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21.
This paper presents an orientation-based representation for planar curves and shapes. The new representation can uniquely represent all types, of planar shapes, be it convex, nonconvex, polygonal, smoothly curved, or piecewise smooth shapes. It is based on a new parameterization, theabsolute integral orientation. This representation is invariant under translation and rotation. The absolute integral orientation is a parameter invariant under scaling. As a result, matching of similar shapes (i.e., determination of the relative orientation and the scaling factor) using the absolute integral orientation as the parameter is easier than using the arclength as the parameter. In addition, the new representation has the feature of adaptive sampling, making it more compact and efficient than arc-length-based representations. 相似文献
22.
讲述了参观Semicon/west94′展览会及考察美国和西德的5个公司、1所大学所了解到的投影光刻技术、电子束曝光技术、透镜面形测试技术的发展。 相似文献
23.
本文介绍了采金船渡汛时的停泊方向及采金船在洪水中可能产生拖曳力的估算方法,为了防止采金船汛期发生溜船事故,建议采用缆绳牵拉固船的措施,以保障采金船的汛期安全。 相似文献
24.
Arjunan Arulchakkaravarthi Rakesh Kumar Parthasarathy Santhanaraghavan Sivaramakrishnan Muralithar Rengasamy Gopalakrishanan Perumalsamy Ramasamy 《Materials Research Innovations》2002,6(5-6):273-276
Organic molecular scintillating crystals are noted for their good timing and particle discrimination process. Trans-stilbene
is one such candidate noted for its good particle detection characteristics for the past five decades. Progressive strengthening
of detection characteristics of trans-stilbene has been attempted by improving crystal perfection. A series of timing resolution
studies have been carried out for the Bridgman grown trans-stilbene crystals under different experimental conditions. The
results were compared with the previously reported values. Pulse shape discrimination process has been carried out for 241Am and 252Cf sources and good discrimination has been obtained for gamma-alpha and gamma-neutron sources from the grown organic phosphor
crystal.
Electronic Publication 相似文献
25.
精密陶瓷部件近净成型技术的发展 总被引:5,自引:0,他引:5
重点介绍了近十年发展起来的陶瓷部件的近净成型技术 ,主要包括直接凝固注模成型、凝胶注模成型、陶瓷注射成型、陶瓷无模成型和微注入成型。对这些新的成型方法的原理、工艺过程及应用特点进行了较全面的分析与比较。 相似文献
26.
Combined shape and sizing optimization of truss structures 总被引:1,自引:0,他引:1
In this paper, an evolutionary optimization method is presented for weight minimum problem of a 3-dimensional truss structure
in terms of nodal coordinates and element cross-sectional areas. The structure is subject to stress, local buckling and displacement
constraints. Two types of design variables with different natures are optimized separately: (1) a fully stressed design (FSD)
and scaling techniques are applied to sizing variables and (2) the evolutionary node shift method is applied to shape variables.
Alternating procedure is utilized to couple the two types of variables and to combine the results. The optimum solution is
achieved gradually from the initial configuration design. Two typical truss structures are examined to illustrate the validity
of the method.
Received: 22 October 2001 / Accepted: 04 June 2002
This research work is supported by the National Natural Science Foundation of China under the guarantees no. 10072050 and
10172072, respectively. 相似文献
27.
A. Moran C. Madden R. Rebis R. Payne M. A. Matteson 《Journal of Thermal Spray Technology》1994,3(2):197-198
Over the past five years, the Annapolis Detachment, Carderock Division, Naval Surface Warfare Center (formerly David Taylor
Research Center) has established a state- of- the- art spray forming facility for the study and exploitation of this near
net shape manufacturing process. Spray forming is a single step gas atomization/deposition process which yields ferrous and
nonferrous, near final shape, near fully dense preforms that has proven to be a viable and cost effective alternative to conventional
metalworking technology for the production of material preforms with properties surpassing those of their cast and wrought
counterparts. Current programs at Carderock Divison Naval Surface Warfare Center are aimed at optimization of the process,
certification of the spray formed products and industrialization of the technology. 相似文献
28.
29.
Microstructure evolution during metal forming processes 总被引:8,自引:0,他引:8
Recrystallization and grain growth evolutions during metal forming processes are considered. Coupling between the thermo-mechanical and microstructure processes is realized. Die forging of a rear-axle flange is simulated numerically on the base of the finite element method. Material parameters of the models are obtained experimentally. The influence of interpass and holding times on grain size distributions in the end product is shown. 相似文献
30.