Solid modeling with precise NURBS boundaries compliant with STEP standard represents the most promising way of designing complicated mechanical products in a CIM environment. In paral- lel to the traditional approach ...Solid modeling with precise NURBS boundaries compliant with STEP standard represents the most promising way of designing complicated mechanical products in a CIM environment. In paral- lel to the traditional approach of putting together volumetric primitives with Boolean operations, an al- ternative way of applying the wireframe and skinning techniques is under development. The latter ap- proach is easy to implement, robust and capable of handling the most sophisticated models, while suf- fers the drawbacks of low efficiency in identifying interactively the boundaries of each surface patch when the line segments are interlaced and located close to each other. This paper describes the essentials of the wireframe and skinning techniques which produce the identical product information model as a solid modeler.展开更多
Intersecting is an important factor which influences the effociency androbustness of Boolean algorithms in solid modeling based on surved-surfaces,andintersecting algorithms are closely related to geometric representa...Intersecting is an important factor which influences the effociency androbustness of Boolean algorithms in solid modeling based on surved-surfaces,andintersecting algorithms are closely related to geometric representations of curved-surfaces.Although surfaces can be commonly represented with NURBS,unnecessary complexitiesare caused in the intersecting of quadric surfaces.Quadrics are frequently used to des-cribe geometric features of shafts,holes and grooves etc.in mechanical part designing,therefore;their intersection algorithms are required to have higher accuracy,higher efficiency and higher robustness.For this reason,a practical representation ofquadric surfaces is studied in detail,and on the basis of that,algorithms of intersectingpoints are developed between quadric suraces and their boundaies,i.e.,conics,quarticnonplanar space curves.展开更多
The principal assumptions about equivalence and energy distribution of the asdorption sites on solidsurfaces used by Langmuir for deriving the equation of monomolecular adsorption are generalized and anew physical ads...The principal assumptions about equivalence and energy distribution of the asdorption sites on solidsurfaces used by Langmuir for deriving the equation of monomolecular adsorption are generalized and anew physical adsorption model is proposed and tested with experimental data published in literature.Themodels of Langmuir,Freundlich,Temkin etc.are only the special cases.Assuming uniform density distributionof adsorption energy,the isotherm equation is given asn=K.1n[1+（bop）1/Mor n=K.1n[1+（boC）1/M]where n is the amount of adsorption per unit weight or area of solid p or C is tbe pressure of gas or the concen-tration of solution respectively.K,bo,M are constants with physical meanings as described in this paper.This equation can be used over wide range to quantitatively represent the five types of physical adsorptionclassified by Brunauer.展开更多
In the previous work, an efficient method has been proposed to represent solid objects as multiple combinations of globally deformed supershapes. In this paper, this framework is applied with a new supershape implicit...In the previous work, an efficient method has been proposed to represent solid objects as multiple combinations of globally deformed supershapes. In this paper, this framework is applied with a new supershape implicit function that is based on the notion of radial distance and results are presented on realistic models composed of hundreds of hierarchically globally deformed supershapes. An implicit equation with guaranteed differential properties is obtained by simple combinations of the primitives~ implicit representations using R-function theory. The surface corresponding to the zero-set of the implicit equation is efficiently and directly polygonized using the primitives,parametric forms. Moreover, hierarchical global deformations are considered to increase the range of shapes that can be modeled. The potential of the approach is illustrated by representing complex models composed of several hundreds of primitives inspired from CAD models of mechanical parts.展开更多
Applying new approaches, methods, and technologies for the estimation of reserves can effectively improve the efficiency and accuracy of assessments of solid mineral resources. After analyzing the development of 3-D g...Applying new approaches, methods, and technologies for the estimation of reserves can effectively improve the efficiency and accuracy of assessments of solid mineral resources. After analyzing the development of 3-D geoscience modeling technology （3-D GMT）, this paper discusses the application of 3-D GMT for the estimation of solid mineral reserves, emphatically introducing its workflow and two key technologies, 3-D orebody surface modeling, and property modeling. Moreover, the paper analyzes the limitations of traditional methods, such as the section method and geological block method, and points out the advantages of 3-D GMT： building more accurate 3-D orebody models, expressing the internal inhomogeneous attributes of an orebody, reducing the potential for errors in the estimation of reserves, and implementing dynamic estimations of reserves.展开更多
Plastic contamination is universal all through the marine condition,yet gauges of the worldwide plenitude and weight of coasting plastics have needed information,especially from the Southern Hemisphere and remote area...Plastic contamination is universal all through the marine condition,yet gauges of the worldwide plenitude and weight of coasting plastics have needed information,especially from the Southern Hemisphere and remote areas.Here we report a gauge of the all-out number of plastic particles and their weight gliding on the planet’s seas from 24 endeavours(2007-2013)over every one of the five subtropical gyres,coastal Australia,Bay of Bengal and the Mediterranean Sea directing surface net tows(N=680)and visual review transects of huge plastic flotsam and debris(N=891).Utilizing an oceanographic model of coasting trash dispersal adjusted by our information,and rectifying for wind-driven vertical blending,we gauge at least 5.25 trillion particles weighing 268,940 tons.When looking at between four size classes,two micro plastic<4.75 mm and meso and micro plastic>4.75 mm,a huge loss of micro plastics is seen from the ocean surface contrasted with anticipated paces of discontinuity,recommending there are systems at play that expel<4.75 mm plastic particles from the sea surface.The focus on the life cycle assessment and the brief overview of the plastic waste management over the ocean surfaces with the various mathematical models has been studied.The impact of the ocean pollution is also being analysed.展开更多
A valid image-processing algorithm of weld pool surface reconstruction according to an input image of weld pool based on shape from shading （SFS） in computer vision is presented. The weld pool surface information is...A valid image-processing algorithm of weld pool surface reconstruction according to an input image of weld pool based on shape from shading （SFS） in computer vision is presented. The weld pool surface information is related to the backside weld width, which is crucial to the quality of weld joint. The image of weld pool is recorded with an optical sensing method. Firstly, the reflectance map model, which specifies the imaging process, is estimated. Then, the algorithm of weld pool surface reconstruction based on SFS is implemented by iteration scheme and speeded by hierarchical structure. The results indicate the accuracy and effectiveness of the approach.展开更多
3D solid models for parts with regular-form surfaces (PRFSs) are effectively generated using traditional parametric design techniques. A new model is obtained by changing some parameters defining the model. The parts ...3D solid models for parts with regular-form surfaces (PRFSs) are effectively generated using traditional parametric design techniques. A new model is obtained by changing some parameters defining the model. The parts with free-form surfaces (PFFSs), however, cannot be defined by several parameters. Usually they are defined by some geometric elements like profile curves. The traditional parametric design approaches have not easily dealt with the PFFSs. A method for generating a solid model and an engineering drawing for PFFSs is proposed in this paper: First, the new profiles are generated from input point data. Second, the profile information is extracted from the existing model. Last, the old profiles are replaced with the new profiles. This method can preserve the associative information of the existing model and automatically generate the drawing including views, dimen- sions, and annotations. The proposed method has been implemented using a commercial CAD/CAM system, Unigraphics, and API functions written in C-language, and were applied to the blades of a turbine generator. Some illustrative examples are pro- vided in order to show the effectiveness of the proposed method.展开更多
Based on the maximum flux principle(MFP),a water quality evaluation model for surface water ecosystem is presented by using self-organization map(SOM) neural network simulation algorithm from the aspect of systematic ...Based on the maximum flux principle(MFP),a water quality evaluation model for surface water ecosystem is presented by using self-organization map(SOM) neural network simulation algorithm from the aspect of systematic structural evolution.This evaluation model is applied to the case of surface water ecosystem in Xindu District of Chengdu City in China.The values reflecting the water quality of five cross-sections of the system at different developing stages are obtained,with stable values of 1.438,2.952,1.869,2.443 and 2.479,respectively.The simulation also indicates that the larger the value,the more serious the water pollution.Furthermore,a classification graph is given to reflect the evolution of structural pattern.The combination of MFP and SOM neural network reveals the formation of different structural patterns in the system during the interaction of internal components.It is shown that a dominant pattern is finally reserved,which starts from a variety of combination patterns for a time period.The results agree with those from traditional evaluation methods,which indicates that the proposed model has high accuracy.This model embodies the evolutionary dynamic mechanisms and characteristics of temporal and spatial changes,which helps to guide the prediction of water quality status of surface water ecosystem.展开更多
In the face of complicated, diversified three-dimensional world, the existing 3D GIS data models suffer from certain issues such as data incompatibility, insufficiency in data representation and representation types, ...In the face of complicated, diversified three-dimensional world, the existing 3D GIS data models suffer from certain issues such as data incompatibility, insufficiency in data representation and representation types, among others. It is often hard to meet the requirements of multiple application purposes(users) related to GIS spatial data management and data query and analysis, especially in the case of massive spatial objects. In this study, according to the habits of human thinking and recognition, discrete expressions(such as discrete curved surface(DCS), and discrete body(DB)) were integrated and two novel representation types(including function structure and mapping structure) were put forward. A flexible and extensible ubiquitous knowledgeable data representation model(UKRM) was then constructed, in which structurally heterogeneous multiple expressions(including boundary representation(B-rep), constructive solid geometry(CSG), functional/parameter representation, etc.) were normalized. GIS's ability in representing the massive, complicated and diversified 3D world was thus greatly enhanced. In addition, data reuse was realized, and the bridge linking static GIS to dynamic GIS was built up. Primary experimental results illustrated that UKRM was overwhelmingly superior to the current data models(e.g. IFC, City GML) in describing both regular and irregular spatial objects.展开更多
文摘Solid modeling with precise NURBS boundaries compliant with STEP standard represents the most promising way of designing complicated mechanical products in a CIM environment. In paral- lel to the traditional approach of putting together volumetric primitives with Boolean operations, an al- ternative way of applying the wireframe and skinning techniques is under development. The latter ap- proach is easy to implement, robust and capable of handling the most sophisticated models, while suf- fers the drawbacks of low efficiency in identifying interactively the boundaries of each surface patch when the line segments are interlaced and located close to each other. This paper describes the essentials of the wireframe and skinning techniques which produce the identical product information model as a solid modeler.
文摘Intersecting is an important factor which influences the effociency androbustness of Boolean algorithms in solid modeling based on surved-surfaces,andintersecting algorithms are closely related to geometric representations of curved-surfaces.Although surfaces can be commonly represented with NURBS,unnecessary complexitiesare caused in the intersecting of quadric surfaces.Quadrics are frequently used to des-cribe geometric features of shafts,holes and grooves etc.in mechanical part designing,therefore;their intersection algorithms are required to have higher accuracy,higher efficiency and higher robustness.For this reason,a practical representation ofquadric surfaces is studied in detail,and on the basis of that,algorithms of intersectingpoints are developed between quadric suraces and their boundaies,i.e.,conics,quarticnonplanar space curves.
文摘The principal assumptions about equivalence and energy distribution of the asdorption sites on solidsurfaces used by Langmuir for deriving the equation of monomolecular adsorption are generalized and anew physical adsorption model is proposed and tested with experimental data published in literature.Themodels of Langmuir,Freundlich,Temkin etc.are only the special cases.Assuming uniform density distributionof adsorption energy,the isotherm equation is given asn=K.1n[1+（bop）1/Mor n=K.1n[1+（boC）1/M]where n is the amount of adsorption per unit weight or area of solid p or C is tbe pressure of gas or the concen-tration of solution respectively.K,bo,M are constants with physical meanings as described in this paper.This equation can be used over wide range to quantitatively represent the five types of physical adsorptionclassified by Brunauer.
文摘In the previous work, an efficient method has been proposed to represent solid objects as multiple combinations of globally deformed supershapes. In this paper, this framework is applied with a new supershape implicit function that is based on the notion of radial distance and results are presented on realistic models composed of hundreds of hierarchically globally deformed supershapes. An implicit equation with guaranteed differential properties is obtained by simple combinations of the primitives~ implicit representations using R-function theory. The surface corresponding to the zero-set of the implicit equation is efficiently and directly polygonized using the primitives,parametric forms. Moreover, hierarchical global deformations are considered to increase the range of shapes that can be modeled. The potential of the approach is illustrated by representing complex models composed of several hundreds of primitives inspired from CAD models of mechanical parts.
文摘Applying new approaches, methods, and technologies for the estimation of reserves can effectively improve the efficiency and accuracy of assessments of solid mineral resources. After analyzing the development of 3-D geoscience modeling technology （3-D GMT）, this paper discusses the application of 3-D GMT for the estimation of solid mineral reserves, emphatically introducing its workflow and two key technologies, 3-D orebody surface modeling, and property modeling. Moreover, the paper analyzes the limitations of traditional methods, such as the section method and geological block method, and points out the advantages of 3-D GMT： building more accurate 3-D orebody models, expressing the internal inhomogeneous attributes of an orebody, reducing the potential for errors in the estimation of reserves, and implementing dynamic estimations of reserves.
文摘Plastic contamination is universal all through the marine condition,yet gauges of the worldwide plenitude and weight of coasting plastics have needed information,especially from the Southern Hemisphere and remote areas.Here we report a gauge of the all-out number of plastic particles and their weight gliding on the planet’s seas from 24 endeavours(2007-2013)over every one of the five subtropical gyres,coastal Australia,Bay of Bengal and the Mediterranean Sea directing surface net tows(N=680)and visual review transects of huge plastic flotsam and debris(N=891).Utilizing an oceanographic model of coasting trash dispersal adjusted by our information,and rectifying for wind-driven vertical blending,we gauge at least 5.25 trillion particles weighing 268,940 tons.When looking at between four size classes,two micro plastic<4.75 mm and meso and micro plastic>4.75 mm,a huge loss of micro plastics is seen from the ocean surface contrasted with anticipated paces of discontinuity,recommending there are systems at play that expel<4.75 mm plastic particles from the sea surface.The focus on the life cycle assessment and the brief overview of the plastic waste management over the ocean surfaces with the various mathematical models has been studied.The impact of the ocean pollution is also being analysed.
基金This project is supported by National Natural Science Foundation of China(No.50575144).
文摘A valid image-processing algorithm of weld pool surface reconstruction according to an input image of weld pool based on shape from shading （SFS） in computer vision is presented. The weld pool surface information is related to the backside weld width, which is crucial to the quality of weld joint. The image of weld pool is recorded with an optical sensing method. Firstly, the reflectance map model, which specifies the imaging process, is estimated. Then, the algorithm of weld pool surface reconstruction based on SFS is implemented by iteration scheme and speeded by hierarchical structure. The results indicate the accuracy and effectiveness of the approach.
文摘3D solid models for parts with regular-form surfaces (PRFSs) are effectively generated using traditional parametric design techniques. A new model is obtained by changing some parameters defining the model. The parts with free-form surfaces (PFFSs), however, cannot be defined by several parameters. Usually they are defined by some geometric elements like profile curves. The traditional parametric design approaches have not easily dealt with the PFFSs. A method for generating a solid model and an engineering drawing for PFFSs is proposed in this paper: First, the new profiles are generated from input point data. Second, the profile information is extracted from the existing model. Last, the old profiles are replaced with the new profiles. This method can preserve the associative information of the existing model and automatically generate the drawing including views, dimen- sions, and annotations. The proposed method has been implemented using a commercial CAD/CAM system, Unigraphics, and API functions written in C-language, and were applied to the blades of a turbine generator. Some illustrative examples are pro- vided in order to show the effectiveness of the proposed method.
基金Supported by National Water Science and Technology Research Project(No.2008ZX07102-001)
文摘Based on the maximum flux principle(MFP),a water quality evaluation model for surface water ecosystem is presented by using self-organization map(SOM) neural network simulation algorithm from the aspect of systematic structural evolution.This evaluation model is applied to the case of surface water ecosystem in Xindu District of Chengdu City in China.The values reflecting the water quality of five cross-sections of the system at different developing stages are obtained,with stable values of 1.438,2.952,1.869,2.443 and 2.479,respectively.The simulation also indicates that the larger the value,the more serious the water pollution.Furthermore,a classification graph is given to reflect the evolution of structural pattern.The combination of MFP and SOM neural network reveals the formation of different structural patterns in the system during the interaction of internal components.It is shown that a dominant pattern is finally reserved,which starts from a variety of combination patterns for a time period.The results agree with those from traditional evaluation methods,which indicates that the proposed model has high accuracy.This model embodies the evolutionary dynamic mechanisms and characteristics of temporal and spatial changes,which helps to guide the prediction of water quality status of surface water ecosystem.
基金supported by the National Natural Science Foundation of China(Grant No.41271196)the Key Project of the 12th Five-year Plan,Chinese Academy of Sciences(Grant No.KZZD-EW-07-02-003)
文摘In the face of complicated, diversified three-dimensional world, the existing 3D GIS data models suffer from certain issues such as data incompatibility, insufficiency in data representation and representation types, among others. It is often hard to meet the requirements of multiple application purposes(users) related to GIS spatial data management and data query and analysis, especially in the case of massive spatial objects. In this study, according to the habits of human thinking and recognition, discrete expressions(such as discrete curved surface(DCS), and discrete body(DB)) were integrated and two novel representation types(including function structure and mapping structure) were put forward. A flexible and extensible ubiquitous knowledgeable data representation model(UKRM) was then constructed, in which structurally heterogeneous multiple expressions(including boundary representation(B-rep), constructive solid geometry(CSG), functional/parameter representation, etc.) were normalized. GIS's ability in representing the massive, complicated and diversified 3D world was thus greatly enhanced. In addition, data reuse was realized, and the bridge linking static GIS to dynamic GIS was built up. Primary experimental results illustrated that UKRM was overwhelmingly superior to the current data models(e.g. IFC, City GML) in describing both regular and irregular spatial objects.
