Creating proper B-spline surface models is a very challenging task for designers in car-body surface design.Due to the tensor-product structure of B-spline surface,some undesirable issues of the redundant control poin...Creating proper B-spline surface models is a very challenging task for designers in car-body surface design.Due to the tensor-product structure of B-spline surface,some undesirable issues of the redundant control points addition,incomplete surface definition and the difficulty of trimming boundary alteration frequently occur,when designing the car-body surface with B-spline surfaces in local-feature-lines construction,full-boundary-merging and visual surface trimming.A more efficient approach is proposed to design the car-body surface by replacing B-spline surface with classical T-spline surface.With the local refinability and multilateral definition offered by Tspline surface,those designing issues related with B-spline surface can be overcomed.Finally,modeling examples of the door,hood and rear-window are given to demonstrate the advantage of T-spline surface over B-spline surface in car-body surface design.展开更多
Smoothly stitching multiple surfaces mainly represented by B-spline or NURBS together is an extremely important issue in complex surfaces modeling and reverse engineering. In recent years, a lot of progress has been m...Smoothly stitching multiple surfaces mainly represented by B-spline or NURBS together is an extremely important issue in complex surfaces modeling and reverse engineering. In recent years, a lot of progress has been made in smooth join of non-trimmed surface patches, while there has been seldom research on smoothly stitching trimmed surface patches together. This paper studies the problem of global continuity adjustment, damaged hole repair and local shape optimization for complex trimmed surface model, and presents a uniform scheme to deal with continuity adjustment of trimmed surfaces and geometric repair of local broken region. Constrained B-spline surface refitting technique and trim calculation are first utilized to achieve global G^1 continuity, and then local shape optimization functional is adopted to reduce fitting error and improve local quality of refitted surface patch. The proposed approach is applied to a discontinuity ship hull surface model with an irregular hole, and the result demonstrates the validation of our method. Furthermore, on the premise of global continuity, the proposed locally repairing damaged surface model provides a better foundation for following research work, such as topology recovery technique for complex surface model after geometric repair.展开更多
An exact-designed mesh shape with favorable surface accuracy is of practical significance to the performance of large cable-network antenna reflectors. In this study, a novel design approach that could guide the gener...An exact-designed mesh shape with favorable surface accuracy is of practical significance to the performance of large cable-network antenna reflectors. In this study, a novel design approach that could guide the generation of exact spatial parabolic mesh configurations of such reflector was proposed. By incorporating the traditional force density method with the standard finite element method, this proposed approach had taken the deformation effects of flexible ring truss supports into consideration, and searched for the desired mesh shapes that can satisfy the requirement that all the free nodes are exactly located on the objective paraboloid. Compared with the conventional design method,a remarkable improvement of surface accuracy in the obtained mesh shapes had been demonstrated by numerical examples. The present work would provide a helpful technical reference for the mesh shape design of such cable-network antenna reflector in engineering practice.展开更多
Large-deflection flexure pivot is widely used in high precision rotation application, but there are less flexure configurations and simple and convenient design methods, This paper presents a novel large-deflection cu...Large-deflection flexure pivot is widely used in high precision rotation application, but there are less flexure configurations and simple and convenient design methods, This paper presents a novel large-deflection curved-compliant annulus-shaped flexure pivot composed of six curved beam flexure elements. It can offer more than lO^angular stroke theoretically. Firstly, main-motion pseudo-rigid-body method is introduced to establish the flexure pivot model. Although pseudo-rigid-body method can be used to analyze the large-deformation flexure pivot performance, the method is definitely a laborious and difficult task for designing this novel flexure pivot. In order to simply the designing process, dimension-design graphs based on the parametric models and finite element analysis is presented. Using the dimension-design method as a tool, the designers can determine the optimal geometry rapidly, based on the stiffness and rotation demands of an annulus-shaped flexure pivot. Finally, dimension-design graph examples are given whose primary design aims to achieve a rotation stroke of annulus-shaped flexure pivot. The finite element analysis results show that the relative designing error between anticipative rotation stroke and graph design result is less than 4%. The dimensionless method used in designing annulus-shaped flexure pivot can reduce design process in both time and complexity. The novel annulus-shaped flexure pivot and dimension-design method are helpful supplement to configuration and design method of large-deflection flexure pivot.展开更多
In this paper,size and shape optimization problem of a machine gun system is addressed with an efficient hybrid method,in which a novel and flexible mesh morphing technique is employed to achieve fast parameterization...In this paper,size and shape optimization problem of a machine gun system is addressed with an efficient hybrid method,in which a novel and flexible mesh morphing technique is employed to achieve fast parameterization and modification of complexity structure without going back to CAD for reconstruction of geometric models or to finite element analysis（ FEA） for remodeling. Design of experiments（ DOE） and response surface method（ RSM） are applied to approximate the constitutive parameters of a machine gun system based on experimental tests. Further FEA,secondary development technique and genetic algorithm（ GA） are introduced to find all the optimal solutions in one go and the optimal design of the demonstrated machine gun system is obtained. Results of the rigid-flexible coupling dynamic analysis and exterior ballistics calculation validate the proposed methodology,which is relatively time-saving,reliable and has the potential to solve similar problems.展开更多
Body mass, volume and surface area are important for many aspects of the physiology and performance of species. Whereas body mass scaling received a lot of attention in the literature, surface areas of animals have no...Body mass, volume and surface area are important for many aspects of the physiology and performance of species. Whereas body mass scaling received a lot of attention in the literature, surface areas of animals have not been measured explicitly in this context. We quantified surface area-volume （SA/V） ratios for the first time using 3D surface models based on a structured light scanning method for 126 species of pollinating insects from 4 orders （Diptera, Hymenoptera, Lepidoptera, and Coleoptera）. Water loss of 67 species was measured gravimetrically at very dry conditions for 2 h at 15 and 30 ℃ to demonstrate the applicability of the new 3D surface measurements and relevance for predicting the performance of insects. Quantified SA/V ratios significantly explained the variation in water loss across species, both directly or after accounting for isometric scaling （residuals of the SA/V - mass2/3 relationship）. Small insects with a proportionally larger surface area had the highest water loss rates. Surface scans of insects to quantify allometric SA/Vratios thus provide a promising method to predict physiological responses, improving the potential of body mass isometry alone that assume geometric similarity.展开更多
Aiming at optimizing the head shape of the CRH3 high speed train, an efficient optimization approach is proposed. The CFD analysis by solving Navier-Stokes equations is coupled with optimization calculation based on t...Aiming at optimizing the head shape of the CRH3 high speed train, an efficient optimization approach is proposed. The CFD analysis by solving Navier-Stokes equations is coupled with optimization calculation based on the multi-objective genetic algorithm, meanwhile the arbitrary shape deformation technique (ASD) is also introduced into the design flow, which greatly shortens the time consumption for geometry regeneration and flow field remeshing. As a result, the efficiency of the optimization calculation is highly improved. Statistical analysis is done to the designs in the design space, and the correlation between the design variables and the objective is studied to find out the key variables that most affect the objective. Response surface analysis is also performed to get the nonlinear relationship between the key design variables and the objective with the Kriging algorithm. Finally, after the optimization, an aerodynamic performance comparison between the optimal shape and the original shape reveals that the original shape of CRH3 high speed train owns a very stable aerodynamic performance and can be trustingly used in industry.展开更多
The study investigates women＇s perception of the workwear, and their awareness about how garment fit can affect one＇s body image. Drawing on the theory of practice, we propose an ethnographic account of women＇s per...The study investigates women＇s perception of the workwear, and their awareness about how garment fit can affect one＇s body image. Drawing on the theory of practice, we propose an ethnographic account of women＇s perception of workwear and their preferred alternative. The study presents a comparative perspective of attitudes, and perceptions about the workwear of women in South Africa and Uganda explored through the habitus. We present pro-vocal recollections of women perceptions on the current workwear ideal for men which omits women＇ body physique. In particular, from the current personal protective equipment （PPE）, we examine ＂the overall＂ common attire at site and an integral part of the PPE. Overalls are designed following the men＇s physique, and women in work place are subjected to put them on yet, differences in body structure/shapes amongst women, namely, hour glass, bottom hourglass, spoon, and pear shape, are hardly considered. The identification of different female body shapes is made possible through the 3D anthropometric measurements using a Three Dimensional （3D） Body Scanner （TC2）. We develop endogenous explanations of what women would want to see as workwear based on the understanding of women found on site in men＇s workwear or without any work weal- in South Africa and Uganda. Using ethnographic design approach, we capture voices of 10 women from South Africa and Uganda through participant observation and unstructured interviews. We analyze data thematically to determine the patterns of their responses toward an appropriate workwear. Moreover, we （re）construct these responses into possible design models that would be ideal workwear for women, which gives them the pride, respect, dignity, and confidence as women.展开更多
文摘Creating proper B-spline surface models is a very challenging task for designers in car-body surface design.Due to the tensor-product structure of B-spline surface,some undesirable issues of the redundant control points addition,incomplete surface definition and the difficulty of trimming boundary alteration frequently occur,when designing the car-body surface with B-spline surfaces in local-feature-lines construction,full-boundary-merging and visual surface trimming.A more efficient approach is proposed to design the car-body surface by replacing B-spline surface with classical T-spline surface.With the local refinability and multilateral definition offered by Tspline surface,those designing issues related with B-spline surface can be overcomed.Finally,modeling examples of the door,hood and rear-window are given to demonstrate the advantage of T-spline surface over B-spline surface in car-body surface design.
基金supported by National Natural Science Foundation of China (Grant No.50575098)
文摘Smoothly stitching multiple surfaces mainly represented by B-spline or NURBS together is an extremely important issue in complex surfaces modeling and reverse engineering. In recent years, a lot of progress has been made in smooth join of non-trimmed surface patches, while there has been seldom research on smoothly stitching trimmed surface patches together. This paper studies the problem of global continuity adjustment, damaged hole repair and local shape optimization for complex trimmed surface model, and presents a uniform scheme to deal with continuity adjustment of trimmed surfaces and geometric repair of local broken region. Constrained B-spline surface refitting technique and trim calculation are first utilized to achieve global G^1 continuity, and then local shape optimization functional is adopted to reduce fitting error and improve local quality of refitted surface patch. The proposed approach is applied to a discontinuity ship hull surface model with an irregular hole, and the result demonstrates the validation of our method. Furthermore, on the premise of global continuity, the proposed locally repairing damaged surface model provides a better foundation for following research work, such as topology recovery technique for complex surface model after geometric repair.
文摘An exact-designed mesh shape with favorable surface accuracy is of practical significance to the performance of large cable-network antenna reflectors. In this study, a novel design approach that could guide the generation of exact spatial parabolic mesh configurations of such reflector was proposed. By incorporating the traditional force density method with the standard finite element method, this proposed approach had taken the deformation effects of flexible ring truss supports into consideration, and searched for the desired mesh shapes that can satisfy the requirement that all the free nodes are exactly located on the objective paraboloid. Compared with the conventional design method,a remarkable improvement of surface accuracy in the obtained mesh shapes had been demonstrated by numerical examples. The present work would provide a helpful technical reference for the mesh shape design of such cable-network antenna reflector in engineering practice.
基金supported by National Natural Science Foundation of China(Grant No. 50675007)Program for New Century Excellent Talents in University of China (Grant No. NCET-06-0165)
文摘Large-deflection flexure pivot is widely used in high precision rotation application, but there are less flexure configurations and simple and convenient design methods, This paper presents a novel large-deflection curved-compliant annulus-shaped flexure pivot composed of six curved beam flexure elements. It can offer more than lO^angular stroke theoretically. Firstly, main-motion pseudo-rigid-body method is introduced to establish the flexure pivot model. Although pseudo-rigid-body method can be used to analyze the large-deformation flexure pivot performance, the method is definitely a laborious and difficult task for designing this novel flexure pivot. In order to simply the designing process, dimension-design graphs based on the parametric models and finite element analysis is presented. Using the dimension-design method as a tool, the designers can determine the optimal geometry rapidly, based on the stiffness and rotation demands of an annulus-shaped flexure pivot. Finally, dimension-design graph examples are given whose primary design aims to achieve a rotation stroke of annulus-shaped flexure pivot. The finite element analysis results show that the relative designing error between anticipative rotation stroke and graph design result is less than 4%. The dimensionless method used in designing annulus-shaped flexure pivot can reduce design process in both time and complexity. The novel annulus-shaped flexure pivot and dimension-design method are helpful supplement to configuration and design method of large-deflection flexure pivot.
基金Supported by the National Natural Science Foundation of China(51376090,51676099)
文摘In this paper,size and shape optimization problem of a machine gun system is addressed with an efficient hybrid method,in which a novel and flexible mesh morphing technique is employed to achieve fast parameterization and modification of complexity structure without going back to CAD for reconstruction of geometric models or to finite element analysis（ FEA） for remodeling. Design of experiments（ DOE） and response surface method（ RSM） are applied to approximate the constitutive parameters of a machine gun system based on experimental tests. Further FEA,secondary development technique and genetic algorithm（ GA） are introduced to find all the optimal solutions in one go and the optimal design of the demonstrated machine gun system is obtained. Results of the rigid-flexible coupling dynamic analysis and exterior ballistics calculation validate the proposed methodology,which is relatively time-saving,reliable and has the potential to solve similar problems.
文摘Body mass, volume and surface area are important for many aspects of the physiology and performance of species. Whereas body mass scaling received a lot of attention in the literature, surface areas of animals have not been measured explicitly in this context. We quantified surface area-volume （SA/V） ratios for the first time using 3D surface models based on a structured light scanning method for 126 species of pollinating insects from 4 orders （Diptera, Hymenoptera, Lepidoptera, and Coleoptera）. Water loss of 67 species was measured gravimetrically at very dry conditions for 2 h at 15 and 30 ℃ to demonstrate the applicability of the new 3D surface measurements and relevance for predicting the performance of insects. Quantified SA/V ratios significantly explained the variation in water loss across species, both directly or after accounting for isometric scaling （residuals of the SA/V - mass2/3 relationship）. Small insects with a proportionally larger surface area had the highest water loss rates. Surface scans of insects to quantify allometric SA/Vratios thus provide a promising method to predict physiological responses, improving the potential of body mass isometry alone that assume geometric similarity.
文摘Aiming at optimizing the head shape of the CRH3 high speed train, an efficient optimization approach is proposed. The CFD analysis by solving Navier-Stokes equations is coupled with optimization calculation based on the multi-objective genetic algorithm, meanwhile the arbitrary shape deformation technique (ASD) is also introduced into the design flow, which greatly shortens the time consumption for geometry regeneration and flow field remeshing. As a result, the efficiency of the optimization calculation is highly improved. Statistical analysis is done to the designs in the design space, and the correlation between the design variables and the objective is studied to find out the key variables that most affect the objective. Response surface analysis is also performed to get the nonlinear relationship between the key design variables and the objective with the Kriging algorithm. Finally, after the optimization, an aerodynamic performance comparison between the optimal shape and the original shape reveals that the original shape of CRH3 high speed train owns a very stable aerodynamic performance and can be trustingly used in industry.
文摘The study investigates women＇s perception of the workwear, and their awareness about how garment fit can affect one＇s body image. Drawing on the theory of practice, we propose an ethnographic account of women＇s perception of workwear and their preferred alternative. The study presents a comparative perspective of attitudes, and perceptions about the workwear of women in South Africa and Uganda explored through the habitus. We present pro-vocal recollections of women perceptions on the current workwear ideal for men which omits women＇ body physique. In particular, from the current personal protective equipment （PPE）, we examine ＂the overall＂ common attire at site and an integral part of the PPE. Overalls are designed following the men＇s physique, and women in work place are subjected to put them on yet, differences in body structure/shapes amongst women, namely, hour glass, bottom hourglass, spoon, and pear shape, are hardly considered. The identification of different female body shapes is made possible through the 3D anthropometric measurements using a Three Dimensional （3D） Body Scanner （TC2）. We develop endogenous explanations of what women would want to see as workwear based on the understanding of women found on site in men＇s workwear or without any work weal- in South Africa and Uganda. Using ethnographic design approach, we capture voices of 10 women from South Africa and Uganda through participant observation and unstructured interviews. We analyze data thematically to determine the patterns of their responses toward an appropriate workwear. Moreover, we （re）construct these responses into possible design models that would be ideal workwear for women, which gives them the pride, respect, dignity, and confidence as women.
