Biocompatible electrospun tactic poly(methyl methacrylate) blend fibers

Uniform and beads free fibers of pristine syndiotactic PMMA (s-PMMA), isotactic PMMA (i-PMMA), and their blends in the ratio of s:i = 3:1, 1:1 and 1:3 were successfully prepared using the electrospinning technique. The tactic PMMA blend fibers showed unique thermal stability and glass transition temperatures compared to their pristine counterparts. An interesting endotherm peak was observed for the s:i = 1:3 electrospun fibers, which might indicate a complex formation between the two tactic PMMAs. Systematic surface functionalities study by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) revealed the interactions between these two tactic PMMAs. Biocompatibility of tactic PMMA and their blend fibers was first time comparably investigated using HeLa as the model mammalian cell line; an intriguing observance was first revealed that the blend fibers showed better biocompatibility than both pristine ones, though the behind mechanism is not well understood yet.     

Biosorption mechanism of Zn2+ from aqueous solution by spent substrates of pleurotus ostreatus

To solve the problem of heavy metal pollution and agricultural wastes reclamation, spent substrate of pleurotus ostreatus (SSPO) was used as adsorbent to remove Zn²⁺ from aqueous solution. The biosorption of zinc ions on SSPO was studied as a function of the solution pH, temperature and initial Zn²⁺ concentration. The equilibrium sorption data were well represented by linear Langmuir isotherm models with R² value of 0.9955 and non-linear Freundlich with R² value of 0.9973. The BET surface area of SSPO can reach 51.16m²g^?1. SEM-EDX and XRD revealed that (NH₄)₂Zn·H₂O and Zn₂PO₄(OH) were the main compounds in metal-loaded SSPO. FTIR analysis indicated the governing functional groups such as O-H, N-H and P=O played an important role in biosorption. The desorption studies showed the reversibility of SSPO. The results indicate that SSPO is a potential adsorbent in wastewater treatment due to its great sorption capacity and low cost.     

重庆某高层建筑的结构改造与加固设计

以某高层建筑改建为实例,对功能改变后的结构进行了计算分析。结合工程现状,综合考虑施工因素,对不满足规范的构件、楼板开洞、混凝土挂板开洞、悬挑梁板的接长等分别进行了分析和加固处理。     

医疗卫生用非织造布的亲水整理

采用SCG亲水柔软整理剂整理丙纶纺粘非织造布,通过正交实验设计确定实验方案,并对结果进行直观分析,确定最佳水平组合。结果表明,经SCG整理后的丙纶纺粘非织造布具有优良的亲水性能,且其本身的强力、透湿、透气等性能并未受到不良影响。     

Polymerization kinetics of polyurethane and vinyl ester resin interpenetrating polymer networks by using fourier transform infrared spectroscopy

Fourier transform infrared spectroscopy (FTIR) was applied to the study of polymerization kinetics of simultaneous interpenetrating polymer networks (SINs) composed of polyurethane (PU) and vinyl ester resin (VER), in which the pendent hydroxyl groups were capped with acetyl groups to minimize the possibility of chemical binding between the two networks. It was found that during the course of synthesis the two pairs of reactants interfere with each other in the SIN systems, giving rise to depressed reaction rates, although they follow different polymerization mechanisms. Increasing the reaction temperature could be more effective than increasing the free-radical initiator level with regard to the final conversions of both components. The reaction sequence could be varied through the amount of the step-growth polymerization catalyst and free-radical initiator as well as the reaction temperature adjustment. Using VER containing pendent hydroxyl groups could strongly affect the reaction kinetics of such SINs and lead to hybrid structures. The quick formation of one network would always depress the conversion of the other network in all SINs studied. © 1996 John Wiley & Sons, Inc.     

Infrared spectroscopic studies of melting behavior of poly(ethylene 2, 6-naphthalenedicarboxylate)

The FTIR method was used to study the melting behavior of poly(ethylene 2, 6-naphthalene-dicarboxylate) (PEN) samples of different thermal history of crystallization. With subtraction of the spectra of PEN samples of different crystallinities and amorphous PEN, the spectra of crystalline trans conformers, amorphous trans conformers, and amorphous gauche conformers were obtained. By following the changes in intensity of various gauche and crystalline bands during heating, the phenomenon of multiple melting endothermic peaks was shown to be due to the melting of imperfect crystalline conformation formed during crystallization. For two-step annealed samples, the crystalline conformational defects change into a more perfect one during annealing at higher temperatures. © 1996 John Wiley & Sons, Inc.     

稀土对Fe-17.5Mn合金阻尼性能的影响

利用倒扭摆仪对比研究了Fe-17.5Mn二元合金和Fe-17.5Mn-0.3Mm(富铈混合稀土)合金的阻尼性能,并借用Olympus显微镜观察分析了合金的微观组织.研究结果表明,在1000℃保温1h后水淬状态下,Fe-17.5Mn-0.3Mm合金的阻尼性能明显优于Fe-17.5Mn二元合金.在微量稀土元素的作用下,Fe-17.5Mn-0.3Mm合金中相对于Fe-17.5Mn二元合金其马氏体数量较多、板条较细薄,板条变薄且单位体积内界面面积增加,使振动的微观阻尼源增多,导致阻尼性能提高.     

冶勒水电站砂砾胶结岩洞室爆破

本文根据冶勒水电站盖重料砂砾胶结岩洞室爆破的爆破试验及爆破参数的选择。对软岩洞室爆破进行了叙述并总结提出了几点施工经验。     

Robust tracking control of an induction motor

This paper address the tracking control problem of a induction motor driving a mechanical load. Based on the nonlinear dynamics of the induction motor, a robust tracking controller is developed which can compensate for parametric uncertainties and additive bounded disturbances throughout the entire electromechanical system. A uniform ultimate bounded (UUB) result is obtained for the rotor position tracking error. Simulation results with full state measurements and a flux observer are presented to illustrate the effectiveness of the proposed controller.