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  • 1
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    Interactive solution-adaptive grid generation (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: TURBO-AD is an interactive solution-adaptive grid generation program under development. The program combines an interactive algebraic grid generation technique and a solution-adaptive grid generation technique into a single interactive solution-adaptive grid generation package. The control point form uses a sparse collection of control points to algebraically generate a field grid. This technique provides local grid control capability and is well suited to interactive work due to its speed and efficiency. A mapping from the physical domain to a parametric domain was used to improve difficulties that had been encountered near outwardly concave boundaries in the control point technique. Therefore, all grid modifications are performed on a unit square in the parametric domain, and the new adapted grid in the parametric domain is then mapped back to the physical domain. The grid adaptation is achieved by first adapting the control points to a numerical solution in the parametric domain using control sources obtained from flow properties. Then a new modified grid is generated from the adapted control net. This solution-adaptive grid generation process is efficient because the number of control points is much less than the number of grid points and the generation of a new grid from the adapted control net is an efficient algebraic process. TURBO-AD provides the user with both local and global grid controls.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Langley Research Center, Software Surface Modeling and Grid Generation Steering Committee; p 347-361
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  • 2
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    An investigation of using an RQP based method to calculate parameter sensitivity derivatives (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Estimation of the sensitivity of problem functions with respect to problem variables forms the basis for many of our modern day algorithms for engineering optimization. The most common application of problem sensitivities has been in the calculation of objective function and constraint partial derivatives for determining search directions and optimality conditions. A second form of sensitivity analysis, parameter sensitivity, has also become an important topic in recent years. By parameter sensitivity, researchers refer to the estimation of changes in the modeling functions and current design point due to small changes in the fixed parameters of the formulation. Methods for calculating these derivatives have been proposed by several authors (Armacost and Fiacco 1974, Sobieski et al 1981, Schmit and Chang 1984, and Vanderplaats and Yoshida 1985). Two drawbacks to estimating parameter sensitivities by current methods have been: (1) the need for second order information about the Lagrangian at the current point, and (2) the estimates assume no change in the active set of constraints. The first of these two problems is addressed here and a new algorithm is proposed that does not require explicit calculation of second order information.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Langley Research Center, Recent Advances in Multidisciplinary Analysis and Optimization, Part 2; p 673-696
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  • 3
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    Issues in knowledge representation to support maintainability: A case study in scientific data preparation (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Scientific data preparation is the process of extracting usable scientific data from raw instrument data. This task involves noise detection (and subsequent noise classification and flagging or removal), extracting data from compressed forms, and construction of derivative or aggregate data (e.g. spectral densities or running averages). A software system called PIPE provides intelligent assistance to users developing scientific data preparation plans using a programming language called Master Plumber. PIPE provides this assistance capability by using a process description to create a dependency model of the scientific data preparation plan. This dependency model can then be used to verify syntactic and semantic constraints on processing steps to perform limited plan validation. PIPE also provides capabilities for using this model to assist in debugging faulty data preparation plans. In this case, the process model is used to focus the developer's attention upon those processing steps and data elements that were used in computing the faulty output values. Finally, the dependency model of a plan can be used to perform plan optimization and runtime estimation. These capabilities allow scientists to spend less time developing data preparation procedures and more time on scientific analysis tasks. Because the scientific data processing modules (called fittings) evolve to match scientists' needs, issues regarding maintainability are of prime importance in PIPE. This paper describes the PIPE system and describes how issues in maintainability affected the knowledge representation used in PIPE to capture knowledge about the behavior of fittings.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Ames Research Center, Working Notes from the 1992 AAAI Workshop on Automating Software Design. Theme: Domain Specific Software Design; p 23-2
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  • 4
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    Interactive solution-adaptive grid generation procedure (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: TURBO-AD is a two dimensional interactive solution adaptive grid generation program. The code uniquely combines a grid adaptation technique that uses parametric mapping with control sources and an algebraic grid generation that uses control points into a single software package. The grid adaptation is achieved by first adapting the control points to a numerical solution in the parametric domain using the control sources obtained from flow properties. Then a new grid is generated from the adapted control net using the control point formulation. The new adapted grid in the parametric domain is then mapped back to the physical domain. This solution adaptive grid generation process is efficient because the number of control points is much less than the number of grid points and the grid generation from the adapted control net is an efficient algebraic process.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: Workshop on Grid Generation and Related Areas; p 123-138
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  • 5
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    Reliable multicast protocol specifications protocol operations (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This appendix contains the complete state tables for Reliable Multicast Protocol (RMP) Normal Operation, Multi-RPC Extensions, Membership Change Extensions, and Reformation Extensions. First the event types are presented. Afterwards, each RMP operation state, normal and extended, is presented individually and its events shown. Events in the RMP specification are one of several things: (1) arriving packets, (2) expired alarms, (3) user events, (4) exceptional conditions.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-200021 , NAS 1.26:200021 , NASA-IVV-95-004 , WVU-SRL-95-004 , WVU-SCS-TR-95-24 , CERC-TR-RN-95-010 , NIPS-96-07265
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  • 6
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    An approach to verification and validation of a reliable multicasting protocol (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper describes the process of implementing a complex communications protocol that provides reliable delivery of data in multicast-capable, packet-switching telecommunication networks. The protocol, called the Reliable Multicasting Protocol (RMP), was developed incrementally using a combination of formal and informal techniques in an attempt to ensure the correctness of its implementation. Our development process involved three concurrent activities: (1) the initial construction and incremental enhancement of a formal state model of the protocol machine; (2) the initial coding and incremental enhancement of the implementation; and (3) model-based testing of iterative implementations of the protocol. These activities were carried out by two separate teams: a design team and a V&V team. The design team built the first version of RMP with limited functionality to handle only nominal requirements of data delivery. In a series of iterative steps, the design team added new functionality to the implementation while the V&V team kept the state model in fidelity with the implementation. This was done by generating test cases based on suspected errant or off-nominal behaviors predicted by the current model. If the execution of a test was different between the model and implementation, then the differences helped identify inconsistencies between the model and implementation. The dialogue between both teams drove the co-evolution of the model and implementation. Testing served as the vehicle for keeping the model and implementation in fidelity with each other. This paper describes (1) our experiences in developing our process model; and (2) three example problems found during the development of RMP.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-200026 , NAS 1.26:200026 , NIPS-96-07270
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  • 7
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    Verification and validation of a reliable multicast protocol (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper describes the methods used to specify and implement a complex communications protocol that provides reliable delivery of data in multicast-capable, packet-switching telecommunication networks. The protocol, called the Reliable Multicasting Protocol (RMP), was developed incrementally by two complementary teams using a combination of formal and informal techniques in an attempt to ensure the correctness of the protocol implementation. The first team, called the Design team, initially specified protocol requirements using a variant of SCR requirements tables and implemented a prototype solution. The second team, called the V&V team, developed a state model based on the requirements tables and derived test cases from these tables to exercise the implementation. In a series of iterative steps, the Design team added new functionality to the implementation while the V&V team kept the state model in fidelity with the implementation through testing. Test cases derived from state transition paths in the formal model formed the dialogue between teams during development and served as the vehicles for keeping the model and implementation in fidelity with each other. This paper describes our experiences in developing our process model, details of our approach, and some example problems found during the development of RMP.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-200023 , NAS 1.26:200023 , NASA-IVV-95-006 , WVU-SLR-95-006 , WVU-SCS-TR-95-26 , CERC-TR-TM-010 , NIPS-96-07267
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  • 8
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    Design, Implementation, and Verification of the Reliable Multicast Protocol (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This document describes the Reliable Multicast Protocol (RMP) design, first implementation, and formal verification. RMP provides a totally ordered, reliable, atomic multicast service on top of an unreliable multicast datagram service. RMP is fully and symmetrically distributed so that no site bears an undue portion of the communications load. RMP provides a wide range of guarantees, from unreliable delivery to totally ordered delivery, to K-resilient, majority resilient, and totally resilient atomic delivery. These guarantees are selectable on a per message basis. RMP provides many communication options, including virtual synchrony, a publisher/subscriber model of message delivery, a client/server model of delivery, mutually exclusive handlers for messages, and mutually exclusive locks. It has been commonly believed that total ordering of messages can only be achieved at great performance expense. RMP discounts this. The first implementation of RMP has been shown to provide high throughput performance on Local Area Networks (LAN). For two or more destinations a single LAN, RMP provides higher throughput than any other protocol that does not use multicast or broadcast technology. The design, implementation, and verification activities of RMP have occurred concurrently. This has allowed the verification to maintain a high fidelity between design model, implementation model, and the verification model. The restrictions of implementation have influenced the design earlier than in normal sequential approaches. The protocol as a whole has matured smoother by the inclusion of several different perspectives into the product development.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-200028 , NAS 1.26:200028 , NASA-IVV-95-011 , WVU-SRL-95-011 , WVU-SCS-TR-95-31 , CERC-TR-TM-95-013 , NIPS-96-07272
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  • 9
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    Reliable multicast protocol specifications flow control and NACK policy (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This appendix presents the flow and congestion control schemes recommended for RMP and a NACK policy based on the whiteboard tool. Because RMP uses a primarily NACK based error detection scheme, there is no direct feedback path through which receivers can signal losses through low buffer space or congestion. Reliable multicast protocols also suffer from the fact that throughput for a multicast group must be divided among the members of the group. This division is usually very dynamic in nature and therefore does not lend itself well to a priori determination. These facts have led the flow and congestion control schemes of RMP to be made completely orthogonal to the protocol specification. This allows several differing schemes to be used in different environments to produce the best results. As a default, a modified sliding window scheme based on previous algorithms are suggested and described below.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-200027 , NAS 1.26:200027 , NASA-IVV-95-010 , WVU-SRL-95-010 , WVU-SCS-TR-95-30 , CERC-TR-RN-95-013 , NIPS-96-07271
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  • 10
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    Fault recovery in the reliable multicast protocol (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Reliable Multicast Protocol (RMP) provides a unique, group-based model for distributed programs that need to handle reconfiguration events at the application layer. This model, called membership views, provides an abstraction in which events such as site failures, network partitions, and normal join-leave events are viewed as group reformations. RMP provides access to this model through an application programming interface (API) that notifies an application when a group is reformed as the result of a some event. RMP provides applications with reliable delivery of messages using an underlying IP Multicast (12, 5) media to other group members in a distributed environment even in the case of reformations. A distributed application can use various Quality of Service (QoS) levels provided by RMP to tolerate group reformations. This paper explores the implementation details of the mechanisms in RMP that provide distributed applications with membership view information and fault recovery capabilities.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-200024 , NAS 1.26:200024 , NASA-IVV-95-007 , WVU-SRL-95-007 , WVU-SCS-TR-95-27 , CERC-TR-TM-95-011 , NIPS-96-07268
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