壳聚糖膜在渗透汽化中的研究进展

渗透汽化膜分离液体混合物不但能耗低,且具有明显的经济优势,因而被广泛应用于食品、医药、农业和化工等多个领域,但其分离性能、热稳定性、耐酸碱性和环保性等方面还有待提高.壳聚糖因具有强亲水性和易改性而使其分离性能优异,此外,壳聚糖稳定性好,来源广泛且具有生物可降解性,是一种极具发展潜力的渗透汽化膜材料.然而,由于单一的壳聚糖膜易吸水溶胀而分离选择性较差,限制了其在渗透汽化领域的应用.因此,对壳聚糖进行改性,使其具有良好的力学性能和选择性至关重要.常用的改性方法有交联、接枝、共混和复合等.交联可提高壳聚糖膜的力学性能,但是会消耗大量的亲水基团,并显著降低渗透通量;共混使壳聚糖膜具有更佳的渗透选择性和渗透通量,但更易吸水溶胀;复合膜中掺入少量的无机粒子可在提高材料分离性的基础上改善其力学性能和热性能,然而,复合膜受聚合物和无机离子之间的界面差异以及无机粒子团聚性影响较大.为了使壳聚糖膜具有更加优异的综合性能,研究者往往会同时采用多种改性方法.本文介绍了渗透汽化技术的研究背景和分离机理,分析了壳聚糖膜的成膜机理、制备和应用.重点从有机物/水和有机物/有机物两个方面综述了壳聚糖膜材料在渗透汽化分离中的研究进展,对其未来的发展趋势进行了展望,以期为快速制备稳定性高、分离性能优异的新型壳聚糖膜提供参考.     

Speed control for the lateral swing of aerial cameras based on an improved extended state observer

This study proposes an improved extended state observer (ESO) to eliminate the effects of disturbances on the speed control system of an aerial camera lateral swing. First, a mechatronics model of lateral swing, which includes a rotating mechanism, principal axis, and motor, is constructed. Meanwhile, a mathematical model of the motor speed loop is built to design the improved ESO. Second, a new nonlinear function that exhibits better continuity and smoothness than previously available functions is proposed to reduce high-frequency ?utter. The improved ESO is designed based on the new nonlinear function. The nonlinear dynamics, model uncertainty, and external disturbances of the speed control system are extended to a new state, and the improved ESO is implemented to observe this state. The overtime variation of the speed control system is predicted and compensated for in real time using the improved ESO. The improved ESO sufficiently eliminates the disturbances on the speed control system of the aerial camera lateral swing. Third, the parameters of the improved ESO are determined, and its convergence is analyzed. Finally, simulation experiments and discussions were conducted and results show that the speed control system with the improved ESO exhibits better performance.     

A VNS-LP algorithm for the robust dynamic maximal covering location problem

This study introduces a robust variant of the well-known dynamic maximal covering location problem (DMCLP) and proposes an integer linear programming formulation of the robust DMCLP. A hybrid approach for solving both deterministic and robust variant of the DMCLP is developed, which is based on hybridization of a Variable neighborhood search and a linear programming technique. The main idea is to split the problem into subproblems and to combine optimal solutions of the obtained subproblems in order to construct solution of the initial problem. The results of the proposed hybrid approach on instances of the deterministic DMCLP are presented and compared with the results of the state-of-the-art approach from the literature and with the results of commercial CPLEX solver. The presented computational analysis shows that the proposed hybrid algorithm outperforms other approaches for the DMCLP. In addition, the algorithm was tested on the instances of the robust variant of DMCLP, and obtained results are discussed in detail.

     

Robust optimization of concrete strength estimation using response surface methodology and Monte Carlo simulation

A new approach is proposed for the robust optimization of concrete strength estimation using response surface methodology and Monte Carlo simulation. The essence of the suggested procedure lies in the reliable prediction of concrete strength as a simple function of unit mass, water/cement ratio, age and superplasticizer content. The derived model provides sufficiently accurate results for the calibration and verification phases, the latter of which is conducted using data that were not used for model development. The results of additional analysis indicate that residuals in the calibration and verification stages have a normal distribution. Is its also shown that the uncertainty of estimated coefficient values has a statistically insignificant effect on concrete strength, confirming the reliability of the proposed model. Moreover, analysis of the effect of laboratory measurement errors indicates the robustness of concrete compressive strength against the variation in measured parameter values.     

SN-38 loading capacity of hydrophobic polymer blend nanoparticles: formulation,optimization and efficacy evaluation

One of the most important problems in nanoencapsulation of extremely hydrophobic drugs is poor drug loading due to rapid drug crystallization outside the polymer core. The effort to use nanoprecipitation, as a simple one-step procedure with good reproducibility and FDA approved polymers like Poly(lactic-co-glycolic acid) (PLGA) and Polycaprolactone (PCL), will only potentiate this issue. Considering that drug loading is one of the key defining characteristics, in this study we attempted to examine whether the nanoparticle (NP) core composed of two hydrophobic polymers will provide increased drug loading for 7-Ethyl-10-hydroxy-camptothecin (SN-38), relative to NPs prepared using individual polymers. D-optimal design was applied to optimize PLGA/PCL ratio in the polymer blend and the mode of addition of the amphiphilic copolymer Lutrol^®F127 in order to maximize SN-38 loading and obtain NPs with acceptable size for passive tumor targeting. Drug/polymer and polymer/polymer interaction analysis pointed to high degree of compatibility and miscibility among both hydrophobic polymers, providing core configuration with higher drug loading capacity. Toxicity studies outlined the biocompatibility of the blank NPs. Increased in vitro efficacy of drug-loaded NPs compared to the free drug was confirmed by growth inhibition studies using SW-480 cell line. Additionally, the optimized NP formulation showed very promising blood circulation profile with elimination half-time of 7.4?h.     

N-羟乙基丙烯酰胺交联改性核壳苯丙乳液的制备及涂膜性能

采用半连续种子乳液聚合法合成稳定的自交联核壳型苯丙乳液。考察了软硬单体配比、N-羟乙基丙烯酰胺(HEMAA)用量对乳液及涂膜性能的影响,初步探讨了HEMAA的改性机理。结果发现,当软硬单体配比m(St)∶m(BA)=2∶1,HEMAA添加量占主单体1%时,合成乳液聚合稳定性高,涂膜耐水性和热稳定性良好。傅里叶变换红外光谱、扫描电镜及透射电镜分析表明,HEMAA接枝到共聚物分子上且有明显的核壳结构;涂膜接触角及热重分析表明,涂膜的疏水性及热稳定性增强,水在涂膜上的接触角较改性前提高了5.26°,苯丙乳胶膜在实验条件下失重5%时,分解温度提高了58.03℃。     

以含偶氮苯基团为侧链对芳香聚酰胺的改性

以对苯二甲酰氯分别与4,4’-二氨基二苯醚和4,4’-二氨基二苯甲烷2种芳二胺反应得到聚酰胺PA1和PA2,然后以含偶氮苯基团的NAzO4Br对PA1和PA2进行结构及性能改性研究,分别得到了5种不同配比改性的NAzO4-PA1和NAzO4-PA2;并通过红外光谱、核磁共振氢谱、紫外可见光谱和X射线衍射等方法对改性聚酰胺进行了结构表征。结果表明,改性得到的聚酰胺NAzO4-PA1和NAzO4-PA2具有较好的光致异构性和热稳定性,而且含偶氮苯基团侧链的引入,使聚酰胺在二甲基乙酰胺(DMAc)、二甲基亚砜(DMSO)和二甲基甲酰胺(DMF)中具有良好的溶解性。     

超支化聚氨酯改性水性环氧树脂固化剂的制备与性能

以异佛尔酮二异氰酸酯(IPDI)、二羟甲基丙酸(DMPA)和二乙醇胺(DEOA)为原料,合成出了超支化聚氨酯核HBPU-0;以IPDI、聚醚多元醇(N210)、DMPA等原料合成线型聚氨酯,然后将线型聚氨酯接枝到HBPU-0上,制备出超支化聚氨酯(HBPU);再以HBPU、环氧树脂E-44、丁基缩水甘油醚单封端的四乙烯五胺(TEPA-660a)为主要原料制备出超支化聚氨酯改性水性环氧树脂固化剂。用红外光谱、核磁共振、透射电镜、扫描电镜和热失重等方法表征和测试了聚合物的结构与性能,研究了HBPU含量对固化膜断面形貌、力学性能、热性能的影响。结果表明,当HBPU质量分数达到24%时,固化膜的综合性能最佳,此时冲击强度为23.4kJ/m2,拉伸强度为52.4 MPa,5%和50%的质量热损失温度分别为287.5℃和376℃,与未改性环氧树脂相比,柔韧性和耐热性均有显著提高。     

Solvothermal synthesis of Ag/ZnO micro/nanostructures with different precursors for advanced photocatalytic applications

Micro/nanostructured systems based on metallic oxide (ZnO) with noble metal (Ag) on the surface (Ag/ZnO) are synthesized by solvothermal method from zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O), zinc acetate dehydrate (Zn(CH₃COO)₂·2H₂O), zinc acetylacetonate hydrate (Zn(C₅H₇O₂)₂·xH₂O) and silver nitrate (Ag(NO₃)) as precursors. In these systems, polyvinylpyrrolidone (PVP) is used as surfactant for controlling particle morphology, size and dispersion. The obtained materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), UV–vis diffuse reflectance spectroscopy (DRS), N₂ gas adsorption–desorption (BET) and Raman spectroscopy (RS). By XRD results, all major peaks are indexed to the hexagonal wurtzite-type structure of the ZnO and samples with noble metal, extra diffraction peaks are detected which correspond to the face-centered-cubic (fcc) structure of the metallic Ag. Depending on used precursor, different morphologies have been obtained. Mainly, ZnO prims-like rods – NRs (with 0.8 ? aspect ratio ? 3.4) – have been observed. Quasi-spherical particles of metallic Ag (with diameters between 558 ± 111 μm and 22 ± 1 nm) have been detected on the ZnO surface. Photocatalytic results (all samples studied >30% MB degradation) verify the important effect of surfactant and the viability of synthesized Ag/ZnO micro/nanocomposites for environmental applications.     

A continuous process for the ultrasonic spray pyrolysis synthesis of RuO2/TiO2 particles and their application as a coating of activated titanium anode

Synthesis and subsequent deposition of sub-micron spherical RuO₂/TiO₂ particles onto titanium were performed by continuous process in two connected reactors, exclusively applied for this purpose. Synthesis of particles was achieved by ultrasonic spray pyrolysis method in the first reactor. The deposition of thus produced RuO₂/TiO₂ onto an expanded titanium substrate was performed at 500 °C afterwards in the second, specially constructed, reactor equipped by high-voltage electrostatic field. Basic electrochemical properties of the obtained RuO₂/TiO₂ particles were checked in a form of the coating on Ti deposited from the suspension of the material produced in the first reactor. Thus prepared anode was investigated by cyclic voltammetry (CV), polarization measurements in O₂ (OER) and Cl₂ (CER) evolution and the accelerated stability test in diluted chloride solution. The morphology and composition of the deposited RuO₂/TiO₂ were checked by scanning electron microscopy/energy dispersive X-ray spectroscopy analysis. Analysis of the results obtained for OER and CER showed that Tafel slopes for these reactions were in accordance with the values for this kind of material. The CV response was of usual characteristics too. The accelerated stability test revealed acceptable anode stability.