Estimation of Supersonic Stage Separation Aerodynamics of Winged-Body Launch Vehicles Using Response Surface Methods

A collection of statistical and mathematical techniques referred to as response surface methodology was used to estimate the longitudinal stage separation aerodynamic characteristics of a generic, bimese, winged multi-stage launch vehicle configuration using data obtained on small-scale models at supersonic speeds in the NASA Langley Research Center Unitary Plan Wind Tunnel. The simulated Mach 3 staging was dominated by multiple shock wave interactions between the orbiter and booster vehicles throughout the relative spatial locations of interest. This motivated a partitioning of the overall inference space into several contiguous regions within which the separation aerodynamics were presumed to be well-behaved and estimable using cuboidal and spherical central composite designs capable of fitting full second-order response functions. The primary goal was to approximate the underlying overall aerodynamic response surfaces of the booster vehicle in belly-to-belly proximity to the orbiter vehicle using relatively simple, lower-order polynomial functions that were piecewise-continuous across the full independent variable ranges of interest. The quality of fit and prediction capabilities of the empirical models were assessed in detail, and the issue of subspace boundary discontinuities was addressed. The potential benefits of augmenting the central composite designs to full third order using computer-generated D-optimality criteria were also evaluated. The usefulness of central composite designs, the subspace sizing, and the practicality of fitting low-order response functions over a partitioned inference space dominated by highly nonlinear and possibly discontinuous shock-induced aerodynamics are discussed

Analysis of Arabidopsis thaliana mutants defective in the oligopeptide transporter OPT3

Abstract only availableThe transport of peptides across membranes is a phenomenon found in both prokaryotes and eukaryotes as a method of obtaining amino acids, nitrogen, and carbon. Peptides can be transported by ATP-dependent transporters, as well as proton-coupled transporters. Among the latter are members of the oligopeptide transport (OPT) family, which transport tetra- and pentapeptides. Sequence comparisons led to the identification of nine OPT genes in Arabidopsis and our laboratory is investigating the role of these transporters in plant growth and development. Previous studies showed that mutations in the OPT3 gene resulted in embryo lethality. More recently, OPT3 expression was shown to increase under conditions of iron limitation, suggesting a possible role for OPT3 in transporting iron-chelates. The lethal nature of OPT3 T-DNA insertion mutation makes them difficult to study in a homozygous condition. Therefore, we sought non-lethal mutations within the OPT3 gene sequence, which can be maintained as homozygous plants. To create such mutations, we used the process of Targeted Induced Local Lesions IN Genomes (TILLING) to identify non-lethal, point mutations in the OPT3 gene. Eight mutant alleles, opt3-1 to opt3-8, were identified by TILLING. These mutants were sequenced and aligned with the other members of the OPT family to determine whether the mutations occurred within conserved regions of the protein. The mutations opt3-5 (P628S) and opt3-8 (P547L) were the first homozygous mutants identified which occurred within a highly conserved region and, therefore, were the likely candidates to disturb OPT3 function. These mutations were followed in segregating populations by CAPS (Cleaved Amplified Polymorphic Sequence) markers. Homozygous mutant lines and wild-type controls were grown on medium containing limited, moderate, or excess iron. The iron effects on the plant were determined by assaying the chlorophyll content in whole plants. These assays revealed no measurable effect of the OPT3 mutations on chlorophyll content under the conditions tested. We are now examining other opt3 alleles for a role in iron transport and other possible phenotypes displayed during plant growth and development.MU Monsanto Undergraduate Research Fellowshi

Preflare magnetic and velocity fields

A characterization is given of the preflare magnetic field, using theoretical models of force free fields together with observed field structure to determine the general morphology. Direct observational evidence for sheared magnetic fields is presented. The role of this magnetic shear in the flare process is considered within the context of a MHD model that describes the buildup of magnetic energy, and the concept of a critical value of shear is explored. The related subject of electric currents in the preflare state is discussed next, with emphasis on new insights provided by direct calculations of the vertical electric current density from vector magnetograph data and on the role of these currents in producing preflare brightenings. Results from investigations concerning velocity fields in flaring active regions, describing observations and analyses of preflare ejecta, sheared velocities, and vortical motions near flaring sites are given. This is followed by a critical review of prevalent concepts concerning the association of flux emergence with flare

Limitations of Absolute Current Densities Derived from the Semel & Skumanich Method

Semel and Skumanich proposed a method to obtain the absolute electric current density, |Jz|, without disambiguation of 180 degree in the transverse field directions. The advantage of the method is that the uncertainty in the determination of the ambiguity in the magnetic azimuth is removed. Here, we investigate the limits of the calculation when applied to a numerical MHD model. We found that the combination of changes in the magnetic azimuth with vanishing horizontal field component leads to errors, where electric current densities are often strong. Where errors occur, the calculation gives |Jz| too small by factors typically 1.2 ~ 2.0.Comment: 10 pages, 4 figures. To appear on Science in China Series G: Physics, Mechanics & Astronomy, October 200

Impact of truck contamination and information sharing on foot-and-mouth disease spreading in beef cattle production systems.

As cattle movement data in the United States are scarce due to the absence of mandatory traceability programs, previous epidemic models for U.S. cattle production systems heavily rely on contact rates estimated based on expert opinions and survey data. These models are often based on static networks and ignore the sequence of movement, possibly overestimating the epidemic sizes. In this research, we adapt and employ an agent-based model that simulates beef cattle production and transportation in southwest Kansas to analyze the between-premises transmission of a highly contagious disease, foot-and-mouth disease. First, we assess the impact of truck contamination on the disease transmission with the truck agent following an independent clean-infected-clean cycle. Second, we add an information-sharing functionality such that producers/packers can trace back and forward their trade records to inform their trade partners during outbreaks. Scenario analysis results show that including indirect contact routes between premises via truck movements can significantly increase the amplitude of disease spread, compared with equivalent scenarios that only consider animal movement. Mitigation strategies informed by information sharing can effectively mitigate epidemics, highlighting the benefit of promoting information sharing in the cattle industry. In addition, we identify salient characteristics that must be considered when designing an information-sharing strategy, including the number of days to trace back and forward in the trade records and the role of different cattle supply chain stakeholders. Sensitivity analysis results show that epidemic sizes are sensitive to variations in parameters of the contamination period for a truck or a loading/unloading area of premises, and indirect contact transmission probability and future studies can focus on a more accurate estimation of these parameters

Predictive combustion trajectory visualization model for study of conventional and advanced direct injection compression ignition combustion modes

There are many diagnostic approaches for determine in-cylinder quantities in an internal combustion engine. Of primary importance in this work are equivalence ratio and flame temperature. These parameters can be measured using expensive and highly modified optical engines or calculated using time consuming computational fluid dynamics and chemical kinetic models. These approaches work well in a lab but become less feasible when trying to implement diagnostics for real world on-board consumer use. With the decreasing cost of in-cylinder pressure transducers, the question arises of the whether or not it is feasible to create a diagnostic model based on in-cylinder pressure data and known engine parameter based on existing engine sensors. Using this model, it may be possible to actively modulate engine parameters to change combustion behavior in order to decrease harmful emissions without penalty to efficiency. In this context, combustion behavior (or a trajectory) is meant to describe the local temperatures and equivalence ratios that exist during burning in a direct injection compression ignition engine’s combustion chamber. This work builds on earlier attempts to model combustion trajectories on the equivalence ratio – temperature plane (Φ-T plane), as calculated from cylinder pressure. This work uses a 1-D non-vaporizing spray model with assumed radial profile. The proposed model accounts for the change in cylinder pressure throughout the combustion process by using a time step based on the resolution of the cylinder pressure data. Based on the predicted equivalence ratio, local flame temperature, calculated heat release, and amount of fuel burned at each portion (control volume) of the spray, a plot of the combustion trajectory can be developed. The temperature and equivalence ratio at which the fuel burns can be tracked to give a full mass weighted history of the combustion event with respect to both the ignition conditions and post-mixing heating and cooling on the Φ-T plane. The model was tested over multiple operating conditions including conventional and late timing diesel combustion, with and without EGR, lower and higher injection pressure. The encouraging results obtained from this study suggest engine control strategies could use this simple approach to reduce harmful emissions in the future. (Published By University of Alabama Libraries