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Software for Continuous Replanning During Execution

Feedback from execution of a plan is used to update the plan continuously. Continuous Activity Scheduling Planning Execution and Replanning (CASPER) is a computer program for automated planning of interdependent activities within a system subject to requirements, constraints, and limitations on resources. Now at the prototype stage of development, CASPER was conceived to enable a robotic exploratory spacecraft to perform onboard, autonomous planning and replanning of scientific observations and other functions in response to diverse unanticipated phenomena that could include unknown or changing environmental conditions, equipment failures, and errors in mathematical models used in planning. On Earth, CASPER could be adapted to use in scheduling operations of production lines and other complex systems.

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An Efficient Algorithm for Propagation of Temporal-Constraint Networks

The computational cost is much less than in prior algorithms. An efficient artificial-intelligence-type algorithm for the propagation of temporal constraints has been devised for incorporation into software that performs scheduling and planning of tasks in real time. This algorithm checks for temporal consistency and computes time windows of time points within temporal-constraint networks, which are often used in scheduling and planning. A C++-language computer program that implements the algorithm has been devised for incorporation into the control software of the Mission Data System of NASA’s Jet Propulsion Laboratory. The algorithm and program could also be applied to industrial planning and scheduling problems.

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Estimating Heterodyne-Interferometer Polarization Leakage

Correction for the nonlinearity contributed by polarization leakage can be made in real time. A method of estimating and correcting for the effect of polarization leakage on the response of a heterodyne optical interferometer has been devised. In a typical application in which a heterodyne interferometer is used as a displacement or length gauge, the effect of the polarization leakage is a nonlinearity that typically gives rise to an error of the order of 1 nm in the displacement or length. By use of the present method, it should eventually be possible, in principle, to reduce the error to the order of 10 pm or less. The technique is primarily computational and does not require any additional interferometer hardware. Moreover, the computations can be performed on almost any modern computer in real time.

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Methodology for Tracking Hazards and Predicting Failures

This methodology can increase safety and reliability while reducing costs in all industries. The Continuous Hazard Tracking and Failure Prediction Methodology (CHTFPM) is a proactive methodology for gathering and analyzing information about a system in order to prevent accidents and system failures. The proactivity of the CHTFPM places it in contrast to conventional formal inductive and deductive hazard-analysis methodologies, which are limited in their effectiveness, in that they do not provide realtime information on whether the conditions in a system are becoming hazardous and could lead to a system malfunction: the conventional methodologies basically provide feedback on hazards after accidents have happened. The CHTFPM could be applied to advantage in almost all industries.

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Cold Flow Calorimeter

This apparatus can measure a rapidly varying heat-transfer coefficient. The cold flow calorimeter is an apparatus for measuring a possibly rapidly varying heat-transfer coefficient on a surface. The cold flow calorimeter includes (1) a small strain gauge bonded to a small, thin steel shim that is placed on the surface of interest and (2) a circuit that controls the electric power supplied to the strain gauge to keep the strain-gauge grid at a constant temperature [e.g., 150 °F (≈66 °C)]. The instantaneous value of the heattransfer coefficient is deduced from the instantaneous power required to maintain the constant temperature. The heat-transfer coefficient measurable by use of this apparatus can range from values characteristic of natural convection to values as large as about 1,000 Btu/(ft·h·°R) [≈1.7 kW/(m·K).

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Refractive Secondary Concentrators for Solar Thermal Systems

Concentration ratios as high as 104 and operating temperatures >2,000 K are anticipated. High-throughput, non-imaging, secondary concentrating optics that utilize refraction and total internal reflection are undergoing development for use in conjunction with advanced primary solar concentrators to provide solar thermal energy for space applications. This development is prompted by (1) a need to concentrate sunlight by factors of as much as 104 to satisfy design and operating requirements for some advanced solar thermal systems and (2) the impracticality of fabricating primary concentrators with sufficient precision to afford such high concentration ratios by themselves. Figure 1 illustrates the operation of a refractive secondary concentrator.

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Model of a Fluidized Bed Containing a Mixture of Particles

Predictions thus far are in reasonable agreement with experimental data. A mathematical model has been developed for use in analyzing the dynamics of an isothermal, non-chemically-reacting mixture of particles in a bubbling fluidized bed. Although the model has generic validity, it is intended, more specifically, to be applied to a fluidized bed that contains a mixture of sand and biomass particles, fluidized by steam. The model includes components in common with the models described in “Model of Pyrolysis of Biomass in a Fluidized-Bed Reactor” (NPO-20708), NASA Tech Briefs, Vol. 25, No. 6 (June 2001), page 59 and “Multiphase-Flow Model of Fluidized-Bed Pyrolysis of Biomass” (NPO-20789), NASA Tech Briefs, Vol. 26, No. 2 (February 2002), page 56.

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