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11.
Andrew Klapper 《Journal of Cryptology》1994,7(1):33-51
A new method of cryptologic attack on binary sequences is given, using their linear complexities relative to odd prime numbers. We show that, relative to a particular prime number p, the linear complexity of a binary geometric sequence is low. It is also shown that the prime p can be determined with high probability by a randomized algorithm if a number of bits much smaller than the linear complexity is known. This determination is made by exploiting the imbalance in the number of zeros and ones in the sequences in question, and uses a new statistical measure, the partial imbalance.This project was sponsored by the National Security Agency under Grant No. MDA904-91-H-0012. The United States Government is authorized to reproduce and distribute reprints notwithstanding any copyright notation hereon. 相似文献
12.
介绍光链路设计的原理和公式 ,给出光链路设计的Java小程序实现 ,以期有效解决在手工进行光链路设计及计算中存在的问题。 相似文献
13.
Silvano Dal Zilio Denis Lugiez 《Applicable Algebra in Engineering, Communication and Computing》2006,17(5):337-377
XML documents may be roughly described as unranked, ordered trees and it is therefore natural to use tree automata to process or validate them. This idea has already been successfully applied in the context of Document Type Definition (DTD), the simplest standard for defining document validity, but additional work is needed to take into account XML Schema, a more advanced standard, for which regular tree automata are not satisfactory. In this paper, we introduce Sheaves Logic (SL), a new tree logic that extends the syntax of the – recursion-free fragment of – W3C XML Schema Definition Language (WXS). Then, we define a new class of automata for unranked trees that provides decision procedures for the basic questions about SL: model-checking; satisfiability; entailment. The same class of automata is also used to answer basic questions about WXS, including recursive schemas: decidability of type-checking documents; testing the emptiness of schemas; testing that a schema subsumes another one.This work was partially supported by the French government research grant ACI TRALALA and by IST Global Computing Profundis. 相似文献
14.
The wireless connectivity in pervasive computing has ephemeral character and can be used for creating ad hoc networks, sensor
networks, connection with RFID (Radio Frequency Identification) tags etc. The communication tasks in such wireless networks
often involve an inquiry over a shared channel, which can be invoked for: discovery of neighboring devices in ad hoc networks,
counting the number of RFID tags that have a certain property, estimating the mean value contained in a group of sensors etc.
Such an inquiry solicits replies from possibly large number of terminals n. This necessitates the usage of algorithms for resolving batch collisions (conflicts) with unknown conflict multiplicity n. In this paper we present a novel approach to the problem of collision resolution for batch conflicts. We show how the conventional
tree algorithms for collision resolution can be used to obtain progressively accurate estimation of the multiplicity. We use
the estimation to propose a more efficient binary tree algorithm, termed Estimating Binary Tree (EBT) algorithm. The EBT algorithm
is suited for implementation when the conflicting nodes are passive, such as e.g. RFID tags. We extend the approach to design
the Interval Estimation Conflict Resolution (IECR) algorithm. For n→∞ we prove that the efficiency achieved by IECR for batch arrivals is identical with the efficiency that Gallager’s FCFS
algorithm achieves for Poisson packet arrivals. For finite n, the simulation results show that IECR is, to the best of our knowledge, the most efficient batch resolution algorithm reported
to date. 相似文献
15.
Gloria Galan-Marin Enrique Merida-Casermeiro Domingo Lopez-Rodriguez 《Neural Processing Letters》2007,26(2):133-143
Detection of isomorphism among kinematic chains is essential in mechanical design, but difficult and computationally expensive.
It has been shown that both traditional methods and previously presented neural networks still have a lot to be desired in
aspects such as simplifying procedure of identification and adapting automatic computation. Therefore, a new algorithm based
on a competitive Hopfield network is developed for automatic computation in the kinematic chain isomorphism problem. The neural
approach provides directly interpretable solutions and does not demand tuning of parameters. We have tested the algorithm
by solving problems reported in the recent mechanical literature. Simulation results show the effectiveness of the network
that rapidly identifies isomorphic kinematic chains. 相似文献
16.
Java语言及其虚拟机技术探讨 总被引:1,自引:0,他引:1
随着Internet的迅猛发展,Internet编程语言Java愈来愈成为计算机行业的焦点。本文在简述了Java的主要特点后,重点对Java最关键的技术──虚拟机进行了深入的探讨。 相似文献
17.
Mait Lang Tiit Nilson Andres Kuusk Andres Kiviste Maris Hordo 《Remote sensing of environment》2007,110(4):445-457
Several published foliage mass and crown radius regression models were tested on the preparation of the input for the reflectance model of Kuusk and Nilson [Kuusk, A. and Nilson, T. (2000), A directional multispectral forest reflectance model. Remote Sensing of Environment, 72(2):244–252.] for 246 forest growth sample plots in Estonia. In each test, foliage mass and crown radius for trees in the sample plots were predicted with a particular pair of allometric regression models. The forest reflectance model was then run using the estimated foliage mass and crown radius values. Reflectance factors were simulated and compared with the reflectance values obtained from three atmospherically corrected Landsat 7 Enhanced Thematic Mapper (ETM+) scenes. The statistics of linear regression between the simulated and measured reflectance factors were used to assess the performance of foliage and crown radius models. The hypothesis was that the best allometric regression models should provide the best fit in reflectance. The strongest correlation between the simulated and measured reflectance factors was found in the short-wave infrared band (ETM + 5) for all the images. The highest R2 = 0.71 was observed in Picea abies dominated stands. No excellent combination of foliage mass and crown radius functions was found, but the ranking based on determination coefficients showed that some linear crown radius models are not applicable to our data. Processing of raster images, reflectance measurement for small sample plots, usage of tree-species-specific fixed parameters (specific leaf area, etc.), and the ignored influence of phenology introduced additional variation into the relationships between simulated and measured reflectance factors. Further studies are needed, but these preliminary results demonstrate that the proposed method could serve as an effective way of testing the performance of foliage mass and canopy cover regressions. 相似文献
18.
Using airborne laser scanning to monitor tree migration in the boreal-alpine transition zone 总被引:1,自引:0,他引:1
The boreal tree line is expected to advance upwards into the mountains and northwards into the tundra due to global warming. The major objective of this study was to find out if it is possible to use high-resolution airborne laser scanner data to detect very small trees — the pioneers that are pushing the tree line up into the mountains and out onto the tundra. The study was conducted in a sub-alpine/alpine environment in southeast Norway. A total of 342 small trees of Norway spruce, Scots pine, and downy birch with tree heights ranging from 0.11 to 5.20 m were precisely georeferenced and measured in field. Laser data were collected with a pulse density of 7.7 m− 2. Three different terrain models were used to process the airborne laser point cloud in order to assess the effects of different pre-processing parameters on small tree detection. Greater than 91% of all trees > 1 m tall registered positive laser height values regardless of terrain model. For smaller trees (< 1 m), positive height values were found in 5-73% of the cases, depending on the terrain model considered. For this group of trees, the highest rate of trees with positive height values was found for spruce. The more smoothed the terrain model was, the larger the portion of the trees that had positive laser height values. The accuracy of tree height derived from the laser data indicated a systematic underestimation of true tree height by 0.40 to 1.01 m. The standard deviation for the differences between laser-derived and field-measured tree heights was 0.11-0.73 m. Commission errors, i.e., the detection of terrain objects — rocks, hummocks — as trees, increased significantly as terrain smoothing increased. Thus, if no classification of objects into classes like small trees and terrain objects is possible, many non-tree objects with a positive height value cannot be separated from those actually being trees. In a monitoring context, i.e., repeated measurements over time, we argue that most other objects like terrain structures, rocks, and hummocks will remain stable over time while the trees will change as they grow and new trees are established. Thus, this study indicates that, given a high laser pulse density and a certain density of newly established trees, it would be possible to detect a sufficient portion of newly established trees over a 10 years period to claim that tree migration is taking place. 相似文献
19.
Given a scalar, stationary, Markov process, this short communication presents a closed-form solution for the first-passage problem for a fixed threshold b. The derivation is based on binary processes and the general formula of Siegert [Siegert AJF. On the first-passage time probability problem. Physical Review 1951; 81:617–23]. The relation for the probability density function of the first-passage time is identical to the commonly used formula that was derived by VanMarcke [VanMarcke E. On the distribution of the first-passage time for normal stationary random processes. Journal of Applied Mechanics ASME 1975; 42:215–20] for Gaussian processes. The present derivation is based on more general conditions and reveals the criteria for the validity of the approximation. Properties of binary processes are also used to derive a hierarchy of upper bounds for any scalar process. 相似文献
20.
张剑 《计算机与数字工程》2012,40(6):51-53,160
随着装备技术的发展,现代作战具有作战单元种类数量多、攻防战术复杂、干扰性欺骗性数据充斥等特点,尤其是协同作战能力和数据交换能力逐步增强,以上都使得现代作战中涉及的信息呈现"海量"特征。为了取得理想的作战效果,指挥员必须对以上海量信息进行处理,从中提取出有用的信息和知识。近年来迅速发展的数据挖掘技术,在处理海量信息方面具有非常明显的优势。文章在介绍现代作战特点和数据挖掘技术的基础上,对数据挖掘技术在现代作战中的应用做了初步的研究。 相似文献