两种群签名方案的安全性分析

群签名允许群成员以匿名的方式代表整个群体对消息进行签名。而且,一旦发生争议,群管理员可以识别出签名者。该文对Posescu(2000)群签名方案和Wang-Fu(2003)群签名方案进行了安全性分析,分别给出一种通用伪造攻击方法,使得任何人可以对任意消息产生有效群签名,而群权威无法追踪到签名伪造者。因此这两个方案都是不安全的。

一个改进的群签名方案的安全性分析

对一个改进的群签名方案的安全性进行了分析,指出了该方案不具有可追踪性,不能防止联合攻击和伪造攻击,并且不具有不关联性。

Inferring Genome Ancestry and Estimating Molecular Relatedness Among 187 Chinese Maize Inbred Lines

The inference of genome ancestry and the estimation of molecular relatedness are of great importance for breeding efficiency and association studies. Seventy SSR loci, evenly distributed in 10 chromosomes, were assayed for polymorphism among 187 commonly used maize （Zea mays L.） inbreds which represent the genetic diversity in China. The identified 290 alleles served as raw data for estimating population structure using the coalescent linked loci, based on the ADMIXTURE model. Population number, K, has been inferred to be between five and seven. Specifying five subpopulations （K = 5） led to a distinct decrease and specifying K to be greater than six resulted in only minimal increases in the likelihood value. Therefore, population number, K, has been inferred into six subpopulations, which are PA, BSSS （includes Reid）, PB, Lan （Lancaster Sure Crop）, LRC （Luda Reb Cob, a Chinese landrace, and its derivatives）, and SPT （Si-ping-tou, a Chinese landrace and its derivatives）. The Kullback-Leibler distance of pairwise subpopulation was also inferred as n × p （187 ×6） Q matrices, which gave a detailed percentage of genetic composition of six subpopulations and molecular relatedness of each line. The genome-wide linkage disequilibrium （LD） indicated that the asso- ciation studies in QTLs and/or candidate genes might avoid nonfunctional and spurious associations, as most of the LD blocks were broken among diverse germplasm. The defined population structure has given us a clear genetic structure of these lines for breeding practice and established a good basis for association analysis.

Correlation Analysis on Male Sterile Lines Characters in Rapeseed(Brassica napus L.)

[Objective] This study was conducted to evaluate the associations of many characters of male sterile lines in Brassica napus L.[Method]10 recessive genetic male sterile（RGMS）lines were used as parents to cross in a half diallel cross method to produce 45 single cross hybrids.These 45 crosses and their 10 parents were evaluated at Guiyang during 2007-2008.[Result]The positive correlations of seed yield with plant height,pods per plant,days to flowering and days to maturity were significant.Their respective correlation coefficients（r）were 0.644,0.583,0.281 and 0.341.Highly significant and negative correlation was observed between seeds per pod and seed size（-0.533）.Direct path coefficients were observed for pods per plant（0.556 2）,seeds per pod（0.407 4）,1 000-seed weight（0.481 3）,and plant height（0.401 7）to seed yield.[Conclusion]Pods per plant,seeds per pod,1 000-seed weight and plant height were positive correlated with seed yield and showed high direct contributions to yield.Other characters including branches per plant,days to flowering,days to maturity and oil content had low contributions to seed yield.

Analysis and evaluation on pressure fluctuations in air dense medium fluidized bed

Pressure fluctuations contribute to the instability of separation process in air dense medium fluidized bed, which provides a high motivation for further study of underlying mechanisms. Reasons for generation and propagation of pressure fluctuations in the air dense medium fluidized bed have been discussed.Drift rate and collision rate of particles were employed to deduce the correlation between voidage and pressure fluctuations. Simultaneously, a dynamic pressure fluctuation measuring and analysis system was established. Based on frequency domain analysis and wavelet analysis, collected signals were disassembled and analyzed. Results show gradually intensive motion of particles increases magnitudes of signal components with lower frequencies. As a result of violent particle motion, the magnitude of real pressure signal's frequency experienced an increase as air velocity increased moderately. Wavelet analysis keeps edge features of the real signal and eliminates the noise efficaciously. The frequency of denoised signal is closed to that of pressure signal identified in frequency domain analysis.

Passive target tracking with intermittent measurement based on random finite set

In the tracking problem for the maritime radiation source by a passive sensor,there are three main difficulties,i.e.,the poor observability of the radiation source,the detection uncertainty(false and missed detections)and the uncertainty of the target appearing/disappearing in the field of view.These difficulties can make the establishment or maintenance of the radiation source target track invalid.By incorporating the elevation information of the passive sensor into the automatic bearings-only tracking(BOT)and consolidating these uncertainties under the framework of random finite set(RFS),a novel approach for tracking maritime radiation source target with intermittent measurement was proposed.Under the RFS framework,the target state was represented as a set that can take on either an empty set or a singleton; meanwhile,the measurement uncertainty was modeled as a Bernoulli random finite set.Moreover,the elevation information of the sensor platform was introduced to ensure observability of passive measurements and obtain the unique target localization.Simulation experiments verify the validity of the proposed approach for tracking maritime radiation source and demonstrate the superiority of the proposed approach in comparison with the traditional integrated probabilistic data association(IPDA)method.The tracking performance under different conditions,particularly involving different existence probabilities and different appearance durations of the target,indicates that the method to solve our problem is robust and effective.

Comultiplications on a wedge of two spheres

In this paper we study the set of comultiplications on a wedge of two spheres. We are primarily interested in the size of this set and properties of the comultiplications such as associativity and commutativity. Our methods involve Whitehead products in wedges of spheres and the Hopf-Hilton invariants. We apply our results to specific examples and determine the number of comultiplications, associative comultiplications and commutative comultiplications in these cases.