A Unified Cognitive Model of Visual Filling-In Based on an Emergic Network Architecture

The Emergic Cognitive Model (ECM) is a unified computational model of visual filling-in based on the Emergic Network architecture. The Emergic Network was designed to help realize systems undergoing continuous change. In this thesis, eight different filling-in phenomena are demonstrated under a regime of continuous eye movement (and under static eye conditions as well). ECM indirectly demonstrates the power of unification inherent with Emergic Networks when cognition is decomposed according to finer-grained functions supporting change. These can interact to raise additional emergent behaviours via cognitive re-use, hence the Emergic prefix throughout. Nevertheless, the model is robust and parameter free. Differential re-use occurs in the nature of model interaction with a particular testing paradigm. ECM has a novel decomposition due to the requirements of handling motion and of supporting unified modelling via finer functional grains. The breadth of phenomenal behaviour covered is largely to lend credence to our novel decomposition. The Emergic Network architecture is a hybrid between classical connectionism and classical computationalism that facilitates the construction of unified cognitive models. It helps cutting up of functionalism into finer-grains distributed over space (by harnessing massive recurrence) and over time (by harnessing continuous change), yet simplifies by using standard computer code to focus on the interaction of information flows. Thus while the structure of the network looks neurocentric, the dynamics are best understood in flowcentric terms. Surprisingly, dynamic system analysis (as usually understood) is not involved. An Emergic Network is engineered much like straightforward software or hardware systems that deal with continuously varying inputs. Ultimately, this thesis addresses the problem of reduction and induction over complex systems, and the Emergic Network architecture is merely a tool to assist in this epistemic endeavour. ECM is strictly a sensory model and apart from perception, yet it is informed by phenomenology. It addresses the attribution problem of how much of a phenomenon is best explained at a sensory level of analysis, rather than at a perceptual one. As the causal information flows are stable under eye movement, we hypothesize that they are the locus of consciousness, howsoever it is ultimately realized

Studies of methods of pre-launch testing of satellite radar altimeters

The radar altimeter operating in a pulse-limited mode has been successful in charting the ocean surfaces of the Earth. The scientific community, in a drive to map rougher terrain, have adopted the same principle. However in order to overcome the problem of slope- induced error, the range window may be widened or narrowed in accordance with the surface roughness. The ERS-1 altimeter included a second range window for operation over ice, but which had to be controlled by macro-command from the ground. The Advanced Terrain-Tracking Altimeter is a prototype altimeter which has an on-board resolution-switching algorithm, allowing the range window to be changed appropriately. This thesis focuses on methods of pre-launch testing of advanced radar altimeters. The early chapters review some of the calibration and testing methods used for the ERS-1 altimeter, presenting a critical assessment of some of the pre-launch methods. The testing procedure for the Adaptive Terrain-Tracking Altimeter is significantly more complex because of the extra resolution-switching algorithm, and a return signal simulator is identified as an essential element in testing the adaptive resolution prior to launch. The core of the thesis therefore describes a novel method of return signal simulation in which sequences of realistic echoes, from all types of surface, are fed in real time to the prototype altimeter, at the appropriate resolution, with the appropriate fading characteristics, and at the appropriate instant in time. Such a simulator is feasible only if the simulated echo is modelled in the deramp domain (i.e range window space) rather than actual delay time. Then the Fourier Transforms of the echoes, rather than the echoes themselves, are calculated at the full pulse repetition frequency and are stored in a memory. The resolution may then be varied by altering the rate at which the echoes are read out of memory. A prototype Return Signal Simulator is built, tested and shown to be capable of testing the Adaptive Terrain-Tracking Altimeter. A test philosophy is defined to assist the testing of the prototype altimeter, which will be undertaken by British Aerospace. A preliminary analysis, using a software implementation of the return signal simulator and realistic echoes, demonstrated that the Model Free Tracker has a superior tracking performance than the generally preferred Offset Centre Of Gravity tracking algorithm. However both algorithms suffer from problems, and these problems are identified. Finally a new approach to the analysis of the effect of chirp phase errors is presented, which leads to a quantitative expression for the height error resulting from chirp phase distortion. Such an approach can be used to apply a correction to the height estimate, unlike previous approaches which could only be used to set a specification for altimeter design

The Telecommunications and Data Acquisition Report

This quarterly publication (July-Sept. 1986) provides archival reports on developments in programs managed by JPL's Office of Telecommunications and Data Acquisition (TDA). In space communications, radio navigation, radio science, and ground-based radio astronomy, it reports on activities of the Deep Space Network (DSN) and its associated Ground Communications Facility (GCF) in planning, in supporting research and technology, in implementation, and in operations. This work is performed for NASA's Office of Space Tracking and Data Systems (OSTDS). In geodynamics, the publication reports on the application of radio interferometry at microwave frequencies for geodynamic measurements. In the search for extraterrestrial intelligence (SETI), it reports on implementation and operations for searching the microwave spectrum. The latter two programs are performed for NASA's Office of Space Science and Applications (OSSA)

Design study for LANDSAT-D attitude control system

The gimballed Ku-band antenna system for communication with TDRS was studied. By means of an error analysis it was demonstrated that the antenna cannot be open loop pointed to TDRS by an onboard programmer, but that an autotrack system was required. After some tradeoffs, a two-axis, azimuth-elevation type gimbal configuration was recommended for the antenna. It is shown that gimbal lock only occurs when LANDSAT-D is over water where a temporary loss of the communication link to TDRS is of no consequence. A preliminary gimbal control system design is also presented. A digital computer program was written that computes antenna gimbal angle profiles, assesses percent antenna beam interference with the solar array, and determines whether the spacecraft is over land or water, a lighted earth or a dark earth, and whether the spacecraft is in eclipse

High Speed Test Interface Module Using MEMS Technology

With the transient frequency of available CMOS technologies exceeding hundreds of gigahertz and the increasing complexity of Integrated Circuit (IC) designs, it is now apparent that the architecture of current testers needs to be greatly improved to keep up with the formidable challenges ahead. Test requirements for modern integrated circuits are becoming more stringent, complex and costly. These requirements include an increasing number of test channels, higher test-speeds and enhanced measurement accuracy and resolution. In a conventional test configuration, the signal path from Automatic Test Equipment (ATE) to the Device-Under-Test (DUT) includes long traces of wires. At frequencies above a few gigahertz, testing integrated circuits becomes a challenging task. The effects on transmission lines become critical requiring impedance matching to minimize signal reflection. AC resistance due to the skin effect and electromagnetic coupling caused by radiation can also become important factors affecting the test results. In the design of a Device Interface Board (DIB), the greater the physical separation of the DUT and the ATE pin electronics, the greater the distortion and signal degradation. In this work, a new Test Interface Module (TIM) based on MEMS technology is proposed to reduce the distance between the tester and device-under-test by orders of magnitude. The proposed solution increases the bandwidth of test channels and reduces the undesired effects of transmission lines on the test results. The MEMS test interface includes a fixed socket and a removable socket. The removable socket incorporates MEMS contact springs to provide temporary with the DUT pads and the fixed socket contains a bed of micro-pins to establish electrical connections with the ATE pin electronics. The MEMS based contact springs have been modified to implement a high-density wafer level test probes for Through Silicon Vias (TSVs) in three dimensional integrated circuits (3D-IC). Prototypes have been fabricated using Silicon On Insulator SOI wafer. Experimental results indicate that the proposed architectures can operate up to 50 GHz without much loss or distortion. The MEMS probes can also maintain a good elastic performance without any damage or deformation in the test phase

Earth imaging with microsatellites: An investigation, design, implementation and in-orbit demonstration of electronic imaging systems for earth observation on-board low-cost microsatellites.

This research programme has studied the possibilities and difficulties of using 50 kg microsatellites to perform remote imaging of the Earth. The design constraints of these missions are quite different to those encountered in larger, conventional spacecraft. While the main attractions of microsatellites are low cost and fast response times, they present the following key limitations: Payload mass under 5 kg, Continuous payload power under 5 Watts, peak power up to 15 Watts, Narrow communications bandwidths (9.6 / 38.4 kbps), Attitude control to within 5°, No moving mechanics. The most significant factor is the limited attitude stability. Without sub-degree attitude control, conventional scanning imaging systems cannot preserve scene geometry, and are therefore poorly suited to current microsatellite capabilities. The foremost conclusion of this thesis is that electronic cameras, which capture entire scenes in a single operation, must be used to overcome the effects of the satellite's motion. The potential applications of electronic cameras, including microsatellite remote sensing, have erupted with the recent availability of high sensitivity field-array CCD (charge-coupled device) image sensors. The research programme has established suitable techniques and architectures necessary for CCD sensors, cameras and entire imaging systems to fulfil scientific/commercial remote sensing despite the difficult conditions on microsatellites. The author has refined these theories by designing, building and exploiting in-orbit five generations of electronic cameras. The major objective of meteorological scale imaging was conclusively demonstrated by the Earth imaging camera flown on the UoSAT-5 spacecraft in 1991. Improved cameras have since been carried by the KITSAT-1 (1992) and PoSAT-1 (1993) microsatellites. PoSAT-1 also flies a medium resolution camera (200 metres) which (despite complete success) has highlighted certain limitations of microsatellites for high resolution remote sensing. A reworked, and extensively modularised, design has been developed for the four camera systems deployed on the FASat-Alfa mission (1995). Based on the success of these missions, this thesis presents many recommendations for the design of microsatellite imaging systems. The novelty of this research programme has been the principle of designing practical camera systems to fit on an existing, highly restrictive, satellite platform, rather than conceiving a fictitious small satellite to support a high performance scanning imager. This pragmatic approach has resulted in the first incontestable demonstrations of the feasibility of remote sensing of the Earth from inexpensive microsatellites

Identification of important locational, physical and economic dimensions in power system transient stability margin estimation

Increasing renewable generation can lead to significant spatial and temporal changes to the rotor angle stability boundary, such that critical contingencies may drastically change. Additionally, the inherent variability of renewables increases the number of operational scenarios that require stability assessment. This paper presents a methodology whereby a series of location-specific Decision Tree Regressors are trained, using power system variables to estimate the Critical Clearing Time (CCT) on a locational basis throughout a network. Permutation feature importance is used to reveal the most important power system variables for CCT estimation at each location (capturing aspects related to physical system characteristics, operational parameters as well as economic dispatch). Consequently, estimation of the duration and location of the critical fault can also be made – along with identification of important system variables that explicitly impact the critical fault. Results on the IEEE 39-bus network show accurate estimation of locational CCTs, with a mean absolute percentage error of 1.19% on average. Moreover, the mean absolute percentage error for the minimum CCT is 0.49%. An analysis of important power system variables is provided, demonstrating how the method can assist in the design of targeted locational interventions to improve the stability margin at specific locations