Traditional MEMS （microelectromechanical system） design methodology is not a structured method and has become an obstacle for MEMS creative design. In this paper, a novel method of mask synthesis and verification fo...Traditional MEMS （microelectromechanical system） design methodology is not a structured method and has become an obstacle for MEMS creative design. In this paper, a novel method of mask synthesis and verification for surface micro-machined MEMS is proposed, which is based on the geometric model of a MEMS device. The emphasis is focused on synthesizing the masks at the basis of the layer model generated from the geometric model of the MEMS device. The method is comprised of several steps： the correction of the layer model, the generation of initial masks and final masks including multi-layer etch masks, and mask simulation. Finally some test resuhs are given.展开更多
The problem of computing a piecewise linear approximation to a surface from its sample has been a focus of research in geometry modeling and graphics due to its widespread applications in computer aided design. In thi...The problem of computing a piecewise linear approximation to a surface from its sample has been a focus of research in geometry modeling and graphics due to its widespread applications in computer aided design. In this paper, we give a new algorithm, to be called offset surface filtering (OSF) algorithm, which computes a piecewise-linear approximation of a smooth surface from a finite set of cloud points. The algorithm has two main stages. First, the surface normal on every point is estimated by the least squares best fitting plane method. Second, we construct a restricted Delaunay triangulation, which is a tubular neighborhood of the surface defined by two offset surfaces. The algorithm is simple and robust. We describe an implementation of it and show example outputs.展开更多
Numerical computation of the flowfield inside a pump is herein used as a numerical laboratory, subject to the limitations of modeling assumptions and to experimental verification. A numerical computation of the flow i...Numerical computation of the flowfield inside a pump is herein used as a numerical laboratory, subject to the limitations of modeling assumptions and to experimental verification. A numerical computation of the flow inside a real industrial centrifugal pump is performed that includes a very sophisticated geometry. Conversely to other computations, in this test case no simplification of the geometry was introduced. Numerical computations are obtained using Spalart-Allmaras turbulence model. A detailed analysis of the turbulent flowstructure is performed for the design point and two off design conditions. Additional computations were performed in order to compare the numerical and experimental pump characteristics; these were obtained under normalized testing conditions. Further computations are presented for the pump working in reverse turbine mode (PAT). Detailed analyses of the flow allow a comparison of the internal flow losses when the pump is operating in direct and reverse mode. This is also useful to help in the selection of an adequate pump geometry that can work in both modes with best efficiency.展开更多
Tooth profile shift will change the thickness of gear teeth and a part of geometrical parameters of a gear pair, thus influencing its mesh stiffness and consequently the dynamic performances. In this paper, an analyti...Tooth profile shift will change the thickness of gear teeth and a part of geometrical parameters of a gear pair, thus influencing its mesh stiffness and consequently the dynamic performances. In this paper, an analytical mesh stiffness calculation model for an internal gear pair in mesh considering the tooth profile shift is developed based on the potential energy principle. Geometrical representations of the tooth profile shift are firstly derived, and then fitted into the analytical tooth stiffness model of gears. This model could supply a convenient way for mesh stiffness calculation of profile shifted spur gears. Then, simulation studies are conducted based on the developed model to demonstrate the effects of tooth profile shift coefficient on the tooth compliances and the mesh stiffness of the internal spur gear pair. The results show that tooth profile shift has an obvious influence on the mean value, amplitude variation and phase of the mesh stiffness, from which it can be predicted that the dynamic response of an internal gear transmission system will be affected by the tooth profile shift.展开更多
基金Project supported by the National Natural Science Foundation of China (Nos. 60273057 and 60403049) and the National Basic Re-search Program (973) of China (No. 2002CB312106)
文摘Traditional MEMS （microelectromechanical system） design methodology is not a structured method and has become an obstacle for MEMS creative design. In this paper, a novel method of mask synthesis and verification for surface micro-machined MEMS is proposed, which is based on the geometric model of a MEMS device. The emphasis is focused on synthesizing the masks at the basis of the layer model generated from the geometric model of the MEMS device. The method is comprised of several steps： the correction of the layer model, the generation of initial masks and final masks including multi-layer etch masks, and mask simulation. Finally some test resuhs are given.
基金Project supported by the National Natural Science Foundation of China (No. 10371110) and the National Basic Research Program (973) of China (No. 2004CB318000)
文摘The problem of computing a piecewise linear approximation to a surface from its sample has been a focus of research in geometry modeling and graphics due to its widespread applications in computer aided design. In this paper, we give a new algorithm, to be called offset surface filtering (OSF) algorithm, which computes a piecewise-linear approximation of a smooth surface from a finite set of cloud points. The algorithm has two main stages. First, the surface normal on every point is estimated by the least squares best fitting plane method. Second, we construct a restricted Delaunay triangulation, which is a tubular neighborhood of the surface defined by two offset surfaces. The algorithm is simple and robust. We describe an implementation of it and show example outputs.
基金supported by CAST-Center for Aerospace Sciences and Technology at University of Beira Interior (Portugal)
文摘Numerical computation of the flowfield inside a pump is herein used as a numerical laboratory, subject to the limitations of modeling assumptions and to experimental verification. A numerical computation of the flow inside a real industrial centrifugal pump is performed that includes a very sophisticated geometry. Conversely to other computations, in this test case no simplification of the geometry was introduced. Numerical computations are obtained using Spalart-Allmaras turbulence model. A detailed analysis of the turbulent flowstructure is performed for the design point and two off design conditions. Additional computations were performed in order to compare the numerical and experimental pump characteristics; these were obtained under normalized testing conditions. Further computations are presented for the pump working in reverse turbine mode (PAT). Detailed analyses of the flow allow a comparison of the internal flow losses when the pump is operating in direct and reverse mode. This is also useful to help in the selection of an adequate pump geometry that can work in both modes with best efficiency.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51405400 & 51375403)the Fundamental Research Funds for the Central Universities (Grant Nos. 2682015ZD12 & 2682016CX125)the Fundamental Research Funds for State Key Laboratory of Traction Power (Grant Nos. 2015TPL_T14 & 2014TPL_T10)
文摘Tooth profile shift will change the thickness of gear teeth and a part of geometrical parameters of a gear pair, thus influencing its mesh stiffness and consequently the dynamic performances. In this paper, an analytical mesh stiffness calculation model for an internal gear pair in mesh considering the tooth profile shift is developed based on the potential energy principle. Geometrical representations of the tooth profile shift are firstly derived, and then fitted into the analytical tooth stiffness model of gears. This model could supply a convenient way for mesh stiffness calculation of profile shifted spur gears. Then, simulation studies are conducted based on the developed model to demonstrate the effects of tooth profile shift coefficient on the tooth compliances and the mesh stiffness of the internal spur gear pair. The results show that tooth profile shift has an obvious influence on the mean value, amplitude variation and phase of the mesh stiffness, from which it can be predicted that the dynamic response of an internal gear transmission system will be affected by the tooth profile shift.
