共查询到20条相似文献，搜索用时 234 毫秒
1.
Multi-proxy signature schemes allow the original signer to delegate his/her signing power to n proxy signers such that all proxy signers must corporately generate a valid proxy signature on behalf of the original signer. We first propose a multi-proxy signature scheme based on discrete logarithms and then adapt it to the elliptic curve cryptosystem. With the integration of self-certified public-key systems and the message recovery signature schemes, our proposed schemes have the following advantages： （1） They do not require the signing message to be transmitted, since the verifier can recover it from the signature; （2） The authentication of the public keys, verification of the signature, and recovery of the message can be simultaneously carried out in a single logical step; （3） No certificate is needed for validating the public keys. Further, the elliptic curve variant with short key lengths especially suits the cryptographic applications with limited computing power and storage space, e.g., smart cards. As compared with the previous work that was implemented with the certificate-based public-key systems, the proposed schemes give better performance in terms of communication bandwidth and computation efforts. 相似文献
2.
分层制造中任意边界簿层分形扫描路径的研究 总被引：2，自引：0，他引：2
The fractal curve is proposed as a novel scanning-path used in Layered Manufacturing.Aiming at a limitation that the fractal curve can only fill a square region,a method is developed to realize the trimming of fractal curve in arbitrary boundary layer by means of undging intersection points between parameterized arbitrary boundary and a FASS(space-filling,self-avoiding,simple and self-similar)fractal curve.Accordingly,the related algorithm concerning with determining intersection points has been investigated according to the recursion reature of the fractal curve,and in the process of the fractal curve traversed,the rule of udging intersection points is ascertained as well,so that the laser-scanning beam can “walk” along the fractal curve inside the desired boundary,and arbitrary contour components are fabricated. 相似文献
3.
An addition scheme applicable to time-delay integration (TDI) CMOS image sensor is proposed,which adds signals in the charge domain in the pixel array.A two-shared pixel structure adopting two-stage charge transfer is introduced,together with the rolling shutter with an undersampling readout timing.Compared with the conventional TDI addition methods,the proposed scheme can reduce the addition operations by half in the pixel array,which decreases the power consumption of addition circuits outside the pixel array.The timing arrangement and pixel structure are analyzed in detail.The simulation results show that the proposed pixel structure can achieve the charge addition with negligible nonlinearity,therefore the power consumption of the periphery addition circuits can be reduced by half theoretically. 相似文献
4.
This study presents a new method of 4-pipelined high-performance split multiply-accumulator （MAC） architecture, which is capable of supporting multiple precisions developed for media processors. To speed up the design further, a novel partial product compression circuit based on interleaved adders and a modified hybrid partial product reduction tree （PPRT） scheme are proposed. The MAC can perform 1-way 32-bit, 4-way 16-bit signed/unsigned multiply or multiply-accumulate operations and 2-way parallel multiply add （PMADD） operations at a high frequency of 1.25 GHz under worst-case conditions and 1.67 GHz under typical-case conditions, respectively. Compared with the MAC in 32-bit microprocessor without interlocked piped stages （MIPS）, the proposed design shows a great advantage in speed. Moreover, an improvement of up to 32% in throughput is achieved. The MAC design has been fabricated with Taiwan Semiconductor Manufacturing Company （TSMC） 90-nm CMOS standard cell technology and has passed a functional test. 相似文献
5.
CAO Juan WANG Guo-zhao 《浙江大学学报(A卷英文版)》2007,8(10):1663-1670
As three control points are fixed and the fourth control point varies, the planar cubic C-curve may take on a loop, a cusp, or zero to two inflection points, depending on the position of the moving point. The plane can, therefore, be partitioned into regions labelled according to the characterization of the curve when the fourth point is in each region. This partitioned plane is called a "characterization diagram". By moving one of the control points but fixing the rest, one can induce different characterization diagrams. In this paper, we investigate the relation among all different characterization diagrams of cubic C-curves based on the singularity conditions proposed by Yang and Wang (2004). We conclude that, no matter what the C-curve type is or which control point varies, the characterization diagrams can be obtained by cutting a common 3D characterization space with a corresponding plane. 相似文献
6.
In five-axis machining,tool orientation above a blade stream surface may lead to tool collision and a decrease in workpiece rigidity.Hence,collisionless tool orientation smoothing(TOS)becomes an important issue.On the basis of a constant scallop height tool path,the triangular facets in the faces,vertices format are constructed from cutter contact(CC)using the Voronoi incremental algorithm.The cutter location(CL)points candidate set is represented by an oblique elliptic cone whose vertex lies at CC using NURBS envelope.Whether the CL point is above its CC is judged by the dot product between the normal vector and the point on triangulation nearest to the CL point.The curvatures at CC are obtained by fitting a moving least square(MLS) quadratic patch to the local neighborhood of a vertex and calculating eigenvectors and eigenvalues of the Hessian matrix.Triangular surface elastic energy is employed as the weight in selection from the NURBS envelope.The collision is judged by NURBS surface intersection.TOS can then be expressed by selecting a CL point for each CC point and converted into a numerical control(NC)code automatically according to the postprocessor type of the machine center.The proposed method is verified by finishing of a cryogenic turboexpander impeller of air separation equipment. 相似文献
7.
Path Planning and Tracking for Vehicle Parallel Parking Based on Preview BP Neural Network PID Controller 总被引：1，自引：0，他引：1
In order to diminish the impacts of external disturbance such as parking speed fluctuation and model uncertainty existing in steering kinematics, this paper presents a parallel path tracking method for vehicle based on preview back propagation(BP) neural network PID controller. The forward BP neural network can adjust the parameters of PID controller in real time. The preview time is optimized by considering path curvature, change in curvature and road boundaries. A fuzzy controller considering barriers and different road conditions is built to select the starting position. In addition, a kind of path planning technology satisfying the requirement of obstacle avoidance is introduced. In order to solve the problem of discontinuous curvature, cubic B spline curve is used for curve fitting. The simulation results and real vehicle tests validate the effectiveness of the proposed path planning and tracking methods. 相似文献
8.
A cluster analyzing algorithm based on grids is introduced in this paper,which is applied to data mining in the city emergency system. In the previous applications, data mining was based on the method of analyzing points and lines, which was not efficient enough in dealing with the geographic information in units of police areas. The proposed algorithm maps an event set stored as a point set to a grid unit set, utilizes the cluster algorithm based on grids to find out all the clusters, and shows the results in the method of visualization. The algorithm performs well when dealing with high dimensional data sets and immense data. It is suitable for the data mining based on geographic information system and is supportive to decision-makings in the city emergency system. 相似文献
9.
To efficiently exploit the performance of single instruction multiple data （SIMD） architectures for video coding, a parallel memory architecture with power-of-two memory modules is proposed. It employs two novel skewing schemes to provide conflict-free access to adjacent elements （8-bit and 16-bit data types） or with power-of-two intervals in both horizontal and vertical directions, which were not possible in previous parallel memory architectures. Area consumptions and delay estimations are given respectively with 4, 8 and 16 memory modules. Under a 0.18-pm CMOS technology, the synthesis results show that the proposed system can achieve 230 MHz clock frequency with 16 memory modules at the cost of 19k gates when read and write latencies are 3 and 2 clock cycles, respectively. We implement the proposed parallel memory architecture on a video signal processor （VSP）. The results show that VSP enhanced with the proposed architecture achieves 1.28× speedups for H.264 real-time decoding. 相似文献
10.
This paper studies phantom linear scalar field （LSF） and phantom non-linear Born-Infeld （NLBI） scalar field with square potential of the form V（Ф） =1/2m^2Ф^2. The equation of state parameter w（z）, and evolution of scale factor a（t） in both phantom LSF and phantom NLBI scalar model are explored. The age of universe Hot and the transition redshift Z are obtained. The Gold data set of 157-SN-Ia is used to constrain parameters of the two models by numerical calculation. The phantom LSF is slightly better than the phantom NLBI type scalar field model for a large m. Although a smaller m corresponding to a slower rolling of field Ф better fits the observation data, the difference between phantom NLBI scalar field and phantom LSF is not distinct in this case. 相似文献
11.
We propose a novel high-performance hardware architecture of processor for elliptic curve scalar multiplication based on the Lopez-Dahab algorithm over GF(2163) in polynomial basis representation. The processor can do all the operations using an efficient modular arithmetic logic unit, which includes an addition unit, a square and a carefully designed multiplication unit. In the proposed architecture, multiplication, addition, and square can be performed in parallel by the decomposition of computation. The point addition and point doubling iteration operations can be performed in six multiplications by optimization and solution of data dependency. The implementation results based on Xilinx Virtexll XC2V6000 FPGA show that the proposed design can do random elliptic curve scalar multiplication GF(2163) in 34.11 μs, occupying 2821 registers and 13 376 LUTs. 相似文献
12.
为了保证充电桩 、充电桩监控系统及运营管理平台之间通信安全与充电桩通信效率,结合区块链技术提出一种基于区块链技术的分布式密钥管理方案。从密钥生成、更新和注销3个方面进行详细介绍。优化改进椭圆曲线加密算法的标量乘法运算,将随机数[k]表示成二进制数形式,减少[kP]运算计算量,以提高椭圆曲线加密算法运算效率。改进后的算法平均只需进行3/2[log2k]次标量乘法运算,最多需进行2[log2k]次标量乘法运算,使在密钥产生阶段与签名阶段消耗的时长相较于椭圆曲线加密算法均缩短了20~30个百分点,在验证阶段缩短了约40~50个百分点,证明该方案具有更高的响应效率和安全性,也更适用于电动汽车充电基础设施。 相似文献
13.
张剑锋 《浙江大学学报(A卷英文版)》2005,6(4):322-328
Let M‘ be a closed submanifold isometrically immersed in a unit sphere S^n p. Denote by R, H and S, the normalized scalar curvature, the mean curvature, and the square of the length of the second fundamental form of M‘, respectively. Suppose R is constant and ≥1. We study the pinching problem on S and prove a rigidity theorem for M‘ immersed in S^n p with parallel normalized mean curvature vector field. When n≥8 or, n=7 and p≤2, the pinching constant is best. 相似文献
14.
姜海益 《浙江大学学报(A卷英文版)》2004,5(7):754-758
Let k,m,n be positive integers,and k≥2,α∈(0,1],0＜r＜min {m,n} an integer,d=r (m-r)/(k α),and iff∈ Ck,α(Rm,R″),A =Cr(f)= {x ∈ Rm ,rank(Df(x))≤r},thenf(A)is d-null.Thus the statement posed by Arthur Sard in 1965 can be completely solved when k≥2. 相似文献
15.
This study examines eighth grade students’ use of a representational metaphor (cups and tiles) for writing and solving equations
in one unknown. Within this study, we focused on the obstacles and difficulties that students experienced when using this
metaphor, with particular emphasis on the operations that can be meaningfully represented through this metaphor. We base our
analysis within a framework of referential relationships of meanings (Kaput 1991; Kaput, Blanton, and Moreno, et al. 2008). Our data consist of videotaped classroom lessons, student interviews, and teacher interviews. Ongoing analyses of these
data were conducted during the teaching sequence. A retrospective analysis, using constant comparison methodology, was then
undertaken in order to generate a thematic analysis. Our results indicate that addition and (implied) multiplication operations
only are the most meaningful with these representational models. Students also very naturally came up with a notation of their
own in making sense of equations involving multiplication and addition. However, only one student was able to construct a
“family of meanings” when negative quantities were involved. We conclude that quantitative unit coordination and conservation
are necessary constructs for overcoming the cognitive dissonance (between the two representations—drawn pictures and the algebraic
equation) experienced by students and teacher. 相似文献
16.
点乘是椭圆曲线密码的基本操作,它的主要性能指标是运算高效性。本算法设计灵活,且适应不同应用要求;执行的结果非常高效,适应于大多数椭圆曲线参数。 相似文献
17.
《British Journal of Educational Studies》2012,60(2):177-192
The University in Society. Edited by Lawrence Stone. 2 vols, pp. viii, 642. Princeton University Press. London: Oxford University Press, 1975. £4.75 each. Education for National Efficiency: the contribution of Sidney and Beatrice Webb. Edited by E. J. T. Brennan. Pp. 208. London: The Athlone Press, 1975. £5.00. Microteaching: A Programme of Teaching Skills. By G. Brown. Pp. 163. London: Methuen, 1975. £7.00 hardback, £3.60 paperback. Heinrich Pestalozzi. Father of Modern Pedagogy. By Robert B. Downs. Pp. 147. Boston, Mass.: Twayne Publishers, Inc., 1975. $7.50 (10% higher outside U.S.). Authority and Organization in the Secondary School. By Elizabeth Richardson. Pp. 146. London and Basingstoke: Macmillan Education Ltd., 1975. (Schools Council Research Studies). £2.25. An Introduction to the Study of Comparative Education. By Vernon Mallinson, University of Reading, 4th ed. London: Heinemann, 1975. The Sociology of Educational Ideas. By Julia Evetts. Pp. via, 168. London: Routledge &; Kegan Paul, 1973. £2.50. Class, Culture and the Curriculum. By Denis Lawton. Pp. ix, 124. London: Routledge &; Kegan Paul, 1975. Cloth £3.00. Paperback £1.25. Ideology and the Imagination. By Fred Inglis. Pp. 244. London: Cambridge University Press, 1975. £4.90 hard cover. £2.00 paperback. Handbook on Curriculum Development. By Centre for Educational Research and Innovation. Pp. 179. Paris: OECD, 1975. £2.80. Looking at Innovation: two approaches to educational reasearch. P. Sheldrake and S. Berry. NFER Publishing Company Ltd., 1975. The Sciences, the Humanities and the Technological Threat. Edited by W. Roy Niblett. Pp. xiv, 168. London: University of London Press, 1975. £3.80. 相似文献
18.
《British Journal of Educational Studies》2012,60(1):60-63
Philosophy and Human Movement. By David Best. Pp. 164. London: George Allen &; Unwin, (Unwin Education Books), 1978. £3.50 (paperback). Perimeters of Social Repair. Edited by W. H. G. Armytage and John Peel. Pp. 157. London, New York and San Francisco: Academic Press, 1978. (No price.) The University of Hull: the first Fifty Years. By T. W. Bamford. Pp. x, 290. London: OUP for University of Hull, 1978. £8.00. Education and Industry in the Nineteenth Century: the English disease? By G. W. Roderick and M. D. Stephens. Pp. ix+196. London: Longman, 1978. £3.95. Education in Britain since 1944. By W. K. Richmond. Pp. 168. London: Methuen, 1978. £7.00. Education paperback £2.95. Paths to Excellence and the Soviet School. By John Dunstan. Pp. 302. Windsor: National Foundation for Educational Research Publishing Company, 1978. £9.75. From Armstrong to Nuffield: Studies in twentieth‐century science education in England and Wales. By E. W. Jenkins. Pp. viii, 318. London: John Murray, 1979. Hardback £7.92, Limp £3.95. Educational Research: the Art and Science of Investigation. By G. J. Monly. Pp. 390. Boston: Allyn and Bacon, 1978. £12.80. Learning Later: Fresh Horizons in English Adult Education. By Enid and Edward Hutchinson. Pp. 200. London: Routledge and Kegan Paul, 1978. £6.95. The Evaluation of In‐Service Teacher Training. By E. S. Henderson. Pp. 224. London: Croom Helm, 1978. £9.95. ISBN: 0 85664 619 9. How Shall I Put It? By Malcolm Young. Pp. 97. Hythe: Marsland Press, 1978. £3.50. ISBN o 85606 060 7. 相似文献
19.
A family of quasi-cubic blended splines and applications 总被引：4，自引：0，他引：4
SU Ben-yue TAN Jie-qing 《浙江大学学报(A卷英文版)》2006,7(9):1550-1560
INTRODUCTION Bézier curves and uniform B-spline curves are powerful tools for constructing free form curves and surfaces (FFC/FFS). But they cannot represent the arcs, hyperbola, sphere, cylinders and other transcendental curves and surfaces exactly. In order to avoid the in- conveniences, many bases are presented in other new spaces (Zhang, 1996; Pe?a, 1997; Walz, 1997; Sánchez-Reyes, 1998; Mainar et al., 2001). Note that, these existing methods can deal with both polynomial curve… 相似文献
20.
《British Journal of Educational Studies》2012,60(2):158-160
Education and Enquiry. By John Anderson, edited by D. Z. Phillips. Pp. 240. Blackwell, 1980, £21.00 hardback, £5.25 paperback. Injustice, Inequality and Ethics. By Robin Barrow. Pp. xii, 204. Brighton: Wheatsheaf Books, 1982. £18.95 (cloth) and £4.95 (paper). Universities, Politicians and Bureaucrats: Europe and the United States. Edited by H. Daalder and E. Shils. Pp. viii, 511. Cambridge: Cambridge University Press, 1982. £37.50. Conflict and Compromise: Class Formation in English Society 1830–1914, A Comparative Study of Birmingham and Sheffield. By Dennis Smith. Pp. xiv, 333. London: Routledge &; Kegan Paul, 1982. £17.95. English Education, Social Change and War 1911–20. By Geoffrey Sherington. Pp. xiii, 194. Manchester University Press, 1981. £14.50. The Sociology of Childhood: Essential Readings. Edited by Chris Jenks. Pp. 290. Batsford Academic Books, 1982. £6.95 paperback. Hooligans or Rebels? By Stephen Humphries. Pp. viii, 279. Oxford: Basil Blackwell, 1981. £12.50. A New Case for the Liberal Arts. By D. G. Winter, D. C. McClelland and A. J. Stewart. Pp. xxvii, 247. London: Sage Publications, 1981. £14.75. Sources for English Local History. By W. B. Stephens. Pp. xvi, 342. Cambridge: University Press, rev. ed., 1981. Hard covers £25.00, paperback £8.95. Innovation in the Science Curriculum. Ed. by John Olson. Pp. 178. London: Croom‐Helm, 1982. £12.50. Brightest and Best. By W. P. Gothard. Pp. 270. Driffield: Nafferton, 1982. £10.95. Verbal Deficit: A Critique. By J. C. B. Gordon. Pp. 181. London: Croom Helm, 1982. Multi‐lingualism and Mother‐tongue Education. By D. P. Pattanayak. Pp. xvii, 185. Delhi: O.U.P., 1982. £7.95. Asia: the Winning of Independence. Ed. Robin Jeffrey, London, the Macmillan Press Ltd., 1981, xv, 337 相似文献