静电纺PA6/CTS/LiCl纳米纤维膜的制备研究

采用静电纺丝技术制备聚酰胺6(PA6)/壳聚糖(CTS)/氯化锂(LiCl)纳米纤维膜,考察了CTS、PA6及LiCl添加量对纳米纤维膜形貌、直径分布的影响。通过场发射扫描电子显微镜、傅里叶变换红外光谱仪对纳米纤维膜的微观形貌及表面官能团进行分析。结果表明:在PA6添加量为1.8g、CTS添加量为0.3g、LiCl添加量为0.12g的条件下,纺丝效果最佳,纤维平均直径为103nm。傅里叶变换红外光谱分析表明PA6/CTS/LiCl纳米纤维膜具有PA6和CTS的特征吸收峰,PA6/CTS/LiCl纳米纤维膜有望作为滤膜材料使用。     

窄直径分布竹节状纳米碳管膜的制备和表征

采用短时间一次阳极氧化法制备了纳米级孔氧化铝(AAO)模板,有效地缩短了模板的制备时间,获得的AAO模板孔洞排列有序程度虽有所下降,但分布依然均匀.该模板有效地增加了表面积,为金属沉积提供了均匀的纳米孔洞.采用电沉积法在AAO模板上沉积了颗粒尺寸一致且分布均匀的钴催化剂层后,用CVD法在该模板上生长纳米碳管.经SEM和TEM观察,所制得的纳米碳管密度高直径分布均匀,具有单一的竹节状结构,而且直径远小于孔径.试用了生长动力学来解释这种竹节状纳米碳管的形成原因.     

模板法制备一维聚合物纳米材料的研究进展

一维聚合物纳米材料具有特殊的结构和性能，在纳米器件、药物释放、纳米传感器等方面有应用前景。采用模板法可以制备结构可控、排列规整的一维聚合物纳米材料。通常选用具有纳米孔洞的多孔膜作模板，通过在模板孔洞中进行电化学或化学聚合，或将聚合物的溶液或熔体引入孔洞中进行制备。文中综述了近年来采用模板法制备一维聚合物纳米材料的研究进展。     

抗打印扫描彩色图像水印算法

目的设计一种适用于彩色打印扫描图像的鲁棒性盲水印算法。方法结合四元数傅里叶变换及离散小波变换的优点,提出了一种双变换域全息水印算法。利用四元数傅里叶变换及离散小波变换,将全息水印信息分散嵌入到彩色宿主图像3个色彩分量的低频小波系数区域,而不引起大的图像失真,同时,算法实现了盲提取。结果算法满足不可见性要求,同时打印扫描实验证明,该算法具有抵抗打印扫描攻击的能力。结论结合四元数傅里叶变换及离散小波变换的双变换域水印算法,保留了2种变换域在处理彩色图像中的优点,在应用于打印扫描彩色图像时,效果比现有算法更好。     

利用傅里叶变换提取图像纹理特征新方法

研究发现,由图像傅里叶周向谱传统算法得到的频谱分布不能够真正反映其频率特性。因此,根据傅里叶变换的共轭对称性,提出了更具有一般性的长方环傅里叶周向谱能量百分比新算法。该算法均匀地把图像功率谱分成20个等间距同心长方环,计算每一个长方环内功率谱能量占总能量的比值作为图像频率分布特征。实验证明,新算法能更好地反映具有一般性的不同频率图像的纹理特征。在对作物缺乏营养元素诊断识别研究中,新算法提取的特征有效性远远高于传统算法,使识别的准确率达到82%以上。     

关于用matlab实现傅里叶变换的探讨

基于matlab强大的数值计算功能,借助快速傅里叶变换,建立一个函数的快速傅里叶变换和逆变换的模型,并进行运行和分析,实现快速傅里叶变换在信号处理方面的强大而简捷的功能。傅里叶分析就是我们测量出复杂波形,然后寻求确定其中有哪些频率成分。确定一个已知波形的频谱的过程。快速傅里叶变换是一种计算机算法,它从计算机采集到的数据中计算频谱。用快速傅里叶分析可以把复杂信号分解成简谐信号之和,看到信号的本质。     

PVA-SbQ/透明质酸复合纳米纤维的制备及表征

以不同质量分数(0%、0.5%、1%、2%)的透明质酸和聚乙烯醇-苯乙烯基吡啶盐缩合物(PVA-SbQ)为原料,通过高压静电纺丝制得PVA-SbQ/透明质酸复合纳米纤维。利用扫描电子显微镜(SEM)观察比较光交联前后复合纳米纤维的形貌特征,采用傅里叶变换红外光谱(FT-IR)测试分析复合纳米纤维膜的化学性质,利用热重分析仪(TGA)表征复合纳米纤维膜的热稳定性能,采用界面张力仪表征复合纳米纤维膜的吸水性能。结果表明,透明质酸的加入使PVA-SbQ/透明质酸复合纳米纤维直径增加,热稳定性降低,吸水性能下降。光交联后,PVA-SbQ/透明质酸复合纳米纤维膜中纤维粗细不均匀,纤维排列更加紧密。该复合材料作为面膜材料的基材具有良好的应用前景。     

PMMA/MMT纳米纤维的制备及表征

以乳液聚合制备的含有不同比例(0%、1%、3%、5%(质量分数))蒙脱土(MMT)的聚甲基丙烯酸甲酯/蒙脱土(PMMA/MMT)为原料,通过高压静电纺丝制得PMMA/MMT复合纳米纤维.采用凝胶渗透色谱法(GPC)、傅里叶变换红外光谱(FT-IR)分别测试分析了聚合物的分子量及分子结构,采用电子显微镜(SEM)观察了纳米纤维毡的整体形貌及直径分布,同时借助液滴形状分析仪对复合纳米纤维润湿性能进行了测试和分析.结果表明,MMT的加入对PMMA的分子量及分子结构均有影响.从而进一步影响了所制备纳米纤维的形貌和亲油性能.     

氧化铝模板的研究进展

阳极氧化铝（Anodic Aluminum Oxide，AAO）模板具有独特的纳米数量级的多孔结构，其孔洞孔径大小一致，排列有序，分布均匀。以阳极氧化铝为模板合成零维纳米材料、一维纳米材料（纳米线，纳米管）具有制备效率高、可靠性好等优点，已成为纳米复制技术的关键之一。目前，利用AAO模板已经可以合成多种介观结构材料。重点综述了近年来AAO模板制备及应用进展。     

静电纺丝法制备聚丙烯腈/聚醋酸乙烯酯复合纳米纤维膜

采用静电纺丝法制备了聚丙烯腈(PAN)/聚醋酸乙烯酯(PVAc)复合纳米纤维膜。利用原子力显微镜(AFM)、电子显微镜(SEM)分析了纤维的直径分布、整体形貌及单根纳米纤维的表面形貌;利用傅里叶变换红外光谱(FT-IR)分析了PAN、PAN/PVAc、PVAc纳米纤维膜的化学组成;同时借助热重(TG)分析了PVAc的加入对复合纤维膜热性能的影响。结果表明,当m(PAN)∶m(PVAc)=5∶5、质量分数为10%时,所得纤维膜最有利于制备聚合物电解质膜;PAN与PVAc之间产生配位键,从而提高了纤维膜的热性能。     

Ru nanostructure fabrication using an anodic aluminum oxide nanotemplate and highly conformal Ru atomic layer deposition

We fabricated metallic nanostructures directly on Si substrates through a hybrid nanoprocess combining atomic layer deposition (ALD) and a self-assembled anodic aluminum oxide (AAO) nanotemplate. ALD Ru films with Ru(DMPD)(EtCp) as a precursor and O(2) as a reactant exhibited high purity and low resistivity with negligible nucleation delay and low roughness. These good growth characteristics resulted in the excellent conformality for nanometer-scale vias and trenches. Additionally, AAO nanotemplates were fabricated directly on Si and Ti/Si substrates through a multiple anodization process. AAO nanotemplates with various hole sizes (30-100?nm) and aspect ratios (2:1-20:1) were fabricated by controlling the anodizing process parameters. The barrier layers between AAO nanotemplates and Si substrates were completely removed by reactive ion etching (RIE) using BCl(3) plasma. By combining the ALD Ru and the AAO nanotemplate, Ru nanostructures with controllable sizes and shapes were prepared on Si and Ti/Si substrates. The Ru nanowire array devices as a platform for sensor devices exhibited befitting properties of good ohmic contact and high surface/volume ratio.     

Fabrication of polypyrrole-based nanoelectrode arrays by colloidal lithography

This paper describes a novel technique to produce polypyrrole-based nanoelectrodes for electrochemical detection purpose. The fabrication process relies on the creation of patterned nanotemplates i.e., nanometric gold spots surrounded by an electrically insulating material (SiO(x)). From these templates, polypyrrole nanopillars are grown by classical electrochemical methods. Atomic force microscopy demonstrates that polypyrrole grows selectively inside the gold nanotemplates. The electrochemical characterization by cyclic voltammetry showed a sigmoidal-shaped voltammogram characterizing the typical nanoelectrode array behavior.     

Phonon confinement effects in hybrid virus-inorganic nanotubes for nanoelectronic applications

Genetically modified viruses have been proposed recently as templates for the assembly of nanometer-scale components of electronic circuits. Here we show that, in addition to their role as nanotemplates, viruses can actually improve the electron transport properties in semiconductor nanotubes grown on them. In the considered hybrid virus-inorganic nanostructures, which consist of silica or silicon nanotubes deposited on tobacco mosaic viruses, the confined acoustic phonons are found to be redistributed between the nanotube shell and the acoustically soft virus enclosure. As a result, the low-temperature electron mobility in the hybrid virus-silicon nanotube can increase by a factor of 4 compared to that of an empty silicon nanotube. Our estimates also indicate an enhancement of the low-temperature thermal conductivity in the virus-silicon nanotube, which can lead to improvements in heat removal from the hybrid nanostructure-based nanocircuits.     

Two-dimensional Corrosion Pit Initiation and Growth Simulation Model

A two-dimensional corrosion initiation and growth model for aircraft aluminum materials is developed. The model takes into account the electro-chemical parameters as well as specific rules governing corrosion mechanisms. The simulation program is implemented in a cellular automata framework. The corrosion initiation and growth patterns obtained from simulations are compared qualitatively and quantitatively to the experimental data obtained from the Center for Materials Diagnostics at the University of Dayton Research Institute, Dayton. The results indicate that the present model effectively captures the corrosion damage process including initiation and growth. The effects of various electro-chemical parameters on the damage growth obtained from the simulation are presented and discussed. The results presented illustrate a new approach to modeling corrosion damage in aircraft aluminum materials. The simulation program is developed in a JAVA environment for ease of portability and usability.     

Polyelectrolyte microshells as carriers for fluorescent sensors: loading and sensing properties of a ruthenium-based oxygen indicator

A strategy for the design and fabrication of microcapsule-based fluorescent biosensors containing indicators and internal references is described. The rationale for this work is the physical immobilization and chemical separation of assay chemistry for use in biological environments. Using the general approach of depositing oppositely charged species on colloidal micro/nanotemplates, a sensor system employing polyelectrolyte microshells for uptake of functional molecules is proposed, and experiments to demonstrate the feasibility of nanoengineering the sensor properties are described in the context of an oxygen sensor. Methods for immobilization and entrapment of fluorescent indicator and reference dyes are shown, along with the pH dependence of this process. Embedded dyes are shown to be stable and retain their function, as demonstrated with oxygen-sensitivity experiments of loaded microcapsules. Although oxygen sensitivity is presented as an example of a specific application, the overall strategy is likely more generally useful. The work suggests that polyelectrolyte microshells may be used as a platform to develop novel sensors by entrapment of functional materials.     

Numerical analysis of heat-induced transients in forced flow helium cooling systems

This work investigates theoretically the consequences of a space and time dependent energy input into the cooling system of a forced flow cooled superconducting magnet. Based on a proved computer code for calculation of instationary fluid flows, a new program was developed which is able quantitatively to calculate pressure and temperature transients caused by heat pulses. The program was checked by comparing the results with those of a simulation experiment. A further test was made by comparison with stationary flow results calculated from a well know program. In combination with computer programs, which are able to calculate the quench propagation in a current loaded superconductor, the numerical procedure allows for the investigation of the influence of transient helium flow processes on the stability of the superconductor. Our program is proposed as a good tool for the design of forced flow cooling systems of large superconducting magnets.     

基于情境感知的O2O小程序设计策略研究

目的探索情境感知理论在O2O小程序设计中的应用,提出基于情境感知理论与KANO-AHP模型的O2O小程序设计流程,旨在定性、定量地分析用户需求,为O2O小程序的设计提供以用户体验为中心的指导建议。方法以情境感知理论为基础,从用户情境、产品情境、环境情境三方面分析用户对O2O小程序功能和设计上的需求,并结合专家用户访谈对需求进行修正,得出用户需求集合;随后运用KANO模型对各项需求进行筛选与分类,构建O2O小程序的用户需求层次结构;再通过AHP法确定各项用户需求权重及重要性排序,进而提出设计策略。结论通过运用情境感知理论和KANO-AHP模型,全面、准确地分析了二十二项O2O小程序用户需求,并对综合权重位列前十的用户需求进行分析,分别从产品架构、内容展示、便捷服务三方面提出设计策略和建议,为O2O小程序的设计提供重点,提高O2O小程序的用户体验和满意度。     

Hollow Ag/Pd triangular nanoplate: a novel activator for electroless nickel deposition

Hollow Ag/Pd triangular nanoplates have been successfully prepared by a galvanic displacement reaction, in which added Pd(2+) ions react with Ag triangular nanoplates as templates. By altering the sizes of the Ag nanotemplates, Ag/Pd triangular nanoplates of different sizes can be prepared. Additionally, the large alloy nanoplates show maximum electrochemical activity when Ag/Pd triangular nanoplates of different sizes are applied as new activators for electroless nickel deposition.     

Patterned assembly of genetically modified viral nanotemplates via nucleic acid hybridization

The patterning of nanoparticles represents a significant obstacle in the assembly of nanoscale materials and devices. In this report, cysteine residues were genetically engineered onto the virion surface of tobacco mosaic virus (TMV), providing attachment sites for fluorescent markers. To pattern these viruses, labeled virions were partially disassembled to expose 5' end RNA sequences and hybridized to virus-specific probe DNA linked to electrodeposited chitosan. Electron microscopy and RNAase treatments confirmed the patterned assembly of the virus templates onto the chitosan surface. These findings demonstrate that TMV nanotemplates can be dimensionally assembled via nucleic acid hybridization.     

Determining the parameters of helium accumulation centers in irradiated silicon carbide from thermodesorption spectra

A model of helium thermodesorption from irradiated silicon carbide is proposed. The yield of helium from this material in the course of thermal annealing is quantitatively estimated. The energy parameters of the defect structure of silicon carbide are determined.