HIGH BIT RATE EXPERIMENTS OVER ACTS

This paper describes two high data rate experiments that are being developed for the gigabit NASA Advanced Communications Technology Satellite (ACTS). The first is a telescience experiment that remotely acquires image data at the Keck telescope from the Caltech campus. The second is a distributed global climate application that is run beween two supercomputer centers interconnected by ACTS. The implementation approach for each is described along with the expected results. Also, the ACTS high data rate (HDR) ground station is also described in detail.     

Effect of Water Activity and Moisture Content on the Stability of Beet Powder Pigments

The effect of water activity (“dry”– 0.84) and moisture content on the stability of beet pigments (betanine and vulgaxanthine I) was investigated in beet powder stored at 35°C. Pigment deterioration followed a first order reaction. Water activity and moisture content had a pronounced exponential effect on pigment stability. A decrease of approximately one order of magnitude in pigment stability was observed when a_w was increased from 0.32 to 0.75. Storing the powder at a_w of 0.12 or below resulted in practically no deterioration of the pigments over a period of several months. Profound differences in pigment stability were attributed to sorption hysteresis and system composition.     

Kinetic Parameter Estimation for Quality Change during Continuous Thermal Processing of Grapefruit Juice

Reaction order, activation energy (E_a) and average rate constant (k_av) were evaluated by dynamic modeling for color degradation of grapefruit juice during thermal processing. Simulated aseptic conditions were: 85–135°C, 40–175 set processing time, and average velocities 5–30 cm/set. Quality was assessed by nonenzymatic browning index (NEBI) and S-hydroxymethyl-furfural (HMF). Average values for reaction-order and energy of activation were: 0 and 21.4 kcal/g-mol (NEBI) and 0.3 and 23.2 kcal/g-mol (HMF), respectively. These values were compared with those contained in the deformed ellipsoid which define the 90% joint confidence interval of all possible parameter combinations. Based on initial and final concentrations, the method can predict effects of processing on liquid foods.     

FROM PLAN CRITIQUING TO CLARIFICATION DIALOGUE FOR COOPERATIVE RESPONSE GENERATION*

Recognizing the plan underlying a query aids in the generation of an appropriate response. In this paper, we address the problem of how to generate cooperative responses when the user's plan is ambiguous. We show that it is not always necessary to resolve the ambiguity, and provide a procedure that estimates whether the ambiguity matters to the task of formulating a response. The procedure makes use of the critiquing of possible plans and identifies plans with the same fault. We illustrate the process of critiquing with examples. If the ambiguity does matter, we propose to resolve the ambiguity by entering into a clarification dialogue with the user and provide a procedure that performs this task. Together, these procedures allow a question-answering system to take advantage of the interactive and collaborative nature of dialogue in order to recognize plans and resolve ambiguity. This work therefore presents a view of generation in advice-giving contexts which is different from the straightforward model of a passive selection of responses to questions asked by users. We also report on a trial implementation in a course-advising domain, which provides insights on the practicality of the procedures and directions for future research.     

Local Atomic Arrangements in a Magnesiowustite Solid Solution

Quantitative studies of diffuse X-ray scattering and measurements of magnetization are reported for (Fe,Mg)O with 15.7 cation % Fe held in a reducing atmosphere at 1400°C and quenched. The diffuse scattering is greater for fast cooling than for slow cooling; in both cases, spinel precipitation occurs, but the amount is much larger in the latter case. From this scattering, short-range order parameters were determined for the clustering between cations, and displacements were obtained between cations and anions. From the magnetic measurements the size of magnetic Fe ion clusters was obtained. Computer simulations of the cation arrangement with the measured short-range order parameters indicate that the magnetic clusters cannot be accounted for by nearest-neighbor Fe^2+] clusters. However, clusters of Fe ions related by first- and/or second-neighbor vectors are of the size found from the magnetic data.