Novel uncertainty relations associated with fractional Fourier transform

In this paper the relations between two spreads, between two group delays, and between one spread and one group delay in fractional Fourier transform (FRFT) domains, are presented and three theorems on the uncertainty principle in FRFT domains are also developed. Theorem 1 gives the bounds of two spreads in two FRFT domains. Theorem 2 shows the uncertainty relation between two group delays in two FRFT domains. Theorem 3 presents the crossed uncertainty relation between one group delay and one spread in two FRFT domains. The novelty of their results lies in connecting the products of different physical measures and giving their physical interpretations. The existing uncertainty principle in the FRFT domain is only a special case of theorem 1, and the conventional uncertainty principle in time-frequency domains is a special case of their results. Therefore, three theorems develop the relations of two spreads in time-frequency domains into the relations between two spreads, between two group delays, and between one spread and one group delay in FRFT domains.     

Almost Desarguesian Maximal Partial Spreads

Constructions are given of various classesof maximal partial spreads in PG(3,2^r) whose partialspreads consist of q/2 reguli sharing a line. Further,characterization results are given for the main classes of constructedmaximal partial spreads.     

A Geometric Relationship Between Equivalent Spreads

By Andrè theory, it is well known how to algebraically convert a spread in a projective space to an equivalent spread (representing the same translation plane) in a projective space of different dimension and of different order (corresponding to a subfield of the kernel). The goal of this paper is to establish a geometric connection between any two such equivalent spreads by embedding them as subspaces and subgeometries of an ambient projective spaces. The connection can be viewed as a generalization of a construction due to Hirschfeld and Thas.     

On the Spectrum of the Sizes of Maximal Partial Line Spreads in <Emphasis Type="Italic">PG</Emphasis>(2<Emphasis Type="Italic">n</Emphasis>,<Emphasis Type="Italic">q</Emphasis>), <Emphasis Type="Italic">n</Emphasis> ≥ 3

A lot of research has been done on the spectrum of the sizes of maximal partial spreads in PG(3,q) [P. Govaerts and L. Storme, Designs Codes and Cryptography, Vol. 28 (2003) pp. 51–63; O. Heden, Discrete Mathematics, Vol. 120 (1993) pp. 75–91; O. Heden, Discrete Mathematics, Vol. 142 (1995) pp. 97–106; O. Heden, Discrete Mathematics, Vol. 243 (2002) pp. 135–150]. In [A. Gács and T. Sznyi, Designs Codes and Cryptography, Vol. 29 (2003) pp. 123–129], results on the spectrum of the sizes of maximal partial line spreads in PG(N,q), N 5, are given. In PG(2n,q), n 3, the largest possible size for a partial line spread is q^2n-1+q^2n-3+...+q³+1. The largest size for the maximal partial line spreads constructed in [A. Gács and T. Sznyi, Designs Codes and Cryptography, Vol. 29 (2003) pp. 123–129] is (q²ⁿ⁺¹–q)/(q²–1)–q³+q²–2q+2. This shows that there is a non-empty interval of values of k for which it is still not known whether there exists a maximal partial line spread of size k in PG(2n,q). We now show that there indeed exists a maximal partial line spread of size k for every value of k in that interval when q 9.J. Eisfeld: Supported by the FWO Research Network WO.011.96NP. Sziklai: The research of this author was partially supported by OTKA D32817, F030737, F043772, FKFP 0063/2001 and Magyary Zoltan grants. The third author is grateful for the hospitality of Ghent University.     

古代中国的宇宙模型

中国古代的创世神话与哲学认为，在“混沌”或“太一”中创生了阴阳，衍生出天地万物。老子与孔子形成天道观的时候，都受到了远古历法的影响。古代流行的盖天说与浑天说都受到远古六龙历的影响，一些学者认为六龙历也是《周易》形成的天学背景。立足于古代地心说的左旋说与右旋说的争论，涉及到唯物主义经验论导向的历学家与唯心主义先验论导向的儒学家的斗争。     

藏族传统天文历算的形成与发展

藏族传统天文历算学是以原始的西藏天文学——物候历为基础,印度时轮历为主体,五行运算和时宪历以及周边其他地区历法为补充逐步发展起来的一门学科,研究的是日月星辰等基本天体在宇宙中的分布、运行和宇宙的结构和发展变化。文章以时间为序,梳理了西藏传统天文历算的发展脉络,分析了其发展演变过程。     

公历置闰年方法的解析

历法的本质是对时间的度量问题,公历的核心问题是置闰年,公历是借助置闰协调历年与回归年之间的误差.利用辗转相除法将公历历年中的平年与回归年的误差同1作辗转相除,并按相除结果将0.242 2表为连分式.依次截取连分式,得到0.242 2的渐近分数序列.在其中选取8/33与31/128近似表示0.242 2,得33年8闰与128年31闰的置闰方法.在此基础上利用单位分数来表示31/128,得到一种复合周期置闰法,这便是公历的置闰规律.     

广告中的视觉符号与视觉传播

本文从视觉思维的角度出发，论述了在现代广告传播中视觉符号的重要作用，强调了符号作为信息载体在视觉传播中不可替代的地位．并对广告传播中的视觉特性作了说明。     

基于统计套利思想的股指期货跨期套利

基于统计套利交易的思想,对沪深300股指期货合约间价差的波动规律进行了研究,并在该波动规律的基础上建立了股指期货的跨期套利模型.从交易的效果来看,我国股指期货市场存在着跨期套利空间.     

On a Particular Class of Minihypers and Its Applications. I. The Result for General q

This article is the first in a series of three articles that discuss a particular class of minihypers and its applications. Proving that for small and < N, a {v _{+ 1}, v ; N, q}-minihyper consists of a sum of -spaces, we show that the excess points of an s-cover with excess of PG(N, q), (s + 1)|(N + 1), form a sum of s-spaces, and that no maximal partial s-spreads with deficiency of PG(N, q), (s + 1)|(N + 1), exist. The case q square will be studied in greater detail in [7] and further applications of these classification results on this class of minihypers will be published in [8].