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.     

改进LSB算法及其在BMP图像中的应用

首先分析了BMP图像文件格式，然后根据传统LSB算法在BMP图像文件中应用，提出一种改进的LSB隐藏算法，提高了伪装图像质量。最后通过仿真验证了该算法的优越性。     

不敏感含能化合物5,7-二氨基-4,6-二硝基苯并连三唑-1-氧化物的合成、表征与性能（英）

以苦基氯和水合肼为原料,经过环化反应和异常亲核取代氢(VNS)反应合成了不敏感含能化合物5,7--二氨基-4,6-二硝基苯并三连唑-1-氧化物(2),总收率为31％.通过1H NMR,13C NMR,FT-IR和元素分析表征了题称化合物及其中间体的结构.优化了VNS反应条件.推测了4,6-二硝基苯并三连唑-1-氧化物(1)环化反应机理.利用量子化学的方法对题称化合物进行了静电势(ESP)和电子轨道的计算.对中间体4,6-二硝基苯并三连唑-1-氧化物和题称化合物进行了物化爆轰及热性能研究.结果表明,确定的适宜的VNS反应条件为:盐酸羟胺为VNS试剂,室温下反应5h.题称化合物具有不敏感特性及良好的热稳定性.化合物1中引入两个氨基后形成的化合物2的密度和热稳定性均有所提高,两种化合物的热分解温度分别为201.3,248.5℃,密度分别为1.73,1.76 g·cm-3,爆速分别为7371.13,7396.7 m·s-1.     

Effect of equivalent and non-equivalent Al substitutions on the structure and electrochemical properties of LiNi0.5Mn0.5O2

Pristine, equivalently and non-equivalently Al substituted LiNi_0.5Mn_0.5O₂ materials were prepared by a combination of co-precipitation and solid-state reaction. As shown by XRD and XPS, lattice volume shrinkage of LiNi_0.5(Mn_0.45Al_0.05)O₂ was attributed to the presence of Ni in both 2+ and 3+, while the lattice volume expansion of Li(Ni_0.45Al_0.05)Mn_0.5O₂ was caused by lowering the average oxidation state of Mn. Electrochemical performance of LiNi_0.5Mn_0.5O₂ materials can be greatly affected by the change of oxidation states of the transition metals by Al substitution. Non-equivalent substitution of Al for Ni leads to deteriorated discharge performance and cyclic stability due to the reduction of the electrochemical active Ni²⁺ and structure supported Mn⁴⁺, while an increase in the amount of Ni²⁺ in LiNi_0.5(Mn_0.45Al_0.05)O₂ brings obvious improvement of the electrochemical properties. EIS analyses of the electrode materials at pristine and charged states indicate that the poor electrochemical performance of Li(Ni_0.45Al_0.05)Mn_0.5O₂ material can be ascribed to the higher charge transfer resistance and surface film resistance, and the observed higher current rate capability of LiNi_0.5(Mn_0.45Al_0.05)O₂ can be understood due to the better charge transfer kinetics.     

B位取代对钛酸锌相结构及介电性能的影响

通过固相烧结法结合半化学法制备了ZnO-(1-x)TiO2-xSnO2(x=0.04~0.20)陶瓷,掺杂1.0%3V2O5(质量分数)-B2O3降低陶瓷的烧结温度,研究了B位取代对ZnTiO3相结构及介电性能的影响。结果表明,Sn的加入促进了六方相分解,形成了立方尖晶石结构的固溶相Zn2(Ti1-xSnx)O4;随烧结温度升高,Sn的固溶量增加,900℃时,最大固溶量为0.08 mol。900℃烧结试样,随x增加,其介电常数ε先增大后减小,而介电损耗tanδ恰好相反,先减小后增大,当x=0.12时,得到ε的最大值(ε=29)和tanδ的最小值(tanδ=9.86×10-5)。900℃烧结的具有优良介电性能的ZnO-(1-x)TiO2-xSnO2(x=0.04~0.20)陶瓷有很好的实际应用前景。     

空分设备的清洗

文章介绍了空分设备及其性能特点，空分设备的工艺流程，空分设备表面清洁度及其检查方法，指出通过清洗降低空分设备表面油脂的残留量对保障空分设备性能的正常发挥有着重要意义，过去通常采用四氯化碳作清洗剂，文章研究了在淘汰ODS新形势下可采用的清洗剂和清洗技术，介绍了在这方面取得的成果和经验。     

In Situ Scanning Electron Microscopy Observation of Growth Kinetics and Catalyst Splitting in Vapor–Liquid–Solid Growth of Nanowires

In situ observations during vapor–liquid–solid (VLS) growth of semiconductor nanowires in the chamber of an environmental scanning electron microscope (ESEM) are reported. For nanowire growth, a powder mixture of CdS and ZnS is used as a source material and silver nanoparticles as a metal catalyst. Through tracing growth kinetics of nanowires, it is found that nanowires with a relatively bigger catalyst droplet on the tip grow faster. Intriguingly, it is also found that the growth of nanowires can involve catalyst splitting: while the majority of catalyst remains at the nanowire tip and continues facilitating the growth, a portion of it is removed from the tip due to the splitting. It remains attached to the nanowire at the position where the splitting occurred and subsequently induces the growth of a nanowire branch. As far as it is known, this is the first time that catalyst splitting is revealed experimentally in situ. It is proposed that the instability of catalyst droplet caused by the volume increase is the main reason for the splitting. It is believed that in situ growth inside the ESEM can largely enrich our understanding on the metal‐catalyzed VLS growth kinetics, which may open up more opportunities for morphology‐controlled synthesis of 1D semiconductor nanowires in future study.     

Zn~(2+)、Sn~(4+)共取代对YIG铁氧体性能的影响

该文通过1 400℃固相烧结制备出Zn2+和Sn4+共取代的Y3Fe5-2xZnxSnxO12(x=0~0.35)铁氧体材料,详细研究了离子取代量对钇铁石榴石铁氧体微观结构及磁性能的影响。研究表明,Zn2+、Sn4+都进入了钇铁石榴石铁氧体的晶格中。随着离子取代量的增加,钇铁石榴石铁氧体的密度与饱和磁化强度先增大后减小;其磁损耗则先减小后增大,在x=0.25时磁损耗取得最小值。该研究进一步说明了Zn2+和Sn4+取代在一定范围内可有效降低材料的磁损耗及控制材料的饱和磁化强度。     

Constructing Na‐Ion Cathodes via Alkali‐Site Substitution

Na‐ion batteries have experienced rapid development over the past decade and received significant attention from the academic and industrial communities. Although a large amount of effort has been made on material innovations, accessible design strategies on peculiar structural chemistry remain elusive. An approach to in situ construction of new Na‐based cathode materials by substitution in alkali sites is proposed to realize long‐term cycling stability and high‐energy density in low‐cost Na‐ion cathodes. A new compound, [K_0.444(1)Na_1.414(1)][Mn_3/4Fe_5/4](CN)₆, is obtained through a rational control of K⁺ content from electrochemical reaction. Results demonstrate that the remaining K⁺ (≈0.444 mol per unit) in the host matrix can stabilize the intrinsic K‐based structure during reversible Na⁺ extraction/insertion process without the structural evolution to the Na‐based structure after cycles. Thereby, the as‐prepared cathode shows the remarkably enhanced structural stability with the capacity retention of >78% after 1800 cycles, and a higher average operation voltage of ≈3.65 V versus Na⁺/Na, directly contrasting the non‐alkali‐site‐substitution cathode materials. This provides new insights into alkali‐site‐substitution constructing advanced Na‐ion cathode materials.     

中国全要素天然气利用效率区域差异性

提高天然气利用效率是促进我国能源资源优化配置,构建清洁低碳、安全高效现代能源体系的重要途径之一。以往对天然气利用效率的研究忽略了要素替代、非径向以及环境约束等问题,致使测算结果存在着一定的偏差。为了从全要素框架的角度去测算天然气利用效率,基于2002—2016年中国各省、直辖市、自治区(以下简称省市区)的面板数据,采用Undesirable-Window-DEA模型,在考虑了能源消费异质性的基础上,测算了中国各区域全要素天然气利用效率。研究结果表明:(1)中国天然气利用效率在2002—2016年间呈现出持续改善的趋势;(2)中国东、中、西部3大区域的天然气利用效率存在着明显的差异,西部地区显著低于东、中部地区;(3) 2007年以后,中部地区天然气利用效率的改善速度远远超过东、西部地区,并且中部和东部的差异正在不断缩小;(4)中国各省市区天然气利用效率变动呈现出明显的两极分化趋势。在此基础上,提出了相关对策建议:(1)坚持绿色发展,优化产业结构,加快培育天然气产业链;(2)实施能源生产革命,构建清洁低碳、安全高效的能源供应体系;(3)优化能源消费结构,不断提高天然气消费比重。