一种控制化学混沌的新方法--在全混沌区的非线性人工神经网络偶然微扰反馈控制

提出了一种控制化学混沌的新方法以稳定控制不稳定周期轨道 (UPO) .这是一种偶然比例反馈控制 (OPF)战略的扩展 ,它克服了OPF局限性 ,即OPF控制律的线性限制 ,并扩展到全混沌区 .本方法利用反传人工神经网络 (BP ANN)来表达非线性控制律 ,以增加控制的鲁棒性 .其有效性通过一个混沌自催化反应模型的数值模拟进行了检验 .     

实验控制Belousov-Zhabotinsky-CSTR化学混沌反应

用两种方法来控制在连续流动釜式反应器(CSTR)中的Belousov-Zhabotinsky(BZ)化学混沌反应:(1)自适应延迟时间反馈控制方案;(2)线性自相互作用控制方案。第一种控制方案是一种微扰控制,并能将BZ-CSTR化学混沌稳定控制到其内嵌的不稳定周期轨道(UPO)上去。这种方法的优越之外可以由系统延迟时间的自适应调节得以显示。第二种控制方案可以驱动BZ-CSTR混沌动力学到达一系列规则的动力学状态,这些动力学状态可能并不是混沌轨道中内嵌的本征轨道。在控制BZ-CSTR化学混沌反应的实验中,这两种方案显示出了很大的灵活性和有效性。     

一种控制化学混沌的新方法

提出了一种控制化学混沌的新方法以稳定控制不稳定周期轨道(UPO).　这是一种偶然比例反馈控制(OPF)战略的扩展,它克服了OPF局限性,即OPF控制律的线性限制,并扩展到全混沌区.　本方法利用反传人工神经网络(BP-ANN)来表达非线性控制律,以增加控制的鲁棒性.　其有效性通过一个混沌自催化反应模型的数值模拟进行了检验.     

利用比例脉冲控制B-Z反应中混沌的变量选择

自二十世纪七十年代以来 ,混沌现象的研究成为非线性科学中的前沿课题。混沌在其无规律的表面下隐藏着惊人的“秩序”,但在许多情况下 ,混沌属于不利因素 ,因此近年来混沌控制又成为倍受关注的热点 ,出现了各种各样的混沌控制方法。这些混沌控制方法可以分为两大类 ,一类以Ott,Grebogi,Yorke提出的 OGY方法 [1]为代表 ,通过对系统参数实行控制达到混沌控制的目的。另一类以比例脉冲控制法[2 ,3] 为代表 ,由控制系统变量利用系统自身非线性特征实现系统自身反馈达到混沌控制目的。这两类方法各自分别能有效地控制不同特点的混沌系统 ,而比…     

一混沌模型系综模拟研究

用随机模拟方法研究了化学混沌模型的介观动力学。对该混沌模型的系综模拟发现,在这种不稳定运动中存在强烈的内部涨落,然而由于混沌运动整体上的稳定性,使得系综中的代表点被限制在混沌吸引子上,并且单个代表点形成的随机轨道很好地保持了确定性混沌吸引子的基本特征。     

恒电位下铜电极电流振荡的延时控制

采用铜电极的阳极溶解作为研究对象,开展电流振荡的延迟控制方法的研究.调节控制信号中延迟时间及控制系数的大小,延迟时间对电流影响作用明显,观察到周期变长和变短的结果,小延时下振荡周期变大,大延时下周期变小.延时控制也使振荡的波形产生明显的变化,并使原有的周期振荡呈现出混沌振荡.控制系数对振荡产生不同的影响,呈现出波形分裂、混合振荡等现象.控制系数加大时,这种峰的分裂变得更加强烈,阳极溶解电流产生了混沌振荡.控制后的振荡频率与原有频率有简单的比例关系.文中对延迟控制产生特定波形的机制进行了分析和讨论.     

混沌系统的变量变化率反馈控制方法研究

设计了一种控制连续非线性系统中混沌的新方法--变量变化率脉冲反馈(VRPF)方法.介绍了VRPF方法的控制原理以及反馈系数和脉冲间隔的选择技巧.将此方法应用到BZ反应3D模型系统混沌的控制中,计算机仿真模拟显示,通过恰当地选择反馈系数和脉冲间隔,可以将系统稳定在1p、2p、3p、4p、…、2n×3mp (n、m为整数)这样不同的周期轨道,从而使系统的功率谱也由混沌态时的连续谱转变为具有分立单峰的分立谱.此外,仿真模拟还发现VRPF方法具有极宽的控制域.     

偶极场扰动与冷却效应对同步运动的影响

在同步加速器特别是冷却存储环中,偶极场扰动和冷却效应将会对粒子的Betatron振荡和同步振荡产生影响。叙述了偶极场扰动对粒子同步运动的影响与高频相位调制等效,重点研究了偶极场扰动与冷却效应同时存在的情况对粒子的同步运动产生的影响。在经典力学框架内把粒子的同步运动方程化为广义的摆方程,然后利用Melnikov方法对系统的稳定性进行了分析,讨论了系统进入Smale马蹄混沌的物理意义,并导出了系统稳定的临界条件。根据稳定性判据,给出了系统稳定性所需要的偶极场扰动的高频相位调制幅度和冷却系数的限制条件。结果表明,系统的稳定性与它的参数有关,只需适当调节这些参数,混沌便可原则上控制或避免。     

人工神经网络与化学混沌控制

非线性化学反应体系表现出复杂的动力学行为，诸如振荡，混沌和孤子等，本文介绍自８０年代后期以来化学混沌控制领域所的主要方法，ＯＧＹ方法，Ｐｙｒａｇａｓ的延迟自反馈法和神经网络法。     

化学混沌

传统的化学理论(热力学和动力学)是以分子的无规热运动和杂乱碰撞,即分子混沌(或微观混沌)的概念为基础的。因此“混沌”(Chaos)一词对化学工作者来说并非完全陌生。但是最近十几年间,混沌一词的含义以及人们对它的     

Size-selective separations of biological macromolecules on mesocylinder silica arrays

In order to control the design functionality of mesocylinder filters for molecular sieving of proteins, we fabricated tight mesocylinder silica nanotube (NT) arrays as promising filter candidates for size-exclusion separation of high-concentration macromolecules, such as insulin (INS), α-amylase (AMY), β-lactoglobulin (β-LG), and myosin (MYO) proteins. In this study, hexagonal mesocylinder structures were fabricated successfully inside anodic alumina membrane (AAM) nanochannels using a variety of cationic and nonionic surfactants as templates. The systematic design of the nanofilters was based on densely patterned polar silane coupling agents ("linkers") onto the AAM nanochannels, leading to the fabrication of mesocylinder silica arrays with vertical alignment and open surfaces of top-bottom ends inside AAM. Further surface coating of silica NTs hybrid AAM with hydrophobic agents facilitated the production of extremely robust constructed sequences of membranes without the formation of air gaps among NT arrays. The fabricated membranes with impermeable coated layers, robust surfaces, and uniformly multidirectional cylinder pores in nanoscale sizes rapidly separate large quantities of proteins within seconds. Meanwhile, comprehensive factors that affect the performance of the molecular transport, diffusivity, and filtration rate through nanofilter membranes were discussed. The mesocylinder filters of macromolecules show promise for the efficient separation and molecular transport of large molecular weight and size as well as concentrations of proteins.     

Mesoporous silica hybrid membranes for precise size-exclusive separation of silver nanoparticles

One-dimensional (1D) nanomaterials have unique applications due to their inherent physical properties. In this study, hexagonally ordered mesoporous silica hybrid anodic alumina membranes (AAM) were synthesized using template-guided synthesis with a number of nonionic n-alkyl-oligo(ethylene oxide), Brij-type (C(x)EO(y)), which are surfactants that have different molecular sizes and characteristics. The hexagonal mesoporous silicas are vertically aligned in the AAM channels with a predominantly columnar orientation. The hollow mesostructured silicas had tunable pore diameters varying from 3.7 to 5.1 nm. In this synthesis protocol, the surfactant molecular natures (corona/core features) are important for the controlled generation of ordered structures throughout AAM channels. The development of ultrafiltration membranes composed of silica mesostructures could be used effectively in separating silver nanoparticles (Ag NPs) in both aqueous and organic solution phases. This would be relevant to the production of well-defined Ag NPs with unique properties. To create a size-exclusive separation system of Ag NPs, we grafted hydrophobic trimethylsilyl (TMS) groups onto the inner pores of the mesoporous silica hybrid AAM. The immobilization of the TMS groups allowed the columnar mesoporous silica inside AAM to retain this inner pore order without distortion during the separation of solution-phase Ag NPs in organic solvents that may cause tortuous-pore membranes. Mesoporous TMS-silicas inside 1D AAM channels were applicable as a size-exclusive separation system to isolate organic solution-phase Ag NPs of uniform morphology and size.     

基于QuEChERS-HPLC法检测油炸食品中丙烯酰胺的含量

建立了基于QuEChERS(quick,easy,cheap,effective,rugged and safe)-HPLC测定油炸食品中丙烯酰胺含量的方法。 该方法的优势在于：改进的QuEChERS前处理方法中没有引入有机溶剂而直接采用纯水消除样品基底的影响。 研究中,使用纯水超声提取丙烯酰胺,丙基乙二胺(PSA)吸附剂分散净化提取液,乙腈和水(体积比1∶99)作为流动相,水系C18色谱柱分离,208 nm紫外波长条件下检测丙烯酰胺的含量。 结果表明,丙烯酰胺在0.020~0.800 μg/g浓度范围内与出峰面积呈线性关系,相关系数r=0.9994;检测限为0.005 μg/g;加标回收率为83.96%~89.43%,相对标准偏差(RSD)为2.13%~5.87%。 该方法具有操作简单、快速、可靠和灵敏度高等特点,成功应用于方便面等油炸食品中丙烯酰胺含量的测定。     

Anthranilamide: a simple, removable ortho-directing modifier for arylboronic acids serving also as a protecting group in cross-coupling reactions

Anthranilamide (AAM) serves as a bifunctional modifier on the boron atom in catalytic transformations of arylboronic acids. It makes boronyl groups unreactive in Suzuki-Miyaura coupling and promotes Ru-catalyzed ortho-silylation. Suzuki-Miyaura coupling of AAM-modified bromophenylboronic acids with tolylboronic acid gave 1,1'-biaryl-4-boronic acid bearing AAM on the boron atom, which subsequently underwent Ru-catalyzed ortho-silylation at the 3-position by virtue of the ortho-directing effect of the AAM group.     

Determination of acrylamide in potato crisps by capillary electrophoresis with quantum dot-mediated LIF detection

Acrylamide or 2-propenamide (AAM), a water-soluble toxic contaminant, has recently caused health concern after it was found in food products made by high-temperature cooking. Due to its weak UV absorption and electrochemically inactive state, common analytical methods do not have sufficient sensitivity to meet the World Health Organization requirement. A LIF detection method mediated by water-soluble CdTe quantum dots capped with mercaptopropyl acid (MPA) is thus developed for AAM quantitation. The optimized conditions are as follows: 30 mmol/L SDS, 0.1 mmol/L quantum dot, and 40 mmol/L phosphate buffer solution at pH 8.0 under 18 kV run voltage with LIF detection at 473 nm excitation and 568 nm fluorescence. The linear quantitation range for AAM was found to vary from 1.0 to 100 mg/kg and a detection limit (S/N=2) at 0.1 mg/kg, showing sufficient sensitivity to meet the maximum AAM specified by the Joint Food and Agriculture Organization/World Health Organization Expert Committee for potato crisps. Recoveries for potato crisps sample spiked with 10, 20, and 100 mg/kg AAM were found to vary between 90 and 95% with RSD <5.7% (n=3).     

铝膜腔体内高度有序的介孔硅SBA-16的合成

在阳极铝膜腔体内, 以三嵌段聚合物F127为表面活性剂合成出一维纳米介孔二氧化硅材料. 采用压力诱导合成方法能使纳米纤维沿着铝膜腔体有序生长排列, 并且只存在于铝膜的腔体内, 在铝膜表面没有残留. 在纳米纤维的两侧可以清楚地观察到具有六边形结构的孔道, 直径为12 nm. 考察了正硅酸乙酯的水解时间以及化合物的不同配比对材料形貌的影响.     

Designs for size-exclusion separation of macromolecules by densely-engineered mesofilters

This critical review reports on the up-to-date development designs of mesofilters for molecular sieving of macromolecules. Tight mesoporous silica nanotubes (NTs) provide a promising candidate as a filter for the size-exclusion separation of large quantities of macromolecules within a short period. First, we focus on the formation of the mesoporous structures inside anodic alumina membrane (AAM) using nanolinker approaches. Second, we discuss the systematic design of the robust mesofilters based on densely-engineered mesopores of silica NTs, which are vertically aligned with the open surfaces of top-bottom ends inside the AAM. Third, we present the bench-top filtration method as a powerful tool for the size-exclusion separation of macromolecules. Significantly, the evaluation of the intrinsic properties of mesofilters (e.g., diffusivity, separation efficiency, long-term stability, and reusability) compared them with commercial, mature membranes used for separation of macromolecules.     

Studies on radiation synthesis of polyethyleneimine/acrylamide hydrogels

Polyethyleneimine(PEI)/acrylamide(AAM) hydrogels were synthesized by γ-radiation-induced polymerization/crosslinking of aqueous mixtures containing different ratios of PEI and AAM. The gel percentage and equilibrium degree of swelling (EDS) of the synthesized hydrogels were investigated. The compositions of the hydrogels produced were found to be different from the feed composition. Ion-chromatography technique was used to determine the amount of Pb (II) and Cd (II) absorbed by the hydrogel. The maximum binding capacity of the PEI/AAM hydrogels, for Pb and Cd was found to be 19 and 12.6 mg/g, respectively, (at 100 ppm). PEI/AAM hydrogels had better metal uptake efficiency than the pure AAM hydrogel at concentrations less than 50 ppm. Pure PEI was observed to be highly degrading type polymer on exposure to gamma radiation. TGA and FT-IR techniques were used to characterize the prepared hydrogels.     

Cubic and hexagonal mesoporous carbon in the pores of anodic alumina membranes

Cubic and circular hexagonal mesoporous carbon phases in the confined environment of the pores of anodic alumina membranes (AAM) were obtained by organic-organic self-assembly of a preformed oligomeric resol precursor and the triblock copolymer templates Pluronic F127 or P123, respectively. Casting and solvent evaporation were followed by self-assembly and the formation of a condensed wall material by thermopolymerization of the precursor oligomers, thus resulting in mesostructured phenolic resin phases. Subsequent thermal decomposition of the surfactant and carbonization were achieved through thermal treatment at temperatures up to 1000 °C under an inert atmosphere. The resulting hierarchical mesoporous composite materials were characterized by small-angle X-ray scattering and nitrogen-sorption measurements. The structural features were directly imaged in TEM cross-sections of the composite membranes. For both structures, the AAM pores were completely filled and no shrinkage was observed due to strong adhesion of the carbon-wall material to the AAM pore walls. As a consequence, the pore size of the mesophase system stays almost constant even after thermal treatment at 1000 °C.     

In situ GISAXS study of the formation of mesostructured phases within the pores of anodic alumina membranes

The formation and subsequent transformations of mesostructured silica within the confined tubular environment of anodic alumina membrane (AAM) channels [porous alumina membrane (PAM) channels] were investigated for the first time in situ with grazing incidence small-angle X-ray scattering (GISAXS) techniques, in combination with ex situ transmission electron microscopy (TEM) of the same samples. A better understanding of the mesostructure formation mechanism within the confined space of the AAM pores is a direct result of this study. Three different surfactants were used as the structure-directing agents in acid-catalyzed silica synthesis solutions. With ionic cetyltrimethylammonium bromide acting as the structure-directing agent, a columnar hexagonal structure with mesopores oriented parallel to the AAM channels was observed to form directly from the beginning of the synthesis. In samples synthesized with the nonionic surfactants Brij 56 and Pluronic P123, a circular hexagonal structure was found to form first; here, the mesopores are aligned around the circumference of the AAM channels. The circular structure subsequently transforms directly into a columnar hexagonal (P123 surfactant), or a mixture of columnar hexagonal and a new curved lamellar phase with lamellae oriented parallel to the walls of the AAM channels (Brij 56 surfactant). These transformations occur after complete solvent evaporation and therefore differ from a simple evaporation-induced phase formation. The existence of a previously postulated lamellar phase could be proven by GISAXS and TEM investigations.