An orthorhombic polycrystal is an orthorhombic aggregate of tiny crystallites. In this paper, we study the effect of the crystalline mean shape on the constitutive relation of the orthorhombic polycrystal. The crystal...An orthorhombic polycrystal is an orthorhombic aggregate of tiny crystallites. In this paper, we study the effect of the crystalline mean shape on the constitutive relation of the orthorhombic polycrystal. The crystalline mean shape and the crystalline orientation arrangement are described by the crystalline shape function （CSF） and the orientation distribution function （ODF）, respectively. The CSF and the ODF are expanded as an infinite series in terms of the Wigner D-functions. The expanded coefficients of the CSF and the ODF are called the shape coefficients s^lm0 and the texture coefficients c^lmn respectively. Assuming that Ceff in the constitutive relation depends on the shape coefficients s^lm0 and the texture coefficients c^lmn by the principle of material frame-indifference we derive an analytical expression for C^eff up to terms linear in s^lmo and c^lmn and the expression would be applicable to the polycrystal whose texture is weak and whose crystalline mean shape has weak anisotropy. C^cff contains six unspecified material constants （λ, μ, c, s1, s2, s3）, five shape coefficients （s^2 00, s^2 20, s^4 00, s^4 20, s^4 40）, and three texture coefficients （c^4 99,c^4 20, c^4 40）, The results based on the perturbation approach are used to determine the five material constants approximately. We also find that the shape coefficients 2 and a s^2mo and s^4m0 are all zero if the crystalline mean shape is a cuboid. Some examples are given to compare our computational results.展开更多
The effect of the laser processing parameters on the composition uniformity and shape coefficient of fusion zone with laser surface alloyed Cr plated on medium carbon low alloy steel has been studied.It was found that...The effect of the laser processing parameters on the composition uniformity and shape coefficient of fusion zone with laser surface alloyed Cr plated on medium carbon low alloy steel has been studied.It was found that the composition uniformity depends on the shape coefficient of fusion zone,and the later is a function of both power density and interaction time.If the power density is fixed to a certain value,the shape coefficient is directly,propor- tional to the interaction time.A completely,uniform molten pool can be obtained,when the shape coefficient is between 1.6 and 3.0.展开更多
This study focused on hydraulic characteristics around a gear-shaped weir in a straight channel. Systematic experiments were carried out for weirs with two different gear heights and eight groups of geometrical parame...This study focused on hydraulic characteristics around a gear-shaped weir in a straight channel. Systematic experiments were carried out for weirs with two different gear heights and eight groups of geometrical parameters. The impacts of various geometrical parameters of gear-shaped weirs on the discharge capacity were investigated. The following conclusions are drawn from the experimental study:(1) The discharge coefficient(m_c) was influenced by the size of the gear: at a constant discharge, the weir with larger values of a/b(a is the width of the gear, and b is the width between the two neighboring gears) and a/c(c is the height of the gear) had a smaller value of m_c. The discharge capacity of the gear-shaped weir was influenced by the water depth in the weir.(2) For type C1 with a gear height of 0.01 m, when the discharge was less than 60m^3/h and H_1=P < 1.0(H_1 is the water depth at the low weir crest, and P is the weir height), m_c significantly increased with the discharge and H_1=P; with further increases of the discharge and H_1=P, m_cshowed insignificant decreases and fluctuated within small ranges. For type C2 with a gear height of 0.02 m, when the discharge was less than 60m^3/h and H_1=P < 1.0, m_csignificantly increased with the discharge and H_1=P; when the discharge was larger than 60m^3/h and H_1=P > 1.0, m_c slowly decreased with the increases of the discharge and H_1=P for a=b 1.0 and a=c 1.0, and slowly increased with the discharge and H_1=P for a=b > 1.0 and a=c > 1.0.(3) A formula of m_cfor gear-shaped weirs was established based on the principle of weir flow, with consideration of the water depth in the weir, the weir height and width, and the height of the gear.展开更多
Shape coefficient is a significant factor accounting for building energy consumption. In order to decrease the building energy consumption of rural residence in severe cold regions,this paper from the perspective of r...Shape coefficient is a significant factor accounting for building energy consumption. In order to decrease the building energy consumption of rural residence in severe cold regions,this paper from the perspective of regulating the shape coefficient limit value,applies the field survey method to statistic and analyze the shape,width and depth of rural residence in severe cold regions and concludes the distribution characteristics and scope of building area. On this basis,though calculating and analyzing the relations between shape coefficient and length-width ratio under different building areas,meanwhile comprehensive considering the building function,farmers' living mode and requirements etc,it put forward that the shape coefficient of rural residence in severe cold regions should below 0. 8. It has important significance for guiding the rural energy-saving house design and construction of severe cold regions.展开更多
Shape has an undeniable impact on particle behaviour,and the shapes of naturally occurring granular matter are typically irregular.Computational studies of irregularly shaped particles are challenging but necessary to...Shape has an undeniable impact on particle behaviour,and the shapes of naturally occurring granular matter are typically irregular.Computational studies of irregularly shaped particles are challenging but necessary to gain a better understanding of the flow of particulate matter.This study focuses on the behaviour of irregular sinter particles and applies the discrete element method to examine the effects of static and rolling friction coefficients and particle shape on the angle of repose and porosity of sinter piles.A three-dimensional model of an irregular sinter particle reconstructed by close-range photogrammetry served as the template for generating multi-sphere particles with varying numbers of sub-spheres(1,3,7,22,and 135)and sphericity ranging from 1 to 0.69.Simulations of particle piles were conducted for a range of values of the coefficients of static and rolling friction.The results indicate that the angle of repose increases with static friction and also increases with rolling friction coefficient when it is lower than the static coefficient.The angle of repose shows clear dependence on particle shape,particularly for lower rolling friction coefficients.The friction coefficients for particles of five different shapes were individually determined through bulk calibration,and irregularly shaped particles in DEM were found to require lower friction coefficients.Porosity was marginally affected by the static and rolling friction coefficients for spherical particles,while non-spherical particles showed porosity increasing with the rolling friction coefficient.The relationship between particle sphericity and porosity was nonlinear:as sphericity decreases from 1.00 to 0.69,the porosity first decreases to a minimum and then increases.The findings confirmed that both friction and particle shape have a significant influence on the structure of sinter piles,with implications for material handling and processing in industrial applications.展开更多
With the aim to enhance the energy conversion efficiency of the rainbow shape piezoelectric transducer, an analysis model of energy conversion efficiency is established based on the elastic mechanics theory and piezoe...With the aim to enhance the energy conversion efficiency of the rainbow shape piezoelectric transducer, an analysis model of energy conversion efficiency is established based on the elastic mechanics theory and piezoelectricity theory. It can be found that the energy conversion efficiency of the rainbow shape piezoelectric transducer mainly depends on its shape parameters and ma- terial properties from the analysis model. Simulation results show that there is an optimal length ratio to generate maximum en- ergy conversion efficiency and the optimal length ratios and energy conversion efficiencies of beryllium bronze substrate trans- ducer and steel substrate transducer are （0.65, 2.21%） and （0.65, 1.64%） respectively. The optimal thickness ratios and energy conversion efficieneies of beryllium bronze substrate transducer and steel substrate transducer are （1.16, 2.56%） and （1.49, 1.57%） respectively. With the increase of width ratio and initial curvature radius, both the energy conversion efficiencies de- crease. Moreover, beryllium bronze flexible substrate transducer is superior to the steel flexible substrate transducer.展开更多
Background： Measurements of tree heights and diameters are essential in forest assessment and modelling. Tree heights are used for estimating timber volume, site index and other important variables related to forest ...Background： Measurements of tree heights and diameters are essential in forest assessment and modelling. Tree heights are used for estimating timber volume, site index and other important variables related to forest growth and yield, succession and carbon budget models. However, the diameter at breast height （dbh） can be more accurately obtained and at lower cost, than total tree height. Hence, generalized height-diameter （h-d） models that predict tree height from dbh, age and other covariates are needed. For a more flexible but biologically plausible estimation of covariate effects we use shape constrained generalized additive models as an extension of existing h-d model approaches. We use causal site parameters such as index of aridity to enhance the generality and causality of the models and to enable predictions under projected changeable climatic conditions. Methods： We develop unconstrained generalized additive models （GAM） and shape constrained generalized additive models （SCAM） for investigating the possible effects of tree-specific parameters such as tree age, relative diameter at breast height, and site-specific parameters such as index of aridity and sum of daily mean temperature during vegetation period, on the h-d relationship of forests in Lower Saxony, Germany. Results： Some of the derived effects, e.g. effects of age, index of aridity and sum of daily mean temperature have significantly non-linear pattern. The need for using SCAM results from the fact that some of the model effects show partially implausible patterns especially at the boundaries of data ranges. The derived model predicts monotonically increasing levels of tree height with increasing age and temperature sum and decreasing aridity and social rank of a tree within a stand, The definition of constraints leads only to marginal or minor decline in the model statistics like AIC An observed structured spatial trend in tree height is modelled via 2-dimensional surface fitting. Conclusions： We demonstrate that the SCAM approach allows optimal regression modelling flexibility similar to the standard GAM but with the additional possibility of defining specific constraints for the model effects. The longitudinal character of the model allows for tree height imputation for the current status of forests but also for future tree height prediction.展开更多
This study proposed a force and shape collaborative control method that combined method of influence coefficients(MIC)and the elitist nondominated sorting genetic algorithm(NSGA-II)to reduce the shape deviation caused...This study proposed a force and shape collaborative control method that combined method of influence coefficients(MIC)and the elitist nondominated sorting genetic algorithm(NSGA-II)to reduce the shape deviation caused by manufacturing errors,gravity deformation,and fixturing errors and improve the shape accuracy of the assembled large composite fuselage panel.This study used a multi-point flexible assembly system driven by hexapod parallel robots.The proposed method simultaneously considers the shape deviation and assembly load of the panel.First,a multi-point flexible assembly system driven by hexapod parallel robots was introduced,with the relevant variables defined in the control process.In addition,the corresponding mathematical model was constructed.Subsequently,MIC was used to establish the prediction models between the displacements of actuators and displacements of panel shape control points,deformation loads applied by the actuators.Following the modeling,the shape deviation of the panel and the assembly load were used as the optimization objectives,and the displacements of actuators were optimized using NSGA-II.Finally,a typical composite fuselage panel case study was considered to demonstrate the effectiveness of the proposed method.展开更多
Though gravel cushions are used worldwide in open-pit mines and railway slopes to control the impact of rolling stones,no universal technical standards have been put in place to guide engineers in their correct design...Though gravel cushions are used worldwide in open-pit mines and railway slopes to control the impact of rolling stones,no universal technical standards have been put in place to guide engineers in their correct design,and few laboratory test results are available with which to characterize collisions between rolling stones and a gravel cushion.We carried out a large number of experiments in which rolling stones made of the same material but differently shaped were dropped from various heights onto cushions with various particle sizes and thicknesses.We investigated the characteristics of the resulting collisions,and the relationships between coefficients of restitution(CORs)of blocks with different shape and release height H,cushion thickness h and particle diameter d are obtained through linear fitting method.Orthogonal testing reveals the relative influence of block shape,release height,and the particle size and thickness of the cushion on the collision characteristics,which can assist engineers in designing a gravel cushion suitable to the distribution and weathering characteristics of rolling stones in a specific area.展开更多
Based on the wave radiation and diffraction theory, this paper investigates a new type breakwater with upper arcshaped plate by using the boundary element method(BEM). By comparing with other three designs of plate ty...Based on the wave radiation and diffraction theory, this paper investigates a new type breakwater with upper arcshaped plate by using the boundary element method(BEM). By comparing with other three designs of plate type breakwater(lower arc-shaped plate, single horizontal plate and double horizontal plate), this new type breakwater has been proved more effective. The wave exiting force, transmission and reflection coefficients are analyzed and discussed. In order to reveal the wave elimination mechanism of this type of breakwater, the velocity field around the breakwater is obtained. It is shown that:(1) The sway exciting force is minimal.(2) When the ratio of the submergence and wave amplitude is 0.05, the wave elimination effect will increase by 50% compared with other three types of breakwater.(3) The obvious backflow is found above the plate in the velocity field analysis.展开更多
Using the method of undetermined coefficients, we construct a set of shape function spaces of nine-node triangular plate elements converging for any meshes, which generalize Spect's element and Veubeke's element.
The red snapper Lutjanus campechanus (Poey, 1860) has a high commercial value that sustains an important fishery in Mexico. In this study, the patterns in morphological variations from early juvenile to adult stages w...The red snapper Lutjanus campechanus (Poey, 1860) has a high commercial value that sustains an important fishery in Mexico. In this study, the patterns in morphological variations from early juvenile to adult stages were assessed by geometric methods (GM) in 194 organisms. Changes in shape were more evident and rapid in the early juvenile stage and decreased during adulthood. The principal components analysis of shape (Relative Warp Analysis, or RWA) identified size and body depth as the main sources of variance associated to both juvenile and adult organisms. The outline of the head and the tail showed the most noticeable differences following the ontogenic pathway visualized by thin-plate splines indicating that the ontogenetic pathway of the upper half and the lower half of the dorsal head profile (DHP) are in relatively opposite directions than those from the tail that bends ventrally. The Two-Block Partial Least Square analysis (2B-PLS) and their CR coefficients showed that the two modules had a moderate linear trend (p = 0.001). Although the blocks have morphological changes at different rates, there is a moderate synchrony in growth by modules. This study is the first to report the use of geometrical morphometry in L. campechanus in Mexico.展开更多
This article first talks about railways in general and ballast in particular. An inventory is then made on the modernization of the Senegalese ballast railways. In the second phase, an experimental work of characteriz...This article first talks about railways in general and ballast in particular. An inventory is then made on the modernization of the Senegalese ballast railways. In the second phase, an experimental work of characterization of basaltic aggregates of Diack (Locality of Ngoundiane, Thiès region, Senegal) is presented. The grain size studied is 25/50 mm as for any material studied for use as railway ballast. Experimental work presented consists of the characterization of the shape of an aggregate using the NF P 18-301 standard. The test consists of comparing the volume of the aggregate to that of an equivalent sphere with the largest diameter of the aggregate, by calculating the average volume coefficient. With a Representative Elementary Volume (REV) of 6 aggregates, the volume coefficient “C<sub><span style="font-family:Verdana;">v</span></sub><span style="font-family:Verdana;">” fluctuates between 0.27 and 0.49 with an average volume coefficient of 0.39 which is well above 0.15</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">. </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">The grains studied are polyhedral and therefore have a high mechanical resistance.</span></span></span>展开更多
Artificial intelligence and computer vision need methods for 2D （two-dimensional） shape retrieval having discrete set of boundary points. A novel method of MHR （Hurwitz-Radon Matrices） is used in shape modeling. P...Artificial intelligence and computer vision need methods for 2D （two-dimensional） shape retrieval having discrete set of boundary points. A novel method of MHR （Hurwitz-Radon Matrices） is used in shape modeling. Proposed method is based on the family of MHR which possess columns composed of orthogonal vectors. 2D curve is retrieved via different functions as probability distribution functions： sine, cosine, tangent, logarithm, exponent, arcsin, arccos, arctan and power function. Created from the family of N-1 MHR and completed with the identical matrix, system of matrices is orthogonal only for dimensions N = 2, 4 or 8. Orthogonality of columns and rows is very significant for stability and high precision of calculations. MHR method is interpolating the function point by point without using any formula of function. Main features of MHR method are： accuracy of curve reconstruction depending on number of nodes and method of choosing nodes, interpolation of L points of the curve is connected with the computational cost of rank O（L）, MHR interpolation is not a linear interpolation.展开更多
To clarify the existence of liquid loading and optimize the production allocation in gas wells,we constructed a model for calculating the critical liquid-carrying velocity based on the equal relationship between the t...To clarify the existence of liquid loading and optimize the production allocation in gas wells,we constructed a model for calculating the critical liquid-carrying velocity based on the equal relationship between the total surface free energy of droplets and the total turbulent kinetic energy of gas and considering the droplet size,droplet deformation and the influence of droplet deformation on surface free energy.Based on the ellipsoid hypothesis and by analyzing the influence of droplet deformation on the surface area and free energy of droplets,the equation for calculation of the maximum diameter of windward surface of droplets was developed.With consideration to the influence of droplet deformation on drags,the expression for the critical liquid-carrying velocity of ellipsoid droplets was clarified.With consideration to the influence of deformation and internal flow of droplets,the drag coefficient of the ellipsoid droplets was determined to be 20%higher than that of the Brauer Model for spheroid.A functional relationship between the deformation parameter K and the critical Weber number W_(ec) was established based on the energy conservation law.In addition,the calculation results were reduced by 10%.During the course,the impacts of gas-well pressure and temperature on surface tension were taken into account.The proposed model was compared with the models developed by Turner,Li Min,Wang Yizhong,Wang Zhibin and Xiong Yu,and on-site verification was conducted in 44 gas wells.The results show that the proposed model provides the prediction results in best coincidence with the actual performance of gas wells.In conclusion,the proposed model can be used to predict liquid loading in gas wells effectively.展开更多
Novel and effective H-shaped chromophores were doped into polymethyl methacrylate （PMMA） to form vip-host polymer thin films. The measurement results of Maker fringe method show that the polymer thin films contain...Novel and effective H-shaped chromophores were doped into polymethyl methacrylate （PMMA） to form vip-host polymer thin films. The measurement results of Maker fringe method show that the polymer thin films containing the H-shaped chromophores as a vip exhibit high second harmonic coefficients （d33） compared with other two-dimensional chromophores.展开更多
In this paper,the influences of the shape of magnetic material on the magnetoelectric（ME）properties of PZT/Metglas magnetoelectric（ME）composites have been investigated.The results indicate that,with the decrease o...In this paper,the influences of the shape of magnetic material on the magnetoelectric（ME）properties of PZT/Metglas magnetoelectric（ME）composites have been investigated.The results indicate that,with the decrease of the waist length（L w）of the dumbbell-shaped Metglas,the magnetic flux density in the center region and ME coefficients（αME）of the composites increase,while the optimal bias magnetic field H dc decreases on the contrary.In an AC magnetic field of 1 k Hz,the maximumαME（αMax）of the composite with L w=20 mm exhibits 1.3 times larger than that of the one with L w=50 mm,and the optimal H dc deceases by 15%.At the resonant frequencies of each composites,αMax is enhanced by1.3 times as L w decreases from 50 to 20 mm.The simulation made by Comsol Multiphysics and the theoretical analysis based on an equivalent magnetic circuit confirm the experimental results.展开更多
基金The project supported by the National Natural Science Foundation of China(10562004)the Oversea Returning Grant of China.
文摘An orthorhombic polycrystal is an orthorhombic aggregate of tiny crystallites. In this paper, we study the effect of the crystalline mean shape on the constitutive relation of the orthorhombic polycrystal. The crystalline mean shape and the crystalline orientation arrangement are described by the crystalline shape function （CSF） and the orientation distribution function （ODF）, respectively. The CSF and the ODF are expanded as an infinite series in terms of the Wigner D-functions. The expanded coefficients of the CSF and the ODF are called the shape coefficients s^lm0 and the texture coefficients c^lmn respectively. Assuming that Ceff in the constitutive relation depends on the shape coefficients s^lm0 and the texture coefficients c^lmn by the principle of material frame-indifference we derive an analytical expression for C^eff up to terms linear in s^lmo and c^lmn and the expression would be applicable to the polycrystal whose texture is weak and whose crystalline mean shape has weak anisotropy. C^cff contains six unspecified material constants （λ, μ, c, s1, s2, s3）, five shape coefficients （s^2 00, s^2 20, s^4 00, s^4 20, s^4 40）, and three texture coefficients （c^4 99,c^4 20, c^4 40）, The results based on the perturbation approach are used to determine the five material constants approximately. We also find that the shape coefficients 2 and a s^2mo and s^4m0 are all zero if the crystalline mean shape is a cuboid. Some examples are given to compare our computational results.
文摘The effect of the laser processing parameters on the composition uniformity and shape coefficient of fusion zone with laser surface alloyed Cr plated on medium carbon low alloy steel has been studied.It was found that the composition uniformity depends on the shape coefficient of fusion zone,and the later is a function of both power density and interaction time.If the power density is fixed to a certain value,the shape coefficient is directly,propor- tional to the interaction time.A completely,uniform molten pool can be obtained,when the shape coefficient is between 1.6 and 3.0.
基金supported by the National Natural Science Foundation of China(Grant No.51409155)
文摘This study focused on hydraulic characteristics around a gear-shaped weir in a straight channel. Systematic experiments were carried out for weirs with two different gear heights and eight groups of geometrical parameters. The impacts of various geometrical parameters of gear-shaped weirs on the discharge capacity were investigated. The following conclusions are drawn from the experimental study:(1) The discharge coefficient(m_c) was influenced by the size of the gear: at a constant discharge, the weir with larger values of a/b(a is the width of the gear, and b is the width between the two neighboring gears) and a/c(c is the height of the gear) had a smaller value of m_c. The discharge capacity of the gear-shaped weir was influenced by the water depth in the weir.(2) For type C1 with a gear height of 0.01 m, when the discharge was less than 60m^3/h and H_1=P < 1.0(H_1 is the water depth at the low weir crest, and P is the weir height), m_c significantly increased with the discharge and H_1=P; with further increases of the discharge and H_1=P, m_cshowed insignificant decreases and fluctuated within small ranges. For type C2 with a gear height of 0.02 m, when the discharge was less than 60m^3/h and H_1=P < 1.0, m_csignificantly increased with the discharge and H_1=P; when the discharge was larger than 60m^3/h and H_1=P > 1.0, m_c slowly decreased with the increases of the discharge and H_1=P for a=b 1.0 and a=c 1.0, and slowly increased with the discharge and H_1=P for a=b > 1.0 and a=c > 1.0.(3) A formula of m_cfor gear-shaped weirs was established based on the principle of weir flow, with consideration of the water depth in the weir, the weir height and width, and the height of the gear.
基金Sponsored by the National Project of Scientific and Technical Supporting Programs Funded by Ministry of Science & Technology of China (Grant No.2011BAJ08B06)
文摘Shape coefficient is a significant factor accounting for building energy consumption. In order to decrease the building energy consumption of rural residence in severe cold regions,this paper from the perspective of regulating the shape coefficient limit value,applies the field survey method to statistic and analyze the shape,width and depth of rural residence in severe cold regions and concludes the distribution characteristics and scope of building area. On this basis,though calculating and analyzing the relations between shape coefficient and length-width ratio under different building areas,meanwhile comprehensive considering the building function,farmers' living mode and requirements etc,it put forward that the shape coefficient of rural residence in severe cold regions should below 0. 8. It has important significance for guiding the rural energy-saving house design and construction of severe cold regions.
基金funded by China Scholarship Council(grant No.202106890009).
文摘Shape has an undeniable impact on particle behaviour,and the shapes of naturally occurring granular matter are typically irregular.Computational studies of irregularly shaped particles are challenging but necessary to gain a better understanding of the flow of particulate matter.This study focuses on the behaviour of irregular sinter particles and applies the discrete element method to examine the effects of static and rolling friction coefficients and particle shape on the angle of repose and porosity of sinter piles.A three-dimensional model of an irregular sinter particle reconstructed by close-range photogrammetry served as the template for generating multi-sphere particles with varying numbers of sub-spheres(1,3,7,22,and 135)and sphericity ranging from 1 to 0.69.Simulations of particle piles were conducted for a range of values of the coefficients of static and rolling friction.The results indicate that the angle of repose increases with static friction and also increases with rolling friction coefficient when it is lower than the static coefficient.The angle of repose shows clear dependence on particle shape,particularly for lower rolling friction coefficients.The friction coefficients for particles of five different shapes were individually determined through bulk calibration,and irregularly shaped particles in DEM were found to require lower friction coefficients.Porosity was marginally affected by the static and rolling friction coefficients for spherical particles,while non-spherical particles showed porosity increasing with the rolling friction coefficient.The relationship between particle sphericity and porosity was nonlinear:as sphericity decreases from 1.00 to 0.69,the porosity first decreases to a minimum and then increases.The findings confirmed that both friction and particle shape have a significant influence on the structure of sinter piles,with implications for material handling and processing in industrial applications.
基金National Natural Science Foundation of China (10972 102)Research Fund for the Doctoral Program of Higher Education of China (200802870007)Technology Research and Development Program of Jiangsu Province (BE2009163)
文摘With the aim to enhance the energy conversion efficiency of the rainbow shape piezoelectric transducer, an analysis model of energy conversion efficiency is established based on the elastic mechanics theory and piezoelectricity theory. It can be found that the energy conversion efficiency of the rainbow shape piezoelectric transducer mainly depends on its shape parameters and ma- terial properties from the analysis model. Simulation results show that there is an optimal length ratio to generate maximum en- ergy conversion efficiency and the optimal length ratios and energy conversion efficiencies of beryllium bronze substrate trans- ducer and steel substrate transducer are （0.65, 2.21%） and （0.65, 1.64%） respectively. The optimal thickness ratios and energy conversion efficieneies of beryllium bronze substrate transducer and steel substrate transducer are （1.16, 2.56%） and （1.49, 1.57%） respectively. With the increase of width ratio and initial curvature radius, both the energy conversion efficiencies de- crease. Moreover, beryllium bronze flexible substrate transducer is superior to the steel flexible substrate transducer.
文摘Background： Measurements of tree heights and diameters are essential in forest assessment and modelling. Tree heights are used for estimating timber volume, site index and other important variables related to forest growth and yield, succession and carbon budget models. However, the diameter at breast height （dbh） can be more accurately obtained and at lower cost, than total tree height. Hence, generalized height-diameter （h-d） models that predict tree height from dbh, age and other covariates are needed. For a more flexible but biologically plausible estimation of covariate effects we use shape constrained generalized additive models as an extension of existing h-d model approaches. We use causal site parameters such as index of aridity to enhance the generality and causality of the models and to enable predictions under projected changeable climatic conditions. Methods： We develop unconstrained generalized additive models （GAM） and shape constrained generalized additive models （SCAM） for investigating the possible effects of tree-specific parameters such as tree age, relative diameter at breast height, and site-specific parameters such as index of aridity and sum of daily mean temperature during vegetation period, on the h-d relationship of forests in Lower Saxony, Germany. Results： Some of the derived effects, e.g. effects of age, index of aridity and sum of daily mean temperature have significantly non-linear pattern. The need for using SCAM results from the fact that some of the model effects show partially implausible patterns especially at the boundaries of data ranges. The derived model predicts monotonically increasing levels of tree height with increasing age and temperature sum and decreasing aridity and social rank of a tree within a stand, The definition of constraints leads only to marginal or minor decline in the model statistics like AIC An observed structured spatial trend in tree height is modelled via 2-dimensional surface fitting. Conclusions： We demonstrate that the SCAM approach allows optimal regression modelling flexibility similar to the standard GAM but with the additional possibility of defining specific constraints for the model effects. The longitudinal character of the model allows for tree height imputation for the current status of forests but also for future tree height prediction.
基金supported by National Natural Science Foundation of China(No.52105502)Fund of National Engineering and Research Center for Commercial Aircraft Manufacturing(Nos.COMAC-SFGS-2019-263 and COMAC-SFGS-2019-3731)the Fundamental Research Funds for the Central Universities(No.3042021601).
文摘This study proposed a force and shape collaborative control method that combined method of influence coefficients(MIC)and the elitist nondominated sorting genetic algorithm(NSGA-II)to reduce the shape deviation caused by manufacturing errors,gravity deformation,and fixturing errors and improve the shape accuracy of the assembled large composite fuselage panel.This study used a multi-point flexible assembly system driven by hexapod parallel robots.The proposed method simultaneously considers the shape deviation and assembly load of the panel.First,a multi-point flexible assembly system driven by hexapod parallel robots was introduced,with the relevant variables defined in the control process.In addition,the corresponding mathematical model was constructed.Subsequently,MIC was used to establish the prediction models between the displacements of actuators and displacements of panel shape control points,deformation loads applied by the actuators.Following the modeling,the shape deviation of the panel and the assembly load were used as the optimization objectives,and the displacements of actuators were optimized using NSGA-II.Finally,a typical composite fuselage panel case study was considered to demonstrate the effectiveness of the proposed method.
基金supported by the Fundamental Research Funds for the Central Universities(No.B210201001)the open fund of Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province(No.ZJRMG-2020-02)+1 种基金the open fund of Engineering Research Center of Development and Management for Low to Ultra-Low Permeability Oil&Gas Reservoirs in West China,Ministry of Education(No.KFJJ-XB-2020-7)the Research and Development Project of Guizhou University of Engineering Science(No.G2018016)。
文摘Though gravel cushions are used worldwide in open-pit mines and railway slopes to control the impact of rolling stones,no universal technical standards have been put in place to guide engineers in their correct design,and few laboratory test results are available with which to characterize collisions between rolling stones and a gravel cushion.We carried out a large number of experiments in which rolling stones made of the same material but differently shaped were dropped from various heights onto cushions with various particle sizes and thicknesses.We investigated the characteristics of the resulting collisions,and the relationships between coefficients of restitution(CORs)of blocks with different shape and release height H,cushion thickness h and particle diameter d are obtained through linear fitting method.Orthogonal testing reveals the relative influence of block shape,release height,and the particle size and thickness of the cushion on the collision characteristics,which can assist engineers in designing a gravel cushion suitable to the distribution and weathering characteristics of rolling stones in a specific area.
基金financially supported by the National Key Basic Research Program of China(Grant No.2013CB036101)the National Natural Science Foundation of China(Grant No.11702054)
文摘Based on the wave radiation and diffraction theory, this paper investigates a new type breakwater with upper arcshaped plate by using the boundary element method(BEM). By comparing with other three designs of plate type breakwater(lower arc-shaped plate, single horizontal plate and double horizontal plate), this new type breakwater has been proved more effective. The wave exiting force, transmission and reflection coefficients are analyzed and discussed. In order to reveal the wave elimination mechanism of this type of breakwater, the velocity field around the breakwater is obtained. It is shown that:(1) The sway exciting force is minimal.(2) When the ratio of the submergence and wave amplitude is 0.05, the wave elimination effect will increase by 50% compared with other three types of breakwater.(3) The obvious backflow is found above the plate in the velocity field analysis.
文摘Using the method of undetermined coefficients, we construct a set of shape function spaces of nine-node triangular plate elements converging for any meshes, which generalize Spect's element and Veubeke's element.
文摘The red snapper Lutjanus campechanus (Poey, 1860) has a high commercial value that sustains an important fishery in Mexico. In this study, the patterns in morphological variations from early juvenile to adult stages were assessed by geometric methods (GM) in 194 organisms. Changes in shape were more evident and rapid in the early juvenile stage and decreased during adulthood. The principal components analysis of shape (Relative Warp Analysis, or RWA) identified size and body depth as the main sources of variance associated to both juvenile and adult organisms. The outline of the head and the tail showed the most noticeable differences following the ontogenic pathway visualized by thin-plate splines indicating that the ontogenetic pathway of the upper half and the lower half of the dorsal head profile (DHP) are in relatively opposite directions than those from the tail that bends ventrally. The Two-Block Partial Least Square analysis (2B-PLS) and their CR coefficients showed that the two modules had a moderate linear trend (p = 0.001). Although the blocks have morphological changes at different rates, there is a moderate synchrony in growth by modules. This study is the first to report the use of geometrical morphometry in L. campechanus in Mexico.
文摘This article first talks about railways in general and ballast in particular. An inventory is then made on the modernization of the Senegalese ballast railways. In the second phase, an experimental work of characterization of basaltic aggregates of Diack (Locality of Ngoundiane, Thiès region, Senegal) is presented. The grain size studied is 25/50 mm as for any material studied for use as railway ballast. Experimental work presented consists of the characterization of the shape of an aggregate using the NF P 18-301 standard. The test consists of comparing the volume of the aggregate to that of an equivalent sphere with the largest diameter of the aggregate, by calculating the average volume coefficient. With a Representative Elementary Volume (REV) of 6 aggregates, the volume coefficient “C<sub><span style="font-family:Verdana;">v</span></sub><span style="font-family:Verdana;">” fluctuates between 0.27 and 0.49 with an average volume coefficient of 0.39 which is well above 0.15</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">. </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">The grains studied are polyhedral and therefore have a high mechanical resistance.</span></span></span>
文摘Artificial intelligence and computer vision need methods for 2D （two-dimensional） shape retrieval having discrete set of boundary points. A novel method of MHR （Hurwitz-Radon Matrices） is used in shape modeling. Proposed method is based on the family of MHR which possess columns composed of orthogonal vectors. 2D curve is retrieved via different functions as probability distribution functions： sine, cosine, tangent, logarithm, exponent, arcsin, arccos, arctan and power function. Created from the family of N-1 MHR and completed with the identical matrix, system of matrices is orthogonal only for dimensions N = 2, 4 or 8. Orthogonality of columns and rows is very significant for stability and high precision of calculations. MHR method is interpolating the function point by point without using any formula of function. Main features of MHR method are： accuracy of curve reconstruction depending on number of nodes and method of choosing nodes, interpolation of L points of the curve is connected with the computational cost of rank O（L）, MHR interpolation is not a linear interpolation.
基金Project supported by the Postdoctoral Research Project of Shaanxi Province“Study on the gas/liquid two-phase helical vortex flow characteristics in the vortex shaft caused by spiral guide plate”(No.2016BSHEDZZ25).
文摘To clarify the existence of liquid loading and optimize the production allocation in gas wells,we constructed a model for calculating the critical liquid-carrying velocity based on the equal relationship between the total surface free energy of droplets and the total turbulent kinetic energy of gas and considering the droplet size,droplet deformation and the influence of droplet deformation on surface free energy.Based on the ellipsoid hypothesis and by analyzing the influence of droplet deformation on the surface area and free energy of droplets,the equation for calculation of the maximum diameter of windward surface of droplets was developed.With consideration to the influence of droplet deformation on drags,the expression for the critical liquid-carrying velocity of ellipsoid droplets was clarified.With consideration to the influence of deformation and internal flow of droplets,the drag coefficient of the ellipsoid droplets was determined to be 20%higher than that of the Brauer Model for spheroid.A functional relationship between the deformation parameter K and the critical Weber number W_(ec) was established based on the energy conservation law.In addition,the calculation results were reduced by 10%.During the course,the impacts of gas-well pressure and temperature on surface tension were taken into account.The proposed model was compared with the models developed by Turner,Li Min,Wang Yizhong,Wang Zhibin and Xiong Yu,and on-site verification was conducted in 44 gas wells.The results show that the proposed model provides the prediction results in best coincidence with the actual performance of gas wells.In conclusion,the proposed model can be used to predict liquid loading in gas wells effectively.
基金supported by a Start-up Grant from Southeast University to Dr Chao-Zhi Zhang and the Science Foundation of Jiangsu Province of China(No.BK2004085).
文摘Novel and effective H-shaped chromophores were doped into polymethyl methacrylate （PMMA） to form vip-host polymer thin films. The measurement results of Maker fringe method show that the polymer thin films containing the H-shaped chromophores as a vip exhibit high second harmonic coefficients （d33） compared with other two-dimensional chromophores.
基金Supported by the National Natural Science Foundation of China(51372174,51132001,11364018 and J1210061)Natural Science Foundation of Hubei Province(2014CFB610)the Excellent Young Innovation Team Project of Hubei Province(T201429)
文摘In this paper,the influences of the shape of magnetic material on the magnetoelectric（ME）properties of PZT/Metglas magnetoelectric（ME）composites have been investigated.The results indicate that,with the decrease of the waist length（L w）of the dumbbell-shaped Metglas,the magnetic flux density in the center region and ME coefficients（αME）of the composites increase,while the optimal bias magnetic field H dc decreases on the contrary.In an AC magnetic field of 1 k Hz,the maximumαME（αMax）of the composite with L w=20 mm exhibits 1.3 times larger than that of the one with L w=50 mm,and the optimal H dc deceases by 15%.At the resonant frequencies of each composites,αMax is enhanced by1.3 times as L w decreases from 50 to 20 mm.The simulation made by Comsol Multiphysics and the theoretical analysis based on an equivalent magnetic circuit confirm the experimental results.
