A novel image encryption algorithm using chaos and reversible cellular automata

In this paper, a novel image encryption scheme is proposed based on reversible cellular automata (RCA) combining chaos. In this algorithm, an intertwining logistic map with complex behavior and periodic boundary reversible cellular automata are used. We split each pixel of image into units of 4 bits, then adopt pseudorandom key stream generated by the intertwining logistic map to permute these units in confusion stage. And in diffusion stage, two-dimensional reversible cellular automata which are discrete dynamical systems are applied to iterate many rounds to achieve diffusion on bit-level, in which we only consider the higher 4 bits in a pixel because the higher 4 bits carry almost the information of an image. Theoretical analysis and experimental results demonstrate the proposed algorithm achieves a high security level and processes good performance against common attacks like differential attack and statistical attack. This algorithm belongs to the class of symmetric systems.     

The electronic and magnetic properties with intrinsic defects in ZnO nanosheets: First-principles prediction

Using full-potential linearized augmented plane wave (FLAPW) method, we investigated the effects of intrinsic vacancies on electronic and magnetic properties in graphene-like ZnO nanosheets. The results show that the oxygen vacancy (V_O) has no influence on magnetism in ZnO nanosheet, whereas the Zn vacancy (V_Zn) lead to spin polarization of the nanostructures with a total magnetic moment of 2.0μ_B due to O-2p and Zn-3d hybridization. When the distance of two V_Zn defects increases to 6.499 Å, the system shows an intriguing half-metallic character with 100% spin-polarized carriers due to O(2p)–Zn(3d)–O(2p) coupling chain between two V_Zn defects.     

Determining polymer film thickness during manufacturing with broadband transmission

A novel broadband transmission method to determine polymer film thickness during manufacturing is proposed, and a measurement system is developed based on this method. The relationship between broadband optical power and film thickness is deduced according to the Lambert-Beer law. The system is composed of a halogen light and an optical power meter. Results show that the measurement error of this method is approximately 1 μm, and the resolution of the system is below 0.4 μm for polymer films with less than 100-μm thickness.     

Insight into 6π Electrocyclic Reactions of 1,8‐Dioxatetraene

A variety of benzofuranone‐based spiroisochromenes were originally designed and synthesized to gain insight into the oxa‐6π electrocyclic reaction of cis,cis‐1,8‐dioxatetraene for the first time. The stability of the 1,8‐dioxatetraene intermediate is governed by its steric congestion and can be fine‐tuned through modification of the backbone structure, leading to the reactivity differences in the 6π electrocyclic reaction and the emergence of photochromic properties.     

Synthesis of CuS@CoS2 Double‐Shelled Nanoboxes with Enhanced Sodium Storage Properties

Metal sulfides have received considerable attention for efficient sodium storage owing to their high capacity and decent redox reversibility. However, the poor rate capability and fast capacity decay greatly hinder their practical application in sodium‐ion batteries. Herein, an elegant multi‐step templating strategy has been developed to rationally synthesize hierarchical double‐shelled nanoboxes with the CoS₂ nanosheet‐constructed outer shell supported on the CuS inner shell. Their structure and composition enable these hierarchical CuS@CoS₂ nanoboxes to show boosted electrochemical properties with high capacity, outstanding rate capability, and long cycle life.     

Preparation,rheological and drag reduction properties of hydrophobically associating polyacrylamide polymer

Hydrophobically associating polymer (HAMDP) was synthesized by using acrylamide, acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid and dodecyl 2-methylacrylate as main monomers. Dynamic rheometer and self-made simulation evaluation apparatus were used to test the rheological and drag reduction properties of HAMDP. With the mass concentration increased, the apparent viscosity of HAMDP increased. The critical aggregation concentration was 2.29g/L. With the changement of the strain, the elastic modulus was larger than viscous modulus. With the increment of HAMDP, the area of thixotropic loop increased. Compared with commercial polyacrylamide, the drag reduction rate of HAMDP could be up to 62.38%.     

同核双金属烯烃聚合催化剂

与单核金属配合物催化剂相比,双核金属配合物催化剂所具的双金属活性中心对烯烃聚合催化活性和所得聚合物的性能(包括聚合物微结构、分子量大小和分子量分布)产生了重要影响。本文综述了双金属配合物作为均相催化剂催化乙烯聚合及共聚合的最新研究,归纳思路包括不同的金属类型,即基于前过渡金属(Zr, Ti, Hf) 和后过渡金属(Ni, Fe, Co) 的双核金属组合; 不同的配体化合物,即CGC配体、酚氧亚胺配体、氮杂环胺配体、α-二亚胺和亚胺吡啶配体等。这些研究表明,前过渡金属催化剂不仅解决了乙烯自聚还实现了乙烯与α-烯烃共聚;后过渡金属催化剂高效催化乙烯自聚合,其中铁和钴催化剂获得高度线性聚乙烯,镍催化剂则产生多支链聚乙烯。     

Strain softening in stretched DNA

The microscopic mechanics of DNA stretching was characterized using extensive molecular dynamics simulations. By employing an anisotropic pressure-control method, realistic force-extension dependences of effectively infinite DNA molecules were obtained. A coexistence of B and S DNA domains was observed during the overstretching transition. The simulations revealed that strain softening may occur in the process of stretching torsionally constrained DNA. The latter observation was qualitatively reconciled with available experimental data using a random-field Ising model.     

尺度缩小合成孔径激光成像雷达的孔径合成实验

设计了一种尺度缩小的合成孔径激光成像雷达(SAIL),在实验室平台上模拟实施远场传输条件,相应地解决了波前测量和外差质量监视技术,实现了一个目标点的方位向孔径合成实验,实验结果与理论预测相近.     

Origin7．5软件在大学物理综合设计性实验教学中的应用探讨

本文采用origin7．5软件对大学物理综合设计性实验数据的处理进行了探讨。实验结果揭示出了热敏电阻温度特性、光敏电阻伏安特性和光照特性。