total of 208 valid samples were collected,and SPSS was employed for reliability and validity tests as well as IPA analysis.The findings were as follows:①Visitors were generally quite satisfied with the overall public services in Huilongguan Sports and Cultural Park.②The highest satisfaction levels were observed in sanitation and environment services and the sports and cultural atmosphere,while lower satisfaction was noted for supporting facility construction and public information services.③The advantage enhancement zone includes sanitation and environment services and sports and cultural atmosphere;and the continuous maintenance zone includes public transportation services and security management amd maintenance;the subsequent opportunity zone includes supporting facility construction and public information services;and there are no dimensions in the urgent improvement zone.The study recommends strengthening the service connotations from three aspects:enhancing facilities with sports as the core,optimizing services with a people-centered approach,and upgrading the information platform through technological efficiency.Additionally,a multi-stakeholder collaborative mechanism involving the government in coordinating policy resources,the operator in improving implementation efficiency,and the public participating in supervision and evaluation is proposed to drive the enhancement of public service quality at Huilongguan Sports and Cultural Park.
基金supported by the National Natural Science Foundation of China(Grant No.52172356)the Hunan Provincial Natural Science Foundation of China(Grant No.2022JJ10012).
文摘The application of multi-material topology optimization affords greater design flexibility compared to traditional single-material methods.However,density-based topology optimization methods encounter three unique challenges when inertial loads become dominant:non-monotonous behavior of the objective function,possible unconstrained characterization of the optimal solution,and parasitic effects.Herein,an improved Guide-Weight approach is introduced,which effectively addresses the structural topology optimization problem when subjected to inertial loads.Smooth and fast convergence of the compliance is achieved by the approach,while also maintaining the effectiveness of the volume constraints.The rational approximation of material properties model and smooth design are utilized to guarantee clear boundaries of the final structure,facilitating its seamless integration into manufacturing processes.The framework provided by the alternating active-phase algorithm is employed to decompose the multi-material topological problem under inertial loading into a set of sub-problems.The optimization of multi-material under inertial loads is accomplished through the effective resolution of these sub-problems using the improved Guide-Weight method.The effectiveness of the proposed approach is demonstrated through numerical examples involving two-phase and multi-phase materials.
基金Supported in part by Natural Science Foundation of Guangxi(2023GXNSFAA026246)in part by the Central Government's Guide to Local Science and Technology Development Fund(GuikeZY23055044)in part by the National Natural Science Foundation of China(62363003)。
文摘In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to obtain the maximal positive definite solution of nonlinear matrix equation X+A^(*)X|^(-α)A=Q with the case 0<α≤1.Based on this method,a new iterative algorithm is developed,and its convergence proof is given.Finally,two numerical examples are provided to show the effectiveness of the proposed method.
基金supported by Anhui Provincial Natural Science Foundation(2408085QA030)Natural Science Research Project of Anhui Educational Committee,China(2022AH050825)+3 种基金Medical Special Cultivation Project of Anhui University of Science and Technology(YZ2023H2C008)the Excellent Research and Innovation Team of Anhui Province,China(2022AH010052)the Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology,China(2021yjrc51)Collaborative Innovation Program of Hefei Science Center,CAS,China(2019HSC-CIP006).
文摘In this paper,a novel method for investigating the particle-crushing behavior of breeding particles in a fusion blanket is proposed.The fractal theory and Weibull distribution are combined to establish a theoretical model,and its validity was verified using a simple impact test.A crushable discrete element method(DEM)framework is built based on the previously established theoretical model.The tensile strength,which considers the fractal theory,size effect,and Weibull variation,was assigned to each generated particle.The assigned strength is then used for crush detection by comparing it with its maximum tensile stress.Mass conservation is ensured by inserting a series of sub-particles whose total mass was equal to the quality loss.Based on the crushable DEM framework,a numerical simulation of the crushing behavior of a pebble bed with hollow cylindrical geometry under a uniaxial compression test was performed.The results of this investigation showed that the particle withstands the external load by contact and sliding at the beginning of the compression process,and the results confirmed that crushing can be considered an important method of resisting the increasing external load.A relatively regular particle arrangement aids in resisting the load and reduces the occurrence of particle crushing.However,a limit exists to the promotion of resistance.When the strain increases beyond this limit,the distribution of the crushing position tends to be isotropic over the entire pebble bed.The theoretical model and crushable DEM framework provide a new method for exploring the pebble bed in a fusion reactor,considering particle crushing.
基金funded by the Beijing Engineering Research Center of Electric Rail Transportation.
文摘Effective partitioning is crucial for enabling parallel restoration of power systems after blackouts.This paper proposes a novel partitioning method based on deep reinforcement learning.First,the partitioning decision process is formulated as a Markov decision process(MDP)model to maximize the modularity.Corresponding key partitioning constraints on parallel restoration are considered.Second,based on the partitioning objective and constraints,the reward function of the partitioning MDP model is set by adopting a relative deviation normalization scheme to reduce mutual interference between the reward and penalty in the reward function.The soft bonus scaling mechanism is introduced to mitigate overestimation caused by abrupt jumps in the reward.Then,the deep Q network method is applied to solve the partitioning MDP model and generate partitioning schemes.Two experience replay buffers are employed to speed up the training process of the method.Finally,case studies on the IEEE 39-bus test system demonstrate that the proposed method can generate a high-modularity partitioning result that meets all key partitioning constraints,thereby improving the parallelism and reliability of the restoration process.Moreover,simulation results demonstrate that an appropriate discount factor is crucial for ensuring both the convergence speed and the stability of the partitioning training.
基金supported by the National Key Research and Develop-ment Program(No.2022YFC3701103)the National Natural Science Foundation of China(Nos.42130714 and 41931287).
文摘The application of nitrogen fertilizers in agricultural fields can lead to the release of nitrogen-containing gases(NCGs),such as NO_(x),NH_(3) and N_(2)O,which can significantly impact regional atmospheric environment and con-tribute to global climate change.However,there remain considerable research gaps in the accurate measurement of NCGs emissions from agricultural fields,hindering the development of effective emission reduction strategies.We improved an open-top dynamic chambers(OTDCs)system and evaluated the performance by comparing the measured and given fluxes of the NCGs.The results showed that the measured fluxes of NO,N_(2)O and NH_(3)were 1%,2%and 7%lower than the given fluxes,respectively.For the determination of NH_(3) concentration,we employed a stripping coil-ion chromatograph(SC-IC)analytical technique,which demonstrated an absorption efficiency for atmospheric NH_(3) exceeding 96.1%across sampling durations of 6 to 60 min.In the summer maize season,we utilized the OTDCs system to measure the exchange fluxes of NO,NH_(3),and N_(2)O from the soil in the North China Plain.Substantial emissions of NO,NH_(3) and N_(2)O were recorded following fertilization,with peaks of 107,309,1239 ng N/(m^(2)·s),respectively.Notably,significant NCGs emissions were observed following sus-tained heavy rainfall one month after fertilization,particularly with NH_(3) peak being 4.5 times higher than that observed immediately after fertilization.Our results demonstrate that the OTDCs system accurately reflects the emission characteristics of soil NCGs and meets the requirements for long-term and continuous flux observation.
基金Supported by the National Natural Science Foundation of China under Grant No.51975138the High-Tech Ship Scientific Research Project from the Ministry of Industry and Information Technology under Grant No.CJ05N20the National Defense Basic Research Project under Grant No.JCKY2023604C006.
文摘Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.
基金supported by the National Natural Science Foundation of China(Project No.42307555).
文摘At present,there is currently a lack of unified standard methods for the determination of antimony content in groundwater in China.The precision and trueness of related detection technologies have not yet been systematically and quantitatively evaluated,which limits the effective implementation of environmental monitoring.In response to this key technical gap,this study aimed to establish a standardized method for determining antimony in groundwater using Hydride Generation–Atomic Fluorescence Spectrometry(HG-AFS).Ten laboratories participated in inter-laboratory collaborative tests,and the statistical analysis of the test data was carried out in strict accordance with the technical specifications of GB/T 6379.2—2004 and GB/T 6379.4—2006.The consistency and outliers of the data were tested by Mandel's h and k statistics,the Grubbs test and the Cochran test,and the outliers were removed to optimize the data,thereby significantly improving the reliability and accuracy.Based on the optimized data,parameters such as the repeatability limit(r),reproducibility limit(R),and method bias value(δ)were determined,and the trueness of the method was statistically evaluated.At the same time,precision-function relationships were established,and all results met the requirements.The results show that the lower the antimony content,the lower the repeatability limit(r)and reproducibility limit(R),indicating that the measurement error mainly originates from the detection limit of the method and instrument sensitivity.Therefore,improving the instrument sensitivity and reducing the detection limit are the keys to controlling the analytical error and improving precision.This study provides reliable data support and a solid technical foundation for the establishment and evaluation of standardized methods for the determination of antimony content in groundwater.
基金Projects(10902086, 50941020, 50875217) supported by the National Natural Science Foundation of China Projects(JC201005) supported by Basic Research Fund of Northwestern Polytechnical University, China Project supported by Graduate Starting Seed Fund and Doctoral Foundation of Northwestern Polytechnical University, China
文摘By utilizing phase field method combined with analysis on free energy and interatomic potentials, pre-precipitation phase formation and transformation process of Ni0.75Al0.05Fe0.2 alloy in early precipitation stage during the ageing process under 1 000 K were studied. And free energy, microstructures, compositions and volume fractions of pre-precipitation phase and equilibrium phase were analyzed. The simulation results indicate that nonstoichiometric Llo pre-precipitation phase formed first, and then would gradually transform into L12 equilibrium phase. It is discovered that the phase transformation process was closely related to free energy and interatomic potentials. Additionally, it is revealed that free energy of Llo pre-precipitation phase was higher and interatomic potential was smaller than that of L12 equilibrium phase. Therefore, it is concluded that Llo phase was unstable, and phase transformation would occur to L12 which was more stable.
基金supported by the National Natural Science Foundation of China (Grant No. 51175484)the Science Foundation of Shandong Province (Grant No. ZR2010EM052)
文摘Deployment of buoy systems is one of the most important procedures for the operation of buoy system. In the present study, a single-point mooring buoy system which contains surface buoy, cable segments with components, anchor and so on is modeled by applying multi-body dynamics method. The motion equations are developed in discrete node description and fully Cartesian coordinates. Then numerical method is used to solve the ordinary differential equations and dynamics simulations are achieved while anchor is casting from board. The trajectories and velocities of different nodes without current and with current in buoy system are obtained. The transient tension force of each part of the cable is analyzed in the process of deployment. Numerical results indicate that the transient payload increases to a peak value when the anchor is touching the seabed and the maximum tension force will vary with different floating configuration. This work is helpful for design and deployment planning of buoy system.
基金supported by National Natural Science Foundation of China(No. 50175034).
文摘Single-point incremental forming （SPIF） is an innovational sheet metal forming method without dedicated dies, which belongs to rapid prototyping technology. In generalizing the SPIF of sheet metal, the deformation analysis on forming process becomes an important and useful method for the planning of shell products, the choice of material, the design of the forming process and the planning of the forming tool. Using solid brick elements, the finite element method（FEM） model of truncated pyramid was established. Based on the theory of anisotropy and assumed strain formulation, the SPIF processes with different parameters were simulated. The resulted comparison between the simulations and the experiments shows that the FEM model is feasible and effective. Then, according to the simulated forming process, the deformation pattern of SPIF can be summarized as the combination of plane-stretching deformation and bending deformation. And the study about the process parameters＇ impact on deformation shows that the process parameter of interlayer spacing is a dominant factor on the deformation. Decreasing interlayer spacing, the strain of one step decreases and the formability of blank will be improved. With bigger interlayer spacing, the plastic deformation zone increases and the forming force will be bigger.
基金NRDMS Division,Department of Science and Technology,Government of India for providing financial assistance for field investigations.
文摘Large-scale slope destabilization could be aggravated due to swift urbanization and ever-rising demands of geoengineering projects such as dams,tunnels,bridges and widening roads.National Highway-58 connects Delhi to Badrinath in India,which passes through complex geomorphological and geological terrain and often encounters cut slopes susceptible to slope failures.In the present investigation,a detailed geotechnical appraisal is conducted along the road cut slopes from Rishikesh to Devprayag in the Himalayas.Twenty vulnerable road cut slopes were demarcated for detailed slope stability analysis using Phase2D finite element modeling simulator.Nonlinear generalized Hoek-Brown(GHB)criterion was adopted for stability analyses.Out of 20 slopes,five slopes(S6,S7,S18,S19 and S20)are unstable with factor of safety(FoS)less than or equal to 1,and thus needs immediate attention.The FoS values of four slopes(S2,S9,S13 and S17)lie between 1 and 1.3,i.e.marginally stable,and slopes S1,S3,S4,S5,S8,S10,Sll,S12,S14,S15 and S16 are stable.Mohr-Coulomb(MC)criterion was also adopted to compare the slope stability analysis with GHB criterion.The FoS calculated from GHB criterion is close to that using MC criterion for lower values of FoS whereas for higher values,the difference is marked.For the jointed rock in the Himalayan region,the nonlinear GHB criterion gives better results as compared to MC criterion and matches with the prevailing field conditions.Accordingly,some suggestions are proposed to strengthen the stability of cut slopes.
基金supported by the National Science Council, Taiwan(No. 96-2221-E-327-027, No. 96-2221-E-327-005-MY2, and No. 96-2628-E-327-004-MY3).
文摘This article presents a multiobjective approach to the design of the controller for the swing-up and handstand control of a general cart-double-pendulum system （CDPS）. The designed controller, which is based on the human-simulated intelligent control （HSIC） method, builds up different control modes to monitor and control the CDPS during four kinetic phases consisting of an initial oscillation phase, a swing-up phase, a posture adjustment phase, and a balance control phase. For the approach, the original method of inequalities-based （MoI） multiobjective genetic algorithm （MMGA） is extended and applied to the case study which uses a set of performance indices that includes the cart displacement over the rail boundary, the number of swings, the settling time, the overshoot of the total energy, and the control effort. The simulation results show good responses of the CDPS with the controllers obtained by the proposed approach.
基金the National Frontier Technology Key R&D Project(Nos.XXX-125 and JXXX-2019-058)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the Collaborative Innovation Center of Advanced Inorganic Functional Composites of Jiangsu Province。
文摘All-inorganic perovskites CsPbX_(3)(X=Cl,Br,I)have attracted worldwide interest due to their excellent lumi-nescent performances.Meanwhile,Cs_(4)PbBr_(6) have been studied because they can enhance the luminescent efficiency and stability of CsPbBr_(3).Herein,we introduced a microfluidic method based on room-temperature supersat-urated recrystallization to synthesize blue-emitting CsPbBr_(3)nanocrystals(NCs)and green-emitting CsPbBr_(3)/Cs_(4)PbBr_(6)NCs.The ultrasmall CsPbBr_(3)NCs emitted at a deep blue wavelength of 461 nm with the full width at half maximum(FWHM)of 15 nm.transmission electron microscopy(TEM)results demonstrated that ultrasmall CsPbBr_(3)NCs with the average particle size of 3.8 nm were synthesized and the CsPbBr_(3)NCs were crystallized as monoclinic structure.
基金supported by the Chinese Academy of Sciences(CAS)“Light of West China”Program(No.2017-XBQNXZ-B-024)the Xinjiang Uygur Autonomous Region“Tianshan innovation team”(No.2018D14008)+3 种基金the Youth Innovation Promotion Association,CAS(No.2016058)the Operation,Maintenance and upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China(MOF)and administrated by CASthe National Natural Science Foundation of China(No.11763007)the Tianshan Youth Project of Xinjiang(No.2017Q014)。
文摘The influence of wind on the pointing accuracy of large aperture radio telescopes is becoming increasingly serious, especially at high observing frequency. Obtaining the wind field characteristics efficiently is very important to reduce the wind disturbance on antenna structure. In this paper, an error evaluation of numerical simulation method is established based on the measured data of single point wind tower, and the wind field characteristics are obtained from the evaluated numerical simulation results combined with the measured data for the 110 m aperture Qi Tai radio Telescope(QTT) site. According to the simulation results, compared with the measured data, the root mean square error(RMSE) of wind speed is less than 1 m s^-1, and the minimum wind speed RMSE is 0.2 m s^-1. An analysis of the wind field characteristics of the QTT site suggests that the active wind resistance design of the antenna periphery should focus on the SSW(south-south-west) direction.
基金support of the János Bolyai Research Fellowship of the Hungarian Academy of Sciences. T.U. is grateful for partial funding of this work by an EPSRC Leadership Fellowship [EP/I005420/1, EP/K039237/1, EP/K034650/1, EP/L018616/1 and EP/K034332/1] for the study of irradiation damage in zirconium alloys
文摘Line profile analysis of X-ray and neutron diffraction patterns is a powerful tool for determining the microstructure of crystalline materials. The Convolutional-Multiple-Whole-Profile (CMWP) procedure is based on physical profile functions for dislocations, domain size, stacking faults and twin boundaries. Order dependence, strain anisotropy, hkl dependent broadening of planar defects and peak shape are used to separate the effect of different lattice defect types. The Marquardt-Levenberg (ML) numerical optimiza-tion procedure has been used successfully to determine crystal defect types and densities. However, in more complex cases like hexagonal materials or multiple phases the ML procedure alone reveals uncer-tainties. In a new approach the ML and a Monte-Carlo statistical method are combined in an alternative manner. The new CMWP procedure eliminates uncertainties and provides globally optimized parameters.
基金Project supported by Tianjin Research Program Application Foundation and Advanced Technology,China(Grant No.15JCQNJC01100)
文摘This paper investigates the phenomenon of three-pulse photon echo in thick rare-earth ions doped crystal whose thickness is far larger than 0.002 cm which is adopted in previous works.The influence of thickness on the three-pulse photon echo＇s amplitude and efficiency is analyzed with the Maxwell-Bloch equations solved by finite-difference timedomain method.We demonstrate that the amplitude of three-pulse echo will increase with the increasing of thickness and the optimum thickness to generate three-pulse photon echo is 0.3 cm for Tm^（3＋）：YAG when the attenuation of the input pulse is taken into account.Meanwhile,we find the expression 0.09 exp（α＇L）,which is previously employed to describe the relationship between echo＇s efficiency and thickness,should be modified as 1.3 · 0.09 exp（2.4 ·α＇L） with the propagation of echo considered.
文摘A new algorithm called homotopy iteration method based on the homotopy function is studied and improved. By the improved homotopy iteration method, Polynomial systems with high Order and deficient can be solved fast and efficiently comparing to the original homotopy iteration method. Numerical examples for the ninepoint path synthesis of four-bar linkages show the advantages and efficiency of the improved homotopy iteration method.
基金This paper is with National Key Research Plan of China(2016YFB0100600).
文摘Pulse-width sequences are identified as the determining factor for common-mode(CM)voltage,which together with CM path generate CM current.This paper introduces a series of pulse-width modulation(PWM)methods,which are focusing on reducing CM noise of three-phase inverters as motor controller.Firstly,theoretic analysis and PWM reduction methods of CM voltage for general three-phase two-level inverters are introduced.Analysis results indicate that the realization of CM noise reduction should take switching frequency and loop impedance into consideration together to avoid CM resonant phenomenon.The regular three-phase two-level inverter is incapable of eliminating CM voltage because of the limitation of topology.Then,optimal PWM methods applied to for advanced topologies can be utilized to eliminate the CM voltage theoretically.Two typical typologies presented in this paper are three-level inverters and paralleled inverters.Three-level inverters can achieve zero-CM output voltage by selecting zero-CM voltage vectors at the expense of power quality.However,for paralleled inverters,zero-CM PWM method is able to achieve zero CM voltage output,as well as the improved output current harmonics and voltage balancing.
