Recent Advances in Randomness Extraction

The area of randomness extraction has seen interesting advances in recent years, with rapid progress on many longstanding open problems, along with the introduction of many new notions that played a key role in this development. We survey this progress and highlight new definitions and notions that have been the subject of intense study in recent work.     

Interplay of Correlation,Randomness and Dimensionality Effects in Weakly-Coupled Half-Filled Random Hubbard Chains

Abstract

We study interplay of electronic correlation, randomness and dimensionality effects in half-filled random Hubbard chains weakly coupled via an interchain one-particle hopping. Based on the two-loop renormalization-group approach, phase diagrams are given in terms of temperature vs. strengths of the intrachain electron-electron umklapp scattering, the random scattering and the interchain one-particle hopping.     

Intrinsical Randomness of Kolmogorov ℤd-Actions on a Lebesgue Space

We introduce a concept of an intrinsically weak and strong randomness of a ^d -action on a Lebesgue space and we show that Kolmogorov ^d -actions are intrinsically weak random, and Bernoulli ^d -actions are intrinsically strong random.     

SiC颗粒增强6061铝合金滑动磨损的周期性与随机性

采用自制盘 -块式高速摩擦试验机研究了SiC颗粒增强 6 0 6 1铝合金试盘同颗粒增强橡胶试块对摩时的滑动磨损行为 ,在滑动速度为 2 0m/s和 40m/s条件下 ,通过持续试验、间歇试验和重复试验 ,考察了试盘磨损行为的周期性和磨损量变化的随机性 .基于对磨损行为的风险率的分析 ,提出了磨损统计模型 ,结合试验数据讨论了周期磨损量概率分布的某些特殊性质 .结果表明 ,周期磨损量的概率平均值及分散程度与滑动速度有关 ,而其下限值与速度无关     

Market efficiency in foreign exchange markets

We investigate the relative market efficiency in financial market data, using the approximate entropy(ApEn) method for a quantification of randomness in time series. We used the global foreign exchange market indices for 17 countries during two periods from 1984 to 1998 and from 1999 to 2004 in order to study the efficiency of various foreign exchange markets around the market crisis. We found that on average, the ApEn values for European and North American foreign exchange markets are larger than those for African and Asian ones except Japan. We also found that the ApEn for Asian markets increased significantly after the Asian currency crisis. Our results suggest that the markets with a larger liquidity such as European and North American foreign exchange markets have a higher market efficiency than those with a smaller liquidity such as the African and Asian markets except Japan.     

Spectra of Anderson type models with decaying randomness

In this paper we consider some Anderson type models, with free parts having long range tails and with the random perturbations decaying at different rates in different directions and prove that there is a.c. spectrum in the model which is pure. In addition, we show that there is pure point spectrum outside some interval. Our models include potentials decaying in all directions in which case absence of singular continuous spectrum is also shown.     

Collective Transport of Coupled Brownian Motors with Low Randomness

The transport properties of coupled Brownian motors in rocking ratchet are investigated via solving Langevin equation. By means of velocity, diffusion coefficient, and their ratio （Peclet number）, different features from a single particle have been found. In the regime of low-to-moderate D, the average velocity of elastically coupled Brownian motors is larger than that of a single Brownian particles; the Peclet number of elastically coupled Brownian motors is peaked functions of intensity of noise D but the Peclet number of a single Brownian motor decreases monotonously with the increase of a single Brownian motor. The results exhibit an interesting cooperative behavior between coupled particles subjected to a rocking force, which can generate directed transport with low randomness or high transport coherence in symmetrical periodic potential.     

考虑随机模糊性时结构广义可靠度计算方法

在元件强度外载既具有随机性又具有模糊性而元件的状态具有确定性的分界线时，元件的可靠度和失效概率可以表示成条件概率，这样就可以在考虑设计人员的经验的情况下降低元件的失效概率，算例结果证明了此结论；文中的另一个内容是给出了元件和结构的状态不存在明确界线时可靠度和失效概率的计算方法，从而更客观地反映结构的安全程度．