Cellulose acetate membranes fabricated by a combined vapor-induced/wet phase separation method: morphology and performance evaluation

Iranian Polymer Journal - Cellulose acetate (CA) microfiltration membranes were fabricated by a combined vapor-induced and wet phase separation technique. A systematic morphology study was...     

Research directions in session-based and sequential recommendation

User Modeling and User-Adapted Interaction -     

The dependence of morphology of solid polymer electrolyte membranes on transient salt type: effect of cation type

The structures of poly(N‐vinyl pyrrolidone) (PVP) and poly(ether sulfone) composite membranes were investigated with transient salt addition. The effects of type and concentration of AgNO₃ and Cu(NO₃)₂ on membrane morphology were evaluated through attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy, differential scanning calorimetry (DSC) and atomic force microscopy. Complex formation between carbonyl groups (on PVP chains) and Cu²⁺ or Ag⁺ decreases the strength of the carbonyl bond as evidenced through ATR‐FTIR spectroscopy. The results indicate that the copper salts create more powerful interactions than the silver salts in the polymer matrix. DSC experiments reveal that the glass transition temperature of polymeric films containing silver or copper cations is lower than that of the PVP reference film. Comparison of the thermograms of PVP + AgNO₃ and PVP + Cu(NO₃)₂ shows that copper ions disrupt the polymer crystallinity more than silver ions. Therefore, DSC observations confirm the ATR‐FTIR results in the case of the strength of the complexes formed. A morphological analysis of membrane surfaces reveals the existence of electrostatic interactions in the polymeric membrane structure. This is a result of the addition of salt to the casting solution, wrinkling the polymer chains including the surface layer, and accordingly the surface of the facilitated transport membranes is rougher than the initial PVP membrane. Copyright © 2010 Society of Chemical Industry     

Low velocity flexural impact behavior of AR glass fabric reinforced cement composites

Fabric–cement composites developed using the pultrusion production process have demonstrated impressive tensile and flexural properties. For instance fabric reinforced composites with bonded Alkali Resistant (AR) glass fabrics exhibit strain-hardening behavior, tensile strength in the range of 20–25 MPa, and strain capacity of the order of 2–5% under static conditions. Properties of these composite systems were investigated under three point bending conditions using an instrumented drop weight impact system. Samples were studied from the viewpoint of the variations of impact load, deflection response, acceleration and absorbed energy. Development of the testing system in terms of components and acceleration response are discussed in detail. Methods of the impact load measurement using three different ways of acceleration response, piezoelectric load washer and conventional strain gage based load cell are discussed. Cement composites with two different fabric contents and four different drop heights of hammer (dropping mass) were tested. Experimental results indicate that for the same drop height, the stiffer beam type specimens have a lower ultimate deflection but a higher load carrying capacity than the plate type specimens. The maximum flexural stress and absorbed energy of composites increase with drop height. In beam specimens, complete fracture does not take place as cracks form and close due to rebound and significant microcracking in the form of radial fan cracking is observed, whereas interlaminar shear is the dominant failure mode in the plate specimens.     

Attacks and Remedies in Collaborative Recommendation

Collaborative-filtering recommender systems are an electronic extension of everyday social recommendation behavior: people share opinions and decide whether or not to act on the basis of what they hear. Collaborative filtering lets you scale such interactions to groups of thousands or even millions. Publicly accessible user-adaptive systems such as collaborative recommender systems introduce security issues that must be solved if users are to perceive these systems as objective, unbiased, and accurate.     

Document Categorization and Query Generation on the World Wide Web Using WebACE

We present WebACE, an agent for exploring and categorizing documents onthe World Wide Web based on a user profile. The heart of the agent is anunsupervised categorization of a set of documents, combined with a processfor generating new queries that is used to search for new relateddocuments and for filtering the resulting documents to extract the onesmost closely related to the starting set. The document categories are notgiven a priori. We present the overall architecture and describe twonovel algorithms which provide significant improvement over HierarchicalAgglomeration Clustering and AutoClass algorithms and form the basis forthe query generation and search component of the agent. We report on theresults of our experiments comparing these new algorithms with moretraditional clustering algorithms and we show that our algorithms are fastand sacalable.     

Modeling of Multilayer Composite Fabrics for Gas Turbine Engine Containment Systems

An experimental and modeling system for the modeling of multilayer composite fabrics used in a gas turbine engine containment system is developed. Specifically, Kevlar 49 (17×17) and Zylon AS (35×35) fabrics are used in the study. The experimental setup is first used to obtain the material properties of these fabrics. Later, one or more layers of these fabrics is tightly wrapped around a steel cylinder that simulates an engine containment housing. A steel penerator (or a blunt nose) is used in a static test by slowly pushing against the fabric. The resulting load-deflection data are used to compute a variety of parameters, including the energy absorption capacity. The material behavior obtained from the experimental study is then used as the constitutive model in a finite element simulation of the static test. The objective is to develop a procedure for understanding the relative strengths and weaknesses of different fabrics and to aid in the development of finite element modeling of actual fan blade-out events.     

Morphological dependency of polymer electrolyte membranes on transient salt type: effects of anion species

Two types of transition metal salts, i.e. Cu(NO₃)₂ and CuCl₂, with different anion species were used to prepare various polyethersulfone‐based poly(N‐vinyl pyrrolidone) (PVP) composite membranes. The polymer crystallinity, strength of some of the bonds in the membrane structure and effects of anion species on the membrane morphology were investigated through X‐ray diffraction (XRD), scanning electron microscopy with energy‐dispersive X‐ray spectrometry (SEM‐EDX), Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy. The XRD results indicated an enhancement of the PVP crystallinity after addition of Cu(NO₃)₂. Moreover, addition of copper salt was accompanied by an increase of effective membrane distances. The FTIR analysis revealed that the nitrate ions might be better distributed than the other salt ions. The complexes created between them and carbonyl oxygens on the PVP chains were thus stronger. More powerful interactions caused a crystallinity enhancement following the addition of Cu(NO₃)₂. The SEM‐EDX experiment gave insight into the copper ion and carbonyl oxygen distributions in the membrane surface and active layer. The uniform distribution of copper ions resulted in a clear distribution of interchain interactions and complexes in the active layer structure and also caused structural order improvement. Copyright © 2010 Society of Chemical Industry     

Brittle fracture in nonceramic insulators: electrical aspects ofmicroscopic flaws in glass reinforced plastic (GRP) rods

Glass Reinforced Plastic (GRP) rods used in Non-Ceramic Insulators (NCI) were examined for microscopic defects in order to evaluate their role in causing brittle fracture. The rods evaluated utilized different types of glass fibers and resin systems. Niemeyer's generalized approach to Partial Discharge (PD) modeling was used to investigate the development of electrical discharges inside the rods. The results indicated that the PD inception voltage was well above the highest system voltage used presently. Thus, it was concluded that the reactive species required for the formation of acids could not be developed inside the rod. The results also suggest that chemical reactions other than acid production can promote stress corrosion cracking of the rod and these may play a significant role in the failure process