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FRACTAL GEOMETRY DERIVED FROM GEOMETRIC INVERSION
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作者 张永平 谢和平 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1990年第11期1075-1079,共5页
In this paper, the conception of fractal geometry derived from geometric inversion is introduced. A ramified self-inverse fractal with symmetry and a self-inverse fractal dust set are constructed. The authors extend t... In this paper, the conception of fractal geometry derived from geometric inversion is introduced. A ramified self-inverse fractal with symmetry and a self-inverse fractal dust set are constructed. The authors extend the conception of the fractal osculation and propose a new notion-fractal envelope. Finally, two examples of self-inverse fractal (soap and egg) are given. 展开更多
关键词 geometric inversion self-inverse fractal fractal osculation fractal envelope
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Analysis of the Influencing Factors of Changes in Foxtail Millet Planting Area in Hebei Province 被引量:2
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作者 Meng LIU Yu ZHAO +3 位作者 Fei LIU Shunguo LI Guirong WANG Xinshi ZHANG 《Asian Agricultural Research》 2013年第3期30-34,共5页
Since reform and open to the outside world,foxtail millet planting area in Hebei Province has constantly reduced,and its planting region has changed from the whole province into some regions,with obvious changes. In t... Since reform and open to the outside world,foxtail millet planting area in Hebei Province has constantly reduced,and its planting region has changed from the whole province into some regions,with obvious changes. In this paper,by using qualitative and quantitative approaches like chart analysis,summarizing,Delphi method and osculating value model,the influencing factors of changes in millet growing region in Hebei Province were studied. The results showed that the changes of millet planting area were closely related to many factors,such as little investment in scientific research,weak policy support,a single consumer product demand,the rapid development of other staple crops, labor migration,relatively low comparative effectiveness and physiological characteristics of the millet itself. Then some suggestions were put forward,such as increasing research support,strengthening scientific research strength,researching and developing deeply processed products, expanding consumer groups,improving millet policy support,providing subsidies for planting the improved varieties,researching and developing various types of machinery,and increasing millet production technology training. 展开更多
关键词 MILLET area CHANGES Influencing FACTORS Osculating
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Method of Precision Control of 3-D Solid Discretization Based on the Second-Order Osculating Surface
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作者 万小利 刘淑艳 +1 位作者 杨梦辰 汪虹 《Journal of Beijing Institute of Technology》 EI CAS 2003年第2期183-185,共3页
A discretization precision control method based on the second order osculating surface is proposed. The discretization precision of 3 D solid is controlled according to the error between the discrete solid surface a... A discretization precision control method based on the second order osculating surface is proposed. The discretization precision of 3 D solid is controlled according to the error between the discrete solid surface and its second order osculating surface. The global maximal error has been gotten after analyzing all the extremums of the error function. It can be used in controlling and optimizing the discretization precision of 3 D solid in computer 3 D modeling and NC milling path generation. 展开更多
关键词 3-D solid DISCRETIZATION precision control osculating surface
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Short-Term Orbit Prediction with J<sub>2</sub>and Mean Orbital Elements
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作者 Shraddha Gupta M. Xavier James Raj R. K. Sharma 《International Journal of Astronomy and Astrophysics》 2011年第3期135-146,共12页
An analytical theory for calculating perturbations of the orbital elements of a satellite due to J2 to accuracy up to fourth power in eccentricity is developed. It is observed that there is significant improvement in ... An analytical theory for calculating perturbations of the orbital elements of a satellite due to J2 to accuracy up to fourth power in eccentricity is developed. It is observed that there is significant improvement in all the orbital elements with the present theory over second-order theory. The theory is used for computing the mean orbital elements, which are found to be more accurate than provided by Bhatnagar and taqvi’s theory (up to second power in eccentricity). Mean elements have a large number of practical applications. 展开更多
关键词 Perturbation DUE to J2 Mean ORBITAL ELEMENTS Short-Periodic Terms Osculating ORBITAL ELEMENTS Fourth Power in Eccentricit
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Mesh theory of angle modified dual tori double-enveloping toroidal worm drive 被引量:4
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作者 ZHAO YaPing1, SU DaiZhong2, ZHANG Zhao1, WEI WenJun3 & DONG XueZhu3 1 College of Machinery and Automation, Wuhan University of Science and Technology, Wuhan 430081, China 2 Advanced Design and Manufacturing Engineering Center, Nottingham Trent University, Nottingham NG1 4BU, UK 3 College of Engineering, China Agricultural University, Beijing 100083, China 《Science China(Technological Sciences)》 SCIE EI CAS 2010年第7期1913-1927,共15页
In this paper, the meshing theory of the angle modified hourglass worm drive is enriched and developed. The ordinary condition of the angle modification is derived and the physical significance of the modification is ... In this paper, the meshing theory of the angle modified hourglass worm drive is enriched and developed. The ordinary condition of the angle modification is derived and the physical significance of the modification is interpreted. A normal section methodology is proposed for meshing analysis, which can be used to compute the normal distance near a singular meshing point of a conjugate surface couple. By means of the method and after analyzing the normal transversals, it is specified that the worm helicoid, the nominal former contact zone and the new contact zone intersect each other along the locus of singular points of the instantaneous contact lines of an angle-modified worm pair. As a result, it is explained clearly that those three osculate each other but the osculations are different in degree. Moreover, the mechanism of removing the twice-contacted zone from the worm gear tooth surface is clarified and the reason of shortening the worm working length is also elucidated. With the help of the theory described in the present paper and the thorough and systematic research on the relevant meshing characteristics, the angle modified dual tori double-enveloping toroidal worm drive has been shown to be an excellent new-fashioned hourglass worm set. 展开更多
关键词 HOURGLASS WORM ANGLE modification double-enveloping osculation normal TRANSVERSAL
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Design concept of three-dimensional section controllable internal waverider hypersonic inlet 被引量:24
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作者 YOU YanCheng LIANG DeWang 《Science China(Technological Sciences)》 SCIE EI CAS 2009年第7期2017-2028,共12页
A new hypersonic inlet named three-dimensional section controllable internal waverider inlet is presented in this paper to achieve the goal of section shape geometric transition and complete capture of the upstream ma... A new hypersonic inlet named three-dimensional section controllable internal waverider inlet is presented in this paper to achieve the goal of section shape geometric transition and complete capture of the upstream mass. On the basis of the association between hypersonic waverider airframe and streamtraced hypersonic inlet, the waverider concept is extended to yield results for the internal flows, namely internal waverider concept. It is proven theoretically that not osculating cones but osculating axisymmetric theory is appropriate for the design of section controllable internal waverider inlet. And two design methods out of the internal waverider concept are proposed subsequently to construct two inlets with specific section shape request, triangle to ellipse and rectangle to ellipse ones. The calculation results show that the inlets are capable of keeping their shock structures and the main flow characteristics exactly as their derived flowfield. Further, the inlets successfully capture all the upstream mass despite their complicated cross-section transitions. It is believed that the concept proposed ex- plores a new way of designing three-dimensional hypersonic inlets with special demand of section shape transition. However, the detailed flow characteristic and the performance of the internal waverider inlets are still under investigation. 展开更多
关键词 SECTION CONTROLLABLE internal WAVERIDER HYPERSONIC INLET osculating flow all mass CAPTURE
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Design methodology of an osculating cone waverider with adjustable sweep and dihedral angles 被引量:1
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作者 Shao-hua CHEN Jun LIU +1 位作者 Wei HUANG Feng DING 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2020年第9期770-782,共13页
When considering the practical engineering application of a waverider,the on-design and off-design aerodynamic characteristics of the design conditions,especially the lift-to-drag ratio and the stability,deserve atten... When considering the practical engineering application of a waverider,the on-design and off-design aerodynamic characteristics of the design conditions,especially the lift-to-drag ratio and the stability,deserve attention.According to recently studies,the planform and rear sight shape of a waverider are closely related to the above aerodynamic performance.Thus,the planform leading-edge profile curve used to design the planform shape of a vehicle is applied to designing an osculating cone waverider.Two key parameters concerned in planform and rear sight shape,namely the plan view sweep angle of the leading edge and the dihedral angle of the underside are introduced to the waverider design process.Each parameter is inserted in the control curve equation.Especially,a parameterization scheme is put forward for the free adjustment of the sweep angle along the leading edge.Finally,three examples are generated for verification and investigation.After the verification process based on the inviscid flow field of one case,the influences of the sweep and dihedral angles on the lift-to-drag ratio and the lateral static stability are evaluated,and meaningful results are obtained.Based on these results,we can conclude that,considering the maximum lift-to-drag ratio,the sweep angle plays a role on the lift-to-drag ratio only at subsonic and trans/supersonic speed as a negligible effect is observed at hypersonic speeds,whereas the dihedral angle is seem to produce a relevant difference at hypersonic speeds.Considering the lateral static stability,the dihedral angles have more influence on the waverider than the sweep angles. 展开更多
关键词 Osculating cone waverider Planform leading-edge profile curve Sweep and dihedral angles Lift-to-drag ratio Lateral static stability
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