一种基于二维Logistic映射的二值图像加密方案

图像置乱变换是信息隐藏中图像加密的常用方法.但传统的图像置乱具有一定的规律性,再加上置乱具有周期性,很容易被攻击者击破.根据幻方变换和Arnold置乱,提出一种基于二维Logistic混沌映射的二值图像加密方案.通过对原图进行分块幻方变换,用二维Logistic混沌映射生成的二值序列与其进行异或操作,并进行Arnold置乱.实验结果表明该方案的加密速度快、效果好,密钥空间大,解密图像与原图像一致性良好,且具有很强的抗干扰能力.     

基于有限元法的石油射孔枪弹间干扰研究

石油射孔弹顺序起爆后,弹间冲击波相互作用是一个高度非线性的力学过程。基于有限元法对这一过程进行显式动力分析,由计算结果得知,高孔密射孔枪弹间干扰产生的主要原因是下位弹在不对称的压力场起爆。设计的不同孔密和不同爆速的导爆索两种情形的爆轰试验结果表明,弹间间距越小(即孔密的增加),弹间干扰越严重;随着导爆索爆速的降低,下位弹射流头部质量集中的"中间"偏转角度增大,上位弹对其干扰越明显。以上结论可用于高孔密射孔枪的优化设计。     

一种新的基于魔方变换的数字图像置乱加密算法

提出一种基于魔方变换的数字图像置乱加密算法,突破了传统的不改变图像像素值、仅通过重新排列图像像素点的位置实现图像置乱加密的方法,在三维空间上实现了对图像数据的置乱加密,打破了原有图像的所有特征.提出了一种新的密钥与魔方变化的编码对应法则,使该加密算法的加密密钥不受类型、大小的限制,具有密钥空间大的特点.仿真结果表明,该算法具有很好的加密、解密结果.     

基于Logistic混沌系统与魔方变换的图像加密方案

设计了一种基于Logistic映射与魔方变换的图像加密方案。该方案采用改进的混沌序列二值化方法,并借用魔方变换的思想,将二值序列转换所得的整数序列与图像像素值运算后,对图像的行列分别作循环移位完成对图像的加密。实验结果分析表明,该加密方案具有良好的图像加密效果,对于常见的攻击具有较强的抗干扰能力。     

Study on Relation between Dynamic Imbalance Degree and Product of Inertia

Based on the study of the relation between the dynamic imbalance degree and the product of inertia,a new static test method of the dynamic imbalance degree is presented.It is theoretically proved that the essence of the imbalance degree test for projectile body is the test of its product of inertia.A more precise calculation formula of dynamic imbalance degree is also given.The experiment results show that this method can not only reduce the cost of equipment,simplify the test procedures,save human resource,but also has more reliable test precision.     

Porous inorganic materials

The field of porous, inorganic materials is experiencing explosive growth, as is shown by more than 6000 literature citations since 1994 along with numerous recent symposia and workshops that have been devoted to this topic. Much of the recent interest has been fueled by new synthetic strategies, such as ‘supramolecular templating’, that have enabled precise engineering of pore size, shape, and connectivity on the mesoscopic scale. In general, template-based approaches involving the cooperative organization of organic—inorganic assemblies as intermediates are emerging as a promising conceptual basis for future developments in the field of porous inorganic materials, such as the synthesis of hierarchical morphologies that mimic the intricate structures found so often in nature.     

射孔弹用炸药药柱耐热试验研究

用自行设计的试验装置,测定了石油射孔弹用四种耐热炸药药柱(JH-16、JO-6、JP-1、JD-1)的热爆炸温度——延滞期特性曲线。用“调整法”测定了51型普通射孔弹(装药为JH-16)及51型超高温射孔弹(装药为JD-1)的2h、48h耐热极限温度。     

The Materiality of Finnish Folk Magic: Objects in the Collections of the National Museum of Finland

Abstract

In Finland the material aspects of magic have long been of marginal interest to scholars. Still, during the late nineteenth and early twentieth centuries several magical objects were gathered into museums, in addition to the archived vast folklore collections describing magic practices. The latter have been widely discussed, while recently also the material culture of magic is becoming the object of study.

This paper discusses the objects classified as magical in the collections of the National Museum in Helsinki. The collection includes, for example, miniature coffins containing an impaled frog or a wooden stick figure, magic pouches with various contents, animal bones and teeth, “snake’s court stones,” and curious growths of trees. The objects date mainly to the late nineteenth and early twentieth centuries. This collection is briefly presented and the process of ascribing magical meanings to a natural or constructed object is analyzed, both from the viewpoint of practitioners and museum personnel.

From the practitioners’ standpoint a complex combination of analogical thinking, potent agencies, and specific contexts resulted in special qualities of objects. In the museum, specific objects used solely for ritual purposes have attracted more attention than multi-purpose everyday items. Moreover, a foreknowledge of what kinds of objects were used ritually has guided choices of cataloguers. As a result the collection is quite limited.     

Magic Sets Revisited

This paper distinguishes among three kinds of linear recursions:canonical strongly linear recursion(CSLR),non-interdependent linear recursion(NILR)and interdependent linear recurstion(ILR)and presents an optimal algorithm for each.First,for the CSLRs,the magic-set method is refined in such a way that queries can be evaluated efficiently.Then,for the NILRs and ILRs,the concept of query dependency graphs is introduced to partition the rules of a program into a set of CSLRs and the computation is elaborated so that the oplimization for CSLRs can also be applied.     

用第2类4阶等值全对称幻方砌块构成的4n阶全对称幻方

给出4n 阶全对称幻方的一类构造方法,即先构造出 n~2个第二类4阶等值全对称幻方砌块。再用这些砌块构成4n 阶全对称幻方.