A horizontal distributor for biogas slurry application was proposed to explore the distribution performance through CFD analysis and verified by field test.The rheological properties of biogas slurry were analyzed at ...A horizontal distributor for biogas slurry application was proposed to explore the distribution performance through CFD analysis and verified by field test.The rheological properties of biogas slurry were analyzed at first,and key parameters were obtained for the next simulation.The effects of distribution modes,inlet direction,and outlets number on the velocity distribution of flow field and mass flow rate of the horizonal distributor were investigated by CFD simulations.Results of rheological properties indicated that biogas slurry was a non-Newtonian fluid and exhibited shear-thinning behavior.It can be well described by power-law model.The simulation results showed that the geometry of rotor,especially the block numbers was the main factor that determining the fluid movement and trajectory of distribution and output.The mode rotor 1 with two blocks reached the lowest variable coefficient of mass flow rate(4.49%),indicating a higher degree of uniformity.The upward inlet direction would obtain less dead zone,and the distributor with an even outlets number would possess more uniform distribution and less dead zone.The field test of the distributor with rotor 1,upward inlet direction,and 24 outlets has been carried on to verify the simulation results,the variable coefficient of mass flow was 13.06%,which was slightly higher than the simulation(9.23%),but it still within the range of requirement(<15%).The proposed model and the findings of this work are of guiding significance for the study of the utilization technology and equipment of liquid biogas residue.展开更多
The evaluation of the performance of distribution uniformity by linearly moved irrigation system(LMIS)should consider the impacts of non uniformity of the water on crop yield.With increasing pressures to improve water...The evaluation of the performance of distribution uniformity by linearly moved irrigation system(LMIS)should consider the impacts of non uniformity of the water on crop yield.With increasing pressures to improve water use efficiency,plant productivity and farm profitability,questions continue to be raised concerning the future direction of irrigated agriculture.This study therefore aimed at evaluating water distribution under LMIS newly designed by the National Research Centre of Fluid Machinery Engineering and Technology,Jiangsu University,China.This article reports the real distribution of irrigation water under the LMIS with respect to sprinkler height above the ground surface as well as the consequence of different operating pressures.Water distribution coefficients used in the performance assessment were Christiansen’s coefficient of uniformity(CU),distribution uniformity(DU),scheduling coefficients(Sc)and the coefficient of variation(CV).The results showed that the mean CU ranged from 82.30%to 93.17%,and mean DU ranged from 70.39%to 88.44%.Also Sc values ranged from 1.13 to 1.42 with CV values ranging from 10.3%to 22.5%.The optimum method and results in this study can provide a reference to the operations for saving water and cost in the application of LMIS.展开更多
The plenum chamber of a heat setting machine is a key structure for distributing hot air to different air channels.Its outlet velocity uniformity directly determines the heating uniformity of textiles,significantly af...The plenum chamber of a heat setting machine is a key structure for distributing hot air to different air channels.Its outlet velocity uniformity directly determines the heating uniformity of textiles,significantly affecting the heat setting performance.In a traditional heat setting machine,the outlet airflow maldistribution of the plenum chamber still exists.In this study,a novel plenum chamber with an airfoil baffle was established to improve the uniformity of the velocity distribution at the outlet in a heat setting machine.The structural influence of the plenum chamber on the velocity distribution was investigated using a computational fluid dynamics program.It was found that a chamber with a smaller outlet partition thickness had a better outlet velocity uniformity.The structural optimization of the plenum chamber was conducted using the particle swarm optimization algorithm.The outlet partition thickness,the transverse distance and the longitudinal distance of the optimized plenum chamber were 20,686.2 and 274.6 mm,respectively.Experiments were carried out.The experimental and simulated results showed that the optimized plenum chamber with an airfoil baffle could improve the outlet velocity uniformity.The air outlet velocity uniformity index of the optimized plenum chamber with an airfoil baffle was 4.75%higher than that of the plenum chamber without an airfoil baffle and 5.98%higher than that of the conventional chamber with a square baffle in a commercial heat setting machine.展开更多
In some old industrial plants,in order to meet the increasingly strict requirements of pollutant emission limits,it is necessary to install the compact filtration and/or purification devices in a given narrow machine ...In some old industrial plants,in order to meet the increasingly strict requirements of pollutant emission limits,it is necessary to install the compact filtration and/or purification devices in a given narrow machine room.Different types of structural configuration might influence air distribution inside these devices.The unreasonable air distribution might lead each part of filtration or purification media to operating at largely different air flow rates.Based on a computational fluid dynamics(CFD)model,this study explores the influence of different outlet positions and different upper heights on the flow field inside chamber.The porous medium model is employed to simulate the air flow in porous media.The changing structural configurations include three positioning cases of the outlet opening and eight height cases of the upper chamber.The root mean square is defined as the non-uniformity coefficient to evaluate the uniformity of air flow distribution.The results show that the farther distance between inlet and outlet openings will bring more uniform air distribution,and the increasing height of upper chamber totally trends to exhibit more uniform air distribution.展开更多
The present study proposes a novel method based on the geometric theory for measuring the distribution of bubble swarms in the circular region of a direct-contact heat exchanger.It was determined that the mixing is un...The present study proposes a novel method based on the geometric theory for measuring the distribution of bubble swarms in the circular region of a direct-contact heat exchanger.It was determined that the mixing is uniform when the average distance between the bubble swarms in the unit circular region is approximately 0.9054,which is the standard reference value.The effect of sample size(i.e.,the number of bubbles)on mixing uniformity was investigated to determine the optimal sample size.It was verified that the metric's accuracy and stability were higher with a sample size of 155.Accordingly,it was proposed to increase the sample size by filling irregular bubbles using a segmentation method,which enabled a further accurate assessment of the mixing uniformity.The mixing uniformity of bubble swarms in the circular region and its maximum internal connection with the square region was accurately quantified.It was revealed that the relative average error increased by approximately 3.47% due to information loss.The proposed method was demonstrated to be rotationally invariant.The present study provided novel insights into evaluating mixing uniformity,which would guide enhanced heat transfer and the effective evaluation of the spatiotemporal characteristics of transient mixing in circular regions or the cross-sections of chemical transport pipelines.展开更多
In this study,the approximate and exact solutions for the stationary-state of the solids model with neglecting reactant consumption for both non-uniform and uniform temperature systems were applied on gas ignition und...In this study,the approximate and exact solutions for the stationary-state of the solids model with neglecting reactant consumption for both non-uniform and uniform temperature systems were applied on gas ignition under a constant pressure condition.The criticality conditions for a slab,an infinite cylinder,and a sphere are determined and discussed using dimensionless temperatures under constant ambient and surface temperatures for a non-uniform temperature system.Exact solution for a Semenov model with convection heat loss was also presented.The solution of the Semenov problem for constant volume or density as a solid and constant pressure were compared.The critical parameterδis calculated and compared with those of Frank-Kamenetskii solution values.The validation of the calculated ignition temperatures with other exact solution and experimental results were offered.The relation between critical parameters form Semenov and F.K.models solution was introduced.展开更多
With the development of modern electronic countermeasure technology,the fight between radar jamming and anti-jamming in aviation military has become increasingly fierce.There are some special requirements for radar co...With the development of modern electronic countermeasure technology,the fight between radar jamming and anti-jamming in aviation military has become increasingly fierce.There are some special requirements for radar countermeasure experiments.For example,such experiments are often divided into several stages,and responses of the previous stages will become factors of the next stages.Moreover,the experiment design can only consider some typical level values of the factors.However,the experiment factors are mostly continuous variables.Thus when there are some jumps in the response,and the value granularity of the factor level is large,the responses fail to reflect the distortion process,which makes it difficult to explore the radar performance boundary.Therefore,it is necessary to study the sequential experiment design method with the optimization goals of response uniformization and response distortion process characterization.In this paper,a sequential experiment design strategy based on Kriging model is established.Firstly,Kriging model is used to fit the initial experimental data to obtain the response surface.In order to enhance the uniformity of response distribution,Shannon entropy is applied to the objective function as the measure of uniformity.While for the situation of response distortion,we consider replacing the existing experiment points with those whose corresponding responses have a larger gradient norm.It means that the response value near these points will change rapidly,so they are more valuable for research.Then we use the peak surface in the three-dimensional space to intuitively verify the effect of the above algorithms on response uniformization and response distortion process characterization,and use the simulated annealing algorithm to solve them.The simulation results show that our sequential experiment strategy has a good effect.Finally,we apply the strategy to the practical problem of radar countermeasure experiment,and the obtained results also perform well.展开更多
Previous studies have demonstrated the negative effects of sub-optimal air quality on profitability,production efficiency,environmental sustainability and animal welfare.Experiments were conducted to assess potential ...Previous studies have demonstrated the negative effects of sub-optimal air quality on profitability,production efficiency,environmental sustainability and animal welfare.Experiments were conducted to assess potential environmental improvement techniques such as installing oil-spraying systems in piggery buildings.The developed spray system worked very well and it was easy to assemble and operate.However,before selecting the most suitable spray heads,their capacity to uniformly distribute the oily mixture and the area covered by the spray heads had to be assessed.Machine vision techniques were used to evaluate the ability of different spray heads to evenly distribute the oil/water mixture.The results indicated that the best coverage was achieved by spray head No.4 and spray head No.1 which covered 79%and 67%of the target area,respectively.Spray distribution uniformity(variance)value was the lowest for spray head No.4(0.015).Spray head No.3 had the highest variance value(0.064).As the lowest variance means higher uniformity,nozzle No.4 was identified as the most suitable spray head for dust reduction in livestock buildings.展开更多
The hydro-floating ship lift originally invented in China is a major innovation in the field of navigation technology.The shaft water levels synchronization of its unique hydraulic-driven system plays a crucial role i...The hydro-floating ship lift originally invented in China is a major innovation in the field of navigation technology.The shaft water levels synchronization of its unique hydraulic-driven system plays a crucial role in reducing the torque of the synchronous shafts and ensuring the safety and stability operation of the ship lift.This study aims to investigate the muti-shaft water level synchronization and the flow velocity uniformity of the combined type hydraulic-driven system.Based on the theory of residual energy,a new index m2 proposed in this study is more suitable for evaluating the flow velocity uniformity of the combined hydraulic-driven system.Finally,the critical value of m2=75 is calculated via the results of the scaled physical mode test as the threshold of water flow uniformity,and it provides a basis for determining the reasonable height of the pressure stabilizing chamber.展开更多
Modular multilevel converters(MMCs)have been widely used owing to their superior performance.However,the rapid switching of power electronics devices causes serious electromagnetic interference(EMI).There are a large ...Modular multilevel converters(MMCs)have been widely used owing to their superior performance.However,the rapid switching of power electronics devices causes serious electromagnetic interference(EMI).There are a large number of obvious EMI peaks in the frequency spectrum of the carrier phase-shifted constant-switching-frequency pulse-width modulation(CSFPWM).Spreading the EMI across a wider frequency range can help to reduce the EMI peaks.In this study,we designed a uniform distribution(UD)spread-spectrum modulation technology using the principle of uniform switching frequency distribution and minimum switching loss for MMC.Its feasibility is verified by theoretical derivation and simulation.Then,the effectiveness of UDPWM in reducing the EMI is verified in experiments with a prototype MMC testbed in the lab.Compared with traditional CSFPWM,UDPWM can reduce conducted EMI by 10-20 dB.Also,compared with random PWM(RPWM),UDPWM can improve efficiency and reduce total harmonic distortion(THD)of output voltage and current in MMC.展开更多
Lithium-sulfur(Li-S)batteries are the promising next-generation secondary energy storage systems,because of their advantages of high energy density and environmental friendliness.Among numerous cathode materials,organ...Lithium-sulfur(Li-S)batteries are the promising next-generation secondary energy storage systems,because of their advantages of high energy density and environmental friendliness.Among numerous cathode materials,organosulfur polymer materials have received extensive attentions because of their controllable structure and uniform sulfur distribution.However,the sulfur content of most organosulfur polymer cathodes is limited(S content<60%)due to the addition of large amounts of conductive agents and binders,which adversely affects the energy density of Li-S batteries.Herein,a hyperbranched sulfur-rich polymer based on modified polyethyleneimine(Ath-PEI)named carbon nanotubeentangled poly(allyl-terminated hyperbranched ethyleneimine-random-sulfur)(CNT/Ath-PEI@S)was prepared by sulfur polymerization and used as a Li-S battery cathode.The high intrinsic viscosity of Ath-PEI provided considerable adhesion and avoided the addition of PVDF binder,thereby increasing the sulfur content of cathodes to 75%.Moreover,considering the uniform distribution of elemental sulfur by the polymer,the utilization of sulfur was successfully improved,thus improving the rate capability and discharge capacity of the battery.The binder-free,sulfur-rich polymer cathode exhibited ultra-high initial discharge capacity(1520.7 mAh g^(−1) at 0.1 C),and high rate capability(804 mAh g^(−1) at 2.0 C).And cell-level calculations show that the electrode exhibits an initial capacity of 942.3 mAh g^(−1) electrode,which is much higher than those of conventional sulfur-polymer electrodes reported in the literature.展开更多
There are very few studies on the application of fertilizers through irrigation water(fertirrigation) using a multi-gate irrigation system in sugarcane AES. Through fertirrigation, the application of fertilizers can b...There are very few studies on the application of fertilizers through irrigation water(fertirrigation) using a multi-gate irrigation system in sugarcane AES. Through fertirrigation, the application of fertilizers can be simplified, and their distribution uniformity in sugarcane fields improved. This paper provides an overview of the state of the art regarding fertirrigation with multi-gate irrigation in sugarcane agroecosystems(AES). In order to systematize, organize, and discuss the scientific data on fertirrigation with low-pressure multi-gate irrigation systems in sugarcane AES, bibliographic material from the following full-text scientific journal databases was screened: the Elsevier Science Direct Freedom Collection, Springer Link, and the International Society for Horticultural Science. Next,a matrix of keywords was used to analyze the interrelationships among the available literature, current issues, and the recent findings.We conclude that development of fertirrigation technologies with low-pressure multi-gate irrigation is much needed.展开更多
Based on the non-Darcian flow law described by exponent m and threshold gradient i 1 under a low hydraulic gradient and the classical nonlinear relationships e-lgσ′ and e-lgk v (Mesri and Rokhsar, 1974), the governi...Based on the non-Darcian flow law described by exponent m and threshold gradient i 1 under a low hydraulic gradient and the classical nonlinear relationships e-lgσ′ and e-lgk v (Mesri and Rokhsar, 1974), the governing equation of 1D nonlinear consolidation was modified by considering both uniform distribution of self-weight stress and linear increment of self-weight stress. The numerical solutions for the governing equation were derived by the finite difference method (FDM). Moreover, the solutions were verified by comparing the numerical results with those by analytical method under a specific case. Finally, consolidation behavior under different parameters was investigated, and the results show that the rate of 1D nonlinear consolidation will slow down when the non-Darcian flow law is considered. The consolidation rate with linear increment of self-weight stress is faster than that with uniform distribution one. Compared to Darcy's flow law, the influence of parameters describing non-linearity of soft soil on consolidation behavior with non-Darcian flow has no significant change.展开更多
The flow field structure on the bipolar plate significantly affects the performance of the proton exchange membrane electrolysis cell(PEMEC).This paper proposes a new interdigitated-jet hole flow field(JHFF)design to ...The flow field structure on the bipolar plate significantly affects the performance of the proton exchange membrane electrolysis cell(PEMEC).This paper proposes a new interdigitated-jet hole flow field(JHFF)design to improve the uniformities of liquid saturation,temperature,and current density distributions.The common single-path serpentine flow field(SSFF)and interdigitated flow field(IFF)are used as comparative references to constitute three PEMEC cases.An advanced numerical model has been established to simulate the performance of the PEMEC using CFD software.The results show that,due to the perpendicular mainstream and the pressure difference,the JHFF enhances the mass and heat transfer inside the porous electrode by introducing strong forced convection,which promotes gas removal underneath the ribs and cooling.Compared with the comparative flow fields,the uniformities of liquid saturation,temperature,and current density distributions by using the JHFF at the anode side are increased by 19.1%,53.2%,and 40.4%,respectively.Further,mainly owing to the largest conductive area,the PEMEC with the JHFF has superior polarization performance,which is 8.05%higher than the PEMEC with the SSFF.展开更多
Supported NiCu bimetallic catalysts have been produced in-situ on commercial Al_(2)O_(3)by using layered double hydroxides as precursors. The resulting catalysts show a uniform Ni and Cu distribution, thus providing g...Supported NiCu bimetallic catalysts have been produced in-situ on commercial Al_(2)O_(3)by using layered double hydroxides as precursors. The resulting catalysts show a uniform Ni and Cu distribution, thus providing good activity and selectivity in the reforming reaction of n-heptane. The catalytic performance has been found to depend on the Cu/Ni ratio, revealing the synergic catalysis between homogeneously dispersed Ni and Cu sites. The good catalysis of Ni Cu bimetallic catalysts makes it possible to partly or even completely replace Pt with NiCu bimetallic catalysts.展开更多
基金supported by the Jiangsu Modern Agricultural Machinery Equipment and Technology Demonstration and Promotion Project(Grant No.NJ2021-23)Jiangsu Province Agricultural Science and Technology Independent Innovation Fund Project(Grant No.CX(22)3093)+1 种基金the Fundamental Research Fund of the Chinese Academy of Agricultural Sciences at the Institute Level(Grant No.S202106-02)the Key Research and Development Program of Hebei Province(Grant No.20327313D).
文摘A horizontal distributor for biogas slurry application was proposed to explore the distribution performance through CFD analysis and verified by field test.The rheological properties of biogas slurry were analyzed at first,and key parameters were obtained for the next simulation.The effects of distribution modes,inlet direction,and outlets number on the velocity distribution of flow field and mass flow rate of the horizonal distributor were investigated by CFD simulations.Results of rheological properties indicated that biogas slurry was a non-Newtonian fluid and exhibited shear-thinning behavior.It can be well described by power-law model.The simulation results showed that the geometry of rotor,especially the block numbers was the main factor that determining the fluid movement and trajectory of distribution and output.The mode rotor 1 with two blocks reached the lowest variable coefficient of mass flow rate(4.49%),indicating a higher degree of uniformity.The upward inlet direction would obtain less dead zone,and the distributor with an even outlets number would possess more uniform distribution and less dead zone.The field test of the distributor with rotor 1,upward inlet direction,and 24 outlets has been carried on to verify the simulation results,the variable coefficient of mass flow was 13.06%,which was slightly higher than the simulation(9.23%),but it still within the range of requirement(<15%).The proposed model and the findings of this work are of guiding significance for the study of the utilization technology and equipment of liquid biogas residue.
基金the National Key Research and Development Program of China(No.2016YFC0400202)the Project of New Agricultural Machinery in Jiangsu Province(No.NJ2016-11)+1 种基金the Postdoctoral Science Foundation Special Support of China(No.2016T90428)Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘The evaluation of the performance of distribution uniformity by linearly moved irrigation system(LMIS)should consider the impacts of non uniformity of the water on crop yield.With increasing pressures to improve water use efficiency,plant productivity and farm profitability,questions continue to be raised concerning the future direction of irrigated agriculture.This study therefore aimed at evaluating water distribution under LMIS newly designed by the National Research Centre of Fluid Machinery Engineering and Technology,Jiangsu University,China.This article reports the real distribution of irrigation water under the LMIS with respect to sprinkler height above the ground surface as well as the consequence of different operating pressures.Water distribution coefficients used in the performance assessment were Christiansen’s coefficient of uniformity(CU),distribution uniformity(DU),scheduling coefficients(Sc)and the coefficient of variation(CV).The results showed that the mean CU ranged from 82.30%to 93.17%,and mean DU ranged from 70.39%to 88.44%.Also Sc values ranged from 1.13 to 1.42 with CV values ranging from 10.3%to 22.5%.The optimum method and results in this study can provide a reference to the operations for saving water and cost in the application of LMIS.
基金National Natural Science Foundation of China(No.62173307)the Key R&D Projects of Science and Technology Department of Zhejiang Province,China(Nos.2023C01158,2022C01065 and 2022C01188)the Fundamental Research Funds of Zhejiang Sci-Tech University,China(No.22242298-Y)。
文摘The plenum chamber of a heat setting machine is a key structure for distributing hot air to different air channels.Its outlet velocity uniformity directly determines the heating uniformity of textiles,significantly affecting the heat setting performance.In a traditional heat setting machine,the outlet airflow maldistribution of the plenum chamber still exists.In this study,a novel plenum chamber with an airfoil baffle was established to improve the uniformity of the velocity distribution at the outlet in a heat setting machine.The structural influence of the plenum chamber on the velocity distribution was investigated using a computational fluid dynamics program.It was found that a chamber with a smaller outlet partition thickness had a better outlet velocity uniformity.The structural optimization of the plenum chamber was conducted using the particle swarm optimization algorithm.The outlet partition thickness,the transverse distance and the longitudinal distance of the optimized plenum chamber were 20,686.2 and 274.6 mm,respectively.Experiments were carried out.The experimental and simulated results showed that the optimized plenum chamber with an airfoil baffle could improve the outlet velocity uniformity.The air outlet velocity uniformity index of the optimized plenum chamber with an airfoil baffle was 4.75%higher than that of the plenum chamber without an airfoil baffle and 5.98%higher than that of the conventional chamber with a square baffle in a commercial heat setting machine.
基金National Key Research and Development Program of China(No.2018YFC0705305)。
文摘In some old industrial plants,in order to meet the increasingly strict requirements of pollutant emission limits,it is necessary to install the compact filtration and/or purification devices in a given narrow machine room.Different types of structural configuration might influence air distribution inside these devices.The unreasonable air distribution might lead each part of filtration or purification media to operating at largely different air flow rates.Based on a computational fluid dynamics(CFD)model,this study explores the influence of different outlet positions and different upper heights on the flow field inside chamber.The porous medium model is employed to simulate the air flow in porous media.The changing structural configurations include three positioning cases of the outlet opening and eight height cases of the upper chamber.The root mean square is defined as the non-uniformity coefficient to evaluate the uniformity of air flow distribution.The results show that the farther distance between inlet and outlet openings will bring more uniform air distribution,and the increasing height of upper chamber totally trends to exhibit more uniform air distribution.
基金the National Natural Science Foundation of China(project No.52166004)Yunnan Major Scientific and Technological Projects(grant No.202202AG050002)+2 种基金Scientific Research Fund Project of Yunnan Education Department,China(grant No.2021j0063)Natural Science FoundationofYunnan Province,China(grant No.202101AU070031)the teaching projects A Quality Course for Graduate Students in Yunnan Province"Numerical Analysis","Advanced Mathematics Teaching Team of Engineering Subjects of Kunming University of Science and Technology".
文摘The present study proposes a novel method based on the geometric theory for measuring the distribution of bubble swarms in the circular region of a direct-contact heat exchanger.It was determined that the mixing is uniform when the average distance between the bubble swarms in the unit circular region is approximately 0.9054,which is the standard reference value.The effect of sample size(i.e.,the number of bubbles)on mixing uniformity was investigated to determine the optimal sample size.It was verified that the metric's accuracy and stability were higher with a sample size of 155.Accordingly,it was proposed to increase the sample size by filling irregular bubbles using a segmentation method,which enabled a further accurate assessment of the mixing uniformity.The mixing uniformity of bubble swarms in the circular region and its maximum internal connection with the square region was accurately quantified.It was revealed that the relative average error increased by approximately 3.47% due to information loss.The proposed method was demonstrated to be rotationally invariant.The present study provided novel insights into evaluating mixing uniformity,which would guide enhanced heat transfer and the effective evaluation of the spatiotemporal characteristics of transient mixing in circular regions or the cross-sections of chemical transport pipelines.
文摘In this study,the approximate and exact solutions for the stationary-state of the solids model with neglecting reactant consumption for both non-uniform and uniform temperature systems were applied on gas ignition under a constant pressure condition.The criticality conditions for a slab,an infinite cylinder,and a sphere are determined and discussed using dimensionless temperatures under constant ambient and surface temperatures for a non-uniform temperature system.Exact solution for a Semenov model with convection heat loss was also presented.The solution of the Semenov problem for constant volume or density as a solid and constant pressure were compared.The critical parameterδis calculated and compared with those of Frank-Kamenetskii solution values.The validation of the calculated ignition temperatures with other exact solution and experimental results were offered.The relation between critical parameters form Semenov and F.K.models solution was introduced.
基金the National Natural Science Foundation of China(No.12071329)the State Key Laboratory of Complex Electromagnetic Environment Effects on Electronics and Information System(No.2021G0301)。
文摘With the development of modern electronic countermeasure technology,the fight between radar jamming and anti-jamming in aviation military has become increasingly fierce.There are some special requirements for radar countermeasure experiments.For example,such experiments are often divided into several stages,and responses of the previous stages will become factors of the next stages.Moreover,the experiment design can only consider some typical level values of the factors.However,the experiment factors are mostly continuous variables.Thus when there are some jumps in the response,and the value granularity of the factor level is large,the responses fail to reflect the distortion process,which makes it difficult to explore the radar performance boundary.Therefore,it is necessary to study the sequential experiment design method with the optimization goals of response uniformization and response distortion process characterization.In this paper,a sequential experiment design strategy based on Kriging model is established.Firstly,Kriging model is used to fit the initial experimental data to obtain the response surface.In order to enhance the uniformity of response distribution,Shannon entropy is applied to the objective function as the measure of uniformity.While for the situation of response distortion,we consider replacing the existing experiment points with those whose corresponding responses have a larger gradient norm.It means that the response value near these points will change rapidly,so they are more valuable for research.Then we use the peak surface in the three-dimensional space to intuitively verify the effect of the above algorithms on response uniformization and response distortion process characterization,and use the simulated annealing algorithm to solve them.The simulation results show that our sequential experiment strategy has a good effect.Finally,we apply the strategy to the practical problem of radar countermeasure experiment,and the obtained results also perform well.
文摘Previous studies have demonstrated the negative effects of sub-optimal air quality on profitability,production efficiency,environmental sustainability and animal welfare.Experiments were conducted to assess potential environmental improvement techniques such as installing oil-spraying systems in piggery buildings.The developed spray system worked very well and it was easy to assemble and operate.However,before selecting the most suitable spray heads,their capacity to uniformly distribute the oily mixture and the area covered by the spray heads had to be assessed.Machine vision techniques were used to evaluate the ability of different spray heads to evenly distribute the oil/water mixture.The results indicated that the best coverage was achieved by spray head No.4 and spray head No.1 which covered 79%and 67%of the target area,respectively.Spray distribution uniformity(variance)value was the lowest for spray head No.4(0.015).Spray head No.3 had the highest variance value(0.064).As the lowest variance means higher uniformity,nozzle No.4 was identified as the most suitable spray head for dust reduction in livestock buildings.
文摘The hydro-floating ship lift originally invented in China is a major innovation in the field of navigation technology.The shaft water levels synchronization of its unique hydraulic-driven system plays a crucial role in reducing the torque of the synchronous shafts and ensuring the safety and stability operation of the ship lift.This study aims to investigate the muti-shaft water level synchronization and the flow velocity uniformity of the combined type hydraulic-driven system.Based on the theory of residual energy,a new index m2 proposed in this study is more suitable for evaluating the flow velocity uniformity of the combined hydraulic-driven system.Finally,the critical value of m2=75 is calculated via the results of the scaled physical mode test as the threshold of water flow uniformity,and it provides a basis for determining the reasonable height of the pressure stabilizing chamber.
基金Supported by the National Natural Science Fundation of China(U1866211)。
文摘Modular multilevel converters(MMCs)have been widely used owing to their superior performance.However,the rapid switching of power electronics devices causes serious electromagnetic interference(EMI).There are a large number of obvious EMI peaks in the frequency spectrum of the carrier phase-shifted constant-switching-frequency pulse-width modulation(CSFPWM).Spreading the EMI across a wider frequency range can help to reduce the EMI peaks.In this study,we designed a uniform distribution(UD)spread-spectrum modulation technology using the principle of uniform switching frequency distribution and minimum switching loss for MMC.Its feasibility is verified by theoretical derivation and simulation.Then,the effectiveness of UDPWM in reducing the EMI is verified in experiments with a prototype MMC testbed in the lab.Compared with traditional CSFPWM,UDPWM can reduce conducted EMI by 10-20 dB.Also,compared with random PWM(RPWM),UDPWM can improve efficiency and reduce total harmonic distortion(THD)of output voltage and current in MMC.
基金CNPC Innovation Found,Grant/Award Number:2021DQ02-1001Liao Ning Revitalization Talents Program,Grant/Award Number:XLYC1907144+2 种基金Xinghai Talent Cultivation Plan,Grant/Award Number:X20200303National Outstanding Youth Science Fund,Grant/Award Number:52222314Fundamental Research Funds for the Central Universities,Grant/Award Numbers:DUT22JC02,DUT22LAB605。
文摘Lithium-sulfur(Li-S)batteries are the promising next-generation secondary energy storage systems,because of their advantages of high energy density and environmental friendliness.Among numerous cathode materials,organosulfur polymer materials have received extensive attentions because of their controllable structure and uniform sulfur distribution.However,the sulfur content of most organosulfur polymer cathodes is limited(S content<60%)due to the addition of large amounts of conductive agents and binders,which adversely affects the energy density of Li-S batteries.Herein,a hyperbranched sulfur-rich polymer based on modified polyethyleneimine(Ath-PEI)named carbon nanotubeentangled poly(allyl-terminated hyperbranched ethyleneimine-random-sulfur)(CNT/Ath-PEI@S)was prepared by sulfur polymerization and used as a Li-S battery cathode.The high intrinsic viscosity of Ath-PEI provided considerable adhesion and avoided the addition of PVDF binder,thereby increasing the sulfur content of cathodes to 75%.Moreover,considering the uniform distribution of elemental sulfur by the polymer,the utilization of sulfur was successfully improved,thus improving the rate capability and discharge capacity of the battery.The binder-free,sulfur-rich polymer cathode exhibited ultra-high initial discharge capacity(1520.7 mAh g^(−1) at 0.1 C),and high rate capability(804 mAh g^(−1) at 2.0 C).And cell-level calculations show that the electrode exhibits an initial capacity of 942.3 mAh g^(−1) electrode,which is much higher than those of conventional sulfur-polymer electrodes reported in the literature.
基金Colegio de Postgraduados Campus Veracruz and Consejo Nacional de Ciencia y Tecnolog'?a (CONACYT) for their financial support
文摘There are very few studies on the application of fertilizers through irrigation water(fertirrigation) using a multi-gate irrigation system in sugarcane AES. Through fertirrigation, the application of fertilizers can be simplified, and their distribution uniformity in sugarcane fields improved. This paper provides an overview of the state of the art regarding fertirrigation with multi-gate irrigation in sugarcane agroecosystems(AES). In order to systematize, organize, and discuss the scientific data on fertirrigation with low-pressure multi-gate irrigation systems in sugarcane AES, bibliographic material from the following full-text scientific journal databases was screened: the Elsevier Science Direct Freedom Collection, Springer Link, and the International Society for Horticultural Science. Next,a matrix of keywords was used to analyze the interrelationships among the available literature, current issues, and the recent findings.We conclude that development of fertirrigation technologies with low-pressure multi-gate irrigation is much needed.
基金Project supported by the National Natural Science Foundation of China (No. 51109092)the National Science Foundation for Post-doctoral Scientists of China (No. 2013M530237)the Jiangsu University Foundation for Advanced Talents (No. 12JDG098), China
文摘Based on the non-Darcian flow law described by exponent m and threshold gradient i 1 under a low hydraulic gradient and the classical nonlinear relationships e-lgσ′ and e-lgk v (Mesri and Rokhsar, 1974), the governing equation of 1D nonlinear consolidation was modified by considering both uniform distribution of self-weight stress and linear increment of self-weight stress. The numerical solutions for the governing equation were derived by the finite difference method (FDM). Moreover, the solutions were verified by comparing the numerical results with those by analytical method under a specific case. Finally, consolidation behavior under different parameters was investigated, and the results show that the rate of 1D nonlinear consolidation will slow down when the non-Darcian flow law is considered. The consolidation rate with linear increment of self-weight stress is faster than that with uniform distribution one. Compared to Darcy's flow law, the influence of parameters describing non-linearity of soft soil on consolidation behavior with non-Darcian flow has no significant change.
基金supported by the National Natural Science Foundation of China(Grant Nos.51821004 and 52090062)the research project from China Three Gorges Corporation(Contract No.202003346)。
文摘The flow field structure on the bipolar plate significantly affects the performance of the proton exchange membrane electrolysis cell(PEMEC).This paper proposes a new interdigitated-jet hole flow field(JHFF)design to improve the uniformities of liquid saturation,temperature,and current density distributions.The common single-path serpentine flow field(SSFF)and interdigitated flow field(IFF)are used as comparative references to constitute three PEMEC cases.An advanced numerical model has been established to simulate the performance of the PEMEC using CFD software.The results show that,due to the perpendicular mainstream and the pressure difference,the JHFF enhances the mass and heat transfer inside the porous electrode by introducing strong forced convection,which promotes gas removal underneath the ribs and cooling.Compared with the comparative flow fields,the uniformities of liquid saturation,temperature,and current density distributions by using the JHFF at the anode side are increased by 19.1%,53.2%,and 40.4%,respectively.Further,mainly owing to the largest conductive area,the PEMEC with the JHFF has superior polarization performance,which is 8.05%higher than the PEMEC with the SSFF.
基金Financial supports from National Nature Science Foundation of China (NSFC, Nos. 91634120 and 21521005)the National Key Research and Development Program of China (No. 2017YFA0206804)the Fundamental Research Funds for the Central Universities(No. XK1802-6)。
文摘Supported NiCu bimetallic catalysts have been produced in-situ on commercial Al_(2)O_(3)by using layered double hydroxides as precursors. The resulting catalysts show a uniform Ni and Cu distribution, thus providing good activity and selectivity in the reforming reaction of n-heptane. The catalytic performance has been found to depend on the Cu/Ni ratio, revealing the synergic catalysis between homogeneously dispersed Ni and Cu sites. The good catalysis of Ni Cu bimetallic catalysts makes it possible to partly or even completely replace Pt with NiCu bimetallic catalysts.
