No abstract

Because of the high cost of quality construction materials, transportation engineers are often forced to seek alternative designs using substandard materials, commercial construction aids, alternative pavement materials, and innovative design practices. Nontraditional soil stabilization additives are being marketed as viable solutions for stabilizing marginal materials as a low-cost alternative to traditional construction materials. Nontraditional additives are diverse in their composition and the way they interact with soil. Unfortunately, little is known about their interaction with geotechnical materials and their fundamental stabilization mechanisms. The objective of this research was to advance current understanding of the chemical and physical bonding mechanisms associated with selected non-traditional stabilizers. The research consisted of conducting qualitative analyses of hypothesized stabilization mechanisms, examining historical literature for supporting documentation, and performing laboratory experiments to improve the understanding of how these nontraditional additives stabilize soils. Laboratory experiments included image analyses, physical characterization, and chemical analyses to determine the primary constituents of the mineral, soil, stabilizer, and stabilized soil composite. The focus of this effort was to provide insight into the proposed mechanisms by using the laboratory data to examine proposed mechanisms from the historical literature and to provide additional hypotheses for the interaction between nontraditional additives and different soil types.

Abstract.Several errors occur when a traditional Doppler beam swinging (DBS) or velocity-azimuth display (VAD) strategy is used to measure turbulence with a lidar. To mitigate some of these errors, a scanning strategy was recently developed which employs six beam positions to independently estimate the u, v, and w velocity variances and covariances. In order to assess the ability of these different scanning techniques to measure turbulence, a Halo scanning lidar, WindCube v2 pulsed lidar, and ZephIR continuous wave lidar were deployed at field sites in Oklahoma and Colorado with collocated sonic anemometers.Results indicate that the six-beam strategy mitigates some of the errors caused by VAD and DBS scans, but the strategy is strongly affected by errors in the variance measured at the different beam positions. The ZephIR and WindCube lidars overestimated horizontal variance values by over 60 % under unstable conditions as a result of variance contamination, where additional variance components contaminate the true value of the variance. A correction method was developed for the WindCube lidar that uses variance calculated from the vertical beam position to reduce variance contamination in the u and v variance components. The correction method reduced WindCube variance estimates by over 20 % at both the Oklahoma and Colorado sites under unstable conditions, when variance contamination is largest. This correction method can be easily applied to other lidars that contain a vertical beam position and is a promising method for accurately estimating turbulence with commercially available lidars.

23Na NMR studies of counterion relaxation behavior in the presence of added electrolytes have been performed to determine the relative binding affinities of Na+, K+, Mg2+, and Ca2+ ions to the homopolymers of poly(sodium acrylate) (NaAA), poly(sodium 2-acrylamido-2-methylpropanesulfonate) (NaAMPS), and poly(sodium 3-acrylamido-3-methylbutanoate) (NaAMB). The addition of Mg2+ and Ca2+ to the biopolymer poly(sodium galacturonate) (NaGAL) was also investigated. Addition of salts yielded the order of binding Ca2+ > Mg2+ > K+ = Na+ for NaAA and NaAMB and Ca2+ = Mg2+ > K+ > Na+ for NaAMPS. Significant differences in the 2SNa NMR behavior for NaAA are observed for added Mg2+ and Ca2+ and were interpreted in terms of hydration of the polyelectrolyte near phase separation, although a conformational change cannot absolutely be ruled out. Differences observed upon addition of Mgz+ and Ca2+ in the NaGAL system are discussed in relation to the "egg-box" model of Ca2+ binding to NaGAL. Viscosity profiles for each of the polymers with the above cations are related to the NMR data. Phase-separation studies on NaAMB demonstrate increased hydrophobicity of the polymer in the presence of excess Ca2+. IntroductionThe behavior of uncharged polymers and polyelectrolytes in the presence of simple electrolytes is a subject of continuing research in our laboratory. The large viscosity losses and, ultimately, phase separation of anionic polyelectrolytes by a divalent cation are due to the strong chelating effect that reduces hydrodynamic volume and solvation. Sufficient inter-and intramolecular binding occurs to reduce the hydration of the polymer to a critical point at which phase separation occurs. The maintenance of viscosity in high concentrations of electrolytes is critical for application of polymers in areas such as enhanced oil recovery, drag reduction, and controlled release. Synthetic efforts have resulted in polymer systems that maintain viscosity in the presence of both monovalent and divalent ions and do not phase separate readil~.l-~ An increased understanding of the ion-binding and phase-separation phenomena of these polymers is necessary for tailoring polymer systems for use in areas where high salt concentrations adversely affect performance.The viscosity behavior and phase stability of polyelectrolytes in the presence of excess salts have been extensively studied.l-14 PoIy(acry1ates)-and hydrolyzed poly-(acrylamide) (HPAM)'lS-ll exhibit large viscosity losses and may phase separate in the presence of divalent counterions such as Mgz+, Ca2+, and Ba2+. Poly(sodium acrylate) (NaAA) precipitates from solution when the concentration of divalent counterion (Mg2+, Ca2+, Ba2+) reaches a critical value relative to the number of anionic sites available (approximately 0.8 on an equivalent basis).6 Macroscopic solution properties (viscosity, phase separation) of poly(vinylsu1fonate) (PVS) are dependent on the nature of the counterion species.13J4Copolymers of acrylamide with sodium 2-acrylamido-2-propanesulfonate (NaAMPS)1*3!4 and 3...

Several factors cause lidars to measure different values of turbulence than an anemometer on a tower, including volume averaging, instrument noise and the use of a scanning circle to estimate the wind field. One way to avoid the use of a scanning circle is to deploy multiple scanning lidars and point them toward the same volume in space to collect velocity measurements and extract high-resolution turbulence information. This paper explores the use of two multi-lidar scanning strategies, the tri-Doppler technique and the virtual tower technique, for measuring 3-D turbulence. In summer 2013, a vertically profiling Leosphere WindCube lidar and three Halo Photonics Streamline lidars were operated at the Southern Great Plains Atmospheric Radiation Measurement site to test these multi-lidar scanning strategies. During the first half of the field campaign, all three scanning lidars were pointed at approximately the same point in space and a tri-Doppler analysis was completed to calculate the three-dimensional wind vector every second. Next, all three scanning lidars were used to build a 'virtual tower' above the WindCube lidar. Results indicate that the tri-Doppler technique measures higher values of horizontal turbulence than the WindCube lidar under stable atmospheric conditions, reduces variance contamination under unstable conditions and can measure high-resolution profiles of mean wind speed and direction. The virtual tower technique provides adequate turbulence information under stable conditions but cannot capture the full temporal variability of turbulence experienced under unstable conditions because of the time needed to readjust the scans.

y y = wall-shearrate A , = eigenvalue = dimensionless mixing cup solute concentration + = distance transverse t o flow = volume fraction of particles Stream functions are derived for a spherical droplet in creeping flow with an arbitrary surface tension gradient a t its interface. The stream functions are used to show theoretically that the terminal velocity is reduced and that the interfacial velocitv is retarded, emeciallv near the rear of the M. DOUGLAS LEVAN and JOHN NEWMAN , I droplet, when a trace of surfactant is present in the exterior phase and when surface aging is controlled by diffusion. SCOPEExperimental investigations of droplet motion in liquid containing a surface active impurity have Shown that, compared to motion in pure liquid, both the terminal Correspondence concerning this paper should be addressed to M. velocity and the interfacial velocity of a droplet are reduced, the latter particularly near the rear of the droplet.Here a theoretical investigation of droplet motion in systems contaminated by surfactant is presented. The ob-

The building of utility-scale wind farms requires knowledge of the wind speed climatology at hub height (typically 80-100 m). As most wind speed measurements are taken at 10 m above ground level, efforts are being made to relate 10-m measurements to approximate hub-height wind speeds. One common extrapolation method is the power law, which uses a shear parameter to estimate the wind shear between a reference height and hub height. The shear parameter is dependent on atmospheric stability and should ideally be determined independently for different atmospheric stability regimes. In this paper, data from the Oklahoma Mesonet are used to classify atmospheric stability and to develop stability-dependent power law fits for a nearby tall tower. Shear exponents developed from one month of data are applied to data from different seasons to determine the robustness of the power law method. In addition, similarity theory-based methods are investigated as possible alternatives to the power law. Results indicate that the power law method performs better than similarity theory methods, particularly under stable conditions, and can easily be applied to wind speed data from different seasons. In addition, the importance of using co-located near-surface and hub-height wind speed measurements to develop extrapolation fits is highlighted.

No abstract