In order to research environment parameters and physiological indices of high-quality and high-yield apple trees, two orchards with young and mature apples trees were investigated to explore structural parameter of ap...In order to research environment parameters and physiological indices of high-quality and high-yield apple trees, two orchards with young and mature apples trees were investigated to explore structural parameter of apple tree and community, and some physiological indices in fields and by room measurements. The results showed that tree height of high-quality orchard was in the range of 260 to 290 cm, branch angle in 70°-75°, and orchard coverage rate in 75%-94%, and the connec-tion rates between rows and trees were lower. Furthermore, the total branches of mature orchard reached 1.04 ×106 per hm2, while the young orchard was 8.79 ×105 per hm2; the leaves were thick and chlorophyl content was high, with SPAD value at 58.22. Additional y, the photosynthesis of the orchard was strong, and net photo-synthetic rate was 17.48-21.8 μmolCO2/(m2·s). The proportions of lateral shoot of bearing part were 81% and 75% respectively.展开更多
Based on the numerical simulation analysis, structure parameters of the high pressure fuel pump and common rail as well as flow limiter are designed and the GD-1 high pressure common rail fuel injection system is self...Based on the numerical simulation analysis, structure parameters of the high pressure fuel pump and common rail as well as flow limiter are designed and the GD-1 high pressure common rail fuel injection system is self-developed. Fuel injection characteristics experiment is performed on the GD-1 system. And double-factor variance analysis is applied to investigate the influence of the rail pressure and injection pulse width on the consistency of fuel injection quantity, thus to test whether the design of structure parameters is sound accordingly. The results of experiment and test show that rail pressure and injection pulse width as well as their mutual-effect have no influence on the injection quantity consistency, which proves that the structure parameters design is successful and performance of GD-1 system is sound.展开更多
The initial efficiency is a very important criterion for carbon anode material of Li-ion battery.The relationship between initial efficiency and structure parameters of carbon anode material of Li-ion battery was inve...The initial efficiency is a very important criterion for carbon anode material of Li-ion battery.The relationship between initial efficiency and structure parameters of carbon anode material of Li-ion battery was investigated by an artificial intelligence approach called Random Forests using D10,D50,D90,BET specific surface area and TP density as inputs,initial efficiency as output.The results give good classification performance with 91%accuracy.The variable importance analysis results show the impact of 5 variables on the initial efficiency descends in the order of D90,TP density,BET specific surface area,D50 and D10;smaller D90 and larger TP density have positive impact on initial efficiency.The contribution of BET specific surface area on classification is only 18.74%,which indicates the shortcoming of BET specific surface area as a widely used parameter for initial efficiency evaluation.展开更多
Textured surfaces are widely used in engineering components as they can improve tribological properties of sliding contacts, while the detailed behaviors of nanoscale reciprocating sliding contacts of textured surface...Textured surfaces are widely used in engineering components as they can improve tribological properties of sliding contacts, while the detailed behaviors of nanoscale reciprocating sliding contacts of textured surfaces are still lack of study. By using multiscale method, two dimensional nanoscale reciprocating sliding contacts of textured surfaces are investigated. The influence of indentation depth, texture shape, texture spacing, and tip radius on the average friction forces and the running-in stages is studied. The results show that the lowest indentation depth can make all the four textured surfaces reach steady state. Surfaces with right-angled trapezoid textures on the right side are better for reducing the running-in stage, and surfaces with right-angled trapezoid textures on the left side are better to reduce wear. Compared with other textured surfaces, the total average friction forces can be reduced by 82.94%–91.49% for the case of the contact between the tip with radius R = 60rand the isosceles trapezoid textured surface. Besides,the total average friction forces increase with the tip radii due to that bigger tip will induce higher contact areas. This research proposes a detailed study on nanoscale reciprocating sliding contacts of textured surfaces, to contribute to design textured surfaces, reduce friction and wear.展开更多
The effect of lateral structure parameters of transistors including emitter width, emitter length, and emitter stripe number on the performance parameters of the active inductor (AI), such as the effective inductanc...The effect of lateral structure parameters of transistors including emitter width, emitter length, and emitter stripe number on the performance parameters of the active inductor (AI), such as the effective inductance Ls, quality factor Q, and self-resonant frequency too is analyzed based on 0.35%tm SiGe BiCMOS process. The simulation results show that for AI operated under fixed current density Jc, the HBT lateral structure parameters have significant effect on Ls but little influence on Q and 090, and the larger Ls can be realized by the narrow, short emitter stripe and few emitter stripes of SiGe HBTs. On the other hand, for AI with fixed HBT size, smaller Jc is beneficial for AI to obtain larger Ls, but with a cost of smaller Q and 090. In addition, under the fixed collector current Ic, the larger the size of HBT is, the larger Ls becomes, but the smaller Q and ab become. The obtained results provide a reference for selecting geometry of transistors and operational condition in the design of active inductors.展开更多
X-ray diffraction line profiles of low density polyethylene(LDPE)/ (ethylene-propylene-octene-1)copolymer(EPO)blends have been analyzed with variance range function method.Theories for determining the microparacrystal...X-ray diffraction line profiles of low density polyethylene(LDPE)/ (ethylene-propylene-octene-1)copolymer(EPO)blends have been analyzed with variance range function method.Theories for determining the microparacrystallite size and the distortion parameter from single reflection have been described,and the value of these two parameters at (110)and(200)directions have been determined.展开更多
The bending section of tube between the bending die and the guider is in a less constrained state during the free bending process.The free bending dies have the important impact on the plastic deformation behavior and...The bending section of tube between the bending die and the guider is in a less constrained state during the free bending process.The free bending dies have the important impact on the plastic deformation behavior and the forming quality of tube.To study the evolution law of the deformation behavior of tube with the die structure parameters and optimize the free bending die parameters,the free bending experiments and the corresponding numerical simulations were carried out.The design principle of free bending die was illustrated.The free bending experiment was conducted to verify the reliability of the numerical simulation method.Based on the numerical simulation results,the influence of the distance between the center point of bending die and the front end of guider on the forming quality of bent tube is more obvious than that of the fillet of guider.However,the fillet of bending die hardly affects the stress and strain distribution and the evolution of the wall thickness.Finally,the free bending experiments with the newly determined free bending dies were conducted.The ultimate bending radius of bent tube is reduced and the forming quality is improved.展开更多
The so-called ORC(Organic Rankine Cycle)heat recovery technology has attracted much attention with regard to medium and low temperature waste heat recovery.In the present study,it is applied to a Tesla turbine.At the ...The so-called ORC(Organic Rankine Cycle)heat recovery technology has attracted much attention with regard to medium and low temperature waste heat recovery.In the present study,it is applied to a Tesla turbine.At the same time,the effects of the disc speed,diameter and inter-disc gap on the internal flow field and output power of the turbine are also investigated by means of CFD(Computational Fluid Dynamics)numerical simulation,by which the pressure,velocity,and output efficiency of the internal flow field are obtained under different internal and external conditions.The highest efficiency(66.4%)is obtained for a number of nozzles equal to 4,a disk thickness of 1 mm,and a gap of 1 mm between the disks.The results of the study serve as a theoretical basis for the structural design and optimization of Tesla turbines.展开更多
A colorless monoclinic crystal of dichloro-benzoxazine was obtained and examined by single crystal X-ray diffraction analysis. At the same time, molecular modeling analysis of nine benzoxazine compounds with different...A colorless monoclinic crystal of dichloro-benzoxazine was obtained and examined by single crystal X-ray diffraction analysis. At the same time, molecular modeling analysis of nine benzoxazine compounds with different substituting groups was performed. Both single crystal X-ray diffraction analysis and molecular modeling analysis provide a detailed picture of molecular structure on molecular level and show good consistence with each other. On the basis of structural analysis, the effects of molecular structure parameters on ring-opening polymerization of ben-zoxazines have been explored.展开更多
Numerical analysis of turbomachinery based on energy method is used to predict the aeroelastic stability of the straight-through labyrinth seal by solving aerodynamic work and vibration modes has been compared.It'...Numerical analysis of turbomachinery based on energy method is used to predict the aeroelastic stability of the straight-through labyrinth seal by solving aerodynamic work and vibration modes has been compared.It's found that the increase of pressure ratio leads to the in the circumferential direction of the labyrinth seal corresponds to the number of vibrating nodal diameters.In order to investigate the influence of structure parameters,the effect of relative thickness of the tooth tip,the width of the seal cavity and the eccentricity of the rotor on the aeroelastic stability of the labyrinth seal has been studied.The result of numerical calculation shows that the change of the structural parameters can affect the aeroelastic stability of the labyrinth seal to a certain extent,and can be applied in the structural optimization.展开更多
Vertical picking method is a predominate method used to harvest cotton crop.However,a vertical picking method may cause spindle bending of the cotton picker if spindles collide with stones on the cotton field.Thus,how...Vertical picking method is a predominate method used to harvest cotton crop.However,a vertical picking method may cause spindle bending of the cotton picker if spindles collide with stones on the cotton field.Thus,how to realize a precise height control of the cotton picker is a crucial issue to be solved.The objective of this study is to design a height control system to avoid the collision.To design it,the mathematical models are established first.Then a multi-objective optimization model represented by structure parameters and control parameters is proposed to take the pressure of chamber without piston,response time and displacement error of the height control system as the opti-mization objectives.An integrated optimization approach that combines optimization via simulation,particle swarm optimization and simulated annealing is proposed to solve the model.Simulation and experimental test results show that the proposed integrated optimization approach can not only reduce the pressure of chamber without piston,but also decrease the response time and displacement error of the height control system.展开更多
We determine structure parameters of the highest occupied molecular orbital(HOMO)of 27 dimers for the molecular tunneling ionization(so called MO-ADK)model of Tong et al.[Phys.Rev.A 66(2002)033402].The molecular wave ...We determine structure parameters of the highest occupied molecular orbital(HOMO)of 27 dimers for the molecular tunneling ionization(so called MO-ADK)model of Tong et al.[Phys.Rev.A 66(2002)033402].The molecular wave functions with correct asymptotic behavior are obtained by solving the time-independent Schr(o|¨)dinger equation with B-spline functions and molecular potentials which are numerically created using the density functional theory.We examine the alignment-dependent tunneling ionization probabilities from MO-ADK model for several molecules by comparing with the molecular strong-field approximation(MO-SFA)calculations.We show the molecular PerelomovPopov-Terent'ev(MO-PPT)can successfully give the laser wavelength dependence of ionization rates(or probabilities).Based on the MO-PPT model,two diatomic molecules having valence orbital with antibonding systems(i.e.,Cl_2,Ne_2)show strong ionization suppression when compared with their corresponding closest companion atoms.展开更多
In the molecular Ammosov–Delone–Krainov(MO-ADK) model of Tong et al. [Phys. Rev. A 66(2002)033402], the ionization rate depends on the structure parameters of the molecular orbital from which the electron is removed...In the molecular Ammosov–Delone–Krainov(MO-ADK) model of Tong et al. [Phys. Rev. A 66(2002)033402], the ionization rate depends on the structure parameters of the molecular orbital from which the electron is removed. We determine systematically and tabulate accurate structure parameters of the highest occupied molecular orbital(HOMO) for 123 gas-phase linear molecules by solving time-independent Schr¨odinger equation with B-spline functions and molecular potentials which are constructed numerically using the modified Leeuwen–Baerends(LBα)model.展开更多
The Ammosov–Delone–Krainov(ADK) and Perelomov–Popov–Terent'ev(PPT) ionization models were widely used in strong-field physics and attosecond science due to their many attractive advantages such as simpler anal...The Ammosov–Delone–Krainov(ADK) and Perelomov–Popov–Terent'ev(PPT) ionization models were widely used in strong-field physics and attosecond science due to their many attractive advantages such as simpler analytical formula, less computational demands, and satisfied accuracy of ionization rate. Based on the density-functional theory, we systematically determine accurate structure parameters of 25 atoms, 24 positive ions and 13 negative ions and tabulate for future applications. The wave function with correct asymptotic behavior is obtained by solving the time-independent Schr?dinger equation with B-spline basis sets and the accurate structure parameters are extracted from this wave function in the asymptotic region. The accuracies of structure parameters are carefully examined by comparing the ionization probabilities(or yields) calculated by PPT and ADK models with those of solving the threedimensional time-dependent Schr?dinger equation and the experimental data.展开更多
The physical and chemical properties of the air-dried residual coal after soaking in the goaf will change,resulting in an increase in its spontaneous combustion tendency.This study aimed to look into the features and ...The physical and chemical properties of the air-dried residual coal after soaking in the goaf will change,resulting in an increase in its spontaneous combustion tendency.This study aimed to look into the features and mechanism of soaked-dried coal's spontaneous combustion.Five samples of coal were dried to various degrees,and the weight loss features during thermal processing were examined.Based on this,the pore structure and chemical structure characteristics of the coal samples with the highest tendency to spontaneous combustion were quantitatively examined,and the mechanism by which soaking-drying afected the spontaneous combustion heating process of the remaining coal in goaf was investigated in turn.The results show that T1 decreases with the increase of drying time,T2–T6 shows a fuctuating change,and the ignition activation energy of 36-S-Coal is smaller than that of other coal samples.The pore type of 36-S-Coal changes from a oneend closed impermeable pore to an open pore,and the pore group area is large.During the 36 h drying process,the internal channels of the coal were dredged,and a large number of gravels and minerals were precipitated from the pores with the air fow.A large number of gravels were around the pores to form a surface structure that was easy to adsorb various gases.Furthermore,infrared spectroscopy was used to analyze the two coal samples.It was found that soaking and drying did not change the functional group types of coal samples,but the fatty chain degree of 36-S-Coal was reduced to 1.56.It shows that the aliphatic chain structure of coal is changed after 36 h of drying after 30 days of soaking,which leads to the continuous shedding of aliphatic chain branches of residual coal,and the skeleton of coal is looser,which makes the low-temperature oxidation reaction of 36-S-Coal easier.Based on the above results,the coal-oxygen composite mechanism of water-immerseddried coal is obtained,and it is considered that the key to the spontaneous combustion oxidation process of coal is to provide oxygen atoms and accelerate the formation of peroxides.展开更多
To design a power source system and mold for electromagnetic soft-contact continuous casting process and to theoretically estimate the heat losses from the charges and the system power, the effect of structure paramet...To design a power source system and mold for electromagnetic soft-contact continuous casting process and to theoretically estimate the heat losses from the charges and the system power, the effect of structure parameters on system power and magnetic flux density distribution was calculated using finite element method. The results show that as for electromagnetic soft-contact continuous casting system with partial-segment type mold, the power consumption is much more than that with a full-segment type mold; about 62% of electric power is dissipated in the mold, and the effective acting range of magnetic field is relatively narrow. Optimizing mold structure is a crucial measure of remarkably reducing mold power consumption and saving electric energy. Increasing slit number, width, and length can remarkably increase the magnetic flux density in the mold and can reduce the electric energy consumption. Among structure parameters, slit number and slit width are relatively more effective to reduce energy consumption. For a round billet electromagnetic continuous casting system with diameter of 178 ram, the reasonable slit number, width, and length are about 24--32, 0. 5--1.0 mm, and 160 mm, respectively.展开更多
A retention prediction system(RPS)of seven O-ethyl N-isopropyl phosphoro(thioureido)- thioates in reversed phase HPLC was investigated.The system is based on the solvent selectivity triangle concept.Three molecular st...A retention prediction system(RPS)of seven O-ethyl N-isopropyl phosphoro(thioureido)- thioates in reversed phase HPLC was investigated.The system is based on the solvent selectivity triangle concept.Three molecular structure parameters(hydrophobicity Ⅱ,substituent length L, and substituent maximum width B_5)were used to describe the quantitative structure-retention relation- ships.With these quantitative relationships,the retention behaviours of other eight homologs for different mobile phase composition were predicted.The predicted values were consistent with the measured values within relative error of 10%,which means that it is possible to apply the reported method to predict retention values for qualitative purposes for different mobile phase compositions.展开更多
The cold flow characteristics are investigated to show the effect of the structural parameters of the flow guide vane on the trapped vortex combustor(TVC). The results show that the structural parameters have signif...The cold flow characteristics are investigated to show the effect of the structural parameters of the flow guide vane on the trapped vortex combustor(TVC). The results show that the structural parameters have significant effects on the TVC. As a/ H increases, the total pressure loss, the wall shear stress at the bottom of the cavity and the turbulent intensity in the main combustion zone increase. b/ B does not have a significant effect on the cavity flow structure and the total pressure loss, and the wall shear stress at the bottom of the cavity increases as b/ B increases. There is no significant increase of the turbulent intensity with the increase of b/ B. The increase of c/ L has little effect on the total pressure loss, and it is not conducive to a stable combustion. As c/ L increases, the wall shear stress at the bottom of the cavity decreases. When a/ H= 0.4, b/ B= 0.4, c/ L= 0.1, a desirable dual-vortex structure is formed with an acceptable pressure loss to achieve a stable combustion. Moreover, to ascertain that the flame is stable for different values of Vm a with the optimal structural parameters, the effect of Vm a on the flow field is discussed. Results suggest that the dual-vortex structure has no relationship with the increase of Vm a. Furthermore, an unsteady simulation is conducted to show the generation and the development of the dual-vortex.展开更多
To solve the problem of low efficiency of NO_(x)emission reduction in self-reflux burners,this study is based on the concept of coordinated control of self-reflux burner structural and thermal parameters.After complet...To solve the problem of low efficiency of NO_(x)emission reduction in self-reflux burners,this study is based on the concept of coordinated control of self-reflux burner structural and thermal parameters.After completing the structural design and optimization of thermal parameters,we continue to adjust the two key structural parameters:the nozzle axis distance and the length of the cylindrical section,to minimize NO_(x)emissions.These are the two parameters that chiefly affect the mixing of flue gas and fuel gas.The results show that increasing nozzle axis distance can delay the mixing of gas and air and create a more uniform oxygen concentration field for the combustion process.The maximum combustion temperature is reduced from 1973.65 K to 1935.88 K and the volume fraction of NO_(x)in the flue gas is reduced from 188.08×10^(–6)to 143.47×10^(–6).However,compared with the nozzle axis distance,the length of the cylindrical section of the burner has little effect on the mixing of the flow field.Under different cylindrical section lengths,the maximum combustion temperature does not change more than 3 K,and the volume fraction of NO_(x)in the flue gas changes within 5×10~(–6).展开更多
The Yellow River Delta(YRD)has China's largest artificial Robinia pseudoacacia forest,which was planted in the late 1970s and suffered extensive dieback in the 1990s.The health grade of the R.pseudoacacia forest(n...The Yellow River Delta(YRD)has China's largest artificial Robinia pseudoacacia forest,which was planted in the late 1970s and suffered extensive dieback in the 1990s.The health grade of the R.pseudoacacia forest(named canopy vigor grade,CVG)could be achieved by using high-resolution images and canopy vigor indicators(CVIs).However,a previous study showed that there was no significant correlation between CVG and the field-estimated aboveground biomass(AGB)of R.pseudoacacia forest.Therefore,this study aims to construct forest health indicators(FHIs)based on canopy spatial structure parameters extracted from LiDAR.The FHIs included Weibull_α(the scale parameter of the Weibull density function that reflects the shape of the tree canopy),VCI(vertical complexity index),sdCC(the standard deviation of canopy cover),H99(the 99th percentile height)and cvLAD(the coefficient of variation of leaf area density),and could significantly distinguish three forest health grades(FHG)(p<0.05).The FHG was positively correlated with forest AGB(rs=0.51,p=0.004),and the similarity value with CVG was 63.33%.The results of this study confirmed that the FHIs can reflect both canopy vigor and tree productivity,and distinguish forest health status without prior classification information.展开更多
基金Supported by Special Fund for Modern Agricultural Industry Technology System(CARS-28)~~
文摘In order to research environment parameters and physiological indices of high-quality and high-yield apple trees, two orchards with young and mature apples trees were investigated to explore structural parameter of apple tree and community, and some physiological indices in fields and by room measurements. The results showed that tree height of high-quality orchard was in the range of 260 to 290 cm, branch angle in 70°-75°, and orchard coverage rate in 75%-94%, and the connec-tion rates between rows and trees were lower. Furthermore, the total branches of mature orchard reached 1.04 ×106 per hm2, while the young orchard was 8.79 ×105 per hm2; the leaves were thick and chlorophyl content was high, with SPAD value at 58.22. Additional y, the photosynthesis of the orchard was strong, and net photo-synthetic rate was 17.48-21.8 μmolCO2/(m2·s). The proportions of lateral shoot of bearing part were 81% and 75% respectively.
文摘Based on the numerical simulation analysis, structure parameters of the high pressure fuel pump and common rail as well as flow limiter are designed and the GD-1 high pressure common rail fuel injection system is self-developed. Fuel injection characteristics experiment is performed on the GD-1 system. And double-factor variance analysis is applied to investigate the influence of the rail pressure and injection pulse width on the consistency of fuel injection quantity, thus to test whether the design of structure parameters is sound accordingly. The results of experiment and test show that rail pressure and injection pulse width as well as their mutual-effect have no influence on the injection quantity consistency, which proves that the structure parameters design is successful and performance of GD-1 system is sound.
基金Project(2001AA501433)supported by the National High-Tech Research and Development Program of China
文摘The initial efficiency is a very important criterion for carbon anode material of Li-ion battery.The relationship between initial efficiency and structure parameters of carbon anode material of Li-ion battery was investigated by an artificial intelligence approach called Random Forests using D10,D50,D90,BET specific surface area and TP density as inputs,initial efficiency as output.The results give good classification performance with 91%accuracy.The variable importance analysis results show the impact of 5 variables on the initial efficiency descends in the order of D90,TP density,BET specific surface area,D50 and D10;smaller D90 and larger TP density have positive impact on initial efficiency.The contribution of BET specific surface area on classification is only 18.74%,which indicates the shortcoming of BET specific surface area as a widely used parameter for initial efficiency evaluation.
基金Supported by National Natural Science Foundation of China(Grant Nos.51675429,51205313)Fundamental Research Funds for the Central Universities,China(Grant No.3102014JCS05009)the 111 Project,China(Grant No.B13044)
文摘Textured surfaces are widely used in engineering components as they can improve tribological properties of sliding contacts, while the detailed behaviors of nanoscale reciprocating sliding contacts of textured surfaces are still lack of study. By using multiscale method, two dimensional nanoscale reciprocating sliding contacts of textured surfaces are investigated. The influence of indentation depth, texture shape, texture spacing, and tip radius on the average friction forces and the running-in stages is studied. The results show that the lowest indentation depth can make all the four textured surfaces reach steady state. Surfaces with right-angled trapezoid textures on the right side are better for reducing the running-in stage, and surfaces with right-angled trapezoid textures on the left side are better to reduce wear. Compared with other textured surfaces, the total average friction forces can be reduced by 82.94%–91.49% for the case of the contact between the tip with radius R = 60rand the isosceles trapezoid textured surface. Besides,the total average friction forces increase with the tip radii due to that bigger tip will induce higher contact areas. This research proposes a detailed study on nanoscale reciprocating sliding contacts of textured surfaces, to contribute to design textured surfaces, reduce friction and wear.
基金Project supported by the Natural Science Foundation of BeijingChina(Grant Nos.4142007 and 4122014)+1 种基金the National Natural Science Foundation of China(Grant No.61574010)the Higher Educational Science and Technology Program of Shandong Province,China(Grant No.J13LN09)
文摘The effect of lateral structure parameters of transistors including emitter width, emitter length, and emitter stripe number on the performance parameters of the active inductor (AI), such as the effective inductance Ls, quality factor Q, and self-resonant frequency too is analyzed based on 0.35%tm SiGe BiCMOS process. The simulation results show that for AI operated under fixed current density Jc, the HBT lateral structure parameters have significant effect on Ls but little influence on Q and 090, and the larger Ls can be realized by the narrow, short emitter stripe and few emitter stripes of SiGe HBTs. On the other hand, for AI with fixed HBT size, smaller Jc is beneficial for AI to obtain larger Ls, but with a cost of smaller Q and 090. In addition, under the fixed collector current Ic, the larger the size of HBT is, the larger Ls becomes, but the smaller Q and ab become. The obtained results provide a reference for selecting geometry of transistors and operational condition in the design of active inductors.
文摘X-ray diffraction line profiles of low density polyethylene(LDPE)/ (ethylene-propylene-octene-1)copolymer(EPO)blends have been analyzed with variance range function method.Theories for determining the microparacrystallite size and the distortion parameter from single reflection have been described,and the value of these two parameters at (110)and(200)directions have been determined.
基金The investigation was supported from the Opening Project of State Key Lab of Digital Manufacturing Equipment&Technology(No.DMETKF2021004)the National Natural Science Foundation of China(Nos.52105360,U1937206,and 52175328)+1 种基金2021 Jiangsu Shuangchuang Talent Program(JSSCBS20210157)Fundamental Research Funds for the Central Universities(No.NS2022061).
文摘The bending section of tube between the bending die and the guider is in a less constrained state during the free bending process.The free bending dies have the important impact on the plastic deformation behavior and the forming quality of tube.To study the evolution law of the deformation behavior of tube with the die structure parameters and optimize the free bending die parameters,the free bending experiments and the corresponding numerical simulations were carried out.The design principle of free bending die was illustrated.The free bending experiment was conducted to verify the reliability of the numerical simulation method.Based on the numerical simulation results,the influence of the distance between the center point of bending die and the front end of guider on the forming quality of bent tube is more obvious than that of the fillet of guider.However,the fillet of bending die hardly affects the stress and strain distribution and the evolution of the wall thickness.Finally,the free bending experiments with the newly determined free bending dies were conducted.The ultimate bending radius of bent tube is reduced and the forming quality is improved.
基金the National Natural Science Foundation of China(No.51876114)Shanghai Engineering Research Center of Marine Renewable Energy(Grant No.19DZ2254800).
文摘The so-called ORC(Organic Rankine Cycle)heat recovery technology has attracted much attention with regard to medium and low temperature waste heat recovery.In the present study,it is applied to a Tesla turbine.At the same time,the effects of the disc speed,diameter and inter-disc gap on the internal flow field and output power of the turbine are also investigated by means of CFD(Computational Fluid Dynamics)numerical simulation,by which the pressure,velocity,and output efficiency of the internal flow field are obtained under different internal and external conditions.The highest efficiency(66.4%)is obtained for a number of nozzles equal to 4,a disk thickness of 1 mm,and a gap of 1 mm between the disks.The results of the study serve as a theoretical basis for the structural design and optimization of Tesla turbines.
基金the National Natural Science Foundation of China (Grant No. 59573008).
文摘A colorless monoclinic crystal of dichloro-benzoxazine was obtained and examined by single crystal X-ray diffraction analysis. At the same time, molecular modeling analysis of nine benzoxazine compounds with different substituting groups was performed. Both single crystal X-ray diffraction analysis and molecular modeling analysis provide a detailed picture of molecular structure on molecular level and show good consistence with each other. On the basis of structural analysis, the effects of molecular structure parameters on ring-opening polymerization of ben-zoxazines have been explored.
基金This work is supported by the National Nature ScienceFoundation of China(No.51475022).
文摘Numerical analysis of turbomachinery based on energy method is used to predict the aeroelastic stability of the straight-through labyrinth seal by solving aerodynamic work and vibration modes has been compared.It's found that the increase of pressure ratio leads to the in the circumferential direction of the labyrinth seal corresponds to the number of vibrating nodal diameters.In order to investigate the influence of structure parameters,the effect of relative thickness of the tooth tip,the width of the seal cavity and the eccentricity of the rotor on the aeroelastic stability of the labyrinth seal has been studied.The result of numerical calculation shows that the change of the structural parameters can affect the aeroelastic stability of the labyrinth seal to a certain extent,and can be applied in the structural optimization.
基金Supported by National Natural Science Foundation of China(Grant No.51905448)Chongqing Technology Innovation and Application Program of China(Grant No.cstc2018jszx-cyzdX0183)Fundamental Research Funds for the Central Universities of China(Grant No.SWU119060).
文摘Vertical picking method is a predominate method used to harvest cotton crop.However,a vertical picking method may cause spindle bending of the cotton picker if spindles collide with stones on the cotton field.Thus,how to realize a precise height control of the cotton picker is a crucial issue to be solved.The objective of this study is to design a height control system to avoid the collision.To design it,the mathematical models are established first.Then a multi-objective optimization model represented by structure parameters and control parameters is proposed to take the pressure of chamber without piston,response time and displacement error of the height control system as the opti-mization objectives.An integrated optimization approach that combines optimization via simulation,particle swarm optimization and simulated annealing is proposed to solve the model.Simulation and experimental test results show that the proposed integrated optimization approach can not only reduce the pressure of chamber without piston,but also decrease the response time and displacement error of the height control system.
基金Supported by National Natural Science Foundation of China under Grant Nos.11164025,11264036,11465016,11364038the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No.20116203120001the Basic Scientific Research Foundation for Institution of Higher Learning of Gansu Province
文摘We determine structure parameters of the highest occupied molecular orbital(HOMO)of 27 dimers for the molecular tunneling ionization(so called MO-ADK)model of Tong et al.[Phys.Rev.A 66(2002)033402].The molecular wave functions with correct asymptotic behavior are obtained by solving the time-independent Schr(o|¨)dinger equation with B-spline functions and molecular potentials which are numerically created using the density functional theory.We examine the alignment-dependent tunneling ionization probabilities from MO-ADK model for several molecules by comparing with the molecular strong-field approximation(MO-SFA)calculations.We show the molecular PerelomovPopov-Terent'ev(MO-PPT)can successfully give the laser wavelength dependence of ionization rates(or probabilities).Based on the MO-PPT model,two diatomic molecules having valence orbital with antibonding systems(i.e.,Cl_2,Ne_2)show strong ionization suppression when compared with their corresponding closest companion atoms.
基金Supported by National Natural Science Foundation of China under Grant Nos.11664035,11674268,11465016,11364038,11364039the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No.20116203120001the Basic Scientific Research Foundation for Institution of Higher Learning of Gansu Province
文摘In the molecular Ammosov–Delone–Krainov(MO-ADK) model of Tong et al. [Phys. Rev. A 66(2002)033402], the ionization rate depends on the structure parameters of the molecular orbital from which the electron is removed. We determine systematically and tabulate accurate structure parameters of the highest occupied molecular orbital(HOMO) for 123 gas-phase linear molecules by solving time-independent Schr¨odinger equation with B-spline functions and molecular potentials which are constructed numerically using the modified Leeuwen–Baerends(LBα)model.
基金Project supported by the National Natural Science Foundation of China under Grant Nos. 11664035, 11864037 and 11765018the Foundation of Northwest Normal University (No. NWNU-LKQN-17-1)。
文摘The Ammosov–Delone–Krainov(ADK) and Perelomov–Popov–Terent'ev(PPT) ionization models were widely used in strong-field physics and attosecond science due to their many attractive advantages such as simpler analytical formula, less computational demands, and satisfied accuracy of ionization rate. Based on the density-functional theory, we systematically determine accurate structure parameters of 25 atoms, 24 positive ions and 13 negative ions and tabulate for future applications. The wave function with correct asymptotic behavior is obtained by solving the time-independent Schr?dinger equation with B-spline basis sets and the accurate structure parameters are extracted from this wave function in the asymptotic region. The accuracies of structure parameters are carefully examined by comparing the ionization probabilities(or yields) calculated by PPT and ADK models with those of solving the threedimensional time-dependent Schr?dinger equation and the experimental data.
基金supported by the fnancial support of the General Projects of National Natural Science Foundation of China(52074156).
文摘The physical and chemical properties of the air-dried residual coal after soaking in the goaf will change,resulting in an increase in its spontaneous combustion tendency.This study aimed to look into the features and mechanism of soaked-dried coal's spontaneous combustion.Five samples of coal were dried to various degrees,and the weight loss features during thermal processing were examined.Based on this,the pore structure and chemical structure characteristics of the coal samples with the highest tendency to spontaneous combustion were quantitatively examined,and the mechanism by which soaking-drying afected the spontaneous combustion heating process of the remaining coal in goaf was investigated in turn.The results show that T1 decreases with the increase of drying time,T2–T6 shows a fuctuating change,and the ignition activation energy of 36-S-Coal is smaller than that of other coal samples.The pore type of 36-S-Coal changes from a oneend closed impermeable pore to an open pore,and the pore group area is large.During the 36 h drying process,the internal channels of the coal were dredged,and a large number of gravels and minerals were precipitated from the pores with the air fow.A large number of gravels were around the pores to form a surface structure that was easy to adsorb various gases.Furthermore,infrared spectroscopy was used to analyze the two coal samples.It was found that soaking and drying did not change the functional group types of coal samples,but the fatty chain degree of 36-S-Coal was reduced to 1.56.It shows that the aliphatic chain structure of coal is changed after 36 h of drying after 30 days of soaking,which leads to the continuous shedding of aliphatic chain branches of residual coal,and the skeleton of coal is looser,which makes the low-temperature oxidation reaction of 36-S-Coal easier.Based on the above results,the coal-oxygen composite mechanism of water-immerseddried coal is obtained,and it is considered that the key to the spontaneous combustion oxidation process of coal is to provide oxygen atoms and accelerate the formation of peroxides.
基金Item Sponsored by National Natural Science Foundation of China(50274203)National High Technology Research and Development Program of China(2001AA337040)
文摘To design a power source system and mold for electromagnetic soft-contact continuous casting process and to theoretically estimate the heat losses from the charges and the system power, the effect of structure parameters on system power and magnetic flux density distribution was calculated using finite element method. The results show that as for electromagnetic soft-contact continuous casting system with partial-segment type mold, the power consumption is much more than that with a full-segment type mold; about 62% of electric power is dissipated in the mold, and the effective acting range of magnetic field is relatively narrow. Optimizing mold structure is a crucial measure of remarkably reducing mold power consumption and saving electric energy. Increasing slit number, width, and length can remarkably increase the magnetic flux density in the mold and can reduce the electric energy consumption. Among structure parameters, slit number and slit width are relatively more effective to reduce energy consumption. For a round billet electromagnetic continuous casting system with diameter of 178 ram, the reasonable slit number, width, and length are about 24--32, 0. 5--1.0 mm, and 160 mm, respectively.
文摘A retention prediction system(RPS)of seven O-ethyl N-isopropyl phosphoro(thioureido)- thioates in reversed phase HPLC was investigated.The system is based on the solvent selectivity triangle concept.Three molecular structure parameters(hydrophobicity Ⅱ,substituent length L, and substituent maximum width B_5)were used to describe the quantitative structure-retention relation- ships.With these quantitative relationships,the retention behaviours of other eight homologs for different mobile phase composition were predicted.The predicted values were consistent with the measured values within relative error of 10%,which means that it is possible to apply the reported method to predict retention values for qualitative purposes for different mobile phase compositions.
基金Project supported by the National Natural Science Foun-dation of China(Grant Nos.51066006,51266013)the Aero-nautical Science Fund(Grant Nos.2013ZB56002,2013ZB56004)
文摘The cold flow characteristics are investigated to show the effect of the structural parameters of the flow guide vane on the trapped vortex combustor(TVC). The results show that the structural parameters have significant effects on the TVC. As a/ H increases, the total pressure loss, the wall shear stress at the bottom of the cavity and the turbulent intensity in the main combustion zone increase. b/ B does not have a significant effect on the cavity flow structure and the total pressure loss, and the wall shear stress at the bottom of the cavity increases as b/ B increases. There is no significant increase of the turbulent intensity with the increase of b/ B. The increase of c/ L has little effect on the total pressure loss, and it is not conducive to a stable combustion. As c/ L increases, the wall shear stress at the bottom of the cavity decreases. When a/ H= 0.4, b/ B= 0.4, c/ L= 0.1, a desirable dual-vortex structure is formed with an acceptable pressure loss to achieve a stable combustion. Moreover, to ascertain that the flame is stable for different values of Vm a with the optimal structural parameters, the effect of Vm a on the flow field is discussed. Results suggest that the dual-vortex structure has no relationship with the increase of Vm a. Furthermore, an unsteady simulation is conducted to show the generation and the development of the dual-vortex.
基金supported by the Fundamental Research Funds for the National Natural Science Foundation of China(No.52006008,62033014)Guangdong Basic and Applied Basic Research Foundation(2019A1515110743)+2 种基金Scientific and Technological Innovation Foundation of Shunde Graduate School of USTB(BK20BE010)Guangdong University Research Findings Commercialization Center(2020JNHB06)the Central Universities of China(FRF-TP-18-074A1,FRF-BD-20-09A)。
文摘To solve the problem of low efficiency of NO_(x)emission reduction in self-reflux burners,this study is based on the concept of coordinated control of self-reflux burner structural and thermal parameters.After completing the structural design and optimization of thermal parameters,we continue to adjust the two key structural parameters:the nozzle axis distance and the length of the cylindrical section,to minimize NO_(x)emissions.These are the two parameters that chiefly affect the mixing of flue gas and fuel gas.The results show that increasing nozzle axis distance can delay the mixing of gas and air and create a more uniform oxygen concentration field for the combustion process.The maximum combustion temperature is reduced from 1973.65 K to 1935.88 K and the volume fraction of NO_(x)in the flue gas is reduced from 188.08×10^(–6)to 143.47×10^(–6).However,compared with the nozzle axis distance,the length of the cylindrical section of the burner has little effect on the mixing of the flow field.Under different cylindrical section lengths,the maximum combustion temperature does not change more than 3 K,and the volume fraction of NO_(x)in the flue gas changes within 5×10~(–6).
基金supported by National Natural Science Foundation of China:[Grant Number No.41471419 and No.31971579].
文摘The Yellow River Delta(YRD)has China's largest artificial Robinia pseudoacacia forest,which was planted in the late 1970s and suffered extensive dieback in the 1990s.The health grade of the R.pseudoacacia forest(named canopy vigor grade,CVG)could be achieved by using high-resolution images and canopy vigor indicators(CVIs).However,a previous study showed that there was no significant correlation between CVG and the field-estimated aboveground biomass(AGB)of R.pseudoacacia forest.Therefore,this study aims to construct forest health indicators(FHIs)based on canopy spatial structure parameters extracted from LiDAR.The FHIs included Weibull_α(the scale parameter of the Weibull density function that reflects the shape of the tree canopy),VCI(vertical complexity index),sdCC(the standard deviation of canopy cover),H99(the 99th percentile height)and cvLAD(the coefficient of variation of leaf area density),and could significantly distinguish three forest health grades(FHG)(p<0.05).The FHG was positively correlated with forest AGB(rs=0.51,p=0.004),and the similarity value with CVG was 63.33%.The results of this study confirmed that the FHIs can reflect both canopy vigor and tree productivity,and distinguish forest health status without prior classification information.