Simultaneous Sparse Approximation Using an Iterative Method with Adaptive Thresholding

This paper studies the problem of Simultaneous Sparse Approximation (SSA). This problem arises in many applications which work with multiple signals maintaining some degree of dependency such as radar and sensor networks. In this paper, we introduce a new method towards joint recovery of several independent sparse signals with the same support. We provide an analytical discussion on the convergence of our method called Simultaneous Iterative Method with Adaptive Thresholding (SIMAT). Additionally, we compare our method with other group-sparse reconstruction techniques, i.e., Simultaneous Orthogonal Matching Pursuit (SOMP), and Block Iterative Method with Adaptive Thresholding (BIMAT) through numerical experiments. The simulation results demonstrate that SIMAT outperforms these algorithms in terms of the metrics Signal to Noise Ratio (SNR) and Success Rate (SR). Moreover, SIMAT is considerably less complicated than BIMAT, which makes it feasible for practical applications such as implementation in MIMO radar systems

Design/cost tradeoff studies. Appendix A. Supporting analyses and tradeoffs, book 2. Earth Observatory Satellite system definition study (EOS)

Attitude reference systems for use with the Earth Observatory Satellite (EOS) are described. The systems considered are fixed and gimbaled star trackers, star mappers, and digital sun sensors. Covariance analyses were performed to determine performance for the most promising candidate in low altitude and synchronous orbits. The performance of attitude estimators that employ gyroscopes which are periodically updated by a star sensor is established by a single axis covariance analysis. The other systems considered are: (1) the propulsion system design, (2) electric power and electrical integration, (3) thermal control, (4) ground data processing, and (5) the test plan and cost reduction aspects of observatory integration and test

Roving vehicle motion control Quarterly report, 1 Mar. - 31 May 1967

System and subsystem requirements for remote control of roving space vehicle motio

Design/cost tradeoff studies. Earth Observatory Satellite system definition study (EOS)

The results of design/cost tradeoff studies conducted during the Earth Observatory Satellite system definition studies are presented. The studies are concerned with the definition of a basic modular spacecraft capable of supporting a variety of operational and/or research and development missions, with the deployment either by conventional launch vehicles or by means of the space shuttle. The three levels investigated during the study are: (1) subsystem tradeoffs, (2) spacecraft tradeoffs, and (3) system tradeoffs. The range of requirements which the modular concept must span is discussed. The mechanical, thermal, power, data and electromagnetic compatibility aspects of modularity are analyzed. Other data are provided for the observatory design concept, the payloads, integration and test, the ground support equipment, and ground data management systems

Earth Observatory Satellite system definition study. Report 3: Design cost trade-off studies and recommendations

An analysis of the design and cost tradeoff aspects of the Earth Observatory Satellite (EOS) development is presented. The design/cost factors that affect a series of mission/system level concepts are discussed. The subjects considered are as follows: (1) spacecraft subsystem cost tradeoffs, (2) ground system cost tradeoffs, and (3) program cost summary. Tables of data are provided to summarize the results of the analyses. Illustrations of the various spacecraft configurations are included

Design/cost tradeoff studies. Appendix A. Supporting analyses and tradeoffs, book 1. Earth Observatory Satellite system definition study (EOS)

A listing of the Earth Observatory Satellite (EOS) candidate missions is presented for use as a baseline in describing the EOS payloads. The missions are identified in terms of first, second, and third generation payloads. The specific applications of the EOS satellites are defined. The subjects considered are: (1) orbit analysis, (2) space shuttle interfaces, (3) thematic mapping subsystem, (4) high resolution pointable imager subsystem, (5) the data collection system, (6) the synthetic aperture radar, (7) the passive multichannel microwave radiometer, and (8) the wideband communications and handling equipment. Illustrations of the satellite and launch vehicle configurations are provided. Block diagrams of the electronic circuits are included

A Matched Filter Hypothesis for Cognitive Control

The prefrontal cortex exerts top-down influences on several aspects of higher-order cognition by functioning as a filtering mechanism that biases bottom-up sensory information toward a response that is optimal in context. However, research also indicates that not all aspects of complex cognition benefit from prefrontal regulation. Here we review and synthesize this research with an emphasis on the domains of learning and creative cognition, and outline how the appropriate level of cognitive control in a given situation can vary depending on the organism's goals and the characteristics of the given task. We offer a Matched Filter Hypothesis for cognitive control, which proposes that the optimal level of cognitive control is task-dependent, with high levels of cognitive control best suited to tasks that are explicit, rule-based, verbal or abstract, and can be accomplished given the capacity limits of working memory and with low levels of cognitive control best suited to tasks that are implicit, reward-based, non-verbal or intuitive, and which can be accomplished irrespective of working memory limitations. Our approach promotes a view of cognitive control as a tool adapted to a subset of common challenges, rather than an all-purpose optimization system suited to every problem the organism might encounter

Human operator performance of remotely controlled tasks: Teleoperator research conducted at NASA's George C. Marshal Space Flight Center

The capabilities within the teleoperator laboratories to perform remote and teleoperated investigations for a wide variety of applications are described. Three major teleoperator issues are addressed: the human operator, the remote control and effecting subsystems, and the human/machine system performance results for specific teleoperated tasks

Hard X-ray imaging facility for space shuttle: A scientific and conceptual engineering study

A shuttle-accommodated instrument for imaging hard X-rays in the study of nonthermal particles and high temperature particles in various solar and cosmic phenomena was defined and its feasibility demonstrated. The imaging system configuration is described as well as the electronics, aspect systems, mechanical and thermal properties and the ground support equipment

The Effects Of Accessibility On Judgment And Decision-Making

When making decisions, individuals may only use a subset of all available information. The experience of thinking about and attending to this accessible information can, atop of the actual content, exert an impact on what information (and the weighting thereof) is employed in judgments. In this dissertation, I examine how experiences associated with memory-based accessibility (i.e., ease-of-recall) and stimulus-based accessibility (i.e., amount of attention allocated, salience) influence decision-making. Accessibility serves as the connecting construct for two essays of this dissertation for a meta-analysis of the ease-of-retrieval effect and how salience affects valuation. In essay one, I meta-analyze an instantiation of how accessibility experiences (i.e., feelings associated with trying to retrieve information from memory) affect decisions: the ease-of-retrieval effect. The ease-of-retrieval effect contends people employ cognitive feelings of ease from recall as an input to judgment. I explore this idea through a common manipulation of ease-of-retrieval in which individuals generate either few or many examples of a given topic such as times they behaved assertively (Schwarz et al. 1991). This manipulation is argued to affect subjective ease and thereby other downstream dependent measures. Specifically, I test whether subjective ease fully mediates the impact of the manipulation. I also test several theoretical moderators of the use of cognitive feelings of ease as information (e.g., misattribution) and how much of the effect may be attributable to publication bias. Across over twenty-years of studies using conceptually-similar manipulations, I find evidence for several theoretical moderators, and find that publication bias only explains a small portion of the effect. Further, I find that subjective ease only partially explains the ease-of-retrieval effect, which means other explanations of the effect may also exist, yet they are understudied in the literature. In essay two, I turn to stimulus-based forms of accessibility: namely, salience, or the amount of attention devoted to a stimulus. While prior theories of decision-making contend greater salience increases information accessibility, they do not specify how salience influences the weighting and valuation of said information. Instead, these theories mostly distinguish between low versus high accessibility due to salience as affecting information used in judgments, and that information valuation occurs separately based on task goals. I demonstrate through three rating-based conjoint experiments across multiple product categories (e.g., cars) that even when all information is highly accessible, differences in salience may have an impact on the valuation and weighting of that information. I show these effects can arise from both perceptual (e.g., position effects) and cognitive (i.e., elaboration in working memory) sources. However, I also demonstrate the persistence of salience-biases differs between these two sources: biases due to cognitive salience decline over repeated decisions, whereas biases from perceptual salience do not