Active control of primary mirror of an orbiting telescope with thermal excitation

The generalization is presented that was made to model a layered structure of a kind that represents a light-weighted mirror. This theory is presented along with the strategy for error suppression. The results of a variety of error-suppression studies are also presented. The computer programs for all parts of this study are included

Eigenvalue assignment strategies in rotor systems

The work done to establish the control and direction of effective eigenvalue excursions of lightly damped, speed dependent rotor systems using passive control is discussed. Both second order and sixth order bi-axis, quasi-linear, speed dependent generic models were investigated. In every case a single, bi-directional control bearing was used in a passive feedback stabilization loop to resist modal destabilization above the rotor critical speed. Assuming incomplete state measurement, sub-optimal control strategies were used to define the preferred location of the control bearing, the most effective measurement locations, and the best set of control gains to extend the speed range of stable operation. Speed dependent control gains were found by Powell's method to maximize the minimum modal damping ratio for the speed dependent linear model. An increase of 300 percent in stable speed operation was obtained for the sixth order linear system using passive control. Simulations were run to examine the effectiveness of the linear control law on nonlinear rotor models with bearing deadband. The maximum level of control effort (force) required by the control bearing to stabilize the rotor at speeds above the critical was determined for the models with bearing deadband

Computer architecture for efficient algorithmic executions in real-time systems: New technology for avionics systems and advanced space vehicles

Improvements and advances in the development of computer architecture now provide innovative technology for the recasting of traditional sequential solutions into high-performance, low-cost, parallel system to increase system performance. Research conducted in development of specialized computer architecture for the algorithmic execution of an avionics system, guidance and control problem in real time is described. A comprehensive treatment of both the hardware and software structures of a customized computer which performs real-time computation of guidance commands with updated estimates of target motion and time-to-go is presented. An optimal, real-time allocation algorithm was developed which maps the algorithmic tasks onto the processing elements. This allocation is based on the critical path analysis. The final stage is the design and development of the hardware structures suitable for the efficient execution of the allocated task graph. The processing element is designed for rapid execution of the allocated tasks. Fault tolerance is a key feature of the overall architecture. Parallel numerical integration techniques, tasks definitions, and allocation algorithms are discussed. The parallel implementation is analytically verified and the experimental results are presented. The design of the data-driven computer architecture, customized for the execution of the particular algorithm, is discussed

LLV - Lunar Logistic Vehicle Final report

Evaluation of systems design training institute for engineering facult

Numerical Computations for Estuarine Flood Plains

Construction on estuarine flood plains can contribute significantly to flooding problems during times of large river inflow. A two dimensional depth averaged finite difference model is presented which allows for improved environmental impact assessment of construction on estuarine flood plains. The model is applied to the delta region above Mobile Bay, Alabama where a railroad crosses the flood plains. The railroad is built on a fill with trestles at established channels. The model is used to evaluate the effect which the railroad has on known flooding problems in the delta region. Partial calibration and verification of the numerical model is accomplished with available prototype data from previous flood events. The numerical model demonstrates that while a great amount of water may be stored on flood plains, conditions are not generally conducive for large flow rates. Most of the flood still moves along major established channels. Construction on flood plains may exert a significant influence on flood stage elevations in certain regions with other regions experiencing a very minor effect. In particular, construction in the interior of the flood plains may produce large effects in the interior with only minor effects propagating to the boundaries

Nanowire Spin Torque Oscillator Driven by Spin Orbit Torques

Spin torque from spin current applied to a nanoscale region of a ferromagnet can act as negative magnetic damping and thereby excite self-oscillations of its magnetization. In contrast, spin torque uniformly applied to the magnetization of an extended ferromagnetic film does not generate self-oscillatory magnetic dynamics but leads to reduction of the saturation magnetization. Here we report studies of the effect of spin torque on a system of intermediate dimensionality - a ferromagnetic nanowire. We observe coherent self-oscillations of magnetization in a ferromagnetic nanowire serving as the active region of a spin torque oscillator driven by spin orbit torques. Our work demonstrates that magnetization self-oscillations can be excited in a one-dimensional magnetic system and that dimensions of the active region of spin torque oscillators can be extended beyond the nanometer length scale.Comment: The link to the published version is http://www.nature.com/ncomms/2014/141205/ncomms6616/full/ncomms6616.htm

All-optical spiking neurosynaptic networks with self-learning capabilities

This is the author accepted manuscript. The final version is available from Nature Research via the DOI in this record.Software implementations of brain-inspired computing underlie many important computational tasks, from image processing to speech recognition, artificial intelligence and deep learning applications. Yet, unlike real neural tissue, traditional computing architectures physically separate the core computing functions of memory and processing, making fast, efficient and low-energy computing difficult to achieve. To overcome such limitations, an attractive alternative is to design hardware that mimics neurons and synapses. Such hardware, when connected in networks or neuromorphic systems, processes information in a way more analogous to brains. Here we present an all-optical version of such a neurosynaptic system, capable of supervised and unsupervised learning. We exploit wavelength division multiplexing techniques to implement a scalable circuit architecture for photonic neural networks, successfully demonstrating pattern recognition directly in the optical domain. Such photonic neurosynaptic networks promise access to the high speed and high bandwidth inherent to optical systems, thus enabling the direct processing of optical telecommunication and visual data.Engineering and Physical Sciences Research Council (EPSRC)European CommissionDeutsche Forschungsgemeinschaft (DFG

The Effects of a Selective and Non-Selective Organic Herbicides on Amaranthus species

The Amaranthus species has adaptive abilities that give them competitive advantages and invasive tendencies. Their high seed production, seed viability, quick growth rate, and C4 metabolism have allowed some of the species to become resistant to some types of herbicides, causing soybean, corn, and cotton crop yield losses in North America. For this investigation, different organic herbicide solutions were analyzed to determine their affects on the Amaranthus species. Different concentrations of acetic acid, eucalyptus volatile oil, and okanin were combined to test the hypothesis that the unique characteristics of each organic herbicides should safely and effectively deter Amaranthus growth, even at low concentrations. The organic herbicide cocktail significantly affected the growth rates and germination percentages of resistant A. palmeri, susceptible A. palmeri, A. viridis, and A. tricolor. Spouts died when the solution was applied daily, and seeds did not germinate after application. The solution did not have a large effect on A. hypochondriacs and A. caudatus, but most of those sprouts’ length was diminished, and growth ceased

Fast and reliable storage using a 5 bit, nonvolatile photonic memory cell

This is the final version. Available from Optical Society of America via the DOI in this record.Optically storing and addressing data on photonic chips is of particular interest as such capability would eliminate optoelectronic conversion losses in data centers. It would also enable on-chip non-von Neumann photonic computing by allowing multinary data storage with high fidelity. Here, we demonstrate such an optically addressed, multilevel memory capable of storing up to 34 nonvolatile reliable and repeatable levels (over 5 bits) using the phase change material Ge2Sb2Te5 integrated on a photonic waveguide. Crucially, we demonstrate for the first time, to the best of our knowledge, a technique that allows us to program the device with a single pulse regardless of the previous state of the material, providing an order of magnitude improvement over previous demonstrations in terms of both time and energy consumption. We also investigate the influence of write-and-erase pulse parameters on the single-pulse recrystallization, amorphization, and readout error in our multilevel memory, thus tailoring pulse properties for optimum performance. Our work represents a significant step in the development of photonic memories and their potential for novel integrated photonic applications.Engineering and Physical Sciences Research Council (EPSRC)European CommissionDeutsche Forschungsgemeinschaft (DFG)Horizon 2020 Framework Programme (H2020