Polymer electrolyte membranes derived from novel fluorine-containing poly(arylene ether ketone)s by controlled post-sulfonation

Precise assignment with ¹H, ¹³C and some two dimensional NMR measurements showed that sulfonation reaction by concentrated sulfuric acid at 30 °C of fluorine-containing poly(arylene ether ketone) copolymers derived from 4,4′-bis(2,4,5,6-pentafluorobenzoyl)diphenyl ether (BPDE) and 9,9-bis(4-hydroxypehnyl)fluorene (HF) and 2,2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane (6FBA) yielded quantitative introduction of sulfonic groups onto 2- and 7-positions of fluorene ring in HF unit. A series of sulfonated poly(arylene ether ketone)s with different ion exchange capacity was prepared by using this method with different compositions of HF and 6FBA, and membranes obtained from these polymers were characterized by TGA, moisture and water uptake, proton conductivity, methanol permeability, and Fenton testing. These membranes showed sufficient thermal stability, high proton conductivity at high humidified condition for PEFC and good balance in proton conductivity in water and methanol permeability for DMFC. On the other hand, they showed relatively high swelling by water probably due to weak intermolecular interaction caused by the existence of fluorine atoms in the polymer structure.     

Simulation of Thermal Conductivity of Nanofluids Using Dissipative Particle Dynamics

The effective thermal conductivity of Al₂O₃/water and CuO/water nanofluids were modeled by numerically solving steady heat flow in one-dimensional microchannels. This was accomplished by using energy conserving dissipative particle dynamics (DPDe).The effects of the interfacial thermal resistance and the Brownian motion of nanoparticles were incorporated in the model by modifying the conductive interaction parameter in the energy equation. The results were presented in the form of the thermal conductivity of nanofluids as functions of particle volume fraction and temperature, and were compared with the available experimental and analytical results. The present model agreed well with the experimental results for Al₂O₃/water nanofluid, whilethere were discrepancies between the model and the results for CuO/water nanofluid.     

Poiseuille Number Correlations for Gas Slip Flow in Micro-Tubes

Fundamental research in fluid flow characteristics in micro-tubes are required for designing microfluidic systems. In this study, Poiseuille number, the product of friction factor and Reynolds number (f · Re) for quasi-fully developed micro-tube flows, was obtained for slip flow regime. The numerical methodology was based on the Arbitrary-Lagrangian-Eulerian (ALE) method and the uncertainties of the results were assessed based on the grid convergence index (GCI). The numerical model was validated with the available experimental and numerical results. The compressible momentum and energy equations were solved for a wide range of Reynolds and Mach numbers with two thermal boundary conditions: constant wall temperature (CWT), and constant heat flux (CHF), respectively. The slip boundary conditions and their numerical implementation are appropriately documented. The tube diameter ranged from 3 to 10 μm and the tube aspect ratio was 200. The stagnation pressure was chosen in such a way that the exit Mach number ranged from 0.1–1.0. The outlet pressure was fixed at the atmospheric condition. It was found that for the case of compressible and slip flows, f · Re correlations are functions of the Mach and Knudsen numbers, and are different from the values obtained from the expression, 64/(1 + 8 Kn), available for the incompressible slip flow regime. The f · Re correlations obtained here are applicable to both no-slip and slip conditions, and for both incompressible and compressible flows. The results are in excellent agreement with the available experimental data.     

Investigating different break-in procedures for reformed methanol high temperature proton exchange membrane fuel cells

The present work focuses on reducing the complexities involved in the mass production of HT-PEM fuel cell systems integrated with a methanol reformer. Different break-in procedures are investigated on a single HT-PEMFC. The work is divided into two parts, the first in which different break-in times are tested in order to reduce the usual break-in time of around 100 h, and the second one, where simulated reformed fuel is tested during and after break-in to understand the impact on degradation over time.In this study, two set of tests are carried out with different break-in times, the normal break-in (100 h), intermediate break-in (30 and 50 h) and no break-in (0 h). After break-in, all the cells were subjected to a load cycling profile between 0.2 and 0.6 A cm^?2 with 5 min at each current density. The test was then carried out to compare the cell performance over time when the break-in is carried out with simulated reformed gas having a composition of 64.7% H₂, 21.3% CO₂, 12% H₂O and 2% CH₃OH. The break-in time for this test was 100 h. The cells are operated at 0.2 A cm^?2 during break-in and thereafter at 0.6 A cm^?2 under normal operation. The cell performance and impedance change over time is analyzed. The different resistances are deduced using equivalent circuit models and analyzed to understand the changes occurring in the MEA during break-in and how they affect the durability of an HT-PEMFC. The degradation rate for the different operating strategy is calculated from the voltage trajectory over time. The comparison of degradation and break-in time suggests that the normal break-in induces a uniform ohmic resistance changes in the cell over time, while the fast cycling leads to non-uniform changes in resistances. However, the performance and degradation are not significantly affected over $\approx$750 h test. The test with simulated reformed fuel indicates that the break-in with pure H₂ is important for longer durability when operation thereafter is with reformed fuel. The cell with reformed fuel break-in degrades much faster compared to the cell with H₂ break-in.     

Migration of bisphenol A and benzophenones from paper and paperboard products used in contact with food

Migration of bisphenol A (BPA) and benzophenones, i.e., benzophenone (BZ), 4-(dimethylamino)benzophenone (DMAB), Michler's ketone (MK) and 4,4'-bis(diethylamino)benzophenone (DEAB), from 21 paper and paperboard products (15 recycled paperboard boxes and 6 virgin paper products) used in contact with food was examined. Migration levels of compounds from recycled paperboard were compared under various food-simulating conditions. BPA showed the highest migration into 20% ethanol and benzophenones into 95% ethanol. No compounds migrated from virgin paper products, but compounds did migrate into food simulants from recycled paperboard food boxes. BPA migrated into 20% ethanol from all recycled paperboard food boxes between 1.0 and 18.7 ng/mL. Into 95% ethanol, migration of BZ was observed in 8 samples (1.0-18.9 ng/mL), DMAB in 12 samples (1.2-3.7 ng/mL), MK in 13 samples (1.9-9.0 ng/mL), and DEAB in 13 samples (1.0-10.6 ng/mL). The highest migration level was 27.2 ng/mL and most of the migration levels were below 10 ng/mL. These values are sufficiently low compared with the TDI and NOAEL levels. Moreover, the amount of food in daily meals that comes into contact with paperboard products is relatively small. Consequently, it was concluded that there was no safety concern regarding the tested compounds in recycled paperboard food boxes.     

BENDING OF SUBMERGED WOODY RIPARIAN VEGETATION AS A FUNCTION OF HYDRAULIC FLOW CONDITIONS

Woody riparian vegetation provides numerous ecological benefits such as stabilizing streambanks, storing and cycling nutrients, shading streams and providing habitat for wildlife. However, vegetation also increases hydraulic roughness and reduces the effective flow area, resulting in an increased water surface elevation for a given streamflow. Balancing the desire to preserve woody vegetation in stream corridors with the need to manage flood risks requires accurate techniques for predicting the influence of vegetation on stream hydraulics. However, this is a challenging problem because woody vegetation responds to the flow field itself by bending and streamlining in response to hydraulic forces. The goal of this study was to predict the bending behaviour of woody riparian vegetation as a function of hydraulic flow conditions. Field tests were performed to elucidate tree biomechanical properties for select riparian taxa of the southwestern USA. Biomechanical results served as input parameters for a numerical algorithm designed to predict tree bending for water velocities likely to be encountered during flood events. Bending simulations revealed appreciable variability in bent tree heights. Variability was likely a manifestation of the extensive variance in plant characteristics and properties inherent in biological specimens. However, no trees were expected to bend to a height lower than approximately 42% of their original height, even in water moving at 2.5 m·s^‐1. The results of this work provide an important first step in an effort to predict a dynamic hydraulic roughness for vegetated channels and floodplains under flood conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermally stable ion conductive polymer composites containing imide-anion-type zwitterions

Summary Zwitterion bearing highly dissociable imide anion (EIm5csI) was used as major component for stable polymer electrolytes. A polymerization of methyl acrylate in the presence of EIm5csI/LiTFSI mixture gave a flexible film with the ionic conductivity of 9.3×10^-6 Scm^-1 at 50 °C. Mixing of poly(lithium acrylate) and EIm5csI/LiTFSI mixture improved ionic conductivity (3.3×10^-5 Scm^-1 at room temperature), lithium transference number (0.44), and thermal stability.     

Psychological and Social Influences on Blog Writing: An Online Survey of Blog Authors in Japan

We conducted a questionnaire survey of personal blog authors (N = 1,434) and examined two hypothesized models using structural equation modeling to clarify the psychological and social process associated with why authors continue to write their blogs. Two final models with good fit were obtained. It was confirmed that being satisfied with benefits to self, relationships with others, and skill in handling information had significant positive effects on the intention to continue blog writing. The psychological traits of private self-consciousness, reassurance-seeking, and information need were hypothesized to be effective in establishing consciousness of the benefits; these also had significant positive effects. In contrast, only positive feedback had a significant influence on satisfaction related to information handling skill, whereas both negative and positive feedback had significant influences on satisfaction related to information handling skill. This suggests that communication with readers who gave positive feedback strongly encouraged blog authors to continue writing. Similarities and differences between the two models and recommendations for further theoretical development are discussed.     

From dissipative particle dynamics scales to physical scales: a coarse-graining study for water flow in microchannel

In the present work, dissipative particle dynamics (DPD) simulation of simple flows is studied based on coarse-graining parameter. Reference scales of DPD are expressed in terms of physical units and DPD parameters and equations are expressed in terms of Reynolds number and apparent Peclet number. DPD parameters for a given coarse-graining are calculated by matching the density and viscosity of water and Reynolds number of the flow. The formulation is applied to water flow in microchannels of height 5 and 10 μm and tested for a wide range of coarse-graining parameter varying from 10⁷ to 10⁹. The results are in a good agreement with the continuum formulation and simulated the correct hydrodynamics of water flow in microchannels. By inspecting the microscopic detail of the interaction between the DPD particles, it is found that diffusivity is low for high coarse-graining parameter, which results in higher values of Schmidt number. Parameters are tested within the continuum assumption. It is shown that correct Schmidt number can be achieved using small coarse-graining parameter. Also, it is observed that low diffusivity or high Schmidt number does not affect the hydrodynamics of water.