Design of a Lighter than Air Vehicle that Achieves Positive Buoyancy in Air Using a Vacuum

Three designs for a Lighter Than Air (LTA) structure that achieve positive buoyancy using a vacuum in place of a lifting gas were proposed and evaluated. The ratio of structure weight to the weight of displaced air was termed Weight/Buoyant Force (W/B) where a W/B1 corresponds to positive buoyancy. Two methods of geometrically stiffening a sphere were investigated and their W/B evaluated. A thin shelled sphere of beryllium stiffened with an isogrid of blade type stiffeners using Ultra High Modulus (UHM) carbon epoxy was predicted to give a W/B= 0.79. A geodesic sphere composed of a frame of cylindrical, UHM, carbon epoxy, pultruded rods with a thin external membrane was evaluated using Finite Element Analysis. A W/B=0.57 was calculated for the frame. The skin was predicted to add 0.37 to the W/B if Zylon was used to reinforce a Mylar membrane, which resulted in a predicted structure W/B=0.94. These structures were optimized using a non-linear programming optimization routine in MATLAB. A unique LTA vehicle concept composed of twin counter-rotating cylinders that made use of a virtual elliptical body to reduce drag and maintain structural integrity with a vacuum was also investigated and found to be infeasible

Nanosatellite Probes in Interplanetary Space: An Augmented Cassini Mission

The exploration of interplanetary space is one of the most challenging and costly ventures in human history. The relatively low amount of information on other sites beyond Earth is largely due to the rarity of effective trajectories as well as the high levels of risk and complexity inherent in innovative space exploration. One solution to this lack of information is the use of deployable satellite probes to help augment the main mission and its instrumentation. This “Mother- Daughter” architecture allows for the low-cost exploration of hazardous sites and numerous points of interest without compromising the primary mission. While the end goal is the use of nanosatellites on future interplanetary missions, this thesis focuses on an existing interplanetary mission, Cassini. The aim to demonstrate the scientific viability of this “Mother-Daughter” architecture can be achieved by locating numerous unexplored sites that could have been surveyed with a nanosatellite probe onboard Cassini. Each of these potential sites can be expanded into a unique science mission of its own, and in many cases the trajectories can be selected and optimized to better suit the practical design of a nanosatellite in the various interplanetary environments

Wolff's Theorem on Ideals for Matrices

We extend Wolff's theorem concerning ideals on H-infinity(D) to the matrix case, giving conditions under which an H-infinity solution G to the equation FG = H exists for all z in D, where F is an m-by-infinity matrix of functions in H-infinity (D), and H is an m-by-1 vector of such functions. We then examine several useful results

Grain legume evaluation

Pea variety evaluation, 89NM20, 89EB22, 89KA68, 89N334, 89EB24, 89SC27, 89A24, 89EB33, 89EB25. Grain legume species evaluation, 89NM21, 89MO41, 89N25, 89MC9, 89NM21, 89A22. Faba bean evaluation, 89MO42, 89A23, 89MC10, 89EB27, 89SG22 Grain legume agronom

The inheritance of resistance to bacterial leaf spot of lettuce caused by Xanthomonas campestris pv. vitians in three lettuce cultivars.

Lettuce yields can be reduced by the disease bacterial leaf spot (BLS) caused by the pathogen Xanthomonas campestris pv. vitians (Xcv) and host resistance is the most feasible method to reduce disease losses. The cultivars La Brillante, Pavane and Little Gem express an incompatible host-pathogen interaction as a hypersensitive response (HR) to California strains of Xcv resulting in resistance. Little was known about the inheritance of resistance; however, resistance to other lettuce pathogens is often determined by resistance gene candidates (RGCs) encoding nucleotide-binding leucine-rich repeat (NB-LRR) proteins. Therefore, we determined the inheritance of BLS resistance in the cultivars La Brillante, Little Gem and Pavane and mapped it relative to RGCs. The reaction to Xcv was analyzed in nine F1, F2 and recombinant inbred line populations of lettuce from HR×compatible or HR×HR crosses. The HR in La Brillante, Pavane and Little Gem is conditioned by single dominant genes, which are either allelic or closely linked genes. The resistance gene in La Brillante was designated Xanthomonas resistance 1 (Xar1) and mapped to lettuce linkage group 2. Xar1 is present in a genomic region that contains numerous NB-LRR encoding RGCs and functional pathogen resistance loci in the RGC2 family. The Xar1 gene confers a high level of BLS resistance in the greenhouse and field that can be introgressed into commercial lettuce cultivars to reduce BLS losses using molecular markers

Coupling of disulfide bond and distal histidine dissociation in human ferrous cytoglobin regulates ligand binding

Earlier kinetics studies on cytoglobin did not assign functional properties to specific structural forms. Here, we used defined monomeric and dimeric forms and cysteine mutants to show that an intramolecular disulfide bond (C38-C83) alters the dissociation rate constant of the intrinsic histidine (H81) (∼1000 fold), thus controlling binding of extrinsic ligands. Through time-resolved spectra we have unequivocally assigned CO binding to hexa- and penta-coordinate forms and have made direct measurement of histidine rebinding following photolysis. We present a model that describes how the cysteine redox state of the monomer controls histidine dissociation rate constants and hence extrinsic ligand binding

Dynamic modelling and response characteristics of a magnetic bearing rotor system including auxiliary bearings

Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotor-dynamic model and assess the dynamic behavior of a magnetic bearing rotor system which includes the effects of auxiliary bearings. Of particular interest is the effects of introducing sideloading into such a system during failure of the magnetic bearing. A model is developed from an experimental test facility and a number of simulation studies are performed. These results are presented and discussed