共查询到20条相似文献，搜索用时 15 毫秒
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On the base of the fairing of free-form surface reconstruction from 3D data points, this paper probes one method based on shape constraints. By making physical model as objective function and using geometric constraints, free form surface reconstruction is realized based on the idea of energy optimization. This method is not only beneficial to the connection of the reconstruction surface and CAD/CAM system, but also to the integration of design, manufacturing and inspection. 相似文献
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讨论了设计素质对于食品工程专业人才的重要性及目前培养模式中存在的问题,并通过课程设置、师资建设、课堂教学方法、引导设计理念及实践教学等方面,探索了有效提高食品专业人才的设计素养。 相似文献
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Physics based modeling is one of the keen free form surface modeling method at present, and it should be a practical surface modeling method in the future. In Physics based modeling, the object is viewed as a physics and not a pure geometry model. According to its physics principle and math representation, the physics based models are mainly classified into two types:energy model and dynamic Lagrangian model. The fundamental theory is introduced, and the principle, development and application state of each model is reviewed. To provide designer more naturally design ability and to introduce more flexible geometric modeling methods are the prospect of future researches on physics based free form surface modeling is outlined at last. 相似文献
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To deal with the contradiction between accuracy and time consuming, a model of reliability analysis of CFT was proposed based on the response surface and nonlinear finite element method, And Initial geometric imperfection was induced by consistent mode imperfection method.The reliability index and sensitivity coefficients of CFT high piers were invested by the proposed model.The effects of slenderness, eccentricity and diameter thickness ratio on reliability index of concrete filled tube high piers were studied by parameter analysis method.Meanwhile, the influence of geometric nonlinearity was also analyzed and the reliability of CFT high pier could be affected by factors mentioned above.Based on the analysis, several suggestions for improving the reliability of CFT high piers were proposed. 相似文献
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基于标记控制分水岭算法的树冠高程模型分割 总被引：1，自引：1，他引：0
树冠高程模型是树冠表面模型和数字高层模型的差值,是森林资源调查的重要数据源。笔者提出利用标记控制分水岭算法进行树冠高程模型分割的方法,首先用高斯滤波平滑树冠高程模型,对树冠边缘做初步检测,然后利用形态学重构方法进行树冠形状确认,在此基础上进行二值图像的距离变换和h-minima变换,并标记树冠顶部,最后对实验数据进行分水岭分割,实现单株木树冠边缘勾勒。误差分析表明,该方法能有效提高分割正确率,当结构元素和h-minima变换中的参数分别等于3、1.5时,树冠分割正确率为78.5%。 相似文献
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Several mathematic methods used in the numerical control system of profile followed grinding robot are described. Cubic parametric Spline surface function is employed to fit the geometric model of the surface grinded with high precision. Improvement of the physics performance of blade is obtained by reconstructing the large size surface of turbine blade based on calculation geometry. Graphic linear transfer technique is provided to users with unique format of programming. Graphic non linear transfer technique is used to solve some more difficult problems successfully including transformation of the coordinates of comtrolled points in multicoordinates system, adjustment of the attitude of grinding head as well as realization of constant pressure grinding. All these mathematics methods are demonstrated feasible and efficient in actual practice and are valuable in developing large size surface grinding robots. 相似文献
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为探索车身非光滑表面特征参数的优化设计方法,在MIRA阶梯背模型尾部分别布置凹坑型、凸包型和沟槽型非光滑表面,进行计算仿真和风洞模型试验对比分析不同非光滑单元的减阻效果。以非光滑单元体间距与高度为设计变量,以模型气动阻力系数为优化目标,采用拉丁超抽样方法进行样本设计,建立Kringing近似模型并检验拟合精度,运用NSGA-II遗传优化算法分别对凹坑型、凸包型和沟槽型非光滑表面特征参数进行优化。对比优化前后流场参数,分析车身非光滑表面减阻的机理。仿真结果和风洞试验数据表明优化后的凹坑、凸包及沟槽型非光滑表面模型的气动阻力均进一步减小,减阻率分别达到6.92%、4.03%、4.24%,减阻效果明显。说明文中所采用的优化设计方法具有一定的有效性和通用性,为车身非光滑表面特征参数优化的后续设计提供参考依据。 相似文献
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The marching cubes (MC) is an effective surface rendering method in three-dimensional visualization for medical image sequence. However, most existing MC algorithms are slow and inefficient because they have to process all the cubes for isosurface extraction. An efficient MC algorithm is proposed by combing the case lookup table and a novel adjacent lookup sub-table to exclude unrelated empty cubes. By explicitly building the fix-length adjacent lookup sub-table that is independent on image sequences, the volumes elements are constrained to those only intersect with the isosurface. Both execution time and temporary storage space are further reduced by incorporating the heap data structure in algorithmic implementation. Experimental results on human head, chest foot CT data sets by using the visualization toolkit package show that the traversal cubes decreases by 95%, and the reconstruction time decreases by 20% without any loss of reconstruction quality. Therefore, the proposed method can remarkably speed up the rendering time and be easily integrated into 3D visualization for clinical application. 相似文献
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Based on a project of pipe truss roof framing in Chengdu, the ultimate limit state analysis is performed on cast steel joints by using FEM, in which Linear hardening elastic-plastic constitutive model is considered. The results show that, the joint has a great accumulation of plastic strain in ultimate loads, and the point of maximum stress is different from that in elastic with the development of the yielding zone. The paper propoes to use rate-type tensor for the large strain geometric nonlinear problem, shows the criterion of failure formation , and indicates that its essential to apply limit state analysis to the determination of the weakest location on cast steel joint design, which provides basis for understanding the failure modes and failure mechanism of cast steel joint and the cast steel joint design. 相似文献
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Geometry of port-combustion chamber has an important effect on the performance of gasoline engines. Methods and approaches in reverse engineering are introduced into surface reconstruction and modification of a port-combustion chamber structure. Free-form surfaces of the port-combustion chamber structure for a gasoline engine with 4-valves and dual-ball type combustion chamber are successfully reconstructed in the reverse way through data processing, surface modeling, surface verifying, surface re-modeling and smooth evaluating etc., based on laser-scanned point cloud data of a sample work piece. It lays a foundation for imitation innovation of gasoline engine by changing the local structural characteristics and dimensions of a prototype model. 相似文献
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Experimental investigation of electrothermal defrost tubes’ arrangement on heat transfer and flow resistance characteristics of evaporator 
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下载免费PDF全文 The paper presents new arrangement types of electrothermal defrost tubes and manufactures four evaporator samples. Through a wind tunnel refrigeration experimental test-bed, relatively experiments for every sample are carried to study heat transfer and flow resistances characteristics of evaporator. The experiment results show that in experimental face velocity range from 1.5 m/s to 4.3 m/s compared with flat-fin evaporator, the unit area of cooling capacity of DK-8 evaporator increased 28.1% to 36.2%, the fin surface coefficient of heat transfer raises 79.2% to 83.5%, the compressor COP (Coefficient of Performance) improves 38.2% to 46.9%, and the air side flow resistance decreases 5.29% to 18.3% in the same experimental condition and geometric size. The increase amplitude of COP is obviously higher than air side flow resistance. The experimental investigation results prove that it is completely feasible optimized combing defrost design with heat transfer enhancement design. 相似文献
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A new image reconstruction algorithm is presented, based on orthogonal wavelets derived from symmetric scale functions. The analysis and practice show that the method lessens greatly the computational time,and improves the reconstruction quality. 相似文献
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Analysis of the mapping and transferring mechanism, and the sensitivity of quality characteristics of Complicated Electromechanical Products (CEP) reveal that the coupling of functionality and structure, and uncertainty in their mapping relations are important factors that influence the quality of CEP. By integrating the principals of Axiomatic Design (AD), this paper proposes a concept of decoupling design for quality characteristics of CEP. A model for decoupling control in the mapping processes of CEP is presented. In the model, formation-process of quality characteristics of CEP is transformed into iterative zigzagging decomposition and mapping between functional-domains. Then mapping matrixes are utilized to facilitate product designers to identify coupled quality characteristics in CEP, and to reduce complexity in function and physical structure and the product development. The model presented is used in the design of the transmission system in the first direct-drive hobbing machine in China, which effectively reduces the complexity of transmission system of hobbing machine and improved gear hobbing accuracy. 相似文献
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In order to improve the error in image reconstruction caused by changeable positions of the electrodes in closed electrical impedance tomography, we propose an open electrical impedance tomography (OEIT) model using fixed electrode array. The problem was approximately assumed to be a virtual field by defining certain local sensitive area instead of solving the boundary problem in the whole electromagnetic field strictly. Modeling and simulation of OEIT have been conducted to define reasonable boundary parameters and electrode array structure. The finite element method is used for forward computation while Newton one step error reconstructor is used for image reconstruction. The target position, area and conductivity change can be reflected by the relative change of the boundary voltage and the reconstructed image is clear. Better resolution and positioning accuracy can be obtained in the shallower surface of the body by OEIT, so it is valuable in clinical applications. 相似文献
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It is proposed to introduce approximate model method to crashworthiness optimization design of thin wall beam,and the approximate model can be optimized by using sequential response surface method.In order to solve the parameterization design problem of finite element model,a parameterization model about material,cross section size and spotweld of thin wall beam is established by developing corresponding procedures.The results show that optimization design can not only improve the performance of absorbing energy of thin wall beam,but also reduce the weight greatly;the approximate model method can greatly improve optimization efficiency. 相似文献
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LIN Yuan-hua~ 《保鲜与加工》2004,(2):24
Based on the research on the motion law of the drilling fluid along the blade, the necessary condition of the blade shape for a high efficiency turbodrill is obtained. Hence a mathematical model how to design a blade shape has been put forward, and the solution method of the model is obtained, which helps to design a high efficiency turbodrill. What's more, a 3 dimension model of the blade has been set up using Pro/E software, which can link with the advanced computer language by a interface routine and modify the 3-D blade model automatically. Based on the theory, a software has been compiled to design the blade automatically, which can improve the design efficiency and the design quality of the turbodrill. 相似文献
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Belt grinding machine with multi axis computer number control(CNC) system can effectively process parts with complex moulding surfaces.In this paper,iso parametric and iso planar tool path planning strategies customized for this kind of machine are proposed.The tool path generation methods are designed based on the analysis of the belt grinding process.By using least square method,optimized cross section normal is computed in the iso planar method.To improve the design efficiency of path planning,reduce experiments and increase economical benefit,the geometric simulation program based on linear grinding model is developed.Experiment on a turbine blade profile shows that the proposed algorithms work satisfyingly. 相似文献
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Based on the current development of industrial building reconstruction with function of manufacturing facilities, in this paper, the authors emphasize the importance of this kind of reconstruction, explore the detailed reconstruction means and analyze the relevant comprehensive affecting elements, at the end, the relevant general design principles are put forward. 相似文献