Rogers P.M.,Graduate Research Assistant |
Stevenson W.R.,University of Wisconsin - Madison
Plant Disease | Year: 2010
Isolates of Alternaria dauci causing Alternaria leaf blight (ALB) were collected from commercial carrot (Daucus carota var. sativus) fields in northeastern North America during 2004. Twenty-two isolates representing a range of genetic diversity were analyzed for their aggressiveness on three commercial carrot varieties (Bolero, Enterprise, and Heritage) varying in disease susceptibility as well as their in vitro response to three fungicides (azoxystrobin, chlorothalonil, and boscalid) commonly used for ALB control. Severity of leaf and petiole blight and leaf chlorosis varied among isolates and carrot varieties in each of three experiments. Visible differences in disease severity, which ranged from 10.9 to 45.1% of the leaf area affected, were apparent 16 days after inoculation. Intensity of chlorosis correlated strongly with blight severity among all isolates. Significant differences were noted among carrot varieties in response to ALB. These varieties may prove useful as differentials capable of distinguishing isolates because variety by isolate interactions were detected. Inhibition of conidial germination ranged from 0.01 to 0.37 μg/ml for azoxystrobin, 0.009 to 0.08 μg/ml for chlorothalonil, and 0.09 to 0.59 μg/ml for boscalid. On average, isolates were more sensitive to chlorothalonil than to azoxystrobin and boscalid. No significant correlation was noted between fungicide sensitivity and aggressiveness. These data provide evidence for phenotypic diversity among A. dauci isolates collected from areas of commercial carrot production. © 2010 The American Phytopathological Society.
Crossley W.A.,Purdue University |
Skillen M.D.,Purdue University |
Skillen M.D.,Graduate Research Assistant |
Frommer J.B.,Purdue University |
And 4 more authors.
Journal of Aircraft | Year: 2011
This paper summarizes design optimization approaches for sizing a morphing aircraft for which the wing can make significant shape changes in flight. The approaches include single-level problems solved by gradient-free and gradient-based optimizers and a multilevel problem solved by gradient-based optimizers; of these, the multilevel approach proved most efficient. In the multilevel approach, a top-level problem minimizes the aircraft gross weight using reference design variables (T=W, S, AR, t=c, Δ, and γ), along with morphing limit variables describing the maximum shape change as a function of the reference geometry (e.g.,Δb,Δc, and ΔΔ). A sublevel problem for each mission segment determines an optimal wing-shape scheduling that minimizes fuel consumption, satisfies performance constraints, and operates within the geometric domain prescribed by the top-level problem. While the empty-weight buildup uses traditional predictors for fixed-geometry components, the wing weight prediction uses a parametric equation derived from structural optimization studies of morphing wings. The multilevel optimization approach then sizes an aircraft for which the wing can change sweep and root chord length, demonstrating: 1) the optimal wing-shape scheduling and maximum shape change for the morphing strategy, 2) the approach's ability to facilitate continuous morphing during mission segment analysis, and 3) improved effectiveness over previous singlelevel morphing aircraft sizing approaches. © Copyright 2010.
Rahjoo S.,Graduate Research Assistant |
Najafi M.,University of Texas at Arlington |
Williammee R.,District Materials Laboratory Supervisor |
Khankarli G.,rth Region Support Center
Pipelines 2012: Innovations in Design, Construction, Operations, and Maintenance - Doing More with Less - Proceedings of the Pipelines 2012 Conference | Year: 2012
Pipe jacking is a trenchless technology method of installing pipes under existing facilities such as roads and railroads. Predicting jacking forces is important for planning, design, and construction phases of these types of projects. The jacking forces dictates shaft or pit locations, thrust block or backstop design, jacking equipment, use of intermediate jacking stations, and pipe bearing capacity. Accurate estimation of jacking forces depends on several site and project parameters, such as soil and site conditions, lubrication, size of overcut and steering corrections. Excessive jacking forces can damage the pipe, instable the thrust block, and may stop project progress. There are different methods of calculating jacking loads presented by researchers and industry organizations. By using different models, a discrepancy can be observed in results, which make precise estimation questionable. It can be concluded that analytical and empirical models are based on certain assumptions and field data, and more research is required. For example, ASCE 27 recommends using experimental values to calculate frictional forces and do not consider the face pressures. Other researchers have considered detailed analysis of soil conditions at the face and recommended including project specific conditions such as pipe depth and bore stability. This paper presents an analysis of literature and provides a framework for design engineers to refer to applicable guidelines for planning pipe jacking operations. A conceptual case study is provided to illustrate the differences. © 2012 American Society of Civil Engineering.
Shkarayev S.,University of Arizona |
Silin D.,University of Arizona |
Silin D.,Graduate Research Assistant
AIAA Journal | Year: 2010
This study addresses the aerodynamics of elastic membrane flapping wings. Several applications of the actuator disk theory to the flapping wings of insects and birds are reviewed. In previous studies, to account for spatial and temporal variance in the wake behind the flapping wings, empirical corrections were proposed for the induced velocity and power. In the present paper, a new procedure for determination of the correction factor is proposed, using membrane-type flapping-wing devices. Wind-tunnel experiments were conducted and the stroke-averaged propulsive thrust was measured on 25-cm-wingspan (flat and 9% camber) and 74-cm-wingspan flapping-wing models. Either flapping frequency or input power was held constant during the tests. Obtained thrust forces werecompared to theoretical values predicted by the actuator disk theory. Empirical correction factors to the actuator disk theory were determined, providing a best fit to the experimental data when the flapping axis aligned with freestream velocity. It is noteworthy that the numerical value for the correction factor for the 25 cm cambered wing agrees with the results obtained on large insects. The theoretical corrections for angle of attack of the flapping wing give satisfactory agreements with the experimental data only for relatively low forward speeds.
Walker J.F.C.,Graduate Research Assistant |
Ahmed A.,Graduate Research Assistant
51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2013 | Year: 2013
Tests were conducted on a specially designed slender delta wing with a 75 deg leading edge sweep and capable of rotational degrees of freedom about longitudinal and vertical axis. Aerodynamic measurements were made for three cases when the model motion was limited to roll only, yaw only and combined roll and yaw. Results were compared to the data for fully constrained case. Roll and yaw oscillations were observed to start near 28o angle of attack however the amplitude of oscillations for the roll decreased from ±30o to ±18o and that of yaw decreased from ±20o to ±5o when the model was allowed to simultaneously roll and yaw indicating unique fluid dynamic coupling. The frequency of yaw oscillations was found to be 1/3 the frequency of roll oscillations indicating stronger dependence of roll on vortex bursting. © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.