基于图像重组和比特置乱的多图像加密

针对现有多图像加密算法只能同时加密多张同类型同大小的图像,适用范围不广、实用性差等问题,提出一种基于图像重组和比特置乱的多图像加密算法.该算法通过将任意数量、不同大小和不同类型的图像重新组合成新多灰度图,一次完成同时加密,极大提高了加密效率和适用范围.首先,依次提取所有待加密图像像素值重新组合出N张m×n新灰度图,并将其转化成m×n×8N二进制矩阵.然后,采用3D比特置乱方式,对高位页进行行列比特置乱,低位页进行整页比特置乱.最后,进行异或扩散操作,得到密文图像.高低位分开置乱提高了算法的抗噪声能力,最终密文信息熵达到7.999以上,很好地掩盖了明文的统计特性.构造一种新型Logistic与广义三阶Fibonacci级联的混沌系统产生随机序列,增加了初值和控制参数范围,扩大了密钥空间,使其达到8×10^84以上,极大地提高了抗穷举攻击能力.既提高了序列随机性,又同时保留了低维混沌系统的快速性.结合明文哈希值(SHA-256)产生密钥,明文像素值发生微小改变后密文像素值变化率达到0.996以上,极大地提高了的明文敏感性和算法抗选择明文攻击的能力.实验分析表明,提出的多图像加密算法安全性高、实用性强.     

Tuning the Composition and Structure of Ni@MoC Nanosheets for Highly Active and Stable Electrocatalysis in Water Splitting

The conventional electrolytic water-splitting process for hydrogen production is plagued by high energy consumption, low efficiency, and the requirement of expensive catalysts. Therefore, finding effective, affordable, and stable catalysts to drive this reaction is urgently needed. We report a nanosheet catalyst composed of carbon nanotubes encapsulated with MoC/Mo₂C, the Ni@MoC-700 nanosheet showcases low overpotentials of 275 mV for the oxygen evolution reaction and 173 mV for the hydrogen evolution reaction at a current density of 10 mA ⋅ cm⁻². Particularly noteworthy is its outstanding performance in a two-electrode system, where a cell potential of merely 1.64 V is sufficient to achieve the desired current density of 10 mA ⋅ cm⁻². Furthermore, the catalyst demonstrates exceptional durability, maintaining its activity over a continuous operation of 40 hours with only minimal attenuation in overpotential. These outstanding activity levels and long-term stability unequivocally highlight the promising potential of the Ni@MoC-700 catalyst for large-scale water-splitting applications.     

微波水热两步法合成高可见光响应Ag2S/ZnO及其光催化性能、机理

在不同的制备条件下,通过微波水热两步法获得了一系列Ag₂S/ZnO光催化剂,采用X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、紫外-可见漫反射吸收光谱(UV-Vis/DRS)、扫描电子显微镜(SEM)和N₂吸附-脱附等测试手段对产物结构和形貌进行了表征。结果表明,产物以六方纤锌矿ZnO为主,其晶型结构并未随着反应温度和Ag₂S物质的量的增加而改变。Ag₂S的引入显著增强了光催化剂在可见光区的吸收,使吸收边带发生红移,同时抑制了ZnO(001)晶面的生长。另外,所得产物的形貌随着Ag₂S物质的量的增加从爆米花状转变为少量的柱体颗粒,且BET比表面积经过复合后明显减小。以罗丹明B为目标降解物,研究并比较了一系列Ag₂S/ZnO光催化剂对罗丹明B的光降解性能。结果表明,n_Ag2S/n_ZnO=1:10时,光催化剂在紫外光、可见光和模拟日光的照射下具有最好的光催化效果,优于目前应用最广泛的市售P25。另外,所制备的光催化材料Ag₂S/ZnO经4次循环使用后,其降解效率没有明显下降,表明该催化材料具有一定的光催化稳定性。经捕获实验研究发现,在Ag₂S/ZnO的光催化反应中空穴起主要作用,并根据绝对电负性估算了复合材料Ag₂S/ZnO的能带位置,据此提出了可能的光催化反应机理。     

一元强碱滴定一元弱酸溶液的林邦滴定曲线方程及其应用

以林邦副反应思想为基础,用质子条件式PBE、物料平衡式MBE、滴定分数和条件稳定常数等知识推导出一元强碱滴定一元弱酸溶液的林邦滴定曲线方程,并用滴定曲线方程讨论了滴定开始至化学计量点时任意一点p H的计算。     

服役温度对多壁碳纳米管/Li1.18Ni0.15Co0.15Mn0.52O2复合正极材料性能的影响

通过煅烧的方式制得多壁碳纳米管(MWCNT)质量分数为3%的MWCNT/Li1.18Ni0.15Co0.15Mn0.52O2锂离子电池复合正极材料,并测试了复合正极材料在不同服役温度环境下的电化学性能:-20和60℃下服役时,其放电容量分别高达169、303 mAh·g^-1,且展示出良好的倍率性能和循环稳定性。结合电化学阻抗测试结果可知,MWCNT均匀附着在层状粒子的表面,有效减少了电解液对电极材料的侵蚀,阻碍了表面膜的生成,同时提高了材料的电子电导率。     

大麻中3种酚类成分测定专用固相萃取柱的设计与应用

大麻中的主要成分大麻二酚(CBD)、大麻酚(CBN)和Δ9-四氢大麻酚(Δ9-THC)的含量决定了其性质和应用。在液相色谱分析中,由于大麻提取液中含有较多杂质,需要净化。该文基于大麻中CBD、CBN和Δ9-THC的结构特征及样品基质组成,根据中性氧化铝、硅酸镁和石墨化炭黑的不同表面特征,考察了这3种吸附剂对大麻提取液中叶绿素、多糖、高级脂肪酸酯及重金属离子的去除率和对3种大麻酚的回收率,确定了3种吸附剂的用量分别为1.80 g、0.15 g、0.05 g混合装填成的2 g/6 mL小柱为3种大麻酚类化合物测定的专用固相萃取柱。该小柱对大麻乙酸乙酯-甲醇提取液样品中CBD、CBN和Δ9-THC的回收率分别为98.9%, 95.7%和99.2%,对叶黄素、叶绿素a和叶绿素b的去除率分别为96.3%、99.2%和95.5%,对总糖的去除率为98.5%,对脂肪酸甘油酯的去除率为96.9%,对重金属离子的平均去除率为85.4%。优化了色谱分析条件,采用Eclipse Plus C18色谱柱(50 mm×2.1 mm, 1.8 μm),在1%乙酸水溶液-乙腈(30∶70, v/v)流动相条件下等度洗脱,流速为0.5 mL/min,柱温为30 ℃,检测波长为210 nm,进样量为1 μL,在10 min内可完成样品分析。方法学考察表明,在0.5~50 mg/L范围内,CBD、CBN和Δ9-THC的液相色谱峰面积与其质量浓度呈良好的线性关系,相关系数(R²)分别为0.9983、0.9995和0.9981,检出限分别为0.45 μg/L、0.53 μg/L和0.38 μg/L,加标回收率为90.3%~97.0%、93.7%~95.6%、90.8%~96.1%,相对标准偏差(RSD)分别为2.2%~6.1%、4.1%~8.0%、2.4%~4.8%。研究结果表明,该文以中性氧化铝、硅酸镁和石墨化炭黑制作的复合型大麻酚类成分测定专用固相萃取柱在大麻植物中3种酚类化合物的测定中具有净化杂质、防止色谱柱污染的功能。由于大麻不同部位的化学成分存在差异,在后续的研究中,还要进一步考察小柱对其他杂质的去除情况,使得制备的固相萃取小柱更具有普适性。     

Wander of a Gaussian-Beam Wave Propagated Through a Non-Kolmogorov Turbulent Atmosphere

Both increasing experimental evidence and some results of theoretical investigation have shown that there exist two kinds of turbulence in the aerosphere, Kolmogorov and non-Kolmogorov turbulence. Thus, it is necessary to improve the theory of optical wave propagation through atmospheric turbulence, namely, study the laser-beam propagation in non-Kolmogorov turbulence, before analyzing the joint influence of the Kolmogorov turbulence and non-Kolmogorov one on satellite laser communication. The beam wander will lead to the performance degradation of satellite laser communication systems and exert an influence on the achievement and stability of its links. In this paper, we consider a theoretical power spectrum of refractive-index fluctuations with a generalized power law in order to derive the variance of Gaussian-beam wave wander in weak turbulence for a horizonal path and analyze the influence of spectral power-law variations on the beam wander. We show that the expression for the beam-wander variance is of concise closed form and independent of the optical wavelength.     

11-钨锌三元杂多阴离子层状化合物的合成、表征及催化活性

用离子交换法将具有K egg in结构11-钨锌三元杂多化合物K8[M ZnW11（H2O）O39]（M=Co2＋、N i2＋、Cu2＋、Cd2＋）嵌入到Zn2A l类水滑石中,得到层状化合物：Zn2A l-[M ZnW11（H2O）O39]（M=Co2＋、N i2＋、Cu2＋、Cd2＋）,并用XRD、IR、UV对其进行了表征。结果表明,杂多阴离子进入水滑石层间后,仍保留了其K egg in结构。利用层状化合物催化合成乙酸正丁酯考察其催化活性,结果表明,层状化合物在酯化反应中显示优良的催化性能。     

Synthesis of biodiesel over ZnO/Ca(OH)2/KF catalyst prepared by the grinding method

A novel ZnO/Ca(OH)₂/KF solid base catalyst was prepared by the grinding method and applied to biodiesel synthesis by the transesterification of soybean oil. The effect of various parameters such as KF molar amount, calcination temperature, the amount of catalyst, molar ratio of methanol to oil, reaction temperature, and time on the activity of the catalyst were investigated. The catalysts were characterized by several techniques of thermogravimetry/derivative thermogravimetry, X–ray diffraction, Hammett indicator method, and scanning electron microscopy. The analysis results indicated that the KF interacted with Ca(OH)₂ and formed KCaF₃ phase before calcination of the catalyst. The formed KCaF₃ crystal phase was the main catalytic active component for the catalyst activity. In addition, the basicity of ZnO/Ca(OH)₂/KF was greatly influenced by the different calcination temperates, and the catalyst activity was correlated closely with the basicity. A desired biodiesel yield of 97.6 % was obtained at catalyst amount of 3 %, methanol/oil of 12:1, and reaction time of 1.5 h at 65 °C.