Hydrophilicity modification of polypropylene microfiltration membrane by ozonation

To improve surface hydrophilicity and to reduce fouling, commercial polypropylene microfiltration membranes were ozonated to generate peroxides as grafting sites for hydrophilic monomers. Ozonation was conducted in aqueous and gaseous phases, respectively. In both phases, the amount of peroxides increased with the ozonation time. A novel way to enhance the generation of peroxides was tested, i.e., adding homogeneous catalyst, CuSO₄, to aqueous ozonation. Results showed that with an optimum dose of 0.05 g/L of CuSO₄, the peroxides generated were 18.2% more than that by the non-catalyzed ozonation in aqueous phase. It was also confirmed by scavenger tests that during the aqueous ozonation both molecular ozone and free radicals contributed to the oxidation of the membranes, the latter was formed from the self-decomposition of ozone in water. Graft polymerization was also conducted after the generation of peroxides. A hydrophilic monomer, acrylic amide, was graft polymerized onto the membrane surface. The successful grafting of acrylic amide was confirmed by the formation of new peaks corresponding to amide groups in FTIR spectra. Results of contact angle measurements and filtration tests indicated that aqueous ozonation was more effective than its gaseous counterpart in terms of hydrophilicity improvement. In addition, the XRD analysis revealed that the ratio of the membrane surface crystallinity to amorphousity was changed by both ozonation and graft polymerization. Results of SEM scanning also showed changes in membrane surfaces after modification.     

An Empirical Study on Factors Influencing Consumers' Initial Trust in Wearable Commerce

This paper focuses on the factors influencing consumers' initial trust in wearable commerce. Specifically, a conceptual model for wearable commerce is created and hypotheses are developed to study the initial trust. Through a survey of 266 valid questionnaires, we carry out an empirical analysis via Structure Equation Modeling method. The results show that five proposed factors (privacy concern, trust propensity, performance expectancy, facilitating conditions, hedonic motivation) all have significant effects on initial trust in wearable commerce. The conclusion is valuable to future research on wearable commerce. Theoretical and practical implications are also presented.     

燃气冷热电三联供在北京医院工程设计中的应用探讨

本文主要阐述了燃气冷热电三联供系统在医院中的应用现状、国家在三联供系统设计方面政策的完善过程，并介绍了北京一家医院三联供系统的情况，重点介绍了三联供系统的电气设计-睛况及在设计过程中遇到的问题。     

Model of DFIG Wind Farm and Study on Its LVRT Capability

As a typical clean and renewable energy,wind power is becoming more and more widely used in electrical industry.However,its characteristics of random and intermittent have brought serious problems to the power system,such as voltage fluctuation and insufficient reactive power.Based on the K-means clustering algorithm,this paper classifies the doubly-fed induction generators(DFIG) according to the operation of propeller pitch angle control.At the same time,to obtain the optimal parameter,advanced particle swarm optimization(PSO) is used.Then the dynamic model of DFIG under the network fault condition is built.What is more,the role that crowbar circuit plays in low voltage ride through(LVRT) is discussed.Finally,simulations in DigSILENT verify the model.     

Effect of dispersion on rheological and mechanical properties of polypropylene/carbon nanotubes nanocomposites

Polypropylene (PP) nanocomposites filled with the pristine multi‐wall carbon nanotubes (CNTs) and the purified CNTs were prepared by melt blending. The microstructure and linear viscoelastic properties wereinvestigated using rheological and morphological measurements. The results show that the purified CNTs disperse uniformly in the PP matrix. At low frequencies, frequency dependence of modulus weakens clearly with the addition of the CNTs, indicating that the long‐range motion of the polymer chains is restrained by the presence of the CNTs. Percolation networks form when the loading levels achieve up to 3 and 1.5 wt% for the composites with the pristine CNTs (PPCNTs) and the purified CNTs (PPcCNTs), respectively. The linear relaxation modulus increases with increasing loading level. And for composites with loading levels above percolation concentration, the modulus appears to reach a plateau at long time scales due to the formation of percolation network. Tensile strength and impact strength are simultaneously improved with the addition of the CNTs. The better the dispersion of the CNTs, the greater the improvement of the tensile strength and the impact strength. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Interlaminar Fracture Testing Method for CFRP Using Tensile Loading with Acoustic Emission Analysis

A method is described to characterize the uniformity of interlaminar fracture toughness of laminated carbon-fiber-reinforced polymer (CFRP) composites fabricated by the modified vacuum assisted resin transfer molding process. To prepare specimens for Mode I fracture toughness tests, pieces were sectioned from the inlet and vent regions of a CFRP plate ([+30/-30]₆), with a starter crack inserted. The specimens were packed between two rectangular epoxy plates to apply a load using a universal testing machine. Acoustic energy signals were monitored using two sensors attached to the epoxy plates during tensile loading. The difference between the material properties of specimens from the inlet and vent regions of the CFRP plate were statistically compared using one-way analysis of variance (ANOVA); we show that the specimens showed no statistically significant differences in the interlaminar fracture characteristics depending on the part of the mold from which they were taken.     

Friction Properties of Fluorinated Graphitized Carbon Blacks

The tribologic properties of graphitized carbon blacks and their fluorinated derivatives are investigated as a function of the fluorination rate. Very low intrinsic friction coefficients are obtained for highly fluorinated compounds. The correlation of the tribologic results and structural investigations of the initial compounds by TEM strongly suggests that the friction mechanisms involve surface effects in the early stage of friction. Long-term tribologic experiments and Raman analyses point out an evolution of the structure and composition of the tribofilms during the friction process leading to similar friction properties of the tribofilms. Wear studies revealed that highly fluorinated derivatives appear less efficient than pristine and weakly fluorinated compounds.