Evaluation of a high temperature adhesive for fabricating graphite/PMR-15 polyimide structures

Tests are conducted to measure shear strength, shear modulus and flatwise tensile strength of the A7F (amide-imide modified LARC-13) adhesive system. An investigation is also conducted to determine the effect of geometric material parameters, and elevated temperature on the static strength of standard joints. Single-lap and double-lap composite joints, and single, double and step lap composite to metal joints are characterized. A series of advanced joints consisting of preformed adherends, adherends with scalloped edges and joints with hybrid interface plies are tested and compared to baseline single and double-lap designs

A Cantor set of tori with monodromy near a focus-focus singularity

We write down an asymptotic expression for action coordinates in an integrable Hamiltonian system with a focus-focus equilibrium. From the singularity in the actions we deduce that the Arnol'd determinant grows infinitely large near the pinched torus. Moreover, we prove that it is possible to globally parametrise the Liouville tori by their frequencies. If one perturbs this integrable system, then the KAM tori form a Whitney smooth family: they can be smoothly interpolated by a torus bundle that is diffeomorphic to the bundle of Liouville tori of the unperturbed integrable system. As is well-known, this bundle of Liouville tori is not trivial. Our result implies that the KAM tori have monodromy. In semi-classical quantum mechanics, quantisation rules select sequences of KAM tori that correspond to quantum levels. Hence a global labeling of quantum levels by two quantum numbers is not possible.Comment: 11 pages, 2 figure

Secure Cloud Controlled Software Defined Radio Network For Bandwidth Allocation

The purpose of this research is to investigate the impact of mobility of wireless devices for opportunistic spectrum access and communications using National Instrument Universal Software Radio Peripherals devices. The overall system utilizes software defined radio networks for frequency allocation, cloud connectivity to maintain up-to-date information, and moving target defense as a security mechanism. Each USRP device sends its geolocation to query the spectrum database for idle channels. The cloud cluster was designed for complex data storage and allocation using a smart load balancer to offer ultra-security to users. This project also explores the advantages of data protection and security through moving target defense. To achieve this, the system would use an array of antennas to split the data into different parts and transmit them across separate antennas. This research provides the design to each of the mentioned projects for the implementation of a fully developed system

Characterizing the Role of Prophages on WHIB7 Expression and Antibiotic Resistance in Mycobacterium Chelonae

Mycobacterial pathogens are responsible for an ongoing public health crisis. Mycobacterium abscessus is the causative agent of lung infections that disproportionately affect immunocompromised individuals and is the most intrinsically antibiotic-resistant bacterial species known. These characteristics make M. abscessus infections difficult to treat, with a success rate of only 45%. While some extensively resistant isolates are caused by mutations in drug targets, others appear to be a result of increased intrinsic drug resistance. Common among these strains is the presence of integrated viral genomes (prophage) that are known to contribute to fitness and antibiotic resistance in other pathogens but whose roles are largely unknown in mycobacteria. M. chelonae is an opprtunisitc pathogen that is closely related to M. abscessus. We have demonstrated that the presence of an M. abscessus cluster R prophage, McProf, in M. chelonae, increased resistance to antibiotics, such as amikacin, relative to strains lacking the prophage. The presence of McProf also enhances amikacin resistance in response to sub-lethal concentrations of antibiotics, or other cellular stresses such as infection by a second phage, BPs. Relative to strains carrying only one of the prophages or no prophage, the strain carrying two prophages, BPs and McProf, had the highest amikacin resistance. This strain also showed increased expression of the transcriptional activator, whiB7, which promotes expression of intrinsic antibiotic resistance genes. We investigated the role of BPs lysogenic gene products in the presence of McProf and showed that individual expression of these genes does not contribute to whiB7 upregulation, indicating that McProf likely plays a larger role in mediating this intrinsic resistance. We identified a McProf-encoded polymorphic toxin system and evaluated its effect on whiB7 expression in M. chelonae carrying the BPs prophage. The polymorphic toxin system elevates whiB7 expression but does not fully account for the dramatic increase in expression observed in the M. chelonae strain carrying both prophages. This work suggests that prophages play a role in increasing intrinsic antibiotic resistance and stress adaptation in pathogenic mycobacteria. Given that most pathogenic mycobacteria carry one or more prophages, characterizing how prophages regulate antibiotic resistance genes and adaptation to stresses will provide insight for developing more effective therapies for mycobacterial diseases

Design, fabrication and test of graphite/polyimide composite joints and attachments

The design, analysis, and testing performed to develop four types of graphite/polyimide (Gr/PI) bonded and bolted composite joints for lightly loaded control surfaces on advanced space transportation systems that operate at temperatures up to 561 K (550 F) are summarized. Material properties and small specimen tests were conducted to establish design data and to evaluate specific design details. Static discriminator tests were conducted on preliminary designs to verify structural adequacy. Scaled up specimens of the final joint designs, representative of production size requirements, were subjected to a series of static and fatigue tests to evaluate joint strength. Effects of environmental conditioning were determined by testing aged (125 hours at 589 K (600 F)) and thermal cycled (116 K to 589 K (-250 F to 600 F), 125 times) specimens. It is concluded Gr/PI joints can be designed and fabricated to carry the specified loads. Test results also indicate a possible resin loss or degradation of laminates after exposure to 589 K (600 F) for 125 hours

Singular reduction for proper actions

The goal of this paper is to give a simplied proof of the singular reduction theorem for a proper Hamiltonian action of a Lie group G on a connected smooth symplectic manifold P which has a coadjoint equivariant mo mentum mapping Our proof does not use the assumption that the coadjoint orbit is locally closed any local normal form or the shifting trick These were essential ingredients of the existing proo

Lightside Atmospheric Revitalization System

The system was studied as a replacement to the present baseline LiOH system for extended duration shuttle missions. The system consists of three subsystems: a solid amine water desorbed regenerable carbon dioxide removal system, a water vapor electrolysis oxygen generating system, and a Sabatier reactor carbon dioxide reduction system. The system is designed for use on a solar powered shuttle vehicle. The majority of the system's power requirements are utilized on the Sun side of each orbit, when solar power is available

Design, Fabrication and Test of Graphite/Polyimide Composite Joints and Attachments for Advanced Aerospace Vehicles

Standard and advanced bonded joint concepts were evaluated to develop a data base for the design and analysis of advanced composite joints for use at elevated temperatures (561K (550F)). Design concepts for specific joint applications and the fundamental parameters controlling the static strength characteristics of such joints were identified. Test results are presented for rail shear and sandwich beam compression tests and tension tests of moisture conditioned specimens and bonded on "T" sections. Coefficients of thermal expansion data are presented for A7F (LARC 13 Amide-imide modified) adhesion. Static discriminator test results for type 1 and type 2 bonded and bolted preliminary attachment concepts are presented and discussed