We are interested by contributing to stochastic problems of which the main distinction is that some tasks may create other tasks. In particular, we present a first approach which represents the problem by an acyclic g...
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We are interested by contributing to stochastic problems of which the main distinction is that some tasks may create other tasks. In particular, we present a first approach which represents the problem by an acyclic graph, and solves each node in a certain order so as to produce an optimal solution. Then, we detail a second algorithm, which solves each task separately, using the first approach, and where an on-line heuristic computes the global actions to execute when the state of a task changes.
Program affordability needs to be built-in at the initial concept formulation stage. For NASA's space exploration vision this is critical for long range sustainability of human presence in space. What is often ove...
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ISBN:
(纸本)1563477270
Program affordability needs to be built-in at the initial concept formulation stage. For NASA's space exploration vision this is critical for long range sustainability of human presence in space. What is often overlooked in the initial concept formulation of a large scale system endeavor such as NASA's Constellation program is the hidden cost of maintaining requisite operational safety margins and redundancy through adequate supply chain logistics. Ensuring adequate supply chain logistics necessitates the integration of operations and maintenance cycles. What enables this integration is the coordination and reconciliation across multiple equipment types of system health features and logistical information such as: (1) prognostic drivers from Integrated Vehicle Health Monitoring (IVHM) systems producing proactive condition-based "maintain me" demands, (2) maintenance management systems tracking usage and producing scheduled maintenance demands, (3) unscheduled maintenance demands resulting from any trouble reports entered by human observers of conditions missed by the IVHM system, and (4) implicit maintenance demands resulting from mission plans which require assignment of vehicular/robotic assets and consequently require assurance of the assigned assets' fitness for the intended tasks. In this paper we discuss how Coordinated Multi-source Maintenance on Demand (CMMD) technology, which is being is transitioned to the USMC Coherent Analytical Computing Environment (CACE) program and the Joint Strike Fighter Program, can be applied to the NASA domain, and its benefits in terms of mission affordability, operations efficiency and system health effectiveness. Using concepts derived from CMMD, we discuss the kind of IVHM capabilities needed to optimize multiple, parallel, yet inter-linked, operations-maintenance cycles, thereby optimizing program affordability while meeting specific mission supportability requirements across a broad range of mission scenarios.
engineering a large software project involves tracking the impact of development and maintenance changes on the software performance. An approach for tracking the impact is regression benchmarking, which involves auto...
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engineering a large software project involves tracking the impact of development and maintenance changes on the software performance. An approach for tracking the impact is regression benchmarking, which involves automated benchmarking and evaluation of performance at regular intervals. Regression benchmarking must tackle the nondeterminism inherent to contemporary computersystems and execution environments and the impact of the nondeterminism on the results. On the example of a fully automated regression benchmarking environment for the mono open-source project, we show how the problems associated with nondeterminism can be tackled using statistical methods.
This paper describes a comprehensive prototype of large-scale fault adaptive embedded software developed for the proposed Fermilab BTeV high energy physics experiment. Lightweight self-optimizing agents embedded withi...
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This paper describes a comprehensive prototype of large-scale fault adaptive embedded software developed for the proposed Fermilab BTeV high energy physics experiment. Lightweight self-optimizing agents embedded within Level 1 of the prototype are responsible for proactive and reactive monitoring and mitigation based on specified layers of competence. The agents are self-protecting, detecting cascading failures using a distributed approach. Adaptive, reconfigurable, and mobile objects for reliablility are designed to be self-configuring to adapt automatically to dynamically changing environments. These objects provide a self-healing layer with the ability to discover, diagnose, and react to discontinuities in real-time processing. A generic modeling environment was developed to facilitate design and implementation of hardware resource specifications, application data flow, and failure mitigation strategies. Level 1 of the planned BTeV trigger system alone will consist of 2500 DSPs, so the number of components and intractable fault scenarios involved make it impossible to design an 'expert system' that applies traditional centralized mitigative strategies based on rules capturing every possible system state. Instead, a distributed reactive approach is implemented using the tools and methodologies developed by the Real-Time Embedded systems group.
The Real Time Embedded systems (RTES) project was created to study the design and implementation of high-performance, heterogeneous, and fault-adaptive real time embedded systems. The driving application for this rese...
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This research proposes to modernize a legacy software system by using Web services as the main building blocks of the software reengineering. For this purpose, a legacy theorem proof checking and derivation tool calle...
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This research proposes to modernize a legacy software system by using Web services as the main building blocks of the software reengineering. For this purpose, a legacy theorem proof checking and derivation tool called Bertie3 is reengineered in terms of service-oriented architecture, service-oriented componentization, and external data representation and serialization. With the Web services of derivation checking engines and first-order markup languages, a minimal amount of development time can be spent working on well-known and well-developed components. More time can be spent updating the features that make the tool unique. This case study shows that modernizing a software system with Web services will allow the business components of the system to be easily expanded and integrated with other application components for future demands.
The real time embedded systems (RTES) project was created to study the design and implementation of high-performance, heterogeneous, and fault-adaptive real time embedded systems. The driving application for this rese...
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The real time embedded systems (RTES) project was created to study the design and implementation of high-performance, heterogeneous, and fault-adaptive real time embedded systems. The driving application for this research was the proposed BTeV high energy physics experiment, which called for large farms of embedded computational elements (DSPs), as well as a large farm of conventional high-performance processors to implement its Level 1 and Level 2/3 triggers. At the time of BTeV's termination early in 2005, the RTES project was within days of completing a prototype implementation for providing a reliable and fault-adaptive infrastructure to the L2/3 farm; a prototype for the L1 farm had been completed in 2003. This paper documents the conclusion of the RTES focus on BTeV, and provides an evaluation of the applicability of the RTES concepts to other systems
software frequently needs to adapt its behavior at run time to respond to changes in its execution environment. Different software components may use different approaches to adaptation. Composing a single adaptive sys...
ISBN:
(纸本)1581139497
software frequently needs to adapt its behavior at run time to respond to changes in its execution environment. Different software components may use different approaches to adaptation. Composing a single adaptive system from existing adaptive components requires an "adaptation infrastructure" to integrate and arbitrate adaptive behaviors. This paper proposes a model for such an infrastructure and describes the design and operation of M2, a prototype implementation. M2 uses a technique called transparent shaping to modify existing components so that they can report events of interest to the M2 core and implement appropriate responses. The architecture and communication infrastructure of M2 are described, followed by a case study in which M2 is used to construct an adaptive multimedia conferencing application from otherwise incompatible components. Copyright 2004 ACM.
We conducted an eye-tracking study of mechanical problem solving from cross-sectional diagrams of devices. Response time, accuracy and eye movement data were collected and analyzed for 72 problem-solving episodes (9 s...
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