Low area field-programmable gate array implementation of PRESENT image encryption with key rotation and substitution

Lightweight ciphers are increasingly employed in cryptography because of the high demand for secure data transmission in wireless sensor network, embedded devices, and Internet of Things. The PRESENT algorithm as an ultra-lightweight block cipher provides better solution for secure hardware cryptography with low power consumption and minimum resource. This study generates the key using key rotation and substitution method, which contains key rotation, key switching, and binary-coded decimal-based key generation used in image encryption. The key rotation and substitution-based PRESENT architecture is proposed to increase security level for data stream and randomness in cipher through providing high resistance to attacks. Lookup table is used to design the key scheduling module, thus reducing the area of architecture. Field-programmable gate array (FPGA) performances are evaluated for the proposed and conventional methods. In Virtex 6 device, the proposed key rotation and substitution PRESENT architecture occupied 72 lookup tables, 65 flip flops, and 35 slices which are comparably less to the existing architecture.     

方腔内耦合传热传质非对称流动数值模拟

对带有质热源的方腔内流体传热传质进行数值研究。针对不同Ra、Nc、Sr和Df，探究对称方腔内流体传热传质的分岔特性。结果表明：存在临界Ra_c使流体流动形态发生转变，当Ra<Ra_c时，流体流线、温度场和浓度场对称分布；当Ra>Ra_c时，流体发生偏斜。增大浮升力，流体更易发生分岔现象。增强Soret和Dufour效应可增强传热对称性并增大流体发生分岔的临界Rayleigh数。     

中压进汽腔的流场数值模拟比较

通过数值模拟计算,对中压对称进汽和切向进汽两种结构的流场进行了分析比较,结果表明,单一切向进汽腔的总压损失更小,出口汽流角的周向分布均匀度更好。更进一步,为整体评估中压进汽腔的流场以及对叶片级的流动影响,对中压进汽腔及第1级叶片的整体流体域流场情况进行了分析比较,结果表明,采用大几何角静叶的切向进汽腔气动性能最优;当采取切向进汽腔时,需合理选择第1级静叶几何角并耦合计算,才能实现进汽腔的气动优化。     

Casting methods for the production of rotationally symmetric copper bimetals

ABSTRACT

Multiple-material products are characterised by a complex property profile which is achieved by combining the particular advantages of at least two different materials. Bimetal casting is an energy- and material-efficient technology for the production of multi-metallic objects. This paper describes the development of a semi-continuous casting process for the formation of a rotationally symmetric bimetal with a cohesive bonding character at the interface of a copper–tin alloy (CuSn6) and pure copper (Cu99.5). Initial experiments are conducted by static casting to evaluate the thermal process window. Based on the results of the initial experiments, a vertical semi-continuous compound casting process is developed. A stable cohesive bond between the joining partners is accomplished by forming a solid solution at the interface.

This paper is part of a Thematic Issue on Copper and its Alloys.     

Isogeometric topology optimization based on energy penalization for symmetric structure

We present an energy penalization method for isogeometric topology optimization using moving morphable components (ITO–MMC), propose an ITO–MMC with an additional bilateral or periodic symmetric constraint for symmetric structures, and then extend the proposed energy penalization method to an ITO–MMC with a symmetric constraint. The energy penalization method can solve the problems of numerical instability and convergence for the ITO–MMC and the ITO–MMC subjected to the structural symmetric constraint with asymmetric loads. Topology optimization problems of asymmetric, bilateral symmetric, and periodic symmetric structures are discussed to validate the effectiveness of the proposed energy penalization approach. Compared with the conventional ITO–MMC, the energy penalization method for the ITO–MMC can improve the convergence rate from 18.6% to 44.5% for the optimization of the asymmetric structure. For the ITO–MMC under a bilateral symmetric constraint, the proposed method can reduce the objective value by 5.6% and obtain a final optimized topology that has a clear boundary with decreased iterations. For the ITO–MMC under a periodic symmetric constraint, the proposed energy penalization method can dramatically reduce the number of iterations and obtain a speedup of more than 2.     

Distribution-free double-sampling precedence monitoring scheme to detect unknown shifts in the location parameter

In most applications, parametric monitoring schemes are used to monitor the majority of industrial and nonindustrial processes in order to improve the quality of the outputs or services. However, parametric monitoring schemes are known to underperform when the normality assumption is not met or when there is not enough information about the symmetry or asymmetry nature of the process underlying distribution. Hence, in this paper, a new nonparametric Phase II Shewhart-type double-sampling (DS) monitoring scheme based on the precedence statistic is proposed in order to efficiently monitor quality processes when the underlying process distribution departs from normality. The performance is investigated using the average run length (ARL), standard deviation of the run length (SDRL), expected ARL (EARL) and expected average number of observations to signal (EANOS), and the average sample sizes (ASS) metrics. The latter metrics are computed using Monte Carlo simulation and exact formulae. In general, it is shown that the new DS precedence scheme outperforms the existing basic Shewhart precedence scheme with and without supplementary runs rules in many situations. A real-life illustrative example based on a filling process of milk bottles is provided to demonstrate the application and implementation of the new DS precedence monitoring scheme.     

基于双通道三维效果宿主图像半色调全息水印

随着现代社会对信息承载量的需求越来越多,提出了一种基于双通道的三维效果宿主图像的半色调全息水印方法。该方法利用双通道技术将两幅三维效果宿主图像的半色调全息水印图像合成一幅图,接着制作成计算全息图,在重现的时候,一幅计算全息图能够显示出两幅水印图像。制作成的计算全息图可以增加信息传输中的安全性与保密性,双通道技术可以增加传输过程中的信息量,三维效果技术可以在不改变编码效率的情况下增强视觉效果。半色调编码全息水印能更好地提升全息水印的鲁棒性。     

基于分块DCT变换的数字盲水印算法的应用

为了解决图片类信息加密易破解的问题,更好地对相关产品的版权加以保护,采用一种基于分块离散余弦变换(DCT)的数字盲水印算法。图像经分块后先进行DCT变换,从空域变换到频域,然后进行水印的嵌入和提取,最后与基于小波变换域的数字水印算法的实验进行对比。研究表明,该算法在峰值信噪比为52.588 3 dB时,可以为图像提供良好的水印透明性,且对噪声、剪切等攻击有明显的抵抗效果,同时具有良好的鲁棒性。     

Trudinger-Moser不等式的两种证明方法

Trudinger-Moser不等式在研究带有临界指数增长非线性项的偏微分方程解的存在性问题上有着重要的应用.在径向空间中利用施瓦兹对称重排，基于单位分解的技巧取截断函数是证明Trudinger-Moser不等式的两种主要方法.     

点对称结构的利用

利用结构力学力法原理和对称性导出点对称结构在正对称荷载和反对称荷载作用下的反力和内力特征，并通过例题验算比较可知利用该结论计算点对称结构更加简便。