A FORTRAN program for the analysis of linear continuous and sample-data systems

A FORTRAN digital computer program which performs the general analysis of linearized control systems is described. State variable techniques are used to analyze continuous, discrete, and sampled data systems. Analysis options include the calculation of system eigenvalues, transfer functions, root loci, root contours, frequency responses, power spectra, and transient responses for open- and closed-loop systems. A flexible data input format allows the user to define systems in a variety of representations. Data may be entered by inputing explicit data matrices or matrices constructed in user written subroutines, by specifying transfer function block diagrams, or by using a combination of these methods

Seismic Q and velocity structure for the magma-hydrothermal system of the Valles Caldera, New Mexico

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989.Science copy is bound in 2 v.Includes bibliographical references (leaves 326-332).by Peter Morse Roberts.Ph.D

Computer Vision for Scene Text Analaysis

The motivation of this dissertation is to develop a 'Seeing-Eye' video-based interface for the visually impaired to access environmental text information. We are concerned with those daily activities of the low-vision people involved with interpreting 'environmental text' or 'scene text' e.g., reading a newspaper, can labels and street signs. First, we discuss the devopement of such a video-based interface. In this interface, the processed image of a scene text is read by o®-the-shelf OCR and converted back to speech by Text-to-Speech(TTS) software. Our challenge is to feed a high quality image of a scene text for o®-the-shelf OCR software under general pose of the the surface on which text is printed. To achieve this, various problems related to feature detection, mosaicing, auto-focus, zoom, and systems integration were solved in the development of the system, and these are described. We employ the video-based interface for the analysis of video of lectures/posters. In this application, the text is assumed to be on a plane. It is necessary for automatic analysis of video content to add modules such as enhancement, text segmentation, preprocessing video content, metric rectification, etc. We provide qualitative results to justify the algorithm and system integration. For more general classes of surfaces that the text is printed on, such as bent or worked paper, we develop a novel method for 3D structure recovery and unwarping method. Deformed paper is isometric with a plane and the Gaussian curvature vanishes on every point on the surface. We show that these constraints lead to a closed set of equations that allow the recovery of the full geometric structure from a single image. We prove that these partial di®erential equations can be reduced to the Hopf equation that arises in non-linear wave propagation, and deformations of the paper can be interpreted in terms of the characteristics of this equation. A new exact integration of these equations relates the 3D structure of the surface to an image of a paper. In addition, we can generate such surfaces using the underlying equations. This method only uses information derived from the image of the boundary. Furthermore, we employ the shape-from-texture method as an alternative to the method above to infer its 3D structure. We showed that for the consistency of normal vector field, we need to add extra conditions based on the surface model. Such conditions are are isometry and zero Gaussian curvature of the surface. The theory underlying the method is novel and it raises new open research issues in the area of 3D reconstruction from single views. The novel contributions are: first, it is shown that certain linear and non-linear clues (contour knowledge information) are su±cient to recover the 3D structure of scene text; second, that with a priori of a page layout information, we can reconstruct a fronto-parallel view of a deformed page from di®erential geometric properties of a surface; third, that with a known cameral model we can recover 3D structure of a bent surface; forth, we present an integrated framework for analysis and rectification of scene texts from single views in general format; fifth, we provide the comparison with shape from texture approach and finally this work can be integrated as a visual prostheses for the visually impaired. Our work has many applications in computer vision and computer graphics. The applications are diverse e.g. a generalized scanning device, digital flattening of creased documents, 3D reconstruction problem when correspondence fails, 3D reconstruction of single old photos, bending and creasing virtual paper, object classification, semantic extraction, scene description and so on

The Telecommunications and Data Acquisition Report

This quarterly publication provides archival reports on developments in programs managed by JPL's Telecommunications and Mission Operations Directorate (TMOD), which now includes the former Telecommunications and Data Acquisition (TDA) Office. In space communications, radio navigation, radio science, and ground-based radio and radar astronomy, it reports on activities of the Deep Space Network (DSN) in planning, supporting research and technology, implementation, and operations. Also included are standards activity at JPL for space data and information systems and reimbursable DSN work performed for other space agencies through NASA. The preceding work is all performed for NASA's Office of Space Communications (OSC)

Electrical Characterisation of III-V Nanowire MOSFETs

The ever increasing demand for faster and more energy-efficient electricalcomputation and communication presents severe challenges for the semiconductor industry and particularly for the metal-oxidesemiconductorfield-effect transistor (MOSFET), which is the workhorse of modern electronics. III-V materials exhibit higher carrier mobilities than the most commonly used MOSFET material Si so that the realisation of III-V MOSFETs can enable higher operation speeds and lower drive voltages than that which is possible in Si electronics. A lowering of the transistor drive voltage can be further facilitated by employing gate-all-around nanowire geometries or novel operation principles. However, III-V materials bring about their own challenges related to material quality and to the quality of the gate oxide on top of a III-V MOSFET channel.This thesis presents detailed electrical characterisations of two types of (vertical) III-V nanowire transistors: MOSFETs based on conventional thermionic emission; and Tunnel FETs, which utilise quantum-mechanical tunnelling instead to control the device current and reach inverse subthreshold slopes below the thermal limit of 60 mV/decade. Transistor characterisations span over fourteen orders of magnitude in frequency/time constants and temperatures from 11 K to 370 K.The first part of the thesis focusses on the characterisation of electrically active material defects (‘traps’) related to the gate stack. Low-frequency noise measurements yielded border trap densities of 10^18 to 10^20 cm^-3 eV^-1 and hysteresis measurements yielded effective trap densities – projected to theoxide/semiconductor interface – of 2x10^12 to 3x10^13 cm^-2 eV^-1. Random telegraph noise measurements revealed that individual oxide traps can locally shift the channel energy bands by a few millielectronvolts and that such defects can be located at energies from inside the semiconductor band gap all the way into the conduction band.Small-signal radio frequency (RF) measurements revealed that parts of the wide oxide trap distribution can still interact with carriers in the MOSFET channel at gigahertz frequencies. This causes frequency hystereses in the small-signal transconductance and capacitances and can decrease the RF gains by a few decibels. A comprehensive small-signal model was developed, which takes into account these dispersions, and the model was applied to guide improvements of the physical structure of vertical RF MOSFETs. This resulted in values for the cutoff frequency fT and the maximum oscillation frequency fmax of about 150 GHz in vertical III-V nanowire MOSFETs.Bias temperature instability measurements and the integration of (lateral) III-V nanowire MOSFETs in a back end of line process were carried out as complements to the main focus of this thesis. The results of this thesis provide a broad perspective of the properties of gate oxide traps and of the RF performance of III-V nanowire transistors and can act as guidelines for further improvement and finally the integration of III-V nanowire MOSFETs in circuits

Design of discrete-time filters for efficient implementation

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 325-333).The cost of implementation of discrete-time filters is often strongly dependent on the number of non-zero filter coefficients or the precision with which the coefficients are represented. This thesis addresses the design of sparse and bit-efficient filters under different constraints on filter performance in the context of frequency response approximation, signal estimation, and signal detection. The results have applications in several areas, including the equalization of communication channels, frequency-selective and frequency-shaping filtering, and minimum-variance distortionless-response beamforming. The design problems considered admit efficient and exact solutions in special cases. For the more difficult general case, two approaches are pursued. The first develops low-complexity algorithms that are shown to yield optimal or near-optimal designs in many instances, but without guarantees. The second focuses on optimal algorithms based on the branch-and-bound procedure. The complexity of branch-and-bound is reduced through the use of bounds that are good approximations to the true optimal cost. Several bounding methods are developed, many involving relaxations of the original problem. The approximation quality of the bounds is characterized and efficient computational methods are discussed. Numerical experiments show that the bounds can result in substantial reductions in computational complexity.by Dennis Wei.Ph.D

Engineering photonic and plasmonic light emission enhancement

Thesis (Ph.D.)--Boston UniversitySemiconductor photonic devices are a rapidly maturing technology which currently occupy multi-billion dollar markets in the areas of LED lighting and optical data communication. LEDs currently demonstrate the highest luminous efficiency of any light source for general lighting. Long-haul optical data communication currently forms the backbone of the global communication network. Proper design of light management is required for photonic devices, which can increase the overall efficiency or add new device functionality. In this thesis, novel methods for the control of light propagation and confinement are developed for the use in integrated photonic devices. The first part of this work focuses on the engineering of field confinement within deep subwavelength plasmonic resonators for the enhancement of light-matter interaction. In this section, plasmonic ring nanocavities are shown to form gap plasmon modes confined to the dielectric region between two metal layers. The scattering properties, near-field enhancement and photonic density of states of nanocavity devices are studied using analytic theory and 3D finite difference time domain simulations. Plasmonic ring nanocavities are fabricated and characterized using photoluminescence intensity and decay rate measurements. A 25 times increase in the radiative decay rate of Er:Si02 is demonstrated in nanocavities where light is confined to volumes as small as 0.01(λ/n)^3 . The potential to achieve lasing, due to the enhancement of stimulated emission rate in ring nanocavities, is studied as a route to Si-compatible plasmon-enhanced nanolasers. The second part of this work focuses on the manipulation of light generated in planar semiconductor devices using arrays of dielectric nanopillars. In particular, aperiodic arrays of nanopillars are engineered for omnidirectional light extraction enhancement. Arrays of Er:SiNx nanopillars are fabricated and a ten times increase in light extraction is experimentally demonstrated, while simultaneously controlling far-field radiation patterns in ways not possible with periodic arrays. Additionally, analytical scalar diffraction theory is used to study light propagation from Vogel spiral arrays and demonstrate generation of OAM. Using phase shifting interferometry, the presence of OAM is experimentally verified. The use of Vogel spirals presents a new method for the generation of OAM with applications for secure optical communications