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  • 1
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    Development of the NASA/FLAGRO computer program (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A preliminary version of a new computer program has been developed for calculating crack propagation in cyclically loaded structures. The new program, titled NASA/FLAGRO, has numerous enhanced features over previous programs used for safe life analysis on space systems. The essential features of the new program consist of modular design, promptive input using a cathode ray tube terminal, improved crack growth rate analytical methods, many new crack case solutions, and incorporation of user-defined files for material properties and fatigue spectrums. Also, five options made available in the program are to compute: (1) safe life of a part with a preexisting crack; (2) critical crack size for a specified stress level; (3) stress-intensity factor numerical values for making comparisons or checks of solutions; (4) least-squares fit of growth rate equations to crack growth rate data; and (5) the conversion of a versus N data to Delta K versus da/dN.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
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    NASA TECHNICAL REPORTS
  • 2
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    Implementation of a frame-based representation in CLIPS (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Knowledge representation is one of the major concerns in expert systems. The representation of domain-specific knowledge should agree with the nature of the domain entities and their use in the real world. For example, architectural applications deal with objects and entities such as spaces, walls, and windows. A natural way of representing these architectural entities is provided by frames. This research explores the potential of using the expert system shell CLIPS, developed by NASA, to implement a frame-based representation that can accommodate architectural knowledge. These frames are similar but quite different from the 'template' construct in version 4.3 of CLIPS. Templates support only the grouping of related information and the assignment of default values to template fields. In addition to these features frames provide other capabilities including definition of classes, inheritance between classes and subclasses, relation of objects of different classes with 'has-a', association of methods (demons) of different types (standard and user-defined) to fields (slots), and creation of new fields at run-time. This frame-based representation is implemented completely in CLIPS. No change to the source code is necessary.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Johnson Space Center, First CLIPS Conference Proceedings, Volume 2; p 570-580
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    NASA TECHNICAL REPORTS
  • 3
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    Implementing a frame representation in CLIPS/COOL (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: An implementation is described and evaluated of frames in COOL. The test case is a frame based semantic network previously implemented in CLIPS (C Language Integrated Production System) Version 4.3 as part of the Intelligent Computer Aided Design System (ICADS) and reported at the first CLIPS conference.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Johnson Space Center, Second CLIPS Conference Proceedings, Volume 2; p 497-504
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    NASA TECHNICAL REPORTS
  • 4
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    ICADS: A cooperative decision making model with CLIPS experts (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A cooperative decision making model is described which is comprised of six concurrently executing domain experts coordinated by a blackboard control expert. The focus application field is architectural design, and the domain experts represent consultants in the area of daylighting, noise control, structural support, cost estimating, space planning, and climate responsiveness. Both the domain experts and the blackboard were implemented as production systems, using an enhanced version of the basic CLIPS package. Acting in unison as an Expert Design Advisor, the domain and control experts react to the evolving design solution progressively developed by the user in a 2-D CAD drawing environment. A Geometry Interpreter maps each drawing action taken by the user to real world objects, such as spaces, walls, windows, and doors. These objects, endowed with geometric and nongeometric attributes, are stored as frames in a semantic network. Object descriptions are derived partly from the geometry of the drawing environment and partly from knowledge bases containing prototypical, generalized information about the building type and site conditions under consideration.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Johnson Space Center, Second CLIPS Conference Proceedings, Volume 1; p 102-111
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    NASA TECHNICAL REPORTS
  • 5
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    Using PVM to host CLIPS in distributed environments (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: It is relatively easy to enhance CLIPS (C Language Integrated Production System) to support multiple expert systems running in a distributed environment with heterogeneous machines. The task is minimized by using the PVM (Parallel Virtual Machine) code from Oak Ridge Labs to provide the distributed utility. PVM is a library of C and FORTRAN subprograms that supports distributive computing on many different UNIX platforms. A PVM deamon is easily installed on each CPU that enters the virtual machine environment. Any user with rsh or rexec access to a machine can use the one PVM deamon to obtain a generous set of distributed facilities. The ready availability of both CLIPS and PVM makes the combination of software particularly attractive for budget conscious experimentation of heterogeneous distributive computing with multiple CLIPS executables. This paper presents a design that is sufficient to provide essential message passing functions in CLIPS and enable the full range of PVM facilities.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Johnson Space Center, Third CLIPS Conference Proceedings, Volume 2; p 203-211
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    NASA TECHNICAL REPORTS
  • 6
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    A machine-learning apprentice for the completion of repetitive forms (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Forms of all types are used in businesses and government agencies, and most of them are filled in by hand. Yet much time and effort has been expended to automate form-filling by programming specific systems or computers. The high cost of programmers and other resources prohibits many organizations from benefiting from efficient office automation. A learning apprentice can be used for such repetitious form-filling tasks. In this paper, we establish the need for learning apprentices, describe a framework for such a system, explain the difficulties of form-filling, and present empirical results of a form-filling system used in our department from September 1991 to April 1992. The form-filling apprentice saves up to 87 percent in keystroke effort and correctly predicts nearly 90 percent of the values on the form.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Johnson Space Center, The Seventh Annual Workshop on Space Operations Applications and Research (SOAR 1993), Volume 1; p 268-275
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    NASA TECHNICAL REPORTS
  • 7
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    Formationkeeping of Spacecraft via Differential Drag (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper examines the use of differential drag in the formationkeeping of spacecraft. In many future space missions one satellite will be required to fly in a specific position with respect to another satellite; this action is referred to as formationkeeping. In this study, differential drag is the difference in drag between the two satellites. Reasons to use differential drag as an actuator for formationkeeping include the avoidance of jet plume impingement effects on closely spaced satellites and possible fuel savings. The equations of relative motion between the two satellites are derived and a mathematical transformation is made to reduce the formationkeeping problem to the simultaneous solution of a double integrator and a harmonic oscillator. A two-part control law is developed that simultaneously and dependently solves the double oscillator and harmonic integrator. Results are presented of eight test cases being driven to a target position; two different simulations are used. The validity of assumptions made in the derivation of the control law is examined in the comparison of similar test cases run through different simulations. The control law developed can drive a satellite from an initial position to a target position and maintain the satellite at that location.
    Keywords: Astrodynamics
    Type: NASA-CR-171939 , NAS 1.26:171939 , CSDL-T-920
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    NASA TECHNICAL REPORTS
  • 8
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    Causal modeling and event-driven simulation for monitoring of continuous systems (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: We describe extensions to the traditional techniques for anomaly detection, as well as new anomaly detection techniques based on alternate models of what distinguishes normal from abnormal behavior. Some of these techniques are designed to capture anomalies at individual sensors; some detect anomalies across collections of sensors. To assist in reasoning about complex global behaviors, we construct and simulate a causal model of the physical system being monitored. These techniques have been tested on data from the ECLSS of Space Station Freedom (SSF) and are being applied in advanced monitoring prototypes for the SSF External Active Thermal Control System of SSF and the Environmental Emergency and Consumables Management subsystem of the Space Shuttle.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: AIAA PAPER 93-4525 , In: AIAA Computing in Aerospace Conference, 9th, San Diego, CA, Oct. 19-21, 1993, Technical Papers. Pt. 1 (A94-11401 01-62); p. 395-405.
    Format: text
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  • 9
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    Event-driven simulation in SELMON: An overview of EDSE (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: EDSE (event-driven simulation engine), a model-based event-driven simulator implemented for SELMON, a tool for sensor selection and anomaly detection in real-time monitoring is described. The simulator is used in conjunction with a causal model to predict future behavior of the model from observed data. The behavior of the causal model is interpreted as equivalent to the behavior of the physical system being modeled. An overview of the functionality of the simulator and the model-based event-driven simulation paradigm on which it is based is provided. Included are high-level descriptions of the following key properties: event consumption and event creation, iterative simulation, synchronization and filtering of monitoring data from the physical system. Finally, how EDSE stands with respect to the relevant open issues of discrete-event and model-based simulation is discussed.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-194505 , JPL-PUBL-92-23 , NAS 1.26:194505
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    NASA TECHNICAL REPORTS
  • 10
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    Application of Statistical Filter Theory to the Optimal Estimation of Position and Velocity on Board a Circumlunar Vehicle (1962)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Statistical filter theory is employed to develop a method for determining the best possible estimate of the position and velocity of a space vehicle in the midcourse phase of flight. Results of a computer simulation are given to illustrate the performance attainable. An on-board system is visualized in which the source of information is an arbitrary sequence of observations of space angles, corrupted by measurement errors. The scheme is in effect a dynamical time-varying filter, implemented by a digital computer, which processes the incoming data to compute an up-to-date optimal estimate of position and velocity.
    Keywords: Astrodynamics
    Type: NASA-TR-R-135
    Format: application/pdf
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