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Cellulose nanocrystal has been widely used as a reinforcement filler in waterborne coatings, but the application of cellulose nanofiber (CNF) as a filler is difficult because of inhomogeneous dispersion. Herein, a facile and effective strategy to improve the dispersion of CNFs in the polymer matrix by mixing with γ-aminopropyltriethoxysilane (APS) is presented. The APS dosages 0.08−0.48 wt % to 0.3 wt % CNFs were investigated, and the dosage 0.16% was found to achieve a superior stability of CNFs in the aqueous solution. The APS(0.16%)-modified CNFs were then incorporated and demonstrated distributing uniformly in the waterborne acrylic coating. The as-prepared coatings retain high light transmittance around 90%, and display improved mechanical properties. The composite coatings show a maximum 500% improvement in Young's modulus, two-level improvement in hardness, and 35% reduction in abrasion loss as compared with those of neat coating. These results reveal that APS modification induces the homogeneous dispersion of CNFs in aqueous solution, and turns the CNF into an ideal reinforced filler for waterborne coatings.

[1] When an open well is installed in an unsaturated zone, gas can flow between the subsurface and the well depending on the gas pressure gradient near the well. This well is called a barometric pumping well (BPW). Quantifying gas flow rate to and from a BPW is indispensable to optimize the passive soil vapor extraction in remediation of volatile organic compounds in the unsaturated zone. This study presents a two-dimensional (2-D) semianalytical solution for a multilayer unsaturated zone (ML solution) to determine gas flow rate to and from a BPW. The gas flow rate is approximated by a decomposing method frequently used in previous studies, that is, first solving the one-dimensional (1-D) vertical flow equation in response to the surface barometric pressure fluctuations and then superimposing this solution on that of the 1-D horizontally radial flow equation. The error induced by this approximation is quantified by a 2-D numerical simulation for the first time in this study. Results show that the maximum error induced is 20% at the peak flow rates. The ML solution is demonstrated to be sufficient for predicting subsurface gas pressure and gas flow rate in a multilayer unsaturated zone by the barometric pumping test at the Hanford site.Citation: You, K., H. Zhan, and J. Li (2011), Gas flow to a barometric pumping well in a multilayer unsaturated zone, Water Resour.

SUMMARYThe residual mechanism of wave-induced pore water pressure accumulation in marine sediments is re-examined. An analytical approximation is derived using a linear relation for pore pressure generation in cyclic loading, and mistakes in previous solutions (Int. J. Numer. Anal. Methods Geomech. 2001; 25:885-907; J. Offshore Mech. Arctic Eng. (ASME) 1989; 111(1):1-11) are corrected. A numerical scheme is then employed to solve the case with a non-linear relation for pore pressure generation. Both analytical and numerical solutions are verified with experimental data (Laboratory and field investigation of wavesediment interaction. Joseph H. Defrees Hydraulics Laboratory, School of Civil and Environmental Engineering, Cornell University, Ithaca, NY, 1983), and provide a better prediction of pore pressure accumulation than the previous solution (J. Offshore Mech. Arctic Eng. (ASME) 1989; 111(1):1-11). The parametric study concludes that the pore pressure accumulation and use of full non-linear relation of pore pressure become more important under the following conditions: (1) large wave amplitude, (2) longer wave period, (3) shallow water, (4) shallow soil and (5) softer soils with a low consolidation coefficient.