酸碱改性ZSM-5分子筛及其噻吩烷基化性能的研究

首先采用碱处理HZSM-5分子筛,然后采用不同浓度的柠檬酸酸洗碱处理后的HZSM-5分子筛,制备具有微孔-介孔多级孔HZSM-5分子筛.通过XRD、SEM、BET和NH3-TPD等表征手段对处理后催化剂进行表征,考察了碱处理后酸洗对HZSM-5分子筛孔结构性质的影响,结果表明:适当浓度的柠檬酸酸洗碱处理后的ZSM-5分子筛,能够清除掉残留在分子筛孔道内的杂质,增大了分子筛的孔径;在小型固定床反应器上,研究了改性前后分子筛的噻吩烷基化反应活性和稳定性,结果表明:碱处理后采用适当浓度的柠檬酸酸洗后,催化剂的初活性虽然低于碱改性的分子筛,但稳定性较好,更适合噻吩烷基化反应.     

Fabrication of crystalline selenium microwire

A method of fabricating selenium(Se) microwire is demonstrated.A multimaterial fiber with amorphous selenium(a-Se) core and multicomponent phosphate glass cladding is drawn by using a conventional optical fiber drawing technique.Then the a-Se core of the fiber is crystallized by a post thermal process at 150 ℃.After the multicomponent phosphate glass cladding is stripped from the multimaterial fiber by marinating the fiber in HF acid solution,a crystalline selenium(c-Se)microwire with high uniformity and smooth surface is obtained.Based on microstructure measurements,the c-Se microwire is identified to consist of most hexagonal state particles and very few trigonal state whiskers.The good photoconduction property of c-Se microwire with high quality and longer continuous length makes it possible to apply to functional devices and arrays.     

The electronic,optical,and thermodynamical properties of tetragonal,monoclinic,and orthorhombic M_3N_4(M=Si,Ge,Sn):A first-principles study

A detailed study of the M_3N_4(M = Si,Ge,Sn) nitrides in their tetragonal,monoclinic and orthorhombic phases has been performed with the plane-wave pseudo-potential method combined with the quasi-harmonic approximation,including the phononic effects.We rationalize the main puzzle,i.e.,the fundamental properties of these phases are unclear,by calculating the crystal structures,density of states,and optical properties.The direct band gaps of t-Ge_3N_4,m-Si_3N_4,and o-Ge_3N_4 benefit the opto-electrical properties,t-,m-,and o-Si_3N_4 can be used as refractive materials while m-M_3N_4(M = Si,Ge,Sn) are optically transparent in the visible light region.Our results improve the understanding of the detailed electronic structures of all compounds,as well as the influences of electronic structure on their stabilities.Furthermore,we find that thermodynamic quantities are sensitive to structures and,therefore,depend on various temperature and pressure conditions.     

四方、单斜和正交Ge3N4的结构、电子结构和热力学性质

数值计算了四方、单斜和正交结构Ge₃N₄的点阵常数、晶胞体积、弹性模量、维氏硬度和态密度.计算结果与已有的实验数据和理论值符合得很好.形成焓为负、晶格形变和晶胞体积随压强呈线性变化,表明三种相在0~20 GPa压强范围内可以保持结构稳定.态密度研究表明三种氮化锗内部存在强烈的s-p杂化.三种相都属于脆性半导体材料,具备各向异性且硬度适中.采用包含原子振动和非谐效应的准谐波近似方案,研究材料的热力学性质,发现压强对赫姆霍兹自由能和内能有显著影响.结果为进一步理解氮化锗三种新结构的电子结构和热力学性质提供初步的物理图像.     

1,1''联萘-2,2''-二胺拉曼和红外光谱的实验和DFT计算研究

实验测量了1,1''-联萘-2,2''-二胺（BINAM）的红外吸收光谱、可见光激发普通拉曼光谱、紫外共振拉曼光谱.用电子密度泛函方法计算了BINAM的基态几何构型、振动频率、普通拉曼和近共振拉曼强度.通过实验和理论计算对比,对所得红外和拉曼提出了详细的指认,并且分析了各振动模式的特征.BINAM的紫外共振拉曼光谱与普通拉曼光谱相比较,发现有若干拉曼谱带出现了选择性共振增强.基于共振拉曼强度分析,讨论了BINAM可能的激发态几何结构的变形.     

Finite-time robust control of uncertain fractional-order Hopfield neural networks via sliding mode control

The finite-time control of uncertain fractional-order Hopfield neural networks is investigated in this paper. A switched terminal sliding surface is proposed for a class of uncertain fractional-order Hopfield neural networks. Then a robust control law is designed to ensure the occurrence of the sliding motion for stabilization of the fractional-order Hopfield neural networks. Besides, for the unknown parameters of the fractional-order Hopfield neural networks, some estimations are made. Based on the fractional-order Lyapunov theory, the finite-time stability of the sliding surface to origin is proved well. Finally, a typical example of three-dimensional uncertain fractional-order Hopfield neural networks is employed to demonstrate the validity of the proposed method.     

Predictions of pressure-induced structural transition, mechanical and thermodynamic properties of α-and β-Si3N4 ceramics: ab initio and quasi-harmonic Debye modeling

The plane-wave pseudo-potential method within the framework of ab initio technique is used to investigate the structural and elastic properties of α-and β-Si3N4.The ground-state parameters accord quite well with the experimental data.Our calculation reveals that α-Si3N4 can retain its stability to at least 40 GPa when compressed at 300 K.The α→β phase transformation would not occur in a pressure range of 0-40 GPa and a temperature range of 0-300 K.Actually,the α→β transition occurs at 1600 K and 7.98 GPa.For α-and β-Si3N4,the c axes are slightly more incompressible than the a axes.We conclude that β-Si3N4 is a hard material and ductile in nature.On the other hand,β-Si3N4 is also found to be an ionic material and can retain its mechanical stability in a pressure range of 0-10 GPa.Besides,the thermodynamic properties such as entropy,heat capacity,and Debye temperature of α-and β-Si3N4 are determined at various temperatures and pressures.Significant features in these properties are observed at high temperature.The calculated results are in good agreement with available experimental data and previous theoretical values.Many fundamental solid-state properties are reported at high pressure and high temperature.Therefore,our results may provide useful information for theoretical and experimental investigations of the Si3N4 polymorphs.     

布尔函数的c导数及其在组合电路故障检测中的应用

提出了布尔函数c导数的定义和性质,并给出了部分性质的证明. 在此基础上,提出了求解“或”搭接及“与”搭接故障测试矢量的2个定理. 通过实例讨论了布尔函数c导数在组合逻辑电路故障检测中的应用.所提出的c导数是对布尔函数的布尔导数和e导数研究的补充与完善.     

基于QuEChERS提取的快速液相色谱-串联质谱法测定婴幼儿谷基辅助食品中的9种真菌毒素

建立了婴幼儿谷基辅助食品中黄曲霉毒素B1、B2、G1、G2、赭曲霉毒素A、玉米赤霉烯酮、T-2毒素、脱氧雪腐镰刀菌烯醇、伏马毒素B1共9种真菌毒素的快速测定方法。试样用改良的QuEChERS方法进行提取,无需进一步净化,直接用液相色谱-串联质谱仪进行测定,基质外标法定量。在较宽的线性范围内,9种毒素的线性相关系数(r²)均不小于0.98,检出限为0.1~15.8 μg/kg,在3个不同添加水平下的加标回收率为77.6%~105.7%,RSD为2.5%~13.7%。采用建立的方法对市面上销售的41批次婴幼儿谷基辅助食品中的9种真菌毒素进行了筛查,数批产品检出不同含量的毒素。该方法准确、灵敏,可适用于婴幼儿谷基辅助食品中多种真菌毒素的快速分析。     

基于聚乙烯醇聚合物点制备荧光纳米复合材料

近年来, 由于聚合物点(PDs)具有良好的荧光性质和光收集能力, 受到了人们广泛的关注, 应用在生物成像和检测等领域. 然而, 目前报道的聚合物点大多数是指共轭聚合物经过组装、固定形成的, 因此聚合物点保持着形成之前的共轭聚合物的相关性质, 且具有更好的稳定性和进一步功能化的能力. 本文中我们研究的聚合物点是指从非共轭线性聚合物为原料而制备的聚合物点, 这类聚合物包括聚环氧乙烯, 多糖等. 聚合物点不仅包含使其具有荧光的碳化中心, 还具有外围的聚合物链结构. 因此, 可以拓展应用聚合物点的聚合物特性. 我们利用PDs的荧光中心和外围的聚合物链双功能性质, 详细研究了基于PDs制备功能性纳米复合材料体系. 首先, 我们原位制备了聚乙烯醇/PDs纳米复合膜材料(PDs是直接通过聚乙烯醇可控碳化而产生的). 复合材料不仅保持了PDs的荧光特性, 还保持了聚乙烯醇易加工的特性, 如可以制备成纳米复合膜材料, PDs含量可以根据需要调控: 0, 20%, 40%, 60%, 80%, 100%. 纳米复合膜材料在不同激发光下具有多颜色发光性质. 进一步的, 我们验证了PDs水溶液可以和很多其他水溶性聚合物, 石墨烯量子点或半导体量子点实现共混, 从而制备双功能性纳米复合材料.