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291.
B-spline curve extension is an important operation in computer aided design systems. In this paper, we present a new extension algorithm for B-spline curves. The algorithm uses curve unclamping to generate a uniform B-spline curve segment from the original curve and gradually extends the segment to pass through every target point. Algorithms of uniform B-spline curves are used such that our algorithm has a low time cost and can easily handle arbitrary-order derivative constraints at the target points. Generalization for non-uniform rational B-spline curve extension is also discussed, and examples show the efficiency of our method. 相似文献
292.
This paper considers a unicast multiuser multiple-input single-output (MISO) downlink system overheard by multiple single-antenna eavesdroppers. The objective is to jointly design the beamforming vectors and the artificial noise (AN) covariance matrix with imperfect channel state information (CSI) at the transmitter, such that the total transmit power is minimized while satisfying probabilistic quality of service (QoS) constraints at legitimate users and the eavesdroppers. Using Bernstein-type inequalities and the S-procedure, we recast the non-convex power minimization problem as two different convex semidefinite programs (SDPs) which can be solved using interior-point methods. Simulation results show that the proposed methods outperform a nonrobust method and the ones using the isotropic AN. 相似文献
293.
Yanrong Lu Lixiang Li Haipeng Peng Yixian Yang 《Peer-to-Peer Networking and Applications》2016,9(2):449-459
The Session Initiation Protocol (SIP) as the core signaling protocol for multimedia services is receiving much attention. Authentication is becoming increasingly crucial issue when a user asks to use SIP services. Many authentication schemes for the SIP have been proposed. Very recently, Zhang et al. has presented an authentication scheme for SIP and claimed their scheme could overcome various attacks while maintaining efficiency. In this research, we illustrate that their scheme is susceptible to the insider attack and does not provide proper mutual authentication. We then propose a modified secure mutual authentication scheme to conquer the security flaws in Zhang et al.’s scheme. Through the informal and formal security analyses, we demonstrate that our scheme is resilient possible known attacks including the attacks found in Zhang et al.’s scheme. In addition, the performance analysis shows that our scheme has better efficiency in comparison with other related ECC-based authentication schemes for SIP. 相似文献
294.
A co-location pattern is a set of spatial features whose instances frequently appear in a spatial neighborhood. This paper efficiently mines the top-k probabilistic prevalent co-locations over spatially uncertain data sets and makes the following contributions: 1) the concept of the top-k probabilistic prevalent co-locations based on a possible world model is defined; 2) a framework for discovering the top-k probabilistic prevalent co-locations is set up; 3) a matrix method is proposed to improve the computation of the prevalence probability of a top-k candidate, and two pruning rules of the matrix block are given to accelerate the search for exact solutions; 4) a polynomial matrix is developed to further speed up the top-k candidate refinement process; 5) an approximate algorithm with compensation factor is introduced so that relatively large quantity of data can be processed quickly. The efficiency of our proposed algorithms as well as the accuracy of the approximation algorithms is evaluated with an extensive set of experiments using both synthetic and real uncertain data sets. 相似文献
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Computational Visual Media - Visual curve completion is a fundamental problem in understanding the principles of the human visual system. This problem is usually divided into two problems: a... 相似文献
297.
介绍了曼维莱水电站枢纽布置设计及优化过程,在合同方案基础上,根据最新的补充勘测资料及多方案研究对比,对坝线选择、引水发电系统方案选择和厂区枢纽布置及优化设计工作做了详细的介绍,可供同类工程参考。 相似文献
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