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排序方式: 共有802条查询结果,搜索用时 15 毫秒
71.
An open question about the asymptotic
cost of connecting many processors to a
large memory using three dimensions for wiring
is answered, and this result is used
to find the full cost of several
cryptanalytic attacks. In many cases this full
cost is higher than the accepted complexity
of a given algorithm based on the number of processor
steps. The full costs of several
cryptanalytic attacks are determined, including
Shanks method for computing discrete
logarithms in cyclic groups of prime order n,
which requires n1/2+o(1) processor steps, but,
when all factors are taken into account, has full
cost n2/3+o(1). Other attacks analyzed are
factoring with the number field sieve, generic
attacks on block ciphers, attacks on double
and triple encryption, and finding hash collisions.
In many cases parallel collision search
gives a significant asymptotic advantage over
well-known generic attacks. 相似文献
72.
73.
余数制和神经网络各有其独特优点,将其有机结合这些优点得以充分发挥。将神经网络结构和方法引人余数制信号处理系统,构造出完成余数约化运算和余/十转换运算以及余数加法运算的新结构,开辟了高速实时信号处理的新途径.将余数制引入神经网络,即神经网络中的数据、权值均按余数制表示和运算,构造出一种新的感知机模型—余数制神经网络,由于余数制运算具有一种独特的非线性特点,使这种模型比常规神经网络具有更强的功能。 相似文献
74.
《国际计算机数学杂志》2012,89(5):573-590
The integer factorization problem (IFP), the finite field discrete logarithm problem (DLP) and the elliptic curve discrete logarithm problem (ECDLP) are essentially the only three mathematical problems that the practical public-key cryptographic systems are based on. For example, the most famous RSA cryptosystem is based on IFP, the US government's Digital Signature Standard, DSS, is based on DLP, whereas the ECC (Elliptic Curve Cryptography) and Elliptic Curve Digital Signature Algorithm (ECDSA) are based on ECDLP. The security of such cryptographic systems relies on the computational intractability of these three mathematical problems. In this paper, we shall present a survey of various methods for solving the IFP/DLP and particularly the ECDLP problems. More specifically, we shall first discuss how the index calculus as well as quantum algorithms can be used to solve IFP/DLP. Then we shall show why the index calculus cannot be used to solve ECDLP. Finally, we shall introduce a new method, xedni calculus , due to Joseph Silverman, for attack ECDLP; some open problems and new research directions, will also be addressed. 相似文献
75.
本文在总结结构风振试验研究的基础上,提出了高层建筑的迎风面、背风面与二侧面的动扭矩是统计独立的假定及相应的计算参数和计算方法。计算实例表明,高层建筑在风荷载作用下的扭转振动是不可忽视的。 相似文献
76.
77.
Hayato Nakada Author Vitae Kiyotsugu Takaba Author Vitae Author Vitae 《Automatica》2005,41(5):905-913
This paper is concerned with the identification of a class of piecewise affine systems called a piecewise affine autoregressive exogenous (PWARX) model. The PWARX model is composed of ARX sub-models each of which corresponds to a polyhedral region of the regression space. Under the temporary assumption that the number of sub-models is known a priori, the input-output data are collected into several clusters by using a statistical clustering algorithm. We utilize support vector classifiers to estimate the boundary hyperplane between two adjacent regions in the regression space. In each cluster, the parameter vector of the sub-model is obtained by the least squares method. It turns out that the present statistical clustering approach enables us to estimate the number of sub-models based on the information criteria such as CAIC and MDL. The estimate of the number of sub-models is performed by applying the identification procedure several times to the same data set, after having fixed the number of sub-models to different values. Finally, we verify the applicability of the present identification method through a numerical example of a Hammerstein model. 相似文献
78.
杜选 《数字社区&智能家居》2006,(12):92-93
在VB应用软件中通过读取用户计算机的硬盘卷序列号作为机器码,加密后生成软件注册码。由于硬盘卷序列号是唯一的,提供的软件注册码也是唯一的,用户利用该软件注册码可实现对VB应用软件的注册。本文阐述了利用硬盘卷序列号实现对VB软件注册的详细实现过程。 相似文献
79.
Byongjoo?KimEmail author Chunkyu?Lee 《Journal of Mechanical Science and Technology》2003,17(4):581-589
Film absorption involves simultaneous heat and mass transfer in the gas-liquid system. While the non-absorbable gas does not
participate directly in the absorption process, its presence does affect the overall heat and mass transfer. An experimental
study was performed to investigate the heat and mass transfer characteristics of LiBr-H2O solution flowing over 6-row horizontal tubes with the water vapor absorption in the presence of non-absorbable gases. The
volumetric concentration of non-absorbable gas. air, was varied from 0.17 to 10.0%. The combined effects of the solution flow
rate and its concentration on the heat and mass transfer coefficients were also examined. The presence of 2% volumetric concentration
of air resulted in a 25% reduction in the Nusselt number and 41% reduction in the Sherwood number. Optimum film Reynolds number
was found to exist at which the heat and mass transfer reach their maximum value independent of air contents. Reduced Nusselt
and Sherwood numbers, defined as the ratio of Nusselt and Sherwood numbers at given non-absorbable gas content to that with
pure water vapor, were correlated to account for the reduction in the heat and mass transfer due to non-absorbable gases in
a falling film absorption process. 相似文献
80.
Jo?Won?ChangEmail author HeeBong?Eun 《Journal of Mechanical Science and Technology》2003,17(8):1234-1245
An experimental study was carried out to investigate the reduced frequency effect on the near-wake of an elliptic airfoil
oscillating in pitch. The airfoil was sinusoidally pitched around the center of the chord between -5° and +25° angles of attack
at an airspeed of 3.4 m/s. The chord Reynolds number and reduced frequencies were 3.3 X104, and 0.1, 0.7, respectively. Phase-averaged
axial velocity and turbulent intensity profiles are presented to show the reduced frequency effects on the near-wake behind
the airfoil oscillating in pitch. Axial velocity defects in the near-wake region have a tendency to increase in response to
a reduced frequency during pitch up motion, whereas it tends to decrease during pitch down motion at a positive angle of attack.
Turbulent intensity at positive angles of attack during the pitch up motion decreased in response to a reduced frequency,
whereas turbulent intensity during the pitch down motion varies considerably with downstream stations. Although the true instantaneous
angle of attack compensated for a phase-lag is large, the wake thickness of an oscillating airfoil is not always large because
of laminar or turbulent separation. 相似文献