597,742 research outputs found

    CLEAR: Communications Link Expert Assistance Resource

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    Communications Link Expert Assistance Resource (CLEAR) is a real time, fault diagnosis expert system for the Cosmic Background Explorer (COBE) Mission Operations Room (MOR). The CLEAR expert system is an operational prototype which assists the MOR operator/analyst by isolating and diagnosing faults in the spacecraft communication link with the Tracking and Data Relay Satellite (TDRS) during periods of realtime data acquisition. The mission domain, user requirements, hardware configuration, expert system concept, tool selection, development approach, and system design were discussed. Development approach and system implementation are emphasized. Also discussed are system architecture, tool selection, operation, and future plans

    Data Communication Between an Expert System Shell and a Conventional Algorithmic Program With Application to Cam Motion Specification

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    Although more and more expert system shells have begun to provide communication interfaces to conventional procedural languages, the interfaces are basically shell- and language-dependent. This paper presents a simple, shell- and language-independent data communication technique between a shell and a procedural language via a concept analogous to the handshake data transmission used in microprocessors. A control file is used for the action of handshake. The communication interface is between two data files in two different language environments. A program written in a LISP-based expert system shell, OPS 5, and one written in a procedural language, FORTRAN, were tested to verify the presented technique. An expert system for cam motion specification, which needs the following three tasks—symbolic representation, numerical computation, and their communication—is described as one of the possible applications of the technique. These three tasks are essential to automated engineering design and analysis

    Data Communication Between an Expert System Shell and a Conventional Algorithmic Program With Application to Cam Motion Specification

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    Although more and more expert system shells have begun to provide communication interfaces to conventional procedural languages, the interfaces are basically shell- and language-dependent. This paper presents a simple, shell- and language-independent data communication technique between a shell and a procedural language via a concept analogous to the handshake data transmission used in microprocessors. A control file is used for the action of handshake. The communication interface is between two data files in two different language environments. A program written in a LISP-based expert system shell, OPS 5, and one written in a procedural language, FORTRAN, were tested to verify the presented technique. An expert system for cam motion specification, which needs the following three tasks—symbolic representation, numerical computation, and their communication—is described as one of the possible applications of the technique. These three tasks are essential to automated engineering design and analysis

    Intelligent Integrated Management for Telecommunication Networks

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    As the size of communication networks keeps on growing, faster connections, cooperating technologies and the divergence of equipment and data communications, the management of the resulting networks gets additional important and time-critical. More advanced tools are needed to support this activity. In this article we describe the design and implementation of a management platform using Artificial Intelligent reasoning technique. For this goal we make use of an expert system. This study focuses on an intelligent framework and a language for formalizing knowledge management descriptions and combining them with existing OSI management model. We propose a new paradigm where the intelligent network management is integrated into the conceptual repository of management information called Managed Information Base (MIB). This paper outlines the development of an expert system prototype based in our propose GDMO+ standard and describes the most important facets, advantages and drawbacks that were found after prototyping our proposal

    Integrating CLIPS applications into heterogeneous distributed systems

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    SOCIAL is an advanced, object-oriented development tool for integrating intelligent and conventional applications across heterogeneous hardware and software platforms. SOCIAL defines a family of 'wrapper' objects called agents, which incorporate predefined capabilities for distributed communication and control. Developers embed applications within agents and establish interactions between distributed agents via non-intrusive message-based interfaces. This paper describes a predefined SOCIAL agent that is specialized for integrating C Language Integrated Production System (CLIPS)-based applications. The agent's high-level Application Programming Interface supports bidirectional flow of data, knowledge, and commands to other agents, enabling CLIPS applications to initiate interactions autonomously, and respond to requests and results from heterogeneous remote systems. The design and operation of CLIPS agents are illustrated with two distributed applications that integrate CLIPS-based expert systems with other intelligent systems for isolating and mapping problems in the Space Shuttle Launch Processing System at the NASA Kennedy Space Center

    Enhanced frequency management for automatic HF radio communication systems

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    The work described in this thesis aims to enhance the frequency management of automatic high frequency (HF) radio communication systems. During the research programme two new frequency management tools were developed; a chirpsounder monitoring tool to provide accuracy enhancement information for propagation prediction programs and an algorithm designed to allow optimisation of signal formats, so that in-band interference is avoided and the overall system throughput rate is increased. Two new HF communication system architectures are presented, which use system design and programming methodologies derived from the fields of artificial intelligence and computer networks.The characteristics of the HF band are presented from a communicator's viewpoint, rather than the generalised, technical approach normally associated with such reviews. The methods employed by current HF communication systems to overcome the inherent time and frequency variability of HF channels are presented in the form of reviews of propagation, natural noise and co-channel interference prediction methods, embedded real-time channel evaluation algorithms and HF communications system architectures. The inadequacies of these current techniques are analysed. The eradication of their shortcomings is the main objective of the work described in the thesis.The short-term inaccuracies associated with current propagation analysis procedures can limit the performance of automatic HF communication systems. An accuracy enhancement methodology is proposed which makes use of measurements made on oblique chirpsounder transmitters. In order to provide accuracy enhancement data, a chirpsounder-based, propagation monitor was constructed. Its implementation and trials are described and methods of using its output to enhance prediction model accuracy are discussed. Ways in which its performance may be improved are detailed.The theory of a technique, termed "template correlation", which provides automatic HF communication systems with signal format adaptation data in order to enable them to avoid in-band interference, is presented. The objective of this work is to enhance the error-free capacity of a channel via adaptation of the signal. The results of computer simulations and laboratory bench trials of template correlation are presented. Enhancements of the technique in the light of the trials results are included.Two proposed design methodologies for automatic HF communication systems are described. The first uses many of the frequency management tools associated with current automatic systems and it combines the information from these using a blackboard-based expert system architecture. The second proposed design is more conceptual than the first. An inductive expert system is employed to produce rules describing the ways in which an automatic HF system should respond to certain path conditions. Examples of how such a system might function are given.The single, most important factor which has enabled the techniques described in this thesis to be feasible is the availability of cheap but powerful microprocessors. Thus the overall philosophy of the work is to improve the performance of automatic HF communication systems via the incorporation of processing power and "intelligent software" into the communication system's terminals

    Adaptive laser link reconfiguration using constraint propagation

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    This paper describes Harris AI research performed on the Adaptive Link Reconfiguration (ALR) study for Rome Lab, and focuses on the application of constraint propagation to the problem of link reconfiguration for the proposed space based Strategic Defense System (SDS) Brilliant Pebbles (BP) communications system. According to the concept of operations at the time of the study, laser communications will exist between BP's and to ground entry points. Long-term links typical of RF transmission will not exist. This study addressed an initial implementation of BP's based on the Global Protection Against Limited Strikes (GPALS) SDI mission. The number of satellites and rings studied was representative of this problem. An orbital dynamics program was used to generate line-of-site data for the modeled architecture. This was input into a discrete event simulation implemented in the Harris developed COnstraint Propagation Expert System (COPES) Shell, developed initially on the Rome Lab BM/C3 study. Using a model of the network and several heuristics, the COPES shell was used to develop the Heuristic Adaptive Link Ordering (HALO) Algorithm to rank and order potential laser links according to probability of communication. A reduced set of links based on this ranking would then be used by a routing algorithm to select the next hop. This paper includes an overview of Constraint Propagation as an Artificial Intelligence technique and its embodiment in the COPES shell. It describes the design and implementation of both the simulation of the GPALS BP network and the HALO algorithm in COPES. This is described using a 59 Data Flow Diagram, State Transition Diagrams, and Structured English PDL. It describes a laser communications model and the heuristics involved in rank-ordering the potential communication links. The generation of simulation data is described along with its interface via COPES to the Harris developed View Net graphical tool for visual analysis of communications networks. Conclusions are presented, including a graphical analysis of results depicting the ordered set of links versus the set of all possible links based on the computed Bit Error Rate (BER). Finally, future research is discussed which includes enhancements to the HALO algorithm, network simulation, and the addition of an intelligent routing algorithm for BP

    Statistical risk estimation for communication system design

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 281-295).Spacecraft are complex systems that involve many subsystems and multiple relationships among them. The design of a spacecraft is an evolutionary process that starts from requirements and evolves over time. During this process, changes can affect mass and power at component, subsystem, and system level. Each spacecraft has to respect overall constraints in terms of mass and power. The current practice in system design deals with this problem by allocating margins to individual components and to individual subsystems. However, a statistical characterization of the fluctuations in mass and power of the overall system (i.e. the spacecraft) is missing. This lack can result in a risky spacecraft design that might not fit the mission constraints and requirements, or in a conservative design that might not fully utilize the available resources. This problem is especially challenging at the initial stage of the design, when high levels of uncertainty due to lack of knowledge are unavoidable. This research proposes a statistical approach to quantify the likelihood that the design of a spacecraft would meet the mission constraints in mass and power consumption, focusing on the initial stage of the design. Due to the complexity of the problem and the different expertise required to develop a complete risk model for a spacecraft design, the scope of this research is focused on risk estimation for a specific spacecraft subsystem: the communication subsystem. The current research aims to be a "proof of concept" of a risk-based design approach, which can then be further expanded to the design of other subsystems as well as to the whole spacecraft. The approach presented in this thesis includes a baseline communication system design tool, and a statistical characterization of the design risks through a combination of historical mission data and expert opinion. Different statistical techniques are explored to ensure that the amount of information extracted from data and expert opinion is maximized. Specifically, for statistics based on data, Kernel Density Estimator is selected as the preferred technique to extract probability densities from a database of previous space missions' components. Expert elicitation is generated through a four-part model which quantifies experts' sensitivity to biases, and uses this measurement to compose properly the assessments from different experts. Finally, an optimization framework is developed to compare multiple possible design architectures, and to select the one that minimizes design objectives, like mass and power consumption, while minimizing the risk associated with the same metrics. Examples of missions are applied to validate the model. Results show that the statistical approach recognizes whether the initial estimate of the system is an overestimation or an underestimation, providing a valuable tool to measure the risk of a communication system at the initial state of the design. Specifically, statistics based on historical data and on expert elicitation allow the designer to size contingency properly, providing a reliable estimation of mass and power in the initial stage of the design. Thanks to this method, the communication system designers will be able to evaluate and compare different communication architectures in a risk trade-off prospective across the evolution of the design. Extensions to different subsystems and to additional metrics (like cost) make this model applicable to a wider range of problems.by Alessandra Babuscia.Ph.D

    Experiencing OptiqueVQS: A Multi-paradigm and Ontology-based Visual Query System for End Users

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    This is author's post-print version, published version available on http://link.springer.com/article/10.1007%2Fs10209-015-0404-5Data access in an enterprise setting is a determining factor for value creation processes, such as sense-making, decision-making, and intelligence analysis. Particularly, in an enterprise setting, intuitive data access tools that directly engage domain experts with data could substantially increase competitiveness and profitability. In this respect, the use of ontologies as a natural communication medium between end users and computers has emerged as a prominent approach. To this end, this article introduces a novel ontology-based visual query system, named OptiqueVQS, for end users. OptiqueVQS is built on a powerful and scalable data access platform and has a user-centric design supported by a widget-based flexible and extensible architecture allowing multiple coordinated representation and interaction paradigms to be employed. The results of a usability experiment performed with non-expert users suggest that OptiqueVQS provides a decent level of expressivity and high usability and hence is quite promising
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