Electrospun fiber membranes from blends of poly(vinylidene fluoride) with fouling‐resistant zwitterionic copolymers

Nonwoven super‐hydrophobic fiber membranes have potential applications in oil–water separation and membrane distillation, but fouling negatively impacts both applications. Membranes were prepared from blends comprising poly(vinylidene fluoride) (PVDF) and random zwitterionic copolymers of poly(methyl methacrylate) (PMMA) with sulfobetaine methacrylate (SBMA) or with sulfobetaine‐2‐vinylpyridine (SB2VP). PVDF imparts mechanical strength to the membrane, while the copolymers enhance fouling resistance. Blend composition was varied by controlling the PVDF‐to‐copolymer ratio. Nonwoven fiber membranes were obtained by electrospinning solutions of PVDF and the copolymers in a mixed solvent of N,N‐dimethylacetamide and acetone. The PVDF crystal phases and crystallinities of the blends were studied using wide‐angle X‐ray diffraction and differential scanning calorimetry (DSC). PVDF crystallized preferentially into its polar β‐phase, though its degree of crystallinity was reduced with increased addition of the random copolymers. Thermogravimetry (TG) showed that the degradation temperatures varied systematically with blend composition. PVDF blends with either copolymer showed significant increase of fouling resistance. Membranes prepared from blends containing 10% P(MMA‐ran‐SB2VP) had the highest fouling resistance, with a fivefold decrease in protein adsorption on the surface, compared to homopolymer PVDF. They also exhibited higher pure water flux, and better oil removal in oil–water separation experiments. © 2018 Society of Chemical Industry     

Optimization of downhole pump setting depths in liquid-dominated geothermal systems: A case study on the Balcova-Narlidere field,Turkey

Downhole pumps are being used increasingly more often in low-enthalpy geothermal wells. The depth at which these pumps are installed depends on the physical and chemical characteristics of the geothermal fluid, the production flow rate, and the reservoir pressure and permeability. In this study we have investigated the factors affecting pump setting depths in low-temperature, liquid-dominated geothermal systems and defined the relationship between flow rate and pressure drawdown based on multi-rate test results. The methodology proposed was applied to the Balcova-Narlidere geothermal field, Turkey. It was found that the most important parameters for determining the capacity and setting depth of a downhole pump were flow performance, non-condensable gas concentration, and temperature. The implementation of the methodology is illustrated.     

Mechanical behaviour of SiC fibre-reinforced titanium/titanium aluminide hybrid composites

The viability of developing an SiC fibre-reinforced titanium/titanium aluminide hybrid matrix composite was explored. The hybrid composites are expected to be used at temperatures beyond those attainable in conventional titanium matrix composites while improving the damage tolerance of the titanium aluminide matrix composites. The room-temperature mechanical characteristics studied were tensile strength, fracture toughness, low-cycle fatigue life and fatigue crack growth rate. The mechanisms of damage initiation and propagation under various loading conditions were also characterized. The directions for developing a satisfactory composite with hybrid titanium/titanium aluminide matrix are also addressed.     

Synthesis and characterization of novel polyacrylate-clay sol-gel materials

Organo-functional silanes which were able to form chemical bonds with kaolinite and could also have an affinity to the materials of concern here, were studied by the sol-gel process. Polymethacrylate with trialkoxy silyl functional groups were prepared, hydrolysed and co-condensed with kaolinite. The progress of the hydrolysis, which proceeded very slowly, was followed by Karl-Fischer titration. Thermal behavior was investigated by differential thermal analysis. The extent of the reaction leading to network formation was qualitatively followed by Fourier transform-infrared spectroscopy and X-ray diffraction. Free-radical polymerization was carried out ultrasonically in the presence of a catalyst. Trimethoxy silane end-capped silane was found to be covalently bonded to kaolinite. The copolymers, with various amounts of kaolinite, were then hydrolysed and co-condensed in the presence of a catalyst to yield sol-gel materials which have a controllable combination of properties of both the polymer and kaolinite.     

Maximization of total surface area of Pt-SnO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst by the Taguchi method

The maximization of the total surface area of Pt-SnO₂/Al₂O₃ catalyst was studied by using the Taguchi method of experimental design. The catalysts were prepared by sol-gel method. The effects of HNO₃, H₂O and aluminum nitrate concentrations and the stirring rate on the total surface area were studied at three levels of each. L₉ orthogonal array leading nine experiments was used in the experimental design. The parameter levels that give maximum total surface area were determined and experimentally verified. In the range of conditions studied it was found that, medium levels of HNO₃ and H₂O concentration and lower levels of aluminum nitrate concentration and stirring rate maximize the total surface area.     

Films formed from polystyrene latex/clay composites: A fluorescence study

This study reports a steady-state fluorescence (SSF) technique for studying film formation from surfactant-free polystyrene (PS) latex and Na-montmorillonite (SNaM) composites. The composite films were prepared from pyrene (P)-labeled PS particles and SNaM clay at room temperature and annealed at elevated temperatures in 10-min intervals above glass transition temperature (t₃) of polystyrene. During the annealing processes, the transparency of the film improved considerably. Scattered light (I_s) and fluorescence intensity (I_p) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of composite films was monitored by using photon transmission intensity, I_tr. Scanning electron microscopy (SEM) was used to detect the variation in physical structure of annealed composite films. Minimum film formation temperature, T_q, and healing temperatures, T_h, were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. It was observed that both activation energies increased as the percent of SNaM was increased in composite films.     

Corrosion behavior of tempered dual-phase steel embedded in concrete

Dual-phase(DP) steels with different martensite contents were obtained by appropriate heat treatment of an SAE1010 structural carbon steel,which was cheap and widely used in the construction industry. The corrosion behavior of DP steels in con-crete was investigated under various tempering conditions. Intercritical annealing heat treatment was applied to the reinforcing steel to obtain DP steels with different contents of martensite. These DP steels were tempered at 200,300,and 400°C for 45 min and then coo...     

Dispersion-strengthening effect of Cu-based Mn, Al, and Zn rich alloys

In this systematic study, dispersion-strengthening effect of the Cu–25.91Mn (wt.%), Cu–26.62Mn–8.99Al (wt.%), Cu–22.17Mn–12.32Zn (wt.%) ingot alloys have been investigated. Samples were homogenized at a high fixed temperature in different periods and cooled with different cooling rates. After processes, microanalysis of the samples were interpreted by using scanning electron microscope (SEM) and weight percentages of the elements of the occurrence phases in the samples obtained by using electron dispersion spectroscopy (EDS) technique. Additionally, some characteristic properties of the heat treated samples with different conditions of Cu–Mn, Cu–Mn–Al, Cu–Mn–Zn ingot alloys were also discussed.     

Studying high impact fix-inducing changes

As software systems continue to play an important role in our daily lives, their quality is of paramount importance. Therefore, a plethora of prior research has focused on predicting components of software that are defect-prone. One aspect of this research focuses on predicting software changes that are fix-inducing. Although the prior research on fix-inducing changes has many advantages in terms of highly accurate results, it has one main drawback: It gives the same level of impact to all fix-inducing changes. We argue that treating all fix-inducing changes the same is not ideal, since a small typo in a change is easier to address by a developer than a thread synchronization issue. Therefore, in this paper, we study high impact fix-inducing changes (HIFCs). Since the impact of a change can be measured in different ways, we first propose a measure of impact of the fix-inducing changes, which takes into account the implementation work that needs to be done by developers in later (fixing) changes. Our measure of impact for a fix-inducing change uses the amount of churn, the number of files and the number of subsystems modified by developers during an associated fix of the fix-inducing change. We perform our study using six large open source projects to build specialized models that identify HIFCs, determine the best indicators of HIFCs and examine the benefits of prioritizing HIFCs. Using change factors, we are able to predict 56 % to 77 % of HIFCs with an average false alarm (misclassification) rate of 16 %. We find that the lines of code added, the number of developers who worked on a change, and the number of prior modifications on the files modified during a change are the best indicators of HIFCs. Lastly, we observe that a specialized model for HIFCs can provide inspection effort savings of 4 % over the state-of-the-art models. We believe our results would help practitioners prioritize their efforts towards the most impactful fix-inducing changes and save inspection effort.