A Rayleigh-Ritz approach to the synthesis of large structures with rotating flexible components

The equations of motion for large structures with rotating flexible components are derived by regarding the structure as an assemblage of substructures. Based on a stationarity principle for rotating structures, it is shown that each continuous or discrete substructure can be simulated by a suitable set of admissible functions or admissible vectors. This substructure synthesis approach provides a rational basis for truncating the number of degrees of freedom both of each substructure and of the assembled structure

Dynamic analysis of the long-term zonal earth energy budget experiment (LZEEBE) spacecraft

The motions of the flexible LZEEBE spacecraft after injection into a circular orbit were analyzed. The spacecraft consists of three spherical balloons connected to a central hub by three long flexible booms which lie in a plane such that the angle between any pair of booms is 120 degrees. The major torques acting on the spacecraft are gravity-gradient torques and torques due to solar radiation pressure acting on the balloons which have different reflective properties. A development of the equations of motion is presented. Computer simulations indicate that the spacecraft will have random motion, provided the injection into orbit does not create conditions favorable to gravity-gradient capture

Structural Dynamics, Stability, and Control of Helicopters

The dynamic synthesis of gyroscopic structures consisting of point-connected substructures is investigated. The objective is to develop a mathematical model capable of an adequate simulation of the modal characteristics of a helicopter using a minimum number of degrees of freedom. The basic approach is to regard the helicopter structure as an assemblage of flexible substructures. The variational equations for the perturbed motion about certain equilibrium solutions are derived. The discretized variational equations can be conveniently exhibited in matrix form, and a great deal of information about the system modal characteristics can be extracted from the coefficient matrices. The derivation of the variational equations requires a monumental amount of algebraic operations. To automate this task a symbolic manipulation program on a digital computer is developed

Large spacecraft pointing and shape control

The overall objective of this program was the development of control algorithms that allow the concurrent operation of slewing, pointing, vibration, and shape control subsystems. This objective is important for near-term space surveillance missions that require the rapid retargeting and precise pointing of large flexible satellites. The success of these missions requires the design and concurrent operation of the various interacting control subsystems. There were two phases conducted: phase 1 was mathematical model development, and phase 2 was control development. The program is detailed and major conclusions given

High-temperature Adhesive Development and Evaluation

High-temperature adhesive systems are evaluated for short and long-term stability at temperatures ranging from 232C to 427C. The resins selected for characterization include: NASA Langley developed polyphenylquinoxaline (PPQ), and commercially available polyimides (PI). The primary method of bond testing is single lap shear. The PPQ candidates are evaluated on 6A1-4V titanium adherends with chromic acid anodize and phosphate fluoride etch surface preparations. The remaining adhesives are evaluated on 15-5 PH stainless steel with a sulfuric acid anodize surface preparation. Preliminary data indicate that the PPQ adhesives tested have stability to 3000 hours at 450F with chromic acid anodize surface preparation. Additional studies are continuing to attempt to improve the PPQ's high-performance by formulating adhesive films with a boron filler and utilizing the phosphate fluoride surface preparation on titanium. Evaluation of the polyimide candidates on stainless-steel adherends indicates that the FM-35 (American Cyanamid), PMR-15 (U.S. Polymeric/Ferro), TRW partially fluorinated polyimide and NR 150B2S6X (DuPont) adhesives show sufficient promise to justify additional testing

A Vavilovian approach to discovering crop-associated microbes with potential to enhance plant immunity

Through active associations with a diverse community of largely non-pathogenic microbes, a plant may be thought of as possessing an “extended genotype,” an interactive cross-organismal genome with potential, exploitable implications for plant immunity. The successful enrichment of plant microbiomes with beneficial species has led to numerous commercial applications, and the hunt for new biocontrol organisms continues. Increasingly flexible and affordable sequencing technologies, supported by increasingly comprehensive taxonomic databases, make the characterization of non-model crop-associated microbiomes a widely accessible research method toward this end; and such studies are becoming more frequent. A summary of this emerging literature reveals, however, the need for a more systematic research lens in the face of what is already a metagenomics data deluge. Considering the processes and consequences of crop evolution and domestication, we assert that the judicious integration of in situ crop wild relatives into phytobiome research efforts presents a singularly powerful tool for separating signal from noise, thereby facilitating a more efficient means of identifying candidate plant-associated microbes with the potential for enhancing the immunity and fitness of crop species

Measurements of an ionizable constituent of low ionosphere using a Lyman-alpha source and blunt probe

Ionizable constituent density measurement of D region using Lyman-alpha source and blunt prob

Perceptions of physiotherapists towards research: a mixed methods study

OBJECTIVES: To explore the perceptions of physiotherapists towards the use of and participation in research. DESIGN: Concurrent mixed methods research, combining in-depth interviews with three questionnaires (demographics, Edmonton Research Orientation Survey, visual analogue scales for confidence and motivation to participate in research). SETTING: One physiotherapy department in a rehabilitation hospital, consisting of seven specialised areas. PARTICIPANTS: Twenty-five subjects {four men and 21 women, mean age 38 [standard deviation (SD) 11] years} who had been registered as a physiotherapist for a mean period of 15 (SD 10) years participated in this study. They were registered with the New Zealand Board of Physiotherapy, held a current practising certificate, and were working as a physiotherapist or physiotherapy/allied health manager at the hospital. MAIN OUTCOME MEASURE: The primary outcome measure was in-depth interviews and the secondary outcome measures were the three questionnaires. RESULTS: Physiotherapists were generally positive towards research, but struggled with the concept of research, the available literature and the time to commit to research. Individual confidence and orientation towards research seemed to influence how these barriers were perceived. CONCLUSION: This study showed that physiotherapists struggle to implement research in their daily practice and become involved in research. Changing physiotherapists' conceptions of research, making it more accessible and providing dedicated research time could facilitate increased involvement in the physiotherapy profession

Photoconductive Metasurfaces for Terahertz Applications

Photoconductive antennas (PCAs) are widely used as terahertz (THz) detectors for spectroscopy and imaging. However, their relatively low efficiency and sensitivity often limits the signal-to-noise and measurement capabilities of experimental systems. By replacing the photoconductive region with an all-dielectric, fully absorbing metasurface the efficiency and sensitivity of PCAs is substantially improved. This thesis describes the design, modelling and experimental testing of highly absorbing metasurfaces made for the purpose of improving PCAs. Perfect absorption is achieved through the degenerate critical coupling of Mie modes. By simple modifications of the metasurface geometry, perfect absorption is obtained across the wavelength range of near-infrared ultrafast lasers commonly used for PCA excitation. When used as PCA detectors, high signal-to-noise is achieved at unprecendently low excitation powers, and extremely low dark resistance enables high sensitivity detection. Furthermore, when integrated with near-field aperture probes, the ultra-thin design of such metasurface PCAs could significantly enhance the spatial resolution and spectral sensitivity of THz near-field systems. In addition to PCA detectors, this thesis investigates whether GaAs metasurfaces could be used for THz emission via ultrafast charge carrier dynamics. Perfect absorption is demonstrated when the metasurface is excited at oblique angles, as necessary for THz emission and out-coupling. This work suggests the possibility of efficient, adaptable and integrable THz sources which do not require external bias for operation. Finally, this thesis explores whether metasurfaces can enhance absorption in low-temperature materials at sub-bandgap energies. It is shown that substantial improvements in absorption are possible using degenerate critical coupling, even for materials with very low absorption coefficients. This finding invites the future development of efficient PCA detectors that use convenient, turn-key operated fiber lasers for excitation - enabling cheaper, more functional THz spectroscopy and imaging systems

Tweeting Tennessee\u27s Collections: Where Bots & Special Collections Meet

This project demonstrates how a Twitterbot can be used as an inclusive outreach initiative that breaks down the barriers between the Web and the reading room to share materials like postcards, music manuscripts, photographs, and cartoons with the public. Once in place, Twitterbots allow our physical materials to converge with the technical and social space of the Web. Twitterbots are ideal for busy professionals because they allow librarians to make meaningful impressions on users without requiring a large time investment. This poster covers my recent implementation of a digital collections bot (@UTKDigCollBot) at the University of Tennessee, Knoxville, and provides documentation and advice on how you might develop a bot to highlight materials at your own institution. This content was presented at the 2018 Rare Books and Manuscripts Section (RBMS) Conference in New Orleans, LA